DFT studies on the electronic structures of TTA dyes for dye-sensitized solar cells

A new series of metal free organic dyes are investigated for application in dye sensitized solar cells (DSSC) based on a donor--acceptor (D--A) design. Here a triphenylamine (TPA) moiety serves as the electron donor, a cyanoacetic acid as the electron acceptor and anchoring group and a tetrathienoacene (TTA) as the -bridge unit. We developed a computational procedure to screen different spacers effect. These chromophores have evaluated by density function theory (DFT) and time dependent DFT approaches in gas phase and in solution. The effects of -bridge on the spectra and electrochemical properties of tetrathienoacene based dyes are demonstrated. The calculated results of these dyes demonstrate that theoretical calculations are useful not only in the description of electrochemical properties, but also in the design of new sensitizers. It was also found that modifying the alkyl chain of the bridge unit is an efficient way to decrease dye aggregation and improve DSSC efficiency.