A decoupled flexible GaAs / perovskite tandem solar cell and its fabrication method

Abstract

This invention belongs to the technical field of flexible two-terminal tandem solar cells, and discloses a decoupled flexible GaAs / perovskite two-terminal tandem solar cell and its fabrication method. The cell includes a flexible substrate, an intermediate interconnecting conductive layer disposed on the flexible substrate, and GaAs sub-cells and perovskite sub-cells disposed on the intermediate interconnecting conductive layer. The GaAs sub-cell and perovskite sub-cell are independently disposed on the intermediate interconnecting conductive layer. The GaAs sub-cell, from bottom to top, includes a hole transport layer, a GaAs absorber layer, and an electrode; the perovskite sub-cell, from bottom to top, includes an electron transport layer, a perovskite absorber layer, a hole transport layer, and an electrode. This invention also discloses the cell fabrication method. The sub-cells of this invention are fabricated independently, avoiding defects introduced by complex processes. Optical performance is independently controlled, and the two sub-cells operate independently, improving system reliability. This invention significantly improves the photovoltaic conversion efficiency of the cell.

Description

Technical Field

[0001] This invention belongs to the field of flexible GaAs / perovskite tandem solar cells, specifically relating to a decoupled flexible GaAs / perovskite tandem solar cell with two ends and its fabrication method. Background Technology

[0002] To improve the performance of single-junction solar cells and meet the future development needs of lightweight, high-efficiency, and wearable flexible electronics technologies, flexible GaAs / perovskite tandem solar cells have attracted widespread attention. Perovskite solar cells have the advantages of simple fabrication processes and low cost. GaAs solar cells have a direct bandgap structure with a bandgap width that matches that of perovskite solar cells. Application No. 202210675836.6 discloses a perovskite / GaAs mechanically tandem solar cell with a metal mesh interconnect layer at both ends. This application fabricates perovskite sub-cells on GaAs sub-cells. The complex perovskite fabrication process inevitably leads to defects in the GaAs sub-cells, resulting in low photovoltaic efficiency. The two sub-cells are an integrated structure; damage to a single sub-cell can paralyze the entire system, resulting in low reliability and the inability to independently control optical performance. Furthermore, its rigid structure cannot meet the requirements of flexible wearable devices, limiting application flexibility. Summary of the Invention

[0003] To overcome the problems of low photovoltaic conversion efficiency, low reliability, poor application flexibility, and inability to independently control optical performance, this invention provides a decoupled flexible GaAs / perovskite tandem solar cell and its fabrication method. This invention improves photovoltaic conversion efficiency, reliability, and optimizes the cell structure by independently fabricating two sub-cells on a flexible substrate and connecting them in series using an intermediate interconnecting conductive layer.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A decoupled flexible GaAs / perovskite tandem solar cell includes a flexible substrate, an intermediate interconnect conductive layer disposed on the flexible substrate, and GaAs sub-cells and perovskite sub-cells disposed on the intermediate interconnect conductive layer. The GaAs sub-cell and the perovskite sub-cell are each independently disposed on the intermediate interconnect conductive layer. The GaAs sub-cell, from bottom to top, includes a hole transport layer, a GaAs absorber layer, and an electrode. The perovskite sub-cell, from bottom to top, includes an electron transport layer, a perovskite absorber layer, a hole transport layer, and an electrode. The hole transport layer in the GaAs sub-cell is disposed on the intermediate interconnect conductive layer, and the electron transport layer in the perovskite sub-cell is disposed on the intermediate interconnect conductive layer.

[0006] The GaAs sub-cell is disposed at one end of the intermediate interconnect conductive layer, and the perovskite sub-cell is disposed at the other end of the intermediate interconnect conductive layer. The GaAs sub-cell and the perovskite sub-cell are not in contact.

[0007] The intermediate interconnect conductive layer is one or more of ITO, Mxene material, and two-dimensional transition metal chalcogenides, preferably ITO.

[0008] The flexible substrate is a PI, PET, PDMS or metal foil flexible substrate, preferably PI.

[0009] In the GaAs sub-battery, the hole transport layer is one or more of graphene, carbon nanotubes, PEDOT, and Mxene materials, preferably graphene or carbon nanotubes.

[0010] In the perovskite sub-cell, the electron transport layer is one or more of TiO2, SnO2, C60, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or PCBM (benzo[c][1,2,5]thiadiazole-4,7-diimide).

[0011] In the perovskite sub-cell, the perovskite absorber layer is one or more of MAPbI3, FAPbI3, and MAPbBr3.

[0012] The hole transport layer in the perovskite sub-cell is one or more of PEDOT, Spiro-OMeTAD, P3HT, and 2PACz.

[0013] In the GaAs sub-cell, the electrode is one or more of the following: Au, Ag, Ti, Cu, Ni, and Pt.

[0014] In the perovskite sub-cell, the electrode is one or more of Ag, Au, Ti, Cu, Ni, and Pt electrodes.

[0015] The GaAs absorber layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 ~1 × 10 18 / cm 3 .

[0016] The GaAs sub-cells and perovskite sub-cells are fabricated independently, and the two sub-cells are connected in series through an intermediate interconnecting conductive layer.

[0017] A method for fabricating a decoupled flexible GaAs / perovskite tandem solar cell includes the following steps:

[0018] 1) A GaAs buffer layer is grown on a GaAs substrate by MBE (molecular beam epitaxy), followed by the growth of an AlAs layer and a GaAs absorber layer. A hole transport layer for a GaAs sub-cell is then fabricated on the surface of the GaAs absorber layer.

[0019] 2) Remove the AlAs layer by wet etching to obtain the GaAs absorber layer / hole transport layer; transfer the GaAs absorber layer / hole transport layer to one end of the intermediate interconnect conductive layer on the flexible substrate, and make contact between the hole transport layer and the intermediate interconnect conductive layer; deposit electrodes on the surface of the GaAs absorber layer and anneal to form ohmic contacts to obtain the GaAs sub-cell.

[0020] 3) Cover the GaAs sub-cell and prepare the electron transport layer of the perovskite sub-cell at the other end of the middle interconnecting conductive layer on the flexible substrate.

[0021] 4) Prepare a solution of the perovskite precursor, spin-coat it on the surface of the electron transport layer, and anneal it using an anti-solvent method to obtain the perovskite absorber layer of the perovskite sub-cell.

[0022] 5) Prepare a hole transport layer for a perovskite sub-cell on the surface of the perovskite absorber layer; deposit electrodes on the hole transport layer to obtain a decoupled flexible GaAs / perovskite tandem solar cell.

[0023] In step 1), the GaAs substrate has a (100) crystal plane, the GaAs buffer layer has a thickness of 1-5 nm, the AlAs layer has a thickness of 20-50 nm, and the GaAs absorber layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 ~1 × 10 18 / cm 3 The thickness is 200~800nm.

[0024] The growth temperature of the AlAs layer is 580℃~620℃, the Al source temperature is 1000℃~1200℃, and the As source temperature is 900℃~950℃.

[0025] The growth temperature of the GaAs absorber layer is 550℃~600℃, the Ga source temperature is 850℃~900℃, the As source temperature is 900℃~950℃, and the Si doping source temperature is 950~1000℃.

[0026] The hole transport layer of the GaAs sub-cell is prepared into a thin film by vacuum filtration or wet transfer and then transferred to the surface of the GaAs absorber layer; the thickness of the hole transport layer of the GaAs sub-cell is 100~200nm.

[0027] The wet etching solution described in step 2) is one or more of HF acid, phosphoric acid, and hydrochloric acid, with a mass concentration of 5% to 10% and an etching time of 10 to 15 minutes.

[0028] The thickness of the electrode mentioned in step 2) is 100~120nm, for example: the electrode is Au, the annealing temperature is 300~330℃, and the annealing time is 15~30s; the thickness of the intermediate interconnect conductive layer is 100~120nm.

[0029] The electron transport layer described in step 3) is prepared by magnetron sputtering under the following conditions: power of 60~120W, vacuum degree of 0.4~0.7Pa, and sputtering time of 10~30min.

[0030] The perovskite precursor mentioned in step 4) is MAI, FAI, MABr, PbI2 and / or PbBr2. The solvent in the solution after the precursor is prepared is DMF and DMSO, and the volume ratio of DMF to DMSO is (3~5):1.

[0031] When the perovskite is MAPbI3, the perovskite precursors are MAI and PbI2;

[0032] When the perovskite is FAPbI3, the perovskite precursors are FAI and PbI2;

[0033] When the perovskite is MAPbBr3, the perovskite precursors are MABr and PbBr2.

[0034] The concentration of the precursor solution is 0.5~1.2M, where the concentration is based on perovskite.

[0035] In step 4), the spin coating speed is 2000~4000 rpm and the spin coating time is 20~60s; in the anti-solvent method, the anti-solvent is added 10~15s before the end of the spin.

[0036] The annealing temperature in step 4) is 80~120℃, and the annealing time is 10~30min.

[0037] The antisolvent used in the antisolvent method is one or more of chlorobenzene, toluene, and ethyl acetate.

[0038] The hole transport layer of the perovskite sub-cell described in step 5) is obtained by spin-coating a solution of the hole transport layer material and then annealing it; the rotation speed is 4000~6000rpm, the spin-coating time is 30~60s, the annealing temperature is 100~150℃, and the annealing time is 10~20min.

[0039] The hole transport layer material is prepared in a solution using one of the solvents: isopropanol, ethanol, or chlorobenzene, with a concentration of 0.5–1.5 mg / mL; the hole transport layer has a thickness of 50–150 nm.

[0040] The thickness of the electrode mentioned in step 5) is 100~120nm.

[0041] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0042] In this invention, two sub-cells are independently fabricated on a flexible substrate and connected in series using an intermediate conductive interconnect layer. This effectively avoids damage to the sub-cells caused by complex fabrication processes, thereby improving photovoltaic conversion efficiency. The optical properties of the battery in this invention can be independently controlled, and the sub-cells can operate independently, exhibiting high reliability and application flexibility. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the decoupled flexible GaAs / perovskite tandem solar cell of the present invention; 1-flexible substrate, 2-intermediate interconnecting conductive layer, 3-hole transport layer of GaAs sub-cell, 4-GaAs absorber layer of GaAs sub-cell, 5-electrode of GaAs sub-cell, 6-electrode transport layer of perovskite sub-cell, 7-perovskite absorber layer, 8-hole transport layer of perovskite sub-cell, 9-electrode of perovskite sub-cell, 10-GaAs sub-cell, 11-perovskite sub-cell;

[0044] Figure 2 This is a flowchart illustrating the fabrication process of the decoupled flexible GaAs / perovskite tandem solar cell in Example 1.

[0045] Figure 3 The image shows the IV curves of the solar cells prepared in Example 1 and Comparative Example 1 after 100 bending cycles. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

[0047] A schematic diagram of a decoupled flexible GaAs / perovskite tandem solar cell is shown below. Figure 1As shown, the device includes a flexible substrate, an intermediate interconnect conductive layer 2 disposed on the flexible substrate 1, and GaAs sub-cells 10 and 11 disposed on the intermediate interconnect conductive layer 2. The GaAs sub-cells 10 and 11 are each independently disposed on the intermediate interconnect conductive layer 2. The GaAs sub-cell 10, from bottom to top, includes a hole transport layer 3, a GaAs absorption layer 4, and an electrode 5. The perovskite sub-cell 11, from bottom to top, includes an electron transport layer 6, a perovskite absorption layer 7, a hole transport layer 8, and an electrode 9. The hole transport layer 3 of the GaAs sub-cell 10 is disposed on the intermediate interconnect conductive layer 2, and the electron transport layer 6 of the perovskite sub-cell 11 is disposed on the intermediate interconnect conductive layer 2.

[0048] The GaAs sub-cell 10 is disposed at one end of the intermediate interconnect conductive layer 2, and the perovskite sub-cell 11 is disposed at the other end of the intermediate interconnect conductive layer 2. The GaAs sub-cell 10 and the perovskite sub-cell 11 are not in contact.

[0049] The intermediate interconnect conductive layer is one or more of ITO, Mxene material, and two-dimensional transition metal chalcogenides, preferably ITO.

[0050] The flexible substrate is a PI, PET, PDMS or metal foil flexible substrate, preferably PI.

[0051] In the GaAs sub-battery, the hole transport layer is one or more of graphene, carbon nanotubes, PEDOT, and Mxene materials, preferably graphene or carbon nanotubes.

[0052] In the perovskite sub-cell, the electron transport layer is one or more of TiO2, SnO2, C60, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or PCBM (benzo[c][1,2,5]thiadiazole-4,7-diimide).

[0053] In the perovskite sub-cell, the perovskite absorber layer is one or more of MAPbI3, FAPbI3, and MAPbBr3.

[0054] In the perovskite sub-cell, the hole transport layer is one or more of PEDOT, Spiro-OMeTAD, P3HT, and 2PACz.

[0055] In a GaAs sub-cell, the electrode (e.g., Au) is divided into two parts, which are respectively set at both ends of the GaAs absorber layer of the GaAs sub-cell.

[0056] In a perovskite sub-cell, the electrode (e.g., Ag) is divided into two parts, which are respectively set at both ends of the hole transport layer of the perovskite sub-cell.

[0057] The GaAs sub-cells and perovskite sub-cells are fabricated independently, and the two sub-cells are connected in series through an intermediate interconnecting conductive layer.

[0058] Example 1

[0059] A method for fabricating a decoupled flexible GaAs / perovskite tandem solar cell includes the following steps:

[0060] 1) A GaAs buffer layer is first epitaxially grown on a GaAs substrate using MBE. The GaAs substrate has a (100) crystal plane, and the thickness of the GaAs buffer layer is 5 nm. Then, an AlAs and GaAs absorber layer are grown. The thickness of the AlAs layer is 20 nm, and the GaAs absorber layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 The thickness is 500 nm. A carbon nanotube film with a thickness of 100 nm was prepared on the surface of the GaAs absorber layer by vacuum filtration, which is to form the hole transport layer of the GaAs sub-cell on the GaAs absorber layer.

[0061] The growth temperature of AlAs is 600℃, the Al source temperature is 1200℃, and the As source temperature is 950℃; the growth temperature of the GaAs absorber layer is 600℃, the Ga source temperature is 900℃, and the As source temperature is 950℃; the Si doping source temperature is 1000℃.

[0062] 2) The AlAs layer was removed by wet etching. The etching solution was HF acid with a mass concentration of 10% and the etching time was 10 min to obtain the GaAs absorber layer / hole transport layer. The GaAs absorber layer / hole transport layer was transferred to one end of the conductive ITO layer on the flexible substrate PI, and the hole transport layer of the GaAs sub-cell was in contact with the conductive layer. An Au electrode was deposited on the surface of the GaAs absorber layer and annealed to form an ohmic contact to obtain the GaAs sub-cell. The thickness of the Au electrode was 120 nm, the annealing temperature was 330 °C, and the annealing time was 30 s. The thickness of the ITO on the flexible substrate PI film was 100 nm.

[0063] 3) Cover the GaAs sub-cell with tape and prepare an electron transport layer on the other end of the conductive layer of the flexible substrate. The electron transport layer is TiO2 and is prepared by magnetron sputtering. The preparation conditions are: power of 80W, vacuum degree of 0.57Pa, and sputtering time of 20min.

[0064] 4) Prepare a solution of perovskite precursor, wherein the perovskite is MAPbI3, the perovskite precursor is MAI and PbI2 (molar ratio of 1:1), the volume ratio of DMF and DMSO is 4:1, and the concentration of the precursor solution is 0.6M; spin-coat the precursor solution onto the electron transport layer and anneal to prepare the perovskite absorber layer; during the preparation of the perovskite absorber layer, the spin-coating speed of the precursor is 4000 rpm and the time is 30 s, and chlorobenzene is used as an antisolvent and added dropwise 10 s before the end of the spin-coating; the annealing temperature is 100℃ and the time is 10 min.

[0065] 5) A PEDOT hole transport layer was prepared on the surface of the perovskite absorber layer by spin coating. After spin coating, annealing was performed at a spin speed of 5000 rpm for 30 s and a temperature of 120℃ for 10 min. The solvent used to prepare the PEDOT solution was isopropanol, and the concentration of the solution was 1 mg / mL. The thickness of the hole transport layer was 100 nm. Finally, an Ag electrode with a thickness of 100 nm was deposited on the hole transport layer to obtain a decoupled flexible GaAs / perovskite tandem solar cell.

[0066] Figure 2 This is a flowchart illustrating the fabrication process of the decoupled flexible GaAs / perovskite tandem solar cell in Example 1.

[0067] Example 2

[0068] A method for fabricating a decoupled flexible GaAs / perovskite tandem solar cell includes the following steps:

[0069] 1) A GaAs buffer layer is first epitaxially grown on a GaAs substrate using MBE. The GaAs substrate has a (100) crystal plane, and the thickness of the GaAs buffer layer is 5 nm. Then, an AlAs and GaAs absorber layer are grown. The thickness of the AlAs layer is 50 nm, and the GaAs absorber layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 The thickness is 800 nm. A graphene film with a thickness of 100 nm was prepared on the surface of the GaAs epitaxial layer by spin coating, that is, a hole transport layer of GaAs sub-cell was prepared on the GaAs absorber layer.

[0070] The growth temperature of AlAs is 620℃, the Al source temperature is 1000℃, and the As source temperature is 950℃; the growth temperature of GaAs is 580℃, the Ga source temperature is 900℃, and the As source temperature is 950℃; the Si doping source temperature is 1000℃.

[0071] 2) The AlAs layer was removed by wet etching. The etching solution was phosphoric acid with a mass concentration of 10% and the etching time was 10 min to obtain the GaAs absorber layer / hole transport layer. The GaAs absorber layer / hole transport layer was transferred to one end of the conductive ITO layer on the flexible substrate PI, and the hole transport layer of the GaAs sub-cell was in contact with the conductive layer. An Au electrode was deposited on the surface of the GaAs absorber layer and annealed to form an ohmic contact to obtain the GaAs sub-cell. The thickness of the Au electrode was 120 nm, the annealing temperature was 330 °C, and the annealing time was 30 s. The thickness of ITO on the flexible substrate PI film was 100 nm.

[0072] 3) Cover the GaAs sub-cell with tape and prepare an electron transport layer on the other end of the conductive layer of the flexible substrate. The electron transport layer is SnO2 and is prepared by magnetron sputtering. The preparation conditions are: power of 120W, vacuum degree of 0.57Pa, and sputtering time of 20min.

[0073] 4) Prepare a solution of perovskite precursor, wherein the perovskite is MAPbI3, the perovskite precursor is MAI and PbI2 (molar ratio of 1:1), the volume ratio of DMF and DMSO is 4:1, and the concentration of the precursor solution is 0.6M; spin-coat the precursor solution onto the electron transport layer and anneal to prepare the perovskite absorber layer; during the preparation of the perovskite absorber layer, the spin-coating speed of the precursor is 4000 rpm and the time is 30 s, and chlorobenzene is used as an antisolvent and added dropwise 10 s before the end of the spin-coating; the annealing temperature is 100℃ and the time is 10 min.

[0074] 5) A 2PACz hole transport layer was prepared on the surface of the perovskite absorber layer by spin coating. After spin coating, the layer was annealed at a spin speed of 5000 rpm for 30 s and a temperature of 100℃ for 10 min. The solvent used to prepare the 2PACz solution was isopropanol with a concentration of 1 mg / mL and a thickness of 100 nm. Finally, an Ag electrode with a thickness of 100 nm was deposited on the hole transport layer to obtain a decoupled flexible GaAs / perovskite tandem solar cell.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Examples 1 and 2 is that the prepared battery is a flexible GaAs / perovskite tandem battery, in which the perovskite sub-cell is directly prepared on top of the GaAs sub-cell, instead of preparing the two sub-cells independently.

[0077] Specific steps:

[0078] 1) A GaAs buffer layer is first epitaxially grown on a GaAs substrate using MBE. The GaAs substrate has a (100) crystal plane, and the thickness of the GaAs buffer layer is 2 nm. Then, AlAs and GaAs layers are grown. The thickness of the AlAs layer is 20 nm, and the GaAs layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 A 500 nm thick carbon nanotube film was prepared on the surface of a GaA layer by vacuum filtration, with a thickness of 100 nm.

[0079] The growth temperature of AlAs is 600℃, the Al source temperature is 1200℃, and the As source temperature is 950℃; the growth temperature of GaAs layer is 600℃, the Ga source temperature is 900℃, and the As source temperature is 950℃; the Si doping source temperature is 1000℃.

[0080] 2) The AlAs layer is removed by wet etching. The etching solution is HF acid with a mass concentration of 10% and the etching time is 10 min to obtain the GaAs layer / hole transport layer. The GaAs layer / hole transport layer is transferred to the surface of the conductive ITO layer on the flexible substrate PI, and the GaAs layer is in contact with the conductive layer. The thickness of ITO on the flexible substrate PI film is 100 nm.

[0081] 3) An intermediate interconnect conductive layer and an electron transport layer of a perovskite sub-cell were sequentially prepared on the surface of the hole transport layer of the GaAs sub-cell. The intermediate interconnect layer was ITO and the electron transport layer was TiO2. Both were prepared by magnetron sputtering under the following conditions: power of 80W, vacuum of 0.57Pa, and sputtering time of 20min.

[0082] 4) Prepare a solution of perovskite precursor, with MAPbI3 as the perovskite and MAI and PbI2 as the perovskite precursors (molar ratio of 1:1). The volume ratio of DMF to DMSO is 4:1, and the concentration of the precursor solution is 0.6M. Spin-coat the precursor solution onto the electron transport layer of the perovskite sub-cell and anneal it to prepare the perovskite absorber layer. During the preparation of the perovskite absorber layer, the spin-coating speed of the precursor is 4000 rpm and the time is 30 s. Chlorobenzene is used as an antisolvent and added dropwise 10 s before the end of the spin-coating. The annealing temperature is 100℃ and the time is 10 min.

[0083] 5) A PEDOT hole transport layer was prepared on the surface of the perovskite absorber layer by spin coating. After spin coating, annealing was performed at a spin speed of 5000 rpm for 30 s and a temperature of 120℃ for 10 min. The solvent used to prepare the PEDOT solution was isopropanol with a concentration of 1 mg / mL. The thickness of the PEDOT hole transport layer was 100 nm. Finally, an Ag electrode with a thickness of 100 nm was deposited on the PEDOT hole transport layer to obtain a solar cell.

[0084] Table 1 shows a comparison of the photovoltaic parameters of the solar cell prepared using Example 1 and the solar cell device prepared using Comparative Example 1 after 100 bending cycles.

[0085] Table 1. Performance parameters of the batteries prepared in Example 1 and Comparative Example 1

[0086]

[0087] Figure 3 The image shows the IV curves of the solar cells prepared in Example 1 and Comparative Example 1.

[0088] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A decoupled flexible GaAs / perovskite tandem solar cell, characterized in that: The device includes a flexible substrate, an intermediate interconnect conductive layer disposed on the flexible substrate, and GaAs sub-cells and perovskite sub-cells disposed on the intermediate interconnect conductive layer. The GaAs sub-cell and perovskite sub-cell are each independently disposed on the intermediate interconnect conductive layer. The GaAs sub-cell, from bottom to top, includes a hole transport layer, a GaAs absorption layer, and an electrode. The perovskite sub-cell, from bottom to top, includes an electron transport layer, a perovskite absorption layer, a hole transport layer, and an electrode. In the GaAs sub-cell, the hole transport layer is disposed on the intermediate interconnect conductive layer, and in the perovskite sub-cell, the electron transport layer is disposed on the intermediate interconnect conductive layer. The GaAs sub-cell and perovskite sub-cell are not in contact. The GaAs absorber layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 ~1 × 10 18 / cm 3 ; The GaAs sub-cell is disposed at one end of the intermediate interconnect conductive layer, and the perovskite sub-cell is disposed at the other end of the intermediate interconnect conductive layer. The intermediate interconnect conductive layer is one or more of ITO, Mxene material, and two-dimensional transition metal chalcogenides; In the GaAs sub-cell, the hole transport layer is one or more of graphene, carbon nanotubes, PEDOT, and MXene. In perovskite sub-cells, the electron transport layer is TiO2, SnO2, C60, BCP, or PCBM; The decoupled flexible GaAs / perovskite tandem solar cell was prepared by the following method: 1) A GaAs buffer layer is grown on a GaAs substrate by molecular beam epitaxy, followed by the growth of an AlAs layer and a GaAs absorber layer. A hole transport layer for a GaAs sub-cell is then fabricated on the surface of the GaAs absorber layer. 2) Remove the AlAs layer by wet etching to obtain the GaAs absorber layer / hole transport layer; transfer the GaAs absorber layer / hole transport layer to one end of the intermediate interconnect conductive layer on the flexible substrate, and make contact between the hole transport layer and the intermediate interconnect conductive layer; deposit electrodes on the GaAs surface by evaporation and anneal to form ohmic contacts to obtain the GaAs sub-cell. 3) Cover the GaAs sub-cell and prepare the electron transport layer of the perovskite sub-cell at the other end of the middle interconnecting conductive layer on the flexible substrate. 4) Prepare a solution of the perovskite precursor, spin-coat it on the surface of the electron transport layer, and anneal it using an anti-solvent method to obtain the perovskite absorber layer of the perovskite sub-cell. 5) Prepare a hole transport layer for a perovskite sub-cell on the surface of the perovskite absorber layer; Electrodes are deposited on the hole transport layer to obtain a decoupled flexible GaAs / perovskite tandem solar cell.

2. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: The intermediate interconnecting conductive layer is ITO; in the GaAs sub-cell, the hole transport layer is one or more of graphene and carbon nanotubes. The flexible substrate is a PI, PET, PDMS, or metal foil flexible substrate; In the perovskite sub-cell, the perovskite absorber layer is one or more of MAPbI3, FAPbI3, and MAPbBr3; In the perovskite sub-cell, the hole transport layer is one or more of PEDOT, Spiro-OMeTAD, P3HT, and 2PACz.

3. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: The intermediate interconnecting conductive layer is a transparent conductive layer; In the GaAs sub-cell, the electrode is one or more of Au, Ag, Ti, Cu, Ni, and Pt electrodes; A perovskite sub-cell, wherein the electrode is one or more of Ag, Au, Ti, Cu, Ni, and Pt electrodes.

4. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: In step 1), the GaAs substrate has a (100) crystal plane, the GaAs buffer layer has a thickness of 1-5 nm, the AlAs layer has a thickness of 20-50 nm, and the GaAs layer is N-type Si doped with a doping concentration of 1 × 10⁻⁶. 17 / cm 3 ~1 × 10 18 / cm 3 The thickness of the GaAs layer is 200~800nm; The growth temperature of AlAs is 580℃~620℃, the Al source temperature is 1000℃~1200℃, and the As source temperature is 900℃~950℃; the growth temperature of the GaAs absorber layer is 550℃~600℃, the Ga source temperature is 850℃~900℃, the As source temperature is 900℃~950℃, and the Si doping source temperature is 950~1000℃. The hole transport layer of the GaAs sub-cell is prepared into a thin film by vacuum filtration or wet transfer and then transferred to the surface of the GaAs absorber layer; the thickness of the hole transport layer of the GaAs sub-cell is 100~200nm.

5. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: The wet etching solution described in step 2) is one or more of HF acid, phosphoric acid, and hydrochloric acid, with a mass concentration of 5% to 10%, and the etching time is 10 to 15 minutes. The electrode in step 2) has a thickness of 100~120nm, an annealing temperature of 300~330℃, and an annealing time of 15~30s; the thickness of the intermediate interconnect conductive layer is 100~120nm. The electron transport layer described in step 3) is prepared by magnetron sputtering under the following conditions: power of 60~120W, vacuum degree of 0.4~0.7Pa, and sputtering time of 10~30min.

6. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: The perovskite precursor mentioned in step 4) is MAI, FAI, MABr, PbI2 and / or PbBr2. The solvent in the solution after the precursor is prepared is DMF and DMSO, and the volume ratio of DMF to DMSO is (3~5):

1. When the perovskite is MAPbI3, the perovskite precursors are MAI and PbI2. When the perovskite is FAPbI3, the perovskite precursors are FAI and PbI2; When the perovskite is MAPbBr3, the perovskite precursors are MABr and PbBr2; The concentration of the solution after the precursor is prepared is 0.5~1.2M, where the concentration is based on perovskite. In step 4), the spin coating speed is 2000~4000 rpm and the spin coating time is 20~60s; in the anti-solvent method, the anti-solvent is added 10~15s before the end of the spin. The annealing temperature in step 4) is 80~120℃, and the annealing time is 10~30min; The antisolvent used in step 4) is one or more of chlorobenzene, toluene, and ethyl acetate.

7. The decoupled flexible GaAs / perovskite tandem solar cell according to claim 1, characterized in that: The hole transport layer of the perovskite sub-cell described in step 5) is obtained by spin-coating a solution of the hole transport layer material and then annealing it; the rotation speed is 4000~6000rpm, the spin-coating time is 30~60s, the annealing temperature is 100~150℃, and the annealing time is 10~20min. The hole transport layer material is prepared in a solution using one of the solvents: isopropanol, ethanol, or chlorobenzene, with a concentration of 0.5–1.5 mg / mL; the hole transport layer has a thickness of 50–150 nm. The thickness of the electrode mentioned in step 5) is 100~120nm.

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