Photovoltaic cell and photovoltaic cell assembly

Abstract

The utility model provides a photovoltaic cell and a photovoltaic cell assembly, relates to the field of photovoltaic technology, and aims to solve the technical problem that a photovoltaic cell is poor in spectral responsiveness to a long wave band. The photovoltaic cell comprises a substrate, a main grid, a dielectric layer, a metal layer and a first passivation layer stacked on the substrate, and the dielectric layer is stacked on the side, away from the substrate, of the passivation layer and located on other areas, except the main grid, of the first passivation layer; the metal layer is stacked on the side, away from the first passivation layer, of the dielectric layer and is separated from the main grid, and the metal layer and the first passivation layer are electrically separated through the dielectric layer. According to the photovoltaic cell, the responsiveness of a long-wave-band spectrum is improved, the short-circuit current density is improved, and the photoelectric conversion efficiency is further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaics, in particular to a photovoltaic cell and a photovoltaic cell assembly. Background Art

[0002] The statements in this section merely provide background technology related to the present invention and do not necessarily constitute prior art.

[0003] Among the Tunnel Oxide Passivated Contact (TOPCon) photovoltaic cells, N-type TOPCon photovoltaic cells have the characteristics of high power generation and strong stability due to their high minority carrier lifetime and low photo-induced attenuation. Although TOPCon photovoltaic cells have excellent passivation effect and obtain good open circuit voltage by using back tunneling oxide passivation contact, the absorption coefficient of crystalline silicon in the 900nm~1200nm band is low, and in order to reduce costs, the thickness of silicon wafers is continuously reduced. Thinner silicon wafers will cause a large amount of infrared light escape loss, which limits the improvement of the short-circuit current density Jsc of TOPCon photovoltaic cells, and also restricts the improvement of photoelectric conversion efficiency. Utility Model Content

[0004] The utility model aims to provide a photovoltaic cell and a photovoltaic cell assembly to solve the technical problem that the photovoltaic cell has poor spectral responsiveness to a long-wave band.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] In a first aspect, the utility model provides a photovoltaic cell, comprising a substrate, a main grid, a dielectric layer, a metal layer, and a first passivation layer stacked on the substrate.

[0007] The dielectric layer is stacked on a side of the first passivation layer facing away from the substrate, and is located on other regions of the first passivation layer except the main gate;

[0008] The metal layer is stacked on a side of the dielectric layer away from the first passivation layer and is spaced apart from the main gate.

[0009] The metal layer and the first passivation layer are electrically isolated from each other by the dielectric layer.

[0010] According to at least one embodiment of the present utility model, the dielectric layer is spaced apart from the main gate.

[0011] According to at least one embodiment of the present utility model, there is a first distance between the dielectric layer and the main grid, and there is a second distance between the metal layer and the main grid, and the second distance is equal to or greater than the first distance.

[0012] According to at least one embodiment of the present utility model, the material of the dielectric layer includes at least one of silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride; and / or,

[0013] the material of the metal layer includes at least one of gold, silver, aluminum, or copper.

[0014] According to at least one embodiment of the present utility model, the thickness of the dielectric layer ranges from 1 nm to 300 nm; and / or,

[0015] the thickness of the metal layer ranges from 200 nm to 1000 nm.

[0016] According to at least one embodiment of the present utility model, the substrate includes a silicon substrate or a germanium substrate.

[0017] According to at least one embodiment of the present utility model, the photovoltaic cell includes one of a tunnel oxide passivated contact photovoltaic cell and an interdigitated back contact photovoltaic cell.

[0018] According to at least one embodiment of the present utility model, the photovoltaic cell further includes a tunnel oxide layer and a doped polysilicon layer, the tunnel oxide layer and the doped polysilicon layer are stacked between the substrate and the first passivation layer, and the tunnel oxide layer and the doped polysilicon layer are arranged in a direction away from the substrate.

[0019] According to at least one embodiment of the present utility model, the photovoltaic cell further includes a diffusion layer, a second passivation layer, and a passivation and antireflection layer, the diffusion layer, the second passivation layer, and the passivation and antireflection layer are sequentially stacked on a side of the substrate facing away from the first passivation layer, and the diffusion layer, the second passivation layer, and the passivation and antireflection layer are arranged in a direction away from the substrate.

[0020] According to at least one embodiment of the present utility model, the doped polysilicon layer is a phosphorus-doped polysilicon layer, and the diffusion layer is a boron-doped diffusion layer.

[0021] In a second aspect, the present utility model further provides a method for manufacturing a photovoltaic cell, including:

[0022] providing a substrate stacked with a first passivation layer;

[0023] stacking a dielectric layer on a side of the first passivation layer facing away from the substrate, and the dielectric layer is located on other regions of the first passivation layer except for the main grid;

[0024] stacking a metal layer on a side of the dielectric layer facing away from the first passivation layer, and spacing the metal layer apart from the main grid;

[0025] Wherein, the metal layer and the first passivation layer are electrically isolated from each other by the dielectric layer.

[0026] According to at least one embodiment of the present invention, in the step of stacking a dielectric layer on a side of the first passivation layer facing away from the substrate, and the dielectric layer is located on other regions of the first passivation layer except for the main gate, it includes:

[0027] Cover a first mask plate on the side of the first passivation layer facing away from the substrate and shield the main gate, wherein the width of a first shielding strip of the first mask plate for shielding the main gate is greater than or equal to the width of the corresponding main gate;

[0028] Evaporate and deposit a dielectric material to form the dielectric layer on the first passivation layer.

[0029] According to at least one embodiment of the present invention, when the width of the first shielding strip is greater than the width of the corresponding main gate, evaporate and deposit a dielectric material to form the dielectric layer on the first passivation layer, wherein the dielectric layer is spaced apart from the main gate.

[0030] According to at least one embodiment of the present invention, in the step of stacking a metal layer on a side of the dielectric layer facing away from the first passivation layer, and spacing the metal layer apart from the main gate, it includes:

[0031] Cover a second mask plate on the side of the dielectric layer facing away from the first passivation layer and shield the main gate, wherein the width of a second shielding strip of the second mask plate for shielding the main gate is greater than or equal to the width of the first shielding strip of the first mask plate;

[0032] Evaporate and deposit a metal material to form the metal layer on the dielectric layer.

[0033] According to at least one embodiment of the present invention, in the step of stacking a dielectric layer on a side of the first passivation layer facing away from the substrate, and the dielectric layer is located on other regions of the first passivation layer except for the main gate, it includes:

[0034] In a vacuum environment, the deposition rate of depositing the dielectric layer is and / or,

[0035] The material of the dielectric layer includes at least one of silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride.

[0036] According to at least one embodiment of the present invention, in the step of stacking a metal layer on a side of the dielectric layer facing away from the first passivation layer, and spacing the metal layer apart from the main gate, it includes:

[0037] In a vacuum environment, the deposition rate of depositing the metal layer to a first preset thickness is 0.05 The deposition rate of depositing the metal layer from the first preset thickness to a second preset thickness is The deposition rate of depositing the metal layer from the second preset thickness to a third preset thickness is The deposition rate of depositing the metal layer from the third preset thickness to a fourth preset thickness is wherein, the first preset thickness, the second preset thickness, the third preset thickness, and the fourth preset thickness increase in sequence; and / or,

[0038] The material of the metal layer includes at least one of gold, silver, aluminum, or copper.

[0039] In a third aspect, the present utility model further provides a photovoltaic cell module, including a plurality of electrically connected photovoltaic cells, at least one of the photovoltaic cells being the photovoltaic cell according to the first aspect, or,

[0040] At least one of the photovoltaic cells is a photovoltaic cell prepared by the preparation method according to the second aspect.

[0041] In one or more technical solutions provided by the exemplary embodiments of the present utility model, at least one of the following beneficial effects can be achieved.

[0042] The photovoltaic cell of the exemplary embodiment of the present utility model forms an anti-reflection structure by stacking a dielectric layer and a metal layer on a passivation layer, so that the spectral response of the photovoltaic cell to the long wavelength band is significantly increased, and the escape loss of incident light is reduced, thereby obtaining a higher photoelectric conversion efficiency. By electrically isolating the metal layer from the passivation layer through the dielectric layer, it is possible to avoid carrier recombination caused by the direct contact between the fine grid on the passivation layer and the metal layer, so that the metal layer can enhance the optical absorption of the photovoltaic cell. At the same time, the applicant found that the carrier mobility of the metal layer is lower than that of the main grid, and the direct contact between the two will also cause carrier recombination at the contact position, thereby reducing the fill factor of the photovoltaic cell. Therefore, separating the metal layer from the main grid, and electrically isolating the metal layer from the fine grid through the dielectric layer can, while ensuring that the fill factor of the photovoltaic cell remains unchanged, utilize the anti-reflection structure formed by the dielectric layer and the metal layer to improve the responsiveness of the photovoltaic cell to the long wavelength band spectrum, increase the short-circuit current density, and thus improve the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings illustrate the exemplary embodiments of the present utility model and are used together with the description to explain the principle of the present utility model, including these drawings to provide a further understanding of the present utility model, and the drawings are included in this specification and form a part of this specification;

[0044] Figure 1It is a schematic cross-sectional structure diagram of a TOPCon photovoltaic cell according to an embodiment of the present invention;

[0045] Figure 2 It is a schematic top view structure diagram of a first mask plate according to an embodiment of the present invention;

[0046] Figure 3 It is a test curve of the internal quantum efficiency and reflectivity before and after the TOPCon photovoltaic cell stacking back-reflection structure according to an embodiment of the present invention;

[0047] Figure 4 It is a test curve of the external quantum efficiency before and after the TOPCon photovoltaic cell stacking back-reflection structure according to an embodiment of the present invention;

[0048] Figure 5 It is a schematic flow chart of a method for manufacturing a photovoltaic cell according to an embodiment of the present invention.

[0049] Reference numerals: 10, substrate; 21, tunneling oxide layer; 22, doped polysilicon layer; 23, first passivation layer; 24, dielectric layer; 25, metal layer; 26, main grid; 31, diffusion layer; 32, second passivation layer; 33, passivation and antireflection layer; 34, gate; 40, first mask plate; 41, first shielding strip. Detailed Embodiments

[0050] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] Before introducing the embodiments of the present invention, the following are the definitions of relevant terms involved in the embodiments of the present invention:

[0052] The main grid, also known as the busbar, is a relatively wide metal conduction path that is responsible for collecting the current conducted from the fine grid lines and leading it out to the external circuit. The busbar is usually made of silver, aluminum or other highly conductive materials to ensure low resistance loss and high efficiency. The busbar generally spans the entire photovoltaic cell, usually having 2 to 5 or more, arranged in parallel. They need to be wide enough to reduce resistance, but not too wide, otherwise they will block too much light and reduce the light absorption efficiency of the photovoltaic cell.

[0053] The fine grid, also known as the finger, is a relatively narrow conductive path that is responsible for collecting charge carriers (electrons and holes) from the surface of a photovoltaic cell and conducting them to the main grid line. The finger is usually made of a highly conductive material such as silver paste. The finger forms a grid-like structure on the cell surface, covering most of the cell surface area. The finger needs to be fine enough to maximize light absorption while ensuring that the resistance is not too high. The density and layout of the finger need to be optimized to capture and conduct as many charges as possible without significantly increasing the resistance.

[0054] Plasmon is a quantum excitation that exists on the surface of a metal and is the result of the interaction between electrons and the electromagnetic field. When light shines on the metal surface, the free electrons in the metal will vibrate under the action of the electric field, thus forming plasmons. Plasmons have many special properties, including surface-enhanced Raman scattering, local field enhancement, surface-enhanced fluorescence, etc.

[0055] Carriers refer to the charged particles that participate in current transmission in semiconductor materials and can be electrons or holes. In a semiconductor, electrons are the main carriers, and they conduct current by moving in the lattice. When electrons obtain energy from atoms and transition to the conduction band, they become free carriers and can move and conduct electricity in the material. On the other hand, holes are positively charged carriers that are left behind due to the transition of electrons in the valence band. The movement of carriers is the basis for the operation of semiconductor devices, including transistors, diodes, etc.

[0056] The fill factor (FF) in photovoltaic cells and other optoelectronic devices can be used to measure the impact of the internal resistance and electron loss of optoelectronic devices on their performance. The fill factor is a characteristic of the current-voltage (I-V) curve. The fill factor represents the ratio of the maximum output power ImVm to the limiting output power IscVoc, that is: FF = ImVm / IscVoc.

[0057] The value range of the fill factor is between 0 and 1, and the closer it is to 1, the better the performance of the optoelectronic device. The fill factor is mainly determined by the series resistance, shunt resistance, and PN junction characteristics. When the series resistance increases, the shunt resistance decreases, and there are defects and impurities in the PN junction and other adverse conditions, the FF will become smaller. In addition, the fill factor increases with the increase of the bandgap width of the cell material.

[0058] The short-circuit current density (Jsc) refers to the current density generated per unit area of a photovoltaic cell in the short-circuit state. In the short-circuit state, the two electrodes of the photovoltaic cell are directly connected together without an external load, and its numerical value is shown as the vertical axis intercept in the schematic diagram of the J-V curve, and the unit is mA / cm2 Jsc is mainly affected by the intensity of incident light and the size of the material absorption bandgap. The smaller the bandgap, the stronger the ability to convert photons into electrical energy. In addition, device thickness, the quality of each thin film layer, and the carrier transport ability will all affect the magnitude of Jsc.

[0059] Open Circuit Voltage (Voc) refers to the voltage difference between two electrodes when a photovoltaic cell is not connected to any load. The specific value of the open circuit voltage is represented as the intercept length on the horizontal number axis in the schematic diagram of the J-V curve, and its unit is generally mV or V.

[0060] External Quantum Efficiency (EQE) refers to the efficiency of a optoelectronic device (such as a photovoltaic cell or a photodiode) to generate current under external light irradiation. It is one of the important indicators to measure the performance of a device, usually expressed as a percentage. Specifically, the external quantum efficiency represents the ratio of the number of electron-hole pairs generated in the device by measuring photons of unit energy to the number of incident photons.

[0061] Internal Quantum Efficiency (IQE) refers to the efficiency of photons being absorbed and converted into electron-hole pairs in an optoelectronic device (such as an LED, a photovoltaic cell, etc.). It measures the generation efficiency of electron-hole pairs in a device. For a photovoltaic cell, the internal quantum efficiency represents the efficiency of photon energy being converted into electron energy. A high internal quantum efficiency means that the photovoltaic cell can convert sunlight into electrical energy more effectively.

[0062] In related technologies, TOPCon photovoltaic cells utilize back surface tunneling oxide passivation contacts with excellent passivation effects and obtain good open circuit voltages. However, the continuously thinning silicon wafer thickness will cause a large amount of infrared light escape loss, restricting the improvement of the short-circuit current density Jsc of TOPCon photovoltaic cells. Depositing metal nanoparticles alone on a TOPCon photovoltaic cell printed with grid lines (including fine grids and main grids) to construct a back surface anti-reflection structure can improve the infrared spectral response of the photovoltaic cell.

[0063] However, directly depositing the metal back surface anti-reflection structure on the grid lines as described above will cause the metal to be in direct contact with the fine grid, resulting in carrier recombination and reducing the fill factor of the photovoltaic cell. The applicant found that when the metal back surface anti-reflection structure is in direct contact with the main grid, the conductivity of the metal back surface anti-reflection structure is less than that of the main grid, which will also cause the conductivity of the main grid to decrease, and further reduce the fill factor of the photovoltaic cell.

[0064] In view of the above problems, the photovoltaic cell provided by the exemplary embodiment of the present utility model forms an anti-reflection structure by stacking a metal layer on a dielectric layer by depositing metal nanoparticles. Under the driving of a light field with a specific frequency, the free electrons on the surface of the metal nanoparticles interact with photons to form localized surface plasmon resonance. The resonance energy can significantly enhance the local field on the surface of the metal nanoparticles, thereby generating multi-angle scattering of the incident light, effectively extending the optical path of light in the absorption medium, especially the spectral response in the long wavelength band can be improved. Further, the metal layer is electrically isolated from the fine grid through the dielectric layer, and at the same time, the metal layer is spaced apart from the main grid located in the back field, so that the metal layer in the anti-reflection structure avoids direct contact with both the fine grid and the main grid. Without changing the fill factor, the reflectivity of the photovoltaic cell in the long wavelength band can be significantly improved, which is beneficial to reducing the escape loss of light in this long wavelength band and improving the spectral response of the photovoltaic cell to the long wavelength band.

[0065] The following will take the TOPCon photovoltaic cell as an example for illustration, and it should not be understood that the structure of the present utility model can only be a TOPCon photovoltaic cell. For example, it can also be an Interdigitated BackContact (IBC) photovoltaic cell, etc.

[0066] Figure 1 is a schematic cross-sectional structure diagram of a TOPCon photovoltaic cell according to an embodiment of the present utility model. As Figure 1 shown, the TOPCon photovoltaic cell provided by the exemplary embodiment of the present utility model includes a substrate 10. On the light-receiving surface of the substrate 10, that is, the front surface of the photovoltaic cell, a diffusion layer 31, a second passivation layer 32, and a passivation and anti-reflection layer 33 are sequentially included along the direction away from the substrate 10. Grid lines are also printed on the front surface of the TOPCon photovoltaic cell, including a front main grid (grid electrode 34) and front fine grid lines (not shown in the figure). In the back field of the substrate 10, that is, on the back surface of the photovoltaic cell, a tunneling oxide layer 21, a doped polysilicon layer 22, and a first passivation layer 23 are sequentially included along the direction away from the substrate 10. Grid lines are also printed on the back field of the photovoltaic cell, including a main grid 26 in the back field and a fine grid in the back field (not shown in the figure). It should be noted that Figure 1 the cross-section of the TOPCon photovoltaic cell shown is a cross-section perpendicular to the extending direction of the main grid 26.

[0067] Exemplarily, the diffusion layer 31 can be a boron-doped diffusion layer, and the second passivation layer 32 can be formed by at least one of aluminum oxide, silicon oxide, gallium oxide, silicon nitride, aluminum nitride, silicon oxynitride, and aluminum oxynitride; the doped polysilicon layer 22 can be a phosphorus-doped polysilicon layer.

[0068] For the convenience of description, unless otherwise specified, the main grid mentioned hereinafter refers to the main grid 26 in the back field, and the fine grid refers to the fine grid in the back field.

[0069] As Figure 1 shown, the TOPCon photovoltaic cell of the exemplary embodiment of the present utility model further includes a back-reflection structure formed by a dielectric layer 24 and a metal layer 25 in the back field. The dielectric layer 24 is stacked on the side of the first passivation layer 23 away from the substrate 10 and is located on other regions of the first passivation layer 23 except for the main grid 26. The metal layer 25 is stacked on the side of the dielectric layer 24 away from the first passivation layer 23 and is spaced apart from the main grid 26. That is, the dielectric layer 24 completely electrically isolates the fine grid on the first passivation layer 23 from the metal layer 25, so as to prevent the direct contact between the metal layer 25 and the fine grid from causing the loss of carrier collection. At the same time, the metal layer 25 is also spaced apart from the main grid 26, that is, there is no direct contact between the metal layer 25 and the main grid 26, avoiding the problem of reduced conductivity of the main grid caused by the lower conductivity of the metal layer 25 than that of the main grid 26, and ensuring that the fill factor of the photovoltaic cell will not decrease. Based on this, the back-reflection structure of the photovoltaic cell of the exemplary embodiment of the present utility model can effectively improve the optical absorption of the TOPCon photovoltaic cell while ensuring that the fill factor remains unchanged, especially the spectral response in the long wavelength band is significantly improved, thereby effectively increasing the short-circuit current density and the photoelectric conversion efficiency of the TOPCon photovoltaic cell.

[0070] In some embodiments, as Figure 1 shown, the dielectric layer 24 is spaced apart from the main grid 26, that is, there are certain spacings on both sides in the width direction of the dielectric layer 24 and the main grid 26 respectively. When the dielectric layer 24 is in direct contact with the main grid 26, it will also affect the conductivity of the main grid 26 and thus lead to a decrease in the fill factor. Based on this, when the dielectric layer 24 is spaced apart from the main grid 26, the above-mentioned adverse effects caused by their direct contact can be avoided.

[0071] Example 1. The preparation of an N-type TOPCon photovoltaic cell includes:

[0072] S1. Texturing and boron diffusion are performed on the front surface of the N-type monocrystalline silicon wafer to obtain a diffusion layer 31;

[0073] S2. A tunneling oxide layer 21 made of silicon oxide with a thickness of 0.5 nm to 3 nm and a doped polysilicon layer 22 with a thickness of 50 nm to 150 nm are sequentially deposited on the back surface of the N-type monocrystalline silicon wafer, and the doping element is phosphorus;

[0074] S3. A second passivation layer 32 and a passivation and antireflection layer 33 are deposited on the diffusion layer 31, and the second passivation layer 32 / passivation and antireflection layer 33 is an alumina / silicon nitride stacked structure; a first passivation layer 23 is deposited on the doped polysilicon layer 22, and the first passivation layer 23 is an alumina layer;

[0075] S4. Deposit an anti-reflection structure on the first passivation layer 23, where the dielectric layer 24 in the anti-reflection structure is made of MgF2 and the metal layer 25 is made of Ag;

[0076] S5. Print main grid and fine grid pastes on the front and back and sinter to form the metal electrodes on the front and the metal electrodes on the back. The metal electrodes on the back penetrate the first passivation layer 23 and contact the doped polysilicon layer 22, and the anti-reflection structure is spaced apart from the metal electrodes on the back to form a TOPCon photovoltaic cell.

[0077] Comparative example: The only difference between this comparative example and Example 1 is that the preparation of the TOPCon photovoltaic cell does not include step S4.

[0078] Figure 3 are the test curves of the internal quantum efficiency and reflectivity of the TOPCon photovoltaic cell before and after stacking the anti-reflection structure according to the embodiments of the present invention. As Figure 3 shown, the abscissa is the spectral wavelength (Wavelength), and the ordinate is the internal quantum efficiency (Internal Quantum Efficiency, IQE) and the reflectivity (R%). In Example 1, a TOPCon photovoltaic cell with a MgF2 / Ag stacked anti-reflection structure was prepared. The average reflectivity in the 900 nm - 1200 nm band is greater than that of the photovoltaic cell without the anti-reflection structure in the comparative example in this band. The excellent reflection characteristics for long-wavelength light are more helpful for improving the long-wavelength spectral response of the TOPCon cell. At the same time, from the test results of the internal quantum efficiency, it can be seen that the TOPCon photovoltaic cell with a MgF2 / Ag stacked anti-reflection structure prepared in Example 1 has a significantly improved spectral response in the 900 nm - 1200 nm band compared with the comparative example, resulting in an increase in the short-circuit current density of the TOPCon photovoltaic cell.

[0079] Figure 4 are the test curves of the external quantum efficiency of the TOPCon photovoltaic cell before and after stacking the anti-reflection structure according to the embodiments of the present invention. As Figure 4 shown, the abscissa is the spectral wavelength (Wavelength), and the ordinate is the external quantum efficiency (External Quantum Efficiency, EQE). In Example 1, a TOPCon photovoltaic cell with a MgF2 / Ag stacked anti-reflection structure was prepared. The spectral response in the 900 nm - 1200 nm band is significantly improved compared with the spectral response of the comparative example, and the short-circuit current density obtained based on the EQE increases by 0.283 mA / cm 2 . It should be noted that the current density is calculated by software according to the EQE integration.

[0080] By Figure 3 and Figure 4From the test results, it can be seen that the TOPCon photovoltaic cell with the MgF2 / Ag stacked back-reflection structure can effectively improve the optical absorption of the TOPCon photovoltaic cell while ensuring that the fill factor remains unchanged, especially improving the spectral response in the long wavelength band, thereby improving the photoelectric conversion efficiency of the TOPCon photovoltaic cell.

[0081] Considering that when the metal layer 25 is stacked on the dielectric layer 24, the metal particles forming the metal layer 25 may bypass the dielectric layer 24 and directly contact the fine grid or the main grid 26, resulting in a decrease in the fill factor caused by carrier recombination. To avoid this situation as much as possible, there is a first spacing L1 between the dielectric layer 24 and the main grid 26, and a second spacing L2 between the metal layer 25 and the main grid 26, and the second spacing L2 is equal to or greater than the first spacing L1.

[0082] As Figure 1 shown, both sides of the main grid 26 refer to both sides in the width direction of the main grid 26, and this width direction is perpendicular to the extension direction of the main grid 26. The fact that there is a first spacing L1 between the above-mentioned dielectric layer 24 and the main grid 26 means that there are first spacings L1 respectively between the dielectric layers 24 on both sides of the main grid 26 and the corresponding side edges of the main grid 26; the fact that there is a second spacing L2 between the above-mentioned metal layer 25 and the main grid 26 means that there are second spacings L2 respectively between the metal layers 25 on both sides of the main grid 26 and the corresponding side edges of the main grid 26.

[0083] Exemplarily, the second spacing L2 can be consistent with the first spacing L1. Optionally, the second spacing L2 can also be greater than the first spacing L1, so that when the metal layer 25 is stacked on the dielectric layer 24, the dielectric layer 24 can fully play the role of electrical isolation to isolate the metal layer 25 from the fine grid.

[0084] Exemplarily, the value range of the first spacing L1 is 0.3 mm to 0.5 mm. For example, L1 can be 0.33 mm, 0.35 mm, 0.39 mm, 0.41 mm, 0.44 mm, 0.47 mm, etc.; the value range of the second spacing L2 is 0.5 mm to 1 mm. For example, L2 can be 0.55 mm, 0.59 mm, 0.65 mm, 0.7 mm, 0.77 mm, 0.85 mm, 0.87 mm, 0.93 mm, etc. Exemplarily, the value range of the width w of the main grid 26 is 30 μm to 80 μm. For example, the width w of the main grid 26 can be 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, etc.

[0085] In some embodiments, the refractive index of the dielectric layer 24 is less than the refractive index of the first passivation layer 23. For example, for the refractive index n0 of the dielectric layer 24, the refractive index n1 of the first passivation layer 23, and the refractive index n2 of the substrate 10, the refractive indices of the three satisfy the following relationship: Meanwhile, the absorption coefficient k of the dielectric layer 24 is 0 in the wavelength band of 900 nm to 1200 nm where the TOPCon photovoltaic cell has spectral response.

[0086] Exemplarily, the material of the dielectric layer 24 includes at least one of silicon oxide, silicon nitride, titanium oxide, aluminum oxide, or magnesium fluoride. The material of the metal layer 25 includes at least one of gold, silver, aluminum, or copper.

[0087] For example, the metal layer 25 is formed on the dielectric layer 24 by depositing metal nanoparticles. Under the driving of a light field with a specific frequency, the free electrons on the surface of the metal nanoparticles interact with photons to form localized surface plasmon resonance. The resonance can significantly enhance the local field on the surface of the metal nanoparticles, thereby generating multi-angle scattering of the incident light and effectively extending the optical path of light in the absorbing medium. Based on this, depositing metal nanoparticles on the dielectric layer 24 to form a back-reflection structure can improve the infrared spectral response of the TOPCon photovoltaic cell.

[0088] For example, the metal layer 25 is a layer formed by depositing silver nanoparticles. The main grid 26 and the fine grid are formed by printing silver paste on the photovoltaic cell. After testing, the conductivity of the main grid 26 and the fine grid is 1.80E5 (1 / Ω·cm); while the conductivity of the metal layer 25 is 1.747E5 (1 / Ω·cm). It can be seen that the conductivity of the metal layer 25 is less than that of the main grid 26 and the fine grid. When they are in direct contact, it will cause the loss of carrier collection. However, the electrical isolation by the dielectric layer 24 between the metal layer 25 and the fine grid can avoid the above-mentioned loss of carrier collection.

[0089] In some embodiments, as Figure 1 shown, the thickness of the dielectric layer 24 ranges from 1 nm to 300 nm. The function of the dielectric layer 24 is to block the direct contact between the metal layer 25 and the fine grid. When the thickness of the dielectric layer 24 is 1 nm, the blocking effect between the metal layer 25 and the fine grid can be ensured.

[0090] In some embodiments, as Figure 1As shown, the thickness of the metal layer 25 ranges from 200 nm to 1000 nm. The back-reflection structure formed by stacking the metal layer 25 on the dielectric layer 24 needs to take into account excellent reflection characteristics. When the thickness of the metal layer 25 is greater than 200 nm, the metal layer 25 can achieve a reflectivity of more than 95% in the wavelength band of 900 nm to 1200 nm, and as the thickness increases, the reflectivity will gradually approach 100%. For example, the 200-nm-thick metal layer 25 formed of silver has an average reflectivity of 97% in the wavelength band of 900 nm to 1200 nm. Considering the high cost of silver, the thickness of the metal layer 25 is set to a maximum of 1000 nm, that is, 1 μm. Exemplarily, the thickness of the metal layer 25 can be 230 nm, 270 nm, 300 nm, 370 nm, 400 nm, 500 nm, 630 nm, 700 nm, 800 nm, 900 nm, 950 nm, etc. It can be understood that the thickness of the above-mentioned metal layer 25 can also be greater than 1 μm.

[0091] Exemplarily, the substrate 10 of the photovoltaic cell according to the exemplary embodiment of the present invention includes a silicon-based material, such as monocrystalline silicon, polycrystalline silicon, amorphous silicon, etc. The substrate 10 can be an N-type crystalline silicon or a P-type crystalline silicon; the substrate 10 can also be copper indium gallium selenide, perovskite, or germanium, etc.

[0092] Figure 5 is a schematic flow chart of a method for manufacturing a photovoltaic cell according to an embodiment of the present invention. As Figure 5 shown, the exemplary embodiment of the present invention further provides a method for manufacturing a photovoltaic cell, which may include the following steps:

[0093] Step 501: Provide a substrate 10 stacked with a first passivation layer 23.

[0094] Stack the first passivation layer 23 in the back field of the substrate 10. The substrate 10 is an N-type crystalline silicon substrate, which serves as the absorption layer of the photovoltaic cell.

[0095] Specifically, as Figure 1 shown, stack a tunneling oxide layer 21, a doped polysilicon layer 22, and the above-mentioned first passivation layer 23 on the back surface of the substrate 10 in sequence; stack a diffusion layer 31, a second passivation layer 32, and a passivation and antireflection layer 33 on the front surface of the substrate 10 in sequence to form a TOPCon photovoltaic cell; and print a gate 34 (front main gate) and corresponding front fine grids on the front surface of the photovoltaic cell, and print a main gate 26 and corresponding fine grids on the back surface of the photovoltaic cell.

[0096] Step 502: Stack a dielectric layer 24 on the side of the first passivation layer 23 facing away from the substrate 10, and the dielectric layer 24 is located on other regions of the first passivation layer 23 except the main gate 26.

[0097] The preparation of the dielectric layer 24 and the metal layer 25 can be formed on the first passivation layer 23 by methods such as plasma enhanced chemical vapor deposition, magnetron sputtering, vacuum evaporation coating, electron beam evaporation, atomic layer deposition, etc. In the exemplary embodiment of the present invention, the preparation method of vacuum evaporation coating is taken as an example for elaboration.

[0098] Figure 2 It is a top view structural schematic diagram of the first mask plate according to an embodiment of the present invention. As Figure 2 shown, the first mask plate 40 is formed by a peripheral frame structure and a plurality of first shielding strips 41 inside. Among them, the position of each first shielding strip 41 corresponds to the main grid 26 in the back surface field of the TOPCon photovoltaic cell. When the first mask plate 40 is covered on the first passivation layer 23, the surfaces of the respective main grids 26 in the back surface field are shielded by the plurality of first shielding strips 41, exposing the surfaces of other regions of the first passivation layer 23 except the main grid 26, so as to form the dielectric layer 24 on the other regions.

[0099] After the surfaces of the respective main grids 26 are shielded by the first mask plate 40, the TOPCon photovoltaic cell is placed in an evaporation machine to evacuate.

[0100] During the formation of the dielectric layer 24, the value range of the evaporation rate is For example, it can be etc.

[0101] In practical applications, when the vacuum degree reaches 5×10 -4 Pa, under the condition that the evaporation rate is , MgF2 with a thickness of 120 nm is deposited on the exposed surface of the first passivation layer 23 facing away from the substrate 10 to form the dielectric layer 24.

[0102] In an optional embodiment, the width W1 of the first shielding strip 41 of the first mask plate 40 is the same as the width w of the main grid 26. In this embodiment, although the deposited dielectric layer 24 does not directly contact the top of the main grid 26, it will contact the side of the main grid 26.

[0103] In some embodiments, the width W1 of the first shielding strip 41 of the first mask plate 40 is greater than the width w of the main grid 26. For example, the first distance L1 between the two sides of the first shielding strip 41 and the two sides of the shielded main grid 26 is 0.3 mm to 0.5 mm. The value range of W1 is 0.63 mm to 1.08 mm. The first shielding strip 41 within this width range can avoid overplating during the deposition of the dielectric layer 24, so that the dielectric layer 24 directly contacts both sides of the main grid 26, that is, the dielectric layer 24 can be spaced apart from the main grid 26, avoiding the possibility of reducing the conductivity of the main grid 26 and resulting in a decrease in the fill factor.

[0104] Step 503: Stack a metal layer 25 on the side of the dielectric layer 24 away from the first passivation layer 23, and space the metal layer 25 apart from the main gate 26; wherein, the metal layer 25 is electrically isolated from the first passivation layer 23 by the dielectric layer 24.

[0105] In order to prevent the metal layer 25 from directly contacting the main gate 26 during the process of stacking the metal layer 25 on the dielectric layer 24, a second mask plate is used to shield the main gate 26. The second mask plate has the same structure as the first mask plate 40, that is, the periphery is a frame structure, and a plurality of second shielding strips corresponding to the main gate 26 are arranged inside. The difference is that the width of the second shielding strips of the second mask plate is greater than the width of the first mask plate 40.

[0106] Exemplarily, when the first shielding strip 41 of the first mask plate 40 is larger than the width of the main gate 26, the structure and dimensions of the second mask plate can be the same as those of the first mask plate 40.

[0107] After the surfaces of the respective main gates 26 are shielded by the second mask plate, the TOPCon photovoltaic cell is placed in an evaporation machine platform for vacuum pumping.

[0108] During the formation of the metal layer 25, the deposition rate of depositing the metal layer to the first preset thickness is Optionally etc.; the deposition rate of depositing the metal layer from the first preset thickness to the second preset thickness is Optionally etc.; the deposition rate of depositing the metal layer from the second preset thickness to the third preset thickness is Optionally etc.; the deposition rate of depositing the metal layer from the third preset thickness to the fourth preset thickness is Optionally etc.; wherein, the first preset thickness, the second preset thickness, the third preset thickness, and the fourth preset thickness increase in sequence. In this way, slow deposition rate at first is beneficial to increasing the adhesion, and fast deposition later is beneficial to shortening the preparation time.

[0109] Exemplarily, the first preset thickness can be 5 nm to 15 nm, optionally 7 nm, 9 nm, 11 nm, 13 nm, etc.; the second preset thickness can be 10 nm to 30 nm, optionally 11 nm, 13 nm, 17 nm, 23 nm, 25 nm, 27 nm, etc.; the third preset thickness can be 20 nm to 70 nm, optionally 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 65 nm, etc.; the fourth preset thickness can be 100 nm to 1000 nm, optionally 110 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, etc.

[0110] In practical applications, when the vacuum degree reaches 5×10 -4 Pa, deposit 0 to 10 nm under the condition that the evaporation rate is , deposit 10 nm to 20 nm under the condition that the evaporation rate is , deposit 20 nm to 50 nm under the condition that the evaporation rate is , deposit 50 nm to 200 nm under the condition that the evaporation rate is , and a total Ag metal layer 25 with a deposition thickness of 200 nm is formed.

[0111] Forming the metal layer 25 with a total deposition thickness of 200 nm under various conditions of increasing evaporation rate is beneficial for the initially formed metal layer 25 to stably adhere to the dielectric layer 24, increasing the mechanical strength of the metal layer 25. Furthermore, evaporating at an increasing evaporation rate can ensure the uniformity of the metal layer 25 and the control of the thickness, so as to obtain the required electrical and physical properties, and then enhance the long-wavelength spectral response of the TOPCon photovoltaic cell.

[0112] When the width of the second shielding strip of the second mask plate used is greater than the width of the first mask plate 40, the formed metal layer 25 can be deposited only on the dielectric layer 24 to prevent the occurrence of overplating on the second shielding strip during the deposition of the metal layer 25, that is, some metal particles bypass the second shielding strip and directly contact the main grid 26 and / or the fine grid, resulting in carrier recombination and reducing the fill factor of the TOPCon photovoltaic cell. Exemplarily, the value range of the second spacing L2 between both sides of the second shielding strip and both sides of the main grid 26 is 0.5 mm to 1 mm. For example, the value range of the width of the second shielding strip is 1.09 mm to 2.08 mm.

[0113] As can be seen from the above, by using the first mask plate 40 and the second mask plate, the surface of the main grid 26 in the back field is shielded respectively when depositing the dielectric layer 24 and the metal layer 25, avoiding the direct contact between the metal layer 25 and the main grid 26. Without reducing the fill factor of the TOPCon photovoltaic cell, the back reflection structure formed by the dielectric layer 24 and the metal layer 25 can reflect light back into the n-type crystalline silicon substrate 10 serving as the absorption layer, effectively improving the long-wavelength spectral response of the TOPCon photovoltaic cell.

[0114] The exemplary embodiment of the present utility model further provides a photovoltaic cell module, including a plurality of electrically connected photovoltaic cells. At least one photovoltaic cell is the photovoltaic cell of the above embodiment, or,

[0115] At least one photovoltaic cell is a photovoltaic cell prepared by the photovoltaic cell preparation method of the above embodiment.

[0116] The technical advantages of the above photovoltaic cell module compared with the prior art are the same as those of the above photovoltaic cell or photovoltaic cell preparation method, and will not be elaborated here.

[0117] Those skilled in the art should understand that the above embodiments are only for clearly illustrating the present utility model, rather than limiting the scope of the present utility model. For those skilled in the art, other changes or modifications can be made on the basis of the above disclosure, and these changes or modifications are still within the scope of the present utility model.

Claims

1. A photovoltaic cell, characterized in that: It includes a substrate, a main gate, a dielectric layer, a metal layer and a first passivation layer stacked on the substrate. The dielectric layer is stacked on a side of the first passivation layer facing away from the substrate, and is located on other regions of the first passivation layer except the main gate; The metal layer is stacked on a side of the dielectric layer away from the first passivation layer and is spaced apart from the main gate. The metal layer and the first passivation layer are electrically isolated from each other by the dielectric layer.

2. The photovoltaic cell according to claim 1, characterized in that: The dielectric layer is spaced apart from the main gate.

3. The photovoltaic cell according to claim 2, characterized in that: There is a first distance between the dielectric layer and the main grid, and there is a second distance between the metal layer and the main grid, and the second distance is equal to or greater than the first distance.

4. The photovoltaic cell according to claim 1, characterized in that: The material of the dielectric layer includes at least one of silicon oxide, silicon nitride, titanium oxide, aluminum oxide or magnesium fluoride; and / or, The material of the metal layer includes at least one of gold, silver, aluminum or copper.

5. The photovoltaic cell according to claim 1, characterized in that: The thickness of the dielectric layer ranges from 1 nm to 300 nm; and / or, The thickness of the metal layer ranges from 200 nm to 1000 nm.

6. The photovoltaic cell according to claim 1, characterized in that: The substrate includes a silicon substrate or a germanium substrate.

7. The photovoltaic cell according to claim 1, characterized in that: The photovoltaic cell comprises one of a tunneling oxidation passivation contact photovoltaic cell and an interdigitated back contact photovoltaic cell.

8. The photovoltaic cell according to claim 1, characterized in that: The photovoltaic cell further includes a tunneling oxide layer and a doped polysilicon layer, wherein the tunneling oxide layer and the doped polysilicon layer are stacked between the substrate and the first passivation layer, and the tunneling oxide layer and the doped polysilicon layer are arranged in a direction away from the substrate.

9. The photovoltaic cell according to claim 8, characterized in that: The photovoltaic cell further comprises a diffusion layer, a second passivation layer and a passivation anti-reflection layer, wherein the diffusion layer, the second passivation layer and the passivation anti-reflection layer are sequentially formed on a side of the substrate away from the first passivation layer, and the diffusion layer, the second passivation layer and the passivation anti-reflection layer are arranged in a direction away from the substrate; and / or, The doped polysilicon layer is a phosphorus-doped polysilicon layer, and the diffusion layer is a boron-doped diffusion layer.

10. A photovoltaic cell assembly, characterized in that: The invention comprises a plurality of electrically connected photovoltaic cells, at least one of the photovoltaic cells is the photovoltaic cell according to any one of claims 1 to 9.

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