Observation of Large Threshold Voltage Shift Induced by Pre-applied Voltage to SiO 2 Gate Dielectric in Organic Field-Effect Transistors.

Field-effect transistors based on organic semiconducting materials (OFETs) have unique advantages of intrinsically mechanical flexibility, simple preparation process, low manufacturing cost, and large-area preparation. Through the innovation of new material design and device structures, the performance of device parameters such as mobility, on–off current ratio, and the threshold voltage (V_TH) of OFETs continues to improve. However, the V_TH shift of OFETs has always been an important problem restricting their practical applications. In this work, we observe that the V_TH of polymer OFETs with the widely investigated device structure of a SiO₂ bottom-gate dielectric is noticeably shifted by pre-applying a large gate voltage. Such a shift in V_TH remains to a large extent, even after modifying the surface of the SiO₂ dielectric using a hexamethyldisilazane (HMDS) self-assembled monolayer. This behavior of V_TH can be ascribed to the charge trappings at the bulk of the SiO₂. In addition, the generality of this observation is further proven by using two other conjugated polymers including p-type PDPP3T and n-type PTzNDI-2FT, and a similar trend is obtained. [ABSTRACT FROM AUTHOR]