| Organic light-emitting diodes(OLEDs) is not only a great point of new flat panel displays,but also one of the first choices of green lighting source of the21century, due to their merits such as low drive voltage,high brightness,wide visual angle,quick response,and simple fabrication technics. At the present time,OLED has still had some shortcoming, such as low efficiency, short lifetime , bad stability and etc. They are the critical problems to hinder the further development of OLEDs. However,to develop new OLED materials with high efficiency and stability, to choose appropriate electrode materials, to adopt new film fabrication technics, to optimize the device configuration, to improve the efficiency of OLED, to prolong the lifetime of device, and to persiut the best scheme of full color OLED, they are still the primary aims of study work..In the chapter 1, the history, development and structure and mechanism of OLED are briefly introduced, and the research content and significance of this paper have been put forward. In the chapter two, the OLED materials, especially the phosphorescence material have been introduced.In the chapter 3, we introduced the theory that why and how to synthesize the new phosphorescence material, and then fabricated a series of devices by making some change the thickness of the dye, the particular devices are ITO/NPB/CBP/(ppy)Pt(bcam)(0.3~2.0nm)/CBP/BCP/Alq3/Mg:Ag. There are four steps in the fabrication technics: surface treatment of ITO glass, deposition of organic layer, deposition of metal layer, encapsulation of device.In the Chapter 4, the OLED characteristics testing and analysis have been done. We have tested the OLED characteristics of the devices with different structure, including J-V-B characteristics, efficiency, EL spectrum, etc. and have also analyzed the results. The thickness of the dopant emitting layer is 0.5nm and the driving voltage is 24.25V, the brightness of this OLED is 8755cd/m2; the thickness of the dopant emitting layer is 1.5nm and the driving voltage is 11.5V, it got the maximum power efficiency 0.826lm/w; the thickness of the dopant layer is 0.5 nm and the current density is 499A/m2, it achieved the maximum current efficiency 3.33cd/A. Under different driving voltage, the EL spectrum of the devices prepared by this material is very steady with only very slight change of the CIE coordinates, and the emitting peak basically appeared at 625nm with the CIE coordinates (0.63, 0.36). Furthermore, we made a farther discuss on investigating the effect of the position of the dopant layer in the CBP. We obtained that the CBP thickness near to the NPB layer is the greater influence factor on the performance of the device then the CBP layer near to the BCP layer.Based on the research of the effect of the position and thickness on the performances of the devices in chapter 4, in chapter 5, we succeeded to design a series of white OLED which use the new phosphorescence material and some general fluorescence materials, and their main OLED characteristics are tested and analyzed. In the research of WOLED, when the structure of the emitting layer is NPB (80nm) /CBP(15nm) /(ppy)Pt(bcam)(0.5nm)/CBP(15nm) /Alq3(1nm) ,it exhibited a good white emission (the CIE of coordinate is x=0.33,y =0.34), and the turn-on voltage is only 3.8V. When the applied voltage is 14V , the device made a maximum brightness up to 9360cd/m2 .When the driving voltage changed in a special range , the EL spectrum nearly didn't change, just with the CIE coordinates from (0.34, 0.33) to (0.33, 0.32) . Because the device with the structure has an excellent performance in the color stability and OLED characteristics, it can be used as the white light materials. |
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