인디고 기반 유기 전계효과 트랜지스터의 전하 이동 및 광전자 특성 연구

Abstract

Organic electronics is one of the most promising fields for next generation when wearable electronics become a reality. Indigo and its derivatives are candidate materials in development of sustainable electronics, due to their low toxicity, good semiconductor characteristics, and chemical stability. During my degree curriculum, I have studied charge transport and optoelectronic properties of these prospective indigo-based semiconductors for applying to various organic devices. In the second chapter, two new thienoisoindigo (TIIG)-based donor-acceptor polymers with either thieno[3,2-b]thiophene (TT) or (E)-2-(2-(thiophene-2-yl)vinyl)thiophene (TVT) moiety were synthesized and characterized. We conducted a systematic investigation on the relationship between the microstructure of the polymer film and charge transport in organic field-effect transistors (OFETs) based on these polymers. It was observed that a TVT moiety has higher crystallinity and denser molecular packing, leading to an increased hole mobility (~0.45 cm2 V-1 s-1) in PTIIG-TVT, compared with PTIIG-TT. In addition, when an Al is used instead of a Au electrode in the OFET, both polymers exhibit ambipolar characteristics. In the third chapter, ambipolar organic phototransistors (OPTs) based on a natural pigment Tyrian Purple (6,6’-dibromoindigo) as the active channel are newly demonstrated. The OPTs are shown to current increase under light illumination with photoresonsivities and external quantum efficiencies as high as 10.3 A W-1 and 2437 % for the n-channel, and 55.4 mA W-1 and 13.1 % for p-channel, respectively. In addition, we simply fabricated complementary inverters by integrating these two ambipolar OFETs. It exhibits that the channel current is dependent on light intensity as well as voltage bias. Therefore, these studies aid the further understanding of the charge transport properties in TIIG-based polymers and the optoelectronic characteristics in indigo-based small molecule.