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유기박막트랜지스터를 위한 DTT 기반 용액공정 유기반도체 개발

Development of Dithieno[3,2-b:2’,3’-d]thiophene (DTT) Derivatives as Solution-Processable Small Molecular Semiconductors for Organic Thin Film Transistors

초록 (요약문)

Novel solution-processable dithieno[3,2-d:2’,3’-d]thiophene (DTT) derivatives with alkylated thiophene or alkyl chain substituents, 2,6-bis(5-octylthiophen-2-yl)dithieno[3,2-b:2',3'-d]thiophene (compound 1), 2,6-bis(5-(2-ethylhexyl)thiophen-2-yl)dithieno[3,2-b:2',3'-d]thiophene (compound 2), and 2,6-dioctyldithieno[3,2-b:2’,3’-d]thiophene (compound 3), have been synthesized and employed as small molecular organic semiconductors for organic thin film transistors (OTFTs). All compounds exhibited good thermal stability over 290 °C, while different side groups of DTT compounds afforded different melting temperatures. The molecular orbital energy levels were experimentally and theoretically calculated, and their trend was almost same. The developed compounds were employed as active layers for top-contact/bottom-gate OTFTs with average charge carrier mobility as high as 0.10 cm2/Vs and current on/off ratio > 107 in ambient atmosphere. Notably, DTT derivative with linear alkyl chain (-octyl) substituents showed best device performance. High device performance could be attributed to the large grains and continuous surface coverages as well as high film texture of the corresponding semiconductor films.

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초록 (요약문)

알킬화된 thiophene 또는 알킬 사슬 치환기가 있는 신규의 용액공정 가능한 dithieno[3,2-d:2’,3’-d]thiophene (DTT) 기반 저분자 유기 반도체 화합물들, 2,6-bis(5-octylthiophen-2-yl)dithieno[3,2-b:2',3'-d]thiophene (화합물 1), 2,6-bis(5-(2-ethylhexyl)thiophen-2-yl)dithieno[3,2-b:2',3'-d]thiophene (화합물 2), 2,6-dioctyldithieno[3,2-b:2’,3’-d]thiophene (화합물 3)을 설계하고 합성하여 유기박막트랜지스터 (OTFT)의 유기반도체로 적용하고 성능을 평가하였다. 모든 물질은 높은 열 안정성을 보였으며, DTT 화합물의 곁사슬에 따라 녹는점이 달랐다. 분자 궤도 에너지 준위는 실험적, 이론적 방법으로 계산되었고 서로 유사한 경향성을 보였다. 개발된 물질은 top-contact/bottom-gate 구조의 유기박막트랜지스터에 활성층으로 이용되었고, 대기 하에서 0.10 cm2/Vs의 이동도와 107보다 높은 점멸비의 성능을 보였다. 특히 선형 알킬 체인(-octyl기) 작용기가 달린 물질이 최고의 전기적 성능을 보였고 이는 해당 반도체 필름의 큰 grain과 연속적인 표면 coverage의 영향 때문이다.

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