Ma Wei, Zhang Xu, Xu Zhe, Guo Haizhong, Lu Gang, Meng Sheng
Ningxia Key Laboratory of Photovoltaic Materials, Ningxia University, Yinchuan 750021, People's Republic of China.
Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
ACS Appl Mater Interfaces. 2020 Mar 11;12(10):12275-12284. doi: 10.1021/acsami.9b20988. Epub 2020 Mar 2.
Despite the booming research in organometal halide perovskite solar cells (PSCs) of recent years, considerable roadblocks remain for their large-scale deployment, ranging from undesirable current-voltage hysteresis to inferior device stability. Among various plausible origins of hysteresis, interfacial ferroelectricity is particularly intriguing and warrants a close scrutiny. Here, we examine interfacial ferroelectricity in MAPbI (FAPbI)/TiO and MAPbI/phenyl-C61-butyric-acid-methyl-ester (PCBM) heterostructures and explore the correlations between the interfacial ferroelectricity and the hysteresis from the perspective of nonadiabatic electronic dynamics. It is found that the ferroelectric order develops at the MAPbI/TiO interface owing to the interaction between the polar MA ions and TiO. The polarization switching of the MA ions under an applied gate field would drastically result in different rates in interfacial photoelectron injection and electron-hole recombination, contributing to the undesirable hysteresis. In sharp contrast, ferroelectricity is suppressed at the FAPbI/TiO and MAPbI/PCBM interfaces, thanks to elimination of the interfacial electric field between perovskite and TiO via substitution of strong polar MA (dipole moment: 2.29 debye) by weak polar FA ions (dipole moment: 0.29 debye) and interface passivation, leading to consistent interfacial electronic dynamics and the absence of hysteresis. The present work sheds light on the physical cause for hysteresis and points to the direction to which the hysteresis could be mitigated in PSCs.
尽管近年来有机金属卤化物钙钛矿太阳能电池（PSC）的研究蓬勃发展，但它们在大规模应用方面仍面临诸多障碍，从不良的电流 - 电压滞后到较差的器件稳定性。在各种可能导致滞后的原因中，界面铁电性尤其引人关注，值得深入研究。在此，我们研究了MAPbI（FAPbI）/TiO和MAPbI/苯基 - C61 - 丁酸甲酯（PCBM）异质结构中的界面铁电性，并从非绝热电子动力学的角度探讨界面铁电性与滞后现象之间的相关性。研究发现，由于极性MA离子与TiO之间的相互作用，在MAPbI/TiO界面处形成了铁电有序。在外加栅极电场下，MA离子的极化切换会极大地导致界面光电子注入和电子 - 空穴复合速率不同，从而产生不良的滞后现象。与之形成鲜明对比的是，在FAPbI/TiO和MAPbI/PCBM界面处，铁电性受到抑制，这得益于通过用弱极性FA离子（偶极矩：0.29德拜）取代强极性MA（偶极矩：2.29德拜）以及界面钝化消除了钙钛矿与TiO之间的界面电场，从而导致界面电子动力学一致且不存在滞后现象。本工作揭示了滞后现象的物理原因，并指出了在PSC中减轻滞后现象的方向。
