A solar cell, a preparation method thereof, and a photovoltaic module

Abstract

The present invention discloses a solar cell, a preparation method thereof, and a photovoltaic module. The solar cell includes a silicon substrate, and an emitter, a first silicon oxide layer, and an aluminum oxide layer are sequentially stacked on the light-receiving surface of the silicon substrate; wherein, the thickness of the first silicon oxide layer is 0.2 nm to 1.2 nm. The present invention can effectively improve the interface stability of the emitter and inhibit the efficiency decay of the solar cell under ultraviolet light irradiation.

Description

Technical Field

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

[0002] As a core component of a photovoltaic module, a solar cell has an important impact on the efficiency of the photovoltaic module. However, under the influence of ultraviolet light irradiation, the photoelectric conversion efficiency of the solar cell will show an early decline phenomenon, resulting in an obvious power attenuation problem of the photovoltaic module. This phenomenon poses a severe challenge to the long-term stable operation of the photovoltaic module, seriously affecting the service life and working efficiency of the photovoltaic module. Summary of the Invention

[0003] In order to reduce the influence of ultraviolet light irradiation on the solar cell, embodiments of the present invention disclose a solar cell, a preparation method thereof, and a photovoltaic module.

[0004] In a first aspect, an embodiment of the present invention provides a solar cell.

[0005] A solar cell includes a silicon substrate, and an emitter, a first silicon oxide layer, an aluminum oxide layer, and a first antireflection layer are sequentially stacked on a light-receiving surface of the silicon substrate;

[0006] Wherein, the thickness of the first silicon oxide layer is 0.2 nm to 1.2 nm.

[0007] As an optional implementation manner, in an embodiment of the present invention, the interface state density of the first silicon oxide layer is 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 .

[0008] As an optional implementation manner, in an embodiment of the present invention, the thickness of the first silicon oxide layer is 0.3 nm to 0.8 nm.

[0009] As an optional implementation manner, in an embodiment of the present invention, the silicon substrate is N-type and the emitter is P-type.

[0010] As an optional implementation manner, in an embodiment of the present invention, the thickness of the aluminum oxide layer is 3 nm to 8 nm;

[0011] and / or,

[0012] The first antireflection layer includes one or a combination of a first silicon nitride layer, a first silicon oxynitride layer, and a second silicon oxide layer.

[0013] As an alternative embodiment, in the embodiment of the present invention, one side of the backlight surface of the silicon substrate includes a dielectric layer, a doped polysilicon layer, and a second anti-reflection layer arranged in sequence;

[0014] The second anti-reflection layer includes one or a combination of a second silicon nitride layer, a second silicon oxynitride layer, and a third silicon oxide layer;

[0015] One side of the light-receiving surface of the silicon substrate is provided with a first electrode, and the first electrode forms an ohmic contact with the emitter; one side of the backlight surface of the silicon substrate is provided with a second electrode, and the second electrode forms an ohmic contact with the doped polysilicon layer.

[0016] In a second aspect, an embodiment of the present invention provides a method for manufacturing a solar cell as described in the first aspect.

[0017] A method for manufacturing a solar cell includes the following steps:

[0018] Provide the silicon substrate having the emitter on the light-receiving surface side;

[0019] Prepare the alumina layer on the surface of the emitter;

[0020] Perform an indirect oxidation treatment to indirectly grow the first silicon oxide layer on the surface of the emitter.

[0021] As an alternative embodiment, in the embodiment of the present invention, the indirect oxidation treatment includes treating the alumina layer with an ionized oxygen source and / or annealing the alumina layer.

[0022] As an alternative embodiment, in the embodiment of the present invention, the oxygen source includes one or more of CO2, N2O, H2O, O2, or O3;

[0023] And / or, the ionization method includes PECVD or LPCVD;

[0024] And / or, the temperature range of the annealing treatment is 400°C to 600°C.

[0025] As an alternative embodiment, in the embodiment of the present invention, the indirect oxidation treatment is the annealing treatment, and O2 or O3 is introduced during the annealing treatment to prepare the first silicon oxide layer.

[0026] As an alternative embodiment, in the embodiment of the present invention, the treatment of the ionized oxygen source is to ionize N2O.

[0027] As an alternative embodiment, in the embodiment of the present invention, the indirect oxidation treatment is the annealing treatment, and the treatment of ionizing N2O is performed during the annealing treatment.

[0028] As an alternative embodiment, in the embodiments of the present invention, the process conditions for ionizing N2O on the alumina layer are as follows:

[0029] The ionization time is 10 s to 120 s, the N2O flow rate is 5000 sccm to 20000 sccm, the temperature is 450°C to 470°C, the radio frequency power is 6000 W to 12000 W, and the radio frequency power supply is 20 ms to 50 ms.

[0030] In a third aspect, an embodiment of the present invention provides a photovoltaic module.

[0031] A photovoltaic module includes a solar cell as in the first aspect or a solar cell prepared by the preparation method as in the second aspect.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] An embodiment of the present invention provides a method, which introduces a first silicon oxide layer with a specific thickness (0.2 nm to 1.2 nm) between the emitter and the alumina layer. This first silicon oxide layer can effectively reduce the density of defect states at the interface between the emitter and the alumina layer, and can improve the anti-ultraviolet attenuation performance of the photovoltaic module.

[0034] First, the first silicon oxide layer with the specific thickness tightly binds with the dangling bonds on the surface of the emitter by using oxygen atoms to form a stable and dense Si-O bond network. This structure passivates the dangling bonds on the surface of the emitter while effectively reducing the number of hydrogen atoms overflowing from the Si-H bonds, effectively inhibiting the migration, accumulation of hydrogen atoms and the formation of hydrogen clusters caused by ultraviolet light irradiation, reducing the recombination of carriers, and thus slowing down the performance attenuation of the solar cell under ultraviolet light. Second, the first silicon oxide layer provides an effective transition buffer between the emitter and the alumina layer, significantly relieving the lattice distortion at the interface, reducing the dangling bond density at the interface, and reducing the recombination of carriers.

[0035] Furthermore, in the present invention, the thickness of the first silicon oxide layer plays a crucial role in the stability of the solar cell under ultraviolet light irradiation. The ultraviolet resistance stability of the solar cell shows a trend of first increasing and then decreasing with the change of the thickness of the first silicon oxide layer. When the thickness of the first silicon oxide layer is less than 0.2 nm, the improvement of the interface passivation performance of the first silicon oxide layer on the emitter is limited, and the interface state density is relatively high. Therefore, the ultraviolet resistance stability of the solar cell is not significantly improved. However, when the thickness of the first silicon oxide layer is in the range of 0.2 to 0.8 nm, the interface passivation effect of the emitter is in a better range, and the interface state density decreases, and the ultraviolet resistance stability of the solar cell is also significantly improved. But once the thickness of the first silicon oxide layer exceeds 1.2 nm, the inventors' experiments have found that the ultraviolet resistance stability of the solar cell will even deteriorate further. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 is a schematic structural diagram of the first solar cell disclosed in the embodiment of the present invention;

[0038] Figure 2 is a schematic structural diagram of the second solar cell disclosed in the embodiment of the present invention;

[0039] Figure 3 is a schematic structural diagram of the third solar cell disclosed in the embodiment of the present invention.

[0040] Reference numerals: 1, silicon substrate; 11, emitter; 111, P-type emitter; 2, first silicon oxide layer; 3, aluminum oxide layer; 4, first antireflection layer; 41, first silicon nitride layer; 411, first silicon nitride sublayer; 412, second silicon nitride sublayer; 413, third silicon nitride sublayer; 42, first silicon oxynitride layer; 43, second silicon oxide layer; 51, dielectric layer; 511, fourth silicon oxide layer; 52, doped polysilicon layer; 6, second antireflection layer; 61, second silicon nitride layer; 71, first electrode; 72, second electrode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0042] In the present invention, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0043] Moreover, in addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0044] In addition, the terms "mounted", "arranged", "provided with", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can be internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In addition, terms such as "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "a plurality" is two or more.

[0046] Under ultraviolet light irradiation in the wavelength range of 300 nm to 400 nm, the photoelectric conversion efficiency of solar cells is prone to attenuation. Specifically, ultraviolet light may cause the silicon-hydrogen bonds (Si-H) in the surface passivation film layer and / or antireflection film layer of the silicon substrate to break. After hydrogen atoms overflow from the silicon-hydrogen bonds, it will reduce the passivation effect of the surface passivation film layer and / or antireflection film layer of the silicon substrate, exacerbate the recombination of carriers, and thus reduce the photoelectric conversion efficiency of the solar cell, mainly manifested as a decrease in the open-circuit voltage. Therefore, optimizing the design and manufacturing process of solar cells to alleviate the performance attenuation caused by ultraviolet light has become the focus of current research.

[0047] The technical solutions of the present invention will be further described below in conjunction with embodiments and drawings.

[0048] In a first aspect, an embodiment of the present invention provides a solar cell.

[0049] Referring to Figure 1 , a solar cell includes a silicon substrate 1, and an emitter 11, a first silicon oxide layer 2, an aluminum oxide layer 3, and a first antireflection layer 4 are sequentially stacked on the light-receiving surface of the silicon substrate 1;

[0050] Among them, the thickness of the first silicon oxide layer 2 is 0.2 nm to 1.2 nm.

[0051] In the present invention, a first silicon oxide layer 2 with a specific thickness (0.2 nm to 1.2 nm) is introduced between the emitter 11 and the aluminum oxide layer 3. Among them, the first silicon oxide layer 2 is not the silicon oxide material directly prepared on the surface of the emitter 11, but uses the oxygen atoms in the aluminum oxide layer 3 and / or oxygen atoms in a high-energy state (such as: ionized oxygen atoms). These oxygen atoms pass through the aluminum oxide layer 3 and act indirectly on the emitter surface, thereby forming the first silicon oxide layer 2 at the interface between the emitter 11 and the aluminum oxide layer 3.

[0052] Since the formation condition of the silicon oxide in the first silicon oxide layer 2 is to migrate the oxygen atoms in the aluminum oxide layer 3 to the surface of the emitter 11, or to act on the aluminum oxide layer 3 through oxygen atoms in a high-energy state (such as: ionized oxygen atoms) to provide an oxygen atom source for the formation of the first silicon oxide layer 2. Therefore, when preparing the silicon oxide layer under air conditions or in the presence of other non-oxygen media, the aluminum oxide layer effectively isolates impurities in the air or impurities in the non-oxygen media, thereby reducing the possibility of impurities doping into the silicon oxide material, and further providing an oxygen atom source with higher purity and fewer impurity atoms for the preparation of the first silicon oxide layer 2, so that the prepared first silicon oxide layer 2 has a lower interface state density and better interface passivation effect.

[0053] It should be noted that traditional methods for preparing a silicon oxide layer include: hydrogen peroxide oxidation, ozone oxidation, wet oxygen oxidation, dry oxygen oxidation, etc. After directly preparing the silicon oxide layer on the surface of the emitter, the alumina layer is then prepared. An oxygen atom source is provided by hydrogen peroxide, an oxygen atmosphere, H2O, or ozone. Since the substance providing the oxygen atom source cannot have 100% purity, and if a high-temperature furnace tube is used to prepare the silicon oxide, the atmosphere in the high-temperature furnace tube cannot achieve an absolute vacuum environment. Considering that the silicon oxide layer at the interface between the emitter 11 and the alumina layer 3 is very thin, not exceeding 2 nm, this makes the silicon oxide layer extremely sensitive to impurities. Even an extremely low-vacuum furnace tube atmosphere cannot provide an oxygen atom source with high purity, which results in the silicon oxide layer prepared on the surface of the emitter 11 being extremely likely to be contaminated with impurities, having an adverse effect on maintaining the stability of the emitter 11 interface for a long time, and being unfavorable for improving the ultraviolet attenuation resistance performance of the solar cell. In contrast, the indirect oxidation treatment method adopted in the present invention can effectively reduce the adverse effects of insufficient oxygen atom source purity and impurities in the preparation environment atmosphere on the process of preparing the silicon oxide layer, and greatly reduce the introduction of impurities into the silicon oxide layer. Therefore, the silicon oxide layer prepared by indirect oxidation treatment has fewer impurities and higher quality, which is more beneficial for enhancing the stability of the solar cell under ultraviolet light irradiation.

[0054] The interface state density of the first silicon oxide layer 2 is in the range of 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 , which can effectively reduce the degree of carrier recombination caused by lattice mismatch at the interface between the emitter 11 and the alumina layer 3, and effectively suppress the performance degradation of the solar cell under ultraviolet light irradiation.

[0055] Specifically, first, the first silicon oxide layer 2 with a specific thickness tightly binds oxygen atoms to the silicon dangling bonds on the surface of the emitter 11 to form a stable, dense Si-O bond network with a low interface state density. This structure can effectively passivate the silicon dangling bonds on the surface of the emitter 11, enabling the surface of the emitter 11 to obtain a low defect state density, thereby providing a better interface passivation effect and a higher open-circuit voltage for the solar cell. In addition, the front surface of the solar cell in this application has a dense alumina layer 3 with a high bond energy, which can effectively block the destruction of the Si-O bonds in the first silicon oxide layer 2 by photons in the ultraviolet band. Moreover, since the alumina layer 3 prepared by ALD contains hydrogen atoms, the hydrogen atoms in the alumina layer 3 will also migrate into the first silicon oxide layer 2, which can further improve the interface passivation effect of the first silicon oxide layer 2, thereby slowing down the electrical performance degradation of the solar cell under ultraviolet light, that is, slowing down the power degradation phenomenon of the photovoltaic module under ultraviolet light irradiation.

[0056] In the present invention, the thickness of the first silicon oxide layer 2 plays a crucial role in the stability of the solar cell under ultraviolet light irradiation. The anti-ultraviolet stability of the solar cell shows a trend of first increasing and then decreasing with the change of the thickness of the first silicon oxide layer 2. When the thickness of the first silicon oxide layer 2 is less than 0.2 nm, the improvement of the interface passivation performance of the first silicon oxide layer 2 on the emitter 11 is limited, and the interface state density is relatively high. Therefore, the interface passivation effect of the solar cell is poor, which is not conducive to the preparation of high-efficiency solar cells. However, when the thickness of the first silicon oxide layer 2 is in the range of 0.2 to 0.8 nm, the interface passivation effect of the emitter 11 is in a better range, and the interface state density decreases, and the anti-ultraviolet stability of the solar cell also increases significantly. But once the thickness of the first silicon oxide layer exceeds 1.2 nm, the inventors found that the anti-ultraviolet stability of the solar cell will even deteriorate further.

[0057] Exemplarily, the thickness of the first silicon oxide layer 2 can be 0.2 nm, 0.3 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.0 nm or 1.2 nm.

[0058] Preferably, the thickness of the first silicon oxide layer 2 is 0.3 nm to 0.8 nm.

[0059] By further adjusting the thickness of the first silicon oxide layer 2 to the above preferred range, not only can the first silicon oxide layer 2 provide better interface passivation performance, but also it can more effectively alleviate the hindrance effect of the field effect of the positive first silicon oxide layer 2 on the hole carrier transport, and is more conducive to the tunneling transport of photo-generated carriers. Thus, through the cooperation of the first silicon oxide layer 2 and the aluminum oxide layer 3, the surface of the emitter 11 has the best interface passivation effect, further improving the anti-ultraviolet attenuation performance of the solar cell.

[0060] In some embodiments, the silicon substrate 1 is N-type and the emitter 11 is P-type.

[0061] The P-type emitter 111 provides hole carriers during the operation of the solar cell. The alumina layer 3 is a negatively charged layer, which can provide a favorable field effect for the transport of hole carriers and facilitate the drift of hole carriers. This mechanism promotes the effective migration of hole carriers. On the contrary, the first silicon oxide layer 2, which carries positive charges, repels hole carriers and constitutes a field-effect obstacle to the drift of hole carriers. By controlling the thickness of the first silicon oxide layer 2 disposed between the P-type emitter 111 and the alumina layer 3 within a specific range, the present invention can effectively reduce the field-effect obstacle of the first silicon oxide layer 2 to the tunneling and drift of hole carriers and promote the migration of hole carriers. At the same time, the first silicon oxide layer 2 can also provide a good interface passivation effect for the interface between the P-type emitter 111 and the alumina layer 3. In addition, the N-type silicon substrate solar cell has high conversion efficiency and long-term reliability. Therefore, the solution of the present invention is particularly suitable for the design using the P-type emitter 111.

[0062] In some embodiments, the thickness of the alumina layer 3 is 3 nm to 8 nm.

[0063] The alumina layer 3 with the above thickness can provide a good passivation effect for the solar cell and is also conducive to oxygen atoms entering the surface of the emitter 11 through the alumina layer 3 to form the first silicon oxide layer 2 with a specific thickness on the surface of the emitter 11.

[0064] Exemplarily, the thickness of the alumina layer 3 can be 3 nm, 5 nm or 8 nm.

[0065] Refer to Figure 2 , in some embodiments, a first antireflection layer 4 is disposed on one side of the alumina layer 3 away from the silicon substrate 1. The first antireflection layer 4 includes one or a combination of a first silicon nitride layer 41, a first silicon oxynitride layer 42, and a second silicon oxide layer 43.

[0066] The first silicon nitride layer 41 and the first silicon oxynitride layer 42 are H-rich film layers. By combining H with Si atoms in the film layer to form Si-H bonds, the interface contact characteristics are effectively optimized, the interface state density of the solar cell is further reduced, the recombination loss of carriers is reduced, and it is beneficial to improve the open-circuit voltage and the electrical performance of the solar cell.

[0067] When the hydrogen atoms in the film layers such as the first silicon nitride layer 41 and / or the first silicon oxynitride layer 42 on the front surface of the solar cell overflow under ultraviolet irradiation, the dense and high-bond-energy alumina layer 3 can also provide an effective barrier for the overflowing hydrogen atoms, thereby slowing down the significant attenuation of the hydrogen atom density in the film layers such as the first silicon nitride layer 41 and / or the first silicon oxynitride layer 42 under ultraviolet irradiation.

[0068] Refer to Figure 3, the first silicon nitride layer 41 includes a first silicon nitride sub-layer 411, a second silicon nitride sub-layer 412, and a third silicon nitride sub-layer 413. By adjusting the ratio of silicon atoms to nitrogen atoms in the first silicon nitride sub-layer 411, the second silicon nitride sub-layer 412, and the third silicon nitride sub-layer 413, the first silicon nitride layer 41 can achieve an excellent antireflection effect.

[0069] The second silicon oxide layer 43 also serves as an effective antireflection material. While ensuring good light transmittance, when combined with the first silicon nitride layer 41 or the first silicon oxynitride layer 42, it can form a multi-layer antireflection structure, further optimizing the spectral response and broadening the light absorption range.

[0070] Referring to Figure 2 , in some embodiments, the first antireflection layer 4 includes a first silicon nitride layer 41, a first silicon oxynitride layer 42, and a second silicon oxide layer 43 that are sequentially stacked.

[0071] Referring back to Figure 1 , in some embodiments, the backlight side of the silicon substrate 1 includes a dielectric layer 51, a doped polysilicon layer 52, and a second antireflection layer 6 that are sequentially arranged;

[0072] The second antireflection layer 6 includes one or a combination of a second silicon nitride layer 61, a second silicon oxynitride layer, and a third silicon oxide layer.

[0073] Furthermore, referring to Figure 2 , in some embodiments, the second antireflection layer 6 is the second silicon nitride layer 61.

[0074] Among them, the material of the dielectric layer 51 can include various dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polysilicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the dielectric layer 51 can be composed of a fourth silicon oxide layer 511 containing silicon oxide. This is because the fourth silicon oxide layer 511 has excellent passivation performance, can minimize the recombination loss of minority carriers on the surface of the emitter 11, and is a film with excellent durability for subsequent high-temperature processes.

[0075] In order to better provide an interface passivation effect for the silicon substrate 1, the thickness of the dielectric layer 51 can be 0.5 nm to 3 nm. For example, the thickness of the dielectric layer 51 can be 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, etc. However, the present invention is not limited thereto, and the thickness of the dielectric layer 51 can have various values.

[0076] The conductivity type of the doped polysilicon layer 52 is opposite to that of the emitter 11 to achieve effective carrier separation and collection. Specifically, if the conductivity type of the emitter 11 is P-type (i.e., mainly doped with an element that accepts electrons, such as boron), the conductivity type of the doped polysilicon layer 52 is correspondingly configured as N-type (i.e., mainly doped with an element that provides electrons). In this case, the conductive element doped in the doped polysilicon layer 52 is an N-type element, typically phosphorus. Phosphorus can introduce extra free electrons into the silicon lattice in the doped polysilicon layer 52, thereby enhancing the electron conductivity of the doped polysilicon layer 52 and being conducive to improving the transport ability of electron carriers.

[0077] Refer back Figure 1 In some embodiments, a first electrode 71 is provided on the light-receiving surface side of the silicon substrate 1, and the first electrode 71 forms an ohmic contact with the emitter 11; a second electrode 72 is provided on the backlight surface side of the silicon substrate 1, and the second electrode 72 forms an ohmic contact with the doped polysilicon layer 52.

[0078] In a second aspect, an embodiment of the present invention provides a method for manufacturing a solar cell.

[0079] A method for manufacturing a solar cell includes the following steps:

[0080] Provide a silicon substrate 1 having an emitter 11 on the light-receiving surface side;

[0081] Prepare an alumina layer 3 on the surface of the emitter 11;

[0082] Perform an indirect oxidation treatment to indirectly grow a first silicon oxide layer 2 on the surface of the emitter 11.

[0083] The inventors found that during the manufacturing process of the solar cell, first prepare the alumina layer 3, and then perform an indirect oxidation treatment to allow the oxygen source to pass through the alumina layer 3 to indirectly grow the first silicon oxide layer 2 on the surface of the emitter 11. Thus, a stable, dense and low interface state density Si-O bond network can be obtained, which can more effectively improve the interface passivation effect between the alumina layer 3 and the emitter 11, enabling the solar cell to have a high open-circuit voltage and photoelectric conversion efficiency. In addition, the structure of the first silicon oxide layer 2 grown by the above indirect oxidation treatment is more dense. When hydrogen atoms in the passivation film layers such as silicon nitride and / or silicon oxynitride on the front side of the solar cell overflow under ultraviolet irradiation, the dense first silicon oxide layer 2 can effectively block the diffusion of hydrogen atoms, which is conducive to improving the anti-ultraviolet attenuation performance of the solar cell.

[0084] If the preparation order of the alumina layer 3 and the first silicon oxide layer 2 is swapped and the silicon oxide layer is prepared by direct oxidation treatment, that is, the silicon oxide layer is prepared first and then the alumina layer 3 is prepared, the quality of the obtained silicon oxide layer is poor and the interface state density is high. The inventor analyzed the mechanism and it may be that: when the direct oxidation treatment method is used to prepare the silicon oxide layer, for example, methods such as hydrogen peroxide oxidation, ozone oxidation, wet oxygen oxidation, and dry oxygen oxidation are used to prepare the silicon oxide layer at the interface between the emitter 11 and the alumina layer 3, and the oxygen atom source is provided by hydrogen peroxide, oxygen atmosphere with low purity, H2O or ozone. Since the substances providing the oxygen atom source cannot have 100% purity in this direct oxidation treatment, and also, if the silicon oxide is prepared in a high-temperature furnace tube, since the atmosphere in the high-temperature furnace tube cannot reach an absolute vacuum environment, considering that the silicon oxide layer at the interface between the emitter 11 and the alumina layer 3 is very thin and will not exceed 2 nm, even the furnace tube atmosphere with a very low vacuum degree cannot provide an oxygen atom source with high purity. Therefore, when the direct oxidation treatment method is used to prepare the silicon oxide layer between the emitter and the alumina layer, the stability of the solar cell under ultraviolet light irradiation is not significantly improved or even worse.

[0085] In some embodiments, the indirect oxidation treatment method includes ionized oxygen source treatment and / or annealing treatment at 400°C to 600°C, and the oxygen source includes one or more of N2O, O2 or O3. Among them, the ionization means in the ionized oxygen source treatment includes PECVD method and LPCVD method.

[0086] After the preparation of the alumina layer 3 is completed, ionized oxygen atoms can be passed through the alumina layer 3 to reach the surface of the emitter 11, and a first silicon oxide layer 2 with a specific thickness is formed on the surface of the emitter 11; among them, since the alumina layer 3 contains H atoms, when the surface treatment of ionized oxygen atoms is performed on the alumina layer 3, the H atoms will also migrate into the first silicon oxide layer 2 during the high-energy treatment process of ionized oxygen atoms and / or during the annealing treatment process at 400°C to 600°C, further enhancing the surface passivation effect of the front emitter of the solar cell and helping to improve the open-circuit voltage and photoelectric conversion efficiency.

[0087] In some embodiments, the indirect oxidation treatment method includes annealing the alumina layer 3 at 400°C to 600°C, and through the high-temperature treatment, the oxygen atoms in the alumina layer 3 migrate into the first silicon oxide layer 2, further enhancing the surface passivation effect of the front emitter of the solar cell and helping to improve the open-circuit voltage and photoelectric conversion efficiency.

[0088] In some embodiments, the indirect oxidation treatment method includes ionizing N2O treatment, with an ionization time of 10 s to 120 s, an N2O flow rate of 5000 sccm to 20000 sccm, a temperature of 450 °C to 470 °C, a radio frequency power of 6000 W to 12000 W, a radio frequency power supply of 20 ms to 50 ms, and heat preservation for 5 min to 60 min; by providing oxygen atoms in a high-energy state, i.e., an ionized state, it is possible to promote the formation of more stable Si-O bonds with silicon atoms on the emitter surface.

[0089] After the first silicon oxide layer 2 is prepared, the first antireflection layer 4 is prepared. The preparation of the first antireflection layer 4 will be described in more detail below. In some embodiments, the first silicon nitride layer 41 is prepared on the side of the alumina layer 3 away from the silicon substrate 1 by PECVD, with a deposition temperature of 450 °C to 470 °C. The first silicon nitride layer 41 is composed of a first silicon nitride sublayer 411, a second silicon nitride sublayer 412, and a third silicon nitride sublayer 413 that are sequentially stacked on the side of the alumina layer 3 away from the first silicon oxide layer 2. Among them, the preparation of the first silicon nitride sublayer 411, the second silicon nitride sublayer 412, and the third silicon nitride sublayer 413 can all be prepared by adjusting the deposition time of PECVD, the SiH4 flow rate, the NH3 flow rate, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply to prepare the corresponding silicon nitride layer. It should be noted that the first silicon nitride layer 41 can be a single layer or multiple layers. Among them, different silicon nitride layers are distinguished by different deposition conditions of the above PECVD. For example, when any one of the process parameters of the deposition time of PECVD, the SiH4 flow rate, the NH3 flow rate, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply is different, in this application, it will be regarded as a silicon nitride film layer with a different structure.

[0090] In some embodiments, the first silicon oxynitride layer 42 is prepared on the side of the first silicon nitride layer 41 away from the N-type monocrystalline silicon wafer by PECVD. Among them, the preparation of the first silicon oxynitride layer 42 can be prepared by adjusting the deposition time of PECVD, the SiH4 flow rate, the N2O flow rate, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply to prepare the corresponding silicon nitride layer. It should be noted that the first silicon oxynitride layer 42 can be a single layer or multiple layers. Among them, different silicon oxynitride layers are distinguished by different deposition conditions of the above PECVD. For example, when any one of the process parameters of the deposition time of PECVD, the SiH4 flow rate, the N2O flow rate, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply is different, in this application, it will be regarded as a silicon oxynitride film layer with a different structure.

[0091] In some embodiments, a second silicon oxide layer 43 is prepared on the side of the first silicon oxynitride layer 42 facing away from the N-type monocrystalline silicon wafer by PECVD. Among them, the second silicon oxide layer 43 can be prepared by adjusting the deposition time of PECVD, the flow rate of SiH4, the flow rate of N2O, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply to prepare the corresponding second silicon oxide layer. It should be noted that the second silicon oxide layer 43 can be a single layer or multiple layers. Among them, different second silicon oxide layers are distinguished by different deposition conditions of the above PECVD. For example, when any one of the process parameters such as the deposition time of PECVD, the flow rate of SiH4, the flow rate of N2O, the deposition pressure, the radio frequency power, and the on and off time of the radio frequency power supply is different, in this application, it will be regarded as a silicon oxynitride film layer with a different structure.

[0092] In a third aspect, an embodiment of the present invention provides a photovoltaic module.

[0093] A photovoltaic module includes a solar cell as mentioned in the first aspect or a solar cell prepared by the preparation method as mentioned in the second aspect.

[0094] The technical solution of the present invention will be further described below in conjunction with more specific embodiments and drawings.

[0095] Embodiment 1

[0096] An embodiment of the present invention provides a solar cell. The preparation method of the solar cell includes the following steps:

[0097] Provide an N-type monocrystalline silicon wafer, form a P-type boron emitter by boron diffusion on the light-receiving surface side of the N-type monocrystalline silicon wafer, and remove the BSG (boron silicon glass) layer by wet processing;

[0098] On the backlight surface of the N-type monocrystalline silicon wafer, a dielectric layer and a phosphorus-doped amorphous silicon layer are sequentially prepared by PECVD, annealed at 950 °C for 90 min, and the phosphorus-doped amorphous silicon layer is crystallized and transformed into a phosphorus-doped polycrystalline silicon layer;

[0099] Remove the natural silicon oxide layer on the light-receiving surface side of the N-type monocrystalline silicon wafer by RCA wet processing;

[0100] Prepare an alumina layer on the surface of the P-type boron emitter by ALD;

[0101] Ionize N2O by PECVD, the ionization time is 30 s, the flow rate of N2O is 10000 sccm, the temperature is 450 °C to 550 °C, the radio frequency power is 8000 W, the radio frequency power supply is 35 ms, and it is processed for 5 min to 60 min under the temperature condition of 450 °C to 550 °C. The first silicon oxide layer is grown on the surface of the P-type boron emitter close to the alumina layer by indirect oxidation treatment;

[0102] The first silicon nitride layer is prepared by PECVD method, and the deposition temperature is 450 °C to 470 °C. The first silicon nitride layer is composed of a first silicon nitride sub-layer, a second silicon nitride sub-layer, and a third silicon nitride sub-layer which are sequentially stacked on the side of the alumina layer facing away from the first silicon oxide layer. Among them, the deposition time of the first silicon nitride sub-layer is 75 s, the flow rate of SiH4 is 2000 sccm, the flow rate of NH3 is 6500 sccm, the pressure is 1600 mTorr, and the RF power is 13500 W; the deposition time of the second silicon nitride sub-layer is 125 s, the flow rate of SiH4 is 1100 sccm, the flow rate of NH3 is 8000 sccm, the pressure is 1600 mTorr, and the RF power is 14000 W; the deposition time of the third silicon nitride sub-layer is 160 s, the flow rate of SiH4 is 1000 sccm, the flow rate of NH3 is 10000 sccm, the pressure is 1600 mTorr, and the RF power is 14000 W. The RF power supply is turned on for 35 ms and turned off for 550 ms.

[0103] The first silicon oxynitride layer is prepared by PECVD method on the side of the first silicon nitride layer facing away from the N-type monocrystalline silicon wafer. The deposition time is 300 s, the flow rate of SiH4 is 900 sccm, the flow rate of NH3 is 3500 sccm, the flow rate of N2O is 7500 sccm, the pressure is 1200 mTorr, the RF power is 13500 W, the RF power supply is turned on for 35 ms, and the RF power supply is turned off for 900 ms.

[0104] The second silicon oxide layer is prepared by PECVD method on the side of the first silicon oxynitride layer facing away from the N-type monocrystalline silicon wafer. The deposition time is 120 s, the flow rate of SiH4 is 750 sccm, the flow rate of N2O is 9500 sccm, the pressure is 1150 mTorr, the RF power is 13500 W, the RF power supply is turned on for 35 ms, and the RF power supply is turned off for 900 ms.

[0105] The second silicon nitride layer is prepared by PECVD method on the side of the phosphorus-doped polysilicon layer facing away from the N-type monocrystalline silicon wafer.

[0106] The first electrode is prepared on the light-receiving surface side, so that the first electrode forms an ohmic contact with the P-type boron emitter. The second electrode is prepared on the backlight surface side, so that the second electrode forms an ohmic contact with the phosphorus-doped polysilicon layer.

[0107] Example Two

[0108] The embodiment of the present invention provides a solar cell, which is different from Example One in that: the thickness of the first silicon oxide layer is different; specifically, in the step of ionizing N2O, the ionization time is 60 s, and the rest is the same as Example One.

[0109] Example Three

[0110] An embodiment of the present invention provides a solar cell, which is different from Embodiment 1 in that: the thickness of the first silicon oxide layer is different; specifically, in the step of ionizing N2O, the ionization time is 120 s, and the rest is the same as that in Embodiment 1.

[0111] Embodiment 4

[0112] An embodiment of the present invention provides a solar cell, which is different from Embodiment 1 in that: the thickness of the first silicon oxide layer is different; specifically, in the step of ionizing N2O, the ionization time is 180 s, and the rest is the same as that in Embodiment 1.

[0113] Comparative Example

[0114] This comparative example provides a solar cell, which is different from Embodiment 3 in that after the alumina layer is prepared, the step of ionizing N2O by PECVD method is omitted, that is, the first silicon oxide layer is not prepared between the alumina layer and the P-type boron emitter, but the silicon nitride layer is directly prepared, and the rest is the same as that in Embodiment 3.

[0115] Experiment 1

[0116] Thickness test of the first silicon oxide layer

[0117] The thickness of the first silicon oxide layer is tested by using the EDS element scanning function in TEM or HR-TEM. The interface boundary line with obvious color difference in the EDS scanning image is selected as the measurement reference for the thickness of the first silicon oxide layer. The thickness test results of the first silicon oxide layer in each embodiment and comparative example are shown in Table 1.

[0118] Experiment 2

[0119] Battery efficiency decay test

[0120] 2.1. Battery cell decay performance test

[0121] The solar cells prepared by the preparation methods of the above embodiments and comparative examples are used as the battery cell samples for testing. The photoelectric conversion efficiency of the battery cell samples before and after ultraviolet aging treatment is tested, and by calculating the photoelectric conversion efficiency before ultraviolet aging treatment minus the photoelectric conversion efficiency after ultraviolet aging treatment, the battery cell efficiency decay difference after ultraviolet aging treatment is obtained.

[0122] Ultraviolet aging treatment: Take the battery cell samples, and the test conditions include: 60 ± 5 °C, wavelength range 280 nm to 400 nm, irradiation intensity 200 W / m 2 , and the battery cells are taken out after continuous and stable irradiation of 60 kWh and the IV is tested again. The percentage of efficiency decay before and after irradiation is the battery cell efficiency decay difference.

[0123] 2.2 Photovoltaic module attenuation performance test

[0124] The solar cells prepared by the preparation methods of the above-mentioned various embodiments and comparative examples are encapsulated into photovoltaic module samples. The maximum power of the photovoltaic module samples before and after ultraviolet aging treatment is tested, and by calculating the power before ultraviolet aging treatment minus the power after ultraviolet aging treatment, the power attenuation difference of the photovoltaic module after ultraviolet aging treatment is obtained.

[0125] Ultraviolet aging treatment: The cell is encapsulated into a double-glass photovoltaic module. After the photovoltaic module is fabricated, the IV is tested after standing for 24 h, and then it is placed in a UV irradiation chamber. The test conditions include: 60 ± 5 °C, wavelength range 280 nm - 400 nm, irradiation intensity 200 W / m 2 , and the module is taken out after continuous and stable irradiation of 60 kWh and the IV is tested again. The power difference of the photovoltaic module before and after irradiation is the power attenuation difference of the photovoltaic module.

[0126] The test results of the cell efficiency attenuation in Experiment 2 are recorded in Table 1. Among them, in view of the possible differences in crystal structures on the silicon substrate surfaces in different regions, the silicon atoms on the emitter surfaces in different regions have different reaction activities. Therefore, under the same indirect oxidation treatment conditions, the thickness of the first silicon oxide layer prepared may fluctuate within a certain numerical range. In this application, for the thickness of the first silicon oxide layer in Embodiments 1 to 4, in combination with the description of the first silicon oxide layer thickness test in Experiment 1, the lowest thickness of the first silicon oxide layer on the test cross-section is selected to define the first silicon oxide thickness in this application; however, if the thickness of the first silicon oxide layer in a specific region of this cross-section is significantly lower than that in other regions and the proportion of this specific region in the selected cross-section exceeds 30%, it is regarded as an abnormal test region and excluded from the test selection region of the first silicon oxide layer thickness.

[0127] Table 1

[0128]

[0129] It can be seen from Table 1 that:

[0130] First, when forming a silicon oxide layer between the emitter and the alumina layer by using the direct oxidation treatment method in Comparative Example 1, both the cell efficiency attenuation difference and the photovoltaic module power attenuation difference are greater than those in Embodiments 1 to 4, indicating that the first silicon oxide layer prepared by the indirect oxidation treatment method adopted in this application between the emitter and the alumina layer has better anti-ultraviolet attenuation performance;

[0131] In a second aspect, compared with Embodiments 1 to 3, the differences in the efficiency decay of the solar cell and the power decay of the photovoltaic module before and after the ultraviolet aging test in Embodiment 4 are relatively high, indicating that too long plasma treatment time using an oxygen source may damage the structure of the alumina layer and / or the first silicon oxide layer, or may exacerbate the damage of the hydrogen-based valence bonds in the alumina layer and / or the first silicon oxide layer, thereby causing the decay of the solar cell efficiency and / or the decay of the ultraviolet aging performance of the solar cell. Therefore, when the thickness range of the first silicon oxide layer is 0.2 nm to 1.2 nm, it is beneficial to alleviate the ultraviolet aging decay performance of the solar cell;

[0132] In a third aspect, compared with other embodiment groups, Embodiment 2 has the lowest differences in the efficiency decay of the solar cell and the power decay of the photovoltaic module before and after the ultraviolet aging test, and has the best ultraviolet decay resistance performance, indicating that the optimal thickness range of the first silicon oxide layer is 0.6 nm to 0.8 nm. Compared with other embodiment groups, Embodiment 2 has the lowest differences in the efficiency decay of the solar cell and the power decay of the photovoltaic module before and after the ultraviolet aging test, and has the best ultraviolet decay resistance performance, indicating that the optimal thickness range of the first silicon oxide layer is 0.6 nm to 0.8 nm.

[0133] The above has introduced in detail the solar cell, its preparation method, and the photovoltaic module disclosed in the embodiments of the present invention. Specific examples are used herein to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the solar cell, its preparation method, the photovoltaic module, and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A solar cell, characterized in that: It comprises a silicon substrate, wherein the light-receiving surface of the silicon substrate is sequentially stacked with an emitter, a first silicon oxide layer, an aluminum oxide layer and a first anti-reflection layer; Wherein, the thickness of the first silicon oxide layer is 0.2 nm to 1.2 nm; The interface state density of the first silicon oxide layer is 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 ; The first anti-reflection layer comprises a first silicon nitride layer, a first silicon oxynitride layer and a second silicon oxide layer; After the aluminum oxide layer is formed, the emitter surface is oxidized to grow the first silicon oxide layer.

2. The solar cell according to claim 1, characterized in that: The thickness of the first silicon oxide layer is 0.3 nm to 0.8 nm.

3. The solar cell according to claim 1, characterized in that: The silicon substrate is of N type, and the emitter is of P type.

4. The solar cell according to claim 1, characterized in that: The thickness of the aluminum oxide layer is 3 nm to 8 nm.

5. The solar cell according to any one of claims 1 to 4, characterized in that: The backlight side of the silicon substrate includes a dielectric layer, a doped polysilicon layer and a second anti-reflection layer arranged in sequence; The second anti-reflection layer comprises one or more combinations of a second silicon nitride layer, a second silicon oxynitride layer and a third silicon oxide layer; A first electrode is disposed on the light-receiving side of the silicon substrate, and the first electrode forms an ohmic contact with the emitter; a second electrode is disposed on the backlight side of the silicon substrate, and the second electrode forms an ohmic contact with the doped polysilicon layer.

6. A method for preparing a solar cell, characterized in that: The method for preparing a solar cell according to any one of claims 1 to 5 comprises the following steps: Providing a silicon substrate having an emitter on one side of the light receiving surface; Preparing an aluminum oxide layer on the surface of the emitter; The indirect oxidation treatment causes the first silicon oxide layer to be indirectly grown on the surface of the emitter.

7. The method for preparing a solar cell according to claim 6, characterized in that: The indirect oxidation treatment includes subjecting the aluminum oxide layer to an ionized oxygen source treatment and / or subjecting the aluminum oxide layer to an annealing treatment.

8. The method for preparing a solar cell according to claim 7, characterized in that: The oxygen source includes one or more of CO2, N2O, H2O, O2 or O3; And / or, the ionized oxygen source method includes PECVD or LPCVD; And / or, the temperature range of the annealing treatment is 400°C to 600°C.

9. The method for preparing a solar cell according to claim 7 or 8, characterized in that: The indirect oxidation treatment is the annealing treatment, and O2 or O3 is introduced during the annealing treatment to prepare the first silicon oxide layer.

10. The method for preparing a solar cell according to claim 7, characterized in that: The treatment of the ionized oxygen source is ionized N2O.

11. The method for preparing a solar cell according to claim 7, characterized in that: The indirect oxidation treatment is the annealing treatment, and a treatment of ionizing N2O is performed during the annealing treatment.

12. The method for preparing a solar cell according to claim 10 or 11, characterized in that: The process conditions for ionizing N2O on the aluminum oxide layer are: The ionization time is 10 s~120 s, the N2O flow rate is 5000 sccm~20000 sccm, the temperature is 450℃~470℃, the RF power is 6000 W~12000 W, and the RF power supply is 20 ms~50 ms.

13. A photovoltaic module, characterized in that: The invention comprises the solar cell as described in any one of claims 1 to 5 or the solar cell prepared by the preparation method as described in any one of claims 6 to 12.

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