Moisture-driven phase transition for improved perovskite solar cells with reduced trap-state density

作     者：Swaminathan Venkatesan Fang Hao Junyoung Kim Yaoguang Rong Zhuan Zhu Yanliang Liang Jiming Bao Yan Yao 

作者机构：Department of Electrical and Computer Engineering and Materials Science and Engineering Program University of Houston Houston Texas 77204 USA Texas Center for Superconductivity at the University of Houston Houston Texas 77204 USA 

出 版 物：《Nano Research》 (纳米研究（英文版）)

年 卷 期：2017年第10卷第4期

页      面：1413-1422页

核心收录：

学科分类：07[理学] 

基　　金：Acknowledgements Y. Y. acknowledges TcSUH Core Funding. The authors acknowledge the support of Steve Ziegler and Dr. Gilbert Min for help with KPFM imaging. J. M. B. acknowledges support from the National Science Foundation (No. ECCS-1240510) and the Robert A. Welch Foundation (No. E-1728) 

主　　题：perovskite solar cells phase transition moisture treatment film growth 

摘      要：We report a mechanistic understanding of a moisture-driven intermediate-phase transition that improves the quality of perovskite thin films based on a lead-acetate precursor, improving the power-conversion effidency. We clarify the composition of the intermediate phase and attribute the transition of this phase to the hygroscopic nature of the organic product, i.e., methylammonium acetate. Thermal annealing aids in the coarsening of the grains. These decoupled processes result in better crystal formation with a lower spatial and energetic distribution of traps. Thermal annealing of the films without exposure to air results in a faster intermediate-phase transition and grain coarsening, which occur simultaneously, leading to disorder in the films and a higher deep trap-state density. Our results indicate the need for a humid environment for the growth of high-quality perovskite films and provide insight into intermediate-phase dissociation and conversion kinetics. Thus, they are useful for the large-scale production of effident solution-processed perovskite solar cells.