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ABSTRACT: State-of-the-art a-SiC:H films have been prepared using RF-PECVD deposition technique. Incorporation of carbon in amorphous silicon network increases the bandgap to >2.0eV and adding H2 during fabrication has led to a material with low defects. A-SiC:H with Eg=2.0eV used as the active layer in single junction solar cell led to an efficiency of ~7%, which also indicated that a-SiC:H is high-quality and that it has potential to be used as photoelectrode. Immersing in pH2 sulphamic acid electrolyte a-SiC:H photoelectrodes exhibit durability for up to 100 hours (so far tested). Jph increases as well as photocurrent onset shifts towards anodically after durability test. This behavior could be due to a change in the surface structure of the a-SiC:H photoelectrode, or partially due to elimination of the surface SiOx layer. HF etch experiment confirmed that the SiOx layer on the surface of a-SiC:H indeed affects both Jph and its onset. After removing SiOx layer, a-SiC:H photoelectrode exhibited a Jph over 6 mA/cm2 at potential -1.4V (vs. Ag/AgCl), compare to that less than 4mA/cm2 (vs. Ag/AgCl). More analysis needs to be done to understand the mechanisms and improve the interface between aSiC:H and electrolyte and hence to increase Jph. Our initial PV/a-SiC:H used as photoelectrode has exhibited ~1.33mA/cm2 current density under zero volt external bias, and the photocurrent onset shifts enormously, from ~ -0.6V to ~ +1.2V, or by a net ~1.6v. Hydrogen production has been demonstrated in this type of hybrid PEC cell. It exhibits good durability in aqueous electrolytes for up to ~150 hours. Work on further increasing the photocurrent in such a PV/a-SiC:H device is underway. We have also shown by simulation that it is possible to achieve STH efficiency >10% using such PV/a-SiC:H devices.
02/2010; , ISBN: 978-953-307-052-0
