导电聚合物有序超薄膜的合成及其作为有机电致发光器件空穴注入层

Synthesis of Ordered Conducting Polymer Ultrathin Film and Its Application as Hole Injection Layer for Organic Light-Emitting Diode

采用修饰多层LB膜的方法制备了导电聚合物聚-3,4-乙烯二氧噻吩/二十烷酸(PEDOT:AA)复合层状有序膜,构筑了一种导电聚合物镶嵌的多层有序膜结构.将这种导电聚合物有序薄膜沉积于ITO电极表面,将其作为有机电致发光二极管(OLED)的空穴注入层,并研究了ITO/(PEDOT:AA)/MEH-PPV/Al器件的性能.研究结果表明,与采用聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT:PSS)自组装膜和旋涂膜作为空穴注入层的ITO/(PEDOT:PSS)/MEH-PPV/Al器件相比,器件的发光效率增加,起亮电压降低.我们认为这是由于PEDOT:AA薄膜提供了一种有序层状结构后,减小了ITO与MEH-PPV间的接触势垒,改善了空穴载流子注入效率.进一步的研究表明,由于PEDOT:AA多层膜间靠较弱的亲水、疏水作用结合,这种导电多层有序膜的热稳定性与普通LB膜相似,在较高温度下发生从层状有序态到无序态的变化,这是导致OLED器件性能发生劣化的主要原因.

A novel layer-ordered ultrathin film of poly（3,4-ethylene dioxythiophene）/arachidic acid （PEDOT：AA） was prepared by a modified Langmuir-Blodgett （LB） technique and an ordered conducting polymer embedded multilayer structure was constructed. The layer-ordered structure was deposited on an indium-tin oxide （ITO） surface as a hole injection layer for use as an organic light-emitting diode （OLED） and the luminance performance of the ITO/（PEDOT： PSS）/MEH-PPV（poly（2-methoxy-5-（2＇-ethyl-hexyloxy）-l,4-phenylene-vinylene））/A1 device was investigated. Compared with electrostatic self-assembly （ESA） and spin-coating the poly（3,4-ethylene dioxythiophene）/polystyrenesulfonate （PEDOT：PSS） film showed enhanced luminance efficiency. The higher luminance at an equivalent voltage and lower turn-on voltage was observed after the PEDOT：AA film was utilized as hole injection layer in OLED. The enhanced carrie injection efficiency was attributed to the good layer-ordered structure of PEDOT：AA film, which decreased the contact resistance between ITO and the emitting layer. Further investigation revealed that this layer-ordered conducting polymer film exhibited poor temperature stability because of weak hydrophilic and hydrophobic interactions between adjacent LB layers. These weak interactions result in the film structure changing from a layer-ordered structure into an unordered structure at higher temperatures.