CN112133793A - Back-junction back-contact solar cell and manufacturing method thereof - Google Patents

Abstract

The invention discloses a manufacturing method of a back-junction back-contact solar cell, comprising: after forming a first intrinsic silicon layer on the back of an N-type silicon substrate, doping the first intrinsic silicon layer with boron to form a doped silicon layer boron layer; after forming a first protective layer on the boron-doped layer, patterning the first protective layer and the boron-doped layer to form a patterned groove to expose part of the area on the backside; forming a second protective layer in the patterned groove In the intrinsic silicon layer, the second intrinsic silicon layer is brought into contact with a part of the area on the backside; the second intrinsic silicon layer is doped with phosphorus to form a phosphorus-doped layer; after the second protective layer is formed on the phosphorus-doped layer, The unnecessary doped regions on the front and side surfaces of the N-type silicon substrate are cleaned; after removing the first protective layer and the second protective layer, electrodes are formed on the boron doped layer and the phosphorus doped layer respectively. The invention also discloses a back-junction back-contact solar cell. The invention solves the problem that the target doped region is damaged due to the circulation of the cleaning liquid when the unnecessary doped region is etched.

Description

A back-junction back-contact solar cell and its fabrication method

technical field

The invention relates to the technical field of solar cell fabrication, in particular to a cell fabrication method capable of reducing the possibility of damage to a pn junction.

Background technique

A more important link in the fabrication process of silicon solar cells is the step of doping on a silicon substrate to form a heterojunction. However, due to the limitation of the existing doping process itself, it cannot be guaranteed that the doped impurities are only diffused in the target area. Therefore, in the actual doping process, it can be found that the doped impurities are not only diffused in the target area (eg: front), but also diffused on other surfaces (eg: back or side) of the silicon substrate, thus forming unnecessary doping Miscellaneous area.

If the unnecessary doped region is left, the photogenerated electrons collected on the front side of the solar cell will be directly transported along the unnecessary doped region to the back side of the solar cell, causing an internal short circuit of the solar cell, so it is necessary to remove the non-essential doped region. Necessary doped regions.

At present, when removing unnecessary doped regions, an alkaline solution is usually used to etch the backside and sides of the silicon substrate. During this process, however, the alkaline solution may flow around to other surfaces of the silicon substrate, potentially damaging the target doped regions.

SUMMARY OF THE INVENTION

For the above-mentioned technical problems, the present invention adopts the following technical solutions:

In one aspect of the present invention, a method for fabricating a back-junction back-contact solar cell is provided, the fabrication method comprising:

After the first intrinsic silicon layer is formed on the back surface of the N-type silicon substrate, boron doping is performed on the first intrinsic silicon layer to form a boron-doped layer;

After forming a first protective layer on the boron-doped layer, patterning the first protective layer and the boron-doped layer to form a patterned groove to expose a partial area of the back surface;

forming a second intrinsic silicon layer in the patterned slot, so that the second intrinsic silicon layer is in contact with a partial area of the back surface;

Doping the second intrinsic silicon layer with phosphorus to form a phosphorus-doped layer;

After forming a second protective layer on the phosphorus-doped layer, cleaning the unnecessary doped regions on the front and side surfaces of the N-type silicon substrate;

After removing the first protective layer and the second protective layer, electrodes are respectively formed on the boron-doped layer and the phosphorus-doped layer.

Preferably, before removing the first protective layer and the second protective layer, the manufacturing method includes:

doping the front side with phosphorus to form a surface field region;

forming a third protective layer on the surface field region;

cleaning unnecessary doped regions on the sides of the N-type silicon substrate;

The third protective layer is removed.

Preferably, after removing the third protective layer, the manufacturing method further includes: sequentially forming a first passivation layer and an antireflection layer on the surface field region.

Preferably, before forming the electrode, the manufacturing method further includes: forming a second passivation layer on the boron-doped layer and the phosphorous-doped layer.

Preferably, the method for forming the electrodes on the boron-doped layer and the phosphorus-doped layer respectively comprises:

printing silver paste containing a corrosive solvent on the second passivation layer, so that the silver paste is etched through the second passivation layer to contact the boron-doped layer and the phosphorus-doped layer;

The silver paste is cured to form the electrode.

Preferably, before forming the first intrinsic silicon layer on the back surface of the N-type silicon substrate, the manufacturing method further includes:

forming a tunnel oxide layer on the backside of the N-type silicon substrate;

Wherein, the first intrinsic silicon layer is formed after the tunnel oxide layer is formed and on the tunnel oxide layer.

Preferably, the first protective layer, the second protective layer and the third protective layer are made of silicon dioxide or silicon nitride.

Preferably, the method for cleaning the unnecessary doped regions includes:

Under room temperature conditions, soak the N-type silicon substrate provided with the second protective layer and/or the third protective layer in a sodium hydroxide solution with a volume ratio of 6% to 18% for 80 seconds ~120 seconds.

Preferably, before forming the first intrinsic silicon layer on the back surface of the N-type silicon substrate, the manufacturing method further includes:

The N-type silicon substrate is immersed in a mixed solution of sodium hydroxide or potassium hydroxide solution and deionized water with a volume ratio of 2% to 5% for polishing; wherein, the temperature of the mixed solution is 70° C. to 80° C. °C, the polishing time is 3 minutes to 5 minutes.

In another aspect of the present invention, a back-junction back-contact solar cell is provided, and the back-junction back-contact solar cell is fabricated by the above-mentioned fabrication method.

When the solar cell is fabricated by the fabrication method provided by the present invention, since a protective layer is arranged on the target doping region after doping, the cleaning solution can be prevented from flowing around and damaging the target doping region when cleaning the unnecessary doping region. In this way, the production quality of back-junction back-contact solar cells is improved.

Description of drawings

1 is a flowchart of a method for fabricating a back-junction back-contact solar cell according to an embodiment of the present invention;

2a-2f are process diagrams of a back-junction back-contact solar cell according to an embodiment of the present invention;

3a to 3d are process diagrams of a back-junction back-contact solar cell according to another embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described with reference to the drawings are merely exemplary and the invention is not limited to these embodiments. Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the related structures and/or processing steps are omitted. Other details not relevant to the invention.

In addition, it will be understood that the so-called front side of the silicon substrate refers to the surface of the silicon substrate that will become the light-receiving surface; the so-called backside of the silicon substrate refers to the surface of the silicon substrate that is opposite to the front side and will become the backlight surface The so-called side surface of the silicon substrate refers to the surface of the silicon substrate used to connect the front surface and the back surface.

As described in the Background Art, the commonly used fabrication methods of solar cells have the risk of damaging the target doped region during the actual fabrication process.

In view of the above technical problems, according to embodiments of the present invention, a method for fabricating a solar cell capable of reducing the possibility of damage to a target doped region is provided, and the details are as follows.

Example 1

This embodiment provides a method for fabricating a back-junction back-contact solar cell, as shown in FIG. 1 and FIG. 2a to FIG. 2f , and the fabrication method includes:

Step S1 , after forming a first intrinsic silicon layer on the back surface 1 b of the N-type silicon substrate 1 , the first intrinsic silicon layer is doped with boron to form a boron-doped layer 2 . Specifically, a chemical vapor deposition process is used to grow intrinsic amorphous silicon or intrinsic polysilicon material with a thickness of 80 nm˜200 nm on the back surface 1 b to form a first intrinsic silicon layer.

Step S2, after forming the first protective layer 3 on the boron-doped layer 2, pattern the first protective layer 3 and the boron-doped layer 2 to form a patterned slot A to expose the back surface Part of the 1b area. Specifically, a chemical vapor deposition process is used to form a silicon nitride material with a thickness of 40 nm to 80 nm on the boron-doped layer 2 to form the first protective layer 3, and then a laser etching process is used to form the first protective layer 3 on the boron-doped layer 2. The protective layer 3 and the boron-doped layer 2 are patterned to form the patterned opening A, so as to expose a part of the back surface 1b.

Step S3 , forming a second intrinsic silicon layer in the patterned slot A, so that the second intrinsic silicon layer is in contact with a part of the back surface 1 b . Specifically, a chemical vapor deposition process is used to deposit intrinsic amorphous silicon or intrinsic polysilicon material with a thickness of 80 nm to 200 nm in the patterned slot A to form the second intrinsic silicon layer.

Step S4 , using an ion implantation process to perform phosphorus doping on the second intrinsic silicon layer to form a phosphorus-doped layer 4 . Specifically, the implantation amount of phosphorus ions is 1×10 ¹⁵ cm ⁻² to 8×10 ¹⁵ cm ⁻² , and the accelerating voltage of phosphorus ions is 5Kv to 16Kv.

Step S5 , after forming a second protective layer 5 on the phosphorus-doped layer 4 , cleaning the non-essential doped regions on the front surface 1 a and the side surfaces of the N-type silicon substrate 1 . Specifically, a chemical vapor deposition process is used to form a silicon nitride material with a thickness of 40 nm to 80 nm on the phosphorus-doped layer 4 to form the second protective layer 5; The unnecessary doped regions on the front surface 1a and the side surfaces of the substrate 1 are etched, thereby removing the unnecessary doped regions.

Step S6 , after removing the first protective layer 3 and the second protective layer 5 , electrodes 6 are respectively formed on the boron-doped layer 2 and the phosphorus-doped layer 4 . Specifically, the first protective layer 3 and the second protective layer 5 are removed by using a hydrofluoric acid solution; then the electrodes 6 are formed on the boron-doped layer 2 and the phosphorus-doped layer 4 by a printing process, respectively. .

According to the specific fabrication steps of this embodiment, it can be confirmed that when a solar cell is fabricated by the fabrication method provided in this embodiment, since a protective layer is provided on the target doping region after doping, when cleaning the unnecessary doping region , it can prevent the situation that the cleaning liquid flows around and damages the target doped region. It can be seen that the manufacturing method provided in this embodiment is beneficial to improve the production quality of the back-junction back-contact solar cell.

Preferably, in order to reduce the recombination rate of photogenerated carriers on the front side 1a of the battery, in this embodiment, before removing the first protective layer 3 and the second protective layer 5, the manufacturing method includes:

Step S51: Doping the front surface 1a with phosphorus to form a surface field region B. As shown in FIG. Specifically, as shown in FIG. 3a, the front surface 1a is doped with phosphorus by using an ion implantation process, so as to form the surface field region B. As shown in FIG. The implantation amount of phosphorus ions is 5×10 ¹⁵ cm ⁻² to 12×10 ¹⁵ cm ⁻² , and the accelerating voltage of phosphorus ions is 6Kv to 12Kv.

Step S52 , forming a third protective layer on the surface field region B. As shown in FIG. Specifically, a chemical vapor deposition process is used to form a silicon nitride material with a thickness of 40 nm˜80 nm on the phosphorus-doped layer 4 to form the third protective layer.

Step S53 , cleaning the unnecessary doped regions on the side surface of the N-type silicon substrate 1 .

Step S54, removing the third protective layer. Specifically, a hydrofluoric acid solution is used to etch the third protective layer.

Further, as shown in FIG. 3 b , after the surface field region B is formed, the manufacturing method further includes: forming a first passivation layer 7 and an antireflection layer 8 on the surface field region B in sequence. Specifically, a chemical vapor deposition process is used to deposit a silicon dioxide material with a thickness of 80 nm to 100 nm on the surface field region B to form the first passivation layer 7 , and a thickness of 90 nm to 90 nm is deposited on the first passivation layer 7 . A 150 nm silicon nitride material layer is formed to form the anti-reflection layer 8 . Wherein, the passivation film can further reduce the carrier recombination rate of the front side 1a of the battery, and the anti-reflection film can reduce the reflectivity of sunlight, so as to improve the photoelectric conversion efficiency of the battery.

Further, in order to improve the passivation effect of the back side of the battery, as shown in FIG. 3c, in this embodiment, before forming the electrode 6, the manufacturing method further includes: adding the boron-doped layer 2 and the phosphorus-doped layer A second passivation layer 9 is formed on layer 4 . Specifically, a chemical vapor deposition process is used to deposit a silicon nitride material with a thickness of 70 nm to 80 nm on the boron-doped layer 2 and the phosphorus-doped layer 4 , thereby forming the second passivation layer 9 . As shown in FIG. 3d, after the second passivation layer 9 is formed, in order to realize the contact between the electrode 6 and the boron-doped layer 2 and the phosphorus-doped layer 4 formed subsequently, in this embodiment, in the A silver paste containing a corrosive solvent is printed on the second passivation layer 9 . The corrosive solvent contains hydrofluoric acid, so that the silver paste can be etched through the second passivation layer 9 to be in contact with the boron-doped layer 2 and the phosphorus-doped layer 4 . The silver paste is then cured to form the electrode 6 .

Specifically, in this embodiment, the method for cleaning the unnecessary doped region is:

Under room temperature conditions, the N-type silicon substrate 1 provided with the second protective layer 5 and/or the third protective layer is immersed in a sodium hydroxide solution with a volume ratio of 6% to 18% for a continuous period of time. 80 seconds to 120 seconds.

More specifically, in order to remove the damaged layer and impurities on the surface of the N-type silicon substrate 1, in this embodiment, before the first intrinsic silicon layer is formed on the back surface 1b of the N-type silicon substrate 1, the The production method also includes:

The N-type silicon substrate 1 is immersed in a mixed solution of sodium hydroxide or potassium hydroxide solution and deionized water with a volume ratio of 2% to 5% for polishing. Wherein, the temperature of the mixed solution is 70°C to 80°C, and the polishing time is 3 minutes to 5 minutes.

Example 2

Different from Embodiment 1, in order to further reduce the recombination rate of photo-generated carriers on the backside, in this embodiment, before forming the first intrinsic silicon layer on the backside of the N-type silicon substrate, A tunnel oxide layer is formed on the backside of the N-type silicon substrate. The first intrinsic silicon layer is formed on the tunnel oxide layer after the tunnel oxide layer is formed. Correspondingly, after the first protective layer and the boron-doped layer are subsequently patterned, the patterned groove will expose a partial region of the tunnel oxide layer; and the second intrinsic silicon formed subsequently The layer will be in contact with a part of the tunnel oxide layer, that is, a tunnel oxide layer is arranged between the N-type silicon substrate and the patterned pn junction (that is, the phosphorus-doped layer and the boron-doped layer), thereby The photo-generated electrons are directly transferred to the emitter through the tunneling effect, thereby reducing the recombination rate of photo-generated carriers on the backside, thereby improving the photoelectric conversion efficiency of the battery.

Example 3

This embodiment provides a back-junction back-contact solar cell, which is fabricated by using the fabrication method of Embodiment 1 or Embodiment 2.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. A method for manufacturing a back junction back contact solar cell, the method comprising:

after a first intrinsic silicon layer is formed on the back surface of the N-type silicon substrate, boron doping is carried out on the first intrinsic silicon layer to form a boron-doped layer;

after forming a first protective layer on the boron-doped layer, patterning the first protective layer and the boron-doped layer to form a patterned groove so as to expose a partial area of the back surface;

forming a second intrinsic silicon layer in the patterned groove, and enabling the second intrinsic silicon layer to be in contact with a partial region of the back surface;

phosphorus doping is carried out on the second intrinsic silicon layer to form a phosphorus-doped layer;

after a second protective layer is formed on the phosphorus-doped layer, cleaning unnecessary doped regions on the front side and the side face of the N-type silicon substrate;

and after removing the first protective layer and the second protective layer, respectively forming electrodes on the boron-doped layer and the phosphorus-doped layer.

2. The fabrication method according to claim 1, wherein before removing the first protective layer and the second protective layer, the fabrication method comprises:

phosphorus doping the front surface to form a surface field region;

forming a third protective layer on the surface field region;

cleaning an unnecessary doped region on the side surface of the N-type silicon substrate;

and removing the third protective layer.

3. The method of claim 2, wherein after removing the third passivation layer, the method further comprises: and sequentially forming a first passivation layer and an anti-reflection layer on the surface field region.

4. The method of manufacturing of any of claims 1 to 3, wherein prior to forming the electrode, the method of manufacturing further comprises: and forming a second passivation layer on the boron-doped layer and the phosphorus-doped layer.

5. The method of claim 4, wherein the forming the electrodes on the boron-doped layer and the phosphorus-doped layer respectively comprises:

printing silver paste containing a corrosive solvent on the second passivation layer, and enabling the silver paste to be in contact with the boron-doped layer and the phosphorus-doped layer after being etched through the second passivation layer;

curing the silver paste to form the electrode.

6. The manufacturing method according to claim 2, wherein the first protective layer, the second protective layer, and the third protective layer are made of silicon dioxide or silicon nitride.

7. The method of claim 1 or 2, wherein the step of cleaning the non-essential doped region comprises:

and soaking the N-type silicon substrate provided with the second protective layer and/or the third protective layer in 6-18% of sodium hydroxide solution at room temperature for 80-120 seconds.

8. The method of fabricating of claim 1, wherein prior to forming the first intrinsic silicon layer on the backside of the N-type silicon substrate, the method further comprises:

soaking the N-type silicon substrate in a mixed solution of 2-5% by volume of sodium hydroxide or potassium hydroxide solution and deionized water for polishing; wherein the temperature of the mixed solution is 70-80 ℃, and the polishing time is 3-5 minutes.

9. A back junction back contact solar cell, wherein the back junction back contact solar cell is manufactured by the manufacturing method of any one of claims 1 to 8.

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