Synthesis And Characterization Of Blue-light Copolymers Based On Fluorene And Indolefluorene

Several advantages of conjugated polymers electroluminescence material brought comprehensive research and have been studied extensively. Light-emitting devices based on copolymers have now achieved performance (luminance, efficiency and lifetime) good enough for practical application. Nevertheless, the external quantum efficiency, lifetime and color purity of the the blue-emitting material are unsatisfactory. Polyfluorene and polyindolefluorene have many advantages, indicate that copolymers based on PF and PIF are promising blue-emitting electroluminescent materials.In this dissertation, we report the synthesis and characterization of novel electroluminescent copolymers based on flurene and indoleflurene.In the chapter 3, 2,6-bis(3-bromophenyl)-4-phenylpyridine and 4-(3,5-dibromophenyl) -2,6-diphenylpyridine were synthesized by Chichibabin. Then, we reported the synthesis and characterization of the fluorene-based conjugated polymers by Pd-catalysed Suzuki coupling reaction: poly[2,7-(9,9-dioctyl)fluorene-co-2,6-bis(3-phenyl)-4-phenylpyridine (PFO-TPP1) and poly[2,7-(9,9-dioctyl)fluorine-co-4-(3,5-diphenyl)-2,6-diphenylpyridine (PFO-TPP2). The resulting copolymers showed photoluminescence (peak 390 nm).The resulting copolymers showed good solubility in common organic solvents, and good film forming ability. The molecular weight of the copolymers are relatively small, we need to study further. The UV-vis absorption peaks of the copolymers PFOTPPl and PFOTPP2 in the THF solution (10^-5 mol/L) are at 325 nm and 329 nm, respectively. It is blue shifted about 30 nm compared to that of polyfluorene (360 nm). The PL emission peaks of the copolymers PFO-TPP1 and PFO-TPP2 in the THF solution (10^-5mol/L) are at 383 nm and 387 nm, respectively. It is blue shifted compared to that of polyfluorene (428 nm). The incorporation of the TPP1 and TPP2 into polyfluorene could significantly reduce the effective conjugated length of the copolymers. The polymers emitted blue light.The LUMO of PFO-TPP1 and PFO-TPP2 are -2.53 eV and -2.64 eV, respectively. It is demonstrated that the inserted TPP groups change the LUMO of the polymers, reduced the injection barrier of electronic on Cathode.In the chapter 4, we present the synthesis and characterization of conjugated polymers based on indolefluorene by Pd-catalysed Suzuki coupling reaction:poly[2,8-6,6,12,12-tetraoctylindolefluorene-co-3,6-N-octylcarbazole] (PIF-CZO), poly[2,8-6,6,12,12-tetraoctylindolefluorene- co-2-(4- phenyl)-N- phenylamine](PIF-TPA) and poly[2,8-6,6,12,12-tetraoctylindolefluorene-co-p-diphenyl oxide] (PIF-DPE). The Eg of the copolymers are at 3.0 eV, 2.78 eV and 2.82 eV, respectively. The resulting copolymers showed good solubility in common organic solvents, and good film forming ability. The molecular weight of the copolymers are relatively small, we need to study further. Efficient light emission was observed with a peak maximum in the blue region. The Uv-vis absorption peaks and PL, EL emission peaks of the all copolymers are bule shifted compared to that of the polyindolefluorene. The incorporation of the CZO, TPA and DPE into polyindolefluorene could significantly reduce the effective conjugated length of the copolymers. A light-emitting diode was constructed with the structure ITO/PVK/Polymer/Ba/Al, when using PVK as buffer layer, the maximal luminous efficiency of 0.22, 0.08 and 0.36 have been seen, respectively. Devices made up of these copolymers emit saturated blue light.