Molecular doping of conjugated polymers is the performance-determining step in the fabrication of organic thermoelectric devices. Although strongly oxidizing salt-type dopants effectively produce charge carriers in polymer chains, their poor solubility in the processing solvents leads to undesired precipitation and complicates the film fabrication process. Thus, it is important to develop a conjugated polymer that can be readily doped in a mixed solution using organic dopants. In this study, we synthesized amorphous but highly electron-rich polymers (PCT1 and PCT2) by combining 4H-cyclopenta[2,1-b:3,4-b']dithiophene and thieno[3,4-b]thiophene moieties, whose full-names are poly[(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl)-alt-(2-ethylhexyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate 4,6-diyl)] (PCTs). The PCT polymers were heavily doped with the organic dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), and the resulting PCT:F4TCNQ complex formed an integer charge transfer complex and promoted the intermolecular ordering of PCT polymers. Notably, the PCT:F4TCNQ complex exhibited unique thermoelectric behaviors, with significantly increased power factors even in the presence of large quantities of F4TCNQ, reaching values 3.2-fold higher than those achieved with FeCl₃ sequential doping. Moreover, the higher-molecular-weight polymer, PCT2, exhibited more efficient molecular ordering and charge carrier transport than PCT1, which are crucial for enhancing the thermoelectric properties.

中文翻译：

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非晶态聚合物的溶液态掺杂辅助分子排序和增强的热电性能

共轭聚合物的分子掺杂是有机热电器件制造中的性能决定步骤。尽管强氧化性盐型掺杂剂有效地在聚合物链中产生电荷载流子，但它们在加工溶剂中的溶解性差会导致不希望的沉淀并使薄膜制造过程复杂化。因此，重要的是开发一种可以使用有机掺杂剂容易地掺杂在混合溶液中的共轭聚合物。在这项研究中，我们通过结合 4H-环戊二烯[2,1- b :3,4- b ']二噻吩和噻吩并[3,4- b ]噻吩部分合成了无定形但高度富电子的聚合物（PCT1和PCT2），其全称是poly[(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1- b :3,4-b ']二噻吩-2,6-二基)-alt-(2-乙基己基-3-氟噻吩并[3,4- b ]噻吩-2-羧酸酯4,6-二基)](PCT)。PCT 聚合物重掺杂有机掺杂剂 2,3,5,6-四氟-7,7,8,8-四氰基醌二甲烷 (F4TCNQ)，所得 PCT:F4TCNQ 复合物形成整数电荷转移复合物并促进分子间PCT聚合物的排序。值得注意的是，PCT:F4TCNQ 复合物表现出独特的热电行为，即使在大量 F4TCNQ 存在的情况下，功率因数也显着增加，达到的值比使用 FeCl ₃达到的值高 3.2 倍顺序掺杂。此外，更高分子量的聚合物 PCT2 表现出比 PCT1 更有效的分子排序和电荷载流子传输，这对于提高热电性能至关重要。