Silicon Gradients-containing Films for Mid- high Temperature Non-vacuum Solar Absorber Coatings

Abstract

A new tandem absorber coating for mid-high temperature solar collectors mainly consists of a stress buffer layer Cr2O3, an infrared reflective layer Ag, a diffusion barrier layer Cr2O3, a silicon-based absorbing layer, including p-Si, μc-Si, nc-Si, α-Si, and an anti-reflection layer SiO2 is designed. Plasma enhanced magnetron sputtering (PEMS) and high temperature chemical vapor deposition (HTCVD) are combined in one chamber to prepare this solar selective coating which is expected to be air-stable and able to operate at mid- high temperatures (300-500°C) and also exhibit good spectral selectivity, thermal stability and oxidation resistance, so that it could be suited for solar power generation. This coating achieved a solar absorptance of 0.82-0.59 in the wavelength range of 0.3-0.7μm, while in the wavelength of 0.3-2.5μm the solar absorptance only reached 0.61-0.35. Amorphous silicon and silver structure are dominant in this tandem layer and no diffraction peaks of Cr2O3 and SiO2 were observed. Thermal stability tests indicate that this tandem absorber is stable after annealing in air at 500°C for 1h.