Interface Engineering for All-Inorganic CsPbIBr₂ Perovskite Solar Cells with Enhanced Power Conversion Efficiency over 11%

Perovskite solar cells (PVSCs) receive great attention due to their excellent photovoltaic performance. Recently, all-inorganic PVSCs have been extensively studied owing to their superior thermal and photo stability. Among them, CsPbIBr₂ perovskite stands out due to its superb phase stability in ambient environment. However, the severe energy loss caused by non-radiative recombination limits its development. Herein, a facile interface engineering method is employed to modify the electron transporting interface and reduce the energy loss. The insertion of a thin polyethylenimine ethoxylated (PEIE) film between SnO₂ and the perovskite can simultaneously tune the work function of SnO₂ and passivate the defects of the perovskite by the amino group in PEIE. Meanwhile, the PEIE interface serves as a modifier to enhance the crystallinity of the perovskite film, leading to enlarged grain size and reduced grain boundaries. As a result, the power conversion efficiency was enhanced from 8.7% for the SnO₂-based device to 11.2% for the SnO₂/PEIE-based device, with an open-circuit voltage of 1.29 V, a short-circuit current of 11.0 mA/cm², and a fill factor of 78.6%. Moreover, the photostability of devices were improved, which retained over 80% of its initial efficiency under continuous one sun illumination for 500 h. This work proves the effectiveness of interface engineering to boost the efficiency and stability of all-inorganic PVSCs.