Method for manufacturing a solar cell

Abstract

The application discloses a manufacturing method of a solar cell, comprising the following steps: establishing a database of power used for laser doping and diffusion sheet samples, wherein the database comprises optimal power corresponding to optimal sheet resistance uniformity; taking a silicon wafer to be manufactured into a solar cell; depositing a doping source on the surface of the silicon wafer to obtain a diffusion sheet; measuring second sheet resistance values of different positions of the diffusion sheet and measuring second reflectivity values of the diffusion sheet; searching for optimal power corresponding to the second sheet resistance values and the second reflectivity values from the database; and performing laser doping according to the optimal power. In the application, the second reflectivity values reflect the thickness of the diffusion sheet, the second sheet resistance values reflect the total amount of the doping source in the diffusion sheet, and different powers of laser are used for doping according to the thickness of the diffusion sheet and the total amount of the doping source, so that the laser doping effect of the prepared solar cell is better.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, and more particularly to a manufacturing method of a solar cell. BACKGROUND

[0002] With the aggravation of environmental pollution and energy crisis, photovoltaic modules using solar energy to generate electricity have become the focus of attention. Renewable energy represented by solar energy has been strongly supported by the country, which has injected new vitality into the solar industry, and the solar industry is booming. The current main solar conversion tool, i.e. solar cell, has the characteristics of high conversion efficiency, low cost and long service life. As a key component of photovoltaic modules, the solar cell bears the important responsibility of converting solar energy into electrical energy. In the related art, when preparing a solar cell, a silicon wafer needs to be doped, and then the doped doping source is pushed into the diffusion layer by laser diffusion. However, the thickness of the doped silicon wafer is different, and the same laser parameters are used for processing, so the doping effect is not good, the sheet resistance uniformity of the solar cell wafer is poor, and the performance of the solar cell wafer is affected.

[0003] Therefore, it is an urgent problem to be solved to reduce the sheet resistance uniformity and improve the performance of the solar cell wafer. SUMMARY

[0004] Therefore, the present application provides a manufacturing method of a solar cell wafer to reduce the sheet resistance uniformity and improve the performance of the solar cell wafer.

[0005] The manufacturing method of the solar cell provided by the present application comprises the following steps:

[0006] A database of powers used for laser doping and diffusion wafer samples is established, and the database comprises optimal powers corresponding to optimal sheet resistance uniformity;

[0007] A silicon wafer to be manufactured into a solar cell is taken;

[0008] A doping source is deposited on the surface of the silicon wafer to obtain a diffusion wafer;

[0009] Second sheet resistance values at different positions of the diffusion wafer are measured, and second reflectivity values of the diffusion wafer are measured;

[0010] An optimal power corresponding to the second sheet resistance values and the second reflectivity values is found from the database;

[0011] Laser doping is performed according to the optimal power.

[0012] Optionally, the database of powers used for laser doping and diffusion wafer samples comprises the following steps:

[0013] A silicon wafer sample is obtained, a doping source is deposited on the surface of the silicon wafer sample to obtain a diffusion wafer sample;

[0014] detecting a plurality of first sheet resistance values at different positions of the diffusion sheet sample;

[0015] detecting a plurality of first reflectivity values at different positions of the diffusion sheet sample, the first reflectivity values being negatively correlated with the thickness of the diffusion sheet sample;

[0016] determining a first power for laser doping according to the first sheet resistance values and the first reflectivity values;

[0017] performing laser doping according to a plurality of the first powers to obtain a doped sample;

[0018] performing sheet resistance uniformity testing on the doped sample, the corresponding first power when the sheet resistance uniformity is optimal being an optimal power, to obtain the database.

[0019] Optionally, the sheet resistance uniformity testing on the doped sample comprises testing sheet resistance values at a plurality of different positions of the doped sample, the sheet resistance uniformity M = (Max-Min) / (Max+Min) x 100%, wherein Max is the maximum value of the sheet resistance values and Min is the minimum value of the sheet resistance values.

[0020] Optionally, the first sheet resistance value increases by 5Ω, and the first power increases by 1%; the first sheet resistance value decreases by 5Ω, and the first power decreases by 1%.

[0021] Optionally, the first reflectivity value increases by 0.5%, and the first power decreases by 1%.

[0022] Optionally, determining the first power for laser doping according to the first sheet resistance values and the first reflectivity values comprises adjusting the current of the laser equipment to regulate the first power according to the first sheet resistance values and the first reflectivity values, and performing laser doping according to a preset laser processing pattern.

[0023] Optionally, the wavelength of the laser equipment when measuring the first reflectivity value and the second reflectivity value is a fixed wavelength.

[0024] Optionally, the number of the first sheet resistance values is at least 5.

[0025] Optionally, at least one of the at least 5 first sheet resistance values corresponds to the middle of the diffusion sheet sample, and the remaining first sheet resistance values correspond to the edges of the diffusion sheet sample.

[0026] Optionally, the first reflectivity value and / or the second reflectivity value is detected according to the following method:

[0027] A CCD reflectivity instrument is additionally provided on the laser equipment, and the first reflectivity value and / or the second reflectivity value is obtained through the CCD reflectivity instrument.

[0028] Compared with the prior art, the method for manufacturing solar cell provided by the application at least has the following beneficial effects:

[0029] The application first establishes a database of power used for laser doping and diffusion sample, the database has optimal power during laser doping, the solar cell sheet obtained by laser doping at the optimal power has optimal sheet resistance uniformity, the establishment of the database can determine the optimal power for diffusion samples with different thickness and different sheet resistance values. Then the steps for manufacturing solar cell include: taking a silicon wafer to be manufactured into solar cell; depositing a doping source on the surface of the silicon wafer to obtain a diffusion sheet; measuring second sheet resistance values at different positions of the diffusion sheet and measuring second reflectivity values of the diffusion sheet; searching for optimal power corresponding to the second sheet resistance values and the second reflectivity values from the database; and performing laser doping according to the optimal power. Therefore, the power during laser doping for manufacturing solar cell is the optimal power, and the sheet resistance uniformity is optimal. According to the second reflectivity values reflecting the thickness of the diffusion sheet, the second sheet resistance values reflecting the total amount of the doping source in the diffusion sheet, and the different thickness and total amount of the doping source, the application uses laser with different power to dope, and the laser doping effect of the prepared solar cell is more optimal.

[0030] Of course, implementing any product of the application does not necessarily need to achieve all the technical effects described above.

[0031] Other features and advantages of the application will become apparent from the following detailed description of exemplary embodiments of the application with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings incorporated in and forming a part of the specification illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0033] Figure 1 is a flow chart of the method for manufacturing solar cell provided by the application;

[0034] Figure 2 is a flow chart of the method for establishing database provided by the application. DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the application will now be described in detail with reference to the accompanying drawings. Note that the relative arrangement, numerical expressions, and numerical values of components and steps set forth in these embodiments are not limiting to the scope of the application unless otherwise specifically stated.

[0036] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application or its application or uses.

[0037] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus should be considered as being part of the specification.

[0038] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary, and not as a limitation. Thus, other examples of exemplary embodiments can have different values.

[0039] It should be noted that like reference numerals and letters in the various figures indicate like elements, and thus, discussions of certain items herein need not be discussed in further detail with respect to subsequent figures.

[0040] The conventional process flow of related art in making solar cells mainly includes: silicon wafer cleaning, silicon wafer texturing, preparation of PN junction, etching, film plating, metallization and detection sorting, etc. In order to prepare the PN junction of the solar cell, the silicon wafer needs to be doped. Doping is to dope the required impurities into the specific area of the silicon substrate in a certain way, and has a specified amount and suitable distribution to form a PN junction. The preparation of the PN junction by doping can be prepared by diffusion method. The quality control of the diffusion junction plays a key role in the characteristics of the solar cell. In the related art, the doped doping source is pushed into the diffusion layer by the method of laser diffusion. The laser technology of conventional phosphorus laser doping is mature. However, for some materials with low diffusion coefficient, such as boron, the diffusion pushing temperature is usually more than 1000℃. Thus, the sheet resistance uniformity of the solar cell wafer made is poor. The sheet resistance uniformity of the whole tube of the conventional low-pressure diffusion equipment is about 5%, which affects the performance of the solar cell wafer.

[0041] Therefore, the present application provides a method for making solar cells to reduce the sheet resistance uniformity of the solar cell wafer and improve the performance of the solar cell wafer. The method for making solar cells will be described in detail.

[0042] Reference Figure 1 , Figure 1 is a flow chart of the method for making solar cells provided by the present application. The method for making solar cells provided by the present application includes the following steps:

[0043] S1: Establishing a database of the power used for laser doping and the diffusion wafer sample, which includes the optimal power corresponding to the optimal sheet resistance uniformity;

[0044] S2: Taking a silicon wafer to be made into a solar cell;

[0045] S3: depositing a doping source on the surface of the silicon wafer to obtain a diffusion wafer;

[0046] S4: measuring the second sheet resistance value of the diffusion wafer at different positions, and measuring the second reflectivity value of the diffusion wafer;

[0047] S5: searching for the optimal power corresponding to the second sheet resistance value and the second reflectivity value from the database;

[0048] S6: performing laser doping according to the optimal power.

[0049] It can be understood that, taking phosphorus as an example, laser doping is to perform heavy doping on the part of the metal gate line in contact with the silicon wafer, and to maintain low-concentration doping on the positions other than the electrode. Through thermal diffusion, pre-diffusion is performed on the surface of the silicon wafer to form light doping; meanwhile, the surface phosphorus-silicon PSG serves as a local laser heavy doping source, and through the local thermal effect of the laser, the phosphorus atoms in the phosphorus-silicon PSG are rapidly diffused into the silicon wafer again to form a local heavy doping area. In combination with laser high-precision patterning, perfect overprinting effect with subsequent screen printing can be achieved. Of course, laser doping in the present application can reduce the series resistance of the solar cell, improve the fill factor, reduce the surface recombination, and improve the surface passivation effect; the surface low-concentration diffusion can improve the short-wave response of the solar cell, improve the short-circuit current and the open-circuit voltage. Of course, laser doping has more advantages, for example, only one step of laser patterning is needed to complete the process, and the process flow is simple; the local laser thermal effect can minimize the thermal damage of high temperature to the silicon wafer; the laser processing process is simple, does not need chemical treatment, and is pollution-free, which will not be described here.

[0050] The inventors find that the laser energy and the medium layer absorption are generally related in the laser doping process. When the laser is in the condition of uneven medium (in the wafer) or the thickness of the medium (diffusion wafer, which is a diffusion wafer formed by depositing a doping source on a silicon substrate) has differences (between different wafers), the thickness of the medium has a certain influence on the absorption of the short-wave end laser; the fixed power laser doping and the fixed linear velocity mode will cause a certain mismatch. The linear velocity is generally controlled by the motor inside the galvanometer, however, the variable speed of the galvanometer scanning affects the accuracy of the laser, so the inventors consider matching the diffusion wafers with different thicknesses and different doping amounts by changing the laser power. The total amount of impurities diffused into the silicon can be characterized by sheet resistance, which refers to the resistance of a square-shaped semiconductor thin layer in the current direction. The sheet resistance mainly depends on the total amount of impurities diffused into the wafer, the more the total amount of impurities, the smaller the sheet resistance. For diffusion wafers of different thicknesses and diffusion wafers of the same thickness, the more the doping amount, the lower the test sheet resistance. However, as the doping amount increases, the refractive index of the diffusion wafer increases, and the reflection of the laser increases. Therefore, in order to make the sheet resistance uniformity after laser doping optimal, the sheet resistance value of the diffusion wafer before laser doping and the reflectivity value of the diffusion wafer need to be considered comprehensively, and different power lasers are used for processing, so that the laser doping effect is more optimal.

[0051] Specifically, in step S1, the optimal power corresponding to the optimal sheet resistance uniformity is obtained through a large amount of data. The data in the database needs to include the optimal power corresponding to any sheet resistance value and any reflectivity value. The data in the database includes: ① the sheet resistance value of the diffusion wafer after the laser power is used as a single variable, ② the sheet resistance value of the diffusion wafer after the laser doping with the same power, and ③ the sheet resistance value of the diffusion wafer with different thicknesses after the laser doping with the same power. Through these data, the optimal power when the sheet resistance value after laser doping is optimal is determined.

[0052] In step S2, a silicon wafer to be made into a solar cell is taken. The silicon wafer can be an N-type silicon wafer or a P-type silicon wafer. Of course, the emitter formed by the deposition and diffusion process is opposite to the conductivity type of the silicon wafer, such as a P-type silicon wafer with an N-type emitter or an N-type silicon wafer with a P-type emitter. The silicon wafer is an N-type substrate, and the solar cell is an N-type solar cell. The silicon wafer is a P-type substrate, and the solar cell is a P-type solar cell. The N-type silicon wafer uses electron conduction, and the P-type silicon wafer uses hole conduction. The N-type solar cell can be a TOPCon (Tunnel Oxide Passivated Contact) cell, which has a longer service life and higher efficiency. The P-type solar cell has a simple process and low cost. The present application does not specifically limit the type of silicon wafer.

[0053] In step S3, the dopant source is deposited on the surface of the silicon wafer to obtain a diffusion wafer. The dopant source can be an N-type impurity or a P-type impurity. In the production of solar cells, boron is a more ideal P-type impurity for N-type silicon wafers, and phosphorus is a more ideal N-type impurity for P-type silicon wafers.

[0054] It can be understood that the process of depositing the dopant source is usually carried out in a diffusion furnace, but the position of the silicon wafer in the diffusion furnace, such as the furnace mouth or the furnace tail, causes the amount of deposited dopant source to be different, resulting in uneven deposition of the dopant source.

[0055] In step S4, the second sheet resistance value of the diffusion wafer at different positions is measured, and the second reflectivity value of the diffusion wafer is measured.

[0056] As described above, the total amount of deposited dopant source is different due to the different positions of the silicon wafer in the diffusion furnace, which determines the second sheet resistance value. In addition, the thicker the thickness of the diffusion wafer, the more energy is required to push the deposited dopant source into the silicon substrate by laser doping. At this time, the second reflectivity value of the diffusion wafer can be used to reflect the thickness of the diffusion wafer. It can be understood that the thicker the thickness of the diffusion wafer, the higher the doping amount, and the lower the second reflectivity value. The thinner the thickness of the diffusion wafer, the lower the doping amount, and the higher the second reflectivity value.

[0057] Generally, the boron diffusion sheet resistance is 60-250 Ω·cm; the phosphorus diffusion high sheet resistance is 140-200 Ω·cm, and the phosphorus diffusion low sheet resistance is 20-60 Ω·cm.

[0058] In step S5, the optimal power corresponding to the second sheet resistance value and the second reflectivity value is found from the database. Since there are a large amount of data in the database, only the optimal power corresponding to the second sheet resistance value and the second reflectivity value needs to be found, and the operation is relatively simple.

[0059] In step S6, laser doping is performed according to the optimal power. After the optimal power is determined according to the second sheet resistance value and the second reflectivity value, laser doping can be performed according to the optimal power, which is simple and convenient to operate.

[0060] Referring to Table 1 below, Table 1 shows the sheet resistance uniformity detection results under different laser powers according to the second reflectivity value and the second sheet resistance value, and the comparison with the detection results of the fixed power.

[0061] Table 1 shows the sheet resistance uniformity detection results under different laser powers according to the second reflectivity value and the second sheet resistance value, and the comparison with the detection results of the fixed power.

[0062]

[0063] As can be seen from Table 1, the sheet resistance uniformity is higher when the laser doping is fixed filtering, reaching 4.2%, while the sheet resistance uniformity is lower after adjusting the laser power through the second sheet resistance and the second emissivity, and the sheet resistance uniformity is less than 3.5%, and the sheet resistance uniformity is better. In the present application, the sheet resistance is tested (5 points or 9 points) after adjusting the laser power through the second sheet resistance and the second emissivity. The sheet resistance uniformity is less than 3.5%.

[0064] The present application first establishes a database of the power used for laser doping and the diffusion sheet sample, and the database has the optimal power during laser doping. The sheet resistance uniformity of the solar cell sheet obtained by laser doping under the optimal power is optimal. The establishment of the database can determine the optimal power for diffusion sheet samples of different thicknesses and different sheet resistance values. Then the steps of manufacturing the solar cell sheet include: taking a silicon wafer to be manufactured into a solar cell; depositing a doping source on the surface of the silicon wafer to obtain a diffusion sheet; measuring the second sheet resistance values at different positions of the diffusion sheet and measuring the second reflectivity values of the diffusion sheet; finding the optimal power corresponding to the second sheet resistance values and the second reflectivity values from the database; and performing laser doping according to the optimal power. Therefore, the power used for laser doping during the manufacturing of the solar cell sheet is the optimal power, and the sheet resistance uniformity is optimal. According to the second reflectivity value reflecting the thickness of the diffusion sheet and the second sheet resistance value reflecting the total amount of the doping source in the diffusion sheet, different powers of the laser are used for doping according to the different thicknesses and total amounts of the doping source, and the laser doping effect of the prepared solar cell is more optimal.

[0065] In some optional embodiments, continuing to refer to Figure 1 , Figure 1 The step S1 of establishing the database of the power used for laser doping and the diffusion sheet sample in the present application can be implemented according to the following steps. Specifically, referring to Figure 2 , Figure 2 is a method flow chart for establishing the database in the present application, Figure 2 The process of establishing the database in the present application includes:

[0066] Step S11: obtaining a silicon wafer sample, depositing a doping source on the surface of the silicon wafer sample to obtain a diffusion sheet sample;

[0067] Step S12: detecting a plurality of first sheet resistance values at different positions of the diffusion sheet sample;

[0068] Step S13: detecting a plurality of first reflectivity values at different positions of the diffusion sheet sample, and the first reflectivity value is negatively correlated with the thickness of the diffusion sheet sample;

[0069] Step S14: determining a first power used for laser doping according to the first sheet resistance value and the first reflectivity value;

[0070] Step S15: laser doping according to the plurality of first powers to obtain a doped sample;

[0071] Step S16: square resistance uniformity test is performed on the doped sample, and when the square resistance uniformity is optimal, the corresponding first power is the optimal power to obtain a database.

[0072] It can be understood that the silicon wafer sample in step S11 is not the same silicon wafer as the silicon wafer in step S2 described above. The silicon wafer sample in the embodiment is a silicon wafer for establishing a database, and is not a silicon wafer for subsequent production of solar cells. A large number of silicon wafer samples are needed to support data.

[0073] It should be noted that the database established in the present application can be data within a silicon wafer sample or data between different silicon wafer samples.

[0074] The first square resistance value in step S12 is the first square resistance value at different positions in the diffusion wafer sample, which reflects the total amount of the doping source in the diffusion wafer sample. The more the first square resistance value determination data, the more the first square resistance value on the same silicon wafer sample, and the more accurate the final determination of the first square resistance value and the optimal power of laser doping.

[0075] In step S13, the present application innovatively considers the thickness of the film layer of the doping source when establishing the database. Thickness testing is relatively time-consuming and difficult. The present application inversely calculates the negative correlation between the reflectivity and the thickness. The first reflectivity value is the first reflectivity value at a plurality of different positions in the diffusion wafer sample. The reflectivity instrument can detect all the first reflectivity values of the entire surface of the diffusion wafer sample. Generally, the thickness of the diffusion wafer is about 120 nm, and the first reflectivity value is 2-3%. A thicker boron-containing oxygen substance can absorb laser of a corresponding wavelength. The thicker the doping source film, the lower the reflectivity at a specific wavelength of the corresponding laser. Because laser doping is to push the impurities on the surface of the diffusion wafer into the interior of the silicon wafer, the thicker the doping source film, the more difficult it is to dope. At present, a large amount of data detection shows that the reflectivity of the boron-doped film layer is 24-30% in the ultraviolet band when the thickness is 30-40 nm.

[0076] Therefore, the present application provides the first reflectivity value to reflect the thickness of the doping source. The first reflectivity value is negatively correlated with the thickness of the diffusion wafer sample, that is, the thicker the thickness of the doping source, the higher the doping amount, and the lower the first reflectivity value. The thinner the thickness of the doping source, the lower the doping amount, and the higher the first reflectivity value.

[0077] In step S14, the first power used for laser doping is determined according to the first sheet resistance value and the first reflectivity value. Of course, when the first sheet resistance value is fixed, different first powers are used for laser doping when the first reflectivity value is different. When the first sheet resistance value is different, different first powers are used for laser doping when the first reflectivity value is the same. When the first sheet resistance value and the first reflectivity value are both changed, different first powers are used for laser doping to obtain a doped sample. In this way, a large amount of data can be obtained as data support for the database, which is convenient for subsequent step S5. After the database is established, the optimal power corresponding to the second sheet resistance and the second reflectivity value can be found in the database. Not only the sheet resistance uniformity can be improved, but also the laser doping efficiency can be improved.

[0078] The purpose of step S16 is to determine the optimal power from the plurality of first powers. The method is to test the sheet resistance uniformity of the doped sample. When the sheet resistance uniformity is optimal, the first power is the optimal power.

[0079] In some optional embodiments, continuing to refer to Figure 2 The sheet resistance uniformity test of the doped sample includes testing the sheet resistance values of a plurality of different positions of the doped sample. The sheet resistance uniformity M=(Max-Min) / (Max+Min)×100%, wherein Max is the maximum value of the sheet resistance value, and Min is the minimum value of the sheet resistance value.

[0080] It can be understood that the optimal power is determined by the sheet resistance uniformity. The sheet resistance values of a plurality of positions of the doped sample are tested. The lower the sheet resistance uniformity value, the smaller the difference between the maximum value of the sheet resistance value and the minimum value of the sheet resistance value, the better the sheet resistance uniformity, and the first power is the optimal power when the sheet resistance uniformity is optimal.

[0081] In some optional embodiments, the first sheet resistance value increases by 5Ω, and the first power increases by 1%; the first sheet resistance value decreases by 5Ω, and the first power decreases by 1%.

[0082] It can be understood that through a large amount of data, it is found that the first power increases by 1% when the first sheet resistance value increases by 5Ω, and the first power decreases by 1% when the first sheet resistance value decreases by 5Ω. The corresponding relationship is used for laser doping, and the sheet resistance uniformity after laser doping is good.

[0083] In addition, the higher the first sheet resistance, the higher the reduction in sheet resistance after laser doping. For example, using the same laser power to dope, the first sheet resistance of 130Ω will be reduced to 80Ω after laser doping, and the first sheet resistance of 90Ω will be reduced to 75Ω after laser doping. That is, the higher the first sheet resistance, the more the sheet resistance will be reduced after laser doping. In order to make the sheet resistance after laser doping closer (that is, the better the uniformity of the sheet resistance), the power of the laser doping can be adjusted to make the reduced sheet resistance closer.

[0084] In some optional embodiments, the first reflectivity value is increased by 0.5%, and the first power is reduced by 1%.

[0085] It can be understood that the thicker the doping source film, the lower the reflectivity at a specific wavelength of the laser. The laser is to push the material on the surface of the doping source into the silicon wafer. The thicker the doping source film, the more difficult it is to dope. Currently, the reflectivity of a boron-doped film layer with a thickness of 30-40 nm in the ultraviolet band is 24-30%. The thinner the first reflectivity value, the easier it is to dope, and the first power can be reduced by 1% to make the sheet resistance after laser doping closer.

[0086] In some optional embodiments, the first power used for laser doping is determined according to the first sheet resistance and the first reflectivity value, including adjusting the current of the laser device to regulate the first power according to the first sheet resistance and the first reflectivity value, and performing laser doping according to a preset laser processing pattern.

[0087] Specifically, when the first sheet resistance and the first reflectivity value are different, more first power is needed to achieve the data of laser doping. At this time, the current of the laser device is adjusted according to the first sheet resistance and the first reflectivity value to regulate the first power, and then the laser doping is performed according to the preset laser processing pattern.

[0088] Of course, it should be noted that when the solar cell is manufactured, that is, in step S6, the current of the laser device can be adjusted to make the corresponding laser power reach the optimal power, and then the laser doping is performed according to the preset laser processing pattern. Here, it is not repeated.

[0089] In some optional embodiments, the wavelength of the laser device when measuring the first reflectivity value and the second reflectivity value is a fixed wavelength.

[0090] The wavelength of the laser device when measuring the first reflectivity value and the second reflectivity value is fixed, for example, 20 nm, 30 nm, or 40 nm. Here, the fixed wavelength is not specifically limited.

[0091] In some optional embodiments, the number of first sheet resistances is at least 5.

[0092] Specifically, in the determination of the first sheet resistance of the silicon wafer sample, 5 points or 9 points are selected to calculate the average value, which is mainly affected by the off-line four-probe sheet resistance test rate. Of course, the on-line sheet resistance tester can obtain multiple test data in the linear direction of a single silicon wafer sample. Here, the number of first sheet resistance values is not specifically limited, as long as it is greater than or equal to 5. Of course, the more the first sheet resistance values, the better. After laser doping processing, the first sheet resistance value of the processing area will decrease, thereby reaching the required range. It can be understood that, under other conditions unchanged, for example, the first reflectivity value is unchanged, the higher the power of laser doping, the more the first sheet resistance value of the processing area decreases after laser doping.

[0093] In some optional embodiments, at least one of the at least 5 first sheet resistance values corresponds to the middle of the diffusion wafer sample, and the remaining first sheet resistance values correspond to the edge of the diffusion wafer sample.

[0094] It should be noted that the more the number of first sheet resistance values, the more the doping amount of the doping source can be reflected. However, the minimum number of first sheet resistance values is 5. The middle first sheet resistance value of a diffusion wafer sample can be tested, and the remaining 4 first sheet resistance values are uniformly distributed on the edge of the diffusion wafer sample, which can uniformly represent the distribution of the doping source in the diffusion wafer.

[0095] In some optional embodiments, the first reflectivity value and / or the second reflectivity value is detected according to the following method:

[0096] A CCD reflectivity instrument is additionally provided on the laser equipment, and the first reflectivity value and / or the second reflectivity value is obtained through the CCD reflectivity instrument, so that full-area reflectivity detection of the silicon wafer sample and the silicon wafer can be performed.

[0097] As can be seen from the above embodiments, the solar cell wafer manufacturing method provided by the present application at least achieves the following beneficial effects:

[0098] The present application first establishes a database of power used for laser doping and diffusion sheet samples, the database has optimal power during laser doping, and the sheet resistance uniformity of solar cell pieces obtained by laser doping at the optimal power is optimal, the establishment of the database can determine the optimal power for diffusion sheet samples with different thicknesses and different sheet resistance values. Then the steps of manufacturing solar cell pieces include: taking a silicon wafer to be manufactured into solar cells; depositing a doping source on the surface of the silicon wafer to obtain a diffusion sheet; measuring second sheet resistance values at different positions of the diffusion sheet, and measuring second reflectivity values of the diffusion sheet; finding the optimal power corresponding to the second sheet resistance values and the second reflectivity values from the database; and performing laser doping according to the optimal power. Therefore, the power during laser doping when manufacturing solar cell pieces is the optimal power, and the sheet resistance uniformity is optimal. According to the second reflectivity value reflecting the thickness of the diffusion sheet, the second sheet resistance value reflecting the total amount of the doping source in the diffusion sheet, and the different thicknesses and total amounts of the doping source, different powers of the laser are used for doping, and the laser doping effect of the prepared solar cells is more optimal.

[0099] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, but not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method for manufacturing a solar cell, characterized in that, include: Establish a database of power used for laser doping and diffuser samples, the database including the optimal power corresponding to the optimal sheet resistance uniformity; the sheet resistance uniformity is less than 3.5%; Take the silicon wafer to be used to make solar cells; A doped source is deposited on the surface of the silicon wafer to obtain a diffused wafer; Measure the second square resistance at different positions of the diffuser, and measure the second reflectivity of the diffuser; Search the database to calculate the optimal power corresponding to the second square resistance value and the second reflectivity value; Perform laser doping according to the optimal power; The establishment of a database of laser doping power and diffuser samples includes: A silicon wafer sample is obtained, and a doping source is deposited on the surface of the silicon wafer sample to obtain a diffused wafer sample; Detect multiple first-square resistance values ​​at different locations in the diffuser sample; Multiple first reflectance values ​​at different locations in the diffuser sample are detected, and the first reflectance values ​​are negatively correlated with the thickness of the diffuser sample. The first power used for laser doping is determined based on the first square resistance value and the first reflectivity value; Laser doping is performed using multiple first powers to obtain doped samples; The sheet resistance uniformity of the doped sample is tested, and the first power corresponding to the optimal sheet resistance uniformity is the optimal power, thus obtaining the database; Increasing the first resistance by 5Ω increases the first power by 1%; decreasing the first resistance by 5Ω decreases the first power by 1%. The first reflectivity value increases by 0.5%, while the first power decreases by 1%.

2. The method for manufacturing a solar cell according to claim 1, characterized in that, The sheet resistance uniformity test is performed on the doped sample, including testing the sheet resistance values ​​at multiple different locations of the doped sample. The sheet resistance uniformity is M = (Max - Min) / (Max + Min) × 100%, where Max is the maximum sheet resistance value and Min is the minimum sheet resistance value.

3. The method for manufacturing a solar cell according to claim 1, characterized in that, Determining the first power used for laser doping based on the first square resistance value and the first reflectivity value includes adjusting the current of the laser device to regulate the first power based on the first square resistance value and the first reflectivity value, and performing laser doping according to a preset laser processing pattern.

4. The method for manufacturing a solar cell according to claim 3, characterized in that, The wavelength of the laser device is a fixed wavelength when measuring the first reflectance value and the second reflectance value.

5. The method for manufacturing a solar cell according to claim 1, characterized in that, The number of the first resistance values ​​is at least 5.

6. The method for manufacturing a solar cell according to claim 5, characterized in that, At least one of the at least five first-square resistance values ​​corresponds to the middle of the diffuser sample, and the remaining first-square resistance values ​​correspond to the edges of the diffuser sample.

7. The method for manufacturing a solar cell according to claim 1, characterized in that, The first reflectance value and / or the second reflectance value are detected according to the following method: A CCD reflectance meter is added to the laser equipment to obtain the first reflectance value and / or the second reflectance value.

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