Synergistic crystallization and defect passivation via eco-friendly anti-solvent additives for air-processed high-performance perovskite solar cells

High-quality perovskite films with lower defect density are a prerequisite for realizing high-performance perovskite solar cells. However, the inherent soft lattice properties of perovskites often lead to many defects in the final polycrystalline films, severely impairing device efficiency and stability. In this work, an environmentally friendly anti-solvent-assisted strategy is adopted for the preparation of high-quality perovskite films with low defects in an open-air environment through using biodegradable and enriched carboxymethyl cellulose sodium (CMCCNa) as an additive for green anti-solvent ethyl acetate (EA). Through theoretical calculations and experiments, it was found that the strong interactions between CMCCNa and Pb2+ ions not only effectively regulate the film-forming process of perovskites but also effectively passivate various Pb-related defects in the annealed polycrystalline films, resulting in significantly improved photovoltaic performance and device stability. As a result, the CMCCNa treatment device prepared in an open-air environment exhibits significantly improved VOC and FF, with a champion efficiency of 23.13%, compared with the controlled device with a power conversion efficiencies of 21.04%. Meanwhile, the unencapsulated optimized device also exhibits superior storage and light stability over the controlled device.