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The subpixel size of high-resolution organic light-emitting diode (OLED) microdisplays measures a few micrometers. To achieve a full-color microdisplay, the current preference is to use photolithography technology on a white OLED instead of using a fine metal mask for patterning. The application of photolithography techniques allows for the creation of microcavity structures or color filters (CFs) to enhance color purity in each emitted color. This paper focuses on investigating specialized OLED device structures for high-resolution microdisplays. The characteristics of each structure, including efficiency and color gamut, are thoroughly discussed. The structure, combining microcavity and CF, achieves the widest color gamut, while microcavity structures show higher efficiency compared to CF-only structures. Tandem structures are also considered for improved efficiency and stability. [ABSTRACT FROM AUTHOR]

In this study, we fabricated sub‐micron organic/inorganic hybrid TFE (Thin Film Encapsulation). We utilize an inkjet printing process to fabricate organic layer. It has excellent industrial applicability by using an industrial printhead with 1024 nozzles. The thickness of the organic layer is optimized through the DPI (Drops Per Inch) of inkjet printing and surface treatment of substrate. The sub‐micron organic/inorganic hybrid TFE was fabricated on a TEOLED (Top Emission Organic Light Emitting Diode), and the OLED (Organic Light Emitting Diode) with the fabricated TFE did not show degradation. Under constant temperature and humidity conditions 30°C, 90 % R.H. (Relative Humidity), the luminance of the OLED remained the same without any defects. The fabricated TFE for the production of OLEDoS has excellent encapsulation properties even at a thin thickness. Finally, we are investigating the optical properties of the ultra‐high‐resolution microdisplay panel applied with the sub‐micron organic/inorganic hybrid TFE. [ABSTRACT FROM AUTHOR]

The optical properties of the materials composing organic light‐emitting diodes (OLEDs) are considered when designing the optical structure of OLEDs. Optical design is related to the optical properties, such as the efficiency, emission spectra, and color coordinates of OLED devices because of the microcavity effect in top‐emitting OLEDs. In this study, the properties of top‐emitting blue OLEDs were optimized by adjusting the thicknesses of the thin metal layer and capping layer (CPL). Deep blue emission was achieved in an OLED structure with a second cavity length, even when the transmittance of the thin metal layer was high. The thin metal film thickness ranges applicable to OLEDs with a second microcavity structure are wide. Instead, the thickness of the thin metal layer determines the optimized thickness of the CPL for high efficiency. A thinner metal layer means that higher efficiency can be obtained in OLED devices with a second microcavity structure. In addition, OLEDs with a thinner metal layer showed less color change as a function of the viewing angle. [ABSTRACT FROM AUTHOR]

In this paper, we developed high color gamut OLED microdisplay. To minimize the crosstalk, a single stack white OLED structure with RGB main peaks was adopted, and RGB color filters were directly patterned on the OLED. In addition, we designed the optical crosstalk prediction model, which could predict the light loss according to the thickness of the passivation layer. As a result, we achieved high color gamut of 125.0% at sRGB, which demonstrated the high color gamut OLED microdisplay. [ABSTRACT FROM AUTHOR]

Microdisplays based on organic light‐emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high‐resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED‐based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard. [ABSTRACT FROM AUTHOR]

Organic light-emitting diode (OLED) microdisplays have attracted much attention as displays for small form factor augmented reality (AR) devices. To realize glass-like thin and wide field of view (FoV) AR devices, we designed a display module with a high aspect ratio microdisplay and a thin optical component. For the high aspect ratio microdisplay, we developed the color OLED microdisplay with a 32:9 aspect ratio and a 0.8-inch diagonal ∼2,490-ppi CMOS backplane. To express color and reduce optical crosstalk, we fabricated the color filter (C/F) patterning directly on the white OLED. We also developed a pin mirror lens with 11 pin mirrors to improve the optical efficiency and quality with a thin lens. By combining the microdisplay with LetinAR's pin mirror lens, we successfully demonstrated an AR device with a wide horizontal FoV of 46° but with a small form factor 4 mm lens. [ABSTRACT FROM AUTHOR]

In this paper, we developed the high aspect ratio color OLED microdisplay and combined with the pin mirror lens, providing a wide FoV AR device in a small form factor. The white OLED exhibited the luminance of 14,072 cd/m2 and current efficiency of 33.8 cd/A at 9 V. To reduce optical crosstalk, color filters were directly patterned on the chip. The high aspect ratio OLED microdisplay was then combined with the pin mirror lens, resulting in maximum horizontal FoV 46.6° at the lens thickness of 4 mm. By using such a simple display module, we successfully demonstrated the small form factor AR device. [ABSTRACT FROM AUTHOR]

Thin-film transistor (TFT)-driven full-color organic light-emitting diodes (OLEDs) with vertically stacked structures are developed herein using photolithography processes, which allow for high-resolution displays of over 2,000 pixels per inch. Vertical stacking of OLEDs by the photolithography process is technically challenging, as OLEDs are vulnerable to moisture, oxygen, solutions for photolithography processes, and temperatures over 100 °C. In this study, we develop a low-temperature processed Al2O3/SiNx bilayered protection layer, which stably protects the OLEDs from photolithography process solutions, as well as from moisture and oxygen. As a result, transparent intermediate electrodes are patterned on top of the OLED elements without degrading the OLED, thereby enabling to fabricate the vertically stacked OLED. The aperture ratio of the full-color-driven OLED pixel is approximately twice as large as conventional sub-pixel structures, due to geometric advantage, despite the TFT integration. To the best of our knowledge, we first demonstrate the TFT-driven vertically stacked full-color OLED. To realize organic light-emitting diodes (OLEDs) with improved resolution for display applications, a method for achieving high yield device fabrication is needed. Here, the authors report vertically-stacked transistor-driven full-color OLEDs with photolithography-processed intermediate electrodes. [ABSTRACT FROM AUTHOR]

The ability to image pressure distribution over complex three-dimensional surfaces would significantly augment the potential applications of electronic skin. However, existing methods show poor spatial and temporal fidelity due to their limited pixel density, low sensitivity, or low conformability. Here, we report an ultraflexible and transparent electroluminescent skin that autonomously displays super-resolution images of pressure distribution in real time. The device comprises a transparent pressure-sensing film with a solution-processable cellulose/nanowire nanohybrid network featuring ultrahigh sensor sensitivity (>5000 kPa−1) and a fast response time (<1 ms), and a quantum dot-based electroluminescent film. The two ultrathin films conform to each contact object and transduce spatial pressure into conductivity distribution in a continuous domain, resulting in super-resolution (>1000 dpi) pressure imaging without the need for pixel structures. Our approach provides a new framework for visualizing accurate stimulus distribution with potential applications in skin prosthesis, robotics, and advanced human-machine interfaces. Electronic skin that spatially maps pressure distribution through imaging shows limited performance despite improvements to data acquisition. Here, the authors report ultraflexible, transparent electroluminescent skin capable of high-resolution imaging of pressure distribution over 3D surfaces. [ABSTRACT FROM AUTHOR]

Microdisplay is a key technology for realizing augmented reality (AR) and mixed reality (MR) devices, which have attracted much attention of late. Even though the operating voltage in the tandem structure is higher than that in the single structure, 2-stack tandem OLED exhibited 20,000 cd/m2 at 9 V, which is compatible with CMOS circuit driving. Due to its top-emitting geometry with a tandem structure, the OLED device with a well-controlled thickness exhibited a white spectrum with (0.26, 0.26) color coordinates. The pixel density of the fabricated microdisplay panel with a white tandem OLED was about 2350 pixels per inch, and the active area of the panel was 0.7 inch diagonally. The resolution of the panel was 1280 × 1024, corresponding to SXGA, and the maximal luminance was 3,000 cd/m2. [ABSTRACT FROM AUTHOR]

Surface-exchanged, partially pyridine-functionalized colloidal quantum dot-based light-emitting diodes (QD-LEDs) that exhibit a low turn-on voltage and high brightness are reported. Pyridine is stochastically exchanged to a greater extent at the interface between the QDs and the hole transport layer via ligand exchange. Pyridine improves the charge balance within the QDs by enhancing the hole injection and hence lowers the turn-on voltage of the QD-LEDs. This strategy is applied to red-, green-, and blue-emitting (three primary colors) QD-LEDs. Pyridine-functionalized QD-LEDs (QD/py-LEDs) show enhanced maximum luminance, lowered driving voltages, and improved current- and power-efficiencies as compared with the original surface ligand-functionalized QD-LEDs. All three types of QD/py-LEDs show narrow emission spectra (full width at half maximum ＜40 nm) and cover 159% of the National Television System Committee 1987 color gamut. [ABSTRACT FROM AUTHOR]

Microdiplay is one of critical factors to determine the performance of AR glasses. A white OLED with tandem structure have been developed for OLED microdiplays. The device has driving voltage of 6.9 V for 1,000 cd/m2 and maximum current efficiency of 19.5 cd/A. Using developed white OLED structure, we have successfully demonstrated a white OLED microdisplay with a 32:9 aspect ratio. This large aspect ratio can be helpful for improving field of view of AR glasses using a pin mirror lens. [ABSTRACT FROM AUTHOR]