Green anti-solvent for efficient and stable larger-size perovskite solar cells and modules

Metal halide perovskites have obtained efficiency more than 26% when applied in small area solar cells, yet maintaining efficiency and stability while scaling area remains a challenge. Anti-solvent treatment is a simple and reliable method to fabricate high quality perovskite films in the lab. However, most of anti-solvents used for larger area perovskite films are toxic halogenated solvent and the studies on green anti-solvent are rare. Herein, we scrutinize the choice of green anti-solvent in the fabrication of larger-area perovskite films for solar modules by examining their intrinsic properties. We choose three green anti-solvents with stepwise change of saturation vapor pressures and boiling points, i.e. ethyl acetate, trifluorotoluene, and anisole to study their impact to the perovskite film morphology, optoelectronic properties, and device performance. We find that perovskite films made with trifluorotoluene having a moderate saturation vapor pressure and boiling point present a more compact morphology, a longer carrier lifetime, and a better performance when assembled in cm-size solar cells and modules. As a result, we achieve champion efficiencies of 19.3% and 18.0% with mask areas of 1.0 cm2 and 10.0 cm2 under AM 1.5G illumination. Moreover, the non-encapsulated devices retained more than 95% of their initial efficiencies after 500 h at ambient condition (ISOS-D-1). These results provide a simple and reproducible procedure for perovskite solar module fabrication in the lab.