Synthesis of Thienoisoindigo-based Quinoidal for N-Channel Organic Field Effect Transistors

[[abstract]]我們研究新型材料醌型硫化異靛藍衍生物，相較於異靛藍結構，硫化異靛藍的共平面性較高，此項特質是有益於材料具有規則性排列。而將結構醌型化最大之優點為：能使分子的最低未佔有電子軌域(Lowest unoccupied molecular orbital, LUMO)降低( -4.41~ -4.46 eV)，促使分子可為空氣下穩定的N型有機場效電晶體之半導體層材料。 我們合成醌型化硫化異靛藍衍生物C2C6-TII-QN 、C8-TII-QN、C4-TII-QN，這三個分子最大的差別在於具有不同的烷基側鏈長，其側鏈分別為2-Ethyl-1- hexylamine、 Octylamine、 N-Butylamine，我們除了探討分子的合成路徑之外，我們也將研究分子的熱穩定性、光學性質、電化學性質。C2C6-TII-QN 、C8-TII-QN、C4-TII-QN的溶解性質佳，液態的最大吸收波長介於601 nm至606 nm；相較於分子的液態吸收，這三個分子的薄膜太吸收光譜都要為紅位移，最大吸收波長則為683至759 nm。將C8-TII-QN應用於N型有機場效電晶體中並測量元件之電性表現，跟文獻不同的是，我們測得了分子傳遞電子而非電洞之性質，元件之電子遷移率為0.016 cm2V-1s-1。從此研究可知此三之化合物具有作為N型有機場效電晶體中半導體層材的潛力，在未來我們將持續選找最佳化的元件製成方式，得到更佳的電子遷移率。[[abstract]]We present here a novel molecular design strategy for developing a thienoisoindigo (TII) based quinoidal small molecules different alkyl side chains, aimed at synthesizing air-stable, structure, properties, and OFET characteristics of a series of TII-QNs. Quinoidal compound as a superior electron acceptors and usually offering low-lying lowest unoccupied molecular orbital (LUMO) energy levels (< -4.0 eV), which cause them potential candidates for high-performance n-channel OSCs for application in OFETs. The inclusion of a TII-based quinoidal acts various significant roles: enhance planarity to the molecular plane via Sulfur-oxygen interactions, inducing further effective conjugation, charge delocalization, and intermolecular π–π interactions. The UV-vis absorption spectrum of C2C6-TII-QN, C8-TII-QN and C4-TII-QN shows wide absorption between 400 nm and 850 nm in thin film, and the optical band-gap calculated from absorption cutoff was 1.4 eV. Thin film of C2C6-TII-QN, C8-TII-QN and C4-TII-QN exhibited a large red shift in comparison with that of the solution state film. These small molecules possess N-channel charge transport characteristics when used as the active semiconductor in organic thin-film transistors (OFETs). The highest electron mobilities of 0.016 cm2V-1s-1 for C8-TII-QN have been achieved in top-contact bottom-gate OFET devices.[[note]]碩