Design and characterization of a robust photoelectrochemical device to generate hydrogen using solar water splitting

Solar water splitting using photoelectrochemical (PEC) devices based on triple-junction amorphous silicon (a-Si) solar cells has the potential to offer an inexpensive, efficient, and renewable source of hydrogen for the future hydrogen economy. This work describes the results of experiments to determine an optimal configuration for an efficient and durable a-Si-based photoelectrode for use in PEC devices. We found that triple-junction a-Si cells coated with indium-tin oxide (ITO) and arranged so that the outer semiconductor layer was a “p-layer” split water in alkaline electrolytes. However, such PEC devices only operated for a few hours and with solar to hydrogen efficiencies of less than 3%. Failure occurred due to corrosion of the ITO and semiconductor layers by the electrolyte. We devised three methods to increase the PEC device lifetime: (1) designing a more durable ITO coating, (2) protecting the ITO with fluorinated tin oxide (SnO2SnO2:F), and (3) protecting the ITO with a glass layer. In particular, a PEC device made using the SnO2SnO2:F method had good solar to hydrogen efficiency (5–6%), has lasted over 31 days, and is still operative, so this method is a major improvement in a-Si-based PEC device construction, which previously had reported lifetimes of less than 18 h.