Co-reporter:Xin Zhang, Sijian Yuan, Haizhou Lu, Huotian Zhang, Pengfei Wang, Xiaolei Cui, Yin Zhang, Qi Liu, Jiao Wang, Yiqiang Zhan, Zhengyi Sun, and Wei Huang
ACS Applied Materials & Interfaces October 25, 2017 Volume 9(Issue 42) pp:36810-36810
Publication Date(Web):October 6, 2017
DOI:10.1021/acsami.7b11168
One-step solution process is the simplest method to fabricate organic–inorganic metal halide perovskite thin films, which however does not work well when employed in the planar-heterojunction (PHJ) solar cells due to the generally poor film morphology. Here we show that hydrazinium chloride can be used as an additive in the precursor solution to produce perovskite films featuring higher coverage and better crystallinity. The light absorption ability and charge carrier lifetime are both significantly improved accordingly. Under the optimal additive ratio, the average power conversion efficiency (PCE) of the inverted PHJ perovskite solar cells greatly increases by as much as 70%, and the champion device shows a satisfying PCE of 12.66%. These results suggest that N2H5Cl is a promising additive for fabricating high-efficiency perovskite solar cells via one-step method, which could be of interest in the future commercial solar cell industry.Keywords: carrier lifetime; hydrazinium salt; inverted planar-heterojunction; morphology; one-step method; perovskite solar cells;
Co-reporter:Wenbin Li, Sijian Yuan, Yiqiang Zhan, and Baofu Ding
The Journal of Physical Chemistry C May 4, 2017 Volume 121(Issue 17) pp:9537-9537
Publication Date(Web):April 10, 2017
DOI:10.1021/acs.jpcc.7b00571
Magneto-photocurrent, namely, magnetic-field-modulated photocurrent, with a single polarity has been observed in perovskite solar cells, and attracted great interest, due to its potential application as a noncontact approach to characterizing and adjusting electro-optic characteristics of perovskite solar cells. Here, we demonstrate that magneto-photocurrent polarity can be tuned between positive and negative ones by adjusting the size of the perovskite crystal domain in perovskite film. The experimental results show that (1) magnetic-field-enhanced intersystem crossing between singlets and triplets, (2) dissociation of the singlets, and (3) diffusion of the triplets have a combined impact on the magneto-photocurrent polarity. Further study reveals that the magnetic-field-induced increase of average dissociation rate and decrease of average diffusion rate lead to negative and positive magneto-photocurrent, respectively. As a result, our investigations on magnetic field effects of perovskite solar cells provide a penetrating insight on the spin-correlated photon-to-charge dynamic process in all perovskite-based optoelectronic devices.
Co-reporter:Haizhou Lu;Huotian Zhang;Sijian Yuan;Jiao Wang;Lirong Zheng
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 6) pp:4516-4521
Publication Date(Web):2017/02/08
DOI:10.1039/C6CP07182A
Recently, perovskite based solar cells have attracted lots of research interest, some of which is in the passivation of perovskite surfaces, particularly the heterojunction based surface passivation. In this study, the optical dynamics of MAPbBr3 single crystals with and without heterojunction passivation were studied systematically by means of a time-resolved spectroscopic technique for the first time. The emission lifetime of MAPbBr3 single crystals under two-photon (1064 nm) excitation is a few orders of magnitude longer than that measured under one-photon (355 nm or 532 nm) excitation. Interestingly, with surface passivation, the lifetime measured at 355 nm excitations could be tuned significantly, whereas the lifetime change under 1064 nm excitations was considerably less. Our results give a direct evidence of surface quench by comparing the lifetimes before and after surface passivation. Furthermore, the results demonstrate that proper MAPbCl3–MAPbBr3 heterojunctions can dramatically reduce the recombination channels in the surface region, which can be potentially useful for perovskite based solar cells, light emitting diodes (LED), and sensitive detectors.
Co-reporter:Li Ling;Sijian Yuan;Pengfei Wang;Huotian Zhang;Li Tu;Jiao Wang;Lirong Zheng
Advanced Functional Materials 2016 Volume 26( Issue 28) pp:5028-5034
Publication Date(Web):
DOI:10.1002/adfm.201601557
Recently, intensive studies on the role of water molecule in the formation of organic–inorganic perovskite film have been reported. However, not only the contradictive phenomena but also the complex processing technique has hindered the widespread use of water molecule in perovskite preparation. Here the hydration water is introduced into the precursors instead of water. By precisely controlling the content of hydration water, a smoother and more uniform perovskite film is obtained through a simple one-step spin coating method. The improvement of perovskite film quality leads to highly efficient planar perovskite solar cells. Summing up the device studies and the investigation of morphology, crystallization, and optical properties, the impact of water molecule in the formation of perovskite crystal and consequences of device performance is understood. Due to its universal adaptability and simplified process, precise control of hydration water is therefore of great utility to high quality perovskite films fabrication and large-scale production of this upcoming photovoltaic technology.
Co-reporter:Zhengyi Sun, Yiqiang Zhan, Shengwei Shi, Mats Fahlman
Organic Electronics 2014 Volume 15(Issue 9) pp:1951-1957
Publication Date(Web):September 2014
DOI:10.1016/j.orgel.2014.05.021
•Donor-type material AOB and acceptor-type material TCNQ can tune the effective work function of Fe.•The interactive spin polarization at organic/Fe interface is investigated by XMCD technique.•The adsorptions of TCNQ and AOB have different influence on the spin polarization of Fe surface.•Detailed magnetic moment of Fe is obtained by the calculation based on XMCD sum rules.•Combination of energy level alignment and spin polarization provides a “full” analysis for the material selection.Energy level alignment and spin polarization at tetracyanoquinodimethane/Fe and acridine orange base/Fe interfaces are investigated by means of photoelectron spectroscopy and X-ray magnetic circular dichroism (XMCD), respectively, to explore their potential application in organic spintronics. Interface dipoles are observed at both hybrid interfaces, and the work function of Fe is increased by 0.7 eV for the tetracyanoquinodimethane (TCNQ) case, while it is decreased by 1.2 eV for the acridine orange base (AOB) case. According to XMCD results, TCNQ molecule has little influence on the spin polarization of Fe surface. In contrast, AOB molecule reduces the interfacial spin polarization of Fe significantly. Induced spin polarization of the two organic molecules at the interfaces is not observed. The results reveal the necessity of investigating the magnetic property changes of both the OSC and the FM during the process of energy level alignment engineering.Graphical abstract
Co-reporter:Yintao You, Kunlong Yang, Sijian Yuan, Shiqi Dong, Huotian Zhang, Qinglan Huang, William P. Gillin, Yiqiang Zhan, Lirong Zheng
Organic Electronics 2014 Volume 15(Issue 9) pp:1983-1989
Publication Date(Web):September 2014
DOI:10.1016/j.orgel.2014.05.032
•A new way to design organic multilevel memory, by combing different physical switching mechanisms.•A simple device structure by using a ferroelectric phase-separated blend as the active layer.•Two switching modes, the ferroelectric switching and filamentary switching, are realized simultaneously in this device, and enable a ternary storage function.•The on–off ratio between the 3 states could be tuned freely and the switching among these states could be realized electrically without any other stimulation.The demand for higher data density memory structures is greater today than ever before. Multilevel resistive organic memory devices (OMD) provide an ideal solution, in being easily fabricated, cost-effective and at the same time promising high storage capacity. However, conventional methods for multilevel OMDs impose demanding requirements on material properties and attain only limited performance. We hereby provide an alternative design concept that combines multiple switching modes in one device to realize multilevel function. The device possesses a simple structure by using a ferroelectric phase-separated blend as the active layer. Two switching modes, the ferroelectric switching and the metallic filament switching, are realized simultaneously in this device, and enable a ternary storage function. The cross-section scanning electron microscope (SEM) images provide a strong evidence of the formation and annihilation of the metallic filament.Graphical abstract
Co-reporter:Yiqiang Zhan;Mats Fahlman
Journal of Polymer Science Part B: Polymer Physics 2012 Volume 50( Issue 21) pp:1453-1462
Publication Date(Web):
DOI:10.1002/polb.23157
Abstract
An overview is given on recent results in organic spintronic research. In particular, so-called spinterfaces, spin-injecting interfaces involving organic semiconductor (OSC) molecules and ferromagnetic metals, are discussed. The interfaces are classified in different categories depending on the type and strength of interface interaction and the relevant physics concerning energy level alignment and spin polarization of interface states are explained. Examples are given on characterization of both interface energetics and spin-related properties obtained from a wide variety of experimental techniques, highlighting the different ways contacting can modify the electronic and magnetic properties of the OSC molecules and the ferromagnetic metals at the resulting spinterfaces. Finally, models for spin injection at spinterfaces are presented and discussed, followed by some speculations on consequences for device design and performance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Co-reporter:Haizhou Lu, Huotian Zhang, Sijian Yuan, Jiao Wang, Yiqiang Zhan and Lirong Zheng
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 6) pp:NaN4521-4521
Publication Date(Web):2017/01/12
DOI:10.1039/C6CP07182A
Recently, perovskite based solar cells have attracted lots of research interest, some of which is in the passivation of perovskite surfaces, particularly the heterojunction based surface passivation. In this study, the optical dynamics of MAPbBr3 single crystals with and without heterojunction passivation were studied systematically by means of a time-resolved spectroscopic technique for the first time. The emission lifetime of MAPbBr3 single crystals under two-photon (1064 nm) excitation is a few orders of magnitude longer than that measured under one-photon (355 nm or 532 nm) excitation. Interestingly, with surface passivation, the lifetime measured at 355 nm excitations could be tuned significantly, whereas the lifetime change under 1064 nm excitations was considerably less. Our results give a direct evidence of surface quench by comparing the lifetimes before and after surface passivation. Furthermore, the results demonstrate that proper MAPbCl3–MAPbBr3 heterojunctions can dramatically reduce the recombination channels in the surface region, which can be potentially useful for perovskite based solar cells, light emitting diodes (LED), and sensitive detectors.
