Space-charge-limited conduction in ethyl–hexyl substituted polyfluorene
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Ethyl–hexyl substituted polyfluorene (PF2/6) is a model blue-emitting polymeric system where the space-charge-limited conduction model within discrete single-level shallow traps can be applied to describe charge transport. Thermal cycling the PF2/6 film to a crystalline phase prevents creation of additional trap states, which is seen in the as-is polymer at higher voltages. These results shed new light on the mechanism of charge transport in polymers. Although PF2/6 has a high degree of interchain disorder, the as-is polymer shows regions of ordering that impacts charge transport through the polymer. Current–voltage characteristics as a function of the polymer thickness reveal the origin of the trap states.
KeywordsCharge Transport Trap State Polymer Thickness Bulk Trap High Luminescence Efficiency
We gratefully acknowledge the support of this work through the National Science Foundation under Grant No. ECCS-0523656. We thank Prof. Kartik Ghosh of Missouri State University for providing us with the ITO substrates.