Preparation method of photoactive layer thin film, organic solar cell and preparation method thereof

Abstract

Embodiments of the present application relate to a method for preparing a photoactive layer thin film, an organic solar cell, and a method for preparing the same. The method for preparing the photoactive layer thin film includes: blending a polymer donor and a small molecule acceptor and dissolving them in an active layer solvent to form a first precursor solution; dissolving an amphiphilic additive in the active layer solvent to form a second precursor solution; mixing the second precursor solution and the first precursor solution according to a predetermined volume ratio to obtain a photoactive layer organic solution doped with the amphiphilic additive; and transferring droplets of the photoactive layer organic solution to an open container containing a culture medium solvent so that they spontaneously diffuse on the liquid surface of the culture medium solvent to form a uniform photoactive layer thin film. By doping the amphiphilic additive into the photoactive layer material, the interfacial tension between the solution droplets and the surface of the culture medium solvent can be regulated, thereby forming a high-quality uniform photoactive layer thin film that spontaneously diffuses on the surface of the culture medium solvent.

Description

Technical Field

[0001] The present application relates to the technical field of organic solar cell preparation, and more specifically, to a method for preparing a photoactive layer thin film, an organic solar cell, and a method for preparing the same. Background Art

[0002] Photovoltaics is an important clean energy source. Organic photovoltaics have received extensive attention due to their outstanding advantages such as solution processability, flexibility, light weight, and transparency. Preparing organic solar cells by solution method under open-air conditions has become a low-cost clean energy technology. Traditional solution processing techniques mainly include spin coating, blade coating, slot coating, etc. Water transfer printing is another solution processing technique, which has become an ultrafast, scalable, and versatile self-spreading film-forming process. Compared with the above traditional solution methods, the self-spreading film-forming process has unique advantages and applications. First, the film-forming process does not require large equipment, only an open container filled with solvent. Second, the entire process does not depend on a strict nitrogen atmosphere, can be completed in air, and is not sensitive to air humidity. In addition, different from the large loss of photoactive layer materials in the spin coating process, the self-spreading film-forming process can improve the material utilization rate through strategies such as multiple transfers and recycling, reducing the waste of expensive photoactive layer materials.

[0003] Currently, research on the selection of photoactive layer materials and the details of the self-spreading film-forming process in this field shows that this process is expected to achieve a uniform thickness distribution and good phase separation morphology of the photoactive layer. On the one hand, all reported self-spreading film-forming processes use high-boiling-point chlorobenzene (132 °C) as the solvent. After the liquid droplet contacts the water surface, while the chlorobenzene slowly volatilizes, the photoactive layer material gradually self-spreads to form a uniform thin film. At the same time, with the self-assembly of the polymer backbone, beneficial phase separation also gradually forms. On the other hand, photoactive layer materials based on non-fullerene Y6 series acceptors have small and discrete oriented crystals in the chloroform system. Therefore, the power conversion efficiency of organic solar cells prepared using photoactive layer materials dissolved in the chloroform system is higher than that of the chlorobenzene system. However, since the boiling point of chloroform is only 61 °C, it volatilizes very quickly in the self-spreading film-forming process. Before the photoactive layer material is completely diffused, the chloroform has completely volatilized, resulting in the inability of the photoactive layer to diffuse into a uniform thin film.

[0004] In summary, there is an urgent need to develop a self-spreading film-forming process for photoactive layer materials suitable for low-boiling-point solvents (such as the chloroform system). With the goal of improving the power conversion efficiency of organic solar cells, innovate the self-spreading process to achieve the preparation of a uniform photoactive layer thin film with a simple and low-cost process. Summary of the Invention

[0005] To solve the above technical problems, the present disclosure provides a method for preparing a photoactive layer thin film, an organic solar cell, and a method for preparing the same. By doping an amphiphilic additive into the photoactive layer material, the interfacial tension between the solution droplet and the liquid surface of the culture medium solvent can be regulated, so as to form a high-quality uniform photoactive layer thin film that spontaneously diffuses on the liquid surface of the culture medium solvent. The photoactive layer obtained by using the preparation method of the present disclosure in an atmospheric environment can be used to prepare an organic solar cell, which can reduce the process complexity and reduce the waste of expensive photoactive layer materials through a process of recycling and reuse.

[0006] The first aspect of the present disclosure provides a method for preparing a photoactive layer thin film, and the photoactive layer thin film is used for an organic solar cell. The preparation method includes: blending a polymer donor and a small molecule acceptor and dissolving them in an active layer solvent to form a first precursor solution; dissolving an amphiphilic additive in the active layer solvent to form a second precursor solution; mixing the second precursor solution and the first precursor solution according to a predetermined volume ratio to obtain a photoactive layer organic solution doped with the amphiphilic additive; and transferring droplets of the photoactive layer organic solution to an open container containing a culture medium solvent so that they spontaneously diffuse on the liquid surface of the culture medium solvent to form a uniform photoactive layer thin film; wherein, the boiling point of the material of the active layer solvent is lower than the boiling point of the culture medium solvent, and the surface tension of the active layer solvent is less than the surface tension of the culture medium solvent; wherein, the material of the amphiphilic additive is selected such that it can interact with the culture medium solvent to promote the diffusion of the droplets on the liquid surface, and at the same time can interact with the active layer solvent to promote the continuity of the photoactive layer thin film.

[0007] The second aspect of the present disclosure provides an organic solar cell. The organic solar cell includes a transparent conductive base layer, a hole transport layer, a photoactive layer, an electron transport layer, and a top electrode layer; wherein, the photoactive layer is obtained by using the photoactive layer thin film prepared by the preparation method described in the first aspect; wherein, the material of the transparent conductive base layer is selected from any one of ITO, FTO, AZO, GZO conductive glass, metal nanowire substrate, and high-transparency metal thin film substrate; the material of the hole transport layer is aqueous PEDOT:PSS or MoO3; the material of the electron transport layer is a combination of ZnO and PEIE; the material of the top electrode layer is selected from any one of Ag, Au, Al, and Pt.

[0008] The third solution of the present disclosure provides a method for preparing an organic solar cell. The preparation method includes the following steps: forming one of the hole transport layer and the electron transport layer on the transparent conductive substrate layer to obtain an intermediate substrate; obtaining the photoactive layer film by using the preparation method described in the first solution; performing a transfer process on the photoactive layer film: sucking the intermediate substrate with a vacuum pen, obliquely pressing and printing it on the photoactive layer film on the water surface, dividing the film at the edge, and then obliquely lifting the intermediate substrate printed with the photoactive layer film, annealing to form the photoactive layer; and sequentially forming the other of the hole transport layer and the electron transport layer, and the top electrode layer above the photoactive layer.

[0009] By using the preparation method of the photoactive layer film provided by the present disclosure, the organic solar cell and its preparation method, the following beneficial effects are achieved compared with the prior art:

[0010] (1) By doping the amphiphilic additive into the photoactive layer material, the interfacial tension between the droplet and the culture medium solvent liquid surface can be regulated, thereby promoting the thickness uniformity of the photoactive layer film formed by spontaneous diffusion film formation; at the same time, the amphiphilic additive can interact with the active layer solvent, thereby promoting the continuity of the photoactive layer film;

[0011] (2) Using the photoactive layer prepared by the spontaneous diffusion film formation method in the atmospheric environment to prepare an organic solar cell can reduce the device process complexity; for the prepared photoactive layer film, the photoactive layers of multiple organic solar cells can be transferred simultaneously, improving the utilization rate of the photoactive layer;

[0012] (3) By re-dissolving the recovered solid mixture into the active layer solvent, the recycling of the remaining photoactive layer material is realized, effectively avoiding the waste of the photoactive layer material and reducing the manufacturing cost. Description of the Drawings

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. At the appropriate time, the same reference numerals are used to refer to the same or similar parts in all the drawings. Such embodiments are illustrative and are not intended to be an exhaustive or exclusive embodiment of the device or method. In the drawings:

[0014] Figure 1 It is a schematic flow chart of the preparation method of the photoactive layer film according to the embodiment of the present disclosure;

[0015] Figure 2Schematic flowchart of a method for preparing an organic solar cell according to an embodiment of the present disclosure;

[0016] Figure 3 Schematic structural diagram of an organic solar cell according to an embodiment of the present disclosure;

[0017] Figure 4 J-V curve of an organic solar cell according to another embodiment of the present disclosure;

[0018] Figure 5 J-V curve of an organic solar cell according to still another embodiment of the present disclosure;

[0019] Figure 6 J-V curve of an organic solar cell according to still another embodiment of the present disclosure;

[0020] Figure 7 Schematic flowchart of a method for preparing an organic solar cell according to still another embodiment of the present disclosure. Detailed implementation manners

[0021] In order to make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0022] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the ordinary meanings understood by those of ordinary skill in the art to which the present application pertains. The "first", "second", and similar terms used in the present application do not denote any order, quantity, or importance, but are only used to distinguish different components. The terms such as "include" or "comprise" mean that the elements or items appearing before this term cover the elements or items listed after this term and their equivalents, without excluding other elements or items. The terms such as "connect" or "couple" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", and "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0023] In order to keep the following description of the embodiments of the present application clear and concise, detailed descriptions of known functions and known components are omitted in the present application.

[0024] Figure 1The figure shows a schematic flowchart of a preparation method 100 of a photoactive layer thin film according to this embodiment. As Figure 1 shown, the preparation method 100 includes steps S110 to S140.

[0025] S110: Blend a polymer donor and a small molecule acceptor, and dissolve them in an active layer solvent to form a first precursor solution.

[0026] S120: Dissolve an amphiphilic additive in the active layer solvent to form a second precursor solution.

[0027] S130: Mix the second precursor solution and the first precursor solution according to a predetermined volume ratio to obtain a photoactive layer organic solution doped with the amphiphilic additive.

[0028] S140: Transfer droplets of the photoactive layer organic solution to an open container filled with a culture medium solvent so that they spontaneously spread on the liquid surface of the culture medium solvent to form a uniform photoactive layer thin film.

[0029] S110 to S140 will be described in detail below.

[0030] As described above, this embodiment is dedicated to developing a self-assembly film-forming process for photoactive layer materials applicable to low-boiling solvents in order to prepare organic solar cells with high power conversion efficiency. Therefore, the active layer solvent in this article should be selected as a low-boiling solvent such as chloroform (boiling point 61 °C), dichloromethane (boiling point 40 °C), 2-methyltetrahydrofuran (boiling point 80 °C) or tetrahydrofuran (boiling point 66 °C), which can be any one of the above solvents or a combination of multiple of them.

[0031] The blend composed of the polymer donor and the small molecule acceptor here can be PM6:Y6, PM6:BTP-eC9, PM6:Y6:PCBM or PM6:BTP-eC9:PCBM.

[0032] The material of the amphiphilic additive is selected so that it can interact with the culture medium solvent to promote the diffusion of the droplets on the liquid surface, and at the same time can interact with the active layer solvent to promote the continuity of the photoactive layer thin film. By adding this amphiphilic additive to the photoactive layer organic solution, in the self-assembly film-forming process, this additive can interact with the culture medium solvent and the active layer solvent, so as to obtain a continuous photoactive layer thin film with uniform thickness and good phase separation effect.

[0033] Preferably, the amphiphilic additive can be a polymer, and more preferably, the amphiphilic additive can include poly(N-isopropylacrylamide) (PNIPAM), Polysorbate 20 (Tween 20), or Pluronic F127 (PF127).

[0034] It should be understood that the active layer solvent in S120 should be the same as the active layer solvent in S110, so that when the polymer donor, small molecule acceptor, and amphiphilic additive are mixed, they can dissolve in the same solvent, ensuring the accuracy of the mixing ratio.

[0035] As can be understood by those skilled in the art, in the spontaneous diffusion film-forming process, the culture medium solvent should be selected as a solvent with a relatively large surface tension and a relatively high boiling point, and the boiling point of the material of the active layer solvent should be lower than that of the culture medium solvent, and the surface tension of the active layer solvent is less than that of the culture medium solvent.

[0036] Preferably, the culture medium solvent can be any one or a combination of more than one of pure water, imidazole-based ionic liquids, pyridine-based ionic liquids, quaternary ammonium salt-based ionic liquids, perfluorooctanesulfonic acid, and fluorocarbon compounds.

[0037] On the other hand, as Figure 2 shown, the present disclosure also provides a preparation method 200 of an organic solar cell, and the structure of the prepared organic solar cell 300 is as Figure 3 shown. This preparation method 200 includes the following steps S210 to S240. Now, in combination with Figure 2 and Figure 3 the above steps S210 to S240 will be described in detail below.

[0038] S210, form one of the hole transport layer 320 and the electron transport layer 340 on the transparent conductive substrate layer 310 to obtain an intermediate substrate.

[0039] S220, obtain the photoactive layer thin film by using the preparation method 100.

[0040] S230, perform a transfer process on the photoactive layer thin film: use a vacuum suction pen to suck the intermediate substrate, obliquely press it onto the photoactive layer thin film on the liquid surface of the culture medium solvent, divide the thin film at the edge, and then obliquely lift the intermediate substrate printed with the photoactive layer thin film and anneal it to form the photoactive layer 330.

[0041] S240, sequentially form the other of the hole transport layer 320 and the electron transport layer 340, and the top electrode layer 350 above the photoactive layer 330.

[0042] To better explain the preparation of the organic solar cell 300 provided by the present disclosure, the following will take pure water as the culture medium solvent, chloroform as the active layer solvent, and the polymer donor: small molecule acceptor group as PM6:Y6 as an example for description.

[0043] In S210, a hole transport layer 320 or an electron transport layer 340 can be formed on the transparent conductive base layer 310 by spin coating. That is, an intermediate substrate composed of the transparent conductive base layer 310 + hole transport layer 320 can be formed (correspondingly, an electron transport layer 340 is formed in subsequent S240 to obtain an organic solar cell with a normal structure), or an intermediate substrate composed of the transparent conductive base layer 310 + electron transport layer 340 can be formed (correspondingly, a hole transport layer 320 is formed in subsequent S240 to obtain an organic solar cell with an inverted structure). The present invention does not limit this here.

[0044] Optionally, the material of the transparent conductive base layer 310 is selected from any one of ITO, FTO, AZO, GZO conductive glass, metal nanowire substrate, and highly transparent metal thin film substrate. The material of the hole transport layer 320 is aqueous PEDOT:PSS or MoO3, and the material of the electron transport layer 340 is a combination of ZnO and PEIE. In Figure 3 In the shown preferred embodiment, the transparent conductive base layer 310 is a glass substrate with an ITO thin film, and the material of the hole transport layer 320 is aqueous PEDOT:PSS.

[0045] In S210, specifically, the ITO conductive substrate of the glass substrate is ultrasonically washed successively with a cleaner, deionized water, and isopropyl alcohol, and after high-temperature drying or air drying, the preparation of the transparent conductive base layer 310 is completed. Then, the hole transport layer 320 is spin-coated on the transparent conductive base layer 310 treated with oxygen plasma. The spin-coated material is aqueous PEDOT:PSS (Al 4083) with a concentration of 50%. The spin-coating conditions are 4 krpm, 30 s, and annealing at 120 °C for 5 min to obtain an intermediate substrate.

[0046] Preferably, the material of the hole transport layer 320 selects Al 4083 as PEDOT:PSS, in view of the fact that Al 4083 has good optoelectronic properties, which helps to improve the photoelectric conversion efficiency of the solar cell and is the best choice for preparing the hole transport layer 320 by solution method in organic solar cells.

[0047] In S220, specifically, a PM6:Y6 solution is prepared. The mass ratio of the polymer donor to the small molecule acceptor is 1:1.2, and the total concentration is 25 mg / mL. PM6:Y6 is dissolved in chloroform (the active layer solvent), and stirred at 50 °C for 1 hour to obtain a first precursor solution. PNIPMA (amphiphilic additive) is dissolved in chloroform at a concentration of 20 mg / mL to obtain a second precursor solution; the obtained second precursor solution and the first precursor solution are mixed according to a predetermined volume ratio; the self-assembly film formation process is carried out at 25 °C and a relative humidity of about 40%. In a petri dish with a diameter of 95 mm, 1 / 2 volume of pure aqueous solution (culture medium solvent) is placed, and 18 μL of the PM6:Y6 solution is taken with a pipette and dropped on the water surface.

[0048] In S230, specifically, after the film on the water surface is dried, transfer is carried out. The intermediate substrate coated with the hole transport layer 320 is sucked by a vacuum pen and pressed obliquely onto the film on the water surface to avoid generating bubbles. After cutting the film at the edge, the substrate is lifted obliquely. This process can be repeated multiple times to avoid material waste. After transfer, the film is placed on a hot stage and annealed at 80 °C for 2 min to obtain the photoactive layer 330.

[0049] In S240, a ZnO solution and a PEIE solution are sequentially spin-coated on the photoactive layer 330 as the electron transport layer 340. The role of PEIE is to improve the device stability; the spin-coating conditions of the ZnO solution are 4 krpm for 30 s, without annealing; the PEIE solution is prepared by dissolving PEIE in ethylene glycol monomethyl ether, with a concentration of 0.5 wt%, and the spin-coating conditions are 3 krpm for 30 s, without annealing. Then, the top electrode layer 350 can be prepared on the electron transport layer 340 by evaporation. The material of the top electrode layer 350 can optionally be any one of Ag, Au, Al, and Pt. In Figure 3 In the preferred embodiment shown, the material of the top electrode layer 350 is preferably Ag.

[0050] It should be noted that the transparent conductive base layer 310, hole transport layer 320, photoactive layer 330, and electron transport layer 340 of the organic solar cell of the present disclosure can all be prepared by solution method in an atmospheric environment, without the need for a strict nitrogen or vacuum atmosphere, thereby reducing the manufacturing complexity of the organic solar cell.

[0051] In the embodiments provided by the present disclosure, in order to verify the influence of amphiphilic additives on the formation of a photoactive layer film with a uniform thickness, the present disclosure designed different volume ratios of the second precursor solution and the first precursor solution, that is, optimized the doping ratio of the amphiphilic additives, with the range being 0.1% - 10%. This is because increasing the doping ratio within a certain range is beneficial to increasing the diffusion diameter of the film, but will reduce the film thickness. The thickness distribution of the undoped PM6:Y6 film is 115 ± 82.6 nm, with a relatively large variance. Taking the amphiphilic additive PNIPAM as an example, the thickness of the PM6:Y6 film doped with 2 vt% PNIPAM is 85.5 ± 7.48 nm, and the thickness distribution is relatively uniform. Continuing to increase the PNIPAM doping ratio, some changes occurred in the spontaneous diffusion process. Due to the excessive aggregation of amphiphilic molecules, agglomeration easily occurred at the center where the droplet fell. After doping 10 vt% PNIPAM, a film with a thickness of 54.3 ± 9.60 nm was formed around the periphery, but a very thick film was formed in the central region due to excessive aggregation. Similar phenomena were also observed in the doping systems of Tween20 and PF127.

[0052] In addition, the present disclosure also verified the influence of different types of amphiphilic additives on the diffusion of the photoactive layer into a film with a uniform thickness.

[0053] Example 1 (without doping amphiphilic additives):

[0054] Accurately weigh 11.4 mg of PM6 and 13.6 mg of Y6, then add 1 mL of chloroform and stir at 50 °C in air for 1 h. Use the spontaneous diffusion film-forming process to prepare the PM6:Y6 film. The spontaneous diffusion process is carried out under the conditions of 25 °C and a relative humidity of about 40%. Place 1 / 2 volume of pure aqueous solution in a petri dish with a diameter of 95 mm. Use a pipette to take 18 μL of the PM6:Y6 solution and drip it onto the water surface at an angle of 45°. Before the PM6:Y6 droplet completely diffused, the chloroform quickly volatilized, resulting in the inability of the photoactive layer to diffuse into a uniform film.

[0055] Example 2 [the amphiphilic additive is poly(N-isopropylacrylamide) PNIPAM)]:

[0056] Other steps of Example 2 are the same as those of Example 1, except that 20 mg of PNIPAM is accurately weighed and added to 1 mL of chloroform and shaken well; before use, 1 μL of the PNIPAM solution is added to every 100 μL of the PM6:Y6 solution to obtain a mixed solution with a PNIPAM doping ratio of 1 vt%. Subsequently, use the spontaneous diffusion film-forming process to prepare the PM6:Y6 film. After the PM6:Y6 droplet is doped with 1 vt% PNIPAM, it can diffuse into a uniform photoactive layer film.

[0057] In Example 2, the PM6:Y6 thin film prepared by the self-assembled diffusion film-forming process was applied to the organic solar cell, and the specific steps are as follows.

[0058] 1) Prepare the active layer solution: Weigh 11.4 mg of PM6 and 13.6 mg of Y6 accurately, add 1 mL of chloroform, and stir at 50 °C in air for 1 h.

[0059] 2) Weigh 20 mg of PNIPAM accurately and add 1 mL of chloroform, then shake well. In the comparative examples, the doping ratio of PNIPAM was optimized. The specific steps were as follows: Add 0.5, 1, 2, 5, and 10 μL of PNIPAM solution to every 100 μL of PM6:Y6 solution respectively, stir at room temperature for 10 min, and then obtain the photoactive layer solutions with PNIPAM doping ratios of 0.5, 1, 2, 5, and 10 vt% respectively, corresponding to Comparative Examples 1-1, 1-2, 1-3, 1-4, and 1-5.

[0060] 3) Ultrasonically wash the ITO conductive substrate of the glass substrate with a cleaner, deionized water, and isopropanol in sequence, and complete the preparation of the hard transparent bottom electrode after high-temperature drying or air blowing.

[0061] 4) Treat the ITO conductive substrate with oxygen plasma for 2 min before spin-coating PEDOT:PSS. The PEDOT:PSS solution was filtered with a 0.45 µm nylon filter head and then spin-coated. The spin-coating conditions were static coating, 4 krpm, 30 s, the film thickness was about 10 nm, and annealed at 120 °C for 5 min.

[0062] 5) Prepare the PM6:Y6 thin film by the self-assembled diffusion film-forming process. Place 1 / 2 volume of pure aqueous solution in a petri dish with a diameter of 95 mm. Use a pipette to take 18 μL of the active layer solution prepared in step 1) and drop it on the water surface at an angle of 45°.

[0063] 6) After the thin film on the water surface is dried, transfer it. Use a vacuum suction pen to suck up the ITO conductive substrate coated with the hole transport layer, and press it obliquely on the thin film on the water surface to avoid generating bubbles. Cut the thin film at the edge and then lift the substrate obliquely. This process can be repeated multiple times to avoid material waste. After transfer, place the device on a hot stage and anneal at 80 °C for 2 min.

[0064] 7) Spin-coat the electron transport layer. Spin-coat the ZnO solution, and the spin-coating conditions are dynamic coating, 4 krpm, 30 s; spin-coat the PEIE solution, the PEIE solution is obtained by dissolving PEIE in ethylene glycol monomethyl ether, with a concentration of 0.5 wt%, and the spin-coating conditions are dynamic coating, 3 krpm, 30 s; the total film thickness is 20 nm.

[0065] 8) Place the prepared thin film substrate in a vacuum chamber and evacuate it to as low as 5×10 -4 Pa. Evaporate an Ag electrode on the upper surface of the electron transport layer at an evaporation rate of 0.5 Å / s and an evaporation film thickness of 60 nm.

[0066] The J-V curve of the organic solar cell in Example 2 is as Figure 4 shown, and the corresponding open circuit voltage ( V OC ), short circuit current density ( J SC ), fill factor (FF), and photoelectric conversion efficiency (PCE) values are shown in Table 1 below. The results show that the best power conversion efficiency of the organic solar cell prepared with the PM6:Y6 thin film doped with 2 vt% PNIPAM is 15.2%. In addition, under the condition of doping 2 vt% PNIPAM, the film thickness formed after the spontaneous diffusion of the droplets is the most uniform, and the film presents an interpenetrating network with a flatter surface, which is beneficial to charge transport and the corresponding fill factor of the organic solar cell is higher.

[0067] Table 1 J-V curve values of Example 2

[0068]

[0069] Example 3 [Polysorbate 20 (Tween 20)]:

[0070] Other steps of Example 3 are the same as those of Example 1, except that 20 mg of Tween 20 is accurately weighed and added to 1 mL of chloroform and shaken well; before use, 1 µL of Tween 20 solution is added to each 100 μL of PM6:Y6 solution to obtain a mixed solution with a Tween 20 doping ratio of 1 vt%. Subsequently, a PM6:Y6 thin film is prepared by the spontaneous dispersion film-forming process. After the PM6:Y6 droplets are doped with Tween 20, they can diffuse into a uniform thin film.

[0071] In Example 3, the PM6:Y6 thin film prepared by the spontaneous dispersion film-forming process is applied to the organic solar cell. The specific steps are the same as those of Example 2, except that in step (2), 20 mg of Tween 20 is accurately weighed and added to 1 mL of chloroform and shaken well. In the comparative example, the doping ratio of Tween 20 is optimized. The specific steps are as follows: 0.1, 0.5, 1, and 2 µL of Tween 20 solution are added to each 100 μL of PM6:Y6 solution, and after stirring at room temperature for 10 min, photoactive layer solutions with Tween doping ratios of 0.1, 0.5, 1, and 2 vt% are obtained, corresponding to Comparative Examples 2-1, 2-2, 2-3, and 2-4, respectively.

[0072] The J-V curve of the organic solar cell in Example 3 is as Figure 5 shown, and the corresponding open-circuit voltage ( V OC ), short-circuit current density ( J SC ), fill factor (FF), and photoelectric conversion efficiency (PCE) values are shown in Table 2 below. The results show that the best power conversion efficiency of the organic solar cells prepared with PM6:Y6 doped with 0.5 vt% and 1 vt% Tween20 is 14.4%.

[0073] Table 2 J-V curve values of Example 3

[0074]

[0075] Example 4 [Poloxamer F127 (Pluronic F127, PF127)]:

[0076] Other steps of Example 4 are the same as those of Example 1, except that 20 mg of PF127 is accurately weighed and added to 1 mL of chloroform and shaken well; before use, 1 μL of PF127 solution is added to each 100 μL of PM6:Y6 solution to obtain a mixed solution with a PF127 doping ratio of 1 vt%. Subsequently, a PM6:Y6 thin film is prepared by the spontaneous spreading film-forming process. After the PM6:Y6 droplets are doped with PF127, they can diffuse into a uniform thin film.

[0077] In Example 4, the PM6:Y6 thin film prepared by the spontaneous diffusion film-forming process is applied to the organic solar cell. The specific steps are the same as those of Example 2, except that in step (2), 20 mg of PF127 is accurately weighed and added to 1 mL of chloroform and shaken well. In the comparative examples, the doping ratio of PF127 is optimized. The specific steps are as follows: 0.1, 0.5, 1, and 2 μL of PF127 solution are added to each 100 μL of PM6:Y6 solution, and after stirring at room temperature for 10 min, photoactive layer solutions with PF127 doping ratios of 0.1, 0.5, 1, and 2 vt% are obtained, corresponding to Comparative Examples 3-1, 3-2, 3-3, and 3-4, respectively.

[0078] The J-V curve of the organic solar cell in Example 4 is as Figure 6 shown, and the corresponding open-circuit voltage ( V OC ), short-circuit current density ( J SC), the fill factor (FF) and the power conversion efficiency (PCE) are shown in Table 3 below. The results show that the best power conversion efficiency of the organic solar cells prepared with PM6:Y6 doped with 0.5 vt% PF127 is 14.9%.

[0079] Table 3 J-V curve values of Example 4

[0080]

[0081] The results of Examples 1-4 show that PM6:Y6 cannot form a uniform self-diffusion film in the chloroform system; however, the doping of amphiphilic polymers such as PNIPAM, Tween20, and PF127 can promote the self-diffusion of droplets. High-quality PM6:Y6 photoactive layers with different doping systems were successfully prepared by the self-diffusion film-forming process and applied to organic solar cells.

[0082] In one embodiment, as Figure 7 shown, in order to further improve the utilization rate of the photoactive material, the preparation method 200 provided by the present disclosure further includes steps S250 to S280.

[0083] S250, scraping the remaining photoactive layer film on the liquid surface with a scraper.

[0084] S260, cleaning the scraper with the active layer solvent, transferring the cleaned solution to a container, and drying to obtain a solid mixture of the polymer donor, the small molecule acceptor, and the amphiphilic additive.

[0085] S270, redissolving the recovered solid mixture in a corresponding volume of the active layer solvent to obtain the photoactive layer organic solution again.

[0086] S280, dropping the photoactive layer organic solution on the liquid surface of the active layer solvent so that it spontaneously diffuses on the liquid surface to form the photoactive layer film.

[0087] For example, a squeegee can be used to skim the water surface to collect all the PM6:Y6 thin film fragments scattered on the water surface after transfer onto the squeegee surface; the squeegee is cleaned with chloroform, and the cleaned solution is collected into a sample bottle. The sample bottle is placed in an oven and dried at 100 °C for 2 hours to evaporate the chloroform and a small amount of residual water, obtaining a mixed solid of PM6 and Y6. This process does not involve the separation of donors, acceptors, and additives, and there is no any purification or filtration operation; the recovered solid PM6:Y6 is accurately weighed, and an appropriate volume of chloroform is added for dissolution to prepare a PM6:Y6 solution with an accurate concentration; the recovered solid contains PM6, Y6, and additives at the same time. During the process of redissolution, there is no need to dope amphiphilic polymers again. After simply adding chloroform for dissolution, a self-spreading photoactive layer thin film can be directly formed on the water surface.

[0088] By repeating the above steps S250 - S280 in a cycle, the waste of photoactive layer materials can be efficiently avoided.

[0089] Compared with the prior art, the present disclosure provides a method for self-spreading film formation and recycling of a photoactive layer of an organic solar cell, including steps such as film formation, transfer, collection, cleaning, and dissolution. By repeating these steps, the self-spreading film formation and recycling of the photoactive layer in a chloroform system can be achieved. During the process of self-spreading of the droplets, by doping amphiphilic additives into the photoactive layer materials, the interfacial tension between the droplets and the liquid surface of the culture medium solvent can be regulated, thereby promoting the uniformity of the thin film on the liquid surface. The photoactive layer prepared by the self-spreading film formation method in an atmospheric environment is used to prepare an organic solar cell, which can reduce the complexity of the device process and effectively avoid the waste of photoactive layer materials.

[0090] The above description is only a preferred embodiment of the present application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosure concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

[0091] In addition, although the operations are depicted in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or in a sequential order. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the present invention. Certain features described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments.

[0092] Although the subject matter has been described in language specific to structural features and / or methodological logical acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are merely example forms of implementing the claims.

[0093] The above has described in detail multiple embodiments of the present application, but the present application is not limited to these specific embodiments. Based on the concept of the present application, those skilled in the art can make various variations and modifications to the embodiments, and these variations and modifications should all fall within the scope claimed by the present application.

Claims

1. A method for preparing a photoactive layer thin film, the photoactive layer thin film being used in an organic solar cell, characterized in that, The preparation method includes the following steps: Blend a polymer donor and a small molecule acceptor and dissolve them in an active layer solvent to form a first precursor solution; Dissolve an amphiphilic additive in the active layer solvent to form a second precursor solution; Mix the second precursor solution and the first precursor solution according to a predetermined volume ratio to obtain a photoactive layer organic solution doped with the amphiphilic additive; and Transfer droplets of the photoactive layer organic solution to an open container containing a culture medium solvent so that they spontaneously spread on the liquid surface of the culture medium solvent to form a uniform photoactive layer thin film; Wherein, the boiling point of the material of the active layer solvent is lower than that of the culture medium solvent, and the surface tension of the active layer solvent is less than that of the culture medium solvent; Wherein, the material of the amphiphilic additive is selected such that it can interact with the culture medium solvent to regulate the interfacial tension between the droplet and the liquid surface of the culture medium solvent, promote the diffusion of the droplet on the liquid surface, thereby promoting the thickness uniformity of the photoactive layer thin film, and at the same time can interact with the active layer solvent to promote the continuity of the photoactive layer thin film; Wherein, the active layer solvent is any one or a combination of chloroform, dichloromethane, 2-methyltetrahydrofuran and tetrahydrofuran.

2. The preparation method according to claim 1, characterized in that, The culture medium solvent is any one or a combination of pure water, imidazole-based ionic liquids, pyridine-based ionic liquids, quaternary ammonium salt-based ionic liquids, perfluorooctanesulfonic acid and fluorocarbon compositions.

3. The preparation method according to claim 2, characterized in that, The amphiphilic additive includes poly-N-isopropylacrylamide, polysorbate 20 or poloxamer F127.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The blend of the polymer donor and the small molecule acceptor includes PM6:Y6, PM6:BTP-eC9, PM6:Y6:PCBM or PM6:BTP-eC9:PCBM.

5. The preparation method according to any one of claims 1 to 3, characterized in that, In the case where the active layer solvent is chloroform and the culture medium solvent is pure water, the concentration of the first precursor solution is 5 mg / mL, the concentration of the second precursor solution is 20 mg / mL, and the predetermined volume ratio is 0.1% - 10%.

6. The preparation method according to claim 5, wherein The predetermined volume ratio is 1%.

7. An organic solar cell, characterized in that, It includes a transparent conductive base layer, a hole transport layer, a photoactive layer, an electron transport layer and a top electrode layer; Wherein, the photoactive layer is obtained by using the photoactive layer thin film prepared by the preparation method according to any one of claims 1 to 6; Wherein, the material of the transparent conductive base layer is selected from any one of ITO, FTO, AZO, GZO conductive glass, metal nanowire substrate and highly transparent metal thin film substrate; The material of the hole transport layer is aqueous PEDOT:PSS or MoO3; The material of the electron transport layer is a combination of ZnO and PEIE; The material of the top electrode layer is selected from any one of Ag, Au, Al and Pt.

8. A method for preparing an organic solar cell, characterized in that, It includes the following steps: Form one of a hole transport layer and an electron transport layer on the transparent conductive base layer to obtain an intermediate substrate; Obtain the photoactive layer thin film by using the preparation method according to any one of claims 1 to 6; Perform a transfer process on the photoactive layer thin film: Use a vacuum suction pen to suck up the intermediate substrate, tilt and imprint it onto the photoactive layer thin film on the liquid surface of the culture medium solvent. After dividing the thin film at the edge, tilt and lift the intermediate substrate printed with the photoactive layer thin film, and anneal to form the photoactive layer; And Form the other of the hole transport layer and the electron transport layer, and the top electrode layer in sequence above the photoactive layer.

9. The preparation method according to claim 8, wherein The preparation method further includes: Use a squeegee to scrape the remaining photoactive layer thin film on the liquid surface; Clean the squeegee with the active layer solvent, transfer the cleaned solution to a container, and obtain a solid mixture of the polymer donor, the small molecule acceptor, and the amphiphilic additive after drying; Redissolve the recovered solid mixture in a corresponding volume of the active layer solvent to obtain the photoactive layer organic solution again; and Drop the photoactive layer organic solution onto the liquid surface of the active layer solvent so that it spontaneously diffuses on the liquid surface to form the photoactive layer thin film.

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