Trap filled limit of conducting organic materials

According to the approximate theory of transport in a conducting organic material containing exponential traps, ln J versus ln V plots are straight lines with slope l=T-C/T, where T-C is the characteristic temperature of the trap distribution. It is assumed in this theory that the concentration p(t) of trapped holes is much larger than the concentration p of free holes. Our experiments and recent literature results show that at high applied voltages the observed ln J versus ln V plots deviate from the straight lines and bend down. The numerical solution presented in this article shows that at high voltages the contribution of p to the space charge does not remain negligible. Calculated ln J versus ln V plots do bend down consistent with our experimental results. The current approaches the trap-filled limit asymptotically as the applied voltage approaches infinity. (C) 2002 American Institute of Physics.