An integrated n-Si/BiVO₄ photoelectrode with an interfacial bi-layer for unassisted solar water splitting

Integrated n-Si/BiVO₄ is one of the most promising candidates for unbiased photoelectrochemical water splitting. However, a direct connection between n-Si and BiVO₄ will not attain overall water splitting due to the small band offset as well as the interfacial defects at the n-Si/BiVO₄ interface that severely impede carrier separation and transport, limiting the photovoltage generation. This paper describes the design and fabrication of an integrated n-Si/BiVO₄ device with enhanced photovoltage extracted from the interfacial bi-layer for unassisted water splitting. An Al₂O₃/indium tin oxide (ITO) interfacial bi-layer was inserted at the n-Si/BiVO₄ interface, which promotes the interfacial carrier transport by enlarging the band offset while healing interfacial defects. When coupled to a separate cathode for hydrogen evolution, spontaneous water splitting could be realized with this n-Si/Al₂O₃/ITO/BiVO₄ tandem anode, with an average solar-to-hydrogen (STH) efficiency of 0.62% for over 1000 hours.