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- 摘要
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16.3: <i>Invited Paper:</i> New development in Red Light‐emitting Diodes (LEDs) using Eu‐doped GaN for Monolithic Micro‐LED Displays
摘要： There has been a strong demand to develop red light-emitting nitride semiconductors for the monolithic integration of the three primary colors (RGB) and the development of a high-resolution display. Such a display is a key device for 'a smart society', in which cyberspace (information processing) and physical space (things) interactively fuse. The ongoing search for an efficient red LED based on GaN is pivotal to those efforts. In blue and green LEDs, InxGa1-xN /GaN multi-quantum wells are used as an active layer. Emission wavelength is determined by In composition in the InGaN. A simple way to realize the red LED is to increase In composition to 0.5. However, lattice mismatch between InGaN and GaN becomes large in InGaN with high In composition, which leads to severe degradation of crystalline quality of InGaN quantum wells. Furthermore, lattice mismatch also induces huge piezoelectric field, resulting in poor radiative recombination due to quantum-confined Stark effects. We have worked on the development of semiconductors intra-center photonics. This novel photonics uses the intra-4f shell transitions of rare-earth ions doped in semiconductors. In 2009, we invented a narrow-band red LED using Eu-doped GaN (GaN:Eu). A main emission line with a half width of less than 1 nm is observed at 621 nm, which can be assigned to the 5D0–7F2 transition of Eu3+ ions. The wavelength is extremely stable against the ambient temperature. Due to optimization of the device processing, the output power of the LED has been increasing steadily to over 1 mW. Utilizing this red LED, small nitride-based monolithic high-resolution optical devices that comprise RGB GaN-based LEDs can be realized for micro-LED displays and/or lighting technology. One of limiting factors for more enhanced light output power is a relatively long radiative lifetime of the Eu emission in GaN:Eu (～300 μs). According to the Fermi’s golden rule, modifying the spontaneous emission rate of Eu ions can be achieved by increasing the photonic density of states at the frequency of spontaneous emission, as already demonstrated with a planar Fabry-Perot cavity. We have boosted the output power by actively manipulating radiative recombination probability at the atomic level of the Eu ions, which can be achieved through control of their photon fields in micro- and nano-cavities. In a GaN:Eu layer embedded in a microcavity consisting of an AlGaN/GaN distributed Bragg reflector (DBR) and a Ag reflecting mirror, a 21-fold increase of the Eu emission intensity was obtained under optical pumping at room temperature. Furthermore, in a preliminary LED with a microcavity consisting of ZrO2/SiO2 and AlInN/GaN DBRs, the output power was enhanced by 10 times. In the talk, current status of the LED and strategies for more improved output power will be presented.
关键词： Monolithic Micro-LED Displays,Eu-doped GaN,Intra-center photonics,Red Light-emitting Diodes,Nitride semiconductors
更新于2025-09-11 14:15:04
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Sacrificial layer for laser lift-off process for flexible-display production
摘要： In this study, we developed a new sacrificial layer (SL) for laser transfer process. Metallic substrate i.e. invar foil was temporarily docked to a glass substrate using glass powder. To ensure successful delamination, the SL was pre-deposited between metal foil and glass substrate. For the first time, the SLs were amorphous gallium nitride and non-stoichiometric gallium oxide which were implemented for laser lift off (LLO) processes of metal foil. Bonding of metal foil to glass sheet was performed using heat treatment while debonding was achieved by LLO method. The laser wavelength was 355 nm which was the best fit for full absorption from SL layers. Transmission electron microscopy, element mapping, and energy dispersive X-ray spectroscopy analyses were performed for investigating elements’ migration and bonding-debonding mechanism.
关键词： Gallium oxide,Flexible displays,Gallium nitride,Laser lift-off,Sacrificial layer
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE/ACM International Symposium on Low Power Electronics and Design (ISLPED) - Lausanne, Switzerland (2019.7.29-2019.7.31)] 2019 IEEE/ACM International Symposium on Low Power Electronics and Design (ISLPED) - FLASH: Content-based Power-saving Design for Scrolling Operations in Browser Applications on Mobile OLED Devices
摘要： As modern people become highly dependent on mobile applications and services, saving the power consumption of browser applications plays an important role for the battery lifetime of mobile devices. This paper investigates how to reduce the power consumption of mobile OLED displays under scrolling operations when displaying web pages. We first propose a content-based analysis to efficiently determine the visual appeal in a web page. Then, two algorithms are presented to dynamically generate power-saving transformation programs for a web page. We next propose a scrolling operation detection to activate the transformation without reducing the user experience. Finally, the results of the extensive experiments conducted on a commercial smart-phone with four real-world web pages to evaluate the performance of the proposed design are very encouraging.
关键词： energy conservation,OLED displays,browser applications,mobile devices,scrolling operations
更新于2025-09-11 14:15:04
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[IEEE 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - Kyoto, Japan (2019.7.2-2019.7.5)] 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - Recent Progress in Inverted OLEDs: Mechanism of Electron Injection without Use of Alkali Metals
摘要： Inverted organic light-emitting diodes (iOLEDs) without the use of alkali metals have attracted extensive attention owing to the demand for the realization of flexible OLEDs that do not require stringent encapsulation; however, the advantage of iOLEDs and the device physics in iOLEDs have seldom been discussed. We show the advantage of iOLEDs over the conventional OLEDs from the fact that the luminance of a conventional-OLED-based flexible display decreases rapidly, whereas our iOLED-based flexible display exhibits approximately half of its initial luminance even after about 392 d. Electrons are injected into iOLEDs effectively by utilizing the solution process and a suitable dopant that can reduce the surface work function.
关键词： air stability,flexible displays,Inverted OLEDs,electron injection,alkali metals
更新于2025-09-11 14:15:04
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[IEEE 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - Kyoto, Japan (2019.7.2-2019.7.5)] 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - New External Compensated Circuit to Achieve Uniform OLED Luminance for High-Resolution AMOLED Displays
摘要： This work proposes a simple-structure pixel circuit composed of low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) and external threshold voltage (VTH) compensation circuit shared by whole row for active-matrix organic light-emitting diode (AMOLED) displays. This proposed circuit combines parallel addressing scheme and voltage-programming method to increase compensation time for accurately detecting threshold voltage variations of driving TFT, and the voltage drop (I-R drop) in power line. Simulation results show that the relative emission current error rates are below 2.93 % and 2.62 % when variations of VTH are ±0.5 V and VDD I-R drop is ±0.5 V, respectively, verifying that the novel pixel design has great potential for use in high resolution AMOLED displays.
关键词： LTPS-TFTs,AMOLED displays,I-R drop,threshold voltage,external compensation
更新于2025-09-11 14:15:04
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Shape-Deformable Self-Healing Electroluminescence Displays
摘要： Self-healing electronic materials can substantially enhance the lifetime of a device as they can self-repair mechanical damages, thereby recovering their initial electronic performance similar to human skin. Despite the development of various self-healing electronic components such as electrodes and semiconducting carrier transport layers, self-healing electroluminescence (EL) layers suitable for deformable displays, which require both high stretchability and self-recovery function, have been rarely demonstrated. Herein, shape-deformable and self-healing EL displays (SSELDs) are presented. Light-emitting materials are fabricated by adding a certain amount of a plasticizer, Triton X-100, to elastomeric poly(urethane) containing light-emitting Cu-doped ZnS microparticles to obtain a viscoelastic composite that undergoes facile shape-deformation and recovery. A capacitive SSELD exhibits frequency-dependent field-induced light emission under alternating current (AC). Color mixing and tuning of EL is conveniently achieved by mechanically mixing two or more Cu-doped ZnS microparticles with different EL characteristics. More importantly, an SSELD self-recovers its EL within few minutes of electrical failure. Further, the AC EL device endures more than 100 cycles of failure-recovery operations. By combining with a shape-deformable ionic liquid, a novel fiber display that exhibits excellent shape-deformable and self-healing EL performance is demonstrated.
关键词： viscoelastic light-emitting composites,self-healing displays,shape-deformable displays,fiber-type displays,polymer plasticizer,alternating current electroluminescence
更新于2025-09-10 09:29:36
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Uniform Insulating Properties of Low-Temperature Curable Gate Dielectric for Organic Thin-Film Transistor Arrays on Plastic Substrate
摘要： Achieving a high-resolution display on a plastic substrate requires a to ensure dimensional stability during fabrication process, including the deposition of gate dielectrics. Evaluation platform to confirm the uniform insulating properties of organic dielectric material prior to actual application to organic thin-film transistor (OTFT) arrays was proposed. This test method enabled verification of the suitability of the low-temperature curable dielectric and chemical resistance during fabrication process. A cross-linked poly(hydroxy imide) (PHI) that can be cured at a low temperature of 130°C exhibited stable insulating properties in a large area that sudden breakdown was not observed in an electric field up to 4 MV/cm. Thiophene-thiazole-based copolymer semiconductor was used as an active layer and inkjet-printed. In all the processes, the temperature of the substrate was kept below 130°C, and 4.8-inch electrophoretic display panels on a polyethylene naphthalate (PEN) substrate with a resolution of 98 dpi was demonstrated.
关键词： Organic thin-film transistors,Organic gate dielectric,Plastic substrates,Low-temperature process,Polymer semiconductor,Flexible displays,Inkjet printing
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) - Tuebingen/Reutlingen, Germany (2018.3.18-2018.3.22)] 2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) - BrightView: Increasing Perceived Brightness of Optical See-Through Head-Mounted Displays Through Unnoticeable Incident Light Reduction
摘要： Optical See-Through Head-Mounted Displays (OST-HMDs) lose the visibility of virtual contents under bright environment illumination due to their see-through nature. We demonstrate how a liquid crystal (LC) ?lter attached to an OST-HMD can be used to dynamically increase the perceived brightness of virtual content without impacting the perceived brightness of the real scene. We present a prototype OST-HMD that continuously adjusts the opacity of the LC ?lter to attenuate the environment light without users becoming aware of the change. Consequently, virtual content appears to be brighter. The proposed approach is evaluated in psychophysical experiments in three scenes, with 16, 31, and 31 participants, respectively. The participants were asked to compare the magnitude of brightness changes of both real and virtual objects, before and after dimming the LC ?lter over a period of 5, 10, and 20 seconds. The results showed that the participants felt increases in the brightness of virtual objects while they were less conscious of reductions of the real scene luminance. These results provide evidence for the effectiveness of our display design. Our design can be applied to a wide range of OST-HMDs to improve the brightness and hence realism of virtual content in augmented reality applications.
关键词： Interaction paradigms,Interaction devices,Human-centered computing,Mixed/augmented reality,Human computer interaction (HCI),Displays and imagers
更新于2025-09-10 09:29:36
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Plastics Get Flexible for Electronics
摘要： Integrated circuitry, “wraparound” electronics, and other conductive applications are being made possible using plastics. Whether plastics are in electronics—or even are the electronics—in consumer and industrial applications, novel conductive polymers and processing methods are helping 21st-century plastics engineers realize new performance and aesthetics benchmarks. In particular, the skyrocketing popularity of portable, personal, or more visually pleasing electronics is driving industry innovation across the board—from flexible electronics used in wearable, automotive, or appliance displays, to high-impact plastics for protecting sensitive electronics on the go. Conductive inks for in-mold use and polymers modified with conductive metal nanoparticles are also spurring searches for commercial uses of novel materials.
关键词： conductive polymers,flexible electronics,automotive displays,plastics,wearable electronics,in-mold electronic inks
更新于2025-09-10 09:29:36
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Graphene mechanical pixels for Interferometric Modulator Displays
摘要： Electro-optic modulators based on micro-electromechanical systems have found success as elements for optical projectors, for simplified optical spectrometers, and as reflective-type screens that make use of light interference (Interferometric Modulator Display technology). The latter concept offers an exciting avenue for graphene nanomechanical structures to replace classical micro-electromechanical devices and bring about enhancement in performance, especially switching speed and voltage. In this work we study the optical response of electrically actuated graphene drumheads by means of spectrometric and stroboscopic experiments. The color reproducibility and speed of these membranes in producing the desired electro-optic modulation makes them suitable as pixels for high refresh rate displays. As a proof of concept, we demonstrate a Graphene Interferometric Modulator Display prototype with 5 μm-in-diameter pixels that compose a high resolution image (2500 pixels per inch)—equivalent to a 5″ display of 12K—whose color can be changed at frame rates of at least 400 Hz.
关键词： high refresh rate displays,electro-optic modulators,Interferometric Modulator Display,micro-electromechanical systems,graphene
更新于2025-09-10 09:29:36