Laser-assisted sintering device and method for solar cell

Abstract

The invention provides a laser-assisted sintering device for a solar cell. 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. The invention further provides a laser-assisted sintering method of the solar battery piece. The laser-assisted sintering process is added after the traditional sintering process, 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 present invention relates to the technical field of solar cell sintering, in particular to a laser-assisted sintering device and method for solar cells. Background Art

[0002] In recent years, traditional PERC technology and new technologies such as TOPCon, HJT, and XBC have developed rapidly, continuously refreshing the conversion efficiency of solar cells. However, there are still technical difficulties in the manufacturing technology of solar cells. Take TOPCon (Tunnel Oxide Passivated Contact) solar cell technology as an example. TOPCon cells are a technical deepening based on PERC cells and are a tunneling oxide passivated contact solar cell technology based on selective carriers. By adding an ultra-thin tunneling oxide layer and 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 increasing the photoelectric conversion efficiency of solar cells.

[0003] Both the front and back electrodes of TOPCon cells require silver paste. Among them, silver-aluminum paste is used for the front emitter of N-type TOPCon cells, and silver paste is used for the back grid electrodes. Since different pastes are used on the front and back of TOPCon cells, a higher sintering temperature is required for the front than for the back during the metallization process. Currently, the existing sintering process slowly heats the front and back of the cell through heating lamps, and the sintering temperatures of the front and back are not much different, resulting in differences in Ohmic contact in the metallization areas of the front and back. It is easy to occur that the silver-aluminum paste on the front is under-fired, resulting in poor Ohmic contact between the grid electrode and silicon, and the silver paste on the back is over-fired, resulting in an increase in series resistance or even burning through the back doped polysilicon layer and tunneling oxide layer, thereby affecting the conversion efficiency of the cell. Summary of the Invention

[0004] To achieve the above object, the present invention provides a laser-assisted sintering device for solar cells, which includes a sintering furnace; a laser assembly located downstream of the sintering furnace for emitting laser to irradiate the cell, and the sintering furnace and the laser assembly are spaced apart along a first direction; a transmission assembly for transmitting the pre-sintered cell in the sintering furnace and passing through the radiation area of the laser.

[0005] As a further improvement of the present invention, the laser assembly is located above the transmission assembly.

[0006] As a further improvement of the present invention, the laser is a strip-shaped laser spot, and the strip-shaped laser spot extends along a second direction, and there is an included angle between the second direction and the first direction.

[0007] As a further improvement of the present invention, the second direction is perpendicular to the first direction, and the length of the bar-shaped laser spot along the second direction is not less than the length of the solar cell along the second direction.

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

[0009] a laser source for emitting the laser;

[0010] a shaping component for shaping the laser into the bar-shaped laser spot;

[0011] wherein, the power of the laser assembly is 20 - 500 W, the wavelength of the bar-shaped laser spot is 500 - 1400 nm, and the width of the bar-shaped laser spot along the first direction is 0.05 - 30 mm.

[0012] The present invention also provides a laser-assisted sintering method for a solar cell, which includes the following steps:

[0013] pre-sintering the solar cell located therein through the sintering furnace;

[0014] turning on the laser assembly to emit laser;

[0015] transferring the pre-sintered solar cell to the laser assembly through the transfer assembly and realizing secondary sintering through the radiation area of the laser.

[0016] As a further improvement of the present invention, the temperature in the sintering furnace is designed such that after pre-sintering, the front surface of the solar cell is in an under-fired state, and the back surface of the solar cell is in a well-sintered or under-fired state.

[0017] As a further improvement of the present invention, the peak temperature in the sintering furnace is 700 - 800 °C.

[0018] As a further improvement of the present invention, after being irradiated by the laser, the front surface temperature of the solar cell is 700 - 800 °C, and the back surface temperature is 600 - 750 °C.

[0019] As a further improvement of the present invention, the transfer assembly maintains a constant speed of transfer, and the transfer speed is 15 - 20 m / min.

[0020] The beneficial effects of the present invention: By adding a laser-assisted sintering process after the traditional sintering process and using a bar-shaped laser to scan the surface of the solar cell, good ohmic contacts can be formed on both the front and back sides of the solar cell, ensuring that the tunneling oxide layer and the doped polysilicon layer have good passivation capabilities, improving the open-circuit voltage and fill factor of the solar cell, and thus enhancing the photoelectric conversion efficiency of the solar cell. Description of the Drawings

[0021] The accompanying drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0022] Figure 1 is a schematic diagram of the overall structure of the laser-assisted sintering device of the present invention;

[0023] Figure 2 is a schematic diagram of the structure of another perspective of the laser-assisted sintering device of the present invention;

[0024] Figure 3 is a schematic diagram of the partial structure of the laser-assisted sintering device of the present invention; Detailed Description of the Invention

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the scope of protection of the present invention.

[0026] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0027] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0028] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0029] Such as Figures 1 to 3As shown in the figure, the present invention provides a laser-assisted sintering device for solar cell wafers, which includes a sintering furnace 100, a laser assembly 200, and a transmission assembly 300. In the present invention, the direction of solar cell wafer transmission is defined as the first direction.

[0030] 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 pre-sinters the solar cell wafer by heating, and the laser emitted by the laser assembly 200 irradiates the front side of the solar cell wafer. The heat of the laser is used to perform secondary sintering on the front side of the solar cell wafer, ensuring good sintering effects on both the front and back sides of the solar cell wafer, reducing the ohmic contact resistance, improving the contact conductivity, and effectively preventing over-burning caused by the heat superposition of the sintering furnace 100 and the laser assembly 200 through the secondary sintering method. The sintering temperature is easier to control, and the sintering furnace 100 and the laser assembly 200 are isolated from each other to prevent mutual influence. The transmission assembly 300 is used to transmit the wafer pre-sintered by the sintering furnace 100 to the laser assembly 200 and pass through the radiation area of the laser, and complete the scanning of the front side of the solar cell wafer by the laser during the transmission of the solar cell wafer.

[0031] Among them, the sintering furnace 100 is used to heat the solar cell wafer to achieve pre-sintering. In this embodiment, heating lamps are arranged inside the sintering furnace 100 to heat and sinter the solar cell wafer, and the heating lamps are distributed on both the upper and lower sides of the transmission assembly 300, so as to simultaneously heat and sinter the front and back sides of the solar cell wafer located inside the sintering furnace 100.

[0032] Since the sintering temperatures required for the front and back sides of the solar cell wafer are inconsistent, and the front side requires a higher sintering temperature than the back side. In the traditional sintering process, when the sintering temperature is relatively high, although a good sintering effect can be achieved on the front side, the back side is prone to over-burning, the passivation effect deteriorates, and the conversion efficiency of the solar cell wafer is affected; when the sintering temperature is relatively low, the sintering effect on the back side is good, but the front side is in an under-sintered state and cannot form a good ohmic contact with silicon.

[0033] In the present invention, the sintering temperature of the sintering furnace 100 is designed such that the pre-sintered solar cell wafer is in an under-sintered state, that is, the front side of the solar cell wafer is in an under-sintered state, and the back side of the solar cell wafer 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 side of the solar cell wafer, so as to prevent over-burning of the back side of the solar cell wafer, and then secondary sintering is performed through the laser assembly 200, so that good sintering effects can be achieved on both the front and back sides of the solar cell wafer.

[0034] Preferably, after pre-sintering, the front side of the solar cell is in an under-fired state, and the back side of the solar cell is in a well-sintered state, thereby reducing the heat required for laser irradiation.

[0035] The laser assembly 200 is used to emit laser radiation to the solar cell. The laser has a certain radiation area. When the solar cell enters this radiation area, the heat of the laser is used to heat-treat the solar cell to achieve secondary sintering.

[0036] In the present invention, the laser assembly 200 is located above the transmission assembly 300, and the solar cell is placed face-up on the transmission assembly 300, so that when the laser assembly 200 emits a strip-shaped laser spot to irradiate the solar cell, it is not affected by the transmission assembly 300.

[0037] The laser assembly 200 only includes a laser source and a shaping component. The laser source is used to emit laser, and the shaping component shapes the emitted laser into a strip-shaped laser spot. The strip-shaped laser spot extends along the second direction. The solar cell moves along the first direction driven by the transmission assembly 300. Without changing the position of the strip-shaped laser spot, the radiation scanning of the strip-shaped laser spot on the solar cell is realized through the movement of the solar cell. Specifically, any one of nanosecond, picosecond, and femtosecond lasers can be used to realize the radiation scanning of the solar cell.

[0038] The second direction and the first direction have an included angle (not parallel). When the solar cell passes through the radiation area of the strip-shaped laser spot during transmission, the radiation sintering of a certain area on the surface of the solar cell can be realized. Preferably, 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 solar cell along the second direction. In this way, as the solar cell moves, the strip-shaped laser spot can realize the full-surface scanning of the solar cell.

[0039] 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.

[0040] Through this scanning method, the laser assembly 200 does not need to add expensive scanning components, greatly reducing the cost of the laser assembly 200; at the same time, during the transmission of the solar cell, secondary sintering is carried out through the strip-shaped laser spot, with high scanning accuracy and no impact on the original production and processing rhythm and production capacity.

[0041] The transfer component 300 is used to convey solar cells. The transfer component 300 includes a connected first transfer section and a second transfer section. The first transfer section is used to transfer the solar cells to be sintered into the sintering furnace 100 for pre-sintering, and the second transfer section is used to transfer the pre-sintered solar cells to the laser component 200. The bar-shaped laser spot emitted by the laser component 200 performs secondary sintering on the solar cells.

[0042] Further, the transfer component 300 can adopt a transfer mesh belt or a driving roller. The transfer mesh belt or the driving roller uses an external driving device such as a motor as a driving source (not shown in the figure) to drive the solar cells to move along the first direction.

[0043] The driving rollers are arranged at intervals along the first direction. The distance between two adjacent groups of driving rollers is preferably one-half of the length of the solar cell along the first direction, which can minimize the contact area with the solar cell while ensuring the transfer stability. The driving rollers can adopt integral or split rollers, and preferably split rollers. The middle of the split rollers is disconnected, and the solar cell only contacts the driving rollers at both ends along the second direction, so as to minimize the contact area between the driving rollers and the solar cell to the greatest extent, and the solar cell can directly receive the heat transferred by the heating lamp tube.

[0044] Further, the sintering device further includes a photoelectric inductor 400. The photoelectric inductor 400 is located between the sintering furnace 100 and the laser component 200. The photoelectric inductor 400 is used to obtain the position of the solar cell. When the solar cell moves to the position of the photoelectric inductor 400, the laser component 200 is turned on. Preferably, the photoelectric inductor 400 can be integrated on the laser component 200.

[0045] The present invention also provides a laser-assisted sintering method for solar cells. Taking an 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 monocrystalline silicon wafer substrate, an ultra-thin tunneling oxide layer, an N-type polysilicon layer, and an anti-reflection film stacked in sequence from the front to the back. The front side of the N-type TOPCon cell is coated with silver-aluminum paste, and the aluminum content in the silver-aluminum paste is 3-5 wt%. The back side is coated with silver paste.

[0046] The sintering steps are as follows:

[0047] Place the cell face up on the first transfer section of the transfer component 300, and the first transfer section conveys the cell into the sintering furnace 100;

[0048] The heating lamps in the sintering furnace 100 heat the front and back surfaces of the solar cells on the transmission assembly 300 simultaneously to achieve pre-sintering, and the pre-sintered solar cells are in an under-fired state;

[0049] The pre-sintered solar cells are conveyed out of the sintering furnace 100 through the second transmission section and move towards the laser assembly 200. When the solar cells move to the photoinductor 400, the laser assembly 200 is turned on;

[0050] The laser assembly 200 emits a strip-shaped laser beam extending in the second direction. When the solar cells pass through the radiation area of the strip-shaped laser beam, the strip-shaped laser beam irradiates the front surface of the solar cells. Under the action of the laser heat, secondary sintering of the solar cells is achieved, enabling the Ag-Si alloy to remelt and recrystallize, thereby reducing the ohmic contact resistance between the grid electrodes and the solar cells and improving the contact conductivity; at the same time, under the action of the laser irradiation, the H atoms in the passivation layer are activated by heating. The light irradiation causes the H atoms to combine with the recombination centers (defects) in the emitter and the silicon substrate to form non-recombination centers, achieving a good passivation effect and improving the open-circuit voltage and fill factor of the finished product.

[0051] Since the strip-shaped laser beam directly irradiates the front surface of the solar cells, after being irradiated by the strip-shaped laser beam, the front surface temperature of the solar cells is 700 - 800 °C, and the back surface temperature is 600 - 750 °C. The front surface sintering temperature is higher than that of the back surface, thus avoiding over-firing of the back surface and enabling both the front and back surfaces of the solar cells to have good sintering effects;

[0052] As the solar cells move, the strip-shaped laser beam gradually completes the full-surface scanning of the front surface of the solar cells. During the scanning process, the solar cells move at a constant speed of 15 - 20 m / min, thereby achieving uniform scanning of the solar cells and obtaining solar cells after laser sintering treatment.

[0053] Further, the temperature in the sintering furnace 100 is designed such that after pre-sintering, the front surface of the solar cells is in an under-fired state, and the back surface of the solar cells is in a well-sintered or under-fired state. That is, the sintering temperature in the sintering furnace 100 is adjusted not to exceed the sintering temperature required for the back surface of the solar cells, thereby preventing over-firing of the back surface of the solar cells. Then, secondary sintering is performed through the laser assembly 200, enabling both the front and back surfaces of the solar cells to achieve good sintering effects. Specifically, the peak temperature in the sintering furnace 100 is 700 - 800 °C.

[0054] 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 pre-set laser scanning route. During the laser scanning process, the battery cell is in a stationary or transporting state; for the stationary battery cell, a device for making the battery cell stationary needs to be added, and after the battery cell is stationary, the laser scanning is completed. This process usually takes longer than the printing process beat, which will affect the production capacity; for the transporting battery cell, the battery cell moves relative to the pre-set scanning route, which solves the problem of production capacity, but will affect the scanning accuracy, and it is very easy to have the situation that the surface of the battery cell cannot be completely and evenly scanned.

[0055] The sintering method provided by the present invention completes the laser scanning of the battery cell during the transportation process of the battery cell. The laser assembly 200 does not need to add an expensive scanning assembly, which greatly reduces the cost of the laser assembly 200; at the same time, during the transportation process of the solar battery cell, secondary sintering is carried out through the strip-shaped laser spot, and the position of the strip-shaped laser spot is kept fixed, with high scanning accuracy, the surface of the battery cell can be completely and evenly scanned, and the original production and processing rhythm and production capacity are not affected.

[0056] In summary, the present invention adds a laser-assisted sintering process after the traditional sintering process, and uses laser to irradiate the surface of the battery cell, so that good ohmic contacts can be formed on the grid lines on both the front and back sides of the battery cell, ensuring that the tunneling oxide layer and the doped polysilicon layer have better passivation ability, improving the open circuit voltage and fill factor of the battery cell, and further improving the photoelectric conversion efficiency of the battery cell.

[0057] It should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0058] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser-assisted sintering device for solar cell wafers, characterized in that, Including: A sintering furnace (100); A laser assembly (200), located downstream of the sintering furnace (100), for emitting laser to irradiate the battery chip, and the sintering furnace (100) and the laser assembly (200) are arranged at intervals along a first direction; A transmission assembly (300), for transmitting the pre-sintered battery chip in the sintering furnace (100) and passing through the irradiation area of the laser.

2. The laser-assisted sintering device for solar cells according to claim 1, wherein: The laser assembly (200) is located above the transmission assembly (300).

3. The laser-assisted sintering device for solar cells according to claim 1, characterized in that: The laser is a strip-shaped laser spot, and the strip-shaped laser spot extends along a second direction, and there is an included angle between the second direction and the first direction.

4. The laser-assisted sintering device for solar cells according to claim 3, wherein: 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 chip along the second direction.

5. The laser-assisted sintering device for solar cells according to claim 3, wherein: The laser assembly (200) only includes: A laser source for emitting the laser; A shaping assembly for shaping the laser into the strip-shaped laser spot; Wherein, the power of the laser assembly (200) is 20 - 500W, the wavelength of the strip-shaped laser spot is 500 - 1400nm, and the width of the strip-shaped laser spot along the first direction is 0.05 - 30mm.

6. A sintering method using the laser-assisted sintering device for solar cell chips as described in any one of claims 1 - 5, which includes the following steps: Pre-sinter the battery chip located therein through the sintering furnace (100); Turn on the laser assembly (200) to emit laser; Transmit the pre-sintered battery chip to the laser assembly (200) through the transmission assembly (300), and perform secondary sintering through the irradiation area of the laser.

7. The laser-assisted sintering method of a solar cell according to claim 6, characterized in that: The temperature in the sintering furnace (100) is designed such that: after pre-sintering, the front side of the battery chip is in an under-fired state, and the back side of the battery chip is in a well-sintered or under-fired state.

8. The laser-assisted sintering method for solar cell wafers according to claim 7, wherein: The peak temperature in the sintering furnace (100) is 700 - 800°C.

9. The laser-assisted sintering method for solar cell wafers according to claim 6, wherein: After being irradiated by the laser, the front side temperature of the battery chip is 700 - 800°C, and the back side temperature is 600 - 750°C.

10. The laser-assisted sintering method of a solar cell according to claim 6, characterized in that: The transmission assembly (300) maintains a uniform transmission, and the transmission speed is 15 - 20m / min.

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