Incorporating double-heterojunction in anisotropic semiconductor nanocrystals for novel optoelectronic applications
type: CreativeWork
description: As semiconductor heterostructures play critical roles in today's electronics and optoelectronics, the introduction of active heterojunctions can impart new and improved capabilities that will enable the use of solution processable colloidal quantum dots (QDs) in future devices. Such heterojunctions incorporated into colloidal nanorods may be especially promising since the inherent shape anisotropy can provide additional benefits of directionality and accessibility in band structure engineering and assembly. Here, we develop double heterojunction nanorods where two distinct semiconductor materials with type II staggered band offset are both in contact with one smaller band gap quantum dot. The double heterojunction can provide independent control over the electron and hole injection/extraction processes while maintaining high photoluminescence yields and shape anisotropy. Developing new synthetic routes for the formation of ideal double heterostructures, we find that unexpected etching of nanocrystals by one of the most commonly used metal precursors, metal oleates. Especially, Zn-oleate is shown to etch CdS nanorods anisotropically, where the length decreases without a significant change in the diameter. Sodium oleate enhances the etch rate whereas oleic acid alone does not cause etching, indicating the importance of counter cation on the rate of oleate induced etching. Subsequent addition of Se precursors to the partially etched nanorod in Zn-oleate solution can lead to epitaxial growth of CdSe particles rather than the expected ZnSe growth despite an excess amount of Zn precursors being present. The composition of this epitaxial growth can be varied from CdSe to ZnSe depending on the amount of excess oleic acid or the reaction temperature. Similar tuning of composition can be observed when starting with collinear CdSe/CdS/CdSe rod/rod/rod heterostructures and spherical CdS (or CdSe/CdS core/shell) nanocrystals. Conversion of collinear rod/rod/rod structures to bar…
abstract: As semiconductor heterostructures play critical roles in today's electronics and optoelectronics, the introduction of active heterojunctions can impart new and improved capabilities that will enable the use of solution processable colloidal quantum dots (QDs) in future devices. Such heterojunctions incorporated into colloidal nanorods may be especially promising since the inherent shape anisotropy can provide additional benefits of directionality and accessibility in band structure engineering and assembly. Here, we develop double heterojunction nanorods where two distinct semiconductor materials with type II staggered band offset are both in contact with one smaller band gap quantum dot. The double heterojunction can provide independent control over the electron and hole injection/extraction processes while maintaining high photoluminescence yields and shape anisotropy. Developing new synthetic routes for the formation of ideal double heterostructures, we find that unexpected etching of nanocrystals by one of the most commonly used metal precursors, metal oleates. Especially, Zn-oleate is shown to etch CdS nanorods anisotropically, where the length decreases without a significant change in the diameter. Sodium oleate enhances the etch rate whereas oleic acid alone does not cause etching, indicating the importance of counter cation on the rate of oleate induced etching. Subsequent addition of Se precursors to the partially etched nanorod in Zn-oleate solution can lead to epitaxial growth of CdSe particles rather than the expected ZnSe growth despite an excess amount of Zn precursors being present. The composition of this epitaxial growth can be varied from CdSe to ZnSe depending on the amount of excess oleic acid or the reaction temperature. Similar tuning of composition can be observed when starting with collinear CdSe/CdS/CdSe rod/rod/rod heterostructures and spherical CdS (or CdSe/CdS core/shell) nanocrystals. Conversion of collinear rod/rod/rod structures to bar…
author: Oh, Nuri
language: en
keywords: Double-Heterojunction Nanorods, Double Heterostructures, Anisotropic Semiconductor Nanocrystal, Quantum Dot, Quantum dot light emitting diode (QD-LEDs), QLED, Bidirectional Display, Cd-Free Quantum Dots
date published: 2016-07-07T21:17:55Z
date modified: 2026-07-22T22:26:34Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/90940