Optimizing the Performance of CsPbI3-Based Perovskite Solar Cells via Doping a ZnO Electron Transport Layer Coupled with Interface Engineering

Interface engineering has been regarded as an effective and noninvasive means to optimize the performance of perovskite solar cells (PSCs). Here, doping engineering of a ZnO electron transport layer (ETL) and CsPbI₃/ZnO interface engineering via introduction of an interfacial layer are employed to improve the performances of CsPbI₃-based PSCs. The results show that when introducing a TiO₂ buffer layer while increasing the ZnO layer doping concentration, the open-circuit voltage, power conversion efficiency, and fill factor of the CsPbI₃-based PSCs can be improved to 1.31 V, 21.06%, and 74.07%, respectively, which are superior to those of PSCs only modified by the TiO₂ buffer layer or high-concentration doping of ZnO layer. On the one hand, the buffer layer relieves the band bending and structural disorder of CsPbI₃. On the other hand, the increased doping concentration of the ZnO layer improves the conductivity of the TiO₂/ZnO bilayer ETL because of the strong interaction between the TiO₂ and ZnO layers. However, such phenomena are not observed for those of a PCBM/ZnO bilayer ETL because of the weak interlayer interaction of the PCBM/ZnO interface. These results provide a comprehensive understanding of the CsPbI₃/ZnO interface and suggest a guideline to design high-performance PSCs.