CN102651420A - Double-junction GaAs lamination laser photovoltaic cell and fabrication method thereof - Google Patents

Abstract

The invention provides a double-junction GaAs laminated laser photovoltaic cell, which includes a GaAs substrate, a conductive layer of N-type GaAs, a first tunnel junction, and a layer of P-type AlGaAs ((Al)GaInP) grown sequentially on the substrate. The first barrier layer, the bottom cell, the second tunnel junction, the second barrier layer of P-type AlGaAs ((Al)GaInP), the top cell, the window layer of AlGaAs (Ga _0.51 In _0.49 P) and the GaAs contact layer, It also includes isolation grooves, which sequentially penetrate the GaAs contact layer until the substrate is exposed, and the isolation grooves are filled with silicon oxide or polyimide glue. The present invention also provides a method for preparing the above-mentioned double-junction GaAs stacked laser photovoltaic cell, which includes the steps of: (1) providing a substrate; (2) sequentially growing a conductive layer, a first tunnel junction, and a first potential on the substrate; Barrier layer, bottom cell, second tunnel junction, second barrier layer, top cell, window layer and GaAs contact layer; (3) Etch the GaAs contact layer by dry or wet etching until the substrate is exposed surface to form an isolation groove; (4) Fill the isolation groove with silicon oxide or polyimide glue.

Description

Double-junction GaAs stacked laser photovoltaic cell and its preparation method

technical field

The invention relates to the field of laser photovoltaic cells, in particular to a double-junction GaAs lamination laser photovoltaic cell and a preparation method thereof.

Background technique

The laser energy supply system is an innovative energy transfer system. With this system, the light emitted by the laser source is transmitted to the laser photovoltaic cell through the optical fiber, which can provide a stable power output. The conversion of light into electricity through optical fiber has more advantages than traditional metal wire and coaxial cable power transmission technology, and can be applied in radio communication, industry where electromagnetic interference needs to be eliminated or electronic devices need to be isolated from the surrounding environment. Sensors, national defense, aviation, medicine, energy and other directions have important applications. The working principle of laser photovoltaic cells is similar to that of solar cells, except that they can obtain higher conversion efficiency, larger output voltage, and can transmit more energy. - Laser light with a wavelength of 850 nm.

GaAs is a III/V group semiconductor material, and the band gap Eg at room temperature is 1.428 eV. GaAs PN junction cells can be used to convert 808 nm laser energy into electrical energy and used as laser cells in laser energy supply systems, but GaAs The open circuit voltage of the battery is only 1 V, and it cannot be directly used as a power source in electronic circuits. In the early laser photovoltaic cells, several single-junction battery cells were connected in series to obtain the required output voltage, and the battery chips per unit area were isolated by etching isolation trenches, and then several single-junction battery cells were connected by wires. Units are connected in series. The greater the number of isolation trenches, the smaller the effective light-receiving area of the cell. To solve this problem, we propose to design each battery cell as a double-junction cell structure connected by a tunnel junction, which can reduce the isolation trench Influenced by the groove, the effective light-receiving area of the laser photocell is increased, and the series resistance of the battery interconnection is reduced, which helps to improve the performance of the device.

Contents of the invention

The technical problem to be solved by the present invention is to provide a double-junction GaAs laminated laser photovoltaic cell and a preparation method thereof.

In order to solve the above problems, the present invention provides a double-junction GaAs laminated laser photovoltaic cell, including a GaAs substrate, and an N-type GaAs conductive layer, a first tunnel junction, and a bottom cell arranged in sequence on the substrate. , a second tunnel junction, a top cell, a window layer of AlGaAs (Ga _0.51 In _0.49 P), and a GaAs contact layer.

The double-junction GaAs laminated laser photovoltaic cell further includes an isolation groove that penetrates from the GaAs contact layer to the substrate until the substrate is exposed, and the isolation groove is filled with silicon oxide or poly imide glue.

Both the first tunneling junction and the second tunneling junction include an N-type GaAs (Ga _0.51 In _0.49 P) layer, a P-type (Al) GaAs layer, and a P-type AlGaAs ((Al) GaInP) layer.

Both the bottom cell and the top cell are GaAs-based PN junction cells, and the respective P regions and N regions of the bottom cell and the top cell are sequentially away from the substrate.

The double-junction GaAs laminated laser photovoltaic cell further includes a positive electrode window, and the positive electrode window penetrates from the GaAs contact layer to the conductive layer until the conductive layer is exposed.

The double-junction GaAs laminated laser photovoltaic cell further includes an anti-reflection film of ZnSe/MgF or TiO2/SiO2 placed on the exposed surface of the window layer.

In order to solve the above problems, the present invention also provides a method for preparing a double-junction GaAs laminated laser photovoltaic cell as described above, including the steps: (1) providing a GaAs substrate; (2) sequentially growing a conductive layer on the substrate, the second a tunnel junction, a bottom cell, a second tunnel junction, a top cell, a window layer and a GaAs contact layer;

The method for preparing a double-junction GaAs laminated laser photovoltaic cell further includes the step of: (3) using a dry or wet etching method to etch from the GaAs contact layer to the substrate until the surface of the substrate is exposed, forming Isolation tank; (4) Fill the isolation tank with silicon oxide or polyimide glue.

The method for preparing a double-junction GaAs laminated laser photovoltaic cell further includes the step of: (5) using a dry or wet etching method to etch from the GaAs contact layer to the substrate until the surface of the conductive layer is exposed, forming Positive electrode window.

The preparation method of the double-junction GaAs laminated laser photovoltaic cell further includes the step of: using dry or wet etching to etch the GaAs contact layer in the designated area until the surface of the window layer is exposed; An anti-reflection film is grown on the surface, and the method for growing the anti-reflection film is any one of chemical vapor deposition, evaporation and sputtering.

The invention provides a double-junction GaAs laminated laser photovoltaic cell and a preparation method thereof, the advantages of which are:

1. Double-junction GaAs laminated laser photovoltaic cells realize that each unit has two cells in series, which reduces the series resistance and is conducive to the improvement of cell efficiency;

2. In the present invention, for photovoltaic cells with the same open circuit voltage, the proportion of the light-receiving area occupied by the isolation groove is reduced, and the loss of incident light on the isolation groove is reduced, which is beneficial to the improvement of cell efficiency;

3. In the present invention, both the GaAs contact layer and the conductive layer use N-type GaAs, which can complete the evaporation or electroplating thickening of the ohmic contact metal of the positive and negative electrodes in one step in the battery process, reducing the one-step photolithography and one-step stripping process, reducing One photolithography plate, saving processing time and reducing costs;

4. The double-junction GaAs laminated laser photovoltaic cell provided by the present invention can obtain an output voltage of about 2N volts by connecting N units in series.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a first embodiment of a double-junction GaAs laminated laser photovoltaic cell provided by the present invention;

2 is a schematic cross-sectional view of the isolation groove structure of the first embodiment of the double-junction GaAs stacked laser photovoltaic cell provided by the present invention;

3 is a schematic cross-sectional view of the product structure of the first embodiment of the double-junction GaAs laminated laser photovoltaic cell provided by the present invention;

4A to 4D are top views of 2V, 4V, 6V, and 12V double-junction GaAs laminated laser photovoltaic cells provided by the present invention, respectively.

Detailed ways

The specific implementation of the double-junction GaAs laminated laser photovoltaic cell and its preparation method provided by the present invention will be described in detail below with reference to the accompanying drawings.

First Embodiment

Fig. 1 is a schematic cross-sectional view of the first embodiment of the double-junction GaAs stacked laser photovoltaic cell.

Fig. 2 is a schematic cross-sectional view of the isolation groove structure of the first embodiment of the double-junction GaAs stacked laser photovoltaic cell.

This embodiment provides a double-junction GaAs laminated laser photovoltaic cell, including a semi-insulating GaAs substrate 01, and an N-type GaAs conductive layer 02, a first tunnel junction 17, and a bottom substrate 01 grown sequentially on the substrate 01. Cell 18 , second tunnel junction 19 , top cell 20 , window layer 15 and GaAs contact layer 16 .

The double-junction GaAs laminated laser photovoltaic cell further includes an isolation groove 22, the isolation groove 22 penetrates from the GaAs contact layer 16 to the substrate 01 until the substrate 01 is exposed, and the isolation groove 22 is filled with Silicon oxide or polyimide glue (Polyimide, referred to as PI glue).

In this embodiment, silicon oxide or polyimide glue is filled in the isolation groove 22 , but the present invention is not limited thereto, and the filler in the isolation groove 22 may also include other photosensitive glue like PI glue.

The first tunnel junction 17 includes an N-type first GaAs (Ga _0.51 In _0.49 P) layer 04, a P-type first (Al) GaAs layer 05, and a P-type AlGaAs ((Al) GaInP) first barrier layer 06.

The second tunnel junction 19 includes an N-type second GaAs (Ga _0.51 In _0.49 P) layer 10, a P-type second (Al) GaAs layer 11, and a P-type AlGaAs ((Al ) GaInP) second barrier layer 12;

As an optional implementation, the first tunnel junction 17 further includes a third barrier layer 03 of N-type AlGaAs ((Al)GaInP), located on the conductive layer 02 and the first N-type GaAs (Ga _0.51 In _0.49 P) between layers 04.

As an optional implementation, the second tunnel junction 19 further includes a fourth barrier layer 09 of N-type AlGaAs ((Al)GaInP), located between the bottom cell 18 and the second N-type GaAs (Ga _0.51 In _0.49 P) Between the layers 10 can also serve as the window layer of the bottom cell 18 .

Wherein, AlGaAs ((Al)GaInP) in this application means AlGaAs or _{AlxGa1 -} xInP, where x is greater than or equal to 0 and less than or equal to 1.

Wherein, GaAs (Ga _0.51 In _0.49 P) in this application means GaAs or Ga _0.51 In _0.49 P.

Wherein, (Al)GaAs in this application means _{AlxGa1 -xAs} , where x is greater than or equal to 0 and less than or equal to 1.

The bottom cell 18 is a GaAs-based PN junction cell, including the first P region 07 of the P-type GaAs absorption layer and the first N region 08 of the N-type GaAs absorption layer, and the first P region 07 and the first N region 08 of the bottom cell 18 An N region 08 is sequentially away from the substrate 01 .

The window layer 15 is an AlGaAs (Ga _0.51 In _0.49 P) layer.

The top cell 20 is a GaAs-based PN junction cell, including the second P region 13 of the P-type GaAs absorption layer and the second N region 14 of the N-type GaAs absorption layer, and the second P region 13 of the top cell 20, the second The two N regions 14 are sequentially away from the substrate 01 .

The GaAs contact layer 16 is N-type GaAs.

According to the structure prepared in Figure 1, the series resistance of the battery is lower than that of multiple single PN structure batteries connected by leads under the same voltage output, which is beneficial to the battery receiving higher optical power density and improving battery efficiency. Therefore, the above structure has a higher conversion efficiency than the PN junction battery, and has good practical application value.

Fig. 3 is a schematic cross-sectional view of the product structure of the first embodiment of the double-junction GaAs laminated laser photovoltaic cell provided by the present invention.

The double-junction GaAs stacked laser photovoltaic cell product further includes a positive electrode window on the double-junction GaAs stacked laser photovoltaic cell structure, and the positive electrode window sequentially penetrates the GaAs contact layer 16 until the conductive layer 02 is exposed. .

The double-junction GaAs laminated laser photovoltaic cell product further includes a positive electrode 24 and a negative electrode 23, the positive electrode 24 is placed on the exposed surface of the conductive layer 02 in the window of the positive electrode; the negative electrode 23 is placed in the window layer 15 on the exposed surface.

An anti-reflection film 25 further comprising ZnSe/MgF or TiO ₂ /SiO ₂ is placed on the exposed surface of the window layer 15 .

Second specific implementation

The preparation of the double-junction GaAs laminated laser photovoltaic cell with the structure shown in Figure 1 includes the steps of:

(1) Grow N-type GaAs conductive layer 02 on semi-insulating GaAs substrate 01;

(2) growing an N-type AlGaAs ((Al)GaInP) third barrier layer 03 on the N-type GaAs conductive layer 02;

(3) On the third barrier layer 03, grow the first GaAs (Ga _0.51 In _0.49 P) layer 04 with an N-type doping concentration greater than 1×10 ¹⁹ cm ^-3 , and then grow a P-type doping concentration greater than 1×10 A first (Al)GaAs layer 05 of ¹⁹ cm ⁻³ to form a first tunnel junction 17;

(4) growing the P-type AlGaAs ((Al)GaInP) first barrier layer 06 of the first tunnel junction 17 on the first (Al)GaAs layer 05, which can also be used as the back field layer of the bottom cell 18;

(5) grow the first P region 07 of the P-type GaAs absorption layer on the above-mentioned first barrier layer 06, and grow the first N region 08 of the N-type GaAs absorption layer on the first P region 07 of the P-type GaAs absorption layer , forming a PN junction as the bottom cell 18;

(6) grow the fourth barrier layer 09 of N-type AlGaAs ((Al)GaInP) on the bottom cell 18;

(7) On the fourth barrier layer 09, grow the second GaAs (Ga _0.51 In _0.49 P) layer 10 with an N-type doping concentration of 1×10 ¹⁹ cm ^-3 or more, and then grow a P-type doping concentration of 1×10 ¹⁹ A second (Al)GaAs layer 11 of more than cm ⁻³ to form a second tunnel junction 19;

(8) The second barrier layer 12 of P-type AlGaAs ((Al)GaInP) growing the second tunnel junction 19 on the second (Al)GaAs layer 11 can also be used as the back field layer of the top cell 20;

(9) grow the second P region 13 of the P-type GaAs absorption layer on the above-mentioned second potential barrier layer 12, grow the second N region 14 of the N-type GaAs absorption layer on the second P region 13, form a PN junction, as the top cell 20;

(10) growing a window layer 15 of N-type Al _x Ga _1-x As (Ga _0.51 In _0.49 P) on the second N region 14;

(11) An N-type highly doped GaAs contact layer 16 is grown on the above-mentioned window layer 15 for use as an ohmic contact.

The above steps (1) to (11) all adopt the MOCVD or MBE method to prepare the double-junction GaAs laminated laser photovoltaic cell.

If the growth in steps (1) to (11) all adopts MOCVD method, then the doping atoms of the N-type doping are any one of Si, Se, S and Te, and the doping atoms of the P-type doping The atom is any one of Zn, Mg and C.

If the growth in steps (1) to (11) is all grown by the MBE method, the dopant atoms of the N-type doping are any one of Si, Se, S, Sn and Te, and the P-type doping The dopant atom is any one of Be, Mg and C.

Further application of battery standard technology for the preparation of double-junction GaAs laminated laser photovoltaic cells, including steps:

(12) As shown in Figure 2, according to the battery standard process, etch from the GaAs contact layer 16 to the substrate 01 by dry or wet etching until the surface of the N-type substrate 01 is exposed, and then fill it with glue or silicon oxide and other materials to form isolation grooves 22;

(13) As shown in Figure 3, according to the battery standard process, etch from the GaAs contact layer 16 to the substrate 01 by dry or wet etching until the surface of the conductive layer 02 is exposed to form the positive electrode window of the battery ;

(14) According to the battery standard process, the negative electrode 23 and the positive electrode 24 of the battery are prepared by electron beam evaporation, thermal evaporation or magnetron sputtering, etc., and the negative electrode 23 and the positive electrode 24 are all AuGe/Ni/Au; Ag ; Au metal material, and form ohmic contact with GaAs contact layer 16 and conductive layer 02 respectively;

(15) According to the battery standard process, the GaAs contact layer 16 except the GaAs contact layer 16 directly below the negative electrode 23 is removed by dry or wet etching until the surface of the window layer 15 is exposed;

(16) According to the battery standard process, the anti-reflection film 25 of the battery is prepared on the exposed window layer 15 by chemical vapor deposition, evaporation or sputtering. ZnSe/MgF or TiO ₂ /SiO ₂ anti-reflection film 25, and The height of the reflective film 25 is lower than the height of the GaAs contact layer 16;

(17) According to the battery standard process, the battery is connected to the positive electrode 24 and the negative electrode 23 of the adjacent unit by using the electrode lead 26 to realize the series connection of the battery.

Next, an embodiment of the present invention is given.

A method for manufacturing a double-junction laminated laser photovoltaic cell, the structure of which is shown in Figure 1, specifically comprising the following steps:

1. Use MOCVD or MBE to grow GaAs double-junction laminated laser photovoltaic cells.

1), using semi-insulating GaAs substrate 01, with a thickness ranging from 200 to 500 microns;

2) Enter the growth chamber of MOCVD or MBE, and first grow an N-type GaAs conductive layer 02 with a thickness ranging from 1000nm to 5000nm, and a doping concentration ranging from 1×10 ¹⁸ cm ^-3 to 1×10 ¹⁹ cm ^-3 ;

3) On the conductive layer 02, grow a third barrier layer 03 of N-type AlGaAs ((Al)GaInP) with a doping concentration of 1×10 ¹⁸ cm ⁻³ or more and a thickness ranging from 10 nm to 50 nm;

4) On the third barrier layer 03, grow the first GaAs (Ga _0.51 In _0.49 P) layer 04 with an N-type doping concentration greater than 1×10 ¹⁹ cm ^-3 and a thickness ranging from 10 nm to 50 nm, and then grow a P-type Doping the first (Al) GaAs layer 05 with a concentration greater than 1×10 ¹⁹ cm ⁻³ of about 10 nm to 50 nm to form a first tunnel junction 17 so that the first P region 07 of the bottom cell 18 and the underlying N-type GaAs The conductive layer 02 can be well connected;

5) On the first (Al)GaAs layer 05, a first barrier layer 06 of P-type AlGaAs ((Al)GaInP) with a doping concentration greater than 1×10 ¹⁸ cm ^-3 of 50 nm to 100 nm is grown, and can be used as the back field layer of the bottom cell 18;

6) On the first barrier layer 06, grow a P-type GaAs absorption layer with a doping concentration of 5×10 ¹⁶ cm ⁻³ to 5×10 ¹⁷ cm ⁻³ in a range of 2500 nm to 3500 nm, that is, the first P region 07 , As the base region of the bottom cell 18, a 100nm to 300nm GaAs absorption layer with an N-type doping concentration of 1×10 ¹⁷ cm ⁻³ to 4×10 ¹⁸ cm ⁻³ is grown again, that is, the first N region 08 to serve as the bottom cell The emission area of 18; form a PN junction, as the bottom cell 18;

7) The fourth potential of the second tunneling junction 19 of N-type AlGaAs ((Al)GaInP) grown on the first N region 08 with a doping concentration greater than 1×10 ¹⁸ cm ^-3 and a thickness ranging from 20 nm to 100 nm The barrier layer 09 can also be used as the window layer of the bottom cell 18;

8) On the fourth barrier layer 09, grow a second GaAs (Ga _0.51 In _0.49 P) layer 10 with an N-type doping concentration greater than 1×10 ¹⁹ cm ^-3 and a thickness ranging from 10 nm to 50 nm, and then grow a P-type Doping the second (Al)GaAs layer 11 with a thickness greater than 1×10 ¹⁹ cm ^{−3 and} having a thickness ranging from 10 nm to 50 nm to form a second tunnel junction 19 ;

9) On the second (Al)GaAs layer 11, grow a second barrier layer 12 of P-type AlGaAs ((Al)GaInP) with a doping concentration of 1×10 ¹⁸ cm ^-3 or more of 50nm to 100nm, which can be used as the back field layer of the top cell 20;

10) On the second barrier layer 12, grow a 300nm to 600nm P-type GaAs absorption layer with a doping concentration of 5×10 ¹⁶ to 5×10 ¹⁷ cm ⁻³ , that is, the second P region 13, as the top cell 20 base region, and then grow a 100nm to 300nm GaAs absorption layer with an N-type doping concentration of 1×10 ¹⁷ to 4×10 ¹⁸ cm ^-3 , which is the second N region 14, (the second P region 13 and the second Two N regions 14 have a total thickness ranging from 600nm to 800nm), serving as the emission region of the top cell 20; forming a PN junction, and serving as the top cell 20;

11) On the second N region 14, grow an N-type Al _x Ga _1-x As or Ga _0.51 In _0.49 P window layer 15 with a doping concentration of 1000 nm to 3000 nm greater than 1×10 ¹⁸ cm ⁻³ , where x The range of is greater than or equal to 0.2 and less than or equal to 1;

12) An N-type GaAs contact layer 16 with a thickness ranging from 100 nm to 300 nm and a doping concentration greater than 1×10 ¹⁸ cm ⁻³ is grown on the window layer 15 for ohmic contact.

2. Prepare double-junction tandem laser photovoltaic cells by standard process.

13) Etching the GaAs contact layer 16, window layer 15, top cell 20, P-type second barrier layer 12, second tunnel junction 19, N Type fourth barrier layer 09, bottom cell 18, P-type first barrier layer 06, first tunnel junction 17, N-type third barrier layer 03, conductive layer 02 until semi-insulating GaAs is exposed The substrate 01 is then isolated by filling glue or silicon oxide electrical insulation materials, as shown in Figure 2.

14) The positive electrode window of the battery is to etch the GaAs contact layer 16, the window layer 15, the top battery 20, the P-type second barrier layer 12, and the second tunnel junction 19 by dry or wet etching. N-type fourth barrier layer 09, bottom cell 18, P-type first barrier layer 06, first tunnel junction 17, N-type third barrier layer 03 until the conductive layer of N-type GaAs is exposed 02, as shown in Figure 3.

15) Prepare the negative electrode 23 and positive electrode 24 of AuGe/Ni/Au=35/10/100nm; Ag=1μm; Au=100nm metal materials by means of electron beam evaporation, thermal evaporation or magnetron sputtering, and form ohmic contacts, as shown in Figure 3.

16) The GaAs contact layer 16 except the GaAs contact layer 16 directly under the negative electrode 23 is removed by dry or wet etching until the window layer 15 is exposed.

17) Prepare an anti-reflection film 25 on the exposed window layer 15 by chemical vapor deposition technology, evaporation or sputtering, using ZnSe/MgF or TiO ₂ /SiO ₂ as the anti-reflection film material, as shown in Figure 3 .

18) Prepare the electrode lead 26, and use the electrode lead 26 to connect the positive electrode 24 and the negative electrode 23 of the adjacent cells of the battery to realize the battery connection, as shown in Figure 3.

FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are top views of double-junction GaAs stacked laser photovoltaic cells of 2V, 4V, 6V, and 12V, respectively.

According to the manufacturing method of the double-junction GaAs laminated laser photovoltaic cell provided by the present invention, several battery cells are connected in series to obtain the required output voltage. The open circuit voltage of a double-junction GaAs stacked laser photovoltaic cell is about 2V, so that each cell has several cells connected in series to have an output voltage of about several volts (such as 2, 4, 6, 12V). The battery is grown on a semi-insulating GaAs substrate to achieve electrical isolation between each unit in the subsequent battery processing process, and then the positive electrode of one battery is connected to the negative electrode of another adjacent battery cell to make several cells in series connect. The result of this design is that both the positive electrode and the negative electrode of the battery are drawn from the epitaxial side of the battery. This design can reduce the shading ratio of the electrodes and fully absorb the laser energy irradiated on the photosensitive surface of the battery. The positive electrode is on the photosensitive surface of the battery. The periphery is connected to the conductive layer at the bottom of the battery.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Be the protection scope of the present invention.

Claims (10)

1. A double-junction GaAs laminated laser photovoltaic cell is characterized in that it comprises a GaAs substrate, and a conductive layer of N-type GaAs arranged in sequence on the substrate, the first tunnel junction, the bottom cell, the second Tunneling junction, top cell, window layer of AlGaAs (Ga _0.51 In _0.49 P), and GaAs contact layer. 2. The double-junction GaAs laminated laser photovoltaic cell according to claim 1, further comprising an isolation groove, the isolation groove penetrates from the GaAs contact layer to the substrate until the substrate is exposed, and the Silicon oxide or polyimide glue is filled in the isolation groove. 3. double-junction GaAs laminated laser photovoltaic cell according to claim 1, is characterized in that, described first tunnel junction, the second tunnel junction all comprise N-type GaAs (Ga _0.51 In _0.49 P) layer, P-type (Al) GaAs layer and P-type AlGaAs ((Al) GaInP) layer. 4. double-junction GaAs lamination laser photovoltaic cell according to claim 1, is characterized in that, described bottom battery, top battery are the PN junction battery based on GaAs, and the respective P regions of described bottom battery and top battery , N regions are sequentially away from the substrate. 5. The double-junction GaAs laminated laser photovoltaic cell according to claim 1, further comprising a positive electrode window, the positive electrode window penetrates from the GaAs contact layer to the conductive layer until the conductive layer is exposed. 6 . The double-junction GaAs stacked laser photovoltaic cell according to claim 1 , further comprising an anti-reflection film of ZnSe/MgF or TiO ₂ /SiO ₂ placed on the exposed surface of the window layer. 7. A method for preparing a double-junction GaAs laminated laser photovoltaic cell as claimed in claim 1, characterized in that it comprises the steps of: (1) providing a GaAs substrate; (2) sequentially growing a conductive layer, the second A tunnel junction, bottom cell, second tunnel junction, top cell, window layer and GaAs contact layer. 8. The method for preparing a double-junction GaAs laminated laser photovoltaic cell according to claim 7, further comprising the step of: (3) using a dry or wet etching method to etch from the GaAs contact layer to the substrate. Etch until the surface of the substrate is exposed to form an isolation groove; (4) Fill the isolation groove with silicon oxide or polyimide glue. 9. The method for preparing a double-junction GaAs laminated laser photovoltaic cell according to claim 8, further comprising the step of: (5) using a dry or wet etching method to etch from the GaAs contact layer to the substrate. etch until the surface of the conductive layer is exposed to form a positive electrode window. 10. The method for preparing a double-junction GaAs laminated laser photovoltaic cell according to claim 7, further comprising the step of: using a dry or wet etching method to etch the GaAs contact layer in a designated area until the exposed The surface of the window layer: growing an anti-reflection film on the exposed surface of the window layer, and the method for growing the anti-reflection film is any one of chemical vapor deposition, evaporation and sputtering.

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