Silicon based tandem cells: novel photocathodes for hydrogen production.

A photovoltaic tandem cell made of amorphous silicon (a-Si) and microcrystalline silicon (µc-Si) was investigated as a photocathode for hydrogen evolution in a photoelectrochemical device. The electronic and electrochemical properties of the samples were characterized using X-ray photoemission spectroscopy (XPS) and cyclic voltammetry (CV), whereas the morphology of the surface in contact with the electrolyte was investigated by scanning electron microscopy (SEM). The electric efficiency of the tandem cell was determined to be 5.2% in a photoelectrochemical (PEC) setup in acidic solution which is only about half of the photovoltaic efficiency of the tandem cell. A significant improvement in efficiency was achieved with platinum as a catalyst which was deposited by physical vapour deposition (PVD) under ultra-high vacuum (UHV) conditions.