Electroluminescent Panel Research Articles

Electroluminescent Panel Based Optical Radiation Sensor

The possibility of using electroluminescent panels as sensors for optical radiation is considered. The presence of a photodielectric effect was noted in them. Oscillograms of the current and voltage of the electroluminescent panel are shown. The dependences of the electric capacity of electroluminescent panels on the level of external illumination are obtained. A block diagram of a system designed to control an electroluminescent panel as a radiation sensor has been developed.

Влияние внешнего излучения на емкостные и токовые характеристики излучающих структур

The electroluminescent light source can be used as flexible compact flat sources of uniform illuminating. The studies on improvement of its main characteristics, especially of color intensity generation, continue. In the paper the possibility of using the changing capacitive and current characteristics of flexible light sources - electroluminescent panels to fix and determine the level of external radiation, which includes the near infrared, optical and ultraviolet ranges, has been shown. The degree of the influence of radiation on the capacitive and current characteristics of these structures based on ZnS: Cu, Mn phosphor using a barium titanate ferroelectric has been revealed. During the studies the instrumental and expert analysis as well as the non-destructive and destructive technological control have been used. It has been found that while changing the radiation intensity from 0 to 2500 kd/m the electric capacity of the structure with 600 cm area becomes 25 % increased, and the intensity increase leads to considerable proportional increase (up to 20 %) of the structure conductivity current

Zwitterionic Sulfobetaine Hydrogel Electrolyte Building Separated Positive/Negative Ion Migration Channels for Aqueous Zn‐MnO2 Batteries with Superior Rate Capabilities

AbstractHydrogel electrolytes have attracted increasing attention due to their potential uses in the fabrication of flexible solid‐state batteries. However, the development of hydrogel electrolytes is still in the initial stage and the number of available strategies is limited. Ideally, the hydrogel electrolyte should exhibit suitable ionic conductivity rate, mechanical strength, and biocompatibility for safety. In this study, a zwitterionic sulfobetaine/cellulose hydrogel electrolyte is fabricated using raw materials from natural plants, which exhibits a good biocompatibility with mammalian cells. The intrinsic zwitterionic groups on sulfobetaine chains can provide separated ion migration channels for positive and negative ions, which largely facilitates electrolyte ion transport. A solid‐state Zn‐MnO2 battery with a fabricated zwitterionic gel electrolyte exhibits a very high rate performance. It exhibits a specific capacity of 275 mA h at 1 C. Even up to 30 C, a high capacity of 74 mA h is maintained during the charging–discharging for up to 10 000 cycles. For wearable applications, the flexible solid‐state batteries can be used as reliable and portable sources to power different wearable electronics such as a commercial smart watch, electroluminescent panel, and color electroluminescence line, which shows their large potentials for use in next‐generation flexible and wearable battery technologies.

A high-performance flexible aqueous Al ion rechargeable battery with long cycle life

With the increasing development of flexible and wearable electronic devices, exploration of advanced power supplies with excellent electrochemical performance, safety and flexibility is highly urgent. In light of natural abundance as well as three-electron redox properties, rechargeable Al ion batteries (AIBs) draw much attention while they still face great challenge of limited Al3+ storage material as well as poorly ionic conductive electrolyte. In our work, an intercalation MoO3 anode and VOPO4 cathode are proposed and mechanically robust gelatin-polyacrylamide hydrogel electrolyte is utilized to fabricate a safe and flexible high-performance rechargeable AIB. The as-assembled AIB exhibits high rate capability of 6 A g−1, high discharge capacity of 88 mAh g−1 and long cyclic stability of 86.2% capacity retention even after 2800 cycles. Besides, the AIB possesses high safety and mechanical flexibility properties, which could serve as reliable power source when even being bent, punctured or cut. Additionally, the aqueous AIB could power 1 m long and 100 cm2 electroluminescent panels, demonstrating their good Al storage property. Considering their favourable electrochemical performance, robustness and safety, the flexible aqueous AIB in our work is believed to open up new avenue in flexible and wearable energy.

Printing process and characterization of fully pad printed electroluminescent panels on curved surfaces

Precision printing of particulate slurries with particle sizes of 5–20 µm using an indirect gravure printing, specifically with pad printing technology, offers interesting applications of functional printing on 3D surfaces. We present our results for printed electroluminescent panels (EL), where printing inks containing luminescent and dielectric particles of such comparatively huge size are transferred from a gravure printing form with gravure patterns not much larger than the particles. Compared with screen printing, the benefit of pad printing is that fairly complex and corrugated surfaces of 3D printed bodies can be endowed with a particulate functional surface. We demonstrated this using commercially available materials for electroluminescent panels. From the electrical point of view, EL panels are capacitors with a luminescent and insulation layer which enables a careful investigation of the printed surface by the characterization of their electrical and optical performance. We emphasize that the printing process we developed is not restricted to EL panels but could also be used for printing protective, electrochemically active, or radiation absorbing metal or metal oxide coatings to 3D printed fused deposition modeling polymer bodies. Printing parameters such as pad hardness, printing velocities, and pad surface tension are investigated. Further, we consider the relation between the printing process, the thickness of the insulation layer, the volume fraction of particulate BaTiO3 in this layer, and EL panel luminance. Our pad printed EL panels, using adapted ink formulations, achieved average luminance of 140 cd/m2 on curved surfaces which also corresponds to the performance standards of conventional screen printed panels.

Improvement of Performance of Electroluminescent Panel by Reducing the Thickness of Dielectric Layer

Alternating-current powder-based electroluminescence is currently the only technique for quick and easy preparation of large area, low cost electroluminescent panels by the means of material printing. Manufacturing of the panels is currently done exclusively by screen printing which is associated with deposition of much thicker layers than typical for other methods of material printing. Typical thickness of layers is in the order of tens of microns and more. The overall thickness of films forming the panel is however a serious shortcoming of the devices because the driving voltage for generation of light needs to be high and the thickness of layers render the panel non transparent from the side of the dielectric layer. One layer of dielectric films screen printed from the commercially available formulation is approximately 10 μm thick and cannot be effectively reduced anymore and thus another printing technique needs to be exploited. The goal of this work is to define and optimize a composition of a novel ink jet printing formulation of dielectric film and verification of parameters of the final layers for use in this type of technology. The major benefits of ink jet printed dielectric layer are the possible preparation of a panel emitting light from both sides with reduced driving voltage needed for its operation.

Waterproof and Tailorable Elastic Rechargeable Yarn Zinc Ion Batteries by a Cross-Linked Polyacrylamide Electrolyte.

Emerging research toward next-generation flexible and wearable electronics has stimulated the efforts to build highly wearable, durable, and deformable energy devices with excellent electrochemical performances. Here, we develop a high-performance, waterproof, tailorable, and stretchable yarn zinc ion battery (ZIB) using double-helix yarn electrodes and a cross-linked polyacrylamide (PAM) electrolyte. Due to the high ionic conductivity of the PAM electrolyte and helix structured electrodes, the yarn ZIB delivers a high specific capacity and volumetric energy density (302.1 mAh g-1 and 53.8 mWh cm-3, respectively) as well as excellent cycling stability (98.5% capacity retention after 500 cycles). More importantly, the quasi-solid-state yarn ZIB also demonstrates superior knittability, good stretchability (up to 300% strain), and superior waterproof capability (high capacity retention of 96.5% after 12 h underwater operation). In addition, the long yarn ZIB can be tailored into short ones, and each part still functions well. Owing to its weavable and tailorable nature, a 1.1 m long yarn ZIB was cut into eight parts and woven into a textile that was used to power a long flexible belt embedded with 100 LEDs and a 100 cm2 flexible electroluminescent panel.

Solid-state fluorescence organic materials as a tool for spectral modification of ZnS-based screen-printed thick layer electroluminescence devices

This work is focused on modification of spectral characteristic of light emitted by alternating current powder-based ZnS electroluminescent device by addition of a color conversion material. A suitable diketopyrrolopyrrole (DPP) derivative with absorption spectrum compatible with emission spectrum of phosphor was found and was added into the printing formulation. Electroluminescent panel was printed by screen printing method and the influence of fluorophore was evaluated from the emission spectra of the electroluminescent device. Color space coordinates of emitted light of pure phosphor and phosphor modified by DPP were plotted into the CIE space for better visualization of the color change. It was found that the presence of fluorophore increased the value of measured quantity—absolute spectral irradiance—more than seven times at 587 nm which corresponds to the maximum of fluorescence emission of DPP. This approach provides useful tool to obtain colors of various wavelengths and therefore various hues without the need to look for new challenging and expensive chemical modifications of the phosphor.

Polar-Electrode-Bridged Electroluminescent Displays: 2D Sensors Remotely Communicating Optically.

A novel geometry for electroluminescent devices, which does not require transparent electrodes for electrical input, is demonstrated, theoretically analyzed, and experimentally characterized. Instead of emitting light through a conventional electrode, light emission occurs through a polar liquid or solid and input electrical electrodes are coplanar, rather than stacked in a sandwich configuration. This new device concept is scalable and easily deployed for a range of modular alternating-current-powered electroluminescent light sources and light-emitting sensing devices. The polar-electrode-bridged electroluminescent displays can be used as remotely readable, spatially responsive sensors that emit light in response to the accumulation and distribution of materials on the device surface. Using this device structure, various types of alternating current devices are demonstrated. These include an umbrella that automatically lights up when it rains, a display that emits light from regions touched by human fingers (or painted upon using a mixture of oil and water), and a sensor that lights up differently in different areas to indicate the presence of water and its freezing. This study extends the dual-stack, coplanar-electrode device geometry to provide displays that emit light from a figure drawn on an electroluminescent panel using a graphite pencil.

Power source for electroluminescent panels

Requirements for the operation mode of power sources of flat electroluminescent panels are formulated. A block diagram of the power source for electroluminescent panels is developed. The effect of the current waveform on parameters of the electroluminescent panel is studied.

Enhanced green luminescence and energy transfer studies in Ce3+/Tb3+-codoped α-zirconium phosphate nanosheet

The rare earth Ce3+ and Tb3+ ions -doped α-zirconium phosphate [Zr(HPO4)2, abbreviated as ZrP] nanosheet phosphors were prepared by direct precipitation process at ambient temperature. The X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence emission and excitation spectra and the fluorescent lifetime measurements were used to characterize the crystal structure, morphology as well as the luminescent properties of the phosphor system. The Ce3+ or/and Tb3+ ions-doped ZrP system clearly exhibited nanosheet structure, as can be confirmed from their XRD and SEM results. Excited with ultra-violet (UV) light 368nm, the Ce3+/Tb3+-codoped ZrP showed intense green emission at 546nm corresponding to the 5D4→7F5 transition of Tb3+. With the increase of Ce3+ doping concentration, the luminescent intensity and fluorescence lifetimes of Tb3+ were gradually increased. The results manifested that the obvious energy transfer phenomenon from Ce3+ to Tb3+ happened, and the energy transfer mechanism should be due to the dipole–quadrupole interaction. Moreover, the chromaticity coordinate of ZrP:Ce3+,Tb3+ nanosheet was also studied, and the emission color can be adjusted from blue-greenish to green by increasing the Ce3+ concentration. The ZrP:Ce3+,Tb3+ nanosheet may be used as a green-light emitting candidate for the optoelectronic devices such as electroluminescence panels or white light-emitting diodes.

Electroluminescent Materials Can Further Enhance the Nighttime Conspicuity of Pedestrians Wearing Retroreflective Materials.

We investigated the nighttime conspicuity benefits of adding electroluminescent (EL) panels to pedestrian clothing that contains retroreflective elements. Researchers have repeatedly documented that pedestrians are too often not sufficiently conspicuous to drivers at night and that retroreflective materials can enhance the conspicuity of pedestrians. However, because retroreflective elements in clothing are effective only when they are illuminated by the headlamps of an approaching driver, they are not useful for pedestrians who are positioned outside the beam pattern of an approaching vehicle's headlamps. Electroluminescent materials-flexible luminous panels that can be attached to clothing-have the potential to be well suited for these conditions. Using an open-road course at night, we compared the distances at which observers responded to pedestrians who were positioned at one of three lateral positions (relative to the vehicle's path) wearing one of two high-visibility garments. The garment that included both EL and retroreflective materials yielded longer response distances than the retroreflective-only garment. This effect was particularly strong when the test pedestrian was positioned farthest outside of the area illuminated by headlamps. These findings suggest that EL materials can further enhance the conspicuity of pedestrians who are wearing retroreflective materials. EL materials can be applied to garments. They may be especially valuable to enhance the conspicuity of roadway workers, emergency responders, and traffic control officers.

A High Power Driver IC for Electroluminescent Panel: Design Challenges and Advantages of using the Emerging LEES-SMART GaN-on-CMOS process

The Electroluminescent (EL) panel is an emerging backplane lighting technology and becoming increasingly popular in advertising display and facade decoration. Despite the increased popularity of the EL panel, driver circuit for large EL panel is nascent in part because of the required high output power. In this paper, a novel high power EL driver IC based on the emerging LEES-SMART GaN-on-CMOS process are presented and we show that this integrated class-D EL driver is advantageous compared to EL driver IC based on state-of-the-art silicon IC process.

Analysis of and increase in working time of electroluminescence panels

Possible reasons for decomposition of the emission layer of working electroluminescence structures that cause a decrease in the working time are considered. Results of a multifactor experiment aimed at a search for the optimal composition of suspensions of the emitting and dielectric layers of the structure are presented. Compositions of dielectric components are proposed. Results of life tests are presented.

Paper No P19: Characteristic of Thermal Behavior and Optical Performance of AC Powder Electroluminescence Panel under Controlled Temperature

AbstractThe self‐heating phenomenon and optical performance of the powder‐based AC electroluminescence panel under controlled temperature have been investigated. Both the self‐heating temperature and the temperature coefficient of luminance were found to increase with drive voltage and frequency.

Precipitation Synthesis and Color‐Tailorable Luminescence of α‐Zr(HPO4)2: RE3+(RE = Eu, Tb) Nanosheet Phosphors

The rare earth (RE = Eu and Tb) ions‐doped α‐Zr(HPO4)2 (ZrP) nanosheet phosphors were synthesized by direct precipitation method, and their structures and photoluminescence properties were investigated. The results of X‐ray diffraction and scanning electron microscopy indicated that the systems of ZrP:RE3+ had similar nanosheet structure except with relatively larger interlayer spacing as compared with pure α‐ZrP. Under the excitation of UV light, the ZrP:RE3+ nanosheet phosphors showed red and green emission peaks corresponding to the 5D0→7F2 transition of Eu3+ and the 5D4→7F5 transition of Tb3+, respectively. After Eu3+ and Tb3+ were co‐doped in ZrP host, not only the red and green emission peaks were simultaneously observed, but also the luminescent intensity and fluorescence lifetimes of Tb3+ were gradually decreased with the increase in Eu3+‐doping concentration, which implied the energy transfer from Tb3+ to Eu3+ happened. It was deduced that the energy transfer from Tb3+ to Eu3+ occurred via exchange interaction. Through optimization to the samples, a nearly white‐light emission with the color coordinate (0.322, 0.263) was achieved under 377 nm excitation. The ZrP:RE3+ nanosheet phosphors may be a potential color‐tailorable candidate for fabricating optoelectronic devices such as electroluminescence panels.

Evaluation of Clinical Usefulness of a Medical Monitor Equipped With an Organic Electroluminescence Panel in Comparison With Liquid Crystal Display Monitors

The medical liquid crystal display (LCD) monitor is a conventionally used imaging device for diagnosis and during endoscopic surgery. Recently, a medical organic electroluminescence panel, the organic light-emitting diode (OLED) monitor, was made available commercially. The advantages of the OLED monitor include good color reproducibility, high contrast, and high video responsiveness. In this nonclinical study, we compared the clinical usefulness and image quality of the OLED monitor and those of the LCD monitor using videos of gynecologic endoscopic surgeries. Monitors were set for blind evaluation. Five evaluators with varying experience in endoscopic surgery evaluated 21 surgery videos played simultaneously on an OLED monitor and two LCD monitors for 2 to 3 minutes twice. Evaluators judged 13 clinical usefulness indices and 11 image quality indices using a 5-point scale (1, very good; 5, very poor) for each video. The mean scores of clinical usefulness indices of the OLED monitor and the LCD monitors 1 and 2 were 2.2 to 2.7, 2.1 to 3.3, and 3.0 to 3.2, respectively. Of seven indices measured, five including motion response, the ability to differentiate organs, recognize lesions, and reproduce actual images, and the general impression of picture quality were statistically superior with use of the OLED monitor compared with the LCD monitor 1, and two including ability to distinguish blood vessels and the ureters were statistically superior with use of the LCD monitor 1 compared with the OLED monitor. The mean scores of image quality indices of the OLED monitor and the LCD monitors 1 and 2 were 1.8 to 3.2, 2.6 to 3.6, and 2.8 to 4.0, respectively. Each index of the OLED monitor was superior to or comparable with those of the LCD monitors. We conclude that the OLED monitor is superior to the LCD monitors insofar as several video presentation characteristics required in gynecologic endoscopic surgery. These findings suggest that the OLED monitor is expected to contribute detailed assessment of organs and the operative field.

Characteristics of distributed-type inorganic electroluminescence panels with comb-shaped electrodes

We deposited comb electrodes with narrow gaps between the teeth on a glass substrate, thus realizing a high electric field intensity that cannot be achieved with conventional structures. Au electrodes are deposited to form a comb shape and then spin-coated with a phosphor layer obtained by mixing ZnS phosphor particles with resins in a certain ratio. An AC voltage was applied to the gaps between the teeth of the comb electrode to emit light, from which the luminance was measured for different electric field intensities. The luminance was not affected by the transmittance of the electrodes themselves when measured from the phosphor layer side. Therefore, it may be possible to produce a display that does not require transparent electrodes by using the phosphor layer side of a device with comb electrodes made of metals, such as Au, for the display.

Luminance and image quality analysis of an organic electroluminescent panel with apatterned microlens array attachment

Luminance and image quality observed from the normal direction of a commercial 2.0 inchpanel based on organic electroluminescence (OEL) technology attached to regular andpatterned microlens array films (MAFs) were studied and analyzed. When applying theregularly arranged MAF on the panel, a luminance enhancement of 23% was observed,accompanied by a reduction of the image quality index as low as 74%. By removing themicrolenses on the emitting areas, the patterned MAF enhances the luminance efficiency ofthe OEL by 52% keeping the image quality index of the display as high as 94%,due to the effective light extraction in the glass substrate being less than thecritical angle. 3D simulation based on a ray-tracing model was also established toinvestigate the spatial distribution of light rays radiated from an OEL pixel withdifferent microstructures which showed consistent results with the experimentalresults.

Effect of Dielectric Layer of a Distributed‐Type Inorganic High‐luminosity Electroluminescent Panel

The inorganic high‐luminosity electroluminescent (EL) panel used in this study is a distributed‐type EL panel, which can be produced using a printing technique. We obtained a panel with a high luminosity of 7940 cd/m2 at 6 kHz. In addition, we believed that the panel temperature and luminosity of this panel were closely related. Therefore, we considered the relationship between the temperature change in the dielectric layer and the luminosity since this relationship is responsible for the supply of electric charge to the phosphor layer. A change in the amount of electric charge by heating in a high‐voltage domain originates at the Curie point of BaTiO3 ferroelectric particles. This indicates that the influence of BaTiO3 was strong.