A star polymer, a perovskite solar cell with a star polymer modification layer and a preparation method thereof

Abstract

The application discloses a star-shaped polymer, a perovskite solar cell with a star-shaped polymer modified layer and a preparation method of the perovskite solar cell. The star-shaped polymer has a three-dimensional structure and contains multiple extended arm molecules, and provides multiple Lewis base functional groups with high-density multi-dentate coordination sites. The functional groups can effectively coordinate with electron-deficient defects on a perovskite lower surface, thereby improving the crystallinity of the perovskite, reducing the defect density and enhancing the adhesion of the perovskite lower surface. After being modified by the star-shaped polymer, the lower surface fracture strength is increased from 0.13 MPa to 1.66 MPa, and the photoelectric conversion efficiency of the obtained device reaches 26.33%. Under the condition that the bending radius is 6 mm, the flexible device modified by the star-shaped polymer can still maintain more than 90% of the initial efficiency after 3000 bending cycles, and exhibits excellent mechanical stability.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a star-shaped polymer, a perovskite solar cell with a star-shaped polymer modification layer, and a method for preparing the same. Background Technology

[0002] Organic-inorganic hybrid perovskite materials have become the most promising next-generation photovoltaic materials due to their excellent photoelectric properties, such as high light absorption coefficient, high carrier mobility, long carrier lifetime, and tunable bandgap, as well as their relatively low production cost. However, the poor operational stability of perovskite solar cells has seriously hindered their commercialization.

[0003] Among the many factors affecting the stability of perovskite solar cells, the interface plays a crucial role. Under certain stress conditions, ion migration, defect accumulation, and degradation reactions often occur at the interface. In particular, the lower surface of the perovskite polycrystalline thin film exhibits severe stability problems. The crystal quality formed at this interface is typically poor, leading to the generation of high-density defects. These defects act as non-radiative recombination centers, hindering charge extraction and transport. Poor wettability of the transport layer beneath the interface further results in uneven nucleation during solution processing, producing interfacial pinholes and incomplete coverage. These defects become channels for ion migration and moisture intrusion. Furthermore, the weak interfacial adhesion between the perovskite and organic layers often leads to delamination under thermal and mechanical stress, ultimately causing device failure.

[0004] To address these issues, researchers have explored various strategies to enhance the stability of the underlying surface, including introducing interface modifiers, developing buffer layers, and optimizing the molecular structure of the transport layer beneath the interface. Among these, the development of multifunctional interface modifiers has attracted widespread attention. Based on molecular structure, interface modifiers can generally be divided into two main categories: small molecule-based and polymer-based. Small molecule modifiers can effectively passivate defects, but they suffer from thermal volatility and uneven distribution during crystallization, leading to compositing and instability. Linear polymers offer better mechanical adhesion and thermal stability, but typically cannot provide the high-density functional groups required to simultaneously achieve defect passivation and interfacial adhesion. Although significant progress has been made in interface engineering of perovskite underlying surfaces, most strategies focus only on a single direction: mechanical reinforcement or chemical passivation.

[0005] Therefore, developing a material that can simultaneously achieve defect passivation and enhance interfacial adhesion, and further developing a preparation method that can improve the stability of perovskite materials based on this material, are key scientific problems that urgently need to be solved in this field at present. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention aims to provide a star-shaped polymer, a perovskite solar cell with a star-shaped polymer modified layer, and a method for preparing the same. The star-shaped polymer can passivate defects on the lower surface of the perovskite while enhancing interfacial adhesion, effectively reducing the defect state density of the perovskite and improving the stability and photoelectric conversion efficiency of the perovskite solar cell.

[0007] In one aspect, the present invention provides a method for preparing a star-shaped polymer, the method comprising the following steps:

[0008] S1. Preparation of PMMA-CTA, specifically:

[0009] MMA monomer, reversible addition-fragmentation chain transfer polymerization reagent DTTCP, initiator AIBN, and solvent DMF are mixed and dissolved. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted in a nitrogen atmosphere at 60-80℃ for 9-11 hours to generate reactants. The reactants are precipitated, washed, and dried to obtain solid PMMA-CTA. The molar ratio of MMA monomer, reversible addition-fragmentation chain transfer polymerization reagent DTTCP, and initiator AIBN is 5000:10:1.

[0010] S2, the synthetic block copolymer PMMA-b-PDMAEMA, specifically:

[0011] The solid PMMA-CTA, DMAEMA monomer, and initiator AIBN prepared in step S1 are mixed and dissolved with solvent THF. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted at 60-80℃ for 9-11 hours in a nitrogen atmosphere to generate reactants. The reactants are precipitated, washed and dried to obtain solid PMMA-b-PDMAEMA. The molar ratio of the solid PMMA-CTA, DMAEMA monomer and initiator AIBN is 43:2500:8.

[0012] S3. The star-shaped polymer is prepared using PMMA-b-PDMAEMA as the arm, specifically as follows:

[0013] The solid PMMA-CTA prepared in step S1, the solid PMMA-b-PDMAEMA prepared in step S2, the initiator AIBN, the crosslinking agent EGDMA, the MMA monomer, and the solvent DMF are mixed and dissolved. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted in a nitrogen atmosphere at 60-80°C for 9-11 hours to generate reactants. The reactants are precipitated, washed, and dried to obtain the star polymer. The concentration of PMMA-CTA in the solution is controlled at 7-9 mmol, and the molar ratio of the solid PMMA-b-PDMAEMA, the initiator AIBN, the crosslinking agent EGDMA, and the MMA monomer is 52:15:1500:500.

[0014] In this invention, PMMA-CTA is a polymethyl methacrylate chain transfer agent (which is essentially a macromolecular chain transfer agent), MMA monomer is methyl methacrylate monomer, DTTCP is 4-cyano-4-(dodecyl trithiocarbonate)valerate, AIBN is azobisisobutyronitrile, DMF is N,N-dimethylformamide, PMMA-b-PDMAEMA is polymethyl methacrylate-b-polydimethylaminoethyl methacrylate, DMAEMA monomer is dimethylaminoethyl methacrylate monomer, THF is tetrahydrofuran, and EGDMA is ethylene glycol dimethacrylate (also known as ethylene glycol dimethacrylate).

[0015] Preferably, in steps S1 to S3 above, the prepared solution can be subjected to three cycles of liquid nitrogen freezing-vacuuming-thawing.

[0016] Preferably, in steps S1 to S3 above, the prepared solution can be transferred to a polymerization tube for corresponding processing and reaction, and the reaction is terminated by quenching with liquid nitrogen before precipitation.

[0017] Preferably, in step S1 above, the precipitation, washing and drying of the reactants are performed as follows: after terminating the reaction, the reaction solution is dropped into ice water to precipitate, the precipitate is washed with anhydrous methanol to remove unreacted substances, and then dried in a vacuum oven to obtain solid PMMA-CTA.

[0018] Preferably, in step S2 above, the precipitation, washing and drying of the reactants are specifically performed as follows: after terminating the reaction, the reaction solution is placed in ice-cold hexane to precipitate, the precipitate is washed with anhydrous methanol to remove unreacted substances, and then dried in a vacuum oven to obtain solid PMMA-b-PDMAEMA.

[0019] Preferably, in step S3 above, the reaction precipitation, washing and drying operation specifically involves: after terminating the reaction, dropping the reaction solution into ice water to precipitate, taking the precipitate and washing it with anhydrous methanol to remove unreacted substances, and then drying it in a vacuum oven to obtain the star-shaped polymer of the present invention.

[0020] It should be noted that in step S3 above, the MMA monomer has the function of "spacer monomer", which works with the crosslinking agent EGDMA to play a spacer role in preventing aggregation.

[0021] The star-shaped polymer prepared by the present invention is a polymer with a high number of arms and a multifunctional structure synthesized by the arm-first-core method. Its topological structure is "star-shaped", hence it is called "star-shaped polymer".

[0022] The three-dimensional structure prepared by this invention comprises multiple extended arm molecules and provides multiple Lewis base functional groups with a high density of multidentate coordination sites. These functional groups can effectively coordinate with electron-deficient defects on the lower surface of perovskite, thereby improving the crystallinity of perovskite, reducing defect density, and enhancing the adhesion of the lower surface of perovskite.

[0023] It is worth mentioning that the preparation method provided by the present invention can precisely control the type, molecular weight and dispersion of the "arms" on the polymer, and the star polymer prepared by this method exhibits excellent dispersibility, no obvious agglomeration, and relatively small particle size.

[0024] On the other hand, based on the above preparation method, the present invention further provides a star-shaped polymer.

[0025] Furthermore, based on the aforementioned star-shaped polymer, this invention further provides a method for preparing a perovskite solar cell with a star-shaped polymer modified layer, the method comprising the following steps:

[0026] S1. Prepare a conductive substrate and clean its surface;

[0027] S2. A hole transport layer is prepared on the surface of the conductive substrate;

[0028] S3. Dissolve the star polymer in DMF solvent to prepare a star polymer precursor solution, wherein the concentration of the star polymer precursor solution is 0.016–0.024 mg / mL;

[0029] S4. Coat the surface of the hole transport layer with the star-shaped polymer precursor solution to prepare a star-shaped polymer modified layer.

[0030] S5. Prepare a perovskite layer on the surface of the star-shaped polymer modified layer;

[0031] S6. An electron transport layer is prepared on the surface of the perovskite layer;

[0032] S7. Electrodes are prepared on the surface of the electron transport layer, thus obtaining the perovskite solar cell.

[0033] Preferably, in step S1 above, the conductive substrate can be FTO conductive glass, ITO conductive glass, or a flexible conductive substrate.

[0034] Preferably, in step S2 above, a precursor solution of hole transport material is coated on the surface of a conductive substrate, and a hole transport layer is formed after heat treatment.

[0035] More preferably, the aforementioned hole transport material can be PTAA or MeO-2PACz, and / or the coating method can include spin coating, spray coating and scraping coating, and / or the heat treatment specifically involves holding at 90-110°C for 10 minutes, which can be carried out in an air atmosphere.

[0036] In this invention, the above-mentioned PTAA is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and MeO-2PACz is 2-(3,6-dimethoxy-9H-carbazole-9-yl)butylphosphonic acid.

[0037] Preferably, in step S3 above, the star polymer can be first dissolved in DMF solvent to prepare a concentrated solution with a mass concentration of 0.8 to 1.2 mg / mL, and then DMF solvent can be added again to dilute the concentration of the concentrated solution to 1 / 50 of the original concentration, i.e., 0.016 to 0.024 mg / mL, thereby preparing the star polymer precursor solution.

[0038] It should be noted that in step S3 above, the DMF solvent is N,N-dimethylformamide.

[0039] Preferably, in step S5 above, a perovskite precursor solution is coated on the surface of the star-shaped polymer modified layer and then heat-treated to form a perovskite layer, which is essentially a perovskite active light-absorbing layer, and together with the star-shaped polymer modified layer, a perovskite thin film is constructed.

[0040] More preferably, the perovskite material used to prepare the above-mentioned perovskite precursor solution is a lead-based halide perovskite, such as FAPbI3, MAPbI3, CsPbI3, FA x MA 1-x PbI3, FA x MA 1-x PbI a Br 3-a FA x Cs y MA 1-x-yPbI3 or FA x Cs y MA 1-x-y PbI a Br 3-a .

[0041] More preferably, the method of coating the perovskite precursor solution and forming the perovskite layer by heat treatment can be: one-step solution spin coating annealing, two-step solution spin coating annealing, and vapor phase evaporation, etc., and / or the heat treatment is specifically: holding at 100-120°C for 15-20 minutes, which can be carried out in an air atmosphere.

[0042] Preferably, in step S6 above, the method for forming an electron transport layer on the surface of the perovskite layer may include deposition methods such as evaporation or sputtering, and / or the electron transport material used to prepare the electron transport layer may be C 60 With BCP.

[0043] In this invention, the above-mentioned C 60 It is a fullerene, and the above BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.

[0044] Preferably, in step S7 above, the method of forming an electrode on the surface of the electron transport layer includes deposition methods such as vapor deposition and sputtering, and / or the electrode can be a metal electrode or a carbon electrode, and the material for preparing the metal electrode can be gold, silver, copper, aluminum or their alloys.

[0045] Furthermore, based on the above preparation method, the present invention provides a perovskite solar cell with a star-shaped polymer modification layer, the perovskite solar cell comprising a conductive substrate, a hole transport layer, a star-shaped polymer modification layer, a perovskite layer, an electron transport layer and an electrode stacked sequentially.

[0046] Preferably, the hole transport layer has a thickness of 3–30 nm, and / or the star polymer modification layer has a thickness of 1–2 nm, and / or the perovskite layer has a thickness of 400–800 nm, and / or the electron transport layer has a thickness of 15–30 nm, and / or the electrode has a thickness of 80–200 nm.

[0047] Compared to existing technologies, in this invention, the perovskite layer is prepared on the surface of a star-shaped polymer-modified layer. The star-shaped polymer effectively passivates prevalent electron-deficient defects, such as uncoordinated lead ions and iodine vacancies, through multiple Lewis base sites on its arms, such as carbonyl and tertiary amine groups. Due to the significant passivation effect of the star-shaped polymer, defects on the lower surface of the perovskite layer are effectively passivated, and the interfacial adhesion is significantly enhanced. Experiments show that after modification with the star-shaped polymer, the fracture strength of the lower surface increases from 0.13 MPa to 1.66 MPa. Simultaneously, the multidentate coordination provided by the star-shaped polymer facilitates strong adhesion with the underlying hole transport layer, thereby enhancing the mechanical stability of the flexible perovskite solar cell device. Therefore, the perovskite solar cell device with a star-shaped polymer modified layer provided by this invention can achieve significant improvements in photoelectric parameters such as open-circuit voltage, fill factor, and photoelectric conversion efficiency. Furthermore, the mechanical stability in flexible devices is also greatly improved. Both stability and photoelectric conversion efficiency are effectively enhanced, with the photoelectric conversion efficiency reaching 26.33%. The unencapsulated flexible perovskite solar cell device with a star-shaped polymer modified lower surface can still maintain more than 90% of its initial efficiency after 3000 bending cycles under environmental conditions (25°C, 20% RH) with a bending radius of 6 mm, demonstrating excellent mechanical stability. Attached Figure Description

[0048] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings. In the drawings, unless otherwise specified, the same reference numerals throughout the various figures denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in the present invention to provide a further understanding of the invention, constitute a part of this application, and should not be considered as limiting the scope of the invention. Wherein:

[0049] Figure 1 This is a synthetic route diagram of the star-shaped polymer provided by the present invention;

[0050] Figure 2 This is a schematic diagram of the structure of the perovskite solar cell provided by the present invention;

[0051] Figure 3 Box plots showing the photoelectric conversion performance of the perovskite solar cell provided by this invention and a reference perovskite solar cell;

[0052] Figure 4 A bar chart showing the calculated fracture strength values ​​of the perovskite thin film provided by this invention and a reference perovskite thin film;

[0053] Figure 5The figure shows the mechanical bending cycle test results of the flexible perovskite solar cell provided by the present invention and a reference flexible perovskite solar cell. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and should not be construed as limiting the invention.

[0055] To effectively reduce the defect state density of perovskite and improve the stability and photoelectric conversion efficiency of perovskite solar cells, this invention provides a star-shaped polymer, the preparation method of which includes the following steps:

[0056] S1. Preparation of PMMA-CTA, specifically:

[0057] Weigh 6g of MMA monomer, 48mg of reversible addition-fragmentation chain transfer polymerization reagent DTTCP, 2mg of initiator AIBN and 30g of solvent DMF, mix and dissolve them, and transfer the prepared solution to a polymerization tube. Then, it is subjected to three cycles of liquid nitrogen freezing-vacuuming-thawing. Nitrogen gas is introduced into the polymerization tube to maintain an inert gas atmosphere. After that, the polymerization tube is thawed and reacted at 70℃ for 10h. After the reaction is completed, the cap is opened by liquid nitrogen quenching to terminate the reaction. Then, the reaction solution is dropped into ice water, and the precipitate is washed with anhydrous methanol to remove unreacted substances. The precipitate is then dried in a vacuum oven to obtain solid PMMA-CTA.

[0058] S2, the synthetic block copolymer PMMA-b-PDMAEMA, specifically:

[0059] Weigh 1.29g of solid PMMA-CTA prepared in step S1, 0.78g of DMAEMA monomer, 2.6mg of initiator AIBN, and 10g of solvent THF, mix and dissolve them, and transfer the prepared solution to a polymerization tube. Then, it is subjected to three cycles of liquid nitrogen freezing-vacuuming-thawing, and nitrogen gas is introduced into the polymerization tube to maintain an inert gas atmosphere. After that, the polymerization tube is thawed and reacted at 70℃ for 10h. After the reaction is completed, the tube is quenched with liquid nitrogen and the cap is opened to terminate the reaction. Then, the tube is precipitated in ice-cold hexane. The precipitate is washed with anhydrous methanol to remove unreacted substances and dried in a vacuum oven to obtain solid PMMA-b-PDMAEMA.

[0060] S3. Star-shaped polymers were prepared using PMMA-b-PDMAEMA as the arms, specifically as follows:

[0061] Weigh 0.77g of solid PMMA-CTA prepared in step S1, 1g of solid PMMA-b-PDMAEMA prepared in step S2, 2.55mg of initiator AIBN, 0.3g of crosslinking agent EGDMA, 0.05g of MMA monomer, and 6.5g of solvent DMF and mix and dissolve them (the concentration of PMMA-CTA in the solution after dissolution is 8mmol). The prepared solution is then transferred to a polymerization tube and subjected to three cycles of liquid nitrogen freezing-vacuuming-thawing. Nitrogen gas is introduced into the polymerization tube to maintain an inert gas atmosphere. The polymerization tube is then thawed and reacted at 70°C for 10h. After the reaction is completed, the tube is quenched with liquid nitrogen to terminate the reaction. The reaction solution is then dropped into ice water, and the precipitate is washed with anhydrous methanol to remove unreacted substances. The precipitate is then dried in a vacuum oven to obtain the star-shaped polymer of the present invention.

[0062] The star-shaped polymer prepared by the present invention is a polymer with a high number of arms and a multifunctional structure synthesized by the arm-first-core method. Its topological structure is "star-shaped", hence it is called "star-shaped polymer".

[0063] The preparation method provided by the present invention can precisely control the type, molecular weight and dispersion of the "arms" on the polymer, and the star polymer prepared by the method exhibits excellent dispersibility, no obvious agglomeration, and relatively small particle size.

[0064] In this embodiment, based on the prepared star-shaped polymer, a perovskite solar cell with a star-shaped polymer modified layer is further prepared. The preparation method includes the following steps:

[0065] S1. Prepare FTO conductive glass or flexible conductive substrate as the conductive substrate, and clean the surface of the conductive substrate;

[0066] S2. Weigh 1 mg of hole transport material MeO-2PACz and mix it with 2 mL of isopropanol solvent. Stir at 15-30℃ for 5-10 h to prepare a MeO-2PACz precursor solution with a mass concentration of 0.5 mg / mL. Then take 80 μL of the MeO-2PACz precursor solution and coat it on the surface of a conductive substrate. Rotate dry at 3000 rpm for 30 s and keep at 100℃ for 10 minutes to prepare a hole transport layer.

[0067] S3. Dissolve the prepared star polymer in DMF solvent to prepare a star polymer precursor solution with a mass concentration of 0.02 mg / mL;

[0068] S4. Take 80 μL of the above star polymer precursor solution and coat it on the surface of the hole transport layer. Rotate dry at 5000 rpm for 30 s to prepare the star polymer modified layer.

[0069] S5, Specific Selection of Perovskite Materials (FA) 0.98 MA 0.02 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.02 3. Specifically, lead iodide, lead bromide, cesium iodide, iodomidine, and methyl bromide are mixed according to (FA... 0.98 MA 0.02 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.02 1.73 mol of chemical formula 3 was weighed and dissolved in a mixed solvent of 0.833 mL DMF and 0.167 mL DMSO (dimethyl sulfoxide). The mixture was stirred for 5 h to prepare a perovskite precursor solution. Then, 100 μL of the perovskite precursor solution was spread onto the surface of the star-shaped polymer modified layer. The mixture was continuously spin-coated at 1000 rpm for 10 s and 5000 rpm for 40 s. During the 37th to 39th s of the total 50 s spin-coating process, 200 μL of chlorobenzene was dropped onto the film surface. The film was then annealed at 110 °C for 20 min under a nitrogen atmosphere to prepare a perovskite layer.

[0070] S6, sequentially on the surface of the perovskite layer... C rate evaporation 60 Electron transport layer was prepared with BCP;

[0071] S7, on the surface of the electron transport layer... The electrode is prepared by evaporating Ag (silver) at a certain rate, thus obtaining the perovskite solar cell of the present invention.

[0072] In this embodiment, the perovskite solar cell with a star-shaped polymer-modified layer prepared by the above method includes a conductive substrate 101, a hole transport layer 102, a star-shaped polymer-modified layer 103, a perovskite layer 104, an electron transport layer 105, and an electrode 106, which are sequentially stacked. The conductive substrate 101, hole transport layer 102, star-shaped polymer-modified layer 103, perovskite layer 104, electron transport layer 105, and electrode 106 are prepared according to steps S1-S7 described above.

[0073] In this embodiment, the hole transport layer 102 has a thickness of 3 nm, the star polymer modification layer 103 has a thickness of 2 nm, the perovskite layer 104 has a thickness of 600 nm, the electron transport layer 105 has a thickness of 26 nm, and the electrode 106 has a thickness of 200 nm.

[0074] like Figure 1As shown, the star polymer is synthesized by cross-linking arm molecules. The topological structure of the star polymer is star-shaped, containing multiple extended arm molecules. The arm molecules have multiple Lewis base functional groups, and the Lewis base functional groups have multidentate coordination sites.

[0075] like Figure 2 As shown, the structure of the perovskite solar cell with a star-shaped polymer-modified layer prepared by the above method is the cell structure of the experimental group.

[0076] like Figure 3 As shown, the average photoelectric conversion efficiency of the reference group without the star-shaped polymer modification layer 103 was 24.5%, while the average photoelectric conversion efficiency of the experimental group increased to 25.8% after the star-shaped polymer modification. This indicates that the star-shaped polymer modification layer significantly improved the photoelectric performance of the perovskite solar cell through defect passivation.

[0077] like Figure 4 As shown, the interfacial fracture strength between the hole transport layer 102 and the perovskite layer 104 was tested. The fracture strength of the reference group was only 0.13 MPa, while the fracture strength of the experimental group with the star-shaped polymer modification layer 103 increased by 10 times, significantly increasing to 1.66 MPa, indicating that the interfacial adhesion between the hole transport layer 102 and the perovskite layer 104 was greatly enhanced.

[0078] like Figure 5 As shown, the bending stability of unencapsulated reference and experimental flexible batteries fabricated on a flexible conductive substrate was tested at 20°C and 20% RH, with a bending radius R = 6 mm. After 500 bends, the photoelectric conversion efficiency of the reference battery decreased by more than 20%, while the photoelectric conversion efficiency of the experimental battery decreased by less than 10% after 3000 bends. This indicates that the interfacial adhesion of the star-shaped polymer-modified experimental group is enhanced, thus improving the bending stability of the battery.

[0079] It should be noted that, unless otherwise specified in the examples, the conditions shall be performed in accordance with conventional conditions or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially.

[0080] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a star polymer, characterized by, The preparation method includes the following steps: S1. Preparation of PMMA-CTA, specifically: MMA monomer, reversible addition-fragmentation chain transfer polymerization reagent DTTCP, initiator AIBN, and solvent DMF are mixed and dissolved. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted in a nitrogen atmosphere at 60-80℃ for 9-11 hours to generate reactants. The reactants are precipitated, washed, and dried to obtain solid PMMA-CTA. The molar ratio of MMA monomer, reversible addition-fragmentation chain transfer polymerization reagent DTTCP, and initiator AIBN is 5000:10:

1. S2, Synthetic block copolymer PMMA-b-PDMAEMA, specifically: The solid PMMA-CTA, DMAEMA monomer, and initiator AIBN prepared in step S1 are mixed and dissolved with solvent THF. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted at 60-80℃ for 9-11 hours in a nitrogen atmosphere to generate reactants. The reactants are precipitated, washed and dried to obtain solid PMMA-b-PDMAEMA. The molar ratio of the solid PMMA-CTA, DMAEMA monomer and initiator AIBN is 43:2500:

8. S3. The star-shaped polymer is prepared using the block copolymer PMMA-b-PDMAEMA as the arm, specifically as follows: The solid PMMA-CTA prepared in step S1, the solid PMMA-b-PDMAEMA prepared in step S2, the initiator AIBN, the crosslinking agent EGDMA, the MMA monomer, and the solvent DMF are mixed and dissolved. The prepared solution is subjected to liquid nitrogen freezing-vacuuming-thawing cycle treatment, and then reacted at 60-80°C for 9-11 hours in a nitrogen atmosphere to generate reactants. The reactants are precipitated, washed, and dried to obtain the star polymer. The amount of PMMA-CTA in the solution is controlled at 7-9 mmol, and the molar ratio of the solid PMMA-b-PDMAEMA, the initiator AIBN, the crosslinking agent EGDMA, and the MMA monomer is 52:15:1500:

500.

2. The preparation method according to claim 1, characterized in that, In steps S1 to S3, the prepared solution undergoes three cycles of liquid nitrogen freezing-vacuuming-thawing.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the precipitation and washing of the reactants specifically involves: dropping the reaction solution into ice water to precipitate, and washing the precipitate with anhydrous methanol to remove unreacted substances; and / or, in step S2, the precipitation and washing of the reactants specifically involves: placing the reaction solution in ice-cold hexane to precipitate, and washing the precipitate with anhydrous methanol to remove unreacted substances; and / or, in step S3, the reaction solution is dropped into ice water to precipitate, and the precipitate is washed with anhydrous methanol to remove unreacted substances.

4. The preparation method according to any one of claims 1 or 2, characterized in that, In steps S1 to S3, the prepared solution is transferred to a polymerization tube for liquid nitrogen freezing-vacuuming-thawing cycle treatment. After the reactants are generated, the polymerization tube is quenched with liquid nitrogen and the cap is opened to terminate the reaction.

5. A star-shaped polymer prepared according to the preparation method according to any one of claims 1-4, characterized in that, The star polymer has a star-shaped topology and contains multiple extended arm molecules, each arm molecule having multiple Lewis base functional groups with multidentate coordination sites.

6. The star-shaped polymer according to claim 5, characterized in that, The Lewis base functional groups include carbonyl groups and / or tertiary amine groups.

7. A method for preparing a perovskite solar cell with a star-shaped polymer-modified layer, characterized in that, The preparation method includes the following steps: S1. Prepare a conductive substrate and clean the surface of the conductive substrate; S2. A hole transport layer is prepared on the surface of the conductive substrate; S3. Dissolve the star polymer in DMF solvent to prepare a star polymer precursor solution, wherein the concentration of the star polymer precursor solution is 0.016-0.024 mg / mL, wherein the star polymer is a star polymer prepared according to any one of claims 1-4 or a star polymer according to claim 5 or 6. S4. Coat the surface of the hole transport layer with the star-shaped polymer precursor solution to prepare the star-shaped polymer modified layer; S5. Prepare a perovskite layer on the surface of the star-shaped polymer modified layer; S6. An electron transport layer is prepared on the surface of the perovskite layer; S7. Electrodes are prepared on the surface of the electron transport layer, thus obtaining the perovskite solar cell.

8. The preparation method according to claim 7, characterized in that, In step S3, the star polymer is first dissolved in DMF solvent to prepare a concentrated solution with a mass concentration of 0.8 to 1.2 mg / mL. Then, DMF solvent is added again to dilute the concentration of the concentrated solution to 1 / 50 of the original concentration, i.e., 0.016 to 0.024 mg / mL, thereby preparing the star polymer precursor solution.

9. A perovskite solar cell prepared according to the preparation method according to any one of claims 7-8, characterized in that, The perovskite solar cell includes a conductive substrate (101), a hole transport layer (102), a star-shaped polymer modification layer (103), a perovskite layer (104), an electron transport layer (105), and an electrode (106) stacked sequentially.

10. The perovskite solar cell according to claim 9, characterized in that, Lewis base functional groups on the arm molecules of the star polymer in the star polymer-modified layer (103) are coordinated with electron-deficient defects on the lower surface of the perovskite layer (104).

Images