Monocrystalline silicon-based tandem configuration for solar-to-hydrogen conversion

Hydrogen gas produced from a photovoltaic power source for water electrolysis is a promising renewable, low-cost, storable, and transportable energy source. Herein, we propose a simply integrated hydrogenated amorphous silicon germanium (a-SiGe:H)/silicon heterojunction (SHJ) tandem configuration as an integrated photovoltaic-electrolysis device. By optimising the a-SiGe:H top cell for high efficiency using various band-gap engineering techniques, we achieve effective performance enhancement, with a maximum V-oc of greater than 1.5 V. Assuming an ideal condition wherein the photovoltaic device operates at maximum power and the output conversion performance is maximized, we estimate a solar-to-hydrogen (STH) conversion performance of 13.1%. The integrated a-SiGe:H/SHJ structure can generate a sufficiently high voltage for water electrolysis while using lesser silicon than single junction silicon solar cells connected in series. Consequently, it is a viable option for a low-cost, high-efficiency integrated photovoltaic-electrolysis system and an alternative to traditional hydrogen production from fossil fuels.