Double-side modification strategy for efficient carbon-based, all-inorganic CsPbIBr2 perovskite solar cells with high photovoltage

CsPbIBr2 has attracted great attention due to its balanced bandgap and stability features. However, one-step prepared CsPbIBr2 films are generally of poor quality, hindering the performance improvement of the resulting perovskite solar cells (PSCs). Herein, we report the fabrication of high-performance carbon-based, all-inorganic CsPbIBr2 PSCs with a double-side modification strategy using PEAI/PEABr. We tune the crystallization behavior and passivate the defects of CsPbIBr2 films with modifications of their bottom and top surfaces with PEAI and PEABr, respectively. This causes the PEA cation to form a double layer of armor on both sides of the CsPbIBr2 precursor film and can provide the anions of the required I and Br. The collaborative strategy of crystallization and defect passivation for CsPbIBr2 films is exceptionally effective. It produces a fully covered CsPbIBr2 film with an average grain size increase of more than 50%, few grain boundaries, and high crystallinity. Moreover, this strategy also suppresses pinhole formation, reduces the charge trap density, and prolongs the carrier recombination lifetime. Hence, carbon-based all-inorganic PSCs with the desired CsPbIBr2 films yield an optimized efficiency of 9.96% with a particularly high photovoltage of 1.32 V. Our work provides guidance for simultaneous crystallization control and defect passivation to further improve the performance of PSCs.