A method of fabricating and structure for a back contact passivated cell

Abstract

The application discloses a preparation method and structure of a back contact passivated cell and belongs to the technical field of solar cells. The method comprises the following steps: firstly, cleaning a semiconductor substrate, and starting preparation of a passivation layer on one side of the substrate; depositing a protective layer on the back side; using a laser device to selectively groove the protective film on the back side; then, putting the semiconductor substrate into a heat diffusion furnace to complete preparation of the first electrode on the back side of the cell; the outermost protective layer can be used as a protective film of the back electrode, then printing a phosphorus paste on the area on the back side which is not treated by the laser, and then performing heat annealing treatment; after the treatment, depositing a passivation anti-reflection film on the front and back sides of the cell; and finally, completing preparation of the cell. The method of using one-step laser solves the possibility of electric leakage of the back contact cell at the electrodes of two different doping types.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cells, and particularly relates to a preparation method and structure of a back contact passivated cell. BACKGROUND

[0002] The back contact type cell is a kind of solar cell technology, which adopts a design different from the traditional crystalline silicon photovoltaic cell, and the electrode thereof is located on the back surface of the cell, which means that the front surface is completely exposed to sunlight, thereby improving the light absorption efficiency, and the design can also reduce the current transmission path, reduce the resistance, and improve the performance of the cell.

[0003] The movement of the minority carriers in the crystalline silicon solar cell is dependent on the built-in electric field of the p-n junction, in order to enable the metal electrode to receive the carriers, the p-n contact of the back contact cell can only be composed of the substrate and different types of doping, but this can also cause the formation of a short circuit channel, and therefore, it is necessary to rely on the laser technology to achieve accurate processing. SUMMARY

[0004] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0005] A preparation method of a back contact passivated cell, comprising the following steps:

[0006] S10, first, the semiconductor substrate is cleaned, and an electronic grade chemical is used for pre-polishing treatment, and then the preparation of the passivation layer on one side of the semiconductor substrate is started, and from inside to outside, the passivation layer is sequentially composed of an oxidation layer and an intrinsic amorphous silicon layer, at this time, the side of the deposited passivation layer is the back surface;

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

[0008] S30, a laser device is used to selectively groove the protective film on the back surface for the preparation of doped polysilicon, and the area not etched by the laser is reserved;

[0009] S40, then it is placed into a thermal diffusion furnace, BCl3 or BBr3 is introduced, the surface concentration after ion doping by in-situ doping at a temperature range of 800-1000 DEG C is 5E19, and after annealing treatment, the intrinsic amorphous silicon at this time is converted into doped polysilicon, i.e., P+poly, the preparation of the first electrode on the back surface of the cell is completed, and an oxidation layer is generated outside the doped polysilicon layer;

[0010] S50, the outermost protective layer can be used as a protective film of the back electrode, and is placed into a groove body for front texturing treatment; finally, the outermost oxidation layer on the back surface and the oxidation layer not treated by the laser are removed;

[0011] S60, then print phosphor paste on the back of the laser non-treatment area;

[0012] S70, then heat annealing treatment, oxygen, nitrogen treatment for 5-20 min;

[0013] S80, in the battery front, back each deposition of 3-10 nm thick Al x O y , using PEALD, ALD, PVD of one of the atomic layer deposition of passivation film, using trimethylaluminum and H2O or trimethylaluminum and O3 to complete; after the completion of the battery, the back of each deposition of a passivation anti-reflection film;

[0014] S90, finally through the metallization process in the boron-doped polysilicon (P+poly) area printed aluminum paste printing to form a positive electrode, in the phosphorus-doped polysilicon layer (N+poly) area printed silver paste to form a negative electrode, complete the preparation of the battery.

[0015] Further, in step S10, the processing liquid is a solution of at least one of NH4OH, NaOH, KOH, H2O, the process temperature is 60-75℃, 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 deposition method of the silicon oxide layer is one of high temperature oxidation, nitric acid oxidation, ozone oxidation, and the deposition method of the intrinsic amorphous silicon layer is one of low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, atomic layer deposition, and hot wire chemical vapor deposition.

[0016] Further, in step S20, the preparation method of the protective layer is 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 treatment area is 200-700um.

[0018] Further, in step S50, the chemical in the tank is a solution of NaOH / KOH, H2O with a volume ratio of 3:20, the temperature is 70-85℃, and the treatment time is 200-500s, at this time the front surface roughness is 8-12%, and finally through the solution of HF, H2O with a volume ratio of 1:20, the cleaning time is 200-400s at room temperature, and the outermost oxide layer and the laser non-treated oxide layer on the back are removed.

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

[0020] Further, in step S70, the annealing temperature atmosphere is 600-1000℃.

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

[0022] Further, in step S90, the process sintering temperature is 700-900℃.

[0023] A structure of a back contact passivated cell, a method for preparing the structure of the back contact passivated cell, the method comprising the following steps:

[0024] A structure of a back contact passivated cell, a method for preparing the structure of the back contact passivated cell, the method comprising the following steps:

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

[0026] The doped polysilicon layer comprises boron-doped polysilicon region, intrinsic amorphous silicon region, phosphorus-doped polysilicon region, intrinsic amorphous silicon region and boron-doped polysilicon region in sequence, and the positive electrode is formed by printing aluminum paste on the boron-doped polysilicon region through a metallization process, and the negative electrode is formed by printing silver paste on the phosphorus-doped polysilicon layer region.

[0027] Advantages:

[0028] The present application adopts a passivation contact technology in the preparation of a back contact cell, and is used for the preparation of a back electrode, so that a high cell conversion efficiency is achieved. And the method of one step laser solves the possibility of leakage of the back contact cell in the two different doped type electrodes.

[0029] The present application can be applied to any one of P-type or N-type semiconductor substrates, and the preparation of the back doped semiconductor type can be a high-temperature ion thermal diffusion method, a laser transfer method or a boron paste or phosphorus paste printing method, so as to complete the preparation of the back electrode, and an intrinsic amorphous silicon which is not doped is generated by adding a one-step laser process, and such amorphous silicon can be used for passivating the semiconductor substrate interface and isolating the regions of different doped types, so that a high production value of the back contact passivated cell and a low-cost production process manufacturing path are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Step flow in the preparation method of the present applicationFigure One ;

[0031] Figure 2 Process flow for the preparation method of the present application Figure Two ;

[0032] Figure 3 Process flow for the preparation method of the present application Figure Three ;

[0033] Figure 4 Process flow for the preparation method of the present application Figure Four ;

[0034] Figure 5 Process flow for the preparation method of the present application Figure Five ;

[0035] Figure 6 Process flow for the preparation method of the present application Figure Six ;

[0036] Figure 7 Process flow for the preparation method of the present application Figure Seven ;

[0037] Figure 8 Process flow for the preparation method of the present application Figure Eight ;

[0038] Figure 9 Process flow for the preparation method of the present application Figure Nine .

[0039] Wherein, 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] Reference Figures One to Nine A preparation method of a structure of a back contact passivated cell, the preparation method comprising the following steps:

[0042] S10, first, the semiconductor substrate is cleaned of oil stains, metal ions, dirt, etc., and pre-polishing treatment is performed using electronic-grade chemicals, which can modify the semiconductor substrate into a relatively flat interface, facilitating the growth of crystal grains and the excellent passivation of intrinsic amorphous silicon. The treatment liquid is a solution of 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 preparation of the passivation layer on one side of the substrate begins, from inside to outside, in order: an oxide layer (SiO x) and intrinsic amorphous silicon 5 layer (Poly-Si), which can achieve high-efficiency passivation and selective collection of carriers on the back surface, the thickness of the oxide layer is about 1-3 nm, the thickness of the intrinsic amorphous silicon 5 layer Poly-Si is 80-300 nm, the deposition method of the silicon oxide layer is one of high-temperature oxidation, nitric acid oxidation, and ozone oxidation, and the deposition method of the intrinsic amorphous silicon 5 layer is one of low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, physical vapor deposition, catalytic chemical vapor deposition, atomic layer deposition, and hot-wire chemical vapor deposition, at this time, the side of the deposited passivation layer is the back surface, such as Figure One ;

[0043] S20, when high-temperature thermal diffusion is needed, the region of the other type of doping needs to be protected from being affected, and a dielectric layer can be selected as an ion diffusion doping prevention layer, so a protective layer is deposited on the back surface, 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, and the protective film can be one of silicon oxide (SiO x ), silicon nitride (Si x N y ), silicon oxynitride (SiO x N y ), or a combination thereof, and the thickness of the protective film is about 30-80 nm, such as Figure Two ;

[0044] S30, in the semiconductor industry, selective etching or regional slotting processing needs to be achieved, photolithography and laser are relatively mature processes, but due to the high cost of photolithography, most processes do not choose it, therefore, a laser device is used to perform selective slotting processing on the protective film on the back surface for the preparation of doped polysilicon, and the region not etched by the laser is reserved, the laser wavelength is 355 nm, the working power is about 70 W, and the laser processing area is about 200-700 um, such as Figure Three ;

[0045] S40, then it is placed in a thermal diffusion furnace, BCl3 or BBr3 is introduced, the temperature range is about 800-1000℃, the surface concentration after thermal diffusion ion doping by in-situ doping is about 5E19, after annealing treatment, the intrinsic amorphous silicon 5 layer will be converted into doped polysilicon (i.e. P+poly), the preparation of the first electrode on the back surface of the cell is completed, and an oxide layer (boron-doped silicon oxide, i.e. borosilicate glass) will be generated outside the doped polysilicon layer, such as Figure Four ;

[0046] S50, the outermost protective layer can be used as a protective film of the back electrode, and is put into a groove to perform a front texturing process, so that a pyramid is generated on the front surface to achieve maximum light absorption of the solar energy. Meanwhile, the protective film can protect the passivation contact area from being damaged. The chemical is a solution of NaOH / KOH and H2O in a volume ratio of about 3:20, and the temperature is about 70-85°C. The treatment time is about 200-500s. At this time, the front surface texturing reflectivity is about 8-12%. Finally, the outermost oxide layer and the laser-unprocessed oxide layer on the back surface are removed by cleaning in a solution of HF and H2O in a volume ratio of about 1:20 at room temperature for about 200-400s, and a sample as shown in Figure Five is obtained.

[0047] S60, then phosphorus paste is printed on the laser-unprocessed area on the back surface. The printing width of the N area is about 300-500um, the solid content of the phosphorus paste is 15-35%, and the viscosity is 20-50Pa. At this time, a sample as shown in Figure Six is obtained.

[0048] S70, then a thermal annealing process is performed. The annealing temperature is about 600-1000°C, and one of oxygen and nitrogen is introduced for about 5-20min. At this time, a sample as shown in Figure Seven is obtained.

[0049] S80, an Al2O3 film with a thickness of about 3-10nm is deposited on the front and back surfaces of the battery. x O y The deposition of the atomic layer passivation film can be realized by one of PEALD, ALD and PVD, and can be completed by using one of trimethylaluminum and H2O or trimethylaluminum and O3. After the completion, a passivation anti-reflection film with a thickness of about 70-110nm and a refractive index of 2.0-2.4% is deposited on the front and back surfaces of the battery. The passivation anti-reflection film can be one of silicon nitride, silicon oxide and silicon oxynitride or any combination thereof, and a sample as shown in Figure Eight is obtained.

[0050] S90, finally, a metalization process is performed to print aluminum paste on the boron-doped polysilicon (P+poly) area to form a positive electrode, and to print silver paste on the phosphorus-doped polysilicon (N+poly) area to form a negative electrode. The process sintering temperature is about 700-900°C. Thus, the preparation of the battery is completed, and a sample as shown in Figure Nine is obtained.

[0051] The present application can be applied to any one of P-type or N-type semiconductor substrates, and the preparation of the back-doped semiconductor type can be high-temperature ion thermal diffusion, laser transfer, boron paste or phosphorus paste printing, thereby completing the preparation of the back electrode, and generating an undoped intrinsic amorphous silicon 5 by adding a step of laser process, which can be used for passivation of the semiconductor substrate interface and isolation of different doped regions, achieving high production value of back contact passivation cells and low-cost production process manufacturing path.

[0052] Embodiment 2

[0053] Reference Figure Nine The present embodiment provides a structure of a back contact passivation cell, which adopts the preparation method of the back contact passivation cell provided in Embodiment 1, comprising:

[0054] The back surface of the semiconductor is sequentially stacked from inside to outside with a tunneling oxide layer 2, a doped polysilicon layer, a back passivation and anti-reflection layer 4; and the back surface of the semiconductor is stacked with a front passivation and anti-reflection layer.

[0055] The doped polysilicon layer comprises boron-doped polysilicon 3 region, intrinsic amorphous silicon 5 region, phosphorus-doped polysilicon 6 region, intrinsic amorphous silicon 5 region and boron-doped polysilicon 3 region in sequence, and the positive electrode 7 is printed by printing aluminum paste on the boron-doped polysilicon region by metallization process, and the negative electrode 8 is printed by printing silver paste on the phosphorus-doped polysilicon layer region.

[0056] The present application adopts passivation contact technology in the preparation of back contact cells, and is used for the preparation of back electrodes, achieving high cell conversion efficiency. And the method of one-step laser solves the possibility of leakage of back contact cells in two different doped electrodes.

[0057] The above is only the preferred embodiment of the present application, and does not limit the technical scope of the present application, so any slight modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.

Claims

1. A method for preparing a back contact passivated battery, characterized in that: The following steps are involved: S10, first cleaning the semiconductor substrate and performing a pre-polishing process using electronic-grade chemicals, then preparing a passivation layer on one side of the semiconductor substrate, which includes an oxide layer and an intrinsic amorphous silicon layer from the inside to the outside. At this time, the side on which 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 layer on the back side for preparing a doped polysilicon layer, while areas not etched by the laser are 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 method to dope with thermal diffusion ions, and then after annealing treatment, the intrinsic amorphous silicon will be converted into a doped polysilicon layer, that is, a boron-doped polysilicon region, 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 oxide 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 protective layer not treated by laser are removed; S60, then printing phosphor paste on the laser-untreated area on the back side; S70, then performing a thermal annealing treatment, introducing either oxygen or nitrogen for 5 to 20 minutes to form a phosphorus-doped polysilicon region, so that the boron-doped polysilicon region, the intrinsic amorphous silicon region, the phosphorus-doped polysilicon region, the intrinsic amorphous silicon region, and the boron-doped polysilicon region are adjacent to each other in sequence; 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 Passivation film, using one of PEALD, ALD, and PVD to achieve the deposition of atomic layer AlxOy 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 of the battery; S90. Finally, aluminum paste is printed on the boron-doped polysilicon area through a metallization process to form a positive electrode, and silver paste is printed on the phosphorus-doped polysilicon 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, wherein: 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, and the thickness of the intrinsic amorphous silicon layer Poly-Si is 80-300nm. The oxide layer is a silicon oxide layer, and the deposition method of the silicon oxide layer is one of high-temperature oxidation, nitric acid oxidation, and ozone oxidation. The deposition method of the intrinsic amorphous silicon layer is one of 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.

3. The method for preparing a back contact passivated battery according to claim 1, wherein: 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, wherein: In step S30, the laser processing area is 200-700 μm.

5. The method for preparing a back contact passivated battery according to claim 1, wherein: 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 200-500 seconds, at which time the front suede reflectivity is 8-12%. Finally, the outermost oxide layer and the laser-untreated protective layer on the back are removed by cleaning in a solution of HF and H2O in a volume ratio of 1:20 at room temperature for 200-400 seconds.

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 μm, the solid content of the phosphorus paste is 15-35%, and the viscosity is 20-50 Pa.s.

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

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

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