Preparation method of solar cell and solar cell

Abstract

The invention provides a preparation method of a solar cell and the solar cell. The preparation method comprises the following steps: providing a silicon substrate; forming at least one first tunneling layer and at least one first doping layer which are alternately arranged on the silicon substrate; and performing heat treatment on the first doping layer by using laser to form a second doping layer, and the second doping layer comprises polycrystalline silicon. According to the invention, the doped layer prepared by alternately performing the method of forming the doped layer and processing the doped layer by using the laser has relatively high doping concentration, and especially when the doping element comprises gallium, the doping concentration of the gallium element in the doped layer can be remarkably improved.

Description

Technical Field

[0001] The present application mainly relates to the field of photovoltaic technology, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0002] The TOPcon passivation structure includes a tunneling layer and a doped polysilicon layer. For the P-type doped polysilicon layer, the doping element can be B or Ga. For the boron-doped polysilicon layer, the boron element is in the tunneling layer (e.g. SiO x ) interface is low, which leads to low passivation performance of P-type doped polysilicon layer. Gallium doping can avoid this problem. At present, gallium-doped polysilicon is mainly prepared by solution method and other processes. After annealing, the activation concentration is low and the contact performance is poor. For the design of stacked Ga / B-doped polysilicon film layers, the process route is complicated and the cost is high, and the doping concentration near the silicon substrate is extremely low, resulting in high contact resistivity. Therefore, how to increase the gallium doping concentration in the doped polysilicon layer, especially the gallium doping concentration near the silicon substrate, is a hot issue in this field. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a method for preparing a solar cell and a solar cell, in which a portion of a doping layer close to a silicon substrate has a higher doping concentration, especially when gallium is doped in the doping layer, a portion close to the silicon substrate has a higher gallium doping concentration.

[0004] To solve the above technical problems, the present application provides a method for preparing a solar cell, comprising: providing a silicon substrate; forming at least one first tunneling layer and at least one first doping layer alternately arranged on the silicon substrate; using a laser to heat treat the first doping layer to form a second doping layer, wherein the second doping layer comprises polycrystalline silicon.

[0005] In one embodiment of the present application, the preparation method also includes: forming at least one second tunneling layer and at least one third doping layer alternately arranged on the second doping layer, and using a laser to heat treat the third doping layer to form a fourth doping layer, wherein the fourth doping layer includes polycrystalline silicon.

[0006] In one embodiment of the present application, at least two first tunneling layers and at least two first doping layers that are alternately arranged are formed on the silicon substrate.

[0007] In one embodiment of the present application, at least two second tunneling layers and at least two third doping layers that are alternately arranged are formed on the silicon substrate.

[0008] In an embodiment of the present application, the first doping layer is doped with gallium, and / or the first doping layer includes any one of carbon, oxygen, and nitrogen.

[0009] In an embodiment of the present application, the third doping layer is doped with gallium, and / or the third doping layer includes any one of carbon, oxygen, and nitrogen.

[0010] In one embodiment of the present application, the laser is a femtosecond laser, a nanosecond laser or an excimer laser, the wavelength of the laser is 126nm to 670nm, the pulse width of the laser is greater than 1ns, and the heat treatment is carried out in a nitrogen, argon or dry air atmosphere.

[0011] In one embodiment of the present application, the method for forming the first doping layer includes: depositing the first doping layer using a plasma enhanced chemical deposition process; or, first depositing an intrinsic amorphous silicon layer, and then forming a doping source layer on the intrinsic amorphous silicon layer, and the doping elements in the doping source layer diffuse into the intrinsic amorphous silicon layer to form the first doping layer; or, first depositing an intrinsic amorphous silicon layer, and then using an ion implantation process to implant doping elements into the intrinsic amorphous silicon layer to form the first doping layer.

[0012] On the other hand, the present application also proposes a solar cell, comprising: a silicon substrate; at least one third tunneling layer and at least one fifth doping layer alternately arranged on the silicon substrate, the fifth doping layer comprising polycrystalline silicon; and an electrode electrically connected to the fifth doping layer.

[0013] In an embodiment of the present application, at least two third tunneling layers and at least two fifth doping layers are disposed on the silicon substrate.

[0014] In one embodiment of the present application, in the fifth doping layer, the doping concentration of the doping element within the range of 0nm to 10nm from the silicon substrate is 1E17 to 5E19 atoms / cm 3 The doping concentration of the doping element within the range of 10nm to 80nm from the silicon substrate is 5E19 to 9E19 atoms / cm 3 , wherein the fifth doping layer is doped with gallium element.

[0015] Compared with the prior art, the present application has the following advantages: the doping layer prepared by the method of alternately executing "forming a doping layer" and "processing the doping layer with a laser" has a higher doping concentration, especially when the doping element includes gallium, the doping concentration of the gallium element in the doping layer can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0017] Figure 1 is a schematic flow chart of a method for preparing a solar cell in one embodiment of the present application;

[0018] Figures 2 to 6 is a schematic cross-sectional view of a solar cell in different steps of a preparation method in an embodiment of the present application;

[0019] Figure 7 It is a cross-sectional schematic diagram of a solar cell in one embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0021] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0022] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0023] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0024] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0025] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0026] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0027] Next, the preparation method of the solar cell and the solar cell of the present application are described through examples.

[0028] refer to Figure 1 The schematic flow chart of a preparation method in an embodiment is shown, and the preparation method in this embodiment includes the following steps S110 to S130.

[0029] S110: providing a silicon substrate;

[0030] S120: forming at least one first tunneling layer and at least one first doping layer alternately arranged on the silicon substrate;

[0031] S130: using laser to perform heat treatment on the first doping layer to form a second doping layer, wherein the second doping layer includes polysilicon.

[0032] Next, steps S110 to S130 are described in detail.

[0033] refer to Figure 2 As shown, in step S110, a silicon substrate 210 is provided. The silicon substrate 210 may be N-type single crystal silicon or P-type single crystal silicon. The present application does not limit the doping elements in the silicon substrate 210. For example, the doping elements may include phosphorus or boron. The front and / or back side of the silicon substrate 210 may have a velvet structure.

[0034] refer to Figure 2 and Figure 3 As shown, in step S120 , first tunneling layers 220 and first doping layers 230 that are alternately arranged are formed on a silicon substrate 210 . Figure 3 The solar cell intermediate body in the embodiment includes two first tunneling layers 220 and two first doping layers 230, and the first tunneling layers 220 and the first doping layers 230 are alternately arranged. It should be noted that the number of the first tunneling layers 220 and the first doping layers 230 is not limited to Figure 3 The two layers shown, for example, may have only one first tunneling layer 220 and one first doping layer 230, or may have three first tunneling layers 220 and three first doping layers 230, and the first tunneling layers 220 and the first doping layers 230 are alternately arranged. Of course, there may be other numbers, which will not be elaborated on.

[0035] The first tunneling layer 220 may include any one of silicon oxide, aluminum oxide, gallium oxide, and silicon nitride. Figure 3The materials of the two first tunneling layers 220 may be the same or different. The thickness of the first tunneling layer 220 may be 1 nm to 2.5 nm, for example, the thickness is 1 nm, 1.5 nm, 2 nm or 2.5 nm. In one embodiment, the thickness of the first tunneling layer 220 located between the two first doping layers 230 may be 0.3 nm to 3 nm, for example, the thickness is 0.3 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm or 3 nm. The method of forming the first tunneling layer 220 includes a thermal oxidation method, a solution method, a plasma enhanced chemical vapor deposition method (PECVD) or a silicon oxide stacking process.

[0036] The first doping layer 230 may include one or more of doped amorphous silicon, doped microcrystalline silicon, and doped polycrystalline silicon. For example, in one embodiment, the first doping layer 230 is doped amorphous silicon, and the doped amorphous silicon may be formed using PECVD, LPCVD, or PVD processes. The first doping layer 230 may be P-type doped or N-type doped. When the first doping layer 230 is P-type doped, the doping element may be selected from IIIA group elements such as boron, aluminum, and gallium. When the first doping layer 230 is P-type or N-type doped, the doping element may be selected from VA group elements such as phosphorus, arsenic, and antimony.

[0037] In one embodiment, the first doping layer 230 is P-type doped, and the first doping layer 230 is doped with gallium; in another embodiment, the first doping layer 230 contains any of carbon, oxygen, and nitrogen; in another embodiment, the first doping layer 230 is doped with gallium and contains any of carbon, oxygen, and nitrogen. The carbon, oxygen, and nitrogen elements in the first doping layer 230 can regulate the band gap of the film layer and regulate the doping concentration.

[0038] The thickness of the single-layer first doping layer 230 may be 30 nm to 100 nm, for example, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0039] In one embodiment, the first doping layer 230 can be formed by any of the following three methods. (1) The first doping layer 230 is deposited using a plasma enhanced chemical deposition process; (2) An intrinsic amorphous silicon layer is first deposited, and then a doping source layer is formed on the intrinsic amorphous silicon layer, and the doping elements in the doping source layer diffuse into the intrinsic amorphous silicon layer, thereby forming the first doping layer 230. When the doping source layer is a gallium source, a solution method, a gallium oxide deposition method, or a diffusion deposition method (such as diffuse deposition of gallium chloride) can be used to form the doping source layer. The process for depositing gallium oxide can be PVD, LPCVD, PECVD, or CVD, wherein the CVD process uses TMGa and H2O as precursors, and the PVD process uses a gallium-doped target and oxygen as precursors; (3) An intrinsic amorphous silicon layer is first deposited, and then an ion implantation process is used to implant doping elements into the intrinsic amorphous silicon layer, thereby forming the first doping layer 230.

[0040] refer to Figure 3 and Figure 4 As shown, in step S130, the first doping layer 230 is heat-treated using a laser to form a second doping layer 240, and the second doping layer 240 includes polycrystalline silicon. Using a laser to treat the first doping layer 230 can increase the doping concentration of the doping element in the second doping layer 240, and can also perform a crystallization process on the first doping layer 230, thereby obtaining a second doping layer 240 containing polycrystalline silicon.

[0041] In one embodiment, the laser is a femtosecond laser, a nanosecond laser or an excimer laser; the wavelength of the laser is 126nm to 670nm, for example, the wavelength is 126nm, 200nm, 300nm, 400nm, 500nm, 600nm or 670nm; the pulse width of the laser is greater than 1ns; and the heat treatment is carried out in a nitrogen, argon or dry air atmosphere.

[0042] In one embodiment, the preparation method of the present application further includes the following steps S140 and S150.

[0043] S140: Reference Figure 4 and Figure 5 As shown, a second tunneling layer 250 and a third doping layer 260 are alternately formed on the second doping layer 240. For the description of the material and the formation method of the second tunneling layer 250, please refer to the description of the first tunneling layer in the previous text, and no further description is given. For the description of the material and the formation method of the third doping layer 260, please refer to the description of the first doping layer in the previous text, and no further description is given. It should be noted that the number of the second tunneling layer 250 and the number of the third doping layer 260 are not limited to Figure 5For example, in some embodiments, two second tunneling layers 250 and two third doping layers 260 are formed, and the second tunneling layers 250 and the third doping layers 260 are arranged alternately. Of course, the number of the second tunneling layers 250 and the number of the third doping layers 260 can also be greater than 2. The thickness of the single-layer third doping layer 260 can be 30nm to 100nm, for example, the thickness is 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

[0044] S150: Reference Figure 5 and Figure 6 As shown, the third doping layer 260 is heat-treated by using laser to form a fourth doping layer 270, and the fourth doping layer 270 includes polysilicon. Please refer to the above description of the laser, which will not be expanded here.

[0045] In one embodiment, the third doping layer 260 is doped with gallium; in another embodiment, the third doping layer 260 includes any one of carbon, oxygen, and nitrogen; in another embodiment, the third doping layer 260 is doped with gallium and also includes any one of carbon, oxygen, and nitrogen.

[0046] refer to Figure 6 As shown, in one embodiment, the doping element of the two second doping layers 240 is gallium, and the fourth doping layer 270 is N-type doped, but the doping element is different from gallium, for example, the doping element of the fourth doping layer 270 is boron. In another embodiment, Figure 6 On the basis of, an N-type doping layer is formed on the fourth doping layer 270, and the doping element of the N-type doping layer is gallium.

[0047] refer to Figure 5 and Figure 6 As shown, the present application prepares the doping layers (240, 270) by alternately performing the methods of "forming the doping layers (230, 260)" and "treating the doping layers (230, 260) using a laser", thereby increasing the concentration of the doping elements (e.g., gallium) in the doping layers (240, 270), especially the concentration of the doping elements in the doping layers (240, 270) close to the silicon substrate.

[0048] On the other hand, the present application also proposes a solar cell, Figure 7As shown, the solar cell includes a silicon substrate 210, two third tunneling layers 280, two fifth doping layers 290 and an electrode 310. Specifically, the third tunneling layers 280 and the fifth doping layers 290 are alternately arranged on the silicon substrate 210. The fifth doping layer 290 includes doped polysilicon, and the fifth doping layer 290 can be N-type doped or P-type doped. For other descriptions of the third tunneling layer 280, please refer to the previous description of the first tunneling layer 220, which will not be expanded here. The electrode 310 is electrically connected to the fifth doping layer 290. It should be noted that the number of layers of the third tunneling layer 280 and the number of layers of the fifth doping layer 290 are not limited to Figure 7 As shown in , for example, the number of layers of the third tunneling layer 280 and the fifth doping layer 290 can be one layer or three layers. The total thickness of the fifth doping layer 290 can be 120nm to 300nm, for example, the total thickness is 120nm, 200nm, 250nm or 300nm.

[0049] refer to Figure 7 As shown, in one embodiment, in the fifth doping layer 290, in the thickness direction of the silicon substrate 210, the doping concentration of the doping element within the range of 0nm to 10nm from the silicon substrate 210 is 1E17 to 5E19 atoms / cm 3 , for example, the doping concentration is 1E17 atoms / cm 3 、1E18 atoms / cm 3 、5E19atoms / cm 3 The doping concentration of the doping element within the range of 10nm to 80nm from the silicon substrate 210 is 5E19 to 9E19 atoms / cm 3 , for example, the doping concentration is 5E19atoms / cm 3 、6E19atoms / cm 3 、7E19atoms / cm 3 、8E19atoms / cm 3 or 9E19atoms / cm 3 , gallium is doped in the fifth doping layer 290. The solar cell of the present application can be prepared by the preparation method as described above. Compared with the prior art, the portion of the fifth doping layer 290 of the present application close to the silicon substrate 210 (for example, the 0 nm to 10 nm described above) has a higher doping concentration.

[0050] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0051] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0052] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0053] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0054] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: include: providing a silicon substrate; Forming at least one first tunneling layer and at least one first doping layer alternately arranged on the silicon substrate; The first doping layer is thermally treated by using a laser to form a second doping layer, wherein the second doping layer includes polysilicon.

2. The preparation method according to claim 1, characterized in that Also includes: At least one second tunneling layer and at least one third doping layer are alternately formed on the second doping layer, and the third doping layer is heat-treated using a laser to form a fourth doping layer, wherein the fourth doping layer includes polysilicon.

3. The preparation method according to claim 1, characterized in that: At least two first tunneling layers and at least two first doping layers that are alternately arranged are formed on the silicon substrate.

4. The preparation method according to claim 2, characterized in that: At least two second tunneling layers and at least two third doping layers which are alternately arranged are formed on the silicon substrate.

5. The preparation method according to claim 1, characterized in that: The first doping layer is doped with gallium, and / or the first doping layer includes any one of carbon, oxygen and nitrogen.

6. The preparation method according to claim 2, characterized in that: The third doping layer is doped with gallium, and / or the third doping layer includes any one of carbon, oxygen and nitrogen.

7. The preparation method according to any one of claims 1 or 2, characterized in that: The laser is a femtosecond laser, a nanosecond laser or an excimer laser, the wavelength of the laser is 126nm to 670nm, the pulse width of the laser is greater than 1ns, and the heat treatment is performed in a nitrogen, argon or dry air atmosphere.

8. The preparation method according to claim 1, characterized in that: The method of forming the first doping layer includes: depositing the first doped layer using a plasma enhanced chemical deposition process; Or, first depositing an intrinsic amorphous silicon layer, and then forming a doping source layer on the intrinsic amorphous silicon layer, wherein the doping elements in the doping source layer diffuse into the intrinsic amorphous silicon layer to form the first doping layer; Alternatively, an intrinsic amorphous silicon layer is first deposited, and then an ion implantation process is used to implant doping elements into the intrinsic amorphous silicon layer to form the first doping layer.

9. A solar cell, characterized in that: include: Silicon substrate; At least one third tunneling layer and at least one fifth doped layer are alternately disposed on the silicon substrate, wherein the fifth doped layer comprises polysilicon; as well as An electrode is electrically connected to the fifth doping layer.

10. The solar cell according to claim 9, characterized in that At least two third tunneling layers and at least two fifth doping layers are arranged on the silicon substrate.

11. The solar cell according to claim 9, wherein: In the fifth doping layer, the doping concentration of the doping element within the range of 0nm to 10nm from the silicon substrate is 1E17 to 5E19 atoms / cm 3 The doping concentration of the doping element within the range of 10nm to 80nm from the silicon substrate is 5E19 to 9E19 atoms / cm 3 , wherein the fifth doping layer is doped with gallium element.

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