Improved Performance by SiO2 Hollow Nanospheres for Silver

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Improved-performance by SiO hollow nanospheres for silver nanowire-based flexible transparent conductive films Liwen Zhang, Longjiang Zhang, Yejun Qiu, Yang Ji, Ya Liu, Hong Liu, Guang Ji Li, and Qiuquan Guo ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b07515 • Publication Date (Web): 20 Sep 2016 Downloaded from http://pubs.acs.org on September 22, 2016

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ACS Applied Materials & Interfaces

Improved-Performance by SiO2 Hollow Nanospheres for Silver Nanowire-Based Flexible Transparent Conductive Films Liwen Zhang‡,a, Longjiang Zhang‡,a, Yejun Qiua,*, Yang Jia, Ya Liua, Hong Liub,*, Guangji Lib, Qiuquan Guo c,* a

Shenzhen Engineering Lab of Flexible Transparent Conductive Films, Department

of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, University Town, Shenzhen, 518055, China. b

School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.

c

Department of Mechanical and Materials Engineering, The University of Western Ontario, London, Ontario, N6A 5B9, Canada

KEYWORDS: transparent conductive films, silver nanowires, silica nanosphere, sheet resistance, thermal stability

ABSTRACT: Recently, flexible transparent conductive films (TCFs) have attracted tremendous interest thanks to the rapid development of portable/flexible/wearable electronics. TCFs on the basis of silver nanowires (AgNWs) with excellent performance are becoming an efficient alternative to replace the brittle transparent

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metal oxide. In this study, a promising method was developed by introducing SiO2 hollow nanospheres (SiO2-HNSs) into the film to significantly improve the performance of AgNW-based TCFs. As SiO2-HNSs have opposite charges to AgNWs, the strong attraction had promoted a uniform distribution of AgNWs and made the distance between AgNWs closer, which could decrease the contact resistance greatly. The introduction of SiO2 layer remarkably enhanced the transmission of visible light and the conductivity. In addition, the TCFs constructed by AgNWs and SiO2-HNSs showed much higher thermal stability and adhesive force than

those

by

only

AgNWs.

As

an

example,

the

transmission

of

AgNW/SiO2-HNS-coated PET could increase about 14.3% in comparison to AgNW-coated PET. Typically, a AgNW/SiO2-HNS-based TCF with a sheet resistance of ca. 33 Ω/sq and transmittance of ca. 98.0% (excluding substrate) could be obtained, with excellent flexibility, adhesion, and thermal stability. At last some devices were fabricated.

Introduction In the past decades, fabrication of flexible and stretchable transparent conductive films (TCFs) has attracted much attention due to its widely used in displays, touch screens, solar cells, and smart windows. Up to now, the most commonly used TCFs material in the industry is still composed of indium tin oxide (ITO). However, the ITO film is not suitable for flexible application and large area application because of its high brittleness, high cost and complicated processing conditions. The rapid


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development of new electronics devices is demanding novel materials to replace ITO. A variety of candidates have been investigated, including conducting polymers1,2, graphene3,4, carbon nanotubes5,6, metal nanostructures7-11, and their hybrids12-15. Among them, silver nanowires (AgNWs) are the most promising candidates due to their high conductivity, flexibility and transparency.

A number of different techniques were developed to improve the performance of AgNW based TCFs. For example, a TCF with 95.2% transmittance and 22.5 Ω/sq sheet resistance was produced for solar cell electrodes16 and a TCF with 99.1% transmittance and 130 Ω/sq sheet resistance was made as conducting films17. However, it is still very challenging to achieve both high conductivity and high transparency at the same time. High conductivity often needs a thicker film, which usually leads to significantly decreased transmittance, and vice versa. Typically, two general routines are adopted to improve the performance. One is from the aspect of materials, while the other is from the aspect of TCF fabrication. Great efforts are devoted to synthesizing AgNWs with small and uniform diameter and high length/diameter ratio18,19, and using mixture of AgNWs with other conductive materials, such as conductive polymers20, carbon nanotubes21,22, graphene23,24, and metal oxide25, in order to combine the advantages of multiple materials. For example, using AgNWs with high length/diameter ratio can lower the percolation resistance to decrease the sheet resistance; mixing AgNWs with carbon nanotubes can benefit the decrease of the haze effect.



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During the fabrication process of TCFs, it is important to widen the light transmission and shorten the electron conducting pathway to ensure excellent optoelectronic performance. However, almost all the AgNWs require sophisticated process and chemical additives to promote the dispersion of AgNWs on substrates26,27, resulting in an increased contact resistance. Although the contact resistance can be decreased by fusion of junctions between AgNWs, such as, thermal annealing28, mechanical pressing29, and plasmonic welding30, such high temperature processes are often not welcome by organic substrates. Other methods like blending or site-selectively growing Ag nanoparticles (NPs) at the junctions were proved to be effective11,31, but the transmission of light was often lowered. Overall, although much progress has been made, realization of both high conductivity and transmittance, along with great flexibility and robustness is still a great challenge for TCFs.

In this work, we have firstly introduced SiO2 hollow nanospheres (SiO2-HNSs) to fabricate TCFs based on AgNWs, which showed excellent performance with not only high conductivity, but also excellent transmittance, along with good flexibility and adhesion. Like other nanoparticles, such as PS32, ITO33, and SiO234-36, SiO2-HNSs can benefit the dispersion of AgNWs in the polymer matrix due to hydrogen bond and Vander Waals force. In addition, the opposite charges of SiO2-HNSs and AgNWs had decreased the distance between AgNWs, leading to a high surface density to lower the percolation resistivity and a thinner thickness of AgNWs, which is highly desirable for transmittance and conductivity enhancement. In addition, nanoparticles, such as Pt37, SiO238-41, and SiO2-TiO242, covered on the substrate can act as an antireflection


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layer when the thickness and refractive index satisfy the antireflection condition. Especially, SiO2-HNSs can not only increase transmittance but also provide the film with good durability and strong adhesions to substrates43,44. In this study, several TCF devices were built and the influence mechanism of SiO2-HNS was discussed.

Experimental Chemicals

and

materials.

Hexadecyltrimethyl

ammonium

bromide

(CTAB), tetraethylorthosilicate (TEOS), n-hexadecane, isopropanol, ammonium hydroxide, deionized water, poly(vinyl alcohol) (PVA), and poly(ethylene terephthalate) (PET, with transmittance of ca. 91%) were purchased from commercial supplier. AgNWs purchased from Guangzhou Qian shun Industrial Material Co., Ltd were supplied as a suspension in isopropyl alcohol (IPA). All chemicals were used without further purification.

Synthesis and characterization of SiO2 hollow and solid nanospheres. In this work, oil-in-water (O/W) microemulsion method was adopted to prepare SiO2 hollow nanospheres (SiO2-HNSs). Firstly, 2 g CTAB was dissolved into 200 mL deionized water by ultra-sonication at 50 °C. Then 5 mL n-hexadecane was added into the solution with stirring at 600 rpm for 5 min to form O/W emulsion system. Thereafter, 20 mL of TEOS and 0.05 g PVA were added, and the mixture was sonicated at 50 °C for 75 min for thoroughly mixing. Finally the sample was aged for another 12 h to obtain the SiO2-HNS solution. To synthesis SiO2 solid nanospheres (SiO2-SNSs), TEOS was hydrolyzed and condensed in alcohol solvent under alkaline conditions.



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Firstly, 50 mL deionized water, 150 mL ethanol and 15 mL ammonium hydroxide were mixed for 5 min. Then 20 mL TEOS was added dropwise into the above solution. After stirring for 30 min, 0.05 g PVA was dissolved into the solution by ultrasonic. Finally the mixture was stirred for another 4 h to obtain the SiO2-SNS solution. To fabricate TCFs, the SiO2 solution was diluted by IPA into different concentrations of 0.16, 0.32, 0.48, 0.64, 0.80, and 0.96 mg/mL. The SiO2 samples were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS, HITACHI S-4700), transmission electron microscopy (TEM, JEM 2010), X-ray diffraction (XRD, Rigaku D/Max 2500/PC), and laser particle size analyzer (Malvern Mastersizer 3000). The refractive index of coatings deposited on PET substrates was measured using a spectroscopic ellipsometer (Alpha-SE, J. A. Woollam Co.). The values of index of refraction were an average of five measurements. The zeta potential of the samples was tested by Malvern Nano-ZS.

Fabrication and characterization of TCFs. Dip-coating method was used to fabricate TCFs composed of AgNWs and SiO2-HNSs. The substrate was cleaned in an ultrasonic bath for 30 min and dried in an oven. Subsequently it was dipped into SiO2-HNS solution, AgNW solution, and SiO2-HNS solution in sequence. Finally the sample was heat-treated in the range of 100-600 oC. The structure of the conductive layer can be well controlled by tuning the coating times and concentration of SiO2-HNS and AgNW solutions. To obtain good surface conductivity of TCFs, it is crucial to control the SiO2-HNS concentration below a certain value to ensure the exposure of AgNWs. In a typical preparation procedure, the SiO2-HNS concentration


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of 0.5 mg/mL was used. The morphology and element composition of TCF samples were characterized by SEM/EDS, their transmittance in the wavelength range of 300-800 nm were measured by a UV-vis-IR spectrophotometer (SHIMADZU, UV-3600), and sheet resistance was measured by a standard four point probe (KEITHLEY 6221/2182A). It should be noted that the average transmittance values at a wavelength of 550 nm was used as the optical transmittance of TCFs, and the reported sheet resistance values were an average of ten measurements on a sample. As an example of symbols, the sample AgNW/SiO2-HNS-coated PET means that the TCF is prepared by coating SiO2-HNS, AgNW, and SiO2-HNS solutions in sequence on PET substrate.

Device fabrication. (1) TCFs with large area. Spray coating method was adopted to fabricate a large area TCF. The SiO2-HNS and AgNW solutions were diluted into certain concentrations and the substrate was pre-heated before spray coating. Then the SiO2-HNS and AgNW solutions were sprayed under a given order. During each coating cycle, the samples should be baked at a certain temperature for several minutes. (2) LED arrays. A conductive pattern was made during the fabrication of TCF. Then through-hole LEDs were anchored on the pattern to form a HIT image. (3) Lighting of a snail. Double-sided conductive TCF was fabricated with the process mentioned above. These two sides were defined as anode and cathode and were well separated by the central PET. Pinholes were made to connect the LEDs, and then 75 LEDs were pasted to form a snail image.



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Results and discussion In this work, SiO2 nanospheres with hollow structure were used to produce TCFs. The hollow nature of the nanospheres is beneficial to match the refractive index between air and substrate, leading to higher transmittance. AgNWs and SiO2-HNSs were synthesized by polyol reduction and microemulsion method, respectively. The optical photos of these two materials are showed in Fig. S1a and b. Clearly, their solutions have good stability and no obvious precipitated substance appears, while their direct mixture would precipitate (Fig. S1c). Figure 1 gives the typical SEM and TEM images of AgNWs and SiO2-HNSs. The AgNWs have high purity and uniform diameter (Fig. 1a and c). The AgNWs have a length/diameter ratio of 250-700 and an average diameter of about 36.7 nm according to Fig. 1e (the data originates from TEM images with low magnification, as shown in Fig. S2a and b). The SiO2-HNS sample has spherical morphology with good mono-dispersion and hollow structure with a wall thickness of 5-15 nm (Fig. 1b and d). And the SiO2-HNSs have an average diameter size of about 49.1 nm according to Fig. 1f (the data originates from laser particle size measurement). Fig. S2c gives the TEM image of SiO2-SNSs, which show the similar diameter size to SiO2-HNSs.


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Figure 1. SEM (a) and TEM (c) images of AgNWs, SEM (b) and TEM (d) images of SiO2-HNSs, and diameter distribution of AgNWs (e) and SiO2-HNSs (f).



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Figure 2. SEM images of different TCF samples: (a) and (c) pure AgNWs; (b) and (d) mixture of SiO2-HNSs and AgNWs. And EDX spectra (e) and XRD patterns (f) of different samples: (I) SiO2-HNSs; (II) AgNWs; (III) mixture of SiO2-HNSs and AgNWs.

The films of AgNW and SiO2-HNS composite with suitable thickness and uniform structure on PET substrate were designed in order to fabricate high performance TCFs. As mentioned above, direct mixing of these two materials was unsuitable due


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to the appearance of precipitate (Fig. S1c). As shown in Fig. S3, in this work, the PET substrate was firstly modified by SiO2-HNS layer, then AgNWs were deposited onto the SiO2-HNS-modified PET, and finally another SiO2-HNS layer was coated on the AgNW layer. The surface SiO2-HNS layer would sink downside along with the evaporation of solvent, thus finally forming a uniform hybrid layer simultaneously containing SiO2-HNSs and AgNWs. To obtain good SiO2-HNS-modified PET substrate, it requires good wetting between SiO2 solution and PET, and adding isopropanol into the as-prepared SiO2 solution can significantly lower the surface tension, leading to a very small contact angle (Fig. S4). Figures 2a-d show the SEM images of two different TCF samples constructed by pure AgNWs and mixture of SiO2-HNSs and AgNWs. A comparison between Fig. 2a and b suggests that the AgNWs would have better dispersion on the SiO2-HNS-modified PET substrate; and as shown in Fig. S5, AgNWs are also well dispersed on the SiO2-SNS-modified PET substrate. One profound phenomena we discovered is that the introduction of SiO2-HNSs could avoid AgNWs to be tip-tilted and shorten the distance between AgNWs at intersections in the vertical direction to the substrate, which is shown in Fig. 2c and d. More importantly, most of AgNWs would still expose in the sample with SiO2, which guarantees the good electrical conductivity on the surface of the TCFs. Fig. S6 provides SEM images of the cross section of the two TCFs by different coating times. The TCF coated with SiO2-HNS, AgNW, and SiO2-HNS solutions has more compact structure than that coated with SiO2-HNS and AgNW solutions. Fig. 2e presents the EDX spectra of the TCF samples constructed by pure SiO2-HNSs, pure



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AgNWs and their mixture. Obviously, the silver and SiO2 components can be well determined. From Fig. 2f, the XRD patterns show the diffraction peaks at 2θ=38.2o, 44.4o, 64.5o, 77.5o and 81.6o corresponding to the crystal faces of (111), (200), (220), (311) and (222) of face-centered cubic (fcc) silver (JCPDS No. 04-0783)45, respectively, and the peak at 2θ=23.7o corresponding to amorphous silica (JCPDS No. 51-1380)46.


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Figure 3. (a) Transmittance (including substrate) of different samples of PET, SiO2-SNS-coated PET, SiO2-HNS-coated PET, AgNW-coated PET, AgNW/SiO2-SNS-coated PET, and AgNW/SiO2-HNS-coated PET; (b) Effect of SiO2-HNS concentration on transmittance and sheet resistance of AgNW-based TCFs; (c) Relationship between transmittance and sheet resistance of different

samples

of

AgNW-coated

PET,

AgNW/SiO2-SNS-coated

PET,

and

AgNW/SiO2-HNS-coated PET; (d) Comparison of transmittance and sheet resistance of the TCFs reported in this work and some literatures; (e) Antireflection mechanism of SiO2-HNS layer on PET substrate; (f) Interaction mechanism between positively charged SiO2-HNS nanospheres and negatively charged AgNWs.

The introduction of SiO2 nanospheres greatly improved both the transmittance and conductivity of the newly prepared TCFs. Fig. 3a gives the transmittance (including substrate) of PET, SiO2-SNS-coated PET, SiO2-HNS-coated PET, AgNW-coated PET, AgNW/SiO2-SNS-coated PET, and AgNW/SiO2-HNS-coated PET, respectively. In comparison with a blank PET, the transmittance of SiO2-HNS-coated and SiO2-SNS-coated PET increases about 3.0% and 1.9% in the wavelength region of 400-800 nm, while the increment of transmittance reaches about 14.3%

and

12.6%

when

comparing

AgNW/SiO2-HNS-coated

PET

and

AgNW/SiO2-SNS-coated PET with AgNW-coated PET, strongly suggesting that the antireflection function is attributed to the synergetic effect of SiO2 nanospheres and AgNWs, moreover SiO2-HNSs are preferred for the better performance. Fig. 3b provides the effect of the SiO2-HNS concentration on transmittance and sheet resistance of the AgNW-based TCFs. It is found that with the increase of SiO2-HNS



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concentration, the transmittance increases first and then decreases, while the sheet resistance decreases first and then increases. Fig. S7 exhibits the effect of SiO2-HNS concentration on the transmittance of blank PET substrate, and a very similar trend was observed. From these results, the optimal SiO2-HNS concentration was found to be 0.5 mg/mL. Here a model of antireflection is schematically established in Fig. 3e. It is well-known that when d=λ/(4n) and n=(n1n2)1/2, the minimum reflection would occur

through

destructive

interference

between

light

reflected

from

the

coating-substrate and the air-coating interfaces47, where d is the coating layer thickness, λ is the reference wavelength, and n, n1 and n2 are the refractive index of the coating layer, the surrounding medium and the substrate, respectively. In this work, the PET substrate have index of refraction n2=1.56-1.65, and ambient air index of refraction n1=1. So an optimum coating index and coating thickness calculated at 550 nm would be 1.25-1.29 and 110 nm, respectively. And our experimental data agree well with these calculation results, as shown in Table S1 and Fig. S6b. That is the reason why the developed TCFs could possess extremely high transmittance after introducing SiO2 hollow nanospheres. Fig. 3c gives the relationship between transmittance and sheet resistance of AgNW-coated PET, AgNW/SiO2-SNS-coated PET, and AgNW/SiO2-HNS-coated PET. Clearly, the introduction of SiO2-HNSs and SiO2-SNSs significantly improves the performance of the AgNW-based TCFs, and the former is preferable. One of the main purposes to introduce opposite charge of SiO2-HNSs is to produce strong electrostatic interaction between SiO2-HNSs and AgNWs, thus promoting the uniform


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distribution of AgNWs on the surface of SiO2-modified substrate and decreasing the contact resistance between AgNWs. In addition, the electrostatic force can help with holding AgNWs in position to minimize undesired motion during solvent evaporation. To further clarify the roles of SiO2-HNSs for such enhancement, Fig. 3f depicts the mechanism of the interaction between SiO2-HNSs and AgNWs. From Zeta potential results, it can be deduced that the positively charged SiO2-HNSs can strongly attract negatively charged AgNWs, which would result in a uniform distribution of AgNWs on SiO2-HNS-modified substrate. Conversely, the AgNWs then would attract the subsequently deposited SiO2-HNSs tightly. Combining with the capillary force induced by the solvent evaporation, this attraction would result in a tight contact between AgNWs, which would definitely enhance the optoelectronic properties of TCFs. Moreover, under these forces, AgNWs would expose but not bury under the SiO2 layer, which is also demonstrated in AgNW/SiO2-SNS-based TCFs (Fig. S5). Finally, a TCF with transmittance of about 98.0% (excluding PET substrate) and the sheet resistance about 33 Ω/sq was fabricated successfully. Fig. 3d shows the results of this work in comparison with other literatures, suggesting that the TCFs developed here exhibit excellent performance.



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Figure 4. Test of reliability: (a) effect of bending radius on sheet resistance of AgNW/SiO2-SNS-based and AgNW/SiO2-HNS-based TCFs (measured at bending status); (b) effect of bending cycles on sheet resistance of AgNW-based, AgNW/SiO2-SNS-based and AgNW/SiO2-HNS-based TCFs (measured after recovering to flat shape); (c) effect of tape peeling cycles on sheet resistance of AgNW-based and AgNW/SiO2-HNS-based TCFs; (d) effect of heat temperature on sheet resistance of AgNW-based and AgNW/SiO2-HNS-based TCFs on PET, PI and glass substrates.

The developed AgNW/SiO2-HNS-based TCFs also possess excellent physical performance, including good reliability, flexibility and adhesion. From Fig. 4a, the sheet resistance of the TCFs constructed by SiO2-HNSs and AgNWs has no obvious change at bending radius in the range of 1-100 mm, while that of the TCFs by using


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SiO2-SNSs increases with the decrease of bending radius. As shown in SEM (Fig. 2b, 2d and S5), the structure of SiO2-HNS in the composite conductive layer is not as compact as that of solid SiO2, which can probably provide slightly more space for bending deformation. Additionally, there are some strong interactions between AgNWs and SiO2-HNSs due to the electric attraction from dissimilar charges and the adhesive force from organic residuals, which are also beneficial to the TCF flexibility to some degree. Fig. 4b shows that both the AgNW/SiO2-HNS-based and AgNW/SiO2-SNS-based TCFs possess excellent stability even after experiencing 3000 times bending cycles. Fig. 4c provides the effect of tape peeling cycles on sheet resistance of AgNW-based and AgNW/SiO2-HNS-based TCFs. Obviously, the stability of AgNW/SiO2-HNS-based TCFs is much better than AgNW-based TCFs during tape peeling cycles, indicating SiO2-HNS has enhanced the adhesive force of the conductive layer on the substrate. The adhesion enhancement should be caused by the existence of a small amount of polymers on the surface SiO2-HNSs. The plausible part is that the polymer at the SiO2 layer has minimum effect on the contact resistance of AgNWs. Fig. 4d exhibits the effect of heat temperature on sheet resistance of AgNW-based and AgNW/SiO2-HNS-based TCFs on PET, PI and glass substrates. The resistance of the TCFs without SiO2-HNS would increase greatly when temperature reaches above 180 oC, while that of the TCFs with SiO2 well maintains before temperature reaches 300 oC, proving that the introduction of SiO2 could greatly improve the thermal stability of AgNW-based TCFs. From Fig. S8, it is found that the change of sheet resistance is closely related to the state of AgNWs, and when the



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AgNWs remain continuous morphology the sheet resistance changes slightly, and vice versa. It is concluded that SiO2 is beneficial to the maintenance of the morphology of AgNWs, while too high temperature reaching 500 oC still could make AgNWs fully fuse into balls, resulting in the evanishment of AgNWs and thus the destruction of the conductive network in the AgNW/SiO2-HNS-based TCFs (Fig. S8g).

Figure 5. (a) a TCF with a size of 20×30 cm; (b)-(d) LED arrays with a shape of HIT based on a patterned TCF; (e)-(g) a LED picture with a shape of snail based on a patterned TCF.


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To illustrate the applications of TCFs developed here, several devices were fabricated, and their optical photos are given in Fig.5. Fig. 5a shows a TCF with a size of 20×30 cm, which can be easily scaled up for the commercial production. It was found that the TCF exhibited good transmittance and uniform resistance. The resistance of eight positions was evaluated to be in the range of 94.0-99.6 Ω. Subsequently, LED arrays were anchored on a patterned TCF to form an image of HIT constructed by 25 lamps (Fig. 5b-d). All the lamps were lightened simultaneously and steady in both the planar and bending states or even after experiencing 500 times bending cycles, indicating good flexibility and stability of this device. Double layer TCF was also constructed by coating both sides of PET substrate with conductive layers. Figures 5e-g present a more complicated LED picture with a shape of snail, which is composed of 75 lamps. To make every lamp lighten, two sides were connected with the positive and negative electrodes of a battery, which provided the voltage of 3 V for lightening LED lamps. Clearly the device has good transmittance and can also work normally even in the bending state. Excitingly the brightness of each lamp is very close, indicating the excellent uniformity of conductivity. To the best of our knowledge, such complex device based on TCF is seldom reported in open literatures. This work focuses on the enhancement in optoelectronic performance as well as reliability by SiO2-HNSs. Due to their excellent properties, the AgNW/SiO2-HNS-based TCFs hold high potential in wide applications. Through further research, the developed technology can be easily adopted for device fabrication.



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Conclusions In this work, SiO2 hollow nanospheres were used to enhance the properties of silver nanowire-constructed TCFs. Compared to other AgNWs based TCFs, the use of both SiO2-HNSs and SiO2-SNSs were beneficial to promote the distribution of AgNWs, reduce the sheet resistance, improve the transmittance and thermal stability of TCFs, and enhance the adhesive force of conductive layer on substrates, while SiO2-HNSs based TCF has shown the best performance. The result of zeta potential showed that the SiO2-HNSs had positive charge while AgNWs had negative one, leading to strong attraction between them, which is essential to achieve the uniform distribution of AgNWs on substrates coated with SiO2-HNS and the tight contact between AgNWs. Through the synergetic effect with SiO2 nanospheres, the antireflection function of AgNW layer was strongly enhanced, moreover, the hollow structure benefited better matching of refractive index, leading to higher transmittance. Thanks to the roles of SiO2 and organic residuals, the thermal stability and adhesion of conductive films were also improved. Overall, the AgNW/SiO2-HNS-constructed TCFs showed excellent conductivity, transmittance, flexibility, thermal stability, and adhesive force. The method can be leveraged to fabricate other high performance TCFs devices.

ASSOCIATED CONTENT

Supporting Information

Optical photos of different samples; Typical TEM images of AgNWs and SiO2-SNSs; Schematic illustration of the TCF fabrication procedures; Images of contact angle on


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PET substrate; SEM images of the cross section; Effect of SiO2-HNS concentration on transmittance of PET substrate; Optical photos of AgNW-based TCFs at different temperature. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION

Corresponding Author *E-mail: [email protected]; [email protected]; [email protected].

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT The work was financially supported by NSFC51102064 and Shenzhen Bureau of Science, Technology and Innovation Commission JCYJ20140417172417151 and JCYJ20160525163956782.

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Table of Contents Graphic


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Improved Performance by SiO2 Hollow Nanospheres for Silver

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