ABSTRACT
The OLEDs are composed with two or more organic layers sandwiched with a cathode and an anode for charge carrier injection [2,3]. A combination of a hole transport layer and an electron transport emissive layer is representative. The most well-known electron transport emissive material is tris(8hydroxyquinolinolato)aluminum (Alq3). In order to achieve efficient luminescence, it is necessary to have a good balancing of electron and hole currents even in such multilayer-type OLEDs [4]. In most cases the hole is majority charge carrier, so that an improvement in electron injection from the cathode is directly related to the performance of the OLED. Generally there exists a large energy barrier for electron injection from the cathode to the organic layer. Several alloys, such as MgAg, AlLi; and Mgln, containing a low work function metal are used as a favorable cathode material [3,5,6]. Recently, it has been found that an ultrathin insulating layer, such as LiF
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