Eliminating the Double-Slope Behavior of Organic Field-Effect Transistors by Functionalizing the Dielectric Surface With a High Electron Affinity Self-Assembly Monolayer

The commonly observed nonideal behavior (namely double-slope) in transfer characteristics of organic field-effect transistors (OFETs) is detrimental to the accurate assessment of carrier mobility. In this work, self-assembled monolayers (SAMs) with different end groups were used to adjust the electron affinity of dielectric surfaces to eliminate the double-slope behavior of OFETs. Results show that the OFETs based on the SAM with a high electron affinity end group of -CN (hereafter named SAM-CN device) display an ideal transfer curve without double-slope behavior and hysteresis. A series of cross-checks, including contact resistance and time-dependent measurements, have been carried out to experimentally confirm that electron traps at the channel/dielectric interface are the origin of double-slope behavior. Furthermore, the suppression of double-slope behavior in SAM-CN devices is attributed to the high electron affinity of the -CN group to withdraw electrons from the trap sites located at the conducting channel. Thus, our results provide an easy and feasible strategy to eliminate the double-slope behavior of OFETs by using a SAM with an appropriate electron affinity.