Article abstract
Nature Materials 6, 985 - 991 (2007)
Published online: 21 October 2007 | doi:10.1038/nmat2034
Subject Categories: Polymers | Optical, photonic and optoelectronic materials
Tuning magnetoresistance between positive and negative values in organic semiconductors
Bin Hu & Yue Wu
Abstract
Magnetic-field-dependent injection current, namely magnetoresistance, is readily observable in organic semiconductor devices. This provides a non-contact approach to tune organic optoelectronic properties by using a magnetic field. Here, we demonstrate that this magnetoresistance can be changed between positive and negative values by adjusting the dissociation and charge reaction in excited states through changing the bipolar charge injection in organic light-emitting diodes. This finding reveals that the magnetic-field-dependent generation of secondary charge carriers from the dissociation and charge reaction affects the injection current by forming further space charges at the organic–electrode interfaces and therefore accounts for the tunable magnetoresistance. Furthermore, the dissociation and charge reaction have opposite dependences on magnetic field in the generation of secondary charge carriers, consequently leading to negative and positive magnetoresistance, respectively. As a result, adjusting the dissociation and charge reaction in excited states provides a convenient pathway to tune the magnetoresistance in organic semiconductors.
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
Correspondence to: Bin Hu e-mail: bhu@utk.edu
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