Ultrasmall HgTe Quantum Dots with Near-Unity Photoluminescent Quantum Yields in the Near and Shortwave Infrared

We demonstrate a low-temperature synthesis of ultrasmall (<2 nm) HgTe quantum dots (QDs) with superlative optical properties in the near and shortwave infrared. The tunable cold-injection synthesis produces HgTe QDs ranging from 1.7 to 2.3 nm in diameter, with photoluminescence maxima ranging from 900 to 1180 nm and a full-width at half-maximum of ∼100 nm (∼130 meV). The synthesized quantum dots display high photoluminescence quantum yields (PLQY) ranging from 80 to 95% based on both relative and absolute methods. Furthermore, samples retain their high PLQY (∼60%) in the solid state, allowing for first-of-their-kind photoluminescence imaging and blinking studies of HgTe QDs. The facile synthesis allows for the isolation of small, photostable HgTe quantum dots, which can provide valuable insight into the extremes of quantum confinement.