Solar cell and preparation method thereof

Abstract

The invention relates to a solar cell and a preparation method thereof. The preparation method of the solar cell comprises the following steps: carrying out double-sided texturing on the substrate; forming a boron-doped layer on the front surface of the substrate; wherein the front surface of the substrate comprises a first region and a second region, and the first region and the second region are arranged at an interval; polishing the back surface of the substrate; a tunneling oxide layer and an amorphous silicon layer are sequentially formed on the back face of the substrate, phosphorus doping is conducted on the back face of the substrate, and the amorphous silicon layer is converted into a polycrystalline silicon layer; forming an aluminum oxide layer on the front surface of the substrate; performing laser processing on the first region to form a boron-aluminum co-doped layer; forming passivation layers on the front surface and the back surface of the substrate respectively; and preparing a front electrode in the first region, wherein the front electrode is electrically connected with the boron-aluminum co-doped layer. The contact resistance of the emitter and the electrode can be further reduced, and the battery efficiency is further improved.

Description

Technical Field

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

[0002] Tunnel Oxide Passivated Contact solar cell (TOPCon) is a solar cell that uses an ultra-thin oxide layer as a passivation layer structure on the back of the cell. TOPCon has attracted widespread attention due to its many advantages such as high conversion efficiency, low attenuation and high stability.

[0003] In the TOPCon related process, the use of patterned emitters can reduce the contact resistance with the electrode and improve the battery efficiency. Therefore, how to further optimize the patterned emitter of TOPCon and its preparation process, further reduce the contact resistance between the emitter and the electrode, and thus further improve the battery efficiency is an urgent problem to be solved. Summary of the invention

[0004] Based on this, the embodiments of the present application provide a solar cell and a method for preparing the same, which can further reduce the contact resistance between the emitter and the electrode, thereby further improving the cell efficiency.

[0005] In order to achieve the above objectives, in a first aspect, some embodiments of the present application provide a method for preparing a solar cell, comprising the following steps:

[0006] Carry out double-sided texturing on the substrate;

[0007] A boron-doped layer is formed on the front surface of the substrate; wherein the front surface of the substrate includes a first region and a second region, and the first region and the second region are arranged at an interval;

[0008] polishing the back side of the substrate;

[0009] A tunneling oxide layer and an amorphous silicon layer are sequentially formed on the back side of the substrate, and phosphorus is doped on the back side of the substrate to convert the amorphous silicon layer into a polycrystalline silicon layer;

[0010] forming an aluminum oxide layer on the front surface of the substrate;

[0011] performing laser processing on the first region to form a boron-aluminum co-doped layer;

[0012] forming a passivation layer on the front side and the back side of the substrate respectively;

[0013] A front electrode is prepared in the first region, and the front electrode is electrically connected to the boron-aluminum co-doped layer.

[0014] In some embodiments of the present application, forming a boron-doped layer on the front side of the substrate includes: forming a boron-doped layer on the front side of the substrate using a high temperature diffusion process. The boron doping concentration is: 1×10 17 cm -3 ~1×10 18 cm -3 .

[0015] In some embodiments of the present application, the doping concentration of aluminum in the boron-aluminum co-doped layer is: 1×10 17 cm -3 ~1×10 18 cm -3 .

[0016] In some embodiments of the present application, laser processing is performed in the first region to form a boron-aluminum co-doped layer, which includes the following steps: using a laser process to push aluminum in the aluminum oxide layer into the first region to form a boron-aluminum co-doped layer.

[0017] In some embodiments of the present application, the wavelength of the laser is: 100nm-3000nm. The frequency of the laser is: 20khz-2Mhz. The scanning rate of the laser is: 1000mm / s-100000mm / s. The power of the laser is: 1W-300W.

[0018] In some embodiments of the present application, depositing an aluminum oxide layer on the front side of the substrate includes: depositing the aluminum oxide layer on the front side of the substrate using an atomic layer deposition process.

[0019] In some embodiments of the present application, the deposition temperature of the atomic layer deposition process is: 100° C.~450° C.; the deposition gas flow rate is: 5 sccm~50 sccm.

[0020] In some embodiments of the present application, the thickness of the aluminum oxide layer is 1 nm to 25 nm.

[0021] In some embodiments of the present application, the ratio of the doping depth of the boron doped layer to the doping depth of the boron aluminum co-doped layer is: 1:1~10:1; the doping depth of the boron doped layer is: 0.2µm~2µm. The doping depth of the boron aluminum co-doped layer is: 0.2µm~2µm.

[0022] In a second aspect, some embodiments of the present application further provide a solar cell, which is prepared using the method for preparing a solar cell as described in the aforementioned embodiments.

[0023] The solar cell and the method for preparing the same provided by the present application may have / at least have the following advantages:

[0024] In the embodiment of the present application, after the double-sided texturing of the substrate, a boron-doped layer is first formed on the front side of the substrate, and then an aluminum oxide layer is formed. The front side of the substrate includes a first region and a second region, and the first region and the second region are arranged at an interval. In this way, by laser processing the first region, the aluminum atoms in the aluminum oxide layer are pushed into the boron-doped layer by the laser, and form a boron-aluminum co-doped layer together with the existing boron atoms. In this way, the second region still retains the boron-doped layer, and the boron-aluminum co-doped layer in the first region can reduce the contact resistance with the electrode, that is, the patterned emitter provided in the embodiment of the present application can further reduce the contact resistance with the electrode, while reducing the recombination loss and increasing the opening voltage, so as to further improve the battery efficiency.

[0025] In addition, in the embodiment of the present application, a boron-doped layer is first formed on the front side of the substrate, instead of forming the boron-doped layer through three processes (pre-boron doping process, laser processing process and post-boron doping process) in the existing process, and then a process of laser processing the first area on the front side of the substrate is added to obtain a patterned emitter. In this way, compared with the existing process, the present application reduces the process steps for forming a patterned emitter, thereby simplifying the preparation process of the solar cell.

[0026] Furthermore, in the embodiments of the present application, by forming a boron-doped layer with a lower boron concentration, compared with the existing process, from the perspective of the battery structure, the passivation can be improved, the recombination can be reduced, and the battery efficiency can be further improved. From the perspective of process operation, the process time can be shortened, the required temperature can be reduced, the requirements for high temperature resistance of the equipment can be reduced, the service life can be increased, and the equipment cost can be saved. In addition, due to the formation of a boron-doped layer with a lower boron concentration, the present application also reduces the process temperature of the high-temperature diffusion process and shortens the diffusion time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic diagram of a process for preparing a solar cell provided in some embodiments of the present application;

[0029] Figure 2 A schematic flow chart of step S100 in a method for preparing a solar cell provided in some embodiments of the present application;

[0030] Figure 3 A schematic diagram of a cross-sectional structure of a structure obtained in step S200 in a method for preparing a solar cell provided in some embodiments of the present application;

[0031] Figure 4 A schematic diagram of a cross-sectional structure of a structure obtained in step S300 in a method for preparing a solar cell provided in some embodiments of the present application;

[0032] Figure 5 A schematic diagram of a cross-sectional structure of a structure obtained in step S400 in a method for preparing a solar cell provided in some embodiments of the present application;

[0033] Figure 6 A schematic diagram of a cross-sectional structure of a structure obtained after polishing the front side of a substrate in a method for preparing a solar cell provided in some embodiments of the present application;

[0034] Figure 7 A schematic cross-sectional view of a structure obtained in step S500 in a method for preparing a solar cell provided in some embodiments of the present application;

[0035] Figure 8 A schematic diagram of a cross-sectional structure of a structure obtained in step S600 in a method for preparing a solar cell provided in some embodiments of the present application;

[0036] Fig. 9 A schematic diagram of a cross-sectional structure of a structure obtained in step S700 in a method for preparing a solar cell provided in some embodiments of the present application;

[0037] Fig.10 A schematic cross-sectional view of a structure obtained in step S800 in a method for preparing a solar cell provided in some embodiments of the present application; and Fig.10 It is also a schematic diagram of a cross-sectional structure of a method for preparing a solar cell provided in some embodiments of the present application.

[0038] Description of reference numerals:

[0039] 10 - substrate; 20 - boron-doped layer; 30 - tunneling oxide layer; 40 - polysilicon layer; 50 - aluminum oxide layer; 60 - boron-aluminum co-doped layer; 70 - passivation layer; 81 - front electrode; 82 - back electrode. DETAILED DESCRIPTION

[0040] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] It should be understood that although the terms first and second can be used to describe various elements, components, regions, layers, collector structures and / or parts, these elements, components, regions, layers, collector structures and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, collector structure or part from another element, component, region, layer, collector structure or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, collector structure or part discussed below can be represented as a second element, component, region, layer or part; for example, the first collector structure can be referred to as the second collector structure, and similarly, the second collector structure can be referred to as the first collector structure; the first collector structure and the second collector structure are different collector structures. It should be understood that in addition to the orientation shown in the figure, the spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below other elements" or "below" or "below" will be oriented as "on" other elements or features. Thus, the exemplary terms "below" and "beneath" can encompass both an orientation of above and below. Furthermore, the device can be included in alternative orientations (eg, rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

[0043] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of the features, integers, steps, operations, elements and / or parts can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0044] Tunnel Oxide Passivated Contact solar cell (TOPCon) is a solar cell that uses an ultra-thin oxide layer as a passivation layer structure on the back of the cell. TOPCon has attracted widespread attention due to its many advantages such as high conversion efficiency, low attenuation and high stability.

[0045] In the TOPCon related process, the use of patterned emitters can reduce the contact resistance with the electrode and improve the efficiency of the battery. For example, the existing TOPCon technology uses a high-temperature diffusion process to diffuse boron on the positive surface of the n-type silicon wafer, and then uses a selective emitter (SE) laser to pattern the metal area of ​​the emitter. The thermal effect of the laser is used to melt the surface of the silicon wafer, and the boron atoms in the borosilicate glass covering the top of the emitter enter the surface of the silicon wafer. After solidification, the doped boron atoms replace the silicon atoms to form a heavily doped layer, which can reduce the contact resistance. However, this method requires three steps of "front boron + SE laser + back boron", which is a complex process. In addition, due to the high concentration of boron doping, the diffusion temperature is high and the time is long.

[0046] Therefore, how to further optimize the patterned emitter of TOPCon and its preparation process, further reduce the contact resistance between the emitter and the electrode, and thus further improve the battery efficiency is an urgent problem to be solved.

[0047] Based on this, the embodiments of the present application provide a solar cell and a method for preparing the same, which can further reduce the contact resistance between the emitter and the electrode, thereby further improving the cell efficiency.

[0048] See also Figure 1 , the present application provides a method for preparing a solar cell, comprising steps S100 to S800.

[0049] S100, performing double-sided texturing on the substrate.

[0050] S200, forming a boron doped layer on the front surface of the substrate, wherein the front surface of the substrate includes a first region and a second region, and the first region and the second region are arranged at an interval.

[0051] S300, polishing the back side of the substrate.

[0052] S400, forming a tunneling oxide layer and an amorphous silicon layer in sequence on the back side of the substrate, and performing phosphorus doping on the back side of the substrate to convert the amorphous silicon layer into a polycrystalline silicon layer.

[0053] S500, forming an aluminum oxide layer on the front surface of the substrate.

[0054] S600, performing laser processing on the first region to form a boron-aluminum co-doped layer.

[0055] S700 , forming a passivation layer on the front side and the back side of the substrate respectively.

[0056] S800, preparing a front electrode in the first region, wherein the front electrode is electrically connected to the boron-aluminum co-doped layer.

[0057] In the embodiment of the present application, after the double-sided texturing of the substrate, a boron-doped layer is first formed on the front side of the substrate, and then an aluminum oxide layer is formed. The front side of the substrate includes a first region and a second region, and the first region and the second region are arranged at an interval. In this way, by laser processing the first region, the aluminum atoms in the aluminum oxide layer are pushed into the boron-doped layer by the laser, and form a boron-aluminum co-doped layer together with the existing boron atoms. In this way, the second region still retains the boron-doped layer, and the boron-aluminum co-doped layer in the first region can reduce the contact resistance with the electrode, that is, the patterned emitter provided in the embodiment of the present application can further reduce the contact resistance with the electrode, while reducing the recombination loss and increasing the opening voltage, so as to further improve the battery efficiency.

[0058] Furthermore, in the embodiment of the present application, a boron-doped layer is first formed on the front side of the substrate, instead of forming the boron-doped layer through three processes (pre-boron doping process, laser processing process and post-boron doping process) in the existing process, and then a process of laser processing the first area on the front side of the substrate is added to obtain a patterned emitter. In this way, compared with the existing process, the present application reduces the process steps of forming a patterned emitter, thereby simplifying the preparation process of the solar cell.

[0059] In some embodiments, step S200 of forming a boron doped layer on the front side of the substrate includes: forming a boron doped layer on the front side of the substrate using a high temperature diffusion process. The boron doping concentration is: 1×10 17 cm -3 ~1×10 18 cm -3 For example, the boron doping concentration can be: 1×10 17 cm -3 , 2×10 17 cm -3 , 3×10 17 cm -3 , 4×10 17 cm -3 , 5×10 17 cm -3 , 6×10 17 cm -3 ,7×10 17 cm -3 , 8×10 17 cm -3 ,9×10 17 cm -3 or 1×10 18 cm -3 etc.

[0060] In some examples, a high temperature diffusion process is used to form a boron doped layer on the front side of the substrate, and forming a PN junction includes: a deposition step, a drive-in step, and an oxidation step.

[0061] For example, the process parameters of the deposition step are: temperature of 700°C-900°C, for example, the temperature can be 700°C, 750°C, 800°C, 850°C or 900°C, etc.; time of 5min-40min, for example, the time can be: 5min, 10min, 15min, 20min, 25min, 30min, 35min or 40min, etc. The pressure is 50mbar-300mbar, for example, the pressure can be: 50mbar, 100mbar, 150mbar, 200mbar, 250mbar or 300mbar, etc.; the flow rate of BCL3 is 100sccm-600sccm, for example, the flow rate of BCL3 can be: 100sccm, 150sccm, 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm or 600sccm, etc.; the flow rate of N2 is 500sccm-5000sccm For example, the flow rate of N2 can be: 500sccm, 1000sccm, 1500sccm, 2000sccm, 2500sccm, 3000sccm, 3500sccm, 4000sccm, 4500sccm or 5000sccm, etc.; the flow rate of O2 is 200sccm-2000sccm, for example, the flow rate of O2 can be: 200sccm, 400sccm, 600sccm, 800sccm, 1000sccm, 1200sccm, 1400sccm, 1600sccm, 1800sccm or 2000sccm, etc.

[0062] For example, the process parameters of the advancement step are: temperature of 800℃-950℃, for example, the temperature can be: 800℃, 850℃, 900℃ or 950℃, etc.; time of 5min-40min, for example, the time can be: 5min, 10min, 15min, 20min, 25min, 30min, 35min or 40min, etc.; pressure of 100mbar-1100mbar, for example, the pressure can be: 100mbar, 200mbar, 300mbar, 400mbar, 500mbar, 600mbar, 700mbar, 800mbar, 900mbar, 1000mbar or 1100mbar, etc.

[0063] Illustratively, the process parameters of the oxidation step are: temperature of 900°C-1100°C, for example, the temperature may be 900°C, 950°C, 1000°C, 1050°C or 1100°C, etc.; time of 30min-120min, for example, the time may be 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min or 120min, etc.; pressure of 100mbar-1100mbar, for example, the pressure may be 100mbar, 200mbar, 300mbar, 400mbar, 500mbar, 600mbar, 700mbar, 800mbar, 900mbar, 1000mbar or 1100mbar, etc.; and the flow rate of O2 is 5000sccm-20000sccm. For example, the flow rate of O2 can be: 5000sccm, 6000sccm, 7000sccm, 8000sccm, 9000sccm, 10000sccm, 11000sccm, 12000sccm, 13000sccm, 14000sccm, 15000sccm, 16000sccm, 17000sccm, 18000sccm, 19000sccm or 20000sccm, etc.

[0064] In the embodiments of the present application, by forming a boron-doped layer with a lower boron concentration, compared with the existing process, from the perspective of battery structure, passivation can be improved, recombination can be reduced, and battery efficiency can be further improved. From the perspective of process operation, the process time can be shortened, the required temperature can be reduced, the requirements for high temperature resistance of the equipment can be reduced, the service life can be increased, and the equipment cost can be saved. In addition, due to the formation of a boron-doped layer with a lower boron concentration, the present application also reduces the process temperature of the high-temperature diffusion process and shortens the diffusion time.

[0065] In some embodiments, the doping concentration of aluminum in the boron-aluminum co-doped layer is: 1×10 17 cm -3 ~1×10 18 cm -3 For example, the doping concentration of aluminum in the boron-aluminum co-doped layer can be: 1×10 17 cm -3 , 2×10 17 cm -3 , 3×10 17 cm -3 , 4×10 17 cm -3 , 5×10 17 cm -3 , 6×10 17 cm -3 ,7×1017 cm -3 , 8×10 17 cm -3 ,9×10 17 cm -3 or 1×10 18 cm -3 etc.

[0066] In some embodiments, step S500 of depositing an aluminum oxide layer on the front side of the substrate includes: depositing an aluminum oxide layer on the front side of the substrate using an atomic layer deposition process.

[0067] In some embodiments, the deposition temperature of the atomic layer deposition process is 100° C. to 450° C. For example, the deposition temperature of the atomic layer deposition process may be 100° C., 150° C., 200° C., 250° C., 300° C., 350° C., 400° C., or 450° C., etc. The deposition gas flow rate is 5 sccm to 50 sccm. For example, the deposition gas flow rate may be 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm, or 50 sccm, etc.

[0068] In some embodiments, the time for depositing gas in the atomic layer deposition process is 5s-30s. For example, the time for depositing gas in the atomic layer deposition process can be 5s, 10s, 15s, 20s, 25s or 30s, etc. The number of cycles of the deposition gas in the atomic layer deposition process is 10 to 50 times. For example, the number of cycles of the deposition gas in the atomic layer deposition process can be 10, 15, 20, 25, 30, 35, 40, 45 or 50 times, etc.

[0069] In some embodiments, the thickness of the aluminum oxide layer is 1 nm to 25 nm. For example, the thickness of the aluminum oxide layer can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, or 25 nm.

[0070] In some embodiments, step S600 performs laser processing on the first region to form a boron-aluminum co-doped layer, including the following steps: using a laser process to push aluminum in the aluminum oxide layer into the first region to form a boron-aluminum co-doped layer.

[0071] In some embodiments, the wavelength of the laser is 100 nm-3000 nm. For example, the wavelength of the laser can be 100 nm, 300 nm, 500 nm, 700 nm, 900 nm, 1100 nm, 1300 nm, 1500 nm, 1700 nm, 1900 nm, 2100 nm, 2300 nm, 2500 nm, 2700 nm or 3000 nm, etc.

[0072] In some examples, the frequency of the laser is: 20khz-2Mhz. For example, the frequency of the laser can be: 20khz, 50khz, 100khz, 200khz, 300khz, 400khz, 500khz, 600khz, 700khz, 800khz, 900khz, 1Mkhz, 1.5Mkhz or 2Mkhz, etc.

[0073] In some examples, the scanning rate of the laser is: 1000 mm / s-100000 mm / s. For example, the scanning rate of the laser can be: 1000 mm / s, 5000 mm / s, 10000 mm / s, 20000 mm / s, 30000 mm / s, 40000 mm / s, 50000 mm / s, 60000 mm / s, 70000 mm / s, 80000 mm / s, 90000 mm / s or 100000 mm / s, etc.

[0074] In some examples, the power of the laser is: 1 W-300 W. For example, the power of the laser can be: 1 W, 5 W, 10 W, 50 W, 100 W, 150 W, 200 W, 250 W or 300 W, etc.

[0075] In some embodiments of the present application, the ratio of the doping depth of the boron doped layer to the doping depth of the boron aluminum co-doped layer is 1:1 to 10:1. For example, the ratio of the doping depth of the boron doped layer to the doping depth of the boron aluminum co-doped layer can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0076] The doping depth of the boron doped layer is 0.2µm to 2µm. For example, the doping depth of the boron doped layer can be 0.2µm, 0.4µm, 0.6µm, 0.8µm, 1µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm or 2µm, etc.

[0077] The doping depth of the boron-aluminum co-doped layer is 0.2µm to 2µm. For example, the doping depth of the boron-aluminum co-doped layer can be 0.2µm, 0.4µm, 0.6µm, 0.8µm, 1µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm or 2µm, etc.

[0078] In the embodiment of the present application, the doping depth of the boron doped layer is not less than the doping depth of the boron aluminum co-doped layer. In this way, it can be ensured that when the aluminum atoms in the aluminum oxide layer are pushed into the boron doped layer by the laser, the aluminum atoms can form a boron aluminum co-doped layer together with the boron atoms.

[0079] It should be noted that in the above embodiments, the execution of each step in the method is not strictly restricted in order, and these steps may not necessarily be executed in the order described, but may be executed in other ways. Moreover, at least a part of any step may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps. The method is limited to being able to achieve the preparation of the corresponding solar cell.

[0080] In order to more clearly illustrate the method for preparing the solar cell provided in the above embodiment, Figure 2~Figure 9 The preparation method is described in detail.

[0081] In step S100, refer to Figure 2 , the substrate 10 is double-sided textured.

[0082] In the embodiment of the present application, the double-sided texturing of the substrate 10 can improve the light absorption rate.

[0083] In some examples, the substrate 10 includes: a single crystal silicon substrate, a polycrystalline silicon substrate, or a substrate structure made of other materials.

[0084] For example, the substrate 10 has a first surface and a second surface that are oppositely disposed, the first surface of the substrate 10 may be the front surface and the second surface may be the back surface, or the first surface of the substrate 10 may be the back surface and the second surface may be the front surface.

[0085] In some examples, before double-sided texturing is performed on the substrate 10, the surface of the substrate 10 is polished and the cutting damage layer is removed.

[0086] In step S200, refer to Figure 3 A boron doped layer 20 is formed on the front surface of the substrate 10. The front surface of the substrate 10 includes a first region 11 and a second region 12, and the first region 11 and the second region 12 are arranged at intervals.

[0087] In some embodiments, forming the boron doped layer 20 on the front surface of the substrate 10 includes: forming the boron doped layer 20 on the front surface of the substrate 10 using a high temperature diffusion process. The boron doping concentration is: 1×10 17 cm -3 ~1×10 18 cm -3 For example, the boron doping concentration can be: 1×10 17 cm -3 , 2×10 17 cm -3, 3×10 17 cm -3 , 4×10 17 cm -3 , 5×10 17 cm -3 , 6×10 17 cm -3 ,7×10 17 cm -3 , 8×10 17 cm -3 ,9×10 17 cm -3 or 1×10 18 cm -3 etc.

[0088] In the embodiment of the present application, by forming a boron-doped layer 20 with a lower boron concentration, compared with the existing process, from the perspective of battery structure, passivation can be improved, recombination can be reduced, and battery efficiency can be further improved. From the perspective of process operation, the process time can be shortened, the required temperature can be reduced, the requirements for high temperature resistance of the equipment can be reduced, the service life can be increased, and the equipment cost can be saved. In addition, due to the formation of a boron-doped layer 20 with a lower boron concentration, the present application also reduces the process temperature of the high-temperature diffusion process and shortens the diffusion time.

[0089] In some examples, the conductivity type of the substrate 10 is opposite to the conductivity type of the boron doped layer 20. For example, the substrate 10 is an n-type substrate and the boron doped layer 20 is a p-type boron doped layer; or the substrate 10 is a p-type substrate and the boron doped layer 20 is an n-type boron doped layer.

[0090] Further, illustratively, the doping element of the n-type substrate is at least one of phosphorus, arsenic or antimony; the doping element of the p-type substrate is at least one of boron, aluminum, gallium, indium and thallium.

[0091] In some embodiments of the present application, the doping depth of the boron doped layer 20 is 0.2µm to 2µm. For example, the doping depth of the boron doped layer can be 0.2µm, 0.4µm, 0.6µm, 0.8µm, 1µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm or 2µm, etc.

[0092] In step S300, refer to Figure 4 , the back side of the substrate 10 is polished.

[0093] In some examples, polishing the back side of substrate 10 includes removing boron doped layer 20 on the back side of substrate 10 .

[0094] In some examples, an etching process may be used to remove the boron doped layer 20 on the back side of the substrate 10 .

[0095] In step S400, refer to Figure 5 , a tunnel oxide layer 30 and an amorphous silicon layer ( Figure 5 ), and phosphorus is doped on the back side of the substrate 10 to convert the amorphous silicon layer into a polycrystalline silicon layer 40.

[0096] In some examples, the tunnel oxide layer 30 includes silicon oxide. For example, the material of the tunnel oxide layer 30 may be silicon oxide.

[0097] In some examples, a tunnel oxide layer 30 and a polysilicon layer 40 may be sequentially formed on the back side of the substrate 10 using a deposition process.

[0098] In some examples, the thickness of the tunnel oxide layer 30 is 1 nm-5 nm. For example, the thickness of the tunnel oxide layer 30 can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, or 5 nm.

[0099] In some examples, the thickness of the polysilicon layer 40 is 100 nm-400 nm. For example, the thickness of the polysilicon layer 40 can be 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, or 400 nm, etc.

[0100] In some examples, the phosphorus doping concentration in the polysilicon layer 40 is: 1e20 cm -3 ~10e20cm -3 For example, the phosphorus doping concentration can be: 1e20cm -3 、2e20cm -3 、3e20cm -3 、4e20cm -3 、5e20cm -3 、6e20cm -3 、7e20cm -3 、8e20cm -3 、9e20cm -3 or 10e20cm -3 .

[0101] In step S500, refer to Figure 5~Figure 7 , an aluminum oxide layer 50 is formed on the front surface of the substrate 10.

[0102] In some embodiments, step S500 of depositing the aluminum oxide layer 50 on the front surface of the substrate 10 includes: depositing the aluminum oxide layer 50 on the front surface of the substrate 10 using an atomic layer deposition process.

[0103] In some embodiments, the deposition temperature of the atomic layer deposition process is 100° C. to 450° C. For example, the deposition temperature of the atomic layer deposition process may be 100° C., 150° C., 200° C., 250° C., 300° C., 350° C., 400° C., or 450° C., etc. The deposition gas flow rate is 5 sccm to 50 sccm. For example, the deposition gas flow rate may be 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm, or 50 sccm, etc.

[0104] In some embodiments, the time for depositing gas in the atomic layer deposition process is 5s-30s. For example, the time for depositing gas in the atomic layer deposition process can be 5s, 10s, 15s, 20s, 25s or 30s, etc. The number of cycles of the deposition gas in the atomic layer deposition process is 10 to 50 times. For example, the number of cycles of the deposition gas in the atomic layer deposition process can be 10, 15, 20, 25, 30, 35, 40, 45 or 50 times, etc.

[0105] In some embodiments, please refer to Figure 5 and Figure 6 Before forming the aluminum oxide layer 50 on the front side of the substrate 10 , the method further includes: polishing the front side of the substrate 10 .

[0106] For some examples, see Figure 5 and Figure 6 Polishing the front side of the substrate 10 includes removing the tunneling oxide layer 30 and the polysilicon layer 40 on the front side of the substrate 10 .

[0107] In some embodiments, please refer to Figure 7 The thickness of the aluminum oxide layer 50 is 1 nm to 25 nm. For example, the thickness of the aluminum oxide layer 50 can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm or 25 nm.

[0108] In some examples, an etching process may be used to remove the tunneling on the front side of the substrate 10 in step S600, see Figure 8 , laser processing is performed on the first region 11 to form a boron-aluminum co-doped layer 60 .

[0109] In some examples, the first region 11 may be used to provide an electrode.

[0110] In some embodiments, the doping concentration of aluminum in the boron-aluminum co-doped layer 60 is: 1×10 17 cm -3 ~1×10 18 cm -3For example, the doping concentration of aluminum in the boron-aluminum co-doped layer 60 may be: 1×10 17 cm -3 , 2×10 17 cm -3 , 3×10 17 cm -3 , 4×10 17 cm -3 , 5×10 17 cm -3 , 6×10 17 cm -3 ,7×10 17 cm -3 , 8×10 17 cm -3 ,9×10 17 cm -3 or 1×10 18 cm -3 etc.

[0111] In some embodiments, step S600 performs laser processing on the first region 11 to form the boron-aluminum co-doped layer 60 , including the following steps: using a laser process to push aluminum in the aluminum oxide layer 50 into the first region 11 to form the boron-aluminum co-doped layer 60 .

[0112] In some embodiments, the wavelength of the laser is 100 nm-3000 nm. For example, the wavelength of the laser can be 100 nm, 300 nm, 500 nm, 700 nm, 900 nm, 1100 nm, 1300 nm, 1500 nm, 1700 nm, 1900 nm, 2100 nm, 2300 nm, 2500 nm, 2700 nm or 3000 nm, etc.

[0113] In some examples, the frequency of the laser is: 20khz-2Mhz. For example, the frequency of the laser can be: 20khz, 50khz, 100khz, 200khz, 300khz, 400khz, 500khz, 600khz, 700khz, 800khz, 900khz, 1Mkhz, 1.5Mkhz or 2Mkhz, etc.

[0114] In some examples, the scanning rate of the laser is: 1000 mm / s-100000 mm / s. For example, the scanning rate of the laser can be: 1000 mm / s, 5000 mm / s, 10000 mm / s, 20000 mm / s, 30000 mm / s, 40000 mm / s, 50000 mm / s, 60000 mm / s, 70000 mm / s, 80000 mm / s, 90000 mm / s or 100000 mm / s, etc.

[0115] In some examples, the power of the laser is: 1 W-300 W. For example, the power of the laser can be: 1 W, 5 W, 10 W, 50 W, 100 W, 150 W, 200 W, 250 W or 300 W, etc.

[0116] In some examples, the doping depth of the boron-aluminum co-doped layer 60 is 0.2µm to 2µm. For example, the doping depth of the boron-aluminum co-doped layer 60 can be 0.2µm, 0.4µm, 0.6µm, 0.8µm, 1µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm or 2µm, etc.

[0117] In step S700, refer to Fig. 9 , a passivation layer 70 is formed on the front and back sides of the substrate 10 respectively.

[0118] In some examples, the passivation layer 70 may be formed on the front side and the back side of the substrate 10 by a deposition process.

[0119] By way of example, the material of the passivation layer 70 includes one or more of silicon oxynitride, silicon nitride or silicon oxide.

[0120] In step S800, refer to Fig.10 A front electrode 81 is prepared in the first region 11 , and the front electrode 81 is electrically connected to the boron-aluminum co-doped layer 60 .

[0121] In some embodiments, step S800 further includes: forming a back electrode 82 on the back side of the substrate 10 .

[0122] For example, the material of the front electrode 81 and the back electrode 82 includes, but is not limited to, one or more of silver, gold, copper or aluminum.

[0123] In some embodiments, please refer to Table 1 and Table 2. Compared with the traditional process, the solar cell prepared by the embodiment of the present disclosure has better electrical performance. Among them, Example 1, Example 2, Example 3 and Example 4 in Table 1 are prepared by the embodiment of the present disclosure, and the comparative example is prepared by the existing TOPCon technology mentioned in the above embodiments.

[0124] For example, the existing TOPCon technology specifically includes the following steps: a pre-boron process, a SE process, and a post-boron process.

[0125] Among them, the pre-boron process includes preparing a PN junction by a step-by-step diffusion method, and the specific diffusion steps are:

[0126] In the first step of diffusion, the process parameters are: the pressure in the furnace is 50mbar~150mbar, the diffusion temperature is 830℃~850℃, the diffusion time is 100s~300s, the nitrogen flow rate is 1000sccm~3000sccm, the boron trichloride flow rate is 100sccm~300sccm, and the oxygen flow rate is 200sccm~500sccm;

[0127] The second step is diffusion, and the process parameters are: the pressure in the furnace is 50mbar~150mbar, the diffusion temperature is 850℃~880℃, the diffusion time is 100s~300s, the nitrogen flow rate is 1000sccm~2000sccm, the boron trichloride flow rate is 100sccm~300sccm, and the oxygen flow rate is 200sccm~500sccm;

[0128] The third step is diffusion, and the process parameters are: the pressure in the furnace is 50mbar~150mbar, the diffusion temperature is 850℃~880℃, the diffusion time is 100s~300s, the nitrogen flow rate is 1000sccm~3000sccm, the boron trichloride flow rate is 100sccm~300sccm, and the oxygen flow rate is 200sccm~500sccm;

[0129] The process parameters for temperature rise and advancement are as follows: the pressure in the furnace is 200mbar~400mbar, the advancement temperature is 900℃~950℃, the advancement time is 400s~600s, the nitrogen flow rate is 7000sccm~10000sccm, and the oxygen flow rate is 0sccm.

[0130] For example, in the SE process, the marking speed is 20000 mm / s to 25000 mm / s, and the power is 30% to 70%.

[0131] For example, in the post-boron process, the process parameters are: the pressure in the furnace is 600mbar-950mbar, the oxidation time is maintained for 2000s-5000s, the oxygen flow rate is 180000sccm-21000sccm, the nitrogen flow rate is 0, and the temperature is 1000℃-1060℃.

[0132] Table 1: Emitter doping concentration corresponding to different preparation processes

[0133]

[0134] Table 2: Related parameters of solar cells corresponding to different preparation processes

[0135]

[0136] Please continue reading Fig. 9Some embodiments of the present application also provide a solar cell, which is prepared using the solar cell preparation method described in the above embodiments.

[0137] In the embodiments of the present application, the technical effects that can be achieved by the solar cell are the same as the technical effects that can be achieved by the method for preparing the solar cell in the aforementioned embodiments, and will not be described in detail here.

[0138] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described 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.

[0139] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing a solar cell, characterized in that: include: Double-sided texturing of the substrate; forming a boron-doped layer on the front surface of the substrate; wherein the front surface of the substrate includes a first region and a second region, and the first region and the second region are arranged at an interval; polishing the back side of the substrate; forming a tunneling oxide layer and an amorphous silicon layer in sequence on the back side of the substrate, and performing phosphorus doping on the back side of the substrate to convert the amorphous silicon layer into a polycrystalline silicon layer; forming an aluminum oxide layer on the front surface of the substrate; Performing laser processing on the first region to form a boron-aluminum co-doped layer; forming a passivation layer on the front and back sides of the substrate respectively; A front electrode is prepared in the first region, and the front electrode is electrically connected to the boron-aluminum co-doped layer.

2. The method for preparing a solar cell according to claim 1, characterized in that: Forming a boron doped layer on the front side of the substrate comprises: forming a boron doped layer on the front side of the substrate by a high temperature diffusion process; wherein the boron doping concentration is: 1×10 17 cm -3 ~1×10 18 cm -3 .

3. The method for preparing a solar cell according to claim 1, wherein: The doping concentration of aluminum in the boron-aluminum co-doped layer is: 1×10 17 cm -3 ~1×10 18 cm -3 .

4. The method for preparing a solar cell according to claim 1, wherein: Performing laser processing on the first region to form a boron-aluminum co-doped layer includes: A laser process is used to push aluminum in the aluminum oxide layer into the first region to form a boron-aluminum co-doped layer.

5. The method for preparing a solar cell according to claim 4, characterized in that: The wavelength of the laser is 100nm-3000nm; the frequency of the laser is 20khz-2Mhz; the scanning rate of the laser is 1000mm / s-100000mm / s; the power of the laser is 1W-300W.

6. The method for preparing a solar cell according to claim 1, characterized in that: Depositing an aluminum oxide layer on the front side of the substrate includes: depositing an aluminum oxide layer on the front side of the substrate using an atomic layer deposition process.

7. The method for preparing a solar cell according to claim 6, characterized in that: The deposition temperature of the atomic layer deposition process is 100° C. to 450° C., and the deposition gas flow rate is 5 sccm to 50 sccm.

8. The method for preparing a solar cell according to claim 1, wherein: The thickness of the aluminum oxide layer is 1 nm to 25 nm.

9. The method for preparing a solar cell according to claim 1, wherein: The ratio of the doping depth of the boron doped layer to the doping depth of the boron-aluminum co-doped layer is: 1:1~10:1; the doping depth of the boron doped layer is: 0.2µm~2µm; the doping depth of the boron-aluminum co-doped layer is: 0.2µm~2µm.

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

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