摻雜有機半導體材料於場效應電晶體與熱電應用之研究

Abstract

近年來，在提升有機場效應電晶體的遷移率和有機熱電材料的電導率上，「摻雜」為常用的方法。尤其是在有機半導體領域。利用摻雜能夠有效調控能階、增加載流子濃度、減少接觸電阻，以實現更高的載流子遷移率。然而，摻雜機制在不同材料之下、摻雜需求的差異，以及對分子排列的潛在負面影響等問題存在，實現材料最佳化的載流子濃度仍然相當困難。因此，有關有機半導體摻雜在有機場效應電晶體和有機熱電發電裝置應用中的研究引起了廣泛關注。本研究旨在探討有機半導體摻雜的效應，並分別應用於有機場效應電晶體和有機熱電發電裝置中。其中，我們結合分子設計的開發和有效的摻雜系統，以改善有機場效應電晶體和有機熱電發電裝置之電性。本篇論文詳細針對摻雜進行探討。 在第二章中，我們成功將一系列具有不同受體與醌體之新型萘二酰亞胺二胺基(NDI)隨機供體-受體共聚物，這一系列四種共聚物命名為rNDI-N、rNDI-S、rNDI-NN、rNDI-SS，並將其進行N型溶液摻雜應用於有機場效應電晶體中。在未摻雜的rNDI-N、rNDI-NN和rNDI-SS樣品中，我們觀察到雙極性載子傳輸行為，而rNDI-S呈現了單極性的N型行為。經過摻雜後，顯著提升了rNDI-N與rNDI-S之電晶體性能，對於1 wt%摻雜的電晶體元件中，提高了3到6倍之電子遷移率。其提升的原因為陷阱態得到填充、接觸電阻降低、活化能降低、結晶度提升且微結構邊向取向的排列有助於載子電荷的傳輸。有趣的是，我們也發現溶液摻雜在醌體之樣品中，rNDI-NN與rNDI-SS的效果並不顯著，因為醌體之供體-受體共聚物具有預共振與分子排列較平面之特性，使得材料較不易進行摻雜，甚至可能會降低器件性能。最後，在第二章中，我們通過開發具有不同受體和醌體之共軛共聚物，並將其進行摻雜，觀察有機半導體與摻雜劑之間的相互作用、薄膜形態和分子取向，以有效優化有機場效應電晶體載子傳輸之性能。 在第三章中，我們提出了一種新穎的方法來製備可拉伸的有機熱電材料，透過混合的方法來提升元件的可拉伸性，該混合系統由剛性半導體高分子和彈性絕緣高分子組成。混合物中包括聚（3-己基噻吩）（P3HT）和聚{3,6-二噻吩-2-基-2,5-二(2-癸基十四烷基)-吡咯[3,4-c]吡咯-1,4-二酮-反-噻吩乙烯-2,5-基}（PDVT-10）作為剛性聚合物（RP），以及聚苯乙烯-乙烯-丁烯-丁烯-苯乙烯共聚物（SEBS）作為彈性聚合物（EP）。主要目標是優化混合物的組成，以實現混合薄膜形貌呈現連續的網絡結構形態，此形貌除了改善了材料的可拉伸性外，在後浸泡摻雜過程中，與摻雜劑具有良好的相容性，具有優良的摻雜效果，材料表現出較低的活化能和較高的載流子濃度，從而表現高的電導率。我們更將本研究中最優化條件之元件進行P-N串聯為一「可拉伸式混合摻雜系統之P-N連接熱電發電機」，並在22.4 K之溫差下，達到1.39 nW的最大輸出功率。本篇論文在有機摻雜系統有機場效應電晶體與有機熱電之應用上提供了有價值的見解，顯示了摻雜有機半導體材料的潛在應用。

Recent advancements in doping strategies have greatly enhanced the mobility of organic field-effect transistors (OFET) and the electrical conductivity of organic thermoelectric (OTE) materials. These achievements primarily focus on organic semiconductors (OSCs) and highlight the crucial role of doping in modulating energy levels, improving carrier concentration (n), reducing contact resistance (RC), and achieving higher charge carrier mobility (µ). However, challenges remain, including the need for efficient doping mechanisms, increased n, variation in doping requirements for OSCs, and potential negative effects on molecular packing. This study aims to bridge the gap between research on OFET and OTE materials and the doping of OSCs, providing a detailed information of advancements in N-type doping of Naphthalenediimide (NDI)-based random donor-acceptor copolymers for OFETs and P-type doping of stretchable semiconducting polymer blends for OTE applications. In Chapter 2, an integrated strategy combining molecular design and conjugated polymer doping is proposed to improve the electronic characteristics of OFETs. In this study, a series of soluble naphthalenediimide (NDI)-based random donor-acceptor copolymers with selenophene π-conjugated linkers and four acceptors of different electron-withdrawing strengths (rNDI-N/S/NN/SS) were synthesized, characterized, and employed in OFETs. N-type doping of the NDI-based copolymers was successfully achieved using a specific potassium triflate adduct, DMBI-BDZC. The undoped rNDI-N, rNDI-NN, and rNDI-SS samples displayed ambipolar charge transport, while rNDI-S exhibited unipolar n-type behavior. Doping with DMBI-BDZC significantly modulated the performance of rNDI-N/S OFETs, leading to a 3-6 fold increase in electron mobility (μe) for the 1 wt% doped device. This improvement was attributed to simultaneous trap mitigation, lower contact resistance (RC), reduced activation energy (EA), and enhanced crystallinity and edge-on orientation for charge transport. However, the doping of intrinsic pro-quinoidal rNDI-NN/SS films did not exhibit significant changes or even showed reduced device performance. These findings highlight the potential to manipulate energy levels by developing conjugated copolymers with different acceptors and quinoids, optimizing dopant-polymer semiconductor interactions, film morphology, and molecular orientation to enhance charge transport in OFETs. In Chapter 3, we present a novel approach to fabricating stretchable OTE materials through the utilization of a doped semiconducting polymer blend system. The blend comprises Regioregular poly(3-hexylthiophene) (P3HT) and poly{3,6-dithiophen-2-yl-2,5-di(2-decyltetradecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thienylenevinylene-2,5-yl} (PDVT-10) as rigid polymers (RP), and SEBS as the elastic polymer (EP). The primary objective is to optimize the blend compositions to achieve a continuous network structure with SEBS, thereby improving stretchability. The resulting optimized polymer films exhibit well-ordered microstructural aggregates, indicative of good miscibility with FeCl3 and enhanced doping efficiency (ηd). Notably, lower activation energy (EA) and higher carrier concentration (n) contribute to improved electrical conductivity under high tensile strain. These findings offer valuable insights and serve as guidelines for the development of stretchable P-N junction OTE generators, achieving a maximum output power of 1.39 nW through the utilization of doped semiconducting polymer blends at a ΔT of 22.4 K. This research opens up potential applications in wearable electronics and energy harvesting.