Spinodal Decomposition of Blends of Semiconducting and Ferroelectric Polymers
Spinodal Decomposition of Blends of Semiconducting and Ferroelectric Polymers
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DOI：
10.1002/adfm.201001505
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发表时间：
2011-05
影响因子：
19
通讯作者：
K. Asadi;H. Wondergem;Reza Saberi Moghaddam;C. McNeill;N. Stingelin;B. Noheda;P. Blom;D. D. de Leeuw-D.
中科院分区：
文献类型：
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作者：
K. Asadi;H. Wondergem;Reza Saberi Moghaddam;C. McNeill;N. Stingelin;B. Noheda;P. Blom;D. D. de Leeuw-D.
基于相分离的有机铁电体和半导体共混物的电阻开关的工作在很大程度上取决于这种系统的微观结构。广泛的分析技术被用于表征铁电无规共聚物聚（偏氟乙烯-三氟乙烯）[P(VDF - TrFE)]和半导体聚合物，区域不规则聚（3 -己基噻吩）（rir - P3HT）的自旋涂膜。共混物分离成镶嵌在结晶P（VDF - TrFE）基体中的无定形rir‐P3HT结构域。rir‐P3HT结构域在整个薄膜中是连续的，从衬底/共混界面到共混/空气界面。我们还研究了rir - P3HT结构域的大小和数目作为组成的函数，并意外地发现，对于给定的rir - P3HT:P（VDF - TrFE）比，结构域的大小分布相当分散。区域尺寸随rir - P3HT含量的增加而增大，表明凝固过程不以成核过程为主。因此，Spinodal分解更可能是导致rir - P3HT:P（VDF - TrFE）共混物微观结构的原因。由于spinodal分解自发发生，而不存在成核步骤，这可以大大促进处理，因为对成核过程（均相或异相）的复杂控制变得不必要。共混物的横向电导率测量表明，rir - P3HT结构域没有电连接，支持微观结构证据。通过薄膜的垂直电流是用Au和Ag电极作为混合成分的函数来测量的。用一个模型来解释电输运。极化到ON -态的Ag二极管的注入优先发生在rir - P3HT结构域的周围。据估计，发生注射的累积宽度约为几百纳米。
The operation of resistive switches based on phase‐separated blends of organic ferroelectrics and semiconductors depends significantly on the microstructure of such systems. A wide range of analysis techniques are used to characterize spin‐coated films of the ferroelectric random copolymer poly(vinylidene fluoride‐trifluoroethylene) [P(VDF‐TrFE)], and the semiconducting polymer, regio‐irregular poly(3‐hexylthiophene) (rir‐P3HT). The blend separates into amorphous rir‐P3HT domains embedded in a crystalline P(VDF‐TrFE) matrix. The rir‐P3HT domains are continuous throughout the film, from the substrate/blend interface to the blend/air interface. We also investigate the rir‐P3HT domain size and number as a function of composition and find – unexpectedly – a rather mono‐disperse domain size distribution for a given rir‐P3HT:P(VDF‐TrFE) ratio. The domain size increases with rir‐P3HT content, indicating that the solidification is not dominated by nucleation processes. Spinodal decomposition is therefore more likely to be responsible for the microstructure induced in the rir‐P3HT:P(VDF‐TrFE) blends. Since spinodal decomposition occurs spontaneously without the presence of a nucleation step, this can facilitate processing considerably, since the intricate control of nucleation processes (homogenous or heterogenous) is rendered unnecessary. Measurement of the lateral conductivity of the blends demonstrates that the rir‐P3HT domains are electrically not connected, supporting the microstructural evidence. A perpendicular current through the film is measured using both Au and Ag electrodes as a function of blend composition. A model was used to interpret the electrical transport. The injection for Ag diodes poled into the ON‐state preferentially occurs at the circumference of the rir‐P3HT domains. An accumulation width over which the injection occurs is estimated to be of the order of a few hundred nm.