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

Abstract CsPbI2Br perovskite solar cells (PSCs) are a suitable bandgap for the fabrication of tandem solar cells and have excellent thermal stability. However, their halide phase separation and water instability lead to challenges for practical industrialization. Here, a molecular stapling strategy is demonstrated to assist in 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 oxyen 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 ~91% of the initial efficiency for more than 1000 h under 85 °C and N2 conditions and ~90% for 2000 h at a relative humidity of 20% 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 12.4% in a large area of 16 cm2 was successfully fabricated.