Quantum chemical investigation of structural and electronic properties of trans- and cis-structures of some azo dyes for dye-sensitized solar cells

Abstract

Trans and cis isomers of a series of azobenzene dyes: dyes 1–3 with the carboxylic acid anchoring group in the ortho-position; dyes 4–6 with an anchoring group in the para-position and dye 7 with a carboxylic acid in the meta-position, are studied with DFT and TDDFT approaches. The donating group of dyes 1, 4 and 7 is dimethylamino. The donating group of dyes 2 and 5 is diethylamino and the donating group of dyes 3 and 6 is dipropylamino. Computational studies let us investigate geometrical structures, UV–Vis absorption spectra, electronic properties, light harvesting efficiency (LHE), chemical hardness (η), the weight of LUMO orbital of the dyes on the carboxylic acid group (QLUMO), exciton binding energy (EBE) and charge transfer of two configurations of these dyes. According to the results, we could justify that how the different donating groups and trans and cis structures of the seven dyes with three positions of anchoring group (ortho-, meta-, and para-) influence the parameters affecting the Jsc and the Voc of DSSCs.