Demonstrating the Thermoradiative Diode: Generating Electrical Power Through Radiative Emission

Thermoradiative power generation is achieved through the emission of light from a warm ambient into a cold surroundings representing a thermodynamically symmetric counterpart to photovoltaic solar power generation. The thermoradiative diode provides a semiconductor implementation of this process whereby radiative emission from a warm diode into a cold environment expels more entropy than supplied by the flow of heat to the diode, hence permitting work to be performed. Under these conditions a reverse bias spontaneously forms across the diode allowing an electrical current to flow and hence delivering electrical power. We report the full IV characteristics from a 0.3eV HgCdTe diode was held at 20.5C and exposed to a radiant surface of different temperatures. Thermoradiative power is generated when the diode faces a cold(< 20.5C surface) delivering a positive photocurrent and negative voltage. In the radiative limit, where all parasitic processes are eliminated, a thermoradiative diode exposed to the cold night sky could deliver electrical power densities of the order of tens of W/ m2, offering the tantalizing prospect of generating useful quantities of electrical power. The linear behaviour of our IV curves is consistent with Auger mediated generation and recombination processes that reduce the power density for currently available commercial diodes to mW/cm2.