Laser doping method and application

Abstract

The invention discloses a laser doping method and application, and belongs to the technical field of new energy batteries. The laser doping method comprises the following steps that S1, a printing procedure is conducted, specifically, slurry containing doping elements is printed on the front face and / or the back face of a semiconductor substrate and dried, a printing area comprises an area A and an area B from inside to outside, and a doping area is covered with the area A; s2, a laser doping process: carrying out laser doping on the area A of the printing area; the power of the laser is P1, and the frequency of the laser is f1; s3, a laser removal process: carrying out laser removal on a region B containing the printing region, wherein the power of the laser is P2, and the frequency of the laser is f2; wherein the monopulse energy E2 is smaller than E1 (E = P / f); and S4, a cleaning process. The laser doping method is applied to preparation of solar cells. According to the method, the time consumption and the use amount of chemical reagents used in the cleaning procedure can be reduced, the production cost is reduced, and the technical problem of environmental pollution is solved.

Description

Technical Field

[0001] The present application belongs to the technical field of solar cells, and specifically relates to a laser doping method and application. Background Art

[0002] A solar cell is a device that converts solar energy directly into electrical energy, and its core part is the photoelectric conversion material. At present, silicon-based solar cells occupy a large share of the global photovoltaic market due to their advantages such as high efficiency, stability and environmental protection. In the manufacturing process of solar cells, doping and cleaning are two key steps. Doping refers to the process of introducing impurity atoms into semiconductor materials to change their electrical properties. Usually, doping can be achieved through high-temperature diffusion or ion implantation. Cleaning refers to the process of removing impurities and residues on the surface of the semiconductor after doping to ensure its performance and quality. In the traditional manufacturing process of solar cells, high-temperature diffusion is usually used for doping, but this method not only has a complicated and time-consuming operation process, but also has high requirements for equipment and processes, and the cost is relatively high, and the uniformity of doping is poor.

[0003] To solve this problem, some researchers have proposed using slurry printing and laser doping to replace high-temperature diffusion. The advantage of this method is that the size and shape of the doped area can be precisely controlled, thereby improving the uniformity of doping. However, this method also has some problems. First, the slurry printing area is often slightly larger than the laser doping area, which makes it more difficult to clean the slurry in the non-laser doped area, and there may be residues, causing contamination and affecting subsequent processes.

[0004] The existing cleaning method mainly uses chemical reagents for cleaning, but this method is not only time-consuming, but also requires a large amount of chemical reagents, which not only increases production costs, but also pollutes the environment. In addition, due to the limited cleaning effect of chemical reagents, it may not be possible to completely remove the slurry residue, which will have a certain impact on the performance and quality of solar cells. Therefore, how to effectively clean the slurry is an urgent problem to be solved in the current solar cell manufacturing process. Summary of the invention

[0005] 1. Problem to be solved

[0006] The present application provides a laser doping method, which aims to solve the technical problem of how to reduce the time consumption and amount of chemical reagents used for cleaning, reduce production costs and reduce environmental pollution. Further application in solar cell preparation can improve the cleaning effect while ensuring the uniformity of slurry doping, and ensure the performance and quality of solar cells.

[0007] 2. Technical solution

[0008] In order to solve the above problems, the technical solutions adopted in this application are as follows:

[0009] As a first aspect of the present application, the present application provides a laser doping method, comprising the following steps:

[0010] S1. Printing process

[0011] Printing a slurry containing doping elements on the front and / or back of the semiconductor substrate and drying it, wherein the printing area includes area A and area B from the inside to the outside, and area A covers the doping area;

[0012] S2. Laser doping process

[0013] Laser doping is performed on area A of the printing area; the laser power is P1, the laser frequency is f1, and the single pulse energy E1 = P1 / f1;

[0014] S3, Laser Removal Process

[0015] Laser removal is performed on the B area including the printing area to remove impurities in the slurry (i.e., the residue after the slurry is dried) without diffusion, so as to facilitate subsequent cleaning; the power of the laser is P2, the frequency of the laser is f2, and the single pulse energy is E2=P2 / f2; wherein, the single pulse energy E2≤E1, preferably E2=(0.3-0.6)E1, a lightly doped area may appear in the B area but it will not have a bad effect, but can help collect carriers, and as long as the metal electrode is formed within the range of the A area, it will have little effect;

[0016] The laser removal process of step S3 may be performed simultaneously with the laser doping process of step S2, or the laser removal process of step S3 may be performed after the laser doping process of step S2 is completed; or the laser removal process of step S3 may be performed before the laser doping process of step S2 is started;

[0017] It should be noted that the laser in the laser removal process should avoid hitting area A as much as possible, because it will increase the doping concentration in area A, which is not conducive to its doping uniformity.

[0018] S4. Cleaning process

[0019] When the laser removal process in step S3 is not performed, that is, the semiconductor substrate after laser doping in step S2 is directly cleaned, the concentration of the acid or alkali used for cleaning is a mol / L, the amount used is b L, and the cleaning time is c min;

[0020] The semiconductor substrate after laser removal in step S3 is cleaned with acid or alkali, the concentration of the acid or alkali is (0.1-0.7)×a mol / L, the amount used is (0.1-0.7)×b L, and the cleaning time is (0.1-0.7)×c min.

[0021] Furthermore, in step S3, the width wμm of region B and the laser parameters meet the following conditions:

[0022] When 0<w≤5, single pulse energy E2=(0.5~0.6)E1;

[0023] When 5<w≤10, single pulse energy E2=(0.4~0.5)E1;

[0024] When 10<w≤20, the single pulse energy E2=(0.3~0.4)E1.

[0025] Furthermore, when E2=E1, in step S2, there is only one layer of laser spot in area A, or there are multiple layers of uniformly overlapping laser spots in area A (the overlapping situation depends on the single pulse energy to ensure that the energy per unit area remains unchanged); in step S3, there is only one layer of laser spot in area B, or when a laser spot with low laser single pulse energy is used in area B, there may also be multiple layers of overlapping laser spots in area B. In this case, the laser conditions are not changed, and the doping area (i.e. area A of the printing area) uses spot overlap to ensure slurry doping, and area B of the printing area uses spot tangency to ensure that the slurry is undoped or lightly doped (no need to switch laser conditions, reducing the time required for laser switching), while removing the slurry and increasing the cleaning effect.

[0026] When E2 is less than E1, the laser conditions required for area A of the printing area (i.e., the doped area) in step S2 are high power and / or low frequency, and area B of the printing area is laser removed using laser conditions with very low energy per unit area (low power and / or high frequency), thereby ensuring that the slurry is removed without being doped, thereby increasing the cleaning effect.

[0027] Furthermore, in step S1, the semiconductor substrate comprises a poly layer, that is, a paste containing doping elements is printed on the poly layer.

[0028] Furthermore, the doping element includes phosphorus or boron.

[0029] Furthermore, the doping of the present invention is suitable for large-area doping. In step S2, a square spot is used, and the width of area A in the printing area (i.e., the doping area) is 150 microns to 250 microns, and the spot size is optimally 50 to 100 microns in side length (excluding 100 microns); the width of area A in the printing area (i.e., the doping area) is more than 250 microns, and the spot size is optimally 100 to 200 microns in side length.

[0030] As a second aspect of the present application, the present application provides an application of the upper laser doping method in preparing a solar cell. When preparing a BC cell, the steps are:

[0031] S1. Printing process

[0032] Printing a boron or phosphorus slurry on the back of the semiconductor substrate and drying it, wherein the printing area includes an A area and a B area from the inside to the outside, and the A area covers the doped area;

[0033] S2. Laser doping process

[0034] Laser doping is performed on the A area of ​​the printing area; the laser power P1 is 35-45W, the laser frequency f1 is 50-150kHz, and the single pulse energy is E1=P1 / f1;

[0035] S3, Laser Removal Process

[0036] The B area including the printing area is laser removed, wherein the laser power P2 is 10-25 W, the laser frequency f2 is 100-200 kHz, and the single pulse energy is E2=P2 / f2; wherein the single pulse energy E2<E1, preferably E2=(0.3-0.6)E1;

[0037] S4. Cleaning process

[0038] When the laser removal process in step S3 is not performed, the concentration a of the acid or alkali used for cleaning is 12.1 mol / L, the amount b used is 500 L, and the cleaning time c is 20 min;

[0039] The semiconductor substrate after laser removal in step S3 is cleaned with acid or alkali, the concentration of the acid or alkali is (0.1-0.7)×a mol / L, the amount used is (0.1-0.7)×b L, and the cleaning time is (0.1-0.7)×c min.

[0040] Furthermore, the laser wavelength in step S2 and step S3 is 300-680 nanometers, preferably a green nano laser with a wavelength of 532 nm.

[0041] As a third aspect of the present application, the present application provides an application of a top laser doping method in preparing a solar cell. When preparing a TOPcon cell, the steps are:

[0042] S1. Printing process

[0043] Printing boron-doped slurry on the front side of the semiconductor substrate and printing phosphorus-doped slurry on the back side, and drying them, wherein the printing area includes area A and area B from the inside to the outside, and area A covers the doped area;

[0044] S2. Laser doping process

[0045] Laser doping is performed on the A area of ​​the printing area; the laser power P1 is 35-45W, the laser frequency f1 is 100-200kHz, and the single pulse energy is E1=P1 / f1;

[0046] S3, Laser Removal Process

[0047] The B area including the printing area is laser removed, wherein the laser power P2 is 10-25 W, the laser frequency f2 is 100-200 kHz, and the single pulse energy is E2=P2 / f2; wherein the single pulse energy E2<E1, preferably E2=(0.3-0.6)E1;

[0048] S4. Cleaning process

[0049] When the laser removal process in step S3 is not performed, the concentration a of the acid or alkali used for cleaning is 12.1 mol / L, the amount b used is 500 L, and the cleaning time c is 20 min;

[0050] The semiconductor substrate after laser removal in step S3 is cleaned with acid or alkali, the concentration of the acid or alkali is (0.1-0.7)×amol / L, the amount used is (0.1-0.7)×b L, and the cleaning time is (0.1-0.7)×c min.

[0051] Furthermore, the laser wavelength in step S2 and step S3 is 300-680 nanometers, preferably a green nano laser with a wavelength of 532 nm.

[0052] 3. Beneficial effects

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] (1) Make the subsequent cleaning process easier: In the laser doping step, different laser conditions or spot conditions are used to apply laser to the non-doped area of ​​the printed area to increase the cleaning effect, thereby avoiding the problem that the slurry in the non-laser doped area is difficult to clean in the traditional method, which may leave residues, cause pollution and affect the subsequent process.

[0055] (2) Reducing production costs and reducing pollution: Compared with the existing chemical reagent cleaning method, the cleaning method of the present invention can not only shorten the cleaning time and reduce production costs, but also be beneficial to environmental protection and reduce pollution to the environment.

[0056] (3) Improving product performance stability: Since the cleaning method of the present invention has low requirements on equipment and process, it can effectively avoid the problem of unstable product performance caused by equipment or process problems, thereby improving the performance stability of the product.

[0057] (4) Suitable for large-scale application: Since the manufacturing method of the present invention simplifies the manufacturing process, reduces the manufacturing cost, and improves the manufacturing efficiency, it is more suitable for large-scale application and helps promote the large-scale popularization of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of an embodiment in which the printing area is larger than the laser area;

[0059] Figure 2 is the overlapping diagram of the light spot position;

[0060] Figure 3 This is a schematic diagram of the structure of a BC battery in an embodiment;

[0061] Figure 4 This is a schematic diagram of the structure of the TOPcon battery cell in Example 5;

[0062] Figure 5 This is a schematic diagram showing that the printing area in Comparative Example 4 is smaller than the laser area. DETAILED DESCRIPTION

[0063] The present application is further described below in conjunction with specific embodiments.

[0064] It should be noted that the terms such as "upper," "lower," "left," "right," and "middle" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments in their relative relationships should be regarded as the scope of implementation of this application without substantially changing the technical content.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0066] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0067] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0068] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" expressly includes only A, only B, only C, and combinations of each thereof.

[0069] Concentration, amount and other numerical data can be presented in range format herein.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges contained in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including single numerals (such as 2,3,4) and sub-ranges (such as 1 to 3, 2 to 4, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5," which should be interpreted as including all the above-mentioned values ​​and ranges.In addition, no matter how the breadth of the described range or feature is, this explanation should be applicable.

[0070] In this application, TOPCon, Tunnel Oxide Passivated Contact, refers to tunnel oxide passivated contact technology.

[0071] In this application, ALD, Atom Layer Deposition, refers to atomic layer deposition.

[0072] In this application, PECVD, Plasma Enhanced Chemical Vapor Deposition, refers to plasma enhanced chemical vapor deposition.

[0073] In this application, Ag / Al Finger refers to silver / aluminum fine grid lines.

[0074] In the present application, average power refers to the laser energy output per unit time in a repetition cycle, and the unit is W (1W=1J / s). It can also be calculated according to "average power=single pulse energy×repetition frequency".

[0075] The doping of the present invention is suitable for the relatively smooth velvet surface on the front side or on the backlight side of the cell (relative to the velvet on the front side, the velvet area on the back side is smaller, or the bumps on the back side are more gentle, so that the excessive absorption of light under laser irradiation will not damage the velvet structure, and the increase in the reflectivity of the front structure is avoided); the doping of the present invention is suitable for the poly surface (reducing the direct damage of the laser to the silicon wafer substrate, and at the same time helping to increase the doping concentration and reduce the contact resistance of the electrode contact area), at this time the uniformity and effect of doping are better)

[0076] Example 1

[0077] A laser doping method in a BC cell of this embodiment comprises the following steps:

[0078] S1. Printing process

[0079] Prepare a silicon-based substrate with a resistivity of 1 to 10 ohm·cm and a thickness of 0.05 to 0.5 mm. Use screen printing to print boron paste containing boron element and phosphorus paste containing phosphorus element on the back of the substrate to form multiple paste areas. At this time, the area of ​​the printed area is slightly larger than the area of ​​the doped area. After printing, it is dried. The printed area is a rectangle, including a rectangular area A and a peripheral area B from the inside to the outside. The A area covers the doped area, such as Figure 1 shown.

[0080] S2. Laser doping process

[0081] After printing and drying, the A area of ​​the printed area is laser doped using a laser with a wavelength of 300 to 680 nanometers. In this embodiment, a green nano laser with a wavelength of 532 nm is preferred for better doping effect. Here, the laser power P1 is 35W and the laser frequency f1 is 150kHz. Under this condition, the doping effect is good and it is not easy to cause damage.

[0082] In order to optimize the doping uniformity, a square spot is used for laser doping. The width of area A (ie, the doping area) in the printing area is 450 microns, and the side of the square spot is 150 microns.

[0083] S3, Laser Removal Process

[0084] A green nano laser with a wavelength of 532nm is also used to remove the B area including the printing area. Here, the laser power P2 is 21W, and the laser frequency f2 is 200kHz; wherein, the single pulse energy E2=0.45E1; the slurry is removed when it is undoped or low-doped, making the subsequent cleaning process simpler.

[0085] It should be noted that the laser removal process of step S3 can be performed simultaneously with the laser doping process of step S2, or the laser removal process of step S3 can be performed after the laser doping process of step S2 is completed, or the laser removal process of step S3 can be performed before the laser doping process of step S2 starts.

[0086] S4. Cleaning process

[0087] The volume of the cleaning tank used in this process is 500L:

[0088] When the laser removal process in step S3 is not performed, the concentration a of the acid or alkali used for cleaning is 12.1 mol / L, the amount b used is 500 L, and the cleaning time c is 20 min;

[0089] The semiconductor substrate after laser removal in step S3 is cleaned with acid or alkali to remove impurities and residues on the surface of the substrate forming the P-type region and the N-type region to ensure the performance and quality of the solar cell. The concentration of the acid or alkali is 4.84 mol / L, the amount used is 200 L, and the cleaning time is 8 minutes.

[0090] S5, annealing process

[0091] The cleaned substrate is annealed at a temperature of 800-1000°C for 5-120 minutes to activate the doped area and achieve local P+ or N+ doping. Annealing promotes doping of Poly, oxide layer and silicon substrate.

[0092] Through the above steps, this embodiment can effectively remove the slurry residue in the non-laser doped area, avoiding contamination and technical problems affecting subsequent processes. At the same time, it reduces the time and amount of chemical reagents used for cleaning, reduces production costs and reduces environmental pollution.

[0093] Example 2

[0094] This embodiment is the same as embodiment 1, except that in step S3: the power P2 of the laser is 14W, and the frequency f2 of the laser is 200kHz; at this time, the single pulse energy is low, and the slurry is not easy to remove cleanly, and there is residue. Acid or alkali is used to clean the semiconductor substrate after laser removal in step S3 to remove impurities and residues on the surface of the substrate forming the P-type region and the N-type region to ensure the performance and quality of the solar cell. The concentration of the acid or alkali is 1.21mol / L, the amount used is 50L, and the cleaning time is 2min. At this time, the cleaning time is short, the slurry cannot be cleaned clean, and the efficiency is affected.

[0095] Example 3

[0096] This embodiment is the same as the embodiment 1, except that in step S3: the power P2 of the laser is 28W, and the frequency f2 of the laser is 200kHz; at this time, light doping may occur in the B region, but it will not have a bad effect, but can help collect carriers, and it will not have much effect as long as the metal electrode is formed in the range of A. The semiconductor substrate after the laser removal in step S3 is cleaned with acid or alkali to remove impurities and residues on the surface of the substrate forming the P-type region and the N-type region, so as to ensure the performance and quality of the solar cell. The concentration of the acid or alkali is 8.47mol / L, the amount used is 350L, and the cleaning time is 14min.

[0097] Example 4

[0098] This embodiment is the same as the embodiment 1, except that the laser conditions in the printing area and the doping area are both 35W in power and 150kHz in frequency. Figure 2As shown, area B of the printing area is doped using low energy density laser conditions (spot tangency), and area A of the printing area is doped using high energy density laser conditions (spot overlap).

[0099] Example 5

[0100] A laser doping method in a TOPcon cell of this embodiment, the TOPcon cell of this embodiment is as follows Figure 4 As shown, the steps are as follows:

[0101] S1. Printing process

[0102] Prepare a silicon-based substrate with a resistivity of 1 to 10 ohm·cm and a thickness of 0.05 to 0.5 mm. Use LP CVD to deposit a tunnel oxide layer and a poly layer on the front and back sides of the silicon wafer, then use screen printing to print a boron paste containing boron elements on the front side and a phosphorus paste containing phosphorus elements on the back side, and dry them, wherein the printing area includes area A and area B from the inside to the outside, and area A covers the doped area;

[0103] S2. Laser doping process

[0104] After printing and drying, the A area of ​​the printed area is laser doped using a laser with a wavelength of 300-680 nanometers. In this embodiment, a green nano laser with a wavelength of 532 nm is preferably used for better doping effect. Here, the laser power P1 is 35-45W, and the laser frequency f1 is 100-200kHz. In this embodiment, P1 is 35W and f1 is 150kHz.

[0105] S3, Laser Removal Process

[0106] Similarly, a green nano laser with a wavelength of 532nm is used to perform laser removal on the B area including the printed area. Here, the laser power P2 is 10-25W, and the laser frequency f2 is 100-200kHz; in this embodiment, P2 is 21W and f2 is 200kHz.

[0107] S4. Cleaning process

[0108] The volume of the cleaning tank used in this process is 500L:

[0109] When the laser removal process in step S3 is not performed, the concentration a of the acid or alkali used for cleaning is 12.1 mol / L, the amount b used is 500 L, and the cleaning time c is 20 min;

[0110] The semiconductor substrate after laser removal in step S3 is cleaned with acid or alkali, the concentration of the acid or alkali is 4.84 mol / L, the amount used is 200 L, and the cleaning time is 8 min.

[0111] Example 6

[0112] This embodiment is the same as embodiment 1, except that LPCVD is used to deposit a tunnel oxide layer and a poly layer on the back of a silicon wafer, and then a boron slurry containing boron element and a phosphorus slurry containing phosphorus element are printed on the poly layer by screen printing to form a plurality of slurry areas; the area of ​​these slurry areas is slightly larger than the area required for doping; and drying is performed after printing. Figure 3 Shown is a schematic structural diagram of the BC battery of this embodiment.

[0113] Example 7

[0114] This embodiment is the same as embodiment 4, except that LPCVD is used to deposit a tunnel oxide layer and a poly layer on the back of a silicon wafer, and then a boron slurry containing boron element and a phosphorus slurry containing phosphorus element are printed on the poly layer by screen printing to form a plurality of slurry areas; the area of ​​these slurry areas is slightly larger than the area required for doping; and drying is performed after printing.

[0115] Example 8

[0116] This embodiment is the same as embodiment 5, except that LPCVD is used to deposit a tunnel oxide layer and a poly layer on the back of a silicon wafer, and then a boron slurry containing boron element and a phosphorus slurry containing phosphorus element are printed on the poly layer by screen printing to form a plurality of slurry areas; the area of ​​these slurry areas is slightly larger than the area required for doping; and drying is performed after printing.

[0117] Example 9

[0118] This embodiment is the same as the embodiment 1, except that in step S3, the width of the B region 0<w≤5μm, and the single pulse energy of the laser E2=(0.3~0.4)E1. This situation includes the following three embodiments:

[0119] Example 9-1: The width of region B is 1 μm, the single pulse energy E2 of the laser is 0.3E1,

[0120] Example 9-2: The width of region B is 3 μm, the single pulse energy E2 of the laser is 0.35E1,

[0121] Example 9-3: The width of region B is 5 μm, and the single pulse energy E2 of the laser is 0.4E1.

[0122] Example 10

[0123] This embodiment is the same as the embodiment 1, except that in step S3, the width of the B region 5<w≤10μm, and the single pulse energy of the laser E2=(0.4~0.5)E1. This situation includes the following three embodiments:

[0124] Example 10-1: The width of region B is 6 μm, the single pulse energy E2 of the laser is 0.4E1,

[0125] Example 10-2: The width of region B is 8 μm, the single pulse energy E2 of the laser is 0.45E1,

[0126] Example 10-3: The width of region B is 10 μm, and the single pulse energy E2 of the laser is 0.5E1.

[0127] Embodiment 11

[0128] This embodiment is the same as the embodiment 1, except that in step S3, the width of the B region is 10<w≤20μm, and the single pulse energy of the laser is E2=(0.5~0.6)E1. This situation includes the following three embodiments:

[0129] Example 11-1: The width of region B is 11 μm, the single pulse energy E2 of the laser is 0.5E1,

[0130] Example 11-2: The width of region B is 15 μm, the single pulse energy E2 of the laser is 0.55E1,

[0131] Example 11-3: The width of region B is 20 μm, and the single pulse energy E2 of the laser is 0.6E1.

[0132] Comparative Example 1

[0133] Comparative Example 1 is the same as Example 1, and the amount of chemical reagents and time used in the cleaning process remain unchanged. The only difference is that step S3 is missing. The cleaning process is directly performed on the semiconductor substrate after laser doping in step S2. At this time, the edge slurry is not cleaned thoroughly, causing pollution to subsequent processes and reducing battery performance.

[0134] Comparative Example 2

[0135] Comparative Example 2 is the same as Example 11, except that the width w of the B region and the laser parameters are no longer distinguished and restricted. In this case, the width of the B region is 50 μm. The edge region uses the same laser parameter condition. In this case, the laser power P1 is 35 W, the laser frequency f1 is 150 kHz, P2 is 21 W, the laser frequency f2 is 200 kHz, and the single pulse energy of the laser E2=0.45E1.

[0136] Comparative Example 3

[0137] Comparative Example 1 is the same as Example 1, except that the laser conditions used in the laser removal process are the same as those in the laser doping process, and the non-doped area will also be doped, affecting the doping uniformity and the performance of the cell.

[0138] Comparative Example 4

[0139] This comparative example is the same as Example 1, except that Figure 5 The printed area is slightly smaller than the doped area. The laser conditions for both the printed and doped areas are 35W power, 150kHz frequency, and overlapping spots. At this time, the slurry is removed while the laser doping process is being performed, eliminating the step of S3, the laser removal process, but this will increase unnecessary laser damage in the area and affect efficiency.

[0140] In combination with the above-mentioned specific embodiments and comparative examples, it can be seen that in the specific embodiments, the method of the present invention saves the use of chemical reagents, reduces cleaning time, reduces production costs, and avoids pollution to the environment.

[0141] The electrical performance tests of the battery cells obtained in the above embodiments and comparative examples are shown in Table 1.

[0142] Table 1 Battery performance test of each embodiment and comparative example

[0143]

[0144] It can be seen from Table 1 that Examples 1-11 adopt the method of the present invention, which saves the use of chemical reagents, reduces cleaning time, reduces production costs, avoids pollution to the environment, and thus improves the conversion efficiency of the battery.

[0145] Combining Example 1 and Comparative Example 1, it can be seen that the amount of chemical reagents and time used in the cleaning process remain unchanged, and laser is not used for the edge slurry removal step. At this time, the edge slurry is not cleaned thoroughly, causing pollution to subsequent processes and reducing battery performance.

[0146] Combining Examples 9 to 11 and Comparative Example 2, it can be seen that distinguishing and limiting the width w of region B and the laser parameters can further improve the cleaning effect, remove the slurry residue, ensure the performance and quality of the solar cell, and thus improve the conversion efficiency of the cell.

[0147] Combining Example 1 and Comparative Example 3, it can be seen that the laser conditions used in the laser removal process are the same as those in the laser doping process. In this case, the non-doped area will also cause doping, affecting the doping uniformity and the performance of the cell.

[0148] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A laser doping method, characterized in that: The following steps are involved: S1. Printing process Printing a slurry containing doping elements on the front and / or back of the semiconductor substrate and drying it, wherein the printing area includes area A and area B from the inside to the outside, and area A covers the doping area; S2. Laser doping process Laser doping is performed on area A of the printing area; the single pulse energy of the laser here is E1; S3, Laser Removal Process Laser removal is performed on the B area including the printing area, where the single pulse energy of the laser is E2, wherein the single pulse energy E2≤E1; wherein the laser removal process of step S3 can be performed simultaneously with the laser doping process of step S2, or the laser removal process of step S3 can be performed after the laser doping process of step S2 is completed; or the laser removal process of step S3 can be performed before the laser doping process of step S2 is started; S4. Cleaning process When cleaning the semiconductor substrate after laser doping in step S2, the concentration of the acid or alkali used for cleaning is a mol / L, the amount used is b L, and the cleaning time is c min; For cleaning the semiconductor substrate after laser removal in step S3, the concentration of the acid or alkali is (0.1-0.7)×a mol / L, the amount used is (0.1-0.7)×b L, and the cleaning time is (0.1-0.7)×c min.

2. A laser doping method according to claim 1, characterized in that: In step S3, E2=(0.3-0.6)E1.

3. The laser doping method according to claim 1, characterized in that: In step S3, the width wμm of region B and the laser parameters meet the following conditions: When 0<w≤5, single pulse energy E2=(0.5~0.6)E1; When 5<w≤10, single pulse energy E2=(0.4~0.5)E1; When 10<w≤20, the single pulse energy E2=(0.3~0.4)E1.

4. A laser method according to claim 1, characterized in that: In step S2, there is only one layer of laser spot in area A, or there are multiple layers of laser spots evenly overlapped in area A; in step S3, there is only one layer of laser spot in area B, or there are multiple layers of laser spots overlapping in area B.

5. A laser doping method according to any one of claims 1 to 4, characterized in that: In step S1, the semiconductor substrate includes a poly layer.

6. A laser doping method according to any one of claims 1 to 4, characterized in that: In step S1, the doping element includes phosphorus or boron.

7. A laser doping method according to any one of claims 1 to 4, characterized in that: In step S2, a square light spot is used, the width of the doped region is 150 microns to 250 microns, and the side length of the light spot is 50 to 100 microns; the width of the doped region is more than 250 microns, and the side length of the light spot is 100 to 200 microns.

8. Use of the method according to any one of claims 1 to 7 in preparing a solar cell, characterized in that: The laser wavelength in step S2 and step S3 is 300-680 nanometers, and a green nano laser with a wavelength of 532 nm is preferred.

9. The use according to claim 8, characterized in that: When the solar cell is a BC cell, in step S2, the laser power P1 is 35-45 W, and the laser frequency f1 is 50-150 kHz; in step S3, the laser power P2 is 10-25 W, and the laser frequency f2 is 100-200 kHz; wherein, the single pulse energy E2<E1, preferably E2=(0.3-0.6)E1.

10. The use according to claim 8, characterized in that: When the solar cell is a TOPcon cell, in step S2, the laser power P1 is 35-45 W, and the laser frequency f1 is 100-200 kHz; in step S3, the laser power P2 is 10-25 W, and the laser frequency f2 is 100-200 kHz; wherein, the single pulse energy E2<E1, preferably E2=(0.3-0.6)E1.

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