Reducing blinking in small spherical CuInS2/ZnS quantum dots via non-injection synthesis: A single particle subpopulation analysis.

by Nguyen, Anh; Heyes, Colin D.; Baucom, Dustin; Gao, Feng

Cadmium-free CuInS2/ZnS core/shell quantum dots are synthesized through a non-injection synthetic method for both the cores and shelling steps. The resulting CuInS2/ZnS quantum dots are small (~ 4-7 nm) and spherical with photoluminescence quantum yields (PLQY) in the range of 40-70%. The structure, chem. compn. and optical properties of CuInS2/ZnS quantum dots at both ensemble and single-particle level are carefully investigated as functions of the synthesis conditions. The results show that overcoating CuInS2 cores using lower Zn(St)2 precursor concns., an extensive cation exchange process occurs followed by forming a thin ZnS shell. Further increasing Zn(St)2 concn. to 2-4 mmol during shelling process leads to thicker shells so that fluorescence intermittency (blinking) is significantly reduced. Moreover, we use a single particle subpopulation anal. to gain a better comprehension of the shelling process and its role on the blinking mechanism.