Preparation method of solar cell and solar cell

Abstract

The invention relates to a preparation method of a solar cell and the solar cell. The method comprises the following steps: printing a grid line on a silicon wafer, and sintering to obtain a battery piece; dividing the battery piece into more than two small battery pieces; carrying out passivation treatment on the small battery piece to form a passivation film; and carrying out laser-assisted sintering treatment on the passivated small battery piece. The laser-assisted sintering process is arranged after the passivation process, so that the problem of temperature tolerance of the metal grid line can be solved, different passivation technologies can be applied, a covering film layer on the metal grid line can be burnt through by high-intensity laser, and assembly welding is facilitated.

Description

Technical Field

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

[0002] With the continuous development of the photovoltaic industry, in order to reduce the cost of single-watt silicon wafers and improve the power generation efficiency per unit area of ​​components, the size of silicon wafers continues to increase. Large-size silicon wafers need to be diced and cut in half to reduce battery current, reduce component packaging losses, and improve component reliability. Different dicing methods will introduce side damage, especially edge damage of the pn junction will lead to edge recombination, reducing battery efficiency by 0.2-0.3%, mainly because it reduces the fill factor. Edge recombination limits the technical development trend of the continued increase in silicon wafer size. In the context of lower and lower recombination on the front and back of the battery, edge passivation is becoming more and more important. At this stage, the passivation technology of the cutting surface is mainly carried out by dicing after metallization and test sorting, and then the battery cell is passivated. The specific passivation can be deposited by ALD, PECVD, thermal oxidation, wet chemical treatment and other methods such as AlOx, SiNx, SiOx and other passivation layers and their laminated structures.

[0003] The metallization preparation method of crystalline silicon solar cells usually adopts screen printing technology to print metal paste on the semi-finished cell, and then dry the metal paste in a drying furnace, and then enter the sintering furnace, and burn the metal paste through the passivation layer and contact with silicon through 800-900℃ sintering to form a gold semi-contact. The metal paste burns through the passivation layer, and the gold semi-contact destroys the passivation layer on the surface of the silicon wafer, causing surface recombination of minority carriers. To solve this problem, the industry's technological progress has introduced laser-assisted sintering technology, that is, using high-intensity lasers to irradiate the cell to excite carriers, and at the same time applying a bias voltage of 10V or more through the electrode, thereby generating a local current of several amperes, and sintering occurs at the corresponding location to cause mutual diffusion of silver paste and silicon, forming a local gold semi-contact. Laser-assisted sintering only forms gold semi-contacts locally, destroys the passivation layer, and maintains the passivation effect while significantly reducing the contact resistance between the metal and the semiconductor, thereby improving the photoelectric conversion efficiency. According to the mechanism of gold semi-contact formation, the laser-assisted sintering process is usually followed by the metal paste screen printing process to form gold semi-contacts. However, while laser-assisted sintering improves efficiency, it also reduces the tolerance of the metal grid lines to subsequent temperatures. Excessively high temperatures will increase the series resistance, which in turn affects battery performance. Side passivation can utilize different deposition technologies, and different deposition technologies have different temperatures, which will affect the metallized part during the side passivation process. In turn, this limits the application of side passivation passivation films and different passivation deposition technologies, places higher requirements on side passivation technology, and has a narrower process window. Figure 1 The production flow chart of solar cell in the prior art is shown as follows: Figure 1As shown, the prior art usually deposits various side passivation films after laser-assisted sintering. This process flow easily causes wrap-around plating on the front and back sides of the battery. In particular, in extreme cases, passivation films are deposited on six sides at the same time. Figure 2 The schematic diagram of the structure of an N-type silicon wafer after the passivation layer is deposited is shown. In this case, it will have a great impact on component welding.

[0004] To address the above problems, no effective solution has been proposed yet. Summary of the invention

[0005] Based on this, it is necessary to provide a method for preparing a solar cell and a solar cell to solve the above technical problems. The present invention can obtain a wider process window, reduce sorting equipment, and reduce equipment investment by arranging the laser-assisted sintering process after the side passivation process.

[0006] According to a first aspect of the present invention, a method for preparing a solar cell comprises:

[0007] Step 1: Print gate lines on silicon wafers and sinter to obtain solar cells;

[0008] Step 2: Divide the battery cell into two or more small battery cells;

[0009] Step 3: Passivate the small battery cell to form a passivation film;

[0010] Step 4: Perform laser-assisted sintering on the small cells after passivation treatment.

[0011] In one implementation of the first aspect of the present invention, the passivation film on the surface of the gate line of the small cell is removed by the laser assisted sintering process.

[0012] In one embodiment of the first aspect of the present invention, the laser-assisted sintering process comprises: irradiating the passivated small battery sheet with laser and applying a deflection voltage at the same time.

[0013] In one implementation of the first aspect of the present invention, the deflection voltage is 5-15V.

[0014] In one implementation of the first aspect of the present invention, the printed grid lines are implemented by screen printing; and the cell segmentation is performed by laser scribing.

[0015] In one embodiment of the first aspect of the present invention, the passivating of the small battery cell includes: passivating a newly generated cut surface of the small battery cell or passivating all surfaces of the small battery cell simultaneously.

[0016] In one embodiment of the first aspect of the present invention, the material of the passivation film includes: one or more of aluminum oxide, silicon oxide, and silicon nitride.

[0017] In one embodiment of the first aspect of the present invention, the passivation treatment method is one or more of ALD, PECVD, thermal oxidation, and chemical passivation.

[0018] In one embodiment of the first aspect of the present invention, the present invention further includes step 5: testing and sorting the small battery cells after laser-assisted sintering.

[0019] In a second aspect of the present invention, the present invention provides a solar cell sheet prepared by any of the above-mentioned preparation methods.

[0020] Beneficial effects of the present invention:

[0021] 1. Laser-assisted sintering process After the side passivation process, high-intensity laser can burn through the covering film layer on the metal grid line, which is beneficial to component welding, improves welding tension, and thus improves component reliability.

[0022] 2. The laser-assisted sintering process solves the temperature tolerance problem of the metal grid line after the side passivation process. Different passivation technologies can be applied, including ALD, PECVD, high-temperature oxidation, wet treatment, etc., which can realize the side passivation of different passivation film layers such as aluminum oxide, silicon nitride, silicon oxide and their stacked structures; and it is not easy to damage the metal grid line printing and sintering.

[0023] 3. Compared with the prior art which performs sorting after laser-assisted sintering and passivation respectively, the present invention only needs to perform sorting once, thus reducing the number of sorting equipment and the equipment investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A production flow chart of solar cells in the prior art;

[0025] Figure 2 It is a schematic diagram of the structure after the passivation layer is deposited on the N-type silicon wafer;

[0026] Figure 3 The solar cell production flow chart for this application DETAILED DESCRIPTION

[0027] The present invention is described in more detail below. Unless otherwise defined, the terms (including technical terms and scientific terms) used herein have the same meanings as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. The terms used herein should be interpreted as having the meanings consistent with their meanings in the context of this specification and in the relevant field, and should not be interpreted in an idealized or overly formal sense, unless specifically defined as such herein.

[0028] A method for preparing a solar cell according to an embodiment of the present invention comprises the following steps:

[0029] Step 1: Print the gate lines on the silicon wafer and sinter to obtain the battery cell.

[0030] In one example, the gate lines on the front and back are screen printed, dried, and then sintered to form metal-semiconductor contacts to obtain a cell. The gate lines can also be formed on the silicon wafer by pad printing, spin coating, slit coating, spraying, laser transfer, etc.

[0031] Step 2: Divide the battery cell into two or more small battery cells.

[0032] In one example, the battery is divided into two or more small battery slices by laser scribing.

[0033] Step 3: Passivate the small battery cell to form a passivation film.

[0034] In one example, the small cell is passivated on the side. The methods that can be used are ALD, PECVD, thermal oxidation, wet chemical treatment, etc., to grow a passivation layer such as aluminum oxide, silicon oxide, silicon nitride and its stacked structure on the side.

[0035] Step 4: Perform laser-assisted sintering on the small cells after passivation treatment.

[0036] In one example, a metal electrode is used to contact the gate line of a small cell after passivation treatment, a bias voltage of more than 10V is applied through the electrode, and a high-intensity laser is used to irradiate the cell.

[0037] Step 5: Test and sort the small cells after laser-assisted sintering.

[0038] For the solar cell mentioned above, since the laser-assisted sintering process is performed after the side passivation process, the high-intensity laser can burn through the covering film layer on the metal grid line, which is beneficial to component welding and solves the temperature tolerance problem of the metal grid line. Different passivation technologies can be applied.

[0039] The present invention is further described below in conjunction with specific embodiments and comparative examples, but the present invention is not limited to the following specific embodiments.

[0040] Example 1

[0041] The method for preparing a solar cell provided in this embodiment includes the following steps.

[0042] Step 1: On the main body of the PERC structure cell, screen print and dry the front and back electrodes respectively, and sinter them.

[0043] Step 2: Laser scribing the sintered semi-finished solar cell using the non-destructive laser cutting TLS method to cut the cell into two halves.

[0044] Step 3: Insert the half-cut disc into the aluminum boat with the cut surface facing up and insert one half-cut disc into one boat slot.

[0045] Step 4: Use the ALD method to deposit 2-15nm aluminum oxide on the six surfaces of the half-cut wafer.

[0046] Step 5: Perform annealing at 300-500°C in an ALD vacuum device to achieve passivation activation.

[0047] Step 6: Apply 5-15V voltage to half of the passivated cell and use a power of 300-1000W / cm 2 The 532nm green laser is used to perform laser-assisted sintering on the half-cut slice after electrical passivation, and at the same time, the aluminum oxide of the metal grid line is burned through.

[0048] 7. The treated batteries were tested, sorted and EL tested. The battery performance is shown in Table 1.

[0049] Table 1

[0050] Group Voc(V) Jsc(mA / cm2) FF(%) Eta.(%) Full cell reference group 0.6756 41.07 82.67 22.94 No passivation after TLS dicing 0.675 41.01 81.95 22.69 After passivation 0.6754 41.04 82.57 22.89

[0051] Example 2

[0052] The method for preparing a solar cell provided in this embodiment includes the following steps.

[0053] Step 1: On the main body of the TOPCon structure battery cell, screen print and dry the front and back electrodes respectively, and sinter them.

[0054] Step 2: Laser scribing the sintered semi-finished solar cell using the non-destructive laser cutting TLS method to cut the cell into two halves.

[0055] Step 3: Put the half-cut sheets together and put them into the special tooling with the cut surfaces facing upwards.

[0056] Step 4: Place the tooling into a circular cavity space-type ALD device and use the ALD method to deposit 30-70nm aluminum oxide on the cut surface.

[0057] Step 5: Apply 5-15V voltage to half of the passivated cell and use 300-1000W / cm 2 A 1064nm infrared laser is used to perform laser-assisted sintering on the electrically passivated half-cell.

[0058] Step 6: The treated batteries were tested, sorted and EL tested. The battery performance is shown in Table 2.

[0059] Table 2

[0060] Group Voc(V) Jsc(mA / cm2) FF(%) Eta.(%) Full cell reference group 0.739 41.98 84.9 26.34 No passivation after TLS dicing 0.7374 41.93 84.47 26.12 After passivation 0.7387 41.95 84.82 26.29

[0061] Comparative Example:

[0062] This comparative example provides a method for preparing a TOPCon solar cell, which includes the following steps.

[0063] Step 1: On the main body of the TOPCon structure battery cell, screen print and dry the front and back electrodes respectively, and sinter them.

[0064] Step 2: Apply 5-15V voltage to half of the passivated cell and use 300-1000W / cm 2 A 1064nm infrared laser is used to perform laser-assisted sintering on the electrically passivated half-cell.

[0065] Step 3: Laser scribing the semi-finished solar cell after laser sintering, using the non-destructive laser cutting TLS method to cut the cell into two half pieces.

[0066] Step 4: Put the half-cut sheets together and put them into the special tooling with the cut surfaces facing upwards.

[0067] Step 5: Place the tooling into a circular cavity space type ALD device and use the ALD method to deposit 30-70nm aluminum oxide on the cut surface. The aluminum oxide deposition temperatures are 200, 220, and 240°C respectively.

[0068] Step 6: Test, sort and EL test the processed batteries.

[0069] Meanwhile, in step 4 of Example 2, aluminum oxide was deposited at 200, 220, and 240° C., respectively.

[0070] The results of the two process batteries are shown in Table 3.

[0071] Table 3

[0072]

[0073] It can be seen that when using the existing method, the higher the passivation temperature, the more the electrical performance decreases. The loss of electrical performance mainly comes from the change of FF, and the main reason is the increase in series resistance. The process temperature of the passivation technology is usually >200°C, and the existing side passivation technology solution will cause parasitic battery performance loss. The existing method for preparing solar cells has higher process requirements and a narrower process window. However, by using the method for preparing solar cells of the present invention, the performance of the obtained solar cells can be significantly better than the existing solution, and the higher the passivation temperature, the more significant the advantages of the preparation method of the present invention.

[0074] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a solar cell, characterized in that: The following steps are involved: Step 1: Print gate lines on silicon wafers and sinter to obtain solar cells; Step 2: Divide the battery cell into two or more small battery cells; Step 3: Passivate the small battery cell to form a passivation film; Step 4: Perform laser-assisted sintering on the small cells after passivation treatment.

2. The method for preparing a solar cell according to claim 1, characterized in that: The passivation film on the surface of the gate line of the small battery cell is removed by the laser-assisted sintering process.

3. The method for preparing a solar cell according to claim 1, characterized in that: The laser-assisted sintering process includes: irradiating the passivated small battery sheet with laser and applying a deflection voltage at the same time.

4. The method for preparing a solar cell according to claim 3, characterized in that: The deflection voltage is 5-15V.

5. The method for preparing a solar cell according to claim 1, characterized in that: The printed grid lines are realized by screen printing; the cell segmentation is performed by laser scribing.

6. The method for preparing a solar cell according to claim 1, characterized in that: The passivation of the small battery cell includes: passivating a newly generated cut surface of the small battery cell or passivating all surfaces of the small battery cell simultaneously.

7. The method for preparing a solar cell according to claim 1, characterized in that: The material of the passivation film includes: one or more of aluminum oxide, silicon oxide, and silicon nitride.

8. The method for preparing a solar cell according to claim 1, characterized in that: The passivation treatment method is one or more of ALD, PECVD, thermal oxidation, and chemical passivation.

9. The method for preparing a solar cell according to claim 1, characterized in that: It also includes step 5: testing and sorting the small battery cells after laser-assisted sintering.

10. A solar cell, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 9.

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