Critical Role of Organoamines in the Irreversible Degradation of a Metal Halide Perovskite Precursor Colloid: Mechanism and Inhibiting Strategy
Qingshun Dong, Wenzhe Shang, Xiaoqiang Yu, Yanfeng Yin, Chen Jiang, Yulin Feng, Jiming Bian, Bo Song, Shengye Jin, Yuanyuan Zhou, Liduo Wang, Yantao Shi
Abstract
Solution processability enables perovskite solar cells (PSCs) as a potentially advantageous candidate over the conventional vacuum-based photovoltaic technologies. Nevertheless, the stability issue of the metal halide perovskite (MHP) precursor colloids seriously retards the future industrialization of PSCs. Herein we elucidate the key role of organoamines─deprotonated organoamine cations─in the degradation of the most commercially promising formamidinium/methylammonium (FA+/MA+) mixed cation MHP precursor and determine that the amine-cation reaction of FA-MA+, rather than MA-FA+, is the main route triggering the irreversible degradation process. Subsequently, based on Schiff-base reactions, aldehydes (such as formaldehyde, benzaldehyde, and 3-thenaldehyde) are used to eliminate organoamines for effective suppression of the irreversible degradation of precursors and passivation of H-vacancy traps in the resultant MHP thin films. Furthermore, the optimal benzaldehyde can lead to reduced grain-boundary density to enhance the power conversion efficiency of PSCs from 20.7% to 23.3% with simultaneous improvement in the operational stability.