Synthesis And Properties Investigation Of White Hyperbranched Conjugated Polymers With Phosphorescent Iridium(Ⅲ) Complexes As The Cores Based On Polyfluorene

White organic light emitting devices(WOLED) have shown great potential applications in the solid state lighting sources, back-lighting for LCD as well as large-area flat-panel displays due to their unique advantages of light-weight, low-power, flexible displays, high contrast and so on. Owing to the spin-orbit coupling effect, iridium(Ⅲ) complexes could capture both singlet and triplet excitons, and theoretically internal quantum efficiency reaches 100 %. However, iridium(Ⅲ) complexes exist serious triplet-triplet annihilation which must be blended in the host materials to fabricate WOLED. Because of the different properties of various components, blended systems exist serious phase separation which will reduce the electroluminescent(EL) performance and be bad for preparing large-area flexible WOLED. At the same time, the fabrication process of devices is complicated and more interfacial problems emerge. In the evaporation process, more complexes are wasted that improves the cost of WOLED. White polymer light emitting devices(WPLED) prepared by blended polymer system have the same problem of phase separation that influences the EL performace. Therefore, single white light emitting polymers appear and show large value in the application which avoid phase separation, simplify the fabrication process and is suitable for preparing large-area flexible devices. On this basis, the research work are carried out as follows:1. Iridium(Ⅲ) complexes introduced to the hyperbranched structure with large steric hindrance could be separated by host chains that effectively restrained the triplet-triplet annihilation. On this basis, tris[1-(4-bromophenyl)-isoquinolinato-C2,N]iridium(III) [Ir(piqBr)3] was designed and synthesized as red emitter reaction monomer. Subsequently, red emitter Ir(piq)3 was covalently connected with polyfluorene segments as blue emitter, and a series of double-color white hyperbranched conjugated polymers were obtained with higher fluorescence quantum yield(57 %~77 %). Among all devices, the device of PF-Ir(piq)3100(0.1 mol% Ir(piq)3) exhibited the best Commission Internationale de l’Eclairage(CIE) coordinate of(0.30, 0.23) closed to the pure white light(0.33, 0.33) with maximum luminance of 824 cd/m2, and maximum current efficiency of 1.97 cd/A.2. The yield of Ir(piq Br)3 was low which would increase the cost of EL materials. Therefore, bis[1-(4-bromophenyl)-isoquinolinato][3-(2-pyridyl)-5-(4-bromophenyl)-1,2,4-triazole]iridium(III) [Ir(piqBr)2(pytzphBr)] with higher yield was designed and synthesized. Double-color white hyperbranched conjugated polymers were synthesized with Ir(piq)2(pytzph) as red cores and PF as blue backbone. When the content of Ir(piq)2(pytzph) was 0.1 mol%, hyperbranched PF-Ir(piq)2(pytzph)100 exhibited better CIE coordinate of(0.25, 0.27) with maximum luminance of 2468 cd/m2, and maximum current efficiency of 1.73 cd/A which proved that different red iridium(III) complexes could realize red emission in the hyperbranched conjugated polymers. Meanwhile, we had synthesized linear polymers Linear PF-Ir(piq)2(pytzph)m with Ir(piq)2(pytzph) incorporated to PF backbone by main ligands and linear polymers End capped PF-Ir(piq)2(pytzph)m with Ir(piq)2(pytzph) as the end capped groups by auxiliary ligand.3. EL spectra of double-color white hyperbranched conjugated polymers were not saturated owing to the loss at 520~580 nm that influenced the quality of white-light emission. Therefore, chromophoric groups with emission peaks at 520~580 nm should be introduced to the hyperbranched conjugated polymers to realize more saturated EL spectra. Poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)](PFBT) was a good green material which could be introduced into the polyfluorene-based hyperbranched conjugated polymer with red Ir(piq)3 as the cores, and then a series of triple-color hyperbranched conjugated polymers were obtained. The synthesized polymers had good thermostability, photophysical properties, electrochemical properties and film forming ability. The diode of PF-BT250-Ir(piq)325(0.25 mol% BT and 0.025 mol% Ir(piq)3) exhibited better CIE coordinate of(0.32, 0.35), and EL spectra covered the whole visible region with maximum luminance of 3267 cd/m2 and maximum current efficiency of 1.60 cd/A。4. The hyperbranched polymers with PFBT as green emission had more saturated EL spectra, however, the current efficiency was low. In order to improve the EL properties, green phosphorescent iridium( Ⅲ) complexes bis(2-phenylpyridine)[3-(2-pyridyl)-5-phenyl-1,2,4-triazole] iridium(III) [Ir(ppy)2(pytzph)] were designed and synthesized which could be introduced into the hyperbranched conjugated polymers to obtain PF-Ir(ppy)2(pytzph)mIr(piq)2(pytzph)n in which green and red iridium(Ⅲ) complexes acted as the cores, respectively, and blue polyfluorene acted as the backbone. The energy transfer from Ir(ppy)2(pytzph) to Ir(piq)2(pytzph) could realize by intermediate PF segment. Among the white polymers, PF-Ir(ppy)2(pytzph)25-Ir(piq)2(pytzph)5(0.25 mol% Ir(ppy)2(pytzph) and 0.05 mol% Ir(piq)2(pytzph)) exhibited excellent EL properties with a CIE coordinate of(0.31, 0.34), color rendering index(CRI) of 92, maximum current efficiency of 7.81 cd/A and maximum luminance of 6030 cd/m2. The introduction of green phosphorescent iridium(Ⅲ) complexes improves the EL performance.In summary, double- and triple-color white hyperbranched conjugated polymers with phosphorescent iridium( Ⅲ) complexes as the cores were designed and synthesized. These hyperbranced conjugated polymers have large steric hindrance which could restrain the triplet-triplet annihilation of iridium(Ⅲ) complexes and improve the EL performance. Phosphorescent iridium(Ⅲ) complexes incorporated to the main chains of hyperbranced structure could impove the energy transfer efficiency, meanwhile, the white hyperbranched conjugated polymers with green iridium(Ⅲ) complexes as the cores have shown the best EL performance. The white hyperbranched conjugated polymers as a kind of single white molecules have large value in the application which would be a promising EL materials.