Broadband and thermally stable tungsten boride absorber

Metal-based perfect absorbers that use metals such as aluminum (Al) can have their optical properties changed with temperature, subsequently affecting the device’s performance. The changes with temperature can critically limit the applications of absorbers at high powers or high temperatures. In this paper, we show a thermally stable broadband absorber based on an ultrathin layer of refractory ceramic, tungsten boride (WB). We experimentally analyze and compare the performance of the absorber with an aluminum (Al) based absorber. The multilayer perfect absorber has absorption higher than 85% in the wavelength range between 500 and 1600 nm over a large range of incident angles (up to 60^◦). We show that a WB absorber has significantly better temperature stability when compared with its Al counterpart, achieving stable operation up to temperatures as high as 270^◦C. These absorbers may find applications in solar thermo-photovoltaic energy conversion.