Etching method, solar cell, preparation method of solar cell and photovoltaic module

Abstract

The invention discloses an etching method, a solar cell, a preparation method of the solar cell and a photovoltaic module. The etching method comprises the following steps: performing laser etching treatment on a barrier layer on a silicon substrate in a preset opening area on a backlight surface of the silicon substrate to expose a polycrystalline silicon layer on the silicon substrate, and controlling oxygen partial pressure in a laser chamber to be less than or equal to 15000 pa during laser etching treatment; and carrying out polishing and etching treatment on the polycrystalline silicon layer and the silicon substrate subjected to laser etching treatment by adopting an etching agent comprising an alkaline solution to form a patterned opening region. According to the invention, the oxygen doping content of the graphical window formed in the preset opening area after laser etching treatment is reduced, and the roughness, alkali liquor etching resistance and the like of the laser etching area are improved, so that the adverse effect of the laser film opening effect on other film structures under the mask layer is improved, the film uniformity of the silicon wafer is improved, and the yield of the silicon wafer is improved. The stability of a laser-wet etching patterning process is improved, a process window is enlarged, the yield of finished battery pieces is improved, and the photoelectric property of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a preparation method thereof and a photovoltaic module. Background Art

[0002] During the preparation process of solar cells, a layer of polysilicon doped with boron or phosphorus is usually grown on the surface of the silicon wafer to passivate the back of the cell, and then laser film opening and wet etching such as chemical etching are used to achieve P / N area isolation. In order to simplify the process flow, laser is usually used to perform preliminary etching of the mask layer on the polysilicon, and then the laser action area is etched to a certain depth with the corresponding alkaline solution to achieve P / N area insulation. After the laser film opening process in traditional technology, there are problems such as incomplete local etching and uneven groove depth in the subsequent wet etching process, and the easy generation of crystalline silicon oxide with stronger alkali corrosion resistance during the laser film opening process, which makes wet process etching difficult. Summary of the invention

[0003] Based on this, it is necessary to provide an etching method. The present invention improves the adverse effects of laser film opening on other film structures under the mask layer by changing the process technology conditions of the laser process, improves the film uniformity of the silicon wafer, improves the stability of the laser-wet etching patterning process, increases the process window, improves the yield rate of the battery cell, and improves the photoelectric performance of the battery.

[0004] An embodiment of the present application provides an etching method.

[0005] An etching method comprises at least the following steps:

[0006] Performing laser etching on the barrier layer on the silicon substrate in a preset opening area on the backlight surface of the silicon substrate to expose the polysilicon layer on the silicon substrate, wherein the oxygen partial pressure in the laser chamber is controlled to be ≤15000 Pa during the laser etching process; and

[0007] The polysilicon layer and the silicon substrate after the laser etching process are polished and etched by using an etchant including an alkaline solution to form a patterned opening area.

[0008] In some of the embodiments, during the laser etching process, one or more of nanosecond laser technology, picosecond laser technology and femtosecond laser technology are used.

[0009] In some embodiments, during the laser etching process, the laser chamber is evacuated and a protective gas is introduced, wherein the protective gas includes N 2 , one or more of Ar, He, Kr, Xe, and Ne.

[0010] In some of the embodiments, during the laser etching process, the oxygen partial pressure in the laser chamber is controlled within a range of 1000 Pa to 15000 Pa.

[0011] In some embodiments, during the laser etching process, the laser energy is 100 mJ / cm 2 ~1000mJ / cm 2 ;

[0012] And / or, during laser etching, the laser wavelength is 200nm to 1000nm.

[0013] In some embodiments, when the laser is an infrared laser, the laser energy is controlled at 100 mJ / cm 2 ~1000mJ / cm 2 Within the range, the wavelength is controlled within the range of 700m~1000nm;

[0014] When the laser is a visible light laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 Within the range, the wavelength is controlled within the range of 400nm to 700nm;

[0015] When the laser is ultraviolet laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 The wavelength is controlled within the range of 200nm to 400nm.

[0016] In some embodiments, the etching method further satisfies at least one of the following conditions:

[0017] (1) During the polishing and etching process, the alkaline solution includes a KOH solution;

[0018] (2) During the polishing and etching treatment, the mass fraction of the alkaline solution is 1% to 10%;

[0019] (3) During the polishing and etching process, the temperature of the alkaline solution is 50°C to 70°C.

[0020] In some embodiments, after polishing and etching, the depth of the preset opening area is 0.5 μm to 5 μm.

[0021] An embodiment of the present application also provides a method for preparing a solar cell.

[0022] A method for preparing a solar cell comprises the following steps:

[0023] A polysilicon layer and a barrier layer are sequentially prepared on the backlight side of the silicon substrate;

[0024] The polysilicon layer and the barrier layer are etched by the etching method to obtain a patterned first opening area, wherein the first opening area extends to the silicon substrate;

[0025] Preparing a second opening region extending to the polysilicon layer on the backlight surface of the silicon substrate; and

[0026] A first electrode and a second electrode are prepared at positions corresponding to the first opening area and the second opening area, respectively.

[0027] In some embodiments, the method for preparing the solar cell further comprises the following steps:

[0028] Pretreatment: using an alkaline solution to pretreat the silicon wafer to obtain the silicon substrate, wherein the pretreatment includes one or more of a damage removal treatment, a polishing treatment, and a cleaning and texturing treatment.

[0029] In some embodiments, the method for preparing the solar cell further satisfies at least one of the following conditions:

[0030] (1) During the pretreatment, the alkaline solution includes a KOH solution;

[0031] (2) During the pretreatment, the mass fraction of the alkaline solution is 1% to 10%;

[0032] (3) During the pretreatment, the temperature of the alkaline solution is 60°C to 80°C.

[0033] In some of the embodiments, when preparing the polysilicon layer and the barrier layer on the backlight side of the silicon substrate, the following steps are included:

[0034] A tunneling layer and an amorphous silicon layer are sequentially prepared on the backlight side of the silicon substrate;

[0035] The doping elements are diffused into the amorphous silicon layer through a diffusion process to form a doped polysilicon layer and a doped oxide layer located on the surface of the doped polysilicon layer, and the doped oxide layer forms the barrier layer.

[0036] In some embodiments, the method for preparing the solar cell further satisfies at least one of the following conditions:

[0037] (1) When preparing the tunnel layer and the amorphous silicon layer on the silicon substrate, a low-pressure chemical vapor deposition method is used;

[0038] (2) The doped oxide layer includes a phosphorus-doped silicon oxide layer or a boron-doped silicon oxide layer;

[0039] (3) The thickness of the tunneling layer is 0.5 nm to 3 nm;

[0040] (4) The thickness of the doped polysilicon layer is 50 nm to 400 nm;

[0041] (5) The thickness of the doped oxide layer is 40nm to 80nm.

[0042] An embodiment of the present application also provides a solar cell.

[0043] A solar cell is prepared by adopting the preparation method.

[0044] An embodiment of the present application also provides a photovoltaic module.

[0045] A photovoltaic assembly comprises the solar cell.

[0046] The above etching method changes the process technical conditions of the laser process, reduces the oxygen doping content of the patterned window formed in the preset opening area after laser etching, improves the roughness and alkali solution etching resistance of the laser etching area, thereby improving the adverse effects of the laser film opening on other film layer structures under the mask layer, improving the film uniformity of the silicon wafer, improving the stability of the laser-wet etching patterning process, increasing the process window, improving the yield of the finished battery cell, and improving the photoelectric performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0048] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0049] Figure 1 A schematic diagram of an etching method according to an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of a method for preparing a solar cell according to an embodiment of the present invention;

[0051] Figure 3 Schematic diagram of step (1) of the method for preparing a solar cell according to Example 1 of the present invention;

[0052] Figure 4 This is a schematic diagram of step (2) of the method for preparing a solar cell according to Example 1 of the present invention;

[0053] Figure 5 This is a schematic diagram of step (3) of the method for preparing a solar cell according to Example 1 of the present invention;

[0054] Figure 6 This is a schematic diagram of step (4) of the method for preparing a solar cell according to Example 1 of the present invention;

[0055] Figure 7 This is a schematic diagram of step (5) of the method for preparing a solar cell according to Example 1 of the present invention;

[0056] Figure 8 This is a schematic diagram of step (6) of the method for preparing a solar cell according to Example 1 of the present invention;

[0057] Fig. 9 Schematic diagram of step (7) of the method for preparing a solar cell according to Example 1 of the present invention;

[0058] Fig.10 This is a schematic diagram of step (9) of the method for preparing a solar cell according to Example 1 of the present invention;

[0059] Fig.11 Schematic diagram of step (10) of the method for preparing a solar cell according to Example 1 of the present invention;

[0060] Fig.12 The Raman spectra of the laser action area after different oxygen partial pressures during laser etching treatment in Example 1 and Comparative Examples 1-2 of the present invention are shown.

[0061] Description of Reference Numerals

[0062] 10. Solar cell; 100. Silicon substrate; 200. Tunneling layer; 300. Doped polysilicon layer; 400. Doped oxide layer; 500. Mask layer; 600. Conductive film layer; 700. Anti-reflection layer; 810. First electrode; 820. Second electrode; 101. First opening region; 102. Second opening region. DETAILED DESCRIPTION

[0063] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0064] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0065] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0067] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0069] The embodiment of the present application provides an etching method to solve the problem that the laser film opening process in the traditional technology leads to incomplete local etching and uneven groove depth in the subsequent wet etching process; and the problem that the traditional laser film opening generates crystalline silicon oxide with stronger alkali corrosion resistance, which makes the wet process etching difficult. The etching method will be described below with reference to the accompanying drawings.

[0070] The etching method provided in the embodiments of the present application is exemplary, please refer to Figure 1 As shown, Figure 1 Schematic diagram of the etching method provided in the embodiment of the present application. The etching method of the present application can be used for the preparation of solar cells 10.

[0071] In order to more clearly explain the etching method, the etching method will be introduced below with reference to the accompanying drawings. Figure 1 As shown, an etching method comprises at least the following steps:

[0072] Performing laser etching on the barrier layer on the silicon substrate 100 in a preset opening area on the backlight surface of the silicon substrate 100 to expose the polysilicon layer on the silicon substrate 100, wherein the oxygen partial pressure in the laser chamber is controlled to be ≤15000 Pa during the laser etching process; and

[0073] The blocking layer and the polysilicon layer after the laser etching process are polished and etched by using an etchant including an alkaline solution to form a patterned opening area.

[0074] In some of the embodiments, during the laser etching process, one or more of nanosecond laser technology, picosecond laser technology and femtosecond laser technology are used.

[0075] In some embodiments, during the laser etching process, the laser chamber is evacuated and a protective gas is introduced, wherein the protective gas includes N 2 , one or more of Ar, He, Kr, Xe, and Ne.

[0076] In some of the embodiments, during the laser etching process, the oxygen partial pressure in the laser chamber is controlled within a range of 1000 Pa to 15000 Pa.

[0077] In some embodiments, during the laser etching process, the laser energy is 100 mJ / cm 2 ~1000mJ / cm 2 ; and / or, during laser etching, the laser wavelength is 200nm to 1000nm.

[0078] In some embodiments, when the laser is an infrared laser, the laser energy is controlled at 100 mJ / cm 2 ~1000mJ / cm2 within the range, the wavelength is controlled within the range of 700 m to 1000 nm;

[0079] When the laser is a visible light laser, the laser energy is controlled at 100 mJ / cm 2 to 1000 mJ / cm 2 within the range, and the wavelength is controlled within the range of 400 nm to 700 nm;

[0080] When the laser is an ultraviolet laser, the laser energy is controlled at 100 mJ / cm 2 to 1000 mJ / cm 2 within the range, and the wavelength is controlled within the range of 200 nm to 400 nm.

[0081] In some embodiments, during the polishing and etching process, the alkaline solution includes a KOH solution.

[0082] In some embodiments, during the polishing and etching process, the mass fraction of the alkaline solution is 1% to 10%.

[0083] In some embodiments, during the polishing and etching process, the temperature of the alkaline solution is 50°C to 70°C.

[0084] In some embodiments, after the polishing and etching process, the depth of the preset opening area is 0.5 μm to 5 μm.

[0085] An embodiment of the present application further provides a method for manufacturing a solar cell 10.

[0086] A method for manufacturing a solar cell 10 includes the following steps:

[0087] Referring to Figure 2 as shown, a polysilicon layer and a barrier layer are sequentially formed on the backlight surface of the silicon substrate 100;

[0088] The barrier layer and the polysilicon layer are etched by an etching method to obtain a patterned first opening area 101, and the first opening area 101 extends to the silicon substrate 100;

[0089] A second opening area extending to the polysilicon layer is formed on the backlight surface of the silicon substrate 100; and

[0090] A first electrode 810 and a second electrode 820 are respectively formed at positions corresponding to the first opening area 101 and the second opening area.

[0091] In some embodiments, the method for manufacturing the solar cell 10 further includes the following steps:

[0092] Pretreatment: The silicon wafer is pretreated with an alkaline solution to obtain a silicon substrate 100. The pretreatment includes one or more of a damage removal treatment, a polishing treatment, and a cleaning and texturing treatment.

[0093] In some embodiments, during the pre-treatment, the alkaline solution includes a KOH solution.

[0094] In some of the embodiments, during the pre-treatment, the mass fraction of the alkaline solution is 1% to 10%.

[0095] In some embodiments, during the pretreatment, the temperature of the alkaline solution is 60°C to 80°C.

[0096] In some embodiments, when a polysilicon layer and a barrier layer are sequentially prepared on the backlight surface of the silicon substrate 100, the following steps are included:

[0097] A tunneling layer 200 and an amorphous silicon layer are sequentially prepared on the backlight surface of the silicon substrate 100;

[0098] The doping elements are diffused into the amorphous silicon layer through a high temperature diffusion process to form a doped polysilicon layer 300 and a doped oxide layer 400 located on the surface of the doped polysilicon layer 300 .

[0099] In some embodiments, the tunneling layer 200 may be specifically a tunneling oxide layer.

[0100] In some of the embodiments, low pressure chemical vapor deposition is used to prepare the tunneling layer 200 and the amorphous silicon layer on the silicon substrate 100 .

[0101] In some embodiments, when etching the barrier layer, a chain machine is used to clean the doped oxide layer 400 on the backlight side in an HF solution with a mass concentration of 2% to 12%, and the doped oxide layer 400 such as BSG and PSG is completely removed by etching for 90-300S to expose the doped polysilicon layer 300. The use of a chain machine in this embodiment can improve process convenience and processing efficiency.

[0102] In some embodiments, the doped oxide layer 400 includes a phosphorus-doped silicon oxide layer PSG and / or a boron-doped silicon oxide layer BSG.

[0103] In some embodiments, the thickness of the tunneling layer 200 is 0.5 nm to 3 nm.

[0104] In some embodiments, the thickness of the doped polysilicon layer 300 is 50 nm to 400 nm.

[0105] In some embodiments, the doped oxide layer 400 has a thickness of 40 nm to 80 nm.

[0106] In some embodiments, the method for preparing the solar cell 10 further includes the following steps:

[0107] The doped oxide layer 400 is removed, and a mask layer 500 is formed on the doped polysilicon layer 300 as a blocking layer.

[0108] In some embodiments, the mask layer 500 may be a silicon oxide layer. The mask layer 500 may be prepared by high temperature deposition.

[0109] In some embodiments, the first electrode 810 and the second electrode 820 can be prepared by screen printing.

[0110] An embodiment of the present application further provides a solar cell 10 .

[0111] A solar cell 10 is prepared by a preparation method.

[0112] An embodiment of the present application further provides a solar cell 10 .

[0113] A solar cell 10, see Fig.10 As shown, it includes a silicon substrate 100 and a tunneling layer 200, a doped polysilicon layer 300, a conductive film layer 600 and an anti-reflection layer 700 sequentially arranged on the backlight surface of the silicon substrate 100, wherein a first opening area 101 and a second opening area 102 are alternately arranged on the backlight surface of the solar cell 10, the first opening area 101 extends to the silicon substrate 100, and the second opening area 102 extends to the doped polysilicon layer 300, and a first electrode 810 and a second electrode 820 are respectively arranged in the first opening area 101 and the second opening area 102.

[0114] The tunneling layer 200 mentioned above may be a tunneling oxide layer.

[0115] An embodiment of the present application also provides a photovoltaic module.

[0116] A photovoltaic module includes a solar cell 10. The solar cell 10 can be packaged by a packaging component.

[0117] Example 1

[0118] This embodiment provides a solar cell 10, and the solar cell 10 is prepared by the following preparation method.

[0119] The method for preparing the solar cell 10 of this embodiment comprises the following steps:

[0120] (1) Pretreatment: see Figure 3 As shown, an alkaline solution is used to perform damage removal, polishing, cleaning and texturing on a silicon wafer to obtain a silicon substrate 100. During the pre-treatment, the alkaline solution includes a KOH solution, the mass fraction of the alkaline solution is 5%, and the temperature of the alkaline solution is 70°C.

[0121] (2) A tunnel oxide layer 200 and an amorphous silicon layer are sequentially prepared on the light-receiving side and the backlight side of the silicon substrate 100 by low-pressure chemical vapor deposition. The thickness of the tunnel oxide layer 200 is 1 nm. The thickness of the doped polysilicon layer is 100 nm. The doped elements are diffused into the amorphous silicon layer by a high-temperature diffusion process to form a doped polysilicon layer 300 and a doped oxide layer 400 located on the surface of the doped polysilicon layer 300, see Figure 4 As shown, the doped oxide layer 400 includes a phosphorus-doped silicon oxide layer or a boron-doped silicon oxide layer. The thickness of the doped oxide layer 400 is 50 nm.

[0122] (3) See Figure 5 As shown, the doped oxide layer 400 on the light-receiving surface of the silicon substrate 100 is removed.

[0123] (4) See Figure 6 As shown, a mask layer 500 is prepared on the doped polysilicon layer 300 on the light-receiving surface of the silicon substrate 100 as a blocking layer.

[0124] (5) See Figure 7 As shown, the mask layer 500 and the doped polysilicon layer 300 are laser etched in the preset opening area on the backlight surface of the silicon substrate 100 using nanosecond laser technology, picosecond laser technology or femtosecond laser technology, and the first opening area 101 extends to the doped polysilicon layer 300 to a depth of 70nm to 80nm. During the laser etching process, the laser chamber is evacuated and a protective gas N is introduced. 2 The oxygen partial pressure in the laser chamber is controlled at 10000pa. The laser is an infrared laser and the laser energy is controlled at 800mJ / cm 2 , the wavelength is controlled at 800nm.

[0125] (6) See Figure 8 As shown, the doped polysilicon layer 300 after laser etching is polished and etched using an etchant including an alkaline solution and an additive to obtain a patterned first opening region 101, see Figure 7 As shown, it extends to the silicon substrate 100. During the polishing and etching process, the alkaline solution includes a KOH solution, the mass fraction of the alkaline solution is 5%, the temperature of the alkaline solution is 60°C, and after the polishing and etching process, the depth of the patterned first opening area 101 extending to the silicon substrate 100 is 1 μm.

[0126] (7) See Fig. 9 As shown, a conductive film layer 600 and an anti-reflection layer 700 are prepared on the backlight surface of the silicon substrate 100 .

[0127] (8) A second opening region 102 is prepared on the conductive film layer 600 and the anti-reflection layer 700 and is spaced apart from the first opening region 101 .

[0128] (9) The first electrode 810 and the second electrode 820 are respectively prepared at positions corresponding to the first opening area 101 and the second opening area 102 by screen printing, see Fig.10 shown.

[0129] (10) The tunneling oxide layer 200, the doped polysilicon layer 300 and the doped oxide layer 400 on the light-receiving surface of the silicon substrate 100 are removed. Fig.11 shown.

[0130] Comparative Example 1

[0131] This comparative example provides a solar cell 10, and the solar cell 10 is prepared by the following preparation method.

[0132] The preparation method of the solar cell 10 of this comparative example is basically the same as that of Example 1, except that in Comparative Example 1, during the laser etching process, the oxygen partial pressure in the laser chamber is controlled to be 20000 Pa.

[0133] Comparative Example 2

[0134] This comparative example provides a solar cell 10, and the solar cell 10 is prepared by the following preparation method.

[0135] The preparation method of the solar cell 10 of this comparative example is basically the same as that of Example 1, except that in Comparative Example 2, during the laser etching process, the oxygen partial pressure in the laser chamber is controlled to be 16000 Pa.

[0136] For Example 1 and Comparative Example 1-2, the Raman spectra of the laser action area after different oxygen partial pressures during laser etching are shown in FIG. Fig.12 As shown, Fig.12 The horizontal axis is wavelength, and the vertical axis is intensity. Fig.12 In the Raman spectrum, the higher the peak, the closer the peak shift is to 512cm -1 , indicating that the higher the crystallization rate of the polysilicon layer. Fig.12It can be seen that under conventional laser technology, the oxygen partial pressure is 21278.25Pa (the oxygen partial pressure is about 20000Pa. For the repeatability and accuracy of the experiment, the upper limit of this experiment is selected as 20000Pa), and the degree of amorphization is serious. In Example 1, by evacuating and introducing other inert atmospheres, the oxygen partial pressure in the laser action chamber is reduced, and the phenomena of incomplete local etching and uneven groove depth during the etching process are avoided, and the crystalline silicon oxide with stronger alkali corrosion resistance is reduced, the roughness of the laser etching area is improved, and the problems of resistance to alkali solution etching are solved, the alkali solution etching effect is improved, the laser etching area is flat, and the crystallization rate of the laser action area is effectively improved, so as to improve the film uniformity of the silicon wafer.

[0137] The final result of this application is reflected in the efficiency of the battery cell, as shown in Table 1. In this application, only the atmosphere of the laser process is improved and optimized, and its implementation cost is low, and it is highly compatible with industrial mass production such as GW and TW.

[0138] Table 1 Effect of oxygen partial pressure during laser etching on final battery performance

[0139]

[0140] By comparing Comparative Examples 1 to 2 with Example 1, it can be seen that under normal standard conditions, the partial pressure of oxygen is about 21278.25 Pa, which is not conducive to the normal production of the solar cell 10. As the oxygen partial pressure decreases, the oxygen content incorporated during the laser process gradually decreases, which helps to improve the graphic process of the solar cell 10. However, considering the actual production process, reducing the oxygen partial pressure is bound to increase the cost of protective gas and increase the process time. In addition, too low oxygen partial pressure will cause the controllability of process conditions to deteriorate to a certain extent. Considering the above comprehensive reasons, the present application sets the oxygen partial pressure within the range of 1000Pa-15000Pa, and its lower limit (1000Pa) is further reduced, which is not only not conducive to industrial implementation, but also greatly causes energy consumption. If the oxygen partial pressure is too high, it will not significantly improve the battery performance. In this application, the oxygen partial pressure is set at 1000Pa-15000Pa and the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 The range can slow down the cooling speed of crystalline silicon and polycrystalline silicon to below the melting point of silicon, increase its crystallization rate, avoid or reduce the occurrence of induced amorphization of silicon, and avoid the phenomenon of incomplete local etching and uneven groove depth in the subsequent wet etching process. In addition, in the present application, when the laser film opening process is carried out at an oxygen partial pressure of 1000Pa-15000Pa, the crystalline silicon oxide with stronger alkali corrosion resistance is reduced, and the difficulty of wet process etching is reduced. The oxygen partial pressure is set at 1000Pa-15000Pa and the laser energy is controlled at 100mJ / cm 2~1000mJ / cm 2 For example, when the laser is an infrared laser, the laser energy is controlled within 100mJ / cm 2 ~1000mJ / cm 2 When the laser is a visible light laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 When the laser is ultraviolet, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 Within this range, by controlling the oxygen partial pressure and laser energy, not only can the patterning process be improved to a certain extent and the process technical conditions of the laser process be changed, the oxygen doping content of the patterned window formed in the preset opening area after laser etching can be effectively reduced, but also its implementation feasibility is high and it is convenient for industrial mass production.

[0141] To sum up, the above etching method changes the process conditions of the laser process, reduces the oxygen doping content of the graphic window formed in the preset opening area after laser etching, avoids incomplete local etching and uneven groove depth during the etching process, reduces the crystalline silicon oxide with stronger alkali corrosion resistance, improves the roughness of the laser etching area, solves problems such as resistance to alkali solution etching, improves the alkali solution etching effect, flattens the laser etching area, effectively improves the crystallization rate of the laser action area, and improves the uniformity of the film layer of the silicon wafer, thereby improving the adverse effects of the laser film opening on other film layer structures under the mask layer, improving the stability of the laser-wet etching graphic process, increasing the process window, improving the yield of the battery cell product, and improving the photoelectric performance of the battery.

[0142] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0143] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An etching method, characterized in that: At least the following steps are included: Performing laser etching on the barrier layer on the silicon substrate in a preset opening area on the backlight surface of the silicon substrate to expose the polysilicon layer on the silicon substrate, wherein the oxygen partial pressure in the laser chamber is controlled to be ≤15000 Pa during the laser etching process; and The polysilicon layer and the silicon substrate after the laser etching process are polished and etched by using an etchant including an alkaline solution to form a patterned opening area.

2. The etching method according to claim 1, characterized in that: During laser etching, one or more of nanosecond laser technology, picosecond laser technology and femtosecond laser technology are used.

3. The etching method according to claim 1, characterized in that: During laser etching, the laser chamber is evacuated and a protective gas is introduced, wherein the protective gas includes one or more of N2, Ar, He, Kr, Xe, and Ne.

4. The etching method according to claim 1, characterized in that: During laser etching, the oxygen partial pressure in the laser chamber is controlled within the range of 1000Pa to 15000Pa.

5. The etching method according to claim 1, characterized in that: During laser etching, the laser energy is 100mJ / cm 2 ~1000mJ / cm 2 ; And / or, during laser etching, the laser wavelength is 200nm to 1000nm.

6. The etching method according to claim 5, characterized in that: During laser etching, when the laser is infrared laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 Within the range, the wavelength is controlled within the range of 700m~1000nm; When the laser is a visible light laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 Within the range, the wavelength is controlled within the range of 400nm to 700nm; When the laser is ultraviolet laser, the laser energy is controlled at 100mJ / cm 2 ~1000mJ / cm 2 The wavelength is controlled within the range of 200nm to 400nm.

7. The etching method according to any one of claims 1 to 6, characterized in that: The etching method also satisfies at least one of the following conditions: (1) During the polishing and etching process, the alkaline solution includes a KOH solution; (2) During the polishing and etching treatment, the mass fraction of the alkaline solution is 1% to 10%; (3) During the polishing and etching process, the temperature of the alkaline solution is 50°C to 70°C.

8. The etching method according to any one of claims 1 to 6, characterized in that: After polishing and etching, the depth of the preset opening area is 0.5 μm to 5 μm.

9. A method for preparing a solar cell, characterized in that: The steps include: A polysilicon layer and a barrier layer are sequentially prepared on the backlight side of the silicon substrate; The polysilicon layer and the barrier layer are etched by the etching method according to any one of claims 1 to 8 to obtain a patterned first opening area, wherein the first opening area extends to the silicon substrate; Preparing a second opening region extending to the polysilicon layer on the backlight surface of the silicon substrate; as well as A first electrode and a second electrode are prepared at positions corresponding to the first opening area and the second opening area, respectively.

10. The method for preparing a solar cell according to claim 9, characterized in that: The method for preparing the solar cell further comprises the following steps: Pretreatment: using an alkaline solution to pretreat the silicon wafer to obtain the silicon substrate, wherein the pretreatment includes one or more of a damage removal treatment, a polishing treatment, and a cleaning and texturing treatment.

11. The method for preparing a solar cell according to claim 10, characterized in that: The method for preparing the solar cell also satisfies at least one of the following conditions: (1) During the pretreatment, the alkaline solution includes a KOH solution; (2) During the pretreatment, the mass fraction of the alkaline solution is 1% to 10%; (3) During the pretreatment, the temperature of the alkaline solution is 60°C to 80°C.

12. The method for preparing a solar cell according to claim 9, characterized in that: When a polysilicon layer and a barrier layer are prepared on the backlight side of a silicon substrate, the following steps are included: A tunneling layer and an amorphous silicon layer are sequentially prepared on the backlight side of the silicon substrate; The doping elements are diffused into the amorphous silicon layer through a diffusion process to form a doped polysilicon layer and a doped oxide layer located on the surface of the doped polysilicon layer.

13. The method for preparing a solar cell according to claim 12, characterized in that: The method for preparing the solar cell also satisfies at least one of the following conditions: (1) When preparing the tunnel layer and the amorphous silicon layer on the silicon substrate, a low-pressure chemical vapor deposition method is used; (2) The doped oxide layer includes a phosphorus-doped silicon oxide layer or a boron-doped silicon oxide layer; (3) The thickness of the tunneling layer is 0.5 nm to 3 nm; (4) The thickness of the doped polysilicon layer is 50 nm to 400 nm; (5) The thickness of the doped oxide layer is 40nm to 80nm.

14. A solar cell, characterized in that: The preparation method is described in any one of claims 9 to 13.

15. A photovoltaic module, characterized in that: Comprising the solar cell as claimed in claim 14.

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