Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises a silicon substrate, and an emitting electrode, a first silicon oxide layer and an aluminum oxide layer are sequentially arranged on the light receiving surface of the silicon substrate in a laminated mode; wherein the thickness of the first silicon oxide layer ranges from 0.2 nm to 1.2 nm. According to the invention, the interface stability of the emitter can be effectively improved, and the efficiency attenuation of the solar cell under ultraviolet irradiation is inhibited.

Description

Technical Field

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

[0002] As the core component of photovoltaic modules, solar cells have an important impact on the efficiency of photovoltaic modules. However, under the influence of ultraviolet light, the photoelectric conversion efficiency of solar cells will decrease prematurely, resulting in obvious power attenuation problems in photovoltaic modules. This phenomenon poses a severe challenge to the long-term stable operation of photovoltaic modules, and seriously affects the service life and working efficiency of photovoltaic modules. Summary of the invention

[0003] In order to reduce the impact of ultraviolet light irradiation on solar cells, the embodiments of the present invention disclose a solar cell and 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 comprises a silicon substrate, wherein an emitter, a first silicon oxide layer, an aluminum oxide layer and a first anti-reflection layer are sequentially stacked on a light-receiving surface of the silicon substrate; Wherein, the thickness of the first silicon oxide layer is 0.2 nm~1.2 nm.

[0006] As an optional implementation, 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 .

[0007] As an optional implementation, in an embodiment of the present invention, the thickness of the first silicon oxide layer is 0.3 nm to 0.8 nm.

[0008] As an optional implementation, in an embodiment of the present invention, the silicon substrate is of N type, and the emitter is of P type.

[0009] As an optional implementation, in an embodiment of the present invention, the thickness of the aluminum oxide layer is 3 nm to 8 nm; and / or, The first anti-reflection layer includes one or a combination of a first silicon nitride layer, a first silicon oxynitride layer and a second silicon oxide layer.

[0010] As an optional implementation, in an embodiment of the present invention, 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.

[0011] In a second aspect, an embodiment of the present invention provides a method for preparing a solar cell as described in the first aspect.

[0012] A method for preparing a solar cell comprises the following steps: Providing the silicon substrate having the emitter on one side of the light receiving surface; Prepare the 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.

[0013] As an optional implementation, in an embodiment of the present invention, the indirect oxidation treatment includes treating the aluminum oxide layer with an ionized oxygen source and / or annealing the aluminum oxide layer.

[0014] As an optional embodiment, in an embodiment of the present invention, the oxygen source includes one or more of CO2, N2O, H2O, O2 or O3; And / or, the ionization method includes PECVD or LPCVD; And / or, the temperature range of the annealing treatment is 400°C to 600°C.

[0015] As an optional implementation manner, in an 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.

[0016] As an optional implementation manner, in an embodiment of the present invention, the processing of the ionized oxygen source is ionized N2O.

[0017] As an optional implementation, in an embodiment of the present invention, the indirect oxidation treatment is the annealing treatment, and a treatment of ionizing N2O is performed during the annealing treatment.

[0018] As an optional implementation, in an embodiment of the present invention, 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.

[0019] In a third aspect, an embodiment of the present invention provides a photovoltaic module.

[0020] A photovoltaic component comprises the solar cell according to the first aspect or the solar cell prepared by the preparation method according to the second aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects: An embodiment of the present invention provides a method of introducing a first silicon oxide layer of a specific thickness (0.2 nm to 1.2 nm) between the emitter and the aluminum oxide layer. The first silicon oxide layer can effectively reduce the defect state density at the interface between the emitter and the aluminum oxide layer, and can improve the anti-ultraviolet attenuation performance of the photovoltaic module.

[0022] First, the first silicon oxide layer of a specific thickness uses oxygen atoms to tightly bond with the dangling bonds on the emitter surface to form a structurally stable and dense Si-O bond network. This structure effectively reduces the number of hydrogen atoms that overflow from the Si-H bond while passivating the dangling bonds on the emitter surface, effectively inhibiting the migration, accumulation and formation of hydrogen clusters caused by ultraviolet light irradiation, reducing the recombination of carriers, and thus slowing down the performance degradation of solar cells under ultraviolet light. Secondly, the first silicon oxide layer provides an effective transition buffer between the emitter and the aluminum oxide layer, significantly alleviating lattice distortion at the interface, reducing the density of dangling bonds at the interface, and reducing the recombination of carriers.

[0023] Furthermore, in the present invention, the thickness of the first silicon oxide layer plays a vital role in the stability of the solar cell under ultraviolet light irradiation, and 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. When the thickness of the first silicon oxide layer is less than 0.2 nm, the first silicon oxide layer has limited improvement in the interface passivation performance of the emitter, and the interface state density is high, so the anti-ultraviolet 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 is reduced, and the anti-ultraviolet stability of the solar cell is also significantly improved. However, once the thickness of the first silicon oxide layer exceeds 1.2 nm, the inventors have found through experiments that the anti-ultraviolet stability of the solar cell will even deteriorate further. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 is a schematic structural diagram of a first solar cell disclosed in an embodiment of the present invention; Figure 2 is a schematic structural diagram of a second solar cell disclosed in an embodiment of the present invention; Figure 3 It is a schematic diagram of the structure of a third solar cell disclosed in an embodiment of the present invention.

[0026] Icons: 1. Silicon substrate; 11. Emitter; 111. P-type emitter; 2. First silicon oxide layer; 3. Aluminum oxide layer; 4. First anti-reflection 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 anti-reflection layer; 61. Second silicon nitride layer; 71. First electrode; 72. Second electrode. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the directions or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0029] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0030] In addition, the terms "installed", "set", "provided with", "connected", and "connected" 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 a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection 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.

[0031] In addition, the terms "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, "plurality" means two or more.

[0032] Under the irradiation of ultraviolet light in the 300 nm ~ 400 nm band, the photoelectric conversion efficiency of solar cells is prone to attenuation. Specifically, ultraviolet light may cause the silicon-hydrogen bond (Si-H) in the passivation film layer and / or anti-reflection film layer on the surface of the silicon substrate to break. After the hydrogen atoms overflow from the silicon-hydrogen bond, they will reduce the passivation effect of the passivation film layer and / or anti-reflection film layer on the surface of the silicon substrate, aggravate the recombination of carriers, and then reduce the photoelectric conversion efficiency of the solar cell, which is mainly reflected in the reduction of 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.

[0033] The technical solution of the present invention will be further described below in conjunction with embodiments and drawings.

[0034] In a first aspect, an embodiment of the present invention provides a solar cell.

[0035] Reference Figure 1 A solar cell comprises a silicon substrate 1, wherein an emitter 11, a first silicon oxide layer 2, an aluminum oxide layer 3 and a first anti-reflection layer 4 are sequentially stacked on a light-receiving surface of the silicon substrate 1; Wherein, the thickness of the first silicon oxide layer 2 is 0.2 nm-1.2 nm.

[0036] The present invention introduces a first silicon oxide layer 2 with a specific thickness (0.2 nm to 1.2 nm) between the emitter 11 and the aluminum oxide layer 3, wherein the first silicon oxide layer 2 is not a silicon oxide material directly prepared on the surface of the emitter 11, but utilizes oxygen atoms and / or oxygen atoms in a high energy state (for example, ionized oxygen atoms) in the aluminum oxide layer 3. These oxygen atoms pass through the aluminum oxide layer 3 and indirectly act 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.

[0037] Since the formation condition of silicon oxide in the first silicon oxide layer 2 is to migrate oxygen atoms in the aluminum oxide layer 3 to the surface of the emitter 11, or to act on the aluminum oxide layer 3 with high energy oxygen atoms (such as ionized oxygen atoms) to provide an oxygen atom source for the formation of the first silicon oxide layer 2, when the silicon oxide layer is prepared under air conditions or containing other non-oxygen media, the aluminum oxide layer effectively isolates impurities in the air or impurities in the non-oxygen medium, thereby reducing the possibility of impurities being doped into the silicon oxide material, thereby 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 a better interface passivation effect.

[0038] It should be noted that the conventional methods for preparing silicon oxide layers include: hydrogen peroxide oxidation, ozone oxidation, wet oxygen oxidation, dry oxygen oxidation, etc. These methods are all to prepare the silicon oxide layer directly on the emitter surface, and then prepare the aluminum oxide layer. The oxygen atom source is provided by hydrogen peroxide, oxygen atmosphere, H2O or ozone. Since the substance providing the oxygen atom source cannot have 100% purity, and if silicon oxide is prepared in a high-temperature furnace tube, the atmosphere of 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 aluminum oxide layer 3 is very thin and does not exceed 2 nm, the silicon oxide layer is extremely sensitive to impurities. Even a furnace tube atmosphere with a very low vacuum degree cannot provide an oxygen atom source with a high purity, which causes the traditional silicon oxide layer prepared on the surface of the emitter 11 to be easily mixed with impurities, which has an adverse effect on the long-term stability of the emitter 11 interface, and is not conducive to improving the anti-ultraviolet attenuation performance of solar cells. In contrast, the indirect oxidation treatment method used in the present invention can effectively reduce the adverse effects of insufficient purity of the oxygen atom source and impurities in the preparation environment atmosphere on the preparation process of the silicon oxide layer, and greatly reduce the introduction of impurities into the silicon oxide layer. Therefore, the silicon oxide layer obtained by indirect oxidation treatment has fewer impurities and higher quality, which is more beneficial to enhancing the stability of solar cells under ultraviolet light irradiation conditions.

[0039] The interface state density of the first silicon oxide layer 2 is 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 Within the range of , the degree of carrier recombination caused by the lattice mismatch at the interface between the emitter 11 and the aluminum oxide layer 3 can be effectively reduced, and the performance degradation of the solar cell under ultraviolet light irradiation is effectively suppressed.

[0040] Specifically, firstly, the first silicon oxide layer 2 of a specific thickness utilizes oxygen atoms to tightly combine with the silicon dangling bonds on the surface of the emitter 11 to form a stable, dense Si-O bond network with low interface state density. This structure can effectively passivate the silicon dangling bonds on the surface of the emitter 11, so that the surface of the emitter 11 obtains a lower defect state density, thereby providing a better interface passivation effect and a higher open circuit voltage for the solar cell; in addition, the front side of the solar cell in the present application has an aluminum oxide layer 3 with a dense structure and 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, and since the aluminum oxide layer 3 prepared by ALD contains hydrogen atoms, the hydrogen atoms in the aluminum oxide layer 3 will also migrate to the first silicon oxide layer 2, thereby further improving the interface passivation effect of the first silicon oxide layer 2, thereby slowing down the attenuation of the electrical performance of the solar cell under ultraviolet light, that is, slowing down the power attenuation phenomenon of the photovoltaic module under ultraviolet irradiation.

[0041] In the present invention, the thickness of the first silicon oxide layer 2 plays a vital role in the stability of the solar cell under ultraviolet light irradiation, and 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 first silicon oxide layer 2 has limited improvement on the interface passivation performance of the emitter 11, and the interface state density is high, so the interface passivation effect of the solar cell is poor, which is not conducive to the preparation of efficient 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 is reduced, and the anti-ultraviolet stability of the solar cell is also significantly improved. However, once the thickness of the first silicon oxide layer exceeds 1.2 nm, the inventors have found that the anti-ultraviolet stability of the solar cell will even deteriorate further.

[0042] Illustratively, the thickness of the first silicon oxide layer 2 may be 0.2 nm, 0.3 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.0 nm or 1.2 nm.

[0043] Preferably, the thickness of the first silicon oxide layer 2 is 0.3 nm-0.8 nm.

[0044] By further adjusting the thickness of the first silicon oxide layer 2 to within the above-mentioned preferred range, not only can the first silicon oxide layer 2 provide better interface passivation performance, but also the field effect of the positive first silicon oxide layer 2 on the hindering effect of hole carrier transmission can be more effectively alleviated, and it is more conducive to the tunneling transmission of photogenerated carriers. Thus, through the cooperation of the above-mentioned first silicon oxide layer 2 and 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.

[0045] In some embodiments, the silicon substrate 1 is of N-type and the emitter 11 is of P-type.

[0046] The P-type emitter 111 provides hole carriers when the solar cell is working, and the aluminum oxide layer 3 is a negative charge layer, which can provide a favorable field effect for the transmission 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 a positive charge, repels hole carriers, which constitutes a field effect obstacle to the drift of hole carriers. The present invention controls the thickness of the first silicon oxide layer 2 disposed between the P-type emitter 111 and the aluminum oxide layer 3 within a specific range, which 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 aluminum oxide layer 3. In addition, the solar cell with an N-type silicon substrate has a higher conversion efficiency and long-term reliability. Therefore, the scheme of the present invention is particularly suitable for the design of using the P-type emitter 111.

[0047] In some embodiments, the thickness of the aluminum oxide layer 3 is 3 nm to 8 nm.

[0048] The aluminum oxide layer 3 of the above thickness can provide a good passivation effect for the solar cell, and is conducive to oxygen atoms entering the surface of the emitter 11 through the aluminum oxide layer 3 to form a first silicon oxide layer 2 with a specific thickness on the surface of the emitter 11 .

[0049] Exemplarily, the thickness of the aluminum oxide layer 3 may be 3 nm, 5 nm or 8 nm.

[0050] Reference Figure 2 In some embodiments, a first anti-reflection layer 4 is disposed on the side of the aluminum oxide layer 3 facing away from the silicon substrate 1 , and the first anti-reflection layer 4 includes one or more combinations of a first silicon nitride layer 41 , a first silicon oxynitride layer 42 and a second silicon oxide layer 43 .

[0051] The first silicon nitride layer 41 and the first silicon oxynitride layer 42 are H-rich film layers, which form Si-H bonds by combining H with Si atoms in the film layers, effectively optimizing the interface contact characteristics, further reducing the interface state density of the solar cell, reducing the recombination loss of carriers, and being beneficial to improving the open circuit voltage and the electrical performance of the solar cell.

[0052] When hydrogen atoms in the first silicon nitride layer 41 and / or the first silicon oxynitride layer 42 and other film layers on the front of the solar cell overflow under ultraviolet light, the aluminum oxide layer 3 with a dense structure and high bond energy can provide effective barriers for the overflowing hydrogen atoms, thereby slowing down the significant attenuation of the hydrogen atom density in the above-mentioned first silicon nitride layer 41 and / or the first silicon oxynitride layer 42 and other film layers under ultraviolet light.

[0053] Reference Figure 3 The first silicon nitride layer 41 includes a first silicon nitride sublayer 411, a second silicon nitride sublayer 412 and a third silicon nitride sublayer 413. By adjusting the ratio of silicon atoms to nitrogen atoms in the first silicon nitride sublayer 411, the second silicon nitride sublayer 412 and the third silicon nitride sublayer 413, the first silicon nitride layer 41 can obtain an excellent anti-reflection effect.

[0054] The second silicon oxide layer 43 is also an effective anti-reflection material. While ensuring good light transmittance, when used in combination with the first silicon nitride layer 41 or the first silicon oxynitride layer 42, a multi-layer anti-reflection structure can be formed to further optimize the spectral response and broaden the light absorption range.

[0055] Reference Figure 2 In some embodiments, the first anti-reflection layer 4 includes a first silicon nitride layer 41, a first silicon oxynitride layer 42, and a second silicon oxide layer 43 which are stacked in sequence.

[0056] Reference 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 anti-reflection layer 6 arranged in sequence; The second anti-reflection 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.

[0057] Further, refer to Figure 2 In some embodiments, the second anti-reflection layer 6 is a second silicon nitride layer 61 .

[0058] The material of the dielectric layer 51 may include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Specifically, the dielectric layer 51 may be composed of a fourth silicon oxide layer 511 containing silicon oxide. This is because the fourth silicon oxide layer 511 has excellent passivation properties, can minimize the recombination loss of minority carriers on the surface of the emitter 11, and is a film with excellent durability to subsequent high-temperature processes.

[0059] In order to better provide the 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.

[0060] 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 elements that accept electrons, such as boron), the conductivity type of the doped polysilicon layer 52 is correspondingly configured as N-type (i.e., mainly doped with elements that provide electrons). In this case, the conductive element doped into the doped polysilicon layer 52 is an N-type element, typically represented by phosphorus, which can introduce additional free electrons into the silicon lattice in the doped polysilicon layer 52, thereby enhancing the electronic conductivity of the doped polysilicon layer 52, which is beneficial to improving the transmission capacity of electronic carriers.

[0061] Reference Figure 1 In some embodiments, a first electrode 71 is disposed on the light-receiving side of the silicon substrate 1 , and the first electrode 71 forms an ohmic contact with the emitter 11 ; a second electrode 72 is disposed on the backlight side of the silicon substrate 1 , and the second electrode 72 forms an ohmic contact with the doped polysilicon layer 52 .

[0062] In a second aspect, an embodiment of the present invention provides a method for preparing a solar cell.

[0063] A method for preparing a solar cell comprises the following steps: Providing a silicon substrate 1 having an emitter 11 on a light receiving surface side; Prepare an aluminum oxide layer 3 on the surface of the emitter 11; The indirect oxidation treatment causes the first silicon oxide layer 2 to indirectly grow on the surface of the emitter 11 .

[0064] The inventors have discovered that, in the process of preparing solar cells, an aluminum oxide layer 3 is first prepared, and then an indirect oxidation treatment is performed, so that the oxygen source passes through the aluminum oxide layer 3 to the surface of the emitter 11 to indirectly grow the first silicon oxide layer 2, thereby obtaining a stable, dense Si-O bond network with low interface state density, which can more effectively improve the interface passivation effect between the aluminum oxide layer 3 and the emitter 11, so that the solar cell has a higher open circuit voltage and photoelectric conversion efficiency. In addition, the structure of the first silicon oxide layer 2 grown by the above-mentioned indirect oxidation treatment is denser. When the hydrogen atoms in the passivation film layers such as silicon nitride and / or silicon oxynitride on the front of the solar cell overflow under ultraviolet irradiation, the densely structured first silicon oxide layer 2 can effectively block the diffusion of hydrogen atoms, which is beneficial to improving the anti-ultraviolet attenuation performance of the solar cell.

[0065] If the preparation order of the aluminum oxide layer 3 and the first silicon oxide layer 2 is changed, a direct oxidation treatment is used to prepare the silicon oxide layer, that is, the silicon oxide layer is prepared first, and then the aluminum oxide layer 3 is prepared, the quality of the silicon oxide layer thus prepared is poor, and the interface state density is high. The inventor analyzed that the mechanism may be: when a direct oxidation treatment method is used to prepare the silicon oxide layer, such as hydrogen peroxide oxidation, ozone oxidation, wet oxygen oxidation, dry oxygen oxidation and other methods are used to prepare the silicon oxide layer at the interface between the emitter 11 and the aluminum oxide layer 3, and the oxygen atom source is provided by hydrogen peroxide, a low-purity oxygen atmosphere, H2O or ozone. This direct oxidation treatment is because the substance providing the oxygen atom source cannot have 100% purity, and if silicon oxide is prepared in a high-temperature furnace tube, the atmosphere of 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 aluminum oxide layer 3 is very thin, it will not exceed 2nm, so even a furnace tube atmosphere with a very low vacuum degree cannot provide an oxygen atom source with a high purity. Therefore, when a silicon oxide layer is prepared between the emitter and the aluminum oxide layer using a direct oxidation treatment method, the stability of the solar cell under ultraviolet light irradiation conditions is not significantly improved or may even be worse.

[0066] 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.

[0067] After the preparation of the aluminum oxide layer 3 is completed, an ionized oxygen source can be used to allow ionized oxygen atoms to pass through the aluminum oxide layer 3 to reach the surface of the emitter 11, and form a first silicon oxide layer 2 with a specific thickness on the surface of the emitter 11; wherein, since the aluminum oxide layer 3 contains H atoms, when the aluminum oxide layer 3 is subjected to surface treatment of ionized oxygen atoms, the H atoms will also migrate to the first silicon oxide layer 2 during the high-energy treatment of the ionized oxygen atoms and / or the 400°C~600°C annealing treatment, further enhancing the surface passivation effect of the front emitter of the solar cell, which helps to improve the open circuit voltage and photoelectric conversion efficiency.

[0068] In some embodiments, the indirect oxidation treatment method includes annealing the aluminum oxide layer 3 at 400°C to 600°C, and the oxygen atoms in the aluminum oxide layer 3 are migrated to the first silicon oxide layer 2 through high temperature treatment, thereby further enhancing the surface passivation effect of the front emitter of the solar cell, which helps to improve the open circuit voltage and photoelectric conversion efficiency.

[0069] In some embodiments, the indirect oxidation treatment method includes ionized N2O treatment, with an ionization time of 10 s~120 s, a N2O flow rate of 5000 sccm~20000 sccm, a temperature of 450℃~470℃, an RF power of 6000 W~12000 W, an RF power supply of 20 ms~50 ms, and insulation for 5min~60min; by providing oxygen atoms in a high energy state, i.e., an ionized state, it can promote the formation of Si-O bonds with a more stable valence bond structure with silicon atoms on the emitter surface.

[0070] After the first silicon oxide layer 2 is prepared, the first anti-reflection layer 4 is prepared. The preparation of the first anti-reflection layer 4 is described in more detail below. In some embodiments, the first silicon nitride layer 41 is prepared on the side of the aluminum oxide layer 3 away from the silicon substrate 1 by the PECVD method, and the deposition temperature is 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 stacked in sequence on the side of the aluminum oxide layer 3 away from the first silicon oxide layer 2, wherein the preparation of the first silicon nitride sublayer 411, the second silicon nitride sublayer 412, and the third silicon nitride sublayer 413 can be prepared by adjusting the deposition time, SiH4 flow rate, NH3 flow rate, deposition pressure, RF power, and the time of turning the RF power on and off of the PECVD to prepare the corresponding silicon nitride layer. It should be noted that the first silicon nitride layer 41 can be a single layer or a multilayer, wherein different silicon nitride layers are distinguished by the different deposition conditions of the above-mentioned PECVD. For example, when any of the process parameters of PECVD deposition time, SiH4 flow rate, NH3 flow rate, deposition pressure, RF power, and the time when the RF power is turned on and off are different, they will be regarded as silicon nitride film layers with different structures in this application.

[0071] In some embodiments, a first silicon oxynitride layer 42 is prepared by a PECVD method on the side of the first silicon nitride layer 41 away from the N-type single crystal silicon wafer, wherein the preparation of the first silicon oxynitride layer 42 can be prepared by adjusting the deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and the time when the RF power is turned on and off by the PECVD to prepare the corresponding silicon nitride layer. It should be noted that the first silicon oxynitride layer 42 can be a single layer or a multilayer, wherein different silicon oxynitride layers are distinguished by the different deposition conditions of the above-mentioned PECVD, for example: when any one of the process parameters of the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and the time when the RF power is turned on and off is different, it will be regarded as a silicon oxynitride film layer with different structures in this application.

[0072] In some embodiments, a second silicon oxide layer 43 is prepared by a PECVD method on the side of the first silicon oxynitride layer 42 away from the N-type single crystal silicon wafer, wherein the preparation of the second silicon oxide layer 43 can be prepared by adjusting the deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and the time when the RF power is turned on and off by the PECVD 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 a multilayer, wherein different second silicon oxide layers are distinguished by the different deposition conditions of the above-mentioned PECVD, for example: when any one of the process parameters of the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and the time when the RF power is turned on and off is different, it will be regarded as a silicon oxynitride film layer with a different structure in this application.

[0073] In a third aspect, an embodiment of the present invention provides a photovoltaic module.

[0074] A photovoltaic component comprises the solar cell mentioned in the first aspect or the solar cell prepared by the preparation method mentioned in the second aspect.

[0075] The technical solution of the present invention will be further described below in conjunction with more specific embodiments and drawings.

[0076] Embodiment 1 An embodiment of the present invention provides a solar cell, and a method for preparing the solar cell comprises the following steps: Providing an N-type single crystal silicon wafer, forming a P-type boron emitter on the light-receiving side of the N-type single crystal silicon wafer by boron diffusion, and removing a BSG (borosilicate glass) layer by wet processing; A dielectric layer and a phosphorus-doped amorphous silicon layer were sequentially prepared on the back-lit side of an N-type single-crystal silicon wafer by PECVD, and then annealed at 950°C for 90 min to crystallize the phosphorus-doped amorphous silicon layer and transform it into a phosphorus-doped polycrystalline silicon layer. RCA wet treatment removes the natural silicon oxide layer on the light-receiving side of the N-type single-crystal silicon wafer; An aluminum oxide layer is prepared on the surface of a P-type boron emitter by using an ALD method; Ionize N2O by PECVD method, the ionization time is 30 s, the flow rate of N2O is 10000sccm, the temperature is 450℃~550℃, the RF power is 8000W, the RF power is 35ms, and the temperature is 450℃~550℃ for 5min~60min, and the first silicon oxide layer is grown by indirect oxidation treatment on the surface of the P-type boron emitter close to the aluminum oxide layer; The first silicon nitride layer was prepared by PECVD method, and the deposition temperature was 450℃~470℃. The first silicon nitride layer consisted of a first silicon nitride sublayer, a second silicon nitride sublayer and a third silicon nitride sublayer which were sequentially stacked on the side of the aluminum oxide layer away from the first silicon oxide layer. The deposition time of the first silicon nitride sublayer was 75 s, the flow rate of SiH4 was 2000 sccm, the flow rate of NH3 was 6500 sccm, the pressure was 1600 mTorr, and the radio frequency power was 13500 W; the deposition time of the second silicon nitride sublayer was 125 s, the flow rate of SiH4 was 1100 sccm, the flow rate of NH3 was 8000 sccm, the pressure was 1600 mTorr, and the radio frequency power was 14000 W; the deposition time of the third silicon nitride sublayer was 160 s, the flow rate of SiH4 was 1000 sccm, the flow rate of NH3 was 10000 sccm, the pressure was 1600 mTorr, and the radio frequency power was 14000 W. W, RF power on for 35 ms, RF power off for 550 ms; The first silicon oxynitride layer was prepared by PECVD on the side of the first silicon nitride layer away from the N-type single crystal silicon wafer, with a deposition time of 300 s, a flow rate of SiH4 of 900 sccm, a flow rate of NH3 of 3500 sccm, a flow rate of N2O of 7500 sccm, a pressure of 1200 mTorr, an RF power of 13500 W, an RF power on time of 35 ms, and an RF power off time of 900 ms; The second silicon oxide layer was prepared by PECVD on the side of the first silicon oxynitride layer away from the N-type single crystal silicon wafer, with a deposition time of 120 s, a SiH4 flow rate of 750 sccm, a N2O flow rate of 9500 sccm, a pressure of 1150 mTorr, an RF power of 13500 W, an RF power on time of 35 ms, and an RF power off time of 900 ms; A second silicon nitride layer is formed on the side of the phosphorus-doped polysilicon layer facing away from the N-type single crystal silicon wafer by a PECVD method; A first electrode is prepared on the light-receiving side so as to form an ohmic contact with the P-type boron emitter, and a second electrode is prepared on the backlight side so as to form an ohmic contact with the phosphorus-doped polysilicon layer.

[0077] Embodiment 2 The embodiment of the present invention provides a solar cell, which is different from the 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 60 s, and the rest is consistent with the embodiment 1.

[0078] Embodiment 3 The embodiment of the present invention provides a solar cell, which is different from the 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 consistent with the embodiment 1.

[0079] Embodiment 4 The embodiment of the present invention provides a solar cell, which is different from the 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 consistent with the embodiment 1.

[0080] Comparative Example This comparative example provides a solar cell, which is different from Example 3 in that after the aluminum oxide layer is prepared, the step of ionizing N2O by the PECVD method is omitted, that is, the first silicon oxide layer is not prepared between the aluminum oxide layer and the P-type boron emitter, but a silicon nitride layer is directly prepared, and the rest is consistent with Example 3.

[0081] Experiment 1 Thickness test of the first silicon oxide layer The thickness of the first silicon oxide layer was tested by using the EDS element scanning function in the TEM or HR-TEM. The interface boundary line with obvious color difference in the EDS scanning image was selected as a measurement reference for the thickness of the first silicon oxide layer. The test results of the thickness of the first silicon oxide layer of each embodiment and comparative example are shown in Table 1.

[0082] Experiment 2 Battery efficiency decay test 2.1. Battery cell attenuation performance test The solar cells prepared by the preparation methods of the above-mentioned embodiments and comparative examples are used as test cell samples. The photoelectric conversion efficiency of the cell samples before and after ultraviolet aging treatment is tested, and the photoelectric conversion efficiency before ultraviolet aging treatment is subtracted from the photoelectric conversion efficiency after ultraviolet aging treatment to obtain the difference in cell efficiency attenuation after ultraviolet aging treatment.

[0083] UV aging treatment: Take the cell samples, the test conditions include: 60±5℃, wavelength range 280nm~400nm, irradiation intensity 200W / m 2 After continuous and stable irradiation for 60 kWh, the battery cell is taken out and IV is tested again. The percentage of efficiency attenuation before and after irradiation is the difference in efficiency attenuation of the battery cell.

[0084] 2.2. Photovoltaic module attenuation performance test The solar cells prepared by the preparation methods of the above embodiments and comparative examples are packaged into photovoltaic module samples. The maximum power of the photovoltaic module samples before and after ultraviolet aging treatment is tested, and the power attenuation difference of the photovoltaic module after ultraviolet aging treatment is obtained by calculating the power before ultraviolet aging treatment minus the power after ultraviolet aging treatment.

[0085] UV aging treatment: The cells were packaged into double-glass photovoltaic modules. After the photovoltaic modules were completed, they were left to stand for 24 hours before IV testing. Then they were placed in a UV irradiation box. The test conditions included: 60±5℃, wavelength range 280 nm~400 nm, irradiation intensity 200 W / m 2 After continuous and stable irradiation of 60 kWh, take out the module and test IV again. The power difference of the photovoltaic module before and after irradiation is the power attenuation difference of the photovoltaic module.

[0086] The results of the battery efficiency attenuation test of Experiment 2 are recorded in Table 1. In view of the fact that there may be differences in the crystal structure of the silicon substrate surface in different regions, the silicon atoms on the emitter surface in different regions have different reactivity. 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, the thickness of the first silicon oxide layer in Examples 1 to 4, combined with the description of the first silicon oxide layer thickness test in Experiment 1, selects the first silicon oxide layer thickness with the lowest thickness on the test section to define the first silicon oxide thickness in this application; however, if the thickness of the first silicon oxide layer in a specific area of ​​the cross section is significantly lower than the thickness of the first silicon oxide layer in other areas and the specific area accounts for more than 30% of the selected cross section, it is deemed to be an abnormal test area and the test selection area of ​​the first silicon oxide layer thickness is excluded.

[0087] Table 1

[0088] From Table 1, we can see that: In the first aspect, when the direct oxidation treatment method is used in Comparative Example 1 to form a silicon oxide layer between the emitter and the aluminum oxide layer, the difference in efficiency attenuation of the cell and the difference in power attenuation of the photovoltaic module are greater than those of Examples 1 to 4, indicating that the first silicon oxide layer prepared between the emitter and the aluminum oxide layer by the indirect oxidation treatment method used in the present application has better anti-ultraviolet attenuation performance; Secondly, compared with Examples 1 to 3, the difference in cell efficiency attenuation and the difference in photovoltaic module power attenuation before and after the UV aging test in Example 4 are relatively high, indicating that the plasma treatment time of the oxygen source is too long and may damage the structure of the aluminum oxide layer and / or the first silicon oxide layer, or may aggravate the destruction of the hydrogen-based valence bonds in the aluminum oxide layer and / or the first silicon oxide layer, thereby causing the attenuation of the cell efficiency and / or the attenuation of the UV aging performance of the cell; therefore, when the thickness of the first silicon oxide layer is in the range of 0.2 nm to 1.2 nm, it is beneficial to alleviate the UV aging attenuation performance of the cell; Thirdly, compared with other embodiment groups, the difference in cell efficiency attenuation before and after the UV aging test and the difference in photovoltaic module power attenuation in embodiment 2 are both the lowest, and it has the best anti-UV attenuation performance, indicating that the optimal thickness range of the first silicon oxide layer is 0.6 nm~0.8 nm. Compared with other embodiment groups, the difference in cell efficiency attenuation before and after the UV aging test and the difference in photovoltaic module power attenuation in embodiment 2 are both the lowest, and it has the best anti-UV attenuation performance, indicating that the optimal thickness range of the first silicon oxide layer is 0.6 nm~0.8 nm.

[0089] The solar cell and its preparation method, and the photovoltaic module disclosed in the embodiments of the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the solar cell and its preparation method, the photovoltaic module and its core concept of the present invention; at the same time, for ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as a limitation on 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~1.2 nm.

2. The solar cell according to claim 1, characterized in that: The interface state density of the first silicon oxide layer is 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 .

3. 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.

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

5. The solar cell according to claim 1, characterized in that: The thickness of the aluminum oxide layer is 3 nm to 8 nm; and / or, The first anti-reflection layer includes one or a combination of a first silicon nitride layer, a first silicon oxynitride layer and a second silicon oxide layer.

6. The solar cell according to any one of claims 1 to 5, 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.

7. A method for preparing a solar cell, characterized in that: The method for preparing the solar cell 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 a first silicon oxide layer to be indirectly grown on the surface of the emitter.

8. The method for preparing a solar cell according to claim 7, 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.

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

10. The method for preparing a solar cell according to claim 8 or 9, 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.

11. The method for preparing a solar cell according to claim 8, characterized in that: The treatment of the ionized oxygen source is ionized N2O.

12. The method for preparing a solar cell according to claim 8, characterized in that: The indirect oxidation treatment is the annealing treatment, and a treatment of ionizing N2O is performed during the annealing treatment.

13. The method for preparing a solar cell according to claim 11 or 12, 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.

14. A photovoltaic module, characterized in that: The invention comprises the solar cell as described in any one of claims 1 to 6 or the solar cell prepared by the preparation method as described in any one of claims 7 to 13.

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