Perovskite solar cells have drawn much attention in recent years, owing to its world-record setting photovoltaic performances. Despite its promising use in tandem applications and flexible devices, its practicality is still limited by its structural instability often arising from ion migration and defect formation. While it is generally understood that ion instability is a primary cause for degradation, there is still a lack of direct evidence of structural transformation at the atomistic scale. Such an understanding is crucial to evaluate and pin-point how such instabilities are induced relative to external perturbations such as illumination or electrical bias with time, allowing researchers to devise effective strategies to mitigate them. Here, we designed an in-situ TEM setup to enable real-time observation of amorphization in double cation mixed perovskite materials under electrical biasing at 1 V. It is found that amorphization occurs along the (001) and (002) planes, which represents the observation of in-situ facet-dependent amorphization of a perovskite crystal. To reverse the degradation, the samples were heated at 50 oC and was found to recrystallize, effectively regaining its performance losses. This work is vital toward understanding fundamental ion-migration phenomena and address instability challenges of perovskite optoelectronics.
@article{arxiv.2010.12509,
title = {Imaging real-time amorphization of hybrid perovskite solar cells under electrical biasing},
author = {Min-cheol Kim and Namyoung Ahn and Diyi Cheng and Mingjie Xu and Xiaoqing Pan and Suk Jun Kim and Yanqi Luo and David P. Fenning and Darren H. S. Tan and Minghao Zhang and So-Yeon Ham and Kiwan Jeong and Mansoo Choi and Ying Shirley Meng},
journal= {arXiv preprint arXiv:2010.12509},
year = {2020}
}