Theoretical study of carbazole–triphenylamine-based dyes for dye-sensitized solar cells

Three carbazole–triphenylamine-based dyes (D1, D2, D3) are designed. The geometries, electronic structures, and electronic absorption spectra of these dyes are studied by DFT and TD-DFT. The calculated geometries indicate that these dyes are all noncoplanar, which can help to inhibit the close intermolecular π–π aggregation effectively. The LUMO and HOMO energy levels of these dyes can be ensuring positive effect on the process of electron injection and dye regeneration. The trend of the calculated HOMO–LUMO gaps nicely compares with the spectral data. The calculated results of these dyes demonstrate that these dyes can be used as potential sensitizers for TiO2 nanocrystalline solar cells.