School of Materials Science and Engineering, Kookmin University, Seoul, 02707, Republic of Korea.
Department of Chemistry, College of Science, Korea University, Seoul, 02841, Republic of Korea.
Small Methods. 2023 Feb;7(2):e2201145. doi: 10.1002/smtd.202201145. Epub 2022 Nov 28.
Thermoelectric (TE) performance of a specific semicrystalline polymer is studied experimentally only in a limited range of doping levels with molecular doping methods. The doping level is finely controlled via in situ electrochemical doping in a wide range of carrier concentrations with an electrolyte ([PMIM] [TFSI] )-gated organic electrochemical transistor system. Then, the charge generation/transport and TE properties of four p-type semicrystalline polymers are analyzed and their dynamic changes of crystalline morphologies and local density of states (DOS) during electrochemical doping are compared. These polymers are synthesized based on poly[(2,5-bis(2-alkyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophene-2-yl)benzo[c][1,2,5]thiadiazole)] by varying side chains: With oligoethylene glycol (OEG) substituents, facile p-doping is achieved because of easy penetration of TFSI ions into the polymer matrix. However, the charge transport is hindered with longer OEG chains length because of the enhanced insulation. Therefore, with the shortest OEG substituents the electrical conductivity (30.1 S cm ) and power factor (2.88 µW m K ) are optimized. It is observed that all polymers exhibit p- to n-type transition in Seebeck coefficients in heavily doped states, which can be achieved by electrochemical doping. These TE behaviors are interpreted based on the relation between the localized DOS band structure and molecular packing structure during electrochemical doping.
采用电解质 ([PMIM] [TFSI] )-门控有机电化学晶体管系统，通过原位电化学掺杂在宽载流子浓度范围内精细地控制掺杂水平，对特定半结晶聚合物的热电 (TE) 性能进行了实验研究。采用分子掺杂方法，仅在有限的掺杂水平范围内对其进行了研究。然后，分析了四种 p 型半结晶聚合物的电荷产生/输运和 TE 性能，并比较了它们在电化学掺杂过程中结晶形态和局部态密度 (DOS) 的动态变化。这些聚合物是基于聚[(2,5-双(2-烷氧基)苯并[1,2-b:4,5-b']二噻吩)-交替-(5,6-二氟-4,7-二(噻吩-2-基)苯并[c][1,2,5]噻二唑)]合成的，通过改变侧链：具有聚乙二醇 (OEG) 取代基，由于 TFSI 离子易于渗透到聚合物基质中，因此可以实现易于 p 掺杂。然而，随着 OEG 链长的增加，电荷输运受到阻碍，因为绝缘性增强。因此，最短的 OEG 取代基优化了电导率 (30.1 S cm ) 和功率因子 (2.88 µW m K )。观察到所有聚合物在重掺杂状态下的 Seebeck 系数都表现出 p 型到 n 型的转变，这可以通过电化学掺杂来实现。这些 TE 行为是基于电化学掺杂过程中局部 DOS 能带结构和分子堆积结构之间的关系来解释的。
