Passivating film layer, preparation method thereof and solar cell

Abstract

The invention discloses a passive film layer, a preparation method thereof and a solar cell. The passivation film layer comprises a first doped polycrystalline silicon layer and a second doped polycrystalline silicon layer which are arranged in a stacked mode, and the first doped polycrystalline silicon layer comprises polycrystalline silicon, boron elements and carbon elements, wherein the boron elements and the carbon elements are doped in the polycrystalline silicon. And the second doped polycrystalline silicon layer comprises polycrystalline silicon, and a boron element, a carbon element and a hydrogen element which are doped in the polycrystalline silicon. The hydrogen passivation effect of the passivation film layer is more obvious, the passivation effect is better, and the battery efficiency is improved more obviously.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a passivation film layer, a preparation method thereof, and a solar cell. Background Art

[0002] In traditional photovoltaic technology, solar cells, such as BC cells (back-contact cells), utilize LPCVD (low-pressure chemical vapor deposition) to deposit a polycrystalline silicon layer and perform in-situ doping during fabrication. Traditional techniques typically use diborane, BCl₃, or borane as boron doping gas sources. Borane is highly reactive, making its use as a reaction source uncontrollable. BCl₃ contains Cl₃ ions, which can damage silicon wafers and easily react with metals, shortening the lifespan of furnace tubes and carriers. Furthermore, the passivation effects of these three boron doping gas sources are suboptimal, making them difficult to meet growing quality demands. Summary of the Invention

[0003] Based on this, it is necessary to provide a passivation film layer. The passivation film layer of the present invention has high passivation performance, thereby effectively improving the efficiency of solar cells.

[0004] One embodiment of the present application provides a passivation film layer.

[0005] A passivation film layer comprises a first doped polysilicon layer and a second doped polysilicon layer which are stacked, wherein the first doped polysilicon layer comprises boron-doped polysilicon and boron and carbon elements doped in the boron-doped polysilicon, and the second doped polysilicon layer comprises boron-doped polysilicon and boron, carbon and hydrogen elements doped in the boron-doped polysilicon.

[0006] In some embodiments, the hydrogen content in the second doped polysilicon layer gradually increases from close to the first doped polysilicon layer to away from the first doped polysilicon layer.

[0007] In some embodiments, in the second doped polysilicon layer, a ratio of carbon content to hydrogen content is 1:1 to 1:4.

[0008] One embodiment of the present application provides a method for preparing a passivation film layer.

[0009] A method for preparing a passivation film layer comprises the following steps:

[0010] Performing a first chemical vapor deposition on the silicon wafer, wherein the gas source of the first chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and hydrogen elements at a first flow rate;

[0011] Vacuum treatment;

[0012] Performing a second chemical vapor deposition on the silicon wafer, wherein the gas source of the second chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and hydrogen elements at a second flow rate;

[0013] Vacuum treatment;

[0014] And, the silicon wafer is subjected to a third chemical vapor deposition, and the gas source of the third chemical vapor deposition includes SiH4 and a third flow rate of an organic boron doping gas source containing carbon and hydrogen elements; wherein the first flow rate, the second flow rate and the third flow rate increase in sequence.

[0015] In some embodiments, the difference between the flow rates of two adjacent depositions using the organic boron doping gas source containing carbon and hydrogen is greater than 0, and the ratio of the flow rates of the two adjacent depositions is 1:1.05 to 1:25.

[0016] In some embodiments, the first flow rate is controlled to be 40 sccm-400 sccm.

[0017] In some embodiments, the second flow rate is controlled to be 400 sccm-1000 sccm.

[0018] In some embodiments, the third flow rate is controlled to be 1000 sccm-1500 sccm.

[0019] In some embodiments, the organic boron doping gas source containing carbon and hydrogen elements includes trimethylboron and / or triethylboron.

[0020] In some embodiments, the deposition time in the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition is controlled to be 1 min to 20 min respectively.

[0021] In some embodiments, at least one of the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition meets the following conditions when SiH4 is introduced: temperature of 400°C~800°C, pressure of 25Pa~50Pa, and SiH4 flow rate controlled to be 30sccm~2000sccm.

[0022] In some embodiments, the method for preparing the passivation film layer further comprises the following steps:

[0023] After the third chemical vapor deposition, the chamber is first vacuumed and then purged with an inert gas.

[0024] In some embodiments, the inert gas comprises nitrogen.

[0025] In some embodiments, the time for purge with inert gas is controlled to be 2 min to 5 min.

[0026] In some embodiments, the method for preparing the passivation film layer further comprises the following steps:

[0027] The silicon wafer obtained by the third vapor deposition process is subjected to a cooling process, and the temperature during cooling is controlled to be 400° C. to 600° C.

[0028] In some embodiments, the method for preparing the passivation film layer further comprises the following steps:

[0029] The silicon wafer purged with the inert gas is subjected to thermal annealing treatment. During the thermal annealing treatment, the temperature is controlled at 850°C to 1000°C, the flow rate of nitrogen is controlled at 1000sccm to 10000sccm, the flow rate of oxygen is controlled at 1000sccm to 10000sccm, and the time is controlled at 10min to 40min.

[0030] An embodiment of the present application also provides a solar cell.

[0031] A solar cell comprises a passivation film layer prepared by the preparation method in any of the above embodiments, or comprises the passivation film layer in any of the above embodiments.

[0032] The doped polysilicon layer grown by the above passivation film preparation method can effectively improve the passivation performance of the film layer, thereby improving the efficiency of the cell. The passivation performance of the film layer containing C is significantly improved, which has a significant impact on the improvement of cell efficiency. During the deposition process, when the doping concentration of the doping gas source is gradually increased, the doped polysilicon layer (Si x C y Poly-Si z ) is grown simultaneously with the new doped polysilicon layer (Si x C y Poly-Si z :H), the new doped polysilicon layer contains boron, carbon and hydrogen, including H-rich Si x C y Poly-Si z The passivation film layer of the H film has a more obvious hydrogen passivation effect, a better passivation effect, and a more significant improvement in battery efficiency. In this application, the passivation film layer formed by in-situ doping of the doping gas source has a better passivation effect and a more significant improvement in efficiency, meeting the growing quality requirements.

[0033] This application utilizes LPCVD in-situ doping to form a passivation film. Specifically, the passivation film is formed by a step-by-step coating process. The boron doping source gas, including TMB and / or TEB, is introduced. As the concentration of the doping source gas gradually increases, a high-low concentration difference is formed between the previous and next steps, effectively improving doping uniformity. The varying doping levels in the first, second, and third chemical vapor deposition stages of this preparation method ensure uniform doping, achieving uniform doping of boron, carbon, and hydrogen. Low doping concentrations are used in the bottom layer near the silicon substrate to effectively reduce recombination, while high doping concentrations are used in the surface layer away from the silicon substrate to effectively form a good contact. The resulting P-POLY layer (boron-doped polysilicon layer) has advantages in improving efficiency in solar cells, such as back-contact cells. After high-temperature annealing, the sheet resistance uniformity is superior to that of traditional boron diffusion processes.

[0034] This application uses high-temperature thermal annealing treatment to redistribute impurities to form effective doping, and the annealing temperature is controlled at 850°C~1000°C, which is lower than traditional boron diffusion (>1050°C). The thermal annealing treatment time is 10min~40min, which is shorter than the traditional boron diffusion annealing process time, which can effectively reduce process costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0036] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0037] Figure 1 This is a schematic flow chart of a method for preparing a passivation film according to an embodiment of the present invention;

[0038] Figure 2 This is a schematic flow chart of a method for preparing a passivation film according to another embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the solar cell structure according to one embodiment of the present invention;

[0040] Figure 4 This is the XPS graph of the film in this application.

[0041] Description of Reference Numerals

[0042] 10. Solar cell structure; 100. N-type silicon substrate; 101. First groove; 200. Tunnel oxide layer; 301. N-type doped polysilicon layer; 302. P-type doped polysilicon layer; 400. Passivation film layer; 501. First electrode; 502. Second electrode. DETAILED DESCRIPTION

[0043] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0044] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0045] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0046] As used herein, "optionally," "optional," and "optional" mean optional, meaning that the option is selected from either of the two parallel options of "with" or "without." If multiple "optional" options appear in a technical solution, each option is independent unless otherwise specified and there are no contradictions or mutual constraints. In this application, expressions such as "optionally contain" and "optionally include" mean "contain or not contain."

[0047] In this document, the terms "light-receiving surface or front side" and "backlight surface or back side" are used solely to distinguish the locations of two opposing surfaces of a cell substrate. In actual operation, the "light-receiving surface" is the surface of the cell substrate that primarily receives light, but the "backlight surface" does not necessarily exclude light. In fact, due to diffuse reflections and other factors, the "backlight surface" can also receive light in actual operation.

[0048] In this article, unless otherwise indicated, each reaction step may be carried out in the order in which it is presented, or may be carried out out of the order in which it is presented. For example, other steps may be included between each reaction step, and the order of the reaction steps may be appropriately reversed. This is something that can be determined by a skilled person based on conventional knowledge and experience. Preferably, the reaction methods described herein are carried out sequentially.

[0049] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is deemed to be continuous and includes the two numerical endpoints of the numerical interval (i.e., the minimum and maximum values), as well as each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe a feature or characteristic, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. "Numerical interval" is broadly allowed to include quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] The present invention provides a passivation film layer and a preparation method thereof to solve at least one of the following problems with conventional technologies using diborane, BCl3, and borane as a boron doping gas source: (1) Borane is uncontrollable when used as a reaction source; (2) BCl3 contains Cl ions, which can cause damage to silicon wafers; (3) Cl ions easily react with metals, shortening the service life of furnace tubes and carriers; and (4) the passivation effects of using diborane, BCl3, and borane as a boron doping gas source are unsatisfactory, making it difficult to meet the growing quality requirements. The passivation film preparation method will be described below with reference to the accompanying drawings.

[0052] An embodiment of the present application provides a passivation film layer.

[0053] A passivation film layer is prepared using the passivation film layer preparation method of any of the above embodiments, wherein the passivation film layer includes a first doped polysilicon layer and a second doped polysilicon layer stacked together, the first doped polysilicon layer includes polysilicon and boron and carbon elements doped in the polysilicon, and the second doped polysilicon layer includes polysilicon and boron, carbon and hydrogen elements doped in the polysilicon.

[0054] When preparing a solar cell, the first doped polysilicon layer of the passivation film layer is arranged close to the silicon substrate, and the second doped polysilicon layer is arranged away from the silicon substrate.

[0055] The passivation film preparation method provided in the embodiment of the present application is exemplary, please refer to Figure 1 As shown, Figure 1 Schematic diagram of the process for preparing a passivation film layer according to an embodiment of the present application. The passivation film layer preparation method of the present application can be used to prepare a passivation film layer of a solar cell, and further to prepare a solar cell such as a back contact cell.

[0056] In order to more clearly illustrate the structure of the passivation film preparation method, the passivation film preparation method will be introduced below with reference to the accompanying drawings.

[0057] For example, see Figure 1 As shown, a method for preparing a passivation film layer includes the following steps:

[0058] S10. Performing a first chemical vapor deposition on the silicon wafer, where a gas source of the first chemical vapor deposition includes SiH 4 and an organic boron doping gas source containing carbon and hydrogen elements at a first flow rate.

[0059] S20, vacuum treatment.

[0060] S30, performing a second chemical vapor deposition on the silicon wafer, wherein the gas source of the second chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and hydrogen elements at a second flow rate.

[0061] S40, vacuum treatment.

[0062] S50. Perform a third chemical vapor deposition on the silicon wafer, where the gas source of the third chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and hydrogen elements at a third flow rate; wherein the first flow rate, the second flow rate and the third flow rate increase in sequence.

[0063] This application utilizes LPCVD in-situ doping to form a passivation film. Specifically, the passivation film is formed by a step-by-step coating process. The boron doping source gas, including TMB and / or TEB, is introduced. As the concentration of the doping source gas gradually increases, a high-low concentration difference is formed between the previous and next steps, effectively improving doping uniformity. The varying doping levels in the first, second, and third chemical vapor deposition stages of this preparation method ensure uniform doping, achieving uniform doping of boron, carbon, and hydrogen. Low doping concentrations are used in the bottom layer near the silicon substrate to effectively reduce recombination, while high doping concentrations are used in the surface layer away from the silicon substrate to effectively form a good contact. The resulting P-POLY layer (boron-doped polysilicon layer) has advantages in improving efficiency in solar cells, such as back-contact cells. After high-temperature annealing, the sheet resistance uniformity is superior to that of traditional boron diffusion processes.

[0064] In some embodiments, step S10 specifically includes the following steps: placing a quartz boat containing silicon wafers into a coated quartz tube, evacuating the coated quartz tube, and then introducing SiH4 into the furnace tube of the coated quartz tube; then introducing a first flow rate of an organic boron doping gas source containing carbon and hydrogen elements, and depositing for a predetermined time.

[0065] In some embodiments, steps S20 and S30 specifically include the following steps: evacuating the coated quartz tube; introducing SiH4 into the furnace tube; and then introducing a second flow rate of an organic boron doping gas source containing carbon and hydrogen elements, and depositing for a predetermined time.

[0066] In some embodiments, steps S40 and S50 specifically include the following steps: evacuating the coated quartz tube; introducing SiH4 into the furnace tube; and then introducing a third flow rate of an organic boron doping gas source containing carbon and hydrogen elements, and depositing for a predetermined time.

[0067] In some embodiments, the difference between the first flow rate and the second flow rate is greater than 0, and the ratio of the first flow rate to the second flow rate is 1:1.05 to 1:25.

[0068] In some embodiments, the difference between the second flow rate and the third flow rate is greater than 0, and the ratio of the first flow rate to the second flow rate is 1:1.05 to 1:3.75.

[0069] In some embodiments, the first flow rate is controlled to be between 40 sccm and 400 sccm. Alternatively, the first flow rate is controlled to be between 80 sccm and 300 sccm. Further, optionally, the first flow rate is controlled to be between 100 sccm and 200 sccm. For example, the value of the first flow rate includes, but is not limited to, 40 sccm, 80 sccm, 100 sccm, 150 sccm, 180 sccm, 200 sccm, 240 sccm, 260 sccm, 300 sccm, 330 sccm, 350 sccm, 370 sccm, 390 sccm, 400 sccm, or a range between any two of the foregoing.

[0070] In some embodiments, the second flow rate is controlled to be between 400 sccm and 1000 sccm. Alternatively, the second flow rate is controlled to be between 600 sccm and 800 sccm. For example, the second flow rate may include, but is not limited to, 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, 800 sccm, 850 sccm, 900 sccm, 950 sccm, 1000 sccm, or a range between any two of the foregoing.

[0071] In some embodiments, the third flow rate is controlled to be between 1000 sccm and 1500 sccm. Alternatively, the third flow rate is controlled to be between 1200 sccm and 1400 sccm. For example, the third flow rate may be set to, but is not limited to, 1000 sccm, 1050 sccm, 1100 sccm, 1150 sccm, 1200 sccm, 1250 sccm, 1300 sccm, 1350 sccm, 1400 sccm, 1450 sccm, 1500 sccm, or a range between any two of the foregoing.

[0072] In some embodiments, the organic boron doping gas source containing carbon and hydrogen elements includes trimethylboron (TMB) and / or triethylboron (TEB). TMB and TEB are liquid at room temperature, highly volatile, and easily vaporized, making them convenient for use in vapor deposition processes. Both TMB and TEB compounds can decompose at relatively low temperatures, making them suitable for low-temperature processes and reducing thermal damage to the substrate. TMB and TEB can effectively provide boron atoms, achieve high-concentration doping, and improve the electrical properties of semiconductor materials. The present application can precisely control the doping level to meet different process requirements by adjusting the flow rate and concentration of TMB and TEB. TMB and TEB have relatively stable chemical properties and low operating risks, making them suitable for industrial applications. They are compatible with a variety of semiconductor processes, produce fewer by-products during decomposition, reduce contamination of equipment and films, and are applicable to a variety of technologies such as CVD.

[0073] In some embodiments, when the organic boron doping gas source containing carbon and hydrogen includes trimethylboron (TMB) and triethylboron (TEB), the volume ratio between trimethylboron (TMB) and triethylboron (TEB) is 0.1:1 to 10:1.

[0074] In some embodiments, the deposition time of the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition is controlled to be 1 min to 20 min. For example, the deposition time includes, but is not limited to, 1 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, or a range between any two of the foregoing.

[0075] In some embodiments, at least one of the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition meets the following conditions when SiH4 is introduced: a temperature of 400°C to 800°C, a pressure of 25Pa to 50Pa, and a SiH4 flow rate controlled to be 30sccm to 2000sccm. Optionally, the process parameters when SiH4 is introduced into the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition are the same. For example, when SiH4 is introduced into the furnace tube of the coated quartz tube, the temperature value includes but is not limited to: 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, or a range between any two of the foregoing. When SiH4 is introduced into the furnace tube of the coated quartz tube, the pressure value includes but is not limited to: 25Pa, 30Pa, 35Pa, 40Pa, 45Pa, 50Pa, or a range between any two of the foregoing. When SiH4 is introduced into the furnace tube of the coated quartz tube, the flow rate includes but is not limited to: 30sccm, 100sccm, 300sccm, 500sccm, 800sccm, 1000sccm, 1500sccm, 2000sccm, 2500sccm, 2800sccm, 3000sccm or a range between any two of the foregoing.

[0076] In some embodiments, see Figure 2 As shown, Figure 2 2 is a flow chart of a method for preparing a passivation film according to another embodiment of the present invention, wherein the method for preparing a passivation film further comprises the following steps:

[0077] S60: After the third chemical vapor deposition, first evacuate the chamber and then introduce an inert gas for purging.

[0078] In some embodiments, step S60 specifically includes the following steps: evacuating the coated quartz tube; and introducing an inert gas into the furnace tube for purging.

[0079] In some embodiments, the inert gas comprises nitrogen.

[0080] In some embodiments, the time for the inert gas purge is controlled to be 2 minutes to 5 minutes. For example, the time for the inert gas purge includes but is not limited to: 2 minutes, 3 minutes, 4 minutes, 5 minutes, or a range between any two of the foregoing.

[0081] In some embodiments, see Figure 2 As shown, the passivation film preparation method further includes the following steps:

[0082] S70, subjecting the silicon wafer obtained by the third vapor deposition process to a cooling process.

[0083] In some embodiments, step S70 specifically includes the following steps: after introducing an inert gas into the furnace tube for purging, the silicon wafer obtained by the third vapor deposition process is cooled.

[0084] In some embodiments, the temperature during cooling is controlled to be 400° C. to 600° C. For example, the temperature during cooling includes but is not limited to: 400° C., 450° C., 500° C., 550° C., 600° C., or a range between any two of the foregoing.

[0085] In some embodiments, the back-pressure charging includes charging nitrogen into the furnace tube and controlling the furnace tube to normal pressure.

[0086] In some embodiments, see Figure 2 As shown, the passivation film preparation method further includes the following steps:

[0087] S80, performing thermal annealing on the silicon wafer obtained by the third vapor deposition process to obtain a passivation film layer.

[0088] In some of the embodiments, step S80 specifically includes the following steps: after the coated quartz tube is cooled, a thermal annealing treatment is performed on the silicon wafer obtained by the third vapor deposition treatment.

[0089] In some embodiments, during the thermal annealing process, the thermal annealing temperature is controlled to be 850°C to 1000°C, the flow rate of the nitrogen gas is controlled to be 1000 sccm to 10,000 sccm, the flow rate of the oxygen gas is controlled to be 1000 sccm to 10,000 sccm, and the thermal annealing time is 10 minutes to 40 minutes. For example, during the thermal annealing process, the thermal annealing temperature includes but is not limited to: 850°C, 900°C, 950°C, 1000°C, or a range between any two of the foregoing. The flow rate of nitrogen gas includes but is not limited to: 1000sccm, 1500sccm, 2000sccm, 2500sccm, 3000sccm, 3500sccm, 4000sccm, 4500sccm, 5000sccm, 5500sccm, 6000sccm, 6500sccm, 7000sccm, 7500sccm, 8000sccm, 8500sccm, 9000sccm, 9500sccm, 10000sccm or the range between any two of the foregoing. The oxygen flow rate includes, but is not limited to, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, 5000 sccm, 5500 sccm, 6000 sccm, 6500 sccm, 7000 sccm, 7500 sccm, 8000 sccm, 8500 sccm, 9000 sccm, 9500 sccm, 10000 sccm, or a range therebetween. The thermal annealing treatment time includes, but is not limited to, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, or a range therebetween.

[0090] This application uses thermal annealing treatment to redistribute impurities to form effective doping, and the annealing temperature is controlled at 850°C~1000°C, which is lower than traditional boron diffusion (>1050°C). The thermal annealing treatment time is 10min~40min, which is shorter than the traditional boron diffusion annealing process time, which can effectively reduce process costs.

[0091] An embodiment of the present application also provides a solar cell.

[0092] A solar cell comprises a passivation film layer prepared by the preparation method in any one of the above embodiments, or comprises a passivation film layer in any one of the above embodiments.

[0093] For example, see Figure 3 As shown, Figure 3This is a schematic diagram of the solar cell structure according to an embodiment of the present invention, a back-contact solar cell, which includes an N-type silicon substrate 100, a tunnel oxide layer 200, an N-type doped polysilicon layer 301, a P-type doped polysilicon layer 302, a passivation film layer 400, a first electrode 501, and a second electrode 502. The backlight surface of the N-type silicon substrate 100 has a first groove 101. The backlight surface of the N-type silicon substrate 100 is sequentially deposited with a tunnel oxide layer 200, an N-type doped polysilicon layer 301, a P-type doped polysilicon layer 302, and a passivation film layer 400, wherein the first electrode 501 is set at a position corresponding to the N-type doped polysilicon layer 301, and the second electrode 502 is set at a position corresponding to the P-type doped polysilicon layer 302. The passivation film layer 400 contains a first doped polysilicon layer and a second doped polysilicon layer, wherein the first doped polysilicon layer Si x C y Poly-Si z The second doped polysilicon layer Si comprises polysilicon and boron and carbon elements doped in the polysilicon. x C y Poly-Si z :H includes polysilicon and boron, carbon and hydrogen elements doped in the polysilicon.

[0094] Example 1

[0095] This embodiment provides a passivation film layer.

[0096] The passivation film layer of this embodiment is prepared by the following preparation method.

[0097] A method for preparing a passivation film layer comprises the following steps:

[0098] S110. Place the quartz boat containing the silicon wafer into the coated quartz tube. At a temperature of 400°C and a pressure of 25 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 30 sccm. Also introduce 40 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB). Deposition proceeds for 1 minute. Vacuum treatment is performed after deposition.

[0099] S210: Evacuate the coated quartz tube. At a temperature of 400°C and a pressure of 25 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 30 sccm. Also introduce 400 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB), for deposition for 1 minute. Evacuate the tube after deposition.

[0100] S310, evacuate the coated quartz tube; at a temperature of 600°C and a pressure of 25Pa, introduce SiH4 into the furnace tube of the coated quartz tube, and control the flow rate of SiH4 to be 30sccm; simultaneously introduce 1000sccm of an organic boron doping gas source containing carbon and hydrogen elements, and the organic boron doping gas source containing carbon and hydrogen elements is trimethylboron (TMB), and deposit for 1 minute.

[0101] S410, evacuate the coated quartz tube; introduce nitrogen into the coated quartz tube for 2 minutes.

[0102] S510, cooling the coated quartz tube to 500° C. and then inflating and back-pressuring the tube, and taking out the quartz boat containing the silicon wafer from the coated quartz tube.

[0103] S610, placing the quartz boat containing the silicon wafer into an annealing furnace tube, and performing thermal annealing on the silicon wafer obtained by the third vapor deposition process, controlling the thermal annealing temperature to 850° C., introducing 1000 sccm of nitrogen and 1000 sccm of oxygen, and the thermal annealing time to 10 minutes.

[0104] The passivation film layer prepared by the preparation method of Example 1 was tested Sinton, and the iVoc was improved compared with the LPCVD+boron diffusion (BCl3) in the traditional technology, and the iVoc improvement was more obvious with the increase of the doping gas source concentration; the iVoc of the film layer obtained by the LPCVD+boron diffusion (BCl3) process in the traditional technology was basically around 700mV, and the iVoc of the passivation film layer prepared by the preparation method of Example 1 of the present application can reach 710mv~715mv, and the iVoc can reach more than 720mv after the doping gas source concentration is increased. The iVoc improvement phenomenon was analyzed and tested. After testing and analysis, it was found that the passivation film layer in the present application contained carbon and hydrogen elements, and the carbon and hydrogen elements contained in the doping gas sources TMB and TEB were simultaneously doped into the polysilicon layer during the doping process to form a new type of passivation film layer, that is, a doped polysilicon layer (Si x C y Poly-Si z ) and polysilicon layer doped with boron, carbon and hydrogen (Si x C y Poly-Si z :H). TMB and TEB contain a large amount of carbon and hydrogen elements. When boron is doped in situ, carbon and hydrogen elements will also be doped simultaneously, thus forming a film structure Si x C y Poly-Si z Studies have shown that the passivation performance of carbon-containing films is significantly improved, which significantly improves battery efficiency. When the concentration of the doping gas source is further increased, another new film structure Si will be formed.x C y Poly-Si z :H, including hydrogen-rich Si x C y Poly-Si z :The passivation film layer of the H film layer has a more obvious hydrogen passivation effect, the passivation effect is better, and the battery efficiency is more significantly improved. Therefore, the passivation performance of the new passivation film layer grown by in-situ doping based on TMB and TEB doping gas sources in this embodiment is better and the battery efficiency is more significantly improved.

[0105] Example 2

[0106] This embodiment provides a passivation film layer.

[0107] The passivation film layer of this embodiment is prepared by the following preparation method.

[0108] A method for preparing a passivation film layer comprises the following steps:

[0109] S110. Place the quartz boat containing the silicon wafer into the coated quartz tube. At a temperature of 800°C and a pressure of 50 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 2000 sccm. Also introduce 400 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB). Deposition proceeds for 20 minutes. Vacuum treatment is performed after deposition.

[0110] S210: Evacuate to bottom pressure. At 800°C and 50 Pa, introduce SiH4 into the furnace of the coated quartz tube at a controlled flow rate of 2000 sccm. Also introduce 1000 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB), for deposition for 20 minutes. Evacuate after deposition.

[0111] S310, evacuate the coated quartz tube; at a temperature of 800°C and a pressure of 50Pa, introduce SiH4 into the furnace tube of the coated quartz tube, and control the flow rate of SiH4 to be 2000sccm; simultaneously introduce 1500sccm of an organic boron doping gas source containing carbon and hydrogen elements, and the organic boron doping gas source containing carbon and hydrogen elements is trimethylboron (TMB), and deposit for 20 minutes.

[0112] S410, evacuate the coated quartz tube; and introduce nitrogen gas into the coated quartz tube for 5 minutes.

[0113] S510, cooling the coated quartz tube to 500° C. and then inflating and back-pressuring the tube, and taking out the quartz boat containing the silicon wafer from the coated quartz tube.

[0114] S610, placing the quartz boat containing the silicon wafer into an annealing furnace tube, and performing thermal annealing on the silicon wafer obtained by the third vapor deposition process, controlling the thermal annealing temperature to 1000° C., introducing 10,000 sccm of nitrogen and 10,000 sccm of oxygen, and the thermal annealing time to 40 minutes.

[0115] Example 3

[0116] This embodiment provides a passivation film layer.

[0117] The passivation film layer of this embodiment is prepared by the following preparation method.

[0118] A method for preparing a passivation film layer comprises the following steps:

[0119] S110. Place the quartz boat with the silicon wafer into the coated quartz tube. At a temperature of 600°C and a pressure of 40Pa, introduce SiH4 into the furnace tube of the coated quartz tube. The SiH4 flow rate is controlled to be 1000sccm. Also, introduce 200sccm of an organic boron doping gas source containing carbon and hydrogen elements. The organic boron doping gas source containing carbon and hydrogen elements is trimethylboron (TMB). Deposition is carried out for 10 minutes.

[0120] S210: Evacuate the coated quartz tube. At a temperature of 600°C and a pressure of 40 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 1000 sccm. Also introduce 800 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB), for deposition for 10 minutes. Evacuate the tube after deposition.

[0121] S310: Evacuate the coated quartz tube to bottom pressure. At 4600°C and 40 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 1000 sccm. Simultaneously, introduce 1300 sccm of an organic boron doping gas source containing carbon and hydrogen elements, using trimethylboron (TMB). Deposition proceeds for 10 minutes. Evacuate the tube after deposition.

[0122] S410, evacuating the coated quartz tube to bottom pressure; and introducing nitrogen gas into the coated quartz tube for 4 minutes.

[0123] S510, cooling the coated quartz tube to 500° C. and then inflating and back-pressuring the tube, and taking out the quartz boat containing the silicon wafer from the coated quartz tube.

[0124] S610, placing the quartz boat containing the silicon wafer into an annealing furnace tube, and performing thermal annealing on the silicon wafer obtained by the third vapor deposition process, controlling the thermal annealing temperature to 900° C., introducing 5000 sccm of nitrogen and 5000 sccm of oxygen, and the thermal annealing time to 20 minutes.

[0125] Example 4

[0126] This embodiment provides a passivation film layer.

[0127] The passivation film layer of this embodiment is prepared by the following preparation method.

[0128] A method for preparing a passivation film layer comprises the following steps:

[0129] S110. Place the quartz boat containing the silicon wafer into the coated quartz tube. At a temperature of 500°C and a pressure of 35 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 800 sccm. Also introduce 300 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB). Deposition proceeds for 10 minutes. Vacuum treatment is performed after deposition.

[0130] S210: Evacuate the coated quartz tube. At a temperature of 500°C and a pressure of 45 Pa, introduce SiH4 into the furnace tube of the coated quartz tube at a controlled flow rate of 1200 sccm. Also introduce 1000 sccm of an organic boron doping gas source containing carbon and hydrogen elements, trimethylboron (TMB), for deposition for 15 minutes. Evacuate the tube after deposition.

[0131] S310, evacuate the coated quartz tube; at a temperature of 500°C and a pressure of 35Pa, introduce SiH4 into the furnace tube of the coated quartz tube, with the SiH4 flow rate controlled at 1200sccm; simultaneously introduce 1400sccm of an organic boron doping gas source containing carbon and hydrogen elements, the organic boron doping gas source containing carbon and hydrogen elements being trimethylboron (TMB), and deposit for 10 minutes.

[0132] S410, evacuate the coated quartz tube; and introduce nitrogen gas into the coated quartz tube for 3 minutes.

[0133] S510, after cooling to 600°C, inflate and back-pressurize, and take out the quartz boat containing the silicon wafer from the coated quartz tube.

[0134] S610, placing the quartz boat containing the silicon wafer into an annealing furnace tube, and performing thermal annealing on the silicon wafer obtained by the third vapor deposition process, controlling the thermal annealing temperature to 950° C., introducing 8000 sccm of nitrogen and 8000 sccm of oxygen, and the thermal annealing time to 25 minutes.

[0135] Example 5

[0136] This embodiment provides a passivation film layer.

[0137] The passivation film layer of this embodiment is prepared by using a preparation method substantially the same as that of embodiment 1. In embodiment 5, the first flow rate is 150 sccm, the second flow rate is 700 sccm, and the third flow rate is 1300 sccm.

[0138] Comparative Example 1

[0139] This comparative example provides a passivation film layer.

[0140] The passivation film layer of this comparative example was prepared using a preparation method substantially the same as that of Example 1.

[0141] The difference is that in this comparative example, the doping gas source is BCl3.

[0142] Comparative Example 2

[0143] This comparative example provides a passivation film layer.

[0144] The passivation film layer of this comparative example was prepared using a preparation method substantially the same as that of Example 2.

[0145] The difference is that, in this comparative example, the first flow rate, the second flow rate, and the third flow rate are the same, which are all 1000 sccm.

[0146] Comparative Example 3

[0147] This comparative example provides a passivation film layer.

[0148] The passivation film layer of this comparative example was prepared using a preparation method substantially the same as that of Example 1.

[0149] The difference is that in this comparative example, the first flow rate, the second flow rate, and the third flow rate gradually decrease. Specifically, the first flow rate is 400 sccm, the second flow rate is 300 sccm, and the third flow rate is 200 sccm.

[0150] The performance tests of the passivation film layers of Example 2 and Comparative Example 1 were respectively carried out. The iVoc of the passivation film layer prepared in Example 2 can reach 705mV, and the iVoc of the passivation film layer prepared in Comparative Example 1 is 700mV. Compared with Comparative Example 1, the efficiency of the passivation film layer in Example 2 is improved by 0.1%.

[0151] Through the performance test parameters of Example 2 and Comparative Example 1, it can be seen that in the process of this application, when the doping concentration of the doping gas source is further increased, the doping of the polysilicon layer Si x C y Poly-Si z A new doped polysilicon layer Si will be grown simultaneously on the basis x C y Poly-Si z :H, the hydrogen passivation effect of the H-rich film is more obvious, the passivation effect is better, and the efficiency improvement is more obvious.

[0152] In summary, the doped polysilicon layer grown by the above passivation film preparation method can effectively improve the passivation performance of the film layer, thereby improving the efficiency of the cell. The passivation performance of the film layer containing C is significantly improved, which has a significant impact on the improvement of cell efficiency. During the deposition process, when the doping concentration of the doping gas source is gradually increased, the doped polysilicon layer (Si x C y Poly-Si z ) is grown simultaneously with the new doped polysilicon layer (Si x C y Poly-Si z :H), this new doped polysilicon layer contains boron, carbon, and hydrogen. The hydrogen-rich doped polysilicon layer has a more pronounced hydrogen passivation effect, a better passivation effect, and a more significant improvement in battery efficiency. In this application, the passivation film layer formed by in-situ doping of the doping gas source has a more excellent passivation effect, a more significant improvement in efficiency, and meets the growing quality requirements.

[0153] See also Figure 4 This is an XPS characterization diagram of the film formed by the conditions of Example 2. XPS (X-ray photoelectron spectroscopy) characterization is a commonly used material analysis technology, mainly used for qualitative analysis and semi-quantitative analysis. Generally, information such as the elemental composition, chemical state and molecular structure of the sample surface can be obtained from the peak position and peak shape of the XPS spectrum, and the element content or concentration of the sample surface can be obtained from the peak intensity. Figure 4 From the XPS characterization diagram, we can see that the film contains silicon, carbon and oxygen elements.

[0154] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0155] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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 above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A passivation film layer, characterized in that: The passivation film layer includes a first doped polysilicon layer and a second doped polysilicon layer arranged in a stacked manner, the first doped polysilicon layer includes polysilicon and boron and carbon elements doped in the polysilicon, and the second doped polysilicon layer includes polysilicon and boron, carbon and hydrogen elements doped in the polysilicon.

2. The passivation film according to claim 1, characterized in that: The hydrogen content in the second doped polysilicon layer gradually increases from close to the first doped polysilicon layer to away from the first doped polysilicon layer.

3. The passivation film according to claim 1, characterized in that: In the second doped polysilicon layer, a ratio of a content of the C element to a content of the hydrogen element is 1:1 to 1:

4.

4. A method for preparing a passivation film, characterized in that: The steps include: Performing a first chemical vapor deposition on the silicon wafer, wherein the gas source of the first chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and H elements at a first flow rate; Vacuum treatment; Performing a second chemical vapor deposition on the silicon wafer, wherein the gas source of the second chemical vapor deposition includes SiH4 and an organic boron doping gas source containing carbon and hydrogen elements at a second flow rate; Vacuum treatment; And, the silicon wafer is subjected to a third chemical vapor deposition, and the gas source of the third chemical vapor deposition includes SiH4 and a third flow rate of an organic boron doping gas source containing carbon and hydrogen elements; wherein the first flow rate, the second flow rate and the third flow rate increase in sequence.

5. The method for preparing a passivation film according to claim 4, wherein: The difference between the flow rates of two adjacent depositions using the organic boron doping gas source containing carbon and hydrogen elements is greater than 0, and the ratio of the flow rates of the two adjacent depositions is 1:1.05 to 1:

25.

6. The method for preparing a passivation film according to claim 5, wherein: The first flow rate is controlled to be 40 sccm-400 sccm.

7. The method for preparing a passivation film according to claim 5, wherein: The second flow rate is controlled to be 400 sccm~1000 sccm.

8. The method for preparing a passivation film according to claim 5, wherein: The third flow rate is controlled to be 1000 sccm~1500 sccm.

9. The method for preparing a passivation film according to any one of claims 4 to 8, wherein: The organic boron doping gas source containing carbon and hydrogen elements includes trimethyl boron and / or triethyl boron.

10. The method for preparing a passivation film according to any one of claims 4 to 8, characterized in that: The deposition time in the first chemical vapor deposition, the second chemical vapor deposition and the third chemical vapor deposition is controlled to be 1 min to 20 min respectively.

11. The method for preparing a passivation film according to any one of claims 4 to 8, characterized in that: At least one of the first chemical vapor deposition, the second chemical vapor deposition, and the third chemical vapor deposition meets the following conditions when SiH4 is introduced: temperature is 400°C~800°C, pressure is 25Pa~50Pa, and SiH4 flow rate is controlled to be 30sccm~2000sccm.

12. The method for preparing a passivation film according to any one of claims 4 to 8, characterized in that: The passivation film preparation method further comprises the following steps: After the third chemical vapor deposition, the chamber is first vacuumed and then purged with an inert gas; Optionally, the inert gas includes nitrogen, and / or the time for purge with the inert gas is controlled to be 2 min to 5 min.

13. The method for preparing a passivation film according to claim 12, wherein: The passivation film preparation method further comprises the following steps: The silicon wafer obtained by the third vapor deposition process is subjected to a cooling process, and the temperature during cooling is controlled to be 400° C. to 600° C.

14. The method for preparing a passivation film according to claim 13, wherein: The passivation film preparation method further comprises the following steps: The silicon wafer purged with the inert gas is subjected to thermal annealing treatment. During the thermal annealing treatment, the temperature is controlled at 850°C to 1000°C, the flow rate of nitrogen is controlled at 1000sccm to 10000sccm, the flow rate of oxygen is controlled at 1000sccm to 10000sccm, and the time is controlled at 10min to 40min.

15. A solar cell, characterized in that: The invention comprises the passivation film layer according to any one of claims 1 to 3, or the passivation film layer prepared by the preparation method according to any one of claims 4 to 14.

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