CN116031142A

CN116031142A - Solar cell BSG cleaning method and TOPCon cell preparation method

Info

Publication number: CN116031142A
Application number: CN202310163066.1A
Authority: CN
Inventors: 吴孙弟; 潘红军; 康忠平; 俞益波; 卢玉荣
Original assignee: Chint New Energy Technology Co Ltd
Current assignee: Chint New Energy Technology Co Ltd
Priority date: 2023-02-14
Filing date: 2023-02-14
Publication date: 2023-04-28

Abstract

The application discloses a solar cell BSG cleaning method and a TOPCon cell preparation method, wherein the cleaning method comprises the following steps: carrying out groove type acid washing on the silicon wafer subjected to boron diffusion by using HF with a first concentration in the groove body so as to clean a BSG layer on the surface of the silicon wafer; washing and drying the silicon wafer; and (3) carrying out chain type acid washing on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer. According to the technical scheme, the BSG layer is cleaned by utilizing the groove type acid washing and the chain type acid washing, and as the back surface and the side surface of the silicon wafer are only partially cleaned by the BSG layer after the groove type acid washing, the BSG layer is cleaned more easily after the groove type acid washing, the back surface and the side surface of the silicon wafer can be cleaned by utilizing the chain type acid washing without high-concentration HF, and the BSG layer removing effect can be improved. And even if the roller level during chain pickling is slightly abnormal, the effect of removing the residual BSG layer is not affected, and the HF consumption is reduced.

Description

Solar cell BSG cleaning method and TOPCon cell preparation method

Technical Field

The application relates to the technical field of TOPCon battery preparation, in particular to a BSG (BSG) cleaning method of a solar cell and a TOPCon battery preparation method.

Background

In the N-type TOPCon battery structure, the front surface of the battery is provided with a PN junction by doping a boron source. The high-efficiency solar cell needs an emitter with low surface concentration, a layer of inactive boron-rich layer is inevitably formed in the boron expansion process, and meanwhile, in order to protect the front surface of the cell from being damaged in the subsequent process, a BSG (boron silicate glass) layer is required to be formed for a long time, and the BSG layer is thicker and is difficult to process.

At present, in the preparation process of the N-type TOPCon battery, one-step chain roller pickling is adopted for removing the BSG layer, but the HF concentration requirement of the chain roller pickling process is higher, generally 55-65% concentration, and the HF production with high concentration has higher requirements on equipment and environment because the BSG layer is thicker. Meanwhile, the BSG layer is not uniformly removed by HF pickling of the chain roller in one step, the removing effect is poor, and the consumption of high-concentration HF is increased due to the problem of roller levelness.

In summary, how to reduce the concentration of HF used for removing BSG and improve the BSG removal effect is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the foregoing, an object of the present application is to provide a method for cleaning BSG of a solar cell and a method for preparing TOPcon cell, which are used for reducing the concentration of HF used for removing BSG and improving the BSG removal effect.

In order to achieve the above object, the present application provides the following technical solutions:

a method of cleaning a BSG of a solar cell, comprising:

carrying out groove type acid washing on the silicon wafer subjected to boron diffusion by using HF with a first concentration contained in the groove body so as to clean a BSG layer on the surface of the silicon wafer;

washing and drying the silicon wafer subjected to the groove type acid washing;

and carrying out chain type acid washing on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

Preferably, the first concentration is less than the second concentration.

Preferably, the first concentration is 5% -10% and the second concentration is 20% -25%.

Preferably, before the dried silicon wafer is subjected to chain pickling by using HF with a second concentration to clean the residual BSG layers on the back and side surfaces of the silicon wafer, the method further comprises:

measuring the reflectivity of the dried silicon wafer surface at a plurality of sampling points;

judging whether the reflectivity at each sampling point is within a set reflectivity range;

if the reflectivity at the sampling point is lower than the minimum value in the set reflectivity range, returning to the step of carrying out groove type acid washing on the silicon wafer after boron diffusion by using HF with the first concentration contained in the groove body so as to clean the BSG layer on the surface of the silicon wafer;

and if the reflectivity at each sampling point is within the set reflectivity range, performing chain pickling on the dried silicon wafer by using HF with a second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

Preferably, the time length of the tank type acid washing is 180s plus or minus 10s, the technological parameters of the chain type acid washing are (3.6 m plus or minus 0.5 m)/min, and the temperatures of the tank type acid washing and the chain type acid washing are 18-25 ℃.

Preferably, the tank body further includes HCL, and when the silicon wafer after boron diffusion is pickled in a tank by using HF with a first concentration contained in the tank body, the method further includes:

cleaning the silicon wafer by using HCL;

and/or, when the dried silicon wafer is subjected to chain pickling by HF with the second concentration, the method further comprises the following steps:

and cleaning the silicon wafer by using HCL.

Preferably, the chain pickling is performed on the dried silicon wafer by adopting HF with a second concentration, which comprises the following steps:

and carrying out chain type acid washing on the dried silicon wafer by adopting the HF with the second concentration arranged in the acid washing tank.

Preferably, the chain pickling of the dried silicon wafer with HF of the second concentration disposed in the pickling tank includes:

carrying out primary chain pickling on the dried silicon wafer by adopting HF with the second concentration arranged in a first pickling tank;

and carrying out secondary chain pickling on the silicon wafer subjected to primary chain pickling by adopting the HF with the second concentration arranged in the second pickling tank.

Preferably, after chain pickling is performed on the dried silicon wafer by using HF with a second concentration to clean the BSG layer remaining on the back and side surfaces of the silicon wafer, the method further comprises:

and washing and drying the silicon wafer subjected to chain type acid washing.

Preferably, when the dried silicon wafer is subjected to chain pickling by using HF with a second concentration to clean the residual BSG layers on the back and side surfaces of the silicon wafer, the method further comprises:

and cleaning the boron-rich layer on the back surface and the side surface of the silicon wafer by using the HF with the second concentration.

A preparation method of an N-type TOPCon battery comprises the following steps:

texturing an N-type silicon wafer to prepare pyramid textured surfaces on the surface of the silicon wafer;

performing boron diffusion on pyramid suede of the silicon wafer;

cleaning a BSG layer on the surface of the silicon wafer after boron diffusion by adopting the solar cell BSG cleaning method;

polishing the back surface of the silicon wafer, and preparing a passivation contact layer on the polished back surface of the silicon wafer;

performing coiling and plating cleaning on the silicon wafer, and preparing an aluminum oxide film and a silicon oxynitride film on the front surface of the silicon wafer;

preparing a silicon nitride film on the back of the silicon wafer;

and preparing electrodes on the front surface and the back surface of the silicon wafer.

The application provides a solar cell BSG cleaning method and a TOPCon cell preparation method, wherein the solar cell BSG cleaning method comprises the following steps: carrying out groove type acid washing on the silicon wafer subjected to boron diffusion by using HF with a first concentration contained in the groove body so as to clean a BSG layer on the surface of the silicon wafer; washing and drying the silicon wafer subjected to the groove type acid washing; and (3) carrying out chain type acid washing on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

According to the technical scheme, HF with the first concentration contained in the tank body is utilized to carry out tank type acid washing on the silicon wafer after boron diffusion, so that the BSG layer on the surface part of the silicon wafer is removed through the tank type acid washing, and then the silicon wafer after the tank type acid washing is washed with water and dried, so that the influence on the subsequent chain type acid washing is avoided. And then, carrying out chain type acid washing on the dried silicon wafer by using HF with the second concentration so as to wash off the residual BSG layers on the back and side surfaces of the silicon wafer. The groove type acid washing is to place the silicon wafer in HF, so that the cleaning of partial BSG layer can be realized without high concentration HF, and the phenomenon that the surface of the residual BSG layer is uniform and the thickness of BSG in the wafer is not extremely poor can be achieved through the groove type acid washing, so as to improve the removal effect of the BSG layer. Because the back and the side of the silicon wafer are only the residual BSG layers after the groove type acid washing, the BSG is easier to clean after the groove type acid washing, the residual BSG layers on the back and the side of the silicon wafer can be cleaned without HF with high concentration when the chain type acid washing is used for cleaning, and the BSG layer removing effect can be improved. On the basis of adopting groove type pickling and chain type pickling, even if the roller level during chain type pickling is slightly abnormal, the effect of removing the residual BSG layer is not affected, so that HF consumption can be reduced, and the later maintenance cost of a machine can be reduced.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present application, and that other drawings may be obtained according to the provided drawings without inventive effort to a person skilled in the art.

Fig. 1 is a flowchart of a method for cleaning a BSG of a solar cell according to an embodiment of the present application;

fig. 2 is a flowchart of a method for preparing an N-type TOPcon battery according to an embodiment of the present application.

Detailed Description

When the N-type TOPCon battery is prepared, the formed BSG layer is thicker, the HF concentration requirement of the chain roller pickling process is higher, generally about 65%, the requirements on the tank liquid level and the roller level are higher, the back BSG layer is easy to be removed uncleanly, and the workshop cost is increased. And high concentration HF production places high demands on equipment and environment.

Therefore, the application provides a BSG cleaning method of a solar cell and a TOPCon cell preparation method, which are used for reducing the concentration of HF used for removing BSG and improving the BSG removal effect.

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Referring to fig. 1, a flowchart of a method for cleaning a BSG of a solar cell according to an embodiment of the present application is shown, where the method for cleaning a BSG of a solar cell according to an embodiment of the present application may include:

s11: and (3) carrying out groove type acid washing on the silicon wafer subjected to boron diffusion by using HF with the first concentration contained in the groove body so as to clean a BSG layer on the surface of the silicon wafer.

In this application, after boron diffusion is performed on a silicon wafer (the silicon wafer mentioned herein is specifically an N-type silicon wafer, and the silicon wafer is specifically used for preparing an N-type TOPcon battery, and a BSG layer is formed on the surface of the silicon wafer after boron diffusion), the silicon wafer after boron diffusion may be placed in a tank body (specifically, the back surface of the silicon wafer may be in contact with HF of a first concentration), where HF of the first concentration is contained. That is, the silicon wafer after boron diffusion may be placed in a tank containing HF of a first concentration, so that the BSG layer on the surface of the silicon wafer after boron diffusion may be cleaned by using HF of the first concentration contained in the tank. The surface of the silicon wafer referred to herein refers to the surface on which the BSG layer is formed, specifically, the back surface, the side surface, and the front surface. Due to the trough-type pickling

In addition, when the pickling is performed in a tank, the removal thickness of the BSG layer can be controlled by controlling the time of the pickling in the tank. Considering that the BSG layer with a certain thickness is required to be reserved on the front surface of the silicon wafer, the BSG layer on a part of the surface of the silicon wafer can be removed through groove type pickling, and particularly, the thickness of the BSG layer remained on the front surface of the silicon wafer can be subjected to groove type cleaning after the preparation requirement of an N-type TOPCon battery is met. Namely, the BSG layer with a certain thickness on the surface of the silicon wafer can be removed through groove type acid washing, so that the residual BSG layer on the surface of the silicon wafer is thinner. In addition, because the BSG layer is cleaned by immersing the silicon wafer in HF with the first concentration, the BSG layer is not required to be cleaned by HF with the high concentration (namely, the first concentration is smaller), the BSG layer is cleaned more uniformly, the surface of the residual BSG layer is also more uniform, and the phenomenon that the thickness of the BSG layer in the same surface is not extremely poor is caused, namely, the cleaning quality of the BSG layer can be improved by the groove type acid cleaning.

From the above, the thickness of BSG and the uniformity of removal of the BSG layer can be controlled more easily by the tank pickling, and the process is simple. The machine can adopt a traditional pickling machine, and the cost is lower.

S12: and washing and drying the silicon wafer subjected to the groove type acid washing.

After the BSG layer on the surface of the silicon wafer is subjected to the trench etching, that is, after the step S11 is performed, the silicon wafer after the trench etching may be subjected to water washing to remove the surface complex (the complex is generated by the reaction between HF and the BSG layer) and the residual HF by water washing, thereby avoiding the influence on the subsequent process.

When the silicon wafer subjected to groove type acid washing is subjected to water washing, two groove bodies can be specifically arranged. In order to distinguish, the tank body containing the HF with the first concentration can be a No. 1 tank (namely, the No. 1 tank is a pickling tank), and the two tank bodies for water washing can be a No. 2 tank and a No. 3 tank (namely, the No. 2 tank and the No. 3 tank are both water washing tanks). And DI water (deionized water) is contained in the No. 2 groove and the No. 3 groove, and the silicon wafer after the groove type acid washing can sequentially enter the No. 2 groove and the No. 3 groove, so that the DI water in the No. 2 groove and the No. 3 groove is utilized to clean the complex and residual HF on the surface of the silicon wafer well. And the total water washing time of the No. 2 groove and the No. 3 groove can be 120s (the time of the No. 2 groove and the No. 3 groove can be evenly distributed, the time in the No. 2 groove can be more, or the time in the No. 3 groove can be more, and the time can be specifically set according to actual demands). Of course, the washing time may be modified according to the actual situation.

After the silicon wafer subjected to the groove type acid washing is washed, the silicon wafer can be dried to remove residual moisture on the surface of the silicon wafer, so that the influence on the subsequent process is avoided. The drying of the silicon wafer can also be performed in a tank body (marked as a No. 4 tank, namely, a No. 4 tank is a drying tank). Wherein, the temperature of the drying can be 75-85 ℃ (namely, the process working condition of the No. 4 tank can be 75-85 ℃), and the drying time can be 300s. Of course, the drying temperature and drying time can be modified according to the actual situation.

As can be seen from the above, the tank type pickling machine and the process steps are connected in series, and the process steps specifically comprise: groove type acid washing-water washing 1-water washing 2-drying.

S13: and (3) carrying out chain type acid washing on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

After the silicon wafer is dried, the dried silicon wafer can be subjected to chain pickling (namely chain roller pickling) by using HF with a second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

Because the BSG layer remained on the back and the side of the silicon wafer after the groove type acid washing is thinner, compared with the existing method that the BSG layer is washed by adopting chain type acid washing, the concentration of HF adopted by the chain type acid washing can be greatly reduced by adopting the mode of firstly carrying out the groove type acid washing and then carrying out the chain type acid washing, so that the requirements of HF production on equipment and environment can be reduced.

The HF concentration requirement can be reduced and the BSG layer removal effect can be improved by adding a tank acid wash before the chain acid wash. And moreover, the situation that the back and side BSG layers are thinned and the residual BSG layers are uniform, and the thickness of the BSG layer in the sheet is not extremely poor is achieved by adding the groove type pickling, so that the residual BSG removing effect is not affected even if the chain type pickling roller is slightly abnormal in level, the later maintenance cost of a machine is further reduced, and the HF consumption can be reduced. For HF consumption, the single-step chain type acid washing (namely chain type acid washing is adopted) is calculated according to the existing liquid exchange period of 120 ten thousand pieces of life, the period HF consumption is 6000L, the groove type acid washing is increased, the groove type life is 24 ten thousand pieces, the chain type acid washing life is 120 ten thousand pieces, the groove type acid washing is added, the chain type acid washing is overlapped through the initial formula and the automatic liquid supplementing parameter adjustment, the period HF consumption is 3600L, the period HF consumption is reduced by 40 percent, and the chemical consumption is obviously reduced. Namely, the thickness of the BSG layer is easier to control in the tank type acid washing process, the total HF consumption is reduced by about 40%, and the cost of factory chemicals is greatly reduced.

The electrical performance of the N-type TOPCon battery prepared by cleaning the BSG layer through the tank type acid cleaning and the chain type acid cleaning is not different from that of the N-type TOPCon battery prepared by one-step chain type acid cleaning.

The embodiment of the application provides a method for cleaning a BSG (solar cell) of a solar cell, wherein the first concentration is smaller than the second concentration.

Because the BSG layer is cleaned and removed by adopting the process of firstly trough-type acid washing and then chain-type acid washing, and the trough-type acid washing only removes partial BSG layer on the surface of the silicon wafer, the concentration of HF used for the trough-type acid washing can be smaller than that used for the chain-type acid washing (namely, the first concentration is smaller than that of the second concentration), and the concentration of HF used for the trough-type acid washing and the concentration of HF used for the chain-type acid washing are smaller than that of the HF used for the chain-type roller acid washing in the prior art.

According to the method for cleaning the BSG of the solar cell, the first concentration is 5% -10%, and the second concentration is 20% -25%.

In this application, the first concentration is in particular 5% to 10% (inclusive), i.e. the HF concentration of the tank pickling is 5% to 10%, and the second concentration is in particular 20% to 25% (inclusive), i.e. the HF concentration of the chain pickling is 20% to 25%.

The BSG layer with a certain thickness is removed by using HF with the concentration of 5% -10% in the tank type pickling, the surface of the residual BSG layer is more uniform, the thickness of the BSG in the sheet is not extremely poor, and the residual BSG layer is removed by using HF with the concentration of 20% -25% in the superposition chain type pickling. Compared with the prior chain type acid cleaning technology which singly adopts the chain type acid cleaning technology to clean the BSG layer, the HF concentration is about 65 percent, and the HF concentration consumption of the superimposed chain type acid cleaning technology is reduced by about 40 percent.

Referring specifically to table 1, process parameters for tank and chain pickling are shown in the table:

TABLE 1 Process parameters table for tank pickling and chain pickling

The front pickling process (namely groove type pickling) uses HF with the concentration of 5% -10%, so that less BSG can be effectively removed, and the matching chain type pickling process is achieved, and the rear pickling process (namely chain type pickling) effectively removes BSG residues on the back under the condition of HF with the concentration of 20% -25%. Note that (1): under the condition that the concentration of the HF for the groove type pickling is low and the concentration of the HF for the chain type pickling is unchanged, the thickness of BSG removed by the groove type pickling is insufficient, so that BSG cannot be completely removed by the chain type pickling, and batch defects are generated; (2) The concentration of the HF for the groove type pickling is normal, and the concentration of the chain type pickling is reduced, so that BSG can not be completely removed after the chain type pickling, and further bad batch production is caused; (3) The concentration of the tank type acid washing and the concentration of the chain type acid washing are reduced simultaneously, so that the reflectivity of the back surface of the tank type acid washing is low, the BSG layer is thicker, the residual BSG cannot be removed by the chain type acid washing, and further batch defects are caused.

Through the process, the thickness of the BSG layer can be reduced from 80nm to 20nm-30nm through groove type acid washing, so that the thickness of the BSG layer is reduced, and the effect of removing the BSG layer on the back and the side can be achieved by using HF with the concentration of about 20% in the subsequent BSG removing process.

According to the method for cleaning the BSG of the solar cell, before chain type acid cleaning is carried out on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back surface and the side surface of the silicon wafer, the method can further comprise the following steps:

measuring reflectivity of the dried silicon wafer surface at a plurality of sampling points;

if the reflectivity at the sampling point is lower than the minimum value of the set reflectivity range, returning to the step of carrying out groove type acid washing on the silicon wafer after boron diffusion by using HF with the first concentration contained in the groove body so as to clean the BSG layer on the surface of the silicon wafer;

and if the reflectivity at each sampling point is within the set reflectivity range, performing chain acid washing on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back and side surfaces of the silicon wafer.

In the application, before chain pickling is performed on the dried silicon wafer by using HF with the second concentration to clean the back surface and the residual BSG layer on the side surface of the silicon wafer, the reflectivity of a plurality of sampling points on the surface of the dried silicon wafer (specifically, the reflectivity of a plurality of sampling points on the back surface can be measured), wherein the higher the reflectivity is, the thinner the BSG is, the lower the reflectivity is, and the thicker the BSG is. Then, it can be judged whether or not the reflectivities at the sampling points are all within a set reflectance range, wherein the set reflectance range can be specifically 5% -8% (the reflectivities can be well matched with chain pickling), and of course, the set reflectance range can be adjusted according to experiments and the like.

If the reflectivity at the sampling point is lower than the minimum value of the set reflectivity range, the residual BSG layer after the trough type pickling is thicker, at the moment, the step of trough type pickling the silicon wafer after boron diffusion by using HF with the first concentration contained in the trough body to clean the BSG layer on the surface of the silicon wafer can be returned, and the trough type pickling is used for cleaning and removing the BSG layer, so that the thickness of the BSG layer is reduced, and the BSG layer removing effect is improved conveniently.

If the reflectivities of all the sampling points are within the set reflectivities, the BSG layer can be well matched with a chain type pickling process, so that the step of carrying out chain type pickling on the dried silicon wafer by using HF with the second concentration to clean the residual BSG layers on the back and the side of the silicon wafer can be carried out, and the residual BSG layers on the back and the side can be well removed.

If the reflectivity at the sampling point is higher than the maximum value of the set reflectivity range, the BSG layer is thinner, and at the moment, the step of carrying out chain acid washing on the dried silicon wafer by using HF with the second concentration to clean the residual BSG layer on the back and the side of the silicon wafer can be carried out so as to remove the residual relatively thinner BSG layer. Or, an alarm and the like can be sent out, so that related personnel can know the condition that the BSG layer is too thin in time, and therefore the time of the tank type pickling can be regulated and controlled, and the performance of the finally prepared N-type TOPCon battery can be improved.

According to the BSG cleaning method for the solar cell, the time length of the tank type acid cleaning is 180 s+/-10 s, the technological parameters of the chain type acid cleaning are (3.6 m+/-0.5 m)/min, and the temperatures of the tank type acid cleaning and the chain type acid cleaning are 18-25 ℃.

In the application, the time length of the tank pickling can be 180 s+/-10 s (180 s is better), and the technological parameters of the chain pickling can be (3.6 m+/-0.5 m)/min (3.6 m/min is better), so that the BSG layer removing effect is improved.

Wherein 3.6m/min is consistent with the one-step chain type pickling process, and the machine can adopt a traditional tank type pickling machine with lower cost due to simple process.

And the temperature of the tank type acid washing and the chain type acid washing can be 18-25 ℃, so that HF can exert better BSG cleaning and removing effects.

According to the method for cleaning the BSG of the solar cell, which is provided by the embodiment of the application, the tank body further comprises HCL, and when the tank type pickling is carried out on the silicon wafer after boron diffusion by utilizing HF with the first concentration contained in the tank body, the method can further comprise the following steps:

cleaning the silicon wafer by using HCL;

and/or, when the dried silicon wafer is subjected to chain pickling by the HF with the second concentration, the method can further comprise:

and cleaning the silicon wafer by using HCL.

In this application, in addition to the first concentration of HF contained in the tank body, HCL may be contained in the tank body, where the concentration of HCL contained in the tank body may be less than a third concentration, and the third concentration may specifically be set according to experiments, experience, and the like, and specifically the third concentration may specifically be 1%. On the basis of the above, when the silicon wafer subjected to boron diffusion is subjected to groove type acid washing by using HF with the first concentration contained in the groove body, HCL contained in the groove body can be used for washing the silicon wafer so as to remove metal ions on the surface of the silicon wafer, and therefore the silicon wafer washing effect is improved.

In addition, after the dried silicon wafer is subjected to chain type acid washing by using HF with the second concentration, the silicon wafer can be cleaned by using HCL. Wherein the concentration of HCL used at this time may also be less than the third concentration. By the method, the residual BSG layer on the surface of the silicon wafer is removed, and meanwhile, HCL is utilized to remove metal ions on the surface of the silicon wafer, so that the cleaning effect of the silicon wafer is improved.

Wherein, the tank type acid washing and the chain type acid washing can both comprise HCL cleaning, or the HCL cleaning can be carried out in one of the tank type acid washing and the chain type acid washing in the acid washing process, so as to reduce the cleaning cost.

The method for cleaning the BSG of the solar cell, provided by the embodiment of the application, adopts HF with the second concentration to carry out chain type acid cleaning on the dried silicon wafer, and can comprise the following steps:

and (3) carrying out chain type acid washing on the dried silicon wafer by adopting HF with the second concentration arranged in the acid washing tank.

In the present application, when chain pickling is performed on the dried silicon wafer by using HF of the second concentration, chain pickling may be performed on the dried silicon wafer by using HF of the second concentration provided in the pickling tank. Specifically, the chain roller can carry the silicon wafer through the pickling tank, and HF with a second concentration in the pickling tank can be sprayed onto the silicon wafer to carry out pickling on the side surface and the back surface of the silicon wafer to remove the BSG layer.

The HF can flow into the pickling tank by chain pickling in the pickling tank, so that the recycling and recovery of the HF are realized, and the safety is ensured.

The method for cleaning the BSG of the solar cell, provided by the embodiment of the application, adopts HF with the second concentration arranged in the pickling tank to carry out chain type pickling on the dried silicon wafer, and can comprise the following steps:

carrying out primary chain type acid washing on the dried silicon wafer by adopting HF with second concentration arranged in the first acid washing tank;

and carrying out secondary chain pickling on the silicon wafer subjected to primary chain pickling by adopting HF with a second concentration arranged in the second pickling tank.

In the present application, when chain pickling is performed on a dried silicon wafer using HF of the second concentration set in the pickling tank, the dried silicon wafer may be subjected to primary chain pickling using HF of the second concentration set in the first pickling tank, and then, the dried silicon wafer may be subjected to secondary chain pickling using HF of the second concentration set in the second pickling tank, so that the removal effect of the back and side surface residual BSG layers may be improved by the secondary chain pickling.

According to the method for cleaning the BSG of the solar cell, after chain type acid cleaning is carried out on the dried silicon wafer by adopting HF with the second concentration so as to clean the residual BSG layers on the back surface and the side surface of the silicon wafer, the method can further comprise the following steps:

and washing and drying the silicon wafer subjected to chain type acid washing.

In the application, after chain pickling is performed on the dried silicon wafer by adopting HF with the second concentration so as to clean the BSG layer remained on the back and the side of the silicon wafer, the chain-pickled silicon wafer can be washed by water. Specifically, the silicon wafer subjected to chain type acid cleaning can be subjected to water cleaning by using a water tank. That is, after chain pickling of the dried silicon wafer with HF at the second concentration, the chain pickled silicon wafer may be fed into a water tank to be washed with water, so that the back complex and acid residue are washed away by water, thereby avoiding the influence on the subsequent preparation process.

After the chain-type acid-washed silicon wafer is washed, the washed silicon wafer can be dried to dry the moisture on the surface of the silicon wafer. Specifically, the dried silicon wafer can be dried by using a drying groove. Thereby avoiding the water on the surface of the silicon wafer from causing images to the subsequent preparation process.

According to the method for cleaning the BSG of the solar cell, when chain type acid cleaning is performed on the dried silicon wafer by using HF with the second concentration so as to clean the residual BSG layers on the back surface and the side surface of the silicon wafer, the method can further comprise the following steps:

and cleaning the boron-rich layer on the back surface and the side surface of the silicon wafer by using HF with the second concentration.

In the application, when chain acid washing is performed on the dried silicon wafer by using HF with the second concentration to clean the residual BSG layers on the back and the side of the silicon wafer, the boron-rich layers (the boron-rich layers are positioned below the BSG layers and close to the silicon wafer) on the back and the side of the silicon wafer can be cleaned by using HF with the second concentration, so that the boron-rich layers are reduced, and the conversion efficiency of the prepared battery piece is improved (specifically, the battery piece efficiency is improved by more than 0.05%).

The embodiment of the application also provides a preparation method of the N-type TOPCon battery, referring to fig. 2, which shows a flow chart of the preparation method of the N-type TOPCon battery, which may include:

texturing is carried out on the N-type silicon wafer so as to prepare pyramid textured surfaces on the surface of the silicon wafer;

performing boron diffusion on pyramid suede of the silicon wafer;

cleaning a BSG layer on the surface of the silicon wafer after boron diffusion by adopting any solar cell BSG cleaning method;

preparing a silicon nitride film on the back of the silicon wafer;

electrodes are prepared on the front and back surfaces of the silicon wafer.

The preparation method of the N-type TOPCon battery provided by the embodiment of the application can comprise the following steps:

1) 1 (100) crystal orientation N-type monocrystalline silicon wafer is selected, and the resistivity of the silicon wafer is 1.2 ohm cm.

2) And preparing (111) crystal orientation pyramid suede on the surface of the silicon wafer by using an alkali suede anisotropic corrosion method.

3) And preparing a uniform emitter on the textured silicon wafer by using a boron furnace tube method, wherein the square resistance of the front surface is 100 omega, and a BSG layer and an oxide layer are grown on the front surface and the back surface.

4) The front-back oxide layer and part of the front-back (and side) BSG layer were removed using a bath of 5% HF, and the surface complex and acid residues were washed off with water, and then dried in a drying bath for 300 seconds.

5) The residual BSG layer on the back (and on the sides) was removed using a chain of 20% HF, and the complex and acid residues were washed off with water and then dried in a drying tank. Namely, the BSG layer on the surface of the silicon wafer after boron diffusion can be cleaned by adopting any one of the solar cell BSG cleaning methods, wherein the BSG cleaning methods of any one of the solar cells can be participated in the aspects of 4) and 5);

6) The back pyramid tips were removed (i.e., the wafer back was polished) using an alkaline polishing anisotropic etch process. The conditions used were: the NaOH concentration was 2.5%, the polishing additive concentration was 0.8%, the solution temperature was 62℃and the time was 180s. After polishing the back of the silicon wafer, the silicon wafer can be washed (removing the alkali solution on the surface of the silicon wafer), then the silicon wafer is washed (removing the organic residues on the surface of the silicon wafer) by alkali and hydrogen peroxide, then the silicon wafer is washed (removing the alkali and hydrogen peroxide on the surface of the silicon wafer), then the silicon wafer is mixed and washed (HF+HCL to neutralize the alkali residues, (2) form a hydrophobic bond, (3) remove the metal ions on the surface of the silicon wafer by HCL), then the silicon wafer is washed, and then the silicon wafer is dried. And the dried silicon wafer can enter the next process, namely, a passivation contact layer is prepared on the back surface of the silicon wafer.

7) And preparing a passivation contact layer (a tunneling oxide layer and a doped polysilicon layer) on the back surface of the N-type silicon wafer by using an LPCVD furnace tube mode, wherein the thickness of the tunneling oxide layer is 1.2nm, and the thickness of the phosphorus doped polysilicon layer is 120nm. During the process, a wrapping coating is formed around the periphery and the edge of the silicon wafer.

8) And removing the peripheral and edge coiling and plating polycrystalline silicon layers by using an alkali etching method, wherein the using conditions are as follows: the NAOH concentration was 4%, the temperature was 58℃and the time was 120s. The surrounding and edge wrapping coating is completely removed after the process is finished.

9) And preparing a passivation alumina layer on the front surface of the silicon wafer by using a plate type upper coating mode, so that the surface recombination is reduced.

10 A front side silicon oxynitride film is prepared by a PECVD method. The thickness of the front silicon oxynitride film is 85nm, and the refractive index is 2.0, so that the front silicon oxynitride film can be used for antireflection passivation.

11 A back side silicon nitride film is prepared by a PECVD method. The back side silicon nitride has a thickness of 75nm and a refractive index of 2.2. Acts as an anti-reflection passivation.

12 Preparing metal electrodes on the two sides of the silicon wafer by using a screen printing superposition sintering mode.

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is inherent to. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. In addition, the parts of the above technical solutions provided in the embodiments of the present application, which are consistent with the implementation principles of the corresponding technical solutions in the prior art, are not described in detail, so that redundant descriptions are avoided.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for cleaning a BSG of a solar cell, comprising:

washing and drying the silicon wafer subjected to the groove type acid washing;

2. The method of claim 1, wherein the first concentration is less than the second concentration.

3. The solar cell BSG cleaning method according to claim 2, wherein the first concentration is 5% -10% and the second concentration is 20% -25%.

4. The method of claim 3, further comprising, before chain pickling the dried silicon wafer with a second concentration of HF to clean the BSG layer remaining on the back and side of the silicon wafer:

5. The method of claim 3, wherein the time period of the acid-washing in the tank is 180 s.+ -. 10s, the process parameter of the acid-washing in the chain is (3.6 m.+ -. 0.5 m)/min, and the temperature of the acid-washing in the tank and the acid-washing in the chain are 18 ℃ to 25 ℃.

6. The method for cleaning a BSG of a solar cell according to claim 1, wherein the tank further comprises HCL, and when the silicon wafer after boron diffusion is subjected to the tank pickling by using HF with a first concentration contained in the tank, the method further comprises:

cleaning the silicon wafer by using HCL;

and cleaning the silicon wafer by using HCL.

7. The method for cleaning a BSG of a solar cell according to claim 1, wherein chain pickling the dried silicon wafer with HF having a second concentration comprises:

8. The method of claim 7, wherein chain pickling the dried silicon wafer with the second concentration of HF disposed in a pickling tank, comprising:

9. The method of claim 1, further comprising, after chain pickling the dried silicon wafer with a second concentration of HF to clean the BSG layer remaining on the back and side of the silicon wafer:

and washing and drying the silicon wafer subjected to chain type acid washing.

10. The method of claim 1, further comprising, when chain-pickling the dried silicon wafer with a second concentration of HF to clean the BSG layer remaining on the back and side of the silicon wafer:

11. A method for preparing an N-type TOPcon battery, comprising:

performing boron diffusion on pyramid suede of the silicon wafer;

cleaning a BSG layer on the surface of the silicon wafer after boron diffusion by adopting the solar cell BSG cleaning method as claimed in any one of claims 1 to 10;

preparing a silicon nitride film on the back of the silicon wafer;