以聚乙烯亚胺作为电子注入层的聚合物发光器件特性研究

在传统结构与倒置结构的有机发光二极管(LED)的聚合物发光层和阴极之间加入聚乙烯亚胺(PEIE)层能够显著地提高器件的发光效率。通过采用不同厚度的PEIE层的器件发光特性研究表明:PEIE层作为电子注入层(EIL)/空穴阻挡层(HBL)来平衡器件中的电子和空穴浓度,这主要来源于PEIE作为界面偶极层,能有效地降低阴极与发光层之间的电子注入势垒。

Polymer LED using ethoxylated polyethylenimine as electron injection layer

To improve luminance efficiency of con ventional and inverted light emitting devices,we implement an ethoxylated polyet hylenimine (PEIE) layer between light emitting polymer and cathode. Studies on c haracterizations of light emitting devices with various PEIE layer thicknesses reveal that ethoxylated pol yethylenimine layer mainly works as an electron injection/hole blocking layer.Conventional and inverted light emitting devices using a PEIE electron injection layer show comparable luminance efficiency to the analogous devices with a CsF o r with a ZnO/PEIE electron injection layer.Analyses of current density-voltage characteristics of single-electron devices manifest that PEIE layer enhances electron injection efficiency by a fac tor of 5-10.Results of X-ray ph otoelectron-spectroscopy (XPS) meas urements indicate that PEIE layer reduces the work function of Al by ca. 1eV,thus significantly decreasing the e lectron injection barrier,which can be attributed to the intrinsic dipole moment of PEIE or the formation of interfacia l dipoles. Apart from excellent electron injection/hole blocking properties,PEIE is air-stable and more compatible with the neighboring organic layer than metal fluorides,which can be processed from aqueous or alcohol solution under a mbient conditions.Thus,PEIE serves as a promising electron injector in organic electron devices and is parti cularly suitable for construction of multilayer devices with versatile and enhan ced properties.