Passivated battery of laser patterned polycrystalline silicon, preparation method of passivated battery and photovoltaic module

Abstract

The invention relates to the technical field of solar cell preparation, and discloses a laser patterned polycrystalline silicon passivation cell, a preparation method and a photovoltaic module. The preparation method comprises the following steps: preparing a passivation contact structure and an oxidation film on the surface of a silicon substrate; laser patterning processing is carried out on the surface of the silicon substrate, the passivation contact structure and the non-metallization area of the oxidation film, so that the processed non-metallization area is not subjected to alkali etching resistance, and doping atoms are pushed into the silicon substrate through laser diffusion to form a doping area; performing alkali wash etching to form an alkali wash etching region etched into the silicon substrate, and leaving a doped region on the silicon substrate exposed in the alkali wash etching region; respectively depositing a passivation antireflection film and an antireflection film on the front surface and the back surface of the silicon substrate; and preparing the metal electrode. According to the preparation method, parasitic absorption loss can be avoided, the transverse transmission capability of internal carriers can be enhanced, the light utilization rate and the photoelectric conversion efficiency of the cell are further improved, the process window is larger, and the process steps are simple.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell preparation, and in particular to a laser patterned polysilicon passivation cell and a preparation method and a photovoltaic module. Background Art

[0002] Solar cells are microelectronic devices that directly convert light energy into electrical energy. After years of development, they have a variety of structures, including PERC (Passivated Emitter and Rear Cell), TOPCon (Tunnel Oxide Passivated Contact Solar Cell), HJT (Heterojunction with Intrinsic Thin Layer), etc. At present, considering the battery efficiency and manufacturing cost, TOPCon cells are undoubtedly the mainstream.

[0003] For N-type TOPCon cells, the cell structure needs to be plated with a layer of n-type doped polysilicon (n-type poly) on the basis of the back tunneling oxide layer. Although n-type doped polysilicon brings better passivation contact performance, it will also cause parasitic absorption losses and reduce the back efficiency of the cell, which is not conducive to the market demand for bifacial cells in the downstream of the solar cell industry chain (such as photovoltaic modules and photovoltaic power stations). How to balance the passivation contact performance and reduce parasitic absorption losses is a major problem in TOPCon cell production.

[0004] To solve this problem, the existing solution, as shown in publication number CN113471304A, proposes to use mask slurry to protect the back metallized area of ​​doped polysilicon, and wet-etch the back non-metallized area not protected by the mask slurry to thin the doped polysilicon, thereby reducing the parasitic absorption loss of the back non-metallized area. However, since this solution only thins the doped polysilicon in the back non-metallized area, but does not completely remove the doped polysilicon in the back non-metallized area, there is still a certain parasitic absorption loss in the back non-metallized area; moreover, the removal process of the mask slurry in the later stage of this method is relatively cumbersome and is also easy to contaminate the battery.

[0005] The existing solution, as shown in publication number CN117334788A, proposes a method of using laser-induced oxidation to prepare a P++ emitter at the location where the metal grid lines are printed (i.e., the metallized area), and thinning the borosilicate glass layer at the processing location, and then using a carrier frame with local openings to prepare a front local passivation contact structure to avoid parasitic absorption losses on the front side. However, the laser of this solution acts on the location where the thinner metal grid lines are printed, which requires a high accuracy of laser alignment, and the process window for mass production is narrow.

[0006] The existing scheme, as shown in the publication number CN117878166A, proposes to laser process the non-metallized area on the back. However, this scheme has at least the following defects: 1. After alkali washing, the polysilicon in the treated area is only thinned to 40-80nm, so there is still a certain parasitic absorption loss in the non-metallized area on the back; 2. The thickness of the polysilicon etched by alkali washing is small and the process window is small; 3. Moreover, the thickness removed by alkali washing is small, so it is difficult to thin and enlarge the tower base in the non-metallized area on the back, and the reflectivity of the non-metallized area on the back is still small, making it difficult to further improve the light utilization rate and photoelectric conversion efficiency of the non-metallized area on the back; 4. In addition, there is no AlOx film (aluminum oxide film) deposited on the back, so the loss caused by the laser and alkali washing will also lead to battery efficiency loss. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a laser patterned polysilicon passivation cell and a preparation method and a photovoltaic module.

[0008] Based on this, the present invention discloses a method for preparing a laser patterned polycrystalline silicon passivation cell, comprising the following preparation steps:

[0009] S1. sequentially preparing a tunneling oxide layer and doped polysilicon on a surface of a silicon substrate to obtain a passivation contact structure, and forming an oxide film on the surface of the passivation contact structure;

[0010] S2, irradiating the non-metallized area on the surface of the passivation contact structure with an oxide film with a laser, so that the surface of the silicon substrate and the non-metallized area of ​​the passivation contact structure and the oxide film are all subjected to laser patterning, so that the non-metallized area after the laser patterning is not resistant to alkali etching, thereby forming a difference in alkali etching resistance with the metallized area, and the doping atoms of the doped polysilicon are diffused into the interior of the silicon substrate by laser to form a doped area;

[0011] S3, performing alkali etching, utilizing the difference in alkali etching resistance between the non-metallized area and the metallized area to etch away the passivation contact structure of the non-metallized area, so as to form an alkali etching area etched to the inside of the silicon substrate, and leaving the doped area on the exposed silicon substrate of the alkali etching area, while retaining the passivation contact structure of the metallized area;

[0012] S4, depositing a passivation film and an anti-reflection film in sequence on the front side of the silicon substrate, and depositing an anti-reflection film on the back side of the silicon substrate;

[0013] S5. Performing metallization treatment on the metallization area of ​​the silicon substrate to obtain a metal electrode.

[0014] The method for preparing a laser patterned polysilicon passivation cell in the above steps S1-S5 of the present invention can be used on the back and / or front of a silicon substrate, preferably on the back of a silicon substrate.

[0015] Preferably, step S1 specifically includes:

[0016] S11, first using physical vapor deposition technology to sequentially prepare a tunneling oxide layer and doped amorphous silicon on the back side of the silicon substrate;

[0017] S11, performing annealing treatment to crystallize the doped amorphous silicon and transform it into doped polysilicon, and forming an annealed oxide film on the entire back side of the doped polysilicon to serve as a protective layer for subsequent alkali etching of the metallization area.

[0018] Preferably, in step S2, the laser used for the laser patterning treatment is an infrared continuous laser; the wavelength of the infrared continuous laser is 700-2500nm, the spot equivalent diameter is 100-400μm, the maximum power is 100W, the power coefficient is 50-100%, the pulse width is 20μs, the scanning speed is 15000-25000mm / s, and the processing area accounts for 40-90% of the area of ​​the non-metallized area on the back.

[0019] Further preferably, in step S3, the back non-metallized area is alkali-etched to form the alkali-etched area with an etching depth of 2-4 μm;

[0020] The alkali cleaning and etching is performed at a temperature of 55-65° C., for a time of 260-480 seconds, with an alkali solution concentration of 2.20% and an alkali cleaning additive concentration of 1.10%. The alkali cleaning and etching mode is bubbling and circulation in an alkali polishing tank.

[0021] Preferably, before performing step S4, the method further comprises the step of cleaning the silicon substrate with an acid solution to remove oxide impurities on the front and back surfaces thereof.

[0022] Preferably, before step S1, the following steps are also included: firstly preparing an emitter on the front side of the silicon substrate after texturing, then single-sided pickling the back side and side of the silicon substrate, and then performing back side polishing to obtain a flat back surface of the silicon substrate;

[0023] In step S4, before depositing the anti-reflection film on the back side of the silicon substrate, a passivation film is deposited on the back side of the silicon substrate;

[0024] In step S4, the passivation film is an aluminum oxide film, and the anti-reflection film is a silicon nitride anti-reflection film.

[0025] Further preferably, step S4 specifically includes:

[0026] S41, using atomic layer deposition technology to deposit aluminum oxide films on the front side of the emitter, the alkali-washed and etched area on the back side of the silicon substrate, and the back side of the doped polysilicon;

[0027] S42. Prepare a silicon nitride anti-reflection film on the outer surface of the aluminum oxide film on the front and back sides by using plasma enhanced chemical vapor deposition or plasma assisted chemical vapor deposition technology.

[0028] Further preferably, step S5 specifically includes: applying metal slurry on both the front metallization area and the back metallization area of ​​the silicon substrate, and obtaining metal electrodes after sintering, the metal electrode in the front metallization area makes ohmic contact with the emitter, and the metal electrode in the back metallization area makes ohmic contact with the doped polysilicon.

[0029] The present invention also discloses a laser patterned polycrystalline silicon passivation cell, which is prepared by the preparation method of the laser patterned polycrystalline silicon passivation cell described above in the present invention.

[0030] Preferably, the passivation cell is an N-type TOPCon cell, so its emitter is a p+ emitter, and its doped polysilicon is n-type doped polysilicon.

[0031] The present invention also discloses a photovoltaic assembly, comprising a plurality of photovoltaic cells connected in series and / or in parallel, wherein the photovoltaic cell is a laser patterned polysilicon passivation cell as described above in the present invention.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] The preparation method of the passivated battery of the present invention comprises the following steps: after preparing doped polysilicon in step S1, laser patterning of the non-metallized area in step S2 (such as infrared continuous laser patterning) and alkali etching in step S3. (1) It can not only avoid parasitic absorption loss in the non-metallized area. (2) Laser patterning makes the non-metallized area on the back easier to be alkali-etched, which helps to form an alkali-etched area with an etching depth of 2-4 μm, which can improve the reflectivity of the non-metallized area on the back, thereby further improving the light utilization rate and photoelectric conversion efficiency of the battery. (3) Laser patterning also makes the doped phosphorus atoms of the doped polysilicon further diffuse into the interior of the silicon substrate, thereby further enhancing the lateral transmission capacity of the internal carriers. (4) Since the laser patterning of the present invention is for the non-metallized area and the alkali etching depth is deep, its process window is larger; and compared with the laser induced oxidation method, the present invention has lower requirements on the accuracy and performance of the laser; compared with the mask method, the present invention does not introduce mask slurry pollution and has high cleanliness. (5) In addition, the process steps of the present invention are simple; no additional steps are required. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the cross-sectional structure of a laser patterned polysilicon passivation cell of this embodiment.

[0035] Figure 2 This is an ECV (electrochemical differential capacitance voltage) test curve of the back side of the silicon substrate after the infrared continuous laser patterning treatment in step 6 in the preparation method of a laser patterned polycrystalline silicon passivation cell of this embodiment.

[0036] Figure 3 This is a 3D microscope image of the back side of the silicon substrate after the alkaline etching treatment in step 7 in the preparation method of a laser patterned polysilicon passivation cell of this embodiment; wherein (a) is a 2D representation, from which the difference in tower base between the metallized area and the non-metallized area on the back surface can be seen; and (b) is a 3D representation, from which the difference in surface height between the metallized area and the non-metallized area on the back surface can be seen.

[0037] Description of the accompanying drawings: silicon substrate 1; tunneling oxide layer 2; n-type doped polysilicon 3; p+ emitter 4; aluminum oxide film 5; silicon nitride anti-reflection film 6; metal electrode 7; alkali etching area 8. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example

[0040] A method for preparing a passivated battery in this embodiment is as follows: Figure 1 , comprising the following preparation steps:

[0041] Step 1: Select a silicon substrate 1 and perform a texturing treatment on the silicon substrate 1 so that a surface (such as a front surface and a back surface) of the silicon substrate 1 forms a pyramid-shaped texturing structure.

[0042] Step 2: performing boron diffusion on the silicon substrate 1 processed in step 1 to form a boron-doped emitter (ie, p+ emitter 4 ) on the front side of the silicon substrate 1 .

[0043] In step 2, after boron diffusion, a wrap-around coating is formed on the back and side surfaces of the silicon substrate 1 , and borosilicate glass is formed on the outer surface of the wrap-around coating and the outer surface of the p+ emitter 4 .

[0044] Step 3: single-sided pickling is performed on the silicon substrate 1 processed in step 2 to remove the coating on the back and side surfaces of the silicon substrate 1 and to remove the borosilicate glass on the outer surface of the coating.

[0045] After step 3, the borosilicate glass on the front side of the p+ emitter 4 is retained to protect the p+ emitter 4 in the subsequent preparation process.

[0046] Step 4: polishing (such as alkali polishing) the back side of the silicon substrate 1 after the treatment in step 3, so that the silicon substrate 1 obtains a flat back surface.

[0047] Step 5: Prepare a TOPCon structure (ie, a passivation contact structure) on the back side of the silicon substrate 1 processed in step 4. The passivation contact structure includes a tunneling oxide layer 2 and an n-type doped polysilicon 3 sequentially prepared on the back side of the silicon substrate 1.

[0048] In practice, there are many specific methods for preparing the passivation contact structure. In one example of this embodiment, the specific method for preparing the passivation contact structure is as follows:

[0049] Step 51, using PVD (physical vapor deposition) technology, using popaid equipment (a new type of physical evaporation thin film preparation equipment), to sequentially prepare a tunneling oxide layer 2 and n-type doped amorphous silicon on the back side of the silicon substrate 1: first, the silicon substrate 1 is sent to the PO chamber of the PVD equipment for deposition, so as to deposit and prepare a tunneling oxide layer 2 on the back side of the silicon substrate 1; then, the silicon substrate 1 is sent to the Paid chamber of the PVD equipment, and the silicon target is bombarded with Ar+ to prepare intrinsic amorphous silicon on the back side of the tunneling oxide layer 2, and PH is introduced. 3 The gas is used as a doping source to dope the intrinsic amorphous silicon with phosphorus to prepare n-type doped amorphous silicon.

[0050] Step 52, annealing the silicon substrate 1 after the treatment in step 51 in an annealing furnace, so that the n-type doped amorphous silicon is crystallized and transformed into n-type doped polysilicon 3 (i.e., n+poly), and an annealed oxide film is formed on the back of the n-type doped polysilicon 3. The annealed oxide film produced by annealing can be used as a protective layer for alkaline washing of the non-laser area (corresponding to the metallized area) on the back of the passivation contact structure in the subsequent steps.

[0051] Step 6, irradiate the laser to the local area of ​​the annealed oxide film on the back side of the passivation contact structure (the local area corresponds to the non-metallized area), so that the laser performs laser patterning on the back surface of the silicon substrate 1 and the non-metallized areas of the passivation contact structure and the annealed oxide film, so that the non-metallized area on the back side after the laser patterning is not resistant to alkali etching, thereby forming an alkali etching rate difference with the metallized area on the back side; and the phosphorus-doped atoms of the n-type doped polysilicon 3 are diffused by the laser into the interior of the silicon substrate 1 to form a doped area.

[0052] In step 6 of this embodiment, the laser used is an infrared continuous laser. Compared with purple light and green light, the infrared continuous laser has a longer wavelength and a deeper depth of graphic processing, which helps the subsequent alkaline etching depth of the non-metallized area on the back to reach 2-4μm.

[0053] The infrared continuous laser has a wavelength of 700-2500nm (such as 1064nm), a spot size of 100*100μm, a maximum power of 100W, a power coefficient of 50-100% (such as 75%), a pulse width of 20μs, and a scanning speed of 25000mm / s.

[0054] In step 6, the actual area of ​​infrared continuous laser patterning is 40-90% (e.g., 65%) of the area of ​​the non-metallized area on the back. If the film opening ratio (i.e., the area of ​​the area on the back that is actually subjected to laser patterning and alkali washing and etching accounts for the area of ​​the non-metallized area on the back) is small, the screen printing alignment is good, the carrier lateral transmission performance is better, the fill factor loss is smaller, but the parasitic absorption on the back is not significantly reduced; if the film opening ratio is large, the opposite is true.

[0055] Step 7, performing alkali etching on the back side of the silicon substrate 1 after the treatment in step 6, and utilizing the difference in alkali etching resistance between the back non-metallized area and the back metallized area, removing the annealed oxide film and the passivation contact structure of the back non-metallized area by alkali etching, thereby alkali etching to a certain depth inside the silicon substrate 1; thus, an alkali etching area 8 with an etching depth of 2-4 μm is formed in the back non-metallized area (that is, the sum of the alkali etching thickness of the annealed oxide film, the passivation contact structure of the back metallized area and the silicon substrate 1 is 2-4 μm, such as 3 μm), so that the silicon substrate 1 exposed by the alkali etching area 8 has the doped area; and since the back metallized area is protected by the annealed oxide film that is not irradiated by the laser, the passivation contact structure of the back metallized area is retained (it should be noted that if the alkali acts on the annealed silicon oxide layer that is not irradiated by the laser for a long time, the annealed silicon oxide layer will also be etched).

[0056] In step 7, the alkali washing treatment can be completed directly in the alkali polishing tank; in this way, there is no need to add other equipment or change the alkali solution formula, which can reduce costs.

[0057] In step 7 of the present embodiment, the process conditions of the alkali etching are as follows: the temperature of the alkali etching is 60°C, the time is 260-480s (such as 330s), the total volume of the solution is 540L, the concentration of the NaOH raw material is 45%, the concentration of the alkali solution in the tank is 2.20%, the concentration of the additive (which is the commonly used additive for the existing alkali etching) is 1.10%, the volume of the additive is 6L, and the mode is bubbling plus circulation. Compared with the prior art, the process time of the alkali etching process of the present embodiment is significantly extended to ensure that the alkali etching area 8 with an etching depth of 2-4μm can be formed in the non-metallized area on the back.

[0058] Step 8: Use an acid solution (such as HF solution or HCl solution) to clean the silicon substrate 1 after the treatment in step 7 to remove the oxides on the front and back sides (such as the annealed oxide film in the back metallization area and the borosilicate glass on the front side).

[0059] Step 9: Using ALD (atomic layer deposition) technology, an aluminum oxide film 5 is deposited on both the front and back sides of the silicon substrate 1 processed in step 8.

[0060] Step 9 is specifically as follows: an aluminum oxide film 5 is deposited on the front of the p+ emitter 4, the alkali-washed and etched area 8 of the non-metallized area on the back of the silicon substrate 1, and the back of the n-type doped polysilicon 3. The aluminum oxide film 5 on the front of the p+ emitter 4 is the front aluminum oxide film; and the alkali-washed and etched area 8 of the non-metallized area on the back of the silicon substrate 1 and the aluminum oxide film 5 on the back of the n-type doped polysilicon 3 are the back aluminum oxide film.

[0061] Compared with the normal process of existing TOPCon battery preparation, step 9 of this embodiment coats an additional layer of back aluminum oxide film. The back aluminum oxide film can not only repair the damage caused by laser patterning, but also enhance the passivation performance of the back side, so as to effectively avoid the loss of battery efficiency caused by laser patterning and alkaline etching.

[0062] Step 10: Using PECVD (plasma enhanced chemical vapor deposition or plasma assisted chemical vapor deposition) technology, a silicon nitride anti-reflection film 6 is prepared on the front and back sides of the silicon substrate 1 processed in step 9.

[0063] Of course, in other examples of this embodiment, other deposition techniques may also be used to prepare the silicon nitride anti-reflection film 6 .

[0064] Step 10 specifically includes: depositing a silicon nitride anti-reflection film 6 on the front side of the front aluminum oxide film and on the back side of the back aluminum oxide film.

[0065] Step 11: Using screen printing technology, metal slurry is applied to both the front metallization area and the back metallization area of ​​the silicon substrate 1 processed in step 10, and the metal electrode 7 is prepared after sintering.

[0066] In step 11, the metal electrode 7 in the front metallization area of ​​the silicon substrate 1 is the front metal electrode, which makes ohmic contact with the p+ emitter 4; and the metal electrode 7 in the back metallization area of ​​the silicon substrate 1 is the back metal electrode, which makes ohmic contact with the n-type doped polysilicon 3.

[0067] After the processing in step 11, a laser patterned polysilicon passivation cell of this embodiment is obtained (the structure of the passivation cell is specifically referred to in Figure 1 ).

[0068] A photovoltaic module of the present embodiment includes a plurality of photovoltaic cells connected in series and / or in parallel. The photovoltaic cells are the laser patterned polysilicon passivation cells described above in the present embodiment.

[0069] Performance Testing

[0070] 1. Perform ECV test on the back side of the silicon substrate sample after the infrared continuous laser patterning treatment in step 6, and obtain Figure 2 The ECV test curve of the back side of the silicon substrate sample is shown. Figure 2 In the figure, the test object of the ECV test curve marked with no laser is: the back metallized area that has not been processed by infrared continuous laser patterning in step 6, and the test object of the ECV test curve marked with laser is: the back non-metallized area that has been processed by infrared continuous laser patterning in step 6.

[0071] from Figure 2 It can be seen that the doped phosphorus atoms (derived from n-type doped polysilicon) in the non-metallized area on the back side after infrared continuous laser patterning diffuse very deeply into the interior of the silicon substrate, that is, the infrared continuous laser patterning treatment in step 6 can also promote the doped phosphorus atoms to further diffuse into the interior of the silicon substrate. This means that even if the alkaline etching depth in step 7 reaches 2-4μm, the doped phosphorus atoms diffused into the interior of the silicon substrate can still have a large gain in the lateral transport of carriers, thereby further enhancing the lateral transport capability of internal carriers.

[0072] 2. Figure 3 (a) The two interlaced stripe regions in the middle correspond to Figure 3 (b) The two spaced-apart raised areas in the middle represent the back metallization areas; Figure 3 (a) and Figure 3 The other three regions in (b) represent the non-metallized areas on the back side.

[0073] from Figure 3 It can be seen that the traces of protrusion thinning (i.e., the tower base becomes larger) can be clearly seen in the back non-metallized area that has been processed by infrared continuous laser patterning in advance. Therefore, the back non-metallized area that has been processed by infrared continuous laser patterning in step 6 is more easily removed by alkali etching in step 7, which makes it possible to reach a depth of 2-4 μm in the back non-metallized area in step 7. Since the alkali etching in step 7 can reach the inside of the silicon substrate (the depth of alkali etching is 2-4 μm), a large degree of alkali etching will make the tower base in the alkali etching area larger, so that the reflectivity of the back non-metallized area will increase accordingly, and then the back non-metallized area can reflect more light to further improve the secondary absorption and utilization of the reflected light by the passivation battery, so that the light utilization rate and photoelectric conversion efficiency can be further improved.

[0074] 3. The passivated battery of this embodiment was tested for electrical performance, and the test data are shown in Table 1 below:

[0075] Table 1

[0076] condition Eta / % Uoc / V Isc / A FF / % BSL 26.13 0.7372 14.103 84.14 This embodiment 26.28 0.7386 14.176 84.02

[0077] In Table 1, BSL represents a TOPCon cell prepared by the existing method for preparing a back-passivated contact cell; compared with the method for preparing a passivated cell of this embodiment, the method for preparing a back-passivated contact cell of this embodiment omits steps 6-7 of this embodiment, and omits the preparation of a back aluminum oxide film in step 9. In Table 1, Eta is the photoelectric conversion efficiency, Uoc is the open circuit voltage, Isc is the short circuit current, and FF is the fill factor.

[0078] From the test results in Table 1, the preparation method of the passivation battery of this embodiment, after preparing n-type doped polycrystalline silicon in step 5, cooperates with the infrared continuous laser patterning treatment of the back non-metallized area in step 6 and the alkaline etching in step 7, and the alkaline etching is carried out to the inside of the silicon substrate (etching depth is 2-4μm), and then cooperates with the preparation of the back aluminum oxide film in the subsequent step 9; in this way, the short-circuit current, open-circuit voltage and photoelectric conversion efficiency of the passivation battery prepared in this embodiment can be further improved.

[0079] In summary, the preparation method of the passivation battery of the present invention, after preparing n-type doped polycrystalline silicon in step 5, is combined with infrared continuous laser patterning treatment of the back non-metallic area in step 6 and alkaline etching in step 7. (1) It can not only avoid the parasitic absorption loss of the back non-metallic area. (2) The infrared continuous laser patterning treatment can make the back non-metallic area easier to be alkali-etched, which helps to subsequently form an alkaline etching area with an etching depth of 2-4μm, which helps to improve the reflectivity of the back non-metallic area, thereby further improving the light utilization rate and photoelectric conversion efficiency. (3) The infrared continuous laser patterning treatment can also make the doped phosphorus atoms of the n-type doped polycrystalline silicon in the back non-metallic area further diffuse into the interior of the silicon substrate, thereby further enhancing the lateral transmission capacity of the internal carriers. (4) Since the infrared continuous laser patterning treatment of the present invention is targeted at the non-metallized area on the back side and the alkali etching depth of this area is deep, its process window is larger; and compared with the laser induced oxidation method, the present invention has lower requirements on the accuracy and performance of the laser; compared with the mask method, the preparation method of the present invention will not introduce mask slurry contamination and has high cleanliness. (5) In conjunction with the subsequent step 9, the back aluminum oxide film is prepared to repair the damage caused by the infrared continuous laser patterning treatment and enhance the passivation performance of the back side, thereby effectively avoiding the loss of battery efficiency caused by laser patterning and alkali etching. (6) In addition, the process steps of the present invention are simple; without the need to add other additional steps, the preparation of the back aluminum oxide film can be completed simultaneously with the plating of the front aluminum oxide film.

[0080] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0081] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a laser patterned polysilicon passivation cell, characterized in that: The method comprises the following preparation steps: S1. sequentially preparing a tunneling oxide layer and doped polysilicon on the surface of a silicon substrate to obtain a passivation contact structure, and forming an oxide film on the surface of the passivation contact structure; S2, irradiating the non-metallized area on the surface of the passivation contact structure with an oxide film with a laser, so that the surface of the silicon substrate and the non-metallized area of ​​the passivation contact structure and the oxide film are all subjected to laser patterning, so that the non-metallized area after the laser patterning is not resistant to alkali etching, thereby forming a difference in alkali etching resistance with the metallized area, and the doping atoms of the doped polysilicon are diffused into the interior of the silicon substrate by laser to form a doped area; S3, performing alkali etching, utilizing the difference in alkali etching resistance between the non-metallized area and the metallized area to etch away the passivation contact structure of the non-metallized area, so as to form an alkali etching area etched to the inside of the silicon substrate, and leaving the doped area on the exposed silicon substrate of the alkali etching area, while retaining the passivation contact structure of the metallized area; S4, depositing a passivation film and an anti-reflection film on the front side of the silicon substrate in sequence, and depositing an anti-reflection film on the back side of the silicon substrate; S5. Performing metallization treatment on the metallization area of ​​the silicon substrate to obtain a metal electrode.

2. The method for preparing a laser patterned polysilicon passivation cell according to claim 1, characterized in that: Step S1 specifically includes: S11, first using physical vapor deposition technology to sequentially prepare a tunneling oxide layer and doped amorphous silicon on the back side of the silicon substrate; S11, performing annealing treatment to crystallize the doped amorphous silicon and transform it into doped polysilicon, and forming an annealed oxide film on the entire back side of the doped polysilicon to serve as a protective layer for subsequent alkali etching of the metallization area.

3. The method for preparing a laser patterned polysilicon passivation cell according to claim 1, characterized in that: In step S2, the laser used for the laser patterning treatment is an infrared continuous laser; the wavelength of the infrared continuous laser is 700-2500nm, the spot equivalent diameter is 100-400μm, the maximum power is 100W, the power coefficient is 50-100%, the pulse width is 20μs, the scanning speed is 15000-25000mm / s, and the processing area accounts for 40-90% of the area of ​​the non-metallized area on the back.

4. The method for preparing a laser patterned polysilicon passivation cell according to claim 1 or 3, characterized in that: In step S3, the back non-metallized area is alkali-etched to form the alkali-etched area with an etching depth of 2-4 μm; The alkali cleaning and etching is performed at a temperature of 55-65° C., for a time of 260-480 seconds, with an alkali solution concentration of 2.20% and an alkali cleaning additive concentration of 1.10%. The alkali cleaning and etching mode is bubbling and circulation in an alkali polishing tank.

5. The method for preparing a laser patterned polysilicon passivation cell according to claim 1, characterized in that: Before performing step S4, the method further includes cleaning the silicon substrate with an acid solution to remove oxide impurities on the front and back sides thereof.

6. The method for preparing a laser patterned polysilicon passivation cell according to claim 1, characterized in that: Before step S1, the method further includes the following steps: firstly preparing an emitter on the front surface of the textured silicon substrate, then single-sidedly pickling the back surface and side surfaces of the silicon substrate, and then performing back surface polishing to obtain a flat back surface of the silicon substrate; In step S4, before depositing the anti-reflection film on the back side of the silicon substrate, a passivation film is deposited on the back side of the silicon substrate; In step S4, the passivation film is an aluminum oxide film, and the anti-reflection film is a silicon nitride anti-reflection film.

7. The method for preparing a laser patterned polysilicon passivation cell according to claim 6, characterized in that: Step S4 specifically includes: S41, using atomic layer deposition technology, depositing aluminum oxide films on the front side of the emitter, the alkali-washed and etched area on the back side of the silicon substrate, and the back side of the doped polysilicon; S42. Prepare a silicon nitride anti-reflection film on the outer surface of the aluminum oxide film on the front and back sides by using plasma enhanced chemical vapor deposition or plasma assisted chemical vapor deposition technology.

8. The method for preparing a laser patterned polysilicon passivation cell according to claim 6, characterized in that: Step S5 specifically includes: coating metal slurry on the front metallization area and the back metallization area of ​​the silicon substrate, and preparing metal electrodes after sintering, the metal electrode in the front metallization area is in ohmic contact with the emitter, and the metal electrode in the back metallization area is in ohmic contact with the doped polysilicon.

9. A laser patterned polysilicon passivation cell, characterized in that: It is prepared by the method for preparing a laser patterned polycrystalline silicon passivation cell according to any one of claims 1 to 8; The passivation cell is an N-type TOPCon cell.

10. A photovoltaic module, characterized in that: It comprises a plurality of photovoltaic cells connected in series and / or in parallel, and the photovoltaic cell is a passivation cell of laser patterned polycrystalline silicon as described in claim 9.

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