Molecule stapling-assisted fabrication of high-quality CsPbI₂Br films for efficient and stable photovoltaic modules

CsPbI₂Br perovskite films have a suitable band gap for the fabrication of tandem solar cells and excellent thermal stability. However, their halide phase separation and water instability lead to challenges for the practical industrialization of CsPbI₂Br perovskite solar cells (PSCs). Here, a molecule stapling strategy is demonstrated to assist the fabrication/stabilization of a high-quality large-area CsPbI₂Br film by using a series of cesium perfluorodioate salts. According to density functional theory and experimental attempts, hexafluoroglutarate anions possessed a stronger interaction between chelated oxygen and surface Pb²⁺ ions due to the matchable stapling configuration, which effectively improved moisture tolerance, reduced defects and further improved the phase stability of the CsPbI₂Br films. In the prepared high-quality CsPbI₂Br films, the fabricated PSCs achieved 16.4% efficiency in a small area. The devices displayed high stability, retaining 92.9% of their initial efficiency for more than 400 h under 85 °C and N₂ conditions and 91% of their initial efficiency for 300 h at a relative humidity of 30% without encapsulation. More importantly, this developed strategy can be employed for the production of large-area perovskite solar modules. A mini perovskite solar module with an efficiency up to 12.35% in a large area of 16 cm² was successfully fabricated.