有機薄膜電晶體材料―噻吩并噻吩吡咯并吡咯二酮拉電子基與二噻吩、噻吩乙烯噻吩及硒吩乙烯硒吩推電子基之 共軛高分子之合成與鑑定

Abstract

本研究致力於合成低能隙共軛高分子材料，研究其材料之光學、電化學及分子間堆疊特性，並利用不同的退火條件，應用於有機薄膜電晶體 (OTFTs)。本研究以具高平面性且多π共軛的3,6-bis(2-bromothieno-[3,2-b]thiophen-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]-pyrrole-1,4-(2H,5H)-dione (TTDPP) 為受體，與二噻吩 (bithiophene, BT)、噻吩乙烯噻吩 (di(2-thienyl)ethene, TVT)、硒吩乙烯硒吩 (di(selenophen-2-yl)ethene, SVS) 三個不同類型的電子施體作共聚，成功合成出PBTTDPP-BT、PBTTDPP-TVT及PBTTDPP-SVS三種共聚物。 並以二噻吩和噻吩乙烯噻吩此兩高分子探討雙鍵插入推電子基團中，發現在吸收光譜中有紅位移，電化學中HOMO能階提升，雙鍵有使能隙降低，且在XRD測量下，lamellar及π-πstacking方向間距降低，電洞遷移率從0.0882 cm2V-1s-1 提升至0.0945 cm2V-1s-1。 而以噻吩乙烯噻吩和硒吩乙烯硒吩在電子施體中透過換原子形成兩個不同的高分子，改變整個高分子電化學性質，HOMO能階些微提升，而LUMO能階大幅下降，使能隙大幅下降，顯示換原子大幅改變高分子HOMO與LUMO的分佈，在XRD測量中，硒吩乙烯硒吩上的硒原子半徑大於硫原子半徑，使π-πstacking方向距離變大，而lamellar方向的訊號 (100)、(200) 的間距則皆降低，電洞遷移率從0.0945 cm2V-1s-1提升兩倍至0.196 cm2V-1s-1。

New D-A systemic copolymers based on 3,6-bis(2-bromothieno-[3,2-b]thiophen-5-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]-pyrrole-1,4-(2H,5H)-dione (TTDPP) combined with three different electron-donating strength monomer bithiophene (BT), di(2-thienyl)ethene (TVT), di(selenophen-2-yl)ethene (SVS) were synthesized. These three polymers’ optical band gap, electrochemical properties and organic thin-film transistors (OTFTs) device performance were systematically investigated. PBTTDPP-BT containing flexible moiety BT and long conjugated chain could modulate the polymer’s energy level and show the good packing on X-ray Diffraction (XRD). In order to get the better molecular packing, the strategy of using double bond as backbone moiety was used to create TVT as a donor unit. PBTTDPP-TVT copolymer showed better packing ability. It showed that OFET mobility of PBTTDPP-BT and PBTTDPP-TVT were 0.0882 cm2 V-1 s-1, 0.0945 cm2 V-1 s-1, respectively. Sequentially, we replaced the sulfur atom with the selenium atom in TVT unit. SVS was also copolymerized with TTDPP to form the polymer PBTTDPP-SVS. PBTTDPP-SVS had smallest d-spacing among three copolymers in lamellar direction. It implied that PBTTDPP-SVS had better intrachain transport charge transfer. Furthermore, PBTTDPP-SVS had suitable HOMO level to help carrier inject into Au electrode from polymer. As a result, PBTTDPP-SVS showed the highest hole mobility of 0.196 cm2V-1s-1 and the lowest threshold voltage -3.60 V in this study.