Back-contact solar cell, solar module and photovoltaic system

Abstract

The present disclosure is applicable to the technical field of solar cells, and provides a back-contact solar cell, a solar module and a photovoltaic system. The back-contact solar cell comprises: an N-type silicon substrate; a plurality of P-type doped polysilicon layers, which are sequentially arranged at intervals on the backside of the silicon substrate; and a plurality of N-type doped polysilicon layers, which are sequentially arranged at intervals on the backside of the silicon substrate, wherein the N-type doped polysilicon layers and the P-type doped polysilicon layers are alternately arranged, the total area of the P-type doped polysilicon layers is greater than the total area of the N-type doped polysilicon layers, and the refractive index of the P-type doped polysilicon layers is less than the refractive index of the N-type doped polysilicon layers. In the back-contact solar cell provided in the present disclosure, the total area of P-type doped polysilicon layers is increased to improve the current collection capability of an emitter, thereby improving the efficiency of the cell; and the refractive index of the P-type doped polysilicon layers is set to be less than the refractive index of N-type doped polysilicon layers, such that the parasitic absorption effect in a P region is reduced, thereby further improving the efficiency of the cell.

Description

Back contact solar cell, cell assembly and photovoltaic system

[0001] Priority information

[0002] The present disclosure claims priority to and the benefit of the patent application with the patent application number 202421459139.8 filed on June 24, 2024 with the China National Intellectual Property Office, and incorporates it herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of solar cells, in particular to a back contact solar cell, a cell assembly and a photovoltaic system. BACKGROUND

[0004] Solar power generation is a sustainable clean energy source, which can convert sunlight into electrical energy by using the photovoltaic effect of semiconductors, and the conversion efficiency is an important indicator of solar cell performance. IBC (Interdigitated back contact) solar cell, also known as interdigital back contact cell, has both positive and negative electrodes designed on the back of the cell, so that the front surface is completely free from the obstruction of metal grid lines, eliminating the optical loss caused by the obstruction of metal grid lines, and the electrode width can be designed wider than the existing one, thereby reducing the series resistance loss and greatly improving the conversion efficiency of the cell. In addition, the design of no electrode on the front surface of the cell makes the product appearance more beautiful, which is suitable for various application scenarios.

[0005] In the prior art, the back surface of the back contact solar cell forms staggered P-type doped polysilicon layers and N-type doped polysilicon layers. Generally, in order to facilitate processing, the area relationship of the P-type doped polysilicon layers and the N-type doped polysilicon layers is not considered to affect the cell efficiency, and the areas of the P-type doped polysilicon layers and the N-type doped polysilicon layers are set to be equal. Especially for the N-type silicon substrate, the total area of the P-type doped polysilicon layers is equal to the total area of the N-type doped polysilicon layers, resulting in poor photoelectric conversion efficiency of the back contact cell.

[0006] Utility model content

[0007] The present disclosure provides a back contact solar cell, which aims to solve the problem of the prior art that the total area of the P-type doped polysilicon layers is equal to the total area of the N-type doped polysilicon layers, and the photoelectric conversion efficiency of the back contact cell is poor.

[0008] The present disclosure is implemented in this way, providing a back contact solar cell, comprising:

[0009] An N-type silicon substrate;

[0010] A plurality of P-type doped polysilicon layers are sequentially and spacedly arranged on the back surface of the silicon substrate;

[0011] a plurality of N-type doped polysilicon layers are sequentially and spacedly arranged on the back surface of the silicon substrate, and the N-type doped polysilicon layers and the P-type doped polysilicon layers are arranged alternately;

[0012] The total area of the plurality of P-type doped polysilicon layers is greater than the total area of the plurality of N-type doped polysilicon layers, and the refractive index of the P-type doped polysilicon layer is less than the refractive index of the N-type doped polysilicon layer.

[0013] Optionally, the area of at least one P-type doped polysilicon layer is greater than the area of any one N-type doped polysilicon layer.

[0014] Optionally, the number of P-type doped polysilicon layers is greater than the number of N-type doped polysilicon layers.

[0015] Optionally, the ratio of the total area of the P-type doped polysilicon layers to the total area of the N-type doped polysilicon layers is 1-2, and is not equal to 1.

[0016] Optionally, the ratio of the total area of the P-type doped polysilicon layers to the total area of the N-type doped polysilicon layers is 1-1.5, and is not equal to 1.

[0017] Optionally, the length of each P-type doped polysilicon layer is equal to the length of each N-type doped polysilicon layer, and the width of each P-type doped polysilicon layer is greater than the width of each N-type doped polysilicon layer.

[0018] Optionally, the ratio of the refractive index of the P-type doped polysilicon layer to the refractive index of the N-type doped polysilicon layer is 0.5-1, and is not equal to 1.

[0019] Optionally, the volume of the P-type doped polysilicon layer is greater than the volume of the N-type doped polysilicon layer.

[0020] The disclosure also provides a battery assembly comprising the back contact solar cell described above.

[0021] The disclosure also provides a photovoltaic system comprising the battery assembly described above.

[0022] The back contact solar cell provided by the disclosure increases the total area of the P-type doped polysilicon layer to be greater than the total area of the N-type doped polysilicon layer, increases the current collection capability of the emitter under the premise that the area of the N-type doped polysilicon layer remains unchanged, thereby improving the battery efficiency; and sets the refractive index of the P-type doped polysilicon layer to be less than the refractive index of the N-type doped polysilicon layer, reduces the parasitic absorption effect of the P region under the premise that the refractive index of the N-type doped polysilicon layer remains unchanged, thereby further improving the battery efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 is a cross-sectional view of a back contact solar cell according to an embodiment of the present disclosure;

[0024] Fig. 2 is a distribution diagram of a P-type doped polysilicon layer and an N-type doped polysilicon layer of a back contact solar cell according to an embodiment of the present disclosure;

[0025] Fig. 3 is a distribution diagram of another embodiment of a P-type doped polysilicon layer and an N-type doped polysilicon layer of a back contact solar cell according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions, and advantages of the present disclosure clearer, further detailed description will be given to the present disclosure in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and not used to limit the present disclosure.

[0027] The back contact solar cell according to the embodiment of the present disclosure sets the total area of the P-type doped polysilicon layer to be greater than the total area of the N-type doped polysilicon layer, increases the total area of the P-type doped polysilicon layer under the premise that the total area of the N-type doped polysilicon layer is unchanged, improves the current collection capability of the emitter, and thus improves the cell efficiency. Moreover, the refractive index of the P-type doped polysilicon layer is set to be less than the refractive index of the N-type doped polysilicon layer, reduces the refractive index of the P-type doped polysilicon layer under the premise that the refractive index of the N-type doped polysilicon layer is unchanged, reduces the parasitic absorption effect of the P region, and thus further improves the cell efficiency.

[0028] Please refer to Figs. 1-3, the embodiment of the present disclosure provides a back contact solar cell, which comprises:

[0029] a silicon substrate 1 of N type;

[0030] a plurality of P-type doped polysilicon layers 2, which are sequentially and spacedly arranged on the back surface of the silicon substrate 1;

[0031] a plurality of N-type doped polysilicon layers 3, which are sequentially and spacedly arranged on the back surface of the silicon substrate 1, and the N-type doped polysilicon layers 3 and the P-type doped polysilicon layers 2 are arranged alternately;

[0032] In the embodiment of the present disclosure, the total area of the P-type doped polysilicon layers 2 is the sum of the areas of all the P-type doped polysilicon layers 2, and the total area of the N-type doped polysilicon layers 3 is the sum of the areas of all the N-type doped polysilicon layers 3.

[0033] In the embodiment of the present disclosure, the total area of the P-type doped polysilicon layers 2 is the sum of the areas of all the P-type doped polysilicon layers 2, and the total area of the N-type doped polysilicon layers 3 is the sum of the areas of all the N-type doped polysilicon layers 3.

[0034] The back contact solar cell provided by the embodiment of the present disclosure increases the total area of the P-type doped polysilicon layer 2 by setting the total area of the plurality of P-type doped polysilicon layers 2 to be greater than the total area of the plurality of N-type doped polysilicon layers 3, under the premise that the total area of the N-type doped polysilicon layer 3 is unchanged, which can improve the current collection capability of the emitter and thus improve the cell efficiency; and the refractive index of the P-type doped polysilicon layer 2 is set to be less than the refractive index of the N-type doped polysilicon layer 3, under the premise that the refractive index of the N-type doped polysilicon layer 3 is unchanged, by reducing the refractive index of the P-type doped polysilicon layer 2, the parasitic absorption effect of the P region can be reduced, and thus the cell efficiency can be further improved.

[0035] In the embodiment of the present disclosure, the specific number of the P-type doped polysilicon layer 2 is not limited, and the plurality of P-type doped polysilicon layers 2 are distributed in an interdigital manner on the back surface of the silicon substrate 1; the specific number of the N-type doped polysilicon layer 3 is not limited, and the plurality of N-type doped polysilicon layers 3 are distributed in an interdigital manner on the back surface of the silicon substrate 1, and the N-type doped polysilicon layer 3 and the P-type doped polysilicon layer 2 are arranged alternately.

[0036] As an embodiment of the present disclosure, the area of at least one P-type doped polysilicon layer 2 is greater than the area of any one N-type doped polysilicon layer 3.

[0037] In the embodiment, the areas of the N-type doped polysilicon layers 3 are equal, and the area of one, two, three or more P-type doped polysilicon layers 2 is greater than the area of any one N-type doped polysilicon layer 3, so that the total area of the plurality of P-type doped polysilicon layers 2 is greater than the total area of the plurality of N-type doped polysilicon layers 3.

[0038] In the embodiment, the number of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3 can be equal (as shown in FIG. 2), and the number of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3 can also be unequal (as shown in FIG. 3), as long as the area of several P-type doped polysilicon layers 2 is greater than the area of the N-type doped polysilicon layer 3, which can ensure that the total area of the plurality of P-type doped polysilicon layers 2 is greater than the total area of the plurality of N-type doped polysilicon layers 3, and can reduce the cost.

[0039] Please refer to FIG. 3, as an embodiment of the present disclosure, the number of the P-type doped polysilicon layer 2 is greater than the number of the N-type doped polysilicon layer 3.

[0040] In the embodiment, the number of the P-type doped polysilicon layer 2 is greater than the number of the N-type doped polysilicon layer 3, and the area of each P-type doped polysilicon layer 2 and the area of each N-type doped polysilicon layer 3 can be equal or unequal, by controlling the number of the P-type doped polysilicon layer 2 to be greater than the number of the N-type doped polysilicon layer 3, the total area of the P-type doped polysilicon layer 2 can also be greater than the total area of the plurality of N-type doped polysilicon layers 3.

[0041] In the embodiment, the number of the N-type doped polysilicon layers 3 is N, and the number of the P-type doped polysilicon layers 2 is N+1.

[0042] As one embodiment of the present disclosure, the ratio of the total area of the P-type doped polysilicon layers 2 to the total area of the N-type doped polysilicon layers 3 is 1-2, and not equal to 1.

[0043] In the embodiment, the ratio of the total area of the P-type doped polysilicon layers 2 to the total area of the N-type doped polysilicon layers 3 is greater than 1 and less than or equal to 2, which can ensure that the total area of the plurality of P-type doped polysilicon layers 2 is greater than the total area of the plurality of N-type doped polysilicon layers 3, and facilitate the preparation of the P-type doped polysilicon layers 2 and the N-type doped polysilicon layers 3.

[0044] As one embodiment of the present disclosure, the ratio of the total area of the P-type doped polysilicon layers 2 to the total area of the N-type doped polysilicon layers 3 is 1-1.5, and not equal to 1.

[0045] In the embodiment, the ratio of the total area of the P-type doped polysilicon layers 2 to the total area of the N-type doped polysilicon layers 3 is greater than 1 and less than or equal to 1.5, which can ensure that the total area of the plurality of P-type doped polysilicon layers 2 is greater than the total area of the plurality of N-type doped polysilicon layers 3, ensure higher cell efficiency, and facilitate the preparation of the P-type doped polysilicon layers 2 and the N-type doped polysilicon layers 3.

[0046] As one embodiment of the present disclosure, the length of each P-type doped polysilicon layer 2 is equal to the length of each N-type doped polysilicon layer 3, and the width d3 of each P-type doped polysilicon layer 2 is greater than the width d4 of each N-type doped polysilicon layer 3.

[0047] In the embodiment, the length of the N-type doped polysilicon layer 3 is equal to the length of the P-type doped polysilicon layer 2, which can increase the area of the P-type doped polysilicon layer 2 by increasing the width d3 of the P-type doped polysilicon layer 2, and the implementation is simple.

[0048] As one preferred embodiment of the present disclosure, the area of each P-type doped polysilicon layer 2 is greater than the area of any one N-type doped polysilicon layer 3, i.e., the area of any one P-type doped polysilicon layer 2 is greater than the area of any one N-type doped polysilicon layer 3, which facilitates the preparation of the P-type doped polysilicon layers 2 and the N-type doped polysilicon layers 3.

[0049] As one embodiment of the present disclosure, the ratio of the refractive index of the P-type doped polysilicon layer 2 to the refractive index of the N-type doped polysilicon layer 3 is 0.5-1, and not equal to 1.

[0050] In the embodiment, the ratio of the refractive index of the P-type doped polysilicon layer 2 to the refractive index of the N-type doped polysilicon layer 3 is greater than or equal to 0.5 and less than 1, which can ensure that the refractive index of the P-type doped polysilicon layer 2 is greater than the refractive index of the N-type doped polysilicon layer 3, ensure higher cell efficiency, and facilitate the preparation of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3.

[0051] Please refer to FIG. 1. As an embodiment of the present disclosure, the thickness d1 of the N-type doped polysilicon layer 3 is greater than the thickness d2 of the P-type doped polysilicon layer 2.

[0052] In the embodiment, by setting the thickness d1 of the N-type doped polysilicon layer 3 to be greater than the thickness d2 of the P-type doped polysilicon layer 2, the thickness d2 of the P-type doped polysilicon layer 2 is reduced compared to the thickness d1 of the N-type doped polysilicon layer 3, which reduces the etching difficulty of the P-type doped polysilicon layer 2, i.e., reduces the patterning process difficulty, facilitates the patterning process of the P-type doped polysilicon layer 2; moreover, reducing the thickness d2 of the P-type doped polysilicon layer 2 can reduce the boron diffusion difficulty, which is conducive to the boron diffusion process and facilitates the preparation of the P-type doped polysilicon layer 2 with higher concentration; furthermore, the thickness d1 of the N-type doped polysilicon layer 3 is greater than the thickness d2 of the P-type doped polysilicon layer 2, and the N-type doped polysilicon layer 3 is thicker than the P-type doped polysilicon layer 2, which can enhance the passivation effect and improve the cell efficiency.

[0053] As an embodiment of the present disclosure, the ratio of the thickness d1 of the N-type doped polysilicon layer 3 to the thickness d2 of the P-type doped polysilicon layer 2 is 1-2 and not equal to 1.

[0054] In the embodiment, the ratio of the thickness d1 of the N-type doped polysilicon layer 3 to the thickness d2 of the P-type doped polysilicon layer 2 is greater than 1 and less than or equal to 2, which can reduce the etching difficulty of the P-type doped polysilicon layer 2, facilitate the patterning process of the P-type doped polysilicon layer 2, and be conducive to the boron diffusion process, reduce the boron diffusion difficulty, and facilitate the preparation of the P-type doped polysilicon layer 2 with higher concentration.

[0055] For example, the ratio of the thickness d1 of the N-type doped polysilicon layer 3 to the thickness d2 of the P-type doped polysilicon layer 2 can be:

[0056] 1.01, or 1.05, or 1.1, or 1.15, 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 1.92, or 2.

[0057] Optionally, when the ratio of d1 and d2 is 1 to 2, the thickness d1 of the N-type doped polysilicon layer 3 is 100nm to 600nm, and the thickness d2 of the P-type doped polysilicon layer 2 can be 50nm to 300nm. When d1 and d2 are in the above range, both the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3 can easily achieve good doping effect, both have good passivation effect, while ensuring less metallization damage and smaller contact resistance, and relatively low cost; in addition, the etching difficulty of the P-type doped polysilicon can be reduced, the patterning process of the P-type doped polysilicon is facilitated, and the boron diffusion process is facilitated, the boron diffusion difficulty is reduced, and the preparation of high-concentration P-type doped polysilicon layer 2 is facilitated.

[0058] As an embodiment of the present disclosure, the volume of the P-type doped polysilicon layer 2 is greater than the volume of the N-type doped polysilicon layer 3.

[0059] In this embodiment, the volume of the P-type doped polysilicon layer 2 is greater than the volume of the N-type doped polysilicon layer 3. Increasing the volume of the P-type doped polysilicon layer 2 can improve the emitter current collection efficiency of the back contact solar cell, thereby improving the cell efficiency. Specifically, the width d3 and the thickness d2 of the P-type doped polysilicon layer 2 can be adjusted accordingly. Under the premise that the volume of the N-type doped polysilicon layer 3 remains unchanged, increasing the volume of the P-type doped polysilicon layer 2 can further increase the current collection capacity of the emitter, thereby improving the cell efficiency.

[0060] As an embodiment of the present disclosure, the ratio of the volume of the P-type doped polysilicon layer 2 to the volume of the N-type doped polysilicon layer 3 is 1 to 2, and not equal to 1.

[0061] In this embodiment, the ratio of the volume of the P-type doped polysilicon layer 2 to the volume of the N-type doped polysilicon layer 3 is 1 to 2. This can ensure that the volume of the P-type doped polysilicon layer 2 and the volume of the N-type doped polysilicon layer 3 remain within a suitable range, maintain high cell efficiency, and facilitate the preparation of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3.

[0062] As an embodiment of the present disclosure, the average grain size of the P-type doped polysilicon layer 2 is greater than the average grain size of the N-type doped polysilicon layer 3.

[0063] In the embodiment, the average grain size of the P-type doped polysilicon layer 2 and the average grain size of the N-type doped polysilicon layer 3 can be measured by an X-ray diffraction (XRD), a scanning electronic microscopy (SEM) or a transmission electron microscope (TEM). The average grain size of the P-type doped polysilicon layer 2 is greater than the average grain size of the N-type doped polysilicon layer 3, which means that the average value of all grain sizes of the P-type doped polysilicon layer 2 in a unit area is greater than the average value of all grain sizes of the N-type doped polysilicon layer 3 in a unit area. In other words, the number of doped polysilicon layers in the N-type doped polysilicon layer 3 in a unit area is greater than that in the P-type doped polysilicon layer 2 in a unit area. Therefore, the number of grain boundaries in the P-type doped polysilicon layer 2 in a unit area is less than that in the N-type doped polysilicon layer 3 in a unit area. As a result, the density of the P-type doped polysilicon layer 2 can be improved, the sheet resistance of the P-type doped polysilicon layer 2 can be reduced, the current loss can be reduced, and thus the battery efficiency can be improved. In addition, the number of grain boundaries in the P-type doped polysilicon layer 2 can be reduced, the metallization damage of the P-type doped polysilicon layer 2 can be reduced, and thus the battery efficiency can be improved.

[0064] As an embodiment of the present disclosure, the back contact solar cell further comprises a first metal electrode 6 in contact with the P-type doped polysilicon layer 2 and a second metal electrode 7 in contact with the N-type doped polysilicon layer 3. The depth of the metal crystal of the first metal electrode 6 into the P-type doped polysilicon layer 2 is greater than the depth of the metal crystal of the second metal electrode 7 into the N-type doped polysilicon layer 3.

[0065] In the embodiment, the depth of the metal crystal of the first metal electrode 6 into the P-type doped polysilicon layer 2 is greater than the depth of the metal crystal of the second metal electrode 7 into the N-type doped polysilicon layer 3, which can increase the contact area of the first metal electrode 6 and the P-type doped polysilicon layer 2, improve the contact effect of the first metal electrode 6 and the P-type doped polysilicon layer 2, and thus improve the conductivity of the first metal electrode 6 and the P-type doped polysilicon layer 2, thereby improving the battery conversion efficiency.

[0066] In the embodiment of the present disclosure, the paste with different burn-through capabilities can be used to print the first metal electrode 6 and the second metal electrode 7, so as to control the depth of the metal crystal of the metal electrode into the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3. For example, the paste burn-through capability of the first metal electrode 6 is greater than the paste burn-through capability of the second metal electrode 7, which can make the depth of the metal crystal of the first metal electrode 6 into the P-type doped polysilicon layer 2 greater than the depth of the metal crystal of the second metal electrode 7 into the N-type doped polysilicon layer 3.

[0067] In this embodiment, the first metal electrode 6 and the second metal electrode 7 each include silver, glass frit, and an organic material component; the glass frit includes at least one of PbO, Bi2O3, ZnO, SiO2, and MgO; the content of the glass frit in the first metal electrode 6 is greater than the content of the glass frit in the second metal electrode 7, so that the slurry burn-through capability of the first metal electrode 6 is greater than the slurry burn-through capability of the second metal electrode 7, and thus the depth of the metal crystal of the first metal electrode 6 into the P-type doped polysilicon layer 2 is greater than the depth of the metal crystal of the second metal electrode 7 into the N-type doped polysilicon layer 3.

[0068] As an embodiment of the present disclosure, the silicon substrate 1 is further provided with a groove 9 between the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3. The P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3 are physically isolated by the groove 9, which can further improve the isolation effect of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3, and further reduce the risk of short circuit or electric leakage. The width of the groove 9 can be flexibly set according to actual needs, which is not limited herein.

[0069] As an embodiment of the present disclosure, the back contact solar cell further includes a back passivation film layer 8 on the surface of the P-type doped polysilicon layer 2 and the N-type doped polysilicon layer 3, the first metal electrode 6 contacts the P-type doped polysilicon layer 2 through the back passivation film layer 8, and the second metal electrode 7 contacts the N-type doped polysilicon layer 3 through the back passivation film layer 8. The back passivation film layer 8 can further improve the conversion efficiency of the back contact solar cell.

[0070] The present disclosure further provides a battery assembly including the back contact solar cell of the above-mentioned embodiments. It should be noted that the battery assembly and the back contact solar cell have the same or similar beneficial effects, and the related parts between the two can be mutually referred to, and to avoid repetition, the details are not described herein.

[0071] The present disclosure further provides a photovoltaic system including the battery assembly of the above-mentioned embodiments. It should be noted that the battery assembly and the back contact solar cell have the same or similar beneficial effects, and the related parts between the two can be mutually referred to, and to avoid repetition, the details are not described herein.

[0072] The back contact solar cell provided by the embodiment of the present disclosure sets the total area of the plurality of P-type doped polysilicon layers to be greater than the total area of the plurality of N-type doped polysilicon layers, increases the total area of the P-type doped polysilicon layer compared with the N-type doped polysilicon layer under the premise that the area of the N-type doped polysilicon layer is unchanged, can improve the current collection capability of the emitter, thereby improving the cell efficiency; and sets the refractive index of the P-type doped polysilicon layer to be less than the refractive index of the N-type doped polysilicon layer, reduces the refractive index of the P-type doped polysilicon layer under the premise that the refractive index of the N-type doped polysilicon layer is unchanged, can reduce the parasitic absorption effect of the P region, thereby further improving the cell efficiency.

[0073] The above merely describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A back-contact solar cell, wherein, include: N-type silicon substrate; Multiple P-type doped polycrystalline silicon layers are sequentially and spaced apart on the back side of the silicon substrate; Multiple N-type doped polysilicon layers are sequentially and spaced apart on the back side of the silicon substrate, and the N-type doped polysilicon layers and the P-type doped polysilicon layers are alternately arranged. The total area of ​​the plurality of P-type doped polysilicon layers is greater than the total area of ​​the plurality of N-type doped polysilicon layers, and the refractive index of the P-type doped polysilicon layers is less than the refractive index of the N-type doped polysilicon layers.

2. The back-contact solar cell according to claim 1, wherein, The area of ​​at least one of the P-type doped polysilicon layers is greater than the area of ​​any one of the N-type doped polysilicon layers.

3. The back-contact solar cell according to claim 1, wherein, The number of P-type doped polysilicon layers is greater than the number of N-type doped polysilicon layers.

4. The back-contact solar cell according to claim 1, wherein, The ratio of the total area of ​​the P-type doped polycrystalline silicon layer to the total area of ​​the N-type doped polycrystalline silicon layer is 1 to 2, but not equal to 1.

5. The back-contact solar cell according to claim 1, wherein, The ratio of the total area of ​​the P-type doped polycrystalline silicon layer to the total area of ​​the N-type doped polycrystalline silicon layer is 1 to 1.5, and is not equal to 1.

6. The back-contact solar cell according to claim 1, wherein, The length of each P-type doped polysilicon layer is equal to the length of each N-type doped polysilicon layer, and the width of each P-type doped polysilicon layer is greater than the width of each N-type doped polysilicon layer.

7. The back-contact solar cell according to claim 1, wherein, The ratio of the refractive index of the P-type doped polycrystalline silicon layer to the refractive index of the N-type doped polycrystalline silicon layer is 0.5 to 1, and is not equal to 1.

8. The back-contact solar cell according to claim 1, wherein, The volume of the P-type doped polycrystalline silicon layer is larger than the volume of the N-type doped polycrystalline silicon layer.

9. A battery assembly, wherein, Including the back-contact solar cell as described in any one of claims 1 to 8.

10. A photovoltaic system, wherein, Includes the battery assembly as described in claim 9.

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