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ABSTRACT The vast majority of power generation in the United States today is produced through the same processes as it was in the late-1800s: heat is applied to water to generate steam, which turns a turbine, which turns a generator, generating electrical power. Researchers today are developing solid-state power generation processes that are more befitting the 21 st -century. Thermophotovoltaic (TPV) cells directly convert radiated thermal energy into electrical power, through a process similar to how traditional photovoltaics work. These TPV generators, however, include additional system components that solar cells do not incorporate. These components, selective-emitters and filters, shape the way the radiated heat is transferred into the TPV cell for conversion and are critical for its efficiency. Here, we present a review of work performed to improve the components in these systems. These improvements will help enable TPV generators to be used with nearly any thermal source for both primary power generation and waste heat harvesting. 

Abstract— A promising technology for waste-heat recovery applications is thermophotovoltaics (TPVs), which use photovoltaic diodes to convert thermal energy into electricity. The most commonly used TPV diode material is gallium antimonide (GaSb). Recently, GaSb TPV diodes were fabricated with front-surface metallic photonic crystal (MPhC) filters to more optimally convert the incident spectrum. This method showed promising initial results, in part due to a shifting of the photogenerated carriers away from the front-surface and into the device. In this paper, we use the Atlas-Silvaco software package to optimize the TPV diode structure for MPhCs. We investigate the addition of an intrinsic region in the device to take advantage of the shifted photogeneration profile from the MPhCs. This design allows for a 10% improvement in internal quantum at the peak MPhC transmission wavelength. https://doi.org/10.1109/MWSCAS.2017.8053055 

Thermophotovoltaics (TPVs) are a potential technology for waste-heat recovery applications and utilize IR sensitive photovoltaic diodes to convert long wavelength photons (>800nm) into electrical energy. The most common conversion regions utilize Gallium Antimonide (GaSb) as the standard semiconductor system for TPV diodes due to its high internal quantum efficiencies (close to 90%) for infrared radiation (~1700nm). However, parasitic losses prevent high conversion efficiencies from being achieved in the final device. One possible avenue to improve the conversion efficiency of these devices is to incorporate metallic photonic crystals (MPhCs) onto the front surface of the diode. In this work, we study the effect of MPhCs on GaSb TPV diodes. Simulations are presented which characterize a specific MPhC design for use with GaSb. E-field intensity vs. wavelength and depth are investigated as well as the effect of the thickness of the PhC on the interaction time between the e-field and semiconductor. It is shown that the thickness of MPhC has little effect on width of the enhancement band, and the depth the ideal p-i-n junction is between 0.6􀈝m and 2.1um. Additionally, simulated results demonstrate an increase of E-field/semiconductor interaction time of approximately 40% and 46% for a MPhC thickness of 350nm and 450nm respectively.