Solar cell and preparation method thereof

Abstract

The invention relates to a solar cell and a preparation method thereof. The preparation method of the solar cell comprises the following steps: circularly introducing a first aluminum precursor and a first oxidizing agent to prepare a first aluminum oxide layer on one side of a silicon substrate; circularly introducing a second aluminum precursor and a second oxidizing agent to prepare a second aluminum oxide layer on one side, far away from the silicon substrate, of the first aluminum oxide layer; in each circulation, the flow of the second aluminum precursor is larger than that of the first aluminum precursor, and the flow of the second oxidizing agent is larger than that of the first oxidizing agent. According to the preparation method, the passivation effect of the first aluminum oxide layer and the second aluminum oxide layer can be effectively improved, and then the photoelectric conversion efficiency of the solar cell is effectively improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and particularly to a solar cell and a method for manufacturing the same. Background Art

[0002] Silicon-based solar cells have become the mainstream in the current market due to the abundant reserves, stable performance, and mature technology of silicon materials. Improving the photoelectric conversion efficiency of silicon-based solar cells has always been the focus of research. In this process, the alumina layer plays a key role: on the one hand, there are a large number of dangling bonds and defect states on the surface of the silicon wafer, resulting in serious carrier recombination. The alumina layer, with its passivation characteristics, can reduce the surface recombination rate and improve the minority carrier lifetime; on the other hand, in a complex battery structure, the adaptation between functional layers is crucial. The alumina layer can optimize the interface characteristics and enhance the overall performance of the battery. However, the alumina layer prepared by traditional methods has limited effect on improving the photoelectric conversion efficiency of solar cells. Summary of the Invention

[0003] Based on this, this application provides a solar cell and a method for manufacturing the same. The manufacturing method of the solar cell can manufacture a solar cell with a relatively high photoelectric conversion efficiency.

[0004] The technical solution for solving the above technical problems in this application is as follows.

[0005] In the first aspect of this application, a method for manufacturing a solar cell is provided, including the following steps:

[0006] Cyclically introducing a first aluminum precursor and a first oxidant to prepare a first alumina layer on one side of the silicon substrate;

[0007] Cyclically introducing a second aluminum precursor and a second oxidant to prepare a second alumina layer on the side of the first alumina layer away from the silicon substrate;

[0008] In each cycle, the flow rate of the second aluminum precursor is greater than that of the first aluminum precursor, and the flow rate of the second oxidant is greater than that of the first oxidant.

[0009] In some embodiments, in the method for manufacturing a solar cell, in each cycle, the flow rate of the first aluminum precursor is 14 sccm to 18 sccm, and the flow rate of the second aluminum precursor is 16 sccm to 20 sccm;

[0010] And / or, in each cycle, the flow rate of the first oxidant is 12 sccm to 16 sccm, and the flow rate of the second oxidant is 16 sccm to 22 sccm.

[0011] In some of these embodiments, in the method for preparing a solar cell, in each cycle, the pulse time of the second aluminum precursor is greater than the pulse time of the first aluminum precursor;

[0012] and / or, in each cycle, the pulse time of the second oxidant is greater than the pulse time of the first oxidant.

[0013] In some of these embodiments, in the method for preparing a solar cell, the number of cycles of the second aluminum precursor and the second oxidant is less than the number of cycles of the first aluminum precursor and the first oxidant.

[0014] In some of these embodiments, in the method for preparing a solar cell, in each cycle, the pulse time of the first aluminum precursor is 4 s to 8 s, and the pulse time of the second aluminum precursor is 5 s to 9 s;

[0015] and / or, in each cycle, the pulse time of the first oxidant is 3 s to 7 s, and the pulse time of the second oxidant is 4 s to 8 s;

[0016] and / or, the number of cycles of the first aluminum precursor and the first oxidant is 15 to 25 times, and the number of cycles of the second aluminum precursor and the second oxidant is 5 to 15 times.

[0017] In some of these embodiments, in the method for preparing a solar cell, the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer are independently 300 °C to 360 °C.

[0018] In some of these embodiments, in the method for preparing a solar cell, the first aluminum precursor and the second aluminum precursor independently include trimethylaluminum;

[0019] and / or, the first oxidant and the second oxidant independently include water vapor.

[0020] In some of these embodiments, in the method for preparing a solar cell, before cyclically introducing the first aluminum precursor and the first oxidant, it includes: introducing ozone to prepare a silicon oxide layer on one side of the silicon substrate.

[0021] In some of these embodiments, in the method for preparing a solar cell, after preparing the silicon oxide layer and before cyclically introducing the first aluminum precursor and the first oxidant, it includes: introducing water vapor to perform a first pretreatment on the surface of the silicon oxide layer away from the silicon substrate;

[0022] and / or, after preparing the first aluminum oxide layer and before cyclically introducing the second aluminum precursor and the second oxidant, it includes: introducing water vapor to perform a second pretreatment on the surface of the first aluminum oxide layer away from the silicon substrate.

[0023] The second aspect of the present application provides a solar cell, which is prepared by using the preparation method of the solar cell provided in the first aspect.

[0024] In the preparation method of the solar cell provided by the present application, a first aluminum precursor and a first oxidant are circulated to prepare a first aluminum oxide layer on one side of the silicon substrate; a second aluminum precursor and a second oxidant are circulated to prepare a second aluminum oxide layer on the side of the first aluminum oxide layer away from the silicon substrate; by controlling the flow rate of the second aluminum precursor to be greater than that of the first aluminum precursor and the flow rate of the second oxidant to be greater than that of the first oxidant in each cycle, the passivation effect of the first aluminum oxide layer and the second aluminum oxide layer is effectively improved, and thus the photoelectric conversion efficiency of the solar cell is effectively improved. Specific Embodiments

[0025] The following further describes the present application in detail in combination with embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and not to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosed content of the present application more thorough and comprehensive.

[0026] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without departing from the connotation of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. For example, features described or depicted as part of one embodiment can be combined in a suitable manner with another embodiment to produce a new embodiment. In addition, in the following description, a large number of specific details are given to provide a more thorough understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing the embodiments and examples and are not intended to limit this application.

[0028] Unless otherwise stated or there is a contradiction, the terms or phrases used herein have the following meanings:

[0029] In the present application, the terms "a plurality of", "a variety of", "multiple times", etc., unless otherwise specified, refer to a quantity greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0030] As used herein, "combinations thereof", "any combination thereof", "any combination mode thereof", etc. include all suitable combination modes of any two or more of the listed items.

[0031] In this application, the "suitable" in "suitable combination mode", "suitable mode", "any suitable mode", etc. is subject to being able to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0032] In this application, "further", "even further", "especially", etc. are used for descriptive purposes, indicating differences in content, but should not be construed as limiting the protection scope of this application.

[0033] In this application, in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumerative description and should be understood not to constitute a closed limitation on quantity.

[0034] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0035] In this application, regarding the numerical interval (i.e., numerical range), unless otherwise specified, the distribution of the optional numerical values within this numerical interval is considered continuous, and includes the two numerical endpoints of this numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within this numerical interval, it includes the two endpoint integers of this numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When providing multiple numerical ranges to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of numerical interval types such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0036] The temperature parameter in this application, unless otherwise specifically limited, allows both constant temperature treatment and fluctuations within a certain temperature range. It should be understood that the so-called constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0037] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, such as 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0038] In this application, for units involving data ranges, if there is only a unit after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of both the left endpoint "3" and the right endpoint "5" are h (hours).

[0039] All documents mentioned in this application are cited as references in this application, just as if each document is cited separately as a reference. Unless it conflicts with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited for all content and all purposes. When this application involves cited documents, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited together. When this application involves cited documents, the examples and preferred methods of the relevant technical features cited can also be incorporated as references into this application, but only to the extent that this application can be implemented. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or be corrected adaptively according to the description in this application.

[0040] The mass or weight of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific content of each component, but also can represent the mass or weight ratio relationship between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass or weight described in the specification of the embodiments of this application can be units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0041] An embodiment of this application provides a method for preparing a solar cell, including the following steps:

[0042] Step S100: Circulatingly introducing a first aluminum precursor and a first oxidant to prepare a first aluminum oxide layer on one side of the silicon substrate;

[0043] Step S200: Circulatingly introducing a second aluminum precursor and a second oxidant to prepare a second aluminum oxide layer on the side of the first aluminum oxide layer away from the silicon substrate;

[0044] In each cycle, the flow rate of the second aluminum precursor is greater than that of the first aluminum precursor, and the flow rate of the second oxidant is greater than that of the first oxidant.

[0045] By controlling the flow rate of the second aluminum precursor to be greater than that of the first aluminum precursor and the flow rate of the second oxidant to be greater than that of the first oxidant in each cycle, the passivation effect of the first aluminum oxide layer and the second aluminum oxide layer can be effectively improved, thereby effectively improving the photoelectric conversion efficiency of the solar cell.

[0046] The flow rate of the second aluminum precursor is greater than that of the first aluminum precursor. The flow rate of the first aluminum precursor is relatively small. The larger the adsorption ratio of the first aluminum precursor on the deposition surface, the less residue remains unadsorbed, effectively improving the atmosphere concentration in the reaction chamber and preventing the first oxidant from reacting with the unadsorbed first aluminum precursor residue to form aluminum oxide powder after the first oxidant is introduced, thus avoiding the consumption of the first oxidant by by-products, promoting the completion of the self-limiting reaction, further controlling the increase in the flow rate of the second aluminum precursor, and effectively improving the film density and the ability of hydrogen passivation.

[0047] It can be understood that introducing the first aluminum precursor and the first oxidant in sequence is one cycle; introducing the second aluminum precursor and the second oxidant in sequence is one cycle; further, it can be understood that the aluminum precursor and the oxidant react to form aluminum oxide. It can be understood that in some examples, in the method for preparing a solar cell, the first aluminum precursor, the first oxidant, the second aluminum precursor, and the second oxidant are all gaseous. Further, it can be understood that the method for preparing the first aluminum oxide layer and the second aluminum oxide layer is ALD (Atomic Layer Deposition).

[0048] Atomic layer deposition (ALD for short) is a nano thin film deposition technology based on the chemisorption of gaseous precursors on the surface of a silicon substrate, and an aluminum oxide film layer of a certain thickness is obtained through a self-limiting reaction.

[0049] ALD is based on the principle of surface self-limiting reaction. By alternately introducing two or more precursors and allowing them to undergo chemisorption reactions, an atomic-level thin film is formed. Taking trimethylaluminum (TMA) as the first aluminum precursor and the second aluminum precursor, and water (H 2 O) as the first oxidant and the second oxidant as an example, first introduce trimethylaluminum (TMA) into the reaction chamber. The aluminum atoms in TMA will react with the hydroxyl groups or other active sites on the surface of the silicon substrate to form chemical bonds and adsorb on the surface. Since the number of surface active sites is limited, when these sites are all occupied by TMA molecules, a saturated monolayer is formed. At this time, even if more TMA molecules are introduced, no further adsorption reaction can occur. This is the first self-limiting; then introduce an inert gas to purge, removing the unreacted TMA molecules and by-products, and then introduce water (H 2O), the oxygen in the water molecule reacts with the adsorbed aluminum atoms to form a part of aluminum oxide, while releasing by-products such as methane. This reaction also only occurs on the adsorbed TMA layer and will not react unrestrictedly at other positions. This is the second self-limitation; after purging again, a deposition cycle is completed. By repeating this process, the layer-by-layer growth of the thin film is achieved.

[0050] In some of these examples, in the method for preparing a solar cell, in each cycle, the flow rate of the first aluminum precursor is 14 sccm to 18 sccm.

[0051] It can be understood that in each cycle, the flow rate of the first aluminum precursor includes but is not limited to 14 sccm, 15 sccm, 16 sccm, 17 sccm, 18 sccm. It can also be understood that the flow rates of the first aluminum precursor in each cycle can be the same or different; in some embodiments, the flow rates of the first aluminum precursor in each cycle are the same. The same applies hereinafter.

[0052] In some of these examples, in the method for preparing a solar cell, in each cycle, the flow rate of the second aluminum precursor is 16 sccm to 20 sccm.

[0053] It can be understood that in each cycle, the flow rate of the second aluminum precursor includes but is not limited to 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm.

[0054] In some of these examples, in the method for preparing a solar cell, in each cycle, the flow rate of the first oxidant is 12 sccm to 16 sccm.

[0055] It can be understood that in each cycle, the flow rate of the first oxidant includes but is not limited to 12 sccm, 13 sccm, 14 sccm, 15 sccm, 16 sccm.

[0056] In some of these examples, in the method for preparing a solar cell, in each cycle, the flow rate of the second oxidant is 16 sccm to 22 sccm.

[0057] It can be understood that in each cycle, the flow rate of the second oxidant includes but is not limited to 16 sccm, 17 sccm, 18 sccm, 19 sccm, 20 sccm, 21 sccm, 22 sccm.

[0058] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the second aluminum precursor is greater than the pulse time of the first aluminum precursor.

[0059] By controlling the pulse time, it is beneficial to the efficient progress of the self-limiting reaction of ALD atomic layer deposition.

[0060] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the first aluminum precursor is 4 s to 8 s.

[0061] It can be understood that in each cycle, the pulse time of the first aluminum precursor includes but is not limited to 4 s, 5 s, 6 s, 7 s, 8 s.

[0062] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the second aluminum precursor is 5 s to 9 s.

[0063] It can be understood that in each cycle, the pulse time of the second aluminum precursor includes but is not limited to 5 s, 6 s, 7 s, 8 s.

[0064] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the second oxidant is greater than that of the first oxidant.

[0065] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the first oxidant is 3 s to 7 s.

[0066] It can be understood that in each cycle, the pulse time of the first oxidant includes but is not limited to 3 s, 4 s, 5 s, 6 s, 7 s.

[0067] In some of these examples, in the method for preparing a solar cell, in each cycle, the pulse time of the second oxidant is 4 s to 8 s.

[0068] It can be understood that in each cycle, the pulse time of the second oxidant includes but is not limited to 4 s, 5 s, 6 s, 7 s, 8 s.

[0069] In some of these examples, in the method for preparing a solar cell, the number of cycles of the second aluminum precursor and the second oxidant is less than that of the first aluminum precursor and the first oxidant.

[0070] On the basis of controlling that the flow rate of the second aluminum precursor is greater than that of the first aluminum precursor and the flow rate of the second oxidant is greater than that of the first oxidant in each cycle, further control the pulse time of the second aluminum precursor to be greater than that of the first aluminum precursor, the pulse time of the second oxidant to be greater than that of the first oxidant, and control the number of cycles of the second aluminum precursor and the second oxidant to be less than that of the first aluminum precursor and the first oxidant, so as to ensure the inherent negative charge density inside the first aluminum oxide layer and the second aluminum oxide layer and improve the field passivation effect.

[0071] In some of these examples, in the method for preparing a solar cell, the number of cycles of the first aluminum precursor and the first oxidant is 15 to 25 times.

[0072] It can be understood that in each cycle, the number of cycles of the first aluminum precursor and the first oxidant includes but is not limited to 15 times, 18 times, 20 times, and 25 times.

[0073] In some of these examples, in the method for preparing a solar cell, the number of cycles of the second aluminum precursor and the second oxidant is 5 to 15 times.

[0074] It can be understood that in each cycle, the number of cycles of the second aluminum precursor and the second oxidant includes but is not limited to 5 times, 8 times, 10 times, and 15 times.

[0075] In some of these examples, in the method for preparing a solar cell, the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer are independently 300°C to 360°C.

[0076] It can be understood that the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer can be the same or different; further, the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer independently include but are not limited to 300°C, 305°C, 310°C, 315°C, 320°C, 325°C, 330°C, 335°C, 340°C, 345°C, 350°C, 355°C, 360°C; in some examples, it can be within the range formed by any two of these point values as the end values, and the same applies hereinafter.

[0077] It can be understood that during the process of heating up to the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer, the surface layer of the silicon substrate will be oxidized to form silicon dioxide (the defect density between the silicon dioxide and the silicon substrate is less than the defect density between the aluminum oxide layer and the silicon substrate), and by controlling the temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer in a higher range (300°C to 360°C), the defect density between the silicon dioxide and the silicon substrate can be further reduced, resulting in the internal structure reorganization of the first aluminum oxide layer and the second aluminum oxide layer, enhancing the inherent negative charge concentration inside the first aluminum oxide layer and the second aluminum oxide layer. At the same time, it is beneficial to increase the activation energy of the precursor on the surface of the silicon matrix during the aluminum oxide deposition process, strengthen the frequency and quantity of chemical adsorption, improve the field passivation performance of the first aluminum oxide layer and the second aluminum oxide layer, increase the densification of the first aluminum oxide layer and the second aluminum oxide layer, and improve the open-circuit voltage and fill factor of the battery; and enhance the diffusion energy of H atoms in the first aluminum oxide layer and the second aluminum oxide layer, promote the combination of H and the dangling bonds on the silicon surface, reduce the defect density on the silicon surface, thereby enhancing the chemical passivation effect of the first aluminum oxide layer and the second aluminum oxide layer, and further improving the battery efficiency.

[0078] The first alumina layer is prepared at a relatively high temperature, the flow rate of the first aluminum precursor is reduced, and the pulse time of the first aluminum precursor is shortened, so that the adsorption effect of the first aluminum precursor on the surface of the silicon substrate is better, promoting the bonding of dangling bonds on the surface of the silicon substrate and the ability of the first oxidant to react with it; the second alumina layer is prepared at a relatively high temperature, the flow rate of the second aluminum precursor is reduced, and the pulse time of the second aluminum precursor is shortened, so that the adsorption effect of the second aluminum precursor on the surface of the silicon substrate is better, promoting the ability of the second oxidant to react with it and the adhesion ability; thereby promoting the interface state density and passivation ability of the first alumina layer and the second alumina layer.

[0079] Compared with preparing the first alumina layer and the second alumina layer at a relatively high temperature (300 °C - 360 °C), the adsorption effect of depositing the aluminum precursor at a relatively low temperature (< 300 °C) is weakened, the dangling bonds on the surface of the silicon substrate cannot be completely bonded, and some dangling bonds still remain in the exposed state; when the oxidant is introduced, the ability to undergo a chemical reaction or the adhesion ability is correspondingly weakened, ultimately resulting in a weakened denseness of the alumina film layer. Similarly, the field passivation and chemical passivation abilities are weakened.

[0080] Furthermore, the temperatures for preparing the first alumina layer and the second alumina layer are independently 310 °C - 340 °C respectively.

[0081] By controlling the flow rates, pulse times, and number of cycles of the first aluminum precursor, the first oxidant, the second aluminum precursor, and the second oxidant, as well as controlling the deposition temperature, the passivation effect of the alumina passivation layer can be effectively improved, thereby improving the battery performance.

[0082] In some examples, in step S100, before cyclically introducing the first aluminum precursor and the first oxidant, it includes step S110:

[0083] Ozone is introduced to prepare a silicon oxide layer on one side of the silicon substrate.

[0084] Based on introducing ozone during the process of heating up to the temperature for preparing the first alumina layer and the second alumina layer before the ALD process (cyclically introducing the first aluminum precursor and the first oxidant), a silicon dioxide layer is formed on the surface layer of the silicon substrate. Combining with the high reaction temperature being beneficial to improving the denseness of the silicon dioxide, the formed silicon dioxide layer is also beneficial to improving the denseness of the alumina thin film (the first alumina layer and the second alumina layer) during the deposition of alumina, thereby improving the passivation performance of the first alumina layer and the second alumina layer.

[0085] In some examples, in step S110, the concentration of the introduced ozone is 1000 ppb - 3000 ppb, and the time range for introducing ozone is 500 s - 2000 s.

[0086] In some of these examples, in the method for preparing a solar cell, the first aluminum precursor and the second aluminum precursor each independently include trimethylaluminum.

[0087] In some of these examples, in the method for preparing a solar cell, the first oxidant and the second oxidant each independently include water vapor.

[0088] In some of these examples, in step S100, after the silicon oxide layer is prepared in step S110 and before the first aluminum precursor and the first oxidant are cyclically introduced, it includes step S120:

[0089] Introduce water vapor to perform a first pretreatment on the surface of the silicon oxide layer away from the silicon substrate.

[0090] Use water vapor to perform a first pretreatment on the silicon oxide layer to provide hydrogen atoms to saturate the unbonded dangling bonds of the silicon oxide layer.

[0091] In some of these examples, in any cycle of step S100, it includes steps S120 to S160:

[0092] Step S120: Introduce water vapor to perform a first pretreatment on the surface of the silicon oxide layer away from the silicon substrate;

[0093] Step S130: Introduce the first aluminum precursor, and the first aluminum precursor adsorbs on the surface of the silicon oxide layer;

[0094] Step S140: Introduce a purge gas to remove the unadsorbed gas;

[0095] Step S150: Introduce the first oxidant to react with the first aluminum precursor adsorbed on the surface of the silicon oxide layer to form a first aluminum oxide layer;

[0096] Step S160: Introduce a purge gas to remove the remaining gas.

[0097] In some of these examples, in step S200, after the first aluminum oxide layer is prepared and before the second aluminum precursor and the second oxidant are cyclically introduced, it includes step S210: Introduce water vapor to perform a second pretreatment on the surface of the first aluminum oxide layer away from the silicon substrate.

[0098] In some of these examples, in any cycle of step S200, it includes steps S210 to S250:

[0099] Step S210: Introduce water vapor to perform a second pretreatment on the surface of the first aluminum oxide layer away from the silicon substrate;

[0100] Step S220: Introduce the second aluminum precursor, and the second aluminum precursor adsorbs on the surface of the first aluminum oxide layer;

[0101] Step S230: Introduce a purge gas to remove the unadsorbed gas;

[0102] Step S240: Introduce a second oxidant to react with the second aluminum precursor adsorbed on the surface of the first alumina layer to form a second alumina layer;

[0103] Step S250: Introduce a purge gas to remove the remaining gas.

[0104] In some examples, in the method for preparing a solar cell, before step S100, it includes step S300:

[0105] Perform boron diffusion on the front side of the silicon substrate to form an emitter.

[0106] In some examples, the boron source used for boron diffusion includes but is not limited to BBr 3 or BCl 3 .

[0107] It can be understood that in some examples, before step S300, it includes the step of texturing the silicon wafer to obtain a silicon substrate.

[0108] Texture the silicon wafer to remove organic substances and metal impurities on the surface of the silicon wafer, reduce recombination centers, form an uneven textured surface, increase the absorption of sunlight by the silicon wafer, and reduce the reflectivity; further, utilize the anisotropic etching characteristics of silicon in a low-concentration alkaline solution to form a pyramid-shaped textured surface on the silicon wafer surface.

[0109] In some examples, in the method for preparing a solar cell, after step S100, it includes step S400:

[0110] Successively prepare a tunneling oxide layer and a doped polysilicon layer on the back side of the silicon substrate.

[0111] Deposit a tunneling oxide layer and a doped polysilicon layer on the back side of the silicon wafer to provide good interface passivation and at the same time provide different carrier tunneling barriers.

[0112] In some examples, step S400 includes: first depositing a tunneling oxide layer, then depositing amorphous silicon, and finally phosphorus diffusion (while the amorphous silicon is converted into polysilicon).

[0113] In some examples, after phosphorus diffusion and before step S100, it includes: removing the front side and edge BSG.

[0114] In some examples, in the method for preparing a solar cell, after step S400, it includes step S500:

[0115] A front anti-reflection layer is prepared on the side of the second aluminum oxide layer away from the first aluminum oxide layer, and a back anti-reflection layer is prepared on the side of the polysilicon layer away from the tunneling oxide layer.

[0116] In some examples, in the method for manufacturing a solar cell, after step S500, a front electrode and a metal back electrode are manufactured.

[0117] The method for manufacturing a solar cell provided by this application has a relatively high production efficiency and can obtain an efficiency gain of more than 0.05%.

[0118] An embodiment of this application provides a solar cell manufactured by using the above method for manufacturing a solar cell.

[0119] It can be understood that the solar cell includes a silicon substrate, and one side of the silicon substrate includes a first aluminum oxide layer and a second aluminum oxide layer arranged in sequence.

[0120] In some examples, in the solar cell, the mass of aluminum in the second aluminum oxide layer is lower than the mass of aluminum in the first aluminum oxide layer.

[0121] In some examples, in the solar cell, the mass of oxygen in the second aluminum oxide layer is lower than the mass of oxygen in the first aluminum oxide layer.

[0122] In some examples, in the solar cell, the mass ratio of aluminum in the first aluminum oxide layer to aluminum in the second aluminum oxide layer is (1.2 - 2):1.

[0123] It can be understood that the mass ratio of aluminum in the second aluminum oxide layer to aluminum in the first aluminum oxide layer includes but is not limited to 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1.

[0124] By controlling the mass relationship of aluminum in the second aluminum oxide layer and the first aluminum oxide layer, it is beneficial to ensure the inherent negative charge density inside the first aluminum oxide layer and the second aluminum oxide layer and improve the field passivation effect.

[0125] In some examples, the solar cell includes at least one of, but is not limited to, crystalline silicon cells and perovskite cells, etc. It can be understood that the crystalline silicon cells include at least one of, but is not limited to, TOPCon cells (tunneling oxide passivated contact cells), HJT cells (heterojunction cells), IBC cells (interdigitated back contact cells), and PERC cells (passivated emitter and rear cells), etc.

[0126] In some examples, the solar cell is a TOPCON cell (tunneling oxide passivated contact cell).

[0127] TOPCon (tunnel oxide passivation contact) cells are fully called tunnel oxide passivation contact cells. The core lies in the ultrathin tunneling oxide layer and the heavily doped polysilicon layer on the back. The ultrathin oxide layer allows electrons to tunnel into the polysilicon layer while blocking the transport of holes, reducing the recombination rate and enhancing the passivation effect and conversion efficiency of the cells.

[0128] In some examples, in a solar cell, including a silicon substrate, the front side of the silicon substrate includes an emitter, a silicon oxide layer, a first aluminum oxide layer, and a second aluminum oxide layer arranged in sequence, and the back side of the silicon substrate includes a tunneling oxide layer and a polysilicon layer arranged in sequence.

[0129] In some examples, the solar cell further includes a front antireflection layer and a front electrode arranged in sequence on the surface of the second aluminum oxide layer away from the first aluminum oxide layer. In some examples, the front antireflection layer includes, but is not limited to, silicon nitride (SiN x ). In some examples, the front electrode includes, but is not limited to, at least one of aluminum and silver.

[0130] In some examples, the solar cell further includes a back antireflection layer and a metal back electrode arranged in sequence on the surface of the polysilicon layer away from the tunneling oxide layer. In some examples, the back antireflection layer includes, but is not limited to, silicon nitride (SiN x ). In some examples, the metal back electrode includes, but is not limited to, silver.

[0131] An embodiment of the present application provides a tandem cell, including the above-mentioned solar cell or a solar cell prepared by the preparation method of the above-mentioned solar cell.

[0132] It can be understood that the tandem cell includes, but is not limited to, a two-terminal tandem cell, a three-terminal tandem cell, and a four-terminal tandem cell. Further, the tandem cell includes, but is not limited to, a perovskite cell stacked with a crystalline silicon cell.

[0133] An embodiment of the present application provides a photovoltaic module, including the above-mentioned provided solar cell, a solar cell prepared by the preparation method of the above-mentioned provided solar cell, or the above-mentioned provided tandem cell.

[0134] In some examples, the photovoltaic module includes:

[0135] A cell string, electrically connected by a plurality of the above-mentioned solar cells or solar cells prepared by the preparation method of the above-mentioned solar cell, or electrically connected by a plurality of the above-mentioned tandem cells;

[0136] An encapsulation adhesive film for covering the surface of the cell string; and

[0137] A cover plate for covering the surface of the encapsulation film facing away from the battery string.

[0138] It can be understood that solar cells or tandem cells are electrically connected in the form of a whole piece or multiple sub-pieces to form multiple battery strings, and the multiple battery strings are electrically connected in series and / or parallel. Further, the solar cells or tandem cells can be whole-piece cells or sliced cells, and the sliced cells refer to cells formed by cutting a complete whole-piece cell through a cutting process.

[0139] In some examples, the multiple battery strings can be electrically connected through conductive bands.

[0140] In some examples, the encapsulation film includes a first encapsulation layer and a second encapsulation layer. The first encapsulation layer covers one of the front and back surfaces of the battery, and the second encapsulation layer covers the other of the front and back surfaces of the battery. Further, the first encapsulation layer and the second encapsulation layer can each independently include at least one of organic encapsulation films such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyolefin elastomer (POE) film, and polyethylene terephthalate (PET) film.

[0141] In some examples, the cover plate can be a cover plate with a light-transmitting function such as a glass cover plate or a plastic cover plate.

[0142] The following further describes the present application in detail in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0143] In the following examples and comparative examples, the first aluminum precursor and the second aluminum precursor are both trimethylaluminum (TMA), and the first oxidant and the second oxidant are both water vapor.

[0144] Example 1

[0145] (1) Texturing the n-type silicon wafer;

[0146] Boron diffusion: Diffusing a p-type element (boron) on the n-type silicon wafer to form a p-n junction and form a p+ layer on the front surface;

[0147] Alkaline polishing: Removing the edge and back surface BSG of the silicon wafer;

[0148] LPCVD: Depositing a tunneling oxide layer and a polysilicon layer on the back surface of the silicon wafer;

[0149] Phosphorus diffusion: Doping the polysilicon layer with phosphorus;

[0150] Front etching: Positive grooving (with water film), water washing, alkaline washing, water washing, acid washing, water washing, and drying to remove the front surface and edge BSG;

[0151] (2) Ozone is introduced into the drying tank of the wet equipment with a flow rate of 1200 ppb for 900 s to form the first silicon oxide layer;

[0152] (3) ALD deposition is used, and it is preheated to a deposition temperature of 325 °C (the second silicon oxide layer is formed during this process), and the first aluminum oxide layer and the second aluminum oxide layer are prepared in sequence:

[0153] (3.1) Water vapor is introduced into the atomic layer deposition chamber for the first pretreatment of the surface of the silicon oxide layer. The flow rate of water vapor is 12 sccm, the pulse time is 25 s, and then an inert gas is introduced for purging for 12 s;

[0154] (3.2) The first aluminum precursor and the first oxidant are cyclically introduced. Each cycle is as follows: the first aluminum precursor is introduced with a flow rate of 16 sccm and a pulse time of 6 s, and then an inert gas is introduced for purging for 12 s; then the first oxidant is introduced with a flow rate of 14 sccm and a pulse time of 5 s, and an inert gas is introduced for purging for 12 s; the number of cycles is 18 times to prepare the first aluminum oxide layer;

[0155] (3.3) Water vapor is introduced into the atomic layer deposition chamber for the second pretreatment of the surface of the first aluminum oxide layer. The flow rate of water vapor is 12 sccm, the pulse time is 25 s, and then an inert gas is introduced for purging for 12 s;

[0156] (3.4) The second aluminum precursor and the second oxidant are cyclically introduced. Each cycle is as follows: the second aluminum precursor is introduced with a flow rate of 18 sccm and a pulse time of 7 s, and then an inert gas is introduced for purging for 12 s; then the second oxidant is introduced with a flow rate of 20 sccm and a pulse time of 6 s, and an inert gas is introduced for purging for 12 s; the number of cycles is 10 times to prepare the second aluminum oxide layer;

[0157] (4) Front and back films: Si 3 H 4 antireflection film;

[0158] Screen-print positive and negative electrodes.

[0159] The micro-conduction process parameters for preparing the first aluminum oxide layer and the second aluminum oxide layer in Example 1 are shown in Table 1.

[0160] Table 1

[0161]

[0162] Example 2

[0163] It is basically the same as Example 1, except that in the preparation of the first aluminum oxide layer and the second aluminum oxide layer, the pulse time of the first aluminum precursor is 7 s and the pulse time of the second aluminum precursor is 6 s.

[0164] Example 3

[0165] It is basically the same as Example 1, except that in the preparation of the first alumina layer and the second alumina layer, the pulse time of the first oxidant is 6 s, and the pulse time of the second oxidant is 5 s.

[0166] Example 4

[0167] It is basically the same as Example 1, except that in the preparation of the first alumina layer and the second alumina layer, the number of cycles of circulating the first aluminum precursor and the first oxidant is 10 times, and the number of cycles of circulating the second aluminum precursor and the second oxidant is 18 times.

[0168] Example 5

[0169] It is basically the same as Example 1, except that the deposition temperature is 300 °C.

[0170] Example 6

[0171] It is basically the same as Example 1, except that the step of introducing ozone in step (2) is omitted, and a first silicon oxide layer is formed during the preheating to the ALD deposition temperature.

[0172] Example 7

[0173] It is basically the same as Example 1, except that the deposition temperature is 265 °C.

[0174] Comparative Example 1

[0175] Prepare an alumina layer according to the parameters in Table 2:

[0176] Table 2

[0177]

[0178] Comparative Example 2

[0179] It is basically the same as Example 1, except that the flow rate of the first aluminum precursor is 18 sccm and the flow rate of the second aluminum precursor is 16 sccm.

[0180] Comparative Example 3

[0181] It is basically the same as Example 1, except that the flow rate of the first oxidant is 20 sccm and the flow rate of the second oxidant is 14 sccm.

[0182] Using a battery performance tester, AM1.5G spectrum, light intensity 1000W / m 2, the electrical performance of the solar cells prepared in each example and comparative example was tested. Among them, Eta is the photoelectric conversion efficiency, Uoc is the open-circuit voltage, Isc is the short-circuit current, and FF is the fill factor; the results are shown in Table 3.

[0183] Table 3

[0184]

[0185] As can be seen from Table 3, compared with Comparative Example 1, the photoelectric conversion efficiency of the batteries prepared in each example is higher.

[0186] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0187] The above-described embodiments only represent several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application specifically and in detail, but should not be construed as a limitation on the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the specification can be used to explain the content of the claims.

Claims

1. A method for preparing a solar cell, characterized in that: The steps include: Circulating a first aluminum precursor and a first oxidant to form a first aluminum oxide layer on one side of the silicon substrate; Circulating a second aluminum precursor and a second oxidant to form a second aluminum oxide layer on a side of the first aluminum oxide layer away from the silicon substrate; In each cycle, the flow rate of the second aluminum precursor is greater than the flow rate of the first aluminum precursor, and the flow rate of the second oxidant is greater than the flow rate of the first oxidant.

2. The method for preparing a solar cell according to claim 1, characterized in that: In each cycle, the flow rate of the first aluminum precursor is 14 sccm-18 sccm, and the flow rate of the second aluminum precursor is 16 sccm-20 sccm; And / or, in each cycle, the flow rate of the first oxidant is 12 sccm-16 sccm, and the flow rate of the second oxidant is 16 sccm-22 sccm.

3. The method for preparing a solar cell according to claim 1, wherein: In each cycle, the pulse time of the second aluminum precursor is greater than the pulse time of the first aluminum precursor; And / or, in each cycle, the pulse time of the second oxidant is greater than the pulse time of the first oxidant.

4. The method for preparing a solar cell according to claim 3, characterized in that: The number of cycles of the second aluminum precursor and the second oxidant is less than the number of cycles of the first aluminum precursor and the first oxidant.

5. The method for preparing a solar cell according to claim 4, characterized in that: In each cycle, the pulse time of the first aluminum precursor is 4 s to 8 s, and the pulse time of the second aluminum precursor is 5 s to 9 s; And / or, in each cycle, the pulse time of the first oxidant is 3 s to 7 s, and the pulse time of the second oxidant is 4 s to 8 s; And / or, the number of cycles of the first aluminum precursor and the first oxidant is 15 to 25 times, and the number of cycles of the second aluminum precursor and the second oxidant is 5 to 15 times.

6. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: The temperatures for preparing the first aluminum oxide layer and the second aluminum oxide layer are independently 300° C. to 360° C.

7. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: The first aluminum precursor and the second aluminum precursor each independently include trimethylaluminum; And / or, the first oxidant and the second oxidant each independently include water vapor.

8. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: Before the first aluminum precursor and the first oxidant are circulated, ozone is introduced to prepare a silicon oxide layer on one side of the silicon substrate.

9. The method for preparing a solar cell according to claim 8, characterized in that: After the silicon oxide layer is prepared, before the first aluminum precursor and the first oxidant are circulated, the method includes: introducing water vapor to perform a first pretreatment on the surface of the silicon oxide layer away from the silicon substrate; And / or, after preparing the first aluminum oxide layer, before circulating the second aluminum precursor and the second oxidant, it includes: introducing water vapor to perform a second pretreatment on the surface of the first aluminum oxide layer away from the silicon substrate.

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

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