Design of an InSb thermoradiative system for harvesting low-grade waste heat

We propose a thin-film InSb-based thermoradiative system (TRS) and assess its performance characteristics by using a parametric design at low-grade waste heat. We consider the effects of several loss mechanisms on system performance, including optical, sub-gap radiation, and non-radiative losses. Our results predict that the 50 nm thick InSb TRS operating with a hot (cold) source at 500 K (300 K) may yield a power density of 113  Wm^-2 and an efficiency limit of 10.5%. To enhance the system performance, more efforts should be paid to optimize the layer thickness, enhance optical radiation, improve surface passivation, and fabricate an Ag back-reflective mirror and an optical filter for frequency-dependent photon recycling. This Letter provides new insights, to the best of our knowledge, for optimal designs and energy loss mechanisms, thus paving a route towards the development of practical TRS at a low temperature of around 500 K.