Computational Studies of Suitability of Triarylmethane-Coumarins as Sensitizer for Dye-Sensitized Solar Cells

Abstract

Triarylmethanes are low cost synthetic dyes with intense absorption in the visible spectrum. This make it attractive to explore their suitability as sensitizer for dye sensitized solar cell. Using malachite green as a lead dye, we made intuitive structural modifications: incorporation of coumarin-3-carboxylic acid as acceptor/anchor, and substituting one or the two N, N-diethylaniline donors with N-propyl-1,6dimethyllutidine(s). The three resulting triarylmethane-coumarin structures were subjected to DFT calculations to investigate their suitability as sensitizers for DSSC applications. The calculation results showed that triarylmethane-coumarins with cationic type chromophores are unsuitable as DSSC sensitizer. The acceptor/anchor, coumarin-3-carboxylic acid, is basically excluded in the intramolecular charge transfer processes of the cationic dyes. Also, the LUMO levels of the cationic dyes are below the conduction band of TiO2, which is energetically uphill to electron injection into TiO2. Ultimately, the cationic triarylmethane-coumarin derivatives are unsuitable as sensitizer for DSSC. However, a charge-free triarylmethane-coumarin derivative shows promise as a sensitizer candidate for DSSC application.