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首页> 外文期刊>Synthetic Metals >Anisotropic conductivity-temperature characteristic of solution-cast poly(3-hexylthiophene) films
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Anisotropic conductivity-temperature characteristic of solution-cast poly(3-hexylthiophene) films

机译：溶液流延聚（3-己基噻吩）薄膜的各向异性电导率-温度特性

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摘要

For the purpose of developing a positive temperature coefficient (PTC) device, thin films of poly(3-hexylthiophene) (P3HT) were prepared by solution-cast from chloroform. In the present work, the P3HTs of high molecular weight (M_w) with various regioregularities were employed, and the structure anisotropy and the temperature dependence of conductivities in directions parallel (sigma_(||)) and perpendicular (sigma_(perpendicular)) to the film surface were investigated. For highly orientated P3HT films, the temperature dependence of sigma_(perpendicular) was found to reflect an amorphous character of charge hopping along this direction. However, the sigma_(||) decreased greatly above 50 deg C, which was attributed to a decrease in the in-plane pi-stacking caused both by the melting of crystallized side chains and the enhanced side-chain disturbance with increasing temperature. Different charge transport mechanisms were proposed to explain the anisotropic conductivity-temperature characteristics observed in the two directions. The high conductivity in the parallel direction was deteriorated significantly by thermal recycles, probably due to a reduction of the orientation degree of P3HT crystallites in the bulk film, rather than a change of conjugated length of polymer backbone. A reversible PTC effect was observed for the P3HT film with a high M_w and medium regioregularity in the perpendicular direction, which suggested that the high M_w was more important than the high regioregularity to design the thin film PTC devices based on the soluble P3HT films.
机译：为了开发正温度系数（PTC）器件，通过从氯仿溶液浇铸制备了聚（3-己基噻吩）（P3HT）薄膜。在目前的工作中，采用具有不同区域规则性的高分子量（M_w）的P3HT，并且在平行于（sigma_（||））和垂直（sigma_（垂直））方向上的结构各向异性和电导率的温度依赖性。研究膜表面。对于高度取向的P3HT薄膜，发现sigma_（垂直）的温度依赖性反映了沿该方向的电荷跳跃的无定形特征。但是，在50℃以上时，sigma_（||）大大降低，这归因于由于结晶侧链的熔化和随温度升高而增强的侧链扰动引起的面内π堆积的减少。提出了不同的电荷传输机制来解释在两个方向上观察到的各向异性电导率-温度特性。平行方向上的高电导率由于热循环而大大降低，这可能是由于块状薄膜中P3HT微晶的取向度降低了，而不是聚合物主链的共轭长度改变了。在垂直方向上具有高M_w和中等区域规则性的P3HT薄膜观察到可逆PTC效应，这表明高M_w比高区域规则性对基于可溶性P3HT薄膜设计薄膜PTC器件更重要。

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