LiF Layer at the Interface of Au Cathode in Organic Light-Emitting Devices: A Nonchemical Induced Carrier Injection Enhancement

Au is not a suitable cathode material of organic light-emitting device because of its high work function resulting in poor electron injection. However, in present work, it is found that the performance of Au-cathode OLEDs can be efficiently improved by introducing a LiF buffer layer and with its optimal thickness can even be comparable to that of conventional Al-cathode device. The relationship between the thickness of LiF layer and the performance improvement is investigated. The experimental results indicate a quite different mechanism of LiF thin layer from that of Al-cathode device, which is not chemical-reaction-mechanism-dominant. Other insulator material buffer layers such as Al2O3 and BCP are also investigated.