Ultra-broadband solar absorber based on multi-layer TiN/TiO 2 structure with near-unity absorption

In this paper, a novel broadband solar absorber based on TiN/TiO2 is presented. The unit cell is composed of a multi-layer disk that is surrounded by a TiN ring. By using the finite-difference time-domain method, the effects of the number of disk layers as well as the height of the ring on the absorption are comprehensively investigated. It is shown that the light with shorter wavelengths is trapped by the disks, while the longer wavelengths are absorbed by the ring. Also, the variation of the absorption due to the period changes is studied. According to the simulation results, the average absorption of the proposed absorber is 93% in the wavelength range of 200–4000 nm. In addition, the absorption is higher than 90% in a wide wavelength range of 200–3000 nm under normal incidence, which covers the whole spectrum of solar radiation. It is shown that the proposed absorber can absorb more than 80% of light for angles less than 50° for both the TE and TM modes. Owing to the use of TiN and TiO2, this solar absorber has high thermal and chemical stability. This structure can act as a blackbody emitter in thermal emitter devices. Due to its high absorption and subwavelength structure, the proposed solar absorber is a suitable candidate for use in many solar-based applications.