Organic active layer ink suitable for intaglio printing, property regulation and control method and application

Abstract

The invention discloses organic active layer ink suitable for intaglio printing, a property regulation and control method and application. The property regulation and control method comprises the following steps: regulating and controlling the molecular weight of a polymer donor material to enable the viscosity to be 15-1500 mPa.s; by adjusting the composition and proportion of the multi-component mixed solvent, the surface tension is 20-40mN / m, and the multi-component mixed solvent has a proper volatilization speed. According to the invention, the viscosity is effectively regulated by adjusting the molecular weight of the polymer donor, so that the situation that the device performance is greatly reduced due to the fact that the photoelectric property is remarkably reduced due to the use of a large amount of thickening agent is avoided; meanwhile, the excessive aggregation of the microstructure of the active layer can be effectively inhibited; the surface tension and the volatilization speed are effectively regulated and controlled through a mixed solvent method, good wettability and appropriate drying time are achieved, an active layer film which is large in area, uniform and excellent in microstructure can be prepared through intaglio printing, and finally the organic solar cell with various excellent properties can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of organic solar cells, and in particular to an organic active layer ink suitable for gravure printing, a property control method and an application thereof. Background Art

[0002] Organic solar cells have the advantages of being flexible, lightweight, non-toxic, and able to be processed by roll-to-roll large-area solutions, which makes them have great application potential in the fields of architectural photovoltaics, portable energy, wearable electronics, and indoor photovoltaics. In recent years, due to the synthesis of new active layer materials, interface engineering, and optimization of active layer morphology, the efficiency of single-cell organic solar cells has exceeded 19%, and stacked organic solar cells have exceeded 20%. The stability of the device has also been greatly improved. However, most of these high-efficiency devices are prepared by spin coating, which is incompatible with roll-to-roll large-area preparation methods, making it difficult to prepare large-area thin films.

[0003] At present, the main large-area preparation methods for organic solar cells are blade coating and slit coating. Although the blade coating process is easy to operate and has low requirements for ink performance, it can produce large-area uniform thin films. However, blade coating does not have the function of patterning. When preparing organic solar cell modules, it is necessary to use expensive lasers to scribing. The process is complicated and the preparation cost is high. Slit coating has the function of one-dimensional patterning, and can directly prepare strip-shaped organic solar cell modules without the help of lasers. However, the pattern prepared by slit coating has obvious edge effects, which will lead to a low geometric filling factor of the prepared organic solar cell module, usually between 50% and 70%. Moreover, slit coating can only prepare strip-shaped modules, which seriously affects the aesthetics of organic solar cell modules. Gravure printing is a preparation method that can be two-dimensionally patterned, high-precision, high-speed and roll-to-roll large-area processing, so gravure printing is expected to solve the problems of low geometric filling factor and poor aesthetics of organic solar cell modules. Gravure printing is a very mature large-area preparation method, which has a wide range of applications in plastic packaging, tobacco and alcohol packaging, banknotes and other fields.

[0004] The function of gravure printing has obvious advantages over coating processes (slot coating and blade coating), but it requires higher rheological properties of ink. The ink for gravure printing usually requires higher viscosity, lower surface tension and appropriate evaporation speed, otherwise it will cause uneven film.

[0005] The viscosity of traditional active layer ink is usually very low, about a few mPa·s. This leads to a large number of irregular stripes in the gravure active layer film, poor quality of the printed active layer film, and a large number of leakage and short circuits in the gravure printed devices.

[0006] In order to solve the viscosity problem, although there is a technical solution in the prior art to increase the viscosity of the ink by adding a thickener to the ink, since most thickeners are non-conductive organic materials, it is easy to cause a serious decline in device performance. In addition, the active layer ink is usually dispersed in a single solvent, and the surface tension and evaporation rate of the ink usually do not meet the requirements of gravure printing. It is difficult to prepare a large-area organic solar active layer with macroscopic uniformity and good microscopic morphology. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide an organic active layer ink suitable for gravure printing, a method for controlling properties and applications.

[0008] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0009] In a first aspect, the present invention provides an organic active layer ink suitable for gravure printing, comprising:

[0010] Polymer donor materials, small molecule acceptor materials and solvents;

[0011] wherein the molecular weight of the polymer donor material is within a selected range so that the viscosity of the organic active layer ink is 15-1500 mPa·s;

[0012] The solvent is selected from a multi-component mixed solvent so that the surface tension of the ink at 25° C. is 20 to 40 mN / m.

[0013] In a second aspect, the present invention also provides a method for controlling the properties of an organic active layer ink suitable for gravure printing, comprising the steps of mixing at least a polymer donor material, a small molecule acceptor material and a solvent to form an ink;

[0014] And specifically include:

[0015] By adjusting the molecular weight of the polymer donor material, the viscosity of the final ink is 15-1500 mPa·s; by adjusting the composition and proportion of the solvent, the solvent is a multi-component mixed solvent, so that the surface tension of the ink at 25° C. is 20-40 mN / m.

[0016] In a third aspect, the present invention further provides the use of the above organic active layer ink or the above property control method in preparing an organic active layer by gravure printing.

[0017] As a specific presentation of the above application, in a fourth aspect, the present invention further provides a method for preparing an organic active layer, which comprises:

[0018] Providing the above-mentioned organic active layer ink or obtaining the organic active layer ink by adjusting the above-mentioned property control method;

[0019] Printing the organic active layer ink to form an active layer precursor by gravure printing;

[0020] The active layer precursor is post-treated to convert the active layer precursor into an organic active layer.

[0021] In a fifth aspect, the present invention also provides an organic active layer obtained by the above preparation method, wherein the organic active layer has excellent uniformity and a thickness deviation within 10%.

[0022] In a sixth aspect, the present invention further provides an organic solar cell, the device structure comprising a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode;

[0023] The active layer is prepared by the above preparation method or selected from the organic active layer provided above.

[0024] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention at least include:

[0025] The organic active layer ink and the method for controlling its properties provided by the present invention effectively control the viscosity of the active layer ink by adjusting the molecular weight of the polymer donor, thereby avoiding the use of a large amount of thickeners to cause a significant decrease in the photoelectric performance of the active layer film, thereby greatly reducing the performance of the device; at the same time, the photoactive layer ink with a higher viscosity can effectively inhibit the excessive aggregation of the microscopic morphology of the active layer; the surface tension and volatilization rate of the organic active layer ink are effectively controlled by a mixed solvent method, so that the ink has good wettability and suitable drying time on the substrate, and then a large-area uniform active layer film with excellent microscopic morphology can be prepared by gravure printing, and finally a large-area, high-efficiency and high-uniformity organic solar cell can be obtained.

[0026] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1a -d is an optical macroscopic photograph of the active layer film prepared by gravure printing on a silver nanowire (AgNW) / zinc oxide (ZnO): polyvinyl pyrrolidone (PVP) composite film using active layer inks of PM6 with different weight-average molecular weights in Example 1 of the present invention.

[0029] Figure 2a -d is an atomic force microscope (AFM) image of the active layer film prepared by gravure printing on the gravure AgNW / ZnO:PVP composite film using active layer inks of PM6 with different weight-average molecular weights in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle, etc. will be further explained as follows. Specifically, the purpose of the technical solution exemplified in the embodiment of the present invention is to develop an organic solar cell active layer ink suitable for gravure printing, and to provide a printing method for an active layer film, and then obtain a large-area active layer film based on gravure printing and a gravure three-layer solar cell device.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0032] An embodiment of the present invention provides an organic active layer ink suitable for gravure printing, comprising: a polymer donor material, a small molecule acceptor material and a solvent; wherein the molecular weight of the polymer donor material is within a selected range so that the viscosity of the organic active layer ink is 15-1500 mPa·s; and the solvent is selected from a multi-component mixed solvent so that the surface tension of the ink at 25°C is 20-40 mN / m.

[0033] In order to obtain the above-mentioned ink product, an embodiment of the present invention further provides a method for controlling the properties of an organic active layer ink suitable for gravure printing, comprising at least the steps of mixing a polymer donor material, a small molecule acceptor material and a solvent to form an ink; and specifically comprising:

[0034] By adjusting the molecular weight of the polymer donor material, the viscosity of the final ink is 15-1500 mPa·s; by adjusting the composition and proportion of the solvent, the solvent is a multi-component mixed solvent, so that the surface tension of the ink at 25° C. is 20-40 mN / m.

[0035] As a typical example of the above technical solution, the organic active layer ink can be prepared according to the following process: first, a formulated amount of polymer donor material, small molecule acceptor material, solvent, and additive are added to a container, and stirred and dissolved until uniformly dispersed to obtain the active layer ink.

[0036] Of course, in the above-mentioned property control method, the corresponding component selection, proportioning and better selection of ink properties can refer to the corresponding characteristics of the above-mentioned ink products.

[0037] In the prior art, in order to achieve the regulation of ink viscosity, it is often necessary to add a thickener to achieve the regulation. Since the thickener is often a non-conductive polymer, this will cause the photoelectric performance of the photoactive layer film to be significantly reduced, thereby causing the performance of the device to be greatly reduced. The present invention adopts a method of adjusting the molecular weight of the donor material, which not only achieves viscosity regulation, but also optimizes the microscopic morphology of the photoactive layer. Of course, in order to achieve gravure printing to prepare a large-area uniform active layer film, it is also necessary to cooperate with the ink's lower surface tension and appropriate evaporation rate. The present invention also achieves the above-mentioned effect through the combined optimization of solvents.

[0038] It is clear that the molecular weight of the donor material can not only improve the rheological properties, but also will not cause a decrease in the photoelectric properties of the film. In addition, it can inhibit the excessive aggregation of the active layer material to achieve the effect of regulating the micromorphology of the active layer. This is different from the multiple functions of the thickener commonly used above.

[0039] The principle of the above effect should be: by changing the molecular weight of the donor material to adjust the length of the polymer chain, thereby regulating the degree of entanglement between the molecular chains, and then achieving the effect of regulating the viscosity of the ink; due to the increase in the viscosity of the ink, the interaction force within the ink also increases significantly, which can inhibit the rapid movement of the small molecules of the receptor, thereby achieving the effect of inhibiting the excessive aggregation of the active layer material and optimizing the microscopic morphology of the film. By selecting solvents with different boiling points and different surface tensions and mixing them with each other, the evaporation rate and surface tension of the ink can be controlled.

[0040] That is to say, the technical contribution made by the present invention is not only reflected in providing a specific formula of organic active layer ink, but also in providing a common standard for adjusting uniformity and micromorphology. The property control method provided by the present invention can obtain a series of gravure inks with higher use effects. Therefore, the technical solution provided by the present invention is not limited to specific products and preparation methods, but also a novel control method and the disclosure of its laws. Some point values ​​and specific cases disclosed in the prior art may fall within the scope summarized by the present invention, but the disclosure of some point values ​​does not mean that the above laws are indicated.

[0041] Specifically, in some embodiments, the molecular weight of the polymer donor material enables the viscosity of the organic active layer ink to be better regulated within the range of 30-700 mPa·s;

[0042] In some embodiments, the concentration of the polymer donor material in the organic active layer ink is 5-25 mg / mL, and more preferably 7-18 mg / mL.

[0043] In some embodiments, the multi-component mixed solvent may be selected from a combination of two or more of o-xylene, chlorobenzene, trimethylbenzene, toluene, chloroform, and tetrahydrofuran;

[0044] In some embodiments, the polymer donor material may include, for example, any one of PM6, D18, PTQ, P3HT, PM7, and D18-Cl, or a combination of two or more thereof;

[0045] In some embodiments, the small molecule acceptor material may include, for example, any one of BO-4Cl, BTP-eC9, PC61BM, PC71BM, L8-BO, and Y6, or a combination of two or more thereof.

[0046] In some embodiments, the molecular weight of the polymer donor material refers to the weight average molecular weight;

[0047] In some embodiments, the weight average molecular weight of the polymer donor material may be, for example, 45-200 kDa.

[0048] The above content is an elaboration of specific regulation details, and in some embodiments, the organic active layer ink may further include additives;

[0049] In some embodiments, the additive includes any one or a combination of two of chloronaphthalene, 1,8-diiodooctane, 1,4-diiodobenzene, 1,3,5-trichlorobenzene and 3,5-dichlorobromobenzene;

[0050] In some embodiments, the liquid additive (preferably comprising chloronaphthalene and / or 1,8-diiodooctane) in the organic active layer ink accounts for 0.1-2%, preferably 0.25-1%, of the total volume of the solvent.

[0051] In some embodiments, the solid additive in the organic active layer ink (preferably comprising any one or more combinations of 1,4-diiodobenzene, 1,3,5-trichlorobenzene and 3,5-dichlorobromobenzene) is 0.5-3 times the mass of the donor material, preferably 0.7-1.5 times.

[0052] Of course, the selection of additives can be adjusted based on actual needs and is not limited to the scope of the above examples.

[0053] As an application of the above ink and method, an embodiment of the present invention further provides an application of the above organic active layer ink or property control method in preparing an organic active layer by gravure printing.

[0054] For example, a specific application of the present invention provides a method for preparing an organic active layer, which includes:

[0055] Providing the organic active layer ink provided in any of the above embodiments or the organic active layer ink obtained by adjusting the above property control method;

[0056] Printing the organic active layer ink to form an active layer precursor by gravure printing;

[0057] The active layer precursor is post-treated to convert the active layer precursor into an organic active layer.

[0058] A specific post-treatment method is film-forming treatment, for example, drying at a drying temperature of 80 to 150° C. and a drying time of 5 to 30 minutes to form a film.

[0059] Correspondingly, the present invention also provides an organic active layer obtained by the above preparation method, wherein the organic active layer has excellent uniformity and a thickness deviation within 10%.

[0060] In further applications, the present invention also provides an organic solar cell, the device structure of which includes a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode; the active layer is prepared by the above preparation method or selected from the above organic active layer.

[0061] In some embodiments, the flexible electrode, the electron transport layer and the active layer are all prepared by gravure printing.

[0062] As some typical application examples of the above technical solution, for example, the organic active layer ink described in one of the present invention can be printed on the surface of a flexible transparent composite substrate by a gravure printing machine, and then the active layer film can be obtained by post-processing.

[0063] Furthermore, the flexible transparent composite substrate is composed of a flexible transparent electrode and a zinc oxide composite film (as an electron transport layer). Furthermore, the flexible transparent electrode may include, for example, flexible ITO, a flexible silver nanowire electrode, a flexible metal grid electrode, a flexible ultra-thin metal electrode, etc., but is not limited thereto. The zinc oxide composite film includes, but is not limited to, a ZnO:PVP film, a ZnO:PEI film, etc., and may also be an electron transport layer of other materials.

[0064] As for the gravure printing method, the gravure roller of the gravure printing machine is prepared by any one of an electronic engraving method, a laser engraving method, a chemical etching method, and a mechanical engraving method; the speed of the gravure printing machine is 5 to 400 m / min; the scraper pressure of the gravure printing machine is 0.1 to 0.5 MPa; the pressure of the impression roller of the gravure printing machine is 0.1 to 0.5 MPa; the number of screen lines of the gravure roller of the gravure printing machine is 10 to 300 lines / cm; the depth of the gravure roller is 5 to 100 μm, and the screen angle of the gravure roller is 30°, 45° or 60°. The shape of the dots of the gravure roller is a rhombus, a quadrilateral, a hexagon or a TB dot. Of course, even if the printing method is different from the above example, it is sufficient to achieve the same gravure printing function.

[0065] The device structure of a flexible organic solar cell specifically exemplified includes a flexible electrode, an electron transport layer, an active layer, a hole transport layer, and a top electrode. Further, the hole layer transport material is one or more of self-poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly-3,4-ethylenedioxythiophene / polystyrene sulfonate, nickel oxide, copper oxide, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene, cuprous thiocyanate, and molybdenum oxide. Further, the top electrode is one or more of an Ag electrode, an Al electrode, an Au electrode, a Cu electrode, a PH1000 polymer electrode, and a metal oxide electrode. And they are not limited to the scope of the above examples.

[0066] The technical solution of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention, and do not limit the scope of the present invention.

[0067] Example 1 A preparation process of an organic solar cell by gravure printing is specifically as follows:

[0068] 1. Preparation of ink

[0069] Take 10 mg of PM6 polymer donor with different weight average molecular weights (99.9, 117.2, 134.5, 150.2 kDa), 12 mg of BO-4Cl small molecule acceptor, mixed solvent: o-xylene (o-XY) and chloroform (CF) in a volume ratio of 3:1, a total of 1 mL, and 5 μL of additive CN, and mix and stir to obtain the corresponding organic active layer ink. The viscosities of PM6 active layer inks with different weight average molecular weights (99.9, 117.2, 134.5, 150.2 kDa) at 25°C are 15.6, 48.3, 370.3, 1085.0 mPa·s, respectively, and the surface tension at 25°C is 29.0 mN / m.

[0070] 2. Preparation of flexible transparent composite substrate

[0071] A 60 nm thick ZnO:PVP film was gravure printed on the surface of the gravure silver wire electrode to form a substrate.

[0072] 3. Gravure printing and film formation of organic active layer

[0073] The precursor film was printed on the substrate surface by gravure printing at a speed of 50 m / min, a blade pressure of 0.3 MPa, an embossing roller pressure of 0.3 MPa, a screen line count of 50 lines / cm, a roller depth of 30 μm, and a screen angle of 45°, and then dried at 100°C for 10 minutes to form an organic active layer.

[0074] 4. Preparation of hole transport layer and top electrode

[0075] By evaporation, a 10nm thick molybdenum oxide was printed on the surface of the organic active layer to form a hole transport layer, and then a 200nm thick Al electrode was evaporated on the surface of the transport layer. Finally, a flexible organic solar cell was obtained.

[0076] Comparative Example 1 A process for preparing an organic solar cell by gravure printing is substantially the same as that of Example 1, except that: the weight average molecular weight (M w )0 is 60.1 kDa (smaller than Example 1), and the viscosity of the ink obtained at this time is 3.2 mPa·s.

[0077] Comparative Example 2 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 1, with the main difference being that the weight average molecular weight of the polymer donor is 240.3 kDa (larger than that of Example 1), and the viscosity of the ink obtained at this time is 2800.5 mPa·s.

[0078] Comparative Example 3 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 1, except that the weight average molecular weight of the polymer donor is 60.1 kDa (smaller than that of Example 1), but an appropriate thickener (polyvinyl pyrrolidone (PVP, M w =1300 kDa)) so that the obtained ink maintains the same viscosity as the example.

[0079] The performance of the flexible organic solar cell devices prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 (named as devices 1-1, 1-2, 1-3, 1-4, 1', 2', 3', respectively) were tested, and the results are shown in Table 1.

[0080] Table 1

[0081]

[0082] Figure 1a -d shows the optical macroscopic photos of active layer films prepared by gravure printing of active layer inks of PM6 with different weight average molecular weights on gravure AgNW / ZnO∶PVP composite films. It can be found from the figure that when the weight average molecular weight (M w ) is 99.9kDa, the viscosity of the ink is 15.6mPa·s, and there are some random stripes and faint defects on the gravure active layer film. As the molecular weight of PM6 gradually increases, the viscosity of the ink gradually increases, the random stripes on the gravure active layer film are completely eliminated, and the defects are also well suppressed. This is because the increase in ink viscosity increases the interaction force within the ink, which makes the ink droplets adhere better to the substrate, and even under the action of printing direction force, there will be no random flow. However, when the molecular weight of PM6 is too large (150.2kDa) and the ink viscosity is too high (1085.0mPa·s), the gravure active layer film will produce periodic silk lines (such as Figure 1d This is mainly because the viscosity of the ink is too high, which will hinder the fusion of ink droplets, thus resulting in the formation of silk lines.

[0083] Figure 2a -d shows the atomic force microscopy images of active layer films prepared by gravure printing of active layer inks of PM6 with different weight-average molecular weights on AgNW / ZnO∶PVP composite films. From the figure, it can be found that as the molecular weight of PM6 increases, the phase separation phase size of the active layer film gradually decreases. When the molecular weight is small, there is a phenomenon of excessive phase separation scale and excessive aggregation. Increasing the molecular weight can inhibit phase separation and aggregation. This is mainly because when the molecular weight of PM6 is large, the viscosity of the ink increases significantly, and the interaction force within the ink increases significantly, which can well inhibit the movement of the molecules of the active layer material, thereby effectively inhibiting phase separation and aggregation.

[0084] From Table 1, it can be found that in Example 1, when the M of PM6 w The device of organic solar cell with three layers of gravure printing in the range of 99.9-150.2 kDa can maintain high device efficiency. w When the M of PM6 is 134.5 kDa, the efficiency of the organic solar cell with three layers of gravure printing reaches the highest value (14.45%), because the active layer film prepared by gravure printing has excellent macroscopic uniformity and suitable microscopic morphology. w The M is too small (60.1 kDa), which makes the ink viscosity too low (3.2 mPa·s), resulting in a large number of random stripes in the gravure active layer film in the printing direction, which in turn causes serious leakage or even short circuit of the gravure organic solar cell device. wThe viscosity of the ink is too high (240.3 kDa), which makes the ink viscosity too high (2800.5 mPa·s). The ink cannot be well filled into the cells of the gravure roller, resulting in very poor uniformity of the gravure active layer film, which in turn causes the gravure organic solar cell device to short-circuit. In Comparative Example 3, due to the introduction of a large amount of PVP, although the viscosity of the ink can be well regulated to prepare a uniform film, the photoelectric properties of the active layer film are seriously lost, resulting in a significant reduction in the performance of the gravure organic solar cell.

[0085] Example 2 A process for preparing an organic solar cell by gravure printing is specifically as follows:

[0086] 1. Preparation of ink

[0087] Take 10 mg of PM6 polymer donor with a weight average molecular weight of 134.5 kDa, 12 mg of BO-4C1 small molecule receptor, mixed solvent: o-xylene and chloroform mixed in a volume ratio of 3:1 and 1:1, a total of 1 mL, and 5 μL of additive CN, and mix and stir thoroughly to obtain the corresponding organic active layer ink. The surface tensions of the active layer inks with different solvent ratios (o-XY:CF) (3:1, 1:1) at 25°C are 29.0 and 28.3 mN / m, respectively.

[0088] Steps 2 to 4 are the same as steps 2 to 4 in Example 1.

[0089] Comparative Example 4 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 2, with the main difference being that the ink is dispersed using pure o-xylene solvent, and the surface tension of the ink is 30.2 mN / m.

[0090] Comparative Example 5 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 2, with the main difference being that the ink is dispersed using pure chloroform solvent, and the surface tension of the ink is 27.1 mN / m.

[0091] The performance of the flexible organic solar cell devices prepared in Example 2, Comparative Example 4 and Comparative Example 5 (named as device 2-1, 2-2, 4', 5', respectively) was tested. The results are shown in Table 2.

[0092] Table 2

[0093]

[0094] From Table 2, it can be found that when o-XY:CF=3:1, the device efficiency of gravure-printed organic solar cells is the highest. This is because the surface tension of the ink is low at this time, which can be well infiltrated on the substrate and has a suitable evaporation rate, making the uniformity of the gravure active layer film excellent. When a single CF solvent is used for dispersion, the gravure-printed organic solar cell cannot work. This is because the boiling point of CF is too low (61.2°C) and the ink evaporates too fast, so that the ink droplets cannot be well fused on the substrate, and there are obvious silk lines in the film, which eventually leads to a short circuit of the gravure-printed organic solar cell. When a single o-XY solvent is used for dispersion, the efficiency of the gravure-printed organic solar cell device is low and the uniformity is poor. This is because the boiling point of the o-XY solvent is too high (144.4°C) and the evaporation rate is slow, which causes the ink droplets to flow excessively on the substrate, resulting in poor film uniformity.

[0095] Example 3 A preparation process of an organic solar cell by gravure printing is specifically as follows:

[0096] 1. Preparation of ink

[0097] Take 10 mg of PM6 polymer donor with a weight average molecular weight of 134.5 kDa, 12 mg of BO-4Cl small molecule acceptor, a mixed solvent: o-xylene and chloroform mixed in a volume ratio of 3:1, a total of 1 mL, and different additives CN of 2.5 and 5 μL (0.25%, 0.5%), and mix and stir to obtain the corresponding organic active layer ink. The viscosity of the active layer ink at 25°C is 370.3 mPa·s, and the surface tension at 25°C is 29.0 mN / m.

[0098] Steps 2 to 4 are the same as steps 2 to 4 in Example 1.

[0099] Comparative Example 6 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 3, with the main difference being that the added CN content is 0.

[0100] Comparative Example 7 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 3, with the main difference being that the added CN content is 2%.

[0101] Table 3

[0102]

[0103] It can be found from Table 3 that when the content of CN is 0.5%, the device efficiency of the gravure-printed organic solar cell is the highest. This is because the addition of an appropriate amount of CN can optimize the microscopic morphology of the active layer film. When the added CN content is too high (2%), the device efficiency of the gravure-printed organic solar cell is significantly reduced, and excessive addition of additives will cause the microscopic morphology of the active layer to deteriorate. When CN is added, the device efficiency of the gravure-printed organic solar cell is only 13.21%, which is significantly lower than the device efficiency with an appropriate amount of additives.

[0104] Example 4 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 1, except that:

[0105] The polymer donor was replaced with PTQ, whose weight average molecular weight was 132.5 kDa and weight was 10 mg; BO-4C1 small molecule receptor 12 mg, mixed solvent: o-xylene (o-XY) and chloroform (CF) were mixed in a volume ratio of 3:1, totaling 1 mL, and additive CN was 5 μL, and the corresponding organic active layer ink was obtained after sufficient mixing and stirring. The viscosity of the active layer ink at 25°C was 320.5 mPa·s, and the surface tension at 25°C was 29.1 mN / m.

[0106] The active layer finally obtained has the same uniformity and the same microscopic morphology, and the conversion efficiency of the obtained solar energy device is also close.

[0107] Example 5 The preparation process of an organic solar cell by gravure printing is substantially the same as that of Example 1, except that:

[0108] The small molecule acceptor was replaced with BTP-eC9, weighing 10 mg, and 10 mg of PM6 polymer donor with a weight average molecular weight of 134.5 kDa was mixed with a solvent of o-xylene (o-XY) and chloroform (CF) in a volume ratio of 3:1, a total of 1 mL, and 5 μL of additive CN, and the corresponding organic active layer ink was obtained after sufficient mixing and stirring. The viscosity of the active layer ink at 25°C was 320.5 mPa·s, and the surface tension at 25°C was 29.1 mN / m.

[0109] The active layer finally obtained has the same uniformity and the same microscopic morphology, and the conversion efficiency of the obtained solar energy device is also close.

[0110] Based on the above embodiments and comparative examples, it can be clearly seen that the organic active layer ink and the method for controlling its properties provided in the embodiments of the present invention effectively control the viscosity of the active layer ink by adjusting the molecular weight of the polymer donor, thereby avoiding the adverse effects of the use of a large amount of thickeners on the performance of the active layer; the volatilization rate of the organic active layer ink is effectively controlled by a mixed solvent method, and the appropriate volatilization rate combined with the adjusted molecular weight of the polymer donor can also comprehensively improve the crystallization quality of the organic active layer, thereby enabling large-area uniform active layer films with excellent crystallization properties to be prepared by gravure printing, and ultimately large-area, high-efficiency and high-uniformity organic solar cells can be obtained.

[0111] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the properties of an organic active layer ink suitable for gravure printing, comprising at least the steps of mixing a polymer donor material, a small molecule acceptor material and a solvent to form an ink; It is characterized in that Specifically include: By adjusting the molecular weight of the polymer donor material, the viscosity of the ink finally formed at 25°C is 15-1500mPa·s; by adjusting the composition and proportion of the solvent, the solvent is a multi-component mixed solvent, so that the surface tension of the ink at 25°C is 20-40mN / m.

2. An organic active layer ink suitable for gravure printing, characterized in that: include: Polymer donor materials, small molecule acceptor materials and solvents; wherein the molecular weight of the polymer donor material is within a selected range so that the viscosity of the ink at 25° C. is 15-1500 mPa·s; The solvent is selected from a multi-component mixed solvent so that the surface tension of the ink at 25° C. is 20 to 40 mN / m.

3. The organic active layer ink according to claim 2, characterized in that: The molecular weight of the polymer donor material controls the viscosity of the organic active layer ink to be 30-700 mPa·s; And / or, the concentration of the polymer donor material in the organic active layer ink is 5-25 mg / mL, preferably 7-18 mg / mL.

4. The organic active layer ink according to claim 2, characterized in that: The multi-component mixed solvent is selected from a combination of two or more of o-xylene, chlorobenzene, trimethylbenzene, toluene, chloroform, and tetrahydrofuran; And / or, the polymer donor material includes any one or a combination of two or more of PM6, D18, PTQ, P3HT, PM7, and D18-Cl; And / or, the small molecule acceptor material includes any one of BO-4Cl, BTP-eC9, PC61BM, PC71BM, L8-BO, and Y6, or a combination of two or more thereof.

5. The organic active layer ink according to claim 2, characterized in that: The molecular weight of the polymer donor material refers to the weight average molecular weight; Preferably, the weight average molecular weight of the polymer donor material is 45-200 kDa.

6. The organic active layer ink according to claim 2, characterized in that: Also includes additives; Preferably, the additive comprises any one or a combination of two of chloronaphthalene, 1,8-diiodooctane, 1,4-diiodobenzene, 1,3,5-trichlorobenzene and 3,5-dichlorobromobenzene; Preferably, the liquid additive in the organic active layer ink accounts for 0.1-2% of the total volume of the solvent, preferably 0.25-1%; Preferably, the liquid additive comprises any one of chloronaphthalene and 1,8-diiodooctane or a combination of two thereof; Preferably, the solid additive in the organic active layer ink is 0.5-3 times the mass of the donor material, preferably 0.7-1.5 times; Preferably, the solid additive includes any one of 1,4-diiodobenzene, 1,3,5-trichlorobenzene, 3,5-dichlorobromobenzene, or a combination of two or more thereof.

7. Use of the property control method according to claim 1 or the organic active layer ink according to any one of claims 2 to 6 in preparing an organic active layer by gravure printing.

8. A method for preparing an organic active layer, characterized in that: include: The organic active layer ink according to any one of claims 2 to 6 is obtained or provided by adjusting the property control method according to claim 1; Printing the organic active layer ink to form an active layer precursor by gravure printing; The active layer precursor is post-treated to convert the active layer precursor into an organic active layer.

9. The organic active layer obtained by the preparation method according to claim 8, characterized in that: The thickness deviation of the organic active layer is within 10%.

10. An organic solar cell, the device structure comprising: Flexible electrode, electron transport layer, active layer, hole transport layer, top electrode; Characterized in that the active layer is prepared by the preparation method described in claim 8 or is selected from the organic active layer described in claim 9; Preferably, the flexible electrode, the electron transport layer and the active layer are all prepared by gravure printing.

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