Solar cell step-shaped isolation groove, preparation method thereof and multi-junction gallium arsenide solar cell

Abstract

The invention provides a solar cell step-shaped isolation groove, a preparation method thereof and a multi-junction gallium arsenide solar cell, the step-shaped isolation groove comprises a wide isolation groove and a narrow isolation groove, the narrow isolation groove is arranged above a lower electrode, the wide isolation groove is arranged above the narrow isolation groove, and the edges of the two sides of the wide isolation groove are located on the opposite outer sides of the edges of the two sides of the narrow isolation groove; the wide isolation groove penetrates through the top cell layer; the depth of the narrow isolation groove penetrates through the middle battery layer and the bottom battery layer. According to the invention, the step-shaped isolation groove is arranged, so that the film material for preparing the antireflection film can enter the isolation groove more easily, and the passivation effect on the isolation groove is improved; by arranging the wide isolation grooves, the top battery does not have a state that the edge is suspended and is not supported, and the mechanical property and the reliability of the battery are improved; and meanwhile, the top cell cannot shield the narrow isolation groove below the top cell, impurities adhered to the narrow isolation groove can be removed more conveniently, and the electrical performance and stability of the solar cell are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cell manufacturing, and in particular relates to a solar cell step-shaped isolation groove and a manufacturing method thereof, and a multi-junction gallium arsenide solar cell. Background Art

[0002] Multi-junction GaAs solar cells isolate different units or areas of the cell through isolation grooves to prevent damage to the semiconductor layer of the cell during the slicing process, which may cause a short circuit in the cell. Because multi-junction GaAs solar cells have tunnel junctions, cap layers, buffer layers, barrier layers, and multiple sub-cells, the traditional method usually uses corrosion to prepare the isolation grooves. It is necessary to use a variety of corrosion solutions alternately to remove the barrier layer and each layer of sub-cells in turn. The corrosion solution not only corrodes downward in the vertical direction, but also spreads to both sides of the cell, thereby widening the edge of the isolation groove; due to the selective corrosion of the corrosion solution, the corrosion rates of different materials are different, resulting in different lateral corrosion rates for each layer of material, which ultimately makes it difficult to accurately control the width of the isolation groove corresponding to each structural layer, and the isolation groove is easily narrow at the top and wide at the bottom, which brings the following problems:

[0003] (1) The intermediate cell and the bottom cell are relatively wide in the isolation grooves prepared by the prior art. When the anti-reflection film is prepared by evaporation or sputtering, the evaporation or sputtering direction of the film material is substantially perpendicular to the upper surface of the cell. Therefore, the side areas of the intermediate cell and the bottom cell blocked by the top cell layer are difficult to be covered by the anti-reflection film, which affects the passivation effect of the isolation grooves.

[0004] (2) Flexible multi-junction GaAs solar cells often need to be bent, folded or rolled during use. Severe side corrosion of the middle and bottom cells causes the edge of the top cell layer to be suspended without support, making the top cells on both sides of the isolation grooves prone to breakage.

[0005] (3) As the edges of the isolation grooves are uneven, impurities are more likely to adhere and store, while the narrow-at-top-and-wide-at-bottom structure makes it difficult to clean and remove impurities, which results in increased edge recombination of the battery cell and affects the electrical performance and reliability of the battery cell. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a solar cell step-shaped isolation groove and a preparation method thereof, and a multi-junction gallium arsenide solar cell, which enhances the passivation effect of the solar cell, improves the mechanical properties of the solar cell, and reduces edge recombination.

[0007] The technical solution adopted by the present invention is: a solar cell step-shaped isolation groove, including a wide isolation groove and a narrow isolation groove, wherein the narrow isolation groove is arranged above the lower electrode, and the wide isolation groove is arranged above the narrow isolation groove, and its two side edges are located on the relatively outer sides of the two side edges of the narrow isolation groove.

[0008] Furthermore, the width of the wide isolation trench is 180-220 μm.

[0009] Furthermore, the width of the narrow isolation groove is 80-120 μm.

[0010] Furthermore, the depth of the wide isolation trench penetrates the top battery layer; the depth of the narrow isolation trench penetrates the middle battery layer and the bottom battery layer.

[0011] The present invention also provides a method for preparing a solar cell step-shaped isolation groove, comprising the following steps:

[0012] Preparing a semi-finished battery with isolation grooves to be engraved;

[0013] forming a first photoresist layer on the front side of the semi-finished battery;

[0014] Photolithographically forming a narrow isolation opening in the first photoresist layer;

[0015] Etching the narrow isolation opening downward to the upper surface of the lower electrode to form a narrow isolation groove;

[0016] removing the remaining first photoresist layer;

[0017] forming a second photoresist layer on the front side of the semi-finished battery;

[0018] Photolithographically forming a wide isolation opening in the second photoresist layer;

[0019] Etching the wide isolation opening downward to the upper surface of the middle battery to form a wide isolation groove;

[0020] The remaining second photoresist layer is removed.

[0021] Furthermore, the semi-finished battery includes an upper electrode, a Cap layer, a top battery layer, a middle battery layer, a bottom battery layer and a lower electrode.

[0022] Furthermore, the narrow isolation groove is formed by a wet etching process, and sulfuric acid solution and potassium dichromate solution are alternately used as etching solutions to remove the top battery layer, the middle battery layer, and the bottom battery layer below the narrow isolation opening.

[0023] Furthermore, the wide isolation groove is formed by the wet etching process, and a mixed solution of phosphoric acid and hydrochloric acid is used as an etching solution to remove the top battery layer below the wide isolation opening.

[0024] Furthermore, the narrow isolation trench and / or the wide isolation trench is formed by a dry etching process.

[0025] The present invention also provides a multi-junction gallium arsenide solar cell having the above-mentioned solar cell step-shaped isolation groove and / or being prepared by the above-mentioned solar cell step-shaped isolation groove preparation method.

[0026] The advantages and positive effects of the present invention are:

[0027] (1) By setting a stepped isolation groove and scientifically and reasonably designing the widths of the wide isolation groove and the narrow isolation groove, it is more conducive to the film material entering the interior of the isolation groove when the anti-reflection film is subsequently prepared by evaporation or sputtering, thereby increasing the coverage area of ​​the film material on the side wall of the isolation groove, thereby improving the passivation effect on the isolation groove.

[0028] (2) By providing a wide isolation groove, all areas of the top cell are on the surface of the middle cell, and there is no longer a state where the edge is suspended without support. This reduces the damage caused by the edge of the solar cell when it is stressed or bent, thereby improving the mechanical properties and reliability of the solar cell.

[0029] (3) By setting up a step-shaped isolation groove with a wide top and a narrow bottom, the top cell will not block the narrow isolation groove below, making it easier to remove impurities adhering to the narrow isolation groove through cleaning, thereby effectively avoiding impurity deposition and ensuring the electrical performance and stability of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a solar cell step-shaped isolation groove structure according to a specific implementation of the present invention;

[0031] Figure 2 It is a process flow chart of a method for preparing a solar cell step-shaped isolation groove according to a specific implementation of the present invention;

[0032] Figure 3 The present invention is a schematic diagram of a process for preparing a step-shaped isolation groove for a solar cell according to a specific embodiment of the present invention.

[0033] Figure 4 It is a schematic diagram of the structure of a solar cell isolation groove formed by a traditional method in a comparative example of the present invention.

[0034] In the figure:

[0035] 1. Lower electrode; 2. Semiconductor layer; 21. Top battery layer; 22. Middle battery layer; 23. Bottom battery layer; 24. Anti-reflection film; 3. Upper electrode; 4. Wide isolation groove; 5. Narrow isolation groove; 6. First photoresist layer; 61. Narrow isolation port; 7. Second photoresist layer; 71. Wide isolation port. DETAILED DESCRIPTION

[0036] Embodiments of the present invention provide a solar cell step-shaped isolation groove and a preparation method thereof, and a multi-junction gallium arsenide solar cell. The embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0037] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set" and "connect" 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 directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0038] like Figure 1 As shown, the first aspect of the present invention provides a solar cell step-shaped isolation groove, including a wide isolation groove 4 and a narrow isolation groove 5, the narrow isolation groove 5 is arranged above the lower electrode 1, and the wide isolation groove 4 is arranged above the narrow isolation groove 5, and its two side edges are located on the relatively outer sides of the two side edges of the narrow isolation groove 5.

[0039] It can be understood that the solar cell has multiple structural layers. The present invention forms a step-like isolation groove that is wide at the top and narrow at the bottom on the front of the solar cell by arranging the above-mentioned wide isolation groove 4 and narrow isolation groove 5. This can prevent the edge of the top battery from being in a suspended state without the support of the bottom layer, increase the mechanical strength of the battery edge, and prevent the solar cell from being broken due to the suspended edge of the top battery layer 21 when it needs to be bent, folded or curled. In addition, the design of wide at the top and narrow at the bottom ensures that the structural layer located above will not block the narrow isolation groove 5 below, making it easier to remove impurities adhering to the narrow isolation groove 5 by cleaning, thereby effectively avoiding impurity deposition and ensuring the electrical performance and stability of the solar cell.

[0040] Specifically, in this embodiment, the width of the wide isolation groove 4 is 180-220μm; the width of the narrow isolation groove 5 is 80-120μm; the inventor of this application has found that in the traditional isolation groove design, a single width is usually used for each layer, and its width is generally designed to be 80-150μm. In the present invention, two isolation grooves with different upper and lower widths are designed, wherein the width of the narrow isolation groove 5 is designed to be 80-120μm, which can meet the minimum width requirement of the dicing machine for the isolation groove; the width of the wide isolation groove 4 is designed to be 180-220μm, which can meet the width difference with the narrow isolation groove 5 while reducing the occupation of the battery preparation area as much as possible.

[0041] In the present invention, the width of the wide isolation trench 4 can be preferably set to 220 μm while satisfying the above-mentioned width, and the width of the narrow isolation trench 5 can be preferably set to 120 μm while satisfying the above-mentioned width.

[0042] In a specific embodiment, the step-shaped isolation groove is used for a multi-junction gallium arsenide solar cell, which includes an upper electrode 3, a lower electrode 1 and a semiconductor layer 2, wherein the upper electrode 3 is arranged on the front surface of the semiconductor layer 2, and the lower electrode 1 is arranged on the back surface of the semiconductor layer 2; the semiconductor layer 2 includes a top cell layer 21, an intermediate cell layer 22 and a bottom cell layer 23 from top to bottom, wherein the upper electrode 3 is arranged on the upper surface of the top cell layer 21, and a Cap layer is arranged at the connection portion between the two; an anti-reflection film 24 is arranged on the upper surface of the top cell layer 21 where the upper electrode 3 is not arranged; and a lower electrode 1 is arranged on the lower surface of the bottom cell. The depth of the wide isolation groove 4 in this embodiment penetrates the top cell layer 21; the narrow isolation groove 5 penetrates the bottom cell layer 23 and the intermediate cell layer 22. Through the above technical scheme, the depth of the narrow isolation groove 5 can meet the isolation function of the isolation groove and the requirements of the dicing process for the isolation groove; the depth of the wide isolation groove 4 is designed to penetrate the top battery layer 21. This is because there is a tunneling layer between the top battery and the middle battery. When preparing the wide isolation groove 4, the material properties of the tunneling layer can prevent the wide isolation groove 4 from continuing to expand downward, thereby enhancing the controllability of the depth of the wide isolation groove 4 during the preparation process.

[0043] Through the above technical scheme, the solar cell step-shaped isolation groove proposed in the present application makes all areas of the top cell on the surface of the middle cell, and there is no longer a state where the edge is suspended without support, thereby avoiding the damage caused by the edge of the solar cell when it is stressed or bent, and improving the mechanical properties and reliability of the battery; at the same time, based on the characteristics of the step-shaped isolation groove being wide at the top and narrow at the bottom, when the anti-reflection film 24 is subsequently prepared by evaporation or sputtering, the evaporation or sputtering direction of the film material is perpendicular to the surface of the cell. Therefore, the step-shaped isolation groove structure that is wide at the top and narrow at the bottom is more conducive to the film material entering the interior of the isolation groove, increasing the coverage area of ​​the film material on the side wall of the isolation groove, thereby improving the passivation effect on the isolation groove.

[0044] like Figure 2 and Figure 3 As shown, the second aspect of the present invention provides a method for preparing a step-shaped isolation groove of a solar cell, comprising the following steps:

[0045] S1, preparing a semi-finished battery with isolation grooves to be engraved;

[0046] In a specific embodiment, the preparation method is used to prepare an isolation groove of a multi-junction gallium arsenide solar cell. The semi-finished cell is a multi-junction gallium arsenide solar cell with an upper electrode 3 and a lower electrode 1 prepared, including an upper electrode 3, a Cap layer, a top cell layer 21, an intermediate cell layer 22, a bottom cell layer 23 and a lower electrode 1; at this time, the Cap layer covers the top cell layer 21.

[0047] S2, forming a first photoresist layer 6 on the front side of the semi-finished battery;

[0048] Specifically, it includes baking the semi-finished battery, then coating the photoresist on the upper surface of the Cap layer, and then baking again to firmly fix the first photoresist layer 6 on the upper surface of the semi-finished battery.

[0049] S3, forming a narrow isolation opening 61 by photolithography on the first photoresist layer 6;

[0050] Specifically, a photolithography machine is used to expose the pattern of the narrow isolation groove 5 on the surface of the first photoresist, and then development and hardening are performed to form the narrow isolation opening 61.

[0051] S4, etching the narrow isolation opening 61 downward to the upper surface of the lower electrode 1 to form a narrow isolation groove 5;

[0052] Specifically, a wet etching process or a dry etching process can be used in this step; when a wet etching process is used to prepare a narrow isolation groove 5 on a solar cell having a GaInP / GaAs / GaInAs structure, a sulfuric acid solution and a potassium dichromate solution are alternately used as etching solutions to remove the Cap layer, the top cell layer 21, the middle cell layer 22 and the bottom cell layer 23 below the narrow isolation opening 61.

[0053] Preferably, a dry etching process is used to effectively control the width of the isolation groove and avoid side etching.

[0054] S5, removing the remaining first photoresist layer 6;

[0055] S6, forming a second photoresist layer 7 on the front side of the semi-finished battery;

[0056] Specifically, the preparation method of the second photoresist layer 7 is the same as the method of forming the first photoresist layer 6 in step S2 , and the second photoresist layer 7 covers the upper surface of the Cap layer and the upper surface of the lower electrode 1 in the narrow isolation trench 5 .

[0057] S7, forming a wide isolation opening 71 by photolithography on the second photoresist layer 7;

[0058] Specifically, a photolithography machine is used to expose the pattern of the narrow isolation groove 5 on the surface of the second photoresist layer 7 on the Cap layer, and then development and hardening are performed to form a wide isolation opening 71 .

[0059] S8, etching the wide isolation opening 71 downward to the upper surface of the middle battery to form a wide isolation groove 4;

[0060] Specifically, a wet etching process or a dry etching process can be used in this step; when a wet etching process is used to prepare a wide isolation groove 4 on a solar cell having a GaInP / GaAs / GaInAs structure, a mixed solution of phosphoric acid and hydrochloric acid is used as an etching solution to remove the top battery layer 21 below the wide isolation opening 71.

[0061] The third aspect of the present application proposes a multi-junction gallium arsenide solar cell having the solar cell step-shaped isolation groove proposed in the first aspect of the present application and / or being prepared using the solar cell step-shaped isolation groove preparation method proposed in the second aspect of the present application.

[0062] Embodiment 1

[0063] A method for preparing a step-shaped isolation groove of a solar cell comprises the following steps:

[0064] S1, preparing a semi-finished battery with isolation grooves to be engraved;

[0065] In a specific embodiment, the preparation method is used to prepare an isolation groove of a multi-junction gallium arsenide solar cell. After photolithography is performed on the front side of the semiconductor layer 2, an upper electrode 3 pattern is obtained. Then, the upper electrode 3 metal is prepared on the front side of the semiconductor layer 2 by evaporation. Then, the lower electrode 1 metal is deposited on the back side of the semiconductor layer 2 to form a semi-finished battery with the upper and lower electrodes 1 prepared. The semiconductor layer 2 includes a Cap layer, a top battery layer 21, an intermediate battery layer 22, a bottom battery layer 23 and a lower electrode 1.

[0066] S2, forming a first photoresist layer 6 on the front side of the semi-finished battery;

[0067] The semi-finished battery is placed in an oven at 150°C for pre-bake for 30 minutes to remove moisture from the surface of the semi-finished battery. Then, a coater is used to spin-coat a layer of 10μm thick positive photoresist to cover the semi-finished battery with the photoresist. Then, it is placed in an oven at 90°C and baked for 40 seconds to increase the firmness between the semi-finished battery and the photoresist.

[0068] S3, forming a narrow isolation opening 61 by photolithography on the first photoresist layer 6;

[0069] Use a photolithography machine to expose the narrow isolation groove 5 pattern, then soak it in AZ400K developer for 60 seconds, put the battery into a cleaning tank and rinse it with deionized water for no less than 5 times, put it into a spin dryer to dry, and then put it into an oven at a temperature of 100°C and bake it for 10 minutes for hardening the film.

[0070] S4, etching the narrow isolation opening 61 downward to the upper surface of the lower electrode 1 to form a narrow isolation groove 5;

[0071] Specifically, in this step, a wet etching process or a dry etching process can be used; when a wet etching process is used to prepare a narrow isolation groove 5 on a solar cell having a GaInP / GaAs / GaInAs structure, a sulfuric acid solution and a potassium dichromate solution are alternately used as etching solutions to remove the Cap layer, the top battery layer 21, the middle battery layer 22 and the bottom battery layer 23 below the narrow isolation opening 61. Specifically, it includes using an etching cleaning machine to alternately use a mixed solution of potassium dichromate and hydrogen peroxide to etch out the narrow isolation groove 5, shaking up and down during the etching process until the bright lower electrode 1 metal on the back is exposed, stopping the etching, and cleaning and drying after the etching is completed.

[0072] S5, removing the remaining first photoresist layer 6;

[0073] The semi-finished battery with the narrow isolation groove 5 is placed in the acetone tank of the etching cleaning machine and soaked until the first photoresist layer 6 on the surface is completely removed. The semi-finished battery with the narrow isolation groove 5 is then placed in anhydrous ethanol and soaked for 3 minutes. After that, it is placed in a cleaning tank filled with deionized water, rinsed for no less than 5 times, and then placed in a spin dryer to dry.

[0074] S6, forming a second photoresist layer 7 on the front side of the semi-finished battery;

[0075] The preparation method of the second photoresist layer 7 is the same as the method of forming the first photoresist layer 6 in step S2 , which will not be repeated here; the formed second photoresist layer 7 covers the upper surface of the Cap layer and the upper surface of the lower electrode 1 in the narrow isolation groove 5 .

[0076] S7, forming a wide isolation opening 71 by photolithography on the second photoresist layer 7;

[0077] Specifically, it includes using a photolithography machine to expose a wide isolation groove 4 pattern, then soaking it in AZ400K developer for 60 seconds, placing the battery in a cleaning tank and rinsing it with deionized water for no less than 5 times, placing it in a spin dryer to dry it, and then placing it in an oven at a temperature of 100°C and baking it for 10 minutes to harden the film.

[0078] S8, etching the wide isolation opening 71 downward to the upper surface of the middle battery to form a wide isolation groove 4;

[0079] Specifically, in this step, a wet etching process or a dry etching process can be used; when a wet etching process is used to prepare a wide isolation groove 4 on a solar cell having a GaInP / GaAs / GaInAs structure, a mixed solution of phosphoric acid and hydrochloric acid is used as an etching solution to remove the top battery layer 21 below the wide isolation port 71; specifically, a corrosion cleaning machine is used to place the semi-finished battery with a wide isolation port 71 into a corrosion tank filled with a mixed solution of phosphoric acid and hydrochloric acid, and the mixture is continuously shaken up and down for 20s±2s. After taking it out, rinse it with deionized water for no less than 5 times. After the corrosion is completed, put it into a spin dryer for cleaning and drying. In order to accurately control the depth of the wide isolation groove 4, a step meter is used to measure the depth of the wide isolation groove 4 after corrosion. If the depth is less than 1μm, the corrosion test is extended by another 5 to 10 seconds.

[0080] At this time, the surface of the semi-finished battery has formed a wide isolation groove 4 and a narrow isolation groove 5 with a set width, and then through the processes of removing the remaining second photoresist layer 7, etching the Cap layer, evaporating the anti-reflection film 24, overlaying the solder joints, removing the solder joint film and scribing, the semi-finished battery can be formed. Figure 1 A solar cell with a stepped isolation groove structure.

[0081] Comparative Example 1

[0082] A multi-junction gallium arsenide solar cell isolation groove formed by a conventional method, such as Figure 4 As shown, the method uses a variety of etching solutions to alternately etch the various structural layers of the multi-junction gallium arsenide solar cell, and the depth of the formed isolation groove penetrates the top cell layer 21, the middle cell layer 22 and the top cell layer 21. Due to the different corrosion rates of different materials, each layer of material has a different lateral corrosion rate, which ultimately causes the width of the isolation groove corresponding to the top cell layer 21 to be smaller than the width of the isolation groove below it, making it easy for the bottom of the isolation groove to absorb some etching solutions or impurities from other sources. At the same time, the isolation groove structure with a narrow top and a wide bottom makes it difficult to remove impurities at the bottom of the groove during the cleaning process. In addition, the isolation groove prepared by this method has severe side corrosion, which makes the edge of part of the top cell in a suspended state without support to the bottom, and is easy to be damaged under stress or bending.

[0083] The advantages and positive effects of the present invention are:

[0084] (1) By setting a stepped isolation groove and scientifically and reasonably designing the widths of the wide isolation groove and the narrow isolation groove, it is more conducive to the film material entering the interior of the isolation groove when the anti-reflection film is subsequently prepared by evaporation or sputtering, thereby increasing the coverage area of ​​the film material on the side wall of the isolation groove, thereby improving the passivation effect on the isolation groove.

[0085] (2) By providing a wide isolation groove, all areas of the top cell are on the surface of the middle cell, and there is no longer a state where the edge is suspended without support. This reduces the damage caused by the edge of the solar cell when it is stressed or bent, thereby improving the mechanical properties and reliability of the solar cell.

[0086] (3) By setting up a step-shaped isolation groove with a wide top and a narrow bottom, the top cell will not block the narrow isolation groove below, making it easier to remove impurities adhering to the narrow isolation groove through cleaning, thereby effectively avoiding impurity deposition and ensuring the electrical performance and stability of the solar cell.

[0087] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A solar cell step-shaped isolation groove, characterized in that: The invention comprises a wide isolation groove and a narrow isolation groove. The narrow isolation groove is arranged above the lower electrode, and the wide isolation groove is arranged above the narrow isolation groove. The two side edges of the wide isolation groove are located at the relatively outer sides of the two side edges of the narrow isolation groove.

2. The solar cell step-shaped isolation groove according to claim 1, characterized in that: The width of the wide isolation trench is 180-220 μm.

3. The solar cell step-shaped isolation groove according to claim 2, characterized in that: The narrow isolation trench has a width of 80-120 μm.

4. The solar cell step-shaped isolation groove according to any one of claims 1 to 3, characterized in that: The depth of the wide isolation trench penetrates the top battery layer; the depth of the narrow isolation trench penetrates the middle battery layer and the bottom battery layer.

5. A method for preparing a step-shaped isolation groove of a solar cell, characterized in that: The following steps are involved: Preparing a semi-finished battery with isolation grooves to be engraved; forming a first photoresist layer on the front side of the semi-finished battery; Photolithographically forming a narrow isolation opening in the first photoresist layer; Etching the narrow isolation opening downward to the upper surface of the lower electrode to form a narrow isolation groove; removing the remaining first photoresist layer; forming a second photoresist layer on the front side of the semi-finished battery; Photolithographically forming a wide isolation opening in the second photoresist layer; Etching the wide isolation opening downward to the upper surface of the middle battery to form a wide isolation groove; The remaining second photoresist layer is removed.

6. The method for preparing a solar cell step-shaped isolation groove according to claim 5, characterized in that: The semi-finished battery includes an upper electrode, a Cap layer, a top battery layer, a middle battery layer, a bottom battery layer and a lower electrode.

7. The method for preparing a solar cell step-shaped isolation groove according to claim 6, characterized in that: The narrow isolation groove is formed by a wet etching process, and sulfuric acid solution and potassium dichromate solution are alternately used as etching solutions to remove the top battery layer, the middle battery layer, and the bottom battery layer below the narrow isolation opening.

8. The method for preparing a solar cell step-shaped isolation groove according to claim 6, characterized in that: The wide isolation groove is formed by the wet etching process, and a mixed solution of phosphoric acid and hydrochloric acid is used as an etching solution to remove the top battery layer below the wide isolation opening.

9. The method for preparing a solar cell step-shaped isolation groove according to claim 5 or 6, characterized in that: The narrow isolation trench and / or the wide isolation trench is / are etched using a dry etching process.

10. A multi-junction gallium arsenide solar cell, characterized in that: The solar cell step-shaped isolation groove is provided as claimed in any one of claims 1 to 3 and / or is prepared by the method for preparing the solar cell step-shaped isolation groove as claimed in any one of claims 4 to 9.

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