[0022] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
[0023] In order to prevent the overall performance of the silicon wafer from degrading after the front electrode is finally formed on the silicon wafer due to the trial printing step, the embodiment of the present invention provides a method for screen printing the front electrode of a solar cell. figure 1 A flowchart of the method is shown, and the method includes the following steps:
[0024] Step S101: Provide a screen printing substrate.
[0025] The screen printing substrate in the embodiment of the present invention can be used repeatedly. At the same time, the electrode of the trial printing needs to be cleaned and removed before being used again. Therefore, the screen printing substrate needs to have certain corrosion resistance and also needs It has certain strength and toughness for subsequent cutting of the screen printing substrate and trial printing operations on it.
[0026] In the embodiment of the present invention, the substrate may be a normal silicon wafer (the silicon wafer will not be used in the subsequent screen printing process) or a waste silicon wafer, etc., or it may be made of polyethylene terephthalate Substrate or substrate made of high-density polyethylene, etc. In one embodiment of the present invention, a substrate made of high-density polyethylene is preferably used.
[0027] Step S102: cutting the screen printing substrate into test prints according to the same size and thickness as the silicon wafer to be printed;
[0028] The function of the test print is to obtain electrodes with correct positions and qualified printing quality by trial printing on the test print, so as to facilitate the use of the parameters of the test printing step to perform screen printing operations on the silicon wafers to be printed, The front side of the wafer has electrodes with correct positions and qualified printing quality. Therefore, the screen printed substrate needs to be cut into test prints according to the same size and thickness as the silicon wafer to be printed, that is, the size and thickness of the test print The size and thickness of the silicon wafer to be printed are the same, where the size can include side length, diameter, perpendicularity, etc.; in addition to the size and thickness, the thickness deviation and total thickness deviation of the test print can also be the same as the silicon to be printed. The thickness deviation of the sheet is consistent with the total thickness deviation and other parameters.
[0029] In some specific examples of the present invention, the size and other requirements of the silicon wafer to be printed can be as shown in the following table:
[0030] Table 1 (for monocrystalline silicon solar cells):
[0031]
[0032] Table 2 (for polycrystalline silicon solar cells):
[0033]
[0034] Step S103: Perform trial printing on the trial printed sheet to obtain trial printed electrodes.
[0035] This step can be carried out by the screen printing step in the traditional process. The only difference is that this step is the test print mentioned above (it can be a silicon wafer, a substrate made of polyethylene terephthalate or A substrate made of high-density polyethylene, etc.). Other specific steps can be performed with reference to the traditional screen printing process of the front electrode of the solar cell. Of course, those skilled in the art can also modify and deform the process according to specific requirements.
[0036] Step S104: Determine whether the test-printed electrodes on the test-printed sheet meet the predetermined requirements, and if so, perform step S105.
[0037] After forming the test print electrode on the test print, it is necessary to judge whether the test print electrode meets the requirements, if it does not meet the requirements, you need to re-print the test print on the test print to obtain the test print electrode, and then judge the test print electrode after re-test printing Whether it meets the requirements, until the trial printed electrode meets the predetermined requirements.
[0038] Wherein, the predetermined requirement may include a predetermined position requirement and/or a predetermined quality requirement, that is, it is determined whether the relative position between the trial printed electrode and the trial printed sheet and/or the quality of the trial printed electrode meets the requirements. In view of the fact that the size and thickness of the test print and the silicon wafer to be printed are consistent, the positional relationship between the test electrode and the test print is equivalent to that when the test electrode is printed on the silicon wafer to be printed. The positional relationship between the silicon wafers; at the same time, the quality of the test electrode printed on the test print is equivalent to the quality of the test electrode printed on the silicon wafer to be printed. Therefore, the test-printed electrode on the test-printed sheet meets the predetermined requirements, which is equivalent to that the test-printed electrode meets the predetermined requirements when printed on the silicon wafer to be printed.
[0039] Specifically, the position of the test electrode on the test print can be represented by (x, y, θ), that is, the coordinate and angle relationship of the test electrode on the test print; the quality of the test electrode can include whether the test electrode has Excessive or missing, the length and width of the test electrode, and whether there is any interruption in the middle of the test electrode (that is, whether the test electrode is continuous), etc. If there are no excess or lack of trial printed electrodes on the trial printed sheet, the length and width of the trial printed electrodes meet the requirements, and each trial printed electrode is continuous, it can be considered that the trial printed electrode meets the predetermined quality requirements.
[0040] In addition, if the test electrode on the test print does not meet the predetermined requirements, you can first clean the test electrode on the test print that does not meet the predetermined requirements, and then repeat the test print on the test print. The step of printing electrodes until the test printing electrodes on the test printing sheet meet the predetermined requirements. Specifically, absolute ethanol and/or terpineol can be used to clean the test-print electrodes that do not meet the predetermined requirements on the test-print sheet.
[0041] Step S105: Determine the screen printing parameters.
[0042] If the test printed electrode on the test printed sheet meets the predetermined requirements, it is equivalent to that the test printed electrode meets the predetermined requirements when printed on the silicon wafer to be printed, so it is determined that the test printed electrode is obtained by the test printed on the test printed sheet in step S103. The parameters used are screen printing parameters.
[0043] Specifically, the screen printing parameters may include screen height, squeegee height, printing pressure, and screen position.
[0044] Step S106: Perform a screen printing step on the front side of the silicon wafer to be printed according to the screen printing parameters determined in step S105 to obtain the front electrode of the solar cell sheet.
[0045] In view of the fact that the test electrode printed on the test sheet using the screen printing parameters in step S104 already meets the predetermined requirement, the front electrode obtained in step S106 also meets the predetermined requirement.
[0046] The screen printing method for the front electrode of the solar cell provided by the embodiment of the present invention performs a test printing operation on a test print sheet with the same size and thickness as the silicon wafer to be printed to obtain a test print electrode that meets the requirements and determine the correctness. According to the screen printing parameters, the screen printing operation is performed on the front surface of the silicon wafer to be printed to obtain the front electrode according to the screen printing parameters. Compared with the prior art, this method avoids directly performing trial printing operations on the silicon wafers to be printed or performing trial printing operations for multiple times, resulting in a decrease in the electrical performance of the silicon wafers to be printed, thereby improving the overall solar cell after forming the front electrodes. performance.
[0047] In addition, in other embodiments of the present invention, before step S103 is executed, the following steps may be further included:
[0048] A. Matte the test print until the surface roughness of the test print is the same as the surface roughness of the silicon wafer to be printed.
[0049] Before the front electrode of the solar cell is prepared, it is generally subjected to a texturing treatment, so the front side of the solar cell is generally a textural surface with a certain degree of roughness. In order to ensure that the trial printed electrodes formed on the trial printed wafer can more accurately reflect the trial printed electrodes formed on the silicon wafer to be printed, the trial printed wafer can be processed so that the surface roughness of the trial printed wafer is consistent with that of the wafer to be printed. The roughness of the front surface is similar or the same, and the test print can be frosted.
[0050] and / or,
[0051] B Use absolute ethanol and/or terpineol to clean the test print,
[0052] In order to ensure that the test print electrodes formed on the test print sheet can more accurately reflect the test print electrodes formed on the silicon wafer to be printed, absolute ethanol and/or terpineol can also be used to clean the test print sheet. In an embodiment of the present invention, absolute ethanol is preferably used in this step.
[0053] It should be noted that the above step A can also be performed before step S102, that is, the screen printing substrate is first frosted, and then the screen printing substrate after the frosting treatment is adjusted to the same size as the substrate to be printed. The size and thickness are cut into test prints.
[0054] In addition, the foregoing step A may be performed before or after the foregoing step B. In an embodiment of the present invention, the foregoing step A is preferably performed before step B.
[0055] It should be noted that the test print in the embodiment of the present invention can be recycled multiple times; the screen printing method of the front electrode of the solar cell provided in the embodiment of the present invention may be suitable for monocrystalline silicon solar cells or polycrystalline silicon solar cells.
[0056] The screen printing method for the front electrode of the solar cell in the embodiment of the present invention can be implemented in a variety of specific ways. In order to make the technical solution of the embodiment of the present invention clearer, some specific examples are used to illustrate these methods. Yes, these examples are only an explanation of the technical solutions of the embodiments of the present invention, and are not used to limit the technical solutions of the present invention. Those of ordinary skill in the art can easily think of other similar or equivalent alternatives on the basis of the technical solutions of the present invention. Similar technical solutions that can achieve the purpose of the present invention that can be obtained without creative work on the basis of the inventive idea are all within the protection scope of the present invention.
[0057] In a specific example of the present invention, the silicon wafer to be printed is used for the manufacture of polycrystalline silicon solar cells. Wherein, the size of the silicon wafer to be printed is the size in Table 2 above. Specifically, the following steps can be used to print electrodes on the front of the solar cell:
[0058] (1) Provide a screen printing substrate made of high-density polyethylene;
[0059] (2) The screen printing substrate made of high-density polyethylene is cut into test prints according to the same parameters as the size and thickness of the above-mentioned silicon wafer to be printed, that is, the parameters of the test print are the same as those in Table 2 above. The parameters are exactly the same;
[0060] (3) Trial printing on a screen-printed test sheet made of high-density polyethylene to obtain a trial-printed electrode, this step can be the same as that of screen-printed on a normal silicon wafer to obtain the electrode;
[0061] (4) Determine whether the test electrode on the test print meets the requirements: if the quality of the test electrode can be tested by observing the printing effect, if the printed lines are not solid at part of the test electrode, it indicates that the screen height is too high; If the pattern position of the printed electrode is shifted (for example, the test printed electrode in some positions exceeds the edge of the test printed sheet), the coordinate and angle relationship of the test printed electrode on the test printed sheet need to be adjusted until the quality of the test printed electrode fully meets the requirements;
[0062] (5) After the quality of the trial printed electrode meets the requirements, it indicates that the printing parameters of the trial printed electrode are correct. At this time, the printing parameters of the trial printed electrode are determined as the screen printing parameters;
[0063] (6) Perform a screen printing step on the front surface of the silicon wafer to be printed according to the screen printing parameters determined in step (5) to obtain the front electrode of the polysilicon solar cell.
[0064] In order to explain in detail the quality of the front electrode of the solar cell obtained by the screen printing method of the front electrode of the solar cell in this specific example, here, the electrical performance of the front electrode of the solar cell in this specific example is the same size as the one prepared by the traditional process. The electrical performance comparison of the front electrode of the polycrystalline silicon solar cell is as follows:
[0065]
[0066] The reverse leakage here refers to the leakage current of the solar cell under the reverse voltage of 12V;
[0067] Wherein M is a polycrystalline silicon solar cell front electrode of the same size prepared by a traditional process, and N is a polycrystalline silicon solar cell prepared by a screen printing method of the solar cell front electrode of this specific example.
[0068] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.
