Blue-Shifted Emission in CdTe/ZnSe Heterostructured Nanocrystals

Properties of colloidal heterostructured nanocrystals are largely determined by the spatial distribution of photogenerated carriers across the junction of semiconductor materials that form the heterostructure. The two known types of carrier distributions are identified based on whether both carriers reside within the same (type I) or opposite (type II) sides of the heterojunction. Here we demonstrate the existence of another type of spatial carrier distribution in heteronanocrystals, which corresponds to the localization of both charges along the material junction. Such localization pattern was realized in novel CdTe/ZnSe heteronanocrystals, where the expected type I infrared emission was dominated by more intense photoluminescence in the 570−600 nm range, corresponding to the recombination of carriers within an interfacial alloy layer, formed by the cation and anion exchange between CdTe and ZnSe phases. Fabricated heteronanocrystals exhibit excellent optical characteristics including near-single-exponential lifetimes, enhanced emission stability, and fluorescence emission quantum yields of up to 24%.