Solar cell and its manufacturing method, photovoltaic module

Abstract

This invention provides a solar cell, a method for manufacturing the same, and a photovoltaic module. [Solution] 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, with the thickness of the first silicon oxide layer being 0.2 nm to 1.2 nm. The present invention can effectively improve the interface stability of the emitter and suppress the efficiency decay of the solar cell under ultraviolet irradiation.

Description

[Technical Field]

[0001] This invention relates to the technology of solar cells, and more particularly to solar cells, methods for manufacturing the same, and photovoltaic modules. [Background technology]

[0002] Solar cells, as a central component of photovoltaic modules, significantly impact the module's efficiency. However, ultraviolet irradiation can cause a premature decline in the photoelectric conversion efficiency of solar cells, leading to a significant power attenuation problem in the photovoltaic module. This phenomenon poses a serious challenge to the long-term stable operation of the photovoltaic module and significantly affects its lifespan and operational performance. [Overview of the project] [Problems that the invention aims to solve]

[0003] To reduce the effects of ultraviolet irradiation on solar cells, embodiments of the present invention disclose a solar cell, a method for manufacturing the same, and a photovoltaic module. [Means for solving the problem]

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

[0005] The solar cell includes a silicon substrate, and on the light-receiving surface of the silicon substrate, an emitter, a first silicon oxide layer, an aluminum oxide layer, and a first anti-reflective layer are sequentially stacked and installed. Of these, the thickness of the first silicon oxide layer is 0.2 nm to 1.2 nm.

[0006] As a selective embodiment, in the embodiment of the present invention, the interfacial density of states of the first silicon oxide layer is 10 11 cm -2 eV -1 ~10 12 cm -2 eV -1 That is the case.

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

[0008] In a selective embodiment, in the embodiment of the present invention, the silicon substrate is N-type and the emitter is P-type.

[0009] As a selective embodiment, in the embodiment of the present invention, the thickness of the aluminum oxide layer is 3 nm to 8 nm. and / or the first anti-reflective layer includes one or more combinations of a first silicon nitride layer, a first silicon nitride oxide layer, and a second silicon oxide layer.

[0010] As a selective embodiment, in an embodiment of the present invention, a dielectric layer, a doped polycrystalline silicon layer, and a second anti-reflective layer are arranged in order on the back surface side of the silicon substrate. The second anti-reflective layer includes one or more combinations of the second silicon nitride layer, the second silicon nitride oxide layer, and the third silicon oxide layer. A first electrode is provided on the light-receiving side of the silicon substrate to form an ohmic contact with the emitter, and a second electrode is provided on the back-light side of the silicon substrate to form an ohmic contact with the doped polycrystalline silicon layer.

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

[0012] The method for manufacturing solar cells is: The steps include providing a silicon substrate having an emitter on the light-receiving surface side, The steps include: creating an aluminum oxide layer on the emitter surface; The method includes the step of indirectly growing a first silicon oxide layer on the emitter surface by an indirect oxidation treatment.

[0013] As an alternative embodiment, in an example of the present invention, the indirect oxidation treatment includes oxygen source ionization treatment on the aluminum oxide layer and / or annealing treatment on the aluminum oxide layer.

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

[0015] As an alternative embodiment, in an example of the present invention, the indirect oxidation treatment is the annealing treatment, and the first silicon oxide layer is formed by introducing O₂ or O₃ during the annealing treatment.

[0016] As an alternative embodiment, in an example of the present invention, the oxygen source ionization treatment is N₂O ionization.

[0017] As an alternative embodiment, in an example of the present invention, the indirect oxidation treatment is the annealing treatment, and N₂O ionization treatment is performed during the annealing treatment.

[0018] As an alternative embodiment, in an example of the present invention, the process conditions for the N₂O ionization treatment on the aluminum oxide layer are: ionization time of 10s to 120s, N₂O flow rate of 5000sccm to 20000sccm, temperature of 450°C to 470°C, RF power of 6000W to 12000W, and on-time of the RF power supply of 20ms to 50ms.

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

[0020] The photovoltaic module includes the solar cell according to the first aspect, or the solar cell manufactured by the manufacturing method according to the second aspect.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0022] Provided in an embodiment of the present invention is that, by introducing a first silicon oxide layer with a specific thickness (0.2 nm to 1.2 nm) between an emitter and an 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 improve the ultraviolet attenuation resistance of the photovoltaic module.

[0023] First, the first silicon oxide layer having the specific thickness utilizes strong bonding between oxygen atoms and dangling bonds on the emitter surface to form a structurally stable and dense Si-O bonding network. This structure passivates the dangling bonds on the emitter surface, effectively reduces the number of hydrogen atoms diffused from Si-H bonds, effectively suppresses the movement and accumulation of hydrogen atoms and the formation of hydrogen clusters caused by ultraviolet irradiation, and reduces carrier recombination, thereby alleviating the performance attenuation of a solar cell under ultraviolet light. In addition, the first silicon oxide layer provides effective interface buffering between the emitter and the aluminum oxide layer, significantly relieves lattice strain at the interface, reduces the density of dangling bonds at the interface, and reduces carrier recombination.

[0024] Furthermore, in this invention, the thickness of the first silicon oxide layer plays a crucial role in the stability of the solar cell under ultraviolet irradiation, and the UV resistance stability of the solar cell tends to increase and then decrease in response to changes in the thickness of the first silicon oxide layer. When the thickness of the first silicon oxide layer is less than 0.2 nm, there is a limit to the improvement in the emitter interface passivation performance by the first silicon oxide layer, and because the interface density of states is high, the UV 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 nm to 0.8 nm, the emitter interface passivation effect is within the optimal range, and the interface density of states is reduced, so the UV resistance stability of the solar cell improves accordingly. However, through experiments, the inventors discovered that when the thickness of the first silicon oxide layer exceeds 1.2 nm, the UV resistance stability of the solar cell deteriorates further. To more clearly describe the technical embodiments of the present invention, the accompanying drawings required for the embodiments are briefly introduced below. The accompanying drawings in the following description represent only a few embodiments of the present invention, and it will be apparent to those skilled in the art that other drawings can be obtained based on these drawings without any creative effort. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram of the configuration of the first solar cell disclosed in the embodiments of the present invention. [Figure 2] This is a schematic diagram of the configuration of a second solar cell disclosed in an embodiment of the present invention. [Figure 3] This is a schematic diagram of the configuration of the third solar cell disclosed in the embodiments of the present invention. [Modes for carrying out the invention]

[0026] The technical modes in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It is clear that the embodiments described are only a selection of embodiments of the present invention, and not all embodiments. Any other embodiments that a person skilled in the art can obtain without creative work based on the embodiments of the present invention are all within the scope of the protection of the present invention.

[0027] In this invention, directions or positional relationships indicated by terms such as "up," "down," "left," "right," "front," "back," "top," "bottom," "inside," "outside," "center," "vertical," "horizontal," "lateral," and "vertical" are based on the directions or positional relationships shown in the accompanying drawings. These terms are used primarily to better describe the invention and its embodiments and do not limit the devices, elements, or components shown to having a specific direction or being configured and operated in a specific direction.

[0028] Furthermore, some of the terms described above may be used to indicate meanings other than direction or positional relationships. For example, the term "up" may, in some cases, be used to indicate a dependency or connection relationship. Those skilled in the art will be able to understand the specific meaning of these terms in the present invention, depending on the specific context.

[0029] Furthermore, terms such as "attach," "install," "provide," "connect," and "link" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integrated structure; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection via an intermediate medium; or it may be internal communication between two devices, elements, or components. A person skilled in the art will be able to understand the specific meaning of the above terms in the present invention depending on the specific situation.

[0030] Furthermore, terms such as "first," "second," etc., are primarily used to distinguish between different devices, elements, or components (which may or may not be of the same type or structure) and are not intended to express or suggest the relative importance or number of the devices, elements, or components being shown. Unless otherwise specified, the term "plural" means two or more.

[0031] Under ultraviolet (UV) irradiation in the 300nm-400nm wavelength range, photoelectric conversion efficiency in solar cells is prone to attenuation. Specifically, UV light can cause the breaking of silicon hydrogen bonds (Si-H) within the passivation and / or anti-reflective coating layers on the surface of the silicon substrate. The diffusion of hydrogen atoms from these silicon hydrogen bonds reduces the passivation effect of the passivation and / or anti-reflective coating layers on the silicon substrate surface, promoting carrier recombination and decreasing the photoelectric conversion efficiency of the solar cell. This mainly manifests as a reduction in open-circuit voltage. Therefore, optimizing the design and fabrication processes of solar cells to mitigate UV-induced performance attenuation is a current focus of research.

[0032] The technical embodiments of the present invention will be further described below based on the examples and accompanying drawings.

[0033] In a first embodiment, the present invention provides a solar cell.

[0034] Refer to Figure 1. The solar cell includes a silicon substrate 1, and on the light-receiving surface of the silicon substrate 1, an emitter 11, a first silicon oxide layer 2, an aluminum oxide layer 3, and a first anti-reflective layer 4 are sequentially stacked and installed. Of these, the thickness of the first silicon oxide layer 2 is 0.2 nm to 1.2 nm.

[0035] In this invention, a first silicon oxide layer 2 having a specific thickness (0.2 nm to 1.2 nm) is introduced between the emitter 11 and the aluminum oxide layer 3. The first silicon oxide layer 2 is not a silicon oxide material directly fabricated on the surface of the emitter 11, but rather the oxygen atoms and / or high-energy oxygen atoms (e.g., ionized oxygen atoms) in the aluminum oxide layer 3 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.

[0036] The conditions for forming silicon oxide in the first silicon oxide layer 2 are to move oxygen atoms in the aluminum oxide layer 3 to the surface of the emitter 11, or to allow high-energy oxygen atoms (e.g., ionized oxygen atoms) to act on the aluminum oxide layer 3, thereby providing an oxygen atom source for the formation of the first silicon oxide layer 2. Therefore, when the silicon oxide layer is fabricated under air conditions or conditions including other non-oxygen media, the aluminum oxide layer effectively blocks impurities in the air or non-oxygen media, reducing the possibility of impurities doping and contaminating the silicon oxide material. This provides a higher purity oxygen atom source with fewer impurity atoms for the fabrication of the first silicon oxide layer 2, enabling the fabricated first silicon oxide layer 2 to have a lower interface state density and a better interface passivation effect.

[0037] Conventional methods for producing a silicon oxide layer include a hydrogen peroxide oxidation method, an ozone oxidation method, a wet oxygen oxidation method, a dry oxygen oxidation method, etc. In all of these methods, a silicon oxide layer is directly formed on the surface of an emitter, and then an aluminum oxide layer is formed. When an oxygen atom source is provided by hydrogen peroxide, oxygen atmosphere, H₂O or ozone, the substance providing the oxygen atom source cannot have 100% purity; furthermore, when silicon oxide is produced by means of a high-temperature furnace tube, the atmosphere inside 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 aluminum oxide layer 3 is extremely thin and does not exceed 2 nm, the silicon oxide layer is very sensitive to impurities. Even in a furnace tube atmosphere with an extremely low vacuum degree, a high-purity oxygen atom source cannot be provided. As a result, impurities are extremely easily mixed into the silicon oxide layer formed on the surface of the emitter 11 as in conventional methods, which adversely affects the long-term maintenance of the interface stability of the emitter 11 and is disadvantageous for improving the ultraviolet attenuation prevention performance of the solar cell. In contrast, the indirect oxidation treatment method adopted by the present invention can effectively reduce the adverse effects of impurities in the production environment atmosphere on the insufficient purity of the oxygen atom source and the production process of the silicon oxide layer, and can greatly reduce the mixing of impurities into the silicon oxide layer. Therefore, the silicon oxide layer produced by indirect oxidation treatment contains fewer impurities and has higher quality, which contributes to improving the stability of the solar cell under ultraviolet irradiation conditions.

[0038] 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 , which can effectively reduce the degree of carrier recombination caused by lattice mismatch at the interface between the emitter 11 and the aluminum oxide layer 3, and effectively suppress the performance attenuation of the solar cell under ultraviolet irradiation.

[0039] Specifically, first, the first silicon oxide layer 2 having a specific thickness utilizes the strong bond between oxygen atoms and silicon dangling bonds on the surface of the emitter 11 to form a stable and dense Si-O bond network with a low interfacial density of states. This structure can effectively passivate the silicon dangling bonds on the surface of the emitter 11, resulting in a low defect density of states on the surface of the emitter 11, providing the solar cell with a superior interfacial passivation effect and a higher open-circuit voltage. Furthermore, since the front surface of the solar cell of this application is provided with an aluminum oxide layer 3 having a dense structure and high bond energy, it can effectively prevent the breakdown of Si-O bonds in the first silicon oxide layer 2 by photons in the ultraviolet wavelength band. In addition, since hydrogen atoms are included in the aluminum oxide layer 3 by ALD, the hydrogen atoms in the aluminum oxide layer 3 also move to the first silicon oxide layer 2, further improving the interfacial passivation effect of the first silicon oxide layer 2, mitigating the electrical performance decay of the solar cell under ultraviolet light, that is, mitigating the phenomenon of photovoltaic module power decay under ultraviolet irradiation.

[0040] 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 irradiation, and the UV resistance stability of the solar cell tends to increase and then decrease depending on 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, there is a limit to the improvement of the interfacial passivation performance of the emitter 11 by the first silicon oxide layer 2, and the interfacial density of states is high, resulting in poor interfacial passivation effect of the solar cell and being unfavorable for the fabrication of high-efficiency solar cells. However, when the thickness of the first silicon oxide layer 2 is in the range of 0.2 nm to 0.8 nm, the interfacial passivation effect of the emitter 11 is within the optimal range, and the interfacial density of states is reduced, so the UV resistance stability of the solar cell is also significantly improved. However, the inventors have found that when the thickness of the first silicon oxide layer exceeds 1.2 nm, the UV resistance stability of the solar cell deteriorates further.

[0041] For example, 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.

[0042] Preferably, the thickness of the first silicon oxide layer 2 is 0.3 nm to 0.8 nm.

[0043] By adjusting the thickness of the first silicon oxide layer 2 to the preferred range described above, the first silicon oxide layer 2 can not only provide good interfacial passivation performance, but also more effectively mitigate the inhibiting effect on hole carrier transmission due to the field effect of the positively charged first silicon oxide layer 2, thereby contributing to tunnel transmission of photogenerated carriers. As a result, the cooperative action of the first silicon oxide layer 2 and the aluminum oxide layer 3 provides optimal interfacial passivation effect on the surface of the emitter 11, further improving the UV attenuation prevention performance of the solar cell.

[0044] In some embodiments, the silicon substrate 1 is N-type and the emitter 11 is P-type.

[0045] The P-type emitter 111 provides hole carriers during the operation of the solar cell, and the aluminum oxide layer 3 is a negatively charged layer, providing a field effect favorable to the transmission of hole carriers and promoting hole carrier drift. This mechanism promotes the efficient movement of hole carriers. On the other hand, the first silicon oxide layer 2 is positively charged, so it repels hole carriers and acts as an inhibiting field effect against hole carrier drift. In this invention, by controlling the thickness of the first silicon oxide layer 2 placed between the P-type emitter 111 and the aluminum oxide layer 3 to a specific range, the inhibiting field effect on tunneling and drift of hole carriers by the first silicon oxide layer 2 can be effectively reduced, and the movement of hole carriers can be promoted. Furthermore, the first silicon oxide layer 2 can also provide a good interfacial passivation effect to the interface between the P-type emitter 111 and the aluminum oxide layer 3. Furthermore, since solar cells using N-type silicon substrates have high conversion efficiency and long-term reliability, the present invention is particularly suitable for designs employing a P-type emitter 111.

[0046] In some examples, the thickness of the aluminum oxide layer 3 is 3 nm to 8 nm.

[0047] The aluminum oxide layer 3 having the thickness described above can provide a good passivation effect to the solar cell, and oxygen atoms can pass through the aluminum oxide layer 3 and enter the surface of the emitter 11, contributing to the formation of a first silicon oxide layer 2 having a specific thickness on the surface of the emitter 11.

[0048] For example, the thickness of the aluminum oxide layer 3 is 3 nm, 5 nm, or 8 nm.

[0049] Refer to Figure 2. In some embodiments, the aluminum oxide layer 3 has a first anti-reflective layer 4 on the opposite side of the silicon substrate 1, and the first anti-reflective layer 4 includes one or more combinations of the first silicon nitride layer 41, the first silicon nitride oxide layer 42, and the second silicon oxide layer 43.

[0050] The first silicon nitride layer 41 and the first silicon nitride oxide layer 42 are film layers rich in H element, and the H element combines with Si atoms in the film layer to form Si-H bonds, which effectively optimizes the interface contact characteristics, further reduces the interface density of states of the solar cell, decreases carrier recombination losses, and contributes to improving the open-circuit voltage and the electrical performance of the solar cell.

[0051] After hydrogen atoms in the film layers such as the first silicon nitride layer 41 and / or the first silicon nitride oxide layer 42 on the front of the solar cell diffuse under ultraviolet irradiation, they are effectively blocked by the aluminum oxide layer 3, which has a dense structure and high bonding energy. This mitigates the significant decrease in the hydrogen atom density in the film layers such as the first silicon nitride layer 41 and / or the first silicon nitride oxide layer 42 under ultraviolet irradiation.

[0052] Refer to 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-reflective effect.

[0053] The second silicon oxide layer 43 also functions as an effective anti-reflective material, ensuring good light transmittance. When used in combination with the first silicon nitride layer 41 or the first silicon nitride oxide layer 42, it forms a multilayer anti-reflective structure, further optimizing the spectral response and expanding the light absorption range.

[0054] Refer to Figure 2. In some embodiments, the first anti-reflective layer 4 includes a first silicon nitride layer 41, a first silicon nitride oxide layer 42, and a second silicon oxide layer 43, which are sequentially laminated.

[0055] Refer back to Figure 1. In some embodiments, the silicon substrate 1 includes a dielectric layer 51, a doped polycrystalline silicon layer 52, and a second anti-reflective layer 6, which are arranged in order on the back surface (i.e., the shadow surface, the side opposite to the light-receiving surface). The second anti-reflective layer 6 includes one or more combinations of the second silicon nitride layer 61, the second silicon nitride oxide layer, and the third silicon oxide layer.

[0056] Furthermore, refer to Figure 2. In some embodiments, the second anti-reflective layer 6 is a second silicon nitride layer 61.

[0057] The dielectric layer 51 may contain at least one of several types of dielectric materials, such as silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxide nitride, 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 performance, can minimize the recombination loss of minority carriers on the surface of the emitter 11, and is a film with excellent durability against subsequent high-temperature processes.

[0058] To provide a good interfacial passivation effect with the silicon substrate 1, the thickness of the dielectric layer 51 may be 0.5 nm to 3 nm. For example, the thickness of the dielectric layer 51 may be 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, etc. However, the present invention is not limited to these, and the thickness of the dielectric layer 51 may be various values.

[0059] The conductivity type of the doped polycrystalline silicon layer 52 is opposite to that of the emitter 11 in order to achieve effective carrier separation and collection. Specifically, if the conductivity type of the emitter 11 is P-type (i.e., mainly electron-accepting elements, such as boron, are doped), then the conductivity type of the doped polycrystalline silicon layer 52 is correspondingly N-type (i.e., mainly electron-providing elements are doped). In this case, the conductive element doped into the doped polycrystalline silicon layer 52 is an N-type element, typically phosphorus. The phosphorus element can introduce extra free electrons into the silicon lattice within the doped polycrystalline silicon layer 52, thereby improving the electronic conductivity of the doped polycrystalline silicon layer 52 and contributing to improved electron carrier transmission capability.

[0060] Refer back to Figure 1. In some embodiments, a first electrode 71 is provided on the light-receiving side of the silicon substrate 1 to form an ohmic contact with the emitter 11, and a second electrode 72 is provided on the back-light side of the silicon substrate 1 to form an ohmic contact with the doped polycrystalline silicon layer 52.

[0061] In a second embodiment, the present invention provides a method for manufacturing a solar cell.

[0062] The method for manufacturing solar cells is: The steps include providing a silicon substrate 1 having an emitter 11 on the light-receiving surface side, The steps include: creating an aluminum oxide layer 3 on the surface of the emitter 11; The method includes the step of indirectly growing a first silicon oxide layer 2 on the surface of the emitter 11 by indirect oxidation treatment.

[0063] According to the inventors' findings, in the solar cell manufacturing process, by first fabricating an aluminum oxide layer 3 and then performing an indirect oxidation treatment, the oxygen source passes through the aluminum oxide layer 3, indirectly growing a first silicon oxide layer 2 on the surface of the emitter 11. This creates a stable and dense Si-O bond network with a low interfacial density of states, more effectively improving the interfacial passivation effect between the aluminum oxide layer 3 and the emitter 11, resulting in a solar cell with a high open-circuit voltage and photoelectric conversion efficiency. Furthermore, the structure of the first silicon oxide layer 2 grown by the above-mentioned indirect oxidation treatment becomes denser, and after hydrogen atoms in the passivation film layer such as silicon nitride and / or silicon nitride oxide on the front of the solar cell diffuse under ultraviolet irradiation, the dense structure of the first silicon oxide layer 2 can effectively prevent the diffusion of hydrogen atoms, contributing to an improvement in the UV attenuation prevention performance of the solar cell.

[0064] When the order in which the aluminum oxide layer 3 and the first silicon oxide layer 2 are fabricated is reversed, and the silicon oxide layer is fabricated by direct oxidation treatment, that is, when the silicon oxide layer is fabricated first and then the aluminum oxide layer 3 is fabricated, a silicon oxide layer of inferior quality and high interfacial density of states is obtained. The inventors analyzed the mechanism and concluded that the reason is as follows. When a silicon oxide layer is fabricated by a direct oxidation method, for example, by methods such as hydrogen peroxide oxidation, ozone oxidation, wet oxidation, or dry oxidation, and an oxygen source is provided by hydrogen peroxide, a low-purity oxygen atmosphere, H2O, or ozone, the oxygen source material cannot be 100% pure in such a direct oxidation process. Furthermore, when silicon oxide is fabricated using a high-temperature furnace tube, the atmosphere of 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 aluminum oxide layer 3 is very thin, not exceeding 2 nm, even a furnace tube atmosphere with a very low vacuum level cannot provide a high-purity oxygen source. Therefore, when a silicon oxide layer is fabricated between the emitter and the aluminum oxide layer by a direct oxidation method, the stability of the solar cell under ultraviolet irradiation conditions does not show any significant improvement; in fact, it may even worsen.

[0065] In some embodiments, the indirect oxidation treatment method includes oxygen source ionization 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 these, the ionization means for the oxygen source ionization treatment includes the PECVD method and the LPCVD method.

[0066] After the fabrication of the aluminum oxide layer 3 is complete, ionized oxygen atoms pass through the aluminum oxide layer 3 due to the ionization of an oxygen source and arrive at the surface of the emitter 11, forming a first silicon oxide layer 2 with a specific thickness on the surface of the emitter 11. Since the aluminum oxide layer 3 contains H atoms, when the aluminum oxide layer 3 is subjected to surface treatment by oxygen atom ionization, the H atoms also move to the first silicon oxide layer 2 during the high-energy oxygen atom ionization treatment and / or the annealing treatment at 400°C to 600°C, further improving the surface passivation effect of the emitter on the front of the solar cell and contributing to improvements in open-circuit voltage and photoelectric conversion efficiency.

[0067] In some embodiments, the indirect oxidation treatment method includes performing an annealing treatment on the aluminum oxide layer 3 at 400°C to 600°C. By moving oxygen atoms in the aluminum oxide layer 3 to the first silicon oxide layer 2 through high-temperature treatment, the surface passivation effect of the emitter on the front of the solar cell is further improved, contributing to an improvement in open-circuit voltage and photoelectric conversion efficiency.

[0068] In some embodiments, the indirect oxidation treatment includes N2O ionization, with an ionization time of 10s to 120s, an N2O flow rate of 5000 sccm to 20000 sccm, a temperature of 450°C to 470°C, an RF power of 6000W to 12000W, an RF power on time of 20ms to 50ms, and a holding time of 5 to 60 minutes. By providing oxygen atoms in a high-energy state, i.e., an ionized state, it is possible to promote the formation of Si-O bonds with a more stable valence bond structure between the oxygen atoms and silicon atoms on the emitter surface.

[0069] After the fabrication of the first silicon oxide layer 2 is completed, the first anti-reflective layer 4 is fabricated. The fabrication of the first anti-reflective layer 4 will be described in more detail below. In some embodiments, the first silicon nitride layer 41 is fabricated on the side of the aluminum oxide layer 3 opposite to the silicon substrate 1 by the PECVD method, with a deposition temperature of 450°C to 470°C. The first silicon nitride layer 41 consists of a first silicon nitride sublayer 411, a second silicon nitride sublayer 412, and a third silicon nitride sublayer 413, which are sequentially stacked on the side of the aluminum oxide layer 3 opposite to the first silicon oxide layer 2. Of these, the first silicon nitride sublayer 411, the second silicon nitride sublayer 412, and the third silicon nitride sublayer 413 can all be fabricated by adjusting the PECVD deposition time, SiH4 flow rate, NH3 flow rate, deposition pressure, RF power, and RF power supply on / off time. The first silicon nitride layer 41 may be a single layer or a multilayer, and different silicon nitride layers are distinguished depending on the PECVD deposition conditions described above. In this application, for example, if any one of the following process parameters differs—PECVD deposition time, SiH4 flow rate, NH3 flow rate, deposition pressure, RF power, or RF power supply on / off time—the silicon nitride film layer is considered to have a different structure.

[0070] In some embodiments, a first silicon nitride layer 42 is fabricated on the side of the first silicon nitride layer 41 opposite to the N-type single-crystal silicon wafer by the PECVD method. In the fabrication of the first silicon nitride layer 42, the corresponding silicon nitride layer can be fabricated by adjusting the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and RF power supply on / off time. The first silicon nitride layer 42 may be a single layer or a multilayer, and different silicon nitride layers are distinguished by the PECVD deposition conditions described above. In this application, for example, if any one of the process parameters among the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and RF power supply on / off time is different, the silicon nitride film layer is considered to have a different structure.

[0071] In some embodiments, a second silicon oxide layer 43 is fabricated on the side of the first silicon oxide oxide layer 42 opposite to the N-type single-crystal silicon wafer by the PECVD method. In the fabrication of the second silicon oxide layer 43, the corresponding second silicon oxide layer is fabricated by adjusting the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and RF power supply on / off time. The second silicon oxide layer 43 may be a single layer or a multilayer, and different second silicon oxide layers are distinguished by the PECVD deposition conditions described above. In this application, for example, if any one of the process parameters among the PECVD deposition time, SiH4 flow rate, N2O flow rate, deposition pressure, RF power, and RF power supply on / off time is different, the silicon oxide oxide film layer is considered to have a different structure.

[0072] In a third embodiment, an example of the present invention provides a photovoltaic module.

[0073] The photovoltaic module includes a solar cell described in the first embodiment, or a solar cell manufactured by the manufacturing method described in the second embodiment.

[0074] The technical embodiments of the present invention will be further described below with reference to more specific examples and attached drawings.

[0075] Example 1 An embodiment of the present invention provides a solar cell, the method for manufacturing the solar cell comprising the following steps.

[0076] An N-type single-crystal silicon wafer is provided, a P-type boron emitter is formed on the light-receiving surface side of the N-type single-crystal silicon wafer by boron diffusion, and the BSG (borosilicate glass) layer is removed by wet processing.

[0077] A dielectric layer and a phosphorus-doped amorphous silicon layer are sequentially fabricated on the back surface of an N-type single-crystal silicon wafer using the PECVD method. The wafer is then annealed at 950°C for 90 minutes, causing the phosphorus-doped amorphous silicon layer to crystallize and be converted into a phosphorus-doped polycrystalline silicon layer.

[0078] The native silicon oxide layer on the light-receiving side of an N-type single-crystal silicon wafer is removed by RCA wet processing.

[0079] An aluminum oxide layer is fabricated on the surface of a P-type boron emitter using the ALD method.

[0080] N2O is ionized by the PECVD method, with an ionization time of 30 s, an N2O flow rate of 10,000 sccm, a temperature of 450°C to 550°C, an RF power of 8,000 W, and an RF power supply on time of 35 ms. The process is carried out for 5 to 60 minutes at a temperature of 450°C to 550°C to grow a first silicon oxide layer on the surface near the aluminum oxide layer of the P-type boron emitter by indirect oxidation.

[0081] A first silicon nitride layer is fabricated by the PECVD method at a deposition temperature of 450°C to 470°C. The first silicon nitride layer consists of a first silicon nitride sublayer, a second silicon nitride sublayer, and a third silicon nitride sublayer, which are sequentially stacked on the opposite side of the first silicon oxide layer of the aluminum oxide layer. Of these, the deposition time for the first silicon nitride sublayer is set to 75 s, the flow rate of SiH4 to 2000 sccm, the flow rate of NH3 to 6500 sccm, the pressure to 1600 mTorr, and the RF power to 13500 W. The deposition time for the second silicon nitride sublayer is set to 125 s, the flow rate of SiH4 to 1100 sccm, the flow rate of NH3 to 8000 sccm, the pressure to 1600 mTorr, and the RF power to 14000 W. The deposition time for the third silicon nitride sublayer is set to 160 s, the flow rate of SiH4 to 1000 sccm, the flow rate of NH3 to 10000 sccm, the pressure to 1600 mTorr, and the RF power to 14000 W. The on-time of the RF power supply is set to 35 ms, and the off-time of the RF power supply is set to 550 ms.

[0082] A first silicon nitride oxide layer was fabricated on the opposite side of the N-type single-crystal silicon wafer from the first silicon nitride layer using the PECVD method, with a deposition time of 300 s, a SiH4 flow rate of 900 sccm, an NH3 flow rate of 3500 sccm, an N2O flow rate 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.

[0083] A second silicon oxide layer was fabricated on the opposite side of the first silicon nitride oxide layer on an N-type single-crystal silicon wafer using the PECVD method, 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.

[0084] A second silicon nitride layer is fabricated on the opposite side of the N-type single-crystal silicon wafer from the phosphorus-doped polycrystalline silicon layer using the PECVD method.

[0085] A first electrode is fabricated on the light-receiving surface side, and an ohmic contact is formed between the first electrode and a P-type boron emitter. A second electrode is fabricated on the back surface side, and an ohmic contact is formed between the second electrode and a phosphorus-doped polycrystalline silicon layer.

[0086] Example 2 An embodiment of the present invention provides a solar cell, the difference from Example 1 being the thickness of the first silicon oxide layer. Specifically, the ionization step of N2O is the same as in Example 1, except that the ionization time is 60 s.

[0087] Example 3 An embodiment of the present invention provides a solar cell, the difference from Example 1 being the thickness of the first silicon oxide layer. Specifically, the ionization step of N2O is the same as in Example 1, except that the ionization time is 120 s.

[0088] Example 4 An embodiment of the present invention provides a solar cell, the difference from Example 1 being the thickness of the first silicon oxide layer. Specifically, the ionization step of N2O is the same as in Example 1, except that the ionization time is 180 s.

[0089] Comparative Example This comparative example provides a solar cell, and the difference from Example 3 is that the step of ionizing N2O by PECVD after the aluminum oxide layer has been fabricated is omitted, that is, the silicon nitride layer is fabricated directly without fabricating a first silicon oxide layer between the aluminum oxide layer and the P-type boron emitter, and otherwise it is the same as Example 3.

[0090] Experiment 1 Measurement of the thickness of the first silicon oxide layer The thickness of the first silicon oxide layer was measured using the EDS elemental scanning function of a TEM or HR-TEM. The interface boundary line with a clear color difference in the EDS scan diagram was used as the measurement standard for the thickness of the first silicon oxide layer, and the measurement results for the thickness of the first silicon oxide layer for each example and comparative example are shown in Table 1.

[0091] Experiment 2 Measurement of battery efficiency decay 2.1 Measurement of Battery Cell Attenuation Performance Solar cells prepared by the methods described above for each example and comparative example are used as measurement cell samples. The photoelectric conversion efficiency of the cell samples is measured before and after UV degradation treatment. The difference in the decay of the cell efficiency after UV degradation treatment is obtained by subtracting the photoelectric conversion efficiency after UV degradation treatment from the photoelectric conversion efficiency before UV degradation treatment.

[0092] UV degradation treatment Battery cell samples were collected and irradiated at 60±5℃, with a wavelength range of 280nm~400nm and an irradiation intensity of 200W / m². 2 Under these measurement conditions, continuous and stable irradiation at 60 kWh was performed, after which the battery cell was removed and the IV was measured again. The percentage of efficiency decay before and after irradiation was defined as the difference in battery cell efficiency decay.

[0093] 2.2 Measurement of photovoltaic module attenuation performance Solar cells fabricated by the methods described in each of the above-mentioned examples and comparative examples are packaged as photovoltaic module samples. The maximum power of the photovoltaic module samples is measured before and after UV degradation treatment, and the difference in photovoltaic module power attenuation after UV degradation treatment is obtained by subtracting the power after UV degradation treatment from the power before UV degradation treatment.

[0094] UV degradation treatment The battery cells were packaged as a double-sided glass photovoltaic module. After the photovoltaic module was fabricated, it was left to stand for 24 hours to measure the photovoltaic current (IV), and then left in a UV irradiation device at 60±5℃, with a wavelength range of 280nm~400nm and an irradiation intensity of 200W / m². 2 Under the specified measurement conditions, continuous and stable irradiation at 60 kWh was performed, after which the module was removed and the IV was measured again. The difference in photovoltaic module power before and after irradiation was defined as the difference in photovoltaic module power decay.

[0095] Table 1 shows the measurement results of the battery efficiency decay in Experiment 2. Because there may be differences in crystal structure in different regions of the silicon substrate surface, silicon atoms in different regions of the emitter surface may have different reaction activity, and the thickness of the first silicon oxide layer produced under the same indirect oxidation conditions may vary within a certain numerical range. In this application, for the thickness of the first silicon oxide layer in Examples 1 to 4, based on the explanation regarding the measurement of the thickness of the first silicon oxide layer in Experiment 1, the lowest thickness of the first silicon oxide layer in the measured cross-section is selected as the thickness of the first silicon oxide in this application. However, if the thickness of the first silicon oxide layer in a specific region of the cross-section is significantly lower than the thickness of the first silicon oxide layer in other regions, and the proportion of the selected cross-section occupied by that specific region exceeds 30%, it is excluded from the measurement selection area for the thickness of the first silicon oxide layer as an abnormal measurement region.

[0096] [Table 1]

[0097] The following can be seen from Table 1.

[0098] (1) In Comparative Example 1, when a silicon oxide layer is formed between the emitter and the aluminum oxide layer by a direct oxidation treatment method, the difference in battery cell efficiency attenuation and the difference in photovoltaic module power attenuation are both larger than in Examples 1 to 4. This indicates that the indirect oxidation treatment method employed in the present invention provides a first silicon oxide layer formed between the emitter and the aluminum oxide layer with excellent UV attenuation prevention performance.

[0099] (2) Compared to Examples 1 to 3, in Example 4, the difference in battery cell efficiency decay and the difference in photovoltaic module power decay before and after the UV degradation test were both relatively higher. This indicates that if the plasma treatment time using the oxygen source is too long, it may destroy the structure of the aluminum oxide layer and / or the first silicon oxide layer, or accelerate the destruction of hydrogen group bonds within the aluminum oxide layer and / or the first silicon oxide layer, causing a decrease in battery cell efficiency and / or a decrease in the UV degradation performance of the battery cell. Therefore, setting the thickness range of the first silicon oxide layer to 0.2 nm to 1.2 nm contributes to mitigating the UV degradation decay performance.

[0100] (3) In Example 2, compared to the other examples, the difference in battery cell efficiency decay before and after the UV degradation test and the difference in photovoltaic module power decay were both the smallest, indicating the best UV decay prevention performance. This indicates that the optimal range for the thickness of the first silicon oxide layer is 0.6 nm to 0.8 nm.

[0101] The solar cell, its manufacturing method, and photovoltaic module disclosed in the embodiments of the present invention have been described in detail above. While the principles and embodiments of the present invention have been explained using specific examples in this specification, the above descriptions of embodiments are merely for the convenience of understanding the solar cell, its manufacturing method, photovoltaic module, and its core concept. Furthermore, those skilled in the art can modify the specific embodiments and scope of application based on the concept of the present invention. Therefore, the contents of this specification should not be construed as limitations on the present invention. [Explanation of Symbols]

[0102] 1. Silicon substrate 11 Emitter 111 P-type emitter 2. First silicon oxide layer 3. Aluminum oxide layer 4. First anti-reflective layer 41 First silicon nitride layer 411 First silicon nitride sublayer 412 Second silicon nitride sublayer 413 Third silicon nitride sublayer 42 First silicon nitride oxide layer 43 Second silicon oxide layer 51 Dielectric layer 511 Fourth silicon oxide layer 52 Doped polycrystalline silicon layer 6. Second anti-reflective layer 61 Second silicon nitride layer 71 First electrode 72 Second electrode

Claims

1. It is a solar cell, The device includes a silicon substrate, and on the light-receiving surface of the silicon substrate, an emitter, a first silicon oxide layer, an aluminum oxide layer, and a first anti-reflective layer are sequentially laminated. A solar cell characterized in that the thickness of the first silicon oxide layer is 0.2 nm to 1.2 nm.

2. The interfacial density of states of the first silicon oxide layer is 10 １１ cm －２ eV －１ ~10 １２ cm －２ eV －１ The solar cell according to claim 1, characterized in that it is the same as described above.

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 N-type and the emitter is P-type.

5. The thickness of the aluminum oxide layer is 3 nm to 8 nm. The solar cell according to claim 1, characterized in that the first anti-reflective layer includes one or more combinations of a first silicon nitride layer, a first silicon nitride oxide layer, and a second silicon oxide layer.

6. The silicon substrate includes, in order, a dielectric layer, a doped polycrystalline silicon layer, and a second anti-reflective layer, which are arranged on the back surface side of the silicon substrate. The second anti-reflective layer includes one or more combinations of the second silicon nitride layer, the second silicon nitride oxide layer, and the third silicon oxide layer. The solar cell according to any one of claims 1 to 5, characterized in that a first electrode is provided on the light-receiving side of the silicon substrate to form an ohmic contact with the emitter, and a second electrode is provided on the back-light side of the silicon substrate to form an ohmic contact with the doped polycrystalline silicon layer.

7. A method for manufacturing solar cells, The steps include providing a silicon substrate having an emitter on the light-receiving surface side, The steps include: creating an aluminum oxide layer on the surface of the emitter; A method for manufacturing a solar cell, characterized by comprising the step of indirectly growing a first silicon oxide layer on the surface of the emitter by an indirect oxidation treatment.

8. The method for manufacturing a solar cell according to claim 7, characterized in that the indirect oxidation treatment includes ionization treatment of the aluminum oxide layer with an oxygen source and / or annealing treatment of the aluminum oxide layer.

9. The oxygen source is CO ２ , N ２ O, H ２ O, O ２ or O ３ comprises one or more of the following, and / or the ionization treatment includes PECVD or LPCVD. The method for manufacturing a solar cell according to claim 8, characterized in that the temperature range of the annealing treatment is 400°C to 600°C.

10. The indirect oxidation treatment is the annealing treatment, and during the annealing treatment, O ２ or O ３ A method for manufacturing a solar cell according to claim 8 or 9, characterized in that the first silicon oxide layer is manufactured by supplying the material.

11. The ionization treatment of the oxygen source is performed by N ２ The method for manufacturing a solar cell according to claim 8, characterized in that it is ionized.

12. The indirect oxidation treatment is the annealing treatment, and during the annealing treatment, N ２ A method for manufacturing a solar cell according to claim 8, characterized in that an ionization process is performed.

13. The N to the aluminum oxide layer ２ The process conditions for O ionization are: ionization time 10s to 120s, N ２ A method for manufacturing a solar cell according to claim 11 or 12, characterized in that the O flow rate is 5000 sccm to 20000 sccm, the temperature is 450°C to 470°C, the RF power is 6000W to 12000W, and the on-time of the RF power supply is 20ms to 50ms.

14. A photovoltaic module characterized by including a solar cell according to any one of claims 1 to 5.

Images