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. (C) 2013 Elsevier B.V. All rights reserved.