GaAs / perovskite laminated solar cell based on pi-pi interaction and preparation method thereof

Abstract

The invention provides a GaAs / perovskite laminated solar cell based on pi-pi interaction and a preparation method of the GaAs / perovskite laminated solar cell. The laminated solar cell is composed of a GaAs sub-cell and a perovskite sub-cell. A CuPc surface functional layer is prepared on the surface of the CNT to form a CuPc / CNT layer, and the CuPc / CNT serves as a hole transport layer of the GaAs sub-cell at the bottom and a hole transport layer of the perovskite sub-cell at the top and also serves as a middle interconnection layer for connecting the upper sub-cell and the lower sub-cell; the process that a complex tunnel junction or a TCO layer needs to be additionally prepared in a traditional laminated cell is avoided, the device structure is simplified, and the manufacturing cost is reduced. The CuPc and the CNT have strong pi-pi interaction and good energy level matching, electrons are induced to be transferred from the CNT to the CuPc, p-type doping of the CNT and the conductivity of the thin film are remarkably enhanced, the charge transmission capacity in the vertical direction is effectively improved, and voltage loss caused by energy level mismatching is reduced to the maximum extent; the photoelectric efficiency is improved.

Description

Technical Field

[0001] This application belongs to the field of GaAs solar cell technology, and particularly relates to a GaAs / perovskite tandem solar cell based on π-π interaction and its fabrication method. Background Technology

[0002] In recent years, GaAs (gallium arsenide) solar cells have been widely used due to their advantages such as direct bandgap, excellent photoelectric conversion efficiency, and radiation resistance. However, the efficiency of single-junction GaAs cells has approached its theoretical limit (~33%), making it difficult to meet the ever-increasing demand for high efficiency. Fabricating tandem solar cells is an effective way to break through the Shockley-Queisser limit and achieve higher photoelectric conversion efficiency.

[0003] In tandem solar cells, the intermediate interconnect layer is a crucial functional layer connecting the top and bottom sub-cells, and its performance directly determines the efficiency and stability of the entire device. An ideal intermediate interconnect layer needs to meet extremely stringent requirements. Currently, the intermediate interconnect layer in GaAs / perovskite tandem solar cells typically employs heavily doped tunnel junctions (such as tunneling junctions) or transparent conductive oxides (TCOs, such as ITO and IZO). However, these approaches have several limitations: tunnel junctions require complex and expensive epitaxial growth processes (such as MOCVD and MBE), increasing manufacturing costs; TCO layers are usually prepared by magnetron sputtering, where high-energy particles may damage the underlying GaAs or organic / perovskite materials, and the interfacial contact between TCOs and organic materials is often poor, resulting in inadequate energy level matching.

[0004] Therefore, developing an intermediate interconnect layer that can simultaneously solve the above-mentioned problems of energy level matching, interface recombination, and stability is of great significance for realizing efficient and stable GaAs / perovskite tandem solar cells. Summary of the Invention

[0005] This application provides a GaAs / perovskite tandem solar cell based on π-π interactions and its fabrication method, to solve the problems existing in related technologies. The technical solution is as follows: In a first aspect, embodiments of this application provide a GaAs / perovskite tandem solar cell based on π-π interactions, including a bottom GaAs sub-cell and a top perovskite sub-cell; the bottom GaAs sub-cell includes a first CNT / CuPc composite functional layer, and the top perovskite sub-cell includes a second CNT / CuPc composite functional layer. The bottom GaAs sub-cell and the top perovskite sub-cell are connected by a first CNT / CuPc composite functional layer as an intermediate interconnection layer. In the CNT / CuPc composite functional layer, CuPc and CNT form an energy-level matched conductive network through π-π interactions.

[0006] In one embodiment, the bottom GaAs sub-cell comprises, from bottom to top, a back electrode, an InGaP back field layer, a GaAs substrate layer, a CuSCN passivation layer, a first CNT layer, and a first CuPc layer; the first CNT layer and the first CuPc layer constitute a first CNT / CuPc composite functional layer.

[0007] In one embodiment, the top perovskite sub-cell comprises, from bottom to top, an electron transport layer, a perovskite absorber layer, a second CNT layer, a second CuPc layer, and a front electrode; the second CNT layer and the second CuPc layer constitute a second CNT / CuPc composite functional layer.

[0008] In one embodiment, the back electrode is Au.

[0009] In one embodiment, the InGaP back field layer is n-type, and the Si doping concentration is (1~3)×10⁻⁶. 17 / cm 3 .

[0010] In one embodiment, the GaAs substrate is an n-type GaAs substrate with a Si doping concentration of (1~3)×10⁻⁶. 18 / cm 3 The crystal plane is (110).

[0011] In one embodiment, the front electrode is Ag.

[0012] In one embodiment, the electron transport layer is TiO2, SnO2, or C. 60 Any of BCP or PCBM.

[0013] In one embodiment, the perovskite absorber layer is any one of MAPbI3, FAPbI3, or MAPbBr3.

[0014] In one embodiment, the thickness of the back electrode is 80-120 nm; the thickness of the InGaP back field layer is 30-60 μm; the thickness of the GaAs substrate layer is 250-350 μm; the thickness of the CuSCN passivation layer is 2-10 nm; the thickness of the first CNT is 100-200 nm; and the thickness of the first CuPc functional layer is 20-60 nm.

[0015] In one embodiment, the electron transport layer has a thickness of 30-60 nm; the perovskite absorber layer has a thickness of 400-600 nm; the second CNT has a thickness of 100-200 nm; the second CuPc functional layer has a thickness of 20-60 nm; and the front electrode has a thickness of 100-200 nm.

[0016] Secondly, embodiments of this application provide a method for fabricating a GaAs / perovskite tandem solar cell based on π-π interactions, comprising the following steps: Step 1: Deposit a back electrode on the back side of the InGaP back field layer / GaAs substrate and anneal to form an ohmic contact. Step 2: Prepare a CuSCN passivation layer on the front side of the InGaP back field layer / GaAs substrate; Step 3: Prepare the first CNT / CuPc composite functional layer on the CuSCN passivation layer and perform annealing treatment; Step 4: Prepare an electron transport layer on the first CNT / CuPc composite functional layer, spin-coat a perovskite precursor solution on the surface of the electron transport layer, and anneal it using an antisolvent method to obtain a perovskite absorber layer. Step 5: Prepare a second CNT / CuPc composite functional layer on the perovskite absorber layer, and deposit a front electrode at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0017] In one embodiment, in step 1, the annealing temperature of the back electrode is 300~330℃, and the annealing time is 15~30s.

[0018] In one embodiment, the CuSCN passivation layer is prepared by spin coating.

[0019] In one embodiment, CNTs are prepared into a filter membrane by vacuum filtration and then attached to the front side of the CuSCN passivation layer for drying; a CuPc layer is prepared on the surface of the CNT membrane by spin coating or thermal evaporation, and the CNT film and the CuPc layer form a first CNT / CuPc composite functional layer.

[0020] In one embodiment, in step 3, the annealing temperature is 80~150°C.

[0021] In one embodiment, the electron transport layer is prepared by magnetron sputtering under the following conditions: power of 60-120W, vacuum of 0.4-0.7Pa, and sputtering time of 10-30min.

[0022] In one embodiment, in step 4, the spin coating speed is 2000~4000 rpm and the spin coating time is 20~60s; in the antisolvent method, the antisolvent is added 10~15s before the end of the spin.

[0023] In one embodiment, the annealing temperature is 80~120°C and the annealing time is 10~30 min.

[0024] In one embodiment, CNTs are prepared into a filter membrane by vacuum filtration and then attached to the front side of the perovskite absorber layer for drying; a CuPc layer is prepared on the surface of the CNT membrane by spin coating or thermal evaporation, and the CNT film and the CuPc layer form a second CNT / CuPc composite functional layer.

[0025] In one embodiment, the perovskite precursor solution contains one or more of MAI, FAI, MABr, PbI2, or PbBr2.

[0026] The solvent is a mixture of DMF and DMSO; the volume ratio of DMF or DMF to DMSO is (3~5):1; In one embodiment, the concentration of the perovskite precursor solution is 0.5~1.2M.

[0027] In one embodiment, the antisolvent used in the antisolvent method is one or a combination of two or more of chlorobenzene, toluene, or ethyl acetate.

[0028] The advantages or beneficial effects of the above technical solutions include at least the following: This application discloses a GaAs / perovskite tandem solar cell based on π-π interactions, comprising GaAs sub-cells and perovskite sub-cells. CuPc / CNTs are used as the hole transport layer for the bottom GaAs sub-cell, the top perovskite sub-cell, and the intermediate interconnect layer connecting the upper and lower sub-cells, effectively enhancing vertical charge transport capability while exhibiting excellent air stability. Specifically, a CuPc surface functional layer is fabricated on the CNT surface. The strong π-π interaction and good energy level matching between CuPc and CNT induce electron transfer from CNT to CuPc, significantly enhancing the p-type doping and thin-film conductivity of CNTs. This allows for step-level energy level modulation of the CNT work function, minimizing voltage loss due to energy level mismatch and reducing additional recombination losses introduced by the multilayer interface.

[0029] The method for fabricating GaAs / perovskite tandem solar cells based on π-π interactions in this application avoids the need for additional fabrication of complex tunnel junctions or TCO layers in traditional tandem cells, thus simplifying the device structure and reducing manufacturing costs.

[0030] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of this application will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0031] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0032] Figure 1 This is a schematic diagram of the GaAs / perovskite tandem solar cell structure based on π-π interactions in Example 1; 1, Au electrode, 2, InGaP back field layer, 3, GaAs substrate layer, 4, CuSCN passivation layer, 5, first CNT layer, 6, first CuPc layer, 7, electron transport layer, 8, perovskite absorber layer, 9, second CNT layer, 10, second CuPc layer, 11, Ag front electrode layer; Figure 2 IV curves of solar cells of Example 1 and Comparative Example 1 before and after the introduction of CuPc. Figure 3 The JV curves are for the solar cells of Example 1 and Comparative Examples 1-3. Figure 4 SEM image of the CNT / CuPc surface after CuPc was introduced in Example 1; Figure 5 Raman plots of CuPc and CNT / CuPc; Figure 6 PL diagrams of the solar cells of Example 1 and Comparative Example 1; Figure 7 The graphs show the stability test results of the solar cells in Example 1 and Comparative Example 1. Detailed Implementation

[0033] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0034] Carbon nanotubes (CNTs) have been explored as hole transport layers in GaAs-based solar cells due to their excellent conductivity, light transmittance, and solution processability. CN114823931A discloses a carbon nanotube / silver nanowire composite film, its gallium arsenide-based heterojunction solar cell, and its fabrication method. Using the carbon nanotube / silver nanowire composite film as a hole transport layer significantly reduces the series resistance of the solar cell and improves the photoelectric conversion efficiency. However, this approach cannot passivate the defect states on the CNT surface, and the inherent dangling bonds and high surface state density of CNTs remain unresolved. Furthermore, it only addresses single-junction cells and does not address the application of CNT-based materials as intermediate interconnect layers in tandem cells, nor does it consider their role in energy level matching and charge recombination regulation between upper and lower sub-cells.

[0035] When CNTs are used directly as the intermediate interconnect layer of a tandem solar cell, three major technical challenges are faced: (1) energy level mismatch: the work function of CNTs is difficult to match ideally with the energy levels of the two sub-cells, resulting in open-circuit voltage loss; (2) severe interface recombination: the high defect density on the surface of CNTs leads to severe carrier recombination; (3) poor stability: the loose CNT network structure cannot effectively isolate water and oxygen, resulting in poor device stability. This application provides a GaAs / perovskite tandem solar cell based on π-π interactions and its fabrication method, which uses CNT-based composite materials as the hole transport layer of the top sub-cell, the hole transport layer of the bottom sub-cell, and the intermediate interconnect layer connecting the two, to solve the above problems in an integrated manner.

[0036] This application provides a GaAs / perovskite tandem solar cell based on π-π interaction, including a bottom GaAs sub-cell and a top perovskite sub-cell; the bottom GaAs sub-cell includes a first CNT / CuPc composite functional layer, and the top perovskite sub-cell includes a second CNT / CuPc composite functional layer. The bottom GaAs sub-cell and the top perovskite sub-cell are connected by a first CNT / CuPc composite functional layer as an intermediate interconnection layer. In the CNT / CuPc composite functional layer, CuPc and CNT form an energy-level matched conductive network through π-π interactions.

[0037] A CuPc functional layer is introduced onto the surface of the CNT hole transport layer. Utilizing the strong π-π interaction between CuPc and CNTs, precise control of energy level matching, effective passivation of CNT surface defects, and induced electron transfer from CNTs to CuPc are achieved, significantly improving vertical conductivity. This significantly enhances the p-type doping and thin-film conductivity of CNTs, effectively improving vertical charge transport capability. An integrated hole transport / interconnect structure is constructed. This structure serves not only as the hole transport layer for both GaAs and perovskite sub-cells but also as the intermediate interconnect layer between the two sub-cells, achieving efficient charge transport and energy level matching while exhibiting excellent air stability. This integrated design avoids the need for additional complex tunnel junctions or TCO layers in traditional tandem solar cells, simplifying the device structure, reducing manufacturing costs, and minimizing additional recombination losses introduced by multilayer interfaces.

[0038] In one embodiment, the bottom GaAs sub-cell comprises, from bottom to top, a back electrode, an InGaP back field layer, a GaAs substrate layer, a CuSCN passivation layer, a first CNT layer, and a first CuPc layer; the first CNT layer and the first CuPc layer constitute a first CNT / CuPc composite functional layer.

[0039] The CuSCN passivation layer and the CuPc layer in the CNT / CuPc composite functional layer together form a dual-interface passivation structure. This application introduces a CuSCN passivation layer on the bottom GaAs substrate surface and a CuPc passivation layer on the CNT surface, forming a dual-interface passivation system. CuSCN passivates dangling bonds and defect states at the GaAs / CNT interface, while CuPc passivates defect states in the CNT bulk phase and the CNT / perovskite interface. The two work synergistically to passivate interface defects in the core region of the device from bottom to top, maximally suppressing carrier recombination throughout the device and providing a highly efficient and stable GaAs / perovskite tandem solar cell.

[0040] In one embodiment, the back electrode is Au; the thickness of the back electrode is 80~120nm.

[0041] In one implementation, the InGaP back field layer is n-type, and the Si doping concentration is 1×10⁻⁶. 17 ~3×10 17 / cm 3 The thickness of the InGaP back field layer is 30~60μm.

[0042] In one implementation, the GaAs substrate is an n-type GaAs substrate, and the Si doping concentration is 1×10⁻⁶. 18 ~3×10 18 / cm 3The crystal plane is (110); the thickness of the GaAs substrate is 250~350μm.

[0043] In one implementation, the CuSCN passivation layer has a thickness of 2-10 nm. The CuSCN passivation layer and the CuPc layer in the CNT / CuPc composite functional layer together form a dual-interface passivation structure.

[0044] In one implementation, the thickness of the first CNT layer is 100-200 nm; the thickness of the first CuPc layer is 20-60 nm. The first CuPc layer serves as the surface functional layer of the GaAs / CNT heterojunction solar cell. The first CNT layer and the first CuPc layer constitute the first CNT / CuPc composite functional layer; CuPc and CNT form an energy-level matched conductive network through π-π interactions, promoting charge transport in the vertical direction. It is located on top of the bottom GaAs sub-cell and simultaneously serves as an intermediate interconnect layer connecting the bottom of the top perovskite sub-cell, thus enabling the stacked connection between the bottom GaAs sub-cell and the top perovskite sub-cell.

[0045] In one embodiment, the top perovskite sub-cell comprises, from bottom to top, an electron transport layer, a perovskite absorber layer, a second CNT layer, a second CuPc layer, and a front electrode; the second CNT layer and the second CuPc layer constitute a second CNT / CuPc composite functional layer.

[0046] In one implementation, the front electrode is Ag; the thickness of the front electrode is 100~200nm.

[0047] In one embodiment, the electron transport layer is TiO2, SnO2, or C. 60 It can be any one of BCP or PCBM. The electron transport layer thickness is 30~60nm.

[0048] In one embodiment, the perovskite absorber layer is any one of MAPbI3, FAPbI3, or MAPbBr3. The thickness of the perovskite absorber layer is 400~600 nm.

[0049] In one embodiment, the thickness of the second CNT layer is 100-200 nm; the thickness of the second CuPc layer is 20-60 nm. The second CNT layer and the second CuPc layer constitute a second CNT / CuPc composite functional layer; CuPc and CNT form an energy-level-matched conductive network through π-π interactions, serving as the hole transport layer of the perovskite solar cell. Thus, in the tandem solar cell of this application, the CNT / CuPc composite functional layer structure not only serves as the hole transport layer for both the GaAs and perovskite sub-cells, but also as the intermediate interconnecting layer between the two sub-cells, achieving efficient charge transport and energy level matching, while also exhibiting excellent air stability.

[0050] This application also provides a method for fabricating a GaAs / perovskite tandem solar cell based on π-π interactions, comprising the following steps: Step 1: Deposit a back electrode on the back side of the InGaP back field layer / GaAs substrate and anneal to form an ohmic contact. Step 2: Prepare a CuSCN passivation layer on the front side of the InGaP back field layer / GaAs substrate; Step 3: Prepare the first CNT / CuPc composite functional layer on the CuSCN passivation layer and perform annealing treatment; Step 4: Prepare an electron transport layer on the first CNT / CuPc composite functional layer, spin-coat a perovskite precursor solution on the surface of the electron transport layer, and anneal it using an antisolvent method to obtain a perovskite absorber layer. Step 5: Prepare a second CNT / CuPc composite functional layer on the perovskite absorber layer, and deposit a front electrode at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0051] In one implementation method, in step 1), the InGaP back field layer is n-type with a thickness of 30~60μm and a Si doping concentration of 1×10⁻⁶. 17 ~3×10 17 / cm 3 .

[0052] The GaAs substrate is an n-type GaAs substrate with a thickness of 250~350μm and a Si doping concentration of 1×10⁻⁶. 18 ~3×10 18 / cm 3 The crystal plane is (110).

[0053] The back electrode is an Au electrode with a thickness of 100~120nm.

[0054] The annealing temperature is 300~330℃, and the annealing time is 15~30s.

[0055] In one implementation method, the CuSCN passivation layer is prepared by spin coating. The thickness of the CuSCN passivation layer is 2~10 nm.

[0056] As one embodiment, the first CNT / CuPc composite functional layer includes a first CNT film and a first CuPc layer preparation process, which includes preparing a filter membrane by vacuum filtration and attaching it to the front side of the CuSCN passivation layer for drying; preparing a CuPc layer on the surface of the CNT film by spin coating or thermal evaporation, and the CNT film and CuPc layer forming the first CNT / CuPc composite functional layer.

[0057] The thickness of the first CNT film is 100~200 nm; the thickness of the first CuPc functional layer is 20~60 nm. In this embodiment, the annealing temperature is 80~150℃ to enhance the π-π interaction between the CuPc functional layer and the CNT layer.

[0058] As one implementation method, the electron transport layer 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.

[0059] In one embodiment, the spin-coating speed of the perovskite precursor solution is 2000~4000 rpm, and the spin-coating time is 20~60 s; in the antisolvent method, the antisolvent is added 10~15 s before the end of the spin. In this embodiment, the annealing temperature is 80~120℃, and the annealing time is 10~30 min.

[0060] As one embodiment, the second CNT / CuPc composite functional layer includes a second CNT film and a second CuPc layer preparation process, which includes preparing a filter membrane by vacuum filtration and attaching it to the front side of the CuSCN passivation layer for drying; preparing a CuPc layer on the surface of the CNT film by spin coating or thermal evaporation, and the CNT film and CuPc layer forming the second CNT / CuPc composite functional layer.

[0061] The thickness of the second CNT film is 100~200nm; the thickness of the second CuPc functional layer is 20~60nm.

[0062] In one embodiment, the perovskite precursor solution contains one or more of MAI, FAI, MABr, PbI2, or PbBr2. In this embodiment, when the perovskite is MAPbI3, the perovskite precursor is MAI and PbI2; when the perovskite is FAPbI3, the perovskite precursor is FAI and PbI2; and when the perovskite is MAPbBr3, the perovskite precursor is MABr and PbBr2.

[0063] The solvent is a mixture of DMF and DMSO; the volume ratio of DMF or DMF to DMSO is (3~5):1; In one embodiment, the concentration of the perovskite precursor solution is 0.5~1.2M, where the concentration is based on perovskite.

[0064] In one embodiment, the antisolvent used in the antisolvent method is one or a combination of two or more of chlorobenzene, toluene, or ethyl acetate.

[0065] The following is a further explanation using specific embodiments.

[0066] Example 1 A GaAs / perovskite tandem solar cell based on π-π interactions and its fabrication method. The schematic diagram of the GaAs / perovskite tandem solar cell based on π-π interactions is shown below. Figure 1 As shown, from bottom to top, it includes a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, a CuSCN passivation layer 4, a first CNT layer 5, a first CuPc layer 6, a TiO2 electron transport layer 7, a MAPbI3 perovskite absorption layer 8, a second CNT layer 9, a second CuPc layer 10, and a front Ag electrode layer 11. The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, a 120nm thick Au back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 330℃ for 30s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate is 50 μm thick, and the Si doping concentration is 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3 The crystal plane is (110); 2) A 5 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 100 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer; a 30 nm thick first CuPc layer was prepared on the first CNT layer by spin coating; and then annealed at 120 °C. 4) A TiO2 electron transport layer was prepared by magnetron sputtering on the first CuPc layer with a power of 80W, a vacuum degree of 0.57Pa, and a sputtering time of 20min; A 0.6 M precursor solution was prepared by mixing perovskite precursors MAI and PbI2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 4:1. The precursor solution was spin-coated onto an electron transport layer at 4000 rpm for 30 s, and 100 μL of chlorobenzene was added dropwise 10 s before the end of spin-coating. The mixture was then annealed at 100 °C for 10 min to prepare the MAPbI3 perovskite absorber layer. 5) A 100 nm thick CNT hole transport layer film was prepared on the perovskite absorber layer by vacuum filtration and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer; a 30 nm thick second CuPc layer was prepared on the second CNT layer by spin coating; and then annealed at 120 °C. 6) A 100nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0067] Example 2 A GaAs / perovskite tandem solar cell based on π-π interactions and its fabrication method. The schematic diagram of the GaAs / perovskite tandem solar cell based on π-π interactions is shown below. Figure 1 As shown, from bottom to top, it includes a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, a CuSCN passivation layer 4, a first CNT layer 5, a first CuPc layer 6, a TiO2 electron transport layer 7, a MAPbI3 perovskite absorption layer 8, a second CNT layer 9, a second CuPc layer 10, and a front Ag electrode layer 11. The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, a 100nm thick Au back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 300℃ for 15s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate has a thickness of 30 μm and a Si doping concentration of 3 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 250 μm, and the Si doping concentration is 3 × 10⁻⁶. 18 / cm 3 The crystal plane is (110); 2) A 10 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 200 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer; a 20 nm thick first CuPc layer was prepared on the first CNT layer by thermal evaporation; and then annealed at 80 °C. 4) A TiO2 electron transport layer was prepared by magnetron sputtering on the first CuPc layer with a power of 60W, a vacuum degree of 0.7Pa, and a sputtering time of 10min; A 1.2 M precursor solution was prepared by mixing perovskite precursors MABr and PbBr2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 3:1. The precursor solution was spin-coated onto an electron transport layer at 2000 rpm for 60 s, and 100 μL of chlorobenzene was added dropwise 15 s before the end of spin-coating. The mixture was then annealed at 80 °C for 30 min to prepare the MAPbBr3 perovskite absorber layer. 5) A 200 nm thick CNT hole transport layer film was prepared on the perovskite absorber layer by vacuum filtration and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer; a 20 nm thick second CuPc layer was prepared on the second CNT layer by thermal evaporation; and then annealed at 80 °C. 6) A 120nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0068] Example 3 A GaAs / perovskite tandem solar cell based on π-π interactions and its fabrication method. The schematic diagram of the GaAs / perovskite tandem solar cell based on π-π interactions is shown below. Figure 1 As shown, from bottom to top, it includes a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, a CuSCN passivation layer 4, a first CNT layer 5, a first CuPc layer 6, a TiO2 electron transport layer 7, a MAPbI3 perovskite absorption layer 8, a second CNT layer 9, a second CuPc layer 10, and a front Ag electrode layer 11. The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, an Au back electrode with a thickness of 110nm is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 315℃ for 22s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate has a thickness of 60 μm and a Si doping concentration of 2 × 10⁻⁶. 17 / cm 3The GaAs thickness is 200 μm, and the Si doping concentration is 2 × 10⁻⁶. 18 / cm 3 The crystal plane is (110); 2) A 2 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 150 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer; a 60 nm thick first CuPc layer was prepared on the first CNT layer by thermal evaporation; and then annealed at 150 °C. 4) A TiO2 electron transport layer was prepared by magnetron sputtering on the first CuPc layer with a power of 120W, a vacuum degree of 0.4Pa, and a sputtering time of 30min. A 0.5 M precursor solution was prepared by mixing perovskite precursors FAI and PbI2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 5:1. The precursor solution was spin-coated onto an electron transport layer at 3000 rpm for 20 s, and 100 μL of chlorobenzene was added dropwise 12 s before the end of spin-coating. The mixture was then annealed at 120 °C for 15 min to prepare the FAPbI3 perovskite absorber layer. 5) A 150 nm thick CNT hole transport layer film was prepared on the perovskite absorber layer by vacuum filtration and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer; a 60 nm thick second CuPc layer was prepared on the second CNT layer by thermal evaporation; and then annealed at 150 °C. 6) A 110 nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0069] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the prepared battery is a GaAs / perovskite tandem battery without a CuPc layer; The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, a 120nm thick Au back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 330℃ for 30s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate is 50 μm thick, and the Si doping concentration is 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm3 The crystal plane is (110); 2) A 5 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 100 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer. 4) A TiO2 electron transport layer was prepared on the first CNT layer by magnetron sputtering with a power of 80W, a vacuum degree of 0.57Pa, and a sputtering time of 20min; A 0.6 M precursor solution was prepared by mixing perovskite precursors MAI and PbI2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 4:1. The precursor solution was spin-coated onto an electron transport layer at 4000 rpm for 30 s, and 100 μL of chlorobenzene was added dropwise 10 s before the end of spin-coating. The mixture was then annealed at 100 °C for 10 min to prepare the MAPbI3 perovskite absorber layer. 5) A CNT hole transport layer film with a thickness of 100 nm was prepared on the perovskite absorber layer by vacuum filtration, and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer. 6) A 100nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0070] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the prepared battery is a GaAs / perovskite tandem battery, and ITO is used as the intermediate interconnect layer of the GaAs / perovskite battery.

[0071] The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, a 120nm thick Au back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 330℃ for 30s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate is 50 μm thick, and the Si doping concentration is 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3 The crystal plane is (110); 2) A 5 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 100 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer. An ITO intermediate interconnect layer with a thickness of 100 nm was prepared by magnetron sputtering on the first CNT layer with a power of 70 W, a vacuum degree of 0.60 Pa, and a sputtering time of 30 min. 4) A TiO2 electron transport layer was prepared on an ITO layer by magnetron sputtering at a power of 80W, a vacuum of 0.57Pa, and a sputtering time of 20min; A 0.6 M precursor solution was prepared by mixing perovskite precursors MAI and PbI2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 4:1. The precursor solution was spin-coated onto an electron transport layer at 4000 rpm for 30 s, and 100 μL of chlorobenzene was added dropwise 10 s before the end of spin-coating. The mixture was then annealed at 100 °C for 10 min to prepare the MAPbI3 perovskite absorber layer. 5) A 100 nm thick CNT hole transport layer film was prepared on the perovskite absorber layer by vacuum filtration and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer; a 30 nm thick second CuPc layer was prepared on the second CNT layer by spin coating; and then annealed at 120 °C. 6) A 100nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0072] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the prepared battery is a GaAs / perovskite tandem battery, and Ag nanowires are used on the CNT surface instead of CuPc surface functional layers. The preparation method includes the following steps: 1) n-type InGaP / GaAs substrate, a 120nm thick Au back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed at 330℃ for 30s to form an ohmic contact. The InGaP layer in the InGaP / GaAs substrate is 50 μm thick, and the Si doping concentration is 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3 The crystal plane is (110); 2) A 5 nm thick CuSCN passivation layer was prepared on the front side of the InGaP back field layer / GaAs substrate by spin coating. 3) A 100 nm thick CNT hole transport layer film was prepared on the CuSCN passivation layer by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried to serve as the first CNT layer; an Ag nanowire layer with a thickness of 5 nm was prepared on the first CNT layer by spin coating to obtain a CNT / Ag nanowire composite film. 4) A TiO2 electron transport layer was prepared by magnetron sputtering on Ag nanowires with a power of 80W, a vacuum of 0.57Pa, and a sputtering time of 20min; A 0.6 M precursor solution was prepared by mixing perovskite precursors MAI and PbI2 in a molar ratio of 1:1 with DMF and DMSO in a volume ratio of 4:1. The precursor solution was spin-coated onto an electron transport layer at 4000 rpm for 30 s, and 100 μL of chlorobenzene was added dropwise 10 s before the end of spin-coating. The mixture was then annealed at 100 °C for 10 min to prepare the MAPbI3 perovskite absorber layer. 5) A 100 nm thick CNT hole transport layer film was prepared on the perovskite absorber layer by vacuum filtration and then attached to the front side of the perovskite absorber layer and dried to serve as the second CNT layer; an Ag nanowire layer with a thickness of 5 nm was prepared on the second CNT layer by spin coating to obtain a CNT / Ag nanowire composite film. 6) A 100nm thick Ag front electrode is deposited at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

[0073] Table 1 shows a comparison of the device parameters of the solar cells prepared in Examples 1-3 and Comparative Examples 1-3. The IV curves of the solar cells in Example 1 and Comparative Example 1 before and after the introduction of CuPc are shown in Figure 1. Figure 2 As shown; The JV curves of the solar cells in Example 1 and Comparative Examples 1-3 are shown below. Figure 3 As shown; SEM images of the CNT / CuPc surface after the introduction of the CuPc functional layer are shown below. Figure 4 As shown; the Raman spectra of CuPc and CNT / CuPc are as follows. Figure 5 As shown; the PL diagrams of the solar cells of Example 1 and Comparative Example 1 are as follows. Figure 6 The figure shows the stability test results of the solar cells in Example 1 and Comparative Example 1.

[0074] Table 1

[0075] As can be seen from the comparison of device performance parameters in Table 1, the technical solution of this invention, which uses a CNT / CuPc composite functional layer as the hole transport layer and intermediate interconnect layer, has significant performance advantages. Comparative Example 1, which does not introduce a CuPc layer and only uses CNT as the hole transport layer, has low photoelectric conversion efficiency. This is because there are a large number of defect states on the CNT surface, leading to severe carrier recombination. Simultaneously, the work function of the CNT does not match the energy levels of the two sub-cells well, resulting in open-circuit voltage (Voc) loss. Comparative Example 2 uses traditional ITO as the intermediate interconnect layer, but the device performance further deteriorates. This is mainly because the magnetron sputtering process of ITO may damage the underlying material, and the interface contact between ITO and organic / perovskite materials is poor, leading to increased series resistance. Comparative Example 3 uses a CNT / Ag nanowire composite film. Although Ag nanowires can enhance conductivity to some extent, they cannot passivate CNT surface defects due to only physical bonding, and poor light transmittance causes optical loss, resulting in the lowest efficiency among all comparative examples.

[0076] In contrast, Examples 1-3 of this invention, which prepared CNT / CuPc composite functional layers using spin coating and thermal evaporation methods respectively, all achieved excellent device performance, with all parameters significantly superior to the comparative examples. This performance advantage stems from the core innovation of this invention: the CNT / CuPc composite functional layer simultaneously performs the triple functions of the bottom sub-cell hole transport layer, the top sub-cell hole transport layer, and the intermediate interconnect layer. Through the π-π interaction between CuPc and CNT, the following synergistic effects are achieved: (1) Inducing electron transfer from CNT to CuPc, enhancing the p-type doping of CNT, and improving vertical conductivity ( Figure 2-3 (as shown in Figure 5); (2) CuPc densely coats the CNT surface, effectively passivating defect states and suppressing carrier recombination (as shown in Figure 5). Figure 4 and 6 As shown), this GaAs / perovskite tandem solar cell also exhibits excellent air stability. Figure 7 ).

[0077] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0079] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A GaAs / perovskite tandem solar cell based on π-π interactions, characterized in that, It includes a bottom GaAs sub-cell and a top perovskite sub-cell; the bottom GaAs sub-cell includes a first CNT / CuPc composite functional layer, and the top perovskite sub-cell includes a second CNT / CuPc composite functional layer. The bottom GaAs sub-cell and the top perovskite sub-cell are connected by a first CNT / CuPc composite functional layer as an intermediate interconnection layer. In the CNT / CuPc composite functional layer, CuPc and CNT form an energy-level matched conductive network through π-π interactions.

2. The GaAs / perovskite tandem solar cell based on π-π interactions according to claim 1, characterized in that, The bottom GaAs sub-cell, from bottom to top, includes a back electrode, an InGaP back field layer, a GaAs substrate layer, a CuSCN passivation layer, a first CNT layer, and a first CuPc layer; the first CNT layer and the first CuPc layer constitute a first CNT / CuPc composite functional layer. The top perovskite sub-cell comprises, from bottom to top, an electron transport layer, a perovskite absorber layer, a second CNT layer, a second CuPc layer, and a front electrode; the second CNT layer and the second CuPc layer constitute a second CNT / CuPc composite functional layer.

3. The GaAs / perovskite tandem solar cell based on π-π interactions according to claim 2, characterized in that, The back electrode is Au; The InGaP back field layer is n-type, and the Si doping concentration is 1×10⁻⁶. 17 / cm 3 ~3×10 17 / cm 3 ; The GaAs substrate is an n-type GaAs substrate with a Si doping concentration of 1×10⁻⁶. 18 / cm 3 ~3×10 18 / cm 3 The crystal plane is (110).

4. The GaAs / perovskite tandem solar cell based on π-π interactions according to claim 2, characterized in that, The front electrode is Ag; The electron transport layer is TiO2, SnO2, C 60 Any one of BCP or PCBM; The perovskite absorber layer is any one of MAPbI3, FAPbI3, or MAPbBr3.

5. The GaAs / perovskite tandem solar cell based on π-π interactions according to claim 2, characterized in that, The thickness of the back electrode is 80~120nm; the thickness of the InGaP back field layer is 30~60μm; the thickness of the GaAs substrate layer is 250~350μm; the thickness of the CuSCN passivation layer is 2~10nm; the thickness of the first CNT is 100~200nm; and the thickness of the first CuPc functional layer is 20~60nm. The electron transport layer has a thickness of 30-60 nm; the perovskite absorber layer has a thickness of 400-600 nm; the second CNT has a thickness of 100-200 nm; the second CuPc functional layer has a thickness of 20-60 nm; and the front electrode has a thickness of 100-200 nm.

6. The method for fabricating a GaAs / perovskite tandem solar cell based on π-π interactions according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Deposit a back electrode on the back side of the InGaP back field layer / GaAs substrate and anneal to form an ohmic contact. Step 2: Prepare a CuSCN passivation layer on the front side of the InGaP back field layer / GaAs substrate; Step 3: Prepare the first CNT / CuPc composite functional layer on the CuSCN passivation layer and perform annealing treatment; Step 4: Prepare an electron transport layer on the first CNT / CuPc composite functional layer, spin-coat a perovskite precursor solution on the surface of the electron transport layer, and anneal it using an antisolvent method to obtain a perovskite absorber layer. Step 5: Prepare a second CNT / CuPc composite functional layer on the perovskite absorber layer, and deposit a front electrode at both ends to obtain a GaAs / perovskite tandem solar cell based on π-π interaction.

7. The method for fabricating GaAs / perovskite tandem solar cells based on π-π interactions according to claim 6, characterized in that, In step 1, the annealing temperature of the back electrode is 300~330℃, and the annealing time is 15~30s; The CuSCN passivation layer was prepared by spin coating.

8. The method for fabricating GaAs / perovskite tandem solar cells based on π-π interactions according to claim 6, characterized in that, CNTs were prepared into a filter membrane by vacuum filtration and then attached to the front side of the CuSCN passivation layer and dried. A CuPc layer was prepared on the surface of the CNT membrane by spin coating or thermal evaporation. The CNT film and the CuPc layer formed the first CNT / CuPc composite functional layer. In step 3, the annealing temperature is 80~150℃.

9. The method for fabricating GaAs / perovskite tandem solar cells based on π-π interactions according to claim 6, characterized in that, The electron transport layer was prepared by magnetron sputtering under the following conditions: power of 60-120 W, vacuum of 0.4-0.7 Pa, and sputtering time of 10-30 min. 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 is 80~120℃ and the annealing time is 10~30min. CNTs were prepared into a filter membrane by vacuum filtration and then attached to the front side of the perovskite absorber layer for drying. A CuPc layer was prepared on the surface of the CNT membrane by spin coating or thermal evaporation. The CNT film and the CuPc layer formed a second CNT / CuPc composite functional layer.

10. The method for fabricating a GaAs / perovskite tandem solar cell based on π-π interactions according to claim 6, characterized in that, In the perovskite precursor solution, the perovskite precursor is one or a combination of two or more of MAI, FAI, MABr, PbI2 or PbBr2. The solvent is a mixture of DMF and DMSO; the volume ratio of DMF or DMF to DMSO is (3~5):1; The concentration of the perovskite precursor solution was 0.5–1.2 M; The antisolvent used in the antisolvent method is one or a combination of two or more of chlorobenzene, toluene, or ethyl acetate.

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