A double-sided battery back electrode, a preparation method and application thereof

Abstract

The application discloses a double-sided battery back electrode and a preparation method and application thereof, and belongs to the technical field of back electrodes. The double-sided battery back electrode comprises an aluminum main grid and an aluminum auxiliary grid, the aluminum main grid is connected by an aluminum fine main grid and a ring-shaped aluminum main grid, the ring-shaped aluminum main grid is distributed at intervals along the length direction of the aluminum main grid, and the two ends of all the ring-shaped aluminum main grids are provided with the aluminum fine main grids which are divergent outward. The structure of the back electrode is optimized, the divergent aluminum main grid structure is adopted, and thus the defects existing in the current back electrode can be effectively solved, the conversion efficiency of the PERC battery is improved, and the quality and reliability of the module are ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of back electrode, more particularly, relates to a back electrode of bifacial cell and a preparation method and application thereof. BACKGROUND

[0002] Bifacial solar cell can be produced by only a small amount of modification to the existing cell and module production line, and can increase the system power generation yield by 5%-25% compared with single-sided cell module product, so that the bifacial cell technology gradually becomes the mainstream technology of the current crystalline silicon cell, and has been widely applied.

[0003] The design of the back electrode is intertwined with the optimization, constraint and compromise of the bifacial rate, carrier collection, paste consumption, module welding and other factors of the bifacial cell. At present, the back electrode structure of the MBB bifacial cell is as shown in Figure 1 The entire back electrode is composed of uniform and parallel distributed sub-grids and main grids, the sub-grids are connected vertically with the main grids to form a so-called H-shaped pattern. The sub-grids are often formed by aluminum paste, the aluminum sub-grid 2 replaces the full coverage aluminum layer of the single-sided cell, and the aluminum sub-grid 2 is connected with the silicon substrate through laser slotting to collect the current of the substrate area and then transmit it to the main grid. The main grid area is generally composed of aluminum main grid 1 and silver electrode 3, the aluminum main grid 1 is directly connected with the aluminum sub-grid 2 to collect the current collected by the sub-grid and then transmit it to the silver electrode 3 to realize current export. The current back electrode pattern design generally adopts 6 segmented silver electrodes, the aluminum main grid directly connected with the silver electrode adopts ring type design (i.e. ring type aluminum main grid 102), and the aluminum main grid (i.e. aluminum thin main grid 101) connecting two silver electrodes 3 adopts straight-through design.

[0004] That is, the current collected by the entire back electrode is first transmitted to the aluminum main grid through the horizontally uniform distributed sub-grids, and then transmitted to the silver electrode for export through the vertically and longitudinally uniform distributed aluminum main grid. However, since the resistivity of aluminum is much larger than that of silver, in order to meet the current transmission requirement, the width of the aluminum main grid is often designed to be more than 1 mm. At the same time, in order to take into account the requirement of the bifacial rate, the aluminum main grid and the aluminum sub-grid need to have the same electrode width and higher electrode height as the front electrode, that is, the aspect ratio is as large as possible. This on the one hand puts forward higher challenges to the improvement of the bifacial rate and the performance requirement of the aluminum paste, and on the other hand, the design of the aluminum electrode with too high height will cause yield and product reliability problems such as module welding, which needs to further adjust the back design to take into account this problem. At present, the existing technology generally separates a space of more than 1.5 mm between the back silver electrode and the aluminum electrode, that is, a blank isolation area 4 (as shown in Figure 2 ) is reserved, so as to reduce the influence of the height difference. However, the existence of the blank isolation area 4 will also cause the number of silver electrode segments to be greatly limited, affecting the back current collection effect and the conversion efficiency of the cell.

[0005] To solve the above problems, patent CN107331735B discloses a manufacturing method of a double-sided PERC solar cell with a back silver grid line, which replaces the original aluminum grid line with a silver grid line in the groove prepared on the aluminum grid line, thereby reducing the resistivity as a whole, improving the cell fill factor, and reducing the back shading area. However, the use of silver grid lines for the back electrode significantly increases the manufacturing cost, which cannot be mass-produced.

[0006] Therefore, how to further improve the conversion efficiency of the PERC cell while ensuring the quality and reliability of the module has become a difficult problem to be solved in the solar cell technology. SUMMARY

[0007] 1. Problem to be solved

[0008] The present application aims to overcome the shortcomings of the H-shaped back electrode structure design of the existing MBB double-sided cell, which is difficult to meet the requirements of double-sided rate, current collection effect and module reliability, and provides a double-sided cell back electrode and its preparation method and application. The present application optimizes the structure of the back electrode and adopts a divergent aluminum main grid structure, thereby effectively solving the above problems and improving the conversion efficiency of the PERC cell while ensuring the quality and reliability of the module.

[0009] 2. Technical solution

[0010] To solve the above problems, the technical solution adopted by the present application is as follows:

[0011] The double-sided cell back electrode of the present application comprises an aluminum main grid and an aluminum auxiliary grid, the aluminum main grid is connected by an aluminum fine main grid and a ring-shaped aluminum main grid, wherein the ring-shaped aluminum main grid is distributed at intervals along the length direction of the aluminum main grid, and both ends of all the ring-shaped aluminum main grids are provided with aluminum fine main grids diverging outward.

[0012] Further, the aluminum fine main grid located at the same end of the ring-shaped aluminum main grid is composed of two aluminum fine main grids diverging outward relative to the end of the ring-shaped aluminum main grid.

[0013] Further, the aluminum fine main grids between adjacent ring-shaped aluminum main grids are connected to form a parallelogram structure.

[0014] Further, the aluminum fine main grid and the ring-shaped aluminum main grid are connected with aluminum auxiliary grids on both sides.

[0015] Further, the ring-shaped aluminum main grid and the aluminum fine main grid are connected with horizontally distributed transverse aluminum auxiliary grids on both sides, and the inner side of the aluminum fine main grid is connected with vertically distributed longitudinal aluminum auxiliary grids.

[0016] Further, the width of the aluminum auxiliary grid is 60-200 μm, and the distance between adjacent transverse aluminum auxiliary grids and adjacent longitudinal aluminum auxiliary grids is 0.8-1.5 mm.

[0017] Further, the width of the aluminum auxiliary grid is 130 μm, and the distance between adjacent transverse aluminum auxiliary grids and adjacent longitudinal aluminum auxiliary grids is 1.15 mm.

[0018] Further, the inner part of the ring-shaped aluminum main grid is provided with a back silver electrode, and the inner ring width is less than the width of the back silver electrode, and the number of segments of the back silver electrode on the same main grid is 8-50.

[0019] Further, the width of a single back silver electrode is 1.2-2.2 mm, and the length is 1.5-5.5 mm; the ring width of the ring-shaped aluminum main grid is 0.1-1 mm, and the inner ring width is 1-2.1 mm.

[0020] Further, the number of segments of the back silver electrode on the same main grid is 12, the width of a single back silver electrode is 2.1 mm, and the length is 2.7 mm; the ring width of the ring-shaped aluminum main grid is 0.4 mm, and the inner ring width is 1.9 mm.

[0021] Further, the number of aluminum main grids is greater than or equal to 9, and the aluminum main grids are arranged in sequence.

[0022] Further, the aluminum fine main grid adopts a bamboo joint gradual change structure.

[0023] Further, the gradual change specification between adjacent bamboo joints of the aluminum fine main grid is 0.06-1.0 mm.

[0024] Further, the aluminum fine main grid adopts a three-stage bamboo joint gradual change specification of 0.4 mm / 0.35 mm / 0.13 mm.

[0025] Secondly, the preparation method of the back electrode of the double-sided battery of the present application performs laser slotting at the corresponding positions of the aluminum auxiliary grid area and the aluminum fine main grid area of the back electrode, and the silver electrode area and the ring-shaped aluminum main grid area are not subjected to laser slotting, and then the aluminum electrode and the back silver electrode are prepared by using a silk screen printing method.

[0026] Further, the non-slotted area corresponding to the silver electrode area and the ring-shaped aluminum main grid area is a rectangle, and the width is 3.1 mm and the length is 5 mm.

[0027] Further, when the aluminum electrode is prepared by using the silk screen printing method, the screen plate specification is as follows: screen mesh 300-400 meshes, wire diameter 12-20 μm, yarn thickness 20-30 μm, and film thickness 15-25 μm.

[0028] Thirdly, the application of the back electrode in the MBB double-sided battery.

[0029] 3. Advantages

[0030] Compared with the prior art, the advantages of the present application are:

[0031] (1) The back electrode of the double-sided battery of the present application adopts a divergent aluminum electrode design, which changes the existing horizontal + vertical current transmission mode, effectively shortens the current collection path, and improves the collection effect. Under the condition of the same aluminum sub-grid design line width, the light shielding area can be reduced by 1.3%.

[0032] (2) The back electrode of the double-sided battery of the present application, the aluminum fine main grid located at the same end of the ring-shaped aluminum main grid is composed of two aluminum fine main grids diverging outward relative to the end of the ring-shaped aluminum main grid, and the two sides of the ring-shaped aluminum main grid and the outer side of the aluminum fine main grid are connected with horizontally distributed transverse aluminum sub- grids, and the inner side of the aluminum fine main grid is connected with vertically distributed longitudinal aluminum sub- grids, thereby facilitating further shortening of the current collection path and improving the collection effect.

[0033] (3) The back electrode of the double-sided battery of the present application, through the structural design of the back electrode, the aluminum sub-grid line width can be appropriately increased and the aluminum electrode height can be reduced under the condition of ensuring the double-sided rate (light shielding area) and the collection effect, thereby eliminating and reducing the limitations caused by the height ratio (height difference), realizing the reduction of the collection blank area and the multi-silver electrode route, and at the same time eliminating the reliability problems of the module caused by the height difference.

[0034] (4) The back electrode of the double-sided battery of the present application, through structural optimization, the number of segmented back silver electrodes on the same main grid can be increased to 8-50, thereby effectively improving the photoelectric conversion efficiency of the battery sheet.

[0035] (5) The preparation method of the back electrode of the double-sided battery of the present application, using the process route of the present application, can realize a substantial improvement in the carrier collection effect of the back electrode without negative effects on the back light shielding area, slurry consumption and module welding performance, and realize an improvement of more than 0.1% in the photoelectric conversion efficiency of the PERC battery sheet.

[0036] (6) The back electrode of the present application applied to the MBB double-sided battery substantially reduces the isolation collection blank area between the aluminum main grid and the silver electrode, improves the improvement of the carrier collection effect of the back electrode, thereby improving the conversion efficiency of the battery sheet, and at the same time breaks the limitation of the multi-segment design, which can provide greater optimization space for the design and promotion of large-size batteries. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The structure diagram of the present MBB back electrode (6 segments);

[0038] Figure 2 is an enlarged schematic view of the electrode area of the back electrode of the MBB of the present application;

[0039] Figure 3 is a schematic view of the structure of the back electrode of the bifacial cell of the present application;

[0040] Figure 4 is an enlarged schematic view of the electrode area of the back electrode of the present application;

[0041] Figure 5 is a laser slotting pattern of the back electrode of the present application;

[0042] Figure 6 is a schematic view of the section of the bifacial cell of the present application.

[0043] In the figure: 1, aluminum main grid; 101, aluminum fine main grid; 102, ring-type aluminum main grid; 2, aluminum auxiliary grid; 201, horizontal aluminum auxiliary grid; 2011, first horizontal aluminum auxiliary grid; 2012, second horizontal aluminum auxiliary grid; 202, vertical aluminum auxiliary grid; 2021, first vertical aluminum auxiliary grid; 2022, second vertical aluminum auxiliary grid; 3, back silver electrode; 4, blank isolation area; 5, non-slotting area; 6, laser slotting area; 7, silicon wafer substrate; 8, front emitter; 801, heavily doped area; 802, shallowly doped area; 9, front oxide layer; 10, passivation and anti-reflection layer; 11, positive electrode; 12, back passivation layer; 13, back laser slotting. DETAILED DESCRIPTION

[0044] In view of the deficiencies in the design of the H-type back electrode structure of the bifacial cell, the present application changes the existing horizontal + vertical current transmission mode by the design of the divergent aluminum electrode, thereby effectively shortening the current collection path and improving the collection effect. Meanwhile, under the condition of ensuring the bifacial rate (light shielding area) and the collection effect, by appropriately increasing the line width of the aluminum auxiliary grid and reducing the height of the aluminum electrode, the problems caused by the height-width ratio (height difference) can be eliminated and reduced, the limitation of the multi-segment design is broken, and the photoelectric conversion efficiency of the cell sheet is further improved.

[0045] Specifically, the back electrode pattern of the present application adopts a multi-main-grid (more than or equal to 9) and multi-segment design, the main grid is an aluminum main grid, and each main grid is distributed in parallel and at intervals. The aluminum main grid 1 is composed of an aluminum fine main grid 101 and a ring-type aluminum main grid 102, wherein the ring-type aluminum main grid 102 is distributed at intervals along the length direction of the aluminum main grid 1, and the back silver electrode 3 is located inside the ring-type aluminum main grid 102 and in electrical contact with the ring-type aluminum main grid 102. Both ends of all the ring-type aluminum main grids 102 are provided with aluminum fine main grids 101 arranged divergently relative thereto, that is, the adjacent ring-type aluminum main grids 102 are connected through the aluminum fine main grids 101, and the two sides of the ring-type aluminum main grid 102 and the aluminum fine main grid 101 are connected with the aluminum auxiliary grid 2.

[0046] Through the aforementioned structural design, this invention effectively shortens the size of the blank isolation area between the silver electrode and the aluminum main grid, allowing the number of back silver electrode segments 3 on a single back electrode main grid to increase from the current 6 to 8-50. Simultaneously, the width of a single back silver electrode 3 is 1.2-2.2 mm, and the length is 1.5-5.5 mm, thus maintaining a relatively constant total silver electrode area. This significant increase in the number of back silver electrodes improves the collection effect of back-side charge carriers, thereby enhancing the conversion efficiency. Preferably, the back silver electrode uses 12 segments, with a width of 2.1 mm and a length of 2.7 mm.

[0047] Further optimizations, such as Figure 3 , Figure 4 As shown, in this invention, the aluminum fine main grid 101 located at the same end of the annular aluminum main grid 102 is composed of two aluminum fine main grids 101 that diverge outward from the end of the annular aluminum main grid 102 (preferably, the aluminum fine main grids 101 are connected to the two end corners of the annular aluminum main grid 102), and the aluminum fine main grids 101 between adjacent annular aluminum main grids 102 are connected to each other to form a parallelogram structure. Further optimization involves connecting horizontally distributed transverse aluminum sub-gates 201 (first transverse aluminum sub-gate 2011, second transverse aluminum sub-gate 2012) to both sides of the annular aluminum main gate 102 and the outer side of the aluminum fine main gate 101. Connecting vertically distributed longitudinal aluminum sub-gates 202 (first longitudinal aluminum sub-gate 2021, second longitudinal aluminum sub-gate 2022) to the inner side of the aluminum fine main gate 101. The width of the aluminum sub-gates 2 is 60μm-200μm, and the spacing between adjacent transverse aluminum sub-gates 201 and adjacent longitudinal aluminum sub-gates 202 is 0.8-1.5mm. The best effect is achieved when the width of the aluminum sub-gates 2 is 130μm and the spacing between adjacent transverse aluminum sub-gates 201 and adjacent longitudinal aluminum sub-gates 202 is equal to 1.15mm.

[0048] Among them, laser grooving is performed at corresponding positions on the aluminum sub-gate 2 and the aluminum fine main gate 101. Figure 5 The non-grooved area 5 (6) is laser-grooved, while the silver electrode area and the annular aluminum main gate area are not laser-grooved. The specifications of this non-grooved area 5 depend on the design specifications of the silver electrode. This non-grooved area is preferably rectangular, with a width of 3.1 mm and a length of 5 mm. The aluminum sub-gate 2 is connected to the silicon substrate through laser grooving to collect the current in the substrate area. The current is then transmitted to the aluminum fine main gate 101, and then to the annular aluminum main gate 102, or directly from the aluminum sub-gate 2 to the annular aluminum main gate 102. Finally, the current is transmitted to the back silver electrode 3 to achieve current extraction.

[0049] To better understand the present invention, the present invention will be further described below with reference to some specific embodiments.

[0050] Example 1

[0051] The back electrode of the double-sided battery of the embodiment comprises aluminum main grids 1 and aluminum auxiliary grids 2, wherein the number of the aluminum main grids 1 is 9, the aluminum main grid 1 is provided with ring-shaped aluminum main grids 102 distributed along the length direction of the aluminum main grid 1 at intervals, and both ends of all the ring-shaped aluminum main grids 102 are provided with two outwardly diverging aluminum fine main grids 101. The two sides of the ring-shaped aluminum main grid 102 and the outer side of the aluminum fine main grid 101 are connected with horizontally distributed transverse aluminum auxiliary grids 201, the inner side of the aluminum fine main grid 101 is connected with vertically distributed longitudinal aluminum auxiliary grids 202, the width of the aluminum auxiliary grid 2 is 100 μm, and the interval between adjacent transverse aluminum auxiliary grids 201 and adjacent longitudinal aluminum auxiliary grids 202 is 1.00 mm.

[0052] The inner part of the ring-shaped aluminum main grid 102 is provided with a back silver electrode 3, the number of the segments of the back silver electrode 3 on the same main grid in the embodiment is 12, the width of the back silver electrode 3 is 2.1 mm, the length is 2.7 mm, the ring-shaped aluminum main grid 102 adopts a rectangular structure, the ring-shaped width is 0.4 mm, the inner ring width is 1.9 mm (smaller than the width of the silver electrode, so as to realize the connection with the silver electrode), and the inner ring length is 4.2 mm. The aluminum fine main grid in the embodiment adopts a three-stage bamboo joint gradual change structure (0.4 mm / 0.35 mm / 0.13 mm) (the farther from the end of the ring-shaped aluminum main grid 102, the thinner the aluminum fine main grid).

[0053] The preparation method of the double-sided battery of the embodiment comprises the following process steps:

[0054] 1. Texturing: single crystal P-type silicon wafer is used as the silicon wafer substrate 7, and alkali is used to form a textured structure on the front and back surfaces.

[0055] 2. Diffusion: the silicon wafer after texturing is reacted with phosphorus oxychloride and the silicon wafer at high temperature to form a PN emission junction (front emitter 8) on the front surface.

[0056] 3. Laser SE: the phosphorus-silicon glass after diffusion is used as a phosphorus source to perform laser doping on the front surface of the silicon wafer and the metallized area corresponding to the positive electrode grid line to form a heavily doped region 801, so as to realize the structure of the selective emitter (heavily doped region 801 and shallowly doped region 802) on the front surface of the silicon wafer. The sheet resistance of the heavily doped region is between 60 Ω / □.

[0057] 4. Thermal oxidation: the silicon wafer after laser SE is subjected to oxygen oxidation.

[0058] 5. PSG removal: the silicon wafer after thermal oxidation is subjected to PSG removal on the back surface and the periphery by using HF.

[0059] 6. Alkali polishing: the silicon wafer after PSG removal is subjected to back surface and edge polishing, and the front surface is subjected to PSG removal.

[0060] 7. Oxidation annealing: the silicon wafer after alkali etching is subjected to oxidation and annealing treatment to form a front surface oxide layer 9.

[0061] 8. Back surface deposition of passivation film: a passivation film, i.e., a back surface passivation layer 12, is prepared on the back surface of the annealed silicon wafer.

[0062] 9. Front surface deposition of anti-reflection film: a passivation and anti-reflection layer 10 is prepared on the front surface of the silicon wafer.

[0063] 10. Back surface laser: a divergent laser is used to groove the pattern corresponding to the aluminum electrode, and laser grooving is performed at positions corresponding to the aluminum sub-grid area and the aluminum fine main grid area of the back surface electrode to form a back surface laser grooving 13, while the silver electrode area and the ring-shaped aluminum main grid area are not subjected to laser grooving. The non-grooving area is selected to be a rectangle with a width of 3.1 mm and a length of 5 mm. Figure 5 ).

[0064] 11. Back silver electrode preparation: a silver electrode 3 is prepared on the corresponding position on the back surface of the silicon wafer by screen printing, and the back silver is selected to be Guangda GB21 silver paste.

[0065] 12. Back aluminum electrode preparation: the back aluminum electrode pattern of the present embodiment is prepared by screen printing and high-precision camera snapping of laser MARK points.

[0066] 13. Front electrode main grid area printing: the front electrode 11 is prepared on the silicon wafer on which the back electrode has been printed by screen printing using the front silver paste.

[0067] 14. Sintering: the silicon wafer on which the front electrode has been printed is subjected to co-sintering, and the sintering peak temperature is 750°C.

[0068] 15. Electro-injection: the sintered cell piece is subjected to electro-injection treatment.

[0069] 16. Finished product: the product cell piece is tested, sorted, packaged and stored.

[0070] The obtained cell structure is shown in Figure 6 Using the technical route of the present embodiment, the collection effect of the back surface electrode on the carriers can be greatly improved without negative impact on the performance of the back surface shading area, paste consumption and module welding, and the photoelectric conversion efficiency of the PERC cell piece is improved by 0.13%.

[0071] Embodiment 2

[0072] The double-sided battery of the embodiment has the same structure as that of Embodiment 1, and the difference mainly lies in that the number of the aluminum main grid 1 is 11, the width of the aluminum auxiliary grid 2 is 60 μm, and the distance between the adjacent transverse aluminum auxiliary grid 201 and the adjacent longitudinal aluminum auxiliary grid 202 is 0.8 mm. In the embodiment, the number of the segments of the back silver electrode 3 on the same main grid is 8, the width is 1.2 mm, the length is 5.4 mm, the width of the ring-shaped aluminum main grid 102 is 0.6 mm, the width of the inner ring is 1.0 mm, and the length of the inner ring is 5.8 mm. The aluminum fine main grid adopts a three-stage bamboo joint gradual change structure of 0.5 mm / 0.42 mm / 0.10 mm.

[0073] The preparation method of the double-sided battery of the embodiment has the same process operation as that of Embodiment 1, and the difference mainly lies in that the sheet resistance of the positive surface thin layer after diffusion is between 120 Ω / □, and the sheet resistance of the heavily doped region is between 30 Ω / □. Figure 5 The screen mesh number of the back aluminum electrode printing is 360 meshes, the wire diameter is 16 μm, the yarn thickness is 26 μm, and the film thickness is 20 μm; the sintering temperature is 720 ℃. The technical route of the embodiment can greatly improve the carrier collection effect of the back electrode without negative impact on the back shading area, slurry consumption, and component welding performance, and can improve the photoelectric conversion efficiency of the PERC battery by 0.15%.

[0074] Embodiment 3

[0075] The double-sided battery of the embodiment has the same structure as that of Embodiment 1, and the difference mainly lies in that the number of the aluminum main grid 1 is 15, the width of the aluminum auxiliary grid 2 is 200 μm, and the distance between the adjacent transverse aluminum auxiliary grid 201 and the adjacent longitudinal aluminum auxiliary grid 202 is 1.5 mm. In the embodiment, the number of the segments of the back silver electrode 3 on the same main grid is 14, the width is 1.8 mm, the length is 3.5 mm, the width of the ring-shaped aluminum main grid 102 is 0.5 mm, the width of the inner ring is 1.6 mm, and the length of the inner ring is 4.2 mm. The aluminum fine main grid adopts a three-stage bamboo joint gradual change structure of 0.8 mm / 0.55 mm / 0.22 mm.

[0076] The preparation method of the double-sided battery of the embodiment has the same process operation as that of Embodiment 1, and the difference mainly lies in that the sheet resistance of the positive surface thin layer after diffusion is between 200 Ω / □, and the sheet resistance of the heavily doped region is between 90 Ω / □. Figure 5325 mesh, line diameter 16 μm, yarn thickness 26 μm, film thickness 20 μm; sintering temperature 800℃. The technical route of the present embodiment can greatly improve the carrier collection effect of the back electrode without negative impact on the back shading area, paste consumption, and module welding, etc., and can improve the photoelectric conversion efficiency of the PERC cell by 0.10%.

[0077] Example 4

[0078] The double-sided cell of the present embodiment has substantially the same structure as that of Example 1, and the main difference is that the number of aluminum main grids 1 is 20, the width of the aluminum auxiliary grid 2 is 140 μm, and the distance between adjacent transverse aluminum auxiliary grids 201 and adjacent longitudinal aluminum auxiliary grids 202 is 1.15 mm. In the present embodiment, the number of segments of the back silver electrode 3 on the same main grid is 25, the width is 1.6 mm, the length is 3.8 mm, the width of the ring-shaped aluminum main grid 102 is 0.7 mm, the inner ring width is 1.4 mm, and the inner ring length is 4.8 mm.

[0079] The preparation method of the double-sided cell of the present embodiment has substantially the same process operation as that of Example 1, and the main difference is that the sheet resistance of the thin layer on the front surface after diffusion is between 140 Ω / □, and the sheet resistance of the heavily doped region is between 70 Ω / □. The width of the non-slotted area of the back laser is 2.4 mm, and the length is 5.3 mm. The mesh number of the screen plate during printing of the back aluminum electrode is 360 mesh, the line diameter is 16 μm, the yarn thickness is 26 μm, and the film thickness is 20 μm; the sintering temperature is 765℃.

[0080] The obtained cell structure is shown in Figure 6 The technical route of the present embodiment can greatly improve the carrier collection effect of the back electrode without negative impact on the back shading area, paste consumption, and module welding, etc., and can improve the photoelectric conversion efficiency of the PERC cell by 0.12%.

[0081] Example 5

[0082] The double-sided cell of the present embodiment has substantially the same structure as that of Example 1, and the main difference is that the number of aluminum main grids 1 is 25, the width of the aluminum auxiliary grid 2 is 170 μm, and the distance between adjacent transverse aluminum auxiliary grids 201 and adjacent longitudinal aluminum auxiliary grids 202 is 1.3 mm. In the present embodiment, the number of segments of the back silver electrode 3 on the same main grid is 18, the width is 1.8 mm, the length is 3.8 mm, the width of the ring-shaped aluminum main grid 102 is 0.5 mm, the inner ring width is 1.6 mm, and the inner ring length is 4.5 mm.

[0083] The preparation method of the double-sided battery of the embodiment is basically the same as that of embodiment 1, and the main difference is that the sheet resistance of the thin layer on the front surface after diffusion in the embodiment is between 165 Ω / □, and the sheet resistance of the heavily doped region is between 55 Ω / □. The width of the non-slotted area of the back laser is 2.5 mm, and the length is 5.5 mm. The screen mesh number of the back aluminum electrode printing is 360 meshes, the wire diameter is 16 μm, the yarn thickness is 22 μm, and the film thickness is 20 μm; the sintering temperature is 740 DEG C.

Claims

1. A bifacial cell back electrode comprising an aluminum main grid (1) and an aluminum secondary grid (2), characterized in that: The aluminum main grid (1) is connected by aluminum fine main grid (101) and ring type aluminum main grid (102), wherein the ring type aluminum main grid (102) is distributed along the length direction of the aluminum main grid (1), and both ends of all ring type aluminum main grids (102) are provided with outward diverging aluminum fine main grid (101), the aluminum fine main grid (101) located at the same end of the ring type aluminum main grid (102) is composed of two aluminum fine main grids (101) diverging outward relative to the end of the ring type aluminum main grid (102), and the aluminum fine main grid (101) between adjacent ring type aluminum main grids (102) is connected to form a parallelogram structure; the two sides of the ring type aluminum main grid (102) and the outer side of the aluminum fine main grid (101) are connected with horizontally distributed transverse aluminum auxiliary grid (201), and the inner side of the aluminum fine main grid (101) is connected with vertically distributed longitudinal aluminum auxiliary grid (202).

2. The dual-sided battery back electrode of claim 1, wherein: The width of the aluminum auxiliary grid (2) is 60-200μm, and the interval of adjacent transverse aluminum auxiliary grid (201) and adjacent longitudinal aluminum auxiliary grid (202) is 0.8-1.5mm.

3. A bi-facial cell back electrode as claimed in claim 2, wherein: The width of the aluminum auxiliary grid (2) is 130μm, and the interval of adjacent transverse aluminum auxiliary grid (201) and adjacent longitudinal aluminum auxiliary grid (202) is 1.15mm.

4. A bi-facial cell back electrode according to any one of claims 1-3, characterized in that: The inner part of the ring type aluminum main grid (102) is provided with back silver electrode (3), and the inner ring width is less than the width of the back silver electrode (3), and the number of segments of the back silver electrode (3) on the same main grid is 8-50.

5. A bi-facial cell back electrode as claimed in claim 4, wherein: The width of a single back silver electrode (3) is 1.2-2.2mm, and the length is 1.5-5.5mm; the ring type width of the ring type aluminum main grid (102) is 0.1-1mm, and the inner ring width is 1-2.1mm.

6. A bi-facial cell back electrode as claimed in claim 5, wherein: The number of segments of the back silver electrode (3) on the same main grid is 12, the width of a single back silver electrode (3) is 2.1mm, and the length is 2.7mm; the ring type width of the ring type aluminum main grid (102) is 0.4mm, and the inner ring width is 1.9mm.

7. A bi-facial cell back electrode as claimed in any one of claims 1 to 3, wherein: The number of the aluminum main grid (1) is greater than or equal to 9, and each aluminum main grid is distributed in parallel.

8. A bi-facial cell back electrode as claimed in any one of claims 1 to 3, wherein: The aluminum fine main grid (101) adopts a bamboo joint gradual change structure.

9. A bi-facial cell back electrode as claimed in claim 8, wherein: The gradual change specification between adjacent bamboo joints of the aluminum fine main grid (101) is 0.06-1.0mm.

10. The bi-facial cell back electrode of claim 8, wherein: The aluminum fine main grid (101) adopts a three-stage bamboo joint gradual change specification of 0.4mm / 0.35mm / 0.13mm.

11. A method of producing a back electrode of a bifacial cell according to any one of claims 1 to 10, characterized by: The back silver electrode area and the aluminum fine main grid area of the back electrode are laser grooved at the corresponding positions, the silver electrode area and the ring type aluminum main grid area are not laser grooved, and then the aluminum electrode and the back silver electrode are prepared by screen printing.

12. The method of claim 11, wherein: The non-grooving area (5) corresponding to the silver electrode area and the ring type aluminum main grid area is a rectangle, the width is 3.1mm, and the length is 5mm.

13. The method of claim 11, wherein: When the aluminum electrode is prepared by screen printing, the screen plate specification is: screen plate mesh 300-400 mesh, wire diameter 12-20μm, yarn thickness 20-30μm, and film thickness 15-25μm.

14. The back electrode according to any one of claims 1-10 is applied in an MBB double-sided battery.

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