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

In this work, a SnO2/ZnO bilayered electron transporting layer (ETL) aimed to achieve low energy loss and large open-circuit voltage (V-oc) for high-efficiency all-inorganic CsPbI2Br perovskite solar cells (PVSCs) is introduced. The high-quality CsPbI2Br film with regular crystal grains and full coverage can be realized on the SnO2/ZnO surface. The higher-lying conduction band minimum of ZnO facilitates desirable cascade energy level alignment between the perovskite and SnO2/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 SnO2/ZnO-based CsPbI2Br PVSCs after being heated at 85 degrees 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.