Development of solar selective absorbers and sky radiators based on two-dimensional diffractive grating surfaces

Spectral properties of two-dimensional (2D) metal surface gratings are investigated to develop high performance solar selective absorbers and sky radiators. Numerical calculations based on rigorous coupled-wave analysis (RCWA) ire performed and surface gratings are fabricated on silicon substrates by means of photolithography and etching process. Reflectivity spectra of the samples are measured and they show good spectral selectivity for each application. In order to fabricate surface microstructures in large area with low cost, direct metal imprinting technology are proposed. A microstructured nickel metal mold for the solar selective absorber surface is fabricated by means of electroplating technique and imprint experiments are performed on copper metal surface using mechanical pressing system. As a result, some parts of the surface structures are successfully transferred onto copper substrate.