AgNW Film Research Articles

Flexible silver nanowire transparent conductive films prepared by an electrostatic adsorption self-assembly process

In this work, we reported a facile approach to fabricate silver nanowire (AgNW) networks on flexible substrates. Through immersing the modified poly (ethylene terephthalate) with positively charged functional group into the AgNW dispersion with anionic dispersant, a flexible AgNW transparent conductive film was formed by electrostatic adsorption self-assembly process. Even without a post-treatment process, the as-prepared flexible AgNW films exhibited excellent optoelectrical property, low surface roughness and high reliability. It was shown that the insulating dispersant on AgNWs could be effectively removed by an ion bombardment method and then greatly decreased the sheet resistance of AgNW networks. Because of the nature of spontaneous adsorption, this preparation method can be suitable for an arbitrary shaped substrate, which will broaden the application of AgNW conductive films in optoelectronic devices.

Facile and Efficient Welding of Silver Nanowires Based on UVA‐Induced Nanoscale Photothermal Process for Roll‐to‐Roll Manufacturing of High‐Performance Transparent Conducting Films

AbstractThe continuous, large‐area solution‐processed production of silver nanowire (AgNW) transparent conducting films with outstanding optoelectronic and mechanical performance remains a challenge. Here, efficient welding of AgNWs is demonstrated using ultraviolet A (UVA) with the specific wavelength range from ≈320 to ≈400 nm based on a nanoscale photothermal process. The AgNW welding shows a self‐terminating and self‐limiting nature, and sensitivity to diameter of AgNWs. Sheet resistance of the UVA‐illuminated (UVAI) AgNW films rapidly drops within 2 min without loss of transmittance. For the UVAI AgNW (30 nm in diameter) film, decrement of sheet resistance approaches three orders of magnitude (≈105–102 Ohm sq−1) with original transmittance being (97%) retained, which significantly enhances its optoelectronic properties. Enhanced mechanical flexibility, electromagnetic interference (EMI) shielding effectiveness (SE), and heating performance are obtained in the UVAI AgNW films. The SE and plateau temperature of the AgNW film increase to 25 dB and 50 °C after illumination, respectively. Smart window, transparent heater, and triboelectric nanogenerator based on the UVAI AgNW film demonstrate its versatile applications in optoelectronics. Finally, the welding method is easily integrated into a roll‐to‐roll process to manufacture AgNW film with a low sheet resistance of 25 Ohm sq−1 and a high transmittance of 90%, and excellent flexibility.

Investigation on the Silver Nanowire/Graphene Transparent Electrode in Electrochromic Device

In this work, we fabricated a flexible silver nanowires (Ag NWs)/graphene transparent conducting film on polyethylene terephthalate (PET) substrate, which was applied in an electrochromic device. The graphene layer was coated on the surface of the Ag NW film utilizing the electrostatic adsorption in order to improve the stability of the metallic nanowire layer and the performance of the electrochromic device. The Ag NWs/graphene composite film exhibited an optical transmittance of 82.5% at 550 nm and a sheet resistance of 57.5 Ω/sq. With the concentration of the adsorbed graphene increased, the transmittance and conductivity of the composite film both decreased. Furthermore, the lifetime of the electrochromic devices based on the tungsten oxide (WO3) thin film and the Ag NW/graphene composite electrodes was greatly extended, compared to that utilizing the pristine Ag NW electrodes. The results indicate that the introduction of the graphene layer could protect the Ag NW film from corrosion of the electrolyte layer, and greatly improve the lifetime and cycle numbers of the electrochromic device. Key words: silver nanowire; graphene; transparent electrode; electrochromic devices

Comprehensive Stability Improvement of Silver Nanowire Networks via Self-Assembled Mercapto Inhibitors.

Instability of silver nanowire (AgNW) has been regarded as a major obstacle to its practical applications in optoelectrical devices as transparent electrodes. Physical barrier layers such as polymer, metal, and graphene have been generally employed to improve the stability of AgNW in previous study. Herein, we first report self-assembled organothiols as an inhibitor for AgNW to achieve an overall enhancement in antioxidation, antisulfidation, thermal stability, and anti-electromigration. The self-assembled monolayers (SAMs) of phenyl azoles, methoxy silane, and methyl alkane were formed on the surface of AgNW via Ag-S covalent bond as barrier layers which provided protective effects against corrosives (e.g., O2, H2S). In particular, the decoration of 2-mercaptobenzimidazole (MBI) offered the best resistance to H2S and excellent stability under a high-temperature and high-humidity environment (85 °C and 85 RH %) for 4 months. Moreover, different SAMs exhibited a stabilizing or destabilizing effect on Plateau-Rayleigh instability of AgNW, which realized the tunability of degradation temperature of AgNWs, for example, increasing by ≥100 °C with MBI SAM or decreasing by ∼50 °C with octadecanethiol SAM compared with pristine AgNWs. Notably, the MBI-decorated AgNWs could survive at 400 °C which is by far the highest bearing temperature for solution-processed AgNW film. As a result, a transparent heater made of the MBI-AgNWs exhibited superior heating characteristics (higher working temperature and durability), as compared with the pristine AgNW-based heater. Our findings on the organothiols decoration not only provide a new paradigm in overall stability improvement of NW of noble metals but also show the potential in morphology controllability of metal NW.

Fabrication of enhanced silver nanowire films via self-assembled gold nanoparticles without post-treatment

Transparent Silver nanowire (AgNW) electrodes have been widely explored in many applications as a promising alternative to relatively expensive indium tin oxide (ITO). For these applications, high contact resistance at the junctions of AgNWs is a main problem to be solved. In this letter, gold nanoparticles (AuNPs)-self-assembled method has been demonstrated to improve the optoelectronic performance of AgNW films. The sheet resistance of this novel AgNW film is measured as low as 13.2 Ω/sq, and the transmittance is high to 86.1%. Self-assembled AuNPs can enrich the percolation paths between AgNWs with negligible loss of optical properties, thereby realizing the excellent optoelectronic performance of AgNW films. Moreover, no extra post-treatment procedures are needed for the fabrication process. All these advantages indicate this method has great potentials for achieving high performance transparent electrodes in emerging optoelectronic devices.

Fabrication of Transparent Conductive Film with Flexible Silver Nanowires Using Roll‐to‐Roll Slot‐Die Coating and Calendering and Its Application to Resistive Touch Panel

AbstractA transparent conductive film incorporating silver nanowires (AgNW TCF) is fabricated through roll‐to‐roll (R2R) slot‐die coating and a subsequent calendering process and applied to a resistive touch panel. To produce a uniform AgNW film on a flexible polyethylene terephthalate substrate, the R2R slot‐die coating is optimized in terms of the solvent, concentration, and flow rate of the AgNW solution, and the length of the AgNWs synthesized using a polyol method. The coated AgNW TCF is calendered between two rolls to produce percolation paths in the film. During the calendering, the roll temperature, applied pressure, and web speed are optimized to yield a low sheet resistance of 28 Ω sq−1 with a transmittance of 86% at 550 nm. To demonstrate the functionality of the AgNW TCF, a coating of SiO2 microspheres is also applied to form a spacer layer, again using R2R slot‐die coating. A resistive touch panel is thus successfully implemented. The effect of the calendering process is confirmed by observing the operation of the touch panel, which is found to be more sensitive and accurate. The integrated manufacturing process for producing an AgNW TCF, presented herein, can be applied to many other major fields.

Investigation the scattering properties of silver nanowires with different densities

In this paper, the effect of spin-coating cycles with different densities on the light scattering properties of Ag nanowires (Ag NWs) transparent conductive films was investigated. The Ag NWs were characterized by scanning electron microscopy (SEM), and UV-Vis spectrophotometry. The results indicate that haze factor and the scattering in reflection and transmission directions increased with an increase in Ag NWs density. The resulting Ag NWs show cross point dropped down from ∼800 nm to ∼600 nm for spin coating 4–7 cycles. The ratio of back and forward scattering for Ag NWs exhibited a cross point that shifted to lower wavelengths with the increase in density. The controlling scattering properties of Ag NWs films may open a new avenue for Ag NWs application.

Coating-free, air-stable silver nanowires for high-performance transparent conductive film

Silver nanowire (Ag NW) based films are considered as a promising alternative for traditional indium tin oxide but still suffer from some limitations, including insufficient conductivity, transparency and environmental instability. We here report a novel etching synthesis strategy to improve the performance of Ag NW films. Different from the traditional methods to synthesize high aspect ratios of NWs or employ electrically conductive coatings, we find it effective to reduce the high-reactivity defects of NWs for optimizing the comprehensive performance of Ag NW films. In this strategy etching can suppress the generation of high-reactivity defects and meanwhile the etching growth of NWs can be accomplished in an uneven ligand distribution environment. The resulting Ag NWs are uniformly straight with a sharp-edged structure. The transparent conductive film obtained exhibits simultaneous improvements in electrical conductivity, transparency and air stability. Even after exposure in air for 200 days and no protective coatings, the film can still meet the highest requirement of practical applications, with a figure of merit 361 (i.e., FoM > 350). These results not only demonstrate the importance of defect control in the synthesis of Ag NWs, but also pave a way for further optimizing the performance of Ag NW-based films.

Selective Wavelength Plasmonic Flash Light Welding of Silver Nanowires for Transparent Electrodes with High Conductivity.

In this work, silver nanowires (AgNWs) printed on a polyethylene terephthalate substrate using a bar coater were welded via selective wavelength plasmonic flash light irradiation. To achieve high electrical conductivity and transparent characteristics, the wavelength of the flash white light was selectively chosen and irradiated by using high-pass, low-pass, and band-pass filters. The flash white light irradiation conditions such as on-time, off-time, and number of pulses were also optimized. The wavelength range (400-500 nm) corresponding to the plasmonic wavelength of the AgNW could efficiently weld the AgNW films and enhance its conductivity. To carry out in-depth study of the welding phenomena with respect to wavelength, a multiphysics COMSOL simulation was conducted. The welded AgNW films under selective plasmonic flash light welding conditions showed the lowest sheet resistance (51.275 Ω/sq) and noteworthy transmittance (95.3%). Finally, the AgNW film, which was welded by selective wavelength plasmonic flash light with optical filters, was successfully used to make a large area transparent heat film and dye-sensitized solar cells showing superior performances.

Solution processed silver-nanowire/zinc oxide based transparent conductive electrode for efficient photovoltaic performance

To replace expensive and scarce Indium Tin Oxide (ITO) as transparent conductive electrode (TCE) in solar cell fabrication, low-cost and solution processed metal nanowires can also be used as a TCE due to its higher conductivity and transparency. Despite of its higher conductivity and transparency, bare Silver nanowire (AgNW) film suffers due to its poor adhesion and smaller contact area with lower-lying n-type buffer layer. In this work, percolation network of AgNWs covered with scalable and solution processed ZnO film as transparent conductive electrode (TCE) is demonstrated and utilized for fabrication of CuInGaSe2 thin film solar cell. The concentration of the AgNWs in percolation network is optimized as areal mass density of AgNWs in the TCE. The conductive atomic force microscope studies are done to conclude the enhancement of current collection by covering the AgNW film with solution processed ZnO layer. The AgNW-based TCE with areal mass density of 242 mg/m2, sheet resistance 11 Ω/sq and transmittance 90% exhibited maximum conversion efficiency of 13.4% which is comparable to the efficiency obtained for vacuum based sputter deposited ITO or ZnO as TCE.

Flexible Transparent Conductive Film Based on Random Networks of Silver Nanowires.

We synthesized silver nanowires (AgNWs) with a mean diameter of about 120 nm and 20–70 μm in length using a polyol process. The flexible transparent conductive AgNWs films were prepared using the vacuum filtration-transferring process, in which random AgNWs networks were transferred to a polyethylene terephthalate (PET) substrate after being deposited on mixed cellulose esters (MCEs). Furthermore, the photoelectric and mechanical properties of the AgNWs films were studied. The scanning electron microscopy images show that the AgNWs randomly, uniformly distribute on the surface of the PET substrate, which indicates that the AgNWs structure was preserved well after the transfer process. The film with 81% transmittance at 550 nm and sheet resistance about 130 Ω·sq−1 can be obtained. It is sufficient to be used as a flexible transparent conductive film. However, the results of the bending test and tape test show that the adhesion of AgNWs and PET substrate is poor, because the sheet resistance of film increases during the bending test and tape test. The 0.06 W LED lamp with a series fixed on the surface of the AgNWs-PET electrode with conductive adhesive was luminous, and it was still luminous after bent.

SWCNT–Ag nanowire composite for transparent stretchable film heater with enhanced electrical stability

The mechanical stability of transparent and stretchable electrode materials is essential for their application in stretchable electronic devices. In this work, single-walled carbon nanotube (SWCNT)–silver nanowire (Ag NW) composite films were developed as electrode materials to improve the thermal stability and anti-electromigration characteristics of transparent stretchable film heaters. By adjusting the mixing ratio of SWCNT–Ag NW suspensions, the mechanical and anti-electromigration properties of SWCNT–Ag NW composite films were systematically investigated. Compared to pristine Ag NW film, the 75:1 SWCNT–Ag NW composite film exhibited an excellent thermal stability, improved anti-electromigration properties, and low sheet resistance of 62.3 Ω/sq with an optical transmittance of 83.4%. Moreover, the same composite film prepared on VHB substrate showed only 23.2% increase in the relative sheet resistance after 1000 times of stretching cycles under the tensile stress. Furthermore, the stretchable film heater with 75:1 SWCNT–Ag NW composite electrode exhibited an improved thermal and mechanical stability even after being exposed to 1000 stretching cycles with a peak strain of 200%.

Mixed polyols synthesis of high aspect ratio silver nanowires for transparent conductive films

Silver nanowires (AgNWs) with high aspect ratio were rapidly synthesized by a mixed polyols process by adding diethylene glycol, triethylene glycol and glycerol into the ethylene glycol to construct the mixed polyols respectively, and the effects of type and volume fraction of mixed polyols on the morphology and aspect ratio of AgNWs were investigated in detail, and the optoelectrical properties of the corresponding transparent conductive electrodes were briefly introduced. The presence of mixed polyols can increase the viscosity of the solution, reduce the migration rate of Ag+ and nuclear in the solution, decrease the diameter of silver nanowires and heighten the length and aspect ratio. Appropriate mixed polyols (triethylene glycol) with the volume fraction of 30% allows the rapid synthesis of AgNWs with the diameter of about 64.2 nm, the length of 66.0 μm and the aspect ratio as high as 1029. The as-prepared AgNWs films possess a transmittance of 89.8% and a sheet resistance of 4.56 Ω/sq. The resultant AgNWs with high aspect ratio can be applied to prepare transparent conductive films.

Conductivity enhancement of silver nanowire networks via simple electrolyte solution treatment and solvent washing

As a promising replacement material for indium tin oxide in flexible electronics, silver nanowires (AgNWs) usually need complicated post-treatment to reduce the high contact resistance across the intersections when used as transparent conductive films. In this work, a widely applicable nano-joining method for improving the overall conductivity of AgNW networks with different kinds of electrolyte solutions is presented. By treatment with an electrolyte solution with appropriate ionic strengths, the insulating surfactant layer (polyvinylpyrrolidone, PVP) on the AgNWs could be desorbed, and the AgNW network could be densified. The sheet resistance of the AgNW film on a glass slide is reduced by 60.9% (from 67.5 to 26.4 Ohm sq−1) with a transmittance of 92.5%. High-resolution transmission electron microscopy analysis indicates that atomic diffusion occurs at the intersection of two AgNWs. Thus, metallurgical bonding on the nanometer scale is achieved across the junctions of the AgNWs, leading to a significant enhancement in the conductivity of the AgNW network.

Silver Nanowires with Pristine Graphene Oxidation Barriers for Stable and High Performance Transparent Conductive Films

One-dimensional (1D) silver nanowires (AgNWs) have emerged as a leading candidate for the development of next-generation optoelectronic and wearable electronic devices. However, a key limitation of AgNW electrodes is that they are readily oxidized, resulting in a shift in properties leading to devices becoming erratic over time. To address this problem, we report a facile method to improve both the stability and performance of AgNW films. The AgNWs were combined with pristine graphene (pG) using an optimal (30/70 wt %) with the goals to prove that the pG sheets can provide a barrier shielding to protect against AgNW oxidation and have the additional benefit of improving the connections between wires and stability of the films. The fabrication of these films was demonstrated on wide range of substrates including glass, plastic, textile, and paper. A surface resistance of 18.23 Ω/sq and an optical transparency of 89% were obtained on the glass substrates, 50 Ω/sq and 88% transparency for poly(ethylene terep...

In-Place Printing of Carbon Nanotube Transistors at Low Temperature

Interest in flexible, stretchable, and wearable electronics has motivated the development of additive printing to fabricate customizable devices and systems directly onto virtually any surface. However, progress has been limited by the relatively high temperatures (>200 °C) required to sinter metallic inks and time-consuming process steps, many of which require removal of the substrate from the printer for coating, washing, or sintering. In this work, we addressed these challenges and demonstrate carbon nanotube thin-film transistors (CNT-TFTs) that are fabricated by aerosol jet printing with the substrate never leaving the printer. The full in-place printing approach, from first step to last, used a maximum process temperature of only 80 °C on the printer platen. Silver nanowire (Ag NW) ink was found to be most viable for low-temperature, in-place sintering while still yielding good electrical interfaces to the CNT thin-film channels. These aerosol-jet printed Ag NW films were conductive immediately afte...

Study on optical films with AgNWs using UV laser patterning

Silver nanowires (AgNWs) with excellent conductive properties can be used to make transparent electrodes with high transmittance, low haze, high electrical conductivity, and high mechanical strength. AgNWs could be a promising material to replace indium tin oxide (ITO). In this study, a polyol method was used to synthesize one-dimension AgNWs. Molecular dynamics simulation software of the Large-scale Atomic/Molecular Massively Parallel Simulator was applied to analyze the micro/nano-scale behavior and predict basic mechanical properties of the materials. For optical properties, a near-field electrospray was combined with ultraviolet 355-nm laser ablation process to direct-write patterning of the transparent conductive AgNWs films as electrodes. Three conductive films with various thicknesses of AgNWs prepared by the near-field electrospray process were coated on glass substrates to analyze the surface morphology and optical properties. A scanning electron microscope and energy dispersive spectrometer were utilized to observe the surface morphology and material composition. An optical integrating sphere and a four-point probe were used to examine the transmittance, haze, and electrical conductivity, respectively. In this study, the optical, electrical and mechanical characteristic as a function of thickness of the films, and laser power levels were characterized.

Electrophoresis deposition of flexible and transparent silver nanowire/graphene composite film and its electrochemical properties

Silver nanowire (Ag NW)/graphene composite films were fabricated on polyethylene terephthalate (PET) substrates using an electrophoresis method, making graphene sheets closely contact with NW networks. As electrophoresis voltage increased from −1 V to −10 V, the transmittance and sheet resistance of the composite film changed in the range of 64.8%–35.2% and 0.98 Ω/sq-6.61 Ω/sq (initial values are 75.7% and 0.77 Ω/sq). Combined advantages of two materials, the stability of the Ag NW film was greatly enhanced due to protection of the graphene layer, and the conductivity of the graphene electrode was remarkably improved ascribed to introduction of the interconnected networks. The areal and specific capacitance of the composite film increased from 1.22 mF/cm2 to 7.6 mF/cm2 and decreased from 108.4 F/g to 25.7 F/g at 100 mV/s in a 1 M LiClO4 solution, as the electrophoresis voltage increased from −1 V to −10 V. Furthermore, the Ag NW/graphene composite film exhibited a good long-term cycling stability with 82.6% capacitance retention after 2500 cycles. Additionally, a symmetric supercapacitor using the Ag NW/graphene films as electrodes exhibited symmetric galvanostatic charge-discharge and similar CV curves under flat and bent conditions, indicating that the fabricated electrode could be considered as one of excellent candidates in flexible and transparent supercapacitors.

One-pot rapid synthesis of high aspect ratio silver nanowires for transparent conductive electrodes

Silver nanowires (AgNWs) with high aspect ratio were rapidly one-pot synthesized by a polyol process in the presence of polyvinylpyrrolidone (PVP) as a stabilizer as well as the anisotropic agent, and the corresponding transparent conductive films were prepared by spin-coating method. The effects of PVP molecular weight and concentration on the morphology and aspect ratio of AgNWs were investigated in detail, and the optoelectrical properties of the transparent conductive films were briefly introduced. The presence of PVP induces the growth of silver directed to form high aspect-ratio nanowires by a high anisotropic mode. Appropriate PVP molecular weight and concentration allows the rapid synthesis of AgNWs with the diameter of about 78.2 nm, the length of 79.52 μm and the aspect ratio as high as 1009.2. The as-prepared AgNWs films possess a transmittance of 81.6% and a sheet resistance of 11.36 Ω/sq. The resultant AgNWs with high aspect ratio can be applied to prepare transparent conductive electrodes.

Preparation of smooth, flexible and stable silver nanowires- polyurethane composite transparent conductive films by transfer method

Silver nanowires (AgNWs)-polyurethane (PU) composite transparent conductive films were fabricated via transfer method using AgNWs conductive inks and polyurethane as starting materials, and the effects of post-treatments including heat treatment, NaCl solution bath and HCl solution bath for AgNWs film on the sheet resistance and transmittance of the composite films were respectively investigated in detail. AgNWs networks are uniformly embedded in the PU layer to improve the adhesion and reduce the surface roughness of AgNWs-PU composite films. Heat treatment can melt and weld the nanowires, and NaCl and HCl solution baths promote the dissolution and re-deposition of silver and the dissolving of the polymer, both which form conduction pathways and improve contact of AgNWs for reducing the sheet resistance. Smooth and flexible AgNWs-PU composite film with a transmittance of 85% and a sheet resistance of 15 Ω · sq−1 is obtained after treated in 0.5 wt% HCl solution bath for 60 s, and the optoelectronic properties of the resultant composite film can maintain after 1000 cycles of bending and 100 days.