TW202209353A - Modified cellulose nanofiber-nanosilver wire conductive film and its manufacturing method and photovoltaic device containing the same - Google Patents

Abstract

The present invention relates to a modified cellulose nanofiber-nanosilver wire conductive film and its manufacturing method and photovoltaic device containing the same. The modified cellulose nanofiber-nanosilver wire conductive film has low coefficient of thermal expansion, excellent transparency, and maintaining certain sheet resistance after many times of bending. The photovoltaic device comprises the modified cellulose nanofiber-nanosilver wire conductive film as conductive film, providing bendability and great power conversion efficiency.

Description

Modified cellulose nanofiber-nanosilver wire conductive film and its manufacturing method and photovoltaic device containing the same

The present invention relates to a method for manufacturing a modified cellulose nanofiber-nanosilver wire conductive film and a photovoltaic device containing the same. The photovoltaic device of the present invention has bendability.

In response to user needs, many new products have been developed into curved or bendable optoelectronic products, such as curved screens and foldable smartphones. Following this trend, photovoltaic power supply technology has also begun to develop flexible organic photovoltaics (OPVs). In addition to the advantages of bendability, bendable organic photovoltaics are lightweight and printable, and at the same time, they are easy to integrate with fabrics or biocompatible substrates, and have great development and market value.

The most efficient bendable organic photovoltaics today use plastics as bendable substrates, such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Previous studies have found that the power conversion efficiency (PCE) of bendable organic photovoltaics can be higher than 13 when using grid-like polyterephthalic acid/silver nanowires (AgNWs) as bendable substrates. %, while the power conversion efficiency can be further increased to 15% when the bendable organic photovoltaics are welded to polyethylene terephthalic acid (PET). However, plastic bendable substrates are polymer substrates with high thermal expansion coefficients, which are prone to severe expansion or contraction under a wide range of temperature changes, resulting in cracks and reduced power conversion efficiency.

In view of the defects of polymer substrates, it is necessary to develop a bendable substrate or a bendable conductive substrate that is more conducive to the use of bendable organic photovoltaics. Organic photovoltaics can withstand a wide range of temperature changes, and are not easy to expand or contract, reducing power conversion efficiency.

Therefore, the purpose of the present invention is to provide a method for manufacturing a modified cellulose nanofiber-nanosilver wire conductive film, comprising: (a) providing a substrate; (b) spraying a nanosilver wire solution onto the substrate (c) distribute a modified cellulose nanofiber solution on the surface of the silver nanowire conductive layer, and form a modified cellulose nanofiber after heating nanofiber layer-nanosilver wire conductive layer; (d) peeling the modified cellulose nanofiber layer-nanosilver wire conductive layer from the surface of the substrate to obtain the modified cellulose nanofiber-nanometer Silver wire conductive film.

In a preferred embodiment, the manufacturing method further comprises: (e) hot pressing the modified cellulose nanofiber-nanosilver wire conductive film.

In a preferred embodiment, the substrate is a silicon substrate, and its surface is treated with a silane compound.

In a preferred embodiment, the silane compound is octadecyltrichlorosilane (ODTS).

In a preferred embodiment, the modified cellulose nanofibers in the modified cellulose nanofiber solution are TEMPO oxidized cellulose nanofibers (TOCN).

In a preferred embodiment, the silver nanowire solution comprises silver nanowires and an organic solvent, and the ratio of the silver nanowires and the organic solvent is 1:10-1:15 (v/v).

In a preferred embodiment, the ratio of the silver nanowires and the organic solvent is 1:12.5 (v/v).

In a preferred embodiment, the organic solvent is isopropanol.

Another object of the present invention is to provide a modified cellulose nanofiber-nanosilver wire conductive film, which is obtained by using the manufacturing method of the modified cellulose nanofiber-nanosilver wire conductive film of the present invention.

Another object of the present invention is to provide a photovoltaic device including a first electrode, an electron transport layer, an active layer, a hole transport layer and a second electrode in sequence; wherein the first electrode is one of the present invention Modified cellulose nanofibers-nanosilver wire conductive film.

Compared with the prior art, the manufacturing method of the present invention can firmly confine the silver nanowires on the surface of the substrate, and provide strong adhesion, avoid heat-induced aggregation, and enable the modified fibers to be formed with subsequent films. The pure nanofiber layer is completely attached and not easy to separate. The modified cellulose nanofiber-nanosilver wire conductive film obtained by the manufacturing method of the present invention has a low thermal expansion coefficient, good light penetration, is not easy to scatter, and still maintains a certain film resistance after being bent for many times. Compared with other photovoltaic devices using biocompatible materials as conductive films, the photovoltaic device of the present invention uses the modified cellulose nanofiber-silver nanowire conductive films as conductive films, which has bendability and good power conversion efficiency.

The following embodiments should not be construed to unduly limit the invention. Modifications and variations of the embodiments discussed herein can be made by those of ordinary skill in the art to which this invention pertains without departing from the spirit or scope of the invention, and still fall within the scope of the invention. Hereinafter, the overall structure of the machine for automatic nucleic acid extraction according to the present invention and related use procedures will be described with reference to the drawings.

Please refer to FIG. 1 , which is a schematic flowchart of the manufacturing method of the modified cellulose nanofiber-nanosilver wire conductive film of the present invention.

The manufacturing method of the modified cellulose nanofiber-nanosilver wire conductive film of the present invention comprises: (a) providing a substrate S, in a preferred embodiment, the substrate S has a modified surface B; (b) ) spray a nano-silver wire solution 1 to the modified surface B of the substrate S (as shown in FIG. 1 , the spray nozzle SP sprays the nano-silver wire solution 1 to the modified surface B), and forms a nano-silver wire after heating The silver wire conductive layer 1'; (c) a modified cellulose nanofiber solution 2 is distributed on the nanosilver wire conductive layer 1', and a modified cellulose nanofiber layer-nanofiber layer is formed after heating The silver wire conductive layer 3'; (d) the modified cellulose nanofiber layer-nanosilver wire conductive layer 3' is peeled off from the surface of the substrate S to obtain the modified cellulose nanofiber-nanometer Silver wire conductive film 3; further, (e) hot pressing the modified cellulose nanofiber-nano silver wire conductive film 3 (as shown in Figure 1, using a hot press HP to hot press the modified cellulose nanofiber Rice fiber-nanosilver wire conductive film 3).

The substrate S can be a silicon substrate, and its surface can be modified by using a silane compound, so as to facilitate the subsequent peeling of the film. The silane compound can be alkyl chlorosilanes, alkyl alkoxy silanes, fluorinated alkyl chlorosilanes or fluorinated alkyl alkoxy silanes, etc. disilazane, octyltrichlorosilane, phenethyltrichlorosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltris(n-propyl) ) oxysilane, n-octadecyltri(isopropyl)oxysilane, triethoxyaminopropylsilane, N[(3-triethoxysilyl)propyl]ethylenediamine, 3 - Glycidyl triethoxypropyl ether silane, allyl trimethoxy silane or trialkoxy (isocyanatoalkyl) silane, and the present invention is not limited to these; Trichlorosilane is preferred. In a preferred embodiment, the substrate S in step (a) is preheated first, and then step (b) is performed.

In this step (b), the nano-silver wire conductive layer 1' completed by spraying is used, and the nano-silver wire has a good coverage, can be uniformly distributed without agglomerates, and can be combined with the modified cellulose that forms a subsequent film. The nanofiber layer is completely attached and is not easy to be separated, which is beneficial for the modified cellulose nanofiber-nanosilver wire conductive film 3 of the present invention as a bendable conductive substrate or conductive film. The layers are separated and the photovoltaic properties are impaired. In this step (b), the heating system is at a temperature of about 90 to 120°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, and the present The invention is not limited to these; among them, 100°C is preferred.

In this step (c), the distribution of the modified cellulose nanofiber solution 2 can be coating (eg spraying or spin coating), or pouring the modified cellulose nanofiber solution 2 onto the nanofibers The silver wire conductive layer 1' is uniformly distributed. The heating system is at a temperature of about 70-100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, etc., and the present invention is not limited to these ; Among them, 80 ° C is better. After heating, the modified cellulose nanofiber layer-nanosilver wire conductive layer 3' will have residual moisture, which can be annealed at a temperature lower than the heating temperature (for example, 60 ° C or below), so that the residual moisture is Moisture evaporates completely.

In this step (e) of the preferred embodiment of the present invention, the pressure of the hot pressing is about 700～800 psi, and the temperature is about 50～80 ℃; preferably the pressure is about 730～780 psi, and the temperature is about 55～75 ℃ ; more preferably a pressure of about 750 psi and a temperature of about 60°C. The hot pressing time is about 40 to 80 minutes, preferably 60 minutes. After hot pressing, the smooth surface of the film can be more beneficial to subsequent device fabrication, as the smoother surface can avoid short circuits.

The nano-silver wire has a diameter of 55-75 µm and a width of 20-40 µm, the diameter is 55 µm, 60 µm, 65 µm, 70 µm or 75 µm, and the width is 20 µm, 25 µm, 30 µm, 35 µm or 40 µm. Not limited to this.

The solvent of the nano-silver wire solution is water or an organic solvent, such as alcohols, such as isopropanol, methanol or ethanol, etc., and the present invention is not limited to these; wherein, isopropanol is preferred. The ratio of the nanosilver wire to the organic solvent is 1:10~1:15(v/v), such as 1:10(v/v), 1:11(v/v), 1:12(v/v) v), 1:12.5(v/v), 1:13(v/v), 1:13(v/v), 1:14(v/v) or 1:15(v/v), and this The invention is not limited to these; among them, 1:12.5 (v/v) is preferred.

The modified cellulose nanofiber solution 2 can use water as a solvent, and the concentration is about 0.1-30 wt %, preferably 0.5 wt %. Wherein, the modified cellulose nanofibers can be TEMPO oxidized cellulose nanofibers (TOCN). TEMPO oxidized cellulose nanofibers use 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) to oxidize natural cellulose such as wood pulp to make the fibers more fine, and have high crystallinity and High aspect ratio.

The modified cellulose nanofiber-nanosilver wire conductive film 3 obtained by the production method of the present invention uses modified cellulose nanofibers to form a film layer, and the modified fibers are more efficient than unmodified cellulose nanofibers. The length and width of the plain nanofibers are relatively small, and they have better dispersion and homogeneity with the silver nanowires. The nanofiber layer and the nanosilver wire conductive film layer 1' can be tightly and not loose, and not easy to separate, and further, the modified cellulose nanofiber-nanosilver wire conductive film 3 can have good light penetration In addition, it can maintain a certain sheet resistance after many times of bending. In addition, the thermal expansion coefficient of the modified cellulose nanofiber-nanosilver wire conductive film 3 is lower than 5 (10 ^-6 /K), which is significantly lower than that of the conventional polymeric substrate (the thermal expansion coefficient is about 20 (10 ^-6 ) /K)). Therefore, the modified cellulose nanofiber-nanosilver wire conductive film 3 obtained by the manufacturing method of the present invention is advantageously used as a conductive film or a conductive substrate of a bendable photovoltaic device.

Please refer to FIG. 2 , which is a cross-sectional view of the photovoltaic device of the present invention.

The photovoltaic device of the present invention sequentially comprises a first electrode of the modified cellulose nanofiber-nanosilver wire conductive film 3 of the present invention, an electron transport layer 4, an active layer 5, a hole transport layer 6 and A second electrode 7 .

The electron transport layer 4 can be an n-type semiconductor metal oxide, such as ZnO, TiO ₂ , SnO ₂ , WO ₃ , Fe ₂ O ₃ , SnO ₃ , BaTiO ₃ and BaSnO ₃ , and the present invention is not limited to these ; Among them, ZnO is preferred.

The active layer 5 can be a general photovoltaic active layer material, such as PBDB-T-2F, PTB7-Th, PCBM, IT-4F, Y6, and the present invention is not limited to these; preferably non-fullerene derivative.

The hole transport layer 6 can be a p-type semiconductor metal compound, such as MoO ₃ , V ₂ O ₅ , VO ₃ , WO ₃ , CuO, CuO ₂ , NiO, NiO ₂ , ReO ₃ , Re ₂ O ₇ , AuNP , AgNP, graphene layer or carbon nanotube layer, and the present invention is not limited to these; among them, MoO ₃ is preferred.

The second electrode 7 can be metal, such as silver, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, tin, lead or a combination thereof, and the present invention is not limited to these; Among them, silver is preferred. [ specific embodiment ]

In the following, the invention will be further described with detailed description and examples. However, it should be understood that these examples are only for helping to make the present invention easier to understand and not for limiting the scope of the present invention.

Example 1. Modified cellulose nanofibers - Nano silver wire conductive film (TOCN/AgNWs membrane ) ( use 1:10(v/v) Nano-silver wire solution to prepare nano-silver wire conductive layer)

Dilute the isopropanol solution containing the silver nanowires with isopropanol (the average diameter of the silver nanowires is 55~75µm and the length is 20~40µm) to prepare the silver nanowires and isopropanol in a ratio of 1:10 (v/v) nanosilver wire solution, ultrasonically shaken for 15 minutes. A modified cellulose nanofiber solution with a concentration of 0.5 wt % was prepared using water and TEMPO oxidized cellulose nanofibers (TOCN), and ultrasonically oscillated for 30 minutes to uniformly mix. The silicon substrate was surface-treated with octadecyltrichlorosilane (ODTS), and subsequently, the silicon substrate was preheated to bring the surface to 100°C. The nano-silver wire solution was sprayed onto the surface of the silicon substrate (area size: 1.5×2.5 cm ² ) to form a nano-silver wire conductive layer. Pour the modified cellulose nanofiber solution onto the silver nanowire conductive layer, so that the modified cellulose nanofiber solution is distributed on the surface of the silver nanowire conductive layer, and heated at 80 ° C for 4.5 hours Then, annealing at 60°C to evaporate the water to obtain the modified cellulose nanofiber layer-nanosilver wire conductive layer. The modified cellulose nanofiber layer-nanosilver wire conductive layer is peeled off from the surface of the silicon substrate to obtain a TOCN/AgNWs film. Finally, the TOCN/AgNWs film was hot-pressed at 60 °C for 30 min.

Example 2. TOCN/AgNWs membrane ( use 1:12.5(v/v) Nano-silver wire solution to prepare nano-silver wire conductive layer)

The preparation process of the TOCN/AgNWs film in Example 2 is the same as that of the TOCN/AgNWs film in Example 1, except that the silver nanowires and the nanosilver solution with the isopropanol ratio of 1:12.5 (v/v) are used differently.

Example 3. TOCN/AgNWs membrane (using 1:15(v/v) Nano-silver wire solution to prepare nano-silver wire conductive layer)

Example 3 The preparation process of the TOCN/AgNWs film is the same as that of the TOCN/AgNWs film in Example 1, the only difference is that the silver nanowires and the nanosilver solution with the isopropanol ratio of 1:15 (v/v) are used.

Comparative example 1. TOCN/AgNWs film; use 1:12.5(v/v) Nano silver wire solution and drop coating method (drop coating) Preparation of nanosilver wire conductive layer

The preparation process of the TOCN/AgNWs film of Comparative Example 1 is the same as that of the TOCN/AgNWs film of Example 1. The difference is that the ratio of nano-silver wires and isopropanol in the nano-silver wire solution is 1:12.5 (v/v), and the nano-silver The silver wire solution is applied on the surface of the silicon substrate using the drop coating method.

Comparative example 2. Cellulose Nanofibers - Nano silver wire conductive film (CNF/AgNWs membrane )

Comparative Example 2 The preparation process of CNF/AgNWs film is the same as that of Example 1 TOCN/AgNWs film, the difference is that 0.5wt% cellulose nanofiber aqueous solution is used instead of 0.5wt% TEMPO oxidized cellulose nanofiber aqueous solution to fabricate CNF/AgNWs film. AgNWs film.

i. Nano-silver wire solution concentration and coating method TOCN/AgNWs Membrane influence

The TOCN/AgNWs films of Examples 1 to 3 and Comparative Example 1 were observed using a scanning electron microscope (SEM), as shown in Figure 3 (a) to (c) (Figure 3 (a) to (c) are examples in sequence 1 to 3), the nano-silver wire conductive layers of the TOCN/AgNWs films of Examples 1 to 3 are completed by spraying, and the nano-silver wires are uniformly distributed and have no aggregates, especially the TOCN/AgNWs film of Example 2. The silver nanowire conductive layer has the highest coverage and uniformity. In contrast, as shown in Figure 3(d), the conductive layer of silver nanowires of the TOCN/AgNWs film of Comparative Example 1 was completed by drop coating, and the silver nanowires were unevenly distributed and tangled into clusters. There are aggregates.

II. TOCN/AgNWs membrane, CNF/AgNWs film and PEN/ITO Surface roughness and interlayer differences

Scanning electron microscope (SEM) and atomic force microscope (AFM) were used to observe the TOCN/AgNWs film of Example 2, the CNF/AgNWs film of Comparative Example 2, and the commercially available polyethylene naphthalate/indium tin oxide substrate (PEN/ ITO) surface and section. As shown in Fig. 4(a), the surface of the TOCN/AgNWs film of Example 2 is smooth and uniform without aggregates, while the CNF/AgNWs film of Comparative Example 2 is not uniform and has aggregates in many places. As shown in Figure 4(b), the TOCN/AgNWs film of Example 2 has a compact structure stacked layer-by-layer, which is similar to the commercially available PEN/ITO, while the CNF/AgNWs film of Comparative Example 2 has a Loose is not only dense. As shown in Figure 4(c), the surface substrate of the TOCN/AgNWs film of Example 2 is relatively smooth. After measurement, the TOCN/AgNWs film of Example 2, the CNF/AgNWs film of Comparative Example 2 and the commercially available PEN/ITO have The surface root mean square roughness (RMS) was 28.0 nm, 35.5 nm and 2.39 nm, respectively. The reason for the difference between Example 2 TOCN/AgNWs film and Comparative Example 2 CNF/AgNWs film is that compared with unmodified cellulose nanofibers (CNF), modified cellulose nanofibers (ie TOCN) The length and width are reduced. When forming a film, it is more favorable to mix with the silver nanowires of the conductive layer of the nanosilver wire, which has better dispersion and homogeneity, and can be tightly wound, so that the obtained film layer is not easy to aggregate body.

III. TOCN/AgNWs membrane, CNF/AgNWs film and PEN/ITO The electrical conductivity and thermal properties of

As shown in Table 1, the sheet resistances of the TOCN/AgNWs film of Example 2 and the CNF/AgNWs film of Comparative Example 2 are 2.62 and 6.89, respectively, that is, the sheet resistances are not high, and have met the conditions for being used as photovoltaic device components. It is worth noting that the sheet resistance of the TOCN/AgNWs film of Example 2 is the lowest and significantly lower than that of the commercially available PEN/ITO. In addition, the thermal expansion coefficient of the TOCN/AgNWs film of Example 2 and the CNF/AgNWs film of Comparative Example 2 is also significantly lower than that of the commercially available PEN/ITO, especially the thermal expansion coefficient of the TOCN/AgNWs film of Example 2 can be as low as 3.37, which is relatively Example 2 The CNF/AgNWs film was 2.2 times lower and the commercially available PEN/ITO was 5.5 times lower. As shown in Figure 5, the thermomechanical analysis (TMA) curves of the three films, L ₀ is the initial length; ΔL is the length change; under the condition of increasing temperature, the TOCN/AgNWs film has the smallest length change, followed by For CNF/AgNWs films, commercially available PEN/ITO will increase in length with increasing temperature, that is, commercially available PEN/ITO will expand with increasing temperature. Therefore, compared with the commercially available PEN/ITO, the TOCN/AgNWs film of Example 2 has a low thermal expansion coefficient, which is more favorable as a conductive film or a conductive substrate.

Table 1 Sheet resistance (Ω/sq) Decomposition temperature (Td, 5%) (℃) Thermal expansion coefficient (10 ^-6 /K) Tensile strength (MPa) Elastic Modulus (GPa) Example 2 TOCN/AgNWs film 2.62 192.9 3.37 70.1 5.59 Comparative Example 2 CNF/AgNWs film 6.89 279.1 7.37 63.2 3.37 Commercially available PEN/ITO 5.08 394.3 18.45 113.1 3.87

IV. TOCN/AgNWs membrane, CNF/AgNWs film and PEN/ITO light penetration

The optical transmittance of Example 2 TOCN/AgNWs film, Comparative Example 2 CNF/AgNWs film and commercially available PEN/ITO was measured using UV transmittance spectroscopy; as shown in Figure 6, compared with commercially available PEN/ITO, Example 2 The TOCN/AgNWs film as a whole has better light transmittance. At a wavelength of 550 nm, the light transmittance of the TOCN/AgNWs film of Example 2 is 78.5%, and the light transmittance of the commercially available PEN/ITO is 76.1%, that is, the TOCN/AgNWs film of Example 2 is slightly better than the commercially available PEN. /ITO. In contrast, the CNF/AgNWs film of Comparative Example 2 had the worst light transmittance, and at 550 nm, the light transmittance of the CNF/AgNWs film of Comparative Example 2 was only 55% at the highest. It is worth noting that the light transmittance of the TOCN/AgNWs film in Example 2 is significantly higher than that of the commercially available PEN/ITO below 440 nm (ie, the short wavelength region). It is obvious that the TOCN/AgNWs film in Example 2 is more suitable for indoor Conductive thin films or conductive substrates for photovoltaic devices. In addition, as shown in Figure 7 (Figure 7(a) to (c) are the commercially available PEN/ITO, Comparative Example 2 CNF/AgNWs film and Example 2 TOCN/AgNWs film in sequence), when the image is placed in the Images can be seen behind the TOCN/AgNWs film of Example 2 and the CNF/AgNWs film of Comparative Example 2, but the images of the CNF/AgNWs film of Comparative Example 2 cannot be clearly seen. As shown in Figure 8 (Figure 8(a) and (b) are the TOCN/AgNWs film of Example 2 and the commercially available PEN/ITO, respectively), the clarity of the TOCN/AgNWs film of Example 2 is significantly higher than that of Comparative Example 2 CNF /AgNWs film, which proves that the light transmittance of the TOCN/AgNWs film in Example 2 is better. The reason for the difference between the TOCN/AgNWs film in Example 2 and the CNF/AgNWs film in Comparative Example 2 is that the CNF/AgNWs film in Comparative Example 2 uses unmodified cellulose nanofibers (CNF), and the length and width ratios are changed. The cellulose nanofibers (ie TOCN) are large, which is unfavorable to mix with the silver nanowires in the nanosilver conductive layer, resulting in looseness and tightness between the cellulose nanofiber layer and the nanosilver conductive layer. , the light is severely scattered when it penetrates between the layers.

V. TOCN/AgNWs membrane, CNF/AgNWs film and PEN/ITO mechanical strength

In addition to having acceptable electrical conductivity and optical transparency, good mechanical strength and stability are also key requirements for flexible conductive substrates. The mechanical properties of these films were first examined, and Figure 9(a) shows their corresponding stress-strain curves. From this curve, the tensile strength and elastic modulus of each substrate were calculated and summarized in Table 1. Due to the increased crystallinity, as shown in Table 1, the tensile strength of the Example 2 TOCN/AgNWs film increased from 63.2 MPa (relative to the Comparative Example 2 CNF/AgNWs film) to 70.1 MPa, however, the Example 2 accordingly The elastic modulus of the 2 TOCN/AgNWs film increased from 3.37 GPa (relative to the Comparative Example 2 CNF/AgNWs film) to 5.59 GPa. In general, high elastic modulus is not conducive to bending and may reduce electrical conductivity and mechanical stability during bending, however, fortunately, this increased elastic modulus does not affect the flexibility of Example 2 TOCN/AgNWs film have a great impact. As shown in Fig. 9(b), the sheet resistance of the TOCN/AgNWs film of Example 2 did not change much under the bending test with a bending radius of 0.8 mm, although the commercially available PEN/ITO had the highest tensile strength and Lower elastic modulus, but the brittleness of ITO may generate potential cracks during bending, resulting in a large increase in sheet resistance after 500 bending experiments, that is, the TOCN/AgNWs film of Example 2 can still be maintained under multiple bendings. It maintains a certain sheet resistance and is more suitable as a bendable conductive substrate for photovoltaic devices than commercially available PEN/ITO.

VI. coating method TOCN/AgNWs Membrane mechanical strength

In order to explore the adhesion between the modified cellulose nanocellulose layer and the nanosilver conductive layer, a tape-peel test was performed using 3M transparent tape, as shown in Figure 10. The silver wire conductive layer was separated from the modified cellulose nanocellulose layer at the first peeling off, while the TOCN/AgNWs film of Example 2 was peeled off 15 times, the nanosilver wire conductive layer and the modified cellulose nanocellulose layer were separated. The nanocellulose layer is still not separated. Therefore, when the nano-silver wire conductive layer is completed by spraying, the nano-silver wire conductive layer and the modified cellulose nano-cellulose layer can have good adhesion. When the silver nanowire conductive layer is completed by conventional drop coating, the adhesion between the nanosilver wire conductive layer and the modified cellulose nanocellulose layer is poor.

VII. TOCN/AgNWs Membrane quality factor (FOM)

)及光導性(

)的比例(

)所界定，其係藉由以下公式所獲得：

，其中，

為波長550nm時的穿透度，Rs為薄膜電阻；光波長設定為波長550nm係因人眼對此波長最為敏感。The figure of merit (FOM) of the present invention is the DC conductivity (

) and photoconductivity (

)proportion(

), which is obtained by the following formula:

,in,

is the transmittance at a wavelength of 550nm, and Rs is the sheet resistance; the light wavelength is set to a wavelength of 550nm because the human eye is most sensitive to this wavelength.

The sheet resistance and 550 nm light transmittance of the TOCN/AgNWs film of Example 2, the CNF/AgNWs film of Comparative Example 2 and other conventional conductive substrates or conductive films were measured respectively, and the quality factor was calculated by the above formula. The results are shown in Table 2 and Figure 11. Compared with the conductive substrates or conductive films of other materials, the TOCN/AgNWs film of Example 2 has the highest quality factor, indicating that the TOCN/AgNWs film of Example 2 is suitable for use as a conductive substrate for photovoltaic devices. film.

Table 2 Sheet resistance ( Ω /sq) Light transmittance (%) at 550nm Quality Factor (FOM) Example 2 TOCN/AgNWs 2.62 78.5 559 Comparative Example 2 CNF/AgNWs 6.89 52.9 73 PEN/ITO 5.08 76.1 254 PET/AgNWs 14.1 92.8 351 PET/PEDOT:PSS 75 86 32 PVA/AgNWs 63 87.5 43 Nanopaper/AgNWs 12 88 238 Nanopaper/ITO 12 65 65 PEN/ITO: polyethylene naphthalate/indium tin oxide substrate ethylenedioxythiophene) polystyrene sulfonate PVA/AgNWs: polyvinyl alcohol/nanosilver wire nanopaper/AgNWs: nanopaper/nanosilver wire nanopaper/ITO: nanopaper/indium oxide Tin substrate

Example 4. TOCN/AgNWs/ZnO/ active layer /MoO ₃ /Ag Photovoltaic installation

The TOCN/AgNWs film is used as the first electrode when preparing the photovoltaic device. In order to maintain stable properties, the ZnO electron transport layer is prepared by using an ethanol solution containing zinc acetone acetone hydrate in this example. The required curing temperature is about 130°C, which is lower than the decomposition temperature (Td) of TOCN/AgNWs film (192.9°C as shown in Table 1), that is, it will not affect the properties of TOCN/AgNWs film during curing. The manufacturing method of the photovoltaic device is as follows:

A ZnO precursor was prepared by dissolving 20 mg of zinc acetone acetone hydrate in 1 ml of ethanol. The ZnO precursor was sprayed onto the TOCN/AgNWs film of Example 2, and annealed at 130°C for 5 minutes to form a ZnO layer. In the absence of other additives, use chloroform to prepare a PM6:Y6 layer precursor solution, wherein the weight ratio of PM6 and Y6 is ₁ :1.5; the precursor solution will be placed in a glove box containing N at 50°C Stir vigorously overnight. Subsequently, the precursor solution was spin-coated on the ZnO layer at a speed of 4000 rpm for 60 seconds to form an active layer. Finally, under high vacuum (<10 ^-6 torr), thermal deposition is performed to sequentially form MoO3 with a thickness of ₁₀ nm and Ag with a thickness of 100 nm on the active layer to serve as the top electrode, that is, to complete the photovoltaic device TOCN/AgNWs/ZnO /active layer/MoO3/ _Ag . After testing, as shown in Figures 12(a) and (b), they are the current-voltage characteristic curves of the photovoltaic device and various photovoltaic characteristic curves under the bending test, respectively.

Comparative example 4. ITO glass substrate /ZnO/ active layer /MoO ₃ /Ag Photovoltaic installation

In order to compare the photovoltaic properties of the TOCN/AgNWs film and the ITO glass substrate, in Comparative Example 4, ZnO with a relatively low curing temperature was also selected to prepare the electron transport layer, and the 2-methyloxyethanol solution containing zinc acetate and ethanolamine was used to prepare the ZnO electron transport layer. For the transmission layer, the curing temperature is about 80~180°C.

Deionized water, acetone, and isopropanol were used to ultrasonically vibrate the ITO glass substrates in sequence for 15 minutes each time. After the ultrasonic oscillations were over, the ITO glass substrates were dried using N ₂ air flow and treated by plasma for 20 minutes. 0.1 g of zinc acetate was dissolved in 1 ml of 2-methyloxyethanol, and 28 μL of ethanolamine was added to prepare a ZnO precursor solution. The ZnO precursor solution was spin-sprayed on the ITO glass substrate, then placed in a glove box, and annealed at 80° C. for 10 minutes and 180° C. for 30 minutes in an air-containing environment in sequence. Use chloroform and chloronaphthalene as additives to prepare the precursor solution of PM6:Y6 layer, wherein the weight ratio of PM6 and Y6 is 1:1.5, and the volume ratio of chloroform and chloronaphthalene is 99.5/0.5 (v/v); The _compound solution was placed in a glove box containing N and stirred vigorously at 50 °C overnight. Subsequently, the precursor solution was spin-coated on the ZnO layer at a speed of 4000 rpm for 60 seconds to form an active layer, which was annealed at 100° C. for 10 minutes. Finally, under high vacuum (<10 ^-6 torr), thermal deposition forms MoO3 with a thickness of ₁₀ nm and Ag with a thickness of 100 nm on the active layer in sequence to serve as the top electrode, that is, to complete the photovoltaic device ITO glass substrate/ZnO /active layer/MoO3/ _Ag .

As shown in Table 3, the maximum power conversion efficiency of the photovoltaic device of Example 4 has reached 55% ((7.47/13.6) × 100%) of the commercially available photovoltaic device and 64% ((7.47/11.7) of the photovoltaic device of Comparative Example 4 ×100%). In addition, as shown in Figure 13, when different biocompatible materials were used as the conductive film, the power conversion efficiency of the photovoltaic device in Example 4 was the best; when TOCN/AgNWs was used as the conductive film, the power conversion efficiency was significantly higher than that of PLA ( PLLA), nanopaper (N-paper), two conventional cellulose nanofibers (CNC) and keratin.

surface 3   electrode electron transport layer Open circuit voltage (V _{oc )} (V) short circuit current ( _Jsc ) (mA cm ^-2 ) fill factor (FF) (%) Maximum power conversion efficiency , PCEmax ( Average power conversion efficiency , PCEavg) (%) Commercially available photovoltaic devices ITO glass substrate Typical curing temperature ZnO

0.0081)0.800 (0.800

0.0081) 24.1 (24.6

0.61 ) 70.3 (67.3

2.0) 13.6 (13.2

0.17) Comparative example 4 ITO glass substrate Low curing temperature ZnO 0.821 (0.822

0.0050) 23.1 (22.2

0.96) 61.8 (61.5

2.2) 11.7 (11.2

0.24) Example 4 TOCN/AgNWs film Low curing temperature ZnO 0.811 (0.813

0.012) 17.0 (16.5

0.69) 54.2 (51.3

2.5) 7.47 (6.88

0.39)

In summary, the present invention provides a facile and printable transfer method to embed Ag NWs into chemically modified CNFs, thereby enabling the successful development of CNF-based flexible conductive substrates. From the results of the above examples, it can be seen that the nanoscale fibers of TOCN and its tighter entangled network can not only be uniformly mixed with Ag NWs, but also allow most of the visible light to pass through this film. Furthermore, the transfer method of the present invention can firmly confine Ag NWs on the substrate surface to provide strong adhesion and avoid thermally induced aggregation. The as-fabricated TOCN/AgNWs films exhibited excellent electrical conductivity and high transparency in the visible and infrared regions, as evidenced by their high FoM values. Furthermore, due to its higher aspect ratio and crystallinity, the TOCN/AgNWs conductive substrate has lower CTE and higher mechanical stability, which can withstand 15 peeling cycles and 500 bending cycles with a bending radius of 0.8 mm, The sheet resistance did not decrease in any way. Flexible OPVs were fabricated using this TOCN/AgNWs film, and the device delivered a high PCE of 7.47%. Furthermore, the fabricated flexible OPV can retain 43.5% of its original PCE after 200 bends. In summary, the present invention provides a facile method for fabricating high-performance biomaterial-based conductive substrates and can facilitate the sustainable development of flexible OPVs.

The present invention has been described in detail above, but what has been described above is only a preferred embodiment of the present invention, which should not limit the scope of the present invention. Changes and modifications should still fall within the scope of the patent of the present invention.

S: substrate B: Modified surface SP: Spray Nozzle HP: Heat Press 1: Nano silver wire solution 1': Nano silver wire conductive layer 2: Modified cellulose nanofiber solution 3': Modified cellulose nanofiber layer - nanosilver wire conductive layer 3: Modified cellulose nanofiber-nanosilver wire conductive film 4: electron transport layer 5: Active layer 6: hole transport layer 7: Second electrode layer

FIG. 1 is a schematic flow chart of the manufacturing method of the modified cellulose nanofiber-nanosilver wire conductive film of the present invention.

2 is a cross-sectional view of the photovoltaic device of the present invention.

Figure 3 is a scanning electron microscope (SEM) image of the surface of the modified cellulose nanofiber-nanosilver conductive film (TOCN/AgNWs film) prepared by using different nanosilver solution concentrations and coating methods: ( a) Using 1:10 (v/v) nano-silver wire solution to prepare nano-silver wire conductive layer; (b) using 1:12.5 (v/v) nano-silver wire solution to prepare nano-silver wire conductive layer; ( c) using 1:15 (v/v) nano-silver wire solution to prepare nano-silver wire conductive layer; and (d) using 1:12.5 (v/v) nano-silver wire solution and drop coating method (drop coating method) coating) to prepare the nano-silver wire conductive layer.

Figure 4. Scanning electron microscope of TOCN/AgNWs film, cellulose nanofiber-silver nanowire conductive film (CNF/AgNWs film) and polyethylene naphthalate/indium tin oxide substrate (PEN/ITO) (SEM) photograph and atomic force microscope (AFM) photograph; Fig. 4(a) is a surface SEM photograph; Fig. 4(b) is a cross-sectional SEM photograph; Fig. 4(c) is a surface AFM photograph.

Figure 5 is a graph of thermomechanical analysis (TMA) of TOCN/AgNWs film, CNF/AgNWs film and PEN/ITO.

Figure 6 is a graph showing the light transmittance of TOCN/AgNWs film, CNF/AgNWs film and PEN/ITO at different wavelengths.

Figure 7 is a perspective photograph of the same image placed behind TOCN/AgNWs film, CNF/AgNWs film and PEN/ITO: (a) PEN/ITO; (b) CNF/AgNWs film; and (c) TOCN/AgNWs film.

Figure 8 is a perspective photograph of images placed behind TOCN/AgNWs film and PEN/ITO: (a) TOCN/AgNWs film and (b) PEN/ITO.

Figure 9 shows the stress-strain curves of TOCN/AgNWs film, CNF/AgNWs film and PEN/ITO, and the change curve of sheet resistance under bending test: (a) stress-strain curve; (b) the variation of sheet resistance Variation graph.

FIG. 10 is a graph showing the change of sheet resistance under peeling test of TOCN/AgNWs films prepared by different nano-silver wire solution coating methods.

FIG. 11 is a distribution diagram of figure of merit calculated according to light transmittance and sheet resistance of different conductive films.

Figure 12 is the current-voltage characteristic curve of the photovoltaic device of the present invention and various photovoltaic characteristic curves under the bending test: (a) the current-voltage characteristic curve of the photovoltaic device; (b) the various characteristic curves of the photovoltaic under the bending test picture.

Figure 13 is a graph showing the power conversion efficiency distribution of different biocompatible substrates as conductive thin films for photovoltaic devices.

3: Modified cellulose nanofiber-nanosilver wire conductive film

4: electron transport layer

5: Active layer

6: hole transport layer

7: Second electrode layer

Claims (10)

A method for manufacturing a modified cellulose nanofiber-nanosilver wire conductive film, comprising: (a) providing a substrate; (b) spraying a nano-silver wire solution onto the surface of the substrate, and forming a nano-silver wire conductive layer after heating; (c) distributing a modified cellulose nanofiber solution on the surface of the silver nanowire conductive layer, and forming a modified cellulose nanofiber layer-silver nanowire conductive layer after heating; (d) peeling the modified cellulose nanofiber layer-nanosilver wire conductive layer from the surface of the substrate to obtain the modified cellulose nanofiber-nanosilver wire conductive film. The manufacturing method as described in claim 1, further comprising: (e) Hot pressing the modified cellulose nanofiber-nanosilver wire conductive film. The manufacturing method of claim 1, wherein the substrate is a silicon substrate, and the surface thereof is treated with a silane compound. The manufacturing method of claim 3, wherein the silane compound is octadecyltrichlorosilane (ODTS). The manufacturing method according to any one of claims 1 to 4, wherein the modified cellulose nanofibers in the modified cellulose nanofiber solution are TEMPO oxidized cellulose nanofibers (TOCN). The manufacturing method according to any one of claims 1 to 4, wherein the silver nanowire solution comprises silver nanowires and an organic solvent, and the ratio of the silver nanowires to the organic solvent is 1:10-1:15 ( v/v). The manufacturing method of claim 6, wherein the ratio of the silver nanowires and the organic solvent is 1:12.5 (v/v). The production method according to claim 7, wherein the organic solvent is isopropanol. A modified cellulose nanofiber-nanosilver wire conductive film, which is obtained by using the manufacturing method according to any one of claims 1 to 8. A photovoltaic device, comprising in sequence a first electrode, an electron transport layer, an active layer, a hole transport layer and a second electrode; wherein the first electrode is the modified cellulose nanofiber of claim 9 -Nanosilver wire conductive film.

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