Effects of high capacitance of solution-processed polymer heterojunction gate dielectrics on the contact resistance of low-voltage n-channel organic transistors

Abstract

Transistors should operate at lower voltages due to heat dissipation, reliability, technology scaling, compatibility, and signal issues. The importance of dielectric materials in low-voltage applications is significant, although, in organic transistors, experimental findings frequently do not correspond with existing theoretical frameworks. There is a lack of research, particularly in the field of n-type organic transistors. Here, the influences of high dielectric capacitance on the performance of low voltage n-channel organic field-effect transistors based on poly([N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)) (P(NDI2OD-T2) OFETs) were examined. Utilizing a low-k dielectric as the initial layer enhances the semiconductor interface for n-channel transport while varying the thickness of a high-k dielectric as the subsequent layer alters the total capacitance (ranging from 13.7 to 29.7 nFcm⁻²). The performance of low-voltage P(NDI2OD-T2) OFETs has been improved in multiple electrical parameters through the utilization of a high dielectric capacitance with a well-optimized interface. The increased capacitance of P(NDI2OD-T2) OFETs resulted in reduced trap density and contact resistance, leading to a transition from contact-dominated to channel-dominated transport behavior, where a boundary of capacitance around 20 nFcm⁻² is recognized in this study. Our research provides an understanding of the operational mechanisms of n-channel OFETs and important information for enhancing low-voltage devices.