Organic photovoltaic device based on gradient donor-acceptor proportion and preparation method and application thereof

Abstract

The invention relates to the technical field of organic photovoltaic devices, in particular to an organic photovoltaic device based on gradient donor-acceptor proportion and a preparation method and application thereof. Blade-coating a first active layer material on the hole transport layer along the limited direction, and preparing a first active layer of which the thickness is gradually reduced along the limited direction; at the end point of blade coating of the first active layer, blade coating a second active layer material along the reverse direction of the limiting direction, and preparing a second active layer of which the thickness is gradually reduced along the reverse direction of the limiting direction; the first active layer and the second active layer have the same thickness gradient. And after the donor or the acceptor in the second active layer is mixed with the first active layer, the proportion of the donor and the acceptor in the whole active layer is gradually changed, so that a gradient donor and acceptor proportion is formed. According to the active layer based on the gradient donor-acceptor ratio, large-range and dense donor-acceptor ratio changes are achieved within the limited length range, and the active layer can be used as a high-throughput screening model to be applied to screening of organic solar cell solution treatment conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photovoltaic devices, and in particular to an organic photovoltaic device based on a gradient donor-acceptor ratio and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Organic photovoltaic cells can be prepared by solution method, which is easy to realize large-area and low-cost roll-to-roll printing, and is considered to be one of the most promising photovoltaic technologies. Organic photovoltaic cells use organic materials as the photosensitive active layer and do not contain toxic heavy metal ions such as lead. The photoelectric conversion efficiency of small-area organic photovoltaic devices based on bulk heterojunction structure in the laboratory has exceeded 20%, becoming an impressive next-generation photovoltaic technology.

[0004] The photoactive layer of high-efficiency organic solar cells adopts a blend heterojunction structure, which mixes electron donors and electron acceptors to form an interpenetrating network structure to achieve effective exciton dissociation and charge transfer. Since the composition ratio of donors and acceptors in the active layer affects the morphology and light absorption of the blend heterojunction, it further affects physical processes such as exciton generation, exciton separation, and carrier transport, which are closely related to the energy conversion efficiency and stability of organic solar cells. In recent years, the emergence of a large number of expensive new donor and acceptor organic photovoltaic materials has made it necessary to optimize the solution processing parameters that affect the performance and stability of organic solar cells, including the ratio between different donor and acceptor materials. A high-throughput manufacturing method is urgently needed to accelerate this process. Summary of the invention

[0005] In order to overcome the above problems, the present invention provides an organic photovoltaic device based on a gradient donor-acceptor ratio and a preparation method and application thereof.

[0006] The first aspect of the present invention provides a method for preparing an organic photovoltaic device based on a gradient donor-acceptor ratio, comprising:

[0007] (1) In an air atmosphere, a hole transport layer is prepared by scraping on the surface of a conductive glass;

[0008] (2) in an air atmosphere, scraping a first active layer material on the hole transport layer along a defined direction to prepare a first active layer whose thickness gradually decreases along the defined direction; at the end point of scraping the first active layer, scraping a second active layer material on the first active layer in the opposite direction of the defined direction to prepare a second active layer whose thickness gradually decreases along the opposite direction of the defined direction; annealing in an inert atmosphere to prepare an active layer;

[0009] (3) preparing an electron transport layer by scraping on the surface of the active layer in an air atmosphere;

[0010] (4) Under vacuum conditions, a cathode is prepared on the electron transport layer.

[0011] The second aspect of the present invention provides an organic photovoltaic device based on a gradient donor-acceptor ratio, comprising a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode stacked in sequence from bottom to top;

[0012] The active layer has a gradient donor-acceptor ratio.

[0013] The third aspect of the present invention provides the use of an organic photovoltaic device based on a gradient donor-acceptor ratio prepared by the preparation method described in the first aspect in screening solution processing conditions for organic solar cells.

[0014] The beneficial effects of the present invention are:

[0015] (1) The active layer based on the gradient donor-acceptor ratio provided by the present invention achieves a wide range and intensive donor-acceptor ratio change within a limited length range (7.5 cm), and can be used as a high-throughput screening model for the screening of solution processing conditions for organic solar cells.

[0016] (2) Compared with traditional organic solar cells, the organic photovoltaic device prepared by the method proposed in the present invention shows the sensitivity of energy conversion efficiency and stability to the donor-acceptor ratio, which facilitates the exploration of the relationship between performance and stability and the donor-acceptor ratio.

[0017] (3) The organic photovoltaic device based on the gradient donor-acceptor ratio provided in the present invention has a simpler preparation process, which greatly reduces the time and resource consumption for preparing and screening the processing conditions of the organic solar cell solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0019] Figure 1 Schematic diagram of the structure of an organic photovoltaic device based on a gradient donor-acceptor ratio;

[0020] Figure 2 The sampling points of organic photovoltaic devices based on gradient donor-acceptor ratio;

[0021] Figure 3The sampling points of the active layer film with a gradient donor-acceptor PM6:L8-BO ratio prepared in Examples 2 to 4, wherein a is the sampling point position of the UV-visible absorption spectrum, and b is the sampling point position of the steady-state fluorescence spectrum; the sampling point position of the UV-visible absorption spectrum is measured by uniformly taking three columns and nine rows of positions on the entire film, and these 27 points are represented in the different positions and donor-acceptor absorption peak ratio diagram, and the sampling point position of the steady-state fluorescence spectrum is 15 points uniformly taken on the midline of the film;

[0022] Figure 4 The UV-visible absorption spectra of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO (a) prepared in Example 2 at different points (b-d), the donor-acceptor absorption peak ratio at different positions (e), and the steady-state fluorescence spectrum (f); wherein 1-1 in Figure b represents the ratio of the donor-acceptor ratio to the L8-BO ratio (b-d) at different points; Figure 3 The first point of the sampling points shown is the first column, 2-1 indicates the second point is the first column, and 3-1 indicates the third point is the first column;

[0023] Figure 5 The UV-visible absorption spectra of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO (a) prepared in Example 3 at different points (b-d), the donor-acceptor absorption peak ratio at different positions (e), and the steady-state fluorescence spectrum (f); wherein 1-2 in Figure b represent the Figure 3 The first point of the sampling points shown is the second column, 2-2 indicates the second point is the second column, and 3-2 indicates the third point is the second column;

[0024] Figure 6 The UV-visible absorption spectra of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO (a) prepared in Example 4 at different points (b-d), the donor-acceptor absorption peak ratio at different positions (e), and the steady-state fluorescence spectrum (f); wherein 1-3 in Figure b represent the Figure 3 The first point of the sampling points shown is the third column, 2-3 indicates the second point is the third column, and 3-3 indicates the third point is the third column;

[0025] Figure 7 The figure is a summary of device performance parameters of different donor-acceptor ratios of the organic photovoltaic device based on the gradient donor-acceptor ratio active layer in Example 2, including open circuit voltage (a), short circuit current density (b), fill factor (c), and power conversion efficiency (d);

[0026] Figure 8 a and b are device performance attenuation diagrams of the organic photovoltaic device based on the gradient donor-acceptor ratio active layer in Example 2 under the conditions of one sun illumination and 60° C. heating;

[0027] Fig. 9This is a graph showing the correlation between the attenuation of the power conversion efficiency of an organic photovoltaic device with a gradient donor-acceptor ratio active layer and the donor-acceptor ratio under one sun illumination and 60° C. heating conditions in Example 2. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] A first typical embodiment of the present invention provides a method for preparing an organic photovoltaic device based on a gradient donor-acceptor ratio, comprising:

[0031] (1) In an air atmosphere, a hole transport layer is prepared by scraping on the surface of a conductive glass;

[0032] (2) in an air atmosphere, scraping a first active layer material on the hole transport layer along a defined direction to prepare a first active layer whose thickness gradually decreases along the defined direction; at the end point of scraping the first active layer, scraping a second active layer material on the first active layer in the opposite direction of the defined direction to prepare a second active layer whose thickness gradually decreases along the opposite direction of the defined direction; annealing in an inert atmosphere to prepare an active layer;

[0033] (3) preparing an electron transport layer by scraping on the surface of the active layer in an air atmosphere;

[0034] (4) Under vacuum conditions, a cathode is prepared on the electron transport layer.

[0035] In one or more embodiments, in step (2), the end point of the first active layer coating is the starting point of the second active layer coating; and the end point of the second active layer coating is the starting point of the first active layer coating.

[0036] In one or more embodiments, in step (2), the first active layer is a donor-acceptor mixed layer, and the second active layer is a donor layer or an acceptor layer;

[0037] Preferably, the donor material is PM6 and the acceptor material is L8-BO.

[0038] In one or more embodiments, in step (2), the first active layer and the second active layer have a thickness variation of 90 to 110 nm along the length direction within a length range of 7.5 to 8 cm.

[0039] It is set that there are two endpoints along the limited direction within the limited length range, namely end A and end B. The thickness gradient direction of the first active layer becomes thinner from end A to end B, and the thickness gradient direction of the first active layer becomes thinner from end B to end A. After the donor or acceptor in the second active layer is mixed with the first active layer, the ratio of the donor to the acceptor in the entire active layer gradually changes, thereby forming a gradient donor-acceptor ratio.

[0040] In one or more embodiments, in step (2), the first active layer and the second active layer have the same scraping speed, both of which are 10-40 mm / s, preferably 25 mm / s; the dripping volume is the same, both of which are 30-70 μL, preferably 45 μL.

[0041] In one or more embodiments, in step (2), during the scraping, the substrate temperature is 60-100° C., preferably 80° C.; in an inert atmosphere, annealing is performed at 40-180° C. for 5-10 min, preferably annealing at 100° C. for 10 min.

[0042] In one or more embodiments, in step (1), the conductive glass is ITO conductive glass. Before preparing the hole transport layer, the ITO conductive glass is ultrasonically cleaned with a cleaning agent, water, acetone, anhydrous ethanol and isopropanol in sequence, dried with nitrogen, and then treated with UV for 15-25 minutes.

[0043] In one or more embodiments, in step (1), the method for preparing the hole transport layer comprises: coating PEDOT:PSS on the surface of the conductive glass, and annealing at 130-180° C. for 10-20 min.

[0044] In one or more embodiments, in step (3), the specific step of preparing the electron transport layer by scraping on the surface of the active layer includes: scraping 0.5-1.5 mg / mL F3N-Br solution onto the active layer at a scraping speed of 10-25 mm / s.

[0045] In one or more embodiments, in step (4), at 2.5×10 -4 -5×10 -4 Under vacuum conditions of 0.3 Pa, 80-100 nm Ag electrodes were prepared by thermal evaporation.

[0046] A second typical embodiment of the present invention provides an organic photovoltaic device based on a gradient donor-acceptor ratio, comprising a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode stacked in sequence from bottom to top;

[0047] The active layer has a gradient donor-acceptor ratio.

[0048] In one or more embodiments, the active layer includes a first active layer and a second active layer stacked sequentially from bottom to top, the first active layer is a donor-acceptor mixed layer, and the second active layer is a donor layer or an acceptor layer;

[0049] The first active layer and the second active layer have the same thickness gradient along the length direction within a limited length range; the thickness gradient direction of the first active layer is opposite to the thickness gradient direction of the second active layer.

[0050] Preferably, the first active layer and the second active layer have a thickness variation of 190-210 nm along the length direction within a length range of 7.5-8 cm.

[0051] It is set that there are two end points along the length direction within a limited length range, namely end A and end B. The thickness gradient direction of the first active layer gradually becomes thinner from end A to end B, and the thickness gradient direction of the first active layer gradually becomes thinner from end B to end A. After the donor or acceptor in the second active layer is stacked with the first active layer, the ratio of donors or acceptors in the entire active layer gradually changes, thereby forming a gradient donor-acceptor ratio.

[0052] In one or more embodiments, the substrate is a glass substrate.

[0053] In one or more embodiments, the anode is indium tin oxide (ITO).

[0054] In one or more embodiments, the hole transport layer is made of PEDOT:PSS.

[0055] In one or more embodiments, the material of the electron transport layer is F3N-Br.

[0056] In one or more embodiments, the cathode is a top metal Ag electrode.

[0057] In one or more embodiments, the donor material is PM6 and the acceptor material is L8-BO.

[0058] A third typical embodiment of the present invention provides the use of an organic photovoltaic device based on a gradient donor-acceptor ratio prepared by the preparation method described in the first aspect in screening solution processing conditions for organic solar cells.

[0059] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0060] Example 1

[0061] Figure 1 The schematic diagram of the structure of an organic photovoltaic device based on a gradient donor-acceptor ratio is shown in FIG. 1 , wherein the organic photovoltaic device based on a gradient donor-acceptor ratio comprises a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode stacked in sequence from bottom to top;

[0062] The active layer has a gradient donor-acceptor ratio.

[0063] During the preparation process, the active layer includes a first active layer and a second active layer stacked from bottom to top, the first active layer is a donor-acceptor blended layer, and the second active layer is a donor layer or an acceptor layer; the first active layer and the second active layer have the same thickness gradient along the length direction within a limited length range; the thickness gradient direction of the first active layer is opposite to the thickness gradient direction of the second active layer. Specifically, the first active layer and the second active layer have a thickness variation of 90 to 110 nm along the length direction within a length range of 7.5 to 8 cm. It is set that there are two end points along the length direction within a limited length range, namely end A and end B. The thickness gradient direction of the first active layer becomes thinner from end A to end B, and the thickness gradient direction of the first active layer becomes thinner from end B to end A; after the donor or acceptor in the second active layer is stacked and blended with the first active layer, the ratio of the donor to the acceptor in the entire active layer gradually changes, thereby forming a gradient donor-acceptor ratio.

[0064] In this embodiment, the substrate is a glass substrate, the anode is ITO, the material of the hole transport layer is PEDOT:PSS, the material of the electron transport layer is F3N-Br, and the cathode is a top metal Ag electrode.

[0065] Example 2

[0066] Preparation of an organic photovoltaic device based on a gradient donor-acceptor ratio:

[0067] (1) The conductive glass is ITO conductive glass; before preparing the hole transport layer, the following operations are performed:

[0068] The ITO conductive glass was ultrasonically cleaned with a cleaning agent, deionized water, acetone, anhydrous ethanol and isopropanol in sequence, dried with nitrogen, and then treated with UV for 15 minutes.

[0069] (2) preparing a hole transport layer by scraping on the surface of the conductive glass, comprising:

[0070] In an air atmosphere, a PEDOT:PSS aqueous solution was scraped on the surface of the conductive glass, wherein PEDOT:PSS was mixed with deionized water in a ratio of 1:1, the scraping speed was 15 mm / s, the drop volume was 100 μL, the substrate temperature was 60°C, and annealing was performed at 150°C for 10 min.

[0071] (3) preparing an active layer by scraping on the surface of the hole transport layer, comprising:

[0072] In an air atmosphere, an active layer material was scraped on the hole transport layer, wherein the concentration of the active layer donor solution was 10 mg / mL, the concentration of the acceptor solution was 12 mg / mL, the solvent used for the solution was o-xylene, the scraping speed was 25 mm / s, the drop volume was 45 μL, the substrate temperature was 80° C., and annealing was performed at 100° C. for 10 min in a nitrogen atmosphere; during the scraping process, the first active layer material was scraped on the hole transport layer along a defined direction (the same conditions as defined in Example 1, from end A to end B), and the thickness of the prepared layer gradually decreased along the defined direction. A small first active layer; at the end point of the first active layer scraping, scrape the second active layer material in the opposite direction of the defined direction (the same conditions as defined in Example 1, from the B end to the A end) to prepare a second active layer whose thickness gradually decreases in the opposite direction of the defined direction; during the scraping process, the end point of the first active layer scraping is the starting point of the second active layer scraping; the end point of the second active layer scraping is the starting point of the first active layer scraping; the first active layer thickness gradually decreases from 110nm to 90nm along the length direction within a length of 7.5cm along the defined direction. The second active layer thickness gradually decreases from 110nm to 90nm along the length direction within a length of 7.5cm along the opposite direction of the defined direction. After the donor or acceptor in the second active layer is laminated with the first active layer, the ratio of the donor to the acceptor in the entire active layer gradually changes, thereby forming a gradient donor-acceptor ratio.

[0073] In this embodiment, the first active layer contains only donor material (the donor-acceptor mass ratio is 1:0), and the second active layer contains only acceptor material.

[0074] (4) preparing an electron transport layer by scraping on the surface of the active layer, comprising:

[0075] A 0.7 mg / mL F3N-Br solution was scraped onto the active layer at a scraping speed of 15 mm / s and the substrate temperature was room temperature.

[0076] (5) Preparing a cathode on the electron transport layer under vacuum conditions, comprising:

[0077] In 4×10 -4 A 100 nm Ag electrode was prepared by thermal evaporation under vacuum conditions of 0.04 Pa.

[0078] Example 3

[0079] The difference between this embodiment and embodiment 2 is that the donor-acceptor mass ratio in the first active layer is 1:2, and the second active layer contains only donor material.

[0080] Example 4

[0081] The difference between this embodiment and embodiment 2 is that the donor-acceptor mass ratio in the first active layer is 1:0.5, and the second active layer contains only donor material.

[0082] Performance parameters of organic solar cells: power conversion efficiency (PCE)

[0083] PCE=J SC ×V OC ×FF / P in ×100%

[0084] Where J SC is the short-circuit current density, V OC is the open circuit voltage, FF is the fill factor, P in is the incident light intensity (AM1.5G), PCE can be directly tested by the solar cell JV curve test system.

[0085] Figure 4 From the UV-visible absorption spectrum and steady-state fluorescence spectrum at different points of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO prepared in Example 2, it can be seen that the absorption peak ratios of the donor and acceptor at different positions are different, representing different donor-acceptor ratios, and the fluorescence peak position of the acceptor tends to blue-shift as the donor-acceptor ratio decreases. Figure 5 The UV-visible absorption spectra and steady-state fluorescence spectra at different points of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO prepared in Example 3 show that the donor-acceptor ratio is more adjusted, and the fluorescence peak of the acceptor moves to about 840 nanometers, and there is a slight blue shift trend as the donor-acceptor ratio increases; Figure 6 From the UV-visible absorption spectrum and steady-state fluorescence spectrum at different points of the active layer film with a gradient donor-acceptor ratio PM6:L8-BO prepared in Example 4, it can be seen that the donor-acceptor ratio is more adjusted, and the fluorescence peak of the acceptor moves to about 880 nanometers, and there is no obvious movement trend with the increase of the donor-acceptor ratio.

[0086] Figure 7 This is a summary diagram of the performance of the device at different points of the active layer film with a gradient PM6:L8-BO ratio prepared in Example 2; it can be seen that as the donor-acceptor ratio increases, the open circuit voltage of the device remains stable, the short circuit current density increases, and the fill factor decreases. Figure 8 and Fig. 9The device performance decay diagram of the device at different points of the active layer film with a gradient PM6:L8-BO ratio prepared in Example 2 under the conditions of one sun illumination and 60°C heating and the fitted performance decay rate (fitted using the exponential function PCE(t)=PCE(0)exp(-b / t), the fitting parameter 1 / t represents the decay rate) and the donor-acceptor ratio are shown. It can be seen that as the donor-acceptor ratio increases, the device performance decays faster. After screening, it was found that the donor-acceptor ratio of the device with both excellent performance and photothermal stability is between 1.05 and 1.25. Therefore, the method shown in the present invention consumes only a small amount of expensive organic materials, and can screen out photovoltaic devices with the best donor-acceptor ratio with better performance and better stability, which is of great significance for organic photovoltaics to move closer to commercialization and large-scale industrial production.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an organic photovoltaic device based on a gradient donor-acceptor ratio, characterized in that: include: (1) In an air atmosphere, a hole transport layer is prepared by scraping on the surface of a conductive glass; (2) in an air atmosphere, scraping a first active layer material on the hole transport layer along a defined direction to prepare a first active layer whose thickness gradually decreases along the defined direction; at the end point of scraping the first active layer, scraping a second active layer material on the first active layer in the opposite direction of the defined direction to prepare a second active layer whose thickness gradually decreases along the opposite direction of the defined direction; annealing in an inert atmosphere to prepare an active layer; (3) preparing an electron transport layer by scraping on the surface of the active layer in an air atmosphere; (4) Under vacuum conditions, a cathode is prepared on the electron transport layer.

2. The preparation method according to claim 1, characterized in that In step (2), the end point of the first active layer scraping is the starting point of the second active layer scraping; and the end point of the second active layer scraping is the starting point of the first active layer scraping.

3. In step (2), the first active layer is a donor-acceptor mixed layer, and the second active layer is a donor layer or an acceptor layer; Preferably, the donor material is PM6 and the acceptor material is L8-BO.

4. The preparation method according to claim 1, characterized in that: In step (2), the first active layer and the second active layer have a thickness variation of 190 to 210 nm along the length direction within a length range of 7.5 to 8 cm.

5. The preparation method according to claim 1, characterized in that: In step (2), the first active layer and the second active layer have the same scraping speed, both of which are 10-40 mm / s, preferably 25 mm / s; the amount of liquid dripped at one time is the same, both of which are 30-70 μL, preferably 45 μL; Or, in step (2), during the scraping, the substrate temperature is 60-100° C., preferably 80° C.; in an inert atmosphere, annealing is performed at 40-180° C. for 5-10 min, preferably annealing at 100° C. for 10 min.

6. The preparation method according to claim 1, characterized in that: In step (1), the conductive glass is ITO conductive glass. Before preparing the hole transport layer, the ITO conductive glass is ultrasonically cleaned with a cleaning agent, water, acetone, anhydrous ethanol and isopropanol in sequence, blown dry with nitrogen, and then treated with UV for 15-25 minutes; Or, in step (1), the preparation method of the hole transport layer comprises: coating PEDOT:PSS on the surface of conductive glass, and annealing at 130-180° C. for 10-20 min; Alternatively, in step (3), the specific steps of preparing the electron transport layer by scraping on the surface of the active layer include: scraping 0.5-1.5 mg / mL F3N-Br solution onto the active layer at a scraping speed of 10-25 mm / s; Or, in step (4), at 2.5×10 -4 -5×10 -4 Under vacuum conditions of 0.3 Pa, 80-100 nm Ag electrodes were prepared by thermal evaporation.

7. An organic photovoltaic device based on a gradient donor-acceptor ratio, characterized in that: It includes a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode which are stacked in sequence from bottom to top; The active layer has a gradient donor-acceptor ratio.

8. The organic photovoltaic device based on gradient donor-acceptor ratio according to claim 7, characterized in that: The active layer comprises a first active layer and a second active layer stacked in sequence from bottom to top, the first active layer is a donor-acceptor mixed layer, and the second active layer is a donor layer or an acceptor layer; The first active layer and the second active layer have the same thickness gradient along the length direction within a limited length range; the thickness gradient direction of the first active layer is opposite to the thickness gradient direction of the second active layer; Preferably, the first active layer and the second active layer have a thickness variation of 90-110 nm along the length direction within a length range of 7.5-8 cm.

9. The organic photovoltaic device based on gradient donor-acceptor ratio according to claim 7, characterized in that: The substrate is a glass substrate; Or, the anode is indium tin oxide; Or, the hole transport layer is made of PEDOT:PSS; Or, the material of the electron transport layer is F3N-Br; Or, the cathode is a top metal Ag electrode; Or, the donor material is PM6 and the acceptor material is L8-BO.

10. Use of an organic photovoltaic device based on a gradient donor-acceptor ratio prepared by the preparation method according to any one of claims 1 to 6 in screening solution treatment conditions for organic solar cells.

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