Heterojunction cell and photovoltaic module

Abstract

The utility model discloses a heterojunction cell and a photovoltaic module, and relates to the technical field of photovoltaics. The heterojunction cell comprises a first transparent conductive layer, an n-type microcrystalline silicon layer, a first intrinsic amorphous silicon layer, an n-type monocrystalline silicon layer, a second intrinsic amorphous silicon layer, a p-type microcrystalline silicon layer and a second transparent conductive layer which are stacked in sequence. The heterojunction cell also includes a first electrode connected to the first transparent conductive layer and a second electrode connected to the second transparent conductive layer. Wherein the first transparent conductive layer comprises a first zinc oxide layer, a first indium tin oxide layer and a first titanium oxide layer which are stacked in sequence. The transparent conductive layer is arranged to be a composite layer structure made of three materials, so that the use amount of expensive indium tin oxide can be remarkably reduced, and the cost is reduced. The first conductive film with the composite layer structure can also relieve the problem of ultraviolet-induced degradation of the heterojunction cell, improve the performance stability of the cell and prolong the service life of the cell.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a heterojunction battery and a photovoltaic module. Background Art

[0002] Heterojunction (HJT) cells are a highly efficient solar cell technology. It combines the stability of crystalline silicon cells with the high efficiency characteristics of thin-film cells and is an important development in the photovoltaic industry. HJT cells have the following advantages: 1) High conversion efficiency: The laboratory efficiency of HJT cells has reached more than 26%, and the mass production efficiency has also reached more than 24%; 2) Low temperature coefficient: The temperature coefficient of HJT cells is low, which means that it can maintain a high output power even in high temperature environments; 3) Bifacial power generation: HJT cells have bifacial power generation capabilities, which can absorb light from the front and back, improving the overall energy collection efficiency; 4) Thinning: HJT cells can use thinner silicon wafers, reducing material costs; 5) Simple process: Compared with other types of high-efficiency cells, the production process of HJT cells is relatively simple, and the requirements for silicon wafer quality are relatively low. The many advantages of HJT cells make them have broad application prospects in photovoltaic power stations, rooftop solar systems, and building integrated photovoltaics (BIPV).

[0003] Transparent conductive layers are provided on both sides of the HJT cell, which are used to collect photogenerated carriers and transport them to the metal electrode. In order to obtain higher cell efficiency, the transparent conductive layer needs to have both good optical and electrical properties. However, at present, the transparent conductive layer of the heterojunction cell in the related technology mainly uses indium tin oxide (ITO), and the conductivity is improved by doping tin into indium oxide. The transparent conductive layer is formed entirely of indium tin oxide, which has a high cost. Utility Model Content

[0004] The purpose of the present application is to provide a heterojunction cell and a photovoltaic module, wherein the transparent conductive layer has both optical and electrical properties as well as lower material cost.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, the present application provides a heterojunction battery, comprising a first transparent conductive layer, an n-type microcrystalline silicon layer, a first intrinsic amorphous silicon layer, an n-type single crystal silicon layer, a second intrinsic amorphous silicon layer, a p-type microcrystalline silicon layer and a second transparent conductive layer stacked in sequence, the heterojunction battery further comprising a first electrode connected to the first transparent conductive layer and a second electrode connected to the second transparent conductive layer;

[0007] The first transparent conductive layer includes a first zinc oxide layer, a first indium tin oxide layer and a first titanium oxide layer which are stacked in sequence.

[0008] In an optional embodiment, the first titanium oxide layer is located on a side of the first indium tin oxide layer close to the n-type microcrystalline silicon layer, and the first zinc oxide layer is located on a side of the first indium tin oxide layer away from the n-type microcrystalline silicon layer and connected to the first electrode.

[0009] In an optional embodiment, the thickness of the first indium tin oxide layer is not greater than the thickness of the first zinc oxide layer, and is greater than the thickness of the first titanium oxide layer.

[0010] In an optional embodiment, the thickness of the first zinc oxide layer is 20-70 nm, the thickness of the first indium tin oxide layer is 20-40 nm, and the thickness of the first titanium oxide layer is 5-15 nm.

[0011] In an optional embodiment, the material of the first zinc oxide layer is one of nitrogen-doped zinc oxide, carbon-doped zinc oxide, aluminum-doped zinc oxide, sulfur-doped zinc oxide, selenium-doped zinc oxide, and tellurium-doped zinc oxide.

[0012] In an optional embodiment, a surface of the n-type single crystal silicon layer connected to the first intrinsic amorphous silicon layer is a velvet surface, and a surface of the n-type single crystal silicon layer connected to the second intrinsic amorphous silicon layer is a velvet surface.

[0013] In an optional embodiment, the second transparent conductive layer includes a second zinc oxide layer, a second indium tin oxide layer, and a second titanium oxide layer which are stacked in sequence.

[0014] In an optional embodiment, an optical anti-reflection layer is provided in a region of the first transparent conductive layer that is away from the n-type microcrystalline silicon layer and is not covered by the first electrode.

[0015] In an optional embodiment, the material of the optical anti-reflection layer is one of zinc sulfide, magnesium fluoride, aluminum oxide, titanium oxide and silicon oxide.

[0016] In an optional embodiment, the thickness of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are both 1-10 nm, and the thickness of the n-type microcrystalline silicon layer and the p-type microcrystalline silicon layer are both 10-30 nm.

[0017] In an optional implementation, the coverage area of ​​the first electrode accounts for 1% to 5% of the area of ​​the first transparent conductive layer.

[0018] In a second aspect, the present application provides a photovoltaic module, comprising the heterojunction cell of any one of the aforementioned embodiments.

[0019] The beneficial effects of the embodiments of the present application are:

[0020] The heterojunction battery provided in the embodiment of the present application includes a first transparent conductive layer, an n-type microcrystalline silicon layer, a first intrinsic amorphous silicon layer, an n-type single crystal silicon layer, a second intrinsic amorphous silicon layer, a p-type microcrystalline silicon layer and a second transparent conductive layer stacked in sequence. The heterojunction battery also includes a first electrode connected to the first transparent conductive layer and a second electrode connected to the second transparent conductive layer. Among them, the first transparent conductive layer includes a first zinc oxide layer, a first indium tin oxide layer and a first titanium oxide layer stacked in sequence. By setting the transparent conductive layer as a composite layer structure of three materials, the use of expensive indium tin oxide can be significantly reduced. ZnO is a direct bandgap semiconductor with a bandgap width of about 3.37eV at room temperature. Its optical properties are closely related to the bandgap width. The ZnO film only absorbs ultraviolet light at 368nm, but has high transmittance to visible light with a wavelength greater than 368nm, and has extremely high transmittance in the visible light range. Moreover, under ultraviolet light irradiation, the transmittance of the ZnO film in the visible light range is basically unchanged. The ZnO film has excellent radiation resistance and can reduce the power attenuation (Ultraviolet Induced Degradation, UVID) of the battery due to ultraviolet light. The TiO2 film has the characteristics of simple preparation, wide bandgap and low cost. It is a semiconductor material with a large bandgap width. The anatase phase TiO2 bandgap is about 3.2eV and has a high carrier mobility. The first transparent conductive layer in the embodiment of the present application adopts a ZnO / ITO / TiO2 laminated structure, which has better performance and can reduce the dependence on ITO materials while ensuring the efficiency of the battery, thereby reducing the material cost of the transparent conductive layer. It can also alleviate the problem of ultraviolet induced attenuation of heterojunction batteries and improve the performance stability and service life of the battery.

[0021] The photovoltaic module provided in the embodiment of the present application includes the above-mentioned heterojunction battery, and therefore also has the above-mentioned corresponding beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a schematic diagram of the structure of a heterojunction battery in one embodiment of the present application;

[0024] Figure 2 This is a schematic diagram of the structure of a heterojunction battery in another embodiment of the present application;

[0025] Figure 3 This is a schematic structural diagram of a heterojunction battery in another embodiment of the present application;

[0026] Figure 4 This is a flow chart of a method for manufacturing a heterojunction battery in one embodiment of the present application.

[0027] Icon: 100-n-type single crystal silicon layer; 110-first intrinsic amorphous silicon layer; 120-second intrinsic amorphous silicon layer; 200-n-type microcrystalline silicon layer; 300-first transparent conductive layer; 310-first zinc oxide layer; 320-first indium tin oxide layer; 330-first titanium oxide layer; 340-optical anti-reflection layer; 400-first electrode; 500-p-type microcrystalline silicon layer; 600-second transparent conductive layer; 610-second zinc oxide layer; 620-second indium tin oxide layer; 630-second titanium oxide layer; 700-second electrode. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0031] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the utility model product is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0033] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] The core of HJT cell lies in its heterojunction structure. It consists of a single crystal silicon substrate and an amorphous silicon film formed on both sides. At the interface between crystalline silicon and amorphous silicon, a special heterojunction is formed, which helps to optimize the light absorption and separation efficiency of carriers (electrons and holes). At the heterojunction interface, a thin layer of intrinsic amorphous silicon is usually inserted to passivate the surface of the cell, thereby reducing surface recombination and improving the conversion efficiency of the cell. Transparent conductive layers are provided on both sides of the HJT cell, which are used to collect photogenerated carriers and transport them to the metal electrode. Sunlight can reach the heterojunction structure through the transparent conductive layer, and the photons are absorbed by the silicon material to generate electron-hole pairs. At the heterojunction interface, due to the difference in energy band structure, electrons and holes are separated, electrons move to the n-type region, and holes move to the p-type region. The separated electrons and holes are collected on both sides of the cell, forming a potential difference. When the external circuit is closed, electrons flow from the n-type side of the cell to the p-type side through the external circuit, thereby forming a current. In heterojunction cells, both the optical and electrical properties of the transparent conductive layer are required to be high. In the related art, indium tin oxide (ITO) is used as the material of the transparent conductive layer. Indium tin oxide has good conductivity and light transmittance, but its material cost is relatively high. In addition, when solar cells are exposed to ultraviolet light, the physical and chemical properties of the materials will change. This change will cause the performance of the solar cells to decline, which is also known as ultraviolet induced degradation (UVID). Therefore, the heterojunction solar cells in the related art still have the problems of poor performance reliability and insufficient service life.

[0035] In order to improve at least one of the shortcomings of the above-mentioned related technologies, the embodiment of the present application provides a heterojunction battery, whose transparent conductive layer adopts a multi-layer composite structure to reduce the use of indium tin oxide, thereby reducing material costs. It can also effectively alleviate ultraviolet induced attenuation and improve the performance stability and service life of the battery.

[0036] Figure 1 This is a schematic diagram of the structure of a heterojunction battery in one embodiment of the present application. Figure 1 As shown, the heterojunction cell provided in the embodiment of the present application is specifically a silicon heterojunction cell, which includes a first transparent conductive layer 300, an n-type microcrystalline silicon layer 200, a first intrinsic amorphous silicon layer 110, an n-type single crystal silicon layer 100, a second intrinsic amorphous silicon layer 120, a p-type microcrystalline silicon layer 500 and a second transparent conductive layer 600 stacked in sequence. The heterojunction cell also includes a first electrode 400 connected to the first transparent conductive layer 300 and a second electrode 700 connected to the second transparent conductive layer 600. In this embodiment, the first transparent conductive layer 300 can be used as the front side of the heterojunction cell, and the second transparent conductive layer 600 can be used as the back side of the heterojunction cell.

[0037] Among them, the n-type single crystal silicon layer 100 not only serves as the basis for the generation of photogenerated carriers in the heterojunction cell, but also provides key support for the cell's high efficiency, high stability and good thermal performance through its excellent physical and chemical properties. As the main light-absorbing layer of the heterojunction cell, the n-type single crystal silicon layer 100 has a high purity and long-life minority carrier, which enables it to effectively absorb sunlight and generate electron-hole pairs. N-type silicon has a lower iron impurity content, which helps to reduce the density of recombination centers, thereby improving carrier lifetime and cell efficiency. The longer minority carrier lifetime of n-type silicon means that electrons and holes have more time to reach the electrode without being recombined, so the open circuit voltage and overall efficiency of the cell can be increased. The surface of the n-type single crystal silicon layer 100 can be passivated by depositing intrinsic amorphous silicon (ia-Si), such as the first intrinsic amorphous silicon layer 110 and the second intrinsic amorphous silicon layer 120 in the embodiment of the present application, thereby reducing surface recombination and further improving efficiency. Hydrogen atoms in amorphous silicon can passivate dangling bonds and reduce surface defects, thereby improving battery performance.

[0038] The temperature coefficient of n-type silicon is low, which means that the efficiency decreases less in high temperature environments, maintaining a higher energy output. Due to the high quality of the n-type single crystal silicon layer 100, the heterojunction cell can be designed as a double-sided cell, which can absorb light from both the front and back sides, thereby increasing the overall power output. The heterojunction structure formed by the n-type single crystal silicon layer 100 and other materials such as amorphous silicon or microcrystalline silicon has good compatibility, and this structure helps to improve the stability and durability of the cell.

[0039] In the embodiment of the present application, the first intrinsic amorphous silicon layer 110 and the second intrinsic amorphous silicon layer 120 are hydrogenated amorphous silicon, which can effectively passivate the dangling bonds on the surface of crystalline silicon and reduce the surface recombination centers, thereby improving the life of carriers and the open circuit voltage (Voc) of the battery. This is due to the presence of hydrogen atoms in the intrinsic amorphous silicon layer, which can terminate the dangling bonds of silicon atoms, reduce defects, and improve the transmission efficiency of charge carriers. The interface between the intrinsic amorphous silicon layer and the n-type single crystal silicon layer 100 forms a heterojunction, that is, an interface between different semiconductor materials. This heterojunction is conducive to improving the separation efficiency of photogenerated carriers, because the difference in energy band structure can promote the effective separation of electrons and holes. The intrinsic amorphous silicon layer has a certain anti-reflection effect, which can reduce the reflection of light at the interface, thereby increasing the amount of light entering the n-type single crystal silicon layer 100 and improving the light absorption efficiency. The intrinsic amorphous silicon layer also helps to improve the long-term stability and durability of the battery and reduce performance degradation; it also makes the heterojunction battery compatible with low-temperature processes, which is of great significance for improving production efficiency and reducing costs.

[0040] In the embodiment of the present application, the n-type microcrystalline silicon layer 200 is hydrogenated microcrystalline silicon (which can be expressed as μc-Si:H), and the grain size of microcrystalline silicon is smaller than the grains in polycrystalline silicon, but larger than the disordered region in amorphous silicon. Microcrystalline silicon generally has a wide spectral absorption range, can absorb short-wavelength light, supplement the insufficient absorption of single crystal silicon in certain wavelength ranges, and improve the total light absorption efficiency of the battery. In this embodiment, one of the main functions of the n-type microcrystalline silicon layer 200 is to serve as an electron injection layer. When sunlight irradiates the battery, the photogenerated electrons are pushed to the n-type microcrystalline silicon layer 200 under the action of the electric field of the pn junction, and then collected to the electrode through the layer (specifically, they are sequentially transported to the first electrode 400 through the n-type microcrystalline silicon layer 200 and the first transparent conductive layer 300). The n-type microcrystalline silicon layer 200 can be made using a low-temperature deposition process, which helps to reduce the thermal stress on the n-type single crystal silicon layer 100 and the first intrinsic amorphous silicon layer 110, avoid the degradation of material properties that may be caused by high-temperature processes, and also reduce production costs.

[0041] In this embodiment, the p-type microcrystalline silicon layer 500 is hydrogenated microcrystalline silicon. The p-type microcrystalline silicon layer 500 participates in the formation of the pn junction. When photons are absorbed and electron-hole pairs are generated, the built-in electric field of the pn junction will cause the electrons and holes to move in opposite directions and gather in the n-type and p-type regions, respectively, thereby generating current. Similar to the n-type microcrystalline silicon layer 200, due to the wide spectrum absorption characteristics of microcrystalline silicon, the p-type microcrystalline silicon layer 500 can enhance the absorption of short-wavelength light, supplement the insufficient absorption of n-type single crystal silicon in certain spectral ranges, and improve the overall light absorption efficiency of the battery. In addition, the p-type microcrystalline silicon layer 500 has the effect of selectively transmitting carriers. The p-type microcrystalline silicon layer 500 acts as an electron blocking layer, mainly allowing holes to pass through, while preventing the reverse flow of electrons, which helps to improve the fill factor of the battery. In addition, the deposition of the p-type microcrystalline silicon layer 500 can also be completed at a relatively low temperature, which reduces the thermal stress on the n-type single crystal silicon layer 100 and the second intrinsic amorphous silicon layer 120 and is beneficial to maintaining the crystal quality and electrical properties of the base material.

[0042] The materials of the first transparent conductive layer 300 and the second transparent conductive layer 600 are both transparent conductive oxides (Transparent Conductive Oxide, TCO). The transparent conductive layers have good conductivity and high transparency. This allows them to not block the incident sunlight, ensuring that the light can fully irradiate the interior of the battery, thereby generating photocurrent. The transparent conductive layer can collect the current generated by the photogenerated carriers (electrons and holes) and guide it to the external circuit through the electrodes, thereby achieving the output of electricity.

[0043] In the present embodiment, the first transparent conductive layer 300 includes a first zinc oxide layer 310, a first indium tin oxide layer 320, and a first titanium oxide layer 330 which are sequentially stacked. Further, in the present embodiment, the first titanium oxide layer 330 is located on a side of the first indium tin oxide layer 320 close to the n-type microcrystalline silicon layer 200 and is in direct contact with the n-type microcrystalline silicon layer 200, and the first zinc oxide layer 310 is located on a side of the first indium tin oxide layer 320 away from the n-type microcrystalline silicon layer 200 and is connected to the first electrode 400. In other optional embodiments, the relative positions of the first titanium oxide layer 330 and the first zinc oxide layer 310 can be reversed, that is, the first titanium oxide layer 330 is connected to the first electrode 400, and the first zinc oxide layer 310 is directly connected to the n-type microcrystalline silicon layer 200.

[0044] Zinc oxide is a direct bandgap semiconductor, and its bandgap width is about 3.37eV at room temperature. The optical properties of zinc oxide are closely related to the bandgap width. Only when the photons with energy greater than its optical bandgap irradiate the zinc oxide film, the electrons in the film will absorb the photons and transition from the valence band to the conduction band, resulting in strong light absorption. Therefore, the ZnO film only absorbs ultraviolet light with a wavelength below 368nm, and has a high transmittance to light with a wavelength greater than 368nm, that is, it has a very high transmittance in the visible light range, so that as much visible light as possible can enter the interior of the heterojunction battery, thereby improving the power generation efficiency. In addition, under ultraviolet light irradiation, the transmittance of the ZnO film in the visible light range does not change substantially, indicating that the ZnO film has excellent radiation resistance. In addition, since the first zinc oxide layer 310 can absorb ultraviolet light of a shorter wavelength and reduce the ultraviolet light entering the battery, the power attenuation (Ultraviolet InducedDegradation, UVID) of the battery due to ultraviolet light can be reduced.

[0045] Further, the material of the first zinc oxide layer 310 is one of nitrogen-doped zinc oxide, carbon-doped zinc oxide, aluminum-doped zinc oxide, sulfur-doped zinc oxide, selenium-doped zinc oxide, and tellurium-doped zinc oxide. By doping elements, the conductivity and stability of the first zinc oxide layer 310 can be improved. Even in a high conductivity state, the first zinc oxide layer 310 doped with the above elements can still maintain high transparency to visible light.

[0046] For example, in nitrogen-doped zinc oxide, nitrogen atoms replace oxygen atoms in the zinc oxide lattice to form donor energy levels, release free electrons, and thus increase the n-type conductivity of the material. The nitrogen-doped first transparent conductive layer 300 has good electrical and optical properties. In carbon-doped zinc oxide, carbon atoms can replace zinc or oxygen atoms in the zinc oxide lattice to form donor or acceptor defects, thereby changing its conductive properties. The carbon-doped first zinc oxide layer 310 can also improve conductivity while maintaining transparency. In aluminum-doped zinc oxide (AZO), the free electron concentration in the material is increased by aluminum doping, thereby significantly improving conductivity. This enables aluminum-doped zinc oxide to efficiently collect and transport photogenerated carriers. Aluminum-doped zinc oxide can be deposited by a variety of methods, such as magnetron sputtering, chemical vapor deposition (CVD), sol-gel method, etc., which makes it have good compatibility and processing flexibility in the manufacturing process. In addition, aluminum-doped zinc oxide also has hydrophobic or oleophobic properties, thereby reducing the adhesion of dust and dirt and keeping the first transparent conductive layer 300 clean and highly transparent.

[0047] The resistivity and transmittance of the first zinc oxide layer 310 doped with various materials are comparable to those of indium tin oxide, and the first zinc oxide layer 310 has lower cost and better stability.

[0048] The first titanium oxide layer 330 has the characteristics of simple preparation, wide bandgap and low cost. It is a semiconductor material with a large bandgap. The bandgap of anatase phase TiO2 is about 3.2eV, and it has a high carrier mobility. The first titanium oxide layer 330 has good chemical stability and weather resistance, and can be used as a protective layer or an enhancement layer to improve the overall performance and life of the first transparent conductive layer 300.

[0049] Furthermore, the first titanium oxide layer 330 may be nitrogen-doped titanium oxide, fluorine-doped titanium oxide or carbon-doped titanium oxide. By doping with nitrogen (N), fluorine (F), carbon (C) and the like, its conductivity may be significantly improved.

[0050] Indium tin oxide (ITO) has good electrical conductivity, which is due to the fact that the doping of tin provides additional free electrons, so that indium tin oxide can be used as a conductive layer to collect and transmit photogenerated carriers. Indium tin oxide has high transparency in the visible spectrum range, allowing visible light to enter the interior of the battery. Indium tin oxide can also provide a surface passivation effect and improve the photoelectric conversion efficiency of the device. In addition, indium tin oxide can also reduce the contact resistance between the metal electrode and the semiconductor material, which helps to smoothly transmit the current. Therefore, the first indium tin oxide layer 320 in the first transparent conductive layer 300 ensures the optical and electrical properties of the first transparent conductive layer 300. Since the material cost of the first indium tin oxide layer 320 is higher than that of the first titanium oxide layer 330 and the first zinc oxide layer 310, in this embodiment, only the middle layer of the first transparent conductive layer 300 is made of indium tin oxide, which can reduce the amount of indium tin oxide used and reduce the material cost of the first transparent conductive layer 300. Using the ZnO / ITO / TiO2 composite film as the first transparent conductive layer 300 can not only reduce the cost, but also help to form a gradient refraction with a high refractive index of the bottom layer, thereby fully absorbing light.

[0051] In this embodiment, the thickness of the first indium tin oxide layer 320 is not greater than the thickness of the first zinc oxide layer 310, and is greater than the thickness of the first titanium oxide layer 330. Since the first indium tin oxide layer 320 is not easy to be too thick or too thin, too large a thickness will lead to higher costs, while too low a thickness may affect the performance of the first transparent conductive layer 300. If the thickness ratio of the first titanium oxide layer 330 is too large, the conductive performance of the first transparent conductive layer 300 may be affected, so the thickness of the controller needs to be less than the thickness of the first indium tin oxide layer 320.

[0052] Optionally, the thickness of the first zinc oxide layer 310 is 20 to 70 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, or a value between any two of the above values. The thickness of the first indium tin oxide layer 320 is 20 to 40 nm, such as 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, or a value between any two of the above values. The thickness of the first titanium oxide layer 330 is 5 to 15 nm, such as 5 nm, 7 nm, 9 nm, 11 nm, 13 nm, 15 nm, or a value between any two of the above values.

[0053] Furthermore, the thickness of the first intrinsic amorphous silicon layer 110 and the second intrinsic amorphous silicon layer 120 are both 1 to 10 nm, for example, 5 nm; the thickness of the n-type microcrystalline silicon layer 200 and the p-type microcrystalline silicon layer 500 are both 10 to 30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm or a value between any two of the above points.

[0054] In this embodiment, the side of the n-type single crystal silicon layer 100 connected to the first intrinsic amorphous silicon layer 110 is a velvet surface, and the side of the n-type single crystal silicon layer 100 connected to the second intrinsic amorphous silicon layer 120 is also a velvet surface. The velvet surface can be formed by a velveting process. The velvet surface is a rough surface (such as a pyramid structure), and the velvet surface can significantly reduce the mirror reflection of the surface of the n-type single crystal silicon layer 100, so that more incident light can enter its interior, thereby improving the light absorption rate. The velvet surface can also increase the optical path length, that is, even if the incident light is reflected and refracted multiple times, the propagation path of the light inside the single crystal silicon is extended, and the opportunity for the interaction between the photons and the silicon material is increased, thereby increasing the probability of the generation of photogenerated carriers. The velvet process can also eliminate surface damage, help reduce surface recombination centers, and increase the life of carriers and the open circuit voltage of the battery. The texture surface can improve surface passivation. The microstructure of the texture surface helps the first intrinsic amorphous silicon layer 110 and the second intrinsic amorphous silicon layer 120 to better cover the surface of the n-type single crystal silicon layer 100, provide more effective surface passivation, and reduce surface recombination.

[0055] In the embodiment of the present application, the coverage area of ​​the first electrode 400 accounts for 1% to 5% of the area of ​​the first transparent conductive layer 300. By controlling the coverage area of ​​the first electrode 400 to be within a relatively low range, as much light as possible can be allowed to enter the heterojunction battery. Similarly, the coverage area of ​​the second electrode 700 can also be controlled, for example, the coverage area of ​​the second electrode 700 accounts for 1% to 5% of the area of ​​the second transparent conductive layer 600.

[0056] Figure 2 This is a schematic diagram of the structure of a heterojunction battery in another embodiment of the present application. Figure 2As shown, in this embodiment, the structure of the second transparent conductive layer 600 can be selected to be the same as the structure of the first transparent conductive layer 300, that is, the second transparent conductive layer 600 includes a second zinc oxide layer 610, a second indium tin oxide layer 620 and a second titanium oxide layer 630 stacked in sequence. Among them, the second titanium oxide layer 630 is located on the side of the second indium tin oxide layer 620 close to the p-type microcrystalline silicon layer 500 and contacts the second intrinsic amorphous silicon layer 120; the second zinc oxide layer 610 is located on the side of the second indium tin oxide layer 620 away from the p-type microcrystalline silicon layer 500 and connected to the second electrode 700. The second transparent conductive layer 600 is also set to a ZnO / ITO / TiO2 composite thin film structure, which can also reduce the material and alleviate the problem of ultraviolet light attenuation while ensuring that the conductive and light-transmitting functions are not affected. Its specific mechanism can refer to the introduction of the first transparent conductive layer 300, which will not be repeated here.

[0057] In this embodiment, the first transparent conductive layer 300 and the second transparent conductive layer 600 may be symmetrical structures to each other.

[0058] In this embodiment, the first electrode 400 and the second electrode 700 are made of metal, such as silver, copper, aluminum, nickel, and molybdenum. The first electrode 400 and the second electrode 700 may also be made of other non-metallic materials, such as graphene, carbon nanotubes, etc.

[0059] Figure 3 This is a schematic diagram of the structure of a heterojunction battery in another embodiment of the present application. Figure 3 As shown, the heterojunction battery of this embodiment is Figure 1 The difference between the heterojunction cell in the embodiment is that an optical anti-reflection layer 340 is laid on the area of ​​the first transparent conductive layer 300 that is away from the n-type microcrystalline silicon layer 200 and is not covered by the first electrode 400. The optical anti-reflection layer 340 can reduce the reflection of sunlight on the surface of the cell, thereby improving the light absorption efficiency of the cell, and further improving the overall photoelectric conversion efficiency. In addition, the optical anti-reflection layer 340 also has a certain physical and chemical stability, which can protect the surface of the heterojunction cell from erosion by the external environment and improve the long-term stability and reliability of the cell.

[0060] Optionally, the material of the optical anti-reflection layer 340 is one of zinc sulfide, magnesium fluoride, aluminum oxide, titanium oxide and silicon oxide.

[0061] In other embodiments, an optical anti-reflection layer 340 may also be disposed outside the second transparent conductive layer 600 .

[0062] Figure 4 Flow chart of a method for manufacturing a heterojunction battery in one embodiment of the present application. Figure 4 As shown, the heterojunction battery provided in the embodiment of the present application can be manufactured by the following steps:

[0063] Step S100 , obtaining an n-type single crystal silicon layer 100 , and cleaning and texturing the n-type single crystal silicon layer 100 .

[0064] Through the texturing process, a textured surface can be formed on the surface of the n-type single crystal silicon layer 100 to be combined with the first intrinsic amorphous silicon layer 110 and the second intrinsic amorphous silicon layer 120 .

[0065] In step S200 , a first intrinsic amorphous silicon layer 110 and an n-type microcrystalline silicon layer 200 are deposited on one side of the n-type single crystal silicon layer 100 , and a second intrinsic amorphous silicon layer 120 and a p-type microcrystalline silicon layer 500 are deposited on the other side.

[0066] In a specific embodiment, the second intrinsic amorphous silicon layer 120 may be deposited first, and then the first intrinsic amorphous silicon layer 110 may be deposited; then the n-type microcrystalline silicon layer 200 may be deposited on the first intrinsic amorphous silicon layer 110, and then the p-type microcrystalline silicon layer 500 may be deposited on the second intrinsic amorphous silicon layer 120. In other embodiments, the above steps may also be adaptively adjusted.

[0067] In step S300 , a first transparent conductive layer 300 is deposited on the n-type microcrystalline silicon layer 200 , and a second transparent conductive layer 600 is deposited on the p-type microcrystalline silicon layer 500 .

[0068] In this embodiment, the first transparent conductive layer 300 and the second transparent conductive layer 600 can be deposited by atomic layer deposition (ALD), chemical vapor deposition (CVD) or physical vapor deposition (PVD). The specific principle can refer to the existing related technology and will not be repeated here.

[0069] In step S400 , a first electrode 400 and a second electrode 700 are formed on the first transparent conductive layer 300 and the second transparent conductive layer 600 , respectively.

[0070] In this embodiment, the first electrode 400 and the second electrode 700 with specific patterns may be formed by screen printing technology or electroplating technology.

[0071] The embodiment of the present application also provides a photovoltaic module (not shown in the figure), including the above-mentioned heterojunction battery.

[0072] In summary, the heterojunction battery provided in the embodiment of the present application includes a first transparent conductive layer 300, an n-type microcrystalline silicon layer 200, a first intrinsic amorphous silicon layer 110, an n-type single crystal silicon layer 100, a second intrinsic amorphous silicon layer 120, a p-type microcrystalline silicon layer 500 and a second transparent conductive layer 600 stacked in sequence. The heterojunction battery also includes a first electrode 400 connected to the first transparent conductive layer 300 and a second electrode 700 connected to the second transparent conductive layer 600. Among them, the first transparent conductive layer 300 includes a first zinc oxide layer 310, a first indium tin oxide layer 320 and a first titanium oxide layer 330 stacked in sequence. By setting the transparent conductive layer as a composite layer structure of three materials, the use of expensive indium tin oxide can be significantly reduced. ZnO belongs to direct bandgap semiconductor, and the bandgap width is about 3.37eV at room temperature. Its optical properties are closely related to the bandgap width. ZnO film only absorbs ultraviolet light under 368nm, and has high transmittance to visible light with a wavelength greater than 368nm, and has extremely high transmittance in the visible light range. Moreover, under ultraviolet light irradiation, the transmittance of ZnO film in the visible light range does not change substantially. ZnO film has excellent radiation resistance, which can reduce the power attenuation (UVID) of the battery due to ultraviolet light. TiO2 film has the characteristics of simple preparation method, wide bandgap and low cost. It is a semiconductor material with a large bandgap width. The bandgap of rutile phase TiO2 is about 3.2eV, and it has a high carrier mobility. The first transparent conductive layer 300 in the embodiment of the present application adopts ZnO / ITO / TiO2 laminated structure, which has better performance and can reduce the dependence on ITO material while ensuring the efficiency of the battery, thereby reducing the material cost of the transparent conductive layer. It can also alleviate the problem of ultraviolet-induced degradation of heterojunction batteries and improve the performance stability and service life of the batteries.

[0073] The photovoltaic module provided in the embodiment of the present application includes the above-mentioned heterojunction battery, and therefore also has the above-mentioned corresponding beneficial effects.

[0074] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A heterojunction battery, characterized in that: The heterojunction battery comprises a first transparent conductive layer (300), an n-type microcrystalline silicon layer (200), a first intrinsic amorphous silicon layer (110), an n-type single crystal silicon layer (100), a second intrinsic amorphous silicon layer (120), a p-type microcrystalline silicon layer (500) and a second transparent conductive layer (600) which are stacked in sequence, and the heterojunction battery further comprises a first electrode (400) connected to the first transparent conductive layer (300) and a second electrode (700) connected to the second transparent conductive layer (600); The first transparent conductive layer (300) comprises a first zinc oxide layer (310), a first indium tin oxide layer (320) and a first titanium oxide layer (330) which are stacked in sequence.

2. The heterojunction battery according to claim 1, characterized in that: The first titanium oxide layer (330) is located on a side of the first indium tin oxide layer (320) close to the n-type microcrystalline silicon layer (200), and the first zinc oxide layer (310) is located on a side of the first indium tin oxide layer (320) away from the n-type microcrystalline silicon layer (200) and connected to the first electrode (400).

3. The heterojunction battery according to claim 1, characterized in that: The thickness of the first indium tin oxide layer (320) is not greater than the thickness of the first zinc oxide layer (310), and is greater than the thickness of the first titanium oxide layer (330).

4. The heterojunction battery according to claim 3, characterized in that: The thickness of the first zinc oxide layer (310) is 20-70 nm, the thickness of the first indium tin oxide layer (320) is 20-40 nm, and the thickness of the first titanium oxide layer (330) is 5-15 nm.

5. The heterojunction battery according to claim 1, characterized in that: The material of the first zinc oxide layer (310) is one of nitrogen-doped zinc oxide, carbon-doped zinc oxide, aluminum-doped zinc oxide, sulfur-doped zinc oxide, selenium-doped zinc oxide, and tellurium-doped zinc oxide.

6. The heterojunction battery according to claim 1, characterized in that: The side of the n-type single crystal silicon layer (100) connected to the first intrinsic amorphous silicon layer (110) is a velvet surface, and the side of the n-type single crystal silicon layer (100) connected to the second intrinsic amorphous silicon layer (120) is a velvet surface.

7. The heterojunction battery according to claim 1, characterized in that: The second transparent conductive layer (600) comprises a second zinc oxide layer (610), a second indium tin oxide layer (620) and a second titanium oxide layer (630) which are stacked in sequence.

8. The heterojunction battery according to any one of claims 1 to 7, characterized in that: An optical anti-reflection layer (340) is provided in a region of the first transparent conductive layer (300) that is away from the n-type microcrystalline silicon layer (200) and is not covered by the first electrode (400).

9. The heterojunction battery according to claim 8, characterized in that: The material of the optical anti-reflection layer (340) is one of zinc sulfide, magnesium fluoride, aluminum oxide, titanium oxide and silicon oxide.

10. The heterojunction battery according to any one of claims 1 to 7, characterized in that: The thickness of the first intrinsic amorphous silicon layer (110) and the second intrinsic amorphous silicon layer (120) are both 1 to 10 nm, and the thickness of the n-type microcrystalline silicon layer (200) and the p-type microcrystalline silicon layer (500) are both 10 to 30 nm.

11. The heterojunction battery according to any one of claims 1 to 7, characterized in that: The coverage area of ​​the first electrode (400) accounts for 1% to 5% of the area of ​​the first transparent conductive layer (300).

12. A photovoltaic module, characterized in that: A heterojunction battery comprising the method according to any one of claims 1 to 11.

Images