Stability enhancement of organic electroluminescent diode through buffer layer or rubrene doping in hole-transporting layer

The stability of organic electroluminescent devices is significantly improved by inserting a buffer layer between ITO and the holetransporting layer or by doping rubrene in the hole layer. The durabilities of the improved devices increase by a factor of about 10. The reasons for the improvements are discussed based on tunnelling theory and the energy-level diagram of the device.