A perovskite / perovskite tandem solar cell with an inverted structure

Abstract

This invention discloses a perovskite / perovskite tandem solar cell with an inverted structure, belonging to the field of solar cell technology. The tandem solar cell, from the substrate to the light-facing surface, comprises, in sequence: a substrate, a non-metallic conductive layer, a first transport layer, a narrow bandgap perovskite layer, a second transport layer, a tunneling composite junction, a third transport layer, a wide bandgap perovskite layer, a fourth transport layer, a buffer layer, and a transparent conductive layer. This invention effectively utilizes the advantages of tandem devices in improving the efficiency of perovskite cells, while simultaneously addressing the stability issues caused by the oxygen sensitivity of lead-tin perovskite. Furthermore, the advanced structure reduces the dependence of perovskite solar cells on flat, transparent, and conductive substrates.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a perovskite / perovskite tandem solar cell with an inverted structure. Background Technology

[0002] Organic-inorganic hybrid perovskite solar cells have attracted much attention internationally due to their excellent photoelectric properties, such as low cost, ease of fabrication, and tunable bandgap. Their development has been rapid, with the photoelectric conversion efficiency increasing from 3.8% in 2009 to 26.4% in 2020. Perovskite materials are also considered the most promising light-absorbing materials for next-generation low-cost solar cells.

[0003] Currently, perovskite / perovskite tandem solar cells are an effective way to overcome the Shockley-Queisser limit of single-junction perovskite solar cells. Perovskite has the advantage of obtaining perovskite materials with different bandgap widths by changing its composition. Generally, doping the composition with bromine yields a wider bandgap perovskite, while doping with tin yields a narrower bandgap perovskite. In perovskite / perovskite tandem solar cells, using a wide-bandgap perovskite as the top cell to absorb short-wavelength sunlight and a narrow-bandgap perovskite as the bottom cell to absorb long-wavelength sunlight improves the utilization of the solar spectrum and reduces the thermal relaxation loss of charge carriers in single-junction cells, thereby improving photoelectric conversion efficiency. Monolithic all-perovskite tandem solar cells (TSCs) have made extremely rapid progress in device performance, achieving a record efficiency of 26.4% in just five years of research, surpassing single-junction perovskite solar cells (PSCs).

[0004] Despite significant advancements in power conversion efficiency (PCE), environmental stability remains a key challenge for the commercialization of perovskite tandem solar cells. Oxygen is one of the most prevalent environmental factors affecting solar cell stability. In all-perovskite tandems, compared to lead-based wide-bandgap perovskites which can be stably stored in air for a period of time, narrow-bandgap materials, primarily lead-tin perovskite, exhibit significant challenges in Sn... 2+ Perovskite solar cells are highly sensitive to oxygen, leading to significant degradation in device performance. While effective encapsulation can prevent oxygen-induced degradation in the active layer or electrodes, there is still a risk of oxidation due to oxygen leakage during assembly and operation. Therefore, it is essential for all-perovskite tandem solar cells to exhibit oxygen stability in rigid or flexible device structures. However, all currently disclosed all-perovskite tandem solar cells employ a "super-substrate orientation" structure, which involves first depositing a wide bandgap absorber layer on a transparent substrate, then depositing a narrow bandgap absorber layer after depositing a tunnel junction, and finally depositing metal electrodes to complete the device fabrication, such as... Figure 1As shown, sunlight is absorbed by two layers of absorbing materials after entering through a transparent substrate. However, this structure has several drawbacks: First, this structure naturally leads to the exposure of easily oxidized lead-tin-based narrow-bandgap perovskite on the outside of the device, posing a serious threat to the device's stability; second, the "super-substrate orientation" of the all-perovskite tandem requires the substrate to be both transparent and conductive, limiting the choice of substrate and increasing the cost of device fabrication; third, the transparent electrodes pre-deposited on the substrate during large-area fabrication of all-perovskite tandem solar cells introduce huge series resistance, limiting performance improvement; fourth, the metal back electrode of the all-perovskite tandem solar cell is prone to metal peeling during large-area fabrication.

[0005] Therefore, designing a novel all-perovskite tandem structure with oxygen resistance is beneficial for achieving more stable tandem devices and promoting the commercialization of all-perovskite tandem solar cells. Summary of the Invention

[0006] To address the technical problem that "super-substrate orientation" all-perovskite stacks are easily damaged by oxygen, severely limiting the long-term stability of devices, this invention provides a perovskite / perovskite stacked solar cell with an inverted structure.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A perovskite / perovskite tandem solar cell comprises, from the substrate to the light-facing surface, the following layers in sequence: substrate, non-metallic conductive layer, first transport layer, narrow bandgap perovskite layer, second transport layer, tunneling composite junction, third transport layer, wide bandgap perovskite layer, fourth transport layer, buffer layer, and transparent conductive layer.

[0009] The substrate is a non-conductive substrate and / or a conductive metal thin film, i.e., a non-conductive substrate or a conductive metal thin film, or a combination of a non-conductive substrate and a conductive metal thin film. The non-conductive substrate is made of glass, polynaphthalene glycol, polyethylene terephthalate, or polyimide; the conductive metal thin film is made of copper, aluminum, titanium, or gold.

[0010] The non-metallic conductive layer is mainly used to prevent potential reactions between the perovskite and the substrate, and is generally made of one or more conductive materials selected from indium tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, fluorine-doped tin oxide, indium zinc oxide, indium tungsten oxide, or graphene.

[0011] The tunneling composite junction consists of a dense layer and a carrier recombination layer. The dense layer is directly connected to the second transport layer. The dense layer protects the pre-deposited perovskite film from damage during subsequent deposition processes, while the carrier recombination layer facilitates electron-hole recombination within the device. The dense layer is made of one or more materials selected from molybdenum oxide, vanadium oxide, 2,9-dimethyl-4,7-biphenyl-1,10-o-phenanthroline, tin oxide, titanium oxide, or tungsten oxide. The dense layer is prepared using physical deposition or chemical deposition methods. Physical deposition methods include, but are not limited to, vacuum evaporation, sputtering, ion beam deposition, and pulsed laser deposition; chemical deposition methods include, but are not limited to, chemical vapor deposition, atomic layer deposition, and sol-gel spin coating. The carrier recombination layer can be made of metal nanoparticle films, non-dense metal island structures, metal oxide nanoparticles, or metal oxide films made of gold, palladium, silver, titanium, chromium, nickel, aluminum, copper, etc. Carrier composite layers can be prepared by deposition methods such as electron beam evaporation, thermal evaporation, magnetron sputtering, atomic layer deposition, spin coating, and blade coating.

[0012] The buffer layer is primarily designed to prevent damage to the already deposited multilayer structure during the deposition of the transparent conductive layer, and is constructed using molybdenum oxide (MoO). x It is made of one or more of the following materials: vanadium oxide (V2O5), 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline (BCP), tin oxide (SnO2), titanium oxide (TiO2), or tungsten oxide (WO3).

[0013] The transparent conductive layer is one or more of the following: indium tin oxide (ITO) film, aluminum-doped zinc oxide (AZO) film, gallium-doped zinc oxide (GZO) film, fluorine-doped tin oxide (FTO) film, indium zinc oxide (IZO) film, indium tungsten oxide (IWO) film, silver nanowires, metal layer, or graphene film.

[0014] Furthermore, the tandem solar cell is a pin structure or a nip structure. In a pin structure, the first transport layer is a hole transport layer, the second transport layer is an electron transport layer, the third transport layer is a hole transport layer, and the fourth transport layer is an electron transport layer. In a nip structure, the first transport layer is an electron transport layer, the second transport layer is a hole transport layer, the third transport layer is an electron transport layer, and the fourth transport layer is a hole transport layer.

[0015] Furthermore, the hole transport layer is made of p-type semiconductor materials, such as nickel oxide (NiO), molybdenum oxide (MoO3), cuprous oxide (Cu2O), copper iodide (CuI), copper phthalocyanine (CuPc), cuprous thiocyanate (CuSCN), reduced graphene oxide, poly(triaryl amine) (PTAA), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), poly(3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS), poly(4-phenyl)(4-butylphenyl)amine (Ploy-TPD), polyvinylcarbazole (PVK), etc.

[0016] Furthermore, the electron transport layer is made of n-type semiconductor materials, such as titanium oxide (TiO2), tin oxide (SnO2), zinc oxide (ZnO), and fullerene (C). 60 ), graphene, fullerene derivatives [6,6]-phenyl-C61-butyrate methyl ester (PCBM), etc.

[0017] Furthermore, the dense layer is prepared using an n-type or p-type semiconductor material. In one embodiment of the invention, tin oxide (SnO2) is used to prepare the dense layer.

[0018] Furthermore, there are metal grid electrodes on the surface of the transparent conductive layer. The metal grid electrodes are prepared using one or more of the following metal materials: gold, palladium, silver, titanium, chromium, nickel, aluminum, or copper. They can be prepared using existing conventional processes such as vacuum evaporation, sputtering, atomic layer deposition, 3D printing, screen printing, and inkjet printing.

[0019] The above-mentioned method for fabricating perovskite / perovskite tandem solar cells includes the following steps:

[0020] Step 1: Prepare a non-conductive substrate or a conductive metal thin film for later use, or deposit a conductive metal thin film on a non-conductive substrate as a substrate for later use.

[0021] Step 2: Prepare a non-metallic conductive layer on the surface of the above substrate;

[0022] Step 3: Prepare the first transport layer on the surface of the non-metallic conductive layer;

[0023] Step 4: Prepare a narrow bandgap perovskite layer on the surface of the first transport layer;

[0024] Step 5: Prepare a second transport layer on the surface of the narrow bandgap perovskite layer;

[0025] Step 6: A dense layer is prepared on the surface of the second transport layer, and then a carrier recombination layer is prepared to obtain a tunneling composite junction;

[0026] Step 7: Prepare a third transport layer on the surface of the tunneling composite junction;

[0027] Step 8: Prepare a wide-bandgap perovskite layer on the surface of the third transport layer;

[0028] Step 9: Prepare a fourth transport layer on the surface of the wide-bandgap perovskite layer;

[0029] Step 10: Prepare a buffer layer on the surface of the fourth transport layer. This can be done using conventional processes such as vacuum evaporation, magnetron sputtering, atomic layer deposition, chemical vapor deposition, ion beam deposition, pulsed laser deposition, spin coating, and blade coating.

[0030] Step 11: Prepare a transparent conductive layer on the surface of the buffer layer. This can be done using conventional processes such as vacuum evaporation, magnetron sputtering, atomic layer deposition, chemical vapor deposition, ion beam deposition, pulsed laser deposition, spin coating, blade coating, 3D printing, printing, spraying, etc., to obtain the stacked solar cell.

[0031] In the two components of an all-perovskite multilayer device, the narrow bandgap portion, primarily composed of mixed lead-tin perovskite, is highly susceptible to performance degradation due to oxygen exposure, while the wide bandgap portion, dominated by lead-based perovskite, is relatively stable against oxygen. Currently reported fabrication processes for all-perovskite multilayer devices involve sequentially depositing wide-bandgap perovskite, tunneling composite junctions, narrow-bandgap perovskite, and metal electrodes on a substrate. However, this process makes the device vulnerable to oxygen degradation. Therefore, this invention proposes a novel process for sequentially depositing narrow-bandgap perovskite, tunneling composite junctions, wide-bandgap perovskite, and transparent electrodes on a substrate.

[0032] This invention introduces inverted stacking technology into perovskite / perovskite tandem solar cells, enabling device fabrication on various substrates such as glass, PEN substrates, and thin metal layers. For example... Figure 4 As shown, photoelectric conversion efficiencies of 24.2%, 23.0%, and 20.0% were achieved on glass, PEN substrates, and copper foil substrates, respectively. Furthermore, compared to conventional "super-substrate orientation" stacks, the inverted stack exhibits better air stability, such as... Figure 5 As shown, when conventional and inverted stacks were placed in dry air to monitor their performance changes, the conventional stacks showed a sharp decline in performance, while the inverted stacks maintained performance without decline for more than 150 hours.

[0033] Compared with the prior art, the perovskite / perovskite tandem solar cell of the present invention has the following advantages: 1) It can prepare perovskite / perovskite tandem solar cells with higher stability; 2) It can realize the preparation of perovskite / perovskite tandem solar cells on all common substrates, with high substrate compatibility; 3) The use of a transparent conductive layer and grid line electrode top design to replace the all-metal capping layer greatly reduces material costs.

[0034] This invention effectively utilizes the advantages of stacked devices to improve the efficiency of perovskite solar cells, while also addressing the stability issues caused by the oxygen sensitivity of lead-tin perovskite. Furthermore, the advanced structure reduces the dependence of perovskite solar cells on flat, transparent, and conductive substrates. Attached Figure Description

[0035] Figure 1 This is a device structure diagram of the "supersubstrate orientation" structure.

[0036] Figure 2 This is a device structure diagram of the perovskite / perovskite tandem solar cell in Embodiment 1 of the present invention.

[0037] Figure 3 This is a scanning electron microscope image of the perovskite / perovskite tandem solar cell in Example 1.

[0038] Figure 4 The current density-voltage curves of the inverted perovskite / perovskite tandem solar cells in the embodiment are shown, with pin structures deposited on glass, PEN, and copper foil, respectively.

[0039] Figure 5 This is a comparison of the air stability of the pin-structured inverted perovskite / perovskite tandem solar cell in Example 1 and the conventional tandem solar cell in Comparative Example 1. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the present invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance of the invention are within the scope of the present invention. Experimental methods and reagents not specifically described in the embodiments are performed according to conventional conditions in the art.

[0041] Example 1

[0042] This embodiment uses glass as a substrate and employs... Figure 2 The inverted perovskite / perovskite tandem solar cell fabricated with the structure shown is prepared using the following specific process:

[0043] 1. A copper thin film of about 20 nm was prepared as the bottom conductive metal film on a cleaned glass substrate by thermal evaporation deposition;

[0044] 2. An ITO layer with a thickness of approximately 10 nm is deposited on the prepared metal thin layer by magnetron sputtering as a non-metallic conductive layer;

[0045] 3. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was used as the hole transport layer, and the annealing temperature was 100℃.

[0046] 4. Deposit narrow-bandgap perovskite FA on the prepared PEDOT:PSS layer. 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3, annealing temperature 100℃, thickness approximately 1100 nm;

[0047] 5. Preparation of a layer of fullerene (C) using thermal evaporation. 60 As an electron transport layer, it is approximately 30 nm thick;

[0048] 6. Using atomic layer deposition on C 60 A SnO2 layer is grown on top as a dense layer, the chamber temperature is 75℃, and the thickness is about 10 nm.

[0049] 7. An ITO thin film with a thickness of 20 nm was obtained by magnetron sputtering at room temperature;

[0050] 8. Prepare a layer of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) of about 20 nm as a hole transport layer;

[0051] 9. Deposit a wide-bandgap perovskite FA layer on the prepared hole transport layer. 0.8 Cs 0.2 Pb(I 0.62 Br 0.38 )3, annealing temperature is 85℃, thickness is approximately 400 nm;

[0052] 10. Preparation of a layer of fullerene (C1) using thermal evaporation. 60 It serves as an electron transport layer, with a thickness of approximately 15 nm;

[0053] 11. An atomic layer deposition layer of SnO2 was grown as a buffer layer with a thickness of approximately 10 nm.

[0054] 12. An indium zinc oxide (IZO) layer with a thickness of approximately 60 nm was grown on the buffer layer by magnetron sputtering as a transparent conductive layer.

[0055] 13. Finally, a 150 nm thick Cu layer was deposited by thermal evaporation as the top gate electrode.

[0056] Example 2

[0057] This embodiment uses PEN as the substrate and employs... Figure 2 The inverted perovskite / perovskite tandem solar cell fabricated with the structure shown is prepared using the following specific process:

[0058] 1. Clean the PEN substrate;

[0059] 2. An ITO non-metallic conductive layer with a thickness of approximately 10 nm was deposited on a PEN substrate by magnetron sputtering;

[0060] 3. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was used as the hole transport layer, and the annealing temperature was 100℃.

[0061] 4. Deposit narrow-bandgap perovskite FA on the prepared PEDOT:PSS layer. 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3, annealing temperature 100℃, thickness approximately 1100 nm;

[0062] 5. Preparation of a layer of fullerene (C) using thermal evaporation. 60 As an electron transport layer, it is approximately 30 nm thick;

[0063] 6. Using atomic layer deposition on C 60 A SnO2 layer is grown on top as a dense layer, the chamber temperature is 75℃, and the thickness is about 10 nm.

[0064] 7. An ITO thin film with a thickness of 20 nm was obtained by magnetron sputtering at room temperature;

[0065] 8. Prepare a layer of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) of about 20 nm as a hole transport layer;

[0066] 9. Deposit a wide-bandgap perovskite FA layer on the prepared hole transport layer. 0.8 Cs 0.2 Pb(I 0.62 Br 0.38 3. Annealing temperature is 85℃, thickness is approximately 400 nm;

[0067] 10. Preparation of a layer of fullerene (C1) using thermal evaporation. 60 It serves as an electron transport layer, with a thickness of approximately 15 nm;

[0068] 11. An atomic layer deposition layer of SnO2 was grown as a buffer layer with a thickness of approximately 10 nm.

[0069] 12. An indium zinc oxide (IZO) layer with a thickness of approximately 60 nm was grown on the buffer layer by magnetron sputtering as a transparent conductive layer.

[0070] 13. Finally, a 150 nm thick Cu layer was deposited by thermal evaporation as the top gate electrode.

[0071] Example 3

[0072] This embodiment directly uses copper foil as a substrate, see reference. Figure 2 The inverted perovskite / perovskite tandem solar cell fabricated with the structure shown is prepared using the following specific process:

[0073] 1. Flatten and properly clean the copper foil;

[0074] 2. A layer of ITO non-metallic conductive layer with a thickness of approximately 10 nm is deposited by magnetron sputtering on the prepared copper foil substrate;

[0075] 3. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was used as the hole transport layer, and the annealing temperature was 100℃;

[0076] 4. Deposit narrow-bandgap perovskite FA on the prepared PEDOT:PSS layer. 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3, annealing temperature 100℃, thickness approximately 1100 nm;

[0077] 5. Preparation of a layer of fullerene (C) using thermal evaporation. 60 As an electron transport layer, it is approximately 30 nm thick;

[0078] 6. Using atomic layer deposition on C 60 A SnO2 layer is grown on top as a dense layer, the chamber temperature is 75℃, and the thickness is about 10 nm.

[0079] 7. An ITO thin film with a thickness of 20 nm was obtained by magnetron sputtering at room temperature;

[0080] 8. Prepare a layer of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) of about 20 nm as a hole transport layer;

[0081] 9. Deposit a wide-bandgap perovskite FA layer on the prepared hole transport layer. 0.8 Cs 0.2 Pb(I0.62 Br 0.38 )3, annealing temperature is 85℃, thickness is approximately 400 nm;

[0082] 10. Preparation of a layer of fullerene (C1) using thermal evaporation. 60 It serves as an electron transport layer, with a thickness of approximately 15 nm;

[0083] 11. An atomic layer deposition layer of SnO2 was grown as a buffer layer with a thickness of approximately 10 nm.

[0084] 12. An indium zinc oxide (IZO) layer with a thickness of approximately 60 nm was grown on the buffer layer by magnetron sputtering as a transparent conductive layer.

[0085] 13. Finally, a 150 nm thick Cu layer was deposited by thermal evaporation as the top gate electrode.

[0086] Comparative Example 1

[0087] This embodiment uses glass as a substrate and employs... Figure 1 The structure shown is used to fabricate a conventional perovskite / perovskite tandem solar cell with super-substrate orientation. The specific fabrication process is as follows:

[0088] 1. Clean the glass / ITO substrate for later use;

[0089] 2. Prepare a layer of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) of about 20 nm as a hole transport layer;

[0090] 3. Deposit a wide-bandgap perovskite FA layer on the prepared hole transport layer. 0.8 Cs 0.2 Pb(I 0.62 Br 0.38 3. Annealing temperature is 100℃, thickness is approximately 400 nm;

[0091] 4. A fullerene (C60) layer with a thickness of approximately 15 nm was prepared by thermal evaporation as an electron transport layer;

[0092] 5. An atomic layer deposition was used to grow a SnO2 layer as a dense layer on C60, with a chamber temperature of 85℃ and a thickness of approximately 10 nm.

[0093] 6. A thin layer of metallic gold with a thickness of 1 nm was deposited on SnO2 using thermal evaporation;

[0094] 7. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was used as the hole transport layer, and the annealing temperature was 100℃;

[0095] 8. Deposit narrow-bandgap perovskite FA on the prepared PEDOT:PSS layer. 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3, annealing temperature 100℃, thickness approximately 1100 nm;

[0096] 9. A fullerene (C60) layer with a thickness of approximately 30 nm was prepared by thermal evaporation as an electron transport layer;

[0097] 10. 150 nm copper was deposited using thermal evaporation as the electrode.

[0098] The SEM cross-sectional image of the tandem solar cell obtained in Example 1 is shown below. Figure 3 As shown, it can be clearly and intuitively seen that the device includes a metal thin film and a non-metallic conductive layer first deposited on the substrate, a thicker narrow-bandgap perovskite layer and a subsequently deposited tunneling composite junction layer, a wide-bandgap layer, and an electrode layer. The thickness of each part is consistent with the above description.

[0099] like Figure 4 As shown, the inverted stacked device using a glass substrate (Example 1) achieved a power conversion efficiency of 24.2%, while the inverted stacked device using a flexible PEN substrate (Example 2) and a flexible copper foil substrate (Example 3) achieved power conversion efficiencies of 23% and 20%, respectively.

[0100] The performance changes of the conventional multilayer device with supersubstrate orientation in Comparative Example 1 and the inverted multilayer device in Example 1 were measured by placing them in dry air. Figure 5 As shown, the performance of conventional stacked devices degrades drastically to 10% of their initial performance within 40 hours, while the performance of inverted stacked devices remains the same as their initial value after 1000 hours.

Claims

1. A perovskite / perovskite tandem solar cell, characterized in that: From the substrate to the light-facing surface, the layers are sequentially: substrate, non-metallic conductive layer, first transport layer, narrow bandgap perovskite layer, second transport layer, tunneling composite junction, third transport layer, wide bandgap perovskite layer, fourth transport layer, buffer layer, and transparent conductive layer. The substrate is a non-conductive substrate, a conductive metal thin film, or a combination of both. The non-conductive substrate is made of glass, polynaphthalene glycol, polyethylene terephthalate, or polyimide; the conductive metal film is made of copper, aluminum, titanium, or gold. The non-metallic conductive layer is made of a conductive material; The non-metallic conductive layer is made of one or more conductive materials selected from indium tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, fluorine-doped tin oxide, indium zinc oxide, indium tungsten oxide, or graphene. The tunneling composite junction consists of a dense layer and a carrier composite layer. The dense layer is directly connected to the second transport layer. The dense layer is made of one or more materials selected from molybdenum oxide, vanadium oxide, 2,9-dimethyl-4,7-biphenyl-1,10-o-phenanthroline, tin oxide, titanium oxide, or tungsten oxide. The carrier composite layer is a metal nanoparticle thin film, a non-dense metal island structure, metal oxide nanoparticles, or a metal oxide thin film. The buffer layer is made of one or more of the following materials: molybdenum oxide, vanadium oxide, 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline, tin oxide, titanium oxide, or tungsten oxide. The dense layer is prepared using an n-type or p-type semiconductor material; The transparent conductive layer is one or more of the following: indium tin oxide film, aluminum-doped zinc oxide film, gallium-doped zinc oxide film, fluorine-doped tin oxide film, indium zinc oxide film, indium tungsten oxide film, silver nanowires, metal layer, or graphene film. There are also metal grid electrodes on the surface of the transparent conductive layer.

2. The perovskite / perovskite tandem solar cell according to claim 1, characterized in that: In the stacked solar cell, the first transport layer is a hole transport layer, the second transport layer is an electron transport layer, the third transport layer is a hole transport layer, and the fourth transport layer is an electron transport layer. Alternatively, the first transport layer can be an electron transport layer, the second transport layer a hole transport layer, the third transport layer an electron transport layer, and the fourth transport layer a hole transport layer.

3. The perovskite / perovskite tandem solar cell according to claim 2, characterized in that: The hole transport layer is made of p-type semiconductor material, and the electron transport layer is made of n-type semiconductor material.

4. The perovskite / perovskite tandem solar cell according to claim 1, characterized in that: The metal grid electrode is made of one or a combination of gold, palladium, silver, titanium, chromium, nickel, aluminum or copper.

5. The method for preparing the perovskite / perovskite tandem solar cell according to any one of claims 1 to 4, characterized in that: Includes the following steps: Step 1, prepare a substrate, wherein the substrate is a non-conductive substrate, a conductive metal thin film, or a combination of both; Step 2: Prepare a non-metallic conductive layer on the surface of the substrate; Step 3: Prepare the first transport layer on the surface of the non-metallic conductive layer; Step 4: Prepare a narrow bandgap perovskite layer on the surface of the first transport layer; Step 5: Prepare a second transport layer on the surface of the narrow bandgap perovskite layer; Step 6: A dense layer is prepared on the surface of the second transport layer, and then a carrier recombination layer is prepared to obtain a tunneling composite junction; Step 7: Prepare a third transport layer on the surface of the tunneling composite junction; Step 8: Prepare a wide-bandgap perovskite layer on the surface of the third transport layer; Step 9: Prepare a fourth transport layer on the surface of the wide-bandgap perovskite layer; Step 10: Prepare a buffer layer on the surface of the fourth transport layer; Step 11: Prepare a transparent conductive layer on the surface of the buffer layer to obtain the stacked solar cell.

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