Design of two novel dyes having maximum absorption in infrared region: A DFT investigation

Abstract

The first dye sensitized solar cell (DSSC) was designed by O'regan and Grätzel in 1991 using ruthenium-based metal complex. Over the years, scientists have thoroughly investigated DSSCs, achieving efficiencies greater than 10%. Present investigation focusses on two novel dyes based on D-π-A and D-π-A-A models for application in DSSC. Absorption region of the sensitizers is expected to lie in the infrared region. Both dyes have same donor and π-bridge moieties, which are carbazole and thiophene respectively. In the first dye (DYE 1), naphthalimide is acceptor, whereas, in the second dye (DYE 2), naphthalimide and benzothiadiazole act as acceptors. The dye structures have been optimized under the framework of density functional theory (DFT) at B3LYP/cc-pVDZ theory level using Gaussian 16W software package. TDDFT calculations were performed at CAM-B3LYP/cc-pVDZ theory level to check absorption maxima in both dyes. TDDFT results confirm that both dyes have absorption profile in the infrared region. DYE 1 and DYE 2 have maximum absorption wavelengths at 1432 nm and 1351 nm respectively. Other parameters calculated for the dyes are light harvesting efficiency, charge injection energy, dye regeneration energy and open circuit voltage.