  Solar energy promises a viable solution to meet the ever-increasing power
demand by providing a clean, renewable energy alternative to fossil fuels. For
solar thermophotovoltaics (STPV), high-temperature absorbers and emitters with
strong spectral selectivity are imperative to efficiently couple solar
radiation into photovoltaic cells. Here, we demonstrate refractory metasurfaces
for STPV with tailored absorptance and emittance characterized by in-situ
high-temperature measurements, featuring thermal stability up to at least 1200
C. Our tungsten-based metasurface absorbers have close-to-unity absorption from
visible to near infrared and strongly suppressed emission at longer
wavelengths, while our metasurface emitters provide wavelength-selective
emission spectrally matched to the band-edge of InGaAsSb photovoltaic cells.
The projected overall STPV efficiency is as high as 18% when employing a fully
integrated absorber/emitter metasurface structure, much higher than those
achievable by stand-alone PV cells. Our work opens a path forward for
high-performance STPV systems based on refractory metasurface structures.
