有机薄膜器件负电阻特性的影响因素

Negative Resistance Characteristic of Organic Dye-doping Polymer Thin Films Devices

研究了影响有机染料掺杂聚合物薄膜器件负电阻特性的因素,为探索有机负电阻的机理提供实验依据。实验中制备了多种有机染料掺杂聚合物薄膜器件,研究了有机小分子染料、聚合物基体、薄膜组成及厚度、ITO和聚苯胺阳极等对有机染料掺杂聚合物薄膜器件负电阻特性的影响。在室温、大气环境下,所制备的多种有机染料掺杂聚合物器件在所加电压为3～4V时,观察到明显的负电阻特性,电流峰谷比最大约为8。负电阻现象及峰谷比的大小受膜厚和器件的结构、制备工艺等影响。提出用负电阻和二极管并联组成的等效电路模型解释影响负电阻特性的因素,认为负电阻特性与载流子的不平衡注入有关。在此基础上设计、合成了主链含二唑电子传输基团的可溶性聚对苯撑乙烯衍生物,该聚合物兼具空穴和电子传输功能,在空气中具有较稳定的N型负电阻特性。进一步控制相关材料和工艺条件,有可能得到易于控制的负阻效应,开发出新型的有机负电阻器件。

Since negative differential resistance phenomenon of the dyedoping polymer thin films was discovered, the mechanism of negative differential resistance has not been well explained due to many affecting factors. Several different interpretations were put forward, but most of them lacked the experimental evidence. In this paper the factors affecting negative differential resistance of the dyedoping polymer thin film devices was studied, and experimental evidence brought forward in order to further interpret the principle of organic negative differential resistance. Many kinds of dyedoping polymer thin films devices were fabricated. Factors affecting negative resistance including different organic dyes and polymeric matrices, varied composition and thickness of the film, ITO and anodic polyaniline were investigated respectively. In an atmosphere, a remarkable negative resistance phenomenon was found in low voltage state (3～4V) at room temperature. The maximum ratio of peak current to valley current was approximately 8. The appearance of the negative differential resistance phenomenon and the magnitude of ratio of peak current to valley current depended on thickness of the film, structure and fabrication technique of the device. When negative differential resistance was big enough, the electrical current flowing past the negative differential device would be small hence the peak of electrical current would be concealed. An equivalent circuit model composed of a diode in parallel with a negative resistance device was put forward in order to interpret negative differential resistance phenomenon. The negative differential resistance appeared to be caused by an imblanced injection of charge carriers. A novel soluble PPV derivative containing oxadiazole electron transporting group on the main chain (OPPV) was designed and synthesized, which had the abilities of hole and electron transmissions. The device showed stable Ntype negative differential resistance characteristics in the atmosphere. Compared to inorganic negative differential resistance device, organic negative differential resistance device has many advantages such as easier fabrication as well as lower cost. If related materials and technologic conditions could be controlled, the negative differential resistance phenomenon would be observed distinctly and it is possible to develop a novel organic negative differential resistance device.