A tungsten-based metamaterial emitter for solar thermophotovoltaic systems

Solar thermophotovoltaic systems are capable of showing efficient photoelectric conversion and are expected to surpass the Shockley-Queisser limit, owing to the spectrum-selective functionality of metamaterial selective emitters. Generally, metamaterial emitters are manufactured from multifarious materials, which also makes their manufacturing process complicated. Here, we propose a tungsten-only emitter composed of two rectangular bars with different widths and heights arranged in a cruciform structure, featuring a rectangular cavity at the top. Results from the simulations reveal that the emissivity of the metamaterial emitter exceeds 90% at the wavelength of 950-1590 nm and drops below 20% for wavelengths exceeding 2025 nm, which can effectively match GaSb photovoltaic cells. The outstanding emission performance is attributed to the coupling effect of surface plasmon resonance, cavity resonance and guided mode resonance, as evidenced by the analysis of electric and magnetic fields. We also explored the radiation spectrum in the 500-2500 K temperature range and found that it performed best at 1400 K. It is concluded that the emission performance is slightly affected by structural parameters and angles. This study presents a meaningful exploration of efficient solar utilization. We propose a tungsten-only emitter with over 90% emissivity in the wavelength range of 950-1590 nm and lower emissivity in the wavelength range exceeding 2000 nm, which can effectively match GaSb cells for thermoelectric conversion.