Study Of Highly Efficient White Organic Light-emitting Devices And Its Applications Based On Solution Process

WOLEDs have attracted enormous attentions, due to their potential application inbacklights for panel displays and also can be used for large size, high efficiency solid statelighting sources, as well as for their advantages of simple process, abundant and cheap supplyof materials. But WOLEDs based on solution process, such as spin coating, ink jetting, andLangmuir Blodgett Film, will play an important role to alleviate the increasing demand forenergy, control environmental pollution, and to realize the sustainable development of humansociety for their advantages of cheap equipment, save materials and easy to produce full colorand large size display.As partial efforts of my Ph.D. study, I focus on the solution processes to research theapplication of WOLEDs in the lighting field at the angle of the structural design andoptimization, process optimization, development and optimization of device structures, lightextraction technology, and so on.We pay more attentions on the development and optimization of the high performancelight emitting system and device structure, which includes two aspects:Firstly, we doped the fluorescent conjugated dendrimer (G0) with RG iridium metalcomplexes with appropriate ratio. The highly properties WOLEDs were achieved, themaximum PE, LE, and EQE were7.7lm W-1,16.9cd A-1, and8.4%, respectively. The CIEcoordinates of (0.312,0.332) close to NTSC standard. The CRI value of the WOLEDsreaches90under the luminance of1000cd m-2, which is very close to the ideal white light.Secondly, we introduced a yellow emitting fluorescent aggregation induced enhancedemission (AIEE) dopant oligo(paraphenylene vinylene) derivative CN DPASDB into the hostG0. AIEE materials emerge as an alternative to solve the exciton quenching at high currentdensity, due to their enhanced emission at the aggregate state which is attributed to therestricted intramolecular rotation in the solid state or aggregate state. Based on this system,we achieved a record efficiency for fluorescent WOLEDs, which with the maximum PE andEQE reached to22lm W-1and9.8%, respectively.Hereafter, how to improve the EQE also is the key for the application of WOLEDs in thelighting field. The out coupling efficiency is only0.33, which means most of light cannotescape from the device in the forward viewing direction. To address the output coupling issue,we developed a novel process to roughen the substrate surface via sandblasting. The roughsurface will change the emitting light's incident angle at the substrate air interface, leading tomore escaped photons in the forward viewing direction. By employing the simple, low cost sandblasting method, the maximum PE, LE, L, and EQE of the WOLEDs were enhanced23.3%,29%,42.5%, and28.9%, respectively. Moreover, the emission spectrum has noaltered caused by the rough surface.Finally, good substrate is the basis for the practical use of the large area WOLEDs.So, we have done a lot of work in the design of substrate structure. ITO has been widely usedas a conductive anode with its excellent light transmittance and good electrical conductivityability. But its applications often cause the problems of current injection difficulties andlighting non uniformity in the large size WOLEDs. In order to help the current injection, weneed to add some high conductivity metal or metal oxides lines on the ITO anode. But thismethod gave some affects to the uniformity of function layer, the cost of the substrate, and soon. So in order to solve this problem, we changed the electrode from one side to two sides,revised the Layout, width and spacing of the high conductivity metal lines. We successfullyprepared4inch WOLED and assembled organic lighting lamp.