Space solar cell and preparation method thereof

Abstract

The invention discloses a space solar cell and a preparation method thereof. The preparation method comprises the following steps: step 1, providing an epitaxial wafer; a plurality of front electrodes are formed on the front surface of the epitaxial wafer, and an exposed area is formed in the area, not covered by the front electrodes, of the front surface of the epitaxial wafer; a back electrode is formed on the back of the epitaxial wafer; 2, spraying a gold nanosphere colloidal solution on the exposed area, and drying to form a gold nanosphere modified area on the surface of the exposed area; the content of the gold element in the gold nanosphere colloidal solution is 0.05 mg / mL to 0.1 mg / mL; step 3, cleaning the epitaxial wafer; and step 4, evaporating an antireflection film on the gold nanosphere modification area. The photoelectric conversion efficiency of the space solar cell is improved, the preparation method is simple, and the application requirements of future spacecrafts are met.

Description

Technical Field

[0001] The invention relates to the field of solar cells, and in particular to a space solar cell and a preparation method thereof. Background Art

[0002] Future spacecraft tend to be large-scale and ultra-miniaturized, which puts higher requirements on the area, weight-to-power ratio and other aspects of space solar cells. At present, space solar cells are mainly triple-junction gallium arsenide solar cells, which are composed of three sub-cells with different energy band gaps connected in series. Three PN junctions are formed between the three sub-cells, which are responsible for absorbing different bands in the solar spectrum to achieve more efficient photoelectric conversion.

[0003] However, the research and development of space solar cells with higher photoelectric performance faces bottlenecks. In order to meet the high requirements of future spacecraft, researchers have tried to use lattice mismatch technology, as well as four-junction, five-junction, and six-junction cell technologies to prepare more efficient space solar cells. However, the feasibility of these solutions is poor and the experimental process is complicated, which limits the development of space solar cell technology.

[0004] Therefore, developing a low-cost and simple method to prepare space solar cells with higher photoelectric performance is an urgent problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a space high-efficiency triple-junction gallium arsenide solar cell and a preparation method thereof, which adopts a gold nanosphere modification method to effectively utilize the excellent localized surface plasmon properties of the gold nanospheres to improve the photoelectric conversion efficiency of the space solar cell.

[0006] In order to achieve the above object, the present invention provides a method for preparing a space solar cell, comprising:

[0007] Step 1, providing an epitaxial wafer; a plurality of front electrodes are formed on the front side of the epitaxial wafer, and the area of ​​the front side of the epitaxial wafer not covered by the front electrodes forms an exposed area; a back electrode is formed on the back side of the epitaxial wafer;

[0008] Step 2, spraying a gold nanosphere colloidal solution on the exposed area, and forming a gold nanosphere modified area on the surface of the exposed area after drying; the content of gold element in the gold nanosphere colloidal solution is 0.05 mg / mL to 0.1 mg / mL;

[0009] Step 3, cleaning the epitaxial wafer;

[0010] Step 4, vapor-depositing an anti-reflection film on the gold nanosphere modified area.

[0011] Furthermore, the size of the gold nanospheres is 15nm to 100nm.

[0012] Furthermore, the step 2 comprises: repeating the step 2 N times until the distribution uniformity and distribution density of the gold nanospheres in the gold nanosphere modified area reach the process target; N is a positive integer.

[0013] Furthermore, the value range of N is 6 to 8.

[0014] Furthermore, the step 3 comprises: using a mixed solution of deionized water and ethanol to clean the epitaxial wafer, wherein the volume fraction of the ethanol is 10% to 25%.

[0015] Furthermore, the material of the front electrode includes Ag and Au, and the purity of Ag and Au is not less than 99.99%.

[0016] Furthermore, the material of the back electrode includes Pt, Ag and Au, and the purity of the Pt, Ag and Au is not less than 99.99%.

[0017] Furthermore, the thickness of the front electrode is 4 μm to 6 μm; the thickness of the back electrode is 4 μm to 6 μm.

[0018] Furthermore, in step 4, the material of the anti-reflection film at least includes TiOx and AlOx, where x represents the relative atomic ratio of oxygen.

[0019] The present invention also provides a space solar cell, characterized in that it is formed by the preparation method described in any one of claims 1 to 9.

[0020] Compared with the prior art, the beneficial effects of the present invention at least include:

[0021] (1) In the preparation method of the space solar cell of the present invention, a gold nanosphere modified area is formed on the surface of the exposed area on the front side of the epitaxial wafer. After the gold nanosphere is irradiated with light of a specific wavelength (resonance wavelength), the plasmon on its surface will be excited, thereby forming a strong local field in the exposed area and penetrating into the semiconductor material below, thereby improving the photoelectric conversion efficiency of the space solar cell. By controlling the concentration of the gold element in the colloidal solution of the sprayed gold nanospheres, selecting gold nanospheres of appropriate size, and adopting multiple spraying and drying methods, the gold nanospheres are evenly distributed in the exposed area and reach an appropriate distribution density, avoiding the defect of reduced utilization of the gold nanospheres due to the agglomeration of the gold nanospheres, thereby further improving the photoelectric conversion efficiency of the space solar cell.

[0022] (2) Furthermore, in the preparation method of the space solar cell of the present invention, by precisely controlling the concentration of ethanol in the cleaning solution, it is ensured that the surfactant and impurities in the gold nanosphere colloidal solution can be effectively removed, while not destroying the photolithography electrode pattern formed on the epitaxial wafer in the previous process, thereby ensuring the reliability of the space solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention provides a process flow chart of the method for preparing the space solar cell.

[0024] Figure 2 It is a schematic diagram of the structure of the space solar cell of the present invention.

[0025] Figure 3 The SEM characterization results of the gold nanospheres in the examples.

[0026] Figure 4 This is the SEM characterization result of the gold nanosphere modified area on the front side of the epitaxial wafer after being modified with gold nanospheres in the example.

[0027] Figure 5 1 is the reflectivity curve of the space solar cell of the embodiment and the comparative example 1.

[0028] Figure 6 1 and 2 are the current and voltage characteristic curves of the space solar cells of the embodiment and comparative example 1.

[0029] Figure 7 This is the SEM characterization result of the gold nanosphere modified area on the front side of the epitaxial wafer modified with gold nanospheres in Comparative Example 2.

[0030] Figure 8 1 and 2 are reflectivity curves of the space solar cells of Example 1 and Comparative Example 2.

[0031] Description of the accompanying drawings:

[0032] Epitaxial wafer 1, front electrode 2, back electrode 3, gold nanospheres 4, anti-reflection film 5. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are 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 limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] As described in the background technology, in order to meet the application needs of future space technology, how to develop simple and low-cost preparation methods and further improve the photoelectric conversion efficiency are the key issues that need to be urgently solved for space solar cells.

[0037] The inventors found that gold nanospheres have excellent localized surface plasmon resonance characteristics, which are expected to improve the photoelectric conversion efficiency of space solar cells. When the gold nanospheres placed on the surface of the semiconductor are irradiated by light of a specific wavelength, the plasmons on the surface of the gold nanospheres will be excited. Since the contact interface between the semiconductor and the gold nanospheres and the interface of the other parts of the gold nanospheres are different in material properties, the plasmons can form a strong local field at the contact interface between the semiconductor and the gold nanospheres, and penetrate into the interior of the semiconductor material, which is conducive to improving the semiconductor material's absorption efficiency of light, thereby improving the photoelectric conversion efficiency of space solar cells. In addition, the inventors unexpectedly found that the plasmon resonance characteristics of the gold nanospheres are also affected by factors such as their size and their distribution morphology on the semiconductor surface. In the present invention, by controlling the concentration of the gold element in the colloidal solution of the sprayed gold nanospheres, selecting gold nanospheres of suitable size, and using multiple spraying and drying methods, the uniform distribution of the gold nanospheres on the semiconductor surface is achieved in a coordinated manner, thereby optimizing the plasmon resonance characteristics of the gold nanospheres, and further improving the photoelectric conversion efficiency of space solar cells.

[0038] To solve the above problems, the present invention provides a method for preparing a triple-junction gallium arsenide space solar cell, such as Figure 1 and Figure 2 As shown, including:

[0039] Step 1, providing an epitaxial wafer; a plurality of front electrodes are formed on the front side of the epitaxial wafer, and the area on the front side of the epitaxial wafer not covered by the front electrodes forms an exposed area; a back electrode is formed on the back side of the epitaxial wafer.

[0040] The epitaxial wafer 1 includes a top subcell, a middle subcell, and a bottom subcell (not shown) stacked in sequence from top to bottom; the bottom subcell (substrate) is made of germanium (Ge) for absorbing infrared light in the solar spectrum; the middle subcell is made of gallium indium arsenide (GaInAs) for absorbing red light and part of infrared light in the solar spectrum; the top subcell is made of gallium indium phosphide (GaInP) for absorbing shorter wavelength light in the solar spectrum. The shorter wavelength light is relative to red light.

[0041] The front electrode 2 is mainly used to collect photogenerated carriers. The preparation method of the front electrode 2 includes: photolithography of an electrode pattern on the surface of the GaInP sub-cell of the epitaxial wafer 1, and using electron beam evaporation to evaporate the front electrode metal on the electrode pattern to form the front electrode 2. In some embodiments, the front electrode metal includes Ag and Au, and the purity of Ag and Au is not less than 99.99%; the thickness of the front electrode 2 is 4μm to 6μm, to ensure that an ohmic contact is formed between the front electrode 2 and the GaInP sub-cell. An exposed area is formed in the area on the surface of the GaInP sub-cell of the epitaxial wafer 1 that is not covered by the front electrode 2, for the sunlight to penetrate, so as to be absorbed by the semiconductor material to generate photogenerated carriers (electrons and holes).

[0042] The back electrode 3 is mainly used to collect and transfer carriers that pass through the semiconductor material and reach the back of the space solar cell. The preparation method of the back electrode 3 includes: on the bottom surface of the Ge substrate of the epitaxial wafer 1, using electron beam evaporation to evaporate the back electrode metal on the bottom surface of the Ge substrate to form the back electrode 3. In some embodiments, the back electrode metal includes Pt, Ag and Au, and the purity of Pt, Ag and Au is not less than 99.99%; the thickness of the back electrode 3 is 4μm to 6μm, to ensure that the back electrode 3 forms an ohmic contact with the Ge substrate.

[0043] Step 2, spraying a gold nanosphere colloidal solution on the exposed area, and forming a gold nanosphere modified area on the surface of the exposed area after drying; the content of gold element in the gold nanosphere colloidal solution is 0.05 mg / mL to 0.1 mg / mL;

[0044] The step 2 further comprises: repeating the step 2 N times until the distribution density and the distribution uniformity of the gold nanospheres in the gold nanosphere modified area reach the process target; N is a positive integer.

[0045] Among them, the size of the gold nanosphere 4 has a significant effect on its plasmon resonance characteristics. In some embodiments, the size of the selected gold nanosphere 4 is 15nm to 100nm, and the plasmon resonance wavelength of the gold nanosphere 4 within this size range is 500nm to 550nm, which falls within the visible light range, so that under the irradiation of sunlight, the plasmon energy on the surface of the gold nanosphere 4 can be greatly excited, forming a strong local field in the exposed area, enhancing the absorption of light by the space solar cell, and thus improving the photoelectric conversion efficiency of the space solar cell. In some embodiments, the gold nanosphere colloidal solution of the present invention comprises gold nanospheres, a surfactant (hexadecyl trimethyl ammonium bromide and / or hexadecyl trimethyl ammonium chloride), and deionized water, and the gold nanospheres and the gold nanosphere colloidal solution can be prepared by reference to the method (Jana, NRet al., Seeding Growth for Size Control of 5-40nm Diameter Gold Nanoparticles, Langmuir, 17, 6782-6786, 2001).

[0046] The distribution morphology of the gold nanospheres 4 formed in the gold nanosphere modification area will also have a significant effect on its plasmon resonance characteristics. If the distribution density of the gold nanospheres 4 in the gold nanosphere modification area is too large, aggregation is likely to occur. When the gold nanospheres 4 are aggregated, part of the surface of the gold nanospheres 4 may not be irradiated by light, so that part of the plasmons cannot be effectively excited, weakening the plasmon resonance characteristics of the gold nanospheres 4. Moreover, the aggregated gold nanospheres 4 may block sunlight, so that part of the front of the epitaxial wafer 1 cannot be irradiated by sunlight, resulting in a decrease in light absorption. In the method of the present invention, on the basis of selecting gold nanospheres with a size of 15nm to 100nm, the content of gold element in the gold nanosphere colloidal solution is specially adjusted to 0.05mg / mL to 0.1mg / mL, and N times of spraying and drying are adopted to coordinately make the distribution uniformity and distribution density of the gold nanospheres 4 in the gold nanosphere modification area reach the process target, avoid the aggregation of gold nanospheres 4, and maximize the use of the plasmon resonance characteristics of gold nanospheres. The process goal requires that the distribution uniformity of the gold nanospheres 4 in the gold nanosphere modified area meets the process requirements (no aggregation phenomenon), and the distribution density of the gold nanospheres 4 meets the process requirements. In some embodiments, the value of N is 6 to 8, and the distribution density of the gold nanospheres 4 is (1×10 7 ~3×10 7 )pcs / mm 2 After each spraying, the epitaxial wafer 1 is dried before the next spraying.

[0047] Step 3, cleaning the epitaxial wafer.

[0048] In some embodiments, the epitaxial wafer 1 is cleaned with a mixed solution of deionized water and ethanol, wherein the volume fraction of the ethanol is 10% to 25%. Specifically, the epitaxial wafer 1 is soaked in the mixed solution for 1 to 5 minutes to remove the surfactant and impurities contained in the gold nanosphere colloidal solution. After soaking, the epitaxial wafer is blown dry with a nitrogen gun or dried with a spin dryer.

[0049] In the method of the present invention, the ethanol solution containing 10% to 25% by volume is selected to ensure that the surfactant introduced in step 2 on the surface of the GaInP subcell of the epitaxial wafer 1 (the front of the epitaxial wafer 1) can be completely removed, and at the same time, the electrode pattern formed by the photoresist in the front process of the epitaxial wafer 1 is not damaged. If the ethanol content is too low, it is easy to cause the surfactant to not be completely removed; if the ethanol content is too high, it may affect the stability of the photoresist, damage the electrode pattern, and affect the subsequent space solar cell process.

[0050] Step 4, vapor-depositing an anti-reflection film on the gold nanosphere modified area.

[0051] In the method of the present invention, an anti-reflection film 5 is evaporated on the gold nanosphere modified area, and the anti-reflection film 5 can reduce the reflection of light, thereby increasing the luminous flux entering the space solar cell and further improving the photoelectric conversion efficiency of the solar cell.

[0052] In some embodiments, the anti-reflection film 5 is a double-layer anti-reflection film, comprising TiO x 、AlO x ; wherein x represents the relative atomic ratio of O, the TiO x 、AlO x The purity of the anti-reflection film 5 is not less than 99.99%. The thickness of the anti-reflection film 5 is 80nm to 120nm.

[0053] The method for preparing space solar cells provided by the present invention does not need to rely on complicated instruments and equipment, has a simple process flow, and is conducive to its large-scale application.

[0054] The technical solution of the present invention is further described below in conjunction with embodiments and drawings.

[0055] Example 1

[0056] Step S101, providing a GaInP / InGaAs / Ge epitaxial wafer (hereinafter referred to as "epitaxial wafer"), wherein the epitaxial wafer is composed of a GaInP sub-cell at the top layer, an InGaAs sub-cell at the middle layer and a Ge substrate at the bottom layer.

[0057] Step S102, photolithography is performed on the surface of the GaInP sub-cell to prepare an electrode pattern, and Ag and Au are evaporated on the electrode pattern by electron beam evaporation to form an Ag-Au front electrode, wherein the metal purity of Ag and Au is 99.99%. By controlling the evaporation process parameters, the thickness of the prepared Ag-Au front electrode is 5.5 μm. The area on the surface of the GaInP sub-cell not covered by the Ag-Au front electrode forms an exposed area.

[0058] Step S103, evaporating Pt, Ag, and Au on the bottom surface of the Ge substrate to form a Pt-Ag-Au back electrode, wherein the metal purity of Pt, Ag, and Au is 99.99%. By controlling the evaporation process parameters, the thickness of the prepared Pt-Ag-Au back electrode is 4.5 μm.

[0059] Step S104, coating a photoresist on the Ag-Au front electrode to ensure that the anti-reflection film evaporated in the subsequent step adheres to the exposed area and does not cover the Ag-Au front electrode.

[0060] Step S105, modifying the exposed area with gold nanospheres to form a gold nanosphere modified area: placing the epitaxial wafer treated in steps S101 to S104 on a sample table, spraying the gold nanosphere colloidal solution, after spraying once, placing the epitaxial wafer on a clean table and letting it stand for 15 minutes to dry. After the epitaxial wafer is completely dry, continue to spray and dry in sequence. In this embodiment, the number of spraying is 8 times. The size of the gold nanospheres used is 30nm, Figure 3 The SEM (scanning electron microscope) characterization results of the gold nanospheres used in this example are shown. The plasmon resonance absorption peak of the gold nanospheres is located at 520 nm, and the content of gold element in the gold nanosphere colloidal solution is 0.08 mg / mL.

[0061] Step S106, cleaning the epitaxial wafer: soaking the epitaxial wafer in a mixed solution of deionized water and ethanol for 1 minute. The volume fraction of ethanol in the mixed solution is 20%. After soaking for 1 minute, take the epitaxial wafer out of the mixed solution and blow dry its surface with a nitrogen gun.

[0062] The surface morphology of the front side of the epitaxial wafer modified with gold nanospheres was measured, such as Figure 4 As shown, it is proved that the preparation method adopted in this embodiment can make the gold nanospheres more evenly distributed on the surface of the semiconductor material, thereby effectively utilizing the plasmon resonance characteristics of the gold nanospheres.

[0063] Step S107, placing the epitaxial wafer modified with gold nanospheres in a chamber of an electron beam evaporation device, and evaporating an anti-reflection film on the gold nanosphere modified area. The anti-reflection film includes TiO x 、AlO x , where x represents the relative atomic ratio of O, TiO x 、AlO x The purity of the anti-reflection film is 99.99%. The thickness of the formed anti-reflection film is 100 nm.

[0064] Step S108, after removing the photoresist above the Ag-Au front electrode with a conventional degumming solution, the preparation of the space solar cell of this embodiment is completed.

[0065] Comparative Example 1

[0066] The difference between this comparative example and the embodiment is that step S105 and step S106 are not performed, and a space solar cell that is not modified with gold nanospheres is prepared.

[0067] The reflectivity and electrical performance of the space solar cells prepared in Example 1 and Comparative Example 1 were measured respectively. The test results are as follows: Figure 5 , Figure 6 As shown. Compared with Comparative Example 1, the reflectivity of the space solar cell prepared in the embodiment is lower and the current is higher, which proves that the localized surface plasmon resonance characteristics of the gold nanospheres enhance the absorption of light by the space solar cell, thereby reducing the reflection of light. Since the gold nanospheres enhance the light absorption, a larger number of photogenerated carriers are generated in the space solar cell of the embodiment, which can generate a higher current, thereby improving its photoelectric conversion efficiency.

[0068] The calculated photoelectric conversion efficiency of the space solar cell prepared in the example is 30.57%, and the photoelectric conversion efficiency of the space solar cell prepared in comparative example 1 is 30.02%, which proves that gold nanosphere modification can effectively improve the photoelectric conversion efficiency of space solar cells.

[0069] Comparative Example 2

[0070] The difference between this comparative example and the embodiment is that in step S105, the content of gold element in the gold nanosphere colloidal solution used is 0.32 mg / mL (4 times that of the embodiment).

[0071] like Figure 7As shown, in this comparative example, increasing the concentration of gold nanospheres makes the gold nanospheres on the front side of the epitaxial wafer more concentrated, and even aggregation occurs, so that the surface of some gold nanospheres may not be fully illuminated by sunlight, thereby failing to maximize the effective utilization of plasmons on the surface of the gold nanospheres; moreover, the concentrated gold nanospheres will also block sunlight, so that part of the front side of the epitaxial wafer cannot be illuminated by sunlight, reducing its light absorption rate.

[0072] The reflectivity of the space solar cells prepared in Comparative Example 2 was measured respectively, and the test results are as follows: Figure 8 Compared with the embodiment, the reflectivity of the space solar cell of comparative example 2 is significantly higher, which means that the light absorption efficiency of comparative example 2 is relatively low, proving that the distribution morphology of gold nanospheres on the surface of space solar cells will affect the light absorption yield of space solar cells, and it is necessary to adjust the gold nanosphere concentration of the gold nanosphere colloid solution and the number of spraying and drying times to form a distribution morphology of gold nanospheres that meets the process requirements.

[0073] Comparative Example 3

[0074] The difference between this comparative example and the embodiment is that in the step S106, the volume fraction of ethanol in the mixed solution of deionized water and ethanol is 40%. After the epitaxial wafer modified with gold nanospheres is immersed in the mixed solution for 1 min, taken out, and blown dry with a nitrogen gun, the inventor found that the photoresist coated on the Ag-Au front electrode prepared in this comparative example was damaged, which would affect the subsequent process of the solar cell, for example, causing the anti-reflection film to be evaporated above the Ag-Au front electrode, thereby affecting the reliability of the space solar cell.

[0075] In summary, in the method for preparing a space solar cell of the present invention, a gold nanosphere modification area is formed on the surface of the front side of the epitaxial wafer, and a strong local field is generated on the front side of the epitaxial wafer by utilizing the plasmon resonance characteristics of the gold nanospheres, thereby improving the photoelectric conversion efficiency. By controlling the concentration of the gold element in the gold nanosphere colloidal solution and adopting a multiple spraying method, the gold nanospheres are evenly distributed on the front side of the epitaxial wafer, agglomeration is avoided, and the photoelectric conversion efficiency is further improved. At the same time, by accurately controlling the ethanol concentration in the cleaning solution, the surfactant and impurities are effectively removed, and the photolithographic electrode pattern is protected, thereby ensuring the reliability of the solar cell.

[0076] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for preparing a space solar cell, characterized in that: include: Step 1, providing an epitaxial wafer; a plurality of front electrodes are formed on the front side of the epitaxial wafer, and the area of ​​the front side of the epitaxial wafer not covered by the front electrodes forms an exposed area; a back electrode is formed on the back side of the epitaxial wafer; Step 2, spraying a gold nanosphere colloidal solution on the exposed area, and forming a gold nanosphere modified area on the surface of the exposed area after drying; the content of gold element in the gold nanosphere colloidal solution is 0.05 mg / mL to 0.1 mg / mL; Step 3, cleaning the epitaxial wafer; Step 4, vapor-depositing an anti-reflection film on the gold nanosphere modified area.

2. The method for preparing a space solar cell according to claim 1, characterized in that: The size of the gold nanospheres is 15nm to 100nm.

3. The method for preparing a space solar cell according to claim 1, characterized in that: The step 2 comprises: repeating the step 2 N times until the distribution uniformity and distribution density of the gold nanospheres in the gold nanosphere modified area reach the process target; N is a positive integer.

4. The method for preparing a space solar cell according to claim 3, characterized in that: The value range of N is 6 to 8.

5. The method for preparing a space solar cell according to claim 1, characterized in that: The step 3 comprises: using a mixed solution of deionized water and ethanol to clean the epitaxial wafer, wherein the volume fraction of the ethanol is 10% to 25%.

6. The method for preparing a space solar cell according to claim 1, characterized in that: The material of the front electrode includes Ag and Au, and the purity of the Ag and Au is not less than 99.99%.

7. The method for preparing a space solar cell according to claim 1, characterized in that: The material of the back electrode includes Pt, Ag and Au, and the purity of the Pt, Ag and Au is not less than 99.99%.

8. The method for preparing a space solar cell according to claim 1, characterized in that: The thickness of the front electrode is 4 μm to 6 μm; the thickness of the back electrode is 4 μm to 6 μm.

9. The method for preparing a space solar cell according to claim 1, characterized in that: In step 4, the material of the anti-reflection film at least comprises TiO x 、AlO x , x represents the relative atomic proportion of oxygen.

10. A space solar cell, characterized in that: The method is formed by any one of claims 1 to 9.

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