Computational Study of Anthracene-Based Organic Dyes for Dye-Sensitized Solar Cells: Effects of Auxiliary Electron Donors

A series of anthracene-based organic dyes with different auxiliary electron donors (diarylamine, carbazole, and indoline) were computationally studied for applications in dye-sensitized solar cells. Density functional theory (DFT) and time-dependent DFT were conducted to reveal electronic and optical properties of 2H-benzophenanthrothienobenzophenanthrothiophene (BPT2) dyes and dye/(TiO2)46 interfaces. Our calculations reveal that all BPT2 dyes show strong light harvesting performance in the red region (620 nm) and a relatively weak optical absorption around 350 nm of the UV–visible spectrum, which is consistent with experimental findings. The intramolecular photoexcitation mainly occurs between the BPT2 unit and the electron acceptor, so the selection of ancillary donors has little influence on the optical properties of the main absorption peak. The introduction of polycyclic aromatic BPT2 moiety to replace the phenyl unit leads to a notably broadened spectrum and a 170-nm redshift in the adsorption peak. Our results are helpful for the molecular design of novel BPT2-based organic dyes for future dye-sensitized solar cells optimizations.