Theoretical Study on the Intermolecular Interactions of Black Dye Dimers and Black Dye–Deoxycholic Acid Complexes in Dye-Sensitized Solar Cells

Abstract

Herein the intermolecular interactions in Ru(H3tcterpy)(NCS)3 (black dye) dimers, where tcterpy is 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine, deoxycholic acid (3α,12α-dihydroxy-5β-cholan-24-oic acid, DCA) dimers, and black dye–DCA complexes in acetonitrile were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). Among the five resulting black dye dimers, the most preferable species (BB1) forms intermolecular hydrogen bonds via the carboxyl groups and has a centrosymmetric structure similar to that reported for a black dye crystal. Theoretical calculations indicate six black dye–DCA complexes, and the most stable configuration (BC1) has three intermolecular hydrogen bonds between the two carboxyl groups of the dye ligand and one carboxyl and two hydroxyl groups of DCA. BC1 has a higher intermolecular interaction energy than BB1. On the basis of these theoretical results, the structure of black dye aggregation and the aggregation suppression mechanism by DCA during the immers...