Interface states and depletion-induced threshold voltage instability in organic metal-insulator-semiconductor structures

We present results obtained from a study of the admittance of metal-insulator-semiconductor capacitors formed from regioregular poly(3-hexylthiophene). Data obtained over a range of applied bias and frequency can be explained by the presence of a distribution of trapping states at the insulator/semiconductor interface as observed in metal-oxide-silicon capacitors. We also observe a depletion-bias instability in the threshold voltage, V-T, that is consistent with negative charge trapping at the insulator/polymer interface. The shift can be relaxed by illumination with bandgap light, lambda = 550 nm, suggesting that the instability arises from an electronic process. (C) 2004 American Institute of Physics.