New organic dyes based on D - π - A structural sensitizers for Dye-sensitized solar cells (DSSC’s): DFT and TD-DFT investigation

The present research aims to design the new dyes with a D-π-A structure to apply Dye-sensitized solar cells. The D-π-A dyes constitute S1 to S9, using 9-vinyl-9H-carbazole (D) as a donor (D); different thiophene derivatives are π- spacers and cynoacrylic acid is an acceptor. For the electronic and optical properties calculation of the studied dyes, use DFT/B3LYP/6-311G++ level of theory by using Gaussian 09W software. Using optimized geometrical structures to calculate the UV absorption spectra, utilize the TD-DFT method in the gas and acetonitrile solvent. The HOMO and LUMO energy gap (Eg) values of S5 and S9 dyes show a narrow band gap with 1.8 eV and 1.7 eV, respectively. So all studied dyes have LUMO values higher than the TiO2 conduction band and HOMO values lower than the electrolyte redox potential. The UV absorption spectral data shows S5 and S9 have maximum absorption at 759 nm and 803 nm, respectively. So all the studied dyes are suitable for DSSC application.