Preparation method of photoactive layer of photovoltaic cell and photovoltaic cell

Abstract

The invention discloses a preparation method of an optical active layer of a photovoltaic cell and the photovoltaic cell, and the preparation method comprises the step of adding a volatile additive diphenyl selenide into the active layer to regulate and control the performance of the active layer. The additive interacts with the terminal structural unit of the receptor in the receptor film forming process, and receptor molecule crystallization is promoted. The aggregation and crystallinity of acceptor molecules are improved in the process, and the carrier mobility is enhanced, so that the fill factor of the device is improved, and the performance of the photovoltaic device is finally improved. The volatilization of the additive avoids the problem of performance reduction caused by the residual of the additive, provides an effective strategy for preparing a high-performance organic solar cell in the future, and provides a new thought for screening the additive for improving the performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cells, and particularly relates to a preparation method of a photoactive layer of a photovoltaic cell and a photovoltaic cell. Background Art

[0002] In recent decades, organic solar cells have received extensive attention due to advantages such as light weight, low cost, flexibility, and application in large-area roll-to-roll industrial production. To optimize the morphology of its key functional layer, namely the photoactive layer morphology, recent studies have proposed methods such as mixed solvents, thermal annealing, and solvent vapor annealing to regulate molecular packing and phase separation. Among them, additives and sequential deposition of donor-acceptor layers are two simple and effective processes that can effectively regulate the molecular arrangement and phase separation within the active layer. Volatile additives can selectively dissolve acceptor or donor materials, prolong the crystallization time, and thus be used to optimize the phase separation and microstructure morphology of the active layer. When additive molecules interact with organic semiconductor materials, the thermodynamic and kinetic parameters between molecules will be effectively regulated. At the same time, due to the volatility of the additives, the defects in the thin film will be greatly reduced after their volatilization and removal, thereby further improving the battery performance. This makes volatile additives a viable alternative to traditional non-volatile additives.

[0003] The sequential deposition process can independently optimize the morphology and crystallinity of each layer, overcome the inherent incompatibility between the donor and the acceptor, thereby expanding the processing window and providing more flexible processing conditions. Among them, the morphology and crystallinity of the upper-layer acceptor small molecules play an important regulatory role in its vertical penetration depth and the number of donor-acceptor interfaces. Therefore, it is crucial to select a suitable additive to regulate the aggregation of acceptor molecules. Despite the inherent advantages of additives, new types of highly efficient additives still need to be developed to further improve the performance of organic solar cells. In addition, the factors determining the phase separation and thin film morphology of the active layer have not been fully understood and still need to be further explored. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of a photoactive layer of a photovoltaic cell.

[0007] To solve the above technical problems, the present invention provides the following technical solutions:

[0008] PM6 was dissolved in chloroform to obtain Solution I;

[0009] The chloroform solution of L8-BO was mixed evenly with a volatile additive to obtain Solution II;

[0010] On the substrate, Solution I was used for the first spin-coating. After the chloroform had evaporated, Solution II was used for the second spin-coating. Finally, after the chloroform had evaporated, a thin film was formed, which was the photoactive layer of the photovoltaic cell.

[0011] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the volatile additive includes one of diphenyl selenide and diphenyldiselenide.

[0012] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the concentration of the volatile additive relative to the chloroform solution of L8-BO is 0.2 to 0.8 vol%.

[0013] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the concentration of PM6 in Solution I is 5 to 10 mg / mL; the concentration of the chloroform solution of L8-BO is 5 to 10 mg / mL.

[0014] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the atmosphere for the first spin-coating is nitrogen, and the rotation speed is 800 to 3000 rpm / min.

[0015] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the atmosphere for the second spin-coating is nitrogen, and the rotation speed is 2000 to 5000 rpm / min.

[0016] As a preferred embodiment of the method for preparing the photoactive layer of the photovoltaic cell according to the present invention, wherein: the temperatures of Solution I and Solution II are both 20 to 35 °C.

[0017] Another object of the present invention is to overcome the deficiencies in the prior art and provide a photoactive layer of a photovoltaic cell prepared by the method for preparing the photoactive layer of a photovoltaic cell.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a photoactive layer of a photovoltaic cell in the preparation of a photovoltaic cell.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a photovoltaic cell.

[0020] To solve the above technical problems, the present invention provides the following technical solutions:

[0021] The photovoltaic cell sequentially includes, from bottom to top,

[0022] a glass substrate with a thickness of 0.8 - 2 mm;

[0023] an indium tin oxide anode layer with a thickness of 100 - 200 nm;

[0024] an anode interface layer;

[0025] a photoactive layer with a thickness of 50 - 300 nm, applying the photoactive layer of the photovoltaic cell described in claim 8;

[0026] a PDINN cathode interface layer with a thickness of 3 - 10 nm;

[0027] an Ag cathode layer with a thickness of 60 - 200 nm;

[0028] The material of the anode interface layer includes one of PEDOT:PSS and 2PACz; the thickness of the anode interface layer of PEDOT:PSS is 20 - 60 nm, and the thickness of the anode interface layer of 2PACz is 2 - 8 nm.

[0029] Advantages of the present invention:

[0030] In the present invention, the volatile additive interacts with the terminal structural unit of the acceptor molecule in the acceptor solution. At the same time, due to its relatively high boiling point, the crystallization time of the acceptor solution is prolonged during the dry film process, enhancing the J-type aggregation and crystallinity of the acceptor small molecules during the dry film process, resulting in enhanced acceptor crystallinity. This significantly enhances the carrier mobility of the device, thereby effectively improving the fill factor and photoelectric conversion efficiency of the photovoltaic device. Description of the drawings

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0032] Figure 1 is the structural diagram of the photovoltaic cell prepared in Example 1 of the present invention.

[0033] Figure 2 is the electron and hole mobility diagram of the thin films of the photovoltaic cells prepared in Example 1 and Comparative Example 1 of the present invention;

[0034] Figure 3 is the current-voltage characteristic curve diagram of the photovoltaic cells prepared in Example 1 and Comparative Examples 1 - 2 of the present invention. Detailed implementation manners

[0035] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific implementation manners of the present invention in conjunction with the embodiments of the specification.

[0036] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] Secondly, the so-called "one embodiment" or "embodiment" herein refers to specific features, structures, or characteristics that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is separate or selectively mutually exclusive with other embodiments.

[0038] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0039] The diphenyl selenide used in the present invention is purchased from Adamas Technology Co., Ltd., with the product number 15156G, CasNo 1132 - 39 - 4, and a molecular weight of 233.17.

[0040] The diphenyldiselenide used in the present invention is purchased from Beijing Innochem Science & Technology Co., Ltd., with the product number A66965, CasNo 1666 - 13 - 3, and a molecular weight of 313.13.

[0041] The dimethyl selenide used in the present invention is purchased from Beijing Innochem Science & Technology Co., Ltd., with the product number A89408, CasNo 593 - 79 - 3, and a molecular weight of 109.03.

[0042] The dimethyldiselenide used in the present invention is purchased from Beijing Innochem Science & Technology Co., Ltd., with the product number A62107, CasNo 7101 - 31 - 7.

[0043] The diethyl selenide used in the present invention is purchased from Aladdin Technology Co., Ltd., with the product number D135868, CasNo 627 - 53 - 2.

[0044] The PM6 used in the present invention is purchased from Shenzhen ERO Solar Technology Co., Ltd., with the product number MS20200922001.

[0045] The L8 - BO used in the present invention is purchased from Shenzhen ERO Solar Technology Co., Ltd., with the product number MS20200922002.

[0046] The PDINN used in the present invention is purchased from Shenzhen Ruixun Optoelectronic Materials Technology Co., Ltd., with the product number S5495.

[0047] The PEDOT:PSS used in the present invention is of model 4083.

[0048] The alkaline cleaning agent used in the present invention is of model ECB-168 and is purchased from IL Shin Chemical Co.

[0049] The method for testing the photoelectric conversion efficiency (PCE) of the organic photovoltaic cell in the present invention in the atmospheric environment is as follows: The illumination conditions are provided by a 3A-class AM1.5G solar simulator (XES-300S1, SAN-EI ELECTRIC CO., LTD, Japan). The light intensity is 100 mW / cm 2 , and after turning on the light, it is stabilized for 30 min. The light intensity is calibrated by a standard silicon cell with a KG-5 filter, and the current density-voltage (J-V) curve test is carried out. The data acquisition is completed by a Keithley 2400 source meter. The test voltage range is -0.2 V to 1 V, and the voltage step is 0.05 V.

[0050] Example 1

[0051] This example provides a method for preparing a photovoltaic cell, specifically as follows:

[0052] (1) Preparation of the anode layer: The indium tin oxide (ITO) glass substrate is ultrasonically cleaned successively with an alkaline cleaning agent, deionized water, and isopropyl alcohol, and then treated with oxygen plasma to obtain an indium tin oxide anode layer;

[0053] (2) Preparation of the anode interface layer: A poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) layer with a thickness of 30 nm is spin-coated on the ITO and annealed at 140 °C for 25 min to obtain a PEDOT:PSS anode interface layer;

[0054] (3) Preparation of the active layer on the anode interface layer by sequential deposition method:

[0055] The chloroform solution of PM6 is spin-coated in nitrogen at a speed of 1500 rpm / min, and the solution temperature is controlled at 25 °C; after the chloroform volatilizes, the L8-BO solution is spin-coated on the PM6 film in nitrogen at a speed of 2500 rpm / min, and the solution temperature is controlled at 25 °C to form a second-layer L8-BO film. The L8-BO solution is obtained by dissolving 7 mg of L8-BO and 5 μL of diphenyl selenide in 1 mL of chloroform; after the chloroform volatilizes, the light-active layer with a total thickness of 100 nm in this example, namely the active layer, is finally obtained;

[0056] (4) Preparation of the cathode interface layer: Spin-coat a PDINN methanol solution with a thickness of 5 nm on the active layer prepared in step (3) at a speed of 3000 rpm / min. Wait for the methanol to evaporate to obtain the cathode interface layer;

[0057] (5) Preparation of the cathode: On the cathode interface layer prepared in step (4), perform vacuum evaporation at 2×10 -4 Pa to deposit Ag with a thickness of 100 nm as the cathode to obtain the final photovoltaic cell.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a photovoltaic cell without volatile additives. The difference from Example 1 is that diphenyl selenide is not added in step (3), and the rest of the preparation processes are the same as those in Example 1. The photoactive layer and photovoltaic cell of this comparative example are prepared.

[0060] The electron and hole mobilities of the thin films of the photovoltaic cells prepared in Example 1 and Comparative Example 1 were tested, and the results are as Figure 2 shown.

[0061] Figure 2 are the current density-voltage curves and the corresponding electron and hole mobilities of the photovoltaic cells prepared in Example 1 and Comparative Example 1. It can be seen that both the electron mobility and the hole mobility of the cell prepared in Comparative Example 1 are relatively low. After adding the additive, the electron mobility and the hole mobility of the cell prepared in Example 1 are increased to more than twice that of Comparative Example 1, thereby improving the fill factor of the cell and finally realizing the improvement of the performance of the photovoltaic device.

[0062] Comparative Example 2

[0063] This comparative example provides a method for preparing a photovoltaic cell containing volatile additives. The difference from Example 1 is that diphenyl selenide in step (3) is adjusted to dimethyl selenide, and the rest of the preparation processes are the same as those in Example 1. The photoactive layer and photovoltaic cell of this comparative example are prepared.

[0064] The photovoltaic cells prepared in Example 1 and Comparative Examples 1-2 were tested for their power conversion efficiency (PCE) and current-voltage characteristic curves in an atmospheric environment, and the results are shown in Table 1 and Figure 3 shown.

[0065] Table 1 Influence of additives on the performance parameters of photovoltaic cells

[0066]

[0067] Figure 3Current-voltage characteristic curves of the photovoltaic cells prepared in Example 1 and Comparative Examples 1 and 2. Among them, Curve 1 is for Comparative Example 1, Curve 2 is for Example 1, and Curve 3 is for Comparative Example 2.

[0068] According to Table 1 and Figure 3 Curves 1 and 2 in, it can be clearly seen that the fill factor and energy conversion efficiency of the photovoltaic cell prepared in Example 1 containing diphenyl selenide additive are significantly improved compared with those without diphenyl selenide additive, increasing from 73.1% and 16.5% to 79.4% and 19.1% respectively. In addition, the photovoltaic cell with diphenyl selenide has a higher short-circuit current than that without this additive. Comparing the performance parameters of Example 1 and Comparative Example 2 in Table 1 and Figure 3 Curves 2 and 3 in, it can be seen that replacing diphenyl selenide with other additives will cause a certain degree of reduction in battery performance, but it is still higher than that of the battery without additives.

[0069] Comparative Example 3

[0070] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that diphenyl diselenide is used instead of diphenyl selenide in step (3), and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0071] Comparative Example 4

[0072] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that dimethyl diselenide is used instead of diphenyl selenide in step (3), and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0073] Comparative Example 5

[0074] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that diethyl diselenide is used instead of diphenyl selenide in step (3), and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0075] Comparative Example 6

[0076] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that diethyl selenide is used instead of diphenyl selenide in step (3), and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0077] The photovoltaic cells prepared in Comparative Examples 3 to 6 were tested for their photoelectric conversion efficiency (PCE) and current-voltage characteristic curves in the atmospheric environment, and the results are shown in Table 2.

[0078] Table 2 Influence of additive types on the performance of photovoltaic cells

[0079]

[0080] Comparing the performance of the photovoltaic cells containing different types of additives in Table 2, it can be seen that the photovoltaic cell prepared with diphenyl diselenide as the additive has the highest energy conversion efficiency, fill factor, and short-circuit current density. This is because the addition of the additive improves the crystallization quality of the acceptor molecules and the formation of the fibrous morphology, thereby promoting exciton dissociation and carrier transport. Therefore, the performance of this cell is the best.

[0081] Comparative Example 7

[0082] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that the amount of diphenyl diselenide in step (3) is adjusted to 2.5 μL, and the rest of the preparation process is the same as that of Example 1. The photoactive layer and photovoltaic cell of this comparative example are prepared.

[0083] Comparative Example 8

[0084] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that the amount of diphenyl diselenide in step (3) is adjusted to 10 μL, and the rest of the preparation process is the same as that of Example 1. The photoactive layer and photovoltaic cell of this comparative example are prepared.

[0085] The photovoltaic cells prepared in Comparative Examples 7 to 8 were tested for their photoelectric conversion efficiency (PCE) and current-voltage characteristic curves in the atmospheric environment, and the results are shown in Table 3.

[0086] Table 3 Influence of the amount of additive on the performance of photovoltaic cells

[0087]

[0088]

[0089] According to Table 3, when the amount of diphenyl diselenide is 5 μL, the short-circuit current density, fill factor, and energy conversion efficiency of the cell are the highest. Increasing or decreasing the amount will result in a deterioration of the performance of the photovoltaic cell. This is because when the addition amount of the volatile additive exceeds 0.8 vol% compared to the chloroform solution of L8-BO, the molecules undergo excessive aggregation, resulting in an overly large phase region size, and the corresponding exciton dissociation and charge transport are also inhibited.

[0090] Comparative Example 9

[0091] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that the solution temperature in step (3) is adjusted to 40 °C, and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0092] Comparative Example 10

[0093] This comparative example provides a method for preparing a photovoltaic cell containing a volatile additive. The difference from Example 1 is that the solution temperature in step (3) is adjusted to 60 °C, and the rest of the preparation processes are the same as those in Example 1, and the photoactive layer and photovoltaic cell of this comparative example are prepared.

[0094] The photovoltaic cells prepared in Comparative Examples 9 - 10 were tested for the photoelectric conversion efficiency (PCE) and current-voltage characteristic curves in the atmospheric environment, and the results are shown in Table 4.

[0095] Table 4 Influence of solution temperature on the performance of photovoltaic cells

[0096]

[0097] By comparing the fill factor and energy conversion efficiency of the photovoltaic cells prepared at different solution temperatures in Table 4, it can be seen that when the solution temperature is controlled at 25 °C, the performance of the photovoltaic cell is the best, and the increase in temperature will lead to a decrease in the energy conversion efficiency and fill factor of the cell.

[0098] Example 2

[0099] This example provides a method for preparing a photovoltaic cell, specifically as follows:

[0100] (1) Prepare the anode layer: The indium tin oxide (ITO) glass substrate is ultrasonically cleaned successively with an alkaline cleaning agent, deionized water, and isopropyl alcohol, and then treated with oxygen plasma to obtain an indium tin oxide anode layer;

[0101] (2) Prepare the anode interfacial layer: Spin-coat a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) layer with a thickness of 30 nm on the ITO, and perform an annealing treatment at 140 °C for 25 min to obtain a PEDOT:PSS anode interfacial layer;

[0102] (3) Prepare the active layer on the anode interfacial layer by sequential deposition:

[0103] Spin-coat a chloroform solution of PM6 at a speed of 2000 rpm / min in nitrogen while controlling the solution temperature at 30 °C; wait for the chloroform to evaporate, and then spin-coat an L8-BO solution on the PM6 film in nitrogen at a speed of 3000 rpm / min while controlling the solution temperature at 30 °C to form a second L8-BO film. The L8-BO solution is obtained by dissolving 7 mg of L8-BO and 5 μL of diphenyl selenide in 1 mL of chloroform; after the chloroform evaporates, a photoactive layer with a total thickness of 100 nm in this example, namely the active layer, is finally obtained.

[0104] (4) Prepare the cathode interface layer: Spin-coat a 5-nm-thick PDINN methanol solution on the active layer prepared in step (3) at a speed of 4000 rpm / min, and wait for the methanol to evaporate to obtain the cathode interface layer.

[0105] (5) Prepare the cathode: On the cathode interface layer prepared in step (4), perform vacuum evaporation at 4 × 10 -4 Pa to deposit 100-nm-thick Ag as the cathode to obtain the final photovoltaic cell.

[0106] Example 3

[0107] This example provides a method for preparing a photovoltaic cell, specifically as follows:

[0108] (1) Prepare the anode layer: Ultrasonically clean a glass substrate of indium tin oxide (ITO) successively with an alkaline cleaning agent, deionized water, and isopropanol, and then treat it with oxygen plasma to obtain an indium tin oxide anode layer.

[0109] (2) Prepare the anode interface layer: Spin-coat a 30-nm-thick poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) layer on the ITO and perform an annealing treatment at 100 °C for 25 min to obtain a PEDOT:PSS anode interface layer.

[0110] (3) Prepare the active layer on the anode interface layer by sequential deposition:

[0111] Spin-coat a chloroform solution of PM6 at a speed of 2500 rpm / min in nitrogen while controlling the solution temperature at 35 °C; wait for the chloroform to evaporate, and then spin-coat an L8-BO solution on the PM6 film in nitrogen at a speed of 4000 rpm / min while controlling the solution temperature at 35 °C to form a second L8-BO film. The L8-BO solution is obtained by dissolving 9 mg of L8-BO and 8 μL of diphenyl selenide in 1 mL of chloroform; after the chloroform evaporates, a photoactive layer with a total thickness of 100 nm in this example, namely the active layer, is finally obtained.

[0112] (4) Preparation of the cathode interface layer: Spin-coat a 5-nm-thick PDINN methanol solution on the active layer prepared in step (3) at a speed of 2000 rpm / min. Wait for the methanol to volatilize to obtain the cathode interface layer;

[0113] Preparation of the cathode: On the cathode interface layer prepared in step (4), perform vacuum evaporation at 3×10 -4 Pa to deposit 100-nm-thick Ag as the cathode to obtain the final photovoltaic cell.

[0114] Test the photoelectric conversion efficiency (PCE) and current-voltage characteristic curves of the photovoltaic cells prepared in Examples 2 to 3 in the atmospheric environment, and it is found that they also have good performance, but are slightly lower than those in Example 1.

[0115] In summary, the present invention provides a method for preparing a photoactive layer of a photovoltaic cell and a photovoltaic cell. In the present invention, the volatile additive diphenyl selenide is added to the active layer to regulate the performance of the active layer. The additive interacts with the receptor terminal structural unit during the receptor film-forming process. At the same time, due to its relatively high boiling point, the receptor solution prolongs the crystallization time during the dry film process, enhances the J-type aggregation and crystallinity of the receptor small molecules during the dry film process, makes the receptor crystallinity enhanced, promotes the crystallization of receptor molecules, improves the aggregation and crystallinity of receptor molecules, which enhances the carrier mobility, thereby improving the fill factor of the device, and finally improves the performance of the photovoltaic device.

[0116] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a photoactive layer of a photovoltaic cell, characterized in that: include, PM6 was dissolved in chloroform to obtain solution I; The chloroform solution of L8-BO and the volatile additive were mixed uniformly to obtain solution II; The first step of spin coating is performed on the substrate using solution I, and the second step of spin coating is performed using solution II after the chloroform evaporates. Finally, a thin film is formed after the chloroform evaporates, namely, the photoactive layer of the photovoltaic cell.

2. The method for preparing a photoactive layer of a photovoltaic cell according to claim 1, characterized in that: The volatile additive includes one of diphenyl selenide and diphenyl diselenide.

3. The method for preparing a photoactive layer of a photovoltaic cell according to claim 1, characterized in that: The concentration of the volatile additive relative to the chloroform solution of L8-BO is 0.2-0.8 vol%.

4. The method for preparing a photoactive layer of a photovoltaic cell according to claim 1, characterized in that: The concentration of PM6 in the solution I is 5 to 10 mg / mL; the concentration of the chloroform solution of L8-BO is 5 to 10 mg / mL.

5. The method for preparing a photoactive layer of a photovoltaic cell according to claim 1, characterized in that: The atmosphere of the first step of spin coating is nitrogen, and the rotation speed is 800-3000 rpm / min.

6. The method for preparing a photoactive layer of a photovoltaic cell according to claim 1, characterized in that: The atmosphere of the second step of spin coating is nitrogen, and the rotation speed is 2000-5000 rpm / min.

7. The method for preparing a film containing a volatile additive as claimed in claim 1, characterized in that: The temperatures of the solution I and the solution II are both 20-35°C.

8. A photovoltaic cell photoactive layer prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the photovoltaic cell photoactive layer according to claim 8 in the preparation of photovoltaic cells.

10. A photovoltaic cell, characterized in that: The photovoltaic cell includes, from bottom to top, Glass substrate, thickness 0.8 to 2 mm; Indium tin oxide anode layer, thickness is 100-200nm; Anode interface layer; A photoactive layer having a thickness of 50 to 300 nm, wherein the photoactive layer of the photovoltaic cell according to claim 8 is applied; PDINN cathode interface layer, thickness 3 to 10 nm; Ag cathode layer, thickness 60-200 nm; The material of the anode interface layer includes one of PEDOT:PSS and 2PACz; the thickness of the anode interface layer of PEDOT:PSS is 20-60nm, and the thickness of the anode interface layer of 2PACz is 2-8nm.

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