Back contact solar cell, cell module and photovoltaic system

Abstract

The utility model is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system. The first doped polycrystalline silicon layer is arranged in a first region on the back surface of the silicon substrate; the second doped polycrystalline silicon layer is arranged in a second region on the back surface of the silicon substrate; the dielectric layer is arranged on one surface, deviating from the silicon substrate, of the first doped polycrystalline silicon layer; the third doped polycrystalline silicon layer is arranged on one surface, deviating from the silicon substrate, of the dielectric layer; the first metal electrode is in contact with the first doped polycrystalline silicon layer; the second metal electrode is in contact with the second doped polycrystalline silicon layer; and the thickness of the third doped polycrystalline silicon layer is greater than that of the first doped polycrystalline silicon layer. According to the back contact solar cell provided by the utility model, the passivation effect of the back surface of the cell can be enhanced, the isolation effect of the third doped polycrystalline silicon layer on the first metal electrode and the second metal electrode can be enhanced, the short circuit risk of the cell is reduced, and the working reliability of the cell is improved.

Description

Technical Field

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

[0002] Solar cell power generation is a sustainable source of clean energy. It uses the photovoltaic effect of semiconductors to convert sunlight into electrical energy, and the conversion efficiency is an important indicator of solar cell performance. IBC (Interdigitated back contact) solar cells, also known as interdigitated back contact cells, have positive and negative electrodes designed on the back of the cell, so that the front surface is completely free from the shading of metal grid lines, eliminating the optical loss caused by the shading of metal grid lines. At the same time, the electrode width can be designed to be wider than the current one, reducing the series resistance loss, thereby greatly improving the cell conversion efficiency. In addition, due to the design of no electrode on the front of the cell, the product appearance is more beautiful and suitable for a variety of application scenarios.

[0003] In the prior art, the back of the back contact solar cell forms a staggered P region and N region. Usually, when the first doped polysilicon layer in the P region and the second doped polysilicon layer in the N region are prepared, the metal electrodes in the P region and the N region are in contact with the corresponding doped polysilicon layers to achieve back passivation contact of the solar cell. However, the doped polysilicon layer on the back of the back contact solar cell is usually set as a single layer, and the back passivation effect of the back contact solar cell is poor, which affects the efficiency of the solar cell; moreover, the metal electrode in the P region and the metal electrode in the N region have poor isolation effect, the risk of battery short circuit is high, and the battery operation reliability is poor. Utility Model Content

[0004] The utility model provides a back-contact solar cell, aiming to solve the problems that the back-contact solar cells in the prior art have poor back passivation effect, which affects the efficiency of the solar cell; and the metal electrode in the P region and the metal electrode in the N region have poor isolation effect, resulting in a high risk of battery short circuit and poor battery operating reliability.

[0005] The utility model is implemented by providing a back contact solar cell, comprising:

[0006] Silicon substrate;

[0007] A first doped polysilicon layer is disposed in a first region on the back side of the silicon substrate;

[0008] A second doped polysilicon layer is disposed in a second region on the back side of the silicon substrate;

[0009] A dielectric layer, disposed on a side of the first doped polysilicon layer away from the silicon substrate;

[0010] A third doped polysilicon layer is disposed on a side of the dielectric layer away from the silicon substrate;

[0011] A first metal electrode is disposed on the back side of the silicon substrate, the first metal electrode is in contact with the first doped polysilicon layer; and

[0012] A second metal electrode is disposed on the back side of the silicon substrate, and the second metal electrode is in contact with the second doped polysilicon layer;

[0013] Wherein, the thickness of the third doped polysilicon layer is greater than the thickness of the first doped polysilicon layer.

[0014] Preferably, the doping polarities of the first doped polysilicon layer and the second doped polysilicon layer are opposite, and the doping polarities of the first doped polysilicon layer and the third doped polysilicon layer are the same or opposite.

[0015] Preferably, the doping polarity of the first doped polysilicon layer is P-type, and the doping polarities of the third doped polysilicon layer and the second doped polysilicon layer are both N-type.

[0016] Preferably, a ratio of a thickness of the third doped polysilicon layer to a thickness of the first doped polysilicon layer is 1-2 and is not equal to 1.

[0017] Preferably, a ratio of a thickness of the third doped polysilicon layer to a thickness of the first doped polysilicon layer is 1-1.5 and is not equal to 1.

[0018] Preferably, the refractive index of the first doped polysilicon layer is smaller than the refractive index of the second doped polysilicon layer.

[0019] Preferably, it also includes:

[0020] The first passivation layer is disposed between the first doped polysilicon layer and the back surface of the silicon substrate, and between the second doped polysilicon layer and the back surface of the silicon substrate.

[0021] Preferably, it also includes:

[0022] A second passivation layer is disposed on the back side of the second doped polysilicon layer and the third doped polysilicon layer away from the silicon substrate.

[0023] Preferably, the doping polarity of the first doped polysilicon layer is opposite to that of the third doped polysilicon layer, and the back-contact solar cell is provided with an opening penetrating the second passivation layer, the third doped polysilicon layer and the dielectric layer, and the first metal electrode directly passes through the opening and contacts the first doped polysilicon layer.

[0024] Preferably, the first doped polysilicon layer and the third doped polysilicon layer have the same doping polarity, and the first metal electrode directly passes through the second passivation layer, the third doped polysilicon layer, and the dielectric layer to contact the first doped polysilicon layer.

[0025] Preferably, the thickness of the first passivation layer is greater than the thickness of the dielectric layer.

[0026] Preferably, the thickness of the first passivation layer is smaller than the thickness of the second passivation layer.

[0027] Preferably, the dielectric layer is a tunneling layer or an insulating layer.

[0028] The utility model also provides a battery assembly, comprising the above-mentioned back contact solar cell.

[0029] The utility model also provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0030] The utility model provides a back-contact solar cell, in which a dielectric layer is arranged on the back side of a first doped polysilicon layer, and a third doped polysilicon layer is arranged on the back side of the dielectric layer, and the third doped polysilicon layer, the dielectric layer and the first doped polysilicon layer form a passivation contact structure. By adding the dielectric layer and the third doped polysilicon layer, the back passivation effect of the back-contact solar cell can be significantly enhanced, and the thickness of the third doped polysilicon layer is greater than the thickness of the first doped polysilicon layer, which can enhance the isolation effect of the third doped polysilicon layer on the first metal electrode and the second metal electrode, thereby reducing the risk of battery short circuit and improving the working reliability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a back-contact solar cell provided by an embodiment of the utility model;

[0032] Figure 2 A schematic diagram of another back-contact solar cell provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0034] The utility model provides a back-contact solar cell, in which a dielectric layer is arranged on the back side of a first doped polysilicon layer, and a third doped polysilicon layer is arranged on the back side of the dielectric layer, and the third doped polysilicon layer, the dielectric layer and the first doped polysilicon layer form a passivation contact structure. By adding the dielectric layer and the third doped polysilicon layer, the back passivation effect of the back-contact solar cell can be enhanced, and the thickness of the third doped polysilicon layer is greater than the thickness of the first doped polysilicon layer, which can enhance the isolation effect of the third doped polysilicon layer on the first metal electrode and the second metal electrode, thereby reducing the risk of battery short circuit and improving the working reliability of the battery.

[0035] Please refer to Figure 1 and Figure 2 The utility model provides a back contact solar cell, comprising:

[0036] Silicon substrate 1;

[0037] A first doped polysilicon layer 2, disposed in a first region on the back side of the silicon substrate 1;

[0038] A second doped polysilicon layer 3 is provided in a second region on the back side of the silicon substrate 1;

[0039] A dielectric layer 7 is provided on a side of the first doped polysilicon layer 2 facing away from the silicon substrate 1;

[0040] A third doped polysilicon layer 4 is disposed on a side of the dielectric layer 7 facing away from the silicon substrate 1;

[0041] A first metal electrode 5 is disposed on the back side of the silicon substrate 1, and the first metal electrode 5 is in contact with the first doped polysilicon layer 2; and

[0042] A second metal electrode 6 is disposed on the back side of the silicon substrate 1, and the second metal electrode 6 is in contact with the second doped polysilicon layer 3;

[0043] The thickness d1 of the third doped polysilicon layer 4 is greater than the thickness d2 of the first doped polysilicon layer 2 .

[0044] In an embodiment of the utility model, a back-contact solar cell is provided in which a dielectric layer 7 is arranged on the back side of a first doped polysilicon layer 2, and a third doped polysilicon layer 4 is arranged on the back side of the dielectric layer 7, and the dielectric layer 7 and the third doped polysilicon layer 4 are used to further enhance the back passivation effect of the back-contact solar cell; moreover, the thickness d1 of the third doped polysilicon layer 4 is set to be greater than the thickness d2 of the first doped polysilicon layer 2, and under the premise of not reducing the thickness of the first doped polysilicon layer 2, that is, under the premise of not affecting the passivation effect of the first doped polysilicon layer 2, by increasing the thickness d1 of the third doped polysilicon layer 4, the wrapping area of ​​the third doped polysilicon layer 4 on the first metal electrode 5 can be increased, and the isolation effect between the first metal electrode 5 and the second metal electrode 6 can be enhanced, thereby reducing the risk of battery short circuit and improving the working reliability of the battery.

[0045] In the embodiment of the utility model, the silicon substrate 1 can be a P-type silicon substrate or an N-type silicon substrate.

[0046] As an embodiment of the present invention, the doping polarities of the first doped polysilicon layer 2 and the second doped polysilicon layer 3 are opposite, and the doping polarities of the first doped polysilicon layer 2 and the third doped polysilicon layer 4 are the same or opposite.

[0047] As an embodiment of the utility model, the doping polarity of the first doped polysilicon layer 2 is P-type, and the doping polarity of the third doped polysilicon layer 4 and the doping polarity of the second doped polysilicon layer 3 are both N-type; of course, it can also be that the doping polarity of the first doped polysilicon layer 2 is N-type, and the doping polarity of the third doped polysilicon layer 4 and the doping polarity of the second doped polysilicon layer 3 are both P-type. Among them, the third doped polysilicon layer 4 and the second doped polysilicon layer 3 are prepared at one time or in steps, and the thickness d1 of the third doped polysilicon layer 4 and the thickness d3 of the second doped polysilicon layer 3 can be equal or unequal.

[0048] As an embodiment of the present invention, the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 is 1-2 and is not equal to 1.

[0049] In this embodiment, the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 is greater than 1 and less than or equal to 2. This can not only enhance the isolation effect of the first metal electrode 5 and the second metal electrode 6 and improve the working reliability of the battery, but also facilitate the preparation of the third doped polysilicon layer 4, the second doped polysilicon layer 3 and the first doped polysilicon layer 2.

[0050] For example, the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 may be:

[0051] 1.01, or 1.05, or 1.1, or 1.05, or 1.2, or 1.25, or 1.3, or 1.35, or 1.4, or 1.45, or 1.5, or 1.55, or 1.6, or 1.65, or 1.7, or 1.75, or 1.8, or 1.85, or 1.9, or 1.95, or 2.

[0052] Optionally, when the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 is 1 to 2, the thickness d1 of the third doped polysilicon layer 4 may be 100 nm to 600 nm, and the thickness d2 of the first doped polysilicon layer 2 may be 50 nm to 300 nm. The thickness d1 of the third doped polysilicon layer 4 is equal to the thickness d3 of the second doped polysilicon layer 3.

[0053] For example, the thickness of the third doped polysilicon layer 4 and the second doped polysilicon layer 3 can be 100nm, or 105nm, or 135nm, or 145nm, or 173nm, or 185nm, or 200nm, or 240nm, or 285nm, or 300nm, or 301nm, or 342nm, or 367nm, or 370nm, or 420nm, or 456nm, or 482nm, or 500nm, or 550nm, or 570nm, or 590nm, or 600nm.

[0054] For example, the thickness d2 of the first doped polysilicon layer 2 can be 50nm, or 45nm, or 52nm, or 60nm, or 66.7nm, or 73nm, or 81nm, or 90nm, or 92nm, or 100nm, or 112nm, or 133nm, or 144nm, or 175nm, or 190nm, or 211nm, or 243nm, or 270nm, or 282nm, or 296nm, or 300nm.

[0055] As an embodiment of the present invention, the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 is 1-1.5.

[0056] In this embodiment, the ratio of the thickness d1 of the third doped polysilicon layer 4 to the thickness d2 of the first doped polysilicon layer 2 is greater than 1 and less than or equal to 1.5. This can not only increase the thickness of the second doped polysilicon layer 3, but also enhance the isolation effect between the first metal electrode 5 and the second metal electrode 6, thereby improving the working reliability of the battery and ensuring that the difference between the thickness d1 of the third doped polysilicon layer 4 and the thickness d2 of the first doped polysilicon layer 2 is within a more appropriate range, thereby ensuring higher battery efficiency.

[0057] As an embodiment of the present invention, the doping polarity of the first doped polysilicon layer 2 is P type, the doping polarity of the third doped polysilicon layer 4 and the doping polarity of the second doped polysilicon layer 3 are both N type; the refractive index of the first doped polysilicon layer 2 is less than the refractive index of the second doped polysilicon layer 3.

[0058] Among them, the refractive index of the second doped polysilicon layer 3 is equal to that of the third doped polysilicon layer 4. The refractive index of the second doped polysilicon layer 3 and the refractive index of the first doped polysilicon layer 2 are flexibly set according to actual needs. It is only necessary to satisfy that the refractive index of the first doped polysilicon layer 2 is less than the refractive index of the second doped polysilicon layer 3. Under the premise that the refractive index of the second doped polysilicon layer 3 remains unchanged, by reducing the refractive index of the first doped polysilicon layer 2, the parasitic absorption effect of the P region can be reduced, thereby further improving the battery efficiency.

[0059] In the embodiment of the utility model, the dielectric layer 7 plays an insulating and isolating role for the first doped polysilicon layer 2 and the third doped polysilicon layer 4 , thereby preventing the first doped polysilicon layer 2 from directly contacting the third doped polysilicon layer 4 .

[0060] As an embodiment of the present invention, the dielectric layer 7 is specifically a tunneling layer or an insulating layer. Specifically, the dielectric layer 7 can be specifically borosilicate glass or borophosphosilicate glass.

[0061] As an embodiment of the utility model, it also includes:

[0062] The first passivation layer 8 is disposed between the first doped polysilicon layer 2 and the back surface of the silicon substrate 1 , and between the second doped polysilicon layer 3 and the back surface of the silicon substrate 1 .

[0063] In this embodiment, the first passivation layer 8 may specifically be a silicon oxide layer. The first passivation layer 8 may be used to further enhance the back passivation effect of the battery.

[0064] As an embodiment of the present invention, the front side of the silicon substrate 1 has a suede structure (not shown), which can achieve a good light trapping effect and improve the conversion efficiency of the back contact solar cell.

[0065] As an embodiment of the present invention, a front passivation anti-reflection film layer 10 may be further provided on the front side of the silicon substrate 1 to further improve the conversion efficiency of the back contact solar cell.

[0066] As an embodiment of the present invention, the back contact solar cell further includes:

[0067] A second passivation layer 11 is disposed on a side of the second doped polysilicon layer 3 and the third doped polysilicon layer 4 away from the silicon substrate 1 .

[0068] In this embodiment, the first metal electrode 5 passes through the second passivation layer 11, the third doped polysilicon layer 4 and the dielectric layer 7 to contact the first doped polysilicon layer 2. The second passivation layer 11 is used to isolate the third doped polysilicon layer 4 from the outside, and further improve the back passivation effect of the back contact solar cell, thereby improving the cell conversion efficiency.

[0069] like Figure 1 As shown, as an embodiment of the utility model, the doping polarities of the first doped polysilicon layer 2 and the third doped polysilicon layer 4 are opposite, and the back-contact solar cell is provided with an opening 41 penetrating the second passivation layer 11, the third doped polysilicon layer 4 and the dielectric layer 7, and the first metal electrode 5 contacts the first doped polysilicon layer 2 through the opening 41.

[0070] In this embodiment, the doping polarity of the first doped polysilicon layer 2 is P type, and the doping polarity of the second doped polysilicon layer 3 and the third doped polysilicon layer 4 is N type; or, the doping polarity of the first doped polysilicon layer 2 is N type, and the doping polarity of the second doped polysilicon layer 3 and the third doped polysilicon layer 4 is P type.

[0071] In this embodiment, the opening 41 is used to isolate the first metal electrode 5 to prevent the first metal electrode 5 from directly conducting the third doped polysilicon layer 4 and the first doped polysilicon layer 2 .

[0072] like Figure 2 As shown, as an embodiment of the utility model, the first doped polysilicon layer 2 and the third doped polysilicon layer 4 have the same doping polarity, and the first metal electrode 5 directly passes through the second passivation layer 11, the third doped polysilicon layer 4, and the dielectric layer 7 to contact the first doped polysilicon layer 2.

[0073] In this embodiment, the doping polarities of the first doped polysilicon layer 2 and the third doped polysilicon layer 4 can both be P-type, and the second doped polysilicon layer 3 can be N-type; or, the doping polarities of the first doped polysilicon layer 2 and the third doped polysilicon layer 4 can both be N-type, and the second doped polysilicon layer 3 can be P-type.

[0074] In this embodiment, the first metal electrode 5 directly passes through the second passivation layer 11 , the third doped polysilicon layer 4 , and the dielectric layer 7 to contact the first doped polysilicon layer 2 , and there is no need to provide an opening 41 , thereby simplifying the processing technology.

[0075] As an embodiment of the present invention, the thickness of the first passivation layer 8 is greater than the thickness of the dielectric layer 7, so that the first passivation layer 8 close to the silicon substrate 1 has a better passivation effect.

[0076] As an embodiment of the present invention, the thickness of the first passivation layer 8 is smaller than the thickness of the second passivation layer 11 , so that the second passivation layer 11 can have a better effect of isolating from the outside world.

[0077] like Figure 1 As shown, as an embodiment of the present invention, the silicon substrate 1 is further provided with a groove 12 between the first doped polysilicon layer 2 and the second doped polysilicon layer 3. The first doped polysilicon layer 2 and the second doped polysilicon layer 3 are physically isolated by the groove 12, which can further enhance the isolation effect between the first doped polysilicon layer 2 and the second doped polysilicon layer 3 and further reduce the risk of short circuit or leakage. The width of the groove 12 can be flexibly set according to actual needs and is not limited here. Of course, if Figure 2 As shown, the back side of the back contact solar cell may not be provided with the groove 12 , and only a gap is provided to isolate the first doped polysilicon layer 2 and the second doped polysilicon layer 3 .

[0078] As an embodiment of the utility model, there is a first height difference between the surface of the first doped polysilicon layer 2 close to the silicon substrate 1 and the surface of the second doped polysilicon layer 3 close to the silicon substrate 1. The surface of the first doped polysilicon layer 2 close to the silicon substrate 1 is farther away from the front side of the silicon substrate 1 than the surface of the second doped polysilicon layer 3 close to the silicon substrate 1.

[0079] In this embodiment, the surface of the silicon substrate 1 close to the first doped polysilicon layer 2 and the surface close to the second doped polysilicon layer 3 are not on the same plane; before the latter doped polysilicon layer is made, the part to be etched in the first doped polysilicon layer is etched more cleanly, and the first doped polysilicon layer 2 and the second doped polysilicon layer 3 in the gap between the first region and the second region are etched more cleanly, and the electrical performance is better. Among them, the first height difference can be flexibly set according to actual needs and is not limited here.

[0080] As an embodiment of the present utility model, there is a second height difference between the surface of the first doped polysilicon layer 2 close to the silicon substrate 1 and the surface of the second doped polysilicon layer 3 away from the silicon substrate 1. The surface of the first doped polysilicon layer 2 close to the silicon substrate 1 is farther away from the front side of the silicon substrate 1 than the surface of the second doped polysilicon layer 3 away from the silicon substrate 1.

[0081] In this embodiment, the surface of the first doped polysilicon layer 2 away from the silicon substrate 1 is farther away from the front of the silicon substrate 1 than the surface of the second doped polysilicon layer 3 away from the silicon substrate 1, and there is a second height difference between the surface of the first doped polysilicon layer 2 away from the silicon substrate 1 and the surface of the second doped polysilicon layer 3 away from the silicon substrate 1, so as to achieve a good isolation effect between the first doped polysilicon layer 2 and the second doped polysilicon layer 3, a good electrical isolation effect, and a lower risk of short circuit or leakage. The second height difference can be flexibly set according to actual needs and is not limited here.

[0082] The present invention also provides a battery assembly, which includes 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 parts between the two can be referenced to each other. In order to avoid repetition, they will not be described here.

[0083] The present invention also provides a photovoltaic system, which includes the battery assembly of the above embodiment. It should be noted that the photovoltaic system has the same or similar beneficial effects as the back contact solar cell, and the relevant parts between the two can be referenced to each other. In order to avoid repetition, it will not be repeated here.

[0084] A back-contact solar cell provided by an embodiment of the utility model is provided with a dielectric layer on the back side of a first doped polysilicon layer, and a third doped polysilicon layer on the back side of the dielectric layer. The third doped polysilicon layer, the dielectric layer and the first doped polysilicon layer form a passivation contact structure. By adding the dielectric layer and the third doped polysilicon layer, the back passivation effect of the back-contact solar cell can be enhanced, and the thickness of the third doped polysilicon layer is greater than the thickness of the first doped polysilicon layer, which can enhance the isolation effect of the third doped polysilicon layer on the first metal electrode and the second metal electrode, thereby reducing the risk of battery short circuit and improving the working reliability of the battery.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: Silicon substrate; A first doped polysilicon layer is disposed in a first region on the back side of the silicon substrate; A second doped polysilicon layer is disposed in a second region on the back side of the silicon substrate; A dielectric layer, disposed on a side of the first doped polysilicon layer away from the silicon substrate; A third doped polysilicon layer is disposed on a side of the dielectric layer away from the silicon substrate; A first metal electrode is disposed on the back side of the silicon substrate, wherein the first metal electrode is in contact with the first doped polysilicon layer; and A second metal electrode is disposed on the back side of the silicon substrate, and the second metal electrode is in contact with the second doped polysilicon layer; Wherein, the thickness of the third doped polysilicon layer is greater than the thickness of the first doped polysilicon layer.

2. The back contact solar cell according to claim 1, characterized in that: The doping polarities of the first doped polysilicon layer and the second doped polysilicon layer are opposite, and the doping polarities of the first doped polysilicon layer and the third doped polysilicon layer are the same as or opposite.

3. The back contact solar cell according to claim 1, characterized in that: The doping polarity of the first doped polysilicon layer is P-type, and the doping polarities of the third doped polysilicon layer and the second doped polysilicon layer are both N-type.

4. The back contact solar cell according to claim 1, characterized in that: The ratio of the thickness of the third doped polysilicon layer to the thickness of the first doped polysilicon layer is 1-2 and is not equal to 1.

5. The back contact solar cell according to claim 1, characterized in that: The ratio of the thickness of the third doped polysilicon layer to the thickness of the first doped polysilicon layer is 1-1.5 and is not equal to 1.

6. The back contact solar cell according to claim 3, characterized in that: The refractive index of the first doped polysilicon layer is less than the refractive index of the second doped polysilicon layer.

7. The back contact solar cell according to claim 1, characterized in that: Also includes: The first passivation layer is disposed between the first doped polysilicon layer and the back surface of the silicon substrate, and between the second doped polysilicon layer and the back surface of the silicon substrate.

8. The back contact solar cell according to claim 7, characterized in that: Also includes: A second passivation layer is disposed on a side of the second doped polysilicon layer and the third doped polysilicon layer away from the silicon substrate.

9. The back contact solar cell according to claim 8, characterized in that: The doping polarities of the first doped polysilicon layer and the third doped polysilicon layer are opposite, the back-contact solar cell is provided with an opening penetrating the second passivation layer, the third doped polysilicon layer and the dielectric layer, and the first metal electrode contacts the first doped polysilicon layer through the opening.

10. The back contact solar cell according to claim 8, characterized in that: The first doped polysilicon layer and the third doped polysilicon layer have the same doping polarity, and the first metal electrode directly passes through the second passivation layer, the third doped polysilicon layer, and the dielectric layer to contact the first doped polysilicon layer.

11. The back contact solar cell according to claim 7, characterized in that: The thickness of the first passivation layer is greater than the thickness of the dielectric layer.

12. The back contact solar cell according to claim 8, characterized in that: The thickness of the first passivation layer is smaller than the thickness of the second passivation layer.

13. The back contact solar cell according to claim 1, characterized in that: The dielectric layer is a tunneling layer or an insulating layer.

14. A battery assembly, characterized in that: A back-contact solar cell comprising the step of:

15. A photovoltaic system, characterized in that: Comprising the battery assembly as claimed in claim 14.

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