Co-reporter:Xinxiu Cao, Zhonghui Du, Liang Chen, Kefeng Zhao, Hongxiang Li, Jiangang Liu, Yanchun Han
Polymer 2017 Volume 118(Volume 118) pp:
Publication Date(Web):2 June 2017
DOI:10.1016/j.polymer.2017.04.076
•Long PDBT-TT nanowires were firstly prepared through a method called slow evaporation of the main solvent.•The preparation of nanowires followed a homogeneous nucleation and growth process.•The concentration and sizes of the nanowires could be controlled.•The key factor in preparing PDBT-TT nanowires is that the aggregate speeds of the molecules should be controlled slowly.The preparation of diketopyrrolopyrrole-based polymer nanowires seems very difficult, probably due to the fact that the nanowires length direction is along the main chain not the π-π direction. For the nanowires whose length direction is along the main chain, the probability of the short nanowires to meet the ends of other molecules to grow longer is very small. Herein, we prepared long 3,6-bis-(thiophen-2-yl)-N,N’-bis(2-octyl-1-dodecyl)-1,4-dioxo-pyrrolo [3,4-c]pyrrole and thieno [3,2-b]thiophene (PDBT-TT) nanowires followed a homogeneous nucleation and growth process by slowing the aggregate speed of the PDBT-TT molecules. Slowing the aggregate speed of the molecules was carried out by slow evaporation of the main solvent (the mixed solvent, consisting of a good solvent chloroform (CF) as the main solvent and a marginal solvent 1,2-dichlorobenzene (ODCB) as the co-solvent). CF evaporating at a speed of 30 μL/h allows the solution to be always in the saturated state and the polymer to aggregate slowly. The resulting nanowires are about 75 nm in width and tens of micrometers in length. The density and length of nanowires could be controlled by adjusting the concentration of the pristine solution and the evaporation process, respectively. Higher concentration of the pristine solution results in higher density of nanowires, and the length of nanowires also changed.Download high-res image (282KB)Download full-size image
Co-reporter:Jiangang Liu;Bin Tang;Qiuju Liang;Yanchun Han;Zhiyuan Xie;Jun Liu
RSC Advances (2011-Present) 2017 vol. 7(Issue 22) pp:13289-13298
Publication Date(Web):2017/02/24
DOI:10.1039/C7RA00244K
Broadening the absorption spectrum and efficiently harvesting photogenerated excitons are crucial tasks to realize high-efficiency polymer solar cells (PSCs). Recently, ternary PSCs with complementary absorptions into a single junction device have been emerging as a promising strategy to enhance the absorption of binary PSCs. However, the effect of ternary PSCs critically depends on the location of the third component according to different principles. Due to the hard control of the third component location, only limited high-performance ternary systems have been demonstrated previously. Here, we develop a new concept of dual Förster resonance energy transfer (dual-FRET), in which the third component acts as an “energy donor” and the donor and acceptor act as an “energy acceptor”. Thus, exciton energy of the third component could transfer energy to both the donor and the acceptor through the FRET principle. Consequently, the third component should only be dispersed uniformly in the binary film regardless of its location. Using this concept, the performance of ternary PSCs, i.e., PTB7-Th (donor)/P(NDI2OD-T2) (accepter)/PF12TBT (the third component), reaches 6.07%, more than about 30% compared to the corresponding binary PSCs (4.70%). Our work provides a novel way for designing ternary structures to boost the efficiency of PSCs.
Co-reporter:Qiaoqiao Zhao, Xinhong Yu, Jiangang Liu, Zhiyuan Xie, Yanchun Han
Organic Electronics 2016 Volume 37() pp:6-13
Publication Date(Web):October 2016
DOI:10.1016/j.orgel.2016.05.044
•H-aggregation and crystallinity of p-DTS(FBTTh2)2 were improved via SVA.•The mechanisms rely on controlling molecular motion ability and prolonging time.•The ratio of H/J could be tuned from 0.71 to 1.47.The proper crystallinity and a balance between H-aggregation and J-aggregation are both necessary for the best performance of small molecule organic solar cells. It is well known that J-aggregation is favorable to form more excitons due to its narrower bad-gap, leading to a high photocurrent. While H-aggregation has a higher lowest excited level which could provide stronger driving force for exciton dissociation. However, for 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(6-fluoro-4(5′-hexyl-[2,2′-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole) (p-DTS(FBTTh2)2)/[6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) blend system, the crystallinity is very low and p-DTS(FBTTh2)2 is mainly in J-aggregation. Thus, increasing H-aggregation of p-DTS(FBTTh2)2 is an effective way to improve photovoltaic efficiency of p-DTS(FBTTh2)2/PC70BM system. In this paper, it was found that solvent vapor annealing (SVA) was an effective method to improve the crystallinity and the H-aggregation of p-DTS(FBTTh2)2 in blend film. Due to the prolonged time for self-organization, the crystallinity of p-DTS(FBTTh2)2 was enhanced. In addition, molecular motion ability of p-DTS(FBTTh2)2 was controlled and p-DTS(FBTTh2)2 could adjust its structure to form H-aggregation. As a result, the ratio of H/J could be tuned from 0.71 to 1.47 and the power conversion efficiencies (PCE) was improved from 2.64% to 6.63%.
Co-reporter:Xinxiu Cao, Qiang Zhang, Ke Zhou, Xinhong Yu, Jiangang Liu, Yanchun Han, Zhiyuan Xie
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016 Volume 506() pp:723-731
Publication Date(Web):5 October 2016
DOI:10.1016/j.colsurfa.2016.07.048
Different amount of fullerene in the mixed phase of P3HT/fullerene was achieved.More fullerenes in the mixed phase induced more interface, bigger οE value and higher local carrier mobility.More fullerenes in the mixed phase were beneficial to the exciton generation and dissociation.Donor and acceptor should have good miscibility to increase the fullerene content in mixed phase.Designing polymeric bulk heterojunction (BHJ) morphology with good exciton separation efficiency is one of the key factors in obtaining high-efficiency polymer solar cells (PSCs). Cascaded energy formed by the energy level difference (οE) between aggregated phase and the mixed phase is thought to encourage spatial separation of the geminate charge pair. However, how the composition of the mixed phase affects the exciton generation and dissociation process is still unknown. In this paper, different amount of fullerene in the mixed phase of poly(3-hexylthiophene) (P3HT)/fullerene was achieved by changing the ratio of two fullerenes ([6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) and its bisadduct bis-PC71BM), which have different miscibility with P3HT. When the content of PC71BM increasing from 0% to about 60%, the mixed phase containing more fullerenes. More donor/acceptor (D/A) interface was formed, and the οE value also increased from 0.19 eV to 0.23 eV. As a result, the maximum exciton generation rate (Gmax) increased from 5.36 ÿ 1027 m⿿3/s to 6.48 ÿ 1027 m⿿3/s, and the exciton dissociation probabilities increased from 47% to 81%. Thus, perfect three-phase morphology for high performance solar cells was proposed, in which not only the donor and acceptor have good crystallinity to form interpenetrating network but also have good miscibility with each other to increase the fullerene content in mixed phase.Different amount of fullerene in the mixed phase of poly(3-hexylthiophene) (P3HT)/fullerene was achieved by changing the ratio of two fullerenes ([6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) and its bisadduct bis-PC71BM), which have different miscibility with P3HT. When the content of PC71BM increasing from 0% to about 60%, the mixed phase containing more fullerenes. Higher content of fullerenes in the mixed phase was beneficial to the exciton generation and dissociation due to the enlarged donor/acceptor (D/A) interface, increased οE value and higher local charge carrier mobility.Download high-res image (151KB)Download full-size image
Co-reporter:Kui Zhao, Xinhong Yu, Ruipeng Li, Aram Amassian and Yanchun Han
Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:9842-9848
Publication Date(Web):07 Sep 2015
DOI:10.1039/C5TC02415C
The mechanistic understanding of the intrinsic molecular self-assembly of conjugated polymers is of immense importance to control the microstructure development in organic semiconducting thin films, with a meaningful impact on charge transport and optoelectronic properties. Yet, to date the vast majority of studies have focused on the fast solution process itself, with studies of slower intrinsic molecular self-assembly in formulations lagging behind. Here we have investigated molecular self-assembly during spontaneous organization and uncovered how changes in formulation influence the microstructure, morphology and transport properties of conjugated polymer thin films. Our results suggest that the polymer–solvent interaction is the key factor for the molecular self-assembly and changes in macroscopic charge transport, which is in contrast with most solution processes, such as spin-coating and blade coating, where solvent drying kinetics dominates the aggregation and crystallization processes. Energetically favourable interactions between the polymer and its solvent are shown to cause chain expansion, resulting in a large hydrodynamic volume and few chain entanglements in solution. This provides molecular freedom for self-assembly and is shown to greatly enhance the local and long range order of the polymer, intra-chain backbone planarity and crystallite size. These improvements, in turn, are shown to endow the conjugated polymer with high carrier transport, as demonstrated by organic thin film transistors.
Co-reporter:Xinxiu Cao, Mingguang Li, Jiangang Liu, Haiyang Wang, Ke Zhou, Yanchun Han
Organic Electronics 2015 Volume 24() pp:280-287
Publication Date(Web):September 2015
DOI:10.1016/j.orgel.2015.05.036
Control over polymeric bulk heterojunction (BHJ) morphology is one of the key factors in obtaining high-efficiency devices. The domain size influence on device performance is widely considered critical. In this paper, the fibril width of 3,6-bis-(thiophen-2-yl)-N,N′-bis(2-octyl-1-dodecyl)-1,4-dioxo-pyrrolo[3,4-c]pyrrole and thieno[3,2-b]thiophene (PDBT-TT):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) blend thin film was adjusted by different processing additives. By decreasing the solubility of PDBT-TT in different additives, the fibril width can be decreased from 65.7 nm to 14.8 nm. It is possible that the PDBT-TT seed-crystallite nuclei concentration is higher in the relatively low solubility solvents than that in the relatively high solubility solvents, thus leading to the formation of narrower fibrils. The PDBT-TT/PC71BM narrow fibrillar interpenetrating network structure was beneficial to exciton separation and charge transport processes. As a result, the solar cell with the narrowest fibril width has a higher short circuit current (Jsc) and fill factor (FF), thus achieving optimized device performance from less than 1% to 4.75%.
Co-reporter:Mingguang Li, Lei Wang, Jiangang Liu, Ke Zhou, Xinhong Yu, Rubo Xing, Yanhou Geng and Yanchun Han
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 10) pp:4528-4537
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3CP55075C
In this work, solvent chloronaphthalene (CN) and polymer acceptor an alternating copolymer of perylene diimide and carbazole (PCPDI) were utilized as co-additives to optimize the nanoscale phase-separated morphology and photovoltaic properties of bulk-heterojunction (BHJ) polymer solar cells based on the poly(3-hexyl thiophene) (P3HT)/N,N′-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (EP-PDI) system. The domain size of EP-PDI molecules together with that of P3HT distinctly decreased by adding a 0.75 vol% CN additive. The optimized lateral phase separation increased the donor–acceptor interfacial area and facilitated the exciton dissociation process, leading to 5-fold enhancement of short-circuit current (JSC). Furthermore, when PCPDI was employed as a co-additive, acceptor materials (including PCPDI and EP-PDI) were prone to aggregation towards the top surface of blend films, improving vertical phase separation of active layers. PCPDI incorporation, which improved the percolation pathways for electron carriers, suppressed the crystallinity of P3HT distinctly. Thus, much more balanced charge transport was achieved by PCPDI addition, which resulted in almost 1-fold enhancement of open-circuit voltage (VOC) by reducing nongeminate recombination. As a consequence, cooperative effects of CN and PCPDI additives improved the nanoscale phase-separated morphology in lateral and vertical directions simultaneously, achieving the enhancement in both VOC and JSC.
Co-reporter:Hua Yang;Lei Wang;Jidong Zhang;Xinhong Yu;Yanhou Geng ;Yanchun Han
Macromolecular Chemistry and Physics 2014 Volume 215( Issue 5) pp:405-411
Publication Date(Web):
DOI:10.1002/macp.201300666
Co-reporter:Xinhong Yu;Chunxia Luo;Qiaoqiao Zhao;Hua Yang ;Yanchun Han
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 15) pp:1030-1036
Publication Date(Web):
DOI:10.1002/polb.23524
ABSTRACT
The morphology transition of binary mixtures of polystyrene-block-poly(butadiene)-block-poly(2-vinylpyridine)(SBV) triblock and polystyrene (PS) homopolymer thin films was investigated as a function of the volume fraction of added homopolymer and the annealing time in benzene vapor. It was found that the weight ratio of PS in the blends influenced the transition process. When PS content was >5%, the order-order transition (OOT) of core-shell cylinders (C) sphere in “diblock Gyroid” (sdG) sphere in lamella (sL) sphere (S) was observed, which was similar to ABC triblock copolymer except for the increased surface area of the PS phase. When PS content reached to 10–30%, the OOT in the sequence of C sL S was observed. The disappearance of the Gyroid phase is due to the change of the effective volume fraction. Further increasing the PS content, C phase also disappeared and sL S was expected to take place. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2014, 52, 1030–1036
Co-reporter:Hua Yang;Lei Wang;Dr. Xinhong Yu;Dr. Jidong Zhang; Yanhou Geng; Yanchun Han
Chemistry – An Asian Journal 2014 Volume 9( Issue 8) pp:2239-2248
Publication Date(Web):
DOI:10.1002/asia.201301610
Abstract
Herein we propose a facile strategy to prepare nanowires and nanowire “shish-kebab” (NWSK) structures by controlling the crystallization behavior of all-conjugated rod–rod diblock copolymers poly[(p-phenylene)-block-(3-hexylthiophene)]s (PPP-b-P3HT (BmTn)) with varying main chain lengths. Depending on the block length and ratio (i.e., PPP/P3HT, abbreviated as B/T), nanowires with low B/T ratios (copolymers with long P3HT blocks; B8T32 and B14T34) and NWSKs with high B/T ratios (copolymers with long PPP blocks; B29T9 and B39T18) were formed for PPP-b-P3HT all-conjugated diblock copolymers. The formation of nanowires is governed by a strong interchain π–π stacking similar to the P3HT homopolymer, with an edge-on orientation of the P3HT moiety, whereas NWSKs are formed as a result of the particular face-on molecular orientation of PPP moiety. As the length of the P3HT moiety was increased (the block ratio of PPP/P3HT reduced), the NWSKs were transformed into nanowires gradually because of the decreasing density of “kebabs”. For diblock copolymers with high PPP/P3HT ratios, the transition of the molecular orientation from face-on to edge-on was obtained by thermal annealing.
Co-reporter:Xiao Li, Xinhong Yu and Yanchun Han
Journal of Materials Chemistry A 2013 vol. 1(Issue 12) pp:2266-2285
Publication Date(Web):08 Jan 2013
DOI:10.1039/C2TC00529H
Polymer thin films for antireflection (AR) coatings are reviewed, with particular emphasis on making different kinds of structures and establishing the relationships between structures and antireflective properties. Three kinds of main structures with antireflective properties, namely, homogeneous, inhomogeneous porous structures, and gradient-refractive-index structures, fabricated by “bottom up” or “top down” approaches are summarized. The transmittance of the polymer thin film can be increased to almost 100% in the single or broadband wavelength region (both of the visible and near-infrared region) by properly manipulating its structures. However, further studies are still needed to achieve reversible transmittance and multifunctional polymer AR due to the soft matter characteristic of polymers. In addition, the challenges of using polymer AR coatings still remain, such as poor solvent resistance, poor mechanical strength, and so on, which gives us the direction of future development for practical applications.
Co-reporter:Jiangang Liu, Liang Chen, Bingrong Gao, Xinxiu Cao, Yanchun Han, Zhiyuan Xie and Lixiang Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 20) pp:6216-6225
Publication Date(Web):28 Mar 2013
DOI:10.1039/C3TA10629B
In this paper, mixed-solvent vapor annealing (M-SVA) was proposed to improve polymer crystallinity and inhibit fullerene intercalation into polymer side chains in a poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT):[6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) blend system. Experiments showed the optimal volume ratio of a mixed solvent, i.e., for tetrahydrofuran (THF) and carbon disulfide (CS2) vapor it is 1:1, and the appropriate annealing time is 5 min. After the M-SVA process, out-of-plane grazing incidence X-ray diffraction (GIXD) and spectroscopic ellipsometry (SE) data show that PCDTBT crystals with larger size and higher crystallinity were formed due to enhanced π–π interaction of polymer chains; the aggregation of PC70BM was promoted as well, which inhibited the intercalation behavior, resulting in a continuous electron path and improved phase purity. The morphology transition improved the carrier mobility, in particular electron mobility. Also, the recombination of a charge transfer (CT) state was reduced and the lifetime of mobile carriers was increased, which could be verified by transient-absorption (TA) spectra. As a result, the power conversion efficiency (PCE) of the BHJ reached 6.60%, an increase of more than 40% compared with the reference device (PCE = 4.54%), even though the thickness of the active layer is up to 220 nm and the PC70BM content is as low as 71.4 wt% by weight.
Co-reporter:Zicheng Ding, Qiaoqiao Zhao, Rubo Xing, Xingdong Wang, Junqiao Ding, Lixiang Wang and Yanchun Han
Journal of Materials Chemistry A 2013 vol. 1(Issue 4) pp:786-792
Publication Date(Web):31 Oct 2012
DOI:10.1039/C2TC00125J
The carbazole-based conjugated dendrimer H2-BCz with tert-butyl surface groups shows selective gelation behavior in a good solvent and anti-solvent mixture. The sol–gel conversion of H2-BCz can be observed on heating and cooling. The H2-BCz xerogel films show three-dimensional porous networks with the nanofibers (layered structures with a period of 1.38 nm) entangling and intersecting with each other. The π–π interactions between the aryl units may be the driving force for the formation of one-dimensional H2-BCz fibers during the gelation process. Due to the electron-donating property of the H2-BCz molecule and the porosity of the fibrous film, the xerogel films can be used as efficient fluorescence quenching based chemsensors for the detection of nitroaromatic explosives, such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). The quenching efficiency was as high as 77% and 91% when exposed to the vapor of TNT and DNT, respectively.
Co-reporter:Jiangang Liu, Xiang Gao, Yue Sun, Yanchun Han
Solar Energy Materials and Solar Cells 2013 Volume 117() pp:421-428
Publication Date(Web):October 2013
DOI:10.1016/j.solmat.2013.06.031
•A quasi-ordered bulk hetertojunction of P3HT/PCBM solar cells was fabricated by zone-casting technique.•P3HT nanofibers aligned in an oriented manner due to the shear stress and solute concentration gradient during zone-casting process.•The oriented alignment of nanofibers could facilitate P3HT chains to bridge nanofibers and improve the ability of hole transfer.•The device efficiency increased to 3.26% without any annealing treatment.In this paper, a quasi-ordered bulk hetertojunction of P3HT/PCBM solar cells (Q-O BHJ device) was fabricated by zone-casting from the solutions with different aging times. P3HT nanofibers aligned in an oriented manner due to the shear stress and solute concentration gradient during zone-casting process. The orientation degree of P3HT nanofibers increased when the aging time of solution was prolonged. Meanwhile, P3HT had a high crystallinity due to the slow evaporation rate of solvent during the film-forming process. The oriented alignment of nanofibers could facilitate the connection between nanofibers by increasing the bridging chains. Furthermore, the bridging chains tended to adopt an untwisted conformation, which results in a reduced energy barrier of hole transfer. As a consequence, the Q-O BHJ device had a higher fill factor (FF) and short-circuit current density (Jsc) compared with the device fabricated by spin coating (BHJ device), leading to an increase by almost more than 50% in device efficiency and a PCE of 3.26% without any annealing treatment.
Co-reporter:Yajun Su, Xiang Gao, Jiangang Liu, Rubo Xing and Yanchun Han
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 34) pp:14396-14404
Publication Date(Web):24 Jun 2013
DOI:10.1039/C3CP51264A
Uniaxially aligned triisopropylsilylethynyl pentacene (TIPS-pentacene) crystals over a large area were fabricated using zone-casting technique. The array of TIPS-pentacene displayed a high orientation degree with a dichroic ratio (DR) of 0.80. The crystals were arranged with c axis perpendicular to the substrate and the long axis of the ribbon corresponded to the a axis of TIPS-pentacene. The properties of the solutions and the processing parameters were shown to influence the formation of the oriented TIPS-pentacene crystalline array. Solvent with a low boiling point (such as chloroform) favoured the orientation of the ribbon-like crystals. The concentration of the solution should be appropriate, ensuring the crystallization velocity of TIPS-pentacene matching with the receding of the meniscus. Besides, we proved that the casting speed should be large enough to induce a sufficient concentration gradient. The orientation mechanism of TIPS-pentacene was attributed to a synergy of the ordered nuclei and a match between the crystallization velocity and the casting speed. Field effect transistors (FETs) based on the oriented TIPS-pentacene crystalline array showed a mobility of 0.67 cm2 V−1 s−1.
Co-reporter:Lidong Zheng, Jiangang Liu and Yanchun Han
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 4) pp:1208-1215
Publication Date(Web):05 Nov 2012
DOI:10.1039/C2CP42614E
This work focuses on both the structure manipulation and the crystallizing mechanism investigation of the well-known methanofullerene, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). PCBM crystals with two novel structures, i.e., five-fold twinned and cubic crystals are obtained by the introduction of the mica substrate and the polymer blenders (P3HT and PS) into PCBM thin films under thermal annealing. The morphology and nanostructure of these crystals have been well investigated with AFM, TEM and XRD techniques. The roles of the mica substrate and the polymer blenders have been studied by varying the annealing temperature, the substrate, the polymer benders and the blending ratio. It has been proved that both the PCBM intermolecular and PCBM-mica interactions influence the PCBM crystallization process. The mica substrate has been proved to have the epitaxial effect on PCBM crystallization. The polymer blenders have been suggested to weaken the PCBM intermolecular interaction and limit PCBM molecular diffusion.
Co-reporter:Zicheng Ding, Rubo Xing, Xingdong Wang, Junqiao Ding, Lixiang Wang and Yanchun Han
Soft Matter 2013 vol. 9(Issue 43) pp:10404-10412
Publication Date(Web):16 Sep 2013
DOI:10.1039/C3SM52191E
Different core moieties can modulate the self-assembly behaviors of second generation carbazole-based conjugated dendrimers with the same dendrons and surface groups in a solvent mixture of a good solvent and an anti-solvent. For TA-D2 with triphenylamine as the core, crystalline spherulites were formed since the more planar molecular configuration of TA-D2 can enhance the π–π interactions between the carbazole dendrimers. For G2 with the large-sized fac-Ir(PBI)3 as the core, amorphous globular particles were obtained because the large core in G2 increases the distance between carbazole dendrimers and decreases the π–π interactions. While for TPO-D2 with triphenylphosphine oxide as the core with moderate size and a twisted molecular configuration, a supramolecular gel consisting of fibers was formed in the solvent mixture of aromatic solvent and alcohol solvent. The sol–gel conversion of TPO-D2 can be observed by simple heating and cooling. Fast cooling and ultrasonication are beneficial to get uniform TPO-D2 gel with small aggregates. The TPO-D2 xerogel shows three-dimensional networks with the nanofibers entangling and intersecting with each other. The moderate π–π interactions between the carbazole units modulated by the core may be the driving force for TPO-D2 to form the gel, the balance phase between the ordered crystal and amorphous precipitate.
Co-reporter:Mingguang Li, Ying Li, Jiangang Liu, Lixiang Wang and Yanchun Han
Soft Matter 2013 vol. 9(Issue 23) pp:5634-5641
Publication Date(Web):09 May 2013
DOI:10.1039/C3SM00082F
Micron-sized fibers of n-type pyrazine-based acene-type molecule (PBA) spin-coated films were formed after solvent vapor annealing (SVA). PBA fibers dramatically transformed into quadrilateral crystals after blending with semiconducting polymers under identical post-treatment procedures. For polymer blended systems, a much longer post-treatment time was needed to achieve the nucleation of PBA molecules. Furthermore, the orientation of PBA molecules in the quadrilateral crystals became much more ordered. There are two prerequisites for choosing the blended polymers: good compatibility with PBA molecules and comparatively strong crystallinity. Even though the blended polymers suppress the PBA nucleation process because of interpenetrating polymer networks, the self-organization of semiconducting polymers may control the diffusion rate of PBA molecules in the mixture and finally facilitate PBA self-assembly into perfect ordered aggregates.
Co-reporter:Yaozhuo Xu, Jiangang Liu, Haiyang Wang and Yanchun Han
RSC Advances 2013 vol. 3(Issue 38) pp:17195-17202
Publication Date(Web):16 Jul 2013
DOI:10.1039/C3RA42128G
We accelerate the disentanglement of poly(3-hexlthiophene) (P3HT) in the P3HT/polystyrene (PS) blend film to improve the crystallinity of P3HT via thermal treatment. When the P3HT/PS blend film was heated at a temperature higher than the glass transition temperature (Tg) of PS, PS with a small molecular weight played a role as a “solvent” to dissolve the P3HT. Thus, the P3HT molecule chains moved relatively freely in PS to accelerate the disentanglement. As the temperature was reduced, the ordered P3HT nanowhiskers formed spontaneously without any confinement. Finally, a network-like hierarchical structure was obtained, which is governed by intrinsic properties of the blend system and crystallization conditions. This work enriches the ways to improve crystalline order in polymer thin films with less chain entanglement during the crystallization process of conjugated polymers.
Co-reporter:Yaozhuo Xu, Jiangang Liu, Haiyang Wang, Lidong Zheng and Yanchun Han
RSC Advances 2013 vol. 3(Issue 30) pp:12069-12074
Publication Date(Web):03 Jun 2013
DOI:10.1039/C3RA40719E
It was found that free poly(3,3′′′-didodecylquaterthiophene) (PQT-12) unimer coils in solution had a significant effect on the formation of aligned fibrils in thin films. Long and parallel aligned nano-fibrils formed easily when more unimer coils existed in solution. In contrast, small rod-like crystals with a random orientation would form when less unimer coils existed in solution. The content of unimer coils in solution was increased by the methods such as choosing proper solvents, elevating the temperature and filtering aggregates in solution, etc. For example, the proportion of PQT-12 unimer coils in chlorobenzene increased from 19.9% to 100% when the temperature was raised from 1 °C to 60 °C. During the evaporation of solvents, the conformation of the unimer coils in solution transformed from coils to extended chains firstly, and then ordered aggregates formed. The ordered aggregates assembled into nano-fibrils via π–π interaction. The rest of ordered aggregates in solution adhered to the boundaries of the nano-fibrils and grew along the boundaries of nano-fibrils to form parallel fibers. The parallel aligned fibers preferred an edge-on orientation without chain-folding due to the high backbone rigidity of PQT-12.
Co-reporter:Zicheng Ding, Rubo Xing, Yue Sun, Lidong Zheng, Xingdong Wang, Junqiao Ding, Lixiang Wang and Yanchun Han
RSC Advances 2013 vol. 3(Issue 21) pp:8037-8046
Publication Date(Web):19 Mar 2013
DOI:10.1039/C3RA23272G
The effects of molecular structures and solvent properties on the self-assembly behavior of carbazole-based conjugated dendrimers by solvent vapor annealing (SVA) were systematically studied. Different film morphology changes from three different carbazole dendrimers through annealing in tetrahydrofuran (THF) and hexane vapor, two solvents with approximately the same vapor pressure but different polarity, were observed. For the first generation dendrimer H1–BCz, the film morphology was changed from random single fibers to spherulites with a decrease of vapor pressure in THF vapor, while only curled fibers and dendrites formed in hexane vapor. For the second generation dendrimer H2–BCz, the film morphology was not changed at low vapor pressure conditions, only fibers formed in THF vapor and nano-sized needle-like aggregates formed at high vapor pressure in hexane vapor. For the second generation dendrimer H28 with n-octyl instead of tert-butyl as the surface groups, only dewetting took place. Through a comparative study of the morphologies and the spectra of the annealed films, we speculated that the molecule–solvent and molecule interactions dominate for H1–BCz films, the molecule–molecule interaction is predominant for H2–BCz films and the solvent–molecule interaction controls the dewetting process of H28 films.
Co-reporter:Yajun Su, Lidong Zheng, Jiangang Liu and Yanchun Han
RSC Advances 2013 vol. 3(Issue 16) pp:5529-5538
Publication Date(Web):01 Feb 2013
DOI:10.1039/C3RA23275A
In this work, by using a post-thermal annealing method, a new morphological and structural evolution of triethylsilylethynyl anthradithiophene (TES-ADT) was observed for the first time. At lower annealing temperature (60–120 °C) sheet crystals were obtained, the sizes of which increased with the enhancement of the annealing temperature. A significant morphological transition from sheet crystals to rod-like crystals was observed when the annealing temperature approached the melting point of TES-ADT (about 130 °C). The in-plane lattice parameters were found to be different between the sheet crystals and the rod-like crystals. We thus attribute the mechanism for the morphological transition to the different thermostability of the crystals, which arises from the changeable lattice configuration. The electrical performances of TES-ADT film were improved through thermal annealing.
Co-reporter:Xiang Gao, Jian-Gang Liu, Yue Sun, Ru-Bo Xing, Yan-Chun Han
Chinese Chemical Letters 2013 Volume 24(Issue 1) pp:23-27
Publication Date(Web):January 2013
DOI:10.1016/j.cclet.2013.01.014
We report on the effects of aggregation of P3HT with ordered conformation in solution on improving the uniaxial alignment of the P3HT nanofibers by zone casting. Two approaches were employed to change the aggregation of P3HT: P3HT blending with coil insulating polymer and ultrasonic oscillating. The insulator polymer (i.e. PS) which has good solubility in the solution would disturb the aggregation of P3HT to prevent the chains entanglement. The ultrasonic oscillation can further improve the P3HT aggregation with ordered conformation in the solution. As a result, the P3HT nanofibers in the film grew much orientedly by zone casting the ultrasonic oscillating P3HT/PS polymer blends solution than the same solvent P3HT solution without ultrasonic oscillating and blending. The P3HT π–π stacking direction is parallel to the alignment direction of the nanofibers. Meanwhile, the P3HT/PS blend ratio and PS molecular weight have influence on the uniaxial alignment of P3HT nanofibers. Only P3HT/PS is 1:1, the P3HT nanofibers oriented well. The low molecular weight PS can make the P3HT nanofibers orient better than that of the high molecular weight.We report on the effects of aggregation of P3HT with ordered conformation in solution on improving the uniaxial alignment of the P3HT nanofibers by zone casting.
Co-reporter:Rubo Xing;Tengling Ye;Yan Ding;Zicheng Ding;Dongge Ma ;Yanchun Han
Chinese Journal of Chemistry 2013 Volume 31( Issue 11) pp:1449-1454
Publication Date(Web):
DOI:10.1002/cjoc.201300507
Abstract
In this paper, thickness uniformity of poly(9,9-di-n-octylfluorene) films patterned by inkjet printing was improved by the use of solvent mixtures (a solvent with higher volatility, higher surface energy and lower viscosity, with another solvent with lower volatility, lower surface energy and higher viscosity). The average thickness of inkjet printed poly(9,9-di-n-octylfluorene) films was increased from ca. 30 nm to ca. 100 nm when solvent mixtures were used instead of pure chlorobenzene. More flat PFO films were formed instead of the original films with concave-lens like cross-section formed by coffee ring effect. This improvement was explained by combination of intense Marangoni flow at early drying process and weak complementary flow at the later drying process formed in the solvent mixture. Patterned poly(9,9-di-n-octylfluorene) films were used for fabrication of electroluminescence devices with improved electronic property. Array of pixels with about 80% effective light-emitting area was obtained.
Co-reporter:Haiyang Wang, Jiangang Liu, Yaozhuo Xu, and Yanchun Han
The Journal of Physical Chemistry B 2013 Volume 117(Issue 19) pp:5996-6006
Publication Date(Web):April 16, 2013
DOI:10.1021/jp402039g
A fibrillar morphology was obtained, compared to the featherless pristine films, via solvent annealing the films of a series of derivatives of poly(3-alkylthiophene)s (P3ATs): poly(3-dodecylthiophene) (P3DDT), poly(3,3‴-didodecyl-quaterthiophene) (PQT12), and poly(2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT12). Among the solvents used, including dichloromethane, chloroform, tetrahydrofuran, and carbon disulfide (CS2), CS2 was the best to induce fibril formation because its solubility parameter is closest to those of the P3AT derivatives. It was found that higher critical CS2 vapor pressures were needed to form crystal nuclei with increasing conjugation length and molecular weight of the P3AT derivatives; i.e., the critical vapor pressures for P3DDT 13.9k and PQT12 15.5k were 59.0% and 80.7%, respectively, and there were no nuclei of fibrils for pBTTT12 15.6k with the highest conjugation length, even at a CS2 vapor pressure of 98.3%. Meanwhile, at the highest vapor pressure, the fibril density decreased with increasing conjugation length and molecular weight of the P3AT derivatives. This is attributed to the rod-like conformation prevailing for polymers with larger conjugation length and higher molecular weight during solvent annealing, making the conformational transition toward coils more difficult and hindering diffusion of molecules. The results presented here are expected to be helpful for the design and processing of conjugated semiconductor polymers.
Co-reporter:Yue Sun;Jian-gang Liu;Yan Ding 韩艳春
Chinese Journal of Polymer Science 2013 Volume 31( Issue 7) pp:1029-1037
Publication Date(Web):2013 July
DOI:10.1007/s10118-013-1295-7
The surface composition of poly(3-hexylthiophene-2,5-diyl) and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) blend films could be changed by controlling the film formation process via using mixed solvents with different evaporation rates. The second solvent, with a higher boiling point than that of the first solvent and much better solubility for PCBM than P3HT, is chosen to mix with the first solvent with a lower boiling point and good solubility for both PCBM and P3HT. The slow evaporation rate of the second solvent provides enough time for PCBM to diffuse upwards during the solvent evaporation. Thus, the weight ratio of PCBM and P3HT (mPCBM/mP3HT) at surface of the blend films was varied from ca. 0.1 to ca. 0.72, i.e., it increases about seven times by changing from single solvent to mixed solvents. Meanwhile, the mixed solvents were in favor to form P3HT naonofiber network and enhance phase separation of P3HT/PCBM blend films. As a result, the power conversion efficiency of the device from mixed solvents with slow evaporation process was about 1.5 times of the one from single solvents.
Co-reporter:Xiang Gao;Ru-bo Xing;Jian-gang Liu
Chinese Journal of Polymer Science 2013 Volume 31( Issue 5) pp:748-759
Publication Date(Web):2013 May
DOI:10.1007/s10118-013-1284-x
The preparation of large area coverage of films with uniaxially aligned poly(3-hexylthiophene) (P3HT) nanofibers by using zone-casting approach is reported. The length and the orientation of the nanofibers are defined by the solubility of the solvent, the P3HT molecular weight and the substrate temperature. The length of the oriented nanofibers could be increased from 1 μm to more than 10 μm by adding poor solvent into the P3HT solution. It is found that for P3HT of relatively low molecular weight, a solvent with relatively low solubility has to be chosen to get the oriented film. While for the high molecular weight P3HT, the solvent with a relatively high solubility has to be used. The well-aligned film could be obtained because of the solute concentration gradient in the region where the critical concentration is reached during the zone-casting process. Particularly, the solvent evaporation rate and crystallization rate must be chosen properly to satisfy the stationary conditions above, which were controlled by an appropriate choice of solvent and substrate temperature. The film prepared by zone-casting approach had microcrystalline P3HT domains with more inter-chain order than spin-coating film. Meanwhile, the P3HT π-π stacking direction was parallel to the alignment direction of the nanofibers.
Co-reporter:Xiang Gao 韩艳春
Chinese Journal of Polymer Science 2013 Volume 31( Issue 4) pp:610-619
Publication Date(Web):2013 April
DOI:10.1007/s10118-013-1259-y
The preparation of the poly(3-hexylthiophene) (P3HT) stripe structure with oriented nanofibrils prepared by controlled inclining evaporative technique is reported. The distance of the adjacent stripes could be controlled from 40 μm to 100 μm by decreasing the inclining angle. The oriented nanofibrils in the stripes can be obtained because the P3HT lamellae diffuse directionally and form 1D crystals at the three-phase contact line of the drop. In order to get the oriented P3HT stripes, the proper solvent evaporation rate which is controlled by the inclining angle and the wettability of the substrate must be carefully chosen to match the P3HT 1D crystallization rate. It is found that large inclining angle and the hydrophilic substrate (for example: glass and PEDOT) are beneficial to get P3HT stripe structure with oriented nanofibrils.
Co-reporter:Haiyang Wang, Jiangang Liu, Yanchun Han
Polymer 2013 Volume 54(Issue 2) pp:948-957
Publication Date(Web):24 January 2013
DOI:10.1016/j.polymer.2012.11.073
A large amount of dispersed pBTTT12 nano-fibrils formed easily by adding the additives to its o-dichlorobenzene solution to change the solution aggregation. It is found that a proper solubility parameter difference between polymer and additives (as large as 4 J1/2 cm−3/2) and a high boiling point of the additives are two important parameters for choosing the additives. 1-dodecanethiol is a promising additive for pBTTT12 o-dichlorobenzene solution, which can decrease the aggregation size distribution and disentangle unimer chains which are the building blocks of nano-fibrils. Under a slow spin-coating speed, coils tend to form dispersed nano-fibrils in terms of both thermodynamics and kinetics. Moreover, 1-dodecanethiol molecules intercalated into the free volume of adjacent alkyl side-chains of pBTTT molecules and change the crystalline structure. It was found that the distance between (100) crystalline planes became larger when the content of 1-dodecanethiol increased.
Co-reporter:Yue Sun, Jiangang Liu, Yan Ding, Yanchun Han
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 421() pp:135-141
Publication Date(Web):20 March 2013
DOI:10.1016/j.colsurfa.2012.12.053
The number of micro-sized PCBM aggregations in P3HT/PCBM blend films was reduced by cooling the solution at 0 °C. P3HT aggregated when the solution was kept at 0 °C for more than 4 h. These P3HT aggregations acted as crystal nucleus, resulting in a network of P3HT nanofibers formation in the spin coated films. Then, after thermal annealing the film at 140 °C for 1 h, the growth of PCBM micro-size aggregations was efficiently prevented by the dense network of P3HT nanofibers, which was formed before PCBM aggregated. As a result, the density of PCBM micro-size aggregations reduced from 6.2% to 1.0% compared to the room temperature solution.P3HT aggregations begin to form in the solution at 0 °C after 4 h. These aggregations act as crystal nucleus during the spin coating, resulting in a dense network of P3HT nanofibers in the blend film. The dense network of P3HT nanofibers prevent PCBM micro-size aggregations growing further because of less space for PCBM diffusion and aggregation during the thermal annealing. So the density of PCBM micro-size aggregations reduces from 6.2% to 1.0%.Highlights► The growth of PCBM micro-size domains can be prevented by a dense network of P3HT nanofibers. ► The dense network of P3HT nanofibers should form before the aggregation of PCBM. ► It can be realized by cooling the solution at 0 °C for more than 4 h.
Co-reporter:Jiangang Liu, Yue Sun, Lidong Zheng, Yanhou Geng, Yanchun Han
Polymer 2013 Volume 54(Issue 1) pp:423-430
Publication Date(Web):8 January 2013
DOI:10.1016/j.polymer.2012.11.011
Poly(3-hexylthiophene) (P3HT) film with a hierarchical ordered structure was fabricated by an approach combining vapor-assisted imprinting in a carbon disulfide (CS2) atmosphere and thermal annealing treatment. In the hierarchical ordered structure, P3HT domains are vertically arranged and the domains are constituted by uniaxially aligned P3HT nanofibrils, furthermore, the chains in it adopted flat-on conformation. The vertically arranged domains are formed by the action of capillarity, the oriented nanofibrils are induced by the crystallization nucleation of P3HT and the directional evaporation of the solvent, and the flat-on conformation of P3HT chains are induced by the enhanced intermolecular interaction of the alkyl side chains in CS2 atmosphere. The arrangement behavior of P3HT crystals and chains facilitate the bridging chains link neighboring grains with minimal distortion, while the enhanced intermolecular interaction enable the formation of larger P3HT crystals, and then reduce the quantity of grain boundary. As a result, this ordered structure provides more delocalized electrons along the direction that perpendicular to the substrate, which would result in an improvement of the carrier mobility along this direction.
Co-reporter:Longjian Xue, Yanchun Han
Progress in Materials Science 2012 Volume 57(Issue 6) pp:947-979
Publication Date(Web):July 2012
DOI:10.1016/j.pmatsci.2012.01.003
Strategies for the inhibition of dewetting of thin polymer films are reviewed. First, a brief introduction to the theory and the dynamics of dewetting of thin polymer films is given. Methods for the inhibition of dewetting of thin polymer films, including the modification of the substrate and the polymer, the cross-linking of the polymer and the addition of an additive as well as their mechanisms for inhibition are discussed. The chemical modification of the substrate or the polymer itself and the phase separation increase the thermodynamic stability of the system, while the cross-linking of the polymers reduces the mobility of the polymer chains, kinetically arresting the dewetting. The addition of an additive appears to thermodynamically and kinetically inhibit the dewetting. Finally, the future outlook in this research field is highlighted.
Co-reporter:Longjian Xue, Jilin Zhang, Yanchun Han
Progress in Polymer Science 2012 Volume 37(Issue 4) pp:564-594
Publication Date(Web):April 2012
DOI:10.1016/j.progpolymsci.2011.09.001
Strategies for the utilization of phase separation to generate ordered pattern in polymer thin film are reviewed. First, the fundamental theory and factors influencing phase separation in polymer thin film are discussed. That is followed by a discussion of the formation of ordered patterns induced by phase separation in polymer thin films under the influence of a chemical heterogeneous substrate, convection or breath figures. The mechanisms and the conditions for well-ordered structures generated by phase separation are then discussed to show that multi-scaled/multi-component patterns, stimuli-responsive patterns may be developed by controlling the preparation conditions or exposing the sample to different environments more complex structures. Finally, applications of fabricated patterns in pattern generation and reproduction, antireflecting coating, catalysis, bio-chips and optoelectronics are also discussed.
Co-reporter:Yajun Su, Jiangang Liu, Lidong Zheng, Zicheng Ding and Yanchun Han
RSC Advances 2012 vol. 2(Issue 13) pp:5779-5788
Publication Date(Web):18 Apr 2012
DOI:10.1039/C2RA20417G
In this work, solution-processing rubrene spherulites were fabricated by blending an amount of polymer into rubrene and subsequent solvent vapor annealing (SVA). The content and molecular weight of the blended polymer, the annealing solvent and the solvent vapor pressure have tremendous influence on the formation of rubrene spherulites. Rubrene spherulites were produced only when a polymer with a high molecular weight was blended and annealed by good solvents of rubrene with high vapor pressures, such as CH2Cl2 and CS2. The sizes of the spherulites decreased with the reduction of the annealing solvent vapor pressure. The rubrene spherulites adopted a triclinic system with c-axis perpendicular to the substrate. The crystallizing kinetics study displayed a rather fast growth of rubrene spherulites and the crystallization of rubrene was controlled by diffusion. A competitive mechanism between the impetus of the annealing solvent vapor and the impeditive force of the polymer on the diffusion of rubrene molecules to the crystal fronts was proposed to explain the formation of rubrene spherulites.
Co-reporter:Lidong Zheng;Jiangang Liu;Yue Sun;Yan Ding;Yanchun Han
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 19) pp:2081-2090
Publication Date(Web):
DOI:10.1002/macp.201200341
Abstract
Trace amount (1% to 5%) of polymers [polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(3-hexylthiophene) (P3HT)] are utilized as additives to manipulate the cold crystallization of [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) thin films. Highly crystalline PCBM films made up of well-connected domains and isolated spherulites with tunable size are produced by adjusting the type, molecular weight, and amount of polymer additives. In the nucleation stage, the polymer additives are demonstrated to have a depressing effect on PCBM nucleation. In the growth stage, we suggest that the PCBM growth rate is determined by PCBM molecular diffusion, which is demonstrated to have close correlations with the molecular mobility and crystallinity of the polymer.
Co-reporter:Lidong Zheng and Yanchun Han
The Journal of Physical Chemistry B 2012 Volume 116(Issue 5) pp:1598-1604
Publication Date(Web):January 19, 2012
DOI:10.1021/jp210937h
This work focuses on the structural exploration of micro-sized crystals based on a well-known methanofullerene, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We have succeeded in producing PCBM crystals with the hexagonal symmetry through the liquid–liquid interfacial precipitation (LLIP) method. We found that smaller but more regular PCBM crystals tend to form in the oversaturated PCBM solutions with solvents of lower solubility for PCBM, such as tetrahydrofuran (THF) and 1,4-dioxane. The structure of the produced crystals also shows a dependence on the solvents, which can be attributed to the incorporation of different solvent molecules into PCBM crystals. Under thermal annealing, for the first time, we have observed a crystalline to crystalline phase transformation of these hexagonal PCBM crystals. Along with the phase transformation, the morphology of the crystals has also been transformed from the hexagon to long needles. In addition, the needlelike crystals arrange themselves with a relative angle of 60° to each other, which implies an intrinsic structural correlation between needlelike and hexagonal crystals.
Co-reporter:Xiao Li, Xinhong Yu, and Yanchun Han
Langmuir 2012 Volume 28(Issue 28) pp:10584-10591
Publication Date(Web):June 21, 2012
DOI:10.1021/la301755a
An erasure-reconstruction porous structure with reversible antireflection (AR) property at near-infrared region (NIR) was prepared for the first time based on solvent-stimuli-responsive phase transformation of polystyrene-block-poly(4-vinypyridine) (PS-b-P4VP). The inhomogeneous porous structure with a dense skin and porous underneath, which was obtained by the nonsolvent-induced phase separation of PS-b-P4VP film from micelle solution with mixed solvents (tetrahydrofuran and dimethylformamide), was used as starting porous film. Then, the film was annealed by PS-selective solvent to erase the nanopores because the PS block was swollen effectively by its selective solvent. Afterward, the nonporous film was immersed in linear aliphatic acid to reconstruct the nanoporous structure (loosely packed micelles) by the combination of the hydrogen bond interaction and the positively charge-induced repulsion between each chain. Thus, an intelligent reversible AR property in the NIR region between a high-transmittance porous state (∼99.0%) and a low-transmittance nonporous state (∼90.0%) was realized by alternate treatments of PS-selective solvent and linear aliphatic acids. This reversible erasure-reconstruction porous structure for switching between AR (98.0%) and non-AR (90.0%) properties could be recycled by at least four times.
Co-reporter:Jiangang Liu;Yanchun Han
Polymer Bulletin 2012 Volume 68( Issue 8) pp:2145-2174
Publication Date(Web):2012 May
DOI:10.1007/s00289-012-0721-2
The performance of bulk heterojunction organic solar cells based upon blends of donor and acceptor materials has been shown to be highly dependent on the microstructure and photoelectric properties of active layer. Recently, various methods, such as post-annealing, microwave annealing and control in the film-forming rate, and so on, have been used to modify the morphology to achieve high device performance. Among these methods, adding additives is a simple and promising approach, which can not only control the morphology but also improve the photon absorption or energy-level distribution of the active layer. In this review, we will introduce the additives that used widely in recent from following aspects: species, mechanism, and performance. First, the additive species and its selection principle according to special donor and acceptor system will be concluded. Then, the mechanisms of improved morphology and photoelectric properties by adding different kinds of additives will be illustrated in brief. At last, we will discuss the influences of additives on device performance.
Co-reporter:Xinhong Yu, Hua Yang, Shupeng Wu, Yanhou Geng, and Yanchun Han
Macromolecules 2012 Volume 45(Issue 1) pp:266-274
Publication Date(Web):December 22, 2011
DOI:10.1021/ma201024z
Microphase separation and crystallization in thin films of all-conjugated diblock copolymers poly(2,5-dihexyloxy-p-phenylene)-block-(3-hexylthiophene) (PPP-b-P3HT) with various main chain lengths were investigated under solvent vapor annealing or thermal annealing. It is shown that crystallization and microphase separation coexisted during thin film forming process due to the incompatibility and crystallization of the two conjugated blocks. When the B34T66 copolymer film was annealed in chlorobenzene vapor or at high temperature, crystallization broke out the microphase-separated structure. On the other hand, upon annealing of the films of B62T38 and B75T25 with higher PPP ratio, crystallization was confined in the microphase-separated domains. The copolymer composition plays a key role in determining the crystallization and the final morphology of the thin films.
Co-reporter:Longjian Xue, Yanchun Han
Progress in Polymer Science 2011 Volume 36(Issue 2) pp:269-293
Publication Date(Web):February 2011
DOI:10.1016/j.progpolymsci.2010.07.004
Strategies for the utilization of dewetting of polymer thin film to fabricate ordered patterns are reviewed. After a brief introduction to the polymer thin film dewetting theory, simulation results of pattern formation induced by physically and chemically patterned substrates, and physical confinement are then summarized. Experimental results including the mechanisms behind and the conditions for good quality of pattern formation based on the dewetting of polymer thin film induced by physical, chemical heterogeneous substrates, topographic structure on film surface, physical confinement and the movement of three-phase line are then discussed. A short introduction to the application of fabricated patterns is also discussed.
Co-reporter:Xiao Li and Yanchun Han
Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:18024-18033
Publication Date(Web):13 Oct 2011
DOI:10.1039/C1JM13704B
Polymer antireflection (AR) coatings have considerable practical value and wide-ranging applications because of their ability to adhere to flexible substrates and because they lend themselves easily to large-area processing. Preparing a suitable polymer porous structure with tunable wavelength AR by a simple approach is a challenge. In the present study, an inhomogeneous porous polymer film with a dense skin and porous structure underneath was obtained by spin coating a micelle solution of polystyrene-block-poly(4-vinypyridine) (PS-b-P4VP) with tetrahydrofuran (THF) and dimethyl formamide (DMF). The film was then subjected to non-solvent-induced phase separation before it reached a dry state. The dense skin surface morphology was fixed because of the rapid evaporation of THF during the spin coating. In the subsequent non-solvent immersion, an inner nanoporous structure was formed because the DMF was replaced by the non-solvent (with similar solubility to DMF). The inhomogeneous porous polymer film showed tunable wavelength AR controlled by the film thickness and immersion time in the non-solvent. The film exhibited an excellent transmittance of 99.6% at visible light wavelengths (400–800 nm) and 99.2% transmittance at near-infrared light wavelengths (800–2000 nm).
Co-reporter:Xiao Li, Longjian Xue and Yanchun Han
Journal of Materials Chemistry A 2011 vol. 21(Issue 15) pp:5817-5826
Publication Date(Web):08 Mar 2011
DOI:10.1039/C0JM04508J
The factors that influence the broadband antireflection of block copolymer/homopolymer blend films were systematically investigated. The gradient refractive index structure, which was generated by removing the PMMA content from a film of PS-b-PMMA/PMMA blends, contributed to the broadband antireflection. The volume fraction of the PMMA block (fPMMA), the total degree of polymerization (N) and the weight percent of the homopolymer played a key role in the formation of the gradient porosity index inner structure. By increasing χN, the PS porous structure was kept from collapsing after removal of the PMMA domain, which led to a stable gradient porosity ratio structure and higher transmittance. While increasing fPMMA, the PMMA domains changed from a dispersed phase to a continuous phase, which caused the residual PS structure to collapse more easily and the transmittance decreased. The best broadband antireflective properties were achieved from the 45 mg mL−1 solution of PS-b-PMMA (Mn = 68000–33500, fPMMA = ∼25%) blended with 30 wt% PMMA: a mean transmittance of 98.4% at full spectrum, and >98.0% in the visible–NIR range between 600 nm and 2000 nm.
Co-reporter:Jianying Wang, Yanchun Han
Journal of Colloid and Interface Science 2011 Volume 357(Issue 1) pp:139-146
Publication Date(Web):1 May 2011
DOI:10.1016/j.jcis.2011.02.007
The inverse opal hydrogel heterostructure (polyacrylamide (PAAm) (left side)–polyacrylic acid (PAA)/PAAm interpenetrating polymer network (IPN) (right side) is created by colloidal crystal templating. The two parts, PAAm and IPN, appear different structural colors due to the varied lattice constants and solvent response behaviors. The IPN part keeps red color and PAAm part shows different colors when the composition of the mixed solvent (ethanol and water) and crosslinking degree are changed. For example, as the ethanol content in the mixed solvents increases from 0% to 70%, the PAAm part color changes from red, yellow, green to blue when the PAAm crosslinking degree is 5 mol% or 1 mol%. Meanwhile, a large blue shift of about 200 nm can be realized covering almost the entire wavelength of visible light due to the decreased lattice spacing induced by the PAAm shrinkage. Thus, multi two-color patterns can be realized by changing the color of PAAm and the color of IPN remain red as background for contrast. Moreover, the IPN part can change from red to green by reducing the PAAm infiltration time in IPN part, which can realize the change from two-color pattern to one-color pattern at green region.Graphical abstractInverse opal hydrogel heterostructure (PAAm–PAA/PAAm IPN) forms a permanent two-color pattern, which shows various color display by controlling the mixed solvent ratio and crosslinking degree.Research highlights► Inverse opal hydrogel heterostructure (PAAm–PAA/PAAm IPN) forms a permanent two-color pattern. ► Multi two-color patterns are obtained by controlling the solvent ratio and crosslinking degree. ► Two-color pattern becomes one-color pattern by reducing the PAAm infiltration degree in IPN part.
Co-reporter:Jianying Wang, Yanchun Han
Journal of Colloid and Interface Science 2011 Volume 353(Issue 2) pp:498-505
Publication Date(Web):15 January 2011
DOI:10.1016/j.jcis.2010.10.002
Polyacrylic acid (PAA) and polyacrylamide (PAAm) double network (DN) hydrogels with high mechanical strength (about 1.5 MPa) are obtained when two kinds of monomer solutions of 4 M AA with 5 mol% crosslinker and 4 M AAm with 0.1 mol% crosslinker are used for the optimal preparation. Their high mechanical strength can be maintained even at high water content (above 50%) and at external stimuli (solvent and pH). This optimized DN hydrogel is used to develop the PAA/PAAm inverse opal hydrogel with DN structure by twice infiltration–polymerization and colloidal templating. Its photonic stop band can be tuned by controlling the solvent and pH. It first shows a small red-shift (about 20 nm), and then a large blue-shift (about 180 nm) with the increased ethanol content. For pH response, the DN inverse opal hydrogel has a large stop-band shift of about 140 nm when the pH increases from 1.2 to 5.6. Moreover, the DN inverse opal hydrogel also shows rapid recovery ability without hysteresis phenomenon in strong acidic environment, good reproducibility and durability. The interaction between the independently crosslinked PAA network and PAAm network plays a significant role in determining the response performance.Graphical abstractPAA and PAAm double network (DN) hydrogels with high mechanical strength are used to develop PAA/PAAm DN inverse opal hydrogels showing good stop-band tunability by controlling the solvent and pH.Research highlights► PAA and PAAm double network (DN) hydrogels show high mechanical strength (above 1 MPa). ► PAA/PAAm DN inverse opal hydrogels show good stop-band tunability by controlling the solvent and pH. ► The response performances depend on the DN structure.
Co-reporter:Lidong Zheng, Jiangang Liu, Yan Ding, and Yanchun Han
The Journal of Physical Chemistry B 2011 Volume 115(Issue 25) pp:8071-8077
Publication Date(Web):May 27, 2011
DOI:10.1021/jp2030279
The film morphology and nanostructure of the soluble fullerene, [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), are crucial for its applications in organic thin film devices, such as organic solar cells and organic thin film transistors. In this work, the morphology, structural transformation, and crystallite orientation of PCBM film under thermal annealing as a function of annealing temperature, processing solvents, and solution concentrations are systematically investigated. Crystalline PCBM films with needle-like crystallites, axialitic aggregates, and faceted slices are formed in the annealing process. The axialites, made up of needle-like aggregates, are proposed to be partially developed spherulites frozen at the early growth stage formed through low-angle branching. The faceted slices are found to be PCBM single crystallites with hexagonal packing in the film plane. The film undergoes both amorphous-to-crystalline and crystalline-to-crystalline phase transformations as the annealing temperature is increased. The former transformation, corresponding to the self-organization of disordered PCBM molecules in the kinetically frozen films, occurs at a relative low temperature once the motion of these molecules is thermally activated, whereas the later one, corresponding to the transformation between two thermally stable crystalline phases, occurs when further increasing the annealing temperature. The PCBM crystallites composing these films are found to have an orientation preference normal to the film surface, which can be attributed to the confinement of film thickness for PCBM crystallite growth.
Co-reporter:Zicheng Ding, Rubo Xing, Lidong Zheng, Yue Sun, Xingdong Wang, Junqiao Ding, Lixiang Wang, and Yanchun Han
The Journal of Physical Chemistry B 2011 Volume 115(Issue 51) pp:15159-15166
Publication Date(Web):November 28, 2011
DOI:10.1021/jp2045492
The self-assembly behavior of H1-BCz, a first-generation dendrimer with phenyl-carbazole as core and carbazole as dendrons, was systemically studied by solvent-vapor annealing. The morphologies of spin-coated H1-BCz film on various substrates changed from giant crystalline fibers of several millimeters to spherulites with a decrease in tetrahydrofuran vapor pressure. At high vapor pressure, dewetting easily took place in the amorphous films, and single fibers or fiber clusters formed. The fibers grew from nuclei formed at the place where it does not dewet. The fibers grew larger by continuous nucleation and growth at the growth front of the fiber until all the substance on the substrate was consumed. As the vapor pressure decreased, dewetting did not so easily happen, and fibers packed more tightly and spherulites were obtained. Through characterization of the crystals and films, we speculate that 3D H1-BCz crystal formed by overlapping 2D lamellar structure. The π–π interactions and van der Waals interactions among H1-BCz molecules and solvent may be the main force driving the self-assembly of H1-BCz.
Co-reporter:Jiangang Liu, Yue Sun, Xiang Gao, Rubo Xing, Lidong Zheng, Shupeng Wu, Yanhou Geng, and Yanchun Han
Langmuir 2011 Volume 27(Issue 7) pp:4212-4219
Publication Date(Web):March 14, 2011
DOI:10.1021/la105109t
In this article, the uniaxial alignment of poly(3-hexylthiophene) (P3HT) nanofibrils with a π−π stacking growth direction in which P3HT chains adopt a flat-on conformation was obtained by solvent directional evaporation using a glass cover slide and a poly(dimethylsiloxane) (PDMS) sheet to press the P3HT film in a carbon disulfide (CS2) atmosphere. By controlling the CS2 vapor pressure during the film-forming process, we got a well-oriented P3HT film whose order parameter reached as high as 0.97. The orientation of the film was induced by the crystallization nucleation of P3HT and the directional evaporation of the solvent. Under a CS2 vapor atmosphere, P3HT crystals preferred to adopt the form II modification, which started by nucleation. Owing to the solvent directional evaporation from the center to the margin, P3HT at the center of the sample would precipitate first to induce nucleation. Then the peripheral P3HT would directly diffuse, precipitate, and then adhere to the nucleus to form the uniaxial alignment of P3HT nanofibrils along the direction of solvent evaporation. Furthermore, in the P3HT nanofibrils, the π−π stacking direction of P3HT lamellae was parallel to the crystal growth direction, which would provide an effective path for charge transport.
Co-reporter:Jilin Zhang and Yanchun Han
Chemical Society Reviews 2010 vol. 39(Issue 2) pp:676-693
Publication Date(Web):05 Oct 2009
DOI:10.1039/B816231J
A central challenge in polymer science today is creating materials that dynamically alter their structures and properties on demand, or in response to changes in their environment. Surfaces represent an attractive area of focus, since they exert disproportionately large effects on properties such as wettability, adhesiveness, optical appearance, and bioactivity, enabling pronounced changes in properties to be accomplished through subtle changes in interfacial structure or chemistry. In this critical review, we review the recent research progress into active and responsive polymer surfaces. The chief purpose of this article is to summarize the advanced preparation techniques and applications in this field from the past decade. This review should be of interest both to new scientists in this field and the interdisciplinary researchers who are working on “intelligent” polymer surfaces (117 references).
Co-reporter:Xiao Li;Junpeng Gao;Longjian Xue ;Yanchun Han
Advanced Functional Materials 2010 Volume 20( Issue 2) pp:259-265
Publication Date(Web):
DOI:10.1002/adfm.200901052
Abstract
Porous polymer films that can be employed for broadband and omnidirectional antireflection coatings are successfully shown. These films form a gradient-refractive-index structure and are achieved by spin-coating the solution of a polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA)/PMMA blend onto an octadecyltrichlorosilane (OTS)-modified glass substrate. Thus, a gradient distribution of PMMA domains in the vertical direction of the entire microphase-separated film is obtained. After those PMMA domains are removed, a PS porous structure with an excellent gradient porosity ratio in the vertical direction of the film is formed. Glass substrates coated with such porous polymer film exhibit both broadband and omnidirectional antireflection properties because the refractive index increases gradually from the top to the bottom of the film. An excellent transmittance of >97% for both visible and near-infrared (NIR) light is achieved in these gradient-refractive-index structures. When the incident angle is increased, the total transmittance for three different incident angles is improved dramatically. Meanwhile, the film possesses a color reproduction character in the visible light range.
Co-reporter:Kui Zhao;Zicheng Ding;Longjian Xue ;Yanchun Han
Macromolecular Rapid Communications 2010 Volume 31( Issue 6) pp:532-538
Publication Date(Web):
DOI:10.1002/marc.200900770
Co-reporter:Jilin Zhang;Xinhong Yu;Ping Yang;Juan Peng;Chunxia Luo;Weihuan Huang;Yanchun Han
Macromolecular Rapid Communications 2010 Volume 31( Issue 7) pp:591-608
Publication Date(Web):
DOI:10.1002/marc.200900541
Co-reporter:Jiangang Liu, Shuyan Shao, Hanfu Wang, Kui Zhao, Longjian Xue, Xiang Gao, Zhiyuan Xie, Yanchun Han
Organic Electronics 2010 Volume 11(Issue 5) pp:775-783
Publication Date(Web):May 2010
DOI:10.1016/j.orgel.2010.01.017
The mechanisms for introduction of the additive to improve the poly(3-hexylthiophene) (P3HT):methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) organic solar cells performance are investigated. We add n-dodecylthiol to P3HT/PCBM solution and find that it both improves P3HT crystallinity and enhances P3HT/PCBM phase separation extent. UV–vis absorption spectroscopy (UV–vis) and dynamic light scattering (DLS) results reveal that n-dodecylthiol reduces the P3HT chains entanglement in the solution, which facilitates coil-to-rod transformation, a premise condition for P3HT crystallization. Also, it discloses that the influence of PCBM on the P3HT molecular interaction is diminished by adding n-dodecylthiol, this consequently benefits the P3HT crystallization during the film-forming process. Furthermore, the enhanced P3HT crystallinity reduces the PCBM amount which dissolved in the amorphous regions of P3HT, then promotes the aggregation of PCBM, which contributes to the controlled scale of phase segregation. Thus an increased P3HT crystallinity and a commensurate scale of phase separation balancing for exciton dissociation and charge transport and/or collection are finally obtained. This results in an almost threefold increase in device efficiencies when the volume fraction of additive is 2.0%, compared with reference devices without any additive in the photoactive layer as a consequence.
Co-reporter:Kui Zhao;Gang Zhou;Qi Wang;Yanchun Han;Lixiang Wang ;Dongge Ma
Macromolecular Chemistry and Physics 2010 Volume 211( Issue 3) pp:313-320
Publication Date(Web):
DOI:10.1002/macp.200900412
Co-reporter:Weihuan Huang;Chunxia Luo;Hanfu Wang;Yanchun Han
Polymer International 2010 Volume 59( Issue 8) pp:1064-1070
Publication Date(Web):
DOI:10.1002/pi.2825
Abstract
In a previous paper, we investigated the solvent-induced crystallization of films made up of spherical micelles, which were prepared by mixing polystyrene-block-poly(acrylic acid) and polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) in the neutral solvent N,N-dimethylformamide (DMF). In the work reported in the present paper, we further studied the cylinder-to-rod-to-sphere evolution of complex micelles in solution and their corresponding solvent-induced crystallization process. The initial morphology of the micelles in the solution was cylindrical due to a rapid growth of micelles with high unimer concentration, and spheres became the dominant form after storage at room temperature for a longer time. Regular square platelets can form after a certain period of treatment for all micelles in DMF vapor for sufficient time. However, the kinetics of their solvent-induced crystallization process is quite different. The aggregation and subsequent nucleation of poly(ethylene oxide) blocks are determined by the distribution of crystallizable poly(ethylene oxide) blocks in the films. Copyright © 2010 Society of Chemical Industry
Co-reporter:Junpeng Gao, Xiao Li, Binyao Li, Yanchun Han
Polymer 2010 Volume 51(Issue 12) pp:2683-2689
Publication Date(Web):28 May 2010
DOI:10.1016/j.polymer.2010.03.035
We demonstrated a method of fabricating antireflective coatings based on the self-assembly of supramolecular block copolymer formed by polystyrene terminated with carboxyl (PS-COOH) and poly(methyl methacrylate) terminated with amine (PMMA-NH2) via hydrogen bonding. Different porous films were generated by selectively removing PS-COOH from the spin-coated films with a selective solvent, cyclohexane, under different conditions. The refractive index of such porous film can be tuned from 1.49 down to 1.26 by controlling the thickness of the porous film. For the porous layer with n ˜ 1.26, the light transmittance of the glass about 97.93% was achieved in the visible range (λ ˜ 574 nm). By varying the solution concentration and exposing time in cyclohexane, inhomogeneous three-layered porous films were generated: top and bottom layers with high porosities and the middle layers with lower porosities, respectively. The light transmittance of the glass coated with this inhomogeneous film was about 98.00% in the near-infrared region corresponding to wavelength between 800 and 1400 nm. The wavelength region of the broadband antireflective films with high transmittance more than 99.00% can be fine tuned to 1200–2000 nm with increasing the film thickness.
Co-reporter:Benhui Hu, Longjian Xue, Ping Yang and Yanchun Han
Langmuir 2010 Volume 26(Issue 9) pp:6350-6356
Publication Date(Web):December 9, 2009
DOI:10.1021/la903969h
This paper reports two novel types of variable-focus liquid microlenses with adjustable sensitivity, which consist of a poly(dimethylsiloxane) (PDMS) lens housing with circular sidewall and a liquid with tunable volume stored in it. The type-I lens housing (“in” bridge structure) is molded from water droplet sandwiched between two plates with identical wettability and the type-II lens housing (“out” bridge structure) is molded from solid microsphere. Because of the variable slope of the sidewall, the altitude of the liquid/air interface, which can be regulated by hydrostatic pressure, determines the curvature of the meniscus and hence the focal length (f). The curvature radius of sidewall, which determines the sensitivity, depends on the surface wettability or the radius of solid microsphere, thus, it is adjustable. Both of the two types of lenses have wide dynamic range, and their tuning tendencies are opposite. The experimental demonstrations and theoretical simulations yield good agreement in the key aspects of the optics.
Co-reporter:Kui Zhao, Longjian Xue, Jiangang Liu, Xiang Gao, Shupeng Wu, Yanchun Han and Yanhou Geng
Langmuir 2010 Volume 26(Issue 1) pp:471-477
Publication Date(Web):November 6, 2009
DOI:10.1021/la903381f
We promoted order−disorder transformation of poly(3-hexylthiophene) (P3HT) in solution by ultrasonic oscillation which substantially improved crystallinity in its pure film. P3HT with low molecular weight (Mw) dispersed very well in p-xylene solvent and few aggregates generated in the solution. For P3HT with high Mw, the results suggested the coexistence of two phases: disordered coils in solution and ordered microcrystals in suspension. Upon ultrasonic oscillating, more ordered precursors generated in solution due to increased self-assembly from disordered to ordered configuration, which resulting from decreased extent of chains entanglement existing in high molecular system, and red shift at absorption maximum and growing intensity of the π−π* absorption at ca. 604 nm were observed in solution. The films prepared from the oscillated solution then showed increased degree of crystallinity, π−π interactions and homogeneously distributed nanofibrils, which should be attributed to the ordered precursors constructed in solution. Furthermore, the best crystallinity of the film was obtained at the oscillating time of 4 min, showing the equilibrium state between the increased content of crystalline molecules and the shortened crystalline length. This simple method paves the way for the decreasing chains entanglement during crystallizing process of conjugated polymer in solution, and it enriches the ways to improve crystalline order in thin films comprising crystallizable polymers.
Co-reporter:Chunxia Luo;Weihuan Huang ;Yanchun Han
Macromolecular Rapid Communications 2009 Volume 30( Issue 22) pp:1917-1921
Publication Date(Web):
DOI:10.1002/marc.200900427
Co-reporter:Hanfu Wang ;Yanchun Han
Macromolecular Rapid Communications 2009 Volume 30( Issue 7) pp:521-527
Publication Date(Web):
DOI:10.1002/marc.200800705
Co-reporter:Chunxia Luo;Weihuan Huang ;Yanchun Han
Macromolecular Rapid Communications 2009 Volume 30( Issue 7) pp:515-520
Publication Date(Web):
DOI:10.1002/marc.200800675
Co-reporter:Ping Yang ;Yanchun Han
Macromolecular Rapid Communications 2009 Volume 30( Issue 17) pp:1509-1514
Publication Date(Web):
DOI:10.1002/marc.200900227
Co-reporter:Kai Yu and Yanchun Han
Soft Matter 2009 vol. 5(Issue 4) pp:759-768
Publication Date(Web):09 Dec 2008
DOI:10.1039/B805611K
Diblock polyampholyte brushes with different block sequences (Si/SiO2/poly(acrylic acid)-b-poly(2-vinylpyridine) (PAA-b-P2VP) brushes and Si/SiO2/P2VP-b-PAA brushes) and different block lengths were synthesized by sequent surface-initiated atom transfer radical polymerization (ATRP). The PAA block was obtained through hydrolysis from the corresponding poly(tert-butyl acrylate). The polyampholyte brushes demonstrated unique pH-responsive behavior. In the intermediate pH region, the brushes exhibited a less hydrophilic wetting behavior and a rougher surface morphology due to the formation of polyelectrolyte complex through electrostatic interaction between oppositely charged blocks. In the low pH and high pH regions, the rearrangement of polyampholyte brushes showed great dependence on the block sequence and block length. The polyampholyte brushes with P2VP-b-PAA sequence underwent rearrangement during alternative treatment by acidic aqueous solution (low pH value) and basic aqueous solution (high pH value). The brushes with PAA-b-P2VP sequence did not show obvious rearrangement. Nevertheless, with increasing the length of inner PAA block for PAA-b-P2VP brushes, the hydrogen-bonding interaction between blocks became strong enough to implement surface rearrangement and eventually localized the inner PAA block at the polymer–air interface in the low pH region. In the high pH region, polymer brushes had least chance of surface rearrangement. P2VP block was more localized at the interface despite of the length of inner block.
Co-reporter:Rubo Xing, Tengling Ye, Yan Ding, Dongge Ma, Yanchun Han
Organic Electronics 2009 Volume 10(Issue 2) pp:313-319
Publication Date(Web):April 2009
DOI:10.1016/j.orgel.2008.12.006
In this paper, low surface energy separators with undercut structures were fabricated through a full-solution process. These low surface energy separators are more suitable for application in inkjet printed passive-matrix displays of polymer light-emitting diodes. A patterned PS film was formed on the P4VP/photoresist film by microtransfer printing firstly. Patterned Au-coated Ni film was formed on the uncovered P4VP/photoresist film by electroless deposition. This metal film was used as mask to pattern the photoresist layer and form undercut structures with the patterned photoresist layer. The surface energy of the metal film also decreased dramatically from 84.6 mJ/m2 to 21.1 mJ/m2 by modification of fluorinated mercaptan self-assemble monolayer on Au surface. The low surface energy separators were used to confine the flow of inkjet printed PFO solution and improve the patterning resolution of inkjet printing successfully. Separated PFO stripes, complement with the pattern of the separators, formed through inkjet printing. The separators also realized the patterning of cathodes. A passive-matrix display device was obtained through the assistant patterning of low surface energy separators.
Co-reporter:Jianying Wang and Yanchun Han
Langmuir 2009 Volume 25(Issue 3) pp:1855-1864
Publication Date(Web):January 8, 2009
DOI:10.1021/la803035m
Methacrylic acid based inverse opal hydrogels (MIOHs) have been prepared by controlling the synthesis conditions, including cross-linker content, solvent content, and water content in solvent mixtures to explore the effect of the synthesis conditions (especially solvent content and mixture) on the response performance. Various response events (pH, solvent, ionic strength, 1,4-phenylenediamine dihydrochloride (PDA) response) have been investigated. For pH, solvent response, the same response behaviors have been observed: both the increased solvent (only ethanol) content and the enhanced water content in solvent will lead to the reduced response level of MIOHs compared to that of the increased cross-linker content. However, two different kinds of response behaviors for ionic strength response have been found by adjusting the synthesis conditions. The kinetics of pH response shows characteristics of a diffusion-limited process, and the equilibrium response time is about 20 min, which cannot be reduced by changing the synthesis conditions. The PDA response of MIOHs shows a PDA concentration dependence: with the increase of PDA concentration, the response level increases and the response time decreases.
Co-reporter:Jun Fu, Yuhan Wei, Longjian Xue, Bin Luan, Caiyuan Pan, Binyao Li, Yanchun Han
Polymer 2009 50(6) pp: 1588-1595
Publication Date(Web):
DOI:10.1016/j.polymer.2009.01.048
Co-reporter:Longjian Xue and Yanchun Han
Langmuir 2009 Volume 25(Issue 9) pp:5135-5140
Publication Date(Web):March 11, 2009
DOI:10.1021/la8041814
The wettability of thin poly(methyl methacrylate) (PMMA) films on a silicon wafer with a native oxide layer exposed to solvent vapors is dependent on the solvent properties. In the nonsolvent vapor, the film spread on the substrate with some protrusions generated on the film surface. In the good solvent vapor, dewetting happened. A new interface formed between the anchored PMMA chains and the swollen upper part of the film. Entropy effects caused the upper movable chains to dewet on the anchored chains. The rim instability depended on the surface tension of solvent (i.e., the finger was generated in acetone vapor (γacetone = 24 mN/m), not in dioxane vapor (γdioxane = 33 mN/m)). The spacing (λ) that grew as an exponential function of film thickness h scaled as ∼h1.31, whereas the mean size (D) of the resulting droplets grew linearly with h.
Co-reporter:Ping Yang and Yanchun Han
Langmuir 2009 Volume 25(Issue 17) pp:9960-9968
Publication Date(Web):May 13, 2009
DOI:10.1021/la901108p
The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation at the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer−substrate interaction. In this case, lower free energy lamellae of an edge-on orientation could be obtained by the gain of free volume of the soluble PS block.
Co-reporter:Longjian Xue, Jian Li, Jun Fu, Yanchun Han
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 338(1–3) pp:15-19
Publication Date(Web):15 April 2009
DOI:10.1016/j.colsurfa.2008.12.016
Super-hydrophobic films with vinyl-modified silica nanoparticles (V-SiOx-NPs) were successfully prepared. The rough surface, which was composed of microstructures of disordered V-SiOx-NPs and nanostructures on the surface of V-SiOx-NPs, rather than the chemical composition devoted to the super-hydrophobicity of film. The relationship between contact angle and diameter of V-SiOx-NPs was then investigated. The sessile contact angles (CA) of films with 150–1600 nm V-SiOx-NPs were around 166° regardless the diameter, while the film with 85 nm V-SiOx-NPs had the lowest CA of about 158°. The packing manner of V-SiOx-NPs determined the air fraction on the surface and then the CA.
Co-reporter:Ping Yang ;Yanchun Han
Macromolecular Rapid Communications 2008 Volume 29( Issue 19) pp:1614-1619
Publication Date(Web):
DOI:10.1002/marc.200800285
Co-reporter:Yuhan Wei;Weihuan Huang;Binyao Li;Yanchun Han;Caiyuan Pan
Macromolecular Rapid Communications 2008 Volume 29( Issue 16) pp:1378-1384
Publication Date(Web):
DOI:10.1002/marc.200800210
Co-reporter:Yuhan Wei, Binyao Li, Yanchun Han and Caiyuan Pan
Soft Matter 2008 vol. 4(Issue 12) pp:2507-2512
Publication Date(Web):08 Sep 2008
DOI:10.1039/B806258G
The formation of ring-shaped structures in an H-shaped block copolymer [a poly(ethylene glycol) backbone with polystyrene branches, i.e., (PS)2PEG(PS)2] thin film was investigated when it was annealed in saturated PEG-selective acetonitrile vapor. Our results clearly indicate that ring formation is determined by the initial morphology of the spin-coated film, the solvent vapor selectivity and the environmental temperature of the solvent-annealing process. Only the films with the initial core–shell cylindrical structure in strongly PEG-selective acetonitrile vapor could form the ring-shaped structures. Environmental temperature has an influence on the formation mechanisms. It was proven that the rings arising from the core–shell cylindrical structure of the pristine spin-coated (PS)2PEG(PS)2 film were caused by the migration of the PEG shells to the top surface in the process of PEG-selective vapor annealing at the environmental temperature of 15 °C. While at a higher environmental temperature (25 °C), the degree of swelling of the film and the chains’ mobility increased and the formation mechanism of the rings in this situation was similar to that in dilute solution.
Co-reporter:Juan Peng;Yanchun Han;Wolfgang Knoll;Dong Ha Kim
Macromolecular Rapid Communications 2007 Volume 28(Issue 13) pp:1422-1428
Publication Date(Web):19 JUN 2007
DOI:10.1002/marc.200700206
We have systematically studied the thin film morphologies of asymmetric polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer subjected to solvent vapors of varying selectivity for the constituent blocks. Upon a short treatment in neutral or PS-selective vapor, the film exhibited a highly ordered array of hexagonally packed, cylindrical microdomains. In the case of PEO selective vapor annealing, such ordered cylindrical microdomains were not obtained. Instead, fractal patterns on the microscale were observed and their growth processes investigated. Furthermore, hierarchical structures could be obtained if the fractal pattern was exposed to neutral or PS selective vapor.
Co-reporter:Jian Li;Longjian Xue;Zhe Wang;Yanchun Han
Colloid and Polymer Science 2007 Volume 285( Issue 9) pp:1037-1041
Publication Date(Web):2007 June
DOI:10.1007/s00396-007-1656-2
In this work, a gradient polystyrene colloidal photonic crystal was fabricated by annealing in a graded temperature field. The lattice constant of the gradient crystal gradually varied along the temperature-gradient direction. The positional bandgap wavelength as well as the attenuation of the bandgap wavelength could be tuned dependent on the position of the gradient colloidal crystal along the gradient direction because of the lattice-constant variation.
Co-reporter:Hanfu Wang;Peng Guo;Yanchun Han
Macromolecular Rapid Communications 2006 Volume 27(Issue 1) pp:63-68
Publication Date(Web):19 DEC 2005
DOI:10.1002/marc.200500601
Summary: Tetraaniline-block-poly(L-lactide) diblock oligomers are synthesized via ring-opening polymerization. The diblock oligomers cast from an L-lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring-like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.
Co-reporter:Libin Liu;Yong Cong;Yanchun Han;Binyao Li;Xiang Gao
Macromolecular Rapid Communications 2006 Volume 27(Issue 4) pp:260-265
Publication Date(Web):15 FEB 2006
DOI:10.1002/marc.200500679
Summary: We report the multiple morphologies and their transformation of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) in low-alkanol solvents. In order to improve the solubility of polystyrene block in alcohol solvents, the solution of block copolymer sample was treated at a higher temperature, and then the influence of rate of decreasing temperature on multiple morphologies (including spheres, rods, vesicles, porous vesicles, large compound vesicles, and large compound micelles) was observed. The transformation of spheres to rods, to tyre-shaped large compound micelles, and to sphere-shaped large compound micelles was also realized. The formation mechanisms of the multiple morphologies and their transformation are discussed briefly.
Co-reporter:Yanchun Han;Jilin Zhang;Weihuan Huang
Macromolecular Rapid Communications 2006 Volume 27(Issue 10) pp:804-808
Publication Date(Web):25 APR 2006
DOI:10.1002/marc.200500842
Summary: A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual-scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an ‘intelligent’ wettability property can be utilized to separate oil and water systems efficiently.
Co-reporter:Kai Yu and Yanchun Han
Soft Matter 2006 vol. 2(Issue 8) pp:705-709
Publication Date(Web):03 Jul 2006
DOI:10.1039/B602880M
A PEO-tethered layer on a PDMS (polydimethylsiloxane) cross-linked network has been prepared by a swelling–deswelling process. During swelling, the PDMS block of a PDMS-b-PEO diblock copolymer penetrates into the PDMS substrate and interacts with PDMS chains because of the van der Waals force and hydrophobic interaction between them. Upon deswelling, the PDMS block is trapped in the PDMS matrix while the PEO, as a hydrophilic block, is tethered to the surface. The PEO-tethered layer showed stability when treated in water for 16 h. The surface fraction of PEO and the wetting property of the PEO-tethered PDMS surface can be controlled by the cross linking density of the PDMS matrix. A patterned PEO-tethered layer on a PDMS network was also created by microcontact printing and water condensation figures (CFs) were used to study the patterned surface with different wetting properties.
Co-reporter:Xinhong Yu, Rubo Xing, Shifang Luan, Zhe Wang, Yanchun Han
Applied Surface Science 2006 Volume 252(Issue 24) pp:8544-8548
Publication Date(Web):15 October 2006
DOI:10.1016/j.apsusc.2005.11.091
Abstract
Micropatterning of functional polymer materials by micromolding in capillaries (MIMIC) with ice mold is reported in this paper. Ice mold was selected due to its thaw or sublimation. Thus, the mold can be easily removed. Furthermore, the polymer solution did not react with, swell, or adhere to the ice mold, so the method is suitable for many kinds of materials (such as P3HT, PMMA Alq3/PVK, PEDOT: PSS, PS, P2VP, etc.). Freestanding polymer microstructures, binary polymer pattern, and microchannels have been fabricated by the use of ice mold freely.
Co-reporter:Yang Wu;Yuming Yang;Yanchun Han;Binyao Li
Journal of Applied Polymer Science 2006 Volume 100(Issue 4) pp:3187-3192
Publication Date(Web):27 FEB 2006
DOI:10.1002/app.23572
The crystallization behavior and morphology of nonreactive and reactive melt-mixed blends of polypropylene (PP) and polyamide (PA12; as the dispersed phase) were investigated. It was found that the crystallization behavior and the size of the PA12 particles were dependent on the content of the compatibilizer (maleic anhydride–modified polypropylene) because an in situ reaction occurred between the maleic anhydride groups of the compatibilizer and the amide end groups of PA12. When the amount of compatibilizer was more than 4%, the PA12 did not crystallize at temperatures typical for bulk crystallization. These finely dispersed PA12 particles crystallized coincidently with the PP phase. The changes in domain size with compatibilizer content were consistent with Wu's theory. These investigations showed that crystallization of the dispersed phase could not be explained solely by the size of the dispersion. The interfacial tension between the polymeric components in the blends may yield information on the fractionation of crystallization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3187–3192, 2006
Co-reporter:Yang Cong;Jun Fu;Ziyong Cheng;Rubo Xing;Yanchun Han;Zexin Zhang;Jian Li
Journal of Applied Polymer Science 2006 Volume 100(Issue 4) pp:2737-2743
Publication Date(Web):9 FEB 2006
DOI:10.1002/app.23063
A combination of microcontact printing and block copolymer nanoreactors succeeded in fabricating arrays of silver nanoparticle aggregates. A complex solution of polystyrene-block-poly(4-vinylpyridine) micelles and silver salt was used as an ink to form thin films or droplets on polydimethylsiloxane stamp protrusions. After these complex aggregates were printed onto silicon substrates under controlled conditions, highly ordered arrays of disklike, dishlike, and dotlike complex aggregates were obtained. A subsequent oxygen reactive ion etching treatment yielded arrays of silver nanoparticle aggregates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2737–2743, 2006
Co-reporter:Jilin Zhang;Xiaoying Lu;Weihuan Huang;Yanchun Han;Jilin Zhang;Weihuan Huang;Yanchun Han;Xiaoying Lu
Macromolecular Rapid Communications 2005 Volume 26(Issue 6) pp:477-480
Publication Date(Web):14 MAR 2005
DOI:10.1002/marc.200400512
Summary: Reversible switching between superhydrophobic and superhydrophilic wettability of a polyamide film with a triangular net-like structure can be achieved by biaxially extending and unloading the elastic film. Both the change of the average side-length of the triangular net-like structure upon biaxial extension and unloading, and the surface tension of the water droplet, are believed to be responsible for the reversible switching between superhydrophobicity and superhydrophilicity.
Co-reporter:Yuhan Wei;Hanfu Wang;Binyao Li;Juan Peng;Yanchun Han;Juan Peng;Yuhan Wei;Hanfu Wang;Binyao Li;Yanchun Han
Macromolecular Rapid Communications 2005 Volume 26(Issue 9) pp:738-743
Publication Date(Web):22 APR 2005
DOI:10.1002/marc.200400665
Summary: We follow the time development of the microdomain structure in symmetric polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer thin films during acetone vapor treatment. Besides the highly ordered nanoscopic spheres or stripes as reported previously, a novel so-called flower-like pattern, which comprises six PS spheres and each PS sphere belongs to three “flowers” is formed. This finding is very helpful to discuss the highly ordered nanoscopic sphere formation process.
Co-reporter:Jun Fu, Yang Cong, Xiang Yu, Jian Li, Caiyuan Pan, Binyao Li, Yanchun Han
Applied Surface Science 2005 Volume 252(Issue 4) pp:1132-1138
Publication Date(Web):15 November 2005
DOI:10.1016/j.apsusc.2005.02.037
Abstract
Crown ether-centered two-armed polymers, i.e., polystyrene-dibenzo-18-crown-6-polystyrene (PSCS) and poly(methyl methacrylate)-dibenzo-18-crown-6-poly(methyl methacrylate) (PMCM), were designed to self-assemble in a proposed manner directed by the specific affinity between the polar crown ether rings. When spin coated onto a silicon wafer surface, macroporous films were obtained. In contrast, the proposed assemblies were strongly adsorbed on a highly polar mica surface, looking like porous islands near the spin center. At areas far from the spin center, these islands slipped to form terrace islands under the huge shear by the centrifugal force. The formation of the porous islands and terrace islands provide further evidence to the proposed assembling of the two-armed polymers.
Co-reporter:Zi-Yong Cheng;Bao-Li Shi;Bao-Xiang Gao;Mao-Lin Pang;Shu-Yun Wang;Jun Lin
European Journal of Inorganic Chemistry 2005 Volume 2005(Issue 1) pp:
Publication Date(Web):24 NOV 2004
DOI:10.1002/ejic.200400501
By utilising 3-aminopropyltrimethoxysilane (APTMOS) cations and PbI2 as the organic and inorganic precursors, respectively, a spin-coated film of a layered perovskite-type organic/inorganic derivative of APTMOS-PbI4 was prepared. The structure of APTMOS-PbI4 was characterised by X-ray diffraction (XRD), UV/Vis absorption and infrared red spectroscopy (IR). The film showed green emission from the excitons of the inorganic layers and a weak blue emission related to the small amount of gel of adjacent APTMOS cations. Furthermore, the significant effect of the size of the inorganic framework on the cross-linking degree of APTMOS molecules is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Co-reporter:Yanchun Han;Jian Li;Jilin Zhang
Macromolecular Rapid Communications 2004 Volume 25(Issue 11) pp:1105-1108
Publication Date(Web):21 MAY 2004
DOI:10.1002/marc.200400065
Summary: A rather simple but yet effective way to achieve a superhydrophobic film by extending a Teflon film is proposed. The water-contact angle can be increased from 118 to 165° by extending to ca. 190%. The fibrous crystals and the increasing distance between the fibrous crystals are believed responsible for the high water-contact angle. It indicates that the density of the aligned microstructures is very important for the superhydrophobicity.
Co-reporter:Yanchun Han;Yu Xuan;Juan Peng;Binyao Li;Hanfu Wang
Macromolecular Rapid Communications 2004 Volume 25(Issue 12) pp:1181-1185
Publication Date(Web):3 JUN 2004
DOI:10.1002/marc.200400060
Summary: Binary symmetric diblock copolymer blends, that is, low-molecular-weight poly(styrene-block-methyl methacrylate) (PS-b-PMMA) and high-molecular-weight poly(styrene-block-methacrylate) (PS-b-PMA), self-assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix.
Co-reporter:Kai Yu, Yang Cong, Jun Fu, Rubo Xing, Nana Zhao, Yanchun Han
Surface Science 2004 Volume 572(2–3) pp:490-496
Publication Date(Web):20 November 2004
DOI:10.1016/j.susc.2004.09.037
Patterned self-adaptive PS/P2VP mixed polymer brushes were prepared by “grafting to” approach combining with microcontact printing (μCP). The properties of the patterned surface were investigated by lateral force microscopy (LFM), XPS and water condensation figures. In the domains with grafted P2VP, the PS/P2VP mixed brushes demonstrated reversible switching behavior upon exposure to selective solvents for different components. The chemical composition of the top layer as well as the surface wettability can be well tuned due to the perpendicular phase segregation in the mixed brushes. While in the domains without grafted P2VP, the grafted PS did not have the capability of switching. The development and erasing of the pattern is reversible under different solvent treatment.
Co-reporter:Z. Wang;J. Yuan;J. Zhang;R. Xing;D. Yan;Y. Han
Advanced Materials 2003 Volume 15(Issue 12) pp:
Publication Date(Web):16 JUN 2003
DOI:10.1002/adma.200304846
Co-reporter:Xiaoshuang Feng;Yanchun Han;Jun Fu;Caiyuan Pan;Yuming Yang;Binyao Li
Macromolecular Rapid Communications 2003 Volume 24(Issue 8) pp:487-491
Publication Date(Web):26 MAY 2003
DOI:10.1002/marc.200390078
A two-armed polymer with a crown ether core self-assembles to produce macroporous films with pores perpendicularly reaching through the film down to the substrate. A possible assembling mechanism is discussed. The pore size can be conveniently adjusted by changing the solution concentration. These through-hole macroporous films provide a template for fabricating an array of Cu nanoparticle aggregates.
Co-reporter:Juan Peng;Binyao Li;Yanchun Han;Jun Fu;Yuming Yang
Macromolecular Chemistry and Physics 2003 Volume 204(Issue 1) pp:125-130
Publication Date(Web):17 FEB 2003
DOI:10.1002/macp.200290068
Ordered macroporous materials recently have attracted much attention. A method that utilizes the condensation of monodisperse water droplets on a polymer solution is proposed for the preparation of honeycomb microporous films. Our results show that it is a general method that can be used for patterning a wide range of polymers. The presence of water vapor and polymer is necessary for the formation of regular holes in films. The formation of hexagonal packing instead of other kinds of packing takes place because the hexagonal packing has the lowest free energy. The formation mechanisms of regular hole pattern and imperfections in the hexagonal packing are proposed.
Co-reporter:Jiangang Liu, Xiang Gao, Yue Sun, Yanchun Han
Solar Energy Materials and Solar Cells (October 2013) Volume 117() pp:421-428
Publication Date(Web):1 October 2013
DOI:10.1016/j.solmat.2013.06.031
•A quasi-ordered bulk hetertojunction of P3HT/PCBM solar cells was fabricated by zone-casting technique.•P3HT nanofibers aligned in an oriented manner due to the shear stress and solute concentration gradient during zone-casting process.•The oriented alignment of nanofibers could facilitate P3HT chains to bridge nanofibers and improve the ability of hole transfer.•The device efficiency increased to 3.26% without any annealing treatment.In this paper, a quasi-ordered bulk hetertojunction of P3HT/PCBM solar cells (Q-O BHJ device) was fabricated by zone-casting from the solutions with different aging times. P3HT nanofibers aligned in an oriented manner due to the shear stress and solute concentration gradient during zone-casting process. The orientation degree of P3HT nanofibers increased when the aging time of solution was prolonged. Meanwhile, P3HT had a high crystallinity due to the slow evaporation rate of solvent during the film-forming process. The oriented alignment of nanofibers could facilitate the connection between nanofibers by increasing the bridging chains. Furthermore, the bridging chains tended to adopt an untwisted conformation, which results in a reduced energy barrier of hole transfer. As a consequence, the Q-O BHJ device had a higher fill factor (FF) and short-circuit current density (Jsc) compared with the device fabricated by spin coating (BHJ device), leading to an increase by almost more than 50% in device efficiency and a PCE of 3.26% without any annealing treatment.
Co-reporter:Lidong Zheng, Jiangang Liu and Yanchun Han
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 4) pp:NaN1215-1215
Publication Date(Web):2012/11/05
DOI:10.1039/C2CP42614E
This work focuses on both the structure manipulation and the crystallizing mechanism investigation of the well-known methanofullerene, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). PCBM crystals with two novel structures, i.e., five-fold twinned and cubic crystals are obtained by the introduction of the mica substrate and the polymer blenders (P3HT and PS) into PCBM thin films under thermal annealing. The morphology and nanostructure of these crystals have been well investigated with AFM, TEM and XRD techniques. The roles of the mica substrate and the polymer blenders have been studied by varying the annealing temperature, the substrate, the polymer benders and the blending ratio. It has been proved that both the PCBM intermolecular and PCBM-mica interactions influence the PCBM crystallization process. The mica substrate has been proved to have the epitaxial effect on PCBM crystallization. The polymer blenders have been suggested to weaken the PCBM intermolecular interaction and limit PCBM molecular diffusion.
Co-reporter:Mingguang Li, Lei Wang, Jiangang Liu, Ke Zhou, Xinhong Yu, Rubo Xing, Yanhou Geng and Yanchun Han
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 10) pp:NaN4537-4537
Publication Date(Web):2014/01/06
DOI:10.1039/C3CP55075C
In this work, solvent chloronaphthalene (CN) and polymer acceptor an alternating copolymer of perylene diimide and carbazole (PCPDI) were utilized as co-additives to optimize the nanoscale phase-separated morphology and photovoltaic properties of bulk-heterojunction (BHJ) polymer solar cells based on the poly(3-hexyl thiophene) (P3HT)/N,N′-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (EP-PDI) system. The domain size of EP-PDI molecules together with that of P3HT distinctly decreased by adding a 0.75 vol% CN additive. The optimized lateral phase separation increased the donor–acceptor interfacial area and facilitated the exciton dissociation process, leading to 5-fold enhancement of short-circuit current (JSC). Furthermore, when PCPDI was employed as a co-additive, acceptor materials (including PCPDI and EP-PDI) were prone to aggregation towards the top surface of blend films, improving vertical phase separation of active layers. PCPDI incorporation, which improved the percolation pathways for electron carriers, suppressed the crystallinity of P3HT distinctly. Thus, much more balanced charge transport was achieved by PCPDI addition, which resulted in almost 1-fold enhancement of open-circuit voltage (VOC) by reducing nongeminate recombination. As a consequence, cooperative effects of CN and PCPDI additives improved the nanoscale phase-separated morphology in lateral and vertical directions simultaneously, achieving the enhancement in both VOC and JSC.
Co-reporter:Xiao Li and Yanchun Han
Journal of Materials Chemistry A 2011 - vol. 21(Issue 44) pp:NaN18033-18033
Publication Date(Web):2011/10/13
DOI:10.1039/C1JM13704B
Polymer antireflection (AR) coatings have considerable practical value and wide-ranging applications because of their ability to adhere to flexible substrates and because they lend themselves easily to large-area processing. Preparing a suitable polymer porous structure with tunable wavelength AR by a simple approach is a challenge. In the present study, an inhomogeneous porous polymer film with a dense skin and porous structure underneath was obtained by spin coating a micelle solution of polystyrene-block-poly(4-vinypyridine) (PS-b-P4VP) with tetrahydrofuran (THF) and dimethyl formamide (DMF). The film was then subjected to non-solvent-induced phase separation before it reached a dry state. The dense skin surface morphology was fixed because of the rapid evaporation of THF during the spin coating. In the subsequent non-solvent immersion, an inner nanoporous structure was formed because the DMF was replaced by the non-solvent (with similar solubility to DMF). The inhomogeneous porous polymer film showed tunable wavelength AR controlled by the film thickness and immersion time in the non-solvent. The film exhibited an excellent transmittance of 99.6% at visible light wavelengths (400–800 nm) and 99.2% transmittance at near-infrared light wavelengths (800–2000 nm).
Co-reporter:Zicheng Ding, Qiaoqiao Zhao, Rubo Xing, Xingdong Wang, Junqiao Ding, Lixiang Wang and Yanchun Han
Journal of Materials Chemistry A 2013 - vol. 1(Issue 4) pp:NaN792-792
Publication Date(Web):2012/10/31
DOI:10.1039/C2TC00125J
The carbazole-based conjugated dendrimer H2-BCz with tert-butyl surface groups shows selective gelation behavior in a good solvent and anti-solvent mixture. The sol–gel conversion of H2-BCz can be observed on heating and cooling. The H2-BCz xerogel films show three-dimensional porous networks with the nanofibers (layered structures with a period of 1.38 nm) entangling and intersecting with each other. The π–π interactions between the aryl units may be the driving force for the formation of one-dimensional H2-BCz fibers during the gelation process. Due to the electron-donating property of the H2-BCz molecule and the porosity of the fibrous film, the xerogel films can be used as efficient fluorescence quenching based chemsensors for the detection of nitroaromatic explosives, such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). The quenching efficiency was as high as 77% and 91% when exposed to the vapor of TNT and DNT, respectively.
Co-reporter:Kui Zhao, Xinhong Yu, Ruipeng Li, Aram Amassian and Yanchun Han
Journal of Materials Chemistry A 2015 - vol. 3(Issue 38) pp:NaN9848-9848
Publication Date(Web):2015/09/07
DOI:10.1039/C5TC02415C
The mechanistic understanding of the intrinsic molecular self-assembly of conjugated polymers is of immense importance to control the microstructure development in organic semiconducting thin films, with a meaningful impact on charge transport and optoelectronic properties. Yet, to date the vast majority of studies have focused on the fast solution process itself, with studies of slower intrinsic molecular self-assembly in formulations lagging behind. Here we have investigated molecular self-assembly during spontaneous organization and uncovered how changes in formulation influence the microstructure, morphology and transport properties of conjugated polymer thin films. Our results suggest that the polymer–solvent interaction is the key factor for the molecular self-assembly and changes in macroscopic charge transport, which is in contrast with most solution processes, such as spin-coating and blade coating, where solvent drying kinetics dominates the aggregation and crystallization processes. Energetically favourable interactions between the polymer and its solvent are shown to cause chain expansion, resulting in a large hydrodynamic volume and few chain entanglements in solution. This provides molecular freedom for self-assembly and is shown to greatly enhance the local and long range order of the polymer, intra-chain backbone planarity and crystallite size. These improvements, in turn, are shown to endow the conjugated polymer with high carrier transport, as demonstrated by organic thin film transistors.
Co-reporter:Jiangang Liu, Liang Chen, Bingrong Gao, Xinxiu Cao, Yanchun Han, Zhiyuan Xie and Lixiang Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 20) pp:NaN6225-6225
Publication Date(Web):2013/03/28
DOI:10.1039/C3TA10629B
In this paper, mixed-solvent vapor annealing (M-SVA) was proposed to improve polymer crystallinity and inhibit fullerene intercalation into polymer side chains in a poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT):[6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) blend system. Experiments showed the optimal volume ratio of a mixed solvent, i.e., for tetrahydrofuran (THF) and carbon disulfide (CS2) vapor it is 1:1, and the appropriate annealing time is 5 min. After the M-SVA process, out-of-plane grazing incidence X-ray diffraction (GIXD) and spectroscopic ellipsometry (SE) data show that PCDTBT crystals with larger size and higher crystallinity were formed due to enhanced π–π interaction of polymer chains; the aggregation of PC70BM was promoted as well, which inhibited the intercalation behavior, resulting in a continuous electron path and improved phase purity. The morphology transition improved the carrier mobility, in particular electron mobility. Also, the recombination of a charge transfer (CT) state was reduced and the lifetime of mobile carriers was increased, which could be verified by transient-absorption (TA) spectra. As a result, the power conversion efficiency (PCE) of the BHJ reached 6.60%, an increase of more than 40% compared with the reference device (PCE = 4.54%), even though the thickness of the active layer is up to 220 nm and the PC70BM content is as low as 71.4 wt% by weight.
Co-reporter:Jilin Zhang and Yanchun Han
Chemical Society Reviews 2010 - vol. 39(Issue 2) pp:NaN693-693
Publication Date(Web):2009/10/05
DOI:10.1039/B816231J
A central challenge in polymer science today is creating materials that dynamically alter their structures and properties on demand, or in response to changes in their environment. Surfaces represent an attractive area of focus, since they exert disproportionately large effects on properties such as wettability, adhesiveness, optical appearance, and bioactivity, enabling pronounced changes in properties to be accomplished through subtle changes in interfacial structure or chemistry. In this critical review, we review the recent research progress into active and responsive polymer surfaces. The chief purpose of this article is to summarize the advanced preparation techniques and applications in this field from the past decade. This review should be of interest both to new scientists in this field and the interdisciplinary researchers who are working on “intelligent” polymer surfaces (117 references).
Co-reporter:Xiao Li, Longjian Xue and Yanchun Han
Journal of Materials Chemistry A 2011 - vol. 21(Issue 15) pp:NaN5826-5826
Publication Date(Web):2011/03/08
DOI:10.1039/C0JM04508J
The factors that influence the broadband antireflection of block copolymer/homopolymer blend films were systematically investigated. The gradient refractive index structure, which was generated by removing the PMMA content from a film of PS-b-PMMA/PMMA blends, contributed to the broadband antireflection. The volume fraction of the PMMA block (fPMMA), the total degree of polymerization (N) and the weight percent of the homopolymer played a key role in the formation of the gradient porosity index inner structure. By increasing χN, the PS porous structure was kept from collapsing after removal of the PMMA domain, which led to a stable gradient porosity ratio structure and higher transmittance. While increasing fPMMA, the PMMA domains changed from a dispersed phase to a continuous phase, which caused the residual PS structure to collapse more easily and the transmittance decreased. The best broadband antireflective properties were achieved from the 45 mg mL−1 solution of PS-b-PMMA (Mn = 68000–33500, fPMMA = ∼25%) blended with 30 wt% PMMA: a mean transmittance of 98.4% at full spectrum, and >98.0% in the visible–NIR range between 600 nm and 2000 nm.
Co-reporter:Yajun Su, Xiang Gao, Jiangang Liu, Rubo Xing and Yanchun Han
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 34) pp:NaN14404-14404
Publication Date(Web):2013/06/24
DOI:10.1039/C3CP51264A
Uniaxially aligned triisopropylsilylethynyl pentacene (TIPS-pentacene) crystals over a large area were fabricated using zone-casting technique. The array of TIPS-pentacene displayed a high orientation degree with a dichroic ratio (DR) of 0.80. The crystals were arranged with c axis perpendicular to the substrate and the long axis of the ribbon corresponded to the a axis of TIPS-pentacene. The properties of the solutions and the processing parameters were shown to influence the formation of the oriented TIPS-pentacene crystalline array. Solvent with a low boiling point (such as chloroform) favoured the orientation of the ribbon-like crystals. The concentration of the solution should be appropriate, ensuring the crystallization velocity of TIPS-pentacene matching with the receding of the meniscus. Besides, we proved that the casting speed should be large enough to induce a sufficient concentration gradient. The orientation mechanism of TIPS-pentacene was attributed to a synergy of the ordered nuclei and a match between the crystallization velocity and the casting speed. Field effect transistors (FETs) based on the oriented TIPS-pentacene crystalline array showed a mobility of 0.67 cm2 V−1 s−1.
Co-reporter:Xiao Li, Xinhong Yu and Yanchun Han
Journal of Materials Chemistry A 2013 - vol. 1(Issue 12) pp:NaN2285-2285
Publication Date(Web):2013/01/08
DOI:10.1039/C2TC00529H
Polymer thin films for antireflection (AR) coatings are reviewed, with particular emphasis on making different kinds of structures and establishing the relationships between structures and antireflective properties. Three kinds of main structures with antireflective properties, namely, homogeneous, inhomogeneous porous structures, and gradient-refractive-index structures, fabricated by “bottom up” or “top down” approaches are summarized. The transmittance of the polymer thin film can be increased to almost 100% in the single or broadband wavelength region (both of the visible and near-infrared region) by properly manipulating its structures. However, further studies are still needed to achieve reversible transmittance and multifunctional polymer AR due to the soft matter characteristic of polymers. In addition, the challenges of using polymer AR coatings still remain, such as poor solvent resistance, poor mechanical strength, and so on, which gives us the direction of future development for practical applications.
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![2,1,3-Benzothiadiazole, 4,4'-[4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl]bis[5-fluoro-7-(5'-hexyl[2,2'-bithiophen]-5-yl)-](/data/chemimg/164900/1402460-84-7.png)
![2,1,3-Benzothiadiazole, 4,4'-[4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl]bis[5-fluoro-7-(5'-hexyl[2,2'-bithiophen]-5-yl)-](/data/chemimg/164900/1402460-84-7_b.png)
![Poly[2,1,3-benzothiadiazole-2,7-diyl-2,5-thiophenediyl(9,9-didodecyl-9
H-fluorene-2,7-diyl)-2,5-thiophenediyl]](/data/chemimg/3395900/749900-96-7.png)
![Poly[2,1,3-benzothiadiazole-2,7-diyl-2,5-thiophenediyl(9,9-didodecyl-9
H-fluorene-2,7-diyl)-2,5-thiophenediyl]](/data/chemimg/3395900/749900-96-7_b.png)
![Poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]](/data/chemimg/133300/782469-77-6.png)
![Poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]](/data/chemimg/133300/782469-77-6_b.png)
