Copolyfluorenes containing pendant bipolar carbazole and 1,2,4‐triazole groups: Synthesis,characterization, and optoelectronic applications

Three novel copolyfluorenes ( P1 ‐ P3 ) containing pendant bipolar groups (2.5–7.7 mol %), directly linked hole‐transporting carbazole and electron‐transporting aromatic 1,2,4‐triazole, were synthesized by the Suzuki coupling reaction and applied to enhance emission efficiency of polymer light‐emitting diodes based on conventional MEH‐PPV. The bipolar groups not only suppress undesirable green emission of polyfluorene under thermal annealing, but also promote electron‐ and hole‐affinity of the resulting copolyfluorenes. Blending the bipolar copolyfluorenes with MEH‐PPV results in significant enhancement of device performance [ITO/PEDOT:PSS/MEH‐PPV+ P1 , P2 or P3 /Ca(50 nm)/Al(100 nm)]. The maximum luminance and luminance efficiency were enhanced from 3230 cd/m² and 0.29 cd/A of MEH‐PPV‐only device to 15,690 cd/m² and 0.81 cd/A (blend device with MEH‐PPV/ P3 = 94/6 containing about 0.46 wt % of pendant bipolar residues), respectively. Our results demonstrate the efficacy of the bipolar copolyfluorenes in enhancing emission efficiency of MEH‐PPV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and electro‐optical properties of light‐emitting polymers containing oxadiazole derivatives for light‐emitting diodes applications

Two PPV‐based bipolar polymers containing 1,3,4‐oxadiazole pendant groups were synthesized via the Gilch polymerization reaction for use in light‐emitting diodes (LEDs). The resulting polymers were characterized using ¹H and ¹³C NMR, elemental analysis, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin‐coated onto glass substrates, producing high optical quality thin films without defects. The electro‐optical properties of ITO/PEDOT/polymer/Al devices based on these polymers were investigated using UV‐visible, PL, and EL spectroscopy. The turn‐on voltages of the OC₁Oxa‐PPV and OC₁₀Oxa‐PPV devices were found to be 8.0 V. The maximum brightness and luminescence efficiency of the OC₁Oxa‐PPV device were found to be 544 cd/m² at 19 V and 0.15 cd/A, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1098–1110, 2008     

Syntheses and electroluminescence properties of conjugated poly(p‐phenylene vinylene) derivatives bearing dendritic pendants

A series of new poly(p‐phenylene vinylene) derivatives with different dendritic pendants—poly{2‐[3′,5′‐bis(2″‐ethylhexyloxy)benzyloxy]‐1,4‐phenylenevinylene} (BE–PPV), poly{2‐[3′,5′‐bis(3″,7″‐dimethyl)octyloxy]‐1,4‐phenylenevinylene} (BD–PPV), poly(2‐{3′,5′‐bis[3″,5″‐bis(2?‐ethylhexyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene) (BBE–PPV), poly(2‐{3′,5′‐bis[3″,5″‐bis(3?,7?‐dimethyloctyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene) (BBD–PPV), and poly[(2‐{3′,5′‐bis[3″,5″‐bis(2?‐ethylhexyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene)‐co‐(2‐{3′,5′‐bis[3″,5″‐bis(3?,7?‐dimethyloctyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene)] (BBE‐co‐BBD–PPV; 1:1)—were successfully synthesized according to the Gilch route. The structures and properties of the monomers and the resulting conjugated polymers were characterized with ¹H and ¹³C NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, ultraviolet–visible absorption spectroscopy, photoluminescence, and electroluminescence spectroscopy. The obtained polymers possessed excellent solubility in common solvents and good thermal stability, with a 5% weight loss temperature of more than 328 °C. The weight‐average molecular weights and polydispersity indices of BE–PPV, BD–PPV, BBE–PPV, BBD–PPV, and BBE‐co‐BBD–PPV (1:1) were in the range of 1.33–2.28 × 10⁵ and 1.35–1.53, respectively. Double‐layer light‐emitting diodes (LEDs) with the configuration of indium tin oxide/polymer/tris(8‐hydroxyquinoline) aluminum/Mg:Ag/Ag devices were fabricated, and they emitted green‐yellow light. The turn‐on voltages of BE–PPV, BD–PPV, BBE–PPV, BBD–PPV, and BBE‐co‐BBD–PPV (1:1) were approximately 5.6, 5.9, 5.5, 5.2, and 4.8 V, respectively. The LED devices of BE–PPV and BD–PPV possessed the highest electroluminescent performance; they exhibited maximum luminance with about 860 cd/m² at 12.8 V and 651 cd/m² at 13 V, respectively. The maximum luminescence efficiency of BE–PPV and BD–PPV was in the range of 0.37–0.40 cd/A. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3126–3140, 2005     

Vinyl copolymers containing pendant 1,4‐distyrylbenzene and 1,3,4‐oxadiazole chromophores: Preparation and optoelectronic properties

We prepared two vinyl copolymers P1 and P2 containing pendant distyrylbenzene and aromatic 1,3,4‐oxadiazole derivatives, respectively, from their precursor poly(styrene‐ran‐4‐vinylbenzyl chloride) (M_w = 11,400, PDI = 1.18), which had been prepared by the controlled radical polymerization (RAFT). Two main chain polymers containing similar isolated distyrylbenzene ( P3) and aromatic 1,3,4‐oxadiazole ( P4 ) chromophores were also synthesized for comparative study. The resulted copolymers ( P1 – P4 ) are soluble in common organic solvents and are basically amorphous materials with 5% weight‐loss temperature higher than 360 °C. The PL spectral results reveal that the architecture of P1 prevents the formation of inter‐ or intramolecular interaction. The HOMO and LUMO levels of P2 , estimated from cyclic voltammetric data, are ?5.96 and ?3.81 eV, respectively, which are much lower than those of P1 (?5.12 and ?3.11 eV). The emission of blend from P1 and P2 are contributed mainly from distyrylbenzene fluorophore (～450 nm) owing to efficient energy transfer. Moreover, the blend exhibits three kinds of redox behavior depending on their weight ratios. The luminance and current efficiency of the EL device lpar;ITO/PEDOT/ MEH ‐ PPV + P2 /Al) are 503 cd/m² and 0.11 cd/A, which can be improved to 1285 cd/m² and 0.44 cd/A, respectively, as the weight ratio of P2 increases from 0 to 20%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5362–5377, 2006     

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     

Synthesis and characterization of a novel electroluminescent polymer based on a phenoxazine derivative

We report the preparation of a new electroluminescent polymer by the oxidative coupling copolymerization of N‐(4‐n‐butylphenyl)phenoxazine and 9,9‐di‐n‐butylfluorene with ferric(III) chloride. The reaction yields soluble polymers with a weight‐average molecular weight as high as 9000. The reactivity has been studied with respect to the reaction time, temperature, and feed ratio of the comonomers. Under optimum conditions, a copolymer with a 50% comonomer incorporation ratio can be obtained in a 75% yield. The polymers have been characterized with differential scanning calorimetry, cyclic voltammetry, and optical spectroscopy. A simple single‐layer light‐emitting‐diode device of an indium tin oxide/polymer/Mg–Ag structure shows a luminance of 200 cd/m² at an 18‐V operating voltage. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4338–4345, 2006     

Enhancing the device performance of a blue light‐emitting copolymer using CdSe/ZnS quantum dots

An alternating triarylamine‐functionalized fluorene‐based copolymer synthesized using a Suzuki–Miyaura cross‐coupling procedure is used as blue emitting layer in polymer light‐emitting diodes (PLEDs). Subsequently, the effects of CdSe/ZnS quantum dots (QDs) on the optoelectronic properties of the copolymer are investigated. Therefore, CdSe/ZnS QDs are embedded into the copolymer matrix and hybrid PLEDs are fabricated. The devices comprised of CdSe/ZnS QDs reveal enhanced performances, yielding about 3.4 times more luminous efficiency than that of the device without QDs. Further enhancement is achieved by using electron transport layer; the luminous efficiency rose from 0.065 to 1.740 cd A^?1 for the hybrid PLEDs, corresponding to a superb 27‐fold intensification of the efficiency. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 147–156     

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     

Design,synthesis, photophysical,and electrochemical properties of DCM‐based conjugated polymers for light‐emitting devices

A series of conjugated hyperbranched polymers, hyperbranched copolymers, and linear polymers containing 2‐pyran‐4‐ylidenemalononitrile (acceptor) and triphenylamine/fluorene (donor) units were synthesized and characterized by FTIR, ¹H NMR, thermogravimetric analyses, differential scanning calorimetry, gel permeation chromatography, UV–visible, photoluminescence, and cyclic voltammetry measurements. All the polymers show red‐light emission in the range of 566–656 nm both in solution and in solid state. The quantum efficiency of the polymers was in the range of 56–82%. Among the six polymers synthesized, only polymers containing fluorene units show T_g and polymers based on triphenylamine not exhibit T_g. The band gap of these polymers were found to be reasonably low; hyperbranched copolymer containing fluorene unit shows lowest band gap of 2.18 eV due to the stabilization of LUMO energy level by the electron withdrawing ? CN groups. The thermal and solubility behavior of the polymers were found to be good. All the EL spectra of the devices (indium‐tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)/polymer/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline/tris(8‐hydroxyquinoline)aluminum)/LiF/Al) show red‐light emission, and the device fabricated with P3 and P4 shows maximum luminance and luminous efficiency of 4104 cd m^?2 and 0.55 cd Å^?1 and 3696 cd m^?2 and 0.47 cd Å^?1, respectively, indicates that they had the best carrier balance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Phenylene vinylene‐based electroluminescent polymers with electron transport block in the main chain

We report a new route for the design of soluble phenylene vinylene (PV) based electroluminescent polymers bearing electron‐deficient oxadizole (OXD) and triazole (TZ) moieties in the main chains with the aryloxy linkage. Both series of the PV‐based polymers were prepared by Wittig reaction. By properly adjusting the OXD and/or TZ content through copolymerization, we can achieve an enhanced balance of hole‐ and electron injections, such that the device efficiency is significantly improved. Light‐emitting diodes fabricated from P1, P2, P3, P4, P5, P6, and P7 with the configuration of Indium–Tin Oxide (ITO)/Poly (styrene sulfonic acid) doped poly (ethylenedioxythiophene) (PEDOT)/polymer/Ca/Al, emit bright green light with the maximum peak around 500 nm. For the device using the optimal polymer (P4) as emitting layer, a maximum brightness of 1300 cd/m² at 20 V and a maximum luminance efficiency of 0.325 cd/A can be obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3469–3478, 2006     

Poly‐(p‐phenylene vinylenes) with pendent 2,4‐difluorophenyl and fluorenyl moieties: Synthesis,characterization, and device performance

To improve efficiency, processability, and stability, three novel poly‐(p‐phenylene vinylenes) (PPVs) derivatives ( P _a , P _b , and P _c ) with pendent 2,4‐difluorophenyl and fluorenyl moieties were synthesized via Gilch reaction. Their structures were characterized by ¹H NMR, ¹³C NMR, and ELEM. ANAL . Compared with those of PPV and MEH‐PPV, the absolute quantum efficiencies of these polymers showed remarkable improvement (measured at 38.7, 37.2, and 20.3%, respectively), which can be attributed to the presence of twisted multiaryl segments and fluorine atoms. TGA revealed that the inflection temperatures of their thermal decomposition curves were above 400 °C. Double‐layered electroluminescent devices with these polymers as light‐emitting layers [ITO/PEDOT:PSS/Polymer/Ba/Al] showed peak emissions at 493/515, 503, and 600 nm and maximum luminance of 2700, 450, and 4700 cd/m² for P _a , P _b , and P _c , respectively, with onset voltages of ～4 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2500–2508, 2009     

Synthesis and light emitting properties of polyacetylenes having pendent fluorene groups

Five novel fluorene‐containing polymers, poly[(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA1 ), poly[(1‐pentyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene) ( PFA2 ), poly[1‐decyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA3 ), poly[1‐phenyl‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA4 ), and poly[1‐(3,4‐difluorophenyl)‐2‐(9,9‐dimethylfluoren‐2‐yl)acetylene] ( PFA5 ) were synthesized by the polymerization of the corresponding fluorene‐substituted acetylenic monomers ( M1–M5), using WCl₆, MoCl_5, and TaCl₅ as catalysts and n‐Bu₄Sn as a cocatalyst. The synthesized polymers were thermally stable and readily soluble in common organic solvents. The degradation temperatures for a 5% weight loss of the polymers were ∼352–503 °C under nitrogen. PFA1–PFA5 show emission peaks from 402 to 590 nm. Besides, their electroluminescent properties were studied in heterostructure light‐emitting diodes (LEDs), using PFA2–PFA5 as an emitting layer. The PFA5 device revealed an orange‐red emission peak at 602 nm with a maximum luminescence of 923 cd/m² at 8 V. A device with the ITO/PEDOT/ a mixture of PFA2 (98 wt %) and PFA5 (2 wt %)/Ca/Al showed near white emission. Its maximum luminance and current efficiency are 450 cd/m² at 15 V and 1.3 cd/A, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 519–531, 2006     

New poly(p‐phenylene vinylene) derivatives with two oxadiazole rings per repeat unit: Synthesis,photophysical properties,electroluminescence, and metal ion recognition

Two new poly(p‐phenylene vinylene) derivatives OX1‐PPV and OX2‐PPV bearing two 1,3,4‐oxadiazole rings per repeat unit and a fully conjugated backbone with solubilizing dodecyloxy side groups were synthesized and investigated. The amorphous conjugated polymers had glass‐transition temperature values of 60–75 °C and emitted intense blue or greenish‐blue light in solution with photoluminescence (PL) emission maxima at 379–492 nm and PL quantum yields of 0.41–0.52. In the solid state they emitted yellowish‐green light with PL emission maxima at 533–555 nm. Cyclic voltammetry showed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n‐type materials. The electron affinity of OX2‐PPV was estimated as 2.85 eV whereas that of OX1‐PPV was 2.75 eV. Yellow electroluminescence (EL) was achieved from single‐layer light‐emitting diodes of OX2‐PPV with an EL emission maximum at 555 nm and a brightness of 70 cd/m². Polymer OX2‐PPV, which was functionalized with 2,6‐bis(1,3,4‐oxadiazole‐2‐yl)pyridine, demonstrated sensitivity to various metal ions as a fluorescence‐mode chemosensor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2112–2123, 2004     

Synthesis of fluorene‐based hyperbranched polymers for solution‐processable blue,green, red,and white light‐emitting devices

For the purpose of making hyperbranched polymer (Hb‐Ps)‐based red, green, blue, and white polymer light‐emitting diodes (PLEDs), three Hb‐Ps Hb‐ terfluorene ( Hb‐TF ), Hb ‐4,7‐bis(9,9′‐dioctylfluoren‐2‐yl)‐2,1,3‐benzothiodiazole ( Hb‐BFBT ), and Hb‐ 4,7‐bis[(9,9′‐dioctylfluoren‐2‐yl)‐thien‐2‐yl]‐2,1,3‐benzothiodiazole ( Hb‐BFTBT ) were synthesized via [2+2+2] polycyclotrimerization of the corresponding diacetylene‐functionalized monomers. All the synthesized polymers showed excellent thermal stability with degradation temperature higher than 355 °C and glass transition temperatures higher than 50 °C. Photoluminance (PL) and electroluminance (EL) spectra of the polymers indicate that Hb‐TF , Hb‐BFBT , and Hb‐BFTBT are blue‐green, green, and red emitting materials. Maximum brightness of the double‐layer devices of Hb‐TF , Hb‐BFBT , and Hb‐BFTBT with the device configuration of indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/light‐emitting polymer/CsF/Al are 48, 42, and 29 cd/m²; the maximum luminance efficiency of the devices are 0.01, 0.02, and 0.01 cd/A. By using host–guest doped system, saturated red electrophosphorescent devices with a maximum luminance efficiency of 1.61 cd/A were obtained when Hb‐TF was used as a host material doped with Os(fptz)₂(PPh₂Me₂)₂ as a guest material. A maximum luminance efficiency of 3.39 cd/A of a red polymer light‐emitting device was also reached when Hb‐BFTBT was used as the guest in the PFO (Poly(9,9‐dioctylfluorene)) host layer. In addition, a series of efficient white devices were, which show low turn‐on voltage (3.5 V) with highest luminance efficiency of 4.98 cd/A, maximum brightness of 1185 cd/m², and the Commission Internationale de l'Eclairage (CIE) coordinates close to ideal white emission (0.33, 0.33), were prepared by using BFBT as auxiliary dopant. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,characterization, and electroluminescent performance of a novel copolyfluorene containing pendant crown ether groups

Copolyfluorene PFC containing pendant crown ether moieties was prepared by the palladium‐catalyzed Suzuki coupling reaction. The photo‐physical and electrochemical properties were investigated by absorption, photoluminescence (PL) spectroscopy, and cyclic voltammetry to elucidate the influence of the crown ether groups. In film state, its PL spectra (peaked at 430 and 452 nm) show noticeable red‐shift relative to 423 and 448 nm of poly(9,9‐dihexylfluorene) ( PF ). Thermal annealing leads to appearance of new emission at about 520 nm which has been attributed to formation of excimer. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of PFC were estimated to be ?5.68 and ?2.65 eV which contributed to balanced charges injection. Double‐layer electroluminescent device using PFC as emitting layer (ITO/PEDOT:PSS/ PFC /Ca/Al) revealed maximum luminance (7910 cd/m²) and maximum luminance efficiency (2.3 cd/A) superior to those of PF device (860 cd/m², 0.29 cd/A). Moreover, inserting a PFC layer between the PF emitting layer and calcium cathode led to reduced turn‐on voltage (4.1 V), much lower than 7.1 and 6.6 V of the double‐layer PFC and PF devices, respectively, and enhanced device performance (2800 cd/m² and 0.53 cd/A). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2985–2995, 2009     

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     

Synthesis and characterization of new blue‐light‐emitting polymers based on PPP and PPV having fluorene pendant at vinyl bridge

The new poly(arylene vinylene) derivatives, which are composed of biphenylene vinylene phenylene vinylene, biphenylene vinylene m‐phenylene vinylene, terphenylene vinylene phenylene vinylene, and terphenylene vinylene m‐phenylene vinylene as backbone and bulky fluorene pendants at each vinyl bridge, were designed, synthesized, and characterized. The obtained polymers showed weight‐average molecular weights of 11,100–39,800 with polydispersity indexes ranging from 1.5 to 2.1. The resulting polymers were amorphous with high thermal stability and readily soluble in common organic solvents. The obtained polymers showed blue emission (λ_max = 456–475 nm) in PL spectra, and polymer 4 containing terphenylene vinylene m‐phenylene vinylene showed the most blue shifted blue emission (λ_max = 456 nm). The double layer light‐emitting diode devices fabricated by using obtained polymers as emitter emitted bright blue light. The device showed turn on voltage around 6.5 V and brightness of 70–250 cd/m². © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4923–4931, 2006     

Solution‐processable and thermally cross‐linkable fluorene‐cored triple‐triphenylamines with terminal vinyl groups to enhance electroluminescence of MEH‐PPV: Synthesis,curing, and optoelectronic properties

This study reports the synthesis, curing, and optoelectronic properties of a solution‐processable, thermally cross‐linkable electron‐ and hole‐blocking material containing fluorene‐core and three periphery N‐phenyl‐N‐(4‐vinylphenyl)benzeneamine ( FTV ). The FTV exhibited good thermal stability with T_d above 478 °C in nitrogen atmosphere. The FTV is readily cross‐linked via terminal vinyl groups by heating at 160 °C for 30 min to obtain homogeneous film with excellent solvent resistance. Multilayer PLED device [ITO/PEDOT:PSS/cured‐ FTV /MEH‐PPV/Ca (50 nm)/Al (100 nm)] was successfully fabricated using solution processed. Inserting cured‐ FTV is between PEDOT:PSS and MEH‐PPV results in simultaneous reduction in hole injection from PEDOT:PSS to MEH‐PPV and blocking in electron transport from MEH‐PPV to anode. The maximum luminance and maximum current efficiency were enhanced from 1810 and 0.27 to 4640 cd/m² and 1.08 cd/A, respectively, after inserting cured‐ FTV layer. Current results demonstrate that the thermally cross‐linkable FTV enhances not only device efficiency but also film homogeneity after thermal curing. FTV is a promising electron‐ and hole‐blocking material applicable for the fabrication of multilayer PLEDs based on PPV derivatives. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012     

Thermally stable red electroluminescent hybrid polymers derived from functionalized silsesquioxane and 4,7‐bis(3‐ethylhexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole

Hyperbranched organic–inorganic hybrid conjugated polymers P1 and P2 were prepared via FeCl₃‐oxiditive polymerization of 4,7‐bis(3‐ethylhexyl‐2‐thienyl)‐2,1,3‐benzothiadiazole ( A ) and octa(3‐ethylhexyl‐2‐thienyl‐phenyl)polyhedral oligomeric silsesquioxane (POSS) ( B ) at different POSS concentrations. Compared to linear polymer PM derived from A , P1 , and P2 exhibit much higher PL quantum efficiency (?_PL‐f) in condensed state with improved thermal stability. ?_PL‐f of P1 and P2 increased by 80% and 400%, and the thermal degradation temperatures of P1 and P2 are increased by 35 °C and 46 °C, respectively. Light‐emitting diodes were fabricated using P1 , P2 , and PM . While the electroluminescent spectra of both P1 and PM show λ_max at 660 nm, P1 exhibits a much narrower EL spectrum and higher electroluminescence (～500%) compared with PM at a same voltage and film thickness. The maximum current efficiency of P1 is more than seven times of that of PM . The turn‐on voltages of the LEDs are in the order of P2 > PM > P1 . LED prepared by blending P1 with MEH‐PPV shows a maximum luminescence of 2.6 × 10³ cd/m² and a current efficiency of 1.40 cd/A, which are more than twice (1.1 × 10³ cd/m²) and five times (0.27 cd/A) of LED of PM /MEH‐PPV blend, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5661–5670, 2009     

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.