摻雜高分子與奈米複合熱電材料： 分析、穿戴式元件應用

Abstract

對可再生能源日益增長的需求使高分子熱電材料受到巨大關注，這種材料以其易於製造、靈活性、低毒性以及在各種工業應用中的潛力而聞名。提升高分子材料的功率因數 (PF) 主要涉及傳統的摻雜和高分子奈米複合材料的開發。 在第一項研究中，我研究了由隨機供體-受體共軛共聚物和單壁奈米碳管 (SWCNTs) 組成的奈米複合材料的熱電性能。通過調控共軛共聚物 二酮吡咯吡咯羅 (DPP) 和異靛藍 (IID) 的組成比例，設計出一系列的隨機共軛共聚物 (DPP0，DPP5，DPP10，DPP30，DPP50，DPP90，DPP95和DPP100)。主要目標是為了改善SWCNTs在溶液態的分散性，使其形成較小的管束，從而提高共聚物/SWCNT奈米複合材料的熱電性能。良好的分散性促進了導電網絡的形成，這對優化熱電性能至關重要。我對薄膜表面形貌的研究表明，DPP95/SWCNT奈米複合材料在兩個材料間展現出最強的交互作用力，導致最高的功率因數值為711.1 μW m–1 K–2。這種卓越的性能源自於高電導率 (σ) 1690 S cm−1和塞貝克係數 (S) 64.8 μV K–1。此外，我們成功利用DPP95/SWCNT膜組裝了熱電發電元件 (TEGs)，在溫差為29.3 K時達到最大功率輸出20.4 μW m–2。這些發現突顯了調控隨機共軛共聚物的組成和混合SWCNTs的奈米複合材應用於穿戴式熱電原件上的潛力。 在第二項研究中，我開發兼具柔軟性和可拉伸性的氯化鐵摻雜隨機共軛共聚物的熱電性能。通過調整隨機共軛共聚物的組成，具體為diindenothieno[2,3-b]thiophene (DITT) 和二酮吡咯吡咯羅的比例，合成了一系列隨機共軛共聚物 (PDPP, DITT10, DITT20, DITT30, DITT50, DITT80, 和DITT100)。目標是在保持其電能的同時提高摻雜薄膜的拉伸性。通過使用低入射角寬角X射線散射 (GIWAXS) 分析，我們觀察到，具有高結晶度的共軛共聚物薄膜在摻雜過程前後都呈現出邊向取向。在測試樣品中，DITT30展現出最高的拉伸性能，能夠承受超過100%的應變，同時還能維持一定的電導率 (σ)。這個結果表明了DITT基團被引入PDPP基質有助於提高薄膜的拉伸性能。此外，摻雜的DITT30膜呈現出良好的穩定性，即使在經過200個拉伸/釋放周期後，仍能保持其電性。此研究展現出一種製作出色熱電性能的拉伸共聚物薄膜的創新方法，使其可以在高應變下運作。這個發現對於開發具有拉伸性能的熱電元件有巨大的幫助，為穿戴式裝置和能源回收提供良好的願景。

The increasing demand for renewable energy has sparked significant interest in polymer-based thermoelectric materials, known for their ease of fabrication, flexibility, low toxicity, and potential in various industrial applications. Efforts to enhance the power factor (PF) values of polymers mainly involve traditional doping and the development of polymer-based nanocomposites. In the first study, we investigated the thermoelectric properties of nanocomposites comprising donor-acceptor random conjugated copolymers and single-walled carbon nanotubes (SWCNTs). By manipulating the composition of the conjugated polymers, specifically the ratio of diketopyrrolopyrrole (DPP) to isoindigo (IID), we designed a series of random conjugated copolymers (DPP0, DPP5, DPP10, DPP30, DPP50, DPP90, DPP95, and DPP100). The main objective was to improve the dispersion of SWCNTs into smaller bundles, leading to enhanced thermoelectric properties of the polymer/SWCNT nanocomposite. This dispersion strategy facilitated the formation of an interconnected conducting network, crucial for optimizing the thermoelectric performance. Our systematic investigation of the morphologies revealed that the DPP95/SWCNT nanocomposite exhibited the strongest interaction, resulting in the highest PF value of 711.1 μW m–1 K–2. This superior performance was derived from its high electrical conductivity (σ)of 1690 S cm−1 and Seebeck coefficient (S) of 64.8 μV K–1. Moreover, we successfully assembled prototype flexible thermoelectric generators (TEGs) using the DPP95/SWCNT film, achieving a maximum power output of 20.4 μW m–2 at a temperature difference of 29.3 K. These findings highlight the potential of manipulating the composition of random conjugated copolymers and incorporating SWCNTs to efficiently harvest low-grade waste heat in wearable thermoelectric devices. In the second study, our focus shifted to the development of thermoelectric properties in flexible and stretchable FeCl3-doped random conjugated copolymers. By adjusting the composition of the random conjugated polymers, particularly the ratio of diindenothieno[2,3-b]thiophene (DITT) to DPP, we synthesized a series of random conjugated copolymers (PDPP, DITT10, DITT20, DITT30, DITT50, DITT80, and DITT100). Our goal was to enhance the stretchability of the doped films while maintaining their electrical properties. Through Grazing-Incidence Wide Angle X-ray Scattering (GIWAXS) analysis, we observed that the spin-coated films with high crystallinity exhibited an edge-on orientation before and after the sequential doping process Among the tested samples, DITT30 demonstrated the highest endurance, withstanding strains exceeding 100% while maintaining decent σ. The incorporation of the DITT unit into the PDPP matrix contributed to the film's exceptional mechanical stretchability. Moreover, the doped DITT30 film exhibited remarkable stability, preserving its electrical properties even after 200 stretch/release cycles. Overall, our results present an innovative approach to fabricating stretchable polymeric thin films that maintain outstanding thermoelectric performance even under high strain levels. These findings hold great potential for the development of stretchable thermoelectric devices, opening up applications in wearable electronics and energy harvesting.