The effects of various anchoring groups on optical and electronic properties of dyes in dye-sensitized solar cells

• Biscarbodithiolic acid-based dyes show the widest absorption spectra and longest lifetimes.
• The planarity of π-conjugated segments affects properties of dyes significantly.
• Deprotonated dyes show blue-shifted maximum absorbance compared to corresponding protonated dyes.

To design a potential high-efficiency dye, the deeper understanding of the nature of anchoring groups is of significance. In the present paper, using density functional theory (DFT) and time-dependent DFT, we have investigated two sets of dyes (CN11s and CN12s) with various anchoring groups, such as biscarbodithiolic acid, sulfonic acid, phosphonic acid, and hydroxamic acid. Our calculations indicate that the biscarbodithiolic acid-based dyes show the best absorption behavior in the visible-light/near-infrared range, i.e. the biggest maximum absorbances (λmax) and the widest absorption spectra. When phosphonic acid is used as the acceptor, dye molecules exhibit the worst absorption properties. Furthermore, the dyes with biscarbodithiolic acid also show the longest lifetime of the first excited state, implying the potentially good ability in electron injection from sensitizer to semi-conductor. The present results reveal that the D-π-A dyes devised with biscarbodithiolic acid may be promising sensitizers for high-efficiency dye-sensitized solar cells.

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