Harnessing near-field interactions in a perfectly tuned metamaterial selective emitter for high-efficiency InSb thermophotovoltaics

Thermophotovoltaic (TPV) systems are gaining attention as a solid-state route for efficient heat-to-electricity conversion, particularly where compact, high-performance power sources are required. A central challenge is the design of emitters that closely match the photovoltaic (PV) cell’s bandgap while minimizing spectral losses. Conventional emitters often radiate broadly, wasting energy outside the useful range, and rely on complex nanostructures that are difficult to fabricate and thermally unstable. The emergence of near-field (NF) emitters, enabled by the recent advances in hyperbolic metamaterials, has provided a new pathway by harnessing evanescent waves and surface polariton modes to enhance radiative heat transfer far beyond the blackbody limit while enabling highly selective emission, but still they suffer from having complex structures. Here, we propose a structurally simple NF emitter based on a metal–dielectric–metal metamaterial, with tantalum (Ta) as both resonator and ground layers and calcite (CaCO3), a uniaxial hyperbolic metamaterial, as the dielectric spacer. The design is tuned to emit strongly at 6.6 μm, ideally matched to the 0.173 eV bandgap of InSb PV cells, achieving near-unity peak emissivity with narrow spectral selectivity. Combining NF enhancement with fabrication-friendly architecture and thermal robustness, this emitter overcomes the limitations of broadband and geometrically complex designs, positioning it as a practical and scalable solution for next-generation TPV technologies.