DFT and TD‐DFT Study on Azobenzene‐Based Dye Covalently Attached to Silane Coupling Agents: Toward Dye‐Sensitized TiO2 Catalyst and Dye‐Sensitized Solar Cell Applications

Abstract Herein, density functional theory (DFT) and time‐dependent DFT (TD‐DFT) studies of 4‐[(4‐methoxyphenyl)diazenyl]naphthalen‐1‐amine (MPDNA) covalently attached to a silane coupling agent (SCA) (namely, 4‐(triethoxysilyl)butane‐1,2‐epoxide (OTES)) with a terminal oxirane group (MPDNA‐OTES) were performed to determine the influence of SCAs on the geometry of photosensitizing dyes with multiple photoisomers or conformers. CH−O interaction between the hydroxyl group, which was formed by an epoxy ring‐opening reaction between MPDNA and OTES, and the 1‐naphthylamine moiety resulted in two conformers of MPDNA‐OTES. The dominant trans ‐isomer conformation of MPDNA‐OTES indicates a high driving force of electron injection (−1.61 eV) and significantly contributes to the photocurrent in dye‐sensitized TiO 2 catalysts and dye‐sensitized solar cells. It is concluded that by combining OTES and a photosensitizing dye containing a 1‐naphthylamine moiety, the CH−O interaction can be utilized to regulate the geometry of the dye to realize characteristics favorable for electron injection into the conduction band of TiO 2 .