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The Use of Thermally Decomposable Ligands for Conductive Films of Semiconductor Nanocrystals

Published online by Cambridge University Press:  01 February 2011

Andrew Wills ,
Moon Sung Kang ,
Ankur Khare ,
Wayne L. L. Gladfelter  and
David Norris
Andrew Wills
Affiliation:
wills060@umn.edu, University of Minnesota, Chemistry, Minneapolis, Minnesota, United States
Moon Sung Kang
Affiliation:
mskang@cems.umn.edu, University of Minnesota, Chemical Engineering and Materials Science, Minneapolis, Minnesota, United States
Ankur Khare
Affiliation:
ankur@umn.edu, University of Minnesota, Chemical Engineering and Materials Science, Minneapolis, Minnesota, United States
Wayne L. L. Gladfelter
Affiliation:
wlg@umn.edu, University of Minnesota, Chemistry, 207 Pleasant St., SE, Minneapolis, Minnesota, 55455, United States
David Norris
Affiliation:
dnorris@umn.edu, University of Minnesota, Chemical Engineering and Materials Science, Minneapolis, Minnesota, United States
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Abstract

Poor conductivity is a bottleneck hindering the production of nanocrystal-based devices. In most nanocrystal syntheses, ligands with long alkyl chains are used to prepare monodisperse, crystalline particles. When these nanocrystals are incorporated into devices as films, the bulky ligands form an insulating layer that prevents charge transfer between particles. While annealing or post-deposition chemical treatments can be used to strip surface ligands, each of these approaches has disadvantages. Here we demonstrate the use of a novel family of ligands comprised of primary alkyl dithiocarbamates to stabilize PbSe/CdSe core-shell nanocrystals. Primary dithiocarbamates, which can bind to cadmium and lead, are known to decompose to the corresponding sulfides when heated under mild conditions. In our scheme, PbSe/CdSe core-shell nanocrystals are first synthesized with standard ligands. These ligands are then exchanged to short chain dithiocarbamates in solution. When a film is cast and annealed at low temperature, the dithiocarbamates are removed. Electron microscopy reveals that the particles move closer together, and, along with x-ray diffraction, shows that the nanocrystals remain quantum confined. Transport measurements show a 10,000-fold increase in conductivity after annealing.

Keywords

nanoscalesinteringannealing
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1260: Symposium T – Photovoltaics and Optoelectronics from Nanoparticles , 2010 , 1260-T12-03
Copyright
Copyright © Materials Research Society 2010

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