Ethyl-hexyl substituted polyfluorene (PF) with its high level of molecular disorder can be described very well by one-carrier space-charge-limited conduction for a discrete set of trap levels with energy ∼ 0.5 eV above the valence band edge. Sweeping the bias above the trap-filling limit in the as-is polymer generates a new set of exponential traps, which is clearly seen in the density of states calculations. The trapped charges in the new set of traps have very long lifetimes and can be detrapped by photoexcitation. Thermal cycling the PF film to a crystalline phase prevents creation of additional traps at higher voltages.
@article{arxiv.cond-mat/0703554,
title = {Polyfluorene as a model system for space-charge-limited conduction},
author = {M. Arif and M. Yun and S. Gangopadhyay and K. Ghosh and L. Fadiga and F. Galbrecht and U. Scherf and S. Guha},
journal= {arXiv preprint arXiv:cond-mat/0703554},
year = {2009}
}
Comments
13 pages, 4 figures. Physical Review B (accepted, 2007)