Journal article
Experimental Tests of Possible Mechanisms for the Organic Magnetoresistive Effect
MRS proceedings, Vol.1032, 1020
2007
DOI: 10.1557/PROC-1032-I10-20
Abstract
We experimentally test three existing models of organic magnetoresistance (OMAR) which are all based on carrier spin dynamics. We first prove that hyperfine field originating from the hydrogen nuclei in organic materials is necessary for observing OMAR by studying C60 sandwich devices using several different electrode materials. We show that C60, unlike many other organic semiconductors, does not exhibit any intrinsic OMAR effect. However, we find that as soon as the carriers in C60 are brought in proximity with hydrogen-containing compounds, either in the form of a polymeric electrode, or side-chain substituents, a weak OMAR effect is observed. Next, we perform charge-induced absorption and electroluminescence spectroscopy in a polyfluorene organic magnetoresistive device. Our experiments allow us to measure the singlet exciton, triplet exciton and polaron densities in a live device under an applied magnetic field, and to distinguish between three models of OMAR. These models are based on different spin-dependent interactions, namely exciton formation, triplet exciton-polaron quenching and bipolaron formation. We show that the singlet exciton, triplet exciton and polaron densities and conductivity all increase with increasing magnetic field. Our data are inconsistent with the exciton formation and triplet-exciton polaron quenching models.
Details
- Title: Subtitle
- Experimental Tests of Possible Mechanisms for the Organic Magnetoresistive Effect
- Creators
- Tho Duc Nguyen - University of IowaJames Rybicki - University of IowaYugang Sheng - University of IowaMarkus Wohlgenannt - University of Iowa
- Contributors
- J-P. Wang (Editor)
- Resource Type
- Journal article
- Publication Details
- MRS proceedings, Vol.1032, 1020
- DOI
- 10.1557/PROC-1032-I10-20
- ISSN
- 0272-9172
- eISSN
- 1946-4274
- Publisher
- Cambridge University Press
- Number of pages
- 6
- Language
- English
- Date published
- 2007
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428781602771
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