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.

Thin film tandem solar cells based on amorphous and microcrystalline silicon (a-Si:H/μc-Si:H) are employed as the cathode in a photoelectrochemical converter for solar water splitting. It is setup in such a way that the silver back contact of the cell is directly connected to the electrolyte and the light enters the cell through the glass substrate. This arrangement offers a number of distinct advantages compared to the conventional designs. The cathode is further optimized by the deposition of platinum nanoparticles to achieve higher conversion efficiencies. The front contact of the photovoltaic cell is connected to a standard platinum counter electrode in a three-electrode arrangement. Photon to current conversion efficiencies can reach up to 3% for our design, which has not been optimized to the requirements of the water splitting reaction, yet. The optimization of such tandem devices made from abundant silicon in combination with nanoparticle catalysts offers an affordable pathway for direct solar-to-fuel conversion devices in form of an artificial inorganic leaf.

The electrochemical properties of single-crystalline p-type 3C-SiC films on p-Si substrate were investigated as an electrode in H2SO4 aqueous solutions in dark and under white light illumination. The photoelectrochemical (PEC) measurements indicates the p-type 3C-SiC film on p-Si substrate can generate a cathodic photocurrent as a photocathode, which corresponds to hydrogen production, and generate an anodic photocurrent as a photo-anode, which corresponds to oxygen evolution. The surface chemical states of the films were investigated by XPS. In order to observe the surface chemical state changes after PEC test, the range of applied potential to the electrode was divided into three zones: -3.6 to 0 V, 0-1.5 V and 1.5-4 V vs. Ag/AgCl. After separated PEC tests in these three areas, XPS shows the surface of the SiC film in the range of -3.6 to 0 V and 0-1.5 V was stable without oxidation except the band bending occurred. But in the range of 1.5-4 V the film surface was oxidized due to anodic oxidation. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.