Enhanced charge-transportation properties of low-temperature processed Al-doped ZnO and its impact on PV cell parameters of organic-inorganic perovskite solar cells

The present work highlights the potential of low-temperature processed Al-doped ZnO (AZO) nanoparticles (NPs) for application in organic-inorganic perovskite solar cells (PSCs). ZnO nanostructured electron-transporting layer (ETL)-based PSCs are superior to ZnO film-based PSCs owing to their relatively lower cost, simpler deposition process, milder sintering temperatures, and higher electron mobility. Moreover, the PSCs based on ZnO nanostructure ETLs are more stable than ZnO film-based PSCs because perovskite films can be easily decomposed into PbI₂ during the annealing process. Al doping in ZnO can reduce the recombination at the ETL/perovskite interface. Thus, low-temperature processed AZO NPs were used as the ETLs for PSCs, and the effects of Al doping on the performance and photovoltaic parameters of PSCs were investigated. The lowest transmission loss was observed for the AZO sample with an Al/Zn molar ratio of 2%, while a higher transportation rate was obtained for the Al/Zn molar ratio of 5%. The effectiveness of Al doping was demonstrated by a conversion efficiency (η) of 13.91% for the Al/Zn molar ratio of 2% (η = 12.28% for ZnO). Moreover, the short-circuit current density (from 18.40 to 19.36 mA/cm²) and fill factor (from 67.87 to 71.18%) increased. The value of shunt resistance gradually increased (from ~799 to 1248 Ωcm²) by Al doping. The values of diode ideality factor (from 2.3221 to 2.3175) and reverse saturation current density (from 11.97 × 10⁻¹⁰ to 7.95 × 10⁻¹⁰ A/cm²) decreased by Al doping, indicating a reduction in the recombination loss. The lowest series resistance was obtained for Al/Zn molar ratio of 2%.