Electrochemical grafting of TiO2-based photo-anodes and its effect in dye-sensitized solar cells

•Electrochemical based strategy to reduce the dark current of DSCs•Covalent attachment of phenyl radicals onto the TiO2 surface•Elucidation of the covalent nature of the grafted radicals by means of XPS spectroscopy

We demonstrate that hydroxyl-groups which are located on the surfaces of mesoporous metal oxides (in particular sintered layers of F-doped tin oxide (FTO) and TiO2 on glass plates) are capable of undergoing reactions with 4-nitrobenzene radicals. The highly reactive benzene radicals are generated by the electrochemical reduction of 4-nitrobenzenediazonium tetrafluoroborate in acetonitrile. We found that the grafting surfaces were chemically inert to strong acids and bases. The grafted surfaces were characterized and analyzed by cyclic voltammetry (CV), attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR), X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). Implementation of electrochemically grafted TiO2 particles as photo-anodes in dye-sensitized solar cells (DSCs) showed that the grafted surface is capable of suppressing the undesired back-electron-transfer processes in dye-sensitized solar cells.

Graphical abstractElectrochemical grafting of TiO2-based photo-anodes and its effect in dye-sensitized solar cells.Figure optionsDownload full-size imageDownload as PowerPoint slide