Highly transparent and flexible field electron emitters based on hybrid carbon nanostructure

We demonstrate a unique strategy to fabricate highly transparent and flexible field electron emitters (FEEs) based on combined carbon nanostructures, i.e., conical nanocarbon structures (CNCSs) and single‐walled carbon nanotubes (SWNTs). The combined structure was prepared by spray coating of 1,2‐dichloroethane (DCE) dispersed SWNTs onto neon ion (Ne⁺) irradiation induced CNCSs on nafion substrate. The field emission (FE) property of SWCNTs on both flat nafion and CNCSs surfaces increased with increasing the SWCNTs amount. The best FE result was attained for the highest amount of SWCNTs on the CNCSs substrate. This kind of collective structures is found to be effective emitters on transparent and flexible ion‐irradiated nafion substrate. Moreover, the combined carbon nanostructures showed improved transparency and emission performance compared to the individual nanostructures. The FE properties of 0.5 ml SWCNTs solution on CNCSs surfaces were equal to those of 1.5 ml SWCNTs solution on flat nafion surface. The hybrid structure based emitters (CNCSs and SWCNTs) produced by this method are lower‐cost cathode materials than hybrid structures of SWCNTs and flat nafion. Thus the combined nanostructures of SWCNTs/CNCSs might have huge prospects for the fabrication of efficient transparent and flexible FEEs and their broad application in next‐generation portable display devices. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fabrication of transparent and flexible carbon‐doped ZnO field emission display on plastic substrate

Transparent and flexible carbon doped ZnO (C:ZnO) field emission device was successfully fabricated on an arylite substrate. Excellent adhesion of deposited C:ZnO on the flexible substrate was achieved with low sputtering power and Ar flow rate. In the fabricated device, nanostructured C:ZnO and as‐deposited thin films were used as field emitter and phosphor screen, respectively. The C:ZnO thin film showed a transparency of about 80% at 550 nm wavelength and average sheet resistance of 1.96 kΩ/□. The C:ZnO phosphor screen emitted red light during the field emission measurement, correlating the dominant cathodoluminescence peak at 646 nm. Thus, a promising transparent and flexible field emission display can be realized with C:ZnO based material.

Transparent and flexible C:ZnO film phosphor screen (anode) and nanocone emitters (cathode) for field emission device.     

Conducting polymer based hybrid structure as transparent and flexible field electron emitter

An efficient cathode material with high transparency (93%) based on conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and single wall carbon nanotubes (SWCNTs) has been developed for the fabrication of highly transparent and flexible field electron emitters (FEE). This kind of material showed superior field emission (FE) performance with very high current density (10^–3A/cm²) at very low electric field. The FE performance of the hybrid materials was dramatically improved compared to either SWCNTs and PEDOT:PSS. Thus the hybrid structures of conducting polymer and SWCNTs might be a good choice for use as a cathode material to enhance the FE performance and for potential application in future portable displays. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controllable fabrication and characterization of conical nanocarbon structures on polymer substrate for transparent and flexible field emission displays

The direct fabrication of fully transparent conical nanocarbon structures (CNCSs) of controlled nanoscopic dimension on a flexible nafion substrate was achieved, using field electron source, by a novel room temperature ion irradiation technique. By controlling the sizes (below the wavelength of visible light) of the CNCSs, the transparency of the substrate can be tailored satisfactorily. The transparency of the CNCSs was observed to be around 90% in the visible regime depending on the ion irradiation time. Our results suggest that the direct fabrication of well controlled fully transparent CNCSs on any transparent and flexible substrate at room temperature could open a novel route for potential applications in future highly transparent, flexible (bendable), low weight and portable field emission displays (FEDs). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

LED柔性照明及显示用超弹性柔性荧光膜

柔性LED是近年来照明及显示领域研究的热点之一.本文提出了一种新的基于有机硅胶(PDMS)制备的兼具超弹性和柔性的荧光薄膜,它不仅在-50~230℃这一较宽的温度范围内展现了良好的热稳定性,还保持了原料荧光粉的光学性能.所制备的透明PDMS基质膜和相应的荧光膜具有完全的柔性和超弹性,其最大伸长率分别高达400%与275%.此外,采用所制掺YAG荧光膜和普通商用1 W蓝光芯片简单封装的白光LED灯珠满足日常白光照明的应用要求,呈现出约6925 K的平均色温,约71的平均显色指数,115.7 lm/W左右的平均发光效率.最后,基于所提出荧光膜成膜工艺而制备的三色3×3柔性阵列显示,可以轻易被拉伸、卷曲和折叠,显示了它在柔性照明及显示器件方面具有应用价值和潜力.     

基于微结构银纳米线的透明电子皮肤器件

Transparent, flexible electronic skin holds a wide range of applications in robotics, humanmachine interfaces, artificial intelligence, prosthetics, and health monitoring. Silver nanowire are mechanically flexible and robust, which exhibit great potential in transparent and electricconducting thin film. Herein, we report on a silver-nanowire spray-coating and electrodemicrostructure replicating strategy to construct a transparent, flexible, and sensitive electronic skin device. The electronic skin device shows highly sensitive piezo-capacitance response to pressure. It is found that micropatterning the surface of dielectric layer polyurethane elastomer by replicating from microstructures of natural-existing surfaces such as lotus leaf, silk, and frosted glass can greatly enhance the piezo-capacitance performance of the device. The microstructured pressure sensors based on silver nanowire exhibit good transparency, excellent flexibility, wide pressure detection range (0-150 kPa), and high sensitivity (1.28 kPa^-1).     

Deposition of ITO Nanopowder Layers on Flexible Substrate by Spin Coating Using Pulsed Nd-YAG Laser for Crystallization and Bonding

A transparent thin layer of indium–tin oxide (ITO) is coated on polyethylene terephthalate (PET) by a spin coating process. The surface is treated by a pulsed Nd-YAG laser. We investigate the effect of laser treatment on crystallization and bonding processes of the thin layer using atomic force microscope (AFM) and scanning electron microscope (SEM). The best results are obtained when the pulse frequency, duration, and energy were 1000 Hz, 0.2 to 20 ms, and 25 to 40 J, respectively. The results show that the ITO layer coated on a flexible PET substrate is conductive and transparent. The sheet resistance obtained is 0.6 kΩ, and the transparency of a 350-nm layer in the visible range is more than 83.6%. Using the Nd-YAG laser treatment, we increase the conductivity by a factor of 100 times, and higher bonding performances are achieved.     

Alternative transparent conducting electrode materials for flexible optoelectronic devices

Transparent Conductive Electrode (TCE) is an essential part of the optoelectronic and display devices such as Liquid Crystal Displays (LCDs), Solar Cells, Light Emitting Diodes (LEDs), Organic Light Emitting Diodes (OLEDs) and touch screens. Indium Tin Oxide (ITO) is a commonly used TCE in these devices because of its high transparency and low sheet resistance. However, scarcity of indium and brittle nature of ITO limit its use in future flexible electronics. In order to develop flexible optoelectronic devices with improved performance, there is a requirement of replacing the ITO with a better alternate TCE. In this work, several alternative TCEs including transparent conductive oxides, carbon nanotubes, conducting polymers, metal nanowires, graphene and composites of these materials are studied with their properties such as sheet resistance, transparency and flexibility. The advantage and current challenges of these materials are also presented in this work.     

Silver‐Based Nanoparticles for Surface Plasmon Resonance in Organic Optoelectronics

Organic optoelectronic devices including organic light‐emitting diodes (OLEDs) and polymer solar cells (PSCs) have many advantages, including low‐cost, mechanical flexibility, and amenability to large‐area fabrication based on printing techniques, and have therefore attracted attention as next‐generation flexible optoelectronic devices. Although almost 100% internal quantum efficiency of OLEDs has been achieved by using phosphorescent emitters and optimizing device structures, the external quantum efficiency (EQE) of OLEDs is still limited due to poor light extraction. Also, although intensive efforts to develop new conjugated polymers and device architectures have improved power conversion efficiency (PCE) up to 8%–9%, device efficiency must be improved to >10% for commercialization of PSCs. The surface plasmon resonance (SPR) effect of metal nanoparticles (NPs) can be an effective way to improve the extraction of light produced by decay of excitons in the emission layer and by absorption of incident light energy within the active layer. Silver (Ag) NPs are promising plasmonic materials due to a strong SPR peak and light‐scattering effect. In this review, different SPR properties of Ag NPs are introduced as a function of size, shape, and surrounding matrix, and review recent progress on application of the SPR effect of AgNPs to OLEDs and PSCs.     

PVDF-driven flexible and transparent loudspeaker

A flexible and transparent loudspeaker driven by piezoelectric polymer was proposed. The core structure was an assemblage of a flexible plastic film with piezoelectric polymer pasted over the whole surface. We fabricated a prototype loudspeaker using polyethersulfone (PES) and polyvinylidenefluoride (PVDF), and it had flexibility and transparency. Its acoustic characteristics and surface vibration mode were investigated. The investigation yielded low distortion characteristics in comparison with those of a loudspeaker made only of PVDF, and its advantages originated from the use of the plastic film as a diaphragm.     

Coupled Ag nanocrystal-based transparent mesh electrodes for transparent and flexible electro-magnetic interference shielding films

In this study, we developed a fabrication method of conductive and transparent Ag mesh electrodes on flexible polymer film at temperatures lower than 100?°C. Random patterned Ag mesh film was fabricated on a flexible PET substrate over 15?×?15?cm² by a self-assembly process. It became conductive by a coupling process at low temperatures. The coupled Ag mesh film showed more than 88% transmittance in visible wavelength and less than 8.2?Ω?sq^?1 in sheet resistance with figure of merit (FoM) value of 350. This transparent flexible EMI shield film fabricated with a coupled Ag mesh pattern showed high EM shielding effectiveness of ?23?dB?at 1.5–10?GHz frequency with a high transparency of 88%.     

Facile one‐step fabrication of highly transparent and flexible superhydrophobic substrate by room‐temperature ion irradiation method

Highly transparent (transparency 96.5%), flexible and antireflective superhydrophobic (water contact angle >150°) surfaces have been fabricated at room temperature by the ion irradiation method. This one‐step fabrication route was fairly easy to carry out without any heat or chemical treatment and can be completed within few seconds. This novel chemical free fabricating strategy could be extended to numerous polymeric substrates to achieve transparent and flexible superhydrophobic structures for their potential applications in diverse fields. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Position-controlled synthesis of single-walled carbon nanotubes on a transparent substrate by laser-induced chemical vapor deposition

The synthesis of single-walled carbon nanotubes (SWCNTs) on a transparent substrate with multiple-catalyst layer (Fe/Al/Cr: 0.5/15/500 nm) using laser-induced chemical vapor deposition is reported. Ethylene (C₂H₄) mixed with hydrogen (H₂) and a continuous wave Nd:YVO₄ laser (532 nm) were used as the precursor gas and the irradiation source, respectively. It was found that the density and quality of the SWCNT dots varied sensitively to laser irradiance and chamber pressure. From subsequent micro-Raman analyses at different excitation sources (488, 514, 633, and 785 nm), the diameters of the SWCNTs were estimated to be within the range of 0.8-2 nm and that the SWCNT dots were composed of both semiconducting and metallic SWCNTs. It is demonstrated that an array of SWCNT dots can be fabricated at precisely controlled positions of a transparent substrate at room temperature with no need of catalysis patterning.     

A new‐generation color converter for high‐power white LED: transparent Ce3+:YAG phosphor‐in‐glass

Currently, the major commercial white light‐emitting diode (WLED) is the phosphor‐converted LED made of the InGaN blue‐emitting chip and the Ce³⁺:Y₃Al₅O₁₂ (Ce:YAG) yellow phosphor dispersed in organic epoxy resin or silicone. However, the organic binder in high‐power WLED may age easily and turn yellow due to the accumulated heat emitted from the chip, which adversely affects the WLED properties such as luminous efficacy and color coordination, and therefore reduces its long‐term reliability as well as lifetime. Herein, an innovative luminescent material: transparent Ce:YAG phosphor‐in‐glass (PiG) inorganic color converter, is developed to replace the conventional resin/silicone‐based phosphor converter for the construction of high‐power WLED. The PiG‐based WLED exhibits not only excellent heat‐resistance and humidity‐resistance characteristics, but also superior optical performances with a luminous efficacy of 124 lm/W, a correlated color temperature of 6674 K and a color rendering index of 70. This easy fabrication, low‐cost and long‐lifetime WLED is expected to be a new‐generation indoor/outdoor high‐power lighting source.     

基于低维相变薄膜的显示器件光学性质的研究

采用传输矩阵模型研究了基于低维相变薄膜的显示器件的光学特性与器件结构的关系。显示器件的类型有反射型和透射型,器件结构的关键参数包括Ge_2Sb_2Te_5(GST)层的厚度、ITO层的厚度、GST层的晶态与非晶态的变化。结果表明:对于反射型器件,ITO层的厚度对器件的反射光谱影响较大,可以通过改变ITO层的厚度达到改变器件颜色的效果;GST层的厚度为12 nm时,GST的晶态与非晶态的变化使器件有最好的颜色对比度且消耗较低的电功率。对于透射型器件,通过使用超薄的GST薄膜,器件的透明度可以保持很高,器件的透明度在GST的厚度超过几纳米后迅速下降。     

生长温度对碳纳米管阴极场发射性能的影响

碳纳米管(Carbon Nanotubes,CNTs)场发射平面显示器(Field Emission Display,FED)与其他显示器比较显示了其独特优点,被认为是未来理想的平面显示器之一。碳纳米管阴极作为器件的核心部分,其性能的好坏直接影响显示器的性能。针对30~60英寸(76.2~152.4cm)大屏幕显示器所用的厚膜工艺,即采用丝网印刷法制备了碳纳米管阴极阵列,研究了化学气相沉积法在不同温度下生长的CNTs的场发射电流-电压特性,找到了适合FED用碳纳米管的最佳生长温度。结果表明生长温度越高(750℃),CNTs场发射性能越好。并用荧光粉阳极测试这些CNTs的场发射发光显示效果,验证了上述结论。     

Transparent,flexible and low‐resistive precision fabric electrode for organic solar cells

We report the use of conducting precision fabrics as transparent and flexible electrode for organic semiconductor‐based thin film devices. Precision fabrics have well‐defined mesh openings, excellent flexibility and are fabricated by high‐throughput roll‐to‐roll manufacturing. Optimized fabrics reached light transmittance over 95% throughout the visible and near infrared spectra. A significant part of the transmitted light is scattered, which is particularly advantageous for solar cell applications. Surface resistivity is as low as ～3 Ohms/square, which decreases Ohmic losses when scaling up to large area devices. We demonstrate that solar cells fabricated onto these electrodes show very similar characteristics to those prepared on ITO. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于CsPbBr3钙钛矿量子点的高柔性绿光发光二极管

众所周知,柔性信息显示将在未来的光电应用中发挥重要作用。然而,由于电极材料和柔性衬底的选择有限,制备高效、稳定的柔性发光二极管仍然存在巨大的挑战。以光聚合物作为柔性衬底、CsPbBr3量子点作为发光层,成功地制备了柔性钙钛矿发光二极管。为了改善电子的注入和传输,采用Ag作阴极。结果表明,高柔性的钙钛矿发光二极管的最高亮度为10325 cd/m2且具有高色纯度(FWHM=19 nm)。此外,制备的钙钛矿发光二极管具有良好的柔性和机械延展性。在大约180°的弯曲角度下反复弯曲100次后,仍然保持着良好的器件性能。该研究为未来柔性显示器的应用奠定了研究基础。     

An alternative flexible electrode for dye-sensitized solar cells

With comparable transparency, flexibility, but a better conductivity, metal-mesh based PEN film provides an alternative low-cost electrode material to the conventional ITO/PEN film for flexible solar cell system. In this article, counter electrodes (CEs) prepared by coating metal-mesh/PEN with a mixture of PEDOT:PSS and carbon black nanoparticle (200?C400?nm) were utilized in flexible dye-sensitized solar cells (DSCs). A high efficiency of 5.5?% was achieved with the DSC based on the metal-mesh/PEN CE, rivaling that of the DSC based on ITO/PEN CE.     

高效透明导电膜荧光屏的研究

介绍了一种新型荧光屏结构,采用透明导电膜代替传统荧光屏中的铝膜作电极.分别测试了新型荧光屏和传统荧光屏的加电特性.实验结果表明新型荧光屏具有较高的耐压性能,对提高X射线变像管的空间分辨率有重要作用,而且能延长变像管的寿命.采用透明导电膜制作荧光屏还具有工艺简单,成本低和成品率高的优点.