Effect of the chemical modifications of thiophene-based N3 dyes on the performance of dye-sensitized solar cells: A density functional theory study

The effect of the chemical modifications of thiophene-based N3 dyes on the dye-sensitized solar cell (DSSC) efficiency is investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT). The properties of excitation were calculated in both the lowest energy excited state and higher excited states. Since the changing of commonly used parameters, light-harvesting efficiency (LHE) and driving force (ΔG), is too limited for all thiophene-based N3 derivatives to characterize the role of chemical modifications in improving the solar-to-electricity conversion efficiency (η), further investigation into the procedure of photo-induced charge transfer of these compounds is carried out. The results show that for thiophene-based N3 derivatives, increase in the electron-withdrawing ability of anchoring group can draw more electrons to this direction during the process of photo-excitation, and, thus, would facilitate the electron injection from sensitizers to the semiconductor. While the photo-induced charge transfer of these thiophene-based N3 sensitizers are unaffected or even reduced when the conjugation length of thiophene-chains is extended.