Back contact solar cell, cell module and photovoltaic system

Abstract

The invention is applicable to the field of photovoltaic technology, and provides a back contact solar cell, which comprises a silicon substrate, non-recessed areas and recessed areas are alternately arranged on the backlight surface of the silicon substrate, and the silicon substrate is provided with extending parts extending and protruding to the upper parts of the recessed areas at the edges of the non-recessed areas and the recessed areas; the first dielectric layer and the first polarity doping layer are sequentially stacked on the non-sunken region and the extension part; the second dielectric layer comprises a first part stacked on the first polarity doping layer and a second part stacked in the sunken region; the second polarity doped layer is stacked on the first portion and the second portion. Under the shielding effect of the extension part, the first polarity doping layer in the non-recessed area is effectively isolated from the second polarity doping layer in the recessed area, and electric leakage is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic technology, and in particular relates to a back-contact solar cell, a battery assembly and a photovoltaic system. Background Art

[0002] In back-contact solar cells, due to process limitations, there is usually a height difference between two adjacent regions, so there is a side wall between the two regions. At the side wall position, two doping layers of different polarities contact each other at the side wall position, forming a leakage channel. These leakage channels will cause the series resistance (Rsh) of the battery to be significantly reduced, thereby increasing the risk of leakage and seriously affecting the reliability and overall performance of the battery.

[0003] To solve this problem, the usual practice is to set a groove between two doping areas of different polarities to achieve physical isolation. Although the setting of the groove can prevent the contact of the two polarity selective contact layers to a certain extent, the manufacturing process of the groove is complicated and requires additional etching steps, which increases the process difficulty and manufacturing cost. The presence of the groove may also lead to local stress concentration and increase the risk of mechanical damage to the battery cell during manufacturing and use. In addition, the groove will affect the propagation path of light and reduce the effective light capture area, which will have an adverse effect on the photoelectric conversion efficiency of the battery. Summary of the invention

[0004] The present invention provides a back-contact solar cell, aiming to solve the problem that leakage channels may lead to a significant reduction in the series resistance of the cell without reducing the photoelectric conversion efficiency.

[0005] The present invention is implemented as follows: a back contact solar cell, characterized in that it comprises:

[0006] A silicon substrate, wherein the silicon substrate has a backlight surface and a light-facing surface that are oppositely arranged, a non-depressed area and a depressed area are alternately arranged along a first direction on the backlight surface of the silicon substrate, the non-depressed area and the depressed area extend along a second direction, and the second direction intersects the first direction; along the first direction, the silicon substrate has an extension portion extending and protruding above the depressed area at the edges of the non-depressed area and the depressed area;

[0007] A first dielectric layer, the first dielectric layer is stacked and arranged on the non-recessed area and the surface of the extension portion facing away from the silicon substrate;

[0008] A first polarity doped layer, wherein the first polarity doped layer is stacked on the first dielectric layer;

[0009] A second dielectric layer, the second dielectric layer comprising a first portion stacked on the first polarity doped layer and a second portion stacked on a bottom surface of the recessed region;

[0010] A second polarity doping layer is stacked on the first portion and the second portion.

[0011] Optionally, the second dielectric layer also includes a wrapping portion connecting the first part and the second part, and the wrapping portion includes a second wrapping portion stacked on the surface of the extension part facing the silicon substrate and a third wrapping portion stacked on the extension part, the first dielectric layer and the first polarity doped layer along the first direction close to the recessed area.

[0012] Optionally, part of the second polarity doped layer is stacked on the third surrounding portion.

[0013] Optionally, part of the second polarity doped layer is stacked on the second wrapping portion, and the thickness of the second polarity doped layer at the second wrapping portion gradually decreases in a direction approaching the extension portion.

[0014] Optionally, the wrapping portion further includes a first wrapping part, and the first wrapping part is stacked on the side wall of the recessed area.

[0015] Optionally, part of the second polarity doped layer is stacked on the first wrapping portion, and the thickness of the second polarity doped layer located at the first wrapping portion gradually decreases in a direction approaching the extension portion.

[0016] Optionally, the bottom surface of the recessed area has a concave-convex texture structure.

[0017] Optionally, the length of the extension portion along the first direction is 0.2um-50um.

[0018] Optionally, along the first direction, the length of the extension portion is 1um-15um.

[0019] Optionally, the sidewall of the recessed area is an inclined surface.

[0020] Optionally, the angle between the inclined surface and the bottom surface of the recessed area is an acute angle.

[0021] Optionally, the angle between the inclined surface and the bottom surface of the recessed area is an obtuse angle.

[0022] The present invention also provides a battery assembly, comprising the above-mentioned back-contact solar cell.

[0023] The present invention also provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0024] The beneficial effect achieved by the present invention is that the non-depressed area and the depressed area are alternately arranged on the backlight surface of the silicon substrate, the depressed area is depressed compared to the non-depressed area, and the silicon substrate has an extended portion extending and protruding above the depressed area at the edge of the non-depressed area and the depressed area. The first dielectric layer, the first polarity doping layer, the second dielectric layer and the second polarity doping layer are stacked on the non-depressed area and the extended portion, and under the shielding effect of the extended portion, the first polarity doping layer of the non-depressed area and the second polarity doping layer of the depressed area are effectively isolated to avoid leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a first back-contact solar cell provided by the present invention;

[0026] Figure 2 is a schematic structural diagram of a second back-contact solar cell provided by the present invention;

[0027] Figure 3 is a schematic structural diagram of a third back-contact solar cell provided by the present invention;

[0028] Figure 4 is a schematic structural diagram of a fourth back-contact solar cell provided by the present invention;

[0029] Figure 5 is a SEM schematic diagram of the extension portion provided by the present invention;

[0030] Figure 6 This is the enlarged view of point A;

[0031] Figure 7 It is several structural schematic diagrams of the inclusion parts in the present invention;

[0032] Figure 8 A schematic structural diagram of a fifth back-contact solar cell provided by the present invention;

[0033] Fig. 9 A schematic structural diagram of a sixth back-contact solar cell provided by the present invention;

[0034] Fig.10 This is a schematic structural diagram of the seventh back-contact solar cell provided by the present invention.

[0035] Description of reference numerals:

[0036] 100. Back-contact solar cell; 101. Non-recessed area; 102. Recessed area; 110. Silicon substrate; 111. Extension portion; 120. First dielectric layer; 130. First polarity doped layer; 140. Second dielectric layer; 141. First portion; 142. Second portion; 143. Wrapping portion; 1431. First wrapping portion; 1432. Second wrapping portion; 1433. Third wrapping portion; 150. Second polarity doped layer; 160. Passivation film layer; 170. First electrode; 180. Second electrode. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0042] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the examples of various specific processes and materials provided by the present invention, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0043] In this embodiment of the present invention, a non-depressed area and a depressed area are alternately arranged on the backlight surface of the silicon substrate, the depressed area is depressed compared to the non-depressed area, and the silicon substrate has an extended portion extending and protruding above the depressed area at the edge of the non-depressed area and the depressed area. A first dielectric layer, a first polarity doping layer, a second dielectric layer, and a second polarity doping layer are stacked on the non-depressed area and the extended portion, and a second dielectric layer and a second polarity doping layer are stacked on the depressed area. The second polarity doping layer and the first polarity doping layer form a leakage contact, which reduces the high thermal risk of the hot spot effect. At the same time, under the shielding effect of the extended portion, the first polarity doping layer in the non-depressed area and the second polarity doping layer in the depressed area are effectively isolated to avoid leakage.

[0044] Embodiment 1

[0045] like Figure 8 As shown, this embodiment provides a back contact solar cell 100, comprising:

[0046] A silicon substrate 110, wherein the silicon substrate 110 has a backlight surface and a light-facing surface that are oppositely arranged, and non-depressed areas 101 and depressed areas 102 are alternately arranged on the backlight surface of the silicon substrate 110, and the distance between the bottom surface of the depressed area 102 and the light-facing surface is smaller than the distance between the bottom surface of the non-depressed area 101 and the light-facing surface; in the arrangement direction of the non-depressed area 101 and the depressed area 102, the silicon substrate 110 has an extension portion 111 extending and protruding above the depressed area 102 at the edges of the non-depressed area 101 and the depressed area 102;

[0047] A first dielectric layer 120, the first dielectric layer 120 is stacked and disposed on the non-recessed area 101 and the surface of the extension portion 111 facing away from the silicon substrate 110;

[0048] A first polarity doping layer 130, wherein the first polarity doping layer 130 is stacked on the first dielectric layer 120;

[0049] A second dielectric layer 140 , the second dielectric layer 140 includes a first portion 141 stacked on the first polarity doping layer 130 and a second portion 142 stacked on the bottom surface of the recessed region 102 ;

[0050] The second polarity doping layer 150 is stacked on the first portion 141 and the second portion 142 .

[0051] The silicon substrate 110 has two main surfaces, a light-facing surface and a backlight surface. The light-facing surface directly faces the sunlight, while the backlight surface is the other surface, and the two surfaces are arranged opposite to each other.

[0052] Two different areas are arranged on the backlight surface of the silicon substrate 110, namely, a non-depressed area 101 and a depressed area 102, which are arranged alternately, and the depressed area has a bottom surface and a side wall connecting the non-depressed area. Specifically, a number of non-depressed areas 101 and a number of depressed areas 102 are arranged alternately along a first direction, and both the non-depressed areas 101 and the depressed areas 102 extend along a second direction, and the second direction intersects the first direction. The non-depressed areas 101 and the depressed areas 102 can be arranged alternately along the lateral direction of the silicon substrate 110 and both extend along the longitudinal direction, that is, the first direction can be the lateral direction of the back contact battery, and the second direction can be the longitudinal direction of the back contact battery, and the two are perpendicular to each other. Of course, in other embodiments, the first direction and the second direction can also be other directions, for example, both can be diagonal directions of the silicon substrate 110, which are not limited here. The non-depressed areas 101 and the depressed areas 102 are arranged alternately adjacent to each other.

[0053] The silicon substrate 110 is generally in the shape of a plate with uniform thickness, that is, the distance between the light-facing surface and the backlight surface is equal. The distance between the bottom surface of the recessed area 102 and the light-facing surface is smaller than the distance between the bottom surface of the non-recessed area 101 and the light-facing surface, that is, the bottom surface of the recessed area 102 sinks into the silicon substrate 110.

[0054] In the arrangement direction of the non-depressed area 101 and the depressed area 102, the silicon substrate 110 has an extension portion 111 extending and protruding above the depressed area 102 at the edge of the non-depressed area 101 and the depressed area 102. The first dielectric layer 120 is stacked on the surface of the non-depressed area 101 and the extension portion 111 facing away from the silicon substrate 110, and the first polarity doping layer 130 is stacked on the first dielectric layer 120 (including the first dielectric layer 120 stacked in the non-depressed area 101 and the first dielectric layer 120 stacked on the extension portion 111). The first dielectric layer 120 can be specifically a tunneling layer, which is used as a transmission path for carriers, reducing the recombination loss of carriers at the interface.

[0055] like Figure 8 As shown, the second dielectric layer 140 includes a first portion 141 and a second portion 142, the first portion 141 is stacked on the first polarity doped layer 130, and the second portion 142 is stacked on the bottom surface of the recessed area 102. There is a height difference between the non-recessed area and the recessed area, that is, there is a height difference between the first portion 141 and the second portion 142 of the second dielectric layer 140, and the first portion 141 and the second portion 142 are not connected. The second dielectric layer 140 can specifically be a tunneling layer, which is used as a transmission path for carriers, reducing the recombination loss of carriers at the interface.

[0056] like Figure 8 As shown, the second polarity doping layer 150 is stacked on the first portion 141 and the second portion 142, respectively. The second polarity doping layer 150 is stacked on the first portion 141. Under the shielding effect of the extension portion 111, the second polarity doping layer 150 cannot be set at the position shielded by the extension portion 111, so that the second polarity doping layer 150 set on the second portion 142 cannot extend along the side wall to form contact with the first polarity doping layer 130, thereby achieving isolation of the two polarity doping layers to avoid leakage.

[0057] The first polarity doping layer 130 and the second polarity doping layer 150 have different polarities. Specifically, the first polarity doping layer 130 may be a P-type doping layer and the second polarity doping layer 150 may be an N-type doping layer, or the first polarity doping layer 130 may be an N-type doping layer and the second polarity doping layer 150 may be a P-type doping layer. The first polarity doping layer 130 and the second polarity doping layer 150 form regions with different electrical characteristics, supporting the formation of a PN junction and the separation of carriers.

[0058] It is understandable that when depositing the second polarity doping layer 150, a directional physical vapor deposition method (PVD) can be selected. When depositing the second polarity doping layer 150, the material of the second polarity doping layer 150 is shielded by the extension portion 111, and there is little or almost no material of the second polarity doping layer 150 in the concave area, thereby achieving effective isolation of the first polarity doping layer 130 and the second polarity doping layer 150, and avoiding the occurrence of leakage.

[0059] When depositing the first dielectric layer 120 , the first polarity doped layer 130 , and the second dielectric layer 140 , chemical vapor deposition (CVD), atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD), etc. may be used, which is not limited here.

[0060] When depositing the second polarity doping layer 150, it is not ruled out that a small amount of material of the second polarity doping layer 150 is deposited on the second dielectric layer 140 in the concave area, so that the first polarity doping layer 130 and the second polarity doping layer 150 can achieve partial leakage contact, playing a role similar to a bypass diode.

[0061] When the solar cell generates electricity normally, the contact area of ​​the first polarity doping layer 130 and the second polarity doping layer 150 also performs photoelectric conversion to generate electricity, thereby increasing the power generation of the solar cell. When the solar cell is blocked, insufficient light will cause the current output of the blocked part to decrease, thereby increasing the voltage of the part, and the contact area forms a conductive path, and other solar cells connected in series with it provide reverse current for the blocked solar cell. A composite leakage current of appropriate size can be generated between the first polarity doping layer 130 and the second polarity doping layer 150 of the solar cell, reducing the voltage across the blocked solar cell (the voltage is less than the sum of the voltages of other solar cells connected in series with the solar cell and not blocked), and the heat generation power of the solar cell will be reduced, thereby reducing the high heat risk of the hot spot effect.

[0062] In actual operation, the depth of the concave structure and the thickness of the material deposited in the concave structure can be controlled by regulating the wet process (etching time, concentration) or the thickness of the BSG layer and the doping concentration of poly-Si, thereby controlling the degree of contact between the two materials and further controlling the degree of leakage, thereby achieving the above-mentioned anti-hot spot function.

[0063] In this embodiment, the non-depressed area 101 and the depressed area 102 are alternately arranged on the backlight surface of the silicon substrate 110, the depressed area 102 is depressed compared to the non-depressed area 101, and the silicon substrate 110 has an extension portion 111 extending and protruding above the depressed area 102 at the edge of the non-depressed area 101 and the depressed area 102. The first dielectric layer 120, the first polarity doping layer 130, the second dielectric layer 140 and the second polarity doping layer 150 are stacked on the non-depressed area 101 and the extension portion 111. Under the shielding effect of the extension portion 111, the materials of the first polarity doping layer 130 and the second polarity doping layer 150 are effectively isolated to avoid leakage.

[0064] It can be understood that the second polarity doping layer 150 may be partially disposed on the sidewalls of the extension portion 111, the first dielectric layer 120 and the first polarity doping layer 130 close to the recessed region 102 along the first direction. Fig. 9 As shown, due to different processes in manufacturing, the second polarity doping layer 150 may be deposited with a certain thickness at the sidewall position.

[0065] In some embodiments, Figure 2 As shown, the second dielectric layer also includes an encapsulating portion 143 connecting the first portion 141 and the second portion 142, and the encapsulating portion 143 includes a second encapsulating portion 1432 of the stacked extension portion 111 facing the surface of the silicon substrate 110 and a third encapsulating portion 1433 of the stacked extension portion 111, the first dielectric layer 120 and the first polarity doping layer 130 along the first direction close to the side wall of the recessed area 102.

[0066] Since there is a height difference between the non-depressed area 101 and the depressed area 102, there is a side wall connecting the non-depressed area 101 and the depressed area 102 between the two, and the wrapping portion 143 extends along the side wall to connect the first portion 141 and the second portion 142. However, in some cases, the extension portion 111 extends toward the depressed area 102 at an acute angle from the connection position with the bottom surface and the side wall of the depressed area 102, so that the surface of the extension portion 111 facing the silicon substrate 110 constitutes the side wall of the depressed area 102, and the first wrapping portion 1431 is stacked on the side wall between the depressed area 102 and the non-depressed area 101. Figure 7As shown in (b), the wrapping portion 143 includes a second wrapping portion 1432 and a third wrapping portion 1433. The third wrapping portion 1433 is stacked on the sidewall of the extension portion 111, the first dielectric layer 120 and the first polarity doping layer 130 close to the recessed area 102 along the first direction, and the second wrapping portion 1432 is connected to the third wrapping portion 1433. In some special cases, the extension portion is triangular, and the first dielectric layer 120 and the first polarity doping layer 130 are stacked on one side of the triangle. In this case, the third wrapping portion 1433 is only stacked on the sidewall of the first dielectric layer 120 and the first polarity doping layer 130 close to the recessed area 102 along the first direction, and the thickness of the extension portion 111 at the stacking position of the third wrapping portion 1433 can be regarded as 0.

[0067] In this embodiment, the first dielectric layer 120 and the first polarity doped layer 130 are arranged on the backlight surface of the silicon substrate 110, and the second dielectric layer 140 is stacked on the outermost contours along the backlight surface of the silicon substrate 110, the first dielectric layer 120 and the first polarity doped layer 130 for easy processing.

[0068] In some embodiments, Fig. 9 As shown, part of the second polarity doping layer 150 is stacked on the third surrounding portion 1433 .

[0069] Specifically, when the side surface formed by the extension portion 111, the first dielectric layer 120 and the first polarity doped layer 130 close to the side wall of the recessed region along the first direction and the bottom surface of the recessed region 102 form an angle less than 90°, Figure 7 As shown in (d), that is, the side surface is inclined toward the bottom surface of the recessed area 102, and the position on the side surface that is farther from the bottom surface of the recessed area 102 blocks the position on the side surface that is closer to the bottom surface of the recessed area 102, so the second polarity doping layer 150 is not provided on the side surface. Figure 2 As shown, the second polarity doping layer is stacked only on the first portion 141 and the second portion 142 .

[0070] When the side surface formed by the extension portion, the first dielectric layer and the first polarity doped layer close to the side wall of the recessed region along the first direction and the bottom surface of the recessed region 102 form an angle equal to or greater than 90°, as Figure 7 As shown in (a)(b)(c), that is, the side surface is inclined in the direction opposite to the bottom surface of the recessed area 102, and there is no blocked position on the side surface, then the second polarity doping layer 150 is partially disposed on the side surface, and the second polarity doping layer 150 is stacked on the first portion 141, the second portion 142 and the third wrapping portion 1433, as shown in FIG. Figure 1 , Figure 3 and Fig. 9 shown.

[0071] In this embodiment, part of the second polarity doping layer 150 is stacked on the third wrapping portion 1433, which can improve the passivation effect on the first polarity doping layer and the side of the extension portion and reduce edge recombination.

[0072] In some embodiments, Figure 4 As shown, part of the second polarity doping layer 150 is stacked on the second enclosing portion 1432 , and the thickness of the second polarity doping layer 150 located at the second enclosing portion 1432 gradually decreases in a direction close to the protruding position of the extension portion 111 .

[0073] The extension part 111 has a shielding effect, so that the thickness of the second polarity doped layer 150 located in the shielded area varies. Along the first direction, the closer the second polarity doped layer 150 is to the extending position of the extension part 111, the smaller the thickness is, and the farther away from the extending position of the extension part 111, the greater the thickness is. The smaller the thickness, the worse the conductive performance is.

[0074] In other embodiments, Figure 1 , 3 As shown in FIG. 6 , the wrapping portion 143 further includes a first wrapping portion 1431 , and the first wrapping portion 1431 is stacked on the side wall of the recessed area 102 .

[0075] Specifically, the extension portion 111 extends from a position a certain distance away from the recessed area 102 along the thickness direction of the silicon substrate 110 toward the recessed area 102 , and the extension portion 111 protrudes from the sidewall of the recessed area 102 , on which the first enveloping portion 1431 is stacked.

[0076] In this embodiment, the first dielectric layer 120 and the first polarity doped layer 130 are arranged on the backlight surface of the silicon substrate 110, and the second dielectric layer 140 is stacked on the outermost contours along the backlight surface of the silicon substrate 110, the first dielectric layer 120 and the first polarity doped layer 130 for easy processing.

[0077] In some embodiments, part of the second polarity doping layer 150 is stacked on the first surrounding portion 1431 , and the thickness of the second polarity doping layer 150 located at the first surrounding portion 1431 gradually decreases in a direction approaching the extension portion 111 .

[0078] The extension portion 111 has a shielding effect, so that the thickness of the second polarity doped layer 150 located in the shielded area varies. Along the thickness direction of the silicon substrate 110, the closer the second polarity doped layer 150 is to the extension portion 111, the smaller the thickness is, and the farther away from the extension portion 111, the greater the thickness is. The smaller the thickness, the worse the conductive performance is.

[0079] In addition, in the embodiments of the present application, Fig.10As shown, the back-contact solar cell 100 may further include a first electrode 170 and a second electrode 180. A passivation film layer 160 may be further provided on the backlight surface of the silicon substrate 110. The passivation film layer 160 may cover the entire backlight surface. The first electrode may be located in the non-recessed area 101 and pass through the passivation film layer 160 to form an ohmic contact with the first doping layer 130 and be insulated and isolated from the second doping layer 150. For example, the first electrode may be located at a position where the first doping layer 130 is not covered by the first extension portion 111 (i.e., the projection of the first doping layer 130 on the silicon substrate 110 is not covered by the projection of the first extension portion 111 on the silicon substrate 110), and the second electrode may be located at the second area 122 and pass through the passivation film layer 160 to form an ohmic contact with the second doping layer 50.

[0080] Embodiment 2

[0081] In some embodiments, the bottom surface of the recessed region 102 has a concavo-convex texture structure.

[0082] On the one hand, the concavo-convex texture structure can change the propagation path of light to a certain extent, so that the incident light is reflected multiple times on the bottom surface of the concave area 102, increasing the optical path length of the light in the silicon substrate 110, thereby improving the light absorption rate. This effect is particularly important for long-wavelength light, because the absorption coefficient of long-wavelength light is lower and it is easier to penetrate the silicon substrate 110. On the other hand, the concavo-convex texture structure can increase the contact area between the second polarity doping layer 150 and the silicon substrate 110, improve the contact performance of the electrode, and reduce the contact resistance.

[0083] Embodiment 3

[0084] In some embodiments, along the first direction, the length of the extension portion 111 is 0.2 um-50 um.

[0085] Usually, if Fig.10 As shown, a passivation film layer 160 covering the entire backlight surface is provided on the backlight surface of the silicon substrate 110. In this way, the length of the extension portion 111 is within a reasonable range to avoid the extension portion 111 being too short and failing to effectively reduce the exchange of plasma with the outside world during the deposition of the passivation film layer 160. It can also avoid the extension portion 111 being too long, resulting in the opening of the groove being too small and the etching process being too difficult. It can also avoid the extension portion 111 being too long, resulting in easy breakage.

[0086] Specifically, in such an embodiment, the length of the extension portion 111 may be 0.2um, 0.4um, 0.6um, 0.8um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 20um, 30um, 40um, 50um or any value between 0.2um-50um.

[0087] Furthermore, according to the research and verification by the inventor of the present application, in order to better prevent the extension part 111 from breaking, while also ensuring the function of reducing the exchange between plasma and the outside world during the deposition of the passivation film layer 160, the length of the extension part 111 in the present application (along the first direction) is most preferably in the range of 1um-15um.

[0088] Embodiment 4

[0089] In some embodiments, the sidewalls of the recessed region 102 are inclined.

[0090] In this way, there are more defects on the vertical crystal planes, and by forming an inclined side surface, the bottom surface defect states of the recessed area 102 can be reduced. Forming an inclined surface can reduce bottom surface recombination and improve battery performance.

[0091] In some embodiments, the inclined surface may form an obtuse angle with the bottom surface of the recessed area 102. Figure 3 ,and Figure 5 As shown, the angle between the inclined surface and the bottom surface of the recessed area 102 is α, α>90°, that is, the inclined surface and the bottom surface of the recessed area 102 form a flared shape, and the flaring means that the shape gradually becomes larger in the direction away from the light surface.

[0092] Obtuse bevels can reduce dead angles during material deposition, allowing materials to be stacked more evenly on the bottom surface, reducing the formation of holes and defects. Obtuse bevels can also better disperse stress, reduce stress concentration at the joints, and improve the mechanical strength and crack resistance of the cell.

[0093] In some other embodiments, the inclined surface forms an acute angle with the bottom surface of the recessed area 102. Figure 2 As shown, the angle between the inclined surface and the bottom surface of the recessed area 102 is α, α<90°, that is, the inclined surface and the bottom surface of the recessed area 102 form a closing shape, and the closing means that the shape gradually becomes smaller in the direction away from the light surface.

[0094] The acute angled surface can serve as a reflection and scattering center for light, changing the incident angle of light so that more light can enter the silicon substrate 110 instead of being reflected by the bottom surface, thereby extending the path of light in the silicon substrate 110 and improving the transmittance and absorptivity of light.

[0095] In some special cases, such as Figure 7As shown in (d), the inclined surface forms an acute angle with the bottom surface of the recessed area 102. At this time, the extension direction of the inclined surface is consistent with the extension direction of the extension portion 111, and the inclined surface is coplanar with the extension portion 111. In addition, the side walls of the extension portion 111, the first dielectric layer 120 and the first polarity doped layer 130 close to the recessed area 102 along the first direction are also coplanar with the inclined surface. At this time, the connection angle between the first enclosing portion 1431 and the third enclosing portion 1433 is 180 degrees, that is, they are on the same plane.

[0096] Embodiment 5

[0097] This embodiment provides a battery assembly, including the back-contact solar cell 100 in the above embodiment.

[0098] The battery assembly may include a plurality of back-contact solar cells 100. The plurality of back-contact solar cells 100 in the battery assembly may be connected in series in sequence to form a battery string. The battery strings may be connected in series, in parallel, or in a combination of series and parallel to achieve current bus output. For example, the connection between the battery cells may be achieved by welding welding strips, and the connection between the battery strings may be achieved by bus bars.

[0099] The battery assembly may also include a metal frame, a back plate, photovoltaic glass and an adhesive film (not shown in the figure). The adhesive film may be filled between the front and photovoltaic glass, the back and the back plate of the back contact solar cell 100, and the adjacent cells. As a filler, it may be a transparent colloid with good light transmission and aging resistance. For example, the adhesive film may be an EVA adhesive film or a POE adhesive film. The specific selection may be based on actual conditions and is not limited here.

[0100] The photovoltaic glass can be laminated on the adhesive film on the front side of the back contact solar cell 100. The photovoltaic glass can be ultra-white glass, which has high light transmittance, high transparency, and excellent physical, mechanical and optical properties. For example, the light transmittance of the ultra-white glass can reach more than 92%, and it can protect the back contact solar cell 100 without affecting the efficiency of the back contact solar cell 100 as much as possible. At the same time, the adhesive film can bond the photovoltaic glass and the back contact solar cell 100 together, and the presence of the adhesive film can seal and insulate the back contact solar cell 100 and make it waterproof and moisture-proof.

[0101] The backplane can be attached to the adhesive film on the back of the back contact solar cell 100. The backplane can protect and support the back contact solar cell 100, and has reliable insulation, water resistance and aging resistance. There are multiple options for the backplane, which can usually be tempered glass, organic glass, aluminum alloy TPT composite adhesive film, etc. It can be set according to specific circumstances and is not limited here. The whole composed of the backplane, back contact solar cell 100, adhesive film and photovoltaic glass can be set on a metal frame. The metal frame serves as the main external support structure of the entire battery assembly and can stably support and install the battery assembly. For example, the battery assembly can be installed at the required installation position through the metal frame.

[0102] The beneficial effects of the battery assembly of this embodiment are equivalent to the beneficial effects of the above-mentioned back-contact solar cell 100, and will not be described in detail here.

[0103] Embodiment 6

[0104] This embodiment provides a photovoltaic system, including the battery assembly in the above embodiment.

[0105] Photovoltaic systems can be used in photovoltaic power stations, such as ground power stations, rooftop power stations, water power stations, etc., and can also be used in equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it is understandable that the application scenarios of photovoltaic systems are not limited to this, that is to say, photovoltaic systems can be used in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple battery components. For example, multiple battery components can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid. After that, it is connected to the mains network to realize solar power supply.

[0106] The beneficial effects of the photovoltaic assembly of this embodiment are equivalent to the beneficial effects of the above-mentioned battery assembly, and will not be described in detail here.

[0107] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein the silicon substrate has a backlight surface and a light-facing surface that are oppositely arranged, non-depressed areas and depressed areas are alternately arranged along a first direction on the backlight surface of the silicon substrate, and the non-depressed areas and the depressed areas extend along a second direction, and the second direction intersects the first direction; Along the first direction, the silicon substrate has an extension portion extending and protruding above the recessed area at the edges of the non-recessed area and the recessed area; A first dielectric layer, the first dielectric layer is stacked and arranged on the non-recessed area and the surface of the extension portion facing away from the silicon substrate; A first polarity doped layer, wherein the first polarity doped layer is stacked on the first dielectric layer; A second dielectric layer, the second dielectric layer comprising a first portion stacked on the first polarity doped layer and a second portion stacked on a bottom surface of the recessed region; A second polarity doping layer is stacked on the first portion and the second portion.

2. The back contact solar cell according to claim 1, characterized in that The second dielectric layer also includes a wrapping portion connecting the first part and the second part, and the wrapping portion includes a second wrapping portion stacked on the surface of the extension part facing the silicon substrate and a third wrapping portion stacked on the extension part, the first dielectric layer and the first polarity doped layer along the first direction close to the recessed area.

3. The back contact solar cell according to claim 2, characterized in that: Part of the second polarity doped layer is stacked and arranged on the third surrounding portion.

4. The back contact solar cell according to claim 3, characterized in that: Part of the second polarity doped layer is stacked on the second surrounding portion, and the thickness of the second polarity doped layer located at the second surrounding portion gradually decreases in a direction approaching the extension portion.

5. The back contact solar cell according to claim 2 or 4, characterized in that: The wrapping portion further includes a first wrapping part, and the first wrapping part is stacked on the side wall of the recessed area.

6. The back contact solar cell according to claim 5, characterized in that Part of the second polarity doped layer is stacked on the first wrapping portion, and the thickness of the second polarity doped layer located at the first wrapping portion gradually decreases in a direction approaching the extension portion.

7. The back contact solar cell according to claim 1, characterized in that: The bottom surface of the concave area has a concave-convex texture structure.

8. The back contact solar cell according to claim 1, characterized in that: The length of the extending portion along the first direction is 0.2um-50um.

9. The back contact solar cell according to claim 8, characterized in that Along the first direction, the length of the extension portion is 1 um-15 um.

10. The back contact solar cell according to claim 1, wherein: The side wall of the recessed area is an inclined surface.

11. The back contact solar cell according to claim 10, characterized in that: The angle between the inclined surface and the bottom surface of the recessed area is an acute angle.

12. The back contact solar cell according to claim 10, characterized in that: An angle between the inclined surface and the bottom surface of the recessed area is an obtuse angle.

13. A battery assembly, characterized in that: A back-contact solar cell comprising any one of claims 1-12.

14. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 13.

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