| Organic light emitting diodes(OLED), have attracted considerable interests, owe to its high brightness, fast response and realizing flexible display. Organic electroluminescent materials can be divided into fluorescent and phosphorescent materials. When compared to fluorescent OLEDs where only singlet states emit the light and the efficiency is reduced because of triplet formation, phosphorescent OLEDs(PHOLEDs) are more efficient because of both singlet and triplets can be harvested for the light emission with close to 100 % internal quantum efficiency. In general, phosphorescent materials are composed of heavy metal materials, such as Os、Ir、Pt. Among them, cyclomatelated Ir complexes are regarded as the most successful phosphorescent materials.Iridium complexes can be roughly divided into small molecule, polymer and dendritic iridium complexes according to its different weight or structure of the molecule. To realize the commercial application of OLEDs in full-color flat panel displays and low-cost solid state lighting, a lot of effort has been devoted to develop various colored Ir complexes with excellent performance. For example, the red(30~40 cd/A) and green(70~80 cd/A) light materials have been meet the requirements of commercialization, but the development of the blue light materials are fall behind of them because of its large band gap. Therefore, the development of blue light materials has very important significance for the full color display and white light lighting.Based on above points, we designed and synthesized a carbazole-modified iridium complex with hole-transporting ability and a series of polymer iridium complexes, the contents are as follows:Firstly, a novel blue iridium complex(Cz-dpy)2Ir(pic) with better hole-transport ability was achieved through introduction of 3-(9H-Carbazol-9-yl)phenyl in the pyridine ring of deep blue iridium complex Ir(dpypy)3. The chemical structures of the Iridium complex were verified by 1H NMR, 13 C NMR,19 F NMR and Mass. The Iridium complex shows good thermal stability, as Td and Tg is 262 ℃and 224 ℃, respectively. The HOMO level of(Cz-dpy)2Ir(pic) is calculated to be-5.50 e V, and close to that of PEDOT: PSS(-5.20 e V). This implied that the injection and transport of hole is easier. In addition, we fabricated a device by doping 8 wt%(Cz-dpy)2Ir(pic) into co-host materials of m CP and TAPC. The turn-on voltage of the device was 6.06 e V, and the device showed a maximum brightness of 15573 cd/m2 and a maximum luminous efficiency of 14.46 cd/A.Secondly, we designed and synthesized a series of blue polymer Iridiums PPOCz-2.5, PPOCz-5, PPOCz-10 by different molar ratios, in which bipolar polymer host PPOCz with high triplet energy(2.83 e V)as the main chain and well-known blue iridium FIrpic as the side chain. The molecular weights of polymers were measured by GPC. The thermal stabilities of polymers were investigated by DSC and TGA. The results imply that the obtained polymers show better thermal stability, as their Tds are about 323~398 ℃ and Tgs are about 95~120 ℃. Device A、B and C were fabricated by using PPOCz-2.5, PPOCz-5, PPOCz-10 alone as the emitting layer. Device A、B and C showed maximum luminous efficiencies of 4.79 cd/A、4.41 cd/A and 3.25 cd/A respectively, and the CIE coordinates are(0.262,0.493) 、(0.251,0.487) and(0.242,0.481), respectively. |
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