Shifting of the absorption edge in TiB2/TiB(N)/Si3N4 solar selective coating for enhanced photothermal conversion

The concentrated solar power systems for solar energy applications demand the development of solar absorber coatings with high spectral selectivity. This is possible by careful compositional selection of absorber thin films with an aim to shift the optical absorption edge towards higher wavelength side. In this context, the present work aims at developing such a coating, based on TiB2/TiB(N)/Si3N4 by tailoring magnetron sputtering parameters. This multilayer exhibits a high absorptance of 0.964 and a moderately low emittance of 0.18 at 82 °C. The attainment of excellent spectral selectivity has been explained in terms of systematic variation or gradient in refractive index and extinction co-efficient throughout the multilayer stack.