Foldable perovskite solar cell and preparation method thereof

Abstract

The application relates to a foldable perovskite solar cell and a preparation method thereof, and belongs to the technical field of solar cells. The application discloses a foldable perovskite solar cell, which has a sandwich structure and comprises, from bottom to top, a polymer substrate, a flexible transparent electrode layer, a first transport layer, a perovskite thin film layer, a second transport layer, a metal back electrode layer and a back polymer layer. The foldable perovskite solar cell further comprises a strain-free neutral layer, which is arranged in any one of the flexible transparent electrode layer, the first transport layer, the perovskite thin film layer, the second transport layer and the metal back electrode layer or between any two adjacent layers. The application further discloses a preparation method of the foldable perovskite solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells and relates to a foldable perovskite solar cell and a preparation method thereof. Background Art

[0002] Foldable solar cells—devices that can withstand bending at extreme micrometer-scale curvature radii—possess features such as arbitrary deformation and size reduction, and have potential applications in portable wearables, aerospace, and other fields. Perovskite solar cells, with their high efficiency, low cost, bendability, and roll-to-roll fabrication, are promising candidates for foldable solar cells. The development of foldable perovskite solar cells has garnered widespread attention.

[0003] For perovskite solar cells, since the substrate thickness is several orders of magnitude higher than the thickness of the functional layers (perovskite layer, electrode layer, etc.), there is usually no strain neutral layer (z NA ) position falls in the middle of the substrate ( Figure 1 a) When the device is folded with an extreme micrometer curvature radius, the functional layer is subjected to extreme strain / stress, which can easily deteriorate the performance of brittle materials such as the ITO electrode and perovskite active layer in the battery, leading to battery performance degradation or even failure, posing a challenge to the realization of foldable perovskite solar cells.

[0004] Currently, researchers have used ultra-thin substrates to move the neutral layer to near the substrate surface ( Figure 1 b), thereby reducing the strain / stress on the functional layer of the device during bending, but the neutral layer (z NA ) still falls on the substrate, and the strain-free neutral layer does not play a protective role on the functional layer.

[0005] Zhu Rui et al. from Peking University (Patent No. CN113193125A) proposed using chemical vapor deposition and ion beam polishing to prepare a Parylene film less than 5 μm thick as a substrate. Combined with a metal grid / transparent conductive oxide composite electrode, they achieved a perovskite solar cell with a performance degradation of less than 5% after 300 bends with a curvature radius of less than 1 mm. The research team has also studied the use of a 25 μm ultra-thin substrate, combined with an ultra-thin Ag electrode instead of an ITO electrode, to achieve a perovskite solar cell that can withstand 50 folds (Sol. RRL 2019, 3, 1800317). Yoon et al. used a 7 μm ultra-thin carbon nanotube-based conductive substrate to achieve a perovskite solar cell that can withstand 10,000 folds at a curvature radius of 0.5 mm (Adv. Sci. 2021, 8, 2004092). Lee et al. used a 2.5μm ultra-thin substrate combined with PEDOT:PSS flexible electrodes to achieve 10,000 folding cycles of perovskite solar cells with a curvature radius of 0.5mm (Energy Environ. Sci. 2019, 12, 3182).

[0006] The above reports indicate that combining structural engineering with materials engineering can improve the mechanical properties of perovskite solar cells. However, the device's resistance to bending at submillimeter curvature radii only preliminarily suggests its foldable potential, but remains a long way from achieving folding stability at extreme micrometer curvature radii. Summary of the Invention

[0007] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to propose a foldable perovskite solar cell with a sandwich structure and folding stability under an extreme curvature radius of microns.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] A foldable perovskite solar cell, the foldable perovskite solar cell having a sandwich structure, comprising, from bottom to top, a polymer substrate, a flexible transparent electrode layer, a first transmission layer, a perovskite thin film layer, a second transmission layer, a metal back electrode layer, and a back polymer layer;

[0010] The foldable perovskite solar cell also has a strain-free neutral layer, which is arranged in any one of the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer, or between two adjacent layers.

[0011] In conventional solar cells, the strain-free neutral layer is located in the middle of the substrate ( Figure 1 a) or near ultra-thin substrate surface ( Figure 1 b), the performance of the brittle material deteriorates during folding, resulting in a decrease in battery performance or even failure; and the foldable perovskite solar cell of the present invention can be folded by regulating the position of the strain-free neutral layer to any one of the flexible transparent electrode layer, the first transmission layer, the perovskite film layer, the second transmission layer, and the metal back electrode layer or the interface between two adjacent layers (such as Figure 1 c) When folded at an extreme micron curvature radius, brittle materials (such as perovskite functional layers) can significantly reduce or even be free from strain / stress, thereby having folding stability at an extreme micron curvature radius.

[0012] Preferably, the strain-free neutral layer is located in the perovskite thin film layer.

[0013] Preferably, the strain-free neutral layer is located in the flexible transparent electrode layer.

[0014] Preferably, the strain-free neutral layer is located at the interface between the flexible transparent electrode layer and the first transmission layer.

[0015] Preferably, the strain-free neutral layer is located at the interface between the first transmission layer and the perovskite thin film layer.

[0016] The strain-free neutral layer is a mechanical concept, which means that when a multi-layer film structure solar cell is bent, one side is subjected to compressive stress and the other side is subjected to tensile stress. There must be a surface that is neither subjected to tensile stress nor compressive stress. This surface is called the strain-free neutral layer.

[0017] Preferably, the functional layer is a collection of a flexible transparent electrode layer, a first transmission layer, a perovskite thin film layer, a second transmission layer, and a metal back electrode layer.

[0018] More preferably, the thickness of the functional layer is 200 to 1000 nm.

[0019] More preferably, the thickness ratio of the flexible transparent electrode layer to the metal back electrode layer is 1:(1-3).

[0020] More preferably, the thickness ratio of the back polymer layer to the functional layer is (5-20):1.

[0021] Preferably, the thickness of the polymer substrate is 5 to 50 μm.

[0022] More preferably, the material of the polymer substrate is one or more of PET, PEN, PI, PMDS, and Ecoflex.

[0023] Preferably, the flexible transparent electrode layer is an electrode of a first dielectric layer / ultra-thin metal / second dielectric layer (DMD) composite structure.

[0024] The first dielectric layer (bottom dielectric layer) acts as a seed layer, allowing the ultra-thin metal film to grow continuously; the second dielectric layer (top dielectric layer) acts as an optical dielectric layer, improving the visible light transmittance of the DMD.

[0025] More preferably, the ultra-thin metal is an Ag and / or Cu thin film with a thickness of 4 to 20 nm.

[0026] This thickness ensures high electrical conductivity while having a certain visible light transmittance.

[0027] More preferably, the first dielectric layer and the second dielectric layer are both metal oxides, including ITO, TiO2, ZnO, SnO2, NiO x One or more of the above, each having a thickness of 10 to 60 nm.

[0028] Preferably, in the nip positive structure, the first transport layer and the second transport layer are respectively an electron transport layer and a hole transport layer; wherein the electron transport layer is a thin film such as TiO2, SnO2, CPTA, etc., and the hole transport layer is a Spiro-OMeTAD thin film.

[0029] More preferably, the hole transport layer and the electron transport layer are prepared by a chemical coating method.

[0030] Preferably, in the pin inversion structure, the first transport layer and the second transport layer are respectively a hole transport layer and an electron transport layer; wherein the hole transport layer is NiO x , P3CT, P3HT films, and the electron transport layer is a PCBM / C60 / BCP composite film.

[0031] More preferably, the hole transport layer and the electron transport layer are both made by one or more processes selected from the group consisting of chemical coating, thermal evaporation, and magnetron sputtering.

[0032] Preferably, the perovskite film layer is composed of perovskite and polyurethane additives; the perovskite structural formula is Cs x (FA y MA 1-y ) 1-x Pb(I z Br 1-z )3, 0≤x<1; 0≤y≤1; 0≤z≤1.

[0033] More preferably, the polyurethane is called 2-ethyl-2-(hydroxymethyl)-1,3-propanediol and bis(isocyanatomethyl)benzene, and its chemical formula is (C 10 H8N2O2·C6H 14 O3) x .

[0034] More preferably, the thickness of the perovskite thin film layer is 100 to 600 nm.

[0035] Preferably, the metal back electrode is made of Ag film and / or Au film with a thickness of 50 to 150 nm.

[0036] Preferably, the thickness of the back polymer layer is calculated based on the thickness of the polymer substrate, the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer, the Young's modulus of each layer, and the position of the strain-free neutral layer. The calculation formula is as follows:

[0037]

[0038]

[0039] Among them E i and t i Represent the Young's modulus and thickness of each layer of film, R is the bending radius, z NP is the neutral layer position without any strain, ε is the strain; z NPThe layer where the layer is located can be called the strain-free neutral layer; Figure 2 shown.

[0040] More preferably, the back polymer layer has a thickness of 4 to 48 μm.

[0041] More preferably, the material of the back polymer layer is one or more of PET, PEN, PI, PMDS, and Ecoflex.

[0042] More preferably, the back polymer layer is a two-layer or multi-layer structure, wherein a metal oxide barrier film is deposited on the side close to and / or away from the metal back electrode layer; the barrier film has a thickness of 20 to 100 nm.

[0043] More preferably, the metal oxide is Al2O3 and / or TiO2.

[0044] Preferably, the thickness and material of the barrier film are adjustable, thereby changing the equivalent Young's modulus of the back polymer layer.

[0045] The materials and thicknesses of the polymer substrate, flexible transparent electrode layer, first transmission layer, perovskite thin film layer, second transmission layer, and metal back electrode layer are maintained, and the total thickness and polymer material of the back polymer layer remain unchanged. Only the thickness and / or material of the barrier film are changed, and the position of the strain-free neutral layer is adjustable.

[0046] Preferably, when the polymer substrate and the back polymer layer are made of the same material, the thickness difference between them is 0.1-2 μm; when the polymer substrate and the back polymer layer are made of different materials, the thickness difference between them is 0-20 μm.

[0047] Further preferably, the materials of the polymer substrate and the back polymer layer are the same, the thickness of the back polymer layer and the thickness of the polymer substrate differ by 0.1 to 2 μm, the thickness of the functional layer is 0.2 to 1 μm, and the position of the strain-free neutral layer is any one of the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer, or the interface between two adjacent layers.

[0048] More preferably, the strain-free neutral layer is located in one of the flexible transparent electrode layer, the perovskite film layer, the flexible transparent electrode layer and the first transmission layer, or the first transmission layer and the perovskite film layer.

[0049] The above arrangement reduces or eliminates the forces on the corresponding layers or between layers during the bending process of the solar cell. During the bending process of the solar cell, the corresponding layers or between layers are protected, the degree of loss is reduced, and the life of the corresponding layers or between layers is extended, thereby extending the bending life of the solar cell.

[0050] Further preferably, the materials of the polymer substrate and the back polymer layer are different, the thickness of the back polymer layer differs from the thickness of the polymer substrate by 0 to 20 μm, the thickness of the functional layer is 0.2 to 1 μm, and the position of the strain-free neutral layer is any one of the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer, or the interface between two adjacent layers.

[0051] More preferably, the strain-free neutral layer is located on the flexible transparent electrode layer.

[0052] The above arrangement reduces or eliminates the force on the flexible transparent electrode layer during the bending process of the solar cell, thereby reducing the degree of loss during the bending process of the solar cell, extending the life of the flexible transparent electrode layer, and thus extending the bending life of the solar cell.

[0053] Preferably, the foldable perovskite solar cell structure is a nip positive structure or a pin inverted structure.

[0054] Further preferably, the nip positive structure is an electron transport layer / perovskite film / hole transport layer, wherein the first transport layer is one or more of TiO2, SnO2, and CPTA films, and the second transport layer is a Spiro-OMeTAD film.

[0055] More preferably, the pin inversion structure is a hole transport layer / perovskite film / electron transport layer, wherein the first transport layer is NiO x , P3CT, P3HT films, and the second transmission layer is a PCBM / C60 / BCP composite film.

[0056] The present invention also discloses a method for preparing a foldable perovskite solar cell, the method comprising the following steps:

[0057] S1. Sequentially preparing a flexible transparent electrode layer, a first transmission layer, a perovskite thin film layer, a second transmission layer, and a metal back electrode layer on a pretreated polymer substrate;

[0058] S2, select the position of the strain-free neutral layer;

[0059] S3. Calculate the thickness of the back polymer layer based on the thickness of the polymer substrate, the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer, the Young's modulus of each layer, and the position of the strain-free neutral layer, and then prepare the back polymer layer on the surface of the metal back electrode layer.

[0060] Preferably, the pretreatment process of the polymer substrate comprises washing with deionized water, acetone and isopropyl alcohol in sequence for 10 to 30 minutes.

[0061] Preferably, in step S1, the flexible transparent electrode layer is a composite structure of a first dielectric layer / ultra-thin metal / second dielectric layer; wherein the first dielectric layer and the second dielectric layer are covered by a magnetron sputtering process; and the ultra-thin metal is covered by a magnetron sputtering or thermal evaporation process.

[0062] Preferably, in step S1, the perovskite thin film layer is added to the perovskite precursor solution by a polyurethane additive at a mass percentage concentration of 0.01 to 10 wt%.

[0063] Preferably, in step S1, the metal back electrode layer is an Ag film and / or Au film produced by an evaporation process.

[0064] Preferably, the foldable perovskite solar cell structure is a nip positive structure or a pin inverted structure.

[0065] Further preferably, the first transmission layer in the nip positive structure is one or more of TiO2, SnO2, and CPTA films, and the second transmission layer is a Spiro-OMeTAD film, and the above films are prepared by chemical coating.

[0066] More preferably, the first transmission layer in the pin inversion structure is NiO x , P3CT, P3HT films, and the second transmission layer is a PCBM / C60 / BCP composite film. The above films can be prepared by chemical coating, thermal evaporation, magnetron sputtering and other processes.

[0067] Preferably, in step S3, the back polymer layer is a two-layer or multi-layer structure, and the back polymer layer includes a polymer film and a barrier film; wherein a metal oxide barrier film is deposited on the side close to and / or away from the metal back electrode layer.

[0068] More preferably, the barrier film is deposited by atomic layer deposition and has a thickness of 20 to 100 nm.

[0069] Preferably, in step S3, a vacuum laminating machine is used to prepare a back polymer layer on the surface of the metal back electrode layer through a lamination process at room temperature and a certain pressure.

[0070] It is worth noting that in the present invention, in the sandwich structure, the functional layers including the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer can be regarded as a whole, and the polymer substrate and the back polymer layer are each a layer, sandwiching the functional layer in the middle, which is convenient for understanding and vividly expressing the structural characteristics of the solar cell of the present invention, that is, using the description of the sandwich structure.

[0071] It is worth noting that in the present invention, the strain-free neutral layer is a mechanical concept, which means that when a multi-layer film structure solar cell is bent, one side is subjected to compressive stress and the other side is subjected to tensile stress. There must be a surface that is neither subjected to tensile stress nor compressive stress. This surface is called the strain-free neutral layer.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] 1. The sandwich-structured foldable perovskite solar cell of the present invention achieves a breakthrough by adjusting the position of the strain-free neutral layer from the polymer substrate to the functional layer, which for the first time enables the strain-free neutral layer to protect the solar cell and extend its life. It also achieves a breakthrough by reducing the strain / stress on the functional layer of the solar cell during folding, preventing the functional layer from cracking or performance degradation due to bending, thereby improving the folding performance of the solar cell.

[0074] 2. In the sandwich-structured foldable perovskite solar cell of the present invention, the thickness and / or material of the polymer substrate and the back polymer layer are adjustable, and the position of the strain-free neutral layer is also adjustable in each layer of the solar cell functional layer or at the interface between any two adjacent layers.

[0075] 3. The sandwich-structured foldable perovskite solar cell of the present invention only adjusts the thickness and / or material of the polymer substrate and the back polymer layer. The position of the strain-free neutral layer is controllable in each layer or between layers in the functional layer of the solar cell. The preparation method of the solar cell is simple and the engineering difficulty is low.

[0076] 4. The thickness of the back polymer layer of the present invention is related to the thickness of the functional layers including the flexible transparent electrode layer, the first transmission layer, the perovskite thin film layer, the second transmission layer, and the metal back electrode layer and the position of the strain-free neutral layer. The layers of the present invention are interrelated and work together.

[0077] 5. The present invention uses polyurethane additives to modify the mechanical properties of the perovskite film layer; and uses an ultra-thin metal-based flexible transparent electrode layer to replace the conventional ITO electrode, improving the folding stability of the perovskite solar cell through the strategy of combining structural engineering with material engineering.

[0078] 6. The back polymer layer of the present invention is a two-layer or multi-layer structure, wherein a barrier film is deposited on the side close to and / or away from the metal back electrode layer. The barrier film is a dense film with excellent oxygen and water isolation properties, so that the unencapsulated perovskite solar cell has excellent environmental stability.

[0079] 7. The sandwich structure design of the present invention does not require a limited ultra-thin thickness substrate, which reduces the difficulty of preparing high-quality functional layers thereon, and is beneficial to improving the photoelectric conversion efficiency of folded perovskite solar cells.

[0080] 8. The back polymer layer of the present invention is attached to the back of the battery through a lamination process. The process is simple, the effect is obvious, and it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 The position of the strain-free neutral layer in the existing solar cell and the position of the strain-free neutral layer of the foldable perovskite solar cell prepared in Example 1 of the present invention.

[0082] Figure 2 Schematic diagram of the multilayer structure and the position structure of the strain-free neutral layer in the present invention.

[0083] Figure 3 Schematic diagram of the structure of the foldable perovskite solar cell prepared in Example 1 of the present invention.

[0084] Figure 4 This is a diagram of the photoelectric conversion efficiency of the foldable perovskite solar cell according to Example 1 of the present invention.

[0085] Figure 5 This is a comparison chart of the performance of the foldable perovskite solar cell of Example 1 of the present invention and the perovskite solar cell of Comparative Example 1 without the back polymer layer 7 under 50% humidity.

[0086] Figure 6 This is a comparison chart of the folding performance of the foldable perovskite solar cell of Example 1 of the present invention and the perovskite solar cell of Comparative Example 1 without the back polymer layer 7 at an extreme curvature radius of microns.

[0087] Description of the drawings: 1. Polymer substrate; 2. Flexible transparent electrode layer; 3. First transmission layer; 4. Perovskite thin film layer; 5. Second transmission layer; 6. Metal back electrode layer; 7. Back polymer layer. DETAILED DESCRIPTION

[0088] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0089] Example 1

[0090] The structural diagram of the foldable perovskite solar cell of this embodiment is shown in FIG. Figure 3As shown, from bottom to top, it includes: a polymer substrate 1 is PET, a flexible transparent electrode layer 2 is an ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 is P3CT, a perovskite thin film layer 4 is PVK, and a second transmission layer 5 is PCBM / C60 / BCP. The first transmission layer 3, the perovskite thin film layer 4 and the second transmission layer 5 are combined to form an inverse structure of P3CT / PVK / PCBM / C60 / BCP. The metal back electrode layer 6 is an Ag thin film electrode, and the back polymer layer 7 is a double-layer structure composed of Al2O3 / PET.

[0091] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 7nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal Ag back electrode layer 6 is 120nm; the thickness of the back polymer layer 7 is 6.03μm, the thickness of the Al2O3 dense film is 30nm, and the thickness of the PET back polymer is 6μm.

[0092] The strain-free neutral layer is located on the perovskite thin film layer 4 .

[0093] The perovskite solar cell of this embodiment is prepared by the following method:

[0094] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each. An ITO / ultra-thin Ag / ITO flexible transparent electrode layer 2 was prepared on the PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0095] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0096] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0097] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, and FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0098] After spin coating 40nm PCBM on the perovskite film layer 4, the sample was transferred to the thermal evaporation chamber, and 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0099] In the thermal evaporation chamber, a 120 nm Ag thin film is prepared on the second transmission layer 5 as the metal back electrode layer 6;

[0100] (2) The strain-free neutral layer was selected to be located in the perovskite film layer 4;

[0101] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 6.03 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0102] The back polymer layer 7 is a 30nm Al2O3 film prepared by atomic layer deposition on 6μm PET, which acts as a water and oxygen barrier.

[0103] Use a vacuum laminator to laminate the back polymer layer 7 to the metal back electrode layer 6 using optically transparent adhesive. Lamination is performed at room temperature and maintained at a pressure of 2 kPa for 60 seconds to achieve a tight bond.

[0104] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0105] It is worth noting that, in this embodiment, the 30 nm Al 2 O 3 film has almost no effect on the Young's modulus of the back polymer layer 7 relative to the 6 μm PET film, that is, the Young's modulus of the back polymer layer 7 is the same as that of the 6 μm PET film.

[0106] Figure 4 This is the photoelectric conversion efficiency diagram. The photoelectric conversion efficiency of the prepared foldable perovskite solar cell is 13.03%.

[0107] Figure 5This is a performance diagram for placement under 50% humidity. The foldable perovskite solar cell prepared in this embodiment contains a back polymer layer 7 of a 30nm Al2O3 film. Compared with existing solar cells, it has better stability in a humid environment, such as 50% humidity, and can still maintain 85.10% of the initial stability after 700 hours.

[0108] The structure of the foldable perovskite solar cell of this embodiment fully utilizes the role of the strain-free neutral layer, and adjusts the position of the strain-free neutral layer to the functional layer, which effectively protects the stress of the functional layer when the battery is bent, so that the foldable perovskite solar cell of the present invention has excellent bending resistance. Taking the bending of the extreme curvature radius of microns as an example, Figure 6 It can be seen that the foldable perovskite solar cell of this embodiment can still maintain 23.65% after being folded 200 times, which is far superior to existing solar cells.

[0109] The sandwich-structured solar cell of the present invention achieves a breakthrough by adjusting the position of the strain-free neutral layer from the polymer substrate to the functional layer, which enables the strain-free neutral layer to protect and extend the life of the solar cell for the first time. It also achieves a breakthrough in reducing the strain / stress on the functional layer of the solar cell when folded, so that the functional layer does not crack or suffer performance degradation due to bending, thereby improving the folding performance of the solar cell.

[0110] Example 2

[0111] The structure of the foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET material, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0112] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 7nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal Ag back electrode layer 6 is 120nm; the thickness of the back polymer layer 7 is 6.03μm, the thickness of the Al2O3 dense film is 30nm, and the thickness of the PET back polymer is 6μm.

[0113] The strain-free neutral layer is located in the perovskite film layer 4.

[0114] The perovskite solar cell of this embodiment is prepared by the following method:

[0115] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0116] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0117] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0118] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0119] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO, and 0.2wt% PU was added to the solution. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated on the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated on the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0120] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0121] In the thermal evaporation chamber, a 120 nm Ag film is further prepared on the second transport layer 5 as the metal back electrode layer 6;

[0122] (2) The strain-free neutral layer was selected to be located in the perovskite film layer 4;

[0123] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 6.03 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell.

[0124] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0125] The foldable perovskite solar cell prepared in this embodiment has a photoelectric conversion efficiency of 14.10%. In a humid environment, such as 50% humidity, it can still maintain the initial 89.20% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 30.20% after folding 200 times.

[0126] Example 3

[0127] The structure of the foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET material, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0128] Among them, the thickness of the polymer substrate 1 made of PET is 5μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 20nm, 4nm, and 20nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 5nm, 100nm, 30nm, 10nm, and 5nm respectively; the thickness of the metal back electrode layer 6 made of metal Ag is 50nm; the thickness of the back polymer layer 7 is 4μm, among which the thickness of the Al2O3 dense film is 20nm, and the thickness of the PET back polymer is 3.98μm.

[0129] The strain-free neutral layer is located on the perovskite thin film layer 4 .

[0130] The perovskite solar cell of this embodiment is prepared by the following method:

[0131] (1) A 5 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 10 min each. An ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on the PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 1×10 -4Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 80W; metal Ag was sputtered by direct current with a sputtering power of 30W, to obtain a flexible transparent electrode layer 2 of 20nm ITO / 4nm Ag / 20nm ITO;

[0132] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 5 nm thick. After spin coating, it was annealed at 80°C for 12 min, and then the sample was transferred to a nitrogen glove box. 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0133] A 0.5M solution of PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution of MAI, MABr, MACl, and FAI dissolved in isopropanol was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at low temperature. Then, the mixed organic cation solution was spin-coated onto the film and annealed at 100°C. The resulting perovskite film had a thickness of 100 nm.

[0134] After spin coating 30nm PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 10nm C60 and 5nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0135] In the thermal evaporation chamber, a 50 nm Ag thin film is prepared on the second transmission layer 5 as the metal back electrode layer 6;

[0136] (2) The strain-free neutral layer was selected to be located in the perovskite film layer 4;

[0137] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 4 μm;

[0138] A back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0139] The back polymer layer 7 is a 20nm Al2O3 film prepared by atomic layer deposition on 3.98μm PET. The Al2O3 film acts as a barrier film to isolate water and oxygen.

[0140] Using a vacuum laminator, 20nm Al2O3 / 3.98μm PET was bonded to the metal back electrode layer 6 using optically clear adhesive. During lamination, a pressure of 5kPa was maintained for 30 seconds at room temperature to achieve a tight bond.

[0141] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0142] It is worth noting that, in this embodiment, the 20 nm Al2O3 film has almost no effect on the Young's modulus of the back polymer layer 7 relative to the 3.98 μm PET film, that is, the Young's modulus of the back polymer layer 7 is the Young's modulus of the PET film.

[0143] The foldable perovskite solar cell of this embodiment has a photoelectric conversion efficiency of 8.10% due to the back polymer layer 7; in a humid environment, such as 50% humidity, it can still maintain the initial 80.17% after 700 hours; taking the bending with an extreme curvature radius of microns as an example, it can still maintain 40.01% after folding 200 times.

[0144] Example 4

[0145] The structure of the foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET material, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0146] Among them, the thickness of the polymer substrate 1 made of PET is 50μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 20nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 600nm, 30nm, 30nm, and 5nm respectively; the thickness of the metal back electrode layer 6 made of metal Ag is 150nm; the thickness of the back polymer layer 7 is 48μm, among which the thickness of the Al2O3 dense film is 100nm, and the thickness of the PET back polymer is 47.9μm.

[0147] The strain-free neutral layer is located on the perovskite thin film layer 4 .

[0148] The perovskite solar cell of this embodiment is prepared by the following method:

[0149] (1) A 50 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0150] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 120W; metal Ag was sputtered by direct current with a sputtering power of 60W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 20nm Ag / 30nm ITO;

[0151] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0152] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0153] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, and FAI 0.23M) was prepared in isopropanol. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 5 minutes. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 600nm.

[0154] After spin coating 30nm PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 30nm C60 and 5nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0155] In the thermal evaporation chamber, a 150 nm Ag thin film is prepared on the second transmission layer 5 as the metal back electrode layer 6;

[0156] (2) The strain-free neutral layer was selected to be located in the perovskite film layer 4;

[0157] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 48 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0158] The back polymer layer 7 is a 100nm Al2O3 film prepared by atomic layer deposition on 47.9μm PET. The Al2O3 film acts as a barrier film to isolate water and oxygen.

[0159] Using a vacuum laminator, 100nm Al2O3 / 47.9μm PET was bonded to the metal back electrode layer 6 using optically clear adhesive. During lamination, a pressure of 1kPa was maintained at room temperature for 80s to achieve a tight bond.

[0160] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0161] It is worth noting that, in this embodiment, the 100 nm Al2O3 film has almost no effect on the Young's modulus of the back polymer layer 7 relative to the 47.9 μm PET film, that is, the Young's modulus of the back polymer layer 7 is the Young's modulus of the PET film.

[0162] The foldable perovskite solar cell of this embodiment includes a back polymer layer 7 of an Al2O3 film, and the photoelectric conversion efficiency of the foldable perovskite solar cell obtained is 13.90%. In a humid environment, such as a humidity of 50%, it can still maintain the initial 87.20% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 39.23% after folding 200 times.

[0163] Example 5

[0164] The structural diagram of the foldable perovskite solar cell of this embodiment is shown in FIG. Figure 3 As shown, from bottom to top, it includes: a polymer substrate 1 of PET, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4 and the second transmission layer 5 are combined to form an inverse structure of P3CT / PVK / PCBM / C60 / BCP, the metal back electrode layer 6 is an Ag thin film electrode, and the back polymer layer 7 is a multilayer structure composed of Al2O3 / TiO2 / PET;

[0165] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thicknesses of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 are 30nm, 7nm, and 30nm respectively; the thicknesses of each layer in P3CT / PVK / PCBM / C60 / BCP are 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal Ag back electrode layer 6 is 120nm; the thickness of the Al2O3 dense film in the back polymer layer 7 is 20nm, the thickness of the TiO2 dense film is 10nm, and the thickness of the PET back polymer is 6μm.

[0166] The strain-free neutral layer is located on the perovskite thin film layer 4 .

[0167] The perovskite solar cell of this embodiment is prepared by the following method:

[0168] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each. An ITO / ultra-thin Ag / ITO flexible transparent electrode layer 2 was prepared on the PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0169] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0170] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0171] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, and FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0172] After spin coating 40nm PCBM on the perovskite film layer 4, the sample was transferred to the thermal evaporation chamber, and 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0173] In the thermal evaporation chamber, a 120 nm Ag thin film is prepared on the second transmission layer 5 as the metal back electrode layer 6;

[0174] (2) The strain-free neutral layer was selected to be located in the perovskite film layer 4;

[0175] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 6.03 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0176] The back polymer layer 7 is a 20nm Al2O3 film and a 10nm TiO2 film prepared sequentially on a 6μm PET by atomic layer deposition process, and the film acts as a water and oxygen barrier;

[0177] Use a vacuum laminator to laminate the back polymer layer 7 to the metal back electrode layer 6 using optically transparent adhesive. Lamination is performed at room temperature and maintained at a pressure of 2 kPa for 60 seconds to achieve a tight bond.

[0178] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0179] It is worth noting that in this embodiment, the 20nmAl2O3 film and the 10nmTiO2 film have almost no effect on the Young's modulus of the back polymer layer 7 relative to the 6μm PET film, that is, the Young's modulus of the back polymer layer 7 is the Young's modulus of the 6μm PET film.

[0180] The foldable perovskite solar cell produced in this embodiment achieved a photoelectric conversion efficiency of 13.04%. In a humid environment, such as 50% humidity, it maintained an initial 88.53% after 700 hours. For example, after 200 folds with an extreme micron radius of curvature, it maintained a 23.71% efficiency. This embodiment utilizes a dual barrier film to better protect the entire cell and enhance its performance.

[0181] Example 6

[0182] The structure of the foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET material, a flexible transparent electrode layer 2 of ITO / ultra-thin Cu / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0183] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thickness of ITO / ultra-thin Cu / ITO in the flexible transparent electrode layer 2 is 30nm, 12nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal back electrode layer 6 made of metal Ag is 120nm; the thickness of the back polymer layer 7 is 5.83μm, among which the thickness of the Al2O3 dense film is 30nm, and the thickness of the PET back polymer is 5.8μm.

[0184] The strain-free neutral layer is located on the flexible transparent electrode layer 2 .

[0185] The perovskite solar cell of this embodiment is prepared by the following method:

[0186] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0187] ITO / ultra-thin Cu / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Cu was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 12nm Cu / 30nm ITO;

[0188] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0189] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02)3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0190] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO, and 0.2wt% PU was added to the solution. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated on the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated on the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0191] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0192] In the thermal evaporation chamber, a 120 nm Ag thin film is prepared on the second transmission layer 5 as the metal back electrode layer 6;

[0193] (2) The strain-free neutral layer is selected to be located at the flexible transparent electrode layer 2;

[0194] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 5.83 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0195] The back polymer layer 7 is a 30nm Al2O3 film prepared by atomic layer deposition on 5.8μm PET. The Al2O3 film acts as a barrier film to isolate water and oxygen.

[0196] Using a vacuum laminator, 30nm Al2O3 / 5.8μm PET was bonded to the metal back electrode layer 6 using optically clear adhesive. During lamination, a pressure of 2kPa was maintained at room temperature for 60s to achieve a tight bond.

[0197] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0198] The foldable perovskite solar cell prepared in this embodiment has a photoelectric conversion efficiency of 14.02%. In a humid environment, such as 50% humidity, it can still maintain the initial 89.01% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 22.50% after folding 200 times.

[0199] Example 7

[0200] The structure of the foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET material, a flexible transparent electrode layer 2, the flexible transparent electrode layer 2 is a TiO2 / ultra-thin Ag / TiO2 composite electrode, a first transmission layer 3 of CPTA, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of Spiro-OMeTAD, the first transmission layer 3, the perovskite thin film layer 4 and the second transmission layer 5 together being expressed as a positive structure of CPTA / PVK / Spiro-OMeTAD, a metal back electrode layer 6 of an Au thin film electrode, and a back polymer layer 7 of a double-layer structure composed of Al2O3 / PET;

[0201] Among them, the thickness of the polymer substrate 1 made of PET material is 7μm; in the flexible transparent electrode layer 2, the thicknesses of the TiO2 / ultra-thin Ag / TiO2 electrode layers are 30nm, 12nm, and 30nm respectively; the thicknesses of each layer in CPTA / PVK / Spiro-OMeTAD are 10nm, 500nm, and 40nm respectively; the thickness of the metal back electrode layer 6 made of metal Au material is 100nm; the thickness of the back polymer layer 7 is 5.83μm, among which the thickness of the Al2O3 dense film is 30nm, and the thickness of the PET back polymer is 5.8μm.

[0202] The strain-free neutral layer is located on the flexible transparent electrode layer 2 .

[0203] The perovskite solar cell of this embodiment is prepared by the following method:

[0204] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each. A TiO2 / ultra-thin Cu / TiO2 composite flexible electrode was deposited on the PET substrate by magnetron sputtering. The vacuum degree of the cavity was 8×10 -4 Pa, TiO2 uses a Ti metal target, a DC power supply, and sputtering in a 0.8PaAr / O2 mixed gas; metal Ag uses DC sputtering with a sputtering power of 40W to obtain a flexible transparent electrode layer 2 of 30nmTiO2 / 12nmAg / 30nmTiO2;

[0205] The first transport layer 3 was prepared by spin coating CPTA on the flexible transparent electrode layer 2. The CPTA hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0206] MAPbI3 thin films with 0.2 wt% PU additive were spin-coated on CPTA using a one-step process as follows:

[0207] 1.4MPbI2 and CH3NH3I were dissolved in a DMF / DMSO solution, and 0.2wt% PU was added to the solution. The solution was then spin-coated onto CPTA. A chlorobenzene antisolvent was added dropwise a few seconds after the start of spin coating. After spin coating, the film was annealed at 70°C for 2 minutes. The resulting perovskite film had a thickness of 500nm.

[0208] Spin-coating a Spiro-OMeTAD film on the perovskite film layer 4 to prepare a second transport layer 5;

[0209] The sample was transferred to a thermal evaporation chamber, and a 120 nm Au film was deposited on the second transport layer 5 as the metal back electrode layer 6;

[0210] (2) The strain-free neutral layer is selected to be located at the flexible transparent electrode layer 2;

[0211] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 5.83 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell;

[0212] The back polymer layer 7 is a 30nm Al2O3 film prepared by atomic layer deposition on 5.8μm PET. The Al2O3 film acts as a barrier film to isolate water and oxygen.

[0213] Using a vacuum laminator, 30nm Al2O3 / 5.8μm PET was bonded to the metal back electrode layer 6 using optically clear adhesive. During lamination, a pressure of 2kPa was maintained at room temperature for 60s to achieve a tight bond.

[0214] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0215] The foldable perovskite solar cell prepared in this embodiment has a photoelectric conversion efficiency of 14.91%. In a humid environment, such as 50% humidity, it can still maintain the initial 80.14% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 22.14% after folding 200 times.

[0216] Example 8

[0217] The foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of an Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0218] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 7nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal Ag back electrode layer 6 is 120nm; the thickness of the back polymer layer 7 is 5.98μm, the thickness of the Al2O3 dense film is 80nm, and the thickness of the PET back polymer is 5.9μm.

[0219] The strain-free neutral layer is located at the interface between the first transport layer 3 and the perovskite thin film layer 4 .

[0220] The perovskite solar cell of this embodiment is prepared by the following method:

[0221] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0222] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0223] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0224] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02)3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0225] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, and FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0226] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0227] In the thermal evaporation chamber, a 120 nm Ag film is further prepared on the second transport layer 5 as the metal back electrode layer 6;

[0228] (2) The strain-free neutral layer is located at the interface between the first transport layer 3 and the perovskite film layer 4;

[0229] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 5.98 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell.

[0230] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0231] The photoelectric conversion efficiency of the foldable perovskite solar cell of this embodiment is 13.01%. In a humid environment, such as 50% humidity, it can still maintain the initial 89.54% after 700 hours. Taking the bending with an extreme curvature radius of microns as an example, it can still maintain 22.85% after folding 200 times.

[0232] Example 9

[0233] The foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of an Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0234] Among them, the thickness of the polymer substrate 1 made of PET is 7μm; the thicknesses of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 are 30nm, 7nm, and 30nm respectively; the thicknesses of each layer in P3CT / PVK / PCBM / C60 / BCP are 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal Ag back electrode layer 6 is 120nm; the thickness of the back polymer layer 7 is 5.9μm, the thickness of the Al2O3 dense film is 100nm, and the thickness of the PET back polymer is 5.8μm.

[0235] The strain-free neutral layer is located at the interface between the flexible transparent electrode layer 2 and the first transmission layer 3 .

[0236] The perovskite solar cell of this embodiment is prepared by the following method:

[0237] (1) A 7 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0238] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0239] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0240] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02)3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0241] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0242] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0243] In the thermal evaporation chamber, a 120 nm Ag film is further prepared on the second transport layer 5 as the metal back electrode layer 6;

[0244] (2) The strain-free neutral layer is located at the interface between the flexible transparent electrode layer 2 and the first transmission layer 3;

[0245] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 5.9 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell.

[0246] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0247] The photoelectric conversion efficiency of the foldable perovskite solar cell of this embodiment is 13.05%. In a humid environment, such as 50% humidity, it can still maintain the initial 89.15% after 700 hours. Taking the bending with an extreme curvature radius of microns as an example, it can still maintain 22.33% after folding 200 times.

[0248] Example 10

[0249] The foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PET, a flexible transparent electrode layer 2 of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PEN;

[0250] Among them, the thickness of the polymer substrate 1 made of PET is 30μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 7nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal back electrode layer 6 made of metal Ag is 120nm; the thickness of the back polymer layer 7 is 27.03μm, among which the thickness of the Al2O3 dense film is 30nm, and the thickness of the PEN back polymer is 27μm.

[0251] The strain-free neutral layer is located in the perovskite film layer 4.

[0252] The perovskite solar cell of this embodiment is prepared by the following method:

[0253] (1) A 30 μm thick PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0254] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0255] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0256] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 )3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0257] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0258] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0259] In the thermal evaporation chamber, a 120 nm Ag film is further prepared on the second transport layer 5 as the metal back electrode layer 6;

[0260] (2) The strain-free neutral layer position was selected as the perovskite film layer 4;

[0261] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 27.03 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell.

[0262] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0263] The photoelectric conversion efficiency of the foldable perovskite solar cell of this embodiment is 13.90%. In a humid environment, such as 50% humidity, it can still maintain the initial 87.10% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 35.10% after folding 200 times.

[0264] Example 11

[0265] The foldable perovskite solar cell of this embodiment includes, from bottom to top: a polymer substrate 1 of PDMS, a flexible transparent electrode layer 2 of an ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 of P3CT, a perovskite thin film layer 4 of PVK, a second transmission layer 5 of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4, and the second transmission layer 5 together forming an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 of an Ag thin film electrode, and a back polymer layer 7 of a double-layer structure of Al2O3 / PET;

[0266] Among them, the thickness of the polymer substrate 1 made of PDMS is 50μm; the thickness of ITO / ultra-thin Ag / ITO in the flexible transparent electrode layer 2 is 30nm, 7nm, and 30nm respectively; the thickness of each layer in P3CT / PVK / PCBM / C60 / BCP is 10nm, 500nm, 40nm, 20nm, and 8nm respectively; the thickness of the metal back electrode layer 6 made of metal Ag is 120nm; the thickness of the back polymer layer 7 is 45.03μm, among which the thickness of the Al2O3 dense film is 30nm and the thickness of the PEN back polymer is 45μm.

[0267] The strain-free neutral layer is located on the flexible transparent electrode layer 2 .

[0268] The perovskite solar cell of this embodiment is prepared by the following method:

[0269] (1) A 50 μm thick PDMS substrate was first cleaned with deionized water, acetone, and isopropanol for 20 min each;

[0270] ITO / ultra-thin Ag / ITO composite flexible transparent electrode layer 2 was prepared on PET substrate by magnetron sputtering. The vacuum degree of the sputtering cavity was 8×10 -4 Pa, room temperature, pure argon atmosphere. Among them, ITO was sputtered by radio frequency with a sputtering power of 100W; metal Ag was sputtered by direct current with a sputtering power of 40W, to obtain a flexible transparent electrode layer 2 of 30nm ITO / 7nm Ag / 30nm ITO;

[0271] The first transport layer 3 was prepared by spin coating P3CT on the flexible transparent electrode layer 2. The P3CT hole transport layer was 10 nm thick. After spin coating, the sample was annealed at 100°C for 8 min and then transferred to a nitrogen glove box.

[0272] Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02)3 thin film preparation of perovskite thin film layer 4, the process of preparing perovskite thin film layer 4 can be as follows:

[0273] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0274] After spin coating PCBM on the perovskite film layer 4, the sample was transferred to a thermal evaporation chamber, and then 20nm C60 and 8nm BCP were evaporated in sequence to complete the preparation of the second transmission layer 5;

[0275] In the thermal evaporation chamber, a 120 nm Ag film is further prepared on the second transport layer 5 as the metal back electrode layer 6;

[0276] (2) The flexible transparent electrode layer 2 at the position of the strain-free neutral layer was selected;

[0277] (3) Based on the thickness of the polymer substrate 1, the flexible transparent electrode layer 2, the first transmission layer 3, the perovskite thin film layer 4, the second transmission layer 5, and the metal back electrode layer 6 and the position of the strain-free neutral layer, the thickness of the back polymer layer 7 is calculated to be 45.03 μm; a back polymer layer 7 of matching thickness is prepared on the metal back electrode layer 6, thereby obtaining a foldable perovskite solar cell.

[0278] Finally, a foldable perovskite solar cell with a sandwich structure was prepared.

[0279] The foldable perovskite solar cell prepared in this embodiment has a photoelectric conversion efficiency of 13.92%. In a humid environment, such as 50% humidity, it can still maintain the initial 87.50% after 700 hours. Taking the bend with an extreme curvature radius of microns as an example, it can still maintain 39.10% after folding 200 times.

[0280] Comparative Example 1

[0281] The structure of the perovskite solar cell in this comparative example includes, from bottom to top, a polymer substrate 1 made of PET material, a flexible transparent electrode layer 2 made of ITO / ultra-thin Ag / ITO composite electrode, a first transmission layer 3 made of P3CT, a perovskite thin film layer 4 made of PVK, a second transmission layer 5 made of PCBM / C60 / BCP, the first transmission layer 3, the perovskite thin film layer 4 and the second transmission layer 5 being combined to form an inverse structure of P3CT / PVK / PCBM / C60 / BCP, a metal back electrode layer 6 made of an Ag thin film electrode,

[0282] The thickness of the PET substrate is 7μm; the thicknesses of the ITO / ultra-thin Ag / ITO electrode layers are 30nm, 7nm, and 30nm respectively; the thicknesses of the P3CT / PVK / PCBM / C60 / BCP layers are 10nm, 500nm, 40nm, 20nm, and 8nm respectively; and the thickness of the metal Ag back electrode is 120nm.

[0283] The perovskite solar cell of this comparative example was prepared by the following method:

[0284] (1) The PET substrate was first cleaned with deionized water, acetone, and isopropyl alcohol for 20 min each;

[0285] (2) Magnetron sputtering of ITO / ultra-thin Ag / ITO composite flexible electrodes on PET substrates was used. The vacuum degree of the cavity during the sputtering process was 8×10 -4 Pa, room temperature, pure argon atmosphere. ITO was deposited using RF sputtering at a power of 100W, while Ag was deposited using DC sputtering at a power of 40W, resulting in a 30nm ITO / 7nm Ag / 30nm ITO flexible transparent electrode.

[0286] (3) A P3CT hole transport layer was spin-coated on the flexible electrode and annealed at 100°C for 8 min. The sample was then transferred to a nitrogen glove box.

[0287] (4) Spin coating (Cs 0.05 FA 0.54 MA 0.41 )Pb(I 0.98 Br 0.02 ) 3 films, specifically as follows:

[0288] 1.3M PbI2 mixed with 5% CsI was dissolved in DMF / DMSO. Separately, a mixed organic cation solution (MAI 0.12M, MABr 0.05M, MACl 0.07M, and FAI 0.23M dissolved in isopropanol) was prepared. The perovskite film was prepared using a two-step process. First, the PbI2 solution was spin-coated onto the sample and annealed at 70°C for 1 minute. The mixed organic cation solution was then spin-coated onto the film and annealed at 100°C for 30 minutes. The resulting perovskite film had a thickness of 500nm.

[0289] (5) Spin-coat a 40 nm PCBM electron transport layer on the perovskite film;

[0290] (6) The sample was transferred to a thermal evaporation chamber and sequentially deposited with 20 nm C60, 8 nm BCP, and 120 nm Ag electrodes.

[0291] The solar cell of this comparative example has no back polymer layer, and the photoelectric conversion efficiency of the solar cell obtained is 13.03%. Figure 5 As shown in the figure, in a humid environment, such as 50% humidity, it can only maintain 50.27% of the initial humidity after 200 hours; Figure 6 As shown, taking the bending with an extreme curvature radius of microns as an example, the performance drops to 14.85% after folding 50 times. If it continues to fold 100 times, the photoelectric conversion efficiency drops to 0 and the functional layer structure is completely destroyed.

[0292] In summary, the sandwich-structured foldable perovskite solar cell prepared by the present invention has made a breakthrough in regulating the position of the strain-free neutral layer from the polymer substrate 1 to the functional layer, and for the first time brought into play the role of the strain-free neutral layer in protecting and extending the life of the solar cell, and has made a breakthrough in reducing the strain / stress on the functional layer of the solar cell during folding, so that the functional layer does not form cracks or performance degradation due to bending, thereby improving the folding performance of the solar cell; and the back polymer layer 7 is a two-layer or multi-layer structure, in which a barrier film is deposited on the side close to and / or away from the metal back electrode layer 6, and the barrier film is a dense thin film with excellent oxygen and water isolation properties, so that the unpackaged perovskite solar cell has excellent environmental stability.

[0293] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A foldable perovskite solar cell, characterized in that: The foldable perovskite solar cell has a sandwich structure, which includes, from bottom to top, a polymer substrate, a flexible transparent electrode layer, a first transmission layer, a perovskite film layer, a second transmission layer, a metal back electrode layer, and a back polymer layer; The foldable perovskite solar cell further has a strain-free neutral layer, which is arranged in any one of the flexible transparent electrode layer, the first transmission layer, the perovskite film layer, the second transmission layer, and the metal back electrode layer, or between two adjacent layers; The thickness of the back polymer layer is calculated based on the thickness of the polymer substrate, the flexible transparent electrode layer, the first transmission layer, the perovskite film layer, the second transmission layer, and the metal back electrode layer, the Young's modulus of each layer, and the position of the strain-free neutral layer. The calculation formula is as follows: ① ② in E i and t i represent the Young's modulus and thickness of each film layer, R is the bending radius, z NP It is the neutral layer position that is not subject to any strain. ε is the strain; z NP The location of the layer can be called the strain-free neutral layer; The functional layer is a combination of a flexible transparent electrode layer, a first transmission layer, a perovskite thin film layer, a second transmission layer, and a metal back electrode layer; the thickness of the functional layer is 200-1000 nm; The back polymer layer has a thickness of 4 to 48 μm; the back polymer layer has a two-layer or multi-layer structure, wherein a metal oxide barrier film is deposited on one side close to and / or away from the metal back electrode layer; the barrier film has a thickness of 20 to 100 nm; The foldable perovskite solar cell has folding stability at an extreme curvature radius of microns.

2. The foldable perovskite solar cell according to claim 1, characterized in that The thickness of the polymer substrate is 5-50 μm.

3. The foldable perovskite solar cell according to claim 1, characterized in that When the polymer substrate and the back polymer layer are made of the same material, the thickness difference between them is 0.1-2 μm; when the polymer substrate and the back polymer layer are made of different materials, the thickness difference between them is 0-20 μm.

4. The foldable perovskite solar cell according to claim 1, characterized in that The perovskite film layer is composed of perovskite and polyurethane additives; the perovskite structural formula is Cs x (FA y MA 1-y ) 1-x Pb(I z Br 1-z )3; the polyurethane additive in the perovskite thin film layer is added to the perovskite precursor solution at a mass percentage concentration of 0.01~10 wt%; the thickness of the perovskite thin film layer is 100~600nm.

5. The foldable perovskite solar cell according to claim 1, characterized in that The flexible transparent electrode layer is an electrode of a composite structure of a first dielectric layer / ultra-thin metal / second dielectric layer; The ultra-thin metal is an Ag and / or Cu thin film with a thickness of 4 to 20 nm; The first dielectric layer and the second dielectric layer are both metal oxides, including ITO, TiO2, ZnO, SnO2, NiO x One or more of the above, each with a thickness of 10~60nm.

6. A method for preparing a foldable perovskite solar cell according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1. Sequentially preparing a flexible transparent electrode layer, a first transmission layer, a perovskite thin film layer, a second transmission layer, and a metal back electrode layer on a pretreated polymer substrate; S2, select the position of the strain-free neutral layer; S3. Calculate the thickness of the back polymer layer based on the thickness of the polymer substrate, flexible transparent electrode layer, first transmission layer, perovskite thin film layer, second transmission layer, and metal back electrode layer, the Young's modulus of each layer, and the position of the strain-free neutral layer, and prepare the back polymer layer on the surface of the metal back electrode layer using a lamination process.

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