CN109713056B

CN109713056B - Preparation method of black silicon solar cell with radial PN junction

Info

Publication number: CN109713056B
Application number: CN201811470762.2A
Authority: CN
Inventors: 沈文忠; 吴飞; 林豪; 李正平
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2018-12-04
Filing date: 2018-12-04
Publication date: 2020-07-10
Anticipated expiration: 2038-12-04
Also published as: CN109713056A

Abstract

The invention discloses a preparation method of a black silicon solar cell with a radial PN junction, which relates to the field of preparation of crystalline silicon solar cells and comprises the following steps: (1) manufacturing a suede with a micron size on a silicon substrate by adopting a chemical wet method; (2) maintaining for 10-60min at the temperature of 800 ℃ and 1000 ℃ and under the condition that the oxygen content is controlled to be 30-100%, and diffusing a diffusion source on the surface of the suede; (3) and manufacturing the surface passivation layer of the suede through annealing. The method can realize the field passivation effect of the PN junction through a simple diffusion process, ensures good light trapping capability, well controls surface recombination and Auger recombination, has low preparation cost of the texture surface, and can well improve the conversion efficiency of the cell.

Description

Preparation method of black silicon solar cell with radial PN junction

Technical Field

The invention relates to the field of crystalline silicon solar cell preparation, in particular to a preparation method of a black silicon solar cell with a radial PN junction.

Background

The black silicon textured by the nano-wires can greatly reduce the reflectivity of the front surface of the solar cell without an additional antireflection layer. Thus, black silicon technology has been considered as an effective means of improving the efficiency of solar cells. However, for the existing black silicon technology, due to the factors of the elongated nano textured surface greatly increasing the surface area, the non-ideal doping distribution and the like, two serious composite channels appear at the emitting end: surface recombination and auger recombination. Jihun Oh et al fully analyzed the effects of these two composite channels on battery performance and proposed two key points to achieve a high efficiency battery: reducing the specific surface area of the textured surface and adjusting the doping depth and concentration of the emitter. This inevitably reduces the antireflective ability of the original black silicon texture, which results in insufficient short-circuit current and limits the cell conversion efficiency to about 18%, so that an additional antireflective layer (such as silicon nitride) is still required to make the cell efficiency exceed 20%. Hele Savin et Al made a significant breakthrough and demonstrated uniform Al₂O₃The film is capable of providing excellent chemical and field passivation on a black silicon nanoweb surface. From 80nm of Al₂O₃The film acts as a passivation and subtractive layer such that the surface recombination rate is reduced to 20cm/s, a breakthrough in back contact IBC cell efficiency of 22%.However, auger recombination, which can be well suppressed in IBC cells, remains a troublesome problem in conventional front junction cell fabrication.

The invention aims to solve the technical problem of how to effectively inhibit surface recombination and Auger recombination while not reducing the antireflection capacity of the black silicon suede.

Therefore, the technical personnel in the field are dedicated to developing a preparation method of a black silicon solar cell with a radial PN junction, the method can realize the field passivation effect of the PN junction through a simple diffusion process, ensure good light trapping capability, better control surface recombination and Auger recombination, lower preparation cost of a texture surface and better improve the conversion efficiency of the cell.

Disclosure of Invention

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to effectively suppress surface recombination and auger recombination without reducing the antireflective ability of the black silicon texture.

In order to achieve the above object, the present invention provides a method for preparing a black silicon solar cell having a radial PN junction, comprising the steps of:

(1) manufacturing a suede with a micron size on a silicon substrate by adopting a chemical wet method;

(2) maintaining for 10-60min at the temperature of 800 ℃ and 1000 ℃ and under the condition that the oxygen content is controlled to be 30-100%, and diffusing a diffusion source on the surface of the suede;

(3) and manufacturing the surface passivation layer of the suede through annealing.

Further, the microscopic shape of the suede in the step (1) is a columnar structure, the ratio of the diameter of an inscribed circle of the columnar structure to the height of the columnar structure is 1.5-5.0, and the columnar structure is a triangular prism, a quadrangular prism, a hexagonal prism or a cylinder.

Further, the diameter of the inscribed circle of the triangular prism, the quadrangular prism, the hexagonal prism, and the cylinder is 1 to 10 micrometers.

Further, the ratio of the average distance between the columnar structures to the diameter of the inscribed circle of the columnar structures is 1.1-2.0.

Further, the diffusion source in the step (2) is a phosphorus source or a boron source.

Further, the diffusion source in the step (2) is diffused into the surface of the suede by adopting a thermal diffusion furnace or a rapid annealing furnace.

Further, the passivation layer in the step (3) is silicon oxide, aluminum oxide or amorphous silicon.

Further, the annealing of the silicon oxide in the step (3) is maintained in a pure oxygen environment of 700-850 ℃, the annealing of the aluminum oxide in the step (3) is performed in a pure nitrogen environment of 450 ℃, and the annealing of the amorphous silicon in the step (3) is performed in a pure nitrogen environment of 200 ℃.

Further, the silicon oxide is generated by a thermal oxidation method, the aluminum oxide is generated by an atomic deposition method, and the amorphous silicon is generated by a plasma enhanced chemical vapor deposition method.

The method can realize the field passivation effect of the PN junction through a simple diffusion process, ensures good light trapping capability, well controls surface recombination and Auger recombination, has low preparation cost of the texture surface, and can well improve the conversion efficiency of the cell.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

Fig. 1 is a schematic structural diagram of a black silicon solar cell with a radial PN junction according to a preferred embodiment of the present invention.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.

The specific implementation includes two examples. One embodiment is a P-type silicon substrate radial P-N⁺And (3) preparing the junction black silicon solar cell.

1. Preparing a black silicon suede of the P-type silicon substrate:

selecting polystyrene pellets with the diameter of 1-10 microns, paving the micron pellets on the surface of a silicon wafer by an injection method, reducing the size of the pellets to 50-90% of the original pellets by reactive ion etching equipment, depositing a metal catalyst on the surface paved with the pellets by an electron beam coating machine, and etching the silicon wafer into a mixed solution of hydrogen peroxide, hydrofluoric acid and alcohol (the volume ratio of the hydrogen peroxide to the hydrofluoric acid to the water to the alcohol is 1:5:10:10) to form columnar structures with different heights in different time.

Then placing the obtained columnar structure into AgNO₃(0.0002M)、HF(2M)and HNO₃Etching in 0.005M mixed solution for 10-15min, passing through deionized water, and adding 10 wt% HNO₃Removing Ag in the solution for 2min, and passing through deionized water. And repeating the step of etching to remove the residual silver ions for multiple times until the silicon substrate 4 with the micrometer pencil array structure on the upper surface is formed.

2. Radial P-N⁺Preparing a knot:

and spin-coating a liquid phosphorus diffusion source on the black silicon suede, pre-drying at 200 ℃, and then putting the black silicon suede into a tubular annealing furnace for thermal diffusion. The temperature range of diffusion is controlled between 800-950 ℃, the time is controlled between 10-60min, and the oxygen content is controlled between 30-100 percent to ensure different doping amounts and form N with different thicknesses⁺A diffusion layer 3 having a depth smaller than the radius of the columnar texture surface to form a radial P-N⁺And (6) knotting.

3. Preparation of a passivation layer:

removing the phosphorosilicate glass by using a hydrofluoric acid solution, and then annealing for 10-60min at the pure oxygen environment of 700-850 ℃ to form silicon dioxide passivation layers 2 with different thicknesses.

4. The back electrode 5 is prepared by aluminum paste, and the front electrode 1 is prepared by adopting a photoetching process.

Second embodiment N-type silicon substrate radial P⁺-a manufacturing step of an N-junction black silicon solar cell.

1. Preparing a black silicon suede of an N-type silicon substrate:

and preparing a photoresist pattern with an array period by adopting a photoetching method, wherein the pattern is one of a triangular prism, a square and a hexagon. Depositing a metal catalyst, removing the photoresist by using acetone, and then putting the silicon wafer into a mixed solution of hydrogen peroxide, hydrofluoric acid and water (the volume ratio of the hydrogen peroxide to the hydrofluoric acid to the water is 1:5:10) to etch the columnar structures with different heights in different time.

Then placing the obtained columnar structure into AgNO₃(0.0002M),HF(2M)and HNO₃Etching in 0.005M mixed solution for 10-15min, passing through deionized water, and adding 10 wt% HNO₃Removing Ag in the solution for 2min, and passing through deionized water. The step of removing the residual silver ions by etching is repeated for a plurality of times until the upper surface shape becomes a tapered structure, forming the silicon substrate 4.

2. Radial direction P⁺-preparation of N junctions:

a gaseous boron diffusion source is adopted for diffusion, the diffusion temperature range is controlled between 850-1000 ℃, the diffusion time is controlled between 10-60min, the oxygen content is controlled between 30-100 percent, so as to ensure different doping amounts and form P with different thicknesses⁺A diffusion layer 3 having a depth smaller than the radius of the columnar texture surface to form a radial direction P⁺-an N junction.

3. Preparation of a passivation layer:

removing borosilicate glass by hydrofluoric acid solution, depositing alumina by adopting an atomic deposition method, and annealing at 450 ℃ in the atmosphere of nitrogen to form an alumina passivation layer 2.

4. The deposition of the back electrode 5 as well as the front electrode 1 is performed.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A preparation method of a black silicon solar cell with a radial PN junction is characterized by comprising the following steps:

(1) manufacturing a suede with a micron size on a silicon substrate by adopting a chemical wet method:

the microscopic shape of the suede is a columnar suede with a columnar structure, the silicon substrate is a P-type silicon substrate or an N-type silicon substrate, wherein:

the preparation of the black silicon suede of the P-type silicon substrate comprises the following steps: selecting polystyrene pellets with the diameter of 1-10 microns, paving the polystyrene pellets on the surface of a silicon wafer by an injection method, reducing the size of the polystyrene pellets to 50-90% of the original size by a reactive ion etching device, depositing a metal catalyst on one surface paved with the polystyrene pellets by an electron beam coating machine, putting the silicon wafer paved with the polystyrene pellets into a mixed solution of hydrogen peroxide, hydrofluoric acid, water and alcohol with the volume ratio of 1:5:10:10, etching to obtain a columnar structure, and putting the columnar structure into AgNO containing 0.0002M₃2M HF, 0.005M HNO₃Etching in the mixed etching solution for 10-15min, passing through deionized water, and adding 10 wt% of HNO₃Removing Ag in the solution for 2min, passing through deionized water, and repeatedly etching to remove residual silver ions until a silicon substrate with a micrometer pencil array structure on the upper surface is formed;

the preparation of the black silicon suede of the N-type silicon substrate comprises the following steps: preparing a photoresist pattern with an array period by adopting a photoetching method, depositing a metal catalyst, removing the photoresist by using acetone, placing a silicon wafer into a mixed solution of hydrogen peroxide, hydrofluoric acid and water according to a volume ratio of 1:5:10 to etch to obtain a columnar structure, and placing the columnar structure into AgNO containing 0.0002M₃2M HF, 0.005M HNO₃Etching in the mixed etching solution for 10-15min, passing through deionized water, and adding 10 wt% of HNO₃Removing Ag in the solution for 2minDeionized water, and the step of removing the residual silver ions by repeated etching is carried out for a plurality of times until the shape of the upper surface is changed into a cone-shaped structure to form a silicon substrate;

(2) maintaining the temperature at 800-1000 ℃ and the oxygen content at 30-100% for 10-60min, and diffusing the diffusion source on the surface of the textured surface, wherein the depth of the diffusion layer is less than the radius of the columnar textured surface;

2. The method of claim 1, wherein the ratio of the diameter of the inscribed circle of the columnar structure to the height of the inscribed circle of the columnar structure is 1.5-5.0, and the columnar structure is a triangular prism, a quadrangular prism, a hexagonal prism, or a cylinder.

3. The method of fabricating a black silicon solar cell with a radial PN junction according to claim 2, wherein the diameter of the inscribed circle of the triangular prism, the quadrangular prism, the hexagonal prism and the cylinder is 1 to 10 μm.

4. The method of claim 2, wherein a ratio of an average distance between the columnar structures to the diameter of the inscribed circle of the columnar structures is 1.1-2.0.

5. The method of claim 1, wherein the diffusion source in step (2) is a phosphorous source or a boron source.

6. The method for preparing a black silicon solar cell with a radial PN junction according to claim 1, wherein the diffusion source in the step (2) is diffused into the surface of the suede by using a thermal diffusion furnace or a rapid annealing furnace.

7. The method for preparing a black silicon solar cell with a radial PN junction as claimed in claim 1, wherein the passivation layer in the step (3) is silicon oxide, aluminum oxide or amorphous silicon.

8. The method as claimed in claim 7, wherein the annealing of the silicon oxide in step (3) is performed in pure oxygen environment at 700-850 ℃, the annealing of the aluminum oxide in step (3) is performed in pure nitrogen environment at 450 ℃, and the annealing of the amorphous silicon in step (3) is performed in pure nitrogen environment at 200 ℃.

9. The method of claim 8, wherein the silicon oxide is produced by a thermal oxidation process, the aluminum oxide is produced by an atomic deposition process, and the amorphous silicon is produced by a plasma enhanced chemical vapor deposition process.