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. A dual bandgap photoelectrode operation is demonstrated with GaAs thin films grown on Si. The III-V/Si photoelectrode is able to generate a larger photocurrent than a conventional photoelectrode made of a commercial GaAs substrate, due to the fact that de Si is photoactive. [Display omitted] •High photocurrents can be generated within cost-efficient GaAs/Si photoelectrodes.•Improved photocurrent performances are related to the Si substrate which is found to be photoactive and contributes to the photo-response of the GaAs/Si photoelectrode.•The concept of dual-bandgap III-V/Si single photoelectrode enables high efficiency and cost efficient photoelectrodes.