Preparation method of solar cell and solar cell

Abstract

The invention provides a preparation method of a solar cell and the solar cell, and belongs to the field of photovoltaic technology, and the preparation method comprises the steps: providing a substrate which is provided with a first surface and a second surface which are opposite to each other; forming a first doping layer on the first surface; sequentially forming a tunneling layer and a second doping layer on the second surface, wherein the doping type of the first doping layer is opposite to that of the second doping layer; forming a silicon oxide layer on the surface, away from the substrate, of the first doping layer and the surface, away from the substrate, of the second doping layer; treating the silicon oxide layer by using a chemical liquid containing aluminum ions, so that the aluminum ions are adsorbed on the silicon oxide layer, and the aluminum ions adsorbed on the silicon oxide layer are self-deposited to form an aluminum oxide layer; and forming a first electrode and a second electrode electrically connected with the first doped layer and the second doped layer respectively.

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] Alumina passivation layer is an important film layer in solar cells, effectively reducing carrier recombination on the silicon wafer surface, thereby improving the minority carrier lifetime and overall cell performance. Furthermore, alumina possesses high chemical stability, protecting the cell surface from damage and corrosion under various environmental conditions, reducing the negative impact of environmental factors on cell performance. Currently, atomic layer deposition (ALD) is used to prepare alumina passivation layers; however, ALD is costly. Therefore, finding a cost-effective way to prepare alumina passivation layers is a hot topic 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 reduce the cost of preparing an alumina passivation layer.

[0004] This application provides a method for fabricating a solar cell, comprising: providing a substrate having a first surface and a second surface opposite to each other; forming a first doped layer on the first surface; sequentially forming a tunneling layer and a second doped layer on the second surface, wherein the doping type of the first doped layer is opposite to that of the second doped layer; forming a silicon oxide layer on the surface of the first doped layer away from the substrate and on the surface of the second doped layer away from the substrate; treating the silicon oxide layer with a chemical solution containing aluminum ions, causing aluminum ions to be adsorbed on the silicon oxide layer, and the aluminum ions adsorbed on the silicon oxide layer self-depositing to form an aluminum oxide layer; and forming a first electrode and a second electrode respectively electrically connected to the first doped layer and the second doped layer.

[0005] This application also proposes a solar cell, which is prepared by the solar cell preparation method described above.

[0006] Compared with the methods used in related technologies to prepare alumina layers using atomic layer deposition, this application first prepares a silicon oxide layer, and then treats the silicon oxide layer with a chemical solution containing aluminum ions to adsorb aluminum ions on the silicon oxide. The aluminum ions adsorbed on the silicon oxide layer self-deposit to form an alumina layer. The preparation method of this application has the advantages of simple process and low cost. 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:

[0008] Figure 1 This is a schematic flowchart of a method for preparing a solar cell according to an embodiment of this application;

[0009] Figures 2 to 5 This is a cross-sectional schematic diagram of the solar cell intermediate in different steps of one embodiment of this application;

[0010] Figure 6 This is a cross-sectional schematic diagram of a solar cell in one embodiment of this application.

[0011] Figure Labels

[0012] Substrate 110, Tunneling layer 130, First electrode 170

[0013] First surface 111, second doped layer 140, second electrode 180

[0014] Second surface 112, silicon oxide layer 150, first passivation layer 190

[0015] First doped layer 120, aluminum oxide layer 160, second passivation layer 210 Detailed Implementation

[0016] 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.

[0017] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The following examples illustrate the preparation method (hereinafter referred to as the preparation method) and the solar cell of this application.

[0024] refer to Figures 1 to 5 As shown, Figure 1 The preparation method in the embodiments includes the following steps S110 to S160.

[0025] S110: A substrate 110 is provided, having a first surface 111 and a second surface 112 opposite to each other;

[0026] S120: A first doped layer 120 is formed on the first surface 111;

[0027] S130: A tunneling layer 130 and a second doped layer 140 are sequentially formed on the second surface 112, and the doping type of the first doped layer 120 is opposite to that of the second doped layer 140.

[0028] S140: A silicon oxide layer 150 is formed on the surface of the first doped layer 120 away from the substrate 110 and on the surface of the second doped layer 140 away from the substrate 110.

[0029] S150: The silicon oxide layer 150 is treated with a chemical solution containing aluminum ions, so that aluminum ions are adsorbed on the silicon oxide layer 150, and the aluminum ions adsorbed on the silicon oxide layer 150 are self-deposited to form an aluminum oxide layer 160.

[0030] S160: Form a first electrode 170 and a second electrode 180 that are electrically connected to the first doped layer 120 and the second doped layer 140, respectively.

[0031] The following describes steps S110 to S160 in detail.

[0032] refer to Figure 2 As shown, in step S110, a substrate 110 is provided. The substrate 110 is N-type doped or P-type doped. The N-type doping element is selected from one or more group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), and arsenic (As), and the P-type doping element is selected from one or more group III elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). In one embodiment, the substrate 110 is an N-type or P-type silicon substrate.

[0033] The substrate 110 has a first surface 111 and a second surface 112 facing each other, with the first surface 111 or the second surface 112 facing the sun when the solar cell is operating. In one embodiment, the first surface 111 and / or the second surface 112 has a pyramidal textured surface, which can trap light and reduce surface reflection, thereby improving the light utilization efficiency of the solar cell.

[0034] refer to Figure 2 and Figure 3 As shown, in step S120, a first doped layer 120 is formed on the first surface 111. The first doped layer 120 is N-type doped or P-type doped. In one embodiment, the first doped layer 120 is N-type doped silicon or P-type doped silicon.

[0035] Continue to refer to Figure 2 and Figure 3 As shown, in step S130, a tunneling layer 130 and a second doped layer 140 are sequentially formed on the second surface 112. The second doped layer 140 is N-type doped or P-type doped, and the doping type of the second doped layer 140 is opposite to that of the first doped layer 120. In one embodiment, the tunneling layer 130 comprises silicon oxide, and the second doped layer 140 comprises N-type doped polysilicon or P-type doped polysilicon. The tunneling layer 130 and the second doped layer 140 can achieve selective collection of charge carriers and have a surface passivation effect.

[0036] In one embodiment, the substrate 110 is an N-type silicon substrate. When the solar cell is working, the first surface 111 faces the sun. The first doped layer 120 is a P-type doped silicon layer, and the second doped layer 140 is an N-type doped polycrystalline silicon layer.

[0037] refer to Figure 3 and Figure 4 As shown, in step S140, a silicon oxide layer 150 is formed on the surface 121 of the first doped layer 120 away from the substrate 110 and the surface 141 of the second doped layer 140 away from the substrate 110.

[0038] In one embodiment, the method for forming the silicon oxide layer 150 includes: oxidizing the first doped layer 120 and the second doped layer 140 with an ozone solution to form the silicon oxide layer 150. The ozone concentration of the ozone solution is 30 ppm to 40 ppm, for example, 30 ppm, 35 ppm, or 40 ppm, and the oxidation treatment duration is 500 s to 600 s, for example, 500 s, 550 s, or 600 s.

[0039] In one embodiment, the thickness of the silicon oxide layer 150 is 2nm to 4nm, for example, the thickness of the silicon oxide layer 150 is 2nm, 3nm or 4nm.

[0040] refer to Figure 4 and Figure 5 As shown, in step S150, the silicon oxide layer 150 is treated with a chemical solution containing aluminum ions, causing aluminum ions to be adsorbed onto the silicon oxide layer 150. The aluminum ions adsorbed on the silicon oxide layer 150 form an aluminum oxide layer through self-deposition. The aluminum oxide layer is located on the surface of the silicon oxide layer 150 away from the substrate 110. In one embodiment, the thickness of the aluminum oxide layer 160 is 2 nm to 3 nm, for example, 2 nm, 2.5 nm, or 3 nm. The aluminum oxide layer 160 has a high charge density (~1.4 × 10⁻⁶). 12 cm -2 This technology can provide good surface passivation for solar cells, thereby effectively reducing electron-hole recombination and improving minority carrier lifetime.

[0041] In one embodiment, an aluminum salt is used to prepare a chemical solution containing aluminum ions, the aluminum ions in the chemical solution originating from the hydrolysis of aluminum salt, which includes aluminum nitrate (Al(NO3)3) and / or aluminum chloride (AlCl3). In a more specific embodiment, a saturated aluminum nitrate solution is used to prepare the chemical solution containing aluminum ions, the volume concentration of the aluminum nitrate solution in the chemical solution containing aluminum ions being 14% to 25%, for example, 14%, 20%, or 25% by volume. The treatment temperature for treating the silicon oxide layer 150 with the chemical solution containing aluminum ions is 75°C to 85°C, for example, 75°C, 80°C, or 85°C, and the treatment time is 700s to 800s, for example, 700s, 750s, or 800s.

[0042] In one embodiment, the method of treating the silicon oxide layer 150 with a chemical solution containing aluminum ions includes, as follows: Figure 4 The solar cell intermediate with silicon oxide layer 150 shown is immersed in a chemical solution containing aluminum ions. The aluminum ions in the chemical solution are adsorbed on silicon oxide layer 150 and self-deposited to form aluminum oxide layer 160.

[0043] In one embodiment, the preparation method further includes: removing the solar cell intermediate with the alumina layer 160 formed from a chemical liquid containing aluminum ions, and drying the solar cell intermediate with the alumina layer 160 formed. A heat treatment furnace can be used to dry the solar cell intermediate with the alumina layer 160 formed. The drying process removes liquid adhering to the solar cell intermediate.

[0044] In one embodiment, after the tunneling layer 130 and the second doped layer 140 are sequentially formed on the second surface 112, and before the silicon oxide layer 150 is formed on the first doped layer 120 and the second doped layer 140, the solar cell intermediate with the second doped layer 140 is subjected to a de-coating process to remove the films (e.g., borosilicate glass, phosphosilicate glass, borosilicate glass, tunneling layer and doped layer) that are coated onto the side surface and non-target surface.

[0045] Compared with the methods for preparing alumina layers using atomic layer deposition (ALD) in related technologies, the method for preparing alumina layer 160 in this application does not require expensive ALD equipment, which greatly reduces costs and simplifies the process.

[0046] refer to Figure 5 and Figure 6 As shown, in step S160, a first electrode 170 and a second electrode 180 are formed, which are electrically connected to the first doped layer 120 and the second doped layer 140, respectively. The first electrode 170 and the second electrode 180 can be fabricated using screen printing and sintering processes.

[0047] refer to Figure 6 As shown, in one embodiment, a first passivation layer 190 is formed on an aluminum oxide layer 160 located on a first surface 111, and a second passivation layer 210 is formed on an aluminum oxide layer 160 located on a second surface 112. The first passivation layer 190 and the second passivation layer 210 may be a single film or a stack comprising silicon nitride and / or silicon oxynitride.

[0048] To better understand the preparation method of this application, a specific non-limiting embodiment is given below, which includes steps 1 to 10 as follows.

[0049] Step 1: After forming the tunneling layer and the second doped layer, remove the phosphosilicate glass (PSG) that has been deposited around the side surface and the first surface of the substrate.

[0050] Step 2: The solar cell intermediate treated in Step 1 is subjected to alkaline washing to remove the second doped layer and tunneling layer deposited onto the side and first surface of the substrate. Referring to Table 1, the solar cell intermediate is subjected to alkaline washing in tank No. 1. Tank No. 1 contains an alkaline solution for alkaline washing, which includes 21 L of saturated KOH solution, 4.5 L of de-coating additive (ADD), and 460 L of deionized water (DI). The alkaline washing temperature is 68±2℃, and the time is 280±20 s.

[0051] Step 3: The solar cell intermediate processed in Step 2 is subjected to acid washing to remove the phosphosilicate glass, borosilicate glass (BSG), and borosilicate phosphosilicate glass (BPSG) that were not removed in the previous steps. Referring to Table 1, the solar cell intermediate is acid washed in tank No. 2, which contains an acid solution for acid washing, consisting of 180L of HF and 300L of deionized water. The acid washing temperature is room temperature, and the time is 240s.

[0052] Step 4: Perform SC1 cleaning on the solar cell intermediates treated in Step 3 to remove any possible organic impurities and increase surface activity. Referring to Table 1, the solar cell intermediates are cleaned using SC1 in tank No. 3. Tank No. 3 contains an SC1 chemical solution, consisting of 2.5 L of KOH solution, 10 L of H2O2, and 460 L of deionized water. The SC1 cleaning temperature is 60 ± 5 °C, and the time is 200 s to 300 s.

[0053] Step 5: Perform SC2 cleaning on the solar cell intermediates treated in Step 4 to complex and remove metal impurities. Referring to Table 1, the solar cell intermediates are cleaned using SC2 in tank No. 4. Tank No. 4 contains an SC2 chemical solution, which includes 5 L of HCl solution, 20 L of H2O2, and 455 L of deionized water. The SC2 cleaning temperature is 60 ± 5 °C, and the time is 200 s to 300 s.

[0054] Step 6: Perform mixed acid cleaning on the solar cell intermediates treated in Step 5 to remove metallic impurities and the oxide layer generated during the cleaning process, and to make the surface hydrophobic. Referring to Table 1, the solar cell intermediates are cleaned with mixed acid in tank No. 5. Tank No. 5 contains a mixed acid chemical solution, including 40 L of HF, 20 L of HCl solution, and 430 L of deionized water. The cleaning temperature is room temperature, and the time is 120 s to 150 s. Further details regarding steps 1 to 6 are not the focus of this application.

[0055] Step 7: Oxidize the solar cell intermediate treated in Step 6 using an ozone solution to form a silicon oxide layer with a thickness of 2nm to 4nm. Referring to Table 1, cell 6 is adjacent to cell 5, allowing for rapid transfer of the solar cell intermediate from cell 5 to cell 6. The oxidation process is performed in cell 6, which contains an ozone solution with an ozone concentration of 35ppm. The ozone oxidation is carried out at room temperature for 500s to 600s.

[0056] Step 8: Treat the solar cell intermediate treated in Step 7 with a chemical solution containing aluminum ions to form an aluminum oxide layer with a thickness of 2nm to 3nm on the silicon oxide layer. Referring to Table 1, the solar cell intermediate is treated in tank No. 7, which contains a chemical solution containing aluminum ions. The chemical solution includes 70L of saturated Al(NO3)3 solution and 410L of deionized water. The treatment temperature is 80±5℃, and the treatment time is 700s to 800s. In some embodiments, the volume concentration of the saturated Al(NO3)3 solution relative to the aluminum nitrate solution containing aluminum ions is 14% to 25%, for example, volume concentrations of 14%, 16%, 18%, 20%, 22%, 24%, and 25%.

[0057] Step 9: Use cold water to slowly lift out the solar cell intermediate processed in step 8. The lifting temperature is room temperature and the lifting time is 20 seconds.

[0058] Step 10: Dry the solar cell intermediate processed in step 9 at a temperature of 90±10℃ for 800s.

[0059] Table 1: Chemical solution ratios and process parameters in steps 2 to 8

[0060]

[0061] Continued from Table 1

[0062]

[0063] This application tested the solar cells prepared by the foregoing embodiments and the solar cells in the comparative examples. The comparative examples used an alumina layer prepared by atomic layer deposition (ALD). The test results are shown in Table 2. As can be seen from Table 2, the minority carrier lifetime, implied open-circuit voltage, and recombination current saturation density of the solar cells in this application are all superior to those of the solar cells in the comparative examples. The passivation effect of the alumina layer prepared by the method of this application is superior to that of the alumina layer prepared by ALD in the comparative examples.

[0064] Table 2 compares the passivation effects of solar cells in the embodiments of this application and in the comparative examples.

[0065] Passivation example Low birth lifespan / us iVoc / V <![CDATA[J0 composite current saturation density]]> Comparative Example 2129 0.7382 1.519E-14 Example 4300 0.7411 2.051E-14

[0066] This application also proposes a solar cell fabricated using the solar cell fabrication method described above. The alumina layer in this solar cell has a lower fabrication cost.

[0067] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0068] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0069] Similarly, 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, 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 present application requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0070] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with 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 the specification and claims 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 scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0071] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the essential spirit of this application will fall within the scope of the claims of this application.

Claims

1. A method for preparing a solar cell, characterized in that, include: A substrate is provided, having opposing first and second surfaces; A first doped layer is formed on the first surface; A tunneling layer and a second doped layer are sequentially formed on the second surface, wherein the doping type of the first doped layer is opposite to that of the second doped layer; A silicon oxide layer is formed on the surface of the first doped layer away from the substrate and on the surface of the second doped layer away from the substrate; The silicon oxide layer is treated with a chemical solution containing aluminum ions, so that aluminum ions are adsorbed on the silicon oxide layer, and the aluminum ions adsorbed on the silicon oxide layer self-deposit to form an aluminum oxide layer. as well as A first electrode and a second electrode are formed that are electrically connected to the first doped layer and the second doped layer, respectively.

2. The method for preparing a solar cell as described in claim 1, characterized in that, The first doped layer and the second doped layer are oxidized using an ozone solution to form the silicon oxide layer.

3. The method for preparing a solar cell as described in claim 1, characterized in that, The thickness of the silicon oxide layer is 2nm to 4nm.

4. The method for preparing a solar cell as described in claim 1, characterized in that, The chemical solution containing aluminum ions is prepared using aluminum salts, wherein the aluminum ions are derived from the aluminum salts, and the aluminum salts include aluminum nitrate and / or aluminum chloride.

5. The method for preparing a solar cell as described in claim 1, characterized in that, The chemical solution containing aluminum ions is prepared using a saturated aluminum nitrate solution, wherein the volume concentration of the saturated aluminum nitrate solution in the chemical solution containing aluminum ions is 14% to 25%. The treatment temperature for treating the silicon oxide layer using the chemical solution containing aluminum ions is 75°C to 85°C, and the treatment time is 700s to 800s.

6. The method for preparing a solar cell as described in claim 1, characterized in that, A method for treating the silicon oxide layer with a chemical solution containing aluminum ions includes immersing a solar cell intermediate on which the silicon oxide layer is formed into the chemical solution to allow aluminum ions to be adsorbed onto the silicon oxide layer.

7. The method for preparing a solar cell as described in claim 6, characterized in that, Also includes: The solar cell intermediate with the alumina layer formed is removed from the chemical solution and dried.

8. The method for preparing a solar cell as described in claim 1, characterized in that, The thickness of the alumina layer is 2nm to 3nm.

9. The method for preparing a solar cell as described in claim 1, characterized in that, After a tunneling layer and a second doped layer are sequentially formed on the second surface, and before a silicon oxide layer is formed on the surface of the first doped layer away from the substrate and the surface of the second doped layer away from the substrate, a de-coating process is performed on the solar cell intermediate on which the second doped layer is formed.

10. A solar cell, characterized in that, The solar cell is prepared by the method for preparing a solar cell as described in any one of claims 1 to 9.

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