Ultra-low-power sub-photon-voltage high-efficiency light-emitting diodes

Abstract

Conventional light-emitting diodes (LEDs) face an efficiency droop at low current due to non-radiative recombination overtaking radiative recombination at low carrier density. To overcome this universal problem, we develop LEDs with high efficiency at ultralow current and voltage, using a novel quantum well design and high-quality interfaces to suppress non-radiative recombination and enhance radiative recombination. The device exhibits close to unity internal quantum efficiency at a low current density of <1 × 10−4 A cm−2, more than three orders of magnitude lower than conventional LEDs. The LED bias voltage is reduced to ~30% below the photon voltage (hν/q). Wireless communication is demonstrated at these low-power conditions, which enables new applications in smart dust and sensor networks 1–6 , low-cost block chain and authentication 7–9 , medical applications 10,11 and wherever high efficiency at low power is needed. New phenomena such as high-efficiency electroluminescent cooling becomes possible as the LED unity internal quantum efficiency extends to smaller voltage and current. By using a single-quantum-well active region with a unique well–cladding design to suppress non-radiative recombination and enhance radiative recombination, light-emitting diodes with close to unity internal quantum efficiency at a low current density of <10−4 A cm−2 are demonstrated.