CN217485456U

CN217485456U - Equipment for reducing contact resistance of crystalline silicon solar cell

Info

Publication number: CN217485456U
Application number: CN202220553790.6U
Authority: CN
Inventors: 张强; 陆红艳; 朱凡; 沈家军; 李刘军; 朱宝胜
Original assignee: Dier Laser Technology Wuxi Co ltd
Current assignee: Dier Laser Technology Wuxi Co ltd
Priority date: 2022-03-14
Filing date: 2022-03-14
Publication date: 2022-09-23
Anticipated expiration: 2032-03-14

Abstract

The application discloses reduce crystalline silicon solar cell contact resistance's equipment, this equipment includes: the conductive wires are arranged in parallel, each conductive wire extends along a first direction of the battery, the length of each conductive wire is not less than that of a main grid line of the battery, and the first direction is the extending direction of the main grid line; the strip-shaped laser spot extends along a second direction of the battery, and the second direction is the extending direction of the auxiliary grid line; the first end of the power supply is electrically connected with each conductive wire, and the second end of the power supply is electrically connected with the back electrode of the battery; when the battery works, each conductive wire is correspondingly pressed on one main grid line, and reverse voltage applied by a power supply is uniformly distributed on the surface of the battery through the conductive wires; the bar-shaped laser facula moves along a first direction to perform scanning radiation on the electrode on the surface of the battery; the invention can effectively prevent the battery from being broken down, can finish the treatment of the large-size battery only by one-way laser scanning, and has high treatment efficiency.

Description

Equipment for reducing contact resistance of crystalline silicon solar cell

Technical Field

The application relates to the technical field of solar cell manufacturing, in particular to equipment for reducing contact resistance of a crystalline silicon solar cell.

Background

The contact resistance between the surface electrode and the back electrode of the crystalline silicon solar cell has a great influence on the fill factor and the conversion efficiency, and the lower the contact resistance is, the higher the fill factor and the conversion efficiency are. Particularly, N-type batteries, because their contact resistance is higher than that of P-type batteries, reducing the contact resistance has become an urgent need for manufacturers of large batteries.

On the other hand, in pursuit of higher conversion efficiency, the sheet resistance of the emitter in the surface electrode of the crystalline silicon solar cell is made higher and higher, resulting in difficulty in forming lower contact resistance, and although many improvements are made in the slurry formulation at present, the result is 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 influenced. Therefore, the high sheet resistance of the emitter and the lower sintering temperature are reasons for limiting the achievement of low contact resistance of the crystalline silicon solar cell.

In order to reduce the contact resistance, the invention patent with publication number CN111742417A, "a method for improving ohmic contact characteristics between a contact grid and an emitter layer of a silicon solar cell" provides the following technical solutions: applying reverse voltage of 1-20V to both ends of the solar cell, and using area is 1 × 10 ³ -1×10 ⁴ Irradiation is carried out by a laser spot of μm2, and 200- ² Current density ofThe locally generated very high current generates very high temperature on the silver-silicon contact point with very high contact resistance, thereby achieving the purpose of sintering once again and further reducing the contact resistance.

The applicant found in the research that this solution still has some drawbacks, which make it impossible to achieve mass production, and in particular it mainly has the following drawbacks:

1. the spot area is too small, only 1X 10 ³ -10 ⁴ μm ² (ii) a Nowadays, the size of the crystalline silicon solar cell is generally expanded to 182mm or even 210mm, if the area is 1 × 10 ³ -1×10 ⁴ um ² When the laser faculae irradiate the large-size silicon wafer, the processing time of the single cell is far more than 1S, and the productivity is seriously influenced.

2. High-energy laser irradiates on the cell, and the generated high current easily causes the high temperature of the cell, so that the cell is easily deformed and fragments appear under the action of stress.

3. Under the action of external reverse voltage, current generated by laser illumination is reverse current in a closed loop, and if the reverse current is too high, PN junction reverse breakdown of the solar cell is caused, and the structure of the cell is damaged.

In addition, the invention patent publication CN109673171A "method for improving ohmic contact characteristics between contact grid and emitter layer of silicon solar cell" provides several devices for connecting solar cell piece with reverse voltage, but still has the technical problem of mass production.

1. The connection structure in the form of the contact brush and the contact roller is too complex, so that the surface of the battery piece is easily scratched and chipped;

2. the connection structure in the form of the contact pieces enables the voltage loaded on the battery piece by the reverse power supply to be uneven, the position closer to the contact pieces can generate enough high current density, the current density generated at the position far away from the contact pieces is very weak, and the battery piece processing effect is uneven;

3. the connection structure of contact pin form also can't make the voltage that reverse power supply provided load evenly on the battery piece, and the contact pin design is in order to guarantee good contact, and inside all can use the spring design, and laser scanning has been of a specified duration can influence the elasticity of contact pin, leads to the contact effect not good.

Disclosure of Invention

In view of at least one of the drawbacks and needs of the prior art, the present invention provides an apparatus for reducing contact resistance of a crystalline silicon solar cell, which is aimed at improving the problems of the cell structure being easily damaged by laser radiation treatment and the low treatment efficiency.

To achieve the above object, according to an aspect of the present invention, there is provided an apparatus for reducing contact resistance of a crystalline silicon solar cell, comprising:

the solar cell comprises a plurality of conductive wires which are arranged in parallel, wherein each conductive wire extends along a first direction and can be pressed on a main grid line of a surface electrode of a solar cell;

the laser processing module generates a strip-shaped laser spot, the strip-shaped laser spot extends along the second direction and moves along the first direction to scan the surface electrode of the solar cell;

a second conductive device contacting the back electrode of the solar cell;

and the first end of the power supply is electrically connected with each conductive wire, and the second end of the power supply is connected with the second conductive device and provides reverse voltage.

Further, according to the device for reducing the contact resistance of the crystalline silicon solar cell, the first direction is the direction of the solar cell main grid line, and the second direction is a direction substantially perpendicular to the first direction.

Further, the device for reducing the contact resistance of the crystalline silicon solar cell further comprises an object stage for bearing the solar cell, wherein the second conductive device is fixed on the object stage;

or the stage is a second electrically conductive device.

Further, according to the device for reducing the contact resistance of the crystalline silicon solar cell, the objective table is a negative pressure adsorption objective table, and/or the objective table is a temperature control objective table.

Furthermore, the device for reducing the contact resistance of the crystalline silicon solar cell further comprises a pressure row frame for supporting the conductive wires, and two ends of each conductive wire are respectively connected to the pressure row frame.

Further, the device for reducing the contact resistance of the crystalline silicon solar cell further comprises a position adjusting component;

the position adjusting component is a lifting component and is fixedly connected with the pressure bar frame, the pressure bar frame is controlled to move up and down, the distance between the conductive wire and the objective table is adjusted, and the conductive wire is close to and tightly presses the solar cell and is far away from the solar cell.

Further, the device for reducing the contact resistance of the crystalline silicon solar cell,

the pressure bar frame comprises fixed shafts respectively arranged at two ends of the conductive wire and a plurality of positioning blocks capable of moving along the shafts, and two ends of the conductive wire are respectively fixed on one positioning block.

Further, according to the device for reducing the contact resistance of the crystalline silicon solar cell, the conductive wire penetrates through the hole in the positioning block and is fixed on the screwing piece on the positioning block, and the conductive wire is locked through the screwing piece.

the laser processing module comprises a laser source for emitting laser;

the shaping assembly is used for shaping the laser into a strip-shaped laser spot extending along the second direction;

and the scanning assembly enables the strip-shaped laser light spot to move along the first direction.

Further, according to the device for reducing the contact resistance of the crystalline silicon solar cell, 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.

Further, according to the device for reducing the contact resistance of the crystalline silicon solar cell, the conductive wire is a copper wire.

Further, according to the device 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, according to the device for reducing the contact resistance of the crystalline silicon solar cell, the size of the strip-shaped laser light spot in the first direction is 0.01-10 mm;

the extension length of the strip-shaped laser light spot is not less than the size of the solar cell in the second direction; when the solar cell is in operation, the radiation range of single scanning of the strip-shaped laser facula covers the whole surface of the solar cell.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the invention can complete the remelting recrystallization treatment of the surface electrode of the large-size solar cell through laser scanning, the Ag-Si alloy interface remelts and recrystallizes under the action of high temperature of laser, the arrangement mode of Ag/Si atoms at the area of the interface deviating from alloying 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 the finished battery is improved.

(2) According to the invention, each main grid line of the solar cell is pressed 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, so that the sintering degrees of different positions are consistent; and the bar-shaped laser facula is used for moving along the direction of the main grid lines, scanning radiation is carried out on the electrodes on the surface of the solar cell, higher photo-generated current is generated under the action of reverse voltage, the photo-generated current is uniformly distributed to each main grid line, and each main grid line can be shared even if the generated radiation current is too high, so that the solar cell is prevented from being broken down to cause damage.

(3) The invention can complete 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 in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

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 view illustrating a pressurizing principle of the solar cell provided in the present embodiment;

fig. 3 is a schematic flow chart of a method for reducing contact resistance of a crystalline silicon solar cell according to the present embodiment;

throughout the drawings, like reference numerals designate like features, and in particular:

1 solar cell

2 main grid line

3 conductive yarn

4 objective table

5 strip-shaped laser facula

6 first direction

7 the second direction

8P type silicon substrate

9N type emitter

10 external resistor

11 fixing part

12 fixed shaft

13 locating block

14 pressing frame

15 elastic screw

16 screw fixing piece

17 position adjusting part

18 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 drawings in the embodiments of the present application.

The terms "first," "second," "third," and the like in the description and claims of this application and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

In other instances, well-known or widely used techniques, elements, structures and processes may not have been described or shown in detail to avoid obscuring the understanding of the present invention by the skilled artisan. Although the drawings represent exemplary embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated or omitted in order to better illustrate and explain the present invention.

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 ensure 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 cell, and the risk of damage of the solar cell caused by high-current breakdown is improved. In addition, the scheme can complete the treatment of the large-size battery only by one-way laser scanning, has high treatment efficiency and is beneficial to improving the productivity.

On one hand, in order to implement the above scheme 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, please refer to fig. 1, and the apparatus for reducing the contact resistance of the crystalline silicon solar cell mainly includes: a plurality of conductive wires 3 arranged in parallel, wherein each conductive wire 3 extends along a first direction 6 of the solar cell 1, and generally, the length of each conductive wire 3 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, configured to provide a bar-shaped laser spot 5, where the bar-shaped laser spot 5 extends along a second direction 7 of the solar cell 1, generally, the second direction is a direction substantially perpendicular to the first direction, and in the battery of the prior art, the second direction 7 is an extending direction of a sub-grid line (not shown in fig. 1), and the bar-shaped laser spot 5 is controlled to move along the first direction of the solar cell 1; a power source (not shown in fig. 1) is further included, a first end of the power source is electrically connected to each conductive wire 3, and a second end of the power source is electrically connected to the back electrode of the solar cell 1.

When the solar cell is in work, 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; and controlling the strip-shaped laser spots 5 to move along the first direction 6, and carrying out scanning radiation on the electrodes on the surface of the solar cell 1, so that the generated radiation current is uniformly converged on each main grid line 2 covered by the strip-shaped laser spots 5.

In one 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 scanned along the extending direction of the bus bar 2 to irradiate the surface of the solar cell 1. Generally, a laser processing module includes a laser source for emitting laser light; and the shaping component shapes the laser into a strip-shaped light spot, and the scanning component enables the strip-shaped laser light spot to move along the first direction. In a non-limiting embodiment, the laser source is a laser, the shaping component is a DOE, a micro lens or other beam shaping component, the strip-shaped laser spot 5 is generated through shaping, the scanning component is a galvanometer, and the strip-shaped laser spot 5 performs scanning radiation on the surface of the solar cell 1 along the extending direction of the main grid line 2 through the scanning mode of the galvanometer.

In a preferred example, the laser processing module generates the stripe-shaped laser spot 5 with an extension length not less than the dimension of the solar cell 1 in the second direction 7, so that the irradiation range of a single scan of the stripe-shaped laser spot can cover the whole surface electrode of the solar cell 1. The size of the stripe-shaped laser spot 5 in the first direction 6 (i.e., the length in the direction along the bus bar line) is not particularly limited, and in one example, the size is 0.01 to 10 mm. Taking 182mm by 182mm solar cells as an example, the stripe-shaped laser spot 5 can be designed to be 0.1 mm by 182mm in size, so that one scan can be performed along the scanning direction, thereby greatly shortening the process time.

In a specific embodiment, the above apparatus for reducing the contact resistance of the crystalline silicon solar cell further comprises an object stage 4 for placing the solar cell 1, the object stage is a metal stage with conductivity, or a second conductive device made of conductive material is fixed on the upper surface of the object stage, the material of the second conductive device is not limited, the solar cell is placed above the object stage 4 with the front side facing upwards, the back side of the solar cell is in contact with the object stage 4, so that the second conductive device on the object stage 4, or the object stage 4 itself is used as the second conductive device and is connected with a power supply. In detail, referring to fig. 2, the solar cell 1 is placed on the object stage 4, the upper surface of the object stage 4 is in contact with the back electrode 18 of the solar cell 1, the N-type emitter 9 of the solar cell faces upward, one conductive wire 3 is pressed 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 a negative electrode of a power supply, and the back electrode 18 of the solar cell 1 is connected to the power supply through the stage 4, thereby forming a conductive path, and the power supply applies a reverse voltage to the solar cell 1.

In a preferred example, the object stage 4 is a vacuum adsorption object stage, which can be vacuum adsorbed, and can better fix the solar cell 1, so as to prevent the solar cell from moving in the working process, which causes the problem that the conductive wire 3 and the main grid line 2 cannot be accurately crimped. Furthermore, the objective table 4 is a temperature control objective table, which can reduce the high temperature generated by the solar cell 1 during the laser radiation, thereby eliminating the deformation of the cell and avoiding the occurrence of fragments. As known to those skilled in the art, the vacuum adsorption function can be realized by providing an adsorption hole on the upper surface of the objective table 4, providing an adsorption cavity on the objective table 4, and connecting the vacuum generation device. Set up the cooling cavity in objective table 4, through modes such as water-cooling or air cooling, can realize objective table 4's accuse temperature.

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 of the external resistor is adjustable, the current in the whole loop is controlled through the external resistor 10, so that the generated radiation current is not greater than the reverse breakdown current of the PN junction, and the solar cell 1 is prevented from being damaged due to the breakdown of the PN junction; 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 power source cathode and the stage 4.

With reference to fig. 1, the apparatus for reducing the contact resistance of the crystalline silicon solar cell further includes two fixing parts 11 distributed at two ends of the conductive wires 3, wherein an end of each conductive wire 3 is connected to one fixing part 11, and each conductive wire 3 is fixed and straightened by the two fixing parts 11, so that the conductive wires 3 can be better pressed on the main grid line 2.

As a specific example, each of the fixing members 11 includes a fixing shaft 12 and a plurality of positioning blocks 13 disposed on the fixing shaft 12; the number of the positioning blocks 13 is not less than the number of the conductive wires 3, and two ends of each conductive wire 3 are fixed on one positioning block 13. Specifically, the conductive wire 3 is wound around a screw on the positioning block 13 after passing through a hole 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 to the fixing shaft 12 and can move axially along the fixing shaft 12, so that the distance between two adjacent positioning blocks 13 can be adjusted as required, 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, thereby ensuring that the device can adapt to solar cells 1 of different sizes and specifications.

In addition, in the present embodiment, the ends of the two fixed shafts 12 are respectively mounted on a platen frame 14, and the platen frame 14 and the fixed member 11 are located above the stage 4; in one specific example, the position where the fixed shaft 12 is connected with the packing frame 14 is fixed by a screw fixing member 16 and a turnbuckle 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 elastic screw 15, and in fig. 1, taking the fixed shaft 12 on the right side as an example, the more the elastic screw 15 is screwed, the more the fixed shaft 12 moves to the right side, so as to tighten the conductive wire 3.

Further, the device for reducing the contact resistance of the 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 component 17 is implemented by using a cylinder structure, the cylinder structure is fixedly connected with the busbar frame 14, and the busbar frame 14 is driven by pneumatic transmission to move up and down, so as to change the distance between the conductive wire 3 and the solar cell 1. Generally, in the case that the stage 4 is fixed, the light-emitting device 1 is placed on the surface of the stage 4 by raising the light-emitting frame 14, and then the light-emitting device 14 is controlled to be lowered so that the conductive wires 3 are just pressed against the bus bars 2 of the light-emitting device 1. Of course, the position adjusting component 17 can be realized by other modes besides the pneumatic transmission, and is within the protection scope of the present scheme. Preferably, the position adjustment fasteners 17 are two (only one is shown in the figure) and are symmetrically arranged on two sides of the battering frame 14, so that the lifting and the falling of the battering frame are more stable.

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 crimped 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 facula extending along the second direction of the solar cell is used for radiating the surface of the cell, the second direction is the extending direction of the auxiliary grid lines, the strip-shaped laser facula is controlled to move along the direction of the main grid lines, and scanning type radiation is carried out on the electrode on the surface of the solar cell, so that the radiation current generated by the irradiation of the facula can be uniformly distributed on each main grid line, even if the generated radiation current is too high, each main grid line can be shared, and the damage caused by the breakdown of the solar cell is prevented.

Fig. 3 is a schematic flow chart of a method for reducing contact resistance of a crystalline silicon solar cell according to the present embodiment, please refer to fig. 3, the method includes the following steps:

s1, pressing each of the conductive wires arranged in parallel onto one main grid line of the solar cell, where the conductive wires extend along a first direction of the solar cell, the length of the conductive wires is generally 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 the main grid line on the solar cell is defined as a first direction, a plurality of conductive wires arranged in parallel along the first direction form a pressure bar 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 pressed on one main grid line correspondingly; the length of each conductive wire cannot be smaller than the extension length of the main grid line; the shape of the conductive wire mainly depends on the shape of the main grid line of the solar cell, and each conductive wire can be tightly pressed on the corresponding main grid line; for example, if the shape of the bus bar is linear, the shape of the conductive wire is also 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 a pressing and arranging structure formed by the conductive wires cannot form excessive shielding on the surface of the cell, and the solar cell is enabled to receive laser scanning to the maximum extent. In addition, if the bus bars on the solar cell are not linear but have other relatively regular shapes, the extending direction of the approximate center line of the bus bar is defined as the first direction.

In one non-limiting specific example, the conductive wires are copper wires, the number of the conductive wires is 5-20, and the cross-sectional area of the conductive wires is 0.05-3.5mm ² The spacing between adjacent conductive filaments is generally the same, 10-30 mm. Preferably, the number of the conductive wires is preferably the same as that of the main grid lines, and the distance between the adjacent conductive wires is the same as that of 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 is a preferable scheme, the number of the conductive wires may be more than or less than that of the main grids, and when the conductive wires are uniformly and correspondingly crimped one by one, the process effect is optimal. In addition, the material of the conductive wire is not limited to copper wire, and other conductive wires with conductivity can be adoptedThe material of (2). The cross section of the conductive filament is not limited to a circle, but may be other shapes such as a square, a rectangle, an ellipse, and the like.

S2, providing a power supply, electrically connecting the first end of the power supply with each conductive wire, and electrically connecting the second end of the power supply with the back electrode of the solar cell; applying reverse voltage through a power supply solar cell, wherein the reverse voltage is uniformly distributed on the surface of the solar cell through a conductive wire;

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 to metal electrodes (denoted as surface electrodes and back electrodes) on the front and back sides of the solar cell; in this embodiment, the solar cell is a P-type PERC cell, the (front) surface electrode of which is the negative electrode. The anode of the power supply is electrically connected with each conductive wire, and the cathode of the power supply is electrically connected with the back electrode of the solar cell; and when the conductive wire is in pressure joint 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 the solar cell with the front side being the positive electrode and the back side being the negative electrode, the positive electrode of the power supply can also be electrically connected with the back electrode of the solar cell, and the negative electrode is electrically connected with each conductive wire, so that the cell piece only needs to be placed with the front side facing downwards and the back side facing upwards in a reverse direction. 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 pressed with one conductive wire, reverse voltage applied by a power supply is uniformly distributed to different areas of the solar surface through the conductive wires, and in the subsequent laser scanning irradiation treatment process, the different areas can have the same process effect, and the condition that the treatment effect is not uniform at 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 secondary grid line;

unlike the commonly used point laser, in the present embodiment, the surface of the solar cell is irradiated by using a bar-shaped laser spot, in one example, the secondary grid line on the solar cell is in a standard linear shape, and the extending direction of the secondary grid line on the solar cell is defined as a second direction, and the bar-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 perpendicular, the second direction is a direction perpendicular to the first direction; the second direction is not perpendicular to the first direction.

S4, the strip-shaped laser spots are controlled to move along the first direction, scanning radiation is carried out on the electrodes on the surface of the solar cell, and the generated radiation current is uniformly collected on each main grid line covered by the strip-shaped laser spots.

In the embodiment, the electrode on the surface of the solar cell is subjected to scanning radiation through the strip-shaped laser spot, under the action of reverse voltage, extremely high photo-generated current is generated in a laser spot irradiation area, and a higher temperature is generated in an area with higher 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 lines and are collected to the main grid lines; because the strip-shaped laser light spots are scanned along the extending direction of the main grid lines, the current collected on each main grid line is the same. Even if higher current is generated due to larger light spot size, the higher current can be borne on 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 vertical to the main grid line (for example, scanning is performed along the extending direction of the auxiliary grid line), the generated current is collected by the main grid line closest to the laser spot, so that the current at the main grid line is too large, and the PN junction is reversely broken down.

By adopting the radiation mode of the example, the more the main grid lines on the surface of the solar cell are, the lower the current shared by each main grid line is, and the more the solar cell is not easy to break down.

In order to ensure that the laser spot can cover the whole surface of the solar cell by one scanning, in a preferred example, the extension length of the strip-shaped laser spot is not less than the dimension of the solar cell in the second direction, so that the irradiation range of the strip-shaped laser spot by one scanning can cover the whole surface electrode of the solar cell. The size of the stripe-shaped laser spot in the first direction (i.e., the length in the direction along the bus bar line) is not particularly limited, and in one example, the size is 0.01 to 10 mm. Taking 182mm solar cells as an example, the stripe-shaped laser spot can be designed to be 0.1 mm 182mm in size, so that one scanning can be performed along the scanning direction without the need of repeatedly scanning small spots back and forth, and the process time is greatly shortened.

In addition, in order to prevent the current generated by laser radiation from being too large and exceeding the breakdown current, in this embodiment, an external resistor with 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 greater 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 600-1500 nm.

S5, after the battery piece is scanned by the laser, the strip-shaped laser light spots and the conductive wires are removed, the battery piece is removed, and the next battery treatment is carried out.

As an example of continuous processing, the pressing frame is lifted, the cell is placed on an object stage for adsorption, then the pressing frame is pressed downwards, so that the conductive wires are pressed on the main grid lines of the electrodes on the surface of the cell one by one, reverse voltage is provided, the strip-shaped laser facula extending along the second direction irradiates the solar cell, and the solar cell is scanned from one end of the solar cell to the other end of the solar cell along the second direction; after the completion, the pressing frame is lifted, the adsorption function of the objective table is closed, and the processed battery piece is moved out. And another untreated cell is placed on the object stage, and the circulation processing is carried out.

It should be noted that although in the above-described embodiments, the operations of the methods of the embodiments of this specification are described in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must 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 execution, and/or one step broken down into multiple step executions.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.

Claims

1. An apparatus for reducing contact resistance of a crystalline silicon solar cell, comprising:

a second conductive device contacting the back electrode of the solar cell;

2. The apparatus for reducing contact resistance of a crystalline silicon solar cell as defined in claim 1, wherein the first direction is a solar cell busbar direction and the second direction is a direction substantially perpendicular to the first direction.

3. The device for reducing the contact resistance of the crystalline silicon solar cell according to claim 1 or 2,

the second conductive device is fixed on the object stage;

or the stage is a second electrically conductive device.

4. The device for reducing the contact resistance of the crystalline silicon solar cell according to claim 3, wherein the object stage is a negative pressure adsorption object stage and/or the object stage is a temperature-controlled object stage.

5. The device for reducing the contact resistance of the crystalline silicon solar cell according to claim 3,

the conductive wire pressing and arranging device further comprises a pressing and arranging frame for supporting the conductive wires, and two ends of each conductive wire are connected to the pressing and arranging frame respectively.

6. The apparatus for reducing the contact resistance of a crystalline silicon solar cell as defined in claim 5, further comprising a position adjusting member;

7. The device for reducing the contact resistance of the crystalline silicon solar cell according to claim 5,

8. The device for reducing the contact resistance of the crystalline silicon solar cell as defined in claim 7, wherein the conductive wire passes through the hole on the positioning block and is fixed on the tightening member on the positioning block, and the conductive wire is locked by the tightening member.

9. The device for reducing the contact resistance of the crystalline silicon solar cell according to claim 1 or 2,

the laser processing module comprises a laser source for emitting laser;

10. The device for reducing the contact resistance of the crystalline silicon solar cell as defined in claim 1 or 2, wherein 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.

11. The device for reducing the contact resistance of the crystalline silicon solar cell as defined in claim 1 or 2, wherein the conductive wire is a copper wire.

12. The device for reducing the contact resistance of the crystalline silicon solar cell as defined in claim 1 or 2, wherein the cross-sectional area of the conductive filaments is 0.05-3.5mm ² 。

13. The device for reducing the contact resistance of the crystalline silicon solar cell as defined in claim 1 or 2, wherein the size of the stripe-shaped laser spot in the first direction is 0.01-10 mm;

the extension length of the strip-shaped laser light spot is not less than the size of the solar cell in the second direction; when the solar cell module works, the radiation range of single scanning of the strip-shaped laser facula covers the whole surface of the solar cell.