Preparation method of photovoltaic cell and photovoltaic cell

Abstract

The invention relates to a preparation method of a photovoltaic cell and the photovoltaic cell. The preparation method comprises the following steps: preparing a silicon substrate; polishing the surface of the silicon substrate; performing cleaning; putting the silicon substrate into a drying tank, and introducing ozone into the drying tank to prepare a first tunneling oxide layer; and putting the silicon substrate into an LPCVD (Low Pressure Chemical Vapor Deposition) cavity, and introducing oxygen into the LPCVD cavity to prepare a second tunneling oxide layer. The surface of the silicon substrate in the drying groove has water vapor, ozone is introduced into the drying groove, the first tunneling oxide layer is formed on the surface of the silicon substrate, the silicon substrate is not exposed in the external environment during drying, the influence of the external environment on the silicon substrate is low, and the cleanliness and compactness of the first tunneling oxide layer are high; hydrogen ions in water on the surface of the silicon substrate can increase hydrogen passivation, and the passivation effect of the first tunneling oxide layer can be improved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a method for preparing a photovoltaic cell and a photovoltaic cell. Background Art

[0002] Photovoltaic cells can use solar energy to convert photons into electrons, thereby generating electricity. They are clean, safe, convenient, and efficient, and have become an emerging industry that has attracted widespread attention and focused development in countries around the world. Photovoltaic cells include a tunneling oxide layer, which provides a good medium for the transmission of electrons, allowing photovoltaic cells to effectively utilize the electrons generated in the silicon substrate. At present, the preparation process of the tunneling oxide layer takes a long time, and the passivation effect after preparation is poor, which affects the power generation efficiency of photovoltaic cells. Summary of the invention

[0003] In view of this, the embodiments of the present application provide a method for preparing a photovoltaic cell and a photovoltaic cell to solve the problem of poor passivation effect of the photovoltaic cell.

[0004] In a first aspect, the present application relates to a method for preparing a photovoltaic cell, the method comprising: preparing a silicon substrate; polishing the surface of the silicon substrate; Cleaning; Placing the silicon substrate into a drying tank, and introducing ozone into the drying tank to prepare a first tunneling oxide layer; The silicon substrate is placed in a LPCVD chamber, and oxygen is introduced into the LPCVD chamber to prepare a second tunneling oxide layer.

[0005] In a possible embodiment, when ozone is introduced into the drying tank, the concentration of the ozone is 0.1 ppm to 40 ppm.

[0006] In a possible embodiment, when ozone is introduced into the drying tank, the temperature in the drying tank is 60° C. to 100° C., and the time for introducing ozone is 360 s to 1200 s.

[0007] In a possible embodiment, the thickness of the first tunnel oxide layer is 0.5 nm to 2 nm.

[0008] In a possible embodiment, when oxygen is introduced into the LPCVD chamber to prepare the second tunneling oxide layer, the flow rate of the oxygen is 1000 sccm to 40000 sccm.

[0009] In a possible embodiment, when oxygen is introduced into the LPCVD chamber to prepare the second tunnel oxide layer, the temperature in the LPCVD chamber is 550° C. to 700° C., and the time for introducing oxygen is 100 s to 3000 s.

[0010] In a possible embodiment, the sum of the thickness of the first tunnel oxide layer and the thickness of the second tunnel oxide layer is 1 nm to 2.5 nm.

[0011] In a second aspect, the present application also relates to a photovoltaic cell, which includes a silicon substrate, the silicon substrate includes a first surface and a second surface, the second surface is provided with a first tunneling oxide layer and a second tunneling oxide layer, and the first tunneling oxide layer and the second tunneling oxide layer are prepared by any of the above-mentioned photovoltaic cell preparation methods.

[0012] In a possible embodiment, the second surface includes a plurality of first doping regions and a plurality of second doping regions, the first doping regions and the second doping regions are alternately arranged, the first tunneling oxide layer and the second tunneling oxide layer are located in the first doping region, a first doping layer is arranged on the surface of the second tunneling oxide layer, a third tunneling oxide layer is arranged in the second doping region, and a second doping layer is arranged on the surface of the third tunneling oxide layer.

[0013] In a possible embodiment, the first surface includes a third doping layer, the second surface includes a fourth doping layer, and the first tunneling oxide layer and the second tunneling oxide layer are disposed between the fourth doping layer and the silicon substrate.

[0014] The present application relates to a method for preparing a photovoltaic cell and a photovoltaic cell, the preparation method comprising: preparing a silicon substrate; polishing the surface of the silicon substrate; cleaning; placing the silicon substrate in a drying tank, introducing ozone into the drying tank to prepare a first tunneling oxide layer; placing the silicon substrate in an LPCVD chamber, introducing oxygen into the LPCVD chamber to prepare a second tunneling oxide layer. The surface of the silicon substrate in the drying tank has water vapor, and ozone is introduced into the drying tank to form a first tunneling oxide layer on the surface of the silicon substrate. During drying, the silicon substrate is not exposed to the external environment and is less affected by the external environment, so that the cleanliness and density of the first tunneling oxide layer are higher, and the hydrogen ions in the water on the surface of the silicon substrate can increase hydrogen passivation, which is beneficial to improving the passivation effect of the first tunneling oxide layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 A flow chart of a method for preparing a photovoltaic cell provided in an embodiment of the present application; Figure 2The structure of the silicon substrate provided for the embodiment of the present application is a schematic diagram; Figure 3 A schematic diagram of the structure after a first tunneling oxide layer is prepared on a silicon substrate provided in an embodiment of the present application; Figure 4 A schematic diagram of the structure after preparing a second tunneling oxide layer on a silicon substrate provided in an embodiment of the present application; Figure 5 A schematic diagram of the structure of an embodiment of a photovoltaic cell provided in an embodiment of the present application; Figure 6 A schematic structural diagram of another embodiment of a photovoltaic cell provided in an embodiment of the present application.

[0017] Reference numerals: 1-Silicon substrate; 11- first surface; 12- second surface; 121- a first doping region; 122- a second doping region; 123-separation area; 2-first tunnel oxide layer; 3-second tunnel oxide layer; 4-third tunnel oxide layer; 5- first doping layer; 6- second doping layer; 7- third doping layer; 8-Fourth doping layer. DETAILED DESCRIPTION

[0018] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0019] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. 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.

[0020] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0021] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0022] The backlight surface of photovoltaic cells such as back contact cells and TOPCON cells is provided with a tunneling oxide layer to improve the passivation effect of the photovoltaic cells and reduce the composite loss. At present, after the silicon substrate 1 is polished, cleaned and dried, the silicon substrate 1 is placed in a tubular LPCVD chamber, and oxygen is introduced into the tubular LPCVD chamber to prepare the tunneling oxide layer under an environment of 550°C to 700°C. After the silicon substrate 1 is dried, it is necessary to move the silicon substrate 1 from the drying tank to the tubular LPCVD chamber. During the transfer process, the bare silicon will contact the external environment, making the silicon substrate 1 susceptible to the external environment, thereby affecting the passivation effect of the tunneling oxide layer. The thickness of the tunneling oxide layer is 1nm to 3nm so that the tunneling oxide layer has a certain passivation effect and is also convenient for carrier tunneling. Therefore, in order to make the thickness of the tunneling oxide layer reach 1nm to 3nm, the time for oxygen to be introduced into the tubular LPCVD chamber is relatively long, resulting in a low preparation efficiency of the photovoltaic cell. After preparing the tunnel oxide layer, silane is introduced into the tubular LPCVD chamber to deposit a 100nm to 400nm amorphous silicon layer at 550°C to 700°C. The amorphous silicon layer is then subjected to high-temperature crystallization treatment and finally boron diffusion to form a doped layer.

[0023] like Figures 1 to 6 As shown, the present application provides a photovoltaic cell, which includes a silicon substrate 1 , wherein the silicon substrate 1 includes a first surface 11 and a second surface 12 , and the second surface 12 is provided with a first tunneling oxide layer 2 and a second tunneling oxide layer 3 .

[0024] The first surface 11 of the silicon substrate 1 is the light-receiving surface of the photovoltaic cell. The first surface 11 is provided with a velvet structure to reduce the reflectivity of the first surface 11, improve the light absorption efficiency of the photovoltaic cell, and improve the power generation efficiency of the photovoltaic cell. The second surface 12 is the backlight surface of the photovoltaic cell. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 are provided on the second surface 12. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 are located between the silicon wafer and the polycrystalline silicon, and can prevent the direct recombination of electrons and holes through physical isolation, and can reduce the recombination current of the second surface 12, thereby improving the open circuit voltage and conversion efficiency of the photovoltaic cell. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 can also improve the passivation effect of the second surface 12, reduce the reflection loss of the incident light, and help improve the power generation efficiency of the photovoltaic cell. The second surface 12 is also provided with an electrode. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 can reduce the metal recombination in the area where the electrode is provided, and reduce the recombination loss.

[0025] like Figures 1 to 4 As shown, the present application provides a method for preparing a photovoltaic cell, the preparation steps comprising: S1, preparing a silicon substrate 1; S2, polishing the surface of the silicon substrate 1; S3, cleaning; S4, placing the silicon substrate 1 into a drying tank, and introducing ozone into the drying tank to prepare a first tunneling oxide layer 2; S5. Place the silicon substrate 1 into a LPCVD chamber, and introduce oxygen into the LPCVD chamber to prepare a second tunneling oxide layer 3.

[0026] The surface of the silicon substrate 1 is polished by an alkaline solution. When cleaning, the silicon substrate 1 needs to be placed in a water tank first, and the alkaline solution on the surface of the silicon substrate 1 is washed away by clean water. Then the silicon substrate 1 is placed in an acid tank and pickled by an acidic solution to neutralize the alkaline solution remaining on the surface of the silicon substrate 1. Finally, the silicon substrate 1 is placed in a water tank again, and the neutral solution and the residual acidic solution on the surface of the silicon substrate 1 are washed away by clean water. After cleaning, there will be water droplets remaining on the surface of the silicon substrate 1. The silicon substrate 1 is placed in a drying tank to dry the water vapor on the surface of the silicon substrate 1. Ozone is introduced into the drying tank. During the drying process, the first surface 11 and the second surface 12 of the silicon substrate 1 can be oxidized to form a first tunneling oxide layer 2. During drying, the silicon substrate 1 is not exposed to the external environment and is less affected by the external environment, so that the cleanliness of the first tunneling oxide layer 2 is higher, and the compactness of the first tunneling oxide layer 2 is enhanced, which can reduce the defects such as black spots and black dots in the photovoltaic cell, and can improve the power generation efficiency of the photovoltaic cell. When the silicon substrate 1 is placed in the drying tank, there is water vapor on the surface of the silicon substrate 1. At this time, ozone is introduced into the drying tank to form a first tunneling oxide layer 2. The hydrogen ions in the water can increase hydrogen passivation, which is beneficial to improve the passivation effect of the first tunneling oxide layer 2. During the drying process, the first tunneling oxide layer 2 is formed on the surface of the silicon substrate 1, which can reduce the preparation time of the photovoltaic cell to improve the production efficiency of the photovoltaic cell. The silicon substrate 1 forms the first tunneling oxide layer 2 in the drying tank, and then is transferred from the drying tank to the LPCVD chamber, which can reduce the possibility of the external environment affecting the silicon substrate 1. Then the silicon substrate 1 with the first tunneling oxide layer 2 is placed in the LPCVD chamber, and a second tunneling oxide layer 3 is prepared on the first tunneling oxide layer 2 to improve the passivation effect of the photovoltaic cell.

[0027] like Figure 3 As shown, in a possible embodiment, the thickness of the first tunnel oxide layer 2 is 0.5 nm to 2 nm.

[0028] According to the quantum tunneling effect, the first tunneling oxide layer 2 and the second tunneling oxide layer 3 allow carriers to efficiently tunnel to the polysilicon layer, while blocking hole recombination to achieve selective carrier transmission. The probability of electron tunneling will decay exponentially with the increase of the thickness of the tunneling oxide layer. If the thickness of the first tunneling oxide layer 2 is greater than 2nm, the preparation of the second tunneling oxide layer 3 on the first tunneling oxide layer 2 will cause the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 to be too large, making it difficult for carriers to pass through, and increasing the series resistance. If the thickness of the first tunneling oxide layer 2 is less than 0.5nm, the first tunneling oxide layer 2 will not be able to completely cover the surface of the silicon substrate 1, and the uncovered part of the silicon substrate 1 will be easily affected by the external environment.

[0029] In a possible embodiment, when ozone is introduced into the drying tank, the concentration of ozone is 0.1 ppm to 40 ppm.

[0030] The concentration of ozone introduced into the drying tank will affect the thickness of the first tunnel oxide layer 2. If the concentration of ozone introduced into the drying tank is less than 0.1ppm, the thickness of the first tunnel oxide layer 2 will be small, and the first tunnel oxide layer 2 cannot completely cover the surface of the silicon substrate 1. The uncovered part of the silicon substrate 1 is easily affected by the external environment; if the concentration of ozone introduced into the drying tank is greater than 40ppm, the thickness of the first tunnel oxide layer 2 will be large, and the second tunnel oxide layer 3 will need to be prepared on the first tunnel oxide layer 2 later, so that the total thickness of the first tunnel oxide layer 2 and the second tunnel oxide layer 3 is large, and it is difficult for carriers to pass through, and the series resistance increases. Therefore, the concentration of ozone introduced into the drying tank can be 0.1ppm, 20ppm, 40ppm, etc., so that the thickness of the first tunnel oxide layer 2 is maintained at 0.5nm to 2nm.

[0031] In a possible embodiment, when ozone is introduced into the drying tank, the temperature in the drying tank is 60° C. to 100° C., and the time for introducing ozone is 360 seconds to 1200 seconds.

[0032] Ozone has strong oxidizing properties. The temperature in the drying tank is 60°C to 100°C. Ozone can oxidize the surface of the silicon substrate 1 to form a first tunneling oxide layer 2. The time for passing ozone into the drying tank will affect the thickness of the first tunneling oxide layer 2. If the time for passing ozone is less than 360s, the thickness of the first tunneling oxide layer 2 will be small, and the first tunneling oxide layer 2 cannot completely cover the surface of the silicon substrate 1. The uncovered part of the silicon substrate 1 is easily affected by the external environment; if the time for passing ozone into the drying tank is greater than 1200s, the thickness of the first tunneling oxide layer 2 will be large, and the second tunneling oxide layer 3 will need to be prepared on the first tunneling oxide layer 2 later, so that the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is large, and it is difficult for carriers to pass through, and the series resistance increases. Therefore, the time for passing ozone into the drying tank can be 360s, 800s, 1200s, etc., so that the thickness of the first tunneling oxide layer 2 is maintained at 0.5nm to 2nm.

[0033] like Figure 4 As shown, in a possible embodiment, after preparing a first tunneling oxide layer 2 on the surface of a silicon substrate 1, the silicon substrate 1 is placed in an LPCVD chamber, and a second tunneling oxide layer 3 is prepared in the LPCVD chamber, so that the sum of the thicknesses of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is 1 nm to 2.5 nm.

[0034] According to the quantum tunneling effect, the first tunneling oxide layer 2 and the second tunneling oxide layer 3 allow carriers to efficiently tunnel to the polysilicon layer, while blocking hole recombination, and realizing selective transmission of carriers. The probability of carrier tunneling will decay exponentially with the increase of the thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3. When the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is less than or equal to 2nm, the tunneling probability of electrons or holes is greater than 50%, so that carriers can efficiently pass through the first tunneling oxide layer 2 and the second tunneling oxide layer 3, reducing resistance loss. If the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is greater than 2.5nm, the tunneling probability of carriers will be greatly reduced, forcing carriers to cross the potential barrier through thermal excitation, resulting in energy loss and reduced power generation efficiency of photovoltaic cells. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 can passivate the dangling bonds on the surface of the silicon substrate 1, can reduce carrier recombination, and increase the open circuit voltage of the photovoltaic cell, so the first tunneling oxide layer 2 and the second tunneling oxide layer 3 also have a passivation effect. If the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is less than 1nm, the passivation layer is incomplete, and the defects on the surface of the silicon substrate 1 are not completely covered, which will lead to poor passivation effects of the first tunneling oxide layer 2 and the second tunneling oxide layer 3, and a high recombination rate on the surface of the silicon substrate 1. If the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is greater than 2.5nm, the tunneling probability of the carriers drops sharply, making it difficult for the carriers to pass through, and the series resistance of the photovoltaic cell increases. Therefore, the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 can be 1nm, 2nm, 2.5nm, etc., so that the first tunneling oxide layer 2 and the second tunneling oxide layer 3 have good tunneling efficiency and passivation effect.

[0035] In a possible embodiment, when oxygen is introduced into the LPCVD chamber to prepare the second tunnel oxide layer 3, the flow rate of the oxygen is 1000 sccm to 40000 sccm.

[0036] The flow rate of oxygen will affect the thickness of the second tunnel oxide layer 3. If the flow rate of oxygen in the LPCVD chamber is less than 1000 sccm, the thickness of the second tunnel oxide layer 3 will be small, resulting in an incomplete passivation layer, the defects on the surface of the silicon substrate 1 are not completely covered, the passivation effect is poor, and the recombination rate on the surface of the silicon substrate 1 is high; if the flow rate of oxygen in the LPCVD chamber is greater than 40000 sccm, the thickness of the second tunnel oxide layer 3 will be large, resulting in difficulty for carriers to pass through, and the series resistance of the photovoltaic cell will increase. Therefore, the oxygen flow rate in the LPCVD chamber can be 1000 sccm, 21000 sccm, 40000 sccm, etc., so that the total thickness of the first tunnel oxide layer 2 and the second tunnel oxide layer 3 is 1nm to 2.5nm.

[0037] In a possible embodiment, when oxygen is introduced into the LPCVD chamber to prepare the second tunnel oxide layer 3, the temperature in the LPCVD chamber is 550° C. to 700° C., and the time for introducing oxygen is 100 s to 3000 s.

[0038] The silicon substrate 1 is oxidized by oxygen to form a second tunneling oxide layer 3, and the temperature in the LPCVD chamber is adjusted to 550°C to 700°C, so that the second tunneling oxide layer 3 can be formed on the surface of the first tunneling oxide layer 2. The time of oxygen introduction will affect the thickness of the second tunneling oxide layer 3. If the time of oxygen introduction is less than 100s, the thickness of the second tunneling oxide layer 3 will be small, resulting in an incomplete passivation layer, the defects on the surface of the silicon substrate 1 are not completely covered, the passivation effect is poor, and the recombination rate on the surface of the silicon substrate 1 is high; if the time of oxygen introduction is greater than 3000s, the thickness of the second tunneling oxide layer 3 will be large, resulting in difficulty for carriers to pass through, and the series resistance of the photovoltaic cell will increase. Therefore, the time of oxygen introduction can be 100s, 1500s, 3000s, etc., so that the total thickness of the first tunneling oxide layer 2 and the second tunneling oxide layer 3 is 1nm to 2.5nm.

[0039] like Figure 5 As shown, in a possible embodiment, the photovoltaic cell can be a back contact cell, and the second surface 12 includes a plurality of first doping regions 121 and a plurality of second doping regions 122, and the first doping regions 121 and the second doping regions 122 are alternately arranged. The first tunneling oxide layer 2 and the second tunneling oxide layer 3 are sequentially arranged in the first doping region 121, and the surface of the second tunneling oxide layer 3 is provided with a first doping layer 5. The second doping region 122 is provided with a third tunneling oxide layer 4, and the surface of the third tunneling oxide layer 4 is provided with a second doping layer 6.

[0040] After preparing the first tunneling oxide layer 2 and the second tunneling oxide layer 3 on the surface of the silicon substrate 1, the preparation method of the photovoltaic cell includes: depositing the first doping layer 5 on the second surface 12, and the first doping layer 5 can be a P-type doping layer; preparing a groove at the position of the second doping area 122; preparing the third tunneling oxide layer 4 and the second doping layer 6 in the groove, and the second doping layer 6 can be an N-type doping layer, and the second doping layer 6 is completely located in the groove; a separation area 123 can be opened between the first doping area 121 and the second doping area 122 by laser; depositing a passivation layer and an anti-reflection layer on the first surface 11 and the second surface 12; and preparing electrodes in the first doping area 121 and the second doping area 122 by screen printing.

[0041] The second doping layer 6 is completely located in the groove, which can reduce the possibility of leakage at the position where the P-type doping layer and the N-type doping layer are close. Therefore, the depth of the groove needs to be greater than the thickness of the third tunneling oxide layer 4 and the second doping layer 6. When preparing the groove, it is necessary to remove the first doping layer 5, the first tunneling oxide layer 2, the second tunneling oxide layer 3 and part of the silicon substrate 1. In order to improve the passivation effect of the second doping region 122 and reduce the recombination of the second doping region 122, it is necessary to prepare the third tunneling oxide layer 4 in the second doping region 122. When preparing the third tunneling oxide layer 4, the third tunneling oxide layer 4 will also be deposited on the surface of the first doping region 121 and the separation region 123. Therefore, before depositing the passivation layer and the anti-reflection layer, it is necessary to remove the third tunneling oxide layer 4 on the surface of the first doping region 121 and the separation region 123. The separation region 123 separates the N-type doping layer and the P-type doping layer, which can improve the parallel resistance, reduce leakage, and thus improve the efficiency of the photovoltaic cell. The separation area 123 of the first surface 11 and the second surface 12 can be set to a velvet structure, which can improve the light absorption effect of the photovoltaic cell to improve the power generation efficiency of the photovoltaic cell. The passivation layer and the anti-reflection layer are deposited on the first surface 11 and the second surface 12, which can improve the photoelectric conversion efficiency of the photovoltaic cell. Electrodes are prepared in the first doping area 121 and the second doping area 122. The electrode in the first doping area 121 is in electrical contact with the first doping layer 5, and the electrode in the second doping area 122 is in electrical contact with the second doping layer 6, so that the electric energy generated in the photovoltaic cell can be led out through the electrode for easy collection.

[0042] like Figure 6 As shown, in a possible embodiment, the photovoltaic cell may be a TOPCON cell, the first surface 11 of the silicon substrate 1 includes a third doping layer 7, and the second surface 12 includes a fourth doping layer 8. A first tunneling oxide layer 2 and a second tunneling oxide layer 3 are disposed between the fourth doping layer 8 and the silicon substrate 1.

[0043] After preparing a first tunneling oxide layer 2 and a second tunneling oxide layer 3 on the surface of a silicon substrate 1, the method for preparing a photovoltaic cell includes: depositing a third doping layer 7 on the surface of the second tunneling oxide layer 3, and depositing a fourth doping layer 8 on the first surface 11; depositing a passivation layer and an anti-reflection layer on the first surface 11 and the second surface 12; and arranging electrodes on the first surface 11 and the second surface 12 by screen printing.

[0044] The passivation layer and the anti-reflection layer are deposited on the first surface 11 and the second surface 12, which can improve the photoelectric conversion efficiency of the photovoltaic cell. Electrodes are arranged on the first surface 11 and the second surface 12, and the electrode of the first surface 11 is in electrical contact with the fourth doping layer 8, and the electrode of the second surface 12 is in electrical contact with the third doping layer 7, so that the electric energy generated in the photovoltaic cell can be led out through the electrodes for easy collection.

[0045] In a possible embodiment, the above preparation method can also be used to prepare photovoltaic cells that further improve the photoelectric conversion efficiency by stacking different high-efficiency cell technologies on back contact cells (Interdigitated Back Contact, IBC). For example, IBC technology is combined with intrinsic thin film heterojunction cells (Heterojunction with Intrinsic Thin-film, HJT) to make HBC cells, or IBC technology is combined with oxide layer passivated contact cells (Tunnel Oxide Passivated Contact, TOPCON) cells to make TBC cells.

[0046] HBC cells use heterojunction technology, combining amorphous silicon and crystalline silicon, and can form a high-quality passivation layer on the surface of the silicon substrate 1, which can effectively reduce surface recombination and increase the open circuit voltage. HBC cells move all metal grid lines to the second surface 12, so that there is no metal blocking the first surface 11, thereby improving the utilization rate of light and the photoelectric conversion efficiency. The second surface 12 forms a heterojunction to achieve efficient carrier collection. This design helps to improve the overall performance of the battery. HBC cells are suitable for photovoltaic building integrated structures, and can fully combine the beauty and architectural art of BC components.

[0047] The TBC cell adopts TOPCon technology and IBC technology, and forms a first tunneling oxide layer 2 and a second tunneling oxide layer 3 on the second surface 12 of the silicon substrate 1 through the above-mentioned preparation method to reduce surface recombination and improve the open circuit voltage of the photovoltaic cell, and all metal grid lines are moved to the second surface 12, so that there is no metal obstruction on the first surface 11, which is beneficial to improve the utilization rate of light and the photoelectric conversion efficiency.

[0048] After the photovoltaic cell is prepared, it is necessary to perform PL detection on the photovoltaic cell to detect the performance of the photovoltaic cell. The following table 1 shows the results of PL detection. PL detection uses the principle of photoluminescence and uses laser as an excitation light source to provide photons of a certain energy, so that the ground state electrons in the photovoltaic cell enter an excited state after absorbing these photons and release infrared light. Then, a highly sensitive and high-resolution camera is used for photosensitive imaging. After imaging, the light intensity is proportional to the non-equilibrium minority carrier concentration at the corresponding position.

[0049] The tunneling oxide layer in the photovoltaic cell of the comparative example is prepared by conventional technology, and the silicon substrate 1 is dried and then prepared by oxygen in a tubular PLCVD. The tunneling oxide layer in the photovoltaic cell of the embodiment includes a first tunneling oxide layer 2 and a second tunneling oxide layer 3 made by the above method. As shown in Table 1 below, except for the PL detection result, the other detection parameters of the comparative example and the embodiment are slightly different. During PL detection, the photovoltaic cells of the comparative example and the embodiment can be irradiated with lasers of 1sun brightness and 0.1sun brightness. PL detection is performed on the photovoltaic cells of the comparative example and the photovoltaic cells of the embodiment by lasers of different brightness. The brightness of the photovoltaic cells in the embodiment is significantly higher than that of the photovoltaic cells of the comparative example, indicating that the internal crystal structure of the photovoltaic cell of the embodiment is complete and has few defects. The photovoltaic cell of the embodiment has a more uniform carrier distribution and a longer carrier lifetime, and the photoelectric conversion efficiency is also higher.

[0050] Table 1

[0051]

[0052] The present application relates to a method for preparing a photovoltaic cell and a photovoltaic cell, the preparation method comprising: preparing a silicon substrate 1; polishing the surface of the silicon substrate 1; cleaning; placing the silicon substrate 1 in a drying tank, introducing ozone into the drying tank to prepare a first tunneling oxide layer 2; placing the silicon substrate 1 in an LPCVD chamber, introducing oxygen into the LPCVD chamber to prepare a second tunneling oxide layer 3. The surface of the silicon substrate 1 in the drying tank has water vapor, and ozone is introduced into the drying tank to form a first tunneling oxide layer 2 on the surface of the silicon substrate 1. During drying, the silicon substrate 1 is not exposed to the external environment and is less affected by the external environment, so that the cleanliness and compactness of the first tunneling oxide layer 2 are higher, and the hydrogen ions in the water on the surface of the silicon substrate 1 can increase hydrogen passivation, which is beneficial to improving the passivation effect of the first tunneling oxide layer 2.

Claims

1. A method for preparing a photovoltaic cell, characterized in that: The preparation method comprises: preparing a silicon substrate (1); Polishing the surface of the silicon substrate (1); Cleaning; Placing the silicon substrate (1) in a drying tank, and introducing ozone into the drying tank to prepare a first tunneling oxide layer (2); The silicon substrate (1) is placed in a LPCVD chamber, and oxygen is introduced into the LPCVD chamber to prepare a second tunneling oxide layer (3).

2. The method for preparing a photovoltaic cell according to claim 1, characterized in that: When ozone is introduced into the drying tank, the concentration of the ozone is 0.1 ppm to 40 ppm.

3. The method for preparing a photovoltaic cell according to claim 2, characterized in that: When ozone is introduced into the drying tank, the temperature in the drying tank is 60° C. to 100° C., and the time for introducing ozone is 360 s to 1200 s.

4. The method for preparing a photovoltaic cell according to claim 3, characterized in that: The thickness of the first tunnel oxide layer (2) is 0.5 nm to 2 nm.

5. The method for preparing a photovoltaic cell according to claim 1, characterized in that: When oxygen is introduced into the LPCVD chamber to prepare the second tunneling oxide layer (3), the flow rate of the oxygen is 1000 sccm to 40000 sccm.

6. The method for preparing a photovoltaic cell according to claim 5, characterized in that: When oxygen is introduced into the LPCVD chamber to prepare the second tunnel oxide layer (3), the temperature in the LPCVD chamber is 550° C. to 700° C., and the time for introducing oxygen is 100 s to 3000 s.

7. The method for preparing a photovoltaic cell according to claim 6, characterized in that: The sum of the thickness of the first tunnel oxide layer (2) and the thickness of the second tunnel oxide layer (3) is 1 nm to 2.5 nm.

8. A photovoltaic cell, characterized in that: The photovoltaic cell comprises a silicon substrate (1), the silicon substrate (1) comprises a first surface (11) and a second surface (12), the second surface (12) is provided with a first tunneling oxide layer (2) and a second tunneling oxide layer (3), the first tunneling oxide layer (2) and the second tunneling oxide layer (3) are prepared by the method for preparing a photovoltaic cell according to any one of claims 1 to 7.

9. The photovoltaic cell according to claim 8, characterized in that: The second surface (12) comprises a plurality of first doping regions (121) and a plurality of second doping regions (122), the first doping regions (121) and the second doping regions (122) being arranged alternately, the first tunneling oxide layer (2) and the second tunneling oxide layer (3) being located in the first doping region (121), the surface of the second tunneling oxide layer (3) being provided with a first doping layer (5), the second doping region (122) being provided with a third tunneling oxide layer (4), and the surface of the third tunneling oxide layer (4) being provided with a second doping layer (6).

10. The photovoltaic cell according to claim 8, characterized in that: The first surface (11) comprises a third doping layer (7), the second surface (12) comprises a fourth doping layer (8), and the first tunneling oxide layer (2) and the second tunneling oxide layer (3) are arranged between the fourth doping layer (8) and the silicon substrate (1).

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