Single layer light‐emitting diodes from copolymers comprised of mesogen‐jacketed polymer containing oxadiazole units and PVK

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A dendritic monomer with bipolar side groups containing dendritic carbazole and oxadiazole structures was synthesized by a convergent strategy. The homopolymer was synthesized through a conventional radical polymerization. The number-average molecular weight determined by gel permeation chromatography was 40,000 g/mol. Its 5% weight loss temperature was 358 C. Its photophysical properties were studied in solution and in film. The photoluminescent emission peak of the film was at 408 nm, which had a blue shift of 9 nm compared with that of the tetrahydrofuran solution. And there was an energy transfer from oxadiazole to carbazole. The highest occupied molecular orbital (HOMO) and lower unoccupied molecular orbital (LUMO) levels calculated from cyclic voltammetry data were -5.55 and -2.52 eV, respectively, and the band gap was 3.03 eV, which suggested that the polymer had both hole-and electron-transporting capabilities. The efficiencies of the single-layer device based on this homopolymer were much higher than those of the same-generation homopolymer without the oxadiazole moiety. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 581-589, 2012

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Jacketed homopolymer with bipolar dendritic side groups and its applications in electroluminescent devices

Zhang¹,

Jin²,

Wang³

et al. 2011

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“…Figure 2 is the UV‐vis absorption spectra of the polymers in solution and in films. With the increase of the oxadiazole content, the absorption peak at about 300 nm attributed to oxadiazole36 increases in intensity, and the peak at about 380 nm attributed to the backbone29 decreases in intensity. This result is as expected.…”

Section: Resultsmentioning

confidence: 98%

Synthesis and characterization of electrophosphorescent jacketed conjugated polymers

Zhang

Jin

Zhou

et al. 2012

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A monomer containing bent side chains with oxadiazole unit was synthesized. And it was copolymerized with polyfluorene at different ratios. The photophysical and electrochemical properties of the copolymers were characterized. The results show that the introduction of the oxidiazole‐containing side chains into the polymer reduces the lowest unoccupied molecular orbital level. And the steric hindrance of the side groups can effectively suppress the aggregation of the polymer backbones. Electroluminescent devices were fabricated with a configuration of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene (PEDOT):PSS/Sample/Ca/Al. All of the devices emit blue light. The device of the copolymer PFOXD50 shows the best performance with the maximum luminance of 1033 cd/m2 and the maximum current efficiency of 0.29 cd/A. Then a cyclometalated iridium complex monomer (ppy)2Ir(BrPhPyBr) was copolymerized with PFOXD50 at different ratios. The devices with the same configuration emit orange light. The efficiency generally increases with the increasing Ir content. Among them, the device of the copolymer PFOXDIr7 shows the best performance with the maximum luminance of 846 cd/m2 and the maximum current efficiency of 0.61 cd/A. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

“…The EL devices based on the block copolymer with a content ratio of 14:86 for the hole‐transport and electron‐transport units doped with Ir (ppy) 3 possessed the best external quantum efficiency that was larger than 10%. Wang et al studied the EL properties of random copolymers containing OXD and carbazole with or without phosphorescent molecules,10–12 and the nondoped devices had an onset voltage of 6.9 V and a maximum brightness of 703.4 cd/m 2 . Tao et al13 studied the nondoped bipolar rod−coil block copolymers containing poly( p ‐phenylenevinylene) as the rod block and OXD‐attached flexible backbone as the coil block and gained the maximum brightness of 103 cd/m 2 and external efficiency of 0.50%.…”

Section: Introductionmentioning

confidence: 99%

Electroluminescent block copolymers containing oxadiazole and thiophene via ATRP

Yang

Jin

et al. 2010

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Block copolymers containing thiophene units in one block and oxadiazole (OXD) units in the other were prepared. Atom transfer radical polymerization method was used to obtain the thiophene-containing mesogen-jacketed polymers, and the kinetic study indicated that the polymerization was controllable and the polymers could be used to initiate the polymerization of the OXD-containing monomers. Photoluminescent spectra indicated that the fluorescence quantum yields of the polymers increased with increasing content of OXD. And, more OXD domains, that is, more interfaces between the hole-transport parts and electron-transport parts, resulting in the higher probability of exciplex formation. The electroluminescent devi-ces containing the block copolymer with 64 mol % OXD as the emissive layer had a maximum brightness of 127 cd/m 2 and an extremely low onset voltage of 7.7 V, which indicated that the injection and transport of charge carriers were facilitated and the number of charge carriers was sufficiently high in early time after the voltage was turned on. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5670-5678, 2010