Material Parameters and Device Models for Thermoradiative Energy Conversion

• Nolan McGrane-Moffitt, Physics, Grinnell College

• Jamie Phillips, Electrical and Computer Engineering, University of Delaware

Thermoradiative (TR) energy conversion is the process of generating electrical power by using net radiative emission from a hot object to a much cooler surrounding environment. When using a p-n junction diode with narrow-bandgap semiconductors, the heat emission results in electrons in the n-type semiconductor jumping to excess holes in the p-type semiconductor, generating an electric current. This work had two primary parts: developing an online tool that could be used to expedite theoretical calculations of the power density produced by TR devices, and investigating/confirming the TR properties bulk InAsSb devices. 

Utilizing the model proposed by Vurgaftman (2023), I produced a calculator that accepts material parameters and operating conditions to output maximum power density calculations, along with graphs of that value in relation to both temperature and bandgap. This will help future users determine the best materials and environments to maximize TR power output for their specific use cases. 

To measure the TR capabilities of our InAsSb device (selected for its narrow bandgap) we used an extreme environment (-100 ºC) and heated the device to different temperatures from 28 ºC to 128 ºC. From this we were able to determine how device size and temperature impact short circuit current and power density. Importantly, we collected the largest ever power density from a TR device. To confirm that this power production was indeed due to TR energy conversion, we constructed an experiment in which we mounted the device to a plate with variable heat and placed a thermoelectric cooler above it, separated with a chopper. Using a Lock-In-Amplifier, we could see the difference in power production when the device was exposed to the cooler and when it was covered. Our results supported that the power production seen previously was a result of thermoradiative processes.