High-Efficiency Plasmonic Metamaterial Selective Emitter Based on an Optimized Spherical Core-Shell Nanostructure for Planar Solar Thermophotovoltaics

Abstract

We propose a high-efficiency plasmonic metamaterial selective emitter based on a tungsten (W) spherical core-shell nanostructure for potential applications in planar solar thermophotovoltaics. This structure consists of silicon dioxide (SiO 2 )-coated W nanospheres periodically distributed on a W substrate and a thin W layer deposited on top. Using a new definition of spectral efficiency, numerical optimization is performed and its optical behaviors are systematically investigated. The numerical results show that our selective emitter has a high emissivity in the short wavelength range below the wavelength corresponding to the bandgap of the back photovoltaic cell and a low emissivity in the long wavelength range beyond it. Its spectral efficiency of 0.39 is much higher than those of other cases without the top W cover layer or the W nanospheres. Such excellent emission selectivity is attributed to the strong photonic interaction within the gaps between the adjacent core-shell nanospheres, the tightly confined optical fields in both the Ω-shaped W-SiO 2 -W nanocavities, and the bottom nanocavities formed by the W nanospheres and the W substrate. It is also very tolerant toward the thicknesses of the SiO 2 layer and the top W cover layer.

Optical Transition Rates in a Cylindrical Quantum Wire with an Inverse Parabolic Potential

“…For an electron wave function of the form given in Eq, the transition rates are found to be [20,21]. (10) where with being photon linear density. The absorption and the emission transition rates, respectively, are explicitly given by (11) and (12) Finally, it is helpful especially for purposes of computation, to replace the Dirac delta function with a Lorentzian factor according to in which is the so-called linewidth of resonance.…”

“…These quantum structures can be employed to realize a plethora of devices which utilize different properties of the quantum structures to perform various functions. The numerous device applications extend over a wide range of fields including biochemical sensing, medicine, energy generation and optoelectronics [5][6][7][8][9][10][11]. The celerity of operation and efficiencies of photonic devices, in particular, depend on optical transition rates of the constituent quantum structures.…”

Selective emitters for thermophotovoltaic applications

“…Metamaterial samples are often made of gold, aluminum, or copper with a dielectric as the spacer, such as alumina. The desire to use these samples in high temperature applications has led to the use of a tungsten and other refractory metals as the conductor and exploration of alternate dielectrics such as spin‐on glass , aluminum nitride , strontium titanate , or Ge 2 Sb 1 Te 4 . Metamaterials were first used as perfect absorbers in 2008, when Landy et al fabricated and analyzed an ERR and wire pattern sized to correspond to a peak wavelength in the microwave regime .…”

“…Metallic nanowires have been incorporated into larger dielectric structures to create polarization independent emitters . Tungsten nanospheres coated in SiO 2 and an additional layer of tungsten generates an emission curve similar to that of a 2D PhC . Concave grating metamaterials generate several sharp peaks due to the multiple polariton modes that appear .…”

A Nanostructure-Based High-Temperature Selective Absorber-Emitter Pair for a Solar Thermophotovoltaic System With Narrowband Thermal Emission

“…Besides the designed excellent spectral selectivity, another essential point is that the intermediate structure should withstand high temperatures, as its performance is limited by the melting points of the construction materials. Therefore, refractory materials are preferred, such as tungsten (W) and tantalum (Ta), whose melting points are not less than 3000 K. At present, many studies have been based on tungsten or tantalum to design the absorber and emitter devices [14][15][16][17][18][19][20][21][22][23][24][25], but the general efficiency is still not high enough. Furthermore, some of the designs use low-melting point dielectric materials to improve the system's performance [21][22][23][24][25], which will apparently limit the application of STPV devices.…”