Interfacial and Doping Synergistic Effect of Versatile Potassium Acetate toward Efficient CsPbI2Br Perovskite Solar Cells

The functional material-based interface and additive engineering are considered as valid approaches to enhance the photovoltaic performance of perovskite solar cells (PSCs). However, most of these materials have been reported to play only one role in PSCs. Herein, we applied versatile potassium acetate (KAc) as the cathode buffer layer (CBL), electron transporting layer (ETL), and perovskite additive in all-inorganic CsPbI2Br PSCs, respectively. All the KAc-incorporated devices yield higher efficiency than the control device. Especially, we achieve the interfacial and doping synergistic effects by introducing KAc CBL between SnO2 ETL and CsPbI2Br perovskite. For the interfacial effect, the KAc CBL can passivate the Sn-related defects and optimize the interfacial energy-level alignment at the SnO2/CsPbI2Br contact. For the doping effect, KAc is partially doped into CsPbI2Br during spin-coating of the perovskite precursor solution due to its good solubility in the solvent of perovskite precursor, which results in the passivation of uncoordinated Pb2+ in the perovskite layer. Owing to the interfacial and doping synergistic effect, the power conversion efficiency (PCE) increases noticeably from 12.91% to 15.71% after inserting KAc CBL. Furthermore, the device with KAc CBL exhibits superior long-term thermal stability. The findings offer a versatile material to simultaneously passivate interfacial and bulk defects and thus enhance the performance of all-inorganic PSCs.