具有共軛阻斷基之本質可拉伸共軛高分子開發暨場效電晶體

Abstract

近年來，有機半導體因其低成本、溶液可加工性、可饒曲性和結構可調性而受到廣泛關注，這些特性供它們成為柔性電子設備及積體電路的材料選擇。為了開發本質性可拉伸的半導體高分子，運用高分子主鏈及側鏈上的加工策略來控制其共軛結晶形態、薄膜形貌以及拉伸性；可惜的是通常這種加工方式無法同時提升高分子的拉伸性以及其載子遷移率。在本質性可拉伸的半導體開發中，相形之下，p型共軛高分子比n型共軛高分子的發展較為成熟。因此，在本論文中將系統地研究關於具共軛阻斷基(conjugation break spacers)隨機三元聚合(random terpolymerization)的萘二亞胺（NDI）衍生物高分子及其本質性可拉伸有機場效電晶體的基礎知識。 本論文章節二，在不同長度的苯酯基共軛阻斷基中引入硫(S)、碳(C)、氧(O)三種不同的異核原子進行探討。相比之下，含硫原子的共軛阻斷基展現較佳的拉伸性，而由於高極性、較僵硬的氧原子在含氧原子基共軛阻斷基中，造成較強的固態聚集及微相分離，還有較高的楊氏係數與玻璃轉化溫度，破壞了其薄膜的本質可拉伸性。另外，研究發現較長(2)的共軛阻斷基有較多的應力釋放元素，使其薄膜在受到較大的應變時，才開始破裂，導致在高應變(60%)下，相較於那些具有較短(1)的共軛阻斷基，展現了較佳的電子遷移率。在60%應變下，S1、S2、C1、C2的平行、正交電子遷移率(μe∥, μe⊥)分別為(0.00072, 0.00101), (0.00134, 0.00141), (0.00097, 0.00127) 與 (0.00107, 0.00153) cm2 V−1 s−1 於本論文章節三，我們將異山梨醇 (ISB)、異甘露醇 (IMN) 和異艾杜糖醇 (IID) 等雙脫水己糖醇(Dianhydrohexitol)引入萘二亞胺衍生聚合物的具共軛阻斷基中，並討論了立體異構效應之影響。具順式結構異甘露醇與異艾杜糖醇的共軛阻斷基展現了與傳統純直碳鏈相似的特性，包含其拉伸性，於10%應變時破裂和側向(edge-on)堆疊取向的結晶排列；而具有反式結構的異山梨醇展現了出色的高分子鏈重新排列能力以及能有效降低薄膜破裂密度；除此之外，雙軸式(bimodal)結晶性排列、較弱的共軛結晶性以及高分子鏈之間的糾纏，促使了他表現出優異的機械性質與高強度拉伸下的元件表現，在受到高應變時能夠維持三維的載子傳輸通道，甚至在其薄膜100%應變下，我們量測到非常好的元件效果，其平行與正交電子遷移率分別為(0.00295, 0.00309) cm2 V-1 s-1，且其對應的電子遷移保留率(mobility retention)為(53, 56) %。這項研究為隨機三元聚合具共軛阻斷基萘二亞胺衍生物高分子的主鏈加工工程提供了基礎研究知識，並為本質性可拉伸高分子場效電晶體的應用添增新的設計構想與見解。

Organic semiconductors have received a lot of attention in recent years because of their solution processability, low cost, lightweight, flexibility and structural tunability. These properties make them interesting choices for flexible electronic devices and integrated circuits. However, to develop intrinsically stretchable polymeric semiconductors, the strategies and variables that influence the polymers’ mobility–stretchability properties are often trade-offs. Additionally, a lagged progress in the development of intrinsically stretchable n-type conjugated polymers compared with p-type ones is observed. Most researchers focus on the p-type Diketopyrrolopyrrole (DPP) backbone polymers due to their superior mobility performances. To improve their mobility–stretchability properties, several methodologies on backbone and side chain engineering have been applied to control their morphologies, solid-state packing, intrinsic stretchability etc. Hence, in this thesis, the fundamental aspects about random terpolymerization and conjugation break spacers (CBSs) were systematically investigated to further enhance the intrinsically stretchable organic field effect transistor (OFET) performances of n-type naphthalenediimide (NDI) derivatives. In chapter 2, three types of heteroatoms including sulfur (thioether), oxygen (ether) and carbon (alkyl) were incorporated into ester functionalized CBSs of different lengths. It has been discovered that thioether-base CBSs demonstrated improved stretchability compared with ether-based and conventional alkyl-based CBSs. Conversely, the highly polar oxygen atoms in ether-based CBSs would induce strong aggregations and phase separation with higher Young’s moduli and glass transition temperature (Tg) that would vitiate the stretchability of the polymer film. As expected, longer CBSs (2) could supply extra strain-releasing elements, which attributed to the delayed crack-onset strain with better μe retention at 60% compared with shorter ones (1). However, the electron mobilities (μe) are undesirable due to the over extended CBSs that disrupts intrachain charge transport. At 60% strain, thioether- (S1,S2) and alkyl-CBSs (C1,C2) demonstrated comparable OFET performances with strains parallel, perpendicular to the device channel (μe∥, μe⊥), which are (0.00072, 0.00101), (0.00134, 0.00141), (0.00097, 0.00127) and (0.00107, 0.00153) cm2 V−1 s−1, respectively. In chapter 3, biobased-dianhydrohexitols including isosorbide (ISB), isomannide (IMN) and isoidide (IID) were introduced into CBSs of NDI-derived polymers and the impact of stereoisomerism effect were discussed. Results show that IMN and IID with cis-conformation chemical structures displayed high resemblance with conventional linear alkyl chains in the 10% crack onset-strain and their edge-on favored solid-state stackings. On the contrary, exceptional chain realigning capability with reduced crack density and higher crack onset-strain were observed in polymers containing trans-conformation ISB. In addition, due to their bimodal preferred lamellar packings, chain entanglements, and weak conjugation crystallinity, ISB incorporated CBSs have exceptional mechanical and mobility–stretchability properties that make it possible for them to maintain their 3D charge transport performance even under intense mechanical strain. Astonishingly, charge transport performance with (μe||, μe⊥) values at (0.00295, 0.00309) cm2 V-1 s-1 and corresponding retention (53, 56) % at 100% strain were observed. This work provides new insights to backbone engineering in terpolymerized, CBSs constituted NDI-derivative polymers in stretchable electronic applications.