Coherently controlled spin-dependent charge carrier transitions in organic semiconductors: properties and applications

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Title Coherently controlled spin-dependent charge carrier transitions in organic semiconductors: properties and applications
Publication Type dissertation
School or College College of Science
Department Physics & Astronomy
Author Baker, William J.
Date 2012-08
Description This thesis is focused on the investigation of the fundamental physical nature and potential technical applications of spin-dependent charge carrier recombination in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene (MEH-PPV), a π conjugated polymer which has been utilized as organic thin film semiconductor. Pulsed electrically detected magnetic resonance (pEDMR) spectroscopy was used to observe how coherent spin motion of paramagnetic charge carrier states (so called polarons) control the macroscopic conductivity of thin (∼100nm) MEH-PPV layers under different charge carrier injection regimes. The pEDMR experiments were conducted at frequencies covering almost three orders of magnitude (∼20MHz to ∼10GHz) and at temperatures between ∼5K and ∼300k. The measurements revealed that under balanced bipolar injection, the conductivity of MEH-PPV is influenced at any temperature by the polaron pair (PP) mechanism, a spin-dependent process previously described in the literature. The experiments showed that PPs are weakly exchange-and dipolar-coupled pairs but they are strongly influenced by proton induced hyperfine fields. Electrical detection of coherent polaron-spin motion revealed extraordinary long coherence times (order of μs) at room temperature which could qualify PPs for quantum information applications. The PP mechanism was also demonstrated to work as an extraordinary sensitive (< 50 nT Hz−1/2) organic thin film probe which uses the polarons gyromagnetic ratio γ as magnetic field standard. γ was observed to be independent of temperature, device-current, and -bias, and degradation of the MEH-PPV device. In addition to the PP mechanism, another spin-dependent process previously described in the literature was confirmed to significantly influence conductivity in MEH-PPV: Triplet-exciton polaron recombination.
Type Text
Publisher University of Utah
Subject Electrically detected; Magnetic resonance; Organic semiconductor
Subject LCSH Organic semiconductors
Dissertation Institution University of Utah
Dissertation Name Doctor of Philosophy
Language eng
Rights Management Copyright © William J. Baker 2012
Format application/pdf
Format Medium application/pdf
Format Extent 5,115,500 bytes
Identifier etd3/id/1789
Source Original in Marriott Library Special Collections, QC3.5 2012 .B34
ARK ark:/87278/s6qz2rt9
Setname ir_etd
ID 195478
Reference URL https://collections.lib.utah.edu/ark:/87278/s6qz2rt9
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