Thermal pumping of light-emitting diodes

Abstract

The work presented here is a study of thermally enhanced injection in light-emitting diodes (LEDs). This effect, which we refer to as "thermal pumping", results from Peltier energy exchange from the lattice to charge carriers when current is injected into an LED. For an applied voltage V such that qV < (hw), where q is the electron charge and (hw) is the average emitted photon energy, thermal pumping can greatly enhance the wall plug efficiency of an LED. Thermal pumping can even give rise to LED wall plug efficiency greater than one, which corresponds to electroluminescent cooling of the diode lattice. Thermal pumping and electroluminescent cooling will be studied through numerical modeling and experiment. Our results include the first ever experimental demonstration of electroluminescent cooling in an LED. Finally we use the intuition gained from the study of thermal pumping to design an LED for maximized optical power output with 100% wall plug efficiency.