Crystalline silicon battery piece laser multi-point focusing beam splitting auxiliary sintering method

Abstract

The invention discloses a laser multi-point focusing beam splitting auxiliary sintering method for a crystalline silicon battery piece. The method comprises the following steps: emitting a laser beam by adopting a continuous fiber laser; a light beam collimator is adopted to collimate and expand the laser beam; segmenting the collimated or low-emission laser beam into a plurality of laser beams in a lossless manner by using a lossless spectroscope; a plurality of laser beams sequentially pass through the high-speed scanning galvanometer and the field lens to form a multi-light-spot pattern, and the multi-light-spot pattern completes scanning processing on a fine grid on the front side of the crystalline silicon battery piece. The multi-spot pattern completes scanning processing on the fine grid on the front surface of the crystalline silicon cell piece, so that the laser processing scanning time on the front surface of the crystalline silicon cell piece can be shortened, and meanwhile, unbalanced carrier generation and collection are improved to reduce the contact resistance of a metal electrode. In addition, the whole surface of the cell does not need to be processed, the sintering time is shortened, and the laser-assisted sintering processing efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic laser processing, and in particular to a method for laser multi-point focusing and beam splitting assisted sintering of a crystalline silicon cell. Background Art

[0002] The formation of low-ohmic contacts between the metal electrodes of crystalline silicon cells and the silicon substrate has always been an important research direction. Laser-assisted sintering separates the two key steps of passivation layer erosion and contact formation during high-temperature sintering. The laser beam forms non-equilibrium carriers, which, combined with the bias voltage, form local currents. The preferred path for local currents is along the low contact resistance path, that is, between the emitter and Ag under the gate line, thereby inducing silver-silicon interdiffusion and reducing contact resistance. The duration of the entire sintering process matches the carrier lifetime, and the laser stops quickly after passing, thereby achieving maximum retention of the original passivation layer and avoiding carrier recombination caused by direct contact between the metal and silicon substrate.

[0003] However, the existing laser processing of the entire surface of the cell not only increases the sintering time, but also is not conducive to the production efficiency of the cell production line; the non-equilibrium carriers generated by the laser far away from the grid line cannot be effectively collected by the grid line, and there is a process recombination behavior. Therefore, how to shorten the processing time and improve the generation of non-equilibrium carriers is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, a method for laser multi-point focusing and beam splitting assisted sintering of crystalline silicon solar cells is provided, aiming to shorten the processing time and improve the generation of non-equilibrium carriers.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for sintering crystalline silicon cell wafers by laser multi-point focusing and beam splitting, comprising:

[0007] A continuous fiber laser is used to emit a laser beam;

[0008] Using a beam collimator to collimate and expand the laser beam;

[0009] Use a lossless beam splitter to losslessly split a collimated or low-dispersion laser beam into several laser beams;

[0010] The plurality of laser beams pass through the high-speed scanning galvanometer and the field mirror in sequence to form a multi-spot pattern, and the multi-spot pattern completes scanning processing on the fine grid on the front side of the crystalline silicon cell.

[0011] Preferably, the wavelength λ of the laser beam emitted by the continuous fiber laser is 355nm-1075nm.

[0012] Preferably, the core diameter of the optical fiber of the continuous fiber laser emitting the laser beam is in the range of 5 μm-65 μm.

[0013] Preferably, the lossless beam splitter losslessly splits a collimated or low-divergence laser beam into 2-9 beams.

[0014] Preferably, the types of the multi-spot pattern include square, diamond, three-spot line and double spot.

[0015] Preferably, a first adjustment ring and a second adjustment ring are provided on the lossless beam splitter, an outer diameter of the first adjustment ring is smaller than an outer diameter of the second adjustment ring, and the first adjustment ring is located on the left side of the second adjustment ring.

[0016] Preferably, the adjustment angle ranges of the first adjustment ring and the second adjustment ring are both 0°-90°.

[0017] Preferably, rotating the first adjustment ring and the second adjustment ring is used to adjust the energy distribution between the light spots and the geometric shape of the light spot layout respectively.

[0018] Compared with the prior art, the present invention provides a method for sintering crystalline silicon cell wafers by laser multi-point focusing and beam splitting, which has the following beneficial effects:

[0019] The method for laser multi-point focusing and beam splitting assisted sintering of crystalline silicon cell provided by the present invention comprises: using a continuous fiber laser to emit a laser beam; using a beam collimator to collimate and expand the laser beam; using a lossless beam splitter to losslessly split a collimated or low-divergence laser beam into a plurality of laser beams; the plurality of laser beams sequentially pass through a high-speed scanning galvanometer and a field lens to form a multi-spot pattern, and the multi-spot pattern completes scanning processing of the fine grid on the front side of the crystalline silicon cell. The present application uses a lossless beam splitter to losslessly split a collimated or low-divergence laser beam into a plurality of beams, and further focuses through a high-speed scanning galvanometer and a field lens to form a multi-spot pattern, and the multi-spot pattern completes scanning processing of the fine grid on the front side of the crystalline silicon cell. Not only can multiple fine grids on the front side of the cell be scanned simultaneously, but the same fine grid can also be scanned simultaneously by the multi-spot pattern, which can shorten the laser processing scanning time compared to a single laser beam, and the multi-spot pattern also increases the luminous flux of the cell. In addition, the multi-spot pattern processes the fine grid on the front of the crystalline silicon cell, realizing the fine grid processing of the crystalline silicon cell tightly around the crystalline silicon cell, thereby improving the generation and collection of unbalanced carriers to reduce the contact resistance of the metal electrode. In addition, the cell does not need to be processed on the entire surface, shortening the sintering time and improving the efficiency of laser-assisted sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the laser multi-point focusing lossless beam splitting assisted sintering of TOPCon solar cell in the present invention;

[0021] Figure 2 This is a schematic diagram of three-spot pattern beam splitting processing in Example 2 of the present invention;

[0022] Figure 3 This is a schematic diagram of the beam splitting processing of a diamond spot pattern in Example 3 of the present invention;

[0023] Figure 4 Schematic diagram of square spot pattern beam splitting processing in Example 4 of the present invention.

[0024] The numbers in the figure are:

[0025] 1. Fiber laser; 2. Beam collimator; 3. Lossless beam splitter; 31. First adjustment ring; 32. Second adjustment ring; 4. High-speed scanning galvanometer; 5. Field lens; 6. Working surface. DETAILED DESCRIPTION

[0026] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0027] Example 1

[0028] Please refer to Figure 1 As shown, a method for laser multi-point focusing and beam splitting assisted sintering of crystalline silicon cell wafers comprises:

[0029] S1, using a continuous fiber laser 1 to emit a laser beam;

[0030] S2, using a beam collimator 2 to collimate and expand the laser beam;

[0031] S3, using a lossless beam splitter 3 to losslessly split the collimated or low-dispersion laser beam into a plurality of laser beams;

[0032] S4, a plurality of laser beams pass through the high-speed scanning galvanometer 4 and the field lens 5 in sequence to form a multi-spot pattern, and the multi-spot pattern completes scanning processing on the fine grid on the front side of the crystalline silicon cell.

[0033] This application uses a lossless beam splitter to losslessly split a collimated or low-divergence laser beam into several beams, which are further focused by a high-speed scanning galvanometer and a field lens to form a multi-spot pattern. The multi-spot pattern completes the scanning process of the fine grid on the front of the crystalline silicon cell. Not only can it scan multiple fine grids on the front of the cell at the same time, but the same fine grid can also be scanned by the multi-spot pattern at the same time. Compared with a single-beam laser, it can shorten the laser processing scanning time, and the multi-spot pattern also increases the luminous flux of the cell. In addition, the multi-spot pattern processes the fine grid on the front of the crystalline silicon cell, and realizes the tight winding of the fine grid of the crystalline silicon cell, thereby improving the generation and collection of unbalanced carriers to reduce the contact resistance of the metal electrode. In addition, the cell does not need to be processed on the entire surface, shortening the sintering time and improving the efficiency of laser-assisted sintering. It should be understood that the tight winding here includes the processing of the fine grid before and after, front and back, up and down, etc.

[0034] Specifically, the wavelength λ of the laser beam emitted by the continuous fiber laser 1 is 355nm-1075nm, the core diameter of the optical fiber of the continuous fiber laser 1 emitting the laser beam is in the range of 5μm-65μm, the focal length of the beam collimator 2 is FC, and the lossless beam splitter 3 losslessly splits the collimated or low-divergence laser beam into 2-9 beams, and adjusts the beam splitting power to reach the power of a single beam, so that the total input power of the laser beam splitting processing is increased. The types of multi-spot patterns include square, diamond, three-spot line and double spot. A variety of light splitting patterns increase the laser processing range, and the number of spots and energy distribution can be adjusted to obtain a process route for laser-assisted sintering to improve the efficiency of solar cells.

[0035] A first adjustment ring 31 and a second adjustment ring 32 are provided on the lossless beam splitter 3. The outer diameter of the first adjustment ring 31 is smaller than the outer diameter of the second adjustment ring 32, and the first adjustment ring 31 is located on the left side of the second adjustment ring 32. The adjustment angle ranges of the first adjustment ring 31 and the second adjustment ring 32 are both 0°-90°. The first adjustment ring 31 and the second adjustment ring 32 are respectively used to adjust the energy distribution between the light spots and the geometric shape of the light spot layout by rotating.

[0036] The multi-spot pattern completes the scanning processing of the fine grid on the front side of the crystalline silicon cell. Specifically, the multi-spot pattern closely follows the laser marking pattern to overprint the fine grid screen printing pattern of the cell. The multi-spot pattern formed by light beam splitting is tightly wrapped around the fine grid. Specifically, the tightly wrapped fine grid processing can improve the generation and collection of unbalanced carriers to reduce the contact resistance of the metal electrode.

[0037] The present application proposes a method for assisted sintering using a lossless beam splitter 3 to perform multi-point laser focusing and lossless beam splitting. This method can not only eliminate the laser processing of the entire front surface of the crystalline silicon cell, shortening the laser assisted sintering processing time; and the multi-point focusing and lossless beam splitting method can form a multi-spot pattern at the focus. By adjusting the first adjustment ring 31 and the second adjustment ring 32, different spot patterns can be formed. The multi-spot is focused on the upper and lower positions of the fine grid on the front of the cell, and the laser scanning process is adapted to the cell screen grid line printing pattern. The multi-point focusing and lossless beam splitting method forms non-equilibrium carriers tightly around the fine grid, which not only reduces the thermal radiation effect of the laser on the cell, but also reduces the diffusion current J. diff Influence.

[0038] Example 2

[0039] In this scheme, if Figure 2 As shown, a solar cell is placed on the working surface 6, and the front fine grating spacing of the solar cell TOPCon is about 1.139mm. By selecting an adaptive lossless beam splitter 3 and field lens 5, the spot spacing is equal to the front fine grating spacing. This solution uses a multi-focus beam splitter lens with three-point beam splitting. The spacing between the lossless beam splitting spot dots (millimeter, mm) is equal to the beam splitting angle α1 (radian, rad) of the beam splitter multiplied by the focal length FL (millimeter, mm) of the field lens, where the size of the beam splitting spot dspot is equal to the product of the focal length FL of the field lens 5 and the core diameter dfiber of the optical fiber divided by the focal length FC (millimeter, mm) of the beam collimator 2. Determine the beam splitting angle α1 of the lossless beam splitter 3, and adjust the lossless beam splitting pattern of three spots and one line by rotating the second adjustment ring 32, and further adjust the three spots and one line to have uniform energy distribution by rotating the second adjustment ring 32. At this time, the laser marking pattern drawn is only one-third of the fine grid printing pattern on the front side, and the laser line spacing of the marking pattern is 3H, that is, the spot beam splitting laser processing time of a single cell can be reduced to about one-third of the single beam laser processing time.

[0040] Example 3

[0041] In this scheme, if Figure 3 As shown, a multi-focus lossless beam splitter 3 with four-point beam splitting is selected. First, by rotating the second adjustment ring 32, the dot distance d2 between the shorter diagonal lines of the light spot in the diamond pattern is adjusted to be larger than the width h of the fine grid on the front side of the TOPCon solar cell, and smaller than the sum of the diameter of the light spot and the width of the fine grid, and the line width center of the longer diagonal line of the light spot coincides with the line width center of the fine grid on the front side of the solar cell. At this time, the laser marking pattern drawn is consistent with the fine grid printed pattern on the front side.

[0042] Example 4

[0043] In this scheme, if Figure 4As shown, the dot spacing d3 (millimeter, mm) of adjacent light spots in the square pattern is equal to the product of the beam splitting angle α2 (radian, rad) of the square side of the lossless beam splitter 3 and the focal length FL (millimeter, mm) of the field lens. This makes d3 of the four-point square pattern equal to the fine grid spacing H on the front of the cell, or d3 of the nine-point square pattern equal to twice the fine grid spacing on the front of the cell. At this time, the spacing of the laser lines in the laser marking patterns of the four-point and nine-point square patterns are respectively 2 times and 3 times the fine grid spacing H on the front of the cell. Compared with single-beam laser processing, this method not only shortens the auxiliary sintering time of the cell, but also increases the luminous flux of the cell.

[0044] In summary, the present invention uses a lossless beam splitter to losslessly split a collimated or low-divergence laser beam into 2-9 beams, and further focuses through a high-speed scanning galvanometer and a field mirror to form a multi-spot pattern. The multi-spot increases the laser's luminous flux to the cell, and adjusts the splitting power to reach the power of a single beam, so that the total input power of the laser beam splitting process is increased; and the multi-spot pattern closely follows the laser marking pattern to overprint the cell fine grid screen printing pattern, and the multi-spot pattern formed by the light beam splitting is closely processed around the fine grid, which improves the generation and collection of non-equilibrium carriers to reduce the contact resistance of the metal electrode. At the same time, a variety of light beam splitting patterns increase the scope of the laser processing technology, and the number of spots and energy distribution can be adjusted to obtain a process route for laser-assisted sintering to improve the efficiency of the cell; in addition, the cell does not need to be processed on the entire surface, which improves the efficiency of the laser-assisted sintering process.

[0045] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for sintering crystalline silicon cells by laser multi-point focusing and beam splitting, characterized in that: include: A continuous fiber laser is used to emit a laser beam; Using a beam collimator to collimate and expand the laser beam; Use a lossless beam splitter to losslessly split a collimated or low-dispersion laser beam into several laser beams; The plurality of laser beams pass through the high-speed scanning galvanometer and the field mirror in sequence to form a multi-spot pattern, and the multi-spot pattern completes scanning processing on the fine grid on the front side of the crystalline silicon cell.

2. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 1, characterized in that: The laser beam wavelength λ emitted by the continuous fiber laser is 355nm-1075nm.

3. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 1, characterized in that: The core diameter of the optical fiber used to emit the laser beam of the continuous optical fiber laser is in the range of 5 μm to 65 μm.

4. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 1, characterized in that: The lossless beamsplitter losslessly splits a collimated or low-divergence laser beam into 2-9 beams.

5. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 1, characterized in that: The types of the multi-spot patterns include square, diamond, three-spot line and double spot.

6. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 1, characterized in that: The lossless beam splitter is provided with a first adjustment ring and a second adjustment ring, the outer diameter of the first adjustment ring is smaller than the outer diameter of the second adjustment ring, and the first adjustment ring is located on the left side of the second adjustment ring.

7. The method for sintering crystalline silicon cells by laser multi-point focusing and beam splitting according to claim 6, characterized in that: The adjustment angle ranges of the first adjustment ring and the second adjustment ring are both 0°-90°.

8. The method for laser multi-point focusing beam splitting assisted sintering of crystalline silicon cell according to claim 6, characterized in that: Rotating the first adjustment ring and the second adjustment ring is used to adjust the energy distribution between the light spots and the geometric shape of the light spot layout respectively.

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