Modulated III–V Triple-Junction Solar Cell Wireless Device for Efficient Water Splitting

We report an efficient wireless device for water splitting using III–V triple-junction solar cells. To maximize the generation efficiency of hydrogen, the surface catalytic electrode has to be well designed to balance with the capability of the solar cell. We find that another important parameter is the path length of light in water, which needs to be short enough to sufficiently activate the germanium bottom layer in the solar cell. The solar-to-hydrogen conversion efficiency of the wireless device under 1 sun illumination without an external bias reaches 11.2% at almost neutral pH, and stoichiometric evolution of hydrogen and oxygen is confirmed.