Computational Study of the Effect of Changing the Auxiliary Acceptor in D-A-π-A Structure Dyes on the Optoelectronic Properties of Dye-Sensitized Solar Cells (DSSCs)

Four D-A-π-A molecules were designed in this study, utilizing triphenylamine as the donor whilst changing the auxiliary acceptor (benzothiadiazole). The molecular structures were analyzed through theoretical investigation with density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Optoelectronic and photovoltaic properties such as EHOMO (the highest occupied molecular orbital), ELUMO (the lowest unoccupied molecular orbital), Egap, VOC (the open-circuit photoelectric voltage), λmax (the maximum absorption wavelength), LHE (the light-harvesting efficiency) and ΔGinj (the free injection energy), were calculated to investigate the effect of auxiliary acceptor switching on the efficiency of sensitizers based on the molecules studied. The results indicate that the D5 dye exhibits the best performance in comparison with other dyes, as it is characterized by a low energy gap (Egap = 1.51 eV) and a maximum wavelength (λmax = 683.8 nm). Consequently, the D5 dye is a favorable candidate for application as a DSSC sensitizer.