Displacement current in bottom-contact organic thin-film transistor

We have used the Shockley-Ramo theorem to calculate the displacement current of drifting charge carriers in bottom-contact organic thin-film transistors (OTFTs). The displacement current is quantified in terms of the weighting field of the sensing electrode. We demonstrated that for the transistors, with dielectric thickness below 100 nm and channel length above 1 mu m, the weighting field near the sensing electrode exponentially decays with the distance from the electrode. This implies that the charge transport near metal contacts can be studied with a measurement of displacement current. The presented model approximation simplifies interpretation of, for example, transient photocurrent measurements and optical de-trapping measurements in OTFTs.