Preparation Process And Properties Of Organic Electroluminescent Devices

The character, history and trends of OLEDs(organic light-emitting devices) wereintroduced in this paper as well as its relative optical-chemical and physical theories.several samples of different structure-single, double fabricated by reactiveevaporating depositions. After that, several parameters which reprensent device'sperformance were measured.Measured results showed that the device with its structure as followingITO/NPB/AlQ/Mg:Ag is far more superior to SL device with the structure ofITO/AlQ/Mg:Ag because the DL-A device better balanced energy band between eacheach layer and the mobility of carriers(electrons and holes), which led to thecombination of carriers taking place in the bulk of emitter and avoided the excitonbeing eliminated by the electrodes which easily occurs in SL devices.The result expresses the thickness of AlQ influence the performance of thedouble layer OLED device,the structure of ITO/NPB(15nm)/AlQ(x)/ Mg:Ag. At lastin the 40nm the brightness,efficiency and stability are the most perfect,but thethickness doesn't influence the spectrum.Compared with the traditional structure, the maximum efficiency and luminance of thedouble heterosturcture were improved. Due to the electron-transporting layer Alq3 andhole-blocking layer BAlq3 were used in the double heterosturcture, the energy matching was morereasonable and the carrier injecting was more balanceable.The degradation of OLED due to the growth of dark spots can be attributed tothe synergy of two external causes: pollution by water vapor and pollution by oxygen.And organic materials can also lead to appearing dark spots in OLED.