A poly(methyl methacrylate) passivated two-dimensional dj-type perovskite thin film, preparation and application thereof

Abstract

This invention relates to a polymethyl methacrylate (PMMA) passivated two-dimensional DJ-type perovskite thin film, its preparation, and its application. By adding a PMMA-containing antisolvent during the DJ perovskite preparation process, DJ perovskite materials with effectively improved film quality and nonlinear optical response can be obtained. Compared with existing technologies, in this invention, the passivating agent PMMA is directly added to the antisolvent, which can directly control the growth of DJ perovskite polycrystalline thin films, thereby effectively passivating defects in the film, increasing grain size, and enhancing nonlinear optical absorption performance. This has important reference value for the subsequent development of perovskite thin film materials with nonlinear optical activity under visible and near-infrared femtosecond pulsed lasers.

Description

Technical Field

[0001] This invention belongs to the fields of inorganic functional composite materials and high-power laser materials, and relates to a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film and its preparation and application. Background Technology

[0002] Organometal halide perovskites have attracted widespread attention due to their unique structure and excellent photoelectric properties, and have shown great potential in solar cells, light-emitting devices, and lasers. Two-dimensional organometal halide perovskites are created by introducing large-sized organic cations into bulk perovskites, thereby "cutting" the perovskite into two-dimensional materials along the crystal plane. Compared with bulk perovskites, two-dimensional perovskites have richer structural scalability, more easily tunable photoelectric properties, and better stability. Currently, the two-dimensional organometal halide perovskites mainly studied are Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) type perovskites based on the (100) crystal plane. In RP type perovskites, the introduced organic cations are monovalent. Therefore, adjacent inorganic metal halide octahedral layers are separated by two layers of organic cations, and van der Waals interstices are formed within the organic layers. In addition, due to the influence of steric hindrance, adjacent RP perovskite cells will be offset. In DJ-type perovskites, divalent organic cations are introduced. These divalent cations are directly connected to the adjacent inorganic layers by hydrogen bonds, thus eliminating van der Waals gaps within the organic layers and improving structural rigidity and charge transport capabilities.

[0003] Due to the difference in dielectric constant between the introduced organic layer and the separated inorganic layer, two-dimensional organometal halide perovskites form a "multiple quantum well" structure. Within this structure, the generated charge carriers are confined within the inorganic layer, resulting in strong quantum and dielectric confinement effects, enhancing light-matter interactions, which is highly beneficial for the generation of nonlinear optical responses. Recent studies have shown that RP-type perovskites possess excellent nonlinear optical responses. However, research on the nonlinear optical absorption properties of DJ perovskite films with higher structural rigidity and charge transport performance is still in its early stages. Furthermore, grain boundary defects in DJ perovskite films can lead to nonradiative recombination, altering band arrangement and even causing cell degradation, limiting the practical application prospects of DJ perovskite films. Therefore, it is necessary to develop a method to improve the quality and nonlinear optical absorption response of DJ perovskite films. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a polymethyl methacrylate passivated two-dimensional DJ perovskite film, its preparation and application, and the prepared passivated DJ perovskite exhibits excellent film quality and nonlinear optical absorption response.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film, comprising the following steps:

[0007] (1) Prepare a DJ perovskite precursor solution containing PbI2 and organic ammonium salt;

[0008] (2) Prepare an antisolvent solution containing PMMA;

[0009] (3) Perovskite thin films were prepared by a two-step spin coating method. First, the DJ perovskite precursor solution was spin coated, then the antisolvent solution was added, and finally the film was annealed to obtain the target product.

[0010] Furthermore, in step (1), the organic ammonium salt is one or a mixture of several of 1,4-butanediamine hydroiodide (BDA), 4-(aminomethyl)piperidine hydroiodide (AMP), and 1,4-p-phenylenediamine hydroiodide (PDMA).

[0011] Furthermore, the molar ratio of PbI2 to the organic ammonium salt is 1:1, and the concentration of the organic ammonium salt in the DJ perovskite precursor solution is 0.3–0.5 mol / L, preferably 0.4 mol / L.

[0012] Furthermore, the solvent used in the DJ perovskite precursor solution is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3-5:1, with the preferred volume ratio being 4:1.

[0013] Furthermore, the antisolvent used in the antisolvent solution is chlorobenzene.

[0014] Furthermore, in the antisolvent solution, the concentration of PMMA is 0 to 4 mg / mL, and is not 0. Specifically, it can be 1 to 4 mg / mL, more preferably 1 to 2 mg / mL. For example, it can be 1 mg / mL, 2 mg / mL or 4 mg / mL.

[0015] Furthermore, the coating amount of the DJ perovskite precursor solution is 50-70 μL / 4cm. 2 Preferably 60μL / 4cm 2 ;

[0016] The coating amount of the antisolvent solution is 180-220 μL / 4cm. 2 Preferably 200 μL / 4cm 2 .

[0017] Furthermore, the two-step spin-coating process is as follows: first, spin at 1000 rpm for 10 seconds, then spin at 4000 rpm for 40 seconds. The antisolvent solution is added 25 seconds after spin-coating. That is, the added DJ perovskite precursor solution is coated onto the substrate in the first 25 seconds, and then the antisolvent solution is spin-coated onto the DJ perovskite film coated on the substrate to promote polycrystalline formation.

[0018] Furthermore, the two-step spin coating process is carried out on a glass substrate, which is first ultrasonically treated with deionized water, ethanol, and isopropanol for 15 minutes in sequence, and then treated with oxygen plasma before use.

[0019] Furthermore, the annealing temperature is 90-110℃, preferably 100℃, and the time is 8-12 minutes, preferably 10 minutes.

[0020] In a second aspect, the present invention provides a polymethyl methacrylate passivated two-dimensional DJ-type perovskite film, prepared using any of the preparation methods described above. The passivated DJ-type perovskite film exhibits better crystallinity, higher X-ray diffraction intensity, larger grain size, and fewer pinhole and pore defects compared to the unpassivated film. Increased fluorescence intensity and lifetime indicate a lower defect content. Furthermore, the passivated DJ-type perovskite film demonstrates higher stability.

[0021] In a third aspect, the present invention provides an application of a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film in the field of femtosecond visible and near-infrared lasers.

[0022] This invention provides PMMA passivated two-dimensional DJ-type perovskite thin films, which exhibit excellent nonlinear optical absorption under excitation by 800 and 515 nm femtosecond laser pulses. Under 800 nm excitation, the passivated (BDA)PbI4, (AMP)PbI4, and (PDMA)PbI4 films all show enhanced two-photon absorption response due to quantum confinement and dielectric confinement effects, while under 515 nm excitation, all three DJ perovskite films exhibit excellent saturation absorption response.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] I. PMMA passivated DJ perovskite films exhibit better crystallinity, fewer defects, and higher stability compared to unpassivated films.

[0025] II. PMMA passivated DJ perovskite films exhibit excellent fluorescence response due to the reduction of defects.

[0026] III. Under irradiation with 800 nm and 515 nm femtosecond lasers, the PMMA passivated DJ perovskite film exhibits enhanced nonlinear optical absorption compared to the unpassivated film. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the synthesis route for the PMMA passivated DJ perovskite thin film prepared in this invention.

[0028] Figure 2 The X-ray diffraction pattern of the PMMA passivated DJ perovskite thin film prepared in Example 1 of this invention;

[0029] Figure 3 This is a scanning electron microscope image of the PMMA passivated DJ perovskite thin film prepared in Example 1 of the present invention;

[0030] Figure 4 The absorption spectrum of the PMMA passivated DJ perovskite film prepared in Example 1 of this invention is shown.

[0031] Figure 5 The fluorescence spectrum and fluorescence lifetime spectrum of the PMMA-passivated DJ perovskite thin film prepared in Example 1 of the present invention are shown.

[0032] Figure 6 The nonlinear optical absorption spectra of the PMMA-passivated DJ perovskite thin film prepared in Example 1 of the present invention under 800 and 515 nm femtosecond pulses.

[0033] Figure 7 This is a water contact angle diagram of the PMMA-passivated DJ perovskite thin film prepared in Example 1 of the present invention;

[0034] Figure 8 The image shows a comparison of X-ray diffraction patterns of the PMMA-passivated DJ perovskite film prepared in Example 1 of this invention after being placed in air for 7 days. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] In the following examples, the organic ammonium salts, PbI2, polymethyl methacrylate, and solvents used in this invention are all commercial products from Anaiji Chemical Reagent Co., Ltd. The spin coater was a KW-4A spin coater from the Institute of Microelectronics, Chinese Academy of Sciences.

[0037] Example 1:

[0038] Preparation of PMMA passivated DJ perovskite thin films (see...) Figure 1):

[0039] First, a perovskite precursor solution was prepared: 185 mg of PbI2 and corresponding molar concentrations of organic ammonium salts (BDA: 138 mg, AMP: 148 mg, PDMA: 157 mg) were weighed into a mixed solution consisting of 0.8 mL of DMF and 0.2 mL of DMSO, and the solution was heated to 80 °C and stirred for 2 h.

[0040] Next, chlorobenzene solutions of PMMA with concentrations of 0, 1, 2, and 4 mg / mL were prepared as antisolvents.

[0041] Then, the glass substrate was processed by ultrasonically treating the 2cm×2cm glass substrate in deionized water, ethanol, and isopropanol for 15 minutes in sequence, and then dried and treated with oxygen plasma for 15 minutes before use.

[0042] Finally, the prepared substrate was placed on a spin coater, and 60 μL of perovskite precursor solution was added. Spin-coating was performed at 1000 rpm for 10 seconds, followed by 4000 rpm for 40 seconds. 200 μL of antisolvent was added 25 seconds after the spin-coating began. After spin-coating, the substrate was annealed at 100℃ for 10 minutes. For easy labeling, the DJ perovskite film samples XPbI4 with antisolvent concentrations of 0, 1, 2, and 4 mg / mL PMMA were named X-0, X-1, X-2, and X-4, respectively, where X = BDA, AMP, and PDMA.

[0043] Figure 2 The X-ray diffraction patterns of PMMA-passivated DJ perovskite films are shown. The (001) plane diffraction peak of (BDA)PbI4 appears at 2θ = 8.6°, indicating that the passivation of (BDA)PbI4 film shows an increase in the intensity of the (001) plane diffraction peak compared to the unpassivated BDA-0 film, with BDA-1 exhibiting the highest diffraction intensity. The (100) and (001) plane diffraction peaks of (AMP)PbI4 appear at 2θ = 14.6° and 8.8°, respectively, indicating the presence of grains with different crystal orientations. Considering the combined diffraction peak intensities of the two crystal planes, AMP-2 exhibits the best crystallinity. Similar to (AMP)PbI4, (PDMA)PbI4 exhibits diffraction peaks at 2θ = 14.6° and 7.2° on its (100) and (001) crystal planes, respectively. PDMA-2 also shows the highest diffraction peaks. This indicates that a PMMA concentration of 1 mg / mL is most suitable for (BDA)PbI4, while a PMMA concentration of 2 mg / mL is better for both (PDMA)PbI4 and (AMP)PbI4.

[0044] Figure 3Scanning electron microscopy (SEM) images of PMMA-passivated DJ perovskite films are shown. All three perovskites exhibit relatively uniform planar surfaces, but low-concentration PMMA passivation effectively reduces the distribution of pinhole defects and increases grain size. High-concentration PMMA, however, causes a simultaneous increase in grain size and pore area, indicating that adding higher concentrations of PMMA is detrimental to film quality. Overall, BDA-1, AMP-2, and PDMA-2 show relatively better film quality, consistent with the X-ray diffraction pattern conclusions.

[0045] Figure 4 The absorption spectra of PMMA-passivated DJ perovskite films are shown. The exciton absorption peaks of (BDA)PbI4, (PDMA)PbI4, and (AMP)PbI4 are located at 506, 541, and 520 nm, respectively. The absorption spectra of the passivated perovskite films are generally similar to those of the unpassivated films, but the band-edge absorption intensity caused by defects is significantly reduced in the spectra of films with low concentrations of PMMA passivation. In addition, the addition of PMMA also caused an enhancement of exciton absorption in (AMP)PbI4 and (PDMA)PbI4 films, which may be related to the increase in grain size and the reduction of defects.

[0046] Figure 5 The fluorescence spectra (ac) and fluorescence lifetime spectra (df) of the PMMA-passivated DJ perovskite films are shown. The exciton radiative recombination fluorescence peaks of (BDA)PbI4, (PDMA)PbI4, and (AMP)PbI4 are located at 506, 541, and 520 nm, respectively, corresponding to exciton optical band gaps of 2.45, 2.29, and 2.38 eV. Due to the reduced defect content, the nonradiative recombination caused by defects is weakened, resulting in higher fluorescence intensity in the passivated perovskite films. For (BDA)PbI4, the fluorescence intensity order is BDA-1>BDA-2>BDA-4>BDA-0, while for (AMP)PbI4, the order is AMP-2>AMP-1>AMP-4>AMP-0, and for (PDMA)PbI4, the order is PDMA-2>PDMA-4>PDMA-1>PDMA-0. Correspondingly, the passivated perovskite film exhibited an extended fluorescence lifetime, corroborating the effective suppression of non-radiative recombination.

[0047] Figure 6 The nonlinear optical absorption spectra of PMMA-passivated DJ perovskite films under femtosecond pulses at 800 nm (ac) and 515 nm (df) are shown. Under the 800 nm femtosecond laser, (BDA)PbI4, (PDMA)PbI4, and (AMP)PbI4 all exhibit two-photon absorption responses. The nonlinear absorption coefficients β of BDA-0, AMP-0, and PDMA-0 are also shown. eff 82.8cm GW-1 100.6cm GW -1 and 38.4cm GW -1 The passivated films exhibit stronger two-photon absorption, which can be attributed to improved film crystallinity and reduced defects. Among them, BDA-1, AMP-2, and PDMA-2 have the largest β... eff The values ​​are 242.8 cm GW. -1 327.9cmGW -1 and 183.2cm GW -1 At 515 nm, (BDA)PbI4, (AMP)PbI4, and (PDMA)PbI4 all exhibit saturated absorption responses. This is because 515 nm is in the resonant absorption region of these perovskite films, and high-intensity laser irradiation induces the Pauli blockade effect. The β-response of BDA-0, AMP-0, and PDMA-0... eff They are -97.0cm GW respectively -1 -459.3cm GW -1 and -309.6cm GW -1 The passivated films also exhibited enhanced saturation absorption, with BDA-1, AMP-2, and PDMA-4 showing particularly strong β-absorption. eff The absolute value of β is the largest. eff They are -242.6cm GW respectively -1 -1002.3cm GW -1 and -981.6cm GW -1 The above results indicate that appropriate concentrations of PMMA passivation can effectively enhance the nonlinear absorption response of various DJ perovskite films.

[0048] Figure 7 The water contact angles of PMMA passivated DJ perovskite films are shown. Figure (ac) shows the water contact angles of the unpassivated films, with BDA-0, AMP-0, and PDMA-0 having water contact angles of 43.7°, 65.6°, and 23.0°, respectively. Figure (df) shows the contact angles of films with added PMMA at a concentration of 2 mg / mL. The water contact angles of BDA-2, AMP-2, and PDMA-2 are 71.8°, 76.1°, and 38.9°, respectively. A significant increase in water contact angles can be observed, which is directly related to the good hydrophobicity of PMMA. The increased hydrophobicity can reduce perovskite grain decomposition caused by water vapor permeation, thereby improving stability.

[0049] Figure 8The X-ray diffraction patterns of PMMA-passivated DJ perovskite films after 7 days of exposure to air are shown. It can be observed that the diffraction peak intensities of the unpassivated films all show a significant decrease, and PDMA-0 also exhibits diffraction peaks related to impurity hydration phases. In contrast, the decrease in diffraction peak intensity of the passivated films is relatively smaller, verifying that PMMA passivation treatment can effectively improve the stability of DJ perovskite films.

[0050] Based on the above results, it can be confirmed that the introduction of PMMA in this invention can effectively improve the quality, nonlinear optical absorption response and stability of DJ perovskite films, providing a reference for the preparation and application of two-dimensional perovskite films in the future.

[0051] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film, characterized in that, Includes the following steps: (1) Prepare a DJ perovskite precursor solution containing PbI2 and organic ammonium salt; (2) Prepare an antisolvent solution containing PMMA; (3) Perovskite thin films were prepared by a two-step spin coating method. First, the DJ perovskite precursor solution was spin coated, then the antisolvent solution was added, and finally the film was annealed to obtain the target product.

2. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, In step (1), the organic ammonium salt is one or a mixture of several of 1,4-butanediamine hydroiodate, 4-(aminomethyl)piperidine hydroiodate and 1,4-p-phenylenediamine hydroiodate.

3. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, The molar ratio of PbI2 to the organic ammonium salt is 1:1, and the concentration of the organic ammonium salt in the DJ perovskite precursor solution is 0.3–0.5 mol / L.

4. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, The solvent used in the DJ perovskite precursor solution is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3-5:

1.

5. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, In the antisolvent solution, the antisolvent used is chlorobenzene; In the antisolvent solution, the concentration of PMMA is 0–4 mg / mL, and is not 0.

6. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, The two-step spin coating process is as follows: first, spin at 1000 rpm for 10 seconds, then spin at 4000 rpm for 40 seconds. The antisolvent solution is added 25 seconds after the start of spin coating.

7. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, The coating amount of the DJ perovskite precursor solution is 50-70 μL / 4cm. 2 ; The coating amount of the antisolvent solution is 180-220 μL / 4cm. 2 .

8. The method for preparing a polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film according to claim 1, characterized in that, The annealing temperature is 90-110℃ and the time is 8-12 minutes.

9. A polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the polymethyl methacrylate passivated two-dimensional DJ-type perovskite thin film as described in claim 9 in the field of femtosecond visible and near-infrared lasers.

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