Negative Differential Resistance Behavior in n‐Channel Organic Thin‐Film Transistors Based on C60and PTCDI‐C8: Electrical Characterization and Parameter Extraction

Abstract

Organic thin‐film transistors (OTFTs), based on two n‐type structures of fullerene (C60) andN,N′‐dioctyl‐3,4,9,10‐perylenedicarboximide (PTCDI‐C8), are investigated. The two OTFT devices reveal a negative differential resistance (NDR) behavior in the saturation region of the output curves. The OTFT based on C60shows a more pronounced NDR than that based on PTCDI‐C8. The main origin of the NDR is ascribed to the trapping states. In addition, the contact resistance (Rc) of the two devices, extracted using the developed voltage transition method (Vtrmethod), as well as the obtained values ofRc, are in fair agreement with the experimental values extracted using the total resistance. The device based on C60exhibits a higherRcthan that based on PTCDI‐C8. OTFT parameters, such as transconductance (gm), mobility (μmax), threshold voltage (Vth,), turn‐on voltage (Von), ratio currentIon/Ioff, and subthreshold slope (SS), are obtained in the linear and saturation regimes. The extracted value of SS for the OTFT based on C60is very small compared with that of the device based on PTCDI‐C8, which indicates an increase in the density of trapping states in the C60film.