An Experimental and Theoretical Investigation of the Electronic Structures and Photoelectrical Properties of Ethyl Red and Carminic Acid for DSSC Application

The photoelectrical properties of two dyes—ethyl red and carminic acid—as sensitizers of dye-sensitized solar cells were investigated in experiments herein described. In order to reveal the reason for the difference between the photoelectrical properties of the two dyes, the ground state and excited state properties of the dyes before and after adsorbed on TiO(2) were calculated via density functional theory (DFT) and time-dependent DFT (TDDFT). The key parameters including the light harvesting efficiency (LHE), the driving force of electron injection ([Formula: see text]) and dye regeneration ([Formula: see text]), the total dipole moment ([Formula: see text]), the conduction band of edge of the semiconductor ([Formula: see text]), and the excited state lifetime (τ) were investigated, which are closely related to the short-circuit current density ([Formula: see text]) and open circuit voltage ([Formula: see text]). It was found that the experimental carminic acid has a larger [Formula: see text] and [Formula: see text] , which are interpreted by a larger amount of dye adsorbed on a TiO(2) photoanode and a larger [Formula: see text] , excited state lifetime (τ), [Formula: see text] , and [Formula: see text]. At the same time, chemical reactivity parameters illustrate that the lower chemical hardness (h) and higher electron accepting power (ω(+)) of carminic acid have an influence on the short-circuit current density. Therefore, carminic acid shows excellent photoelectric conversion efficiency in comparison with ethyl red.