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/cm(2), 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.