A Novel Strategy for Scalable High‐Efficiency Planar Perovskite Solar Cells with New Precursors and Cation Displacement Approach

Abstract Methylammonium iodide (MAI) and lead iodide (PbI₂) have been extensively employed as precursors for solution‐processed MAPbI₃ perovskite solar cells (PSCs). However, the MAPbI₃ perovskite films directly deposited from the precursor solutions, usually suffer from poor surface coverage due to uncontrolled nucleation and crystal growth of the perovskite during the film formation, resulting in low photovoltaic conversion efficiency and poor reproducibility. Herein, propylammonium iodide and PbI₂ are employed as precursors for solution deposition of propylammonium lead iodide (PAPbI₃) perovskite film. It is found that the precursors have good film formability, enabling the deposition of a large‐area and homogeneous PAPbI₃ perovskite film by a scalable dip‐coating technique. The dip‐coated PAPbI₃ film is then subjected to an organic‐cation displacement reaction, resulting in MAPbI₃ film with high surface coverage and crystallinity. With the MAPbI₃ film as the light absorber, planar PSCs are fabricated, and stabilized power conversion efficiencies of 19.27% and 15.68% can be achieved for the devices with active areas of 0.09 and 5.02 cm², respectively. The technology reported here provides a robust and efficient approach to fabricate large‐area and high‐efficiency perovskite cells for practical application.