High-performance graphene-based transparent flexible heaters

We demonstrate high-performance, flexible, transparent heaters based on large-scale graphene films synthesized by chemical vapor deposition on Cu foils. After multiple transfers and chemical doping processes, the graphene films show sheet resistance as low as ～43 Ohm/sq with ～89% optical transmittance, which are ideal as low-voltage transparent heaters. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional transparent heaters based on indium tin oxide. In addition, we confirmed that mechanical strain as high as ～4% did not substantially affect heater performance. Therefore, graphene-based, flexible, transparent heaters are expected to find uses in a broad range of applications, including automobile defogging/deicing systems and heatable smart windows.     

Fabrication of high-quality silver nanowire conductive film and its application for transparent film heaters

Here,we report a facile method to produce pure silver nanowires (AgNWs) with high yield.A highly conductive dispersant was used to ensure uniform dispersion of the AgNWs.Without any posttreatment,the AgNW networks,deposited on flexible substrates,showed excellent optoelectrical performance owing to minimal junction resistance between the AgNWs.To explore their potential in flexible optoelectronic devices,a transparent film heater was constructed based on the present AgNW networks.The heater could achieve rapid response at low input voltage and reach a relatively high temperature in a short response time.Since this high-quality AgNW film exhibits relatively low production costs and fast production time,it may have value for future electronic industry applications.     

Flexible and transparent electrothermal film heaters based on graphene materials

High-performance and novel graphene-based electrothermal films are fabricated through a simple yet versatile solution process. Their electrothermal performances are studied in terms of applied voltage, heating rate, and input power density. The electrothermal films annealed at high temperature show high transmittance and display good heating performance. For example, the graphene-based film annealed at 800 °C, which shows transmittance of over 80% at 550 nm, can reach a saturated temperature of up to 42 °C when 60 V is applied for 2 min. Graphene-based films annealed at 900 and 1000 °C can exhibit high steady-state temperatures of 150 and 206 °C under an applied voltage of 60 V with a maximum heating rate of over 7 °C s(-1) . For flexible heating films patterned on polyimide, a steady-state temperature of 72 °C could be reached in less than 10 s with a maximum heating rate exceeding 16 °C s(-1) at 60 V. These excellent results, combined with the high chemical stability and mechanical flexibility of graphene, indicate that graphene-based electrothermal elements hold great promise for many practical applications, such as defrosting and antifogging devices.     

Highly flexible and transparent conducting silver nanowire/ZnO composite film for organic solar cells

High efficiency and flexible inverted organic solar cells have been fabricated using solution-processed silver nanowire/zinc oxide composite transparent electrodes. The transparent electrodes showed a low sheet resistance of -13 ff）.sq-1 and high transmittance of -93% as well as superior mechanical flexibility. Power conversion efficiencies of -7.57% and -7.21% were achieved for devices fabricated on glass and plastic substrate, respectively. Moreover, the flexible devices did not show any degradation in their performance even after being folded with a radius of-480 μm.     

Ink-jet printed transparent and flexible electrodes based on silver nanoparticles

In recent, silver (Ag) nanowires (NWs) have received much attention as an alternative to indium tin oxide (ITO) for transparent electrode application in printed and transparent electronics. However, Ag NWs have its breakup problem by joule heating during current. To overcome this problem, this paper demonstrates a mesh type electrode based on Ag nanoparticles, which is fabricated on PET substrate through an ink-jet printing technique. The proposed electrode has a low resistance of 108.5 Ω/sq and a good optical transparency around 92% at 300–800 nm. It has a relationship that the sheet resistance drops with the decrease of transparency due to depending hole size and the best curing temperature is found to be 120 °C. It also demonstrate an excellent flexible stability, showing <?2% resistance change after over 100 bending cycles. These resistance and transparency are similar with that of commercially ITO electrode, and are superior to other alternatives such as carbon nanotube electrodes. The proposed electrode can be considered as a commercial electrode to as an alternative to ITO electrode.     

Highly conductive supercapacitor based on laser-induced graphene and silver nanowires

One of the foremost necessary desires of energy systems has been the existence of efficient, flexible, transportable, and eco-friendly devices. Among all the energy storage systems, supercapacitors have attracted plenty of attention thanks to their distinctive properties. Among all capacitor technologies, laser-induced graphene (LIG)-based capacitors are within the spotlight nowadays due to their high flexibility and simple manufacture. The most downside with LIG-based capacitors is their low conductivity and low charge capacity. During this work, to overcome this problem, the surface of LIG is covered with silver nanowires (AgNWs) and LIG/AgNWs composite is employed to form supercapacitor. In this study, all the electrochemical properties of the prepared composite were investigated, and therefore the results showed that AgNWs could increase the electrical conductivity of LIG by about 2.25 times, improve electrode–electrolyte interaction, and increase areal capacitance by 1.3 times. Additionally, the synthesized supercapacitor shows stable cyclic behavior and retention capacity equal to 78% after 1000 charge–discharge cycles. A singular increase in LIG conductivity and improved in its cyclic performance. Furthermore, galvanostatic charge/discharge curves indicated acceptable charge capacity of the LIG/AgNWs supercapacitor.

     

高拉曼散射信号增强衬底材料:银分形网络

基于扩散限制聚集过程机制合成的大型银分形网络被用作表面增强拉曼散射活性衬底材料.此衬底材料具有很好的拉曼增强特性以及很宽的动态响应范围.其较大的增强因子可归结为高度局域化的等离激元共振.     

Spray deposition of highly transparent, low-resistance networks of silver nanowires over large areas

A method to produce scalable, low-resistance, high-transparency, percolating networks of silver nanowires by spray coating is presented. By optimizing the spraying parameters, networks with a sheet resistance of R(s) ≈ 50 Ω □(-1) at a transparency of T = 90% can be produced. The critical processing parameter is shown to be the spraying pressure. Optimizing the pressure reduces the droplet size resulting in more uniform networks. High uniformity leads to a low percolation exponent, which is essential for low-resistance, high-transparency films.     

Highly transparent polymer substrates for flexible displays using semi-interconnected interpenetrating polymer networks

Semi-interconnected interpenetrating polymer networks (SIPNs) based on unsaturated polyurethane (UP) and different monomers, including styrene and acrylate with an UP ratio of 50 wt%, were synthesized. The resulting SIPN films exhibited excellent optical transparency in the visible range with > 90% transmittance at 400 nm. The glass transition temperature (Tg) varied in the range of 100 approximately 135 degrees C depending on the unsaturated monomers introduced. They also had good flexibility compared to the conventional rigid polystyrene or polyacrylate due to the homogeneously dispersed elastic urethane moiety in the SIPNs. Below the glass transition temperature (Tg) of the SIPN substrates, the ITO-grown SIPN films exhibited good electrical and optical properties, showing potential as a promising substrate in flexible display applications.     

基于真空辅助层层自组装的透明柔性纳米芳纶薄膜的制备

通过二甲基亚砜（DMSO）-KOH体系溶解宏观芳纶纤维（AF）成功制备了直径为40~50 nm、长度为2~5 μm的纳米芳纶纤维（NAF）,并利用SEM、TEM、FTIR、Raman和XRD对NAF和AF的微观形貌、化学结构、结晶结构进行了分析。结果表明,NAF与AF具有相似的化学结构,同时NAF保留了AF大部分的结晶结构,只是纤维尺寸有一定的差异。通过真空辅助层层自组装法制备了具有层状致密结构的NAF复合薄膜,该薄膜展现出很好的透明、柔性、耐温性和力学性能,具有一定的亲液性能（接触角为81.5°）及优异的抗液体渗透和抗液体吸收性能。      

Highly conductive, transparent flexible films based on open rings of multi-walled carbon nanotubes

Open rings of multi-walled carbon nanotubes were stacked to form porous networks on a poly(ethylene terephthalate) substrate to form a flexible conducting film (MWCNT-PET) with good electrical conductivity and transparency by a combination of ultrasonic atomization and spin-coating technique. To enhance the electric flexibility, we spin-coated a cast film of poly(vinyl alcohol) onto the MWCNT-PET substrate, which then underwent a thermo-compression process. Field-emission scanning electron microscopy of the cross-sectional morphology illustrates that the film has a robust network with a thickness of ~ 175 nm, and it remarkably exhibits a sheet resistance of approximately 370 Ω/sq with ~ 77% transmittance at 550 nm even after 500 bending cycles. This electrical conductivity is much superior to that of other MWCNT-based transparent flexible films.     

Highly transparent oxide-based ultraviolet photodetectors for flexible electronics

Journal of Materials Science: Materials in Electronics - Flexible ultraviolet (UV) photodetectors have attracted great interests for applications in portable and wearable optoelectronic systems. In...     

Synthesis of oxidation-resistant cupronickel nanowires for transparent conducting nanowire networks

Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.     

Highly conductive interwoven carbon nanotube and silver nanowire transparent electrodes

Abstract

Electrodes fabricated using commercially available silver nanowires (AgNWs) and single walled carbon nanotubes (SWCNTs) produced sheet resistances in the range 4–24 Ω □^?1 with specular transparencies up to 82 %. Increasing the aqueous dispersibility of SWCNTs decreased the bundle size present in the film resulting in improved SWCNT surface dispersion in the films without compromising transparency or sheet resistance. In addition to providing conduction pathways between the AgNW network, the SWCNTs also provide structural support, creating stable self-supporting films. Entanglement of the AgNWs and SWCNTs was demonstrated to occur in solution prior to deposition by monitoring the transverse plasmon resonance mode of the AgNWs during processing. The interwoven AgNW/SWCNT structures show potential for use in optoelectronic applications as transparent electrodes and as an ITO replacement.     

柔性碳纳米管透明导电薄膜国内外研究进展

综述了碳纳米管透明导电薄膜(CNTs-TCF)的主要制备方法以及存在的优缺点,介绍了碳纳米管(CNTs)的制备、金属性/半导体性、纯度与石墨化以及均匀分散CNTs溶液制备过程对CNTs-TCF电学性能产生的影响及相应的改进方法。最后简单介绍了CNTs-TCF在平板显示器、太阳能电池和触控面板上的应用情况,并对CNTs-TCF下一步研究进行了展望。     

Fabrication of high optical transparent and conductive SWNT based transparent conducting film on flexible plastic substrate using ozone as a redox dopant

In the present work, single-wall carbon nanotubes-transparent conducting films (SWNTs-TCFs) were fabricated at room temperature on a flexible polycarbonate substrate using the ultrosonication-dip-coating technique. Ozone was employed to reduce the sheet resistance of conductive film. As a result, the sheet resistance of film was decreased drastically after 1.5 hr ozone (O3) treatment and could reach up to 170 omega/square at 80% T at 550 nm wavelength. In addition, aminopropyltriethoxysilane (APTS) was further applied as an adhesion promoter in order to enhance the adhesion between the SWNTs films and the substrate. Experimental results show that ATPS can greatly improve the adhesion of SWNTs coating to the substrate without the loss of conductivity.     

Fully transparent thin-film transistor devices based on SnO2 nanowires

We report on studies of field-effect transistor (FET) and transparent thin-film transistor (TFT) devices based on lightly Ta-doped SnO2 nano-wires. The nanowire-based devices exhibit uniform characteristics with average field-effect mobilities exceeding 100 cm2/V x s. Prototype nano-wire-based TFT (NW-TFT) devices on glass substrates showed excellent optical transparency and transistor performance in terms of transconductance, bias voltage range, and on/off ratio. High on-currents and field-effect mobilities were obtained from the NW-TFT devices even at low nanowire coverage. The SnO2 nanowire-based TFT approach offers a number of desirable properties such as low growth cost, high electron mobility, and optical transparency and low operation voltage, and may lead to large-scale applications of transparent electronics on diverse substrates.     

Highly flexible silver nanowire electrodes for shape-memory polymer light-emitting diodes

Shape-memory polymer light-emitting diodes (PLEDs) using a new silver nanowire/polymer electrode are reported. The electrode can be stretched by up to 16% with only a small increase in sheet resistance. Large deformation shape change and recovery of the PLEDs to various bistable curvatures result in minimal loss of electroluminescence performance.     

Novel transparent and flexible nanocomposite film prepared from chrysotile nanofibres

In the present study, chrysotile nanofibres, obtained from physicochemical dispersion of natural chrysotile, were used to prepare nanofibre sheets by vacuum filtration. As-prepared sheets were then impregnated by UV-curable resin and cured by ultraviolet light to fabricate the flexible and transparent nanocomposite films. Observed from SEM, the transparent films showed a smooth surface and a typical sandwich structure in cross section, viz. nanofibre sheet filled with resin was sandwiched by two layers of resin. XRD patterns indicated the amorphous nature of cured resin and characteristic crystallographic structure of chrysotile in nanocomposite films. Though the nanofibre sheets were white in colour, and nanofibre contents in nanocomposites were as much as 43.4 wt%, the nanocomposite films displayed an excellent optical transparency with about 85% light transmittance in the visible light range. Tensile tests showed that the addition of nanofibres resulted in a great improvement in mechanical strength of the nanocomposite films; with the increase of nanofibre contents, the modulus and tensile strength of nanocomposite films increased gradually.