Interface Engineering for All‐Inorganic CsPbI2Br Perovskite Solar Cells with Efficiency over 14%

Abstract In this work, a SnO 2 /ZnO bilayered electron transporting layer (ETL) aimed to achieve low energy loss and large open‐circuit voltage ( V oc ) for high‐efficiency all‐inorganic CsPbI 2 Br perovskite solar cells (PVSCs) is introduced. The high‐quality CsPbI 2 Br film with regular crystal grains and full coverage can be realized on the SnO 2 /ZnO surface. The higher‐lying conduction band minimum of ZnO facilitates desirable cascade energy level alignment between the perovskite and SnO 2 /ZnO bilayered ETL with superior electron extraction capability, resulting in a suppressed interfacial trap‐assisted recombination with lower charge recombination rate and greater charge extraction efficiency. The as‐optimized all‐inorganic PVSC delivers a high V oc of 1.23 V and power conversion efficiency (PCE) of 14.6%, which is one of the best efficiencies reported for the Cs‐based all‐inorganic PVSCs to date. More importantly, decent thermal stability with only 20% PCE loss is demonstrated for the SnO 2 /ZnO‐based CsPbI 2 Br PVSCs after being heated at 85 °C for 300 h. These findings provide important interface design insights that will be crucial to further improve the efficiency of all‐inorganic PVSCs in the future.