Papers by Keyword: Electroluminescence

Abstract: A bright blue emission material, bis {(benzimidazol-2-yl) Pyridenato} magnesium (MgBIP) used for organic light emitting devices, has been synthesized. The decomposition temperature was observed at 517 °C and no melting transition (Tm) of MgBIP was observed up to 400 °C. For three-layer LED devices with the configuration of ITO/NPB/MgBIP/ Alq₃/MgAg, the white light emission covering the whole visible region from 400 to 750 nm with the maximum brightness of 2770 cd/m² and current density of 304 mA/cm² was observed.

Abstract: We demonstrated high-speed imaging of photoluminescence (PL) and electroluminescence (EL) for not only band-to-band but also multiple deep-level emissions in a multicrystalline Si solar cell. We used a cooled InGaAs camera with a photosensitive range of 900 - 1700 nm equipped with band-pass filters for the selective detection of various deep-level emissions. The exposure time for imaging was only 1 - 10 seconds. Comparisons of the present PL images with the microscopic PL mappings confirmed for us that essentially the same luminescence patterns were obtained.

Abstract: An emission material, bis{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Magnesium (MgNIP) used for organic light emitting devices, has been synthesized. The decomposition temperature was observed at 510°C and no melting transition (Tm) of MgNIP was observed up to 400°C. The emission spectrum of organic emitting device using MgNIP as emitted layer exhibits a broad maximum at 531 nm. The color of the emitted light is in the orange region in the CIE coordinate of x = 0.46 y = 0.46.

Abstract: The electroluminescence properties of ferromagnetic GaMnSb/GaAs diodes have been investigated. It has been found that diodes properties are significantly dependent on GaMnSb layer electrical properties. The intensity of electroluminescence of the diode with semiconductor GaMnSb contact is relatively low, that is due to a high potential barrier at the interface. In case of metallic GaMnSb/GaAs contact high hole injection efficiency provides relatively high electroluminescence intensity. Investigated light-emitting diodes can be prospective for investigation of spin injection effects.

Abstract: We report preparation of Tb3+ or Eu3+ doped zirconia nanoparticles by sub- and supercritical hydrothermal reaction and luminescence properties. Experiments were performed by a flow-type hydrothermal reaction system. We investigated the effect of the reaction temperature on crystal structure, particle size and photo-, electro-luminescence properties. Reaction temperature was varied in the ranges of 150 to 400 C and reaction pressure was fixed to 30MPa. Characteristics of the products were performed by XRD, TEM, SEM-EDS and PL, EL measurements. The product transformed from amorphous zirconium hydroxide to tetragonal ZrO2 with an increase in the reaction temperature, regardless of the doped ion species. The ZrO2:Eu particles obtained at 400C were spherical with around 5 nm in diameter. ZrO2:Eu nanoparticles obtained under supercritical water condision showed typical photoluminescence spectra of f-f transition of Eu3+; however ZrO2:Tb nanoparticle obtained under the same condition showed no photoluminescence. Furthermore, the ZrO2:Eu nanoparticles obtained at 400 C showed high electroluminescence properties at electric field of 350V and 1kHz.

Abstract: a fluorine functionalized 1,10-phenanthroline ligand, 3-ethyl-2-(2-fluorophenyl) imidazo[4,5-f]1,10-phenanthroline(EFPIP) and the corresponding red-emitting Eu(ΙΙΙ) complex Eu(DBM)₃(EFPIP) (DBM = dibenzoylmethanate) was synthesized and the photophysical properties and electroluminescent(EL) performances were researched. When Eu(DBM)₃(EFPIP) was used as emitting material in organic devices, the maximum efficiency and luminance of red emission achieved from the EL device with the configuration of ITO/m-MTDATA (30 nm)/NPB (20 nm)/ x wt% Eu(DBM)₃(EFPIP) doped in CBP (30 nm)/Bphen (20 nm)/Alq₃ (20 nm)/LiF (0.8 nm)/Al were 3.6 cd/A and 563 cd/m², respectively. Compared with the previously reported devices based on methyl or chlorine substitute Eu(ΙΙΙ) complexes, the EL performances of the device using Eu(DBM)₃(EFPIP) as an emitter was significantly enhanced due to the introduction of fluorine.

Abstract: The synthesis, structure and luminescent properties of a cyclometalated iridium (ΙΙΙ) complex are reported. The cyclometalated ligand and auxiliary ligand are 2-(2-fluorophenyl)-benzothiazole (F-BT) and acetylacetone (Hacac), respectively. The complex (F-BT)2Ir(acac) exhibits bright photoluminescence (PL) at room temperature with a high solution PL quantum efficiency of 0.62. Organic electroluminescent (EL) devices are fabricated employing (F-BT)2Ir(acac) as an emissive dopant in 4,4′-N,N′-dicarbazole-biphenyl (CBP) host. EL efficiency shows weak dependence on doping concentration and current density. While the optimized device exhibits a peak efficiency of 28.5 cd/A and a maximum brightness of 49880 cd/m2. An efficiency of 22.7 cd/A at 100 mA/cm2, 80% of the maximum, can be achieved.

Abstract: Cathodoluminescence (CL) in SEM and electroluminescence (EL) techniques are widely used for investigation of optical properties of electronic structures. It is assumed that the CL signal represents the local properties of the region irradiated by the electron beam. However, this assumption is true if there is no electric field in the excitation region. In the opposite case the electron-hole pairs generated by the electron beam are separated by the electric field and the local voltage source is generated. The voltage is distributed all over the structure through resistance paths and it causes a current flow, which presence affects the registered CL signal. A range of this effect depends on the resistance distribution within the structure and on the value of electron beam current. The range may be much longer than the diffusion length of minority carriers. When EL signal is measured in SEM, it represents the mean properties of the whole structure. The comparison of the CL results with the EL ones detected in SEM gives valuable information about the examined structures, as will be shown in the present investigations. The AlGaAs/GaAs heterostructures with 8 nm InGaAs quantum well have been examined. For that aim also special test structures for CL and EL measurements have been formed on standard epitaxial structures.

Abstract: Soluble polypyrrole was obtained by naturally oxidizing pyrrole in air at room temperature for one to four years. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and ultraviolet-visible absorption spectroscopy were employed to characterize the chemical structures of the naturally oxidized polypyrrole. The electroluminescence from the naturally oxidized polypyrrole was recorded. The electroluminescence of the naturally oxidized polypyrrole was broad with its peak located at about 480 nm. Prototyped thin-film display panels were developed using the naturally oxidized polypyrrole as active medium.

Abstract: If there are local defects in the solar cell module, the output efficiency of the module will decrease. This article introduces the detection of local defect of solar cell module based on the infrared image technology. It finally establishes an image library which contains some infrared images of seven kinds of defects and a basic standard which can judge the quality of the module. The reasons of some defects are listed in the article. The unqualified rate will greatly decrease for the technique. The research is helpful to eliminate the module that contains recessive defects. The life of the modules also will be extended.