Method for preparing silicon heterojunction solar cell and solar cell thereof

Abstract

An embodiment of the present invention provides a method for preparing a silicon heterojunction solar cell, comprising: providing a silicon wafer into a reactor chamber; providing a first gas containing oxygen into the reactor chamber, for attaching the first oxygen-containing gas molecules to the inner wall of the reactor chamber; evacuating the reactor chamber to a pressure less than 0.1 Pa; providing a second gas containing silicon and hydrogen into the reactor chamber; and sequentially depositing a silicon compound containing hydrogen and oxygen onto the surface of the silicon wafer and then depositing a compound containing hydrogen and silicon onto the surface of the silicon wafer to form a passivation film layer with a gradient decreasing oxygen content, thereby forming a passivation film layer on the silicon heterojunction solar cell, in which the oxygen content gradually decreases from a side close to the silicon wafer surface to a side away from the silicon wafer surface, so that the oxygen content in the passivation film layer is distributed in a gradient, so that the battery performance is optimized, and the photoelectric conversion efficiency and stability of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a silicon heterojunction solar cell and a solar cell thereof. Background Art

[0002] Traditional crystalline silicon and amorphous silicon solar cells have the advantages of simple process and low manufacturing cost, making them the mainstream solar cells. However, due to the defects of low conversion efficiency and the continuous decline of conversion efficiency with the illumination time, the application of crystalline silicon and amorphous silicon solar cells is limited. Amorphous silicon / crystalline silicon heterojunction solar cells overcome the defects of crystalline silicon and amorphous silicon solar cells. With its advantages of lower preparation process temperature, higher photoelectric conversion efficiency, excellent high temperature / weak light power generation and lower attenuation, it has become an important development direction of the current photovoltaic industry. With the rapid development of solar cell technology, its performance has shown a qualitative change, especially the conversion efficiency has increased year by year, and the efficiency of silicon heterojunction cells is far ahead.

[0003] Silicon heterojunction solar cells are composed of multiple film layers and have multiple heterogeneous material interfaces. Among them, in the preparation process of silicon heterojunction solar cells, the passivation of the interface between amorphous silicon and single crystal silicon (a-Si:H / c-Si) has become one of the core technologies of silicon heterojunction solar cells. Passivation treatment can treat surface defects such as dangling bonds on the surface of silicon wafers, reduce surface activity, and thus reduce the rate of minority carrier surface recombination to obtain a longer minority carrier lifetime and enhance the performance of silicon heterojunction solar cells. The processes for improving the passivation effect of the a-Si:H / c-Si interface include increasing the dissociation degree of silane, reducing the deposition temperature of the intrinsic layer, or depositing a high-quality passivation film layer in the amorphous silicon to microcrystalline silicon conversion zone. However, the current process window for improving the passivation of the a-Si:H / c-Si interface is relatively narrow, and there are problems such as complex processes or difficulty in stable control. Therefore, how to use an easy-to-implement and easy-to-control method to improve the passivation effect of the a-Si:H / c-Si interface is a technical problem that needs to be solved in this field. Summary of the invention

[0004] In order to solve the problem in the prior art that the minority carrier recombination rate at the interface of the passivation film layer is high and the stability of the passivation film layer is poor, which affects the performance of silicon heterojunction solar cells, the purpose of the present invention is to provide a silicon heterojunction solar cell and a preparation method thereof. The specific technical solution is as follows:

[0005] In one aspect, a method for preparing a silicon heterojunction solar cell is provided, comprising:

[0006] providing a silicon wafer into a reactor chamber;

[0007] Providing a first gas containing oxygen into the reactor chamber to attach the first gas molecules containing oxygen to the inner wall of the reactor chamber;

[0008] The reactor chamber is evacuated to a pressure less than 0.1 Pa;

[0009] providing a second gas comprising silicon and hydrogen into the reactor chamber;

[0010] And, the groups containing hydroxyl or oxygen-containing groups and hydrogen-containing groups are deposited in sequence, and then the groups containing hydrogen are further deposited, so as to form a passivation film layer on the surface of the silicon wafer, in which the oxygen content gradually decreases from the side close to the silicon wafer to the side away from the silicon wafer.

[0011] Optionally, the gas pressure of the first gas containing oxygen provided to the reactor chamber is less than 200 Pa.

[0012] Optionally, the second gas containing silicon and hydrogen is provided to the reactor chamber at a pressure of 20Pa-100Pa.

[0013] Optionally, the first oxygen-containing gas is at least one of H2O, NO, and NO2.

[0014] Optionally, the second gas of silicon and hydrogen includes a mixed gas of SiH4 and H2, or a mixed gas of Si2H6 and H2.

[0015] Optionally, in the second gas containing silicon and hydrogen, the mass ratio of the silicon to the mass ratio of the second gas is 3% to 8%.

[0016] Optionally, before providing the first gas containing oxygen to the reactor chamber, the gas pressure of the reactor chamber is less than 0.1 Pa.

[0017] Optionally, before providing the first gas containing oxygen to the reactor chamber, hydrogen is first filled into the reactor chamber, and then the reactor chamber is evacuated to a pressure of less than 0.1 Pa.

[0018] This technical solution cleverly utilizes the fact that it is extremely difficult to completely remove water vapor in a vacuum chamber, and controllably utilizes the vacuum after water vapor is passed into the reactor chamber to remove the water molecules suspended in the reactor chamber, while retaining the characteristic of water molecules attached to the inner wall of the reactor; and then through the PECVD deposition reaction, the first gas containing oxygen and the second gas containing silicon and hydrogen form SiO on the surface of the battery. x :H deposits, and as the oxygen-containing first gas in the reactor is consumed, the SiO generated by the reaction x :H deposits gradually decrease, thus forming a SiO2-containing layer from the side close to the silicon wafer to the side away from the silicon wafer.x :The passivation film layer with a reduced H substance gradient is beneficial to improving the passivation effect on the silicon wafer surface and increasing the short-circuit current density of the battery.

[0019] On the other hand, a silicon heterojunction solar cell prepared according to the above preparation method includes a passivation film layer, wherein the oxygen content in the passivation film layer decreases gradually from a side close to the silicon wafer to a side away from the silicon wafer, and the mass content of oxygen on the side close to the silicon wafer is less than 1%.

[0020] Optionally, the silicon heterojunction solar cell comprises:

[0021] Sequentially forming the passivation layer, the N-type amorphous silicon layer, the front transparent conductive layer, and the front metal electrode on the front transparent conductive layer on the front side of the silicon wafer;

[0022] The passivation layer, the P-type amorphous silicon layer, the back transparent conductive layer and the back metal electrode on the back transparent conductive layer are sequentially formed on the back side of the silicon wafer.

[0023] SiO is formed on the surface of the cell by using a first gas containing oxygen and a second gas containing silicon and hydrogen. x :H deposits are deposited on the silicon heterojunction solar cell to form a passivation film layer with a gradient decrease in oxygen content from the side close to the silicon wafer surface to the side away from the silicon wafer surface, so that the oxygen content in the passivation film layer is distributed in a gradient manner, which not only ensures that the silicon interface on the silicon wafer is passivated by SiOx:H, but also realizes a transition layer with a gradually reduced oxygen content, thereby optimizing the battery performance and improving the battery's photoelectric conversion efficiency and battery stability.

[0024] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0026] Figure 1 This is a flow chart of a method for preparing a silicon heterojunction solar cell according to a first embodiment of the present invention;

[0027] Figure 2 It is a structural diagram of a silicon heterojunction solar cell according to an embodiment of the present invention.

[0028] 1-Silicon heterojunction solar cells, 2-SiOx :H deposition, 3-silicon wafer, 4-passivation film layer, 5-N-type amorphous silicon, 6-P-type amorphous silicon, 7-transparent conductive layer, 8-electrode DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0032] In some embodiments, a method for preparing a silicon heterojunction solar cell is provided, such as Figure 1 As shown, the specific steps include:

[0033] S1 provides a silicon wafer into a reactor chamber;

[0034] S2 provides a first gas containing oxygen into the reactor chamber, so as to attach the first gas molecules containing oxygen to the inner wall of the reactor chamber;

[0035] S3 evacuates the reactor chamber to a pressure less than 0.1 Pa;

[0036] S4 provides a second gas containing silicon and hydrogen into the reactor chamber;

[0037] S5 sequentially deposits groups containing hydroxyl groups, or oxygen-containing groups and hydrogen-containing groups, and then continues to deposit hydrogen-containing groups, thereby forming a passivation film layer on the surface of the silicon wafer with an oxygen content gradually decreasing from a side close to the silicon wafer to a side away from the silicon wafer.

[0038] In step S1, the silicon wafer is an N-type double-sided polished silicon wafer or a P-type double-sided polished silicon wafer, with a thickness of less than 150 μm, and optionally, a thickness of less than 90 μm; and a resistivity of less than 7 Ω·cm; the silicon wafer is subjected to the following processing steps before entering the chamber, including:

[0039] (1) Silicon wafer cleaning: The standard RCA process is used to clean the silicon wafer. The specific steps are as follows:

[0040] 1) The silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol in sequence for 10 to 15 minutes to remove organic matter on the surface of the silicon wafer.

[0041] 2) Place in RCAI (NH4OH:H2O2:H2O=(1~3):(1~3):(3~8)) solution and place in a 70℃ water bath for 8~15min to remove organic impurities, metal ions and particle contamination.

[0042] 3) Rinse in 3% to 8% HF for 1 to 5 minutes to remove the surface oxide layer formed by the RCAI solution.

[0043] 4) Place in RCAII (NH4OH:H2O2:H2O=(1~3):(1~3):(3~8)) solution in a 70℃ water bath to remove metal ions Al, Fe, Ni, and Na.

[0044] 5) Rinse in 1% to 3% HF for 1 to 5 minutes to remove the surface oxide layer formed by the RCAI solution.

[0045] (2) Dry the silicon wafer with nitrogen and place it in a spare reactor chamber for deposition coating.

[0046] Furthermore, in step S5, the deposition is performed by plasma enhanced chemical vapor deposition (PECVD). In addition, physical vapor deposition (PVD) can also be selected. The principle of PECVD film formation is as follows:

[0047] (1) Under vacuum, electrons gain energy in a high-frequency electric field and collide with a first gas containing oxygen and a second gas containing silicon and hydrogen, causing the gases to be excited and decomposed to form plasma, generating various thin film growth groups.

[0048] (2) During the glow discharge process, chemical reactions further occur between the groups, and the groups that finally reach the surface of the silicon wafer are mainly SiH, SiH2, SiH3, O, OH, and H groups.

[0049] (3) After the radicals reach the surface of the silicon wafer, a series of changes occur, mainly including adsorption, reaction, diffusion, and detachment. The adsorbed radicals migrate on the surface of the silicon wafer and find a stable position to achieve the growth of the film, generating a SiO x :H(x=0~2) deposition film.

[0050] During the deposition of the passivation film in the reactor chamber, the chamber must be cleaned before the chamber is turned on. However, since it is difficult to remove impurities by vacuuming the gas, there will always be some residual gas. The present technical solution cleverly utilizes the fact that it is extremely difficult to completely remove impurities from the reactor cavity. The first oxygen-containing gas is introduced into the reactor chamber to dilute the impurities and then empty the chamber. In other words, the first oxygen-containing gas is passed into the reactor chamber and then vacuumed to fully mix the impurity gas with the first oxygen-containing gas, dilute the impurity gas concentration, and then remove the first oxygen-containing gas and impurity gas suspended in the reactor chamber. The inner wall of the reactor remains in the reactor chamber due to the adsorption effect of the first oxygen-containing gas attached to the inner wall of the reactor. Then, through the PECVD deposition reaction, the first oxygen-containing gas and the second silicon-containing gas are activated, and radicals are formed during the deposition reaction, and deposited on the surface of the silicon wafer, finally forming SiO x :H deposits, and as the oxygen-containing first gas in the reactor is consumed, the SiO generated by the reaction x :H deposits gradually decrease, thereby forming a layer containing SiO from the side close to the silicon wafer to the side away from the silicon wafer. x :The passivation film layer with a reduced H substance gradient is beneficial to improving the passivation effect on the silicon wafer surface and increasing the short-circuit current density of the battery.

[0051] In some embodiments, the first gas containing oxygen is provided to the reactor chamber at a pressure of less than 200 Pa. Specifically, the first gas is provided to the reactor chamber and maintained for 10s to 60s, and then the reactor chamber is evacuated to reduce the pressure of the reactor chamber to below 0.1Pa, and then a second gas containing silicon and hydrogen is provided to the reactor chamber; and a deposit containing hydrogen and oxygen is deposited on the surface of the silicon wafer in sequence, and then a deposit containing hydrogen and silicon is deposited on the surface of the silicon wafer to form a passivation film layer with a gradient of decreasing oxygen content. During the deposition reaction, the first gas and the second gas are subjected to plasma vapor deposition, so that the first gas and the second gas provided undergo a decomposition reaction to decompose to generate SiH, SiH2, SiH3, O, OH, and H groups, and then these groups are deposited on the surface of the silicon wafer, and SiO x :H (x = 0 ~ 2) deposits, and finally form a passivation film containing oxygen atoms. Because the first gas and the second gas provided are decomposed and deposited on the surface of the silicon wafer at the same time during the deposition reaction, therefore, in the early stage of the formation of the passivation film, the oxygen atom content in the part of the passivation film that contacts the silicon wafer surface is relatively high, thereby generating SiO on the silicon wafer surface. x :H (x = 0 ~ 2) deposits, as the oxygen atoms in the reactor chamber gradually decrease, the content of oxygen atoms in the passivation film gradually decreases during the subsequent deposition process, so that in the passivation film away from the silicon wafer surface, the main components of the passivation film are SiH, SiH2, SiH3 compounds, and finally in the passivation film, the oxygen content shows a gradient decrease from close to the silicon wafer surface to far away from the silicon wafer surface. Because SiO appears at the silicon interface on the silicon wafer x :H deposits effectively passivate the surface of the silicon wafer and realize a transition layer with a gradually reduced oxygen content, which optimizes the battery performance and improves the battery's photoelectric conversion efficiency and battery stability.

[0052] In some embodiments, after providing the first gas containing oxygen to the reactor chamber, the gas pressure of the reactor chamber is 20-100 Pa. Specifically, because the vacuum degree in the reactor deposition chamber can affect the collision probability between reactive groups and their residence time in the chamber, the gas pressure of the reactor chamber is higher than 100 Pa, which is easy to form (SiH2) in the passivation film layer. n Polymers greatly reduce the quality of amorphous silicon thin films and are not conducive to the uniformity of the passivation film layer.

[0053] In some embodiments, the oxygen-containing first gas is H2O, NO, or NO2. Optionally, the first gas is H2O. Specifically, during the deposition reaction in the reactor chamber, the H, O, and OH groups in the first gas react with the silicon wafer to generate SiO x :H (x = 0 ~ 2) sediments, eventually forming SiO x :H (x = 0 ~ 2) passivation film, and as the first gas containing oxygen in the reactor is consumed, the SiO generated by the reaction x :H deposits gradually decrease, thus forming a SiO2-containing layer from the side close to the silicon wafer to the side away from the silicon wafer. x :H The passivation film layer with a reduced deposition gradient is beneficial to improving the passivation effect on the silicon wafer surface and increasing the short-circuit current density of the battery.

[0054] In some embodiments, the second gas of silicon and hydrogen includes SiH4 or Si2H6, or a mixed gas of SiH4 and H2, or a mixed gas of Si2H6 and H2. The pressure of the second gas of silicon and hydrogen in the reactor chamber is 10 to 200 Pa. Optionally, the silicon in the second gas containing silicon and hydrogen accounts for 3% to 8% of the mass of the second gas. During the PECVD vapor deposition process, by controlling the silicon in the second gas containing silicon and hydrogen to account for 3% to 8% of the mass of the second gas, the crystallization of the thin film due to low SiH4 deposition is avoided, and the epitaxial growth of the passivation film layer is reduced. At the same time, the SiH4 deposition exceeding 8% will cause the thin film deposition rate to be too large, making it difficult to control the deposition process of the passivation film layer, reducing the quality of the passivation film layer, and affecting the battery efficiency.

[0055] In some embodiments, before the first gas containing oxygen is provided to the reactor chamber, the gas pressure of the reactor chamber is less than 0.1 Pa. In some embodiments, before the first gas containing oxygen is provided to the reactor chamber, hydrogen gas is firstly filled into the reactor chamber, and then the reactor chamber is evacuated to a gas pressure of less than 0.1 Pa. By filling hydrogen gas before providing the first gas containing oxygen to the reactor chamber, impurity gases in the reactor chamber can be discharged, effectively reducing the influence of impurities in the reactor chamber on deposition and film formation.

[0056] In some embodiments, after the first gas containing oxygen is provided, the reactor chamber is evacuated to make the vacuum degree of the reactor chamber less than 0.1 Pa. Specifically, the vacuum degree of the reactor chamber is made less than 0.1 Pa, and the first gas containing oxygen suspended in the chamber is discharged from the reactor chamber, and after evacuation, the first gas adsorbed on the inner wall of the reactor chamber is retained, and this part of the adsorbed first gas and the provided second gas containing silicon and hydrogen are plasma vapor deposited on the surface of the silicon wafer, thereby forming a gradient doping of oxygen atoms in the passivation film layer on the surface of the silicon wafer, reducing the defects of the passivation film layer, and improving the light transmittance of the passivation film.

[0057] In some embodiments, a silicon heterojunction solar cell is provided, such as Figure 2 As shown, the silicon heterojunction solar cell 1 includes a passivation film layer 4, wherein SiO x The content of H deposit 2 decreases gradually from the side close to silicon wafer 3 to the side far from silicon wafer 3, and the mass content of oxygen on the side close to silicon wafer 3 is less than 1%.

[0058] In some embodiments, a silicon heterojunction solar cell is provided, such as Figure 2 As shown, a silicon heterojunction solar cell 1 includes a passivation layer 4, an N-type amorphous silicon layer 5, a front transparent conductive layer 7, and a front metal electrode 8 on the front transparent conductive layer 7, which are sequentially formed on the front side of a silicon wafer 3; and a passivation layer 4, a P-type amorphous silicon layer 6, a back transparent conductive layer 7, and a back metal electrode 8 on the back transparent conductive layer 7, which are sequentially formed on the back side of the silicon wafer 3. Among them, the SiO x The content of H deposit 2 decreases gradually from the side close to silicon wafer 3 to the side far from silicon wafer 3, and the mass content of oxygen on the side close to silicon wafer 3 is less than 1%.

[0059] SiO is formed on the surface of the cell by using a first gas containing oxygen and a second gas containing silicon and hydrogen. x :H deposits are deposited on the silicon heterojunction solar cell to form a passivation film layer with a gradient decreasing oxygen content from the side close to the silicon wafer surface to the side away from the silicon wafer surface, so that the oxygen content in the passivation film layer is distributed in a gradient decreasing manner, which not only ensures that the silicon interface on the silicon wafer is passivated by SiOx:H, but also realizes a transition layer with a gradually decreasing oxygen content, thereby optimizing the battery performance and improving the battery's photoelectric conversion efficiency and battery stability.

[0060] Example 1

[0061] S1 provides an N-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 150μm. After silicon wafer cleaning (using a standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 10 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (the silicon wafer is placed in a RCAI (NH4OH:H2O2:H2O=1:1:3) solution and bathed in 70°C water for 8 minutes) to remove organic impurities, metal ions and particle contamination, rinsed in 3% HF for 1 minute to remove the surface oxide layer formed by the RCAI solution, placed in a RCAIINH4OH:H2O2:H2O=(1:1:3) solution and bathed in 70°C water to remove metal ions Al, Fe, Ni, and Na, rinsed in 1% HF for 1 minute to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to a reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0062] S2 provides H2O (gaseous) into the reactor chamber, the pressure of H2O in the reactor chamber is 20Pa, the H2O pressure is maintained for 10s, so that H2O molecules adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0063] S3 provides a mixed gas of SiH4 and H2 into the reactor chamber and maintains the pressure of the reactor chamber at 50 Pa, wherein the mass concentration of silicon is 3%.

[0064] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and H2O attached to the wall of the reactor chamber. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0~2) on the surface of the silicon wafer. As the H2O molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0065] Example 2

[0066] S1 provides a P-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 90μm. After silicon wafer cleaning (using the standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 15 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (placed in a solution of RCAI (NH4OH:H2O2:H2O=1:2:5) in a 70°C water bath for 8 minutes) to remove organic impurities, metal ions and particle contamination, rinsed in 3% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, placed in a RCAII solution of NH4OH:H2O2:H2O=(1:3:8) in a 70°C water bath to remove metal ions Al, Fe, Ni, and Na, rinsed in 3% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to a reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0067] S2 provides H2O (gaseous) into the reactor chamber, the pressure of H2O in the reactor chamber is 200Pa, and the H2O pressure is maintained for 60s to allow H2O molecules to adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0068] S3 provides a mixed gas of Si2H6 and H2 into the reactor chamber and maintains the pressure of the reactor chamber at 50 Pa, wherein the mass concentration of silicon is 8%.

[0069] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and H2O attached to the wall of the reactor chamber. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0~2) on the surface of the silicon wafer. As the H2O molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0070] Example 3

[0071] S1 provides an N-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 150μm. After silicon wafer cleaning (using the standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 15 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (placed in a RCAI (NH4OH:H2O2:H2O=3:1:3) solution, 70℃ water bath for 8 minutes) to remove organic impurities, metal ions and particle contamination, rinsed in 1% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, placed in RCAII NH4OH:H2O2:H2O=(3:3:8) solution, 70℃ water bath to remove metal ions Al, Fe, Ni, Na, rinsed in 3% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to the reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0072] S2 provides H2O (gaseous) into the reactor chamber, the pressure of H2O in the reactor chamber is 50Pa, and the H2O pressure is maintained for 30s to allow H2O molecules to adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0073] S3 provides a mixed gas of SiH4 and H2 into the reactor chamber and maintains the pressure of the reactor chamber at 50 Pa, wherein the mass concentration of silicon is 5%.

[0074] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and H2O attached to the wall of the reactor chamber. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0~2) on the surface of the silicon wafer. As the H2O molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0075] Example 4

[0076] S1 provides a P-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 90μm. After silicon wafer cleaning (using the standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 13 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (placed in a RCAI (NH4OH:H2O2:H2O=3:1:3) solution, 70℃ water bath for 8 minutes), organic impurities, metal ions and particle contamination are removed, rinsed in 1% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, placed in RCAII NH4OH:H2O2:H2O=(3:3:8) solution, 70℃ water bath, remove metal ions Al, Fe, Ni, Na, rinsed in 3% HF for 3 minutes to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to the reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0077] S2 provides H2O (gaseous) into the reactor chamber, the pressure of H2O in the reactor chamber is 100Pa, and the H2O pressure is maintained for 30s to allow H2O molecules to adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0078] S3 provides a mixed gas of SiH4 and H2 into the reactor chamber and maintains the pressure of the reactor chamber at 10 Pa, wherein the mass concentration of silicon is 3%.

[0079] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and H2O attached to the wall of the reactor chamber. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0~2) on the surface of the silicon wafer. As the H2O molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0080] Example 5

[0081] S1 provides an N-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 150μm. After silicon wafer cleaning (using the standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 13 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (placed in a solution of RCAI (NH4OH:H2O2:H2O=3:1:3) and water bathed at 70℃ for 8min), organic impurities, metal ions and particle contamination are removed, rinsed in 1% HF for 5min to remove the surface oxide layer formed by the RCAI solution, placed in a RCAII solution of NH4OH:H2O2:H2O=(3:3:8), water bathed at 70℃ to remove metal ions Al, Fe, Ni, and Na, rinsed in 3% HF for 3min to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to a reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0082] S2 provides NO (gaseous state) into the reactor chamber, and the NO pressure in the reactor chamber is 20Pa. The NO pressure is maintained for 30s to allow NO molecules to adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0083] S3 provides a mixed gas of Si2H6 and H2 into the reactor chamber and maintains the pressure of the reactor chamber at 10 Pa, wherein the proportion of Si in the reactor chamber is maintained at 3%.

[0084] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and NO attached to the reactor chamber wall. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0-2) on the surface of the silicon wafer. As the NO molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0085] Example 6

[0086] S1 provides an N-type polished silicon wafer with a length and width of 158mm*158mm and a thickness of 150μm. After silicon wafer cleaning (using the standard RCA process to clean the silicon wafer, the silicon wafer is ultrasonically cleaned with deionized water, acetone, and alcohol for 14 minutes in sequence to remove organic matter on the surface of the silicon wafer), impurity removal (placed in a RCAI (NH4OH:H2O2:H2O=3:1:3) solution, 70℃ water bath for 8 minutes), organic impurities, metal ions and particle contamination are removed, rinsed in 1% HF for 5 minutes to remove the surface oxide layer formed by the RCAI solution, placed in RCAII NH4OH:H2O2:H2O=(3:3:8) solution, 70℃ water bath, remove metal ions Al, Fe, Ni, Na, rinsed in 3% HF for 2 minutes to remove the surface oxide layer formed by the RCAI solution, and after drying with nitrogen, transferred to the reactor chamber, the vacuum degree of the reactor chamber is 0.1Pa.

[0087] S2 provides NO2 (gaseous) into the reactor chamber, and the NO2 pressure in the reactor chamber is 20Pa. The NO2 pressure is maintained for 30s to allow NO2 molecules to adhere to the inner wall of the reactor chamber, and then the reactor chamber is evacuated to reduce the gas pressure to 0.1Pa.

[0088] S3 provides SiH 4 into the reactor chamber and maintains the SiH 4 pressure in the reactor chamber at 50 Pa, wherein the proportion of Si in the reactor chamber is maintained at 5%.

[0089] S4 uses the power supply of the PECVD system to perform plasma vapor deposition on SiH4 and N2O attached to the wall of the reactor chamber. The deposition time is 60s. During the plasma vapor deposition process, SiH, SiH2, SiH3, O, OH, and H groups are first decomposed and then deposited on the surface of the silicon wafer, forming a deposit film containing SiOx:H (x=0~2) on the surface of the silicon wafer. As the NO2 molecules are gradually consumed, a passivation film layer with a gradient concentration of oxygen atoms will be formed. See Table 1 for specific electrical performance tests.

[0090] Comparative Example 1

[0091] S1 provides a silicon wafer with a length and width of 158mm*158mm and a thickness of 150μm into the reactor chamber. The vacuum degree of the reactor chamber is 0.1Pa.

[0092] S2 provides SiH4 into the reactor chamber, the pressure of the reactor chamber is 50 Pa, wherein the proportion of Si in the reactor chamber is maintained at 10%.

[0093] S3 uses a PECVD system to perform a plasma vapor deposition reaction to form SiH, SiH2, and SiH3 deposits on the surface of the silicon wafer for 60 seconds to form a passivation film layer. The specific electrical performance test is shown in Table 1.

[0094] Comparative Example 2

[0095] S1 provides a silicon wafer with a length and width of 158mm*158mm and a thickness of 90μm into the reactor chamber. The vacuum degree of the reactor chamber is 0.05Pa.

[0096] S2 provides SiH4 and H2 into the reactor chamber, the pressure of the reactor chamber is 100 Pa, wherein the proportion of Si in the reactor chamber is maintained at 2%.

[0097] S3 uses a PECVD system to perform a plasma vapor deposition reaction to form SiH, SiH2, and SiH3 deposits on the surface of the silicon wafer to form a passivation film layer. The specific electrical performance test is shown in Table 1.

[0098] Table 1 (Irradiance: 1000w / m 2 )

[0099]

[0100] By utilizing the first gas containing oxygen to be deposited onto the surface of the silicon wafer, a passivation film layer is formed on the silicon heterojunction solar cell, in which the oxygen content gradually decreases from the side close to the silicon wafer surface to the side away from the silicon wafer surface, as shown in Table 1, so that the oxygen content in the passivation film layer is distributed in a gradient, which not only ensures that the SiOx:H passivation is achieved at the silicon interface on the silicon wafer, but also realizes a transition layer with gradually reduced oxygen content, so that the battery performance is optimized, and the photoelectric conversion efficiency and stability of the battery are improved.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon heterojunction solar cell, characterized in that: include: providing a silicon wafer into a reactor chamber; Providing a first gas containing oxygen into the reactor chamber to attach the first gas molecules containing oxygen to the inner wall of the reactor chamber; The reactor chamber is evacuated to a pressure less than 0.1 Pa; providing a second gas comprising silicon and hydrogen into the reactor chamber; And, sequentially decomposing the first gas and the second gas to obtain hydrogen-oxygen groups, or depositing the oxygen-containing groups and the hydrogen-containing groups, and then continuing to deposit the hydrogen-containing groups, thereby forming a passivation film layer on the surface of the silicon wafer, in which the oxygen content gradually decreases from a side close to the silicon wafer to a side away from the silicon wafer; Providing the second gas containing silicon and hydrogen into the reactor chamber at a pressure of 20 Pa to 100 Pa; The first oxygen-containing gas is at least one of H2O, NO, and NO2; The second gas of silicon and hydrogen includes a mixed gas of SiH4 and H2, or a mixed gas of Si2H6 and H2; In the second gas containing silicon and hydrogen, the mass ratio of the silicon to the mass ratio of the second gas is 3% to 8%.

2. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: The first gas including oxygen is provided into the reactor chamber at a pressure of less than 200 Pa.

3. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: Before providing the first gas including oxygen to the reactor chamber, the gas pressure of the reactor chamber is less than 0.1 Pa.

4. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that: Before providing the first gas containing oxygen to the reactor chamber, hydrogen is firstly filled into the reactor chamber, and then the reactor chamber is evacuated to a pressure of less than 0.1Pa.

5. A silicon heterojunction solar cell prepared by the preparation method according to any one of claims 1 to 4, comprising a passivation film layer, characterized in that: The oxygen content in the passivation film layer decreases gradually from the side close to the silicon wafer to the side away from the silicon wafer, and the mass content of oxygen on the side close to the silicon wafer is less than 1%.

6. The silicon heterojunction solar cell according to claim 5, characterized in that: The method comprises sequentially forming the passivation film layer, the N-type amorphous silicon layer, the front transparent conductive layer, and the front metal electrode on the front transparent conductive layer on the front side of the silicon wafer; The passivation film layer, the P-type amorphous silicon layer, the back transparent conductive layer and the back metal electrode on the back transparent conductive layer are sequentially formed on the back side of the silicon wafer.

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