Show all abstracts
View Session
- Front Matter: Volume 7852
- Display Session
- LED Session
- OLED Session
- Poster Session
Front Matter: Volume 7852
Front Matter: Volume 7852
Show abstract
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.
Display Session
Design and fabrication of an ultra-slim light guide for LCD backlights
Show abstract
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.
Design of multilayer light guide films for multifunctional keypad
Show abstract
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.
Evaluating the uniformity of color spaces and performance of color difference formulae
Show abstract
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.
Performance simulation of diffuser with microstructure for LCD backlight system
Show abstract
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.
The technology of multiuser large display area and auto free-viewing stereoscopic display
Show abstract
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.
Study on the heat dissipation of high-power LEDs
Show abstract
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.
LED Session
LED white lights with high CRI and high luminous efficacy
Show abstract
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.
A kind of side-emitting LED backlight light guide panel net dot design method
Show abstract
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.
Design of precision approach path indicator with LEDs as its light sources
Show abstract
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.
Tunable emission wavelength of InGaN/GaN multiquantum wells employing strain-accommodative structures
Show abstract
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 InxGa1-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 illuminance light-emitting diode headlight for medical applications
Show abstract
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.
Study of key technologies of visible light communications based on white LED
Show abstract
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.
Three-chip LED illumination system for laparoscopy and minimal access surgery applications
Show abstract
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.
The cinema LED lighting system design based on SCM
Show abstract
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.
OLED Session
Full color polymer light-emitting diodes with photo-patterning process
Show abstract
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.
n-Type doping in organic electronic devices
Lixin Xiao,
Jiaxiu Luo,
Fei Wang,
et al.
Show abstract
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 (Voc), 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 Voc) with poly(3,4-ethylene dioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS)
(improve hole transport to increase Jsc) on the modification of the anode, higher than 1.85% for the device without ReO3.
An electron transporting blue emitter for OLED
Boyuan Qi,
Jiaxiu Luo,
Suyue Li,
et al.
Show abstract
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 in organic light-emitting devices
Show abstract
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.
Poster Session
Fault diagnosis in LED illuminating circuits based on cloud model
Show abstract
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 Ex, the Entropy En and the Hyper entropy He 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.
Monocular 3D display unit using soft actuator for parallax image shift
Show abstract
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.
Invisible code display for robots' eye communication using polarization control by LCD panel
Show abstract
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.
A design of LED adaptive dimming lighting system based on incremental PID controller
Show abstract
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.
Vibronic coupling parameters and luminescent properties of Eu2+ doped complex alkaline earth thioaluminates
Show abstract
The luminescent properties of different MII
xMII
1-xAl2S4:Eu and MIIAl2S4: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 MII
xMII
1-xAl2S4:Eu and MIIAl2S4: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 BaxMg1-xAl2S4:Eu and Ca1-ySryAl2S4:Eu respectively, the complex thioaluminates gives better
luminescent performance and a broad tunable emission color can be achieved.
The investigation of light outcoupling in blue top-emitting OLEDs
Ling-ling Deng,
Shu-fen Chen,
Wei Huang,
et al.
Show abstract
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.
Investigation of hole injection characteristics in NPB/Alq3 heterojunction devices
Show abstract
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.
A study of power saving LED back light module
Show abstract
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.
The ferroelectric analysis of LCoS
Show abstract
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.
Effect of BCP layer on electroluminescent performances in blue top-emitting organic light-emitting devices
Jun Xie,
Shufen Chen,
Lingling Deng,
et al.
Show abstract
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.
Free-form lens design for LED indoor illumination
Show abstract
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.
Improvement of OLED properties with anti-reflection coatings
Show abstract
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.
Improvement of OLED properties with the AlN insulated layer
Show abstract
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.
Effect of junction temperature on the performance of high-power white LEDs
Show abstract
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.
Synthesis of Eu3+ doped yttrium orthosilicate phosphor by sol-combustion method
Li Guan,
Litao Jin,
Guoqi Jia,
et al.
Show abstract
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.
Study on the luminescent properties of Tb3+ doped pyrosilicate phosphor
Li Guan,
Guoqi Jia,
Wenhao Chen,
et al.
Show abstract
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 4 - 4 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.