Introduction: Dye Sensitized Solar Cells (DSSCs) are the most promising solar cells and alternative to the conventional silicon solar cells due to low cost, facile fabrication, ability to work under low-light conditions and eco-friendly nature. Generally, the visible light is converted into electricity in DSSCs through dye sensitized wide bandgap semiconductors such as SnO₂, SrTiO₃, Nb₂O₅, ZnO and TiO₂. Among the metal oxides explored for DSSCs so far, TiO₂ remains the most promising material due to its transparency under visible light, high refractive index, thermal stability and high surface states. However, the performance of the device is limited due to limited spectral response and poor electron transport of carriers in porous TiO₂, and recombination of the injected electrons with the oxidized redox species and relaxation of oxidized dyes. Doping is considered as one of the strategies to overcome the above problems and transition metal doped TiO₂ nanomaterials do it effectively.

Methods and Results: In this study, initially solvothermally synthesised Zn-doped TiO₂ and wet chemically synthesized Ni-doped TiO₂, and Ru-doped TiO₂ nanomaterials were structurally and optically characterized by X-ray diffraction (XRD), Energy-dispersive X-ray (EDX), and UV-Visible (UV–Vis) spectroscopies. The XRD patterns of un-doped, Zn-doped, Ni-doped and Ru-doped TiO₂ nanomaterials confirmed the absence of phase transformation of TiO₂ and the presence of constituent transition metal elements in doped nanomaterials was evident in the respective EDX spectra. UV-Visible absorption spectra of doped TiO₂ showed red shifts on Zn, Ni, and Ru doping. Further, the optimized individual DSSCs with separate Zn-doped, Ni-doped and Ru-doped TiO₂ photoanodes exhibited Power Conversion Efficiencies (PCEs) with 35, 20, and 20 % enhancement, respectively when compared to the control device under simulated irradiation of intensity 100 mW/cm² with AM 1.5 filter.

Conclusions: It should be noted that, the improvement in PCE was mainly due to the increase in short-circuit current density (J_SC) as a result of the enhanced visible light harvesting ability, and reduced recombination rate / improved charge transport which were confirmed by Electrochemical Impedance Spectroscopy (EIS).

Keywords: Transition metals; Zinc; Nickel; Ruthenium; Doped TiO₂; DSSC