CN111755563B - P-type monocrystalline silicon boron back-field double-sided battery and preparation method thereof - Google Patents

P-type monocrystalline silicon boron back-field double-sided battery and preparation method thereof Download PDF

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CN111755563B
CN111755563B CN202010456637.7A CN202010456637A CN111755563B CN 111755563 B CN111755563 B CN 111755563B CN 202010456637 A CN202010456637 A CN 202010456637A CN 111755563 B CN111755563 B CN 111755563B
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曹兵
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JA Solar Technology Yangzhou Co Ltd
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Abstract

The invention discloses a P-type monocrystalline silicon boron back-field double-sided battery and a preparation method thereof. Belongs to the technical field of solar cells and solves the problems that in the prior art, boron doping cannot be realized on a P-type monocrystalline silicon substrate by adopting laser and the like. The invention provides a preparation method of a P-type monocrystalline silicon boron back surface field double-sided battery, which comprises the following steps: providing a P-type silicon substrate, and cleaning and texturing the P-type silicon substrate; performing phosphorus diffusion on the texturing surface on the front surface of the P-type silicon substrate to form a phosphorus diffusion area; wet etching is carried out on the back surface of the P-type silicon substrate to remove edge junctions and partial back junctions; depositing a borosilicate glass layer on the P-type silicon substrate after the wet etching on the back of the P-type silicon substrate is finished; depositing an absorbing layer dielectric film on the borosilicate glass layer; carrying out surface scanning on the absorbing layer dielectric film by using laser; removing the absorbing layer dielectric film and the borosilicate glass layer; and then carrying out thermal annealing on the silicon wafer to obtain a boron back field. The invention can realize the preparation of the P-type monocrystalline silicon boron back surface field double-sided battery and has better battery performance.

Description

P-type monocrystalline silicon boron back-field double-sided battery and preparation method thereof
Technical Field
The invention belongs to the technical field of solar cells, and particularly relates to a P-type monocrystalline silicon boron back surface field double-sided cell and a preparation method thereof.
Background
The solar cell is one of effective schemes for solving energy problems in the future as a clean energy. Particularly, through the rapid development in recent years, the application of the coal-fired power generation device is wide, the process is mature, and the power generation cost of the coal-fired power generation device is equivalent to that of coal power.
P-type single crystal silicon cells are a conventional cell, and the back surface of the P-type single crystal silicon cell is usually printed with aluminum paste on the whole surface and then sintered to form a back electric field so as to reduce minority carrier recombination. However, the sintering of large-area aluminum paste leads to large metal recombination, which limits the improvement of battery efficiency. The direct boron doping of the P-type monocrystalline silicon substrate requires very high temperature, usually over 900 ℃, which greatly damages the minority carrier lifetime in the substrate, and other defects are also introduced into the silicon wafer in the high temperature process; at present, boron doping can not be realized by directly adopting laser on a P-type monocrystalline silicon substrate. Boron back field structures have long been proposed and are difficult or impractical to implement. In the prior art, boron diffusion is directly carried out on a P-type silicon substrate to form a back electric field, but continuous high temperature is required, such as over 900 degrees (usually 950-; at present, a boron source is deposited on a back passivation layer of a P-type silicon substrate, and then boron is driven into a matrix by laser to form a local back electric field.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a P-type single crystal silicon boron back-field double-sided battery and a preparation method thereof, which can solve at least one of the following technical problems: (1) in the prior art, the boron doping of a P-type monocrystalline silicon substrate needs very high temperature, and the silicon wafer can introduce defects in the high-temperature process, so that the service life is reduced; (2) in the prior art, boron doping cannot be realized on a P-type single crystal silicon substrate by adopting laser.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a preparation method of a P-type monocrystalline silicon boron back-field double-sided battery, which comprises the following steps:
s1, providing a P-type silicon substrate, and cleaning and texturing the P-type silicon substrate;
s2, performing phosphorus diffusion on the texturing surface of the front surface of the P-type silicon substrate to form a phosphorus diffusion area;
s3, carrying out wet etching on the back surface of the P-type silicon substrate to remove the edge junction and part of the back junction;
s4, depositing a borosilicate glass layer on the P-type silicon substrate after the wet etching of the back of the P-type silicon substrate is finished;
s5, depositing an absorbing layer dielectric film on the borosilicate glass layer;
s6, performing surface scanning on the absorbing layer dielectric film by using laser;
s7, removing the absorbing layer dielectric film and the borosilicate glass layer; and then carrying out thermal annealing on the silicon wafer to obtain a boron back field.
Further, S7 is followed by:
s8, plating anti-reflection films on the phosphorus diffusion area and the boron back surface field respectively;
and S9, forming a front electrode and a back electrode, and sintering.
Further, in S4, a borosilicate glass layer is deposited by an atmospheric pressure chemical vapor deposition method.
Further, in S4, the deposition temperature is 350-450 ℃.
Further, in S4, the borosilicate glass layer has a thickness of 20 to 150 nm.
Further, in S5, a dielectric film of the absorption layer is deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD).
Further, in S5, the thickness of the dielectric film of the absorption layer is 50-100 nm.
Further, in S5, the absorbing layer dielectric film is made of any one, multiple or mixture of silicon nitride layer, silicon oxynitride layer, aluminum nitride layer, silicon carbide layer or polysilicon.
Furthermore, the wavelength of the laser is 355 nm-600 nm, the spot size is 50-150 um, the power is 20-45 w, and the scanning speed is 5-20 m/s.
On the other hand, the invention also provides a P-type monocrystalline silicon boron back-field double-sided battery which comprises a P-type silicon substrate, wherein the front side of the P-type silicon substrate is sequentially provided with a phosphorus expansion region, an anti-reflection film and a front electrode along the direction far away from the P-type silicon substrate; the back surface of the P-type silicon substrate is sequentially provided with a boron back field, an antireflection film and a back electrode along the direction far away from the P-type silicon substrate; wherein the thickness of the boron back field is 80-400 nm.
Compared with the prior art, the invention can at least realize one of the following technical effects:
(1) the preparation method of the P-type monocrystalline silicon boron back surface field double-sided battery directly deposits the borosilicate glass layer and the absorbing layer dielectric film on the back surface of the battery without adopting aluminum paste, and then carries out surface scanning by using laser, so that the structure of the double-sided battery can be realized without alignment during printing, and because only the thin grid lines are printed for contact, the metal composition can be obviously reduced, the process is simple, and the implementation is convenient.
(2) According to the preparation method of the P-type monocrystalline silicon boron back surface field double-sided battery, when boron doping is realized, the borosilicate glass layer and the absorption layer dielectric film are deposited on the back surface of the battery, and the surface scanning is performed by using laser, so that the phenomenon that the service life is reduced due to other defects introduced in the high-temperature process of a silicon wafer is avoided without adopting overhigh temperature.
(3) Compared with the traditional P-type aluminum back field battery, the P-type monocrystalline silicon boron back field double-sided battery can obviously reduce the metal composition on the back of the battery, can simply and effectively realize the production of the double-sided battery (alignment is not needed during back printing), and has better electrical property.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a side view of a cell structure prior to plating of an anti-reflective coating in accordance with the present invention;
FIG. 2 is a side view of a P-type single crystal silicon boron back field bifacial cell of the present invention;
fig. 3 is the boron doping concentration results of the boron back field of the P-type single crystal silicon boron back field double sided cell of example 1 of the present invention;
fig. 4 is the boron doping concentration results of the boron back field of the P-type single crystal silicon boron back field double sided cell of example 2 of the present invention;
fig. 5 is a boron doping concentration profile of the cell back side boron back field in comparative example 2 of the present invention.
Reference numerals:
the field effect transistor comprises a 1-P type silicon substrate, a 2-phosphorus expansion region, a 3-borosilicate glass layer, a 4-absorption layer dielectric film, a 5-antireflection film, a 6-boron back field, a 7-front electrode and an 8-back electrode.
Detailed Description
A P-type single crystal silicon boron back-field bifacial cell and a method for making the same are described in further detail below with reference to specific examples, which are provided for purposes of comparison and explanation only and to which the present invention is not limited.
Various structural schematics according to embodiments of the present invention are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers, and relative sizes and positional relationships therebetween shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, as actually required.
In the context of the present invention, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.
The invention discloses a preparation method of a P-type monocrystalline silicon boron back surface field double-sided battery, which comprises the following steps:
s1, providing the P-type silicon substrate 1, and cleaning and texturing the P-type silicon substrate 1;
s2, performing phosphorus diffusion on the texturing surface of the front surface of the P-type silicon substrate to form a phosphorus diffusion region 2;
s3, carrying out wet etching on the back surface of the P-type silicon substrate to remove the edge junction and part of the back junction;
s4, depositing a borosilicate glass layer 3 on the P-type silicon substrate after the wet etching of the back surface of the P-type silicon substrate is finished;
s5, depositing an absorbing layer dielectric film 4 on the borosilicate glass layer 3;
s6, performing surface scanning on the absorbing layer dielectric film 4 by using laser;
s7, removing the absorbing layer dielectric film and the borosilicate glass layer (namely BSG); then, carrying out thermal annealing on the silicon wafer to obtain a boron back field 6;
s8, plating anti-reflection films 5 on the phosphorus diffusion area 2 and the boron back surface field 6 respectively;
and S9, printing the silver thin grid lines and the main grid lines on the front side to form a front electrode 7, printing the silver (or aluminum) thin grid lines and the silver main grid lines on the back side to form a back electrode 8, and sintering to obtain the P-type monocrystalline silicon boron back field double-sided battery.
Specifically, in the above S1, the thickness of the P-type silicon substrate is selected to be 150-200 μm, which results in excessive material waste, increased series resistance, decreased FF (fill factor) of the battery, and a large fraction rate due to too low thickness.
Considering that the electrical resistivity of the P-type silicon substrate is too large, the series resistance of the battery is increased, and the light attenuation of the battery is increased if the electrical resistivity of the P-type silicon substrate is too small. Thus, the resistivity of the P-type silicon substrate is selected to be 1-3 ohms cm.
In S2, the phosphorus diffusion includes multiple depositions and advances, the maximum advance temperature is 840 degrees, the maximum advance temperature is 30 minutes, and the diffusion sheet resistance is 100 (ohm/□).
In the above step S3, HF/HNO is used for wet etching3The mixed acid solution is etched to reduce weight by 0.2-0.4 g/tablet.
Specifically, in S4, the borosilicate glass layer is deposited by an Atmospheric Pressure Chemical Vapor Deposition (APCVD) method. Deposition process parameters: by using B2H6Carrying out a deposition of2H6The concentration ratio (mol ratio) of the precursor to other gases is 8-30%, the higher the concentration ratio is, the higher the final doping concentration is, the deposition temperature is not too high, and the deposition temperature is controlled to be 350-450 ℃.
Specifically, in S4, the thickness of the borosilicate glass layer is not too large or too small, and the thickness of the borosilicate glass layer is too large or too small, which may affect the effect of the final laser doping. Accordingly, the thickness of the borosilicate glass layer is controlled to be 20 to 150nm, and illustratively, the thickness of the borosilicate glass layer is 50 nm.
Specifically, in S5, the absorbing dielectric film may be made of any one, multiple, or mixture of silicon nitride, silicon oxynitride, aluminum nitride, silicon carbide, or polysilicon.
Specifically, in S5, the thickness of the absorber dielectric film should not be too large or too small, which would affect the final laser doping effect, and therefore the thickness of the absorber dielectric film is controlled to be 50-100 nm.
Specifically, in S5, the refractive index of the absorbing dielectric film is 1.9 or more, and the absorption coefficient of the absorbing dielectric film for laser light is 3 × 106cm-1This is because of the doping effect after laser scanningIt is preferable.
Specifically, in S5, a dielectric film of the absorption layer is deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). The refractive index after deposition is more than 1.9, the thickness is preferably controlled within 50-110nm, therefore, the deposition conditions are controlled as follows: silane flow rate is 0.6-0.8(slm), ammonia flow rate is 6-8(slm), equipment power is 4-5kW, deposition temperature is 450-.
It should be noted that in the above S6, in consideration of the matching problem of the process, the wavelength of the laser is controlled to be 355nm to 600nm, the spot size is 50 to 150um, the power is 20 to 45w, and the scanning speed is 5 to 20 m/S.
In S5 and S6, the thickness of the borosilicate glass layer, the thickness of the absorbing dielectric film, the refractive index of the absorbing dielectric film, and the parameters related to the laser need to be matched with each other, and the overall consideration and the overall coordination are required in the implementation.
Specifically, in S7, the removing the absorber dielectric film and the borosilicate glass layer includes: soaking the whole silicon wafer in a mixed solution of hydrofluoric acid and deionized water for 5-20 minutes, and then spin-drying the silicon wafer.
Specifically, in S7, the volume ratio of hydrofluoric acid to deionized water is 1:4 or more, which results in a better cleaning effect and enables the remaining dielectric film of the absorption layer and the borosilicate glass layer to be cleaned away.
Specifically, in S7, the thermal annealing step includes: during the period, nitrogen is introduced, and the service life of the silicon wafer is damaged when the temperature is too high; therefore, the temperature is controlled to be 750-810 ℃; the service life of the silicon wafer is damaged even if the time is too long, so that the control time is 20-50 minutes.
Specifically, in the above S7, the thickness of the boron back field is 80 to 400 nm.
Specifically, in the above S8, the process temperature for plating the anti-reflection film is 450-.
Specifically, in S8, the minimum wavelength shifts in the long-wavelength direction due to an excessively large thickness of the antireflection film; too small a wavelength results in a shift of the minimum wavelength in the short-wave direction. Therefore, the thickness of the antireflection film is controlled to be 90 to 110 nm.
The invention also provides a P-type monocrystalline silicon boron back-field double-sided battery, which comprises a P-type silicon substrate 1, wherein the front surface of the P-type silicon substrate 1 is sequentially provided with a phosphorus expansion region 2, an anti-reflection film 5 and a front electrode 7 along the direction far away from the P-type silicon substrate 1; the back surface of the P-type silicon substrate 1 is sequentially provided with a boron back field 6, an antireflection film 5 and a back electrode 8 along the direction far away from the P-type silicon substrate 1; wherein the thickness of the boron back field 6 is 80-400 nm.
Compared with the prior art, the preparation method of the P-type monocrystalline silicon boron back surface field double-sided battery directly deposits the borosilicate glass layer and the absorbing layer dielectric film on the back surface of the battery without adopting aluminum paste, and then performs surface scanning by using laser, so that the structure of the double-sided battery can be realized without alignment during printing, and because only the thin grid lines are printed for contact, the metal recombination can be obviously reduced, the process is simple, and the implementation is convenient.
Compared with the traditional P-type aluminum back field battery, the P-type monocrystalline silicon boron back field double-sided battery can obviously reduce the metal composition on the back of the battery, can simply and effectively realize the production of the double-sided battery (alignment is not needed during back printing), and has better electrical property.
Example 1
The embodiment provides a P-type monocrystalline silicon boron back-field double-sided battery, as shown in fig. 2, which comprises a P-type silicon substrate 1, wherein a phosphorus diffusion region 2, an anti-reflection film 5 and a front electrode 7 are sequentially arranged on the front surface of the P-type silicon substrate 1 along a direction away from the P-type silicon substrate 1; the back surface of the P-type silicon substrate 1 is sequentially provided with a boron back field 6, an antireflection film 5 and a back electrode 8 along the direction far away from the P-type silicon substrate 1; wherein the thickness of the boron back field 6 is 400nm, see fig. 3.
The P-type monocrystalline silicon boron back-field double-sided battery of the embodiment is prepared by adopting the following method:
step 101, selecting a P-type single crystal silicon substrate with a certain thickness (150-;
102, performing phosphorus diffusion on the texturing surface of the front surface of the P-type silicon substrate, and performing multiple deposition and propulsion, wherein the maximum propulsion temperature is 840 ℃ for 30 minutes, and the sheet resistance after diffusion is 100 (ohm/□);
103, wet etching the back surface of the P-type silicon substrate to remove edge junctions and partial back junctions;
104, depositing a borosilicate glass layer on the wet facet by adopting an atmospheric pressure chemical vapor deposition method (APCVD), wherein the thickness of the borosilicate glass layer is 50 nm; wherein the deposition temperature is 400 ℃; b is2H6The concentration ratio (molar ratio) of (a) is 15%;
105, depositing a silicon nitride (SiNx) film as an absorbing layer dielectric film on the borosilicate glass layer by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, wherein the thickness of the absorbing layer dielectric film is 75nm, and the refractive index of the absorbing layer dielectric film is 2.1; wherein the deposition conditions are as follows: silane flow rate is 0.68(slm), ammonia flow rate is 7.5(slm), equipment power is 4.6kw, deposition temperature is 500 ℃, and deposition time is 8 min;
step 106, performing surface scanning on the silicon nitride (SiNx) film by adopting laser (green light), wherein the power of the laser is 32w, and the scanning speed is 15 m/s;
step 107, cleaning the silicon wafer by using a hydrofluoric acid solution to remove the silicon nitride film and the borosilicate glass layer on the back surface of the silicon wafer, wherein the volume ratio of hydrofluoric acid to deionized water in the hydrofluoric acid solution is 2:5, and the soaking time is 15 minutes; spin-drying the silicon wafer;
108, putting the silicon wafer into a furnace tube for thermal annealing so as to enable the boron source on the back to be distributed more uniformly and obtain a boron back field; the annealing temperature is 750 ℃, the time is 30 minutes, and nitrogen is introduced during the annealing;
step 109, plating anti-reflection films on the phosphorus diffusion area 2 and the boron back surface field respectively; wherein the process temperature for plating the anti-reflection film is 500 ℃, the silane flow is 0.56(slm), the ammonia flow is 6.6(slm), and the deposition time is 8.5 minutes; the thickness of the antireflection film is 100 nm;
and 110, printing the silver thin grid lines and the main grid lines on the front side to form a front electrode 7, printing the silver (or aluminum) thin grid lines and the silver main grid lines on the back side to form a back electrode 8, and sintering to obtain the P-type monocrystalline silicon boron back field double-sided battery.
Example 2
The embodiment provides a P-type monocrystalline silicon boron back-field double-sided battery, as shown in fig. 2, which comprises a P-type silicon substrate 1, wherein a phosphorus diffusion region 2, an anti-reflection film 5 and a front electrode 7 are sequentially arranged on the front surface of the P-type silicon substrate 1 along a direction away from the P-type silicon substrate 1; the back surface of the P-type silicon substrate 1 is sequentially provided with a boron back field 6, an antireflection film 5 and a back electrode 8 along the direction far away from the P-type silicon substrate 1; wherein the thickness of the boron back field 6 is 350nm, see fig. 4.
The preparation method of the P-type single crystal silicon boron back field double-sided battery of the present embodiment is the same as that of embodiment 1, and is not described herein again, except that:
in step 105, a silicon oxynitride (SiON) film is deposited on the borosilicate glass layer by Plasma Enhanced Chemical Vapor Deposition (PECVD) to serve as an absorbing layer dielectric film, wherein the absorbing layer dielectric film has a thickness of 75nm and a refractive index of 2.1.
Comparative example 1
Comparative example 1 provides a P-type aluminum back surface field single-sided battery, which is prepared by the following method:
step 301: selecting a P-type single crystal silicon substrate with certain thickness (150-;
step 302: phosphorus diffusion is carried out on the texturing surface of the front surface of the P-type silicon substrate, and after multiple times of deposition and propulsion, the maximum propulsion temperature is 840 ℃, the maximum propulsion temperature is 30 minutes, and the square resistance after the diffusion is 100 (ohm/□);
step 303: wet etching is carried out on the back surface of the P-type silicon substrate to remove edge junctions and partial back junctions;
step 304: plating an anti-reflection film on the phosphorus diffusion region 2, wherein the film thickness is 80nm, and the refractive index is 2.08;
step 305: and printing the fine grid lines and the main grid lines of silver on the front surface, printing a back electrode and aluminum paste on the back surface, and sintering to obtain the P-type aluminum back surface field single-sided battery.
Comparative example 2
Comparative example 2 provides a P-type boron back field cell, prepared by the following method:
step 401: selecting a P-type single crystal silicon substrate with certain thickness (150-;
step 402: phosphorus diffusion is carried out on the texturing surface of the front surface of the P-type silicon substrate, and after multiple times of deposition and propulsion, the maximum propulsion temperature is 840 ℃, the maximum propulsion temperature is 30 minutes, and the square resistance after the diffusion is 100 (ohm/□);
step 403: wet etching is carried out on the back surface of the P-type silicon substrate to remove edge junctions and partial back junctions;
step 404: depositing a borosilicate glass layer on the wet facet by an atmospheric pressure chemical vapor deposition method (APCVD), wherein the thickness of the borosilicate glass layer is 50 nm;
step 405: performing surface scanning on the borosilicate glass layer on the back surface of the cell piece by adopting laser (green light), wherein the energy of the laser is 32 watts, and the scanning speed is 15 m/s;
step 406: cleaning the silicon wafer by using hydrofluoric acid solution to remove the residual borosilicate glass layer on the back surface of the silicon wafer, wherein the volume ratio of hydrofluoric acid to deionized water in the hydrofluoric acid solution is 2:5, and the soaking time is 15 minutes; spin-drying the silicon wafer;
step 407: respectively plating anti-reflection films on the phosphorus diffusion region 2 and the boron back field;
step 408: and printing the silver thin grid lines and the main grid lines on the front side to form a front electrode 7, printing the silver (or aluminum) thin grid lines and the silver main grid lines on the back side to form a back electrode 8, and sintering to obtain the P-type monocrystalline silicon boron back field double-sided battery.
Fig. 3 is the boron doping concentration results of the boron back field of the P-type single crystal silicon boron back field double sided cell of example 1 of the present invention; fig. 4 shows the boron doping concentration result of the boron back field of the P-type single crystal silicon boron back field double-sided battery of embodiment 2 of the present invention, and it can be seen from fig. 3 and 4 that the boron doping effect of the P-type single crystal silicon boron back field double-sided battery of embodiments 1-2 is better. Fig. 5 shows the doping concentration profile of the boron back field on the back side of the cell in comparative example 2, and it can be seen from fig. 5 that the source in the borosilicate glass is not doped and is the doping concentration of the silicon wafer substrate, so there is no back field effect.
The results of the performance test on examples 1-2 and comparative examples 1-2 are shown in table 1, and it can be seen from table 1 that examples 1-2 of the present invention have higher short-circuit current, open-circuit voltage, and cell efficiency than comparative examples 1-2, and lower series resistance than comparative examples 1-2. In comparative example 2, the cell electrical performance was very poor due to the absence of back electric field, poor passivation and current collection, and too high cell series resistance.
TABLE 1 results of the correlation between the performance tests of examples 1-2 and comparative examples 1-2
Figure BDA0002509457550000111
Figure BDA0002509457550000121
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (8)

1. A preparation method of a P-type monocrystalline silicon boron back-field double-sided battery is characterized by comprising the following steps:
s1, providing a P-type silicon substrate (1), and cleaning and texturing the P-type silicon substrate (1);
s2, performing phosphorus diffusion on the texturing surface of the front surface of the P-type silicon substrate to form a phosphorus diffusion region (2);
s3, carrying out wet etching on the back surface of the P-type silicon substrate to remove the edge junction and part of the back junction;
s4, depositing a borosilicate glass layer (3) on the P-type silicon substrate after the wet etching of the back surface of the P-type silicon substrate is finished;
s5, depositing an absorbing layer dielectric film (4) on the borosilicate glass layer (3);
s6, performing surface scanning on the absorbing layer dielectric film (4) by using laser;
s7, removing the absorbing layer dielectric film and the borosilicate glass layer; then carrying out thermal annealing on the silicon wafer to obtain a boron back field (6);
s8, plating an anti-reflection film (5) on the phosphorus diffusion region (2) and the boron back field (6) respectively;
s9, forming a front electrode (7) and a back electrode (8), and sintering;
in the S4, the thickness of the borosilicate glass layer is 20-150 nm;
the absorbing layer dielectric film is made of any one layer, multiple layers or mixed material layers of a silicon nitride layer, a silicon oxynitride layer, an aluminum nitride layer, a silicon carbide layer or polycrystalline silicon;
the refractive index of the absorbing layer dielectric film is more than 1.9, and the absorption coefficient of the absorbing layer dielectric film to laser is 3 multiplied by 106cm-1The above;
the thermal annealing comprises the following steps: introducing nitrogen during the period, controlling the temperature to be 750-810 ℃ and the time to be 20-50 minutes;
in S7, the thickness of the boron back field is 80-400 nm.
2. The method according to claim 1, wherein in S4, the borosilicate glass layer is deposited by an atmospheric pressure chemical vapor deposition method.
3. The method as claimed in claim 2, wherein the deposition temperature in S4 is 350-450 ℃.
4. The method according to claim 1, wherein in S4, the borosilicate glass layer has a thickness of 50 to 150 nm.
5. The method according to claim 4, wherein in S5, a dielectric film of the absorption layer is deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD).
6. The method according to claim 5, wherein in S5, the thickness of the dielectric film of the absorption layer is 50-100 nm.
7. The method according to any one of claims 1 to 6, wherein the laser has a wavelength of 355nm to 600nm, a spot size of 50 to 150um, a power of 20 to 45w, and a scanning speed of 5 to 20 m/s.
8. A P-type monocrystalline silicon boron back-field double-sided battery is characterized by being prepared by the preparation method of any one of claims 1 to 7; the front surface of the P-type silicon substrate (1) is sequentially provided with a phosphorus expansion region (2), a antireflection film (5) and a front surface electrode (7) along the direction far away from the P-type silicon substrate (1); the back surface of the P-type silicon substrate (1) is sequentially provided with a boron back field (6), an antireflection film (5) and a back electrode (8) along the direction far away from the P-type silicon substrate (1); wherein the thickness of the boron back field (6) is 80-400 nm.
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