Closing the Stability-Performance Gap in Organic Thermoelectrics by Adjusting the Partial to Integer Charge Transfer Ratio.,Macromolecules

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Closing the Stability-Performance Gap in Organic Thermoelectrics by Adjusting the Partial to Integer Charge Transfer Ratio.
Macromolecules ( IF 5.1 ) Pub Date : 2020-01-08 , DOI: 10.1021/acs.macromol.9b02263
Osnat Zapata-Arteaga ₁ , Bernhard Dörling ₁ , Aleksandr Perevedentsev ₁ , Jaime Martín _{2,

3} , J Sebastian Reparaz ₁ , Mariano Campoy-Quiles ₁

Affiliation

Two doping mechanisms are known for the well-studied materials poly(3-hexylthiophene) (P3HT) and poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), namely, integer charge transfer (ICT) and charge transfer complex (CTC) formation. Yet, there is poor understanding of the effect of doping mechanism on thermal stability and the thermoelectric properties. In this work, we present a method to finely adjust the ICT to CTC ratio. Using it, we characterize electrical and thermal conductivities as well as the Seebeck coefficient and the long-term stability under thermal stress of P3HT and PBTTT of different ICT/CTC ratios. We establish that doping through the CTC results in more stable, yet lower conductivity samples compared to ICT doped films. Importantly, moderate CTC fractions of ∼33% are found to improve the long-term stability without a significant sacrifice in electrical conductivity. Through visible and IR spectroscopies, polarized optical microscopy, and grazing-incidence wide-angle X-ray scattering, we find that the CTC dopant molecule access sites within the polymer network are less prone to dedoping upon thermal exposure.

中文翻译：

通过调整部分与整数电荷转移比来缩小有机热电材料的稳定性与性能差距。

经过充分研究的材料聚(3-己基噻吩) (P3HT) 和聚(2,5-双(3-烷基噻吩-2-基)噻吩并[3,2-b]噻吩) (PBTTT) 已知两种掺杂机制，即整数电荷转移（ICT）和电荷转移复合物（CTC）形成。然而，人们对掺杂机制对热稳定性和热电性能的影响知之甚少。在这项工作中，我们提出了一种精细调整 ICT 与 CTC 比率的方法。利用它，我们表征了不同 ICT/CTC 比率的 P3HT 和 PBTTT 的电导率和热导率以及塞贝克系数和热应力下的长期稳定性。我们发现，与 ICT 掺杂薄膜相比，通过 CTC 掺杂可以得到更稳定但电导率更低的样品。重要的是，发现约 33% 的中等 CTC 分数可以提高长期稳定性，而不会显着牺牲电导率。通过可见光和红外光谱、偏光光学显微镜和掠入射广角 X 射线散射，我们发现聚合物网络内的 CTC 掺杂剂分子进入位点在热暴露时不易去掺杂。

更新日期：2020-01-08

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