This PDF file contains the front matter associated with SPIE Proceedings Volume 7852, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A five-inch light guide plate by arranging special cone dots on the surface of optical polycarbonate film was designed. Then an optical model was built by using TracePro and the luminance distribution of the light guide was simulated by using ray tracing method to achieve an efficient and uniform radiation of light from the light-guide. The above light guide was fabricated by roll to roll hot embossing process instead of injection molding. The fabrication of the hotembossing mold was investigated. Finally, a 5 inch light guide with the average luminance greater than 3000 cd/m² and the uniformity above 80% was fabricated. This process will contribute to the production of an ultra slim light guide in the future.

Multilayer light guide films(MLGF) with LED lighting for multifunctional display has been proposed. Based on the MLGF technology, keys can be illuminated separately on different mode. The fabrication process similar to LIGA technology including laser etching, electroforming and hot nanoimprinting is developed. The depth of the light guide dots can be controlled by laser pulse numbers and the influence of dots depth to the luminance uniformity is simulated. The MLGF sample composed of 2 layers is designed and fabricated, the total thickness the module is about 0.4mm and the depth of light guide dots ranges from 0.5 um to 10um.The optical performances testing results are given. MLGF provides an ultrathin solution for multifunctional keypad and the fabrication process is high throughput, low cost for large area light guide films.

Using small color difference data sets (Macadam ellipses dataset and RIT-DuPont suprathreshold color difference ellipses dataset), and large color difference data sets (Munsell Renovation Data and OSA Uniform Color Scales dataset), the uniformity of several color spaces and performance of color difference formulae based on these color spaces are evaluated. The color spaces used are CIELAB, DIN99d, IPT, and CIECAM02-UCS. It is found that the uniformity of lightness is better than saturation and hue. Overall, for all these color spaces, the uniformity in the blue area is inferior to the other area. The uniformity of CIECAM02-UCS is superior to the other color spaces for the whole color-difference range from small to large. The uniformity of CIELAB and IPT for the large color difference data sets is better than it for the small color difference data sets, but the DIN99d is opposite. Two common performance factors (PF/3 and STRESS) and the statistical F-test are calculated to test the performance of color difference formula. The results show that the performance of color difference formulae based on these four color spaces is consistent with the uniformity of these color spaces.

Direct-light type backlight module is widely used for large size liquid crystal displays (LCDs). Many methods have been proposed to thinner the thickness and simplify the structure. In this paper a new kind of diffuser, with micro prisms on the top and micro spheres on the bottom, is used to reduce the thickness for the direct-light type backlight module. Simulated results show the microstructures on the diffuser can help to reduce the thickness between the diffuser and the light source, while keeping the illumination uniformity and increasing the light efficiency.

No-glasses optical grating stereoscopic display is one of a chief development of stereoscopic display, but it is always confined by the range of stereoscopic visible and quantity of stereoscopic information and quantity of users. This research use the combination of Fresnel lens array and controllable point lights to output information of the two eyes of different users separately. Combining the technology of eyes-tracking, it can make no-glasses optical grating stereoscopic display be visible in 3D orientation range by multiuser in the condition of two-angle image sources. And it also can be visible in 360° stereoscopic overlook by one user in the condition of multi-angle image sources.

Heat dissipation is a crucial issue for development and applications of high power LEDs. In this paper, heat conductions of various light sources are compared, and the necessity of heat dissipation of high-power LEDs was further pointed out. The packaging structure of high power LEDs is introduced, and the heat transfer procedure is analyzed. Finally, some considerations to dissipate heat effectively to keep good performance of high-power LEDs are given.

The models for spectra of a phosphor-coated white (p-W) LED and a white light LED cluster are developed based on the principle of additive color mixture. The simulation results show that p-W LEDs consisting of a blue chip (450nm), green phosphor (507 nm), yellow phosphor (580 nm) and red phosphor (655 nm) could realize color rendering indices (CRIs) above 97.7 and special CRIs of R1 to R14 above 91.1, but luminous efficacies of radiation (LERs) below 250.3 lm/W, that white/red clusters consisting of red LEDs and p-W LEDs with a blue chip (450nm), green (507 nm) and yellow (580 nm) phosphors could realize given color temperature white light with CRIs above 97.9 and special CRIs of R1 to R14 above 89.6, as well as LERs above 296.3 lm/W, and that a neutral-white /red//blue cluster consisting of blue LEDs (465 nm), red LEDs (628 nm) and neutral-white LEDs with a blue chip (452 nm), green (530 nm) and yellow (586 nm) phosphors could realize CCT tunable white lights with CRIs above 97.9 and special CRIs of R1 to R14 above 89.6, as well as LER above 296.3 lm/W.

In this paper, the transmission principle of light crossing the light guide panel was analyzed and a calculating method of the net dot distribution was deduced according to the illumination distribution of LED. Using this method, the light guide panel net dot distribution of a small size backlight was calculated. And, in the light of net not distribution regulation, the net dot layout was optimized and simplified associating with area segmentation adjustment method. Optical model was made and ray tracing was done by optical design software, the simulation result indicate that the surface luminance uniformity of the backlight is 87% and the light efficiency is 71%, which is achieved by less LED sources and area segmentations compared with the same size backlight. The net dot of light guide panel sample was made by laser engraving. The luminance uniformity of testing is consistent with that of simulation.

Traditional PAPIs commonly use halogen lamps as their light sources, which have short lifetime. LEDs have much longer lifetime and thus can enhance the reliability of PAPIs. In this paper, a new design of a PAPI based on LED light sources is introduced. White and red LEDs are used to emit white and red beam separately. The white and red LEDs are separated into two cases. In each case there is a single lens in front of the LED, separately. The LEDs are placed exactly at the focal planes of the lens. The white LED is fixed below the optical axis to project the white light in the upper part, and the red LED is fixed oppositely. Baffles are used to form a sharp separation of the beam. Optical simulation is carried out to verify the design. The measurement results of the finally realized model show that it meets the requirements of the technical criterion.

In this paper, we focused on tuning the emission wavelength of InGaN/GaN multi-quantum wells (MQW) employing strain-accommodative structures. Generally, the adjustment of emitting wavelength is realized by controlling the quantum well (QW) thickness and the QW growth temperature, which decides the indium concentration. It needs large thickness and low temperature to emit long wavelength photons. However, the material quality, electrical and optical properties will degrade with low growth temperature or wide QW. Meanwhile, the growth of long wavelength LEDs based on the InGaN material still faces severe difficulties because of the large (11%) lattice mismatch between InN and GaN and the strong piezoelectric field-induced quantum-confined Stark effect (QCSE) induced by the high strain due to lattice mismatch. Compared to the conventional LEDs, LEDs with proper strain-accommodative structures not only increase the emitting wavelength but also reduce the strain in InGaN well. It provides an alternative approach to tune the wavelength. Two types of strain-accommodative structures are inserted between n-GaN and the multi-quantum wells: one is short period super lattices (SPSL) consisted of 15 period of the 1-nm-thick InGaN well and the 2-nm-thick GaN barrier , and the other is 45nm In_xGa_1-xN (x=0.07-0.09). The samples with strain-accommodative structures demonstrate that: firstly the two structures would efficiently increase the wavelength, which should be attributed to the relief of strain in the InGaN/GaN MQWs. The wavelengths of the two structures in the electroluminescence measurement were 561.6nm and 531nm, respectively. It is longer than that of the control sample (511.8nm). Secondly; the structures can weaken the QSCE. When the current increased from 3mA to 20mA during the electroluminescence measurement, the peak wavelength blue-shift were 5.1nm and 3.1nm, respectively. It is smaller than that of the control sample (7.4nm).

High brightness light emitting diodes have been used to develop high illuminance headlight for medical applications. It provides various advantages such as high illuminance, long life time, reduced infra red light, extended operation time with battery and light weight. A 3 W LED was employed to achieve the high performance medical headlight. The optical design includes two lenses for high energy transmission and high illuminance. The LED headlight shows 42,000 lux with spot diameter of 80 mm at the distance of 300 mm. For comparison purpose, 5 W LED was also used to obtain the high illuminance headlight. However, the large divergence angle and large spot size of the 5 W LED limits the illuminance to 31,000 lux with increased burden on heat dissipation. The thermal images of the heat sinks indicate that the temperature of the headlight using a 3 W LED is below 50 degree C, which is suitable for medical applications.

With the feature of energy-saving, reliability, long life and so on, LED lighting is considered as the next generation of mainstream lighting technology. Based on the characteristics of LED's higher switching speed than fluorescent lamp and incandescent, the technology that uses the white LED light source of interior lighting as the communication base station to transmit information wirelessly, is the hot technology being studied at home and abroad-visible light communication technology. In this paper, the study status of the white LED visible-light wireless communication technology is briefly described; its key technologies are analyzed; and the development trend of LED visible light wireless communication technology is elaborated from the application point of view.

Light-emitting diodes (LEDs) bring great flexibility in color choice and high luminous efficacy design for biomedical illumination. Based on the state-of-the-art LED chips, a three-chip LED illumination system was developed specially for laparoscopy and minimal access surgery. White light is produced by mixing three specific wavelengths of amber red, true green and blue, and then coupled into a fiber-optic light guide with 2mm diameter. The whole device has a compact size of 145mm × 92mm × 84 mm which is more suitable than a conventional xenon lamp source for portable endoscopes. The illuminance and color characteristic of the three-chip model were analyzed, compared to those of traditional light source. A maximum illuminance of 1960 lux was obtained at the distance of 100 mm, with the average current of 450 mA of the LEDs. Additionally, a simulation environment had been set up to find out the performance of the endo-illuminator in the specific circumstance, which was closer distance and crawl space. Experiments showed that images taken under the three-chip LED illumination had better contrast and saturation. With the temperature of 31.5 degrees Celsius at the end of the fiber bundle, the endo-illuminator is also a cold light source.

A LED lighting system in the modern theater and the corresponding control program is introduced. Studies show that moderate and mutative brightness in the space would attract audiences' attention on the screen easily. SCM controls LED dynamically by outputting PWM pulse in different duty cycle. That cinema dome lights' intensity can vary with the plot changed, make people get a better view of experience. This article expounds the architecture of hardware system in the schedule and the control flow of the host of the solution. Besides, it introduces the design of software as well. At last, the system which is proved energy-saving, reliable, good visual effect and having using value by means of producing a small-scale model, which reproduce the whole system and achieves the desired result.

Full-color polymer light-emitting diode (PLED) arrays presently are mainly produced by ink-jet printing. Here, we report a new approach for fabricating full-color PLED arrays that takes advantage of the low-cost and high throughput spin-coating and photo-patterning processes. Compared to previous approaches that also employed photo-patterning, our approach does not require wet processing steps, and the spectra of the colors emitted are not sensitive to the photopatterning time. Because the photo-pattering is a traditional technology which was proved to be successfully used in producing liquid crystal displays and other electrical productions, this method may provide a low-cost and high throughput procedure to manufacture polymeric flat-panel display devices.

A facile way to fabricate highly efficient organic light emitting devices (OLEDs) with insulator MnO as an electron injecting and transporting material was devised, which eliminates the problem of the oxidation of reactive dopants. The power efficiency of 1.1 lm/W by inserting 3-nm-thick MnO as the electron injecting layer was obtained, higher than the 0.8 lm/W efficiency for the reference device with 0.5-nm-thick LiF. A thermal co-evaporation layer containing 10% weight of MnO and tris(8-hydroxyquinolato)aluminum (Alq₃) as the electron transporting layer showed more efficient electron transport ability, with turn-on voltage of 3.8 V, lower than 7.4 V for the intrinsic Alq₃. Meanwhile, the insertion of thin MnO layer between organic photoactive layer and inorganic metal electrode significantly improved performance and stability of organic solar cell compared to device without it. The power conversion efficiency (PCE) of 2.91% by inserting 3-nm-thick MnO was obtained, higher than the 0.91% efficiency for the device without it, and 2.59% for the device with 0.5-nm-thick LiF. Charge transport of rhenium trioxide (ReO₃) in organic electronic devices was investigated. The hole injection/transport was blocked and the electron injection/transport was enhanced with doping of ReO₃ in organic electronic devices. Thus the charge balance and efficiency of the OLED were improved, 2.7 cd/A of current efficiency (CE) at 20 mA/cm² for the device with ReO₃ was higher than 1.5 cd/A for the device without it. In the case of organic photovoltaic cells (OPV), the open-circuit voltage (V_oc), 0.58 V, was higher compared to the device without ReO₃ (0.44 V) due to the improvement of interface properties. The PCE was increased to 2.27% by the combination of ReO₃ (increasing V_oc) with poly(3,4-ethylene dioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) (improve hole transport to increase J_sc) on the modification of the anode, higher than 1.85% for the device without ReO₃.

After the premier commercialization of OLED in 1997, OLED has been considered as the candidate for the next generation of flat panel display. In comparison to liquid crystal display (LCD) and plasma display panel (PDP), OLED exhibits promising merits for display, e.g., flexible, printable, micro-buildable and multiple designable. Although many efforts have been made on electroluminescent (EL) materials and devices, obtaining highly efficient and pure blue light is still a great challenge. In order to improve the emission efficiency and purity of the blue emission, a new bipolar blue light emitter, 2,7-di(2,2′:6′,2"-terpyridine)- 2,7-diethynyl-9,9-dioctyl-9H-fluorene (TPEF), was designed and synthesized. A blue OLED was obtained with the configuration of ITO/PEDOT/PVK:CBP:TPEF/LiF/Al. The device exhibits a turn-on voltage of 9 V and a maximum brightness of 12 cd/m² at 15 V. The device gives a deep blue emission located at 420 nm with the Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.10). We also use TPEF as electron transporting material in the device of ITO/PPV/TPEF/LiF/Al, the turn-on voltage is 3 V. It is proved the current in the device was enhanced indeed by using the new material.

The escaped and trapped emission of organic light-emitting diodes was investigated by an integrating sphere and a fiber spectrometer. It was found that the ratio of escaped emission to the escaped and trapped in the substrate emission is 71%. In order to explain our experimental results, we extended the half-space dipole model, in which the dipole radiation pattern is taken into account. The calculated escaped and trapped emission of devices agreed well with our experiments. Our experimental and theoretical results is expected to be an instruction to the optimization of device structures for improving the out-coupling efficiency.

For gaining effective features to realize fault diagnosis in the LED illuminating circuits, a method of fault diagnosis in analog circuits based on cloud model is proposed. In this paper, the analog circuit with a sinusoidal input is simulated and its output is sampled to extract sequences of each layer of wavelet coefficients as the initial fault feature vectors. Then, the backward cloud algorithm of cloud model is applied to obtain corresponding digital features of the wavelet coefficients, which include the Expected value E_x, the Entropy E_n and the Hyper entropy H_e as new fault feature vectors, named fault cloud feature vectors. Finally, Fault cloud feature vectors are used to BP neural networks to classify fault and realize the fault diagnosis in analog circuits. The simulation result on the LED illuminating circuits shows that this method is feasible and has many powerful virtues, such as diagnosing and locating faults quickly and exactly.

The human vision system has visual functions for viewing 3D images with a correct depth. These functions are called accommodation, vergence and binocular stereopsis. Most 3D display system utilizes binocular stereopsis. The authors have developed a monocular 3D vision system with accommodation mechanism, which is useful function for perceiving depth. This vision unit needs an image shift optics for generating monocular parallax images. But conventional image shift mechanism is heavy because of its linear actuator system. To improve this problem, we developed a light-weight 3D vision unit for presenting monocular stereoscopic images using a soft linear actuator made of a polypyrrole film.

An invisible code is one of the useful technologies for a computer interaction. In this paper, we propose a method to display invisible codes using LCD panels and to detect a polarized symbol image with a conventional CCD camera. The authors have been developing the mobile robots which can cooperation between robots. The robots should communicate with each other in order to cooperate together. Therefore, the communication between robots is very important problem to be solved. These robots generally utilize wireless transmission system. The transmission sets send and receive on the same frequency or channel to establish the radio communication. This is called working simplex. The robots cannot start communication if both sets use different frequency channels. It is important to perform an initial configuration for establishing the radio signal transmission at a first contact among strange mobile robots. To solve this problem, this paper describes an information transmission system using an invisible code on displays which show an expression of robot's eyes.

As a new generation energy-saving lighting source, LED is applied widely in various technology and industry fields. The requirement of its adaptive lighting technology is more and more rigorous, especially in the automatic on-line detecting system. In this paper, a closed loop feedback LED adaptive dimming lighting system based on incremental PID controller is designed, which consists of MEGA16 chip as a Micro-controller Unit (MCU), the ambient light sensor BH1750 chip with Inter-Integrated Circuit (I2C), and constant-current driving circuit. A given value of light intensity required for the on-line detecting environment need to be saved to the register of MCU. The optical intensity, detected by BH1750 chip in real time, is converted to digital signal by AD converter of the BH1750 chip, and then transmitted to MEGA16 chip through I2C serial bus. Since the variation law of light intensity in the on-line detecting environment is usually not easy to be established, incremental Proportional-Integral-Differential (PID) algorithm is applied in this system. Control variable obtained by the incremental PID determines duty cycle of Pulse-Width Modulation (PWM). Consequently, LED's forward current is adjusted by PWM, and the luminous intensity of the detection environment is stabilized by self-adaptation. The coefficients of incremental PID are obtained respectively after experiments. Compared with the traditional LED dimming system, it has advantages of anti-interference, simple construction, fast response, and high stability by the use of incremental PID algorithm and BH1750 chip with I2C serial bus. Therefore, it is suitable for the adaptive on-line detecting applications.

The luminescent properties of different M^II _xM^II _1-xAl₂S₄:Eu and M^IIAl₂S₄:Eu are researched in this paper. A novel assessment method is used to evaluate these materials base on the configuration coordinates model. Vibronic coupling parameters of these phosphor materials can be calculated by the formula. With the calculation of characteristic energy and unitless factors, performances of M^II _xM^II _1-xAl₂S₄:Eu and M^IIAl₂S₄:Eu are evaluated. We then concluded that BaAl₂S₄:Eu shows highest Φ value comparing with other single or complex thioaluminates. With increasing amounts of Ba and Ca ions in the Ba_xMg_1-xAl₂S₄:Eu and Ca_1-ySr_yAl₂S₄:Eu respectively, the complex thioaluminates gives better luminescent performance and a broad tunable emission color can be achieved.

A classic electromagnetic theory is used in this paper to investigate the light outcoupling in blue top-emitting organic light-emitting devices (TEOLEDs) with a samarium/silver (Sm/Ag) bilayer cathode. With the method, the outcoupling efficiency and the spectra of the devices with different top-electrodes and outcoupling layers were simulated. The calculated results demonstrate that in the devices, the increasing thickness of the Ag film would result in the redshift of blue emission and the decrease of emission intensity. While the thickness of the Sm film only influences the emission intensity of the devices. The thickness of the outcoupling layer is varied to obtain the saturated and efficient blue emission and then the optimal thickness is determined. The microcavity effect induced mainly by the bilayer cathode with a relatively high reflectivity is considered to explain the optical characteristics of the blue TEOLEDs, including some abnormal phenomena. The simulated results show good agreement with the measured data.

The effect of ozone and O₂ plasma treatment of ITO on the charge-carrier injection in ITO/N, N'-bis-(1-napthyl)-N, N'- diphenyl-1,1'biphenyl-4,4'-diamine (NPB)/tris(8-quinolinolato)-aluminum (Alq₃)/Al organic heterojunction devices have been studied through the analysis of current-voltage characteristics. From the experiments, it is demonstrated that the average electric field inside Alq₃ layer is larger than the average field in the NPB layer. The investigation demonstrated that the hole injection into NPB from anode is Fowler-Nordheim (FN) tunneling and the electron injection into Alq3 from cathode is Richardson-Schottky (RS) thermonic emission.

LED play the role at such the kind of modern display light source thanks to its power consumption and the most important, outstanding colour gamut. Modern displays are required to be much thinner and thinner with best colour gamut. We have manipulated the pattern distribution of the micro features to obtain the required optical characteristics. A light guide plate (LGP) of 3.5 inch dimension using an LED light source is used as an example for the study of integrated LGPs. This research designs a piece of light guide film (LGF) at the back of LGP. It may induct the exterior light, and enables the backlight module to achieve the energy conservation. In addition, the special-designed light pipe and freeform optics will induce external light, which will contribute 15% power savings.

In order to utilize the LCoS, this paper advances a new patten liquid material which is ferroelectric liquid crystal. It has the characteristics, such as time division-style full-color display, high resolution, low voltage and high speed response. If it is used in the microdisplay, we can attain large area visual display, high open rate and high responding time. The alignment of ferroelectric liquid crystal is very complicated, so we use photo-alignment, rubbing or hybrid-alignment to determine the direction of liquid. Once the liquid layer has been fabricated, we use space parameter method to analyse the liquid layer, and we make sure the detailed optical thickness and pretilted angle.

The organic compound, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was used as a light outcoupling layer in top-emitting organic light-emitting devices (TEOLEDs) with an iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C2'] picolinate (FIrpic) emission layer. It was different from the conventional TEOLEDs that use ITO as a thickness adjustment layer to make the cavity length matchable with the resonant wavelength of the blue light. The total thickness (105 nm) of organic materials sandwiched between the cathode and the anode in this TEOLED was almost same with that in a conventional bottom-emitting OLED (BEOLED). The influence of the BCP outcoupling layer on EL intensity, luminous efficiency, and EL spectra was explored by combining experimental data with microcavity and transfer matrix theories. The experimental data was basically consistent with theoretical results. As a result, the high performances such as high brightness, large luminous efficiency, and saturated chromaticity were obtained in the blue TEOLED, which were comparative to those in the BEOLEDs.

This paper presents a free-form lens design for indoor illumination. The lens consists of a TIR (total internal reflection) surface on the sidewall, a refractive surface on the front side, and a concave surface on the rear side. The TIR surface is decorated with a free-form profile that light rays emitted from the LED with a larger spread angle to the axis will experience a total internal refection and output from the front refractive surface. While the central part of the front refractive surface has a convex surface that makes light rays closing to the optical axis more evenly distributed. The purpose of the rear concave surface is to let light rays emitted from the LED enter the lens straightforwardly. With this lens light rays from a Lambertian-type LED light source can be redistributed so that a uniform illumination can be achieved. The optical simulation results show that the measured optical efficiency is 75% while the uniformity is 80% on a target plane of 6-m diameter and at 2.5-m away.

An anti-reflection (AR) coating system was inserted between the anode (ITO) and the glass substrate in the red light organic electroluminescent devices (OLED) for the structure being K9/ITO/NPB (60nm)/DCJTB (0.3nm)/Alq₃ (60nm)/ LiF(0.3nm)/Al. The AR film system structure was K9/TiO₂/Al₂O₃/2-ITO, and the optical thicknesses of TiO₂ and Al₂O₃ coatings were also quarter wave length. The results indicated that the maximum transmissivity of AR coating was by 95 %( 610nm); it increased by 8% compared with only using ITO as AR coating. The average luminance increased by about 30%, the average energy efficiency increased by about 60%, while reducing the threshold voltage of the devices. The processing is simple and high efficient, and can change AR coating structure according to the OLED device different emission wavelength, therefore, can be widely applied to the OLED devices.

The thin aluminum nitride(AlN) film using as an insulating layer was inserted between the anode (ITO) and the NPB organic film in the organic light-emitting devices(OLED) for the structure being K9/ITO/AlN/NPB/Alq₃/LiF/Al.The effect of the different thickness AlN film on the device performance was investigated. After optimization, improvement of OLEDs properties is biggest when the AlN film thickness is about 0.4nm.Such a structure with AlN layer facilitates the increase of current density and decrease of threshold voltage, resulting in an improved luminance and energy efficiency. The average luminance increased by about 30% and an improvement of 21.8% on the average current density. The lifetime experiment of the devices has proved an improvement on stability because of inserted AlN film. This phenomenon is mainly because of the insulating capability of the aluminum nitride coating and the passivation role of AlN film to the ITO surface. The processing is simple and high efficient, can be widely applied to the OLED devices.

Junction temperature is a critically important parameter for high-power white LED applications. It has directly influence upon light output, device life time, reliability, and emitting wavelength of an LED. In this paper, the principle and common types of LED is introduced. The effects of the junction temperature on performance of high-power LED are discussed. The influencing factors of the junction temperature are analyzed, and some general guidelines to maintain a low junction temperature to keep good performance of an LED are given.

Eu³⁺ doped yttrium orthosilicate (Y₂SiO₅) phosphor was prepared by the sol-combustion method using citric acid as complexing agent in this experiment. The X-ray diffraction (XRD) pattern, excitation and emission spectra were used to investigate the crystal structure and luminescent properties of the phosphor. XRD pattern showed that pure Y₂SiO₅:Eu³⁺ phosphor was obtained. The excitation spectrum was composed of a broad band from 200-350 nm and a series of narrow bands from 350-500 nm, in which the excitation peaks at 400 nm and 470 nm were stronger. The emission spectrum showed the most intense emission peak was located at 613 nm, which corresponded to the ⁵D₀→⁷F₂ transition of Eu³⁺. The results showed that this phosphor could be excited by UV or blue light and emit red light. The luminescent intensity depends on the concentration of Eu³⁺ and it reached the maximum when the molar concentration of Eu³⁺ was 4 mol%. In this study, we found that the emission intensity reached maximum when the ratio of citric acid and Y³⁺ was 1.5:1. The results indicated that Y₂SiO₅:Eu³⁺ is a potential red-emitting candidate phosphor for white light-emitting diodes.

The Y₂Si₂O₇:Tb³⁺ phosphor was synthesized by high temperature solid state method. The crystal structure and luminescent properties of phosphors were studied by XRD pattern, excitation and emission spectra in this paper. XRD pattern showed that the sample was single phase Y₂Si₂O₇ crystal and the crystal lattice constants a=0.806nm, b=0.934 nm, and c=0.692 nm. The excitation spectrum is composed of a broad band centered 290nm and three narrow bands corresponding to 4ƒ - 4ƒ transition of Tb³⁺ centered 378 nm, 400nm and 420nm, respectively. The emission peaks of phosphor were located at 487nm, 546nm, 584nm and 623nm, which were corresponding to ⁵D₄-⁷F₆, ⁵D₄-⁷F₅, ⁵D₄-⁷F₄ and ⁵D₄-⁷F₃, respectively. The influences of Tb³⁺ concentration on the luminescent intensity of Y₂Si₂O₇:Tb³⁺ phosphor was studied. The results indicated that this phosphor could act as a candidate green phosphor for UV-excited white LED.