Computational Investigation of the Influence of π-Bridge Conjugation Order of Thiophene and Thiazole Units in Triphenylamine Based Dyes in Dye-Sensitized Solar Cells

In this study, ten triphenylamine based dyes were investigated by varying the pi-bridge size with a different order of thiophene and thiazole units to understand their potential use in dye-sensitized solar cells (DSSCs). Geometry optimization, the energy levels and electron density of the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and UV-visible absorption spectra were calculated using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The electron injection driving force, dye regeneration driving force, natural bond orbital (NBO) analysis of dye-(TiO2)(8) cluster and dye reorganization energy were calculated to predict the most suitable dyes for DSSC application. Dye 4 ((Z)-2-cyano-3-(2-((E)-4-(diphenylamino)styryl)-[2,5-bithiazol]-4-yl)acrylic acid) followed by Dye 6 ((Z)-2-cyano-3-(5-(2-((E)-4-(diphenylamino)styryl)thiazol-5-yl)thiophen-3-yl)acrylic acid) having two linker moieties were identified as the potential candidates.