Synthesis of Metal–Quantum Dot Core–Satellite Nanoparticles and Plasmonic Cavity-Induced Recovery of Quantum Yield for High External Quantum Efficiency

Quantum dots (QDs) have been extensively studied for their unique optical and electronic properties arising from quantum confinement. In particular, less toxic and environment-friendly InP/ZnSe/ZnS QDs have been successfully commercialized in display devices, but their low absorption characteristic still limits external quantum efficiency (EQE). As multidirectional structural engineering has brought internal quantum yield (QY) close to unity, further improvements in EQE now depend on enhancing light absorption, often achieved via photonic cavities integrated with plasmonic materials. However, optical interactions between plasmonic cavities and InP-based QDs remain largely unexplored to fully exploit the potential, primarily due to their nonunified decay dynamics and the synthetic difficulty of establishing consistent photonic environments across all emitters. Here, we present a silanol-alcohol condensation-based chemistry to precisely and stably form plasmonic cavity-coupled QDs (Ag nanosphere-InP/ZnSe/ZnS QD core-satellite nanoparticles, AgNS-QD CSPs). We demonstrate that plasmonic nanostructures can reorganize internal carrier dynamics by redirecting nonradiative decay pathways into radiative ones, offering a strategy to recover QY reduced by environmental degradation. Such postsynthetic modulation provides a previously inaccessible route to surpass the performance ceiling imposed by structural optimization of QDs, while simultaneously enhancing the absolute absorption with an unexpectedly large photoluminescence. To highlight practical applicability, we fabricate color conversion films incorporating plasmonic cavities and achieve an EQE of 34%, unattainable in color conversion films relying solely on QDs. These findings suggest that plasmonic cavities can significantly improve the efficiency and broaden the applicable scope of QD-based technologies, including display devices and other optoelectronic applications.