Photoelectrolysis of water using thin copper gallium diselenide electrodes

Thin CuGaSe2 films were deposited by vacuum co-evaporation and characterized for their structure, properties and performance as hydrogen-evolving photoelectrodes. The 0.9 μm thick films were nearly stoichiometric with very slight copper deficiency and showed polycrystalline structure with grain sizes of tens of nanometers. An electrode based on such a film was demonstrated operating with outdoor 1-sun photocurrent of up to 13 mA/cm2. Spectral response data show significant incident-photon-to-current efficiency throughout the visible spectrum, peaking at 63% at 640 nm. Photocurrent output under simulated 1-sun Air Mass 1.5 light was stable over 4 h. Unassisted water-splitting is not possible due to high band edge positions, but operation in tandem configuration with a suitable bottom junction is feasible.