The aim of this study is to describe the performance of the aluminum oxide nanoparticle and metal aluminate spinel nanoparticle as photo-anodes in quantum dot photovoltaic. By using a sol–gel auto combustion method, Al₂O₃ NPs, CoAl₂O₄, CuAl₂O₄, NiAl₂O₄, and ZnAl₂O₄ were successfully synthesized. The formation of Al₂O₃ NPs and MAl₂O₄ (M=Co, Cu, Ni, Zn) nanocomposite was confirmed by using several characteristics such as XRD, UV–Vis, FTIR, FE-SEM, and EDX spectra. The XRD shows that the CoAl₂O₄ has a smaller crystallite size (12.37 nm) than CuAl₂O_4, NiAl₂O₄, and ZnAl₂O₄. The formation of a single-phase spinel structure of the calcined samples at 1100 °C was confirmed by FTIR. Our studies showed that the pure Al₂O₃ NP_s have a lower energy gap (1.37 eV) than synthesized MAl₂O₄ under UV–Vis irradiation. Due to the well separation between the light-generated electrons and the formed holes, the cell containing ZnAl₂O₄ nanocomposite with CdS QDs has the highest efficiency of 8.22% and the current density of 22.86 mA cm⁻², while the cell based on NiAl₂O₄ as a photoelectrode, six cycles of CdS/ZnS QDs, and P-rGO as a counter electrode achieved the best (PCE) power conversion efficiency of 15.14% and the current density of 28.22 mA cm⁻². Electrochemical impedance spectroscopy shows that ZnAl₂O₄ and NiAl₂O₄ nanocomposites have the highest life times of the photogenerated electrons (τ_n) of 11*10⁻² and 96*10⁻³ ms, respectively, and the lowest diffusion rates (K_eff) of 9.09 and 10.42 ms⁻¹, respectively.