Wavelength dependent photochemical charge transfer at the Cu2O–BiVO4 particle interface – evidence for tandem excitation

The understanding of the photochemical charge transfer properties of powdered semiconductors is of relevance to artificial photosynthesis and the production of solar fuels. Here we use surface photovoltage spectroscopy to probe photoelectrochemical charge transfer between bismuth vanadate (BiVO4) and cuprous oxide (Cu2O) particles as a function of wavelength and film thickness. Optimized conditions produce a -2.10 V photovoltage under 2.5 eV (0.1 mW cm-2) illumination, which suggests the possibility of a water splitting system based on a BiVO4-Cu2O direct contact particle tandem.