Near-unity, full-spectrum, nanoscale solar absorbers and near-perfect blackbody emitters

The design of sub-wavelength structure with full-spectrum near-unity solar absorption is a long-sought-after goal of crucial importance for optoelectronic materials and technology. To date, numerous attempts to tackle this problem consisted either of using stronger absorption-but narrowband or the broader spectrum-but moderate light trapping mechanisms. Herein, a novel strategy that achieves perfect absorption for solar energy in the full-spectrum range of the sun's radiance is presented by the thin-film refractory metal resonators. This impressive absorption mainly stems from the cooperative effect of strong plasmonic resonances and the intrinsic broadband spectral responses by the refractory metals, such as Ti, V, W, etc. The full-spectrum weighted solar absorption efficiency is exceeding 98%, showing a near-unity light trapping for the sun's radiation. Moreover, excellent thermal emitting with the spectral averaged efficiency similar to 91% is achieved in the wavelength range (280-4000 nm) by the W-based absorber, suggesting a platform for near-perfect blackbody emitting source. More importantly, the investigations on achieving full-spectrum solar absorbers and thermal emitters provide new insight on the mechanism and philosophy for the design. Just like the proverb, in order to catch bandits, the first thing is to catch the ringleader. As for the purpose of achieving full-spectrum near-unity absorbers or radiators, the key point is to perfectly trap or excite the solar/thermal power in the main distribution ranges for the sunlight or the blackbody radiation. Accordingly, these attractive properties and findings suggest that the investigation and the related full-spectrum solar absorbers and blackbody radiator might have promising applications in the fields related to energy harvesting and conversion.