Organic Crosslinked Tin Oxide Mitigating Buried Interface Defects for Efficient and Stable Perovskite Solar Cells

Tin dioxide (SnO 2 ) stands as a promising material for the electron transport layer (ETL) in perovskite solar cells (PSCs) attributed to its superlative optoelectronic properties. The attainment of superior power conversion efficiency hinges critically on the preparation of high‐quality SnO 2 thin films. However, conventional nanoparticle SnO 2 colloids often suffer from inherent issues such as numerous oxygen vacancy defects and film non‐uniformity. In this study, we report a strategy to homogenize SnO 2 with reduced defects for high‐performance PSCs. The commercial SnO 2 colloid is modulated with bisphenol S (BPS) crosslinking to achieve a better annealing intermediate state. The phenolic hydroxyl groups on BPS bond with the hydroxyl groups on the SnO 2 surface, passivating defects as well as promoting superb regularity of the films by forming a network of the SnO 2 nanoparticles. Additionally, the sulfone groups on BPS coordinate with Pb 2+ , regulating the crystallization of PbI 2 and FAPbI 3 , which leads to better interface contact at the buried interface. The FAPbI 3 perovskite solar cells based on BPS‐crosslinked SnO 2 layers achieved a champion efficiency of 24.87 % and retained 95 % of their initial PCE after 1000 hours of continuous light soaking under N 2 atmosphere.