Back contact solar cell and preparation method thereof, cell string, cell module and photovoltaic system

Abstract

The embodiment of the invention discloses a back contact solar cell and a preparation method thereof, a cell string, a cell assembly and a photovoltaic system. The back contact solar cell includes: a silicon substrate disposed in a first conductivity type; the first dielectric layer is located on the first surface; the first tunneling layer is located on the side, away from the first surface, of the first dielectric layer; the second tunneling layer is located on the first surface; the first doping layer is arranged to be of the first conduction type and is located on the side, away from the first dielectric layer, of the first tunneling layer; the second doping layer is arranged to be of a second conduction type and located on the side, away from the second surface, of the second tunneling layer; the first electrode layer is located on the side, away from the first tunneling layer, of the first doping layer; the second electrode layer is located on the side, away from the second tunneling layer, of the second doping layer. According to the technical scheme of the embodiment of the invention, the leakage current of the back contact solar cell can be reduced, the carrier separation efficiency is improved, and the conversion efficiency of the back contact solar cell is improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a back-contact solar cell, its preparation method, cell string, cell module, and photovoltaic system. Background Technology

[0002] Solar cells are used to directly convert solar energy into electrical energy. With the continuous development of photovoltaic technology, solar cell products, as semiconductor devices that convert solar energy into electrical energy, have been rapidly developed, with a focus on low cost and high efficiency. Among them, interdigitated back contact (IBC) cells, due to the absence of grid lines on the light-facing side of the cell and the placement of both the positive and negative electrodes on the back side, exhibit high front-side power, thus improving the energy conversion efficiency of IBC cells. Tunnel oxide passivated contact (TOPCon) cells, which combine with IBC, possess both high passivation quality and good contact characteristics, while also featuring the advantage of no grid lines obstructing the light-facing side, improving the utilization rate of incident light.

[0003] Existing TBC cells use silicon oxide as a tunneling layer to block holes and collect electrons. However, when the thickness of the silicon oxide film is small, the quantum tunneling effect is significantly enhanced, but the leakage current increases sharply. When the thickness of the silicon oxide film is large, the quantum tunneling effect weakens and the conversion efficiency of the solar cell decreases. Summary of the Invention

[0004] This invention provides a back-contact solar cell and its fabrication method, cell string, cell module and photovoltaic system, to reduce leakage current of back-contact solar cells, improve carrier separation efficiency and improve conversion efficiency of back-contact solar cells.

[0005] According to one aspect of the present invention, a back-contact solar cell is provided, the back-contact solar cell comprising:

[0006] A silicon substrate, including a first surface and a second surface disposed opposite to each other; the silicon substrate is configured with a first conductivity type;

[0007] A first dielectric layer is located on the first surface; the material of the first dielectric layer includes molybdenum oxide.

[0008] A first tunneling layer is located on the side of the first dielectric layer away from the first surface; a second tunneling layer is located on the first surface; on the first surface, the first tunneling layer and the second tunneling layer extend along a first direction and are alternately arranged along a second direction; the vertical projection of the first dielectric layer on the silicon substrate overlaps with the vertical projection of the first tunneling layer on the silicon substrate, but does not overlap with the vertical projection of the second tunneling layer on the silicon substrate.

[0009] The first doped layer is configured with a first conductivity type and is located on the side of the first tunneling layer away from the first dielectric layer; the second doped layer is configured with a second conductivity type and is located on the side of the second tunneling layer away from the first surface.

[0010] The first electrode layer is located on the side of the first doped layer away from the first tunneling layer; the second electrode layer is located on the side of the second doped layer away from the second tunneling layer.

[0011] Optionally, the sum of the thicknesses of the first dielectric layer and the first tunneling layer is greater than or equal to 1.5 nanometers and less than or equal to 4 nanometers.

[0012] Optionally, the thickness of the first dielectric layer is 34%-50% of the sum of the thicknesses of the first dielectric layer and the first tunneling layer.

[0013] Optionally, the thickness of the first dielectric layer is greater than or equal to 0.5 nanometers and less than or equal to 2 nanometers.

[0014] Optionally, the thickness of the first doped layer is greater than or equal to 150 nanometers and less than or equal to 250 nanometers.

[0015] Optionally, the molar ratio of oxygen atoms to molybdenum atoms in the first dielectric layer is 3:1.

[0016] Optionally, the back-contact solar cell also includes:

[0017] The second dielectric layer is located on the side of the first doped layer away from the first tunneling layer; the material of the second dielectric layer includes molybdenum oxide.

[0018] Optionally, the thickness of the second dielectric layer is greater than or equal to 0.1 nanometers and less than or equal to 0.5 nanometers.

[0019] Optionally, the molar ratio of oxygen atoms to molybdenum atoms in the second dielectric layer is 3:1.

[0020] Optionally, the back-contact solar cell may also include: an anti-reflection layer;

[0021] The antireflection layer is located on the side of the second dielectric layer away from the first doped layer.

[0022] According to another aspect of the present invention, a method for fabricating a back-contact solar cell is provided, the method comprising:

[0023] A silicon substrate is provided; the silicon substrate includes a first surface and a second surface disposed opposite to each other; the silicon substrate is configured with a first conductivity type;

[0024] A first dielectric layer is formed on the first surface; the material of the first dielectric layer includes molybdenum oxide.

[0025] A first tunneling layer is formed on the side of the first dielectric layer away from the first surface;

[0026] A second tunneling layer is formed on a first surface; on the first surface, the first tunneling layer and the second tunneling layer extend along a first direction and are alternately arranged along a second direction; the vertical projection of the first dielectric layer on the silicon substrate overlaps with the vertical projection of the first tunneling layer on the silicon substrate, but does not overlap with the vertical projection of the second tunneling layer on the silicon substrate.

[0027] A first doped layer is formed on the side of the first tunneling layer away from the first dielectric layer; the first doped layer is configured with a first conductivity type.

[0028] A second doped layer is formed on the side of the second tunneling layer away from the second surface; the second doped layer is configured with a second conductivity type.

[0029] A first electrode layer is formed on the side of the first doped layer that is away from the first tunneling layer;

[0030] A second electrode layer is formed on the side of the second doped layer away from the second tunneling layer.

[0031] Optionally, a first dielectric layer is formed on the first surface, including:

[0032] The first dielectric layer is formed on the first surface by evaporation, atomic layer deposition, pulsed laser deposition, or chemical vapor deposition.

[0033] According to another aspect of the present invention, a battery string is provided, including a back-contact solar cell according to any embodiment of the present invention.

[0034] According to another aspect of the present invention, a battery assembly is provided, including a back-contact solar cell or a battery string according to any embodiment of the present invention.

[0035] According to another aspect of the present invention, a photovoltaic system is provided, including a battery module according to any embodiment of the present invention.

[0036] The technical solution of this invention provides a stacked structure consisting of a first dielectric layer, a first tunneling layer, and a first doped layer. Compared to the existing structure combining a tunneling layer and a doped layer, the stacked structure of this invention forms a molybdenum-doped amorphous silicon oxide transition layer at the interface between the first dielectric layer and the first tunneling layer, enhancing interface adhesion and improving interface stability. The first dielectric layer and the first tunneling layer have similar coefficients of thermal expansion, preventing interface delamination due to stress differences during high-temperature processing, thus extending the lifespan of the back-contact solar cell. Furthermore, the high work function of the first dielectric layer provides selective electron collection, and as a hole-blocking layer, the interface recombination rate can be reduced to 10 cm / s or below, blocking holes and improving electron collection capability. The first dielectric layer and the first doped layer form a dual-selectivity mechanism, enhancing carrier selectivity and improving open-circuit voltage and fill factor. As an electron collection layer, the first dielectric layer can reduce leakage current in the back-contact solar cell, improve carrier separation efficiency, and increase the conversion efficiency of the back-contact solar cell.

[0037] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a back-contact solar cell according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of the present invention;

[0041] Figure 3 This is a flowchart of a method for fabricating a back-contact solar cell according to an embodiment of the present invention;

[0042] Figures 4-7 This is a cross-sectional view of each step in a method for fabricating a back-contact solar cell according to an embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] Figure 1 This is a schematic diagram of a back-contact solar cell according to an embodiment of the present invention. Figure 1 As shown, the back-contact solar cell includes: a silicon substrate 10, including a first surface 101 and a second surface 102 disposed opposite to each other; the silicon substrate 10 is configured with a first conductivity type; a first dielectric layer 20 located on the first surface 101; the material of the first dielectric layer 20 includes molybdenum oxide; a first tunneling layer 30 located on the side of the first dielectric layer 20 away from the first surface 101; a second tunneling layer 40 located on the first surface 101; on the first surface 101, the first tunneling layer 30 and the second tunneling layer 40 extend along a first direction and are alternately disposed along a second direction X; the first dielectric layer 20 on... The vertical projection of the silicon substrate 10 overlaps with the vertical projection of the first tunneling layer 30 on the silicon substrate 10, but does not overlap with the vertical projection of the second tunneling layer 40 on the silicon substrate 10; the first doped layer 50 is configured as a first conductivity type and is located on the side of the first tunneling layer 30 away from the first dielectric layer 20; the second doped layer 60 is configured as a second conductivity type and is located on the side of the second tunneling layer 40 away from the first surface; the first electrode layer 70 is located on the side of the first doped layer 50 away from the first tunneling layer 30; and the second electrode layer 80 is located on the side of the second doped layer 60 away from the second tunneling layer 40.

[0046] In this embodiment of the invention, the silicon substrate 10 includes a first surface 101 and a second surface 102. Exemplarily, the first surface 101 can be a non-light-receiving surface (backlight surface), and the second surface 102 can be a light-receiving surface. The light-receiving surface is the side that receives illumination from a light source, while the backlight surface is located on the side opposite to the light-receiving surface. An aluminum oxide layer 103, a silicon nitride layer 104, and a silicon oxide layer 105 may be sequentially disposed on the side of the second surface 102 away from the first surface 101 to protect the silicon substrate 10, optimize the optical performance of the back-contact solar cell, and improve the stability of the back-contact solar cell. The aluminum oxide layer 103 is used for passivation protection, reducing surface defects and charge recombination of the silicon substrate 10, while also blocking the intrusion of external contaminants such as moisture or impurities. The silicon nitride layer 104 is used for anti-reflection and passivation, reducing the reflection loss of incident light, allowing more light to enter the light-receiving surface, and further improving the passivation effect. The silicon oxide layer 105 is used for insulation and protection, improving the insulation performance of the back-contact solar cell surface and blocking mechanical wear and chemical corrosion.

[0047] The first doped layer 50 has the same conductivity type as the silicon substrate 10, and the second doped layer 60 has the opposite conductivity type to the silicon substrate 10. The first conductivity type can be N-type or P-type. Furthermore, the first conductivity type is opposite to the second conductivity type; when the first conductivity type is N-type, the second conductivity type is P-type; and when the first conductivity type is P-type, the second conductivity type is N-type. For example, the silicon substrate 10 can be an N-type silicon substrate, the first doped layer 50 can be an N-type doped layer, and the second doped layer 60 can be a P-type doped layer. Alternatively, the silicon substrate 10 can be a P-type silicon substrate, the first doped layer 50 can be a P-type doped layer, and the second doped layer 60 can be an N-type doped layer. The P-type dopant can be at least one of boron (B), aluminum (Al), or gallium (Ga), and this invention is not specifically limited thereto. The N-type dopant can be at least one of phosphorus (P), arsenic (As), or antimony (Sb), and this invention is not specifically limited thereto.

[0048] This embodiment of the invention uses an N-type silicon substrate 10 as an example. The first doped layer 50 can be an N-type polycrystalline silicon doped layer, and the second doped layer 60 can be a P-type polycrystalline silicon doped layer. The first doped layer 50 is used to collect electrons, and the second doped layer 60 is used to collect holes. The collected carriers are then transferred to the first electrode layer 70 and the second electrode layer 80, respectively, forming a pathway with the external load. Therefore, the first doped layer 50 and the second doped layer 60 cannot be in direct contact; otherwise, the carriers cannot be effectively collected.

[0049] The material of the first dielectric layer 20 is molybdenum oxide, which can be molybdenum trioxide (Mo). The materials of the first tunneling layer 30 and the second tunneling layer 40 are both silicon dioxide ( In this embodiment of the invention, a stacked structure of a first dielectric layer 20, a first tunneling layer 30, and a first doped layer 50 is formed. and It has good interface compatibility. and A molybdenum-doped amorphous silicon oxide transition layer forms at the interface, enhancing interfacial adhesion and improving interface stability. Furthermore... and Their coefficients of thermal expansion are similar, and they will not peel off at the interface due to stress differences during high-temperature processes. It can withstand high-temperature processes, exhibits good thermal stability, and can withstand process temperatures of 550-650℃. It remains stable in phosphorus diffusion processes (850-900℃) without decomposition or phase transition, even after brief exposure at higher temperatures. The crystal structure and electrical properties can also remain relatively stable. The stacked structure composed of the first dielectric layer 20, the first tunneling layer 30, and the first doped layer 50 can improve the electron collection capability, wherein... As the first dielectric layer 20, its high work function provides selective electron collection, while as a hole blocking layer, the interfacial recombination rate can be reduced to 10 cm / s or less. The first tunneling layer 30 serves as a passivation layer, reducing the surface state density and acting as an electron tunneling channel. The N-type polysilicon doped layer 50 provides a low-resistance electron transport path and serves as the attachment layer for the first electrode layer 70.

[0050] The materials of the first electrode layer 70 and the second electrode layer 80 include, but are not limited to, silver or copper. By making the first electrode layer 70 in close contact with the first doped layer 50 and the second electrode layer 80 in close contact with the second doped layer 60, efficient carrier transport and circuit connectivity are achieved.

[0051] The technical solution of this invention provides a stacked structure consisting of a first dielectric layer, a first tunneling layer, and a first doped layer. Compared to the existing structure combining a tunneling layer and a doped layer, the stacked structure of this invention forms a molybdenum-doped amorphous silicon oxide transition layer at the interface between the first dielectric layer and the first tunneling layer, enhancing interface adhesion and improving interface stability. The first dielectric layer and the first tunneling layer have similar coefficients of thermal expansion, preventing interface delamination due to stress differences during high-temperature processing, thus extending the lifespan of the back-contact solar cell. Furthermore, the high work function of the first dielectric layer provides selective electron collection, and as a hole-blocking layer, the interface recombination rate can be reduced to 10 cm / s or below, blocking holes and improving electron collection capability. The first dielectric layer and the first doped layer form a dual-selectivity mechanism, enhancing carrier selectivity and improving open-circuit voltage and fill factor. As an electron collection layer, the first dielectric layer can reduce leakage current in the back-contact solar cell, improve carrier separation efficiency, and increase the conversion efficiency of the back-contact solar cell.

[0052] In an optional embodiment of the present invention, reference is made to... Figure 1 The sum of the thicknesses of the first dielectric layer 20 and the first tunneling layer 30 is greater than or equal to 1.5 nanometers and less than or equal to 4 nanometers.

[0053] In this embodiment of the invention, the sum of the thicknesses of the first dielectric layer 20 and the first tunneling layer 30 is controlled between 1.5 nm and 4 nm, which does not affect the carrier tunneling efficiency, optimizes passivation and interface performance, and adapts to high-temperature processes and structural compatibility.

[0054] In an optional embodiment of the present invention, reference is made to... Figure 1 The thickness of the first dielectric layer 20 is 34%-50% of the sum of the thicknesses of the first dielectric layer 20 and the first tunneling layer 30.

[0055] In this embodiment of the invention, the thickness of the first dielectric layer 20 is controlled between 34% and 50% to maximize the electron collection efficiency and stability of the stacked structure. The minimum thickness of the first dielectric layer 20 is 34% to ensure that its thickness maintains high work function characteristics, effectively achieving selective electron collection and hole blocking, and preventing functional failure due to excessively low thickness. The maximum thickness of the first dielectric layer 20 is 50% to prevent excessive thickness from compressing the first tunneling layer 30, ensuring that the first tunneling layer 30 effectively performs its passivation function while providing a low-resistance transport channel for electrons.

[0056] In an optional embodiment of the present invention, reference is made to... Figure 1 The thickness of the first dielectric layer 20 is greater than or equal to 0.5 nanometers and less than or equal to 2 nanometers.

[0057] In this embodiment of the invention, the thickness of the first dielectric layer 20 is set to 0.5nm to 2nm, which can maintain the high work function and selectivity of the first dielectric layer 20, effectively realize the selective collection of electrons and the blocking of holes, avoid functional failure due to insufficient thickness, and at the same time avoid the electron transport path from increasing due to excessive thickness.

[0058] In an optional embodiment of the present invention, reference is made to... Figure 1 The thickness of the first doped layer 50 is greater than or equal to 150 nanometers and less than or equal to 250 nanometers.

[0059] In this embodiment of the invention, the thickness of the first doped layer 50 is greater than or equal to 150 nm and less than or equal to 250 nm, which can provide a low-resistance electron transport path and serve as an attachment layer for the first electrode layer 70.

[0060] In an optional embodiment of the present invention, reference is made to... Figure 1 The molar ratio of oxygen atoms to molybdenum atoms in the first dielectric layer 20 is 3:1.

[0061] In this embodiment of the invention, the molar ratio of oxygen atoms to molybdenum atoms in the first dielectric layer 20 is set to 3:1 to ensure the integrity of the molybdenum trioxide crystal structure, improve the electron transport speed to the first tunneling layer 30, and at the same time improve interface stability and thermal stability.

[0062] Figure 2 This is a schematic diagram of another back-contact solar cell provided according to an embodiment of the present invention. Figure 2 As shown, the back-contact solar cell further includes a second dielectric layer 90 located on the side of the first doped layer 50 away from the first tunneling layer 30; the material of the second dielectric layer 90 includes molybdenum oxide.

[0063] In this embodiment of the invention, a second dielectric layer 90 is provided on the side of the first doped layer 50 away from the first tunneling layer 30 to improve electron collection capability and increase contact with the first electrode layer 70, thereby reducing contact resistance.

[0064] In an optional embodiment of the present invention, reference is made to... Figure 2 The thickness of the second dielectric layer 90 is greater than or equal to 0.1 nanometers and less than or equal to 0.5 nanometers.

[0065] In this embodiment of the invention, the thickness of the second dielectric layer 90 is set to be in the range of 0.1 nm to 0.5 nm to enhance electron collection and interface contact and avoid hindering electron transport.

[0066] In an optional embodiment of the present invention, reference is made to... Figure 2 The molar ratio of oxygen atoms to molybdenum atoms in the second dielectric layer 90 is 3:1.

[0067] In this embodiment of the invention, the molar ratio of oxygen atoms to molybdenum atoms in the second dielectric layer 90 is set to 3:1 to ensure the integrity of the molybdenum trioxide crystal structure, improve the electron transport speed to the first electrode layer 70, and at the same time improve interface stability and thermal stability.

[0068] In optional embodiments of the present invention, reference continues to be made to... Figure 2 The back-contact solar cell also includes an anti-reflection layer 100; the anti-reflection layer 100 is located on the side of the second dielectric layer 90 away from the first doped layer 50.

[0069] In this embodiment of the invention, the antireflection layer 100 may be one or more combinations of an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer. Providing the antireflection layer 100 can enhance the antireflection effect, increase light absorption and utilization, and thus improve the performance of the back-contact solar cell.

[0070] Figure 3This is a flowchart illustrating a method for fabricating a back-contact solar cell according to an embodiment of the present invention. This embodiment is applicable to the fabrication of back-contact solar cells, and the method for fabricating this back-contact solar cell can be performed by an apparatus for fabricating a back-contact solar cell. Figure 3 As shown, the fabrication method of this back-contact solar cell includes:

[0071] S110, A silicon substrate is provided; the silicon substrate includes a first surface and a second surface disposed opposite to each other; the silicon substrate is configured with a first conductivity type.

[0072] refer to Figure 4 The silicon substrate 10 includes a first surface 101 and a second surface 102. For example, the first surface 101 can be a non-light-receiving surface (backlight surface), and the second surface 102 can be a light-receiving surface. The light-receiving surface is the side that receives illumination from a light source, while the backlight surface is located on the side opposite to the light-receiving surface.

[0073] S120, A first dielectric layer is formed on the first surface; the material of the first dielectric layer includes molybdenum oxide.

[0074] refer to Figure 5 On the first surface 101 of the silicon substrate 10, molybdenum oxide is deposited by magnetron sputtering or atomic layer deposition to form a first dielectric layer 20, which improves electron collection capability and provides a smooth interface for the subsequent formation of the first tunneling layer. When forming the first dielectric layer 20 by magnetron sputtering, a molybdenum target with a purity of 99.95% and an oxygen atmosphere can be provided, the temperature of the silicon substrate 10 can be less than or equal to 200°C, the deposition rate can be 0.1-0.3 nm / s, and the thickness of the first dielectric layer 20 can be precisely controlled between 0.5 nm and 2 nm.

[0075] It should be noted that a dipole layer may form at the interface between molybdenum trioxide and silicon dioxide, affecting electron transport. Therefore, before depositing molybdenum trioxide to form the first dielectric layer 20, the silicon substrate is hydrogen passivated, or an appropriate amount of oxygen vacancies is introduced into the molybdenum trioxide (by controlling the oxygen partial pressure during deposition) to optimize the interface electronic structure.

[0076] In an optional embodiment of the present invention, S120, forming a first dielectric layer on the first surface includes: forming the first dielectric layer on the first surface by vapor deposition, atomic layer deposition, pulsed laser deposition or chemical vapor deposition.

[0077] Specifically, the first dielectric layer is formed by vapor deposition, atomic layer deposition, pulsed laser deposition, or chemical vapor deposition. The resulting film has excellent quality, reduces defects and porosity, and has strong process controllability, allowing precise control of the film thickness to match the carrier transport requirements, while also exhibiting high stability.

[0078] S130, a first tunneling layer is formed on the side of the first dielectric layer away from the first surface.

[0079] refer to Figure 6 A first tunneling layer 30 is formed on the side of the first dielectric layer 20 away from the first surface 101. It can be formed by thermal oxidation (dry or wet oxidation) or plasma-enhanced chemical vapor deposition (PECVD) of silicon. When forming the first tunneling layer 30 using thermal oxidation, the reaction temperature is controlled at 900-1000℃ and the reaction time is 5-10 min. When forming the first tunneling layer 30 using PECVD, the reaction temperature is controlled at 300-400℃, and the reaction source is silane and nitrous oxide. The thickness of the first tunneling layer 30 is controlled between 1-2 nm, providing passivation while also serving as an electron quantum tunneling channel.

[0080] S140. A second tunneling layer is formed on the first surface. On the first surface, the first tunneling layer and the second tunneling layer extend along a first direction and are alternately arranged along a second direction. The vertical projection of the first dielectric layer on the silicon substrate overlaps with the vertical projection of the first tunneling layer on the silicon substrate, but does not overlap with the vertical projection of the second tunneling layer on the silicon substrate.

[0081] Continue to refer to Figure 6 A second tunneling layer 40 is formed on the first surface 101. The second tunneling layer 40 can be formed simultaneously with the first tunneling layer 30, or the first tunneling layer 30 can be formed first and then the second tunneling layer 40, or the second tunneling layer 40 can be formed first and then the first tunneling layer 30. This embodiment of the invention does not specifically limit the formation of the second tunneling layer 30. The first tunneling layer 30 and the second tunneling layer 40 extend along a first direction (not shown in the figure) and are alternately arranged along a second direction X. A top view of the back-contact solar cell shows the first tunneling layer 30 and the second tunneling layer 40 extending along the first direction.

[0082] S150, A first doped layer is formed on the side of the first tunneling layer away from the first dielectric layer; the first doped layer is configured with a first conductivity type.

[0083] refer to Figure 7 A first doped layer 50 is formed on the side of the first tunneling layer 30 away from the first dielectric layer 20. The first doped layer 50 is configured with a first conductivity type, for example, N-type. The first doped layer 50 is formed by depositing polycrystalline silicon using low-pressure chemical vapor deposition (LPCVD) or PECVD. The process parameters are: reaction temperature of 550-980℃, deposition time of 40-160 min, and phosphorus doping (using phosphorus oxychloride as the dopant source). The first doped layer 50 can provide a low-resistance electron transport path and can also serve as an attachment layer for metal electrodes.

[0084] S160, a second doped layer is formed on the side of the second tunneling layer away from the first surface; the second doped layer is configured with a second conductivity type.

[0085] Continue to refer to Figure 7 A second doped layer 60 is formed on the side of the second tunneling layer 40 away from the first surface 101; the second doped layer 60 is configured with a second conductivity type, for example, the second doped layer 60 is configured as P-type. The formation process and thickness of the second doped layer 60 are the same as those of the first doped layer 50.

[0086] S170, a first electrode layer is formed on the side of the first doped layer away from the first tunneling layer.

[0087] refer to Figure 1 On the side of the first doped layer 50 away from the first tunneling layer 30, a first electrode layer 70 is formed by electroplating copper or silver.

[0088] S180, a second electrode layer is formed on the side of the second doped layer away from the second tunneling layer.

[0089] refer to Figure 1 On the side of the second doped layer 60 away from the second tunneling layer 40, a second electrode layer 80 is formed by electroplating copper or silver.

[0090] The technical solution of this invention forms a stacked structure consisting of a first dielectric layer, a first tunneling layer, and a first doped layer. Compared with the structure of the tunneling layer and doped layer in the prior art, the stacked structure of this invention forms a molybdenum-doped amorphous silicon oxide transition layer at the interface between the first dielectric layer and the first tunneling layer, enhancing the interface bonding and improving interface stability. The thermal expansion coefficients of the first dielectric layer and the first tunneling layer are similar, preventing interface peeling due to stress differences during high-temperature processing, thus extending the lifespan of the back-contact solar cell. Furthermore, the high work function of the first dielectric layer provides selective electron collection, and as a hole-blocking layer, the interface recombination rate can be reduced to 10 cm / s or below, blocking holes and improving electron collection capability. The first dielectric layer and the first doped layer form a dual-selectivity mechanism, enhancing carrier selectivity and improving open-circuit voltage and fill factor. As an electron collection layer, the first dielectric layer can reduce the leakage current of the back-contact solar cell, improve carrier separation efficiency, and increase the conversion efficiency of the back-contact solar cell.

[0091] This invention provides a battery string, wherein the battery string includes any back-contact solar cell provided in any of the above embodiments of this invention, and possesses the beneficial effects of any back-contact solar cell provided in any of the above embodiments of this invention. The battery string can be formed by connecting multiple back-contact solar cells in series.

[0092] This invention provides a battery assembly, wherein the battery assembly includes any back-contact solar cell provided in any of the above embodiments of this invention, or the battery assembly includes a battery string provided in any of the above embodiments of this invention.

[0093] A battery module may include multiple back-contact solar cells, which can be connected in series to form a battery string. These battery strings can be connected in series, parallel, or a combination of series and parallel to achieve current output. For example, the connection between individual cells can be achieved by welding ribbons, or the connection between battery strings can be achieved by busbars. The battery module may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film can be filled between the light-facing side of the back-contact solar cells and the photovoltaic glass, the back-facing side and the backsheet, and adjacent cells. As a filler, it can be a transparent colloid with good light transmittance and aging resistance; for example, the encapsulating film can be EVA film or POE film, and the specific choice can be made according to the actual situation, without limitation.

[0094] Photovoltaic glass can be applied to the encapsulating film on the light-facing side of the back-contact solar cell. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 92%. It can protect the back-contact solar cell while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the back-contact solar cell together, providing sealing, insulation, and waterproofing / moisture protection for the back-contact solar cell.

[0095] The backsheet can be attached to the adhesive film on the back side of the back-contact solar cell. The backsheet protects and supports the back-contact solar cell, providing reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, and aluminum alloy TPT composite adhesive film, etc. The specific choice depends on the specific circumstances and is not limited here. The backsheet, back-contact solar cell, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire battery module, providing stable support and installation. For example, the battery module can be installed at the desired location using the metal frame.

[0096] The battery assembly provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention.

[0097] This invention provides a photovoltaic system, wherein the photovoltaic system includes the battery module provided in the above embodiments of this invention, and has the beneficial effects of the battery module provided in the above embodiments of this invention.

[0098] Photovoltaic systems can be applied in photovoltaic power plants, such as ground-mounted, rooftop, and floating power plants, as well as in equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it's understandable that the application scenarios of photovoltaic systems are not limited to these; that is, photovoltaic systems can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation network as an example, a photovoltaic system can include photovoltaic arrays, combiner boxes, and inverters. A photovoltaic array can be a combination of multiple battery modules; for example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic arrays are connected to combiner boxes, which collect the current generated by the photovoltaic arrays. The collected current flows through an inverter and is converted into AC power required by the mains grid before being connected to the mains grid to achieve solar power supply.

[0099] Since the battery module provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention, the photovoltaic system provided in the embodiments of the present invention has the beneficial effects of any back-contact solar cell or battery string provided in any of the above embodiments of the present invention.

[0100] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0101] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon substrate, including a first surface and a second surface disposed opposite to each other; the silicon substrate is configured with a first conductivity type; A first dielectric layer is located on the first surface; The material of the first dielectric layer includes molybdenum oxide; The first tunneling layer is located on the side of the first dielectric layer away from the first surface; A second tunneling layer is located on the first surface; on the first surface, the first tunneling layer and the second tunneling layer extend along a first direction and are alternately arranged along a second direction; the vertical projection of the first dielectric layer on the silicon substrate overlaps with the vertical projection of the first tunneling layer on the silicon substrate, but does not overlap with the vertical projection of the second tunneling layer on the silicon substrate. The first doped layer is configured with a first conductivity type and is located on the side of the first tunneling layer away from the first dielectric layer. The second doped layer is configured with a second conductivity type and is located on the side of the second tunneling layer away from the first surface; The first electrode layer is located on the side of the first doped layer away from the first tunneling layer; the second electrode layer is located on the side of the second doped layer away from the second tunneling layer.

2. The back-contact solar cell according to claim 1, characterized in that, The sum of the thicknesses of the first dielectric layer and the first tunneling layer is greater than or equal to 1.5 nanometers and less than or equal to 4 nanometers.

3. The back-contact solar cell according to claim 2, characterized in that, The thickness of the first dielectric layer is 34%-50% of the sum of the thicknesses of the first dielectric layer and the first tunneling layer.

4. The back-contact solar cell according to claim 3, characterized in that, The thickness of the first dielectric layer is greater than or equal to 0.5 nanometers and less than or equal to 2 nanometers.

5. The back-contact solar cell according to claim 1, characterized in that, The thickness of the first doped layer is greater than or equal to 150 nanometers and less than or equal to 250 nanometers.

6. The back-contact solar cell according to claim 1, characterized in that, The molar ratio of oxygen atoms to molybdenum atoms in the first dielectric layer is 3:

1.

7. The back-contact solar cell according to claim 1, characterized in that, The back-contact solar cell also includes: The second dielectric layer is located on the side of the first doped layer away from the first tunneling layer; the material of the second dielectric layer includes molybdenum oxide.

8. The back-contact solar cell according to claim 7, characterized in that, The thickness of the second dielectric layer is greater than or equal to 0.1 nanometers and less than or equal to 0.5 nanometers.

9. The back-contact solar cell according to claim 7, characterized in that, The molar ratio of oxygen atoms to molybdenum atoms in the second dielectric layer is 3:

1.

10. The back-contact solar cell according to claim 7, characterized in that, The back-contact solar cell further includes: an anti-reflection layer; The antireflection layer is located on the side of the second dielectric layer away from the first doped layer.

11. A method for fabricating a back-contact solar cell, characterized in that, include: Provide silicon substrate; The silicon substrate includes a first surface and a second surface disposed opposite to each other; the silicon substrate is configured with a first conductivity type; A first dielectric layer is formed on the first surface; The material of the first dielectric layer includes molybdenum oxide; A first tunneling layer is formed on the side of the first dielectric layer away from the first surface; A second tunneling layer is formed on the first surface; on the first surface, the first tunneling layer and the second tunneling layer extend along a first direction and are alternately arranged along a second direction; the vertical projection of the first dielectric layer on the silicon substrate overlaps with the vertical projection of the first tunneling layer on the silicon substrate, but does not overlap with the vertical projection of the second tunneling layer on the silicon substrate. A first doped layer is formed on the side of the first tunneling layer away from the first dielectric layer; the first doped layer is configured with a first conductivity type. A second doped layer is formed on the side of the second tunneling layer away from the second surface; the second doped layer is configured with a second conductivity type; A first electrode layer is formed on the side of the first doped layer away from the first tunneling layer; A second electrode layer is formed on the side of the second doped layer away from the second tunneling layer.

12. The method for fabricating a back-contact solar cell according to claim 11, characterized in that, A first dielectric layer is formed on the first surface, including: A first dielectric layer is formed on the first surface by means of vapor deposition, atomic layer deposition, pulsed laser deposition or chemical vapor deposition.

13. A battery string, characterized in that, Including the back-contact solar cell as described in any one of claims 1-10.

14. A battery assembly, characterized in that, This includes the back-contact solar cell as described in any one of claims 1-10 or the battery string as described in claim 13.

15. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 14.

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