Self-Cleaning Transparent Photovoltaic p–n Junction Based on CuAlO2/Tm/Bi2O3/ZnO Nanoarrays

Self-cleaning transparent photovoltaic p–n junctions in CuAlO2/Tm/Bi2O3/ZnO nanoarrays are prepared via a method involving sol–gel annealing, followed by chemical and hydrothermal treatments. CuAlO2/Tm/Bi2O3/ZnO exhibits a transmittance of ∼85–90%, photovoltaic enhancement of ∼2.8 × 103-fold (photovoltaic conversion efficiency of ∼1.12%), stable output in a 6-month cycle, and decent self-cleaning performance (∼85%/25 min). The promising performance of this material can mainly be attributed to multifunctional Tm/Bi2O3 nanoparticles, the appropriate Fermi level, and high quantum yield, which can improve carrier kinetic equilibrium for optimizing photovoltaic conversion/transparency, as supported by density functional theory calculations. The upconversion fluorescence of Tm-doping can further improve solar efficiency and achieve good self-cleaning performance. Extra hole carriers caused by Cu vacancies can promote kinetic equilibrium, whereas ZnO orderly nanoarrays with higher Young's modulus and hydrophilicity can further improve the photovoltaic stability and self-cleaning performance.