有机发光显示器件的研究及应用

有机发光显示器具有自主发光、功耗小、驱动电压低、视角宽、响应速度快等优点,已成为平板显示技术新的研究热点.在介绍有机电致发光器件结构和发光原理基础上,系统介绍了有机显示器件的三个核心部分-有机发光材料、显示面板和驱动技术的研究进展,分析了有机发光显示器的市场前景及可能的应用领域,最后指出有机发光显示器在产业化进程中所需要解决的问题.     

有机发光显示技术的进展

有机发光显示被认为是下一代最理想的显示技术,具有自主发光、功耗小、视角宽、成本低和响应速度快等优点。本文在简述有机电致发光器件的电极结构和发光材料的基础上,重点介绍了有机显示器件的驱动技术和面板的研发成果,并展望未来发展的前景。     

有机白光发光二极管研究进展

有机白光发光二极管是实现全色显示的重要原型器件之一,而且作为一种超薄光源还可用作液晶的背光源以及一些特殊场合的照明.本文从发光区域、器件结构、材料选择等方面回顾了有机白光发光研究的一些进展情况.     

Advanced organic light-emitting devices for enhancing display performances

Various advanced organic light-emitting devices (OLEDs) for enhancing performances of OLED displays, particularly active-matrix OLED displays, are reviewed in this paper. These include top-emitting OLEDs, inverted OLEDs, high-contrast OLEDs, microcavity OLEDs, and their combinations. How these device structures enhance display performances, such as color saturation, brightness or emission efficiency, contrast, and aperture ratio of pixels, etc., are discussed. The critical technical issues and the status of development associated with each device technology are reviewed.     

High-performance polycrystalline silicon thin-film transistor technology using low-temperature metal-induced unilateral crystallization

Low-temperature metal-induced unilaterally crystallized polycrystalline silicon thin-film transistors (TFTs) have been developed and characterized. These TFTs are better than their solid-phase crystallized counterparts in many process and device performance measures, such as shorter and simpler process flow, higher field-effect mobility, reduced leakage current, better immunity to early drain breakdown and much improved spatial uniformity of device parameters. They have been used to realize active matrices for liquid-crystal (LC) and organic light-emitting diode (OLED) flat-panel displays.     

Pentacene TFT driven AM OLED displays

Pentacene organic thin-film transistors (TFTs)-driven active matrix organic light-emitting diode (OLED) displays has been investigated. This letter addresses several process issues unique to this type of display which are important in achieving bright and uniform displays. A bottom contact structure was used to fabricate the pentacene TFT backplane. Polyvinyl alcohol and parylene were used to isolate the pentacene active layer and passivate the backplane. The low processing temperature may allow the use of polymeric substrates and lower cost processing. Uniform TFT performance is achieved with reasonably good mobility and on/off ratio on the backplane. The initial OLED display performance is also presented.     

High-Performance Chemical-Bath-Deposited Zinc Oxide Thin-Film Transistors

Solution-processed transparent zinc oxide (ZnO) transistors are demonstrated using a chemical bath deposition process for ZnO deposition. The process is glass compatible and amenable to producing fully transparent electronics. Mobility as high as 3.5 cm²/V ldr s with on-off ratios of ~10⁵ is realized. The transparency of ZnO allows for complete coverage of the pixel by the pixel drive transistors; analysis shows that the performance achieved herein is sufficient even to drive high-brightness organic light-emitting diode (OLED) displays by exploiting the high mobility and optical transparency of these devices. This makes this technology extremely attractive for use in active-matrix OLED display applications.     

Design of an organic pixel addressing circuit for an active-matrix OLED display

In this paper, we present a design of a flat-panel display (FPD) based on organic light-emitting diodes (OLEDs) and on organic thin-film transistors (OTFTs). Addressing mode, circuit topology, layout, and drive scheme are developed in order to reach the desired frame rate and to control the gray levels against the threshold voltage dispersions of OTFTs and OLEDs. The design shows that the current OLED and OTFT technology are suitable for FPD technology, though setting serious constraints on driver design.     

Assessment of Mobile Technologies for Displaying Medical Images

We compared the characteristics of state-of-the-art mobile display systems based on reflective and transmissive liquid crystal displays (LCDs) and an organic light-emitting display with respect to physical characterization metrics and observer studies. Physical performance factors provided information on the differences among display technologies. Observer studies resulted in different system ranking between the task-based performance and user-preference approaches. The results of the physical characterization and preference study showed that the reflective LCD ranked lower. We also found that ambient illumination played a lesser role than previously seen in large-format workstation displays. The methodology developed in this study provides an initial insight into the comparison of alternative technologies for display of diagnostic images in small portable devices.      

State of flat-panel display technology and future trends

The rivalry between the cathode-ray tube and flat-panel displays (FPDs) has intensified as performance of some FPDs now exceeds that of that entrenched leader in many cases. Besides the well-known active-matrix-addressed liquid-crystal display, plasma, organic light-emitting diodes, and liquid-crystal-on-silicon displays are now finding new applications as the manufacturing, process engineering, materials, and cost structures become standardized and suitable for large markets     

Using Integrated Optical Feedback to Counter Pixel Aging and Stabilize Light Output of Organic LED Display Technology

We define a metric of useful operating lifetime of an organic light-emitting device (OLED) display and relate it to the commonly measured half-life of constituent OLED pixels. We enumerate sources of OLED operational instability and propose an optical feedback solution in a novel integrated configuration to counter pixel aging and maintain stable light output across all of the pixels of an OLED display. Such optical feedback can correct pixel imperfections in both active matrix and passive matrix OLED displays. As an example, we analyze lifetime data previously published by Kwong . in 2002, and demonstrate that our optical feedback technique could maintain 100 cd/m$^{2}$ display light output within a 2% brightness accuracy for more than 25 000 hours of continuous use for this specific OLED system. From this example we draw conclusions generally applicable to extending stable operating lifetime of other OLED structures.      

PtYCAM三线态有机磷光材料

OLED显示技术凭借其各方面的优势能完全取代CRT,LCD,LED等显示器,有着巨大的市场和应用前景。OLED显示的发光材料特别是磷光材料成为近年来的热点,但自旋禁阻使得OLED的发光效率受到限制。利用三线态激子的辐射衰减可以使磷光材料在理论上具有100％的发光效率。因此磷光材料中的金属配合物材料成为了国内外有机磷光材料的研究重点。     

柔性OLED封装方法的研究靠

有机电致发光二极管与其他显示器件相比,最大的优势就是可以制备在聚合物基板上,实现柔性显示,但聚合物对水、氧的阻挡能力远不如玻璃.因此,为了延长柔性OLED器件寿命,就要在柔性器件的基板和盖板上制作薄膜阻挡层,进行有效的封装.介绍了OLED的封装方式的进展,并提出了一些柔性OLED的封装方案.     

OLED封装薄膜水汽透过率测试方法研究

柔性显示是未来显示技术的重要发展方向之一,有机电致发光二极管(OLED)能否实现柔性应用依赖于薄膜封装技术的发展,而封装薄膜的水汽阻隔性能,标志着薄膜封装性能的好坏。介绍了OLED器件失效的原因,封装的必要及其对于封装的要求,重点介绍并分析了3种常用的OLED测试水汽透过率(WVTR)的方法,库伦电量法、重水法以及钙法。     

Driving schemes for a-Si and LTPS AMOLED displays

Design of stable active matrix organic light-emitting diode (AMOLED) displays comes with significant challenges that stem from the electrical property of the backplane materials, line parasitics in the matrix, and the opto-electronic property of the organic light-emitting diode (OLED). This paper reviews voltage and current programming schemes for AMOLEDs. Following a systematic review of pixel circuits, design considerations are examined for both current and voltage schemes with focus on stability and programming speed for both amorphous silicon (a-Si) and low temperature polysilicon (LTPS) pixel circuits. In particular, spatial parameter variations and stability, which hinder reliable operation of AMOLED display backplanes, are discussed. Analysis shows that while driving schemes reported hitherto maybe suitable for small and medium size displays, new schemes are critically needed for large-area high-resolution AMOLED displays.     

Roll-up displays: fact or fiction?

Many companies have undertaken the challenge of creating flexible displays but the perfect specimen is still some way off. This article looks at the numerous technological challenges involved in making a display flexible, including the thickness of the display relative to its rigidity, and finding a set of technologies that can combine to create a large, stable matrix of individually addressable pixels that will flex. In addition, a number of flexible display technologies under development are described, including liquid crystal displays (LCDs), electrophoretic light-controlling material-based displays, plastic semiconductor backplanes and semiconductors based on organic polymers for plastic electronics, organic light emitting diode (OLED) displays, organic thin film transistor (TFT) technology, an enhanced ink jet-based patterning technique for organic polymer materials, and the development of new emissive materials to go with the flexible backplanes.     

Power Consumption and Temperature Increase in Large Area Active-Matrix OLED Displays

We model and analyze the power consumption and resulting temperature rise in active-matrix organic-light-emitting device (AMOLED) displays as a function of the OLED efficiency, display resolution and display size. Power consumption is a critical issue for mobile display applications as it directly impacts battery requirements, and it is also very important for large area applications where it affects the display temperature rise, which directly impacts the panel lifetime. Phosphorescent OLEDs (PHOLEDs) are shown to offer significant advantage as compared to conventional fluorescent OLEDs due to high luminous efficiency resulting in lower pixel currents, reducing both the power consumed in the OLED devices and the series connected driving thin-film transistor (TFT). The power consumption and temperature rise of OLED displays are calculated as a function of the device efficiency, display size, display luminance and the type of backplane technology employed. The impact of using top-emission OLEDs is also discussed.     

Integration of organic LEDs and amorphous Si TFTs onto flexible andlightweight metal foil substrates

We report the integration of organic light emitting devices (OLEDs) and amorphous Si (a-Si) thin-film transistors (TFTs) on both glass, and unbreakable and lightweight thin stainless steel foil substrates. The doped-polymer OLEDs were built following fabrication of driver TFTs in a stacked structure. Due to the opacity of the steel substrate, top-emitting OLED structures were developed. It is shown that the a-Si TFTs provide adequate current levels to drive the OLEDs at video brightness (~100 cd/m²). This work demonstrates that lightweight and rugged TFT backplanes with integrated OLEDs are essential elements for robust and highly portable active-matrix emissive flat-panel displays     

Parallel Addressing Scheme for Voltage-Programmed Active-Matrix OLED Displays

This paper presents a novel parallel addressing scheme for voltage-programmed active-matrix organic light-emitting diode (OLED) displays which provides high precision recovery of the threshold voltage shift. As a result, the uniformity over the panel is significantly improved. In addition, a new pixel circuit is presented that is capable of providing a predictably higher current as the pixel ages, so as to compensate for the OLED luminance degradation     

Measurement of Electron Mobility in Alq3 From Optical Modulation Measurements in Multilayer Organic Light-Emitting Diodes

The dynamic characteristics of multilayer organic light-emitting diodes (OLEDs) determine the refresh rate in display applications, and are of great importance for practical organic displays. They also serve as an important tool in studying the transport mechanisms in organic conductors. Here, the modulation characteristics of several conventional small-molecule OLED structures [consisting of ITO/PEDOT:PSS(50 nm)/TPD(50 nm)/Alq₃(various)/LiF(1 nm)/Al(90 nm)] are measured and analyzed in terms of mobility in and thickness of the Alq ₃ layer. Their optical response was shown to be limited by electron transport across the Alq₃. Extracted electron mobilities were about 2-4times10^-6 cm²/Vmiddots (consistent with that reported in the literature) and near-identical values for mobility were obtained from devices of different thicknesses, suggesting that this method measures mobility independent of interface trap charging. This novel technique is a complement to large signal time of flight or delay time measurements (which can include interface and trap charging during the measurement) and can serve as a flexible method to study transport in actual devices