Opto-electronic and interfacial charge transfer properties of azobenzene dyes on anatase TiO 2 (001) surface – The effect of anchoring group

Abstract

The opto-electronic and interfacial charge transfer properties of azobenzene dye with different anchoring groups, carboxylic acid, alkoxysilyl and tropolone were studied for dye sensitized solar cell applications. Frontier molecular orbital analysis shows that the lowest unoccupied molecular orbital of azobenzene dye with tropolone anchoring group is delocalized on the anchoring group and azobenzene chromophore, which indicates the possibility of efficient electron transfer from dye molecule to TiO2 conduction band. The azobenzene dye with tropolone anchoring group is having maximum absorption wavelength of 458 nm and light harvesting efficiency of 0.94. The driving force for electron injection (ΔGinject) and dye regeneration (ΔGreg), excited state life time (τ) and open-circuit voltage (eVOC) of designed dye molecules were calculated. The calculated adsorption energies of dye/TiO2 interface indicates that the azobenzene dye with topolone anchoring group possess strong interaction with anatase TiO2 (001) surface. The analysis of density of states shows the electrostatic interaction between dye molecule and TiO2 surface and feasible channel for photo-induced electron transfer from dye to TiO2. It is observed that the tropolone anchoring group is suitable for the dye sensitized solar cell applications than the carboxylic acid and alkoxysilyl anchoring groups for azobenzene dye with anatase TiO2 semiconductor.