Highly versatile near-infrared emitters based on an atomically defined HgS interlayer embedded into a CdSe/CdS quantum dot

The availability of colloidal quantum dots with highly efficient, fast and 'non-blinking' near-infrared emission would benefit numerous applications, from advanced optical communication and quantum networks to biomedical diagnostics. Here, we report high-quality near-infrared emitters that are based on well known CdSe/CdS heterostructures. By incorporating an HgS interlayer at the quantum dot core/shell interface, we convert normally visible emitters into highly efficient near-infrared fluorophores. Employing thermodynamically controlled sequential deposition of metal and chalcogen ions, we achieve atomic-level precision in defining the thickness of the HgS interlayer (H). This manifests in 'quantized' jumps of the photoluminescence spectrum when H changes in discrete, atomic steps. The synthesized structures show highly efficient photoluminescence, tunable from 700 to 1,370 nm, and fast radiative rates of similar to 1/60 ns(-1). The emission from individual CdSe/HgS/CdS colloidal quantum dots is virtually blinking free and exhibits nearly perfect single-photon purity. In addition, when incorporated into a light-emitting-diode architecture, these quantum dots demonstrate strong electroluminescence with a sub-bandgap turn-on voltage.

Automated summary

This study presents high-quality near-infrared emitters based on CdSe/CdS heterostructures, which are converted from normally visible emitters to highly efficient near-infrared fluorophores by incorporating an HgS interlayer. The structures synthesized in this study exhibit highly efficient photoluminescence with atomic-level precision in defining the thickness of the HgS interlayer, resulting in 'quantized' jumps of the photoluminescence spectrum. Furthermore, the emission from these colloidal quantum dots is virtually blinking free and shows nearly perfect single-photon purity, making them promising for various applications.