Enhancing Electron Injection in Dye‐Sensitized Solar Cells by Adopting W6+‐Doped TiO2 Nanowires: A Theoretical Study

Abstract

AbstractAs a donor type dopant in titanium dioxide, W6+ was found to move the conduction band (CB) edge of TiO2 downward and also to influence the electron‐injection process in dye‐sensitized solar cells (DSSCs). To investigate the electron‐injection capabilities of DSSCs and to optimize their efficiency by W6+ doping, the geometry and electronic properties of both free and adsorbed TiO2 nanowires were investigated on the basis of extensive density functional theory calculations. A four‐layer (TiO2)12 nanowire with 12 possible doping sites was set up, and the effect of W6+ in different positions was analyzed. The results indicate that in the W6+‐doped (TiO2)12 systems, the Ti–OW (OW = oxygen atom that is connected to the W atom) bonds are longer than the corresponding Ti–O bonds in (TiO2)12. The CB edge is significantly influenced by the doping position. The CB energy level moves upward gradually as doped W6+ moves deep into (TiO2)12. For all adsorbed catechol/(TiO2)12 systems with the W6+ dopant, the LUMO maps are distributed over the layer in which W6+ is doped. The W6+ doping position plays a crucial role in the electron‐injection and electron‐transport process in DSSCs. Therefore, different positions of W6+ doping in TiO2 would be a feasible strategy to control and improve semiconductor materials to obtain DSSCs with more efficient electron injection.