Bias Stability Modulated by the Surface-Polarity Control of Gate Dielectrics in Organic Field-Effect Transistors

We investigate the bias stability of organic field-effect transistors (OFETs) according to the surface polarity of polymer interfacial layers. Three types of polymers with diverse polarities were employed as interfacial layers on the OFETs, and the surface polarity was obtained by a contact angle measurement. The electrical performance of the OFETs with the polymer interfacial layers is evaluated prior to the bias stability, and the OFETs with the nearly zero surface polarity-interfacial layer exhibit a 5-fold increased field-effect mobility that results from the reduced surface trap density and enlarged grains. The bias stability of the OFETs with the polymer interfacial layers will be studied based on the bias-stress-induced threshold voltage shift and will be quantitatively analyzed by the stretched hyperbola function. It is found that an interfacial layer with a relatively low surface polarity can increase the activation energy for trap creation in the OFETs, which results in less charge trapping and consequently, a low threshold voltage shift.