Modulation on Dye/TiO2 Bending Energy and Charge Transfer to High Performance Triphenylamine Based Sensitizers in Solar Cells: A DFT Study

In this paper, dye sensitized solar cells (DSSCs) based on triphenylamine-thiophene are investigated by using density functional computations. The main focus is on the C214 and C215 dyes and their resulting bridged free and adsorbed molecules on the semiconductor (TiO2)(9), during the electron injection process. The optimized geometry of the molecule and complexes are calculated by using B3LYP/6-31G(d)//(base LANL2DZ for the titan atoms) level, in order to investigate the effect of the expansion, or bridging the thiophenic pi-conjugated spacer by the C(CH3)(2) donor group on the adsorption energies, charge distribution, electron transfer and electronic parameters of the resulting dye. The computational results suggest that our bridging process promotes the adsorption on the semiconductor (TiO2)(9) of the dyes having the bridged donor group close to the surface of (TiO2)(9) C214-B, C215-D bridge dyes by a reinforcement of the donating as well as accepting electrons character, respectively, of the donor part (TPA-thiophenes-bridged) and cyanoacrylic acid. This study may help to understand well the details of the electron transfer mechanism between the dye and the TiO2 semiconductor in DSSC dye solar cells.