Method for manufacturing a solar cell and solar cell

Abstract

The application provides a preparation method of a solar cell and the solar cell, and relates to the technical field of photovoltaics. The preparation method of the solar cell comprises the following steps: providing a silicon substrate; forming a tunneling layer on at least one side of the silicon substrate, wherein the tunneling layer has a plurality of protruding structures facing away from the silicon substrate, and the protruding structures have top surfaces and side surfaces connected with the top surfaces; performing carbon doping treatment on the side surfaces of the protruding structures; and performing heat treatment on the carbon-doped regions after the carbon doping treatment.

Description

Technical Field

[0001] This application relates primarily to the field of photovoltaic technology, and in particular to a method for preparing a solar cell and the solar cell itself. Background Technology

[0002] In crystalline silicon solar cells, the tunneling layer is one of the most important film layers. Typically located between the silicon substrate and the doped layer, the tunneling layer improves carrier transport and interface passivation. It selectively allows carriers to pass through, thereby reducing carrier recombination. Improving the passivation effect of the tunneling layer is one of the hot topics in this field. Summary of the Invention

[0003] The technical problem to be solved by this application is to provide a method for preparing a solar cell and a solar cell, which can improve the passivation effect of the tunneling layer.

[0004] This application discloses a method for fabricating a solar cell, comprising: providing a silicon substrate; forming a tunneling layer on at least one side of the silicon substrate, the tunneling layer having a plurality of protrusions facing away from the silicon substrate, the protrusions having a top surface and a side surface connected to the top surface; performing a carbon doping treatment on the side surface of the protrusions; and performing a heat treatment on the carbon doping region after the carbon doping treatment.

[0005] This application also proposes a solar cell comprising: a silicon substrate; and a tunneling layer located on at least one side of the silicon substrate, the tunneling layer having a plurality of protrusions facing away from the silicon substrate, the protrusions having a top surface and a side surface connected to the top surface, the side surface containing carbon.

[0006] The technical solution of this application has the following technical effects: by performing carbon doping and heat treatment on the side of the tunneling layer, pinholes located on the side of the tunneling layer can be eliminated or reduced, thereby improving the passivation effect, while taking into account the negative impact of carbon doping on contact resistivity. Attached Figure Description

[0007] The accompanying drawings are included to provide a further understanding of this application; they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of this application and, together with this specification, serve to explain the principles of this application. In the drawings: Figure 1 This is a schematic flowchart of a solar cell fabrication method according to an embodiment of this application; Figure 2 This is a cross-sectional schematic diagram of a solar cell according to an embodiment of this application; Figure 3 yes Figure 2A magnified view of a portion of point A in the middle; Figures 4 to 9 This is a cross-sectional schematic diagram of the solar cell in different steps of the solar cell fabrication method in one embodiment of this application; Figure 10 This is a scanning electron microscope image of the tunneling layer without carbon doping treatment; Figure 11 This is a scanning electron microscope image of the tunneling layer after carbon doping and heat treatment in one embodiment of this application; Figure 12 The effect of carbon doping area on contact resistivity is shown; Figure 13 This is a cross-sectional schematic diagram of the solar cell in Comparative Example 1.

[0008] Reference numerals: silicon substrate 210, front side of silicon substrate 211, back side of silicon substrate 212, second doped layer 220, passivation layer 230, antireflection layer 240, tunneling layer 250, protrusion structure 251, top surface 2511, side surface 2512, tower base structure 260, first doped layer 270, carbon doped region 280, first electrode 290, second electrode 310. Detailed Implementation

[0009] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0010] As indicated in this application, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0011] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0012] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0013] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0014] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0015] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0016] The following specific embodiments illustrate the solar cell fabrication method (hereinafter referred to as the fabrication method) and the solar cell of this application.

[0017] refer to Figures 1 to 4 In one embodiment, the preparation method includes the following steps S110 to S140.

[0018] Step S110: Provide silicon substrate 210; Step S120: A tunneling layer 250 is formed on at least one side of the silicon substrate 210. The tunneling layer 250 has a plurality of protrusions 251 facing away from the silicon substrate 210. The protrusions 251 have a top surface 2511 and a side surface 2512 connected to the top surface 2511. Step S130: Perform carbon doping treatment on the side surface 2512; Step S140: After the carbon doping treatment, the carbon doped region 280 is subjected to heat treatment.

[0019] The following is a detailed explanation of steps S110 to S140.

[0020] refer to Figure 2 and Figure 3 In step S110, a silicon substrate 210 is provided, having a front side 211 and a back side 212 facing each other in a second direction D2 (i.e., the thickness direction of the silicon substrate 210). When the solar cell is operating, either the front side 211 or the back side 212 faces the sun. The silicon substrate 210 may comprise N-type doped monocrystalline silicon or P-type doped monocrystalline silicon.

[0021] The back side of the silicon substrate 212 has a pyramidal textured structure 260, which is formed as follows: Before the tunneling layer 250 is formed, the back side of the silicon substrate 212 has a pyramidal textured structure. When polishing the pyramidal textured structure, due to process limitations, it is difficult to completely remove the pyramidal textured structure. As a result, at least part of the pyramidal structure, which is removed at the top but not completely eliminated, remains on the back side, thus forming the pyramidal textured structure 260.

[0022] refer to Figure 2 and Figure 3 In step S120, a tunneling layer 250 is formed on the back side 212 of the silicon substrate. The tunneling layer 250 may include silicon dioxide (SiO2) or silicon nitride (SiN). x ), silicon oxynitride (SiO) x N y One or more of aluminum oxide (Al2O3). Due to the presence of the tower base structure 260, the tunneling layer 250 has a plurality of protrusions 251 facing away from the silicon substrate 210, the protrusions 251 having a top surface 2511 and a side surface 2512.

[0023] In one embodiment, the width of the top surface 2511 (its dimension in the first direction D1) accounts for 80% to 95% of the width of the protrusion structure 251 (its dimension in the first direction D1), for example, 80%, 85%, 90%, or 95%. The width of the top surface 2511 is related to the size of the pyramid structure and the polishing treatment. In one embodiment, the width of the protrusion structure 251 is 10 μm to 15 μm, for example, 10 μm, 12 μm, 14 μm, or 15 μm.

[0024] It should be noted that the tunneling layer 250 can be formed solely on the front side 211 of the silicon substrate, or it can be formed simultaneously on both the front side 211 and the back side 212 of the silicon substrate. For ease of explanation, the following text will refer to this. Figure 2 The fabrication method and the solar cell will be explained in the case where a tunneling layer 250 is formed on the back side 212 of the silicon substrate.

[0025] refer to Figure 2 and Figure 4 In step S130, carbon doping is performed on the side surface 2512, forming a carbon-doped region 280 at the side surface 2512. In one embodiment, the carbon doping process includes carbon doping using an ion implantation process or carbon doping using a laser doping process.

[0026] refer to Figures 4 to 9 In one embodiment, after carbon doping treatment, the carbon atomic concentration of side surface 2512 is 5E19 atoms / cm². -3 ~5E21atoms / cm -3For example, the atomic concentration of carbon is 5E19 atoms / cm³. -3 5E20atoms / cm -3 Or 5E21 atoms / cm -3 .

[0027] refer to Figure 4 In step S140, the carbon-doped side surface 2512 is heat-treated. This heat treatment facilitates the diffusion of the doped carbon elements to the back surface 212 of the silicon substrate. The heat treatment, in conjunction with the carbon doping treatment, repairs pinholes on the side surface 2512. In one embodiment, the heat treatment temperature is 800°C to 1000°C, for example, 850°C, 900°C, 950°C, or 1000°C, and the duration is 20 min to 60 min, for example, 20 min, 30 min, 40 min, 50 min, or 60 min.

[0028] refer to Figure 10 , Figure 10 This is a scanning electron microscope image of the tunneling layer without carbon doping treatment. Figure 10 The middle arrow points to the side of the tunneling layer. This application found that the side of the tunneling layer has a relatively large number of pinholes (such as...) Figure 10 (As shown in the middle circle), these pinholes reduce the passivation effect of the tunneling layer. This application eliminates or reduces pinholes on the sides of the tunneling layer by performing carbon doping and heat treatment, thereby improving the passivation effect. (Comparison) Figure 10 and Figure 11 ,in, Figure 11 This is a scanning electron microscope image of the tunneling layer after carbon doping and heat treatment. Figure 11 The middle arrow points to the side of the tunneling layer. As can be seen, after carbon doping and heat treatment, pinholes are no longer visible in the scanning electron microscope image.

[0029] refer to Figure 3 and Figure 4 In one embodiment, the side surface 2512 is carbon-doped, but the top surface 2511 is not carbon-doped. The reason for this is that, as... Figure 10 As shown, pinholes are mostly concentrated on the side 2512. In the protruding structure 251, the area ratio of the side 2512 is smaller than that of the top surface 2511. Carbon doping treatment is applied only to the side 2512, which can eliminate or reduce the pinholes located on the side 2512 while reducing the impact on contact resistivity.

[0030] This application presents an experiment investigating the effect of carbon-doped region area on contact resistivity. (Reference) Figure 12 and Figure 13The vertical axis represents contact resistivity, and the horizontal axis represents the experimental sample number. In Example 1, only the side surface of the protruding structure 251 was carbon-doped; in Comparative Example 1, reference was made... Figure 13 The sides and top surface of the protruding structure 251 are indiscriminately treated with carbon, and the carbon-doped region 280 formed in Comparative Example 1 is compared with... Figure 8 The difference in the carbon-doped region 280 is that... Figure 8 The carbon-doped region 280 only applies carbon doping treatment to the sides of the protruding structure 251. From Figure 12 It can be seen that the contact resistivity of Example 1 is lower than that of Comparative Example 1.

[0031] refer to Figure 1 and Figure 2 The fabrication process also includes forming a second doped layer 220 on the front side 211 of the silicon substrate. The second doped layer 220 is either P-type doped or N-type doped. When it is P-type doped, the doping element may include boron (B), and when it is N-type doped, the doping element may include phosphorus (P).

[0032] refer to Figure 5 The fabrication process also includes forming a first doped layer 270 on the surface of the tunneling layer 250 away from the silicon substrate 210. The first doped layer 270 is either P-type or N-type doped, and the doping type of the first doped layer 270 is opposite to that of the second doped layer 220. The first doped layer 270 may include doped polysilicon.

[0033] refer to Figure 6 In one embodiment, the preparation process further includes forming a passivation layer 230 on the surface of the first doped layer 270 away from the silicon substrate 210 and on the surface of the second doped layer 220 away from the silicon substrate 210. The passivation layer 230 may include Al2O3 and has a passivation effect.

[0034] refer to Figure 7 In one embodiment, the fabrication process further includes forming an antireflection layer 240 on the surface of the passivation layer 230 away from the silicon substrate 210. A first electrode 290 is disposed on the front side 211 of the silicon substrate, penetrating the passivation layer 230 and the antireflection layer 240, with its end near the silicon substrate 210 contacting the surface of the first doped layer 270 away from the silicon substrate 210, and may also extend into the interior of the first doped layer 270. A second electrode 310 is disposed on the back side 212 of the silicon substrate, penetrating the passivation layer 230 and the antireflection layer 240, with its end near the silicon substrate 210 contacting the surface of the first doped layer 270 away from the silicon substrate 210, and may also extend into the interior of the first doped layer 270.

[0035] Besides performing carbon doping on the tunneling layer 250 before forming the first doped layer 270, carbon doping can also be performed after forming the first doped layer 270. To elaborate, refer to... Figure 8 In one embodiment, after forming the first doped layer 270, the side surface 2512 is carbon-doped to form a carbon-doped region 280. The carbon-doped region 280 penetrates the tunneling layer 250 and the first doped layer 270; that is, the region containing carbon extends from the first doped layer 270 to the side of the tunneling layer 250 near the back surface 212 of the silicon substrate, and may further extend to the back surface 212 of the silicon substrate. (Comparison) Figure 8 and Figure 7 , Figure 7 The structure in the text corresponds to "carbohydrate doping of the tunneling layer 250 before the formation of the first doped layer 270", therefore Figure 7 The carbon-doped region 280 does not extend to the first doped layer 270.

[0036] Besides performing carbon doping on the tunneling layer 250 before forming the first doped layer 270, and performing carbon doping after forming the first doped layer 270, carbon doping can also be performed after forming the passivation layer 230 located on the first doped layer 270. To elaborate, refer to... Figure 9 In one embodiment, after forming the passivation layer 230 on the first doped layer 270, carbon doping is performed on the side to form a carbon-doped region 280. 280 penetrates the tunneling layer 250, the first doped layer 270, and the passivation layer 230; that is, the region containing carbon extends from the passivation layer 230 to the side of the tunneling layer 250 near the back surface 212 of the silicon substrate, and may further extend to the back surface 212 of the silicon substrate. (Comparison) Figure 8 and Figure 9 , Figure 8 The structure in the text corresponds to "carbohydrate treatment before the formation of passivation layer 230", therefore Figure 8 The carbon-doped region 280 does not extend to the passivation layer 230.

[0037] To better understand the preparation method of this application, a specific non-limiting example 2 is given here, referring to... Figure 8 Example 2 includes the following steps 1 to 8.

[0038] Step 1: Provide a silicon substrate 210, and clean and texturize the silicon substrate 210; In this step, the silicon substrate 210 is N-type doped, and the silicon substrate 210 is cleaned and texturized to form a pyramid-shaped textured structure. The thickness of the silicon substrate 210 is 130µm and the resistivity is 1 ohm·cm.

[0039] Step 2: Perform boron diffusion treatment on the front side 211 of the silicon substrate to prepare the second doped layer 220; In this step, the sheet resistance of the second doped layer 220 is 400 ohm / sq.

[0040] Step 3: Polish the back side of the silicon substrate 212, and sequentially form a tunneling layer 250 and a first doped layer 270 on the back side of the silicon substrate 212; In this step, after polishing the back side 212 of the silicon substrate, a tower base structure 260 is formed. The width of the tower base structure 260 is 10 μm. A tunneling layer 250 and a first doped layer 270 are sequentially formed using the PECVD (Plasma Enhanced Chemical Vapor Deposition) method. The tunneling layer 250 has a protrusion structure 251 and a thickness of 1.5 nm. The first doped layer 270 is N-type doped, and the doping element includes phosphorus, wherein the concentration of phosphorus is 5E20 atoms / cm³. -3 The thickness of the first doped layer 270 is 50 nm.

[0041] Step 4: Carbon doping of the side 2512 is performed using ion implantation. In this step, after carbon doping treatment, the carbon concentration of side surface 2512 is 1E20 atoms / cm². -3 .

[0042] Step 5: Anneal the silicon wafer; In this step, the solar cell intermediate with the carbon-doped region 280 is annealed at a temperature of 950°C for 30 minutes. The annealing process serves two purposes: firstly, it works in conjunction with the carbon doping treatment to repair pinholes on the side 2512; secondly, it activates the doping elements and crystallizes the first doped layer 270.

[0043] Step 6: Form a passivation layer 230 on one side of the front side 211 of the silicon substrate and on one side of the back side 212 of the silicon substrate; In this step, an ALD (Atomic Layer Deposition) method is used to deposit a passivation layer 230 on top of the first doped layer 270 and the second doped layer 220. The passivation layer 230 includes aluminum oxide and has a thickness of 5 nm.

[0044] Step 7: Form an anti-reflection layer 240 on one side of the front side 211 of the silicon substrate and on one side of the back side 212 of the silicon substrate; In this step, an antireflection layer 240 is formed using a PECVD method. The antireflection layer 240 comprises silicon nitride and has a thickness of 80 nm.

[0045] Step 8: Form a first electrode 290 and a second electrode 310 on the front side 211 and the back side 212 of the silicon substrate, respectively.

[0046] In this step, the first electrode 290 and the second electrode 310 are formed using a screen printing method.

[0047] Comparative Example 2 was designed. The difference between Comparative Example 2 and Example 2 is that the tunneling layer in Comparative Example 2 was not carbonized.

[0048] Experiments were conducted on the solar cells in Example 2 and Comparative Example 2 using quokka3 software for simulation. The experimental results are shown in Table 1. The conversion efficiency of Example 2 is greater than that of Comparative Example 2.

[0049] Table 1: Experimental results of Example 2 and Comparative Example 2

[0050] This application also proposes a solar cell, as shown in [reference]. Figure 2 and Figure 3 The solar cell includes a silicon substrate 210 and a tunneling layer 250 located on at least one side of the silicon substrate 210. The tunneling layer 250 has a plurality of protrusions 251 facing away from the silicon substrate 210. The protrusions 251 have side surfaces 2512 and a top surface 2511 connected to the side surfaces 2512. The side surfaces 2512 contain carbon elements.

[0051] In one embodiment, the carbon atomic concentration is 5E19 atoms / cm³. -3 ~5E21atoms / cm -3 .

[0052] In one embodiment, the width of the protrusion structure 251 in the first direction D1 ranges from 10 μm to 15 μm.

[0053] The aforementioned solar cells can be prepared using the preparation method described above. For other details regarding solar cells, please refer to the description of the preparation method above, which will not be repeated here.

[0054] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0055] It should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the application requires more features than those mentioned. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0056] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used to describe embodiments are sometimes modified by the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in this application are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

Claims

1. A method for preparing a solar cell, characterized in that, include: Provide silicon substrate; A pyramidal textured structure is formed on at least one side of the silicon substrate; The pyramid-shaped velvet surface is polished to form the base structure; A tunneling layer is formed on the tower base structure, the tunneling layer having a plurality of protrusions facing away from the silicon substrate, the protrusions having a top surface and a side surface connected to the top surface; The sides of the protruding structure are treated with carbon doping. as well as After the carbon doping treatment, the carbon-doped area is subjected to heat treatment.

2. The method for preparing a solar cell as described in claim 1, characterized in that, The carbon doping process includes carbon doping using ion implantation or carbon doping using laser doping.

3. The method for preparing a solar cell as described in claim 1, characterized in that, The atomic concentration of carbon in the side surface is 5E19 atoms / cm². -3 ~5E21atoms / cm -3 .

4. The method for preparing a solar cell as described in claim 1, characterized in that, The heat treatment temperature is 800℃~1000℃, and the duration is 20min~60min.

5. The method for preparing a solar cell as described in claim 1, characterized in that, A doped polycrystalline silicon layer is formed on the tunneling layer, and after the doped polycrystalline silicon layer is formed, the side surface is subjected to carbon doping treatment.

6. The method for preparing a solar cell as described in claim 5, characterized in that, A passivation layer is formed on the doped polycrystalline silicon layer, and after the passivation layer is formed, the side surface is subjected to carbon doping treatment.

7. The method for preparing a solar cell as described in claim 1, characterized in that, The width of the protrusion structure is 10μm~15μm.

8. The method for preparing a solar cell as described in claim 1, characterized in that, The central region of the protruding structure was not treated with carbon doping.

9. A solar cell, characterized in that, include: Silicon substrate; as well as A tunneling layer located on at least one side of the silicon substrate, the tunneling layer having a plurality of protrusions facing away from the silicon substrate, the protrusions having a top surface and a side surface connected to the top surface, the side surface containing carbon.

10. The solar cell as claimed in claim 9, characterized in that, The atomic concentration of carbon in the side surface is 5E19 atoms / cm². -3 ~5E21atoms / cm -3 .

11. The solar cell as claimed in claim 9, characterized in that, The width of the protrusion structure is 10μm~15μm.

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