Solar cell, cell slice, cell assembly and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, and particularly discloses a solar cell piece, a cell slice, a cell assembly and a photovoltaic system.The cell piece comprises a silicon substrate, a doping layer and a tunneling passivation layer, the silicon substrate is provided with a first end face and a second end face which are opposite, the doping layer is arranged on the second end face, and the tunneling passivation layer is arranged between the second end face and the doping layer. And the thickness of the tunneling passivation layer is gradually reduced from the peripheral edge of the second end face to the middle. According to the tunneling passivation layer disclosed by the invention, better stress loss resistance and higher carrier transmission efficiency can be taken into consideration on the whole, and the condition that the transportation of carriers is hindered by stress damage in the preparation process is avoided, so that the conversion efficiency of the battery is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell sheet, a cell slice, a cell assembly and a photovoltaic system. Background Art

[0002] In some existing solar cells, a tunneling passivation layer with uniform thickness is introduced to maintain a good chemical passivation effect and achieve selective carrier transport. Most existing solar cells use the tunneling characteristics of the tunneling passivation layer to promote carrier transport, and the tunneling characteristics are extremely sensitive to thickness. The tunneling passivation layer needs to be extremely thin so that the tunneling characteristics can be better exerted. Therefore, the thickness of the tunneling passivation layer on the current solar cells is made extremely thin.

[0003] However, the inventors found that in the actual preparation process, after the ultra-thin tunneling passivation layer is deposited, the solar cell still needs to undergo laser grooving, thermal processing, cell cutting, lamination and other steps. These steps can easily cause stress damage to the tunneling passivation layer. These stress damages will hinder the transport of carriers, reduce the transport efficiency of carriers, and affect the photoelectric conversion efficiency of solar cells. Summary of the invention

[0004] The purpose of the present invention is to provide a solar cell, a cell slice, a cell assembly and a photovoltaic system in view of the existing technical status.

[0005] The tunnel passivation layer of the present invention as a whole can take into account both better ability to resist stress loss and higher carrier transfer efficiency, avoiding the obstruction of carrier transport caused by stress damage during the preparation process, thereby effectively improving the battery conversion efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] First, the present invention provides a solar cell, comprising:

[0008] A silicon substrate having a first end surface and a second end surface opposite to each other,

[0009] a doping layer, disposed on the second end surface,

[0010] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0011] In some embodiments, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1<a≤2.7.

[0012] In some embodiments, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.3≤a≤2.7.

[0013] In some embodiments, the thickness of the maximum thickness end is 1.4 nm to 2.4 nm, and the thickness of the minimum thickness end is 0.8 nm to 1.8 nm.

[0014] In some embodiments, the thickness of the tunnel passivation layer satisfies the following formula:

[0015]

[0016] Wherein, H(x, y) is the thickness of the tunnel passivation layer at the point (x, y) on the second end surface, x and y are the horizontal distance and vertical distance from the center of the second end surface to the point (x, y), 0<x<0.5a, 0<y<0.5b, H0 is the thickness of the edge of the tunnel passivation layer, H c is the thickness of the tunnel passivation layer at the center of the second end face, k is a constant coefficient, and k>0, a is the length of the tunnel passivation layer, b is the width of the tunnel passivation layer, β is an adjustment coefficient, and ρ is a deviation coefficient.

[0017] In some embodiments, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0018] In some embodiments, the doping layer is a first polarity doping layer, and the polarity of the first polarity doping layer is the same as the polarity of the silicon substrate.

[0019] In some embodiments, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0020] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0021] In some embodiments, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0022] In some embodiments, the density of the P-region holes is greater than the density of the N-region holes.

[0023] In some embodiments, the density of the holes in the P region is 1×10 7 cm -2 ~1×1010 cm -2 .

[0024] In some embodiments, the density of the holes in the N region is 1×10 6 cm -2 ~1×10 9 cm -2 .

[0025] Secondly, the present invention provides a cell segment, which is obtained by segmenting the above-mentioned solar cell sheet.

[0026] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0027] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0028] The beneficial effects of the present invention are:

[0029] 1) Due to the steps of laser grooving, thermal processing, cell cutting, lamination, etc., these steps easily cause the tunneling passivation layer to be damaged by stress, and the closer the area is to the edge of the backlight surface, the greater the stress damage it suffers. In the present invention, the thickness of the tunneling passivation layer is gradually reduced from the edges of the second end face to the middle, so that the tunneling passivation layer has a higher ability to withstand and resist stress loss as it is closer to the edges of the second end face, thereby preventing stress damage from hindering the transport of carriers. At the same time, compared with simply increasing the thickness of the entire material layer, the thickness of the tunneling passivation layer of the present invention is thinner as it is closer to the middle of the second end face, ensuring that the tunneling passivation layer can not only prevent stress damage from hindering the transport of carriers, but also has a higher overall carrier transmission efficiency, thereby effectively improving the battery conversion efficiency.

[0030] 2) In the present invention, holes are provided on the tunneling passivation layer, and these holes can serve as the main carrier transport channels, thereby allowing some carriers to directly pass through the tunneling passivation layer through the tunneling characteristics, and some carriers are first captured by the holes, and then transition to the energy level on the other side through the tunneling process or thermal excitation. The hole transport channel cooperates with the tunneling characteristics of the tunneling passivation layer to effectively improve the carrier transmission efficiency, and can reduce the sensitivity and dependence of carrier transmission on the ultra-thin thickness of the tunneling passivation layer. The thickness of the tunneling passivation layer can be made relatively thicker, so as to obtain a better interface passivation effect, and then obtain a tunneling passivation layer with good carrier transmission efficiency and passivation effect, effectively improving the photoelectric conversion efficiency of the battery.

[0031] At the same time, the places where the thickness of the tunnel passivation layer is relatively large are located at the edges around the second end face, that is, the places where stress damage is most likely to occur. By setting the density of the holes to increase as the thickness of the tunnel passivation layer decreases, relatively fewer holes are set in places where stress damage is likely to occur to avoid the impact of too many holes on the ability to resist stress damage, and as many holes as possible are set in places where the stress impact is small, so that the tunnel passivation layer has more transmission channels on the basis of effectively preventing stress damage from hindering the transport of carriers, ensuring the overall carrier transmission efficiency, thereby further improving the battery conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure is a schematic diagram of the structure of a tunnel passivation layer of a solar cell of the present invention.

[0033] Figure 2 This is a scanning electron microscope image of the tunneling passivation layer of the present invention (the length scale in the image is 1 μm).

[0034] Figure 3 It is a schematic structural diagram of an implementation manner of a solar cell of the present invention.

[0035] Figure 4 It is a schematic structural diagram of another embodiment of a solar cell of the present invention.

[0036] Figure 5 for Figure 4 A partial enlarged view of part A. 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] Reference to "embodiment" or "implementation" herein means that a particular feature, component, or characteristic described in conjunction with the embodiment or implementation may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] 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.

[0040] First, see Figure 1 As shown, the present invention provides a solar cell, comprising:

[0041] A silicon substrate 1, wherein the silicon substrate 1 has a first end surface and a second end surface opposite to each other,

[0042] A doping layer 2 is provided on the second end surface,

[0043] A tunnel passivation layer 3 is disposed between the second end surface and the doping layer 2 , and the thickness of the tunnel passivation layer 3 decreases from the edges around the second end surface to the middle.

[0044] It can be understood that the tunnel passivation layer 3 can be prepared by atomic layer deposition (ALD), plasma enhanced chemical vapor deposition (PECVD), low-energy oxygen plasma oxidation, thermal oxidation, etc., but is not limited thereto.

[0045] Due to the steps of laser grooving, heat treatment, cell cutting, lamination, etc., these steps easily cause the tunneling passivation layer 3 to be damaged by stress, and the closer the area is to the edge of the backlight surface, the greater the stress damage it suffers. In the present invention, the thickness of the tunneling passivation layer 3 is gradually reduced from the edges of the second end face to the middle, so that the tunneling passivation layer 3 has a higher ability to withstand and resist stress loss as it is closer to the edges of the second end face, thereby preventing stress damage from hindering the transport of carriers. At the same time, compared to simply increasing the thickness of the entire material layer, the thickness of the tunneling passivation layer 3 of the present invention is thinner as it is closer to the middle of the second end face, ensuring that the tunneling passivation layer 3 can not only prevent stress damage from hindering the transport of carriers, but also has a higher carrier transmission efficiency as a whole, thereby effectively improving the battery conversion efficiency.

[0046] At the same time, in the actual preparation process, it is only necessary to control the growth temperature and the diffusion of the source gas from the edges around the second end face to the middle position, so as to form a tunneling passivation layer 3 whose thickness decreases from the edges around the second end face to the middle. The tunneling passivation layer 3 is easy to produce and manufacture, which is conducive to industrial production.

[0047] Exemplarily, the tunnel passivation layer 3 may be made of silicon oxide.

[0048] Exemplarily, the doping layer 2 may be made of polysilicon.

[0049] The silicon substrate may be P-type single crystal silicon, N-type single crystal silicon, P-type polycrystalline silicon or N-type polycrystalline silicon, but is not limited thereto. Preferably, the silicon substrate is N-type single crystal silicon.

[0050] In some embodiments, see Figure 1 As shown, the tunnel passivation layer 3 has a maximum thickness end 31 with the largest thickness and a minimum thickness end 32 with the smallest thickness, and a ratio a of the maximum thickness end 31 to the minimum thickness end 32 is 1<a≤2.7.

[0051] Exemplarily, the ratio a of the maximum thickness end 31 to the minimum thickness end 32 is 1.05, 1.08, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.55, 2.6, 2.65 or 2.7, but is not limited thereto. When the ratio a is too large, it is easy to affect the flatness of other material layers subsequently arranged on the tunnel passivation layer 3.

[0052] In some embodiments, the tunnel passivation layer 3 has a maximum thickness end 31 with the largest thickness and a minimum thickness end 32 with the smallest thickness, and a ratio a of the maximum thickness end 31 to the minimum thickness end 32 is 1.3≤a≤2.7.

[0053] In some embodiments, the tunnel passivation layer 3 has a maximum thickness end 31 with the largest thickness and a minimum thickness end 32 with the smallest thickness, and a ratio a of the maximum thickness end 31 to the minimum thickness end 32 is 1.3≤a≤1.7.

[0054] In some embodiments, the thickness of the maximum thickness end 31 is 1.4nm to 2.4nm, and the thickness of the minimum thickness end 32 is 0.8nm to 1.8nm. Within this range, the tunnel passivation layer 3 as a whole can take into account better ability to resist stress loss and higher carrier transfer efficiency, and has better overall performance.

[0055] Exemplarily, the thickness of the maximum thickness end 31 is 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2.0 nm, 2.1 nm, 2.2 nm, 2.3 nm or 2.4 nm, but is not limited thereto.

[0056] Exemplarily, the thickness of the minimum thickness end 32 is 0.8nm, 0.9nm, 1.0nm, 1.1nm, 1.2nm, 2.7nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm or 1.8nm, but is not limited thereto. If the thickness of the tunneling passivation layer 3 is too small, the passivation effect is poor and the production difficulty increases.

[0057] In some embodiments, the thickness of the tunnel passivation layer 3 satisfies the following formula:

[0058]

[0059] Wherein, H(x, y) is the thickness of the tunnel passivation layer 3 at the point (x, y) on the second end surface, x and y are the horizontal distance and vertical distance from the center of the second end surface to the point (x, y), 0<x<0.5a, 0<y<0.5b, H0 is the thickness of the edge of the tunnel passivation layer 3, H c is the thickness of the tunnel passivation layer 3 at the center of the second end face, k is a constant coefficient, and k>0, a is the length of the tunnel passivation layer 3, b is the width of the tunnel passivation layer 3, β is an adjustment coefficient, and ρ is a deviation coefficient.

[0060] The thickness of the tunnel passivation layer 3 transitions relatively smoothly from the edges around the second end face to the middle position. The tunnel passivation layer 3 as a whole can take into account both better ability to resist stress loss and higher carrier transmission efficiency, and has better comprehensive performance.

[0061] In some embodiments, see Figures 2 to 5 As shown, the tunnel passivation layer 3 is provided with holes opening toward the doping layer 2 , and the density of the holes increases as the thickness of the tunnel passivation layer 3 decreases.

[0062] In the present invention, holes are provided on the tunneling passivation layer 3, and these holes can serve as the main carrier transport channels, thereby allowing some carriers to directly pass through the tunneling passivation layer 3 through the tunneling characteristics, and some carriers are first captured by the holes, and then transition to the energy level on the other side through the tunneling process or thermal excitation. The hole transport channels and the tunneling characteristics of the tunneling passivation layer 3 work together to effectively improve the carrier transmission efficiency, and can reduce the sensitivity and dependence of carrier transmission on the ultra-thin thickness of the tunneling passivation layer 3. The thickness of the tunneling passivation layer 3 can be made relatively thicker, so as to obtain a better interface passivation effect, and then obtain a tunneling passivation layer 3 with both good carrier transmission efficiency and passivation effect, thereby effectively improving the photoelectric conversion efficiency of the battery.

[0063] At the same time, the places where the tunneling passivation layer 3 is thicker are located at the edges of the second end face, that is, the places where stress damage is most likely to occur. By setting the density of the holes to increase as the thickness of the tunneling passivation layer 3 decreases, relatively fewer holes are set in places where stress damage is likely to occur to avoid the impact of too many holes on the ability to resist stress damage, and as many holes as possible are set in places where the stress effect is smaller, so that the tunneling passivation layer 3 can effectively prevent stress damage from hindering the transport of carriers and has more transmission channels to ensure the overall carrier transmission efficiency, thereby further improving the battery conversion efficiency.

[0064] In the first embodiment, see Figure 3 As shown, the doping layer 2 is a first polarity doping layer 23 , and the polarity of the first polarity doping layer 23 is the same as the polarity of the silicon substrate 1 .

[0065] Optional, see Figure 3 As shown, a second polarity doping layer 24 having a polarity opposite to that of the first polarity doping layer 23 is provided on the first end surface of the silicon substrate 1 .

[0066] Exemplarily, the silicon substrate 1 is an N-type silicon wafer, the first polarity doping layer 23 is an N-type doping layer, and the doping concentration of the N-type dopant in the N-type doping layer is greater than that of the N-type silicon wafer, and a P-type doping layer is provided on the first end surface of the silicon substrate 1.

[0067] Exemplarily, the silicon substrate 1 is a P-type silicon wafer, the first polarity doping layer 23 is a P-type doping layer, and the doping concentration of the P-type dopant in the P-type doping layer is greater than that of the P-type silicon wafer, and an N-type doping layer is provided on the first end surface of the silicon substrate 1.

[0068] In the second embodiment, see Figures 4 to 5 As shown, the doping layer 2 includes N-type doping regions 21 and P-type doping regions 22 that are alternately arranged.

[0069] The tunneling passivation layer 3 includes an N-region passivation layer 33 corresponding to the inner side of the N-type doping region 21 and a P-region passivation layer 34 corresponding to the inner side of the P-type doping region 22. The N-region passivation layer 33 is provided with an N-region hole 331 opening toward the doping layer 2, and the P-region passivation layer 34 is provided with a P-region hole 341 opening toward the doping layer 2.

[0070] It can be understood that the P-type dopant of the P-type doping region 22 and the P-type doping layer may be boron, and the N-type dopant of the N-type doping region 21 and the N-type doping layer may be phosphorus, but it is not limited thereto.

[0071] In some embodiments, a passivation layer is provided on the side of the doping layer 2 facing away from the tunnel passivation layer 3 , and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end surface.

[0072] In some embodiments, the density of the N-region holes 331 and / or the P-region holes 341 increases as the thickness of the tunnel passivation layer 3 decreases.

[0073] In some embodiments, see Figures 4 to 5 As shown, the density of the P-region holes 341 is greater than the density of the N-region holes 331 .

[0074] Since the movement speed of holes is slower than that of electrons, by controlling the density of P-region holes 341 located in the corresponding area inside the P-type doping region 22 (P-region passivation layer 34) to be greater than the density of N-region holes 331 located in the corresponding area inside the N-type doping region 21 (N-region passivation layer 33), the number of P-region holes 341 is made greater than the number of N-region holes 331, and the holes have more channels, thereby balancing the carriers, thereby further improving the photoelectric conversion efficiency of the battery.

[0075] In some embodiments, the density of the P region holes 341 is 1×10 7 cm -2 ~1×10 10 cm -2 .

[0076] For example, the density of the P region holes 341 is 1×10 7 cm -2 , 2.5×10 7 cm -2 , 5×10 7 cm -2 , 8×10 7 cm -2 , 1×10 8 cm -2 , 2.5×10 8 cm -2 , 5×10 8 cm -2 , 8×10 8 cm -2 , 1×10 9 cm -2 , 2.5×10 9 cm -2 , 5×10 9 cm -2 , 8×10 9 cm -2 or 1×10 10 cm -2 , but not limited to this.

[0077] When the density of the P region holes 341 is too low, the total number of the P region holes 341 and the N region holes 331 is too small to form an effective channel, which affects the carrier transmission efficiency. When the density of the P region holes 341 is too high, the passivation effect of the P region passivation layer 34 is affected.

[0078] In some embodiments, the density of the N-region holes 331 is 1×10 6 cm -2 ~1×10 9 cm -2 .

[0079] For example, the density of the N-region holes 331 is 1×10 6 cm -2 , 2.5×10 6 cm -2 , 5×10 6 cm -2 , 8×10 6 cm -2 , 1×10 7 cm -2 , 2.5×10 7 cm -2 , 5×10 7 cm -2 , 8×10 7 cm -2 , 1×10 8 cm -2 , 2.5×10 8 cm -2 , 5×10 8 cm -2 , 8×10 8 cm -2 or 1×10 9 cm -2 , but not limited to this.

[0080] When the density of the N-region holes 331 is too low, it is difficult to form an effective channel, which affects the carrier transmission efficiency. When the density of the N-region holes 331 is too high, the density of the P-region holes 341 needs to be set higher, which easily causes the density of the P-region holes 341 to be too high, affecting the passivation effect of the P-region passivation layer 34.

[0081] The present invention also provides a battery split, which is obtained by splitting the above-mentioned solar cell sheet.

[0082] The battery slices may be half slices or quarter slices, but are not limited thereto.

[0083] It can be understood that when the battery is divided into half cells, it is cut from the central axis of the battery cell, and the cutting edge is located at the position of the original central axis of the battery cell, so the thickness of the tunneling passivation layer 3 increases from the midpoint of the cutting edge of the second end face toward the other three sides.

[0084] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0085] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0086] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0087] Example 1

[0088] First, the present invention provides a solar cell, comprising:

[0089] A silicon substrate, wherein the silicon substrate has a first end face and a second end face opposite to each other, wherein the second end face is a backlight face, and the silicon substrate is N-type single crystal silicon,

[0090] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0091] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0092] The doped layer comprises N-type doped regions and P-type doped regions arranged alternately, a passivation layer is provided on the side of the doped layer facing away from the tunnel passivation layer, and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end face.

[0093] In this embodiment, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.33.

[0094] In this embodiment, the thickness of the maximum thickness end is 2.4 nm, and the thickness of the minimum thickness end is 1.8 nm.

[0095] In this embodiment, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0096] In this embodiment, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0097] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0098] In this embodiment, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0099] In this embodiment, the density of the holes in the P region is greater than the density of the holes in the N region.

[0100] In this embodiment, the density of the holes in the P region increases from 1×10 7 cm -2 Increase to 5×10 8 cm -2 .

[0101] In this embodiment, the density of the holes in the N region increases from 1×10 6 cm -2 Increase to 5×10 6 cm -2 .

[0102] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0103] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0104] Example 2

[0105] First, the present invention provides a solar cell, comprising:

[0106] A silicon substrate, wherein the silicon substrate has a first end face and a second end face opposite to each other, wherein the second end face is a backlight face, and the silicon substrate is N-type single crystal silicon,

[0107] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0108] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0109] The doped layer comprises N-type doped regions and P-type doped regions arranged alternately, a passivation layer is provided on the side of the doped layer facing away from the tunnel passivation layer, and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end face.

[0110] In this embodiment, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.13.

[0111] In this embodiment, the thickness of the maximum thickness end is 1.8 nm, and the thickness of the minimum thickness end is 1.6 nm.

[0112] In this embodiment, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0113] In this embodiment, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0114] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0115] In this embodiment, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0116] In this embodiment, the density of the holes in the P region is greater than the density of the holes in the N region.

[0117] In this embodiment, the density of the holes in the P region increases from 5×10 8 cm -2 Incremental to 1×10 9 cm -2 .

[0118] In this embodiment, the density of the holes in the N region increases from 5×10 6 cm -2 Incremental to 1×10 7 cm -2 .

[0119] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0120] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0121] Example 3

[0122] First, the present invention provides a solar cell, comprising:

[0123] A silicon substrate, wherein the silicon substrate has a first end face and a second end face opposite to each other, wherein the second end face is a backlight face, and the silicon substrate is N-type single crystal silicon,

[0124] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0125] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0126] The doped layer comprises N-type doped regions and P-type doped regions arranged alternately, a passivation layer is provided on the side of the doped layer facing away from the tunnel passivation layer, and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end face.

[0127] In this embodiment, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.23.

[0128] In this embodiment, the thickness of the maximum thickness end is 1.6 nm, and the thickness of the minimum thickness end is 1.3 nm.

[0129] In this embodiment, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0130] In this embodiment, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0131] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0132] In this embodiment, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0133] In this embodiment, the density of the holes in the P region is greater than the density of the holes in the N region.

[0134] In this embodiment, the density of the holes in the P region increases from 1×10 9 Increase to 5×10 9 cm -2 .

[0135] In this embodiment, the density of the holes in the N region increases from 1×10 7 cm-2 Increase to 1×10 8 cm -2 .

[0136] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0137] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0138] Example 4

[0139] First, the present invention provides a solar cell, comprising:

[0140] A silicon substrate, wherein the silicon substrate has a first end surface and a second end surface opposite to each other, and the silicon substrate is N-type single crystal silicon,

[0141] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0142] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0143] In this embodiment, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.23.

[0144] In this embodiment, the thickness of the maximum thickness end is 1.6 nm, and the thickness of the minimum thickness end is 1.3 nm.

[0145] In this embodiment, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases. The hole density of the tunnel passivation layer increases from 1×10 7 cm -2 Increase to 1×10 8 cm -2 .

[0146] In this embodiment, the doping layer is a first polarity doping layer, and the polarity of the first polarity doping layer is the same as the polarity of the silicon substrate.

[0147] The silicon substrate is an N-type silicon wafer, the first polarity doping layer is an N-type doping layer, and the doping concentration of the N-type dopant in the N-type doping layer is greater than that of the N-type silicon wafer, and a P-type doping layer is provided on the first end surface of the silicon substrate.

[0148] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0149] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0150] Example 5

[0151] First, the present invention provides a solar cell, comprising:

[0152] A silicon substrate, wherein the silicon substrate has a first end face and a second end face opposite to each other, wherein the second end face is a backlight face, and the silicon substrate is N-type single crystal silicon,

[0153] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0154] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

[0155] The doped layer comprises N-type doped regions and P-type doped regions arranged alternately, a passivation layer is provided on the side of the doped layer facing away from the tunnel passivation layer, and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end face.

[0156] In this embodiment, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.63.

[0157] In this embodiment, the thickness of the maximum thickness end is 1.3 nm, and the thickness of the minimum thickness end is 0.8 nm.

[0158] In this embodiment, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0159] In this embodiment, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0160] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0161] In this embodiment, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0162] In this embodiment, the density of the holes in the P region is greater than the density of the holes in the N region.

[0163] In this embodiment, the density of the holes in the P region increases from 5×109 Incremental to 1×10 10 cm -2 .

[0164] In this embodiment, the density of the holes in the N region increases from 1×10 8 cm -2 Incremental to 1×10 9 cm -2 .

[0165] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0166] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0167] Comparative Example 1

[0168] First, the present invention provides a solar cell, comprising:

[0169] A silicon substrate, wherein the silicon substrate has a first end face and a second end face opposite to each other, wherein the second end face is a backlight face, and the silicon substrate is N-type single crystal silicon,

[0170] A doping layer is provided on the second end surface, and the doping layer is made of polycrystalline silicon.

[0171] A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer increases gradually from the edges around the second end surface to the middle.

[0172] The doped layer comprises N-type doped regions and P-type doped regions arranged alternately, a passivation layer is provided on the side of the doped layer facing away from the tunnel passivation layer, and a front surface field, a passivation layer and an anti-reflection layer are sequentially provided on the first end face.

[0173] In this comparative example, the tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.33.

[0174] In this comparative example, the thickness at the maximum thickness end is 2.4 nm, and the thickness at the minimum thickness end is 1.8 nm.

[0175] In this comparative example, the tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

[0176] In this comparative example, the doping layer includes N-type doping regions and P-type doping regions that are alternately arranged.

[0177] The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

[0178] In this comparative example, the density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

[0179] In this comparative example, the density of the holes in the P region is greater than the density of the holes in the N region.

[0180] In this comparative example, the density of the holes in the P region increases from 5×10 8 cm -2 Decrease to 1×10 7 cm -2 .

[0181] In this comparative example, the density of the holes in the N region increases from 5×10 6 cm -2 Decrease to 1×10 6 cm -2 .

[0182] Secondly, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0183] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0184] The solar cells prepared in Examples 1 to 5 and Comparative Example 1 were subjected to performance tests, and the test results are as follows:

[0185]

[0186] By comparing Examples 1 to 5 with Comparative Example 1, it can be seen that the present invention sets the thickness of the tunneling passivation layer to decrease from the edges of the second end surface to the middle, and correspondingly sets the holes of the tunneling passivation layer to increase from the edges of the second end surface to the middle, which can effectively improve the battery conversion efficiency.

[0187] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the field can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon substrate having a first end surface and a second end surface opposite to each other, a doping layer, disposed on the second end surface, A tunnel passivation layer is provided between the second end surface and the doping layer, and the thickness of the tunnel passivation layer decreases gradually from the edges around the second end surface to the middle.

2. A solar cell according to claim 1, characterized in that: The tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1<a≤2.

7.

3. A solar cell according to claim 2, characterized in that: The tunnel passivation layer has a maximum thickness end with the largest thickness and a minimum thickness end with the smallest thickness, and a ratio a of the maximum thickness end to the minimum thickness end is 1.3≤a≤2.

7.

4. A solar cell according to claim 1, characterized in that: The thickness of the maximum thickness end is 1.4 nm to 2.4 nm, and the thickness of the minimum thickness end is 0.8 nm to 1.8 nm.

5. The solar cell according to claim 1, characterized in that: The thickness of the tunnel passivation layer satisfies the following formula: Wherein, H(x, y) is the thickness of the tunnel passivation layer at the point (x, y) on the second end surface, x and y are the horizontal distance and vertical distance from the center of the second end surface to the point (x, y), 0<x<0.5a, 0<y<0.5b, H0 is the thickness of the edge of the tunnel passivation layer, H c is the thickness of the tunnel passivation layer at the center of the second end face, k is a constant coefficient, and k>0, a is the length of the tunnel passivation layer, b is the width of the tunnel passivation layer, β is an adjustment coefficient, and ρ is a deviation coefficient.

6. The solar cell according to claim 1, characterized in that: The tunnel passivation layer is provided with holes opening toward the doping layer, and the density of the holes increases as the thickness of the tunnel passivation layer decreases.

7. A solar cell according to claim 6, characterized in that: The doping layer is a first polarity doping layer, and the polarity of the first polarity doping layer is the same as the polarity of the silicon substrate.

8. The solar cell according to claim 6, characterized in that: The doping layer includes N-type doping regions and P-type doping regions that are alternately arranged. The tunneling passivation layer includes an N-region passivation layer corresponding to the inner side of the N-type doping region and a P-region passivation layer corresponding to the inner side of the P-type doping region, the N-region passivation layer is provided with an N-region hole opening toward the doping layer, and the P-region passivation layer is provided with a P-region hole opening toward the doping layer.

9. A solar cell according to claim 8, characterized in that: The density of the N-region holes and / or the P-region holes increases as the thickness of the tunnel passivation layer decreases.

10. The solar cell according to claim 8, characterized in that: The density of the holes in the P region is greater than the density of the holes in the N region.

11. The solar cell according to claim 8, characterized in that: The density of the holes in the P region is 1×10 7 cm -2 ~1×10 10 cm -2 .

12. The solar cell according to claim 8, characterized in that: The density of the holes in the N region is 1×10 6 cm -2 ~1×10 9 cm -2 .

13. A battery slice, characterized in that: The solar cell is obtained by dividing the solar cell according to any one of claims 1 to 12.

14. A battery assembly, characterized in that: It comprises a solar cell according to any one of claims 1 to 12.

15. A photovoltaic system, characterized in that: Includes the battery assembly according to claim 13, or includes the battery assembly according to claim 14.

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