Infrared light-emitting diodes based on colloidal PbSe/PbS core/shell nanocrystals**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0401702), the National Natural Science Foundation of China (Grant Nos. 61674074 and 61405089), Development and Reform Commission of Shenzhen Project, China (Grant No. [2017]1395), Shenzhen Peacock Team Project, China (Grant No. KQTD2016030111203005), Shenzhen Key Laboratory for Advanced Quantum

Abstract

Colloidal PbSe nanocrystals (NCs) have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges. However, the fast degradation of colloidal PbSe NCs in ambient conditions hampers their widespread applications in infrared optoelectronics. It is well-known that the inorganic thick-shell over core improves the stability of NCs. Here, we present the synthesis of PbSe/PbS core/shell NCs showing wide spectral tunability, in which the molar ratio of lead (Pb) and sulfur (S) precursors, and the concentration of sulfur and PbSe NCs in solvent have a significant effect on the efficient PbS shell growth. The infrared light-emitting diodes (IR-LEDs) fabricated with the PbSe/PbS core/shell NCs exhibit an external quantum efficiency (EQE) of 1.3 % at 1280 nm. The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on PbSe/PbS NC-LEDs. Our results provide evidence for the promising potential of PbSe/PbS NCs over the wide range of infrared optoelectronic applications.