Solar cell and preparation method thereof

Abstract

The invention relates to a solar cell piece and a preparation method of the solar cell piece, and belongs to the field of photovoltaic technology, the solar cell piece at least comprises a substrate, a tunneling oxide layer, a tin oxide layer and a doped polycrystalline silicon layer, the tunneling oxide layer is arranged on the surface of the substrate along the thickness direction of the substrate, and the tin 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 in the thickness direction of the substrate, and the doped polycrystalline silicon layer is arranged on the surface of the tin oxide layer in the thickness direction of the substrate, so that the tin oxide layer is located between the tunneling oxide layer and the doped polycrystalline silicon layer. The ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer is larger than or equal to 1.9 and smaller than or equal to 2.1. The tin oxide layer is arranged between the tunneling oxide layer and the doped polycrystalline silicon layer, and the tin oxide layer has excellent conductivity and light transmission, so that parasitic absorption can be 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, and particularly to a solar cell and a method for manufacturing the solar cell. Background Art

[0002] Currently, the passivated contact of a solar cell can effectively improve the passivation effect and the photoelectric conversion efficiency of the solar cell. The passivated contact structure generally includes a passivation layer and a doping layer. However, there is serious parasitic absorption in the doping layer of the passivated contact structure, that is, there is a problem of non-ideal absorption of light, resulting in a reduction in the light utilization rate of the solar cell, thereby affecting the photoelectric conversion efficiency of the solar cell. Summary of the Invention

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

[0004] In a first aspect of this application, a solar cell is provided, which at least includes: a substrate; a tunneling oxide layer, which is disposed on the surface of the substrate along the thickness direction of the substrate; an indium tin oxide layer, which is disposed on the surface of the tunneling oxide layer along the thickness direction of the substrate; a doped polysilicon layer, which is disposed on the surface of the indium tin oxide layer along the thickness direction of the substrate, so that the indium 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 indium tin oxide layer satisfies: 1.9 ≤ F ≤ 2.1.

[0005] In this solution, the tin oxide layer is disposed between the tunneling oxide layer and the doped polysilicon layer. Since the optical bandgap of the tin oxide layer is smaller than that of the doped polysilicon layer, that is, the tin oxide layer has a weaker absorption of visible light, so that 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, it is beneficial to reduce parasitic absorption and reduce non-ideal absorption of light, so that more light can be absorbed by the substrate, which is beneficial to increasing 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 is between the refractive indices of the tunneling oxide layer and the doped polysilicon layer, the doped polysilicon layer, the tin oxide layer and the tunneling oxide layer form a three-layer structure with a refractive gradient, which is beneficial to reducing reflection at the interface and increasing the light transmittance, so that the substrate can absorb more light energy. In addition, the tin oxide layer has good electrical conductivity, so that the tin oxide layer can be used as an electron transport layer. Then, by combining the tin oxide layer and the tunneling oxide layer, it helps to improve the carrier transport efficiency, reduce carrier recombination, improve the passivation performance of the solar cell, and is beneficial to reducing the contact resistivity, thus enhancing the photoelectric conversion efficiency of the solar cell.

[0006] When 1.9 ≤ F ≤ 2.1, it is close to the stoichiometric ratio, which is beneficial to reducing oxygen vacancy defects in the tin oxide layer, balancing the electrical conductivity and chemical stability of the tin oxide layer, thereby reducing the risk of carrier generation and recombination, and improving the passivation performance. At the same time, it is beneficial to reducing the risk of generating non-active oxides in the tin oxide layer to improve the electron transport efficiency, thus further improving the photoelectric conversion efficiency of the solar cell.

[0007] In this solution, the sum of the contact resistivities ρc1 of the solar cell satisfies: 5 mΩcm 2 ≤ ρc1 ≤ 10 mΩcm 2 .

[0008] 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 .

[0009] In this solution, along the thickness direction of the substrate, the thickness D1 of the tunneling oxide layer satisfies: 1 nm ≤ D1 ≤ 2 nm, the thickness D2 of the tin oxide layer satisfies: 1 nm ≤ D2 ≤ 100 nm, and the thickness D3 of the doped polysilicon layer satisfies: 1 nm ≤ D3 ≤ 100 nm.

[0010] In this solution, the phosphorus doping concentration α of the tunneling 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 .

[0011] In this solution, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer satisfies: 2 Å ≤ L ≤ 2.1 Å.

[0012] The second aspect of this application provides a method for manufacturing a solar cell. The method for manufacturing a solar cell is used to manufacture the above-mentioned solar cell. The method for manufacturing a solar cell at least includes the following steps: Clean the substrate; Deposit the tunneling oxide layer on the surface of the substrate along the thickness direction; Deposit the tin oxide layer on the surface of the tunneling oxide layer along the thickness direction with the ratio S of the tin source input amount to the oxygen source input amount satisfying: 0.2 ≤ S ≤ 0.5; Deposit an amorphous silicon layer on the surface of the tin oxide layer along the thickness direction; Perform high-temperature annealing and doping under the high-temperature annealing conditions to convert the amorphous silicon layer into the doped polysilicon layer.

[0013] In this solution, in the step of depositing the tin oxide layer, the method for manufacturing a solar cell further includes a cyclic deposition step. The cyclic deposition step at least includes: Introduce the tin source and nitrogen gas and keep for a duration T1. Among them, the tin source is dimethylaminotin, the input amount m1 of the tin source satisfies: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, and the time T1 satisfies: 5 s ≤ T1 ≤ 30 s; After completing the step of introducing the tin source, introduce the oxygen source and nitrogen gas and keep for a duration T2. Among them, the oxygen source is oxygen, the input amount m2 of the oxygen source satisfies: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min, and the time T2 satisfies: 5 s ≤ T2 ≤ 30 s.

[0014] In this solution, between the step of introducing the tin source and the step of introducing the oxygen source, and after completing the step of introducing the oxygen source, the cyclic deposition step further includes: Introduce nitrogen gas for a duration of T3, and the introduced amount m3 of the nitrogen gas satisfies: 5 L / min ≤ m3 ≤ 10 L / min, and the time T3 satisfies: 10 s ≤ T3 ≤ 60 s.

[0015] In this solution, after completing the cyclic deposition step, the method for preparing the solar cell further includes: Perform heat treatment on the tin oxide layer for a duration of T4, and the temperature W of the heat treatment satisfies: 100 °C ≤ W ≤ 300 °C, and the time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

[0016] It should be understood that the above general description and the following detailed description are only exemplary and do not limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a passivation contact structure in a specific embodiment of the solar cell provided by this application; Figure 2 For preparing Figure 1 It is a step diagram of the passivation contact structure provided in a specific embodiment; Figure 3 It is a flowchart of the method for preparing the solar cell provided by this application in a specific embodiment.

[0018] DESCRIPTION OF THE REFERENCE NUMERALS: 1 - Substrate; 2 - Tunneling oxide layer; 3 - Tin oxide layer; 4 - Amorphous silicon layer; 5 - Doped polysilicon layer.

[0019] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0021] In a specific embodiment, the following will further describe this application in detail through specific embodiments and in combination with the accompanying drawings.

[0022] It should be clear that the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope protected by this application.

[0023] 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", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise.

[0024] It should be understood that the term "and / or" used herein is merely a description of the relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally indicates that the associated objects before and after are in an "or" relationship.

[0025] It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described from the angles shown in the drawings and should not be construed as limiting the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that one element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0026] The present application provides a solar cell, as Figure 1 shown, the solar cell at least includes a substrate 1, a tunneling oxide layer 2, an indium tin oxide layer 3, and a doped polysilicon layer 5.

[0027] The tunneling oxide layer 2 is disposed on the surface of the substrate 1 along the thickness direction of the substrate 1, the indium tin oxide layer 3 is disposed on the surface of the tunneling oxide layer 2 along the thickness direction of the substrate 1, and the doped polysilicon layer 5 is disposed on the surface of the indium tin oxide layer 3 along the thickness direction of the substrate 1, so that the indium tin oxide layer 3 is located between the tunneling oxide layer 2 and the doped polysilicon layer 5.

[0028] The ratio F of the number of oxygen atoms to the number of tin atoms in the indium tin oxide layer 3 satisfies: 1.9 ≤ F ≤ 2.1.

[0029] 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 bandgap 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, so that 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 increasing 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 indices 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 light transmittance, so that the substrate 1 can absorb more light energy. In addition, the tin oxide layer 3 has good electrical conductivity, so that the tin oxide layer 3 can be used as an electron transport layer. Furthermore, by combining the tin oxide layer 3 and the tunneling oxide layer 2, it helps to improve the carrier transport efficiency, reduce carrier recombination, improve the passivation performance of the solar cell, and is beneficial to reducing the contact resistivity, thus improving the photoelectric conversion efficiency of the solar cell.

[0030] In addition, 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. In some embodiments, F can be 1.9, 1.92, 1.94, 1.95, 1.96, 1.98, 2, 2.1.

[0031] When 1.9 ≤ F ≤ 2.1, the number of oxygen atoms and tin atoms in the tin oxide layer 3 is closer to the stoichiometric ratio, so that the formed 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 higher, and the ionic radius size of the tin ions is moderate, which is more conducive to forming a dense crystal structure, improving the chemical structure stability of the tin oxide layer 3, effectively inhibiting lattice expansion or contraction at the same time, and being beneficial to reducing oxygen vacancy defects in the tin oxide layer 3, improving the light transmittance, and further being beneficial to balancing the electrical conductivity and chemical stability of the tin oxide layer 3, thereby reducing the risk of carrier generation and recombination, and improving the passivation performance. At the same time, it is beneficial to reducing the risk of generating non-active oxides in the tin oxide layer 3 to improve the electron transport efficiency, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0032] In some possible embodiments, the substrate 1 can be made of any one of single-crystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, copper indium gallium selenide, and perovskite. Preferably, in one possible implementation, the substrate 1 can be an N-type substrate, and any one of phosphorus, arsenic, and antimony can be selected as the doping element. In another possible implementation, the substrate 1 can be a P-type substrate, and any one of boron, aluminum, gallium, and indium can be selected as the doping element. In one possible implementation, as Figure 1 shown, the contact resistivity ρc1 of the solar cell satisfies: 5 mΩ·cm 2 ≤ρc1≤10 mΩ·cm 2 . In some embodiments, ρc1 can be 5 mΩ·cm 2 , 6 mΩ·cm 2 , 7 mΩ·cm 2 , 8 mΩ·cm 2 , 9 mΩ·cm 2 , 10 mΩ·cm 2 and so on.

[0033] When 5 mΩ·cm 2 ≤ρc1≤10 mΩ·cm 2 , the contact resistivity of the solar cell is moderate, and the contact resistivities of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polycrystalline silicon layer 5 are all moderate. The tin oxide layer 3 with high mobility is arranged between the tunneling oxide layer 2 and the doped polycrystalline silicon layer 5, which can significantly reduce the interface resistance. At the same time, due to the good contact performance of the doped polycrystalline silicon layer 5, it is beneficial to reduce the contact resistivity, reduce the interface recombination rate, improve the extraction of carriers, and reduce the series resistance, thereby improving the fill factor and photoelectric conversion efficiency of the solar cell.

[0034] Among them, the four-probe method can be used to measure the contact resistivity of the solar cell. By measuring the current-voltage characteristics of electrodes with different spacings, the contact resistivity of the solar cell can be calculated. The contact resistivity of the solar cell can also be calculated using the Transmission Line Model (TLM for short).

[0035] The oxygen vacancy concentration refers to the number of defects formed due to 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 means such as X-ray Photoelectron Spectroscopy (XPS for short), Electron Paramagnetic Resonance (EPR for short), and Hall effect testing. In one possible implementation, as Figure 1 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 can 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 etc.

[0036] When 1 × 10 15 cm -3 ≤ λ ≤ 1 × 10 18 cm -3 is satisfied, the oxygen vacancy concentration λ in the tin oxide layer 3 is moderate, which is beneficial to improving the conductivity of the tin oxide layer 3, promoting the effective separation of photo-generated electrons and holes, reducing recombination, and at the same time being beneficial to reducing the absorption rate of visible light with wavelengths in the range of 400 nm - 500 nm by the oxygen vacancies in the tin oxide layer 3. Furthermore, the transmittance of the tin oxide layer 3 is effectively improved, so that more visible light can be absorbed by the substrate 1, further improving the photoelectric conversion efficiency of the solar cell.

[0037] In a possible implementation manner, as Figure 1 shown, along the thickness direction of the substrate 1, the thickness D1 of the tunneling oxide layer 2 satisfies: 1 nm ≤ D1 ≤ 2 nm, the thickness D2 of the tin oxide layer 3 satisfies: 1 nm ≤ D2 ≤ 100 nm, and the thickness D3 of the doped polysilicon layer 5 satisfies: 1 nm ≤ D3 ≤ 100 nm.

[0038] In some embodiments, the thickness D1 of the tunneling oxide layer 2 can 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 can 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 can be 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc.

[0039] When D1 satisfies: 1 nm ≤ D1 ≤ 2 nm, D2 satisfies: 1 nm ≤ D2 ≤ 100 nm, and D3 satisfies: 1 nm ≤ D3 ≤ 100 nm, so that the thicknesses D1 of the tunneling oxide layer 2, D2 of the tin oxide layer 3, and D3 of the doped polysilicon layer 5 are all appropriate, so that the three-layer structure formed by the combination of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 has a lower contact resistivity, and is conducive to balancing the passivation effect and the carrier transport efficiency, reducing the interface recombination rate, and enabling the structure to 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 being conducive to increasing the current density of the solar cell.

[0040] In a possible implementation, as Figure 1 shown, 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 , and 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 tunneling oxide layer 2 can 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 etc. 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 etc. 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 etc.

[0041] In this embodiment, when the phosphorus doping concentration α of the tunneling oxide layer 2 satisfies: 1×10 13 cm -3 ≤α≤1×10 16 cm -3 , the selective transport of carriers is improved, the open-circuit voltage is increased, and the risk of damaging the internal crystal structure of the tunneling oxide layer 2 is reduced, so that the tunneling oxide layer 2 maintains good insulation performance. When 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 in the tin oxide layer 3 is made moderate, the conductivity of the tin oxide layer 3 is made moderate, the tin oxide layer 3 is maintained to have good carrier mobility, and the tin oxide layer 3 has good light transmittance, which is beneficial for the substrate 1 to absorb 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 it is in this range, it is beneficial to enhance the carrier concentration and improve the conductivity.

[0042] 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, reduce the parasitic absorption, and at the same time enable the tunneling oxide layer 2 to have good carrier selective transmission performance, promote 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.

[0043] In a possible implementation manner, as Figure 1 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 can 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 atomic nucleus and the tin atomic nucleus forming the chemical bond, that is, the bond length.

[0044] In this embodiment, the chemical bond distance L in the tin oxide layer 3 is made moderate, so that the lattice in the tin oxide layer 3 is highly ordered, so that the tin oxide layer 3 has excellent chemical stability, reduces the lattice distortion or defects in the tin oxide layer 3, and thus is beneficial to reducing the light scattering of the tin oxide layer 3 and improving the light utilization rate, and at the same time is beneficial to improving the light transmittance of the tin oxide layer 3.

[0045] Among them, the chemical bond distance L in the tin oxide layer 3 can be measured by the measurement method of X-ray Crystallography. Specifically, by emitting X-rays to the crystal sample and analyzing the scattered X-ray pattern (diffraction pattern), the precise position of the atoms in the lattice can be determined, and thus the chemical bond distance can be calculated. The chemical bond distance L in the tin oxide layer 3 can also be measured by electron microscopy techniques such as transmission electron microscopy (TEM) or scanning tunneling microscopy (STM).

[0046] When the above solar cell is a Tunnel Oxide Passivated Contact (TOPCon) cell, along its thickness direction, the TOPCon cell sequentially includes a metallic silver electrode, a front surface silicon nitride passivation layer, a boron-doped emitter, an N-type substrate silicon layer, a tunneling oxide layer 2, a tin oxide layer 3, a doped polysilicon layer 5, silicon nitride, and a metallic silver electrode. The N-type substrate silicon layer, the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 together form a passivated contact structure. This structure can block the recombination of minority carriers (holes), improving the open-circuit voltage and short-circuit current of the cell. The tunneling oxide layer 2 allows majority carriers (electrons) to tunnel into the doped polysilicon layer 5 while blocking the recombination of minority carriers (holes). The good passivation effect of the tunneling oxide layer 2, the tin oxide layer 3, and the doped polysilicon layer 5 causes the energy band on the silicon wafer surface to bend, thus forming a field passivation effect. The probability of electron tunneling increases significantly, effectively reducing parasitic absorption, decreasing the contact resistance, improving the open-circuit voltage and short-circuit current of the cell, and thereby enhancing the cell conversion efficiency.

[0047] When the above solar cell is a Back Contact (BC) cell, the BC cell disposes the emitter, the surface field, and the metallic electrodes on the back surface of the cell and distributes them in a cross pattern. The back surface of the cell uses a passivation layer (SiNx), a doped polysilicon layer 5, a tin oxide layer 3, and a tunneling oxide layer 2 as multiple anti-reflection and passivation thin films, so that there is no metallic electrode blocking on the front surface of the cell, enabling the cell to receive more incident light, reducing optical losses, and improving the photoelectric conversion efficiency.

[0048] This application also provides a preparation method for a solar cell, as Figure 2 and Figure 3 shown, the preparation method for the solar cell is used for the solar cell in any of the above embodiments. The preparation method for the solar cell at least includes the following steps: S0: Clean the substrate 1 to remove impurities and contaminants on the surface of the substrate 1, optimizing the adhesion effect of subsequent processes.

[0049] S1: Deposit the tunneling oxide layer 2 on the surface of the substrate 1 along the thickness direction.

[0050] S2: Deposit the tin oxide layer 3 on the surface of the tunneling oxide layer 2 along the thickness direction with the ratio of the tin source input amount to the oxygen source input amount being S, satisfying: 0.2 ≤ S ≤ 0.5.

[0051] S3: Deposit an amorphous silicon layer 4 on the surface of the tin oxide layer 3 along the thickness direction.

[0052] S4: Perform high-temperature annealing and doping under this high-temperature annealing condition to convert the amorphous silicon layer 4 into a doped polysilicon layer 5.

[0053] In this embodiment, in step S2, the tin oxide layer 3 can be deposited by Atomic Layer Deposition (ALD). Since the density of the tin oxide layer 3 is significantly different from that of the tunneling oxide layer 2, and the atomic size in the tin oxide layer 3 is different from that of the atoms in the tunneling oxide layer 2, the atomic layer deposition process can precisely control monolayer production, which can inhibit the formation of pores at the interface between the tin oxide layer 3 and the tunneling oxide layer 2, ensure no significant element segregation at the interface connection, and is conducive to improving lattice matching, enabling the atoms in the tin oxide layer 3 to uniformly cover the tunneling oxide layer 2, 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.

[0054] In addition, when depositing the tin oxide layer 3, the tin oxide layer 3 is deposited with the ratio of the tin source input amount to the oxygen source input amount being S, and it satisfies: 0.2 ≤ S ≤ 0.5, so that the input amount of the tin source is moderate compared to the input amount of the oxygen source, enabling the atomic spacing between oxygen atoms and tin atoms in the tin oxide layer 3 to be precisely matched, thereby reducing lattice distortion and defects and improving the chemical stability of the tin oxide layer 3. At the same time, precisely controlling the oxygen vacancy concentration in the tin oxide layer 3 to be within a moderate range is conducive to improving the conductivity and light transmittance of the tin oxide layer 3, thereby effectively reducing parasitic absorption and improving the photoelectric conversion efficiency of the solar cell.

[0055] In some embodiments, the ratio of the tin source input amount to the oxygen source input amount, S, can be 0.2, 0.3, 0.4, 0.5, etc.

[0056] In addition, in step S4, by performing high-temperature annealing and doping under this high-temperature annealing condition, the amorphous silicon layer 4 is converted into a doped polycrystalline silicon layer 5, which is conducive to improving the carrier mobility in the doped polycrystalline silicon layer 5. At the same time, a part of the doping elements will also diffuse into the tin oxide layer 3, which is conducive to improving the conductivity of the tin oxide layer 3 and reducing the contact resistance.

[0057] It should be noted that in the doping step, different one or more doping elements can be selected according to the different substrate types and the different types of batteries to be prepared. Specifically, when preparing a TOPCon battery, an N-type substrate is selected, and phosphorus elements can be doped in the doping step. When preparing a Back Contact (BC) battery, a P-type doping region and an N-doping region should be formed on the surface of the battery, and phosphorus elements and boron elements can be doped in the doping step.

[0058] In addition, in step S1, the tunneling oxide layer 2 can be deposited by Atomic Layer Deposition (ALD), and in step S3, the amorphous silicon layer 4 can be deposited by Low Pressure Chemical Vapor Deposition (LPCVD).

[0059] Specifically, the radius of a tin atom is approximately 0.14 nm, the radius of an 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 of tin oxide is approximately 3.186 Å. Here, the lattice constant, also known as the lattice parameter, 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. In this application, by controlling conditions such as the temperature of the Atomic Layer Deposition (ALD) process and the amount of oxygen source and tin source introduced, the lattice constant a, lattice constant c, and chemical bond distance L of the deposited tin oxide layer 3 are all approximately the ideal values. At the same time, the atomic spacing between oxygen atoms and tin atoms in the tin oxide layer 3 can be precisely matched and highly ordered, thereby reducing lattice distortion and defects.

[0060] In a possible implementation, the temperature Q of the high-temperature annealing in step S4 satisfies: 800°C ≤ Q ≤ 1100°C, and the high-temperature annealing time T5 satisfies: 1 min ≤ T5 ≤ 50 min. In some embodiments, the temperature Q of the high-temperature annealing 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.

[0061] When the temperature Q of the high-temperature annealing satisfies: 800°C ≤ Q ≤ 1100°C, and the high-temperature annealing time T5 satisfies: 1 min ≤ T5 ≤ 50 min, it is beneficial to precisely control the depth and distribution of the doping region doped with doping elements, so that the doping concentrations in the doped polysilicon layer 5, tin oxide layer 3, and tunneling oxide layer 2 are relatively moderate, enabling each thin film layer to have excellent optoelectronic properties. At the same time, during the process of converting the amorphous silicon layer 4 into the doped polysilicon layer 5, the grain growth rate is moderate, reducing crystal defects and the risk of lattice damage, and further improving the optoelectronic conversion efficiency of the solar cell.

[0062] In addition, the phosphorus source that can be used in the doping step is phosphorus oxychloride ( ).

[0063] In a possible implementation, as Figure 3 shown, in the step of depositing the tin oxide layer 3, the method for preparing the solar cell further includes a cyclic deposition step, and the cyclic deposition step at least includes: S21: Introduce a tin source and nitrogen into the deposition chamber in a pulse form and for a duration T1. Among them, the tin source is dimethylaminotin, and the input amount m1 of the tin source satisfies: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, and the time T1 satisfies: 5 s ≤ T1 ≤ 30 s. Among them, nitrogen is used as the carrier of dimethylaminotin.

[0064] In some embodiments, the input amount m1 of the tin source 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.

[0065] When the input amount m1 of the tin source satisfies: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, so that 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, the risk of supersaturated adsorption is reduced, and at the same time, the deposition rate is controlled to be moderate, the risk of generating defects inside the tin oxide layer 3 is reduced, so that the tin oxide layer 3 film has good continuity and uniformity.

[0066] When the time T1 satisfies: 5 s ≤ T1 ≤ 30 s, the duration of introducing the tin source is moderate, the adsorption amount of the tin source on the surface of the tunneling oxide layer 2 is controlled to be moderate, and further the risk of generating tin clusters or impurities is reduced, so that the deposited tin oxide layer 3 has good conductivity and passivation effect.

[0067] Therefore, when the input amount m1 of the tin source satisfies: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, and the duration T1 of introducing the tin source satisfies: 5 s ≤ T1 ≤ 30 s, it is beneficial to improve the continuity and uniformity of the deposition of the tin oxide layer 3 on the tunneling oxide layer 2, is beneficial to improving the passivation effect of the solar cell, and improves the photoelectric conversion efficiency.

[0068] After completing the step of introducing the tin source, the cyclic deposition step further includes: S23: Introduce an oxygen source and nitrogen into the deposition chamber in the form of pulses for a duration T2. The oxygen source reacts with the tin source adsorbed on the tunneling oxide layer 2 to produce a tin oxide thin film layer. Here, the oxygen source is oxygen, and the introduced amount m2 of the oxygen source satisfies: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min, and the time T2 satisfies: 5 s ≤ T2 ≤ 30 s. Here, nitrogen acts as a carrier for oxygen.

[0069] In some embodiments, the introduced amount m2 of the oxygen source 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.

[0070] When the introduced amount m2 of the oxygen source satisfies: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min, the amount of the introduced oxygen source is made appropriate, so that the stoichiometric ratio between the oxygen source and the tin source is relatively balanced, reducing the risk of over-oxidation of the tin oxide layer 3, and reducing the risk of defects inside and on the surface of the tin oxide layer 3, 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 in a moderate range, increasing the carrier concentration.

[0071] When the time T2 satisfies: 5 s ≤ T2 ≤ 30 s, 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 and cracks in the tin oxide layer 3 is reduced, which is beneficial to improving the structural strength and light transmittance of the tin oxide layer 3.

[0072] Therefore, when the introduced amount m2 of the oxygen source satisfies: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min, and the duration T2 of the oxygen source introduction satisfies: 5 s ≤ T2 ≤ 30 s, the carrier concentration is increased, and the structural strength and light transmittance of the tin oxide layer 3 are improved.

[0073] In a possible implementation manner, as Figure 3 shown, between the step of introducing the tin source and the step of introducing the oxygen source, the cyclic deposition step further includes: S22: Introduce nitrogen for a duration T3, the introduced amount m3 of nitrogen satisfies: 5 L / min ≤ m3 ≤ 10 L / min, and the time T3 satisfies: 10 s ≤ T3 ≤ 60 s.

[0074] In this embodiment, nitrogen is introduced for a duration of T3 to remove excess tin source and by-product impurities in the deposition chamber, prevent cross-contamination, improve the passivation effect of the deposited tin oxide layer 3, and reduce the contact resistivity of the tin oxide layer 3.

[0075] In addition, after the step of introducing the oxygen source is completed, the cyclic deposition step further includes: S24: Introduce nitrogen for a duration of T3, where the introduction amount m3 of nitrogen satisfies: 5 L / min ≤ m3 ≤ 10 L / min, and the time T3 satisfies: 10 s ≤ T3 ≤ 60 s.

[0076] In this embodiment, nitrogen is introduced for a duration of T3 to remove excess oxygen source and by-product impurities in the deposition chamber, prevent cross-contamination, and facilitate the subsequent cyclic deposition to form a tin oxide layer 3 with good uniformity.

[0077] In some embodiments, the introduction amount m3 of nitrogen 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.

[0078] When the introduction amount m3 of nitrogen satisfies: 5 L / min ≤ m3 ≤ 10 L / min, and the time T3 satisfies: 10 s ≤ T3 ≤ 60 s, it is beneficial to balance the introduction amount and introduction time of nitrogen, improve the efficiency of removing the oxygen source and other by-product impurities, or improve the efficiency of removing the tin source and other by-product impurities, and reduce the production cost.

[0079] In a possible implementation manner, as Figure 3 shown, in the step of depositing the tin oxide layer 3, the method for preparing a solar cell further includes: S25: Cyclically perform the cyclic deposition step 100 - 1000 times, that is, cyclically perform steps S21 - S24 100 - 1000 times, and make the thickness of the substances generated in each cyclic reaction basically the same, so as to deposit a tin oxide layer 3 with a certain thickness and a relatively uniform internal lattice distribution. Among them, the number of cycles can be 100 times, 200 times, 280 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, 1000 times, etc.

[0080] In a possible implementation manner, as Figure 3 shown, after the cyclic deposition step is completed, the method for preparing a solar cell further includes: S26: Heat-treat the tin oxide layer 3 on a titanium-based hot stage for a duration T4, where the temperature W of the heat treatment satisfies: 100°C ≤ W ≤ 300°C, and the time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

[0081] In this embodiment, heat treatment can promote the orderly rearrangement of atoms inside the tin oxide layer 3, repair internal lattice defects, and help appropriately fill 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.

[0082] In some embodiments, the temperature W of the heat treatment can 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 can 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.

[0083] When the temperature W of the heat treatment satisfies: 100°C ≤ W ≤ 300°C, and the time T4 satisfies: 1 min ≤ T4 ≤ 120 min, the heat treatment temperature and duration are appropriate, reducing the risk of cracking of the tin oxide layer 3 thin film, facilitating the growth of internal grains of tin oxide, reducing the resistivity, and reducing the risk of the tin oxide layer 3 decomposing to form other products, so that the tin oxide layer 3 maintains good conductivity and transmittance.

[0084] Table 1

[0085] As shown in Table 1, in the tin oxide layer 3 of the solar cell chip of Example 1, the ratio F of the number of oxygen atoms to tin atoms is 2, 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 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 . Among them, as can be seen from Table 1, the average contact resistivity of the solar cell chip of Example 1 calculated using 2534 sample chips of Example 1 is about 5 mΩcm 2, the average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 92%, the average conversion efficiency Eta of the solar cell is about 26.41%, the average open-circuit voltage Voc is about 0.7401 V, the average short-circuit current Isc is about 13.936 A, and the average fill factor FF is about 85.76%.

[0086] 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 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 . Among them, as can be seen from Table 1, the average contact resistivity of the solar cell of Comparative Example 1 calculated using 2534 cell samples of Comparative Example 1 is about 15 mΩ·cm 2 , the average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 85%, the average conversion efficiency Eta of the solar cell is about 25.80%, the average open-circuit voltage Voc is about 0.7305 V, the average short-circuit current Isc is about 13.800 A, and the average fill factor FF is about 83.20%.

[0087] 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 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 . Among them, as can be seen from Table 1, the average contact resistivity of the solar cell of Comparative Example 2 calculated using 2534 cell samples of Comparative Example 2 is about 12 mΩ·cm 2 , the average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 83%, the average conversion efficiency Eta of the solar cell is about 25.90%, the average open-circuit voltage Voc is about 0.7350 V, the average short-circuit current Isc is about 13.850 A, and the average fill factor FF is about 83.00%.

[0088] In Example 1, the ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer 3 is different from that in Comparative Example 1 and Comparative Example 2, which in turn affects the different oxygen vacancy concentrations λ. Moreover, the other structures and the parameters of each layer are the same. As can be seen from Table 1, the light 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 Example 1 and Comparative Example 2. Therefore, controlling the ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer 3 to satisfy 1.9 ≤ F ≤ 2.1 can significantly improve the light transmittance of the solar cell and improve the contact resistivity, which in turn is beneficial to improving the conversion efficiency Eta, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF of the solar cell.

[0089] Table 2

[0090] In the solar cell of Comparative Example 3, the oxygen vacancy concentration λ in the tin oxide layer 3 is 5×10 18 cm -3 , the ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer 3 is 2, 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 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 . Among them, as can be seen from Table 2, the average contact resistivity of the solar cell of Comparative Example 3 calculated using 2534 cell samples of Comparative Example 3 is about 12 mΩcm 2 , the average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 87%, the average conversion efficiency Eta of the solar cell is about 26.05%, the average open-circuit voltage Voc is about 0.7352 V, the average short-circuit current Isc is about 13.875 A, and the average fill factor FF is about 84.10%.

[0091] In the solar cell of Comparative Example 4, the oxygen vacancy concentration λ in the tin oxide layer 3 is 8×10 14 cm -3 , the ratio F of the number of oxygen atoms to the number of tin atoms in the tin oxide layer 3 is 2, 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 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 -3Among them, as can be seen from Table 2, the average contact resistivity of the solar cell of Comparative Example 4 calculated using 2,534 solar cell samples of Comparative Example 4 is about 30 mΩ·cm. 2 The average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 95%, the average conversion efficiency Eta of the solar cell is about 23.80%, the average open circuit voltage Voc is about 0.7050 V, the average short circuit current Isc is about 13.950 A, and the average fill factor FF is about 75.50%.

[0092] Therefore, the oxygen vacancy concentration λ in the tin oxide layer 3 in Example 1 is different from that in Comparative Example 3 and Comparative Example 4, and the other structures and the 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 in Example 1 are all better than those in Comparative Example 3 and Comparative Example 4. Although the light transmittance and short circuit current Isc in Comparative Example 3 are higher than those in Example 1, the contact resistance in Comparative Example 3 increases significantly, thus greatly reducing the photoelectric conversion efficiency of the solar cell. Therefore, controlling the oxygen vacancy concentration λ in the tin oxide layer 3 to satisfy: 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 can significantly balance the light transmittance and contact resistivity of the solar cell, and thus is beneficial to improving the conversion efficiency Eta, open circuit voltage Voc, and fill factor FF of the solar cell.

[0093] Table 3

[0094] In the solar cell of Comparative Example 5, the thickness D2 of the tin oxide layer 3 is 0.8 nm, 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 . Among them, as can be seen from Table 3, the average contact resistivity of the solar cell of Comparative Example 5 calculated using 2,534 solar cell samples of Comparative Example 5 is about 25 mΩ·cm. 2 The average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 65%, the average conversion efficiency Eta of the solar cell is about 24.30%, the average open circuit voltage Voc is about 0.7105 V, the average short circuit current Isc is about 11.87 A, and the average fill factor FF is about 79.20%.

[0095] 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 . Among them, as can be seen from Table 3, the average contact resistivity of the solar cell of Comparative Example 6 calculated using 2534 samples of the solar cells of Comparative Example 6 is about 18 mΩ·cm 2 , the average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 78%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open-circuit voltage Voc is about 0.7250 V, the average short-circuit current Isc is about 13.00 A, and the average fill factor FF is about 82.50%.

[0096] Therefore, in Example 1, the thickness D2 of the tin oxide layer 3 in Comparative Example 5 and Comparative Example 6 is different, and the other structures and the parameters of each layer are the same. As can be seen from Table 3, the light 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 Example 5 and Comparative Example 6. Therefore, controlling the thickness D2 of the tin oxide layer 3 to satisfy 1 nm ≤ D2 ≤ 100 nm can significantly improve the light transmittance of the solar cell and improve the contact resistivity, and thus is beneficial to improving the conversion efficiency Eta, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF of the solar cell.

[0097] Table 4

[0098] In the solar cell of Comparative Example 7, the phosphorus doping concentration β of the tin oxide layer 3 is 5×10 14 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 -3Among them, as can be seen from Table 4, the average contact resistivity of the solar cell of Comparative Example 7 calculated using 2,534 cell samples of Comparative Example 7 is about 18 mΩ·cm. 2 The average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 90%, the average conversion efficiency Eta of the solar cell is about 25.10%, the average open-circuit voltage Voc is about 0.725 V, the average short-circuit current Isc is about 13.907 A, and the average fill factor FF is about 82.00%.

[0099] 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 Among them, as can be seen from Table 4, the average contact resistivity of the solar cell of Comparative Example 8 calculated using 2,534 cell samples of Comparative Example 8 is about 10 mΩ·cm. 2 The average light transmittance of the tin oxide layer 3 under light with a wavelength of 550 nm is about 85%, the average conversion efficiency Eta of the solar cell is about 25.80%, the average open-circuit voltage Voc is about 0.7355 V, the average short-circuit current Isc is about 13.860 A, and the average fill factor FF is about 84.20%.

[0100] Therefore, the doping concentration of the tin oxide layer 3 in Example 1 is different from that in Comparative Example 7 and Comparative Example 8, and other structures and the parameters of each layer are the same. As can be seen from Table 4, the light 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 Example 7 and Comparative Example 8. Therefore, controlling the phosphorus doping concentration β of the tin oxide layer 3 to satisfy: 1×10 15 cm -3 ≤β≤1×10 20 cm -3 can significantly improve the light transmittance of the solar cell and improve the contact resistivity, and thus is beneficial to improving the conversion efficiency Eta, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF of the solar cell.

[0101] Table 5

[0102] In the solar cell of Comparative Example 9, the chemical bond distance L between tin atoms and 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 . Among them, as can be seen from Table 5, the average contact resistivity of the solar cell of Comparative Example 9 calculated using 2534 solar cell samples of Comparative Example 9 is about 9 mΩ·cm 2 , the average light transmittance of the tin oxide layer 3 at a wavelength of 550 nm is about 88%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open circuit voltage Voc is about 0.732 V, the average short circuit current Isc is about 13.88 A, and the average fill factor FF is about 83.50%.

[0103] In the solar cell of Comparative Example 10, the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 of the solar cell 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, 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 . Among them, as can be seen from Table 5, the average contact resistivity of the solar cell of Comparative Example 10 calculated using 2534 solar cell samples of Comparative Example 10 is about 22 mΩ·cm 2 , the average light transmittance of the tin oxide layer 3 at a wavelength of 550 nm is about 73%, the average conversion efficiency Eta of the solar cell is about 25.60%, the average open circuit voltage Voc is about 0.715 V, the average short circuit current Isc is about 12.76 A, and the average fill factor FF is about 78.50%.

[0104] Therefore, the doping concentrations of the tin oxide layer 3 in Example 1, Comparative Example 9, and Comparative Example 10 are all different, and the other structures and the parameters of each layer are the same. As can be seen from Table 5, the light 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 Example 9 and Comparative Example 10. Therefore, controlling the chemical bond distance L between tin atoms and oxygen atoms in the tin oxide layer 3 to satisfy: 2.00 Å ≤ L ≤ 2.10 Å can significantly improve the light 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.

[0105] Table 6

[0106] As shown in Table 6, the preparation method of the solar cell (tunnel oxide passivated contact cell - TOPcon cell) in Example 1 has at least the following steps: Prepare an N-type crystalline silicon substrate 1, perform standard RCA cleaning on the crystalline silicon substrate 1, and then deposit a tunnel oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1 by ALD deposition process. Then, deposit a tin oxide layer 3 on the surface of the tunnel oxide layer 2 by ALD deposition process, control the flow rate of dimethylaminotin to be 0.5 mmol / min, the oxygen flow rate to be 0.8 mmol / min, and cycle 280 times to prepare a tin oxide layer 3 with a thickness of 30 nm. Then, heat-treat the tin oxide layer 3 at 200 °C for 30 minutes. Then, deposit an amorphous silicon layer 4 on the surface of the tin oxide layer 3 by LPCVD deposition process, control the thickness of the amorphous silicon layer 4 to be 100 nm, and then perform high-temperature annealing at 900 °C for 30 min and phosphorus diffusion under this high-temperature annealing condition in the LPCVD deposition process, so that the amorphous silicon layer 4 is crystallized into a doped polysilicon layer 5.

[0107] The preparation method of the solar cell (tunnel oxide passivated contact cell - TOPcon cell) in Comparative Example 11 has at least the following steps: Prepare an N-type crystalline silicon substrate 1, then perform standard RCA cleaning on the crystalline silicon substrate 1, and then deposit a tunnel oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1 by ALD deposition process. Then, deposit an amorphous silicon layer 4 on the surface of the tunnel oxide layer 2 by LPCVD deposition process, control the thickness of the amorphous silicon layer 4 to be 100 nm, and then perform high-temperature annealing at 900 °C for 30 min and phosphorus diffusion under this high-temperature annealing condition in the LPCVD deposition process, so that the amorphous silicon layer 4 is crystallized into a doped polysilicon layer 5.

[0108] Example 1 is a solar cell wafer prepared by the above method, with a tin oxide layer 3 deposited between the tunneling oxide layer 2 and the doped polysilicon layer 5. Using 2534 cell wafer samples of Example 1, the average conversion efficiency Eta of the solar cell wafer of Example 1 is calculated to be 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%.

[0109] Comparative Example 11 has no tin oxide layer 3 compared to Example 1. Using 2534 cell wafer samples of Comparative Example 11, the average conversion efficiency Eta of the solar cell wafer of Comparative Example 11 is calculated to be approximately 26.13%, the average open-circuit voltage Voc is approximately 0.7363 V, the average short-circuit current Isc is approximately 13.922 A, and the average fill factor FF is approximately 85.36%. Among them, the contact resistivity of Comparative Example 11 is 8 mΩcm 2 .

[0110] Therefore, except for the structure and steps without depositing the tin oxide layer 3, Comparative Example 11 is the same as the other steps and structures in 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 wafer provided by Example 1 are all better than those of Comparative Example 11. Therefore, depositing a tin oxide layer 3 between the tunneling oxide layer 2 and the doped polysilicon layer 5 can significantly improve the conversion efficiency Eta, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF of the solar cell wafer.

[0111] The preparation method of the solar cell wafer (tunneling oxide passivated contact cell - TOPcon cell) in Comparative Example 12 has at least the following steps: Prepare an N-type crystalline silicon substrate 1, then perform standard RCA cleaning on the crystalline silicon substrate 1, then deposit a tunneling oxide layer 2 with a thickness of 1.5 nm on the surface of the crystalline silicon substrate 1 by ALD deposition process, then deposit an amorphous silicon layer 4 on the surface of the tunneling oxide layer 2 by LPCVD deposition process, control the thickness of the amorphous silicon layer 4 to be 130 nm, and then perform high-temperature annealing at 900 °C for 30 min and phosphorus diffusion under this high-temperature annealing condition in the LPCVD deposition process, so that the amorphous silicon layer 4 is crystallized into a doped polysilicon layer 5.

[0112] Comparative Example 12 has no tin oxide layer 3 compared to Example 1, 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 wafer samples of Comparative Example 12, the average conversion efficiency Eta of the solar cell wafer of Comparative Example 12 is calculated to be approximately 26.26%, the average open-circuit voltage Voc is approximately 0.7387 V, the average short-circuit current Isc is approximately 13.918 A, and the average fill factor FF is approximately 85.53%.

[0113] Therefore, 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 superior to those of Comparative Example 12. That is, by appropriately thinning the thickness of the amorphous silicon layer 4 and replacing the thinned structure with the tin oxide layer 3 disposed between the tunneling oxide layer 2 and the doped polysilicon 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.

[0114] The preparation method of the solar cell of Comparative Example 13 (tunneling oxide layer passivated contact cell - TOPcon cell) has at least the following steps: Prepare an N-type crystalline silicon substrate 1, perform standard RCA cleaning on the crystalline silicon substrate 1, and then deposit a tin oxide layer 3 on the surface of the crystalline silicon substrate 1 by ALD deposition process. Control the flow rate of dimethylaminotin to be 0.5 mmol / min and the flow rate of oxygen to be 0.8 mmol / min, and cycle 280 times to prepare a tin oxide layer 3 with a thickness of 30 nm. Then, heat-treat the tin oxide layer 3 at 200 °C for 30 minutes. Subsequently, deposit an amorphous silicon layer 4 on the surface of the tin oxide layer 3 by LPCVD deposition process, control the thickness of the amorphous silicon layer 4 to be 100 nm, and then perform high-temperature annealing at 900 °C for 30 min and phosphorus diffusion under this high-temperature annealing condition in the LPCVD deposition process, so that the amorphous silicon layer 4 is crystallized into a doped polysilicon layer 5. Among them, the contact resistivity of the solar cell of Comparative Example 13 is 18 mΩcm 2 .

[0115] Therefore, except for the structure and steps of not depositing the tunneling oxide layer 2, the other steps and structures in Comparative Example 13 are the same as those in Example 1. Using 2534 cell samples of Comparative Example 13, 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%.

[0116] 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 superior to those of Comparative Example 13. Therefore, setting the tunneling oxide layer 2 can effectively reduce the contact resistance, and thus effectively and significantly improve the conversion efficiency Eta, open-circuit voltage Voc, short-circuit current Isc, and fill factor FF of the solar cell.

[0117] By comparing Example 1 with Comparative Example 11 and Comparative Example 13 simultaneously, it can be seen that the simultaneous provision of the tunneling oxide layer 2 and the tin oxide layer 3 on the solar cell 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.

[0118] The above are only the specific implementation manners of the embodiments of the present application, but the protection scope 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 should be covered within the protection scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

1. A solar cell, characterized in that, The solar cell slice at least includes: a substrate (1); a tunneling oxide layer (2), which is disposed on the surface of the substrate (1) along the thickness direction of the substrate (1); an indium tin oxide layer (3), which is disposed on the surface of the tunneling oxide layer (2) along the thickness direction of the substrate (1); a doped polysilicon layer (5), which is disposed on the surface of the indium tin oxide layer (3) along the thickness direction of the substrate (1), so that the indium 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 the number of tin atoms in the indium tin oxide layer (3) satisfies: 1.9 ≤ F ≤ 2.

1.

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

3. The solar cell according to claim 1, wherein, The oxygen vacancy concentration λ in the tin oxide layer (3) satisfies: 1×10 15 cm -3 ≤λ≤1×10 18 cm -3 .

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

5. 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 .

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

7. A method for preparing a solar cell chip, characterized in that, The preparation method of the solar cell slice is used for the solar cell slice described in any one of claims 1-6, and the preparation method of the solar cell slice at least includes the following steps: Clean the substrate (1); Deposit a tunneling oxide layer (2) on the surface of the substrate (1) along the thickness direction; Deposit an indium tin oxide layer (3) on the surface of the tunneling oxide layer (2) along the thickness direction with the ratio S of the tin source input amount to the oxygen source input amount, satisfying: 0.2 ≤ S ≤ 0.5; Deposit an amorphous silicon layer (4) on the surface of the indium tin oxide layer (3) along the thickness direction; Perform high-temperature annealing and doping under the high-temperature annealing conditions to convert the amorphous silicon layer (4) into a doped polysilicon layer (5).

8. The method for preparing a solar cell according to claim 7, wherein In the step of depositing the indium tin oxide layer (3), the preparation method of the solar cell slice further includes a cyclic deposition step, and the cyclic deposition step at least includes: Introduce the tin source and nitrogen gas and keep for a duration T1, where the tin source is dimethylaminotin, the input amount m1 of the tin source satisfies: 0.1 mmol / min ≤ m1 ≤ 1 mmol / min, and the time T1 satisfies: 5 s ≤ T1 ≤ 30 s; After completing the step of introducing the tin source, introduce the oxygen source and nitrogen gas and keep for a duration T2, where the oxygen source is oxygen, the input amount m2 of the oxygen source satisfies: 0.5 mmol / min ≤ m2 ≤ 2 mmol / min, and the time T2 satisfies: 5 s ≤ T2 ≤ 30 s.

9. The method for preparing a solar cell according to claim 8, wherein, Between the step of introducing the tin source and the step of introducing the oxygen source, and after completing the step of introducing the oxygen source, the cyclic deposition step further includes: Introduce nitrogen gas and keep for a duration T3, the input amount m3 of the nitrogen gas satisfies: 5 L / min ≤ m3 ≤ 10 L / min, and the time T3 satisfies: 10 s ≤ T3 ≤ 60 s.

10. The manufacturing method of the solar cell according to claim 8, characterized in that, After completing the cyclic deposition step, the preparation method of the solar cell slice further includes: The tin oxide layer (3) is heat-treated for a duration T4, and the temperature W of the heat treatment satisfies: 100°C ≤ W ≤ 300°C, and the time T4 satisfies: 1 min ≤ T4 ≤ 120 min.

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