Degraded off-State Current of Organic Thin-Film Transistor and Annealing Effect

We report a significant increase in the off-state leakage current (
I

_OFF
) of an organic thin-film transistor with polystyrene (PS) gate dielectric following air exposure. The increased
I

_OFF
was found to be caused by the degradation of the PS insulation property. The gate leakage current continuously increased, following air exposure for four weeks. Interestingly, the gate leakage current was reduced after the degraded device underwent annealing at 70degC which is lower than the PS glass temperature. The change in the gate leakage is well correlated with
V

_FB
shift observed in both the air exposure and the following anneal. Based on the observation, we believe that the enhancement of the leakage is likely attributed to the trap generation inside the PS layer.