The Design And Preparation Of Organic Electroluminescent Devices

The character, history and trends of OLEDs(organic light-emitting devices) were introduced in this paper as well as its relative optical-chemical and physical theories. several samples of different structure-single, double and doped-were designed and fabricated by selecting appropriate materials. After that, several parameters which reprensent device's performance were measured.Measured results showed that the DL-A device with its structure as following ITO/NPB/AlQ/Mg:Ag was far more superior to SL device with the structure of ITO/AlQ/Mg:Ag because the DL-A device better balanced energy band between each each layer and the mobility of carriers(electrons and holes), which led to the combination of carriers taking place in the bulk of emitter and avoided the excitons being eliminated by the electrodes which easily occurs in SL devices.As to the doped devices, measurements demonstrated an excellent device with its maximum brightness was 25000cd/m2. It also showed that doping concentration as well as the dopant itself had great influence on device character; the EL spectrum of devices indicated that the emitting sites in the doped devices shifted from AlQ molecules to the dopant and the current mechanism of the device was also changed when doping in the host. The lowering of device performance when the doping concentration became higher is caused by the "concentration effect " of the dopant. Rudimental degrading experiments by oberserving the change of surface morphology as time going on gave some advices on the course of OLEDs' degradation: water and oxygen in the air corrupted metal cathode and penetrated into the inner of devices and then made the emitter layer degraded until the device became utterly malfunctional...