Poole-Frenkel mobility field dependence in molecularly doped polymers revisited

- Multiple trapping model is used to describe charge carrier transport.
- Early time current measurements have been done using an electron gun.
- Due to non-equilibrium transport, the overall Poole-Frenkel effect is a composite one.
- The contribution of the operational mechanism to this effect is appreciable.
- The proposed model explains the experimental data satisfactorily.

We have examined the Poole-Frenkel mobility field dependence in a molecularly doped polymer (MDP) both experimentally and theoretically trying to separate two physically different contributions to this phenomenon, one constituting a real physical effect and the other arising from the fact that the charge carrier transport in MDP is not fully equilibrated. The former is ascribed to the influence of an electric field on the transport process itself affecting at least one of the model parameters. The latter should be associated with the mobility field effect under conditions when neither model parameter is field sensitive. Numerical calculations have been used to achieve their deconvolution. On the experimental front, we relied on the time of flight technique specifically modified to suit this task. Both approaches show that the contribution of the second (operational) field effect in the investigated MDP is quite appreciable. This result is compared with the traditional interpretation of the Poole-Frenkel effect in molecularly doped polymers.

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