Method for preparing solar cell, solar cell and application of solar cell

Abstract

The invention discloses a method for preparing a solar cell, the solar cell and an application of the solar cell. The method comprises the following steps: (1) cleaning and drying a silicon wafer; (2) performing oxygen plasma treatment on the dried silicon wafer; (3) annealing the silicon wafer; and (4) performing ALD on the surface of the silicon wafer to deposit an aluminum oxide layer. According to the method, oxygen plasma pretreatment is carried out on the silicon wafer before ALD deposition of the aluminum oxide layer, the OH <-> concentration of the surface of the silicon wafer is improved, and therefore the growth quality and the growth rate of bottom layer aluminum oxide are improved, and meanwhile the passivation quality of the aluminum oxide layer is also improved. Besides, after the oxygen plasma pretreatment, the low-temperature annealing treatment is added, so that the formed H < + > can be activated into the silicon wafer body, the silicon substrate and dangling bonds on the surface can be fully passivated, surface recombination can be reduced, and stress concentration and membrane explosion caused by excessive accumulation of H < + > can be avoided.

Description

Technical Field

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

[0002] Atomic layer deposition (ALD) is a method that can deposit materials on the surface of a substrate layer by layer in the form of a single atomic film. In the time-type ALD, the former precursor reacts with the OH-group on the surface of the silicon wafer for a half reaction, and after nitrogen purges the gas produced by the reaction, another precursor is introduced to complete the other half reaction, and then the secondary gas produced by the reaction is purged to form a cycle to complete the single-layer atomic layer deposition. Therefore, the thickness of the atomic layer deposition film is determined by the number of cycles.

[0003] Thermal atomic layer deposition of aluminum oxide is the current mainstream aluminum oxide passivation film preparation method. The precursors used are trimethylaluminum and water. The reaction process is:

[0004] 1)Al(CH3)3+OH-=>O-Al-(CH3)2+CH4;

[0005] 2) Use N2 to purge to remove the remaining Al(CH3)3 gas and CH4 gas;

[0006] 3)O-Al-(CH3)2+H2O=>O-AlOH-(2)+(O)2-Al-CH3+CH4;

[0007] 4) Use N2 to purge to remove the remaining H2O and CH4. Complete a single cycle.

[0008] At present, before ALD deposition, the silicon wafer with emitter and after texturing needs to be cleaned by acidic chemical etching to remove the oxide layer that is plated around the front and edge during Poly preparation, so as to facilitate subsequent surface passivation. After acidic chemical etching, the surface of the silicon wafer has H ends, and the concentration of its surface reactive groups OH- is low. However, in the initial deposition of atomic layer deposition, especially the first ALD reaction cycle, the interaction between the original substrate surface and the precursor will affect the initial growth characteristics of ALD. According to the first half reaction of aluminum oxide deposition, trimethylaluminum reacts with the reactive group OH- to generate O-Al-(CH3)2. The concentration of reactive groups OH- on the substrate surface can significantly affect the atomic concentration of Al in the adsorption reaction, affecting the saturation and growth rate of the reaction. However, the reactive OH- on the substrate surface after acidic chemical etching is low, which seriously affects the saturation and growth rate of the reaction, and seriously affects the passivation quality of aluminum oxide film. Summary of the invention

[0009] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to propose a method for preparing a solar cell, a solar cell and its application. The present application increases the OH- concentration on the surface of the silicon wafer by oxygen plasma pretreatment of the silicon wafer before the ALD deposition of the aluminum oxide layer, thereby improving the growth quality and growth rate of the underlying aluminum oxide, and at the same time, the passivation quality of the aluminum oxide layer is also improved, thereby improving the light conversion efficiency of the solar cell. In addition, the present application adds a low-temperature annealing treatment after the oxygen plasma pretreatment, so that the formed H+ can be activated into the silicon wafer body, thereby being able to fully passivate the silicon substrate and the dangling bonds on the surface, reducing surface recombination, and also avoiding stress concentration caused by excessive accumulation of H+, resulting in film explosion.

[0010] In one aspect of the present application, the present application proposes a method for preparing a solar cell. According to an embodiment of the present application, the method includes:

[0011] (1) Cleaning and drying the silicon wafer;

[0012] (2) treating the dried silicon wafer with oxygen plasma;

[0013] (3) performing annealing treatment on the silicon wafer;

[0014] (4) ALD is performed to deposit an aluminum oxide layer on the surface of the silicon wafer.

[0015] According to the method for preparing solar cells in the embodiment of the present application, by pre-treating the silicon wafer with oxygen plasma before the ALD deposition of the aluminum oxide layer, the OH- concentration on the surface of the silicon wafer is increased, thereby improving the growth quality and growth rate of the underlying aluminum oxide, and at the same time, the passivation quality of the aluminum oxide layer is also improved, thereby improving the light conversion efficiency of the solar cell. In addition, after the oxygen plasma pre-treatment, the present application adds a low-temperature annealing treatment so that the formed H+ can be activated into the silicon wafer body, thereby fully passivating the silicon substrate and the dangling bonds on the surface, reducing surface recombination, and also avoiding stress concentration caused by excessive accumulation of H+, resulting in film explosion.

[0016] In addition, the method for preparing a solar cell according to the above embodiment of the present application may also have the following additional technical features:

[0017] In some embodiments of the present application, in step (1), the silicon wafer is acid cleaned.

[0018] In some embodiments of the present application, in step (2), the oxygen gas flow rate range of the oxygen plasma treatment is 5000 sccm to 8000 sccm, the temperature range of the oxygen plasma treatment is 150°C to 260°C, the pressure range of the oxygen plasma treatment is 1000mTorr to 2000mTorr, the RF power of the oxygen plasma treatment is 10000W to 15000W, and the time of the oxygen plasma treatment is 30s to 40s.

[0019] In some embodiments of the present application, in step (2), the gas used for oxygen plasma treatment of the dried silicon wafer is semiconductor-grade purity oxygen.

[0020] In some embodiments of the present application, in step (3), the temperature range of annealing the silicon wafer is 200° C. to 600° C., and the annealing time is 5 min to 20 min.

[0021] In some embodiments of the present application, the atmosphere used for annealing the silicon wafer includes at least one of nitrogen, helium, neon, and argon.

[0022] In some embodiments of the present application, in step (4), the deposition source of the ALD deposition of the aluminum oxide layer on the surface of the silicon wafer includes trimethylaluminum vapor and water vapor, and the deposition temperature is 250°C to 280°C.

[0023] In some embodiments of the present application, in step (4), ALD deposition of an aluminum oxide layer on the surface of the silicon wafer includes a first layer reaction cycle and multiple subsequent layer reaction cycles, and the ventilation amount of the trimethylaluminum vapor in the first layer reaction cycle is higher than the ventilation amount of the trimethylaluminum vapor in each of the subsequent layer reaction cycles.

[0024] In some embodiments of the present application, in step (4), the first layer reaction cycle and each of the subsequent layer reaction cycles independently include a trimethylaluminum vapor pulse and a water vapor pulse, the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the trimethylaluminum vapor pulse in each of the subsequent layer reaction cycles, and the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the water vapor pulse in the first layer reaction cycle.

[0025] In the second aspect of the present application, the present application proposes a solar cell. According to the embodiment of the present application, the solar cell is prepared by the method of the above embodiment, and the solar cell includes: a silicon wafer; an Al-rich aluminum oxide bottom layer, the Al-rich aluminum oxide bottom layer is arranged on at least one side of the silicon wafer; an aluminum oxide surface layer, the aluminum oxide surface layer is arranged on the surface of the Al-rich aluminum oxide bottom layer away from the silicon wafer; the aluminum content of the Al-rich aluminum oxide bottom layer is greater than the aluminum content of the aluminum oxide surface layer. As a result, the passivation quality of the aluminum oxide layer of the solar cell is high, thereby improving the light conversion efficiency of the solar cell. At the same time, it can also avoid the film explosion phenomenon of the solar cell.

[0026] In addition, the solar cell according to the above embodiment of the present application may also have the following additional technical features:

[0027] In some embodiments of the present application, the thickness of the Al-rich aluminum oxide bottom layer is 1 nm to 2 nm; and / or the thickness of the aluminum oxide surface layer is 2 nm to 7 nm.

[0028] In the third aspect of the present invention, a solar cell module is provided. According to an embodiment of the present invention, the solar cell module has the solar cell of the above embodiment. Therefore, the solar cell in the solar cell module has a higher photoelectric conversion efficiency.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0031] Figure 1 A schematic diagram of a process for preparing a solar cell according to an embodiment of the present application;

[0032] Figure 2 Schematic diagram of the structure of a solar cell according to an embodiment of the present application.

[0033] Reference numerals:

[0034] 1-silicon wafer, 2-aluminum oxide layer, 2-1-Al-rich alumina bottom layer, 2-2-aluminum oxide surface layer, 3-silicon nitride layer. DETAILED DESCRIPTION

[0035] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0036] In one aspect of the present application, the present application proposes a method for preparing a solar cell. According to an embodiment of the present application, the method includes: (1) cleaning and drying the silicon wafer; (2) subjecting the dried silicon wafer to oxygen plasma treatment; (3) subjecting the silicon wafer to annealing treatment; (4) performing ALD deposition of an aluminum oxide layer on the surface of the silicon wafer. Thus, the present application increases the OH- concentration on the surface of the silicon wafer by performing oxygen plasma pretreatment on the silicon wafer before ALD deposition of the aluminum oxide layer, thereby improving the growth quality and growth rate of the underlying aluminum oxide, and at the same time, the passivation quality of the aluminum oxide layer is also improved, thereby improving the light conversion efficiency of the solar cell. In addition, the present application adds a low-temperature annealing treatment after the oxygen plasma pretreatment, so that the formed H+ can be activated into the silicon wafer body, thereby being able to fully passivate the silicon substrate and the dangling bonds on the surface, reduce surface recombination, and also avoid stress concentration caused by excessive accumulation of H+, resulting in film explosion.

[0037] The following is a detailed description of the principle by which the method for preparing a solar cell proposed by the present invention can achieve the above beneficial effects:

[0038] In the related art, before ALD deposition, the silicon wafer with the emitter and the textured wafer needs to be cleaned by acidic chemical etching (such as RCA cleaning) to remove the oxide layer that is plated around the front and edge during Poly preparation, so as to facilitate subsequent surface passivation. After acidic chemical etching cleaning, the surface of the silicon wafer has an H end, and the concentration of its surface reactive group OH- is low. However, in the initial deposition of atomic layer deposition, especially the first ALD reaction cycle, the interaction between the original substrate surface and the precursor will affect the initial growth characteristics of ALD. According to the first half reaction of aluminum oxide deposition, trimethylaluminum reacts with the reactive group OH- to generate O-Al-(CH3)2. The concentration of the reactive group OH- on the substrate surface can significantly affect the atomic concentration of Al in the adsorption reaction, affecting the saturation and growth rate of the reaction. The reactive OH- on the substrate surface after acidic chemical etching cleaning is low, which seriously affects the saturation and growth rate of the reaction, and seriously affects the passivation quality of the aluminum oxide film.

[0039] In view of this, the present application performs oxygen plasma pretreatment on the silicon wafer before ALD deposition of the aluminum oxide layer. During the oxygen plasma pretreatment, the surface of the silicon wafer is exposed to a high-energy oxygen ion beam, and the oxygen ions react chemically with the silicon surface through collision, and finally generate hydroxyl groups (OH-), thereby increasing the OH- concentration on the surface of the silicon wafer. The increase in the OH- concentration on the surface of the silicon wafer is conducive to improving the growth quality and growth rate of the underlying aluminum oxide, and the passivation quality of the aluminum oxide layer is also improved, thereby improving the light conversion efficiency of the solar cell.

[0040] It should be noted that the H element in the hydroxyl group (OH-) generated during the oxygen plasma pretreatment is derived from the H end on the surface of the silicon wafer.

[0041] At the same time, due to the bombardment of oxygen plasma, some OH- bonds will break, and the generated O can be reconfigured with Al in the subsequent ALD deposition of aluminum oxide to form additional O-Al-O bonds, which helps to reduce vacancy defects. The Al here comes from the Al source carried by trimethylaluminum. However, the H+ released from the OH- bond may accumulate on the surface of the silicon wafer, resulting in excessive accumulation of hydrogen on the surface of the silicon wafer, and subsequent deposition of aluminum oxide layer will cause film explosion. At the same time, excessive accumulation of positively charged H+ will affect the electric field formed by the fixed negative charge on the silicon wafer interface, causing inversion and weakening the passivation effect of the aluminum oxide field.

[0042] Therefore, after the oxygen plasma pretreatment, the present application needs to add a low-temperature annealing treatment step so that the formed H+ can be activated into the silicon wafer body, fully passivating the silicon substrate and the dangling bonds on the surface, reducing surface recombination, and at the same time avoiding stress concentration caused by excessive H+ accumulation, resulting in film explosion.

[0043] Specifically, refer to the attached Figure 1 The above method for preparing a solar cell comprises the following steps:

[0044] S100: Cleaning and drying of silicon wafers

[0045] In this step, the silicon wafer with the emitter and after texturing is cleaned to remove the oxide layer plated on the front and edge of the silicon wafer during Poly preparation to facilitate the subsequent passivation of the silicon wafer surface, and then dried.

[0046] According to some specific embodiments of the present application, the silicon wafer with the emitter and after the texturing is acid-cleaned (e.g., RCA cleaning) to ensure the effective removal of the oxide layer that is plated around the front and edge of the silicon wafer during the Poly preparation. After RCA acid washing, the surface of the silicon wafer has an H end to maintain the hydrophobicity of the silicon wafer surface. However, after acid cleaning, the surface of the silicon wafer has an H end (the H end on the surface of the silicon wafer exists in the form of a chemical bond Si-H), and the concentration of the surface reactive group OH- is low. However, in the initial deposition of atomic layer deposition, especially the first ALD reaction cycle, the interaction between the original substrate surface and the precursor will affect the initial growth characteristics of ALD. According to the first half reaction of alumina deposition, trimethylaluminum reacts with the reactive group OH- to generate O-Al-(CH3)2. The concentration of the reactive group OH- on the substrate surface can significantly affect the atomic concentration of Al in the adsorption reaction, affecting the saturation and growth rate of the reaction. However, the reactive OH- on the substrate surface after acidic chemical etching is low, which seriously affects the saturation and growth rate of the reaction, and seriously affects the passivation quality of the aluminum oxide film.

[0047] S200: Oxygen plasma treatment of dried silicon wafers

[0048] In this step, plasma treatment equipment can be used to perform oxygen plasma treatment on the dried silicon wafer. During the oxygen plasma pretreatment process, the surface of the silicon wafer is exposed to a high-energy oxygen ion beam. The oxygen ions react chemically with the silicon surface through collision, and finally generate hydroxyl groups (OH-), thereby increasing the OH- concentration on the surface of the silicon wafer. The increase in the OH- concentration on the surface of the silicon wafer is conducive to improving the growth quality and growth rate of the underlying aluminum oxide, and the passivation quality of the aluminum oxide layer is also improved.

[0049] According to some further specific embodiments of the present application, the oxygen flow rate range of the oxygen plasma treatment is 5000sccm-8000sccm (as an example, it can be 5000sccm, 5500sccm, 6000sccm, 6500sccm, 7000sccm, 7500sccm, 8000sccm, etc.), the temperature range of the oxygen plasma treatment is 150°C-260°C (as an example, it can be 150°C, 180°C, 200°C, 220°C, 240°C, 260°C, etc.), and the pressure range of the oxygen plasma treatment is 1000mTorr-2000mTorr (as an example, it can be 1000mTorr, 1200mTorr, 1400mTorr, 1600mTorr, 1800mTorr, 2000mTorr, etc.). rr, etc.), the RF power of the oxygen plasma treatment is 10000W~15000W (as an example, it can be 10000W, 11000W, 12000W, 13000W, 14000W, 15000W, etc.), and the time of the oxygen plasma treatment is 30s~40s (as an example, it can be 30s, 31s, 32s, 33s, 34s, 35s, 36s, 37s, 38s, 39s, 40s, etc.). Therefore, by limiting the oxygen flow rate, RF power and treatment time of the oxygen plasma treatment within the above ranges, it can be further ensured that during the oxygen plasma pretreatment, the surface of the silicon wafer is exposed to the high-energy oxygen ion beam, and the oxygen ions chemically react with the silicon surface through collision to finally generate hydroxyl groups (OH-), thereby further ensuring that the OH- concentration on the surface of the silicon wafer is increased.

[0050] According to some other specific embodiments of the present application, the gas used for oxygen plasma treatment of the dried silicon wafer is semiconductor-grade purity oxygen, thereby further ensuring that the OH- concentration on the surface of the silicon wafer is increased and avoiding the introduction of new impurities.

[0051] S300: Annealing of silicon wafers

[0052] Due to the bombardment of the plasma in step S200, some OH- bonds will break, and the generated O can be reconfigured with Al in the subsequent ALD deposition of aluminum oxide to form additional O-Al-O bonds, which helps to reduce vacancy defects. The Al here comes from the Al source carried by trimethylaluminum. However, the H+ released from the OH- bond may accumulate on the surface of the silicon wafer, resulting in excessive accumulation of hydrogen on the surface of the silicon wafer, and the subsequent deposition of the aluminum oxide layer will cause a film explosion phenomenon. At the same time, too much H+ accumulation with a positive valence will affect the electric field formed by the fixed negative charge on the silicon wafer interface, causing inversion and weakening the passivation effect of the aluminum oxide field. Therefore, after the oxygen plasma pretreatment, the present application needs to add a step of low-temperature annealing treatment so that the H+ formed by the oxygen plasma bombardment can be activated into the silicon wafer body, fully passivating the silicon substrate and the dangling bonds on the surface, reducing surface recombination, and also avoiding the stress concentration caused by excessive accumulation of H+, resulting in a film explosion.

[0053] According to some other specific embodiments of the present application, the temperature range for annealing the silicon wafer is 200°C to 600°C (as an example, it can be 200°C, 250°C, 300°C, 400°C, 500°C, 600°C, etc.), and the annealing time is 5min to 20min (as an example, it can be 5min, 7min, 10min, 12min, 15min, 20min, etc.). By limiting the temperature and time of the annealing treatment to the above range, it can further ensure that the H+ formed by the oxygen plasma bombardment is activated into the silicon wafer body, fully passivating the silicon substrate and the dangling bonds on the surface, reducing surface recombination, and at the same time further avoiding stress concentration caused by excessive accumulation of H+, resulting in film explosion.

[0054] According to some other specific embodiments of the present application, the atmosphere used for annealing the silicon wafer includes at least one of nitrogen, helium, neon and argon, thereby further ensuring the annealing effect. Nitrogen is preferred because it is cheap and easily available.

[0055] S400: ALD deposition of aluminum oxide layer on the surface of silicon wafer

[0056] In this step, an aluminum oxide layer is deposited on the surface of the silicon wafer by ALD. According to some specific embodiments of the present application, the deposition source of the aluminum oxide layer deposited by ALD on the surface of the silicon wafer includes trimethylaluminum vapor and water vapor, and the deposition temperature is 250°C to 280°C, for example, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, etc., thereby further ensuring the deposition quality of the deposited aluminum oxide layer.

[0057] According to some other specific embodiments of the present application, ALD deposition of an aluminum oxide layer on the surface of a silicon wafer includes a first layer reaction cycle and multiple subsequent layer reaction cycles (for example, a second layer reaction cycle, a third layer reaction cycle ... an nth layer reaction cycle), and the ventilation volume of trimethylaluminum vapor in the first layer reaction cycle is higher than the ventilation volume of trimethylaluminum vapor in each subsequent layer reaction cycle, thereby effectively increasing the Al atomic concentration in the aluminum oxide bottom layer, which is beneficial to the reaction with OH- on the surface of the silicon wafer, thereby improving the film quality and passivation effect of the aluminum oxide layer.

[0058] It should be noted that the ventilation amount of trimethylaluminum vapor = flow rate of trimethylaluminum vapor × ventilation time, and the ventilation amount of water = flow rate of water × ventilation time.

[0059] In the embodiment of the present application, the aluminum oxide layer can be deposited by tubular ALD or plate ALD. In the process of depositing the aluminum oxide layer by tubular ALD, the first layer reaction cycle and each subsequent layer reaction cycle independently include a trimethylaluminum vapor pulse and a water vapor pulse, the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the trimethylaluminum vapor pulse in each subsequent layer reaction cycle, and the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the water vapor pulse in the first layer reaction cycle, thereby further effectively increasing the Al atom concentration in the aluminum oxide bottom layer, thereby facilitating the reaction with OH- on the surface of the silicon wafer, and improving the film quality and passivation effect of the aluminum oxide layer. As some specific embodiments, the flow rate of TMA in the first layer reaction cycle is 20sccm~25sccm, the time is 5s~10s, the flow rate of water is 18sccm~22sccm, and the time is 4s~8s; the flow rate of TMA in the subsequent layer reaction cycle is 18sccm~23sccm, the time is 5s~10s, the flow rate of water is 18sccm~23sccm, and the time is 5s~8s.

[0060] As some preferred embodiments, the number of cycles of tubular ALD deposition of aluminum oxide layer is 20 to 40 times, and the film thickness ranges from 4 nm to 5 nm, wherein the first 4 to 8 cycles form an Al-rich aluminum oxide bottom layer, and the subsequent cycles form an aluminum oxide surface layer.

[0061] In the embodiment of the present application, during the plate-type ALD deposition of the aluminum oxide layer, step-by-step deposition is performed, the first step is to pass TMA gas alone, the preferred gas flow rate is 1500sccm to 1800sccm (as an example, it can be 1500sccm, 1600sccm, 1700sccm, 1800sccm, etc.), and the source time is 3s to 5s (as an example, it can be 3s, 4s, 5s, etc.). The second step is to pass TMA gas and water vapor at the same time, the preferred TMA flow rate is 1750sccm to 1850sccm, the water flow rate is 1850sccm to 1950scmm, and the source time is 5s to 6s. This method can also effectively increase the Al atomic concentration in the aluminum oxide bottom layer, which is conducive to the reaction with OH- on the surface of the silicon wafer, and improves the film quality and passivation effect of the aluminum oxide layer.

[0062] As some preferred embodiments, the number of cycles of plate-type ALD deposition of aluminum oxide layer is 4 to 5 times, and the film thickness ranges from 8 nm to 9 nm, wherein the first cycle forms an Al-rich aluminum oxide bottom layer, and the subsequent cycles form an aluminum oxide surface layer.

[0063] It can be seen that the film thickness range varies depending on the aluminum oxide deposition method used.

[0064] In the second aspect of the present application, the present application proposes a solar cell. According to the embodiment of the present application, the solar cell is prepared by the method of the above embodiment. As a result, the passivation quality of the aluminum oxide layer of the solar cell is high, thereby improving the light conversion efficiency of the solar cell. At the same time, the film explosion phenomenon of the solar cell can also be avoided.

[0065] According to some specific embodiments of the present application, Figure 2 The solar cell comprises: a silicon wafer 1; an Al-rich aluminum oxide bottom layer 2-1, which is disposed on at least one side of the silicon wafer 1; an aluminum oxide surface layer 2-2, which is disposed on the surface of the Al-rich aluminum oxide bottom layer 2-1 away from the silicon wafer 1; the aluminum content of the Al-rich aluminum oxide bottom layer 2-1 is greater than the aluminum content of the aluminum oxide surface layer 2-2. The Al-rich aluminum oxide bottom layer 2-1 and the aluminum oxide surface layer 2-2 together form an aluminum oxide layer 2. The silicon wafer 1 is a silicon wafer 1 that has been subjected to oxygen plasma treatment and annealing treatment in sequence, and the aluminum content of the Al-rich aluminum oxide bottom layer 2-1 is relatively high, which improves the film quality and passivation effect of the aluminum oxide layer, thereby improving the light conversion efficiency of the solar cell.

[0066] According to some specific embodiments of the present application, the thickness of the Al-rich aluminum oxide bottom layer can be 1nm to 2nm, and the thickness of the aluminum oxide surface layer can be 2nm to 7nm. Thus, the film quality and passivation effect of the aluminum oxide layer are further ensured, thereby improving the light conversion efficiency of the solar cell.

[0067] Further, see Attachment Figure 2 The solar cell further comprises: a silicon nitride layer 3, which is arranged on a surface of the aluminum oxide surface layer 2-2 away from the Al-rich aluminum oxide bottom layer 2-1, thereby further ensuring the passivation effect of the solar cell.

[0068] In the third aspect of the present invention, a solar cell module is provided. According to an embodiment of the present invention, the solar cell module has the solar cell of the above embodiment. Therefore, the solar cell in the solar cell module has a higher photoelectric conversion efficiency.

[0069] A battery module is a finished module with power generation output function produced by connecting multiple of the above-mentioned solar cells in series and / or in parallel, and undergoing processes such as lamination and packaging. Specifically, the battery module includes photovoltaic glass, packaging film, battery cells, packaging film, backplane, etc.

[0070] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. Wherein, the concentrated sulfuric acid used below is a concentrated sulfuric acid chemical with a mass fraction of 98%. In addition, if not explicitly stated, all reagents used in the following embodiments are commercially available, or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0071] Example 1

[0072] This embodiment provides a method for preparing a solar cell, comprising:

[0073] 1) Provide an N-type single crystal silicon wafer with an emitter and a velvet surface, and perform RCA cleaning and drying.

[0074] 2) The silicon wafer is treated with oxygen plasma using a plasma treatment device having a radio frequency power supply and a high frequency generator. The gas used is semiconductor-grade purity oxygen, the oxygen flow rate is 7000 sccm, the radio frequency power is 13000 W, the temperature is 250°C, the pressure is 1500 mTorr, and the treatment time is 35 s.

[0075] 3) After the oxygen plasma pretreatment, the silicon wafer is subjected to low-temperature annealing treatment, the atmosphere used is nitrogen, the annealing temperature is 250° C., and the annealing time is 12 min.

[0076] 4) The pre-treated silicon wafer was deposited with aluminum oxide film using tubular ALD at a process temperature of 280°C. In the first reaction cycle, the ventilation time of TMA was 6s, the flow rate was 20sccm, the ventilation time of water was 5s, and the flow rate was 18sccm. In the subsequent cycles, the ventilation time of TMA was 5s, the flow rate was 20sccm, and the ventilation time of water was 5s, and the flow rate was 20sccm. The number of tubular ALD deposition cycles was 30, and the film thickness was about 5nm.

[0077] Example 2

[0078] The preparation method of Example 2 is basically the same as that of Example 1, except that:

[0079] 2) The silicon wafer is treated with oxygen plasma using a plasma treatment device having a radio frequency power supply and a high frequency generator. The gas used is semiconductor-grade pure oxygen, the oxygen flow rate is 5000 sccm, the radio frequency power is 10000 W, the temperature is 150°C, the pressure is 1000 mTorr, and the treatment time is 40 s.

[0080] Example 3

[0081] The preparation method of Example 3 is basically the same as that of Example 1, except that:

[0082] 2) The silicon wafer is treated with oxygen plasma using a plasma treatment device having a radio frequency power supply and a high frequency generator. The gas used is semiconductor-grade pure oxygen, the oxygen flow rate is 6000 sccm, the radio frequency power is 12000 W, the temperature is 200°C, the pressure is 1200 mTorr, and the treatment time is 38 s.

[0083] Example 4

[0084] The preparation method of Example 4 is basically the same as that of Example 1, except that:

[0085] 2) The silicon wafer is treated with oxygen plasma using a plasma treatment device having a radio frequency power supply and a high frequency generator. The gas used is semiconductor-grade pure oxygen, the oxygen flow rate is 8000 sccm, the radio frequency power is 15000 W, the temperature is 260°C, the pressure is 2000 mTorr, and the treatment time is 30 s.

[0086] Example 5

[0087] The preparation method of Example 5 is basically the same as that of Example 1, except that:

[0088] 3) Annealing time is 5 minutes.

[0089] Example 6

[0090] The preparation method of Example 6 is basically the same as that of Example 1, except that:

[0091] 3) Annealing time is 7 minutes.

[0092] Example 7

[0093] The preparation method of Example 7 is basically the same as that of Example 1, except that:

[0094] 3) Annealing time is 10 minutes.

[0095] Example 8

[0096] The preparation method of Example 8 is basically the same as that of Example 1, except that:

[0097] 3) Annealing time is 15 minutes.

[0098] Example 9

[0099] The preparation method of Example 9 is basically the same as that of Example 1, except that:

[0100] 3) Annealing time is 20 minutes.

[0101] Example 10

[0102] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0103] 3) The temperature of the annealing treatment is 200°C.

[0104] Embodiment 11

[0105] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0106] 3) The temperature of the annealing treatment is 300°C.

[0107] Example 12

[0108] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0109] 3) The temperature of the annealing treatment is 400°C.

[0110] Embodiment 13

[0111] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0112] 3) The temperature of the annealing treatment is 500°C.

[0113] Embodiment 14

[0114] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0115] 3) The temperature of the annealing treatment is 600°C.

[0116] Embodiment 15

[0117] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0118] 4) Tubular ALD was used to deposit aluminum oxide thin films. In the first reaction cycle, the aeration time of TMA was 5 s, the flow rate was 25 sccm, the aeration time of water was 5 s, the flow rate was 20 sccm, and in each subsequent cycle, the aeration time of TMA was 5 s, the flow rate was 22 sccm, the aeration time of water was 5 s, the flow rate was 22 sccm, and the aeration time of water was 5 s, the flow rate was 22 sccm.

[0119] Example 16

[0120] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0121] 4) Plate-type ALD was used to deposit aluminum oxide film at a process temperature of 250°C. The deposition method used was step-by-step deposition. The first step was to pass TMA gas alone, with a TMA gas flow rate of 1600 sccm and a source flow time of 4 seconds. The second step was to pass TMA and water simultaneously, with a TMA flow rate of 1800 sccm, a water flow rate of 1900 scmm, and a source flow time of 5 seconds. The film thickness was about 9 nm.

[0122] Comparative Example 1

[0123] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that:

[0124] The N-type single crystal silicon wafer in step 1) is not subjected to oxygen plasma treatment and annealing treatment, that is, step 2) and step 3) are not included, and the ALD deposition of aluminum oxide film is directly performed on the N-type single crystal silicon wafer after cleaning and drying.

[0125] Comparative Example 2

[0126] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that:

[0127] The N-type single crystal silicon wafer treated by oxygen plasma is not subjected to annealing treatment, that is, step 3) is not included, and the ALD deposition of aluminum oxide film is directly performed on the N-type single crystal silicon wafer treated by oxygen plasma.

[0128] A silicon nitride layer was deposited on the surface of the aluminum oxide film of Examples 1 to 16 and Comparative Examples 1 to 2, respectively. Then, the battery cells of Examples 1 to 16 and Comparative Examples 1 to 2 were tested for minority carrier lifetime and open circuit voltage iVoc on a WCT-120 device, respectively. The results are shown in Table 1.

[0129] Table 1

[0130] Minority carrier lifetime (μs) iVoc(V) Example 1 2576.452 0.73316 Example 2 2568.247 0.733115 Example 3 2542.65 0.733069 Example 4 2546.149 0.733289 Example 5 2436.86 0.73311 Example 6 2487.43 0.73315 Example 7 2596.47 0.73328 Example 8 2537.86 0.72916 Example 9 2446.86 0.72831 Example 10 2447.89 0.73209 Embodiment 11 2623.65 0.73337 Example 12 2656.83 0.73354 Embodiment 13 2680.147 0.733765 Embodiment 14 2468.55 0.72913 Embodiment 15 2567.81 0.73321 Example 16 2558.43 0.73315 Comparative Example 1 1623.318 0.728332 Comparative Example 2 1816.611 0.730613

[0131] It can be seen from Table 1 that compared with Comparative Examples 1 and 2, the minority carrier lifetime and open circuit voltage iVoc of Examples 1 to 16 are significantly improved, which shows that the passivation performance of the battery can be effectively improved by subjecting the silicon wafer to oxygen plasma treatment and annealing treatment.

[0132] It can be seen from Example 1 and Examples 5 to 9 that as the annealing time increases, the passivation performance of the battery gradually improves, but when the annealing time exceeds 10 minutes, the passivation performance decreases. At the same time, it can be seen that when the annealing time is between 7 minutes and 15 minutes, the passivation performance of the battery is excellent.

[0133] It can be seen from Example 1 and Examples 10 to 14 that with the increase of annealing temperature, the passivation performance of the battery gradually improves, but when the annealing temperature exceeds 500°C, its passivation performance decreases. At the same time, it can be seen that when the annealing temperature is between 250°C and 500°C, the passivation performance of the battery is excellent.

[0134] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0135] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that: include: (1) Cleaning and drying the silicon wafer; (2) treating the dried silicon wafer with oxygen plasma; (3) performing annealing treatment on the silicon wafer; (4) ALD is performed to deposit an aluminum oxide layer on the surface of the silicon wafer.

2. The method according to claim 1, characterized in that In step (1), the silicon wafer is cleaned with acid.

3. The method according to claim 1, characterized in that In step (2), the oxygen flow rate range of the oxygen plasma treatment is 5000sccm to 8000sccm, the temperature range of the oxygen plasma treatment is 150°C to 260°C, the pressure range of the oxygen plasma treatment is 1000mTorr to 2000mTorr, the RF power of the oxygen plasma treatment is 10000W to 15000W, and the time of the oxygen plasma treatment is 30s to 40s.

4. The method according to claim 3, characterized in that In step (2), the gas used for oxygen plasma treatment of the dried silicon wafer is semiconductor-grade purity oxygen.

5. The method according to claim 1, characterized in that In step (3), the temperature range of annealing treatment on the silicon wafer is 200° C. to 600° C., and the annealing time is 5 min to 20 min.

6. The method according to claim 5, characterized in that The atmosphere used for annealing the silicon wafer includes at least one of nitrogen, helium, neon and argon.

7. The method according to any one of claims 1 to 6, characterized in that: In step (4), an aluminum oxide layer is deposited on the surface of the silicon wafer using ALD as a deposition source including trimethylaluminum vapor and water vapor, and the deposition temperature is 250° C. to 280° C.

8. The method according to claim 7, characterized in that In step (4), ALD deposition of an aluminum oxide layer on the surface of the silicon wafer includes a first layer reaction cycle and multiple subsequent layer reaction cycles, and the ventilation amount of the trimethylaluminum vapor in the first layer reaction cycle is higher than the ventilation amount of the trimethylaluminum vapor in each of the subsequent layer reaction cycles.

9. The method according to claim 8, characterized in that In step (4), the first layer reaction cycle and each of the subsequent layer reaction cycles independently include a trimethylaluminum vapor pulse and a water vapor pulse, the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the trimethylaluminum vapor pulse in each of the subsequent layer reaction cycles, and the ventilation volume of the trimethylaluminum vapor pulse in the first layer reaction cycle is greater than the ventilation volume of the water vapor pulse in the first layer reaction cycle.

10. A solar cell, characterized in that: Prepared by the method according to any one of claims 1 to 9, the solar cell comprises: Silicon wafer; An Al-rich alumina bottom layer, wherein the Al-rich alumina bottom layer is disposed on at least one side of the silicon wafer; an aluminum oxide surface layer, the aluminum oxide surface layer being arranged on a surface of the Al-rich aluminum oxide bottom layer away from the silicon wafer; The aluminum content of the Al-rich aluminum oxide bottom layer is greater than the aluminum content of the aluminum oxide surface layer.

11. The solar cell according to claim 10, characterized in that The thickness of the Al-rich alumina bottom layer is 1 nm to 2 nm; And / or, the thickness of the aluminum oxide surface layer is 2nm to 7nm.

12. A solar cell module, characterized in that: A solar cell manufactured by the method according to any one of claims 1 to 9 or a solar cell according to claim 10 or 11.

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