Charge transport of small molecules is measured well with scanning tunneling microscopy, conducting atomic force microscopy, break junction, nanopore, and covalently bridging gaps. However, the manipulation and measurement of polymer chains remain a long-standing fundamental issue in conjugated polymers and full of challenge since conjugated polymers are naturally disordered materials. Here, a fundamental breakthrough in generating high-quality conjugated-polymer nanocrystals with extended conjugation and exceptionally high degrees of order using a surface-supported topochemical polymerization method is demonstrated. In the crystal the conjugated-polymer chains are extended along the long axis of the crystal with the side chains perpendicular to the long axis. Devices with conducting channels along the polymer chains show efficient charge transport, nearly two orders of magnitude greater than the interchain charge transport along the π–π stacking direction. This is the first example to clarify intra- and interchain charge transport based on an individual single crystal of conjugated polymers, and demonstrate the importance of intrachain charge transport in plastic electronics.

Noncovalent conformational locks are broadly employed to construct highly planar π-conjugated semiconductors exhibiting substantial charge transport characteristics. However, current chalcogen-based conformational lock strategies for organic semiconductors are limited to S···X (X = O, N, halide) weak interactions. An easily accessible (minimal synthetic steps) and structurally planar selenophene-based building block, 1,2-diethoxy-1,2-bisselenylvinylene (DESVS), with novel Se···O noncovalent conformational locks is designed and synthesized. DESVS unique properties are supported by density functional theory computed electronic structures, single crystal structures, and experimental lattice cohesion metrics. Based on this building block, a new class of stable, structurally planar, and solution-processable conjugated polymers are synthesized and implemented in organic thin-film transistors (TFT) and organic photovoltaic (OPV) cells. DESVS-based polymers exhibit carrier mobilities in air as high as 1.49 cm2 V−1 s−1 (p-type) and 0.65 cm2 V−1 s−1 (n-type) in TFTs, and power conversion efficiency >5% in OPV cells.

The development of optical and electrical organic semiconductors is crucial for the construction of integrated optoelectronic devices. Herein, a new anthracene derivative, 2,6-diphenyl-9,10-bis(phenylethynyl)anthracene (DP-BPEA), was designed and synthesized by enlarging the π-conjugation of 9,10-bis(phenylethynyl)anthracene (BPEA) via 2,6-diphenyl substitution. Compared with the parent BPEA molecule, an improved field-effect mobility of 1.37 cm2 V−1 s−1 with a comparable solid fluorescence efficiency of 32% is obtained for DP-BPEA, suggesting its potential applications in integrated optoelectronic devices.

Two novel asymmetric thiophene/pyridine flanked diketopyrrolopyrrole (DPP) based polymers, named PPyTDPP-TT and PPyTDPP-BT were designed, synthesized and applied in organic field-effect transistors (OFETs) and polymer solar cells (PSCs). In contrast to the reported bipyridine flanked DPP, the asymmetric DPP polymers incorporating thiophene/pyridine flankers exhibited narrower bandgaps of ∼1.5 eV and deeper HOMO energy levels, thus leading to a broadened absorption from 500 to 850 nm and were potentially beneficial for low-energy photon harvesting. Both polymers displayed promising ambipolar semiconducting properties. The hole and electron mobilities of PPyTDPP-TT reach 0.48 cm2 V−1 s−1 and 0.18 cm2 V−1 s−1; and PPyTDPP-BT reach 0.55 cm2 V−1 s−1 and 0.08 cm2 V−1 s−1, respectively. Intriguingly, due to their ambipolar properties, two polymers can play an ambipolar role, both as electron donors and acceptors with PC71BM and P3HT in PSCs. Photovoltaic devices based on PPyTDPP-BT as the donor material reach PCEs of 7.56% and achieve 0.59% as the acceptor material, while those based on PPyTDPP-TT reach 5.48% with PC71BM and 0.82% with P3HT, respectively. These results suggest that the adoption of asymmetric flanker DPP polymers can effectively tune the absorption properties of polymers as excellent ambipolar transporting polymers towards high performance in both OFETs and PSCs.

Cocrystal polymorphs based on sym-triiodo-trifluorobenzene (IFB) with 1,4-di(4′-pyridyl)-1,3-diacetylene (DPDA) are formed with halogen bond interactions. Two cocrystal phases were obtained by using different solvents, acetonitrile and methylene chloride, and confirmed by their single crystal structure data. In the application direction, the different photo-physical properties of the two phases were discussed carefully.

Compact molecular packing with short π-π stacking and large π-overlap in organic semiconductors is desirable for efficient charge transport and high carrier mobility. Thus charge transport anisotropy along different directions is commonly observed in organic semiconductors. Interestingly, in this article, we found that comparable charge transport property were achieved based on the single crystals of a bis-fused tetrathiafulvalene derivative (EM-TTP) compound along two interaction directions, that is, the multiple strong S···S intermolecular interactions and the π-π stacking direction, with the measured electrical conductivity and hole mobility of 0.4 S cm−1, 0.94 cm2 V−1 s−1 and 0.2 S cm−1, 0.65 cm2 V−1 s−1, respectively. This finding provides us a new molecular design concept for developing novel organic semiconductors with isotropic charge transport property through the synergistic effect of multiple intermolecular interactions (such as S···S interactions) and π-π stacking.

It is a common phenomenon for organic semiconductors to crystallize in two or more polymorphs, leading to various molecular packings and different charge transport properties. Therefore, it is a crucial issue of tuning molecular crystal polymorphs (i.e., adjusting the same molecule with different packing arrangements in solid state) towards efficient charge transport and high performance devices. Here, the choice of solvent had a marked effect on controlling the growth of α-phase ribbon and β-phase platelet during crystallization for an indenofluorene (IF) π-extended tetrathiafulvalene (TTF)-based cruciform molecule, named as IF-TTF. The charge carrier mobility of the α-phase IF-TTF crystals was more than one order of magnitude higher than that of β-phase crystals, suggesting the importance of reasonably tuning molecular packing in solid state for the improvement of charge transport in organic semiconductors.有机分子溶剂的选择对于调控不同晶相来说有着关键性作用. 本文通过两种溶剂的调控, 成功得到茚并芴四硫富瓦烯(IF-TTF)两种不同的晶相—α相带状晶体和β相片状晶体, 并对两种晶相的内部分子排列堆积情况进行了一系列的对比分析. 结果表明场效应电荷传输能力随着晶相的不同而有所差异, 直接证明了分子堆积的合理调控对实现有机半导体材料高性能电荷传输性能的重要性.

Conjugated polymers have attracted the world’s attentions since their discovery due to their great promise for optoelectronic devices. However, the fundamental understanding of charge transport in conjugated polymers remains far from clear. The origin of this challenge is the natural disorder of polymers with complex molecular structures in the solid state. Moreover, an effective way to examine the intrinsic properties of conjugated polymers is absent. Optoelectronic devices are always based on spin-coated films. In films, polymers tend to form highly disordered structures at nanometer to micrometer length scales due to the high degree of conformational freedom of macromolecular chains and the irregular interchain entanglement, thus typically resulting in much lower charge transport properties than their intrinsic performance. Furthermore, a subtle change of processing conditions may dramatically affect the film formation—inducing large variations in the morphology, crystallinity, microstructure, molecular packing, and alignment, and finally varying the effective charge transport significantly and leading to great inconsistency over an order of magnitude even for devices based on the same polymer semiconductor. Meanwhile, the charge transport mechanism in conjugated polymers is still unclear and its investigation is challenging based on such complex microstructures of polymers in films. Therefore, how to objectively evaluate the charge transport and probe the charge transport mechanism of conjugated polymers has confronted the world for decades.In this Account, we present our recent progress on multilevel charge transport in conjugated polymers, from disordered films, uniaxially aligned thin films, and single crystalline micro- or nanowires to molecular scale, where a derivative of poly(para-phenylene ethynylene) with thioacetyl end groups (TA-PPE) is selected as the candidate for investigation, which could also be extended to other conjugated polymer systems. Our systematic investigations demonstrated that 3–4 orders higher charge transport properties could be achieved with the improvement of polymer chain order and confirmed efficient charge transport along the conjugated polymer backbones. Moreover, with downscaling to molecular scale, many novel phenomena were observed such as the largely quantized electronic structure for an 18 nm-long TA-PPE and the modulation of the redox center of tetrathiafulvalene (TTF) units on tunneling charge transport, which opens the door for conjugated polymers used in nanometer quantum devices. We hope the understanding of charge transport in PPE and its related conjugated polymer at multilevel scale in this Account will provide a new method to sketch the charge transport properties of conjugated polymers, and new insights into the combination of more conjugated polymer materials in the multilevel optoelectronic and other related functional devices, which will offer great promise for the next generation of electronic devices.

A series of acceptor–donor–acceptor (A–D–A) conjugated molecules based on naphthalene diimide dimers bridged with different π-conjugated heterocyclic units (NDI–π–NDI) have been designed and synthesized. By an ingenious design strategy, the LUMO (the lowest unoccupied molecular orbital) of the NDI-based small molecules is well controlled to a relatively constant value of −3.8 to −3.9 eV, whereas their HOMO (the highest occupied molecular orbital) could be tuned over a wide range, from −6.5 eV (compound 1) to −5.5 eV (compound 5), leading to varied band gaps from 2.6 eV to 1.5 eV. Organic field-effect transistor (OFET) characterization of these NDI–π–NDI molecules shows that compounds 1, 2, and 3 have good n-type semiconducting properties in a N2 atmosphere with the maximum electron mobilities up to 0.15 cm2 V−1 s−1, 0.46 cm2 V−1 s−1 and 0.57 cm2 V−1 s−1, respectively. Compounds 4 and 5, due to the high-lying HOMO levels and reduced energy band gaps, have ambipolar semiconducting properties and OFETs based on 5 show the highest electron and hole mobilities up to 1.23 cm2 V−1 s−1 and 0.0074 cm2 V−1 s−1, respectively. Moreover, the performances are enhanced under thermal treatment because of the increased crystallinity as evidenced by X-ray diffraction (XRD) and atomic force microscopy (AFM). The easily tunable electronic energy levels make the NDI-based semiconductors promising n-channel and ambipolar components in organic devices.

Poor charge injection and transport at the electrode/semiconductor contacts has been so far a severe performance hurdle for bottom-contact bottom-gate (BCBG) organic field-effect transistors (OFETs). Here, we have developed a simple, economic, and effective method to improve the carrier injection efficiency and obtained high-performance devices with low cost and widely used source/drain (S/D) electrodes (Ag/Cu). Through the simple electrode etching process, the work function of the electrodes is more aligned with the semiconductors, which reduces the energy barrier and facilitates the charge injection. Besides, the formation of the thinned electrode edge with desirable micro/nanostructures not only leads to the enlarged contact side area beneficial for the carrier injection but also is in favor of the molecular self-organization for continuous crystal growth at the contact/active channel interface, which is better for the charge injection and transport. These effects give rise to the great reduction of contact resistance and the amazing improvement of the low-cost bottom-contact configuration OFETs performance.Keywords: bottom-contact organic field-effect transistor; contact resistance; low-cost electrode; micro/nanostructures; soft-etching method

Large-area highly-ordered F-NDI films were obtained by epitaxial-crystallization on highly-oriented PE substrates through vacuum deposition. An electron mobility of 0.2 cm2 V−1 s−1 was achieved based on such epitaxially-crystallized F-NDI films, which is 4 times higher than that of its un-oriented thin film devices.

•Epitaxial crystallization of PESE on highly oriented PE substrate.•The different PESE crystalline morphologies due to different substrate temperatures.•The different electrical characteristics depend on different crystalline morphologies.•The mobility is 2 orders higher than the unoriented film transistors.Epitaxial crystallization of perylo[1,12-b,c,d]selenophene (PESE) on highly oriented polyethylene (PE) substrate through vapor phase deposition has been achieved. Oriented PESE crystals with different crystalline morphologies can be fabricated by changing the temperature of PE substrate during vacuum evaporation. When the PE substrate temperature is lower than 70 °C, sparsely dispersed PESE lathlike crystals are produced with their long axis preferentially aligned perpendicular to the chain direction of PE crystals. While the close films of PESE with lathlike crystals aligned with long axis parallel to the chain direction of PE film were obtained above 90 °C. Transistors based on expitaxially crystallized PESE films have been fabricated and the transistor properties were also studied. It is found that transistors show different electrical characteristics depending on the preparation conditions of expitaxially crystallized PESE films. The transistors based on the PESE/PE-SiO2/Si with PESE deposited on oriented PE film at low temperature, i.e., <70 °C, display a similar poor properties with the PESE/OTS-SiO2/Si type transistors. However, when the deposition temperature was elevated to 90 °C, the transistors exhibit a maximum field-effect mobility of 4.4 × 10−2 cm2 V−1 s−1 and maximum on/off ratio of 2.0 × 105, which are about 2 orders of magnitudes higher than the PESE/OTS-SiO2/Si based transistors.

Organic cocrystals are crystalline, single-phase materials composed of two or more molecular and/or ionic compounds, generally, in a stoichiometric ratio. A feature of organic cocrystals is that special optoelectronic properties such as ferroelectricity are easy to realize in these materials. In this perspective, we systematically introduce the recent research advances in organic cocrystal ferroelectrics, and we study in depth the molecular structure and self-assembling behaviors of cocrystals for ferroelectric applications. Finally, combined with an understanding of recent progress and achievements in this field, we discuss the challenges and opportunities for ferroelectric materials based on organic cocrystals, as well as the promising applications of these materials.“有机共晶” 作为一种由两种或者两种以上分子按照一定比例形成的多组份体系在实现一些物理化学特性方面显示了独特的优势, 譬如铁电特性. 本文系统介绍了有机共晶铁电材料方面的研究进展, 深入分析了有机共晶在实现铁电性能方面的分子结构特征、 共晶体系组装策略、 以及铁电性能. 最后, 结合对这些研究进展和结果的分析, 作者指出了利用有机共晶实现铁电特性研究领域中所存在的各种挑战与机遇以及有机共晶铁电材料潜在的应用前景.

An anthracene derivative, 2,6-diphenyl anthracene (DPA), was successfully synthesized with three simple steps and a high yield. The compound was determined to be a durable high performing semiconductor with thin film device mobility over 10 cm2 V−1 s−1. The efficient synthesis and high performance indicates its great potential in organic electronics.

A phototransistor, a kind of optoelectronic device that realizes the functionality of light detection and signal magnification in a single device, is an important component of optoelectronic integration. Polymer phototransistors, compared to traditional inorganic phototransistors, demonstrate attractive advantages of light-weight, low-cost, easy solution processing and flexibility, and are the best candidates for Plastic Optoelectronics. Over the past few years, significant advances have been made in polymer phototransistors with the development of new polymer semiconductor materials and the optimization of device fabrication techniques. In this review, we will give an overview of the recent advances in polymer phototransistors, from a brief introduction of the device geometry, working mechanism, performance parameters to the development of the device performance and the exploration of their flexible optoelectronic devices. Finally, a perspective and conclusion is also briefly addressed.

A new naphthalene diimide (NDI) derivative with an asymmetric aromatic backbone of 2-tetradecylbenzo[lmn]benzo[4,5]imidazo[2,1-b][3,8]phenanthroline-1,3,6(2H)-trione (IZ0) was designed and synthesized. Low LUMO level, large energy gap, and high thermal stability are characterized for this IZ0 compound. The OFET devices based on an IZ0 semiconductor exhibit typical n-type behavior. Through continuously optimizing the fabrication conditions, high performance n-channel OFETs were fabricated based on IZ0 films and single crystals, with the highest carrier mobility of 0.072 cm2 V−1 s−1 and 0.22 cm2 V−1 s−1, respectively.

Organic cocrystal (also “co-crystal”), formed with two or more different components via non-covalent intermolecular interactions, possesses novel, unpredicted and unique properties, which are not the simple sum of those molecular components, e.g., with effect of 1+1>2. In this regard, organic cocrystals provide a distinctive strategy for the synthesis of novel multifunctional materials, and an important platform for exploring new fundamental physicochemical phenomena in molecular systems, such as high conductivity, ambipolar charge transportation, photovoltaic behavior, white light-emitting, room-temperature phosphorescence, nonlinear optics and ferroelectricity etc., with potential application even in liquid crystal engineering and drug industry.本文简明扼要地介绍了“有机共晶”这个重要研究领域的兴起和发展过程, 在有争议的方面, 如共晶定义和如何判定分子排布等, 给出了作者独到的见解. 特别重要的是, 通过阐述该领域当前存在的问题和挑战, 结合分析最新的研究进展和结果, 使得人们对共晶的认识更为系统和深入. 基于此, 作者同时分析和指出了未来可能重点发展的研究方向.

Organic-inorganic halide perovskites have attracted considerable attention owing to their outstanding solar cell efficiency. Meanwhile, these halide perovskites exhibit good light emitting in visible and near-infrared range with high fluorescence quantum yield, resulting in electroluminescence. However, it remains challenging for lighting and display due to the low luminance and poor long-term stability. Herein, high performance green light-emitting diodes are fabricated from bromine based perovskite (CH3NH3PbBr3) by systematically adjusting the preparation conditions and optimizing the emitting layer thickness. A high luminance up to 1500 cd m−2 (one of the highest values for perovskites-based light-emitting diodes) was achieved with 80 nm perovskites-emitting layer, due to the well-crystallized, full-coverage property of the films. This result further confirms the great prospect of organic-inorganic perovskites in optoelectronics.有机金属卤化钙钛矿(CH3NH3PbX3)作为一种新型的半导体材料在光伏领域引起了广泛的关注. 同时, 有机金属卤化钙钛矿所拥有的光致发光以及较高荧光量子产率为其电致发光提供了可能. 因而, 研究有机金属卤化钙钛矿的电致发光行为对于进一步拓展其在光电领域的应用具有重要意义. 溴化钙钛矿(CH3NH3PbBr3)具备良好的光致发光性能, 具有较高的荧光量子产率, 同时在空气中具有较好的稳定性. 本文挑选CH3NH3PbBr3作为发光层, 借用气体辅助法得到了高质量的CH3NH3PbBr3薄膜, 并成功构建了发光二极管. 基于CH3NH3PbBr3的发光二极管电致发光为536 nm的绿光, 发光亮度达到1000 cd m−2, 外量子效率为0.1%. 该研究对于探索有机金属卤化钙钛矿的电致发光行为大有裨益, 同时也拓宽了有机金属卤化钙钛矿在光电领域的应用潜能.

In the light of the principle of aggregation-induced emission enhancement (AIEE), the rubrene analogue with orange light-emitting properties is designed and synthesized by substituting the phenyl side groups of rubrene with thienyl groups. To the best of our knowledge, this is the first report on the synthesis of rubrene with AIEE behaviour, thus paving the way for the development of light-emitting rubrene derivatives.

By introducing phenyl groups into the 2- and 6-positions of 11,11,12,12-tetracyano-9,10-anthraquinodimethane, a material (dP-TCAQ) with aggregation-induced emission enhancement (AEE) characteristics was synthesized. The AEE phenomenon was explained by analysis of its solid-state packing mode. To our best knowledge, this is the first report regarding 11,11,12,12-tetracyano-9,10-anthraquinodimethane with AEE behaviour.

Molecular order and orientation significantly influence the physical properties of organic materials and their corresponding device properties. Therefore ordering organic molecules especially conjugated polymer molecules in the active layer has been a hot topic in organic electronics for high performance organic electronics and remarkable progress has been demonstrated recently. The purpose of this minireview is to highlight the novel strategies for controlling conjugated polymer molecule orders in the solid state, including rational chemical design, optimizing solution-processing techniques and growth of high quality polymer crystalline micro/nanostructures. Moreover, the charge transport mechanisms in conjugated polymers and the relationship of oriented polymer molecules with their field-effect properties are also discussed. Finally, a concise conclusion and perspective of highly ordered conjugated polymer molecules in organic electronics are also addressed.

In this manuscript, two chloro-substituted derivatives of indolo[3,2-b]carbazole (ICZ), 2,8-dichloro-indolo[3,2-b]carbazole (CICZ) and 2,8-dichloro-5,11-dihexyl-indolo[3,2-b]carbazole (CHICZ) were designed and synthesized. The only difference between CICZ and CHICZ is at the N-5 and N-11 positions with or without long alkyl side chains. Interestingly, CICZ and CHICZ exhibited similar thermal, optical, and electrochemical properties, while their molecular packing motifs in solid state and corresponding charge transport properties were significantly different. The alkyl chains at N-5 and N-11 positions were proved not only enhancing the solubility and self-organization of the compounds but also shifting the molecular packing from herringbone (CICZ) to one-dimensional π–π stacking (CHICZ). Moreover, nearly no field-effect performance was observed for CICZ, while the mobility of CHICZ was as high as 0.14 cm2 V−1 s−1 for its thin films and 0.5 cm2 V−1 s−1 for its single crystals. These results confirmed that the chemical substitutions are a powerful molecular design tool to tune the molecular packing motifs of organic semiconductors and their corresponding electronic properties.

The performance of organic field-effect transistors (OFETs) depends not only on the properties of organic semiconductors, gate dielectrics and electrodes, but it is also determined by the nature of the contact interfaces between the different functional components. Therefore, interface engineering to optimize the contacts becomes critically important for the fabrication of high performance OFETs. In this Perspective, representative strategies of interface engineering and the basic requirements for different functional components to enable high performance OFETs are highlighted.

A novel pseudo rubrene analogue, 6,11-di(thiophen-2-yl)-tetracene-5,12-dione (DTTDO) was synthesized, in which two thienyl groups and two carbonyl groups replacing four phenyl groups in the rubrene molecule were connected to the backbone of tetracene. This compound was characterized by single crystal X-ray structure analysis, thermogravimetric analysis, absorption spectra and electrochemical measurements. Unlike rubrene, DTTDO exhibited excellent film forming ability by normal vacuum deposition, indicating its promising applications in organic thin film transistors.

Anthracene and its derivatives are used to demonstrate a simple way to cast assemble nanowires of organic semiconductors with tuning of intermolecular non-covalent interactions by molecular design. The tuning of intermolecular interactions could be achieved by (i) decreasing intermolecular hydrophobic interactions by linking hydrophilic side chains to anthracene rings, (ii) increasing intermolecular interaction for self-assembly with the assistance of hydrogen bonds, and (iii) enhancing molecular π–π interaction by increasing the conjugated dimension of the compounds.

Organic single crystals hold great promise for the development of organic semiconductor materials, because they could reveal the intrinsic electronic properties of these materials, providing high-performance electronic devices and probing the structure-property relationships. This article reviews the preparation methods for organic single crystals or crystalline micro/nanostructures, including vapor phase growth methods and solution-processed methods, and summarizes a few methods employed in the fabrication of field-effect transistors along with dozens of examples concerning both small molecules and polymers with high field-effect performance.

Charge-transfer (CT) interactions between donor (D) and acceptor (A) groups, as well as CT exciton dynamics, play important roles in optoelectronic devices, such as organic solar cells, photodetectors, and light-emitting sources, which are not yet well understood. In this contribution, the self-assembly behavior, molecular stacking structure, CT interactions, density functional theory (DFT) calculations, and corresponding physicochemical properties of two similar halogen-bonded co-crystals are comprehensively investigated and compared, to construct an “assembly–structure–CT-property” relationship. Bpe-IFB wire-like crystals (where Bpe = 1,2-bis(4-pyridyl)ethylene and IFB = 1,3,5-trifluoro-2,4,6-triiodobenzene), packed in a segregated stacking form with CT ground and excited states, are measured to be quasi-one-dimensional (1D) semiconductors and show strong violet-blue photoluminescence (PL) from the lowest CT1 excitons (ΦPL = 26.1%), which can be confined and propagate oppositely along the 1D axial direction. In comparison, Bpe-F4DIB block-like crystals (F4DIB = 1,4-diiodotetrafluorobenzene), packed in a mixed stacking form without CT interactions, are determined to be insulators and exhibit unique white light emission and two-dimensional optical waveguide property. Surprisingly, it seems that the intrinsic spectroscopic states of Bpe and F4DIB do not change after co-crystallization, which is also confirmed by theoretical calculations, thus offering a new design principle for white light emitting materials. More importantly, we show that the CT interactions in co-crystals are related to their molecular packing and can be triggered or suppressed by crystal engineering, which eventually leads to distinct optoelectronic properties. These results help us to rationally control the CT interactions in organic D–A systems by tuning the molecular stacking, toward the development of a fantastic “optoelectronic world”.

Large-area highly-ordered F-NDI films were obtained by epitaxial-crystallization on highly-oriented PE substrates through vacuum deposition. An electron mobility of 0.2 cm2 V−1 s−1 was achieved based on such epitaxially-crystallized F-NDI films, which is 4 times higher than that of its un-oriented thin film devices.

An anthracene derivative, 2,6-diphenyl anthracene (DPA), was successfully synthesized with three simple steps and a high yield. The compound was determined to be a durable high performing semiconductor with thin film device mobility over 10 cm2 V−1 s−1. The efficient synthesis and high performance indicates its great potential in organic electronics.

By introducing phenyl groups into the 2- and 6-positions of 11,11,12,12-tetracyano-9,10-anthraquinodimethane, a material (dP-TCAQ) with aggregation-induced emission enhancement (AEE) characteristics was synthesized. The AEE phenomenon was explained by analysis of its solid-state packing mode. To our best knowledge, this is the first report regarding 11,11,12,12-tetracyano-9,10-anthraquinodimethane with AEE behaviour.

A series of acceptor–donor–acceptor (A–D–A) conjugated molecules based on naphthalene diimide dimers bridged with different π-conjugated heterocyclic units (NDI–π–NDI) have been designed and synthesized. By an ingenious design strategy, the LUMO (the lowest unoccupied molecular orbital) of the NDI-based small molecules is well controlled to a relatively constant value of −3.8 to −3.9 eV, whereas their HOMO (the highest occupied molecular orbital) could be tuned over a wide range, from −6.5 eV (compound 1) to −5.5 eV (compound 5), leading to varied band gaps from 2.6 eV to 1.5 eV. Organic field-effect transistor (OFET) characterization of these NDI–π–NDI molecules shows that compounds 1, 2, and 3 have good n-type semiconducting properties in a N2 atmosphere with the maximum electron mobilities up to 0.15 cm2 V−1 s−1, 0.46 cm2 V−1 s−1 and 0.57 cm2 V−1 s−1, respectively. Compounds 4 and 5, due to the high-lying HOMO levels and reduced energy band gaps, have ambipolar semiconducting properties and OFETs based on 5 show the highest electron and hole mobilities up to 1.23 cm2 V−1 s−1 and 0.0074 cm2 V−1 s−1, respectively. Moreover, the performances are enhanced under thermal treatment because of the increased crystallinity as evidenced by X-ray diffraction (XRD) and atomic force microscopy (AFM). The easily tunable electronic energy levels make the NDI-based semiconductors promising n-channel and ambipolar components in organic devices.

In this manuscript, two chloro-substituted derivatives of indolo[3,2-b]carbazole (ICZ), 2,8-dichloro-indolo[3,2-b]carbazole (CICZ) and 2,8-dichloro-5,11-dihexyl-indolo[3,2-b]carbazole (CHICZ) were designed and synthesized. The only difference between CICZ and CHICZ is at the N-5 and N-11 positions with or without long alkyl side chains. Interestingly, CICZ and CHICZ exhibited similar thermal, optical, and electrochemical properties, while their molecular packing motifs in solid state and corresponding charge transport properties were significantly different. The alkyl chains at N-5 and N-11 positions were proved not only enhancing the solubility and self-organization of the compounds but also shifting the molecular packing from herringbone (CICZ) to one-dimensional π–π stacking (CHICZ). Moreover, nearly no field-effect performance was observed for CICZ, while the mobility of CHICZ was as high as 0.14 cm2 V−1 s−1 for its thin films and 0.5 cm2 V−1 s−1 for its single crystals. These results confirmed that the chemical substitutions are a powerful molecular design tool to tune the molecular packing motifs of organic semiconductors and their corresponding electronic properties.

In the light of the principle of aggregation-induced emission enhancement (AIEE), the rubrene analogue with orange light-emitting properties is designed and synthesized by substituting the phenyl side groups of rubrene with thienyl groups. To the best of our knowledge, this is the first report on the synthesis of rubrene with AIEE behaviour, thus paving the way for the development of light-emitting rubrene derivatives.

A new naphthalene diimide (NDI) derivative with an asymmetric aromatic backbone of 2-tetradecylbenzo[lmn]benzo[4,5]imidazo[2,1-b][3,8]phenanthroline-1,3,6(2H)-trione (IZ0) was designed and synthesized. Low LUMO level, large energy gap, and high thermal stability are characterized for this IZ0 compound. The OFET devices based on an IZ0 semiconductor exhibit typical n-type behavior. Through continuously optimizing the fabrication conditions, high performance n-channel OFETs were fabricated based on IZ0 films and single crystals, with the highest carrier mobility of 0.072 cm2 V−1 s−1 and 0.22 cm2 V−1 s−1, respectively.

The performance of organic field-effect transistors (OFETs) depends not only on the properties of organic semiconductors, gate dielectrics and electrodes, but it is also determined by the nature of the contact interfaces between the different functional components. Therefore, interface engineering to optimize the contacts becomes critically important for the fabrication of high performance OFETs. In this Perspective, representative strategies of interface engineering and the basic requirements for different functional components to enable high performance OFETs are highlighted.

With the rapid development of organic electronics, one-dimensional (1D) organic p–n heterojunctions have attracted increasing interest because of their unique optoelectronic properties and potential as building blocks for sophisticated integrated circuits. Recently, significant progress has been made in the methods for synthesizing or fabricating 1D organic p–n heterojunctions, including two typical types of organic–organic heterojunctions and organic–inorganic heterojunctions. Various device applications have been demonstrated based on these 1D organic heterojunctions with new or enhanced optical and/or electrical properties. This MiniRev highlights the recent remarkable advances in this field with a concise summary of the various preparation methods such as solution process, physical vapor techniques, template and templateless methods, etc., to form segmented, cross-stacked, bilayer, and core–shelled structures. The potential applications of these 1D organic heterojunctions in optoelectronic devices, such as ambipolar transistors, photovoltaics, photodetectors and diodes, are demonstrated in the second part. Finally, the challenges and potential opportunities existing in this field are also deeply discussed.

The development of optical and electrical organic semiconductors is crucial for the construction of integrated optoelectronic devices. Herein, a new anthracene derivative, 2,6-diphenyl-9,10-bis(phenylethynyl)anthracene (DP-BPEA), was designed and synthesized by enlarging the π-conjugation of 9,10-bis(phenylethynyl)anthracene (BPEA) via 2,6-diphenyl substitution. Compared with the parent BPEA molecule, an improved field-effect mobility of 1.37 cm2 V−1 s−1 with a comparable solid fluorescence efficiency of 32% is obtained for DP-BPEA, suggesting its potential applications in integrated optoelectronic devices.

Two novel asymmetric thiophene/pyridine flanked diketopyrrolopyrrole (DPP) based polymers, named PPyTDPP-TT and PPyTDPP-BT were designed, synthesized and applied in organic field-effect transistors (OFETs) and polymer solar cells (PSCs). In contrast to the reported bipyridine flanked DPP, the asymmetric DPP polymers incorporating thiophene/pyridine flankers exhibited narrower bandgaps of ∼1.5 eV and deeper HOMO energy levels, thus leading to a broadened absorption from 500 to 850 nm and were potentially beneficial for low-energy photon harvesting. Both polymers displayed promising ambipolar semiconducting properties. The hole and electron mobilities of PPyTDPP-TT reach 0.48 cm2 V−1 s−1 and 0.18 cm2 V−1 s−1; and PPyTDPP-BT reach 0.55 cm2 V−1 s−1 and 0.08 cm2 V−1 s−1, respectively. Intriguingly, due to their ambipolar properties, two polymers can play an ambipolar role, both as electron donors and acceptors with PC71BM and P3HT in PSCs. Photovoltaic devices based on PPyTDPP-BT as the donor material reach PCEs of 7.56% and achieve 0.59% as the acceptor material, while those based on PPyTDPP-TT reach 5.48% with PC71BM and 0.82% with P3HT, respectively. These results suggest that the adoption of asymmetric flanker DPP polymers can effectively tune the absorption properties of polymers as excellent ambipolar transporting polymers towards high performance in both OFETs and PSCs.