Ultra-broadband perfect solar absorber by an ultra-thin refractory titanium nitride meta-surface

Electromagnetic wave absorbers with thinner structural thickness but with broader spectral absorption bandwidth are more desirable for various applications in solar energy and optoelectronics. In this work, a refractory titanium nitride meta-surface with efficient, ultra-broadband solar energy absorption is theoretically designed and numerically demonstrated. The resulting 250-nm-thick meta-surface absorber exhibits an ultra-broadband perfect absorption over the whole ultraviolet-visible-near infrared range. With taking the A > 90% into account, the absorption bandwidth is up to 1110 nm with the wavelength range varied from 0.316 μm to 1.426 μm. The titanium nitride nano-resonators array and its coating structure of titanium dioxide array cooperatively provide multiple resonant modes, which therefore introduce strong coupling with the solar radiation and eventually produce an ultra-broadband absorption. The absorption spectrum can be feasibly manipulated via tuning the structural parameters. Most importantly, in sharp contrast to the common absorbers formed with metallic nano-resonators, the titanium nitride based solar absorber is with much stronger thermal stability, illustrating the impressive promise for wide applications such as thermo-photovoltaics and other high-power optoelectronic processes.