Dual bandgap operation of a GaAs/Si photoelectrode

The development of high-efficiency photoelectrodes at low manufacturing cost is of great interest for the production of renewable and green hydrogen through solar-driven water splitting. In this work, we use structural, optical, and photoelectrochemical characterizations to study the performance of unprotected epitaxial GaAs/Si photoelectrodes during photocorrosion. More specifically, we demonstrate that photoanodes including 1-μm thick GaAs epitaxially grown thin film on a low-cost Si substrate can produce a higher photocurrent than those measured for expensive commercial GaAs wafers. Based on photoelectrochemical experiments under monochromatic excitation, we show that the improved photocurrent has to be related to the dual-bandgap operation of the GaAs/Si photoelectrode, benefiting from both GaAs and Si photo-generated carriers. This result opens new possibilities to further design efficient and low-cost dual-bandgap photoelectrodes.