Design and Synthesis of Planar Organic Molecules for Organic Thin Film Transistors (OTFTs)

Abstract

Organic electronic materials have been actively researched in recent decades and commercialization of electronic devices (TVs, wearable devices, e-books, etc.) using them has been drawing attention worldwide. Organic thin film transistors (OTFTs) have the advantage of being capable of easy synthesis, flexibility, lightweight, and solution processing compared to conventional inorganic transistors. However, due to the low charge mobility and instability of the material, the utilization is not much wide. In order to improve these points, we intend to design and synthesize new organic materials. In this study, we designed and synthesized small organic molecules, 2-(benzo[b]thiophen-2-ylmethylene)-1H-indene-1,3(2H)-dione and 2-(2-(benzo[b]thiophen-2-ylmethylene)-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile, having benzo[b]thiophene moiety attached with 1,3-indandione or 2-(3-oxo-indan-1-ylidene)malononitrile moieties. And we designed and synthesized 2,7-bis(5-(2-ethylhexyl)thiophen-2-yl)-9H-fluorene, 2,7-bis(5-octylthiophen-2-yl)-9H-fluorene and 5,5'-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(2-(2-ethylhexyl)thiophene) for OTFTs derived from 9H-fluorene, 9,9-dioctyl-fluorene, tributyl(5-(2-ethylhexyl)thiophen-2-yl)stannane, and tributyl(5-octylthiophen-2-yl)stannane. But they do not show mobilities as OTFTs. Therefore, we design and synthesize a 4H-cyclopenta[2'',1'':5,6;3'',4'':5',6']diindeno[1,2-b:1',2'-b']dithiophene, 7,12-dihydro-4,4,7,7,12,12-hexaoctyl-(FDCT-C8).

최근 몇 십 년간 유기 전자 소재는 활발히 연구되는 분야이며, 이를 이용한 전자 기기(TV, wearable device, 전자책 등)의 상용화가 시작되어 세계적으로 주목을 받고 있다. 유기박막트랜지스터(Organic Thin Film Transistor; 이하 OTFT)는 기존의 무기트랜지스터에 비해 쉽게 합성이 가능하다는 점과 유연하고 가벼우며 용액 공정이 가능하다는 장점이 있다. 하지만 낮은 전하 이동도와 소재의 불안정성 때문에 활용도가 떨어진다. 이러한 점들을 개선하기 위해 새로운 유기 재료를 디자인하여 합성하고자 한다. 이 연구에서는 benzo[b]thiophene과 1H-indene-1,3(2H)-dione, 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile을 사용하여 2-(benzo[b]thiophen-2-ylmethylene)-1H-indene-1,3(2H)-dione과 2-(2-(benzo[b]thiophen-2-ylmethylene)-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile, 을 디자인하여 합성하였다. 9H-Fluorene, 9,9-dioctyl-fluorene, tributyl(5-(2-ethylhexyl)thiophen-2-yl)stannane, and tributyl(5-octylthiophen-2-yl)stannan을 사용하여 2,7-bis(5-(2-ethylhexyl)thiophen-2-yl)-9H-fluorene, 2,7-bis(5-octylthiophen-2-yl)-9H-fluorene, 5,5'-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(2-(2-ethylhexyl)thiophene)을 합성하여 OTFT로써 성능 및 특성을 측정하였다. 그리고, 7,12-dihydro-4,4,7,7,12,12-hexaoctyl-4H Cyclopenta[2”,1”:5,6;3”,4”:5’,6’]diindeno[1,2-b:1’,2’-b’]dithiophene (FDCT-C8) 새로 디자인하고, 합성하고자 한다.