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

Tin dioxide (SnO₂) 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 SnO₂ thin films. However, conventional nanoparticle SnO₂ 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 SnO₂ with reduced defects for high-performance PSCs. The commercial SnO₂ 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 SnO₂ surface, passivating defects as well as promoting superb regularity of the films by forming a network of the SnO₂ nanoparticles. Additionally, the sulfone groups on BPS coordinate with Pb²⁺, regulating the crystallization of PbI₂ and FAPbI₃, which leads to better interface contact at the buried interface. The FAPbI₃ perovskite solar cells based on BPS-crosslinked SnO₂ layers achieved a champion efficiency of 24.87 % and retained 95 % of their initial PCE after 1000 hours of continuous light soaking under N₂ atmosphere.