Surface Temperature above 100 °C under Solar Light through Intrinsic Selective Solar Absorbers

Abstract The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers to maximize solar energy to heat conversion, which is critical to several advanced applications1,2. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption3. Typically, intrinsic materials exhibit high performances only when they are integrated as a component in multilayered complex solar absorbers, due to their limited spectral selectivity and solar absorption4. In this study, we propose CoSbx(2<x<3) as a new and highly efficient selective solar absorber. The low bandgap nature of CoSbx endows broadband solar absorption of 0.98 over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region. Here we report a high intrinsic spectral solar selectivity of 5.4 for the nanostructured narrow bandgap semiconductor CoSbx. Under 1 sun illumination, the heat concentrates on the surface of the thin film of CoSbx, and a high temperature of 101.7 °C is reached, demonstrating the highest value among reported selective solar absorbers. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg∙m-2∙h-1. This study may broaden the application of narrow bandgap semiconductors for use as highly efficient intrinsic selective solar absorbers and high surface temperature usage under solar illumination.