A quasi-planar heterojunction active layer, method for preparing an organic photovoltaic cell

Abstract

This invention discloses a method for preparing a quasi-planar heterojunction active layer and an organic photovoltaic cell. The method includes: depositing a first layer on a substrate using electrostatic spraying; and depositing a second layer on the first layer using electrostatic spraying to obtain the quasi-planar heterojunction active layer; wherein the first layer is a donor layer and the second layer is an acceptor layer; or, the first layer is an acceptor layer and the second layer is a donor layer. This method for preparing a quasi-planar heterojunction has the following advantages: it does not wash away the underlying acceptor / donor during the deposition of the upper donor / acceptor layer, resulting in high material utilization; the fusion between the donor and acceptor layers can be adjusted and controlled by adjusting the substrate temperature and spray flow rate during the deposition of the second layer; it has high adaptability to substrate shape, allowing for co-formation on curved or slit flexible substrates; and the prepared quasi-planar heterojunction organic photovoltaic cell exhibits superior performance compared to electrostatically sprayed heterojunction organic photovoltaic cells.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a method for preparing a quasi-planar heterojunction active layer and an organic photovoltaic cell. Background Technology

[0002] Organic photovoltaic (PV) cells offer advantages such as low cost, light weight, flexibility, semi-transparency, and solution-based manufacturing, enabling high-volume, low-cost roll-to-roll printing, making them suitable for integration into building and electronic equipment. The photoelectric conversion process in PV cells occurs in the photosensitive active layer, which primarily comprises two structures: bulk heterojunctions and quasi-planar heterojunctions. Research indicates that for non-fullerene acceptor-based PV cells, quasi-planar heterojunction active layers obtained through layer-by-layer deposition outperform bulk heterojunctions in terms of exciton dissociation and recombination, device lifetime, and film morphology. Layer-by-layer deposition of organic photosensitive active layers typically employs spin coating, blade coating, or slot coating methods. These methods are all continuous-phase solution preparation methods, requiring the initial dripping of a large amount of solution onto the substrate, followed by rotation or dragging to uniformly distribute the solution into a film. Therefore, when depositing the second active layer, a portion of the first layer is easily washed away, resulting in uneven film thickness, material waste, difficulty in controlling the fusion between the two active layers, and unsuitability for co-forming films on curved substrates or cut-out paper substrates.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a quasi-planar heterojunction active layer and an organic photovoltaic cell, which aims to solve the problems of uneven distribution of donor and acceptor materials in the quasi-planar heterojunction film, material waste, and difficulty in controlling the degree of fusion between the two active materials in the existing layer-by-layer deposition method of organic photosensitive active layer.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a quasi-planar heterojunction active layer, comprising the steps of:

[0007] The first layer was deposited on the substrate using an electrostatic spraying method;

[0008] A second layer is deposited on the first layer using an electrostatic spraying method to obtain a quasi-planar heterojunction active layer.

[0009] Wherein, the first layer is a donor layer and the second layer is a acceptor layer; or, the first layer is a acceptor layer and the second layer is a donor layer.

[0010] Optionally, the step of depositing the first layer on the substrate using an electrostatic spraying method specifically includes:

[0011] The first layer material solution is added to an electrostatic spraying device, and the first layer material solution is sprayed onto the substrate through the electrostatic spraying device and dried to obtain the first layer.

[0012] Further optionally, the process parameters for depositing the first layer on the substrate using the electrostatic spraying method are as follows: the flow rate of the first layer material solution electrostatic spraying is 10-40 μl / min, the temperature of the substrate is 0-25°C, and the electrostatic spraying time of the first layer material solution is 15-60 s.

[0013] Further, optionally, the first layer of material solution is sprayed onto the substrate in a circular mist pattern using the electrostatic spraying device;

[0014] Alternatively, the electrostatic spraying device may be an electrostatic spraying device equipped with four electrodes, through which the first layer of material solution is sprayed onto the substrate in a long strip-shaped mist pattern.

[0015] Optionally, the step of depositing a second layer on the first layer using an electrostatic spraying method specifically includes: adding a second layer material solution to an electrostatic spraying device, spraying the second layer material solution onto the first layer through the electrostatic spraying device, and drying to obtain the second layer.

[0016] Further optionally, the operating parameters of the electrostatic spraying device are as follows: the flow rate of the second layer material solution electrostatic spraying is 10-25 μl / min, the temperature of the substrate is 25-80°C, and the electrostatic spraying time of the second layer material solution is 40-150 s.

[0017] Further optionally, the second layer material solution is sprayed onto the first layer in a circular mist pattern using the electrostatic spraying device;

[0018] Alternatively, the electrostatic spraying device may be an electrostatic spraying device equipped with four electrodes, through which the second layer material solution is sprayed onto the first layer in a long strip-shaped mist pattern.

[0019] Alternatively, the solvent used in the second layer material solution may be one or more of chloroform, chlorobenzene, toluene, and o-xylene.

[0020] Optionally, the material of the donor layer is selected from one or more of PM6, PTQ10, D18, and D18-Cl;

[0021] The material of the receptor layer is selected from one or more of Y6-BO, Y6, BTP-eC9, and N3.

[0022] A method for preparing an organic photovoltaic cell, comprising the steps of:

[0023] Provide a substrate with a first electrode on its surface;

[0024] A first functional layer is fabricated on the first electrode;

[0025] A quasi-planar heterojunction active layer is prepared on the first functional layer using the method described in this invention;

[0026] A second functional layer is prepared on the quasi-planar heterojunction active layer;

[0027] A second electrode is fabricated on the second functional layer to obtain an organic photovoltaic cell.

[0028] Optionally, the first electrode is an anode, the first functional layer is a hole transport layer, the second functional layer is an electron transport layer, the second electrode is a cathode, the donor layer is attached to the hole transport layer, and the acceptor layer is attached to the electron transport layer.

[0029] Alternatively, the first electrode is a cathode, the first functional layer is an electron transport layer, the second functional layer is a hole transport layer, the second electrode is an anode, the donor layer is bonded to the hole transport layer, and the acceptor layer is bonded to the electron transport layer.

[0030] Beneficial Effects: Electrostatic spraying is a droplet deposition method where uniformly sized monodisperse droplets are deposited on a substrate, forming a thin film through the stacking and fusion of droplets. This invention utilizes electrostatic spraying for layer-by-layer deposition to prepare quasi-planar heterojunctions, offering the following advantages: the deposition of the upper donor / acceptor layer does not wash away the lower-layer acceptor / acceptor layer, resulting in high material utilization; the fusion between the donor and acceptor layers can be adjusted and controlled by regulating the substrate temperature and spray flow rate during the second layer deposition; it exhibits high adaptability to substrate shapes, enabling film co-formation on curved and slit flexible substrates; the prepared quasi-planar heterojunction organic photovoltaic cells outperform electrostatic sprayed heterojunction organic photovoltaic cells in performance; and the electrostatic spraying technology is compatible with industrial roll-to-roll processing. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a typical electrostatic spray device.

[0032] Figure 2 This is a schematic diagram of a four-electrode electrostatic spraying device.

[0033] Figure 3 This is a schematic diagram of an upright organic photovoltaic cell structure.

[0034] Figure 4 This is a schematic diagram of an inverted organic photovoltaic cell.

[0035] Figure 5 The image shows the film morphology and donor / acceptor fusion degree at different substrate temperatures during electrostatic spraying of the acceptor in Example 2.

[0036] Figure 6 The image shows the film morphology and donor / acceptor fusion degree under different four-electrode electrostatic spray flow rates in Example 3. Detailed Implementation

[0037] This invention provides a quasi-planar heterojunction active layer and a method for preparing an organic photovoltaic cell. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0038] In recent years, organic photovoltaic cells based on quasi-planar heterojunction active layers deposited layer by layer have exhibited superior performance. Existing methods for layer-by-layer deposition of organic photosensitive active layers include spin coating, blade coating, and slot coating, all of which belong to continuous phase solution preparation methods. However, existing methods have the following drawbacks: 1) The deposition of the upper active layer causes erosion of the lower active material, resulting in uneven distribution of donor and acceptor materials within the quasi-planar heterojunction film; 2) Material waste; 3) Difficulty in controlling the degree of fusion and spatial distribution of the donor and acceptor layers; 4) Inability to form films on curved substrates; 5) Difficulty in forming films of uniform thickness on slit-structured substrates.

[0039] Based on this, embodiments of the present invention provide a method for preparing a quasi-planar heterojunction active layer, comprising the following steps:

[0040] S1. The first layer is deposited on the substrate using an electrostatic spraying method;

[0041] S2. A second layer is deposited on the first layer using an electrostatic spraying method to obtain a quasi-planar heterojunction active layer;

[0042] Wherein, the first layer is a donor layer and the second layer is a acceptor layer; or, the first layer is a acceptor layer and the second layer is a donor layer.

[0043] Electrostatic spraying is a droplet deposition method in which uniformly sized monodisperse droplets are deposited on a substrate, and a thin film is formed through the stacking and fusion of the droplets. This embodiment uses electrostatic spraying to sequentially deposit a donor layer and an acceptor layer, or vice versa, to obtain a quasi-planar heterojunction active layer. This embodiment of electrostatic spraying for layer-by-layer deposition of the quasi-planar heterojunction active layer has the following advantages: the deposit of the upper donor / acceptor layer does not wash away the lower acceptor / acceptor layer; the morphology of the film and the degree of fusion between the donor / acceptor layers can be optimized by adjusting the substrate temperature and spray flow rate during the deposition of the upper layer (i.e., the second layer). Furthermore, electrostatic spraying offers high material utilization, high adaptability to substrate shape, and compatibility with roll-to-roll and automated production methods. In addition, this method can use green solvents to prepare high-efficiency quasi-planar heterojunction devices.

[0044] Specifically, the method of this embodiment has the following technical advantages:

[0045] 1) The prepared organic photovoltaic cells outperform electrostatic spray heterojunction organic photovoltaic cells in performance; 2) It saves materials and costs, as electrostatic spraying is an additive manufacturing method where droplets mostly fall onto the substrate, resulting in no material loss; 3) By adjusting the substrate temperature and spray flow rate during the second layer deposition, the fusion between the donor and acceptor layers can be adjusted and controlled; 4) It is suitable for the fabrication of large-area devices and modules; 5) It has high adaptability to substrate shape and can co-form films on curved and slit flexible substrates; 6) It is compatible with roll-to-roll and automated production methods.

[0046] In this embodiment, the apparatus for depositing the donor and acceptor layers is an electrostatic spraying device. The electrostatic spraying device can be a conventional electrostatic spraying device or a four-electrode electrostatic spraying device (i.e., an electrostatic spraying device equipped with four electrodes). A conventional electrostatic spraying device, such as... Figure 1 As shown, the key components of the device are the needle (such as a steel needle) and the high-voltage power supply. Through the pushing action of the injection pump, the donor / receptor layer solution flows uniformly from the needle. Under the influence of the electric field and surface tension, the solution forms a Taylor cone at the needle tip. In this state, the generated droplets are essentially uniform in size, resulting in circular spray spots. A four-electrode electrostatic spraying device is shown below. Figure 2 As shown, the device is in Figure 1 The addition of a pair of four electrodes to the existing electrostatic spray system compresses the circular mist spot into a long strip, improving the fusion between electrostatic spray droplets. Both conventional electrostatic spray devices and four-electrode electrostatic spray devices are existing technologies and will not be elaborated upon here.

[0047] In some embodiments, step S1 specifically includes: adding a first layer material solution to an electrostatic spraying device, spraying the first layer material solution onto a substrate through the electrostatic spraying device, and drying it to obtain the first layer.

[0048] Furthermore, the process parameters for depositing the first layer on the substrate using the electrostatic spraying method are as follows: the flow rate of the first layer material solution electrostatic spraying is 10–40 μl / min, the temperature of the substrate is 0–25°C, and the electrostatic spraying time of the first layer material solution is 15–60 s.

[0049] Furthermore, the electrostatic spraying device is a common electrostatic spraying device, which sprays the first layer of material solution onto the substrate in a circular mist pattern;

[0050] Alternatively, the electrostatic spraying device may be an electrostatic spraying device equipped with four electrodes, through which the first layer of material solution is sprayed onto the substrate in a long strip-shaped mist pattern.

[0051] Furthermore, the distance between the spray needle of the electrostatic spraying device and the substrate is 3 to 5 cm.

[0052] Furthermore, the solvent used in the first layer material solution is one or more of chloroform, chlorobenzene, toluene, o-xylene, etc.

[0053] In some specific embodiments, the ordinary electrostatic spraying device includes a syringe, a needle, a substrate, a syringe pump, and a high-voltage power supply; step S1 specifically includes:

[0054] The first layer material solution is drawn into the syringe, the syringe is connected to the needle, the needle is connected to the high voltage electrode, the substrate is connected to the ground electrode, the flow rate of the first layer material solution of the injection pump is set, the injection pump is turned on to push the first layer material solution in the syringe, the high voltage power is turned on until the solution below the needle forms a Taylor cone pattern.

[0055] The substrate is placed in the center of the fog spot on the substrate, and the first layer material solution is sprayed onto the substrate and dried to obtain the first layer deposited on the substrate.

[0056] In some embodiments, step S2 specifically includes: adding a second layer material solution to an electrostatic spraying device, spraying the second layer material solution onto the first layer through the electrostatic spraying device, and drying it to obtain the second layer.

[0057] Furthermore, the process parameters for depositing the second layer on the first layer using the electrostatic spraying method are as follows: the flow rate of the second layer material solution electrostatic spraying is 10-25 μl / min, the temperature of the substrate is 25-80°C, and the electrostatic spraying time of the second layer material solution is 40-150 s.

[0058] Furthermore, the solvent used in the second layer material solution is one or more of chloroform, chlorobenzene, toluene, o-xylene, etc.

[0059] In some specific embodiments, the electrostatic spraying device is a common electrostatic spraying device, which includes a syringe, a needle, a substrate, a syringe pump, and a high-voltage power supply; step S2 specifically includes:

[0060] The second layer material solution is drawn into the syringe, the syringe is connected to the needle, the needle is connected to the high voltage electrode, the substrate is connected to the ground electrode, the flow rate of the second layer material solution of the injection pump is set, the injection pump is turned on to push the second layer material solution in the syringe, the high voltage power is turned on until the solution below the needle forms a Taylor cone pattern.

[0061] A substrate with a first layer deposited on its surface is placed in the center of a fog spot on a substrate. The second layer material solution is sprayed onto the first layer and dried to obtain the second layer.

[0062] In some specific embodiments, the electrostatic spraying device is a four-electrode electrostatic spraying device, which includes a syringe, a needle, a substrate, a syringe pump, a high-voltage power supply, and four electrodes; step S2 specifically includes:

[0063] The second layer material solution is drawn into the syringe, the syringe is connected to the needle, the needle is connected to a pair of opposite electrodes of the four electrodes to the high voltage electrode, the substrate is connected to the other pair of opposite electrodes of the four electrodes to the ground electrode, the flow rate of the second layer material solution of the injection pump is set, the injection pump is turned on to push the second layer material solution in the syringe, the high voltage power is turned on until a long strip of fog forms in the solution below the needle.

[0064] A substrate with a first layer deposited on its surface is placed in the center of a fog spot on a substrate. The moving speed of the substrate is set, and the second layer material solution is sprayed onto the first layer in a long strip fog spot pattern. After drying, the second layer is obtained.

[0065] Furthermore, the distance between the spray needle of the electrostatic spraying device and the substrate is 3-5 cm.

[0066] Furthermore, the substrate moving speed is 0.1 to 0.4 mm / s.

[0067] For electrostatic spray heterojunctions, since only one thin film is deposited, there is no need to consider the impact on the underlying layer. Provided a Taylor cone can be formed, the spray flow rate can be adjusted within a wide range. However, in this embodiment, when preparing the quasi-planar heterojunction active layer by layer deposition using electrostatic spraying, the impact of the upper layer on the underlying layer must be considered. For example: 1) The flow rate of the second layer material solution cannot be too high, otherwise it will dissolve the underlying film, leading to penetration of the underlying film; 2) The substrate temperature cannot be too high or too low. Too high a temperature will promote the dissolution of the underlying layer by the upper layer, leading to penetration of the underlying film. Too low a temperature will prolong the drying time of the upper film and reduce the solubility of the material, leading to solute precipitation; 3) When depositing the upper layer, the saturated vapor pressure of the selected solvent cannot be too low, otherwise the solvent will evaporate too slowly, leading to the dissolution of the donor. Therefore, this embodiment, for the layer-by-layer deposition of quasi-planar heterojunctions, controls the spray flow rate, substrate temperature, and solvent characteristics when depositing the upper layer on the underlying film, thereby optimizing the degree of fusion between the donor / acceptor and the film morphology, and thus obtaining a quasi-planar heterojunction device with excellent performance.

[0068] In some embodiments, the material of the donor layer is selected from one or more of PM6, PTQ10, D18, D18-Cl, etc.

[0069] In some embodiments, the material of the receptor layer is selected from one or more of Y6-BO, Y6, BTP-eC9, N3, etc.

[0070] This invention provides a method for preparing an organic photovoltaic cell, comprising the following steps:

[0071] Provide a substrate with a first electrode on its surface;

[0072] A first functional layer is fabricated on the first electrode;

[0073] A quasi-planar heterojunction active layer is prepared on the first functional layer using the method described above;

[0074] A second functional layer is prepared on the quasi-planar heterojunction active layer;

[0075] A second electrode is fabricated on the second functional layer to obtain an organic photovoltaic cell.

[0076] Existing methods for layer-by-layer deposition of quasi-planar heterojunction active layers mainly include spin coating, blade coating, and slot coating. These are contact-based film formation methods and are not suitable for co-forming films on curved substrates or cut-out paper substrates. Unlike existing methods, this embodiment uses electrostatic spraying to deposit the quasi-planar heterojunction active layer layer-by-layer. This is a non-contact film formation method with high adaptability to substrate shape, allowing for co-forming films on curved or cut-out flexible substrates. Furthermore, the deposition of the upper layer solution does not wash away the lower layer film, saving material. Additionally, by adjusting the substrate temperature and spray flow rate during electrostatic spraying, the degree of fusion between the donor and acceptor can be well controlled. The power conversion efficiency (PCE) of the device obtained by layer-by-layer deposition of the quasi-planar heterojunction active layer using electrostatic spraying is superior to that of electrostatically sprayed heterojunction devices. Moreover, electrostatic spraying is suitable for large-area device fabrication, is compatible with roll-to-roll production, and can be used to fabricate fully sprayed organic photovoltaic cells.

[0077] In this embodiment, the organic photovoltaic cells are divided into two categories: upright organic photovoltaic cells and inverted organic photovoltaic cells. For upright organic photovoltaic cells, a donor layer is first prepared, followed by an acceptor layer on top of the donor layer; for inverted organic photovoltaic cells, an acceptor layer is first prepared, followed by a donor layer on top of the acceptor layer.

[0078] In some embodiments, the upright organic photovoltaic cell includes a substrate (such as glass), an anode (such as an ITO (Indium Tin Oxide) layer), a hole transport layer (such as a PEDOT:PSS layer), a donor layer, an acceptor layer, an electron transport layer (such as a PNDIT-F3N layer), and a cathode, which are stacked sequentially. Figure 3 As shown. That is, the first electrode is the anode, the first functional layer is the hole transport layer, the second functional layer is the electron transport layer, the second electrode is the cathode, the donor layer is attached to the hole transport layer, and the acceptor layer is attached to the electron transport layer.

[0079] In some embodiments, the inverted organic photovoltaic cell includes a substrate (such as glass), a cathode (such as an ITO layer), an electron transport layer, an acceptor layer, a donor layer, a hole transport layer (such as a PEDOT:PSS layer), and an anode, which are stacked sequentially. Figure 4 As shown. That is, the first electrode is the cathode, the first functional layer is the electron transport layer, the second functional layer is the hole transport layer, the second electrode is the anode, the donor layer is attached to the hole transport layer, and the acceptor layer is attached to the electron transport layer.

[0080] In some embodiments, the substrate may be glass, or a flexible substrate such as PET (Polyethyleneterephthalate), PC (Polycarbonate), or PDMS (Polydimethylsiloxane).

[0081] In some embodiments, the first electrode can be ITO or a transparent electrode such as silver nanowires.

[0082] In this embodiment, the detailed steps and related details regarding the preparation of the quasi-planar heterojunction active layer on the first functional layer are described above and will not be repeated here.

[0083] The present invention will be further described below through several embodiments.

[0084] Example 1

[0085] 1) The donor PM6 and acceptor Y6-BO are used as active layer materials. The device structure is ITO / PEDOT:PSS / PM6 / Y6-BO (annealing temperature is 100℃, annealing time is 10min, PM6 layer thickness is 70nm, Y6-BO layer thickness is 60nm) / PNDIT-F3N / Ag (thickness 100nm).

[0086] 2) PM6 was dissolved in a mixed solvent of chloroform (CF) and chlorobenzene (CB) (CF:CB volume ratio 7:3) to obtain a PM6 solution with a concentration of 1.2 mg / ml; Y6-BO was dissolved in a mixed solvent of CF and CB (CF:CB volume ratio 4:1) to obtain a Y6-BO solution with a concentration of 1.5 mg / ml. Both the PM6 and Y6-BO solutions were heated and stirred at 70°C for 12 hours, and then allowed to stand at room temperature for later use.

[0087] 3) The PM6 layer uses a common electrostatic spraying device (such as...) Figure 1 The preparation process included the following conditions: the electrostatic spray flow rate was set to 30 μl / min, the distance between the needle and the substrate was 4 cm, and the substrate temperature was 5 °C. Due to the low substrate temperature, the evaporation of the solvent was slowed down, resulting in a wet donor film. The film was then placed on a hot plate at 60 °C for heating and drying to form a smooth PM6 donor film.

[0088] 4) The Y6-BO layer uses a four-electrode electrostatic spraying device (such as...). Figure 2 The process was carried out to obtain a dense receptor film, wherein the process conditions were as follows: the electrostatic spray flow rate was 20 μl / min, the distance between the needle and the substrate was 3 cm, the substrate temperature was room temperature, and the substrate moving speed was 0.2 mm / s.

[0089] 5) Except for the PM6 layer and the Y6-BO layer, which were prepared by electrostatic spraying, all other layers were prepared by spin coating.

[0090] Comparative Example 1

[0091] The device structure is ITO / PEDOT:PSS / electrosprayed bulk heterojunction active layer / PNDIT-F3N / Ag (thickness 100nm). This device is basically the same as in Example 1, except that the bulk heterojunction active layer is prepared using an electrostatic spraying method. The specific steps for preparing the bulk heterojunction active layer using the electrostatic spraying method are as follows: PM6 and Y6-BO are dissolved in a mixed solvent of chloroform:chlorobenzene = 4:1 (vol / vol) at a mass ratio of 1:1.2 (the total concentration of PM6 and Y6-BO is 2.2 mg / ml), heated and stirred at 70°C for 12 hours, using a common electrostatic spraying device (such as...). Figure 1 The electrostatic spraying process was carried out under the following conditions: the electrostatic spraying flow rate was set to 40 μl / min, the distance between the needle and the substrate was 4 cm, the substrate temperature was 25 °C, and the spraying time was 50 s to obtain a thin film with a thickness of 100 nm.

[0092] The parameters of the device in Example 1 are shown in Table 1, which contains data on quasi-planar heterojunction devices. The parameters of the device in Comparative Example 1 are shown in Table 1, which contains data on bulk heterojunction devices. These results demonstrate that the electrostatic spraying method has a good effect on the preparation of quasi-planar heterojunction devices.

[0093] Table 1. Performance parameters of organic photovoltaic cells with quasi-planar heterojunctions and electrostatically sprayed heterojunctions deposited layer by layer by electrostatic spraying.

[0094]

[0095] Example 2

[0096] The results are basically the same as in Example 1, except that the substrate temperature during the four-electrode electrostatic spraying acceptor was changed to 40°C, 50°C, 60°C, 70°C, and 80°C, and the morphology of the prepared active layer film is as follows. Figure 5 As shown in Table 2, the device performance parameters are as follows. The results show that as the substrate temperature increases, the dissolution of the donor layer by the acceptor layer gradually increases, and the distribution of solute in the film becomes more uneven, resulting in a decrease in all device parameters as the substrate temperature increases during acceptor deposition.

[0097] Table 2. Device performance at different acceptor deposition substrate temperatures

[0098]

[0099] Example 3

[0100] The process is essentially the same as in Example 1, except that the flow rates at the four-electrode spray acceptor were changed to 10 μl / min, 15 μl / min, and 25 μl / min, respectively. The morphology of the prepared active layer film is as follows: Figure 6 As shown in Table 3, the results indicate that with increasing four-electrode spray flow rate, the acceptor droplet gradually increases in size, the droplet drying time becomes longer, and the dissolution of the donor layer by the acceptor layer gradually increases. However, the fusion of the acceptor layer with the donor layer is not necessarily better the more abundant it is; rather, there exists an optimal miscibility. The device performance parameters are shown in Table 3. With increasing acceptor spray flow rate, the device PCE first increases and then decreases. At an acceptor flow rate of 20 μl / min, the donor and acceptor layers exhibit optimal miscibility, and the device PCE reaches its maximum value of 15.61%.

[0101] Table 3. Device performance under different receptor spray flow rates

[0102]

[0103]

[0104] In summary, the present invention provides a method for preparing a quasi-planar heterojunction active layer and an organic photovoltaic cell. The method employing electrostatic spraying for layer-by-layer deposition of the quasi-planar heterojunction has the following advantages: 1) The prepared quasi-planar heterojunction organic photovoltaic cell outperforms bulk heterojunction devices in performance; 2) It saves materials and costs, as the electrostatic spray droplets almost entirely fall onto the substrate, resulting in no material loss; 3) By adjusting the substrate temperature and spray flow rate during the second layer deposition, the fusion between the donor and acceptor layers can be adjusted and controlled; 4) It is suitable for the fabrication of large-area devices and modules; 5) It has high adaptability to substrate shapes and can co-form films on curved or slit flexible substrates; 6) It is compatible with roll-to-roll and automated production methods.

[0105] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a quasi-planar heterojunction active layer, characterized in that, Including the following steps: The first layer was deposited on the substrate using an electrostatic spraying method; A second layer is deposited on the first layer using an electrostatic spraying method to obtain a quasi-planar heterojunction active layer. Wherein, the first layer is a donor layer and the second layer is a acceptor layer; or, the first layer is a acceptor layer and the second layer is a donor layer; The step of depositing the first layer on the substrate using an electrostatic spraying method specifically includes: The first layer material solution is added to an electrostatic spraying device, and the first layer material solution is sprayed onto the substrate through the electrostatic spraying device and dried to obtain the first layer. The process parameters for depositing the first layer on the substrate using electrostatic spraying are as follows: the flow rate of the first layer material solution electrostatic spraying is 10-40 μl / min, the temperature of the substrate is 0-25℃, and the electrostatic spraying time of the first layer material solution is 15-60 s. The first layer of material solution is sprayed onto the substrate in a circular mist pattern using the electrostatic spraying device. Alternatively, the electrostatic spraying device is an electrostatic spraying device equipped with four electrodes, through which the first layer of material solution is sprayed onto the substrate in a long strip-shaped mist pattern; The step of depositing a second layer on the first layer using electrostatic spraying specifically includes: adding a second layer material solution into an electrostatic spraying device, spraying the second layer material solution onto the first layer through the electrostatic spraying device, and drying it to obtain the second layer. The process parameters for depositing the second layer on the first layer using electrostatic spraying are as follows: the flow rate of the second layer material solution electrostatic spraying is 10-25 μl / min, the temperature of the substrate is 25-80℃, and the electrostatic spraying time of the second layer material solution is 40-150 s. The solvent used in the second layer material solution is one or more of chloroform, chlorobenzene, toluene, and o-xylene; The second layer material solution is sprayed onto the first layer in a circular mist pattern using the electrostatic spraying device. Alternatively, the electrostatic spraying device is an electrostatic spraying device equipped with four electrodes, through which the second layer material solution is sprayed onto the first layer in a long strip-shaped mist pattern; The material of the donor layer is selected from one or more of PM6, PTQ10, D18, and D18-Cl; The material of the receptor layer is selected from one or more of Y6-BO, Y6, BTP-eC9, and N3.

2. A method for preparing an organic photovoltaic cell, characterized in that, Including the following steps: Provide a substrate with a first electrode on its surface; A first functional layer is fabricated on the first electrode; A quasi-planar heterojunction active layer is prepared on the first functional layer using the method described in claim 1; A second functional layer is prepared on the quasi-planar heterojunction active layer; A second electrode is fabricated on the second functional layer to obtain an organic photovoltaic cell.

3. The method for preparing organic photovoltaic cells according to claim 2, characterized in that, The first electrode is an anode, the first functional layer is a hole transport layer, the second functional layer is an electron transport layer, the second electrode is a cathode, the donor layer is attached to the hole transport layer, and the acceptor layer is attached to the electron transport layer. Alternatively, the first electrode is a cathode, the first functional layer is an electron transport layer, the second functional layer is a hole transport layer, the second electrode is an anode, the donor layer is bonded to the hole transport layer, and the acceptor layer is bonded to the electron transport layer.

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