柔性显示器件的衬底材料及封装技术

有机电致发光显示器件(OLED)被认为是最理想、最具发展前景的下一代显示技术之一.在柔性衬底上制备的有机电致发光器件拓宽了OLED的使用范围,是其重要发展方向.本文综述了柔性显示器件的衬底材料及封装技术的发展概况,比较了玻璃、聚合物、金属3种衬底材料的优缺点,并简单介绍了以这3种材料为衬底的柔性显示器件的封装技术.     

聚合物电致发光材料及器件

聚合物电致发光器件由于其卓越的性能,在近年来取得了飞速发展,成为科研领域的又一热点。阐述了聚合物ＥＬＤ的工作原理,器件结构、聚合物材料的种类及分子结构,综述了影响器件发光效率和寿命的因素和解决办法,介绍了聚合物电致发光材料及器件的发展现状和目前存在的问题,并对其今后的发展趋势和应用前景进行了展望。     

红荧烯衍生物的红光电致发光器件及其在照明中的应用

合成了一种红荧烯的衍生物,2-甲酰基红荧烯作为一种红光掺杂剂,掺杂在N,N-diphenyl-N,N-bis 1-naphthyl–1,1-biphenyl-4,4-diamine(NPB)中制备的电致发光器件,发射峰位于598nm,电流效率为2.1cd/A。用这个红光掺杂系统制备了一个白光电致发光器件,在白光器件中,2-甲酰基红荧烯,八-羟基喹啉铝(Alq3),以及NPB分别组成了白光中的红、绿以及蓝的发光成分,获得了一个白光器件,该器件显色指数高达89.8,在11V时,色坐标达(0.33,0.33),最大亮度为5000cd/m2以及最大发光效率为4.7cd/A。这些性能参数表明这个白光器件具有潜在的照明应用。另外,还讨论了器件的结构设计以及电致发光过程及机理。     

喷墨打印技术在功能材料精密器件加工中的应用

喷墨打印技术应用于聚合物成膜或成型,已成为功能聚合物沉积和精密器件加工领域的核心技术之一。介绍了喷墨打印技术在聚合物电致发光器件、有机薄膜晶体管、太阳能电池和传感器等领域的研究和应用进展,包括聚合物墨水的制备、薄膜均匀性、聚合物溶液与打印性能的关系、新型功能材料的研究和开发等问题,并指出了存在的问题和面临的挑战。     

界面激基复合物或激发二聚体形成和在有机电致发光的应用（英文）

由于有机材料的电致发光(EL)器件能够在平板显示和固态照明的应用使得人们对其抱有很大的兴趣。在通常的EL器件结构中,要么使用多层结构要么使用混合层结构以便平衡载流子的注入和复合。一般来说,人们关注的是这种器件的EL发射来源于体成分或搀杂剂成分。但是本评论讨论的EL发射确是来源与不同有机(聚合物)分子间界面激基复合物或同种有机(聚合物)分子间形成的激发二聚体。本评论将对激基复合物和激发二聚体对EL器件的积极或负面影响给予讨论,对于负面影响,将提出如何克服那些负面影响和充分利用它们白光OLED(WOLED)的一个成分,这样,可以简化器件结构和制作工艺。     

有机电致发光材料的研发现状

有机电致发光器件 (OLED)具有驱动电压低、主动发光等优势 ,在平板显示领域具有极大的应用前景而引起了广泛的关注。与此同时有机电致发光材料的研发也取得了很大的进展。本文介绍了近年来有机电致发光材料 (包括小分子发光材料和聚合物发光材料 )的研发状况     

纳米复合技术在聚合物电致发光材料与器件中的应用

纳米复合技术的问世为改善聚合物电致发光材料与器件的性能开辟了新的途径,本文论述了纳米复合技术在聚合物电致发光材料与器件中的应用及发展前景.     

白光OLED的研究进展

有机电致发光器件(Organic light-emitting device,OLED)具有质轻且薄、视角宽、色彩鲜艳、节能环保、柔性弯曲的独特优点。白光OLED在未来固态照明和平板显示方面展现出了美好的应用前景,成为国内外的研究重点。通过结构设计和器件优化,目前白光OLED的发光效率已经能够达到荧光灯的效率。主要讨论了近年来白光OLED的主要发展,并从发光染料的角度讨论了不同类型白光器件的研究状况。     

有机电致发光器件的研究进展

有机电致发光器件(OELD)具有驱动电压低,功耗小,亮度高,响应速度快等优点,由其制作有机发光显示器件已被视为下一代最理想的显示技术.在简要介绍OELD器件结构、发光机理和制备工艺的基础上系统阐述了有机发光材料、OELD显示器件及驱动技术的研究进展,最后展望了该领域目前存在的问题及可能的解决方向.     

聚合物电致发光材料的研究现状及应用前景

聚合物电致发光材料是近几年来取得很大进展而倍受关注的新型功能材料。电致发光薄膜器件激发电压低、发光效率高、易得到彩色显示 ,而且容易实现大屏幕平板化。本文综述这类薄膜电致发光器件的发光原理、发光材料、器件的制备方法以及改善器件特性的方法     

Flexible Blade‐Coated Multicolor Polymer Light‐Emitting Diodes for Optoelectronic Sensors

A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light‐emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface‐energy‐patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near‐infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.     

Large‐Area Organic Solar Cells: Material Requirements,Modular Designs,and Printing Methods

The printing of large‐area organic solar cells (OSCs) has become a frontier for organic electronics and is also regarded as a critical step in their industrial applications. With the rapid progress in the field of OSCs, the highest power conversion efficiency (PCE) for small‐area devices is approaching 15%, whereas the PCE for large‐area devices has also surpassed 10% in a single cell with an area of ≈1 cm². Here, the progress of this fast developing area is reviewed, mainly focusing on: 1) material requirements (materials that are able to form efficient thick active layer films for large‐area printing); 2) modular designs (effective designs that can suppress electrical, geometric, optical, and additional losses, leading to a reduction in the PCE of the devices, as a consequence of substrate area expansion); and 3) printing methods (various scalable fabrication techniques that are employed for large‐area fabrication, including knife coating, slot‐die coating, screen printing, inkjet printing, gravure printing, flexographic printing, pad printing, and brush coating). By combining thick‐film material systems with efficient modular designs exhibiting low‐efficiency losses and employing the right printing methods, the fabrication of large‐area OSCs will be successfully realized in the near future.     

Scalable Fabrication of Highly Crystalline Organic Semiconductor Thin Film by Channel‐Restricted Screen Printing toward the Low‐Cost Fabrication of High‐Performance Transistor Arrays

Control over the morphology and crystallinity of small‐molecule organic semiconductor (OSC) films is of key importance to enable high‐performance organic optoelectronic devices. However, such control remains particularly challenging for solution‐processed OSC devices because of the complex crystallization kinetics of small‐molecule OSC materials in the dynamic flow of inks. Here, a simple yet effective channel‐restricted screen‐printing method is reported, which uses small‐molecule OSCs/insulating polymer to yield large‐grained small‐molecule OSC thin‐film arrays with good crystallization and preferred orientation. The use of cross‐linked organic polymer banks produces a confinement effect to trigger the outward convective flow at two sides of the channel by the fast solvent evaporation, which imparts the transport of small‐molecule OSC solutes and promotes the growth of small‐molecule OSC crystals parallel to the channel. The small‐molecule OSC thin‐film array produced by screen printing exhibits excellent performance characteristics with an average mobility of 7.94 cm² V^?1 s^?1 and a maximum mobility of 12.10 cm² V^?1 s^?1, which are on par with its single crystal. Finally, screen printing can be carried out using a flexible substrate, with good performance. These demonstrations bring this robust screen‐printing method closer to industrial application and expand its applicability to various flexible electronics.     

Optical property of poly(9,9-dioctylfluorene) gel with β phase and application to polymer light emitting diode

Poly (9,9-dioctylfluorene)(F8) gel with β phase has been investigated in terms of optical absorption, photoluminescence measurements and Fourier transform infrared spectroscopy. The optical properties of the F8 gel markedly changed in the temperature range from 70 to 80 °C owing to the vibration of polymer chain related to the glass transition temperature of F8. F8 films by thermal printing method had the characteristic particulate morphology. Current efficiencies of polymer light emitting diodes (PLEDs) with the β phase of F8 fabricated by the thermal printing method were better than that with the amorphous phase of F8 by the spin-coating method. We demonstrate the β phase effects of PLEDs characteristics by the thermal printing method.     

Turning Trash into Treasure: Additive Free MXene Sediment Inks for Screen-Printed Micro-Supercapacitors

Printed functional conductive inks have triggered scalable production of smart electronics such as energy-storage devices, antennas, wearable electronics, etc. Of particular interest are highly conductive-additive-free inks devoid of costly postdeposition treatments to eliminate sacrificial components. Due to the high filler concentration required, formulation of such waste-free inks has proven quite challenging. Here, additive-free, 2D titanium carbide MXene aqueous inks with appropriate rheological properties for scalable screen printing are demonstrated. Importantly, the inks consist essentially of the sediments of unetched precursor and multilayered MXene, which are usually discarded after delamination. Screen-printed structures are presented on paper with high resolution and spatial uniformity, including micro-supercapacitors, conductive tracks, integrated circuit paths, and others. It is revealed that the delaminated nanosheets among the layered particles function as efficient conductive binders, maintaining the mechanical integrity and thus the metallic conductive network. The areal capacitance (158 mF cm⁻²) and energy density (1.64 µWh cm⁻²) of the printed micro-supercapacitors are much superior to other devices based on MXene or graphene. The ink formulation strategy of “turning trash into treasure” for screen printing highlights the potential of waste-free MXene sediment printing for scalable and sustainable production of next-generation wearable smart electronics.     

Coated and Printed Perovskites for Photovoltaic Applications

Hybrid organic–inorganic metal halide perovskite semiconductors provide opportunities and challenges for the fabrication of low‐cost thin‐film photovoltaic devices. The opportunities are clear: the power conversion efficiency (PCE) of small‐area perovskite photovoltaics has surpassed many established thin‐film technologies. However, the large‐scale solution‐based deposition of perovskite layers introduces challenges. To form perovskite layers, precursor solutions are coated or printed and these must then be crystallized into the perovskite structure. The nucleation and crystal growth must be controlled during film formation and subsequent treatments in order to obtain high‐quality, pin‐hole‐free films over large areas. A great deal of understanding regarding material engineering during the perovskite film formation process has been gained through spin‐coating studies. Based on this, significant progress has been made on transferring material engineering strategies to processes capable of scale‐up, such as blade coating, spray coating, inkjet printing, screen printing, relief printing, and gravure printing. Here, an overview is provided of the strategies that led to devices deposited by these scalable techniques with PCEs as high as 21%. Finally, the opportunities to fully close the shrinking gap to record spin‐coated solar cells and to scale these efficiencies to large areas are highlighted.     

Bi-layer gravure printed nanoscale thick organic layers for organic light emitting diode

The gravure printed single layer structure and bi-layer structure of MEH-PPV/rubrene organic light emitting diodes (OLEDs) were investigated in this work. Typically, the formation of bi-layers in polymer light emitting diodes (PLEDs) is challenging. The brightness and efficiency polymer light emitting materials were enhanced by the gravure printed bi-layer structure in this work. The layer structure of the OLED devices was glass/ITO/PEDOT:PSS/active layer/LiF/Al. The active layers were made using two different processes-one was a gravure printed single organic layer made of a blended mixture of MEH-PPV and rubrene, and the other was a gravure printed bi-layer of MEH-PPV and rubrene. The gravure printed bi-layer devices exhibited a higher brightness and efficiency than the blended devices. The efficiency of the bi-layer MEH-PPV/rubrene structure was improved by a factor of 1.6 approximately 3.2, and the brightness was improved by a factor of 1.9 approximately 2.0 compared to the blended single layer structure. This work demonstrated that organic bi-layers could be formed using gravure printing technology and the bi-layer structure exhibited a higher efficiency than the blended single layer structure.     

Improvement of emission efficiency in polymer light-emitting devices based on phosphorescent polymers

We report improvement of emission efficiency in polymer light-emitting devices (PLEDs) employing phosphorescent polymers. A hole-blocking layer was inserted between the emissive layer and the cathode to enhance recombination efficiency for the injected holes and electrons. Aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolato (BAlq) was used for the hole-blocking layer. The resultant PLEDs exhibited significant improvement of emission efficiency. The respective external quantum efficiencies for red, green and blue PLEDs were 6.6, 11 and 6.9%. These values are very high compared with those based on conventional fluorescent polymers.     

Printable Transparent Conductive Films for Flexible Electronics

Printed electronics are an important enabling technology for the development of low‐cost, large‐area, and flexible optoelectronic devices. Transparent conductive films (TCFs) made from solution‐processable transparent conductive materials, such as metal nanoparticles/nanowires, carbon nanotubes, graphene, and conductive polymers, can simultaneously exhibit high mechanical flexibility, low cost, and better photoelectric properties compared to the commonly used sputtered indium‐tin‐oxide‐based TCFs, and are thus receiving great attention. This Review summarizes recent advances of large‐area flexible TCFs enabled by several roll‐to‐roll‐compatible printed techniques including inkjet printing, screen printing, offset printing, and gravure printing using the emerging transparent conductive materials. The preparation of TCFs including ink formulation, substrate treatment, patterning, and postprocessing, and their potential applications in solar cells, organic light‐emitting diodes, and touch panels are discussed in detail. The rational combination of a variety of printed techniques with emerging transparent conductive materials is believed to extend the opportunities for the development of printed electronics within the realm of flexible electronics and beyond.     

Light emitting diodes containing Langmuir-Blodgett films of copolymer of a poly(p-phenylene-vinylene) derivative and poly(octaneoxide)

The properties of Langmuir and Langmuir-Blodgett (LB) films from a block copolymer with polyethylene oxide and phenylene-vinylene moieties are reported. The LB films were successfully transferred onto several types of substrates, with sufficient quality to allow for evaporation of a metallic electrode on top of the LB films to produce polymer light emitting diodes (PLEDs). The photoluminescence and electroluminescence spectra of the LB film and device were similar, featuring an emission at ca. 475 nm, from which we could infer that the emission mechanisms are essentially the same as in poly(p-phenylene) derivatives. Analogously to other PLEDs the current versus voltage characteristics of the LB-based device could be explained with the Arkhipov model according to which charge transport occurs among localized sites. The implications for nanotechnology of the level of control that may be achieved with LB devices will also be discussed.