Processing method of main-grid-free photovoltaic cell and photovoltaic cell

Abstract

A processing method of a main-grid-free photovoltaic cell comprises the following steps: step S1, providing a plurality of battery packs and welding foils, and superposing the welding foils and the battery packs; s2, a first laser is adopted to carry out fusion welding on the welding foil according to a first preset pattern, and therefore conduction between the welding foil and the thin grid lines of all the battery packs is achieved; wherein the first preset pattern is a track formed by connecting non-main-grid battery pieces of each battery pack in series; s3, cutting the welding foil by adopting a second laser according to a second preset pattern so as to process integrated welding foil belts and welding foil strips on the plurality of battery packs, so that a plurality of battery strings are formed by the plurality of welding foil belts, and the plurality of battery strings are connected in parallel by the welding foil strips to form batteries; wherein the second preset pattern comprises contour lines of the welding foil strip and the welding foil strip. The invention also provides a main-grid-free photovoltaic cell using the method. Compared with the prior art, the method provided by the invention can simplify the production process, improve the production efficiency and reduce the production cost.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic cells, and in particular relates to a processing method of a main grid-free photovoltaic cell and a photovoltaic cell manufactured by the method. Background Art

[0002] Zero Bus Bar (0BB) photovoltaic cells have no main grid, which can reduce their electrode area, reduce the series resistance and dark current density of photovoltaic cells, and effectively improve their conversion efficiency (about 0.7-1%) and fill factor. Through the reasonable combination of components, the final photovoltaic cell can achieve a power increase of more than 3-5W. In addition, 0BB technology can also simplify the grid line printing process, reduce silver paste consumption, effectively reduce production and equipment costs, and reduce battery costs by about 3-5%. Therefore, the development and optimization of 0BB technology has important research significance and practical value for achieving efficiency improvement and cost reduction of photovoltaic cells.

[0003] At present, 0BB technology can be mainly divided into four routes: welding dispensing, dispensing, laminating, and SmartWire. Among them, for the three routes of welding dispensing, dispensing and SmartWire, the welding dispensing route is a high-temperature process, which has high requirements for the welding system and requires the use of glue and low-temperature solder tape (the use of traditional solder tape requires a higher welding temperature, which is easy to damage the skin membrane and even affect the entire component and the performance of the component); both welding dispensing and dispensing require dispensing, which is done through a needle, with slow speed and poor uniformity; the SmartWire route requires prefabricated copper wire composite film with embedded circular copper welding tape, which has high process complexity and high material cost, and the copper wire composite film is prone to cause more serious optical occlusion. For the above four routes, on the one hand, they all require solder tape fixing materials (such as solder dispensing and dispensing use glue, laminating uses adhesive film, and SmartWire uses copper wire composite film) to fix the solder tape to the battery cell to avoid dislocation of the solder tape during handling and transfer, resulting in poor welding in the later stage. However, the use of solder tape fixing materials greatly increases the material cost. On the other hand, the laser used in the welding process or the needle used for dispensing glue needs to be accurately aligned with the solder strip, which requires equipment with high processing precision. The processing is difficult and has high requirements on the equipment. Otherwise, some parts of the solder strip cannot be connected or fixed, which is prone to poor welding and low yield.

[0004] In response to some of the above problems, some researchers have proposed that the battery cells, solder ribbons, adhesive films and glass can be laminated in advance and then the solder ribbons can be interconnected with the crystalline silicon battery cells through laser sintering. Although this strategy eliminates the need for adhesives or skin films to fix the solder ribbons, it still requires ultra-low temperature solder ribbons with relatively high costs for welding. In addition, local heat generation during the welding process can cause irreversible damage or destruction to the adhesive film and even the entire device, affecting the subsequent practical application of the product. Secondly, the omission of solder ribbon fixing materials may cause the solder ribbon to be misaligned during the lamination process, and the preset laser path may not be able to accurately cover the solder ribbon, resulting in poor welding. In addition, since the welding process is after the lamination process, defective products will be difficult to detect after the welding is completed, and the battery series yield monitoring is difficult and difficult to repair, which in turn increases production costs.

[0005] After the soldering tape is welded and fixed to the battery cell, the busbar needs to be connected to the soldering tape by hot pressing welding or dispensing welding, which makes the overall process more steps, complicated and high in production cost. In addition, the welding point between the soldering tape and the busbar is prone to cold welding and broken welding, and it is also easy to cause efficiency loss of the battery assembly due to too many welding areas. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for processing a busbar-free photovoltaic cell.

[0007] To achieve the above objectives, the present invention discloses a method for processing a busbar-free photovoltaic cell, comprising the following steps:

[0008] Step S1, providing a plurality of battery packs and welding foils, and stacking the welding foils and the battery packs;

[0009] Step S2, using a first laser to perform melting welding on the welding foil according to a first preset pattern, so as to achieve conduction between the welding foil and the fine grid lines of all battery packs;

[0010] Wherein, the first preset pattern is a track formed by connecting the busbar-free battery cells of each battery pack in series;

[0011] Step S3, using a second laser to cut the welding foil according to a second preset pattern, so as to process integrated welding foil strips and welding foil bars on multiple battery packs, so that multiple battery strings are formed by multiple welding foil strips, and multiple battery strings are connected in parallel by welding foil bars to form batteries;

[0012] Wherein, the second preset pattern includes the outline of the welding foil band and the welding foil strip.

[0013] Preferably, the step of stacking the welding foil and the battery pack is:

[0014] The first step is to continuously bend the welding foil to form a bending portion vertical to the plane where the welding foil is located;

[0015] Step 2: Repeat the first step to form a plurality of bending parts;

[0016] Step 3: Place the busbar-free cells of each battery group on one side of each bending part in turn;

[0017] Step 4: bend the bent portion toward one side of the corresponding busbar-free solar cell, so that the bent portion contacts the fine grid line on the top surface of the corresponding busbar-free solar cell.

[0018] Further preferably, a pre-cutting area is formed between the top fine grid lines and the bottom fine grid lines of each busbar-free solar cell;

[0019] When executing step S3, the second laser also cuts according to the contour of the pre-cut area.

[0020] Further preferably, the bending portion is two bending surfaces that fit each other.

[0021] Further preferably, the fourth step is more specifically: bending the bent portion toward one side of the corresponding busbar-free solar cell, so that the bent portion can cover and contact all the fine grid lines on the top surface of the corresponding busbar-free solar cell.

[0022] Preferably, when executing step S3, the second laser repeatedly cuts the welding foil multiple times according to the second preset pattern.

[0023] Preferably, the thickness of the welding foil is 0.5 mm to 1 mm.

[0024] Preferably, the first laser is a CO2 laser or a visible light semiconductor laser.

[0025] Preferably, the first laser is an infrared laser, and when executing step S2, the infrared laser power is 30W to 200W, and the laser action time is 10ms to 300ms.

[0026] The present invention also provides a busbar-free photovoltaic cell manufactured using the above-mentioned busbar-free photovoltaic cell processing method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) After all battery packs and welding foils are stacked, the first laser is used to fix the welding foils to all battery packs, and then the second laser is used to process an integrated welding foil strip and welding foil strip. In this way, the welding foil strip can be cut at the same time as the welding foil strip. Compared with the processing technology of welding strips and bus bars in the prior art (connecting the welding strips to the battery cells, processing the bus bars, transporting the bus bars, and connecting the bus bars to the welding strips), the process steps are greatly simplified, the production time is shortened, and the production efficiency is greatly improved. The integrated welding foil strip and welding foil strip not only reduce the welding process and related equipment costs of the traditional bus bars and welding strips, save production costs, but also help to avoid poor welding between the traditional welding strips and bus bars, help to improve the yield, and avoid the loss of battery efficiency caused by too many welding areas between the bus bars and multiple welding strips.

[0029] (2) Welding foil is used to stack and weld multiple battery packs. Since the size of the welding foil is larger than that of the traditional welding ribbon, even if the welding foil is offset or misaligned during transportation, there is still welding foil relative to the battery pack to ensure welding. In this way, the use of adhesives, skin films or coatings and other welding ribbon fixing materials can be reduced or even eliminated, which can reduce material costs. Since there is no welding ribbon fixing material, there is no problem of high temperature affecting the welding ribbon fixing material during welding. Therefore, ordinary welding foil can be used instead of ultra-low temperature welding ribbon or coated copper wire, further reducing material costs.

[0030] (3) The welding of the first laser is not affected by the offset and misalignment of the welding foil, which can improve the welding quality and yield rate, and also reduce the precision requirements for the welding equipment.

[0031] During the cutting process, the second laser only needs to remove the material outside the second preset pattern outline. The cutting can be performed along the outline or the periphery of the outline. This does not require high cutting accuracy and reduces the requirements for the equipment.

[0032] (4) The welding and cutting processes are carried out before the lamination process, which makes it easier to detect defective products and repair them in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is one of the schematic diagrams of the state where the welding foil and all battery packs are stacked in Example 1;

[0034] Figure 2 The second schematic diagram of the state where the welding foil and all battery packs are stacked in Example 1;

[0035] Figure 3 The third schematic diagram of the state where the welding foil and all battery packs are stacked in Example 1;

[0036] Figure 4 The fourth schematic diagram of the state where the welding foil and all battery packs are stacked in Example 1;

[0037] Figure 5 The fifth schematic diagram of the state where the welding foil and all battery packs are stacked in Example 1;

[0038] Figure 6 This is one of the state diagrams of executing step 4 in Example 1;

[0039] Figure 7 This is the second state diagram of executing step 4 in Example 1;

[0040] Figure 8 This is the third state diagram of executing step 4 in Example 1;

[0041] Fig. 9 This is a schematic diagram of the state of multiple battery packs being welded in Example 1;

[0042] Fig.10 This is a schematic diagram of the state of multiple battery packs being welded in Example 1;

[0043] Fig.11 This is a schematic diagram of the state of multiple battery packs after cutting in Example 1;

[0044] Battery pack 1; main grid-free battery cell 2; welding foil 3; bending portion 31; bending surface 311; pre-cut area 32; transverse track 4; welding foil strip 5; welding foil strip 6. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Example 1

[0047] A method for processing a busbar-free photovoltaic cell comprises the following steps:

[0048] Step 1: provide multiple battery packs 1 and welding foils 3, and stack the welding foils 3 and all the battery packs 1.

[0049] Each battery group 1 includes a plurality of busbar-free cells 2 arranged horizontally, and a plurality of battery groups 1 are arranged vertically. In this step, the busbar-free cells 2 are bifacial cells, and the front and back sides thereof are provided with fine grid lines, but no busbar lines are provided; in other embodiments, the busbar-free cells 2 may also be single-sided cells. In addition, the number of battery groups 1 and the number of busbar-free cells 2 in each battery group 1 may be adaptively set according to the specific type of photovoltaic cells and actual needs, such as in Figure 3-Figure 5 Each battery group 1 has four main grid-free battery cells 2. Figure 6-Figure 8 Each battery group 1 has four main-grid-free battery cells 2. Figure 9-11There are two battery groups 1, each battery group 1 has four main-grid-free battery cells 2.

[0050] Among them, the solder foil 3 is preferably tin solder foil, the projected area of ​​the solder foil 3 is larger than the sum of the projected areas of all battery packs 1, and the thickness is 0.5mm~1mm, preferably 0.7mm~0.9mm, specifically 0.7mm, 0.8mm, 0.9mm. The solder foil 3 with this thickness is suitable for most existing laser welding technologies, avoiding the problem of insufficient solder and poor welding due to too thin thickness, or reducing welding efficiency and cutting efficiency due to too thick thickness.

[0051] In step 1, see Figure 1-Figure 5 The specific steps of stacking the welding foil 3 and all the battery packs 1 are as follows:

[0052] In the first step, the solder foil 3 is continuously bent to form a bent portion 31 vertically disposed on the plane where the solder foil 3 is located. After continuous bending, the bent portion 31 is formed by two bent surfaces 311. In order to allow the bent portion 31 to be fully melted and connected to the fine grid line, reduce the problem of poor welding, and facilitate cutting, the two bent surfaces 311 are configured to fit each other. It should be noted that Figure 2-Figure 5 In order to clearly show the structure of the bending portion 31, there is a gap between the two bending surfaces 311 of the bending portion 31. In practice, the two bending surfaces 311 of the bending portion 31 should fit each other (e.g. Figure 6-Figure 8 shown).

[0053] In the second step, the first step is repeated to form a plurality of bending portions 31, such as Figure 2 Four bending parts 31 are bent in the middle.

[0054] In the third step, the busbar-free battery cells 2 of each battery group 1 are sequentially placed on one side of each bending portion 31, for example Figure 3 The four busbar-free battery cells 2 of the battery pack 1 are placed in sequence on the right side of the bent portion 31 .

[0055] Step 4: bend the bent portion 31 toward the side of the corresponding busbar-free battery cell 2 so that the bent portion 31 contacts the fine grid line on the top surface of the corresponding busbar-free battery cell 2. Figure 4-Figure 5 As shown, four bending portions 31 are bent to the right, and each bending portion 31 can be bent to contact the fine grid lines on the top surface of the corresponding busbar-free battery cell 2. In order to ensure that each bending portion 31 can contact all the fine grid lines of the busbar-free battery cell 2 and improve the effect of collecting current, the bending portion 31 can cover all the fine grid lines on the top surface of the corresponding busbar-free battery cell 2 after bending.

[0056] In the process of stacking the above main-grid-free battery cell 2 and the welding foil 3, the bending portion 31 is first bent, and then the main-grid-free battery cell 2 is placed on the welding foil 3, which can reduce the damage to the main-grid-free battery cell 2 caused by continuous bending. After the main-grid-free battery cell 2 is placed on one side of the bending portion 31, the main-grid-free battery cell 2 and the welding foil 3 are stacked on one side, and after the bending portion 31 is bent, the main-grid-free battery cell 2 and the welding foil 3 are stacked on the other side. Since the top and bottom surfaces of the main-grid-free battery cell 2 are both stacked with the welding foil 3, and the welding foil 3 on the top and bottom surfaces is an integrated structure, the main-grid-free battery cell 2 and the welding foil 3 form a relatively stable structure, which is not easy to be misaligned, and further reduces the impact on welding and cutting. In addition, whether it is the bending portion or the welding foil located at the top and bottom of the main-grid-free battery cell 2 after bending, it can play a positioning role for the main-grid-free battery cell.

[0057] Among them, Fig. 9 As shown, there are two battery packs 1, each battery pack 1 has four busbar-free battery cells 2, and the busbar-free battery cells 2 of the two battery packs 1 are arranged one by one along the vertical direction shown in the figure. Taking these two battery packs 1 as an example, each bending portion 31 contacts the fine grid lines on the top surfaces of the two busbar-free battery cells 2 in the same column after bending.

[0058] Step 2: Use a first laser to weld the welding foil 3 according to a first preset pattern, so as to achieve conduction between the welding foil 3 and the fine grid lines of all battery groups 1, wherein the first preset pattern is a track formed by the series connection of the non-busbar battery cells 2 of each battery group 1. Fig.10 In the two battery packs 1, the first preset pattern is eight transverse tracks 4, which intersect with the fine grid lines of the busbar-free battery cells 2, preferably perpendicularly (the relationship between the two is not shown in the figure). The first laser moves along the eight transverse tracks 4 during welding, and welds at the positions on the transverse tracks 4 corresponding to the fine grid lines, thereby achieving conduction between the welding foil 3 and the fine grid lines of the two battery packs 1.

[0059] Among them, since there are welding foils 3 on the top and bottom surfaces of the main grid-free battery cell 2 that need to be welded, there are at least two first lasers, preferably two, and the two first lasers are respectively arranged above and below the multiple groups of battery packs 1, so that the two first lasers can weld the top welding foil 3 and the bottom welding foil 3 at the same time, thereby improving the welding efficiency.

[0060] Wherein, the first laser is a CO2 laser or a visible light semiconductor laser, preferably, the first laser is an infrared laser, and when performing step 2, the infrared laser power is 30W to 200W, and the laser action time is 10ms to 300ms, so that it can avoid damaging the main grid-free battery cell 2 and completely melt the welding foil 3 to ensure the connection quality with the fine grid line. In addition, the use of ultraviolet lasers above 325nm should be avoided to avoid damaging the main grid-free battery cell 2.

[0061] Step three, use a second laser to cut the welding foil 3 according to the contour of the second preset pattern, so as to process an integrated welding foil strip 5 and welding foil strip 6 on multiple battery groups 1, so that multiple battery strings are formed by multiple welding foil strips 5, and multiple battery strings are connected in parallel by welding foil strips 6 to form batteries. Among them, the second preset pattern is the contour line of the welding foil strip 5 and the welding foil strip 6. Specifically, in step three, welding has been performed along eight transverse tracks 4. After welding, eight transverse tracks 4 form eight welding foil strips 5 correspondingly, and the eight welding foil strips 5 connected in parallel are welding foil strips 6. During the cutting process, the second laser only needs to remove the material outside the contour of the second preset pattern, so the cutting can be performed along its contour or the periphery of the contour.

[0062] There are at least two second lasers, preferably two, and the two second lasers are respectively arranged above and below the plurality of battery groups 1. Since the solder foil 3 is continuously bent to contact the top and bottom surfaces of the busbar-free battery cell 2, the top fine grid lines and the bottom fine grid lines are short-circuited, so a pre-cut area 32 (such as Figure 7 As shown). One of the second lasers performs the step 3, and the other second laser cuts according to the contour of the pre-cut area 32 and the solder foil strip. For example, when cutting to form the solder foil strip 5, the two second lasers are performed synchronously. When one of the second lasers is cutting the solder foil strip 6, the other laser is cutting the pre-cut area 32 to disconnect the top and bottom fine grid lines of the busbar-free solar cell 2 (as shown in FIG. Figure 7-Figure 8 As shown), cutting the welding foil strip 6 and the pre-cutting area 32 are performed synchronously, which improves the cutting efficiency. Wherein, preferably, the pre-cutting area 32 is L-shaped or U-shaped.

[0063] Among them, when executing the step three, the second laser repeatedly cuts the solder foil 3 according to the contour of the second preset pattern. In other words, the solder foil 3 is cut by reducing the power of the second laser and increasing the number of cutting times during the cutting process, which can reduce damage to the battery cell.

[0064] The processing method of the above-mentioned busbar-free photovoltaic cell of this embodiment has the following effects:

[0065] (1) After all battery packs and welding foils are stacked, the first laser is used to fix the welding foils to all battery packs, and then the second laser is used to process an integrated welding foil strip and welding foil strip. In this way, the welding foil strip can be cut at the same time as the welding foil strip. Compared with the processing technology of welding strips and bus bars in the prior art (connecting the welding strips to the battery cells, processing the bus bars, transporting the bus bars, and connecting the bus bars to the welding strips), the process steps are greatly simplified, the production time is shortened, and the production efficiency is greatly improved. The integrated welding foil strip and welding foil strip not only reduce the welding process and related equipment costs of the traditional bus bars and welding strips, save production costs, but also help to avoid poor welding between the traditional welding strips and bus bars, help to improve the yield, and avoid the loss of battery efficiency caused by too many welding areas between the bus bars and multiple welding strips.

[0066] (2) Welding foil is used to stack and weld multiple battery packs. Since the size of the welding foil is larger than that of the traditional welding ribbon, even if the welding foil is offset or misaligned during transportation, there is still welding foil relative to the battery pack to ensure welding. In this way, the use of adhesives, skin films or coatings and other welding ribbon fixing materials can be reduced or even eliminated, which can reduce material costs. Since there is no welding ribbon fixing material, there is no problem of high temperature affecting the welding ribbon fixing material during welding. Therefore, ordinary welding foil can be used instead of ultra-low temperature welding ribbon or coated copper wire, further reducing material costs.

[0067] (3) The welding of the first laser is not affected by the offset and misalignment of the welding foil, which can improve the welding quality and yield rate, and also reduce the precision requirements for the welding equipment.

[0068] During the cutting process, the second laser only needs to remove the material outside the second preset pattern outline. The cutting can be performed along the outline or the periphery of the outline. This does not require high cutting accuracy and reduces the requirements for the equipment.

[0069] (4) The welding and cutting processes are carried out before the lamination process, which makes it easier to detect defective products and repair them in time.

[0070] Example 2

[0071] A busbar-free photovoltaic cell is manufactured by the processing method of the busbar-free photovoltaic cell of embodiment 1.

[0072] The busbarless photovoltaic cell includes multiple groups of battery groups 1, interconnection welding strips, busbar welding strips and busbars 6. Each group of battery groups 1 includes multiple horizontally arranged busbarless battery cells 2. Two adjacent busbarless battery cells 2 are connected by interconnection welding strips 5. Multiple groups of battery groups 1 are arranged vertically, and each group of battery groups 1 is connected to the busbar 6 by a busbar welding strip 5.

[0073] The busbars 5 and the busbars 6 are manufactured into an integrated structure by the processing method of the busbar-free photovoltaic cell of Example 1.

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A processing method for a busbar-free photovoltaic cell, It is characterized in that The following steps are involved: Step S1, providing a plurality of battery packs and welding foils, and stacking the welding foils and the battery packs; Step S2, using a first laser to perform melting welding on the welding foil according to a first preset pattern, so as to achieve conduction between the welding foil and the fine grid lines of all battery packs; Wherein, the first preset pattern is a track formed by connecting the busbar-free battery cells of each battery pack in series; Step S3, using a second laser to cut the welding foil according to a second preset pattern, so as to process integrated welding foil strips and welding foil bars on multiple battery packs, so that multiple battery strings are formed by multiple welding foil strips, and multiple battery strings are connected in parallel by welding foil bars to form batteries; Wherein, the second preset pattern includes the outline of the welding foil band and the welding foil strip.

2. The method for processing a busbar-free photovoltaic cell according to claim 1, Features: The steps of stacking the welding foil and the battery pack are as follows: The first step is to continuously bend the welding foil to form a bending portion vertical to the plane where the welding foil is located; Step 2: Repeat the first step to form a plurality of bending parts; Step 3: Place the busbar-free cells of each battery group on one side of each bending part in turn; Step 4: bend the bent portion toward one side of the corresponding busbar-free solar cell, so that the bent portion contacts the fine grid line on the top surface of the corresponding busbar-free solar cell.

3. The method for processing a busbar-free photovoltaic cell according to claim 2, Features: A pre-cutting area is formed between the top fine grid lines and the bottom fine grid lines of each busbar-free solar cell; When executing step S3, the second laser also cuts according to the contour of the pre-cut area.

4. The method for processing a busbar-free photovoltaic cell according to claim 2, Features: The bending portion is two bending surfaces that fit each other.

5. The method for processing a busbar-free photovoltaic cell according to claim 2, Features: The fourth step is more specifically: bending the bent portion toward one side of the corresponding busbar-free solar cell, so that the bent portion can cover and contact all the fine grid lines on the top surface of the corresponding busbar-free solar cell.

6. The method for processing a busbar-free photovoltaic cell according to any one of claims 1 to 5, Features: When executing step S3, the second laser repeatedly cuts the solder foil multiple times according to the second preset pattern.

7. The method for processing a busbar-free photovoltaic cell according to any one of claims 1 to 5, Features: The thickness of the welding foil is 0.5 mm to 1 mm.

8. The method for processing a busbar-free photovoltaic cell according to any one of claims 1 to 5, Features: The first laser is CO 2 Laser or visible light semiconductor laser.

9. The method for processing a busbar-free photovoltaic cell according to any one of claims 1 to 5, Features: The first laser is an infrared laser. When executing step S2, the infrared laser power is 30W to 200W, and the laser action time is 10ms to 300ms.

10. A main grid-free photovoltaic cell, Features: The photovoltaic cell is manufactured by the processing method of the busbar-free photovoltaic cell as described in any one of claims 1 to 9.

Images