Gallium arsenide solar cell top electrode for low-cost space and preparation method of gallium arsenide solar cell top electrode

Abstract

The invention discloses a method for preparing an upper electrode of a gallium arsenide solar cell for a low-cost space, which comprises the following steps of: corroding a gallium arsenide epitaxial wafer taking germanium as a substrate in a mixed acid corrosion solution, removing an oxide layer and pollutants on the surface of the epitaxial wafer, taking out the epitaxial wafer, and cleaning the epitaxial wafer in deionized water; the surface of the active layer of the epitaxial wafer is tightly attached to the metal grid mesh, the epitaxial wafer is put into vacuum evaporation equipment, electrode metal is evaporated layer by layer in an electron beam evaporation mode, and after evaporation is completed, the epitaxial wafer is taken out from the vacuum evaporation equipment when the epitaxial wafer is cooled to 100 DEG C or below; and placing in a vacuum sintering furnace, heating at a constant temperature for a period of time, cooling to below 100 DEG C, and taking out to obtain the space gallium arsenide solar cell top electrode. A traditional photoetching process is replaced by a metal grid mesh, the surface of an active layer of an epitaxial wafer is tightly attached to the metal grid mesh, and then the epitaxial wafer is put into a vacuum coating machine to be subjected to metal evaporation. And the evaporated metal is deposited on the surface of the epitaxial wafer through gaps of the grid mesh to prepare a conductive upper electrode.

Description

Technical Field

[0001] The invention belongs to the field of solar cells, and in particular relates to a low-cost upper electrode of a gallium arsenide solar cell for space use and a preparation method thereof. Background Art

[0002] In recent years, commercial aerospace has developed rapidly around the world. In 2023, the number of satellites launched by SpaceX in the United States was 2,514, accounting for 87% of the total number of satellites launched worldwide. As a private commercial aerospace company, SpaceX has become the main force of American aerospace. Commercial aerospace is a market-oriented and commercially profitable aerospace activity that aims to carry out the research and development, manufacturing, launch and application of aerospace technology and services through the commercial market. Therefore, reducing costs and improving the profitability of enterprises are the foundation for the sustainable development of commercial aerospace.

[0003] The traditional method for preparing the top electrode of GaAs solar cells for space use is to first prepare a photoresist mask pattern on an epitaxial wafer through a photolithography process, and then prepare it through vacuum evaporation of metal. Both the photolithography equipment and the photoresist materials used are expensive, making the preparation cost of the top electrode of GaAs solar cells high. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a low-cost gallium arsenide solar cell upper electrode for space use and a preparation method thereof. The preparation process is simple, which not only ensures the reliability of the electrode and meets the requirements of the space environment, but also can greatly reduce the preparation cost.

[0005] The present invention adopts the following technical solution: a method for preparing a low-cost upper electrode of a gallium arsenide solar cell for space use, comprising the following steps:

[0006] (1) placing a gallium arsenide epitaxial wafer with germanium as the substrate in a mixed acid etching solution to remove the oxide layer and contaminants on the surface of the epitaxial wafer, taking out the epitaxial wafer and placing it in deionized water for cleaning;

[0007] (2) The active layer surface of the epitaxial wafer is closely attached to the metal grid and placed in a vacuum evaporation device. The evaporation chamber is evacuated to a certain vacuum degree, and then heated to a constant temperature for a period of time. Electron beam evaporation is used to evaporate the upper electrode metal layer by layer. The evaporated metal is deposited on the surface of the epitaxial wafer through the gaps in the grid. After the evaporation is completed, the epitaxial wafer is cooled to below 100° C. and then taken out from the vacuum evaporation device;

[0008] (3) The epitaxial wafer with the metal electrode evaporated is placed in a vacuum sintering furnace, heated and kept at a constant temperature for a period of time to strengthen the firmness of the electrode, and then cooled to below 100°C and taken out to obtain the upper electrode of the gallium arsenide solar cell for space use.

[0009] In step (1), the mixed acid etching solution is an acid etching mixture of sulfuric acid: hydrogen peroxide: deionized water = 1:1:20 in volume ratio, and the etching time is 30s to 60s.

[0010] In step (2), the metal grid is made of stainless steel and has a thickness of 2 mm to 3 mm. The gap distribution of the grid is designed to be the pattern of the electrode grid lines on the battery, and the minimum width of the gap is 100 μm.

[0011] In step (2), the vacuum degree during evaporation should be no less than 5×10 -4 Pa, the chamber heating temperature during evaporation is 150℃~200℃.

[0012] In step (2), the evaporation chamber is in a constant temperature heating state during the entire metal evaporation process.

[0013] In step (3), the heating temperature in the vacuum sintering furnace is 300° C. to 350° C., and the constant temperature time is 20 min to 30 min.

[0014] The metal deposited on the metal grid is cleaned by concentrated nitric acid, and the grid can be used repeatedly after being cleaned.

[0015] The low-cost gallium arsenide solar cell upper electrode for space use is prepared by the preparation method.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] (1) In the traditional process of preparing the upper electrode of gallium arsenide solar cells for space use, a photoresist pattern is first prepared on the surface of the epitaxial wafer by a photolithography process, and then a metal electrode is vacuum evaporated. Finally, the photoresist needs to be removed and the excess deposited metal on the surface of the epitaxial wafer needs to be stripped off. The preparation process is complicated, and the photolithography machine and photoresist used are expensive. The present invention replaces the entire traditional photolithography process with a metal grid, which will greatly save the processing cycle and cost of the upper electrode of the solar cell.

[0018] (2) The photoresist generally used for metal stripping cannot withstand high temperatures. In the conventional process of preparing the electrodes on gallium arsenide solar cells for space use, low-temperature evaporation is generally used. Since the present invention uses a high-temperature resistant metal grid as a mask, the metal electrode can be evaporated at a higher temperature environment, making the electrode more solid and improving the reliability of the solar cell. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] The method for preparing the upper electrode of a low-cost gallium arsenide solar cell for space use of the present invention comprises the following steps:

[0021] (1) placing a gallium arsenide epitaxial wafer with germanium as the substrate in a mixed acid etching solution to remove the oxide layer and contaminants on the surface of the epitaxial wafer, taking out the epitaxial wafer and placing it in deionized water for cleaning;

[0022] (2) The active layer surface of the epitaxial wafer is closely attached to the metal grid and placed in a vacuum evaporation device. The evaporation chamber is evacuated to a certain vacuum degree, and then heated to a constant temperature for a period of time. Electron beam evaporation is used to evaporate the upper electrode metal layer by layer. The evaporated metal is deposited on the surface of the epitaxial wafer through the gaps in the grid. After the evaporation is completed, the epitaxial wafer is cooled to below 100° C. and then taken out from the vacuum evaporation device;

[0023] (3) The epitaxial wafer with the metal electrode evaporated is placed in a vacuum sintering furnace, heated and kept at a constant temperature for a period of time to strengthen the firmness of the electrode, and then cooled to below 100°C and taken out to obtain the upper electrode of the gallium arsenide solar cell for space use.

[0024] Furthermore, in step (1), the mixed acid etching solution is an acid etching mixture of sulfuric acid: hydrogen peroxide: deionized water = 1:1:20 in volume ratio, and the etching time is 30s to 60s.

[0025] Furthermore, in step (2), the metal grid is made of stainless steel and has a thickness of 2 mm to 3 mm. The gap distribution of the grid is designed to be the pattern of the electrode grid lines on the battery, and the minimum width of the gap is 100 μm.

[0026] Furthermore, in step (2), the vacuum degree during evaporation should be no less than 5×10 -4 Pa, the chamber heating temperature during evaporation is 150℃~200℃.

[0027] Furthermore, in step (2), the evaporation chamber is in a constant temperature heating state during the entire metal evaporation process.

[0028] Furthermore, in step (3), the heating temperature in the vacuum sintering furnace is 300° C. to 350° C., and the constant temperature time is 20 min to 30 min.

[0029] Furthermore, the metal deposited on the metal grid is cleaned by concentrated nitric acid, and the grid can be used repeatedly after being cleaned.

[0030] The low-cost gallium arsenide solar cell upper electrode for space use is prepared by the preparation method.

[0031] The method for preparing the upper electrode of the low-cost gallium arsenide solar cell for space use of the present invention replaces the traditional photolithography process with a metal grid, closely fits the active layer surface of the epitaxial wafer with the metal grid, and then puts it into a vacuum coating machine for metal evaporation. The evaporated metal is deposited on the surface of the epitaxial wafer through the gaps of the grid to prepare an upper electrode for conduction.

[0032] In order to further understand the content, features and effects of the present invention, the following examples are given, but the embodiments of the present invention are not limited thereto:

[0033] (1) Place the GaAs epitaxial wafer with germanium as the substrate in a sulfuric acid and hydrogen peroxide mixed etching solution for 60 seconds to remove the oxide layer and pollutants on the surface of the epitaxial wafer. The etching solution ratio (volume ratio) is sulfuric acid: hydrogen peroxide: deionized water = 1:1:20. After the etching is completed, take out the epitaxial wafer and place it in deionized water for cleaning;

[0034] (2) The active layer surface of the epitaxial wafer is closely attached to the metal grid and fixed with a movable clamp, and then placed in a vacuum evaporation device;

[0035] (3) First, evaporation chamber is pumped to 5×10 -4 Pa, then heated to 200°C and kept at a constant temperature for 30 minutes, and the upper electrode metal was evaporated layer by layer by electron beam evaporation. The evaporated metal was deposited on the surface of the epitaxial wafer through the gaps in the grid. The evaporation chamber was in a constant temperature heating state during the entire metal evaporation process;

[0036] (4) After the evaporation is completed, the epitaxial wafer is cooled to below 100° C. and then taken out from the vacuum evaporation equipment;

[0037] (5) Place the epitaxial wafer with the metal electrode deposited in a vacuum sintering furnace, heat it to 340°C and keep it at a constant temperature for 30 minutes to strengthen the firmness of the electrode. Then cool it to below 100°C and take it out to obtain the GaAs solar cell electrode for space use;

[0038] (6) The metal vapor-deposited on the metal grid can be cleaned with concentrated nitric acid. After cleaning, the grid can be reused.

[0039] The above embodiment is one implementation mode of the present invention, but the implementation mode of the present invention is not limited to the said embodiment. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a low-cost upper electrode of a gallium arsenide solar cell for space use, characterized in that: The following steps are involved: (1) placing a gallium arsenide epitaxial wafer with germanium as the substrate in a mixed acid etching solution to remove the oxide layer and contaminants on the surface of the epitaxial wafer, taking out the epitaxial wafer and placing it in deionized water for cleaning; (2) The active layer surface of the epitaxial wafer is closely attached to the metal grid and placed in a vacuum evaporation device. The evaporation chamber is evacuated to a certain vacuum degree, and then heated to a constant temperature for a period of time. Electron beam evaporation is used to evaporate the upper electrode metal layer by layer. The evaporated metal is deposited on the surface of the epitaxial wafer through the gaps in the grid. After the evaporation is completed, the epitaxial wafer is cooled to below 100° C. and then taken out from the vacuum evaporation device; (3) The epitaxial wafer with the metal electrode evaporated is placed in a vacuum sintering furnace, heated and kept at a constant temperature for a period of time to strengthen the firmness of the electrode, and then cooled to below 100°C and taken out to obtain the upper electrode of the gallium arsenide solar cell for space use.

2. The method for preparing the top electrode of a low-cost gallium arsenide solar cell for space use according to claim 1, characterized in that: In step (1), the mixed acid etching solution is an acid etching mixture of sulfuric acid: hydrogen peroxide: deionized water = 1:1:20 in volume ratio, and the etching time is 30s to 60s.

3. The method for preparing the top electrode of a low-cost gallium arsenide solar cell for space use according to claim 1, characterized in that: In step (2), the metal grid is made of stainless steel and has a thickness of 2 mm to 3 mm. The gap distribution of the grid is designed to be the pattern of the electrode grid lines on the battery, and the minimum width of the gap is 100 μm.

4. The method for preparing the top electrode of a low-cost gallium arsenide solar cell for space use according to claim 1, characterized in that: In step (2), the vacuum degree during evaporation should be no less than 5×10 -4 Pa, the chamber heating temperature during evaporation is 150℃~200℃.

5. The method for preparing the top electrode of a low-cost gallium arsenide solar cell for space use according to claim 1, characterized in that: In step (2), the evaporation chamber is in a constant temperature heating state during the entire metal evaporation process.

6. The method for preparing the upper electrode of a low-cost gallium arsenide solar cell for space use according to claim 1, characterized in that: In step (3), the heating temperature in the vacuum sintering furnace is 300° C. to 350° C., and the constant temperature time is 20 min to 30 min.

7. The method for preparing the top electrode of a low-cost gallium arsenide solar cell for space use according to any one of claims 1 to 6, characterized in that: The metal deposited on the metal grid is cleaned by concentrated nitric acid, and the grid can be used repeatedly after being cleaned.

8. A low-cost gallium arsenide solar cell upper electrode for space use prepared by the preparation method according to any one of claims 1 to 7.