Stress Regulation via Surface Micro-etching and Reconstruction for Enhancing Triple-Cation Perovskite Solar Cells with the Efficiency of 25.54%

Residual stresses generated within perovskite films during the high-temperature annealing and cooling process are the key contributors to reduce device performance and lifespan deterioration. Herein, a strategy of surface micro-etching and reconstruction is developed to regulate the stresses in triple-cation (formamidine, methylamine, cesium) perovskite film. Precise stoichiometric mixture of L-lactic acid (LA) and isopropanol (IPA) is used to controllably dissolve the surface of perovskite film, followed by octylammonium iodide (OAI) post-treatment, enabling a sinking reconstruction of 2D perovskite from surface to bulk phase and achieving a benign transition from surface tensile stress to compressive stress, as well as a more matchable interface energy level. As a result, the target perovskite solar cells (PSCs) yield an obviously enhanced power conversion efficiency (PCE) of 25.54%, which is the highest reported PCE for triple-cation PSCs. Meanwhile, PSC modules with 10.4 cm2 achieve a PCE of 21.02%. Furthermore, the surface micro-etched and reconstructed PSCs exhibit superior stability, and the PSC devices without encapsulation can maintain 83% of original efficiency after 500 hours illumination at maximum power point (MPPT) tracking in N2 atmosphere. The research provides a valuable avenue to improve PSC stability and efficiency by regulating residual stresses through surface micro-etching and reconstruction.