Synthesis and blue light-emitting properties of 4,4＇-bis（diphenylamino）-quinque（p-phenyl）s

An excellent organic blue light-emitting diode based on 4,4＇-bis（diphenylamino）-quinque（p-phenylene）s （OPP（5）-NPh） with a maximum luminance of up to 5000 cd/m^2 and a luminanous efficiency of 1.3 cd/A was reported. This diode was made by using a wide band-gap hole-blocking layer, F-TBB instead of PBD in the OLED devices. We attribute the good performance to the one trade-off involved in the use of F-TBB to obtain higher luminance is the increased turn-on voltages and slightly decreased device efficiencies.     

Bipolar copoly(aryl ether) containing distyrylbenzene,triphenylamine, and 1,2,4‐triazole moieties: Synthesis and optoelectronic properties

A novel copoly(aryl ether) ( P1 ) consisting of alternate emitting segments (distyrylbenzene) and a bipolar moiety composed of directly linked electron‐transporting aromatic 1,2,4‐triazole and hole‐transporting triphenylamine was synthesized. The copoly(aryl ether) is readily soluble in common organic solvents and exhibit good thermal stability with thermal decomposition temperature above 450 °C. The emission and the photoluminescence quantum yield of the copolymer are dominated by the emitting segments (distyrylbenzene) with longer emissive wavelength. Electron affinity of P1 is evidently enhanced after introducing the isolated bipolar unit, as confirmed by the lowered lowest unoccupied molecular orbital level (–2.77 eV) relative to P0 without bipolar unit (–2.34 eV). This results in improved emission efficiency of its polymer light‐emitting diode (indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/ P1 /LiF/Ca/Al) due to more balanced charges injection and transport. Blending P1 with poly(9,9‐dihexylfluorene) ( PF ) further improves the efficiency of the device; the best performance was obtained for PF / P1 = 20/0.8 (w/w) with maximum luminance and maximum luminance efficiency being significantly enhanced to 3260 cd/m² and 1.08 cd/A, respectively, from 380 cd/m² and 0.009 cd/A of P1 ‐based device. These results demonstrate that the bipolar moiety can be used to enhance charges injection and transport of electroluminescent polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Improved Efficiency Roll-Off and Operational Lifetime of Organic Light-Emitting Diodes with a Tetradentate Platinum(II) Complex by Using an n-Doped Electron-Transporting Layer

The efficiency roll-off and operational lifetime of organic light-emitting diodes (OLEDs) with a tetradentate Pt(II) emitter is improved by engaging an n-doped electron-transporting layer (ETL). Compared to those devices with non-doped ETL, the driving voltage is lowered, the charged carrier is balanced, and the exciton density in the emissive layer (EML) is decreased in the device with n-doped ETL with 8-hydroxyquinolinolatolithium (Liq). High luminance of almost 70,000 cd m⁻² and high current efficiency of 40.5 cd A⁻¹ at high luminance of 10,000 cd m⁻² is achieved in the device with 50 wt%-Liq-doped ETL. More importantly, the extended operational lifetime of 1945 h is recorded at the initial luminance of 1000 cd m⁻² in the 50 wt%-Liq-doped device, which is longer than that of the device with non-doped ETL by almost 10 times. This result manifests the potential application of tetradentate Pt(II) complexes in the OLED industry.     

Electroluminescent properties of a partially‐conjugated hyperbranched poly(p‐phenylene vinylene)

In this paper, the electroluminescent properties of a new partially‐conjugated hyperbranched poly (p‐phenylene vinylene) (HPPV) were studied. The single layer light‐emitting device with HPPV as the emitting layer emits blue‐green light at 496 nm, with a luminance of 160 cd/m² at 9 V, a turn‐on voltage of 4.3 V and an electroluminescent efficiency of 0.028 cd/A. By doping an electron‐transport material [2‐(4‐biphenylyl)‐5‐phenyl‐1,3,4‐oxadiazole, PBD] into the emitting layer and inserting a thin layer of tris(8‐hydroxy‐quinoline)aluminum (Alq₃) as electron transporting/hole blocking layer for the devices, the electroluminescent efficiency of 1.42 cd/A and luminance of 1700 cd/m² were achieved. The results demonstrate that the devices with the hyperbranched polymers as emitting material can achieve high efficiency through optimization of device structures. Copyright © 2006 John Wiley & Sons, Ltd.     

聚芳烃二乙炔类共轭高分子的合成及其发光性质的研究

通过Glaser-Hay氧化偶联反应合成含有咔唑与对烷氧基苯结构单元的聚芳烃二乙炔。利用核磁共振、红外光谱、凝胶渗透色谱、紫外光谱、电致发光光谱、热重分析等测试手段表征其结构,测定相对分子质量及其分布,并研究光学、热学和电化学方面的性能。并将这种聚合物作为器件的发光层,其器件结构为ITO/PEDOT/Polymer/Ba/Al,结果表明起亮电压为6.5V,其外量子效率达到0.21%,最大亮度达到90 cd/m2。     

Crosslinkable poly(p‐phenylenevinylene) derivative

To simplify the fabrication of multilayer light‐emitting diodes, we prepared a p‐phenylenevinylene‐based polymer capped with crosslinkable styrene through a Wittig reaction. Insoluble poly(p‐phenylenevinylene) derivative (PPVD) films were prepared by a thermal treatment. The photoluminescence and ultraviolet–visible (UV–vis) absorbance of crosslinked films and noncrosslinked films were studied. We also studied the solvent resistance of crosslinked PPV films with UV–vis absorption spectra and atomic force microscopy. Double‐layer devices using crosslinked PPVD as an emitting layer, 2‐(4‐tert‐butylphenyl)‐5‐phenyl‐1,3,4‐oxadiazole (PBD) in poly(methyl methacrylate) as an electron‐transporting layer, and calcium as a cathode were fabricated. A maximum luminance efficiency of 0.70 cd/A and a maximum brightness of 740 cd/m² at 16 V were demonstrated. A 12‐fold improvement in the luminance efficiency with respect to that of single‐layer devices was realized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2124–2129, 2004     

Copoly(p‐phenylene)s containing bipolar triphenylamine and 1,2,4‐triazole groups: Synthesis,optoelectronic properties,and applications

Two novel copoly(p‐phenylene)s ( P1 – P2 ) containing bipolar groups (12.8 and 6.8 mol %, respectively), directly linked hole transporting triphenylamine and electron transporting aromatic 1,2,4‐triazole, were synthesized to enhance electroluminescence (EL) of poly(p‐phenylene vinylene) (PPV) derivatives. The bipolar groups not only enhance thermal stability but also promote electron affinity and hole affinity of the resulting copoly(p‐phenylene)s. Blending the bipolar copoly‐(p‐phenylene)s ( P1 – P2 ) with PPV derivatives ( d6‐PPV ) as an emitting layer effectively improve the emission efficiency of its electroluminescent devices [indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene) (PEDOT):poly(styrenesulfonate) (PSS)/polymer blend/Ca (50 nm)/Al (100 nm)]. The maximum luminance and maximum luminance efficiency were significantly enhanced from 310 cd m^?2 and 0.03 cd A^?1 ( d6‐PPV ‐based device) to 1450 cd m^?2 and 0.20 cd A^?1 (blend device with d6‐PPV / P1 = 96/4 containing ～0.5 wt % of bipolar groups), respectively. Our results demonstrate the efficacy of the copoly(p‐phenylene)s with bipolar groups in enhancing EL of PPV derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

New family of highly emissive,soluble poly(1,4‐fluorenylenevinylene) derivatives: Synthesis and characterization

A new poly(arylene vinylene) derivative, poly(1,4‐fluorenylenevinylene), with the advantages of poly(p‐phenylene vinylene) and polyfluorene (PF), was designed, synthesized, and characterized. The polymer showed a defect‐free structure and a number‐average molecular weight of 32,600. The resulting polymer was thermally stable with a high glass‐transition temperature (200 °C) and was readily soluble in common organic solvents. The polymer film showed a maximum emission at 515 nm and had a photoluminescence quantum yield of 58 ± 5%. A cyclic voltammetry study revealed that the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the polymer were 2.9 and 5.51 eV, respectively. The double‐layer light‐emitting‐diode devices fabricated from the polymer emitted bright green light with a maximum around 515 nm. The device showed a maximum luminous efficiency of 0.13 cd/A and a maximum luminance value of 600 cd/m² at 17 V. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6515–6523, 2005     

具有空穴传输性能高效蓝光咔唑芘

A novel bifunctional blue-light material, 9-(pyren-1-yl)-9H-carbazole (CzPy), has been syn-thesized and its structure is identified by electron ionization mass spectrometry, ¹H NMR, and element analysis. The absorption, photoluminescence spectra and thermal properties were studied, results showedthat CzPy was stable under ambient conditions with a blue-light emission (461 nm).Additionally, its electroluminescence properties were characterized with four different devices. Results indicated a maximum luminous efficiency reached 1.56 cd/A and maximum luminance up to 3526 cd/m² at 10 V with commission international De L'Eclairage coordinates of (0.20, 0.24) when it was used as emitter. Furthermore, CzPy also indicated hole-transporting ability.     

Red Electroluminescence and Photoluminescence from Novel Binuclear Europium Complex with Squaric Acid Ligand

Organic electroluminescent devices (OELDs) have attracted much attention for several years because of their potential application in large area, multi-colored flat panel displays1-5. The green organic EL display using Alq3 as emitter was commercialized in 19976. However, red-emitting OELD with excellent properties has not been well developed. In order to realize practical full-color OELDs, it is considered very important to develop red and blue emitting materials with excellent propert…     

Synthesis and Luminescence Property of 4,4＇-Bis（2,2-di（4-fluorophenyl）vinyl）biphenyl for Organic Blue-Light-Emitting Diodes

The novel fluorinated distyrylarylene, 4,4＇-bis（2,2-di（4-fluorophenyl）vinyl）biphenyl （DFPVBi）, was synthesized and fully characterized. The structure was confirmed with IR, 1↑H NMR, 13↑C NMR, 19↑F NMR and MS analyses. Its electronic and photoluminescence properties were investigated by UV-Vis absorption, cyclic voltammetry and fluorescence spectroscopy. The energy levels of the highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） are --5.77 and --2.75 eV, respectively. The electroluminescence proper- ties of the organic light-emitting diode fabricated by DFPVBi were also studied. The device exhibits a pure blue emission peaked at 454 nm, which indicates a maximum luminance of 5872 cd/m ^2 at 14.2 V and a maximum current efficiency of 2.82 cd/A at 10V, respectively.     

Synthesis, characterization and photophysics of fluorene-alt-oxadiazole copolymers containing pendent iridium (III) complex moiety

A series of fluorene-alt-oxadiazole copolymers containing a pendent phosphor chromophore of the (piq)₂Ir(pic) complex were synthesized via the palladium-catalyzed Suzuki coupling reaction, where piq is 1-phenylisoquinoline and pic is picolinic acid. These copolymers exhibited a similar absorption spectrum with a peak at about 330 nm and a typical emission peak at 408 nm in CH₂Cl₂ from the fluorene-alt-oxadiazole backbone. However, a significantly red-shifted emission peak at about 625 nm was observed in the neat films of these copolymers, which are attributed to the pendent iridium (III) complex unit. Using these copolymers as single emission layer, the polymer light-emitting devices with a configuration of ITO/PEDOT:PSS/copolymers/LiF/Al exhibited a saturated red emission with a peak at 632 nm. Significant influence of the attached iridium (III) complex ratio on EL performance was presented. A maximum current efficiency of 1.2 cd/A at 63 mA/cm² and a maximum luminance of 1125 cd/m² at 12 V were achieved from the device with the copolymer containing iridium (III) complex in a 3% molar ratio.     

Electroluminescence from Exciplex on the Interface Between TPD and La（PMIP）3（Bipy）

The bilayer organic light-emitting diode(OLED) with a blue fluorescent lanthanum complex, tris(1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone)-(2,2′-dipyridyl) lanthanum [La(PMIP)3(Bipy)], as a light emitting material and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine(TPD) as a hole transporting material emits bright green light instead of blue light. The data of the absorption, the photoluminescence(PL) and the photoluminescence excitation(PLE) spectra of TPD, La(PMIP)3(Bipy) and the mixture of TPD and La(PMIP)3(Bipy)(molar ratio 1∶1) prove that the electroluminescent emission originates from the exciplex on the interface between TPD and La(PMIP)3(Bipy). By improving device configuration with tris(8-hydroxyquinoline) aluminum(ALQ) as an electron transporting material, a maximum luminance of 800 cd/m2 was obtained.     

Novel orange-red light-emitting polymers with cyclometaled iridium complex grafted in alkyl chain

Novel poly(fluorene-alt-carbazole) (PFCz) based copolymers with 3,6-carbazole-N-alkyl grafted iridium complex using 2,3-diphenylpyrazine as ligand (IrBpz) were synthesized by Suzuki polycondensation. The emission of host polymer, PFCz, was completely quenched when the copolymer with 1 mol% of iridium complex. An orange-red emission with CIE coordinate of (0.56, 0.42) was observed from Phosphorescent polymer light-emitting diodes (PhPLEDs). The PhPLEDs made by this copolymer-iridium complex showed a maximum luminous efficiency (LE) of 5.58 cd/A and a maximal luminance of 8625 cd/m². White light with CIE coordinate of (0.33, 0.27) was observed from white PhPLEDs (WPhPLEDs) made by the copolymer containing 0.4 mol% iridium complex. A LE of 2.30 cd/A with luminance of 2068 cd/m² was observed from WPhPLEDs.     

Bis(4-diphenylaminophenyl)carbazole end-capped fluorene as solution-processed deep-blue light-emitting and hole-transporting materials for electroluminescent devices

A new highly fluorescent bis(4-diphenylaminophenyl)carbazole end-capped fluorene (TCF) is synthesized and characterized. TCF is an amorphous molecular glass with a high glass transition temperature of 169 °C, is electrochemically stable, and gives strong blue emission both in solution and solid state. It showed greater ability as a solution processed blue emitter and hole-transporter for OLEDs than commonly used NPB. High-efficiency, deep-blue and Alq3-based green devices with luminance efficiencies and CIE coordinates of 0.93 cd/A and (0.16, 0.09), and 3.78 cd/A and (0.29, 0.45) were achieved, respectively.     

Synthesis and characterization of electrophosphorescent jacketed conjugated polymers

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     

Green-synthesized,low-cost tetracyanodiazafluorene (TCAF) as electron injection material for organic light-emitting diodes

As facile,green,low-cost as possible:One more electron-deficient azaacene (TCAF) with deep LUMO (-4.52 eV), strong electronic affinity,excellent yield,and simple purification procedure was successfully created and explored as good electron injection material.It is believed TCAF would be a promising and pervasive acceptor material and bring in more significant achievements to green and sustainable organic electronics including OLEDs,OFETs,OPVs, and perovskite solar cells,etc.     

Green-synthesized,low-cost tetracyanodiazafluorene (TCAF) as electron injection material for organic light-emitting diodes

Two electron-deficient azaacenes including di- and tetra-cyanodiazafluorene (DCAF and TCAF) with the advantages of deep lowest unoccupied molecular orbital (LUMO), green-synthesis, low-cost, simply purification method, excellent yields have been obtained, characterized and used as electron injection materials (EIMs) in three groups of electroluminescence devices. Device B with TCAF as EIM exhibited the best performance including turn-on voltage of 5.0 V, stronger maximum luminance intensity of 31,549 cd/m², higher luminance efficiency of 62.34 cd/A and larger power efficiency of 21.74 lm/W which are 0.53, 6.7, 9.3 and 15.3 times than that of device A with DCAF as EIMs, respectively. The enhanced interfacial electron injection ability of TCAF than that of DCAF is supported by its better electron mobility in electron-only device, deeper LUMO (-4.52 eV), and stronger electronic affinity. Best external quantum efficiency of 16.56% was achieved with optimized thicknesses of TCAF as EIM and TPBi as electron transporting layer. As a new comer of acceptor family, TCAF would push forward organic electronics with more fascinating and significant applications.     

Poly(triarylamine): Its synthesis,properties, and blend with polyfluorene for white‐light electroluminescence

A new high‐molecular‐weight poly(triarylamine), poly[di(1‐naphthyl)‐4‐anisylamine] (PDNAA), was successfully synthesized by oxidative coupling polymerization from di(1‐naphthyl)‐4‐anisylamine (DNAA) with FeCl₃ as an oxidant. PDNAA was readily soluble in common organic solvents and could be processed into freestanding films with high thermal decomposition and softening temperatures. Cyclic voltammograms of DNAA and PDNAA exhibited reversible oxidative redox couples at the potentials of 0.85 and 0.85 V, respectively, because of the oxidation of the main‐chain triarylamine unit. This suggested that PDNAA is a hole‐transporting material with an estimated HOMO level of 5.19 eV. The absorption maximum of a PDNAA film appeared at 370 nm, with an estimated band gap of 2.86 eV from the absorption edge. Unusual multiple photoluminescence maxima were observed at 546 nm, and this suggested its potential application in white‐light‐emission devices. Nearly white‐light‐emission devices could be obtained with either a bilayer‐structure approach {indium tin oxide/poly(ethylenedioxythiophene):poly(styrene sulfonate)/PDNAA/poly[2,7‐(9,9‐dihexylfluorene)] (PF)/Ca} or a polymer‐blend approach (PF/PDNAA = 95:5). The luminance yield and maximum external quantum efficiency of the light‐emitting diode with the PF/PDNAA blend as the emissive layer were 1.29 cd/A and 0.71%, respectively, and were significantly higher than those of the homopolymer. This study suggests that the PDNAA is a versatile material for electronic and optoelectronic applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1727–1736, 2007     

3-[2-(8-羟基喹啉基)-乙烯基]-N-芳基咔唑及其金属配合物的合成和光电性能研究

设计合成了3-[2-(8-羟基喹啉基)-乙烯基]-N-对甲苯基咔唑(8)和3-[2-(8-羟基喹啉基)-乙烯基]-N-对甲氧苯基咔唑(9)及其金属锌配合物(10和11), 用UV-Vis, FTIR, ESI-MS, FAB-MS, ¹H NMR和元素分析确认了化合物的结构. 热重分析实验结果表明, 金属锌配合物(10和11)有很好的热稳定性, 这对真空蒸镀制电致发光器件是有益的. 金属锌配合物组装成有机单层发光器件的结构为ITO/Organ layer(50 nm)/Al(100 nm), 其荧光发射峰分别位于592和583 nm, 为稳定的黄色光. 这两个发光器件的最大亮度分别为489和402 cd/m², 最大电流效率分别为0.41和1.81 cd/A. 电致发光研究表明, 通过化学修饰8-羟基喹啉的2-位取代基可以改变这两个金属锌配合物的电致发光性能.