Thermoradiative Power Conversion from HgCdTe Photodiodes and Their Current-Voltage Characteristics

The thermoradiative diode represents the less well-known symmetric counterpart to solar photovoltaics that instead utilizes the net emission of light rather than absorption to generate power. While there are promising theoretical predications for its application in night-sky power generation and waste heat recovery, the current technological limits have not been explored. Here we explicitly measure the electro-optical characteristics of HgCdTe photodiodes across a range of bandgap energies in both thermoradiative and photovoltaic operation, supported by theoretical calculations that include critical nonradiative processes. At a temperature differential of only 12.5 degrees C, we measure a peak thermoradiative electrical power density of 2.26 mW/m2 for a photodiode emitting near 4.7 mu m, with an estimated radiative efficiency of 1.8%. Our results highlight the need for achieving high radiative efficiencies with mid-infrared semiconductors to deliver on the promise of thermoradiative power generation.