Intaglio printing metal oxide ink, composite film and preparation method and application thereof

Abstract

The invention discloses intaglio printing metal oxide ink, a composite film as well as a preparation method and application of the intaglio printing metal oxide ink. The intaglio printing metal oxide ink comprises metal oxide nanoparticles, a high-molecular polymer additive and an organic alcohol solvent, wherein the high-molecular polymer additive comprises polyvinyl butyral. The preparation method of the composite film comprises the following steps: printing intaglio printing metal oxide ink on the surface of a conductive film by adopting an intaglio printing method to form a metal oxide film, and then performing post-treatment to obtain the composite film. The stability and fluid characteristics of the ink are greatly improved based on cooperative regulation and control, the regulated and controlled metal oxide ink is used for preparing the thin film, the fusion and leveling process of liquid drops is effectively controlled due to regulation of the fluid characteristics of the ink, a printing rib structure on the macroscopic morphology is eliminated, and the printing quality of the thin film is improved. The quality and uniformity of the prepared film and the precision of patterning printing are greatly improved, and about 20-30% of materials can be saved for commercial application of the film.

Description

Technical Field

[0001] The present invention relates to an intaglio printing metal oxide ink, and in particular to an intaglio printing metal oxide ink, a corresponding intaglio printing composite film, and a preparation method and application thereof, belonging to the technical field of organic solar cells. Background Art

[0002] Organic solar cells (OSCs) have many advantages such as solution preparation, light weight, mechanical flexibility, wide material sources, patterning ability, and environmental friendliness, and have received extensive attention in the field of new-generation photovoltaic cells.

[0003] Intaglio printing is a promising large-scale manufacturing method for flexible organic solar cells (FOSCs) because it is compatible with two-dimensional patterning roll-to-roll manufacturing. ZnO nanoparticle ink has been widely used in the large-area printing preparation of the electron transport layer of organic solar cells due to its advantages such as high electron mobility, high transmittance, low work function, and low-temperature preparation by solution method. For ZnO nanoparticle ink, low-boiling alcohols are often used as dispersion solvents; however, the prepared ZnO ink has poor dispersion and stability in alcohol solvents, and is prone to agglomeration to form large particles and aggregates, resulting in a sharp decline in the stability of the ink. In addition, the interaction force between ZnO nanoparticles is weak, resulting in low viscosity of the ink. Therefore, adjusting the viscosity and dispersion of zinc oxide ink is the key to obtaining high-quality printed films.

[0004] Generally, the dispersion of the ink is adjusted by adding small-molecule stabilizers such as alkanolamines, and the method of increasing the viscosity of the ink is mainly to introduce thickeners. In order to simultaneously adjust the dispersion and fluid properties of the ink, in the existing process, the dispersion and fluid properties of the ink are separately regulated by adding stabilizers and thickeners at the same time, that is, the dispersion of the ink and the fluid properties of the ink are separately regulated by adding corresponding functional substances, and no scheme for synergistically regulating the dispersion and fluid properties of the composite ink has been found. Such a method usually has cumbersome steps, which is disadvantageous for the industrial application of the composite ink, increases the time cost and material consumption, etc., and increases the process cost in large-scale applications. Therefore, it is very necessary to optimize the adjustment of the existing intaglio printing ZnO ink and seek a method for synergistically regulating the viscosity and dispersion of the ink. Summary of the Invention

[0005] The main purpose of the present invention is to provide an intaglio printing metal oxide ink to overcome the defects existing in the prior art.

[0006] Another object of the present invention is to provide a composite film based on intaglio printing, and a preparation method and application thereof.

[0007] To achieve the foregoing invention purposes, the technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides an intaglio printing metal oxide ink, which includes: metal oxide nanoparticles, a polymer additive, and an organic alcohol solvent. The polymer additive includes polyvinyl butyral. At low concentrations, the polymer additive causes the viscosity to rise gently through solvation. When the concentration exceeds the critical value, the molecular chains entangle to form a three-dimensional network structure, and the viscosity increases sharply, accompanied by shear thinning characteristics. This characteristic makes it suitable for high-precision coating and printing processes (such as slot coating and intaglio printing). The viscosity of PVB (polyvinyl butyral) increases more significantly at high concentrations, which is attributed to the stable regulation relying on hydrogen bonds and van der Waals forces.

[0009] An embodiment of the present invention also provides a preparation method of the intaglio printing metal oxide ink, which includes: uniformly mixing metal oxide nanoparticles, a polymer additive, and an organic alcohol solvent to obtain the intaglio printing metal oxide ink.

[0010] An embodiment of the present invention also provides a preparation method of a composite film, which includes: using the intaglio printing method to print the aforementioned intaglio printing metal oxide ink onto the surface of a conductive film to form a metal oxide film on the conductive film, and then performing post-treatment to obtain the composite film.

[0011] An embodiment of the present invention also provides a composite film prepared by the aforementioned method, which includes a conductive film and a metal oxide film disposed on the conductive film.

[0012] Furthermore, an embodiment of the present invention also provides an application of the intaglio printing metal oxide ink or the composite film in an organic solar cell.

[0013] Correspondingly, an embodiment of the present invention also provides an organic solar cell, which includes a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode sequentially arranged in a set direction. The flexible electrode or the electron transport layer includes the aforementioned composite film.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects:

[0015] 1) The intaglio printing metal oxide ink provided by the present invention can significantly regulate the viscosity of the ink between 5 and 200 mPa by regulating the addition amount of the polymer additive;

[0016] 2) The intaglio printing metal oxide ink provided by the present invention greatly improves the stability of the ink based on synergistic regulation. The particle size of the nanoparticles is mostly reduced to within 25 nm, and the agglomeration phenomenon of the ink nanoparticles is significantly inhibited;

[0017] 3) Prepare a thin film using the regulated metal oxide ink. Since the fluid properties of the ink are adjusted, the droplet coalescence and leveling processes are effectively controlled, eliminating the printing rib structure in the macroscopic morphology and greatly improving the quality and uniformity of the prepared thin film. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figures 1a - 1f Particle size distribution diagrams of a series of ZnO:PVB composite inks prepared in Example 1 and Comparative Example 1 of the present invention (using newly prepared ZnO nanoparticles);

[0020] Figures 2a - 2f Particle size distribution diagrams of a series of ZnO:PVB composite inks prepared in Example 1 and Comparative Example 1 of the present invention (using ZnO nanoparticles placed for one month);

[0021] Figure 3 and Figure 4 Macroscopic photos of a series of ZnO:PVB composite inks and the inks after placement prepared in Example 1 and Comparative Example 1 of the present invention;

[0022] Figures 5a - 5b Graph of the viscosity change of a series of ZnO:PVB composite inks prepared in Example 2 and Comparative Example 2 of the present invention with shear stress;

[0023] Figure 6 Schematic diagram of the viscosity of a series of ZnO:PVB composite inks prepared in Example 2 and Comparative Example 2 of the present invention at a shear rate of 1;

[0024] Figure 7 Scanning electron microscope images of intaglio-printed silver nanowire-zinc oxide composite thin films prepared in Example 3 and Comparative Example 3 of the present invention;

[0025] Figure 8 3D confocal laser microscope images of intaglio-printed silver nanowire-zinc oxide composite thin films prepared in Example 3 and Comparative Example 3 of the present invention;

[0026] Figure 9 Optical microscope images of intaglio-printed silver nanowire-zinc oxide composite thin films prepared in Example 3 and Comparative Example 3 of the present invention;

[0027] Figures 10a - 10dMacroscopic test photos of the fine-patterned printed metal oxide thin films prepared in Example 6 and Comparative Example 6 of the present invention;

[0028] Figure 11 AFM atomic force microscope images of the gravure-printed silver nanowire-zinc oxide composite thin films prepared in Example 3 and Comparative Example 3 of the present invention. Detailed implementation manners

[0029] In view of the problems of poor dispersibility and low viscosity of metal oxide inks in alcohol solvents in the prior art, the inventors of this case have proposed the technical solution of the present invention through long-term research and a large number of practices. It mainly proposes a method for synergistically regulating the dispersibility and fluid characteristics of gravure-printed metal oxide inks, and adding a polymer additive with a synergistic dispersing effect to the ink. The following will further explain the technical solution, its implementation process and principle, etc., but it should not be understood as a limitation on the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the above content of the present invention still fall within the protection scope of the present invention.

[0030] As an aspect of the technical solution of the present invention, it provides a gravure-printed metal oxide ink, which is characterized in that it includes: metal oxide nanoparticles, a polymer additive, and an organic alcohol solvent. The polymer additive has the functions of synergistically regulating dispersion and the viscosity of the ink, and is specifically selected as polyvinyl butyral (PVB). The specific mechanism of action is as follows:

[0031] (1) Adsorption-entanglement coupling effect

[0032] After PVB adsorbs on the surface of the metal oxide, its unadsorbed free chain segments can still participate in chain entanglement in the solvent. This "partially adsorbed and partially free" state forms a "particle-polymer network" composite structure: Enhanced dispersibility: The adsorption layer inhibits particle aggregation, and the steric hindrance of the free chain segments further isolates the particles. Dynamic viscosity regulation: The viscosity of the entanglement network is determined by the total concentration of PVB, and the amount of adsorbed PVB affects the concentration of free chain segments, thereby indirectly regulating the viscosity.

[0033] (2) Bidirectional effect of solvation effect

[0034] Influence on dispersibility: The solvophilic chain segments of PVB (such as hydroxyl groups) form a solvation layer with the solvent (such as ethanol), reducing the van der Waals force between particles and improving the dispersion stability. Influence on viscosity: The degree of solvation affects the extensibility of the PVB chain. The fully solvated chain is more extended, enhancing the steric hindrance (beneficial for dispersion), while increasing the chain entanglement (increasing the viscosity). The balance between the two needs to be regulated by the solvent polarity.

[0035] In some embodiments, the addition amount of the polymer additive in the gravure printing metal oxide ink is generally controlled at 2.5-25 mg / mL.

[0036] Further, for the concentration of the additive, when the concentration of the metal oxide nanoparticles is fixed at 25 mg / mL, the optimal addition concentration of PVB is 2.5-25 mg / mL.

[0037] In some embodiments, the weight average molecular weight of the polymer additive is 170,000-250,000.

[0038] In some embodiments, the viscosity of the gravure printing metal oxide ink is 5-200 mPa·s, preferably 5-50 mPa·s. The present invention can significantly regulate the viscosity of the composite ink between 5-200 mPa·s by regulating the addition amount of the polymer resin. If inks with higher viscosities are needed, they can be flexibly regulated by flexibly adjusting the concentration of zinc oxide nanoparticles and the addition amount of polyvinyl butyral, which has great flexibility and variability.

[0039] In some embodiments, the organic alcohol solvent can be a single alcohol or a mixed alcohol solvent. Specifically, it can be selected from, but not limited to, any one or a combination of ethanol, butanol, n-propanol, etc. However, the carbon chain of the alcohol should not be too long, as the increase in the carbon chain significantly affects the evaporation rate. In the selection of the green solvent in the present invention, the dispersion state of the zinc oxide ink and the influence of the evaporation rate of the mixed ink on the film-forming state should be dynamically observed.

[0040] In some more preferred embodiments, the organic alcohol solvent includes a mixed solvent of ethanol and butanol, and the two can be blended in any ratio to obtain the desired ink system.

[0041] In some embodiments, the metal oxide nanoparticles include zinc oxide nanoparticles, but are not limited thereto.

[0042] In some embodiments, the particle size of the metal oxide nanoparticles is within 150 nm, preferably within 25 nm. Based on the synergistic regulation, the stability of the ink of the present invention is greatly improved. Most of the nanoparticle sizes of the ink are significantly reduced to within 25 nm, and the agglomeration phenomenon of the ink nanoparticles is significantly inhibited accordingly.

[0043] In summary, the viscosity of the gravure printing metal oxide ink provided by the present invention is 5 to 50 mPa·s, and the particle size Z-average of the metal oxide nanoparticles is within 25 nm, which is suitable for large-area thin film printing. If inks with higher viscosity requirements are needed, the addition amount of PVB can be correspondingly increased. It should be noted that the concentration of the metal oxide ink should be increased simultaneously at this time to avoid a significant decrease in the optoelectronic transmission performance of the organic solar cell caused by an excessive proportion of PVB.

[0044] As another aspect of the technical solution of the present invention, a preparation method of a gravure printing metal oxide ink is provided, including: uniformly mixing metal oxide nanoparticles, a polymer additive, and an organic alcohol solvent to prepare a gravure printing metal oxide ink with good dispersibility and viscosity.

[0045] The preparation method of the present invention optimizes the two cumbersome steps in the existing process of regulating dispersibility by adding small-molecule alkanolamines and regulating viscosity by adding resin polymers, simplifies the operation steps for the industrial application of composite inks, and saves time costs.

[0046] In some embodiments, the preparation method specifically includes:

[0047] Mixing metal oxide nanoparticles with an organic alcohol solvent to form a first dispersion;

[0048] Mixing the polymer additive with an organic alcohol solvent to form a second dispersion;

[0049] Mixing the first dispersion and the second dispersion, and performing ultrasonic dispersion to prepare the gravure printing metal oxide ink.

[0050] In some preferred embodiments, the concentration of the first dispersion is 10 to 100 mg / mL, preferably 20 to 60 mg / mL.

[0051] Further, taking zinc oxide nanoparticles as an example, the preparation method includes: first dispersing zinc oxide nanoparticles in an organic alcohol solvent, which can be a single alcohol or a mixed alcohol solvent.

[0052] In some preferred embodiments, the concentration of the second dispersion is 5 to 50 mg / mL.

[0053] As another aspect of the technical solution of the present invention, a preparation method of a composite film is also provided, including:

[0054] By means of intaglio printing, the aforementioned intaglio printing metal oxide ink is printed onto the surface of the conductive film to form a metal oxide film on the conductive film, and then post-treatment is carried out to obtain a composite film (hereinafter also referred to as "silver nanowire-metal oxide composite film").

[0055] In some embodiments, the specific process parameters of the intaglio printing include: the screen ruling of the gravure cylinder is 20 - 200 lines / cm, preferably 50 - 100 lines / cm, the cell depth is 20 - 90 μm, and the screening angle of the printing plate cylinder is 35° - 55°.

[0056] Furthermore, the printing speed of the intaglio printing is generally fixed at 10 - 100 m / min, the doctor blade pressure is 0.2 - 0.4 MPa, and the impression roller pressure is 0.2 - 0.4 MPa.

[0057] In some embodiments, the dot shape of the printing plate cylinder of the printing equipment used for the intaglio printing is generally diamond-shaped, but is not limited thereto.

[0058] In some embodiments, the conductive film includes a flexible silver nanowire transparent conductive film with a thickness of 20 - 100 μm.

[0059] Furthermore, the sheet resistance of the flexible silver nanowire transparent conductive film is 5 - 150 Ω / sq, the transmittance is 85% - 99.5%, and the roughness is 5 - 30 nm.

[0060] In some preferred embodiments, the intaglio printing metal oxide ink prepared in the present invention has a strong adhesion to the silver nanowire substrate, and there is no need to perform corresponding surface treatment on the silver nanowire substrate, and the corresponding printing film work can be directly carried out.

[0061] In some preferred embodiments, the post-treatment includes annealing treatment. Printing is directly carried out according to the above parameters, and the obtained film is post-treated by annealing. The temperature of the annealing treatment is preferably 110 - 140 °C, and the time is 10 - 20 min.

[0062] In some more specific preferred embodiments, a method for preparing a silver nanowire-zinc oxide composite film specifically includes:[[]]END]

[0063] By means of intaglio printing, zinc oxide ink is printed onto the surface of the flexible silver nanowire transparent conductive film to form a zinc oxide film, and then through post-treatment, a silver nanowire-zinc oxide composite film based on intaglio printing is obtained.

[0064] As another aspect of the technical solution of the present invention, it also provides a composite film prepared by the above preparation method, including a conductive film and a metal oxide film disposed on the conductive film.

[0065] Further, the thickness of the metal oxide thin film is 20-100 nm.

[0066] The present invention uses the regulated gravure printing metal oxide ink to prepare a thin film. Due to the adjustment of the fluid characteristics of the ink, the fusion and leveling processes of the droplets are effectively controlled, the printing rib structure on the macroscopic morphology is eliminated, and the quality and uniformity of the prepared thin film are greatly improved.

[0067] As another aspect of the technical solution of the present invention, it also provides the application of the gravure printing metal oxide ink or the composite thin film in an organic solar cell.

[0068] Correspondingly, another aspect of the technical solution of the present invention also provides an organic solar cell, including a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode sequentially arranged in a set direction. Among them, the electron transport layer uses the aforementioned composite thin film.

[0069] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and several preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention. The test methods in the following embodiments without specific conditions are carried out according to conventional conditions. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0070] Example 1 A ZnO composite ink with good ink dispersibility

[0071] This example provides a formulation for preparing an ink that is easy to store and has good dispersibility. The formulation method of the ink is as follows:

[0072] Step 1: Use newly prepared ZnO nanoparticles and ZnO nanoparticles placed for one month to prepare ZnO NPs butanol dispersion solutions respectively, and dilute their concentrations to the required concentration of 50 mg / mL.

[0073] Step 2: Dissolve polyvinyl butyral (PVB: relative molecular weight is about 170,000-250,000) in ethanol solvents respectively to prepare PVB resin ethanol solutions with concentrations of 2.5 mg / mL, 5 mg / mL, 7.5 mg / mL, 10 mg / mL, 15 mg / mL, and 20 mg / mL respectively for later use.

[0074] Step 3: Mix the solutions configured in Step 1 and Step 2 in a ratio of 1:1 to prepare a ZnO:PVB composite ink of 50% butanol and 50% ethanol. The content of PVB is half of that in Step 2, and the concentration of ZnO NPs is half of that in Step 1. Since the volume doubles after mixing, the concentration is halved.

[0075] Step 4: After performing the corresponding ultrasonic dispersion operation on the configured solution in an ultrasonic machine for about 2 minutes, place it in a refrigerator at 3 - 5°C for standby.

[0076] Step 5: Conduct corresponding macroscopic observations and microscopic particle size change tests on the ZnO:PVB composite ink after ultrasonic treatment in Step 4, and measure the particle size using a DLS dynamic light scattering instrument. The characterization results and macroscopic photos of the solution are as Figures 1a - 1f 、 Figures 2a - 2f 、 Figure 3 、 Figure 4 shown.

[0077] Comparative Example 1

[0078] This comparative example uses the same ink formulation work as in Example 1. The only difference is that no resin polymer polyvinyl butyral (PVB) is added, and only ethanol solvent is added to dilute the concentration of ZnO NPs particles. The test method is the same as in Example 1, and the test results are as Figures 1a - 1f 、 Figures 2a - 2f 、 Figure 3 、 Figure 4 shown, which are the particle size distribution diagram of ZnO ink and the macroscopic photo of the ink respectively.

[0079] Example 2 A ZnO Composite Ink with a Wide Viscosity Regulation Range

[0080] This example provides a method for regulating the fluid properties (viscosity) of ink within a wide range through polyvinyl butyral (PVB) and the preparation of the ink. The preparation method is as follows:

[0081] Step 1: Use newly prepared ZnO nanoparticles to prepare a butanol dispersion solution of ZnO NPs, and dilute its concentration to the required concentration of 50 mg / mL.

[0082] Step 2: Dissolve polyvinyl butyral (PVB: relative molecular weight is about 170000 - 250000) in ethanol solvent respectively to prepare PVB resin ethanol solutions with concentrations of 2.5 mg / mL, 5 mg / mL, 7.5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, and 50 mg / mL for later use.

[0083] Step 3: Mix the solutions prepared in Step 1 and Step 2 in a ratio of 1:1 to prepare a ZnO:PVB composite ink of 50% butanol and 50% ethanol. The content of PVB is half of that in Step 2, and the concentration of ZnO NPs is half of that in Step 1. Since the volume doubles after mixing, the concentration is halved.

[0084] Step 4: After performing the corresponding ultrasonic dispersion operation on the prepared solution in an ultrasonic machine for about 2 minutes, place it in a refrigerator at 3 - 5°C for standby.

[0085] Step 5: Characterize the fluid properties (viscosity, shear stress, etc.) of the composite ink prepared in Step 4 using a rotational rheometer, and finally perform corresponding data processing and use origin for data fitting. The test results are as Figures 5a - 5b 、 Figure 6 shown, which are respectively the graph of the viscosity of ZnO ink varying with shear stress and the viscosity of ZnO ink at a shear rate of 1.

[0086] As described above, the change in ink viscosity is due to the fact that at low concentrations, molecules cause the viscosity to rise gently through solvation, while when the concentration exceeds the critical value, molecular chains entangle to form a three-dimensional network structure, resulting in a sharp increase in viscosity and accompanied by shear thinning characteristics. This characteristic makes it suitable for high-precision coating and printing processes (such as slot coating and gravure printing). The viscosity of PVB (polyvinyl butyral) increases more significantly at high concentrations, which is attributed to the stable regulation relying on hydrogen bonds and van der Waals forces; regarding the change in shear rate, PVB regulates the rheological behavior of ZnO ink, making its shear stress response dependent on concentration and shear rate. High-concentration PVB significantly enhances the shear stress sensitivity of the system by enhancing intermolecular forces or forming a network structure.

[0087] Comparative Example 2

[0088] This comparative example uses the same ink formulation work as in Example 2. The only difference is that: no resin polymer polyvinyl butyral (PVB) is added, and only ethanol solvent is added to dilute the concentration of ZnONPs particles. The test method is the same as in Example 2, and the test results are as Figures 5a - 5b 、 Figure 6 shown, which are respectively the graph of the viscosity of ZnO ink varying with shear stress and the viscosity of ZnO ink at a shear rate of 1.

[0089] Example 3 A method for preparing a gravure-printed silver nanowire-zinc oxide composite film

[0090] Step 1: Use silver nanowire ink to prepare a patterned silver wire electrode on a PET film by gravure printing. The sheet resistance of the silver wire electrode is 13 - 14 Ω / □, and the corresponding transmittance is 94.2%.

[0091] Step 2: Gravure print a solution of zinc oxide polyvinyl butyral (ZnO:PVB) with 50% ethanol and 50% butanol on the silver nanowire electrode (the solid content of the zinc oxide solution is 25 mg / mL, the average particle size of zinc oxide nanoparticles is about 20 nm, the PVB concentrations are 2.5 mg / mL, 5 mg / mL, 7.5 mg / mL, and 10 mg / mL respectively, the printing speed is 50 m / min, the screen ruling of the gravure roll is 50 lines / cm, the screening angle is 45°, and the diamond-shaped cells are used). Then anneal at 130 °C for 10 min in an oven to obtain a zinc oxide composite film.

[0092] Step 3: Then characterize the microstructure of the ZnO:PVB composite film by scanning electron microscopy and 3D confocal laser microscopy, and characterize the ZnO:PVB composite film in a slightly larger range by optical microscopy.

[0093] From Figure 7 、 Figure 8 、 Figure 9 it can be found that the ZnO:PVB composite film prepared by gravure printing on the silver wire electrode with the ZnO:PVB composite ink dispersed in 50% ethanol and 50% butanol has very good uniformity. This is because the ink has a more appropriate evaporation rate at this time, and the addition of PVB provides good fluid properties, increasing its adhesion to the substrate, which helps to print a better film.

[0094] Comparative Example 3

[0095] A method for preparing a ZnO film provided in this Comparative Example 3 is only different in that: the solute only contains the corresponding ZnO nanoparticles and does not contain the added PVB polymer resin. The ZnO ink prepared in this way has great differences in fluid properties and ink dispersibility compared with those in Example 3. Finally, the same characterization means as in Example 3 are selected to compare the differences in the improvement of the comparison method, and the characterization result diagrams are as shown in Figure 7 、 Figure 8 、 Figure 9 shown.

[0096] The AFM atomic force microscopy diagrams of the gravure-printed silver nanowire-zinc oxide composite films prepared in Example 3 and Comparative Example 3 are as shown in Figure 11 shown.

[0097] Example 4 A method for preparing a flexible organic solar cell based on a gravure-printed silver wire-zinc oxide composite film

[0098] The preparation method of this flexible organic solar cell is as follows:

[0099] Step 1: Using silver nanowire ink, a patterned silver wire electrode was prepared on a PET film by gravure printing. The sheet resistance of the silver wire electrode was 13 - 14 Ω / □, the corresponding transmittance was 97.2%, and the roughness was 20 nm.

[0100] Step 2: A solution of zinc oxide polyvinyl butyral (ZnO:PVB) with 50% ethanol and 50% butanol was gravure printed on the silver nanowire electrode (the solid content of the zinc oxide solution was 25 mg / mL, the average particle size of the zinc oxide nanoparticles was about 20 - 40 nm, and the PVB concentration was 10 mg / mL). The printing speed was 50 m / min, the screen ruling of the gravure roll was 50 lines / cm, the cell depth was 50 μm, the screening angle was 45°, the doctor blade pressure was 0.3 MPa, and the impression roll pressure was 0.3 MPa. A diamond-shaped cell was used. Then it was annealed in an oven at 130 °C for 10 min to obtain a zinc oxide composite film with a thickness of about 80 nm.

[0101] Step 3: A PM6:L8-BO active layer solution was spin-coated on the surface of the zinc oxide film, where the PM6 content was 7.5 mg / mL, the L8-BO content was 9 mg / mL, and the DIB addition amount was 8.25 mg / mL. The spin-coating speed was 3000 r / min, and then it was annealed on a hot stage at 85 °C for 10 min in a glove box under a nitrogen atmosphere to obtain an active layer film.

[0102] Step 4: A MoO3 film with a thickness of about 10 nm and Al with a thickness of about 100 nm were sequentially evaporated on the active layer film, and finally a flexible organic solar cell was obtained.

[0103] Step 5: A 100-nm-thick active layer PM6:BO-4Cl chloroform solution was spin-coated on the ZnO layer prepared in Step 4 and annealed at 85 °C for 5 min.

[0104] Step 6: A 15-nm-thick MoO X layer was evaporated on the active layer prepared in Step 5 by vacuum thermal evaporation deposition.

[0105] Comparative Example 4

[0106] The preparation method of the organic solar cell in this comparative example was the same as that of Example 4 above, with the only difference being that the ZnO ink did not add PVB resin and was a standard ZnO solution, and finally a standard ZnO film was prepared. The device performances of the flexible organic solar cells prepared from Example 4 and Comparative Example 4 were tested, and the results are shown in Table 1.

[0107] Table 1 Performances of a series of flexible organic solar cell devices prepared from Example 4 and Comparative Example 4

[0108]

[0109] As can be seen from Table 1, when the ZnO concentration is fixed at 25 mg / mL, the device efficiency reaches the maximum value of 14.25% when the PVB concentration is added at 15 mg / mL. Compared with the device in Comparative Example 4 (without adding PVB) with an efficiency of 12.04%, there is an obvious improvement, indicating that the addition of PVB improves the ink dispersibility and rheological properties, resulting in an improvement in the uniformity of the prepared film, thereby enhancing the Jsc and FF of the device, and thus improving the PCE of the device.

[0110] Similarly, as can be seen from Table 1, when the viscosity of the ZnO:PVB solution is maintained at 5 - 50 mPa·s, the performance of the device is relatively good. When the viscosity increases to 100 mPa·s, the fill factor FF of the device starts to decrease significantly, and the device performance deteriorates. This may be due to the fact that the solution viscosity is too high, and obvious defects exist in the formed ZnO:PVB film.

[0111] Example 4 - 1

[0112] This example is different from Example 4 only in that:

[0113] Step 2: Gravure print a solution of zinc oxide polyvinyl butyral (ZnO:PVB) with 50% ethanol and 50% butanol on the silver nanowire electrode (the solid content of the zinc oxide solution is 25 mg / mL, the average particle size of zinc oxide nanoparticles is about 20 - 40 nm, and the PVB concentration is 10 mg / mL), the printing speed is 10 m / min, the screen ruling of the gravure roll is 20 lines / cm, the cell depth is 20 μm, the screening angle is 35°, the doctor blade pressure is 0.2 MPa, the impression roll pressure is 0.2 MPa, and a diamond-shaped cell is used. Then anneal at 110 °C for 10 min in an oven to obtain a zinc oxide composite film.

[0114] Example 4 - 2

[0115] This example is different from Example 4 only in that:

[0116] Step 2: Gravure print a solution of zinc oxide polyvinyl butyral (ZnO:PVB) with 50% ethanol and 50% butanol on the silver nanowire electrode (the solid content of the zinc oxide solution is 25 mg / mL, the average particle size of zinc oxide nanoparticles is about 20 - 40 nm, and the PVB concentration is 10 mg / mL), the printing speed is 100 m / min, the screen ruling of the gravure roll is 200 lines / cm, the cell depth is 90 μm, the screening angle is 55°, the doctor blade pressure is 0.4 MPa, the impression roll pressure is 0.4 MPa, and a diamond-shaped cell is used. Then anneal at 130 °C for 10 min in an oven to obtain a zinc oxide composite film.

[0117] Preparation of Organic Solar Cells with a Wider ZnO Thin Film Printing Window in Example 5

[0118] The preparation method of this organic solar cell is as follows:

[0119] Step 1: Using silver nanowire ink, a patterned silver wire electrode was prepared on a PET film by gravure printing. The sheet resistance of the silver wire electrode was 13 - 14 Ω / □, and the corresponding transmittance was 94.2%.

[0120] Step 2: A solution of zinc oxide polyvinyl butyral (ZnO:PVB) in 50% ethanol and 50% butanol was gravure - printed on the silver nanowire electrode (the solid content of the zinc oxide solution was 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL respectively, the average particle size of zinc oxide nanoparticles was about 20 nm, and the PVB concentration was 10 mg / mL). The concentration of zinc oxide has a proportional relationship with the thickness of the prepared thin film. The greater the zinc oxide concentration, the greater the thickness of the prepared film. The printing speed was 50 m / min, the screen ruling of the gravure roll was 50 lines / cm, the screening angle was 45°, and a diamond - shaped cell was used. Then it was annealed at 130 °C for 10 min in an oven to obtain a zinc oxide composite thin film.

[0121] Step 3: Spin - coat a PM6:L8 - BO active layer solution on the surface of the zinc oxide thin film, where the PM6 content was 7.5 mg / mL, the L8 - BO content was 9 mg / mL, and the DIB addition amount was 8.25 mg / mL. The spin - coating speed was 3000 r / min, and then it was annealed on a hot stage at 85 °C for 10 min in a glove box under a nitrogen atmosphere to obtain an active layer thin film.

[0122] Step 4: Evaporate a MoO3 thin film with a thickness of about 10 nm and Al with a thickness of about 100 nm successively on the active layer thin film to finally obtain a flexible organic solar cell.

[0123] Step 5: Spin - coat a 100 - nm - thick active layer PM6:BO - 4Cl chloroform solution on the ZnO layer prepared in Step 4 and anneal it at 85 °C for 5 min.

[0124] Step 6: Evaporate a 15 - nm - thick MoO X layer on the active layer prepared in Step 5 by vacuum thermal evaporation deposition.

[0125] Comparative Example 5

[0126] The preparation method of the organic solar cell in this comparative example is the same as that of Example 5 above. The only difference is that the ZnO ink does not add PVB resin and is a standard ZnO solution, and the finally prepared is a standard ZnO thin film. The device performance of the flexible organic solar cells prepared from Example 5 and Comparative Example 5 was tested, and the results are shown in Table 2.

[0127] Table 2 Performance of a series of flexible organic solar cell devices prepared in Example 5 and Comparative Example 5

[0128]

[0129]

[0130] As can be seen from Table 2, when the PVB polymer resin was added, the PCE of the device showed an increasing trend in the range of ZnO concentration from 20 to 50 mg / mL, indicating that the addition of PVB improved the sensitivity of the printed film thickness of the organic solar cell interface layer, which is of great significance for large-scale R2R industrial preparation in the later stage. At the same time, by comparing with the comparative device, it can be found that the comparative device showed a decreasing trend in the range of ZnO concentration from 20 to 50 mg / mL, indicating that the increase in ZnO concentration led to the thickening of the film thickness, which had a significant impact on the device prepared with the standard ZnO interface layer film without PVB, and it was highly sensitive to the film thickness. Therefore, the addition of PVB is of great significance for improving the film thickness sensitivity.

[0131] Preparation of the fine-patterned metal oxide electron transport layer composite film in Example 6

[0132] The preparation method of the fine-patterned electron transport layer composite film is as follows:

[0133] Select a PET substrate without any pretreatment, and use a gravure printing machine to print a solution of zinc oxide polyvinyl butyral (ZnO:PVB) with 50% ethanol and 50% butanol (the solid content of the zinc oxide solution is 25 mg / mL, the average particle size of zinc oxide nanoparticles is about 20 nm, and the PVB concentration is 10 mg / mL). The printing speed is 50 m / min, the screen ruling of the gravure roll is 50 lines / cm, the screening angle is 45°, and a patterned printing cell is used. Then anneal at 130 °C for 10 min in an oven to obtain a fine-patterned zinc oxide composite film, as Figure 10a 、 Figure 10c shown.

[0134] It can be observed that due to the regulation of PVB, the ink is quickly fixed in the corresponding position after being transferred to the PET substrate and does not show a tendency to spread outward. This benefits from the regulation of the viscosity of the ink by PVB, so that the adhesion of the composite ink to the substrate is enhanced, and finally the required pattern is formed.

[0135] It should be noted that fine patterning printing has higher requirements for the ink flow characteristics. Therefore, the optimal range of the addition amount of PVB is greater than 7.5 mg / mL and less than 17.5 mg / mL. The patterns printed within this range are the sharpest, and the pattern marginalization effect is minimized and effectively controlled.

[0136] Comparative Example 6

[0137] Similarly, a PET substrate was selected. The difference is that the ZnO ink without the synergistic regulation effect of PVB has poor fluid characteristics and poor wettability on PET. First, the surface of the PET substrate was treated with plasma to improve the wettability of the ZnO ink on it. Second, a gravure printing press was used to gravure print a zinc oxide solution of 50% ethanol and 50% butanol (the solid content of the zinc oxide solution was 25 mg / mL, and the average particle size of the zinc oxide nanoparticles was about 20 nm). The printing speed was 50 m / min, the screen ruling of the gravure roll was 50 lines / cm, the screening angle was 45°, and a patterned printing cell was used. Then, it was annealed at 130 °C for 10 min in an oven to obtain a patterned zinc oxide composite film, and the patterns as shown in Figure 10b and Figure 10d were obtained.

[0138] It can be observed that the marginalization effect of the patterned film printed with the original zinc oxide ink is very serious. Around the graphics, it shows a shape of outward diffusion. This is mainly because the viscosity of the original zinc oxide ink is too low, and the adhesion to the substrate is relatively weak. After the ink is transferred to the PET substrate, it cannot be effectively fixed in the corresponding position, and the ink still diverges to the outside. Only then does the solvent volatilize accordingly, resulting in the formation of the final pattern.

[0139] In addition, the inventors of this case also referred to the foregoing embodiments and conducted tests with other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0140] All aspects, embodiments, features, and examples of the present invention should be considered illustrative in all respects and are not intended to limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed present invention, those skilled in the art will understand other embodiments, modifications, and uses.

[0141] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and / or additions can be made without departing from the spirit and scope of the present invention and elements of the embodiments can be replaced with substantially equivalent ones. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the present invention. Accordingly, it is not intended that the present invention be limited to the particular embodiments disclosed for carrying out the present invention, but rather that the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. An intaglio printing metal oxide ink, characterized in that, Comprising: Metal oxide nanoparticles, a polymer additive, and an organic alcohol solvent, wherein the polymer additive includes polyvinyl butyral.

2. The gravure printing metal oxide ink according to claim 1, characterized in that: The content of the polymer additive in the gravure printing metal oxide ink is 2.5 - 25 mg / mL; and / or, the weight average molecular weight of the polymer additive is 170,000 - 250,000; and / or, the viscosity of the gravure printing metal oxide ink is 5 - 200 mPa·s, preferably 5 - 50 mPa·s.

3. The gravure printing metal oxide ink according to claim 1, wherein: The organic alcohol solvent includes any one or a combination of ethanol, butanol, and n-propanol; preferably, the organic alcohol solvent includes a mixed solvent of ethanol and butanol; and / or, the metal oxide nanoparticles include zinc oxide nanoparticles; and / or, the particle size of the metal oxide nanoparticles is within 150 nm, preferably within 25 nm.

4. The preparation method of the gravure printing metal oxide ink according to any one of claims 1-3, characterized in that, Comprising: The metal oxide nanoparticles, the polymer additive, and the organic alcohol solvent are uniformly mixed to obtain the gravure printing metal oxide ink.

5. The preparation method according to claim 4, characterized in that, Comprising: The metal oxide nanoparticles are mixed with the organic alcohol solvent to form a first dispersion; The polymer additive is mixed with the organic alcohol solvent to form a second dispersion; The first dispersion and the second dispersion are mixed and ultrasonically dispersed to obtain the gravure printing metal oxide ink; Preferably, the concentration of the first dispersion is 10 - 100 mg / mL, preferably 20 - 60 mg / mL; Preferably, the concentration of the second dispersion is 5 - 50 mg / mL.

6. A method for preparing a composite film, characterized in that, Comprising: By using the gravure printing method, the gravure printing metal oxide ink according to any one of claims 1 - 3 is printed on the surface of a conductive film to form a metal oxide film on the conductive film, and then post-treatment is performed to obtain a composite film.

7. The preparation method according to claim 6, wherein The specific process parameters of the gravure printing include: the screen ruling of the gravure roll is 20 - 200 lines / cm, preferably 50 - 100 lines / cm, the cell depth is 20 - 90 μm, and the screening angle of the printing plate roll is 35° - 55°; and / or, the dot shape of the printing plate roll of the printing equipment used for the gravure printing is rhombus; and / or, the printing speed of the gravure printing is 10 - 100 m / min, the doctor blade pressure is 0.2 - 0.4 MPa, and the impression roll pressure is 0.2 - 0.4 MPa; and / or, the conductive film includes a flexible silver nanowire transparent conductive film with a thickness of 20 - 100 μm. Preferably, the sheet resistance of the flexible silver nanowire transparent conductive film is 5 - 150 Ω / square, the transmittance is 85% - 99.5%, and the roughness is 5 - 30 nm; and / or, the post-treatment includes annealing treatment, and the temperature of the annealing treatment is 110 - 140 °C and the time is 10 - 20 min.

8. A composite film prepared by the preparation method according to any one of claims 6 - 7, comprising a conductive film and a metal oxide film disposed on the conductive film; preferably, the thickness of the metal oxide film is 20 - 100 nm.

9. Use of the gravure printing metal oxide ink according to any one of claims 1 to 3 or the composite film according to claim 8 in an organic solar cell.

10. An organic solar cell, comprising a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode sequentially arranged in a set direction, characterized in that: The electron transport layer comprises the composite film according to claim 8.

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