PEDOT纳米线复合薄膜的构筑及其热电功率因子增强机制研究

Compared with inorganic thermoelectric (TE) materials, organic TE materials are very promising since they are lightweight, composed of earth-abundant elements, and easy to process, environmental friendly and having intrinsically low thermal conductivity etc. But their low TE power factors hinder their pathway for potential applications in low-/moderate-temperature heat harvesting. Recently, the PI has demonstrated that the energy filtering (EF) effect can enhance power factors of poly(3,4-ethylenedioxythiophene) (PEDOT) based nanocomposites, however, there is still a lack of fundamental understanding and consensus on the significance potential of interfacial energy filteirng, and resultant enhancement of PEDOT nanocomposites is not that notable. In this proposal, in order to further improve TE performance of PEDOT based materials, full polymer TE nanocomposite films consisted of tosylate doped PEDOT (PEDOT:Tos) nanowire and another type of PEDOT nanowire will be constructed. The inherent relationship between nanowire structure, carrier transport and energy filtering will be elucidated through theoretical calculations and experimental investigation. By analyzing the carrier transport mechanism of PEDOT nanowire, an improved theoretical model based on the polymer carrier transport will be proposed to understand how carrier transport affects energy filtering effect. Finally, exceptional TE power factors of PEDOT nanocomposite films can be achieved by rationally modulating the energy barrier height. This project will provide groundbreaking knowledge on understanding interfacial energy filtering for outstanding polymer TE materials, and will lead to a breakthrough in the field of polymer-based TE conversion.

与无机热电材料相比，聚合物热电材料具有质轻、取材丰富以及低热导率等优势，但其热电性能较差（功率因子低），限制了其在中低温废热回收领域的应用。近期申请人初步证明能量过滤效应可增强聚（3,4-二氧乙基噻吩）（PEDOT）基纳米复合材料的功率因子，但其增强机制不清且所获热电性能仍较低。本项目拟以提高PEDOT的功率因子为目的，以甲苯磺酸盐掺杂PEDOT（PEDOT:Tos）纳米线为主要组分，构筑纳米线全聚合物复合薄膜，引入能量过滤效应，阐明纳米线形态结构-载流子输运特性-界面能量过滤效应三者的内在关联；揭示纳米线形态结构对其载流子迁移率的影响规律，明确纳米线薄膜的载流子输运特性；建立基于PEDOT纳米线输运特性的理论预测模型，阐释载流子输运特性与界面能量过滤效应的理论关系，最终获得高功率因子的PEDOT基热电复合薄膜材料，为设计开发高性能聚合物热电材料提供新思路、新方法和一定的理论支撑。

1. 项目背景.柔性导电高分子基热电材料具有高性能、低成本、低毒、良好可加工性等特点，在物联网、智能可穿戴等领域具有潜在应用前景。目前，导电聚合物材料的功率因子S2σ较低。其中，主要原因之一为其过低的聚合物基体迁移率（~0.1 cm2/V·s），这不仅导致其本征功率因子较低并很难有效调控，而且一些新策略如能量过滤效应无法得到充分发挥。能量过滤效应在聚合物热电材料中的适用性和作用机理依然不清。.2. 研究内容.本项目以具有高结晶度和有序度的导电高分子纳米线（PEDOT 纳米线）为研究对象，构筑基于PEDOT纳米线的全聚合物复合薄膜，引入界面能量过滤效应，提高PEDOT聚合物的功率因子S2σ。通过研究PEDOT纳米线形态结构-载流子输运特性-界面能量过滤效应三者的内在关联，揭示载流子迁移率对能量过滤效应的影响规律，阐明能量过滤效应与S2σ增强的理论关系，最终获得高热电功率因子的PEDOT基热电材料。.3. 研究结果.（1）基本阐释了PEDOT纳米线的形态结构与载流子迁移率的内在关联。 .（2）揭示了纯PEDOT纳米线薄膜的载流子输运机理符合可变程跃迁模型（Variable range hopping）。.（3）构筑基于PEDOT纳米线的有机/有机复合薄膜以及有机/无机复合薄膜，建立基于聚合物输运特性的理论预测模型，基本阐明能量过滤效应在导电高分子复合材料中的适用性。.4. 关键数据及其科学意义.（1）优化PEDOT纳米线构筑方法使PEDOT纳米线薄膜载流子迁移率μ提高至1-10 cm2/V·s水平。.（2）制备了基于PEDOT纳米线的PEDOT纳米线/PPy纳米线复合薄膜以及PEDOT纳米线/碲纳米线复合薄膜，在可变程跃迁模型及Kang-Snyder模型理论框架下，利用蒙特卡洛方法阐明能量过滤效应在导电高分子复合材料中的适用性。