A solar cell and a method for manufacturing a solar cell

Abstract

The application relates to a solar cell and a preparation method of the solar cell, and belongs to the technical field of photovoltaics. The solar cell comprises at least a substrate, a tunneling oxide layer, a tin oxide layer and a doped polysilicon layer. The tunneling oxide layer is arranged on the surface of the substrate along the thickness direction of the substrate. The tin oxide layer is arranged on the surface of the tunneling oxide layer along the thickness direction of the substrate. The doped polysilicon layer is arranged on the surface of the tin oxide layer along the thickness direction of the substrate, so that the tin oxide layer is located between the tunneling oxide layer and the doped polysilicon layer. The ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer satisfies 1.9<=F<=2.1. The tin oxide layer is arranged between the tunneling oxide layer and the doped polysilicon layer. Since the tin oxide layer has excellent conductivity and light transmittance, parasitic absorption is reduced, more light can be absorbed by the substrate, and the photoelectric conversion efficiency of the solar cell is improved.

Description

Technical Field

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

[0002] Currently, the addition of passivation contacts to solar cells can effectively improve the passivation effect and the photovoltaic conversion efficiency of solar cells. Passivation contact structures typically include a passivation layer and a doping layer. However, the doping layer in the passivation contact structure suffers from severe parasitic absorption, i.e., non-ideal absorption of light. This reduces the solar cell's light utilization, thereby affecting the solar cell's photovoltaic conversion efficiency. Summary of the Invention

[0003] The present application provides a solar cell and a method for preparing the solar cell, which are used to solve the problem of parasitic absorption in solar cells.

[0004] In a first aspect, the present application provides a solar cell, the solar cell comprising at least:

[0005] substrate;

[0006] a tunneling oxide layer, arranged on the surface of the substrate along the thickness direction of the substrate;

[0007] a tin oxide layer, disposed on a surface of the tunneling oxide layer along a thickness direction of the substrate;

[0008] a doped polysilicon layer, wherein the doped polysilicon layer is disposed on a surface of the tin oxide layer along a thickness direction of the substrate so that the tin oxide layer is located between the tunneling oxide layer and the doped polysilicon layer;

[0009] The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer satisfies: 1.9≤F≤2.1.

[0010] In this solution, a tin oxide layer is disposed between the tunneling oxide layer and the doped polysilicon layer. Because the optical band gap of the tin oxide layer is smaller than that of the doped polysilicon layer, i.e., the tin oxide layer has weaker absorption of visible light, the tin oxide layer has good light transmittance. By appropriately thinning the doped polysilicon layer and depositing the tin oxide layer between the tunneling oxide layer and the doped polysilicon layer, parasitic absorption and non-ideal absorption of light are reduced, allowing more light to be absorbed by the substrate, thereby improving the short-circuit current density of the solar cell and the photovoltaic conversion efficiency of the solar cell. Furthermore, because the refractive index of the tin oxide layer is between that of the tunneling oxide layer and the doped polysilicon layer, the doped polysilicon layer, tin oxide layer, and tunneling oxide layer form a three-layer structure with a refractive gradient, which helps reduce reflection at the interface and increase light transmittance, allowing the substrate to absorb more light energy. In addition, the tin oxide layer has good conductivity, so that the tin oxide layer can serve as an electron transport layer, and then through the combination of the tin oxide layer and the tunneling oxide layer, it helps to improve the carrier transmission efficiency, reduce the recombination of carriers, improve the passivation performance of the solar cell, and help reduce the contact resistivity, thereby improving the photoelectric conversion efficiency of the solar cell.

[0011] When 1.9≤F≤2.1 is satisfied, it is close to the stoichiometric ratio, which is beneficial to reducing oxygen vacancy defects in the tin oxide layer and balancing the conductivity and chemical stability of the tin oxide layer, thereby reducing the risk of carrier recombination and improving the passivation performance. At the same time, it is beneficial to reduce the risk of generating inactive oxides in the tin oxide layer, thereby improving the electron transmission efficiency, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0012] In this solution, the sum of the contact resistivity of the solar cell ρc1 satisfies: 5mΩcm 2 ≤ρc1≤10mΩcm 2 .

[0013] In this solution, the oxygen vacancy concentration λ in the tin oxide layer satisfies: 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 .

[0014] In this solution, along the thickness direction of the substrate, the thickness D1 of the tunneling oxide layer satisfies: 1nm≤D1≤2nm, the thickness D2 of the tin oxide layer satisfies: 1nm≤D2≤100nm, and the thickness D3 of the doped polysilicon layer satisfies: 1nm≤D3≤100nm.

[0015] In this solution, the phosphorus doping concentration α of the tunnel oxide layer satisfies: 1×10 13 cm -3 ≤α≤1×1016 cm -3 , the phosphorus doping concentration β of the tin oxide layer satisfies: 1×10 15 cm -3 ≤β≤1×10 20 cm -3 , the phosphorus doping concentration γ of the doped polysilicon layer satisfies: 1×10 19 cm -3 ≤γ≤1×10 21 cm -3 .

[0016] In this solution, the chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer satisfies: 2 Å≤L≤2.1 Å.

[0017] A second aspect of the present application provides a method for preparing a solar cell. The method is used to prepare the solar cell described above, and the method comprises at least the following steps:

[0018] cleaning the substrate;

[0019] Depositing the tunneling oxide layer on the surface of the substrate along the thickness direction;

[0020] Depositing the tin oxide layer on the surface of the tunneling oxide layer along the thickness direction with a ratio of the tin source flow amount to the oxygen source flow amount as S, satisfying: 0.2≤S≤0.5;

[0021] Depositing an amorphous silicon layer on the surface of the tin oxide layer along the thickness direction;

[0022] High temperature annealing and doping under the high temperature annealing condition to transform the amorphous silicon layer into the doped polysilicon layer.

[0023] In this embodiment, in the step of depositing the tin oxide layer, the method for preparing the solar cell further includes a cyclic deposition step, and the cyclic deposition step at least includes:

[0024] The tin source and nitrogen are introduced for a duration of T1, wherein the tin source is dimethylaminotin, the amount of the tin source introduced m1 satisfies: 0.1 mmol / min≤m1≤1 mmol / min, and the time T1 satisfies: 5s≤T1≤30s;

[0025] After the step of introducing the tin source is completed, the oxygen source and nitrogen are introduced for a duration of T2, wherein the oxygen source is oxygen gas, the introduction amount m2 of the oxygen source satisfies: 0.5mmol / min≤m2≤2mmol / min, and the time T2 satisfies: 5s≤T2≤30s.

[0026] In this embodiment, between the step of introducing the tin source and the step of introducing the oxygen source, and after the step of introducing the oxygen source is completed, the cyclic deposition step further includes:

[0027] Nitrogen is introduced for a duration of T3, wherein the nitrogen introduction amount m3 satisfies: 5 L / min≤m3≤10 L / min, and the time T3 satisfies: 10s≤T3≤60s.

[0028] In this solution, after completing the cyclic deposition step, the method for preparing a solar cell further comprises:

[0029] The tin oxide layer is heat-treated for a duration of T4, wherein the heat treatment temperature W satisfies: 100° C. ≤ W ≤ 300° C., and the heat treatment time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

[0030] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of a passivation contact structure in a solar cell provided in this application in a specific embodiment;

[0032] Figure 2 For preparation Figure 1 A diagram of steps in a specific embodiment of the passivation contact structure provided in FIG.

[0033] Figure 3 This is a flow chart of a specific embodiment of the method for preparing a solar cell provided in this application.

[0034] Description of reference numerals:

[0035] 1-substrate;

[0036] 2- tunneling oxide layer;

[0037] 3-tin oxide layer;

[0038] 4-amorphous silicon layer;

[0039] 5-Doped polysilicon layer.

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0041] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0042] In a specific embodiment, the present application is further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0043] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0045] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0046] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described based on the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it should be understood that when it is mentioned that an element is connected to another element "on" or "under", it can not only be directly connected to the other element "on" or "under", but also be indirectly connected to the other element "on" or "under" through an intermediate element.

[0047] The present application provides a solar cell, such as Figure 1 As shown, the solar cell at least includes a substrate 1 , a tunneling oxide layer 2 , a tin oxide layer 3 and a doped polysilicon layer 5 .

[0048] A tunneling oxide layer 2 is arranged on the surface of the substrate 1 along the thickness direction of the substrate 1, a tin oxide layer 3 is arranged on the surface of the tunneling oxide layer 2 along the thickness direction of the substrate 1, and a doped polysilicon layer 5 is arranged on the surface of the tin oxide layer 3 along the thickness direction of the substrate 1, so that the tin oxide layer 3 is located between the tunneling oxide layer 2 and the doped polysilicon layer 5.

[0049] The ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer 3 satisfies: 1.9≤F≤2.1.

[0050] In this embodiment, the tin oxide layer 3 is disposed between the tunneling oxide layer 2 and the doped polysilicon layer 5. Since the optical band gap of the tin oxide layer 3 is smaller than that of the doped polysilicon layer 5, that is, the tin oxide layer 3 has a weaker absorption of visible light, the tin oxide layer 3 has good light transmittance. By appropriately thinning the doped polysilicon layer 5 and depositing the tin oxide layer 3 between the tunneling oxide layer 2 and the doped polysilicon layer 5, it is beneficial to reduce parasitic absorption and reduce non-ideal absorption of light, so that more light can be absorbed by the substrate 1, which is beneficial to improving the short-circuit current density of the solar cell and improving the photoelectric conversion efficiency of the solar cell. At the same time, since the refractive index of the tin oxide layer 3 is between the refractive indexes of the tunneling oxide layer 2 and the doped polysilicon layer 5, the doped polysilicon layer 5, the tin oxide layer 3, and the tunneling oxide layer 2 form a three-layer structure with a refractive gradient, which is beneficial to reducing reflection at the interface and increasing the transmittance of light, so that the substrate 1 can absorb more light energy. In addition, the tin oxide layer 3 has good conductivity, so that the tin oxide layer 3 can serve as an electron transport layer, and then through the combination of the tin oxide layer 3 and the tunneling oxide layer 2, it helps to improve the carrier transmission efficiency, reduce the carrier recombination, improve the passivation performance of the solar cell, and help reduce the contact resistivity, thereby improving the photoelectric conversion efficiency of the solar cell.

[0051] In addition, the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 satisfies: 1.9≤F≤2.1. In some embodiments, F may be 1.9, 1.92, 1.94, 1.95, 1.96, 1.98, 2, or 2.1.

[0052] When 1.9≤F≤2.1 is satisfied, the number of oxygen atoms and tin atoms in the tin oxide layer 3 is closer to the stoichiometric ratio, so that the tin oxide layer 3 forms a relatively stable rutile structure, that is, the chemical bond strength between the tin oxide ions and oxygen ions in the formed tin oxide layer 3 is controlled to be higher, and the ionic radius of the tin ions is made moderate, which is more conducive to forming a compact crystal structure, improving the chemical structure stability of the tin oxide layer 3, and effectively inhibiting lattice expansion or contraction, and is conducive to reducing oxygen vacancy defects in the tin oxide layer 3, improving light transmittance, and thus balancing the conductivity and chemical stability of the tin oxide layer 3, thereby reducing the risk of carrier recombination and improving passivation performance. At the same time, it is conducive to reducing the risk of generating inactive oxides in the tin oxide layer 3, so as to improve electron transmission efficiency, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0053] In some possible embodiments, the substrate 1 may be made of any material selected from single crystal silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, copper indium gallium selenide, and perovskite. Preferably, in one possible implementation, the substrate 1 may be an N-type substrate, wherein the doping element may be selected from any one of phosphorus, arsenic, and antimony. In another possible implementation, the substrate 1 may be a P-type substrate, wherein the doping element may be selected from any one of boron, aluminum, gallium, and indium. In one possible implementation, as Figure 1 As shown, the solar cell ρc1 satisfies: 5mΩcm 2 ≤ρc1≤10mΩcm 2 In some embodiments, ρc1 may be 5 mΩ cm 2 , 6mΩcm 2 , 7mΩcm 2 , 8mΩcm 2 , 9mΩcm 2 , 10mΩcm 2 wait.

[0054] When 5mΩcm 2 ≤ρc1≤10mΩcm 2 When the contact resistivity of the solar cell is moderate, the contact resistivity of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 are all moderate. The high-mobility tin oxide layer 3 is disposed between the tunneling oxide layer 2 and the doped polysilicon layer 5, which can significantly reduce the interface resistance. At the same time, because the doped polysilicon layer 5 has good contact properties, it is beneficial to reduce the contact resistivity, reduce the interface recombination rate, and improve the extraction of carriers. It also helps to reduce the series resistance, thereby improving the fill factor and photoelectric conversion efficiency of the solar cell.

[0055] The contact resistivity of solar cells can be measured using the four-probe method. By measuring the current-voltage characteristics of electrodes with different spacings, the contact resistivity of the solar cell can be calculated. Alternatively, the transmission line model (TLM) can be used to calculate the contact resistivity of solar cells.

[0056] The oxygen vacancy concentration refers to the number of defects formed by the absence of oxygen atoms in a compound or material containing oxygen atoms. The oxygen vacancy concentration in the tin oxide layer 3 can be measured by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), Hall effect test, etc. In one possible embodiment, Figure 1 As shown, the oxygen vacancy concentration λ in the tin oxide layer 3 satisfies: 1×1015 cm -3 ≤λ≤1×10 18 cm -3 In some embodiments, λ may be 1×10 15 cm -3 , 2×10 15 cm -3 , 5×10 15 cm -3 , 6×10 15 cm -3 , 8×10 15 cm -3 , 1×10 16 cm -3 , 2×10 16 cm -3 , 5×10 16 cm -3 , 6×10 16 cm -3 , 8×10 16 cm -3 , 1×10 17 cm -3 , 2×10 17 cm -3 , 5×10 17 cm -3 , 6×10 17 cm -3 , 8×10 17 cm -3 , 1×10 18 cm -3 wait.

[0057] When 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 When the oxygen vacancy concentration λ in the tin oxide layer 3 is moderate, it is beneficial to improve the conductivity of the tin oxide layer 3, and is beneficial to promote the effective separation of photogenerated electrons and holes, reduce recombination, and at the same time, it is beneficial to reduce the absorption rate of oxygen vacancies in the tin oxide layer 3 to visible light with a wavelength in the range of 400nm-500nm, thereby effectively improving the transmittance of the tin oxide layer 3, thereby allowing more visible light to be absorbed by the substrate 1, and further improving the photoelectric conversion efficiency of the solar cell.

[0058] In one possible implementation, Figure 1 As shown, along the thickness direction of the substrate 1, the thickness D1 of the tunneling oxide layer 2 satisfies: 1nm≤D1≤2nm, the thickness D2 of the tin oxide layer 3 satisfies: 1nm≤D2≤100nm, and the thickness D3 of the doped polysilicon layer 5 satisfies: 1nm≤D3≤100nm.

[0059] In some embodiments, the thickness D1 of the tunnel oxide layer 2 may be 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, etc. The thickness D2 of the tin oxide layer 3 may be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc. The thickness D3 of the doped polysilicon layer 5 may be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc.

[0060] When D1 satisfies: 1nm≤D1≤2nm, D2 satisfies: 1nm≤D2≤100nm, and D3 satisfies: 1nm≤D3≤100nm, the thickness D1 of the tunneling oxide layer 2, the thickness D2 of the tin oxide layer 3, and the thickness D3 of the doped polysilicon layer 5 are all moderate, so that the three-layer structure composed of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 has a low contact resistivity, and is conducive to balancing the passivation effect and the carrier transport efficiency, reducing the interface recombination rate, and making the structure have a good quantum tunneling effect, that is, increasing the tunneling probability of carriers tunneling through the tunneling oxide layer 2 to the substrate 1, thereby facilitating an increase in the current density of the solar cell.

[0061] In one possible implementation, Figure 1 As shown, the phosphorus doping concentration α of the tunnel oxide layer 2 satisfies: 1×10 13 cm -3 ≤α≤1×10 16 cm -3 , the phosphorus doping concentration β of the tin oxide layer 3 satisfies: 1×10 15 cm -3 ≤β≤1×10 20 cm -3 , the phosphorus doping concentration γ of the doped polysilicon layer 5 satisfies: 1×10 19 cm -3 ≤γ≤1×10 21 cm -3 In some embodiments, the phosphorus doping concentration α of the tunnel oxide layer 2 may be 1×10 13 cm -3 , 5×10 13 cm -3 , 1×10 14 cm -3 , 5×10 14 cm -3 , 1×10 15 cm -3 , 5×1015 cm -3 , 1×10 16 cm -3 The phosphorus doping concentration β of the tin oxide layer 3 can be 1×10 15 cm -3 , 5×10 15 cm -3 , 1×10 16 cm -3 , 5×10 16 cm -3 , 1×10 17 cm -3 , 5×10 17 cm -3 , 1×10 18 cm -3 , 5×10 18 cm -3 , 1×10 19 cm -3 , 5×10 19 cm -3 , 1×10 20 cm -3 The phosphorus doping concentration γ of the doped polysilicon layer 5 can be 1×10 19 cm -3 , 5×10 19 cm -3 , 1×10 20 cm -3 , 5×10 20 cm -3 , 1×10 21 cm -3 wait.

[0062] In this embodiment, when the phosphorus doping concentration α of the tunnel oxide layer 2 satisfies: 1×10 13 cm -3 ≤α≤1×10 16 cm -3 When the phosphorus doping concentration β of the tin oxide layer 3 satisfies: 1×10 15 cm -3 ≤β≤1×10 20 cm -3 When the phosphorus doping concentration in the tin oxide layer 3 is moderate, the conductivity of the tin oxide layer 3 is moderate, the tin oxide layer 3 has good carrier mobility, and the tin oxide layer 3 has good light transmittance, which is conducive to the substrate 1 absorbing more light energy. The phosphorus doping concentration γ of the doped polysilicon layer 5 satisfies: 1×10 19 cm-3 ≤γ≤1×10 21 cm -3 When the charge carrier concentration is increased, the conductivity is improved.

[0063] Therefore, when the phosphorus doping concentrations of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 all meet the above ranges, it helps to reduce the energy loss when the current in the solar cell passes through the electrode and the doped polysilicon layer 5 and the tin oxide layer 3, reduces parasitic absorption, and at the same time enables the tunneling oxide layer 2 to have good carrier selective transmission performance, promotes the separation of carriers in the substrate 1, thereby improving the photoelectric conversion efficiency of the substrate 1, and further improving the photoelectric conversion efficiency of the solar cell.

[0064] In one possible implementation, Figure 1 As shown, the chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer 3 satisfies: 2 Å ≤ L ≤ 2.1 Å. In some embodiments, the chemical bond distance L may be 2.00 Å, 2.01 Å, 2.02 Å, 2.03 Å, 2.04 Å, 2.05 Å, 2.06 Å, 2.07 Å, 2.08 Å, 2.09 Å, 2.1 Å, etc. The chemical bond distance L refers to the average distance between the oxygen nuclei and the tin nuclei that form the chemical bond, that is, the bond length.

[0065] In this embodiment, the chemical bond distance L in the tin oxide layer 3 is moderate, and the lattice in the tin oxide layer 3 is highly ordered, so that the tin oxide layer 3 has excellent chemical stability, and the distortion or defects of the lattice in the tin oxide layer 3 are reduced, which is beneficial to reducing the light scattering of the tin oxide layer 3, improving the utilization rate of light, and at the same time helping to improve the light transmittance of the tin oxide layer 3.

[0066] X-ray crystallography can be used to measure the chemical bond distance L in the tin oxide layer 3. Specifically, by emitting X-rays to a crystal sample and analyzing the scattered X-ray pattern (diffraction pattern), the precise position of atoms in the crystal lattice can be determined, thereby calculating the chemical bond distance. Electron microscopy techniques, such as transmission electron microscopy (TEM) or scanning tunneling microscopy (STM), can also be used to measure the chemical bond distance L in the tin oxide layer 3.

[0067] When the solar cell is a tunnel oxide passivated contact (TOPCon) cell, the TOPCon cell comprises, along its thickness, a silver electrode, a front silicon nitride passivation layer, a boron-doped emitter, an N-type substrate silicon layer, a tunnel oxide layer 2, a tin oxide layer 3, a doped polysilicon layer 5, silicon nitride, and a silver electrode. The N-type substrate silicon layer, tunnel oxide layer 2, tin oxide layer 3, and doped polysilicon layer 5 together form a passivation contact structure. This structure blocks minority carrier-hole recombination, improving the cell's open-circuit voltage and short-circuit current. The tunnel oxide layer 2 allows majority electrons to tunnel into the doped polysilicon layer 5 while blocking minority carrier-hole recombination. The excellent passivation effect of the tunnel oxide layer 2, tin oxide layer 3, and doped polysilicon layer 5 causes surface band bending on the silicon wafer, creating a field passivation effect. This significantly increases the probability of electron tunneling, effectively reduces parasitic absorption, and reduces contact resistance, thereby increasing the cell's open-circuit voltage and short-circuit current, thereby improving the cell's conversion efficiency.

[0068] When the above-mentioned solar cell is a back contact cell (BC), the BC cell sets the emitter, surface field and metal electrode on the back of the cell and distributes them in a cross-pattern. The back of the cell adopts a multi-layer anti-reflection passivation film including a passivation layer (SiNx), a doped polysilicon layer 5, a tin oxide layer 3 and a tunneling oxide layer 2, so that the front of the cell is not blocked by the metal electrode, so that the cell can receive more incident light, reduce optical loss and improve the photoelectric conversion efficiency.

[0069] The present application also provides a method for preparing a solar cell, such as Figure 2 and Figure 3 As shown, the method for preparing a solar cell is used for the solar cell in any of the above embodiments, and the method for preparing a solar cell comprises at least the following steps:

[0070] S0: Cleaning the substrate 1 to remove impurities and contaminants on the surface of the substrate 1 and optimize the adhesion effect of subsequent processes.

[0071] S1: depositing a tunneling oxide layer 2 on the surface of the substrate 1 along the thickness direction.

[0072] S2: depositing a tin oxide layer 3 on the surface of the tunneling oxide layer 2 along the thickness direction with a ratio of the amount of tin source introduced to the amount of oxygen source introduced being S, satisfying: 0.2≤S≤0.5.

[0073] S3: depositing an amorphous silicon layer 4 on the surface of the tin oxide layer 3 along the thickness direction.

[0074] S4 : high temperature annealing and doping under the high temperature annealing condition, so that the amorphous silicon layer 4 is converted into a doped polysilicon layer 5 .

[0075] In this embodiment, in step S2, the tin oxide layer 3 can be deposited using an atomic layer deposition (ALD) process. Since the density of the tin oxide layer 3 is significantly different from the density of the tunneling oxide layer 2, and the atomic size in the tin oxide layer 3 is different from the atomic size in the tunneling oxide layer 2, the atomic layer deposition process is used to precisely control the production of a single layer, which can inhibit the formation of pores at the interface between the tin oxide layer 3 and the tunneling oxide layer 2, ensure that there is no significant element segregation at the interface connection, and is conducive to improving the lattice adaptation, so that each atom in the tin oxide layer 3 can be evenly covered on the tunneling oxide layer 2, thereby improving the uniformity of the deposition of the tin oxide layer 3 on the tunneling oxide layer 2. At the same time, the atomic layer deposition process can precisely control the growth rate of the tin oxide layer 3, reduce the risk of lattice mismatch, and improve the chemical stability of the tin oxide layer 3.

[0076] Furthermore, when depositing the tin oxide layer 3, the tin oxide layer 3 is deposited with a ratio of the tin source flow rate to the oxygen source flow rate being S, and satisfying the following relationship: 0.2≤S≤0.5. This ensures that the tin source flow rate is moderate compared to the oxygen source flow rate, allowing for precise matching of the interatomic distances between oxygen atoms and tin atoms in the tin oxide layer 3, thereby reducing lattice distortion and defects and improving the chemical stability of the tin oxide layer 3. Furthermore, precisely controlling the oxygen vacancy concentration in the tin oxide layer 3 to remain within a moderate range is beneficial for improving the conductivity and transmittance of the tin oxide layer 3, thereby effectively reducing parasitic absorption and improving the photoelectric conversion efficiency of the solar cell.

[0077] In some embodiments, the ratio S of the amount of tin source introduced to the amount of oxygen source introduced can be 0.2, 0.3, 0.4, 0.5, etc.

[0078] In addition, in step S4, the amorphous silicon layer 4 is converted into a doped polysilicon layer 5 by high-temperature annealing and doping under the high-temperature annealing conditions, which is beneficial to improving the carrier mobility in the doped polysilicon layer 5. At the same time, a part of the doping elements will also diffuse into the tin oxide layer 3, which is beneficial to improving the conductivity of the tin oxide layer 3 and reducing the contact resistance.

[0079] It should be noted that during the doping step, one or more doping elements can be selected depending on the substrate type and the type of cell being prepared. Specifically, when preparing a TOPCon cell, an N-type substrate is used, and phosphorus can be doped during the doping step. For example, when preparing a back contact (BC) cell, a P-type doped region and an N-doped region are formed on the cell surface, and phosphorus and boron can be doped during the doping step.

[0080] In addition, in step S1 , the tunnel oxide layer 2 may be deposited by atomic layer deposition (ALD) and in step S3 , the amorphous silicon layer 4 may be deposited by low pressure chemical vapor deposition (LPCVD).

[0081] Specifically, the radius of the tin atom is approximately 0.14 nm, the radius of the oxygen atom is approximately 0.06 nm, the ideal value of the chemical bond distance L of tin oxide is approximately 2.05 Å, the ideal value of the lattice constant a of tin oxide is approximately 4.737 Å, and the ideal value of the lattice constant c is approximately 3.186 Å, where the lattice constant (lattice constant), also known as the lattice constant, refers to the size of the unit cell, the lattice constant a refers to the length of the unit cell along the x-axis and y-axis directions, and the lattice constant c refers to the height of the unit cell along the z-axis direction. This application controls the temperature and other conditions of the atomic layer deposition (ALD) process, as well as the amount of oxygen source and the amount of tin source introduced, so that the lattice constant a, lattice constant c, and chemical bond distance L of the deposited tin oxide layer 3 are approximately ideal values. At the same time, it can effectively control the atomic spacing between oxygen atoms and tin atoms in the tin oxide layer 3 to accurately match and highly ordered, thereby reducing lattice distortion and defects.

[0082] In one possible embodiment, the high-temperature annealing temperature Q in step S4 satisfies the following conditions: 800°C ≤ Q ≤ 1100°C, and the high-temperature annealing time T5 satisfies the following conditions: 1 min ≤ T5 ≤ 50 min. In some embodiments, the high-temperature annealing temperature Q can be 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, etc. The high-temperature annealing time T5 can be 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, etc.

[0083] When the high-temperature annealing temperature Q satisfies: 800°C ≤ Q ≤ 1100°C, and the high-temperature annealing time T5 satisfies: 1min ≤ T5 ≤ 50min, it is beneficial to accurately control the depth and distribution of the doped region doped with the doping element, so that the doping concentrations in the doped polysilicon layer 5, the tin oxide layer 3, and the tunneling oxide layer 2 are relatively moderate, so that different thin film layers have excellent photoelectric properties. At the same time, the grain growth rate in the process of converting the amorphous silicon layer 4 into the doped polysilicon layer 5 is moderate, thereby reducing crystal defects, reducing the risk of lattice damage, and further improving the photoelectric conversion efficiency of the solar cell.

[0084] In addition, the phosphorus source that can be used in the doping step is phosphorus oxychloride ( ).

[0085] In one possible implementation, Figure 3 As shown, in the step of depositing the tin oxide layer 3, the method for preparing the solar cell further includes a cyclic deposition step, which at least includes:

[0086] S21: A tin source and nitrogen gas are introduced into the deposition chamber in a pulsed manner for a duration of T1, wherein the tin source is dimethylaminotin, the amount of the tin source introduced m1 satisfies the following conditions: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, and the duration T1 satisfies the following conditions: 5 s ≤ T1 ≤ 30 s. The nitrogen gas serves as a carrier for the dimethylaminotin.

[0087] In some embodiments, the amount of tin source introduced m1 can be 0.1 mmol / min, 0.2 mmol / min, 0.3 mmol / min, 0.4 mmol / min, 0.5 mmol / min, 0.6 mmol / min, 0.7 mmol / min, 0.8 mmol / min, 0.9 mmol / min, 1 mmol / min, etc. The time T1 can be 5 s, 6 s, 8 s, 10 s, 12 s, 14 s, 15 s, 16 s, 18 s, 20 s, 22 s, 24 s, 25 s, 26 s, 28 s, 30 s, etc.

[0088] When the amount of tin source introduced m1 satisfies: 0.1mmol / min≤m1≤1mmol / min, the tin source is saturatedly adsorbed on the surface of the tunneling oxide layer 2, that is, the adsorption amount of the tin source on the surface of the tunneling oxide layer 2 is controlled to be moderate, reducing the risk of oversaturated adsorption, and at the same time controlling the deposition rate to be moderate, reducing the risk of defects in the tin oxide layer 3, so that the tin oxide layer 3 film has good continuity and uniformity.

[0089] When the time T1 satisfies: 5s≤T1≤30s, the duration of the tin source introduction is moderate, and the adsorption amount of the tin source on the surface of the tunneling oxide layer 2 is controlled to be moderate, thereby reducing the risk of generating tin clusters or impurities, and making the deposited tin oxide layer 3 have good conductivity and passivation effect.

[0090] Therefore, when the amount of tin source introduced m1 satisfies: 0.1mmol / min≤m1≤1mmol / min, and the duration of tin source introduction T1 satisfies: 5s≤T1≤30s, it is beneficial to improve the continuity and uniformity of the tin oxide layer 3 deposited on the tunneling oxide layer 2, which is beneficial to improve the passivation effect of the solar cell and improve the photoelectric conversion efficiency.

[0091] After the step of introducing the tin source is completed, the cyclic deposition step further comprises:

[0092] S23: Pulsed oxygen and nitrogen are introduced into the deposition chamber for a duration of T2. The oxygen reacts with the tin source adsorbed on the tunneling oxide layer 2 to produce a tin oxide thin film. The oxygen source is oxygen gas, and the oxygen source flow rate m2 satisfies the following conditions: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min. The duration T2 satisfies the following conditions: 5 s ≤ T2 ≤ 30 s. Nitrogen gas serves as a carrier for the oxygen.

[0093] In some embodiments, the amount of oxygen source introduced m2 can be 0.5 mmol / min, 0.6 mmol / min, 0.8 mmol / min, 1 mmol / min, 1.2 mmol / min, 1.5 mmol / min, 1.6 mmol / min, 1.8 mmol / min, 2 mmol / min, etc. The time T2 can be 5 s, 6 s, 8 s, 10 s, 12 s, 14 s, 15 s, 16 s, 18 s, 20 s, 22 s, 24 s, 25 s, 26 s, 28 s, 30 s, etc.

[0094] When the oxygen source introduction amount m2 satisfies: 0.5mmol / min≤m2≤2mmol / min, the oxygen source introduction amount is moderate, the stoichiometric ratio of the oxygen source and the tin source is relatively balanced, the risk of excessive oxidation of the tin oxide layer 3 is reduced, and the risk of defects inside and on the surface of the tin oxide layer 3 is reduced, which is beneficial to improving the quality, uniformity and flatness of the tin oxide layer 3. At the same time, the oxygen vacancy concentration in the tin oxide layer 3 is controlled to be maintained in a moderate range, thereby increasing the carrier concentration.

[0095] When the time T2 satisfies: 5s≤T2≤30s, the risk of over-oxidation of the tin oxide layer 3 is reduced, the generation of by-products such as impurities is avoided, and the risk of lattice distortion cracks in the tin oxide layer 3 is reduced, which is beneficial to improving the structural strength and transmittance of the tin oxide layer 3.

[0096] Therefore, when the oxygen source introduction amount m2 satisfies: 0.5mmol / min≤m2≤2mmol / min, and the oxygen source introduction duration T2 satisfies: 5s≤T2≤30s, the carrier concentration is increased, and the structural strength and transmittance of the tin oxide layer 3 are improved.

[0097] In one possible implementation, Figure 3 As shown, between the step of introducing the tin source and the step of introducing the oxygen source, the cyclic deposition step further comprises:

[0098] S22: Nitrogen is introduced for a duration of T3, wherein the nitrogen introduction amount m3 satisfies: 5 L / min≤m3≤10 L / min, and the time T3 satisfies: 10s≤T3≤60s.

[0099] In this embodiment, nitrogen is introduced for a duration of T3 to remove excess tin source and by-product impurities in the deposition chamber to prevent cross contamination, thereby improving the passivation effect of the deposited tin oxide layer 3 and reducing the contact resistivity of the tin oxide layer 3.

[0100] In addition, after the step of introducing the oxygen source is completed, the cyclic deposition step further comprises:

[0101] S24: nitrogen is introduced for a duration of T3, wherein the nitrogen introduction amount m3 satisfies: 5 L / min≤m3≤10 L / min, and the time T3 satisfies: 10s≤T3≤60s.

[0102] In this embodiment, nitrogen gas is introduced for a duration of T3 to remove excess oxygen source and by-product impurities in the deposition chamber to prevent cross contamination, so that the subsequent cyclic deposition can form a tin oxide layer 3 with good uniformity.

[0103] In some embodiments, the nitrogen flow rate m3 can be 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, etc. The time T3 can be 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.

[0104] When the nitrogen introduction amount m3 satisfies: 5L / min≤m3≤10L / min, and the time T3 satisfies: 10s≤T3≤60s, it is beneficial to balance the nitrogen introduction amount and introduction time, which is beneficial to improving the efficiency of removing oxygen sources and other by-product impurities, or, it is beneficial to improving the efficiency of removing tin sources and other by-product impurities, which is beneficial to reducing production costs.

[0105] In one possible implementation, Figure 3 As shown, in the step of depositing the tin oxide layer 3, the method for preparing a solar cell further includes:

[0106] S25: Repeat the deposition step 100-1000 times, i.e., repeat steps S21-S24 100-1000 times, and make the thickness of the reaction product substantially uniform in each cycle, so as to deposit a tin oxide layer 3 having a certain thickness and a relatively uniform internal lattice distribution. The number of cycles can be 100, 200, 280, 300, 400, 500, 600, 700, 800, 900, 1000, etc.

[0107] In one possible implementation, Figure 3 As shown, after completing the cyclic deposition step, the method for preparing a solar cell further includes:

[0108] S26: heat-treating the tin oxide layer 3 on a titanium-based hot stage for a duration of T4, wherein the heat treatment temperature W satisfies: 100° C. ≤ W ≤ 300° C., and the heat treatment time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

[0109] In this embodiment, heat treatment can promote the orderly rearrangement of atoms inside the tin oxide layer 3, repair internal lattice defects, and help to properly fill the oxygen vacancies in the tin oxide layer 3, thereby optimizing the crystallinity and oxygen vacancy concentration inside the tin oxide layer 3, which is beneficial to improving conductivity.

[0110] In some embodiments, the temperature W of the heat treatment may be 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., 290° C., 300° C., etc. The time T4 may be 1 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.

[0111] When the heat treatment temperature W satisfies: 100°C ≤ W ≤ 300°C, and the time T4 satisfies: 1min ≤ T4 ≤ 120min, so that the heat treatment temperature and duration are moderate, the risk of cracking of the tin oxide layer 3 thin film is reduced, and it is beneficial to promote the growth of grains inside the tin oxide, which is beneficial to reduce the resistivity and reduce the risk of the tin oxide layer 3 decomposing to generate other products, so that the tin oxide layer 3 maintains good conductivity and transmittance.

[0112] Table 1

[0113]

[0114] As shown in Table 1, the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 of the solar cell of Example 1 is 2, and the oxygen vacancy concentration λ is 5×10 17 cm -3 The phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The thickness D2 of the tin oxide layer 3 is 30 nm, the chemical bond distance L between the tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 1, it can be seen that the average contact resistivity of the solar cell of Example 1 is about 5 mΩcm, calculated by using 2534 cell samples of Example 1. 2The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 92%, the average conversion efficiency Eta of the solar cell is about 26.41%, the average open circuit voltage Voc is about 0.7401V, the average short circuit current Isc is about 13.936A, and the average fill factor FF is about 85.76%.

[0115] In the solar cell of Comparative Example 1, the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 1.8, and the oxygen vacancy concentration λ is 5×10 18 cm -3 The phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The thickness D2 of the tin oxide layer 3 is 30 nm, the chemical bond distance L between the tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 1, it can be seen that the average contact resistivity of the solar cell of Comparative Example 1 is about 15 mΩcm, calculated by using 2534 cell samples of Comparative Example 1. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 85%, the average conversion efficiency Eta of the solar cell is about 25.80%, the average open circuit voltage Voc is about 0.7305V, the average short circuit current Isc is about 13.800A, and the average fill factor FF is about 83.20%.

[0116] In the solar cell of Comparative Example 2, the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2.3, and the oxygen vacancy concentration λ is 7×10 14 cm -3 The phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The thickness D2 of the tin oxide layer 3 is 30 nm, the chemical bond distance L between the tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 1, it can be seen that the average contact resistivity of the solar cell of Comparative Example 2 is about 12 mΩcm, calculated by using 2534 cell samples of Comparative Example 2. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 83%, the average conversion efficiency Eta of the solar cell is about 25.90%, the average open circuit voltage Voc is about 0.7350V, the average short circuit current Isc is about 13.850A, and the average fill factor FF is about 83.00%.

[0117] The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is different from that in Comparative Examples 1 and 2, which in turn affects the oxygen vacancy concentration λ differently, and the other structures and parameters of each layer are the same. As can be seen from Table 1, the transmittance, contact resistivity, conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are all better than those in Comparative Examples 1 and 2. Therefore, the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is controlled to satisfy: 1.9≤F≤2.1, which can significantly improve the transmittance of the solar cell and improve the contact resistivity, thereby helping to improve the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0118] Table 2

[0119]

[0120] The oxygen vacancy concentration λ in the tin oxide layer 3 of the solar cell of comparative example 3 is 5×10 18 cm -3 , the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The thickness D2 of the tin oxide layer 3 is 30 nm, the chemical bond distance L between the tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 2, it can be seen that the average contact resistivity of the solar cell of Comparative Example 3 is about 12 mΩcm, calculated by using 2534 cell samples of Comparative Example 3. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 87%, the average conversion efficiency Eta of the solar cell is about 26.05%, the average open circuit voltage Voc is about 0.7352V, the average short circuit current Isc is about 13.875A, and the average fill factor FF is about 84.10%.

[0121] The oxygen vacancy concentration λ in the tin oxide layer 3 of the solar cell of comparative example 4 is 8×10 14 cm -3 , the ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The thickness D2 of the tin oxide layer 3 is 30 nm, the chemical bond distance L between the tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3From Table 2, it can be seen that the average contact resistance of the solar cell of Comparative Example 4 is about 30 mΩcm, calculated by using 2534 cell samples of Comparative Example 4. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 95%, the average conversion efficiency Eta of the solar cell is about 23.80%, the average open circuit voltage Voc is about 0.7050V, the average short circuit current Isc is about 13.950A, and the average fill factor FF is about 75.50%.

[0122] Therefore, the oxygen vacancy concentration λ in the tin oxide layer 3 of Example 1 is different from that of Comparative Examples 3 and 4, and the other structures and parameters of each layer are the same. As can be seen from Table 2, the contact resistivity, conversion efficiency Eta, open circuit voltage Voc and fill factor FF of the solar cell provided by Example 1 are all better than those of Comparative Examples 3 and 4. Although the transmittance and short-circuit current Isc in Comparative Example 3 are higher than those in Example 1, the contact resistance in Comparative Example 3 is greatly increased, thereby greatly reducing the photoelectric conversion efficiency of the solar cell. Therefore, the oxygen vacancy concentration λ in the tin oxide layer 3 is controlled to meet the following requirements: 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 , which can significantly balance the transmittance and contact resistivity of solar cells, thereby helping to improve the conversion efficiency Eta, open circuit voltage Voc and fill factor FF of solar cells.

[0123] Table 3

[0124]

[0125] In the solar cell of Comparative Example 5, the thickness D2 of the tin oxide layer 3 is 0.8 nm, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3 The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 3, it can be seen that the average contact resistivity of the solar cell of Comparative Example 5 is about 25 mΩcm, calculated by using 2534 cell samples of Comparative Example 5. 2The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 65%, the average conversion efficiency Eta of the solar cell is about 24.30%, the average open circuit voltage Voc is about 0.7105V, the average short circuit current Isc is about 11.87A, and the average fill factor FF is about 79.20%.

[0126] In the solar cell of Comparative Example 6, the thickness D2 of the tin oxide layer 3 is 120 nm, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3 The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 3, it can be seen that the average contact resistivity of the solar cell of Comparative Example 6 is about 18 mΩcm, calculated by using 2534 cell samples of Comparative Example 6. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 78%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open circuit voltage Voc is about 0.7250V, the average short circuit current Isc is about 13.00A, and the average fill factor FF is about 82.50%.

[0127] Therefore, the thickness D2 of the tin oxide layer 3 in Example 1 is different from that in Comparative Examples 5 and 6, and the other structures and parameters of each layer are the same. As can be seen from Table 3, the transmittance, contact resistivity, conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are better than those in Comparative Examples 5 and 6. Therefore, the thickness D2 of the tin oxide layer 3 is controlled to satisfy: 1nm≤D2≤100nm, which can significantly improve the transmittance of the solar cell and improve the contact resistivity, thereby helping to improve the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0128] Table 4

[0129]

[0130] The phosphorus doping concentration β of the tin oxide layer 3 in the solar cell of Comparative Example 7 is 5×10 14 cm -3 The oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, the thickness D2 of the tin oxide layer 3 is 30 nm, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 4, it can be seen that the average contact resistivity of the solar cell of Comparative Example 7 is about 18 mΩcm, calculated by using 2534 cell samples of Comparative Example 7. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 90%, the average conversion efficiency Eta of the solar cell is about 25.10%, the average open circuit voltage Voc is about 0.725V, the average short circuit current Isc is about 13.907A, and the average fill factor FF is about 82.00%.

[0131] The phosphorus doping concentration β of the tin oxide layer 3 in the solar cell of Comparative Example 8 is 5×10 20 cm -3 The oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3 The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 is 2.05 Å, the thickness D2 of the tin oxide layer 3 is 30 nm, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 4, it can be seen that the average contact resistivity of the solar cell of Comparative Example 8 is about 10 mΩcm, calculated by using 2534 cell samples of Comparative Example 8. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 85%, the average conversion efficiency Eta of the solar cell is about 25.80%, the average open circuit voltage Voc is about 0.7355V, the average short circuit current Isc is about 13.860A, and the average fill factor FF is about 84.20%.

[0132] Therefore, the doping concentration of the tin oxide layer 3 in Example 1 is different from that in Comparative Examples 7 and 8, and the parameters of other structures and layers are the same. As can be seen from Table 4, the transmittance, contact resistivity, conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided by Example 1 are all better than those of Comparative Examples 7 and 8. Therefore, the phosphorus doping concentration β of the tin oxide layer 3 is controlled to meet the following requirements: 1×10 15 cm -3 ≤β≤1×10 20 cm -3, which can significantly improve the transmittance of solar cells and improve the contact resistivity, thereby helping to improve the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of solar cells.

[0133] Table 5

[0134]

[0135] In the solar cell of Comparative Example 9, the chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer 3 is 1.98 Å, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 The oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3 The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, the thickness of the tin oxide layer 3 is 30 nm, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 5, it can be seen that the average contact resistivity of the solar cell of Comparative Example 9 is about 9 mΩcm, calculated by using 2534 cell samples of Comparative Example 9. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 88%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open circuit voltage Voc is about 0.732V, the average short circuit current Isc is about 13.88A, and the average fill factor FF is about 83.50%.

[0136] In the solar cell of Comparative Example 10, the chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer 3 is 2.15 Å, and the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 19 cm -3 , the thickness of the tin oxide layer 3 is 30 nm, and the oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 17 cm -3 The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer 3 is 2, and the phosphorus doping concentration γ of the doped polysilicon layer 5 is 5×10 20 cm -3 From Table 5, it can be seen that the average contact resistivity of the solar cell of Comparative Example 10 is about 22 mΩcm, calculated by using 2534 cell samples of Comparative Example 10. 2 The average light transmittance of the tin oxide layer 3 under light of 550nm wavelength is about 73%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open circuit voltage Voc is about 0.715V, the average short circuit current Isc is about 12.76A, and the average fill factor FF is about 78.50%.

[0137] Therefore, the doping concentration of the tin oxide layer 3 in Example 1 is different from that in Comparative Examples 9 and 10, and the parameters of the other structures and layers are the same. As can be seen from Table 5, the transmittance, contact resistivity, conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are better than those in Comparative Examples 9 and 10. Therefore, the chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer 3 is controlled to satisfy: 2.00 Å ≤ L ≤ 2.10 Å, which can significantly improve the transmittance of the solar cell and improve the contact resistivity, thereby facilitating the improvement of the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0138] Table 6

[0139]

[0140] As shown in Table 6, the method for preparing a solar cell (tunneling oxide passivation contact cell - TOPcon cell) of Example 1 comprises at least the following steps: preparing an N-type crystalline silicon substrate 1, performing standard RCA cleaning on the crystalline silicon substrate 1, and then depositing a tunneling oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1 by an ALD deposition process, and then depositing a tin oxide layer 3 on the surface of the tunneling oxide layer 2 by an ALD deposition process, controlling the flow rate of dimethylaminotin to 0.5 mmol / min and the flow rate of oxygen to 0.8 mmol / min, and repeating the steps 280 times to prepare a tin oxide layer 3 with a thickness of 30 nm, and then heat-treating the tin oxide layer 3 at 200° C. for 30 minutes, and then depositing an amorphous silicon layer 4 on the surface of the tin oxide layer 3 by an LPCVD deposition process, controlling the thickness of the amorphous silicon layer 4 to 100 nm, and then performing high-temperature annealing at 900° C. for 30 minutes in the LPCVD deposition process and performing phosphorus diffusion under the high-temperature annealing conditions, thereby crystallizing the amorphous silicon layer 4 into a doped polycrystalline silicon layer 5.

[0141] The at least steps of the preparation method of the solar cell (tunneling oxide passivation contact cell - TOPcon cell) in Comparative Example 11 are as follows: preparing an N-type crystalline silicon substrate 1, then performing standard RCA cleaning on the crystalline silicon substrate 1, and then using an ALD deposition process to deposit a tunneling oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1, and then using an LPCVD deposition process to deposit an amorphous silicon layer 4 on the surface of the tunneling oxide layer 2, and controlling the thickness of the amorphous silicon layer 4 to be 100 nm. Then, in the LPCVD deposition process, high-temperature annealing is performed at 900°C for 30 minutes and phosphorus diffusion is performed under the high-temperature annealing conditions, so that the amorphous silicon layer 4 is crystallized into a doped polycrystalline silicon layer 5.

[0142] In Example 1, a solar cell having a tin oxide layer 3 deposited between a tunnel oxide layer 2 and a doped polysilicon layer 5 is prepared by the above method. 2534 cell samples of Example 1 are used to calculate that the average conversion efficiency Eta of the solar cell of Example 1 is approximately 26.41%, the average open circuit voltage Voc is approximately 0.7401 V, the average short circuit current Isc is approximately 13.936 A, and the average fill factor FF is approximately 85.76%.

[0143] Comparative Example 11, compared to Example 1 without the tin oxide layer 3, uses 2534 cell samples of Comparative Example 11 to calculate the average conversion efficiency Eta of the solar cell of Comparative Example 11 to be approximately 26.13%, the average open circuit voltage Voc to be approximately 0.7363V, the average short circuit current Isc to be approximately 13.922A, and the average fill factor FF to be approximately 85.36%. The contact resistivity of Comparative Example 11 is 8 mΩcm 2 .

[0144] Therefore, except for the structure and steps of not depositing the tin oxide layer 3, the other steps and structures of Comparative Example 1 are the same as those of Example 1. As can be seen from Table 6, the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are better than those of Comparative Example 11. Therefore, the tin oxide layer 3 is deposited between the tunneling oxide layer 2 and the doped polysilicon layer 5, which can significantly improve the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0145] The at least steps of the preparation method of the solar cell (tunneling oxide passivation contact cell - TOPcon cell) in Comparative Example 12 are as follows: preparing an N-type crystalline silicon substrate 1, then performing standard RCA cleaning on the crystalline silicon substrate 1, and then using an ALD deposition process to deposit a tunneling oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1, and then using an LPCVD deposition process to deposit an amorphous silicon layer 4 on the surface of the tunneling oxide layer 2, controlling the thickness of the amorphous silicon layer 4 to be 130 nm, and then performing high-temperature annealing at 900°C for 30 minutes in the LPCVD deposition process and diffusing phosphorus under the high-temperature annealing conditions, so that the amorphous silicon layer 4 is crystallized into a doped polycrystalline silicon layer 5.

[0146] Compared with Example 1, Comparative Example 12 does not have a tin oxide layer 3, and the thickness of the amorphous silicon layer 4 in Comparative Example 12 is equal to the sum of the thicknesses of the tin oxide layer 3 and the amorphous silicon layer 4 in Example 1. Using 2534 cell samples of Comparative Example 12, it is calculated that the average conversion efficiency Eta of the solar cell of Comparative Example 12 is approximately 26.26%, the average open circuit voltage Voc is approximately 0.7387V, the average short-circuit current Isc is approximately 13.918A, and the average fill factor FF is approximately 85.53%.

[0147] Therefore, it can be seen from Table 6 that the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are all better than those of Comparative Example 12, that is, by appropriately thinning the thickness of the amorphous silicon layer 4 and replacing the thinned structure with a tin oxide layer 3 arranged between the tunneling oxide layer 2 and the doped polycrystalline silicon layer 5, the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell can also be effectively and significantly improved.

[0148] The method for preparing a solar cell (tunneling oxide passivation contact cell - TOPcon cell) of Comparative Example 13 comprises at least the following steps: preparing an N-type crystalline silicon substrate 1, performing a standard RCA cleaning on the crystalline silicon substrate 1, then depositing a tin oxide layer 3 on the surface of the crystalline silicon substrate 1 using an ALD deposition process, controlling the amount of dimethylaminotin introduced to 0.5 mmol / min and the amount of oxygen introduced to 0.8 mmol / min, and repeating the process 280 times to prepare a tin oxide layer 3 with a thickness of 30 nm, then heat-treating the tin oxide layer 3 at 200°C for 30 minutes, then depositing an amorphous silicon layer 4 on the surface of the tin oxide layer 3 using an LPCVD deposition process, controlling the thickness of the amorphous silicon layer 4 to 100 nm, then performing a high-temperature annealing at 900°C for 30 minutes in the LPCVD deposition process and performing phosphorus diffusion under the high-temperature annealing conditions, thereby crystallizing the amorphous silicon layer 4 into a doped polycrystalline silicon layer 5. The contact resistivity of the solar cell of Comparative Example 13 is 18 mΩcm. 2 .

[0149] Therefore, except for the structure and steps of not depositing the tunnel oxide layer 2, the other steps and structures of Comparative Example 13 are the same as those in Example 1. Using 2534 cell samples of Comparative Example 13, it is calculated that the average conversion efficiency Eta of the solar cell of Comparative Example 13 is approximately 24.10%, the average open circuit voltage Voc is approximately 0.7150 V, the average short-circuit current Isc is approximately 12.801 A, and the average fill factor FF is approximately 78.20%.

[0150] As can be seen from Table 6, the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell provided in Example 1 are all better than those in Comparative Example 13. Therefore, providing a tunneling oxide layer 2 can effectively reduce the contact resistance, thereby effectively and significantly improving the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0151] At the same time, by comparing Example 1 with Comparative Examples 11 and 13, it can be seen that the solar cell is provided with a tunneling oxide layer 2 and a tin oxide layer 3 at the same time, which can greatly reduce the contact resistance, and the tin oxide layer 3 has good light transmittance and high mobility, effectively and significantly improving the conversion efficiency Eta, open circuit voltage Voc, short circuit current Isc and fill factor FF of the solar cell.

[0152] The above description is merely a specific implementation of the embodiments of the present application, but the scope of protection of the embodiments of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of the present application shall be included in the scope of protection of the embodiments of the present application. Therefore, the scope of protection of the embodiments of the present application shall be based on the scope of protection of the claims.

Claims

1. A solar cell, characterized in that: The solar cell comprises at least: substrate (1); A tunneling oxide layer (2), arranged on the surface of the substrate (1) along the thickness direction of the substrate (1); A tin oxide layer (3), arranged on the surface of the tunneling oxide layer (2) along the thickness direction of the substrate (1); a doped polysilicon layer (5), wherein the doped polysilicon layer (5) is arranged on the surface of the tin oxide layer (3) along the thickness direction of the substrate (1), so that the tin oxide layer (3) is located between the tunneling oxide layer (2) and the doped polysilicon layer (5); The ratio F of the number of oxygen atoms to tin atoms in the tin oxide layer (3) satisfies: 1.9≤F≤2.1; The oxygen vacancy concentration λ in the tin oxide layer (3) satisfies: 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 .

2. The solar cell according to claim 1, wherein: The contact resistivity ρc1 of the solar cell satisfies: 5mΩcm 2 ≤ρc1≤10mΩcm 2 .

3. The solar cell according to claim 1, wherein: Along the thickness direction of the substrate (1), the thickness D1 of the tunneling oxide layer (2) satisfies: 1nm≤D1≤2nm, the thickness D2 of the tin oxide layer (3) satisfies: 1nm≤D2≤100nm, and the thickness D3 of the doped polysilicon layer (5) satisfies: 1nm≤D3≤100nm.

4. The solar cell according to claim 1, wherein: The phosphorus doping concentration α of the tunneling oxide layer (2) satisfies: 1×10 13 cm -3 ≤α≤1×10 16 cm -3 , the phosphorus doping concentration β of the tin oxide layer (3) satisfies: 1×10 15 cm -3 ≤β≤1×10 20 cm -3 , the phosphorus doping concentration γ of the doped polysilicon layer (5) satisfies: 1×10 19 cm -3 ≤γ≤1×10 21 cm -3 .

5. The solar cell according to claim 1, wherein: The chemical bond distance L between the tin atoms and the oxygen atoms in the tin oxide layer (3) satisfies: 2.00 Å≤L≤2.10 Å.

6. A method for preparing a solar cell, characterized in that: The method for preparing a solar cell is used for the solar cell according to any one of claims 1 to 5, and the method for preparing a solar cell comprises at least the following steps: cleaning the substrate (1); Depositing a tunneling oxide layer (2) on the surface of the substrate (1) along the thickness direction; Depositing a tin oxide layer (3) on the surface of the tunneling oxide layer (2) along the thickness direction with a ratio of a tin source flow amount to an oxygen source flow amount as S, satisfying: 0.2≤S≤0.5; Depositing an amorphous silicon layer (4) on the surface of the tin oxide layer (3) along the thickness direction; High-temperature annealing and doping under the high-temperature annealing conditions are performed to convert the amorphous silicon layer (4) into a doped polysilicon layer (5).

7. The method for preparing a solar cell according to claim 6, wherein: In the step of depositing the tin oxide layer (3), the method for preparing the solar cell further comprises a cyclic deposition step, wherein the cyclic deposition step at least comprises: The tin source and nitrogen are introduced for a duration of T1, wherein the tin source is dimethylaminotin, the amount of the tin source introduced m1 satisfies: 0.1 mmol / min≤m1≤1 mmol / min, and the time T1 satisfies: 5s≤T1≤30s; After the step of introducing the tin source is completed, the oxygen source and nitrogen are introduced for a duration of T2, wherein the oxygen source is oxygen gas, the introduction amount m2 of the oxygen source satisfies: 0.5mmol / min≤m2≤2mmol / min, and the time T2 satisfies: 5s≤T2≤30s.

8. The method for preparing a solar cell according to claim 7, wherein: Between the step of introducing the tin source and the step of introducing the oxygen source, and after the step of introducing the oxygen source is completed, the cyclic deposition step further comprises: Nitrogen is introduced for a duration of T3, wherein the nitrogen introduction amount m3 satisfies: 5 L / min≤m3≤10 L / min, and the time T3 satisfies: 10s≤T3≤60s.

9. The method for preparing a solar cell according to claim 7, wherein: After completing the cyclic deposition step, the method for preparing a solar cell further comprises: The tin oxide layer (3) is heat-treated for a duration of T4, wherein the heat treatment temperature W satisfies: 100° C. ≤ W ≤ 300° C., and the heat treatment time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

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