9.1‐inch stretchable AMOLED display based on LTPS technology

In this work, we report a freeform shaped active‐matrix organic light‐emitting diode (AMOLED) display based on low‐temperature polycrystalline silicon technology. It was found that our AMOLED, developed with a unique pixel structure, can withstand in various desired shapes featuring its stretchable property with no degradation of image quality and device characteristics. We demonstrated unprecedented convex/concave shape of the 9.1‐inch AMOLED display by low‐temperature thermoforming process. The AMOLED display with freeform design is promising for future display applications such as automotive, Internet of things devices, and wearable electronics.     

5.8‐inch QHD flexible AMOLED display with enhanced bendability of LTPS TFTs

By applying the curve‐type thin film transistor (TFT) with longitudinal strain, TFT parameters do change little down to the 2R bending. The mobility variation range reduces down to 4% compared with 28% of the line‐type channel with transverse strain. The smaller variation is preferred for a high quality display. We clarified that majority carrier's effective mass and scattering rate are dominant factors influencing the bended TFT's performance, which can be controlled by the strain orientation and channel shape. This understanding and improvement was embedded in the 5.8″ flexible QHD active matrix organic light emitting diode panel with multi edge curvature of Galaxy S8. Through this achievement, we made our flexible premium active matrix organic light emitting diode panels more performable, reliable, and highly productive in small R bending circumstance.     

Improvement in image quality of a 5.8‐in. OTFT‐driven flexible AMOLED display

Abstract— The image quality of an OTFT‐driven flexible AMOLED display has been improved by enhancing the performance of OTFTs and OLEDs. To reduce the operating voltage of OTFTs on a plastic film, Ta²O⁵ with a high dielectric constant was used as a gate insulator. The organic semiconductor layer of the OTFT was successfully patterned by a polymer separator, which is an isolating wall structure using an organic material. The OTFT performance, such as its current on/off ratio, carrier mobility, and spatial uniformity on the backplane, was enhanced. A highly efficient phosphorescent OLED was used as a light‐emission device. A very thin molybdenum oxide film was introduced as a carrier‐injection layer on a pixel electrode to reduce the operating voltage of the OLED. After an OTFT‐driven flexible AMOLED display was fabricated, the luminance and uniformity on the display was improved. The fabricated display also showed clear moving images, even when it was bent at a low operating voltage.     

A 3.0‐in. 308‐ppi WVGA AMOLED with a top‐emission white OLED and color filter

Abstract— A 3.0‐in. 308‐ppi WVGA top‐emission AMOLED display with a white OLED and color filters, driven by LTPS TFTs demonstrating a color gamut of >90% and a Δ(u′,v′) of <0.02 is reported. A white‐emission source with a unique device structure was developed using all fluorescent materials and yielded efficiencies of 8.45% and 16 cd/A at 4000 nits with CIE color coordinates of (0.30, 0.32).     

Development of 8‐in. oxide‐TFT‐driven flexible AMOLED display using high‐performance red phosphorescent OLED

An 8‐in. flexible active‐matrix organic light‐emitting diode (AMOLED) display driven by oxide thin‐film transistors (TFTs) has been developed. In‐Ga‐Zn‐O (IGZO)‐TFTs used as driving devices were fabricated directly on a plastic film at a low temperature below 200 °C. To form a SiO_x layer for use as the gate insulator of the TFTs, direct current pulse sputtering was used for the deposition at a low temperature. The fabricated TFT shows a good transfer characteristic and enough carrier mobility to drive OLED displays with Video Graphic Array pixels. A solution‐processable photo‐sensitive polymer was also used as a passivation layer of the TFTs. Furthermore, a high‐performance phosphorescent OLED was developed as a red‐light‐emitting device. Both lower power consumption and longer lifetime were achieved in the OLED, which used an efficient energy transfer from the host material to the guest material in the emission layer. By assembling these technologies, a flexible AMOLED display was fabricated on the plastic film. We obtained a clear and uniform moving color image on the display.     

Fabrication of 5.8‐in. OTFT‐driven flexible color AMOLED display using dual protection scheme for organic semiconductor patterning

Abstract— A 5.8‐in. wide‐QQVGA flexible color active‐matrix organic light‐emitting‐diode (AMOLED) display consisting of organic thin‐film transistors (OTFTs) and phosphorescent OLEDs was fabricated on a plastic film. To reduce the operating voltage of the OTFTs, Ta₂O₅ with a high dielectric constant was employed as a gate insulator. Pentacene was used for the semiconductor layer of the OTFTs. This layer was patterned by photolithography and dry‐etched using a dual protection layer of poly p‐xylylene and SiO₂ film. Uniform transistor performance was achieved in the OTFT backplane with QQVGA pixels. The RGB emission layers of the pixels were formed by vacuum deposition of phosphorescent small molecules. The resulting display could clearly show color moving images even when it was bent and operated at a low driving voltage (below 15 V).     

Low‐temperature fabrication of 5‐in. QVGA flexible AMOLED display driven by OTFTs using olefin polymer as the gate insulator

Abstract— A 5‐in. QVGA flexible AMOLED display driven by OTFTs has been fabricated at a low temperature of 130°C. A polyethylene naphthalate film was used as the flexible substrate and an olefin polymer was used as the gate insulator for the OTFT. This layer was formed by spin‐coating and baking at 130°C. Pentacene was used as the organic semiconductor layer. The OTFT performance to drive the flexible display with QVGA pixels in terms of current on/off ratio, carrier mobility, and spatial uniformity on the backplane have been obtained. Phosphorescent and fluorescent OLEDs were used as light‐emitting devices on a flexible display. Those layers were formed by vacuum deposition. After the flexible display was fabricated, a clear and uniform moving image was obtained on the display. The display also showed a stable moving image even when it was bent.     

Implementation of delta—sigma analog‐to‐digital converter in LTPS process

Abstract— An on‐panel delta—sigma analog‐to‐digital converter (ADC) has been implemented and verified for 3‐μm low‐temperature polysilicon (LTPS) technology with two basic blocks: a delta—sigma modulator and a decimation filter. From the experimental results, the digital output from the delta—sigma modulator is correctly matched with the analog input voltage ratio such that the digital output can be converted into 8‐bit digital code successfully under a supply voltage of 10 V from the decimation filter. The implemented on‐panel delta—sigma ADC can be used for the application of temperature‐to‐digital converter on glass substrate.     

Development of 55‐in. 8K AMOLED TV based on coplanar oxide thin‐film transistors and inkjet printing process

In this paper, we presented 55‐in. 8K4K AMOLED TV employing coplanar oxide thin‐film transistor (TFT) backplane, top emissive inkjet‐printing organic light‐emitting diode (OLED) device, gate driver on array (GOA), and compensation technologies. It is so far the largest prototype AMOLED TV fabricated by using inkjet printing process with 8K resolution. It shows the stunning display quality, thanks to the high resolution and fast refresh frequency. It proves that the inkjet printing process is not only cost competitive but also can deliver premium display.     

A 550‐PPI LCD using 1.5 µm channel width LTPS TFTs with low frame rate driving

A 550 PPI low‐temperature polycrystalline silicon thin‐film transistor liquid‐crystal display has been developed. Shrinkage of the channel width of pixel thin‐film transistor together with thinner insulator for the storage capacitor allows high display quality in terms of vertical cross‐talk and flicker. Thirty hertz frame rate driving is implemented to offer low power while keeping high display quality.     

A high efficiency inductor‐less broadband fully integrated CMOS power amplifier

This work presents the design and implementation of a novel broadband completely inductor‐less 300 MHz–2.4 GHz power amplifier (PA) in 180 nm CMOS, primarily for applications in the ultrahigh frequency (UHF) industrial scientific and medical band. This is capable of delivering up to 15.6 dBm saturated output power with an associated peak power added efficiency of 31% in measurement. Although amplifiers with higher output power have been reported, this amplifier occupies only 0.086 mm² and does not require any off chip component for its operation, even at the UHF band. It also achieves the highest power density among a similar class of PA's below 10 GHz. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:311–320, 2015.     

Fast voltage‐driving scheme for AMOLED displays based on internal feedback

Abstract— A new driving scheme for active‐matrix organic light‐emitting diodes (AMOLED) displays based on voltage programming is proposed. While conventional voltage drivers have a trade‐off between speed and accuracy, the new scheme is inherently fast and accurate. Based on the new driving scheme, a fast pixel circuit is designed using amorphous‐silicon (a‐Si) thin‐film transistors (TFTs). As the simulation results indicate, this pixel circuit can compensate the threshold‐voltage shift (VT shift) of the driver transistors. This pixel can be programmed in just 10 μsec, and it can compensate the threshold‐voltage shifts over 5 V with an error rate of less than 5% for a 1 ‐μA pixel current.     

High‐uniformity 2T1C AMOLED panels by a built‐in trimming method

Abstract— A new built‐in trimming scheme boosting the OLED driving current through analog programming of the driver p‐channel TFT is proposed. By using a selective programming operation, the current variation on the LTPS panel can be reduced to less than 1%. Another blanket‐boosting method is investigated for concurrent programming of the entire panel. This blanket‐boosting scheme has been successfully demonstrated on a 2.4‐in. AMOLED panel where the non‐uniformity improved from 8.1 to 4.9% under a worst‐case condition.     

Analysis and design of a fully integrated CMOS low‐noise amplifier for concurrent dual‐band receivers

This article thoroughly analyzes a concurrent dual‐band low‐noise amplifier (LNA) and carefully examines the effects of both active and passive elements on the performance of the dual‐band LNA. As an example of the analysis, a fully integrated dual‐band LNA is designed in a standard 0.18‐μm 6M1P CMOS technology from the system viewpoint for the first time to provide a higher gain at the high band in order to compensate the high‐band signal's extra loss over the air transmission. The LNA drains 6.21 mA of current from a 1.5‐V supply voltage and achieves voltage gains of 14 and 22 dB, input S₁₁ of 15 and 18 dB, and noise figures of 2.45 and 2.51 dB at 2.4 and 5.2 GHz, respectively. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

A 5.5‐inch full HD foldable AMOLED display based on neutral‐plane splitting concept

Splitting of the mechanical neutral plane is a promising concept for foldable displays because it reduces the folding stress in each layer of the display. We verified the splitting concept experimentally and revealed a linear relation between the relative position of the neutral plane and the logarithm of the adhesive's elastic modulus. As the modulus decreased, the position of the neutral plane approached that of perfect splitting. On the basis of the neutral‐plane splitting concept, we developed 5.5‐inch full high‐definition foldable active matrix organic light‐emitting diode (AMOLED) displays, which endured 150 k inward folding cycles and 150 k outward folding cycles with folding radii of 3 and 5 mm, respectively. This study is expected to improve the flexibility of designing foldable AMOLED displays, enabling better balance of the portability versus practicality trade‐off in mobile displays.     

Reflective full‐color LCD using low‐temperature polysilicon TFTs in low‐frequency driving: Analysis of image persistence and flicker with scientific CMOS camera

Image persistence and flicker are major issues for low‐frequency driving of LCDs. Detailed investigation of the mechanisms that produce these phenomena, using image analysis with a scientific CMOS camera, enabled us to reduce it to acceptable levels. We successfully developed a 7.0‐in. WUXGA (1200 × RGBW × 1920) reflective color LCD driven by low‐temperature polysilicon TFTs at 1 Hz.     

Novel analog feedback current programming architecture compatible with 2‐transistor 1‐capacitor pixel for active matrix organic light‐emitting diode displays

A new feedback current programming architecture is described, which is compatible with active matrix organic light‐emitting diode (AMOLED) displays having the 2T1C pixel structure. The new pixel programming approach is compatible with all TFT technologies and can compensate for non‐uniformities in both threshold voltage and carrier mobility of the pixel OLED drive TFT. Based on circuit simulations, a pixel drive current of less than 10 nA can be programmed in less than 50 µ. This new approach can be implemented within an AMOLED external or integrated display data driver.     

A fully differential transimpedance amplifier with integrated differential photodetector in standard CMOS process for optical communications and interconnects

A fully differential transimpedance amplifier (TIA) with integrated differential photodetector in standard CMOS technologies has been realized for optical receivers in optical communications and optical interconnects. And a novel, fully differential photodetector aiming to convert the incident light into a pair of fully differential photo-generated currents and ensure the differential symmetry on circuit configuration and model has also been proposed for the differential TIA to achieve the fully differentia...     

A flexible 2.1‐in. active‐matrix electrophoretic display with high resolution and a thickness of 100 μm

Abstract— A paper‐thin QVGA, flexible 2.1‐in. active‐matrix electrophoretic display (AMEPD) that features 100‐μm thick and a 192‐ppi resolution has been developed. An LTPS‐TFT backplane with integrated peripheral driver circuits was first fabricated on a glass substrate and then transferred to a very thin (30‐μm) plastic film by employing surface‐free technology by laser ablation/annealing (SUFTLA®). A micro‐encapsulated electrophoretic imaging sheet was laminated on the backplane. A supporting substrate was used to support the LTPS‐TFT backplane. Fine images were successfully displayed on the rollable AM‐EPD. The integrated driver circuits dramatically reduce the number of external connection terminals, thus easily boosting the reliability of electrical connections even on such a thin plastic film.     

A 5.8‐in. phosphorescent color AMOLED display fabricated by ink‐jet printing on plastic substrate

Abstract— A flexible phosphorescent color active‐matrix organic light‐emitting‐diode (AMOLED) display on a plastic substrate has been fabricated. Phosphorescent polymer materials are used for the emitting layer, which is patterned using ink‐jet printing. A mixed solvent system with a high‐viscosity solvent is used for ink formulation to obtain jetting reliability. The effects of evaporation and the baking condition on the film profile and OLED performances were investigated. An organic thin‐film‐transistor (OTFT) backplane, fabricated using pentacene, is used to drive the OLEDs. The OTFT exhibited a current on/off ratio of 10⁶ and a mobility of 0.1 cm²/V‐sec. Color moving images were successfully shown on the fabricated display.