Halogen Anion Management in Solution‐Processed Perovskite Films for Efficient Solar Cells

Abstract

Solution processability is a prominent advantage for the commercial fabrication of perovskite solar cells (PSCs). However, ionic side reactions can cause perovskite solutions to age, which greatly limits the industrial prospects for reproducible production of PSCs. Herein, the mechanism of underlying halogen anion side reactions is elucidated and an effective scheme for managing halogen anions is proposed. The oxidation of halogen anions is the main factor of solution aging. The addition of iodine monobromide (IBr) stabilizes the precursor solution by promoting the reverse oxidation reaction. Meanwhile, IBr can manage the loss of halogen anion in perovskite layers, effectively reducing the defect density. Moreover, IBr can improve the crystallization process to prepare perovskite films with large‐sized grains and high crystallinity. As a result, the IBr‐based perovskite solution can be stored for 14 days, the optimal device efficiency (24.05% at 0.09 cm2) and long‐term operational stability are far superior to control samples. By this strategy, a large‐area perovskite solar module with an efficiency of 19.34% is fabricated on the 6 × 6 cm2 substrate. This study is dedicated to providing a strategy for managing halogen anions to inhibit solution aging and improve film quality.