Back contact solar cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a back contact solar cell, a preparation method thereof and a photovoltaic module. The back contact solar cell includes a crystalline silicon substrate and a first functional film. The back of the crystalline silicon substrate is provided with a first region and an isolation region, and the isolation region is arranged on one side of the first region. The first functional film is arranged on the first area in a stacked mode, the first functional film is provided with a light trapping part close to the isolation area, the light trapping part is provided with at least one of a light trapping valley and a light trapping peak, the light trapping valley shrinks in the direction from the groove opening to the groove bottom, and the side wall of the light trapping peak expands outwards in the direction from the top end to the bottom end. Wherein the shrunk light trapping valley and the expanded light trapping peak can reflect incident light towards the interior of the first functional film and the crystalline silicon substrate, so that a light trapping effect is achieved, the utilization rate of back incident light is increased, and the double-sided rate of the back contact solar cell is effectively increased; therefore, the efficiency of the back contact solar cell can be further improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a back-contact solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Under the actual working conditions of the back-contact solar cell, light will not only be incident on the front side of the back-contact solar cell, but also be incident on the back side of the back-contact solar cell after being reflected. Although the back-contact solar cell can make full use of the incident light from the front side, the utilization efficiency of the light incident from the back side of the back-contact solar cell is low, which limits the bifaciality of the back-contact solar cell. Summary of the invention

[0003] Based on this, it is necessary to provide a back-contact solar cell that can improve the utilization rate of back light in order to address the problems in the above-mentioned background technology.

[0004] The present application provides a back-contact solar cell, comprising:

[0005] A crystalline silicon substrate, wherein a first region, a second region and an isolation region are disposed on the back side of the crystalline silicon substrate, wherein the isolation region is disposed between the first region and the second region, and the first region and the second region are separated by the isolation region;

[0006] a first functional film, the first functional film comprising a first tunneling layer and a first doping layer, the first tunneling layer and the first doping layer being sequentially stacked on the first region, the first functional film having a light trapping portion close to the isolation region, the light trapping portion being provided with at least one of a light trapping valley and a light trapping peak, wherein, in a thickness direction close to the crystalline silicon substrate, the light trapping valley shrinks from a groove opening to a groove bottom, and a side wall of the light trapping peak expands from a top end to a bottom end; and

[0007] The second functional film includes a second tunneling layer and a second doping layer, the second tunneling layer and the second doping layer are sequentially stacked on the second region, and the second doping layer and the first doping layer have opposite doping types.

[0008] In some embodiments of the present application, the light-trapping portion includes a plurality of continuously arranged light-trapping peaks, and the bottom ends of the side walls of two adjacent light-trapping peaks are connected.

[0009] In some embodiments of the present application, the first functional film has a first boundary close to the isolation region, the second functional film has a second boundary close to the isolation region, and the fluctuation variance of the spacing of the first boundary relative to the centerline of the isolation region is greater than the fluctuation variance of the spacing of the second boundary relative to the centerline of the isolation region.

[0010] In some embodiments of the present application, the value of the fluctuation variance of the first boundary is 30~100.

[0011] In some embodiments of the present application, a height difference between an end of the light trapping portion closest to the crystalline silicon substrate and a top surface of the first functional film is 0.5 μm to 6 μm.

[0012] In some embodiments of the present application, a height difference between an end of the light trapping portion closest to the crystalline silicon substrate and a top surface of the first functional film is 3 μm to 6 μm.

[0013] In some embodiments of the present application, the surface of the isolation region of the crystalline silicon substrate has a velvet structure, and the height difference between the bottom end of the light trapping portion and the top surface of the first functional film is greater than the height difference between the bottom end of the isolation region adjacent to it and the top surface of the first functional film.

[0014] In some embodiments of the present application, the doping type of the first doping layer is N-type, and the doping type of the second doping layer is P-type.

[0015] In some embodiments of the present application, the first functional film further includes at least one of a first passivation layer and a first anti-reflection layer stacked on the first doping layer; and / or,

[0016] The second functional film further includes at least one of a second passivation layer and a second anti-reflection layer stacked on the second doping layer.

[0017] Furthermore, the present application also provides a method for preparing a back-contact solar cell according to any of the above embodiments, comprising the following steps:

[0018] forming the second tunneling layer and the second doping layer in sequence on the second region of the crystalline silicon substrate, and forming the first tunneling layer, the first doping layer and the first doped oxide layer in sequence on the first region of the crystalline silicon substrate;

[0019] The first doped oxide layer has a light trapping process area close to the isolation region, and a portion of the first doped oxide layer in the light trapping process area is removed to expose the first doped layer located therebelow;

[0020] The first doped oxide layer, the first doped layer and the first tunneling layer are corroded by alkaline solution to form the light trapping portion.

[0021] In some embodiments of the present application, the step of removing a portion of the first doped oxide layer in the light trapping process area includes: scanning the light trapping process area using a target laser;

[0022] During the scanning process, the target laser spot includes a high-energy area and a low-energy area, and the power density of the high-energy area is greater than 0.25 J / cm 2 , the power density of the low energy zone is ≤0.25J / cm 2 ;or,

[0023] During the scanning process, the target laser is controlled to scan only a local area of ​​the light trapping process area.

[0024] In some embodiments of the present application, in the step of depositing the first tunneling layer and the first doping layer on the crystalline silicon substrate, the first tunneling layer, the first doping layer and the first doped oxide layer are extended and deposited on the isolation region;

[0025] The preparation method further comprises the step of removing the first doped oxide layer located on the isolation region by laser ablation of the isolation region.

[0026] In some embodiments of the present application, in the step of corroding the first tunneling layer and the first doping layer with alkaline solution, a texturing agent is used as the alkaline solution, and the texturing agent is simultaneously used to perform texturing treatment on the front and back sides of the crystalline silicon substrate.

[0027] Furthermore, the present application also provides a photovoltaic module, which includes the back-contact solar cell as described in the above embodiment, or the photovoltaic module includes the back-contact solar cell prepared by the preparation method of the back-contact solar cell as described in the above embodiment.

[0028] The back-contact solar cell of the present application is provided with a crystalline silicon substrate, a first functional film and a second functional film stacked on the crystalline silicon substrate, the first functional film and the second functional film are respectively used to derive two different types of carriers, and the first functional film has a light-trapping portion close to the isolation region. The light-trapping portion is provided with a light-trapping valley and a light-trapping peak. The contracted light-trapping valley and the expanded light-trapping peak can both reduce the reflectivity of the light incident from the back side of the back-contact solar cell toward the inside of the first functional film and the crystalline silicon substrate, thereby improving the utilization rate of the light incident from the back side of the back-contact solar cell by the crystalline silicon substrate, so as to play a light-trapping role and increase the utilization rate of the incident light from the back side, which can effectively increase the bifaciality of the back-contact solar cell, thereby further improving the efficiency of the back-contact solar cell.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of the cross-sectional structure of a back-contact solar cell of the present application;

[0032] Figure 2A for Figure 1 A schematic diagram of a partial cross-sectional structure of the first functional film containing a light trapping portion, Figure 2B for Figure 2A The optical path diagram of the incident light ray is shown;

[0033] Figure 3 for Figure 1 A schematic diagram of a partial top-view cross-sectional structure of the first functional film, the isolation region and the second functional film;

[0034] Figure 4 A schematic diagram of the steps of a method for preparing a back-contact solar cell;

[0035] Figure 5 It is a schematic diagram of the cross-sectional structure of depositing a second tunneling layer and a second doping layer on a crystalline silicon substrate;

[0036] Figure 6 For Figure 5 A schematic diagram of a structure in which the second tunneling layer and the second doping layer outside the second region are removed based on the structure shown;

[0037] Figure 7 For Figure 6 A schematic diagram of a structure in which a first tunneling layer and a first doping layer are deposited on the basis of the structure shown;

[0038] Figure 8 A schematic diagram of controlling the energy density distribution of the target laser spot;

[0039] Fig. 9 A schematic diagram of the structure for controlling the scanning area of ​​the target laser;

[0040] Fig.10 for Figure 7 A schematic diagram of the cross-sectional structure of the structure shown after being corroded by alkali solution;

[0041] Fig.11 It is a partial enlarged top view of the light trapping portion in Example 1;

[0042] Fig.12 This is a top view of the isolation area;

[0043] Fig.13 It is a schematic diagram of the cross-sectional structure of the isolation region having the light trapping portion.

[0044] The reference numerals and their meanings are as follows:

[0045] 100, crystalline silicon substrate; 1001, first boundary; 1002, second boundary; 101, first region; 102, second region; 103, isolation region; 110, first functional film; 1100, light trapping portion; 1101, light trapping peak; 1102, light trapping valley; 1103, side wall; 111, first tunneling layer; 112, first doped layer; 113, first passivation layer; 114, first anti-reflection layer; 120, second functional film; 121, second tunneling layer; 122, second doped layer; 123, second passivation layer; 124, second anti-reflection layer; 130, front passivation layer; 140, front anti-reflection layer; 150, first electrode; 160, second electrode; 210, first doped oxide layer; 220, second doped oxide layer. 301, light trapping process area; 310, target laser; 311, high energy area; 312, low energy area. DETAILED DESCRIPTION

[0046] To facilitate understanding of the present invention, a more comprehensive description of the present invention is provided below. The preferred embodiments of the present invention are given herein. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the content of the present invention more thorough and comprehensive.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this document pertains. The terms used herein in the specification of this document are only for describing specific embodiments and are not intended to limit this document.

[0048] It should be understood that when an element or layer is referred to as being "on, "adjacent to, "connected to, or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, "directly adjacent to, "directly connected to, or "directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion.

[0049] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein for ease of description to describe the relationship of one element or feature to other elements or features. It should be understood that the spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be otherwise oriented (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used may be interpreted accordingly.

[0050] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "a", "an" and "the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0051] The present application provides a back contact solar cell, comprising a crystalline silicon substrate, a first functional film and a second functional film. The back of the crystalline silicon substrate is provided with a first region, a second region and an isolation region, the isolation region is provided between the first region and the second region, and the first region and the second region are separated by the isolation region. The first functional film comprises a first tunneling layer and a first doping layer, and the first tunneling layer and the first doping layer are sequentially stacked and arranged on the first region. The first functional film has a light trapping portion close to the isolation region, and the light trapping portion is provided with at least one of a light trapping valley and a light trapping peak. Among them, the light trapping peak refers to a convex structure with a pointed top or a nearly pointed top shape located on the crystalline silicon substrate, and the light trapping valley can be close to the light trapping peak and present a narrow and long channel shape, or can be separated from the light trapping peak and present a groove shape. The light trapping valley shrinks from the groove to the bottom of the groove, and the side wall of the light trapping peak expands from the top to the bottom. Among them, the top of the side wall refers to the end of the side wall farthest from the crystalline silicon substrate, and the bottom of the side wall refers to the end of the side wall closest to the crystalline silicon substrate. The second functional film includes a second tunneling layer and a second doping layer, which are sequentially stacked on the second region, and the second doping layer and the first doping layer have opposite doping types.

[0052] The back-contact solar cell of the present application is provided with a crystalline silicon substrate, a first functional film and a second functional film stacked on the crystalline silicon substrate, the first functional film and the second functional film are respectively used to derive two different types of carriers, and the first functional film has a light-trapping portion close to the isolation region. The light-trapping portion is provided with a light-trapping valley and a light-trapping peak. Among them, along the thickness direction close to the crystalline silicon substrate, the contracted light-trapping valley and the expanded light-trapping peak can both reduce the reflectivity of the light incident from the back of the back-contact solar cell toward the inside of the first functional film and the crystalline silicon substrate, thereby improving the utilization rate of the light incident from the back of the back-contact solar cell absorbed by the crystalline silicon substrate, so as to play a light-trapping role and increase the utilization rate of the crystalline silicon substrate for the light incident from the back, which can effectively increase the bifaciality of the back-contact solar cell, thereby further improving the efficiency of the back-contact solar cell.

[0053] Figure 1 This is a schematic diagram of the cross-sectional structure of a back-contact solar cell of the present application. Figure 1 As shown, the back contact solar cell includes a crystalline silicon substrate 100, a first functional film 110 and a second functional film 120. A first region 101, a second region 102 and an isolation region 103 are provided on the back of the crystalline silicon substrate 100, and the isolation region 103 is provided between the first region 101 and the second region 102. The first functional film 110 is stacked on the first region 101, and the second functional film 120 is stacked on the second region 102.

[0054] It can be understood that among the photogenerated carriers generated in the crystalline silicon substrate 100 , carriers of one conductivity type are derived from the first region 101 , and carriers of another conductivity type are derived from the second region 102 .

[0055] Reference Figure 1 As shown, it can be understood that the first functional film 110 and the second functional film 120 are separated by the isolation region 103. The doping type in the first functional film 110 is different from the doping type in the second functional film 120. The first functional film 110 and the second functional film 120 are respectively used to guide carriers of different conductivity types from the crystalline silicon substrate 100. In addition, the first functional film 110 and the second functional film 120 are also used to passivate the surface of the crystalline silicon substrate 100, thereby reducing the interface recombination loss of carriers between the crystalline silicon substrate and the doping layer.

[0056] Reference Figure 1 As shown in some examples of this embodiment, the crystalline silicon substrate 100 may have a plurality of first regions 101 and second regions 102, and each first region 101 is separated from an adjacent second region 102 by an isolation region 103. A first functional film 110 is disposed on each first region 101, and a second functional film 120 is disposed on each second region 102.

[0057] Figure 2A FIG. 1 is a schematic diagram of a partial cross-sectional structure of a light trapping portion 1100 in the first functional film 110. Figure 2A As shown, the light trapping portion 1100 is arranged close to the isolation region 103, and at least one of a light trapping valley 1102 and a light trapping peak 1101 is arranged in the light trapping portion 1100. In the thickness direction close to the crystalline silicon substrate 100, the light trapping valley 1102 shrinks from the groove opening to the groove bottom, and the side wall of the light trapping peak 1101 expands from the top to the bottom.

[0058] Reference Figure 2A As shown, as some examples of this embodiment, the light trapping portion 1100 can be provided with a light trapping valley 1102 and a light trapping peak 1101 at the same time, so as to further enhance the light trapping capability of the first functional film 110 for light.

[0059] Reference Figure 2A As shown in some examples of this embodiment, the light trapping portion 1100 may include a plurality of continuously arranged light trapping peaks 1101. The bottom ends of the side walls of two adjacent light trapping peaks 1101 are connected. The plurality of continuously arranged light trapping peaks 1101 form a sawtooth structure in the direction along the surface of the crystalline silicon substrate 100. Compared with a single light trapping peak 1101, two adjacent side walls in the plurality of light trapping peaks 1101 are reflected back and forth to further enhance the absorption rate of the light trapping portion 1100 for incident light from the back side of the back contact solar cell.

[0060] In this example, the top of a single light-trapping peak 1101 is in the shape of a pointed top, that is, the top of the light-trapping peak 1101 is in the shape of a point or a line. When the top of a single light-trapping peak 1101 is in the shape of a line, the light-trapping peak 1101 as a whole may be in the shape of a ridge, and when the top of a single light-trapping peak 1101 is in the shape of a point, the light-trapping peak 1101 as a whole may be in the shape of a peak.

[0061] Reference Figure 2A As shown, as an example of this embodiment, the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 is 0.5μm~6μm. For example, the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 is 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, 6μm, or the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 can also be between any two of the above height difference values.

[0062] It can be understood that the top of the light trapping portion 1100 is the end of the overall structure of the light trapping portion 1100 that is farthest from the crystalline silicon substrate 100, and the bottom of the light trapping portion 1100 is the end of the overall structure of the light trapping portion 1100 that is closest to the crystalline silicon substrate 100.

[0063] Further, the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 is 3μm to 6μm, for example, the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 is 3μm, 3.5μm, 4μm, 5μm, 6μm, or the height difference between the end of the light trapping portion 1100 closest to the crystalline silicon substrate 100 and the top surface of the first functional film 110 can also be between any two of the above height difference values. This height difference is significantly higher than the height of a general pyramid velvet structure. Such a setting can further increase the interception area of ​​the light trapping portion 1100 for incident light from the back of the battery, thereby improving the utilization rate of the crystalline silicon substrate 100 for the incident light.

[0064] Reference Figure 2A As shown, as an example of this embodiment, the surface of the isolation region 103 of the crystalline silicon substrate 100 has a velvet structure. It can be understood that the velvet structure is uneven, and the overall structure of the velvet structure has a top farthest from the crystalline silicon substrate 100 and a bottom closest to the crystalline silicon substrate 100. The height difference between the bottom end of the light trapping portion 1100 and the top surface of the first functional film 110 is greater than the height difference between the bottom end of the isolation region 103 adjacent thereto and the top surface of the first functional film 110.

[0065] As some examples of this embodiment, the distance between the top and the bottom of each light trapping peak 1101 is 0.5 μm to 6 μm. The light trapping peak 1101 with this height can provide better light trapping performance while increasing the area ratio of the first functional film 110 on the back of the battery as much as possible, ensuring that the first functional film 110 still has good passivation performance and carrier collection ability.

[0066] In this example, the height difference between the top and bottom of the light trap peak 1101 can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, or the height difference between the top and bottom of the light trap peak 1101 can be between any two of the above height difference values. It can be understood that the heights of the multiple light trap peaks 1101 can be the same or different.

[0067] Figure 2A A cross section of the light-trapping valley 1102 is shown. It can be understood that the light-trapping valley 1102 as a whole may have a cone or pyramid shape, that is, the bottom of the light-trapping valley 1102 is pointed.

[0068] As some examples of this embodiment, the light trapping portion 1100 includes a light trapping valley 1102 and a light trapping peak 1101 , and the light trapping valley 1102 is disposed on a side of the light trapping peak 1101 away from the isolation region 103 .

[0069] As some examples of this embodiment, a plurality of light-trapping valleys 1102 may be provided in the light-trapping portion 1100 , and two adjacent light-trapping valleys 1102 may be provided closely to each other or spaced apart.

[0070] As some examples of this embodiment, the depth of the light-trapped valley 1102 may be 0.5 μm to 6 μm. Further, the depth of the light-trapped valley 1102 may be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, or the depth of the light-trapped valley 1102 may be between any two of the above depth values.

[0071] Understandably, Figure 2A The extending direction from the isolation region 103 toward the first region 101 (ie Figure 1 1 (x direction in FIG. 1 ), which shows only one light trapping portion 1100. As some examples of this embodiment, the first functional film 110 includes a plurality of light trapping portions 1100, and the plurality of light trapping portions 1100 are all close to the isolation region 103 and are arranged at intervals.

[0072] Figure 2B for Figure 2A Optical path diagram of the incident light ray is shown. Figure 2B The solid lines with arrows in the figure represent incident light rays. Figure 2B As shown, when the incident light irradiates the side wall 1103 of the light trap peak 1101, part of the incident light passes through the light trap peak 1101 and enters the crystalline silicon substrate 100 and is absorbed by the crystalline silicon substrate 100, and the other part is reflected on the side wall of the light trap peak 1101 to a direction close to the crystalline silicon substrate 100 and then absorbed by the crystalline silicon substrate 100. In addition, compared with the conventional pyramid velvet structure, the height dimension of the light trap peak 1101 in this embodiment is significantly larger, and the depth dimension of the light trap valley 1102 is also significantly larger, which is also conducive to allowing more incident light to be refracted or reflected by the light trap peak 1101 and the light trap valley 1102. Therefore, the light trap portion 1100 having the light trap peak 1101 and the light trap valley 1102 can significantly improve the absorption rate of the incident light.

[0073] Figure 3 for Figure 1 FIG. 1 is a schematic diagram of a partial top view of a cross-sectional structure of the first functional film 110, the isolation region 103, and the second functional film 120. In this embodiment, the extension direction of the boundary line between the first region 101 and the isolation region 103 (i.e. Figure 3 y direction in the Figure 1 The plane in which the cross section lies is perpendicular. Figure 3As shown, a plurality of light trapping portions 1100 can be sequentially arranged along the boundary between the first region 101 and the isolation region 103. The plurality of light trapping portions 1100 can further improve the light absorption rate of the back side of the crystalline silicon substrate 100, and the plurality of light trapping portions 1100 arranged at intervals can reduce the damage to the first functional film 110 while increasing the area proportion of the light trapping portions 1100 on the back side of the battery, thereby ensuring that the first functional film 110 still has a good carrier collection capability. In addition, if the entire edge of the first functional film 110 close to the isolation region 103 is set as a light trapping portion 1100, although a better light absorption rate can be obtained and more carriers can be generated, the proportion of the first functional film 110 will be reduced, thereby reducing the carrier collection capability.

[0074] It can be understood that the light trapping portion 1100 has an end farthest from the isolation region 103, and the end of the light trapping portion 1100 farthest from the isolation region 103 can be determined based on the light trapping valley 1102 and / or light trapping peak 1101 farthest from the isolation region 103. Figure 3 As shown, the spacing between the end of the light trapping portion 1100 farthest from the isolation region 103 and the isolation region 103 is d1. As some examples of this embodiment, the spacing d1 between the end of the light trapping portion 1100 farthest from the isolation region 103 and the isolation region 103 is ≤25μm. For example, the spacing d1 between the end of the light trapping portion 1100 farthest from the isolation region 103 and the isolation region 103 is 5μm, 10μm, 15μm, 20μm, 25μm, or the spacing d1 between the end of the light trapping portion 1100 farthest from the isolation region 103 and the isolation region 103 can also be between any two of the above spacings. The design of the light trapping portion 1100 with a specific spacing range can take into account good light absorption performance and is conducive to maintaining the first functional film 110 with good carrier collection ability, thereby significantly improving the efficiency of the back contact solar cell.

[0075] Reference Figure 3 As shown, the spacing between two adjacent light trapping portions 1100 is d2, that is, there is a spacing of length d2 between the tail end of the previous light trapping portion 1100 and the head end of the next light trapping portion 1100. As some examples of this embodiment, the spacing d2 between two adjacent light trapping portions 1100 is 20μm~200μm. The first functional film 110 located between the two adjacent light trapping portions 1100 can maintain a complete passivation contact structure. The above-mentioned light trapping portion design with a specific spacing can take into account good light absorption performance and is conducive to ensuring the carrier collection ability of the first functional film 110, thereby significantly improving the efficiency of the back contact solar cell.

[0076] In this example, the spacing between two adjacent light trapping portions 1100 may be 20 μm, 30 μm, 50 μm, 70 μm, 100 μm, 120 μm, 150 μm, 170 μm, or 200 μm, or the spacing between two adjacent light trapping portions 1100 may be between any two of the above spacings.

[0077] Reference Figure 3 As shown, along the extension direction of the boundary between the first region 101 and the isolation region 103, the single light trapping portion 1100 has a length d3. As some examples of this embodiment, the length d3 of the single light trapping portion 1100 is 10 μm to 90 μm. In this example, the length of the single light trapping portion 1100 can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or the length of the single light trapping portion 1100 can also be between any two of the above lengths.

[0078] Reference Figure 3 and Fig.12 As shown, the first functional film 110 has a first boundary 1001 close to the isolation region 103, and the second functional film 120 has a second boundary 1002 close to the isolation region 103, and the overall fluctuation variance of the first boundary 1001 is greater than the overall fluctuation variance of the second boundary 1002. The "fluctuation variance" of the first boundary 1001 and the second boundary 1002 should be understood as the degree of deviation of the first boundary 1001 relative to the extension direction of the isolation region 103. It can be understood that since the first functional film 110 has a light trap 1100 at the first boundary 1001 close to the isolation region 103, the overall fluctuation variance of the first boundary 1001 is greater than the overall fluctuation variance of the second boundary 1002.

[0079] As an example, the fluctuation variance value of the first boundary 1001 is 30-100. The above-mentioned first boundary design with a specific fluctuation variance range can take into account good light absorption performance and is conducive to ensuring the carrier collection ability of the first functional film 110, so that the efficiency of the back contact solar cell is more significantly improved. As an example, the "fluctuation variance" of the first boundary 1001 can be determined in the following way: first, select an isolation area 103 with a length of 100um-500um, select multiple points evenly distributed on the first boundary 1001 as a whole, and some of the multiple points should be located at the light trap 1100. At the same time, select a line located in the center area of ​​the isolation area 103 and substantially parallel to the extension direction of the isolation area 103 as a reference line, respectively obtain the distances of multiple points on the first boundary 1001 relative to the reference line, and calculate the variance of these obtained distances. The larger the variance, the larger the distribution deviation of these distances, that is, the larger the fluctuation variance of the first boundary 1001. The fluctuation variance of the second boundary 1002 can be obtained by the same method.

[0080] As some examples of this embodiment, the first functional film 110 includes a first tunneling layer 111 and a first doping layer 112, which are sequentially stacked on the first region 101 of the crystalline silicon substrate 100. The first tunneling layer 111 is used to separate the first doping layer 112 and the crystalline silicon substrate 100, and the first tunneling layer 111 is used to allow carriers to pass through while passivating the crystalline silicon substrate 100. The first doping layer 112 is used to selectively collect carriers.

[0081] As some examples of this embodiment, the material of the first tunneling layer 111 may be selected from one or more of amorphous silicon, intrinsic amorphous silicon, hydrogenated amorphous silicon, hydrogenated intrinsic amorphous silicon or silicon oxide.

[0082] As some examples of this embodiment, the thickness of the first tunneling layer 111 may be 1 nm to 3 nm.

[0083] As some examples of this embodiment, the doping type of the first doping layer 112 is N-type. Further, the doping element in the first doping layer 112 may be phosphorus. The N-type doped film layer is more conducive to preparing the light trapping portion 1100 in the actual process.

[0084] As some examples of this embodiment, the material of the first doping layer 112 may include doped polysilicon.

[0085] As some examples of this embodiment, the thickness of the first doping layer 112 may be 100 nm to 400 nm.

[0086] As some examples of this embodiment, the second functional film 120 includes a second tunneling layer 121 and a second doping layer 122, which are sequentially stacked on the second region 102 of the crystalline silicon substrate 100. The second tunneling layer 121 is used to separate the second doping layer 122 and the crystalline silicon substrate 100, and the second tunneling layer 121 is used to allow carriers to pass through while passivating the crystalline silicon substrate 100. The second doping layer 122 is used to selectively collect carriers.

[0087] As some examples of this embodiment, the material of the second tunneling layer 121 may be selected from one or more of amorphous silicon, intrinsic amorphous silicon, hydrogenated amorphous silicon, hydrogenated intrinsic amorphous silicon, or silicon oxide.

[0088] As some examples of this embodiment, the thickness of the second tunneling layer 121 may be 1 nm to 3 nm.

[0089] As some examples of this embodiment, the doping type of the second doping layer 122 is P-type. Further, the doping element in the second doping layer 122 may be boron.

[0090] As some examples of this embodiment, the material of the second doping layer 122 may include doped polysilicon.

[0091] As some examples of this embodiment, the thickness of the second doping layer 122 may be 100 nm to 400 nm.

[0092] Reference Figure 1 As shown, as some examples of this embodiment, the first functional film 110 may also include at least one of a first passivation layer 113 and a first anti-reflection layer 114, and the first passivation layer 113 and the first anti-reflection layer 114 are stacked on the first doping layer 112 and cover the first doping layer 112.

[0093] Reference Figure 1 As shown, as some examples of this embodiment, the second functional film 120 may further include at least one of a second passivation layer 123 , and the second passivation layer 123 and a second anti-reflection layer 124 are stacked on the second doping layer 122 and cover the second doping layer 122 .

[0094] As some examples of this embodiment, the first passivation layer 113 and the second passivation layer 123 may be an integrated structure, and the materials of the first passivation layer 113 and the second passivation layer 123 may include aluminum oxide. Further, the first passivation layer 113 and the second passivation layer 123 may also cover the isolation region 103.

[0095] As some examples of this embodiment, the first anti-reflection layer 114 and the second anti-reflection layer 124 may be an integrated structure, and the materials of the first anti-reflection layer 114 and the second anti-reflection layer 124 may include hydrogenated silicon nitride, hydrogenated silicon oxynitride or a combination thereof. Further, the first anti-reflection layer 114 and the second anti-reflection layer 124 may also cover the isolation region 103.

[0096] Reference Figure 1 As shown, as some examples of this embodiment, the back contact solar cell may further include a front passivation layer 130. The front passivation layer 130 is stacked and disposed on a side of the crystalline silicon substrate 100 away from the first functional film 110 and the second functional film 120.

[0097] As some examples of this embodiment, the material of the front passivation layer 130 may include aluminum oxide.

[0098] Reference Figure 1 As shown, as some examples of this embodiment, the back contact solar cell may further include a front anti-reflection layer 140 . The front anti-reflection layer 140 is stacked on the side of the front passivation layer 130 away from the crystalline silicon substrate 100 , and covers the front passivation layer 130 .

[0099] As some examples of this embodiment, the material of the front anti-reflection layer 140 may include one of hydrogenated silicon nitride and hydrogenated silicon oxynitride, or a combination of the two.

[0100] Reference Figure 1 As shown in some examples of this embodiment, the back-contact solar cell further includes a first electrode 150 and a second electrode 160, both of which are disposed on the back side of the crystalline silicon substrate 100. The first electrode 150 is disposed on the first region 101 and is electrically connected to the first doping layer 112. The second electrode 160 is disposed on the second region 102 and is electrically connected to the second doping layer 122.

[0101] The present application also provides a method for preparing the back-contact solar cell in the above embodiment. Figure 4 Schematic diagram of the steps of the preparation method of the back contact solar cell. Figure 4 As shown, the preparation method includes steps S1 to S3.

[0102] Step S1 : forming a first tunneling layer 111 , a first doping layer 112 , a first doped oxide layer 210 , a second tunneling layer 121 , and a second doping layer 122 on a crystalline silicon substrate 100 .

[0103] As some examples of this embodiment, a crystalline silicon material is adopted as the crystalline silicon substrate 100 .

[0104] As some examples of this embodiment, the second tunneling layer 121 and the second doping layer 122 can be formed before the first tunneling layer 111 and the first doping layer 112, which makes the subsequent process of forming the light trapping portion 1100 on the first tunneling layer 111 and the first doping layer 112 simpler.

[0105] As some examples of this embodiment, the steps of forming the second tunneling layer 121 and the second doping layer 122 include: depositing the second tunneling layer 121 and the second doping layer 122 on the semiconductor, and patterning the deposited second tunneling layer 121 and the second doping layer 122 .

[0106] Figure 5 FIG. 1 is a schematic diagram of a cross-sectional structure of depositing a second tunneling layer 121 and a second doping layer 122 on a crystalline silicon substrate 100. Figure 5 As shown, in this embodiment, the deposited second tunneling layer 121 and the second doping layer 122 cover the first region 101 , the second region 102 and the isolation region 103 on the back side of the crystalline silicon substrate 100 .

[0107] As some examples of this embodiment, the second tunneling layer 121 and the second doping layer 122 include the second tunneling layer 121 and the second doping layer 122 which are sequentially stacked.

[0108] As some examples of this embodiment, the steps of forming the second tunneling layer 121 and the second doping layer 122 include: sequentially depositing the second tunneling layer 121, the silicon material layer, and the second doped oxide layer 220 by chemical vapor deposition, and heating so that the doping elements in the second doped oxide layer 220 diffuse into the silicon material layer to form the second doping layer 122. The chemical vapor deposition method may specifically be LPCVD or PECVD.

[0109] For example, in this example, the material of the second doped oxide layer 220 may be borosilicate glass. Heating can cause the boron element in the borosilicate glass to diffuse into the silicon material layer to form P-type doped polysilicon, which can serve as the second doped layer 122 .

[0110] As some other examples of this embodiment, the steps of forming the second tunneling layer 121 and the second doping layer 122 include: depositing the second tunneling layer 121 and the second doping layer 122 in sequence by chemical vapor deposition. The chemical vapor deposition method may be LPCVD or PECVD. The second tunneling layer 121 and the second doping layer 122 may be deposited in the same deposition chamber. After depositing the second doping layer 122, a second doped oxide layer 220 may also be deposited.

[0111] It can be understood that the deposited second tunneling layer 121 and the second doping layer 122 not only cover the second region 102 on the back side of the crystalline silicon substrate 100, but also extend to cover the first region 101 and the isolation region 103. As some examples of this embodiment, after the second tunneling layer 121 and the second doping layer 122 are deposited and formed, the second tunneling layer 121 and the second doping layer 122 are further patterned to remove the second tunneling layer 121 and the second doping layer 122 outside the second region 102. In this embodiment, the pre-formed second doped oxide layer 220 can also be used as a mask in the subsequent patterning process.

[0112] Figure 6 For Figure 5 The schematic diagram of the structure shown in FIG. 1 is a schematic diagram of the structure in which the second tunneling layer 121 and the second doping layer 122 outside the second region 102 are removed. Figure 6 As shown, only the second tunneling layer 121 and the second doping layer 122 located on the second region 102 are retained, and the first region 101 and the isolation region 103 of the crystalline silicon substrate 100 are exposed from the openings of the second tunneling layer 121 and the second doping layer 122 .

[0113] As some examples of this embodiment, the method of patterning the second tunneling layer 121 and the second doping layer 122 may include: using a target laser 310 to ablate and remove the second doped oxide layer 220 on the first region 101 and the isolation region 103, and then using alkaline solution etching to remove the second doping layer 122 and the second tunneling layer 121 exposed from the target laser 310 ablation area.

[0114] Furthermore, in the step of etching the second doped layer 122 and the second tunneling layer 121 with an alkaline solution, the etching time can be controlled to ensure that the second doped oxide layer 220 with a thickness of more than 6 nm is retained on the second region 102. This can play a certain protective role on the second tunneling layer 121 and the second doped layer 122 in subsequent processes.

[0115] Reference Figure 6 As shown, the second tunneling layer 121 and the second doping layer 122 located on the first region 101 and the isolation region 103 are removed, and only the second tunneling layer 121 and the second doping layer 122 and the second doped oxide layer 220 located on the second region 102 are retained.

[0116] Figure 7 For Figure 6 A schematic diagram of a structure in which a first tunneling layer 111 and a first doping layer 112 are deposited on the basis of the structure shown in FIG. Figure 7 As shown, in this example, the first tunneling layer 111 and the first doping layer 112 cover the first region 101 and the isolation region 103 on the back side of the crystalline silicon substrate 100 , and the first tunneling layer 111 and the first doping layer 112 also extend to cover the second tunneling layer 121 and the second doping layer 122 .

[0117] As some examples of this embodiment, the first tunneling layer 111 and the first doping layer 112 include the first tunneling layer 111 and the first doping layer 112 which are sequentially stacked.

[0118] As some examples of this embodiment, the steps of forming the first tunneling layer 111 and the first doping layer 112 include: sequentially depositing the first tunneling layer 111, the silicon material layer and the first doped oxide layer 210 by chemical vapor deposition, and heating so that the doping elements in the first doped oxide layer 210 diffuse into the silicon material layer to form the first doping layer 112. The chemical vapor deposition method may specifically be LPCVD or PECVD.

[0119] For example, in this example, the material of the first doped oxide layer 210 may be phosphosilicate glass, and heating can cause the phosphorus element in the phosphosilicate glass to diffuse into the silicon material layer to form N-type doped polysilicon, which can serve as the first doped layer 112 .

[0120] As some other examples of this embodiment, the steps of forming the first tunneling layer 111 and the first doping layer 112 include: depositing the first tunneling layer 111 and the first doping layer 112 in sequence by chemical vapor deposition. The chemical vapor deposition method may be plasma enhanced chemical vapor deposition (PECVD). The first tunneling layer 111 and the first doping layer 112 may be deposited in the same deposition chamber. After depositing the first doping layer 112, a first doped oxide layer 210 may also be deposited.

[0121] In step S2 , a portion of the first doped oxide layer 210 in the light trapping process area 301 is removed to expose the first doped layer 112 thereunder.

[0122] It can be understood that the exposed first doped layer 112 can be corroded preferentially in the subsequent alkaline solution corrosion process to form a light trap valley 1102 , while the corrosion of the portion of the first doped layer 112 still blocked by the first doped oxide layer 210 is relatively slow to form a light trap peak 1101 .

[0123] In this embodiment, the step of removing part of the first doped oxide layer 210 in the light trapping process area 301 includes: scanning the light trapping process area 301 with a target laser 310. During the scanning process, the spot of the target laser 310 includes a high energy area 311 and a low energy area 312, and the power density of the high energy area 311 is greater than 0.25 J / cm 2 The power density of the low energy zone 312 is ≤ 0.25 J / cm 2 Alternatively, during the scanning process, the target laser 310 is controlled to scan only a local area of ​​the light trapping process area 301.

[0124] As an example of this embodiment, the spot size of the target laser 310 is 50 μm to 300 μm.

[0125] In this embodiment, when the target laser 310 scans the light trapping process area 301, the first doped oxide layer 210 has a higher melting point and a higher light transmittance, so the target laser 310 actually acts mainly on the first doped layer 112. After the first doped layer 112 melts, it will destroy the first doped oxide layer 210 above it, thereby achieving the purpose of removing the first doped oxide layer 210. By setting the spot energy distribution of the target laser 310 (i.e., having a high energy zone 311 and a low energy zone 312), the first doped oxide layer 210 can be selectively removed. Alternatively, by changing the spot shape of the target laser 310 located on the light trapping process area 301, the target laser 310 can only scan a local area of ​​the light trapping process area 301, thereby achieving the selective removal of the first doped oxide layer 210.

[0126] Figure 8Schematic diagram of controlling the energy density distribution of the spot of the target laser 310. Figure 8 As shown in some examples of this embodiment, in the step of scanning the light trapping process area 301 with the target laser 310, the spot of the target laser 310 includes a high energy area 311 and a low energy area 312, and the power density of the high energy area 311 is greater than 0.25 J / cm 2 , the power density of low energy zone 312 is ≤0.25J / cm 2 Understandably, Figure 8 In the process, the target laser 310 is controlled to move intermittently along the light trapping process area 301. The target laser 310 in the high energy area 311 can remove the first doped oxide layer 210, while the target laser 310 in the low energy area 312 is difficult to remove the first doped oxide layer 210, thereby achieving local removal of the first doped oxide layer 210.

[0127] As some examples of this embodiment, the power density of the high energy region 311 of the target laser 310 is 0.25 J / cm 2 ~0.5J / cm 2 For example, the power density of the high energy region 311 of the target laser 310 is 0.25 J / cm 2 , 0.28J / cm 2 , 0.3J / cm 2 , 0.32J / cm 2 , 0.35J / cm 2 , 0.38J / cm 2 , 0.4J / cm 2 , 0.45J / cm 2 , 0.5J / cm 2 Alternatively, the power density of the target laser 310 may also be between any two of the above power densities. Using the target laser 310 with this power density is more conducive to controlling the ablation degree of the target laser 310 on the first tunneling layer 111 and the first doping layer 112.

[0128] As some examples of this embodiment, the power density of the low energy region 312 of the target laser 310 is 0.13 J / cm 2 ~0.25J / cm 2 For example, the power density of the low energy region 312 of the target laser 310 is 0.13 J / cm 2 , 0.15J / cm 2 , 0.17J / cm 2 , 0.19J / cm 2 , 0.2J / cm 2 , 0.22J / cm 2 Alternatively, the power density of the low energy region 312 of the target laser 310 may also be between any two of the above power densities.

[0129] Fig. 9 FIG. 3 is a schematic diagram of a structure for controlling the scanning area of ​​the target laser 310. Fig. 9 As shown, as some other examples of this embodiment, during the scanning process, the target laser 310 is controlled to scan only a local area of ​​the light trapping process area 301 .

[0130] Reference Fig. 9 In this embodiment, during the scanning process, the spot of the target laser 310 can be in a square, rectangular or diamond shape. By rotating the spot of the target laser 310 and making the target laser 310 falling into the light trapping process area 301 in a triangular shape, during the scanning process, the target laser 310 can only irradiate a portion of the light trapping process area 301.

[0131] It can be understood that the above-mentioned method of scanning with the target laser 310 is only one method of removing part of the first doped oxide layer 210. In the actual process, there are many ways to selectively remove part of the first doped oxide layer 210 in the light trapping process area 301. For example, the surface of part of the first doped oxide layer 210 can be damaged by mechanical processing, thereby removing part of the first doped oxide layer 210. Alternatively, chemical etching can be used to spot-coat or screen-print the corrosive agent on the surface of the first doped oxide layer 210, thereby removing part of the first doped oxide layer 210.

[0132] As some examples of this embodiment, in the step of forming the first tunneling layer 111, the first doping layer 112 and the first doped oxide layer 210, the formed first tunneling layer 111, the first doping layer 112 and the first doped oxide layer 210 extend on the isolation region 103. The preparation method further includes the step of removing the first doped oxide layer 210 on the isolation region 103 by laser ablation of the isolation region.

[0133] For example, the isolation region laser ablation is used to remove the first doped oxide layer 210 located on the isolation region 103. During the ablation process, the isolation region laser can be switched to the target laser 310 and irradiate the first doped oxide layer 210 on the light trapping process area 301. The target laser 310 and the isolation region laser can use the same laser source or different laser sources.

[0134] As some examples of this embodiment, the power density of the isolation region laser is 0.25 J / cm 2 ~0.5J / cm 2 For example, the power density of the laser in the isolation area is 0.25 J / cm 2 , 0.28J / cm 2 , 0.3J / cm 2 , 0.32J / cm 2, 0.35J / cm 2 , 0.38J / cm 2 , 0.4J / cm 2 , 0.45J / cm 2 , 0.5J / cm 2 Alternatively, the power density of the laser in the isolation region may be between any two of the above power densities.

[0135] As some examples of this embodiment, in the step of using isolation area laser ablation, the isolation area laser is scanned along the isolation area 103, and during the scanning process, the overlap rate of the light spots of two adjacent isolation area lasers is 20%~60%, that is, the light spots of two adjacent isolation area lasers overlap by 20%~60% of the irradiation area, which can remove the first tunneling layer 111 and the first doping layer 112 as fully and evenly as possible.

[0136] The purpose of using the isolation region laser ablation is to remove the first doped oxide layer 210 on the isolation region 103. The purpose of the target laser 310 irradiation is to locally remove the first doped oxide layer 210 on the light trapping process region 301, so as to form the light trapping valley 1102 and the light trapping peak 1101 in the subsequent alkaline solution corrosion process.

[0137] As some examples of this embodiment, in the step of ablating the first tunneling layer 111 and the first doping layer 112 by using the isolation region laser, the first doped oxide layer 210 and the first tunneling layer 111 and the first doping layer 112 on the second region 102 are also ablated.

[0138] In step S3 , the first doped oxide layer 210 , the first doped layer 112 and the first tunneling layer 111 are corroded by using an alkaline solution to form a light trapping portion 1100 .

[0139] Fig.10 for Figure 7 The schematic diagram of the cross-sectional structure of the structure shown in the figure after being corroded by alkali solution. Fig.10 As shown, in the process of corroding the first doped oxide layer 210, the first doped layer 112 and the first tunneling layer 111 with alkaline solution, since only a portion of the first doped oxide layer 210 on the light trapping process area 301 is removed, the exposed first doped layer 112 and the first tunneling layer 111 are corroded relatively faster, and the other unexposed first doped layer 112 and the first tunneling layer 111 are corroded relatively slowly, thereby forming a light trap valley 1102 and / or a light trap peak 1101.

[0140] In this embodiment, the N-type first doping layer 112 is more susceptible to corrosion by alkaline solution, so the light trapping structure prepared based on the N-type doped first doping layer 112 has the advantage of lower process difficulty. In other embodiments, the light trapping structure can also be prepared using the P-type doped first doping layer 112.

[0141] As some examples of this embodiment, in the step of using alkaline solution to corrode the first tunneling layer 111 and the first doping layer 112, a texturing agent is used as the alkaline solution, and the front side of the crystalline silicon substrate 100 is texturized by the texturing agent at the same time. The texturing agent can be an alkaline texturing agent that forms a velvet structure, which can include sodium hydroxide and a texturing additive. Using the texturing agent as an alkaline solution can not only form the light trapping portion 1100, but also form a velvet structure on the surface of the isolation region 103 of the crystalline silicon substrate 100 and the front side of the crystalline silicon substrate 100.

[0142] In the process of forming the light trapping portion 1100, the remaining first doped oxide layer 210 and the second doped oxide layer 220 can be removed, that is, the first tunneling layer 111 and the first doped layer 112 on the first region 101 and the second tunneling layer 121 and the second doped layer 122 on the second region 102 can be exposed. In addition, the problem of wrap-around plating may also occur in the process of depositing each film layer, and the wrap-around plated material can also be removed in the process of using alkaline solution corrosion.

[0143] As some examples of this embodiment, after the light trapping portion 1100 is formed by etching with an alkaline solution, a step of depositing a first passivation layer 113 , a second passivation layer 123 and a front passivation layer 130 may be further included.

[0144] As some examples of this embodiment, after depositing the first passivation layer 113 , the second passivation layer 123 and the front passivation layer 130 , the step of depositing the first anti-reflection layer 114 , the second anti-reflection layer 124 and the front anti-reflection layer 140 may be further included.

[0145] As some examples of this embodiment, after forming the first passivation layer 113 and the second passivation layer 123, the step of preparing the first electrode 150 and the second electrode 160 may be further included. The first electrode 150 and the second electrode 160 may be prepared by screen printing, electroplating, and PVD (Physical Vapor Deposition).

[0146] Through the above steps S1 to S3, the back contact solar cell of the present application can be formed.

[0147] Furthermore, the present application also provides a photovoltaic module, which includes a back-contact solar cell as in any embodiment. Alternatively, the photovoltaic module includes a back-contact solar cell prepared by the method for preparing a back-contact solar cell as in any embodiment.

[0148] Furthermore, the present application also provides the following more specific embodiments and comparative examples to further illustrate the specific implementation methods of the present application and the corresponding beneficial effects.

[0149] Example 1

[0150] Taking crystalline silicon as the crystalline silicon substrate, LPCVD is used to deposit 2nm thick silicon dioxide on its back as the second tunneling layer, and then 300nm thick intrinsic amorphous silicon and 50nm thick borosilicate glass are deposited. High-temperature annealing is performed to form P-type doped polysilicon as the second doping layer.

[0151] The borosilicate glass corresponding to the first region and the isolation region is etched by laser, and then the second doping layer and the second tunneling layer corresponding to the first region and the isolation region are corroded by alkaline solution until the crystalline silicon substrate is exposed.

[0152] LPCVD is used to deposit 2nm thick silicon dioxide on the back of the crystalline silicon substrate as the first tunneling layer, and then 300nm thick intrinsic amorphous silicon and 50nm thick phosphosilicate glass are deposited. High-temperature annealing is performed to form N-type doped polysilicon as the first doping layer.

[0153] The isolation area laser is used to scan according to a preset pattern to ablate the second area and the isolation area, and the target laser is used to ablate the first area close to the isolation area. The light spots of the target laser and the isolation area laser are both square. The target laser irradiated on the first area has a high energy area and a low energy area, and the power density of the high energy area is 0.3J / cm 2 , the power density in the low energy zone is 0.15J / cm 2 Along the boundary between the isolation area and the first area, the target laser is irradiated once every 100 μm, and each irradiation extends 25 μm along the boundary and 15 μm into the first area. The power density of the isolation area laser is 0.4 J / cm 2 , the energy of the laser in the isolation area is evenly distributed.

[0154] The plating material on the surface of the crystalline silicon substrate is removed, and the front side, isolation area and the area scanned by the target laser are treated with a texturing agent. A velvet structure is formed on the front side and isolation area of ​​the crystalline silicon substrate, and a light-trapping valley and a light-trapping peak are formed in the area scanned by the target laser.

[0155] An aluminum oxide passivation layer and a hydrogenated silicon nitride anti-reflection layer are deposited on the front and back sides of the crystalline silicon substrate respectively, and a positive electrode and a negative electrode are screen-printed on the back side of the crystalline silicon substrate.

[0156] Comparative Example 1

[0157] Comparative Example 1 is substantially the same as Example 1, with the main difference being that Comparative Example 1 only uses laser scanning of the isolation area, does not use target laser scanning, and does not form a light trapping portion.

[0158] Experiment 1: The surface morphology of the isolation region and the first region near the isolation region of Example 1 was observed using a scanning electron microscope. The observation results can be seen at Figure 11~Figure 13 .in, Fig.11 This is an enlarged partial top view of a light trapping portion in Example 1. Fig.12 This is a reduced partial top view of the embodiment 1 containing multiple light trapping portions. Fig.13 This is a schematic diagram of the cross-sectional structure of Example 1.

[0159] Experiment 2: The electrical properties of the above embodiments were tested. The specific results can be seen in Table 1.

[0160] Table 1 Electrical performance test table of Example 1 and Comparative Example 2

[0161]

[0162] Reference Fig.11 As shown, in the back contact solar cell prepared in Example 1, a velvet structure is formed on the surface of the isolation region 103. A first region is provided on one side of the isolation region 103, and a film layer is provided on the first region, and the film layer is a passivation contact film composed of N-type doped polysilicon and a silicon dioxide layer. A light trapping portion 1100 is formed in the passivation contact film, and the light trapping portion 1100 is provided with a light trapping valley 1102 and a plurality of continuous light trapping peaks 1101.

[0163] Reference Fig.12 As shown, Fig.12 The white dotted line in the figure represents the baseline of the isolation area 103, which is automatically recognized by the GetData software. Fig.12 183 points located on the first boundary 1001 are obtained from the GetData software, and the distances of these 183 points relative to the baseline of the isolation area 103 are obtained respectively, and the variance is calculated to be 52.85. Fig.12183 points located on the second boundary 1002 are obtained, and the distances of these 183 points relative to the baseline of the isolation zone 103 are obtained respectively, and the variance is calculated to be 27.27. Therefore, the fluctuation variance of the first boundary 1001 is significantly greater than the fluctuation variance of the second boundary 1002. It should be noted that when using the GetData software to automatically identify the points on the first boundary and the second boundary, as long as the points are evenly distributed in the direction along the baseline of the isolation zone, they can represent the degree of deviation of the first boundary or the second boundary relative to the baseline of the isolation zone. The number of points on the first boundary may not be equal to the number of points on the second boundary. Generally, the ratio of the number of points on the first boundary to the number of points on the second boundary is between 0.5-2, which is a more reasonable way to obtain points.

[0164] Reference Fig.13 As shown, Fig.13 The height difference between the bottom end of the light trapping portion 1100 and the top surface of the first functional film 110 is 3.92 μm. The isolation region 103 has a suede structure. The height difference between the bottom end of the suede structure and the top surface of the first functional film 110 is 2.85 μm, indicating that the height difference between the bottom end of the light trapping portion 1100 and the top surface of the first functional film 110 is greater than the height difference between the bottom end of the isolation region 103 and the top surface of the first functional film 110.

[0165] As shown in Table 1, Comparative Example 1 adopts the traditional method and does not use target laser irradiation, so no light trap is formed. Compared with Comparative Example 1, Example 1 uses target laser irradiation and forms a light trap, and the short-circuit current density and conversion efficiency of Example 1 are significantly improved.

[0166] Please note that the above embodiments are for illustrative purposes only and are not meant to be limiting of this document.

[0167] It should be understood that, unless otherwise specified herein, there is no strict order restriction for the execution of the steps, and the steps may be executed in other orders. Moreover, at least a portion of the steps in the preparation process may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0168] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0169] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A back contact solar cell, characterized in that: include: A crystalline silicon substrate, wherein a first region, a second region and an isolation region are disposed on the back side of the crystalline silicon substrate, wherein the isolation region is disposed between the first region and the second region, and the first region and the second region are separated by the isolation region; a first functional film, the first functional film comprising a first tunneling layer and a first doping layer, the first tunneling layer and the first doping layer being sequentially stacked on the first region, the first functional film having a light trapping portion close to the isolation region, the light trapping portion being provided with at least one of a light trapping valley and a light trapping peak, wherein, in a thickness direction close to the crystalline silicon substrate, the light trapping valley shrinks from a groove opening to a groove bottom, and a side wall of the light trapping peak expands from a top end to a bottom end; and The second functional film includes a second tunneling layer and a second doping layer, the second tunneling layer and the second doping layer are sequentially stacked on the second region, and the second doping layer and the first doping layer have opposite doping types.

2. The back contact solar cell according to claim 1, characterized in that: The light trapping portion includes a plurality of continuously arranged light trapping peaks, and the bottom ends of the side walls of two adjacent light trapping peaks are connected.

3. The back contact solar cell according to claim 1, characterized in that: The first functional film has a first boundary close to the isolation region, the second functional film has a second boundary close to the isolation region, and a fluctuation variance of the first boundary is greater than a fluctuation variance of the second boundary.

4. The back contact solar cell according to claim 3, characterized in that: The value of the fluctuation variance of the first boundary is 30~100.

5. The back contact solar cell according to claim 1, characterized in that: A height difference between an end of the light trapping portion closest to the crystalline silicon substrate and a top surface of the first functional film is 0.5 μm to 6 μm.

6. The back contact solar cell according to claim 5, characterized in that: A height difference between an end of the light trapping portion closest to the crystalline silicon substrate and a top surface of the first functional film is 3 μm to 6 μm.

7. The back contact solar cell according to claim 1, characterized in that: The isolation region surface of the crystalline silicon substrate has a suede structure, and the height difference between the bottom end of the light trapping portion and the top surface of the first functional film is greater than the height difference between the bottom end of the adjacent isolation region and the top surface of the first functional film.

8. The back contact solar cell according to any one of claims 1 to 7, characterized in that: The doping type of the first doping layer is N-type, and the doping type of the second doping layer is P-type.

9. The back contact solar cell according to any one of claims 1 to 7, characterized in that: The first functional film further includes at least one of a first passivation layer and a first anti-reflection layer stacked on the first doping layer; and / or, The second functional film further includes at least one of a second passivation layer and a second anti-reflection layer stacked on the second doping layer.

10. A method for preparing a back contact solar cell according to any one of claims 1 to 9, characterized in that: The steps include: forming the second tunneling layer and the second doping layer in sequence on the second region of the crystalline silicon substrate, and forming the first tunneling layer, the first doping layer and the first doped oxide layer in sequence on the first region of the crystalline silicon substrate; The first doped oxide layer has a light trapping process area close to the isolation region, and a portion of the first doped oxide layer in the light trapping process area is removed to expose the first doped layer located therebelow; The first doped oxide layer, the first doped layer and the first tunneling layer are corroded by alkaline solution to form the light trapping portion.

11. The method for preparing a back contact solar cell according to claim 10, characterized in that: The step of removing a portion of the first doped oxide layer in the light trapping process area includes: scanning the light trapping process area with a target laser; During the scanning process, the target laser spot includes a high-energy area and a low-energy area, and the power density of the high-energy area is greater than 0.25 J / cm 2 , the power density of the low energy zone is ≤0.25J / cm 2 ;or, During the scanning process, the target laser is controlled to scan only a local area of ​​the light trapping process area.

12. The method for preparing a back contact solar cell according to any one of claims 10 to 11, characterized in that: In the step of depositing the first tunneling layer and the first doping layer on the crystalline silicon substrate, the first tunneling layer, the first doping layer and the first doped oxide layer are extended and deposited on the isolation region; The preparation method further comprises the step of removing the first doped oxide layer located on the isolation region by laser ablation of the isolation region.

13. The method for preparing a back contact solar cell according to any one of claims 10 to 11, characterized in that: In the step of corroding the first tunneling layer and the first doping layer with an alkaline solution, a texturing agent is used as the alkaline solution, and the texturing agent is used to perform texturing treatment on the front and back sides of the crystalline silicon substrate.

14. A photovoltaic module, characterized in that: The photovoltaic module comprises a back-contact solar cell according to any one of claims 1 to 9; Alternatively, the photovoltaic module includes the back-contact solar cell prepared by the method for preparing a back-contact solar cell according to any one of claims 10 to 13.

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