Spectral properties and microstructure of sputtered WO_x films for solar conversion applications

Abstract

Tungsten oxides (WO x ) films have gained promising attention in terms of selective solar absorption due to its high intrinsic absorption properties. We fabricated a series of single-layer WO x films on aluminum substrates by a magnetron sputtering system.The optical absorption properties of the film were investigated by spectrophotometer and ellipsometry. We found that the optical properties of the film were very sensitive to the change of the thickness. The result showed the highest α value can reach up 0.82 with the thickness of 26 nm at 0.6 Pa or 70 nm at 1.5 Pa, and both ε values was around 0.05, indicating the high spectral selectivity properties. The different reflectance evolutions presented a wide range of color appearances, such as yellow, reddish, cyan, and blue. Moreover, the surface morphologies and phase structures of single-layer WO x films were investigated by SEM, XRD, and Raman. A WO x /SiO 2 solar selective absorber coating indicated that the as-obtained WO x film was a promising application in solar-thermal conversion. K E Y W O R D Ssolar selective absorber coating, spectral properties, tungsten oxides, chromaticity

Microstructure and optical properties of W/W‐WxN/WOx multilayer metal‐dielectric solar selective absorbing coating

“…15 Furthermore, completely oxidized WO x films have a better-prohibited bandwidth and can be used as antireflective layers. [16][17][18] Li et al prepared fully oxidized tungsten films using DC reactive magnetron sputtering and found that such films have high transmittance ($80%) and low absorption (<10%). 19 This paper selects metal W as the doping component based on the conventional metal-dielectric thin-film structure, and innovatively designs a W/W-W x N(H)/W-W x N(L)/WO x composite coating to prepare SSACs by medium frequency reactive magnetron sputtering of a single metal target, focusing on the relationship between absorption rate, emission rate, and surface structure was researched to propose an optimum solution for optimizing the preparation process and extending the service life of collector tubes for CSP systems.…”

“…The transition metal W exhibits excellent properties such as high melting point (melting temperature T m = 3693 K), high density, wear resistance, and low thermal emissivity, 14 whereas the excellent diffusion barrier properties of its nitride W 2 N allow it to be stable in high‐temperature environments and is commonly used as a diffusion barrier material for microelectronic devices 15 . Furthermore, completely oxidized WO x films have a better‐prohibited bandwidth and can be used as antireflective layers 16–18 . Li et al prepared fully oxidized tungsten films using DC reactive magnetron sputtering and found that such films have high transmittance (~80%) and low absorption (<10%) 19 .…”