High‐resolution and high‐brightness full‐colour “Silicon Display” for augmented and mixed reality

High‐brightness micro‐LED display bonded onto silicon backplane has been successfully demonstrated. The 0.38‐inch full‐colour active matrix LED microdisplay system consists of 352 × 198 pixels. Each pixel is 24 μm square composed of red, green, and blue (RGB) subpixels corresponding to a pixel resolution of 1053 ppi. Quantum‐dot materials are formed on III‐nitride blue micro‐LED array to convert blue light into red and green for full‐colour operation. We have confirmed that this microdisplay, which we call “Silicon Display” has wide colour gamut exceeding 120% of sRGB. We describe the advantage of this colour‐converting approach for the full‐colour micro‐LEDs. Progress toward higher resolution is also described. Brightness of more than 30 000 cd/m² has been confirmed at a driving current density of 4 A/cm² for 3000 ppi blue monochrome micro‐LED prepared for full‐colour Silicon Display. We believe our “Silicon Display” is ideally suited for near‐to‐eye displays for augmented and mixed reality.     

Implementation of an LED backlight for avionics displays

Abstract— The replacement of conventional light sources used to backlight displays with LEDs is very attractive in avionics. Today's LED technology provides devices suitable to implement display backlight sources but specific requirements need to be satisfied for avionics displays. This paper covers the development of an innovative LED backlight dedicated to avionics displays, realized in a new box geometry in order to generate more than 10,000 cd/m² on a 6 × 5‐in. active area using less than 28 W of power.     

Very‐high‐brightness diodes for passive‐matrix display applications

Abstract— The development of a high‐brightness low‐voltage yellow‐light‐emitting polymer system suitable for use in low‐cost passive‐matrix displays will be reported. Average device efficiencies of 16 lm/W at 100 and 1000 cd/m² are achieved at 2.1 and 2.4 V, respectively. A luminance level of 100,000 cd/m² is achieved at 5.5 V.     

Large‐screen displays using metal—insulator—metal cathode arrays

Abstract— Large‐screen (32‐in. WXGA and 17‐in. VGA) displays using metal—insulator—metal (MIM) cathode arrays have been developed. A cathode structure with low‐resistance electrodes and low‐capacitance emitters shortens signal delay and decreases the voltage drop in large MIM‐cathode arrays. By using a dual‐scan method, the signal delay was suppressed to less than 30% of the horizontal scan time in the 32‐in. WXGA panel. Emission efficiency of the cathode array was improved to 3% by reducing the surface work function of the top electrode from 4.7 to 3.9 eV. The cathode life was also improved to more than 10,000 hours. The display panel incorporating the cathode arrays and high‐efficiency P22‐phosphor screens with 3‐mm spacers showed high screen brightness (average brightness, 378 cd/m²; peak brightness, 832 cd/m²) at an anode voltage of 10 kV.     

Electro‐optical characteristics of a radio‐frequency plasma‐display module

Abstract— Plasma‐display modules intended for piled screens driven by a radio‐frequency voltage were investigated. The frequency range of a high‐efficiency RF discharge was determined. An efficiency of 4 lm/W at a brightness of 5000 cd/m² was obtained.     

Towards a low‐cost high‐quality carbon‐nanotube field‐emission display

Abstract— We have developed field‐emission‐display technology driven by chemical‐vapor‐deposition‐grown carbon‐nanotube emitters incorporated in a simple, low‐cost device structure. Here, we report on frit‐sealed test displays with a brightness of 3000 cd/m² at 3 kV and a lifetime of 9000 hours with only 45% degradation. We also demonstrate the scalability of the technology with a uniform high‐brightness 6‐in. QVGA that displays video images with a switching voltage of 40 V.     

Fluorescent‐based tandem white OLEDs designed for display and solid‐state‐lighting applications

Abstract— Highly efficient tandem white OLEDs based on fluorescent materials were developed for display and solid‐state‐lighting (SSL) applications. In both cases, the white OLED must have high power efficiency and long lifetime, but there are a number of attributes unique to each application that also must be considered. Tandem OLED technology has been demonstrated as an effective approach to increase luminance, extend OLED lifetime, and allow for use of different emitters in the individual stacks for tuning the emission spectrum to achieve desired performance. Here, examples of bottom‐emission tandem white OLEDs based on small‐molecule fluorescent emitters designed for displays and for SSL applications are reported. A two‐stack tandem white OLED designed for display applications achieved 36.5‐cd/A luminance efficiency, 8500K color temperature, and lifetime estimated to exceed 50,000 hours at 1000 cd/m². This performance is expected to meet the specifications for large AMOLED displays. A two‐stack tandem white OLED designed for SSL applications achieved 20‐lm/W power efficiency, 38‐cd/A luminance efficiency, 3500K color temperature, and lifetime estimated to exceed 140,000 hours at 1000 cd/m². With the use of proven light‐extraction techniques, it is estimated that this tandem device will exceed 40 lm/W with more than 500,000‐hour lifetime, performance that should be sufficient for first‐generation lighting products.     

GaN‐based emissive microdisplays: A very promising technology for compact,ultra‐high brightness display systems

High‐brightness GaN‐based emissive microdisplays can be fabricated with different approaches that are listed and described. They consist either of hybridizing a GaN LED array on a CMOS circuit or building a monolithic component on a single substrate. Using the hybridization approach, two types of 10‐μm pixel pitch GaN microdisplay prototypes were developed: (1) directly driven, 300 × 252 pixels and (2) active‐matrix, 873 × 500 pixels. Brightness as high as 1 × 10⁶ and 1 × 10⁷ cd/m² for blue and green arrays, respectively, were reached. GaN‐based emissive microdisplays are suitable for augmented reality systems or head‐up displays, but some challenges remain before they can be put in production.     

A low‐cost low‐temperature thin‐film‐transistor backplane based on oxide semiconductor

Abstract— An indium‐gallium‐zinc‐oxide (IGZO) thin‐film transistor (TFT) based on an anodized aluminum‐oxide gate dielectric and photoresist passivation has been fabricated. The TFT showed a field‐effect mobility of as high as 18 cm²/V‐sec and a threshold voltage of only 0.5 V. A 50 × 50 AMOLED display based on this type of TFT was designed and fabricated. The average luminance of the panel was 150 cd/m², and the maximum pixel luminance was 900 cd/m².     

Highly efficient large‐sized LED display with improved ergonomics

Abstract— We have proposed a new approach to engineering and manufacturing an indoor indicator based on energy‐effective super‐bright LEDs. In our design, the light from a small number of such LEDs was uniformly redistributed using a special light guide. Recently, we developed a multi‐segment (40) LED indicator with improved ergonomics and a luminance of up to 4000 cd/m². This indicator is also capable of displaying (apart from the digits) special symbols.     

Solution‐processable double‐layered ionic p‐i‐n organic light‐emitting diodes

Abstract— Solution‐processed double‐layered ionic p‐i‐n organic light‐emitting diodes (OLEDs), comprised of an emitting material layer doped with an organometallic green phosphor and a photo‐cross‐linked hole‐transporting layer doped with photo‐initiator is reported. The fabricated OLEDs were annealed using simultaneous thermal and electrical treatments to form a double‐layered ionic p‐i‐n structure. As a result, an annealed double‐layered OLED with a peak brightness over 20,000 cd/m² (20 V, 390 mA/cm²) and a peak efficiency of 15 cd/A (6 V, 210 cd/m²) was achieved.     

PIN OLEDs — Improved structures and materials to enhance device lifetime

Abstract— Currently, three issues are identified that decide upon the commercial success of organic light‐emitting diodes (OLEDs), both in display and lighting applications: power efficiency, lifetime, and price competitiveness. PIN OLEDs are widely seen as the preferred way to maximize power efficiency. Here, it is reported that this concept also delivers the world longest lifetimes. For a highly efficient deep‐red PIN OLED, a half‐lifetime of 25,000 hours for a starting brightness of 10,000 cd/m² and a minimal voltage increase over lifetime is reported. This value corresponds to more than 1 × 10⁶ hours at 1000 cd/m² using an exponent of n = 1.7, which was measured by driving the OLEDs at different starting luminances. Because there is no initial luminance drop, these PIN OLEDs also exhibit a very high 80% lifetime (>300,000 hours at 1000 cd/m²). New record lifetime values for blue and green will be reported as well. Additionally, further topics that have impact on the production yield and cost such as the newly developed air‐stable organic n‐doping material NDN‐26 and top‐emitting structures will be discussed.     

OLED‐based pico‐projection system

Abstract— Two pico‐projection systems, a monochrome green and a full‐color system, based on high‐efficiency OLED microdisplays (VGA; pixel size, 12 μm) are presented. Both optical systems are described by a numerical aperture of about 0.3, a magnification of 15x, and a working distance of 300–360 mm. The frequency limit of both systems is 42 cycles/mm at an image contrast of about 60%. The monochrome projection system with a volume smaller than 10 cm³ consists of one green OLED and a projection lens with five elements. The measured luminance in the image plane is about 0.061 lm. The image has a diagonal of 150 mm with a working distance of about 300 mm and has a considerable image contrast of 396:1. The second system combines three high‐brightness OLEDs, red, green, and blue colored, together with a projection lens and an image‐combining element, and an X‐Cube to achieve full‐color projection. The estimated luminance value for the three‐panel projection unit with an OLED luminance of 10,000 cd/m² for each display will be about Φcalculated = 0.147 lm. In this paper, the system concepts, the optical designs, and the realized prototypes of the monochrome and full‐color projection system are presented.     

Circuits and AMOLED display with self‐aligned a‐IGZO TFTs on polyimide foil

A process to make self‐aligned top‐gate amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) thin‐film transistors (TFTs) on polyimide foil is presented. The source/drain (S/D) region's parasitic resistance reduced during the SiN interlayer deposition step. The sheet resistivity of S/D region after exposure to SiN interlayer deposition decreased to 1.5 kΩ/□. TFTs show field‐effect mobility of 12.0 cm²/(V.s), sub‐threshold slope of 0.5 V/decade, and current ratio (I_ON/OFF) of >10⁷. The threshold voltage shifts of the TFTs were 0.5 V in positive (+1.0 MV/cm) bias direction and 1.5 V in negative (?1.0 MV/cm) bias direction after extended stressing time of 10⁴ s. We achieve a stage‐delay of ~19.6 ns at V_DD = 20 V measured in a 41‐stage ring oscillator. A top‐emitting quarter‐quarter‐video‐graphics‐array active‐matrix organic light‐emitting diode display with 85 ppi (pixels per inch) resolution has been realized using only five lithographic mask steps. For operation at 6 V supply voltage (V_DD), the brightness of the display exceeds 150 cd/m².     

Highly efficient white organic light‐emitting diodes with over 100 lm/W for next‐generation solid‐state lighting

High‐performance two‐unit all‐phosphorescent white devices on a built‐up light extraction substrate that comprised high‐index materials were studied. As a result of suitable optical and electrical design, the device showed an extremely high efficacy of 114 lm/W at 1000 cd/m². The device also showed 102 lm/W with long lifetime (LT70) of over 10,000 h at 3000 cd/m². Outstanding external quantum efficiency of almost 50% was also achieved in a flat panel with an emissive area of 25 cm². Color coordinates of the panel met the Energy Star ® criteria of solid‐state lighting with CIE (Commission Internationale de l'Éclairage) 1931 (x, y) = (0.477, 0.423), and the color rendering index was 81.     

High‐performance 55‐in. diagonal WXGA PDP with extended ALIS technology

Abstract— We have developed a high‐performance 55‐in. diagonal WXGA PDP module with a novel structure by using Extended ALIS (Alternate Lighting of Surfaces) technology. The new cell structure that uses the common bus electrode concept was invented with a new driving scheme aimed toward progressive lighting. A new method of reducing dynamic false contour (DFC), motion adaptive subfield coding, was also developed. The newly developed 55‐in. WXGA panel has a 1000‐cd/m² peak luminance and a 160‐cd/m² full‐screen white luminance with a 9000 K color temperature at a 350‐W display power consumption.     

Practical CNT‐FED structure for high‐luminance character displays

Abstract— A high‐luminance CNT‐FED character display using a simple line rib structure was constructed. The display panel had 48 × 480 dots and the subpixel pitch was 1 mm. The greatest benefit of a display using CNT technology is high luminance performance with low‐power consumption. The luminance of the green‐color dot wasca. 10,000 cd/m² under 1/1 6 duty‐cycle driving at a 6‐kV anode voltage. The high luminance of the display panel can provide good visibility when installed even in outdoor locations, and the power consumption was ca. 4 W at the character displaying module. This, a CNT‐FED for character displays also has potential multifunctionality, which could be battery driven. It should be useful for public displays even under emergency no‐power conditions. In this work, a practical structure and process technologies for making ribs with reasonable cost were developed. The newly introduced 2‐mm‐tall line ribs as spacers were formed by using innovative production processes; i.e., the rib paste was pushed out of a multi‐slit nozzle, and the rib shape was formed by UV‐light irradiation. The developed panel structure and manufacturing processes also had the advantages of size flexibility and high production yield.     

WRGB LEDs spot‐lighting with zooming fixture capabilities

Abstract— An array of WRGB (white, red, green, and blue) LEDs used as a spot‐lighting fixture with zoom capabilities has been developed. The array of WRGB LEDs are packaged inside a light tunnel for color mixing. A zoom lens at the exit of the tunnel projects light through a diffuser film that is used to eliminate the virtual spot phenomenon generated by the light tunnel. Three different position arrangements of the individual WRGB elements in the LED array are discussed, and the optimized arrangement can produce a uniform color light pattern with a 83% optical efficiency when a diffuser film with a 70% transmission haze is used. Through the use of projection zoom lenses, the experimental lighting fixture has a selectable illumination full angle from 20 to 60° with 6000‐lm output and 20.97 lm/W of power consumption, enabling its use in many outdoor commercial lighting applications such as a concert or highlighting a building exterior.     

Thermally cross‐linkable copolymer and its evaluation as a hole transport layer in organic light‐emitting diode devices

This study reports on the synthesis of new thermally cross‐linkable copolymers containing a reactive cross‐linking comonomer. Synthesized polymers showed narrow molecular weight distribution (polydispersity) between 1.18 to 1.22 and 54 to 67% monomer conversion and incorporation of 2 to 7 mol% vinylbenzylcyclobutene comonomer. The polymer was soluble in nonpolar organic solvents such as chloroform, dichloromethane, toluene, and chlorobenzenes, and when cross‐linked, showed resistance to solubility in the previously listed solvents. The cross‐linked films exhibited uniform surface roughness below 1 nm. A polymer containing ~3.6 mol% vinylbenzylcyclobutene was thermally cross‐linked and evaluated as a hole‐transporting layer in green organic light‐emitting diode devices. The devices showed a maximum current efficiency of 39.5 cd/A at a current density of 2.7 mA/cm² and a brightness of 1000 cd/m² with an International Commission on Illumination coordinate (0.33, 0.62). The device performances are found comparable with the ones with the conventional hole‐transporting layer material, NPD.     

High‐efficiency p‐i‐n organic light‐emitting diodes with long lifetime

Abstract— High‐performance organic light‐emitting diodes (OLEDs) are promoting future applications of solid‐state lighting and flat‐panel displays. We demonstrate here that the performance demands for OLEDs are met by the PIN (p‐doped hole‐transport layer/intrinsically conductive emission layer/n‐doped electron‐transport layer) approach. This approach enables high current efficiency, low driving voltage, as well as long OLED lifetimes. Data on very‐high‐efficiency diodes (power efficiencies exceeding 70 lm/W) incorporating a double‐emission layer, comprised of two bipolar layers doped with tris(phenylpyridine)iridium [Ir(ppy)₃], into the PIN architecture are shown. Lifetimes of more than 220,000 hours at a brightness of 150 cd/m² are reported for a red PIN diode. The PIN approach further allows the integration of highly efficient top‐emitting diodes on a wide range of substrates. This is an important factor, especially for display applications where the compatibility of PIN OLEDs with various kinds of substrates is a key advantage. The PIN concept is very compatible with different backplanes, including passive‐matrix substrates as well as active‐matrix substrates on low‐temperature polysilicon (LTPS) or, in particular, amorphous silicon (a‐Si).