Manifestations of Varying Grading Level in CdSe/ZnSe Core-Shell Nanocrystals

Graded interface core shell nanocrystals (NCs) are being investigated to attain highly luminescent systems and are also anticipated to be "blinking-free" at the single-particle level. In the present work, CdSe/ZnSe-graded core-shell NCs with varying confinement potential profile are studied at the single-particle level. The internal structure of NCs is determined with the aid of optical, structural, and chemical probes. Notably, the radiative lifetime for different nanostructures decays monoexponentially. The variation in the radiative lifetime due to differing internal structure is understood on the basis of recently reported first-principles study on different interfaces of core-shell NCs, in particular attributed to varying overlap of electron hole wave functions. The single NC measurements reveal that the percentage of nonblinking NCs is higher for slowly varying confinement potential. Statistically suppressed blinking (similar to 80%) and a single exponential PL decay curve,-accompanied by a very narrow (similar to 30 meV) emission 'line at the single NC level, are observed in graded CdSe/ZnSe core shell NCs.