Crystalline Liquid-like Behavior: Surface-Induced Secondary Grain Growth of Photovoltaic Perovskite Thin Film
Jingjing Xue,1,# Rui Wang,1,# Kai-Li Wang,2,# Zhao-Kui Wang,*,1,2 Ilhan Yavuz,3 Yang Wang,4 Yingguo Yang,5 Xingyu Gao,5 Tianyi Huang,1 Selbi Nuryyeva,1 Jin-Wook Lee,1 Yu Duan,1 Liang-Sheng Liao,*,2 Richard Kaner,1 and Yang Yang*,1
1Department of Materials Science and Engineering and California NanoSystems Institute, University of California Los Angeles, California 90095, United States
2Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, China
3Department of Physics, Marmara University, 34722, Ziverbey, Istanbul, Turkey
4School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China
5Shanghai Synchrotron Radiation Facility (SSRF), Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
Surface effects usually become negligible on the micrometer or sub-micrometer scale due to lower surface-to bulk ratio compared to nanomaterials. In lead halide perovskites, however, their “soft” nature renders them highly responsive to the external field, allowing for extended depth scale affected by the surface. Herein, by taking advantage of this unique feature of perovskites we demonstrate a methodology for property manipulation of perovskite thin films based on secondary grain growth, where tuning of the surface induces the internal property evolution of the entire perovskite film. While in conventional microelectronic techniques secondary grain growth generally involves harsh conditions such as high temperature and straining, it is easily triggered in a perovskite thin film by a simple surface post-treatment, producing enlarged grain sizes of up to 4 μm. The resulting photovoltaic devices exhibit significantly enhanced power conversion efficiency and operational stability over a course of 1000 h and an ambient shelf stability of over 4000 h while maintaining over 90% of its original efficiency.