CN112635588A - Solar cell, back electrode thereof and preparation method - Google Patents
Solar cell, back electrode thereof and preparation method Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 281
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 281
- 229910052709 silver Inorganic materials 0.000 claims abstract description 80
- 239000004332 silver Substances 0.000 claims abstract description 80
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 79
- 238000007639 printing Methods 0.000 claims abstract description 35
- 230000002093 peripheral effect Effects 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 claims description 16
- 238000007650 screen-printing Methods 0.000 claims description 13
- 239000007787 solid Substances 0.000 claims description 3
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- 230000000694 effects Effects 0.000 abstract description 12
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 18
- 229910052710 silicon Inorganic materials 0.000 description 18
- 239000010703 silicon Substances 0.000 description 18
- 238000002161 passivation Methods 0.000 description 12
- 238000005516 engineering process Methods 0.000 description 6
- 238000003466 welding Methods 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
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- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- XHXFXVLFKHQFAL-UHFFFAOYSA-N phosphoryl trichloride Chemical compound ClP(Cl)(Cl)=O XHXFXVLFKHQFAL-UHFFFAOYSA-N 0.000 description 2
- 229910000679 solder Inorganic materials 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
- H01L31/022433—Particular geometry of the grid contacts
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- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
- H01L31/022441—Electrode arrangements specially adapted for back-contact solar cells
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Abstract
The invention discloses a solar cell, a back electrode of the solar cell and a preparation method of the back electrode, and belongs to the technical field of solar cells. The back electrode comprises aluminum main grids, aluminum auxiliary grids and back silver electrodes, wherein the aluminum main grids are composed of annular aluminum main grids which are distributed at intervals and straight-through aluminum main grids which are connected with adjacent annular aluminum main grids, the back silver electrodes are positioned in the annular aluminum main grids and are electrically connected with the annular aluminum main grids, and the straight-through aluminum main grids are composed of central straight-through aluminum main grids and peripheral straight-through aluminum main grids which are positioned above the central straight-through aluminum main grids. According to the invention, through the back electrode pattern design and the step-by-step printing process, the current carrier collection effect of the back electrode can be greatly improved under the condition of no negative influence on the back shading area and the slurry consumption, so that the effective conversion efficiency of the cell is improved.
Description
Technical Field
The invention belongs to the technical field of solar cells, and particularly relates to a solar cell, a back electrode of the solar cell and a preparation method of the back electrode.
Background
The Multi-main grid (MBB) and double-sided battery technology become the mainstream technology of the existing crystalline silicon battery and are popularized and applied in a large scale. The MBB technology realizes the reduction of shading area and the great improvement of current collection capacity simultaneously through the increase of the number of the main grids of the battery piece, the narrowing of the width of a single main grid and the design of welding spots, thereby improving the conversion efficiency of the battery by 0.3 percent and reducing the unit consumption of silver paste by more than 10 mg. The double-sided battery technology has the advantages that the production can be carried out only by slightly changing the existing single-sided battery and assembly production line, the system power generation income can be increased by 5% -25% compared with a single-sided battery assembly product, and the like, and the double-sided battery technology is also popularized and applied on a large scale.
At present, the back electrode structure of the existing MBB double-sided battery is generally shown in fig. 1, a single main grid generally adopts a 6-segment back silver electrode 11, an aluminum auxiliary grid 10 replaces a full-coverage aluminum layer of a PERC battery, and the aluminum auxiliary grid 10 is connected with a silicon substrate through laser grooving to realize current collection; then the aluminum secondary grid 10 collects current to be transmitted to the aluminum main grid 9, and finally the current is led out through the back silver electrode 11. In addition, the aluminum main grid directly connected with the back silver electrode 11 area adopts a ring-shaped design, and the aluminum main grid connected between the two back silver electrodes 11 adopts a through design (i.e. as shown in fig. 2, the aluminum main grid 9 consists of a through aluminum main grid 9-1 and a ring-shaped aluminum main grid 9-2, and the back silver electrode 11 is arranged inside the ring-shaped aluminum main grid 9-2).
Because the resistivity of aluminum is much larger than that of silver, in order to meet the requirements of current transmission and back double-sided rate, the aluminum electrode needs to have a narrower electrode width and a higher electrode height as the front electrode, namely, the aspect ratio of the aluminum electrode needs to be as large as possible. However, the too high aluminum electrode design causes a height difference of more than 15 μm between the back silver electrode 11 and the aluminum main grid 9 (as shown in fig. 3). When the MBB component adopts the superfine solder strip, the height difference easily causes the problems of insufficient solder and the like of the component, thereby influencing the yield of the component and the reliability of the product. Currently, in order to solve the problem, the industry mainly reserves a blank isolation region 12 by optimizing the design of the back electrode, that is, isolating the back silver electrode and the aluminum electrode by a distance of more than 1.5mm, so as to reduce the influence of the height difference. Meanwhile, the length and the width of the back silver electrode cannot be too small so as to ensure the reliability of component welding.
However, the above-mentioned space between the back silver electrode and the aluminum electrode, i.e. the blank isolation region 12, will be the blank region for back carrier collection, and the area of this collection blank region caused by the design with different space lengths accounts for about 1% -3% in the current 6-segment pattern design, thereby affecting the conversion efficiency of the battery. Therefore, how to further improve the conversion efficiency of the PERC cell and ensure the quality and reliability of the device becomes a difficult problem to be solved continuously by the solar cell technology.
The application with the Chinese patent application number of 2017107571568 discloses a manufacturing method of a double-sided PERC solar cell with a back silver grid line, wherein a groove is manufactured on an aluminum grid line, and the silver grid line is used for replacing the original aluminum grid line in the groove, so that the resistivity can be integrally reduced, the filling factor of the cell is improved, and the back shading area is reduced. However, the back electrode adopts a silver grid line mode, which can significantly increase the manufacturing cost, thereby causing that the back electrode cannot be popularized in batches.
Disclosure of Invention
1. Problems to be solved
The invention aims to solve the problems that the current-carrying carrier collection effect of a back electrode and the double-sided rate of a battery of the conventional MBB double-sided battery cannot meet the use requirements and still needs to be further improved, and provides a solar battery, a back electrode and a preparation method thereof. By adopting the technical scheme of the invention, the current carrier collecting effect of the back electrode can be greatly improved under the condition of no negative influence on the back shading area and the slurry consumption, so that the effective conversion efficiency of the cell is improved.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the back silver electrode is positioned in the annular aluminum main grid and is electrically connected with the annular aluminum main grid, and the straight-through aluminum main grid consists of a central straight-through aluminum main grid and a peripheral straight-through aluminum main grid positioned above the central straight-through aluminum main grid.
Furthermore, the height of the back silver electrode corresponds to that of the straight-through aluminum main grid in the central area, and the height of the back silver electrode is smaller than that of the straight-through aluminum main grid in the peripheral area.
Furthermore, the peripheral area straight-through aluminum main grids are positioned at two sides above the central area straight-through aluminum main grid, and the internal width of the peripheral area straight-through aluminum main grids is smaller than that of the central area straight-through aluminum main grid; preferably, the internal width W4 of the straight-through aluminum main grid in the peripheral area is 0.4-1.4mm, and the width W3 of the straight-through aluminum main grid in the central area is 0.5-1.5 mm.
Furthermore, the number of the segments of the back silver electrode corresponding to the same aluminum main grid is 8-50, the width W1 of the single back silver electrode is 1.2-2.2mm, and the length H1 is 1.5-5.5 mm.
Furthermore, the internal length of the annular aluminum main grid is greater than that of the back silver electrode, and the internal width of the annular aluminum main grid is smaller than that of the back silver electrode; preferably, the internal length H2 of the ring-shaped aluminum main grid is 1.7-5.8mm, and the internal width W2 of the ring-shaped aluminum main grid is 1.0-2.1 mm.
Furthermore, the number of the aluminum main grids is more than or equal to 9, the aluminum auxiliary grids are perpendicular to the aluminum main grids and are uniformly distributed at intervals, the width of the aluminum auxiliary grids is 60-200 mu m, and the distance between the aluminum auxiliary grids is 0.8-1.5 mm.
Secondly, in the manufacturing method of the solar cell back electrode, the aluminum main grid and the aluminum auxiliary grid adopt a step-by-step printing method, and the specific process is as follows: firstly, simultaneously printing a central area straight-through aluminum main grid and a bottom layer aluminum auxiliary grid in a screen printing mode to ensure that the height of the central area straight-through aluminum main grid is matched with the back silver electrode; and then, printing the direct-through aluminum main grid, the annular aluminum main grid and the upper aluminum auxiliary grid in the peripheral area at the same time.
Furthermore, 60-80% of double-sided aluminum paste with low solid content and contact resistivity less than or equal to 10m omega cm is adopted for the first printing-2The low contact resistance type aluminum paste is preferably the Ruxing 8401S double-sided aluminum paste; the resistivity of the double-sided aluminum paste adopted by grid lines in the second printing is less than or equal to 1 multiplied by 10-5Ω·cm-2The high-conductivity aluminum paste is preferably the juxing 8401U-1 double-sided aluminum paste.
Furthermore, the screen mesh number of the first printing is 430-520 meshes, the wire diameter is 11-13 μm, the yarn thickness is 10-15 μm, and the film thickness is 4-10 μm, and the screen mesh number of the second printing is 325-360 meshes, the wire diameter is 15-20 μm, the yarn thickness is 22-28 μm, and the film thickness is 15-25 μm.
Thirdly, the solar cell of the invention adopts the back electrode structure.
Fourthly, the preparation method of the solar cell adopts a step-by-step printing mode to prepare the aluminum grid line of the back electrode, specifically, the straight-through aluminum main grid in the central area and the aluminum auxiliary grid at the bottom layer are printed simultaneously, so that the height of the straight-through aluminum main grid in the central area is matched with that of the back silver electrode; and then, printing the direct-through aluminum main grid, the annular aluminum main grid and the upper aluminum auxiliary grid in the peripheral area at the same time.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the back electrode of the solar cell comprises the aluminum main grid, the aluminum auxiliary grid and the back silver electrode, and the back electrode pattern is optimally designed, so that the current carrier collecting effect of the back electrode can be greatly improved under the condition of no negative influence on the back shading area and the slurry consumption, and the conversion efficiency of the cell can be improved.
(2) The back electrode of the solar cell is characterized in that the straight-through aluminum main grid is designed to be composed of a central area straight-through aluminum main grid and a peripheral area straight-through aluminum main grid positioned above the central area straight-through aluminum main grid, and the height of the central area straight-through aluminum main grid corresponds to the height of the back silver electrode, so that the problems of assembly false welding and the like caused by the height difference between the aluminum main grid and the back silver electrode in the welding direction can be effectively avoided, the isolated collection blank area between the aluminum main grid and the back silver electrode is greatly reduced, the collection effect of the back electrode on current carriers is improved, and the conversion efficiency of a cell is further improved. Meanwhile, the invention breaks the limitation of multi-segment design through the graphic optimization of the back electrode, thereby providing a larger optimization space for the design and popularization of large-size batteries.
(3) According to the manufacturing method of the solar cell back electrode, the aluminum grid lines of the back electrode are printed step by step, and the height of the straight-through aluminum main grid in the central area is controlled to correspond to the height of the back silver electrode, so that the isolated collection blank area between the aluminum main grid and the back silver electrode can be reduced, the number of the segments of the back silver electrode is increased, and the carrier collection effect of the back electrode and the conversion efficiency of a cell are improved.
(4) According to the manufacturing method of the solar cell back electrode, different aluminum pastes can be matched according to needs through the selection of the aluminum grid line step-by-step printing process, so that the current transmission effect of the aluminum electrode can be further improved, the lateral corrosion of the aluminum paste to the laser grooving area passivation layer is reduced, the conversion efficiency of the cell is further improved, and the reliability of the double-sided cell is improved.
(5) According to the solar cell, through the graphic design of the back electrode, the photoelectric conversion efficiency of the PERC double-sided cell can be improved by more than 0.08%, and the PID of the back of the double-sided cell is improved by more than 0.2%.
Drawings
FIG. 1 is a schematic diagram of a back electrode of a conventional solar cell;
FIG. 2 is a schematic enlarged view of a portion of a back electrode of a conventional solar cell;
FIG. 3 is a sectional view of a back electrode of a conventional solar cell;
FIG. 4 is a schematic diagram of a back side electrode of a solar cell of the present invention;
FIG. 5 is a partially enlarged schematic view of the back electrode of the present invention;
FIG. 6 is a cross-sectional view of a back electrode of the present invention;
FIG. 7 is a schematic view of the distribution of the back silver electrode (12 segment) of the present invention;
FIG. 8 is a first printing of an aluminum back field of the present invention;
FIG. 9 is a second printing of the aluminum back field of the present invention;
fig. 10 is a schematic structural view of a solar cell according to the present invention.
In the figure: 1. a silicon wafer substrate; 2. a front emitter; 2-1, shallow doped region; 2-2, a heavily doped region; 3. an oxide layer; 4. a passivation and anti-reflection layer; 5. a positive electrode; 6. a back passivation layer; 7. a back electrode; 8. laser grooving on the back; 9. an aluminum main grid; 9-1, a straight-through aluminum main grid; 9-1-1, the central area is directly communicated with an aluminum main grid; 9-1-2, a peripheral area is directly communicated with an aluminum main grid; 9-2, a ring-shaped aluminum main grid; 10. an aluminum sub-grid; 11. a back silver electrode; 12. and a blank isolation region.
Detailed Description
In order to meet the requirements of current transmission and back double-sided rate, the back electrode main grid line of the MBB double-sided battery is required to have an aspect ratio as large as possible, so that the height difference between the back silver electrode 11 and the aluminum main grid 9 is large (more than 15 μm), problems such as component cold joint are caused, and the component yield and the product reliability are affected. At present, in the prior art, the problem caused by the height difference is mainly solved by increasing the distance between the back silver electrode and the aluminum electrode, that is, by setting the blank isolation region 12, so that the number of the back silver electrodes 11 is limited (the back silver electrode of the existing MBB double-sided battery is generally designed in 6 sections), the current collection effect and the conversion efficiency of the battery are affected, and meanwhile, the width of the aluminum main grid cannot be further reduced, so that the double-sided rate of the battery cannot be further improved. With the increase of the size of the silicon chip, the problems of current carrier collection effect, double-sided rate, slurry consumption, assembly welding reliability and the like caused by 6-segment design are further highlighted.
Aiming at the problems, on one hand, the invention designs a through type aluminum main grid through a back electrode graph, namely the through type aluminum main grid is composed of a central area through type aluminum main grid and a peripheral area through type aluminum main grid positioned above the central area through type aluminum main grid, the height of a back silver electrode is controlled to correspond to the height of the central area through type aluminum main grid, and the height of the back silver electrode is controlled to be smaller than the height of the peripheral area through type aluminum main grid, so that the assembly virtual welding and the influence on the product reliability caused by the height difference between the back silver electrode and the aluminum main grid can be effectively avoided on the basis of ensuring the current transmission and the back double-face rate, the distance between the back silver electrode and the aluminum main grid can be greatly reduced, namely the length of a blank isolation area 12, the segmentation quantity of the back silver electrode is effectively improved, can be increased from the current 6 to 8-50, and meanwhile, the width W1 of a single silver electrode is 1.2-2.2, the length H1 is 1.5-5.5mm, thereby maintaining the total silver electrode area substantially constant. Through the great increase of silver electrode quantity, promoted the collection effect of back carrier to the conversion efficiency of battery has been promoted.
On the other hand, the invention adopts the step-by-step printing process to print the aluminum grid wire, and the first step of printing comprises the following steps: firstly, simultaneously printing a central area straight-through aluminum main grid and a bottom aluminum auxiliary grid to ensure that the height of the central area straight-through aluminum main grid is matched with the back silver electrode; then, a second printing step: the direct-through aluminum main grid in the peripheral area, the annular aluminum main grid and the aluminum auxiliary grid on the upper layer are printed simultaneously, so that different aluminum pastes can be matched according to needs, the height difference between the aluminum main grid and the back silver electrode can be effectively reduced through matching of the specifications of the screen plate and the pastes, possibility is provided for realizing a back electrode multi-silver electrode (8-50), the current transmission effect of the aluminum electrode is further improved, the lateral corrosion of the aluminum paste to a laser grooving area passivation layer is reduced, the conversion efficiency of the battery is further improved, and the reliability of the double-sided battery is improved.
Specifically, the back electrode of the solar cell comprises an aluminum main grid 9, an aluminum auxiliary grid 10 and a back silver electrode 11, wherein the aluminum main grid 9 is composed of annular aluminum main grids 9-2 which are distributed at intervals and a through type aluminum main grid 9-1 which is connected with the adjacent annular aluminum main grids 9-2, and the back silver electrode 11 is positioned inside the annular aluminum main grid 9-2 and is electrically connected with the annular aluminum main grid 9-2. The straight-through type aluminum main grid 9-1 consists of a central area straight-through aluminum main grid 9-1-1 and a peripheral area straight-through aluminum main grid 9-1-2 positioned above the central area straight-through aluminum main grid 9-1-1, wherein the height of the back silver electrode 11 corresponds to that of the central area straight-through aluminum main grid 9-1-1, and is smaller than that of the peripheral area straight-through aluminum main grid 9-1-2. The number of the segments of the back silver electrode 11 corresponding to the same aluminum main grid 9 is 8-50, the width W1 of the single back silver electrode 11 is 1.2-2.2mm, and the length H1 is 1.5-5.5 mm. The peripheral area straight-through aluminum main grid 9-1-2 is positioned at two sides above the central area straight-through aluminum main grid 9-1-1, and the internal width of the peripheral area straight-through aluminum main grid is smaller than that of the central area straight-through aluminum main grid 9-1-1. Preferably, the internal width W4 of the straight-through aluminum main grid 9-1-2 in the peripheral area is 0.4-1.4mm, and the width W3 of the straight-through aluminum main grid 9-1-1 in the central area is 0.5-1.5 mm. The internal length of the annular aluminum main grid is greater than that of the back silver electrode 11, and the internal width of the annular aluminum main grid is less than that of the back silver electrode 11; preferably, the internal length H2 of the annular aluminum main grid is 1.7-5.8mm, the internal width W2 of the annular aluminum main grid is 1.0-2.1mm, and the length of the annular aluminum main grid is slightly greater than the length of the silver electrode, so that the silver and aluminum are isolated in the direction of the main grid, and the problem of component welding caused by the overlapping height difference of the area is avoided. The number of the aluminum main grids 9 is more than or equal to 9, the aluminum auxiliary grids 10 are perpendicular to the aluminum main grids 9 and are uniformly distributed at intervals, the width of each aluminum auxiliary grid is 60-200 mu m, and the distance between the aluminum auxiliary grids is 0.8-1.5 mm.
According to the manufacturing method of the solar cell back electrode, the aluminum main grid 9 and the aluminum auxiliary grid 10 adopt a step-by-step printing method, and the specific process is as follows: firstly, simultaneously printing a central straight-through aluminum main grid 9-1-1 and a bottom aluminum auxiliary grid 10 by a screen printing mode, so that the height of the central straight-through aluminum main grid 9-1-1 is matched with that of a back silver electrode 11; and then, in the second step, the direct-through aluminum main grid 9-1-2, the annular aluminum main grid 9-2 and the aluminum auxiliary grid 10 on the upper layer in the peripheral area are printed simultaneously. Wherein, the double-sided aluminum paste is 60 to 80 percent low solid content and has the contact resistivity less than or equal to 10m omega cm during the first printing-2The contact resistance is reduced by the low contact resistance type aluminum paste, preferably, the Ruxing 8401S double-sided aluminum paste; the screen mesh number of 430-520 meshes, the line diameter of 11-13 μm, the yarn thickness of 10-15 μm and the film thickness of 4-10 μm during the first printing, preferably the screen mesh number of 430 meshes, the line diameter of 13 μm, the yarn thickness of 15 μm and the film thickness of 5 μm; then, the screen mesh number was 480 or 520 mesh, the yarn diameter was 11 μm, the yarn thickness was 15 μm, and the film thickness was 5 μm. The resistivity of the double-sided aluminum paste adopted by grid lines in the second printing is less than or equal to 1 multiplied by 10-5Ω·cm-2The high-conductivity aluminum paste is used for reducing the resistivity and lateral corrosion of the aluminum paste to a passivation layer of a laser opening area, preferably Ruxing 8401U-1 double-sided aluminum paste, and during second printing, the mesh number of a screen is 325-360 meshes, the wire diameter is 15-20 mu m, the yarn thickness is 22-28 mu m, and the film thickness is 15-25 mu m, preferably the mesh number of the screen is 360 meshes, the wire diameter is 16 mu m, the yarn thickness is 22, 26 or 28 mu m, and the film thickness is 20 mu m; then, the screen mesh number was 325 mesh, the yarn diameter was 16 μm, the yarn thickness was 26 or 28 μm, and the film thickness was 20 μm.
Example 1
With reference to fig. 4-6, the back electrode of the solar cell of this embodiment includes an aluminum main grid 9, an aluminum sub-grid 10, and a back silver electrode 11, where the aluminum main grid 9 is composed of annular aluminum main grids 9-2 distributed at intervals and a straight-through aluminum main grid 9-1 connecting adjacent annular aluminum main grids 9-2, and the back silver electrode 11 is located inside the annular aluminum main grid 9-2 and electrically connected thereto. The straight-through type aluminum main grid 9-1 consists of a central area straight-through aluminum main grid 9-1-1 and a peripheral area straight-through aluminum main grid 9-1-2 positioned above the central area straight-through aluminum main grid 9-1-1, wherein the height of the back silver electrode 11 corresponds to that of the central area straight-through aluminum main grid 9-1-1, and is smaller than that of the peripheral area straight-through aluminum main grid 9-1-2. Specifically, as shown in fig. 7, the number of segments of the back silver electrode 11 corresponding to the same aluminum main grid 9 in the present embodiment is 12, the width W1 of a single back silver electrode 11 is 2.1mm, and the length H1 is 2.7 mm. The internal width W4 of the peripheral region straight-through aluminum main grid 9-1-2 is 1.0mm, and the width W3 of the central region straight-through aluminum main grid 9-1-1 is 1.1 mm. The internal length H2 of the annular aluminum main grid is 3.0mm, and the internal width W2 of the annular aluminum main grid is 1.9 mm. The number of the aluminum main grids 9 is 9, the aluminum auxiliary grids 10 are perpendicular to the aluminum main grids 9 and are evenly distributed at intervals, the width of each aluminum auxiliary grid is 110 micrometers, and the distance between the aluminum auxiliary grids is 1.106 mm.
In the method for manufacturing the back electrode of the solar cell in this embodiment, the aluminum main grid 9 and the aluminum auxiliary grid 10 are printed step by step, and the specific processes are as follows with reference to fig. 8 and 9: synchronously printing a central straight-through aluminum main grid 9-1-1 and a bottom aluminum auxiliary grid 10 by a screen printing mode to ensure that the height of the central straight-through aluminum main grid 9-1-1 is matched with that of a back silver electrode 11; then, the direct-through aluminum main grid 9-1-2 in the peripheral area, the annular aluminum main grid 9-2 and the aluminum auxiliary grid 10 on the upper layer are synchronously printed. Wherein, the double-sided aluminum paste adopts 8401S double-sided aluminum paste during the first printing, the mesh number of the screen printing plate is 430 meshes, the wire diameter is 13 mu m, the screen thickness is 15 mu m, and the film thickness is 5 mu m, the double-sided aluminum paste adopts the Ruxing 8401U-1 double-sided aluminum paste during the second printing, and the specification of the screen printing plate is as follows: the screen mesh number is 360 meshes, the wire diameter is 16 μm, the yarn thickness is 28 μm, and the film thickness is 20 μm.
As shown in fig. 10, the solar cell of this embodiment includes a back electrode 7, a back passivation layer 6, a silicon substrate 1, a front emitter 2, a front oxide layer 3, a front passivation and antireflection layer 4, and a positive electrode 5, which are sequentially disposed from bottom to top, and the specific preparation process is as follows:
1. texturing: a single crystal P-type silicon wafer (in the embodiment, single crystal silicon is taken as an example for explanation, and the single crystal silicon is not limited in practice) is used, and front and back texturing is carried out by alkali to form a textured structure.
2. Diffusion: and (3) reacting the silicon wafer after texturing with phosphorus oxychloride at high temperature to enable the front surface to diffuse to form a PN emitter junction (namely a front emitter 2), wherein the square resistance of the front surface thin layer after diffusion is 160 omega/□.
3. Laser SE: and (3) performing laser doping on the front surface of the diffused silicon wafer and the metalized area corresponding to the positive electrode grid line by using the diffused phosphorosilicate glass as a phosphorus source to form a heavily doped area 2-2, so that a structure (consisting of the heavily doped area 2-2 and the shallow doped area 2-1) for selecting an emitter is realized on the front surface of the silicon wafer, and the square resistance of the heavily doped area is 80 omega/□.
4. Thermal oxidation: and introducing oxygen into the silicon wafer after the laser SE for oxidation.
5. Removing PSG: and (4) removing the PSG on the back surface and the periphery of the silicon wafer after thermal oxidation by using HF.
6. Alkali polishing: and polishing the back and the edge of the silicon wafer after the PSG is removed, and removing the PSG on the front side.
7. Oxidizing and annealing: and (3) carrying out oxidation and annealing treatment on the silicon wafer subjected to the alkali polishing to form an oxide layer 3.
8. Depositing a passivation film on the back: and preparing a passivation film, namely a back passivation layer 6, on the back of the annealed silicon wafer.
9. Front side deposition of an antireflection film: and preparing a passivation and antireflection layer 4 on the front surface of the silicon wafer.
10. Back laser: and (3) carrying out laser drilling on the silicon wafer with the passivation film prepared on the back surface to form a back surface laser groove 8.
11. Preparing a back electrode: by adopting the preparation process of the back electrode, the aluminum auxiliary grids 10 are distributed in parallel and uniformly, the positions of the aluminum auxiliary grids correspond to the positions of the back laser grooves 8, and the aluminum auxiliary grids 10 are in contact with the silicon wafer substrate 1 through the back laser grooves 8.
12. Printing a positive electrode main gate region: and adopting the front silver paste to prepare the positive electrode 5 on the silicon wafer printed with the back electrode by screen printing.
13. And (3) sintering: and (3) co-sintering the silicon chip with the front electrode printed, wherein the sintering peak temperature is 760 ℃.
14. Electric injection: and performing electro-injection treatment on the sintered battery piece.
15. And (3) finished product: and testing, sorting, packaging and warehousing the product battery pieces.
Example 2
With reference to fig. 4 to 6, the structure of the back electrode of the solar cell of this embodiment is basically the same as that of embodiment 1, and the differences are mainly as follows: in this embodiment, the number of segments of the back silver electrode 11 corresponding to the same aluminum main grid 9 is 10, the width W1 of a single back silver electrode 11 is 2.0mm, the length H1 is 3.0mm, the internal length H2 of the ring-shaped aluminum main grid is 3.4mm, and the internal width W2 of the ring-shaped aluminum main grid is 1.8 mm. The internal width W4 of the peripheral region straight-through aluminum main grid 9-1-2 is 1.2mm, and the width W3 of the central region straight-through aluminum main grid 9-1-1 is 1.3 mm. The number of the aluminum main grids 9 is 9, the aluminum auxiliary grids 10 are perpendicular to the aluminum main grids 9 and are evenly distributed at intervals, the width of each aluminum auxiliary grid is 110 micrometers, and the distance between the aluminum auxiliary grids is 1.106 mm.
The method for manufacturing the back electrode of the solar cell in this embodiment is basically the same as that in embodiment 1, and the differences are mainly that: in this embodiment, the specification of the screen printing plate during the first printing is: the mesh number of the screen printing plate is 480 meshes, the wire diameter is 11 mu m, the yarn thickness is 15 mu m, the film thickness is 5 mu m, and the specification of the screen printing plate during the second printing is as follows: the screen mesh number is 325 meshes, the wire diameter is 16 μm, the yarn thickness is 26 μm, and the film thickness is 20 μm.
The process of the solar cell of this embodiment is substantially the same as that of embodiment 1, and the difference is mainly that: in the embodiment, the sheet resistance of the front surface thin layer after diffusion is 140 omega/□, the sheet resistance of the heavily doped region is 60 omega/□, and the sintering peak temperature is 720 ℃.
Example 3
With reference to fig. 4 to 6, the structure of the back electrode of the solar cell of this embodiment is basically the same as that of embodiment 1, and the differences are mainly as follows: in this embodiment, the number of segments of the back silver electrode 11 corresponding to the same aluminum main grid 9 is 20, the width W1 of a single back silver electrode 11 is 1.4mm, the length H1 is 1.9mm, the internal length H2 of the ring-shaped aluminum main grid is 2.2mm, and the internal width W2 of the ring-shaped aluminum main grid is 1.3 mm. The internal width W4 of the peripheral region straight-through aluminum main grid 9-1-2 is 1.0mm, and the width W3 of the central region straight-through aluminum main grid 9-1-1 is 0.9 mm. The number of the aluminum main grids 9 is 12, the aluminum auxiliary grids 10 are perpendicular to the aluminum main grids 9 and are evenly distributed at intervals, the width of each aluminum auxiliary grid is 80 mu m, and the distance between the aluminum auxiliary grids is 1.0 mm.
The method for manufacturing the back electrode of the solar cell in this embodiment is basically the same as that in embodiment 1, and the differences are mainly that: in this embodiment, the specification of the screen printing plate during the first printing is: the mesh number of the screen printing plate is 520 meshes, the wire diameter is 11 mu m, the screen thickness is 15 mu m, the film thickness is 5 mu m, and the specification of the screen printing plate during the second printing is as follows: the screen mesh number is 360 meshes, the wire diameter is 16 μm, the yarn thickness is 26 μm, and the film thickness is 20 μm.
The process of the solar cell of this embodiment is substantially the same as that of embodiment 1, and the difference is mainly that: in the embodiment, the sheet resistance of the front surface thin layer after diffusion is 135 Ω/□, the sheet resistance of the heavily doped region is 90 Ω/□, and the sintering peak temperature is 800 ℃.
Claims (11)
1. A back electrode of a solar cell comprises an aluminum main grid (9), an aluminum auxiliary grid (10) and a back silver electrode (11), and is characterized in that: the aluminum main grid (9) is composed of annular aluminum main grids (9-2) distributed at intervals and through type aluminum main grids (9-1) connected with the adjacent annular aluminum main grids (9-2), the back silver electrode (11) is located inside the annular aluminum main grids (9-2) and electrically connected with the annular aluminum main grids, and the through type aluminum main grids (9-1) are composed of central area through type aluminum main grids (9-1-1) and peripheral area through type aluminum main grids (9-1-2) located above the central area through type aluminum main grids (9-1-1).
2. The back electrode for a solar cell according to claim 1, wherein: the height of the back silver electrode (11) corresponds to that of the central area straight-through aluminum main grid (9-1-1), and the height of the back silver electrode is smaller than that of the peripheral area straight-through aluminum main grid (9-1-2).
3. The back electrode for a solar cell according to claim 2, wherein: the peripheral area straight-through aluminum main grids (9-1-2) are positioned at two sides above the central area straight-through aluminum main grid (9-1-1), and the internal width of the peripheral area straight-through aluminum main grid is smaller than that of the central area straight-through aluminum main grid (9-1-1); the internal width W4 of the peripheral area straight-through aluminum main grid (9-1-2) is 0.4-1.4mm, and the width W3 of the central area straight-through aluminum main grid (9-1-1) is 0.5-1.5 mm; the internal length of the annular aluminum main grid is greater than that of the back silver electrode (11), and the internal width of the annular aluminum main grid is less than that of the back silver electrode (11); the internal length H2 of the annular aluminum main grid is 1.7-5.8mm, and the internal width W2 of the annular aluminum main grid is 1.0-2.1 mm.
4. The back electrode for a solar cell according to any one of claims 1 to 3, wherein: the number of the segments of the back silver electrode (11) corresponding to the same aluminum main grid (9) is 8-50, the width W1 of the single back silver electrode (11) is 1.2-2.2mm, and the length H1 is 1.5-5.5 mm.
5. The back electrode for a solar cell according to any one of claims 1 to 3, wherein: the number of the aluminum main grids (9) is more than or equal to 9, the aluminum auxiliary grids (10) are perpendicular to the aluminum main grids (9) and are uniformly distributed at intervals, the width of the aluminum auxiliary grids is 60-200 mu m, and the distance between the aluminum auxiliary grids is 0.8-1.5 mm.
6. A method for manufacturing a solar cell back electrode according to any one of claims 1 to 5, wherein the aluminum main grid (9) and the aluminum auxiliary grid (10) adopt a step-by-step printing method, and the specific process is as follows: firstly, simultaneously printing a central area straight-through aluminum main grid (9-1-1) and a bottom aluminum auxiliary grid (10) in a screen printing mode, so that the height of the central area straight-through aluminum main grid (9-1-1) is matched with a back silver electrode (11); then, the peripheral area straight-through aluminum main grid (9-1-2), the annular aluminum main grid (9-2) and the upper aluminum auxiliary grid (10) are printed simultaneously.
7. The method for manufacturing a back electrode of a solar cell according to claim 6, wherein: the double-sided aluminum paste is printed for the first time by adopting 60-80 percent of low solid content and contact resistivity less than or equal to 10m omega cm-2The low contact resistance type aluminum paste adopts grid line resistivity not more than 1 multiplied by 10 when the double-sided aluminum paste is printed for the second time-5Ω·cm-2The high conductivity aluminum paste of (1).
8. The method for manufacturing a back electrode of a solar cell according to claim 7, wherein: the double-sided aluminum paste is the juxing 8401S double-sided aluminum paste during the first printing, and the juxing 8401U-1 double-sided aluminum paste during the second printing.
9. The method for manufacturing a back electrode of a solar cell according to claim 6, wherein: the screen mesh number of 430-.
10. A solar cell, characterized by: use of a back electrode as claimed in any one of claims 1 to 5.
11. A method of manufacturing a solar cell according to claim 10, characterized in that: preparing an aluminum grid line of a back electrode by adopting a step-by-step printing mode, specifically, simultaneously printing a central area straight-through aluminum main grid (9-1-1) and a bottom aluminum auxiliary grid (10) to ensure that the height of the central area straight-through aluminum main grid (9-1-1) is matched with a back silver electrode (11); then, the peripheral area straight-through aluminum main grid (9-1-2), the annular aluminum main grid (9-2) and the upper aluminum auxiliary grid (10) are printed simultaneously.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116072746A (en) * | 2023-02-27 | 2023-05-05 | 通威太阳能（安徽）有限公司 | Photovoltaic module, battery piece and electrode structure |
| WO2023169507A1 (en) * | 2022-03-09 | 2023-09-14 | 天合光能科技(盐城)有限公司 | Laser grooving structure on the back surface of double-sided solar cell |
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2021
- 2021-01-20 CN CN202110075085.XA patent/CN112635588A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023169507A1 (en) * | 2022-03-09 | 2023-09-14 | 天合光能科技(盐城)有限公司 | Laser grooving structure on the back surface of double-sided solar cell |
| CN116072746A (en) * | 2023-02-27 | 2023-05-05 | 通威太阳能（安徽）有限公司 | Photovoltaic module, battery piece and electrode structure |
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