具有非共轭支链的有机共轭聚合物压阻效应研究

The project proposes that the piezoresistance effect of the organic semiconductor of conjugated polymer with unconjugated branch, together with their hardness and Young's modulus, should be studied. The correlated stress, strain, voltage, and current of the devices with some novel derivatives of polythiophene or poly-(pphenylene vinylenes), would be measured under different loads, together with their hardness and Young's modulus would be measured using nano-indention technique.The devices with the same organic material but different electrodes would be fabricated, e.g. ITO/ITO, ITO/Au for hole-only injection, and Ca/Ca, Mg:Ag/Ca for electron-only injection. The influence of the stress on the conducting behavior of electron (or hole) will be revealed by the injection-limited devices. The devices with full carrier injection and limited carrier transporting, which with different thicknesses of organic film, would be fabricated, and their piezoresistance would be measured. Then the influence of carrier injection and bulk transport on the piezoresistance would be revealed. The presented project would be helpful in comprehension of the piezoresistance mechanisms in organic semiconductors. It would lay the foundation for a novel, flexible, and high sensitive pressure- or tactile- sensor,which would be better than those with the conductive silicon gel.

本项目研究具有非共轭支链的有机半导体共轭聚合物的压阻效应,以及相关的硬度和杨氏模量。主要测试有机半导体高分子薄膜器件，如聚噻吩、聚对苯乙炔类材料在外加压力下，其应力-应变-电压-电流的关系，利用纳米压痕技术测量其硬度和杨氏模量，解释压阻效应的机理。通过构建材料相同，但界面注入不同的器件（如ITO/ITO、ITO/Au电极只注入空穴，Ca/Ca、Mg:Ag/Ca电极只注入电子），分析在只传输空穴或只传输电子的器件中，界面接触对压阻性能的影响，揭示外加压力如何影响电子和空穴的导电行为。还构建具有充足载流子注入的器件，研究材料厚度变化对器件压阻性能的影响。揭示载流子的界面注入和体内传输如何影响材料的压阻特性，有助于理解有机半导体的压阻效应，为制造高灵敏、可弯曲、综合性能优于导电硅胶的新型触觉(或压力)传感器打下基础。

本项目研究了具有非共轭支链的有机半导体共轭聚合物的压阻效应。主要测试了聚对苯乙炔类,聚噻吩类、聚芴类共轭聚合物在外加压力下的应力-应变-电压-电流关系，揭示了材料结构与电学和力学特性关系，解释了压阻效应的机理。利用纳米压痕技术测量其载荷曲线和杨氏模量，用罗纳德琼斯势理论解释了载荷曲线，并由拟合参数推导得到了杨氏模量表达式。研究了电极材料和有机层厚度对器件压阻性能的影响。得到以下五点主要结论：（1）材料侧链（烷链）一般以2-6个碳原子为宜。（2）提高材料压阻性能的原则是：材料主链的刚性和导电性越强越好;侧链长度适中，越柔软且回弹越快越好。（3）发现了有机材料混合（化合或多层）后的杨氏模量估算方法。（4）提出了用罗纳德琼斯势拟合并解释载荷曲线，通过拟合参数得到杨氏模量随压入深度和载荷变化的公式。（5）在所研究的三类材料中，MDMO-PPV具有最好的压阻特性。