Laser-assisted sintering device for solar cells

Abstract

The utility model provides a laser-assisted sintering device for solar cells. The laser-assisted sintering device comprises a sintering furnace, the laser assembly is located at the downstream of the sintering furnace and used for emitting laser for radiating the battery piece, and the sintering furnace and the laser assembly are arranged in a spaced mode in the first direction; and the transmission assembly is used for transmitting the pre-sintered battery piece in the sintering furnace and enabling the battery piece to pass through the laser radiation area. According to the utility model, laser-assisted sintering is added behind a traditional sintering furnace, and the surface of the cell is scanned by laser, so that the grid lines on the front and back surfaces of the cell can form good ohmic contact, the tunneling oxide layer and the doped polycrystalline silicon layer are ensured to have good passivation capability, the open-circuit voltage and fill factor of the cell are improved, and the performance of the cell is improved. And the photoelectric conversion efficiency of the cell is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cell sintering, in particular to a laser-assisted sintering device for solar cell sheets. Background Art

[0002] In recent years, traditional PERC technology and new technologies such as TOPCon, HJT, and XBC have developed rapidly, refreshing the conversion efficiency of solar cells again and again. However, there are still technical difficulties in the manufacturing technology of solar cells. For example, TOPCon (Tunnel Oxide Passivated Contact) solar cell technology is a technical deepening based on PERC cells. It is a tunnel oxide passivated contact solar cell technology based on selective carriers. By adding an ultra-thin tunnel oxide layer and a doped polysilicon layer on the back of the cell, TOPCon cell technology can improve the open circuit voltage and fill factor of the cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0003] Silver paste is required for both the front and back electrodes of TOPCon cells. The front emitter of N-type TOPCon cells uses silver-aluminum paste, and the back gate electrode uses silver paste. Since different pastes are used on the front and back of TOPCon cells, the front side requires a higher sintering temperature than the back side during the metallization process. The current sintering process is to slowly heat the front and back sides of the cell using a heating lamp. The sintering temperatures of the front and back sides are not much different, resulting in differences in the ohmic contact of the front and back metallized areas. It is easy for the front silver-aluminum paste to be under-fired, resulting in a failure to form a good ohmic contact between the gate electrode and silicon, and the back silver paste to be over-fired, resulting in an increase in series resistance or even burning through the back doped polysilicon layer and tunnel oxide layer, thereby affecting the conversion efficiency of the cell. Utility Model Content

[0004] In order to achieve the above-mentioned purpose, the utility model provides a laser-assisted sintering device for solar cell sheets, which includes a sintering furnace; a laser assembly, located downstream of the sintering furnace, used to emit a laser to radiate the solar cell sheets, the sintering furnace and the laser assembly are arranged at intervals along a first direction; and a transmission assembly, used to transmit the pre-sintered solar cell sheets in the sintering furnace and pass through the radiation area of ​​the laser.

[0005] As a further improvement of the present invention, a heating lamp tube is provided in the sintering furnace, and the heating lamp tube is located at the upper and lower sides of the transmission component.

[0006] As a further improvement of the present invention, the laser component is located above the transmission component.

[0007] As a further improvement of the present invention, the laser is a strip-shaped laser spot, the strip-shaped laser spot extends along a second direction, and there is an angle between the second direction and the first direction.

[0008] As a further improvement of the present invention, the laser assembly only includes:

[0009] A laser source, used to emit the laser;

[0010] A shaping component shapes the laser into the strip-shaped laser spot.

[0011] As a further improvement of the present invention, the second direction is perpendicular to the first direction, and the length of the strip-shaped laser spot along the second direction is not less than the length of the battery cell along the second direction.

[0012] As a further improvement of the present invention, the power of the laser assembly is 20-500 W, the laser wavelength is 500-1400 nm, and the width of the laser along the first direction is 0.05-30 mm.

[0013] As a further improvement of the present invention, the transmission component is a transmission mesh belt or a transmission roller.

[0014] As a further improvement of the present invention, the transmission roller is an integrated or split roller.

[0015] As a further improvement of the utility model, a photoelectric sensor is also included between the sintering furnace and the laser assembly.

[0016] The beneficial effects of the utility model are as follows: by adding laser-assisted sintering after the traditional sintering furnace, and using a strip laser to scan the surface of the battery cell, the gate lines on both the front and back sides of the battery cell can form good ohmic contact, ensuring that the tunneling oxide layer and the doped polysilicon layer have good passivation capabilities, thereby improving the open circuit voltage and fill factor of the battery cell, thereby improving the photoelectric conversion efficiency of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0018] Figure 1 This is a schematic diagram of the overall structure of the laser-assisted sintering device of the utility model;

[0019] Figure 2 This is a schematic structural diagram of the laser-assisted sintering device of the utility model from another perspective;

[0020] Figure 3 It is a schematic diagram of the partial structure of the laser-assisted sintering device of the utility model; DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be clearly and completely described below in combination with the specific embodiments of the utility model and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0022] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0023] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the description of the present utility model, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection of two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0025] like Figures 1 to 3 As shown, the laser-assisted sintering device of the solar cell of the present invention comprises a sintering furnace 100, a laser assembly 200 and a transmission assembly 300. The present invention defines the direction of transmission of the solar cell as a first direction.

[0026] The sintering furnace 100 and the laser assembly 200 are arranged at intervals along the first direction, and the laser assembly 200 is located downstream of the sintering furnace 100. The sintering furnace 100 heats and pre-sinters the solar cell. The laser emitted by the laser assembly 200 radiates the front of the solar cell, and the heat of the laser is used to perform secondary sintering on the front of the solar cell, ensuring that both the front and back of the solar cell can achieve a good sintering effect, reducing the ohmic contact resistance, and improving the contact conductivity. The secondary sintering method can effectively prevent over-burning caused by the superposition of the heat of the sintering furnace 100 and the laser assembly 200, and the sintering temperature is easier to control. The sintering furnace 100 and the laser assembly 200 are isolated to prevent the two from affecting each other. The transmission assembly 300 is used to transmit the solar cell pre-sintered by the sintering furnace 100 to the laser assembly 200 and pass through the radiation area of ​​the laser, and complete the laser scanning of the front of the solar cell during the transmission of the solar cell.

[0027] The sintering furnace 100 is used to heat the solar cell to achieve pre-sintering. In this embodiment, the sintering furnace 100 is provided with heating lamps to heat and sinter the solar cell, and the heating lamps are distributed on the upper and lower sides of the transmission assembly 300, so as to heat and sinter the front and back sides of the solar cell in the sintering furnace 100 at the same time.

[0028] Since the sintering temperatures required for the front and back of solar cells are inconsistent, the front side requires a higher sintering temperature than the back side. In the traditional sintering process, when the sintering temperature is high, although the front side can achieve a better sintering effect, the back side is prone to over-burning, and the passivation effect deteriorates, affecting the conversion efficiency of the solar cell; when the sintering temperature is low, the back side has a good sintering effect, but the front side is under-burned and cannot form a good ohmic contact with silicon.

[0029] In the present invention, the sintering temperature of the sintering furnace 100 is designed so that the solar cell after pre-sintering is in an under-sintered state, that is, the front of the solar cell is in an under-sintered state, and the back of the solar cell is in a well-sintered state or an under-sintered state. Specifically, the sintering temperature in the sintering furnace 100 is adjusted not to exceed the sintering temperature required for the back of the solar cell, thereby preventing the back of the solar cell from being over-sintered, and then the laser assembly 200 is used for secondary sintering, so that both the front and back of the solar cell can achieve a good sintering effect.

[0030] Preferably, after pre-sintering, the front side of the solar cell is in an under-sintered state, and the back side of the solar cell is in a well-sintered state, thereby reducing the heat required for laser irradiation.

[0031] The laser assembly 200 is used to emit laser to irradiate the solar cell. The laser has a certain radiation area. When the solar cell enters the radiation area, the heat of the laser is used to heat the solar cell to achieve secondary sintering.

[0032] In the present invention, the laser component 200 is located above the transmission component 300, and the solar cell is placed on the transmission component 300 with the front side facing upward, so that the solar cell is not affected by the transmission component 300 when the laser component 200 emits a strip laser spot to irradiate the solar cell.

[0033] The laser assembly 200 only includes a laser source and a shaping assembly, wherein the laser source is used to emit laser light, and the shaping assembly shapes the emitted laser light into a strip-shaped laser spot, wherein the strip-shaped laser spot extends along the second direction, and the solar cell moves along the first direction driven by the transmission assembly 300, and the strip-shaped laser spot is used to radiate and scan the solar cell while keeping the position of the strip-shaped laser spot fixed. Specifically, any one of nanosecond, picosecond, and femtosecond lasers can be used to radiate and scan the solar cell.

[0034] The second direction has an angle with the first direction (not parallel), and when the solar cell passes through the radiation area of ​​the strip laser spot, radiation sintering in a certain area on the surface of the solar cell can be achieved. Preferably, the second direction is perpendicular to the first direction, and the length of the strip laser spot along the second direction is not less than the length of the solar cell along the second direction, so that as the solar cell moves, the strip laser spot can scan the entire surface of the solar cell.

[0035] Furthermore, the power of the laser assembly 200 is 20-500 W, the laser wavelength is 500-1400 nm, the width along the first direction is 0.05-30 mm, and the distance between the laser source and the solar cell is 5-60 cm.

[0036] Through this scanning method, the laser component 200 does not need to add expensive scanning components, which greatly reduces the cost of the laser component 200; at the same time, during the transmission process of the solar cell, the strip laser spot is used for secondary sintering, and the scanning accuracy is high without affecting the original production and processing rhythm and production capacity.

[0037] The transmission component 300 is used to transport solar cells. The transmission component 300 includes a first transmission section and a second transmission section that are connected. The first transmission section is used to transmit the solar cells to be sintered to the sintering furnace 100 for pre-sintering. The second transmission section is used to transmit the pre-sintered solar cells to the laser component 200. The laser component 200 emits a strip-shaped laser spot to perform secondary sintering on the solar cells.

[0038] Furthermore, the transmission component 300 may use a transmission mesh belt or a transmission roller, which uses an external driving device such as a motor as a driving source (not shown in the figure) to drive the solar cell to move along the first direction.

[0039] The transmission rollers are arranged at intervals along the first direction, and the spacing between two adjacent groups of the transmission rollers is preferably one-half of the length of the solar cell along the first direction, so as to minimize the contact area with the solar cell while ensuring the transmission stability. The transmission rollers can be integrated or split rollers, preferably split rollers, which are disconnected in the middle, so that only the two ends of the solar cell along the second direction are in contact with the transmission rollers, thereby minimizing the contact area between the transmission rollers and the solar cell, and the solar cell can directly receive the heat transferred by the heating lamp.

[0040] Furthermore, the sintering device further includes a photoelectric sensor 400, which is located between the sintering furnace 100 and the laser assembly 200. The photoelectric sensor 400 is used to obtain the position of the solar cell. When the solar cell moves to the position of the photoelectric sensor 400, the laser assembly 200 is turned on. Preferably, the photoelectric sensor 400 can be integrated on the laser assembly 200.

[0041] Taking the N-type TOPCon cell as an example, the structure of the N-type TOPCon cell is: a passivation / anti-reflection film, a passivation layer, a P-type emitter, an N-type single crystal silicon wafer substrate, an ultra-thin tunneling oxide layer, an N-type polysilicon layer, and an anti-reflection film are stacked in sequence from the front to the back. The front of the N-type TOPCon cell is coated with silver-aluminum paste, the aluminum content of the silver-aluminum paste is 3-5wt%, and the back is coated with silver paste.

[0042] The sintering steps of this device are as follows:

[0043] Place the battery cell with the front side facing upward on the first transmission section of the transmission assembly 300, and the first transmission section transmits the battery cell to the sintering furnace 100;

[0044] The heating lamps in the sintering furnace 100 heat the front and back sides of the battery cells on the transmission assembly 300 simultaneously to achieve pre-sintering, and the pre-sintered battery cells are in an under-sintered state;

[0045] The pre-sintered cell is transported out of the sintering furnace 100 through the second transmission section and moves toward the laser assembly 200. When the cell moves to the photoelectric sensor 400, the laser assembly 200 is turned on.

[0046] The laser assembly 200 emits a strip-shaped laser spot extending along the second direction. When the battery cell passes through the radiation area of ​​the strip-shaped laser spot, the strip-shaped laser spot is irradiated on the front side of the battery cell. Under the action of laser heat, the battery cell is secondary sintered, so that the Ag-Si alloy is remelted and recrystallized, thereby reducing the ohmic contact resistance between the gate electrode and the battery cell and improving the contact conductivity. At the same time, under the action of laser irradiation, the temperature is increased to activate the H atoms in the passivation layer. The light causes the H atoms to combine with the recombination center (defect) at the emitter and the silicon substrate to form a non-recombination center, thereby achieving a good passivation effect and improving the open circuit voltage and fill factor of the finished product.

[0047] Since the strip-shaped laser spot is directly radiated on the front side of the cell, after being radiated by the strip-shaped laser spot, the front side temperature of the cell is 700-800°C, and the back side temperature is 600-750°C. The front side sintering temperature is higher than the back side temperature, thereby avoiding over-burning of the back side, so that both the front side and the back side of the cell have good sintering effects;

[0048] As the battery cell moves, the strip laser spot gradually completes the scanning of the entire front surface of the battery cell. During the scanning process, the battery cell keeps moving at a uniform speed of 15-20m / min, thereby achieving uniform scanning of the battery cell and obtaining the battery cell after laser sintering.

[0049] Furthermore, the temperature in the sintering furnace 100 is designed such that after pre-sintering, the front of the cell is in an under-sintered state, and the back of the cell is in a well-sintered or under-sintered state. That is, the sintering temperature in the sintering furnace 100 is adjusted not to exceed the sintering temperature required for the back of the solar cell, thereby preventing the back of the solar cell from being over-sintered, and then secondary sintering is performed through the laser assembly 200, so that both the front and back of the solar cell can achieve a good sintering effect. Specifically, the peak temperature in the sintering furnace 100 is 700-800°C.

[0050] In the prior art, it is necessary to first confirm the position of the battery cell and then scan back and forth according to a preset laser scanning route. During the laser scanning process, the battery cell is either stationary or transmitting. When the battery cell is stationary, it is necessary to add a device to achieve the stationary state of the battery cell, and then complete the laser scanning after the battery cell is stationary. This process often takes longer than the printing process cycle, which will affect production capacity. When the battery cell is in a transmitting state, the battery cell moves relative to the preset scanning route, which solves the problem of production capacity, but affects the scanning accuracy. It is easy for the surface of the battery cell to not be completely and evenly scanned.

[0051] The sintering device provided by the utility model completes the laser scanning of the solar cell during the transportation of the solar cell. The laser component 200 does not need to add an expensive scanning component, which greatly reduces the cost of the laser component 200. At the same time, during the transmission of the solar cell, the strip laser spot is used for secondary sintering to keep the position of the strip laser spot fixed, with high scanning accuracy. The surface of the solar cell can be completely and evenly scanned without affecting the original production and processing rhythm and production capacity.

[0052] In summary, the utility model adds laser-assisted sintering after the traditional sintering furnace and utilizes laser to irradiate the surface of the cell so that the gate lines on both the front and back sides of the cell can form good ohmic contact, ensuring that the tunneling oxide layer and the doped polysilicon layer have good passivation ability, thereby improving the open circuit voltage and fill factor of the cell, and thus improving the photoelectric conversion efficiency of the cell.

[0053] It should be understood that although the present specification is described according to embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0054] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the utility model and are not intended to limit the protection scope of the utility model. Any equivalent embodiments or changes that do not deviate from the technical spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A laser-assisted sintering device for solar cells, characterized in that: include: Sintering furnace (100); A laser assembly (200) is located downstream of the sintering furnace (100) and is used to emit laser light for radiating the solar cell. The sintering furnace (100) and the laser assembly (200) are arranged at intervals along a first direction. A transmission component (300) is used to transmit the pre-sintered battery cell in the sintering furnace (100) and pass through the radiation area of ​​the laser; The laser is a strip-shaped laser spot, the strip-shaped laser spot extends along a second direction, and an angle is formed between the second direction and the first direction.

2. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: A heating lamp tube is arranged in the sintering furnace (100), and the heating lamp tube is located at the upper and lower sides of the transmission component (300).

3. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The laser component (200) is located above the transmission component (300).

4. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The second direction is perpendicular to the first direction, and the length of the strip-shaped laser spot along the second direction is not less than the length of the battery cell along the second direction.

5. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The laser assembly (200) comprises only: A laser source, used to emit the laser; A shaping component shapes the laser into the strip-shaped laser spot.

6. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The power of the laser component (200) is 20-500 W, the wavelength of the laser is 500-1400 nm, and the width of the laser along the first direction is 0.05-30 mm.

7. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The transmission component (300) is a transmission mesh belt or a transmission roller.

8. The laser-assisted sintering device for solar cells according to claim 7, characterized in that: The transmission roller is an integrated roller or a split roller.

9. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: It also includes a photoelectric sensor (400) located between the sintering furnace (100) and the laser assembly (200).

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