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Institute of Energy and Climate Research

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In the context of the DFG Priority Program (1613 )“Fuels Produced Regeneratively Through Light-Driven Water Splitting: Clarification of the Elemental Processes Involved and Prospects for Implementation in Technological Concepts” the research project” „Photoelectrochemical water splitting using adapted silicon based semiconductor multijunction cell structures“ is funded at the FZJ:

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Light induced water splitting using photo-electrochemical devices without additional bias voltage has only been achieved with tandem or triple junction cells with reasonable efficiencies so far. But these devices are still limited in their performance, since they either deliver insufficient photovoltages and/or low photocurrents. Therefore, we want to explore in the present project specifically designed thin film multi-junction (tandem, triple and quadruple junction) structures based on inexpensive microcrystalline/amorphous Si absorbers adapted for hydrogen and oxygen generation from water using visible sunlight. For this purpose silicon based adapted multi-junction cell structures must be prepared to provide sufficient but defined photovoltages to drive both the H2 and O2 evolution reactions.

To reach high H2 yields and to minimize corrosive side reactions the atomic and electronic structure of the semiconductor surface must be modified in an appropriate way involving ultrathin passivation layers and specifically designed nano-sized metallic catalysts. Ultrahigh vacuum based synthesis and analysis techniques as well as electrochemical characterization tools are used to clarify the involved elementary processes at the semiconductor/electrolyte interface during solar water splitting. The obtained results shall contribute to the improvement of the total efficiency of light induced H2 formation to a level, which is sufficient for technological use.

Project partners:
TU Darmstadt, Forschungszentrum Jülich