Design of Selective Metasurface Filter for Thermophotovoltaic Energy Conversion

Optical filters with narrow transmission band above the bandgap of thermophotovoltaic (TPV) cells are not restrained by the rigorous thermal reliability as needed for the emitters. In this work, a novel metasurface filter made of an aluminum nanopillar (AlNP) array on a quartz substrate is proposed to achieve spectrally selective transmission above the bandgap of the TPV cell. Optical simulations using Finite-difference time-domain were carefully performed to determine the appropriate AlNP period, diameter, and height such that the resulting nanopillar array will show narrowband transmission at a wavelength of 1.9 μm, which is close to the bandgap of a commercial gallium antimonide (GaSb) TPV cell. The narrow-band transmission enhancement can be attributed to the magnetic polariton (MP) resonance between neighboring Al nanopillars. The MP mechanism is further confirmed by an inductor-capacitor circuit model and the effects of the nanopillars' period, diameter, height, as well as incidence angles were discussed. Moreover, open-circuit voltage, short-circuit current density, output electric power, and conversion efficiency were evaluated for the GaSb TPV cell coupled with the AlNP metasurface filter structure with enhanced TPV performance.