Controlled Synthesis of Water-Soluble Conjugated Polyelectrolytes Leading to Excellent Hole Transport Mobility
Controlled Synthesis of Water-Soluble Conjugated Polyelectrolytes Leading to Excellent Hole Transport Mobility
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DOI：
10.1021/cm500500t
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发表时间：
2014-03-25
影响因子：
8.6
通讯作者：
Thelakkat, Mukundan
中科院分区：
文献类型：
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作者：
Brendel, Johannes C.;Schmidt, Martina M.;Thelakkat, Mukundan
共轭聚电解质（CPE）由于其在水溶液或强极性溶剂中的溶解性而得到广泛的应用。然而，在外加电场下的离子重组和低电荷载流子迁移率限制了它们作为电子器件中的活性层的用途。在这里，我们提出了一种新的控制合成路线的CPE基于聚噻吩携带磺酸侧基。我们制备了三种不同的聚合物具有不同的分子量和窄的多分散性。对于分子量最大的CPE，我们观察到在水溶液中形成小聚集体，这是通过紫外-可见吸收光谱和荧光光谱证实的。在紫外-可见光谱中，观察到振动带，这些振动带保持在薄膜中。这些吸收带与结晶聚（3-己基噻吩）的吸收带相似。这些聚集体的荧光信号几乎完全猝灭。加入其他极性溶剂如DMSO导致聚集体的溶解，这通过UV-vis中的振动带的减少和荧光信号的增加来指示。该聚合物还表现出非常高的空穴传输迁移率，如通过空间电荷限制电流方法测定的，为（1.2 +/-0.5）× 10（-2）cm（2）/（Vs）。通过电流（J）-电压（V）测量和阻抗谱研究了潜在的输运机制。前者显示出J与V的二次依赖性和经典半导体的微秒内的快速响应特性，而后者没有显示出任何离子运动的迹象。与其他报道的CPE相比，这里的regioregular链构象和窄的分子量分布促进了聚集体的形成，从而提高了整个本体的电子电荷传输。此外，空间要求的抗衡离子的存在抑制离子运动和重组，导致具有高空穴传输迁移率的水溶性半导体材料。
Conjugated polyelectrolytes (CPE) find wide-spread applications due to their solubility in aqueous systems or highly polar solvents. However, ion reorganization under applied fields and low charge carrier mobility limit their use as active layers in electronic devices. Here, we present a novel controlled synthetic route for CPEs based on polythiophene carrying sulfonate side groups. We prepared three different polymers with varying molecular weights and narrow polydispersity. For the CPE with the highest molecular weight, we observed the formation of small aggregates in aqueous solution which was confirmed by UV-vis absorption and fluorescence spectroscopy. In the UV-vis spectrum, vibrational bands are observed, Which are maintained in the thin film. These absorption bands are similar to those of crystalline poly(3-hexylthiophene). The fluorescence signal is almost completely quenched for these aggregates. Adding other polar solvents such as DMSO results in the dissolution of the aggregates indicated by the decrease of the vibrational bands in UV-vis and the increase of the fluorescence signal. This polymer further exhibits a remarkably high hole transport mobility of (1.2 +/- 0.5) x 10(-2) cm(2)/(V s) as determined by the space charge limited current method. The underlying transport mechanism was studied by current (J)-voltage (V) measurements and impedance spectroscopy. The former shows a quadratic dependence of J vs V and a fast response within microseconds characteristic for a classical semiconductor, while the latter shows no sign of any ion motion. In contrast to other reported CPEs, the regioregular chain conformation and the narrow molecular weight distribution here promote the formation of aggregates which improve the electronic charge transport throughout the bulk. Additionally, the presence of sterically demanding counterions suppress the ion motion and reorganization, resulting in a water-soluble semiconducting material with high hole transport mobility.