Improved Open-Circuit Voltage of AZO/CsPbBr3/Carbon Structure Perovskite Solar Cells by an Al-Doped ZnO Electron Transport Layer

The ZnO/CsPbBr3 heterojunction interface often has poor chemical stability, resulting in the low photovoltaic efficiency of the solar cell. Here, we reported a method to fabricate an electron transport layer (ETL) using an Al element-doped ZnO (AZO) sol to improve the interfacial defects of the ZnO/CsPbBr3 heterojunction. The results showed that the interfacial defects first decreased and then increased with the change of the Al element ratio from 0 to 10%. The device had the least interfacial defects by 7% (atomic ratio) Al doping into ZnO. A 1.27 V open-circuit voltage (VOC) and 6.25% photoelectric conversion efficiency (PCE) were achieved by 7% Al element doping into ZnO in a ZnO/CsPbBr3/carbon structure solar cell. Moreover, the interfacial defect distribution and carrier recombination mechanism of the device were, respectively, illustrated by a varying light intensity test and electrochemical impedance spectroscopy. This work showed that an Al-doped ZnO film prepared by a sol–gel method could significantly improve the performance of solar cells.