TiO2-ZnO rodlike nanocomposite as photoanode in DSSC yielding 7.38% power conversion efficiency with N3 dye

TiO₂-ZnO nanocomposites synthesised via a simple direct chemical precipitation route were investigated as composition controlled photoanodes in dye-sensitized solar cells (DSSCs) operating under low irradiance conditions. A systematic examination of the TiO₂:ZnO molar ratio impact on structural, morphological, optical, and photovoltaic properties was conducted. X-ray diffraction confirmed the presence of both rutile TiO₂ and hexagonal wurtzite ZnO phases, without any secondary phases being formed, while electron microscopy showed interconnected nanorod assemblies, most pronounced in the TiO₂ rich composite with a 3:1 molar ratio (AB3). A gradual red shift and reduction in the effective optical bandgap from 3.10 to 2.95 eV across a composite series were observed using UV-visible spectroscopy, and were attributed to interfacial and defect related electronic states rather than a modification to the bulk band structure. X-ray photoelectron spectroscopy confirmed the expected oxidation states of Ti and Zn, with O 1s asymmetry indicating oxygen-vacancy-related or interfacial states. DSSCs made with an AB3 photoanode achieved the highest power conversion efficiency of 7.38% under low light conditions of 20 mW cm−2, utilising a 0.1 M I−/I₃− redox electrolyte, with a short circuit current density of 3.25 mA cm−2, an open circuit voltage of 946.96 mV, and a fill factor of 48%. Electrochemical impedance spectroscopy revealed a lower charge transfer resistance in AB3, suggesting reduced interfacial recombination. These results confirm the efficacy of TiO₂-ZnO nanorod composites in facilitating efficient DSSC operation under low light conditions.