Thickness-dependent Shell Homogeneity of ZnSe/CdSe Core/Shell Nanocrystals and Their Spectroscopic and Electron- and Hole-transfer Dynamics Properties

作者：Cao, Jun; Jiang, Zhong-Jie^*

来源：Journal of Physical Chemistry C, 2020, 124(22): 12049-12064.

DOI：10.1021/acs.jpcc.0c01964

• CDSE QUANTUM DOTS
• I CORE-SHELL
• CHARGE SEPARATION
• REPRODUCIBLE SYNTHESIS
• RADIATIVE LIFETIMES
• OPTICAL-PROPERTIES
• SURFACE
• SIZE
• FLUORESCENCE
• ENERGY

Core/Shell structured ZnSe/CdSe NCs were synthesized in this work. It shows that, for a given 2.79 +/- 0.28 nm core the carrier localization regime of the ZnSe/CdSe nanocrystals (NCs) can be tuned from type-I to typeII and then to inverse type-I by simply increasing the shell thickness from 0.55 +/- 0.08 to 1.86 +/- 0.11 nm. The spectroscopic properties and carrier localization regime of the ZnSe/CdSe NCs can be well-predicted using the effective mass approximation model, in which the influences of the interdiffusion, lattice mismatch, and optical band bowing on the electron/hole wave function distribution and energetic potentials are considered. The photoluminescence (PL) decay dynamics of the ZnSe/CdSe NCs are in good agreement with the carrier localization regime predicted from the calculation. The cation interdiffusion was demonstrated to have a profound influence on the spectroscopic properties of ZnSe/CdSe NCs. At 280 degrees C, the cation interdiffusion constant estimated from the spectroscopic analysis is 0.015 +/- 0.002 nm(2) min(-1). The PL quenching results indicate that electrons and holes in the ZnSe/CdSe NCs can be readily transferred to the surface electron and hole quenchers, regardless of the shell thickness and carrier localization regime. The shell growth of the ZnSe/CdSe NCs is found to comply with a Stranski-Krastanov model, where the CdSe shell grows uniformly with thickness less than 0.55 +/- 0.08 nm, at the initial monolayers, followed by the inhomogeneous shell thickness increase.