(608h) Temperature-Dependent Modeling of Formation and Growth of II-VI Semiconductor Nanocrystals

Authors: 
Abolhasani, M., Massachusetts Institute of Technology
Jensen, K. F., Massachusetts Institute of Technology
Structural and spectroscopic characteristics of quantum dots (QD) have been experimentally studied for more than a decade owing to their unique physicochemical properties that enable a wide range of applications (e.g. photovoltaics, LED displays, and bio-imaging). Nevertheless, only few studies have attempted to model their formation.[1, 2] Typically, the average size of prepared II-VI QDs can be controlled,[3] but the field lacks the quantitative understanding resulting from comparison between experimental observations (e.g. size distributions and concentrations) and model predictions. Therefore, the aim of this work is to: i) develop a deterministic model describing the formation and growth of II-VI QDs; ii) validate the model against experimental results; and iii) provide insights into the key kinetic parameters and their temperature dependency.

The experimental model system selected is cadmium selenide (CdSe) because of the good control and reproducibility offered by this class of semiconductor nanocrystals. Performing microfluidic experiments in-situ absorption spectroscopy, we obtain average time-dependent properties of CdSe QDs (i.e. concentration, average size and distribution width) at temperatures between 160-220oC.[4] Based on population-balance equations, a kinetic deterministic model is developed and the formation of CdSe QDs is described in good agreement with the CdSe experimental data. The present model opens up the possibility to optimize the synthesis of II-VI QDs, while providing temperature dependent kinetic rates for different stages of the QD formation (e.g. nucleation, growth, and dissociation).

Literature:

[1] Abe S, Capek RK, De Geyter B, Hens Z. Reaction Chemistry/Nanocrystal Property Relations in the Hot Injection Synthesis, the Role of the Solute Solubility. Acs Nano. 2013;7:943-9.

[2] Rempel JY, Bawendi MG, Jensen KF. Insights into the Kinetics of Semiconductor Nanocrystal Nucleation and Growth. J Am Chem Soc. 2009;131:4479-89.

[3] van Embden J, Chesman ASR, Jasieniak JJ. The Heat-Up Synthesis of Colloidal Nanocrystals. Chem Mater. 2015;27:2246-85.

[4] Abolhasani M, Coley CW, Xie LS, Chen O, Bawendi MG, Jensen KF. Oscillatory Microprocessor for Growth and in Situ Characterization of Semiconductor Nanocrystals. Chem Mater. 2015;27:6131-8.