Effect of substituent in the acceptor on optical and electronic properties of triphenylamine based dyes: A density functional theory/time-dependent density functional theory investigation

The performance of dye-sensitized solar cells (DSSCs) depends on the absorption of light by dye molecules and subsequent charge transfer to metal-oxide semiconductors. In this study, triphenylamine based dyes have been modified theoretically by replacing the S atom in the benzothiazole unit with NH, O, Se and Te substituents; the optical and electronic properties of the novel sensitizers were investigated using density functional theory and time-dependent density functional theory. Besides the influence of the substituents on the optoelectronic properties, the effects of two anchoring groups, namely cyanoacrylic acid and hydantoin have been examined. The features, such as red-shifted electronic absorption spectra, improved when sulfur was replaced by oxygen, selenium, or tellurium. In comparison to cyanoacrylic acid-dyes, a more spontaneous charge injection is anticipated with hydantoin-dyes. The calculated binding energies of the dyes with (TiO2)6 cluster varied from −7.6 to −9.4 eV increasing with heteroatom size increase. Heavier chalcogen-containing (Se and Te) dyes are worthy of experimental synthesis for use in higher perfomance DSSCs.