Preparation method and structure of back contact passivation battery

Abstract

The invention discloses a preparation method and structure of a back contact passivation cell, and belongs to the technical field of solar cells, and the preparation method comprises the steps: firstly, cleaning a semiconductor substrate, and starting to prepare a passivation layer on one surface of the substrate; depositing a protective layer on a single side of the back surface; selective grooving treatment is conducted on the protective film on the back face through laser equipment; then putting into a thermal diffusion furnace to complete the preparation of a first electrode on the back surface of the battery; the outermost protection layer can be used as a protection film of a back electrode, then phosphorus slurry is printed above a laser untreated area on the back surface of the protection layer, then thermal annealing treatment is carried out, and a passivation anti-reflection film is deposited on each of the front surface and the back surface of the cell after thermal annealing treatment is completed; and finally completing the preparation of the battery. According to the invention, a one-step laser method is used to solve the possibility that the back contact cell generates electric leakage at the electrodes of two different doping types.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a back contact passivation cell and a structure thereof. Background Art

[0002] Back-contact cells are a type of solar cell technology that uses a design different from traditional crystalline silicon photovoltaic cells. Its electrodes are located on the back of the cell, which means that the front is fully exposed to sunlight, improving the efficiency of light absorption. This design can also reduce the path of current transmission, reduce resistance, and improve cell performance.

[0003] The movement of minority carriers in crystalline silicon solar cells relies on the built-in electric field of the pn junction. In order for the metal electrode to receive carriers, the pn contact of the back contact cell can only be composed of a substrate and different types of doping, but this will also lead to the formation of a short-circuit channel. Therefore, it is essential to rely on laser technology to achieve precise process processing. Summary of the invention

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a back contact passivation battery comprises the following steps:

[0006] S10, firstly, the semiconductor substrate is cleaned and pre-polished using electronic grade chemicals, and then a passivation layer is prepared on one side of the semiconductor substrate, which is an oxide layer and an intrinsic amorphous silicon layer from the inside to the outside. At this time, the side where the passivation layer is deposited is the back side;

[0007] S20, depositing a protective layer on one side of the back surface, wherein the protective layer is one of silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof;

[0008] S30, using a laser device to selectively groove the protective film on the back side for preparation of doped polysilicon, while the area not etched by the laser is retained;

[0009] S40, then put it into a thermal diffusion furnace, introduce BCl3 or BBr3 at a temperature range of 800-1000°C, use in-situ doping to achieve a surface concentration of 5E19 after thermal diffusion ion doping, and then after annealing, the intrinsic amorphous silicon will be converted into doped polysilicon, i.e., P+poly, completing the preparation of the first electrode on the back of the battery, and an oxide layer will be generated outside the doped polysilicon layer;

[0010] S50, the outermost protective layer can be used as a protective film for the back electrode, and is placed in a tank for front texturing treatment; finally, the outermost oxide layer on the back and the oxide layer not treated by laser are removed;

[0011] S60, then printing phosphor paste on the area on the back side which is not laser treated;

[0012] S70, then perform thermal annealing treatment, introducing either oxygen or nitrogen for 5 to 20 minutes;

[0013] S80, deposit a layer of Al with a thickness of 3 to 10 nm on the front and back of the battery x O y , using one of PEALD, ALD, and PVD to achieve the deposition of the atomic layer passivation film, using one of trimethylaluminum and H2O or trimethylaluminum and O3; after completion, a passivation anti-reflection film is deposited on the front and back sides of the battery;

[0014] S90. Finally, aluminum paste is printed on the boron-doped polysilicon (P+poly) area through a metallization process to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon layer (N+poly) area to form a negative electrode, thereby completing the preparation of the battery.

[0015] Further, in step S10, the processing liquid is a solution of at least one of NH4OH, NaOH, KOH, and H2O, the process temperature is 60-75°C, and the process time is 200s; the thickness of the oxide layer is 1-3nm, the thickness of the intrinsic amorphous silicon layer Poly-Si is 80-300nm, the silicon oxide layer is deposited by high-temperature oxidation, nitric acid oxidation, and ozone oxidation, and the intrinsic amorphous silicon layer is deposited by low-pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, atomic layer deposition, and hot filamentation vapor deposition.

[0016] Further, in step S20, the protective layer is prepared by one of low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, and atomic layer deposition.

[0017] Further, in step S30, the laser processing area is 200-700 um.

[0018] Further, in step S50, the chemicals in the tank body are treated in a solution of NaOH / KOH and H2O in a volume ratio of 3:20 at a temperature of 70-85°C for 200-500s, at which time the front suede reflectivity is 8-12%. Finally, the chemicals are cleaned in a solution of HF and H2O in a volume ratio of 1:20 at room temperature for 200-400s to remove the outermost oxide layer and the oxide layer not treated by laser on the back.

[0019] Furthermore, in step S60, the printing width of the N zone is 300-500 um, the solid content of the phosphorus paste is 15-35%, and the viscosity is 20-50 Pa.

[0020] Furthermore, in step S70, the annealing temperature atmosphere is 600-1000°C.

[0021] Further, in step S80, the passivation anti-reflection film has a thickness of 70-110 nm and a refractive index of 2.0-2.4%, and the passivation anti-reflection film is made of one or any combination of silicon nitride, silicon oxide, and silicon oxynitride.

[0022] Furthermore, in step S90, the process sintering temperature is 700-900°C.

[0023] A back contact passivated battery structure is used to prepare the back contact passivated battery structure described above, and the preparation method comprises the following steps:

[0024] A structure of a back contact passivated battery, using any of the above methods for preparing a back contact passivated battery, comprising:

[0025] A semiconductor, wherein the backlight surface of the semiconductor is sequentially stacked with a tunneling oxide layer, a doped polysilicon layer, and a back passivation layer anti-reflection layer from the inside to the outside; and the backlight surface of the semiconductor is stacked with a front passivation layer anti-reflection layer;

[0026] Among them, the doped polysilicon layer includes a boron-doped polysilicon region, an intrinsic amorphous silicon region, a phosphorus-doped polysilicon region, an intrinsic amorphous silicon region and a boron-doped polysilicon region, and aluminum paste is printed on the boron-doped polysilicon region through a metallization process to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon layer region to form a negative electrode.

[0027] Beneficial effects:

[0028] The invention adopts the passivation contact technology when preparing the back contact battery and uses it for the preparation of the back electrode, thereby achieving a higher battery conversion efficiency. The one-step laser method is used to solve the possibility of leakage in the back contact battery between two electrodes of different doping types.

[0029] The present invention can be applied to any one of P-type or N-type semiconductor substrates. The preparation of the back-doped semiconductor type can be a high-temperature ion thermal diffusion method, a laser transfer method, or a boron slurry or phosphorus slurry coating method, thereby completing the preparation of the back electrode, and adding a laser process step to produce an intrinsic amorphous silicon without any doping. Such amorphous silicon can be used to passivate the semiconductor substrate interface and to isolate regions of different doping types, thereby achieving a higher mass production value of the back contact passivated battery and a lower-cost production process manufacturing path. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The steps in the preparation method of the present invention are as follows Figure 1 ;

[0031] Figure 2 The steps in the preparation method of the present invention are as follows Figure 2 ;

[0032] Figure 3 The steps in the preparation method of the present invention are as follows Figure 3 ;

[0033] Figure 4 The steps in the preparation method of the present invention are as follows Figure 4 ;

[0034] Figure 5 The steps in the preparation method of the present invention are as follows Figure 5 ;

[0035] Figure 6 The steps in the preparation method of the present invention are as follows Figure 6 ;

[0036] Figure 7 The steps in the preparation method of the present invention are as follows Figure 7 ;

[0037] Figure 8 The steps in the preparation method of the present invention are as follows Figure 8 ;

[0038] Fig. 9 The steps in the preparation method of the present invention are as follows Figure 9 .

[0039] Among them, 1. front passivation anti-reflection layer; 2. tunneling oxide layer; 3. boron-doped polysilicon; 4. back passivation anti-reflection layer; 5. intrinsic amorphous silicon; 6. phosphorus-doped polysilicon; 7. positive electrode; 8. negative electrode. DETAILED DESCRIPTION

[0040] Example 1

[0041] refer to Figures 1 to 9 , a method for preparing a structure of a back contact passivated battery, the preparation method comprising the following steps:

[0042] S10. First, the semiconductor substrate is cleaned of oil, metal ions, dirt, etc., and pre-polished with electronic-grade chemicals. The semiconductor substrate can be modified into a relatively flat interface to facilitate the growth of grains and excellent passivation of intrinsic amorphous silicon. The treatment liquid is at least one of NH4OH, NaOH, KOH, and H2O. The process temperature is about 60-75°C and the process time is about 200s. Then, the passivation layer is prepared on one side of the substrate, and the oxide layer (SiO x) and 5 layers of intrinsic amorphous silicon (Poly-Si), which can realize efficient passivation of the back side and selective collection of carriers. The thickness of the oxide layer is about 1-3nm, the thickness of the 5 layers of intrinsic amorphous silicon Poly-Si is 80-300nm, the silicon oxide layer is deposited by high temperature oxidation, nitric acid oxidation, ozone oxidation, and the deposition method of the 5 layers of intrinsic amorphous silicon is low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, atomic layer deposition, and hot wire vapor deposition. At this time, the side on which the passivation layer is deposited is the back side, such as Figure 1 ;

[0043] S20. During high-temperature thermal diffusion, it is necessary to protect the area of ​​another doping type from being affected. A dielectric layer can be selected to prevent ion diffusion and doping. Therefore, a protective layer is deposited on one side of the back. The preparation method of the protective layer can be one of low-pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, and atomic layer deposition. The protective film can be silicon oxide (SiO x ), silicon nitride (Si x N y ), silicon oxynitride (SiO x N y ) or a combination thereof, the thickness of the protective film is about 30 to 80 nm, such as Figure 2 ;

[0044] S30. In the semiconductor industry, selective etching or regional grooving is required. Photolithography and laser are relatively mature processes, but due to the high cost of photolithography, it is not selected by most processes. Therefore, laser equipment is used to selectively groove the protective film on the back for the preparation of doped polysilicon, while the area not etched by the laser is retained. The laser wavelength is 355nm, the working power is about 70W, and the laser processing area is about 200~700um. Figure 3 ;

[0045] S40, then put it into a thermal diffusion furnace, introduce BCl3 or BBr3 at a temperature range of about 800-1000°C, use in-situ doping to achieve a surface concentration of about 5E19 after thermal diffusion ion doping, and then after annealing, the intrinsic amorphous silicon 5 will be converted into doped polysilicon (i.e. P+poly), completing the preparation of the first electrode on the back of the battery, and an oxide layer will be generated outside the doped polysilicon layer (boron-doped silicon oxide is borosilicate glass), such as Figure 4 ;

[0046] S50, the outermost protective layer can be used as a protective film for the back electrode, and is placed in a tank for front texturing treatment, so that a pyramid is generated on the front to achieve maximum light absorption of solar energy. At the same time, the existence of the protective film can protect the passivation contact area from being damaged; wherein the chemicals are treated in a solution of NaOH / KOH and H2O in a volume ratio of about 3:20 at a temperature of about 70-85°C for about 200-500s, at which time the front velvet reflectivity is about 8-12%, and finally, it is cleaned in a solution of HF and H2O in a volume ratio of about 1:20 at room temperature for about 200-400s to remove the outermost oxide layer on the back and the oxide layer not treated by laser, and obtain Figure 5 ;

[0047] S60, then print phosphorus paste on the untreated area on the back side, the N area printing width is about 300-500um, the solid content of phosphorus paste is 15-35%, and the viscosity is 20-50Pa. Figure 6 samples;

[0048] S70, then perform thermal annealing treatment, the annealing temperature atmosphere is about 600-1000°C, and one of oxygen and nitrogen is introduced for about 5-20 minutes. Figure 7 ;

[0049] S80, deposit a layer of Al with a thickness of about 3 to 10 nm on the front and back of the battery x O y , one of PEALD, ALD, and PVD can be used to achieve the deposition of atomic layer passivation film, which can be completed by using trimethylaluminum and H2O or trimethylaluminum and O3; after completion, a passivation anti-reflection film is deposited on the front and back sides of the battery, with a film thickness of about 70 to 110nm and a refractive index of 2.0 to 2.4%. The passivation anti-reflection film can be one of silicon nitride, silicon oxide, silicon oxynitride, or any combination thereof, to obtain Figure 8 ;

[0050] S90, finally, through the metallization process, aluminum paste is printed on the boron-doped polysilicon (P+poly) area to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon layer (N+poly) area to form a negative electrode, wherein the process sintering temperature is about 700-900°C, thus completing the preparation of the battery, such as Figure 9 .

[0051] The present invention can be applied to any one of P-type or N-type semiconductor substrates. The preparation of the back-doped semiconductor type can be a high-temperature ion thermal diffusion method, a laser transfer method, or a boron slurry or phosphorus slurry coating method, thereby completing the preparation of the back electrode, and adding a laser process step to produce an intrinsic amorphous silicon 5 without any doping. This type of amorphous silicon can be used to passivate the semiconductor substrate interface and to isolate regions of different doping types, thereby achieving a higher mass production value of the back contact passivated battery and a lower cost production process manufacturing path.

[0052] Example 2

[0053] refer to Figure 9 This embodiment provides a structure of a back-contact passivated battery, and adopts the method for preparing the back-contact passivated battery provided in Embodiment 1, comprising:

[0054] Semiconductor, the backlight side of the semiconductor is stacked with a tunneling oxide layer 2, a doped polysilicon layer, and a back passivation anti-reflection layer 4 in sequence from the inside to the outside; the backlight side of the semiconductor is stacked with a front passivation anti-reflection layer;

[0055] Among them, the doped polysilicon layer includes a boron-doped polysilicon 3 region, an intrinsic amorphous silicon 5 region, a phosphorus-doped polysilicon 6 region, an intrinsic amorphous silicon 5 region and a boron-doped polysilicon 3 region, and aluminum paste is printed on the boron-doped polysilicon region through a metallization process to form a positive electrode 7, and silver paste is printed on the phosphorus-doped polysilicon layer region to form a negative electrode 8.

[0056] The invention adopts the passivation contact technology when preparing the back contact battery and uses it for the preparation of the back electrode, thereby achieving a higher battery conversion efficiency. The one-step laser method is used to solve the possibility of leakage in the back contact battery between two electrodes of different doping types.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a back contact passivated battery, characterized in that: The following steps are involved: S10, firstly, the semiconductor substrate is cleaned and pre-polished using electronic grade chemicals, and then a passivation layer is prepared on one side of the semiconductor substrate, which is an oxide layer and an intrinsic amorphous silicon layer from the inside to the outside. At this time, the side where the passivation layer is deposited is the back side; S20, depositing a protective layer on one side of the back surface, wherein the protective layer is one of silicon oxide, silicon nitride, silicon oxynitride, or a combination thereof; S30, using a laser device to selectively groove the protective film on the back side for preparation of doped polysilicon, while the area not etched by the laser is retained; S40, then put it into a thermal diffusion furnace, introduce BCl3 or BBr3 at a temperature range of 800-1000°C, use in-situ doping to achieve a surface concentration of 5E19 after thermal diffusion ion doping, and then after annealing, the intrinsic amorphous silicon will be converted into doped polysilicon, i.e., P+poly, completing the preparation of the first electrode on the back of the battery, and an oxide layer will be generated outside the doped polysilicon layer; S50, the outermost protective layer can be used as a protective film for the back electrode, and is placed in a tank for front texturing treatment; finally, the outermost oxide layer on the back and the oxide layer not treated by laser are removed; S60, then printing phosphor paste on the area on the back side which is not laser treated; S70, then perform thermal annealing treatment, introducing either oxygen or nitrogen for 5 to 20 minutes; S80, deposit a layer of Al with a thickness of 3 to 10 nm on the front and back of the battery x O y , using one of PEALD, ALD, and PVD to achieve the deposition of the atomic layer passivation film, using one of trimethylaluminum and H2O or trimethylaluminum and O3; after completion, a passivation anti-reflection film is deposited on the front and back sides of the battery; S90. Finally, aluminum paste is printed on the boron-doped polysilicon (P+poly) area through a metallization process to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon layer (N+poly) area to form a negative electrode, thereby completing the preparation of the battery.

2. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S10, the processing liquid is a solution of at least one of NH4OH, NaOH, KOH, and H2O, the process temperature is 60-75°C, and the process time is 200s; the thickness of the oxide layer is 1-3nm, the thickness of the intrinsic amorphous silicon layer Poly-Si is 80-300nm, the silicon oxide layer is deposited by high-temperature oxidation, nitric acid oxidation, and ozone oxidation, and the intrinsic amorphous silicon layer is deposited by low-pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, atomic layer deposition, and hot wire vapor deposition.

3. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S20, the protective layer is prepared by one of low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition and atomic layer deposition.

4. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S30, the laser processing area is 200-700 um.

5. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S50, the chemicals in the tank are treated in a solution of NaOH / KOH and H2O in a volume ratio of 3:20 at a temperature of 70-85°C for 200-500s, at which time the front suede reflectivity is 8-12%. Finally, the chemicals are cleaned in a solution of HF and H2O in a volume ratio of 1:20 at room temperature for 200-400s to remove the outermost oxide layer on the back and the oxide layer not treated by laser.

6. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S60, the printing width of the N zone is 300-500 um, the solid content of the phosphorus paste is 15-35%, and the viscosity is 20-50 Pa.

7. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S70 , the annealing temperature atmosphere is 600 to 1000° C.

8. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S80, the passivation anti-reflection film has a thickness of 70-110 nm and a refractive index of 2.0-2.4%. The passivation anti-reflection film is made of silicon nitride, silicon oxide, silicon oxynitride or any combination thereof.

9. The method for preparing a back contact passivated battery according to claim 1, characterized in that: In step S90, the process sintering temperature is 700-900°C.

10. A structure of a back contact passivated battery, characterized in that: A method for preparing a back contact passivated battery according to any one of claims 1 to 9, comprising: A semiconductor, wherein the backlight surface of the semiconductor is sequentially stacked with a tunneling oxide layer, a doped polysilicon layer, and a back passivation layer anti-reflection layer from the inside to the outside; and the backlight surface of the semiconductor is stacked with a front passivation layer anti-reflection layer; Among them, the doped polysilicon layer includes a boron-doped polysilicon region, an intrinsic amorphous silicon region, a phosphorus-doped polysilicon region, an intrinsic amorphous silicon region and a boron-doped polysilicon region, and aluminum paste is printed on the boron-doped polysilicon region through a metallization process to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon layer region to form a negative electrode.

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