The Synthesis of Nb-doped TiO₂ Nanoparticles for Improved-Performance Dye Sensitized Solar Cells

Highlights: • A synthesis of Nb-doped TiO₂ nanoparticles for photoanode is developed. • The Nb-doping suppresses the surface recombination at TiO₂-electrolyte interface. • The positive shift of conduction band minimum enhances the electron injection. • The DSSCs based on 2.0 mol% Nb-doped TiO₂ achieve 18.9% improvement of efficiency. - Abstract: The current co-hydrolysis used for the preparation of Nb-doped TiO₂ starts from expensive and unstable niobium-based precursors, which is not suitable for mass production. In this paper, a scalable synthesis of Nb-doped TiO₂ nanoparticles (NPs) made by mixing TiO₂ paste with functionalized Nb₂O₅ sol gel is developed for the photoanodes in dye-sensitized solar cells (DSSCs). By doping Nb into TiO₂, the positive shift of conduction band minimum (CBM) enhances the electron injection and the improved electron conductivity facilitates the electron transport, leading to an improved J_sc. In addition, the Nb-doping suppresses the surface recombination at TiO₂-electrolyte interface, resulting in the increase of V_oc. Therefore, the DSSCs based on 2.0 mol% Nb-doped TiO₂ photoanodes improve both J_sc and V_oc to achieve 18.9% improvement of photoconversion efficiency as compared with the standard DSSCs. The DSSCs with Nb-doped TiO₂ photoanode is also shown an improved long-term stability.