Sewvandi Galhenage A, Kodera Kei, Ma Hao, Nakanishi Shunsuke, Feng Qi
Department of Materials Science and Engineering, Faculty of Engineering, University of Moratuwa, Katubedda, SriLanka.
Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396, Japan.
Sci Rep. 2016 Jul 29;6:30680. doi: 10.1038/srep30680.
Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.
钙钛矿太阳能电池（PSCs）因其高性能而引起了科学界的关注。一些研究人员认为，由于离子迁移或铁电行为，PSCs对极化存在异常行为。实验结果和理论计算表明，有机-无机钙钛矿中存在铁电性的可能性。然而，仍没有研究具体排除PSCs中钙钛矿吸收层的铁电性质。P-E（极化-电场）回线的滞后现象是确认铁电性的重要证据。在本研究中，对CH3NH3PbI3-xClx钙钛矿进行了P-E回线测量、深入的结构研究、介电行为分析以及相变研究。结果表明，CH3NH3PbI3-xClx钙钛矿在室温下处于反铁电相。通过极化处理可将反铁电相转变为铁电相，并在室温附近表现出类似铁电的滞后P-E回线和介电行为；也就是说，钙钛矿在PSCs工作条件下可产生铁电极化。此外，我们还讨论了铁电极化对PSCs电荷分离的影响。
