Strategic side-chain engineering has led to an increase in the power factor of isoindigo-based conjugated polymers (CPs) by an order of magnitude. We investigated the effect of side chains on the electrical properties of doped isoindigo-based CPs and gained insight into structure–electrical property–thermoelectric transport intercorrelation for optimization of thermoelectric CPs. For this study, we designed and synthesized four isoindigo-based polymers having different types of alkyl chains. The size of the alkyl chains significantly affected the crystallinity of the films, which subsequently resulted in different charge carrier mobilities and diffusion efficiencies of the molecular dopant. Amorphous polymers with bulkier alkyl chains promoted efficient dopant diffusion while their carrier mobility was relatively lower than that of crystalline CPs. Systematic characterizations on the structural, electrical, and thermoelectrical properties of the CP films showed a trade-off effect for these side-chain structures for optimization of the thermoelectric effect, and with the optimized structure, we obtained a significantly improved power factor up to 37.8 μW·m^–1·K^–2. This study suggests that exercising fine control of crystallinity through side-chain modification of the fixed polymer backbone can be a simple but very effective approach to maximizing organic thermoelectric effects of CPs.

中文翻译：

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优化基于异靛蓝的共轭聚合物热电性能的策略性侧链工程方法

战略性的侧链工程已使基于异靛蓝的共轭聚合物（CP）的功率因数提高了一个数量级。我们研究了侧链对掺杂的基于靛蓝的CP的电学性能的影响，并深入了解了结构-电学性质-热电输运互相关以优化热电CP。对于本研究，我们设计并合成了四种具有不同类型烷基链的基于异靛蓝的聚合物。烷基链的大小显着影响薄膜的结晶度，随后导致不同的电荷载流子迁移率和分子掺杂剂的扩散效率。具有更大烷基链的无定形聚合物促进了有效的掺杂剂扩散，而其载流子迁移率却相对低于晶体CPs。^–1 ·K ^–2。这项研究表明，通过固定聚合物主链的侧链修饰对结晶度进行精细控制可能是使CPs最大化有机热电效应的简单但非常有效的方法。