Observation of Peltier Cooling and Great Potential of Electroluminescent Cooling in GaN-Based Light-Emitting Diodes

Light-emitting diodes (LEDs) are essential for future energy-saving lighting and display technology owing to their high efficiency, long lifetime, and low cost. To further enhance the performance of GaN-based LEDs, electroluminescent (EL) cooling has been widely predicted to be useful over the past several decades; however, it has not been experimentally achieved. Herein, thermoelectric and phonon-pumped GaN-based LEDs have been demonstrated by both experimental measurements and theoretical modeling. It is surprisingly found that the effect of increasing temperature changes from negative to positive when the operating point is moved to the high-efficiency, midvoltage range. The power efficiency exhibits a maximum 2.24-fold improvement with increasing temperature (from room temperature to 473 K), and the peak efficiency at all elevated temperatures outperforms that at room temperature, where the Peltier effect changes from Peltier heat to Peltier cooling. Under lower biases, the phonon-assisted Peltier cooling provides additional energy for carriers to overcome the potential barrier and achieve recombination. The findings not only give an insightful understanding of EL cooling but also provide guidelines on thermal management and designing high-performance GaN-based LED devices and arrays (e.g., micro-LEDs), which can be further extended to other kinds of LEDs and optoelectronic devices.