Modified Cathode Of The Organic Light Emitting Diodes

In this dissertation, we focus on device structure, performance and luminescence mechanism etc. of organic light emiting diodes (OLEDs). Firstly, the EL characteristics of the devices with Sm as the electron buffer layer have been investigated. Secondly, the devices with the C₆₀ and CuPc as the buffer layer have been studied, respectively.1. EL characteristics of the devices with Sm as the electron buffer layer have been investigated. Compared with the normal device with Al cathode, the efficiency and brightness of the devcies with Sm/Al as cathode have been effectively enhanced, and the power efficiency of the latter has been improved to be about 2 times. We think the incorporation of the Sm layer will effectively enhance the electron injection and the electrons and the holes will be balanced in the emitting layer. Furthermore the Sm layer will block the diffusion of the Al atoms to A1Q layer and thus decrease the quenching centers.The devices with the cathode structure of Sm/LiF/Al and LiF/Sm/Al have been studied, respectively. The enhanced electron injection should account for the improved performance of these devices.2. The thin CuPc layer has been used as the hole and electron injecting layer respectively in the fabrication of the devices. The hole-injecting CuPc layer can improve the brightness and efficiency of the devices. Yet, when the thin CuPc layer was used as the electron- injecting layer, the device performance was decreased. The thin layer of C₆₀ has also been used as the hole and electron-injection layer respectively. When the thin C₆₀ layer was solely used in the interface of ITO/organic and Al/organic, the performance of device was not improved. When the C₆₀ layer and LiF layer were both used in the device fabrication, the performance can be enhanced effectively. This enhancement was due to the ohmic contact that formed at the C₆₀/LiF contact.