Engineering Core Size of InP Quantum Dot with Incipient ZnS for Blue Emission

Blue indium phosphide quantum dot (InP QD) is an emerging colloidal semiconductor nanocrystal, considered as a promising next-generation photoactive material for light-emitting purposes. Despite the tremendous progress in blue InP QDs, the synthetic method for tailoring InP core size to realize the blue-emissive QDs still lags behind. This work suggests a synthetic method for blue-emitting InP QDs by engineering the core size with an incipient ZnS (i-ZnS) shell. The formation of i-ZnS complexes, before the tris(trimethylsilyl)phosphine injection (e.g., before core growth process), restrains the overgrowth of InP nuclei by rapidly forming a ZnS shell on its surface, thereby resulting in further dwarfed InP cores. With additional ZnS shell coating, the blue QDs exhibit a photoluminescence quantum yield of ≈52% at 483 nm. The origin of bandgap diminution with the increase of shell thickness, or with the utilization of ZnSe shell is unraveled via the first-principles density functional theory simulations. Simulational evidence on InP-core densification with the shell coating, along with accompanying changes in chemical and structural properties, is presented. The blue-emitting InP QD device shows a maximum luminance of 1162 cd m⁻² and external quantum efficiency of 1.4%.