OLED Panel Research Articles

87‐3: The Study of Brightness Drop of AMOLED Based on LTPS Process

The phenomenon of brightness drop (B/D) during one frame period exist in OLED panel using LTPS process. We analyzed how TFT leakage current lead to B/D in conventional circuit, and we also found that hysteresis is another important reason for B/D. Meanwhile, lots of approaches to improving B/D are discussed.

13‐1: Invited Paper: New Frontier in Display Technology: OPD Sensor in OLEDs for Healthcare Application

People's interest in health care has increased these days. As various health care platforms are emerging, the corresponding market is also expanding. In order to monitor health conditions in everyday life, no physical damage should be made. One of the non‐invasive method, using light for sensing, is preferred due to this effect. In general, as the wavelength increases, light can penetrate deeper into the skin, leading to different bio‐signals. For example, All‐in‐One Sensor Display, which was announced by Samsung Display at SID 2023, used green light to selectively sense fingerprints on the skin surface by reducing the depth of skin penetration. To apply this progress to health care, red light can also be used for OPDs in the All‐in‐One Sensor Display. In this case, red light from red pixel is used as the light source. The light can reach blood vessels under the epidermis because the skin penetration depth is deeper than green light. The light reaching the blood vessel becomes a signal to gather biometric information. This biometric information is then collected at OPD as the signal reaches the OPD in the panel again. For these series of processes, an OPD capable of effective detecting of light in the 625 nm region emitted by red pixels is required. In this study, OPD was fabricated using RD‐01, a high absorption donor material suitable for red light absorption, and RA‐01, a non‐fullerene acceptor for mass production, to respond to red light near 625 nm. The EQE of the OPD was 25% at wavelength of 625 nm. In addition, absorption spectrum of the OPD covers the Red emission effectively. Our results represent that OLED panel can be used for not only fingerprint recognition but also health care platform.

A Wearable Assistant Device for the Hearing Impaired to Recognize Emergency Vehicle Sirens with Edge Computing.

Wearable assistant devices play an important role in daily life for people with disabilities. Those who have hearing impairments may face dangers while walking or driving on the road. The major danger is their inability to hear warning sounds from cars or ambulances. Thus, the aim of this study is to develop a wearable assistant device with edge computing, allowing the hearing impaired to recognize the warning sounds from vehicles on the road. An EfficientNet-based, fuzzy rank-based ensemble model was proposed to classify seven audio sounds, and it was embedded in an Arduino Nano 33 BLE Sense development board. The audio files were obtained from the CREMA-D dataset and the Large-Scale Audio dataset of emergency vehicle sirens on the road, with a total number of 8756 files. The seven audio sounds included four vocalizations and three sirens. The audio signal was converted into a spectrogram by using the short-time Fourier transform for feature extraction. When one of the three sirens was detected, the wearable assistant device presented alarms by vibrating and displaying messages on the OLED panel. The performances of the EfficientNet-based, fuzzy rank-based ensemble model in offline computing achieved an accuracy of 97.1%, precision of 97.79%, sensitivity of 96.8%, and specificity of 97.04%. In edge computing, the results comprised an accuracy of 95.2%, precision of 93.2%, sensitivity of 95.3%, and specificity of 95.1%. Thus, the proposed wearable assistant device has the potential benefit of helping the hearing impaired to avoid traffic accidents.

54‐2: Invited Paper: Novel Display Application beyond OLED: All‐in‐one Sensor Display

Since OLED was first mass‐produced by Samsung Display, various researches related to OLEDs have been actively conducted and now days, People are using OLED displays every single day. As a next generation organic‐optoelectronic display, we suggest the All‐in‐one Sensor Display which can be used for fingerprint recognition, proximity sensor, illuminance sensing and photoplethysmogram which is an area of rapid interest in recent years. To demonstrate the All‐in‐one Sensor Display in entire display area, in this research, we successfully fabricated organic photodetectors (OPDs) in the OLED panels with our own materials, D‐01 and A‐01. Since designing a donor material and an acceptor material is key issue for high Signal to Noise ratio (SNR), we designed and synthesized the D‐01 and A‐01. With our own material based OPDs, All‐in‐one Sensor Display showed good characteristics and successfully recognized fingerprints. This research shows the possibility of the mass production of next organic diode and we believe that All‐in‐one Sensor Display will be the next display application beyond the OLEDs.

15‐2: A Novel Compensation Algorithm for Multi‐Frame‐Drop on AMOLED Display

In this paper, a novel compensation algorithm is proposed for improving multi‐frame drop (MFD) on AMOLED display. The MFD phenomenon occurs as the image switching or sliding when the display with extremely low brightness, resulting in the color shift and distortion at the edge of moving objects. Because the current is too small and the emission time is too short at extremely low brightness, more than one frame is needed to alleviate the impact of the parasitic capacitance between the gate and drain node of driving TFT (DTFT), and the gradual changing of drain voltage (VD) causes the DTFT to move from the linear to saturation region, which also aggravates this phenomenon. This paper analyzes the MFD phenomenon based on the existing 7T1C pixel circuits, records the grayscale changes of multiple frames, and gives the different offsets at dropped frames. By experiment results, this method is not changing the pixel circuit, such as the 8T1C, which could compensate for the dropped frames for reducing MFD issues and is easily implemented in the display driver IC for many different OLED panels.

25‐3: Design and fabricate of Under‐Display Camera OLED panel

5.5inch FHD UDC OLED panel is designed and fabricated. The OLED panel is divided into three parts, i.e., UDC, transition and nomal area. Transition area locates at the left and right side of UDC area, the height and width of transition area and UDC area are the same. Drive circuits corresponding to EL in UDC area locate at odd rows of transition area, while drive circuits corresponding to EL in the transition area locate at even rows of transition area. Meanwhile, drive circuit in the transition area correspondes to two EL with the same color in UDC or transition area.

AI Smart Gun using ESP32 Cam

The creation of a smart gun using ESP32-Cam is accomplished using the surrounding data and Internet of Battlefield Things (IoBT) in conjunction with a server which is further connected to the ESP32-CAM for more precise identification of the enemies. The user receives information from the server, which serves as the main framework of the system. Here, the server that has the acquired data goes through several processes to provide precise information that is then given to the user. After the user receives the information from the server, the output of the information is shown on an OLED panel that is positioned on the equipment. The user receives directions from the OLED display, which in turn aids in enemy detection

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

A Study of Thin Film Encapsulation on Improving Electrical Characteristics and Reliability for Flexible OLEDs

In this work, we investigated the effect of thin film encapsulation on Vth shift in a-IGZ0 TFTs. The result shows that decreasing the NH3 flow rate of deposited SiON films, the trend of Vth shift under the operation mode can vary from negative to positive direction, which can be attributed to lower amount of hydrogen diffused from SiON to the a-IGZO TFTs. Beside, we designed the TFE with stable inorganic-organic-inorganic stack structure, of which the CVD1 deposited with low NH3 flow rate and the CVD2 with high barrier property, and a 16.9-inch high performance flexible OLED panel with controlled Vth shift and RA lifetime over 475 h was achieved at the condition of 85 °C and 85% RH. This study demonstrates the influence of TFE on a-IGZO TFTs, and offers an optimized TFE structure which promises both electrical characteristics and reliability for flexible OLEDs.

A Novel FOD Solution with High-PPI Flexible Sensor under OLED Panel

A Novel FOD Solution with High-PPI Flexible Sensor under OLED Panel

Organic/Inorganic Hybrid Thin-Film Encapsulation Using Inkjet Printing and PEALD for Industrial Large-Area Process Suitability and Flexible OLED Application.

We present herein the first report of organic/inorganic hybrid thin-film encapsulation (TFE) developed as an encapsulation process for mass production in the display industry. The proposed method was applied to fabricate a top-emitting organic light-emitting device (TEOLED). The organic/inorganic hybrid TFE has a 1.5 dyad structure and was fabricated using plasma-enhanced atomic layer deposition (PEALD) and inkjet printing (IJP) processes that can be applied to mass production operations in the industry. Currently, industries use inorganic thin films such as SiNx and SiOxNy fabricated through plasma-enhanced chemical vapor deposition (PECVD), which results in film thickness >1 μm; however, in the present work, an Al2O3 inorganic thin film with a thickness of 30 nm was successfully fabricated using ALD. Furthermore, to decouple the crack propagation between the adjacent Al2O3 thin films, an acrylate-based polymer layer was printed between these layers using IJP to finally obtain the 1.5 dyad hybrid TFE. The proposed method can be applied to optoelectronic devices with various form factors such as rollables and stretchable displays. The hybrid TFE developed in this study has a transmittance of 95% or more in the entire visible light region and a very low surface roughness of less than 1 nm. In addition, the measurement of water vapor transmission rate (WVTR) using commercial MOCON equipment yielded a value of 5 × 10-5 gm-2 day-1 (37.8 °C and 100% RH) or less, approaching the limit of the measuring equipment. The TFE was applied to TEOLEDs and the improvement in optical properties of the device was demonstrated. The OLED panel was manufactured and operated stably, showing excellent consistency even in the actual display manufacturing process. The panel operated normally even after 363 days in air. The proposed organic/inorganic hybrid encapsulant manufacturing process is applicable to the display industry and this study provides basic guidelines that can serve as a foothold for the development of various technologies in academia and industry alike.

Electrothermal Tristability Causes Sudden Burn‐In Phenomena in Organic LEDs

AbstractOrganic light‐emitting diodes (OLEDs) have been established as a mature display pixel technology. While introducing the same technology in a large‐area form factor to general lighting and signage applications, some key questions remain unanswered. Under high‐brightness conditions, OLED panels were reported to exhibit nonlinear electrothermal behavior causing lateral brightness inhomogeneities and even regions of switched‐back luminance. Also, the physical understanding of sudden device failure and burn‐ins is still rudimentary. A safe and stable operation of lighting tiles, therefore, requires an in‐depth understanding of these physical phenomena. Here, it is shown that the electrothermal treatment of thin‐film devices allows grasping the underlying physics. Configurations of OLEDs with different lateral dimensions are studied as a role model and it is reported that devices exceeding a certain panel size develop three stable, self heating‐induced operating branches. Switching between them causes the sudden formation of dark spots in devices without any preexisting inhomogeneities. A current‐stabilized operation mode is commonly used in the lighting industry, as it ensures degradation‐induced voltage adjustments. Here, it is demonstrated that a tristable operation always leads to destructive switching, independent of applying constant currents or voltages. With this new understanding of the effects at high operation brightness, it will be possible to adjust driving schemes accordingly, design more resilient system integrations, and develop additional failure mitigation strategies.

P‐9: Understanding Diffusion Behaviors of Light Elements in OLEDs

In the OLED panel, we have been investigated to understand diffusion behaviors of light element in various perspectives. It has evaluated by using advanced analytical tools such nano‐SIMS. we could find the diffused hydrogen from insulating film in channel area of bad sample. Increased hydrogen is directly attributed to the negative Vth shift. Also, we make the cross sectional sample and find the diffusion source of internal outgassing using the cross‐sectional Ion Mapping analysis method.

Multi-hardness hybrid silicone pad to laminate the bended cover window in a flexible OLED display

According to the evolving requirements of smartphone consumers, the form of smartphone displays is becoming more advanced and diversified. In particular, the shape of the cover window of smartphones is changing from a conventional flat rigid shape to a bended shape with multiple curvatures. However, a relatively advanced lamination process is required to bond the flexible OLED panel to the bended cover window. To overcome this limitation, in this study, a hybrid structured silicone pad with multi-hardness was developed as a pad to be used for the lamination. Hybrid silicone pads were modeled in various shapes, considering the stress points and spreading characteristics of the pad pertaining to the vertical, horizontal, and center orientations during compression in the lamination process. In addition, the compression strength of the proposed pad was evaluated through simulation, and the compression results and reliability of the pad were validated through lamination process experiments performed using an optically clear adhesive.

Realizing Thin‐Film Encapsulation's Benefits for Large‐Scale OLED Panels

AbstractOLED is poised to be the dominant next‐generation display technology, but it needs high‐mobility thin‐film transistors to get there.

17.5: Luminance Instability of OLED panels at Various Situations

To decrease tack time during Demura process, images are captured directly after turning on panels or changing patterns and then used to generate compensation data which determines the Demura results. However, the panel's luminance stability in those situations have not been paid enough attention. Seven panels from five different OLED panel producers were tested at various situations which are from turning off to turning on the panel, changing patterns from different gray levels of the same color or from the same gray level but with different colors. Even after the panels were turned on for a while, their luminance is still instable, therefore luminance's stability was also tested. We found that when turning on panels or changing patterns from different colors, the luminance will go up or down 1–5% of the mean of the relatively stable luminance and need 4–30 seconds to get stable. However, when changing patterns among different gray levels but with the same color, there almost no luminance's sudden change at high gray level (above 160) while the luminance goes up or down 0–3% and need half time to get stable at low gray level (32). The results provide a choice to avoid the sudden change of panels' luminance when changing patterns during Demura process while not increasing the tack time so much and also a possible reason that why the Demura results are not good enough. We also found that the luminance instability could be 0–4% at high gray level (RGB192) and 0.3–4.9% at low gray level (RGB32) which should be paid enough attention since the compensation data based on only one image could not be accurate enough if the panels' luminance is not stable.

13‐3: Improvement of Blue Pixels in OLED Panels with more Efficient Fluorescent and TADF Emitters

The missing high‐efficiency Blue OLEDs are still the bottleneck for the power consumption in today’s OLED panels. One way to improve the efficiency of the blue pixel is the use of narrow‐type fluorescent emitters in a classical fluorescent stack for top‐emission OLED devices where the optical cavity effect favors narrow over a broader emission. In this paper, we will show how narrow‐type fluorescent emitters can deliver >30% efficiency improvement over traditional commercial fluorescent blue emitters to reach >200 cd/A/CIEy in top‐emission devices. For further efficiency increase, those fluorescent emitters can be combined with TADF emitters which can increase the internal quantum efficiency from 25% to 100%. In order to make such a hyper‐fluorescent system work efficiently, the combination of TADF and fluorescent emitter has to be chosen carefully as they have to match the materials perfectly.

P‐207: Late‐News‐Poster: Infrared Down‐conversion of Organic Light Emitting Diode Emission for Medical Use and Vein Authentication

A flexible infrared surface light source is fabricated for medical and vein authentication purpose. The light source is composed of red‐emissive OLED device and infrared down‐conversion film covering the red OLED. The light source exhibits the emission wavelength between 700‐1000 nm, and provides enough radiances for medical and authentication system at voltage below 4V. A vein authentication prototype was fabricated for comparison between conventional LEDs and down‐converted OLEDs. The peak wavelength for the prototype is 834 nm and the radiant flux at the wavelength is 2.7‐6.0 mW using the 15x15‐mm2 OLED panel. Testing result clearly shows the merit of surface light source in terms of authentication accuracy, especially for false rejection rate.

Sound Quality Enhancement by using the Single Core Exciter in OLED Panel

Sound Quality Enhancement by using the Single Core Exciter in OLED Panel

45.3: TADF Emitters for Deep‐Blue OLEDs

Blue fluorescent OLEDs are still the bottleneck for the power consumption in today's OLED panels. In recent years, the TADF technology has shown fast progress towards high‐efficiency deep‐blue emitter systems. The TADF technology can be used in a self‐emitting or in a co‐emitting (or hyper) approach. To make the co‐emitting system work efficiently, the combination of TADF and fluorescent emitter has to be chosen carefully. In this paper, we will discuss how to match TADF and fluorescent emitter combinations for the co‐emitting approach. We will also show results for highly efficient deep‐blue hyper‐fluorescent devices.