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

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, we elucidate the mechanism of underlying halogen anion side reactions and propose an effective scheme for managing halogen anions. The oxidation of halogen anions is the main factor of the solution aging. 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 size 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 cm 2 ) 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% was fabricated on the 6 × 6 cm 2 substrate. This study is dedicated to providing a strategy for managing halogen anions to inhibit solution aging and improve film quality. This article is protected by copyright. All rights reserved.