A bifacial back-contact solar cell and its back structure

Abstract

This application is applicable to the field of solar cell technology, and provides a bifacial back-contact solar cell and its back structure. The back structure includes a P-type contact region structure and an N-type contact region structure alternately disposed on the back surface of a silicon substrate. The P-type contact region structure is connected to a first conductive layer, and the N-type contact region structure is connected to a second conductive layer; at least one of the P-type contact region structure and the N-type contact region structure is a selective passivation contact structure; the selective passivation contact structure includes alternately arranged first passivation contact regions and second passivation contact regions; the first passivation contact region includes a first doped layer, a first passivation layer, and a second doped layer sequentially stacked on the silicon substrate; the second passivation contact region includes a second passivation layer, a third doped layer, and a third passivation layer sequentially stacked on the silicon substrate; the thickness of the second doped layer is greater than that of the third doped layer, and the doping polarities of the second doped layer and the third doped layer are the same.

Description

Technical Field

[0001] This application belongs to the technical field of solar cells, and particularly relates to a bifacial back-contact solar cell and its back structure. Background Art

[0002] The electricity generated by solar cells is a sustainable clean energy source. Solar cells can convert sunlight into electrical energy by utilizing the photovoltaic effect of the semiconductor p-n junction. Therefore, the photoelectric conversion efficiency is an important indicator for measuring the performance of solar cells. In solar cells, the loss of photoelectric conversion efficiency includes two aspects: electrical loss and optical loss. Electrical loss mainly includes recombination loss and resistance loss caused by metal-semiconductor contact, while optical loss mainly includes the shielding of the light-receiving surface metal grid lines and the parasitic absorption of the front doping layer.

[0003] Solar cells in related technologies have significant electrical properties by setting a passivated contact structure, and can simultaneously obtain a low contact resistivity and a low surface recombination. The passivated contact structure usually includes a passivation layer and a doping layer.

[0004] However, the absorption of light by the doping layer in the passivated contact structure is a 'parasitic' absorption and does not contribute to the photocurrent, resulting in serious parasitic absorption in the passivated contact area and low current of the solar cell. Based on this, how to reduce the parasitic absorption of solar cells has become an urgent technical problem to be solved. Summary of the Invention

[0005] Embodiments of this application provide a bifacial back-contact solar cell and its back structure, aiming to solve the problem of how to reduce the parasitic absorption of solar cells.

[0006] The back structure of the bifacial back-contact solar cell in the embodiments of this application includes a P-type contact area structure and an N-type contact area structure alternately arranged on the back of the silicon substrate of the bifacial back-contact solar cell. The P-type contact area structure is connected to the first conductive layer of the bifacial back-contact solar cell, and the N-type contact area structure is connected to the second conductive layer of the bifacial back-contact solar cell; at least one of the P-type contact area structure and the N-type contact area structure is a selective passivated contact structure; the selective passivated contact structure includes alternately arranged first passivated contact areas and second passivated contact areas; the first passivated contact area includes a first doping layer, a first passivation layer, and a second doping layer sequentially stacked on the silicon substrate; the second passivated contact area includes a second passivation layer, a third doping layer, and a third passivation layer sequentially stacked on the silicon substrate; the thickness of the second doping layer is greater than the thickness of the third doping layer, and the doping polarities of the second doping layer and the third doping layer are the same.

[0007] Further, the doping polarities of the first doping layer and the second doping layer are the same; the second passivation contact region further includes a fourth doping layer disposed between the silicon substrate and the second passivation layer, and the doping polarities of the fourth doping layer and the third doping layer are the same.

[0008] Further, the second passivation layer is a porous structure, and the fourth doping layer and / or the third doping layer are / is present in the pore regions of the second passivation layer, and the third doping layer and the fourth doping layer are connected through the doped pore regions.

[0009] Further, the first passivation layer is a porous structure, and the first doping layer and / or the second doping layer are / is present in the pore regions of the first passivation layer, and the second doping layer and the first doping layer are connected through the doped pore regions.

[0010] Further, the first passivation layer is a porous structure, and the average pore diameter of the pores of the first passivation layer is less than 1000 nm; and / or, the second passivation layer is a porous structure, and the average pore diameter of the pores of the second passivation layer is less than 1000 nm.

[0011] Further, the first passivation layer is a porous structure, and the pores of the first passivation layer are formed by means of thermal diffusion shock; and / or, the second passivation layer is a porous structure, and the pores of the second passivation layer are formed by means of thermal diffusion shock.

[0012] Further, the first passivation layer is a porous structure, and the pores of the first passivation layer are scattered and sparsely distributed on the first passivation layer; and / or, the second passivation layer is a porous structure, and the pores of the second passivation layer are scattered and sparsely distributed on the second passivation layer.

[0013] Further, the first passivation layer is a porous structure, and the ratio of the area of the pore regions of the first passivation layer to the overall area of the first passivation layer is less than 20%; and / or, the second passivation layer is a porous structure, and the ratio of the area of the pore regions of the second passivation layer to the overall area of the second passivation layer is less than 20%.

[0014] Further, the first passivation layer is a porous structure, and the first doping layer is discretely and locally distributed in the pore regions of the first passivation layer; and / or, the second passivation layer is a porous structure, and the second passivation contact region further includes a fourth doping layer disposed between the silicon substrate and the second passivation layer, and the fourth doping layer is discretely and locally distributed in the pore regions of the second passivation layer.

[0015] Further, the first passivation layer is a porous structure, and the first doping layer is disposed completely continuously between the silicon substrate and the first passivation layer; and / or, the second passivation layer is a porous structure, and the second passivation contact region further includes a fourth doping layer disposed between the silicon substrate and the second passivation layer, and the fourth doping layer is disposed completely continuously between the silicon substrate and the second passivation layer.

[0016] Further, the first passivation layer is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer; and / or, the second passivation layer is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer.

[0017] Further, the oxide layer is composed of one or more layers of a silicon oxide layer and an aluminum oxide layer.

[0018] Further, the second passivation contact region further includes a fourth doping layer disposed between the silicon substrate and the second passivation layer, and the doping concentration of the first doping layer is greater than or equal to the doping concentration of the fourth doping layer.

[0019] Further, the thickness of the third doping layer is 0 - 500 nm.

[0020] The double-sided back-contact solar cell of the embodiment of the present application includes the back structure of the double-sided back-contact solar cell according to any one of the above.

[0021] Further, the P-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a first conductive layer, the first conductive layer is connected to the second doping layer, and the width of the first conductive layer is greater than the width of the second doping layer; and / or, the N-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a second conductive layer, the second conductive layer is connected to the second doping layer, and the width of the second conductive layer is greater than the width of the second doping layer.

[0022] Further, the P-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a first conductive layer, a fourth passivation layer is provided on the second doping layer, the fourth passivation layer is formed with an opening, and the first conductive layer passes through the opening and is connected to the second doping layer;

[0023] and / or, the N-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a second conductive layer, a fourth passivation layer is provided on the second doping layer, the fourth passivation layer is formed with an opening, and the second conductive layer passes through the opening and is connected to the second doping layer.

[0024] For the double-sided back-contact solar cell and its back structure according to the embodiments of the present application, since the thickness of the third doping layer is small, the parasitic absorption in the second passivation contact region can be reduced, and the short-circuit current can be increased. At the same time, since the thickness of the second doping layer is large, the conductive layer can be prevented from burning through the second doping layer, and the open-circuit voltage can be increased. At the same time, excellent interface passivation performance and low contact resistance can be achieved. At the same time, since both the P-type contact region structure and the N-type contact region structure are disposed on the back surface of the silicon substrate, the grid line shielding on the front surface of the silicon substrate can be reduced. In this way, the photoelectric conversion efficiency of the solar cell can be maximized. Description of the Drawings

[0025] Figure 1 FIG. is a schematic structural diagram of the back structure of a double-sided back-contact solar cell according to an embodiment of the present application in various implementations;

[0026] Figures 2 - 5 FIG. is a schematic structural diagram of the selective passivation contact structure in the back structure of a double-sided back-contact solar cell according to an embodiment of the present application in various implementations;

[0027] Figures 6 - 10 FIG. is a schematic structural diagram of a double-sided back-contact solar cell according to an embodiment of the present application in various implementations.

[0028] Main Element Symbol Description:

[0029] Double-sided back-contact solar cell 1000, P-type contact region structure 101, N-type contact region structure 102, selective passivation contact structure 100, silicon substrate 10, first passivation contact region 11, first doping layer 111, first passivation layer 112, second doping layer 113, fourth passivation layer 114, opening 1141, second passivation contact region 12, fourth doping layer 121, second passivation layer 122, third doping layer 123, third passivation layer 124; undoped region 200, first conductive layer 30, second conductive layer 50, second surface passivation layer 70. Detailed Description of the Embodiments

[0030] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] In this application, unless otherwise clearly specified and defined, the terms "install", "connect", "join", "fix", etc. shall 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 or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] In this application, due to the small thickness of the third doping layer, the parasitic absorption of the second passivated contact region can be reduced and the current can be increased. At the same time, due to the large thickness of the second doping layer, the conductive layer can be prevented from burning through the second doping layer. At the same time, excellent interface passivation performance and low contact resistance can be achieved. At the same time, since both the P-type contact region structure and the N-type contact region structure are provided on the back surface of the silicon substrate, the gate line shielding on the front surface of the silicon substrate can be reduced. In this way, the photoelectric conversion efficiency of the solar cell can be maximized.

[0033] Example 1

[0034] Embodiment 1 of this application provides a back structure of a double-sided back-contact solar cell. For the convenience of description, only the parts related to the embodiments of this application are shown.

[0035] Please refer to Figure 1 and Figure 2 , the back structure 1001 of the double-sided back-contact solar cell provided by the embodiment of this application includes a P-type contact region structure 101 and an N-type contact region structure 102 alternately provided on the back surface of the silicon substrate 10 of the double-sided back-contact solar cell; the P-type contact region structure 101 is connected to the first conductive layer of the double-sided back-contact solar cell, and the N-type contact region structure 102 is connected to the second conductive layer of the double-sided back-contact solar cell; at least one of the P-type contact region structure 101 and the N-type contact region structure 102 is a selective passivated contact structure 100;

[0036] The selective passivated contact structure 100 includes: a first passivated contact region 11 and a second passivated contact region 12 arranged alternately; the first passivated contact region 11 includes a first doping layer 111, a first passivation layer 112, and a second doping layer 113 stacked in sequence on the silicon substrate 10; the second passivated contact region 12 includes a second passivation layer 122, a third doping layer 123, and a third passivation layer 124 stacked in sequence on the silicon substrate 10; the thickness of the second doping layer 113 is greater than the thickness of the third doping layer 123, and the doping polarities of the second doping layer 113 and the third doping layer 123 are the same.

[0037] The back structure 1001 of the double-sided back-contact solar cell according to the embodiment of the present application has a small thickness of the third doping layer 123, so the parasitic absorption of the second passivation contact region 12 can be reduced, and the short-circuit current can be increased. At the same time, due to the large thickness of the second doping layer 113, the conductive layer can be prevented from burning through the second doping layer 113, and the open-circuit voltage can be increased. At the same time, excellent interface passivation performance and low contact resistance can be achieved. At the same time, since both the P-type contact region structure 101 and the N-type contact region structure 102 are provided on the back surface of the silicon substrate 10, the grid line shielding on the front surface of the silicon substrate 10 can be reduced. In this way, the photoelectric conversion efficiency of the solar cell can be maximized.

[0038] Specifically, the silicon substrate 10 has a front surface facing the sun and a back surface facing away from the sun during normal operation. The front surface is the light-receiving surface of the solar cell, and the back surface is provided on the other side of the silicon substrate 10 away from the front surface. That is to say, the front surface and the back surface are located on opposite sides of the silicon substrate 10. In this embodiment, the silicon substrate 10 is an N-type single-crystalline silicon wafer. It can be understood that in other embodiments, the silicon substrate 10 can also be other types of silicon wafers such as polycrystalline silicon wafers or quasi-single-crystalline silicon wafers, and the silicon substrate 10 can also be P-type. Thus, the silicon substrate 10 can be set according to actual use needs, and the specific form of the silicon substrate 10 is not limited herein.

[0039] Specifically, an antireflection structure can be formed on the front surface of the silicon substrate 10. For example, a random pyramid structure, an inverted pyramid structure, a spherical crown structure, a V-groove structure. The antireflection structure can be formed by texturing the front surface of the silicon substrate 10. In this way, the reflection of sunlight on the front surface can be reduced, and the photoelectric conversion efficiency can be increased.

[0040] Specifically, the back surface of the silicon substrate 10 can be a polished surface. For example, an alkali-polished surface, an acid-polished surface, a mechanical-polished surface, etc.

[0041] Specifically, "at least one of the P-type contact region structure 101 and the N-type contact region structure 102 is a selective passivation contact structure 100" means that: the P-type contact region structure 101 is not a selective passivation contact structure 100, and the N-type contact region structure 102 is a selective passivation contact structure 100, as Figure 1 shown; or, the P-type contact region structure 101 is a selective passivation contact structure 100, and the N-type contact region structure 102 is not a selective passivation contact structure 100; or, both the P-type contact region structure 101 and the N-type contact region structure 102 are selective passivation contact structures 100. It can be understood that when the P-type contact region structure 101 or the N-type contact region structure 102 is not a selective passivation contact structure 100, it can be other structures such as a doping structure.

[0042] This text takes the case where the P-type contact region structure 101 is not a selective passivation contact structure 100 and the N-type contact region structure 102 is a selective passivation contact structure 100 as an example for illustration.

[0043] Specifically, "the doping polarities of the second doping layer 113 and the third doping layer 123 are the same" means that: the doping polarities of both the second doping layer 113 and the third doping layer 123 are N-type; or, the doping polarities of both the second doping layer 113 and the third doping layer 123 are P-type.

[0044] Please note that in the case where the P-type contact region structure 101 is a selective passivation contact structure 100, the first doping layer 111, the second doping layer 113, the third doping layer 123, and the fourth doping layer 121 are all P-type doping layers; in the case where the N-type contact region structure 102 is a selective passivation contact structure 100, the first doping layer 111, the second doping layer 113, the third doping layer 123, and the fourth doping layer 121 are all N-type doping layers.

[0045] Specifically, the P-type contact region structure 101 and the N-type contact region structure 102 are alternately disposed on the back surface of the silicon substrate 10, which means that one P-type contact region structure 101 is disposed between two N-type contact region structures 102, and one N-type contact region structure 102 is disposed between two P-type contact region structures 101. In other words, along the direction of the alternating arrangement, the N-type contact region structure 102, the P-type contact region structure 101, the N-type contact region structure 102, the P-type contact region structure 101, and the N-type contact region structure 102 are arranged in sequence.

[0046] Specifically, the alternate arrangement of the first passivation contact region 11 and the second passivation contact region 12 means that in the selective passivation contact structure 100, one first passivation contact region 11 is disposed between two second passivation contact regions 12. In other words, along the direction of the alternating arrangement, the second passivation contact region 12, the first passivation contact region 11, and the second passivation contact region 12 are arranged in sequence.

[0047] Specifically, the direction of the alternate arrangement of the first passivation contact region 11 and the second passivation contact region 12 is perpendicular to the thickness direction of the silicon substrate 10. The direction of the alternate arrangement of the first passivation contact region 11 and the second passivation contact region 12 can be parallel to the length direction of the silicon substrate 10, perpendicular to the length direction of the silicon substrate 10, or at an acute or obtuse angle to the length direction of the silicon substrate.

[0048] Please refer to Figure 2, optionally, the thickness of the first doped layer 111 ranges from 50 nm to 2000 nm. For example, it is 50 nm, 51 nm, 60 nm, 100 nm, 500 nm, 1000 nm, 1500 nm, 1900 nm, 2000 nm. In this way, the contact resistance can be reduced and a field passivation effect can be provided.

[0049] Note that in other embodiments, the thickness of the first doped layer 111 can be 0 nm. In other words, the first doped layer 111 can be omitted, and the first passivated contact region 11 includes a first passivation layer 112 and a second doped layer 113 that are sequentially stacked on the silicon substrate 10.

[0050] Please refer to Figure 2 , optionally, the first doped layer 111 is a doped single-crystalline silicon layer. Further, the first doped layer 111 can be formed by diffusion, ion implantation, source coating diffusion or other processes; also, when preparing the second doped layer 113, the doping source can directly pass through the first passivation layer 112 or through the holes in the porous structure to form the first doped layer 111 in the silicon substrate 10.

[0051] Please refer to Figure 2 , optionally, the doping concentration of the first doped layer 111 is less than that of the second doped layer 113. In this way, by light doping, the lateral transport of carriers can be improved.

[0052] Please refer to Figure 2 , optionally, the thickness of the first passivation layer 112 is 0.5 nm - 20 nm. For example, it is 0.5 nm, 0.6 nm, 1 nm, 1.5 nm, 5 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm.

[0053] Please refer to Figure 2 , optionally, the first passivation layer 112 includes one or more of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer. Further, the oxide layer includes one or more of a silicon oxide layer and an aluminum oxide layer. In this way, an excellent interface passivation effect can be provided.

[0054] Further, the silicon carbide layer includes a hydrogenated silicon carbide layer. In this way, the hydrogen in the hydrogenated silicon carbide layer enters the silicon substrate 10 under the action of the diffusion mechanism and the thermal effect, can neutralize the dangling bonds on the back surface of the silicon substrate 10, passivate the defects of the silicon substrate 10, thereby reducing the defect energy levels in the bandgap and increasing the probability of carriers entering the second doped layer 113 through the first passivation layer 112.

[0055] Please refer to Figure 3, optionally, the first passivation layer 112 is a porous structure, and the first doping layer 111 and / or the second doping layer 113 are / is in the pore region of the first passivation layer 112, and the second doping layer 113 is connected to the first doping layer 111 through the doped pore region. Specifically, the second doping layer 113 is connected to the silicon substrate 10 through the doped pore region and the first doping layer 111. In this way, a conductive channel is formed in the pore region of the first passivation layer 112, so that the first passivation layer 112 has a good resistivity, reduces the sensitivity of the resistance to the thickness of the first passivation layer 112, and thus reduces the control requirement for the thickness of the first passivation layer 112. At the same time, the first doping layer 111 disposed between the silicon substrate 10 and the first passivation layer 112 can form an electric field for enhancing the separation of surface electron holes, thereby improving the field passivation effect. At the same time, since the Fermi levels of the first doping layer 111 and the silicon substrate 10 are different, the first doping layer 111 changes the Fermi level, increases the solid concentration of impurities (transition metals), and can form an additional gettering effect. At the same time, the second doping layer 113 is connected to the silicon substrate 10 through the doped pore region and the first doping layer 111 on the porous structure, further reducing the overall resistance of the prepared battery, and finally improving the conversion efficiency of the battery.

[0056] In one example, the first doping layer 111 is in the pore region and the second doping layer 113 is not; in another example, the second doping layer 113 is in the pore region and the first doping layer 111 is not; in still another example, both the first doping layer 111 and the second doping layer 113 are in the pore region. In addition, the first doping layer 111 and / or the second doping layer 113 can fill one or more pores, can also fill a part of one pore or a part of multiple pores, and there can also be some pores not filled with the first doping layer 111 and the second doping layer 113. The specific doping form of the pore region is not limited herein.

[0057] It can be understood that in other embodiments, the first passivation layer 112 can also be a completely continuous structure. In other words, the first passivation layer 112 may not include pores.

[0058] Please refer to Figure 3, optionally, the first passivation layer 112 is a porous structure, and the average pore diameter of the pores in the first passivation layer 112 is less than 1000 nm. For example, it is 4 nm, 10 nm, 16 nm, 50 nm, 480 nm, 830 nm, 960 nm, 999 nm. In this way, the average pore diameter of the porous structure is nanoscale, which can greatly reduce the total contact area between the second doping layer 113 and the silicon substrate 10, and reduce the recombination loss. Further, the average pore diameter of the porous structure is less than 500 nm. In this way, the total contact area between the second doping layer 113 and the silicon substrate 10 is further reduced, thereby further reducing the recombination loss. Further, the average pore diameter of 90% of the through holes is less than 1000 nm. In this way, a certain floating space is given. While ensuring a small recombination loss, the product yield can be guaranteed, the production efficiency can be improved, and no additional processes such as laser via opening are required, and the preparation process is simple.

[0059] Please refer to Figure 3 , optionally, the first passivation layer 112 is a porous structure, and the pores in the first passivation layer 112 are formed by means of thermal diffusion shock. Specifically, the temperature range of the thermal diffusion shock is 500°C - 1200°C. For example, it is 500°C, 510°C, 550°C, 600°C, 700°C, 800°C, 820°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C. Preferably, the thermal diffusion shock temperature is 800°C - 1100°C. For example, it is 800°C, 820°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C. In this way, the formed porous structure has smaller pores, the average pore diameter is less than 1000 nm, which is beneficial to reducing the recombination loss. Moreover, the surface density of the pores is higher, up to 10 6 -10 8 / cm 2 , which can reduce the lateral transport distance, eliminate the current crowding effect, reduce the resistance loss, and make the effect of reducing the resistance better. It can be understood that in other embodiments, the porous structure can also be formed by chemical etching, dry etching or other methods.

[0060] Please refer to Figure 3 , optionally, the first passivation layer 112 is a porous structure, and the pores in the first passivation layer 112 are scattered and sparsely distributed on the first passivation layer 112. In this way, there is no need to strictly control the distribution state of the pores, which is beneficial to improving the production efficiency.

[0061] Please refer to Figure 3, optionally, the first passivation layer 112 is a porous structure, and the ratio of the area of the hole region of the first passivation layer 112 to the overall area of the first passivation layer 112 is less than 20%. In this way, by controlling the total area of the hole region through the ratio of the area, the total contact area between the second doping layer 113 and the silicon substrate 10 can be made smaller, and while ensuring a low contact resistance, the recombination loss can be reduced.

[0062] Please refer to Figure 3 , optionally, the first passivation layer 112 is a porous structure, and the first doping layer 111 is discretely and locally distributed in each hole region of the first passivation layer 112. In this way, in the case where the first doping layer 111 is discretely distributed, it can also be ensured that the positive projection of the holes in the passivation layer on the silicon substrate 10 is covered by the positive projection of the first doping layer 111 on the silicon substrate 10, so as to ensure that the second doping layer 113 cannot directly contact the silicon substrate 10, avoiding serious recombination caused by the second doping layer 113 directly contacting the silicon substrate 10.

[0063] Please refer to Figure 3 , optionally, the first passivation layer 112 is a porous structure, and the first doping layer 111 is completely continuously disposed between the silicon substrate 10 and the first passivation layer 112. In this way, due to the completely continuous setting of the first doping layer 111, the positive projection of the holes in the passivation layer on the silicon substrate 10 must be covered by the positive projection of the first doping layer 111 on the silicon substrate 10, and the second doping layer 113 must not be able to directly contact the silicon substrate 10, avoiding serious recombination caused by the second doping layer 113 directly contacting the silicon substrate 10.

[0064] Furthermore, the distribution of the first doping layer 111 can be controlled by the doping duration. The longer the doping time, the more the doping amount, and the higher the continuous ratio of the first doping layer 111 will be until a completely covered first doping layer 111 is formed on the silicon substrate 10. Further, the junction depth of the first doping layer 111 is less than 1.5 um. In this way, the contact resistance can be reduced and the field effect passivation can be improved.

[0065] Specifically, the thickness range of the second doping layer 113 is 0 nm - 500 nm. For example, it is 0.1 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm. In this way, the thickness range of the second doping layer 113 is relatively wide, which can adapt to different requirements during actual production.

[0066] Preferably, the thickness range of the second doping layer 113 is 100 nm - 500 nm. For example, it can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm. In this way, the relatively thick second doping layer 113 can prevent the conductive layer from burning through the second doping layer 113, reduce contact recombination, increase the open-circuit voltage, and at the same time increase the process width, ensuring the product yield.

[0067] Specifically, the second doping layer 113 includes a doped polysilicon layer, a doped silicon carbide layer, or a doped amorphous silicon layer. Preferably, the second doping layer 113 includes a doped silicon carbide layer. In this way, due to the wide optical bandgap and low absorption coefficient of the silicon carbide material, parasitic absorption can be reduced, effectively increasing the short-circuit current density. Further, the doped silicon carbide layer is composed of at least one doped silicon carbide film with different refractive indices, and the refractive index of each doped silicon carbide film decreases sequentially from the silicon substrate 10 outwards. In this way, a refractive index gradient can be formed to achieve the effect of gradient extinction. Furthermore, the doped silicon carbide layer in the second doping layer 113 includes a doped hydrogenated silicon carbide layer, and the conductivity of the doped hydrogenated silicon carbide layer is greater than 0.01 S·cm and the thickness is greater than 10 nm. In this way, the conductivity requirements of the second doping layer 113 can be met, and it has lower parasitic absorption, increasing the short-circuit current.

[0068] Please refer to Figure 4 , optionally, the doping polarities of the first doping layer 111 and the second doping layer 113 are the same; the second passivation contact region 12 further includes a fourth doping layer 121 disposed between the silicon substrate 10 and the second passivation layer 122, and the doping polarities of the fourth doping layer 121 and the third doping layer 123 are the same. In this way, effective field passivation can be formed and the contact resistance can be reduced.

[0069] It can be understood that, as described above, the doping polarities of the second doping layer 113 and the third doping layer 123 are the same, so the doping polarities of the first doping layer 111, the second doping layer 113, the third doping layer 123, and the fourth doping layer 121 are all the same. That is: the doping polarities of the first doping layer 111, the second doping layer 113, the third doping layer 123, and the fourth doping layer 121 are all N-type; or, the doping polarities of the first doping layer 111, the second doping layer 113, the third doping layer 123, and the fourth doping layer 121 are all P-type.

[0070] Please refer to Figure 5 , optionally, the second passivation contact region 12 further includes a fourth doping layer 121 disposed between the silicon substrate 10 and the second passivation layer 122, and the doping concentration of the first doping layer 111 is greater than or equal to the doping concentration of the fourth doping layer 121. In this way, the carrier transport can be increased, which is beneficial to improving the photoelectric conversion efficiency.

[0071] Specifically, the peak doping concentration of the first doping layer 111 ranges from 10 17 / cm 3 to 10 20 / cm 3 , and the peak doping concentration of the fourth doping layer 121 ranges from 10 17 / cm 3 to 10 20 / cm 3 .

[0072] Please refer to Figure 5 , optionally, the doping concentration of the fourth doping layer 121 is less than that of the third doping layer 123. Thus, by lightly doping the fourth doping layer 121, the lateral carrier transport can be improved.

[0073] Please refer to Figure 5 , optionally, the second passivation layer 122 is a porous structure, and the fourth doping layer 121 and / or the third doping layer 123 are / is present in the hole region of the second passivation layer 122, and the third doping layer 123 is connected to the fourth doping layer 121 through the doped hole region. Specifically, the third doping layer 123 is connected to the silicon substrate 10 through the doped hole region and the fourth doping layer 121. Optionally, the second passivation layer 122 is a porous structure, and the average pore diameter of the holes in the second passivation layer 122 is less than 1000 nm. Optionally, the second passivation layer 122 is a porous structure, and the second passivation layer 122 is formed by means of thermal diffusion shock. Optionally, the second passivation layer 122 is a porous structure, and the holes in the second passivation layer 122 are scattered and sparse on the second passivation layer 122. Optionally, the second passivation layer 122 is a porous structure, and the ratio of the area of the hole region of the second passivation layer 122 to the overall area of the second passivation layer 122 is less than 20%. Optionally, the second passivation layer 122 is a porous structure, and the second passivation contact region 12 further includes a fourth doping layer 121 disposed between the silicon substrate 10 and the second passivation layer 122, and the fourth doping layer 121 is discretely and locally distributed in the hole regions of the second passivation layer 122. Optionally, the second passivation layer 122 is a porous structure, and the second passivation contact region 12 further includes a fourth doping layer 121 disposed between the silicon substrate 10 and the second passivation layer 122, and the fourth doping layer 121 is completely continuously provided between the silicon substrate 10 and the second passivation layer 122. Optionally, the first passivation layer 112 is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer. Optionally, the second passivation layer 122 is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer. Optionally, the oxide layer is composed of one or more layers of a silicon oxide layer and an aluminum oxide layer.

[0074] Please note that for the explanation and description of this part, reference can be made to the previous part regarding the first passivation layer 112 being a porous structure. To avoid redundancy, it will not be elaborated here.

[0075] Please refer to Figure 2 , optionally, the thickness range of the third doped layer 123 is 0 nm - 500 nm. For example, it can be 0 nm, 0.01 nm, 0.8 nm, 1 nm, 5 nm, 10 nm, 35 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 198 nm, 200 nm, 250 nm, 300 nm, 450 nm, 500 nm. In this way, parasitic absorption can be reduced and lateral carrier transport can be ensured. It can be understood that when the thickness of the third doped layer 123 is 0, that is to say, the third doped layer 123 can be omitted.

[0076] Furthermore, the thickness range of the third doped layer 123 is 0 nm - 120 nm. For example, it can be 0 nm, 0.01 nm, 0.8 nm, 1 nm, 5 nm, 10 nm, 35 nm, 50 nm, 80 nm, 100 nm, 120 nm. In this way, minimizing parasitic absorption and ensuring lateral carrier transport can be balanced. It can be understood that when the thickness of the third doped layer 123 is 0, the parasitic absorption is the least; when the thickness of the third doped layer 123 is 120 nm, lateral transport can be ensured, and at the same time, the parasitic absorption is also less than that at the second doped layer 113.

[0077] Preferably, the thickness range of the third doped layer 123 is 20 nm - 120 nm. For example, it can be 20 nm, 22 nm, 35 nm, 50 nm, 80 nm, 100 nm, 120 nm. In this way, under the condition of balancing parasitic absorption and ensuring lateral carrier transport, the overall performance of the battery is the best.

[0078] Please refer to Figure 2 , optionally, the third passivation layer 124 includes one or more of an alumina layer, a silicon nitride layer, a silicon oxynitride layer, a silicon carbide layer, an amorphous silicon layer, and a silicon oxide layer. In this way, antireflection can be achieved and the surface recombination rate can be reduced. Further, the third passivation layer 124 can be composed of at least one passivation film with different refractive indices, and the refractive index of each passivation film decreases sequentially from the silicon substrate 10 outwards.

[0079] Optionally, the selective passivation contact structure 100 may include a protective layer disposed in the second passivation contact region 12, and the distance from the top surface of the protective layer to the silicon substrate 10 is greater than the distance from the top surface of the second doped layer to the silicon substrate. In this way, the second doped layer can be protected by the protective layer to avoid being scratched. Specifically, the protective layer may be disposed between the third passivation layer 124 and the third doped layer, or on the side of the third passivation layer 124 away from the third doped layer 123. Specifically, the protective layer may include an insulating layer. In this way, leakage can be avoided.

[0080] For the back structure 1001 of the double-sided back-contact solar cell according to the embodiment of the present application, since the thickness of the third doped layer 123 is small, the parasitic absorption in the second passivation contact region 12 can be reduced and the current can be increased. At the same time, since the thickness of the second doped layer 113 is large, the conductive layer can be prevented from burning through the second doped layer 113. At the same time, since both the P-type contact region structure 101 and the N-type contact region structure 102 are disposed on the back surface of the silicon substrate 10, the grid line shielding on the front surface of the silicon substrate 10 can be reduced. In this way, the photoelectric conversion efficiency of the solar cell can be maximized.

[0081] Example 2

[0082] Please refer to Figure 6 , Embodiment II of the present application further provides a double-sided back-contact solar cell 1000, which includes the back structure 1001 of the double-sided back-contact solar cell in Embodiment I.

[0083] For the double-sided back-contact solar cell 1000 according to the embodiment of the present application, since the thickness of the third doped layer 123 is small, the parasitic absorption in the second passivation contact region 12 can be reduced and the short-circuit current can be increased. At the same time, since the thickness of the second doped layer 113 is large, the first conductive layer 30 can be prevented from burning through the second doped layer 113, and the open-circuit voltage can be increased. At the same time, excellent interface passivation performance and low contact resistance can be achieved. At the same time, since both the P-type contact region structure 101 and the N-type contact region structure 102 are disposed on the back surface of the silicon substrate 10, the grid line shielding on the front surface of the silicon substrate 10 can be reduced. In this way, the photoelectric conversion efficiency of the solar cell can be maximized.

[0084] Other explanations and descriptions regarding this part can be referred to the previous text. To avoid redundancy, they will not be elaborated here.

[0085] Optionally, the P-type contact region structure 101 is a selective passivation contact structure 100, and the double-sided back-contact solar cell 1000 includes a first conductive layer 30, and the first conductive layer 30 is connected to the second doped layer 113.

[0086] Specifically, the first conductive layer 30 is a fine grid. In this way, restricting the selective passivation contact structure 100 under the fine grid can reduce the blocked sunlight and improve the photoelectric conversion efficiency. It can be understood that in other embodiments, the first conductive layer 30 can also be a main grid.

[0087] Optionally, the first conductive layer 30 can include a transparent conductive oxide (TCO). In this way, the TCO can effectively collect the current of the double-sided back-contact solar cell 1000, ensuring the normal operation of the double-sided back-contact solar cell 1000. Moreover, the TCO has high transparency and can reduce reflection, which can reduce the loss of sunlight. In this way, it is beneficial to improve the photoelectric conversion efficiency.

[0088] Further, the TCO includes one or more of fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), aluminum-doped tin oxide (ATO), indium-doped gallium oxide (IGO). It can be understood that the first conductive layer 30 can also include metals such as silver, gold, aluminum, copper, molybdenum, tungsten, nickel, magnesium, tin, tantalum, etc. The first conductive layer 30 can also include a TCO and a metal electrode.

[0089] Optionally, the N-type contact region structure 102 is a selective passivation contact structure 100, and the double-sided back-contact solar cell 1000 includes a second conductive layer 50, and the second conductive layer 50 is connected to the second doping layer 113.

[0090] Please note that the explanations and descriptions regarding the second conductive layer 50 can be referred to those of the first conductive layer 30. To avoid redundancy, they are not elaborated here.

[0091] Please refer to Figure 6 , optionally, a non-doped region 200 is provided between the P-type contact region structure 101 and the N-type contact region structure 102.

[0092] It can be understood that the non-doped region 200 refers to the region where no doping is performed on the silicon substrate 10. In this way, the adjacent P-type contact region structure 101 and N-type contact region structure 102 can be spaced apart through the non-doped region 200, without the need to provide grooves, bosses, trenches, or insulating parts between the two adjacent P-type contact region structures 101 and N-type contact region structures 102, which is beneficial to improving the production efficiency.

[0093] Further, multiple selective passivation contact structures 100 can be formed by high-temperature diffusion. Before the high-temperature diffusion, a surface passivation layer such as a silicon nitride layer can be prepared in the non-doped region 200, which can improve the minority carrier lifetime.

[0094] Specifically, please refer to Figure 7, a plurality of grooves are spaced on the back surface of the silicon substrate 10, the P-type contact region structure 101 and the N-type contact region structure 102 are arranged in each groove, and the region between two adjacent grooves forms a boss. In this way, the spacing between the P-type contact region structure 101 and the N-type contact region structure 102 arranged in two adjacent grooves can be realized. Further, the grooves can be formed by a combination of laser ablation or through a mask (such as a hard mask, a silicon oxide mask, a silicon nitride mask, a photoresist mask, etc.) and wet / dry etching. Further, the grooves can be rectangular, arc-shaped, trapezoidal, or square. The shapes of the plurality of grooves can be all the same, all different, or partially the same and partially different.

[0095] In other embodiments, please refer to Figure 8 , a plurality of grooves are spaced on the back surface of the silicon substrate 10, the region between two adjacent grooves forms a boss, and one of the two adjacent P-type contact region structures 101 and N-type contact region structures 102 is arranged in the groove, and the other is arranged on the boss. In this way, through the height difference between the groove and the boss, the spacing between the two adjacent P-type contact region structures 101 and N-type contact region structures 102 is realized.

[0096] In other embodiments, please refer to Figure 9 , a plurality of grooves are spaced on the back surface of the silicon substrate 10, the region between two adjacent grooves forms a boss, and the P-type contact region structure 101 and the N-type contact region structure 102 are arranged on each boss. In this way, through the grooves between the bosses, the spacing between the adjacent P-type contact region structures 101 and N-type contact region structures 102 is realized. [[ID=D12]]

[0097] In other embodiments, a groove can be arranged between the adjacent P-type contact region structure 101 and the N-type contact region structure 102. In this way, the spacing between the adjacent P-type contact region structure 101 and the N-type contact region structure 102 is realized through the groove.

[0098] In other embodiments, an insulating member can be arranged between the adjacent P-type contact region structure 101 and the N-type contact region structure 102. In this way, the spacing between the adjacent P-type contact region structure 101 and the N-type contact region structure 102 is realized through the insulating member. Further, the insulating member includes at least one of EPE (pearl cotton), EVA (ethylene-vinyl acetate copolymer), and PET (polyethylene glycol terephthalate). In this way, it can play a buffering role while insulating, which is beneficial to protecting the battery.

[0099] Specifically, the number of the back structures 1001 may be 2, 3, 4, 5 or other values, and the specific number of the back structures 1001 is not limited herein.

[0100] Specifically, please refer to Figure 6 , in this embodiment, the orthographic projection of the selective passivation contact structure 100 on the silicon substrate 10 covers and exceeds the orthographic projection of the first conductive layer 30 on the silicon substrate 10. In other embodiments, it may also be that the orthographic projection of the selective passivation contact structure 100 on the silicon substrate 10 completely overlaps with the orthographic projection of the first conductive layer 30 on the silicon substrate 10; it may also be that the orthographic projection of the selective passivation contact structure 100 on the silicon substrate 10 is located within the orthographic projection of the first conductive layer 30 on the silicon substrate 10. The specific positional relationship between the selective passivation contact structure 100 and the first conductive layer 30 is not limited herein. In addition, the relationships between multiple selective passivation contact structures 100 and the corresponding first conductive layers 30 may be all the same, all different, or partially the same.

[0101] Specifically, please refer to Figure 6 , in this embodiment, the lengths, widths, and thicknesses of multiple selective passivation contact structures 100 are all the same, the lengths, widths, and thicknesses of the first doping layers 111 in multiple selective passivation contact structures 100 are all the same, the lengths, widths, and thicknesses of the first passivation layers 112 in multiple selective passivation contact structures 100 are all the same, the lengths, widths, and thicknesses of the second doping layers 113 in multiple selective passivation contact structures 100 are all the same, the lengths, widths, and thicknesses of the second passivation layers 122 in multiple selective passivation contact structures 100 are all the same, the lengths, widths, and thicknesses of the third doping layers 123 in multiple selective passivation contact structures 100 are all the same, and the lengths, widths, and thicknesses of the third passivation layers 124 in multiple selective passivation contact structures 100 are all the same. That is, the sizes of multiple selective passivation contact structures 100 are the same, and the sizes of the internal structures of multiple selective passivation contacts correspond to each other.

[0102] In other embodiments, the lengths of multiple selective passivation contact structures 100 may be all different or partially the same; the widths of multiple selective passivation contact structures 100 may be all different or partially the same; the thicknesses of multiple selective passivation contact structures 100 may be all different or partially the same. Similarly, the sizes of the internal structures of multiple selective passivation contact structures 100 may also correspond to each other, be all different, or partially correspond to each other. The specific size relationship of multiple selective passivation contact structures 100 is not limited herein.

[0103] In this embodiment, the distance between two adjacent selective passivation contact structures 100 is 0.1 mm - 10 mm. For example, it is 0.1 mm, 0.11 mm, 0.15 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 8 mm, 10 mm.

[0104] Please refer to Figure 6 , optionally, the P-type contact region structure 101 is a selective passivation contact structure 100, and the width of the first conductive layer 30 is greater than the width of the second doped layer 113. In this way, the thickness of the second doped layer 113 in contact with the first conductive layer 30 is larger, having a lower contact resistance, and can serve as an effective barrier layer to prevent the part of the first conductive layer 30 in contact with the second doped layer 113 from contacting the silicon substrate 10, so that the metal contact recombination is lower. At the same time, the third doped layer 123 and the third passivation layer 124 can serve as effective barrier layers to prevent the part of the first conductive layer 30 not in contact with the second doped layer 113 from contacting the silicon substrate 10, so that the recombination is lower.

[0105] Specifically, the first conductive layer 30 can be fabricated by an electroplating process. In this way, the adhesion of the first conductive layer 30 is stronger, the contact with the second doped layer 113 is closer, and it is not easy to fall off.

[0106] It can be understood that when the N-type contact region structure 102 is a selective passivation contact structure 100, the width of the second conductive layer 50 is greater than the width of the second doped layer 113. The explanation and description of this part can refer to the foregoing, and for the sake of avoiding redundancy, it will not be elaborated here.

[0107] Please refer to Figure 10 , optionally, a fourth passivation layer 114 is provided on the second doped layer 113, and the fourth passivation layer 114 is formed with an opening 1141, and the first conductive layer 30 passes through the opening 1141 to be connected to the second doped layer 113. In this way, leakage can be prevented. At the same time, the width of the first conductive layer 30 is smaller, which can reduce the material consumption of the first conductive layer 30 and also reduce the light shielding area, which is beneficial to improving the photoelectric conversion efficiency.

[0108] Specifically, the first conductive layer 30 can be fabricated on the fourth passivation layer 114 by a screen printing process. In this way, the first conductive layer 30 can directly burn through the fourth passivation layer 114 to contact the second doped layer 113, which is beneficial to improving the production efficiency. At the same time, the width of the second doped layer 113 can provide a tolerance for the alignment of screen printing, which is beneficial to improving the yield of the battery.

[0109] Specifically, the fourth passivation layer 114 includes one or more of an alumina layer, a silicon nitride layer, a silicon oxynitride layer, a silicon carbide layer, an amorphous silicon layer, and a silicon oxide layer.

[0110] Specifically, the fourth passivation layer 114 may be composed of at least one passivation film with different refractive indices, and the refractive index of each passivation film decreases sequentially from the silicon substrate 10 outward. In this way, a refractive index gradient can be formed to achieve the effect of gradient extinction.

[0111] It can be understood that when the N-type contact region structure 102 is a selective passivated contact structure 100, the second conductive layer 50 passes through the opening 1141 and is connected to the second doped layer 113. For the explanation and description of this part, reference can be made to the previous text. To avoid redundancy, it will not be elaborated here.

[0112] Please refer to Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 and Figure 10 , optionally, the double-sided back-contact solar cell 1000 may further include a first surface passivation layer 60, and the first surface passivation layer 60 is disposed between the plurality of first conductive layers 30 and the plurality of second conductive layers 50. In this way, antireflection can be achieved and the surface recombination rate can be reduced.

[0113] Specifically, in the examples of Figure 6 、 Figure 7 、 Figure 8 and Figure 9 , the orthographic projection of the first conductive layer 30 on the silicon substrate 10 covers and exceeds the orthographic projection of the second doped layer 113 on the silicon substrate 10, and the orthographic projection of the second conductive layer 50 on the silicon substrate 10 completely covers the orthographic projection of the P-type contact region structure 101 on the silicon substrate 10.

[0114] The orthographic projection of the first surface passivation layer 60 on the silicon substrate 10 is located outside the orthographic projections of the second conductive layer 50 and the second doped layer 113 on the silicon substrate 10, and the orthographic projections of the first surface passivation layer 60, the second conductive layer 50, and the second doped layer 113 on the silicon substrate 10 cover the entire area of the silicon substrate 10.

[0115] In this way, except for the conductive contact regions of the first conductive layer 30 and the second conductive layer 50, the entire back surface of the battery is covered by the first surface passivation layer 60, which can fully avoid leakage and reduce the surface recombination rate. It should be noted that the conductive contact region of the first conductive layer 30 refers to the region where the first conductive layer 30 contacts the second doped layer 113. The conductive contact region of the second conductive layer 50 refers to the region where the second conductive layer 50 contacts the P-type contact region structure 101.

[0116] It can be understood that the third passivation layer 124 is a partial structure of the first surface passivation layer 60 and covers the third doping layer 123. The third passivation layer 124 and the part of the first surface passivation layer 60 other than the third passivation layer 124 may be made of the same material or different materials. In this embodiment, the third passivation layer 124 and the part of the first surface passivation layer 60 other than the third passivation layer 124 are made of the same material simultaneously. In this way, the production efficiency can be improved.

[0117] Please note that the first surface passivation layer 60 fills the gaps between the first conductive layer 30, the second doping layer 113, and the third doping layer 123. In this way, leakage can be avoided.

[0118] Specifically, the first surface passivation layer 60 includes one or more of an alumina layer, a silicon nitride layer, a silicon oxynitride layer, a silicon carbide layer, an amorphous silicon layer, and a silicon oxide layer.

[0119] Specifically, the first surface passivation layer 60 may be composed of at least one passivation film with different refractive indices, and the refractive indices of the respective passivation films decrease sequentially from the silicon substrate 10 outwards. In this way, a refractive index gradient can be formed to achieve the effect of gradient extinction.

[0120] Specifically, in Figure 10 the example, the orthographic projection of the first conductive layer 30 on the silicon substrate 10 is located within the orthographic projection of the second doping layer 113 on the silicon substrate 10, and the orthographic projection of the second conductive layer 50 on the silicon substrate 10 is located within the orthographic projection of the P-type contact region structure 101 on the silicon substrate 10.

[0121] The orthographic projection of the first surface passivation layer 60 on the silicon substrate 10 is located outside the orthographic projections of the first conductive layer 30 and the second conductive layer 50 on the silicon substrate 10, and the orthographic projections of the first surface passivation layer 60, the first conductive layer 30, and the second conductive layer 50 on the silicon substrate 10 cover the entire area of the silicon substrate 10.

[0122] In this way, except for the conductive contact regions of the first conductive layer 30 and the second conductive layer 50, the entire area is covered by the first surface passivation layer 60, which can fully avoid leakage and reduce the surface recombination rate.

[0123] It can be understood that the third passivation layer 124 is a partial structure of the first surface passivation layer 60 and covers the third doped layer 123. The fourth passivation layer 114 is a partial structure of the first surface passivation layer 60 and covers the region of the second doped layer 113 that is not in contact with the first conductive layer 30. The third passivation layer 124, the fourth passivation layer 114, and the portion of the first surface passivation layer 60 other than the third passivation layer 124 and the fourth passivation layer 114 may have the same material or different materials. In this embodiment, the third passivation layer 124, the fourth passivation layer 114, and the portion of the first surface passivation layer 60 other than the third passivation layer 124 and the fourth passivation layer 114 are made of the same material simultaneously. In this way, the production efficiency can be improved.

[0124] Please refer to Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 , optionally, the double-sided back-contact solar cell 1000 may further include a second surface passivation layer 70, and the second surface passivation layer 70 is disposed on the front surface of the silicon substrate 10. In this way, antireflection can be achieved and the surface recombination rate can be reduced.

[0125] Specifically, the second surface passivation layer 70 includes one or more of an alumina layer, a silicon nitride layer, a silicon oxynitride layer, a silicon carbide layer, an amorphous silicon layer, and a silicon oxide layer.

[0126] Specifically, the second surface passivation layer 70 may be composed of at least one passivation film with different refractive indices, and the refractive indices of the respective passivation films decrease sequentially from the silicon substrate 10 outwards. In this way, a refractive index gradient can be formed to achieve the effect of gradient extinction.

[0127] Specifically, when the structure of the second surface passivation layer 70 is the same as that of the first surface passivation layer 60, the front and back surfaces of the silicon substrate 10 can be prepared by the same process respectively. In this way, it is beneficial to improve the production efficiency. It can be understood that the structure of the second surface passivation layer 70 may also be different from that of the first surface passivation layer.

[0128] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. The back structure of a double-sided back-contact solar cell, characterized in that, It includes a P-type contact region structure and an N-type contact region structure alternately disposed on the back surface of the silicon substrate of the double-sided back-contact solar cell. The P-type contact region structure is connected to the first conductive layer of the double-sided back-contact solar cell, and the N-type contact region structure is connected to the second conductive layer of the double-sided back-contact solar cell; at least one of the P-type contact region structure and the N-type contact region structure is a selective passivation contact structure; The selective passivation contact structure includes alternately arranged first passivation contact regions and second passivation contact regions; the first passivation contact region includes a first doped layer, a first passivation layer, and a second doped layer sequentially stacked on the silicon substrate; the second passivation contact region includes a second passivation layer, a third doped layer, and a third passivation layer sequentially stacked on the silicon substrate; the thickness of the second doped layer is greater than the thickness of the third doped layer, and the second doped layer and the third doped layer have the same doping polarity; The doping concentration of the first doped layer is less than the doping concentration of the second doped layer, the thickness range of the first doped layer is 500nm - 2000nm, and the thickness range of the second doped layer is 100nm - 450nm; The second passivation contact region further includes a fourth doped layer disposed between the silicon substrate and the second passivation layer, and the doping concentration of the first doped layer is greater than or equal to the doping concentration of the fourth doped layer.

2. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first doped layer and the second doped layer have the same doping polarity; the second passivation contact region further includes a fourth doped layer disposed between the silicon substrate and the second passivation layer, and the fourth doped layer and the third doped layer have the same doping polarity.

3. The back structure of the double-sided back-contact solar cell according to claim 2, characterized in that The second passivation layer is a porous structure, and the fourth doped layer and / or the third doped layer are / is present in the pore region of the second passivation layer, and the third doped layer and the fourth doped layer are connected through the doped pore region.

4. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is a porous structure, and the first doped layer and / or the second doped layer are / is present in the pore region of the first passivation layer, and the second doped layer and the first doped layer are connected through the doped pore region.

5. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is a porous structure, and the average pore diameter of the pores of the first passivation layer is less than 1000nm; And / or, the second passivation layer is a porous structure, and the average pore diameter of the pores of the second passivation layer is less than 1000nm.

6. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is a porous structure, and the pores of the first passivation layer are formed by means of thermal diffusion shock; And / or, the second passivation layer is a porous structure, and the pores of the second passivation layer are formed by means of thermal diffusion shock.

7. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is a porous structure, and the ratio of the area of the pore region of the first passivation layer to the overall area of the first passivation layer is less than 20%; And / or, the second passivation layer is a porous structure, and the ratio of the area of the pore region of the second passivation layer to the overall area of the second passivation layer is less than 20%.

8. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is a porous structure, and the first doped layer is discretely and locally distributed in each pore region of the first passivation layer; And / or, the second passivation layer is a porous structure, and the second passivation contact region further includes a fourth doped layer disposed between the silicon substrate and the second passivation layer, and the fourth doped layer is discretely and locally distributed in each hole region of the second passivation layer.

9. The back structure of the double-sided back-contact solar cell according to claim 1, wherein, The first passivation layer is a porous structure, and the first doped layer is disposed between the silicon substrate and the first passivation layer in a completely continuous manner; And / or, the second passivation layer is a porous structure, and the second passivation contact region further includes a fourth doped layer disposed between the silicon substrate and the second passivation layer, and the fourth doped layer is disposed between the silicon substrate and the second passivation layer in a completely continuous manner.

10. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The first passivation layer is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer; And / or, the second passivation layer is one or a combination of an oxide layer, a nitride layer, a oxynitride layer, a silicon carbide layer, and an amorphous silicon layer.

11. The back structure of the double-sided back-contact solar cell according to claim 10, characterized in that, The oxide layer is composed of one or more layers of a silicon oxide layer and an aluminum oxide layer.

12. The back structure of the double-sided back-contact solar cell according to claim 1, characterized in that, The thickness of the third doped layer is 0 - 500 nm.

13. A double-sided back-contact solar cell, characterized in that, It includes the back structure of the double-sided back-contact solar cell according to any one of claims 1 - 12.

14. The double-sided back-contact solar cell according to claim 13, wherein, The P-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a first conductive layer, the first conductive layer is connected to the second doped layer, and the width of the first conductive layer is greater than the width of the second doped layer; And / or, the N-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a second conductive layer, the second conductive layer is connected to the second doped layer, and the width of the second conductive layer is greater than the width of the second doped layer.

15. The bifacial back-contact solar cell according to claim 13, characterized in that, The P-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a first conductive layer, a fourth passivation layer is provided on the second doped layer, the fourth passivation layer is formed with an opening, and the first conductive layer passes through the opening and is connected to the second doped layer; And / or, the N-type contact region structure is a selective passivation contact structure, and the double-sided back-contact solar cell includes a second conductive layer, a fourth passivation layer is provided on the second doped layer, the fourth passivation layer is formed with an opening, and the second conductive layer passes through the opening and is connected to the second doped layer.

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