ETRI Knowledge Sharing Platform : Relationship between the liquid crystallinity and field‐effect‐transistor behavior of fluorene

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Journal Article Relationship between the liquid crystallinity and field‐effect‐transistor behavior of fluorene–thiophene‐based conjugated copolymers

Cited 51 time in scopus

Authors: Eun Hee Lim, Young Mi Kim, Jeong Ik Lee, Byung Jun Jung, Nam Sung Cho, Jae Min Lee, Lee Mi Do, Hong Ku Shim

Citation: Journal of Polymer Science Part A : Polymer Chemistry, v.44, no.16, pp.4709-4721

Abstract: A series of fluorene-thiophene-based semiconducting materials, poly(9,9??-dioctylfluorene-慣慣??-bisthieno[3,2-b]thiophene) (F8TT2), poly(9,9??-di(3,6-dioxaheptyl) fluorene-alt-thieno[3,2-b] thiophene) (BDOHF8TT), poly(9,9??-di(3,6-dioxaheptyl)fluorene-alt- bithiophene) (BDOHF8T2), and poly(9,9??-dioctylfluorene-co-bithiophene-co- [4-(2-ethylhexyloxyl)phenyl]diphenylamine) (F8T2TPA), was synthesized through a palladium-catalyzed Suzuki coupling reaction. F8TT2, BDOHF8TT, BDOHF8T2, and F8T2TPA films exhibited photoluminescence maxima at 523, 550, 522, and 559 nm, respectively. Solution-processed field-effect transistors (FETs) fabricated with all the copolymers except F8T2TPA showed p-type organic FET characteristics. Studies of the differential scanning calorimetry scans and FETs of the polymers revealed that more crystalline polymers gave better FET device performance. The greater planarity and rigidity of thieno[3,2-b]thiophene in comparison with bithiophene resulted in higher crystallinity of the polymer backbone, which led to improved FET performance. On the other hand, the random incorporation of the triphenylamine moiety into F8T2TPA caused the polymer chains to lose crystallinity, resulting in an absence of FET characteristics. With this study, we could assess the liquid-crystallinity dependence of the field-effect carrier mobility on organic FETs based on liquid-crystalline copolymers. © 2006 Wiley Periodicals, Inc.

KSP Keywords: Carrier mobility, Collaborative Optimization(CO), Conjugated copolymers, Crystalline polymers, Differential scanning calorimetry(photo-DSC), FET devices, Field-effect transistors(FETs), Liquid Crystallinity, Palladium-catalyzed, Polymer chain, Scanning calorimetry(DSC)