A polymer diode

using PVCz doped with perylene and TPA as a hole transporting layer

Alq3 as an electron transporting layer and Mg-Ag metel as a back electrode

reachs brightness as high as 10008cd/m

2

and quantum efficiency 0.58%

which are much higher than the device with Al electrode as the back electrode.In order to analyse the difference of the two kind of devices

the work function of electrodes and the HOMO levels of PVCz and Alq3 have been measured

from which and our previously reported data about their optical absorption the energy band diagram of the divece was constructed.Accorthing to this diagram the charactrictics of the devices have been explained.