Triphenylamine-based D-A-π-A dyes for DSSC applications: Theoretical study on the impact of auxiliary acceptor groups and π-bridges on photovoltaic performance using DFT and TD-DFT calculations

In this study, a series of eight D-A_i-π_i-A organic dyes designed by chemically modifying a previously synthesized D-π-A-type organic dye, called DPA-azo-A (R), were examined to assess the impact of the inclusion of different auxiliary acceptor groups (A_i, i = 4) and the substitution of the anthracene π-spacer group by thionothiophene/furofuran π_i-bridge on their performance in dye-sensitized solar cells (DSSCs). Density functional theory (DFT) and time-dependent DFT (TD-DFT) computational methods were used to investigate geometrical structures, optoelectronic properties, and some key short-circuit current-related parameters, such as light-harvesting efficiency (LHE), electron injection driving force (ΔG_inject), electron regeneration energy (ΔG_reg), excitation lifetime (τ) and chemical reactivity. In addition, we identified the most stable TiO₂-dye complex. The results showed that these new dyes show a reduced gap, significant absorption, strong adsorption, excellent light harvesting efficiency and better intramolecular charge transfer properties than the reference dye, translating into better photovoltaic performance. Consequently, this theoretical study breaks new ground by offering valuable guidance for the experimental synthesis of highly efficient triphenylamine-based organic dyes for DSSC applications.