Improved broadband spectral selectivity of absorbers/emitters for solar thermophotovoltaics based on 2D photonic crystal heterostructures

We propose a novel heterostructure based on 2D photonic crystals as broadband selective absorbers/emitters for solar thermophotovoltaics. Alternating hafnium oxide (${\mathrm{HfO}}_2$) and titanium oxide (${\mathrm{TiO}}_2$) filled cylinder cavities with tetragonal lattices are embedded into antireflection-coated tungsten ($\mathrm{W}$) film. The simulated results show that the designed structures can obtain high solar collection efficiency ${\eta }_{\mathrm{c}}$ of 87.9% as an absorber and great spectral emission efficiency ${\eta }_{\mathrm{e}}$ of 81.6% as an emitter. Meanwhile, high average absorptivity of 84.5% under 45° oblique incidence exhibits good performance of wide-angle absorption. This study provides a new way to acquire broadband spectral selective absorbers/emitters.