Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Chemistry

Language

English (en)

Date of Award

5-24-2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

William Buhro

Abstract

My research aims to study the formation mechanism of CdSe quantum belts: QBs) and the surface passivation of CdTe quantum wires: QWs). Investigation of QB morphology and QW passivation are fundamentally important to avoid nonradiative recombination and to increase electron-transport efficiency in semiconductor solar-cell devices. The origin of CdSe QBs is a lamellar structure of cadmium-octylamine precursor complex, with an intermediate state of stripe-like assembly of CdSe magic-sized nanoclusters. Transformation of: CdSe)13 nanoclusters to CdSe quantum belts: QBs) is conducted by higher annealing-temperature and confirmed by their optical and structural characterization. The QBs possess a thickness of 1.5-2.0 nm with a width of 7-15 nm and length of >1 micrometer. Most remarkably, the QBs have a superior morphology with noticeably high quantum efficiency: QE, 30 ± 10 %), comparable to quantum rods. High QE is explained by a delocalized exciton recombination with a lower density of defect sites. The colloidal CdTe quantum wires: QWs) are preferred for solar-cell applications due to a tunable diameter range: 5-60 nm), a long length dimensionality: > 5 micrometer), and near-IR band-gap emission energy: 1.5 eV). Successive surface passivation with Lewis acids and bases successfully passivates the QW surface. A significantly enhanced CdTe QW quantum efficiency: QE, 5-8 %) is achieved, which is two orders of magnitude larger than the previous disappointing QE: < 0.01 %). Enhanced photoluminescence: PL) emission reveals intrinsic higher and lower emission bands for CdTe QWs. Enhanced photoluminescence excitation: PLE) features consistently match previous theoretical calculations for electronic transitions. Significantly high QEs of CdSe QBs: 30 ± 10 %) and CdTe QWs: 5-8 %) promise colloidal 1D quantum structures suitable for bio-imaging and solar-cell applications.

DOI

https://doi.org/10.7936/K7QC01J4

Comments

Permanent URL: http://dx.doi.org/10.7936/K7QC01J4

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