P + emitter, solar cell comprising P + emitter and preparation method of solar cell

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a P + emitter, a solar cell containing the P + emitter and a preparation method. According to the preparation method of the P + emitter provided by the invention, a BSG, namely a first film layer and a second film layer, is deposited in a layered manner by adopting a low-temperature deposition means; wherein the first film layer is a doped layer with a boron source, and the thickness of the first film layer is small, so that the consumption of special gas used in the preparation process is small, the second film layer is a silicon dioxide layer, special gas is not needed in the preparation process, and the deposition rate is high; on the basis, the time consumption and the cost of the whole process can be reduced; in addition, the first film layer and the second film layer are two mutually independent functional layers, so that the flexibility of process and debugging is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a P+ emitter, a solar cell containing the P+ emitter, and a preparation method thereof. Background Art

[0002] With the development of the photovoltaic industry, the conversion efficiency of crystalline silicon solar cells has been continuously improved, gradually approaching the theoretical limit. In the future, if the efficiency of cells is to be further improved, better passivation of the contact area is needed, especially for P-type contacts, which are traditionally more difficult to passivate than N-type contacts.

[0003] Conventional means to improve the passivation level of the contact area include selective emitters or surface fields, which can achieve lower contact recombination by increasing the local doping concentration. However, traditional P-type selective emitters generally use high-temperature boron diffusion, with temperatures exceeding 1000°C. This not only takes a long time, but also has high process costs due to energy consumption and quartz component loss, which is one of the important obstacles to reducing the non-silicon cost of solar cells.

[0004] In recent years, many research institutions have tried to use borosilicate glass (BSG) layers deposited at low temperatures such as APCVD and PECVD as boron sources, supplemented by masking, etching, or laser doping and other graphical methods to prepare selective emitters. Laser doping has the advantages of less time consumption, flexible patterns, and local heating of silicon wafers. However, unlike the BSG layer deposited at high temperature, the BSG layer deposited at low temperature has a lower boron content and film thickness, which also brings challenges to the subsequent laser process selection, and it is difficult to achieve low-damage local doping. If the low-temperature deposited BSG layer needs to reach the thickness of the high-temperature deposited BSG layer, it will result in higher process time and special gas (TMB, etc.) costs. Summary of the invention

[0005] 1. Problem to be solved In view of at least one of the above problems, one of the objectives of the present invention is to provide a method for preparing a P+ emitter; At the same time, the present invention also provides a P+ emitter prepared by the method; The front structure of the solar cell and the preparation process of the solar cell.

[0006] 2. Technical solution In order to solve the problems pointed out in the above background technology, the technical solution provided by the present invention is: A first aspect of the present invention provides a method for preparing a P+ emitter, comprising: 1) forming a first film layer on the surface of a silicon wafer by low temperature deposition, wherein the first film layer contains boron-doped amorphous silicon; Wherein, the temperature of the low temperature deposition does not exceed 600°C; 2) forming a second film layer on the surface of the silicon wafer by low temperature deposition, wherein the second film layer is a silicon oxide layer; Wherein, the temperature of the low temperature deposition does not exceed 600°C; 3) performing laser treatment on the surface of the silicon wafer to form a heavily doped boron region in the laser treated area; 4) etching the laser-treated area on the surface of the silicon wafer using an alkali-containing liquid; 5) etching the surface of the silicon wafer using an acid-containing liquid to remove the second film layer; 6) performing high temperature annealing treatment on the silicon wafer to oxidize the first film layer on the surface; 7) Etching the surface of the silicon wafer using an acid-containing liquid to remove silicon oxide formed at high temperature.

[0007] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 1), the temperature of the low-temperature deposition can be selected from any value within any of the following numerical ranges: 400-600°C, 400-550°C, 400-500°C, 400-450°C, 450-600°C, 500-600°C, 550-600°C.

[0008] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 1), the first film layer further contains silicon oxide.

[0009] Furthermore, in order to ensure the relative accuracy and controllability of the doping result achieved when the boron-doped amorphous silicon in the first film layer is used as a boron source (because the boron in the amorphous silicon in the first film layer will be preferentially doped with the silicon oxide in the first film layer), it is preferred that in the first film layer, the amount of the boron-doped amorphous silicon is not less than 70wt% when the sum of the boron-doped amorphous silicon and silicon oxide is 100wt%; Further preferably, the amount of the boron-doped amorphous silicon is 80-90wt%.

[0010] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 1), the thickness of the first film layer is 1-20 nm.

[0011] Preferably, the thickness of the first film layer is 5-15 nm.

[0012] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 1), a special gas is introduced, and the special gas includes trimethylboron (C3H9B, TMB) and / or diborane (B2H6).

[0013] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 1), the amount of the special gas used does not exceed 500 mL / tube; Preferably, the amount of special gas used is 200-400mL.

[0014] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 2), the temperature of the low-temperature deposition can be selected from any value within any of the following numerical ranges: 400-600°C, 400-550°C, 400-500°C, 400-450°C, 450-600°C, 500-600°C, 550-600°C.

[0015] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 2), the thickness of the second film layer is 10-200 nm.

[0016] Preferably, the second film layer has a thickness of 10-150 nm.

[0017] Further preferably, the thickness of the second film layer is 20-110 nm.

[0018] According to the method for preparing a P+ emitter according to any embodiment of the first aspect of the present invention, in step 3), the wavelength of the laser treatment is 300-1100 nm.

[0019] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, if the thickness of the second film layer is 10≤thickness≤40nm (hereinafter represented as [10-40] nm), the wavelength of the laser treatment in step 3) is 300-500nm; If the thickness of the second film layer is 40<thickness≤80nm (hereinafter referred to as (40-80]nm), the wavelength of the laser treatment in step 3) is 520~800nm; If the thickness of the second film layer is 80<thickness≤200nm (hereinafter referred to as (80-200]nm), the wavelength of the laser treatment in step 3) is 850-1100nm; For example, the wavelength of the laser processing and the thickness of the second film layer may have the following corresponding relationship:

[0020] According to the method for preparing a P+ emitter in any embodiment of the first aspect of the present invention, in step 3), other parameters of the laser processing include: Frequency: 500-100000kHz; Scanning speed: 0.1-100m / s.

[0021] Further, the frequency of the laser treatment can be selected from any value within any of the following numerical ranges: 500-10000kHz, 500-1000kHz, 500-100kHz, 1000-100000kHz, 2000-100000kHz, 3000-100000kHz, 4000-100000kHz, 5000-100000kHz, 10000-100000kHz, 50000-100000kHz; Further, the scanning speed of the laser treatment can be selected from any value within any of the following numerical ranges: 0.1-100m / s, 1-100m / s, 5-100m / s, 10-100m / s, 15-100m / s, 20-100m / s, 25-100m / s, 30-100m / s, 40-100m / s, 50-100m / s / s, 60-100m / s, 70-100m / s, 80-100m / s, 90-100m / s, 0.1-90m / s, 0.1-80m / s, 0.1-70m / s, 0.1-60m / s, 0.1-50m / s, 0.1-40m / s, 0.1-30m / s, 0.1-20m / s, 0.1-10m / s.

[0022] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 6), the annealing temperature ranges from 800 to 950° C., and the annealing time is from 0.2 to 1 hour.

[0023] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 6), the temperature of the high temperature annealing is controlled to be greater than or equal to 900°C, and the annealing time is greater than or equal to 0.8 hours, so as to form a lightly doped region of boron in the non-laser treated area.

[0024] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 6), the temperature of the high temperature annealing is controlled to be: 900°C≤temperature≤950°C (hereinafter expressed as [900-950]°C), and the annealing time is: 0.8≤annealing time≤1 hour (hereinafter expressed as [0.8-1] hour), and a lightly doped boron region is formed in the non-laser treated area.

[0025] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 6), if the temperature of the high temperature annealing is controlled to be less than 900°C, or the annealing time is less than 0.8 hours, a lightly doped region of boron will not be formed in the non-laser treated area.

[0026] According to the method for preparing a P+ emitter of any embodiment of the first aspect of the present invention, in step 6), the temperature of the high temperature annealing is controlled to be: 800°C≤temperature<900°C (hereinafter expressed as [800-900)°C), or the annealing time is: 0.2≤annealing time<0.8 hours (hereinafter expressed as [0.2-0.8) hours), and no lightly doped boron region is formed in the non-laser treated area.

[0027] According to the method for preparing a P+ emitter in any embodiment of the first aspect of the present invention, the boron doping surface concentration of the heavily boron doped region is 1e18-1e20cm -3 ; The boron doping junction depth of the boron heavily doped region is 200-2000nm; The sheet resistance of the heavily boron doped region is 20-200Ω / sq The square reflectivity of the heavily boron doped region is 12-18%; According to the method for preparing a P+ emitter in any embodiment of the first aspect of the present invention, the boron doping surface concentration of the lightly boron doped region is 1e17-1e19 cm -3 ; The boron doping junction depth of the lightly boron doped region is 50-500nm; The sheet resistance of the lightly boron doped region is 200-20000Ω / sq; The square reflectivity of the lightly boron-doped region is 8-14%.

[0028] It should be noted that the "lightly doped boron region" described herein is relative to the "heavily doped boron region", and the boron-doped surface concentration of the lightly doped boron region is lower than the boron-doped surface concentration of the heavily doped boron region; the boron-doped junction depth of the lightly doped boron region is lower than the boron-doped junction depth of the heavily doped boron region; the square resistance of the lightly doped boron region is greater than the square resistance of the heavily doped boron region; the reflectivity of the lightly doped boron region is lower than the reflectivity of the heavily doped boron region.

[0029] A second aspect of the present invention provides a P+ emitter, wherein the P+ emitter is prepared according to a method of any embodiment of the first aspect of the present invention.

[0030] A third aspect of the present invention provides a front structure of a TOPCon solar cell, wherein the front structure of the TOPCon solar cell comprises a layer structure, a P+ emitter and a front electrode; The P+ emitter is arranged on the front side of the silicon wafer substrate of the TOPCon solar cell, and the P+ emitter is prepared according to the method of any embodiment of the first aspect of the present invention; The layer structure comprises a front passivation layer and a front anti-reflection layer stacked on the front side of the silicon wafer substrate of the TOPCon solar cell; The front electrode contacts the heavily boron-doped region of the P+ emitter through the passivation layer and the anti-reflection layer.

[0031] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the boron doping surface concentration of the boron heavily doped region is 1e18-1e20cm -3 ; The boron doping junction depth of the boron heavily doped region is 200-2000nm; The sheet resistance of the heavily boron doped region is 20-200Ω / sq The square reflectivity of the heavily boron doped region is 12-18%; According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the boron doping surface concentration of the lightly boron doped region is less than the boron doping surface concentration of the heavily boron doped region; The boron doping junction depth of the lightly boron doped region is less than the boron doping junction depth of the heavily boron doped region; The sheet resistance of the lightly boron-doped region is greater than the sheet resistance of the heavily boron-doped region; The reflectivity of the lightly boron-doped region is lower than the reflectivity of the heavily boron-doped region.

[0032] Furthermore, the boron doping surface concentration of the lightly boron doped region is 1e17-1e19 cm -3 ; The boron doping junction depth of the lightly boron doped region is 50-500nm; The sheet resistance of the lightly boron doped region is 200-20000Ω / sq; The square reflectivity of the lightly boron-doped region is 8-14%.

[0033] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the front passivation layer is 1-10 nm.

[0034] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the front anti-reflection layer is 20-200 nm.

[0035] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the front passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0036] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the front anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0037] According to the front structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the front electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0038] A fourth aspect of the present invention provides a TOPCon solar cell, which comprises a back structure and a front structure of the TOPCon solar cell provided by any embodiment of the third aspect of the present invention.

[0039] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the back structure includes a tunneling oxide layer, a phosphorus-doped polysilicon layer, a back passivation layer, a back anti-reflection layer and a back electrode stacked on the back of the silicon wafer substrate of the TOPCon solar cell.

[0040] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the thickness of the tunneling oxide layer is 1-5 nm.

[0041] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the thickness of the phosphorus-doped polycrystalline silicon layer is 20-500 nm.

[0042] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the doping concentration of the phosphorus-doped polysilicon layer is 1e19-1e21cm -3 .

[0043] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the thickness of the back passivation layer is 1-10 nm.

[0044] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the thickness of the back anti-reflection layer is 20-200 nm.

[0045] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0046] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0047] According to the TOPCon solar cell of any embodiment of the fourth aspect of the present invention, the back electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0048] A fifth aspect of the present invention provides a back structure of a BC solar cell, the back structure of the BC solar cell comprising a layer structure, a P+ emitter and a back electrode; The P+ emitter is arranged on the back side of the silicon wafer substrate of the BC solar cell, and the P+ emitter is prepared according to the method of any embodiment of the first aspect of the present invention; The layer structure includes a back passivation layer and a back anti-reflection layer stacked on the back of the silicon wafer substrate of the BC solar cell; The back electrode passes through the passivation layer and the anti-reflection layer and contacts the heavily doped boron region of the P+ emitter.

[0049] According to the back structure of the BC solar cell of any embodiment of the fifth aspect of the present invention, the thickness of the back passivation layer is 1-10 nm.

[0050] According to the back structure of the BC solar cell of any embodiment of the fifth aspect of the present invention, the thickness of the back anti-reflection layer is 20-200 nm.

[0051] According to the back structure of the BC solar cell of any embodiment of the fifth aspect of the present invention, the back passivation layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0052] According to the back structure of the BC solar cell of any embodiment of the fifth aspect of the present invention, the back anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0053] According to the back structure of the BC solar cell of any embodiment of the fifth aspect of the present invention, the back electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0054] A sixth aspect of the present invention provides a BC solar cell, wherein the BC solar cell comprises a front structure and a back structure of the BC solar cell provided by any embodiment of the fifth aspect of the present invention.

[0055] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the front structure includes an N+ front surface field, a front passivation layer, a front anti-reflection layer and a front electrode arranged on the front side of the silicon wafer substrate of the BC solar cell.

[0056] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the thickness of the front passivation layer is 1-10 nm.

[0057] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the thickness of the front anti-reflection layer is 20-200 nm.

[0058] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0059] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0060] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the front electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0061] According to the BC solar cell of any embodiment of the sixth aspect of the present invention, the doping concentration of the N+ front surface field is 1e18-1e20cm -3 ; The junction depth is 100-1000nm.

[0062] Beneficial Effects (1) In the existing method of preparing the P+ emitter by using a low-temperature deposited borosilicate glass (BSG) layer as a boron source, supplemented by masking, etching, or laser doping and other graphic methods, the BSG layer deposited at low temperature cannot reach the thickness of the BSG layer deposited at high temperature, or to achieve the thickness of the BSG layer deposited at high temperature requires a long process time and special gases (TMB, etc.); The preparation method of the P+ emitter provided by the present invention adopts low-temperature deposition to deposit BSG in layers, namely, a first film layer and a second film layer; wherein the first film layer is a doped layer having a boron source, and the thickness of the first film layer is low, so the consumption of special gases (TMB, etc.) used in the preparation process is small, and the second film layer is a silicon dioxide layer, and no special gases are required in the preparation process, and the deposition rate is fast; Based on this, the time and cost of the overall process can be reduced; In addition, the first film layer and the second film layer are two independent functional layers, which increases the flexibility of process and debugging.

[0063] (2) In the method for preparing the P+ emitter provided by the present invention, the second film layer is used for optical matching and protection during the preparation process, and has the characteristic of adjustable optical performance to match the different parameters (wavelength, pulse width, etc.) of the subsequent laser, thereby minimizing the surface damage during the preparation process.

[0064] (3) In the method for preparing the P+ emitter provided by the present invention, the second film layer can also be used as a mask in the subsequent etching process to repair the damage in the laser area while protecting the doping layer in the non-laser area to avoid damage to the doping layer in the non-laser area.

[0065] (4) In the method for preparing the P+ emitter provided by the present invention, the first film layer is removed by high-temperature oxidation, which can not only further repair the laser damage, but also adjust the annealing temperature according to the needs of different battery structures to determine whether to form a P-type lightly doped layer in the non-laser area. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a P+ emitter structure with a lightly doped layer; Figure 2 A P+ emitter without a lightly doped layer; In the figure: 100, N-type base silicon wafer; 110, boron heavily doped region; 120, boron lightly doped region. DETAILED DESCRIPTION

[0067] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments. The structures, proportions, sizes, etc. illustrated in the accompanying drawings of this specification are only used to match the content disclosed in the specification, so that people familiar with this technology can understand and read, and are not used to limit the limiting conditions that the present invention can implement, so they have no technical substantive significance. Any structural modification, change in proportional relationship, or adjustment of size should still fall within the scope that the technical content disclosed by the present invention can cover without affecting the effect that the present invention can produce and the purpose that can be achieved. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and the like cited in this specification are also only for the convenience of narration, and are not used to limit the scope that can be implemented. The change or adjustment of its relative relationship should also be regarded as the scope that the present invention can implement without substantially changing the technical content.

[0068] Example 1 In this embodiment, if Figure 1 As shown, this embodiment provides a P+ emitter (P+-1); The P+ emitter provided in this embodiment can be applied to a TOPCon solar cell, especially the front structure of the TOPCon solar cell; Specifically, the P+ emitter provided in this embodiment includes a heavily doped boron region 110 and a lightly doped boron region 120 located on an N-type base silicon wafer 100; other relevant information is shown in Table 1 below: Table 1:

[0069] The method for preparing a P+ emitter (P+-1) provided by the present invention comprises the steps of: 1) forming a first film layer on the surface of a silicon wafer by low temperature deposition, wherein the first film layer contains boron-doped amorphous silicon and silicon oxide, and introducing special gas TMB / B2H6 during the low temperature deposition process; Wherein, the low temperature deposition method may be atmospheric pressure chemical vapor deposition (APCVD) or plasma enhanced chemical vapor deposition (PECVD); The temperature of the low temperature deposition is not more than 600°C, preferably the temperature of the low temperature deposition is 400-600°C, and more preferably the temperature of the low temperature deposition is 400-500°C; The amount of the boron-doped amorphous silicon is not less than 70wt% based on the total amount of the boron-doped amorphous silicon and silicon oxide being 100wt%. Preferably, the amount of the boron-doped amorphous silicon is 80-90wt%. The thickness of the first film layer is 1-20 nm; preferably, the thickness of the first film layer is 5-15 nm.

[0070] The special gas types include trimethylboron (C3H9B, TMB) and / or diborane (B2H6).

[0071] The amount of special gas used does not exceed 500mL / 500mL; preferably, the amount of special gas used is 200-400mL.

[0072] Specifically in this embodiment, to prepare a P+ emitter as shown in Table 1, the low-temperature deposition method in step 1) is plasma enhanced chemical vapor deposition (PECVD); The temperature of the plasma enhanced chemical vapor deposition (PECVD) is 450°C; The amount of the boron-doped amorphous silicon is 85wt% based on the sum of the boron-doped amorphous silicon and silicon oxide being 100wt%; The thickness of the first film layer is 10 nm; The type of special gas is TMB, and the usage is 250mL / 600 tablets (equivalent to 0.42mL / tablet).

[0073] 2) forming a second film layer on the surface of the silicon wafer by low temperature deposition, wherein the second film layer is a silicon oxide layer; Wherein, the low temperature deposition method may be atmospheric pressure chemical vapor deposition (APCVD) or plasma enhanced chemical vapor deposition (PECVD); The temperature of the low temperature deposition is not more than 600°C, preferably the temperature of the low temperature deposition is 400-600°C, and more preferably the temperature of the low temperature deposition is 400-500°C; The thickness of the second film layer is 10-200 nm; preferably, the thickness of the second film layer is 20-150 nm.

[0074] Specifically in this embodiment, to prepare a P+ emitter as shown in Table 1, the low-temperature deposition method in step 2) is plasma enhanced chemical vapor deposition (PECVD); The temperature of the plasma enhanced chemical vapor deposition (PECVD) is 450°C; The thickness of the second film layer is 100 nm; In summary, in this specific embodiment, after steps 1) and 2), a BSG layer similar to high-temperature boron diffusion is formed, which takes a total of 1 hour, and the amount of special gas TMB used is 250 mL; 3) performing laser treatment on the surface of the silicon wafer to form a heavily doped boron region in the laser treated area; Other parameters of the laser treatment include: Laser wavelength: 300-1100nm; Frequency: 10-100000kHz; Scanning speed: 0.1-100m / s; Specifically in this embodiment, to prepare a P+ emitter as shown in Table 1, the parameters of the laser processing in step 3) are: The wavelength of laser treatment is 1064nm; The frequency is 5000kHz; The scanning speed is 2.5m / s.

[0075] In fact, according to the different wavelengths of the laser used in step 3), the thickness of the second film layer in step 2) can be adjusted according to the following rules to achieve the best optical matching. If the thickness of the second film layer is 10≤thickness≤40nm (hereinafter represented as [10-40] nm), the wavelength of the laser treatment in step 3) is 300-500nm; If the thickness of the second film layer is 40<thickness≤80nm (hereinafter referred to as (40-80]nm), the wavelength of the laser treatment in step 3) is 520~800nm; If the thickness of the second film layer is 80<thickness≤200nm (hereinafter referred to as (80-200]nm), the wavelength of the laser treatment in step 3) is 850-1100nm; For example, the wavelength of the laser processing and the thickness of the second film layer may have a corresponding relationship as shown in Table 2 below: Table 2:

[0076] 4) etching the laser-treated area of ​​the silicon wafer surface with an alkali-containing liquid to remove the surface loss caused by the laser treatment; The etching may be wet etching, that is, etching in an alkali solution or a mixed solution of alkali and hydrogen peroxide to remove surface damage in the laser area, with the concentration of the alkali solution being 10-60%; Specifically in this embodiment, in order to prepare a P+ emitter as shown in Table 1, an alkali solution is used for etching to remove surface damage in the laser area, and the concentration of the alkali solution is 25wt%; the single-sided thinning amount after completion is 100nm.

[0077] 5) etching the surface of the silicon wafer using an acid-containing liquid to remove the second film layer; The etching may be performed using hydrofluoric acid, with a hydrofluoric acid concentration of 1-50%; Specifically in this embodiment, in order to prepare a P+ emitter as shown in Table 1, hydrofluoric acid is used for etching, and the concentration of the hydrofluoric acid is 10wt%.

[0078] 6) performing high temperature annealing treatment on the silicon wafer to oxidize the first film layer on the surface; The annealing temperature range is 800-950°C, and the annealing time is 0.2-1 hour; The temperature of the high temperature annealing is controlled to be greater than or equal to 900°C, and the annealing time is greater than or equal to 0.8 hours, so that a lightly doped region of boron is formed in the non-laser processed area. Preferably, the temperature of the high temperature annealing is controlled to be 900°C≤high temperature annealing temperature≤950°C, and the annealing time is 0.8≤annealing time≤1 hour, so that a lightly doped region of boron can be formed in the non-laser processed area.

[0079] Based on the above treatment, the boron doping surface concentration of the heavily doped boron region of the P+ emitter can be controlled to be 1e18-1e20cm -3 ; The boron doping junction depth of the heavily boron doped region is 200-2000nm; the square resistance of the heavily boron doped region is 20-200Ω / sq; the square reflectivity of the heavily boron doped region is 12-18%; The boron doping surface concentration of the lightly boron doped region of the P+ emitter is 1e17-1e19 cm -3 ; The boron doping junction depth of the lightly boron doped region is 50-500nm; the square resistance of the lightly boron doped region is 200-20000Ω / sq; the square reflectivity of the lightly boron doped region is 8-14%.

[0080] However, it should be made clear that for the same P+ emitter, the boron-doped surface concentration of the lightly boron-doped region is lower than the boron-doped surface concentration of the heavily boron-doped region; the boron-doped junction depth of the lightly boron-doped region is lower than the boron-doped junction depth of the heavily boron-doped region; the square resistance of the lightly boron-doped region is higher than the square resistance of the heavily boron-doped region; and the reflectivity of the lightly boron-doped region is lower than the reflectivity of the heavily boron-doped region.

[0081] If the temperature of the high temperature annealing is controlled to be less than 900°C, or the annealing time is less than 0.8 hours, no lightly doped region of boron is formed in the non-laser processed area. Preferably, the temperature of the high temperature annealing is controlled to be 800°C≤high temperature annealing temperature<900°C, and the annealing time is 0.2≤annealing time<0.8 hours, and no lightly doped region of boron is formed in the non-laser processed area.

[0082] Specifically in this embodiment, in order to prepare a P+ emitter having a lightly boron-doped region 120 as shown in Table 1, the temperature of the high temperature annealing is controlled to be 920° C., and the annealing time is 1 hour; 7) Etching the surface of the silicon wafer using an acid-containing liquid to remove silicon oxide formed at high temperature.

[0083] The etching may be performed using hydrofluoric acid, with a hydrofluoric acid concentration of 1-50%; Specifically in this embodiment, in order to prepare a P+ emitter as shown in Table 1, hydrofluoric acid is used for etching, and the concentration of the hydrofluoric acid is 10wt%.

[0084] Example 2 like Figure 2 As shown, this embodiment provides a P+ emitter (P+-2); The P+ emitter provided in this embodiment can be applied to a BC solar cell, especially the back structure of the BC solar cell; wherein the BC solar cell can be an IBC cell or a TBC cell; Specifically, the P+ emitter provided in this embodiment includes a heavily doped region 110 of boron located in an N-type base silicon wafer 100 , and does not have a lightly doped region 120 of boron; other relevant information is the same as Table 1 of Embodiment 1.

[0085] In addition, the preparation method of the P+ emitter in this embodiment is basically the same as that in Embodiment 1, the only difference being step 6): Specifically in this embodiment, in order to prepare a P+ emitter substantially as shown in Table 1 but without the lightly doped region 120 of boron, the temperature of the high temperature annealing is controlled to be 850° C. and the annealing time is 0.5 hours.

[0086] Example 3 like Figure 1 As shown, the P+ emitter (P+-1) provided in this embodiment has the same related information as Table 1 of Embodiment 1.

[0087] The only difference is the preparation method. The preparation method of the P+ emitter in this embodiment is basically the same as that in Embodiment 1, except that the parameters of the laser treatment in step 3) are: The wavelength of the laser treatment is different from that in Example 1. The laser wavelength in this example is 532 nm. The frequency is 500kHz; The scanning speed is 2.5m / s.

[0088] Comparative Example 1 In this comparative example, the conventional high temperature boron diffusion method is used to prepare the P+ emitter (P+-1) of Example 1; Specifically, the preparation method of the P+ emitter (P+-1) in this embodiment is as follows: 1) forming a boron-containing film layer on the surface of a silicon wafer by high-temperature thermal diffusion; a special gas containing the boron element is introduced during the deposition process; The special gas type is boron tribromide (BBr3) or boron trichloride (BCl3), and the usage amount is 1.5-2mL / piece.

[0089] 2) laser processing is performed on the surface of the silicon wafer after the boron diffusion to form a heavily doped boron region in the laser processed region; the laser processing conditions are the same as those in Example 1; 3) Place the laser-treated sample into a tube furnace for high-temperature oxidation treatment; 5) BSG removal and polishing: the sample is passed through an HF chain cleaning tank to remove the BSG on the back side, and then enters a mixed solution of NaOH and polishing additives to remove the back junction and perform back polishing. In step 1) and step 3) of this comparative example, in order to prepare BSG with a thickness as in Example 1 of the present invention, the total high-temperature process time is 5-6 hours, the process temperature is up to 1050 degrees, and the amount of special gas BBr3 / BCl3 used is 900~1200mL / 600 pieces (equivalent to 1.5-2mL / piece), which is far more than the level of Example 1.

[0090] Example 4 In this embodiment, a front structure of a solar cell including a P+ emitter (P+-1) prepared in Embodiment 1 is provided, and a front structure of a TOPCon solar cell is provided. The front structure of the TOPCon solar cell includes a layer structure, a P+ emitter and a front electrode; The P+ emitter is arranged on the front side of the silicon wafer substrate of the TOPCon solar cell, and the P+ emitter is the P+ emitter (P+-1) prepared in Example 1; The layer structure comprises a front passivation layer and a front anti-reflection layer stacked on the front side of the silicon wafer substrate of the TOPCon solar cell; The front electrode contacts the heavily boron-doped region of the P+ emitter through the passivation layer and the anti-reflection layer.

[0091] The thickness of the front passivation layer is 1-10 nm, and the front passivation layer includes any one, two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0092] The thickness of the front anti-reflection layer is 20-200 nm, and the front anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0093] The front electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0094] Example 5 In this embodiment, a solar cell including the P+ emitter (P+-1) prepared in Embodiment 1 is provided; a TOPCon solar cell having a front side structure and a back side structure.

[0095] The front structure includes a layer structure, a P+ emitter and a front electrode; The P+ emitter is arranged on the front side of the silicon wafer substrate of the TOPCon solar cell, and the P+ emitter is the P+ emitter (P+-1) prepared in Example 1; The layer structure comprises a front passivation layer and a front anti-reflection layer stacked on the front side of the silicon wafer substrate of the TOPCon solar cell; The front electrode contacts the heavily boron-doped region of the P+ emitter through the passivation layer and the anti-reflection layer.

[0096] The thickness of the front passivation layer is 1-10 nm, and the front passivation layer includes any one, two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0097] The thickness of the front anti-reflection layer is 20-200 nm, and the front anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0098] The front electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0099] The back structure includes a tunneling oxide layer, a phosphorus-doped polysilicon layer, a back passivation layer, a back anti-reflection layer, and a back electrode stacked on the back of the silicon wafer substrate of the TOPCon solar cell. The thickness of the tunneling oxide layer is 1-5nm. The thickness of the phosphorus-doped polysilicon layer is 20-500nm, and the doping concentration of the phosphorus-doped polysilicon layer is 1e19-1e21cm -3. The thickness of the back passivation layer is 1-10nm, and the passivation layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, and silicon carbide); for example, the passivation layer is an aluminum oxide layer. The thickness of the back anti-reflection layer is 20-200nm, and the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, and silicon carbide); for example, the anti-reflection layer is a silicon nitride layer. The back electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0100] Example 6 In this embodiment, a back structure of a BC solar cell containing a P+ emitter (P+-1) prepared in Embodiment 1 is provided, wherein the back structure of the BC solar cell comprises a layer structure, a P+ emitter and a back electrode; The P+ emitter is arranged on the back side of the silicon wafer substrate of the TOPCon solar cell, and the P+ emitter is the P+ emitter (P+-1) prepared in Example 1; The layer structure includes a back passivation layer and a back anti-reflection layer stacked on the back of the silicon wafer substrate of the BC solar cell; The back electrode passes through the passivation layer and the anti-reflection layer and contacts the heavily doped boron region of the P+ emitter.

[0101] The thickness of the back passivation layer is 1-10 nm, and the back passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0102] The thickness of the back anti-reflection layer is 20-200 nm, and the back anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0103] The back electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0104] Example 7 In this embodiment, a BC solar cell containing the P+ emitter (P+-1) prepared in Embodiment 1 is provided. The BC solar cell has a front side structure and a back side structure.

[0105] The back structure of the BC solar cell includes a layer structure, a P+ emitter and a back electrode; The P+ emitter is arranged on the back side of the silicon wafer substrate of the TOPCon solar cell, and the P+ emitter is the P+ emitter (P+-1) prepared in Example 1; The layer structure includes a back passivation layer and a back anti-reflection layer stacked on the back of the silicon wafer substrate of the BC solar cell; The back electrode passes through the passivation layer and the anti-reflection layer and contacts the heavily doped boron region of the P+ emitter.

[0106] The thickness of the back passivation layer is 1-10 nm, and the back passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0107] The thickness of the back anti-reflection layer is 20-200 nm, and the back anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0108] The back electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0109] The front structure includes an N+ front surface field, a front passivation layer, a front anti-reflection layer and a front electrode arranged on the front of the silicon wafer substrate of the BC solar cell. The thickness of the front passivation layer is 1-10nm, and the passivation layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, and silicon carbide); for example, the passivation layer is an aluminum oxide layer. The thickness of the front anti-reflection layer is 20-200nm, and the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, and silicon carbide); for example, the anti-reflection layer is a silicon nitride layer. The front electrode is a metal electrode, and the metal electrode includes any one or two or more of silver electrode, copper electrode, aluminum electrode, tin-clad copper electrode, and silver-clad copper electrode. The doping concentration of the N+ front surface field is 1e18-1e20cm -3 , the junction depth is 100-1000nm.

[0110] Example 8 In this embodiment, the following solar cells containing the P+ emitter (P+-2) prepared in Example 2 are provided; IBC solar cell, in particular, the back structure of the IBC solar cell has the P+ emitter (P+-2); The TBC solar cell, in particular the back structure of the TBC solar cell has the P+ emitter (P+-2).

[0111] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a P+ emitter, characterized in that: include: 1) forming a first film layer on the surface of a silicon wafer by low temperature deposition, wherein the first film layer contains boron-doped amorphous silicon; Wherein, the temperature of the low temperature deposition does not exceed 600°C; 2) forming a second film layer on the surface of the silicon wafer by low temperature deposition, wherein the second film layer is a silicon oxide layer; Wherein, the temperature of the low temperature deposition does not exceed 600°C; 3) performing laser treatment on the surface of the silicon wafer to form a heavily doped boron region in the laser treated area; 4) etching the laser-treated area on the surface of the silicon wafer using an alkali-containing liquid; 5) etching the surface of the silicon wafer using an acid-containing liquid to remove the second film layer; 6) performing high temperature annealing treatment on the silicon wafer to oxidize the first film layer on the surface; 7) Etching the surface of the silicon wafer using an acid-containing liquid to remove silicon oxide formed at high temperature.

2. The method for preparing a P+ emitter according to claim 1, characterized in that: In step 1), the temperature of the low temperature deposition is 400-600°C; And / or, in step 2), the temperature of the low temperature deposition is 400-600°C.

3. The method for preparing a P+ emitter according to claim 2, characterized in that: In step 1), the temperature of the low temperature deposition is 400-500°C; And / or, in step 2), the temperature of the low temperature deposition is 400-500°C.

4. The method for preparing a P+ emitter according to any one of claims 1 to 3, characterized in that: In step 1), the thickness of the first film layer is 1-20 nm; And / or, in step 2), the thickness of the second film layer is 10-200 nm.

5. The method for preparing a P+ emitter according to any one of claims 1 to 3, characterized in that: In step 1), the first film layer further contains silicon oxide; Based on the sum of the boron-doped amorphous silicon and silicon oxide being 100 wt %, the amount of the boron-doped amorphous silicon is not less than 70 wt %.

6. The method for preparing a P+ emitter according to claim 5, characterized in that: In step 3), the wavelength of the laser treatment is 300-1100 nm.

7. The method for preparing a P+ emitter according to claim 6, characterized in that: If the thickness of the second film layer is 10≤thickness≤40nm, the wavelength of the laser treatment in step 3) is 300-500nm; If the thickness of the second film layer is 40<thickness≤80nm, the wavelength of the laser treatment in step 3) is 520~800nm; If the thickness of the second film layer is 80<thickness≤200nm, the wavelength of the laser treatment in step 3) is 850-1100nm.

8. The method for preparing a P+ emitter according to any one of claims 6 to 7, characterized in that: In step 6), the temperature range of the high temperature annealing is 800-950° C., and the annealing time is 0.2-1 hour.

9. The method for preparing a P+ emitter according to claim 8, characterized in that: In step 6), the temperature of the high temperature annealing is controlled to be greater than or equal to 900° C., and the annealing time is greater than or equal to 0.8 hours.

10. The method for preparing a P+ emitter according to claim 8, characterized in that: In step 6), the temperature of the high temperature annealing is controlled to be less than 900°C; and / or, The annealing time of the high temperature annealing is controlled to be less than 0.8 hours.

11. The method for preparing a P+ emitter according to claim 8, characterized in that: The boron doping surface concentration of the heavily boron doped region is 1e18-1e20cm -3 ; And / or, the boron doping junction depth of the boron heavily doped region is 200-2000nm; And / or, the sheet resistance of the heavily boron doped region is 20-200Ω / sq.

12. P+ emitter, characterized in that: The P+ emitter is prepared according to the method for preparing a P+ emitter according to any one of claims 1 to 11.

13. A front structure of a solar cell having a P+ emitter, characterized in that: The P+ emitter is prepared according to the method for preparing a P+ emitter according to any one of claims 1 to 11.

14. A back structure of a solar cell having a P+ emitter, characterized in that: The P+ emitter is prepared according to the method for preparing a P+ emitter according to any one of claims 1 to 11.

15. A solar cell having a P+ emitter, characterized in that: The P+ emitter is prepared according to the method for preparing a P+ emitter according to any one of claims 1 to 11.

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