Idealizing Air‐Processed Perovskite Film Competitive by Surface Lattice Etching‐Reconstruction for High‐Efficiency Solar Cells

Air-processed perovskite solar cells are desirable for the large-scale manufacturing application in the future, yet the presence of moisture and oxygen goes against perovskite crystallization and deteriorates phase stabilization, leading to the formation of substantial defective nano-impurities, especially on the vulnerable surface. Here, we propose a strategy to simultaneously remove superficial defect layer and solidify the surface by soaking air-fabricated perovskite film into low-polar organic esters at elevated temperature to trigger an in situ dynamic surface lattice disassemble and reconstruction process. Molecular dynamics simulations and experimental results indicate that the inorganic CsPbI₂Br perovskite is first dissolved and then the Br-rich phase is recrystallized at solid-liquid interface owing to the balance between weak solubility and high-temperature induced annealing process, thus hardening the soft surface and releasing the lattice tensile stress, which benefits the minimization of interfacial recombination and improvement of the structural stability. As a result, we prepare a carbon-based CsPbI₂Br device in complete air without precise control on humidity, achieving a champion efficiency of 15.37 % with excellent resistance to harsh attackers. This method offers a promising avenue for overcoming the limit of processing conditions on advancing perovskite-based optoelectronic devices.