Broadband photoelectric hot carrier collection with wafer-scale metallic-semiconductor photonic crystals

Photoelectric hot carrier generation in metal-semiconductor junctions can enable optical-to-electrical energy conversion at photon energies below the bandgap of the semiconductor. Here, we present the simulated and experimental results of our wafer-scale Au/TiO₂ metallic-semiconductor photonic crystal (MSPhC). We demonstrate a broadband sub-bandgap photoresponse with a FWHM of 235 nm centered at 590 nm due to surface plasmon absorption, and we also show a photoresponse enhancement factor of 4.5 at 639 nm compared to a flat chip. Photoresponse is also shown to increase with decreasing metal thickness down to 13 nm. Applications of our results could lead to low-cost and robust photoelectrochemical and thermo-photovoltaic devices.