Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency

Abstract

A heated semiconductor light-emitting diode at low forward bias voltage V<k(B)T/q is shown to use electrical work to pump heat from the lattice to the photon field. Here the rates of both radiative and nonradiative recombination have contributions at linear order in V. As a result the device's wall-plug (i.e., power conversion) efficiency is inversely proportional to its output power and diverges as V approaches zero. Experiments directly confirm for the first time that this behavior continues beyond the conventional limit of unity electrical-to-optical power conversion efficiency.

A design of a PhC-enhanced LED for electroluminescence cooling

“…[1][2][3] In this scenario, the wall-plug efficiency (WPE, η W P E ) of the LED is over 100% and net cooling might be observed. The phenomenon is called electroluminescent cooling (ELC) and has been studied for over half a century.…”

“…The thermoelectrical pumping effects in LEDs of various wavelength were also observed and reported by experimentalists. [10][11][12][13] The first observation of η W P E > 1 is reported in 2012 when Santhanam et al used lock-in measurement tools to demonstrate an infrared GaInAsSb/GaSb LED with η W P E over 200% at 135 • C. 1 In 2013, higher-than-unity η W P E was achieved in mid-infrared LEDs at room temperature. 14 All these ultra-efficient LEDs operated at extremely low bias (qV kT ), and their output power densities were merely several hundreds nW/cm 2 , which is not enough for direct observation of temperature drop.…”

Yield and leakage currents of large area lattice matched InP/InGaAs heterostructures

“…6 While EL cooling at technologically relevant power levels is yet to be demonstrated, the expectations for functional thermophotonic coolers have very recently been reinforced by the progress and first demonstrations of optical refrigeration in doped glasses 7,8 and II-IV compound semiconductors 9 as well as the demonstrations of very low power EL cooling in GaSb/InGaAsSb LEDs. 10,11 Although the first EL cooling demonstrations took place under very low bias voltages, they demonstrated electricityto-light conversion efficiencies exceeding unity by a large margin. However, to increase the cooling power, optimized large area LED structures are needed.…”

An Actively Quenched Single Photon Detector with a Light Emitting Diode

“…The LED has grown in popularity dramatically due to its low energy requirements for lighting applications; in fact, the LED can even operate above unit efficiency by pumping heat from the environment into visible light (Santhanam, Gray, & Ram, 2012). However, it is not the lighting capabilities of the LED that we wish to explore.…”