Xia Guozhan, Huang Boyuan, Zhang Ying, Zhao Xingyu, Wang Chen, Jia Chunmei, Zhao Jinjin, Chen Weiqiu, Li Jiangyu
Department of Mechanical Engineering, University of Washington, Seattle, WA, 98195-2600, USA.
Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
Adv Mater. 2019 Sep;31(36):e1902870. doi: 10.1002/adma.201902870. Epub 2019 Jul 19.
Triple-cation mixed-halide perovskites of composition Cs (FA MA ) Pb(I Br ) (CsFAMA) have been reported to possess excellent photovoltaic efficiency with minimal hysteresis; in this work, nanoscale insight is shed into the roles of illumination-induced polarization and ionic migration in photovoltaic hysteresis. By examining the concurrent evolution of ionic distribution and spontaneous polarization of CsFAMA under light illumination using dynamic-strain-based scanning probe microscopy, strong linear piezoelectricity arising from photoenhanced polarization is observed, while ionic migration is found to be not significantly increased by lightening. Nanoscale photocurrents are mapped under a series of biases using conductive atomic force microscopy, revealing negligible difference between forward and backward scans, and local IV curves reconstructed from principal component analysis show minimal hysteresis of just 1%. These observations at the nanoscale are confirmed in a macroscopic perovskite solar cell made of CsFAMA, exhibiting a high efficiency of 20.11% and with hysteresis index as small as 3%. Ionic migration, polarization, and photocurrent hysteresis are thus directly correlated at the nanoscale, and photoenhanced polarization in triple-cation mixed-halide perovskites is established, which does not contribute to the photovoltaic hysteresis.
据报道，组成为Cs(FA MA ) Pb(I Br )（CsFAMA）的三阳离子混合卤化物钙钛矿具有出色的光伏效率且滞后极小；在这项工作中，对光照诱导极化和离子迁移在光伏滞后中的作用进行了纳米尺度的深入研究。通过使用基于动态应变的扫描探针显微镜检查光照下CsFAMA的离子分布和自发极化的同时演变，观察到光增强极化产生的强线性压电性，而发现光照并未显著增加离子迁移。使用导电原子力显微镜在一系列偏压下绘制纳米级光电流图，揭示正向和反向扫描之间的差异可忽略不计，并且从主成分分析重建的局部IV曲线显示滞后极小，仅为1%。在由CsFAMA制成的宏观钙钛矿太阳能电池中证实了这些纳米级观察结果，该电池表现出20.11%的高效率且滞后指数低至3%。因此，离子迁移、极化和光电流滞后在纳米尺度上直接相关，并且在三阳离子混合卤化物钙钛矿中建立了光增强极化，其对光伏滞后没有贡献。
