Solar cell

Abstract

The application relates to the technical field of solar cells, and provides a passivation structure and a solar cell. The passivation structure comprises a first surface, and a plurality of curved grooves are arranged on the first surface. According to the application, the curved grooves are formed on the surface of the passivation structure, and after the light of the solar cell enters the curved grooves of the passivation structure, the light can be emitted and refracted in the curved grooves for multiple times. Therefore, the advancing direction of the light in the solar cell is changed, the optical path is prolonged, the light penetrating through the solar cell can be reflected back to the inside of the solar cell, the absorption of the solar cell to the penetrating light is increased, and the short-circuit current of the solar cell is improved.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell. Background Technology

[0002] Crystalline silicon solar cells have passivation structures on both the front and back sides. The passivation structures include one or more films of silicon nitride, silicon oxide, silicon carbide, and silicon oxynitride. These passivation structures can not only passivate the solar cells, but also provide a textured surface on the front side as an excellent anti-reflection structure to increase the amount of sunlight entering the solar cells. However, some sunlight passes directly through the solar cells, resulting in some long-wavelength sunlight not being effectively utilized. Utility Model Content

[0003] Based on this, this application provides a passivation structure and a solar cell for improving the light utilization efficiency of solar cells.

[0004] In a first aspect, this application provides a passivation structure, the passivation structure including a first surface, on which a plurality of curved grooves are provided.

[0005] In some embodiments, the opening area of ​​a single curved groove is 3 μm. 2 -50μm 2 .

[0006] In some embodiments, the total opening area of ​​the plurality of said curved grooves accounts for 0.001% to 1.2% of the area of ​​the first surface.

[0007] In some embodiments, the radius of curvature of the curved groove is 2μm to 12μm.

[0008] In some embodiments, the arc height of the curved groove is 0.05 μm to 1.00 μm.

[0009] In some embodiments, the passivation layer further includes a second surface disposed opposite to the first surface, the second surface having a plurality of curved protrusions.

[0010] In some embodiments, the radius of curvature of the surface protrusion is 2μm to 12μm.

[0011] In some embodiments, the arc height of the curved protrusion is 0.1 μm to 1.05 μm.

[0012] Secondly, this application provides a solar cell, the solar cell comprising:

[0013] A silicon substrate, the silicon substrate including a front side and a back side disposed opposite to each other;

[0014] A back passivation structure (40) is disposed on the back side and includes a passivation structure as described in the first aspect, wherein the first surface of the passivation structure faces the silicon substrate.

[0015] In some embodiments, the solar cell further includes a tunneling layer, a polycrystalline silicon layer, and a first metal layer, wherein the tunneling layer and the polycrystalline silicon layer are sequentially disposed between the silicon substrate and the back passivation structure in a direction away from the silicon substrate; the first metal layer is disposed on the side surface of the back passivation structure away from the silicon substrate, and the first metal layer is electrically connected to the polycrystalline silicon layer at least partially through the back passivation structure.

[0016] In some embodiments, the solar cell further includes an emitter layer, a front passivation layer, and a second metal layer, wherein the emitter layer, the front passivation layer, and the second metal layer are sequentially disposed on the front side in a direction away from the silicon substrate.

[0017] Compared with traditional technologies, this application has at least the following beneficial effects:

[0018] This application forms curved grooves on the surface of a passivation structure. When light enters the curved grooves of the passivation structure in a solar cell, it can be reflected multiple times within the grooves, thereby changing the transmission direction of light in the solar cell and extending the optical path. This allows light transmitted through the solar cell to be reflected back into the solar cell, increasing the absorption of transmitted light by the solar cell and improving the short-circuit current of the solar cell. Attached Figure Description

[0019] Figure 1 This is a cross-sectional schematic diagram of a passivation structure provided in one embodiment of this application; wherein, r1 refers to the radius of curvature of the curved groove, h1 represents the arc height of the curved groove; r2 refers to the radius of curvature of the curved protrusion, and h2 represents the arc height of the curved protrusion;

[0020] Figure 2 This is a schematic diagram of light reflection at a curved groove in a passivation structure provided in one embodiment of this application;

[0021] Figure 3 This is a cross-sectional SEM image of the curved groove in the passivation structure of the solar cell in Embodiment 1 of this application;

[0022] Figure 4 This is a planar SEM image of the curved groove in the passivation structure of the solar cell in Embodiment 1 of this application, where the white spots are the curved grooves;

[0023] Figure 5 This is a schematic diagram of the structure of a solar cell provided in one embodiment of this application.

[0024] 100 - Passivation structure; 110 - Curved groove; 120 - Curved protrusion;

[0025] 10-Silicon substrate; 20-Tunneling layer; 30-Polycrystalline silicon layer; 40-Back passivation structure; 50-First metal layer; 60-Emitter layer; 70-Front passivation layer; 71-First passivation layer; 72-Second passivation layer; 80-Second metal layer. Detailed Implementation

[0026] In traditional technology, in order to reflect as much light as possible back into the cell or to make the most of the light entering the cell, multiple layers of films with different refractive indices are designed on the back side. By matching the refractive indices of each film, the optical path is maximized and the light utilization rate is improved. However, this design has limited light trapping effect and the process of matching multiple film layers is complicated.

[0027] Based on this, the first aspect of this application provides a passivation structure, such as Figure 1 As shown, the passivation structure 100 includes a first surface and a second surface disposed opposite to each other, and a plurality of curved grooves 110 are provided on the first surface of the passivation structure 100.

[0028] This application forms a curved groove 110 on the surface of the passivation structure 100, such as Figure 2 As shown, after light enters the curved groove 110 of the passivation structure 100 in the solar cell, the light can be reflected multiple times within the curved groove 110, thereby changing the direction of light propagation in the solar cell and extending the optical path. This allows the light transmitted through the solar cell to be reflected back into the solar cell, increasing the absorption of transmitted light by the solar cell and improving the short-circuit current of the solar cell.

[0029] It is understood that in this application, the curved groove 110 refers to a groove with a curved surface. For example, it can be a partially spherical groove with a constant radius of curvature, or a partially ellipsoidal groove with a changing radius of curvature. It should be noted that "partially spherical" means that the inner wall shape of the curved groove 110 is a part of a spherical curved surface, and "partially ellipsoidal" means that the inner wall shape is a part of an ellipsoidal curved surface.

[0030] In some embodiments, the opening area of ​​a single curved groove 110 is 3 μm. 2 ~50μm 2 For example, it could be 3μm 2 4μm 2 10μm 2 20μm 2 30μm 2 40μm 2 or 50μm 2The opening area of ​​the curved groove 110 refers to the area of ​​the opening shape on the first surface of the curved groove 110, which can be calculated by the opening size. For example, when the opening of the curved groove 110 is circular, the opening diameter can be measured by SEM image and then calculated. The opening area of ​​other shapes can also be calculated accordingly. The opening area of ​​a single curved groove 110 is set as described above in this application, so that the passivation structure 100 has both good passivation effect and light trapping effect.

[0031] In some embodiments, the total opening area of ​​the plurality of curved grooves 110 accounts for 0.001% to 1.2% of the area of ​​the first surface, for example, it can be 0.001%, 0.01%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, or 1.2%. This percentage can be calculated by calculating the ratio of the total opening area of ​​the curved grooves 110 to the area of ​​the first surface, or by calculating the ratio of the sum of the opening areas of each curved groove 110 in the SEM image to the imaged area. The present application uses the above-mentioned total opening area of ​​the curved grooves 110 to ensure the contact stability between the passivation structure 100 and other film layers of the solar cell, and to ensure that the passivation structure 100 has good passivation and light-trapping effects.

[0032] In some of these embodiments, such as Figure 1 As shown, the radius of curvature r1 of the curved groove 110 is 2μm to 12μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm or 12μm. It can be understood that the radius of curvature of a point on the curved surface reflects the degree of curvature of the surface. When the radius of curvature at any point on the curved surface is a fixed value, that is, the structure of the curved groove 110 is part of a spherical structure, such as a hemispherical groove or a quarter-spherical groove. When the radius of curvature on the curved surface changes, that is, the radius of curvature changes within a certain range, then the curved groove 110 presents as part of an ellipsoidal structure.

[0033] In some of these embodiments, for example... Figure 1 As shown, the arc height h1 of the curved groove 110 is 0.05μm to 1.00μm, for example, it can be 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, or 1.0μm. It should be noted that the arc height refers to the vertical distance from the highest point of the curved surface to the chord line, also called the bow height. Taking the curved groove 110 as an example, the arc height can be understood as the distance between the lowest point of the curved groove 110 and the first surface.

[0034] By selecting the curvature radius and arc height of the curved groove 110 as described above, this application can increase the number of times the incident light undergoes multiple reflections in the curved groove 110, and enable more light to be reflected into the solar cell for absorption and utilization.

[0035] It is understandable that the arrangement of the curved grooves 110 can meet different reflection requirements. They can be arranged at equal intervals or randomly on the passivation structure 100. When the curved grooves 110 are arranged at equal intervals, they can be arranged in a matrix or other array structure on the first surface.

[0036] It should be noted that the passivation structure 100 in this application can be prepared by template method, thereby forming a structure with curved groove 110. Alternatively, hydrogen overflow can be utilized during the preparation process. This requires the passivation structure to contain sufficient hydrogen ions while avoiding excessive hydrogen ion overflow that could negatively impact film performance. For example, the preparation method could include: S1, controlling the ALD (Atomic Layer Deposition) loading and unloading and machine humidity to 40%–50%, with a Q-time within 1 hour, allowing the poly layer (polycrystalline silicon layer) surface to adsorb appropriate moisture before ALD deposition; S2, during the ALD process, the water pulse time for the 5th to 20th cycles is 8–19 seconds, and the purging time is 8–19 seconds; S3, controlling the passivation structure annealing temperature to 400℃–550℃, with an annealing time of 400–1200 seconds; S4, controlling the sintering peak temperature to 600℃–800℃, with a peak temperature maintenance time of 0.1–2 seconds. During sintering, hydrogen overflow lifts the passivation structure, forming a curved groove on the surface of the passivation structure near the poly layer, while simultaneously forming a curved protrusion on the other side of the passivation structure.

[0037] In some of these embodiments, for example... Figure 1 As shown, the passivation structure 100 also includes a second surface disposed opposite to the first surface, and a plurality of curved protrusions 120 are disposed on the second surface. This application provides a plurality of curved protrusions 120 on the second surface to reflect incident light entering the passivation structure 100 again, thereby improving the utilization rate of the solar cell for light reflected by the passivation structure 100. Figure 2 As shown, light is reflected multiple times on the inner surface of the curved protrusion 120, thereby reflecting more light into the solar cell and further improving the solar cell's light utilization efficiency.

[0038] It is understood that in this application, the curved protrusion 120 refers to a protrusion with a curved appearance. For example, it can be a partially spherical protrusion or a partially ellipsoidal protrusion.

[0039] In some of these embodiments, as well as Figure 1As shown, the radius of curvature r2 of the curved protrusion 120 is 2μm to 12μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm or 12μm. The arc height h2 of the curved protrusion 120 is 0.1μm to 1.05μm, for example, it can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 1.05μm. By selecting the radius of curvature and arc height of the curved protrusion 120 as described above, this application effectively increases the number of reflections of light on the inner surface of the curved protrusion 120, allowing more light to be reflected back into the solar cell, further improving the light utilization rate.

[0040] Optionally, the location of the curved groove 110 corresponds to the location of the curved protrusion 120. That is, the curved groove 110 is projected onto the corresponding position of the second surface along a direction perpendicular to the first surface, and the curved protrusion 120 is provided at that position.

[0041] In some embodiments, the passivation structure 100 includes at least one of a silicon nitride layer, a silicon oxide layer, a silicon carbide layer, and a silicon oxynitride layer.

[0042] The second aspect of this application provides a solar cell, such as... Figure 5 As shown, the solar cell includes a silicon substrate 10 and a back passivation structure 40.

[0043] The silicon substrate 10 includes a front side and a back side disposed opposite to each other. A back passivation structure 40 is disposed on the back side of the silicon substrate 10 and includes a passivation structure 100 as described in the first aspect, with the first surface of the passivation structure 100 facing the silicon substrate 10.

[0044] Optionally, the solar cell can be a PERC cell, a TOPCon cell, a TBC cell, or an HTBC cell. The passivation structure 100 can be disposed on the back of the solar cell to reflect light from the solar cell, allowing more light to be reflected into the solar cell and effectively improving light utilization.

[0045] In one embodiment, the solar cell may be a TOPCon cell, and the solar cell further includes a tunneling layer 20, a polycrystalline silicon layer 30, and a first metal layer 50. The tunneling layer 20 and the polycrystalline silicon layer 30 are sequentially disposed between the silicon substrate 10 and the back passivation structure 40 along a direction away from the silicon substrate 10. The first metal layer 50 is disposed on the surface of the back passivation structure 40 away from the silicon substrate 10, and the first metal layer 50 is electrically connected to the polycrystalline silicon layer 30 at least partially through the back passivation structure 40. It should be noted that a cavity formed by curved grooves 110 may be formed between the polycrystalline silicon layer 30 and the back passivation structure 40 in the solar cell of this application.

[0046] In one embodiment, the solar cell further includes an emitter layer 60, a front passivation layer 70, and a second metal layer 80, which are sequentially disposed on the front side along a direction away from the silicon substrate 10. Optionally, the emitter layer 60 may be a boron diffusion layer.

[0047] The front passivation layer 70 may include a first passivation layer 71 and a second passivation layer 72 stacked sequentially along the direction away from the emitter layer 60, wherein the first passivation layer 71 may be an aluminum oxide layer, and the second passivation layer 72 may be made of the same material as the passivation structure 100.

[0048] It should be noted that the first metal layer 50 contacts the polysilicon layer 30 at least partially through the back passivation structure 40, thereby enabling current conduction. The second metal layer 80 contacts the emitter layer 60 at least partially through the front passivation layer 70, thereby enabling current conduction. Alternatively, grooves can be pre-formed on the back passivation structure 40 and the front passivation layer 70 to form the first metal layer 50 and the second metal layer 80 within the grooves.

[0049] For example, this application provides a method for forming the above-mentioned solar cell, comprising the following steps:

[0050] S1. Provide a silicon substrate 10, and use an alkaline solution and additives to perform double-sided texturing on the silicon substrate 10.

[0051] S2. Boron diffusion is performed on the texturized silicon substrate 10 to prepare the emitter layer 60.

[0052] S3. Perform single-sided etching and polishing on the back side of the silicon substrate 10, and remove edge BSG and edge expansion.

[0053] S4. A tunneling layer 20, a polycrystalline silicon layer 30, and a PSG are sequentially prepared on one side of the back surface of the polished silicon substrate 10.

[0054] S5. In a chain-type device, use hydrofluoric acid solution to remove PSG from the front side and edges of the silicon substrate 10 after step S4.

[0055] S6. Using the RCA process, remove the polysilicon wrapped around the front and edges of the silicon substrate 10 after step S5, and remove the front BSG and the back PSG.

[0056] S7. A first passivation layer 71 is deposited on the front side of the silicon substrate 10 after step S6, wherein the first passivation layer 71 may be an aluminum oxide layer.

[0057] S7. Deposit on the front and back sides of the silicon substrate 10 after step S6. Form a second passivation layer 72 covering the first passivation layer 71 on the front side and a back passivation structure 40 covering the polysilicon layer 30 on the back side. The back passivation structure 40 is the passivation structure 100 mentioned above. Both the second passivation layer 72 and the passivation structure 100 are made of silicon nitride material.

[0058] S8. Electrode gate lines are screen-printed on the front and back sides of the silicon substrate 10 after the process in step S7, thereby forming the first metal layer 50 and the second metal layer 80, respectively.

[0059] Example 1

[0060] This embodiment provides a TOPCon battery, including a silicon substrate 10. A boron diffusion layer, an aluminum oxide layer, a silicon nitride layer, and a silver electrode layer are sequentially stacked on the front side of the silicon substrate 10 along a direction away from the silicon substrate 10. A tunneling layer 20, a polycrystalline silicon layer 30, a passivation structure 100, and a silver electrode layer are sequentially stacked on the back side of the silicon substrate 10 along a direction away from the silicon substrate 10. Combined with... Figure 3 and Figure 4 As shown, the first surface of the passivation structure 100 (i.e., the surface in contact with the polysilicon layer 30) has multiple curved grooves 110. The diameter radius of curvature of the curved grooves 110 is 5 μm, and the arc height is 0.6 μm. Figure 4 Each white spot represents a curved groove 110, and the area of ​​each white spot is the opening area of ​​the curved groove 110. The opening area of ​​a single curved groove 110 is 12 μm. 2 The total opening area of ​​the multiple curved grooves 110 accounts for 0.5% of the area of ​​the first surface. The second surface of the passivation structure 100 also has multiple curved protrusions 120, the positions of which correspond to the positions of the curved grooves 110. The radius of curvature of the curved protrusions 120 is 5 μm, and the arc height is 0.68 μm.

[0061] The sheet resistance of the boron diffusion layer is 400 Ω / sq, the thickness of the alumina layer is 4 nm, the thickness of the silicon nitride layer is 80 nm, the thickness of the tunneling layer 20 is 2 nm, the thickness of the polysilicon layer 30 is 150 nm, and the thickness of the passivation structure 100 is 80 nm.

[0062] Comparative Example 1

[0063] Compared with Example 1, the only difference is that the first surface of the passivation structure 100 does not have a curved groove 110, and the second surface does not have a curved protrusion 120.

[0064] The photoelectric conversion efficiency of the solar cells in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from the table above, the curved groove 110 structure provided on the passivation structure 100 in this application can reflect the incident light of the solar cell back into the solar cell, thereby improving the light utilization rate of the solar cell and thus improving the photoelectric conversion efficiency of the solar cell.

[0068] In summary, this application forms a curved groove 110 on the surface of the passivation structure 100. After the light from the solar cell enters the curved groove 110 of the passivation structure 100, the light can be reflected multiple times within the curved groove 110, thereby changing the direction of light propagation in the solar cell and extending the optical path, increasing the absorption and utilization rate of long-wavelength light in the solar cell, and improving the short-circuit current of the solar cell.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A solar cell, characterized in that, The solar cell includes: A silicon substrate (10) comprising a front side and a back side disposed opposite to each other; A back passivation structure (40) is disposed on the back side and includes a passivation structure (100); the passivation structure (100) includes a first surface on which a plurality of curved grooves (110) are disposed; the first surface of the passivation structure (100) faces the silicon substrate (10).

2. The solar cell as described in claim 1, characterized in that, The opening area of ​​a single curved groove (110) is 3 μm. 2 ~50μm 2 ; And / or, the total opening area of ​​the plurality of said curved grooves (110) accounts for 0.001% to 1.2% of the area of ​​the first surface.

3. The solar cell as described in claim 1, characterized in that, The radius of curvature of the curved groove (110) is 2μm~12μm.

4. The solar cell as described in claim 1, characterized in that, The arc height of the curved groove (110) is 0.05μm~1.00μm.

5. The solar cell according to any one of claims 1-4, characterized in that, The passivation structure (100) further includes a second surface disposed opposite to the first surface, and the second surface is provided with a plurality of curved protrusions (120).

6. The solar cell as described in claim 5, characterized in that, The radius of curvature of the curved protrusion (120) is 2μm~12μm.

7. The solar cell as described in claim 5, characterized in that, The arc height of the curved protrusion (120) is 0.1μm~1.05μm.

8. The solar cell as described in claim 1, characterized in that, The solar cell further includes a tunneling layer (20), a polycrystalline silicon layer (30), and a first metal layer (50). The tunneling layer (20) and the polycrystalline silicon layer (30) are sequentially disposed between the silicon substrate (10) and the back passivation structure (40) in a direction away from the silicon substrate (10). The first metal layer (50) is disposed on the side surface of the back passivation structure (40) away from the silicon substrate (10), and the first metal layer (50) is electrically connected to the polycrystalline silicon layer (30) at least partially through the back passivation structure (40).

9. The solar cell as described in claim 1 or 8, characterized in that, The solar cell further includes an emitter layer (60), a front passivation layer (70), and a second metal layer (80), wherein the emitter layer (60), the front passivation layer (70), and the second metal layer (80) are sequentially disposed on the front side in a direction away from the silicon substrate (10).

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