Flexible Displays Research Articles

Radioluminescent Cu-Au Metal Nanoclusters: Synthesis and Self-Assembly for Efficient X-ray Scintillation and Imaging.

Zero-dimensional (0D) scintillation materials have drawn tremendous attention due to their inherent advantages in the fabrication of flexible high-energy radiation scintillation screens by solution processes. Although considerable progress has been made in the development of 0D scintillators, such as the current leading lead-halide perovskite nanocrystals and quantum dots, challenges still persist, including potential issues with self-absorption, air stability, and eco-friendliness. Here, we present a strategy to overcome those limitations by synthesis and self-assembly of a new class of scintillators based on metal nanoclusters. We demonstrate the gram-scale synthesis of an atomically precise nanocluster with a Cu-Au alloy core exhibiting high phosphorescence quantum yield, aggregation-induced emission enhancement (AIEE) behavior, and intense radioluminescence. By controlling solvent interactions, the AIEE-active nanoclusters were self-assembled into submicron spherical superparticles in solution, which we exploited as a novel building block for flexible particle-deposited scintillation films with high-resolution X-ray imaging performance. This work reveals metal nanoclusters and their self-assembled superstructures as a promising class of scintillators for practical applications in high-energy radiation detection and imaging.

Implementation of flexible and customizable free-from mirror heads-up display

Implementation of flexible and customizable free-from mirror heads-up display

81‐3: Design of Narrow Border Flexible OLED Display Based on Simulation Analysis and Optimization

This paper analyzes the design of the down border of the flexible OLED display, and studies the influence of the neutral layer and the sensitivity of SD strain of different stacks of Pad Bending in the narrow border area based on the finite element simulation. The neutral layer is located in the PI2 layer, and the order of the strain sensitivity of SD at Bending edge is MCL>Organic layer>PI1>PI2, MCL thickness has the greatest influence on SD strain. Through the stacking optimization design based on the sensitivity analysis results, the SD strain is reduced from 11.1% to 6.6%. Finally realize the industry's smallest R0.1mm Pad Bending design. Based on bending strain gauge and 25N static push test, SD strain is at a safe level and pass more than 50 times push tests. Narrow border products with R0.1mm Pad Bending can pass various environmental reliability tests to meet the environmental requirements of terminal products.

58‐1: Research on 360 Degree Folding AMOLED Display and Optimization Design of Terminal Product By FEA

Aimed at in‐foldable and out‐foldable mobile phone terminal products on the market, a new 360 ° folding terminal scheme which integrates in & out‐foldable is proposed to realize three application modes: in‐fold portable, out‐fold mobile phone and large screen display. According to the application concept of product, the 360 degree hinge and flexible screen have been developed with U‐shaped out‐fold and water‐drop shaped in‐fold. Based on the finite element method, the mechanical simulation model of flexible screen is established, and the modeling method is programmed which is applied to practical engineering test. Based on Lagrange equation and multi‐body system dynamics theory, a system‐level simulation model of rigid‐flexible coupling of 360‐degree folding terminal is established to solve the complex kinematics and dynamic problems, and to achieve the optimal design of each functional module in the mechanism. Combined with the monomer bending test of the flexible screen, the simulation and test results show good consistency. The screen module pass 360 ° bending for 100000 times which verifies the correctness and universality of the scheme of 360 ° folding mechanism.

45‐2: 14.6‐inch 202‐ppi Rollable Micro LED Display with Color Conversion Technology

The 14.6‐inch 202‐ppi rollable micro LED display was fabricated on flexible LTPS TFT backplanes. The tiny micro LEDs, those size are less than 30 um, were bonded on backplanes by flip‐chip soldering technologies. More than 11 million micro LEDs were transferred to achieve brightness of >1000 nits, contrast ratio of >1,000,000:1 and resolution of 2560xRGBx1440. We investigated the structure and mechanism to achieve the rollable capability for micro LED displays.

88‐3: Late‐News Paper: IGZO Backplane for Full‐color Electrophoretic Display

E Ink's Gallery™ 3 with SDTC's IGZO backplane are being developed to have short page update time and good color image quality for full‐color EPD. Since the backplane for Gallery™ 3 must be driven by high voltage approximately close to +/‐ 30V, stable TFT characteristics and low TFT off‐leakage under high voltage application are important. SDTC's IGZO TFT was confirmed to be superior in terms of stability against high voltage application. An 8‐inch 300dpi Gallery™ 3, which is now in mass production, achieves page update time of less than 1 second in full color mode and 0.35 seconds in monochrome mode. Beyond the IGZO TFT employed in the 8‐ inch Gallery™ 3 panel, we have also proved the IGZO TFT with further high mobility, whose mobility is 3‐times higher than that of the current 8” panel, developed at SDTC has excellent characteristics stability against high voltage application as well, and it is currently being developed for mass production of EPD. We are also developing flexible IGZO EPD and large screen size IGZO signage EPD as the future technologies.

P‐144: Late‐News Poster: Evaluation for Flexible Substrates According to the Number of Rollings

A scratch test was performed to evaluate the substrate deformation according to the number of rolling times for the rollable display. For polyimide and thermal plastics polyurethane, the critical loads are analyzed according to the number of rolling times. As increasing the load, friction coefficients were measured during the scratch on films. The effect of substrate rolling times on plastic n and elastic deformations were evaluated.

72‐1: Invited Paper: Improving Improving Thermal Stability of The Coatable Polarizer by Optimization of Materials

In this paper, we fabricated the coatable polarizer based on guest‐host effect between the host polymerizable liquid crystal and the guest dichroic dye. However, its thermal stability is poor. We had attempts to optimize the structure of its materials and we obtained the optimized polarizer. It had a very small color difference of 2.91, and its DOP was only reduced from 99.0% to 96.2% with a samll loss of 2.7% after being heated at 90°C for 120 hours. It shows that the thermal stability is greatly enhanced. It will benefit the coatable polarizer's development of applications in ultra‐thin, ultra‐wide size and flexible display fields.

74‐1: Invited Paper: Highly Stretchable and Shrinkable AMOLED for Free Deformation

Flexible display technology has been successfully commercialized with foldable and rollable displays. Because of the limitation of the flexible technology, stretchable displays have attracted great attention which capable of realizing freeform design as a post‐flexible display. However, no technology has yet provided sufficient stretchability and resolution to realize genuine free‐form displays. We report on a highly deformable AMOLED display which capable of elongation over 20%. Moreover, our display is capable of more than 15% shrinkage deformation. We also developed low‐temperature thermal shrink process to make the most of the potential of the display. The fabricated full‐color stretchable AMOLED shows excellent deformability with high pixel density.

43‐2: Distinguished Student Paper: High‐Performance, Coplanar Amorphous IGZO TFTs by Spray Pyrolysis on PI Substrate for Low Cost Manufacturing of Foldable AMOLED Display

We report a method for low‐cost deposition of bubble‐free and high‐quality amorphous InGaZnO (a‐IGZO) on polyimide (PI) substrate for foldable AMOLED display by spray pyrolysis. The coplanar thin‐film transistor (TFT) with spray‐pyrolyzed (SP) a‐IGZO on PI substrate exhibits VTH of ‐0.8 V, μSAT of 40.95 cm2V‐1s‐1, and SS of 0.18 Vdec‐1 with on/off current ratio of ~108. The TFT shows VTH shift of ‐0.40 V and +0.05 V under tesnsile bending and positive bias temperature stress, respectively. The ring oscillator made of SP a‐IGZO TFTs exhibits an oscillation frequency of 2.38 MHz at VDD of 10 V. The SP a‐IGZO TFT can be used for low‐cost, high‐performance, and flexible display TFT backplanes.

Template‐Assisted Fabrication of Flexible Perovskite Scintillators for X‐Ray Detection and Imaging

AbstractMetal halide perovskites have recently emerged as exceptional scintillator materials for ionizing radiation detection devices. Their chemical composition consists of elements with high atomic numbers, leading them to have a high attenuation coefficient. Their high attenuation coefficient, in combination with their excellent optoelectronic properties, versatile chemical tunability, and facile and low‐cost fabrication processes, makes them the ideal scintillator material. However, existing perovskite‐based scintillators suffer from poor material stability, especially in humid atmospheres. Moreover, current perovskite films have morphologies that have been optimized for photovoltaics, which results in the relatively long charge carrier lifetimes, a property that is detrimental for fast scintillation. Furthermore, existing reports of perovskite‐based scintillators have shown limited spatial resolution due to poor light transmittance that arises from light scattering from large aggregates of perovskite grains. To address these issues, this work introduces a template‐assisted in situ polymerization‐based process to prepare perovskite/polymer composite scintillators that simultaneously reduces afterglow effects, improves perovskite stability, and is industrially scalable. The optimized perovskite scintillators are then incorporated into X‐ray detection devices to investigate detection performance and device stability. Compared with existing commercial scintillators, the perovskite scintillators show superior detection performance metrics for imaging, indicating the great potential of perovskites for next‐generation, large‐area, and flexible scintillation screens.

2D Perovskite Mn2+ -Doped Cs2 CdBr2 Cl2 Scintillator for Low-Dose High-Resolution X-ray Imaging.

High-performance X-ray scintillators with low detection limits and high light yield are of great importance and are a challenge for low-dose X-ray imaging in medical diagnosis and industrial detection. In this work, the synthesis of a new 2D perovskite, Cs2 CdBr2 Cl2 , via hydrothermal reaction is reported. By doping Mn2+ into the perovskite, a yellow emission located at 593nm is obtained, and the photoluminescence quantum yield (PLQY) of Cs2 CdBr2 Cl2 :5%Mn2+ perovskite reaches the highest value of 98.52%. The near-unity PLQY and negligible self-absorption of Cs2 CdBr2 Cl2 :5%Mn2+ enable excellent X-ray scintillation performance with a high light yield of 64 950 photons MeV-1 and low detection limit of 17.82 nGyair s-1 . Moreover, combining Cs2 CdBr2 Cl2 :5%Mn2+ with poly(dimethylsiloxane) to fabricate a flexible scintillator screen achieves low-dose X-ray imaging with a high resolution of 12.3 line pairs (lp) mm-1 . The results suggest that Cs2 CdBr2 Cl2 :5%Mn2+ is a promising candidate for low-dose and high-resolution X-ray imaging. The study presents a new approach to designing high-performance scintillators through metal-ion doping.

Theoretical insight on the charge transport properties: The formation of "head-to-tail" and "head-to-head" stacking of asymmetric aryl anthracene derivatives.

Organic semiconductors (OSCs) are widely used in flexible display, renewable energy, and biosensors, owing to their unique solid-state physical and optoelectronic properties. Among the abundant crystal library of OSCs, asymmetric aryl anthracene derivatives have irreplaceable advantages due to the interplay between their distinct π-conjugated geometry and molecular stacking as well as efficient light emission and charge transport properties that can be simultaneously utilized. However, the poor crystal stacking patterns of most asymmetric molecules limit their utility as excellent OSCs. Thus, it is crucial to clarify the structural features that enable the extremely ordered stacking and favorable electronic structure of asymmetric anthracene derivatives to become high-performance OSCs. This contribution investigates the charge transport properties of a series of asymmetric aryl anthracene derivatives to reveal the modulation factors of the molecular stacking modes and to explore the structural factors, which are beneficial to charge transport. The analysis demonstrated that the vinyl-linker facilitated the injection of hole carriers, and the alkynyl-linker effectively reduces the reorganization energy. Importantly, the linear polarizability and permanent dipole moment of a single molecule play a vital regulation to molecular stacking modes and the transfer integral of the dimer. The "head-to-head stacking" motif shows a compact stacking pattern and the maximum 2D anisotropic mobility more than 10cm2V-1s-1. These findings sharpen our understanding of the charge transport properties in asymmetric organic semiconductors and are essential for developing a diverse range of high-performance OSC materials.

Study on the Film-Forming Mechanism of Polymer-Metal Oxide Composite Ink Systems Containing Different Polymer Molecules.

A printable, flexible display panel is an important trend in the field of information display, which requires better mechanical and electrical properties of device materials. Polymer-metal oxide composite materials are promising in the functional layer of a thin-film transistor (TFT) and can be sufficiently fabricated by polymer-metal salt solution systems through the sol-gel process. For the development of polymer-metal oxide composite ink, it is necessary to study the film-forming mechanism of the composite film during solidification, which is an important reference in ink component design. However, the evolution of the composite structure is quite complex, which brings a challenge to characterization and analyzation. We applied a series of characterization methods to study the film-forming process of composite ink from sol to gel and to solid, and an emerging testing technology, nano-infrared spectroscopy (nano-IR), was applied to characterize the gel film. The research conclusion showed that the type of functional group can significantly affect the morphology of the initial particle and can finally determine the microstructure of the composite film. The study provides references for the development of composite ink as well as the characterization method for ink and film with complex composition.

Modified luminescent properties from green afterglow to efficient orange emission in zirconium-based organometallic chloride scintillator by Sb3+ doping

Zero-dimension (0D) metal halides based on metals with the 5s2 lone pair have attracted great attentions due to their strong triplet broadband emission. However, the conversion from weak afterglow to efficient and fast photoluminescence by regulating the composition of 0D metal halides is still a tough challenge. Herein, Sb3+ ions-doped 0D (Ph4P)2ZrCl6·4CH3CN metal halides were synthesized by a simple solution crystallization method. Compared with the weak triplet green 560 nm afterglow from the organic Ph4P+ components, the emission of the Sb3+-doped material exhibits a strong orange photoluminescence at 660 nm with a high photoluminescence quantum yield of 72% by a host to dopant energy transfer process. In addition, a flexible large-sized X-ray scintillator screen with an area of 16 cm2 was prepared using polydimethylsiloxane as the host matrix, which exhibits excellent scintillation properties with light yields of 8,290 photons/MeV, low detectable limits of 0.986 μGy/s, and a near-infrared broadband emission from 600 nm to 850 nm under steady-state X-ray excitation, which is highly compatible with the response range of the long-wave sensitive silicon-based photodetectors. Therefore, this work not only provides a deep insight into the energy transfer process in the 0D metal halide materials but also opens an alternative approach to realize flexible large-size near-infrared X-ray imaging based on the 0D metal halide scintillator.

High‐performance, coplanar amorphous InGaZnO thin‐film transistors by spray pyrolysis on polyimide substrate for low‐cost manufacturing of foldable active‐matrix organic light emitting diode display

AbstractWe report a method for low‐cost deposition of bubble‐free, high‐quality amorphous InGaZnO (a‐IGZO) on polyimide (PI) substrate for foldable active‐matrix organic light emitting diode (AMOLED) display by spray pyrolysis. The coplanar thin‐film transistor (TFT) with spray‐pyrolyzed (SP) a‐IGZO on PI substrate exhibits threshold voltage (VTH) of −0.8 V, saturation mobility of 40.95 cm2 V−1 s−1, and subthreshold swing of 0.18 V per decade with on/off drain current ratio of ~108. The high mobility TFT could be achieved using high substrate temperature (350°C) and low contact resistance by NF3 plasma on the SP a‐IGZO. The TFT shows a ΔVTH of −0.4 V when it is bent on a cylinder of 1‐mm radius. The TFT shows the ΔVTH of +0.05 V for positive bias temperature stress at +20 V at 60°C for 1 h. The ring oscillator made of a‐IGZO TFTs exhibits an oscillation frequency of 2.38 MHz at VDD of 10 V with a propagation delay of 9.13 ns per stage. Therefore, the a‐IGZO TFT by spray pyrolysis could be used for low‐cost, high‐performance, and flexible display TFT backplane.

Hydrogen bonding-induced high-performance stretchable organic semiconductors: a Review.

Semiconductors are widely used in electron devices. With the development of wearable soft-electron devices, conventional inorganic semiconductors are unable to meet the demand because of their high rigidity and high cost. Thus, scientists construct organic semiconductors with high charge mobility, low cost, eco-friendly, stretchable, etc. Due to the excellent performance of stretchable organic semiconductors, they can be widely used as wearable soft-electron devices, such as stretchable organic field-effect transistors (OFETs), organic solar cells (OSCs), etc. Contains flexible display devices and flexible power sources, which are of great interest for applications of future electron devices. However, there are still some challenges that need to be solved. Commonly, enhancing the stretchability may cause the degradation of charge mobility, because of the destruction of the conjugated system. Currently, scientists find that hydrogen bonding can enhance the stretchability of organic semiconductors with high charge mobility. Thus in this review, based on the structure and design strategies of hydrogen bonding, various hydrogen bonding induced stretchable organic semiconductors are introduced. In addition, the applications of the hydrogen bonding induced stretchable organic semiconductors are reviewed. Finally, the stretchable organic semiconductors design concept and potential evolution trends are discussed. The final goal is to outline a theoretical scaffold for the design of high-performance wearable soft-electron devices, which can also further advance the development of stretchable organic semiconductors for applications.

Deep-Blue Organic Light-Emitting Diodes Employed Traditional Hole Transporting Material as Emitter for 31-Inch 4K Flexible Display

High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, it is challenging to obtain deep-blue fluorescent OLEDs with a high external quantum efficiency (EQE) (reaching the theoretical limit of 5%). In this work, we have successfully employed a hole-transporting material for an emitter, which can increase the efficiency in deep-blue OLEDs. The device employed with the proposed hole-transporting material exhibits deep-blue emission peaks at 427.0 nm with CIE coordinates of (0.155, 0.051), a turn-on voltage (Von) of 4.5 V, and an EQE of 4.5%. The performance of the OLED can be improved by 5.0% by optimizing the device structure. Finally, the flexible display when using the OLED devices exhibited a high image quality.

A Study on Flexible Transparent Electrode Materials for Touch Sensor

<div class="section abstract"><div class="htmlview paragraph">As the AVN display in the car interior becomes larger and located above the center fascia, the driver's visual visibility is becoming important. In addition, since an expensive touch sensor is installed, a transparent electrode cost reduction technology for a display touch sensor that can replace an indium material, which is an expensive rare metal, is required. In this paper, we developed new transparent electrode materials and manufacturing methods for the touch sensor film which light reflectance is low and flexible without a separate low-reflection multi-layer, so that the design freedom is high and the material cost is low. By optimizing the amount of fluorine doping ratio in tin oxide, excellent electrical conductivity and high optical transmittance are secured, and the surface reflectance is reduced by adjusting the diameter and length of the silver nanowire. As a result, it was shown that the AVN display image and font readability was improved. In addition, we verified that the material has probability to adoption to a curved and flexible display applications for future mobility based on autonomous driving.</div></div>

P‐13.2: Bending Performance Analysis of Flexible OLED Screens

OLEDs have become a promising candidate for flexible displays. It is obvious that the requirements on the mechanical property of a flexible OLED screen are higher than common OLED displays. However, with a stacked structure and a complicated property of optically clear adhesive (OCA), it is very difficult to theoretically compute or experimentally measure the stress and strain distributions on each layer during the bending process. The paper employs finite element analysis to evaluate the bending property of a flexible OLED screen. For common U‐shaped bending, the maximum stress increases rapidly as the bending radius decreases. For small bending radius, the water‐drop‐shaped mode presents higher structure reliability than U‐shaped bending.