Constructing Interfacial Prestress to Achieve Homogeneously Strained Perovskites

Vertically inhomogeneous strain within perovskite crystalline layers remains a critical challenge for achieving high efficiency and enhanced stability in perovskite solar cells. Herein, we address this issue by integrating ascorbyl glucoside into hydrothermally synthesized TiO₂ nanocrystals from TiCl₄ to reduce the surface energy of the TiO₂ electron transport layer. The reduced surface energy establishes a liquid/solid/air interface, creating a dewetting effect to trigger stressed perovskite lattice at the bottom region. This design aligns with the liquid/air interface at the top, typically accompanied by formation of an inevitably strained top surface of the perovskite crystals. By precisely controlling the crystallization conditions of the liquid/solid/air interface, we successfully achieved a compressively strained perovskite film that is homogeneously strained throughout the out-of-plane direction. This uniformly strained perovskite film exhibits a significant efficiency, along with remarkable operational stability, maintaining over 95% of its initial efficiency (T95) for over 2,000 hours.