Bifunctional flexible electrochromic energy storage devices based on silver nanowire flexible transparent electrodes

Flexible electrochromic energy storage devices(FECESDs)for powering flexible electronics have attracted considerable attention.Silver nanowires(AgNWs)are one kind of the most promising flexible transparent electrodes(FTEs)materials for the emerging flexible devices.Currently,fabricating FECESD based on AgNWs FTEs is still hindered by their intrinsic poor electrochemical stability.To address this issue,a hybrid AgNWs/Co(OH)_(2)/PEDOT:PSS electrode is proposed.The PEDOT:PSS could not only improve the resistance against electrochemical corrosion of AgNWs,but also work as functional layer to realize the color-changing and energy storage properties.Moreover,the Co(OH)_(2)interlayer further improved the color-changing and energy storage performance.Based on the improvement,we assembled the symmetrical FECESDs.Under the same condition,the areal capacitance(0.8 mF cm^(−2))and coloration efficiency(269.80 cm^(2)C−1)of AgNWs/Co(OH)_(2)/PEDOT:PSS FECESDs were obviously higher than AgNWs/PEDOT:PSS FECESDs.Furthermore,the obtained FECESDs exhibited excellent stability against the mechanical deformation.The areal capacitance remained stable during 1000 times cyclic bending with a 25 mm curvature radius.These results demonstrated the broad application potential of the AgNWs/Co(OH)_(2)/PEDOT:PSS FECESD for the emerging portable and multifunctional electronics.

Fluxless bonding with silver nanowires aerogel in die-attached interconnection

The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.

Silver Nanowire Electrodes: Conductivity Improvement Without Post-treatment and Application in Capacitive Pressure Sensors

Transparent electrode based on silver nanowires(Ag NWs) emerges as an outstanding alternative of indium tin oxide film especially for flexible electronics. However, the conductivity of Ag NWs transparent electrode is still dramatically limited by the contact resistance between nanowires at high transmittance. Polyvinylpyrrolidone(PVP) layer adsorbed on the nanowire surface acts as an electrically insulating barrier at wire–wire junctions, and some devastating post-treatment methods are proposed to reduce or eliminate PVP layer, which usually limit the application of the substrates susceptible to heat or pressure and burden the fabrication with high-cost, time-consuming, or inefficient processes. In this work, a simple and rapid pre-treatment washing method was proposed to reduce the thickness of PVP layer from 13.19 to0.96 nm and improve the contact between wires. Ag NW electrodes with sheet resistances of 15.6 and 204 X sq-1have been achieved at transmittances of 90 and 97.5 %, respectively. This method avoided any post-treatments and popularized the application of high-performance Ag NW transparent electrode on more substrates. The improved Ag NWs were successfully employed in a capacitive pressure sensor with high transparency, sensitivity, and reproducibility.

Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

Silver nanowire(AgNW) film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers(VCSELs) with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality.Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm.The performance of VCSELs with and without AgNW film was studied.When the AgNW film was applied to the surface of VCSELs,due to its better current spreading effect,the maximum output optical power increased from 23.4 mW to 24.4 mW,the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA,the differential resistance decreased from 23.95 Ω to 21.13 Ω,and the far field pattern at 50 mA decreased from 21.6° to 19.2°.At the same time,the near field test results showed that the light in the aperture was more uniform,and the far field exhibited a better single peak characteristic.Various results showed that VCSELs with AgNW on the surface showed better beam quality.

Precise assembly and joining of silver nanowires in three dimensions for highly conductive composite structures

Three-dimensional(3D)electrically conductive micro/nanostructures are now a key component in a broad range of research and industry fields.In this work,a novel method is developed to realize metallic 3D micro/nanostructures with silver-thiol-acrylate composites via two-photon polymerization followed by femtosecond laser nanojoining.Complex 3D micro/nanoscale conductive structures have been successfully fabricated with∼200 nm resolution.The loading of silver nanowires(AgNWs)and joining of junctions successfully enhance the electrical conductivity of the composites from insulating to 92.9 Sm^−1 at room temperature.Moreover,for the first time,a reversible switching to a higher conductivity is observed,up to∼10^5Sm^−1 at 523 K.The temperature-dependent conductivity of the composite is analyzed following the variable range hopping and thermal activation models.The nanomaterial assembly and joining method demonstrated in this study pave a way towards a wide range of device applications,including 3D electronics,sensors,memristors,micro/nanoelectromechanical systems,and biomedical devices,etc.

Silver Nanowires Contained Nanofluids with Enhanced Optical Absorption and Thermal Transportation Properties

Two kinds of silver nanowires(100 nm in diameter, 20 μm and 100 μm in length) are prepared. The thermo-physical characteristics, viscosity, and photothermal conversion performance of the silver nanowires(AgNWs)contained ethylene glycol nanofluids are investigated in detail. It is found that thermal conductivity of 100 μm AgNWs contained nanofluids is higher than that of 20 μm AgNWs with the same diameters of 100 nm. Viscosity test shows that the nanofluid is a Newtonian fluid, and the longer silver nanowires, the greater viscosity. In addition, photothermal conversion efficiency of silver nanowires contained nanofluid is studied. We can observe that the 100 μm AgNWs contained nanofluid has a higher photothermal conversion efficiency than that containing 20 μm AgNWs. Moreover, we find that there is a certain correlation between heat transfer and photothermal conversion of nanofluid. It demonstrates that the high heat transfer property of nanofluid will benefit for its photothermal conversion efficiency and the mechanism is proposed. This work provides a new idea to improve photothermal conversion efficiency. We can choose materials with high thermal conductivity and strong light absorption ability to enhance the photothermal conversion performance of nanofluids.

Fabrication of High-Haze Flexible Transparent Conductive PMMA Films Embedded with Silver Nanowires

High-haze flexible transparent conductive polymethyl methacrylate(PMMA) films embedded with silver nanowires(AgNWs) are fabricated by a low-cost and simple process. The volatilization rate of the solvent in PMMA solution affects the surface microstructures and morphologies, which results in different haze factors of the composite films. The areal mass density of AgNW shows a significant influence on the optical and electrical properties of composite films. The AgNW/PMMA transparent conductive fihns with the sheet resistance of 5.5 Ωsq^(-1) exhibit an excellent performance with a high haze factor of 81.0% at 550 nm.

Stretchable and self-healing conductive fibers from hierarchical silver nanowires-assembled network

Conductive fibers(CFs)with features of high conductivity,stretchability,self-healability,and electromechanical stability are key components of the increasingly popular wearable electronics.However,since the lack of structural design of conductive network and interfacial interaction between soft polymer and conductive additives,it is still hard to enable CFs to meet above requirements.Here,we describe a facial drawing method from a hydrogel reservoir which is remolded into ultrathin and stretchable CFs with excellent multi-responsive self-healability.The hydrogel reservoir was fabricated in synergy of an ice-templating method and in situ polymerization using the assembled framework as a crosslinker.Relying on the effective fabrication mechanism,the diameter of CFs could be well-tuned from 90 to 400μm by adjusting the dipping depth of the glass rod,accompanied with conductivity increased from 0.75 to 2.5 S/m.Since the hierarchical network structure was well maintained in the CFs,professional performances have been proved on the stretchability and electromechanical stability.The presence of massive hydrogen bonding and Ag–S bond enabled the CFs with excellent self-healability under the conditions of contact,electric field,and near infrared light,respectively.Excitingly,the CFs with high sensing property could be integrated into an advanced textile sensor through an effective healing-induced integration strategy,demonstrating its great potentials as superior two-dimensional(2D)electronic skins.

Patternable and transferable silver nanowire conductors via plasma-enhanced cryo-transferring process towards highly stretchable and transparent capacitive touch sensor array

Stretchable transparent electrode(STE)plays a key role in numerous emerging applications as an indispensable component for future stretchable devices.The embedded STE,as a promising candidate,possesses balanced performances and facile preparation procedures.However,it still suffers from the defects of conductive materials caused by the transferring,which results in the irreversible failure of devices.In this work,a patternable silver nanowire(AgNW)STE was fabricated by a plasma-enhanced cryo-transferring(PEC-transferring)process.Owing to the plasma-induced sintering,the AgNW network obtained remarkable improvement in robustness,which ensured the intact network after transferring and thus led to superior tensile electrical properties of the STE.Furthermore,serpentine patterns were utilized to optimize the tensile electrical properties of the STE,which achieved a figure of merit of 292.8 and 150%resistance changing under 50%strain.As a practical application,a 4×3 array of the mutual-capacitive type stretchable touch sensors was demonstrated for future touch sensors in stretchable devices.The PEC-transferring process opened a new avenue for patternable embedded STEs and exhibited its high potential in wearable electronics and the Internet of Thing devices.

Highly stretchable polymer/silver nanowires composite sensor for human health monitoring

Flexible strain sensors exhibit outstanding advantages in terms of sensitivity and stability by detecting changes in physical signals.It can be easily attached to human skin and clothed to achieve monitoring of human motion and health.However,general sensing material shows low stretchability and cannot respond to signals under large deformation.In this work,a highly stretchable polymer composite was developed by adding small amount(0.17 wt.%)of silver nanowires(AgNWs)in stretchable conductive polymer materials.The conductivity of polymer/AgNWs composite is 1.3 S/m with the stretchability up to 500%.The stretchable strain sensor based on the polymer/AgNWs composite can respond to strain signals in real time,even for 1%strain response,and shows excellent stability over 1,000 loading/unloading cycles.Moreover,the strain sensor can be attached to human skin and clothed to monitor joints,throat and pulse of the human body.The human body electrocardiogram(ECG)signal was detected successfully with the polymer/AgNWs electrode,which is comparable to the signal obtained by the commercial electrode.Overall,the sensors enable monitoring of human movement and health.These advantages make it a potential application in wearable devices and electronic skin.

3D printing of high-performance micro-supercapacitors with patterned exfoliated graphene/carbon nanotube/silver nanowire electrodes

Micro-supercapacitors(MSCs)show great potential as on-chip energy storage devices for portable electronics.The major flaw of thin-film MSCs is their low energy density.To improve the energy density,thicker electrodes are required.However,the fabrication of MSCs with thick electrodes remains a challenge.In this work,a novel 3D printing method is employed to fabricate high-performance MSCs with interdigitated exfoliated graphene(EG)/carbon nanotube(CNT)/silver nanowire(Ag NW)electrodes.The nanowelding of Ag NW junction plays a critical role in the realization of 3D printing.To enhance the electrochemical performances of EG,phosphorus atoms are incorporated into the carbon framework with 1.7 at%.The areal capacitance of the 3D printed MSC is 21.6 mF cm^(-2)at a scan rate of 0.01 V s^(-1).The areal energy density of the MSC ranges from 0.5 to 2μWh cm^(-2)with a maximum power density of 2.5 mW cm^(-2).

Plasmon-enhanced nanosoldering of silver nanoparticles for high-conductive nanowires electrodes

The silver nanowires(Ag NWs)electrodes,which consist of incompact Ag nanoparticles(NPs)formed by multi-photon photoreduction,usually have poor conductivities.An effective strategy for enhancing conductivity of the Ag NWs elec-trodes is plasmon-enhanced nanosoldering(PLNS)by laser irradiation.Here,plasmon-enhanced photothermal effect is used to locally solder Ag NPs and then aggregates of these NPs grow into large irregular particles in PLNS process.Fi-nite element method(FEM)simulations indicate that the soldering process is triggered by localized surface plasmon-in-duced electric field enhancement at“hot-spots”.The effectiveness of PLNS for enhancing conductivity depends on laser power density and irradiation time.By optimizing the conditions of PLNS,the electrical conductivity of Ag NWs is signific-antly enhanced and the conductivityσs is increased to 2.45×107 S/m,which is about 39%of the bulk Ag.This PLNS of Ag NWs provides an efficient and cost-effective technique to rapidly produce large-area metal nanowire electrodes and capacitors with high conductivity,excellent uniformity,and good flexibility.

Femtosecond laser irradiation induced heterojunctions between carbon nanofibers and silver nanowires for a flexible strain sensor

We report the direct joining of carbon nanofibers(CNFs)to silver nanowire(Ag NWs)by controlled irradiation with femtosecond(fs)laser pulses.Two separate types of nano-junction dependent on joint geometry,laser fluence and irradiation time are identified in irradiated mixtures.In one type of junction,the tip of an Ag NW is melted and flows to form a bond with an adjacent CNF.The second type of junction occurs without significant heating of the Ag NW and involves the softening and flow of carbon in the CNF in response to the transfer of plasmonic energy from the Ag NW into the CNF.Bonding in a T-type joint configuration can be of either kind depending on the relative orientation of the incident optical field and the long axis of the Ag NW.FDTD simulations were used to explore this effect for different joint geometries and laser polarization.The electrical properties of a heterojunction involving a single Ag NW-CNF structure have been measured,and it is found that the junction resistance can be reduced by six orders of magnitude after laser joining.Finally,we have investigated the properties of a strain sensor based on an Ag NW-CNF hybrid nanowire network and find that this device can exhibit high sensitivity.This sensitivity occurs as nano-junctions induced by fs laser irradiation greatly reduces the initial resistance.This laser-based technique for direct nanojoining of CNF and Ag NWs may enable the design of robust nanowire structures for application in a variety of new devices.

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(Ag NWs)with high yield.A highly conductive dispersant was used to ensure uniform dispersion of the Ag NWs.Without any posttreatment,the Ag NW networks,deposited on flexible substrates,showed excellent optoelectrical performance owing to minimal junction resistance between the Ag NWs.To explore their potential in flexible optoelectronic devices,a transparent film heater was constructed based on the present Ag NW 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 Ag NW film exhibits relatively low production costs and fast production time,it may have value for future electronic industry applications.

Silver nanowire/polymer composite soft conductive film fabricated by large-area compatible coating for flexible pressure sensor array

Soft conductive films composed of a silver nanowire(AgNW) network, a neutral-pH PEDOT:PSS overcoating layer and a polydimethylsiloxane(PDMS) elastomer substrate are fabricated by large area compatible coating processes. The neutral-pH PEDOT:PSS layer is shown to be able to significantly improve the conductivity,stretchability and air stability of the conductive films. The soft conductive films are patterned using a simple maskless patterning approach to fabricate an 8 x 8 flexible pressure sensor array. It is shown that such soft conductive films can help to improve the sensitivity and reduce the signal crosstalk over the pressure sensor array.

One-step plasmonic welding and photolithographic patterning of silver nanowire network by UV-programable surface atom diffusion

Silver nanowire(AgNW)based transparent electrode(TE)plays a pivotal role in optoelectronics where TE is generally required to have fine pattern and high performance.Despite the rapid technological advances in either welding or patterning of AgNWs,there are few studies that combine the two processes in a simple and practical manner.Here,aiming to fabricate high-performance patterned AgNW TE,we develop a simplified photolithography that enables both plasmonic nanowelding with low-level UV exposure(20 mW/cm^(2))and high-resolution micropatterning without photoresist and etching process by conjugating AgNW with diphenyliodonium nitrate(DPIN)and UV-curable cellulose.The cellulose as a binder can effectively enhance plasmonic heating,adhesion,and stability,while the photosensitive DPIN,capable of modulating surface atom diffusion,can boost the plasmonic welding at AgNW junction and induce patterning in AgNW network with Plateau-Rayleigh instability.The fabricated AgNW TE has high figure of merit of up to 1,000(3.7Ω/sq at 90%transmittance)and minimal pattern size down to 3µm,along with superior robustness.Finally,a flexible smart window with high performance is demonstrated using the patterned and welded AgNW TEs,verifying the applicability of the simplified photolithography technique to optoelectronic devices.

Printable elastic silver nanowire-based conductor for washable electronic textiles

Printable elastic conductors promote the wide application of consumable electronic textiles (e-textiles) for pervasive healthcare monitoring and wearable computation. To assure a clean appearance, the e-textiles require a washing process to clean up the dirt after daily use. Thus, it is crucial to develop low-cost printable elastic conductors with strong adhesion to the textiles. Here, we report a composite elastic conductor based on Ag nanowires (NWs) and polyurethane elastomer. The composite could be dispersed into ink and easily printed onto textiles. One-step print could form robust conductive coatings without sealing on the textiles. Interestingly, the regional concentration of Ag NWs within the polyurethane matrix was observed during phase inversion, endowing the elastic conductor with a low percolation threshold of 0.12 vol.% and high conductivity of 3,668 S·cm^−1. Thanks to the high adhesion of the elastic conductors, the resulted e-textiles could withstand repeated stretching, folding, and machine washing (20 times) without obvious performance decay, which reveals its potential application in consumable e-textiles.

High-resolution and large-size stretchable electrodes based on patterned silver nanowires composites

Electrodes based on composites of silver nanowires(AgNWs)and elastic polymers have been widely studied and applied in various stretchable electronic devices.However,due to the high aspect ratio of nanowires,the patterning of AgNW-based composite electrodes remains a huge challenge,especially for high-resolution complex circuit wiring on large-size elastic substrates.In this paper,we propose a method for preparing large-size stretchable circuit boards with high-resolution electrodes by the combination of screen printing and vacuum filtration of AgNWs/polydimethylsiloxane(PDMS)composite.The as-prepared stretchable electrodes have smooth edges with patterning resolution up to-50 μm.The conductivity of the composite electrode can be precisely controlled by varying deposition densities of AgNWs and have reached to 1.07 x 10^(4) S/cm when the deposition density was 2.0 mg/cm^(2).In addition,the uniformity of conductivity and the resistance-strain characteristics of composite electrodes were systematically evaluated with different AgNWs deposition densities.The composite electrodes have been successfully employed to construct a large-size programmable display system and an 18-channel surface electromyography(EMG)recording,showing great potentials for some strain-insensitive stretchable circuits in wearable and health-related electronic applications.

High performance flexible metal oxide/silver nanowire based transparent conductive films by a scalable lamination-assisted solution method

Flexible MoO_(3)/silver nanowire(AgNW)/MoO_(3)/TiO_(2)/Epoxy electrodes with comparable performance to ITO were fabricated by a scalable solution-processed method with lamination assistance for transparent and conductive applications.Silver nanoparticle-based electrodes were also prepared for comparison.Using a simple spin-coating and lamination-assisted planarization method,a full solution-based approach allows preparation of AgNW-based composite electrodes at temperatures as low as 140℃.The resulting flexible AgNW-based electrodes exhibit higher transmittance of 82%at 550 nm and lower sheet resistance about 12-15Ωsq^(-1),in comparison with the values of 68%and 22-25Ωsq^(-1) separately for AgNP based electrodes.Scanning electron microscopy(SEM)and Atomic force microscopy(AFM)reveals that the multi-stacked metal-oxide layers embedded with the AgNWs possess lower surface roughness(<15 nm).The AgNW/MoO_(3) composite network could enhance the charge transport and collection efficiency by broadening the lateral conduction range due to the built of an efficient charge transport network with long-sized nanowire.In consideration of the manufacturing cost,the laminationassisted solution-processed method is cost-effective and scalable,which is desire for large-area fabrication.While in view of the materials cost and comparable performance,this AgNW-based transparent and conductive electrodes is potential as an alternative to ITO for various optoelectronic applications.

High corrosion-resistant silver nanowire/poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonate)@nickel electrode for transparent electromagnetic shielding film

Silver nanowire(AgNW)has become one of the best candidates for flexible transparent electromagnetic(EMI)shielding materials,while the low corrosion resistance of AgNW hinders its application in environments with high content of corrosive substances.Herein,an AgNW/poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonate)(PEDOT:PSS)@nickel electrode was prepared through ultrasonic spray coating and electroplating methods.PEDOT:PSS is sprayed to improve the conductivity of the AgNW network,and a 9.8-16.5 nm Ni layer is deposited on the AgNW/PEDOT:PSS to protect the AgNWs from corrosion.The AgNW/PEDOT:PSS@Ni electrode shows a sheet resistance of 29 U·sq^(-1),a transmittance of 78.18%,an average EMI shielding efficiency of 19.64 dB and excellent corrosion resistance in Na2S solution.The resultant AgNW/PEDOT:PSS@Ni electrode is promisingly used in high corrosion resistance transparent EMI shielding film.