Thermal emittance of sputter deposited infrared reflectors in spectrally selective tandem solar absorbers

The thermal emittance of infrared reflectors, deposited by DC-magnetron sputtering on glass substrates of spectrally selective solar absorbers was studied. The deposition process was optimized in order to decrease the thermal emittance of the absorber. The sputter deposition process was optimized with regard to applied power and argon pressure for nickel–vanadium, copper–nickel and copper. The results show that the thermal emittance of the infrared reflector in a tandem solar absorber can be reduced from 0.12 to 0.06 by replacing nickel–chromium by copper–nickel. The copper–nickel alloy has a higher deposition rate and is less sensitive to the sputtering conditions, which is also favorable in large-scale industrial production.