Preparation method of photovoltaic cell and photovoltaic cell

Abstract

The invention provides a preparation method of a photovoltaic cell and the photovoltaic cell, relates to the technical field of photovoltaics, and can solve the technical problem that the conversion efficiency of the cell is affected by poor combination of a copper grid line and a substrate in a cell copper manufacturing process. The preparation method of the photovoltaic cell comprises the following steps: providing a base material; forming a photosensitive material layer on at least one side surface of the base material, and exposing and developing the photosensitive material layer to form a patterned photosensitive material layer; performing extreme ultraviolet ray irradiation on the patterned photosensitive material layers and the exposed surface of the base material between the patterned photosensitive material layers; and electroplating a copper grid line on the exposed surface of the base material to obtain the photovoltaic cell.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaics, and in particular to a method for preparing a photovoltaic cell and a photovoltaic cell. Background Art

[0002] Currently, when preparing the grid lines of crystalline silicon solar cells, the requirements for the thinning of the copper electroplating process are getting higher and higher, resulting in an increasingly thinner opening width of the grid lines, and the "capillary" phenomenon at the openings will become more and more serious. In the electroplating method, which involves the step of redox electroplating copper grid lines in metallization, there is a process where the pretreatment potion and the electroplating potion contact the surface of the film layer and penetrate into the groove after patterning to contact the blue film or the seed copper substrate. If the wettability is not good, it will affect the subsequent growth of the copper grid lines, and further affect parameters such as the photoelectric conversion efficiency of the cell.

[0003] In order to increase the wettability of the potion, currently, some long-chain alkyl surfactants are often added to the electroplating potion. Since the content of C element in the surfactant is too high, this often means a greater risk of bubbles (risk of broken grid or dropped grid) during the electroplating process, and impurities containing C element will be mixed in the grid lines, greatly reducing the line resistance of the grid lines themselves. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a photovoltaic cell and a photovoltaic cell, so as to solve the technical problem in the prior art that the poor bonding between the copper grid lines and the substrate in the copper process of the battery affects the conversion efficiency of the battery.

[0005] In order to solve the above technical problem, the technical solution provided by the present invention lies in:

[0006] The first aspect of the present invention provides a method for preparing a photovoltaic cell, including:

[0007] Providing a substrate;

[0008] Forming a photosensitive material layer on at least one surface of the substrate, and exposing and developing the photosensitive material layer to form a patterned photosensitive material layer;

[0009] Irradiating the exposed surface of the substrate between the patterned photosensitive material layer and the patterned photosensitive material layer with extreme ultraviolet light;

[0010] Electroplating copper grid lines on the exposed surface of the substrate to obtain the photovoltaic cell.

[0011] Optionally, the providing the substrate includes:

[0012] Depositing a transparent conductive layer on at least one of the upper and lower sides of the silicon-based substrate to form the substrate.

[0013] Optionally, forming a photosensitive material layer on at least one surface of the substrate includes:

[0014] Coating a photosensitive material on the transparent conductive layer on at least one of the upper and lower side surfaces of the silicon-based substrate, and thermosetting the photosensitive material to form the photosensitive material layer, wherein the curing temperature is 80-150°C, the curing duration is 0.5-5 min, and the thickness of the photosensitive material layer is 5-20 μm.

[0015] Optionally, the photosensitive material includes one of photoresist, ink or dry film, and the coating process of the photosensitive material includes one of screen printing, spin coating, spraying, roll coating, dip coating or offset printing.

[0016] Optionally, exposing the photosensitive material layer includes:

[0017] Performing ultraviolet curing on the photosensitive material layer, wherein the wavelength of the ultraviolet light is 365 nm - 405 nm, and the curing duration is 0.1 s - 5 s.

[0018] Optionally, the wavelength of the extreme ultraviolet light is 172 nm - 254 nm, and the irradiation duration is 15 s - 60 s.

[0019] Optionally, electroplating copper grid lines on the exposed surface of the substrate includes:

[0020] Performing reduction pretreatment on the exposed surface after being irradiated by extreme ultraviolet light, and then electroplating copper grid lines on the exposed surface, and the thickness of the formed copper grid lines is 8-15 μm.

[0021] Optionally, electroplating copper grid lines on the exposed surface of the substrate further includes stripping the film, specifically including:

[0022] After electroplating the copper grid lines, washing away the patterned photosensitive material layer after development with potassium hydroxide or sodium hydroxide solution.

[0023] Optionally, electroplating copper grid lines on the exposed surface of the substrate further includes tin plating, specifically including:

[0024] After stripping the film, a tin layer with a thickness of 0.5-3 μm is formed on the upper surface of the copper grid lines.

[0025] An embodiment of the second aspect of the present invention provides a photovoltaic cell, which is prepared by the preparation method of the photovoltaic cell according to any one of the embodiments of the first aspect above.

[0026] After patterning the photosensitive material layer in the preparation method of the photovoltaic cell of the present invention, EUV extreme ultraviolet light irradiation is used on the exposed surface of the substrate (i.e., the electrode reserved position), so that the exposed surface of the substrate is reformed. Furthermore, the contact angle between the electroplating copper solution and the exposed surface of the substrate in the pretreatment is reduced, thereby improving the wettability of the solution on the exposed surface of the substrate, enabling the solution to completely contact the exposed substrate material, reducing the contact resistance and wire resistance, increasing the typical value of the fill factor (FF), and further improving the photoelectric conversion efficiency of the battery.

[0027] From the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more clearly aware of the above and other objects, advantages, and features of the present invention. Brief Description of the Drawings

[0028] Some specific embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale.

[0029] In the drawings:

[0030] Figure 1 is a flowchart of the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of preparing a substrate in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of coating a photosensitive material layer in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0033] Figure 4 is a schematic diagram when exposing the photosensitive material layer in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0034] Figure 5 is a schematic diagram after developing the photosensitive material layer in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0035] Figure 6 is a schematic diagram when performing extreme ultraviolet light irradiation in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0036] Figure 7 is a schematic diagram when electroplating copper grid lines in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0037] Figure 8 is a schematic diagram when removing the film in the preparation method of the photovoltaic cell according to an embodiment of the present invention;

[0038] Figure 9Schematic diagram of tin chemicalization in the preparation method of the photovoltaic cell according to the embodiment of the present invention;

[0039] Figure 10 SEM image of the bare surface of the substrate before being irradiated by extreme ultraviolet light in the preparation method of the photovoltaic cell according to the embodiment of the present invention;

[0040] Figure 11 SEM image of the bare surface of the substrate after being irradiated by extreme ultraviolet light in the preparation method of the photovoltaic cell according to the embodiment of the present invention;

[0041] Figure 12 SEM cross-sectional image of the copper grid line of a conventional photovoltaic cell;

[0042] Figure 13 SEM cross-sectional image of the copper grid line of the photovoltaic cell prepared by the preparation method of the photovoltaic cell according to the embodiment of the present invention;

[0043] Figure 14 Test result diagram of the water contact angle between the bare surface of the substrate after being irradiated by extreme ultraviolet light and the bare surface of a conventional substrate in the preparation method of the photovoltaic cell according to the embodiment of the present invention.

[0044] Explanation of reference numerals:

[0045] Substrate - 100; silicon-based substrate - 110; transparent conductive layer - 120; photosensitive material layer - 200; copper grid line - 300; tin layer - 400; mask - 500. Detailed implementation manners

[0046] In the description of this embodiment, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "height", "upper", "lower", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0047] As a specific embodiment of the present invention, as Figure 1 shown, a preparation method of a photovoltaic cell provided according to the embodiment of the present invention may include:

[0048] S1, providing a substrate;

[0049] S2, forming a photosensitive material layer on at least one surface of the substrate, and performing exposure and development on the photosensitive material layer to form a patterned photosensitive material layer;

[0050] S3. Irradiate the exposed surface of the substrate between the patterned photosensitive material layer and the patterned photosensitive material layer with extreme ultraviolet light;

[0051] S4. Electroplate copper grid lines on the exposed surface of the substrate to obtain the photovoltaic cell.

[0052] Specifically, in the process of preparing a photovoltaic cell by the method of the embodiment of the present invention, a photosensitive material is directly coated on at least one side surface of the substrate, and exposure and development are carried out, without the need to print a seed layer with a certain thickness on the surface of the substrate in the prior art to serve as a base for electroplating grid lines. Since the screen-printed seed layer contains polymer materials (polymer materials and solvents are not conductive), doping in the subsequently electroplated grid lines will affect the conductivity of the grid lines, so that the photovoltaic cell prepared by the present invention has better conductivity.

[0053] In addition, after patterning the photosensitive material layer, the exposed surface of the substrate (i.e., the electrode reserved position) is irradiated with EUV extreme ultraviolet light, so that the exposed surface of the substrate is reformed, and the contact angle between the electroplated copper solution and the exposed surface of the substrate in the pretreatment is reduced, thereby improving the wettability of the solution to the exposed surface of the substrate, enabling the solution to completely contact the exposed base material, reducing the contact resistance and line resistance, increasing the typical value of the fill factor (FF), and further improving the photoelectric conversion efficiency of the battery.

[0054] In addition, the preparation method of the present invention replaces the addition of surfactants in the electroplating solution, reduces the risk of bubble breakage of the grid during electroplating, and reduces the line resistance of the copper grid lines.

[0055] As a specific embodiment of the present invention, as Figure 2 shown, the provided substrate 100 may include:

[0056] Deposit a transparent conductive layer 120 on at least one of the upper and lower side surfaces of the silicon-based substrate 110 to form the substrate 100. That is to say, the substrate 100 is obtained by forming a transparent conductive layer 120 on one side surface or both surfaces of the silicon-based substrate 110. Among them, the transparent conductive layer may be an indium tin oxide film or a sheet source with a seed copper layer deposited on the indium tin oxide film.

[0057] As a specific embodiment of the present invention, as Figure 3 shown, forming a photosensitive material layer 200 on at least one side surface of the substrate 100 may include: coating a photosensitive material on the transparent conductive layer 120 on at least one of the upper and lower side surfaces of the silicon-based substrate 110, and thermosetting the photosensitive material to form the photosensitive material layer 200, wherein the curing temperature is 80-150°C, the curing duration is 0.5-5 min, and the thickness of the photosensitive material layer 200 is 5-20 μm.

[0058] Specifically, through the curing under this condition, the organic solvents inside the paste-like photosensitive material volatilize, forming a film layer (solid) with a certain hardness, which provides a certain rigidity for restricting the shape of the copper grid lines in subsequent electroplating.

[0059] Preferably, the photosensitive material includes one of photoresist, ink or dry film, and the coating process of the photosensitive material includes one of screen printing, spin coating, spraying, roll coating, dip coating or offset printing.

[0060] Specifically, the photoresist and ink are wet films, while the dry film is attached to the surface of the transparent conductive layer by means of hot pressing. These three films are all patterned by exposure and development subsequently.

[0061] As a specific embodiment of the present invention, as Figure 4 shown, exposing the photosensitive material layer 200 may include: performing ultraviolet curing on the photosensitive material layer 200, wherein the wavelength of the ultraviolet light is 365 nm to 405 nm, and the curing duration is 0.1 s to 5 s.

[0062] Specifically, when performing exposure, a mask plate 500 is covered on the surface of the photosensitive material layer 200. The mask plate 500 is composed of light-shielding and transparent parts. The area of the photosensitive material layer 200 cured by the ultraviolet light passing through the transparent part is the material retention area, while the light-shielding part blocks the ultraviolet light, and the corresponding area of the photosensitive material layer 200 is the part that needs to be washed away after development (see Figure 5 shown). In addition, through the ultraviolet curing under this condition, the crosslinkability of the polymer groups inside the already thermoset film layer can be promoted, providing a light-curing condition for developing grooves, and also providing a certain rigidity for restricting the shape of the copper grid lines in subsequent electroplating.

[0063] Preferably, the wavelength of the extreme ultraviolet light is 172 nm to 254 nm, and the irradiation duration is 15 s to 60 s.

[0064] That is to say, by irradiating with extreme ultraviolet light under this condition, the polymer hydrophobic bonds can be decomposed, and the unsaturated bonds combine with the hydrophilic bonds in the air to form hydrophilicity, changing the hydrophilicity of the film layer and the surface of the substrate 100, making the exposed surface more complete under aqueous solution treatment.

[0065] Specifically, after developing the photosensitive material layer 200, as Figure 6 shown, the patterned photosensitive material layer and the exposed surface of the substrate (that is, the part of the transparent conductive layer 120 exposed between the photosensitive material layers 200) are irradiated with extreme ultraviolet light. The exposed surface of the substrate is fully reduced, which can reduce the contact angle between the electroplated copper solution and the exposed surface of the substrate during pretreatment. As an example, Figure 10The figure shows the condition of the exposed surface of the substrate after conventional development, wherein the middle portion (i.e., within the dotted line frame) is reduced, while the side portions are not reduced. Figure 11 The exposed surface of the substrate after development and exposure to extreme ultraviolet light is shown in FIG. 1 , and it can be seen that the exposed portion is substantially completely restored. Figure 14 As shown in the figure, five points were selected on a conventional film source for water contact angle test, and the results showed that the contact angle was about 75°. After the same type of film source was irradiated with extreme ultraviolet light for 60 seconds, five points at the same position were tested again, and it was found that the contact angle dropped to about 37°. It was found that the hydrophilicity of the film source surface after irradiation was greatly increased.

[0066] In addition, the exposure to extreme ultraviolet light does not have a curing effect on the exposed surface of the substrate. On the contrary, the C=C double bond covalent bond will be broken after exposure to extreme ultraviolet light, and it will combine with hydroxyl radicals in the air, thereby playing a hydrophilic role, making the pretreatment wetting effect better before electroplating, and the copper grid line is in more complete contact with the base material during electroplating.

[0067] As a specific embodiment of the present invention, Figure 7 As shown, electroplating copper grid lines 300 on the exposed surface of the substrate 100 includes:

[0068] The exposed surface after being irradiated with extreme ultraviolet light is first subjected to reduction pretreatment, and then the exposed surface is electroplated with copper grid lines 300, and the thickness of the formed copper grid lines 300 is 8-15 μm. The material of the copper grid lines 300 can be pure copper.

[0069] Specifically, after being irradiated with extreme ultraviolet light, the structural layer including the substrate 100 and the photosensitive material layer 200 is horizontally floated in a container filled with a reducing solution (which can be a solution of potassium pyrophosphate, indium sulfate, etc.), and then the conductive wire is connected to the structural layer to float upward on the back side, and then an electric current is applied to form an electrochemical reduction reaction, thereby achieving a reduction pretreatment effect. Among them, through the reduction pretreatment effect, some oxides will be generated after the surface of the substrate is reduced. The oxide will show reducing properties during the electroplating process, and undergo an oxidation-reduction reaction with the copper sulfate solution of the electroplating solution, thereby generating a copper layer on the treated surface. The copper grid line 300 is made of pure copper material, which makes the conductive performance better.

[0070] In addition, after being irradiated with extreme ultraviolet light, the exposed surface of the substrate 100 is thoroughly pre-treated, and the blue film will not be corroded by the electrochemical reaction solution during electroplating, thereby improving the conductivity between the substrate 100 and the copper grid line 300, thereby improving the FF of the battery. As shown in Table 1, compared with conventional batteries, the conversion efficiency of the battery obtained after being irradiated with extreme ultraviolet light has increased by nearly 0.1%, and the FF has increased by 0.34% due to better contact adhesion after irradiation.

[0071] Table 1 Comparison Table of IV Data Before and After Extreme Ultraviolet Light Irradiation

[0072]

[0073]

[0074] As an example, Figure 12 The cross-sectional SEM image of the copper grid line of a conventional photovoltaic cell is shown. It can be seen that there are gaps between both sides of the grid line (inside the dashed circle) and the substrate surface, which is caused by incomplete reduction of the substrate surface. Figure 13 The cross-sectional SEM image of the copper grid line of the photovoltaic cell of the present invention is shown. It can be seen that the grid line is in complete contact with the substrate surface. Thus, it can be seen that the substrate surface is completely reduced after extreme ultraviolet light irradiation, effectively improving the bonding force with the electroplated grid line.

[0075] As a specific embodiment of the present invention, as Figure 8 shown, electroplating the copper grid line 300 on the exposed surface of the substrate 100 further includes film removal, specifically including: after electroplating the copper grid line 300 is completed, using potassium hydroxide or sodium hydroxide solution to wash away the patterned photosensitive material layer 200 after development.

[0076] As a specific embodiment of the present invention, as Figure 9 shown, electroplating the copper grid line on the exposed surface of the substrate 100 further includes tin plating, specifically including: after film removal, a tin layer with a thickness of 0.5 - 3 μm is formed on the upper surface of the copper grid line.

[0077] A photovoltaic cell according to an embodiment of the second aspect of the present invention is prepared by the preparation method of the photovoltaic cell according to any one of the embodiments of the first aspect above.

[0078] At this point, those skilled in the art should recognize that although multiple exemplary embodiments of the present invention have been shown and described in detail herein, still, without departing from the spirit and scope of the present invention, many other variations or modifications that conform to the principles of the present invention can be directly determined or derived based on the content disclosed in the present invention. Therefore, the scope of the present invention should be understood and determined to cover all these other variations or modifications.

Claims

1. A method for preparing a photovoltaic cell, characterized in that: include: Providing a substrate; forming a photosensitive material layer on at least one side of the substrate, and exposing and developing the photosensitive material layer to form a patterned photosensitive material layer; Expose the patterned photosensitive material layer and the exposed surface of the substrate between the patterned photosensitive material layers to extreme ultraviolet light; The photovoltaic cell is manufactured by electroplating copper grid lines on the exposed surface of the substrate.

2. The method for preparing a photovoltaic cell according to claim 1, characterized in that: The providing of a substrate comprises: A transparent conductive layer is deposited on at least one of the upper and lower sides of the silicon-based substrate to form the base material.

3. The method for preparing a photovoltaic cell according to claim 2, characterized in that: The step of forming a photosensitive material layer on at least one surface of the substrate comprises: A photosensitive material is coated on the transparent conductive layer on at least one of the upper and lower sides of the silicon-based substrate, and the photosensitive material is thermally cured to form the photosensitive material layer, wherein the curing temperature is 80 to 150° C., the curing time is 0.5 to 5 minutes, and the thickness of the photosensitive material layer is 5 to 20 μm.

4. The method for preparing a photovoltaic cell according to claim 3, characterized in that: The photosensitive material includes one of photoresist, ink or dry film, The coating process of the photosensitive material includes one of screen printing, spin coating, spray coating, roll coating, dip coating or offset printing.

5. The method for preparing a photovoltaic cell according to claim 3, characterized in that: The exposing the photosensitive material layer comprises: The photosensitive material layer is cured by ultraviolet light, wherein the wavelength of the ultraviolet light is 365nm to 405nm and the curing time is 0.1s to 5s.

6. The method for preparing a photovoltaic cell according to claim 1, characterized in that: The wavelength of the extreme ultraviolet light is 172nm to 254nm, and the irradiation time is 15s to 60s.

7. The method for preparing a photovoltaic cell according to claim 1, characterized in that: The step of electroplating copper grid lines on the exposed surface of the substrate comprises: The exposed surface after being irradiated with extreme ultraviolet light is firstly subjected to reduction pretreatment, and then the exposed surface is subjected to copper grid line electroplating, and the thickness of the formed copper grid line is 8-15 μm.

8. The method for preparing a photovoltaic cell according to claim 7, characterized in that: The electroplating of copper grid lines on the exposed surface of the substrate further includes film removal, specifically including: After the copper grid lines are electroplated, potassium hydroxide or sodium hydroxide solution is used to wash away the photosensitive material layer patterned after development.

9. The method for preparing a photovoltaic cell according to claim 8, characterized in that: The electroplating of the copper grid lines on the exposed surface of the substrate further includes tin plating, specifically including: After the film is removed, a tin layer with a thickness of 0.5 to 3 μm is formed on the upper surface of the copper grid line.

10. A photovoltaic cell, characterized in that: The photovoltaic cell is prepared by the method for preparing the photovoltaic cell according to any one of claims 1 to 9.

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