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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]

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 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]