In situ tuning of the performance of polymer field-effect transistors by soft plasma etching

Abstract

Organic semiconductor films prepared by solution methods usually produce a large number of charge traps, which significantly increase the subthreshold swing (SS) of organic field-effect transistors (OFETs) with threshold voltage (V_th) far from 0 V, making it difficult for the OFETs to operate at low voltages. In this work, we found that after soft plasma (air pressure below 15 Pa) etching, the SS of the semiconductor poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b′]-dithiophen-2-yl)- alt-[1,2,5]thiadiazolo-[3,4-c]pyridine (PCDTPT)-based OFETs reduces by approximately 60%, and V_th approaches 0 V. Meanwhile, the hysteresis of the OFETs is eliminated, indicating that soft plasma etching can improve operational stability. It was also found that the soft plasma could increase the on–off ratio by two orders of magnitude of the damaged OFETs and reduce the V_th to around 0 V. In addition, we have also demonstrated the importance and universality of the soft plasma post-treatment process in other p-type materials and heterojunction systems and have built a preliminary invertor structure based on this.