The proposed IOF research programme addresses crucial issues of fundamental and technological importance in the field of solar fuel generation. The key success factor is a strong multidisciplinary approach combining top-level electrochemistry, high-end epitaxial III-V device preparation and cutting-edge surface science analytics. At the core of the project are the objectives of:► obtaining record solar to hydrogen efficiencies and lifetimes with III-V/Si tandem devices► enhancing III-V device stability in contact with electrolyte using dilute nitride materials► advancing the scientific understanding of the decomposition of III-Vs by advanced analyticsThe applicant, Dr. Henning Döscher, is an expert both in III-V heteroepitaxy on silicon and in semiconductor surface science and has accomplished significant contributions to the in situ analysis and advanced control of anti-phase disorder at polar on non-polar interfaces. He has authored and co-authored more than 20 papers including 4 Applied Physics Letters, 2 Surface Science, 2 Journal of Applied Physics, and 2 Physical Review B over the last 4 years.The outgoing phase will be hosted by the pioneer of III-V-based water-splitting, Dr. John Turner at the National Renewable Energy Laboratory (NREL), where the fellow will also collaborate with the world’s reference group in multijunction photovoltaics around Dr. Jerry Olson. Advanced interface analysis will be done with one of the leading soft X-ray spectroscopy groups in the USA, headed by Prof. Clemens Heske at the University of Nevada, Las Vegas (UNLV). The return host, Prof. Thomas Hannappel, currently builds a new, integrated epitaxy and surface science group at the Ilmenau University of Technology (TUI), strengthening his unique strategy for in-depth in situ analysis and benchmarking.