Computational molecular design of NIR dyes with varying anchoring groups for improving the efficiency and stability of dye-sensitized solar cells

Abstract

Design and development of near-infrared (NIR) dyes with strong binding on the TiO2 surface is inevitable for the realization of the dye-sensitized solar cells (DSSCs) with improved efficiency and stability. A series of NIR dyes bearing different anchoring groups have been designed considering their suitability as sensitizers for DSSCs based-on TiO2 and iodine-based redox electrolytes. Under the Gaussian program, density functional theory (DFT)/6-311G/B3PW91 level of theory and time-dependent-DFT using the polarizable continuum model is shown optimum for the prediction of the highest occupied molecular orbital energy level and electronic absorption spectra. The reliability of the calculated results was validated by corresponding experimental results for some of the representative dyes. It has been demonstrated that λ max at full width at half maximum in calculated absorption spectra exhibited an excellent match with the experimentally estimated Eg of the sensitizers leading to the proposal of a new method for the construction of the theoretical energy band diagram. Amongst newly designed sensitizers, dyes bearing dual anchoring groups like SQ-149, SQ-150, SQ-158, SQ-161 and SQ-162 are highly promising not only for good NIR photon harvesting but also to impart to improved DSSC stability.