Top‐Down Induced Crystallization Orientation toward Highly Efficient p‐i‐n Perovskite Solar Cells

Abstract Crystallization orientation plays a crucial role in determining the performance and stability of perovskite solar cells (PVSCs), whereas effective strategies for realizing oriented perovskite crystallization is still lacking. Herein, a facile and efficient top‐down strategy is reported to manipulate the crystallization orientation via treating perovskite wet film with propylamine chloride (PACl) before annealing. The PA + ions tend to be adsorbed on the (001) facet of the perovskite surface, resulting in the reduced cleavage energy to induce (001) orientation‐dominated growth of perovskite film and then reduce the temperature of phase transition, meanwhile, the penetrating Cl ions further regulate the crystallization process. As‐prepared (001)‐dominant perovskite films exhibit the ameliorative film homogeneity in terms of vertical and horizontal scale, leading to alleviated lattice mismatch and lowered defect density. The resultant PVSC devices deliver a champion power conversion efficiency (PCE) of 25.07% with enhanced stability, and the unencapsulated PVSC device maintains 95% of its initial PCE after 1000 h of operation at the maximum power point under simulated AM 1.5G illumination.