Solar cell and photovoltaic module

Abstract

The utility model provides a solar cell and a photovoltaic module, the solar cell comprises a silicon substrate, the back surface of the silicon substrate comprises first doped regions and second doped regions which are alternately arranged, and an isolation region is arranged between the adjacent first doped region and second doped region; the part, located in the isolation area, of the back face of the silicon substrate is provided with first micro-unit structures, the multiple first micro-unit structures form a first suede structure, the surface of the first suede structure is provided with a first passivation layer, and each first micro-unit structure comprises a threaded first micro-unit structure and a pyramid-shaped first micro-unit structure. The percentage a1 of the number of the threaded first micro-unit structures in the total number of the first micro-unit structures is larger than or equal to 20% and smaller than or equal to 70%. According to the back contact solar cell, the film forming quality of the first passivation layer can be improved, and the photoelectric conversion efficiency of the back contact solar cell is further improved.

Description

Technical Field

[0001] This application relates to the field of solar cells, and particularly to a solar cell and a photovoltaic module. Background Art

[0002] A solar cell is a device that converts solar energy into electrical energy, which has the advantages of being clean and pollution-free and has been widely used in the power generation industry.

[0003] A back-contact solar cell is a solar cell with no metal grid lines on the front side, and the metal grid lines of the P / N regions are distributed in a finger-like cross pattern on the back side of the cell. How to improve the photoelectric conversion efficiency of the back-contact solar cell has become a technical problem to be solved urgently. Summary of the Utility Model

[0004] In order to solve the above technical problems, this application discloses a solar cell and a photovoltaic module to improve the photoelectric conversion efficiency of the back-contact solar cell.

[0005] In a first aspect, this application provides a solar cell, comprising:

[0006] A silicon substrate, the back side of the silicon substrate includes alternately arranged first doping regions and second doping regions, and an isolation region is provided between adjacent first doping regions and second doping regions; the part of the back side of the silicon substrate located in the isolation region has a first micro-unit structure, and a plurality of the first micro-unit structures form a first textured surface structure, the surface of the first textured surface structure has a first passivation layer, the first micro-unit structure includes a spiral-shaped first micro-unit structure and a pyramid-shaped first micro-unit structure, wherein the percentage of the number of the spiral-shaped first micro-unit structures in the total number of the first micro-unit structures is a1, 20% ≤ a1 ≤ 70%.

[0007] In some embodiments of this application, the percentage of the number of the pyramid-shaped first micro-unit structures in the total number of the first micro-unit structures is b1, 30% ≤ b1 ≤ 80%.

[0008] In some embodiments of this application, the front side of the silicon substrate has a second micro-unit structure, a plurality of the second micro-unit structures form a second textured surface structure, the surface of the second textured surface structure has a second passivation layer, the second micro-unit structure includes a spiral-shaped second micro-unit structure and a pyramid-shaped second micro-unit structure, wherein the percentage of the number of the spiral-shaped second micro-unit structures in the total number of the second micro-unit structures is a2, 15% ≤ a2 ≤ 65%.

[0009] In some embodiments of this application, the percentage of the number of the pyramid-shaped second micro-unit structures in the total number of the second micro-unit structures is b2, 35% ≤ b2 ≤ 85%.

[0010] In some embodiments of the present application, a1 > a2.

[0011] In some embodiments of the present application, multiple said spiral-shaped first micro-unit structures are irregularly distributed in the first suede structure; and / or, multiple said spiral-shaped second micro-unit structures are irregularly distributed in the second suede structure.

[0012] In some embodiments of the present application, the lateral average size of the pyramid-shaped first micro-unit structure is d1, and the longitudinal average size is h1, where 0 μm < d1 ≤ 5 μm and 0 μm < h1 ≤ 3 μm.

[0013] In some embodiments of the present application, the lateral average size of the pyramid-shaped second micro-unit structure is d2, and the longitudinal average size is h2, where 0 μm < d2 ≤ 6 μm and 0 μm < h2 ≤ 3.5 μm.

[0014] In some embodiments of the present application, the width w1 of the first doping region is 300 μm to 600 μm, and / or, the width w2 of the second doping region is 300 μm to 600 μm.

[0015] In some embodiments of the present application, a first dielectric layer and a first doping layer are sequentially disposed on the back surface of the silicon substrate located in the first doping region;

[0016] A second dielectric layer and a second doping layer are sequentially disposed on the back surface of the silicon substrate located in the second doping region;

[0017] The first doping layer and the second doping layer have different conduction types.

[0018] In some embodiments of the present application,

[0019] In a second aspect, the present application provides a photovoltaic module, and the photovoltaic module includes the solar cell as described in the first aspect.

[0020] Compared with the prior art, the present application has at least the following beneficial effects:

[0021] The present application provides a solar cell and a photovoltaic module. The solar cell includes a silicon substrate. The back surface of the silicon substrate includes alternately arranged first doped regions and second doped regions, and an isolation region is provided between adjacent first doped regions and second doped regions. The isolation region serves to separate the first doped regions and the second doped regions, avoiding the leakage phenomenon caused by the conduction between the first doped regions and the second doped regions. Moreover, a part of the back surface of the silicon substrate located in the isolation region has a first micro-unit structure, and the first micro-unit structure includes a spiral first micro-unit structure and a pyramid-shaped first micro-unit structure. The percentage of the number of spiral first micro-unit structures in the total number of the first micro-unit structures is a1, and 20% ≤ a1 ≤ 70%. By controlling a1 within the range of the present application, it is possible to avoid the problem of incomplete first textured structure caused by too few spiral first micro-unit structures, and also avoid the problem of uneven film formation of the first passivation layer caused by too many spiral first micro-unit structures, thereby improving the film formation quality of the first passivation layer, and further improving the photoelectric conversion efficiency of the back-contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 Schematic structural diagram of a solar cell in an implementation solution of the present application;

[0024] Figure 2 Scanning electron microscope (SEM) image of the first textured structure in an implementation manner of the present application;

[0025] Figure 3 Schematic structural diagram of a microstructural unit in an implementation solution of the present application;

[0026] Figure 4 Schematic structural diagram of a solar cell in another implementation solution of the present application;

[0027] Figure 5 Schematic structural diagram of a semi-finished solar cell after the first coating treatment of the present application;

[0028] Figure 6 Schematic structural diagram of a semi-finished solar cell after the first patterning treatment of the present application;

[0029] Figure 7 Schematic diagram of a patterned area in an implementation solution of the present application;

[0030] Figure 8 It is a schematic structural diagram of a semi-finished solar cell after the second coating process of this application;

[0031] Figure 9 It is a schematic structural diagram of a semi-finished solar cell after the second patterning process of this application;

[0032] Figure 10 It is a schematic structural diagram of a solar cell in another embodiment of this application.

[0033] Explanation of reference numerals: silicon substrate - 1, first doped region - 2, second doped region - 3, isolation region - 4, first dielectric layer - 21, first doped layer - 22, first silicon oxide mask layer - 23, second dielectric layer - 31, second doped layer - 32, second silicon oxide mask layer - 33, first textured structure - 41, first passivation layer - 42, second textured structure - 51, second passivation layer - 52, second antireflection layer - 53. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of this application.

[0035] In this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0036] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0037] In addition, the terms "mounted", "arranged", "provided with", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral structure; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, or there may be internal communication between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, components, or parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components, or parts. Unless otherwise specified, the meaning of "a plurality of" is two or more.

[0039] The technical solutions of this application will be further described below in conjunction with embodiments and the accompanying drawings.

[0040] In a first aspect, this application provides a solar cell, as Figure 1 shown, the solar cell includes:

[0041] A silicon substrate 1, the back surface of the silicon substrate 1 includes alternately arranged first doping regions 2 and second doping regions 3, and an isolation region 4 is provided between adjacent first doping regions 2 and second doping regions 3. The doping types of the first doping region and the second doping region are different. When the first doping region is an N-type doping region, the second doping region is a P-type doping region; when the first doping region is a P-type doping region, the second doping region is an N-type doping region. The part of the back surface of the silicon substrate 1 located in the isolation region 4 has a first micro-unit structure, and a plurality of the first micro-unit structures form a first textured structure 41. The surface of the first textured structure 41 has a first passivation layer 42. The first micro-unit structure includes a spiral first micro-unit structure and a pyramid-shaped first micro-unit structure. The percentage of the number of spiral first micro-unit structures in the total number of the first micro-unit structures is a1, and 20% ≤ a1 ≤ 70%.

[0042] The inventors of the present application have found through research that the proportion of the number of spiral-shaped first micro-unit structures in the first micro-unit structures will affect the first matte structure, thereby affecting the film-forming quality of the first passivation layer: when a1 is too small, it indicates that the proportion of the number of spiral-shaped first micro-unit structures in the first micro-unit structures is too low. At this time, vacancy areas are likely to appear on the surface of the first matte structure, reducing the integrity of the first matte structure, and thus affecting the film-forming quality of the first passivation layer. Without being limited to any theory, this may be because the pyramid-shaped first micro-unit structures are conventional pyramid structures. When the proportion of conventional pyramid structures is relatively high, intersections will be formed between the bottom angles of different pyramids. The position of the intersection is recessed below the plane formed by multiple pyramid apex angles, and there are narrow angles at the lowest point of the recess. Due to reasons such as surface tension and steric hindrance, problems such as the film layer not being deposited at the narrow angles will occur during the coating process of the first passivation layer. The spiral-shaped first micro-unit structures are unconventional pyramid structures and are usually formed between multiple conventional pyramid structures, which can reduce the height difference between the recessed bottom angles formed between the bottom angles of the pyramids and the pyramid apex angles, and at the same time increase the bottom angle, promoting the passivation effect of the first passivation layer at the bottom angle position; when a1 is too large, it indicates that the proportion of the number of spiral-shaped first micro-unit structures in the first micro-unit structures is too high. Since the shape of the spiral-shaped first micro-unit structures is more uneven than that of the pyramid-shaped first micro-unit structures, when the material used to form the first passivation layer is deposited on the spiral-shaped first micro-unit structures, the uniformity of the formed first passivation layer will also be affected. By controlling a1 within the above range, the present application can not only improve the integrity of the first matte structure but also improve the film-forming uniformity of the first passivation layer, thereby improving the film-forming quality of the first passivation layer.

[0043] The material of the first passivation layer of the present application may include aluminum oxide, and the thickness of the first passivation layer may be 3 nm to 8 nm.

[0044] In an optional embodiment, the percentage of the number of the pyramid-shaped first micro-unit structures in the total number of the first micro-unit structures is b1, and 30% ≤ b1 ≤ 80%. In this way, it is beneficial to reduce the vacancy areas in the first matte structure, thereby improving the integrity of the first matte structure and being beneficial to improving the film-forming quality of the first passivation layer.

[0045] In an optional embodiment, referring to Figure 1 , the front surface of the silicon substrate 1 has second micro-unit structures, and a plurality of the second micro-unit structures form a second matte structure 51. The surface of the second matte structure 51 has a second passivation layer 52. The second micro-unit structures include spiral-shaped second micro-unit structures and pyramid-shaped second micro-unit structures. Among them, the percentage of the number of the spiral-shaped second micro-unit structures in the total number of the second micro-unit structures is a2, and 15% ≤ a2 ≤ 65%.

[0046] The inventors of the present application further studied and found that the proportion of the spiral-shaped second micro-unit structure in the second micro-unit structure will affect the second suede structure, thereby affecting the film-forming quality of the second passivation layer: when a2 is too small, it indicates that the proportion of the spiral-shaped second micro-unit structure in the second micro-unit structure is too low. At this time, vacant areas are also likely to appear on the surface of the second suede structure, reducing the integrity of the second suede structure, and thus affecting the film-forming quality of the second passivation layer; when a2 is too large, it indicates that the proportion of the spiral-shaped second micro-unit structure in the second micro-unit structure is too high. Since the shape of the spiral-shaped second micro-unit structure is more uneven than that of the pyramid-shaped second micro-unit structure, on the one hand, it will cause light to be more easily reflected after hitting the spiral-shaped second micro-unit structure, affecting the absorption of sunlight by the front of the battery, and on the other hand, it will also affect the uniformity of the second passivation layer. By controlling a2 within the above range, the present application can not only improve the integrity of the second suede structure, but also improve the absorption performance of the front of the battery to sunlight, and can also improve the film-forming uniformity of the second passivation layer, thereby improving the photoelectric conversion efficiency of the back-contact solar cell.

[0047] In an optional embodiment, the percentage of the pyramid-shaped second micro-unit structure in the total number of the second micro-unit structures is b2, and 35% ≤ b2 ≤ 85%. In this way, it is beneficial to reduce the vacant areas on the surface of the second suede structure, improve the integrity of the second suede structure, and is beneficial to improving the film-forming quality of the second passivation layer.

[0048] In an optional embodiment, a1 > a2. Since there is a height difference between the isolation region and the first doping region and the second doping region, and there is a height difference between the bottom and the top of the first micro-unit structure located in the isolation region, when a1 is larger, it has a better gap-filling effect on the bottom-angle depression formed by multiple first micro-unit structures, making the first suede structure relatively flatter, and at the same time reducing the difference with the first doping region and the second doping region to a certain extent, and reducing the difference in the implementation of good passivation effects in the three regions of the isolation region, the first doping region and the second doping region under the same conditions.

[0049] In an optional embodiment, multiple spiral-shaped first micro-unit structures are irregularly distributed in the first suede structure; and / or, multiple spiral-shaped second micro-unit structures are irregularly distributed in the second suede structure. Figure 2 is the SEM image of the first suede structure in an embodiment of the present application. Refer to Figure 2 , there are multiple spiral-shaped first micro-unit structures (marked with a dotted square) in the observation area, and these spiral-shaped first micro-unit structures are irregularly distributed in the first suede structure. It can be understood that there are also spiral-shaped second micro-unit structures with irregular distribution in the second suede structure.

[0050] In an alternative embodiment, the lateral average size of the pyramidal first micro-unit structure is d1, and the longitudinal average size is h1, where 0 μm < d1 ≤ 5 μm and 0 μm < h1 ≤ 3 μm. Refer to Figure 2 , the lateral size means: taking the bright spot at the tip of the micro-unit structure in the shape of a pyramid as the intersection point, and drawing the size of the micro-unit structure along the cross-shaped reflected light under a 3D microscope. The average value of the two intersecting line segments is the lateral size of the micro-unit structure; refer to Figure 3 , the longitudinal size means: the vertical distance from point C at the top of the pyramidal micro-unit structure to the bottom surface. By adjusting d1 and h1 within the above ranges, it is beneficial to obtain a first micro-unit structure with a smaller size, and the first textured surface structure is less likely to have passivation dead corners, which is beneficial to improving the film formation quality of the first passivation layer.

[0051] In an alternative embodiment, the lateral average size of the pyramidal second micro-unit structure is d2, and the longitudinal average size is h2, where 0 μm < d2 ≤ 6 μm and 0 μm < h2 ≤ 3.5 μm.

[0052] In an alternative embodiment, refer to Figure 4 , the width w1 of the first doped region 2 is 300 μm to 600 μm, and / or the width w2 of the second doped region 3 is 300 μm to 600 μm. By controlling w1 and w2 within the above ranges, it is beneficial to form a solar cell having the structure of the present application.

[0053] In an alternative embodiment, refer to Figure 4 , a first dielectric layer 21 and a first doped layer 22 are sequentially provided on the back surface of the silicon substrate 1 located in the first doped region 2; a second dielectric layer 31 and a second doped layer 32 are sequentially provided on the back surface of the silicon substrate 1 located in the second doped region 3; the first doped layer 22 and the second doped layer 32 have different conductivity types. For example, when the conductivity type of the first doped layer is N-type, the conductivity type of the second doped layer is P-type; when the conductivity type of the first doped layer is P-type, the conductivity type of the second doped layer is N-type.

[0054] The materials of the dielectric layer in this application may include various dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the dielectric layer may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high-temperature processes. In order to better provide interface passivation for the substrate, the thickness of the dielectric layer may be 0.1 nm to 5 nm. For example, the thickness of the dielectric layer may be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc. However, this application is not limited thereto, and the thickness of the dielectric layer may have various values. As a barrier for electrons and holes, the dielectric layer can combine with the polycrystalline silicon layer to prevent minority carriers from passing through. The dielectric layer can also have the function of pinhole channels, enabling the carriers in the solar cell to move freely, and generating selective passage for majority carriers through heavily doped polycrystalline silicon, which is beneficial to reducing the recombination loss of minority carriers. In addition, the dielectric layer can be used as a diffusion barrier to prevent the dopant in the doped polycrystalline silicon layer from diffusing into the semiconductor substrate.

[0055] The thickness of the silicon substrate in this application is 100 μm to 200 μm, and this application does not make specific limitations.

[0056] This application does not particularly limit the preparation method of the solar cell. Exemplarily, it can be prepared through the following steps:

[0057] Polishing treatment: Use an alkali solution to etch and polish the silicon substrate to achieve the purpose of removing wire marks and oil stains. The alkali solution can be an NaOH solution or a KOH solution, the concentration of the alkali solution is 0.5 wt% to 5 wt%, and the process temperature is 60 °C to 80 °C. After polishing, use a mixed solution containing hydrofluoric acid (concentration of 1 wt% to 6 wt%) and hydrochloric acid (concentration of 1.5 wt% to 5 wt%) for cleaning, and then clean and dry with deionized water;

[0058] First coating treatment: Use low-pressure chemical vapor deposition (LPCVD) to sequentially deposit a first dielectric layer and an intrinsic amorphous silicon layer on the back of the silicon substrate. The thickness of the first dielectric layer is 0.5 nm to 3 nm, and the thickness of the intrinsic amorphous silicon layer is 100 nm to 300 nm; then dope the intrinsic crystalline silicon layer of the solar cell semi-finished product by thermal diffusion. For example, use BCl3 as the doping source to obtain a P-type doped crystalline silicon layer with a thickness of 200 nm to 400 nm, that is, the first doped layer; then form a first silicon oxide mask layer with a thickness of 20 nm to 60 nm on the surface of the first doped layer. The structure of the solar cell semi-finished product obtained after the first coating treatment is as Figure 5As shown, on the back of the silicon substrate are, in sequence, a first dielectric layer 21, a first doped layer 22, and a first silicon oxide mask layer 23.

[0059] First patterning process: The semi-finished solar cell is subjected to a first patterning process by means of laser scanning to form a patterned area. The effective depth of the patterning process is ≥ the thickness of the first silicon oxide mask layer, thereby damaging the compactness of the first silicon oxide mask layer in the patterned area. A picosecond laser is used with a power of 50 W to 100 W; then, a 1 wt% to 5 wt% NaOH solution is used for alkali cleaning to locally remove the first doped layer in the patterned area. After washing with water, a hydrofluoric acid solution (concentration 0.2 wt% to 1 wt%) is used for acid cleaning, and after washing with water, drying and other processes, the structure of the semi-finished solar cell obtained after the first patterning process is as Figure 6 shown; when observing along the thickness direction of the silicon substrate, the patterned area is as Figure 7 shown.

[0060] Second coating process: Using the method of enhanced plasma chemical vapor deposition (PECVD), a second dielectric layer, a second doped amorphous silicon layer are sequentially grown on the patterned area, non-patterned area, and side of the back of the semi-finished solar cell after the first patterning process, and a second silicon oxide mask layer with a thickness of 20 nm to 60 nm is formed on the surface of the second doped crystalline silicon layer. Among them, the doping type of the second doped amorphous silicon layer is opposite to that of the first doped layer; at the same time, crystallization is achieved in a high-temperature environment (temperature 700 °C to 900 °C), and the doped amorphous silicon in the second doped amorphous silicon layer is transformed into doped polycrystalline silicon to form a second doped layer. The structure of the semi-finished solar cell obtained after the second coating process is as Figure 8 shown, and a second dielectric layer 31, a second doped layer 32, and a second silicon oxide mask layer 33 are sequentially formed on the back of the silicon substrate.

[0061] Second patterning process: The semi-finished solar cell after the second coating process is subjected to a second patterning process by means of laser scanning: the second silicon oxide mask layer in the patterned area is removed by laser to form a patterned second doped layer; or, the semi-finished solar cell after the second coating process is subjected to a second patterning process by hydrofluoric acid: a patternable area is formed by screen-printing an acid-resistant mask paste on the surface of the second silicon oxide mask layer, and then the second silicon oxide mask layer in the patterned area is removed by hydrofluoric acid to form a patterned second doped layer. The laser-related parameters of this application can be: the laser type is at least one of nanosecond laser, picosecond laser, and femtosecond laser, the light type is any one of infrared laser, visible light laser, and ultraviolet laser, and the energy density of the laser is 30 mJ / cm 2 ~3000 mJ / cm 2, with a wavelength of 700 nm to 1000 nm, and the laser spot size is a rectangular spot of (20 - 400) μm × (20 - 400) μm. The structure of the semi-finished solar cell obtained after the second patterning process is as shown in Figure 9 . A patterned first doping layer 22 and a second doping layer 32 are formed on the back surface of the silicon substrate, and corresponding silicon oxide mask layers are retained on the surfaces of the first doping layer 22 and the second doping layer 32.

[0062] Texturing: Use a mixed solution of a texturing additive and NaOH to texture the semi-finished solar cell after the second patterning process. On the back surface of the semi-finished solar cell, a first textured surface structure is formed on the surface of the silicon substrate in the isolation region; on the front surface of the semi-finished solar cell, a second textured surface structure is formed on the surface of the silicon substrate. The reaction time is 400 s to 600 s, and the process temperature is 65 °C to 70 °C. In the mixed solution, the mass concentration of the texturing additive is 1% to 3%, and the mass concentration of NaOH is 0.5% to 2%. The texturing additive can be a commercially available texturing additive, which contains carboxymethyl cellulose, a defoaming agent, and sodium lignosulfonate. Among them, the mass concentration of carboxymethyl cellulose is 1% to 2%, the mass concentration of the defoaming agent is 1% to 2%, and the mass concentration of sodium lignosulfonate is 0.5% to 2%.

[0063] This application does not particularly limit the method of regulating the proportion of the number of spiral first micro-unit structures and the proportion of the number of spiral second micro-unit structures. The proportion of the number of spiral micro-unit structures generally shows a trend of increasing first and then decreasing with the increase of the reaction time. Based on this, the proportion of the number of spiral first micro-unit structures and the proportion of the number of spiral second micro-unit structures can be regulated by regulating the reaction time in the texturing process.

[0064] Preparation of the functional layer: After removing the silicon oxide mask layers on the surfaces of the first doping region and the second doping region, use PECVD to deposit an aluminum oxide layer as a passivation layer on the light-receiving surface and the backlight surface of the textured semi-finished solar cell, and then deposit a silicon nitride layer as an antireflection layer on the surface of the aluminum oxide passivation layer respectively; among them, referring to Figure 10 , the thickness of the first passivation layer 42 is 3 nm to 8 nm, and the thickness of the first antireflection layer 43 is 60 nm to 90 nm; the thickness of the second passivation layer 52 is 3 nm to 8 nm, and the thickness of the second antireflection layer 53 is 80 nm to 110 nm.

[0065] Preparation of the electrode grid lines: On the backlight surface of the semi-finished solar cell with the functional layer, apply the electrode paste on the first doping region and the second doping region by screen printing, and then sinter to form the electrode grid lines.

[0066] This application provides a photovoltaic module, and the photovoltaic module includes the solar cell described in any of the above embodiments.

[0067] The present application also provides a photovoltaic module, which is used to convert the received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; an encapsulation film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the encapsulation film facing away from the battery string.

[0068] Embodiment

[0069] The solar cell, its processing method, and the photovoltaic module according to the embodiments of the present application will be further described below with reference to more specific embodiments.

[0070] Embodiment 1

[0071] <Polishing treatment>

[0072] The silicon substrate is etched and polished using a NaOH solution (concentration: 1 wt%), and the process temperature is 60°C. After polishing, it is cleaned using a mixed solution containing hydrofluoric acid (concentration: 3 wt%) and hydrochloric acid (concentration: 3 wt%), and then cleaned with deionized water, dried, and reserved for use.

[0073] <First coating treatment>

[0074] Using low-pressure chemical vapor deposition (LPCVD), a first dielectric layer and an intrinsic amorphous silicon layer are sequentially deposited on the backlight surface of the silicon substrate. The thickness of the first dielectric layer is 1 nm, and the thickness of the intrinsic amorphous silicon layer is 200 nm. The deposition temperature of LPCVD is 600°C; then the semi-finished solar cell is doped with the intrinsic crystalline silicon layer by thermal diffusion using BCl3 as the doping source to obtain a P-type doped crystalline silicon layer with a thickness of 300 nm as the first doping layer; then a silicon oxide mask layer with a thickness of 40 nm is formed on the surface of the first doping layer.

[0075] <First patterning treatment>

[0076] The semi-finished solar cell is patterned by laser scanning to form a patterned area. The laser uses a picosecond laser with a power of 70 W; then it is alkali-washed with a 5 wt% NaOH solution to locally remove the first doping layer in the patterned area, and after washing with water, it is acid-washed with a hydrofluoric acid solution (concentration: 0.5 wt%), and after processes such as washing with water and drying, the semi-finished solar cell after the first patterning treatment is obtained;

[0077] <Second coating treatment>

[0078] Using PECVD, a second dielectric layer and a second doped amorphous silicon layer are sequentially grown on the patterned area, non-patterned area, and side of the backlight surface of the semi-finished solar cell after the first patterning process. A second silicon oxide mask layer with a thickness of 40 nm is formed on the surface of the second doped crystalline silicon layer. Among them, the doping type of the second doped amorphous silicon layer is opposite to that of the first doped layer. At the same time, crystallization is achieved in a high-temperature environment (temperature 800 °C), and the doped amorphous silicon in the second doped amorphous silicon layer is transformed into doped polycrystalline silicon to form a second doped layer.

[0079] <Second patterning process>

[0080] The semi-finished solar cell after the second coating process is subjected to a second patterning process by laser scanning to form a patterned second doped layer. The laser-related parameters of this application can be: the laser type is picosecond laser, the light type is ultraviolet laser, the energy density of the laser is 1000 mJ / cm 2 , the wavelength is 700 nm, and the laser spot size is a rectangular spot of 100 μm × 100 μm.

[0081] <Texturing>

[0082] The semi-finished solar cell after the de-bonding process is textured using a mixed solution of a texturing additive and NaOH. On the backlight surface of the semi-finished solar cell, a first textured surface structure is formed on the silicon substrate surface in the isolation area; on the light-receiving surface of the semi-finished solar cell, a second textured surface structure is formed on the silicon substrate surface. In the mixed solution, the mass concentration of the texturing additive is 1%, the mass concentration of NaOH is 2%, the reaction time is 500 s, and the process temperature is 65 °C. The texturing additive includes carboxymethyl cellulose, a defoaming agent, and sodium lignosulfonate. Among them, the mass concentration of carboxymethyl cellulose is 1%, the mass concentration of the defoaming agent is 1%, and the mass concentration of sodium lignosulfonate is 0.5%.

[0083] <Preparation of functional layer>

[0084] After removing the mask layers on the surfaces of the first doped area and the second doped area, using PECVD, an alumina layer is deposited on the light-receiving surface and the backlight surface of the textured semi-finished solar cell as a passivation layer, and then a silicon nitride layer is deposited on the surface of the alumina passivation layer as an antireflection layer respectively; among them, the thickness of the first passivation layer 42 is 5 nm, and the thickness of the first antireflection layer 43 is 80 nm; the thickness of the second passivation layer 52 is 5 nm, and the thickness of the second antireflection layer 53 is 100 nm.

[0085] <Preparation of electrode grid lines>

[0086] On the backlight surface of the semi-finished solar cell with the functional layer, electrode paste is applied to the first doped area and the second doped area by screen printing, and then sintered to form electrode grid lines.

[0087] Example 2

[0088] Except in <texturing>, adjusting the reaction time to 550 s, the rest is the same as in Example 1.

[0089] Example 3

[0090] Except in <texturing>, adjusting the reaction time to 400 s, the rest is the same as in Example 1.

[0091] Example 4

[0092] Except in <texturing>, adjusting the process temperature to 600 s, the rest is the same as in Example 1.

[0093] Example 5

[0094] Except in <texturing>, adjusting the process temperature to 700 s, the rest is the same as in Example 1.

[0095] Comparative Example 1

[0096] Except in <texturing>, adjusting the reaction time to 1000 s, the rest is the same as in Example 1.

[0097] Comparative Example 2

[0098] Except in <texturing>, adjusting the reaction time to 300 s, the rest is the same as in Example 1.

[0099] Table 1 First and second surface texture structure parameters of each example and comparative example

[0100]

[0101] In Table 1, " / " indicates that the relevant test parameters do not exist.

[0102] Performance test:

[0103] Test for the proportion of the number of spiral micro-unit structures:

[0104] Place the solar cell under SEM and observe the first or second surface texture structure at a magnification of 3K. Select any 5 regions of 14 μm × 21 μm in the field of view and save the pictures. For the first surface texture structure, record the number of the first spiral micro-unit structures and the number of the first pyramid-shaped micro-unit structures in the selected regions, and then calculate the proportion of the number of spiral micro-unit structures; the second surface texture structure is calculated in the same way.

[0105] Test for the lateral average size of the pyramid-shaped micro-unit structures:

[0106] The first texture structure or the second texture structure of the solar cell was observed under SEM at a magnification of 3K, and any 5 regions of 14μm×21μm were selected in the field of view. Then, the lateral dimensions of the pyramidal micro-unit structures were measured respectively under the SEM on-line dimension option conditions. After the measurement was completed, the lateral average dimension values of the pyramidal micro-unit structures were obtained by summarizing and statistics.

[0107] Open-circuit voltage, short-circuit current, fill factor test:

[0108] The current (I)-voltage (V) of the solar cells of each example and comparative example was measured using an I-V tester (model: MX-MPVC-A20, manufacturer: Suzhou Maiwei Technology Co., Ltd.) to obtain the open-circuit voltage, short-circuit current and fill factor of the solar cells.

[0109] Photovoltaic conversion efficiency test:

[0110] The current (I)-voltage (V) of the solar cells of each example and comparative example was measured using an I-V tester (model: MX-MPVC-A20, manufacturer: Suzhou Maiwei Technology Co., Ltd.) to obtain the photovoltaic conversion efficiency (Eta) of the solar cells.

[0111] Table 2 Performance data of each example and comparative example

[0112]

[0113] It can be seen from Examples 1 to 5 and Comparative Examples 1 to 2 that the open-circuit voltage, short-circuit current, fill factor and photovoltaic conversion efficiency of the solar cell of Comparative Example 1 are all low. This may be because the a1 value of Comparative Example 1 is too large, resulting in too high a proportion of the number of spiral first micro-unit structures, which affects the film-forming quality of the first passivation layer; the open-circuit voltage, short-circuit current, fill factor and photovoltaic conversion efficiency of the solar cell of Comparative Example 2 are also all low. This may be because the a1 value of Comparative Example 2 is too small, resulting in too low a proportion of the number of spiral first micro-unit structures, and vacancy regions are likely to appear on the surface of the first texture structure, reducing the integrity of the first texture structure, which will also affect the film-forming quality of the first passivation layer; while the solar cells of the present application have higher performance such as open-circuit voltage, short-circuit current, fill factor, and photovoltaic conversion efficiency compared to Comparative Example 1 and Comparative Example 2.

[0114] The above has introduced in detail a solar cell and a photovoltaic module disclosed in this application. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the technical solution and the core invention point of the embodiments of this application. At the same time, for those of ordinary skill in the art, according to the idea of this application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A solar cell, characterized in that, Comprising: A silicon substrate, the back surface of the silicon substrate includes alternately arranged first doping regions and second doping regions, and an isolation region is provided between adjacent first doping regions and second doping regions; The part of the back surface of the silicon substrate located in the isolation region has a first micro-unit structure, a plurality of the first micro-unit structures form a first matte structure, the surface of the first matte structure has a first passivation layer, and the first micro-unit structure includes a spiral first micro-unit structure and a pyramid-shaped first micro-unit structure, wherein, The percentage of the number of the spiral first micro-unit structures in the total number of the first micro-unit structures is a1, 20% ≤ a1 ≤ 70%.

2. The solar cell according to claim 1, wherein The percentage of the number of the pyramid-shaped first micro-unit structures in the total number of the first micro-unit structures is b1, 30% ≤ b1 ≤ 80%.

3. The solar cell according to claim 1, characterized in that, The front surface of the silicon substrate has a second micro-unit structure, a plurality of the second micro-unit structures form a second matte structure, the surface of the second matte structure has a second passivation layer, and the second micro-unit structure includes a spiral second micro-unit structure and a pyramid-shaped second micro-unit structure, wherein, The percentage of the number of the spiral second micro-unit structures in the total number of the second micro-unit structures is a2, 15% ≤ a2 ≤ 65%.

4. The solar cell according to claim 3, characterized in that, The percentage of the number of the pyramid-shaped second micro-unit structures in the total number of the second micro-unit structures is b2, 35% ≤ b2 ≤ 85%.

5. The solar cell according to claim 3, characterized in that, a1 > a2.

6. The solar cell according to claim 3, wherein, A plurality of the spiral first micro-unit structures are irregularly distributed in the first matte structure; And / or, a plurality of the spiral second micro-unit structures are irregularly distributed in the second matte structure.

7. The solar cell according to claim 2, wherein The lateral average size of the pyramid-shaped first micro-unit structure is d1, and the longitudinal average size is h1, 0μm < d1 ≤ 5μm, 0μm < h1 ≤ 3μm.

8. The solar cell according to claim 4, characterized in that, The lateral average size of the pyramid-shaped second micro-unit structure is d2, and the longitudinal average size is h2, 0μm < d2 ≤ 6μm, 0μm < h2 ≤ 3.5μm.

9. The solar cell according to claim 1, characterized in that, The width w1 of the first doping region is 300μm to 600μm, and / or, the width w2 of the second doping region is 300μm to 600μm.

10. The solar cell according to claim 1, characterized in that, A first dielectric layer and a first doping layer are sequentially provided on the back surface of the silicon substrate located in the first doping region; A second dielectric layer and a second doping layer are sequentially provided on the back surface of the silicon substrate located in the second doping region; The conductive types of the first doping layer and the second doping layer are different.

11. A photovoltaic module, characterized in that, The photovoltaic module includes the solar cell according to any one of claims 1 to 10.

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