Abstract
Binary gratings with high or low metal filling ratios in a grating region have been demonstrated as successful candidates in enhancing the emittance of emitters for thermophotovoltaics since they could support surface plasmons (SPs), the Rayleigh–Wood anomaly (RWA), or cavity resonance (CR) within their geometries. This work shows that combining a tungsten binary grating with a low and high filling ratio to form a pyramid grating can significantly increase the emittance, which is nearly perfect in the wavelength region from 0.6 to 1.72 μm, while being 0.1 at wavelengths longer than 2.5 μm. Moreover, the emittance spectrum of the hybrid tungsten grating is insensitive to the angle of incidence. The enhancement demonstrated by magnetic field and Poynting vector patterns is due to the interplay between SPs and RWA modes at short wavelengths, and CR at long wavelengths. Furthermore, a combined grating made of nickel is also proposed providing enhanced emittance in a wide angle of incidence.
Highlights
Thermophotovoltaic (TPV) devices used to generate electricity directly from heat have attracted great attention since they could solve many problems of conventional energy resources such as cleanness, portability, or low maintenance [1]
The transverse magnetic (TM) wave is considered here due to its enhancement attributed to many excitations including surface plasmons (SPs), localized SPs, magnetic polaritons (MPs), Rayleigh–Wood anomaly (RWA), or cavity resonance (CR) compared with the transverse electric (TE) wave
The results presented in figure 7 with the analytical solutions demonstrated in equations (1)–(3) confirmed that the enhancement of magnetic fields in the grating structure with Λ = 800 nm at the short wavelength is due to the interplay of the SPs and the RWA, while the maximum emittance at longer wavelengths obtained from both optimized gratings is attributed to the CR modes
Summary
Thermophotovoltaic (TPV) devices used to generate electricity directly from heat have attracted great attention since they could solve many problems of conventional energy resources such as cleanness, portability, or low maintenance [1]. Many researchers using different evolutionary optimizations and design-based physical studies have tried various grating structures with rectangular, triangular, or blazed profiles to achieve maximum emittance [2,3,4,5,6,7,8,9, 11,12,13,14,15, 17,18,19,20,21,22,23,24,25, 35]. The transverse magnetic (TM) wave is considered here due to its enhancement attributed to many excitations including SPs, localized SPs, MPs, RWA, or CR compared with the transverse electric (TE) wave. It is incident on the grating layer depicted by a wavevector k and an incidence angle (θ)
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