Air Annealing Facilitates Crystallization Reconstruction of Quasi-2D Perovskite

Although the photovoltaic performance of perovskite solar cells (PSCs) has reached commercial standards, the processing environment of a purely inert gas atmosphere significantly increases the cost of installing manufacturing facilities in actual manufacturing plants and hinders their commercial mass production. The thermal annealing condition of quasi-2D perovskite films can significantly affect the self-assembly behavior of bulky organic cations, which modulates the phase distribution of 2D species with different n values. Herein, the properties of quasi-2D perovskite annealing in a N₂ versus an environment representative of industrial conditions, i.e., open-air with 30% humidity are compared. It is found that the crystallization process of perovskites is regulated by air annealing, leading to high-quality 2D perovskite films with reduced trap density, well-aligned phase distribution, and released residual strain. The resulting devices prepared by air annealing achieve a power conversion efficiency of 18% with high reproducibility and suppressed voltage loss. The enhanced thermal stability of the air-annealed films is proved by in situ grazing incidence wide-angle X-ray scattering. The combination of air annealing and simple planar structures would facilitate the mass production of PSCs.