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In the present work SiNx thin films, grown by PECVD technique using dichlorosilane, were used in electroluminescent device (EL) structure. Series of experiments were carried out by varying the flow of H2 and SiH2Cl2, and after all the depositions and subsequent result analysis, a set of conditions were identified as M1, M2, M3, and M4 according to the physical thickness of the samples, their PL emission color and intensity of the emission. M3 and M4 conditions were identified as of key interest because of their intense whiteemission. After the photoluminescence (PL) analysis, EL was carried out, and a device structure was fabricated for the study. Role of quantum confinement effect was found for the white emission from the calculated nanocrystals from 2.5 to 5 nm. These results could be an important step for the establishment of optoelectronic devices such as silicon LEDs in the near future. [ABSTRACT FROM AUTHOR]

All-inorganic quantum dot light-emitting diodes (QLEDs) with excellent device stability have attracted significant attention for solid state lighting and flat panel display applications. However, the performance for the present all-inorganic QLEDs is far inferior to that of the well-developed QLEDs with organic charge transport layers. Our all-inorganic full-colour QLEDs show the maximum brightness and efficiency values of 21,600 cd/m 2 and 6.52%, respectively, which are record-breaking among the existing all-inorganic QLEDs. The outstanding performance is achieved by an efficient design of device architecture with solution-processed charge transport layers (CTLs). Meanwhile, the ultrathin double-sided insulating layers are inserted between the quantum dot emissive layer and their adjacent oxide electron transport layers to better balance charge injection in the device and reduce the quenching effects for inorganic CTLs on QD emission. This study is the first account for high-performance, all-inorganic QLEDs insightfully offering detailed investigations into the performance promotion for inorganic electroluminescent devices. [ABSTRACT FROM AUTHOR]

The performed evaluation consisted of two phases: measurement of the illumination levels of (new) LED system and carrying out the public opinion poll on the subjective visual performance of LED in traffic lights. The results of the measured levels of illumination show that deposition of dirt considerably affects its values. The survey results confirm an overall positive impression on LED performances in traffic lights. [ABSTRACT FROM AUTHOR]

A series of new monodisperse oligofluorenes mainly based on 9,9-bis(2-methylbutyl)fluorene units whose rigid core has been extended with 1-(trifluoromethyl)benzene termini ( F1, F2, F3 ) or hydrogen termini ( 8, 12 ) are designed and synthesized. The effects of conjugated length and end-capper groups on thermal, optical and electrochemical properties are studied. The oligofluorenes exhibit a narrower bandgap, higher HOMO, lower LUMO and red-shift on absorption/emission spectra with increasing number of fluorene units. Based on the comparing data of the compounds which have the same number of fluorene units, oligomers terminaled with electron-withdrawing group have a higher T g , narrower bandgap and red-shifts on absorption/emission spectra. Furthermore, in order to investigate the possibility of using these molecules as emitters in organic light-emitting diodes (OLEDs), solution-processed OLEDs with structure of ITO/PEDOT:PSS/PVK:oligomers/CsF/Al are fabricated. All devices based on the oligomers emit deep-blue light peaked at ca. 392–420 nm. Among these devices, the device based on hydrogen-terminated compound ( 12 ) displays the best performance with a high maximum luminance of 670 cd/m 2 , a low turn-on voltage of 4.20 V, and a maximum luminance efficiency of 0.38 cd/A. [ABSTRACT FROM AUTHOR]

The Escherichia coli(E. coli) isGram negative bacteria, that normally live in the digestive tracts of humans and animals, can cause bloody diarrhea, severe anemia or kidney falureand other illnesses which can lead to death.Systemic therapy with antibiotic cause bacteria resistant. So, an alternative method is needed, one of them is Photodynamic therapy (PDT).This research aims to investigate antimicrobial photodynamic effects of the light emitting diode (LED) activated bymagnetic fields 1.8 mT irradiation to bacteria viability . To determine the antimicrobial effect of treatments, three measurements of bacterial colony growth (in %) were carried out. Three measurements groups as follow: Groups I to measurements the effects of LED irradiation by varying wavelength (469nm, 541 nm and 626 nm); Groups II to measurements effects of magnetic fields 1.8 mT to antimicrobial efficacy; Groups III to determine the effects and efficacy of LED 541 nm and magnetic fields irradiation with varying LED intensity (0.62, 2.50, 6.27, and 8.21) mW/cm2 and time irradiation (20, 30, 40, 50) minutes, respectively. The suspension was planted on sterile media and incubated at a temperature of 37°C for 24 hours. After incubation, the number of colony-forming units per milliliter (CFU/ml) was determined. The results were analyzed by analysis of variance (ANOVA) and the Tukey test. A P value ⩽0.05 was considered to indicate a statistically significant difference. The LED treatment group 469 nm, 541 nm and 626 nm resulted in statistically significant decrease of CFU (p<0.05) compared to each other. The LED 541 nm treatment group with magnetic fields resulted significantly differ with treatment group without magnetic fields. The LED 541 nm treatment with magnetic fields 1.8 mT at various light intensity and time irradiation resulted significantly differ each other (p<0.05). LED irradiation with intensity 6.27 mW/cm2 and time irradiation 50 minutes (energy dose 18.81 J/cm2) resulted highest decreases the number of bacteria E.coli 80%. LED irradiation combined by magnetic fields can improve the efficacy of antimicrobial photodynamic effects. [ABSTRACT FROM AUTHOR]

The article offers brief information about light emitting diode (LED) lights including the CXA High-Density LED Arrays from Cree Lighting Co., 215Im/W LED tube from Osram AG and TruColour CMI lamp from Sylvania Lighting.

We have investigated the effect of ambient gases on the structural, electrical and optical characteristics of indium tin oxide (ITO) thin films intended for use as anode contacts in organic light emitting diode (OLED) devices. These ITO thin films are deposited by radio frequency magnetron sputtering under different ambient gases (Ar, Ar+O2 and Ar+H2) at 300°C. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0·5 to 5 sccm and from 0·1 to 1 sccm, respectively. The intensity of the (400) peak in the ITO thin films increases with increasing H2 flow rate, while the (400) peak was nearly invisible in an atmosphere of Ar+O2. The electrical resistivity of the ITO thin films increases with increasing O2 flow rate, whereas the electrical resistivity decreases sharply under an Ar+H2 atmosphere and is nearly similar regardless of the H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition is mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. All the films show an average transmittance of >80% in the visible range. The optical band gap of the ITO films increases with increasing H2 flow rates, whereas the optical band gap of the ITO films deposited in an O2 atmosphere decreases with increasing O2 flow rates. The current density and the luminance of the OLED devices with ITO thin films deposited in 1 sccm of H2 ambient gas are the highest among all the films. The optical band gap energy of ITO thin films plays a major role in OLED device performance, especially the current density and luminance. [ABSTRACT FROM AUTHOR]

The article discusses issues relevant to designing a light emitting diode (LED) lighting in relation to safety and performance. Concepts that need to be understood in relation to LED are LED light source, LED module, LED lamp and LED luminaire. Photobiological damage is one of the safety concerns in LEDs.

The aim of this study was to evaluate the influence of previous enamel etch and light emitting diode (LED) curing on gap formation of self-etch adhesive systems in Class I composite restorations after thermomechanical aging (TMA). Thus, on 192 human molars, a box-shaped Class I cavity was prepared maintaining enamel margins. Self-etch adhesives (Clearfil SE and Clearfil $3) were used to restore the preparation with a microhybrid composite. Before application of the adhesives, half of the teeth were enamel etched for 15 seconds with 37% phosphoric acid; the other half were not etched. For the photoactivation of the adhesives and composite, three lightcuring units (LCUs) were used: one polywave (Ultra-Lume LED 5, UL) and two single-peak (FlashLite 1401, FL and Radii-cal, RD) LEDs. After this, epoxy resin replicas of the occlusal surface were made, and the specimens were submitted to TMA. New replicas were made from the aged specimens for marginal adaptation analysis by scanning electron microscopy. Data were submitted to Kruskal-Wallis and Wilcoxon tests (α=0.05). Before TMA, when enamel was etched before the application of $3, no gap formation was observed; however, there were gaps at the interface for the other tested conditions, with a statistical difference (p≤0.05). After TMA, the selective enamel etching previous to the $3 application, regardless of the LCU, promoted higher marginal adapta tion compared to the other tested groups (p≤0.05). Prior to TMA, higher marginal integrity was observed, in comparison with specimens after TMA (p≤0.05). With regard to Clearfil SE and Clearfil Tri-S cured with FL, no differences of gap formation were found between before and after aging (5.3 ± 3.8 and 7.4 ± 7.5, respectively), especially when the Clearfil Tri-S was used in the conventional protocol. When cured with RD or UL and not etched, Clearfil Tri-S presented the higher gap formation. In conclusion, additional enamel etching promoted better marginal integrity for Clearfil Tri-S, showing it to be an efficient technique for Class I composite restorations. The two-step self-etch adhesive was not influenced by selective enamel etching or by the LED-curing unit. [ABSTRACT FROM AUTHOR]

Abstract: For the purposes of reducing the non-uniformity of images in LED display panel further, propose an algorithm. First, analyze the causes of the problem which images in LED display panel have shortcomings of the non-uniformity of images. Second, introduce the development course of the correction techniques which are used to reduce the nonuniformity of images. Simultaneously, point out the ground that location correction must be carried out. Third, for the example of a LED display panel which is spliced by modules, construct the algorithm model. Forth, describe the realization steps of the algorithm in accordance with this constructed model. Finally, this algorithm is implemented in a LED display panel, whose resolution is 640×480. Experimental results show that this algorithm is able to reduce the non-uniformity of images obviously. [Copyright &y& Elsevier]

A 460 nm InGaN/GaN light-emitting diode (LED) with a self-textured oxide mask (STOM) structure was demonstrated using metal-organic chemical vapor deposition (MOCVD). The fabricating of STOM employed a low temperature (850°C) GaN template to form a textured surface onto which the SiO2 mask was fabricated. Measurements of optical and electrical properties of the LED showed that the corrugated STOM structure increases light scattering and reflection to enhance light output, and also reduces the dislocations to inhibit non-radiative recombination. Under an injection current of 20 mA, the forward voltages of the STOM-LED and conventional LED (C-LED) were nearly identical at 3.41 V. The leakage current of the STOM-LED was lower than that of C-LED, and the STOM-LED's light output power was approximately 47% higher (at 20 mA). This significant improvement was attributed to the enhanced light extraction via the STOM array. [ABSTRACT FROM AUTHOR]

A novel broadband emission phosphor Ba3LiMgV3O12: Eu3+ is synthesized by a solid-state reaction method. The X-ray diffraction analysis indicate that Ba3LiMgV3O12 single phase obtained at 800°C show the same crystal structure with Ba3V2O8. The excitation and emission spectra exhibit that the excitation band distributes between 260 nm and 395 nm and peaks at 343 nm, emission band covers from 400 nm to 600 nm and centers at 500 nm, respectively. The emission band peaks at 613 nm originated from charge transfer transitions from Ba3LiMgV3O12 host to doped Eu3+ ions can be observed when the Eu3+ ions doped into the host. White light can be obtained with coordinate of (0.312, 0.321) from the fabricated light emitting diodes (LEDs) with the doped content of Eu3+ ions at 5.0 mol%, which shows that the phosphor is a promising single-phase phosphor for near ultraviolet (NUV) LEDs. [ABSTRACT FROM AUTHOR]

Cadmium sulphide films having energy band gap of 2.4 eV found applications in solar cells and electroluminescent devices. CdS polycrystalline films have been prepared on ultra-clean glass substrate by screen-printing technique and then sintered in air. Optimum conditions for preparing good quality screen-printed films have been found. The optical band gaps 'Eg' of the CdS films were determined from the UV transmission spectroscopy and were found to be 2.47eV. The Wurtzite structure of CdS films was confirmed by X-ray diffraction analysis. DC conductivity and activation energy of films was also measured in vacuum by two-probe technique. [ABSTRACT FROM AUTHOR]

Green emitting alternating current thin film electroluminescent devices were fabricated on glass substrates in the conventional MISIM structure using ZnGa2O4:Mn as the active layer. The devices were fabricated varying the deposition time of the active/phosphor layer at two different substrate temperatures, 500 and 600°C. The active layer and top dielectric layer were deposited using rf magnetron sputtering technique. All devices gave an emission in the green region of the visible spectrum even without any post deposition annealing. The EL emission could be de-convoluted into two/three peaks attributed to the 4T1 - 6A1 transition of Mn2+ centers at various sites in the host lattice. The intensity of the 502 nm EL emission was found to increase with active layer thickness. The luminance versus voltage plots exhibit an increase in threshold voltage with increase in phosphor layer thickness. The purity of the EL emissions is gauged using CIE coordinates that are found to lie in the green region of the chromaticity diagram. [ABSTRACT FROM AUTHOR]

Transparent Ti-doped zinc oxide (TZO) thin films with high conductivity were fabricated using radio frequency (rf) magnetron sputtering on glass substrates. The material properties of the TZO films correlated with sputtering parameters were discussed. The TZO thin films with thickness of 258.5-nm-thick were used as anodes of organic light emitting diode devices and the devices exhibited lower turn-on voltage (3 V) and higher current efficiency than the commercial indium tin oxide (ITO) anodes. The TZO thin film may be a potential alternative to an ITO anode due to its low operating voltage, low price, and non-toxicity. [ABSTRACT FROM AUTHOR]

A method for improving the uniformity of the radiation light from dental light-curing units (LCUs), and the effect on the polymerization of light-activated composite resin are investigated. Quartz-tungsten halogen, plasma-arc, and light-emitting diode LCUs were used, and additional optical elements such as a mixing tube and diffusing screen were employed to reduce the inhomogeneity of the radiation light. The distribution of the light intensity from the light guide tip was measured across the guide tip, as well as the distribution of the surface hardness of the light-activated resin emitted with the LCUs. Although the additional optical elements caused 13.2-25.9% attenuation of the light intensity, the uniformity of the light intensity of the LCUs was significantly improved in the modified LCIJs, and the uniformity of the surface hardness of the resin was also improved. Our results indicate that the addition of optical elements to the LCU may be a simple and effective method for reducing inhomogeneity in radiation light from the LCUs. [ABSTRACT FROM AUTHOR]

This paper highlights the metrological analysis of the diffuse transmitter based on the integrating sphere with the cosine radiation sources. We propose novel simplified calibration methods of diffuse emitters. [ABSTRACT FROM AUTHOR]

Flip-chip bonding is a kind of chip packaging technology, which can make fabricated chips lighter and smaller Thermo-ultrasonic flip-chip bonding is a technology that directly joins gold pad and gold bump. This study combines principle component analysis and gray relational analysis to determine the optimal processing parameters for multiple quality characteristics of light emitting diodes (LEDs). The quality characteristics of this experiment include the candle light, forward voltage, and leakage current of LED and thrust value. First, this study determines the processing parameters that may affect the thermo-ultrasonic flip-chip bonding with the L18 orthogonal array, including substrate temperature, bonding downforce, ultrasonic working time, ultrasonic power, and rising and delay time of tool head bonding. Then, the gray relational analysis is applied to indicate the optimal processing parameters for the multiple quality characteristics of LED. Since the Taguchi method only takes one single quality characteristic into consideration, this study applies the Taguchi method to reduce the number of thermo-ultrasonic flip-chip bonding experiments. The experimental results prove that the optimal LED has good integral quality, which is above industrial standard. [ABSTRACT FROM AUTHOR]

We report the enhancement of the electroluminescent property of top emitting organic light emitting diodes (TEOLEDs) using thermally evaporated copper oxide (CuOx) as a hole injection layer (HIL) between UV ozone-treated silver (Ag) anodes and 4,4'-bis[N-(l-naphthyl)-N-phenylamino]biphenyl (α-NPD). The operation voltage of TEOLEDs at 1 mA/cm2 decreased from 6.2 to 5.0 V as a 2 nm thick CuOx. layer was used as the HIL. α-NPD layers were separately in situ deposited on both Ag and thermally evaporated CuOx-coated Ag (Ag/CuOx and their interface dipole energies were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of Ag/CuOx. is higher by 0.53 eV than that of Ag. The corresponding interface dipole energies were -0.93 eV for Ag and -0.88 eV for Ag/CuOx. As a result, CuOx. plays a role in reducing the hole injection barrier from 1.63 to 0.96 eV, resulting in a decrease in the turn-on voltage of TEOLEDs. [ABSTRACT FROM AUTHOR]

Bluish green-emitting Eu2+-doped barium silicate (Ba2Si3O8:Eu2+) phosphor was synthesized via a conventional solid-state reaction chemistry, and Eu concentration and firing temperature were optimized toward its highest luminescent efficiency. Ba2Si3O8:Eu2+ phosphor could be excited under near-UV wavelengths and exhibited a broad emission band (5d → 4f transition of Eu2+) due to the strong coupling of Eu activator with the surrounding host. Phosphor-converted (pc) light-emitting diode (LED) was fabricated by combining Ba2Si3O8:Eu2+ phosphor with a near-UV LED. To fabricate white LED with a high color rendering index, a highly efficient orange-emitting ZnCdSe/ZnSe core/shell quantum dot was incorporated with an unconventional layered design into the above Ba2Si3O8:Eu2+ phosphor-based pc-LED and their electroluminescent properties are described. [ABSTRACT FROM AUTHOR]

An Eu2+-activated BaSi7N10 cyan phosphor for UV-pumping white light-emitting diodes (LEDs) was successfully synthesized by direct gas reduction and nitridation of the homogeneous oxide precursor of a BaO-SiO2-Eu2O3 system in flowing NH3 and CH4 mixture gas. The phase purity, morphology, chemical composition, and luminescence properties were investigated. The effect of activator concentration on the optical properties of Eu2+ in BaSi7N10 was discussed. The synthesized powders have a nearly pure BaSi7N10 phase and consist of microsized particles. Eu2+-doped BaSi7N10 phosphors absorb strongly in the UV part of the electromagnetic spectrum and exhibit an intense cyan emission band centered at 482-500 nm, which agrees with earlier papers. The optical properties depend greatly on the Eu2+ concentration. Under an UV excitation, BaSi7N10:Eu2+ phosphors doped with a 20 atom % activator give the best luminescent properties, such as high emission intensity, high quantum efficiency, and very low thermal quenching, which suggests that Eu2+-doped BaSi7N10 can be a good green-blue phosphor for UV-pumping white LEDs. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrated an organic light emitting device based on both lithium fluoride (LiF)-doped hole transporting layer (HTL) and electron transporting layer (ETL). The optimization LiF dual doping device shows dramatic improved luminance and current efficiency. The maximum luminance and current efficiency are 28,180 cd/m² and 4.7 cd/A, respectively, for the dual doping device and 12,320 cd/m² and 3.7 cd/A, respectively, for the traditional LiF/Al cathode device. Furthermore, the maximum current efficiency shows a decline proportion of 25% for the LiF dual doping device and 46% for the traditional LiF/Al cathode device. Such improved properties are attributed to the enhanced carrier transporting and balanced numbers of holes and electrons injected into the emitter layer by LiF dual-doped HTL and ETL. [ABSTRACT FROM AUTHOR]

A H3BO3 or B2O3 flux was added to a mixture of BaS, EuS, Al, and S to synthesize a Eu-doped cubic BaAI2S4 phosphor. The formation temperature of the cubic BaAI2S4 phase was lowered to 600°C, which was 60°C below the temperature of a case without a flux. To improve the crystallinity and color purity, a two-step annealing process that involved low temperature annealing (130°C for H3BO3 and 400°C for B,03) was proposed for a uniform immersion of a flux into a starting mixture and a high temperature annealing (600°C) for the formation of BaAl2S4. The phosphor synthesized by the two-step process with a 2 wt % H3BO3 flux showed a distinct cubic BaAI2S4 phase and a strong photoluminescence (PL) intensity at 475 nm. The PL intensity was 6.6 times stronger than that of the phosphor without a flux. The phosphor synthesized with a B2O3 flux showed only an orthorhombic phase, while direct annealing at 600° with the flux showed a mixture of cubic and orthorhombic phases. The role of the fluxes in the formation mechanism of the cubic and orthorhombic BaAI2S4 phases was described. [ABSTRACT FROM AUTHOR]

Highly efficient white phosphorescent organic lightemitting diodes with a mixed-host structure are developed and the device characteristics are studied. The introduction of a hole-transport-type host (N, N′- dicarbazolyl-3-3-benzen (mCP)) into an electrontransport- type host (m-bis-(triphenylsilyl)benzene (UGH3)) as a mixed-host emissive layer effectively achieves higher current density and lower driving voltage. The peak external quantum and power efficiency with the mixed-host structure improve up to 18.9% and 40.9 lm/W, respectively. Moreover, this mixed-host structure device shows over 30% enhanced performance compared with a single-host structure device at a luminance of 10,000 cd/m² without any change in the electroluminescence spectra. [ABSTRACT FROM AUTHOR]

In this paper, we report two easily synthesized pure blue-emitting phosphorescent Cu(I)-based emitters. The phosphorescent nature of the blue emissions (λem = 442 and 450 nm) has been identified by both theoretical calculations and experimental data. The blue emissions are the closest to pure blue light among phosphorescent Cu(I) complexes, and their photoluminescence characters are comparable with those of reported noble metal complexes. An electroluminescent device using one of the blue-emitting emitters is fabricated, and a maximum brightness of 1140 cd/m2 is achieved. [ABSTRACT FROM AUTHOR]

A two-stage method for the preparation of Eu[sup2+]-doped Ca[sub3]SiO[sub4]CI[sub2] is reported. It was observed that the emission intensity is significantly enhanced up to 30% by the two-stage method. The critical concentration of Eu[sup2+] was found to be 0.01 mol % and the critical radius was -31.9 A. The broad excitation band and strong emission indicate that the Ca[sub3]SiO[sub4]Cl[sub2]:Eu[sup2+] phosphor could be a good green-phosphor candidate for creating white light in phosphor-converted white light-emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]

We have developed high-efficiency red organic light emitting diodes (OLEDs) incorporating 1,3,5-tris(1-pyrenyl)benzene (TPB3) as the host material and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the dopant. The highly efficient energy transfer, which arose as a result of (i) perfect overlap between the photolurninescence spectrum of TPB3 and the absorption spectrum of DCJTB and (ii) the high fluorescence quantum yield of TPB3, allowed us to fabricate red OLEDs exhibiting improved efficiency. A device having the configuration of indium-tin oxide/ N,N'-bis(1-naphthyl)-N,N'-diphenyl-1, 1'-biphenyl-4,4'-diamine/TPB3:DCJTB (2%)/LiF/Al exhibited a maximum luminance at 13.5 V of 70,600 cd/m², ca. four times higher than that of the device incorporating Alq3 as the host material at the same potential. The device's current efficiency was 4.38 cd/A; its power efficiency was 2.12 lm/W at 20 mA/cm². The current and power efficiencies were greater than 4 cd/A and 1 lm/W, respectively, over a large range of potentials (3.5-13.5 V), with good Commission lnternationale de l'Eclairage coordinates of (0.63, 0.37). These results indicate that searching for a suitable host material is a promising approach toward achieving high-efficiency red OLEDs. [ABSTRACT FROM AUTHOR]

New electroluminescent copolymers with fluoro groups in vinylene units, poly(2-(3'-dimethyloctylsilylphenyl)-p-phenyl-enevinylene-co-p-phenylenedifluorovinylene)s (SiPhPPVPDFVs), have been synthesized by the Gilch polymerization. The fluoro groups were introduced onto the vinylene units to increase electron affinity of the copolymers. The HOMO energy levels of the copolymers were between 5.30-5.35 eV. The EL spectra of devices with the configuration of ITO/PEDOT:PSS/polymer/Al showed maximum peaks between 526-560 nm. By adjusting the feed ratios of PPDFV in SiPhPPVPDFVs, the CIE coordinates moved from yellow to green. The luminescence efficiencies of the copolymers at room temperature ranged from 0.35-2.03 cd/A. SiPhPPVPDFV3 showed the maximum brightness of 4451 cd/m² and the highest luminescence efficiency of 2.03 cd/A. Introduction of up to 30% of PPDFV in the copolymers with m-SiPhPPV enhanced the device performance to result in high current density, brightness and efficiency due to increased electron injection ability caused by the presence of fluoro groups in the vinylene units. [ABSTRACT FROM AUTHOR]

The, novel phosphors of KSrPO4 doped with Eu2+, Tb3+, and Sm3+ were synthesized by solid-state reaction, and their luminescence properties were investigated. The phosphors show pure three-basal-color (red-green-blue) luminescence in the ClE1931 chromaticity diagram, and it was observed that the concentration quenching was dependent on the different dopant contents. This series of phosphate-based phosphors shows higher thermally stable luminescence, which was found to be better than commercially available Y3Al5O12:Ce3+ phosphor at temperatures higher than 200°C. Considering the situation of high color-rendering index and chemical stability, we have demonstrated that KSrPO4:Ln (Ln = Eu, Tb, Sm) are potentially useful new scintillation materials for white-light-emitting diodes. [ABSTRACT FROM AUTHOR]

Eu2+ and Mn2+ co-doped a- and β-Ca2P2O7 are prepared by solid-state reaction. An orange emission band originating from the 4T1(4G)-6A1(6S) transition of Mn2+ is observed in both phases upon UV excitation through energy transfer from Eu2+ to Mn2+ Photoluminescence and energy transfer in α-Ca2P2O7:Eu2+, Mn2+ are investigated as a function of Mn2+ concentrations. The energy transfer rates are calculated based on the analysis of the luminescence dynamical process as well as fluorescence lifetime measurements. The intensity ratios of the orange to blue band as a function of Mn2+ concentrations are also calculated and the results are in good agreement with that obtained directly from emission spectra. A white light emitting diode (LED) fabricated through the integration of a GaN near-UV chip and two phosphor blends (α-Ca2P2O7:Eu2+, Mn2+ blue-orange phosphor and Ba2SiO4:Eu2+ green phosphor) into a single package shows a warm white light of 3797 K correlated color temperature, a good color rendering index (CRI) of 84, and a luminescent efficiency of 11 lm/W with color coordinates of x 0.39, y = 0.40. Moreover, the CRI can be improved to 94 by using blue Ca2(PO4)3Cl:Eu2+ phosphor added to the two phosphor blends. [ABSTRACT FROM AUTHOR]

A facing target sputtering (FTS) system with a configuration of vertically parallel facing Al targets and a substrate holder perpendicular to the Al target plane was designed for direct sputtering of Al cathode on organic layers at a low substrate temperature. The linear FTS system has a linear twin target gun with ladder-type magnet arrays for more effective and uniform confinement of high-density plasma. Due to more effective confinement of high-density plasma and a perpendicularly placed substrate position, we were able to deposit an Al cathode layer directly on an organic layer at a low temperature of ∼50°C without an additional substrate cooling system. It was found that organic light-emitting diodes (OLEDs) with linear FTS-grown Al cathodes have a lower leakage current density than that of OLEDs with dc-sputtered Al cathodes. The leakage current of OLEDs with linear FTS-grown Al cathodes is similar to reference OLEDs with Al cathodes grown by thermal evaporation. The low leakage current density at reverse and forward bias demonstrates that there is no plasma damage effect caused by the bombardment of energetic particles. This indicates that the FTS system with ladder-type magnet array could be effective in direct Al cathode sputtering on OLEDs or organic photovoltaics. [ABSTRACT FROM AUTHOR]

This review thoroughly accumulated information regarding new technologies for state-of-the-art light curing of resin composite materials. Visible light cured resin-based composites allow the dentist to navigate the initiation of the polymerization step for each layer being applied. Curing technology was regularly subjected to changes zduring the last decades, but meanwhile the LED era is hilly established. Today four main polymerization types are available, i.e. halogen bulbs, plasma arc lamps, argon ion lasers, and light emitting diodes. Additionally, different curing protocols should help to improve photopolymerization in terms of less stress being generated. Conclusions were: (1) with high-power LED units of the latest generation, curing time of 2 mm thick increments of resin composite can be reduced to 20 seconds to obtain durable results: (2) curing depth is fundamentally dependent on the distance of the resin composite to the light source, but only decisive when exceeding 6 mm: (3) polymerization kinetics can be modified for better marginal adaptation by softstart polymerization; however, in the majority of cavities this may not be the case; (4) adhesives should be light-cured separately for at least 10 seconds when resin composite is applied directly; (5) photocuring through indirect restorations such as ceramics is still a problem, therefore, both dual-cured adhesives and dual-cured composites and resin coating in any way are recommended: and (6) heat generation with high-power photopolymerization units should not be underestimated as a biological problem for both gingival and pulpal tissues. [ABSTRACT FROM AUTHOR]

We investigated the effect of atmospheric-pressure plasma (APP) and low-pressure plasma (LPP) treatments on the performance of organic light emitting diodes (OLEDs) with an indium tin oxide (ITO) layer. The Owens-Wendt and Lifshitz-van der Waals acid-base methods revealed that the increase of surface energy was mainly attributed to polar component (-y~) and Lewis base (-y) interactions, respectively, independent of either APP or LPP treatments. Unlike APP treatment, LPP treatment more plentifuIl~' produced reactive oxygen species in the plasma. Therefore, the LPP-treated ITO surfaces slowly proceeded with reorientation compared to APP-treated ITO. The carbon content in untreated ITO was approximately 0.045%, while those of Ar APP-, Ar/02 APP-, and 02 LPP-treated ITO were 0.014,0.011, and 0.010%, respectively, mostly containing incorporated reactive oxygen. The 02 LPP-treated surface showed more uniform roughness than Ar or Ar/O2 APP-treated surfaces. The highest work-function (1) value (4.58 eV) was obtained from 02 LPP-treated ITO, intermediate values (4.47-4.48 eV) from Ar and Ar/O2 APP-treated ITOs, and the smallest value from untreated ITO (4.46 eV). Thus, OLED fabricated on the surface of 02 LPP-treated ITO substrate exhibited superior performance among all plasma-treated samples. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) was employed to synthesize Sr2SiO3.5NO333:Eu2+, Sr2SiO3N0667:Eu2+, and Sr2SiO2N1.333:Eu2+ for use in white light emitting diodes (LED) lightings. The SPS technique enabled a complete, rapid synthesis of these phosphors with ease, whereas it is difficult to produce nitridosilicate phosphors by any other conventional synthesis methods. The photolumines- cent (PL) spectrum of Sr2SiO3.5N0.333:Eu2+ had two emission peaks, one at 420 and the other at 526 nm. There existed a single peak at 529 nm in the case of Sr2SiO3N0.667:Eu2+ The PL spectrum of Sr2SiO2N1.333:Eu2+ also had two peaks, one at 529 and the other at 600 nm. Even though the exact structure was not identified, it was revealed that the X-ray diffraction pattern of Sr2SiO35N0.333:Eu2+, Sr2SiO3N0.667:Eu2+, and Sr2SiO2N1.333:Eu2+ was consistent with the PL data. The phosphor with the highest nitrogen content, Sr2SiO2N1.333:Eu2+, showed a broad emission band spanning almost the entire visible range, which may work best if coupled with either UV or blue LEDs. [ABSTRACT FROM AUTHOR]

Capacitance-voltage profiles, admittance spectra, deep-level spectra, current-voltage characteristics, and microcathodoluminescence (MCL) spectra were measured before and after electron irradiation of n-GaN/InGaN multi-quantum-well (MQW) structures typical of the active region of GaN/InGaN blue light emitting diodes. Electron irradiation produces strong compensation of the conductivity in the MQW and introduces interface traps with ionization energies of 100 and 190 meV, in addition to a broad band of interface traps closer to the middle of the bandgap, acceptor traps near Ec - 1.1 eV and hole traps near Ev + 0.9 eV in the GaN barriers and at the GaN/InGaN interfaces in the QWs. The dose of electrons at which measurable changes occur in the MCL spectra is 1015 cm-2, while measurable changes in the electrical properties are observed after doses exceeding 1016 cm-2 electrons. [ABSTRACT FROM AUTHOR]

The characteristics of a SiNx passivation layer grown by a specially designed catalyzer-enhanced chemical vapor deposition (CECVD) system for top-emitting organic light-emitting diodes (TOLEDs) were investigated. Using a tungsten catalyzer connected in series, a high-density SiNx passivation layer with high transmittance was deposited on TOLEDs at a substrate temperature of 50°C. Even at low substrate temperature, 150 nm thick SiNx passivation layer prepared by CECVD exhibited a low water vapor transmission rate of 2-6 x 10-2 g/m²/day. In addition, it was found that the transmittance of SiNx film at 550 nm was significantly influenced by the hydrogen flow rate. Current density-voltage-luminescence results of TOLEDs passivated with a 150 nm thick SiNx film indicated that the electrical and optical properties of TOLEDs were not affected by the high temperature tungsten catalyzer during the SiNx deposition. The lifetime to half initial luminance of a TOLED passivated with a 150 nm thick SiNx layer was much longer than that of a nonpassivated reference sample. This shows that the CECVD is a promising plasma free thin-film passivation technique for high-performance TOLEDs and flexible displays. [ABSTRACT FROM AUTHOR]

An active-matrix organic light-emitting diode (AMOLED) display employing hydrogenated amorphous silicon thin-film transistor (TFT) prefers a cathode-contact structure rather than an anode-contact structure. In this paper, a normal top-emitting OLED (TOLED) employing cathode-contact structure has been proposed. The TOLED employing a thin Cr and a highly reflective AlNd alloy as an anode was fabricated. The current efficiency of AlNd alloy with 3 nm thick Cr as a hole-injection layer could be improved to a level of 6.3 cdA due to a highly reflective anode. In order to implement the normal TOLED structure, the cathode layer on top is separated as subpixels by negative photoresist separator. The AMOLED employing cathode-contact structure shows longer lifetime compared to that employing anode-contact structure. [ABSTRACT FROM AUTHOR]

Localized electroluminescent (EL) light emissions have been imaged in ZnS/Cu ac EL (ACEL) powder phosphor particles embedded under high-refractive index glass. Undistorted well-resolved images recorded at a series of depths from base to apex of individual particles show that in sharp focus the EL emissions are always small (1-2 µm) bright dots, often arranged along short straight lines. Comparison with backlit images shows that EL emission sites are near the phosphor surface. Image series recorded over a range of excitation voltages show that this surface luminous structure is unaltered under increased field strength, but more sites become active. There is no evidence for luminous comets within the particles. The data, clearly showing alternation of EL emission from side to side of the particles on opposite-polarity ac half-cycles, continue to support a mechanistic model in which electrons and holes are separated during one polarity and then undergo radiative recombination when that polarity is reversed on the succeeding half cycle. The small, surface-positioned emissive spots indicate that this charge-carrier separation does not occur at long acicular internal structures but rather at short Cu2S structures active only at the ZnS surface. [ABSTRACT FROM AUTHOR]

Nitride-based light emitting diode (LED) with dual-stage multiquantum well (MQW) structure is proposed and fabricated. It was found that we could improve crystal quality, reduce reverse leakage current, and reduce forward voltage of the LED by inserting the electron emitter MQW structure. With 20 mA current injection, it was found that measured output powers were 3.2 and 4.7 mW for the conventional single-stage MQW LED and the dual-stage MQW LED, respectively. Furthermore, it was found that electrostatic discharge characteristics of the dual-stage MQW LED are better. [ABSTRACT FROM AUTHOR]

Crystallization of organic layers in small organic light-emitting diode (OLED) devices has a detrimental impact on their performance, such as current density-voltage characteristics. Using scanning tunneling microscopy, we investigated the crystallization process of organic films grown on indium tin oxide substrates. N,N′-diphenyl-N,N-bis(3-methyl-phenyl)-1,1′-biphenyl-4, 4′-diamine (TPD), typically used as a hole transport layer in OLEDs, was employed as the sample material. As-grown TPD films consisted of separate spheroid-shaped grains. These grains were relatively unstable and they easily transformed into crystallized grains. The crystallization process proceeded grain by grain. Crystallized grains changed to a ball-like shape, suggesting that reconstruction of the molecular stacking structure inside the grains had occurred. Slab optical wave guide spectroscopy revealed that a new absorption band appeared at 250 nm in the annealed film, in addition to the normal absorption band at 380 nm. This suggests that annealing changed the molecular stacking structure in an H aggregate fashion, which is energetically stable, resulting in a blueshift in the absorption band. These crystallized grains formed clusters. The growth of these clusters was largely enhanced by heat. However, the dimensions of each crystallized grain remained unchanged. As the clusters grew, they aggregated and caused macroscopic deformation in the film. [ABSTRACT FROM AUTHOR]

A new green phosphor, Ce3+-activated CaSc2O4, was developed, which shows green luminescence with a peak wavelength of 515 nm under excitation with blue light. Ce3+-activated CaSc2O4 can be used as a material for color conversion of white-light-emitting diodes (LEDs), which consist of a blue LED, a green phosphor, and a red phosphor, because the luminescence efficiency of this phosphor is comparable to those of commercial phosphors such as Y3Al5O12:Ce3+ The host crystal of this phosphor has an orthorhombic CaFe2O4 structure, and the Ce ion probably exists in an eight-coordinated Ca position. We investigated the dependency of the firing temperature and dopant concentration for luminescence intensity and found that the optimum temperature and concentration were 1600°C and 1 mol % of Ce substituted to the Ca position. The luminescence peak wavelength was shifted toward longer wavelengths by replacing Ca with Mg. In contrast, replacing Ca with Sr resulted in a shift toward shorter wavelengths. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon carbide alternating-current thin-film light-emitting diodes (a-SiC:H ACTFLEDs) have been successfully fabricated on indium-tin-oxide-coated glass substrates and characterized. The electroluminescence (EL) spectra of an obtained ACTFLED under either a dc (positive or negative) bias or a sinusoidal ac voltage were qualitatively very similar, with a peak wavelength at about 655 nm and a shoulder at about 620 nm. The EL threshold voltage and brightness of the ACTFLEDs were sensitive to the contact behavior between the metal electrode employed and amorphous film. Moreover, the EL intensity of an ACTFLED increased with the frequency up to 500 kHz and then decreased rapidly and became very weak as the frequency increased to about 1 MHz. A model based on the equivalent circuit has also been proposed to explain this frequency-dependent EL behavior. [ABSTRACT FROM AUTHOR]

Si unit-fused diphenylamine-containing polymers were prepared and the properties of these compounds were studied. Selective dilithiation of 2,2′,4,4′-tetrabromodiphenylamine derivatives using n-butyllithium, followed by addition of dichlorosilane and 1,2-dichloro-1,1,2,2-tetramethyldisilane, produced monosilane and disilane unit-fused diphenylamines (Phenaz and DSiAzep, respectively). Siloxane unit-fused diphenylamine (SiO) was prepared by oxidation of DSiAzep. Polymers with Si unit-fused diphenylamine were prepared by using an organometallic process to obtain structurally well-defined polymers. Siloxane unit-fused diphenylamine-containing polymers were also prepared by oxidation of relative disilane unit-fused diphenylamine-containing polymers. The obtained polymers were useful for electrochromic devices, electroluminescent devices, functional additives for resins, and so on. The properties and functionalities of the polymers were changed by fusing Si unit and by changing the substituent on the N atom or Si atom. [ABSTRACT FROM AUTHOR]