CN111816554A - Front-side local re-expansion method of P-type back-junction contact passivated battery and battery preparation method - Google Patents

Front-side local re-expansion method of P-type back-junction contact passivated battery and battery preparation method Download PDF

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CN111816554A
CN111816554A CN202010915777.6A CN202010915777A CN111816554A CN 111816554 A CN111816554 A CN 111816554A CN 202010915777 A CN202010915777 A CN 202010915777A CN 111816554 A CN111816554 A CN 111816554A
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boron
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silicon
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袁声召
崔艳峰
庄宇峰
于元元
胡玉婷
杨斌
张文超
万义茂
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Risen Energy Co Ltd
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Abstract

The application relates to the field of solar cells, in particular to a front local re-expansion method of a P-type back junction contact passivated cell and a cell preparation method. Printing boron slurry on a front metal area of a P-type silicon wafer with a tunneling oxide layer and a polycrystalline silicon film deposited on the back surface; the boron in the boron slurry is then driven into the silicon using a laser. According to the method, the boron slurry is used as a boron source for local re-expansion of the front surface of the silicon wafer, then the boron in the boron slurry is driven into the silicon by laser, and a local re-expansion area can be formed on the front surface of the P-type back junction contact passivation battery to form ohmic contact, so that the conversion efficiency of the P-type back junction contact passivation battery is improved. And the method adopts the boron slurry as the boron source for the local re-expansion of the front surface of the silicon wafer, can greatly reduce the production cost of the P-type back junction contact passivation battery, and is suitable for industrialization. The boron in the boron slurry is driven into the silicon by laser, so that the process steps are simple and the operability is strong.

Description

Front-side local re-expansion method of P-type back-junction contact passivated battery and battery preparation method
Technical Field
The application relates to the field of solar cells, in particular to a front local re-expansion method of a P-type back junction contact passivated cell and a cell preparation method.
Background
A contact passivated cell (TOPCon) uses tunnel oxide to passivate the surface of a crystalline silicon to obtain surface passivation and to achieve selective contact with a highly doped silicon film. The surface recombination rate is effectively reduced due to the surface passivation of the contact passivated cell (TOPCon). And because the contact passivation cell (TOPCon) realizes selective contact by a highly doped silicon film, the back open contact process of some back oxide passivation high-efficiency cells is avoided.
Due to the excellent performance of the contact passivated cell (TOPCon), it was rapidly becoming a popular technique in the photovoltaic industry since the birth of 2013. Contact passivated cells (TOPCon) have a rapid increase in laboratory cell efficiency. In 2017, the efficiency of the small-area N-type TOPCon battery released by the German Fraunhofeise research organization reaches 25.8 percent. Compared with a PERC battery, the TOPCon battery efficiency is 0.5-1% higher; and TOPCon cells have no light decay compared to PERC cells.
However, most of the current studies on contact passivated cells (TOPCon) have focused on N-type TOPCon cells. For example, chinese CN 110571304 a discloses a method for manufacturing an N-type passivated contact double-sided solar cell, which mainly includes: depositing a silicon nitride film on the back, removing the winding degree and texturing, isolating the edge, removing BSG, depositing an aluminum oxide layer and a silicon nitride layer of a front passivation layer, and performing screen printing and sintering to obtain the passivated contact double-sided solar cell. Chinese patent CN 110299434 a discloses a method for manufacturing an N-type double-sided solar cell, which mainly comprises: pre-cleaning an N-type silicon wafer, performing phosphorus diffusion on the back surface to form an N + layer, and removing PSG on the surface, the edge of the silicon wafer and the diffusion layer on the front surface; covering a silicon nitride layer on the back of the silicon wafer, removing the silicon nitride layer on the front, and texturing on the front of the silicon wafer; performing boron diffusion on the front surface of the silicon wafer to prepare a PN junction, and then removing BSG; and preparing a passivation layer and an antireflection layer on the front side of the silicon wafer, and printing and sintering to obtain the N-type double-sided battery.
However, these N-type TOPCon batteries still suffer from efficiency loss due to their structural limitations.
Disclosure of Invention
An object of the embodiments of the present application is to provide a method for locally re-expanding a front surface of a P-type back contact passivated cell and a method for manufacturing a cell, which can form a locally re-expanded region on the front surface of the P-type back contact passivated cell to form an ohmic contact, thereby improving the conversion efficiency of the back contact passivated cell and having simple process steps.
In a first aspect, the present application provides a method for local re-expansion of a front surface of a P-type back contact passivated cell, comprising the steps of:
printing boron slurry on a front metal area of a P-type silicon wafer with a tunneling oxide layer and a polycrystalline silicon film deposited on the back surface; the boron in the boron slurry is then driven into the silicon using a laser.
In a second aspect, the present application provides a method for preparing a P-type back contact passivated cell, comprising:
the method for the front local re-expansion of the P-type back junction contact passivated battery is adopted to carry out the front local re-expansion.
The beneficial effects of the invention include: according to the method, the boron slurry is used as a boron source for local re-expansion of the front surface of the silicon wafer, then the boron in the boron slurry is driven into the silicon by laser, and a local re-expansion area can be formed on the front surface of the P-type back junction contact passivation battery to form ohmic contact, so that the conversion efficiency of the P-type back junction contact passivation battery is improved. In addition, the boron slurry is used as a boron source for local re-expansion of the front surface of the silicon wafer, and the boron in the boron slurry is driven into the silicon by laser, so that the method is simple in process step and strong in operability. Compared with the prior art, the N-type TOPCon battery needs to carry out boron diffusion on the front surface to form a boron diffusion emitter junction, the P-type substrate is adopted in the method, the boron diffusion step is avoided, and the TOPCon battery production process is greatly simplified. And the cost of the boron slurry is low, the production cost of the P-type back junction contact passivation battery can be greatly reduced, and the method is more suitable for industrialization.
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In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a graph of the sheet resistance distribution after laser doping (picture is gray-processed);
fig. 2 is a graph of doping concentration.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments obtained by a person skilled in the art without making any inventive step are within the scope of protection of the present application.
The inventors have studied to find that the main efficiency loss of N-type TOPCon cells comes from the passivation and lateral transport of the front-side boron-diffused emitter junction. The inventor finds that if the N-type TOPCon battery is changed into a P-type back junction contact passivation battery, the P-type substrate can bear the lateral transportation of majority ions in a P-type region, so that a boron diffusion step on the front surface can be omitted, the process step is simplified, and the passivation of the front surface is improved. Meanwhile, the inventor finds that the P-type back junction contact passivated cell of the P-type substrate needs to form a local re-expansion area on the front surface of the cell to form an ohmic contact.
The embodiment of the application provides a method for local re-expansion of the front surface of a P-type back junction contact passivated battery, which comprises the following steps:
printing boron slurry on a front metal area of a P-type silicon wafer with a tunneling oxide layer and a polycrystalline silicon film deposited on the back surface; the boron in the boron slurry is then driven into the silicon using a laser.
According to the method, the boron slurry is used as a boron source for local re-expansion of the front surface of the silicon wafer, then the boron in the boron slurry is driven into the silicon by laser, and a local re-expansion area can be formed on the front surface of the P-type back junction contact passivation battery to form ohmic contact, so that the conversion efficiency of the P-type back junction contact passivation battery is improved.
Furthermore, the embodiment of the application adopts the boron slurry as the boron source for local re-expansion of the front surface of the silicon wafer, can greatly reduce the production cost of the P-type back junction contact passivation cell, and is suitable for industrialization. The boron in the boron slurry is driven into the silicon by laser, so that the process steps are simple and the operability is strong.
In some embodiments of the present application, a method of making a P-type back contact passivated cell comprises: the method for the front-surface local re-expansion of the P-type back-junction contact passivated battery provided by the embodiment is adopted to perform the front-surface local re-expansion.
The preparation method of the P-type back junction contact passivated battery comprises the following steps:
and step S1, polishing.
And polishing the silicon wafer.
Furthermore, the silicon wafer is a P-type monocrystalline silicon wafer. Namely, a P-type monocrystalline silicon wafer is adopted as a silicon substrate. The P-type substrate can take on the lateral transport of many seeds of the P-type region. In the preparation process of a junction contact passivation cell (TOPCon), the P-type substrate can save boron diffusion on the front surface, simplify the process steps and improve the passivation of the front surface.
Further, when polishing the silicon wafer, an alkali solution is used for the polishing.
Further alternatively, the alkali solution may be KOH, NaOH, or the like.
In some embodiments of the present application, the alkali solution is prepared by mixing KOH, an additive, and water according to a certain ratio.
The additive may be selected from alcohol-containing additives. For example: isopropyl alcohol, and the like.
Further optionally, the alkali solution is KOH, an additive and water in a mass ratio of: 15-25: 2-5: 155-165.
Further optionally, the alkali solution is KOH, an additive and water in a mass ratio of: 18 to 22:4 to 6:158 to 162.
Illustratively, the alkali solution is prepared by KOH, additives and water according to the mass ratio of 20:3: 160.
Further, the polishing treatment of the silicon wafer is carried out at a temperature of 70 to 90 ℃.
Further optionally, the polishing treatment is performed at a temperature of 75-85 ℃.
Illustratively, the above polishing treatment of the silicon wafer is carried out at a temperature of 80 ℃.
Further, the polishing process for the silicon wafer further comprises: after being treated by alkali solution, the cleaning agent is also cleaned.
Further optionally, the cleaning is to clean the surface of the silicon wafer by using an HF solution.
Further optionally, the HF solution is an HF solution with a volume concentration of 2-5%.
Further optionally, the HF solution is an HF solution with a volume concentration of 2.5-4.5%.
Illustratively, the HF solution described above is an HF solution having a volume concentration of 4%; or the HF solution is 3% HF solution by volume concentration; or the HF solution is 3.5% HF solution by volume concentration.
And step S2, depositing tunneling silicon oxide and polysilicon films.
Further, the step of depositing the tunneling oxide layer and the polysilicon film on the back surface of the silicon wafer comprises:
firstly, depositing a tunneling oxide layer on the back surface of a silicon wafer, and then depositing a polysilicon film.
Further optionally, the deposition temperature for depositing the tunneling oxide layer on the back surface of the silicon wafer is 500-700 ℃.
Further optionally, the deposition temperature for depositing the tunneling oxide layer on the back surface of the silicon wafer is 550-650 ℃.
Illustratively, the deposition temperature for depositing the tunnel oxide layer on the back surface of the silicon wafer is 560 ℃, 580 ℃, 600 ℃, 620 ℃ or 640 ℃.
Further, the tunneling oxide layer is tunneling SiO2A film.
Further, tunneling of SiO2The thickness of the film is less than 2 nm.
Further optionally, tunneling SiO2The thickness of the film is 0.1 to 1.9 nm.
Further optionally, tunneling SiO2The thickness of the film is 0.5 to 1.8 nm.
Further optionally, tunneling SiO2The thickness of the film is 1 to 1.8 nm.
Illustratively, tunneling SiO2The thickness of the film is 0.6 nm, 1.1 nm, 1.2 nm or 1.5 nm.
And further, depositing a polysilicon film on the back surface of the silicon wafer.
And depositing a polysilicon film on the back of the silicon wafer by introducing silane.
Furthermore, the thickness of the polysilicon film is 100-200 nm.
Further optionally, the thickness of the polysilicon thin film is 105 to 195 nm.
Further optionally, the thickness of the polysilicon thin film is 115-190 nm.
Illustratively, the polysilicon thin film has a thickness of 120nm, 130 nm, 140 nm, 150 nm, 160 nm, 170nm, or 180 nm.
Furthermore, after a polysilicon film is deposited on the back surface of the silicon wafer, phosphorus is doped into the polysilicon film.
Optionally, the step of doping phosphorus into the polysilicon thin film comprises: and (3) carrying out phosphorus diffusion in a diffusion furnace tube, wherein the diffusion temperature is 700-900 ℃.
Further optionally, phosphorus diffusion is carried out in a diffusion furnace tube, wherein the diffusion temperature is 750-850 ℃.
Further optionally, phosphorus diffusion is carried out in a diffusion furnace tube, wherein the diffusion temperature is 760-840 ℃.
Illustratively, the phosphorus diffusion is carried out in a diffusion furnace tube at 770 deg.C, 780 deg.C, 790 deg.C, 800 deg.C, 820 deg.C, or 830 deg.C.
Further, the diffusion furnace tube may be a conventional phosphorus diffusion furnace tube commonly used in the art.
Furthermore, the square resistance range formed after the polysilicon thin film is doped with phosphorus is 40-150 ohm/□.
Further optionally, the sheet resistance formed after the polysilicon thin film is doped with phosphorus is in a range of 45-145 ohm/□.
Illustratively, the sheet resistance formed after the polysilicon thin film is doped with phosphorus is 50ohm/□, 60ohm/□, 70ohm/□, 80ohm/□, 100ohm/□, 120ohm/□ or 130 ohm/□.
In other alternative embodiments of the present application, a silicon wafer with a tunnel oxide layer and a polysilicon film deposited on the back side may also be purchased directly.
Further, after the step of doping phosphorus into the polycrystalline silicon film, a silicon nitride film is deposited on the back surface of the silicon wafer.
Further optionally, the thickness of the silicon nitride film is 80-120 nm.
Further optionally, the thickness of the silicon nitride film is 85-115 nm.
Illustratively, the silicon nitride film has a thickness of 90nm, 95nm, 100nm, 105 nm, or 110 nm.
Further, after the step of depositing the silicon nitride film on the back surface of the silicon wafer, the SiN film which is coated around the front surface of the silicon wafer is also removed.
Further optionally, removing the silicon nitride plated around the front surface by using an HF solution with the volume concentration of 5-15%.
Further optionally, removing the silicon nitride plated around the front surface by using an HF solution with the volume concentration of 6-14%.
Illustratively, the silicon nitride that has been plated around to the front surface is removed with an HF solution having a volume concentration of 8%, 10%, or 12%.
Further, after the step of removing the SiN film wound and plated on the front surface of the silicon wafer, the front surface of the battery is subjected to texturing treatment by using the back surface silicon nitride as a mask.
In some embodiments of the present application, the front surface of the battery is subjected to a texturing treatment by using the back surface silicon nitride as a mask, and the texturing treatment is performed by using an alkaline solution.
Further alternatively, the alkali solution may be KOH, NaOH, or the like.
In some embodiments of the present application, the alkali solution is prepared by mixing KOH, an additive, and water according to a certain ratio.
The additives mentioned above may be selected from alcohol-containing additives, such as: isopropyl alcohol, and the like.
Further optionally, the alkali solution is KOH, an additive and water in a mass ratio of: 15-25: 2-5: 155-165.
Further optionally, the alkali solution is KOH, an additive and water in a mass ratio of: 18 to 22:4 to 6:158 to 162.
Illustratively, the alkali solution is prepared by KOH, additives and water according to the mass ratio of 20:3: 160.
Further, the texturing treatment is carried out at a temperature of 70 to 90 ℃. Illustratively, the texturing process is carried out at a temperature of 75 ℃, 80 ℃ or 85 ℃.
Furthermore, cleaning is carried out after the texturing treatment.
Further alternatively, the cleaning is to clean the surface of the silicon wafer by using an HF solution with a volume concentration of 2-5%.
Step S3, printing boron paste on the front metal area of the silicon wafer with the tunneling oxide layer and the polysilicon film deposited on the back surface.
The method has the advantages that the boron slurry is low in cost and simple in process, the boron slurry is used as a boron source for local re-expansion of the front surface of the silicon wafer, the production cost of the P-type back junction contact passivation battery can be greatly reduced, and the method is suitable for industrialization.
Further, the solid content of the printing boron paste is 10-30%.
Further optionally, the solid content of the printing boron paste is 15-25%.
Illustratively, the above-described printing boron paste has a solids content of 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, or 24%.
Further, the step of printing the boron paste includes: printing boron paste, and drying the printed boron paste at the temperature of 200-400 ℃.
Further optionally, the step of printing the boron paste comprises: printing boron paste, and drying the printed boron paste at the temperature of 250-350 ℃.
Illustratively, the step of printing the boron paste comprises: printing boron paste, and drying the printed boron paste at 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃ or 340 ℃.
Step S4 is to drive boron in the boron slurry into the silicon with a laser.
By using a laser to drive boron from the boron slurry into the silicon, a locally re-expanded region can be formed on the front side of the P-type back contact passivated cell to form an ohmic contact.
Further, the spot of the laser irradiated on the surface of the printed boron paste is square or rectangular. Furthermore, the side length of the light spot is within the range of 80-150 um.
Further optionally, the side length of the light spot is in the range of 85-145 um.
Further optionally, the side length of the light spot is in a range of 90-140 um.
Illustratively, the laser described above employs a square spot with a spot side length of 90um, 100um, 110 um, 120 um, or 130 um. Or the laser adopts a rectangular light spot, and the side length (length multiplied by width) of the light spot is 110 × 90um, 100 × 90um, 120 × 110 um, 130 × 120 um or 140 × 130 um.
Further, the single pulse energy density of the laser is 1.5-3.5J/cm2。
The selection of the single pulse energy density of the laser in the range is comprehensively considered by combining the characteristics of the P-type back contact passivated cell, and in the range, the formation of a local re-expansion area on the front surface of the P-type back contact passivated cell to form ohmic contact can be effectively ensured, and the good performance of the P-type back contact passivated cell is ensured.
Further optionally, the single pulse energy density of the laser is 1.5-3.5J/cm2。
Further optionally, the single pulse energy density of the laser is 2.0-3.0J/cm2。
Illustratively, the laser has a single pulse fluence of 2.1J/cm2、2.2J/cm2、2.3J/cm2、2.4J/cm2、2.5J/cm2、2.6J/cm2、2.6J/cm2、2.7J/cm2、2.8J/cm2Or 2.9J/cm2。
Furthermore, the scanning speed of the laser is 5-30 m/s.
Under the laser scanning speed, boron in the boron slurry can be effectively driven into silicon, so that a local re-expansion area is formed on the front surface of the P-type back junction contact passivation cell to form ohmic contact.
Further optionally, the scanning speed of the laser is 6-29 m/s.
Further optionally, the scanning speed of the laser is 7-28 m/s.
Further optionally, the scanning speed of the laser is 10-25 m/s.
Illustratively, the scanning speed of the laser is 12m/s, 14m/s, 15m/s, 16m/s, 18m/s, 20m/s, 22m/s, or 24 m/s.
And step S5, after the step of driving the boron in the boron slurry into the silicon by using the laser, removing the residual boron slurry on the front surface of the silicon wafer.
Further, the step of removing the residual boron slurry on the front side of the silicon wafer comprises the following steps: firstly, cleaning the front side of the silicon wafer by using a KOH solution with the volume concentration of 2-8%, and then cleaning the front side of the silicon wafer by using an HF solution with the volume concentration of 2-5%.
Further optionally, the step of removing the remaining boron slurry on the front surface of the silicon wafer comprises: firstly, KOH solution with the volume concentration of 2.5-7.5% is adopted to clean the front surface of the silicon chip, and then HF solution with the volume concentration of 2.5-4.5% is adopted to clean the front surface of the silicon chip.
Further optionally, the step of removing the remaining boron slurry on the front surface of the silicon wafer comprises: firstly, KOH solution with the volume concentration of 3-7% is adopted to clean the front side of the silicon wafer, and then HF solution with the volume concentration of 3-4% is adopted to clean the front side of the silicon wafer.
Illustratively, the step of removing the remaining boron slurry from the front surface of the silicon wafer comprises: firstly, KOH solution with volume concentration of 5% is adopted to clean the front surface of the silicon wafer, and then HF solution with volume concentration of 2.5% is adopted to clean the front surface of the silicon wafer.
In some embodiments of the present application, the method for preparing a P-type back contact passivated cell further includes a step S6 of depositing an aluminum oxide film on the front surface of the cell, a step S7 of depositing a silicon nitride film on the front surface of the cell, and a step S8 of screen-printing the main grid lines and the sub grid lines.
Specifically, the method comprises the following steps:
and step S6, depositing an aluminum oxide film on the front surface of the battery.
The process of depositing the aluminum oxide film on the front side of the cell may be performed according to a conventional method in the art.
Further, in the embodiment of the present application, the thickness of the alumina thin film is 2 to 25 nm; further optionally, the thickness of the alumina film is 5-20 nm; further optionally, the thickness of the alumina film is 10-15 nm.
Illustratively, the thickness of the aluminum oxide film is 6 nm; 12 nm; 18 nm; 22nm or 24 nm.
And step S7, depositing a silicon nitride film on the front surface of the battery.
The process of depositing the silicon nitride film on the front side of the cell can be performed according to conventional methods in the art.
Further, in the embodiment of the present application, the thickness of the silicon nitride film is 70 to 85 nm; further optionally, the thickness of the silicon nitride film is 71-84 nm; further optionally, the thickness of the silicon nitride film is 75-80 nm.
Illustratively, the silicon nitride film has a thickness of 72nm, 73nm, 74nm, 75nm, 76nm, 77nm, 78nm, 79nm, 80nm, or 82 nm.
And S8, screen printing the main grid line and the auxiliary grid line.
In the embodiment of the present application, screen printing and sintering are performed according to a screen pattern.
Furthermore, when screen printing is carried out, the width of the grid line on the front surface is less than 50 microns, the height of the grid line is more than 5 microns, the peak temperature during sintering is 750-770 ℃, and the time is 30-50 seconds.
Illustratively, the screen printing was carried out with a front grid width of 45 μm and a height of 6 μm, a peak temperature at sintering of 760 ℃ and a time of 40 seconds.
Some embodiments of the present application further provide a method for front-side local re-expansion of a P-type back-junction contact passivated cell, which includes the step of front-side local re-expansion in the method for preparing a P-type back-junction contact passivated cell in the foregoing embodiments.
The preparation method of the P-type back contact passivated battery provided by the embodiment of the application can form the local re-expansion area on the front surface of the battery to form ohmic contact, is low in cost and simple in process steps, and can be suitable for industrialization of the P-type back contact passivated battery.
The features and properties of the present application will be described in detail below with reference to examples and comparative examples.
Example 1
The P-type back junction contact passivated battery is manufactured according to the following steps:
s1, polishing: with a P-type single crystal silicon wafer as a silicon substrate, a polishing treatment is first performed using a solution, usually a KOH solution. The KOH solution was prepared as follows: additive: h2The mass ratio of O =20:3:160, and the temperature is 80 ℃. Then cleaning the silicon wafer in an HF solution with the volume concentration of 2-5%, and cleaning the surface of the silicon wafer;
s2, depositing tunneling silicon oxide and polycrystalline silicon films: firstly introducing oxygen, depositing a tunneling oxide layer on the surface of a silicon wafer, wherein the thickness of the tunneling oxide layer is less than 2nm, and then introducing silane to deposit a polycrystalline silicon film, wherein the thickness of the polycrystalline silicon film is controlled to be 100-200 nm;
s3, expanding by phosphorus: and (4) carrying out a phosphorus diffusion process, doping phosphorus into the polycrystalline silicon film, and regulating and controlling the work function of the polycrystalline silicon film. The diffusion temperature is 700-900 ℃, and the formed square resistance range is 40-150 ohm/□;
s4, back silicon nitride deposition: depositing a silicon nitride film with the thickness of 80-120 nm on the back of the battery;
s5, removing the silicon nitride wound and plated on the front surface by adopting chain type equipment, wherein the used chemical is an HF solution with the volume concentration of 5-15%;
s6, texturing: using the back silicon nitride as a mask to conduct counter currentThe front side of the cell is subjected to a texturing treatment, the solution used is typically a KOH solution, typically in terms of KOH: additive: h2The mass ratio of O =20:3:160, and the temperature is 80 ℃. Then cleaning the silicon wafer in an HF solution with the volume concentration of 2-5%, and cleaning the surface of the silicon wafer;
s7, printing boron paste: printing boron slurry in a front metal area, wherein the solid content of the boron slurry is 10%, and the drying temperature is 200 ℃;
s8, laser doping: the boron in the boron slurry is driven into the silicon by laser to form local heavy doping, the laser equipment is square spot laser equipment, the side length of a spot is 150 mu m, and the single-pulse energy density is 3.5J/cm2Scanning speed of 30 m/s;
s9, cleaning: removing the residual boron slurry, wherein the used solution is a KOH solution with the volume concentration of 5 percent, and then cleaning the silicon wafer surface in an HF solution with the volume concentration of 2-5 percent;
s10, depositing aluminum oxide: and depositing aluminum oxide on the front surface of the cell by using PECVD or ALD equipment, wherein the thickness of the aluminum oxide is 2-25 nm.
S11, double-sided silicon nitride deposition: and depositing a SiN film on the front surface of the cell, wherein the thickness of the SiN film on the front surface is 70-85 nm.
S12, screen printing: when screen printing and sintering are carried out according to the screen printing plate pattern, the width of the grid line on the front surface is controlled to be less than 50 mu m, and the height is controlled to be more than 5 mu m. The sintering peak temperature is about 760 ℃ and the time is 40 seconds.
Example 2
A P-type back contact passivated cell is provided. The preparation procedure was substantially the same as that of example 1, except that:
s7, printing boron paste: printing boron slurry in a front metal area, wherein the solid content of the boron slurry is 30%, and the drying temperature is 400 ℃;
s8, laser doping: the boron in the boron slurry is driven into the silicon by laser to form local heavy doping, the laser equipment is square spot laser equipment, the side length of a spot is 80 mu m, and the single-pulse energy density is 1.5J/cm2The scanning speed was 5 m/s.
Example 3
A P-type back contact passivated cell is provided. The preparation procedure was substantially the same as that of example 1, except that:
s7, printing boron paste: printing boron slurry in a front metal area, wherein the solid content of the boron slurry is 20%, and the drying temperature is 300 ℃;
s8, laser doping: the boron in the boron slurry is driven into the silicon by laser to form local heavy doping, the laser equipment is square spot laser equipment, the side length of a spot is 100um, and the single-pulse energy density is 2.5J/cm2The scanning speed was 15 m/s.
The front local re-expansion effect of the P-type back junction contact passivated cell provided in the embodiments 1-3 of the present application is examined.
Experimental example 1
And (4) testing the samples prepared in the steps S8 in the embodiments 1-3 by adopting 4 probes to test the front local re-expansion effect.
The test results are shown in the attached figure 1 of the specification.
Fig. 1 is a distribution diagram of sheet resistance after whole surface laser doping, and it can be seen from fig. 1 that the sheet resistance distribution after whole surface laser doping of the whole surface printed boron paste is relatively uniform, which shows that the printing thickness of the boron paste and the laser energy are relatively uniform.
Experimental example 2
The samples obtained in the steps S8 prepared in examples 1 to 3 were tested by ECV (electrochemical capacitance-voltage method) to test the front-side local re-spreading effect.
The test results are shown in the attached figure 2 of the specification.
Fig. 2 is a doping concentration curve, and it can be seen from fig. 2 that both the junction depth and the surface concentration can meet the requirements of metal contact.
In summary, the P-type back contact passivated cell provided in embodiments 1 to 3 of the present application has a good front local re-spreading effect.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A method for local re-expanding of the front surface of a P-type back junction contact passivated battery is characterized by comprising the following steps:
printing boron slurry on a front metal area of a P-type silicon wafer with a tunneling oxide layer and a polycrystalline silicon film deposited on the back surface; and then driving the boron in the boron slurry into the silicon by using laser.
2. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to claim 1,
the solid content of the printing boron paste is 10-30%.
3. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to claim 1 wherein the step of printing the boron paste comprises:
printing boron slurry, and drying the printed boron slurry at the temperature of 200-400 ℃.
4. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to any one of claims 1-3,
the light spot of the laser irradiated on the surface of the printed boron paste is square or rectangular;
optionally, the side length of the light spot is in the range of 80-150 um.
5. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to any one of claims 1-3,
the single pulse energy density of the laser is 1.5-3.5J/cm2。
6. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to any one of claims 1-3,
the scanning speed of the laser is 5-30 m/s.
7. The method for locally re-expanding the front surface of the P-type back contact passivated cell according to claim 1 wherein the step of preparing the P-type silicon wafer with the tunnel oxide layer and the polysilicon film deposited on the back surface comprises:
depositing a tunneling oxide layer on the back surface of a P-type silicon wafer, depositing a polycrystalline silicon film, and doping phosphorus into the polycrystalline silicon film;
optionally, the thickness of the tunneling oxide layer is less than 2nm, and the deposition temperature is 500-700 ℃;
optionally, the thickness of the polycrystalline silicon thin film is 100-200 nm;
optionally, the step of doping phosphorus into the polysilicon thin film includes: carrying out phosphorus diffusion in a diffusion furnace tube, wherein the diffusion temperature is 700-900 ℃;
optionally, after the polysilicon film is doped with phosphorus, the sheet resistance formed is in the range of 40-150 ohm/□.
8. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to claim 7,
after the step of doping phosphorus into the polycrystalline silicon film, depositing a silicon nitride film on the back surface of the P-type silicon wafer;
optionally, the thickness of the silicon nitride film is 80-120 nm.
9. The method for locally re-expanding the front surface of a P-type back contact passivated cell according to claim 1,
after the step of driving boron in the boron slurry into silicon by using laser, removing the residual boron slurry on the front surface of the P-type silicon wafer;
optionally, the step of removing the remaining boron slurry on the front surface of the P-type silicon wafer comprises: firstly, cleaning the front side of the silicon wafer by using a KOH solution with the volume concentration of 2-8%, and then cleaning the front side of the silicon wafer by using an HF solution with the volume concentration of 2-5%.
10. A preparation method of a P-type back junction contact passivated battery is characterized by comprising the following steps:
the method for performing front-surface local re-expansion on the P-type back-junction contact passivated battery according to any one of claims 1 to 9.
CN202010915777.6A 2020-09-03 2020-09-03 Front-side local re-expansion method of P-type back-junction contact passivated battery and battery preparation method Pending CN111816554A (en)

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CN110085699A (en) * 2019-04-22 2019-08-02 通威太阳能（成都）有限公司 A kind of p-type high-efficiency battery and preparation method thereof with passivation contact structures
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Application publication date: 20201023