Researches On Solution Processed Organic Light-Emitting Diodes

In this thesis a series of new electroluminescent materials which are suitable for solution processible device preparation have been studied. Highly efficient polymeric green, blue, orange and white emitting electrophosphorescent diodes have been obtained. In addition, exploring work has also been carried out in the area of solution processible small molecular OLEDs. The main results of the thesis are summarized as follows:(1) By doping green emitting Ir(pppy)₃ into the PVK and PBD matrix, highly efficient single layer polymeric electrophosphorescent have been obtained in the proper optimized devices. The maximum luminance efficiency of 33.7 cd/A and the maximum luminance of 30,100cd/m2 have been obtained with a low turn on voltage of less than 4V, which is one of the best polymeric electrophosphorescent diodes reported to date.(2) Applying a serial of new Ir(pppy)₃ derivates to PLEDs, highly efficient greenish blue and light blue electrophosphorescent diodes have been obtained through endothermic energy transfer. In Ir(F-pppy)₃ doped devices, a peak luminance efficiency of 32.8 cd/A and a maximum luminance of 11,500 cd/m² have been obtained, and the corresponding CIE coordination is (0.18, 0.46). In Ir(F₂-pppy)₃ doped devices, a maximum luminance efficiency 12.3cd/A and the CIE coordination(0.19, 0.36) have been obtained. These devices are among the best greenish blue and blue electrophosphorescent diodes based on endothermic energy transfer.(3) Multi-layer small molecular electrophosphorescent diodes have been successfully fabricated, by combining spinning-coating and vacuum deposition method in device fabrication, using small molecular phosphorescent host and pinene group substituted Ir(pppy)₃ guest. The maximum luminance efficiency 22.0cd/A, and the maximum luminance 26,600 cd/m² have been obtained, which are comparable with the state of the art electrophosphorescent devices. Our work is essentially important for reducing the cost of organic light-emitting displays, and expanding the host selection range for solution-processed OLEDs preparation.(4) Solution processed small molecular single layer and two layer devices have been successfully fabricated. The single layer device obtains a maximum luminance efficiency of 0.7 cd/A; the doped device obtains the maximum luminance efficiency of 1.3 cd/A, which brings forward a new idea for solution processed device fabrication and may profoundly promote the research in solution processed small molecular OLEDs.