Solar cell with selective phosphorus doping structure
By dividing the surface of the phosphorus-doped polycrystalline silicon layer into heavily doped regions and lightly doped regions, and fine doping treatment is carried out, the problem of difficult to control the phosphorus doping concentration in the prior art is solved, and the performance of solar cells is improved.
Patent Information
- Application Number
- CN202422116358.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-06-13
- Estimated Expiration
- 2034-08-30
AI Technical Summary
In the process of high-temperature phosphorus diffusion of the amorphous silicon layer, it is difficult to finely control the phosphorus concentration in the polycrystalline silicon, which makes it difficult to reach the ideal value of the phosphorus doping concentration, affecting the field passivation effect of the battery and the transportation of photogenerated carriers.
By dividing the surface of the phosphorus-doped polysilicon layer into a heavily doped region and a light doped region, and performing heavy and light doping treatments respectively, the low doping concentration of the light doped region reduces the carrier recombination, and the high doping concentration of the heavily doped region reduces the contact resistance between the electrode and the polysilicon layer.
The fine control of the phosphorus doping concentration is achieved, the light absorption rate and photoelectric conversion efficiency of solar cells are improved, and the problem of poor phosphorus doping concentration control of the polycrystalline silicon layer is avoided.
Smart Images
Figure CN222981922U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of new energy, and particularly to solar cells. Background Art
[0002] Currently, in the technology of crystalline silicon solar cells, TOPCon (Tunnel Oxide Passivated Contact) technology, as the mainstream representative of passivated contact technology, has entered the stage of large-scale mass production. The back passivated contact structure of a typical TOPCon cell includes: a tunnel oxide layer, a phosphorus-doped polysilicon layer, and an antireflection layer sequentially covered on the back surface of an n-type silicon substrate. The first electrode forms an ohmic contact with the doped polysilicon layer by sintering at high temperature through a silicon nitride layer and an aluminum oxide layer.
[0003] The phosphorus-doped polysilicon layer provides the main passivation effect for the cell. Usually, the polysilicon layer is phosphorus-doped by high-temperature phosphorus diffusion and dopant atom push process to obtain the phosphorus-doped polysilicon layer. In the existing technical means, during the high-temperature phosphorus diffusion process of the amorphous silicon layer, it is difficult to finely control the phosphorus concentration in the polysilicon, and the phosphorus doping concentration is difficult to reach the ideal value. If the phosphorus concentration is too high, the phosphorus diffused into the silicon substrate will increase accordingly, which will reduce the field passivation effect of the polysilicon layer; if the phosphorus concentration is too low, it will increase the contact resistance between the electrode and the polysilicon, which is not conducive to the transportation of photo-generated carriers. Summary of the Invention
[0004] Embodiments of this application provide a solar cell with a selective phosphorus doping structure and a preparation method thereof to solve the technical problem that it is difficult to finely control the phosphorus doping concentration in the polysilicon layer.
[0005] In a first aspect, embodiments of this application provide a solar cell with a selective phosphorus doping structure, and the solar cell with a selective phosphorus doping structure includes:
[0006] An n-type silicon substrate;
[0007] A tunnel oxide layer disposed on the back surface of the n-type silicon substrate;
[0008] A phosphorus-doped polysilicon layer disposed on the surface of the tunnel oxide layer, wherein the surface of the phosphorus-doped polysilicon layer is divided into a heavily doped region and a lightly doped region, and the doping concentration of phosphorus atoms in the heavily doped region is higher than that in the lightly doped region;
[0009] A first passivation layer disposed on the surface of the lightly doped region;
[0010] A first antireflection layer disposed on the surface of the first passivation layer;
[0011] A first electrode disposed on the surface of the heavily doped region, wherein one side of the first electrode is in ohmic contact with the heavily doped region, and the other side of the first electrode protrudes from the surface of the first antireflection layer.
[0012] In some embodiments of the present application, the doping concentration of phosphorus atoms in the lightly doped region is 1E+19; and / or,
[0013] the doping concentration of phosphorus atoms in the heavily doped region is 5E+20.
[0014] In some embodiments of the present application, the solar cell with a selective phosphorus doping structure further includes:
[0015] a boron-doped oxide layer disposed on the positive surface of the n-type silicon substrate;
[0016] a second passivation layer disposed on the surface of the boron-doped oxide layer;
[0017] a second antireflection layer disposed on the surface of the second passivation layer;
[0018] a second electrode, one side of the second electrode is in ohmic contact with the boron-doped oxide layer, and the other side of the second electrode protrudes from the surface of the second antireflection layer.
[0019] In some embodiments of the present application, the material of the first passivation layer is alumina; and / or,
[0020] the material of the second passivation layer is alumina; and / or,
[0021] the material of the first antireflection layer is silicon nitride; and / or,
[0022] the material of the second antireflection layer is silicon nitride.
[0023] In some embodiments of the present application, the thickness of the tunneling oxide layer is 1-2 nm; and / or,
[0024] the thickness of the phosphorus-doped polysilicon layer is 10-50 nm; and / or,
[0025] the thickness of the boron-doped oxide layer is 30-150 nm; and / or,
[0026] the thickness of the first passivation layer is 5-20 nm; and / or,
[0027] the thickness of the second passivation layer is 5-20 nm; and / or,
[0028] the thickness of the first antireflection layer is 20-100 nm; and / or,
[0029] the thickness of the second antireflection layer is 20-100 nm.
[0030] Second aspect, an embodiment of the present application provides a method for manufacturing a solar cell with a selective phosphorus doping structure. The method for manufacturing the solar cell with a selective phosphorus doping structure includes the following steps:
[0031] Provide an n-type silicon wafer, where the n-type silicon wafer includes an n-type silicon substrate and a boron-doped oxide layer provided on the front surface of the n-type silicon substrate;
[0032] Sequentially prepare a tunneling oxide layer and a polysilicon layer on the back surface of the n-type silicon wafer;
[0033] Plan a preset area for forming an electrode on the surface of the polysilicon layer, and set phosphorus-silicon paste in the preset area by screen printing;
[0034] Perform high-temperature phosphorus diffusion treatment on the polysilicon layer;
[0035] Remove the phosphorus-doped material formed by diffusion around the surface of the boron-doped oxide layer;
[0036] Activate the phosphorus atoms in the polysilicon layer that has undergone the high-temperature phosphorus diffusion treatment by annealing, so that the polysilicon layer is transformed into a phosphorus-doped polysilicon layer;
[0037] Deposit a first passivation layer on the surface of the phosphorus-doped polysilicon layer, and deposit a second passivation layer on the surface of the boron-doped oxide layer;
[0038] Deposit a first antireflection layer on the surface of the first passivation layer, and deposit a second antireflection layer on the surface of the second passivation layer;
[0039] After printing electrode paste on the surfaces of the first antireflection layer and the second antireflection layer, sinter the electrode paste to form a first electrode in ohmic contact with the heavily doped region and a second electrode in ohmic contact with the boron-doped oxide layer.
[0040] In some embodiments of the present application, the phosphorus-silicon paste includes nano-silicon powder and phosphorus pentoxide with a mass ratio of 1:5 to 19; and / or,
[0041] The doping concentration of phosphorus atoms in the lightly doped region is 1E+10 to 9E+19; and / or,
[0042] The doping concentration of phosphorus atoms in the heavily doped region is 1E+20 to 5E+20.
[0043] In some embodiments of the present application, providing an n-type silicon wafer with a boron-doped oxide layer on the front surface includes the following steps:
[0044] Provide an n-type silicon substrate;
[0045] Texturize the n-type silicon substrate;
[0046] Perform a high-temperature boron diffusion treatment on the front surface of the n-type silicon substrate;
[0047] Remove the boron-doped material formed by the back-surface over-diffusion of the n-type silicon substrate.
[0048] In some embodiments of the present application, the material of the first passivation layer is alumina; and / or,
[0049] the material of the second passivation layer is alumina; and / or,
[0050] the material of the first anti-reflection layer is silicon nitride; and / or,
[0051] the material of the second anti-reflection layer is silicon nitride.
[0052] In some embodiments of the present application, the thickness of the tunneling oxide layer is 1 - 2 nm; and / or,
[0053] the thickness of the phosphorus-doped polysilicon layer is 10 - 50 nm; and / or,
[0054] the thickness of the boron-doped oxide layer is 30 - 150 nm; and / or,
[0055] the thickness of the first passivation layer is 5 - 20 nm; and / or,
[0056] the thickness of the second passivation layer is 5 - 20 nm; and / or,
[0057] the thickness of the first anti-reflection layer is 20 - 100 nm; and / or,
[0058] the thickness of the second anti-reflection layer is 20 - 100 nm.
[0059] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:
[0060] The solar cell with a selective phosphorus doping structure provided by the embodiments of the present application divides the surface of the phosphorus-doped polysilicon layer into a heavily doped region and a lightly doped region. The lightly doped region can be obtained by performing a mild doping treatment, and the heavily doped region can be obtained by performing a heavy doping treatment. The low doping concentration in the lightly doped region is beneficial to reducing carrier recombination, and the heavy doping concentration in the heavily doped region is beneficial to reducing the contact resistance between the first electrode and the phosphorus-doped polysilicon layer. The realization of the functions of the lightly doped region and the heavily doped region does not require very precise control of the doping concentration. By dividing the surface of the phosphorus-doped polysilicon layer into a heavily doped region and a lightly doped region, the present application avoids the technical problem of inaccurate control of the phosphorus doping concentration in the polysilicon layer without the need for very precise control of the doping concentrations in the lightly doped region and the heavily doped region. Brief Description of the Drawings
[0061] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.
[0062] To more clearly illustrate the technical solutions in the embodiments of this application or in the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0063] Figure 1 It is a schematic structural diagram of the intermediate product obtained in step Sa of Embodiment 1 of this application;
[0064] Figure 2 It is a schematic structural diagram of the intermediate product obtained in step Sb of Embodiment 1 of this application;
[0065] Figure 3 It is a schematic structural diagram of the intermediate product obtained in step Sc of Embodiment 1 of this application;
[0066] Figure 4 It is a schematic structural diagram of the intermediate product obtained in step Sd of Embodiment 1 of this application;
[0067] Figure 5 It is a schematic structural diagram of the intermediate product obtained in step Se of Embodiment 1 of this application;
[0068] Figure 6 It is a schematic structural diagram of the intermediate product obtained in step Sf of Embodiment 1 of this application;
[0069] Figure 7 It is a schematic structural diagram of the intermediate product obtained in step Sg of Embodiment 1 of this application;
[0070] Figure 8 It is a schematic structural diagram of the intermediate product obtained in step Sh of Embodiment 1 of this application;
[0071] Figure 9 It is a schematic structural diagram of the solar cell obtained in Embodiment 1 of this application. Detailed implementation manners
[0072] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this application without creative efforts fall within the scope of protection of this application.
[0073] Unless otherwise specifically stated, the terms used in this document should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used in this document have the same meaning as the general understanding of those skilled in the art to which this application belongs. In case of any contradiction, this specification shall prevail.
[0074] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in this application can be obtained through market purchases or can be prepared by existing methods.
[0075] The definitions of all English abbreviations used in this application are as follows.
[0076] TOPCon: Tunnel Oxide Passivated Contact solar cell (TOPcon)
[0077] PECVD: Plasma Enhanced Chemical Vapor Deposition
[0078] LPCVD: Low Pressure Chemical Vapor Deposition
[0079] PVD: Physical Vapor Deposition
[0080] Currently, there is a technical problem that the phosphorus doping concentration of the polysilicon layer in TOPCon cells is difficult to precisely control.
[0081] The technical solutions provided in the embodiments of this application to solve the above technical problems are generally as follows:
[0082] In a first aspect, the embodiments of this application provide a solar cell with a selective phosphorus doping structure. The solar cell with a selective phosphorus doping structure includes:
[0083] An n-type silicon substrate;
[0084] A tunneling oxide layer disposed on the back surface of the n-type silicon substrate;
[0085] A phosphorus-doped polysilicon layer disposed on the surface of the tunneling oxide layer, wherein the surface of the phosphorus-doped polysilicon layer is divided into a heavily doped region and a lightly doped region, and the doping concentration of phosphorus atoms in the heavily doped region is higher than that in the lightly doped region;
[0086] A first passivation layer disposed on the surface of the lightly doped region;
[0087] The first antireflection layer disposed on the surface of the first passivation layer;
[0088] The first electrode disposed on the surface of the heavily doped region, wherein one side of the first electrode is in ohmic contact with the heavily doped region, and the other side of the first electrode protrudes from the surface of the first antireflection layer.
[0089] Those skilled in the art can understand that the n-type silicon substrate is also called an n-type lightly doped substrate, which is an n-type solar cell blue film formed by lightly doping and diffusing a phosphorus source on a crystalline silicon wafer.
[0090] Those skilled in the art can understand that the tunneling oxide layer is a conventional structure in the art. The function of the tunneling oxide layer is to reduce the interface state density between the silicon wafer substrate and the doped polysilicon layer through chemical passivation. The majority carrier concentration is much higher than that of the minority carriers. While reducing the electron-hole recombination probability, it also increases the resistivity to form a selective contact for majority carriers. In the tunneling oxide layer, electrons pass through the oxide layer from the metal surface and enter the metal surface on the other side. This phenomenon only occurs in very thin oxide layers, usually less than a few nanometers. In this case, the wavelength of the electrons is comparable to the thickness of the tunneling oxide layer, so the electrons can pass through the tunneling oxide layer. Preparing the tunneling oxide layer is a conventional technical solution in the art. As an example, the tunneling oxide layer can be prepared by methods such as PECVD, LPCVD, etc., and the deposition atmosphere can include N 2 O and SiH 4 , oxygen, etc.
[0091] Those skilled in the art can understand that the phosphorus-doped polysilicon layer is a conventional structure in the art. In a TOPCon cell, the phosphorus-doped polysilicon layer is the n-type semiconductor in the PN junction. The preparation of the phosphorus-doped polysilicon layer requires first preparing a polysilicon layer on the tunneling oxide layer. The polysilicon layer can be prepared by methods such as PECVD, LPCVD, PVD, etc.; then the polysilicon layer is phosphorus-doped through a phosphorus doping process to form a phosphorus-doped polysilicon layer. The phosphorus doping process can be, for example, high-temperature phosphorus diffusion.
[0092] Those skilled in the art can understand that the passivation layer is also called an insulating layer and can be made of silicon nitride, aluminum oxide, titanium oxide, or silicon oxide, or any combination thereof. The passivation layer can be deposited by chemical vapor deposition, sputtering, atomic deposition, or other means. The first passivation layer and the second passivation layer described in this application both belong to the above passivation layer.
[0093] Those skilled in the art can understand that the function of the antireflection layer enables incident light to undergo multiple refractions and scatterings when reaching the surface of the silicon wafer, thereby reducing the direct reflection of light and increasing the absorption path of light inside the silicon wafer. Due to the reduction of the direct reflection of light, more sunlight can enter the silicon wafer and be converted into electrical energy, thereby improving the light absorption rate and photoelectric conversion efficiency of the battery. The materials of the antireflection layer include silicon nitride, aluminum oxide, titanium oxide, silicon oxide, etc. These materials have good optical properties and chemical stability, and can effectively passivate and protect the surface of the silicon wafer while ensuring light transmittance. The antireflection layer can be prepared by methods such as PECVD, LPCVD, PVD, etc. The first antireflection layer and the second antireflection layer described in this application both belong to the above antireflection layer.
[0094] Those skilled in the art can understand that the electrode is a conventional structure in the art. The material of the electrode is generally formed by conductive electrode paste. For example, the metalized silver paste applied to p-type crystalline silicon cells in the market can be used as the electrode paste, such as the silver paste containing Pb-Te-O glass powder. As an exemplary preparation method, the electrode paste can be applied to the silicon wafer in a required patterned form by screen printing, and post-treatment such as sintering is carried out after drying. The conductive layer formed by the electrode paste forms an electrical contact with the silicon wafer to form an electrode. The first electrode and the second electrode described in this application both belong to the above electrode.
[0095] In this application, the surface of the phosphorus-doped polysilicon layer is divided into a heavily doped region and a lightly doped region. The lightly doped region can be obtained by performing a mild doping treatment, and the heavily doped region can be obtained by performing a heavy doping treatment. The low doping concentration in the lightly doped region is beneficial to reducing carrier recombination, and the heavy doping concentration in the heavily doped region is beneficial to reducing the contact resistance between the first electrode and the phosphorus-doped polysilicon layer. The realization of the functions of the lightly doped region and the heavily doped region does not require very precise control of the doping concentration. By dividing the surface of the phosphorus-doped polysilicon layer into a heavily doped region and a lightly doped region in this application, the technical problem of imprecise control of the phosphorus doping concentration in the polysilicon layer is avoided without very precise control of the doping concentrations of the lightly doped region and the heavily doped region.
[0096] In some embodiments of this application, the doping concentration of phosphorus atoms in the lightly doped region is 1E+19; and / or,
[0097] The doping concentration of phosphorus atoms in the heavily doped region is 5E+20.
[0098] In some embodiments of this application, the solar cell with a selective phosphorus doping structure further includes:
[0099] A boron-doped oxide layer provided on the positive surface of the n-type silicon substrate;
[0100] A second passivation layer provided on the surface of the boron-doped oxide layer;
[0101] A second antireflection layer disposed on the surface of the second passivation layer;
[0102] A second electrode, one side of the second electrode is in ohmic contact with the boron-doped oxide layer, and the other side of the second electrode protrudes from the surface of the second antireflection layer.
[0103] Those skilled in the art can understand that the boron-doped oxide layer is a conventional structure in the art. The boron-doped oxide layer is also referred to as a Boro-silicate Glass layer. In a Topcon cell, the boron-doped oxide layer is formed during the process of performing a high-temperature boron diffusion process on an n-type silicon substrate.
[0104] In some embodiments of the present application, the material of the first passivation layer is alumina; and / or,
[0105] the material of the second passivation layer is alumina; and / or,
[0106] the material of the first antireflection layer is silicon nitride; and / or,
[0107] the material of the second antireflection layer is silicon nitride.
[0108] In some embodiments of the present application, the thickness of the tunneling oxide layer is 1-2 nm; and / or,
[0109] the thickness of the phosphorus-doped polysilicon layer is 10-50 nm; and / or,
[0110] the thickness of the boron-doped oxide layer is 30-150 nm; and / or,
[0111] the thickness of the first passivation layer is 5-20 nm; and / or,
[0112] the thickness of the second passivation layer is 5-20 nm; and / or,
[0113] the thickness of the first antireflection layer is 20-100 nm; and / or,
[0114] the thickness of the second antireflection layer is 20-100 nm.
[0115] As an example, the thickness of the tunneling oxide layer can be 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 2.8 nm, 2 nm,
[0116] As an example, the thickness of the phosphorus-doped polysilicon layer can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm,
[0117] As an example, the thickness of the boron-doped oxide layer can be 30 nm, 60 nm, 90 nm, 120 nm, 150 nm.
[0118] As an example, the thickness of the first passivation layer can be 5 nm, 10 nm, 15 nm, 20 nm.
[0119] As an example, the thickness of the second passivation layer can be 5 nm, 10 nm, 15 nm, 20 nm.
[0120] As an example, the thickness of the first antireflection layer can be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm.
[0121] As an example, the thickness of the second antireflection layer can be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm.
[0122] In a second aspect, an embodiment of the present application provides a method for manufacturing a solar cell with a selective phosphorus doping structure. The method for manufacturing a solar cell with a selective phosphorus doping structure includes the following steps:
[0123] S1: Provide an n-type silicon wafer, where the n-type silicon wafer includes an n-type silicon substrate and a boron-doped oxide layer provided on the front surface of the n-type silicon substrate;
[0124] S2: Sequentially prepare a tunneling oxide layer and a polysilicon layer on the back surface of the n-type silicon wafer;
[0125] S3: Plan a preset area for forming an electrode on the surface of the polysilicon layer, and set phosphorus-silicon paste in the preset area by screen printing;
[0126] S4: Perform high-temperature phosphorus diffusion treatment on the polysilicon layer;
[0127] S5: Remove the phosphorus-doped material formed by diffusion around the surface of the boron-doped oxide layer;
[0128] S6: Activate the phosphorus atoms in the polysilicon layer that has undergone the high-temperature phosphorus diffusion treatment by annealing, so that the polysilicon layer is transformed into a phosphorus-doped polysilicon layer;
[0129] S7: Deposit a first passivation layer on the surface of the phosphorus-doped polysilicon layer, and deposit a second passivation layer on the surface of the boron-doped oxide layer;
[0130] S8: Deposit a first antireflection layer on the surface of the first passivation layer, and deposit a second antireflection layer on the surface of the second passivation layer;
[0131] S9: After printing electrode paste on the surfaces of the first antireflection layer and the second antireflection layer, sinter the electrode paste to form a first electrode in ohmic contact with the heavily doped region and a second electrode in ohmic contact with the boron-doped oxide layer.
[0132] The method described in the second aspect of the present application can be used to prepare the solar cell with a selective phosphorus doping structure described in any embodiment of the first aspect of the present application. The method described in any embodiment of the second aspect of the present application can prepare the solar cell with a selective phosphorus doping structure described in the first aspect of the present application.
[0133] It should be noted that the heavily doped region should coincide with the preset region. The heavily doped region is formed by the diffusion of phosphorus in the phosphorus-silicon paste into the polysilicon layer.
[0134] Those skilled in the art can understand that the tunneling oxide layer can be prepared by methods such as PECVD and LPCVD, and the deposition atmosphere can include N 2 O and SiH 4 , oxygen, etc.
[0135] Those skilled in the art can understand that the polysilicon layer can be prepared by methods such as PECVD, LPCVD, and PVD.
[0136] Those skilled in the art can understand that high-temperature phosphorus diffusion refers to the process of diffusing phosphorus atoms into a silicon wafer through high-temperature treatment in the presence of a phosphorus source to combine with silicon atoms to form an n-type doped region. The most commonly used phosphorus source for high-temperature phosphorus diffusion is POCl 3 .
[0137] Those skilled in the art can understand that out-diffusion refers to the unexpected diffusion or deposition of dopants (such as phosphorus and boron) or deposition layers (such as polysilicon layers) at the edges or back of a solar cell. Some out-diffusion phenomena are caused by improper process parameters, while some are inevitable and difficult to avoid by adjusting process parameters. As an exemplary illustration of out-diffusion, the high-temperature phosphorus diffusion process is a phosphorus doping process for the polysilicon layer, but during the implementation of the high-temperature phosphorus diffusion process, a small amount of phosphorus atoms will inevitably be incorporated into the boron-doped oxide layer. The boron-doped materials, phosphorus-doped materials, etc. formed by out-diffusion can all be removed by conventional methods in the art. For example, the boron-doped oxide layer can be removed by hydrofluoric acid.
[0138] Those skilled in the art can understand that the passivation layer can be deposited by methods such as chemical vapor deposition, sputtering, atomic deposition, or others.
[0139] Those skilled in the art can understand that the antireflection layer can be prepared by methods such as PECVD, LPCVD, and PVD.
[0140] In some embodiments of the present application, the phosphorus-silicon paste includes nano-silicon powder and phosphorus pentoxide with a mass ratio of 1:5 to 19; and / or,
[0141] The doping concentration of phosphorus atoms in the lightly doped region is 1E+10 to 9E+19; and / or,
[0142] The doping concentration of phosphorus atoms in the heavily doped region is 1E+20 to 5E+20.
[0143] In some embodiments of the present application, providing an n-type silicon wafer with a boron-doped oxide layer on the positive surface includes the following steps:
[0144] Provide an n-type silicon substrate;
[0145] Perform texturing treatment on the n-type silicon substrate;
[0146] Perform high-temperature boron diffusion treatment on the positive surface of the n-type silicon substrate;
[0147] Remove the boron-doped material formed by the back-surface diffusion around the n-type silicon substrate.
[0148] Those skilled in the art can understand that high-temperature boron diffusion means that in the presence of a boron source, boron atoms diffuse into the n-type silicon substrate through high-temperature treatment and combine with silicon atoms to form a p-type doping region. Currently, the commonly used boron source for high-temperature boron diffusion is BCl 3 or BBr 3 . At high temperatures, BCl 3 or BBr 3 will react with oxygen to form boron oxide, and the boron oxide will then react with the silicon dioxide on the surface of the n-type silicon substrate to form borosilicate glass. High-temperature boron diffusion is one of the steps for boron doping of the n-type silicon substrate. Boron doping of the n-type silicon substrate is generally achieved in the following manner: First, a boron-doped oxide layer is grown on the surface of the n-type silicon substrate that has undergone texturing and cleaning, and then boron atoms in the boron-doped oxide layer are further diffused into the n-type silicon substrate through processes such as high-temperature treatment and laser propulsion to achieve boron doping.
[0149] In some embodiments of the present application, the material of the first passivation layer is alumina; and / or,
[0150] The material of the second passivation layer is alumina; and / or,
[0151] The material of the first antireflection layer is silicon nitride; and / or,
[0152] The material of the second antireflection layer is silicon nitride.
[0153] In some embodiments of the present application, the thickness of the tunneling oxide layer is 1 to 2 nm; and / or,
[0154] The thickness of the phosphorus-doped polysilicon layer is 10 to 50 nm; and / or,
[0155] The thickness of the boron-doped oxide layer is 30 to 150 nm; and / or,
[0156] The thickness of the first passivation layer is 5 to 20 nm; and / or,
[0157] The thickness of the second passivation layer is 5 to 20 nm; and / or,
[0158] The thickness of the first antireflection layer is 20 to 100 nm; and / or,
[0159] The thickness of the second antireflection layer is 20 to 100 nm.
[0160] The following further elaborates on this application with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.
[0161] Example 1
[0162] This example provides a method for preparing a selective phosphorus-doped structure, including the following steps:
[0163] Sa: Provide silicon wafer 1, texture the surface of silicon wafer 1. For the structure of the resulting intermediate product, please refer to Figure 1 ;
[0164] Sb: Deposit boron on one side of the silicon wafer 1 to form a P+ emitter 2. For the structure of the resulting intermediate product, please refer to Figure 2 ;
[0165] Sc: Polish the other side of the silicon wafer 1 so that one side of the silicon wafer 1 is the textured surface 2 and the other side is the polished surface. For the structure of the resulting intermediate product, please refer to Figure 3 ;
[0166] Sd: Prepare a tunneling oxide layer 3 on the polished other side of the silicon wafer 1. For the structure of the resulting intermediate product, please refer to Figure 4 ;
[0167] Se: Deposit and prepare a 50-nm-thick phosphorus-doped polysilicon layer 4 on the tunneling oxide layer 3. For the structure of the resulting intermediate product, please refer to Figure 5 ;
[0168] Sf: Form a selective heavy doping region 8 by screen-printing phosphorus-silicon paste and then annealing. For the structure of the resulting intermediate product, please refer to Figure 6 ;
[0169] Sg: The AlOx passivation layers 51 and 52 are formed by atomic deposition. For the structure of the resulting intermediate product, please refer to Figure 7 ;
[0170] Sh: The double-sided SiNx antireflection layers 61 and 62 are formed by PECVD. For the structure of the resulting intermediate product, please refer to Figure 8 ;
[0171] Si: The metal electrodes 7 are formed by screen printing silver paste.
[0172] Among them, in step Se, the phosphorus-silicon paste is made by vacuum ball milling nano-silicon powder, phosphorus pentoxide, and methanol in a mass ratio of 1:8:1, and then dispersed in methyl pentanol.
[0173] This embodiment also provides a solar cell prepared by the above method. Please refer to Figure 9 , and the solar cell includes:
[0174] A silicon wafer 1, one side of the silicon wafer 1 is a textured surface, and the other side is a polished surface;
[0175] A tunneling oxide layer 3, disposed on the polished surface;
[0176] A lightly doped polysilicon thin film 4, disposed on the tunneling oxide layer 3;
[0177] A selective heavily doped region 8, disposed on the lightly doped polysilicon thin film 4;
[0178] A first antireflection layer, disposed on the polysilicon thin film 4;
[0179] A first electrode 71, connected to the selective heavily doped region 8 and extending to the surface of the first antireflection layer 61;
[0180] A boron-doped layer 2, disposed on the textured surface;
[0181] AlOx passivation layers 51 and 52, respectively disposed on the boron-doped layer 2 and the polysilicon thin film 4;
[0182] A second antireflection layer 62, disposed on the passivation layer 52;
[0183] A second electrode 72, connected to the boron-doped layer 2 and extending to the surface of the second antireflection layer 62.
[0184] Example 2
[0185] The difference between this embodiment and Example 1 is only that:
[0186] In step Sf, the ratio of nanosilicon to phosphorus pentoxide in the printed phosphorus-silicon paste is different, and the ratio of nanosilicon to phosphorus pentoxide is 1:9.
[0187] Example 3
[0188] The difference between this example and Example 1 is only that:
[0189] In step Sf, the ratio of nanosilicon to phosphorus pentoxide in the printed phosphorus-silicon paste is different, and the ratio of nanosilicon to phosphorus pentoxide is 1:19.
[0190] Comparative example
[0191] The difference between this comparative example and Example 1 is only that:
[0192] Step Sf is not carried out.
[0193] Relevant experiments and effect data:
[0194] Test the short-circuit voltage of the solar cells obtained in Examples 1 to 3 and the comparative example. The test results are shown in Table 1:
[0195] Table 1
[0196] Example 1 Example 2 Example 3 Comparative Example 1 Isc (mA) 14.29 14.32 14.33 14.26
[0197] It can be found from Table 1 that the short-circuit voltages of Examples 1 to 3 are significantly higher than those of the comparative example. This shows that the selective re-doping region prepared by the phosphorus-silicon paste in this application is beneficial to improving the performance of solar cells.
[0198] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any recited number (fraction or integer) within the indicated range.
[0199] In this application, unless otherwise specified, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the attached drawings. Additionally, in the description of the specification of this application, the terms "include", "comprise", etc. mean "include but not limited to". Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising..." does not exclude the existence of additional identical elements in the process, method, article or device comprising said element. In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that these three associated objects can exist alone in any one item, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can represent that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this text, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one item (piece) below" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one item (piece) among a, b, or c", or, "at least one item (piece) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.
[0200] The above are only specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.
Claims
1. A solar cell with a selective phosphorus doping structure, characterized in that: The solar cell with a selective phosphorus doping structure comprises: n-type silicon-based; A tunneling oxide layer disposed on the back surface of the n-type silicon substrate; A phosphorus-doped polysilicon layer is disposed on the surface of the tunnel oxide layer, wherein the surface of the phosphorus-doped polysilicon layer is divided into a heavily doped region and a lightly doped region, and the phosphorus atom doping concentration of the heavily doped region is higher than that of the lightly doped region; A first passivation layer disposed on the surface of the lightly doped region; A first anti-reflection layer disposed on the surface of the first passivation layer; A first electrode is disposed on the surface of the heavily doped region, wherein one side of the first electrode is in ohmic contact with the heavily doped region, and the other side of the first electrode protrudes from the surface of the first anti-reflection layer.
2. The solar cell with a selective phosphorus doping structure according to claim 1, characterized in that: The phosphorus atom doping concentration of the lightly doped region is 1E+19; and / or, The phosphorus atom doping concentration in the heavily doped region is 5E+20.
3. The solar cell with a selective phosphorus doping structure according to claim 1, characterized in that: The solar cell with a selective phosphorus doping structure further comprises: A boron-doped oxide layer disposed on the front surface of the n-type silicon substrate; A second passivation layer disposed on the surface of the boron-doped oxide layer; A second anti-reflection layer disposed on the surface of the second passivation layer; A second electrode, one side of the second electrode is in ohmic contact with the boron-doped oxide layer, and the other side of the second electrode protrudes from the surface of the second anti-reflection layer.
4. The solar cell with a selective phosphorus doping structure according to claim 3, characterized in that: The material of the first passivation layer is aluminum oxide; and / or, The material of the second passivation layer is aluminum oxide; and / or, The material of the first anti-reflection layer is silicon nitride; and / or, The material of the second anti-reflection layer is silicon nitride.
5. The solar cell with a selective phosphorus doping structure according to claim 3, characterized in that: The thickness of the tunnel oxide layer is 1-2 nm; and / or, The thickness of the phosphorus-doped polysilicon layer is 10 to 50 nm; and / or, The thickness of the boron-doped oxide layer is 30 to 150 nm; and / or, The thickness of the first passivation layer is 5 to 20 nm; and / or, The thickness of the second passivation layer is 5 to 20 nm; and / or, The thickness of the first anti-reflection layer is 20-100 nm; and / or, The thickness of the second anti-reflection layer is 20-100 nm.