Transport and excess noise in polyacenes under trap-filling transition

Recent measurements in organic semiconductors (polyacenes) have evidenced a strong superlinear increase of the current-voltage characteristics associated with a sharp peak of the relative spectral density of current noise. Both features occur at the trap filling transition (TFT), i.e. at voltages corresponding to the transition between the Ohmic regime and the space charge limited current (SCLC) regime. Here we discuss the interpretation of this behavior in terms of a contribution from trapping and detrapping (TD) processes of the injected carriers. We found an excellent agreement between the predictions of our model and the experimental results in tetracene, which allows us to conclude that TD processes are responsible for the significant enhancement of the relative current noise observed in polyacenes in the TFT region.