近年來，有機電化學電晶體(OECT)因其能夠滿足低成本、高生物相容性和輕薄可穿戴式生物電子元件的需求而引起了研究熱潮。共軛高分子(CP)是OECT中常用的主動層材料，過去的研究大多集中在改良共軛高分子側鏈的親水性。本研究提出了兩種側鏈修飾之外的方法來提升OECT之性能。在第二章中，我們合成了三種以聚(3-己基噻吩)(P3HT)為共軛鏈段的嵌段共聚物(BCP)用於OECT，其中包含不同的絕緣鏈段(聚丙烯酸丁酯(PBA)、聚苯乙烯(PS)和聚環氧乙烷(PEO))。其中，P3HT-b-PBA展現出最優異的性能，其在170 F s−1 cm−1 V−1的載子遷移率和電容乘積(μC*)高於P3HT均聚物(58 F s−1 cm−1 V−1)。此外，P3HT-b-PBA在10次開關週期後的電流相對於第1圈電流維持了88%，而P3HT均聚物則為85%。P3HT-b-PBA性能的改善推測與PBA柔韌和疏水的主鏈有關。在經過電解液浸泡後，它的排列結構幾乎沒有被破壞，與P3HT均聚物和親水性嵌段共聚物P3HT-b-PEO相比，較能維持其原始結構。在第三章中，我們通過添加乙腈(ACN)並進行超音波震盪和紫外光照射，製備了三種P3HT奈米纖維。與僅溶於氯苯中形成的P3HT緻密薄膜相比，添加ACN使P3HT聚集並形成纖維形貌，且透過超音波震盪和紫外光照射促進奈米聚集體自組裝和形成π–π作用力。結果顯示，P3HT奈米纖維具有39.9 F s−1 cm−1 V−1的μC*，高於P3HT緻密薄膜的15.3 F s−1 cm−1 V−1，推測是由於P3HT奈米纖維具有更高的表面積與體積電容。然而，由於P3HT緻密薄膜的排列狀態在電化學摻雜時幾乎沒有被破壞，與P3HT奈米纖維相比，表現出更好的操作穩定性。但是P3HT奈米纖維表現出極高的側向結構排列和強烈的π–π堆疊特性，導致相對較高的載子遷移率。總結來說，本研究探討了聚噻吩型嵌段共聚物和奈米纖維在OECT中的應用，並研究了它們在結構與混合離子–電子傳輸性能上的關聯，為未來設計共軛高分子作為OECT主動層提供了新的思路。

The recent interest in developing low-cost, biocompatible, and lightweight bioelectronic devices has focused on organic electrochemical transistors (OECTs), which have the potential to fulfill these requirements. Conjugated polymers (CPs) are a popular candidate for the OECT active layer. Most previous research has focused on modifying the hydrophilic side chains of CPs. This study proposes two methods to enhance OECT performance beyond the side chain modification. In Chapter 2, we synthesized three types of poly(3-hexylthiophene) (P3HT)-based block copolymers (BCPs) with different insulating blocks (poly(n-butyl acrylate) (PBA), polystyrene (PS), and poly(ethylene oxide) (PEO)) for OECT applications. P3HT-b-PBA showed superior performance with higher mobility and capacitance (μC*) at 170 F s−1 cm−1 V−1 than the P3HT homopolymer at 58 F s−1 cm−1 V−1. In addition, P3HT-b-PBA exhibits better stability with 88% retention over 10 ON/OFF switching cycles, while P3HT homopolymer shows 85% retention. The improved performance of P3HT-b-PBA is regarded to be related to its soft and hydrophobic backbone. It experienced minimal structural disorder when swelled by the electrolyte, maintaining its original structure compared to the counterparts of P3HT homopolymer and the hydrophilic BCP of P3HT-b-PEO. In Chapter 3, we fabricated three types of P3HT nanofibrils by adding acetonitrile (ACN), ultrasonication, and UV irradiation. In contrast to the P3HT dense film dissolved in chlorobenzene only, adding ACN makes P3HT aggregate and forms nanofibrillar morphology due to their poor interaction. In addition, ultrasonication and UV irradiation make the aggregates assemble and facilitate π–π interactions. P3HT nanofibrils exhibited better OECT performance with μC* at 39.9 F s−1 cm−1 V−1 than that of the P3HT dense films at 15.3 F s−1 cm−1 V−1, possibly due to the nanofibrils’ high surface area and capacitance. However, P3HT dense film presents better operational stability due to minimal structural disorder when electrochemical doped, maintaining its original packing compared to the P3HT nanofibrils. But P3HT nanofibrils show high edge-on orientation and strong π–π stacking characteristics, resulting in relatively high mobility. In summary, this study represents the exploration of P3HT-based BCPs and P3HT nanofibrils for OECT applications and investigates their structure–performance relationships in mixed ionic–electronic conductors. It offers another direction for designing P3HT-based CPs as active layers in OECT.

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