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Turn-on Voltage (turn-on + voltage)
Kinds of Turn-on Voltage Selected AbstractsTris-Cyclometalated Iridium(III) Complexes of Carbazole(fluorenyl)pyridine Ligands: Synthesis, Redox and Photophysical Properties, and Electrophosphorescent Light-Emitting DiodesCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007Sylvia Bettington Dr. Abstract Using ligands synthesized by Suzuki cross-coupling methodology, new phosphorescent homoleptic tris-cyclometalated complexes have been obtained, namely fac -[Ir(Cz-2-FlnPy)3] (1,d,f) and fac -[Ir(Cz-3-FlnPy)3] (2,d,f), which are solution-processible triplet emitters (Cz denotes N -hexylcarbazole, n is the number of 9,9,-dihexylfluorene (Fl) units (n=0,1,2) and Py is pyridine). In all cases, Py and Fl are substituted at the 2- and 2,7-positions, respectively, and Cz moieties are substituted by either Py or Fl at the 2- or 3-positions, in series 1 and 2, respectively. The oxidation potential of 1,d studied by cyclic voltammetry (=0.14,V, versus Ag/AgNO3, CH2Cl2) is less positive (i.e. raised HOMO level) compared to that of the isomer 2,d (=0.30,V), where the Cz-nitrogen is meta to the Ir center. Ligand-centered oxidations occur at more positive potentials, leading to 7+ oxidation states with good chemical reversibility and electrochemical quasi-reversibility, for example, for 2,f =0.45 (1e), 0.95 (3e), 1.24,V (3e). Striking differences are seen in the solution-state photophysical data between complexes [Ir(Cz-2-Py)3] (1,d) and [Ir(Cz-3-Py)3] (2,d), in which the Cz moiety is bonded directly to the metal center: for the latter there is an 85,nm blue-shift in emission, a decrease in the luminescence lifetime and an increase in the PLQY value. Organic light emitting devices were made by spin-coating using polyspirobifluorene:bis(triphenyl)diamine (PSBF:TAD) copolymer as host and the complexes 1,d or 2,d as dopants. Turn-on voltages are low (3,4,V). With 1,d orange light is emitted at ,max=590,nm with an EQE of 1.3,% (at 7.5,mA,cm,2) and an emission intensity (luminance) of 4354,cd,m,2 (at 267,mA,m,2). The green emission from 2,d devices (,max=500,nm) is due to the reduced electron-donating ability of the carbazole unit in 2,d. Recording the EL spectra of the 1,d device at 6,V (current density, 100,mA,cm,2) established that the time to half brightness was about 9,h under continuous operation with no change in the spectral profile, confirming the high chemical stability of the complex. [source] Charge-Transporting Polymers based on Phenylbenzoimidazole MoietiesADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Marc Debeaux Abstract A series of novel styrene functionalized monomers with phenylbenzo[d]imidazole units and the corresponding homopolymers are prepared. These side-chain polymers show high glass-transition temperatures that even exceed the corresponding value for the common electron-transporting material 1,3,5-tris(1-phenyl-1H -benzo[d]imidazol-2-yl)benzene (TPBI). Similar electronic behavior between the polymers and TPBI is shown. The polymers are used as matrices for phosphorescent dopants. The fabricated devices exhibit current efficiencies up to 38.5,cd A,1 at 100,cd,m,2 and maximum luminances of 7400,cd m,2 at 10,V with a minimum turn-on voltage as low as 2.70,V in single-layer devices with an ITO/PEDOT:PSS anode (ITO,=,indium tin oxide, PEDOT:PSS,=,poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)) and a CsF/Ca/Ag cathode. [source] A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl-Substituted Fluorene Units for Highly Efficient Blue ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Fang-Ming Hsu Abstract Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N -diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato- N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenyl-phosphoryl)fluorene segment linked through the sp3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (ET) of 2.75,eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest. In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7,wt% FIrpic exhibits a very low turn-on voltage (2.5,V) and high electroluminescence efficiencies (20.6% and 36.7,lm W,1). Even at the practical brightnesses of 100 and 1000,cd m,2, the efficiencies remain high (20.2%/33.8,lm W,1 and 18.8%/24.3,lm W,1, respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources. [source] Characterization of Quantum Dot/Conducting Polymer Hybrid Films and Their Application to Light-Emitting DiodesADVANCED MATERIALS, Issue 48 2009Jeonghun Kwak Quantum dot/conducting polymer hybrid films are used to prepare light-emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution-based processes and are also easily micropatterned. The LEDs exhibit a turn-on voltage of 4,V, an external quantum efficiency greater than 1.5%, and almost pure-green quantum-dot electroluminescence. [source] Controlling Electrical Properties of Conjugated Polymers via a Solution-Based p-Type Doping,ADVANCED MATERIALS, Issue 17 2008Keng-Hoong Yim Tetrafluoro-tetracyano-quinodimethane (F4TCNQ) is used to p-dope conjugated polymers with a wide range of the HOMO levels via co-blending in a common organic solvent. Doping results in several orders of magnitude increase in the bulk conductivity and hole-current with reduced turn-on voltage. The effectiveness of doping increases as the HOMO level of the polymer becomes smaller. [source] DC and small-signal comparison of horizontal emitter designs of InGaP/GaAs heterojunction bipolar transistorsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2009Juan M. López-González Abstract This paper describes the DC and small-signal performance of two InGaP/GaAs heterojunction bipolar transistors (HBTs) that have the same chip size. This is done in order to compare emitter,base designs using the TCAD ATLAS device simulator. The HBT devices analyzed have the same cutoff and maximum frequencies but significant differences are observed in other characteristics such as base,emitter turn-on voltage, saturation collector,emitter voltage, forward current gain, maximum transducer gain and maximum stable gain. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis and characterization of novel poly(arylenevinylene) derivativeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Song Se-Yong Abstract The new poly(arylenevinylene) derivative composed naphthalene phenylene vinylene backbone was developed. The theoretical calculation showed that the model compound of the obtained polymer was highly distorted between the stryl and naphthalene units as well as between the backbone and fluorene side units. The polymer was synthesized by the palladium catalyzed Suzuki coupling reaction with 2,6-(1,,2,-ethylborate)-1,5-dihexyloxynaphtalene and 1,2-bis(4,-bromophenyl)-1-(9,,9,-dihexyl-3-fluorenyl)ethene. The structure of the polymer was confirmed by 1H NMR, IR, and elemental analysis. The weight,average molecular weight of the polymer is 29,800 with the polydispersity index of 1.87. The new polymer showed good thermal stability with high Tg of 195°C. The bright blue fluorescence (,max = 475 nm) was observed both in solution and film of new polymer with naphthalene phenylene vinylene backbone. Double layer LED devices with the configuration of ITO/PEDOT/polymer/LiF/Ca/Al showed a turn-on voltage at around 4.5 V, the maximum luminance of 150 cd/m2, and the maximum efficiency of 0.1 cd/A. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and electroluminescent properties of polyfluorene-based conjugated polymers containing bipolar groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Sheng-Tung Huang Abstract A bipolar dibromo monomer, bis-(4-bromophenyl)[4-(3,5-diphenyl-1,2,4- triazole-4-yl)-phenyl]amine (9), containing electro-rich triphenylamine and electro-deficient 1,2,4-triazole moieties was newly synthesized and characterized. Two fluorescent fluorene-based conjugated copolymers (TPAF, TPABTF) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7-dibromo-2,1,3-benzothiadiazole (BTDZ), and 9,9-dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (Tg) higher than 135 °C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 °C. Single layer polymer light-emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF. The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn-on voltage of 5 V, a maximum electroluminance of 696 cd/m2, and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231,6245, 2009 [source] Synthesis and white electroluminescent properties of multicomponent copolymers containing polyfluorene, oligo(phenylenevinylene), and porphyrin derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Hui Li Abstract Two novel multicomponent copolymers (P1 and P2) containing polyfluorene (PF), oligo(phenylenevinylene) (OPV), and porphyrin (Por) derivatives were synthesized according to the Suzuki polymerization method. The structures, optical, and electrochemical properties of the two model compounds (OPV and Por) and multicomponent copolymers were characterized by 1H NMR, FTIR, elemental analysis, UV,vis spectroscopy, photoluminescence, and cyclic voltammetry, respectively. Both of the copolymers exhibit thermotropic liquid crystalline properties and represent the characteristic Schlieren textures in a wide temperature range. Electroluminescence spectra of these copolymers exhibit broadband emissions covering the entire visible region from 400 to 700 nm. The single layer polymer light emitting diodes device based on P2 with a configuration of indium tin oxide/poly(ethylenedioxythiophene):poly(styrenesulfonic acid)/polymers/Ca/Al emits white light with the Commission Internationale de l,Eclairage chromaticity coordinates of (0.29, 0.30), maximum brightness of 443 cd/m2. The white-light-emitting devices based on the novel multicomponent copolymers exhibit low turn-on voltage, and good color stability at different driving voltages as well. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5291,5303, 2009 [source] Synthesis and characterization of new carbazole/fluorene-based derivatives for blue-light-emitting devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2006Saulius Grigalevicius Abstract 2,7-Bis(9-ethylcarbazol-3-yl)-9,9-di(2-ethylhexyl)fluorene and a segmented copolymer composed of the same chromophores alternated with hexamethylene fragments were synthesized. The obtained materials possess good solubility in common organic solvents, high thermal stability with 1% weight loss temperature of 350,370 °C, and suitable glass transition temperatures. Both derivatives show blue fluorescence in dilute solutions as well as in solid state, demonstrating that excimers are not formed in the thin films. The fluorescence spectra of the materials do not show any peaks in the long-wavelength region even after annealing at 200 °C in air. An organic LED with the configuration of ITO/copolymer/Al generates blue electroluminescence with the maximum peak at 416 nm, rather low turn-on voltage (4.0 V), and brightness of about 400 cd/m2. The heterostructure device based on model derivative emitted stable blue light with low operation voltage (100 cd/m2 at ,11 V) and demonstrated luminescence efficiency of 0.8 cd/A. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5987,5994, 2006 [source] Conjugated Triphenylene Polymers for Blue OLED DevicesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2009Moussa Saleh Abstract Three polytriphenylene derivatives with phenyl and alkyl groups as side chains have been tested as blue light emitters. The best performance in terms of turn-on voltage and luminance efficiencies was obtained for poly(2-heptyl-3-(4-octylphenyl)-1,4-diphenyl-6,11-triphenylenyl-1,4-benzene) (1), which was additionally blended with an electron-transporting and a hole-injection material in the device, and had an onset of 4.6,V and reached 0.73,cd,·,A,1. [source] Integration of enhancement and depletion-mode AlGaN/GaN MIS-HFETs by fluoride-based plasma treatmentPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007Ruonan Wang Abstract Enhancement-mode AlGaN/GaN metal,insulator,semiconductor HFETs (MIS-HFETs) are demonstrated by combining CF4 plasma treatment technique and a two-step Si3N4 deposition process. The threshold voltage has been shifted from ,4 to 2 V using this technique. A 15 nm Si3N4 layer is inserted under the gate to provide additional isolation between the gate metal and AlGaN surface, which can lead to higher gate turn-on voltage. The two-step Si3N4 deposition process is developed to reduce the gate coupling capacitances in the source and drain access regions, while assuring the plasma-treated gate region being fully covered by the gate electrode. The forward gate turn-on voltage can be as large as 6.8 V. By tuning the plasma treatment parameters, the threshold voltage of the enhancement-mode MIS-HFETs can be raised to as high as 4.3 V. By integrating with depletion-mode MIS-HFETs, a direct-coupled FET logic inverter has been fabricated, with logic low and high noise margins of 2.1 and 2 V. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface treatments of indium-tin oxide substrates for polymer electroluminescent devicesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2006Z. Y. Zhong Abstract In this work, three different sets of processing techniques (wet, dry, and combined treatments) were utilized to modify the surfaces of indium-tin oxide (ITO) substrates for polymer electroluminescent devices (PELDs), and the influence of surface treatments on the surface properties of ITO substrates were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle, and four-point probe. The surface energies of ITO substrates were also calculated from the measured contact angles. Experimental results show that the surface properties of the ITO substrates strongly depend on the surface treatments. Oxygen plasma treatment effectively improves the ITO surface properties since plasma decreases the surface roughness and sheet resistance, improves the surface stoichiometry and wetting. Furthermore, the PELDs with the differently treated ITO substrates as hole-injecting electrodes were fabricated and characterized. We observe that the optical and electrical characteristics of devices are greatly influenced by the surface treatments on ITO substrates. Oxygen plasma treatment decreases turn-on voltage, increases brightness and efficiency, and thereby improves the device performance of PELDs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of a novel luminescent copolymer based on bisphenol APOLYMER INTERNATIONAL, Issue 9 2005Hager Trad Abstract A new luminescent copolymer (BPAEt2 -BP; Scheme 1), with short alternating divinylbiphenyl units and O -diethylated bisphenol A (BPAEt2), was synthesized via the Wittig reaction. The polymer is fully soluble in common organic solvents and has a number-average molecular weight of 4600 g mol,1 with a polydispersity index of 1.79. The structure of the polymer was confirmed by 1H NMR, 13C NMR, FTIR and Raman analysis. Thermal analysis of the polymer showed good stability up to 280 °C. Furthermore, polymer film absorbs at 360 nm and emits in the blue at 426 and 451 nm. The band-gap calculated from the UV-vis spectrum was about 2.80 eV. A single-layer device of the configuration indium tin oxide (ITO)/BPAEt2 -BP/Al has a relatively low turn-on voltage of 3 V. Copyright © 2005 Society of Chemical Industry [source] Synthesis, characterization, and electroluminescence of new conjugated PPV derivatives bearing triphenylamine side-chain through a vinylene bridgePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2007Zhan'ao Tan Abstract Three new conjugated poly(p -phenylene vinylene) (PPV) derivatives bearing triphenylamine side-chain through a vinylene bridge, poly(2-(4,-(diphenylamino)phenylenevinyl)-1,4-phenylene-vinylene) (DP-PPV), poly(2-(3,-(3,,7,-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene- alt -2-(4,- (diphenylamino)phenylenevinyl)-1,4-phenylenevinylene) (DODP-PPV), and poly(2-(4,-(diphenylamino)phenylenevinyl)-1,4-phenylenevinylene-co-2-(3,,5,-bis(3,,7,-dimethyloctyloxy)-1,4-phenylenevinylene) (DP-co-BD-PPV), were synthesized according to the Gilch or Wittig method. Among the three polymers, the copolymer DP-co-BD-PPV is soluble in common solvents with good thermal stability with 5% weight loss at temperatures higher than 386°C. The weight-average molecular weight (Mw) and polydispersity index (PDI) of DP-co-BD-PPV were 1.83,×,105 and 2.33, respectively. The single-layer polymer light-emitting diodes (PLEDs) with the configuration of Indium tin oxide (ITO)/poly (3,4-ethylenedioxythiophene): poly(4-styrene sulfonate)(PEDOT:PSS)/DP-co-BD-PPV/Ca/Al were fabricated. The PLED emitted yellow-green light with the turn-on voltage of ca. 4.9,V, the maximum luminance of ca. 990,cd/m2 at 15.8,V, and the maximum electroluminescence (EL) efficiency of 0.22,cd/A. Copyright © 2007 John Wiley & Sons, Ltd. [source] Electroluminescent properties of a partially-conjugated hyperbranched poly(p -phenylene vinylene)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2006Benhu Fan Abstract 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. [source] A Highly Efficient Universal Bipolar Host for Blue, Green, and Red Phosphorescent OLEDsADVANCED MATERIALS, Issue 22 2010Ho-Hsiu Chou The bipolar host material BCPO (bis-4- (N-carbazolyl)phenylphosphine oxide) containing a phosphine oxide and two carbazole groups, synthesized in three steps, shows a high triplet energy gap of 3.01,eV. The material can be used as a universal host for blue, green, and red phosphorescent devices, all giving extremely high efficiencies with turn-on voltages within 3 V. [source] PCPP derivatives containing carbazole pendant as hole transporting moiety for efficient blue electroluminescenceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2009Jinwoo Kim Abstract The syntheses and characterization of poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H -cyclopenta[def]phenanthrene))- co -(2,6-(4,4-bis(4-(((9-carbazolyl)hexyl)oxy)phenyl))-4H- cyclopenta[def]phenanthrene)) (BCzPh-PCPPs) and poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H -cyclopenta[def]phenanthrene))- co -(2,6-(4-(4-(((9-carbazolyl)hexyl)oxy)phenyl)-4-(4-((2-ethylhexyl)oxy)phenyl)-4H- cyclopenta[def]phenanthrene))) (CzPh-PCPPs), with carbazole unit as pendants, are presented. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. The devices of the polymers with the configurations of ITO/PEDOT:PSS/polymers/Ca/Al generate EL emission with maximum peaks at 400,450 nm, CIE coordinates of (x = 0.11,0.29, y = 0.11,0.33), low turn-on voltages of 4,6 V, maximum brightness of 60,810 cd/m2, and luminescence efficiencies of 0.04,0.22 cd/A. The PL spectra of CzPh-PCPPs films did not show any peak at around 550 nm, which corresponds to keto defect or aggregate/excimer formation, even after annealing for 30 h at 150 °C in air. Out of the series, CzPh-PCPP1 (PCPP derivative with 10% of carbazole moiety as pendant) shows blue emission with the maximum brightness of 810 cd/m2 at 9 V, and the highest luminescence efficiency of 0.22 cd/A at 395 mA/cm2. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1327,1342, 2009 [source] Efficient blue-green-emitting poly[(5-diphenylamino-1,3-phenylenevinylene)- alt -(2,5-dihexyloxy-1,4-phenylenevinylene)] derivatives: Synthesis and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2006Liang Liao Abstract New poly(phenylene vinylene) derivatives with a 5-diphenylamino-1,3-phenylene linkage (including polymers 2, 3, and 5) have been synthesized to improve the charge-injection properties. These polymers are highly photoluminescent with fluorescent quantum yields as high as 76% in tetrahydrofuran solutions. With effective ,-conjugation interruption at adjacent m -phenylene units, chromophores of different conjugation lengths can be incorporated into the polymer chain in a controllable manner. In polymer 2, the structural regularity leads to an isolated, well-defined emitting chromophore. Isomeric polymer 3 of a random chain sequence, however, allows the effective emitting chromophores to be joined in sequence by sharing a common m -phenylene linkage (as shown in a molecular fragment). Double-layer light-emitting-diode devices using 2, 3, and 5 as emitting layers have turn-on voltages of about 3.5 V and produce blue-green emissions with peaks at 493, 492, and 482 nm and external quantum efficiencies up to 1.42, 0.98, and 1.53%, respectively. In comparison with a light-emitting diode using 2, a device using 3 shows improved charge injection and displays increased brightness by a factor of ,3 to 1400 cd/m2 at an 8-V bias. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2307,2315, 2006 [source] Synthesis and Light-Emitting Properties of New Polyimides Containing Ethynylene Units in the Main ChainMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2007Jun Ho Chi Abstract Two new polyimides (ODA-PI and HDA-PI) having 1,4-phenylenediethynylene unit and octyloxy groups were synthesized. Judging from inherent viscosities of their precursor PAAs (1.42 and 1.62 dL,·,g,1), the two PIs were very high in molecular weight. Casting and thermal imidization of PAAs results polyimides with good-quality films. They were stable up to 364,°C and showed no crystallites. UV-vis and PL spectra in NMP solutions of both PIs showed maxima at 442 and 501 nm, respectively, while PL spectra in ,10 µm thick films exhibited a maximum at 540 nm. CV indicates that two PIs were electrochemically active in redox region. The devices with construction of ITO/PEDOT/PIs/BAlq3/LiF/Al exhibited turn-on voltages of 6.5 V in ODA-PI and 7.5 V in HDA-PI and emitted a bright bluish-green light. ODA-PI and HDA-PI showed maximum luminescence of 256 and 316 cd,·,cm,2, respectively, at the same voltage of 12 V. [source] A New Class of Blue-Emitting Materials for LED Applications: Triarylamine N -Functionalised 2,7-Linked Carbazole PolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2007Hunan Yi Abstract Attachment of triarylamino-functional groups at the 9-position of 2,7-linked carbazole polymers results in blue-emitting materials with two independent redox processes that were attributed to the triarylamino groups and the polymer backbone, respectively. This new class of blue-emitting conjugated polymers was prepared via a Suzuki cross-coupling reaction and showed low turn-on voltages in electroluminescent devices as a result of their low ionisation potentials. The photophysical, electrochemical and electroluminescent properties of these materials are discussed. [source] | ||||||||||||||||||||||