Layering strip, EL detection system and EL detection method for EL detection of solar cell

Abstract

The present disclosure describes a pressure strip for EL detection of solar cells, an EL detection system and an EL detection method. The pressure strip is used to press on the main grid line of the solar cell, and the main body of the pressure strip is composed of a contact section and a non-contact section. The contact section corresponds to the length of the main grid line from the starting point pad to the end point pad, and the non-contact section corresponds to the harpoon mouth of the solar cell. The pressure strip is provided with a contact layer for continuous contact with the main grid line on the contact section, and the pressure strip is configured with a notch in the non-contact section to avoid contact with the harpoon mouth.

Description

Technical Field

[0001] The present disclosure relates to the technical field of photovoltaic cell detection, and in particular to a layering strip, an EL detection system and an EL detection method for EL detection of a solar cell. Background Art

[0002] Photovoltaic modules are mainly composed of cells, module frames, tempered glass, packaging materials, junction boxes, etc. The quality of the cells will directly affect the power generation efficiency of the photovoltaic power generation system. During the production process, the surface of solar cells may have defects such as broken grids, cracks, cold solder joints, hidden cracks, leakage, foreign matter, etc. due to improper operation, etc., resulting in reduced power or even no output power of the photovoltaic module. In order to improve the qualified rate of the modules, the industry usually uses electroluminescence or field luminescence (EL, Electroluminescent) technology to monitor solar cell defects.

[0003] The principle of electroluminescence is: when the built-in electric field of the crystalline silicon cell is in balance, the currents in the P region and the N region cancel each other out, and the internal current is zero. When a forward bias is added, the built-in electric field is weakened accordingly, and the balance between the electron flow and the hole flow is broken, prompting the electrons to move to the P region and the holes to move to the N region. These electrons entering the P region and the holes entering the N region are collectively referred to as unbalanced minority carriers, which meet with the majority carriers in the original region to produce composite luminescence.

[0004] Generally, the EL monitoring system generally includes a transmission mechanism for transmitting the cell, a pressing structure including multiple metal probe rows, a regulated DC power supply for supplying power to the metal probe row, an imaging system and a display device, etc. Each probe on the probe row is used to accurately press down to each process point on the cell; the regulated power supply is used to supply current to complete power-on after the probe contacts the process point; the imaging system is used to obtain the EL image of the cell; the display device displays the captured image on the display screen, which is convenient for the staff to view and judge defects.

[0005] The traditional probe mechanism includes a front and back probe row, each row is composed of multiple circular metal probes evenly arranged, and intermittently contacted from the upper edge to the lower edge of the battery cell. In order to solve the problem that some grid lines cannot be detected due to the gap between the probes, CN219226226U discloses a battery test probe structure, the upper probe row includes a first electrode strip, a second electrode strip and an insulating plate reinforcement strip, and the lower probe structure includes a lower probe row; the first electrode strip and the second electrode strip are respectively connected to both sides of the reinforcement strip; it eliminates the gap between the probes by changing the traditional columnar probes into strip-shaped first electrode strips and second electrode strips, which is equivalent to connecting the probes into one.

[0006] However, the inventors of the present application realize that the prior art still has problems such as uneven EL imaging and missed detection of broken harpoon mouths. Summary of the invention

[0007] On one hand, the present disclosure provides a pressure strip for EL detection of a solar cell, and the pressure strip is used to be pressed on the main grid line of the solar cell. The main body of the pressure strip is composed of a contact section and a non-contact section, wherein the contact section corresponds to the length of the main grid line from the starting point pad to the end point pad, and the non-contact section corresponds to the harpoon mouth of the solar cell. Among them, the contact section is used to continuously contact the main grid line, and the pressure strip is configured with a notch in the non-contact section to avoid contact with the harpoon mouth.

[0008] Alternatively, the barrier strip is provided with a contact layer in the contact section for continuous contact with the main grid line.

[0009] Alternatively, the bead has a width that narrows toward the contact layer in cross section. In particular, the contact layer may have a width of 1.5 to 2.5 mm. More particularly, the contact layer may have a width of 2 mm, and the main body of the bead has a width of 2.5 mm away from the end face of the solar cell.

[0010] Alternatively, the body of the bead may be made of copper or an alloy material, and the contact layer may be made of gold, silver or an alloy material.

[0011] Another aspect of the present disclosure provides an EL detection system for a solar cell, comprising:

[0012] A conveying device configured to convey the solar cell sheet to the darkroom;

[0013] A pressing device is arranged in a dark room, and comprises a pressure strip assembly and an actuator, wherein the pressure strip assembly comprises an upper pressure strip row and a lower pressure strip row, wherein the upper pressure strip row and the lower pressure strip row each comprise a plurality of the pressure strips arranged along the front or back main grid lines of the solar cell, and the actuator is configured to move each pressure strip in the upper pressure strip row and the lower pressure strip row toward the solar cell until a contact section of each pressure strip is in contact with a corresponding one of the main grid lines on the front and back of the solar cell, respectively, and does not contact the harpoon mouth of the solar cell;

[0014] a DC power source electrically connected to the batten assembly and configured to apply a forward bias to the batten assembly;

[0015] The imaging device is arranged in the dark room and is configured to obtain an EL image of the solar cell.

[0016] Alternatively, the DC power source is configured with the positive pole connected to the upper pressing bar row and the negative pole connected to the lower pressing bar row.

[0017] Alternatively, the EL detection system also includes an alignment device, which is configured to move the solar cell or the batten assembly so that the contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the length of the main grid line of the solar cell from the starting point pad to the ending point pad, and the non-contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the harpoon mouth.

[0018] Another aspect of the present disclosure provides an EL detection method for a solar cell, which uses the above-mentioned EL detection system and is characterized by comprising the following steps:

[0019] The solar cell sheets are transported to the dark room by the transport device;

[0020] The actuator moves the upper and lower batten rows of the batten assembly respectively until the contact section of each batten in the upper and lower batten rows contacts a corresponding one of the busbars on the front and back sides of the solar cell, respectively, and does not contact the harpoon of the solar cell;

[0021] Applying a forward bias voltage to the layering assembly from a DC power supply;

[0022] The EL image of the solar cell is acquired by an imaging device.

[0023] Alternatively, after the step of conveying the solar cell to the darkroom by the conveying device, the EL detection method may further include: aligning the relative positions of the solar cell and the batten assembly so that the contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the length of the main grid line of the solar cell from the starting point pad to the ending point pad, and the non-contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the harpoon mouth.

[0024] The pressure strips, EL detection system and EL detection method for EL detection of solar cells provided by the present invention achieve more uniform EL imaging that is closer to the front EL of the component end, and avoid the effect of being unable to identify the broken grid at the harpoon mouth, by using upper and lower pressure strip rows that are in continuous contact with the welding pads of the main grid lines on the front and back sides of the solar cells but not in contact with the harpoon mouth. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the main plane of a solar cell;

[0026] Figure 2 A schematic front view of a pressure strip pressed onto a solar cell sheet according to the present disclosure is shown;

[0027] Figure 3A bottom view schematically shows a press strip according to the present disclosure being pressed onto a solar cell sheet;

[0028] Figure 4 A partially enlarged bottom view schematic diagram of a pressure strip pressed onto a solar cell sheet according to the present disclosure is shown;

[0029] Figure 5 A side view schematic diagram of a pressure strip according to the present disclosure being pressed onto a solar cell sheet is shown. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the layering strip, EL detection system and EL detection method for EL detection of solar cells disclosed in the present invention in combination with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following detailed description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, which are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0031] Reference Figure 1 The structure of the solar cell 10 is described. The solar cell 10 may include a plurality of interconnected units 20, and the front and back sides of each unit 20 may each include a plurality of main grid lines 11, a plurality of auxiliary grid lines 12, and a plurality of pads (PADs) 14, 15, 16. Each main grid line 11 extends along the vertical direction of the cell 10 (the vertical direction shown in the drawings) and is evenly spaced apart from each other in the horizontal direction; each auxiliary grid line 12 extends substantially along the horizontal direction of the cell 10 (the horizontal direction shown in the drawings) and is evenly spaced apart from each other in the vertical direction. The main grid lines 11 and the auxiliary grid lines 12 may cross each other. The main grid lines 11 may have a width of about 1 to 1.5 mm.

[0032] Each of the multiple groups of pads is arranged along a main grid line 11 and is electrically connected in series by the main grid line 11. Each group of pads may include a starting pad 14, a finishing pad 15 and one or more intermediate pads 16. The starting pad 14 and the finishing pad 15 are respectively located at the two ends of the main grid line 11, and the one or more intermediate pads 16 are located between the starting pad 14 and the finishing pad 15. The starting pad 14 and the finishing pad 15 are arranged at a certain distance from the edge of the battery cell unit 20. It should be understood that, depending on the welding direction, in the same battery cell unit 20, the positions of the starting pad 14 and the finishing pad 15 can be interchanged. Multiple auxiliary grid lines 12 are arranged to run through multiple main grid lines 11, or multiple main grid lines 11 and multiple groups of pads. The front and back sides of each battery cell unit 20 can also be arranged with vertically extending auxiliary grid lines 12.

[0033] like Figure 1As shown, a harpoon opening 13 is provided at both ends of the main grid line 11. Two harpoon openings 13 are formed near the unit cutting line OC and are symmetrically distributed. The harpoon opening 13 serves to collect current and eliminate line of sight difference. The harpoon opening 13 is composed of two secondary grid lines extending from the starting welding point pad 14 or the ending welding point pad 15 to the upper and lower edges of the battery cell unit 20. The harpoon opening 13 defines a gap at the upper and lower edges of the battery cell unit 20.

[0034] exist Figure 1 In the specific example shown, the cell 10 includes two units 20 , each unit 20 has nine busbars 11 on the front side, and correspondingly, also has nine busbars 11 on the back side.

[0035] In the existing probe row for EL testing of solar cells, the probe row or silver bar contacts the vertical range from the upper edge to the lower edge of the cell, including the secondary grid line forming the harpoon mouth. In this way, when the secondary grid line forming the harpoon mouth is broken, the probe row or silver bar plays the role of conducting current, thus causing missed judgment.

[0036] Reference Figure 2-5 A batten assembly according to the present disclosure is described.

[0037] In a first aspect, the present disclosure provides a pressure strip 30 for EL detection of a solar cell. The pressure strip 30 is used to be pressed onto a main grid line 11 of a solar cell 10 .

[0038] The bead 30 is configured in a substantially strip shape, and its cross section is substantially rectangular. The bead 30 may extend over the entire vertical range of the battery cell 10. For example, for the battery cell 10 shown in the drawings, the length of the bead 30 may be 168 mm.

[0039] The main body of the pressure strip 30 is composed of a contact section 31 and a non-contact section 32. The contact section 31 corresponds to the length of the main grid line 11 from the starting pad 14 to the ending pad 15, and the non-contact section 32 corresponds to the harpoon mouth 13 of the solar cell 10.

[0040] The correspondence between the contact section 31 and the main grid line 11 is achieved through the length of the contact section 31. In particular, the length of the contact section 31 is consistent with the length of the main grid line 11 from the starting point pad 14 to the ending point pad 15. The correspondence between the non-contact section 32 and the harpoon mouth 13 is achieved through the range of the non-contact section 32. Specifically, for the harpoon mouth 13 located at the upper and lower edges of the battery cell 11, according to the length of the pressure strip 30 relative to the battery cell 10, an inner end point of the vertical range of the non-contact section 32 corresponding to the harpoon mouth 13 does not enter the range of the harpoon mouth 13, and its outer end point can be located above the vertical range of the harpoon mouth 13 without contacting it, such as Figure 5As best shown. For the two harpoon openings 13 located in the middle of the cell 11, i.e., near the unit cutting line OC, which are axially symmetrically distributed and opposite to each other, the vertical range of the non-contact section 32 corresponding to the harpoon opening 13 extends from the welding point pad 14 of the upper cell unit 20 to the welding point pad 14 of the lower cell unit 20. This corresponding relationship makes it possible for the main grid line 11 to be continuously in contact with the harpoon opening 13 from the welding point pad 14 to the end point pad 15 when the pressure strip 30 is pressed on the main grid line 11, and there is a gap above the harpoon opening 13, which is not in contact with the pressure strip 30. Therefore, when the secondary grid line constituting the harpoon opening 13 is broken, the current is not conducted, and blackening appears in the EL image, so the broken grid of the harpoon opening 13 can be accurately identified.

[0041] The pressure strip 30 is provided with a contact layer in the contact section 31 for continuous contact with the busbar 11 (and thus with the pad on the busbar 11). The contact layer extends continuously on the side of the contact section 31 facing the cell 11, and its width may be less than or equal to the width of the side.

[0042] In particular, in some embodiments, the pressure strip 30 may also be provided with a contact layer on the remaining side surfaces that are not used for contacting the main grid line 11 .

[0043] The pressure strip 30 is configured with a notch in the non-contact section 32 to avoid contact with the harpoon mouth 13, such as Figure 5 As shown. When the bead 30 is pressed onto the main grid line 11 of the battery cell 10, a gap is formed between the bead 30 and the harpoon mouth 13. The gap is filled with air for insulation. The non-contact section 32 can be implemented by removing material from the bead 30 to form a gap. Alternatively, the bead 30 can be formed by casting, forging, additive manufacturing, etc. without removing material.

[0044] In particular, the main body of the pressure strip 30 can be made of metal materials such as copper or alloy materials, and the contact layer can be made of metal materials such as gold, silver or alloy materials. In this way, the pressure strip 30 has good conductivity, low hardness, and less debris caused during the pressing process.

[0045] Alternatively, the bead 30 may be shaped in cross section, such as Figure 4 As shown, the width of the bead 30 narrows toward the contact layer. It should be understood that the narrowing of the width can start at any height of the bead 30; that is, for the bead located on the front side of the battery cell 10, above this height, the width of the bead 30 is uniform, and below this height, the width of the bead 30 gradually narrows.

[0046] In particular, in some embodiments, the contact layer may have a width of 1.5 to 2.5 mm.

[0047] More specifically, in an exemplary embodiment, the contact layer may have a width of 2 mm, and the main body of the bead away from the end surface of the solar cell has a width of 2.5 mm. In this way, the bead 30 can ensure its rigidity and strength so as not to deform or even fail during the lamination process.

[0048] As used herein, the thickness of the contact layer refers to its minimum thickness value, for example, in the case where the contact layer has a rectangular cross-section, such as Figure 4 As shown, the thickness of the contact layer refers to the thickness of the surface of the contact layer in contact with the battery cell 10 , and the thickness of the remaining portion of the contact layer may be greater than the thickness of the surface of the contact layer in contact with the battery cell 10 .

[0049] The second aspect of the present disclosure discloses an EL detection system for a solar cell, comprising:

[0050] A conveying device, configured to convey the solar cell sheet 10 to a dark room;

[0051] A pressing device, arranged in a dark room, having a bead assembly and an actuator, wherein the bead assembly comprises an upper bead row and a lower bead row, wherein the upper bead row and the lower bead row each comprise a plurality of the above-mentioned beading bars 30 arranged along the front or back main grid lines 11 of the solar cell 10, and the actuator is configured to move each beading bar 30 in the upper bead row and the lower bead row toward the solar cell 10 until a contact section 31 of each beading bar 30, in particular a contact layer, contacts a corresponding one of the main grid lines 11 of the front and back of the solar cell 10, respectively, and does not contact the harpoon mouth 13 of the solar cell 10;

[0052] a DC power source electrically connected to the batten assembly and configured to apply a forward bias to the batten assembly;

[0053] The imaging device, arranged in a dark room, is configured to acquire an EL image of the solar cell 10 .

[0054] The darkroom may be surrounded by light shielding material to prevent external light from entering the imaging device.

[0055] The conveyor device may be implemented as a conveyor belt, which may have a plurality of rollers. The battery slice 10 may be moved on the conveyor device.

[0056] The actuator can be selected from any one of a hydraulic actuator, a pneumatic actuator, and an electric actuator. In particular, the actuator can be implemented as a pneumatic actuator controlled by a solenoid valve.

[0057] The upper and lower batten rows may each include a base for fixing the plurality of battens 30 .

[0058] In a specific embodiment according to the present disclosure, the upper batten row and the lower batten row each include 9 battens 30 .

[0059] The imaging device may be implemented as a short-wave infrared camera, a CCD infrared camera, a CMOS infrared camera, or the like.

[0060] The EL detection system may also include image transmission elements, image processing elements, and display devices, etc. The image transmission element may include network cables, routers, and other devices or equipment for transmitting images; the image processing element refers to an electronic device with one or more processors, which may be, but is not limited to, a computer, a server, etc., and should also have a readable memory for storing detection programs and detection results; the display device has a display screen for displaying images.

[0061] Alternatively, the DC power source is configured with the positive pole connected to the upper pressing bar row and the negative pole connected to the lower pressing bar row.

[0062] Alternatively, the EL detection system may further include an alignment device, which is configured to move the solar cell 10 or the bead assembly, preferably the solar cell 10, so that the contact section 31 of each bead 30 in the upper bead row and the lower bead row is respectively located directly above and directly below the length of the main grid line 11 of the solar cell 10 from the starting point pad to the ending point pad, and the non-contact section 32 of each bead 30 in the upper bead row and the lower bead row is respectively located directly above and directly below the harpoon mouth 13. In this way, the actuator drives the upper bead row to move vertically downward and the lower bead row to move vertically upward to achieve the upper bead row and the lower bead row being properly pressed on the solar cell 10.

[0063] The third aspect of the present disclosure discloses an EL detection method for a solar cell, which uses the above-mentioned EL detection system and includes the following steps:

[0064] The solar cell sheet 10 is transported to a dark room by a transport device;

[0065] The actuator moves the upper and lower batten rows of the batten assembly to the contact section 31, especially the contact layer, of each batten 30 in the upper and lower batten rows, respectively, to contact with a corresponding one of the busbars 11 on the front and back sides of the solar cell 10, and not to contact with the harpoon mouth 13 of the solar cell 10;

[0066] Applying a forward bias voltage to the layering assembly from a DC power supply;

[0067] An EL image of the solar cell 10 is acquired by an imaging device.

[0068] Alternatively, in some embodiments, after the step of conveying the solar cell 10 to the darkroom by the conveying device, the EL detection method may further include: aligning the relative positions of the solar cell 10 and the pressure strip assembly, so that the contact section 31 of each pressure strip 30 in the upper pressure strip row and the lower pressure strip row is respectively located directly above and directly below the length of the main grid line 11 of the solar cell 10 from the starting point pad 14 to the ending point pad 15, and the non-contact section 32 of each pressure strip 30 in the upper pressure strip row and the lower pressure strip row is respectively located directly above and directly below the harpoon mouth 13.

[0069] Alternatively, in some embodiments, the EL detection method may further include a display device displaying the EL image of the solar cell 10 acquired by the imaging device.

[0070] The pressure strips, EL detection system and EL detection method for EL detection of solar cells provided by the present invention achieve more uniform EL imaging that is closer to the front EL of the component end, and avoid the effect of being unable to identify the broken grid at the harpoon mouth, by using upper and lower pressure strip rows that are in continuous contact with the welding pads of the main grid lines on the front and back sides of the solar cells but not in contact with the harpoon mouth.

[0071] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0072] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0073] As used in this disclosure and the appended claims, the singular forms "a", "an", "said", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0074] Obviously, those skilled in the art can make various changes and modifications to the layering strip, EL detection system and EL detection method for EL detection of solar cells disclosed in the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A pressure strip for EL detection of a solar cell, the pressure strip being used to be pressed onto the main grid line of the solar cell, characterized in that: The main body of the pressure strip is composed of a contact section and a non-contact section, wherein the contact section corresponds to the length of the main grid line from the starting point pad to the ending point pad, and the non-contact section corresponds to the harpoon mouth of the solar cell; The contact section is used for continuous contact with the main grid line, and the pressure strip is configured as a notch in the non-contact section to avoid contact with the harpoon mouth.

2. The layering strip according to claim 1, characterized in that: The pressure strip is provided with a contact layer in the contact section for continuous contact with the main grid line.

3. The layering strip according to claim 2, characterized in that: The bead has a width in cross section that narrows toward the contact layer.

4. The layering strip according to claim 3, characterized in that: The contact layer has a width of 1.5 to 2.5 mm. Preferably, the contact layer has a width of 2 mm. The end surface of the main body of the pressure strip away from the solar cell has a width of 2.5 mm.

5. The layering strip according to claim 2, characterized in that: The main body of the pressure strip is made of copper or alloy material, and the contact layer is made of gold, silver or alloy material.

6. An EL detection system for a solar cell, characterized in that: include: A conveying device, configured to convey the solar cell sheet to a dark room; A pressing device, arranged in the darkroom, comprising a pressure strip assembly and an actuator assembly, wherein the pressure strip assembly comprises an upper pressure strip row and a lower pressure strip row, wherein the upper pressure strip row and the lower pressure strip row each comprise a plurality of pressure strips according to any one of claims 1 to 5 arranged along the front or back main grid lines of the solar cell, wherein the actuator assembly is configured to move each pressure strip in the upper pressure strip row and the lower pressure strip row toward the solar cell until a contact section of each pressure strip is in contact with a corresponding one of the main grid lines on the front and back of the solar cell, respectively, and does not contact the harpoon mouth of the solar cell; a DC power supply electrically connected to the layering bar assembly and configured to apply a forward bias voltage to the layering bar assembly; The imaging device is arranged in the dark room and is configured to obtain an EL image of the solar cell.

7. The EL detection system according to claim 6, characterized in that: The pressure strip is provided with a contact layer in the contact section for continuous contact with the main grid line.

8. The EL detection system according to claim 6 or 7, characterized in that: It also includes an alignment device, which is configured to move the solar cell or the batten assembly so that the contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the length of the main grid line of the solar cell from the starting point pad to the ending point pad, and the non-contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the harpoon mouth.

9. An EL detection method for a solar cell, using the EL detection system according to any one of claims 6 to 8, characterized in that: The following steps are involved: The conveying device conveys the solar cell sheet to the darkroom; The actuator assembly moves the upper and lower batten rows of the batten assembly respectively until the contact section of each batten in the upper and lower batten rows contacts with a corresponding one of the busbars on the front and back sides of the solar cell, and does not contact with the harpoon of the solar cell; Applying a forward bias voltage to the layering assembly by the DC power supply; The imaging device acquires an EL image of the solar cell.

10. The EL detection method according to claim 9, characterized in that: After the step of conveying the solar cell sheet to the darkroom by the conveying device, the EL detection method further comprises: The relative positions of the solar cell and the batten assembly are aligned so that the contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the length of the main grid line of the solar cell from the starting point pad to the ending point pad, and the non-contact section of each batten in the upper batten row and the lower batten row is respectively located directly above and directly below the harpoon mouth.

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