전해질 게이트 트랜지스터를 이용한 ∏-공액 폴리머 필름의 이온 교환 도핑에 대한 연구

Abstract

Ion exchange doping, which is mediated by an ionic liquid and can be done with the effective exchange between a conventional molecular dopant anion and the second anion in an ionic liquid, is an emerging chemical doping process of π-conjugated polymer film. This process can provide an exceptionally high doping level and enhanced stability of the doped semiconducting polymer film. In this study, we investigated the mechanism of the ion exchange doping process by using the electrolyte-gated transistor platform, which can electrochemically modulate a driving force for ion exchange doping of the π-conjugated polymer semiconducting film. For this, we fabricated an electrochemical transistor where 1-ethyl-3-methylimidazolium-bis(trifluormethylsulfonyl), [EMIM] [TFSI] and tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) doped poly(2,5-bis(3-tetradecylthiophen-2yl)thieon(3,2-b)thiophene) PBTTT-C14 polymer film as electrolyte gate medium and conducting channel layer. The electrolyte-gated transistor shows a reversible process that the conductivity of the doped PBTTT polymer film initially increased and then arrived at the maximized conductivity but decreased again after the critical point as the bias applied to the gate electrode increased. With the electrolyte-gated transistor platform, the intrinsically possible maximum doping level in the PBTTT-film could be estimated.