喷墨打印技术在材料科学中的应用

近年来,采用喷墨打印技术制备功能陶瓷、金属导线、聚合物电致发光二极管以及生物芯片等材料引起了国内外研究人员的广泛关注。介绍了喷墨打印技术在陶瓷墨水喷墨打印无模成型、单分散胶体球体自组装、金属纳米粒子的图案化排列以及有机分子多层膜的微图形蚀刻中的研究和应用进展,讨论了喷墨成型技术在材料制备中存在的问题和发展趋势,指出喷墨打印技术已成为材料领域基础研究和产品研发的一个有力工具。     

Perspectives on organic light-emitting diodes for display applications

Herein, we describe a number of key issues that concern the commercialization of organic light-emitting diodes for display applications. We will firstly outline the historical and market contexts that show the potential for organic electronics as a viable display technology. Next, we will discuss the chemical structures for a range of both small-molecular and polymer organic semiconducting compounds, and how the electronic properties are governed thereof. Also we will briefly discuss various common film deposition and device fabrication strategies. Then, we will describe two factors that are highly relevant for commercially viable organic light-emitting diodes, namely charge balance, and device degradation. Finally, we will outline some methods for achieving the high-volume throughput of organic electronics via well-established technologies that are used in the printing industry.     

Stacking layered structure of polymer light emitting diodes prepared by evaporative spray deposition using ultradilute solution for improving carrier balance

Polymer light-emitting diodes (PLEDs) with staking layered structures are prepared by the evaporative spray deposition using ultradilute solution (ESDUS) method, which has enabled forming a polymer layer onto another polymer layer even if both polymers are soluble in a solvent used for the preparation. By this method, polymers having various HOMO and LUMO levels can be stacked as a hole transport layer, an emitting layer and an electron transport layer as commonly employed in small molecule-based organic light emitting diodes. Here we demonstrated that a PLED having a tri-layer structure using three kinds of polymers showed significant improvement in quantum efficiency compared with those having a single or bi-layer structure of corresponding polymers.     

Polymeric white organic light-emitting diodes with two emission layers

A white light-emitting diode was fabricated by preparing multilayer emitting films with an inserted buffer layer. The device structures are ITO/PEDOT:PSS/Emissive layer/LiF/Al. The emissive layer comprises a yellow-emitting layer of Poly[9,9-dioctylfluorenyl-2,7-diyl]-co-1,4-benzo-(2,1,3)-thiadiazole (F8BT), a blue-emitting layer of Poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] (BEHF) and PEDOT:PSS as a buffer layer between the emission layers. The solution processed multi-layer polymer light-emitting diodes (PLED) were prepared by introduction of a water-soluble buffer layer between organic solvent soluble layers. We present white organic light-emitting diodes (WOLEDs) that has bilayer emission zones. This device exhibits a brightness of 280 cd/m2 and emission efficiency of 1.18 cd/A at 12.6 V. The device with a doped PEDOT:PSS layer and a thicker blue-emission layer exhibits CIE color coordinates of (0.30, 0.34), which is close to the white coordinates of (0.33, 0.33) used by the standard CIE color coordinates.     

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.     

Effects of the introduced single-wall carbon nanotubes on the performance of blue phosphorescence organic light-emitting diodes

In this paper, the effects of single-walled carbon nanotubes (SWCNTs) on the performance of blue phosphorescence organic light-emitting diodes (OLEDs) are investigated by altering the place of SWCNTs in prepared devices. Three kinds of OLEDs in which SWCNTs are spin-coated between the organic layer and the cathode or doped into the organic emitting layer or into the hole-injection layer are prepared. It is found that the SWCNTs doped into the hole-injection layer can enhance the current efficiency because the SWCNTs can reduce hole transport ability and balance two kinds of carriers. Even though SWCNTs doped into the organic emitting layer can improve the transport characteristics of polymer, excess holes lead to an imbalance of holes and electrons in the organic layer, and a lower current efficiency is obtained. SWCNTs located between the organic layer and the cathode can enhance the electron injection from the cathode to the organic layer, and the luminance and current efficiency characteristics are effectively improved.     

Pure white phosphorescent organic light-emitting diodes using a phosphine oxide derivative as a high triplet energy host material

Pure white phosphorescent organic light-emitting diodes were developed using a high triplet energy (3.02 eV) host material (PPO1) with a carbazole and a phosphine oxide unit. Deep blue emitting tris((3,5-difluoro-4-cyanophenyl)pyridine) iridium was doped into the wide triplet bandgap PPO1 host material and the blue emitting layer was combined with a red/green phosphorescent emitting layer. The doping concentration, thickness of the emitting layer and the electron transport material were managed to optimize the device performance of the white device. A pure white color with a color coordinate of (0.29,0.33) and a high current efficiency of 27.2 cd/A was achieved from the white organic light-emitting diodes with the PPO1 host after optimization.     

Semitransparent passive matrix organic light-emitting displays

There has been an increased interest in developing top emission organic light-emitting diodes (OLEDs) that are able to emit light from both sides of the OLED display. One important application of the top emission device structure is to achieve monolithic integration of a top-emitting OLED on a polycrystalline or amorphous silicon thin film transistors used in active matrix displays. A high performance dual-sided top-emitting polymer OLED developed in this work exhibited a total luminous efficiency of ∼5.0 cd/A at 4.0 V, which is comparable to that observed for a control device having bottom emission structure. A laser ablation technology was developed to define the pixels. The cathode separation was achieved without using the conventional reverse trapezoid type separators that are normally used for pixellated OLED displays. A prototype of semitransparent polymer light-emitting passive matrix display has a matrix of 100 × 32 with a display area of 32.25 mm by 11.15 mm.     

Gravure printed organic light emitting diodes for lighting applications

A major advantage of polymer based organic light emitting diodes (OLED) is the capability to be manufacturing them with low cost, high-throughput printing techniques. In this paper, we report on double layer gravure printed polymer based OLED light sources with an active area of 0.16 cm² on glass substrate. The devices exhibit brightness of 100 cd/m² and 1000 cd/m² at 4.2 V and 5.4 V, respectively. Furthermore, a large area OLED of 30 cm² in which both polymer layers are gravure printed is demonstrated for lighting applications. Based on the results presented in this paper, the feasibility of the gravure printing technique for the fabrication of large area OLEDs in large-scale production is proved.     

AC field-induced polymer electroluminescence with single wall carbon nanotubes

We developed a high-performance field-induced polymer electroluminescence (FPEL) device consisting of four stacked layers: a top metal electrode/thin solution-processed nanocomposite film of single wall carbon nanotubes (SWNTs) and a fluorescent polymer/insulator/transparent bottom electrode working under an alternating current (AC) electric field. A small amount of SWNTs that were highly dispersed in the fluorescent polymer matrix by a conjugate block copolymer dispersant significantly enhanced EL, and we were able to realize an SWNT-FPEL device with a light emission of approximately 350 cd/m(2) at an applied voltage of ±25 V and an AC frequency of 300 kHz. The brightness of the SWNT-FPEL device is much greater than those of other AC-based organic or even inorganic ELs that generally require at least a few hundred volts. Light is emitted from our SWNT-FPEL device because of the sequential injection of field-induced holes and then electron carriers through ambipolar carbon nanotubes under an AC field, followed by exciton formation in the conjugated organic layer. Field-induced bipolar charge injection provides great material design freedom for our devices; the energy level does not have to be aligned between the electrode and the emission layer, and the balance of the carrier injected and transported can be altered in contrast to that in conventional organic light-emitting diodes, leading to an extremely cost-effective and unified device architecture that is applicable to all red-green-blue fluorescent polymers.     

Pyridine substituted spirofluorene derivative as an electron transport material for high efficiency in blue organic light-emitting diodes

The quantum efficiency of blue fluorescent organic light-emitting diodes was enhanced by 20% using a pyridine substituted spirofluorene-benzofluorene derivative as an electron transport material. 2′,7′-Di(pyridin-3-yl)spiro[benzofluorene-7,9′-fluorene] (SPBP) was synthesized and it was used as the electron transport material to block the hole leakage from the emitting layer. The improvement of the quantum efficiency and power efficiency of the blue fluorescent organic light-emitting diodes using the SPBP was investigated.     

喷墨印刷技术研究现状与发展对策

目的通过研究印刷技术的原理、产生和发展,为喷墨印刷技术的应用开拓研究思路。方法通过研究喷墨印刷技术原理和国内外研究现状,分析我国现有喷墨印刷技术发展中存在的问题,总结该项技术在研究应用中关键技术问题,并提出未来研究的主要发展方向和对策。结论现阶段研究应主要着力于以下5个方面,喷墨印刷系统本体研究,尤其是集成数字化喷墨复合设备的研发;加大突破喷头研发攻关,研发出适用性好且有独立知识产权的高速、低成本喷头;在提高墨滴喷射精度的同时,提升控制系统的集成度和适用性;针对不同油墨,积极研发适用性强的智能供墨系统,实时为喷头腔体提供理想墨流环境;加强和培养复合型人才。     

High external quantum efficiency in deep blue phosphorescent organic light emitting diodes using a simple device structure

Simple high efficiency deep blue phosphorescent organic light-emitting diodes were developed using a mixed host of high triplet energy host materials. A hole transport type host was used both as the hole transport layer and host in the mixed host emitting layer and an electron transport type host was mixed with the hole transport type host in the emitting layer. A three organic layer device structure of the hole transport layer/emitting layer/electron transport layer gave high external quantum efficiency of 26.4% with a color coordinate of (0.14, 0.19).     

Characteristics of organic light emitting diodes with copper iodide as injection layer

We have studied the use of a thin copper iodide (CuI) film as an efficient injection layer of holes from indium tin oxide (ITO) anode in a light-emitting diode structure based on tris-8-hydroxyquinoline aluminium (Alq3). The results of impedance analysis of two types of diode structures, ITO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al and ITO/Alq3/poly(ethylene glycol) dimethyl ether/Al, are presented. Comparative analysis of their current density-voltage, luminance-voltage and impedance characteristics shows that presence of CuI layer facilitates injection of holes from ITO anode into the light-emitting layer Alq3 and increases electroluminescence efficiency of the organic light emitting diodes.     

Inkjet Printing in Liquid Environments

Inkjet printing (IJP) is an old but still vivifying technique for flexible and cost‐effective printing of various kinds of functional inks. Normally, IJP can only work in gaseous environments. Here, it is shown that traditional piezoelectric IJP can be performed in liquid environments with a totally different droplet dispensing and manipulating mechanism. With the same piezoelectric nozzle, the volume of the droplets printed in a carrier liquid can be thousands of times smaller than those printed in air. Therefore, this work demonstrates a working mode of traditional IJP with a highly improved resolution opening possibilities for novel applications of the IJP technique.     

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。     

3D Printed Polymer Photodetectors

Extrusion‐based 3D printing, an emerging technology, has been previously used in the comprehensive fabrication of light‐emitting diodes using various functional inks, without cleanrooms or conventional microfabrication techniques. Here, polymer‐based photodetectors exhibiting high performance are fully 3D printed and thoroughly characterized. A semiconducting polymer ink is printed and optimized for the active layer of the photodetector, achieving an external quantum efficiency of 25.3%, which is comparable to that of microfabricated counterparts and yet created solely via a one‐pot custom built 3D‐printing tool housed under ambient conditions. The devices are integrated into image sensing arrays with high sensitivity and wide field of view, by 3D printing interconnected photodetectors directly on flexible substrates and hemispherical surfaces. This approach is further extended to create integrated multifunctional devices consisting of optically coupled photodetectors and light‐emitting diodes, demonstrating for the first time the multifunctional integration of multiple semiconducting device types which are fully 3D printed on a single platform. The 3D‐printed optoelectronic devices are made without conventional microfabrication facilities, allowing for flexibility in the design and manufacturing of next‐generation wearable and 3D‐structured optoelectronics, and validating the potential of 3D printing to achieve high‐performance integrated active electronic materials and devices.     

喷墨打印基材表面纳米涂层的研究进展

目的综述了目前喷墨打印基材表面纳米涂层的研究成果和发展趋势。方法基于对近年国内外关于表面纳米涂层的研究成果,介绍喷墨打印表面纳米涂层的组成、固化机理及其物化性能和光学性能,进一步对喷墨打印涂层的发展趋势及挑战进行总结与分析。结果表面纳米涂层能够改变材料及其制件表面的物理结构和化学组成。在喷墨打印过程中,喷墨打印基材表面纳米涂层质量直接影响印品的质量,文中通过对喷墨打印纳米涂层的性能、研究现状、发展趋势及挑战等方面的论述,为未来的喷墨打印纳米涂层相关研究和应用提出了建议。结论喷墨打印技术作为数字成像技术的典型代表,可实现印刷品的种类多样化、个性化,想要得到复制完美的制品,需优化基材表面的化学组成或物理结构,而表面涂层技术能够改变材料及其制件表面成分和组织结构,所以对喷墨打印基材表面纳米涂层的研究至关重要。     

OLED manufacturing for large area lighting applications

We present first results of a new developed large area manufacturing system for organic light-emitting diodes (OLED) dedicated to lighting and signage applications. The system combines high throughput with flexibility in production at highly-precise deposition conditions. After introducing the system with its modules, first results for organic and metal layer deposition properties are shown. Next orange/red p-i-n type OLED samples are prepared on large ITO substrates and the characterization by luminance and current measurements are presented. The devices achieve very high efficiencies up to 31 cd/A on large area substrates which are comparable to devices on smaller substrates.     

基于喷墨印刷的OTFT的制备与性能研究

介绍了喷墨印刷技术和OTFT的结构,通过建立几个模型,分别模拟了喷墨印刷过程中聚合物油墨的粘度和喷墨印刷过程中的瞬间油墨液滴的状态,以及印制成型后OTFT基本的性能.通过模型模拟来展示在用喷墨的方法来印制OTFT的过程中需要注意的问题,并且作出了对印制好的OTFT的性能的测定指标.