Preparation method of low-resistance ultra-stable silver nanowire-based transparent conductive film and light emitter

Abstract

The present invention provides a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film and a light emitter. First, a layer of SnO2 is sputtered onto the surface of a PET substrate to improve its hydrophilicity. A SnO2 / AgNWs transparent conductive film is then prepared using spin-coating. Silver obtained from reduction in NaCl solution is used to soft-solder the wire-to-wire junctions in the AgNWs network. Then, Nd2O3 obtained by hydrolysis in NdF3 solution is used to encapsulate the AgNWs to obtain an AgNWs@Nd2O3 transparent conductive film. Finally, PU is used for encapsulation to prepare a low-resistance and ultra-stable SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. The prepared transparent conductive film not only exhibits excellent photoelectric properties but also demonstrates significant environmental stability, bending resistance, and waterproof performance. After 28 days in ambient air and at a bending radius of 5.5 mm, it exhibits resistivity changes of 24% and 4.8%, respectively. Even after coating with a water layer, it can still maintain a current of 0.10 A at 4V. In addition, PU encapsulation significantly reduces the surface roughness of the AgNWs transparent conductive film, thereby significantly improving the luminescent performance of ACEL.

Description

Technical Field

[0001] This invention relates to the field of conductive thin film preparation, and in particular to a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film and a light emitter. Background Technology

[0002] In current technologies, with the rapid development of society, there is an urgent need for flexible TCFs (transparent conductive films) in the fields of electronics, optoelectronics, and energy. Due to their excellent mechanical flexibility, flexible TCFs are frequently incorporated into key components of optoelectronic devices, such as touchscreen panels, solar cells, liquid crystal displays, photodetectors, wearable sensors, and flexible heaters. Although metal oxide transparent conductive films possess excellent conductivity and transmittance, such as In₂O₃:Sn (ITO), SnO₂:F (FTO), and ZnO:Al (AZO), their brittleness affects their performance. The development of flexible TCFs has become a current research focus, including metal nanowires (MNW), graphene, and conductive polymers. Each of these flexible TCFs has its own performance limitations: metal nanowire TCFs have poor environmental stability, graphene TCFs are costly and unsuitable for large-area fabrication, and conductive polymer TCFs have low conductivity and transparency.

[0003] Silver nanowire conductive films (AgNWs transparent conductive films) are an ideal flexible TCF due to their high conductivity, excellent transmittance, good flexibility, and low fabrication cost. However, several issues limit their commercial application, such as poor adhesion between silver nanowires and the substrate, high contact resistance at line-to-line junctions in the silver nanowire conductive network, high surface roughness, and poor environmental stability. Capillary forces generated by solvent evaporation can effectively reduce junction resistance, but ambient humidity may affect the solvent evaporation rate and capillary bridge formation, thus impacting the line-to-line junction welding effect. Reducing junction resistance through mechanical pressure and thermoforming can easily lead to silver nanowire breakage. Electrodeposition of ZnO onto the AgNWs network using low-temperature solution treatment reduces junction resistance and improves the stability of the AgNWs transparent conductive film. However, this method is inefficient and environmentally unfriendly. Treating the AgNWs transparent conductive film with a dilute ferric chloride solution can reduce its chemical resistance and enhance its stability, but this method is inefficient and requires a 90-minute processing time. In addition to the junction resistance issues mentioned above, problems such as the environmental stability, bending resistance, and waterproof performance of AgNWs transparent conductive films limit their commercial application. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film and a light emitter, aiming to solve the problems of stability and electrical performance limitations of AgNWs transparent conductive films.

[0005] To achieve the above objectives, the present invention provides a method for preparing a stable silver nanowire transparent conductive film, comprising:

[0006] S1. Sputter a SnO2 layer onto the surface of a PET substrate to improve its hydrophilicity;

[0007] S2. A SnO2 / AgNWs transparent conductive film is formed by spin-coating AgNWs liquid onto the surface of the SnO2 layer.

[0008] S3. Soak the SnO2 / AgNWs transparent conductive film in a NaCl solution of 1.4 to 1.9 mol / L and then solder the wire-to-wire junction of the silver nanowire conductive network. After cleaning off the excess NaCl on the surface, a SnO2 / AgNWs transparent conductive film with low resistance is obtained.

[0009] S4. After immersing the SnO2 / AgNWs transparent conductive film with low resistance characteristics in a solution of 0.8 to 1.2 mg / mL NdF3, a core-shell structured SnO2 / AgNWs@Nd2O3 transparent conductive film is obtained.

[0010] S5. After coating a layer of PU onto the surface of the SnO2 / AgNWs@Nd2O3 transparent conductive film, dry it to obtain an ultra-stable SnO2 / AgNWs@Nd2O3 / PU transparent conductive film with low surface roughness.

[0011] Furthermore, in step S1, the thickness of the PET substrate is 30 to 150 micrometers, and the thickness of the SnO2 layer is 300 to 400 nanometers.

[0012] Furthermore, in step S3, the concentration of the NaCl solution is 1.8 mol / L; in step S4, the concentration of the NdF3 solution is 1 mg / mL.

[0013] Furthermore, in step S3, the SnO2 / AgNWs transparent conductive film is immersed for 20 to 40 seconds.

[0014] Furthermore, in step S4, the modified low-resistance SnO2 / AgNWs transparent conductive film is immersed in NdF3 solution for 2.5 to 3.5 hours.

[0015] Further, step S5 includes:

[0016] A PU layer is spin-coated onto the surface of a SnO2 / AgNWs@Nd2O3 transparent conductive film at a rotation speed of 2500 to 3500 rpm for 0.5 to 2.0 minutes, followed by drying at 50 to 70 degrees Celsius to obtain the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film.

[0017] Further, step S5 includes:

[0018] After partially masking the surface of the SnO2 / AgNWs@Nd2O3 transparent conductive film by covering it with a mask, a layer of PU is coated on the surface.

[0019] Remove the mask, process silver electrodes in the masked areas, and finally dry to obtain a SnO2 / AgNWs@Nd2O3 / PU transparent conductive film equipped with electrodes.

[0020] As an application, the present invention also provides a method for fabricating a light emitter, using the aforementioned SnO2 / AgNWs@Nd2O3 / PU transparent conductive film, comprising:

[0021] K1. Thoroughly mix PDMS solution, ZnS:Cu and BaTiO3 to prepare a slurry.

[0022] K2, the slurry is coated on the surface of SnO2 / AgNWs@Nd2O3 / PU transparent conductive film and dried to form a light-emitting / dielectric composite layer;

[0023] K3. A silver conductive layer is fabricated on the surface of the light-emitting / dielectric composite layer to complete the fabrication of the light emitter.

[0024] Furthermore, in step K2, the slurry is applied by screen printing.

[0025] Furthermore, the steps of K2 include:

[0026] The surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film is covered with a mask to form partial shielding;

[0027] The slurry is coated on the surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. After the mask is removed and dried, a light-emitting / dielectric composite layer is formed.

[0028] This invention provides a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film and a light emitter. A two-step process is used to prepare a SnO2 / AgNWs@Nd2O3 transparent conductive film with a core (AgNWs)-shell (Nd2O3) structure. Wire-to-wire junctions in the AgNWs network are soldered using silver obtained from reduction in NaCl solution, and then the AgNWs are encapsulated in Nd2O3 obtained by hydrolysis in NdF3 solution. The prepared transparent conductive film not only exhibits excellent photoelectric properties (thin-film resistivity of 11.6 ohms / cubic meter and transmittance of 86.6%), but also demonstrates significant environmental stability and bending resistance, showing resistivity changes of 24% and 4.8% after 28 days in ambient air and at a bending radius of 5.5 mm, respectively. The encapsulated SnO2 / AgNWs@Nd2O3PU transparent conductive film exhibits excellent waterproof properties, maintaining a current of 0.10 A at 4V even after coating with a water layer. Surface roughness analysis revealed that TCF significantly affects the luminescence characteristics of alternating current electroluminescent devices (ACELs). An ACEL device fabricated using a low-roughness SnO2 / AgNWs@Nd2O3 / PU transparent conductive film as a flexible transparent electrode achieved a luminous intensity of 43.11 candela per square centimeter and exhibited stable bending luminescence performance with negligible variations in brightness uniformity. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the characterization of the modified low-resistance SnO2 / AgNWs transparent conductive film in Example 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the characterization of the SnO2 / AgNWs@Nd2O3 transparent conductive film in Example 1 of the present invention.

[0031] Figure 3 These are the XRD patterns and XPS measurements of the SnO2 / AgNWs@Nd2O3 transparent conductive film in Example 1 of this invention.

[0032] Figure 4 This is a performance comparison of Embodiment 1 of the present invention with other types of conductive films.

[0033] Figure 5 This is an analysis of the characteristics of the present invention in Embodiment 1.

[0034] Figure 6 This is the surface analysis of Embodiment 1 of the present invention. Detailed Implementation

[0035] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, units, modules, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, units, modules, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connection or wireless coupling. The term “and / or” as used herein includes all or any of the units and all combinations of one or more associated listed items.

[0037] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0038] Example 1

[0039] A method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film is provided.

[0040] The silver nanowire solution was purchased from Nanjing Xianfeng Nanotechnology Co., Ltd., with a concentration of 5 mg / mL, a length of 20 μm, and a diameter of 30 nm.

[0041] NdF3 powder was purchased from Shanghai Yien Chemical Technology Co., Ltd.

[0042] Anhydrous ethanol (AR) reagent was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0043] The polyethylene terephthalate (PET) substrate was purchased from Yiyang Huanan Xiangcheng Technology Co., Ltd.

[0044] Polyurethane resin (PU, with the molecular structure [-O-(C3H6O)m-NH-CO-OC]) 15 H 10 N2O2-]n) was purchased from Yoshida Chemical Co., Ltd.

[0045] The cold wire driver was purchased from Zhengzhou Debei Culture Media Co., Ltd.

[0046] SnO2 target material (purity: 99.9%, size: 60 mm × 3 mm) was purchased from Zhangzhou Heqitajite Technology Co., Ltd.

[0047] Morphological characterization was performed using a JEOL JEM-F200 field emission transmission electron microscope (TEM) with a GatanRio16 camera and an acceleration voltage of 200 kV.

[0048] The surface morphology of TFC was analyzed using a FEIQuanta200F scanning electron microscope.

[0049] XRD analysis was performed using a D8 Advance (Bruker) to examine the TCF crystal structure. The operating voltage and current were 40 kV and 40 mA, respectively. The CuK-α wavelength was λ = 1.54056 nm, and the scan step size was 0.02 nm.

[0050] The transmittance of TCF was measured using a Lambda 850 UV-Vis spectrophotometer manufactured by Platinum-Elmer.

[0051] The thin-film resistance of TCF was measured using a KDY-1 resistivity / resistance four-probe tester manufactured by Guangzhou Kundel. The thin-film resistance data were obtained by measuring 10 times.

[0052] The water resistance of TCF was characterized using a PRECI-200 series benchtop water meter, which has a water layer covering its surface.

[0053] The phase structure of the sample was examined using X-ray photoelectron spectroscopy (ThermoScientificK-Alpha instrument). The excitation source used was AlKα X-rays, the beam spot size was 400 micrometers, and the operating parameters were set to a voltage of 12 kV and a filament current of 6 mA.

[0054] Use a Fluke multimeter to test the resistance between the electrode pairs on the TCF.

[0055] In the preparation process, firstly, a SnO2 layer (30 μm thick) is sputtered onto the surface of a PET substrate treated with a semiconductor cleaning process to improve its hydrophilicity. The magnetron sputtering parameters are set as follows: 100 W sputtering power, 1.0 Pa working pressure, 40 ppm Ar flow rate, and 15 min sputtering time. After sputtering a 300 nm thick SnO2 layer onto the PET substrate surface, hydrophilicity and adhesion are further enhanced.

[0056] Next, the AgNWs solution was spin-coated onto the surface of the SnO2 layer at 600 rpm for 10 seconds, and then the SnO2 / AgNWs transparent conductive film was prepared by spin coating at 1500 rpm for 22 seconds.

[0057] Then, the SnO2 / AgNWs transparent conductive film is immersed in a NaCl solution (1.4 mol / L) for 20-30 seconds, removed, and the excess NaCl on the surface is washed away with deionized water and ethanol, resulting in a low-resistance SnO2 / AgNWs transparent conductive film with tight wire-to-wire junction contact. In this process, Ag reduced by NaCl is used for soft soldering of the wire-to-wire junctions, allowing the AgNWs to make better contact at the junction. The principle is that the Ag on the AgNWs first undergoes a redox reaction and dissolves, while Cl⁻ in the NaCl solution acts as a catalyst to increase the redox rate. Conversely, the dissolved Ag⁺ will redeposit on the surface of the AgNWs through an autocatalytic reaction, resulting in tight wire-to-wire junction contact.

[0058] Continuing, 40 mg of NdF3 was placed in a beaker, 20 g of deionized water was added, and the mixture was stirred thoroughly until dissolved. Then, anhydrous ethanol was added to obtain a 0.8 mg / mL NdF3 solution, which was stirred for 1 hour using a magnetic stirrer. The modified low-resistivity SnO2 / AgNWs transparent conductive film was immersed in the NdF3 solution at 50°C and stirred continuously for 2.5-3.0 hours. Considering the advantages of rare earth element Nd in preparing core-shell structured AgNWs@Nd2O3 transparent conductive films, such as mild reaction conditions, in-situ shell formation, chemical stability, strong interfacial bonding, and suitable dielectric properties, Nd2O3 generated by the hydrolysis of NdF3 was used to encapsulate silver nanowires.

[0059] Finally, SnO2 / AgNWs@Nd2O3 was encapsulated with PU to obtain a highly stable, low-surface-roughness, and flexible AgNWs@Nd2O3 / PU transparent conductive film. Specifically, a PU solution was dropped onto the SnO2 / AgNWs@Nd2O3 transparent conductive film and coated using a spin coater for 30 seconds at a speed of 2500 rpm. After removing the SnO2 / AgNWs@Nd2O3 transparent conductive film, it was placed in a drying oven at 60 degrees Celsius for 6 hours to obtain the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film, which exhibited excellent stability and water resistance. In some embodiments, a mask can be first applied to the surface of the SnO2 / AgNWs@Nd2O3 transparent conductive film to form partial shielding, then a layer of PU can be coated on the surface, the mask can be removed, and silver electrodes can be processed in the masked areas. Finally, the film is dried to obtain a SnO2 / AgNWs@Nd2O3 / PU transparent conductive film with electrodes.

[0060] Figure 1This is a schematic diagram characterizing the modified low-resistivity SnO2 / AgNWs transparent conductive film in Example 1 of the present invention. Image a shows the contact angle test of the PET substrate; image b shows the SEM image of the PET / AgNWs transparent conductive film; image c shows the contact angle of the PET / SnO2 substrate surface; image d shows the SEM image of the PET / SnO2 / AgNWs transparent conductive film; image e shows the SEM image of relaxed line-to-line junction contacts in the silver nanowire network of the SnO2 / AgNWs transparent conductive film; and image f shows the SEM image of tight line-to-line junction contacts in the silver nanowire network of the modified low-resistivity SnO2 / AgNWs transparent conductive film. Figure 1 As can be seen from the a-part diagram, the contact angle of the PET substrate surface is as high as 84.64 degrees, indicating poor hydrophilicity. Figure 1 As can be seen from the middle b-figure, when preparing AgNWs transparent conductive films by spin coating on PET substrates under high-speed rotation, the poor adhesion between the substrate and silver nanowires due to poor hydrophilicity and the sparse AgNWs on the PET substrate also leads to poor conductivity of the AgNWs transparent conductive films. Figure 1 As can be seen from the c-section diagram, the contact angle of the PET / SnO2 surface decreased to 66.40 degrees, which improved the hydrophilicity. Figure 1 The middle d-part image is a SEM image of the SnO2 / AgNWs transparent conductive film, which shows that the AgNWs are uniformly distributed and have a high density. Figure 1 The figure in the middle shows the AgNWs network of the SnO2 / AgNWs transparent conductive film before NaCl solution immersion treatment. The line-to-line junction contacts are loose, which leads to high junction resistance. Figure 1 The middle f-image is a SEM image of the modified low-resistivity SnO2 / AgNWs transparent conductive film. It can be seen from the image that the line-to-line junctions in the AgNWs network become tightly connected after treatment with NaCl solution.

[0061] Figure 2 This is a schematic diagram of the characterization of the SnO2 / AgNWs@Nd2O3 transparent conductive film in Embodiment 1 of the present invention. Image a is a high-resolution transmission electron microscope (TEM) image of the pure AgNWs network; image b is a magnified image of image a; image c shows a high-resolution TEM image of the SnO2 / AgNWs@Nd2O3 transparent conductive film; image d shows a magnified image of image c; and image e shows the EDS distribution map of the SnO2 / AgNWs@Nd2O3 transparent conductive film. Figure 2 The a-part image is a high-resolution transmission electron microscope image of a pure AgNWs network, which shows that AgNWs have precise contours and smooth surfaces without any signs of encapsulation. Figure 2 The b-part image is a magnified view of the a-part image, showing only a clear Ag lattice. Figure 2The c-part image shows a high-resolution transmission electron microscope image of the AgNWs network after being modified with Nd2O3, showing that the surface of AgNWs is coated with Nd2O3. Figure 2 The d-part diagram shows a magnified image of the c-part diagram, from which the two lattice arrays are clearly visible. Figure 2 In the d-plane diagram, the upper right corner is the (111) crystal plane of Ag with a spacing of 0.2403 nm, while the lower right corner is the (100) crystal plane of Nd2O3 with a spacing of 0.3204 nm. Figure 2 The middle part of the figure shows the EDS distribution of AgNWs@Nd2O3, showing the distribution of Ag, Nd and O atoms respectively. It can also be clearly seen from the figure that the distribution of Nd and O atoms is wider than that of Ag atoms, which indicates that the surface of AgNWs is wrapped by Nd2O3, forming a core (AgNWs) and shell (Nd2O3) structure.

[0062] The Nd2O3 layer was prepared by the hydrolysis reaction of NdF3 as follows:

[0063] NdF3+3H2O→Nd(OH)3+3HF(1)

[0064] 2Nd(OH)3→Nd2O3+3H2O(2)

[0065] F- in NdF3 forms hydrogen bonds with H+ in H2O, leading to the ionization of water molecules and the generation of OH− and H+. Nd3+ combines with OH− to form Nd(OH)3, while H+ combines with F- to form HF, as shown in equation (1). The results show that when the solution temperature is maintained at 50°C, Nd(OH)3 is converted into the more stable H2O and Nd2O3, as shown in equation (2). Nd2O3 is deposited on the surface of AgNWs, forming a uniform Nd2O3 shell with a thickness of approximately 6.64 nm.

[0066] Figure 3 These are the XRD patterns and XPS spectra of the SnO2 / AgNWs@Nd2O3 transparent conductive film in Example 1 of this invention. Sub-figure a shows the XRD pattern of the SnO2 / AgNWs@Nd2O3 transparent conductive film; sub-figure b shows the full XPS spectrum of the SnO2 / AgNWs@Nd2O3 transparent conductive film; sub-figure c shows the XPS spectrum of Ag3d in the SnO2 / AgNWs@Nd2O3 transparent conductive film; sub-figure d shows the XPS spectrum of O1s in the SnO2 / AgNWs@Nd2O3 transparent conductive film; and sub-figure e shows the XPS spectrum of Nd3d in the SnO2 / AgNWs@Nd2O3 transparent conductive film. Figure 3The middle a-part figure shows the XRD pattern of the SnO2 / AgNWs@Nd2O3 transparent conductive film, which further illustrates that the Nd2O3 modified AgNWs network forms a core-shell structure; the peak at 26.8 degrees corresponds to the (100) plane of Nd2O3, the peak at 38.1 degrees corresponds to the (111) plane of Ag, and the peak at 54.8 degrees corresponds to the (220) plane of SnO2. Figure 3 The a-diffraction pattern shows a very strong Nd₂O₃(100) surface diffraction peak, indicating good crystallinity of the Nd₂O₃. The thickness of the coating layer is calculated to be approximately 6.64 nm according to the Scherrer formula. It also shows a weaker Ag(111) surface diffraction peak, indicating that the Nd₂O₃ coating of the silver nanowires weakens the Ag(111) signal. Figure 3 The XPS full spectrum shown in the middle b-plot reveals that the SnO2 / AgNWs@Nd2O3 transparent conductive film is mainly composed of Ag, Nd, O, Sn, and C elements, without any obvious impurities, which is in excellent agreement with the EDX results. The XPS spectrum of the SnO2 / AgNWs@Nd2O3 transparent conductive film is shown below. Figure 3 The CE subplot is shown below. Figure 3 As shown in the c-plot, two peaks appear at 374 eV and 368 eV, corresponding to 3d³ / ² and Ag³d⁵ / ² of zero-valent Ag, respectively. From... Figure 3 As can be seen from the d-plot, O1s was fitted with a Gaussian to two peaks. The peak at 531.3 eV corresponds to O bonded to trivalent Nd, and the peak at 532.6 eV corresponds to oxygen adsorbed on the silver surface. Figure 3 As shown in the middle e-fraction diagram, two peaks appear at 982 eV and 1003 eV, corresponding to Nd3d5 / 2 and Nd3d3 / 2 respectively, indicating that it is in the positive trivalent oxidation state, and Nd is attached to the surface of AgNWs in the form of Nd2O3.

[0067] The resistivity of the SnO2 / AgNWs@Nd2O3 transparent conductive film decreases with increasing AgNWs spin-coating layer number, but its optical transmittance also decreases. For example, the resistivity of the SnO2 / AgNWs transparent conductive film with 1 and 5 AgNWs spin-coated layers is 43.8 ohms / cubic meter and the transmittance is 92.1%, while the resistivity is 7.3 ohms / cubic meter and the transmittance is 78.2%. The resistivity and transmittance of the SnO2 / AgNWs@Nd2O3 transparent conductive film with 1 and 5 spin-coated layers are 44.1 ohms / cubic meter and 91.9%, while the resistivity is 7.4 ohms / cubic meter and the transmittance is 78.8%. This phenomenon is caused by the fact that as the density of the silver nanowire network increases with the number of spin-coated layers, the transmittance gradually decreases due to the enhanced scattering and light reflection of the AgNWs network, and the increased conductive channels lead to a decrease in resistivity. It is worth noting that the presence of the coating layer does not reduce the transmittance of the film. Conversely, the transmittance of the SnO2 / AgNWs@Nd2O3 transparent conductive film is slightly higher than that of the SnO2 / AgNWs transparent conductive film, which may be due to the anti-reflection effect of the Nd2O3 layer.

[0068] To evaluate the photoelectric properties of the SnO2 / AgNWs@Nd2O3 transparent conductive film, the quality factor (FoM) can be calculated.

[0069]

[0070] Z is the free space impedance, with a value of 377Ω, R is the sheet resistance, and T is the transmittance. A higher FoM value is better, as this film possesses comprehensive optoelectronic properties.

[0071] The FoM values ​​of SnO2 / AgNWs transparent conductive films and SnO2 / AgNWs@Nd2O3 transparent conductive films with different spin-coating numbers are as follows: For SnO2 / AgNWs transparent conductive films with 1, 2, 3, 4, and 5 spin-coating numbers, the FoM values ​​are 102.5, 166.5, 216.3, 208.3, and 197.4, respectively; while for SnO2 / AgNWs@Nd2O3 transparent conductive films with 1, 2, 3, 4, and 5 spin-coating numbers, the FoM values ​​are 99.1, 157.8, 217.9, 212, and 201.3, respectively. The results show that the three-layer spin-coating has the best overall photoelectric performance. For example, the FoM value of the three-layer SnO2 / AgNWs@Nd2O3 transparent conductive film is 217.9, its resistance is 11.6 ohms / cube, and its transmittance is 86.6%.

[0072] Figure 4 This is a performance comparison of Embodiment 1 of the present invention with other types of conductive films. Figure 4A comparison of the FoM (Formula of Optoelectronic Performance) of the SnO2 / AgNWs@Nd2O3 transparent conductive film (3 layers) with other transparent conductive films is shown, including ITO, AZO / AgNWs / AZO, TIO / AgNWs / TIO, AgNWs / polymer, FLW / AgNWs, Au-coated AgNWs, ITO / AgNWs / ITO, mixed graphene / CNT, graphene / AgNWs / graphene, AgNWs / FZO, electrospun NWs, and AgNWs-rGO. This indicates that the SnO2 / AgNWs@Nd2O3 transparent conductive film exhibits the best overall optoelectronic performance. The curves in the figure represent FoM values, with values ​​from left to right of 200, 150, 100, and 50.

[0073] Figure 5 This is an analysis of the usage characteristics of Embodiment 1 of the present invention. Figure a shows the change in sheet resistance of the SnO2 / AgNWs@Nd2O3 transparent conductive film after 0 to 28 days in air at room temperature; Figure b shows the increase rate of sheet resistance for the SnO2 / AgNWs, SnO2 / AgNWs@Nd2O3, and SnO2 / AgNWs@Nd2O3 / PU transparent conductive films under different bending radii; Figure c shows an image of the TCF during bending; Figure d shows the change in current across the electrode pair when a 4V layer is applied to the TCF before and after coating with a water layer; Figure e shows the temperature change of the TCF under a 4V application before and after coating with a water layer; Figure f shows images of the TCF surface before and after coating with a water layer. Figure 5 The figure in section a shows the change in sheet resistance of the SnO2 / AgNWs@Nd2O3 transparent conductive film after being exposed to air for 0, 7, 14, 21, and 28 days. It can be seen that after 28 days of exposure to air, the sheet resistance of the SnO2 / AgNWs transparent conductive film increased from 11.4 ohms / square to 42.5 ohms / square, an increase of 272%. However, the rate of increase in sheet resistance of the SnO2 / AgNWs@Nd2O3 transparent conductive film was lower with longer immersion time in NdF3 solution. After immersion for 1, 2, 3, and 4 hours, the resistance increase rates of the SnO2 / AgNWs@Nd2O3 transparent conductive film were 179%, 132%, 24%, and 23%, respectively. The excellent electrical stability should be attributed to the favorable core-shell structure of AgNWs@Nd2O3. The shell of Nd2O3 exhibits good oxidation resistance. As the immersion time of the AgNWs network in NdF3 solution increases, the Nd2O3 shell becomes thicker, enhancing its oxidation resistance. Considering the preparation efficiency of SnO2 / AgNWs@Nd2O3 transparent conductive films, the AgNWs network exhibits excellent oxidation resistance after immersion in NdF3 solution for 3 hours.

[0074] Figure 5 The middle b-plot shows the results of the bending resistance test after 500 bends. Figure 5 The diagram in section c shows a schematic of the TCF bending. The greater the degree of bending, the greater the rate of resistance increase. When the bending degree is maximum (radius 1.0 mm), the resistance increase rates of SnO2 / AgNWs@Nd2O3 / PU transparent conductive film, SnO2 / AgNWs@Nd2O3 transparent conductive film, and SnO2 / AgNWs transparent conductive film are 7.9%, 12.4%, and 58.0%, respectively. The excellent bending resistance of SnO2 / AgNWs@Nd2O3 / PU transparent conductive film and SnO2 / AgNWs@Nd2O3 transparent conductive film is attributed to the strong line-to-line junction (AgNWs) shell (Nd2O3) structure of the AgNWs network and the PU encapsulation. The robust line-to-line connection of the AgNWs network makes it difficult to loosen. For the core-shell structure of the conductive channels, the Nd2O3 encapsulation layer improves the mechanical bending resistance of the AgNWs conductive channels, making them less prone to breakage.

[0075] Figure 5 The d-plot shows the results of the waterproof performance test. Figure 5 Images f show the physical characteristics of the TCF surface before and after water droplets were applied. During the waterproof test, a voltage of 4V was used. A layer of water was applied across the electrodes after the film surface was coated with a water droplet. Figure 5 As can be seen from d, the SnO2 / AgNWs transparent conductive film reaches its maximum current of 0.14 Amperes after 10 seconds of energization, and then drops linearly to 0. The total duration of conduction time is 20 seconds, indicating that the conductivity of the SnO2 / AgNWs transparent conductive film has failed.

[0076] Figure 5The electrothermal effect in the e-plot also shows that the temperature rapidly drops to 35.7 degrees Celsius after 10 seconds, reaching a peak of 77.9 degrees Celsius. This electrothermal effect further confirms that the conductivity of the SnO2 / AgNWs transparent conductive film fails after 10 seconds. However, the SnO2 / AgNWs@Nd2O3 transparent conductive film exhibits some water resistance. The SnO2 / AgNWs@Nd2O3 transparent conductive film reaches a maximum current of 0.13 amperes after 10 seconds of energization, then slowly decreases to 0.02 amperes within 10-60 seconds, maintaining the same current value within 60-120 seconds. These results indicate that the conductivity of the SnO2 / AgNWs@Nd2O3 transparent conductive film is not completely ineffective. The SnO2 / AgNWs@Nd2O3TCF exhibits some water resistance, which should be attributed to the protective effect of the Nd2O3 shell. Nd₂O₃ prevents water molecules from directly contacting AgNWs and does not reduce the conductivity of AgNWs due to oxidation and corrosion. The reason why the conductivity of SnO₂ / AgNWs@Nd₂O₃TCF decreases significantly under high humidity conditions is that the core-shell structure in the AgNWs network is not fully realized, or some Nd₂O₃ shells are too thin to fully exert their waterproofing effect.

[0077] Figure 5 As shown in the d-plot, the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film reaches a maximum current of 0.13 A after 5 seconds of energization, then drops to 0.10 A during 10-15 seconds, and maintains this current value during 15-120 seconds. This indicates that the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film has excellent waterproof performance. Figure 5 The stable electrothermal effect of 72.4 degrees Celsius observed in the middle e-plot within 0-120 seconds further demonstrates the excellent waterproof performance. Figure 5 The f-plot shows images of the TCF surface before and after the water layer was applied.

[0078] Figure 6 For atomic force microscopy analysis, sub-images a, b, and c are SEM, AFM, and AFM-3D images of the SnO2 / AgNWs transparent conductive film, respectively. Figure 6 The d-image, e-image, and f-image are SEM, AFM, and AFM-3D images of the SnO2 / AgNWs@Nd2O3 transparent conductive film, respectively. Figure 6 The g-part, h-part, and i-part images are SEM, AFM, and AFM-3D images of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film, respectively. Combined with... Figure 6SEM images of the a, d, and g sub-plots show that the surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film is sealed by a dense PU layer, which can effectively isolate water molecules from direct contact with the SnO2 / AgNWs@Nd2O3 transparent conductive film, thereby resisting oxidation and corrosion of the conductive channels. Figure 6 The b-plot and c-plot show the AFM plot and AFM-3D image of the SnO2 / AgNWs transparent conductive film, where the difference between the lowest and highest positions on the film surface is 250.6 nm, and the RMS surface roughness is 27.8 nm. Figure 6 The e-plot and f-plot show the AFM plot and AFM-3D image of the SnO2 / AgNWs@Nd2O3 transparent conductive film, where the difference between the lowest and highest positions on the film surface is 243.4 nm, corresponding to a surface roughness of 27.3 nm according to RMS. Figure 6 The h-plot and i-plot show the AFM and AFM-3D images of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. They reveal that the difference between the lowest and highest points on the film surface is 22 nm, corresponding to an RMS surface roughness of 2.1 nm. These results demonstrate that the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film possesses very low surface roughness, meeting the requirements for electroluminescent devices.

[0079] In summary, a SnO2 / AgNWs@Nd2O3 transparent conductive film with a core (AgNWs)-shell (Nd2O3) structure was prepared via a two-step process: first, wire-to-wire junctions in the AgNWs network were soldered using silver soft soldering obtained from reduction in NaCl solution; then, AgNWs were encapsulated using Nd2O3 obtained from hydrolysis in NdF3 solution. The prepared transparent conductive film not only exhibited excellent photoelectric properties (11.6 ohms / cubic meter resistivity and 86.6% transmittance), but also demonstrated significant environmental stability and bending resistance, showing resistivity changes of 24% and 4.8% after 28 days in ambient air and at a bending radius of 5.5 mm, respectively. After encapsulation with polyurethane (PU), the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film exhibited excellent waterproof properties, maintaining a current of 0.10 A at 4V even after coating with a water layer. Surface roughness analysis shows that the surface roughness of TCF significantly affects the luminescence characteristics of ACEL devices. An ACEL device fabricated using a low-roughness SnO2 / AgNWs@Nd2O3 / PU transparent conductive film as a flexible transparent electrode achieved a luminous intensity of 43.11 candela per square centimeter and exhibited stable bending luminescence performance with negligible variation in brightness uniformity.

[0080] Example 2

[0081] Example 2 provides a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film, which differs from Example 1 in that: the PET substrate is 150 μm thick, and the sputtered SnO2 layer is 400 nm thick; the SnO2 / AgNWs transparent conductive film is immersed in NaCl solution (1.9 mol / L) for 40 seconds; the NdF3 solution is 1.2 mg / mL, and the mixture is continuously stirred for 3.5 hours. The spin coating speed in the PU process is set to 3500 rpm for two minutes.

[0082] In Example 2, the FoM value of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film with 3 spin-coated layers is 170.4.

[0083] Example 3

[0084] Example 3 provides a method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film, which differs from Example 1 in that: the SnO2 / AgNWs transparent conductive film is immersed in NaCl solution (1.9 mol / L) for 20 to 40 seconds; the NdF3 solution is 1.0 mg / mL.

[0085] In Example 3, the FoM value of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film with three spin-coated layers is 179.4.

[0086] Example 4

[0087] As an application, this embodiment provides a method for preparing an ACEL (acetylene-emitting diode). First, PDMS (polydimethylsiloxane) and a curing agent (Dow Corning SYLGARD) are mixed in a 10:1 ratio to form a PDMS solution. The PDMS solution was purchased from Shenzhen Songxin New Material Technology Co., Ltd. The phosphorescent powder is ZnS:Cu, and the dielectric powder is BaTiO3. ZnS:Cu, BaTiO3, and the PDMS solution are mixed in a 1.3:1:1 ratio to form a slurry. ZnS:Cu and BaTiO3 were purchased from Shenzhen Yilai Technology Co., Ltd. The luminescent layer is made of a mixture containing ZnS:Cu luminescent particles, BaTiO3, and the PDMS solution. Fluorescence is generated by exciting the ZnS:Cu particles with a strong electric field produced by applying an AC voltage between two electrodes. ZnS is the primary luminescent material; when doped with Cu, Cu2+ acts as an activator, introducing energy levels into the ZnS lattice. Excited electrons transition to the energy levels introduced by Cu2+, recombine, and emit light. BaTiO3 has a high dielectric constant, which on the one hand can significantly improve the tolerance to strong electric fields applied to the light-emitting layer, and help improve the excitation efficiency of electrons and holes, thereby increasing the brightness of light emission; on the other hand, as a dielectric material, BaTiO3 can effectively isolate the electrodes and the light-emitting layer, preventing current from directly passing through the light-emitting layer, reducing current leakage and heat loss.

[0088] A mask was used to cover the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film from Example 1. The paste was screen-printed onto the surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. After removing the mask, the resulting wet film was placed in a drying oven and dried at 60 degrees Celsius until the paste completely solidified, forming a light-emitting / dielectric composite layer. A silver conductive layer was then fabricated on the surface of the light-emitting / dielectric composite layer (by printing or sputtering, etc.) to complete the fabrication of the light emitter. Using the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film as the TCF of the flexible ACEL, the luminescence of the bent ACEL was 42.84 candela per square centimeter, slightly lower than the 43.11 candela per square meter of the unbent ACEL. When using SnO2 / AgNWs@Nd2O3 transparent conductive film as the TCF for flexible ACEL, the luminance of the bent ACEL is 24.32 candela per square meter, lower than the 27.01 candela per square meter of the unbent ACEL. When using SnO2 / AgNWs / PU transparent conductive film as the TCF for flexible ACEL devices, the luminance of the bent ACEL is 39.03 candela per square meter. This value is lower than the 42.84 candela per square meter achieved by devices using SnO2 / AgNWs@Nd2O3 / PU transparent conductive film as the TCF.

[0089] After bending the flexible ACEL, the relative change in brightness based on both the SnO2 / AgNWs@Nd2O3 / transparent conductive film and the SnO2 / AgNWs / PU transparent conductive film was greater than that based on the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. This indicates that the encapsulated structure has better bending resistance than the unencapsulated structure.

[0090] The structure obtained by encapsulating AgNWs with Nd2O3 obtained from NdF3 hydrolysis exhibits excellent oxidation resistance and bending resistance. The SnO2 / AgNWs@Nd2O3 / PU transparent conductive film encapsulated with SnO2 / AgNWs@Nd2O3 possesses extremely low surface roughness and excellent waterproof performance, improving the luminescent performance of ACEL devices. The surface roughness of TCF significantly affects the brightness of ACELs. ACELs prepared using flexible SnO2 / AgNWs@Nd2O3 / PU transparent conductive films with low surface roughness as transparent electrodes exhibit high and uniform brightness and stable luminescent performance under bending conditions.

[0091] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film, characterized in that, include: S1. Sputtering a SnO2 layer onto the surface of a PET substrate; S2. A SnO2 / AgNWs transparent conductive film is formed by spin-coating AgNWs liquid onto the surface of the SnO2 layer. S3. After immersing the SnO2 / AgNWs transparent conductive film in a NaCl solution of 1.4 to 1.9 mol / L, wash away the excess NaCl on the surface to obtain the modified low-resistance SnO2 / AgNWs transparent conductive film. S4. After immersing the modified low-resistance SnO2 / AgNWs transparent conductive film in a NdF3 solution of 0.8 to 1.2 mg / mL, a core-shell structured SnO2 / AgNWs@Nd2O3 transparent conductive film is obtained. S5. After coating a layer of PU onto the surface of the SnO2 / AgNWs@Nd2O3 transparent conductive film, dry it to obtain the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film.

2. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, In step S1, the thickness of the PET substrate is 30 to 150 micrometers, and the thickness of the SnO2 layer is 300 to 400 nanometers.

3. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, In step S3, the concentration of the NaCl solution is 1.8 mol / L; in step S4, the concentration of the NdF3 solution is 1 mg / mL.

4. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, In step S3, the SnO2 / AgNWs transparent conductive film is immersed for 20 to 40 seconds.

5. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, In step S4, the modified low-resistance SnO2 / AgNWs transparent conductive film is immersed in NdF3 solution for 2.5 to 3.5 hours.

6. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, The steps in S5 include: A PU layer is spin-coated onto the surface of a SnO2 / AgNWs@Nd2O3 transparent conductive film at a rotation speed of 2500 to 3500 rpm for 0.5 to 2.0 minutes, followed by drying at 50 to 70 degrees Celsius to obtain the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film.

7. The method for preparing a low-resistance, ultra-stable silver nanowire-based transparent conductive film according to claim 1, characterized in that, The steps in S5 include: After partially masking the surface of the SnO2 / AgNWs@Nd2O3 transparent conductive film by covering it with a mask, a layer of PU is coated on the surface. Remove the mask, process silver electrodes in the masked areas, and finally dry to obtain a SnO2 / AgNWs@Nd2O3 / PU transparent conductive film with electrodes.

8. A method for fabricating a light emitter, using a SnO2 / AgNWs@Nd2O3 / PU transparent conductive film prepared by the method for preparing a low-resistance ultra-stable silver nanowire-based transparent conductive film according to any one of claims 1 to 7, characterized in that, include: K1. Thoroughly mix PDMS solution, ZnS:Cu and BaTiO3 to prepare a slurry. K2, the slurry is coated on the surface of SnO2 / AgNWs@Nd2O3 / PU transparent conductive film and dried to form a light-emitting / dielectric composite layer; K3. A silver conductive layer is fabricated on the surface of the light-emitting / dielectric composite layer to complete the fabrication of the light emitter.

9. The method for preparing a light emitter according to claim 8, characterized in that, In step K2, the slurry is applied by screen printing.

10. The method for preparing a light emitter according to claim 8, characterized in that, The steps in K2 include: The surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film is covered with a mask to form partial shielding; The slurry is coated on the surface of the SnO2 / AgNWs@Nd2O3 / PU transparent conductive film. After the mask is removed and dried, a light-emitting / dielectric composite layer is formed.

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