Passivated contact structures, solar cells and their fabrication methods and electrical devices

Abstract

This application relates to a passivated contact structure, a solar cell, a method for fabricating the same, and an electrical device thereof. The method for fabricating the passivated contact structure includes the following steps: using SiH4 as the reactant gas, or using H2 and SiH4 in a volume ratio of 2-3:1 as the reactant gas, a first deposition treatment is performed on the surface of a tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer; using H2 and SiH4 as the reactant gas, a second deposition treatment and a third deposition treatment are performed sequentially on the intrinsic polycrystalline silicon film layer to form a transition silicon film layer and a microcrystalline silicon film layer sequentially on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer; in the second deposition treatment, the volume ratio of H2 to SiH4 is 3.5-16:1, and in the third deposition treatment, the volume ratio of H2 to SiH4 is 17-40:1; the intrinsic polycrystalline silicon film layer, the transition silicon film layer, and the microcrystalline silicon film layer are boron-doped to form a boron-doped intrinsic polycrystalline silicon film layer, a boron-doped transition silicon film layer, and a boron-doped microcrystalline silicon film layer, respectively. This passivated contact structure exhibits good passivation performance.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a passivated contact structure, a solar cell, a method for fabricating the same, and an electrical device thereof. Background Technology

[0002] With the rapid development of photovoltaic technology, the conversion efficiency of crystalline silicon solar cells has been increasing year by year. Currently, TOPCon cells have almost replaced P-type bifacial PERC cells as the mainstream product in the solar cell manufacturing industry. At the same time, various manufacturers have begun research and development of next-generation cells with even higher efficiency than TOPCon cells. Among them, TBC cells stand out due to their high conversion efficiency and high compatibility with TOPCon cell production lines. In the preparation process of the TBC cell passivation layer, a tunneling oxide layer and an intrinsic poly layer are first prepared, and then impurities are doped through boron diffusion to form P-Poly (boron-doped polycrystalline silicon layer). The passivation effect of the TBC cell passivation layer prepared by traditional methods is relatively poor.

[0003] Therefore, it is necessary to improve traditional technologies. Summary of the Invention

[0004] Based on this, this application provides a passivated contact structure with good passivation effect, a solar cell, a method for fabricating the same, and an electrical device thereof.

[0005] The technical solution to the above-mentioned technical problems in this application is as follows.

[0006] The first aspect of this application provides a method for preparing a passivated contact structure, comprising the following steps:

[0007] Using SiH4 as the reactant gas, or using H2 and SiH4 in a volume ratio of 2 to 3:1 as the reactant gas, a first deposition process is performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer.

[0008] Using H2 and SiH4 as reactant gases, a second deposition process and a third deposition process are sequentially performed on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer to sequentially form a transition silicon film layer and a microcrystalline silicon film layer on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer; the volume ratio of H2 to SiH4 in the second deposition process is 3.5~16:1, and the volume ratio of H2 to SiH4 in the third deposition process is 17~40:1;

[0009] The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film are boron-doped to form a boron-doped intrinsic polycrystalline silicon film, a boron-doped transition silicon film, and a boron-doped microcrystalline silicon film, respectively.

[0010] In some embodiments, in the method for preparing the passivated contact structure, H2 and SiH4 with a volume ratio of 2 to 3:1 are used as reaction gases. In the first deposition process, the flow rate of H2 is 7000 sccm to 8000 sccm, and the flow rate of SiH4 is 3000 sccm to 3500 sccm.

[0011] In some embodiments, in the method for preparing the passivated contact structure, during the second deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 500 sccm ~ 2000 sccm.

[0012] In some embodiments, in the method for preparing the passivated contact structure, during the third deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 200 sccm ~ 400 sccm.

[0013] In some embodiments, in the method for preparing the passivated contact structure, the deposition method of the first deposition treatment includes at least one of PECVD and LPCVD, and the deposition method of the second and third deposition treatments is PECVD.

[0014] In some embodiments, the temperature of PECVD in the method for preparing the passivated contact structure is 400°C to 500°C, and the temperature of LPCVD is 500°C to 650°C.

[0015] In some embodiments, the method for preparing the passivated contact structure satisfies at least one of the following characteristics:

[0016] (1) The time for the first deposition treatment is 120 s to 1600 s;

[0017] (2) The second deposition treatment time is 600 s to 3200 s;

[0018] (3) The time for the third deposition treatment is 2000 s to 18000 s.

[0019] In some embodiments, the boron doping conditions in the method for preparing the passivated contact structure are: the boron doping temperature is 840℃~990℃, and the flow rate of the boron source is 100 sccm~400 sccm.

[0020] The second aspect of this application provides a passivated contact structure, which is prepared using the above-described method.

[0021] A third aspect of this application provides a passivated contact structure, comprising a tunneling oxide layer, a boron-doped intrinsic polycrystalline silicon film layer, a boron-doped transition silicon film layer, and a boron-doped microcrystalline silicon film layer arranged sequentially.

[0022] In some embodiments, the passivated contact structure satisfies at least one of the following characteristics:

[0023] (1) The thickness of the boron-doped intrinsic polycrystalline silicon film is 20 nm to 100 nm;

[0024] (2) The thickness of the boron-doped transition silicon film is 50 nm to 200 nm;

[0025] (3) The thickness of the boron-doped microcrystalline silicon film is 50 nm to 200 nm.

[0026] A fourth aspect of this application provides a solar cell, comprising a silicon wafer, the aforementioned passivation contact structure, and an electrode arranged sequentially, wherein a tunneling oxide layer in the passivation contact structure is disposed between the back surface of the silicon wafer and the boron-doped intrinsic polycrystalline silicon film.

[0027] In some embodiments, the solar cell further includes an AlOx film and a SiNx film. The AlOx film is disposed on the front surface of the silicon wafer and on the surface of the boron-doped microcrystalline silicon film away from the boron-doped transition silicon film. The SiNx film is disposed on the surface of the AlOx film away from the silicon wafer.

[0028] The fifth aspect of this application provides a method for preparing a solar cell, comprising the following steps:

[0029] A tunneling oxide layer is prepared on the back side of the silicon wafer;

[0030] Using SiH4 as the reactant gas, or using H2 and SiH4 in a volume ratio of 2 to 3:1 as the reactant gas, a first deposition process is performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer.

[0031] Using H2 and SiH4 as reactant gases, a second deposition process and a third deposition process are sequentially performed on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer to sequentially form a transition silicon film layer and a microcrystalline silicon film layer on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer; the volume ratio of H2 to SiH4 in the second deposition process is 3.5~16:1, and the volume ratio of H2 to SiH4 in the third deposition process is 17~40:1;

[0032] The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film are boron-doped to form a boron-doped intrinsic polycrystalline silicon film, a boron-doped transition silicon film, and a boron-doped microcrystalline silicon film, respectively.

[0033] An electrode is fabricated on the surface of the boron-doped microcrystalline silicon film layer away from the boron-doped transition silicon film layer.

[0034] The sixth aspect of this application provides an electrical device, including the solar cell described above or the solar cell prepared by the above method.

[0035] Compared with the prior art, the method for preparing the passivated contact structure in this application has the following advantages:

[0036] The method for preparing the passivation contact structure in this application involves controlling the volume ratio of reactive gases H2 and SiH4, and sequentially performing a first deposition treatment, a second deposition treatment, and a third deposition treatment on the surface of the tunneling oxide layer to sequentially form an intrinsic polycrystalline silicon film, a transition silicon film, and a microcrystalline silicon film on the surface of the tunneling oxide layer. The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film have high quality and density, which makes it possible to further boron-dopat the intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film, resulting in boron-doped intrinsic polycrystalline silicon film, boron-doped transition silicon film, and boron-doped microcrystalline silicon film with high quality and density, fewer impurity elements that can penetrate the structure and tunnel through the oxide layer, thereby effectively improving the passivation effect of the passivation contact structure. Detailed Implementation

[0037] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0038] Therefore, this invention is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the invention are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0040] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element preceded by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The indefinite articles “a” and “an” preceding an element or component of the invention are not restrictive in terms of the number of elements or components (i.e., the number of times they appear). Therefore, “an” or “an” should be interpreted as including one or at least one, and singular elements or components also include plural forms, unless the quantity clearly refers only to the singular. “A plurality” means at least two, such as two, three, etc., unless otherwise expressly specified.

[0041] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0042] Unless otherwise shown or indicated in the operational embodiments, all figures used to represent the amounts, physicochemical properties, etc., of ingredients in the specification and claims are to be understood to be adjusted by the term "about" in all cases. For example, therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired characteristics by utilizing the teachings disclosed herein. The use of numerical ranges indicated by endpoints includes all numbers within that range and any range within that range; for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0043] Analysis suggests that the boron-doped poly layer of TBC cells prepared by traditional methods has low quality and density of intrinsic polycrystalline silicon film. When boron doping is further carried out, the high temperature of boron diffusion requires a large amount of heat during the impurity diffusion process. Impurity boron can easily penetrate the intrinsic polycrystalline silicon film and tunnel through the oxide layer, and penetrate into the substrate, resulting in poor passivation effect of the TBC cell passivation layer.

[0044] One embodiment of this application provides a method for preparing a passivated contact structure, including the following steps:

[0045] Step S10: Using SiH4 as the reaction gas, or using H2 and SiH4 in a volume ratio of 2~3:1 as the reaction gas, a first deposition treatment is performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer.

[0046] Using H2 and SiH4 as reactant gases, a second deposition process and a third deposition process are sequentially performed on the surface of the intrinsic polycrystalline silicon film away from the tunneling oxide layer to sequentially form a transition silicon film layer and a microcrystalline silicon film layer on the surface of the intrinsic polycrystalline silicon film away from the tunneling oxide layer; the volume ratio of H2 to SiH4 in the second deposition process is 3.5~16:1, and the volume ratio of H2 to SiH4 in the third deposition process is 17~40:1.

[0047] By controlling the volume ratio of reactant gas H2 to SiH4, a first deposition treatment, a second deposition treatment, and a third deposition treatment are sequentially performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film, a transition silicon film, and a microcrystalline silicon film on the surface of the tunneling oxide layer. The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film have high quality and density.

[0048] It can be understood that the transition silicon film layer includes polycrystalline silicon and microcrystalline silicon; further, it can be understood that the proportion of polycrystalline silicon is higher in the region of the transition silicon film layer closer to the polycrystalline silicon film layer, and conversely, the proportion of microcrystalline silicon is higher in the region of the transition silicon film layer closer to the microcrystalline silicon film layer.

[0049] Furthermore, it can be understood that when H2 and SiH4 are used as reactant gases in a volume ratio of 2 to 3:1, the volume ratio of H2 to SiH4 in the first deposition process includes, but is not limited to, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, and 3:1. It is understood that the volume ratio of H2 to SiH4 in the second deposition process includes, but is not limited to, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15: 1. 15.5:1, 16:1; The volume ratio of H2 to SiH4 in the third deposition process includes, but is not limited to, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, and 40:1. In some examples, any two of these point values ​​can be used as endpoints within a range, and the same applies below. For example, in the first deposition treatment, the volume ratio of H2 to SiH4 is 2.2~2.8:1, 2~2.5:1, or 2.5~3:1, etc.; in the second deposition treatment, the volume ratio of H2 to SiH4 is 5~15:1, 8~16:1, or 3.5~10:1, etc.; and in the third deposition treatment, the volume ratio of H2 to SiH4 is 20~30:1, 17~30:1, or 25~35:1, etc.

[0050] Optionally, the volume ratio of H2 to SiH4 in the first deposition process is 2.2 to 2.7:1.

[0051] Optionally, the volume ratio of H2 to SiH4 in the second deposition process is 6~12:1.

[0052] Optionally, the volume ratio of H2 to SiH4 in the third deposition process is 25~35:1.

[0053] In some of these examples, in step S10, during the first deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 3000 sccm ~ 3500 sccm.

[0054] It is understood that in the first deposition process, the flow rate of H2 includes, but is not limited to, 7000 sccm, 7100 sccm, 7200 sccm, 7300 sccm, 7400 sccm, 7500 sccm, 7600 sccm, 7700 sccm, 7800 sccm, 7900 sccm, and 8000 sccm, and the flow rate of SiH4 includes, but is not limited to, 3000 sccm, 3050 sccm, 3100 sccm, 3150 sccm, 3200 sccm, 3250 sccm, 3300 sccm, 3350 sccm, 3400 sccm, 3450 sccm, and 3500 sccm.

[0055] Optionally, in the first deposition process, the SiH4 flow rate is 3100 sccm ~ 3300 sccm.

[0056] In some of these examples, in step S10, during the second deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 500 sccm ~ 2000 sccm.

[0057] It is understood that in the second deposition process, the flow rate of H2 includes, but is not limited to, 7000 sccm, 7100 sccm, 7200 sccm, 7300 sccm, 7400 sccm, 7500 sccm, 7600 sccm, 7700 sccm, 7800 sccm, 7900 sccm, and 8000 sccm, and the flow rate of SiH4 includes, but is not limited to, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, 1800 sccm, 1900 sccm, and 2000 sccm.

[0058] Optionally, in the second deposition process, the SiH4 flow rate is 1000 sccm ~ 1800 sccm.

[0059] In some of these examples, in step S10, during the third deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 200 sccm ~ 400 sccm.

[0060] It is understood that in the third deposition process, the flow rate of H2 includes, but is not limited to, 7000 sccm, 7100 sccm, 7200 sccm, 7300 sccm, 7400 sccm, 7500 sccm, 7600 sccm, 7700 sccm, 7800 sccm, 7900 sccm, and 8000 sccm, and the flow rate of SiH4 includes, but is not limited to, 200 sccm, 210 sccm, 220 sccm, 240 sccm, 250 sccm, 260 sccm, 280 sccm, 300 sccm, 310 sccm, 320 sccm, 340 sccm, 350 sccm, 360 sccm, 380 sccm, and 400 sccm.

[0061] Optionally, in the third deposition process, the SiH4 flow rate is 250 sccm ~ 350 sccm.

[0062] By controlling the volume ratio of reactant gases H2 to SiH4, further controlling the flow rates of H2 and SiH4 in the first, second, and third deposition processes can further improve the quality and density of the obtained intrinsic polycrystalline silicon films, transition silicon films, and microcrystalline silicon films.

[0063] In some examples, in step S10, the deposition method of the first deposition treatment includes at least one of PECVD (plasma-enhanced chemical vapor deposition) and LPCVD (low-pressure chemical vapor deposition), and the deposition method of the second and third deposition treatments is PECVD.

[0064] It is understandable that in the first deposition process, if LPCVD is used for deposition, SiH4 is used as the reaction gas, and if PECVD is used for deposition, H2 and SiH4 with a volume ratio of 2~3:1 are used as the reaction gas.

[0065] Under current large-scale industrial production methods, LPCVD can only deposit intrinsic polycrystalline silicon films and cannot form transition silicon films or microcrystalline silicon films.

[0066] Preferably, the deposition method for the first deposition treatment, the second deposition treatment, and the third deposition treatment is PECVD.

[0067] In actual production processes, a very slow deposition rate is not conducive to large-scale industrial production.

[0068] Compared to LPCVD, PECVD is used for the first, second, and third deposition processes, controlling the volume ratio of H2 to SiH4 in the reaction gases during these processes to form intrinsic polycrystalline silicon, transition silicon, and microcrystalline silicon films. This ensures high quality and density of the intrinsic polycrystalline silicon, transition silicon, and microcrystalline silicon films, guaranteeing high quality and density of the boron-doped intrinsic polycrystalline silicon, boron-doped transition silicon, and boron-doped microcrystalline silicon films after subsequent boron doping. This results in better passivation of the passivation contact structure and effectively increases the deposition rate, thus facilitating large-scale industrial production.

[0069] In some of these examples, the first deposition process in step S10 takes 120 s to 1600 s.

[0070] Furthermore, when using PECVD for the first deposition process, and / or using H2 and SiH4 in a volume ratio of 2 to 3:1 as the reaction gas, the first deposition process takes 120 to 600 seconds.

[0071] At this time, the time for the first deposition process includes, but is not limited to, 120 s, 150 s, 180 s, 200 s, 220 s, 250 s, 280 s, 300 s, 320 s, 350 s, 380 s, 400 s, 420 s, 450 s, 480 s, 500 s, 520 s, 550 s, 580 s, and 600 s.

[0072] In some of these examples, the second deposition process in step S10 takes 600 s to 3200 s.

[0073] It is understood that the time for the second deposition process includes, but is not limited to, 600 s, 800 s, 1000 s, 1200 s, 1500 s, 1800 s, 2000 s, 2200 s, 2500 s, 2800 s, 3000 s, and 3200 s.

[0074] In some of these examples, the third deposition process in step S10 takes 2000 s to 18000 s.

[0075] It is understood that the time for the third deposition process includes, but is not limited to, 2000 s, 3000 s, 4000 s, 5000 s, 6000 s, 7000 s, 8000 s, 9000 s, 10000 s, 11000 s, 12000 s, 13000 s, 14000 s, 15000 s, 16000 s, 17000 s, and 18000 s.

[0076] It can be understood that by controlling the gas flow rate and time of the first deposition process, the second deposition process, and the third deposition process, the thickness of the formed intrinsic polycrystalline silicon film, transition silicon film, and microcrystalline silicon film can be controlled, thereby controlling the thickness of the boron-doped intrinsic polycrystalline silicon film, the boron-doped transition silicon film, and the boron-doped microcrystalline silicon film.

[0077] In some of these examples, in step S10, the temperature of PECVD is 400℃~500℃, and the temperature of LPCVD is 500℃~650℃.

[0078] It is understood that PECVD temperatures include, but are not limited to, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, and 500℃; and LPCVD temperatures include, but are not limited to, 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, and 650℃. It is also understood that the temperatures for the first, second, and third deposition treatments can be the same or different.

[0079] Optionally, the PECVD temperature is 430℃~470℃.

[0080] Furthermore, in the PECVD method, the pressure is 0.2~0.4 standard atmospheres, the power is 8000 W~20000 W, and the duty cycle is 20:500~1200; in the LPCVD method, the pressure is 0.1~0.3 standard atmospheres.

[0081] Step S20: Boron doping is performed on the intrinsic polycrystalline silicon film layer, the transition silicon film layer, and the microcrystalline silicon film layer to form a boron-doped intrinsic polycrystalline silicon film layer, a boron-doped transition silicon film layer, and a boron-doped microcrystalline silicon film layer, respectively.

[0082] The intrinsic polycrystalline silicon film, transition silicon film, and microcrystalline silicon film obtained in step S10 have high quality and density, which makes the boron-doped intrinsic polycrystalline silicon film, boron-doped transition silicon film, and boron-doped microcrystalline silicon film obtained by further boron doping have high quality and density. They also have fewer impurity elements that can penetrate the structure and tunnel through the oxide layer, thereby effectively improving the passivation effect of the passivation contact structure.

[0083] It is understandable that in step S20, boron doping can be performed simultaneously after the intrinsic polycrystalline silicon film, transition silicon film, and microcrystalline silicon film are formed sequentially on the surface of the tunnel oxide layer, or boron doping can be performed once after the intrinsic polycrystalline silicon film is formed, a second boron doping can be performed after the transition silicon film is formed, and a third boron doping can be performed after the microcrystalline silicon film is formed; the latter process will take longer.

[0084] In some of these examples, in step S20, the boron doping temperature is 840°C to 990°C, and the flow rate of the boron source is 100 sccm to 400 sccm.

[0085] Furthermore, in the boron doping step, the temperature for depositing boron is 800℃~880℃, preferably 840℃~860℃; the boron propagation temperature is 900℃~990℃, preferably 930℃~970℃.

[0086] Furthermore, the flow rate of the boron source is 150 sccm to 300 sccm.

[0087] One embodiment of this application provides a passivated contact structure, which is prepared using the above-described method.

[0088] One embodiment of this application provides a passivated contact structure, comprising a tunneling oxide layer, a boron-doped intrinsic polycrystalline silicon film layer, a boron-doped transition silicon film layer, and a boron-doped microcrystalline silicon film layer arranged sequentially.

[0089] In some examples, the thickness of the boron-doped intrinsic polycrystalline silicon film in the passivated contact structure is 20 nm to 100 nm. Optionally, the thickness of the boron-doped intrinsic polycrystalline silicon film is 20 nm to 50 nm.

[0090] In some examples, the thickness of the boron-doped transition silicon film in the passivated contact structure is 50 nm to 200 nm. Alternatively, the thickness of the boron-doped transition silicon film is 50 nm to 150 nm.

[0091] In some examples, the thickness of the boron-doped microcrystalline silicon film in the passivated contact structure is 50 nm to 200 nm. Alternatively, the thickness of the boron-doped microcrystalline silicon film is 50 nm to 100 nm.

[0092] The passivation effect of the passivated contact structure provided in this application is good.

[0093] One embodiment of this application provides the application of the above-described passivated contact structure in the fabrication of solar cells.

[0094] It is understood that the above-mentioned passivated contact structure can be applied to solar cells including but not limited to TBC cells and TOPCon cells.

[0095] Another embodiment of this application provides a solar cell, including a silicon wafer, the above-mentioned passivation contact structure, and an electrode arranged sequentially, wherein the tunneling oxide layer in the passivation contact structure is disposed between the back surface of the silicon wafer and the boron-doped intrinsic polycrystalline silicon film.

[0096] The solar cell provided in this application includes the aforementioned passivated contact structure, giving the solar cell the same advantages as the aforementioned passivated contact structure, namely, fewer impurity elements can penetrate the structure and tunnel through the oxide layer to reach the substrate, thereby effectively improving the passivation effect and photoelectric conversion efficiency of the solar cell.

[0097] In some examples, the solar cell further includes an AlOx film and a SiNx film, with the AlOx film disposed on the front surface of the silicon wafer and the boron-doped microcrystalline silicon film on the surface away from the boron-doped transition silicon film, and the SiNx film disposed on the surface of the AlOx film away from the silicon wafer.

[0098] It can be understood that the solar cell at this time includes a SiNx film layer, an AlOx film layer, a silicon wafer, a tunnel oxide layer, a boron-doped intrinsic polycrystalline silicon film layer, a boron-doped transition silicon film layer, a boron-doped microcrystalline silicon film layer, an AlOx film layer, a SiNx film layer, and an electrode arranged sequentially.

[0099] It is understood that this application does not limit the types of SiNx films, AlOx films, and electrodes; any material applicable to solar cells in this field is acceptable. Furthermore, it is understood that the solar cell provided in this application may also include functional layers, passivation layers, activation layers, etc., that are applicable to solar cells in this field.

[0100] One embodiment of this application provides a method for preparing a solar cell, comprising the following steps:

[0101] A tunneling oxide layer is prepared on the back side of the silicon wafer;

[0102] Using H2 and SiH4 as reactant gases, a first deposition process, a second deposition process, and a third deposition process are sequentially performed on the surface of the tunneling oxide layer away from the silicon wafer to sequentially form an intrinsic polycrystalline silicon film, a transition silicon film, and a microcrystalline silicon film on the surface of the tunneling oxide layer. In the first deposition process, the volume ratio of H2 to SiH4 is 2~3:1, in the second deposition process it is 3.5~16:1, and in the third deposition process it is 17~40:1.

[0103] Boron doping was performed on the intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film to form boron-doped intrinsic polycrystalline silicon film, boron-doped transition silicon film, and boron-doped microcrystalline silicon film, respectively.

[0104] An electrode is fabricated on the surface of a boron-doped microcrystalline silicon film that is far from a boron-doped transition silicon film.

[0105] It is understood that the method for fabricating the solar cell provided in this application can be used to fabricate the aforementioned solar cell. Furthermore, it is understood that some features of the method for fabricating the solar cell provided in this application and the method for fabricating the passivated contact structure described above can be shared.

[0106] In some of these examples, the method of preparing the tunneling oxide layer in the fabrication of solar cells includes at least one of PECVD and LPCVD.

[0107] Similarly, compared to using LPCVD, using PECVD to deposit tunnel oxide layers can effectively increase the deposition rate, which is beneficial for large-scale industrial production.

[0108] In some examples, the method for fabricating solar cells includes, after the boron doping step, a step of sequentially depositing an AlOx film and a SiNx film on the positive surface of a silicon wafer and on the surface of a boron-doped microcrystalline silicon film away from the boron-doped transition silicon film.

[0109] In some examples, the method for fabricating solar cells includes an alkaline polishing step of the silicon wafer before the step of preparing a tunneling oxide layer on the back side of the silicon wafer.

[0110] It is understood that the method for preparing solar cells provided in this application may also include other steps conventionally used in the art to prepare other conventional films in the art.

[0111] One embodiment of this application provides a photovoltaic module, including the solar cell described above or the solar cell prepared by the above method.

[0112] It is understandable that photovoltaic (PV) modules can be used in PV power plants, such as ground-mounted, rooftop, and floating power plants, as well as in equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. It can also be understood that the application scenarios of PV modules are not limited to these; that is, PV modules can be used in all fields that require solar energy to generate electricity. Taking a PV power generation system grid as an example, a PV system can include PV arrays, combiner boxes, and inverters. A PV array can be a combination of multiple PV modules; for example, multiple PV modules can form multiple PV arrays. The PV arrays are connected to combiner boxes, which collect the current generated by the PV arrays. The collected current flows through an inverter and is converted into AC power required by the mains grid before being connected to the mains grid to achieve solar power supply.

[0113] The photovoltaic modules provided in this application can be used, but are not limited to, in electrical installations such as vehicles, ships, or aircraft. A power system comprising the photovoltaic modules provided in this application can be used to construct such an electrical installation.

[0114] This application provides an electrical device including the solar cell described above or the solar cell prepared by the above method.

[0115] Furthermore, the electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0116] The present application will be described in further detail below with reference to specific embodiments, but the embodiments of the present application are not limited thereto.

[0117] Example 1

[0118] (1) Perform alkaline polishing on the back side of the silicon wafer;

[0119] (2) A tunneling oxide layer was prepared on the back side of the alkaline polished silicon wafer by PECVD. The pressure was 0.2~0.35 standard atmospheres, the power was 9000 W~20000 W, the duty cycle was 20:700~20:400, the time was 80 s~140 s, and the temperature was 450℃~470℃.

[0120] (3) Using H2 and SiH4 as reactants, at 450°C, PECVD was performed at 0.3 standard atmospheres, with a power of 10000 W and a duty cycle of 20:800. The first, second, and third deposition processes were sequentially performed on the surface of the tunneling oxide layer away from the silicon wafer. Intrinsic polycrystalline silicon, transition silicon, and microcrystalline silicon films were sequentially formed on the surface of the tunneling oxide layer. In the first deposition process, the flow rate of H2 was 7000 sccm, the flow rate of SiH4 was 3500 sccm, the volume ratio of H2 to SiH4 was approximately 2:1, and the time was 240 s. In the second deposition process, the flow rate of H2 was 8000 sccm, the flow rate of SiH4 was 500 sccm, the volume ratio of H2 to SiH4 was 16:1, and the time was 2880 s. In the third deposition process, the flow rate of H2 was 8000 sccm, the flow rate of SiH4 was 200 sccm, and the flow rate of SiH4 was 200 sccm. The volume ratio of H2 to SiH4 was 40:1, and the time was 4800 s; the thickness of the intrinsic polycrystalline silicon film was 40 nm, the thickness of the transition silicon film was 120 nm, and the thickness of the microcrystalline silicon film was 80 nm.

[0121] (4) Boron doping is performed on the intrinsic polycrystalline silicon film, transition silicon film and microcrystalline silicon film in the silicon wafer. The boron deposition temperature is 850℃, the boron propulsion temperature is 950℃, and the flow rate of the boron source is 200 sccm. Boron doped intrinsic polycrystalline silicon film, boron doped transition silicon film and boron doped microcrystalline silicon film are formed respectively, and passivated contact structure products are obtained.

[0122] Example 2

[0123] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 7000 sccm, the flow rate of SiH4 is 3000 sccm, the volume ratio of H2 to SiH4 is about 2.3:1, and the time is 252 s; in the second deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 500 sccm, the volume ratio of H2 to SiH4 is 14:1, and the time is 2400 s; in the third deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 200 sccm, the volume ratio of H2 to SiH4 is 35:1, and the time is 3200 s; the thickness of the intrinsic polycrystalline silicon film is 40 nm, the thickness of the transition silicon film is 120 nm, and the thickness of the microcrystalline silicon film is 80 nm.

[0124] Example 3

[0125] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 8000 sccm, the flow rate of SiH4 is 3200 sccm, the volume ratio of H2 to SiH4 is about 2.5:1, and the time is 267 s; in the second deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 1400 sccm, the volume ratio of H2 to SiH4 is 5:1, and the time is 1200 s; in the third deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 280 sccm, the volume ratio of H2 to SiH4 is 25:1, and the time is 2660 s; the thickness of the intrinsic polycrystalline silicon film is 40 nm, the thickness of the transition silicon film is 120 nm, and the thickness of the microcrystalline silicon film is 80 nm.

[0126] Example 4

[0127] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 8000 sccm, the flow rate of SiH4 is 3000 sccm, the volume ratio of H2 to SiH4 is about 2.7:1, and the time is 273 s; in the second deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 2000 sccm, the volume ratio of H2 to SiH4 is 3.5:1, and the time is 960 s; in the third deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 400 sccm, the volume ratio of H2 to SiH4 is 17.5:1, and the time is 2180 s; the thickness of the intrinsic polycrystalline silicon film is 40 nm, the thickness of the transition silicon film is 120 nm, and the thickness of the microcrystalline silicon film is 80 nm.

[0128] Example 5

[0129] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 7500 sccm, the flow rate of SiH4 is 3400 sccm, the volume ratio of H2 to SiH4 in step (3) is about 2.2:1, and the time is 247 s; in the second deposition process, the flow rate of H2 is 7500 sccm, the flow rate of SiH4 is 750 sccm, the volume ratio of H2 to SiH4 is 10:1, and the time is 1800 s; in the third deposition process, the flow rate of H2 is 7500 sccm, the flow rate of SiH4 is 250 sccm, the volume ratio of H2 to SiH4 is 30:1, and the time is 2820 s; the thickness of the intrinsic polycrystalline silicon film is 40 nm, the thickness of the transition silicon film is 120 nm, and the thickness of the microcrystalline silicon film is 80 nm.

[0130] Example 6

[0131] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 7000 sccm, the flow rate of SiH4 is 3500 sccm, the volume ratio of H2 to SiH4 is about 2:1, and the time is 240 s; in the second deposition process, the flow rate of H2 is 8000 sccm, the flow rate of SiH4 is 500 sccm, the volume ratio of H2 to SiH4 in the second deposition process is 16:1, and the time is 2880 s; in the third deposition process, the flow rate of H2 is 8000 sccm, the flow rate of SiH4 is 200 sccm, the volume ratio of H2 to SiH4 is 40:1, and the time is 2400 s; the thickness of the intrinsic polycrystalline silicon film is 40 nm, the thickness of the transition silicon film is 120 nm, and the thickness of the microcrystalline silicon film is 40 nm.

[0132] Example 7

[0133] The process is basically the same as in Example 1, except that in step (3), SiH4 is used as the reaction gas, and at a temperature of 550°C, LPCVD is used to perform the first deposition process on the surface of the tunnel oxide layer away from the silicon wafer under a pressure of 0.2 standard atmospheres. The deposition rate is 1.5 nm / min, and the deposition time for an intrinsic polycrystalline silicon film with a thickness of 40 nm is 1600 s. The second and third deposition processes are the same as in Example 1, using PECVD.

[0134] The first deposition treatment uses LPCVD, while the second and third deposition treatments use PECVD. This involves the use of two types of instruments. Compared with Examples 1-6, which only use PECVD, Example 7 has a higher cost and lower deposition efficiency. This shows that using PECVD for the first deposition treatment can effectively improve the deposition efficiency while ensuring a good passivation effect on the passivated contact structure, which is beneficial for large-scale industrial production.

[0135] Comparative Example 1

[0136] The process is basically the same as in Example 1, except that step (3) is as follows: H2 and SiH4 are used as reaction gases. At a temperature of 450°C, PECVD is used to deposit the tunnel oxide layer on the surface of the silicon wafer away from the silicon wafer to form a transition silicon film layer on the surface of the tunnel oxide layer. The flow rate of H2 during the deposition process is 8000 sccm, the flow rate of SiH4 is 500 sccm, the volume ratio of H2 to SiH4 is 16:1, and the time is 7920 s.

[0137] Comparative Example 2

[0138] The process is basically the same as in Example 1, except that step (3) is as follows: SiH4 is used as the reaction gas with a flow rate of 1800 sccm~3500 sccm. At a temperature of 450°C, LPCVD is used at a deposition rate of 1 nm / min under a standard atmospheric pressure of 0.2 atmospheres. The deposition process is carried out on the surface of the tunneling oxide layer away from the silicon wafer, and an intrinsic polycrystalline silicon film layer of 240 nm is formed on the surface of the tunneling oxide layer. The process takes 14400 s.

[0139] Comparative Example 3

[0140] It is basically the same as Example 1, except that in step (3), the second deposition process is omitted, and the time of the first deposition process is extended to 3120 s.

[0141] Comparative Example 4

[0142] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the first deposition process is 7000 sccm, the flow rate of SiH4 is 700 sccm, and the volume ratio of H2 to SiH4 is about 10:1.

[0143] Comparative Example 5

[0144] The process is basically the same as in Example 1, except that in step (3), the flow rate of H2 in the second deposition process is 8000 sccm, the flow rate of SiH4 is 200 sccm, and the volume ratio of H2 to SiH4 in the second deposition process is 40:1; in the third deposition process, the flow rate of H2 is 7000 sccm, the flow rate of SiH4 is 70 sccm, and the volume ratio of H2 to SiH4 is 100:1.

[0145] Table 1 shows some parameters of the first, second, and third deposition treatments in each embodiment and comparative example.

[0146] Table 1

[0147]

[0148] In Table 1, “volume ratio” refers to the volume ratio of H2 to SiH4 in each deposition treatment.

[0149] PL photoluminescence was used to obtain the PL sensitivity value (exposure conditions: BT imaging time 0.5s, 1 Sun). The implicit open-circuit voltage (iVOC) was measured using a WCT120. The passivation effect was judged by the PL sensitivity value and iVOC. The higher the PL sensitivity value and iVOC, the better the passivation effect. The results are shown in Table 2.

[0150] Table 2

[0151]

[0152] In Table 2, the deposition efficiency of the first deposition process is equal to the thickness of the intrinsic polycrystalline silicon film and the time of the first deposition process.

[0153] Average deposition efficiency = (thickness of intrinsic polycrystalline silicon film + thickness of transition silicon film + thickness of microcrystalline silicon film) / (time of first deposition process + time of second deposition process + time of third deposition process).

[0154] As shown in Table 2, compared to the comparative examples, the passivated contact structure products prepared in each embodiment have higher PL photosensitivity and iVoc, indicating better passivation performance. In Comparative Example 1, the formation of a single transition silicon film layer has poor ability to block impurity penetration, leading to a significant reduction in passivation performance. In Comparative Example 2, the intrinsic polycrystalline silicon film layer deposited using the traditional LPCVD method resulted in a reduced passivation performance. In Comparative Example 3, no transition silicon film layer was deposited, but intrinsic polycrystalline silicon and microcrystalline silicon films were deposited; even with prolonged deposition time of the intrinsic polycrystalline silicon film layer, the passivation performance still decreased. Comparative Examples 4 and 5 show that the volume ratio of H2 to SiH4 in the first, second, and third deposition steps also has a significant impact on the passivation performance of the formed passivated contact structure; the volume ratio of H2 to SiH4 needs to be maintained within a suitable range.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a passivated contact structure, characterized in that, Includes the following steps: Using SiH4 as the reactant gas, or using H2 and SiH4 in a volume ratio of 2 to 3:1 as the reactant gas, a first deposition process is performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer. Using H2 and SiH4 as reactant gases, a second deposition process and a third deposition process are sequentially performed on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer to sequentially form a transition silicon film layer and a microcrystalline silicon film layer on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer; the volume ratio of H2 to SiH4 in the second deposition process is 3.5~16:1, and the volume ratio of H2 to SiH4 in the third deposition process is 17~40:1; The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film are boron-doped to form a boron-doped intrinsic polycrystalline silicon film, a boron-doped transition silicon film, and a boron-doped microcrystalline silicon film, respectively.

2. The preparation method according to claim 1, characterized in that, In the first deposition process, H2 and SiH4 with a volume ratio of 2 to 3:1 are used as reaction gases, with a flow rate of 7000 sccm to 8000 sccm for H2 and a flow rate of 3000 sccm to 3500 sccm for SiH4.

3. The preparation method according to claim 1, characterized in that, In the second deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 500 sccm ~ 2000 sccm.

4. The preparation method according to claim 1, characterized in that, In the third deposition process, the flow rate of H2 is 7000 sccm ~ 8000 sccm, and the flow rate of SiH4 is 200 sccm ~ 400 sccm.

5. The preparation method according to claim 1, characterized in that, The deposition method of the first deposition treatment includes at least one of PECVD and LPCVD, and the deposition method of the second and third deposition treatments is PECVD.

6. The preparation method according to claim 5, characterized in that, The temperature of the PECVD is 400℃~500℃, and the temperature of the LPCVD is 500℃~650℃.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method satisfies at least one of the following characteristics: (1) The time for the first deposition treatment is 120 s to 1600 s; (2) The second deposition treatment time is 600 s to 3200 s; (3) The time for the third deposition treatment is 2000 s to 18000 s.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The conditions for boron doping are as follows: the boron doping temperature is 840℃~990℃, and the flow rate of the boron source is 100 sccm~400 sccm.

9. A passivated contact structure, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The passivated contact structure as described in claim 9, characterized in that, The passivated contact structure includes a tunneling oxide layer, a boron-doped intrinsic polycrystalline silicon film, a boron-doped transition silicon film, and a boron-doped microcrystalline silicon film arranged sequentially.

11. The passivated contact structure as described in claim 10, characterized in that, The passivated contact structure satisfies at least one of the following characteristics: (1) The thickness of the boron-doped intrinsic polycrystalline silicon film is 20 nm to 100 nm; (2) The thickness of the boron-doped transition silicon film is 50 nm to 200 nm; (3) The thickness of the boron-doped microcrystalline silicon film is 50 nm to 200 nm.

12. A solar cell, characterized in that, The device includes a silicon wafer, a passivation contact structure as described in any one of claims 9 to 11, and an electrode arranged sequentially, wherein the tunneling oxide layer in the passivation contact structure is disposed between the back surface of the silicon wafer and the boron-doped intrinsic polycrystalline silicon film.

13. The solar cell according to claim 12, characterized in that, The solar cell further includes an AlOx film layer and a SiNx film layer. The AlOx film layer is disposed on the front surface of the silicon wafer and on the surface of the boron-doped microcrystalline silicon film layer away from the boron-doped transition silicon film layer. The SiNx film layer is disposed on the surface of the AlOx film layer away from the silicon wafer.

14. A method for preparing a solar cell, characterized in that, Includes the following steps: A tunneling oxide layer is prepared on the back side of the silicon wafer; Using SiH4 as the reactant gas, or using H2 and SiH4 in a volume ratio of 2 to 3:1 as the reactant gas, a first deposition process is performed on the surface of the tunneling oxide layer to form an intrinsic polycrystalline silicon film layer on the surface of the tunneling oxide layer. Using H2 and SiH4 as reactant gases, a second deposition process and a third deposition process are sequentially performed on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer to sequentially form a transition silicon film layer and a microcrystalline silicon film layer on the surface of the intrinsic polycrystalline silicon film layer away from the tunneling oxide layer; the volume ratio of H2 to SiH4 in the second deposition process is 3.5~16:1, and the volume ratio of H2 to SiH4 in the third deposition process is 17~40:1; The intrinsic polycrystalline silicon film, the transition silicon film, and the microcrystalline silicon film are boron-doped to form a boron-doped intrinsic polycrystalline silicon film, a boron-doped transition silicon film, and a boron-doped microcrystalline silicon film, respectively. An electrode is fabricated on the surface of the boron-doped microcrystalline silicon film layer away from the boron-doped transition silicon film layer.

15. An electrical appliance, characterized in that, This includes solar cells as described in claim 12 or 13, or solar cells prepared by the method described in claim 14.

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