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Embedded Ag Grid Electrodes as Current Collector for Ultra-Flexible Transparent Solid-State Supercapacitor Jian-Long Xu, Yan-Hua Liu, Xu Gao, Yilin Sun, Su Shen, Xinlei Cai, Linsen Chen, and Sui-Dong Wang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b06184 • Publication Date (Web): 31 Jul 2017 Downloaded from http://pubs.acs.org on July 31, 2017

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ACS Applied Materials & Interfaces

Embedded Ag Grid Electrodes as Current Collector for Ultra-Flexible Transparent Solid-State Supercapacitor Jian-Long Xu1*, Yan-Hua Liu2*, Xu Gao1, Yilin Sun3, Su Shen2, Xinlei Cai1, Linsen Chen2, Sui-Dong Wang1* 1

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory

for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, P R China 2

College of Physics, Optoelectronics and Energy, Key Lab of Advanced Optical

Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou, Jiangsu 215006, P R China 3

Institute of Microelectronics, Tsinghua National Laboratory for Information Science

and Technology (TNList), Tsinghua University, Beijing 100084, P R China KEYWORDS: Soft-Nanoimprinting, Embedded Ag Grid, Current Collector, Flexible Transparent, Solid-State Supercapacitor

ABSTRACT: Flexible transparent solid-state supercapacitors have attracted immerse attention for the power supply of next-generation flexible “see-through” or “invisible” electronics. 1

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To fabricate such devices, high-performance flexible transparent current collectors are highly desired. In this paper, the utilization of embedded Ag grid transparent conductive electrodes (TCEs) fabricated by a facile soft ultraviolet imprinting lithography method combined with scrap techniques, as the current collector for flexible transparent solid-state supercapacitors, is demonstrated. The embedded Ag grid TCEs exhibit not only excellent optoelectronic (RS ~ 2.0 Ωsq-1 & T ~ 89.74%) but also robust mechanical properties, which could meet the conductivity, transparency and flexibility needs of current collectors for flexible transparent supercapacitors. The obtained supercapacitor exhibits large specific capacitance, long cycling life, high optical transparency (T ~ 80.58 % at 550 nm), high flexibility and high stability. Owing to the embedded Ag grid TCE structure, the device shows a slight capacitance loss of 2.6% even after 1000 cycles of repetitive bending for a bending radius of up to 2.0 mm. This paves the way for developing high-performance current collectors and thus flexible transparent energy storage devices, and their general applicability opens up opportunities for flexible transparent electronics.

1. INTRODUCTION In recent years, flexible transparent electronic devices have attracted immerse attention as promising candidates in many emerging applications, including heads-up display, automobile wind-shield display, electrochromic devices, smart window devices, sensors and conformable products.1-6 A suitable energy storage and power supply

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source is a vital part for realizing such self-powered flexible transparent electronic systems. Typical energy storage devices include flexible transparent supercapacitors and Li-ion batteries that can be intimately attached to clothes or to portable electronic products or even skin at anytime and anywhere, or act as integrated power sources for smart windows.7-11 In past decades, numerous efforts have been devoted to fabricating flexible transparent supercapacitors, and thus great progress has been made.12-17

For

example, Dai et al. reported transparent and stretchable high-performance supercapacitors with wrinkled graphene as current collectors, which exhibited a high transparency (57% at 550 nm) and could be stretched up to 40% strain without obvious performance change over hundreds of cycles.12 Zhou et al. proposed a free-standing flexible transparent molybdenum trioxide nanopaper as both current collector and active electrode materials for flexible transparent supercapacitors with high transmittance and excellent electrochemical behaviors.13 In general, a typical all-solid-state supercapacitor device is composed of current collector, active electrode materials and solid-state electrolytes.18 Most of the previous work about the flexible solid-state supercapacitors mainly focused on the active electrode materials and solid-state electrolytes.12-17, 19-23 The researches and achievements of the high-performance current collectors available for flexible transparent supercapacitors are still very limited. At present, the most widely used current collector for flexible transparent supercapacitors is carbon nanomaterials such as graphene, carbon nanotubes, woven from fabrics, nanostructured carbon, etc.19-22 Carbon nanomaterials

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show excellent mechanical flexibility and rather high transparency. However, their relatively low electrical conductivity is not satisfying for current collector applications in high-performance supercapacitor devices, which obviously influence the charge/discharge process of the device especially under high current density conditions. Another widely used flexible transparent current collector is transparent conductive oxide (TCO), among which the most representative one is indium tin oxide (ITO) TCE.23-24 Nevertheless, their brittleness and high costs for the scarcity of indium make them unsuitable for future flexible transparent current collector applications. Moreover, the embossed Ag grid TCEs fabricated through inkjet-printing or self-assembling methods, have also been adopted as current collectors for flexible transparent supercapacitors, however, large surface non-polarity (~µm) and weak adhesion between the Ag grid and substrate usually lead to poor flexibility and stability behaviors.25-26 Therefore, it is very important and necessary to design and fabricate a suitable current collector with high electrical conductivity and optical transmittance, as well as excellent mechanical flexibility for high-performance flexible transparent supercapacitor applications. Herein, we report the usage of embedded Ag grid TCEs as the current collectors for flexible transparent all-solid-state supercapacitors. The embedded Ag grid electrode is fabricated by employing soft ultra-violet nanoimprinting lithography (UV-NIL) and scraping techniques, which is compatible with standard semiconductor process and beneficial for industry production. In our process, the soft mold can provide a better

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conformal contact with the substrate, and the de-molding process can be achieved by peeling the soft mold from imprinted substrate with an effectively smaller de-molding area, which is extremely beneficial for the attainment of a high aspect-ratio structure replication. The most important is that the soft PUA mold can be replicated thousands of times or even more, which greatly reduces the master fabrication costs. As a result, owing to the embedded Ag grid electrode structure and the Ag nanoparticle properties, the obtained TCE exhibits not only excellent optoelectronic properties but also mechanical robustness to meet the conductivity, transparency and flexibility needs of current collectors for flexible transparent supercapacitors. Utilizing the embedded Ag grid

TCE

as

current

collector,

and

solution-processed

poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) films as the active electrode material, the fabricated flexible transparent all-solid-state supercapacitor is constructed and fabricated on flexible PET substrates. It shows large specific capacitance, long cycling life and high optical transparency (T~80.58% at 550 nm), and meanwhile demonstrates high mechanical flexibility and stability with a slight capacitance loss of 2.6% after 1000 cycles of repetitive bending for a bending radius of up to 2.0 mm, and thus making it suitable for next-generation flexible transparent energy storage devices. The above experimental results demonstrate that the embedded Ag grid TCEs are suitable and promising current collectors for high-performance flexible transparent supercapacitors.

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2. EXPERIMENTAL SECTION 2.1 Fabrication of Embedded Ag Grid TCEs. A schematic diagram of the procedures for fabricating the embedded Ag grid electrode based flexible transparent supercapacitors is given in Figure 1. It comprises the fabrication of embedded Ag grid electrodes, hybrid electrodes and the assembly of supercapacitor devices. First, the photoresist layer on glass substrate was patterned into the brick wall arrangement grooves structure by laser direct-writing techniques. Then the patterned structure was replicated to a soft polyurethane acrylate (PUA) mold. By introducing an intermediate transferring PUA mold generated by UV-NIL, no costliest and time-consuming fabrication steps in traditional semiconductor process such as thermal process, electrodeposition, etc. are required for mold fabrication, which is economical, time-saving and preferred for future low-cost manufacturing. For brick wall arrangement patterns transfer, the patterned PUA soft mold composed of brick arrangement micro-bridges on PET was placed on the dispersed UV-curable resin (D10, PhiChem) on PET and fixed through a roll-to-roll process. Then the UV resin was cured by exposure to UV light (UV light-emitting diode (LED), 1000 mW/cm2) at a distance of 1 cm for only 2 s. After curing, the soft mold was peeled off from the UV resin and the brick wall arrangement micro-grooves pattern were generated in the UV resin on PET substrate. Subsequently, the Ag nanoparticles ink (concentration of 70%, viscosity of 25 cps, and particle diameter between 200 and 300 nm) was drop-dispensed onto the UV resin layer, and the Ag nanoparticles were filled into

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the patterned micro-grooves through scrape techniques. Next, the resultant film was sintered at 80 oC for 20 min and the embedded conductive brick arrangement Ag grid was thus obtained in the UV resin. The thickness of the obtained Ag grid is about 2 µm, and it can be simply modified by the Ag ink concentration and scraping cycles. Meanwhile, to further construct flexible devices, the wiping process with nontoxic organic solvents is preferred for obtaining clear surfaces. It is noteworthy that the above fabrication process of embedded Ag grid TCE is free from complicated vacuum-based processes and is entirely solution-processed at low temperatures, which is essential for low cost manufacturing. 2.2 Fabrication of Embedded Ag Grid/PEDOT: PSS Hybrid TCEs. The embedded Ag grid/PEDOT: PSS hybrid electrode was then fabricated by spin-coating PEDOT: PSS solution (1.3 wt. % dispersion in H2O, purchased from Sigma-Aldrich, and then mixed with 7.0 wt. % ethylene glycol and 0.25 wt. % surfactant Triton-X 100) onto the embedded Ag grid electrodes. Before spin-coating, the electrode surface was treated with oxygen plasma for 10 s to enhance its wettability. The spin-coating process was performed at 3000 rpm for 40 s and the as-prepared film was annealed at 120 ℃ for 20 min in air ambient for PEDOT: PSS film curing. 2.3 Assembly of Flexible Transparent All-Solid-State Supercapacitor Device. For all-solid-state supercapacitor applications, the polymer electrolyte (PE) was firstly prepared as follows: 10 mL of concentrated H3PO4 was added into 90 mL of deionized water, followed by 10 g of poly (vinyl alcohol) (Mw~19500, PVA) powder. The 7



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whole mixture was then heated to 90℃ while stirring constantly until the solution became clear. After cooling down, the electrolyte was sequentially drop-dispersed onto the embedded Ag grid/PEDOT: PSS hybrid electrode surface. Before the assembly of the supercapacitor device, the hybrid TCE film was painted with silver paste and then attached to the copper wires for electrochemical measurements. Subsequently, with the assembly of another hybrid TCE film, they were pressed together under a constant pressure for a period of time, making the PE spread over uniformly between them and the two electrode films tightly sticking together. After drying for 2 days under ambient conditions, the flexible transparent all-solid-state supercapacitors were obtained. 2.4 Characterization. The surface morphologies and sheet resistance levels of the embedded Ag grid TCE and embedded Ag grid /PEDOT: PSS hybrid TCE were characterized by field emission scanning electron microscopy (SEM) (Carl Zeiss, Supra 55) and a four-point probe system (CMT SR2000, A. I. T.), respectively. The collimated transmittance spectra in the visible range (300-800 nm) of the fabricated TCEs and supercapacitors were measured using a UV-vis spectrophotometer (UV-2550, SHIMADZU). All the electrochemical measurements of the supercapacitors were performed in a two-electrode system with a CHI 660B electrochemical workstation (Shanghai CH Instrument Company, China).

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The specific capacitance of the supercapacitor with thin film electrode systems in our work is determined by the area capacitance, which can be calculated as follows: CA =

1 I ( t )dt ∆V ⋅ A ∫

(1)

Where ∆V is the potential range, I(t) is the measured current during CV testing, t is the time and A is the area of the electrodes (1.5 cm×1.5 cm in our experiments). Moreover, the electrochemical impedance spectroscopy measurements were carried out at open circuit potential with a sinusoidal signal over a frequency ranged from 0.1 Hz to 100 kHz at amplitude of 10 mV.

3. RESULTS AND DISCUSSION

Figure 1. Schematic illustrations of the fabrication process for the embedded Ag grid TCEs and thus the flexible transparent solid-state supercapacitors: (a) Photoresist spin-coating, (b) Laser direct-writing patterning, (c) PUA mold forming, (d) Soft nanoimprinting, (e) Ag ink scraping, (f) 9



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PEDOT: PSS spin-coating and thin film forming, (g) Electrolyte drop-casting and (h) Device assembling

A representative scanning electron microscopy (SEM) image of the embedded Ag grid TCE is presented in Figure 2a, and it can be clearly observed that the large area embedded Ag grid pattern is distributed uniformly in the UV resin layer. The period of brick arrangement Ag grid is about 320 µm, and the Ag grid width is 4 µm. After the deposition of PEDOT: PSS layer by spin-coating process, the Ag grid TCE maintains its original surface morphology as evidenced by low magnification SEM images (Figures 2a and S1), indicating the high transparency of PEDOT: PSS films. The Ag nanoparticles are fully and neatly filled into the patterned microgrooves (Figure 2b), and the diameter of Ag nanoparticles are found to be 200-300 nm (Figure S2). Moreover, after spin-coating PEDOT: PSS, all Ag nanoparticles in the patterned microgroove are coated by PEDOT: PSS the voids between the Ag nanoparticles are also bridged by the solution-processed PEDOT: PSS layer. The resultant PEDOT: PSS layer on the embedded Ag grid electrode surface shows smooth and continuous coverage on the UV resin and also the Ag grid surface. Therefore, the electrical conductivity and surface roughness of the embedded Ag grid/PEDOT: PSS hybrid TCE can be improved drastically, making it more suitable for device applications. Meanwhile, the PEDOT: PSS layer here also contributes to the electrochemical performances of the supercapacitor.

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The obtained large-scale embedded Ag grid TCE exhibits excellent optoelectronic and mechanical flexibility properties. As shown in Figure 2d, the obtained embedded Ag grid TCE on PET possesses a high transmittance around 90% within a broad spectrum from 400 - 800 nm (89.54% at 550 nm), with the bare PET substrate exhibiting the transmittance of 92% within the visible spectrum. After coating with the PEDOT: PSS layer, the embedded Ag grid/PEDOT: PSS hybrid TCE exhibits a satisfactory transmittance of around 88% (87.54% at 550 nm), which is reduced by only 2% compared to that before PEDOT: PSS layer spin-coating. Meanwhile, the obtained Ag grid TCE exhibits high electrical conductivity with the sheet resistance as low as 2.0 Ωsq-1, lower than most other reported flexible transparent conductive electrodes. Therefore, the high electrical conductivity and optical transmittance of the embedded Ag grid TCE are both beneficial to act as the high-performance current collectors of the flexible transparent supercapacitors. In addition, the digital photograph of the Ag grid TCE with a large size of 15 cm×15 cm exhibits excellent flexibility, high transparency, and can lighten up a LED lamp, as shown in the inset image of Figure 2d. Furthermore, for flexible device applications, the mechanical flexibility and stability properties of the embedded Ag grid TCEs are evaluated by measuring the normalized sheet resistance change ∆R/Rinitial after bending process in which ∆R is the change in sheet resistance and Rinitial is the initial sheet resistance of the embedded Ag grid electrodes before any bending process. Figure 2e illustrates the sheet resistance change

versus bending times of the commercial ITO TCE and our embedded Ag grid TCE

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with a bending radius of 10 mm with the commercial ITO TCE as a comparison. The

∆R/Rinitial of the commercial ITO electrode increases sharply after just 500 repetitive bending cycles and becomes nearly nonconductive, however, the embedded Ag grid electrode displays excellent mechanical flexibility. Even after 10000 repetitive bending cycles, the ∆R/Rinitial value is almost zero, or the resistance after 10000 repetitive bending cycles almost keeps the same with that before any bending process, indicating the excellent bending stability properties of the embedded Ag grid TCE. Figure 2f presents the ∆R/Rinitial of the commercial ITO and embedded Ag grid electrodes under no bending and various bending radii ranging from 3.5 mm to 0.5 mm. The ∆R/Rinitial value can almost be negligible even though the bending radius becomes approximately as small as 0.5 mm, demonstrating the excellent mechanical flexibility properties of our embedded Ag grid TCE. Figure S3 shows the SEM images of commercial ITO and our Ag grid TCEs before any bending process and after 10000 repetitive bending cycles with a radius of 2 mm. As can be seen, there are obvious cracks in commercial ITO TCEs along the direction perpendicular to the bending stress, which greatly deteriorates its electrical performances and thus limits its applications in flexible devices. However, for our Ag grid based TCE, uniform electrode surface excluding any microscopic cracks can be observed. The excellent mechanical flexibility and stability of the Ag grid TCE shown above can be attributed to its embedded nature, which helps to retain the Ag nanoparticles firmly attached to the UV resin micro-grooves under various bending conditions. The electro-optical and mechanical flexibility properties

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of our fabricated embedded Ag grid TCE and other Ag grid TCEs are summarized in Table S1. The embedded Ag grid TCE in this work demonstrates not only excellent optoelectronic (RS ~ 2.0 Ωsq-1 & T ~ 89.74%) but also mechanically flexible properties (no degradation after 10000 repetitive bending cycles), superior to other Ag grid based TCEs fabricated by other techniques such as inkjet-printing,26 selective laser sintering,27 thermal-processing,28 direct imprinting,29 etc. Benefitting from this, the supercapacitors utilizing the embedded Ag grid TCE as the current collector are also expected to exhibit superior mechanical flexibility behaviors.

Figure 2. Structural, optoelectronic and flexible properties of the embedded Ag grid TCEs: (a)

Top SEM images of embedded Ag grid TCE, scale bar: 400 µm, (b) Magnified SEM image of

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embedded Ag grid TCE, scale bar: 5 µm, (c) Magnified SEM image of embedded Ag grid/PEDOT: PSS hybrid TCE, scale bar: 5 µm. (d) Transmittance spectra of the embedded Ag grid TCE and embedded Ag grid/PEDOT: PSS hybrid TCE on PET substrates. Insets are the photographs of the fabricated embedded Ag grid TCEs indicating its large-scaled, excellent electrical conductivity and high optical transparency properties. (e) Sheet resistance change versus bending times properties with a bending radius of 10 mm and (f) variations of the sheet resistance as a function of bending radius properties of the fabricated embedded Ag grid TCE on PET and commercial ITO/PET TCEs.

The fabricated supercapacitor device achieves a high transparency with a ~80% transmittance in the visible light range (80.58% at 550 nm), while the transmittance of the Ag grid TCE/PET and PEDOT: PSS/Ag grid/PET hybrid TCE is measured to be 89.74% and 88.91% at 550 nm, respectively, as shown in Figure 3a. The optical transmittance of our supercapacitor device is higher than most previous reported ones. As shown in the inset photograph, the supercapacitor device is sufficiently transparent and the leaf behind it can be seen clearly, which is very promising for the future smart invisible electronics applications. The overall high transmittance of solid-state supercapacitor device can be attributed to the high transmittance of our embedded Ag grid electrodes, solution processed PEDOT: PSS films and also the electrolyte. The transmittance of the devices can be further improved by using thinner PET substrates or enlarging the period of Ag grid. Figure 3b presents the typical cyclic voltammetry

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(CV) curves of a single supercapacitor device at a scan rate of 0.01, 0.05, 0.10, 0.20, 0.50 and 1.00 V/s, respectively. The supercapacitor device shows almost rectangular CV curves even at a relatively high scan rate of 1.00 V/s, indicating the good energy capacitive performance and rate capability. The CV curves show a pair of redox waves at around 0.45 V, resulting from the capacitive behaviors of PEDOT: PSS films. At a low scan rate of 0.01 V/s, the area capacitance CA is calculated to be 2.79 mF/cm2 according to the equation (1), decreasing to be 0.85 mF/cm2 with the scan rate increasing to 1.00 V/s, as shown in Figure 3c. The electrochemical properties shown above are superior to many reported electric double-layer capacitors (EDLCs) including graphene, carbon nanotubes, nanoporous carbon, etc.,30-32 which can be attributed to the excellent conductivity of our embedded Ag grid current collectors and relatively high electrochemical properties of PEDOT: PSS electrode layers. Although this specific capacitance value of the fabricated device is lower when compared to other supercapacitors based on high capacity conducting polymers such as polyaniline,33-34 PEDOT: PSS still exhibits some advantages over other high capacity conducting polymers in terms of electrochemical activity in a wide potential window and electrical activity in aqueous, organic and ionic liquid electrolytes. The specific capacitance can be improved by increasing the PEDOT: PSS film thickness,35 however, thicker PEDOT: PSS film will decrease the device optical transparency. It is a trade-off between transparency and electrochemical performances, and which one is preferred depends on the practical application situations.

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Figure 3d shows the galvanostatic charge/discharge (GCD) curves of the corresponding supercapacitor device in the potential range of 0-0.8 V at different current densities of 0.05, 0.10, 0.15, 0.20 and 0.25 mA/cm2. All GCD curves exhibit almost linear profiles and nearly symmetric triangular shapes with almost negligible voltage drops at the initial region of the discharge curve, which further confirms the good capacitance behaviors of the device. Moreover, a slight inflection can be observed in GCD curves corresponding to the redox wave in the CV curves. With the increasing of applied current density, the time required for a charge/discharge cycle decreases from 18.3 s (0.05 mA/cm2) to 2.2 s (0.25 mA/cm2), indicating fast charge propagation processes across the electrodes and thus the low equivalent series resistance (ESR) value of the device. Additionally, the frequency responses of the device are also examined by electrochemical impedance spectroscopy (EIS) measurements as presented in Figure 3e. The straight line is almost parallel to the imaginary axis in the low frequency regions and the absence of semicircle in the high frequency regions can also be observed from the Nyquist plots, indicating no charge transfer resistance and high ionic conductivity at electrode/electrolyte interfaces.36 The vertical nature of the spectrum with respect to the imaginary axis is illustrative of the high rate capability of our supercapacitor device. The inset shows the zoom-in view of the impedance spectra in the high frequency region, from which the ESR value can be extracted from the x-intercept. The extracted ESR value is much lower than those of most reported EDLC supercapacitors, arising from the high conductivity of embedded Ag grid cur-

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rent collector. It is consistent with the above CV and GCD results that an ideal capacitive behavior and a very low equivalent series resistance in the device can be observed benefiting from the ultrahigh conductivity of the embedded Ag grid current collector and also the good conductivity and electrochemical performance of PEDOT: PSS film. Furthermore, the cycling stability is a critical parameter for practical applications. Figure 3f presents the electrochemical cycling stability properties of our supercapacitor device. It can be seen that the device can maintain more than 92% of the initial capacitance value even after 10000 continuous charge/discharge cycles, indicating the excellent electrochemical cycling stability. The good cycling stability properties can be attributed to the relatively good electrochemical stability of PEDOT: PSS layer and the good encapsulation effects of PEDOT: PSS layer on the embedded Ag grid current collectors. Moreover, the symmetric sandwiched structure of our supercapacitor device also results in good encapsulation capacity of the gel electrolyte and thus the excellent air stability.

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Figure 3. Optical and electrochemical performances of the flexible transparent all-solid-state su-

percapacitors utilizing the embedded Ag grid TCE as current collectors: (a) Transmittance spectra of the embedded Ag grid TCE (black), embedded Ag grid/PEDOT: PSS/ hybrid TCE (red) and the hybrid TCE based flexible transparent supercapacitors (blue). Inset shows the digital paragraph of our fabricated flexible transparent supercapacitor device. (b) Typical capacitance versus potential (CV) curves of the supercapacitor device at a scan rate of 0.01, 0.05, 0.10, 0.20, 0.50 and 1.00 V/s, respectively. (c) Area capacitance of the supercapacitance device measured as a function of the 18


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scan rate. (d) Potential versus time (GCD plot) curves of the supercapacitor at different applied current densities. (e) Imaginary impedance Z’’ versus real impedance Z’ (Nyquist plot) in the frequency range from 0.1 Hz to 100 KHz. Inset shows the magnified part for the low real impedance part. (f) Capacitance retention versus charge/discharge cycles properties of the supercapacitor device.

The fabricated transparent supercapacitor device utilizing the embedded Ag grid electrodes as current collector depicted above also shows excellent mechanical flexibility properties, as presented in Figure 4. Here, the scan rate is set as 1.00 V/s during the CV curves measurement. Inset of Figure 4a shows the CV curves of the supercapacitor device without bending and under different bending radii of 12.0, 7.0, 6.0, 5.0, 4.0 and 2.0 mm. It can be clearly seen that the device shows no noticeable performance degradation in the CV curves with the bending radius decreasing from 12.0 mm to 2.0 mm, and also compared to the case before any bending process. The normalized area capacitance is extracted from the measured CV curves and plotted in Figure 4a. The resulting supercapacitor device exhibits stable electrochemical performance with a slight area capacitance loss of 1.2% at a bending radius of 2.0 mm at a scan rate of 1.00 V/s. Moreover, the device also processed good cycling stability in the bending and relaxing tests. As shown in Figure 4b, after repetitive bending for 1000 times at a bending radius of 2.0 mm, the resulting area capacitance remains almost constant with a slight decrease within 2.6 % at a scan rate of 1.00 V/s. This mechanical flexibility is

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comparable or higher than those of most previously reported flexible transparent supercapacitors. Obviously, this arises from the good mechanical robustness of the embedded Ag grid current collector (Figures 2e - 2f), PEDOT: PSS films and also the solid-state PVA/H3PO4 electrolyte. Combined with the high optical transparency (Figure 3a), the supercapacitor device is promising for application in flexible transparent energy storage and power supply devices for “see-through” or “invisible” electronics. Therefore, we can declare that our fabricated embedded Ag grid electrode with high optical transparency, high conductivity and good mechanical flexibility is an excellent current collector for flexible transparent solid-state supercapacitors.

Figure 4. Mechanical flexibility properties of the flexible transparent supercapacitor devices uti-

lizing the embedded Ag grid TCE as current collectors: (a) Capacitance retention versus bending 20


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radius curves. Inset shows the CV curves of the supercapacitor device under no bending and with a bending radius of 12.0, 7.0, 6.0, 5.0, 4.0 and 2.0 mm at a scan rate of 1.00 V/s. (b) Capacitance retention properties of the supercapacitor as a function of repetitive bending times at a bending radius of 2 mm. Inset exhibits the corresponding CV curves before and after repetitive bending to 2 mm for different times at a scan rate of 1.00 V/s.

4. CONCLUSIONS

In conclusion, we have fabricated a high-performance ultra-flexible transparent all-solid-state supercapacitor using the embedded Ag grid TCE as the current collector. The embedded Ag grid TCE, fabricated by a facile soft ultraviolet imprinting lithography method combined with scrap techniques, exhibit not only excellent optoelectronic (RS ~ 2.0 Ωsq-1 & T ~ 89.74%) but also mechanically flexible properties, which could meet the conductivity, transparency and flexibility needs of current collectors for flexible transparent supercapacitors. Combined with solution-processed PEDOT: PSS films as active electrode materials, the fabricated supercapacitor devices exhibit large specific capacitance, long cycling life, high optical transparency and meanwhile maintain high flexibility and stability. The excellent performance of the device is attributed to the ultra-high conductivity and transparency (to compete with ITO and carbon materials), remarkable mechanical flexibility (to tolerate small bending radii for repetitive bending cycles, owing to the embedded nature of the Ag grid) of the embedded Ag grid electrode, and the excellent electrochemical properties of the 21



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PEDOT: PSS. Meanwhile, the fabricated process based on the roll-to-roll UV-NIL and scrap techniques is facile and amenable to scale up. Such embedded Ag grid TCE, acting as the current collector, could find wide applications in future supercapacitors and other energy storage devices.

ASSOCIATED CONTENT

Supporting Information The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org. SEM images of the PEDOT: PSS/embedded Ag grid hybrid electrode and Ag nanoparticles.

AUTHOR INFORMATION Corresponding Author *Email: [email protected] (Jian-Long Xu) *Email: [email protected] (Yan-Hua Liu) *Email: [email protected] (Sui-Dong Wang)

Author Contributions

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All authors contributed to the experimental design and data analyses. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Notes Any additional relevant notes should be placed here.

ACKNOWLEDGMENT We acknowledge financial support from the National Natural Science Foundation of China (Nos. 61675143, 11661131002, 61405133, 91323303 and 61575133), from the Natural Science Foundation of Jiangsu Province (Nos. BK20160328 and BK20140348) and from the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133201120027). This project is also funded by the Collaborative Innovation Center of Suzhou Nano Science and Technology, and by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

REFERENCES 1. Nomura, K.; Ohta, H.; Takagi, A.; Kamiya, T.; Hirano, M.; Hosono, H. Room-Temperature Fabrication of Transparent Flexible Thin-Film Transistors Using Amorphous Oxide Semiconductors. Nature 2004, 432, 488-492. 2. Duy, L. T.; Trung, T. Q.; Dang, V. Q.; Hwang, B. –U.; Siddiqui, S.; Son, II-Y.; Yoon, S. K.; Chung, D. J.; Lee, N. –E. Flexible Transparent Reduced Graphene Oxide Sensor 23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Coupled with Organic Dye Molecules for Rapid Dual‐Mode Ammonia Gas Detection. Adv. Funct. Mater. 2016, 26, 4329-4338. 3. Zhang, J. L.; Wang, C.; Zhou, C. W. Rigid/Flexible Transparent Electronics Based on Separated Carbon Nanotube Thin-Film Transistors and Their Application in Display Electronics. ACS Nano 2012, 6, 7412-7419. 4. Georgiou, T.; Jalil, R.; Belle, B. D.; Britnell, L.; Gorbachev, R. V.; Morozov, S. V.; Kim, Y. J.; Gholinia, A.; Haigh, S. J.; Makarovsky, O.; Eaves, L.; Ponomarenko, L. A.; Geim, A. K.; Novoselov, K. S.; Mishchenko, A. Vertical Field-Effect Transistor Based on Graphene-WS2 Heterostructures for Flexible and Transparent Electronics. Nat. Nanotechnol. 2013, 8, 100-103. 5. Wang, J. X.; Yan, C. Y.; Lin, M. –F.; Tsukagoshi, K.; Lee, P. S. Solution-Assembled Nanowires for High Performance Flexible and Transparent Solar-Blind Photodetectors. J. Mater. Chem. C 2015, 3, 596-600. 6. Zhang, C. F.; Higgins, T. M.; Park, S. –H.; O’Brien, S. E.; Long, D. H.; Coleman, J. N.; Nicolosi, V. Highly Flexible and Transparent Solid-State Supercapacitors Based on RuO 2/PEDOT:

PSS Conductive Ultrathin Films. Nano Energy 2016, 28, 495-505.

7. Chen, T.; Dai, L. M. Flexible Supercapacitors Based on Carbon Nanomaterials. J. Mater. Chem. A 2014, 2, 10756-10775. 8. Zhou, G. M.; Li, F.; Cheng, H. –M. Progress in Flexible Lithium Batteries and Future Prospects. Energy Environ. Sci. 2014, 7, 1307-1338.

24


Page 24 of 29

Page 25 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9. Zuo, W. H.; Li, R. Z.; Zhou, C.; Li, Y. Y.; Xia, J. L.; Liu, J. P. Battery-Supercapacitor Hybrid Devices: Recent Progress and Future Prospects. Adv. Sci. 2017, 1600539. 10. Zang, X. B.; Chen, Q.; Li, P. X.; He, Y. J.; Li, X.; Zhu, M.; Li, X. M.; Wang, K. L.; Zhong, M. L.; Wu, D. H.; Zhu, H. W. Highly Flexible and Adaptable, All‐Solid‐State Supercapacitors Based on Graphene Woven‐Fabric Film Electrodes. Small 2014, 10, 2583-2588. 11. Wang, K.; Wu, H.; Meng, Y.; Zhang, Y.; Wei, Z. Integrated Energy Storage and Electrochromic Function in One Flexible Device: An Energy Storage Smart Window. Energy Environ. Sci. 2012, 5, 8384-8389. 12. Chen, T.; Xue, Y.; Roy, A. K.; Dai, L. Transparent and Stretchable High-Performance Supercapacitors Based on Wrinkled Graphene Electrodes. ACS Nano 2013, 8, 1039-1046. 13. Yao, B.; Huang, L.; Zhang, J.; Gao, X.; Wu, J.; Cheng, Y.; Xiao, X.; Wang, B.; Li, Y.; Zhou, J. Flexible Transparent Molybdenum Trioxide Nanopaper for Energy Storage. Adv. Mater. 2016, 28, 6353-6358. 14. Li, N.; Huang, X.; Zhang, H.; Li, Y.; Wang, C. Transparent and Self-Supporting Graphene Films with Wrinkled-Graphene-Wall-Assembled Opening Polyhedron Building Blocks for High Performance Flexible/Transparent Supercapacitors. ACS Appl. Mater. Interfaces 2017, 9, 9763-9771. 15. Li, N.; Yang, G.; Sun, Y.; Song, H.; Cui, H.; Yang, G. W.; Wang, C. Free-Standing and Transparent Graphene Membrane of Polyhedron Box-Shaped Basic Building Units Di-

25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

rectly Grown Using a NaCl Template for Flexible Transparent and Stretchable Solid-State Supercapacitors. Nano Lett. 2015, 15, 3195-3203. 16. Liu, Y. H.; Xu, J. L.; Shen, S.; Cai, X. L.; Chen, L. S.; Wang, S. D. High-Performance, Ultra-Flexible and Transparent Embedded Metallic Mesh Electrodes by Selective Electrodeposition for All-Solid-State Supercapacitor Applications. J. Mater. Chem. A 2017, 5, 9032-9041. 17. Higgins, T. M.; Coleman, J. N. Avoiding Resistance Limitations in High-Performance Transparent Supercapacitor Electrodes Based on Large-Area, High-Conductivity PEDOT: PSS Films. ACS Appl. Mater. Interfaces 2015, 7, 16495- 16506. 18. Lu, X. H.; Yu, M. H.; Wang, G. M.; Tong, Y. X.; Li, Y. Flexible Solid-State Supercapacitors: Design, Fabrication and Applications. Energy Environ. Sci. 2014, 7, 2160-2181. 19. Yu, A.; Roes, I.; Davies, A.; Chen, Z. Ultrathin, Transparent, and Flexible Graphene Films for Supercapacitor Application. Appl. Phys. Lett. 2010, 96, 253105. 20. Chen, T.; Peng, H.; Durstock, M.; Dai, L. High-Performance Transparent Stretchable All-Solid Supercapacitors based on Highly Aligned Carbon Nanotube Sheets. Sci. Reports 2014, 4, 3612. 21. Jung, H. Y.; Karimi, M. B.; Hahm, M. G.; Ajayan, P. M.; Jung, Y.J. Transparent, Flexible Supercapacitors from Nano-Engineered Carbon Films. Sci. reports 2012, 2, 773. 22. Gao, K.; Shao, Z.; Wu, X.; Wang, X.; Zhang, Y.; Wang, W.; Wang, F. Paper-Based Transparent Flexible Thin Film Supercapacitors. Nanoscale 2013, 5, 5307-5311.

26


Page 26 of 29

Page 27 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


23. Liu, X. Y.; Gao, Y. Q.; Yang, G. W. A Flexible, Transparent and Super-Long-Life Supercapacitor Based on Ultrafine Co3O4 Nanocrystal Electrodes. Nanoscale 2016, 8, 4227-4235. 24. Xue, M.; Xie, Z.; Zhang, L.; Ma, X.; Wu, X.; Guo, Y.; Song, W.; Li, Z.; Cao, T. Microfluidic Etching for Fabrication of Flexible and All-Solid-State Micro Supercapacitor Based on MnO2 Nanoparticles. Nanoscale 2011, 3, 2703-2708. 25. Cai, G.; Darmawan, P.; Cui, M. Q.; Wang, J. X.; Chen, J. W.; Magdassi, S.; Lee, P. S. Highly Stable Transparent Conductive Silver Grid/PEDOT: PSS Electrodes for Integrated Bifunctional Flexible Electrochromic Supercapacitors. Adv. Energy Mater. 2016, 6, 1501882. 26. Cheng, T.; Zhang, Y.; Yi, J. P.; Yang, L.; Zhang, J.; Lai, W. Y.; Huang W. Inkjet-Printed Flexible, Transparent and Aesthetic Energy Storage Devices Based on PEDOT: PSS/Ag Grid Electrodes. J. Mater. Chem. A 2016, 4, 13754-13763. 27. Hong, S.; Yeo, J.; Kim, G.; Kim, D.; Lee, H.; Kwon, J.; Lee, H.; Lee, P.; Ko, S. H. Nonvacuum Maskless Fabrication of a Flexible Metal Grid Transparent Conductor by Low-temperature Selective Laser Sintering of Nanoparticle Ink. ACS Nano 2013, 7, 5024-5031. 28. Lee, Y.; Jin, W. Y.; Cho, K. Y.; Kang, J. W.; Kim, J. Thermal Pressing of a Metal-Grid Transparent Electrode into a Plastic Substrate for Flexible Electronic Devices. J. Mater. Chem. C 2016, 4, 7577-7583.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

29. Oh, Y. S.; Choi, D. Y.; Sung, H. J. Direct Imprinting of Thermally Reduced Silver Nanoparticles via Deformation-Driven Ink Injection for High-Performance, Flexible Metal Grid Embedded Transparent Conductors. RSC Adv. 2015, 5, 64661-64668. 30. In, J. B.; Hsia, B.; Yoo, J. H.; Hyun, S.; Carraro, C.; Maboudian, R.; Grigoropoulos, C. P. Facile Fabrication of Flexible All Solid-State Micro-Supercapacitor by Direct Laser Writing of Porous Carbon in Polyimide. Carbon 2015, 83, 144-151. 31. Sheng, K.; Sun, Y.; Li, C.; Yuan, W.; Shi, G. Ultrahigh-Rate Supercapacitors Based on Eletrochemically Reduced Graphene Oxide for AC Line-Filtering. Sci. Reports 2012, 2, 247. 32. Pu, J.; Wang, X.; Xu, R.; Komvopoulos, K. Highly Stretchable Microsupercapacitor Arrays with Honeycomb Structures for Integrated Wearable Electronic Systems. ACS Nano 2016, 10, 9306. 33. Song, B.; Li, L.; Lin, Z.; Wu, Z. K.; Moon, K. S.; Wong, C. P. Water-Dispersible Graphene/Polyaniline Composites for Flexible Micro-Supercapacitors with High Energy Densities. Nano Energy 2015, 16, 470-478. 34. Wang, K.; Zou, W.; Quan, B.; Yu, A.; Wu, H.; Jiang, P.; Wei, Z. An All‐Solid‐State Flexible Micro‐Supercapacitor on a Chip. Adv. Energy Mater. 2011, 1, 1068-1072. 35. Kurra, N.; Hota, M. K.; Alshareef, H. N. Conducting Polymer Micro-Supercapacitors for Flexible Energy Storage and AC Line-Filtering. Nano Energy 2015, 13, 500-508.

28


Page 28 of 29

Page 29 of 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


36. Pushparaj, V. L.; Shaijumon, M. M.; Kumar, A.; Murugesan, S.; Ci, L.; Vajtai, R.; Linhardt, R. J.; Nalamasu, O.; Ajayan, P. M. Flexible Energy Storage Devices Based on Nanocomposite Paper. Proc. Nat. Acad. Sc. U. S. A. 2007, 104, 13574-13577.

Table of Content

Flexible transparent solid-state supercapacitors were achieved utilizing the embedded Ag grid transparent conductive electrodes (TCEs) fabricated by a facile soft ultraviolet imprinting lithography method combined with scrap techniques as the current collector. 29


Embedded Ag Grid Electrodes as Current Collector ... - ACS Publications

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