DPP 기반의 고분자 반도체를 갖는 ambipolar OFET에 관한 연구

Abstract

Organic Field-Effect Transistors (OFETs) are expected to be used as a critical component of flexible electronics due to their low-cost solution-processibility and mechanical flexibility of organic semiconductors. In particular, there have been lots of interests on the OFETs fabricated with ambipolar semiconductors, that have both p-type and n-type properties in single active layer because of their advantages that potentially allow easy fabrication of light-emitting transistors or inverting logic circuits. A promising class of organic materials for such ambipolar characteristics is based on diketopyrrolopyrrole (DPP)-containing copolymers, that consist of DPP-acceptor and a large variety of donor blocks and exhibit a high mobility up to >10 cm2/Vs, as has been reported by several groups. In the thesis, we have fabricated OFETs using diketopyrrolopyrrole (DPP)-containing polymer semiconductors, which are known to have ambipolar properties, as active layers. The DPP polymer semiconductors used in this study were based on 3,6-di-2-thienyl-1,4-diketopyrrolo[3,4-c]pyrrole (T-DPP-T) alternating with intermediate 1,4-phenylene units (PDPPTPT), 2,5-thienylene units (PDPP3T), and thieno[3,2-b]thiophenes units (PDPP2T-TT). First, we examined the effects of the vacuum annealing on the ambipolar characteristics of the DPP based polymer semiconductor FETs with BG/TC structure. Next, we have analyzed on morphology and crystallinity of DPP based polymer semiconductor films and then fabricated ambipolar OFET with TG/BC structure. After the electrical characteristics measurements on the DPP based ambipolar OFETs, the activation energy and the density of state (DOS) were obtained by low-temperature experiment. Finally, we have investigated the effects of donor block in DPP based polymers on the charge transfer characteristics by applying the low-temperature experimental results to the Gaussian Disorder Model (GDM).