CN111015369A - Polishing solution additive for back surface of silicon wafer, polishing solution and polishing method for silicon wafer of back-passivated crystalline silicon solar cell - Google Patents

Polishing solution additive for back surface of silicon wafer, polishing solution and polishing method for silicon wafer of back-passivated crystalline silicon solar cell Download PDF

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CN111015369A
CN111015369A CN201911015464.9A CN201911015464A CN111015369A CN 111015369 A CN111015369 A CN 111015369A CN 201911015464 A CN201911015464 A CN 201911015464A CN 111015369 A CN111015369 A CN 111015369A
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silicon wafer
polishing
polishing solution
cleaning
tank
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陈坤
谢毅
苏荣
王岚
李忠涌
张鹏
王璞
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Tongwei Solar Meishan Co Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B57/00Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
    • B24B57/02Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30604Chemical etching
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

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Abstract

A polishing solution additive and a polishing solution for the back surface of a silicon wafer and a polishing method for the silicon wafer of a back-passivated crystalline silicon solar cell belong to the technical field of solar cells. The polishing solution additive comprises the following components in percentage by weight: 1-3% of alkyl trimethyl ammonium hydroxide, 0.5-2% of sodium phosphate, 2-5% of nonionic surfactant and 90-96.5% of water. The polishing solution comprises the following components in percentage by weight: 3-5% of alkali substance, 2-5% of polishing solution additive and 90-95% of water. The polishing method of the silicon wafer of the back passivation crystalline silicon solar cell comprises the following steps: acid polishing is carried out on the back of the silicon chip after the diffusion process is carried out to remove the phosphorosilicate glass; then cleaning the silicon wafer; and polishing the back of the cleaned silicon wafer by using the polishing solution. The method can improve the reflectivity and minority carrier lifetime of the back of the silicon wafer and can improve the cell efficiency of the back-passivated crystalline silicon solar cell.

Description

Polishing solution additive for back surface of silicon wafer, polishing solution and polishing method for silicon wafer of back-passivated crystalline silicon solar cell
Technical Field
The application relates to the technical field of solar cells, in particular to a polishing solution additive and a polishing solution for the back surface of a silicon wafer and a polishing method for the silicon wafer of a back-passivated crystalline silicon solar cell.
Background
At present, a solar cell mainly uses crystalline silicon as a substrate material, and a large number of dangling bonds (dangling bonds) are generated due to periodic damage on the surface of a silicon wafer, so that a large number of defect energy levels in a band gap exist on the surface of the crystal; in addition, the deposition of dislocations, chemical residues and surface metals can introduce defect energy levels, so that the surface of the silicon wafer becomes a recombination center, a large surface recombination rate is caused, and the conversion efficiency is limited. Compared with the conventional battery, the back passivated battery has the main advantages of reducing the interface state of the back surface of the battery piece, improving the passivation capability, prolonging the light path, and improving the long-wave response and the short-circuit current, so that the conversion efficiency of the back passivated battery is improved by 1.0-1.2% or even more compared with the conventional battery. Wherein, the back surface structure form contacting with the passivation layer plays a core role in the subsequent passivation layer deposition quality and interface form co-fusion.
The back Passivation (PERC) solar cell in the prior art mainly comprises the following processes: texturing, phosphorus diffusion, back etching, annealing, back coating AlOx, back coating SiNx, front coating SiNx, back passivation layer laser grooving, front and back electrode electric field printing and high-temperature sintering, and finally forming the back passivation solar cell. The back surface of the cell is deposited with an insulating passivation layer, so that the interface state of the back surface is reduced, the passivation effect is improved, the light path is prolonged, the long-wave response and the short-circuit current are improved, then, part of the passivation layer is selectively etched through laser etching to expose the silicon layer, and then, back electric field aluminum paste is printed in a laser etching area to form direct contact with the silicon layer, so that the conduction is realized. Therefore, the surface topography of the silicon substrate, which contacts the passivation layer on the back surface, directly affects the overall back surface passivation effect, thereby affecting the conversion efficiency of the cell.
Disclosure of Invention
The application provides a polishing solution additive and a polishing solution for the back surface of a silicon wafer and a polishing method for the silicon wafer of a back-passivated crystalline silicon solar cell, and aims to improve the reflectivity and the minority carrier lifetime of the back surface of the silicon wafer and improve the cell efficiency of the back-passivated crystalline silicon solar cell.
The embodiment of the application is realized as follows:
in a first aspect, an embodiment of the present application provides a polishing solution additive for a silicon wafer back surface, where the polishing solution additive includes, by weight: 1-3% of alkyl trimethyl ammonium hydroxide, 0.5-2% of sodium phosphate, 2-5% of nonionic surfactant and 90-96.5% of water.
In the technical scheme, when the polishing solution additive and the alkali substance are used together for polishing the back surface of the silicon wafer, the alkyl trimethyl ammonium hydroxide, the sodium phosphate and the nonionic surfactant in the proportion are used for synergistic action with the alkali substance, so that the reflectivity and the minority carrier lifetime of the back surface of the silicon wafer can be improved, and the cell efficiency of the back-passivated crystalline silicon solar cell can be improved. This is probably because alkyl trimethyl ammonium hydroxide is a weak base, which can slow down the corrosion of alkali substances to the back of the silicon wafer; the sodium phosphate can be adsorbed on the surface of the silicon wafer, so that the corrosion of alkaline substances to the surface of the silicon wafer is weakened, the effect of protecting a PN junction on the front surface of the silicon wafer is achieved, and in addition, the sodium phosphate can also be complexed with metal ions to clean the metal ions on the surface of the silicon wafer; the alkali substance and the back of the silicon wafer are subjected to corrosion reaction to generate more hydrogen, and the nonionic surfactant can play a defoaming role, so that the corrosion is more uniform, the back of the silicon wafer is smoother, and the reflectivity of the back of the silicon wafer is improved.
In one possible embodiment, the polishing solution additive comprises, in weight percent: 2% of alkyl trimethyl ammonium hydroxide, 1-2% of sodium phosphate, 3-4% of nonionic surfactant and 92-94% of water.
In the technical scheme, the reflectivity of the back of the silicon wafer can be better improved under the combined action of the alkyl trimethyl ammonium hydroxide, the sodium phosphate and the nonionic surfactant in the proportion, the PN junction on the front of the silicon wafer is protected from being corroded and damaged in the polishing process, and the cell efficiency of the solar cell can be better improved.
In one possible embodiment, the alkyltrimethylammonium hydroxide is selected from either or both of dodecyltrimethylammonium hydroxide and hexadecyltrimethylammonium hydroxide.
In the technical scheme, the dodecyl trimethyl ammonium hydroxide and the hexadecyl trimethyl ammonium hydroxide are weak bases, and act on the back of the silicon wafer together with alkali substances, so that a good corrosion inhibition effect can be achieved.
In one possible embodiment, the sodium phosphate salt is selected from any one or any plurality of sodium tripolyphosphate, sodium pyrophosphate, and sodium hexametaphosphate.
In the technical scheme, sodium tripolyphosphate, sodium pyrophosphate and hexametaphosphate can be adsorbed on the surface of the silicon wafer, so that the corrosion of alkali substances to the surface of the silicon wafer is weakened, the positive PN junction of the silicon wafer is protected, metal ions can be complexed, and the metal ions on the surface of the silicon wafer are cleaned, wherein the sodium tripolyphosphate, the sodium pyrophosphate and the hexametaphosphate are easily obtained.
In one possible embodiment, the nonionic surfactant is selected from either or both of polyethylene glycol ethers and polyethylene glycols.
In the technical scheme, the polyethylene glycol ether and the polyethylene glycol have a defoaming effect, so that corrosion becomes more uniform, the back surface of the silicon wafer is smoother, and in addition, the polyethylene glycol ether and the polyethylene glycol are easy to obtain and have lower cost.
In a second aspect, an embodiment of the present application further provides a polishing solution for a back surface of a silicon wafer, where the polishing solution includes, by weight: 3-5% of alkali substance, 2-5% of the polishing solution additive and 90-95% of water.
In the technical scheme, the polishing solution additive and the alkali substance are mixed according to the proportion, so that the reflectivity and the minority carrier lifetime of the back surface of the silicon wafer can be improved, and the conversion efficiency of the solar cell can be improved.
In one possible embodiment, the polishing solution comprises, in weight percent: 3% of alkali substance, 3-5% of polishing solution additive and 92-94% of water.
In the technical scheme, the polishing solution additive and the alkali substance in the proportion are mixed, so that the reflectivity of the back surface of the silicon wafer can be better improved. Optionally, the alkali substance is selected from at least one of sodium hydroxide and potassium hydroxide.
In a third aspect, an embodiment of the present application further provides a polishing method for a silicon wafer of a back-passivated crystalline silicon solar cell, including:
acid polishing is carried out on the back of the silicon chip after the diffusion process is carried out to remove the phosphorosilicate glass;
then cleaning the silicon wafer;
and performing alkali polishing on the back surface of the cleaned silicon wafer by using the polishing solution.
According to the technical scheme, the phosphorosilicate glass on the back surface of the silicon wafer is removed by using acid, then the silicon wafer is cleaned to remove redundant acid, and then the polishing solution is used for polishing the back surface of the silicon wafer, so that the reflectivity and the minority carrier lifetime of the back surface of the silicon wafer can be improved, and the conversion efficiency of the solar cell can be improved.
In one possible embodiment, the temperature of the alkali polishing step is 65-75 ℃; optionally, the polishing time of the alkali polishing step is 2-5 min.
In the technical scheme, when the polishing solution is used for polishing the back surface of the silicon wafer, the temperature is controlled to be 65-75 ℃, the polishing solution can better play a role, and a better polishing effect can be achieved. In addition, the polishing time is controlled within 2-5 min, the corrosion degree of the back surface of the silicon wafer is more appropriate, and the conversion efficiency of the solar cell is improved.
In a possible implementation scheme, the cleaning liquid used for cleaning the silicon wafer comprises 2-5 wt% of alkali and 3-8 wt% of hydrogen peroxide.
In the technical scheme, the silicon wafer is cleaned by the alkali and hydrogen peroxide cleaning solution according to the proportion, so that not only can redundant acid be removed, but also organic pollutants can be effectively removed.
Optionally, the temperature of the cleaning step is 80-100 ℃. The silicon wafer is cleaned at the temperature, so that organic pollutants on the silicon wafer can be effectively removed.
Drawings
In order to more clearly illustrate 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 for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a microscope picture of a dried silicon wafer according to example 5 of the present application;
FIG. 2 is a microscope photograph of the dried silicon wafer of comparative example 9 of the present application.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In the present embodiment, "plural" means two or more.
The following specifically describes a polishing solution additive and a polishing solution for the back surface of a silicon wafer and a polishing method for a silicon wafer of a back-passivated crystalline silicon solar cell according to the embodiment of the present application:
the embodiment of the application provides a polishing solution additive for the back of a silicon wafer, which comprises the following components in percentage by weight: 1-3% of alkyl trimethyl ammonium hydroxide, 0.5-2% of sodium phosphate, 2-5% of nonionic surfactant and 90-96.5% of water.
Illustratively, the polishing solution additive comprises alkyl trimethyl ammonium hydroxide, sodium phosphate salt, nonionic surfactant and water, wherein the alkyl trimethyl ammonium hydroxide accounts for 1%, 1.5%, 2%, 2.5% or 3% by weight; sodium phosphate is 0.5%, 1%, 1.5% or 2%; the content of the nonionic surfactant is 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, and it should be noted that the content of the alkyltrimethyl ammonium hydroxide, the sodium phosphate salt and the nonionic surfactant in the polishing solution additive can be any combination of the above ratio values, and the balance is water.
In one possible embodiment, the polishing solution additive comprises, in weight percent: 2% of alkyl trimethyl ammonium hydroxide, 1-2% of sodium phosphate, 3-4% of nonionic surfactant and 92-94% of water.
The sodium phosphate salt is a sodium phosphate salt in a broad sense, and may be a sodium orthophosphate salt, a sodium pyrophosphate salt or a sodium metaphosphate salt. Illustratively, in one possible embodiment, the sodium phosphate salt is selected from any one or any plurality of sodium tripolyphosphate, sodium pyrophosphate, and sodium hexametaphosphate. Wherein, when the sodium tripolyphosphate, the sodium pyrophosphate and the sodium hexametaphosphate are mixed, no reaction occurs among the substances.
In one possible embodiment, the nonionic surfactant is selected from either or both of Polyethylene glycol ether and Polyethylene glycol (PEG for short). Illustratively, the polyethylene glycol may be PEG200 or PEG 400.
In one possible embodiment, the alkyltrimethylammonium hydroxide is selected from either or both of dodecyltrimethylammonium hydroxide and hexadecyltrimethylammonium hydroxide. Wherein, when the dodecyl trimethyl ammonium hydroxide and the hexadecyl trimethyl ammonium hydroxide are mixed, no reaction occurs.
The embodiment of the application also provides a polishing solution for the back surface of a silicon wafer, which comprises the following components in percentage by weight: 3-5% of alkali substance, 2-5% of the polishing solution additive and 90-95% of water.
Illustratively, the alkali substance is 3%, 3.5%, 4%, 4.5% or 5% by weight; the polishing solution additive is 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%. The contents of the alkaline substance and the polishing solution additive in the polishing solution can be any combination of the above ratio values, and the balance is water. Illustratively, the alkali substance may be sodium hydroxide or potassium hydroxide.
In one possible embodiment, the polishing solution comprises, in weight percent: 3% of alkali substances, 3-5% of polishing solution additives and 92-94% of water.
When the polishing solution additive is used together with the alkaline substances, the reflectivity of the back of the silicon wafer can be improved, and the transmission loss of light is reduced, so that the output current is increased, and the minority carrier lifetime can be prolonged. According to the weight percentage, when the polishing solution additive comprises 2% of alkyl trimethyl ammonium hydroxide, 1-2% of sodium phosphate, 3-4% of nonionic surfactant and 92-94% of water, and meanwhile, the mass percentage of the alkali substances in the polishing solution is 3% and the mass percentage of the polishing solution additive is 3-5%, the reflectivity of the back surface of the silicon wafer can be better improved, and the minority carrier lifetime can be prolonged.
The embodiment of the application also provides a polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell, which comprises the following steps:
s1: and performing acid polishing on the back surface of the silicon wafer subjected to the diffusion process to remove phosphorosilicate Glass (PSG for short, and is called phosphorus-Silicate Glass).
Illustratively, the solution of the acid polishing step is a mixture of hydrofluoric acid and nitric acid. Nitric acid in the mixed solution reacts with silicon to form silicon dioxide, and hydrofluoric acid can corrode the formed silicon dioxide, so that the mixed solution can continuously corrode the silicon surface. Illustratively, the concentration ratio of hydrofluoric acid to nitric acid is 1: 3.
S2: and cleaning the silicon wafer for the first time.
Wherein the first wash is used to wash excess acid. Illustratively, the cleaning solution adopted in the first cleaning comprises 2-5 wt% of alkali and 3-8 wt% of hydrogen peroxide. Namely, the solute in the cleaning liquid is alkali and hydrogen peroxide, the solvent is water, and the mass ratio of the alkali to the hydrogen peroxide is (2-5) to (3-8).
Illustratively, the first wash employs a wash solution comprising 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt% alkali. Alternatively, the base is sodium hydroxide or potassium hydroxide.
Illustratively, the first cleaning employs a cleaning solution comprising 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 7 wt%, 7.5 wt%, or 8 wt% hydrogen peroxide.
In one possible embodiment, the temperature of the first washing step is 80 to 100 ℃. Illustratively, the temperature of the first washing step is 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃, 98 ℃ or 100 ℃.
S3: and performing alkali polishing on the back of the silicon wafer after the first cleaning by using polishing solution.
In one possible embodiment, the temperature of the alkaline polishing step is 65 to 75 ℃. Illustratively, the temperature of the alkaline polishing step is 65 ℃, 66 ℃, 67 ℃, 68 ℃, 69 ℃, 70 ℃, 71 ℃, 72 ℃, 73 ℃, 74 ℃ or 75 ℃.
In a possible embodiment, the polishing time of the alkali polishing step is 2 to 5 min. Illustratively, the polishing time of the alkali polishing step is 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, or 5 min.
S4: and cleaning the silicon wafer for the second time, wherein the cleaning solution adopted for the second cleaning comprises hydrochloric acid and hydrogen peroxide. And the second cleaning adopts a strong reducing agent mode to remove residual alkali liquor and hydrogen peroxide in the previous working procedure, so as to realize the cleaning of the surface of the silicon wafer.
S5: and performing acid polishing on the front surface of the silicon wafer cleaned for the second time to remove the phosphorosilicate glass. Illustratively, an acid solution used for acid polishing of the silicon wafer is hydrofluoric acid, wherein the volume concentration of the hydrofluoric acid is 3-5%.
S6: the wafer is subjected to a third cleaning, illustratively, with water.
S7: and drying the surface of the silicon wafer.
The polishing solution additive for the back surface of the silicon wafer, the polishing solution and the polishing method for the silicon wafer of the back passivated crystalline silicon solar cell are further described in detail with reference to the following examples.
Example 1
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 85 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 70 ℃, and the treatment time is 3 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 2%, and the balance is water. Wherein, the polishing solution additive comprises 1 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 95 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 3%. And then spraying, cleaning and drying the silicon wafer.
Example 2
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 90 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 75 ℃, and the treatment time is 4 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 3%, the mass percent of the polishing solution additive is 5%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 94 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 5%. And then spraying, cleaning and drying the silicon wafer.
Example 3
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 3 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 93 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Example 4
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 90 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 75 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of potassium hydroxide in the polishing solution is 5%, the mass percent of the polishing solution additive is 2%, and the balance is water. Wherein, the polishing solution additive comprises 1 wt% of dodecyl trimethyl ammonium hydroxide, 0.5 wt% of sodium pyrophosphate, 2 wt% of polyethylene glycol and 96.5 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Example 5
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 100 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 3%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 2 wt% of dodecyl trimethyl ammonium hydroxide, 1 wt% of sodium hexametaphosphate, 3 wt% of polyethylene glycol and 94 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 5%. And then spraying, cleaning and drying the silicon wafer.
Example 6
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 85 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 3%, the mass percent of the polishing solution additive is 5%, and the balance is water. Wherein, the polishing solution additive comprises 1.5 wt% of hexadecyl trimethyl ammonium hydroxide, 1.5 wt% of sodium hexametaphosphate, 5 wt% of polyethylene glycol ether and 92 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Example 7
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 75 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 3%, the mass percent of the polishing solution additive is 3%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of hexadecyl trimethyl ammonium hydroxide, 2 weight percent of sodium tripolyphosphate, 4 weight percent of polyethylene glycol ether and 90 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 1
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of dodecyl trimethyl ammonium hydroxide, 0.3 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 94.7 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 2
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
Conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, controlling the temperature in the pre-cleaning tank to be 80 ℃, and the processing time to be 30S.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 1 weight percent of polyglycol ether and 96 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 3
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
Conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, controlling the temperature in the pre-cleaning tank to be 80 ℃, and the processing time to be 30S.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 0.5 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 95.5 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%.
Comparative example 4
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of dodecyl trimethyl ammonium hydroxide, 2.5 weight percent of sodium tripolyphosphate, 3 weight percent of polyethylene glycol ether and 92.5 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%.
Comparative example 5
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 2 weight percent of dodecyl trimethyl ammonium hydroxide, 1 weight percent of sodium tripolyphosphate, 5.5 weight percent of polyethylene glycol ether and 91.5 weight percent of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 6
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 4 wt% of dodecyl trimethyl ammonium hydroxide, 1 wt% of sodium tripolyphosphate, 3 wt% of polyethylene glycol ether and 92 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 7
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, a silicon wafer is manufacturedAnd (3) fluffing and diffusing, namely conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical loading machine, spraying a water film on the front side of the silicon wafer, and performing PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 90 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 75 ℃, and the treatment time is 4 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 3%, the mass percent of the polishing solution additive is 5%, and the balance is water. Wherein, the polishing solution additive comprises 2 wt% of dodecyl trimethyl ammonium hydroxide and 98 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 5%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 8
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 80 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into an alkali polishing tank, wherein the temperature of the alkali polishing tank is controlled at 65 ℃, and the treatment time is 5 min. The polishing solution is filled in the alkali polishing tank, the mass percent of sodium hydroxide in the polishing solution is 4%, the mass percent of the polishing solution additive is 4%, and the balance is water. Wherein, the polishing solution additive comprises 3 wt% of dodecyl trimethyl ammonium hydroxide and 98 wt% of deionized water.
And then conveying the silicon wafer into a cleaning tank for secondary cleaning, wherein the cleaning liquid adopted by the secondary cleaning comprises hydrochloric acid and hydrogen peroxide. And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 4%. And then spraying, cleaning and drying the silicon wafer.
Comparative example 9
A polishing method of a silicon wafer of a back-passivated crystalline silicon solar cell comprises the following steps:
firstly, texturing and diffusing the silicon wafer, conveying the diffused silicon wafer into a back PSG acid polishing groove by using a mechanical upper wafer, spraying a water film on the front side of the silicon wafer, and carrying out PSG acid polishing on the back side of the silicon wafer for 30 s. HF and HNO in acid polishing tank3Is 1: and 3, wherein the mass percent concentration of the HF is 49%, and the mass percent concentration of the nitric acid is 68%.
And conveying the silicon wafer into a pre-cleaning tank for first cleaning, wherein the mass percent of sodium hydroxide and the mass percent of hydrogen peroxide in the pre-cleaning tank are respectively 3% and 5%, the temperature in the pre-cleaning tank is controlled at 85 ℃, and the treatment time is 30 s.
And then conveying the silicon wafer into a front surface PSG removal tank for acid polishing to remove phosphorosilicate glass on the front surface of the silicon wafer, wherein the volume concentration of HF in the tank is 3%. And then spraying, cleaning and drying the silicon wafer.
In the examples 1 to 7 and comparative examples 1 to 8, some parameters are shown in Table 1.
TABLE 1 some parameters of examples 1 to 7 and comparative examples 1 to 8
Figure BDA0002245327710000201
Figure BDA0002245327710000211
Test example 1
The back surface reflectivity and minority carrier lifetime of the silicon wafers dried in the examples 1 to 7 and the comparative examples 1 to 9 are tested, and the cell efficiency of the back-passivated solar cell prepared by using the silicon wafers dried in the examples 1 to 7 and the comparative examples 1 to 9 is tested.
(1) Back surface reflectance: the reflectivity of the back side of the silicon wafer after drying in examples 1 to 7 and comparative examples 1 to 9 was measured by a D8 reflectivity tester, and the results are recorded in table 2. Wherein, the environmental temperature is kept at 24 +/-3 ℃ and the humidity is kept at 50 +/-10% in the testing process by adopting the D8 reflectivity tester, the xenon lamp is used by the D8 reflectivity tester, the rated power of the xenon lamp is 75W, and the current is 5A.
(2) The minority carrier lifetime of the polished and dried silicon wafers of examples 1 to 7 and comparative examples 1 to 9 is tested by adopting a microwave photoconductive decay method: the method comprises injecting 904nm laser into the silicon wafer to generate electron-hole pairs, detecting the change of conductance with time with a minority carrier lifetime tester to obtain the minority carrier lifetime when the external light injection is removed, and recording the result in Table 2. Wherein the ambient temperature is 25 +/-2 ℃, the humidity is 50% +/-10%,
(3) annealing the silicon wafers treated by the polishing methods of examples 1 to 7 and comparative examples 1 to 9, coating a passivation dielectric layer on the back surface, coating a silicon nitride film on the front surface, performing laser grooving on the back passivation layer, printing an electric field of a front electrode and a back electrode, and sintering at a high temperature to form a back passivation solar cell, and testing the cell efficiency of the back passivation solar cell prepared in examples 1 to 7 and comparative examples 1 to 9 by using a Halm electrical property tester, wherein the results are recorded in Table 2. Wherein the environmental temperature in the test process is 25 + -2 deg.C, the humidity is 50% + -10%, the spectrum of the adopted light source is AM1.5, and the light intensity is 1000W/m2. The steps and process parameters for manufacturing the back-passivated solar cell by using the silicon wafers treated by the polishing methods of examples 1 to 7 and comparative examples 1 to 9 are the same.
TABLE 2 Performance test results for silicon wafers and back-passivated solar cells
Figure BDA0002245327710000221
As can be seen from the results in Table 2, the silicon wafers of examples 1 to 7 of the present application have both better back surface reflectance and better minority carrier lifetime performance than the silicon wafers of comparative examples 1 to 9. The cell efficiency of the back-passivated solar cells made of the silicon wafers in embodiments 1 to 7 is superior to that of the back-passivated solar cells made of the silicon wafers in comparative examples 1 to 9, and the polishing solution additive and the polishing solution for the back of the silicon wafer and the polishing method for the silicon wafer of the back-passivated crystalline silicon solar cell in embodiments of the present application can improve the reflectivity and the minority carrier lifetime of the back of the silicon wafer and can improve the cell efficiency of the back-passivated crystalline silicon solar cell.
Test example 2
The back surfaces of the silicon wafers after being dried in the embodiment 5 and the comparative example 9 are observed under an electron microscope Zeta-20, the environmental temperature is kept at 24 +/-3 ℃ and the humidity is kept at 50% +/-10% in the observation process, and the electron microscope Zeta-20 adopts a direct current voltage of 24V and a current of 2A. The results are shown in fig. 1 and fig. 2, respectively. Wherein, the scale bar of fig. 1 and fig. 2 is 21 μm.
And (4) analyzing results: as can be seen from the results of fig. 1 and 2, the silicon wafer surface of fig. 1 is flatter than the silicon wafer surface of fig. 2, which illustrates that the polishing solution additive and the polishing solution for the silicon wafer back surface and the method for polishing the silicon wafer of the back-passivated crystalline silicon solar cell according to the embodiment of the present application can improve the flatness of the silicon wafer back surface.
The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to 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. The polishing solution additive for the back surface of the silicon wafer is characterized by comprising the following components in percentage by weight: 1-3% of alkyl trimethyl ammonium hydroxide, 0.5-2% of sodium phosphate, 2-5% of nonionic surfactant and 90-96.5% of water.
2. The polishing solution additive as set forth in claim 1, wherein the polishing solution additive comprises, in weight percent: 2% of alkyl trimethyl ammonium hydroxide, 1-2% of sodium phosphate, 3-4% of nonionic surfactant and 92-94% of water.
3. The additive according to claim 1 or 2, wherein the alkyltrimethylammonium hydroxide is selected from any one or both of dodecyltrimethylammonium hydroxide and hexadecyltrimethylammonium hydroxide.
4. The additive according to claim 1 or 2, wherein the sodium phosphate salt is selected from any one or more of sodium tripolyphosphate, sodium pyrophosphate and sodium hexametaphosphate.
5. The additive according to claim 1 or 2, wherein the nonionic surfactant is selected from either or both of polyethylene glycol ethers and polyethylene glycols.
6. The polishing solution for the back surface of the silicon wafer is characterized by comprising the following components in percentage by weight: 3-5% of alkali substance, 2-5% of the polishing solution additive according to any one of claims 1-5, and 90-95% of water.
7. The polishing solution for the back surface of a silicon wafer as set forth in claim 6, wherein the polishing solution comprises, in weight percent: 3% of the alkali substance, 3-5% of the polishing solution additive and 92-94% of the water; optionally, the alkali substance is selected from at least one of sodium hydroxide and potassium hydroxide.
8. A polishing method for a silicon wafer of a back-passivated crystalline silicon solar cell is characterized by comprising the following steps:
acid polishing is carried out on the back of the silicon chip after the diffusion process is carried out to remove the phosphorosilicate glass;
then cleaning the silicon wafer;
and performing alkali polishing on the back surface of the cleaned silicon wafer by using the polishing solution as defined in claim 6 or 7.
9. The polishing method for the silicon wafer of the back passivated crystalline silicon solar cell as recited in claim 8, wherein the temperature of the alkali polishing step is 65-75 ℃; optionally, the polishing time of the alkali polishing step is 2-5 min.
10. The polishing method of the silicon wafer of the back-passivated crystalline silicon solar cell according to claim 8, characterized in that a cleaning solution used for cleaning the silicon wafer comprises 2-5 wt% of alkali and 3-8 wt% of hydrogen peroxide; the temperature of the cleaning step is 80-100 ℃.
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Application publication date: 20200417