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.