Optoelectronic design points to ways for LEDs to chill out

Advances in optoelectronics have led to foundational technologies like optical communication, by which we all access the internet. Optoelectronics also includes other real-world products, such as light-emitting diodes and solar cells. As these devices continue to become more efficient, they hold important implications for unexpected uses. In the Journal of Applied Physics, a group of researchers suggest that LEDs can even provide refrigeration.

The scientists claim that highly efficient LEDs should become cold as they emit light. They examined the practical efficiency limits of present optoelectronic technology for cooling applications by optimizing gallium arsenide/indium gallium phosphide (GaAs/GaInP) double heterostructure LEDs. In a practical design, based on presently available optoelectronic materials, they predict their design is capable of reaching an external LED efficiency in excess of 97 percent. Any efficiency above 80 percent produces net cooling.

After optimizing the LED for efficiency, the designed device is projected to emit photons whose energy exceeds the applied voltage, reducing the number of photons wasted as heat. Heat in the form of lattice vibrations makes up for this energy shortfall, leading to a refrigeration effect.

After providing refrigeration, the LED light is recovered as electricity in a photovoltaic cell, further reducing the device’s inefficiency. A vacuum spacer separates the warm photovoltaic cell from the cold LED, eliminating heat leakage. In effect, a flow of light is the refrigerator’s working fluid.

The research group envisions that, at moderate power densities, the electroluminescent LED refrigerator can exceed the performance of thermoelectric refrigerators near room temperature and be substantially more efficient at temperatures of 100 to 200 kelvins, where thermoelectric refrigerators cannot compete at all.

Source: “Electroluminescent refrigeration by ultra-efficient GaAs light-emitting diodes,” by T. Patrick Xiao, Kaifeng Chen, Parthiban Santhanam, Shanhui Fan, and Eli Yablonovitch, Journal of Applied Physics (2018). The article can be accessed at https://doi.org/10.1063/1.5019764 .