Does current noise arise from the competition between conductive and insulating phase at the trap-filling transition in organic semiconductors?

The relative current noise power spectral density S = S(I)(f)/I(2) observed in organic semiconductors exhibits a maximum at the trap filling transition between the ohmic and the space-charge-limited-current regime. The electrostatic conditions determining the crossover from ohmic to space-charge-limited transport at the trap filling transition are here discussed. These arguments shed light on the need to adopt a percolative fluctuations model to account for the competition between insulating and conductive phases as the voltage increases.