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Title page for ETD etd-11162015-094907


Type of Document Dissertation
Author Orfield, Noah Jeremiah
Author's Email Address noahjorfield@gmail.com
URN etd-11162015-094907
Title Correlation of the Atomic Structure and Photoluminescence of the Same Colloidal Quantum Dot
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Sandra J. Rosenthal Committee Chair
Janet E. Macdonald Committee Member
John A. McLean Committee Member
Richard F. Haglund Committee Member
Timothy P. Hanusa Committee Member
Keywords
  • quantum dot
  • scanning transmission electron microscopy
  • fluorescence microscopy
  • correlation
Date of Defense 2015-11-03
Availability unrestricted
Abstract
Colloidal quantum dots (QDs) promise to revolutionize light harvesting for photovoltaics and controlled light emission from devices such as LEDs, lasers, and even nanometer-scale single-QD optical switches and routers. Extremely large extinction coefficients, precisely tunable optical properties, and the robust inorganic nature of these QDs make them excellent light absorbers; however, control over charge separation and exciton recombination has proven extremely challenging to achieve, both on the single-QD and ensemble scales. Furthermore, inherent heterogeneity in the shape, size, and morphology of core/shell QDs results in a distribution of expressed optical behaviors due to the interplay of the physical structure and electronic structure of the QD. Broadened ensemble photoluminescence linewidths and absorption spectra, varying radiative and nonradiative recombination rates of the exciton, and charge trapping rates all depend on the morphology of each individual QD. In this work, a correlative imaging technique was developed to allow complete investigation of physical properties (precise atomic structure, shape, size, and spatially-resolved chemical composition) and photoluminescence behavior (quantum yield, radiative decay lifetime, biexciton quantum yield, and blinking statistics) of single QDs. This simple, unambiguous correlation strategy provides a means for investigating structure-function relationships for single QDs. Implementation of the correlation technique allowed deleterious optical properties to be correlated with structural defects in a commercially available and well-studied QD system. Use of the technique also facilitated discovery of quantum yield heterogeneity among nonblinking “giant” CdSe/CdS core/shell QDs—an unexpected finding that explains the reduced photoluminescence quantum yield observed on the ensemble level for this QD system. Finally, the utility of this technique as a helpful feedback generator in the synthetic refinement processes for QDs and other nanostructured systems is discussed.
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