Annealing method and solar cell

Abstract

The invention provides an annealing method and a solar cell. The annealing method comprises the following steps: firstly carrying out hydrotreating on a silicon wafer by adopting hydrogen, and then carrying out oxidation treatment on the silicon wafer by adopting oxygen to form a silicon oxide thin layer; wherein in the hydrogenation treatment process, the flow rate of the introduced hydrogen is 20 sccm to 1000 sccm; in the hydrogenation treatment and oxidation treatment processes, the temperature of the silicon wafer is kept at 600-800 DEG C. By adopting the annealing method to prepare the silicon oxide thin layer, the growth speed of silicon oxide is relatively high, and the time required by annealing treatment is shortened, so that the consumption of electric energy is reduced, and the production cost of the solar cell is reduced; the silicon oxide thin layer prepared by adopting the method has better compactness and lattice integrity, and the passivation effect of the surface of the silicon wafer can be improved, so that the conversion efficiency of the solar cell can be improved.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically, to annealing methods and solar cells. Background Technology

[0002] Annealing is an important process step in the current manufacturing of solar cells. Commonly used annealing processes have the following disadvantages: slow growth rate of silicon oxide thin layer, long processing time, and large power consumption, resulting in high manufacturing cost of solar cells. In addition, the low density and high defect density of silicon oxide thin layer lead to low cell conversion efficiency.

[0003] Therefore, current annealing methods and solar cells still need improvement. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] Annealing is a crucial process in solar cell manufacturing. Typically, it involves introducing nitrogen and oxygen at high temperatures of 600-1200℃. At this high temperature, silicon atoms within the silicon wafer rearrange and integrate, eliminating defects caused by the diffusion process and activating the electrochemical activity of doped atoms. A thin silicon oxide layer forms on the wafer surface through the reaction of silicon and oxygen atoms, eliminating dangling bonds in silicon atoms, reducing surface carrier recombination rates, and improving solar cell performance. Improving the quality of the silicon oxide layer on the wafer surface is essential for enhancing cell performance. Existing research primarily focuses on optimizing the properties and thickness of the silicon oxide film by adjusting process parameters such as temperature, time, and pressure.

[0006] While optimizing the properties and thickness of silicon oxide thin films by adjusting process parameters (such as temperature, time, and pressure) can improve solar cell performance to some extent, some shortcomings remain. For example, the growth rate of silicon oxide thin films is relatively slow due to the control of surface chemical reactions, generally requiring a long high-temperature reaction time. Maintaining this reaction consumes a large amount of electrical energy, increasing the manufacturing cost of solar cells. Furthermore, the properties of silicon oxide thin films, such as density and dislocation density, cannot be fundamentally improved by adjusting process parameters, thus failing to further enhance the photoelectric conversion efficiency of solar cells.

[0007] The present invention aims to at least alleviate or resolve at least one of the aforementioned problems to some extent.

[0008] In one aspect of the invention, an annealing method is provided. In some embodiments of the invention, the annealing method includes: first hydrogenating the silicon wafer with hydrogen gas, and then oxidizing the silicon wafer with oxygen gas to form a thin layer of silicon oxide; wherein, during the hydrogenation process, the flow rate of hydrogen gas is 20 sccm-1000 sccm; and during the hydrogenation and oxidation processes, the temperature of the silicon wafer is maintained at 600℃-800℃. The silicon oxide thin layer prepared by the above annealing method exhibits a relatively fast silicon oxide growth rate, which helps to shorten the annealing time, thereby reducing energy consumption and lowering the production cost of solar cells. The silicon oxide thin layer prepared by this method has good density and lattice integrity, which can improve the passivation effect of the silicon wafer surface, thus improving the conversion efficiency of solar cells. When the hydrogen flow rate is within the above range, it can react with the silicon wafer in a short time to generate a certain amount of silicon hydride, which helps to further shorten the annealing time. Maintaining the silicon wafer temperature at 600℃-800℃ is conducive to the hydrogenation and oxidation processes, thus facilitating the formation of the silicon oxide thin layer.

[0009] In some embodiments of the present invention, the hydrogen gas is introduced for 1-10 minutes during the hydrogenation process. When the hydrogen gas introduction time is within this range, the hydrogen gas can react with the silicon wafer to generate a certain amount of silicon hydride, which is beneficial for the subsequent oxidation reaction.

[0010] In some embodiments of the present invention, during the oxidation process, the oxygen flow rate is 500 sccm-3000 sccm. Thus, the oxygen reacts with silicon hydride, with oxygen atoms gradually replacing hydrogen atoms in the silicon hydride to generate silicon oxide and water molecules. The water molecules can quickly pass through the silicon oxide layer and react with silicon to generate silicon oxide. The oxygen flow rate within the aforementioned range facilitates rapid reaction, thereby further shortening the time required for the annealing process.

[0011] In some embodiments of the present invention, oxygen is introduced for 5-15 minutes during the oxidation process. This allows the oxygen to react fully with the silicon hydride, and also helps to improve the density and lattice integrity of the silicon oxide thin layer.

[0012] In some embodiments of the present invention, before introducing hydrogen gas, the silicon wafer is placed in an annealing furnace, nitrogen gas is introduced into the annealing furnace, and the furnace is heated to a temperature of 600°C-800°C. This temperature range is beneficial for hydrogenation and oxidation processes, thereby facilitating the formation of a thin silicon oxide layer.

[0013] In some embodiments of the present invention, during the heating of the silicon wafer in the annealing furnace, the flow rate of nitrogen gas introduced into the annealing furnace is 1000 sccm-10000 sccm.

[0014] In some embodiments of the present invention, the pressure in the annealing furnace is 200 mbar-1000 mbar during the heating of the silicon wafer in the annealing furnace.

[0015] In some embodiments of the present invention, when oxygen is introduced into the annealing furnace, the flow rate of nitrogen is adjusted to 500 sccm-8000 sccm.

[0016] In some embodiments of the present invention, the annealing method further includes: stopping the introduction of oxygen into the annealing furnace, continuing to introduce nitrogen into the annealing furnace, and cooling down; and removing the silicon wafer from the annealing furnace.

[0017] In another aspect, the present invention provides a solar cell. In some embodiments of the present invention, the solar cell includes a silicon wafer and a thin layer of silicon oxide on the silicon wafer, the thin layer of silicon oxide being prepared using the annealing method described above. Therefore, the thin layer of silicon oxide in this solar cell has good density and lattice integrity, the silicon wafer surface has good passivation effect, and the solar cell has high photoelectric conversion efficiency. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0019] Figure 1 A flowchart of a method for annealing a silicon wafer according to an embodiment of the present invention is shown. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In one aspect of the invention, an annealing method is provided. In some embodiments of the invention, reference is made to... Figure 1 The annealing method may include the following steps:

[0022] S100: Hydrogenation of silicon wafers is performed using hydrogen gas.

[0023] First, hydrogen is used to hydrogenate the silicon wafer, so that the hydrogen reacts with the surface of the silicon wafer to generate hydrogenated silicon.

[0024] In some embodiments of the present invention, during the hydrogenation process, the flow rate of hydrogen gas can be 20 sccm-1000 sccm. For example, the flow rate of hydrogen gas can be 20 sccm, 50 sccm, 80 sccm, 100 sccm, 120 sccm, 200 sccm, 300 sccm, 500 sccm, 800 sccm, 1000 sccm, etc. The flow rate of hydrogen gas within the above range is conducive to the rapid reaction of hydrogen gas with silicon wafer, and to the generation of a certain amount of hydrogenated silicon in a short period of time.

[0025] In some embodiments of the present invention, the hydrogen gas is introduced for 1-10 minutes during the hydrogenation process; for example, the hydrogen gas can be introduced for 1 minute, 3 minutes, 5 minutes, 8 minutes, or 10 minutes. This allows the hydrogen gas to react more fully with the silicon wafer, generating a certain amount of hydrogenated silicon.

[0026] Before annealing, the silicon wafer can be placed in an annealing furnace for subsequent operations.

[0027] In some embodiments of the present invention, silicon wafers can be loaded into the annealing furnace using an automatic transfer device. The specific type and structure of the automatic transfer device are not particularly limited in the present invention; those skilled in the art can select one according to actual circumstances and needs, as long as it can place the silicon wafers into the annealing furnace.

[0028] In some embodiments of the present invention, during the hydrogenation process, the pressure in the annealing furnace can be maintained at 200 mbar-1000 mbar, for example, the pressure can be maintained at 200 mbar, 400 mbar, 500 mbar, 700 mbar or 1000 mbar. The pressure meeting the above conditions is beneficial to the hydrogenation reaction.

[0029] In some embodiments of the present invention, during the hydrogenation process, nitrogen gas can be introduced into the annealing furnace at a flow rate of 1000 sccm to 10000 sccm, for example, 2000 sccm, 4000 sccm, 5000 sccm, 7000 sccm, or 8000 sccm. Meeting these nitrogen flow rate conditions helps maintain stable pressure, uniform temperature and gas flow distribution within the annealing furnace, allowing hydrogen to be rapidly and uniformly distributed within the diffusion furnace, thereby facilitating the rapid progress of the hydrogenation process.

[0030] In some embodiments of the present invention, nitrogen gas can be introduced into the annealing furnace before hydrogen gas is introduced into the annealing furnace to heat the silicon wafer in the annealing furnace, raising the temperature in the annealing furnace to 600°C-800°C. For example, the temperature in the annealing furnace can be raised to 600°C, 620°C, 650°C, 670°C, 700°C, 710°C, 730°C, 750°C, 780°C or 800°C by heating. When the temperature is within the above range, the subsequently introduced hydrogen gas can react rapidly with the silicon wafer to generate silicon hydride.

[0031] In some embodiments of the present invention, during the heating of the silicon wafer in the annealing furnace, the flow rate of nitrogen gas introduced into the annealing furnace can be 1000 sccm-10000 sccm, for example, the flow rate of nitrogen gas can be 2000 sccm, 3000 sccm, 5000 sccm, 8000 sccm, or 9000 sccm, and the pressure in the annealing furnace can be 200 mbar-1000 mbar, for example, the pressure in the annealing furnace can be 300 mbar, 400 mbar, 500 mbar, 700 mbar, 800 mbar, or 1000 mbar. Nitrogen gas can act as a protective gas and heat transfer substance. Under certain flow rates and pressures, it can protect the silicon wafer at high temperatures, prevent the silicon wafer from reacting with air, and improve the uniformity of temperature distribution.

[0032] In some embodiments of the present invention, the silicon wafer is placed in an annealing furnace, and then nitrogen gas can be introduced for purging. After purging, a vacuum can be drawn, the flow rate of nitrogen gas is adjusted and kept flowing, so that the pressure in the annealing furnace is maintained at 200 mbar-1000 mbar, and heating begins.

[0033] In some embodiments of the present invention, the silicon wafer may undergo pre-processing before being placed in the annealing furnace. For PERC (Passivated Emitter back contact) cells, the pre-processing may include texturing, diffusion treatment, laser doping, oxidation treatment, removal of PSG (borosilicate glass), alkaline polishing, and other steps.

[0034] S200: Oxidation treatment of silicon wafers using oxygen.

[0035] After hydrogenation of the silicon wafer, oxygen is used to oxidize the silicon wafer, so that the hydrogen atoms in the hydrogenated silicon are replaced by oxygen atoms, generating silicon oxide and water molecules. The water molecules can quickly penetrate the silicon oxide layer and react with silicon to generate silicon oxide, forming a thin silicon oxide layer.

[0036] In some embodiments of the present invention, during the oxidation process, the flow rate of oxygen introduced into the annealing furnace can be 500 sccm-3000 sccm. For example, the flow rate of oxygen can be 500 sccm, 800 sccm, 1000 sccm, 1200 sccm, 1500 sccm, 1700 sccm, 2000 sccm, 2500 sccm, 3000 sccm, etc. With a suitable flow rate, oxygen can react fully with silicon hydride in a short time to generate silicon oxide and water molecules. Water molecules can quickly pass through the silicon oxide layer and react with silicon to generate silicon oxide, which helps to further shorten the time required for annealing and thus helps to reduce production costs.

[0037] In some embodiments of the present invention, the oxygen is introduced into the annealing furnace for 5-15 minutes, for example, for 5 minutes, 6 minutes, 8 minutes, 10 minutes, 12 minutes, or 15 minutes. This allows the oxygen to react fully with silicon hydride, with oxygen atoms replacing hydrogen atoms in the silicon hydride to generate silicon oxide and water molecules. The water molecules quickly penetrate the silicon oxide layer and react with silicon to form silicon oxide, rapidly forming a thin silicon oxide layer.

[0038] In some embodiments of the present invention, when oxygen is introduced into the annealing furnace, the nitrogen flow rate can be adjusted to 500 sccm-8000 sccm. For example, the nitrogen flow rate can be adjusted to 500 sccm, 800 sccm, 1000 sccm, 3000 sccm, 5000 sccm, or 8000 sccm. A nitrogen flow rate within the above range allows oxygen to be rapidly and uniformly distributed within the annealing furnace, which is beneficial for the rapid and uniform formation of the silicon oxide film.

[0039] In some embodiments of the present invention, during the hydrogenation and oxidation processes, the temperature in the annealing furnace can be maintained in the range of 600°C-800°C. For example, the temperature in the annealing furnace can be maintained at 600°C, 630°C, 650°C, 680°C, 700°C, 720°C, 750°C, 770°C, or 800°C. This temperature is conducive to the rapid progress of the hydrogenation and oxidation reactions, and also conducive to the formation of a relatively dense silicon oxide thin layer with good lattice integrity.

[0040] In some embodiments of the present invention, the annealing method may further include the following steps: after the oxidation reaction (oxidation treatment) is completed, the oxygen pipe is shut off, the oxygen supply to the annealing furnace is stopped, and nitrogen is continued to be supplied to the annealing furnace to cool down; the silicon wafer is then removed from the annealing furnace. In some specific embodiments of the present invention, the oxygen supply to the annealing furnace is stopped, and nitrogen is continued to be supplied. The nitrogen flow rate can be 3000 sccm-20000 sccm, for example, the nitrogen flow rate can be 3000 sccm, 5000 sccm, 10000 sccm, 15000 sccm or 20000 sccm. Using nitrogen at the above flow rate for purging can lower the temperature of the silicon wafer in a shorter time, thereby further shortening the annealing time.

[0041] In some specific embodiments of the present invention, after the oxidation reaction is completed, the oxygen pipeline is shut off, the oxygen supply is stopped, heating is stopped, the nitrogen flow rate is increased, and cooling begins. After sufficient cooling, the silicon wafer is removed from the annealing furnace. Specifically: once the temperature of the silicon wafer inside the annealing furnace drops below 600°C, the furnace door is opened, and the silicon wafer is removed from the annealing furnace. After the annealing process is completed, subsequent process steps can be performed.

[0042] In some embodiments of the present invention, for PERC cells, after completing the above-described annealing process and forming a thin silicon oxide layer on the silicon wafer, the following process flow can also be performed: back passivation → back coating → front coating → screen printing → sintering. After sintering, the PERC cells can be tested and sorted. It should be noted that this specification uses PERC cells as an example, but the annealing method described is equally applicable to the production of any other cells that require an oxygen-based high-temperature annealing process.

[0043] The above method is used to anneal silicon wafers. First, the introduced hydrogen gas reacts chemically with the silicon wafer surface at high temperature to form silicon hydride. Subsequently, the introduced oxygen gas reacts with the silicon hydride at high temperature, with oxygen atoms gradually replacing hydrogen atoms to form silicon oxide and water molecules. The diffusion activation energy of water molecules in the silicon oxide film is approximately 0.79 eV, while that of oxygen atoms is approximately 1.18 eV. Compared to oxygen atoms, water molecules have a higher diffusion coefficient in silicon oxide, enabling them to quickly penetrate the silicon oxide thin layer and react with silicon atoms to form silicon oxide and hydrogen gas. The hydrogen gas then dissipates from the silicon oxide-silicon interface. Under the same temperature conditions, the reaction rate of water molecules with silicon is faster than that of oxygen with silicon, resulting in rapid growth of the silicon oxide thin layer. Because of the faster growth rate of the silicon oxide thin layer, the time required to reach the desired thickness is shortened, thereby reducing energy consumption and lowering the production cost of the battery.

[0044] Furthermore, some of the hydrogen atoms released from the silicon oxide-silicon interface will enter the silicon oxide thin layer. Since the silicon oxide thin layer formed by thermal oxidation of silicon is amorphous and contains numerous lattice defects and pores, the hydrogen atoms entering the silicon oxide thin layer can repair these lattice defects, reduce defect density, and thus improve the density and lattice integrity of the silicon oxide thin layer. This improved performance of the silicon oxide thin layer can reduce recombination, enhance the passivation effect on the silicon wafer surface, and ultimately increase the conversion efficiency of the battery.

[0045] In another aspect, the present invention proposes a solar cell. In some embodiments of the present invention, the solar cell may include a silicon wafer and a thin silicon oxide layer on the silicon wafer, the thin silicon oxide layer being prepared using the annealing method described above. Processing the silicon wafer using the annealing method described above can rapidly generate a thin silicon oxide layer, and the thin silicon oxide layer has good density and lattice integrity, which can improve the passivation effect on the silicon wafer surface, thereby improving the conversion efficiency of the solar cell.

[0046] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0047] Comparative example:

[0048] The silicon wafers undergo texturing, diffusion treatment, laser doping, oxidation treatment, PSG removal treatment, and alkaline polishing treatment.

[0049] After the silicon wafers have completed the previous process steps, they are loaded into the annealing furnace through an automatic transfer device, and then nitrogen gas is introduced for purging. After purging, a vacuum is drawn, the nitrogen flow rate is adjusted and kept flowing, and the pressure in the annealing furnace is maintained at 400 mbar during the process. Heating is then started.

[0050] A1. Continuously introduce nitrogen gas at a flow rate of 5000 sccm; wait for the silicon wafer temperature inside the annealing furnace to rise to 780℃;

[0051] A2. Maintain the silicon wafer temperature at 780℃, adjust the nitrogen flow rate to 1000 sccm, and introduce oxygen at a flow rate of 5000 sccm for 23 minutes.

[0052] A3. Close the oxygen pipeline, adjust the nitrogen flow rate to 5000 sccm, turn off the heating, and begin cooling;

[0053] A4. Once the temperature of the silicon wafers inside the annealing furnace drops below 600℃, open the furnace door and remove the silicon wafers from the annealing furnace.

[0054] The subsequent process steps are then carried out to obtain the PERC battery. The subsequent process steps are as follows: back passivation → back coating → front coating → screen printing → sintering.

[0055] Example:

[0056] The silicon wafers undergo texturing, diffusion treatment, laser doping, oxidation treatment, PSG removal treatment, and alkaline polishing treatment.

[0057] After the silicon wafers have completed the previous process steps, they are loaded into the annealing furnace through an automatic transfer device. Then, nitrogen gas is introduced for purging. After purging, a vacuum is drawn, the flow rate of nitrogen is adjusted and kept flowing, and the pressure inside the annealing furnace is maintained at 400 mbar during the process. Heating is then started.

[0058] B1. Continuously introduce nitrogen gas at a flow rate of 5000 sccm until the temperature of the silicon wafer in the annealing furnace rises to 680℃;

[0059] B2. Maintain the silicon wafer temperature at 680℃, and keep the nitrogen flow rate at 5000 sccm; and introduce hydrogen gas at a flow rate of 100 sccm for 3 minutes.

[0060] B3. Maintain the silicon wafer temperature at 680℃, shut off the hydrogen pipeline, adjust the nitrogen flow rate to 1000 sccm, and introduce oxygen at a flow rate of 1000 sccm for 13 minutes.

[0061] B4. Close the oxygen pipeline, adjust the nitrogen flow rate to 5000 sccm, turn off the heating, and begin cooling;

[0062] B5. Once the temperature of the silicon wafers inside the annealing furnace drops below 600°C, open the furnace door and remove the silicon wafers from the annealing furnace.

[0063] The subsequent process steps are then carried out to obtain the PERC battery. The subsequent process steps are as follows: back passivation → back coating → front coating → screen printing → sintering.

[0064] The performance of the silicon oxide thin films obtained by annealing in the examples and comparative examples, the annealing process time, and the performance parameters of the solar cells are recorded in Table 1.

[0065] Table 1

[0066]

[0067] It should be noted that the annealing process time includes the time for nitrogen purging, vacuuming, heating the silicon wafer, hydrogenation, oxidation, and cooling. Jsc is the short-circuit current, Voc is the open-circuit voltage, FF is the fill factor, and Eta is the cell conversion efficiency.

[0068] Compared to the comparative example, the annealing process proposed in this invention is used to anneal the silicon wafers in this embodiment. This accelerates the growth rate of the silicon oxide thin layer, shortens the process time by 10 minutes, reduces the process temperature by 100°C, and lowers the energy consumption throughout the annealing process, thereby reducing production costs. Furthermore, the annealing process proposed in this invention reduces the pore concentration in the resulting silicon oxide thin layer, increases film density, and improves the performance of the silicon oxide thin layer. This enhances the passivation effect on the silicon wafer surface, reduces recombination, and improves the open-circuit voltage and fill factor of the battery, ultimately increasing the battery's conversion efficiency.

[0069] In the description of this specification, references to terms such as "one embodiment," "some embodiments," and "some specific embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An annealing method, characterized in that, include: First, hydrogen is used to hydrogenate the silicon wafer, and then oxygen is used to oxidize the silicon wafer to form a thin layer of silicon oxide. During the hydrogenation process, the flow rate of hydrogen gas is 20 sccm-1000 sccm; during the hydrogenation and oxidation processes, the temperature of the silicon wafer is maintained at 600℃-800℃.

2. The annealing method according to claim 1, characterized in that, During the hydrogenation process, hydrogen gas is introduced for 1-10 minutes.

3. The annealing method according to claim 1, characterized in that, During the oxidation process, the oxygen flow rate is 500 sccm-3000 sccm.

4. The annealing method according to claim 1, characterized in that, During the oxidation process, oxygen is introduced for 5-15 minutes.

5. The annealing method according to any one of claims 1-4, characterized in that, Before introducing hydrogen, the silicon wafer is placed in an annealing furnace, nitrogen is introduced into the annealing furnace, and the furnace is heated to raise the temperature to 600℃-800℃.

6. The annealing method according to claim 5, characterized in that, During the heating of the silicon wafer in the annealing furnace, the flow rate of nitrogen gas introduced into the annealing furnace is 1000 sccm-10000 sccm.

7. The annealing method according to claim 6, characterized in that, During the heating of the silicon wafer in the annealing furnace, the pressure in the annealing furnace is 200mbar-1000mbar.

8. The annealing method according to claim 6 or 7, characterized in that, When oxygen is introduced into the annealing furnace, the flow rate of nitrogen is adjusted to 500 sccm-8000 sccm.

9. The annealing method according to claim 5, characterized in that, The annealing method further includes: stopping the introduction of oxygen into the annealing furnace, continuing to introduce nitrogen into the annealing furnace, and cooling down; The silicon wafer is removed from the annealing furnace.

10. A solar cell, characterized in that, The solar cell includes a silicon wafer and a thin layer of silicon oxide on the silicon wafer, the thin layer of silicon oxide being prepared by the annealing method according to any one of claims 1-9.

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