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Thermophotovoltaics (TPV) is a versatile technology to generate high electrical power density utilizing multiple sources of heat, such as solar irradiation, radioisotope heaters, combustible materials, thermal storage systems, waste industrial heat etc., as input. TPV systems aim to surpass the efficiency beyond the Shockley-Queisser limit for photovoltaic conversion by tailoring the spectrum of the incident solar light to match the spectral response of a PV cell. Spectrally selective absorbers and emitters can greatly enhance the TPV conversion efficiency by maximizing the absorption of the incident sunlight and suppressing the emission of sub-bandgap and excessive energy photons. One approach of achieving spectral selectivity is through the use of micro and nanostructures to control light emission from surfaces. This presentation reviews optical modeling and characterization techniques of various types of novel nanostructures, including random textures, nanocones, nanoholes, and m ultilayer metal dielectric stack etc., for the design of high-performance selective surfaces needed for efficient TPV systems. In addition, the fabrication of a GaSb-based experimental TPV system comprising a multilayer metal-dielectric (Si3N4-W-Si3N4) coating-based selective emitter is also presented. The performance of the TPV system was evaluated using a high-power laser as a simulated input for concentrated solar power. The overall power conversion efficiency of 8.4% was measured at 1676 K.
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