One-dimensional Microstructure Tungsten Gratings for Thermo Photovoltaic Applications

Abstract

In this study, a one-dimensional microstructure tungsten grating is optimized for potential application as Thermo Photovoltaic (TPV) emitter. The influence of gratings geometric parameters on the spectral emittance are studied by using the Rigorous Coupled-Wave Analysis (RCWA). The results show that the spectral emittance is affected by the gratings geometrical parameters and insensitive to the direction. The optimum parameters of the proposed structure are grating period 1.4 µm, a filling ratio 0.8 and grating height 0.2 µm. A broad peak of high emittance is obtained at wavelengths between 0.5 and 1.8 µm. A peak emittance close to unity at wavelengths between 0.5 and 2 µm is achieved and it drops below 0.2 at wavelengths above 2 µm. This can be explained by the surface plasmon polaritons excitation coupled with the grating microstructures. At longer wavelengths, the emittance remains low and this is highly desired for thermo photovoltaic applications to reduce the thermal leakage due to low-energy photons that do not produce any photocurrent. The proposed structure can be used as a selective emitter for TPV applications.

Laser Sintering of Tungsten Nanoparticles for Solar Thermal Receivers

“…Similar results were observed in [40] where they used rectangular periodical 1D gratings and peaks between 1 -2.5 µm were observed which were due to SPP excitation. We have observed increased absorption at 6 µm which is much further away in the IR than was observed by [40] and [41]. And there are no other reports that show enhanced absorption at beyond 4 µm for tungsten surface.…”

“…The sample was illuminated by IR wavelengths ranging from 2.5 to 12.5 microns and the reflected IR light was captured to provide a reflectance versus wavelength data. SPPs are local excitation of electromagnetic waves and they exist and propagate along the interface of two different media [41]. The energy of surface plasmons in metals usually exist near the ultraviolet range or visible range for some metals.…”

“…Fig. 25 below is taken from [41] to demonstrate the enhanced absorption caused by SPPs in the near IR region. It shows the structure of 1D tungsten periodical grating that was used for calculations to see the effect of grating height on absorptance in visible and near IR region.…”

“…The dispersive properties of metals depend on the complex dielectric function which leads to varying optical properties across the spectrum. Previous work[40][41] has shown that increased absorption in the near IR region of tungsten periodical gratings can take place due to surface plasmon polaritons (SPP) excitation.…”