Fundamental Efficiency Bounds for the Conversion of a Radiative Heat Engine's Own Emission into Work

The thermoradiative diode is a novel heat engine that converts athermal radiative emission from a hot converter to a colder environment into work. This stands in contrast to essentially all radiative heat engines realized to date, where an external hot reservoir radiates toward a converter that resides at (and can be reversibly coupled to) a cold reservoir. We derive the fundamental bounds on conversion efficiency and power production for generalized far-field hot-side heat engines with radiative exchange that can be black body (thermal) or, more generally, athermal. This is followed by the corresponding derivation for the rich landscape of performance bounds for the specific case of thermoradiative diodes, including why the Landsberg-efficiency limit associated with heat engines that include radiative exchange can be surpassed, and how the ultimate Carrot-efficiency limit could be approached.