Doping effects on catechol functionalized anatase TiO2(101) surface for dye-sensitized solar cells

Abstract

Doping effects of Al, Mg and Cr on the structural and photoelectric properties of catechol functionalized anatase TiO2(101) surface (CFAS) have been studied using density-functional theory. The results indicate that the adsorption processes of CFAS and catechol functionalized doped anatase TiO2(101) surfaces (CFDAS) are all exothermic and these adsorption systems are quite stable. The relative lower formation energy of Al-doped TiO2 means that it is energetically favorable structure under Ti-rich conditions. For band structure of catechol-Cr-doped-TiO2, the electron transition energy will be reduced, and visible light absorption will be extended on account of the decreased band gap and widespread impurity states. The positive Fermi energy shift of Cr-doped TiO2 suggests that it is beneficial to increase the open circuit voltage compared with pure TiO2 under the same conditions. When catechol as a model organic sensitizer functionalizing the pure and Al, Mg and Cr doped TiO2 (101) surfaces, a positive shift of the Fermi energies is observed in comparison with those materials without catechol functionalization. Compared with the optical properties of CFDAS, Cr doping has a greater effect on the optical properties of anatase TiO2 (101) surface than that of Al or Mg doping. The results show that Cr doped anatase TiO2 (101) surface is a better photoanode material and can be applied in Dye-Sensitized Solar Cells.