Dispersive aspects of the high-field hopping mobility of molecularly doped solids with dipolar disorder
✍ Scribed by P. E. Parris; D. H. Dunlap; V. M. Kenkre
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 140 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-6266
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✦ Synopsis
The time-of-flight mobility of photoinjected charges in molecularly doped polymers obeys a Poole-Frenkel law, m ϰ exp( g E), which is commonly viewed as arising from hopping transport among sites with a large degree of energetic disorder. Recent theoretical investigations have focused on long-range correlations that characterize site energies when the dominant mechanism for energetic fluctuations is the interaction of charge carriers with randomly-oriented permanent dipoles of the dopant and host polymer. An exact calculation of the steady-state drift velocity v d for a onedimensional system with correlated dipolar disorder predicts a Poole-Frenkel law similar to that observed. In order to investigate another feature commonly observed in the high-field measurements, namely, the anomalous dispersion of the current-time transients, we have performed an exact calculation of the field-dependent diffusion constant D for the same dipolar disorder model. In the bulk limit we obtain an expression D Å (KT/e)Ìv d /ÌE that generalizes the normal Einstein relation and predicts a strongly field-dependent diffusion constant.