CN113990984B - Cleaning method of PERC crystalline silicon battery - Google Patents
Cleaning method of PERC crystalline silicon battery Download PDFInfo
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- 229910021419 crystalline silicon Inorganic materials 0.000 title claims description 27
- 239000002253 acid Substances 0.000 claims abstract description 109
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 94
- 238000005406 washing Methods 0.000 claims abstract description 63
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000007788 liquid Substances 0.000 claims abstract description 36
- 238000002791 soaking Methods 0.000 claims abstract description 35
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 32
- 239000010703 silicon Substances 0.000 claims abstract description 32
- 238000005554 pickling Methods 0.000 claims abstract description 27
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor 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
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02057—Cleaning during device manufacture
- H01L21/0206—Cleaning during device manufacture during, before or after processing of insulating layers
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
A cleaning method of PERC crystal silicon battery belongs to the field of photovoltaics. The cleaning method is applied to the preparation process of the PERC battery, and the silicon wafer is cleaned after texturing, diffusion, laser heavy doping, oxidization and back oxide layer removal. The cleaning method comprises the following steps: sequentially performing alkali liquor cleaning, acid cleaning and mixed acid cleaning on the battery piece after the back oxide layer is removed; wherein, the acid washing comprises soaking the battery piece by hydrofluoric acid; the mixed acid cleaning comprises the step of soaking the battery piece by using mixed acid liquid of hydrofluoric acid and hydrochloric acid. And the hydrogen ion concentration of hydrofluoric acid in the pickling operation is greater than that of the acid used in the mixed acid cleaning. The cleaning method can clean the back of the battery piece more thoroughly, thereby obtaining a high-quality surface, facilitating the manufacture of a back passivation structure with good passivation effect and obtaining a battery with high conversion efficiency.
Description
Technical Field
The application relates to the field of photovoltaics, in particular to a cleaning method of a PERC crystalline silicon battery.
Background
Based on the pursuit of high cell efficiency, some emerging technologies are developed in the photovoltaic field. Since the PERC crystalline silicon cell has high conversion efficiency, and it mainly involves passivation of the back surface of the cell, and thus has good compatibility with other improved cell conversion efficiency. An important improvement point of the PERC crystal silicon battery is as follows: passivation is performed on the back side of the cell by a thin passivation film (mainly oxide).
In the actual production process, the stability of the conversion efficiency of the PERC crystal silicon battery is required to be improved.
Disclosure of Invention
In view of the above-mentioned shortcomings, the present application provides a cleaning method for a PERC crystalline silicon battery, so as to partially or fully improve or even solve the problem of unstable conversion efficiency of the battery in the PERC crystalline silicon battery.
The application is realized in the following way:
in a first aspect, the present application provides a method for cleaning a PERC crystalline silicon cell, which is applied to a process of preparing a PERC cell, and cleans a silicon wafer after texturing, diffusion, laser heavy doping, oxidation and back surface oxide layer removal.
The cleaning method comprises the following steps:
sequentially performing alkali liquor cleaning, acid cleaning and mixed acid cleaning on the battery piece after the back oxide layer is removed;
pickling includes immersing the battery pieces with hydrofluoric acid;
the mixed acid cleaning comprises the steps of soaking the battery piece by using mixed acid liquid of hydrofluoric acid and hydrochloric acid;
wherein the hydrogen ion concentration of hydrofluoric acid in the pickling operation is greater than the hydrogen ion concentration of the acid used in the mixed acid cleaning.
The cleaning method provided by the exemplary scheme of the application can be used for obtaining the battery piece with the high-quality back surface by combining alkali polishing and acid cleaning so as to manufacture the back passivation film layer of the PERC crystalline silicon battery on the high-quality back surface. In this case, since the acid washing operation may leave a part of the metal ions, particularly in the case of low purity in the acid solution, the remaining metal ions may be removed by the supplemental mixed acid washing operation.
In addition, since a low concentration of acid is used in the mixed acid cleaning step, metal ions possibly introduced in the mixed acid cleaning can be reduced, and the low concentration of mixed acid can also avoid the formation of H-Si bonds between hydrogen ions and dangling bonds on the silicon surface.
Meanwhile, the alkali liquor can be used for cleaning to obtain a smoother back structure, and the back reflectivity can reach more than 43%. If the acid liquid is adopted for cleaning, the back polishing effect is poor due to different reaction mechanisms, and the reflectivity of the back of the silicon wafer after the acid liquid is cleaned is lower than 38%. To the best of the inventors' knowledge, a flatter backside structure is more advantageous for backside passivation during the fabrication process of the PERC cell, and thus has higher conversion efficiency. Thus, in the present example, alkali liquor washing is selected, and then acid washing and mixed acid washing are performed.
According to some examples of the application, a cleaning method includes:
water washing is performed between alkali liquor washing and acid washing, and water washing is performed between acid washing and mixed acid washing.
According to some examples of the application, the alkaline washing comprises alkali soaking with a first alkaline washing liquid, a second alkaline washing liquid and a third alkaline washing liquid in sequence, wherein the first alkaline washing liquid is a mixed aqueous solution of hydrogen peroxide and sodium hydroxide, the second alkaline washing liquid is a sodium hydroxide solution, and the third alkaline washing liquid is a mixed aqueous solution of hydrogen peroxide and sodium hydroxide.
According to some examples of the application, a cleaning method includes:
in the alkaline washing process, the washing is performed after the first alkaline washing liquid, before the second alkaline washing liquid, and the washing is performed after the second alkaline washing liquid, before the third alkaline washing liquid.
In a second aspect, an example of the present application provides a method of cleaning a PERC crystalline silicon cell for use in a process for preparing a PERC cell.
The method is used for cleaning the silicon wafer after texturing, diffusion, laser heavy doping, oxidation, back oxide layer removal, alkali liquor cleaning and acid cleaning.
The cleaning method comprises the following steps:
performing mixed acid cleaning operation on the battery piece after acid cleaning to remove metal ions remained on the back surface of the battery piece; wherein the mixed acid cleaning operation comprises: the battery piece is soaked in mixed acid, and the hydrogen ion concentration of the mixed acid is smaller than that of the acid used in the pickling operation.
According to some examples of the application, hydrofluoric acid is used in the pickling operation and a mixed acid of hydrofluoric acid and hydrochloric acid is used in the mixed acid cleaning operation.
According to some examples of the application, hydrofluoric acid having a concentration of 3wt% to 4wt% is used in the pickling operation.
According to some examples of the application, the concentration of hydrochloric acid in the mixed acid cleaning operation is 0.1wt% to 1.0wt% and the concentration of hydrofluoric acid is 0.1wt% to 1.0wt%.
According to some examples of the application, the soaking time of the battery pieces in hydrofluoric acid is 100 seconds to 150 seconds in the pickling operation;
in the mixed acid cleaning operation, the soaking time of the battery piece in the mixed acid liquid composed of hydrofluoric acid and hydrochloric acid is 100 seconds to 150 seconds.
In a third aspect, the present example provides a method for cleaning a PERC crystalline silicon cell. The method is applied to the preparation process of PERC batteries, and the silicon wafer is cleaned after texturing, diffusion, laser heavy doping, oxidation, back oxide layer removal and alkali liquor cleaning.
The cleaning method comprises the following steps: and soaking and cleaning the battery piece after the alkaline liquid cleaning by sequentially using a first acid liquid and a second acid liquid with the hydrogen ion concentration gradient decreasing, wherein the first acid liquid is hydrofluoric acid liquid, and the second acid liquid is mixed acid liquid of hydrofluoric acid and hydrochloric acid.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic diagram of a current process flow for preparing PERC crystalline silicon cells;
FIG. 2 shows a flow chart of a process of the present application for alkaline cleaning and pickling in the production of PERC crystal silicon cells;
fig. 3 is a schematic structural diagram of a battery plate used in the loading step in the process of fig. 2.
Detailed Description
Referring to fig. 1, the present inventors generally adopt a preparation method in a PERC crystalline silicon cell production line, which comprises the following steps:
p-type silicon wafer texturing (pyramid texturing is formed), diffusion (P-N junction is formed by preparing an N-type layer), SE (laser re-doping), oxidation (surface oxidation layer is formed), PSG removal (back oxidation layer removal), alkaline polishing (back polishing), acid washing (residue removal and dehydration removal), slow extraction and dehydration and drying.
Wherein, alkali polishing and acid washing are both schemes for thoroughly cleaning the back of the battery and improving the cleanliness of the back.
However, in practice, the inventors have found that the pickling operation therein has some problems, resulting in unstable and significant fluctuation in the conversion efficiency of the battery, and generally manifesting as a decrease in the conversion efficiency of the battery.
In the above process, the current acid washing mostly uses 3wt% to 5wt% hydrofluoric acid, and the acid washing is used to remove the potentially residual phosphosilicate glass (PSG). The principle is that the corrosion reaction activity of hydrofluoric acid is utilized to form a fluorine complex; the fluorine complex may be removed from the back surface of the silicon by hydrophobic cleaning.
As a result of the study, the inventors believe that this is mainly because hydrofluoric acid, such as that currently used in the pickling step, is mainly EL grade. While the hydrofluoric acid of this grade still contains a small amount of metal ions. And F in HF solution + The gold ion residue after alkali washing cannot be effectively removed, so that the metal ion residue in the process of the crystalline silicon battery is easy to cause. These residual metal ions can form recombination centers in the cell, thereby affecting the conversion efficiency of the solar crystalline silicon cell.
In response to the above problems, some attempts have been made to use hydrofluoric acid of higher purity. However, this significantly increases the process costs, which is disadvantageous for industrial applications.
In view of this, in the examples of the present application, the inventors have chosen that improving the wafer backside cleanliness (e.g., reducing the metal ion residues) is achieved by optimizing the acid washing step without using higher purity grade materials, thereby helping to improve the quality of the subsequently fabricated passivation film layer and thus the conversion efficiency of the battery.
In an example, the inventors added a mixed acid cleaning step after the acid washing operation of the fabrication process of the PERC crystalline silicon cell. By this step, the metal ions which have not been removed (remain) after the pickling operation are removed.
Further, it is considered that hydrogen ions may combine with dangling bonds on the surface of the silicon wafer to form H-Si bonds, thereby affecting the state of the surface of the silicon wafer. Thus, in this added mixed acid cleaning step, the mixed acid uses a hydrogen ion concentration lower than that of the acid solution used in the acid cleaning operation of the previous step.
Illustratively, as previously described, the acid wash operation of the previous step uses hydrofluoric acid and has a concentration of 3wt% to 4wt%. Thus, in the corresponding added mixed acid cleaning step, a mixed acid solution of hydrofluoric acid and hydrochloric acid is used. And wherein the concentration of hydrofluoric acid is lower than the concentration of hydrofluoric acid in the pickling operation (3 wt% to 4 wt%), and the concentration of hydrochloric acid in the mixed acid solution is also lower than the concentration of hydrofluoric acid in the pickling operation (3 wt% to 4 wt%). In some examples, the concentration of hydrofluoric acid in the mixed acid solution is 0.1wt% to 1wt%, and the concentration of hydrochloric acid is 0.1wt% to 1.0wt%.
Thus, in general, in the present example, the inventors mainly used two different acid solutions to soak and clean the silicon wafer after alkali washing/alkali polishing by using an acidic substance after alkali washing in the current process of manufacturing a PERC crystalline silicon cell. I.e., after the oxidation step and before the annealing step, the alkali polishing step is increased by a plurality of times (in the example, twice) of pickling. And the hydrogen ion concentration of the two different acid solutions is gradually decreased according to the sequence of the process flow. The concentration of hydrogen ions in the acid solution used in the previous cleaning is greater than that in the acid solution used in the subsequent cleaning. Or in some examples, multiple purges with the same acid may be attempted with each acid having a progressively decreasing hydrogen ion concentration. But generally only one acid solution will perform the same. In the example of the application, different acid solutions are used for acid washing before and after acid washing, and the concentration of hydrogen ions is controlled, so that more ideal cleaning effect can be realized.
In other words, in the example of the present application, another acid washing is added after the acid washing operation, and a mixed acid composed of hydrofluoric acid with a low concentration and hydrochloric acid with a low concentration is used in the another acid washing operation, by which metal ions and other impurities on the surface of the silicon wafer are effectively removed. The oxide layer is removed from the back surface of the silicon by the existing acid with relatively high concentration, so that a purer silicon wafer is obtained. And then washed with a relatively low concentration of mixed acid. If the mixed acid with low concentration is directly used for cleaning, the oxide layer can be removed incompletely; if the mixed acid with high concentration is directly used, the H-Si bond is easily generated in a large amount.
Based on the above proposed pickling scheme, the example also proposes a cleaning scheme combining alkali polishing and pickling, and the flow thereof is shown in fig. 2. In this FIG. 2, one of the main improvements of the solution of the application is the implementation of the pickling 2 step.
Wherein the additive is a commercial product, and the components are composed of a surfactant and an additive; the concentration of the additive in the solution stored in the alkaline polishing tank may be selected to be 2wt% to 3wt%.
In addition, in the process steps shown in fig. 2, the "feeding" step refers to the process of texturing (forming pyramid texture) the P-type silicon wafer, diffusing (preparing N-type layer to form P-N junction), and re-doping SE (laser for forming N + Emitter), oxidizing (forming a surface oxide layer) and removing the PSG (removing a back oxide layer). The battery plate used for feeding has a P-type silicon substrate, an N-type doped layer on the front surface of the substrate, and N formed in partial region of the N-type doped layer + An oxide layer over the emitter and the N-doped layer; the structure of which is shown in figure 3.
The alkaline polishing and acid washing of the battery sheet formed after the above process is performed in consideration of the defect in the surface quality of the back surface of the battery sheet (such as the residual of metal ions) and the subsequent obtaining of a high-quality (good passivation effect) back passivation film structure after the above PSG removal process. It should be noted that the alkaline polishing operation may be acid polishing in some examples, but from the aspect of chemical consumption, acid polishing requires a large amount of chemicals, which leads to a significant increase in process cost. The reagents and process conditions used for the caustic polishing and pickling can follow the existing production line scheme, and no special adjustment is required in the application.
In the PERC process currently practiced by the inventors, a monomer pickling tank is used. The wafer is etched/oxidized by the front end (process operation prior to pickling 1) and then immersed in a single acid solution in a monomer pickling tank for 100-150S. The monomer pickling tank in the example uses an EL grade HF solution with a concentration of 3wt% to 4wt%.
Hydrofluoric acid can be mixed with residual PSG (phosphorus-containing oxidation mixture/phosphosilicate glass) on the surface of a silicon wafer and Na-containing material introduced in alkaline washing process + And (3) a mixture of salts and bases to form a hexafluorocomplex. Because the hexafluoro complex has good hydrophobicity, the reaction product (hexafluoro complex) and residual HF can be rinsed cleanly in a washing tank after the acid tank is washed by deionized water, so that the surface of the silicon wafer is purer and ready for subsequent passivation.
However, as the aforementioned reagents may not be of high purity (EL grade chemicals themselves have impurities) or metal ion impurities may be introduced due to environmental, carrier, automation equipment, etc. conditions in the manufacturing process, F in HF solution + Is not matched with Fe in solution + 、Al + 、Ca + And reacting the trace metal ions. This results in metal particles being deposited on the silicon wafer surface and constituting surface recombination centers in the subsequent high temperature passivation process, which can affect the conversion efficiency of the battery plate.
For such a practical situation, the inventors have selected to perform cleaning by adding a mixed acid. In the mixed acid, on the one hand, salts are introducedAn acid which can be mixed with Fe as described above + 、Al + 、Ca + The trace metal ions react, so that most of the metal particles can be removed by rinsing with deionized water later. On the other hand, HF can continuously generate a complex through the reaction of a small amount of oxides of the silicon wafer, and ensures the hydrophobicity of the surface of the silicon wafer, so that the silicon wafer is favorable for rinsing with high-purity deionized water after the mixed acid is cleaned, and the reaction product is removed through rinsing with high-purity water. Further, considering that a high hydrogen ion concentration forms an h—si bond with silicon, the hydrogen ion concentrations of hydrofluoric acid and hydrochloric acid used in the mixed acid are both lower than those of hydrofluoric acid used in the previous step.
In other words, the use of hydrochloric acid can provide an effective cleaning effect against the existing case where metal ions are not removed after the pickling operation. However, the hydrophobicity of the back surface of the battery sheet is difficult to be ensured, so that the effect of rinsing with deionized water is greatly reduced, and the problem can be well overcome by using hydrofluoric acid.
The foregoing describes embodiments of the present application in detail with reference to examples, but it will be understood by those skilled in the art that the examples are for illustration only and are not to be construed as limiting the scope of the application. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The present application is described in further detail below with reference to examples.
The structure of the PERC crystalline silicon cell in the following example is as follows:
a P-type silicon substrate;
front side of P-type silicon substrate: an n+ doped layer (with a selective emitter), an oxide layer over the n+ doped layer and a front electrode;
back side of P-type silicon substrate: a passivation film layer, a locally contacted aluminum back surface field and a back electrode over the passivation film.
The battery sheet for performing the cleaning operation is a structure formed before the passivation film layer is manufactured, and refer to fig. 3.
Example 1
The cleaning scheme of the structure (see the battery piece of fig. 3) before the passivation film layer is manufactured in the PERC crystalline silicon battery with the structure is as follows:
(1) The battery piece is soaked in a mixed solution of sodium hydroxide solution and hydrogen peroxide at the temperature of 40 ℃ for 40s. The mass fraction of NaOH in the mixed solution is 0.1%, H 2 O 2 Is 0.1% by mass.
(2) And fishing out the battery piece, and rinsing in deionized water for 120 seconds.
(3) The cell sheet was fished out and immersed in a solution containing NaOH and additives (surfactant and deaerator, commercially available products). The concentration of the additive is 2.0%, wherein the mass fraction of NaOH is 1%, the temperature is 64 ℃, and the soaking time is 240s.
(4) And after the battery piece is fished out, rinsing with deionized water for 120 seconds.
(5) And fishing out the battery piece and soaking the battery piece in a mixed solution of sodium hydroxide solution and hydrogen peroxide. Wherein the mass fraction of NaOH is 1%, H 2 O 2 The mass fraction of the mixture is 1%, the temperature of the mixed solution is 30 ℃, and the soaking time is 120s.
(6) Placing the battery piece into deionized water for rinsing, wherein the rinsing time is 120s;
(7) And fishing out the battery piece and soaking the battery piece in hydrofluoric acid solution. The temperature of hydrofluoric acid is normal temperature (23 ℃), the soaking time is 120s, and the concentration of HF is 1%.
(8) And fishing out the battery pieces and soaking the battery pieces in mixed acid liquid of hydrofluoric acid and hydrochloric acid. The temperature of the mixed acid solution is normal temperature (23 ℃), and the soaking time is 120s; wherein the mass concentration of HF is 0.8% and the mass concentration of HCl is 0.5%.
(9) The battery piece is fished out and rinsed by deionized water; the deionized water temperature was room temperature (23 ℃) and the rinsing time was 100s. After the rinsing is finished, the battery piece is lifted out of the water surface in a slow lifting mode;
(10) And drying the proposed battery piece.
Comparative example 1
The cleaning scheme of the structure (see the battery piece of fig. 3) before the passivation film layer is manufactured in the PERC crystalline silicon battery with the structure is as follows:
(1) The battery piece is soaked in a mixed solution of sodium hydroxide solution and hydrogen peroxide at the temperature of 40 ℃ for 40s. The mass fraction of NaOH in the mixed solution is 0.1%, H 2 O 2 Is 0.1% by mass.
(2) And fishing out the battery piece, and rinsing in deionized water for 120 seconds.
(3) The battery pieces were fished out and immersed in a solution containing NaOH and additives (the same additives as in example 1). Wherein the concentration of the additive is 2.0%, the mass fraction of NaOH is 1%, the temperature is 64 ℃, and the soaking time is 240s.
(4) And after the battery piece is fished out, rinsing with deionized water for 120 seconds.
(5) And fishing out the battery piece and soaking the battery piece in a mixed solution of sodium hydroxide solution and hydrogen peroxide. Wherein the mass fraction of NaOH is 1%, H 2 O 2 The mass fraction of the mixture is 1%, the temperature of the mixed solution is 30 ℃, and the soaking time is 120s.
(6) Placing the battery piece into deionized water for rinsing, wherein the rinsing time is 120s;
(7) And fishing out the battery piece and soaking the battery piece in hydrofluoric acid solution. The temperature of hydrofluoric acid is normal temperature (23 ℃), the soaking time is 120s, and the concentration of HF is 1%.
(8) The battery piece is fished out and rinsed by deionized water; the deionized water temperature was room temperature (23 ℃) and the rinsing time was 100s. After the rinsing is finished, the battery piece is lifted out of the water surface in a slow lifting mode;
(9) And drying the proposed battery piece.
The plurality of battery pieces on the two production lines were collected respectively for electrical performance testing, and the test results are shown in table 1 below.
Table 1 performance of batteries fabricated under different process conditions.
From the data of table 1, it is understood that the battery obtained by adding the mixed acid cleaning solution in the exemplary embodiment of the present application can obtain the effects of 1.4mV higher in the open voltage, 12mA higher in the short-circuit current and 5 Ω higher in the resistance, and the conversion efficiency is increased to 0.018% (about 0.02%).
Example 2
The cleaning scheme of the structure (see the battery piece of fig. 3) before the passivation film layer is manufactured in the PERC crystalline silicon battery with the structure is as follows:
(1) The battery piece is soaked in a mixed solution of sodium hydroxide solution and hydrogen peroxide at the temperature of 40 ℃ for 40s. The mass fraction of NaOH in the mixed solution is 0.1%, H 2 O 2 Is 0.1% by mass.
(2) And fishing out the battery piece, and rinsing in deionized water for 120 seconds.
(3) The battery pieces were fished out and immersed in a solution containing NaOH and additives (same as the additives in example 1). Wherein the concentration of the additive is 2.0%, the mass fraction of NaOH is 1%, the temperature is 64 ℃, and the soaking time is 240s.
(4) After the battery is broken and fished out, the battery is rinsed by deionized water, and the rinsing time is 120s.
(5) And fishing out the battery piece and soaking the battery piece in a mixed solution of sodium hydroxide solution and hydrogen peroxide. Wherein the mass fraction of NaOH is 1%, H 2 O 2 The mass fraction of the mixture is 1%, the temperature of the mixed solution is 30 ℃, and the soaking time is 120s.
(6) Placing the battery piece into deionized water for rinsing, wherein the rinsing time is 120s;
(7) And fishing out the battery piece and soaking the battery piece in hydrofluoric acid solution. The temperature of hydrofluoric acid is normal temperature (23 ℃), the soaking time is 120s, and the concentration of HF is 1%.
(8) And fishing out the battery pieces and soaking the battery pieces in mixed acid liquid of hydrofluoric acid and hydrochloric acid. The temperature of the mixed acid solution is normal temperature (23 ℃), and the soaking time is 120s; wherein the mass concentration of HF is 2.0% and the mass concentration of HCl is 0.5%.
(9) The battery piece is fished out and rinsed by deionized water; the deionized water temperature was room temperature (23 ℃) and the rinsing time was 100s. After the rinsing is finished, the battery piece is lifted out of the water surface in a slow lifting mode;
(10) And drying the proposed battery piece.
Comparative example 2
The cleaning scheme of the structure (see the battery piece of fig. 3) before the passivation film layer is manufactured in the PERC crystalline silicon battery with the structure is as follows:
(1) The battery piece is soaked in a mixed solution of sodium hydroxide solution and hydrogen peroxide at the temperature of 40 ℃ for 40s. The mass fraction of NaOH in the mixed solution is 0.1%, H 2 O 2 Is 0.1% by mass.
(2) And fishing out the battery piece, and rinsing in deionized water for 120 seconds.
(3) The battery pieces were fished out and immersed in a solution containing NaOH and additives (same as the additives in example 1). Wherein the concentration of the additive is 2.0%, the mass fraction of NaOH is 1%, the temperature is 64 ℃, and the soaking time is 240s.
(4) And after the battery piece is fished out, rinsing with deionized water for 120 seconds.
(5) And fishing out the battery piece and soaking the battery piece in a mixed solution of sodium hydroxide solution and hydrogen peroxide. Wherein the mass fraction of NaOH is 1%, H 2 O 2 The mass fraction of the mixture is 1%, the temperature of the mixed solution is 30 ℃, and the soaking time is 120s.
(6) Placing the battery piece into deionized water for rinsing, wherein the rinsing time is 120s;
(7) And fishing out the battery piece and soaking the battery piece in hydrofluoric acid solution. The temperature of hydrofluoric acid is normal temperature (23 ℃), the soaking time is 120s, and the concentration of HF is 1%.
(8) The battery piece is fished out and rinsed by deionized water; the deionized water temperature was room temperature (23 ℃) and the rinsing time was 100s. After the rinsing is finished, the battery piece is lifted out of the water surface in a slow lifting mode;
(9) And drying the proposed battery piece.
The plurality of battery pieces on the two production lines were collected respectively for electrical performance testing, and the test results are shown in table 2 below.
Table 2 performance of batteries fabricated under different process conditions.
From the data in table 2, it can be seen that the increase in the exemplary embodiment of the present application uses a mixed acid cleaning solution to obtain a battery, and when the HF concentration in the mixed acid is higher than that in the pickling 1 tank, the open voltage can be reduced by 0.5mV, the short-circuit current is reduced by 4mA, the leakage current is increased by 5.6mA, and the conversion efficiency is lost by 0.014%. The inventors analyzed that this is mainly because the HF solution concentration was too large, resulting in metal ion residues therein, and thus, excessive leakage current.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (7)
1. The cleaning method of the PERC crystal silicon battery is characterized by being applied to the preparation process of the PERC battery, and cleaning is carried out on a silicon wafer after texturing, diffusion, laser heavy doping, oxidation and back surface oxide layer removal, and the cleaning method comprises the following steps:
sequentially performing alkali liquor cleaning, acid cleaning and mixed acid cleaning on the battery piece after the back oxide layer is removed;
the pickling comprises soaking the battery piece with hydrofluoric acid;
the mixed acid cleaning comprises the steps of soaking the battery piece by using mixed acid liquid of hydrofluoric acid and hydrochloric acid;
wherein the hydrogen ion concentration of hydrofluoric acid in the pickling operation is greater than the hydrogen ion concentration of the acid used in the mixed acid cleaning.
2. The method for cleaning a PERC crystalline silicon cell according to claim 1, characterized in that the cleaning method comprises:
water washing is performed between alkali liquor washing and acid washing, and water washing is performed between acid washing and mixed acid washing.
3. The method for cleaning a PERC crystalline silicon cell according to claim 1 or 2, wherein the alkali cleaning comprises alkali soaking with a first alkali washing liquid, a second alkali washing liquid and a third alkali washing liquid in sequence, respectively, wherein the first alkali washing liquid is a mixed aqueous solution of hydrogen peroxide and sodium hydroxide, the second alkali washing liquid is a sodium hydroxide solution, and the third alkali washing liquid is a mixed aqueous solution of hydrogen peroxide and sodium hydroxide.
4. The method for cleaning a PERC crystalline silicon cell according to claim 3, comprising:
in the alkaline washing process, the washing is performed after the first alkaline washing liquid, before the second alkaline washing liquid, and the washing is performed after the second alkaline washing liquid, before the third alkaline washing liquid.
5. The method for cleaning a PERC crystalline silicon cell according to claim 1 or 2, wherein hydrofluoric acid having a concentration of 3wt% to 4wt% is used in the acid washing operation.
6. The method of cleaning a PERC crystalline silicon cell according to claim 5, wherein the concentration of hydrochloric acid in the mixed acid cleaning operation is 0.1wt% to 1.0wt%, and the concentration of hydrofluoric acid is 0.1wt% to 1.0wt%.
7. The method for cleaning a PERC crystalline silicon cell according to claim 6, wherein the pickling operation is performed for a time period of 100 seconds to 150 seconds for immersing the cell in hydrofluoric acid;
in the mixed acid cleaning operation, the soaking time of the battery piece in the mixed acid liquid formed by hydrofluoric acid and hydrochloric acid is 100 seconds to 150 seconds.
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