Computational study of excitons and biexcitons in semiconductor core/shell nanocrystals of type I and type II
Author(s)
Advisor
Demir, Hilmi VolkanDate
2013Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
In this thesis, we studied electronic structure and optical properties of Type-I,
Type-II, and quasi Type-II semiconductor nanocrystals (also known as colloidal
quantum dots). For a parametric study, we developed quantum mechanical models
and solved them using both analytical and numerical techniques. The simulation
results were compared to the experimental findings. We showed that charge
carrier localization at di↵erent spatial locations could be tuned by controlling size
parameters of the core and shell.
While tuning charge localization, we also predicted photoluminescence peaks
of these core/shell nanocrystals using our theoretical and numerical calculations.
We demonstrated that Type-II nanocrystals exhibit di↵erent tuning trends compared
to the Type-I ones.
We also investigated biexcitonic properties of nanocrystals using quantum
mechanical simulations, which are important especially in lasing applications.
We showed that two-photon absorption mechanism can be tuned by changing
the core and shell size in quantum dots. We calculated at which core and shell
sizes biexcitons in quantum dots show attractive or repulsive interaction. The
computational studies presented in this thesis played an important role in the
experimental demonstrations and understanding of controlling excitonic features
of core/shell nanocrystals.
Keywords
Nanocrystalsquantum dots
two photon absorption
exciton
biexciton
amplified spontaneous emission