This PDF file contains the front matter associated with SPIE Proceedings Volume 6828, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We report novel bipolar host materials for high efficiency red and green phosphorescent OLEDs (PHOLEDs). Phenyl moieties were inserted in a 4,4'-N,N'-dicarbazolebipheyl (CBP) compound to provide much easier electron injection and to increase electron mobility. The efficiency increase and voltage reduction by this modification were observed in red and green PHOLEDs. At a given constant luminance of 1000 cd/m², the power efficiency was enhanced at least by twenty percent in the general red and green PHOLED devices.

For stable and efficienct organic light-emitting diodes, it is essential to find molecules with high photoluminescent efficiency, little self-quenching and balanced charge transporting properties. Recently, we've designed and synthesized some highly emissive naphtho[2,3-c][1,2,5]thiadiazole (NTD) derivatives and naphtho[2,3-c][1,2,5]selenadiazole (NSeD) derivatives with unusual ambipolar transporting properties. The ambipolar transporting properties of the NTDs were explained by Marcus theory with carrier reorganization energies and charge-transfer integrals. We obtained high quality single crystals of 4,9-di(biphenyl-4-yl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD02) and 4,9-bis(4-(2,2-diphenylvinyl)phenyl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD05). They have disordered NTD rings' orientation with the opposite directions in the center of the molecule because of NTD's planar configuration and the single-bond connection with the phenyl substituents. The packing structure of NTD02 shows the planar arrangement of NTD rings, forming a "charge transporting channel". Quantum calculation also confirms that the π-π stacking interaction in NTD derivatives benefits the charge transporting via intermolecular hopping on NTD rings. The hole and electron mobilities of NTD05 are 7.16×10^-4 cm2/V·s and 6.19×10^-4 cm²/V•s at an electronic field E = 2.0×10⁵ V/cm, respectively. The hole mobility of NTD05 is close to that of N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine (NPB) and the electron mobility of NTD05 is two orders-of-magnitude higher than that of tris(8-hydroxyquinoline) aluminum (Alq₃). For the NTD derivatives, NTD05 also shows the best performance in non-doped OLEDs. CIE coordinates of (0.65, 0.35) and a peak efficiency of 2.4% are achieved for a double layer OLED with NPB as the hole transporting layer and NTD05 as the emitting layer. Moreover, we get ultimate red emission with CIE coordinates of (0.71, 0.29) for some of the NSeD based non-doped OLEDs.

A novel family of 9,9'-spirobifluorene functionalized head-tail regular n-hexyl-substituted oligothiophenes, which exhibit good solubility in common organic solvents, has been successfully developed in this contribution. The study of the redox behavior of the spiro-type molecules indicates that their HOMO and LUMO energy levels are adjusted to match the electrode work function by varying the attaching oligothiophene moieties and their attaching patterns to 9,9'- spirobifluorene. The two series of spiro-type oligothiophenes still remained the similar electrochemical properties of common oligothiophenes while their processability and morphologic stability being improved by the spiro-junction.

In recent years, fabrication and characterization of various inorganic nanostructures has attracted great attention. On the other hand, studies on the synthesis of organic nanostructures have been scarce. Yet, organic nanostructures offer great potential for the fabrication of organic devices with improved performance. It is expected that the organic nanostructures can have improved charge transport properties due to different packing of molecules. Organic nanostructures can be fabricated using a simple low vacuum evaporation system in the flow of a carrier gas (organic vapor phase deposition OVPD). Here, we investigated the structural and optical properties of a range of organic nanostructured materials, such as 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA), 3,4,9,10-perylene-tetracarboxylic diimide (PTCDI), 1,4,5,8- naphthalene-tetracarboxylic-dianhydride (NTCDA), lead phthalocyanine (PbPc) and titanyl phthalocyanine (TiOPc), prepared using OVPD. The obtained nanostructures were characterized by scanning electron microscopy (SEM) and photoluminescence (PL). The effect of the substrate temperature on the morphology and emission properties of the materials will be discussed in detail.

In this article the effect of molecular weight of polyvinylcarbazol (PVK) on the photoluminescence (PL) spectra of the solution of Coumarin 6 (C6) dye and the polymer in their common solvent and also thin film of PVK and the dye is studied. By adding PVK to the C6 solution in dichloroethane, an extra peak was observed in the PL spectra of the solution. The extra peak was more intense when high molecular weight PVK was used as compared with using the low molecular weight polymer. Therefore in each polymer-dye solution, two peaks were detected in their photoluminescence spectrum. The first peak is attributed to C6 emission and the second one may be related to the interaction of the C6 molecules with the solution of PVK in dichloroethane. This effect was only observed at low concentration of C6. At high concentration of C₆, excimer emission dominates PL spectra and results in a red shift for both peaks. At higher concentrations, only one peak was observable and the excimer emission is stronger than that of lower concentrations. In this case only one peak was observed.

A novel soluble phenothiazine-based derivative, poly(3, 7-divinylene-N-octyl-phenothiazine 2, 3-diethylquinoxaline-5,8- diyl) (PQDN), is synthesized for application in red light-emitting diodes. PQDN was characterized by the measurements of cyclic voltammetry (CV), absorption and photoluminescence (PL) spectra. The band gap (Eg) was determined to be 1.89 eV. The smaller band gap suggested that the polymer is a good candidate for red electroluminescent materials. Polymer light-emitting diodes (PLEDs) with double-layer configuration of indium tin oxide (ITO) / (polyethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) / PQDN: poly(N-vinylcarbazole) (PVK) (100:0, 80:20, 60:40, and 20:80 wt.%) / Mg:Ag were fabricated. The electroluminescent (EL) property was studied in details. In order to improve the EL performance further, the devices were thermally annealed at 100oC for one hour under the protection of nitrogen. Luminance is increased obviously. EL peak wavelength and the Commision International de L'Eclairage (CIE) coordinates are unaltered and located in red region with the increase of the operating voltages,.

A starburst molecule (T) with triphenylamine (TPA) and benzothiodiazole (BTD) as constructing units was synthesized via two step Heck coupling reaction. As compared with its linear counterpart, it shows better solubility and amorphous film-forming ability. Spectroscopic properties show that it emits red light with emission peak at 651 nm in CH₂Cl₂. The red light emitting arises from the intramoleculasr charger transfer state. White light emitting diode (WLED) was fabricated with the starburst molecule as red light emitting composite. The luminance and efficiency maximum was 3960 cd/m², and 1.22 cd/A for the WLED device with only 0.05%.(W/W) doping content of the light emitting composite. The high performance of WLED is attributed to the high chromorphore density and electron coupling effect of multi-branches. It is reasonable to conclude that starburst structure is superior to its linear and less branch counterparts in the fabrication of LED devices.

A new DCM derivative 4-(dicyanomethylene)-2-t-butyl-6-(9-ethylphenothiazine-2-enyl)-4H-pyran (DCPTZ) has been used as an orange-red fluorescent dye molecule in organic light-emitting diodes (OLEDs). EL devices with the structure ITO/PEDOT-PSS/α-NPD/Alq₃:DCPTZ/Alq₃/LiF/Al were fabricated with various DCPTZ doping concentrations. The maxima in the EL spectra of the devices varied from 580 to 620 nm depending on the doping concentration of the dye molecule. An EL device with 0.5% dopant concentration was found to exhibit a maximum brightness of 81,500 cd/m² at 13.3 V and a power efficiency of 4.1 lm/W with CIE coordinates (0.51, 0.47) at a luminance of 100 cd/m². White lightemitting devices with the structure ITO/PEDOT-PSS/a-NPD/a-NPD:DCPTZ/DPVBi/Alq₃/ LiF/Al were also fabricated. The thickness of the blue light-emitting 1,4-bis(2,2-diphenylvinyl)benzene (DPVBi) layer was varied to obtain white light emission. White light emission from the device was observed when the thickness of the DPVBi layer was greater than 10 nm. The maximum brightness and power efficiency of the device with a 20 nm DPVBi layer were found to be 30,300 cd/m² and 2.0 lm/W respectively, with CIE coordinates (0.33, 0.36). In addition, the white EL device exhibits a relatively high color rendering index (CRI) of about 83.

A number of novel vinyl monomers containing either a fluorescent or a phosphorescent moiety were synthesized. The vinyl monomers have either hole or electron transporting properties and luminescence in near-UV, blue, green, to red. The overall charge transport properties and emission hue can be tuned by applying and the various monomers at different mix ratios. The vinyl monomers were copolymerized into high molecular weight yet soluble conductive copolymers using traditional solution free radical polymerization method. The vinyl monomers prepared including electron transporting 11-vinyl-phenanthro[9.10-b]quinoxaline (QP) and 1-vinyl pyrene (PY), hole transporting 9-(4-methoxyphenyl)-3-vinyl-9H-carbazole (KPA) and N-phenyl-N-(4-vinylphenyl) naphthalene -1-amine (NPA), and a red-emitting phosphorescent monomer based on the Europiujm complex [Eu(DBM)₃H-EtPIP]. The optical, thermal and electrical properties of the copolymers were characterized. Homojunction OLED based on the copolymers were prepared by spin-coating. The EL spectra and I-V-L characteristics were obtained and will be reported.

This Electroluminescence(EL) of organic materials has been known since the 1960s. Resulting devices are commonly called "organic light-emitting diodes" (OLED). Organic light-emitting devices have attracted much attention owing to their potential application for flat-panel displays. Rare earth complexes containing β-diketonate ligands have attracted very much attention, because their special properties in organic light-emitting diodes, like narrow emission bands and nearly 100% quantum efficiency in theory. How to improve their efficiency and stability are important problems which people study. Thin film OLEDs usually consist of multiple organic and metallic layers on an ITO-covered glass plate. In this paper, a novel Europium Complex , Eu(DBM)₃L[L= 4,4'-bis(4-methyphenyl-1,3,4-oxadiazole)-2,2'-bipyridine] functionalized by a carbozole fragment, was synthesized and used as emitting material in organic electroluminescent (EL) devices. Their absorption spectrum , luminescence properties were studied. The light-emitting units were based on 4,4'-bipyridine and oxadiazole derivatives. It was found that the EL performance based on lanthanide complex can be effectively improved by chemical modification on the second ligand.

In this paper, the light emitting efficiency, spectrum, and the lifetime of the phosphorescent devices, whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping induced by the emissive dopant, are explained by differences in the energy levels of the host, dopant, and nearby transport layers. On the basis of our finding on device performance and photocurrent measurement data by time-of-flight (TOF), we suggest a detailed emission mechanism, along with a physical interpretation and practical design scheme for improving the efficiency and lifetime of devices. Moreover, the effects of the modification of charge (both hole and electrons) transporting layers which results in a drop of operating voltage and improved efficiency on the performance of electrophosphorescent device are investigated experimentally. Using the Ir-based phosphorescent emitter, vacuumevaporated, solution-processed, and composition of their hybrid structures are designed for better charge carrier balance and efficient exciton blocking behavior.

Red emission was achieved in electroluminescent devices by using a novel charged Ir-copolymer. The electroluminescent device, with the configuration of ITO/PEDOT:PSS/Ir-copolymer/Au, exhibited the characteristics of light-emitting electrochemical cell (LEC), in which the redistribution of ions resulted in the ionic junction. The maximum external quantum efficiency (EQE) of 0.19 % and the maximum luminance of 352 cd/m² were obtained after the device was driven to the maximum luminance at 7V. When aluminum (Al) was used as cathode, the maximum EQE of 0.15 % and the maximum luminance of 340cd/m² were achieved, which were comparable with the results from the Au cathode device. After a 30nm thick TPBI (1,3,5-tris(2-N-phenylbenzimidazolyl)-benzene layer was inserted between light emitting layer and the Al cathode, the device performances were significantly enhanced. The maximum EQE and the maximum luminance reached 10.7 % and 2170 cd/m², respectively, a more than 10 fold increase compared to the devices without TPBI layer. The TPBI layer not only functioned as hole blocking layer which made holes and electrons more balanced inside the device, but also moved the recombination zone away from the cathode, thereby enhancing the device performances.

In this paper, a boron-doped poly-Si crystallized by solution-based metal induced (S-MIC) as the anode of organic light emitting diode (OLED) was studied. The semi-transparent and semi-reflective anode of OLED systemized with the high reflectivity of Al cathode could form a micro-cavity structure with a low Q to improve the efficiency. The maximum luminance efficiency of red OLED made by Alq3: DCJTB (1.5wt %)( 30nm) with the poly-Si anode is 2.66cd/A, higher than that of the OLED with the ITO anodes by 30%. In order to improve the device performance, some key to optimize the character of MIC poly-Si thin film are analyzed theoretically. A new kind of TFT/OLED coupling structure in AMOLED was proposed, in which the pixel electrode of OLED was made by the same poly-Si thin film with its driver TFT's drain electrode. So that this coupling structure will simplify the AMOLED processes flow.

A LED light coupler is designed with rigorous geometrical optics analysis for coupling light from a mini side white LED of 0.6mm height, the thinnest commercially available LED, into to a very thin (~0.3mm) light guide on the edge side. The ultra thin thickness of the light guide limits the application of conventional LED coupling due to short coupling efficiency. Furthermore the polychromatic spectral band of the LED excludes the use of diffractive gratings which were proposed for a nearly monochromatic LED coupling to a thin light guide. The coupler is essentially comprised of a collimator and a concentrator lens. The coupler first collimates the light from the LED and then concentrates the collimated light into the light guide. The exit surface of the coupler is additionally textured to have micro patterns in order to control the radiance profile. The coupling efficiency is improved from 50%~60% without any couplers to 86% with the proposed LED coupler.

A series of saturated red emission copolymers, polyfluorene copolymers (PFO-DBT), were synthesized and characterized. The saturated red EL emission from the copolymer peaking at about 677 nm and electroluminescence (EL) efficiency of 1.4% based on simple device structure of ITO/PEDOT/PFO-DBT/Ba/Al, were achieved. The operation mechanism of the device was discussed and it was found that hole carrier injection is the major obstacle for improving EL efficiency and EL stability. To overcome such problem, we utilized MEH-PPV which has low HOMO level blended with the PFO-DBT copolymer to improve EL efficiency to 1.7%. Simultaneously, the EL emission lifetime of the device with PFO-DBT:MEH-PPV (50:50) blended polymer extended to 2000hrs. Monochrome passive red emission displays with the blended polymer were fabricated, and exhibited excellent pictures.

Device performances of green phosphorescent organic light-emitting diodes with triplet mixed host emitting layer were correlated with energy levels and composition of host materials. Two hole transport type host materials, (4,4'-N,N'- dicarbazole)biphenyl(CBP) and 4,4',4"-tris(N-carbazolyl)triphenylamine(TCTA), were combined with two electron transport type host materials, 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene(TPBI) and PH1. Maximum quantum efficiency was obtained in 5:5 mixed host in the case of TCTA:TPBI and TCTA:PH1, while CBP:PH1 showed the best performances in 9:1 mixed host. Quantum efficiency of green mixed host devices could be improved by more than 50 % compared with that of corresponding single host devices. Effect of dopant energy levels on device performances of triplet mixed host devices was also investigated and optimum composition for high efficiency depended on energy levels on dopant materials.

We report a significant enhancement of the electron injection from n-Si bottom cathodes to organics by using a thin layer of Cs₂CO₃ as electron injection layer, leading to the reduction of the turn-on voltages and the improvement of the efficiencies in Alq₃ based inverted top-emitting OLEDs with n-Si directly as cathodes. With structure of n-Si/ Cs₂CO₃ (2 nm)/TPBi (10 nm)/ Alq₃ (40 nm)/ NPB (40 nm)/ MoO₃ (2 nm)/Ag (20 nm)/ Alq₃ (40 nm), where the 10 nm TPBi is hole blocking layer for improving charge balance in emission zone and the 40 nm Alq₃ layer on Ag anode is the capping layer for improving light out-coupling efficiency, the inverted top-emitting OLEDs show a turn on voltage of 6 V and a driving voltage of 10 V for 100 cd/m² with a maximum efficiency of around 1.5 cd/A, which are superior compared to the relevant results ever reported.

We report improved efficiency in Alq based top-emitting OLEDs with p-Si anode by using an effective electron injection layer and a hole blocking layer to realize better charge balance and recombination. With structure of p-Si/SiO₂/MoO₃ (2 nm)/NPB (40 nm)/Alq (40 nm)/TPBI (10 nm)/Cs₂CO₃ (2 nm)/Ag (20 nm)/Alq (40 nm), where the 40 nm Alq capping layer on top Ag cathode was used to improve out-coupling efficiency, the devices show a turn on voltage of 5.5 V and a driving voltage of 10 V for 100 cd/m² with a maximum efficiency of exceeding 1.2 cd/A and a maximum power efficiency of 0.4 lm/W, which are comparable with the conventional OLEDs and encouraging and promising for Si based OLEDs and optoelectronics.

Electro luminescence spectra and in-suit micro-Raman spectra was used to study voltaic aging of organic light emitting devices with two kinds of conjugated macromolecule polymer emission layer, one is called PFO-BT15 and the other is poly (2-(4-Ethylhexyl) phenyl-1 , 4-phenylene vinylene) (P-PPV) polymer. The first device has a configuration of ITO glass/ PEDOT( 120nm ) PFO-BT15(80nm)/Ba( 4nm )/Al(200nm) , and we encapsulated the cathode of diode with epoxy resin to reduce the entrance of oxygen and water. After long time current stress, the electro luminescent spectra and Raman spectra show that the polymer device's molecular configuration of polymer layer is unchanged , but the PEDOT anode's breakage which lead to the emission failure of the device, which indicates that this kind of polymer materials have relatively steady photoelectric performance . The second device, during current stress , the reduction of conjugation length is provided by Raman spectroscopy. This reduction of the conjugation length , which dramatically increases the resistance and cuts off the current density , was the main reason for the failure of lighting. These findings provide an important insight into the intrinsic degradation mechanisms of the polymer LEDs and help in the development of even more stable devices.

In this paper, it is reported that the design and fabrication of high-brightness and high-power InGaAlP single-side red LED with electrodes which are interdigitated with the fingers. High-brightness and high-power InGaAlP LED is a new kind of visible light LED developed in recent years, which is driven by large current capacity, high luminous efficiency and excellent heat resistance. It has been used in various fields, such as large area displays, traffic lights, brake lights and so on. As compared with the conventional double-side LED, the single-side LED is more flexible to integrate with other devices and its fabrication is simplified. The size of chip is 1mm². The fabrication of single-side LED, essentially, is the same as conventional LED, involving photolithography, PECVD SiO₂, wet etching, evaporating, lift off and rapid thermal annealing using four masks. To control the widths of mesa and N electrode precisely, the selecting etch technique has been adopted, using HCL: H₂O:H₂O₂ as the InGaAlP etching solution. I-V characteristics, light emission spectrum, luminous flux, luminous intensity and luminous efficiency of this LED have been measured. The characteristics are obtained with turn-on voltage of 1.5V and forward current of 400mA at its forward voltage of 3V. The peak wavelength is 635nm, which corresponds to red light, and the Full Width of Half Maximum is 16.4nm at injection current of 350mA. The luminous intensity is 830 mcd. The color coordinates is x=0.6943, y=0.3056 and the color index is 18.4. So we will conclude that the high-brightness and high-power InGaAlP single-side red LED will become new focus in both scientific research and industrial investment for its wide application.

High quality GaN films with low dislocation density have been grown on sapphire substrate which is pretreated by a new and simple method in order to overcome those problems existing in the conventional ELO technique. Etch pits on sapphire substrate surface are formed after surface treating. GaN films have been grown by LP-MOCVD on the sapphire substrate, which a half of it is treated by chemical etch. Both the thickness and dispersion of the refractive index of GaN films are obtained by spectroscopic ellipsometry. With the dispersion of the refractive index, the transmission spectrum of GaN is studied and the thickness of GaN epilayer is calculated. The two values of the thickness obtained by these two different methods are in good agreement. The epilayer grown on the surface treated sapphire substrate exhibits superior optical properties and crystal properties, in which the yellow luminescence is nearly invisible in the photoluminescence spectrum, the higher transmission ratio and the greater modulation depth can be shown in the transmission spectrum.

An online non-contact fault detection technique of LED chips is presented based on the photovoltaic effect in diodes. By observing the current in the bonding lead frame of a LED chip, which is induced by illuminating the chip, the LED chip and its electric connection with the lead frame during packaging are checked. The fault detection principle is described in detail in this paper. Red, yellow and green LED chips are tested in the experiment. The experimental results show that the method can be easily realized, and thus can be used for online fault detection of LED chips in packaging.

A standard white light compounding algorithm based on combination of chroma coordinates acquisition system with computer working current control system is presented for three-color LED. The chroma coordinates acquisition system consist of grating spectrometer and integrating sphere. The computer adjust and control the working current of three-color LED, then achieved chroma coordinates error between the compounded white light and standard white light D65, until the chroma coordinates is less than the threshold beforehand set by this technique. The compounded white light meet the chroma error demanded that is able to be changed, at the same time the chroma coordinates acquisition system and the working current control system are eliminated. The proposed algorithm the offset of central wavelength and the change of chroma coordinates due to working current variety for LEDs. Experimental results show that the proposed algorithm achieved lesser chroma error uv=0.001 relative to standard white light D65, enhanced chroma uniformity of illumination field.

Nowadays, high power LED is often packaged with flip chip method. The gold bump is usually made by electroplating or gold evaporation, which cause the environment pollution and material waste. A gold wire bump manufacture technology for high power LED flip chip is described in this paper. The wire bond device is used and different bump making parameters, such as weld temperature, pressure and ultrasonic power, are optimized through experiments. At the same time, a new bump wire tail height managing process is introduced. The gold wire bump with this method height difference keep in 3 micrometers and which is convenient for flip chip. Then, rapid annealing is taken to make sure the gold wire bump has a well adherence to the wafer. At last, the bump weld result is tested and the bump invalidation is analyzed with the SEM. The bonding force between bump and wafer more than 10 grams. The flip chip high power LED with gold wire bump has low forth voltage and heat resistance. All of above proved that the gold wire bump is convenient and reliable for high power flip chip LED.

GaN-based light-emitting diode (LED) has been widely used in recent years, and tremendous progress has been achieved in GaN-based semiconductor materials and relevant process. However, owing to the large refractive index contrast between GaN-based semiconductor materials and air, light can be easily totally internally reflected at the semiconductor/air interface, and the critical angle for light to escape from the semiconductor is small. Therefore, the light extraction efficiency for GaN-based LED is still low and needs improving. Some of the leading approaches to enhance light extraction efficiency of GaN-based LED such as surface texturing or roughening, omnidirectional reflectors, photonic crystals, laser liftoff, transparent electrode, patterned substrate and so on are introduced in detail. For each approach, how the variation in device structure or material improves the light extraction efficiency is analyzed thoroughly. At last, some of mentioned approaches that are promising are evaluated and viewed briefly.

At pulse laser pumping, stimulated emissions are observed in ZnxMg1-xO epilayers. Among them, spectral blue shifts are dependent on the Mg substitution concentration; and the highest lasing photon energy (in ZnO series materials even reported) of 3.51 eV is observed. Furthermore, experimental results also show that by high concentration Mg substitution, a red shift of the electron-hole plasma stimulated emission is reduced and its efficiency doesn't decrease with the Mg substitution concentration. These results imply that the lasing frequency of ZnO series materials can be modified by substitution. Secondly, lasing with low threshold in a closed micro-cavity filling with high scattering and irregular structure gain medium is observed. Furthermore, the usual laser physics and random laser can't explain the sharp bandwidth of lasing in sub-micron ZnO micro-crystals; a new concept of lasing needs to be proposed, which is important to the develop in physics of carrier and lasing.

Nanocrystalline silicon carbide (nc-SiC) thin films were deposited by helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) technique at different hydrogen dilution ratio (RH). The PL peak energy and intensity were systemically analyzed using photoluminescent (PL) and photoluminescent excitation (PLE) methods. As a whole, the PL intensity shows an increasing trend and the PL peak energy presents continuous blue shifts with increasing hydrogen dilution ratio. In addition, it is found that the spectra band of samples deposited at low RH are composed of two components, the high energy band comes from quantum confinement effect and the low energy band is related to radiation of surface defect. The low energy band has a decreasing trend with increasing hydrogen dilution ratio and even disappears finally at high RH. We explain dependence of PL properties in terms of the variation of film microstructure induced by hydrogen dilution during film deposition. The increasing of PL intensity and the decreasing of the low energy band can both be accounted by the microstructure improvement. The decrease of PL peak energy is related to the size decrease of SiC nanocrystals.

Ba₂SiO₃Cl₂:Eu²⁺, Mn²⁺ phosphor was synthesized by high-temperature solid state reaction at 900~1200°C in a slightly reducing atmosphere for 2.0~8.0 hours. The raw materials were the mixture of BaCO₃, SiO₂, MnCO₃, NH₄Cl, and Eu₂O₃ in the mol ratio of 3, 2, 0.004, 2 and 0.02. Ba₂SiO₃Cl₂:Eu²⁺, Mn²⁺ phosphor's absorption and luminescence spectra were studied. The results indicated that the emission band consists of three peaks located at 425 nm, 492nm and 608nm, respectively. The emission peaks at 425 and 492nm originate from the transition 5d→4f of Eu²⁺ ions that occupy the two Ba²⁺ sites in the crystal of Ba₂SiO₃Cl₂, while the 608nm emission is attributed to the energy transfer from Eu2+ ions to Mn²⁺ ions. The white light can be obtained by mixing the three emission colors of blue (425 nm), green (492 nm) and red-orange (608 nm) in the single host. When the concentrations of the Eu²⁺ ions and Mn²⁺ ions were 0.02mol and 0.004mol respectively, the sample presented intense white emitting. The excitation spectra of the three emissions extending from 300 nm to 460 nm indicated that Ba₂SiO₃Cl₂:Eu²⁺ phosphor can be excitated by InGaN chip UV emission effectively, and it is a single-phase white phosphor with low-cost and high brightness for white LEDs.

The continuing research efforts in white light created by mixing red, green and blue light emitting diodes (RGB LED) will allow their applications in high quality lighting systems in the (near) future. There are still many issues to tackle in this kind of light source, for instance the color uniformity and the change of color-render property owing to the change of LED's temperature. In this paper we simulate the effects on color uniformity of the near-field light distribution due to different LED-chips arrays (at optimum packaging density for uniform irradiance) using High-Power RGB LED-chips. The results showing the color uniformity of near-field which can be achieved with different RGB LED-chips arrays are presented. Several configurations of RGB LED-chips arrays and relevant data for color variation are given respectively. An analysis of luminous efficacy of radiation (LER) and color rendering index (CRI) of this source is performed, which are affected by the peak wavelength, spectral width, and the output peak emission power ratio of LED-chips.

Monitoring of different phytoplankton biomass is an important task for environmental management. Here, a novel submersible phytoplankton fluorometer which use light emitting diode (LED) array as excitation source is presented. Six LEDs of different wavelength are included in the excitation LED-array, the maximal emission wavelength are 380nm, 450nm,520nm,570nm,590nm and 610nm. By means of pulse excitation of different LED, fluorescence of Chl-a in different phytoplankton cells is collected and recorded. Comparing to excitation fluorescence spectral and using multivariate linear regression, chlorophyll-a content of different spectral group phytoplankton can be retrieved. With temperature and pressure probe, information of water temperature and depth also can be recorded. Consequently, the submersible phytoplankton fluorometer can used to measure chlorophyll-a content of different spectral groups phytoplankton in vitro and in situ. Potential application of the submersible phytoplankton fluorometer in environment monitoring is further elucidated.

In this paper we present our studies of optical switching process in planar azo-dye Methyl Red doped polymeric waveguides by using an Ar ion laser (488 nm) as pump beam and a He-Ne laser (633) as probe beam. The effects of different parameters on optical switching process and effects of probe and pump beams on absorption spectrum of sample were studied experimentally. The switching process is attributed to trans-cis photoisomerization of azodyes followed by cis-trans thermal or optical relaxation that induces a reversible birefringence and dichroism in dye-doped polymeric waveguides when pumped with polarized light.