Characterization of high-performance organic dyes for dye-sensitized solar cell: a DFT/TDDFT study

Dye-sensitized solar cell (DSSC) is currently a promising technology that makes solar energy efficient and cost-effective to harness. In DSSC, metal-free dyes such as indoline-containing D149 and D205 have been proven to be potential alternatives for traditional metal organic dyes. In this work, a DFT/TDDFT characterization for D149 and D205 was carried out using different functionals, including B3LYP, MPW1K, CAM–B3LYP, and PBE0. Three different conformers for D149 and four different conformers for D205 were identified and calculated in a vacuum. The performance of different functionals on calculating the maximum absorbance of the dyes in a vacuum and five common solvents (acetonitrile, chloroform, ethanol, methanol, and THF) were examined and compared to determine the suitable computational setting for predicting properties of these two dyes. Furthermore, deprotonated D149 and D205 in solvents were also considered, and the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated, which elucidates the substitution effect on the rhodanine ring of D149 and D205 dyes on their efficiency. Finally, D149 and D205 molecules were confirmed to be firmly anchored on ZnO surface by periodic DFT calculations. These results shed light on the design of new, highly efficient metal-free dyes.