Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite

Shulin Chen,Qing Zhao,Jiangyu Li,Jian Cao,Ning Li,Peng Gao,Jingmin Zhang,Yue Yu,Ningan Xu,Qian Li,Xinzheng Li,Junlei Qi,Guoli Kong,Ying Zhang,Xiaowei Zhang,Dapeng Yu,Jinjin Zhao,Jicai Feng,Kaihui Liu

doi:10.1038/s41467-018-07177-y

Abstract

Organic–inorganic hybrid perovskites are promising candidates for the next-generation solar cells. Many efforts have been made to study their structures in the search for a better mechanistic understanding to guide the materials optimization. Here, we investigate the structure instability of the single-crystalline CH3NH3PbI3 (MAPbI3) film by using transmission electron microscopy. We find that MAPbI3 is very sensitive to the electron beam illumination and rapidly decomposes into the hexagonal PbI2. We propose a decomposition pathway, initiated with the loss of iodine ions, resulting in eventual collapse of perovskite structure and its decomposition into PbI2. These findings impose important question on the interpretation of experimental data based on electron diffraction and highlight the need to circumvent material decomposition in future electron microscopy studies. The structural evolution during decomposition process also sheds light on the structure instability of organic–inorganic hybrid perovskites in solar cell applications.

Highlights

Organic–inorganic hybrid perovskites are promising candidates for the next-generation solar cells
The single-crystalline nature is further confirmed by synchrotron X-ray diffraction (XRD) (Supplementary Fig. 1b) with the measured (004)c reflection denoted in the pseudo-cubic setting
When MAPbI3 crystal was put into transmission electron microscopy (TEM), the acquired electron diffraction (ED) and fast Fourier transform (FFT) patterns do not match those of a perfect tetragonal perovskite structure

Summary

Introduction

Organic–inorganic hybrid perovskites are promising candidates for the next-generation solar cells. If we can only observe {2h, 2k, 0} diffraction spots along the [001] direction and while the {2h+1, 2k+1, 0} reflections [e.g., (110)] are absent, it is highly likely that the tetragonal perovskite phase has already decomposed into a hexagonal PbI2 structure along the [441] zone axis.

Results

Conclusion