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Flexible Transparent Conductive Film Based on Random Networks of Silver Nanowires Hui Xie 1 , Xing Yang 2 , Dexi Du 2 , Yuzhen Zhao 3 and Yuehui Wang 1, * 1 2

3

*

Department of Chemistry and Biology, University of Electronic Science and Technology of China Zhongshan Institute, Zhongshan 528402, China; [email protected] State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronics and Solid-State Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China; [email protected] (X.Y.); [email protected] (D.D.) Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China; [email protected] Correspondence: [email protected]; Tel.: +86-159-0002-0061

Received: 21 May 2018; Accepted: 1 June 2018; Published: 13 June 2018

Abstract: 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. Keywords: silver nanowires; flexible transparent film; polyethylene terephthalate; sheet resistance

1. Introduction There is increasing demand for suitable flexible transparent conductive materials due to the emergence of flexible plastic devices and the scarcity of indium resources. In recent years, silver nanowires (AgNWs) utilized for fabricating flexible transparent conducting films (FTCFs) for flexible electronics and transparent heaters have attracted significant attention for their excellent mechanical, optical, thermal, and electrical properties [1–8]. However, critical issues still exist that need to be addressed for the large scale application of AgNWs networks electrodes: (1) the low adhesion between AgNWs and the bare substrate; (2) the large contact resistance across the silver wire-wire junction [9–17]. To further optimize the performance of AgNWs-based electrodes, scientists have made much progress at improving the performance of silver nanowires networks electrodes. The adhesion of AgNWs to the surface of the substrate can be enhanced using the adhesion layer between AgNWs and the substrate, and high-intensity pulsed light sintering and pressure [9,10]. In addition, the removal of the insulating layer covered on the surface of the nanowires, or pressure treatment or heat treatment, can improve contact resistance across the silver wire-wire junction [10,13,14]. Until now, many approaches used to prepare silver nanowires networks have been presented including vacuum filtration, the drop-cast method, Meyer rod coating, and the transfer-printing Micromachines 2018, 9, 295; doi:10.3390/mi9060295

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technique [18–27]. However, it is very difficult to achieve a high quality film with low sheet resistance, technique [18–27]. However,and it is good very difficult to between achieve athe high quality film low sheet resistance, high optical transmittance, adhesion nanowires andwith substrate surface at the high optical transmittance, and good adhesion between the nanowires and substrate surface at the same time. Vacuum filtration method is a commonly-used process in film production, which affords same Vacuum filtration such method is a commonly-used process in film production, which affords films time. with some advantages as surface uniformity, controllable thickness, and reproducibility. films with some advantages such as surface uniformity, controllable thickness, and reproducibility. To fabricate the flexible transparent conductive film, AgNWs networks usually are transferred to a To fabricate the flexible transparent conductive film,mixed AgNWs networks are constitutes transferredthe to transparent substrate after being deposited on the cellulose esterusually film; this avacuum transparent substrate after being deposited on the cellulose ester film; the filtration-transferring process. Moreover, it ismixed very easy to generate cracksthis andconstitutes other adverse vacuum filtration-transferring process. Moreover, it is very easy to generate cracks and other adverse defects during the transferring process from mixed cellulose ester to polyethylene terephthalate defects (PET). during the transferring process from mixed cellulose ester to polyethylene terephthalate (PET). Our Our initial initial work work was was the the fabrication fabrication of of flexible flexible transparent transparent AgNWs AgNWs conductive conductive film film with with the the mixed cellulose eater (MCE) as a substrate; we obtained a good conductive structure on the MCE mixed cellulose eater (MCE) as a substrate; we obtained a good conductive structure on the MCE film film using using the the improved improved vacuum-filtrating vacuum-filtrating method method [28]. [28]. In In this this work, work, we we further further transfer transfer AgNWs AgNWs on on the the surface of MCE to polyethylene terephthalate (PET) after dissolving the MCE. The good transferred surface of MCE to polyethylene terephthalate (PET) after dissolving the MCE. The good transferred conductive conductive structure structure was was obtained obtained under under our our experimental experimental conditions, conditions, and and the the photoelectric photoelectric and and mechanical properties of the AgNWs films were discussed. mechanical properties of the AgNWs films were discussed. 2. 2. Materials Materials and and Methods Methods Silver nitrate (AgNO3 , ≥99.8%) was purchased from Guangdong Guanghua Chemical Reagent Silver nitrate (AgNO3, ≥99.8%) was purchased from Guangdong Guanghua Chemical Reagent Co., (Guangdong,China), China),poly(vinylprrolidone) poly(vinylprrolidone) (PVP, C69NO) H9 NO) n ; K30, Mw ≈ 10,000, Co., Ltd. Ltd. (Guangdong, (PVP, C6H n; K30, Mw ≈ 10,000, was was purchased from Guoyao Group Chemical Reagent Co., Ltd. (Shanghai, China); ferric ferric chloride purchased from Guoyao Group Chemical Reagent Co., Ltd. (Shanghai, China); chloride (FeCl3 ·6H2 O, ≥99.5%) was purchased from Chengdu Kelong chemical Co., Ltd. (Chengdu, China); (FeCl3·6H2O, ≥99.5%) was purchased from Chengdu Kelong chemical Co., Ltd. (Chengdu, China); and ethylene glycol (EG, (HOCH2 )2 , ≥99.7%) and ethanol absolute (CH3 CH2 OH, ≥99.7%) were and ethylene glycol (EG, (HOCH2)2, ≥99.7%) and ethanol absolute (CH3CH2OH, ≥99.7%) were purchased purchased from from Tianjin Tianjin Yongda Yongdachemical chemicalCo., Co.,Ltd. Ltd. (Tianjing, (Tianjing, China). China). 125 125 µm-thick μm-thick polyethylene polyethylene terephthalate (PET)film film was purchased Shanghai Xia Hardware Plastic Hardware Co., Ltd. terephthalate (PET) was purchased fromfrom Shanghai Fei XiaFei Plastic Co., Ltd. (Shanghai, (Shanghai, China). Water mixed cellulose esters membrane (MCE, Φ50, 0.4 µm) was purchased China). Water mixed cellulose esters membrane (MCE, Ф50, 0.4 μm) was purchased from Tianjin Jin from Jin Teng experimental equipment Co.,China). Ltd. (Shanghai, China).were Silver nanowiresin were Teng Tianjin experimental equipment Co., Ltd. (Shanghai, Silver nanowires synthesized our synthesized in our laboratory. All the chemicals were used as received. laboratory. All the chemicals were used as received. Silver a mean diameter of about 120 nm120 andnm a length synthesized Silvernanowires nanowireswith with a mean diameter of about and of a 20–70 lengthµm of were 20–70 μm were − 1 by our reported polyol process [27].process 12.67 mg ·mL were diluted to synthesized by our reported polyol [27]. 12.67AgNWs mg·mL−1suspensions AgNWs suspensions weredown diluted −1 with deionized water and sonicated for one minute. AgNWs diluent dispersions were 0.0022 mg · mL down to 0.0022 mg·mL−1 with deionized water and sonicated for one minute. AgNWs diluent dispersed into 500dispersed mL deionized water deposited onand porous MCE membrane form AgNWs dispersions were into 500 mLand deionized water deposited on porous to MCE membrane networks with different densities by vacuum filtration. The AgNWs-MCE film was placed on a hard to form AgNWs networks with different densities by vacuum filtration. The AgNWs-MCE film was ◦ C for 30 min. Further, the AgNWs-MCE film plastic plate with binder clips and dried by oven at 80 placed on a hard plastic plate with binder clips and dried by oven at 80 °C for 30 min. Further, the was fixed with four in the middle each boundary on a PET by adhesive tapes ensure AgNWs-MCE film pins was located fixed with four pins of located in the middle of each boundary on atoPET by the MCE entirely was completely in contact with the PET. The AgNWs-PET-MCE film was treated adhesive tapes to ensure the MCE entirely was completely in contact with the PET. The AgNWs-PET◦ for 15 min. Then, the sample was immersed into acetone at 60 ◦ C for with at 80 MCEacetone film wasvapor treated withCacetone vapor at 80 °C for 15 min. Then, the sample was immersed into 10 min toatcompletely the MCE. Figure shows theFigure schematic illustration of theillustration preparing acetone 60 °C for 10dissolve min to completely dissolve1 the MCE. 1 shows the schematic AgNWs film process. of the preparing AgNWs film process.

1. Schematic illustration of the preparing preparing AgNWs-PET AgNWs-PET film film process. process. Figure 1.

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All scanning electron microscopy (SEM) images were taken on a FE-SEM Field emission scanning electronelectron microscopy, S3400 N, Hitachi Co., were Tokyo, Japan). sheetField resistance of the FTCFs All scanning microscopy (SEM) images taken on aThe FE-SEM emission scanning was measured using a ST2263 four-point probe instrument (Suzhou Jingge Co., Ltd., Suzhou, China). electron microscopy, S3400 N, Hitachi Co., Tokyo, Japan). The sheet resistance of the FTCFs was Optical transmittance (Ts) spectrum measured using(Suzhou ultraviolet-visible (UV-1800 measured using a ST2263 four-pointwas probe instrument Jingge Co.,light Ltd.,detector Suzhou, China). SHIMADZU Co., Kyoto, Japan). The phase structures were determined by X-ray diffraction (XRD) Optical transmittance (Ts) spectrum was measured using ultraviolet-visible light detector (UV-1800 (Rigaku 2500 X-Ray DIFFRRACTOMETER, Rigaku Co., Japan ) on a scintage diffractometer with SHIMADZU Co., Kyoto, Japan). The phase structures were determined by X-ray diffraction (XRD) Cukα1 radiation (λ =DIFFRRACTOMETER, 1.54060 Å) at a scanning rate Co., of 2°/min 2θ range from 20 to 90°. 3M tape (Rigaku 2500 X-Ray Rigaku Japan )inonthe a scintage diffractometer with Cuk α1 with finger pressure as a method of mechanical tape test is adopted to evaluate AgNWs adhesion ◦ ◦ radiation (λ = 1.54060 Å) at a scanning rate of 2 /min in the 2θ range from 20 to 90 . 3 M tape with property to the adhesiontape performance of the AgNWsAgNWs to the adhesion PET substrate is finger pressure as substrate. a method ofThe mechanical test is adopted to evaluate property characterized through the sheet resistance changes. The sheet resistance is measured after 3 M tape to the substrate. The adhesion performance of the AgNWs to the PET substrate is characterized was stripped off from the AgNWs film each 5 times. The bending test was outwas with lab-made through the sheet resistance changes. The sheet resistance is measured aftercarried 3 M tape stripped off apparatus with software recording film resistance and cycle number. from the AgNWs film each 5 times. The bending test was carried out with lab-made apparatus with software recording film resistance and cycle number. 3. Results 3. Results SEM image (Figure 2a) and XRD (Figure 2b) of the synthesized AgNWs are shown in Figure 2. A photo the synthesized AgNWs a solvothermal process is inserted Figure 2a.inSeen from SEMof image (Figure 2a) and XRDby (Figure 2b) of the synthesized AgNWsinare shown Figure 2. Figure of diameter of AgNWs is about 120 nm, andisthe range of length aboutfrom 20– A photo2a,ofthe therange synthesized AgNWs by a solvothermal process inserted inthe Figure 2a.isSeen 70 μm. 2a, Thethe color of the gray. 2b shows five diffraction Figure range of synthesized diameter of AgNWs AgNWs solution is aboutis120 nm,Figure and the range of the length is peaks, about indexed to the (111), (200), (220), (311), and (222) planes of pure face-centered-cubic (fcc) peaks, silver 20–70 µm. The color of the synthesized AgNWs solution is gray. Figure 2b shows five diffraction crystals. to the (111), (200), (220), (311), and (222) planes of pure face-centered-cubic (fcc) silver crystals. indexed The optical optical transmittance transmittance spectra spectra (Figure (Figure 3a) 3a) and and the the sheet sheet resistance resistance (Rs) (Rs) of of AgNWs AgNWs films films with with The different deposition depositiondensities densities(in (ingrams gramsdeposited depositedper persquare squaremeter) meter)ofofAgNWs AgNWsare areshown shown Figure different inin Figure 3. 3. The relationship the andthe thetransmittance transmittanceatat550 550nm nmof ofAgNWs AgNWsfilm film is is inserted inserted in in Figure The relationship of of the RsRs and Figure 3b. 3b. The transmittance transmittancewas was measured a transparent film as the Both reference. Both of the The measured withwith a transparent PET filmPET as the reference. of the transmittance transmittance and the Rsfilms of the AgNWs films with the increase of deposition of and the Rs of the AgNWs decrease with thedecrease increase of deposition density of AgNWs. density When the −2, the transmittance of AgNWs film at − 2 AgNWs. When the deposition density of AgNWs is 242 mg·m deposition density of AgNWs is 242 mg·m , the transmittance of AgNWs film at 550 nm is over −1. Increasing the deposition density of AgNWs−to −1 . Increasing 550 nm over and the 130 Ω·sqthe 84%, andis the Rs84%, is above 130Rs Ω·is sqabove deposition density of AgNWs to 267 mg·m 2 , −2 −1 − 1 mg·m decrease , a dramatic decrease (38 Ω·sq ) wasinobserved inand Figure and the transmittance a267 dramatic in the Rs (38 in Ω·the sq Rs) was observed Figure 3b, the 3b, transmittance of AgNWs of AgNWs film at 550 nm is 81% (Figure 3a), which is better applied to the transparent conductive film at 550 nm is 81% (Figure 3a), which is better applied to the transparent conductive film. The Rs and −2 deposition density decreases −2 deposition film. The Rs and the transmittance of AgNWs with 400 mg·m to the transmittance of AgNWs film with 400 mg·mfilm density decreases to 9 Ω·sq−1 and 71%, −1 9 Ω·sq and 71%, respectively. It is clear that the conductive networks of AgNWs increase respectively. It is clear that the conductive networks of AgNWs gradually increasegradually with the increase with the increase of the deposition density of AgNWs. Under the condition of the low deposition of the deposition density of AgNWs. Under the condition of the low deposition density of AgNWs, density of AgNWs, theamount increase a small ofthe AgNWs can improve the conductivity the increase of a small of of AgNWs canamount improve conductivity significantly. However, significantly. However, when the deposition density of AgNWs reaches a certain value, effective when the deposition density of AgNWs reaches a certain value, effective conductive networks form, conductive networks form, which has a small effect on the deposition density of AgNWs with which has a small effect on the deposition density of AgNWs with regard to conductivity. Theregard dense to conductivity. The dense lead to aofdecrease in transmittance of film. conductive networks lead toconductive a decreasenetworks in transmittance film.

Figure 2.2.(a) (a)SEM SEM image (b) of XRD of thenanowires. silver nanowires. photonanowires of silversynthesized nanowires Figure image andand (b) XRD the silver The photoThe of silver synthesized by a solvothermal process is inserted in Figure 2a. by a solvothermal process is inserted in Figure 2a.

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Figure Figure3.3.Relationship Relationshipofofoptical opticaltransmittance transmittancespectra spectra(a) (a)and andthe thesheet sheetresistance resistance(b) (b)ofofAgNWs AgNWsfilms films Figure 3. Relationship of optical transmittance spectra (a) and the sheet resistance (b) of AgNWs films versus versusthe thesilver silvernanowires nanowiresdeposition depositiondensities densitiesof ofAgNWs-PET AgNWs-PETfilms. films. versus the silver nanowires deposition densities of AgNWs-PET films.

The photos of AgNWs films with different deposition densities are shown in Figure 4.4.Seen from The photos photos of of AgNWs AgNWs films films with with different different deposition deposition densities densities are are shown shown in in Figure Figure 4. Seen from from The Seen Figure 4, the transparency of AgNWs films decrease with increasing deposition densities of AgNWs. Figure 4, 4, the the transparency transparency of of AgNWs AgNWs films films decrease decrease with with increasing increasing deposition depositiondensities densitiesof ofAgNWs. AgNWs. Figure However, the distribution of AgNWs transferred to the PET substrate is uniform. However, the distribution of AgNWs transferred to the PET substrate is uniform. However, the distribution of AgNWs transferred to the PET substrate is uniform.

Figure 4. Photos of AgNWs-PET films with different silver nanowires volumes. Figure 4. Photos of AgNWs-PET films with different silver nanowires volumes. Figure 4. Photos of AgNWs-PET films with different silver nanowires volumes.

Figure 5 shows SEM images of the AgNW-PET films with 363 (Figure 5a), 303 (Figure 5b), 267 Figure 5 shows SEM images of the AgNW-PET films with 363 (Figure 5a), 303 (Figure 5b), 267 (Figure 5c), and 242 mg·m−2 (Figure 5d) AgNWs, respectively. Seen from Figure 5, AgNWs covered Figure 5 shows SEM−2images the AgNW-PET films with (Figure 303 (Figure 5b), (Figure 5c), and 242 mg·m (Figureof5d) AgNWs, respectively. Seen363 from Figure5a), 5, AgNWs covered on the surface of the PET substrate to form conductive network by crosslinking. The distribution of −2 (Figure 267 (Figure 5c), and 242 mg · m 5d) AgNWs, respectively. Seen from Figure 5, AgNWs covered on the surface of the PET substrate to form conductive network by crosslinking. The distribution of AgNWs transferred to the PET substrate is uniform. This is consistent with the phenomenon shown on the surface of theto PET to form conductive network by crosslinking. The distribution of AgNWs transferred thesubstrate PET substrate is uniform. This is consistent with the phenomenon shown in the Figure 4. In this work, the sample-treated temperature with acetone vapor at 80 °C, and the AgNWs transferred to the PET substrate is uniform. This is consistent with the phenomenon shown in the Figure 4. In this work, the sample-treated temperature with acetone vapor at 80 °C, and the sample-fixed with four pins located in the middle of each boundary on a PET were used. The highly in the Figure with 4. In four this pins work,located the sample-treated with on acetone 80 ◦The C, and the sample-fixed in the middle temperature of each boundary a PETvapor were at used. highly treated temperature shortened the melting time of MEC, and the fixed sample reduced the sample-fixed with fourshortened pins located the middle each boundary on afixed PET were used. The highly treated temperature theinmelting timeof of MEC, and the sample reduced the deformation of the sample, thus preventing the accumulation of silver nanowires. Photos of silver treated temperature shortened the melting time of MEC, and the fixed sample reduced the deformation deformation of the sample, thus preventing the accumulation of silver nanowires. Photos of silver nanowires films can be seen in Figure 5. The silver nanowires are evenly coated on the surface of PET, of the sample, thus the accumulation silver nanowires. Photos of silver nanowires films canpreventing be seen in Figure 5. The silverofnanowires are evenly coated on thenanowires surface of films PET, indicating that the transfer process is good. With the increase of AgNWs’ deposition density, more can be seen in Figure 5. The silver nanowires are evenly coated on the surface of PET, indicating that the indicating that the transfer process is good. With the increase of AgNWs’ deposition density, more and more conductive networks are formed. transfer process is good. With the increase of AgNWs’ deposition density, more and more conductive and more conductive networks are formed. networks are formed.

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Figure 5. SEM images of AgNWs-PET films with different deposition densities of AgNWs, (a) 363, (b) Figure 5. SEM SEMimages imagesofofAgNWs-PET AgNWs-PET films with different deposition densities of AgNWs, (a) 363, Figure 303, (c) 5. 267, and (d) 242 mg·m−2. −2 films with different deposition densities of AgNWs, (a) 363, (b) (b) 303, (c) 267, and (d) 242 mg−2·.m . 303, (c) 267, and (d) 242 mg·m

Figure 6 shows the relationship of Rs of AgNWs film (the deposition density of 267 mg m−2) to 6 shows the relationship relationship of Rs Rs offor AgNWs film (thedeposition deposition density 267mg mg m−−22 ) to the of of AgNWs (the density 267 cyclesFigure of folding up (Figure 6a) and tape test 5 timesfilm (Figure 6b). The inserted is of aofphoto of m folding (Figure (Figure Thefolding inserted photo of folding cycles of folding up (Figure 6a) and test for times 6b). of is athe up. Seen from Figure 6, with the tape increase of 5the cycle member up, Rs gradually Seenfrom fromFigure Figure 6, with the increase ofcycle the cycle member of folding up,gradually the Rs gradually up. Seen 6, with the increase of the member of folding up, the Rs increases. increases. After the 50 cycles of folding up, the Rs changed linearly depending on cycle members. Rs increases. After the 50 cycles of folding up, the Rs changed linearly depending on cycle members. Rs After the 50 cycles of folding up, the Rs changed linearly depending on cycle members. Rs of AgNWs of AgNWs film increased nearly 2 times at 100 cycles of folding up. It is clear that after many cycles of AgNWs film increased nearly 2 times at 100 cycles of folding up. It is clear that after many cycles film increased nearly 2 times at 100 cycles of folding up. It is clear that after many cycles of folding of folding up, some of the AgNWs came off the surface of the PET substrate because of the poor of folding the AgNWs offof the surface of the PET substrate because of theof poor up, some of the AgNWs came off the came surface the PET substrate because of thetopoor adhesion of Ag adhesion ofup, Agsome NWsofand PET substrate, so the Rs decreased gradually due the decrease the adhesion Agsubstrate, NWs andsoPET substrate, so the Rs decreased due decrease of the NWs and of PET the Rs decreased to gradually the decrease ofto thethe conductive paths. conductive paths. We did not obtain the sheetgradually resistancedue of film after tape test was repeated 6 times. conductive paths. We did not obtain the sheet resistance of film after tape test was repeated 6 times. We did not obtain the sheet resistance of film after tape test was repeated 6 times. It is clear that the Rs It is clear that the Rs gradually decreases after tape test. We observed the AgNWs were removed from It is clear that the Rs gradually decreases after tape test. We observed the AgNWs were removed from gradually decreases after tape test. We tape observed were removedthat from the PET substrate the PET substrate and adhered to the after the eachAgNWs tape test, indicating the adhesion of the the PET substrate and adhered to the tape after each tape test, indicating that the adhesion ofPET the and adhered to the tape after each tape test, indicating that the adhesion of the AgNWs to the AgNWs to the PET substrate is weak. AgNWs toisthe PET substrate is weak. substrate weak.

Figure 6. Rs of AgNWs films versus cycle time of folding up (a) and tape test (b). Figure 6. Rs of AgNWs films versus cycle time of folding up (a) and tape test (b).

Figure 7 shows the SEM images of samples after folding up (Figure 7a) and tape test (Figure 7b). Figurewith shows the SEM samples after up 7a) (Figure 7b). Figure 77 shows the SEM images ofthat samples after folding folding up (Figure (Figure 7a) and and tape test (Figure 7b). Compared Figure 5c, it images is clearof the deposition density of AgNWs ontape the test surface of PET Compared with Figure 5c, it is clear that the deposition density of AgNWs on the surface of PET Compared with Figure 5c, it is clear that the deposition density of AgNWs on the surface of PET deceases after the cycles of folding up and tape test, indicating that the AgNWs fell off from the PET. deceases after after the the cycles deceases cycles of of folding folding up up and and tape tape test, test, indicating indicating that that the the AgNWs AgNWs fell fell off off from from the the PET. PET.

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Figure 7. SEM images of samples after folding up (a) and tape test (b). Figure 7. SEM images of samples after folding up (a) and tape test (b). Figure 7. SEM images of samples after folding up (a) and tape test (b).

One 0.06 W LED lamp with series fixed on the surface of AgNWs-PET electrode with conductive One 0.06 LED with series the AgNWs-PET Onewere 0.06 W W LED lamp lamp with series fixed on the surface surface ofbent AgNWs-PET electrode with with conductive conductive adhesive luminous, and they werefixed still on luminous afterof (Figure 8).electrode adhesive were luminous, and they were still luminous after bent (Figure 8). adhesive were luminous, and they were still luminous after bent (Figure 8).

Figure 8. Photos of LED lamp device. Figure 8. Photos of LED lamp device. Figure 8. Photos of LED lamp device.

4. Conclusions 4. Conclusions Silver nanowires with a mean diameter of about 120 nm and 20–70 μm in length were 4. Conclusions Silver nanowires withprocess. a mean diameter of abouttransparent 120 nm and 20–70 μm in length were synthesized using a polyol Further, the flexible conductive AgNWs films with Silver nanowires with a mean diameter of about 120 nm and 20–70 µm in length were synthesized synthesized using were a polyol process. Further, the flexible transparent conductive filmsshow with PET as a substrate prepared using the vacuum filtration-transferring process.AgNWs The results using a polyol process. Further, the flexible transparent conductive AgNWs films with PET as a PET the as aAgNWs substraterandomly were prepared using the vacuum filtration-transferring process. The resultswhich show that and uniformly distribute on the surface of the PET substrate, substrate were prepared using the vacuum filtration-transferring process. The results show that the that the AgNWs randomly and uniformly distribute on the thetransfer surfaceprocess. of the PET substrate, which indicates that the AgNWs structure is preserved well after The film with 81% of AgNWs randomly and uniformly distribute on the surface of the PET substrate, which indicates that the indicates that the AgNWs structure is preserved well after thecan transfer process.when The film 81% of the transmittance at 550 nm and 130 Ω·sq−1 sheet resistance be obtained the with deposition AgNWs structure is preserved well after the−1transfer process. The film with 81% of the transmittance −2. It the transmittance 550 mg·m nm and 130 Ω·sq sheet resistance be obtained when the deposition density of AgNWs at is 242 is sufficient to be used as acan flexible transparent conductive film. at 550 nm and 130 Ω·sq−1 sheet−2resistance can be obtained when the deposition density of AgNWs density of AgNWs is 242 mg·m . ItRs is sufficient be used with as a flexible transparent conductive film. The bending test indicated that the graduallyto increases the increase of the cycle member of is 242 mg·m−2 . It is sufficient to be used as a flexible transparent conductive film. The bending test The bending test the indicated thatofthe Rs gradually increases with the increase of the of folding up. After 50 cycles folding up, the Rs changed linearly depending oncycle cyclemember members. indicated that the Rs gradually increases with the increase of the cycle member of folding up. After the folding up. After the 50 cycles of folding up, the Rs changed linearly depending on cycle members. The tape test indicated that the Rs gradually decreases after the tape test and the sheet resistance of 50 cycles of folding up, the Rs changed linearly depending on cycle members. The tape test indicated The did tapenot testobtained indicatedafter that the the tape Rs gradually the indicating tape test and sheet resistance of film test was decreases repeated 6after times, thatthe the adhesion of the that the Rs gradually decreases after the tape test and the sheet resistance of film did not obtained after film did to notthe obtained after theistape test was repeated times,with indicating of the AgNWs PET substrate poor. The 0.06 W LED6 lamp series that fixedthe onadhesion the surface of the tape test was repeated 6 times, indicating that the adhesion of the AgNWs to the PET substrate is AgNWs to the PET substrate is poor. adhesive The 0.06 was W LED lamp and withit series fixed on theafter surface of AgNWs-PET electrode with conductive luminous, was still luminous being poor. The 0.06 W LED lamp with series fixed on the surface of AgNWs-PET electrode with conductive AgNWs-PET electrode with conductive adhesive was luminous, and it was still luminous after being bent. adhesive was luminous, and it was still luminous after being bent. bent. Author Contributions: H.X., X.Y. and Y.W. conceived and designed the experiments; X.Y., H.X., and D.D. Author Contributions: H.X., X.Y. and Y.W. conceived and designed the experiments; X.Y., H.X., and D.D. performed the H.X. and Y.W. analyzed thethe data; Y.Z. contributed reagents/materials/analysis Author Contributions: H.X., X.Y. and Y.W. conceived and designed the experiments; X.Y., H.X., andtools; D.D. performed theexperiments; experiments; H.X. and Y.W. analyzed data; Y.Z. contributed reagents/materials/analysis and H.X. the paper. AllH.X. authors have analyzed read approved thecontributed final tools; andwrote H.X. wrote the paper. All authors haveand read and approved themanuscript. final manuscript. performed the experiments; and Y.W. the data; Y.Z. reagents/materials/analysis tools; and H.X. wrote the paper. All authors have read and approved the final manuscript. Acknowledgments: This work work was financially financially supported by National National Science Foundation of of China China under under grants grants This was supported by Science Foundation of (61302044, 61671140, 61771118) and State Key Laboratory of Electronic State Key Laboratory of Electronic Thin of (61302044, 61671140, 61771118) and State Keysupported LaboratorybyofNational Electronic State Key Laboratory of Electronic Thin Acknowledgments: This work was financially Science Foundation of China under grants Film and Integrate (Zhongshan) and Zhongshan Science and Technology Projects (2015B2312, 2015B2300). Film and Integrate (Zhongshan) and Science andofTechnology Projects 2015B2300). of (61302044, 61671140, 61771118) andZhongshan State Key Laboratory Electronic State Key(2015B2312, Laboratory of Electronic Thin Conflicts Interest: The authorsand declare no conflict of interest. Film and of Integrate (Zhongshan) Zhongshan Science and Technology Projects (2015B2312, 2015B2300). Conflicts of Interest: The authors declare no conflict of interest. Conflicts of Interest: The authors declare no conflict of interest.


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