Wang-Lin Yu

Blue polymer light-emitting diodes from poly(9,9-dihexylfluorene-alt-co-2, 5-didecyloxy-para-phenylene)

Deep blue photoluminescence and electroluminescence are demonstrated from a soluble conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-para-phenylene). The PL quantum efficiency is approximately 40%. Cyclic voltammetry measurements indicate that the highest occupied molecular orbital and lowest unoccupied molecular orbital energies are 5.66 and 2.62 eV below vacuum, respectively. Single-layer and multilayer light-emitting diodes emit deep blue light (peak at ∼420 nm).

Electrically conducting poly [3-(ω-hydroxyalkyl thiophenes]

Abstract A series of poly[3-(ω-hydroxyalkyl)thiophenes] was synthesized by chemical oxidative polymerization using FeCl 3 and characterized by FT-IR, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Upon doping with iodine the polymers attained electrical conductivities of between 0.5 and 38 S cm −1 . Electrical conductivities of doped samples were found to increase with alkyl chain lengths, being optimum for the octyl pendant moiety. Thereafter, the conductivity decreased, as the doping and dedoping for the polymers became more difficult. Increasing the hydrocarbon chain length of the pendant substituent also resulted in decreased thermal stability of the polymers. XPS results showed that some C–OH groups in the polymers were oxidized to CO in the polymerization process.

Hole-injection enhancement by copper phthalocyanine (CuPc) in blue polymer light-emitting diodes

This article reports the study on enhancement of copper phthalocyanine (CuPc) for hole injection in blue polymer light-emitting diodes based on three blue emissive polymeric materials with different electronic structures under the circumstances of including or excluding an additional poly(N-vinylcarbazole) (PVK) layer. A thin CuPc layer may effectively enhance the hole injection from the anode to the emissive polymer layer and results in a dramatic decrease of operating voltage of the device. The thickness of the CuPc layer is optimized. The addition of a PVK layer between CuPc and emissive polymer may prevent the potential problem of the undesired electron flow from the emissive layer to the CuPc layer. The efficiency of CuPc for enhancing hole injection is almost independent of the energy levels of the highest occupied molecular orbitals of the polymers which are contacted with it. It is suggested that the higher affinity between the two organic materials in comparison with that between indium–tin–oxide...

New efficient blue light emitting polymer for light emitting diodes

The synthesis, by the Suzuki coupling reaction, of a novel soluble blue light emitting polymer, poly{(9,9-dihexyl-2,7-fluorene–alt-co-[2,5-bis(decyloxy)-1,4-phenylene]} (PDHFDDOP) is reported. PDHFDDOP exhibits photoluminescence (PL quantum efficiency of 40% in neat films) and electroluminescence (EL) with deep blue emission.

Synthesis and electrochemical characterization of a new polymer constituted of alternating carbazole and oxadiazole moieties

Abstract We report herein the synthesis and electrochemical characterization of a novel copolymer containing an electron rich carbazole moiety and an electron deficient oxadiazole unit—poly[N-(2′-ethylhexyl)-carbazole-3,6-diyl-1″,3″,4″-oxadiazole-2″,5″-diyl] (PCO). PCO can be dissolved in THF, CHCl3, xylene, and DMSO. The structure of the polymer is confirmed by FT-IR, NMR and elemental analysis. The optical and electronic properties of the polymer are investigated by UV–Vis absorption spectroscopy and photoluminescence spectroscopy as well as cyclic voltammetry. The results show that the polymer films emit greenish-blue light (λmax 485 nm) upon UV excitation. Both p-doping and n-doping processes are observed in cyclic voltammetric investigation. A comparison between the properties of polycarbazole and polycarbazole–oxadiazole has been presented.

Synthesis and characterization of a cyano-substituted electroluminescent polymer with well-defined conjugation length

Abstract A novel copolymer, poly[1,6–hexanedioxy–1,4–phenylene–1,2–ethenylene–(2,5–dicyano–1,4–phenylene)–1,2–ethenylene–1,4–phenylene] (HCN-PPV), with alternating conjugated and non-conjugated blocks is synthesized by the Wittig reaction. The conjugated block containing one unit of 2,5-dicyano-1,4-phenylene vinylene is linked to a flexible linear hexyl chain spacer by an ether group in the backbone. The polymer is soluble in common organic solvents such as CHCl 3 and CH 2 Cl 2 . The number average molecular weight ( M n ) is 2517 with a polydispersity index of 1.75. The optical bandgap of HCN-PPV is 2.48 eV. λ max of the PL spectrum of the polymer film sample lies at 533 nm, corresponding to green light emission. The polymer also shows good thermal stability with a decomposition temperature of 304°C under air atmosphere. Cyclic voltammetric investigation of the polymer reveals a reversible n -doping process and an irreversible p -doping process. The onset for the n -doping process occurs at −1.48 V (vs. SCE), while the onset for the p -doping process occurs at 1.19 V (vs. SCE). The results imply that HCN-PPV is an n -dope type electroluminescent polymer.

The Synthesis and Characterisation of Fluorescent Poly(heteroaromatic oxadiazole)s

Five polymers comprising alternating electron-donating thiophene and electron-withdrawing oxadiazole units have been synthesised by polycondensation reaction. The optical and charge transporting properties of the polymers were investigated by UV-Vis absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. Thermal stability of the polymers has also been studied. All polymers depicted blue fluorescence and high fluorescence quantum efficiency. The influence of the introduction of an electron-donating alkoxy group to both the 3- and 4-positions of the thiophene ring and the length of the alkoxy side chain on properties of the polymers were discussed.

The synthesis and characterization of an efficient green electroluminescent conjugated polymer: poly[2,7-bis(4-hexylthienyl)-9,9-dihexylfluorene]

A novel soluble electroluminescent (EL) material, poly[(4-hexylthiophene-2,5-diyl)(9,9-dihexyl-9H-fluoren-2,7-ylene )(4-hexylthiophene-2,5-diyl)] (PHTDHFHT), with high absolute photoluminescence (PL) quantum efficiency (32 ± 3%) compared with other polythiophene derivatives, was synthesized and a green EL is observed.

A novel triarylamine-based conjugated polymer and its unusual light-emitting properties

A new soluble triphenylamine-based conjugated polymer, poly[N-(4′-butylphenyl)imino(1,1′∶4′,1 ″-terphenyl-4′4″-ylene)], (PBPITP), has been synthesized, which emits blue photoluminescence (PL) with high absolute PL quantum efficiency (45 ± 3%) but exhibits red electroluminescence (red shifted by as much as 157 nm from the PL spectrum).

Synthesis and characterization of electrically conducting copolymers of ethylenedioxythiophene and 1,3-propylenedioxythiophene with ω-functional substituents

Abstracts are not published in this journal