CN109148262B - Cleaning method of solar polycrystalline black silicon wafer - Google Patents
Cleaning method of solar polycrystalline black silicon wafer Download PDFInfo
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- CN109148262B CN109148262B CN201810813246.9A CN201810813246A CN109148262B CN 109148262 B CN109148262 B CN 109148262B CN 201810813246 A CN201810813246 A CN 201810813246A CN 109148262 B CN109148262 B CN 109148262B
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- 229910021418 black silicon Inorganic materials 0.000 title claims abstract description 142
- 238000004140 cleaning Methods 0.000 title claims abstract description 82
- 238000000034 method Methods 0.000 title claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000005406 washing Methods 0.000 claims abstract description 31
- 238000006243 chemical reaction Methods 0.000 claims abstract description 25
- 239000002253 acid Substances 0.000 claims abstract description 24
- 238000002310 reflectometry Methods 0.000 claims abstract description 14
- 238000009792 diffusion process Methods 0.000 claims abstract description 8
- 235000012431 wafers Nutrition 0.000 claims description 134
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 40
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 40
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 33
- 239000003513 alkali Substances 0.000 claims description 22
- 239000008367 deionised water Substances 0.000 claims description 20
- 229910021641 deionized water Inorganic materials 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 5
- 238000005554 pickling Methods 0.000 claims description 5
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 2
- 239000012498 ultrapure water Substances 0.000 claims description 2
- 238000011049 filling Methods 0.000 abstract description 7
- 238000003860 storage Methods 0.000 abstract description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 4
- 238000009501 film coating Methods 0.000 abstract description 3
- 239000007888 film coating Substances 0.000 abstract description 3
- 230000003749 cleanliness Effects 0.000 abstract description 2
- 229910052710 silicon Inorganic materials 0.000 abstract description 2
- 239000010703 silicon Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 44
- 239000012535 impurity Substances 0.000 description 16
- 230000035484 reaction time Effects 0.000 description 8
- 239000011259 mixed solution Substances 0.000 description 7
- 238000011109 contamination Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 239000012459 cleaning agent Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000000428 dust Substances 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- 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
- H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
- H01L21/02052—Wet cleaning only
-
- 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
-
- 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
The invention relates to the field of solar polycrystalline black silicon chips and discloses a cleaning method of a solar polycrystalline black silicon chip. The cleaning method comprises primary water washing, alkaline washing, primary rinsing, mixed acid washing and secondary rinsing, and the method is suitable for cleaning the black silicon wafer with oxidized or polluted surface after long-time storage or transportation. The cleaning method can ensure that the reflectivity change of the black silicon wafer is not more than 2% before and after cleaning, and can obtain higher short-circuit current. The surface cleanliness of the cleaned silicon wafer is improved, and subsequent diffusion, film coating and other processes are facilitated. Meanwhile, the alkaline washing step in the cleaning method can modify the suede of the black silicon wafer again, so that higher open-circuit voltage and filling factors are obtained, and a battery wafer with higher conversion efficiency is obtained.
Description
Technical Field
The invention relates to the field of solar polycrystalline black silicon chips, in particular to a cleaning method of a solar polycrystalline black silicon chip.
Background
The polycrystalline black silicon wafer has relatively low reflectivity and is the mainstream of future polycrystalline battery wafers, but expensive dry equipment and a wet process with environmental protection pressure can only inhibit the preparation technology of black silicon by some enterprises. And because the efficiency of the traditional additive diamond wire is low, the black silicon wafer after texturing replaces the original silicon wafer, so that the effective way of improving the conversion efficiency of the polycrystalline cell is provided.
At present, the preparation method of the black silicon mainly comprises a reaction ion etching method and a metal auxiliary chemical solution etching method, and no matter which black silicon piece is purchased in a battery factory, the problems of the storage time and the transportation time exist, and the black silicon piece is easily oxidized and polluted in the process. Before the black silicon wafer enters the diffusion process, a one-step cleaning process is needed to ensure the conversion efficiency of the black silicon wafer, and meanwhile, the pollution problem of the cell is reduced to the maximum extent.
The surfaces of the black silicon wafers after long-time storage and transportation are easily oxidized and polluted, so a one-step cleaning process is required before diffusion. At present, the cleaning method of the black silicon wafer mainly adopts mixed acid liquid to clean through different cleaning equipment. Although the cleaning method can remove the metal impurities on the surface of the black silicon wafer, the damage of the texture surface of the black silicon wafer after placement or transportation cannot be removed, and the conversion efficiency of the cleaned black silicon wafer is not obviously improved.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for cleaning a solar polycrystalline black silicon wafer. The cleaning method is specially designed for black silicon wafers which are placed for a long time or have surfaces contaminated or oxidized during transportation. The cleaning method can improve the surface cleanliness of the black silicon wafer, reduce the pollution proportion of the black silicon wafer, and modify the suede of the black silicon wafer to a certain extent. The cleaning method can improve the open-circuit voltage and the filling factor of the black silicon wafer and improve the conversion efficiency of the solar polycrystalline black silicon wafer.
The specific technical scheme of the invention is as follows: a cleaning method of a solar polycrystalline black silicon wafer comprises the following steps:
(1) primary water washing: washing the surface of the black silicon wafer with water for 10-60s at normal temperature;
(2) alkali washing: treating the black silicon wafer treated in the step (1) with 0.5-5wt% of potassium hydroxide solution for 10-100s, wherein the temperature of the potassium hydroxide solution is 20-30 ℃, and adding the potassium hydroxide solution along with the reaction;
(3) primary rinsing: washing the black silicon wafer treated in the step (2) with water for 10-60s at normal temperature;
(4) mixed pickling: treating the black silicon wafer treated in the step (3) for 10-100s by using a mixed acid solution prepared from a hydrochloric acid solution with the concentration of 6-20wt%, a hydrofluoric acid solution with the concentration of 1-7wt% and water, wherein the volume ratio of the hydrochloric acid solution to the hydrofluoric acid solution to the water in the mixed acid solution is 3-10:1-6:2-14, the temperature is 20-30 ℃, and the mixed acid solution is replenished along with the reaction;
(5) and (3) secondary rinsing: and (3) finally, washing the black silicon wafer treated in the step (4) with water for 10-60s at normal temperature, drying the black silicon wafer for 30-60s at the temperature of 50-100 ℃, and then performing subsequent processes.
According to the invention, the black silicon wafer is cleaned by water, alkali solution and mixed acid solution, the treatment temperature is very mild, so that the surface of the black silicon wafer is cleaner, the subsequent processes of diffusion, film coating and the like are facilitated, and the pollution problem of the cell can be reduced. The suede of the black silicon wafer can be modified by alkali washing, and the reflectivity change before and after cleaning is not more than 2%, so that the short-circuit current, the open-circuit voltage and the filling factor of the black silicon wafer are improved. And the acid cleaning can remove metal impurities and silicon oxide layers on the surfaces of the black silicon wafers. The invention adopts the mixed acid solution of the hydrochloric acid solution and the hydrofluoric acid solution for cleaningComplexing Pt with chloride ions in black silicon wafer and hydrochloric acid solution2+、Au3+、Ag+、Cd2+、Hg2+、Cu+And metal ions are generated, so that metal impurities on the surface of the black silicon wafer can be effectively removed. The hydrofluoric acid solution can remove a very thin silicon oxide layer formed on the surface of the black silicon wafer in the storage or transportation process. Adjusting the cleaning time of water can wash away impurities and residual acid and alkali solution on the surface of the black silicon wafer. The concentration of acid and alkali solution and the cleaning time are adjusted to obtain higher open-circuit voltage and filling factor, and finally the battery piece with high conversion efficiency is obtained.
By the cleaning method, the pollution proportion of the black silicon wafer is reduced to one ninth of the original pollution proportion, and the conversion efficiency of the black silicon wafer is improved by 0.1%. At present, the conversion efficiency of a common polycrystalline black silicon wafer in the prior art is low, the development of the polycrystalline black silicon wafer reaches the bottleneck period, and the conversion efficiency is difficult to improve. After the surface of the black silicon wafer is oxidized or polluted, the conversion efficiency is reduced to some extent, and the performance of the solar polycrystalline cell is influenced. At present, no cleaning method is available at home and abroad, which can not only remove impurities on the surface of the black silicon wafer, but also can ensure that the conversion efficiency of the cleaned black silicon wafer reaches the level before the black silicon wafer is polluted. The inventor removes impurities and an oxide layer on the surface of the black silicon wafer and improves the conversion efficiency of the black silicon wafer by adjusting the reagent concentration and the cleaning time in the cleaning process of the black silicon wafer. Although the 0.1% improvement is literally small, the 0.1% improvement in conversion efficiency is also very difficult in the field of solar multicrystalline silicon.
The cleaning process of the invention is not greatly different from the similar product texturing cleaning in the prior art, but in the field of solar polycrystalline black silicon wafers, the number of commonly used cleaning agents is several, the selection of the cleaning agents is difficult to break through at present, and the performance difference of the black silicon wafers after cleaning mainly comes from the adjustment of the concentration, the proportion and the cleaning time of different cleaning agents. For a certain performance of the black silicon wafer after cleaning, a better performance can be obtained through a simple limited number of tests, but the comprehensive performance of the cleaned solar polycrystalline black silicon wafer is not imaginarily simple to improve. For example, increasing the concentration or amount of a cleaning agent during the cleaning process may reduce the contamination ratio to near zero, but at the same time, it may affect the surface reflectivity and short-circuit current of the black silicon wafer, and at present, people cannot summarize a more obvious rule from such a complicated and numerous experiment. The method is also the reason that no cleaning method which can remove impurities on the surface of the polycrystalline black silicon wafer and ensure that the conversion efficiency of the cleaned black silicon wafer reaches the level before the black silicon wafer is polluted exists at present.
Preferably, the black silicon wafer is prepared by a wet method, wherein the surface of the black silicon wafer is polluted or oxidized during long-time placement or transportation after texturing and cleaning and before diffusion.
The cleaning method is specially designed for the black silicon wafer prepared by the wet method, the surface of which is polluted or oxidized after the flocking cleaning and before the diffusion, and the black silicon wafer is placed for a long time or transported. The cleaning step of the present invention is also designed according to the characteristics of the black silicon wafer in terms of impurities generated on the surface thereof during long-term storage or transportation.
Preferably, the concentration of the potassium hydroxide solution in the step (2) is 1 to 4 wt%. The potassium hydroxide solution can wash off oil stains on the surface of the black silicon wafer and modify the suede of the black silicon wafer again. The change value of the surface reflectivity of the cleaned black silicon wafer is larger than 2% due to the excessively high concentration of the potassium hydroxide, and the short-circuit current of the black silicon wafer is reduced. The reflectivity, open-circuit voltage and filling factor of the black silicon wafer before and after cleaning can be controlled by adjusting the concentration of the potassium hydroxide solution and the cleaning time.
Preferably, the addition amount of the potassium hydroxide solution in the step (2) is 20-50ml for every 100 black silicon wafers processed. As the reaction time progresses, the concentration of alkali in the solution decreases, so that addition of alkali solution is required.
Preferably, the addition amount of the mixed acid solution in the step (4) is that 100-200ml of hydrochloric acid solution and 40-100ml of hydrofluoric acid solution are added for each 100 black silicon wafers to be processed. The concentration of acid in the solution is reduced along with the reaction time, so that hydrochloric acid and hydrofluoric acid are required to be supplemented, and the hydrochloric acid solution and the hydrofluoric acid solution are supplemented according to the volume ratio of the hydrochloric acid solution to the hydrofluoric acid solution in the original mixed solution.
Preferably, the water in the steps (1), (3) and (5) is at least one of deionized water and ultrapure water.
Preferably, the time for washing water in the step (1) is 30-60s, the time for treating the potassium hydroxide solution in the step (2) is 40-60s, the time for washing water in the step (3) is 40-60s, the time for treating the mixed acid solution in the step (4) is 40-60s, and the time for washing water in the step (5) is 40-60 s.
The water cleaning time in the step (1) of the cleaning method is preferably 30-60s, and the cleaning time is too short, so that impurities such as dust attached to the surface of the black silicon wafer can not be washed cleanly. The treatment time of the potassium hydroxide solution in the step (2) is preferably 40-60s, the cleaning time is too short, oil stains on the surface of the black silicon wafer are not cleaned, and the treatment time is too long, so that the reflectivity of the surface of the black silicon wafer is increased. And (3) washing with water mainly comprises washing off alkali liquor remaining on the surface of the black silicon wafer treated in the step (2), and if the washing time is too short, the black silicon wafer cannot be washed cleanly. The cleaning time of the mixed acid solution in the step (4) is preferably 40-60s, the cleaning time is too short, metal impurities and a silicon oxide layer on the surface of the black silicon wafer are not completely removed, and the conversion efficiency of the black silicon wafer is affected due to too long cleaning time. The water cleaning time in the step (5) is preferably 40-60s, and the cleaning time is too short, so that residual acid liquor on the surface of the black silicon wafer can not be completely removed.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, the black silicon wafer is cleaned by water, alkali solution and mixed acid solution, so that the surface is cleaner, and the subsequent processes of diffusion, film coating and the like are facilitated. The suede of the black silicon wafer can be modified by alkali cleaning, and the reflectivity change before and after cleaning is not more than 2%, so that higher short-circuit current, open-circuit voltage and filling factor are obtained.
Detailed Description
The present invention will be further described with reference to the following examples. The devices, connections, and methods referred to in this disclosure are those known in the art, unless otherwise indicated.
Example 1
A cleaning method of a solar polycrystalline black silicon wafer comprises the following steps:
(1) primary water washing: and (3) cleaning the surface of the black silicon wafer for 30s by using deionized water at normal temperature, and cleaning impurities such as dust on the surface of the black silicon wafer.
(2) Alkali washing: and (3) treating the black silicon wafer cleaned by deionized water with a potassium hydroxide solution with the concentration of 1 wt% for 40s, wherein the temperature of the potassium hydroxide solution is 20 ℃, and 30mL of potassium hydroxide solution is added for every 100 black silicon wafers treated along with the reaction time. The process can modify the structure of the surface of the black silicon wafer again, and the change of the reflectivity before and after the process is controlled not to exceed 2 percent, otherwise, the short-circuit current of the black silicon wafer is reduced.
(3) Primary rinsing: and (3) cleaning the black silicon wafer treated by the potassium hydroxide solution with deionized water at normal temperature for 40s, and cleaning the residual potassium hydroxide solution.
(4) Mixed pickling: then, the black silicon wafer cleaned by the deionized water is treated for 40 seconds by using a mixed solution prepared by 30L of 6 wt% hydrochloric acid solution, 10L of 1 wt% hydrofluoric acid solution and 140L of deionized water, and the temperature is 20 ℃. As the reaction time progressed, 100mL of hydrochloric acid solution and 40mL of hydrofluoric acid solution were added for each 100 black silicon wafers treated. The mixed solution of hydrochloric acid and hydrofluoric acid can remove residual alkali liquor and impurity metal ions.
(5) And (3) secondary rinsing: and finally, washing the acid liquor remained on the surface of the black silicon wafer by using deionized water at normal temperature for 40s, drying the black silicon wafer for 40s at the temperature of 50 ℃, and then performing subsequent processes.
Example 2:
a cleaning method of a solar polycrystalline black silicon wafer comprises the following steps:
(1) primary water washing: and (3) cleaning the surface of the black silicon wafer for 50s at normal temperature by using deionized water, and cleaning impurities such as dust on the surface of the black silicon wafer.
(2) Alkali washing: and (3) treating the black silicon wafer cleaned by the deionized water for 50s by using a 2 wt% potassium hydroxide solution, wherein the temperature of the potassium hydroxide solution is 25 ℃, and adding 40mL of potassium hydroxide solution into every 100 black silicon wafers treated along with the reaction time. The process can modify the structure of the surface of the black silicon wafer again, and the change of the reflectivity before and after the process is controlled not to exceed 2 percent, otherwise, the short-circuit current of the black silicon wafer is reduced.
(3) Primary rinsing: and (3) cleaning the black silicon wafer treated by the potassium hydroxide solution by using deionized water at normal temperature for 50s, and cleaning the residual potassium hydroxide solution.
(4) Mixed pickling: then, the black silicon wafer cleaned by the deionized water is treated for 50s by using a mixed solution prepared by 90L of hydrochloric acid solution with the concentration of 18 wt%, 30L of hydrofluoric acid solution with the concentration of 3.3 wt% and 60L of deionized water, and the temperature is 25 ℃. As the reaction time progressed, 150mL of hydrochloric acid solution and 60mL of hydrofluoric acid solution were added for each 100 black silicon wafers treated. The mixed solution of hydrochloric acid and hydrofluoric acid can remove residual alkali liquor and impurity metal ions.
(5) And (3) secondary rinsing: and finally, washing the acid liquor remained on the surface of the black silicon wafer by using deionized water at normal temperature for 50s, drying the black silicon wafer for 50s at 75 ℃, and then performing subsequent processes.
Example 3:
a cleaning method of a solar polycrystalline black silicon wafer comprises the following steps:
(1) primary water washing: and (3) cleaning the surface of the black silicon wafer for 50s at normal temperature by using deionized water, and cleaning impurities such as dust on the surface of the black silicon wafer.
(2) Alkali washing: and (3) treating the black silicon wafer cleaned by the deionized water for 50s by using a potassium hydroxide solution with the concentration of 4wt%, wherein the temperature of the potassium hydroxide solution is 30 ℃, and 50mL of potassium hydroxide solution is added for every 100 black silicon wafers treated along with the reaction time. The process can modify the structure of the surface of the black silicon wafer again, and the change of the reflectivity before and after the process is controlled not to exceed 2 percent, otherwise, the short-circuit current of the black silicon wafer is reduced.
(3) Primary rinsing: and (3) cleaning the black silicon wafer treated by the potassium hydroxide solution with deionized water at normal temperature for 60s, and cleaning the residual potassium hydroxide solution.
(4) Mixed pickling: then, the black silicon wafer cleaned by the deionized water is treated for 50s by using a mixed solution prepared by 100L of hydrochloric acid solution with the concentration of 20wt%, 60L of hydrofluoric acid solution with the concentration of 6.7 wt% and 20L of deionized water, and the temperature is 30 ℃. As the reaction time progressed, 200mL of hydrochloric acid solution and 100mL of hydrofluoric acid solution were added for each 100 black silicon wafers treated. The mixed solution of hydrochloric acid and hydrofluoric acid can remove residual alkali liquor and impurity metal ions.
(5) And (3) secondary rinsing: and finally, washing the acid liquor remained on the surface of the black silicon wafer by using deionized water at normal temperature for 60s, drying the black silicon wafer for 60s at the temperature of 100 ℃, and then performing subsequent processes.
Evaluation of Performance
The black silicon wafer is divided into sister wafers before cleaning, examples 1-3 and a comparison group (not cleaned) are different except for the cleaning process, and the conditions of other battery wafer manufacturing processes are ensured to be the same. Table 1 below shows the measured electrical parameters of examples 1-3 and the comparative group (not cleaned). The following Table 2 shows the contamination ratio of the cell pieces after screen printing of examples 1-3 and the comparative group (not cleaned).
TABLE 1
| Uoc(V) | Isc(A) | Rs(mΩ) | Rsh(Ω) | FF(％) | NCell(％) | |
| Example 1 | 0.6390 | 9.1799 | 2.41 | 314.32 | 79.30 | 18.93 |
| Example 2 | 0.6399 | 9.1900 | 2.32 | 375.44 | 79.32 | 18.98 |
| Example 3 | 0.6410 | 9.1630 | 2.42 | 323.44 | 79.30 | 18.95 |
| Comparison group | 0.6385 | 9.1700 | 2.22 | 380.44 | 79.23 | 18.88 |
TABLE 2
| Proportion of pollution | |
| Example 1 | 0.15％ |
| Example 2 | 0.1％ |
| Example 3 | 0.1％ |
| Comparison group | 0.9％ |
Wherein Uoc is open-circuit voltage, Isc is short-circuit current, Rs is series resistance, Rsh is parallel resistance, FF is fill factor, and Ncell is conversion efficiency of the cell. The comparative groups were evaluated using the same evaluation parameters as those used in examples 1 to 3. Compared with a comparison group, the open-circuit voltage, the short-circuit current and the filling factor of the alkali cleaning step in the embodiment 1, the embodiment 2 and the embodiment 3 are improved to a certain extent, the concentration of alkali in the alkali cleaning step in the embodiment 3 is 2 times of that in the embodiment 2, and the alkali cleaning temperature is higher. The reflectivity of the black silicon wafer after cleaning in example 3 is increased by 2%, so the short-circuit current of example 3 is reduced compared with that of example 2, while the reflectivity of example 2 is increased by only 1%, so the conversion efficiency of the black silicon wafer after treatment in example 3 is low. From the contamination ratio data, the contamination ratios in examples 1 to 3 were all reduced to a large extent, and the minimum contamination ratios in examples 2 and 3 were substantially ensured. Therefore, the conversion efficiency and the contamination ratio were combined to finally determine that example 2 is the best example, and the conversion efficiency of the black silicon wafer was improved by 0.1% compared with the unwashed comparative group. Although the improvement of 0.1% is relatively small in a literal view, the improvement of 0.1% in the conversion efficiency is already a very large improvement in the field of solar polycrystalline silicon.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.
Claims (6)
1. A method for cleaning a solar polycrystalline black silicon wafer is characterized by comprising the following steps:
(1) primary water washing: washing the surface of the black silicon wafer with water for 10-60s at normal temperature;
(2) alkali washing: treating the black silicon wafer treated in the step (1) with 0.5-5wt% of potassium hydroxide solution for 10-100s, wherein the temperature of the potassium hydroxide solution is 20-30 ℃, and adding the potassium hydroxide solution along with the reaction; the reflectivity change is controlled not to exceed 2% in the alkali washing process;
(3) primary rinsing: washing the black silicon wafer treated in the step (2) with water for 10-60s at normal temperature;
(4) mixed pickling: treating the black silicon wafer treated in the step (3) for 10-100s by using a mixed acid solution prepared from a hydrochloric acid solution with the concentration of 6-20wt%, a hydrofluoric acid solution with the concentration of 1-7wt% and water, wherein the volume ratio of the hydrochloric acid solution to the hydrofluoric acid solution to the water in the mixed acid solution is 3-10:1-6:2-14, the temperature is 20-30 ℃, and the mixed acid solution is replenished along with the reaction;
(5) and (3) secondary rinsing: finally, washing the black silicon wafer treated in the step (4) with water for 10-60s at normal temperature, drying the black silicon wafer for 30-60s at 50-100 ℃, and then performing subsequent processes;
the black silicon wafer is prepared by a wet method, wherein the surface of the black silicon wafer is polluted or oxidized in the long-time placement or transportation process after the texturing and cleaning process and before the diffusion process.
2. The method for cleaning the solar polycrystalline black silicon wafer according to claim 1, wherein the concentration of the potassium hydroxide solution in the step (2) is 1 to 4 wt%.
3. The method for cleaning the solar polycrystalline black silicon wafer according to claim 1, wherein the potassium hydroxide solution is added in an amount of 20 to 50ml per 100 black silicon wafers processed in the step (2).
4. The method for cleaning solar polycrystalline black silicon wafer as claimed in claim 1, wherein the amount of the mixed acid solution added in the step (4) is 200ml of hydrochloric acid solution and 40-100ml of hydrofluoric acid solution added for every 100 black silicon wafers processed.
5. The method for cleaning solar polycrystalline black silicon wafer according to claim 1, wherein the water in the steps (1), (3) and (5) is at least one of deionized water and ultrapure water.
6. The method for cleaning the solar polycrystalline black silicon wafer according to claim 1, wherein the time for cleaning the water in the step (1) is 30 to 60 seconds, the time for treating the potassium hydroxide solution in the step (2) is 40 to 60 seconds, the time for cleaning the water in the step (3) is 40 to 60 seconds, the time for treating the mixed acid solution in the step (4) is 40 to 60 seconds, and the time for cleaning the water in the step (5) is 30 to 60 seconds.
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| CN201810813246.9A CN109148262B (en) | 2018-07-23 | 2018-07-23 | Cleaning method of solar polycrystalline black silicon wafer |
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| CN109148262B true CN109148262B (en) | 2020-09-01 |
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| CN102102207A (en) * | 2009-12-16 | 2011-06-22 | 北大方正集团有限公司 | Method for cleaning silicon chip before polycrystal etching |
| CN203900007U (en) * | 2014-06-12 | 2014-10-29 | 陕西天宏硅材料有限责任公司 | Solar silicon wafer cleaning device |
| CN104393114A (en) * | 2014-11-17 | 2015-03-04 | 中国电子科技集团公司第四十八研究所 | Preparation method of polycrystalline black silicon of micro-nano composite suede structure |
| CN104835879A (en) * | 2015-05-30 | 2015-08-12 | 润峰电力有限公司 | Texturing method of polysilicon solar cell |
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| CN102102207A (en) * | 2009-12-16 | 2011-06-22 | 北大方正集团有限公司 | Method for cleaning silicon chip before polycrystal etching |
| CN203900007U (en) * | 2014-06-12 | 2014-10-29 | 陕西天宏硅材料有限责任公司 | Solar silicon wafer cleaning device |
| CN104393114A (en) * | 2014-11-17 | 2015-03-04 | 中国电子科技集团公司第四十八研究所 | Preparation method of polycrystalline black silicon of micro-nano composite suede structure |
| CN104835879A (en) * | 2015-05-30 | 2015-08-12 | 润峰电力有限公司 | Texturing method of polysilicon solar cell |
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