Rapid efficiency loss of FAPbI3 perovskite solar cells in 2-methoxyethanol-based precursor solutions

Abstract

N,N-Dimethylformamide (DMF)-free perovskite precursor solution systems have attracted significant attention due to their potential to enhance the quality of large-area perovskite films. However, the complexity and instability of these systems make it challenging to control the film quality during aging, which affects the phase purity and optoelectronic properties of the perovskite films in a time-dependent manner. In this work, we investigate the effects of precursor solution aging on the performance of FAPbI₃-based PSCs prepared using a 2-methoxyethanol (2-ME) solvent. 2-ME-based perovskite precursor solutions exhibit rapid degradation, significantly impacting device efficiency within just several hours. Through morphological, structural, and in situ optical characterization, we identify the formation of PbI₂-impurity as an intermediate product prior to the widely reported N-methylformamidinium lead triiodide (MFAPbI₃). This impurity hinders the formation of the α-FAPbI₃ phase, deteriorating film morphology and reducing crystallinity and phase purity, due to the participation of methylammonium chloride (MACl) in the aging process. Sequential incorporation can avoid the adverse effects of aging and enhance device efficiency. This study highlights the importance of understanding and controlling precursor solution aging to optimize perovskite film quality and device performance, offering valuable insights applicable to other perovskite precursor solution systems.