Wireless Solar Water Splitting Using Silicon-Based Semiconductors and Earth-Abundant Catalysts

We describe the development of solar water-splitting cells comprising earth-abundant elements that operate in near-neutral pH conditions, both with and without connecting wires. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen- and oxygen-evolving catalysts made from an alloy of earth-abundant metals and a cobalt|borate catalyst, respectively. The devices described here carry out the solar-driven water-splitting reaction at efficiencies of 4.7 % for a wired configuration and 2.5 % for a wireless configuration when illuminated with 1 sun (100 milliwatts per square centimeter) of air mass 1.5 simulated sunlight. Fuel-forming catalysts interfaced with light-harvesting semiconductors afford a pathway to direct solar-to-fuels conversion that captures many of the basic functional elements of a leaf. Although solar photovoltaic (PV) cellsnormally generate electricity, they canbe used to generate fuels such as hydro-gen from water, thus providing a storage mecha-nism for sunlight (1). Such schemes mimic the photosynthetic process within a leaf that converts the energy of sunlight into chemical energy by splitting water to produce O2 and hydrogen equiv