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Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire Electrodes

transparent electrodes.Second,we devel-

rod coating technique for scalable roll-to-deposition of Ag NWs.Third,a facile electrochemi-uneven local heating.Controlled drying is achieving a uniform?lm coating.36Figure 8in.by8in.uniform coating of Ag NWs on

Ag NW ink in ethanol solvent with concentration of2.7mg/mL.(b)Meyer rod coating setup for plastic substrate.The PET plastic substrate is put on a?at glass plate and a Meyer rod is pulled which leaves a uniform layer of Ag NW ink with thicknesses ranging from4to60?m.(c)Finished PET substrate.The Ag NW coating looks uniform over the entire substrate shown in the?gure.(d) coating shown in panel c.The sheet resistance is?50?/?.

applications in which the charge carrier mean length is less than the hole size.The incorpo-other materials,such as CNTs or PEDOT,could the size of the openings for better electri-distribution.

transmittance over a large wavelength range tance of the Ag NW electrode is constant infrared regions,while the transmittance electrode decreases for wavelengths?1100 decreased transmittance is due to ITO’s plasma nant wavelength at?1300nm,which depends doping level.37The constant transmittance

images of Ag NW?lms with different densities.The different densities of Ag NW?lms lead to

100,(b and c)50,and(d)15?/?.The diameters of the Ag NWs are in the range of40?100nm. Optical transmittance of transparent Ag NW electrodes measured with a UV?vis spectrometer,without ITO on PET are obtained from CPFIlms(www.cp?https://www.sodocs.net/doc/d17222022.html,).

by regular ultraviolet?visible

in its transmittance mode.After the base-spectroscopy is set by scanning a blank glass),a sample is installed on a solid trode,like thin metal?lms,loses transmittance

re?ection,not absorption.2

To be used in optoelectronic devices,transparent Ag NW electrodes must meet certain mechanical

Diffusive and specular transmittances of glass,ITO on glass,CNT on glass,and Ag NWs with different glass substrates.The differences in the diffusive transmittance and the specular transmittance are also scattering of the light by the material.The ITO substrate is from Solaronix Inc.(https://www.sodocs.net/doc/d17222022.html,) resistance of50ohms/sq.The CNT coating on glass is fabricated exactly according to ref22,with sheet

s

/R s be less than30%.This requirement different device applications and compa-modi?ed recipe(right).The modi?ed recipe ?50%thinner Ag NWs.The diameters of Ag

Mechanical and chemical stability of Ag NW?lms on plastic substrates.(a)The sheet resistances of PET before and after a taping test.When the Ag NW?lm is encapsulated with20nm Te?on,the

much smaller resistance increase.(b)Bending test of Ag NW?lms,with and without encapsulation, substrate.Ag NW electrodes show much better bending properties.(c)The sheet resistance changes of heat(120C for123h),water for10min,acetone for10min,and IPA for10min.Ag NW?lms on resistances to exposure.

strated that Ag NW electrodes can be used as either an-or cathode.43Our solar cell performance indicates

the Ag NWs are chemically stable when in contact the solar cell active layer.We did not perform sta-

test under extended-time UV exposure,but we believe this is not going to cause any issues since Ag are well buried under the active layer materials

encapsulated properly.Overall,performances of silver contacts were deposited by E-beam lithography and allow us to measure the resistance along each NW and the junction resistances.The resistances

two Ag NWs are260and320ohms,respectively,

the junction resistance is larger than1G?.Another method to increase the conductivity is to decrease junction resistance between the NWs.We found that replacement is an effective method to do this.The

6.(a)Schematic to show that the competition between Br-and ethylene glycol for Ag?retards the supply of silver

and results in more effective anisotropic growth of the nanowires.(b)SEM con?rms that the addition of KBr helps longer and thinner wires,from50?100nm to30?50nm.(c)Transmittance at500nm and sheet resistances for electrodes based on regular NWs and thin/long wires with KBr addition in the NW preparation step.The performance CNT,and graphene are shown for comparison.

The transmission electron microscopy(TEM) Figure7c shows the presence of Au in the wire coating.The image was taken on an FEI CM20 the Stanford Nanocharacterization Laboratory. dispersive spectroscopy(EDS)was performed to the change in junction resistance,as veri?ed junction resistance measurement.The surface

ogies of Ag?Au alloyed nanowires can be controlled by the titration rate of HAuCl4.Smoother surfaces

be achieved when slower titration is used(Figure

(a)Electrical measurement of individual Ag NWs and a junction.The junction shows much higher resistances

the wires themselves.The junction resistance dramatically decreases from?1G?to450?after the Au coating.

the two wires are?10?m each.(b)Schematic of Au?Ag alloy network formation by the solution process.

showing the nanowire after the Au replacement.(d)Au replacement with different Au addition time.

nanowires is smoother when Au is supplied more slowly.

Figure8.(a)SEM of Ag NW network after mechanical press;AFM images of the Ag NW network(b)before and(c)after pressing.The pressing signi?cantly improves the smoothness.The surface roughness decreases from110to47nm after chanical pressing.

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