CN116632102A - Method for reducing contact resistance of crystalline silicon solar cell - Google Patents
Method for reducing contact resistance of crystalline silicon solar cell Download PDFInfo
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- CN116632102A CN116632102A CN202210247161.5A CN202210247161A CN116632102A CN 116632102 A CN116632102 A CN 116632102A CN 202210247161 A CN202210247161 A CN 202210247161A CN 116632102 A CN116632102 A CN 116632102A
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- 238000000034 method Methods 0.000 title claims abstract description 51
- 229910021419 crystalline silicon Inorganic materials 0.000 title claims abstract description 42
- 239000000463 material Substances 0.000 claims abstract description 6
- 239000002184 metal Substances 0.000 claims abstract description 5
- 229910052751 metal Inorganic materials 0.000 claims abstract description 5
- 239000004065 semiconductor Substances 0.000 claims abstract description 3
- 230000005855 radiation Effects 0.000 claims description 23
- 230000015556 catabolic process Effects 0.000 claims description 7
- 230000001276 controlling effect Effects 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 230000008569 process Effects 0.000 description 11
- 230000000694 effects Effects 0.000 description 7
- 230000009471 action Effects 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- 238000001179 sorption measurement Methods 0.000 description 6
- 238000007493 shaping process Methods 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 229910017982 Ag—Si Inorganic materials 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
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- 238000004519 manufacturing process Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000002788 crimping Methods 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 101001073212 Arabidopsis thaliana Peroxidase 33 Proteins 0.000 description 1
- 101001123325 Homo sapiens Peroxisome proliferator-activated receptor gamma coactivator 1-beta Proteins 0.000 description 1
- 102100028961 Peroxisome proliferator-activated receptor gamma coactivator 1-beta Human genes 0.000 description 1
- XNRNVYYTHRPBDD-UHFFFAOYSA-N [Si][Ag] Chemical compound [Si][Ag] XNRNVYYTHRPBDD-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
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- 238000007906 compression Methods 0.000 description 1
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- 230000007547 defect Effects 0.000 description 1
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- 238000003825 pressing Methods 0.000 description 1
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- 238000005215 recombination Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/02002—Arrangements for conducting electric current to or from the device in operations
- H01L31/02005—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier
- H01L31/02008—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier for solar cells or solar cell modules
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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Abstract
The application discloses a method for reducing contact resistance of a crystalline silicon solar cell, which comprises the following steps: each conductive wire arranged in parallel is correspondingly pressed and connected to one main grid line of the surface electrode of the solar cell, and the conductive wires extend along the extending direction of the main grid line; the first end of a power supply is electrically connected with each conductive wire, the second end of the power supply is electrically connected with the back electrode of the solar cell, and reverse voltage is applied to the solar cell through the power supply; a strip-shaped laser spot irradiates the solar cell, and the strip-shaped laser spot extends along a second direction; the strip-shaped laser light spots move along the extending direction of the main grid line, scan the surface electrode of the solar cell, and remelt and recrystallize atoms of the metal and semiconductor materials at the interface; the application can effectively prevent the battery from being broken down, and can finish the treatment of the large-size battery only by one-way scanning of laser, thereby having high treatment efficiency.
Description
Technical Field
The application relates to the technical field of solar cell manufacturing, in particular to a method for reducing contact resistance of a crystalline silicon solar cell.
Background
The contact resistance between the front electrode and the back electrode of the crystalline silicon solar cell has a great influence on the filling factor and the conversion efficiency, and the lower the contact resistance is, the higher the filling factor and the conversion efficiency are. Particularly, N-type batteries, have become urgent demands of various large battery manufacturers because of their higher contact resistance relative to P-type batteries.
On the other hand, in order to pursue higher conversion efficiency, the sheet resistance of the emitter in the surface electrode of the crystalline silicon solar cell is becoming higher and higher, and it is also difficult to achieve lower contact resistance, and although many improvements are made from the slurry formulation at present, the results are still not ideal. Meanwhile, in the sintering process of the battery piece, the contact resistance is reduced by adopting a higher sintering temperature, but the passivation performance of the battery piece is affected. Therefore, the high sheet resistance of the emitter and the low sintering temperature are all reasons for restricting the low contact resistance of the crystalline silicon solar cell.
In order to reduce the contact resistance, the application patent with publication number CN111742417a "method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell" provides the following technical solutions: the reverse voltage of 1-20V is loaded at two ends of the solar cell, the use area is 1 multiplied by 10 3 -1×10 4 μm 2 Is irradiated by a laser spot to generate 200-20000A/cm locally 2 Current density ofThe very high current locally generated in the seed layer generates very high temperature at the silver-silicon contact point with very high contact resistance, thereby achieving the purpose of re-sintering once and further achieving the purpose of reducing the contact resistance.
The applicant has found in the study that this solution still has some drawbacks, which lead to the impossibility of mass production, in particular it has mainly the following drawbacks:
1. the spot area is too small, only 1×10 3 -10 4 μm 2 The method comprises the steps of carrying out a first treatment on the surface of the Crystalline silicon solar cells are nowadays widely expanded to 182mm or even 210mm in size, if an area of 1 x 10 is used 3 -1×10 4 um 2 The processing time of a single battery is far more than 1S when a large-size silicon wafer is irradiated by a laser spot, and the productivity is seriously affected.
2. The high-energy laser irradiates on the battery piece, the generated high current easily causes the battery piece to be high in temperature, the battery piece is easy to deform, and fragments appear under the action of stress.
3. Under the action of external reverse voltage, the current generated by laser illumination is reverse current in a closed loop, and if the reverse current is too high, the PN junction of the solar cell is reversely broken down, so that the structure of the cell is damaged.
In addition, the application patent publication CN109673171a, "method of improving ohmic contact characteristics between the contact grid and the emitter layer of the silicon solar cell" provides several means of connecting the solar cell to the reverse voltage, but still has a technical problem of mass production.
1. The connecting structure of the contact brush and the contact roller is too complex, which easily leads to scratch and fragments on the surface of the battery piece;
2. the connecting structure in the form of the contact piece ensures that the voltage of the reverse power supply loaded on the battery piece is uneven, the position closer to the contact piece can generate high enough current density, and the current density generated at the position far from the contact piece is weak, so that the battery piece treatment effect is uneven;
3. the connection structure in the form of contact pins also cannot uniformly load the voltage supplied by the reverse power supply on the battery plate, and in order to ensure good contact, the contact pins are designed by springs, and the elasticity of the contact pins is affected after laser scanning, so that the contact effect is poor.
Disclosure of Invention
In view of at least one defect or improvement requirement of the prior art, the application provides a method for reducing contact resistance of a crystalline silicon solar cell, which aims to solve the problems that a cell structure is easy to damage by laser radiation treatment and treatment efficiency is low.
To achieve the above object, according to one aspect of the present application, there is provided a method of reducing contact resistance of a crystalline silicon solar cell, comprising:
each conductive wire arranged in parallel is correspondingly pressed and connected to one main grid line of the surface electrode of the solar cell, and the conductive wires extend along the extending direction of the main grid line;
the first end of a power supply is electrically connected with each conductive wire, the second end of the power supply is electrically connected with the back electrode of the solar cell, and reverse voltage is applied to the solar cell through the power supply;
a strip-shaped laser spot irradiates the solar cell, and the strip-shaped laser spot extends along a second direction;
and the strip-shaped laser light spots move along the extending direction of the main grid line, the surface electrode of the solar cell is scanned, and atoms of the metal and semiconductor materials are remelted and recrystallized at the interface.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the length of the conductive wire is not smaller than the length of the main grid line of the solar cell.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the conductive wires and the main grid lines are arranged in one-to-one correspondence.
Further, the method for reducing the contact resistance of the crystalline silicon solar cell,
the second direction is a direction basically perpendicular to the main grid, and the length of the strip-shaped laser light spot in the second direction is not smaller than the dimension of the solar cell in the second direction; when the solar cell works, the radiation range of single scanning of the strip-shaped laser spots covers the whole surface of the solar cell.
Further, the method for reducing the contact resistance of the crystalline silicon solar cell further comprises the following steps:
an external resistor with adjustable resistance is arranged between the first end of the power supply and the conductive wire or between the second end of the power supply and the back electrode of the solar cell, and the current of the whole loop is regulated to be not more than the reverse breakdown current of the PN junction through the external resistor.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the projection width of the conductive wire on the surface of the solar cell is not larger than the width of the main grid line.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the cross section area of the conductive wire is 0.05-3.5mm 2 。
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the dimension of the strip-shaped laser spot in the extending direction of the main grid line is 0.01-10mm.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the power density of the laser spot is 500-1000W/cm 2 The reverse voltage is 5-20V, and the laser wavelength is 600-1500nm.
Further, the method for reducing the contact resistance of the crystalline silicon solar cell further comprises the step of controlling the temperature of the solar cell.
Further, in the method for reducing the contact resistance of the crystalline silicon solar cell, the solar cell is placed on the conductive object stage, two ends of the conductive wire are fixed on the press-arranging frame above the object stage and lifted by the lifting assembly, so that the conductive wire is close to and tightly presses the solar cell and is far away from the solar cell, and the second end of the power supply is electrically connected with the back electrode of the solar cell through the conductive object stage.
In general, the above technical solutions conceived by the present application, compared with the prior art, enable the following beneficial effects to be obtained:
(1) According to the application, remelting and recrystallization treatment of the surface electrode of the large-size solar cell can be completed through laser scanning, under the action of laser high temperature, the Ag-Si alloy interface remelts and recrystallizes, the arrangement mode of Ag/Si atoms at the interface deviated from the alloyed area is repaired, the eutectic generation rate at the whole Ag-Si alloy interface is obviously improved, and the contact conductivity is improved. On the other hand, under the combined action of reverse bias and laser radiation, H atoms in the passivation layer are driven to diffuse to the interface, broken bonds at the Ag-Si alloy interface are further passivated, carrier recombination is reduced, and the open-circuit voltage of a finished battery is improved.
(2) According to the application, one conductive wire is crimped on each main grid line of the solar cell, the surface electrode of the solar cell is electrically connected with an external power supply through each conductive wire, and reverse voltage applied by the external power supply is uniformly distributed on the surface electrode of the cell through the conductive wires, so that the consistency of sintering degrees of different positions is ensured; and the strip-shaped laser light spots are used for moving along the direction of the main grid line, scanning type radiation is carried out on the electrode on the surface of the solar cell, high photo-generated current is generated under the action of reverse voltage, the photo-generated current is uniformly distributed on each main grid line, and even if the generated radiation current is too high, the generated radiation current can be distributed on each main grid line, so that the solar cell is prevented from being broken down to cause damage.
(3) The application can finish the treatment of the large-size battery by one-way laser scanning, has high treatment efficiency and is beneficial to improving the productivity.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of an apparatus for reducing contact resistance of a crystalline silicon solar cell according to the present embodiment;
fig. 2 is a schematic diagram of the solar cell pressurization principle provided in the present embodiment;
fig. 3 is a flow chart of a method for reducing contact resistance of a crystalline silicon solar cell according to the present embodiment;
like reference numerals denote like technical features throughout the drawings, in particular:
1. solar cell
2. Main grid line
3. Conductive wire
4. Object stage
5. Stripe laser spot
6. First direction
7. Second direction
8P type silicon substrate
9N type emitter
10. External resistor
11. Fixing component
12. Fixed shaft
13. Positioning block
14. Press row frame
15. Elastic screw
16. Screw fixing piece
17. Position adjusting member
18. And a back electrode.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.
The terms first, second, third and the like in the description and in the claims and in the above drawings, are used for distinguishing between different objects and not necessarily for describing a particular sequential or chronological order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.
Furthermore, well-known or widely-used techniques, elements, structures, and processes may not be described or shown in detail in order to avoid obscuring the understanding of the present application by the skilled artisan. Although the drawings represent exemplary embodiments of the present application, the drawings are not necessarily to scale and certain features may be exaggerated or omitted in order to better illustrate and explain the present application.
The application provides a scheme for reducing the contact resistance of a crystalline silicon solar cell, which can uniformly disperse reverse voltages applied to two ends of the cell at different positions on the surface of the solar cell, and ensures that the process effects at different positions are consistent; the current generated by laser irradiation can be uniformly distributed on each main grid line of the battery, so that the risk of damage of the solar battery caused by high-current breakdown is improved. In addition, the scheme can finish the treatment of the large-size battery only by one-way laser scanning, has high treatment efficiency and is beneficial to improving the productivity.
In order to achieve the above-mentioned solution for reducing the contact resistance of the crystalline silicon solar cell, the present application provides an apparatus for reducing the contact resistance of the crystalline silicon solar cell, fig. 1 is a schematic structural diagram of the apparatus, and referring to fig. 1, the apparatus for reducing the contact resistance of the crystalline silicon solar cell mainly includes: a plurality of parallel conductive wires 3, wherein each conductive wire 3 extends along a first direction 6 of the solar cell 1, and generally, the length of each conductive wire is not less than the length of the main grid line 2 of the solar cell 1, and the first direction 6 is the extending direction of the main grid line 2; a laser processing module for providing a strip-shaped laser spot 5, wherein the strip-shaped laser spot 5 extends along a second direction 7 of the solar cell 1, and the second direction is generally a direction substantially perpendicular to the first direction, and the second direction 7 is generally an extending direction of a sub-grid line (not shown) of the prior art cell, and controls the strip-shaped laser spot 5 to move along the first direction of the solar cell 1; also included is a power supply (not shown in fig. 1) having a first end electrically connected to each conductive filament 3 and a second end electrically connected to the back electrode of the solar cell 1.
When the solar cell is in operation, each conductive wire 3 is correspondingly pressed on one main grid line 2 of the solar cell, and reverse voltage applied by a power supply is uniformly distributed on the surface of the solar cell 1 through the conductive wires 3; the strip-shaped laser spots 5 are controlled to move along the first direction 6, and scanning radiation is carried out on the electrodes on the surface of the solar cell 1, so that generated radiation current is uniformly collected on each main grid line 2 covered by the strip-shaped laser spots 5.
In a specific embodiment, the strip-shaped laser spot 5 is generated by a laser processing module (not shown) disposed above the solar cell, and the strip-shaped laser spot 5 generated by the laser source is made to perform scanning radiation on the surface of the solar cell 1 along the extending direction of the main grid line 2. Generally, the laser processing module includes a laser source for emitting laser; and the shaping assembly is used for shaping the laser into a strip-shaped light spot, and the scanning assembly is used for enabling the strip-shaped laser light spot to move along a first direction. In one non-limiting embodiment, the laser source is a laser, the shaping component is a DOE, a microlens or other shaping component, the strip-shaped laser spot 5 is generated by shaping, the scanning component is a galvanometer, and the strip-shaped laser spot 5 scans the surface of the solar cell 1 along the extending direction of the main grid line 2 by means of the galvanometer.
In a preferred example, the extension length of the strip-shaped laser spot 5 generated by the laser processing module is not smaller than the dimension of the solar cell 1 in the second direction 7, so that the radiation range of the single scanning of the strip-shaped laser spot can cover the whole surface electrode of the solar cell 1. The dimension of the stripe laser spot 5 in the first direction 6 (i.e., the length in the main grid line direction) is not particularly limited, and in one example, the dimension is 0.01 to 10mm. Taking 182mm x 182mm solar cells as an example, the strip laser spot 5 can be designed to have a size of 0.1 x 182mm, so that one scan is performed along the scan direction, thereby greatly shortening the process time.
In a specific embodiment, the apparatus for reducing contact resistance of a crystalline silicon solar cell further includes a stage 4 for placing the solar cell 1, where the stage is a metal stage with conductive properties, or a second conductive device with a conductive material fixed on the upper surface of the stage, where the material is not limited, and the solar cell is placed above the stage 4 with its front surface facing upwards, and the back surface is in contact with the stage 4, so that the second conductive device on the stage 4, or the stage 4 itself is used as the second conductive device, and is connected to a power source. In detail, referring to fig. 2, a solar cell 1 is placed on the stage 4, the upper surface of the stage 4 contacts with a back electrode 18 of the solar cell 1, an N-type emitter 9 of the solar cell faces upwards, and a conductive wire 3 is crimped on each main grid line 2 of the surface electrode during operation, and since each conductive wire 3 is connected with the positive electrode of the power supply, the N-type emitter 9 of the solar cell is connected with the positive electrode of the power supply through the conductive wire 3; the stage 4 is electrically connected to the negative electrode of the power source, and the back electrode 18 of the solar cell 1 is connected to the power source through the stage 4, thereby forming a conductive path, and the power source applies a reverse voltage to the solar cell 1.
In a preferred example, the stage 4 is a vacuum adsorption stage, which can be used for vacuum adsorption, so that the solar cell 1 can be better fixed, and the situation that the conductive wire 3 cannot be accurately pressed against the main grid line 2 due to movement of the solar cell during the working process is avoided. Furthermore, the stage 4 is a temperature control stage, which can reduce the high temperature generated when the solar cell 1 irradiates with laser, thereby eliminating the deformation of the cell and avoiding the occurrence of fragments. Those skilled in the art know that the vacuum adsorption function can be realized by arranging the adsorption holes on the upper surface of the objective table 4 and arranging the adsorption cavity on the objective table 4 and connecting the vacuum generating device. The stage 4 is provided with a cooling cavity, and the temperature of the stage 4 can be controlled by water cooling, air cooling or the like.
In fig. 2, an external resistor 10 is arranged between the positive electrode of the power supply and the conductive wire 3, the external resistor 10 is an adjustable resistor, the resistance value of the external resistor is adjustable, and the current in the whole loop is controlled through the external resistor 10, so that the generated radiation current is not more than the reverse breakdown current of the PN junction, and the damage of the solar cell 1 caused by the breakdown of the PN junction is avoided; in one specific example, the external resistor has a resistance value of 0-10 ohms. Of course, the external resistor 10 may be disposed between the negative electrode of the power source and the stage 4.
With continued reference to fig. 1, the apparatus for reducing contact resistance of a crystalline silicon solar cell further includes two fixing members 11 distributed at two ends of the conductive wire 3, where the end of each conductive wire 3 is connected to one fixing member 11, and each conductive wire 3 is fixed and straightened by the two fixing members 11, so that the conductive wire 3 can be better crimped on the main grid line 2.
As a specific example, each of the fixing parts 11 includes a fixing shaft 12 and a plurality of positioning blocks 13 provided on the fixing shaft 12; the number of the positioning blocks 13 is not less than that of the conductive wires 3, and two ends of each conductive wire 3 are fixed on one positioning block 13. Specifically, after the conductive wire 3 passes through the hole on the positioning block 13, the conductive wire 3 is wound on the screw on the positioning block 13, and the conductive wire 3 is locked by screwing the screw. In this example, each positioning block 13 is movably connected with the fixed shaft 12, and can move along the axial direction of the fixed shaft 12, so that the distance between two adjacent positioning blocks 13 can be adjusted according to the requirement, and the distance between two adjacent conductive wires 3 can be adjusted according to the distance between the main grid lines 2 on the solar cell 1, so that the device can adapt to solar cells 1 with different sizes and specifications.
In addition, in the present embodiment, the end portions of the two fixed shafts 12 are respectively mounted on a press-row frame 14, and the press-row frame 14 and the fixing member 11 are located above the stage 4; in a specific example, the position where the fixed shaft 12 is connected to the press-row frame 14 is fixed by a screw fixing member 16 and a tightening screw 15. In addition, the position of the fixed shaft 12 in the first direction can be adjusted by the screw fixing member 16 and the tightening screw 15, and in fig. 1, the tightening screw 15 is tightened to move the fixed shaft 12 to the right as the fixed shaft 12 on the right is screwed, so as to tighten the conductive wire 3.
Further, the above-mentioned device for reducing contact resistance of crystalline silicon solar cell further comprises a position adjusting component 17; the position adjusting part 17 is mainly used to control the fixing part 11 to move up and down, thereby adjusting the distance between the conductive wire 3 mounted on the fixing part 11 and the surface of the solar cell 1 placed on the stage 4.
As a specific example, the position adjusting part 17 is implemented by a cylinder structure fixedly connected to the press-bar frame 14, and drives the press-bar frame 14 to move up and down by pneumatic transmission, thereby changing the distance between the conductive wires 3 and the solar cell 1. Generally, when the stage 4 is fixed, the press-row frame 14 is raised first, the solar cell 1 is placed on the surface of the stage 4, and then the press-row frame 14 is controlled to descend, so that the conductive wire 3 is pressed against the main grid line 2 of the solar cell 1. Of course, the position adjusting part 17 may be implemented in other ways than pneumatic transmission, which are all within the scope of the present solution. Preferably, the two position adjusting firmware parts 17 (only one is shown in the figure) are symmetrically arranged at two sides of the press-row frame 14, so that the press-row frame is more stable to lift.
On the other hand, the application also provides a method for reducing the contact resistance of the crystalline silicon solar cell, wherein each main grid line of the solar cell is in pressure connection with one conductive wire, the surface electrode of the solar cell is electrically connected with an external power supply through each conductive wire, and reverse voltage applied by the external power supply is uniformly distributed on the surface electrode of the cell through the conductive wires; the strip-shaped laser light spots extending along the second direction of the solar cell are used for radiating the surface of the cell, the second direction is the extending direction of the auxiliary grid line, the strip-shaped laser light spots are controlled to move along the direction of the main grid line, scanning type radiation is carried out on the electrode on the surface of the solar cell, so that radiation current generated by light spot irradiation can be uniformly distributed to each main grid line, even if the generated radiation current is too high, each main grid line can be shared, and the solar cell is prevented from being broken down to cause damage.
Fig. 3 is a flowchart of a method for reducing contact resistance of a crystalline silicon solar cell according to the present embodiment, referring to fig. 3, the method includes the following steps:
s1, correspondingly crimping each parallel conductive wire on one main grid line of a solar cell, wherein the conductive wires extend along a first direction of the solar cell, and generally, the length of the conductive wires is not less than the length of the main grid line of the solar cell, and the first direction is the extending direction of the main grid line;
in the step, the extending direction of a main grid line on a solar cell is defined as a first direction, a plurality of conductive wires which are arranged in parallel along the first direction form a pressing structure, and the extending direction of the conductive wires is consistent with the direction of the main grid line of the solar cell, so that each conductive wire can be just correspondingly pressed on one main grid line; the length of each conductive wire cannot be smaller than the extension length of the main grid line; the shape of the conductive wires mainly depends on the shape of the main grid line of the solar cell, so that each conductive wire can be tightly pressed on the corresponding main grid line; for example, if the shape of the main gate line is linear, the shape of the conductive wire is also set to be linear. In addition, the projection width of each conductive wire on the surface of the solar cell is preferably not larger than the width of the main grid line, so that the press-row structure formed by the conductive wires can not form excessive shielding on the surface of the cell, and the solar cell can receive laser scanning to the greatest extent. Note that, if the main grid line on the solar cell is not a straight line but has another relatively regular shape, the extending direction of the approximate center line of the main grid line is defined as the first direction.
In one non-limiting specific example, the conductive wires are copper wires in an amount of 5-20 and have a cross-sectional area of 0.05-3.5mm 2 The distance between adjacent conductive wires is generally the same and is 10-30mm. Preferably, the number of the conductive wires is preferably consistent with that of the main grid lines, and the distance between the adjacent conductive wires is consistent with that between the adjacent main grid lines, that is, the conductive wires are in one-to-one correspondence with the main grid lines in a crimping manner, and the conductive wires are in one-to-one correspondence with the main grid lines. The above preferable scheme can also be that the number of the conductive wires can be more or less than that of the main grids, and the process effect is optimal when the number is consistent and the main grids are in one-to-one corresponding compression joint. In addition, the material of the conductive wire is not limited to copper wire, and may be other materials having conductive properties. The cross section of the conductive wire is not limited to a circle, but may be other shapes such as a square, a rectangle, an ellipse, etc.
S2, providing a power supply, electrically connecting a first end of the power supply with each conductive wire, and electrically connecting a second end of the power supply with a back electrode of the solar cell; applying reverse voltage to the solar cell through a power supply, wherein the reverse voltage is uniformly distributed on the surface of the solar cell through conductive wires;
in this step, the power supply is mainly used to apply a reverse voltage to the solar cell, and therefore, the positive and negative electrodes of the power supply need to be electrically connected with metal electrodes (denoted as a surface electrode and a back electrode) on the front and back surfaces of the solar cell; in this embodiment, the solar cell is a P-type PERC cell, and the (front) surface electrode thereof is a negative electrode. The positive electrode of the power supply is electrically connected with each conductive wire, and the negative electrode of the power supply is electrically connected with the back electrode of the solar cell; after the conductive wire is pressed and connected with the main grid line of the surface electrode, the positive electrode of the power supply is electrically connected with the main grid line. Of course, for a solar cell with a positive electrode on the front side and a negative electrode on the back side, the positive electrode of the power supply may be electrically connected to the back electrode of the solar cell, while the negative electrode is electrically connected to each conductive wire, and the battery sheet is only required to be placed in a reverse direction with the front side facing down and the back side facing up. Both of the above connection methods can apply a reverse voltage to the solar cell.
Because each main grid line on the surface of the solar cell is in pressure connection with one conductive wire, reverse voltage applied by a power supply is uniformly distributed to different areas on the surface of the solar cell through the conductive wires, and the different areas have the same technological effect in the subsequent laser scanning irradiation treatment process, so that the condition of uneven treatment effect of different positions of the cell is avoided.
S3, providing a strip-shaped laser spot, wherein the strip-shaped laser spot extends along a second direction of the solar cell, and the second direction is the extending direction of the auxiliary grid line;
in this embodiment, a strip-shaped laser spot is used to radiate the surface of the solar cell, and in one example, the sub-grid line on the solar cell is in a standard linear shape, and the extending direction of the sub-grid line on the solar cell is defined as a second direction, where the strip-shaped laser spot extends along the second direction of the solar cell; when the main grid line and the auxiliary grid line of the solar cell are vertical, the second direction is a direction vertical to the first direction; the second direction is not perpendicular to the first direction.
S4, controlling the strip-shaped laser light spots to move along the first direction, and carrying out scanning radiation on the electrodes on the surface of the solar cell, so that generated radiation current is uniformly collected on each main grid line covered by the strip-shaped laser light spots.
In the embodiment, the electrode on the surface of the solar cell is subjected to scanning radiation through the strip-shaped laser light spot, extremely high photo-generated current is generated in the irradiation area of the laser light spot under the action of reverse voltage, and higher temperature is generated in the area with higher flowing contact resistance, so that the effect similar to secondary sintering is achieved, and the contact resistance is reduced; in the process, carriers generated by laser radiation are absorbed by the auxiliary grid line and collected to the main grid line; the strip-shaped laser spots are scanned along the extending direction of the main grid lines, so that the current collected on each main grid line is the same. Even if higher current is generated due to larger light spot size, the current can be born to each main grid line, and the PN junction is prevented from being broken down. If the scanning direction of the strip-shaped laser spot is perpendicular to the main grid line (such as scanning along the extending direction of the auxiliary grid line), the generated current is collected by the main grid line nearest to the laser spot, so that the current at the main grid line is overlarge, and the PN junction is reversely broken down.
With the radiation method of this example, the more main grid lines on the surface of the solar cell, the lower the current shared by each main grid line, the less likely it is to be broken down.
In order to ensure that the laser spot can cover the entire surface of the solar cell by one scan, in a preferred example, the extension length of the strip-shaped laser spot is not smaller than the dimension of the solar cell in the second direction, so that the radiation range of the single scan of the strip-shaped laser spot can cover the entire surface electrode of the solar cell. The dimension of the stripe laser spot in the first direction (i.e., the length in the main grid line direction) is not particularly limited, and in one example, the dimension is 0.01 to 10mm. Taking 182mm x 182mm solar cells as an example, the strip laser light spot can be designed to be 0.1 x 182mm in size, so that one scanning can be performed along the scanning direction, the small light spot is not required to be scanned back and forth for multiple times, and the process time is greatly shortened.
In addition, in order to prevent the overlarge current generated by laser radiation from exceeding the breakdown current, an external resistor with an adjustable resistance value is arranged between the first end of the power supply and the conductive wire or between the second end of the power supply and the back electrode of the solar cell, and the current in the whole loop is controlled through the external resistor, so that the generated radiation current is not more than the reverse breakdown current of the PN junction; in one specific example, the external resistor has a resistance value of 0-10 ohms.
In more detail, in the application, the power density of the laser spot is 500-1000W/cm 2 The reverse voltage is 5-20V, and the laser wavelength is 600-1500nm.
And S5, after the scanning of the battery piece is completed by the laser, removing the strip-shaped laser light spots and the conductive wires, removing the battery piece, and carrying out the next battery treatment.
As an example of continuous processing, the press-row frame is lifted, the battery piece is placed on the object stage to be adsorbed, then the press-row frame is pressed down, the conductive wires are pressed on the main grid line of the electrode on the surface of the battery one by one, reverse voltage is provided, and the strip-shaped laser light spots extending along the second direction are irradiated to the solar battery piece and scanned from one end to the other end of the solar battery along the second direction; after the completion, will press row frame to lift up, objective table adsorption function closes, and the battery piece of accomplishing is removed. The other untreated battery piece was placed on the stage and processed in such a cycle.
It should be noted that while in the above-described embodiments the operations of the methods of the embodiments of the present specification are described in a particular order, this does not require or imply that the operations must be performed in that particular order or that all of the illustrated operations be performed in order to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step to perform, and/or one step decomposed into multiple steps to perform.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the application and is not intended to limit the application, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the application are intended to be included within the scope of the application.
Claims (11)
1. A method for reducing contact resistance of a crystalline silicon solar cell, comprising:
each conductive wire arranged in parallel is correspondingly pressed and connected to one main grid line of the surface electrode of the solar cell, and the conductive wires extend along the extending direction of the main grid line;
the first end of a power supply is electrically connected with each conductive wire, the second end of the power supply is electrically connected with the back electrode of the solar cell, and reverse voltage is applied to the solar cell through the power supply;
a strip-shaped laser spot irradiates the solar cell, and the strip-shaped laser spot extends along a second direction;
and the strip-shaped laser light spots move along the extending direction of the main grid line, the surface electrode of the solar cell is scanned, and atoms of the metal and semiconductor materials are remelted and recrystallized at the interface.
2. The method of reducing contact resistance of a crystalline silicon solar cell according to claim 1, wherein the length of the conductive wire is not less than the length of the main grid line of the solar cell.
3. The method for reducing contact resistance of a crystalline silicon solar cell according to claim 1, wherein the conductive wires and the main grid lines are arranged in a one-to-one correspondence.
4. A method for reducing contact resistance of a crystalline silicon solar cell according to any one of claim 1 to 3,
the second direction is a direction basically perpendicular to the main grid, and the length of the strip-shaped laser light spot in the second direction is not smaller than the dimension of the solar cell in the second direction; when the solar cell works, the radiation range of single scanning of the strip-shaped laser spots covers the whole surface of the solar cell.
5. A method of reducing contact resistance of a crystalline silicon solar cell as claimed in any one of claims 1 to 3, further comprising:
an external resistor with adjustable resistance is arranged between the first end of the power supply and the conductive wire or between the second end of the power supply and the back electrode of the solar cell, and the current of the whole loop is regulated to be not more than the reverse breakdown current of the PN junction through the external resistor.
6. A method of reducing contact resistance of a crystalline silicon solar cell as claimed in any one of claims 1 to 3 wherein the projected width of the conductive filaments on the surface of the solar cell is no greater than the width of the main grid line.
7. A method for reducing contact resistance of a crystalline silicon solar cell as claimed in any one of claims 1 to 3, wherein the cross-sectional area of the conductive wire is 0.05-3.5mm 2 。
8. A method of reducing contact resistance of a crystalline silicon solar cell as claimed in any one of claims 1 to 3 wherein the dimension of the stripe-shaped laser spot in the direction of extension of the main grid line is 0.01-10mm.
9. A method of reducing contact resistance of a crystalline silicon solar cell according to any one of claims 1 to 3, wherein the power density of the laser spot is 500-1000W/cm 2 The reverse voltage is 5-20V, and the laser wavelength is 600-1500nm.
10. A method of reducing contact resistance of a crystalline silicon solar cell according to any one of claims 1 to 3, further comprising controlling the temperature of the solar cell.
11. A method of reducing contact resistance of a crystalline silicon solar cell as claimed in any one of claims 1 to 3 wherein the solar cell is placed on a conductive stage, the ends of the conductive wire are secured to a press frame above the stage and lifted by a lifting assembly to bring the wire closer to and farther from the solar cell, and the second end of the power supply is electrically connected to the back electrode of the solar cell via the conductive stage.
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