Doctoral thesis viva voce: Clémentine Javaux

Study of the blinking reduction in thick-shell CdSe/CdS semiconductor nanocrystals

Clémentine Javaud, doctorante - PhD student Crédits : ESPCI ParisTechSemiconductor colloidal nanocrystals exhibit a blinking phenomenon, which appears as an obstacle for many applications. In this work we were interested in the suppression of the blinking phenomenon in nanocrystals composed of a CdSe core and a thick CdS shell.

We developed an easy, rapid and robust protocol for the synthesis of thick-shell CdSe/CdS non-blinking semiconductor nanocrystals. The study of the temperature dependence of the optical properties of these nanocrystals at the single particle level led us to determine the origin of the blinking suppression in these structures. We evidenced the thermal activation of the non-radiative Auger recombination, which is responsible for blinking in these nanocrystals. This thermal activation is linked to the temperature dependence of the electron localisation. At cryogenic temperature, these nanocrystals are negatively charged and exhibit excellent optical properties : they have a radiative lifetime shorter than 10 ns and a 100% quantum yield. These remarkable features allowed the direct study of the nanocrystals magneto-optic properties. These results open the way to the design of nanocrystals with a 100% quantum yield at room temperature.