Ultra‐Thin Infrared Optical Gain Medium and Optically‐Pumped Stimulated Emission in PbS Colloidal Quantum Dot LEDs.

Colloidal semiconductor quantum dots (QDs) can be considered a promising material platform for solution‐processed laser diodes. However, due to some fundamental challenges, the realization of electrically pumped lasing based on QDs remains unresolved. Here, a binary blend of QDs and ZnO nanocrystals is employed, which serve as nano‐sized scatterers to facilitate waveguide gain in ultra‐thin films. By carefully engineering the electric field in these films, an infrared amplified spontaneous emission in a record thin colloidal gain medium is observed, with a thickness of 16 nm, at a wavelength of 1675 nm. Employing these binary blends as a gain medium, an optically pumped infrared stimulated emission in a full‐stacked light‐emitting diode (LED) device is demonstrated. The functional LED device, which comprises a single layer of graphene as an anode electrode, shows strong electroluminescence under electrical injection. This study suggests a promising device for realizing infrared QD‐based laser diodes. [ABSTRACT FROM AUTHOR]