Radical reinforced defect passivation strategy for efficient and stable MAPbI3 perovskite solar cells fabricated in air using a green anti-solvent process

Compared with traditional processes for perovskite solar cell (PSC) fabrication using toxic anti-solvents in an inert environment, the air process using a green anti-solvent is significantly more eco-friendly and economical. However, such perovskite films contain more defects owing to moisture and non-optimal anti-solvents. To solve this problem, a new radical-strengthened defect passivation strategy is proposed, for enhancing the electron density of Lewis bases to reduce defect states in perovskite films. By introducing a donor–acceptor structure and free radical to improve the electron donation ability of Cl groups, a stable radical derivative (OTTM) with methoxy and multiple Cl groups was designed and used as a green anti-solvent additive for perovskite passivation. The mechanisms of radical-enhanced defect passivation are uncovered by theoretical and experimental results. As a consequence, a 21% power conversion efficiency with high stability was achieved based on the air process with a green anti-solvent for MAPbI3 PSCs.