Tuning magnetoresistance and magnetic-field-dependent electroluminescence through mixing a strong-spin-orbital-coupling molecule and a weak-spin-orbital-coupling polymer

Yue Wu, Zhihua Xu, Bin Hu, and Jane Howe
Phys. Rev. B 75, 035214 – Published 26 January 2007

Abstract

We report a tunable magnetoresistance by uniformly mixing strong-spin-orbital-coupling molecule fac-tris (2-phenylpyridinato) iridium [Ir(ppy)3] and weak-spin-orbital-coupling polymer poly(N-vinyl carbazole) (PVK). Three possible mechanisms, namely charge transport distribution, energy transfer, and intermolecular spin-orbital interaction, are discussed to interpret the Ir(ppy)3 concentration-dependent magnetoresistance in the PVK+Ir(ppy)3 composite. The comparison between the magnetic field effects measured from energy-transfer and nonenergy-transfer Ir(ppy)3 doped polymer composites indicates that energy transfer and intermolecular spin-orbital interaction lead to rough and fine tuning for the magnetoresistance, respectively. Furthermore, the photocurrent dependence of magnetic field implies that the excited states contribute to the magnetoresistance through dissociation. As a result, the modification of singlet or triplet ratio of excited states through energy transfer and intermolecular spin-orbital interaction form a mechanism to tune the magnetoresistance in organic semiconducting materials.

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  • Received 21 July 2006

DOI:https://doi.org/10.1103/PhysRevB.75.035214

©2007 American Physical Society

Authors & Affiliations

Yue Wu, Zhihua Xu, and Bin Hu*

  • Department of Materials Science and Engineering, University of Tennessee, Tennessee 37996, USA

Jane Howe

  • Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • *Electronic address: bhu@utk.edu

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Issue

Vol. 75, Iss. 3 — 15 January 2007

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