High-efficiency BCN quantum dots with enhanced carrier kinetics enabled by synergistic control of the atomic ratio and interface engineering.

Ternary quantum dots composed of boron, carbon, and nitrogen (BCN QDs) have drawn tremendous attention because they combine the advantages of boron nitride (BN), graphene, and carbon nitride (CN), and are promising in lighting, photocatalysis, energy, and other optoelectronic fields. However, their optical performance presently lags behind that of binary QDs due to the compositional complexity of the ternary system during synthesis, the overlooked electron deficiency of the boron site and the formation of concomitant impurity defects. In this work, a synergistic strategy is proposed that combines precise atomic ratio tuning with interface oxygen defect engineering of BCN QDs, enabling tailored carrier kinetics for diverse application scenarios. Systematic investigations demonstrate that appropriate substitutional boron doping optimizes the electronic structure and conjugated π-system of carbon nitride and promotes the formation of mid-localized states from oxygen defect sites, thus remarkably boosting radiative electron-hole recombination. Consequently, the high-efficiency deep blue BCN QDs exhibit a record quantum yield of 80%, which is far superior to most previously reported BN or CN QDs. This affords deep-blue electroluminescence and tunable white photoluminescence. Furthermore, when engineered with an increased density of interface oxygen defects, the BCN QDs demonstrate advantages in photocatalysis, with a 2-fold improvement in HO production compared to pristine CN. This work reveals a coordinated and effective strategy that involves carrier kinetics regulation of metal-free ternary nanomaterials for controlled optoelectronic performance and expanded applications.