Multifunctional Polymer Capping Frameworks Enable High-Efficiency and Stable All-Inorganic Perovskite Solar Cells

All-inorganic perovskite solar cells (PSCs) have shown great potential to balance the efficiency and stability of traditional organic–inorganic hybrid species. However, arising from the rapid crystal nucleation rate and soft lattice of perovskite crystals, solution-processed film fabrication technology generally leads to morphologic flaws, including defective grain boundaries (GBs) and surfaces, which in turn accelerate perovskite phase decomposition upon persistent stimuli and then reduce the photovoltaic performance of PSCs. Herein, polymeric poly(vinylpyrrolidone) (PVP) with enormous functional carbon–oxygen groups is introduced into the CsPbIBr2 precursor as a multifunctional polymer capping framework to effectively improve the film quality and heal the lattice defects (uncoordinated Pb2+). By carefully maximizing the film crystallization and grain coverage, a significantly enhanced PCE of 10.54% coupled with the remarkably enhanced stability under air (≤20% relative humidity, >99% retention for 100 days) for a carbon-electrode-based device is achieved. This work paves a comprehensive promotion strategy for the development of perovskite-based optoelectronics.