Computational Investigations of a Novel Charge Transfer Complex for Potential Application in Dye-Sensitized Solar Cells

Abstract

The computational study of a novel charge-transfer complex as a photoactive blend for potential application in dye-sensitized solar cells was carried out using the semi-empirical method. The adsorption of two natural dyes, 1S,3R,4R,5R-3-(3,4-dihydroxyphenyl)acryloyloxy)-1,4,5-trihydroxycyclohexane carboxylic acid (DHTH) and 2-Phenyl-4H-chromen-4-one (PCO) was achieved independently on to 1×1×1 TiO2 crystal to form TiO2-DHTH and TiO2-PCO adsorption complexes. Semiempirical calculations were performed on the optimized molecules, as well as on the adsorption complexes, to obtain the total energies and EHOMO/ELUMO values, manifesting a flow of electrons from DHTH/PCO to TiO2. The theoretical electronic absorption spectra calculated via ZINDO/s method revealed a large bathochromic shift to 810 nm and 526 nm for TiO2-DHTH and TiO2-PCO, respectively, indicating the formation of a charge-transfer complex. Subsequently, the co-adsorption of PCO and DHTH on TiO2 was accomplished with the aim to minimize the possible charge recombination in the photoactive blend. The semiempirical PM3 calculations evidenced the high stability of the co-adsorption complex, TiO2-PCO-DHTH, with the total energy of -200678.578 kcal/mol. The positions of HOMO and LUMO orbitals as obtained from single-point energy calculations, coincided accurately with our proposition of electron flow in a cascade manner from DHTH to PCO and finally to TiO2. The theoretical electronic absorption spectrum ofTiO2-PCO-DHTH evinced absorption range of 351.8-800 nm demonstrating the high potential of TiO2-PCO-DHTH to be used as a photoactive blend for solar cells.