Influences of metallic doping on anatase crystalline titanium dioxide: From electronic structure aspects to efficiency of TiO2-based dye sensitized solar cell (DSSC)

• Ca, Al and W dopants strongly distort the lattice and narrowed the band gap.
• Nb negatively shifts while the others positive shift the conduction band bottom.
• Nb and W dopants reduce Ti4+ to Ti3+ without forming oxygen vacancy.
• Be, Mg, Ca, Zn and Al dopants induce oxygen vacancy without Ti3+.
• Nb and W inhibit the surface defects while the others do the reversed manner.

In this work, we examined the influences of metallic X dopants (X = Be, Mg, Ca, Zn, Al, W and Nb) on the electronic structure of anatase TiO2 in the framework of density functional theory (DFT). The dopant-induced electronic structure modifications are believed to directly change the photovoltaic (PV) behaviors of the X-doped TiO2 based DSSCs. The dopants are shown to either directly inhibit the intrinsic Ti3+ and oxygen vacancy surface defects of TiO2 or enhance these defects depending on their valence states. These dopant-induced defect modifications, in turn, strongly affect the PV behaviors of the DSSCs. The combined effect of electronic structure and surface-defect modifications determined the photoelectric efficiency of the device.