Abstract
We report a tunable magnetoresistance by uniformly mixing strong-spin-orbital-coupling molecule fac-tris (2-phenylpyridinato) iridium and weak-spin-orbital-coupling polymer poly(-vinyl carbazole) (PVK). Three possible mechanisms, namely charge transport distribution, energy transfer, and intermolecular spin-orbital interaction, are discussed to interpret the concentration-dependent magnetoresistance in the composite. The comparison between the magnetic field effects measured from energy-transfer and nonenergy-transfer 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.
1 More- Received 21 July 2006
DOI:https://doi.org/10.1103/PhysRevB.75.035214
©2007 American Physical Society