Back contact solar cell, cell module and photovoltaic system

Abstract

The invention is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system, the back contact solar cell comprises a silicon substrate, the back surface of the silicon substrate comprises a P-type doped region and an N-type doped region; the first interface layer is arranged in the P-type doped region and comprises at least one aluminum oxide layer, and the ratio of the number of oxygen atoms to the number of aluminum atoms of the aluminum oxide layer is 1.49-1.65; the second interface layer is arranged in the N-type doped region; the P-type doped layer is arranged on the first interface layer; and the N-type doped layer is arranged on the second interface layer. According to the back contact solar cell provided by the invention, the matching of a good chemical passivation effect and a good field passivation effect of the first interface layer of the P-type doped region can be realized, and the comprehensive passivation performance of the first interface layer of the P-type doped region can be improved, so that the cell efficiency is improved.

Description

Technical Field

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

[0002] Solar cells, also known as photovoltaic cells, are devices that use the photovoltaic effect to directly convert light energy into direct current. Back-contact solar cells, with both positive and negative electrodes located on the back of the cell, offer a significant improvement in conversion efficiency compared to bifacial solar cells, as the front surface of the cell is shielded by metal grid lines, eliminating the optical losses associated with such obstructions.

[0003] In the related art, the back side of the silicon substrate of the back-contact solar cell includes P-type doped regions and N-type doped regions arranged alternately at intervals. The P-type doped region is usually provided with an interface layer, a P-type doped layer, and a metal electrode in sequence; the N-type doped region is usually provided with an interface layer, an N-type doped layer, and a metal electrode in sequence; however, the interface layers of the P-type doped region and the N-type doped region are usually provided with silicon oxide layers, and the P-type doped region uses a silicon oxide layer as the interface layer. Although the silicon oxide layer has an extremely low interface state density and has good chemical passivation ability, the silicon oxide layer has a positive charge inside and repels holes, and has a certain negative effect on the passivation of the P-type doped region, which weakens the extraction rate of holes in the P-type doped region, weakens the field passivation of the P-type doped region, and makes the carrier extraction effect poor, resulting in poor battery efficiency. Summary of the Invention

[0004] The present invention provides a back-contact solar cell, aiming to solve the problem in the prior art of back-contact solar cells that the field passivation effect of the P-type doped region is poor, resulting in poor cell efficiency.

[0005] The present invention is implemented by providing a back-contact solar cell, comprising:

[0006] A silicon substrate, wherein the back surface of the silicon substrate comprises a P-type doping region and an N-type doping region;

[0007] A first interface layer provided in the P-type doped region, the first interface layer comprising at least one aluminum oxide layer, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer is 1.49 to 1.65;

[0008] a second interface layer provided in the N-type doping region;

[0009] a P-type doped layer disposed on the first interface layer; and

[0010] An N-type doped layer is provided on the second interface layer.

[0011] Preferably, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer is 1.51 to 1.58.

[0012] Preferably, the second interface layer includes at least one silicon oxide layer.

[0013] Preferably, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer is 1.92 to 2.10.

[0014] Preferably, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer is 1.96 to 2.02.

[0015] Preferably, the first interface layer further includes a first silicon oxide layer, and the first silicon oxide layer and the aluminum oxide layer are sequentially stacked on the P-type doped region.

[0016] Preferably, the first interface layer further includes a second silicon oxide layer, and the first silicon oxide layer, the aluminum oxide layer, and the second silicon oxide layer are sequentially stacked on the P-type doped region.

[0017] Preferably, the total thickness of the first silicon oxide layer, the aluminum oxide layer, and the second silicon oxide layer is 1 to 5 nanometers.

[0018] Preferably, the thickness of the aluminum oxide layer is 0.2 to 4.5 nanometers, the thickness of the first silicon oxide layer is 0.2 to 3 nanometers, and the thickness of the second silicon oxide layer is 0.3 to 2.6 nanometers.

[0019] Preferably, the first silicon oxide layer is amorphous, and the ratio of the number of oxygen atoms to silicon atoms in the first silicon oxide layer is greater than the ratio of the number of oxygen atoms to silicon atoms in the second silicon oxide layer.

[0020] Preferably, the silicon substrate includes an aluminum-doped region less than 50 nanometers away from the surface of the first interface layer, and the aluminum atomic concentration of the aluminum-doped region is greater than 1×10 15 atoms / cm 3 .

[0021] Preferably, the hydrogen concentration of the aluminum oxide layer is less than 10%.

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

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

[0024] A back-contact solar cell provided by the present invention sets the first interface layer of the P-type doping region to include at least one aluminum oxide layer, and controls the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer to be 1.49-1.65. Compared with the back-contact solar cell in which the P-type doping region uses a silicon oxide layer as the interface layer, the P-type doping region uses at least one aluminum oxide layer as the interface layer, which can enhance the field passivation effect of the P-type doping region, improve the hole extraction capability, and enhance the passivation effect of the P-type doping region, thereby enhancing the cell efficiency of the back-contact solar cell. Moreover, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer is controlled to be 1.49-1.65. Within this reasonable range, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer can achieve a low interface state density of the aluminum oxide layer to form a good chemical passivation effect, and at the same time, achieve a stable fixed negative charge density of the aluminum oxide layer to achieve a good field passivation effect, thereby achieving the best match between the good chemical passivation effect and the good field passivation effect of the first interface layer of the P-type doping region, and can well enhance the comprehensive passivation performance of the first interface layer of the P-type doping region, thereby enhancing the cell efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic cross-sectional view of a back-contact solar cell provided by an embodiment of the present invention;

[0026] Figure 2 Another cross-sectional schematic diagram of a back-contact solar cell provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Examples of 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 are not to 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.

[0028] In the description of the present invention, it should be understood that the terms "upper", "lower", "back", "front", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0030] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art will recognize the application of other processes and / or the use scenarios of other materials.

[0031] A back-contact solar cell provided by an embodiment of the present invention sets the first interface layer of the P-type doping region to include at least one aluminum oxide layer, and controls the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer to be 1.49 to 1.65. Compared with the P-type doping region using a silicon oxide layer as the interface layer, the P-type doping region of the back-contact solar cell of the present invention uses at least one aluminum oxide layer as the interface layer, which can improve the field passivation effect of the P-type doping region and improve the battery efficiency of the back-contact solar cell; moreover, controlling the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer to be 1.49 to 1.65 can achieve both good chemical passivation effect of the aluminum oxide layer and good field passivation effect of the aluminum oxide layer, taking into account the dual passivation performance of the aluminum oxide layer, and achieving the best match between the good chemical passivation effect and the good field passivation effect of the first interface layer of the P-type doping region, which can well improve the comprehensive passivation performance of the first interface layer of the P-type doping region, thereby improving the battery efficiency.

[0032] Please refer to Figure 1-Figure 2 , an embodiment of the present invention provides a back-contact solar cell, comprising:

[0033] A silicon substrate 1, the back side of the silicon substrate 1 including a P-type doping region 11 and an N-type doping region 12;

[0034] A first interface layer 2 provided in the P-type doping region 11, the first interface layer 2 comprising at least one aluminum oxide layer 21, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 is 1.49 to 1.65;

[0035] A second interface layer 3 provided in the N-type doping region 12;

[0036] a P-type doped layer 4 disposed on the first interface layer 2; and

[0037] An N-type doped layer 5 is provided on the second interface layer 3 .

[0038] In the embodiment of the present invention, the back side of the silicon substrate 1 is the side facing away from sunlight when the back-contact solar cell is in operation, and the front side of the silicon substrate 1 is the side facing sunlight when the back-contact solar cell is in operation. There are multiple P-type doping regions 11 and N-type doping regions 12, and the P-type doping regions 11 and N-type doping regions 12 are alternately arranged on the back side of the silicon substrate 1. The P-type doping region 11 is the region where the P-type doping layer 4 is arranged, and the N-type doping region 12 is the region where the N-type doping layer 5 is arranged. Optionally, a spacer 13 is provided between the P-type doping region 11 and the N-type doping region 12 to achieve physical isolation between the P-type doping layer 4 and the N-type doping layer 5.

[0039] In an embodiment of the present invention, the doping polarities of the P-type doped layer 4 and the N-type doped layer 5 are opposite. The P-type doped layer 4 is one or a combination of a polycrystalline silicon layer, a microcrystalline silicon layer, or an amorphous silicon layer containing a P-type dopant, and the N-type doped layer 5 is one or a combination of a polycrystalline silicon layer, a microcrystalline silicon layer, or an amorphous silicon layer containing an N-type dopant. The P-type dopant is a Group IIIA element dopant, and the N-type dopant is a Group VA element dopant. For example, the P-type dopant may be a boron dopant, and the N-type dopant may be a phosphorus dopant.

[0040] In the embodiment of the present invention, the first interface layer 2 is a film structure located between the silicon substrate 1 and the P-type doped layer 4, and the second interface layer 3 is a film structure located between the silicon substrate 1 and the N-type doped layer 5. Both the first interface layer 2 and the second interface layer 3 can be a single layer structure or a stacked layer structure. The first interface layer 2 is provided on the P-type doped region 11 and is used to passivate the P-type doped region 11 of the silicon substrate 1 and selectively transport holes. The second interface layer 3 is provided on the N-type doped region 12 and is used to passivate the N-type doped region 12 of the silicon substrate 1 and selectively transport electrons.

[0041] In an embodiment of the present invention, a back-contact solar cell is provided by setting the first interface layer 2 of the P-type doping region 11 to include at least one aluminum oxide layer 21, and controlling the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 to be 1.49 to 1.65; on the one hand, compared with the related art, in which the interface layer of the P-type doping region of the back-contact solar cell adopts a silicon oxide layer, the P-type doping region 11 of the present invention adopts the aluminum oxide layer 21 as the interface layer. Compared with the P-type doping region 11 adopting a single silicon oxide layer as the interface layer, the aluminum oxide layer 21 has the advantage of having a higher fixed negative charge density, which can improve the field passivation effect of the P-type doping region 11, thereby improving The battery efficiency of the back-contact solar cell is improved; moreover, by controlling the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 to be 1.49 to 1.65, the low interface state density of the aluminum oxide layer 21 can be achieved to form a good chemical passivation effect, and at the same time, a stable fixed negative charge density of the aluminum oxide layer 21 can be achieved to achieve a good field passivation effect, taking into account the dual passivation performance of the aluminum oxide layer 21, and achieving the best match between the good chemical passivation effect and the good field passivation effect of the first interface layer 2 of the P-type doping region 11, which can greatly improve the comprehensive passivation performance of the first interface layer 2 of the P-type doping region 11, thereby improving the carrier extraction effect, and then improving the battery efficiency.

[0042] In the embodiment of the present invention, the first interface layer 2 and the second interface layer 3 may both be single-layer structures or multi-layer structures, or one of the first interface layer 2 and the second interface layer 3 may be a single-layer structure and the other a multi-layer structure.

[0043] In the embodiment of the present invention, the first interface layer 2 may include only one aluminum oxide layer 21, or the first interface layer 2 may include multiple aluminum oxide layers 21. Of course, the first interface layer 2 may also include film layers of other materials, and the first interface layer 2 may be a stacked structure of the aluminum oxide layer 21 and film layers of other materials. For example, the first interface layer 2 may be a stacked structure of at least two of the following: an aluminum oxide layer 21, a silicon oxide layer, a silicon oxynitride layer, and a silicon carbide layer.

[0044] In the embodiment of the present invention, the second interface layer 3 may include only one silicon oxide layer, or may include multiple silicon oxide layers. Of course, the second interface layer 3 may also include film layers of other materials. For example, the first interface layer 2 may include a stacked structure of at least two of a silicon oxide layer, a silicon oxynitride layer, and a silicon carbide layer.

[0045] In the embodiment of the present invention, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 of the first interface layer 2 can be specifically 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.57, 1.59, 1.60, 1.61, 1.62, 1.63, or 1.65. Of course, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 of the first interface layer 2 is not limited to the above values.

[0046] As one embodiment of the present invention, the aluminum oxide in the aluminum oxide layer 21 is primarily amorphous, which further enhances the chemical and field passivation effects of the first interface layer 2 of the P-type doped region 11. Optionally, the aluminum oxide content of the aluminum oxide layer 21 is less than 45%. Furthermore, the grain size of the aluminum oxide layer 21 is less than 5 nanometers, which further enhances the chemical and field passivation effects of the first interface layer 2 of the P-type doped region 11.

[0047] As an embodiment of the present invention, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 is 1.51 to 1.58.

[0048] In this embodiment, the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 is further controlled to be 1.51 to 1.58. The ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer 21 is within this range, which can further enhance the chemical passivation effect and the field passivation effect of the aluminum oxide layer 21, further achieve the best match between the good chemical passivation effect and the good field passivation effect of the first interface layer 2, and further improve the comprehensive passivation performance of the first interface layer 2 of the P-type doping region 11, thereby enhancing the battery efficiency and achieving more optimized battery efficiency.

[0049] As an embodiment of the present invention, the second interface layer 3 includes at least one silicon oxide layer.

[0050] In this embodiment, the second interface layer 3 may include a single silicon oxide layer or multiple silicon oxide layers. Of course, the second interface layer 3 may also include film layers of other materials; for example, the second interface layer 3 may be a stacked structure of at least two of a silicon oxide layer, a silicon oxynitride layer, and a silicon carbide layer.

[0051] In this embodiment, the first interface layer 2 of the P-type doping region 11 includes an aluminum oxide layer 21, and the second interface layer 3 includes a silicon oxide layer. The P-type doping region 11 uses the aluminum oxide layer 21 as the first interface layer, and the N-type doping region 12 uses the silicon oxide layer as the interface layer, that is, the P-type doping region 11 and the N-type doping region 12 use different interface layers. Compared with the case where both the P-type doping region 11 and the N-type doping region 12 use the silicon oxide layer as the interface layer, since the P-type doping region 11 of the present invention uses the aluminum oxide layer 21 as the interface layer, it can achieve good chemical passivation effect and good field passivation effect of the P-type doping region 11, and the N-type doping region 12 uses the silicon oxide layer as the interface layer, it can achieve good chemical passivation effect and good field passivation effect of the N-type doping region 12. With this combined design, both the P-type doping region 11 and the N-type doping region 12 achieve good chemical passivation effect and good field passivation effect, which can further improve battery efficiency.

[0052] As an embodiment of the present invention, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer 3 is 1.92 to 2.10.

[0053] In this embodiment, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer 3 is controlled to be 1.92 to 2.10. The ratio of the number of oxygen atoms to the number of silicon atoms in the second interface layer 3 is within a suitable range, which is beneficial to further enhance the chemical passivation effect and field passivation effect of the second interface layer 3.

[0054] As an embodiment of the present invention, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer 3 is 1.96 to 2.02.

[0055] In this embodiment, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer 3 is controlled to be 1.96 to 2.02, and the ratio of the number of oxygen atoms to the number of silicon atoms in the second interface layer 3 is further optimized, which is beneficial to further enhance the chemical passivation effect and field passivation effect of the second interface layer 3.

[0056] As an embodiment of the present invention, the first interface layer 2 further includes a first silicon oxide layer 22 . The first silicon oxide layer 22 and the aluminum oxide layer 21 are sequentially stacked on the P-type doping region 11 .

[0057] In this embodiment, the first interface layer 2 also includes a first silicon oxide layer 22, and the first silicon oxide layer 22 is arranged between the silicon substrate 1 and the aluminum oxide layer 21. The first interface layer 2 of the P-type doped region 11 is configured to include the aluminum oxide layer 21 and the first silicon oxide layer 22. Since the interface state density of aluminum oxide is greater than the interface state density of silicon oxide, the chemical passivation of silicon oxide is better than that of aluminum oxide, and the field passivation of aluminum oxide in the P-type doped region 11 is better than the field passivation of silicon oxide in the P-type doped region 11. Therefore, the P-type doped region 11 utilizes silicon oxide with good chemical passivation superimposed on aluminum oxide with good field passivation, thereby superimposing the advantages of silicon oxide and aluminum oxide. Compared with the interface layer of the P-type doped region 11 using a single silicon oxide or a single aluminum oxide, the present invention has a better comprehensive passivation effect, thereby further improving the comprehensive passivation effect of the first interface layer 2 of the P-type doped region 11, which is conducive to further improving the battery efficiency.

[0058] As one embodiment of the present invention, the thickness of the first silicon oxide layer 22 is less than the thickness of the aluminum oxide layer 21. Since the thickness of the first silicon oxide layer 22 is thinner than that of the aluminum oxide layer 21, the negative impact of the fixed charge density of the first silicon oxide layer 22 can be further reduced, thereby further improving the passivation effect of the first interface layer 2 of the P-type doped region 11.

[0059] As an embodiment of the present invention, the first interface layer 2 further includes a second silicon oxide layer 23 . The first silicon oxide layer 22 , the aluminum oxide layer 21 , and the second silicon oxide layer 23 are sequentially stacked on the P-type doped region 11 .

[0060] In this embodiment, the first interface layer 2 also includes a second silicon oxide layer 23. The first silicon oxide layer 22, the aluminum oxide layer 21, and the second silicon oxide layer 23 are stacked in sequence on the P-type doped region 11. The first interface layer 2 utilizes the stacked structure of the first silicon oxide layer 22, the aluminum oxide layer 21, and the second silicon oxide layer 23 to further enhance the passivation effect of the P-type doped region 11.

[0061] As an embodiment of the present invention, the proportion of high-valent silicon in the first silicon oxide layer 22 is greater than the proportion of high-valent silicon in the second silicon oxide layer 23 .

[0062] The valence state of silicon in the first silicon oxide layer 22 and the second silicon oxide layer 23 may specifically include Si 4+ 、Si 3+ 、Si 2 + 、Si 1+ and Si 0 Among them, the valence state of silicon in crystalline silicon is mainly Si 0 Exists; the silicon valence state in silicon dioxide is mainly Si 4+ The high-valent silicon in the first silicon oxide layer 22 and the second silicon oxide layer 23 specifically includes Si 4+and Si 3+ The proportion of high-valent silicon in the first silicon oxide layer 22 is greater than that in the second silicon oxide layer 23. It can be understood that the Si in the first silicon oxide layer 22 4+ The proportion is greater than that of Si in the second silicon oxide layer 23 4+ The proportion of Si in the first silicon oxide layer 22 3+ The proportion is greater than that of Si in the second silicon oxide layer 23 3+ The ratio of oxygen atoms to silicon atoms in the first silicon oxide layer 22 is greater than that in the second silicon oxide layer 23, so that the silicon valence state of the first silicon oxide layer 22 is closer to that of silicon dioxide, which is beneficial to further enhance the chemical passivation effect of the first silicon oxide layer 22, thereby enhancing the passivation performance of the P-type doped region 11. As an embodiment of the present invention, the first silicon oxide layer 22 is amorphous, and the ratio of oxygen atoms to silicon atoms in the first silicon oxide layer 22 is greater than the ratio of oxygen atoms to silicon atoms in the second silicon oxide layer 23.

[0063] In this embodiment, since the first silicon oxide layer 22 is closer to the silicon substrate 1 than the second silicon oxide layer 23, the first silicon oxide layer 22 is amorphous, and the ratio of the number of oxygen atoms to silicon atoms in the first silicon oxide layer 22 is controlled to be greater than the ratio of the number of oxygen atoms to silicon atoms in the second silicon oxide layer 23, which is beneficial to reducing internal defects in the first silicon oxide layer 22 and further improving the chemical passivation effect of the first silicon oxide layer 22, thereby improving the passivation performance of the P-type doped region 11.

[0064] As an embodiment of the present invention, the total thickness of the first silicon oxide layer 22 , the aluminum oxide layer 21 , and the second silicon oxide layer 23 is 1 to 5 nanometers.

[0065] In this embodiment, the total thickness of the first silicon oxide layer 22 , the aluminum oxide layer 21 , and the second silicon oxide layer 23 is controlled to be 1 to 5 nanometers to prevent the first interface layer 2 from being too thick or too thin, thereby further ensuring good passivation and conductive effects of the P-type doped region 11 .

[0066] As an embodiment of the present invention, the thickness of the aluminum oxide layer 21 is 0.2 to 4.5 nanometers, the thickness of the first silicon oxide layer 22 is 0.2 to 3 nanometers, and the thickness of the second silicon oxide layer 23 is 0.3 to 2.6 nanometers.

[0067] In this embodiment, the thickness of the aluminum oxide layer 21 is 0.2 to 4.5 nanometers, the thickness of the first silicon oxide layer 22 is 0.2 to 3 nanometers, and the thickness of the second silicon oxide layer 23 is 0.3 to 2.6 nanometers. The thickness ranges of the first silicon oxide layer 22, the aluminum oxide layer 21, and the second silicon oxide layer 23 can be well matched, taking into account the passivation effect and the conductive effect of the first silicon oxide layer 22, the aluminum oxide layer 21, and the second silicon oxide layer 23, which is conducive to further ensuring the passivation effect and the conductive effect of the first interface layer 2.

[0068] As an embodiment of the present invention, the silicon substrate 1 includes an aluminum-doped region 10 less than 50 nanometers away from the surface of the first interface layer 2, and the aluminum atomic concentration of the aluminum-doped region 10 is greater than 1×10 15 atoms / cm 3 .

[0069] In this embodiment, since the first interface layer 2 includes the aluminum oxide layer 21, and some aluminum atoms of the aluminum oxide layer 21 can diffuse into the silicon substrate 1, and the aluminum atom concentration of the aluminum doped region is greater than 1×10 15 atoms / cm 3 , the P-type doping concentration of the aluminum-doped region 10 of the silicon substrate 1 can be increased, which can repel electrons. Electrons cannot pass through the aluminum-doped region 10, only holes can pass through, so it has good selective transmission capability. At the same time, the depth of the aluminum-doped region 10 is controlled to be less than 50 nanometers to prevent aluminum atoms from penetrating too deeply into the silicon substrate 1, reducing Auger recombination, which is beneficial to improving the power generation efficiency of the battery.

[0070] As an embodiment of the present invention, the hydrogen concentration of the aluminum oxide layer 21 is less than 10%.

[0071] In this embodiment, the hydrogen concentration of the aluminum oxide layer 21 is controlled to be less than 10% to avoid excessive hydrogen concentration causing bubbles to affect the passivation performance of the aluminum oxide layer 21 , thereby improving the passivation performance of the aluminum oxide layer 21 .

[0072] As an embodiment of the present invention, the back contact solar cell further includes:

[0073] a first electrode 6 in contact with the P-type doped layer 4;

[0074] The second electrode 7 is in contact with the N-type doped layer 5 .

[0075] In this embodiment, the first electrode 6 and the second electrode 7 have opposite polarities, and the first electrode 6 and the second electrode 7 can be silver electrodes.

[0076] As an embodiment of the present invention, the back contact solar cell further includes:

[0077] The back passivation layer 8 covers the P-type doped layer 4 and the N-type doped layer 5 . The first electrode 6 passes through the back passivation layer 8 and contacts the P-type doped layer 4 . The second electrode 7 passes through the back passivation layer 8 and contacts the N-type doped layer 5 .

[0078] In this embodiment, the back passivation layer 8 is used to passivate the P-type doped layer 4 and the N-type doped layer 5, further enhancing the back passivation effect of the battery. Optionally, the back passivation layer 8 can be a silicon nitride layer. The first electrode 6 passes through the back passivation layer 8 to contact the P-type doped layer 4, and the second electrode 7 passes through the back passivation layer 8 to contact the N-type doped layer 5.

[0079] In order to demonstrate the technical effect of providing an aluminum oxide layer in the P-type doped region, three groups of experiments were conducted, namely, control group 1, example group 1, and example group 2. The battery cells in control group 1, example group 1, and example group 2 differed only in the first interface layer, and the other structures were the same. In addition, the thickness of the first interface layer of the battery cells in control group 1, example group 1, and example group 2 was the same, and the thickness of the second interface layer in control group 1, experimental group 2, and experimental group 3 was the same.

[0080] Control group 1: The first and second interface layers of the cell in control group 1 are both single-layer silicon oxide layers;

[0081] Example Group 1: The first interface layer of the cell of Example Group 1 is a single-layer aluminum oxide layer, and the second interface layer is a single-layer silicon oxide layer;

[0082] Example Group 2: The first interface layer of the cell of Example Group 2 includes a first silicon oxide layer, an aluminum oxide layer, and a second silicon oxide layer, and the second interface layer is a single silicon oxide layer;

[0083] The measured minority carrier lifetimes of the P-type doped regions and cell efficiencies of each group of cells are shown in Table 1 below:

[0084] Table 1

[0085] serial number Minority carrier lifetime in P-type doping region (microseconds) Battery efficiency Control group 1 1980 26.43％ Example Group 1 2460 26.48％ Example Group 2 2920 26.52％

[0086] As can be seen from Table 1, by comparing Example Group 2 and Example Group 1 with Control Group 1, it can be seen that providing an aluminum oxide layer at the interface layer of the P-type doped region can increase the minority carrier lifetime of the P-type doped region and improve the battery efficiency.

[0087] In order to further demonstrate the effect of the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer on the battery efficiency, the following five sets of experiments were conducted;

[0088] Experimental Group 1: The first interface layer of the cell in Experimental Group 1 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.2.

[0089] Experimental Group 2: The first interface layer of the cell in Experimental Group 2 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.4.

[0090] Experimental Group 3: The first interface layer of the cell in Experimental Group 3 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.49.

[0091] Experimental Group 4: The first interface layer of the cell in Experimental Group 4 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.55.

[0092] Experimental Group 5: The first interface layer of the cell in Experimental Group 5 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.6.

[0093] Experimental Group 6: The first interface layer of the cell in Experimental Group 6 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.65.

[0094] Experimental Group 7: The first interface layer of the cell in Experimental Group 7 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.68.

[0095] Experimental Group 8: The first interface layer of the cell in Experimental Group 8 is a single layer of aluminum oxide, and the second interface layer is a single layer of silicon oxide. The ratio of the number of oxygen atoms in the aluminum oxide layer to the number of aluminum atoms is 1.70.

[0096] The measured minority carrier lifetimes of the P-type doped regions and cell efficiencies for each group of cells are shown in Table 2 below:

[0097] Table 2

[0098]

[0099]

[0100] As shown in Table 2, controlling the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer of the first interface layer of the P-type doped region to be between 1.49 and 1.65 can significantly increase the minority carrier lifetime of the P-type doped region, and the battery efficiency is higher within this ratio range.

[0101] An embodiment of the present invention further provides a battery assembly comprising the back-contact solar cell of the above embodiment. It should be noted that the battery assembly and the back-contact solar cell have the same or similar beneficial effects, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they are not further described here.

[0102] The present invention also provides a photovoltaic system including the battery assembly of the above embodiment. It should be noted that the photovoltaic system and the battery assembly have the same or similar beneficial effects, and the relevant aspects between the two can be referenced to each other. To avoid repetition, they will not be described here.

[0103] In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple battery modules. For example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

[0104] Throughout this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" indicate that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0105] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein the back surface of the silicon substrate comprises a P-type doping region and an N-type doping region; A first interface layer provided in the P-type doped region, the first interface layer comprising at least one aluminum oxide layer, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer is 1.49 to 1.65; a second interface layer provided in the N-type doping region; a P-type doped layer disposed on the first interface layer; and An N-type doped layer is provided on the second interface layer.

2. The back contact solar cell according to claim 1, wherein: The ratio of the number of oxygen atoms to the number of aluminum atoms in the aluminum oxide layer is 1.51 to 1.

58.

3. The back contact solar cell according to claim 1, wherein: The second interface layer includes at least one silicon oxide layer.

4. The back contact solar cell according to claim 3, characterized in that The ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer is 1.92 to 2.

10.

5. The back contact solar cell according to claim 3 or 4, characterized in that The ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer of the second interface layer is 1.96 to 2.

02.

6. The back contact solar cell according to claim 1, wherein: The first interface layer further includes a first silicon oxide layer, and the first silicon oxide layer and the aluminum oxide layer are sequentially stacked on the P-type doping region.

7. The back contact solar cell according to claim 6, characterized in that The first interface layer further includes a second silicon oxide layer. The first silicon oxide layer, the aluminum oxide layer, and the second silicon oxide layer are sequentially stacked on the P-type doped region.

8. The back contact solar cell according to claim 7, characterized in that The total thickness of the first silicon oxide layer, the aluminum oxide layer, and the second silicon oxide layer is 1 to 5 nanometers.

9. The back contact solar cell according to claim 7 or 8, characterized in that The thickness of the aluminum oxide layer is 0.2 to 4.5 nanometers, the thickness of the first silicon oxide layer is 0.2 to 3 nanometers, and the thickness of the second silicon oxide layer is 0.3 to 2.6 nanometers.

10. The back contact solar cell according to claim 7, characterized in that The first silicon oxide layer is in an amorphous state, and a ratio of oxygen atoms to silicon atoms in the first silicon oxide layer is greater than a ratio of oxygen atoms to silicon atoms in the second silicon oxide layer.

11. The back contact solar cell according to claim 1, wherein: The silicon substrate includes an aluminum-doped region less than 50 nanometers away from the surface of the first interface layer, and the aluminum atomic concentration of the aluminum-doped region is greater than 1×10 15 atoms / cm 3 .

12. The back contact solar cell according to claim 1, wherein: The hydrogen concentration of the aluminum oxide layer is less than 10%.

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

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

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