Design of a High Performance Selective Solar Absorber with the Structure of SiO₂-TiO₂-TiN_xO_y-Cu

Using TiN x O y thin film as the absorbing layer, a spectrally selective solar absorber (SSA) with the structure of SiO 2 -TiO 2 -TiN x O y -Cu has been designed; and the SSA performance has been evaluated by both calculation and experiment. The TiN x O y layer is fabricated by RF magnetron sputtering of a pure TiN target with Ar and N 2 gases. The introduction of oxygen in the TiN x O y is realized by using the residual oxygen in the deposition chamber. It is found that the N 2 flow rate has a large effect on the complex refractive index of the TiN x O y thin film and thus the SSA performance can be optimized by controlling the N 2 flow rate. With the TiN x O y absorbing layer deposited with the N 2 flow rate of 2 sccm, the SSA achieves the highest solar thermal conversion efficiency for a solar radiation concentration factor of equal to or larger than 5. The SSA based on the TiN x O y layer deposited with the N 2 flow rate of 2 sccm has a solar absorbance of 96.29% and a thermal emittance of 6.11% at the temperature of 400 C.