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The emission characteristics and transient electroluminescence (EL) of organic light-emitting diodes (OLEDs) using tris(8-hydroxyquinolinato)aluminum (Alq3) as an emissive layer with LiF/Al cathode and LiF doped Al composite cathode (LiF:Al alloy cathode) were investigated. A device with LiF:Al (1:10) alloy cathode showed the maximum current efficiency of 4 cd/A. The emission characteristics of this device were almost the same as that with LiF/Al cathode. Rise time of the device with LiF:Al alloy cathode was shorter than that of a device with LiF/Al cathode, because the waveform rounding of current density occurred for the device with LiF/Al cathode. [ABSTRACT FROM PUBLISHER]

This study focused on the performance of solution-processed multilayer polymer light-emitting diodes (PLEDs) with both the hole and electron transport layers using poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an active layer. By insertion of both the hole and electron transport layers, improved emission and transient characteristics were achieved for the electro-optical conversion devices. For the multilayer device, the maximum current efficiency of 2.2 cd/A and the short response times of electroluminescence (ca. 30 ns) were achieved. [ABSTRACT FROM PUBLISHER]

This study focuses on the performance of organic light-emitting diodes (OLEDs) using an emissive material with high hole drift mobility, tris[4-(5-phenylthiophen- 2-yl)]amine (TPTPA), which exhibits the highest level of hole drift mobility (1.0 × 10-2 cm2 V-1 s-1) among those reported for organic disordered systems. Clear blue emission was observed from TPTPA which was used as the hole transporting and emissive layer in the OLEDs. The maximum luminance of 1.2 × 104 cd/m2, and the maximum current efficiency of 3.9 cd/A were achieved. The short response times of electroluminescence (ca. 10 ns) were achieved under the application of rectangular-shaped voltages. [ABSTRACT FROM AUTHOR]

Organic electroluminescent diode (OELD) has been investigated for use as a light source of polymeric optical integrated devices. The OLED was fabricated by organic molecular beam deposition (OMBD) technique. The OLEDs were fabricated on both glass and polymeric substrates. The device fabricated on a polymeric substrate shows similar device characteristics to those on a glass substrate. Optical signals of faster than 100 MHz has been created by applying pulsed voltages directly. Optical photo detectors (OPDs) utilizing phthalocyanine superlattice structure provide increased pulse response with optical signals and have response for optical pulse of faster than 1 MHz. [ABSTRACT FROM AUTHOR]

Reports on the electroluminescent (EL) characteristics of the EL diode with evaporated metal-free phthalocyanine (H2Pc) film. Optical measurement of the organic thin film of H2Pc to form EL diode; Findings and discussion of the experiments; Conclusions.

For the purpose of exploring near-infrared emission, the photoluminescence (PL) and electro- luminescence (EL) of N,N′-bis(neopentyl)-3,4:9,10-perylenebis(dicarboximide) (BNPTCD): tris(8-quinolinolato)aluminum (Alq3) mixed films were investigated. It was found that BNPTCD:Alq3 mixed films exhibit PL in the near-infrared wavelength region and that organic light-emitting diodes using Alq3 highly doped with BNPTCD as an emitting layer exhibit near-infrared EL with a peak at 805 nm originating from BNPTCD aggregates. [ABSTRACT FROM AUTHOR]

Examines the spectral narrowing and emission energy shift in organic electroluminescent (EL) diode utilizing 8-hydroxyquinoline aluminum or aromatic diamine multilayer structure. Components of the organic EL diode; Mechanism of spectral narrowing and the emission energy; Results of the confined carriers in the multilayer system.

Abstract: The optical and electroluminescent properties of 3,4,6-triphenyl-α-pyrone (α-pyrone), a new blue fluoresce dye, are investigated using films prepared by wet and dry process and organic light-emitting diodes (OLEDs) fabricated with an α-pyrone-emitting layer. The optical properties of α-pyrone are found to be affected by its crystallinity. In the fabrication of OLEDs, wet processing (spin coating) is shown to be more suitable for preparation of the α-pyrone layer than dry processing (thermal evaporation). The best device performance is obtained for a device prepared using poly (n-vinylcarbazole) as the dye host, and a bathocuproine/tris-(8-hydroxyquinoline)aluminum bilayer as a hole-blocking and carrier-injection layer. The maximum luminance of this device is 3000cd/m2 at a current density of 0.2A/cm2, with a current efficiency of 1.8cd/A at 0.02A/cm2. [Copyright &y& Elsevier]

Abstract: We investigated the transient electroluminescence (EL) and modulation characteristics of red organic light-emitting diodes (OLEDs) consisting of 4-(dicyanomethylene)-2-i-propyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTI) and 5,6,11,12-tetraphenylnaphthacene (rubrene) doped into tris(8-hydroxyquinoline)aluminum (Alq3). The transient EL waveforms showed two components, an initial overshooting peak followed by a constant component, indicating that the excess amount of accumulated charges simultaneously recombine at the moment of onset. This overshoot effect reduced the rise time of transient EL and enhanced the optical output of the OLEDs, and hence the cutoff frequency was increased when the pulse voltage was applied to the device. We demonstrated that the red OLEDs are suitable for use in high-speed switching applications driven at more than 100 MHz, and in electro-optical conversion devices for transmitting video signals. [Copyright &y& Elsevier]

We demonstrate high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent dye doped into a low-molecule material. Methoxy-substituted 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB) was selected as the host material for the phosphorescent dopant fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)3], and organic films were fabricated by spin-coating. A peak external quantum efficiency of 8.2% (29 cd/A), luminous power efficiency of 17.3 lm/W, and luminance of 33,000 cd/m2 were achieved at 9.4 V with a 90 nm-thick emitting layer. Emission from the host TDAPB material was not observed in the electroluminescence (EL) and photoluminescence (PL) spectra. The decrease in efficiencies at a high current is analyzed using the triplet–triplet annihilation model. The high performance for the simple device structure in this study is attributed to excellent film forming properties of the material and efficient energy transfer from the host to dopants. [Copyright &y& Elsevier]

Abstract: The optical and electroluminescent (EL) properties of newly synthesized tris(hexafluoroacethylacetonato)(phenanthroline)samarium(III)mono-methanol [Sm(hfa)3(phen)2MeOH]-based organic light-emitting diodes (OLEDs) were investigated. The as-prepared photoluminescence (PL) spectrum of Sm(hfa)3(phen)2MeOH-doped PMMA film exhibits the peaks at the wavelength around 564, 598, 645 and 710 nm which correspond to the 4G5/2 → 7H5/2, 4G7/2 → 7H7/2, 4G5/2 → 7H9/2 and 4G5/2 → 7H11/2 transitions of the Sm3+ ion, respectively. The best organic light-emitting device performance is obtained for a device using 8 wt.% Sm(hfa)3(phen)2MeOH and 40 wt.% 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4,-oxadiazole doped in poly(N-vinylcarbazole) as a emitting layer. The optimal device exhibits maximum luminance of 135 candela (cd)/m2 at the current density of 0.16 A/cm2, with current efficiency of 0.1 cd/A at the current density of 0.08 A/cm2. The EL spectrum from optimal device has the Commission Internationale De L''Eclairage (CIE) coordinate of (0.60, 0.36). [Copyright &y& Elsevier]