Tensile strain regulation via grain boundary buffering for flexible perovskite solar cells.

Flexible perovskite solar cells show promise in photovoltaics due to their high energy-to-power efficiency and adaptability, making them a top choice for third-generation thin-film solar applications. However, the inherent defect and mechanical fragility of polycrystalline films posed a challenge that limited their photovoltaic and mechanical performance. Here, the nanomechanical properties of perovskite films are regulated to varying degrees by introducing metal chelates. Specifically, the metal chelates are embedded into the grain boundaries of perovskite, thereby creating a uniformly distributed tensile strain field. Through nanomechanical investigations of the tensile strain-induced modifications in the microstructure and photovoltaic performance of perovskite films, the flexible perovskite solar cells achieve a power conversion efficiency of 24.47%. This regulation strategy not only focuses on the nanomechanical properties of perovskite films but also reveals the correlation between the physical properties and the mechanical flexibility of perovskite solar cells.