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Light-emitting Polymer (light-emitting + polymer)
Selected AbstractsVariations in Hole Injection due to Fast and Slow Interfacial Traps in Polymer Light-Emitting Diodes with InterlayersADVANCED FUNCTIONAL MATERIALS, Issue 1 2010M. James Harding Abstract Detailed studies on the effect of placing a thin (10,nm) solution-processable interlayer between a light-emitting polymer (LEP) layer and a poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic)-acid-coated indium tin oxide anode is reported; particular attention is directed at the effects on the hole injection into three different LEPs. All three different interlayer polymers have low ionization potentials, which are similar to those of the LEPs, so the observed changes in hole injection are not due to variations in injection barrier height. It is instead shown that changes are due to variations in hole trapping at the injecting interface, which is responsible for varying the hole current by up to two orders of magnitude. Transient measurements show the presence of very fast interfacial traps, which fill the moment charge is injected from the anode. These can be considered as injection pathway dead-ends, effectively reducing the active contact surface area. This is followed by slower interfacial traps, which fill on timescales longer than the carrier transit time across the device, further reducing the total current. The interlayers may increase or decrease the trap densities depending on the particular LEP involved, indicating the dominant role of interfacial chain morphology in injection. Penetration of the interlayer into the LEP layer can also occur, resulting in additional changes in the bulk LEP transport properties. [source] Energy-Modulated Heterostructures Made with Conjugated Polymers for Directional Energy Transfer and Carrier Confinement,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007R. Favarim Abstract In this paper we demonstrate that multilayer structures with modulated bandgaps can be used for efficient energy transfer and carrier confinement inside a nanostructured film of a light-emitting polymer. The films were produced with the layer-by-layer technique (LbL) with a poly(p -phenylene vinylene) (PPV) precursor and a long chain dodecylbenzenesulfonate ion (DBS). DBS is incorporated selectively into the precursor chain, and with a rapid, low temperature conversion process (100,°C) superstructures with variable HOMO,LUMO gap could be formed along the deposition direction by changing the DBS concentration. Structures with different stair-type energy modulations were produced, which are thermally stable and reproducible, as demonstrated by UV-VIS. absorption measurements. Energy differences of up to 0.5,eV between the lowest and highest conjugated layers inside the stair structure could be achieved, which was sufficient to guide the excitation over long distances to the lower bandgap layer. [source] Synthesis and characterization of the soluble fluorescent poly[2-decyloxy-5-(2,-(6,-dodecyloxy)naphthyl)-1,4-phenylenevinylene]JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Hung-Te Chang Abstract A new soluble fluorescent polymer, poly[2-decyloxy-5-(2,-(6,-dodecyl-oxy)naphthyl)-1,4-phenylenevinylene] (DDN-PPV), with no tolane-bisbenzyl (TBB) structure defects is prepared by the dehydrohalogenation of 1,4-bis(bromomethyl)-2-decyloxy-5-(2,-(6,-dodecyloxy)naphthyl)benzene (as monomer) in this study. The aforementioned monomer is synthesized via such chemical reactions as alkylation, bromination, and Suzuki coupling reactions. The structure and properties of the DDN-PPV are examined by 1H NMR, FTIR, UV/vis, TGA, photoluminescence (PL), and electroluminescence (EL) analyses. The two asymmetric decyloxy and 6,-dodecyloxynaphthyl substituents on the phenylene ring make the DDN-PPV soluble in organic solvents and eliminate the TBB structure defects. With the DDN-PPV acting as a light-emitting polymer, a device is fabricated with a sequential lamination of ITO/PEDOT/DDN-PPV/Ca/Ag. The EL spectrum of the device shows a maximum emission at 538 nm. The turn on voltage of the device is about 16.6 V. Its maximum brightness is 14 cd/m2 at a voltage of 18.2 V. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2734,2741, 2007 [source] Phenothiazine- S,S -dioxide- and fluorene-based light-emitting polymers: Introduction of e, -deficient S,S -dioxide into e, -rich phenothiazineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2007Jonghee Lee Abstract A novel series of poly(10-hexyl-phenothiazine- S,S -dioxide-3,7-diyl) and poly(9,9,-dioctyl-fluorene-2,7-diyl- alt -10-hexyl-3,7-phenothiazine- S,S -dioxide) (PFPTZ-SS) compounds were synthesized through Ni(0)-mediated Yamamoto polymerization and Pd(II)-catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ-SS compounds were highly fluorescent with bright blue emissions in the solid state. Light-emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish-blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine- S,S -dioxide property, triggered by the introduction of an electron-deficient SO2 unit into the electron-rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ-SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236,1246, 2007 [source] Novel light-emitting polymers containing donor and acceptor architecturesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2003Yun Chen We present the synthesis and properties of four novel donor,acceptor conjugated polymers composed of iminodibenzyl, distyrylbenzene, and 1,3,4-oxidazole units. The absorption and photoluminescence spectra are mainly determined by the donor segments (iminodibenzyl and distyrylbenzene) or conjugation length (1,3,4-oxidazole and pendant 1,3,4-oxidazole) of the acceptor segments. Electrochemical studies reveal that P1,P4 possess high-lying highest occupied molecular orbital energy levels (from ,5.14 to ,5.24 eV) and low-lying lowest unoccupied molecular orbital energy levels (from ,2.63 to ,2.83 eV) because of the alternate donor and acceptor conjugated units. The brightness and luminence efficiency of ITO/P2/Al configuration were up to 1864 cd/m2 and 0.22 cd/A, respectively. 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