Highly-efficient thermoelectric-driven light-emitting diodes based on colloidal quantum dots

Driven by sub-bandgap electric work and Peltier heat, thermoelectric-driven light-emitting diodes (TED-LEDs) not only offer much enhanced power-conversion-efficiency but also eliminate the waste heat generated during the operation of LEDs. However, cost-effective and high-efficiency TED-LEDs are not readily accessible for the epitaxially grown III-V LEDs due to the high chip cost and efficiency droop at low-medium brightness (current densities). Here we show that electroluminescence of colloidal quantum dots (QDs) LEDs (QLEDs) circumvents the deficiencies faced by conventional LEDs. The optimal red-emitting device fabricated by cost-effective solution processing technics exhibits external- and internal-power-conversion-efficiency of 21.5% and 93.5% at 100 cd/m², suited for high-efficiency solid-state lighting and high-resolution display. At this brightness, the electric driving voltage (V) of 1.89 V is lower than the photon voltage (V_p = hv/q = 1.96 V, q being the elemental charge). With typical V_p = 1.96 V, electroluminescence can be detected with the driving voltage as low as 1.0–1.2 V. Luminance of the thermoelectric-driven QLEDs (TED-QLEDs) remains ideally diffusion-dominated with the driving voltage lower than ~ 1.5 V, and further improvement on charge transport is expected to extend the linear ideality to all practical driving voltages.