Effects of functionalization and side defects on single-photon emission in boron nitride quantum dots

Boron nitride quantum dots (BNQDs) functionalized with chemical ligands exhibit intriguing optoelectronic properties due to the quantum confinement effect. This paper presents peculiar insights on the effect of side defects on the electronic structure and optical properties of BNQDs functionalized with different chemical bonds including hydrogen (H), nitrogen (N), hydroxyl (OH), amine (${\mathrm{NH}}_{2}$), and thiol groups (inspired by experimental reports of functionalized BN nanosheets and nanotubes) Weng et al., Chem. Soc. Rev. 45, 3989 (2016). Hybrid density functional simulations and Green's function calculations indicate an intriguing coexistence of two different Peierls-like distortions in the functionalized low-dimensional material. The presence of side defects increases the side strain and creates interband electronic states. As a result, the band gap of BNQDs could vary in a wide range depending on the type of chemical bonds and surface disorders. Enhanced edge states also improve the photoluminescence emission of the quantum dots. These side-defect enriched states in BNQDs create optical and electrical responses which could offer unprecedented potential for large scale nanophotonics such as photovoltaic, bioimaging, and quantum communication.