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The authors report excellent white organic light-emitting diodes (WOLEDs) made of 9,9bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(diphenylamino)fluorene (TADPF) or 9,9-bis[4-(di-p-tolyl)aminophenyl]-2,7-bis(9-carbazolyl)fluorene (TAKF). The superposition of a yellow emission coming from the TADPF or TAKF electromer and a blue emission originating from bis(2-(2-hydroxyphenyl)benzothiazolate)zinc gives rise to a pure white-light emission. The multilayer device using TADPF shows a maximum luminance of 5123 cd/m2, a current efficiency of 2.8 cd/A, and Commission Internationale d’Eclairage chromaticity coordinates of (0.33, 0.33). This result is the optimal for WOLEDs based on electromers so far reported. [ABSTRACT FROM AUTHOR]

We demonstrate modification of the indium tin oxide (ITO) surface with an ultrathin layer of hexadecafluorocopper phthalocyanine (F16CuPc) can significantly enhance hole injection as a result of the formation of an interfacial dipole layer. The dipole layer produces a surface potential shift, which reduces the hole injection energy barriers and thus improves the hole injection efficiency. The devices with anode modification exhibit significantly enhanced luminance efficiencies and dramatically decreased operation voltages, compared to devices with the bare ITO anode. The minimum turn-on voltage of 2.6 V and the maximum efficiency of 5.1 cd/A are achieved. [ABSTRACT FROM AUTHOR]

We report an efficient blue light-emitting diode (LED) using N, N′-bis(1-naphthyl)-N, N′-diphenylbenzidine as an emitting layer and tetra(β-naphthyl)silane (TNS) as a hole-blocking layer (HBL). We find that the hole-blocking performance, thermal stability, and film-forming ability of TNS are improved over those of the prototypical hole-blocking material 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The device that used TNS as the HBL exhibits a narrower light emission and higher current efficiency (2.5 cd/A) as compared with the device containing BCP as the HBL. TNS should be promising as an excellent hole-blocking layer in LEDs. [ABSTRACT FROM AUTHOR]

Demonstrates the optical and electroluminescence (EL) properties of light-emitting diodes on an alternating copolymer containing triphenylamine and phenylene units. Observation of EL in semiconducting conjugated polymer; Synthesis of the copolymer using the Horner reaction; Photoluminescence properties.

A new twisted polymer, poly[9,9'-spirobifluoren-2,2'-ylenevinylene-alt-2,5-di(n-buthoxy)-1,4-phenylene-vinylene] (PSBF-PV), which consists of phenylenevinylene chromophores linked through 9,9'-spirobifuorene, was synthesized through the Horner-Emons condensation. PSBF-PV showed strong green emission in solution and film. The single-layer light-emitting diode (LED) exhibited weak emission, and an improved performance with the maximum external quantum efficiency of 0.25% and luminance maxima of 1168 cd/m² was achieved using Alq3 as electron injection layer in double layer LED for PSBF-PV. [ABSTRACT FROM AUTHOR]

A bent ladder-type hexaphenylene with a carbazole core and spiro-linkage is designed and synthesized by using the ortho-linked spirobifluorene. The design eliminates the possibility of forming a positional isomer. As a blue-emitter, the BLHPC shows good thermal and color stability. A simple light-emitting device fabricated from BLHPC exhibits a maximum current efficiency of 1.46 cd/A and a maximum luminance of 505 cd/m2. [ABSTRACT FROM AUTHOR]

Two novel wide-energy-gap molecules, 1,3-bis(9-phenyl-9H-fluoren-9-yl)benzene (mDPFB) and 1,4-bis(9-phenyl-9H-fluoren-9-yl)benzene (pDPFB), suitable for blue phosphorescent host materials, were designed and prepared. The thermal, photophysical, and electrochemical properties as well as electroluminescence characteristics were fully investigated. Both mDPFB and pDPFB possess high singlet (4.0 eV) and triplet (2.8 eV) energies, well energy-matched with the deep-blue phosphorescent dopant, iridium(III) bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). The single crystals of the newly synthesized compounds mDPFB and pDPFB were grown, and their crystal structures were determined by X-ray diffraction. Both molecules adopt a rigid twisted tetrahedral crystallographic conformation, and no facial to facial π−π stacking exists in the solid state. The substituents at the 1,4-positions of benzene enhance the twisted degree of the fluorenyl rings and have predominant influence on the thermal and morphological properties. Both molecules possess excellent thermal stability with decomposition temperatures (Td) of 354 and 386 °C in nitrogen, respectively. Blue phosphorescent organic light-emitting diodes (OLEDs) were fabricated using pDPFB or mDPFB as host materials and FIr6 as a blue phosphorescent dopant with the configuration of ITO/NPB/mCP/host:FIr6/BCP/Ca:Ag. Devices based on the pDPFB host showed a maximum luminous power efficiency of 18.9 lm/W, with CIE coordinates (x, y) of (0.18, 0.33), improved by a factor of over 10 compared with the reference devices based on N,N′-dicarbazolyl-3,5-benzene (mCP) host. We discussed the mechanism and demonstrated that highly efficient blue phosphorescent OLEDs can be achieved in designing host materials which possess matched energy levels with the phosphorescent dopant, with high miscibility to the dopant, and with excellent film-forming ability and thermal and morphological stability. [ABSTRACT FROM AUTHOR]

A series of monodisperse, pyrene-modified oligocarbazoles were synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag molecular beckbone and stable, size-independent absorption, and emission were observed from these oligomers in solutions because their conjugation length was confined. Oligorners with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures (types 1-4) based on these oligomers were fabricated and investigated. Pyrene- modified carbazole oligorners exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 presented an external quantum efficiency of 0.69% and a maximum brightness of 1782 cd/m2 at 13.5 V, which indicated these oligomers were promising optoelectric materials. [ABSTRACT FROM AUTHOR]