Bandgap engineering of CuO/TiO2 nanocomposites and their synergistic effect on the performance of dye-sensitized solar cells

The study presents CuO/TiO2 nanocomposites synthesized via the sol gel method to modify the optical reactivity of TiO2 from UV to visible spectrum. Different weight percentages (10, 20, 30 wt%) of CuO in TiO2 are investigated. Structural analysis confirms the transition from anatase to rutile phase with increasing CuO content and nanocomposite crystallite sizes ranging from 15.63 nm to 17 nm. Additionally, EDX mapping, Raman and XPS analysis confirm the formation and composition of CuO/TiO2. UV-DRS demonstrates enhanced visible light absorption in 20 wt% CuO/TiO2 compared to others. This is evident in a significant reduction in band gap energy to 2.25 eV. The observed low PL intensity of 20 wt% CuO/TiO2 suggests that it is particularly efficient at trapping electrons with a reduced charge carrier recombination. Theoretical investigation on the influence of Cu2+ on to the TiO2 lattice is explored. The DSSCs using 20 wt% CuO/TiO2 coupled with natural dye sensitizer has achieved an efficiency of 3.43% under LED illumination of 20 mW/cm2. Impedance measurements indicate a decreased charge transfer resistance, highlighting 20 wt% CuO/TiO2 as a promising candidate for photoanode in DSSC.