Back contact solar cell and photovoltaic module
By setting a common pad in the back metal electrode structure of the back contact solar cell and replacing the voltage probe as a current probe during testing, the problems of uneven current distribution and uneven light and darkness of the EL defect measurement images in traditional tests are solved, and more accurate and reliable test results are achieved.
Patent Information
- Application Number
- CN202422020563.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-19
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2034-08-19
AI Technical Summary
During testing of traditional back contact solar cells, contact with the opposite electrode of the main gate can easily lead to a short circuit in the battery and uneven current distribution, resulting in uneven light and darkness of the EL defect measurement image.
Design the structure of the back contact metal electrode in the back of the solar cell, set up a common pad on the positive main gate and the negative main gate. During the test, replace the voltage probes with current probes, and amplify the size of the common pads in a representative area and increase the voltage probe for testing.
Through this structural design, voltage testing is taken into account, while ensuring the uniformity of the light and darkness of the EL defect measurement image, improving the accuracy and reliability of the test results.
Smart Images
Figure CN223040484U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of solar cells, and in particular relates to a back contact solar cell and a photovoltaic module. Background Art
[0002] A solar cell is a device that can convert light energy into electrical energy. When the cell is exposed to light, the cell substrate absorbs photons to generate electron-hole pairs. Under the action of the built-in electric field of the PN junction, the electron-hole pairs are separated and led out from the emitter and back field of the solar cell, and finally collected by the electrodes arranged on the substrate and transmitted to the outside.
[0003] The positive electrode and negative electrode of the traditional Topcon cell (Tunnel Oxide Passivated Contact) are located on the front and back sides of the cell respectively, while the positive electrode and negative electrode in the back contact solar cell (Back Contact, referred to as BC cell) are both arranged on the back side of the cell, and there is no metal electrode blocking the front side of the cell, thereby increasing the short-circuit current of the cell.
[0004] In addition, the test probe row of the traditional Topcon battery mostly adopts a structure in which the current probe and the voltage probe are alternately arranged, in which the voltage probe is responsible for collecting voltage and the current probe is responsible for collecting current. At the same time, the probe pressed against the front of the battery is connected to the positive electrode, and the probe pressed against the back of the battery is connected to the negative electrode. Unlike the Topcon battery, the electrodes of the back-contact solar cell are all arranged on the back of the battery, and the two sides of the main grid are covered with fine grids of opposite electrodes, so the test probe can only be pressed against the PAD point to prevent the probe from contacting the fine grids of the opposite electrodes on both sides of the main grid and causing the battery to short-circuit. If the probe of the back-contact solar cell is the same as the probe structure of the Topcon battery mentioned above during the test, the area of the current collected by a single current probe will be too large, which is easily affected by factors such as the current transmission distance and the uniformity of the square resistance of the battery sheet, resulting in uneven current distribution. At the same time, some voltage probes will cause uneven brightness of the EL defect measurement image due to reasons such as line resistance; if the back-contact solar cell only retains the voltage probes in some areas during the test, and the other probes are replaced with current probes, there is also the problem that the area where some voltage probes are retained will be obviously dark.
[0005] Therefore, in the art, there is an urgent need to develop a back metal electrode for a back-contact solar cell to solve the above problems. Utility Model Content
[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a back-contact solar cell and a photovoltaic module.
[0007] To achieve the purpose of this utility model, the following technical solutions are adopted in this utility model:
[0008] In a first aspect, this utility model provides a back-contact solar cell, which includes a silicon substrate and a metal electrode disposed on the back surface of the silicon substrate. The metal electrode includes a positive main grid and a negative main grid arranged alternately in a first direction. The positive main grid includes positive pads arranged at intervals in a second direction perpendicular to the first direction. At least one of the positive main grids further includes a positive common pad, and the length of the positive common pad in the second direction is greater than the length of the positive pad in the second direction. The positive pad is used to cooperate with the abutting test of the positive current probe, and the positive common pad can simultaneously cooperate with the abutting tests of the positive current probe and the positive voltage probe;
[0009] The negative main grid includes negative pads arranged at intervals in the second direction. At least one of the negative main grids further includes a negative common pad, and the length of the negative common pad in the second direction is greater than the length of the negative pad in the second direction. The negative pad is used to cooperate with the abutting test of the negative current probe, and the negative common pad can simultaneously cooperate with the abutting tests of the negative current probe and the negative voltage probe.
[0010] By designing the structure of the back metal electrode in the back-contact solar cell, this utility model respectively sets common pads for testing on the positive main grid and the negative main grid. During the test, all voltage test probes are replaced with current test probes, and the current test probes are arranged according to the structure of the back metal electrode. Then, some representative areas are selected to enlarge the size of the common pads therein, and additional voltage test probes are added for testing, so that the voltage test probes can also be pressed on the same pad, thereby ensuring the uniformity of the brightness and darkness of the EL defect measurement image while taking into account the voltage test.
[0011] In this utility model, the back-contact solar cell includes, but is not limited to, a back-contact crystalline silicon solar cell.
[0012] Preferably, the positive common pads and the negative common pads are grouped in pairs, and the positive common pad and the negative common pad in the same group are respectively arranged on adjacent positive main grids and negative main grids.
[0013] Preferably, the positive common pad and the negative common pad in the same group are arranged corresponding to each other in the first direction.
[0014] Preferably, the positive common pads and the negative common pads are set in four groups and are respectively located in different areas on the surface of the silicon substrate.
[0015] Preferably, the silicon substrate has a first center line extending in a first direction and a second center line extending in a second direction. The first center line and the second center line evenly divide the silicon substrate into four regions, and a set of the positive common pads and the negative common pads are respectively arranged in each region.
[0016] Preferably, the length of the positive pad and the negative pad are each independently 1-2 mm, and the width of each is independently 1-2 mm.
[0017] Preferably, the length of the positive common pad is 3-10 mm and the width is 1-2 mm;
[0018] Preferably, the length of the negative common pad is 3-10 mm and the width is 1-2 mm.
[0019] In the present utility model, the shapes of the positive common pad and the negative common pad may both be rectangles, for example.
[0020] In the present utility model, by adjusting the sizes of the positive common pad and the negative common pad during testing, the area thereof is made to be large enough to contact two test probes.
[0021] Preferably, the total number of the positive main grids and the negative main grids is 16-24.
[0022] Preferably, the positive common pad is located at the x-th positive main grid.
[0023] Preferably, when the number n of the positive main grids is an even number, the value of x is 2 to (n / 2 - 1) or (n / 2 + 2) to (n - 1);
[0024] Preferably, when the number n of the positive main grids is an odd number, the value of x is 2 to (n / 2 - 1 / 2) or (n / 2 + 3 / 2) to (n - 1).
[0025] Preferably, along the extending direction of the positive main grid, at least one positive pad is arranged between the positive common pad and the edge of the silicon substrate; along the extending direction of the negative main grid, at least one negative pad is arranged between the negative common pad and the edge of the silicon substrate.
[0026] In the present utility model, by selecting specific positions to arrange the positive common pad and the negative common pad, not only can the accuracy and reliability of the test results be ensured, but also the overall performance of the back contact solar cell can be better reflected.
[0027] In a second aspect, the present utility model provides a photovoltaic module, comprising a plurality of solar cells, wherein the solar cells are the back-contact solar cells according to the first aspect, or the solar cells are obtained by dividing the back-contact solar cells according to the first aspect.
[0028] Compared with the prior art, the present utility model has the following beneficial effects:
[0029] The present utility model provides a back-contact solar cell. By designing the structure of the back metal electrodes in the back-contact solar cell, common pads for testing are respectively arranged on the positive main grid and the negative main grid. During testing, all voltage test probes are replaced with current test probes, and the current test probes are arranged according to the structure of the back metal electrodes. Then, some representative regions are selected to enlarge the size of the common pads therein, and additional voltage test probes are added for testing, so that the voltage test probes can also be pressed on the same pad, thereby ensuring the uniformity of the brightness and darkness of the EL defect measurement image while taking into account voltage testing. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 is a schematic diagram of the electrode design of a Topcon cell disclosed in the prior art;
[0031] Figure 2 is a schematic diagram of the back electrode and test probes of a back-contact solar cell disclosed in the prior art;
[0032] Figure 3 is a schematic diagram of the back electrode and test probes of the back-contact solar cell provided by the present utility model;
[0033] Figure 4 is a schematic diagram of EL measurement of the back-contact solar cell provided by the present utility model;
[0034] 1 - positive electrode, 2 - negative electrode, 3 - silicon substrate, 10 - positive main grid, 20 - negative main grid, 101 - positive pad, 201 - negative pad, 102 - positive common pad, 202 - negative common pad. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0035] The technical solution of the present utility model will be further described below by combining the drawings and specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present utility model and should not be regarded as specific limitations to the present utility model.
[0036] As Figure 1 shown, the positive electrode 1 and the negative electrode 2 of a traditional Topcon cell are respectively located on the front and back sides of the silicon substrate 3, and the matching test probe rows mostly adopt a structure in which current probes and voltage probes are alternately arranged; asFigure 2 As shown, the positive main grid 10 and the negative main grid 20 of the back-contact solar cell are both arranged on the back of the cell. The positive main grid 10 is provided with a positive electrode pad 101, and the negative main grid 20 is provided with a negative electrode pad 201. The voltage probes and current probes are arranged alternately and pressed against the above-mentioned positive electrode pad 101 and negative electrode pad 201 (as Figure 2 shown). Among them, the area for a single current probe to collect current is too large, which is easily affected by factors such as the current transmission distance and the uniformity of the sheet resistance of the cell, resulting in uneven current distribution. At the same time, due to reasons such as wire resistance, some voltage probes cause uneven brightness and darkness in the EL defect measurement image. Based on this, the present utility model provides a back electrode of a back-contact solar cell and a back-contact solar cell test device matched therewith to overcome the above defects. The technical solution of the present utility model will be described below with specific embodiments.
[0037] This embodiment provides a back-contact solar cell as Figure 3 shown. The back-contact solar cell includes a silicon substrate and a metal electrode provided on the back of the silicon substrate. The metal electrode includes a positive main grid 10 and a negative main grid 20 arranged alternately along a first direction. The number of the positive main grid 10 and the negative main grid 20 is the same or differs by one, depending on the graphic design of the P region and N region on the back of the silicon substrate.
[0038] Here, the total number of the positive main grid 10 and the negative main grid 20 is 16 - 24. The positive main grid 10 includes positive electrode pads 101 arranged at intervals along a second direction perpendicular to the first direction. At least one of the positive main grids 10 further includes a positive common electrode pad 102. The length of the positive common electrode pad 102 along the second direction is greater than the length of the positive electrode pad 101 along the second direction. The positive electrode pad 101 is used to cooperate with the abutting test of the positive current probe. The positive common electrode pad 102 can simultaneously cooperate with the abutting tests of the positive current probe and the positive voltage probe. The negative main grid 20 includes negative electrode pads 201 arranged at intervals along the second direction. At least one of the negative main grids 20 further includes a negative common electrode pad 202. The length of the negative common electrode pad 202 along the second direction is greater than the length of the negative electrode pad 201 along the second direction. The negative electrode pad 201 is used to cooperate with the abutting test of the negative current probe. The negative common electrode pad 202 can simultaneously cooperate with the abutting tests of the negative current probe and the negative voltage probe.
[0039] Among them, the positive common pads 102 and the negative common pads 202 are grouped in pairs. The positive common pads 102 and the negative common pads 202 in the same group are respectively arranged on adjacent positive main grids 10 and negative main grids 20, and the positive common pads 102 and the negative common pads 202 in the same group are arranged corresponding to each other in the first direction. The positive common pads 102 and the negative common pads 202 are set in four groups and are respectively located in different areas on the surface of the silicon substrate. The silicon substrate is generally rectangular, and the silicon substrate has a first center line extending in the first direction and a second center line extending in the second direction. The first center line and the second center line evenly divide the silicon substrate into four areas, and each area is respectively provided with a group of positive common pads 102 and negative common pads 202.
[0040] The positive common pads 102 and the negative common pads 202 are arranged away from the edges of the silicon substrate. At the same time, the positive common pads 102 and the negative common pads 202 are also arranged away from the first center line and the second center line, ensuring the reliability of the test results and making the test results better characterize the battery quality of the corresponding area. In other words, for the four areas divided by the first center line and the second center line, the positive common pads 102 and the negative common pads 202 are both arranged at the central positions of each area.
[0041] Specifically, along the extension direction of the positive main grid 10, at least one positive pad 101 is arranged between the positive common pad 102 and the edge of the silicon substrate; along the extension direction of the negative main grid 20, at least one negative pad 201 is arranged between the negative common pad 202 and the edge of the silicon substrate.
[0042] The lengths of the positive pads 101 and the negative pads 201 are independently 1-2 mm, for example, they can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.; the widths are independently 1-2 mm, for example, they can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.
[0043] The lengths of the positive electrode common pad 102 and the negative electrode common pad 202 are each independently 3 - 10 mm. The above-mentioned "length" refers to the extension distance of the positive electrode common pad 102 and the negative electrode common pad 202 along the positive electrode main grid 10 and the negative electrode main grid 20. For example, it can be 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, 4.8 mm, 5 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6 mm, 6.2 mm, 6.5 mm, 6.8 mm, 7 mm, 7.2 mm, 7.5 mm, 7.8 mm, 8 mm, 8.2 mm, 8.5 mm, 8.8 mm, 9 mm, 9.2 mm, 9.5 mm, 9.8 mm, 10 mm, etc.; the widths are each independently 1 - 2 mm, for example, it can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.
[0044] This embodiment also provides a preparation method for the above-mentioned back-contact crystalline silicon solar cell, which includes the following main steps:
[0045] (1) Pre-clean the selected P-type monocrystalline silicon wafer. The specific parameters are resistivity of 0.5 - 3 Ω·cm and thickness of 150 ± 10 μm to remove the damaged layer.
[0046] (2) Use a low-pressure chemical vapor deposition (LPCVD) device on the back to deposit a tunneling oxide layer by low pressure.
[0047] (3) Perform phosphorus diffusion on both sides.
[0048] (4) Make Mark points and pattern on the back.
[0049] (5) Polish the silicon wafer to form a P region and expose the P-region silicon substrate.
[0050] (6) Perform two-sided tube thermal oxidation annealing to form a protective layer to protect the back pattern.
[0051] (7) Remove the oxide layer on the front through a chain HF device to expose the silicon substrate for subsequent texturing.
[0052] (8) Use trough texturing to form a textured surface.
[0053] (9) Prepare double-sided aluminum oxide on the front and back using an atomic layer deposition (ALD) device.
[0054] (10) Perform double-sided silicon nitride passivation using a plasma-enhanced chemical vapor deposition (PECVD) device, with the order being the front first and then the back.
[0055] (11) Use a nanosecond pulsed laser to open holes in some areas.
[0056] (12) Print the graphics described in the above solution, and form a back electrode after sintering.
[0057] Perform an EL defect measurement test on the back-contact solar cell provided in the foregoing embodiment. The test method is as follows:
[0058] Use an EL defect detector to detect the back-contact solar cell of the above embodiment. Figure 4 It can be seen that by designing the structure of the back electrode, the present invention sets a positive common pad and a negative common pad in a predetermined area, avoiding local poor contact, ensuring the reliability of the test results, making the EL measurement image of a normal battery more uniform, and enabling the EL defect measurement image to more accurately and obviously reflect the battery quality problem.
[0059] The applicant declares that the present invention uses the above embodiments to illustrate the process method of the present invention, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the raw materials selected by the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.
Claims
1. A back-contact solar cell, comprising a silicon substrate and a metal electrode disposed on the back of the silicon substrate, wherein the metal electrode comprises a positive main grid and a negative main grid alternately arranged along a first direction, characterized in that: The positive electrode main grid includes positive electrode pads arranged at intervals along a second direction perpendicular to the first direction, at least one of the positive electrode main grids also includes a positive electrode common pad, the length of the positive electrode common pad along the second direction is greater than the length of the positive electrode pad along the second direction, the positive electrode pad is used to cooperate with the abutment test of the positive current probe, and the positive electrode common pad can cooperate with the abutment test of the positive current probe and the positive voltage probe at the same time; The negative electrode main grid includes negative electrode pads arranged at intervals along the second direction, and at least one of the negative electrode main grids also includes a negative electrode common pad, the length of the negative electrode common pad along the second direction is greater than the length of the negative electrode pad along the second direction, and the negative electrode pad is used to cooperate with the abutment test of the negative electrode current probe, and the negative electrode common pad can simultaneously cooperate with the abutment test of the negative electrode current probe and the negative electrode voltage probe.
2. The back contact solar cell according to claim 1, characterized in that: The positive electrode common pads and the negative electrode common pads are grouped in pairs, and the positive electrode common pads and the negative electrode common pads in the same group are respectively arranged on the adjacent positive electrode main grid and the negative electrode main grid.
3. The back contact solar cell according to claim 2, characterized in that: The positive electrode common pad and the negative electrode common pad of the same group are arranged correspondingly along the first direction.
4. The back contact solar cell according to claim 2, characterized in that: The positive electrode common pads and the negative electrode common pads are arranged in four groups and are respectively located in different areas of the surface of the silicon substrate.
5. The back contact solar cell according to claim 4, characterized in that: The silicon substrate has a first center line extending along a first direction and a second center line extending along a second direction. The first center line and the second center line evenly divide the silicon substrate into four areas, and each area is respectively provided with a group of the positive electrode common pads and the negative electrode common pads.
6. The back contact solar cell according to claim 1, characterized in that: The length of the positive electrode pad and the negative electrode pad are independently 1-2 mm, and the width is independently 1-2 mm; The positive electrode common pad has a length of 3-10 mm and a width of 1-2 mm; The negative electrode common welding pad has a length of 3-10 mm and a width of 1-2 mm.
7. The back contact solar cell according to claim 1, characterized in that: The total number of the positive electrode main grid and the negative electrode main grid is 16-24.
8. The back contact solar cell according to claim 1, characterized in that: The positive electrode common pad is located at the xth positive electrode main grid; When the number n of the positive electrode main grid is an even number, the value of x is 2 to (n / 2-1) or (n / 2+2) to (n-1); When the number n of the positive electrode main grids is an odd number, the value of x is 2 to (n / 2-1 / 2) or (n / 2+3 / 2) to (n-1).
9. The back contact solar cell according to claim 1, characterized in that: Along the extension direction of the positive main grid, at least one positive electrode pad is arranged between the positive common pad and the edge of the silicon substrate; along the extension direction of the negative main grid, at least one negative electrode pad is arranged between the negative common pad and the edge of the silicon substrate.
10. A photovoltaic module, comprising a plurality of cells, characterized in that: The cell is the back-contact solar cell according to any one of claims 1 to 9, or the cell is obtained by dividing the back-contact solar cell according to any one of claims 1 to 9.