Flexible perovskite solar cell and preparation method thereof

Abstract

The invention discloses a flexible perovskite solar cell and a preparation method thereof. The flexible perovskite solar cell comprises a charge transport layer and a perovskite layer, an interface modification layer is arranged between the charge transport layer and the perovskite layer; the interface modification layer comprises bifunctional molecules, the structural formula of the bifunctional molecules is B-R-T, and B is an anchoring group and comprises at least one of-PO (OH) 2,-COOH and-SOOH; r is an intermediate link and comprises at least one of-CH2-and phenylene; and T is a terminal group and comprises at least one of-NH2,-OH,-I,-Cl,-Br and-F. Therefore, the flexible perovskite solar cell provided by the invention has excellent photoelectric conversion efficiency and perovskite crystal quality.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic solar cells, and more particularly, relates to a flexible perovskite solar cell and a preparation method thereof. Background Art

[0002] As traditional fossil energy gradually approaches depletion, the human demand for new energy has become increasingly urgent. Among numerous renewable energy sources, solar energy has received extensive attention due to its unique advantages. In particular, perovskite solar cells have witnessed astonishing development speed. Thanks to the high absorption coefficient, suitable and adjustable bandgap, long carrier lifetime, and high carrier mobility of perovskite materials, their photoelectric conversion efficiency has achieved a leap from 3.8% to 26.15% in just over a decade.

[0003] Among them, flexible perovskite solar cells have a wider range of application scenarios due to their high power density and mechanical flexibility, such as wearable electronic devices, building-integrated photovoltaics, aerospace aircraft, etc. However, compared with rigid substrates, flexible substrates have greater surface roughness, poorer surface adhesion, and higher thermal expansion coefficients, making the crystallization process of perovskite films more difficult to control and interfacial carrier recombination more serious. The poor crystallization and interface quality result in significantly lower efficiency of flexible perovskite solar cells compared to their rigid counterparts. The reported record efficiency of small-area flexible cells is only 24.90% at present. Therefore, it is of great significance to improve the photoelectric conversion efficiency of flexible perovskite solar cells. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. For this purpose, the present invention provides a flexible perovskite solar cell and a preparation method thereof, and the flexible perovskite solar cell of the present invention has excellent photoelectric conversion efficiency and perovskite crystallization quality.

[0005] Therefore, in the first aspect of the present invention, the present invention proposes a flexible perovskite solar cell, comprising: a charge transport layer and a perovskite layer;

[0006] An interface modification layer is provided between the charge transport layer and the perovskite layer;

[0007] The interface modification layer comprises a bifunctional molecule, and the structural formula of the bifunctional molecule is: B-R-T,

[0008] wherein, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate linker, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

[0009] In the present invention, the bifunctional molecules in the interface modification layer can directionally passivate the interface defects between the electron transport layer and the perovskite layer on both sides, simultaneously regulate the crystallization process of the perovskite layer, eliminate the holes in the perovskite layer, thereby forming a flexible perovskite solar cell with good performance. Thereby, the photoelectric conversion efficiency and the perovskite crystallization quality of the flexible perovskite solar cell are further improved.

[0010] In some embodiments, the bifunctional molecules include at least one of β-alanine, 3-iodopropanol, 3-iodopropionic acid, 3-bromopropionic acid, 3-chloropropionic acid, and 3-fluoropropionic acid.

[0011] In some embodiments, the thickness of the interface modification layer is 1-5 nm.

[0012] In some embodiments, the flexible perovskite solar cell includes a flexible conductive layer, an electron transport layer, an interface modification layer, a perovskite layer, a hole transport layer, and an electrode layer that are sequentially stacked.

[0013] In some embodiments, the thickness of the electron transport layer is 10-30 nm; the thickness of the perovskite layer is 500-700 nm; the thickness of the hole transport layer is 100-200 nm; the thickness of the electrode layer is 50-150 nm.

[0014] In some embodiments, the flexible conductive layer includes at least one of PEN and PET; the electron transport layer includes at least one of SnO2, TiO2, and ZnO; the perovskite layer includes a metal halide perovskite, and the crystal structure of the metal halide perovskite is ABX3, where A includes at least one of formamidinium ion, methylammonium ion, cesium ion, and rubidium ion, B includes at least one of lead ion and tin ion, and X includes at least one of chloride ion, bromide ion, and iodide ion; the hole transport layer includes at least one of Spiro-OMeTAD, PTAA, and PEDOT:PSS; the electrode layer includes at least one of gold, silver, copper, aluminum, carbon, and transparent conductive oxide.

[0015] In a second aspect of the present invention, the present invention provides a method for preparing a flexible perovskite solar cell, which is characterized by including the following steps:

[0016] Form an interface modification layer on the surface of the charge transport layer;

[0017] Form a perovskite layer on the surface of the interface modification layer; the interface modification layer includes bifunctional molecules, and the structural formula of the bifunctional molecules is: B-R-T,

[0018] Among them, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate linker, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

[0019] The preparation method of the present invention is simple and efficient, and the cost is controllable. Therefore, a flexible perovskite solar cell with excellent performance can be obtained.

[0020] In some embodiments, the method for forming an interface modification layer on the surface of the charge transport layer includes:

[0021] Mix a bifunctional molecule with a solvent to form a solution;

[0022] Form a coating of the solution on the charge transport layer, and perform annealing treatment to form an interface modification layer.

[0023] In some embodiments, the solvent includes at least one of water, ethanol, and isopropanol; and / or, the concentration of the bifunctional molecule in the solution is 0.5 - 5 mg / mL.

[0024] In some embodiments, the method for forming a coating of the solution on the charge transport layer includes a spin coating method, and the spin coating method satisfies: the spin coating speed is 2000 - 5000 rpm, and the spin coating time is 20 - 40 s;

[0025] and / or, the annealing treatment satisfies: the annealing temperature is 60 - 100 °C, and the annealing time is 5 - 10 min.

[0026] Compared with the prior art, the beneficial technical effects achieved by the present invention are:

[0027] The bifunctional molecule contained in the interface modification layer of the present invention can be bonded to the electron transport layer and the perovskite layer respectively through the anchoring group and the terminal group to form a molecular layer with a specific orientation, optimize the interfacial energy band structure, and promote the separation and transportation of carriers. At the same time, the anchoring group in the bifunctional molecule passivates the oxygen vacancy defects on the surface of the electron transport layer, and the terminal group with lone pair electrons acts as a Lewis base to coordinate with the uncoordinated Pb 2+ in the lower interface of the perovskite, thereby weakening the adsorption of the electron transport layer to precursor solvents such as DMSO, promoting its volatilization, eliminating the holes in the lower interface of the perovskite, and improving the crystallization quality of the two-step perovskite film. The flexible perovskite solar cell prepared thereby has obtained a relatively high photoelectric conversion efficiency of 23.45%. At the same time, the battery can still maintain 90% of the initial efficiency after being stored for 1500 hours under unencapsulated conditions, and can still maintain 92% of the initial efficiency after being bent 10000 times with a bending radius of 10 mm, increasing the environmental and mechanical stability of the flexible battery.

[0028] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0030] Figure 1 Schematic diagram of the flexible perovskite solar cell structure prepared in Example 1 of the present invention; wherein, 1 - flexible conductive layer, 2 - electron transport layer, 3 - interface modification layer, 4 - perovskite layer, 5 - hole transport layer, 6 - electrode layer;

[0031] Figure 2 Time-of-flight secondary ion mass spectrometry (TOF-SIMS) images of the longitudinal distribution of lead iodide (PbI2) and metal halide perovskite (MHP) in Comparative Example 1 and Example 3 of the present invention;

[0032] Figure 3 Scanning electron microscope images of the surface of lead iodide films in Comparative Example 1, Example 1, Example 2, and Example 3 of the present invention;

[0033] Figure 4 Scanning electron microscope images of the upper surface of perovskite in Comparative Example 1, Example 1, Example 2, and Example 3;

[0034] Figure 5 Scanning electron microscope images of the lower surface of perovskite in Comparative Example 1, Example 1, Example 2, and Example 3;

[0035] Figure 6 X-ray diffraction patterns of the perovskite layers in Comparative Example 1, Example 1, Example 2, and Example 3;

[0036] Figure 7 J-V (current-voltage) test curves measured under the AM1.5 solar spectrum for the flexible perovskite solar cells prepared in Comparative Example 1, Example 1, Example 2, and Example 3. Detailed Description of the Embodiments

[0037] Embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0038] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0039] The endpoints and any values disclosed in this text for a range are not limited to that precise range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this text.

[0040] In this text, the term "comprising" or "including" is an open-ended expression, that is, it includes the content specified by the present invention, but does not exclude other aspects of the content.

[0041] In the first aspect of the embodiments of the present invention, the present invention provides a flexible perovskite solar cell, comprising: a charge transport layer and a perovskite layer;

[0042] An interface modification layer is provided between the charge transport layer and the perovskite layer;

[0043] The interface modification layer comprises a bifunctional molecule, and the structural formula of the bifunctional molecule is: B-R-T,

[0044] Wherein, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate linker, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

[0045] In the present invention, the bifunctional molecule can be bonded to the electron transport layer and the perovskite layer through the anchoring group and the terminal group respectively to form a molecular layer with a specific orientation, optimize the interfacial energy band structure, and promote the separation and transport of carriers. At the same time, the anchoring group in the bifunctional molecule passivates the oxygen vacancy defects on the surface of the electron transport layer, and the terminal group with lone pair electrons coordinates with the uncoordinated metal ions at the perovskite lower interface (the interface between the electron transport layer and the perovskite layer is collectively referred to as the perovskite lower interface or buried interface), thereby weakening the adsorption of the solvent in the preparation process of the perovskite layer by the electron transport layer, promoting the solvent volatilization, and further eliminating the holes at the buried interface and improving the crystallization quality of the perovskite thin film. Thus, the flexible perovskite solar cell prepared by the present invention has excellent perovskite crystallization quality and high photoelectric conversion efficiency.

[0046] In some embodiments of the present invention, the bifunctional molecule includes at least one of β-alanine, 3-iodopropanol, 3-iodopropionic acid, 3-bromopropionic acid, 3-chloropropionic acid, and 3-fluoropropionic acid.

[0047] In some embodiments of the present invention, the thickness of the interface modification layer is 1 - 5 nm.

[0048] The interface modification layer can directionally passivate the interface defects between the electron transport layer and the perovskite layer on both sides, while regulating the crystallization process of the perovskite layer and eliminating the holes on the electron transport layer, thereby forming a flexible perovskite solar cell with good performance. As a result, the photoelectric conversion efficiency and mechanical stability of the flexible perovskite solar cell are further improved.

[0049] As an example, the thickness of the interface modification layer is 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm.

[0050] In some embodiments of the present invention, the flexible perovskite solar cell includes a flexible conductive layer, an electron transport layer, an interface modification layer, a perovskite layer, a hole transport layer, and an electrode layer stacked in sequence.

[0051] In some embodiments of the present invention, the thickness of the electron transport layer is 10 - 30 nm; the thickness of the perovskite layer is 500 - 700 nm; the thickness of the hole transport layer is 100 - 200 nm; the thickness of the electrode layer is 50 - 150 nm.

[0052] As a result, the photoelectric conversion efficiency and mechanical stability of the flexible perovskite solar cell are further improved.

[0053] In some embodiments of the present invention, the flexible conductive layer includes at least one of polyethylene naphthalate (PEN) and polyethylene terephthalate (PET); the electron transport layer includes at least one of SnO2, TiO2, and ZnO; the perovskite layer includes metal halide perovskite, and the crystal structure of the metal halide perovskite is ABX3, where A includes at least one of formamidinium ion, methylammonium ion, cesium ion, and rubidium ion, B includes at least one of lead ion and tin ion, and X includes at least one of chloride ion, bromide ion, and iodide ion; the hole transport layer includes at least one of Spiro-OMeTAD, PTAA, and PEDOT:PSS; the electrode layer includes at least one of gold, silver, copper, aluminum, carbon, and transparent conductive oxide.

[0054] As a result, the performance of the flexible perovskite solar cell is further improved.

[0055] In the second aspect of the embodiments of the present invention, a method for preparing a flexible perovskite solar cell is provided, which is characterized by comprising the following steps:

[0056] Form an interfacial modification layer on the surface of the charge transport layer;

[0057] Form a perovskite layer on the surface of the interfacial modification layer; the interfacial modification layer comprises a bifunctional molecule, and the structural formula of the bifunctional molecule is: B-R-T,

[0058] wherein, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate linker, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

[0059] The preparation method of the present invention is simple and efficient, and the cost is controllable. Thus, a flexible perovskite solar cell with excellent performance can be obtained.

[0060] In some embodiments of the present invention, the method for forming an interfacial modification layer on the surface of the charge transport layer includes:

[0061] Mix the bifunctional molecule with a solvent to form a solution;

[0062] Form a coating of the solution on the charge transport layer and perform annealing treatment to form the interfacial modification layer.

[0063] In some embodiments of the present invention, the solvent includes at least one of water, ethanol, and isopropanol.

[0064] In some embodiments of the present invention, the concentration of the bifunctional molecule in the solution is 0.5 - 5 mg / mL.

[0065] As an example, the concentrations are 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL, 5 mg / mL.

[0066] In some embodiments of the present invention, the method for forming a coating of the solution on the electron transport layer includes the spin coating method, and the spin coating method satisfies: the spin coating speed is 2000 - 5000 rpm, and the spin coating time is 20 - 40 s.

[0067] As an example, the spin coating speeds are 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm.

[0068] As an example, the spin-coating time is 20 s, 25 s, 30 s, 35 s, 40 s.

[0069] In some embodiments of the present invention, the annealing treatment satisfies: the annealing temperature is 60 - 100 °C, and the annealing time is 5 - 10 min.

[0070] As an example, the annealing temperature is 60 °C, 70 °C, 80 °C, 90 °C, 100 °C.

[0071] As an example, the annealing time is 5 min, 6 min, 7 min, 8 min, 9 min, 10 min.

[0072] In some embodiments of the present invention, before forming the electron transport layer on at least one side of the flexible conductive layer, it further includes treating the flexible conductive layer, and the treatment methods include:

[0073] Ultrasonically bath-clean the flexible conductive layer material in detergent, water, ethanol, and isopropyl alcohol in sequence for 15 min, dry it, and perform ozone treatment for 10 - 40 min.

[0074] In some embodiments of the present invention, the method for forming the electron transport layer on at least one side of the flexible conductive layer includes:

[0075] Spin-coat the electron transport layer solution on the surface of the flexible conductive layer, perform annealing treatment to form the electron transport layer; the rotation speed of spin-coating is 500 - 5000 rpm, the spin-coating time is 10 - 60 s; the temperature of annealing treatment is 80 - 150 °C, and the annealing time is 5 - 40 min.

[0076] In some embodiments of the present invention, the method for forming the perovskite layer on the surface of the interface modification layer includes:

[0077] Mix the iodide with the solvent to form a solution, spin-coat it on the surface of the interface modification layer at 1000 - 2000 rpm for 30 s, perform annealing treatment at 60 - 80 °C for 30 - 90 s to form a porous layer; the iodide includes PbI2, the solvent includes DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide), and the mass ratio of the two is 9:1, and the concentration of the solution is 1.5 mol / L;

[0078] Then spin-coat the organic salt solution on the surface of the porous layer at 1500 - 2500 rpm for 30 s, perform annealing treatment at 120 - 160 °C for 10 - 15 min to form the perovskite layer; the organic salt solution includes FAI (formamidinium iodide), MACl (methylammonium chloride), IPA (isopropyl alcohol), wherein the mass ratio of FAI and MACl is 9:1, and the solution concentration is 0.5 mol / L.

[0079] In some embodiments of the present invention, the method for forming a hole transport layer on the surface of the perovskite layer includes:

[0080] Spin-coating a hole transport layer solution on the surface of the perovskite layer, followed by annealing treatment to form a hole transport layer; the rotation speed for spin-coating is 3000 - 5000 rpm, and the spin-coating time is 20 - 40 s.

[0081] In some embodiments of the present invention, the method for forming an electrode layer on the surface of the hole transport layer includes at least one of evaporation deposition method, doctor blade method, and magnetron sputtering method; the evaporation deposition method includes depositing a metal on the surface of the hole transport layer at an evaporation rate of 0.01 - 0.1 nm / s to form an electrode layer.

[0082] The solution of the present invention will be explained below in conjunction with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified as to the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0083] Example 1:

[0084] As Figure 1 shown, the perovskite solar cell, from bottom to top, has PEN / ITO as the transparent flexible conductive layer, SnO2 as the electron transport layer, β-alanine as the interfacial modification layer, FAPbI3 as the perovskite layer, Spiro-OMeTAD as the hole transport layer, and gold as the electrode layer. The specific preparation steps are as follows:

[0085] (1) Treatment of the flexible conductive layer: The flexible substrate is cut into a size of 20 mm * 20 mm by laser etching, ultrasonically cleaned with deionized water, ethanol, and isopropanol for 15 minutes each, and then dried in an oven; the ITO transparent conductive PEN is pasted on the glass substrate coated with a PDMS adhesive layer and treated with an ultraviolet ozone device for 15 minutes for standby;

[0086] (2) Preparation of the electron transport layer: A SnO2 precursor solution is prepared by mixing a 12 wt.% SnO2 colloidal aqueous solution and deionized water at a volume ratio of 1:3; 100 μL of the SnO2 precursor solution is taken and coated on the ITO flexible substrate, with a spin-coating speed of 4000 rpm and a spin-coating time of 30 s. After spin-coating, it is annealed at 120 °C for 40 minutes. A 25-nm-thick SnO2 electron transport layer is deposited.

[0087] (3) Preparation of the interface modification layer: First, weigh 1 mg of β-alanine and dissolve it in 1 mL of deionized water solvent. After shaking evenly, take out 100 μL and spin-coat it on the electron transport layer prepared in (2) at a spin-coating speed of 4000 rpm for 30 s. After spin-coating, anneal at 60 °C for 5 minutes to deposit an interface modification layer with a thickness of 2 nm.

[0088] (4) Preparation of the perovskite light layer: Weigh 691.5 mg of PbI2 and dissolve it in a mixed solution of 1 mL of DMF and DMSO (V DMF :V DMSO = 9:1) to prepare a PbI2 precursor solution. Take 50 μL and spin-coat it statically on the small molecule interface modification layer at a speed of 1500 rpm for 30 s, and anneal at 70 °C for 60 s to obtain a PbI2 porous layer; Weigh 180.0 mg of FAI and 36.0 mg of MACl and dissolve them in 2 ml of IPA to prepare an organic salt solution. Take 100 μL and spin-coat it statically on the PbI2 porous layer at a speed of 2000 rpm for 30 s, and anneal at 150 °C for 15 min to obtain a perovskite layer with a thickness of 700 nm.

[0089] (5) Preparation of the hole transport layer: Weigh 72.3 mg of Spiro-OMeTAD, 30 μL of 4-tert-butylpyridine, and 35 μL of lithium salt acetonitrile solution and add them to 1 mL of chlorobenzene to prepare a Spiro-OMeTAD hole transport layer solution. Take 60 μL and spin-coat it on the surface of the perovskite layer prepared in step (4) at a spin-coating speed of 4000 rpm for 30 s to obtain a hole transport layer with a thickness of 150 nm.

[0090] (6) Preparation of the electrode layer: Peel the flexible device from the glass substrate and place it in a thermal evaporation vacuum coating instrument to deposit a metal gold electrode with a thickness of 80 nm at a speed of 0.03 nm / s to complete the preparation of the entire perovskite solar cell, and prepare a perovskite solar cell device with the structure of PEN / ITO / SnO2 / β-alanine / FAPbI3 / Spiro-OMeTAD / Au as shown. Figure 1 The structure shown is a perovskite solar cell device of PEN / ITO / SnO2 / β-alanine / FAPbI3 / Spiro-OMeTAD / Au.

[0091] Example 2:

[0092] Difference between Example 2 and Example 1: In step (3) of Example 2, weigh 1 mg of 3-iodopropanol and dissolve it in 1 mL of isopropanol solvent to prepare the interface modification layer.

[0093] Example 3:

[0094] Difference between Example 3 and Example 1: In step (3) of Example 3, weigh 1 mg of 3-iodopropionic acid and dissolve it in 1 mL of ethanol solvent to prepare the interface modification layer.

[0095] Example 4:

[0096] The difference between Example 4 and Example 3: In Example 4, 0.5 mg of 3-iodopropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0097] Example 5:

[0098] The difference between Example 5 and Example 3: In Example 5, 2 mg of 3-iodopropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0099] Example 6:

[0100] The difference between Example 6 and Example 3: In Example 6, 5 mg of 3-iodopropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0101] Example 7:

[0102] The difference between Example 7 and Example 1: In step (3) of Example 7, 1 mg of 3-bromopropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0103] Example 8:

[0104] The difference between Example 8 and Example 1: In step (3) of Example 7, 1 mg of 3-chloropropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0105] Example 9:

[0106] The difference between Example 7 and Example 1: In step (3) of Example 7, 1 mg of 3-fluoropropionic acid was weighed and dissolved in 1 mL of ethanol solvent to prepare an interfacial modification layer.

[0107] Comparative Example 1:

[0108] The difference between Comparative Example 1 and Example 1: In Comparative Example 1, the preparation of the interfacial modification layer in step (3) was not carried out, and step (4) was directly carried out after step (2) of Example 1.

[0109] Analysis of experimental results:

[0110] Figure 2Longitudinal DMSO profiles of lead iodide and metal halide perovskite in Comparative Example 1 and Example 3. When the sputtering time is less than 300 s, the detection area is the perovskite layer, and when the sputtering time is between 300 and 400 s, the detection area is the lower interface of the perovskite. In the lead iodide (PbI2) film spin-coated in the first step, DMSO exists in both the bulk phase and the lower interface, while in the perovskite (MHP) film after two-step spin-coating, DMSO only exists in the lower interface. The DMSO residue of lead iodide and metal halide perovskite in Example 3 is significantly lower than that in Comparative Example 1, indicating that the modification with bifunctional molecules can effectively promote the volatilization of DMSO and avoid its enrichment at the buried interface. Thus, it shows that the bifunctional molecules in the interface modification layer of the present invention can effectively eliminate the holes on the lower surface of the perovskite, thereby forming a flexible perovskite solar cell with good performance and further improving the photoelectric conversion efficiency of the flexible perovskite solar cell.

[0111] Figure 3 Surface microtopographies of lead iodide films in Comparative Example 1 and Examples 1, 2, and 3. The lead iodide film in Comparative Example 1 is flat and dense, lacking pores and hexagonal crystal nuclei, which is not conducive to the infiltration of organic salts such as FAI and the crystallization growth of perovskite during the second-step spin-coating; the modified lead iodide films in Examples 1, 2, and 3 are porous and have many hexagonal grains on the surface because the bifunctional molecules promote the volatilization of solvents such as DMSO and thus improve the crystallization of PbI2. Thus, it shows that the present invention can effectively improve the crystallization quality of perovskite and increase the photoelectric conversion efficiency of the solar cell.

[0112] Figure 4 and Figure 5 Surface and cross-sectional microtopographies of the perovskite layer in Comparative Example 1 and Examples 1, 2, and 3, respectively. Compared with Comparative Example 1, the number of holes on the surface of the perovskite film in Example 1 is reduced, the white needle-like precipitate FAI is reduced, and the holes and cracks at the buried interface are reduced. The perovskite films in Examples 2 and 3 have no holes and precipitates on the surface, and the lower surface is flat, dense, and crack-free because the PbI2 modified with bifunctional molecules is porous, which is conducive to the full reaction with FAI and the further volatilization of DMSO. Thus, it shows that the bifunctional molecule modification layer can improve the perovskite morphology, and when the terminal group is -I, the effect on morphology improvement is better than that of -NH2.

[0113] By Figure 6It can be seen that the perovskite layers prepared in Examples 1, 2, and 3 have higher diffraction intensities compared to the perovskite layer prepared in Comparative Example 1, indicating that the perovskite layers in Examples 1, 2, and 3 have higher crystallinity, and the ratio of the diffraction peak intensity of perovskite to lead iodide increases, indicating a reduction in the amount of residual lead iodide. This is because the modification with bifunctional molecules in Examples 1, 2, and 3 promotes the volatilization of DMSO, forming a porous PbI2 layer that fully reacts with FAI, and hexagonal PbI2 can serve as a nucleation site to promote the crystallization growth of perovskite. Thus, it is shown that the bifunctional molecule modification layer can effectively improve the perovskite morphology and enhance the crystallization quality of the perovskite layer.

[0114] The current-voltage characteristic curves of the flexible perovskite solar cells of Examples 1-9 and Comparative Example 1 were tested under the AM1.5 solar spectrum, and the results are shown in Table 1 and Figure 7 as follows. The efficiency of the perovskite solar cell of Example 3 modified with 3-iodopropionic acid is as high as 23.45%, which is 3.26% higher than the efficiency of 20.19% of the unmodified perovskite solar cell of Comparative Example 1. The efficiency improvement is mainly reflected in the open-circuit voltage (V OC ) and the fill factor (FF), mainly due to the elimination of holes in the electron transport layer, resulting in improved interface and crystallization quality. In Examples 4 and 5, when the concentration of 3-iodopropionic acid decreases or increases, the performance of the perovskite solar cell slightly decreases due to poor molecular coverage and molecular aggregation. Thus, it is shown that the flexible perovskite solar cell of the present invention has excellent photoelectric conversion efficiency.

[0115] Table 1 Main performance parameters of the flexible perovskite solar cells in Comparative Example 1 and Examples 1-9

[0116]

[0117] Table 2 shows the environmental stability and bending stability tests of Examples 1-9 and Comparative Example 1. After storing the unencapsulated flexible battery in an atmospheric environment with 35% relative humidity and 23 °C for 1000 h, the efficiency of Comparative Example 1 decreased to 70.1%, while the efficiency of Example 3 remained stable at 91.9% after 1500 h of storage. The improvement in environmental stability mainly comes from the improvement of perovskite crystallization quality and the reduction of impurity phases. After bending the flexible battery 5000 times with a bending diameter of 10 mm, the efficiency of Comparative Example 1 decreased to 64.2%, while the efficiency retention rate of Example 3 was 93.3% after bending 10000 times. The improvement in bending stability mainly comes from the elimination of holes at the buried interface and the enhancement of interface bonding force. Thus, it is shown that the flexible perovskite solar cell of the present invention has excellent stability.

[0118] Table 2 Stability of the flexible perovskite solar cells in Comparative Example 1 and Examples 1-9

[0119]

[0120]

[0121] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0122] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A flexible perovskite solar cell, characterized in that, Comprising: A charge transport layer and a perovskite layer; An interface modification layer is disposed between the charge transport layer and the perovskite layer; The interface modification layer comprises a bifunctional molecule, and the structural formula of the bifunctional molecule is: B-R-T, wherein, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate link, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

2. The flexible perovskite solar cell according to claim 1, characterized in that, The bifunctional molecule includes at least one of β-alanine, 3-iodopropanol, 3-iodopropionic acid, 3-bromopropionic acid, 3-chloropropionic acid, 3-fluoropropionic acid.

3. The flexible perovskite solar cell according to claim 1 or 2, characterized in that, The thickness of the interface modification layer is 1 to 5 nm.

4. The flexible perovskite solar cell according to claim 1 or 2, characterized in that, The flexible perovskite solar cell includes a flexible conductive layer, an electron transport layer, an interface modification layer, a perovskite layer, a hole transport layer, and an electrode layer that are sequentially stacked.

5. The flexible perovskite solar cell according to claim 4, wherein The thickness of the electron transport layer is 10 to 30 nm; the thickness of the perovskite layer is 500 to 700 nm; the thickness of the hole transport layer is 100 to 200 nm; the thickness of the electrode layer is 50 to 150 nm.

6. The flexible perovskite solar cell according to claim 4, wherein The flexible conductive layer includes at least one of PEN, PET; the electron transport layer includes at least one of SnO2, TiO2, ZnO; the perovskite layer includes a metal halide perovskite, and the crystal structure of the metal halide perovskite is ABX3, wherein A includes at least one of formamidinium ion, methylammonium ion, cesium ion, rubidium ion, B includes at least one of lead ion, tin ion, and X includes at least one of chloride ion, bromide ion, iodide ion; the hole transport layer includes at least one of Spiro-OMeTAD, PTAA, PEDOT:PSS; the electrode layer includes at least one of gold, silver, copper, aluminum, carbon, transparent conductive oxide.

7. A method for preparing a flexible perovskite solar cell, characterized in that, Including the following steps: Forming an interface modification layer on the surface of the charge transport layer; Forming a perovskite layer on the surface of the interface modification layer; the interface modification layer comprises a bifunctional molecule, and the structural formula of the bifunctional molecule is: B-R-T, wherein, B is an anchoring group, including at least one of -PO(OH)2, -COOH, -SOOH; R is an intermediate link, including at least one of at least one -CH2-, phenylene; T is a terminal group, including at least one of -NH2, -OH, -I, -Cl, -Br, -F.

8. The preparation method according to claim 7, characterized in that, The method for forming the interface modification layer on the surface of the charge transport layer includes: Mixing the bifunctional molecule with a solvent to form a solution; Forming a coating of the solution on the charge transport layer and performing annealing treatment to form an interface modification layer.

9. According to the preparation method of claim 8, wherein The solvent includes at least one of water, ethanol, isopropanol; And / or, the concentration of the bifunctional molecule in the solution is 0.5 to 5 mg / mL.

10. The preparation method according to claim 8 or 9, characterized in that, The method of forming a coating of the solution on the charge transport layer includes a spin coating method, and the spin coating method satisfies that the spin coating speed is 2000-5000 rpm and the spin coating time is 20-40 s; And / or, the annealing treatment satisfies that the annealing temperature is 60-100 °C and the annealing time is 5-10 min.

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