Method for improving flexibility and mechanical properties of flexible perovskite solar cells

Abstract

Method for improving flexibility and mechanical properties of flexible perovskite solar cells. When a conductive substrate is defined as the bottom layer, the solar cell includes, from bottom to top in sequence: a conductive substrate layer; an electron transport layer; a perovskite light-absorbing layer modified with polymers and inorganic metal oxide nanoparticles; a hole transport layer; a counter electrode; the polymer is one or more of chitosan, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and poly(vinylidene fluoride-co-hexafluoropropylene); the inorganic metal nano-oxide is one or more of TiO2, ZnO, Al2O3, SiO2, and ZrO2. The present invention improves the flexibility and environmental stability of the device, inhibits ion migration in the perovskite film, stabilizes the perovskite crystal, and simultaneously plays a role in releasing stress by performing bulk doping of appropriate polymers and inorganic metal nano-oxide nanoparticles on the perovskite layer.

Description

Technical Field

[0001] The present invention relates to a method for improving the performance of flexible perovskite solar cells, and particularly to a method for improving the flexibility and mechanical properties of flexible perovskite solar cells. Background Art

[0002] Due to its unique optical and physical properties, low cost, and the ability to be prepared by low-temperature solution processes, metal perovskite has become an ideal material for constructing flexible solar cells. With the support of technologies such as composite engineering, surface passivation, interface modification, and optimization of manufacturing processes, combined with the research and development of low-temperature charge transport layers, perovskite light-absorbing layers, and flexible conductive substrates, the power conversion efficiency of flexible perovskite solar cells (F-PSCs) has exceeded 21%. These excellent results demonstrate the great potential of F-PSCs in wearable and portable electronic devices, curved electronic displays, etc. However, problems such as the efficiency, stability, and film quality under large-area printing of F-PSCs are still bottlenecks restricting their commercial applications.

[0003] The research in the field of F-PSCs has developed rapidly since its first appearance, and many developments in rigid PSCs have been replicated in F-PSCs. However, there are still many important factors restricting the further improvement of the efficiency of F-PSCs. For example, it is difficult to prepare high-quality low-temperature electron transport layers. The plastic substrate undergoes thermal deformation during annealing, resulting in an increase in resistance and charge carrier loss at the interface between the electrode and the charge transport layer. The surface roughness of the plastic substrate is poor, leading to poor morphology of the top layer including the electron transport layer and the perovskite layer. The transmittance of the plastic substrate in the ultraviolet and visible light ranges is low, etc. These problems essentially make the efficiency of flexible devices still lag behind that of rigid devices.

[0004] With the continuous improvement of the efficiency of F-PSCs, the environmental stability, flexibility, and stretchability of the devices have become more prominent aspects of concern. Therefore, how to improve the stability of F-PSCs to meet various wearable and portable electronic devices has become a major challenge in today's society. Currently, researchers are constantly shifting their focus towards stability. It has been found that in the presence of air, moisture, and heating cycles, the perovskite layer, organic electron transport layer, and hole transport layer will accelerate degradation. The degradation and phase transformation of perovskite crystals are mainly attributed to their ionic nature, and oxygen, moisture, ultraviolet radiation, and heat are the main factors for the degradation of perovskite crystals. However, the degradation mechanism of the perovskite layer has not been fully understood. In addition, the polymer substrate has a weak barrier against the intrusion of moisture and oxygen, and the water and oxygen permeating through the flexible substrate will cause further degradation of the perovskite layer and other component layers. Therefore, F-PSCs have serious long-term environmental stability problems. Improving the stability of F-PSCs requires considering many factors, such as the composition of perovskite, the uniformity and crystallinity of the perovskite thin film, interface engineering, the selection of charge transport materials and electrodes, and encapsulation technology. In addition, bending stability is one of the important factors that need to be solved for the commercial application of F-PSCs. Bending stability is mainly limited by the mechanical strength of the transparent electrode and the adhesion performance between the charge transport layer and the perovskite thin film. Traditional high-efficiency flexible perovskite devices are fabricated on ITO / PET or PEN substrates. After repeated bending, the rigid characteristics of ITO will cause cracks in the thin film, resulting in carrier leakage and an increase in series resistance, thus causing the device to fail.

[0005] CN 107104189 A discloses a perovskite thin film solar cell, which includes a cathode, a perovskite light-absorbing layer, and an anode. An electrode interface modification layer is further provided between the anode and the perovskite light-absorbing layer. The electrode interface modification layer contains atoms and / or ions that can react with the perovskite light-absorbing layer to promote the crystallinity of perovskite crystals, and the electrode interface modification layer is also used to improve the surface roughness and morphology of the anode. This battery uses oxide particles and polymers on the perovskite upper interface as the interface modification layer to improve the humidity stability of the device, does not mention how to improve the stability of the perovskite light-absorbing layer, lacks research on the bending stability of flexible devices, and the obtained device has a low photoelectric conversion efficiency. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for improving the flexibility and mechanical properties of flexible perovskite solar cells.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows: a method for improving the flexibility and mechanical properties of a flexible perovskite solar cell. When a conductive substrate is defined as the bottom layer, the solar cell sequentially includes from bottom to top: a conductive substrate layer; an electron transport layer; a perovskite light-absorbing layer modified with a polymer and inorganic metal oxide nanoparticles; a hole transport layer; and a counter electrode.

[0008] Preferably, the conductive substrate layer is a transparent polyethylene terephthalate flexible substrate (ITO-PEN).

[0009] Preferably, the electron transport layer is an SnO2, TiO2, ZnO or PCBM electron transport layer.

[0010] Preferably, the polymer is one or more of chitosan, polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF-HFP); the inorganic metal nano-oxide is one or more of TiO2, ZnO, Al2O3, SiO2 and ZrO2.

[0011] Preferably, the perovskite light-absorbing layer is an ABX3 perovskite light-absorbing layer, where A is CH3NH3 or Cs, B is Pb, Sn, In or Ge, and X is one or more of I, Br or Cl.

[0012] Preferably, the hole transport material is a small molecule polymer, more preferably one or more of Spiro-OMeTAD, PSS, P3HT, PEDOT and NiO, and further preferably Spiro-OMeTAD and / or P3HT.

[0013] Preferably, the method for improving the flexibility and mechanical properties of the flexible perovskite solar cell specifically includes the following steps:

[0014] (1) Clean the transparent ITO-PEN to obtain a transparent conductive substrate;

[0015] (2) Prepare an electron transport layer on the surface of the obtained conductive substrate;

[0016] (3) Prepare a perovskite ABX3 light-absorbing layer modified with a polymer and inorganic metal oxide nanoparticles on the surface of the obtained electron transport layer;

[0017] (4) Prepare a hole transport layer on the surface of the obtained perovskite ABX3 light-absorbing layer modified with a polymer and inorganic metal oxide nanoparticles;

[0018] (5) Evaporate a thin metal counter electrode on the surface of the obtained hole transport layer to complete.

[0019] More preferably, in step (1), the cleaning method is as follows: place the transparent ITO-PEN conductive glass in deionized water, anhydrous ethanol, and isopropyl alcohol respectively, and ultrasonically vibrate for 10-20 min, bake at 80-120 °C for 10-25 min (to remove visible impurities on the surface), and perform ultraviolet ozone treatment for 20-30 min (to remove surface organic groups to reduce the water contact angle).

[0020] More preferably, in step (2), the preparation method of the electron transport layer is as follows: drop the electron transport material dispersion liquid on the surface of the conductive substrate, and spin-coat at 4000-6000 rpm for 20-40 s (to form a uniform film), and heat at 150-200 °C for 30-40 min to obtain the electron transport layer.

[0021] Further preferably, in step (2), the electron transport material dispersion liquid is prepared by mixing an electron transport material (SnO2, TiO2, ZnO, or PCBM) with a solvent (deionized water, isopropyl alcohol, or chlorobenzene) in a volume ratio of 1:1-8 and ultrasonically dispersing them.

[0022] More preferably, in step (3), the filtered perovskite precursor solution is dropped on the surface of the electron transport layer, spin-coated, heat-treated, and annealed to obtain a perovskite ABX3 light-absorbing layer modified with polymers and inorganic metal oxide nanoparticles.

[0023] More preferably, in step (3), the preparation method of the perovskite precursor solution modified with polymers and inorganic metal oxide nanoparticles is as follows: dissolve polymers, inorganic oxide nanoparticles, AX, and BX2 in a solution of dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF), and heat and stir at 65-75 °C for 4-12 h.

[0024] Further preferably, in step (3), in the perovskite precursor solution, the addition amount of the polymer is 0-10% of the total mass of the precursor solution, the addition amount of the inorganic metal oxide nanoparticles is 0-10% of the total mass of the precursor solution, the addition amount of AX is 10-20% of the total mass of the precursor solution, the addition amount of BX2 is 20-30% of the total mass of the precursor solution, the addition amount of dimethyl sulfoxide is 20%-60% of the total mass of the precursor solution, and the addition amount of N,N-dimethylformamide is 0%-50% of the total mass of the precursor solution.

[0025] Further preferably, in step (3), the diameter of the filter head used for filtration is 0.22-0.45 .

[0026] Further preferably, in step (3), the rotation speed of spin coating is 3500-7500 rpm, and the time is 20-40 s.

[0027] More preferably, in step (3), when the spin coating countdown reaches 10 - 24 s, 200 - 300 ethyl acetate or chlorobenzene solution is added (to assist the rapid crystallization of perovskite).

[0028] More preferably, in step (3), the temperature of the heat treatment is 70 - 110 °C, and the time is 10 - 20 min; through the heat treatment in this way, a smooth perovskite thin film is obtained by annealing.

[0029] Even more preferably, in step (4), the hole - transporting solution is dropped onto the surface of the perovskite light - absorbing layer modified by polymer and inorganic metal oxide nanoparticles, and then spin - coated to obtain the hole - transporting layer.

[0030] More preferably, in step (4), in the hole - transporting solution, the mass of lithium bis(trifluoromethanesulfonyl)imide is 0.2 - 2% of the total mass of the solution, the mass of 4 - tert - butylpyridine is 0.8 - 3% of the total mass of the solution, the mass of chlorobenzene is 60 - 80% of the total mass of the solution, and the mass of the hole - transporting material is 10% - 30% of the total mass of the solution.

[0031] More preferably, in step (4), the rotation speed of the spin coating is 2000 - 3500 rpm, and the time is 30 - 40 s.

[0032] Even more preferably, in step (5), a thin metal counter electrode is deposited by vacuum evaporation.

[0033] Even more preferably, in step (5), the rate of the vacuum evaporation is 0.1 - 0.6 nm / s, and the thickness of the thin metal counter electrode is 10 - 60 nm.

[0034] More preferably, the metal to be plated is gold or silver.

[0035] The present invention provides a method for improving the flexibility and mechanical properties of flexible perovskite solar cells. By doping the perovskite layer with appropriate amounts of polymers and inorganic metal oxide nanoparticles in the bulk phase, the crystallization process of the polymers will fill the voids in the perovskite film, making the perovskite grains more compact and reducing the generation of defects and traps. When the flexible device is bent, the perovskite film will be damaged, causing deformation of the crystal structure. However, polymers with good flexibility can act as plasticizers for the perovskite film, forming a cross-linked network structure around the perovskite grains, which can reduce the ability of the perovskite film to crack internally and enhance the hydrophobicity of the perovskite film, thereby improving the flexibility and environmental stability of the flexible device. In addition, on the basis of polymer doping, inorganic metal oxide nanoparticles are added to dope the perovskite light-absorbing layer. The surface activity of the inorganic metal oxide nanoparticles is very high, and their surface contains abundant hydroxyl groups, which can form hydrogen bond connections with various components in the polymer matrix as a rigid skeleton, jointly further improving the mechanical properties and bending stability of the flexible device. Generally speaking, the present invention will provide a theoretical and technical basis for improving the flexibility and mechanical properties of flexible perovskite solar cells.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) In the present invention, by doping the perovskite layer with appropriate amounts of polymers and inorganic metal oxide nanoparticles in the bulk phase, the defects of the perovskite grains are filled by the crystallization of the polymers, and a cross-linked network structure is formed between the polymers and the perovskite by using the toughness of the polymers, so as to enhance the flexibility and environmental stability of the device; the surface of the inorganic oxide nanoparticles has hydroxyl groups, which can form complexes with polymer molecules, prevent the perovskite from being eroded by water and oxygen, further inhibit the ion migration in the perovskite film. In addition, the inorganic oxide nanoparticles can also reduce the crystallinity of the polymer molecules, so as to stabilize the perovskite crystal and release stress at the same time;

[0038] (2) In the present invention, the perovskite light-absorbing layer is modified by co-doping of polymers and inorganic oxide nanoparticles, which improves the quality of the perovskite film, improves the contact of each functional layer, reduces the charge recombination rate, and enhances the charge transport ability;

[0039] (3) The present invention can evaporate an ultrathin metal counter electrode, reduce the device cost, and construct a flexible perovskite solar cell to achieve the effect of double-sided light response. Detailed implementation manners

[0040] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0041] Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present invention.

[0042] Unless otherwise specified, various reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0043] Example 1

[0044] In this example, a polymer (chitosan) and an inorganic nano-oxide nanoparticle (TiO2) are used to modify the perovskite layer. This example is based on a method for improving the flexibility and mechanical properties of flexible perovskite solar cells. When the conductive substrate is defined as the bottom layer, from bottom to top, it includes: a transparent ITO-PEN conductive substrate; a tin dioxide electron transport layer; an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer modified with chitosan (polymer) and TiO2 (inorganic oxide nanoparticle); a hole transport layer; and a gold counter electrode.

[0045] This example is based on a method for improving the flexibility and mechanical properties of flexible perovskite solar cells, and its preparation method includes the following steps:

[0046] (1) Cleaning the transparent ITO-PEN to obtain a transparent conductive substrate: The ITO-PEN conductive substrate is ultrasonically oscillated for 10 min respectively with deionized water, absolute ethanol, and isopropanol. After ultrasonic treatment, it is placed in an oven and baked at 100 °C for 15 min to remove visible impurities on the surface. Subsequently, it is treated on an ultraviolet ozone treatment machine for 25 min to remove surface organic groups and reduce the water contact angle.

[0047] (2) Preparing a tin dioxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): A tin dioxide colloid dispersion liquid is dropped on the transparent conductive substrate after ozone treatment, and spin-coated at 5000 rpm for 20 s to form a uniform film, and then heated on a heating table at 160 °C for 35 min to obtain a tin dioxide electron transport layer. The tin dioxide colloid dispersion liquid is prepared by mixing tin dioxide colloid and deionized water in a volume ratio of 1:4 and ultrasonically dispersing them.

[0048] (3) Preparing a chitosan and TiO2 modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer on the surface of the tin dioxide electron transport layer obtained in step (2);

[0049] (3-I) Dissolve chitosan, TiO2, CH3NH3I and PbI2 with a molar ratio of 1:1 in a mixed solution of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) with a volume ratio of 1:4, heat and stir at 60 °C for 12 h to obtain a chitosan and TiO2 modified organic-inorganic hybrid perovskite precursor solution. The addition amount of chitosan is equivalent to 1% of the total mass, the addition amount of TiO2 is equivalent to 2% of the total mass, the addition amount of CH3NH3I is equivalent to 15% of the total mass, the addition amount of PbI2 is equivalent to 22% of the total mass, the addition amount of DMSO solvent is equivalent to 13% of the total mass, and the addition amount of DMF solvent is equivalent to 50% of the total mass;

[0050] (3-II) Filter the chitosan and TiO2 modified organic-inorganic hybrid perovskite precursor solution obtained in step (3-I) through a filter head with a diameter of 0.22 μm, and then drop it on the tin dioxide electron transport layer obtained in step (2). A chitosan and TiO2 modified organic-inorganic hybrid perovskite CH3NH3PbI3 light absorption layer is obtained by spin coating. Set the spin coating process to 5000 rpm for 30 s; when the spin coating countdown reaches 23 s, add 250 μL of ethyl acetate solution and heat-treat at 100 °C for 10 min, and anneal to obtain a smooth perovskite film;

[0051] (4) Prepare a hole transport layer on the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light absorption layer obtained in step (3): The addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1.5% of the total solution mass, 4-tert-butylpyridine accounts for 2.5% of the total solution mass, the addition amount of chlorobenzene accounts for 66% of the total solution mass, and the addition amount of P3HT (hole transport material) accounts for 30% of the total solution mass. Drop the P3HT solution onto the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light absorption layer, and obtain a hole transport layer by spin coating. Set the spin coating process to 3000 rpm for 30 s;

[0052] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: Using the vacuum evaporation method, vacuum evaporate a 40 nm gold counter electrode at a rate of 0.4 nm / s, and it is done.

[0053] Test the performance of the semi-transparent flexible organic-inorganic hybrid perovskite solar cell based on polymers and inorganic oxide nanoparticles obtained in this example: In a room temperature environment with a humidity greater than 50%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective light illumination area is 0.25 cm 2The photoelectric conversion efficiency is 22%. After being placed for 290 days without encapsulation, the photoelectric efficiency drops to 97% of the initial value. After 3000 cycles of bending (with a bending radius of 3 mm), it can still maintain 95% of the initial efficiency.

[0054] Example 2

[0055] In this example, a polymer (PEO) and inorganic nano-oxide nanoparticles (ZnO) are used to modify the perovskite layer. Based on the method of improving the flexibility and mechanical properties of flexible perovskite solar cells, when the conductive substrate is defined as the bottom layer, from bottom to top, it includes: a transparent ITO-PEN conductive substrate; a tin dioxide electron transport layer; an organic-inorganic hybrid perovskite CH3NH3SnClI2 light-absorbing layer modified with PEO (polymer) and ZnO (inorganic oxide nanoparticles); a hole transport layer; and a gold counter electrode.

[0056] This example is a semi-transparent flexible organic-inorganic hybrid perovskite solar cell based on a polymer and inorganic oxide nanoparticles, and its preparation method includes the following steps:

[0057] (1) Clean the transparent ITO-PEN to obtain a transparent conductive substrate: Ultrasonically vibrate the ITO-PEN conductive substrate with deionized water, absolute ethanol, and isopropanol for 15 min respectively. After ultrasonic treatment, put it into an oven and bake at 80 °C for 15 min to remove visible impurities on the surface. Subsequently, treat it on an ultraviolet ozone treatment machine for 30 min to remove surface organic groups and reduce the water contact angle.

[0058] (2) Prepare a tin dioxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): Drop a tin dioxide colloid dispersion liquid on the ozone-treated transparent conductive substrate, and spin-coat it at 4000 rpm for 30 s to form a uniform film. Heat it on a heating table at 150 °C for 30 min to obtain a tin dioxide electron transport layer. The tin dioxide colloid dispersion liquid is prepared by mixing tin dioxide colloid and deionized water in a volume ratio of 1:1 and ultrasonically dispersing them.

[0059] (3) Prepare a PEO and ZnO-modified organic-inorganic hybrid perovskite CH3NH3SnClI2 light-absorbing layer on the surface of the tin dioxide electron transport layer obtained in step (2);

[0060] (3-I) Dissolve PEO, ZnO, CH3NH3Cl and SnI2 with a molar ratio of 1:1 in a mixed solution of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) with a volume ratio of 2:1, heat and stir at 65 °C for 4 h to obtain a PEO and ZnO modified organic-inorganic hybrid perovskite precursor solution, where the addition amount of PEO is equivalent to 2% of the total mass, the addition amount of ZnO is equivalent to 2% of the total mass, the addition amount of CH3NH3Cl is equivalent to 15% of the total mass, the addition amount of SnI2 is equivalent to 15% of the total mass, the addition amount of DMSO solvent is equivalent to 60% of the total mass, and the addition amount of DMF solvent is equivalent to 6% of the total mass;

[0061] (3-II) Filter the PEO and ZnO modified organic-inorganic hybrid perovskite precursor solution obtained in step (3-I) through a filter head with a diameter of 0.22 μm, and then drop it on the tin dioxide electron transport layer obtained in step (2). A PEO and ZnO modified organic-inorganic hybrid perovskite CH3NH3SnClI2 light-absorbing layer is obtained by spin coating. Set the spin coating process to 5500 rpm for 35 s; when the spin coating countdown reaches 25 s, add 200 μL of chlorobenzene solution and heat-treat at 105 °C for 10 min, and anneal to obtain a smooth perovskite film;

[0062] (4) Prepare a hole transport layer on the surface of the PEO and ZnO modified organic-inorganic hybrid perovskite CH3NH3SnClI2 light-absorbing layer obtained in step (3): The addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1% of the total solution mass, 4-tert-butylpyridine accounts for 2% of the total solution mass, the addition amount of chlorobenzene accounts for 65% of the total solution mass, and the addition amount of Spiro-OMeTAD (hole transport material) accounts for 32% of the total solution mass. Drop the Spiro-OMeTAD solution onto the surface of the PEO and ZnO modified organic-inorganic hybrid perovskite CH3NH3SnClI2 light-absorbing layer, and obtain a hole transport layer by spin coating. Set the spin coating process to 3500 rpm for 25 s;

[0063] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: Using the vacuum evaporation method, vacuum evaporate a 60 nm silver counter electrode at a rate of 0.4 nm / s, and that's it.

[0064] Test the performance of the semi-transparent flexible organic-inorganic hybrid perovskite solar cell based on polymers and inorganic oxide nanoparticles obtained in this example: In a room temperature environment with a humidity greater than 60%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective illumination area is 0.25 cm 2The photoelectric conversion efficiency is 21%. After being placed for 300 days without encapsulation, the photoelectric efficiency drops to 96% of the initial value. After 3500 cycles of bending (with a bending radius of 3 mm), it can still maintain 92% of the initial efficiency.

[0065] Example 3

[0066] In this example, a polymer (PMMA) and inorganic nano-oxide nanoparticles (Al2O3) are used to modify the perovskite layer. Based on the method for improving the flexibility and mechanical properties of flexible perovskite solar cells, when the conductive substrate is defined as the bottom layer, from bottom to top, it includes: a transparent ITO-PEN conductive substrate; a zinc oxide electron transport layer; an inorganic perovskite CsPbI3 light-absorbing layer modified with PMMA (polymer) and Al2O3 (inorganic oxide nanoparticles); a hole transport layer; and a gold counter electrode.

[0067] Based on the method for improving the flexibility and mechanical properties of semi-transparent flexible perovskite solar cells, its preparation method includes the following steps:

[0068] (1) Clean the transparent ITO-PEN to obtain a transparent conductive substrate: Use deionized water, absolute ethanol, and isopropanol to ultrasonically vibrate the ITO-PEN conductive substrate for 15 min respectively. After ultrasonic treatment, put it into an oven and bake at 100 °C for 15 min to remove visible impurities on the surface. Subsequently, treat it on an ultraviolet ozone treatment machine for 20 min to remove surface organic groups and reduce the water contact angle.

[0069] (2) Prepare a zinc oxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): Drop a zinc oxide dispersion liquid on the ozone-treated transparent conductive substrate and spin-coat it at 5000 rpm for 25 s to form a uniform film. Heat it on a heating table at 180 °C for 35 min to obtain a zinc oxide electron transport layer. The zinc oxide colloidal dispersion liquid is prepared by mixing zinc oxide colloid and deionized water in a volume ratio of 1:2 and ultrasonically dispersing them.

[0070] (3) Prepare an inorganic perovskite CsPbI3 light-absorbing layer modified with PMMA and Al2O3 on the surface of the zinc oxide electron transport layer obtained in step (2);

[0071] (3-I) Dissolve PMMA, Al2O3, CsI and PbI2 with a molar ratio of 1:1 in a dimethyl sulfoxide (DMSO) solution, heat and stir at 70 °C for 8 h to obtain a PEO and ZnO modified inorganic perovskite precursor solution, where the addition amount of PMMA is equivalent to 10% of the total mass, the addition amount of Al2O3 is equivalent to 10% of the total mass, the addition amount of CsI is equivalent to 20% of the total mass, the addition amount of PbI2 is equivalent to 20% of the total mass, and the addition amount of DMSO solvent is equivalent to 40% of the total mass;

[0072] (3-II) Filter the PMMA and Al2O3 modified inorganic perovskite precursor solution obtained in step (3-I) through a filter head with a diameter of 0.45 μm, and then drop it onto the zinc oxide electron transport layer obtained in step (2), and obtain a PMMA and Al2O3 modified inorganic perovskite CsPbI3 light absorption layer by spin coating. Set the spin coating process to 4500 rpm for 30 s; when the spin coating countdown reaches 25 s, add 300 μL of chlorobenzene solution and heat-treat at 160 °C for 10 min, and anneal to obtain a smooth perovskite film;

[0073] (4) Prepare a hole transport layer on the surface of the PMMA and Al2O3 modified inorganic perovskite CsPbI3 light absorption layer obtained in step (3): the addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1.5% of the total solution mass, 4-tert-butylpyridine accounts for 2.8% of the total solution mass, the addition amount of chlorobenzene accounts for 64% of the total solution mass, and the addition amount of Spiro-OMeTAD (hole transport material) accounts for 31.7% of the total solution mass. Drop the Spiro-OMeTAD solution onto the surface of the PEO and ZnO modified inorganic perovskite CsPbI3 light absorption layer, and obtain a hole transport layer by spin coating. Set the spin coating process to 3500 rpm for 30 s;

[0074] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: adopt the vacuum evaporation method, and vacuum evaporate a 60 nm silver counter electrode at a rate of 0.3 nm / s, and it is done.

[0075] Test the performance of the semi-transparent flexible inorganic perovskite solar cell based on polymers and inorganic oxide nanoparticles obtained in this example: in a room temperature environment with a humidity less than 30%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective light illumination area is 0.25 cm 2 , and the photoelectric conversion efficiency is 16%. After being placed for 150 days without encapsulation, the photoelectric efficiency drops to 90% of the initial value, and it can still maintain 94% of the initial efficiency after 3000 cycles of bending (the bending radius is 3 mm).

[0076] Comparative Example 1 (compared with Example 1)

[0077] In this comparative example, polymers and inorganic oxide nanoparticles are not used to modify the perovskite layer. Based on the method for improving the flexibility and mechanical properties of flexible perovskite solar cells, when the conductive substrate is defined as the bottom layer, from bottom to top, it sequentially includes: a transparent ITO-PEN conductive substrate; a tin dioxide electron transport layer; an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer; a hole transport layer; and a gold counter electrode.

[0078] Based on the method for improving the flexibility and mechanical properties of semi-transparent flexible perovskite solar cells, its preparation method includes the following steps:

[0079] (1) Cleaning the transparent ITO-PEN to obtain a transparent conductive substrate: The ITO-PEN conductive substrate is ultrasonically oscillated for 10 min respectively with deionized water, absolute ethanol, and isopropanol. After ultrasonic treatment, it is placed in an oven and baked at 100 °C for 15 min to remove visible impurities on the surface. Subsequently, it is treated on an ultraviolet ozone treatment machine for 25 min to remove surface organic groups and reduce the water contact angle;

[0080] (2) Preparing a tin dioxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): A tin dioxide colloidal dispersion liquid is dropped on the ozone-treated transparent conductive substrate, and spin-coated at 5000 rpm for 20 s to form a uniform film, and then heated on a heating table at 160 °C for 35 min to obtain a tin dioxide electron transport layer. The tin dioxide colloidal dispersion liquid is prepared by mixing tin dioxide colloid and deionized water in a volume ratio of 1:4 and ultrasonically dispersing;

[0081] (3) Preparing an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer on the surface of the tin dioxide electron transport layer obtained in step (2);

[0082] (3-I) Dissolving CH3NH3I and PbI2 with a molar ratio of 1:1 in a mixed solution of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) with a volume ratio of 1:4, heating and stirring at 60 °C for 12 h to obtain an organic-inorganic hybrid perovskite precursor solution, where the addition amount of CH3NH3I is equivalent to 18% of the total mass, the addition amount of PbI2 is equivalent to 25% of the total mass, and the addition amount of DMSO solvent is equivalent to 57% of the total mass;

[0083] (3-II) Filter the organic-inorganic perovskite precursor solution obtained in step (3-I) through a 0.22 μm filter head, and then drop it onto the tin dioxide electron transport layer obtained in step (2). An organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer is obtained by spin coating. Set the spin coating process to 5000 rpm for 30 s; add 250 μL of ethyl acetate solution when the spin coating countdown reaches 23 s, and perform heat treatment at 110 °C for 10 min, and anneal to obtain a smooth perovskite film;

[0084] (4) Prepare a hole transport layer on the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer obtained in step (3): The addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1.5% of the total solution mass, 4-tert-butylpyridine accounts for 2.5% of the total solution mass, the addition amount of chlorobenzene accounts for 66% of the total solution mass, and the addition amount of Spiro-OMeTAD (hole transport material) accounts for 30% of the total solution mass. Drop the Spiro-OMeTAD solution onto the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer, and obtain a hole transport layer by spin coating. Set the spin coating process to 3000 rpm for 30 s;

[0085] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: Using the vacuum evaporation method, vacuum evaporate a 40 nm silver counter electrode at a rate of 0.3 nm / s, and that's it.

[0086] Test the performance of the semi-transparent flexible inorganic perovskite solar cell obtained in this comparative example: In a room temperature environment with a humidity greater than 50%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective light illumination area is 0.25 cm 2 The photoelectric conversion efficiency is 14%. After being placed for 30 days without encapsulation, the photoelectric efficiency drops to 12% of the initial value, and it can still maintain 10% of the initial efficiency after 500 cycles of bending (the bending radius is 3 mm).

[0087] Comparative Example 2 (compared with Example 1)

[0088] In this comparative example, a polymer is used to modify the perovskite layer. Based on the method of improving the flexibility and mechanical properties of flexible perovskite solar cells, when the conductive substrate is defined as the bottom layer, from bottom to top, it includes: a transparent ITO-PEN conductive substrate; a tin dioxide electron transport layer; a chitosan-modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer; a hole transport layer; a gold counter electrode.

[0089] Based on the method of improving the flexibility and mechanical properties of semi-transparent flexible perovskite solar cells, its preparation method includes the following steps:

[0090] (1) Clean the transparent ITO-PEN to obtain a transparent conductive substrate: ultrasonically vibrate the ITO-PEN conductive substrate with deionized water, absolute ethanol, and isopropanol for 10 min respectively. After ultrasonic treatment, place it in an oven and bake at 100 °C for 15 min to remove visible impurities on the surface. Subsequently, treat it on an ultraviolet ozone treatment machine for 25 min to remove surface organic groups and reduce the water contact angle.

[0091] (2) Prepare a tin dioxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): drop a tin dioxide colloidal dispersion on the ozone-treated transparent conductive substrate, and spin-coat it at 5000 rpm for 20 s to form a uniform film. Heat it on a heating table at 160 °C for 35 min to obtain a tin dioxide electron transport layer. The tin dioxide colloidal dispersion is prepared by mixing tin dioxide colloid and deionized water in a volume ratio of 1:4 and ultrasonically dispersing them.

[0092] (3) Prepare an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer on the surface of the tin dioxide electron transport layer obtained in step (2).

[0093] (3-I) Dissolve chitosan, CH3NH3I and PbI2 with a molar ratio of 1:1 in a mixed solution of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) with a volume ratio of 1:4, and heat and stir at 60 °C for 12 h to obtain an organic-inorganic hybrid perovskite precursor solution. The addition amount of chitosan is equivalent to 1% of the total mass, the addition amount of CH3NH3I is equivalent to 18% of the total mass, the addition amount of PbI2 is equivalent to 25% of the total mass, and the addition amount of DMSO solvent is equivalent to 56% of the total mass.

[0094] (3-II) Filter the organic-inorganic perovskite precursor solution obtained in step (3-I) through a 0.22 μm filter head, and then drop it on the tin dioxide electron transport layer obtained in step (2). Obtain an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer by spin-coating. Set the spin-coating process to 5000 rpm for 30 s; add 250 μL of ethyl acetate solution when the spin-coating countdown reaches 23 s, and perform heat treatment at 110 °C for 10 min to anneal to obtain a smooth perovskite film.

[0095] (4) Prepare a hole transport layer on the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer obtained in step (3): The addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1.5% of the total solution mass, 4-tert-butylpyridine accounts for 2.5% of the total solution mass, the addition amount of chlorobenzene accounts for 66% of the total solution mass, and the addition amount of Spiro-OMeTAD (hole transport material) accounts for 30% of the total solution mass. Drop the Spiro-OMeTAD solution onto the surface of the organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer, and obtain the hole transport layer by spin coating. Set the spin coating process to 3000 rpm for 30 s;

[0096] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: Using the vacuum evaporation method, vacuum evaporate a 40 nm silver counter electrode at a rate of 0.3 nm / s, and that's it.

[0097] Test the performance of the polymer-based semi-transparent flexible inorganic perovskite solar cell obtained in this comparative example: In a room temperature environment with a humidity greater than 60%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective light illumination area is 0.25 cm 2 The photoelectric conversion efficiency is 16%. After being placed for 200 days without encapsulation, the photoelectric efficiency drops to 32% of the initial value. After 1500 cycles of bending (the bending radius is 3 mm), it can still maintain 20% of the initial efficiency.

[0098] Comparative Example 3 (compared with Example 1)

[0099] This comparative example uses inorganic oxide nanoparticles to modify the perovskite layer. Based on the method of improving the flexibility and mechanical properties of flexible perovskite solar cells, when the conductive substrate is defined as the bottom layer, from bottom to top, it includes: a transparent ITO-PEN conductive substrate; a tin dioxide electron transport layer; an organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer modified with TiO2 (inorganic oxide nanoparticles); a hole transport layer; a gold counter electrode.

[0100] This comparative example is based on the method of improving the flexibility and mechanical properties of flexible perovskite solar cells, and its preparation method includes the following steps:

[0101] (1) Clean the transparent ITO-PEN to obtain a transparent conductive substrate: Ultrasonically oscillate the ITO-PEN conductive substrate with deionized water, absolute ethanol, and isopropanol for 10 min respectively. After ultrasonic treatment, put it into an oven and bake it at 100 °C for 15 min to remove visible impurities on the surface. Subsequently, treat it on an ultraviolet ozone treatment machine for 25 min to remove the surface organic groups to reduce the water contact angle;

[0102] (2) Prepare a tin dioxide electron transport layer on the surface of the transparent conductive substrate obtained in step (1): Drop a tin dioxide colloidal dispersion on the ozone-treated transparent conductive substrate, and spin-coat it at 5000 rpm for 20 s to form a uniform film. Heat it on a heating table at 160 °C for 35 min to obtain a tin dioxide electron transport layer. The tin dioxide colloidal dispersion is prepared by mixing tin dioxide colloid and deionized water in a volume ratio of 1:4 and ultrasonically dispersing them;

[0103] (3) Prepare a TiO2-modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer on the surface of the tin dioxide electron transport layer obtained in step (2);

[0104] (3-I) Dissolve TiO2, CH3NH3I and PbI2 with a molar ratio of 1:1 in a mixed solution of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) with a volume ratio of 1:4, and heat and stir at 60 °C for 12 h to obtain a TiO2-modified organic-inorganic hybrid perovskite precursor solution. The addition amount of TiO2 is equivalent to 3% of the total mass, the addition amount of CH3NH3I is equivalent to 15% of the total mass, the addition amount of PbI2 is equivalent to 22% of the total mass, the addition amount of DMSO solvent is equivalent to 13% of the total mass, and the addition amount of DMF solvent is equivalent to 50% of the total mass;

[0105] (3-II) Filter the TiO2-modified organic-inorganic hybrid perovskite precursor solution obtained in step (3-I) through a filter head with a diameter of 0.22 μm, and then drop it on the tin dioxide electron transport layer obtained in step (2). A TiO2-modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer is obtained by spin-coating. Set the spin-coating process to 5000 rpm for 30 s; Add 250 μL of ethyl acetate solution when the spin-coating countdown reaches 23 s, and heat-treat it at 100 °C for 10 min to anneal to obtain a smooth perovskite film;

[0106] (4) Prepare a hole transport layer on the surface of the TiO2-modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer obtained in step (3): The addition amount of lithium bis(trifluoromethanesulfonyl)imide in the hole transport solution accounts for 1.5% of the total solution mass, 4-tert-butylpyridine accounts for 2.5% of the total solution mass, the addition amount of chlorobenzene accounts for 66% of the total solution mass, and the addition amount of P3HT (hole transport material) accounts for 30% of the total solution mass. Drop the P3HT solution on the surface of the TiO2-modified organic-inorganic hybrid perovskite CH3NH3PbI3 light-absorbing layer, and a hole transport layer is obtained by spin-coating. Set the spin-coating process to 3000 rpm for 30 s;

[0107] (5) Evaporate a thin metal counter electrode on the surface of the hole transport layer: Using the vacuum evaporation method, evaporate a 40-nm gold counter electrode at a rate of 0.4 nm / s in vacuum, and it is completed.

[0108] Test the performance of the semi-transparent flexible organic-inorganic hybrid perovskite solar cell based on inorganic oxide nanoparticles obtained in this comparative example: In a room temperature environment with a humidity greater than 50%, use a xenon lamp to simulate sunlight with a light intensity of 100 mW / cm 2 , and the effective illumination area is 0.25 cm 2 . The photoelectric conversion efficiency is 15%. After being placed for 100 days without encapsulation, the photoelectric efficiency drops to 30% of the initial value. After 2000 cycles of bending (the bending radius is 3 mm), it can still maintain 45% of the initial efficiency.

Claims

1. A method for improving the flexibility and mechanical properties of flexible perovskite solar cells, characterized in that, When the conductive substrate is defined as the bottom layer, the solar cell sequentially includes, from bottom to top: a conductive substrate layer; an electron transport layer; a perovskite light-absorbing layer modified with polymer and inorganic metal oxide nanoparticles; a hole transport layer; a counter electrode; The conductive substrate layer is a transparent polyethylene terephthalate flexible substrate; the electron transport layer is an SnO2, TiO2, ZnO or PCBM electron transport layer; the hole transport layer is one or more of Spiro-OMeTAD, PSS, P3HT, PEDOT and NiO; the polymer is one or more of chitosan, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate and PVDF-HFP; the inorganic metal oxide is one or more of TiO2, ZnO, Al2O3 and ZrO2; the perovskite light-absorbing layer is an ABX3 perovskite light-absorbing layer, where A is CH3NH3 or Cs, B is Pb, Sn, In or Ge, and X is one or more of I, Br or Cl.

2. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 1, wherein Specifically, it includes the following steps: (1) Clean the transparent polyethylene terephthalate flexible substrate to obtain a transparent conductive substrate; (2) Prepare an electron transport layer on the surface of the obtained conductive substrate; (3) Prepare a perovskite ABX3 light-absorbing layer modified with polymer and inorganic metal oxide nanoparticles on the surface of the obtained electron transport layer; (4) Prepare a hole transport layer on the surface of the obtained perovskite ABX3 light-absorbing layer modified with polymer and inorganic metal oxide nanoparticles; (5) Evaporate a thin metal counter electrode on the surface of the obtained hole transport layer to complete.

3. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 2, wherein In step (1), the cleaning method is: place the transparent FTO conductive glass in deionized water, absolute ethanol, and isopropanol respectively and ultrasonically vibrate for 10 - 20 min, bake at 80 - 120 °C for 10 - 25 min, and perform ultraviolet ozone treatment for 20 - 30 min.

4. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 2 or 3, characterized in that In step (2), the preparation method of the electron transport layer is: drop the electron transport material dispersion on the surface of the conductive substrate, spin-coat at 4000 - 6000 rpm for 20 - 40 s, and heat at 150 - 200 °C for 30 - 40 min to complete; the electron transport material dispersion is prepared by mixing the electron transport material and the solvent according to a volume ratio of 1:1 - 8 and ultrasonically dispersing; the electron transport material can be SnO2, TiO2, ZnO or PCBM, and the solvent can be deionized water or isopropanol or chlorobenzene.

5. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 2 or 3, characterized in that, In step (3), the filtered perovskite precursor solution is dropped on the surface of the electron transport layer, spin-coated, heat-treated, and annealed to obtain a perovskite light-absorbing layer; the preparation method of the perovskite precursor solution is: dissolve the polymer, inorganic oxide nanoparticles, AX and BX2 in a solution of dimethyl sulfoxide or N,N-dimethylformamide, and heat and stir at 65 - 75 °C for 4 - 12 h.

6. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 5, characterized in that, In step (3), in the perovskite precursor solution, the addition amount of the polymer is 0 to 10% of the total mass of the precursor solution, the addition amount of the inorganic metal oxide nanoparticles is 0 to 10% of the total mass of the precursor solution, the addition amount of AX is 10 to 20% of the total mass of the precursor solution, the addition amount of BX2 is 20 to 30% of the total mass of the precursor solution, the addition amount of dimethyl sulfoxide is 20% to 60% of the total mass of the precursor solution, and the addition amount of N,N-dimethylformamide is 0% to 50% of the total mass of the precursor solution; the diameter of the filter head used for filtration is 0.22 to 0.45 m; the rotation speed of spin coating is 3500 to 7500 rpm, and the time is 20 to 40 s; 200 to 300 L of methyl acetate, ethyl acetate or chlorobenzene solution is added when the spin coating counts down to 10 to 24 s; the temperature of the heat treatment is 70 to 200 °C, and the time is 5 to 20 min.

7. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 2 or 3, characterized in that In step (4), the hole transport solution is dropped on the surface of the perovskite light-absorbing layer and spin-coated to obtain a hole transport layer.

8. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 7, characterized in that, In step (4), in the hole transport solution, the mass of lithium bis(trifluoromethanesulfonyl)imide is 0.2% to 2% of the total mass of the solution, the mass of 4-tert-butylpyridine is 0.8% to 3% of the total mass of the solution, the mass of chlorobenzene is 60% to 80% of the total mass of the solution, and the mass of the hole transport material is 10% to 30% of the total mass of the solution; the rotation speed of spin coating is 2000 to 3500 rpm, and the time is 30 to 40 s.

9. The method for improving the flexibility and mechanical properties of a flexible perovskite solar cell according to claim 2 or 3, characterized in that, In step (5), a thin metal counter electrode is deposited by vacuum evaporation; the rate of the vacuum evaporation is 0.1 to 0.6 nm / s, and the thickness of the thin metal counter electrode is 10 to 60 nm; the counter electrode is gold or silver.