A battery piece, a battery string group, a battery module
By setting an anti-reflective layer on the TCO layer and metal grid lines of the solar cell and improving optical alignment, the problems of ITO layer thickness and metal grid line oxidation were solved, resulting in cost reduction and performance improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SUZHOU JBAO TECH LTD
- Filing Date
- 2025-04-25
- Publication Date
- 2026-06-16
AI Technical Summary
Traditional solar cells have difficulty reducing the thickness of the ITO layer to decrease the amount of indium used. At the same time, the metal grid lines are prone to oxidation, resulting in low cell efficiency and weak welding bonding, which affects the performance of battery strings and modules.
An anti-reflective layer is set on the TCO layer and metal grid lines of the solar cell, and part of the anti-reflective layer is removed at the location to be welded to increase the welding layer, thereby improving the optical alignment and positioning accuracy and welding quality.
It reduces the amount of indium used, improves carrier conduction speed and cell efficiency, prevents oxidation of metal grid lines, ensures welding bonding strength, and enhances the overall performance of battery strings and modules.
Smart Images
Figure CN224368231U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of photovoltaic products, and in particular to a battery cell, battery string, and battery module. Background Technology
[0002] Traditional solar cells typically involve depositing a TCO layer 200 on both the N-side and P-side of a silicon wafer 100, with the TCO layer usually being an ITO layer. Metal grid lines 300 are then fabricated on the TCO layers, and subsequently soldered to the metal grid lines 300 using solder-coated wire rods 400 (e.g.,...). Figure 1 (As shown).
[0003] In this type of traditional solar cell, the ITO layer has two main functions: as a conductive layer and as a light-transmitting layer. The ITO layer laterally transmits the electron flow generated by the photoelectric effect, which is then collected, converged, and discharged through metal grid lines. Theoretically, the thinner the ITO film, the less scattering electrons encounter, the faster the carrier conduction, and thus the better the conductivity. Furthermore, since a major component of the ITO layer is indium, which is very expensive, a thinner ITO film requires less indium, thus reducing costs. However, if the ITO layer is too thin, light can easily penetrate and be reflected back, resulting in less light energy being retained by the cell and thus lower efficiency. Therefore, to maintain the current cell efficiency, the ITO layer cannot be made thinner, and consequently, the amount of indium used cannot be reduced, and thus cannot be reduced further.
[0004] Furthermore, because the metal grid lines have no protection, they are prone to oxidation due to contact with moisture and oxygen in the air. This not only affects the conductivity of the metal grid lines, but also causes great problems for subsequent stringing. After stringing, the bond strength between the oxidized copper metal grid lines and the stringing electrodes is much weaker, which ultimately leads to a reduction in the performance of the entire battery string and battery module.
[0005] Furthermore, during string soldering, ideally the soldering electrode should fall precisely on the copper metal grid lines to be soldered (e.g., Figure 1As shown), because the welding rod is generally circular, the advantage of a circular welding rod is that after the light from the solar cell is reflected onto the circular welding rod, it can be reflected again to the surface of the solar cell, resulting in a process of localized incident light (the source of photoelectric conversion) and localized reflection. Thus, the light-shielding area of the circular welding rod is much smaller than its diameter, which also reduces the light-shielding area between the welding rod and the copper metal grid lines. However, because the width of the metal grid lines on traditional solar cells is becoming increasingly thinner to reduce the light shading, and because the tops of the parts that need to be welded to the welding rod and the parts that do not need to be welded to the welding rod are the same, it is difficult to accurately position the metal grid lines to be welded to the welding rod during stringing. Therefore, in traditional stringing, the optical positioning mechanism on the stringing machine can only position the four edges of the solar cell, which inevitably leads to a misalignment of the welding rod position relative to the metal grid lines. If the welding rod is still on the metal grid lines but only offset to one side (e.g....), Figure 2 As shown), the two can still be welded, but the weld bond is extremely weak, and they are prone to detachment, thus affecting the quality of the battery string assembly and subsequent battery modules; if the welding electrode falls directly on the TCO layer (such as... Figure 3 As shown in the diagram, in addition to the weak weld bond mentioned above, the contact resistance at the string weld joint will also increase significantly, thus affecting the conductivity and the efficiency of the solar cell. Furthermore, regardless of the type of offset, it will lead to an increase in the shading area, further reducing the efficiency of the solar cell.
[0006] Moreover, traditional battery cells do not have a welding layer on their copper metal grid lines; the welding layer is only on the welding rods. If the solder on the welding rods is heated unevenly, the melting coverage will be uneven, which will reduce the welding bond strength and may even lead to poor soldering, thus affecting the overall performance of the battery string and battery module. Utility Model Content
[0007] The purpose of this utility model is to overcome the above-mentioned shortcomings and provide a battery cell, battery string, and battery module that have low manufacturing costs and guaranteed performance.
[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:
[0009] A solar cell includes a silicon wafer, an N-doped layer, a TCO layer, and copper metal grid lines sequentially disposed on the front side of the silicon wafer, and a P-doped layer, a TCO layer, and copper metal grid lines sequentially disposed on the back side of the silicon wafer. The copper metal grid lines are provided with a bonding layer, wherein a portion of the copper metal grid lines are configured as metal bonding wires to be wired for bonding. Except for the top of the bonding layer on the portion of the copper metal grid lines, the other areas of the front and back sides of the solar cell are covered with an anti-reflective layer.
[0010] The anti-reflective layer is configured as a silicon nitride layer, a silicon oxide layer, or a tin oxide layer.
[0011] The thickness of the anti-reflective layer is 5nm-50nm.
[0012] The thickness of the TCO layer is 5nm-150nm.
[0013] The TCO layer is an AZO layer, an IWO layer, or an ITO layer.
[0014] The welding layer is set as a solder layer, and the thickness of the welding layer is 0.1um-5um.
[0015] A seed layer is also provided between the copper metal gate line and the TCO layer.
[0016] A battery string assembly includes a welding rod and at least two battery cells, wherein the welding rod is stacked and connected to the exposed copper metal grid lines to be welded.
[0017] The outer surface of the welding rod is covered with a layer of solder.
[0018] A battery module includes the aforementioned battery cells or the aforementioned battery string assembly.
[0019] Because this utility model adopts the above-mentioned technical solution, it has the following beneficial technical effects:
[0020] 1. The TCO layer without metal grid lines is covered by the anti-reflective layer, which is equivalent to replacing the traditional TCO layer with "one TCO layer + one anti-reflective layer" in this invention. The anti-reflective layer reduces light reflectivity, allowing the TCO layer to be made thinner than in a traditional cell. This not only reduces the amount of indium used, thus lowering the manufacturing cost of the cell, but also shortens the carrier transport distance, thereby increasing the carrier conduction speed and improving the efficiency of this invention.
[0021] 2. The anti-reflective layer can isolate the TCO layer from moisture and oxygen in the air, thereby ensuring the stability of the ITO layer's performance, which in turn ensures the stability of the cell's performance.
[0022] 3. The anti-reflective layer on the weld layer of the metal grid line that does not need to be welded to the welding rod is not removed. Therefore, this part of the metal grid line is completely covered under the anti-reflective layer. That is, the anti-reflective layer isolates this part of the metal grid line from the moisture and oxygen in the air, thereby preventing the metal grid line from oxidizing. Although the anti-reflective layer on the copper metal grid line to be welded is removed, because there is a weld layer on it, and its two sides and the two sides of the weld layer are still covered with anti-reflective layers, the weld layer and the anti-reflective layer together isolate the metal grid line to be welded to the welding rod from the moisture and oxygen in the air, preventing it from being oxidized and affecting the firmness of the subsequent welding.
[0023] 4. Because the anti-reflective layer on the metal grid lines to be welded to the wire rod is removed, the welding layer on these copper metal grid lines is exposed, without the need to remove the anti-reflective layer on the welding layer of the metal grid lines to be welded to the wire rod. Thus, the entire cell will only expose the grid lines to be welded, and these grid lines will form a higher resolution optical contrast with the background color of the overall cell. Therefore, during subsequent wire welding alignment, the actual grid line position to be welded can be used instead of the original edge of the cell as the optical alignment reference, thereby achieving more accurate wire welding positioning and avoiding the wire rod from shifting relative to the copper metal grid lines to be welded, thus avoiding problems caused by the wire rod shift.
[0024] 5. After the aforementioned optical alignment system performs more precise stringing positioning based on the location of the copper metal grid lines to be strung, even if there are still slight offsets, the slight offsets can be corrected by the micro-traction phenomenon between the same material when the welding layer on the grid lines and the solder on the stringing rod are made of the same tin material, because the two are fused by heating. Furthermore, since both contact layers are in a molten state, faster and better bonding can be achieved, thereby further reducing the occurrence of stringing offsets and ensuring more precise stringing alignment; thus ensuring the bonding strength after stringing, reducing the light shading rate of the solar cells, ensuring the light absorption rate of the solar cells, that is, ensuring the efficiency of the solar cells, and thus ensuring the overall performance of the battery string and battery module.
[0025] 6. Because the copper metal grid lines to be welded to the welding rods have a welding layer, even if the solder on the welding rods is heated unevenly during the welding process, resulting in uneven molten coverage, the solder in the welding layer on the copper metal grid lines will also melt. This improves the uniformity of the overall solder molten coverage, allowing for more uniform and faster welding, reducing the possibility of incomplete welds, and further improving the welding bond between the copper metal grid lines and the welding rods, thus ensuring the overall performance of the battery string and battery module. Attached Figure Description
[0026] Figure 1 This is a schematic diagram illustrating the precise alignment of welding electrodes for traditional solar cells.
[0027] Figure 2 This is a schematic diagram illustrating the positional deviation between the welding rods and the metal grid lines to be welded in a traditional solar cell.
[0028] Figure 3 This is a schematic diagram showing the deviation of the wire bonding electrode of a traditional solar cell falling onto the TCO layer;
[0029] Figure 4 This is a schematic diagram of the battery cell of this utility model;
[0030] Figure 5 This is a schematic diagram of the battery cell of this utility model after the seed layer has been deposited;
[0031] Figure 6 This is a schematic diagram of the battery cell of this utility model after the patterned mask layer has been prepared;
[0032] Figure 7 This is a schematic diagram of the battery cell of this utility model after the copper metal grid lines and welding layers are fabricated;
[0033] Figure 8 This is a schematic diagram of the battery cell of this utility model after the mask layer and seed layer have been removed;
[0034] Figure 9 This is a schematic diagram of the battery cell after the anti-reflection layer has been deposited.
[0035] Figure 10 This is a schematic diagram of the battery string assembly of this utility model. Figure 1 ;
[0036] Figure 11 This is a schematic diagram of the battery string assembly of this utility model. Figure 2 ;
[0037] Figure 12 This is a schematic diagram of a traditional solar cell;
[0038] Figure 13 This is a schematic diagram of the battery cell used in this application;
[0039] Figure 14 This is a schematic diagram of the battery string assembly of the present invention;
[0040] Figure 15 This is a schematic diagram showing a misaligned solder joint in a traditional battery string assembly. Detailed Implementation
[0041] The preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings.
[0042] like Figure 4As shown, this utility model discloses a solar cell 500, which includes a silicon wafer 1, an N-doped layer 2, a TCO layer 4, and copper metal grid lines 5 sequentially disposed on the front side of the silicon wafer 1, and a P-doped layer 3, a TCO layer 4, and copper metal grid lines 5 sequentially disposed on the back side of the silicon wafer 1. The copper metal grid lines 5 are provided with a welding layer 6, wherein a portion of the copper metal grid lines 5 is set as metal grid lines to be wired together, that is, set as wires to be wired together with wire bonding rods 11. Except for the top of the welding layer 6 on the portion of the copper metal grid lines 5, the other areas of the front and back sides of the solar cell 500 are covered with an anti-reflection layer 7. That is, only the top of the welding layer 6 on the copper metal grid lines 5 to be wired together is not covered by the anti-reflection layer 7.
[0043] The TCO layer 4 can be configured as an AZO layer, an IWO layer, or an ITO layer. When the TCO layer 4 is a single AZO layer, it is preferable to use an AZO material with a ratio of (ZnO:Al2O3=90:10)-(ZnO:Al2O3=99:1).
[0044] When the TCO layer 4 is a single IWO layer, preferably, an IWO material with a ratio of (In2O3:W=90:10) to (In2O3:W=99:1) is used. When the TCO layer 4 is a single ITO layer, preferably, an ITO material with a ratio of (In2O3:SnO2=90:10) to (In2O3:SnO2=99:1) is used.
[0045] In other embodiments, the TCO layer 4 may also be a composite layer of two or three of AZO, IWO, and ITO.
[0046] The thickness of the TCO layer 4 is 5nm-150nm. Preferably, the thickness of the TCO layer 4 can be 10, 15, 20, 30, 35, 40, 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 140 or 145nm.
[0047] The anti-reflection layer 7 can be configured as a silicon nitride layer, a silicon oxide layer, or a tin oxide layer, which can reduce the reflectivity of light.
[0048] The thickness of the anti-reflective layer 7 is 5nm-150nm, preferably 5nm-50nm. Further, the thickness of the anti-reflective layer 7 is set to 10, 20, 30, 40, 60, 70, 80, 90, 100, 120, 130, or 140nm.
[0049] The thickness of the TCO layer 4 and the anti-reflection layer 7 are set as described above, so that the overall refractive index of the battery cell can be maintained between 2.0% and 2.1%. The low refractive index can improve the light energy retention rate and thus improve the efficiency of the battery cell.
[0050] The thickness of the copper metal gate line 5 is 5um-25um; preferably, the thickness of the copper metal gate line 5 is 6um-8um. The thickness of the copper metal gate line 5 can also be 10, 12, 15, 18, 20, 22, or 24um. The width of the metal gate line to be wire-welded ranges from 10um to 300um, thus allowing for better adaptation to the wire-welding electrode 11. In this embodiment, the metal gate line includes a main gate 51 and a fine gate 52 (combined with...). Figure 4 and Figure 11 As shown in the figure, the width of the main grid 51 is 50-100 μm, and the width of the fine grid 52 is 15 μm; the main grid 51 is configured to be subsequently welded to the welding rod 11. In other embodiments, other grid lines can also be configured as metal grid lines to be welded according to actual needs.
[0051] In this embodiment, the welding layer 6 is set as a solder layer, balancing welding performance and cost. The thickness of the welding layer 6 is 0.1um-5um. Preferably, the thickness of the welding layer 6 is 0.5um-1um. The thickness of the welding layer 6 can also be 0.2, 0.8, 1.5, 2, 2.5, 3, 3.5, 4, or 4.5um. In other embodiments, the welding layer 6 can also be made of other welding materials.
[0052] In this embodiment, preferably, a seed layer 8 is further disposed between the copper metal grid line 5 and the TCO layer 4, and the thickness of the seed layer 8 is in the range of 5nm-150nm. The seed layer 8 can enhance the bonding force between the copper metal grid line 5 and the TCO layer 4, so that the copper metal grid line 5 is not easily detached from the solar cell, thereby ensuring the photoelectric conversion efficiency of the solar cell.
[0053] The battery cell can be prepared according to the following steps:
[0054] S1. Prepare a solar cell with a pre-fabricated P-doped layer 3 and N-doped layer 2. Deposit an ITO layer on the P-doped layer 3 and N-doped layer 2 to obtain the TCO layer (e.g., ...). Figure 5 (as shown)
[0055] S2. Prepare a patterned mask layer 9 to obtain trenches 10 (e.g., Figure 6 (as shown)
[0056] S3, Electroplating copper metal grid lines 5 (such as...) within the trench 10 Figure 7 (as shown)
[0057] S4. Deposit a solder layer 6 (e.g., on each copper metal grid line 5) on each copper metal grid line 5. Figure 7 (as shown)
[0058] S5, Remove mask layer 9 (e.g.) Figure 8 (as shown)
[0059] S6. Deposit an anti-reflective layer 7 on the solar cell (e.g.) Figure 9 (as shown)
[0060] S7. Remove the anti-reflective layer 7 from the portion of the welding layer 6 to be welded to the welding rod 11, thereby obtaining the battery cell of this utility model.
[0061] In step S1, the solar cell with the prepared P-doped layer 3 and N-doped layer 2 can be fed into a PVD device for TCO layer deposition to obtain the TCO layer. During the deposition operation, the PVD deposition power is set to 1KW-10KW, and the deposition time is 30 seconds-600 seconds.
[0062] The TCO deposition layer can be obtained by depositing a single TCO material among AZO, IWO, or ITO, or by depositing a composite TCO material of two or three of AZO, IWO, and ITO.
[0063] In one embodiment, ITO material with the above-mentioned ratio is used for deposition, and the deposition power is set to 1KW and the deposition time is 1 minute, so that an ITO layer with a thickness of 35nm can be obtained.
[0064] In step S2, a mask layer 9 is coated onto the battery cell, and after curing the mask layer 9, exposure and development operations are performed to obtain a patterned mask layer 9 (e.g., ...). Figure 6 (As shown). In this embodiment, the thickness of the mask layer 9 is 13um-15um.
[0065] Specifically, a mask is applied to the battery cells after the previous steps using a printing process, and then dried and cured under atmospheric conditions. During curing, the temperature is set to 90°C. o C-100 o C, curing time is 400-750 seconds.
[0066] The exposure can be performed using a direct-write exposure machine (commonly known as LDI), and during exposure, the wavelength range is 355nm-365nm, and the exposure energy range is 145mj / cm2-150mj / cm2, thereby completing the pattern transfer process.
[0067] The developing process uses a sodium carbonate developing solution with a concentration of 1.2%-1.5% and a developing temperature of 30°C. o C-35 oC, the spray pressure range is 3.0Kg / cm2-3.5Kg / cm2, and the development time is 150-280 seconds.
[0068] If the seed layer 8 is not set, the patterned mask layer 9 is prepared on the TCO. If the seed layer 8 is set, the patterned mask layer 9 is prepared on the seed layer 8.
[0069] After the patterned mask layer 9 is prepared, a groove 10 is naturally formed between the mask layer 9 and the battery cell, in preparation for the subsequent electroplating of copper metal grid lines 5.
[0070] The electroplated copper metal grid line 5 in step S3 can be produced using any known and feasible technology, so it will not be described in detail here.
[0071] In step S4, depositing the solder layer 6 can be achieved using an electroplating process, whereby the solder layer 6 is electroplated onto each copper metal gate line 5 (e.g., ...). Figure 7 (As shown); alternatively, the battery cell with the prepared copper metal grid 5 can be fed into a PVD device for chemical deposition of the welding layer 6.
[0072] During PVD deposition, the deposition power was set to 1.5-2.5 kW, and the deposition temperature was 150-260 °C. o C, the deposition time is 180-360 seconds. Preferably, the power is set to 2KW and the deposition temperature is 200℃. o C, deposition time is 300 seconds.
[0073] In step S5, the mask layer 9 can be removed using sodium carbonate with a concentration of 2.8% to 3% at a temperature of 60°C. o C~65 o C, injection pressure is 3.0Kg / cm2~3.5Kg / cm2, time is 220-360 seconds.
[0074] In step S6, the solar cell that has completed the previous steps is loaded into a vacuum deposition apparatus (including but not limited to PECVD, PVD, and CVD) to deposit an anti-reflection layer 7. The anti-reflection layer 7 may be, but is not limited to, a silicon nitride (SiNx) layer, a tin oxide (SnOx) layer, or a silicon oxide (SiOx) layer.
[0075] When preparing the silicon nitride antireflective layer 7, it can be obtained through PEVCD deposition. Specifically, the solar cell, after completing the preceding steps, is loaded into a plasma-enhanced chemical vapor deposition (PECVD) apparatus to deposit the silicon nitride layer. The deposition conditions are set as follows: temperature 180°C. o C~200 oAt pressure C, the gas precursors are silane (SiH4), ammonia (NH3), and nitrogen (N2), with a flow rate ratio of SiH4:NH3:N2 = 1:5:5; the radio frequency (RF) power is 38W~58W, the RF frequency is 13.56 MHz, and the deposition time is 200~400 seconds. Thus, a silicon nitride layer with a thickness of 5~50 nm can be obtained.
[0076] The silicon nitride antireflective layer 7 can also be obtained by CVD chemical vapor deposition. Specifically, the solar cell that has completed the preceding steps is loaded into the CVD equipment, and the deposition conditions are set as follows:
[0077] Using SiH4 as the silicon source and ammonia (NH3) as the nitrogen source, with a SiH4 to NH3 flow rate ratio of 1:3 to 1:5 and a total flow rate of 5–70 sccm, and oxygen as the oxygen source, with an oxygen flow rate of 50–500 sccm, the deposition temperature is set to 200–800℃, and the deposition time is set to 30–600 seconds. This yields silicon nitride layers with a thickness of 5 nm–10 nm.
[0078] When preparing the silicon oxide antireflective layer 7, it can be obtained by CVD chemical vapor deposition. The solar cell that has completed the previous steps is loaded into the CVD equipment for deposition, and the deposition conditions are set as follows:
[0079] Using SiH4 as the silicon source, the SiH4 flow rate is 5~70 sccm; using oxygen as the oxygen source, the oxygen flow rate is 50~500 sccm; the deposition temperature is 200℃~800℃, the deposition time is 30sec~600sec, and a silicon oxide antireflection layer 7 is generated, with a thickness of 5nm-10nm.
[0080] To prepare the tin oxide antireflective layer 7, it can be fabricated using vacuum deposition (PVD) with a tin oxide target. During deposition, the power is set to 1 kW to 2 kW, the deposition temperature to 180°C to 200°C, and the deposition time to 30 to 300 seconds. This yields the tin oxide antireflective layer 7 with a thickness of 5 nm to 65 nm.
[0081] In step S7, since a portion of the copper metal grid line 5 is configured to be welded to the welding rod 11 in subsequent operations, the welding layer 6 of this portion of the copper metal grid line 5 needs to be exposed and not covered by the anti-reflective layer 7. Therefore, the anti-reflective layer 7 at the corresponding position needs to be removed.
[0082] The anti-reflective layer 7 can be removed using laser, preferably using a picosecond laser with a wavelength of 355nm ultraviolet light. During operation, the solar cell is fed into a picosecond laser with a wavelength of 355nm ultraviolet light, and the parameters for removing the anti-reflective layer using the picosecond laser are set as follows: power density 1.0-3.0 J / cm², frequency 50-150kHz, spot size 10µm-50µm, and scanning speed 0.5-2 m / s.
[0083] In one embodiment, the optical power density is set to 1.3 J / cm², the frequency is set to 100 kHz, the spot width is 35 μm or 50 μm, and the scanning speed is 2 m / s.
[0084] In another embodiment, the optical power density of the picosecond laser device is set to 1.2 J / cm², the frequency is set to 80 kHz, the spot width is set to 30 μm, and the scanning speed is 1.5 m / s.
[0085] In another embodiment, the optical power density of the picosecond laser device is set to 1.3 J / cm², the frequency is set to 150 kHz, the spot width is 30 μm, and the scanning speed is set to 2 m / s.
[0086] The picosecond laser device described above scans the positions of the copper metal grid lines 5 to be strung on the solar cell, removing the anti-reflective layer 7 from these copper metal grid lines 5 and exposing the solder layer. Thus, among all the copper metal wires, the top of the copper metal wires to be strung is free of the anti-reflective layer 7, while the tops of the other copper metal grid lines 5 are still covered by the anti-reflective layer 7. That is to say, only the grid lines to be strung are exposed on the entire solar cell, and these grid lines create a higher resolution optical contrast with the overall background color of the solar cell. Therefore, during subsequent optical alignment during stringing, the actual grid line positions to be strung can be used instead of the original edge of the solar cell as the optical alignment reference, thereby achieving more precise stringing positioning.
[0087] Furthermore, because the main grid is set as copper metal grid lines to be soldered, after removing the anti-reflective layer 7 on top, the fine grids on the solar cell are almost invisible to the naked eye (e.g., Figure 13 As shown, the vertical lines represent the main grid, and the horizontal lines represent the fine grid. Only the main grid after the anti-reflective layer has been removed using a laser is clearly visible. This differs from traditional solar cells (such as...). Figure 12 The difference (as shown) is very obvious, from Figure 12 As can be seen, the fine grids on traditional solar cells are also very obvious. Compared to the past, the solar cells produced by the method of this invention are more aesthetically pleasing and have less color difference.
[0088] If the seed layer 8 is provided, then the seed layer 8 is deposited on the TCO layer after step S1 and before step S3. Specifically, the solar cell with the ITO layer already formed is loaded into the PVD equipment, and the seed layer 8 deposition process is performed on the TCO layer. This seed layer 8, like the TCO layer, is a continuous, single layer (e.g., ...). Figure 5 (As shown). Seed layer 8 includes, but is not limited to, deposits of metals such as gold, silver, copper, titanium, nickel, tungsten, and bismuth, or deposits of their alloys.
[0089] When depositing the seed layer 8, the deposition conditions are set as follows: power of 1KW-10KW and deposition time of 30 seconds-600 seconds. In one embodiment, taking the seed layer 8 as a copper metal layer as an example, the power is set to 3KW and the deposition time is set to 3 minutes, thus obtaining a copper seed layer 8 with a thickness of 100nm covering the ITO layer.
[0090] Furthermore, if the seed layer 8 is provided, the excess seed layer 8 needs to be removed after removing the mask layer 9 and before preparing the anti-reflection layer 7. Specifically, the seed layer 8 not located between the copper metal gate line 5 and the TCO layer 4 is removed, and only the seed layer 8 between the copper metal gate line 5 and the TCO layer 4 is retained (e.g., Figure 4 , 8 (As shown).
[0091] Excess seed layer can be removed using sulfuric acid at a concentration of 1%-2% and a temperature of 30°C. o C-35 o C, spray pressure is 1-1.5Kg / cm2, time is 50-300 seconds.
[0092] Each of the above steps is for processing one side of the solar cell. To process both sides, one side is processed first, and then the other side is processed.
[0093] like Figure 10 , 11 As shown, this utility model also discloses a battery string assembly, which includes a welding rod 11 and at least two of the aforementioned battery cells. The welding rod 11 is stacked and connected to the exposed welding layer 6 of the copper metal grid line 5 to be welded, that is, stacked on the welding layer 6 on top of the copper metal grid line 5 to be welded. In this embodiment, because the main grid is set as the copper metal grid line to be welded, the welding rod 11 is stacked and connected to the main grid.
[0094] To prepare the battery string assembly, at least two battery cells are fed into a string welding machine and aligned. Then, a string welding rod 11 is placed on the exposed welding layer 6 of the copper metal grid line 5 to be stringed, so that the string welding rod 11 is in contact with the welding layer 6 of the copper metal grid line 5 to be stringed. Then, the string welding process is performed to obtain the battery string assembly.
[0095] In this embodiment, preferably, because the metal grid lines to be strung on the battery cell of the present invention form a higher resolution optical contrast with the overall background color of the battery cell, the optical alignment system of the stringer can optically position the battery cell according to the location of the copper metal grid lines 5 to be strung on. That is to say, the basis of optical positioning is changed from the four edges of the traditional battery cell to the welding layer 6 exposed on top of the copper metal grid lines 5 to be strung on. In this way, the position where the stringer bars 11 are to be stacked can be more accurately positioned, thereby avoiding a large offset between the stringer bars 11 and the copper metal grid lines 5 to be strung on, and thus avoiding problems caused by the offset of the stringer bars 11. The above optical alignment principle is a well-known technology, so it will not be described in detail here.
[0096] The heat source of the stringer is infrared radiation. During stringing, the infrared wavelength is set to 0.76μm-1.6μm, the temperature is set to 80℃-200℃, and the infrared irradiation time is 2-5 seconds. In one embodiment, after the solar cells are loaded onto the stringer and optically aligned, the temperature is set to 130℃. o C. The downward pressure is set to 1.5 kg / cm. 2 The battery cells and the welding rod 11 were welded together under the condition of an irradiation time of 3 seconds.
[0097] The soldering bar 11 is circular with a diameter of 120µm-250µm, and its outer surface is covered with a layer of solder with a thickness of 1µm-10µm. Preferably, the solder is made of the same material as the welding layer 6 on the copper metal grid line 5, i.e., solder. With this configuration, after the aforementioned optical alignment system performs more precise soldering positioning based on the location of the copper metal grid line 5 to be soldered, even if there is still a slight offset, the slight offset can be corrected by the micro-traction phenomenon between the same material when the welding layer on the grid line and the solder on the soldering bar are made of the same tin material and are fused together by heating. Furthermore, since both contact layers are in a molten state, faster and better bonding can be achieved, thereby further reducing the occurrence of soldering offset and ensuring more precise soldering alignment. Figure 14 The image shows the battery string assembly after precise alignment and welding according to the present invention; as shown Figure 15 The diagram shown illustrates the issue of misaligned solder joints in traditional battery string arrays. Figure 15It is evident that there is a significant positional misalignment between the welding rod and the metal grid lines to be welded. Precise alignment of the two avoids the problem of increased shading rate of the solar cells caused by the misalignment of the welding rod 11, ensuring the light absorption rate of the solar cells, i.e., ensuring the efficiency of the solar cells, and thus ensuring the overall performance of the battery string assembly; it also ensures the bonding strength after welding. Furthermore, because the copper metal grid lines 5 to be welded have a welding layer 6, even if the solder on the welding rod 11 is heated unevenly during welding, resulting in uneven melting and coverage, the solder on the welding layer 6 of the copper metal grid lines 5 will also melt. Thus, the solder from both parts can completely cover the welding surface of the welding rod and the copper metal grid lines, reducing the possibility of incomplete welding, thereby improving the welding bonding strength between the copper metal grid lines 5 and the welding rod 11, further ensuring the overall performance of the battery string assembly.
[0098] As described above, because the areas of the TCO layer 4 of the present invention without metal grid lines are all covered by the anti-reflection layer 7, it is equivalent to replacing the single TCO layer 4 of a conventional battery cell with "one TCO layer 4 + one anti-reflection layer 7" of the present invention. The anti-reflection layer 7 can reduce light reflectivity, thus allowing the TCO layer 4 of the present invention to be made thinner than that of a conventional TCO layer 4, with a thickness selectable within the range of 5nm-150nm. This not only reduces the amount of indium used, thereby reducing the manufacturing cost of the battery cell, but also shortens the carrier transport distance, thereby increasing the carrier conduction speed, thus improving the performance of the present invention's battery cell. Efficiency; moreover, the anti-reflective layer 7 can isolate the TCO layer 4 covering it from moisture and oxygen in the air, thereby ensuring the stability of the ITO layer performance, that is, ensuring the stability of the cell performance; in addition, the anti-reflective layer 7 can isolate the copper metal grid line 5 covering it from moisture and oxygen in the air, thereby preventing the metal grid line from oxidizing; although the anti-reflective layer 7 on the copper metal grid line to be wired is removed, because there is a welding layer 6 on it, and its two sides and the two sides of the welding layer 6 are still covered by the anti-reflective layer 7, the welding layer 6 and the anti-reflective layer 7 together isolate the metal grid line to be wired with the wired welding rod 11 from moisture and oxygen in the air, preventing it from being oxidized and affecting the firmness of the subsequent wired welding, thereby ensuring the performance of the battery string.
[0099] This utility model also discloses a battery module, which includes the above-mentioned battery cells or battery strings.
[0100] To prepare the battery module, the battery string group, encapsulation mold, backplate, and glass are arranged according to the lamination process requirements and then the components are laminated. The lamination time is set to 5 minutes to 30 minutes, the lamination temperature is 180℃ to 220℃, and the lamination pressure is 0.5MPa to 1.5MPa to obtain the battery module.
[0101] In one embodiment, the lamination time is 20 minutes and the lamination temperature is 200°C. o C, lamination pressure is 1.0 MPa.
[0102] In other embodiments, the lamination time can be set to 8, 10, 15, 18, 22, 25 or 28 minutes, the lamination temperature can be set to 190, 195, 205, 210 or 215°C, and the lamination pressure can be set to 0.8, 0.9, 1.2, 1.3 or 1.4 MPa.
[0103] The lamination process can be a conventional technical solution, so it will not be described in detail here.
[0104] Because the battery cells and battery strings of this utility model have the aforementioned beneficial technical effects, the battery module of this application also has the corresponding beneficial technical effects.
[0105] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.
Claims
1. A battery cell, characterized in that: The cell includes a silicon wafer, an N-doped layer, a TCO layer, and copper metal grid lines sequentially disposed on the front side of the silicon wafer, and a P-doped layer, a TCO layer, and copper metal grid lines sequentially disposed on the back side of the silicon wafer. The copper metal grid lines are provided with a bonding layer, and some of the copper metal grid lines are set as metal bonding wires to be wired for bonding. Except for the top of the bonding layer on the copper metal grid lines, the other areas of the front and back sides of the cell are covered with an anti-reflective layer.
2. The battery cell according to claim 1, characterized in that: The anti-reflective layer is configured as a silicon nitride layer, a silicon oxide layer, or a tin oxide layer.
3. The battery cell according to claim 1 or 2, characterized in that: The thickness of the anti-reflective layer is 5nm-50nm.
4. The battery cell according to claim 3, characterized in that: The thickness of the TCO layer is 5nm-150nm.
5. The battery cell according to any one of claims 1 to 2 and 4, characterized in that: The TCO layer is an AZO layer, an IWO layer, or an ITO layer.
6. The battery cell according to any one of claims 1 to 2 and 4, characterized in that: The welding layer is set as a solder layer.
7. The battery cell according to claim 6, characterized in that: The thickness of the weld layer is 0.1um-5um.
8. The battery cell according to any one of claims 1 to 2, 4, and 7, characterized in that: A seed layer is also provided between the copper metal gate line and the TCO layer.
9. A battery string assembly, characterized in that: It includes a welding rod and at least two battery cells as claimed in any one of claims 1 to 8, wherein the welding rod is stacked and connected to the exposed copper metal grid line to be welded.
10. The battery string pack according to claim 9, characterized in that: The outer surface of the welding rod is covered with a layer of solder.
11. A battery module, characterized in that: Includes the battery cell as claimed in any one of claims 1 to 8 or the battery string as claimed in any one of claims 9 to 10.