2D Photonic-crystals for high spectral conversion efficiency in solar thermophotovoltaics

We present a novel solar thermophotovoltaic (STPV) device, which for the first time, incorporates a two-dimensional photonic-crystal (2D PhC) absorber-emitter to achieve spectral conversion efficiencies >10%. These results were achieved by tailoring the spectral properties of the absorber-emitter through surface nanostructuring of tantalum (Ta) and minimizing parasitic thermal losses through an innovative vacuum-enclosed experimental setup. By incorporating a sub-bandgap photon reflecting filter on the PV surface and optimizing the absorber-emitter ratio, we present how the demonstrated 2D Ta PhCs enable a realistic STPV configuration to exceed the Shockley-Queisser ultimate efficiency of a 0.55 eV cell.