Side edge functional structure for back contact crystalline silicon solar cell and solar cell

Abstract

The present disclosure provides a side functional structure for a back contact crystalline silicon solar cell, which is arranged on at least one sidewall of a silicon substrate, and comprises, in sequence from top to bottom, a boron inner diffusion layer, a first silicon oxide layer, a P-type doped polysilicon layer, a borosilicate glass layer, a second silicon oxide layer and an N-type doped polysilicon layer, which are arranged on the surface of the sidewall of the silicon substrate in sequence from top to bottom in the horizontal direction of the crystalline silicon; wherein the reference plane of the region of the sidewall of the silicon substrate where the side functional structure is arranged is higher than the reference plane of a non-side functional structure region which is not provided with the side functional structure; and the non-side functional structure region forms a pyramid light-trapping structure on the surface of the crystalline silicon substrate. The present disclosure also provides a back contact crystalline silicon solar cell having the side functional structure and a preparation method thereof. The side functional structure of the present disclosure can achieve effective electrical isolation between the P region and the N region, thereby reducing the risk of side short circuit.

Description

Technical Field

[0001] This disclosure relates to the field of solar cell technology, and in particular to a side functional structure for a back-contact crystalline silicon solar cell, a solar cell having the side functional structure, and a method for fabricating the same. Background Technology

[0002] In back-contact crystalline silicon solar cells, the back side of the crystalline silicon typically possesses both P-type and N-type regions, enabling selective carrier collection. However, because the P- and N-type regions are adjacent on the back side of the crystalline silicon, the polycrystalline silicon doped layer on the back side may extend to the cell's sides, leading to severe carrier recombination in the side regions. Simultaneously, the physical distance between the P- and N-type regions is significantly reduced in the side direction, easily forming electrical short-circuit channels. Current back-contact crystalline silicon solar cells only form a single insulating or passivation layer on the cell's sides, making it difficult to simultaneously achieve P / N polarity blocking, electrical isolation, and low surface recombination. Summary of the Invention

[0003] This disclosure provides a side functional structure for a back-contact crystalline silicon solar cell. The side functional structure is disposed on at least one sidewall of a crystalline silicon substrate. The side functional structure includes the following layers sequentially stacked along the horizontal direction of the crystalline silicon on the surface of the sidewall of the crystalline silicon substrate: 1) a boron inner expansion layer, 2) a first silicon oxide layer, 3) a P-type doped polycrystalline silicon layer, 4) a borosilicate glass layer, 5) a second silicon oxide layer, and 6) an N-type doped polycrystalline silicon layer. The reference plane of the region where the side functional structure is located in the sidewall of the silicon substrate is higher than the reference plane of the region without the side functional structure. The region without the side functional structure forms a pyramid light-trapping structure on the surface of the crystalline silicon substrate.

[0004] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the side functional structure further includes a passivation layer and / or an anti-reflection film located outside the N-type doped polycrystalline silicon layer along the horizontal direction of the crystalline silicon.

[0005] According to the side functional structure for a back-contact crystalline silicon solar cell disclosed herein, the thickness of the silicon oxide layer is 0.5-3.0 nm, the thickness of the doped polycrystalline silicon layer is 20-400 nm, and the thickness of the borosilicate glass layer is 5-100 nm.

[0006] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the side functional structure accounts for 5% to 99% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0007] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

[0008] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the passivation layer is an aluminum oxide passivation layer, and the antireflection film is a silicon nitride, silicon oxynitride, silicon oxide monolayer film, or a combination of these films.

[0009] This disclosure also provides a back-contact crystalline silicon solar cell, which has a side functional structure. The side functional structure includes a first silicon oxide layer, a P-type doped polycrystalline silicon layer, a borosilicate glass layer, a second silicon oxide layer, and an N-type doped polycrystalline silicon layer, which are sequentially stacked on the sidewall surface of a crystalline silicon substrate along the horizontal direction of the crystalline silicon.

[0010] According to the back-contact crystalline silicon solar cell of this disclosure, the side functional structure accounts for 5% to 99% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0011] This disclosure also provides a method for fabricating the above-mentioned back-contact crystalline silicon solar cell, comprising: Constructing PN junctions on the entire surface of a crystalline silicon substrate; Part of the BSG was removed using a single-sided laser process, and part of the PN junction was removed using an alkaline polishing solution. A tunneling oxide layer and an intrinsic polycrystalline silicon layer are formed on the surface of a crystalline silicon substrate; A phosphorus-silicon glass layer is deposited on the intrinsic polycrystalline silicon layer to complete the full-area phosphorus-doped polycrystalline silicon passivation contact structure, while simultaneously forming the side functional structure of the silicon substrate sidewall.

[0012] According to the method for fabricating a back-contact crystalline silicon solar cell disclosed herein, the lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

[0013] According to this disclosure, the back-contact crystalline silicon solar cell achieves effective electrical isolation between the P-region and the N-region in the side direction of the cell through the synergistic effect of multiple functional thin films in the side functional structure, thereby reducing the risk of side short circuit; furthermore, a borosilicate glass layer is introduced between the P-type and N-type polycrystalline silicon layers to achieve polarity blocking and suppress undesired carrier transport. Attached Figure Description

[0014] Figure 1 This is a schematic structural diagram of a back-contact crystalline silicon solar cell according to the present disclosure.

[0015] Figures 2 to 9 This is a schematic diagram of the steps in the fabrication method of a back-contact crystalline silicon solar cell according to the present disclosure. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be described in detail below with reference to the accompanying drawings.

[0017] Exemplary embodiments will be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of this disclosure.

[0018] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0019] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded.

[0021] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so defined herein.

[0022] This disclosure provides a side functional structure for a back-contact crystalline silicon solar cell. The side functional structure is disposed on at least one sidewall of a crystalline silicon substrate. The side functional structure includes the following layers sequentially stacked on the surface of the sidewall of the crystalline silicon substrate along the horizontal direction of the crystalline silicon: 1) a boron inner expansion layer, 2) a first silicon oxide layer, 3) a P-type doped polycrystalline silicon layer, 4) a borosilicate glass layer, 5) a second silicon oxide layer and 6) an N-type doped polycrystalline silicon layer. In this case, the reference plane of the region where the side functional structure is located in the sidewall of the silicon substrate is higher than the reference plane of the region without side functional structure; the region without side functional structure forms a pyramid light trapping structure on the surface of the crystalline silicon substrate.

[0023] The borosilicate glass layer is used to suppress undesirable carrier transport in the side direction of the battery and to form electrical isolation between the P-type polycrystalline silicon layer and the N-type polycrystalline silicon layer.

[0024] According to the side functional structure for a back-contact crystalline silicon solar cell described in this disclosure, the thickness of the silicon oxide layer is 0.5-3.0 nm, the thickness of the doped polycrystalline silicon layer is 20-400 nm, and the thickness of the borosilicate glass layer is 5-100 nm.

[0025] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the side functional structure further includes a passivation layer and / or an anti-reflection film located outside the N-type doped polycrystalline silicon layer along the horizontal direction of the crystalline silicon.

[0026] According to the side-side functional structure described in this disclosure, the passivation layer is an aluminum oxide passivation layer, and the antireflection film is a silicon nitride, silicon oxynitride, silicon oxide monolayer, or a combination thereof. The Al2O3 passivation layer is used to reduce the surface recombination rate of the sidewalls of the crystalline silicon substrate.

[0027] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the side functional structure accounts for 5% to 99% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0028] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

[0029] According to the side functional structure for back-contact crystalline silicon solar cells described in this disclosure, the passivation layer is an aluminum oxide passivation layer, and the antireflection film is a silicon nitride, silicon oxynitride, silicon oxide monolayer film, or a combination of these films.

[0030] This disclosure also provides a back-contact crystalline silicon solar cell, which has a side functional structure. The side functional structure includes a first silicon oxide layer, a P-type doped polycrystalline silicon layer, a borosilicate glass layer, a second silicon oxide layer, and an N-type doped polycrystalline silicon layer, which are sequentially stacked on the sidewall surface of a crystalline silicon substrate along the horizontal direction of the crystalline silicon.

[0031] According to the back-contact crystalline silicon solar cell of this disclosure, the side functional structure accounts for 5% to 99% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0032] In the side-side functional structure described in this disclosure, the boron inner layer is used to achieve good passivation contact properties; the first silicon oxide layer is used for interface passivation; the P-type doped polysilicon layer is used to form local electrical contacts; the borosilicate glass layer is used for sidewall protection and local doping diffusion; the second silicon oxide layer is used for further passivation and electrical isolation; the N-type doped polysilicon layer is used to form sidewall electrical contacts with the opposite conductivity type to the P-type layer; and the pyramid light-trapping structure in the non-side-side functional structure region is used for light-trapping enhancement.

[0033] This disclosure also provides a method for fabricating the above-mentioned back-contact crystalline silicon solar cell, comprising: Constructing PN junctions on the entire surface of a crystalline silicon substrate; Part of the borosilicate glass layer was removed using a single-sided laser process, and part of the PN junction was removed using an alkaline polishing solution. A tunneling oxide layer and an intrinsic polycrystalline silicon layer are formed on the surface of a crystalline silicon substrate; A phosphorus-silicon glass layer is deposited on the intrinsic polycrystalline silicon layer to complete the full-area phosphorus-doped polycrystalline silicon passivation contact structure, while simultaneously forming the side functional structure of the silicon substrate sidewall.

[0034] According to the method for fabricating a back-contact crystalline silicon solar cell disclosed herein, the lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

[0035] The borosilicate glass layer and the phosphosilicate glass layer are used to provide doping sources to the adjacent polycrystalline silicon layer during heat treatment.

[0036] According to one embodiment of this disclosure, the method for fabricating the back-contact crystalline silicon solar cell includes the following steps: S1: As Figure 2 As shown, an alkaline polishing chemical treatment is applied to the surface of a crystalline silicon substrate to form a low-roughness surface morphology; S2: As Figure 3 As shown, boron is deposited and diffused on the surface of a crystalline silicon substrate to construct a PN junction; The deposition can be formed by LPCVD, PECVD or other methods, and the PN junction can be a double-layer SiOx / double-layer p+ poly-Si PN junction.

[0037] S3: As Figure 4 As shown, part of the borosilicate glass layer was selectively removed, and part of the PN junction structure was also removed; Among these methods, a portion of the borosilicate glass layer can be selectively removed using a single-sided laser process, and a portion of the PN junction structure can be removed using an alkaline polishing solution.

[0038] S4: As Figure 5As shown, a tunneling oxide layer and an intrinsic polycrystalline silicon layer (i poly-Si) are formed on the surface of a crystalline silicon substrate, and a phosphorus silicon glass layer is deposited on the intrinsic polycrystalline silicon layer to form a full-area phosphorus-doped polycrystalline silicon passivation contact, while the side functional structure is formed. Among them, low-pressure chemical vapor deposition (LPCVD) technology can be used to form a tunneling oxide layer and an intrinsic polycrystalline silicon layer, and thermal diffusion technology can be used to deposit a full-area phosphorus-doped polycrystalline silicon passivation contact structure on i poly-Si. S5: As Figure 6 As shown, an isolation trench is formed in the region of the full-area phosphorus-doped polycrystalline silicon passivation contact, and the front silicon film is removed; Laser processing can be used to form isolation trenches and remove the front silicon film.

[0039] S6: As Figure 7 As shown, the exposed portion of the crystalline silicon is etched using an alkaline solution to form a pyramid light-trapping structure, thus completing the side functional structure. S7: As Figure 8 As shown, an aluminum oxide passivation film is deposited on the surface of the crystalline silicon substrate, and an anti-reflection coating is formed on the front and back sides of the crystalline silicon substrate; An aluminum oxide passivation film can be deposited on the surface of the crystalline silicon substrate using atomic layer deposition (ALD); an anti-reflection coating can be formed on the front and back sides of the crystalline silicon substrate using PECVD.

[0040] S8: As Figure 9 As shown, metal grid lines are printed on the back side of the crystalline silicon substrate and sintered to form an electrode pattern.

[0041] Compared with the prior art, the back-contact crystalline silicon solar cell according to this disclosure has the following advantages: Through the synergistic effect of multiple functional thin films in the side-side functional structure, effective electrical isolation between the P-region and N-region is achieved in the side direction of the battery, thereby reducing the risk of side-side short circuits. Introducing an alumina passivation layer on the battery side significantly reduces the side-side surface recombination rate. Furthermore, introducing a borosilicate glass layer between the P-type and N-type polycrystalline silicon layers achieves polarity blocking and suppresses undesired carrier transport. The method for forming the side-side functional structure is compatible with existing back-contact crystalline silicon battery fabrication methods, offering a wide process window suitable for large-scale production.

[0042] To enable those skilled in the art to more clearly understand the technical solutions provided by the embodiments of this disclosure, the technical solutions provided by the embodiments of this disclosure will be described in detail below through specific embodiments: Example 1 N-type crystalline silicon was selected, and the surface of the crystalline silicon substrate was subjected to alkaline polishing chemical treatment to form a low-roughness surface morphology. A double-layer SiOx / double-layer p+ poly-Si PN junction was constructed by depositing and diffusing boron on the surface of the crystalline silicon substrate through LPCVD. Part of the borosilicate glass layer was selectively removed by single-sided laser process, and part of the PN junction structure was removed by alkaline polishing solution. A tunneling oxide layer and an intrinsic polycrystalline silicon layer were formed by low-pressure chemical vapor deposition (LPCVD) technology, and then a full-area phosphorus-doped polycrystalline silicon passivation contact structure was deposited on i poly-Si by thermal diffusion technology. Laser processing can be used to form isolation trenches in the area of ​​the full-area phosphorus-doped polycrystalline silicon passivation contact and remove the front silicon film; an alkaline solution is used to etch the exposed part of the crystalline silicon to form a pyramid light-trapping structure, thus completing the side multilayer functional structure; an aluminum oxide passivation film is deposited on the surface of the crystalline silicon substrate using atomic layer deposition (ALD) technology, and anti-reflection coatings are formed on the front and back sides of the crystalline silicon substrate using PECVD; metal grid lines are printed on the back side of the crystalline silicon substrate and sintered to form an electrode pattern.

[0043] The side-layer functional structure accounts for 5% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0044] Example 2 The back-contact crystalline silicon solar cell was prepared according to Example 1, except that the side-layer functional structure accounts for 30% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0045] Example 3 The back-contact crystalline silicon solar cell was prepared according to Example 1, except that the side-layer functional structure accounts for 70% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0046] Example 4 The back-contact crystalline silicon solar cell was prepared according to Example 1, except that the side-layer functional structure accounts for 90% of the total area of ​​the sidewall of the crystalline silicon substrate.

[0047] Comparative Example 1 A back-contact crystalline silicon solar cell was prepared according to Example 1, except that the back-contact crystalline silicon solar cell did not have a side-layer multilayer functional structure.

[0048] Comparative Example 2 A crystalline silicon solar cell with a side-side functional structure is prepared according to the method described in patent application CN119907362A, wherein a P-type polycrystalline silicon layer, a borosilicate glass layer, and an N-type polycrystalline silicon layer are respectively disposed on the sidewall.

[0049] The back-contact crystalline silicon solar cells prepared in the above embodiments and comparative examples were subjected to performance tests, and the test data are detailed in Table 1 below.

[0050] Table 1 As shown in Table 1, compared with Comparative Example 1 (without side multilayer functional structure), the back contact crystalline silicon solar cell with side multilayer functional structure has significantly improved in all key performance parameters.

[0051] Comparative Example 1 has an open-circuit voltage (Voc) of 739.5 mV, a short-circuit current density (Jsc) of 41.7 mA / cm², a fill factor (FF) of 82.20%, and a conversion efficiency of 25.35%. Comparative Example 2 uses a P-type polycrystalline silicon layer, a borosilicate glass layer, and an N-type polycrystalline silicon layer structure, without an inner expansion layer or tunneling oxygen structure. This results in a significant enhancement of side-side carrier recombination, and the open-circuit voltage is only 725.6 mV.

[0052] In Example 1, when the proportion of the side-side multilayer functional structure to the total sidewall area is 5%, the Voc of the battery increases to 742.7 mV, Jsc increases to 42.1 mA / cm², FF increases to 83.25%, and the conversion efficiency reaches 26.03%, which is 0.68 percentage points higher than that of Comparative Example 1. These results demonstrate that even a smaller proportion of the side-side multilayer functional structure can effectively suppress side recombination, improve carrier selectivity, and thus enhance the overall performance of the battery.

[0053] As the area ratio of the side-mounted multi-layered functional structure further increases, the battery performance shows a continuous improvement trend. When the area ratio of the side-mounted functional structure is 30% (Example 2), the conversion efficiency reaches 26.10%; when the area ratio of the side-mounted functional structure increases to 70% (Example 3), the Voc further increases to 743.5 mV, the FF reaches 83.85%, and the conversion efficiency reaches 26.25%; when the area ratio of the side-mounted functional structure reaches 90% (Example 4), the battery Voc reaches 743.8 mV, the FF reaches 84.10%, the Jsc reaches 42.2 mA / cm², and the highest conversion efficiency reaches 26.40%, which is 1.05 percentage points higher than that of Comparative Example 1.

[0054] The above results demonstrate that the side-layer functional structure can effectively passivate dangling bonds and defect states on the sidewalls of the crystalline silicon substrate, reduce the recombination rate at the battery side boundary, and decrease minority carrier recombination losses, thereby significantly improving the open-circuit voltage and fill factor of the battery. Simultaneously, the introduction of the side-layer functional structure also helps improve the short-circuit current density of the battery, which is closely related to the effective suppression of side leakage current. In summary, the larger the area ratio of the side-layer functional structure, the more significant the passivation effect and the more pronounced the improvement in battery performance.

[0055] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in connection with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in connection with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this disclosure as set forth by the appended claims.

Claims

1. A side functional structure for a back-contact crystalline silicon solar cell, the side functional structure being disposed on at least one sidewall of a crystalline silicon substrate, characterized in that: The side functional structure includes structures that are sequentially stacked on the surface of the sidewall of the crystalline silicon substrate along the horizontal direction of the crystalline silicon: 1) Boron inner layer expansion, 2) First silicon oxide layer, 3) P-type doped polycrystalline silicon layer, 4) Borosilicate glass layer, 5) Second silicon oxide layer, and 6) N-type doped polycrystalline silicon layer; In this case, the reference plane of the region where the side functional structure is located in the sidewall of the silicon substrate is higher than the reference plane of the region without side functional structure; the region without side functional structure forms a pyramid light trapping structure on the surface of the crystalline silicon substrate.

2. The side functional structure according to claim 1, wherein, The side functional structure also includes a passivation layer and / or an antireflection film located outside the N-type doped polycrystalline silicon layer along the horizontal direction of the crystalline silicon.

3. The side functional structure according to claim 1, wherein, The thickness of the silicon oxide layer is 0.5-3.0 nm, the thickness of the doped polycrystalline silicon layer is 20-400 nm, and the thickness of the borosilicate glass layer is 5-100 nm.

4. The side functional structure according to claim 1, wherein, The side functional structures account for 5% to 99% of the total area of ​​the sidewalls of the crystalline silicon substrate.

5. The side functional structure according to claim 1, wherein, The lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

6. The side functional structure according to claim 2, wherein, The passivation layer is an aluminum oxide passivation layer, and the antireflection film is a single layer or combination of silicon nitride, silicon oxynitride, and silicon oxide.

7. A back-contact crystalline silicon solar cell, characterized in that, The back-contact crystalline silicon solar cell has a side-side functional structure as described in any one of claims 1-6, wherein the side-side functional structure comprises a first silicon oxide layer, a P-type doped polycrystalline silicon layer, a borosilicate glass layer, a second silicon oxide layer, and an N-type doped polycrystalline silicon layer sequentially stacked on the sidewall surface of the crystalline silicon substrate along the horizontal direction of the crystalline silicon.

8. The back-contact crystalline silicon solar cell according to claim 7, wherein, The side functional structures account for 5% to 99% of the total area of ​​the sidewalls of the crystalline silicon substrate.

9. A method for preparing a back-contact crystalline silicon solar cell according to claims 7-8, characterized in that, The preparation method includes: Constructing PN junctions on the entire surface of a crystalline silicon substrate; Part of the BSG was removed using a single-sided laser process, and part of the PN junction was removed using an alkaline polishing solution. A tunneling oxide layer and an intrinsic polycrystalline silicon layer are formed on the surface of a crystalline silicon substrate; A phosphorus-silicon glass layer is deposited on the intrinsic polycrystalline silicon layer to complete the full-area phosphorus-doped polycrystalline silicon passivation contact structure, while simultaneously forming the side functional structure of the silicon substrate sidewall.

10. The method for preparing a back-contact crystalline silicon solar cell according to claim 9, wherein, The lengths of each layer in the side functional structure along the thickness direction of the silicon substrate are equal.

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