Abstract
A thermophotovoltaic (TPV) system converts heat that is absorbed via conduction, convection, and/or radiation to electricity. The efficiency of TPV energy conversion can be improved with a narrowband selective emitter that emits photons at just above the bandgap energy towards the TPV photodiode. We numerically report a selective metamaterial (MM) emitter design with a single layer of cylindrical structures of p-type silicon (boron-doped). Our design (substrate-free) features a peak absorbance of 94.8% at the wavelength of 3.47 μm with the smallest lateral dimension of 0.8 μm. The absorption is found to be due to the resonance of electric and magnetic fields in the structure. The larger dimensions of our selective MM emitter design make it significantly easier to pattern than many of previously reported selective MM emitters operating at similar wavelengths to that of our work. We believe that our work demonstrates a path forward for future research on larger-area all-semiconductor selective MM emitters with a variety of peak absorbance wavelengths for TPV applications.
Highlights
Thermophotovoltaic (TPV) systems are similar to photovoltaic systems except that they convert heat to electricity instead of focusing more on the visible wavelengths
These selective MM emitters are made of multiple dielectric and metallic layers or have nanometer-scale feature sizes where fabrication is difficult and can lead to pattern imperfections that may lower the performances
We are interested in all-semiconductor narrowband selective MM emitters with larger lateral feature sizes as deposition height can be controlled more in nanometer scales compared to lateral dimensions
Summary
Thermophotovoltaic (TPV) systems are similar to photovoltaic systems except that they convert heat (infrared light) to electricity instead of focusing more on the visible wavelengths. According to Kirchhoff’s law,[1,2] at thermal equilibrium, the emissivity of an object is equal to its absorptivity. For this reason, the terms ‘‘absorption’’ and ‘‘emission’’ may be interchangeably used elsewhere in this paper unless they have to be technically distinguished. The MM emitter’s performance may be more likely to decrease with time with more materials used or more interfaces between different materials due to optical property variation or/and compound formation at elevated temperatures. This provides motivation to develop larger-feature-sized, more structured
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