Photoelectrochemistry of para-diethynylbenzene copper(I) acetylides deposited as thin films onto copper electrodes

The photoelectrochemical behaviour of copper mono- and disubstituted para-diethynylbenzene, deposited electrochemically and chemically as thin films onto copper electrodes, was investigated in 0.1 M LiOH. These materials behave as p-type semiconductors with band gaps of 2.2. and 2.1 eV, respectively, in a rectifying liquid junction with a flatband potential of 0.3 V vs. SCE. High photocurrents (8.0 mA cm-2) and photovoltages (0.5 V) are displayed by the disubstituted compound under oxygen and 35 mW cm-2 white light; monochromatic quantum yields of 12-13% are achieved. These results represent a remarkable improvement with respect to previously investigated copper acetylide systems. Photoelectrochemical parameters were also evaluated with reversible redox couples in the gap. The performances of a regenerative photoelectrochemical cell based on the 2.6-anthraquinone disulfonate redox couple were explored.