CN114267581A - Method and liquid for smoothly modifying crystalline silicon solar cell - Google Patents
Method and liquid for smoothly modifying crystalline silicon solar cell Download PDFInfo
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Abstract
The invention discloses a crystal silicon solar cell smooth modification method and a smooth modification liquid thereof, wherein a textured crystal silicon wafer is placed in the smooth modification liquid, etching is carried out for 15-180 s at the temperature of 8-40 ℃, and the top and bottom positions of the pyramid-shaped structure of the crystal silicon wafer are etched and modified into a smooth transition structure, so that deposition of a passivation film is facilitated, and the composition of the junction of the top and the bottom is reduced. The smooth modification method of the crystalline silicon solar cell provided by the invention has a simple process, the modified pyramid structure is more beneficial to conformal deposition of a film, the reflectivity of the modified pyramid is increased by less than 1%, and meanwhile, the optical and electrical properties of the cell are considered; meanwhile, the adopted smoothing modification liquid does not contain nitrogen, the emission of nitric acid in the smoothing treatment liquid in the prior art is effectively avoided, the waste liquid treatment cost is low, the pressure on environmental protection is low, the chemical liquid medicine of the raw materials is low in cost and easy to obtain, and the pollution to the environment is reduced while the production cost is reduced.
Description
Technical Field
The invention belongs to the technical field of crystalline silicon solar cells, and particularly relates to a crystalline silicon solar cell smooth modification method and a smooth modification liquid thereof.
Background
High efficiency and low cost have been the driving force for the development of solar cells. High-efficiency crystalline silicon solar cells always occupy the mainstream of the photovoltaic power generation market. The heterojunction solar cell has the characteristics of high conversion efficiency, low power consumption cost, simple process flow, no attenuation, high double-sided rate and the like, and is one of the development directions of high-efficiency crystalline silicon cells.
Texturing is the first process of a crystalline silicon solar cell process, and a good textured structure plays a crucial role in the subsequent process. Generally, the monocrystalline silicon solar cell adopts the anisotropic etching of alkali to prepare the regular pyramid structure, so that the reflection times of light on the surface of a silicon wafer are increased, and the surface reflectivity is greatly reduced. However, the pyramid tip and the tower bottom are relatively sharp, and subsequent thin film deposition is easy to generate a large number of defects at the pyramid tip and the tower bottom, which causes battery leakage and further affects the conversion efficiency of the solar battery.
For a heterojunction solar cell, a common mode in the industry at present is to corrode a pyramid suede by adopting a mixed solution of hydrofluoric acid and nitric acid, and smooth the pyramid tip and the tower bottom, so that the subsequent conformal deposition of a thin film is facilitated, and the recombination is reduced. In addition, the smooth pyramid suede can reduce the risk of the pyramid tip being ground off caused by silicon wafer friction.
The existing smoothing treatment process needs to prepare nitric acid with the concentration of 50-80%, and the chemical cost is high. The waste water in the nitric acid contains a large amount of nitrogen elements, which causes great pressure on environmental protection, and the treatment of the waste acid containing nitrogen is high. HF/HNO, on the other hand3The reaction rate of the mixed solution is relatively fast, and the reaction rate is generally controlled by lowering the reaction temperature to 8 ℃. On the other hand, the reflectivity of the silicon wafer after the rounding treatment can be increased by more than 1 percent, and the short-circuit current is reduced.
Disclosure of Invention
Aiming at the defects, the invention aims to provide a crystal silicon solar cell smoothing modification method and a smoothing modification liquid thereof, which have the advantages of simple process, controllable reflectivity, capability of smoothing the top and the bottom of a pyramid, unobvious increase of the surface reflectivity of a crystal silicon wafer, reduced recombination and reflectivity.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a crystal silicon solar cell smooth modification method comprises the following steps:
(1) preparing a textured crystal silicon wafer, wherein the texture surface of the crystal silicon wafer has a pyramid appearance structure, the bottom side of the pyramid appearance structure is 1-10 microns, and the height of the pyramid appearance structure is 0.7-7 microns;
(2) preparing a smooth finishing liquid: mixing a fluoride ion source, a chloride ion source, an oxidant and deionized water to obtain a smooth modification liquid, wherein the concentration of the fluoride ion source is 0.1-8 mol/L, the concentration of the chloride ion source is 0.01-13 mol/L, and the concentration of the oxidant is 0.01-3 mol/L;
(3) smooth modification: the textured crystal silicon wafer is placed in the smooth modification liquid and etched for 15-180 s at the temperature of 8-40 ℃, preferably for 30-90 s at the temperature of 15-30 ℃, and the top and bottom positions of the pyramid-shaped structure of the crystal silicon wafer can be etched and modified into a smooth transition structure, so that the subsequent thin film deposition is facilitated, and the carrier recombination at the junction of the top and the bottom is reduced. The reflectivity of the surface of the modified silicon wafer is not obviously increased, the reflectivity is increased by less than 1%, and the reflectivity is considered while the composition is reduced. The modified inverted pyramid structure is beneficial to conformal deposition of subsequent films, so that the performance of the solar cell is improved.
As a preferable scheme of the invention, the crystal silicon wafer is a P-type silicon wafer or an N-type silicon wafer.
As a preferred scheme of the invention, after the smooth modification is finished, the etching depth at the junction of the top of the pyramid-shaped structure and the bottoms of two adjacent pyramid-shaped structures is 10 nm-100 nm.
As a preferred embodiment of the present invention, the fluoride ion source is selected from hydrofluoric acid.
In a preferred embodiment of the present invention, the chlorine-containing ion source is selected from hydrochloric acid, sodium hypochlorite, sodium chlorite, chlorine dioxide, chlorine gas, sodium chlorate or sodium perchlorate.
In a preferred embodiment of the present invention, the oxidizing agent is one or more selected from sodium persulfate, hydrogen peroxide, acetic acid, peroxyacetic acid, potassium permanganate, and concentrated sulfuric acid.
In a preferable embodiment of the present invention, an additive is further added in the step (2), and the mass ratio of the additive to the rounding off modification liquid is 0.2-5: 100. After the additive is added, the smooth modification process is more stable, and the smooth modification effect is improved.
As a preferable scheme of the invention, the additive comprises the following components in parts by mass: 0.1-5 parts by mass of benzyltrimethylammonium chloride, 1-3 parts by mass of sodium citrate, 0.5-3 parts by mass of guar gum and 100 parts by mass of water.
In a preferable embodiment of the present invention, the additive is one or more of benzyl trimethyl ammonium chloride, sodium citrate, and guar gum.
A smooth modification liquid used in a crystalline silicon solar cell smooth modification method. The smooth modification liquid has the advantages of reasonable formula, no nitrogen, low waste liquid treatment cost, small environmental protection pressure, low chemical liquid cost and production cost reduction.
The invention has the beneficial effects that: the smooth modification method of the crystalline silicon solar cell provided by the invention has a simple process, is compatible with the existing texturing process, the modified pyramid structure is more favorable for angle-preserving deposition of a film, the reflectivity of the modified pyramid is increased by less than 1%, and meanwhile, the optical and electrical properties of the cell are considered; meanwhile, the adopted smoothing modification liquid does not contain nitrogen, the emission of nitric acid in the smoothing treatment liquid in the prior art is effectively avoided, the waste liquid treatment cost is low, the pressure on environmental protection is low, the chemical liquid medicine of the raw materials is low in cost and easy to obtain, and the pollution to the environment is reduced while the production cost is reduced.
The invention is further illustrated below with reference to the figures and examples.
Drawings
FIG. 1 is a SEM surface structure diagram of a silicon wafer before rounding modification.
FIG. 2 is a structural view of an SEM cross section of a silicon wafer before rounding.
FIG. 3 is a structural view of an SEM cross section of a silicon wafer after being smoothly modified by the technical scheme of the invention.
FIG. 4 is a structural view of an SEM cross section of a silicon wafer after being smoothly modified by the technical scheme of the invention.
Detailed Description
In the embodiment of the invention, taking an N-type monocrystalline silicon wafer after texturing as an example, the monocrystalline silicon wafer has a textured surface with a pyramid morphology structure, the bottom side of the pyramid morphology structure is 1-10 micrometers, and the height is the bottom side
The side length (i.e., height) of (a) is about 0.7 to 7 micrometers, preferably 2 to 5 micrometers. See in particular fig. 1. In other embodiments, the single crystal silicon wafer may also be a P-type silicon wafer.
Example 1: in this embodiment, the sodium hypochlorite has an effect of an oxidant at the same time, and no additional oxidant needs to be added, and of course, in other embodiments, an oxidant may also be added. Mixing hydrofluoric acid, sodium hypochlorite and deionized water to obtain a smooth modification liquid, wherein the concentration of the sodium hypochlorite is 0.1mol/L, the concentration of the hydrofluoric acid is 1.0mol/L, adding an additive into the smooth modification liquid, and the mass ratio of the additive to the smooth modification liquid is 3: 100. wherein the additive comprises 1 part by mass of benzyltrimethylammonium chloride, 2 parts by mass of sodium citrate, 0.5 part by mass of guar gum and 100 parts by mass of water.
And (3) placing the textured monocrystalline silicon wafer into the smooth modification liquid, modifying for 30s at the reaction temperature of 25 ℃, and etching and modifying the top and bottom positions of the pyramid morphology structure of the monocrystalline silicon wafer into a smooth transition structure. Referring to fig. 3 and 4, the tip and the bottom of the pyramid feature are rounded to facilitate conformal deposition of subsequent films. The test shows that the reflectivity of the modified pyramid suede is 11.3%.
Example 2: the embodiment provides a method for smoothly modifying a crystalline silicon solar cell, which is basically the same as embodiment 1, and is characterized in that hydrofluoric acid, hydrogen peroxide, hydrochloric acid and an additive are prepared. Mixing hydrofluoric acid, hydrogen peroxide and hydrochloric acid to obtain a smooth modification solution, wherein the concentration of the hydrofluoric acid is 0.3mol/L, the concentration of the hydrogen peroxide is 0.4mol/L, and the concentration of the hydrochloric acid is 10 mol/L; adding an additive into the rounding modification liquid, wherein the mass ratio of the additive to the rounding modification liquid is 2: 100. the additive consists of 2 parts by mass of benzyltrimethylammonium chloride, 1 part by mass of sodium citrate, 1 part by mass of guar gum and 100 parts by mass of water.
And placing the textured monocrystalline silicon wafer into the smooth modification liquid, and modifying for 90s at the reaction temperature of 15 ℃ to realize etching modification of the top and bottom positions of the pyramid-shaped structure of the monocrystalline silicon wafer into a smooth transition structure. The test shows that the reflectivity of the modified pyramid suede is 11.7%.
Example 3: this example provides a method for smoothing a crystalline silicon solar cell, which is substantially the same as example 1, except that hydrofluoric acid, sodium perchlorate, and hydrochloric acid are prepared. In this embodiment, sodium perchlorate has the effect of an oxidant at the same time, and no additional oxidant is needed, and certainly, in other embodiments, an oxidant may be added. Mixing hydrofluoric acid, sodium perchlorate and hydrochloric acid to obtain a smooth modification solution, wherein the concentration of the hydrofluoric acid is 1mol/L, the concentration of the sodium perchlorate is 0.2mol/L, and the concentration of the hydrochloric acid is 8 mol/L;
and placing the textured monocrystalline silicon wafer into the smooth modification liquid, and modifying for 60s at the reaction temperature of 30 ℃ to realize etching modification of the top and bottom positions of the pyramid-shaped structure of the monocrystalline silicon wafer into a smooth transition structure. The test shows that the reflectivity of the modified pyramid suede is 11.5%.
Comparative example 1
The sheets after being made into the velvetPlacing the crystal silicon wafer in HF and HNO3Treating in mixed acid solution at 8 deg.C for 90 s; wherein the mass percent of HF in the mixed acid liquid is 1%, and HNO3The mass percentage of (A) is 70%; the test shows that the reflectivity of the modified pyramid suede is 12.5%.
Solar cells prepared according to the HIT process flow in examples 1-3 and comparative example 1 were compared to test the performance of the solar cells, and the specific results are shown in Table 1:
TABLE 1
| ΔUoc(mV) | ΔJsc(mA/cm2) | ΔFF(％) | ΔEff(％) | |
| Example 1 | 1.2 | 0.02 | 0.21 | 0.106 |
| Example 2 | 1.5 | 0.01 | 0.12 | 0.084 |
| Example 3 | 1.6 | 0.01 | 0.20 | 0.111 |
| Comparative example 1 | 0 | 0 | 0 | 0 |
By comparison in table 1, the performance of the solar cell prepared from the monocrystalline silicon wafer treated by the method for smoothly modifying the crystalline silicon solar cell according to the HIT process flow is basically superior to that of the solar cell prepared by the traditional process. And the smooth modification liquid adopted in the method for smoothly modifying the crystalline silicon solar cell is reasonable in formula, does not contain nitrogen, and effectively avoids HF/HNO3The discharge of nitrogen in the mixed acid modification liquid has low waste liquid treatment cost and low environmental protection pressure, reduces the production cost and simultaneously reduces the pollution to the environment.
The method for smoothly modifying the crystalline silicon solar cell is compatible with the existing production line texturing process, has simple process, has good smoothing effect on the top and the bottom of the pyramid shape structure, is more beneficial to corner protection deposition of subsequent films, has controllable reflectivity, obtains better balance on the optical and electrical properties of the solar cell, and finally improves the cell efficiency. The above examples are only preferred embodiments of the present invention, and the present invention is not limited to all embodiments, and any technical solution using one of the above examples or equivalent changes made according to the above examples is within the scope of the present invention.
Variations and modifications to the above-described embodiments may occur to those skilled in the art, which fall within the scope and spirit of the above description. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. In addition, although specific terms are used herein, they are used for convenience of description and are not to be construed as limiting the present invention in any way, and other methods similar or equivalent thereto are also within the scope of the present invention.
Claims (10)
1. A smooth modification method for a crystalline silicon solar cell is characterized by comprising the following steps:
(1) preparing a textured crystal silicon wafer, wherein the texture surface of the crystal silicon wafer has a pyramid appearance structure, the bottom side of the pyramid appearance structure is 1-10 microns, and the height of the pyramid appearance structure is 0.7-7 microns;
(2) preparing a smooth finishing liquid: mixing a fluoride ion source, a chloride ion source, an oxidant and deionized water to obtain a smooth modification liquid, wherein the concentration of the fluoride ion source is 0.1-8 mol/L, the concentration of the chloride ion source is 0.01-13 mol/L, and the concentration of the oxidant is 0.01-3 mol/L;
(3) smooth modification: and placing the textured crystal silicon wafer into a smooth modification liquid, etching for 15-180 s at the temperature of 8-40 ℃, and etching and modifying the top and bottom positions of the pyramid-shaped structure of the crystal silicon wafer into a smooth transition structure, so that deposition of a passivation film is facilitated, and the composition of the junction of the tip and the bottom of the tower is reduced.
2. The crystalline silicon solar cell smoothing method of claim 1, wherein the crystalline silicon wafer is a P-type silicon wafer or an N-type silicon wafer.
3. The method for smoothly modifying the crystalline silicon solar cell according to claim 1, wherein after the smooth modification is finished, the etching depth at the junction of the top of the pyramid-shaped structure and the bottoms of two adjacent pyramid-shaped structures is 10nm to 100 nm.
4. The crystalline silicon solar cell smoothing method of claim 1, wherein the fluoride ion source is selected from hydrofluoric acid.
5. The method for smoothly modifying a crystalline silicon solar cell according to claim 1, wherein the chlorine-containing ion source is selected from hydrochloric acid, sodium hypochlorite, sodium chlorite, chlorine dioxide, chlorine gas, sodium chlorate or sodium perchlorate.
6. The method for smoothly modifying the crystalline silicon solar cell according to claim 1, wherein the oxidant is one or more selected from sodium persulfate, hydrogen peroxide, acetic acid, peroxyacetic acid, potassium permanganate and concentrated sulfuric acid.
7. The method for smoothly modifying the crystalline silicon solar cell according to any one of claims 1 to 6, wherein an additive is further added in the step (2), and the mass ratio of the additive to the smooth modification solution is 0.2-5: 100.
8. The crystalline silicon solar cell smoothing modification method of claim 7, wherein the additive comprises the following components in parts by mass: 0.1-5 parts by mass of benzyltrimethylammonium chloride, 1-3 parts by mass of sodium citrate, 0.5-3 parts by mass of guar gum and 100 parts by mass of water.
9. The method for smoothly modifying the crystalline silicon solar cell according to claim 7, wherein the additive is one or more of benzyl trimethyl ammonium chloride, sodium citrate and guar gum.
10. A rounding modification liquid used in the method for rounding a crystalline silicon solar cell according to any one of claims 1 to 9.
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| CN115000202A (en) * | 2022-06-01 | 2022-09-02 | 松山湖材料实验室 | Low-reflection suede structure, texturing additive and texturing method |
| CN115000202B (en) * | 2022-06-01 | 2023-06-09 | 松山湖材料实验室 | Low-reflection suede structure, suede additive and suede method |
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Effective date of registration: 20230801 Address after: Building A1, innovation city, Songshanhu University, Dongguan, Guangdong 523000 Applicant after: Material Laboratory of Songshan Lake Applicant after: INSTITUTE OF PHYSICS, CHINESE ACADEMY OF SCIENCES Address before: Building A1, innovation city, Songshanhu University, Dongguan, Guangdong 523000 Applicant before: Material Laboratory of Songshan Lake |