A back contact solar cell

Abstract

The present disclosure relates to the technical field of solar cells, and discloses a back contact solar cell. The cell comprises a substrate layer, first and second doped layers alternately and spaced apart on the back side of the substrate layer in a first direction; the first substrate layer corresponding to the first doped layer comprises a first inner expansion layer close to the side of the first doped layer; the first inner expansion layer comprises a first upper inner expansion layer and a first lower inner expansion layer stacked; the second substrate layer corresponding to the second doped layer comprises a second inner expansion layer close to the side of the second doped layer; the second inner expansion layer comprises a second upper inner expansion layer and a second lower inner expansion layer stacked; the inner expansion depth of the first inner expansion layer is less than that of the second inner expansion layer; and the density of first doped extensions in the first lower inner expansion layer is greater than that of second doped extensions in the second lower inner expansion layer. The present disclosure can effectively increase the junction area and improve the carrier separation and collection performance.

Description

Technical Field

[0001] This disclosure relates to the field of solar cell technology, and specifically to a back-contact solar cell. Background Technology

[0002] As a representative of next-generation n-type cells, back-contact batteries place all metal grid lines on the back side, avoiding the effects of front-side shading and resulting in excellent optical performance. Furthermore, unlike the front-side PN structure of conventional TOPCon cells, back-contact batteries simultaneously place the PN junction on the back side, making carrier transport primarily lateral and longitudinal. The P-type and N-type doped layers are contacted to the silicon substrate through P-type and N-type inner extension layers, respectively, forming junction regions. In related technologies, the junction area is relatively small, resulting in poor carrier separation and collection performance, and consequently, poor carrier transport performance.

[0003] Therefore, a solution is needed to increase the junction area and improve carrier transport performance. Summary of the Invention

[0004] In view of this, the present disclosure provides a back-contact solar cell to solve the problem that the junction area of ​​the P-type doped layer and N-type doped layer in existing back-contact solar cells is small, resulting in poor carrier separation and collection performance, and thus poor carrier transport performance.

[0005] In a first aspect, this disclosure provides a back-contact solar cell, comprising:

[0006] The base layer includes a light-receiving surface and a backlighting surface that are positioned opposite to each other;

[0007] The first doped layer and the second doped layer are alternately disposed on the back side of the substrate layer along the first direction; the substrate layers corresponding to the first doped layer and the second doped layer are the first substrate layer and the second substrate layer, respectively.

[0008] The first substrate layer includes a first inner expansion layer near the first doped layer; the first inner expansion layer includes a first upper inner expansion layer and a first lower inner expansion layer stacked together; the first upper inner expansion layer is relatively close to the first doped layer; the first lower inner expansion layer includes a plurality of first doped extensions, the first doped extensions extending from the first upper inner expansion layer into the first substrate layer.

[0009] The second substrate layer includes a second inner expansion layer near the second doped layer; the second inner expansion layer includes a second upper inner expansion layer and a second lower inner expansion layer stacked together; the second upper inner expansion layer is relatively close to the second doped layer; the second lower inner expansion layer includes a plurality of second doped extensions, which extend from the second upper inner expansion layer into the second substrate layer.

[0010] Beneficial effects: The back-contact solar cell provided in this disclosure includes a first lower inner extension layer comprising a plurality of first doped extensions extending from the first upper inner extension layer to the first substrate layer; and a second lower inner extension layer comprising a plurality of second doped extensions extending from the second upper inner extension layer to the second substrate layer. By providing a plurality of first doped extensions and a plurality of second doped extensions, the junction area can be effectively increased, and the carrier separation and collection performance can be improved.

[0011] In one optional embodiment, the first doped layer is a P-type doped layer; the second doped layer is an N-type doped layer.

[0012] The first inner expansion layer is a P-type inner expansion layer; the second inner expansion layer is an N-type inner expansion layer;

[0013] The doped atoms in the first doped layer and the first inner extension layer include boron atoms;

[0014] The doped atoms of the second doped layer and the second inner extension layer include phosphorus atoms;

[0015] The substrate is a silicon substrate.

[0016] In one optional implementation, the inner expansion depth of the first inner expansion layer is smaller than the inner expansion depth of the second inner expansion layer.

[0017] The density of the first doped extension in the first lower inner layer is greater than the density of the second doped extension in the second lower inner layer.

[0018] Beneficial Effects: The back-contact solar cell provided in this disclosure has several advantages. First, the inner depth of the P-type inner extension layer is less than that of the N-type inner extension layer. This avoids the problem of defects in the substrate layer caused by an excessively deep P-type inner extension layer, effectively reducing bulk recombination in the substrate layer and improving the passivation performance of the cell. Second, the density of the first doped extension in the first lower inner extension layer is greater than that of the second doped extension in the second lower inner extension layer. This effectively increases the effective area of ​​the PN junction and improves the carrier separation performance of the PN junction. Furthermore, since the transport barrier for carriers entering the P-type doped layer is higher than that for carriers entering the N-type doped layer, the carrier transport performance of the P-type doped layer is relatively poor. By controlling the density of the first doped extension to be greater than that of the second doped extension, carrier separation at the PN junction can be promoted, thereby improving the carrier transport performance of the P-type doped layer. This effectively balances the difference in collection performance between the P-type and N-type doped layers. Therefore, the back-contact solar cell provided in this disclosure can improve the carrier separation performance of the PN junction while reducing bulk recombination in the substrate layer, thereby improving the carrier transport performance of the P-type doped layer and effectively balancing the collection performance difference between the P-type doped layer and the N-type doped layer.

[0019] In one alternative embodiment, the back-contact solar cell further includes:

[0020] An isolation trench is located between adjacent first and second doped layers and extends into the substrate layer; the isolation trench also penetrates the first and second inner expansion layers; the isolation trench separates adjacent first and second doped layers and adjacent first and second inner expansion layers.

[0021] The first tunneling oxide layer is located between the first doped layer and the first inner expansion layer; the first tunneling oxide layer is in contact with the first upper inner expansion layer.

[0022] The second tunneling oxide layer is located between the second doped layer and the second inner expansion layer; the second tunneling oxide layer is in contact with the second upper inner expansion layer.

[0023] The isolation groove is also located between the adjacent first and second tunneling oxide layers.

[0024] In one alternative implementation, the doping concentration of the first doped layer is less than or equal to the doping concentration of the second doped layer;

[0025] The thickness of the first doped layer is greater than or equal to the thickness of the second doped layer.

[0026] Beneficial effects: The back-contact solar cell provided in this disclosure, by increasing the thickness of the P-type doped layer (the thickness of the P-type doped layer is greater than or equal to the thickness of the N-type doped layer), can, on the one hand, make the carrier concentration gradient in the P-type doped layer more gradual, thereby reducing the effective width of the carrier tunneling path and significantly increasing the carrier tunneling probability; on the other hand, a thicker P-type doped layer can have a higher doping concentration, which can maximize the doping concentration of the P-type doped layer, thereby forming a strong local electric field at the interface of the P-type tunneling oxide layer, significantly reducing the barrier height of the P-type tunneling oxide layer, improving the carrier tunneling efficiency in the P-type doped layer, and thus reducing the contact resistance between the metal electrode and the P-type doped layer, improving the conductivity of the P-type doped layer.

[0027] In one alternative embodiment, the doping concentration of the first doped layer is 1E19~1E20 cm⁻¹. -3 ;

[0028] The doping concentration of the second doped layer is 1E20~1E21 cm⁻¹ -3 ;

[0029] The thickness of the first doped layer is 100~300 nm;

[0030] The thickness of the second doped layer is 60~280 nm.

[0031] Beneficial effects: The back-contact solar cell provided in this disclosure, on the one hand, has a doping concentration of 1E19~1E20 cm⁻¹ in the first doped layer. -3 The doping concentration of the second doped layer is 1E20~1E21 cm⁻¹ -3 This approach can reduce surface and bulk recombination in both the first and second doped layers while ensuring low gold / semiconductor contact resistance between the first and second doped layers and the electrodes. Furthermore, the thickness of the first doped layer (100–300 nm) and the second doped layer (60–280 nm) can reduce parasitic absorption of incident light by the doped polysilicon, improving light utilization while maintaining low contact resistance between both layers and reducing carrier transport losses within the first and second doped layers.

[0032] In one alternative embodiment, the thickness of the first tunneling oxide layer is greater than or equal to the thickness of the second tunneling oxide layer.

[0033] Beneficial effects: The back-contact solar cell provided in this disclosure, by increasing the thickness of the first tunneling oxide layer at the corresponding position of the P-type doped layer, can avoid the accumulation of boron doped atoms at the interface between the first tunneling oxide layer and the substrate, thus preventing a significant decrease in the passivation performance of the first tunneling oxide layer and improving the passivation performance of the first doped layer.

[0034] In one alternative embodiment, the thickness of the first tunneling oxide layer is 2~10 nm;

[0035] The thickness of the second tunneling oxide layer is 1~5 nm.

[0036] Beneficial Effects: The back-contact solar cell provided in this disclosure has a first tunneling oxide layer with a thickness of 2-10 nm and a second tunneling oxide layer with a thickness of 1-5 nm. This can improve the efficiency of carrier tunneling from the substrate to the first or second doped layer, thereby improving carrier transport performance while ensuring the passivation effect of the substrate surface. If the thickness of the first or second tunneling oxide layer is too high, it will severely hinder the efficiency of carrier tunneling from the silicon substrate to the first or second doped layer, affecting carrier transport performance. If the thickness of the first or second tunneling oxide layer is too thin, the tunneling oxide layer will not be able to fully passivate the silicon substrate surface, reducing the passivation effect.

[0037] In one alternative implementation, the inner expansion depth of the first upper inner expansion layer is less than the inner expansion depth of the second upper inner expansion layer.

[0038] The average inner expansion depth of the multiple first doped extensions in the first lower inner expansion layer is less than the average inner expansion depth of the multiple second doped extensions in the second lower inner expansion layer.

[0039] Beneficial effects: The back-contact solar cell provided in this disclosure, by setting the inner expansion depth of the first upper inner expansion layer to be smaller than the inner expansion depth of the second upper inner expansion layer, and the average inner expansion depth of the plurality of first doped extensions to be smaller than the average inner expansion depth of the plurality of second doped extensions, can effectively reduce defects inside the substrate layer, thereby effectively reducing bulk recombination in the substrate layer and improving the electrical performance of the cell.

[0040] In one optional implementation, the inner expansion depth of the first upper inner expansion layer is 0.1~0.3 μm;

[0041] The inner expansion depth of the second upper inner expansion layer is 0.2~0.5 μm;

[0042] The inner extension depth of the first doped extension is 0.1~1 μm;

[0043] The inner extension depth of the second doped extension is greater than or equal to 0.2 μm.

[0044] Beneficial Effects: The back-contact solar cell provided in this disclosure, on the one hand, has an inner expansion depth of 0.1~0.3 μm for the first upper inner expansion layer and 0.2~0.5 μm for the second upper inner expansion layer. This can improve carrier separation and transport performance while reducing the bulk recombination of carriers. If the inner expansion depth of the first or second upper inner expansion layer is too high, it will exacerbate the bulk recombination of carriers. If the inner expansion depth of the first or second upper inner expansion layer is too low, it will increase the carrier transport barrier and reduce the junction area, affecting carrier separation and transport performance. On the other hand, the inner expansion depth of the first doped extension is 0.1~1 μm; the inner expansion depth of the second doped extension is greater than or equal to 0.2 μm. This can further improve carrier transport and collection performance while taking into account passivation performance.

[0045] In one alternative embodiment, the average width / diameter of the plurality of first doped extensions in the first lower inner expansion layer is greater than or equal to the average width / diameter of the plurality of second doped extensions in the second lower inner expansion layer.

[0046] Beneficial effects: The back-contact solar cell provided in this disclosure, by controlling the average size (width or diameter) and density of the first doped extension, can not only prevent a large number of boron doped atoms from accumulating near the tunneling oxide layer, but also effectively increase the effective area of ​​the PN junction in the extended doped layer, thereby improving carrier separation and transport performance.

[0047] In one alternative implementation, the surface of the first upper inner expansion layer is not parallel to the light-receiving surface on the side closest to the light-receiving surface.

[0048] The second upper inner expansion layer has a surface that is not parallel to the light-receiving surface on the side closest to the light-receiving surface;

[0049] The surface of the first inner layer is not parallel to the light-receiving surface on the side closest to the light-receiving surface;

[0050] The second inner expansion layer has a surface that is not parallel to the light-receiving surface on the side closest to it. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the structure of a back-contact solar cell according to an embodiment of the present disclosure.

[0053] Figure 2 This is a schematic diagram of the structure of the first and second substrate layers of another back-contact solar cell according to an embodiment of the present disclosure.

[0054] Figure 3 This is a schematic flowchart of a method for fabricating a back-contact solar cell according to an embodiment of the present disclosure.

[0055] Figure 4 This is a schematic diagram illustrating the specific process of a method for fabricating a back-contact solar cell according to an embodiment of this disclosure.

[0056] Explanation of reference numerals in the attached figures:

[0057] 10. Substrate layer; 20. First doped layer; 30. Second doped layer; 40. Isolation trench; 50. First tunneling oxide layer; 60. Second tunneling oxide layer; 101. First substrate layer; 102. Second substrate layer;

[0058] 11. First inner expansion layer; 111. First upper inner expansion layer; 112. First lower inner expansion layer; 71. First doped extension;

[0059] 12. Second inner expansion layer; 121. Second upper inner expansion layer; 122. Second lower inner expansion layer; 72. Second doped extension. Detailed Implementation

[0060] The present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present disclosure and not intended to limit it. It should also be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the drawings, not all structures. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present disclosure. The accompanying drawings show various structural schematic diagrams according to embodiments of the present disclosure. These drawings are not drawn to scale, and some details are enlarged for clarity and may be omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of this disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if one layer / component is "above" another layer / component in one orientation, then when the orientation is reversed, that layer / component can be "below" that other layer / component.

[0061] As a representative of next-generation n-type cells, back-contact batteries place all metal grid lines on the back side, avoiding the effects of front-side shading and resulting in excellent optical performance. Furthermore, unlike the front-side PN structure of conventional TOPCon cells, back-contact batteries simultaneously place the PN junction on the back side, making carrier transport primarily lateral and longitudinal. The P-type and N-type doped layers are contacted to the silicon substrate through P-type and N-type inner extension layers, respectively, forming junction regions. In related technologies, the junction area is relatively small, resulting in poor carrier separation and collection performance, and consequently, poor carrier transport performance.

[0062] Therefore, a solution is needed to increase the junction area and improve carrier transport performance.

[0063] Meanwhile, as a core process in back-contact batteries, the fabrication conditions of p-poly / n-poly significantly affect the subsequent carrier transport and collection mechanisms within the silicon substrate, leading to poor carrier separation at the PN junction. Compared to N-type doped layers, p-type doped layers exhibit inferior carrier transport performance. Furthermore, compared to N-type inner-layer layers, p-type inner-layer layers are more prone to substrate defects and bulk recombination, affecting the battery's passivation performance. Additionally, they can result in excessively high contact resistance between the metal electrode and the p-type doped layer, impacting contact performance.

[0064] refer to Figure 1 and Figure 2 This embodiment provides a back-contact solar cell, comprising:

[0065] The substrate 10 includes a light-receiving surface and a back-lighting surface that are disposed opposite to each other.

[0066] The first doped layer 20 and the second doped layer 30 are alternately disposed on the back side of the substrate 10 along the first direction; the substrate 10 corresponding to the first doped layer 20 and the second doped layer 30 are the first substrate 101 and the second substrate 102, respectively.

[0067] The first substrate layer 101 includes a first inner expansion layer 11 near the first doped layer 20; the first inner expansion layer 11 includes a first upper inner expansion layer 111 and a first lower inner expansion layer 112 stacked together; the first upper inner expansion layer 111 is relatively close to the first doped layer 20; the first lower inner expansion layer 112 includes a plurality of first doped extensions 71, the first doped extensions 71 extending from the first upper inner expansion layer 111 into the first substrate layer 101;

[0068] The second substrate layer 102 includes a second inner expansion layer 12 near the second doped layer 30; the second inner expansion layer 12 includes a second upper inner expansion layer 121 and a second lower inner expansion layer 122 stacked together; the second upper inner expansion layer 121 is relatively close to the second doped layer 30; the second lower inner expansion layer 122 includes a plurality of second doped extensions 72, the second doped extensions 72 extending from the second upper inner expansion layer 121 into the second substrate layer 102.

[0069] It should be noted that, as Figure 2 As shown, "the first doped layer 20 and the second doped layer 30 correspond to the first substrate layer 101 and the second substrate layer 102, respectively." This is only a definition; in reality, both are part of the substrate layer 10, and the entire substrate layer 10 is a single structure. The inner expansion depth of the first inner expansion layer 11 refers to the depth of expansion from the backlight surface of the first substrate layer 101 inwards; the inner expansion depth of the second inner expansion layer 12 refers to the depth of expansion from the backlight surface of the second substrate layer 102 inwards.

[0070] Beneficial effects: The back-contact solar cell provided in this disclosure includes a first lower inner extension layer 112 comprising a plurality of first doped extensions 71 extending from the first upper inner extension layer 111 to the first substrate layer 101; and a second lower inner extension layer 122 comprising a plurality of second doped extensions 72 extending from the second upper inner extension layer 121 to the second substrate layer 102. By providing a plurality of first doped extensions 71 and a plurality of second doped extensions 72, the junction area can be effectively increased, and the carrier separation and collection performance can be improved.

[0071] In some alternative embodiments, the first doped layer 20 is a P-type doped layer; the second doped layer 30 is an N-type doped layer;

[0072] The first inner expansion layer 11 is a P-type inner expansion layer; the second inner expansion layer 12 is an N-type inner expansion layer;

[0073] The doped atoms of the first doped layer 20 and the first inner extension layer 11 include boron atoms;

[0074] The doped atoms of the second doped layer 30 and the second inner extension layer 12 include phosphorus atoms;

[0075] The first doped layer 20 is a P-type polycrystalline silicon doped layer; the second doped layer 30 is an N-type polycrystalline silicon doped layer;

[0076] The substrate 10 is a silicon substrate.

[0077] In specific implementation, the first doped layer 20 is a P-type doped layer; the second doped layer 30 is an N-type doped layer; and the silicon substrate, except for the first inner extension layer 11 and the second inner extension layer 12, is an N-type substrate. A PN junction exists between the first substrate layer 101 and the first doped layer 20 / first inner extension layer 11, and the inner extension depth of the first inner extension layer 11 is the junction depth of the PN junction. The PN junction mainly functions to separate charge carriers in the battery. The density of the first doped extension 71 is greater than the density of the second doped extension 72, meaning that the same area corresponds to the preset regions of the first doped layer 20 and the second doped layer 30, respectively. The number of first doped extensions 71 is greater than the number of second doped extensions 72, which can increase the contact area between the N-type substrate and the first inner extension layer 11, that is, increase the effective area of ​​the PN junction.

[0078] In related technologies, carrier separation at the PN junction is poor, and the carrier transport performance of the P-type doped layer is worse than that of the N-type doped layer. Furthermore, compared to the N-type inner extension layer, the P-type inner extension layer is more prone to causing defects in the substrate layer, leading to bulk recombination and affecting the passivation performance of the battery. In addition, it can also result in excessively high contact resistance between the metal electrode and the P-type doped layer, affecting contact performance.

[0079] In some alternative embodiments, the first doped layer 20 and the first inner expansion layer 11 are adapted to be formed by a boron diffusion process and a localized laser annealing process; the second doped layer 30 and the second inner expansion layer 12 are adapted to be formed by a phosphorus diffusion process and a localized laser annealing process.

[0080] In some alternative implementations, the inner expansion depth of the first inner expansion layer 11 is less than the inner expansion depth of the second inner expansion layer 12.

[0081] In some alternative embodiments, the density of the first doped extension 71 in the first lower inner extension layer 112 is greater than the density of the second doped extension 72 in the second lower inner extension layer 122.

[0082] In practice, compared to the atomic radius of phosphorus (~107 pm), the atomic radius of boron (~84 pm) differs significantly from that of silicon (~111 pm), making it easier to cause lattice distortion and defect generation in silicon during doping. This means that the first inner extension layer 11 is more prone to causing defects in the substrate layer 10 compared to the second inner extension layer 12. Therefore, if the inner extension depth of the first inner extension layer 11 is too large, it will lead to more defects within the corresponding first substrate layer 101. Thus, controlling the inner extension depth of the first inner extension layer 11 to be smaller than that of the second inner extension layer 12 can reduce defects within the silicon substrate, thereby effectively reducing bulk recombination in the substrate layer 10. However, simply reducing the inner extension depth of the first inner extension layer 11 will reduce the carrier separation performance of the PN junction. Therefore, by increasing the density of the first doped extension 71, the contact area between the first substrate layer 101 and the first inner extension layer 11 can be increased, thereby improving the carrier separation performance of the PN junction.

[0083] Beneficial Effects: The back-contact solar cell provided in this embodiment has several advantages. First, the inner depth of the P-type inner extension layer is less than that of the N-type inner extension layer. This avoids the problem of defects arising inside the substrate layer 10 due to an excessively deep P-type inner extension layer, effectively reducing bulk recombination in the substrate layer 10 and improving the passivation performance of the cell. Second, the density of the first doped extension 71 in the first lower inner extension layer 112 is greater than the density of the second doped extension 72 in the second lower inner extension layer 122. This effectively increases the effective area of ​​the PN junction and improves the carrier separation performance of the PN junction. Furthermore, since the transport barrier for carriers entering the P-type doped layer is higher than that for carriers entering the N-type doped layer, the carrier transport performance of the P-type doped layer is relatively poor. By controlling the density of the first doped extension 71 to be greater than that of the second doped extension 72, carrier separation at the PN junction can be promoted, thereby improving the carrier transport performance of the P-type doped layer. This effectively balances the difference in collection performance between the P-type and N-type doped layers. Therefore, the back-contact solar cell provided in this embodiment can improve the carrier separation performance of the PN junction while reducing the bulk recombination of the substrate layer 10, thereby improving the carrier transport performance of the P-type doped layer and effectively balancing the collection performance difference between the P-type doped layer and the N-type doped layer.

[0084] In some alternative implementations, the backlight surface of the first substrate layer 101 and the backlight surface of the second substrate layer 102 are not on the same plane. There may be a height difference between the backlight surface of the first substrate layer 101 and the backlight surface of the second substrate layer 102.

[0085] In some alternative embodiments, the back-contact solar cell further includes:

[0086] An isolation groove 40 is located between adjacent first doped layers 20 and second doped layers 30 and extends into the substrate layer 10; the isolation groove 40 separates adjacent first doped layers 20 and second doped layers 30.

[0087] The first tunneling oxide layer 50 is located between the first doped layer 20 and the first inner expansion layer 11; the first tunneling oxide layer 50 is in contact with the first upper inner expansion layer 111.

[0088] The second tunneling oxide layer 60 is located between the second doped layer 30 and the second inner expansion layer 12; the second tunneling oxide layer 60 is in contact with the second upper inner expansion layer 121.

[0089] The isolation groove 40 is also located between the adjacent first tunneling oxide layer 50 and second tunneling oxide layer 60.

[0090] In some alternative embodiments, the isolation groove 40 is also located between adjacent first inner expansion layer 11 and second inner expansion layer 12 and extends into the base layer 10 to space the adjacent first inner expansion layer 11 and second inner expansion layer 12.

[0091] In some alternative implementations, the doping concentration of the first doped layer 20 is less than or equal to the doping concentration of the second doped layer 30;

[0092] The thickness of the first doped layer 20 is greater than or equal to the thickness of the second doped layer 30.

[0093] In specific implementation, the first doped layer 20 is a P-type doped layer; the second doped layer 30 is an N-type doped layer. Due to the lower concentration of boron doped atoms in the first doped layer 20 formed by the boron diffusion process compared to the concentration of phosphorus doped atoms in the second doped layer 30, the contact resistance between the subsequently formed metal electrode and the first doped layer 20 is too high, resulting in greater carrier loss in the first doped layer 20. At the same time, since the internal conductivity type of the first doped layer 20 is holes (positive charge), while that of the second doped layer 30 is electrons (negative charge), the conductivity of the first doped layer 20 is even weaker than that of the second doped layer 30.

[0094] Beneficial effects: The back-contact solar cell provided in this embodiment, by increasing the thickness of the P-type doped layer (the thickness of the P-type doped layer is greater than or equal to the thickness of the N-type doped layer), can, on the one hand, make the carrier concentration gradient in the P-type doped layer more gradual, thereby reducing the effective width of the carrier tunneling path and significantly increasing the carrier tunneling probability; on the other hand, a thicker P-type doped layer can have a higher doping concentration, which can maximize the total number of carriers in the P-type doped layer, thereby forming a strong local electric field at the interface of the first tunneling oxide layer 50, significantly reducing the barrier height of the first tunneling oxide layer 50, improving the carrier tunneling efficiency in the P-type doped layer, and thus reducing the contact resistance between the metal electrode and the P-type doped layer, improving the conductivity of the P-type doped layer.

[0095] In some alternative embodiments, the doping concentration of the first doped layer 20 is 1E19~1E20 cm⁻¹. -3 ;

[0096] The doping concentration of the second doped layer 30 is 1E20~1E21 cm⁻¹. -3 .

[0097] Specifically, if the boron atom doping concentration of the first doped layer 20 is greater than 1E20 cm⁻¹ -3 This will significantly increase the probability of defects induced by impurity phosphorus atoms, leading to increased surface and bulk recombination; if the doping concentration of the first doped layer 20 is less than 1E19 cm⁻¹ -3 This will increase the resistance of the subsequent gold / semiconductor contact. Therefore, the doping concentration of the first doped layer 20 is 1E19~1E20 cm⁻¹. -3 At the same time, it can reduce surface recombination and bulk recombination of the first doped layer 20, while also ensuring a low gold / semi-contact resistance between the first doped layer 20 and the electrode.

[0098] Furthermore, unlike boron doping atoms, phosphorus doping atoms have atomic radii closer to those of silicon atoms, resulting in fewer lattice defects. Therefore, the phosphorus doping concentration can be relatively increased to maximize the reduction of gold / semiconductor contact resistance and enhance field passivation effects. Thus, the doping concentration of the second doped layer 30 is, to a certain extent, higher than that of the first doped layer 20, specifically, the doping concentration of the second doped layer 30 is 1E20~1E21 cm⁻¹. -3 If the phosphorus atom doping concentration of the second doped layer 30 is greater than 1E21 cm⁻¹ -3 This significantly increases the probability of defects induced by impurity phosphorus atoms, leading to increased surface and bulk recombination; if the doping concentration of the second doped layer 30 is less than 1E20 cm⁻¹ -3 This will increase the subsequent gold / semiconductor contact resistance. Therefore, the doping concentration of the second doped layer 30 is 1E20~1E21 cm⁻¹. -3At the same time, it is possible to reduce surface recombination and bulk recombination of the second doped layer 30 while also achieving a lower gold / semi contact resistance between the second doped layer 30 and the electrode.

[0099] In some alternative embodiments, the thickness of the first doped layer 20 is 100~300 nm;

[0100] The thickness of the second doped layer 30 is 60~280 nm.

[0101] Specifically, if the thickness of the first doped layer 20 is greater than 300 nm, it will increase the parasitic absorption of incident light by the doped polycrystalline silicon, leading to a decrease in light utilization. If the thickness is less than 100 nm, it will increase the resistance of the doped polycrystalline silicon film, resulting in an increase in the resistance of the subsequent gold / semiconductor contact and also increasing the carrier transport loss in this film. Therefore, a thickness of 100~300 nm for the first doped layer 20 can improve light utilization while ensuring a low gold / semiconductor contact resistance between the first doped layer 20 and the electrode, without additionally increasing the carrier transport loss in this film.

[0102] Furthermore, since the phosphorus atom concentration of the second doped layer 30 (i.e., the phosphorus-doped polycrystalline silicon layer) is higher than the boron atom concentration of the first doped layer 20 (i.e., the boron-doped polycrystalline silicon layer), the film thickness of the second doped layer 30 can be relatively thinner than that of the first doped layer 20. While maintaining the contact performance without degrading, the parasitic absorption problem caused by the thickness of the second doped layer 30 can be reduced as much as possible, thereby improving the optical performance.

[0103] If the thickness of the second doped layer 30 is greater than 280 nm, it will increase the parasitic absorption of incident light by the doped polysilicon, leading to a decrease in light utilization. If the thickness is less than 60 nm, it will increase the resistance of the doped polysilicon film, resulting in an increase in the subsequent gold / semiconductor contact resistance and also increasing the carrier transport loss in this film. Therefore, the thickness of the second doped layer 30 is 60~280 nm, which can improve the light utilization while ensuring a low gold / semiconductor contact resistance between the second doped layer 30 and the electrode, without additionally increasing the carrier transport loss in this film.

[0104] Beneficial effects: In the back-contact solar cell provided in this embodiment, the doping concentration of the first doped layer 20 is 1E19~1E20 cm⁻¹. -3 The doping concentration of the second doped layer 30 is 1E20~1E21 cm⁻¹. -3This design reduces surface and bulk recombination in the first doped layer 20 and the second doped layer 30 while ensuring low gold / semiconductor contact resistance between the first doped layer 20 and the electrode, and between the second doped layer 30 and the electrode. Furthermore, the thickness of the first doped layer 20 is 100–300 nm, and the thickness of the second doped layer 30 is 60–280 nm. This reduces parasitic absorption of incident light by the doped polysilicon, improving light utilization, while ensuring low contact resistance between the first doped layer 20 and the electrode, and between the second doped layer 30 and the electrode, and reducing carrier transport losses within the first and second doped layers 20 and 30.

[0105] In some alternative embodiments, the thickness of the first tunneling oxide layer 50 is greater than or equal to the thickness of the second tunneling oxide layer 60.

[0106] The passivation performance of the conventional first doped layer 20 is weaker than that of the second doped layer 30, mainly for the following reasons: Because the boron doped atoms in the first doped layer 20 are present in Si and SiO... x The segregation coefficient and solid solubility in the middle layer differ from those of the phosphorus-doped atoms in the second doped layer 30, while boron atoms are readily soluble in SiO. x In contrast, phosphorus atoms tend to accumulate in the first tunneling oxide layer 50 at the bottom of the first doped layer 20 during boron diffusion. This significantly reduces the passivation performance of the first tunneling oxide layer 50, fundamentally damaging its passivation properties and potentially leading to passivation layer failure. Therefore, to ensure the passivation performance of the first tunneling oxide layer 50 and prevent passivation layer failure, the thickness of the first tunneling oxide layer 50 is relatively thicker than that of the second tunneling oxide layer 60.

[0107] Beneficial effects: The back contact solar cell provided in this embodiment can avoid the accumulation of boron doped atoms at the interface between the first tunneling oxide layer and the substrate by increasing the thickness of the first tunneling oxide layer 50 at the corresponding position of the P-type doped layer, thus preventing a significant decrease in the passivation performance of the first tunneling oxide layer 50 and improving the passivation performance of the first doped layer 20.

[0108] In some alternative embodiments, the thickness of the first tunneling oxide layer 50 is 2 to 10 nm; the thickness of the second tunneling oxide layer 60 is 1 to 5 nm.

[0109] Beneficial Effects: In the back-contact solar cell provided in this embodiment, the thickness of the first tunneling oxide layer 50 is 2-10 nm, and the thickness of the second tunneling oxide layer 60 is 1-5 nm. This can improve the efficiency of carrier tunneling from the substrate layer 10 to the first doped layer 20 or the second doped layer 30, thereby improving carrier transport performance while ensuring the passivation effect of the substrate surface. If the thickness of the first tunneling oxide layer 50 or the second tunneling oxide layer 60 is too high, it will severely hinder the efficiency of carrier tunneling from the substrate layer 10 to the first doped layer 20 or the second doped layer 30, affecting carrier transport performance. If the thickness of the first tunneling oxide layer 50 or the second tunneling oxide layer 60 is too thin, the tunneling oxide layer will not be able to fully passivate the silicon substrate surface, reducing the passivation effect.

[0110] In some alternative implementations, the inner expansion depth of the first upper inner expansion layer 111 is less than the inner expansion depth of the second upper inner expansion layer 121.

[0111] Specifically, the inner expansion depth of the first upper inner expansion layer 111 refers to the depth of the inner expansion from the backlight surface of the first base layer 101, that is... Figure 1 The thickness of the first upper inner expansion layer 111; the inner expansion depth of the second upper inner expansion layer 121 refers to the depth of the inner expansion from the backlight surface of the second substrate layer 102, i.e. Figure 1 The thickness of the second upper inner expansion layer 121.

[0112] In some alternative embodiments, the average inner depth of the plurality of first doped extensions 71 in the first lower inner extension layer 112 is less than the average inner depth of the plurality of second doped extensions 72 in the second lower inner extension layer 122.

[0113] Specifically, the average inward expansion depth of the plurality of first doped extensions 71 in the first lower inner expansion layer 112 refers to the depth of inward expansion from the surface of the first upper inner expansion layer 111 facing away from the first doped layer 20 into the interior of the first substrate layer 101, that is... Figure 1 The average extension length of the plurality of first doped extensions 71. The average inward expansion depth of the plurality of second doped extensions 72 in the second lower inner expansion layer 122 refers to the depth of inward expansion from the surface of the second upper inner expansion layer 121 facing away from the second doped layer 30 into the interior of the second substrate layer 102, i.e. Figure 1 The average extension length of the multiple second doped extensions 72.

[0114] In specific implementation, the inner expansion depths of the plurality of first doped extensions 71 in the first lower inner expansion layer 112 can be the same or can have certain differences. The inner expansion depths of the plurality of second doped extensions 72 in the second lower inner expansion layer 122 can be the same or can have certain differences. The average inner expansion depth of the plurality of first doped extensions 71 is less than the average inner expansion depth of the plurality of second doped extensions 72.

[0115] Beneficial effects: The back-contact solar cell provided in this embodiment can effectively reduce defects inside the substrate layer 10 by setting the inner expansion depth of the first upper inner expansion layer 111 to be smaller than the inner expansion depth of the second upper inner expansion layer 121, and the average inner expansion depth of the plurality of first doped extensions 71 to be smaller than the average inner expansion depth of the plurality of second doped extensions 72, thereby effectively reducing the bulk recombination of the substrate layer 10 and improving the electrical performance of the cell.

[0116] In some optional embodiments, the inner expansion depth of the first upper inner expansion layer 111 is 0.1~0.3 μm; and the inner expansion depth of the second upper inner expansion layer 121 is 0.2~0.5 μm.

[0117] In some alternative embodiments, the inner depth of the first doped extension 71 is 0.1~1 μm;

[0118] The inner extension depth of the second doped extension 72 is greater than or equal to 0.2 μm.

[0119] Beneficial Effects: The back-contact solar cell provided in this embodiment has the following advantages: Firstly, the inner expansion depth of the first upper inner expansion layer 111 is 0.1~0.3 μm, and the inner expansion depth of the second upper inner expansion layer 121 is 0.2~0.5 μm. This can improve carrier separation and transport performance while reducing the bulk recombination degree of carriers. If the inner expansion depth of the first upper inner expansion layer 111 or the second upper inner expansion layer 121 is too high, it will aggravate the bulk recombination degree of carriers in the substrate layer 10. If the inner expansion depth of the first upper inner expansion layer 111 or the second upper inner expansion layer 121 is too low, it will increase the carrier transport barrier and reduce the junction area, affecting the carrier separation and transport performance. Secondly, the inner expansion depth of the first doped extension 71 is 0.1~1 μm, and the inner expansion depth of the second doped extension 72 is greater than or equal to 0.2 μm. This can further improve carrier transport and collection performance while taking into account passivation performance.

[0120] In some alternative embodiments, the average width / average diameter of the plurality of first doped extensions 71 in the first lower inner layer 112 is greater than or equal to the average width / average diameter of the plurality of second doped extensions 72 in the second lower inner layer 122.

[0121] Because the segregation coefficient and solid solubility of boron doped atoms in the first inner extension layer 11 differ from those of phosphorus doped atoms in the second inner extension layer 12, boron doped atoms are more likely to accumulate in the tunneling oxide layer, thereby compromising the passivation performance of the tunneling oxide layer. To address this issue, increasing the average size (width or diameter) and density of the first doped extension 71 not only prevents a large number of boron doped atoms from accumulating near the tunneling oxide layer but also effectively increases the effective area of ​​the PN junction in the extended doped layer, improving carrier separation and transport performance.

[0122] In some alternative embodiments, the isolation groove 40 can be a trench structure that is relatively recessed on the surface of the first doped layer 20 and the second doped layer 30, obtained by laser etching and wet cleaning. In this embodiment, the isolation trench extends a certain distance into the substrate layer 10, and the bottom of the isolation groove 40 is a textured structure. In some examples, the textured structure is a pyramid textured surface.

[0123] It should be noted that the isolation groove 40 is located between adjacent first doped layers 20 and second doped layers 30, meaning that the isolation groove 40 penetrates the first doped layer 20 and second doped layer 30 from the surface of the first doped layer 20 and the surface of the second doped layer 30 toward the substrate layer 10. Figure 1 and Figure 2 The isolation groove 40 extends downwards. The isolation groove 40 also extends downwards through the first tunneling oxide layer 50 and the second tunneling oxide layer 60. While penetrating deep into the substrate layer 10, the isolation groove 40 also penetrates the first inner expansion layer 11 and the second inner expansion layer 12.

[0124] In some alternative embodiments, the surface of the first upper inner expansion layer 111 is not parallel to the light-receiving surface on the side closest to the light-receiving surface;

[0125] The second upper inner expansion layer 121 has a surface that is not parallel to the light-receiving surface on the side closest to the light-receiving surface;

[0126] At least some of the first doped extensions 71 in the first lower inner expansion layer 112 have different inner expansion depths; the surface of the first lower inner expansion layer 112 on the side closer to the light-receiving surface is not parallel to the light-receiving surface.

[0127] At least some of the second doped extensions 72 in the second lower inner expansion layer 122 have different inner expansion depths; the surface of the second lower inner expansion layer 122 on the side closer to the light-receiving surface is not parallel to the light-receiving surface.

[0128] Specifically, the bottom of the first upper inner expansion layer 111 and the second upper inner expansion layer 121 can be a flat surface or an uneven surface, that is, the inner expansion depth is different at least in some positions.

[0129] In some alternative implementations, the light-receiving surface and the back-lighting surface of the substrate 10 are parallel.

[0130] In some alternative implementations, the backlight surface of the first substrate 101 and the backlight surface of the second substrate 102 are not on the same plane.

[0131] The surface of the first upper inner expansion layer 111 near the light-receiving surface is not on the same plane as the surface of the second upper inner expansion layer 121 near the light-receiving surface.

[0132] The surface of the first lower inner expansion layer 112 near the light-receiving surface is not on the same plane as the surface of the second lower inner expansion layer 122 near the light-receiving surface.

[0133] In some alternative implementations, the backlight surface of the first substrate 101 and the backlight surface of the second substrate 102 are parallel.

[0134] refer to Figure 3 This disclosure also provides a method for preparing a back-contact solar cell, which includes the following steps S101 to S104.

[0135] Step S101: Provide a substrate layer 10, which includes a light-receiving surface and a backlight surface disposed opposite to each other.

[0136] In a specific implementation, the substrate 10 is a silicon substrate. In one example, the substrate 10 is an n-type silicon wafer. The substrate 10 includes a first substrate 101 and a second substrate 102 that are alternately spaced along a first direction in the vertical direction. In subsequent processes, a first doped layer 20 is formed on the surface of the first substrate 101, and a second doped layer 30 is formed on the surface of the second substrate 102. In some embodiments, the backlight surface of the first substrate 101 and the backlight surface of the second substrate 102 are not on the same plane.

[0137] In step S102, a first doped layer 20 and a second doped layer 30 with alternating intervals in a first direction are formed on one side of the backlight surface of the substrate layer 10. At the same time, a first upper inner expansion layer 111 and a second upper inner expansion layer 121 are formed in the substrate layer 10. The first upper inner expansion layer 111 is located on the side close to the first doped layer 20. The second upper inner expansion layer 121 is located on the side close to the second doped layer 30. The first doped layer 20 is a P-type doped layer. The second doped layer 30 is an N-type doped layer.

[0138] In step S103, a first lower inner expansion layer 112 is formed on the side of the first upper inner expansion layer 111 facing away from the first doped layer 20 using a local laser annealing process. The first lower inner expansion layer 112 includes a plurality of first doped extensions 71. The first upper inner expansion layer 111 and the first lower inner expansion layer 112 constitute the first inner expansion layer 11. The first inner expansion layer 11 is a P-type inner expansion layer.

[0139] In step S104, a second lower inner expansion layer 122 is formed on the side of the second upper inner expansion layer 121 opposite to the second doped layer 30 using a local laser annealing process. The second lower inner expansion layer 122 includes a plurality of second doped extensions 72. The second upper inner expansion layer 121 and the second lower inner expansion layer 122 constitute the second inner expansion layer 12. The second inner expansion layer 12 is an N-type inner expansion layer. The density of the first doped extension 71 in the first lower inner expansion layer 112 is greater than the density of the second doped extension 72 in the second lower inner expansion layer 122. The inner expansion depth of the first inner expansion layer 11 is less than the inner expansion depth of the second inner expansion layer 12.

[0140] In some optional embodiments, step S102 includes: forming a first tunneling oxide layer 50 and a second tunneling oxide layer 60 with alternating spacing in a first direction, and a first doped layer 20 and a second doped layer 30 with alternating spacing in a first direction on the backlight side of the substrate layer 10; simultaneously forming a first upper inner expansion layer 111 and a second upper inner expansion layer 121 in the substrate layer 10 near the backlight side; the first upper inner expansion layer 111 is located near the first doped layer 20; the second upper inner expansion layer 121 is located near the second doped layer 30; the first tunneling oxide layer 50 is located between the first doped layer 20 and the first inner expansion layer 11; the second tunneling oxide layer 60 is located between the second doped layer 30 and the second inner expansion layer 12.

[0141] Steps S101 to S104 are only illustrative examples and are not intended to limit the specific order of process steps. In some optional embodiments, the order of the above steps can be adjusted according to the actual situation. For example, step S104 can be executed first, followed by step S103.

[0142] refer to Figure 4 This disclosure also provides a schematic flowchart of a method for preparing a back-contact solar cell, including the following steps S201 to S205.

[0143] Step S201, a substrate layer 10 is provided, the substrate layer 10 includes a light-receiving surface and a backlight surface disposed opposite to each other; the substrate layer 10 includes a first substrate layer 101 and a second substrate layer 102 that are alternately distributed along a first direction in the vertical direction.

[0144] In a specific implementation, the substrate 10 is a silicon substrate. In one example, the substrate 10 is an N-type silicon wafer. In subsequent processes, a first doped layer 20 is formed on the back surface of the first substrate 101, and a second doped layer 30 is formed on the back surface of the second substrate 102. In some embodiments, the back surface of the first substrate 101 and the back surface of the second substrate 102 are not on the same plane.

[0145] In step S202, an initial first oxide layer and an initial first polysilicon layer are formed on the back surface of the first substrate layer 101; and a first doped layer 20 is formed on the initial first polysilicon layer and a first tunneling oxide layer 50 is formed on the initial first oxide layer through a boron doping process. At the same time, a first upper inner expansion layer 111 is formed on the first substrate layer 101. The first upper inner expansion layer 111 is located on the side close to the first tunneling oxide layer 50. The first doped layer is a P-type doped layer.

[0146] In step S203, a first lower inner expansion layer 112 is formed on the side of the first upper inner expansion layer 111 opposite to the first doped layer 20 using a local laser annealing process. The first lower inner expansion layer 112 includes a plurality of first doped extensions 71. The first upper inner expansion layer 111 and the first lower inner expansion layer 112 constitute the first inner expansion layer 11.

[0147] In step S204, an initial second oxide layer and an initial second polysilicon layer are formed on the back surface of the second substrate layer 102; and a second doped layer 30 is formed from the initial second polysilicon layer and a second tunneling oxide layer 60 is formed from the initial second oxide layer through a phosphorus doping process. At the same time, a second upper inner expansion layer 121 is formed in the second substrate layer 102; the second upper inner expansion layer 121 is located on the side close to the second tunneling oxide layer 60; the second doped layer 30 is an N-type doped layer; the thickness of the first doped layer 20 is greater than or equal to the thickness of the second doped layer 30; and the thickness of the first tunneling oxide layer 50 is greater than or equal to the thickness of the second tunneling oxide layer 60.

[0148] In specific implementation, the thickness of the initial first polysilicon layer is greater than or equal to the initial second polysilicon layer, thereby making the thickness of the first doped layer 20 greater than or equal to the thickness of the second doped layer 30. The thickness of the initial first oxide layer is greater than or equal to the initial second oxide layer, thereby making the thickness of the first tunneling oxide layer 50 greater than or equal to the thickness of the second tunneling oxide layer 60.

[0149] In step S205, a second lower inner expansion layer 122 is formed on the side of the second upper inner expansion layer 121 opposite to the second doped layer 30 using a local laser annealing process. The second lower inner expansion layer 122 includes multiple second doped extensions. The second upper inner expansion layer 121 and the second lower inner expansion layer 122 constitute the second inner expansion layer 12. The density of the first doped extension 71 in the first lower inner expansion layer 112 is greater than the density of the second doped extension 72 in the second lower inner expansion layer 122. The inner expansion depth of the first inner expansion layer 11 is less than the inner expansion depth of the second inner expansion layer 12. The first inner expansion layer 11 is a P-type inner expansion layer. The second inner expansion layer 12 is an N-type inner expansion layer.

[0150] In specific implementation, the inner expansion depth of the first inner expansion layer 11 is controlled to be less than that of the second inner expansion layer 12 by controlling the deposition process of the initial first oxide layer and the initial second oxide layer, the phosphorus doping process and the conditions of the phosphorus doping process, and the conditions of the local laser annealing process. At the same time, the density of the first doped extension 71 is made greater than the density of the second doped extension 72 by controlling the conditions of the local laser annealing process.

[0151] For example, by controlling the deposition temperature and deposition time of the initial first oxide layer and the initial second oxide layer, the porosity of the initial first oxide layer is made smaller than that of the initial second oxide layer. At the same time, by controlling the intensity of the laser region in the local laser annealing process, the inner expansion depth of the first inner expansion layer 11 is made smaller than that of the second inner expansion layer 12.

[0152] By controlling the density of the laser region in the local laser annealing process, the density of the first doped extension 71 is made greater than the density of the second doped extension 72.

[0153] In some optional embodiments, by controlling the deposition temperature and deposition time of the initial first oxide layer and the initial second oxide layer, the porosity of the initial first oxide layer is made smaller than that of the initial second oxide layer, thereby making the inner expansion depth of the first upper inner expansion layer 111 smaller than that of the second upper inner expansion layer 121. Based on this, by further controlling the intensity of the laser region in the domain laser annealing process, the average inner expansion depth of the plurality of first doped extensions 71 in the first lower inner expansion layer 112 can be made smaller than the average inner expansion depth of the plurality of second doped extensions 72 in the second lower inner expansion layer 122.

[0154] In some alternative implementations, by controlling the shape and size of the laser region in the local laser annealing process, the average width / diameter of the plurality of first doped extensions 71 in the first lower inner expansion layer 112 can be controlled to be greater than or equal to the average width / diameter of the plurality of second doped extensions 72 in the second lower inner expansion layer 122.

[0155] In some alternative embodiments, the method for fabricating a back-contact solar cell further includes:

[0156] An isolation groove 40 is formed between adjacent first doped layers 20 and second doped layers 30 and extends into the substrate layer 10; the isolation groove 40 separates adjacent first doped layers 20 and second doped layers 30; the isolation groove 40 is also located between adjacent first tunneling oxide layers 50 and second tunneling oxide layers 60.

[0157] In some alternative embodiments, the isolation groove 40 is also located between adjacent first inner expansion layer 11 and second inner expansion layer 12 and extends into the base layer 10 to space the adjacent first inner expansion layer 11 and second inner expansion layer 12.

[0158] In some alternative embodiments, the method for fabricating a back-contact solar cell further includes:

[0159] A passivation layer is formed, which is located on the surface of the first doped layer 20 and the surface of the second doped layer 30, and covers the inner wall of the isolation groove 40.

[0160] In some alternative implementations, the passivation layer also covers the light-receiving surface and sides of the substrate 10.

[0161] In some alternative embodiments, the method for fabricating a back-contact solar cell further includes:

[0162] A first electrode is formed on the surface of the first doped layer 20; a second electrode is formed on the surface of the second doped layer 30.

[0163] The materials of the first and second electrodes include metals.

[0164] Steps S201 to S205 are only illustrative examples and are not intended to limit the specific order of process steps. In some optional embodiments, the order of the above steps can be adjusted according to the actual situation.

[0165] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0166] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A back-contact solar cell, characterized in that, include: The base layer includes a light-receiving surface and a backlighting surface that are positioned opposite to each other; A first doped layer and a second doped layer are alternately disposed on one side of the back surface of the substrate layer along a first direction; the substrate layers corresponding to the first doped layer and the second doped layer are the first substrate layer and the second substrate layer, respectively. The first substrate layer includes a first inner expansion layer near the first doped layer; the first inner expansion layer includes a first upper inner expansion layer and a first lower inner expansion layer stacked together; the first upper inner expansion layer is relatively close to the first doped layer; the first lower inner expansion layer includes a plurality of first doped extensions, the first doped extensions extending from the first upper inner expansion layer into the first substrate layer; The second substrate layer includes a second inner expansion layer near the second doped layer; the second inner expansion layer includes a second upper inner expansion layer and a second lower inner expansion layer stacked together; the second upper inner expansion layer is relatively close to the second doped layer; the second lower inner expansion layer includes a plurality of second doped extensions, the second doped extensions extending from the second upper inner expansion layer into the second substrate layer; Wherein, the first doped layer is a P-type doped layer; the second doped layer is an N-type doped layer; the first inner expansion layer is a P-type inner expansion layer; the second inner expansion layer is an N-type inner expansion layer; the doping atoms of the first doped layer and the first inner expansion layer include boron atoms; the doping atoms of the second doped layer and the second inner expansion layer include phosphorus atoms; the substrate layer is an N-type silicon substrate; The inner expansion depth of the first inner expansion layer is less than the inner expansion depth of the second inner expansion layer; the density of the first doped extension in the first lower inner expansion layer is greater than the density of the second doped extension in the second lower inner expansion layer.

2. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell also includes: An isolation groove is located between adjacent first doped layers and second doped layers and extends into the substrate layer; the isolation groove also penetrates the first inner expansion layer and the second inner expansion layer; the isolation groove separates adjacent first doped layers and second doped layers, and also separates adjacent first inner expansion layers and second inner expansion layers. A first tunneling oxide layer is located between the first doped layer and the first inner expansion layer; the first tunneling oxide layer is in contact with the first upper inner expansion layer. The second tunneling oxide layer is located between the second doped layer and the second inner expansion layer; the second tunneling oxide layer is in contact with the second upper inner expansion layer. The isolation groove is also located between adjacent first tunneling oxide layers and second tunneling oxide layers.

3. The back-contact solar cell according to claim 1, characterized in that, The doping concentration of the first doped layer is less than or equal to the doping concentration of the second doped layer; The thickness of the first doped layer is greater than or equal to the thickness of the second doped layer.

4. The back-contact solar cell according to claim 1, characterized in that, The doping concentration of the first doped layer is 1E19~1E20 cm⁻¹ -3 ; The doping concentration of the second doped layer is 1E20~1E21 cm⁻¹ -3 ; The thickness of the first doped layer is 100~300 nm; The thickness of the second doped layer is 60~280 nm.

5. The back-contact solar cell according to claim 2, characterized in that, The thickness of the first tunneling oxide layer is greater than or equal to the thickness of the second tunneling oxide layer.

6. The back-contact solar cell according to claim 2, characterized in that, The thickness of the first tunneling oxide layer is 2~10 nm; The thickness of the second tunneling oxide layer is 1~5 nm.

7. The back-contact solar cell according to claim 1, characterized in that, The inner expansion depth of the first upper inner expansion layer is smaller than the inner expansion depth of the second upper inner expansion layer; The average inner expansion depth of the plurality of first doped extensions in the first lower inner expansion layer is less than the average inner expansion depth of the plurality of second doped extensions in the second lower inner expansion layer.

8. The back-contact solar cell according to claim 1, characterized in that, The inner expansion depth of the first upper inner expansion layer is 0.1~0.3 μm; The inner expansion depth of the second upper inner expansion layer is 0.2~0.5 μm; The inner extension depth of the first doped extension is 0.1~1 μm; The inner extension depth of the second doped extension is greater than or equal to 0.2 μm.

9. The back-contact solar cell according to claim 1, characterized in that, The average width or average diameter of the plurality of first doped extensions in the first lower inner expansion layer is greater than or equal to the average width or average diameter of the plurality of second doped extensions in the second lower inner expansion layer.

10. The back-contact solar cell according to claim 1, characterized in that, The surface of the first upper inner expansion layer is not parallel to the light-receiving surface on the side closest to the light-receiving surface; The second upper inner expansion layer has a surface that is not parallel to the light-receiving surface on the side closest to the light-receiving surface; The surface of the first lower inner expansion layer is not parallel to the light-receiving surface on the side closest to the light-receiving surface; The second lower inner expansion layer is not parallel to the light-receiving surface on the side closest to the light-receiving surface.

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