Active matrix monolithic micro‐LED full‐color micro‐display

An active matrix monolithic micro‐LED full‐color micro‐display with a pixel density of 317 ppi is demonstrated. Starting from large‐scale and low‐cost GaN‐on‐Si epilayers, monolithic 64 × 36 blue micro‐LED arrays are fabricated and further transformed to full‐color micro‐displays by applying a photo‐patternable color conversion layer. This full‐color fabrication scheme shows feasible manufacturability, suggesting a potential for volume production of micro‐LED full‐color micro‐display.     

Inorganic light‐emitting diode displays using micro‐transfer printing

Large quantities of microscopic red, green, and blue light‐emitting diodes (LEDs) made of crystalline inorganic semiconductor materials micro‐transfer printed in large quantities onto rigid or flexible substrates form monochrome and color displays having a wide range of sizes and interesting properties. Transfer‐printed micro‐LED displays promise excellent environmental robustness, brightness, spatial resolution, and efficiency. Passive‐matrix and active‐matrix inorganic LED displays were constructed, operated, and their attributes measured. Tests demonstrate that inorganic micro‐LED displays have outstanding color, viewing angle, and transparency. Yield improvement techniques include redundancy, physical repair, and electronic correction. Micro‐transfer printing enables revolutionary manufacturing strategies in which microscale LEDs are first assembled into miniaturized micro‐system “light engines,” and then micro‐transfer printed and interconnected directly to metallized large‐format panels. This paper reviews micro‐transfer printing technology for micro‐LED displays.     

Active matrix QD‐LED with top emission structure by UV lithography for RGB patterning

We have developed full colour top emitting quantum dot light‐emitting diode (QD‐LED) display driven by a 176‐ppi active matrix of metal oxide thin‐film transistors. Red, green and blue (RGB) QD‐LED subpixel emission layers are patterned by our original UV photolithography process and materials. We also demonstrate the potential to achieve high resolution such as 528 ppi using this process.     

Toward high‐resolution,inkjet‐printed,quantum dot light‐emitting diodes for next‐generation displays

We have investigated the possibility of fabricating quantum dot light‐emitting diodes (QLEDs) using inkjet printing technology, which is the most attractive method for the full‐color patterning of QLED displays. By controlling the quantum dot (QD) ink formulation and inkjet printing condition, we successfully patterned QLED pixels in the 60‐in ultrahigh definition TV format, which has a resolution of 73 pixels per inch. The inkjet‐printed QLEDs exhibited a maximum luminance of 2500 cd/m². Although the performance of inkjet‐printed QLEDs is low compared with that of QLEDs fabricated using the spin‐coating process, our results clearly indicate that the inkjet printing technology is suitable for patterning QD emissive layers to realize high‐resolution, full‐color QLED displays.     

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.     

A new current‐mirror pixel circuit employing poly‐Si TFTs for active‐matrix organic light‐emitting‐diode displays

Abstract— A novel active‐matrix organic light‐emitting‐diode (AMOLED) display employing a new current‐mirror pixel circuit, which requires four‐poly‐Si TFTs and one‐capacitor and no additional signal lines, has been proposed and sucessfully fabricated. The experimental results show that a new current mirror can considerably compensate luminance non‐uniformity and scale down a data current more than a conventional current‐mirror circuit in order to reduce the pixel charging time and increase the minimum data current. Compared with a conventional two‐TFT pixel, the luminance non‐uniformity induced by the grain boundaries of poly‐Si TFTs can be decreased considerably from 41% to 9.1%.     

Prospects and challenges of mini‐LED and micro‐LED displays

We review the emerging mini/micro–light‐emitting diode (LED) displays featuring high dynamic range and good sunlight readability. For mini‐LED backlit liquid crystal displays (LCDs), we quantitatively evaluate how the device contrast ratio, local dimming zone number, and local light profile affect the image quality. For the emissive mini/micro‐LED displays, the challenges of ambient contrast ratio and size‐dependent power efficiency are analyzed. Two figure‐of‐merits are proposed for optimizing the optical and electrical performances of mini/micro‐LED displays.     

Ten micrometer pixel,quantum dots color conversion layer for high resolution and full color active matrix micro‐LED display

A fine patternable quantum dots (QDs) color conversion layer (CCL) for high resolution and full color active matrix (AM) micro‐LED (μ‐LED) display is demonstrated. QDs CCL could be patterned until 10 μm using photolithography process. It is found that multicoatings with red and green QDs (R‐ and G‐QDs) CCLs on LED array can provide full color AM display.     

Simple pixel circuits for high resolution and high image quality organic light emitting diode‐on‐silicon microdisplays with wide data voltage range

Two simple pixel circuits are proposed for high resolution and high image quality organic light‐emitting diode‐on‐silicon microdisplays. The proposed pixel circuits achieve high resolution due to simple pixel structure comprising three n‐type MOSFETs and one storage capacitor, which are integrated into a unit subpixel area of 3 × 9 µm² using a 90 nm CMOS process. The proposed pixel circuits improve image quality by compensating for the threshold voltage variation of the driving transistors and extending the data voltage range. To verify the performance of the proposed pixel circuits, the emission currents of 24 pixel circuits are measured. The measured emission current deviation error of the proposed pixel circuits A and B ranges from ?2.59% to +2.78%, and from ?1.86% to +1.84%, respectively, which are improved from the emission current deviation error of the conventional current‐source type pixel circuit when the threshold voltage variation is not compensated for, which ranges from ?14.87% to +14.67%. In addition, the data voltage ranges of the proposed pixel circuits A and B are 1.193 V and 1.792 V, respectively, which are 2.38 and 3.57 times wider than the data voltage range of the conventional current‐source type pixel circuit of 0.501 V.     

Flexible quantum dot light‐emitting devices for targeted photomedical applications

Quantum dot light‐emitting devices (QLEDs), originally developed for displays, were recently demonstrated to be promising light sources for various photomedical applications, including photodynamic therapy cancer cell treatment and photobimodulation cell metabolism enhancement. With exceptional emission wavelength tunability and potential flexibility, QLEDs could enable wearable, targeted photomedicine with maximized absorption of different medical photosensitizers. In this paper, we report, for the first time, the in vitro study to demonstrate that QLEDs‐based photodynamic therapy can effectively kill Methicillin‐resistant Staphylococcus aureus, an antibiotic‐resistant bacterium. We then present successful synthesis of highly efficient quantum dots with narrow spectra and specific peak wavelengths to match the absorption peaks of different photosensitizers for targeted photomedicine. Flexible QLEDs with a peak external quantum efficiency of 8.2% and a luminance of over 20,000 cd/m² at a low driving voltage of 6 V were achieved. The tunable, flexible QLEDs could be employed for oral cancer treatment or diabetic wound repairs in the near future. These results represent one fresh stride toward realizing QLEDs' long‐term goal to enable the wide clinical adoption of photomedicine.     

A 13‐bit universal column driver for various displays of OLED and LCD

A universal column driver is implemented in a 0.13‐µm high‐voltage CMOS process for not only TFT‐LCD but also OLED applications. The proposed column driver employs 13‐bit linear DAC to cover all gamma curves of display applications and address‐based configuration for intra‐ panel interface protocol to support both TV and IT applications. Measured results demonstrate the average voltage of output channels (AVO) is under 1mv, which satisfies 1‐LSB resolution at 18.5V of AVDD.     

Light‐emitting polymers for full‐color display applications

The latest developments in light‐emitting‐polymer (LEP) technology at CDT continue to show steady progress. Device performance for blue, green, and red systems as well as a high‐performance yellow system in terms of device efficiency and stability will be described. Some of the issues associated with the commercialization of LEP technology including the development of direct‐patterning techniques enabling full‐color passive‐ and active‐matrix display will be discussed.     

Development of 1.5‐in. full‐color double‐sided active‐matrix OLED with novel array design

Abstract— A 1.5‐in. full‐color double‐sided AMOLED with a novel array design was fabricated. Different images on both sides of the panel can be controlled by using only one IC driver. High color gamuts of 67% and 81% on the bottom‐ and top‐emitting sides, respectively, were achieved. In addition, good performance on both sides, such as brightness and white balance, were also achieved.     

High performance color‐converted micro‐LED displays

A full‐color micro‐LED display can be achieved by red, green, and blue (RGB) chips or by a blue/ultraviolet (UV) micro‐LED array to pump downconverters. The latter helps relieve the burden of epitaxial growth of tri‐color micro‐LED chips. However, such a color‐converted micro‐LED system usually suffers from color crosstalk and low efficiency due to limited optical density of color converters. With funnel‐tube array and reflective coating on its inner surface, the crosstalk is eliminated, and the optical efficiency can be improved by more than two times. In addition, the ambient contrast ratio is also improved because of higher light intensity. The color gamut of this device is approximately 92% of DCI‐P3 standard.     

AMOLED displays with transfer‐printed integrated circuits

Abstract— Small integrated circuits of crystalline silicon (chiplets) transfer‐printed onto a flat‐panel‐display substrate provide greatly improved electrical performance and uniformity in active‐matrix organic light‐emitting‐diode (OLED) displays. The integrated circuits are formed in high‐performance crystalline silicon using conventional photolithographic processes and then transfer‐printed onto a substrate using a stamp that transfers hundreds or thousands of chiplets at once. The chiplets are connected to an external controller and to pixel elements using conventional photolithographic substrate processing methods. Active‐matrix OLED (AMOLED) displays using transfer‐printed chiplets have good yields, excellent uniformity, and electrical performance and are thermally robust.     

A controller design for micro‐cup active‐matrix electrophoretic displays

Abstract— The active‐matrix electrophoretic display (AMEPD) has been commonly used for the applications of smart handheld reading devices such as e‐books and e‐newspapers. This paper presents a controller IC design for the AMEPD backend system which reduces the total hardware cost compared to that of the conventional design. By contrast, this study also provides a driving method for image displays. The prototyped controller is connected to a 6‐in. AMEPD panel, and good display quality has demonstrated the effectiveness of the proposed controller design.     

In‐pixel temperature sensor for high‐luminance active matrix micro‐light‐emitting diode display using low‐temperature polycrystalline silicon and oxide thin‐film‐transistors

We propose an in‐pixel temperature sensor using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistor (TFTs) for high‐luminance active matrix (AM) micro‐light‐emitting diode (LED) displays. By taking advantage of the different off‐current characteristics of p‐type LTPS TFTs and n‐type a‐IGZO TFTs under temperature change, we designed and fabricated a temperature sensor consists of only LTPO TFTs without additional sensing component or material. The fabricated sensor exhibits excellent temperature sensitivity of up to 71.8 mV/°C. In addition, a 64 × 64 temperature sensor array with 3T sensing pixel and integrated gate driver has also been fabricated, which demonstrates potential approach for maxing out the performance of high‐luminance AM micro‐LED display with real‐time in‐pixel temperature monitoring.     

Imaging performance of displays: Past,present, and future*

Abstract— Some display devices that were tried unsuccessfully in the past are reviewed briefly. Then the display devices that are in use at present are described and their advantages and disadvantages discussed. Properties where improvements are needed include greater consistency between pictures displayed from the same signals on different devices, greater color gamut, less impairment by ambient illumination, and better resolution. Finally, consideration is given to some of the ways in which these needs may be met.     

Modeling of threshold‐voltage‐shift dependency on drain bias in amorphous‐silicon thin‐film transistors in active‐matrix organic light‐emitting‐diode displays

Abstract— A theoretical model to interpret appearances of the threshold voltage shift in hydrogenated amorphous‐silicon (a‐Si:H) thin‐film transistors (TFTs) is developed to better understand the instability of a‐Si:H TFTs for the driving transistors in active‐matrix organic light‐emitting‐diode (AMOLED) displays. This model assumes that the defect creation at channel in a‐Si:H is proportional to the carrier concentration, leading to the defect density varying along the channel depending on the bias conditions. The model interprets a threshold‐voltage‐shift dependency on the drain‐stress bias. The model predicts the threshold voltage shift stressed under a given gate bias applying the drain saturation voltage is 66% of that with zero drain bias, and it even goes down to 50–60% of that when stressed by applying twice the drain saturation voltage.     

Multi‐planar plenoptic displays

Multi‐planar plenoptic displays consist of multiple spatially varying light‐emitting and light‐modulating planes. In this work, we introduce a framework to display light field data on this new type of display device. First, we present a mathematical notation that describes each of the layers in terms of the corresponding light transport operators. Next, we explain an algorithm that renders a light field with depth into a given multi‐planar plenoptic display and analyze the approximation error. We show two different physical prototypes that we have designed and built: The first design uses a dynamic parallax barrier and a number of bi‐state (translucent/opaque) screens. The second design uses a beam splitter to co‐locate two pairs of parallax barriers and static image projection screens. We evaluate both designs on a number of different 3D scenes. Finally, we present simulated and real results for different display configurations.