Radiant refrigeration by semiconductor diodes

Dousmanis et al. [Phys. Rev. 133, A316 (1964)] demonstrated that GaAs light‐emitting diodes could produce a cooling effect if the quantum efficiency (ratio of photon flux to junction current) is very close to unity (e.g., >0.97). Here, it is pointed out that for narrow‐bandgap semiconductors, the quantum efficiency need not be so high to produce cooling. Also, for narrow‐bandgap semiconductors there is an additional cooling mode in which the reverse‐biased diode cools its radiant environment by absorbing infrared radiation. Maximum cooling rates per unit of junction area are on the order of n2σT4, where n is the index of refraction, σ is the Stefan–Boltzmann constant, and T is the temperature. For small cooling rates the efficiency for cooling can approach the limit imposed by the second law of thermodynamics.