Photovoltaic cell with selective passivation anti-reflection film on front surface and preparation method of photovoltaic cell

Abstract

The invention relates to the technical field of photovoltaic cells, and discloses a photovoltaic cell with a selective passivation anti-reflection film on the front side and a preparation method of the photovoltaic cell. The preparation method of the photovoltaic cell comprises the following steps: preparing a first passivation anti-reflection film on a pyramid textured surface on the front surface of a silicon substrate; selectively removing the first passivation anti-reflection film in a non-grid line area; preparing a second passivation anti-reflection film on the front surface of the silicon substrate so as to increase the thickness of the passivation anti-reflection film in a front surface grid line area; preparing a back passivation film; printing first grid line slurry and second grid line slurry on the front grid line area and the back grid line area respectively; sintering to enable the second grid line slurry to locally corrode the back passivation film to form a back metal grid line in contact with the back of the silicon substrate; and after sintering and auxiliary sintering, enabling the first grid line slurry to locally corrode the second passivation anti-reflection film and the first passivation anti-reflection film to form a front metal grid line in contact with the front surface of the silicon substrate. According to the preparation method, the binding force of the front metal grid line can be improved, the grid line is prevented from stripping, and the passivation performance and the open-circuit voltage can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and specifically relates to a photovoltaic cell with a selective passivation and antireflection film on the front side and a preparation method thereof. Background Art

[0002] Laser-assisted sintering technology can improve the open-circuit voltage of photovoltaic cells and is a research hotspot in the current photovoltaic industry. See Figure 11 , however, the contact structure 91 of the front metal grid lines of the photovoltaic cells sintered by auxiliary sintering (such as the JSIM auxiliary sintering process) is different from the silver nail piercing structure of the conventional non-auxiliary sintered photovoltaic cells. Instead, a low-corrosive grid line paste (such as a low-corrosive aluminum-free pure silver paste) is used to make it contact with the emitter of the cell substrate under the action of a high current density and form a semi-ellipsoidal silver-silicon alloy. Moreover, the SEM images of the photovoltaic cells sintered by auxiliary sintering before and after laser in the conference report published by the 19th China Solar Grade Silicon and Photovoltaic Power Generation Symposium show that the contact points of the contact structure 91 of the front metal grid lines are mainly located at the tips of the pyramid texture on the front side of the photovoltaic cell (such as the corrosion area 71 of the low-corrosive grid line paste on the front side is mainly at the tips of the pyramid texture of the front passivation and antireflection film 7). Due to the low corrosiveness of the grid line paste used in the contact structure 91 of the front metal grid lines, the front passivation and antireflection film 7 at the remaining body positions of the pyramid texture is retained, so it can provide a better passivation effect than the conventional non-auxiliary sintered photovoltaic cells and improve the open-circuit voltage.

[0003] However, the low corrosiveness of the front grid line paste of the auxiliary sintered photovoltaic cells will result in fewer contact points of the semi-ellipsoidal silver-silicon alloy than the silver microcrystal contact points of the non-auxiliary sintered photovoltaic cells. Therefore, the contact area between the low-corrosive positive silver paste and the emitter and the front passivation and antireflection film 7 will be reduced. Furthermore, the bonding force between the front metal grid lines and the cell substrate of the auxiliary sintered photovoltaic cells will be weakened, and the metal grid lines are prone to falling off.

[0004] Currently, the improvement in the bonding force of the metal grid lines of existing photovoltaic cells mainly focuses on the optimization of the composition of the grid line paste used to form the metal grid lines and the optimization of the structure and materials of the metal grid lines (as shown in CN114551609A). Currently, there is no specific improvement scheme for the bonding force problem of the front metal grid lines of the auxiliary sintered photovoltaic cells. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a photovoltaic cell with a selective passivation and antireflection film on the front side and a preparation method thereof.

[0006] Based on this, the present invention discloses a preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front side, including the following preparation steps:

[0007] S1. Prepare a first passivation and antireflection film on the pyramid-textured surface of the front side of the silicon substrate;

[0008] S2. Remove the first passivation and antireflection film in the non-grid line area, and retain the first passivation and antireflection film in the grid line area;

[0009] S3. Prepare a second passivation and antireflection film on the front side of the silicon substrate to increase the thickness of the passivation and antireflection film in the grid line area of the front side of the silicon substrate; then prepare a back passivation film on the back side of the silicon substrate;

[0010] S4. Print the first grid line paste and the second grid line paste in the front grid line area and the back grid line area respectively; sinter. After the second grid line paste locally corrodes the back passivation film, form a back metal grid line that makes an ohmic contact with the back side of the silicon substrate; after sintering, perform auxiliary sintering so that the first grid line paste locally corrodes the second passivation and antireflection film and the first passivation and antireflection film in sequence, and then form a front metal grid line that makes an ohmic contact with the front side of the silicon substrate.

[0011] Preferably, the materials of the first passivation and antireflection film and the second passivation and antireflection film include one or more of silicon nitride, silicon oxynitride, and aluminum oxide.

[0012] More preferably, the first passivation and antireflection film is a first silicon nitride film, and the second passivation and antireflection film includes a second silicon nitride film;

[0013] Before step S1, it further includes: the step of preparing an aluminum oxide film on the front side of the silicon substrate; or, after step S2, it further includes: the step of preparing an aluminum oxide film on the front side of the silicon substrate.

[0014] More preferably, the first passivation and antireflection film includes a first aluminum oxide film and a first silicon nitride film, and the second passivation and antireflection film includes a second aluminum oxide film and a second silicon nitride film;

[0015] Step S1 includes: sequentially preparing a first aluminum oxide film and a first silicon nitride film on the front side of the silicon substrate; step S3 includes: sequentially preparing a second aluminum oxide film and a second silicon nitride film on the front side of the silicon substrate.

[0016] Even more preferably, the first silicon nitride film is prepared by plasma-enhanced chemical vapor deposition, the SiH4 flow rate is 700 - 1000 sccm, the NH3 flow rate is 10000 - 13000 sccm, the heating temperature is 400 - 550 °C, and the deposition time is 60 - 1400 s; the thickness of the first silicon nitride film is 5 - 200 nm;

[0017] The aluminum oxide film is prepared by atomic layer deposition.

[0018] More preferably, the second silicon nitride film is prepared by plasma enhanced chemical vapor deposition, with the SiH4 flow rate being 600 - 1200 sccm, the NH3 flow rate being 9000 - 15000 sccm, the heating temperature being 400 - 550 °C, and the deposition time being 700 - 900 s; the thickness of the second silicon nitride film is 80 - 90 nm.

[0019] Preferably, in step S2, a laser etching method is used to remove the first passivation and antireflection film in the non-grid line area; the laser etching is performed using an ultraviolet continuous laser or a pulsed laser, with the laser spot size being 60 - 80 μm and the laser power being 10 - 20 W.

[0020] Preferably, the process conditions for the auxiliary sintering include: applying a reverse bias voltage of more than 10 V to the photovoltaic cell and scanning the surface of the photovoltaic cell with a laser, with the laser spot size being 100 - 400 μm and the laser power being 20 - 100 W;

[0021] Preferably, before step S1, it further includes: cleaning and texturing the silicon substrate, then preparing a selective emitter on the pyramid textured surface on the front of the silicon substrate, then cleaning and polishing the back of the silicon substrate, preparing a passivated contact structure on the polished back of the silicon substrate, and then cleaning the silicon substrate with a buffered oxide etchant.

[0022] The present invention discloses a photovoltaic cell with a selective passivation and antireflection film on the front, which is prepared by using the preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front as described above in the content of the present invention.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] In the present invention, a passivation and antireflection film thicker than that in the non-grid line area is prepared in the grid line area (the thickness of the first passivation and antireflection film on the front side is the increased thickness of the passivation and antireflection film); since the contact points of the contact structure of the front metal grid lines are mainly formed at the tips of the pyramid-shaped texture on the front side of the photovoltaic cell during auxiliary sintering, that is, the first grid line paste mainly corrodes the tips of the pyramid-shaped texture on the front side, the first passivation and antireflection film and the second passivation and antireflection film at the positions other than the tips of the pyramid-shaped texture can be retained. Therefore, in the present invention, the increase in the thickness of the passivation and antireflection film in the front grid line area, on the one hand, allows the use of a first grid line paste with higher corrosiveness on the front side, providing a deeper space for the penetration and corrosion of the first grid line paste in the longitudinal direction, and through corrosion, enabling a larger contact area in the longitudinal depth between the first grid line paste and the passivation and antireflection film, increasing the contact area between the first grid line paste and the first passivation and antireflection film and the second passivation and antireflection film, thereby greatly enhancing the bonding force of the front metal grid lines and effectively solving the problem of easy shedding of the metal grid lines; on the other hand, it can also provide more hydrogen to passivate the defects of the silicon substrate, improve the passivation effect, reduce recombination, extend the minority carrier lifetime, be beneficial to the increase of the open circuit voltage of the photovoltaic cell during auxiliary sintering, and thus be beneficial to the improvement of the cell conversion efficiency.

[0025] Further, the two-step deposition method of steps S1 to S3 of the present invention is adopted to increase the thickness of the passivation and antireflection film in the grid line area. In this way, even if the removal of the first passivation and antireflection film in the non-grid line area in step S2 brings some defects and damages to the front side of the silicon substrate, the second passivation and antireflection film prepared in the subsequent step S3 can repair these defects and damages, so that the recombination will not increase. Description of the Drawings

[0026] Figure 1 Schematic cross-sectional structure diagram of the silicon substrate after step one of the preparation method of the photovoltaic cell in Example 1.

[0027] Figure 2 Schematic cross-sectional structure diagram of the silicon substrate after step two of the preparation method of the photovoltaic cell in Example 1.

[0028] Figure 3 Schematic cross-sectional structure diagram of the silicon substrate after step four of the preparation method of the photovoltaic cell in Example 1.

[0029] Figure 4 Schematic cross-sectional structure diagram of the silicon substrate after step five of the preparation method of the photovoltaic cell in Example 1.

[0030] Figure 5 Schematic cross-sectional structure diagram of the silicon substrate after step six of the preparation method of the photovoltaic cell in Example 1.

[0031] Figure 6Schematic cross-sectional structure diagram of the silicon substrate after step nine in the preparation method of the photovoltaic cell of Example 1.

[0032] Figure 7 Schematic cross-sectional structure diagram of the silicon substrate after step ten in the preparation method of the photovoltaic cell of Example 1.

[0033] Figure 8 Schematic cross-sectional structure diagram of the silicon substrate after step eleven in the preparation method of the photovoltaic cell of Example 1.

[0034] Figure 9 Schematic cross-sectional structure diagram of the silicon substrate after step twelve in the preparation method of the photovoltaic cell of Example 1.

[0035] Figure 10 Schematic cross-sectional structure diagram of the photovoltaic cell of Example 1.

[0036] Figure 11 Schematic cross-sectional structure diagram of the contact structure of the front metal grid line of the existing photovoltaic cell after auxiliary sintering.

[0037] Figure 12 Schematic cross-sectional structure diagram of the contact structure of the front metal grid line of the photovoltaic cell after auxiliary sintering prepared by the present invention.

[0038] Explanation of the reference numerals in the drawings: N-type silicon substrate 1; boron-doped layer 2; lightly doped region 3; heavily doped region 4; tunneling oxide layer 5; doped polysilicon layer 6; front passivation and antireflection film 7; corrosion region 71; alumina film 72; first silicon nitride film 73; second silicon nitride film 74; back silicon nitride film 8; front metal grid line 9; contact structure 91 of the front metal grid line; back metal grid line 10. Detailed implementation manners

[0039] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0040] A preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front surface according to the present invention includes the following preparation steps:

[0041] S1. Prepare a first passivation and antireflection film on the pyramid-textured surface on the front surface of the silicon substrate;

[0042] S2. Remove the first passivation and antireflection film in the non-grid line region and retain the first passivation and antireflection film in the grid line region;

[0043] S3. Prepare a second passivation and antireflection film on the front surface of the silicon substrate to increase the thickness of the passivation and antireflection film in the grid line region on the front surface of the silicon substrate; then prepare a back passivation film on the back surface of the silicon substrate.

[0044] S4. Print the first grid paste and the second grid paste in the front grid line area and the back grid line area respectively; sinter. After the second grid paste locally corrodes the back passivation film, a back metal grid line in ohmic contact with the back of the silicon substrate is formed; after sintering, auxiliary sintering is carried out so that the first grid paste sequentially locally corrodes the second passivation and antireflection film and the first passivation and antireflection film, and then a front metal grid line in ohmic contact with the front of the silicon substrate is formed.

[0045] Among them, the materials of the first passivation and antireflection film and the second passivation and antireflection film include, but are not limited to, one or more of silicon nitride, silicon oxynitride, and aluminum oxide.

[0046] The following embodiments are used to detail the preparation process of a preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front.

[0047] Example 1

[0048] In a preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front in this embodiment, the first passivation and antireflection film is the first silicon nitride film 73, and the second passivation and antireflection film is the second silicon nitride film 74; the preparation method of this photovoltaic cell includes the following preparation steps:

[0049] Step 1. Clean and texture the silicon substrate to form pyramid-shaped textured surfaces on the front and back of the silicon substrate. In Step 1, the silicon substrate is preferably an N-type silicon substrate 1. The structure of the silicon substrate after completing Step 1 is as Figure 1 shown.

[0050] Step 2. Perform doping diffusion on the front of the textured silicon substrate. In Step 1, it is preferably to perform boron doping diffusion on the front of the silicon substrate to form a boron-doped layer 2 on the front of the silicon substrate. The structure of the silicon substrate after completing Step 2 is as Figure 2 shown.

[0051] Step 3. Perform selective doping on the boron-doped layer 2 to form a heavily doped region 4 in the grid line area, and the non-grid line area of the boron-doped layer 2 is the lightly doped region 3; in this way, an SE (selective emitter) is fabricated on the front of the silicon substrate.

[0052] Step 4. Perform oxidation treatment on the selectively doped silicon substrate to obtain a better PN junction type on the front of the silicon substrate. The structure of the silicon substrate after completing Step 4 is as Figure 3 shown.

[0053] Step 5. Clean the back of the silicon substrate to remove the doped silicon glass (such as borosilicate glass) formed on the back of the silicon substrate due to doping diffusion; then polish the back of the silicon substrate to obtain a smooth and flat morphology on the back of the silicon substrate. In Step 5, the cleaning is preferably acid cleaning; the polishing treatment is preferably alkaline polishing. The structure of the silicon substrate after completing Step 5 is asFigure 4 as shown

[0054] Step Six: Prepare a passivated contact structure on the back of the polished silicon substrate. The passivated contact structure includes a tunneling oxide layer 5 and a polysilicon layer (preferably a doped polysilicon layer 6) disposed on the back of the tunneling oxide layer 5. In Step Six, the specific preparation process of the passivated contact structure is preferably as follows: Deposit the tunneling oxide layer 5 and an amorphous silicon layer on the back of the silicon substrate in sequence, and then perform an annealing process to convert the amorphous silicon layer into a polysilicon layer. The structure of the silicon substrate after completing Step Six is as Figure 5 as shown

[0055] Step Seven: Clean the silicon substrate to remove surface impurities and doped silicon glass (such as borosilicate glass, phosphosilicate glass) brought by annealing. In Step Seven, the cleaning is preferably BOE (buffered oxide etchant) cleaning.

[0056] Step Eight: Prepare an alumina film 72 on the front of the silicon substrate. In Step Eight, the alumina film 72 is located on the front of the selective emitter; the alumina film 72 is preferably prepared by ALD (atomic layer deposition). The preparation process and thickness of the alumina film 72 refer to the front alumina film 72 of the existing photovoltaic cell, so it will not be elaborated here.

[0057] Step Nine: Then prepare a first SiNx film (first silicon nitride film 73) on the entire front of the silicon substrate. In Step Nine, the first silicon nitride film 73 is located on the front of the alumina film 72.

[0058] In an example of this embodiment, the first silicon nitride film 73 is preferably prepared by PECVD (plasma enhanced chemical vapor deposition), the SiH4 flow rate is 700 - 1000 sccm (such as 850 sccm), the NH3 flow rate is 10000 - 13000 sccm (such as 12000 sccm), the heating temperature is 400 - 550 °C (such as 505 °C), and the deposition time is 60 - 1400 s (such as 900 s). The thickness of the first SiNx film deposited on the front in Step Nine can be specifically adjusted according to the corrosivity difference of the first grid line paste to be used later. The thickness of the first SiNx film is 5 - 200 nm (preferably 60 - 150 nm, such as 80 nm). The structure of the silicon substrate after completing Step Nine is as Figure 6 as shown

[0059] Step Ten: Remove the first silicon nitride film 73 in the non-grid line area and retain the first silicon nitride film 73 in the grid line area.

[0060] In an example of this embodiment, it is preferably to use a laser etching method to completely remove the first silicon nitride film 73 in the non-grid line region. Specifically, this laser etching process includes: positioning according to the mark points in the SE of step three to determine the position of the non-grid line region, and then using an ultraviolet continuous laser or a pulsed laser for etching. The laser spot size is 60 - 80 μm (such as 70 μm), and the laser power is 10 - 20 W (such as 13 W). Using the laser etching method to directly remove the redundant passivation and antireflection film in the non-grid line region is more convenient and concise, and has high controllability.

[0061] In other examples of this embodiment, a mask method can also be used to remove the first passivation and antireflection film in the non-grid line region. The silicon substrate structure after completing step ten is as Figure 7 shown.

[0062] Using the laser etching method to directly remove the redundant passivation and antireflection film in the non-grid line region is more convenient and concise, and has high controllability.

[0063] Step eleven: Prepare a second SiNx film (second silicon nitride film 74) on the entire front surface of the silicon substrate. At this time, the grid line region contains two layers of SiNx films (i.e., the first SiNx film and the second SiNx film), while the non-grid line region only has the second SiNx film. In step eleven, the second SiNx film in the grid line region is located on the front surface of the first SiNx film, and the second SiNx film in the non-grid line region is located on the front surface of the alumina film 72.

[0064] In step eleven, this second SiNx film can be a single-layer film with a constant refractive index; it can also be a double-layer film or a gradient film with different refractive indexes; it can also be a composite film layer with passivation and antireflection effects, such as SiOx (silicon oxide), SiOxNy (silicon oxynitride). The thickness of this second SiNx film is 80 - 90 nm (such as 85 nm).

[0065] In an example of this embodiment, this second silicon nitride film 74 is preferably prepared by PECVD. The SiH4 flow rate is 600 - 1200 sccm (such as 800 sccm), the NH3 flow rate is 9000 - 15000 sccm (such as 11000 sccm), the heating temperature is 400 - 550 °C (such as 500 °C), and the deposition time is 700 - 900 s (such as 800 s). The silicon substrate structure after completing step eleven is as Figure 8 shown.

[0066] It should be noted that if the two-step deposition method in Steps 9 to 11 of this embodiment is not adopted to increase the thickness of the silicon nitride film in the gate line region (the thickness of the first silicon nitride film 73 is the increased thickness of the silicon nitride film in the gate line region); instead, the thickness of two layers of silicon nitride film is directly deposited at one time, and then the thickness of the silicon nitride film in the gate line region is thinned. In this way, the thinning process will introduce more damage, defects, surface states, etc. on the surface of the silicon nitride film in the non-gate line region, and there is no other structure and method in the follow-up to repair these damages, defects, surface states, etc., which will lead to an increase in recombination and affect the improvement of the battery conversion efficiency.

[0067] If the two-step deposition method in Steps 9 to 11 of this embodiment is adopted, even if some defects are brought by the laser etching in Step 10, the second silicon nitride film 74 deposited in Step 11 can repair the defects, so it will not lead to an increase in recombination.

[0068] Step 12: Prepare a backside silicon nitride film 8 on the entire backside of the silicon substrate. The backside silicon nitride film 8 is located on the backside of the doped polysilicon layer 6 of the passivated contact structure; the preparation method, structure and thickness of the backside silicon nitride film 8 can all refer to the second SiNx film in Step 11, so it will not be elaborated here. The structure of the silicon substrate after completing Step 12 is as Figure 9 shown.

[0069] Step 13: Print metal gate lines. In Step 13, the metal gate lines include a front metal gate line 9 and a back metal gate line 10. Among them, the first gate paste is used to prepare the front metal gate line 9 in this embodiment, and the second gate paste is used to prepare the back metal gate line 10. Both the first gate paste and the second gate paste are commercially available gate pastes; the second gate paste refers to the gate paste used for the back metal gate line 10 of existing photovoltaic cells, so it will not be elaborated here.

[0070] Among them, the corrosiveness of the first gate paste used to prepare the front metal gate line 9 in this embodiment is greater than that of the gate paste used for the front metal gate line of existing photovoltaic cells that have undergone auxiliary sintering (such as the JSIM auxiliary sintering process). The corrosiveness of the gate paste is generally changed by controlling the content or properties of the glass powder. In one example of this embodiment, the first gate paste can be selected as the crystalline silicon solar cell front silver paste with the model number AC007Y49N provided by Shanghai Taiju New Materials Co., Ltd. Of course, in other examples of this embodiment, the first gate paste can also adopt other commercially available gate pastes with stronger corrosiveness.

[0071] In Step Thirteen, it is preferably to screen-print the first grid paste and the second grid paste in the front grid line area and the back grid line area respectively; then through sintering, during the sintering process, the second grid paste locally corrodes the back silicon nitride film 8 to form the back metal grid line 10 in ohmic contact with the doped polysilicon layer 6, and the first grid paste sequentially locally corrodes the second silicon nitride film 74, the first silicon nitride film 73 and the alumina film 72. Most of the corrosion process of the front first grid paste is completed during the sintering process. If it is necessary to form the front metal grid line 9 in ohmic contact with the heavily doped region 4, an additional sintering process of Step Fourteen is required after sintering; only a very small part of the corrosion occurs in the additional sintering process of Step Fourteen, and the additional sintering mainly forms the front metal grid line 9 in ohmic contact.

[0072] Step Fourteen: Use an additional sintering process to process the cell obtained in Step Thirteen to enable the first grid paste to continue to corrode and form the front metal grid line 9 in ohmic contact with the heavily doped region 4 of the selective emitter: Apply a reverse bias voltage of more than 10 V (such as 15 V) to the cell, and use a laser (infrared continuous laser or pulsed laser) to scan the surface of the cell. The laser spot size is 100 - 400 μm (such as 200 μm), and the laser power is 20 - 100 W (such as 36 W). Compared with the front metal grid line 9 formed by the low-corrosion grid paste of the existing photovoltaic cell with additional sintering (such as the JSIM additional sintering process) in the photovoltaic cell with the same structure, the number of contact points of the front metal grid line 9 formed by the highly corrosive first grid paste in this embodiment is 3 - 15% (such as 10%) more or the contact point size is 5 - 35% (such as 20%) larger. After completing Step Fourteen, the additionally sintered photovoltaic cell of this embodiment is obtained, and the structure of the photovoltaic cell is as Figure 10 shown.

[0073] In this embodiment, a thicker silicon nitride film is prepared in the front grid line area than in the front non-grid line area (the thickness of the front first silicon nitride film 73 is the increased thickness of the silicon nitride film), so that it is possible to use the highly corrosive first grid paste; thus, without changing the width of the front metal grid line 9 and without affecting the short-circuit current, the bonding force of the front metal grid line 9 of the additionally sintered photovoltaic cell can be improved, effectively solving the problem that the front metal grid line 9 is prone to peeling, and further improving the passivation performance of the photovoltaic cell and increasing the open-circuit voltage.

[0074] See Figures 11 - 12, since the contact points of the contact structure 91 of the front metal grid lines are mainly formed at the tips of the pyramid textures on the front side of the auxiliary sintered photovoltaic cell (for example, the corrosion area 71 of the first grid line paste is mainly at the tips of the pyramid textures of the front passivation and antireflection film 7), after the front metal grid lines 9 are prepared, the first silicon nitride film 73 and the second silicon nitride film 74 in the area outside the tips of the pyramid textures can be retained (that is, it is difficult to be corroded by the first grid line paste). Therefore, the increase in the thickness of the silicon nitride film in the front grid line area can provide more hydrogen to passivate the defects of the silicon substrate and the selective emitter, so the passivation effect is improved, and thus the open voltage of the battery will also be correspondingly increased.

[0075] From Figures 11 - 12 It can be seen that due to the enhanced corrosiveness of the first grid line paste, the corrosion depth of the first grid line paste in the front passivation and antireflection film 7 (the front passivation and antireflection film 7 in this embodiment includes the alumina film 72, the second silicon nitride film 74 and the first silicon nitride film 73) will increase. Therefore, after corrosion, the side contact area between the front metal grid line 9 and the front passivation and antireflection film 7 will increase compared with the grid line paste with low corrosiveness, so the bonding force of the front metal grid line 9 will be greatly improved.

[0076] In addition, if the passivation and antireflection film in the front non-grid line area is too thick, it will affect the antireflection effect in the front non-grid line area. Therefore, in this embodiment, only the second silicon nitride film 74 is retained in the front non-grid line area, and the first silicon nitride film 73 is removed; and the sunlight in the front grid line area will be blocked by the front metal grid line 9 itself, and there is no antireflection problem. Therefore, increasing the thickness of the passivation and antireflection film in the grid line area will not affect the light absorption rate of the front sunlight.

[0077] Example 2

[0078] A method for preparing a photovoltaic cell with a selective passivation and antireflection film on the front side in this embodiment, the first passivation and antireflection film is the first silicon nitride film, and the second passivation and antireflection film includes an alumina film and a second silicon nitride film; the steps 1 to 7 of the method for preparing the photovoltaic cell in this embodiment are respectively referred to the steps 1 to 7 of Example 1, and the steps 12 to 14 of this embodiment are respectively referred to the steps 12 to 14 of Example 1; the difference between the method for preparing the photovoltaic cell in this embodiment and that in Example 1 is as follows:

[0079] Step 8, prepare the first silicon nitride film on the entire front side of the silicon substrate. Since no alumina film is prepared before step 8 in this embodiment, this first silicon nitride film is located on the front side of the selective emitter. The step 8 of this embodiment is specifically referred to the step 9 of Example 1.

[0080] Step 9, remove the first silicon nitride film in the non-grid line area and retain the first silicon nitride film in the grid line area. The step 9 of this embodiment is specifically referred to the step 10 of Example 1.

[0081] Step ten: Prepare an alumina film on the front side of the silicon substrate. Step ten of this embodiment specifically refers to step eight of Embodiment 1; the alumina film in the non-gate line region is located on the front side of the lightly doped region of the selective emitter, while the alumina film in the metal gate line region is located on the front side of the first silicon nitride film.

[0082] Step eleven: Prepare a second silicon nitride film on the entire front side of the silicon substrate. At this time, the second silicon nitride film is located on the front side of the alumina film. Step eleven of this embodiment specifically refers to step eleven of Embodiment 1.

[0083] Therefore, in this embodiment, the passivation and antireflection film structure in the front gate line region from the inside to the outside is successively: the first silicon nitride film, the alumina film, and the second silicon nitride film; while the passivation and antireflection film structure in the front non-gate line region is the same as that in Embodiment 1, still being: the alumina film and the second silicon nitride film located on the front side of the alumina film. Thus, after step fourteen, the assisted sintered photovoltaic cell of this embodiment is obtained.

[0084] The assisted sintered photovoltaic cell of this embodiment can improve the bonding force of the front metal gate line of the assisted sintered photovoltaic cell, effectively avoid the peeling of the front metal gate line, on the basis of not changing the width of the front metal gate line and not affecting the short-circuit current; it can also further improve the passivation performance of the photovoltaic cell and increase the open-circuit voltage; and using the deposition methods in steps eight to eleven above to increase the thickness of the passivation and antireflection film in the front gate line region will not affect the light absorption rate of the front sunlight, and the alumina film and the second silicon nitride film can repair the defects, damages, etc. brought by removing the first silicon nitride film in the non-gate line region, so it will not increase the recombination either.

[0085] Embodiment 3

[0086] In the preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front side of this embodiment, the first passivation and antireflection film includes a first alumina film and a first silicon nitride film, and the second passivation and antireflection film includes a second alumina film and a second silicon nitride film; the steps one to seven of the preparation method of the photovoltaic cell in this embodiment all refer to steps one to seven of Embodiment 1, and steps thirteen to fifteen of this embodiment respectively refer to steps twelve to fourteen of Embodiment 1; the difference between the preparation method of the photovoltaic cell in this embodiment and that in Embodiment 1 is:

[0087] Step eight: Refer to step eight of Embodiment 1 and prepare a first alumina film on the front side of the silicon substrate.

[0088] Step nine: Refer to step nine of Embodiment 1 and prepare a first silicon nitride film on the entire front side of the silicon substrate.

[0089] Step Ten: Referring to Step Ten of Embodiment 1, remove both the first silicon nitride film and the first aluminum oxide film in the non-grid line area, and retain the first silicon nitride film and the first aluminum oxide film in the grid line area.

[0090] Step Eleven: Referring to Step Eight of Embodiment 1, prepare a second aluminum oxide film on the front surface of the silicon substrate; at this time, the second aluminum oxide film in the non-grid line area is located on the front surface of the lightly doped area of the selective emitter, while the second aluminum oxide film in the grid line area is located on the front surface of the first silicon nitride film.

[0091] Step Twelve: Referring to Step Eleven of Embodiment 1, prepare a second silicon nitride film on the entire front surface of the silicon substrate; at this time, the second silicon nitride film is located on the front surface of the second aluminum oxide film.

[0092] Therefore, in this embodiment, the passivation and antireflection film structure in the front grid line area from the inside to the outside is successively: the first aluminum oxide film, the first silicon nitride film, the second aluminum oxide film, and the second silicon nitride film; while the passivation and antireflection film structure in the front non-grid line area from the inside to the outside is successively: the second aluminum oxide film and the second silicon nitride film located on the front surface of the second aluminum oxide film. Thus, after Step Fifteen, the auxiliary sintered photovoltaic cell of this embodiment is obtained.

[0093] The auxiliary sintered photovoltaic cell of this embodiment can improve the bonding force of the front metal grid lines of the auxiliary sintered photovoltaic cell, effectively avoid the peeling of the front metal grid lines, on the basis of not changing the width of the front metal grid lines and not affecting the short-circuit current; it can further improve the passivation performance of the photovoltaic cell and increase the open-circuit voltage; and using the deposition methods in Steps Eight to Twelve above to increase the thickness of the passivation and antireflection film in the front grid line area will not affect the light absorption rate of the front sunlight, and the second aluminum oxide film and the second silicon nitride film can repair the defects, damages, etc. brought by removing the first silicon nitride film and the first aluminum oxide film in the non-grid line area, so it will not increase the recombination either.

[0094] Although the preferred embodiments of the embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

[0095] The technical solutions provided by the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a photovoltaic cell with a selective passivation and antireflection film on the front side, characterized in that, It includes the following preparation steps: S1. Prepare a first passivation and antireflection film on the pyramid-textured surface on the front side of the silicon substrate; S2. Remove the first passivation and antireflection film in the non-grid-line area, and retain the first passivation and antireflection film in the grid-line area; S3. Prepare a second passivation and antireflection film on the front side of the silicon substrate to increase the thickness of the passivation and antireflection film in the grid-line area on the front side of the silicon substrate; then prepare a back passivation film on the back side of the silicon substrate; S4. Print the first grid-line paste and the second grid-line paste in the front grid-line area and the back grid-line area respectively; Sintering: After the second grid-line paste locally corrodes the back passivation film, a back metal grid line that makes an ohmic contact with the back side of the silicon substrate is formed; after sintering, auxiliary sintering is carried out so that the first grid-line paste sequentially locally corrodes the second passivation and antireflection film and the first passivation and antireflection film, and then a front metal grid line that makes an ohmic contact with the front side of the silicon substrate is formed.

2. The preparation method of a photovoltaic cell with a selectively passivated antireflection film on the front side according to claim 1, characterized in that The materials of the first passivation and antireflection film and the second passivation and antireflection film include one or more of silicon nitride, silicon oxynitride, and aluminum oxide.

3. The preparation method of a photovoltaic cell with a selective passivation and antireflection film on the front side according to claim 2, characterized in that, The first passivation and antireflection film is a first silicon nitride film, and the second passivation and antireflection film includes a second silicon nitride film; Before step S1, it further includes: the step of preparing an aluminum oxide film on the front side of the silicon substrate; or, after step S2, it further includes: the step of preparing an aluminum oxide film on the front side of the silicon substrate.

4. The preparation method of a photovoltaic cell with a selectively passivated antireflection film on the front side according to claim 2, characterized in that, The first passivation and antireflection film includes a first aluminum oxide film and a first silicon nitride film, and the second passivation and antireflection film includes a second aluminum oxide film and a second silicon nitride film; Step S1 includes: sequentially preparing a first aluminum oxide film and a first silicon nitride film on the front side of the silicon substrate; step S3 includes: sequentially preparing a second aluminum oxide film and a second silicon nitride film on the front side of the silicon substrate.

5. The preparation method of a photovoltaic cell with a selectively passivated and antireflective film on the front side according to claim 3 or 4, characterized in that, The first silicon nitride film is prepared by plasma-enhanced chemical vapor deposition. The flow rate of SiH4 is 700 - 1000 sccm, the flow rate of NH3 is 10000 - 13000 sccm, the heating temperature is 400 - 550 °C, and the deposition time is 60 - 1400 s; the thickness of the first silicon nitride film is 5 - 200 nm; The aluminum oxide film is prepared by atomic layer deposition.

6. The preparation method of a photovoltaic cell with a selectively passivated and antireflective film on the front side according to claim 3 or 4, characterized in that, The second silicon nitride film is prepared by plasma-enhanced chemical vapor deposition. The flow rate of SiH4 is 600 - 1200 sccm, the flow rate of NH3 is 9000 - 15000 sccm, the heating temperature is 400 - 550 °C, and the deposition time is 700 - 900 s; the thickness of the second silicon nitride film is 80 - 90 nm.

7. The preparation method of a photovoltaic cell with a selectively passivated and antireflective film on the front side according to claim 1, characterized in that, In step S2, a laser etching method is used to remove the first passivation and antireflection film in the non-grid-line area; the laser etching is carried out using an ultraviolet continuous laser or a pulsed laser, the laser spot size is 60 - 80 μm, and the laser power is 10 - 20 W.

8. The preparation method of a photovoltaic cell with a selectively passivated antireflection film on the front side according to claim 1, characterized in that, The process conditions of the auxiliary sintering include: applying a reverse bias voltage of more than 10 V to the photovoltaic cell, and scanning the surface of the photovoltaic cell with a laser, the laser spot size is 100 - 400 μm, and the laser power is 20 - 100 W.

9. The preparation method of a photovoltaic cell with a selectively passivated antireflection film on the front side according to claim 1, characterized in that, Before step S1, it further includes: cleaning and texturing the silicon substrate, then preparing a selective emitter on the pyramid-textured surface on the front of the silicon substrate, then cleaning and polishing the back of the silicon substrate, preparing a passivated contact structure on the polished back of the silicon substrate, and then cleaning the silicon substrate with a buffered oxide etchant.

10. A photovoltaic cell with a selectively passivated antireflection film on the front side, characterized in that, The photovoltaic cell is prepared by the preparation method according to any one of claims 1-9.

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