Surface Passivation of Colloidal II-IV Semiconductor Quantum Belts and Quantum Wires: Synthesis, Mechanism and Optical Studies

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.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2010

Author dc:creator

• Liu, Yi-Hsin

Contributors dc:contributor

• William Buhro

• Chemistry
• Inorganic
• Physical
• Physics
• Condensed Matter
• CdSe
• CdTe
• NANOCLUSTERS
• QUANTUM BELTS
• QUANTUM WIRES
• SURFACE PASSIVATION

Language dc:language

English (en)

DOI

https://doi.org/10.7936/K7QC01J4

OAI identifier oai:identifier

oai:openscholarship.wustl.edu:etd-1850