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Abstract: Four electroactive molecular materials with donor-π-acceptor-π-donor structures have been synthesized for investigation of structure–properties relationships, and used as dopant for electroluminescent applications. The optical and electrical properties of these materials are electronically manipulated by attaching different donors. The twisted intramolecular charge transfer (TICT) model is proposed by photophysical behaviors observed with increasing solvent polarity. Red electroluminescence devices were fabricated by spin coating the blend of polymer host and fluorescent guest. Highly efficient energy transfer leads to a saturated red emission with emission peak at 623nm, narrow bandwidth of 75nm and an external quantum efficiency of 0.38%. [Copyright &y& Elsevier]

Abstract: Two new linear divinylenes FN and PN that contained fluorene and phenylene, respectively, as central unit and naphthalimide terminal groups were synthesized by Heck coupling. In addition, two new star-shaped trivinylenes TPA-P and TPP-P that contained triphenylamine and 2,4,6-triphenylpyridine, respectively, as central core, and terminal phthalimide groups were similarly synthesized. All molecules were very soluble in common organic solvents due to their high fraction of aliphatic moieties which were attached to the central unit and/or the terminal imides. Trivinylenes showed higher thermal stability and higher glass transition temperature (118–126°C) than divinylenes. FN, PN and TPA-P emitted green-orange light with maximum at 518–586nm, while TPP-P emitted blue light with maximum at 444–462nm due to the kinked central core of 2,4,6-triphenylpyridine. The maximum luminance among the four molecules is 583cd/m2 at current density of 186mA/cm2 and applied voltage of 19.5V based on TPA-P, with a luminance efficiency maximum (η max) of 1.7cd/A. [Copyright &y& Elsevier]

Two aggregation-induced emission active luminogens (TPE- pTPA and TPE- mTPA) were successfully synthesized. For comparison, another six similar compounds were prepared. Because of the introduced hole-dominated triphenylamine (TPA), fluorene groups with high luminous efficiency, and unconjugated linkages, the π conjugation length of the obtained luminogens is effectively restricted to ensure their blue emission. The undoped organic light-emitting diodes based on TPE- pTPA and TPE- mTPA exhibited blue or deep-blue emissions, low turn-on voltages (3 V), and high electroluminescence efficiencies with Lmax, ηC,max, and ηP,max values of up to 26 697 cd m−2, 3.37 cd A−1, and 2.40 Lm W−1. [ABSTRACT FROM AUTHOR]

Two novel zinc Schiff-base complexes, bis-( N-(2-hydroxybenzidene)- p-aminodimethylaniline)zinc(II) ( 2) and bis-( N-(2-hydroxy-1-naphthidene)- p-aminodimethylaniline)zinc(II) ( 4) were designed and synthesized. Both the complexes exhibit good solubility in organic solvents and excellent thermal stabilities. A single crystal of 2 was grown and its crystalline structure was determined from X-ray diffraction data. Analysis of the electronic structures of both the zinc complexes calculated by density functional theory reveals a localization of orbital. The UV-Vis absorption and photoluminescence profiles of 4 in thin film are similar to those of 2, but the emission for 4 is red-shifted compared to 2. Three-layered devices with a configuration of ITO/NPB/ 2/Alq/LiF/Al and ITO/NPB/ 4/Alq/LiF/Al show a yellow and red emission, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Electromer is a unique excited-state species which can only be formed under electrical excitation. Currently, a clear understanding of electromer has not been realized yet. A big obstacle is that the electromer emission can hardly be separated from the emission of molecular excitons. Obtaining a complete electromer emission is essential for photophysical investigations of this kind of excited-state species and is useful for its potential application in optoelectronic logic gates. We report that a complete electromer emission can be achieved by introduction of a weak-fluorescence layer in organic light-emitting diodes, which will quench the molecular excitons produced in the adjacent emissive layer but leave the electromers undisturbed. In addition, a possible mechanism for the electromer formation is proposed based on the analysis of the single crystal structure of the compound 9,9-bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(9-carbazolyl)fluorene which can produce electromers. [Copyright &y& Elsevier]

Abstract: Simple molecule possesses high power: 1,3,6,8-Tetrakis[(triisopropylsilyl)ethynyl]pyrene (TTIPSEPy), a simple-structured molecule, shows strong solid-state photoluminescence with unity emission efficiency. Highly efficient non-doped organic light-emitting diodes are fabricated using TTIPSEPy as emitter, exhibiting stable yellow light (CIE=0.41, 0.56) with high luminance and efficiency up to 26,400cd/m2 and 9.2cd/A, respectively. [Copyright &y& Elsevier]

Abstract: A novel dicyanovinyl-functionalized N,N,N’,N’-tetraphenylbenzidine (TPD) derivative, N,N’-bis[4-(1,1-dicyanovinyl)phenyl]-N,N’-bis(4-fluorophenyl)benzidine and a novel triphenylamine-based derivative, 4,4′,4″-tris{[di(p-tolyl)amino]phenyl}triphenylamine were synthesized and employed as red molecular emitter and hole-transporting layer, respectively, in an undoped organic light-emitting diode devices. The device based on the TPD-FCN emitter and DBTPA hole-transporting material, which was fabricated in a facile non-doped configuration, achieved maximum luminance of 3400 cd m−2 at a driven voltage of 17.5 V and maximum luminous efficiency of 3.04 cd A−1. Interestingly, the device reached a brightness of 1399 cd m−2 and luminous efficiency of 2.85 cd A−1 at the low current density of 20 mA cm−2. [Copyright &y& Elsevier]

Abstract: A series of blue-emitting materials with sp3 Si cores were synthesized by Suzuki Coupling reaction and characterized by spectroscopy. Their usages as blue emitters in organic light-emitting diodes (OLEDs) were preliminary investigated. Blue emission with comparable brightness and efficiency were obtained with structure of ITO/NPB/tetraarylsilane/TPBi/LiF/Al. Moreover, these tetraarylsilane compounds exhibited high thermal decomposition temperatures (T ds) which indicated that these compounds might be explored for potential application in flat panel display. [Copyright &y& Elsevier]

Abstract: Three new trimers PV, FV and CV were synthesized by Heck coupling of 4(4-bromophenyl)-2,6-diphenylpyridine with substituted divinylbenzene, divinylfluorene and divinylcarbazole, respectively. They were very soluble in chloroform, dichloromethane, tetrahydrofuran and toluene. FV and CV were more thermally stable and showed higher glass transition temperature than PV. Their absorption maximum was located at 327–397nm with optical band gap of 2.53–2.73eV. FV and CV emitted blue-green light with emission maximum at 455–489nm while PV emitted green-yellow light with emission maximum at 496–530nm. Upon protonation, the trimer thin films displayed red-shifts of the emission maximum. The electrochemical and electroluminescent properties of the trimers were studied. Light-emitting diodes (LEDs) based on these trimers were fabricated. These LEDs showed bright blue light for FV, CV and bluish-green light for PV which are in line with their photoluminescence spectra. The maximum brightness was reached approximate 1000cd/m2 for PV, 380 for FV, and 400 for CV, at current density of 200mA/cm2. [Copyright &y& Elsevier]

Abstract: A series of well-defined, highly fluorescent starburst compounds with a carbazole core and oligo(2,7-fluorene ethynylene) arms have been synthesized by Sonogashira coupling reaction and fully characterized. These conjugated compounds exhibit good solubility, high thermal stability, and excellent fluorescence quantum yields (up to 0.99). The incorporation of carbazole core interrupted the main-chain conjugation and resulted in blue-shifted absorption and emission. Moreover, deep blue light has been approached from organic light-emitting diodes (OLEDs) adopting these compounds as emitting layer. [Copyright &y& Elsevier]

Abstract: A series of blue light-emitting compounds with different molecular shapes were synthesized by the Pd/Cu-catalyzed Sonogashira coupling reaction. These compounds composed of hole-transporting group (carbazole) and strong fluorescent group (pyrene), which linked through 9,9-dihexyl-2,7-fluorene ethynylene. The photoluminescent (PL) and electroluminescent (EL) behavior of these compounds was investigated. [Copyright &y& Elsevier]

Abstract: Three donor–acceptor conjugated polymers P1–P3 derived from 3,5-dicyano-2,4,6-tristyrylpyridine (PY) have been synthesized through the Knoevenagel reaction. The polymers are characterized by 1H NMR, FTIR, UV–vis and elemental analysis. P1 and P2 have high molecular weight up to 2.3×105 and 29.5×105 and show excellent solubility in common solvents such as THF, CH2Cl2, CHCl3 and DMF. They all have relatively good thermal stability with the 5% weight loss temperature at 402, 264 and 364°C in argon, respectively. The fluorescence spectrum of P1 displayed the maximum at 588nm in chloroform solution and at 596nm in thin film. Two bilayer light-emitting diodes, with 5% or 10% of P1 fabricated in poly (N-vinylcarbazole) (PVK), emitted light at 549 or 552nm, respectively, and with the increasing content of P1, the electroluminescence efficiencies of the blend devices increased. The optical limiting performance of P1 had been measured at 532nm with nanosecond pulse, the limiting threshold of P1 was 728mJ/cm2, and the throughput of P1 was limited to 344mJ/cm2 for incident fluence as high as 1.1J/cm2. The preliminary electroluminescent results and optical limiting effect of P1 suggested that P1 may be promising as light-emitting polymer and optical limiting material. [Copyright &y& Elsevier]

Abstract: A carbazole compound was synthesized by Knovenagel condensation and characterized by the measurements of 1H NMR, IR and melting point. A multilayer organic light-emitting diode (OLED) using this compound as an active layer was fabricated by vacuum-deposition. This OLED showed a turn-on voltage of approximately 4.5V and a maximum luminance of 910cd/m2. Additionally, the maximum luminous efficiency was found as 0.95cd/A, at this point the device luminance was measured as 146cd/m2 at an operating voltage of 7V. The coordinate value of CIE 1931 was calculated as (x, y)=(0.3843, 0.5345) from the electroluminescence (EL) spectrum, which suggested that the device can emit a yellow-green light. [Copyright &y& Elsevier]

Abstract: A series of ethynyl-linked π-conjugated light-emitting molecules with good photoluminescence properties were designed and synthesized through Pd/Cu-catalyzed Sonogashira coupling reaction. The main structure comprised of different fluorophors (pyrene, carbazole, and fluorene), which were linked with triple bonds in order to be screened for high emission efficiency. Optical properties of these synthesized compounds (I a –I f ) were examined in solutions, thin films and solid states, respectively. All of them showed relative high quantum yields both in solutions (Φ s: 0.70–0.83) and in films (Φ f: 0.17–0.34). Light-emitting diode using I e as an emissive layer was fabricated in the ITO/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS)/I e/2, 2′, 2″-(1, 3, 5)-benzene-triyl)tris[1-phenyl-1H-benzimidazole] (TPBI)/Al configuration. The maximum emission wavelength of the device was 496nm. The maximum luminance and electroluminescence efficiency was 1000cd/m2 and 0.41%, respectively. [Copyright &y& Elsevier]

Abstract: A new emitting material, tetra(β-naphthyl)silane (TNS), was synthesized and used as hole blocking material in organic light-emitting devices (OLEDs). Devices with a configuration of ITO/α-NPB/TNS/Alq3/Al have been constructed, where ITO is indium–tin-oxide, α-NPB is (4,4′-bis[N-(1-naphthyl)-N-phenylamino] biphenyl), and Alq3 is (8-quinolinolato) aluminum. A high performance blue light OLED was obtained, which emits blue light with a peak at 439 nm and starts to emit light at 6 V and the luminance can reach to 3800 cd/m2 at 13 V and 250 mA/cm2. [Copyright &y& Elsevier]

Abstract: Three novel phenyl-substituted poly(p-phenylene vinylene) (PPV) derivatives, BDP-PPV, BDMP-PPV, and BDP-co-BDMP-PPV (1:1), have been successfully synthesized according to the Gilch route. The structures and properties of the monomers and the resulting polymers were characterized by using 1H, 13C NMR, elemental analysis, GPC, TGA, UV–vis absorption spectroscopy, photoluminescence (PL) and electroluminescence (EL) spectroscopy. The EL polymers possess excellent solubility in common solvents, good thermal stability with 5% weight loss temperature of more than 370°C, and higher photostability. The number-average molecular weight (M n) and polydispersity index (PDI) of the polymers were in the range of (1.52–2.53)×105 and 1.22–1.36, respectively. Double-layer light-emitting diodes (LEDs) with the configuration of ITO/polymer/Alq3/Al devices revealed that the copolymer, BDP-co-BDMP-PPV (1:1), possessed the highest luminescence properties, which exhibited maximum luminance of up to 3850cd/m2 at 23.5V, and maximum luminescence efficiency of up to 2.68cd/A. [Copyright &y& Elsevier]

We report the photophysical and electroluminescence (EL) properties of two fluorene-based copolymers, poly{[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl]-alt-[6,6′- bis(3-phenylquinoxaline)-2,2′-diyl]} (Qx-PF) and poly{[9,9-bis(2- ethylhexyl)fluorene-2,7-diyl]-alt-[N,N′-diphenyl-N,N′-bis(4-phenyl)-1,1′-biphenyl-4,4′-diamine]} (TPD-PF). The two copolymers in thin films show blue emission approximately 429-452 nm with relatively narrow bandwidth upon photoexcitation. Electroluminescence has been demonstrated using TPD-PF as the active polymer in the light-emitting electrochemical cell (LEC) with a turn-on voltage at 2.8 V and an EL efficiency of 0.002 cd/A. Due to the improved electron-transporting property, the Qx-PF-based LEC achieves the EL efficiency of 0.07 cd/A, 35 times higher than that of the TPD-PF-based device. Compared to the photoluminescence spectra, EL spectra show enhanced excimer emission, which is primarily related to self-heating of the devices during operation. The main process involved in the decrease of the light intensity during device operation is the electrochemical degradation of the polymer blend. [Copyright &y& Elsevier]

The authors reported organic phototransistors (PTs) with octadecyltrichlorosilane treated SiO2/Si substrate based on anthra[2,3-b]benzo[d]thiophene. The organic PTs show a high mobility of 0.4 cm2 V-1 s-1, a maximum photoresponsivity of about 1000 A/W, and photocurrent/dark-current ratio of around 800 under white light irradiation with 30 μW/cm2. The data are comparable with those of PTs based on amorphous silicon. Meanwhile, it is interesting to see that the devices show a high air-stable property and high photosensitivity via electric-field enhanced process. All these phenomena were attributed to the intrinsic optic-electronic property of the organic semiconductor and optic-electric field effect. [ABSTRACT FROM AUTHOR]