Semiconductor optical cooling as heat-to-light energy conversion

Abstract Semiconductor optical cooling can be viewed as a heat-to-light energy-conversion process in which thermal energy is incorporated into electronically excited states and extracted from the material through luminescence. This Progress Report reviews the development of semiconductor optical cooling and the remaining challenges. We first describe the fundamental physics of optical cooling from the viewpoints of energy balance and thermodynamics, and then survey experimental studies of semiconductor optical cooling, with particular attention to halide perovskites. We further distinguish among the condition for net cooling, the achievable cooling power, and the actual attainable temperature, and discuss how photon recycling and Auger recombination affect the cooling efficiency and cooling power, as well as the factors that determine the attainable temperature. Finally, we discuss material design strategies for controlling heat-to-light energy conversion and perspectives toward thermo-optical materials physics.