High-precision patterning method for perovskite thin film and application thereof

Abstract

The application provides a high-precision patterning method of a perovskite film, and the method comprises the following steps: S1, adding a polymer and a perovskite precursor into a solvent, and heating and stirring to obtain a perovskite precursor solution; S2, coating the perovskite precursor solution onto a substrate to obtain a perovskite precursor film; S3, annealing the perovskite precursor film to obtain a perovskite film; and S4, processing the perovskite film by using a femtosecond laser direct writing technology to obtain a high-precision patterned perovskite film. By using the ultrahigh peak intensity of the femtosecond laser and the digital processing characteristics of the laser direct writing system, high-precision laser ablation patterning can be realized on a specified area of the perovskite film, and the minimum feature size can reach 80 nm, which is about λ / 10 of the exposure source, and the optical diffraction limit is broken, which cannot be realized by other patterning technologies.

Description

Technical Field

[0001] This invention relates to the field of patterning technology, specifically to a high-precision patterning method and application for perovskite thin films. Background Technology

[0002] Metal halide perovskites are considered ideal candidate materials for next-generation optoelectronic devices due to their excellent optoelectronic properties and cost-effectiveness. They have achieved remarkable research results in fields such as solar cells, light-emitting diodes, photodetectors, and advanced anti-counterfeiting, and are gradually being applied. As a fluorescent material, perovskites possess tunable emission wavelengths, high photoluminescence quantum yields, high color purity, and low-cost processing capabilities, making them ideal for information storage, encryption, and anti-counterfeiting applications.

[0003] Patterning and arraying are crucial steps in fabricating perovskite materials into optoelectronic devices. By constructing ordered patterns and writing specific information, special properties can be imparted to the material, such as integrated photodetector arrays for image sensing and LED arrays for displays. The ability to fabricate high-precision, high-quality patterned thin films determines whether corresponding high-quality applications can be realized. Therefore, improving the quality of patterned thin films is a key step in improving device performance and expanding the application fields of perovskite materials. Considering the integration and miniaturization of system applications, micro / nanoscale patterned perovskites can store more information within the same size, promoting applications with higher integration. Therefore, developing a new technology to stably achieve high-resolution patterned perovskites is critical. Inkjet printing is a maskless patterning technique that has been extensively studied for achieving high-quality patterned perovskite thin films. However, due to the influence of nozzle size and ink rheological properties, the pixel size is limited to within 5 μm. Photolithography is a precise perovskite patterning technique, but when the material is exposed to traditional photolithography solvents, it negatively affects its performance, severely limiting the development of perovskite-based devices. Nanoimprinting technology has advantages such as high precision, high efficiency and low cost, and is the most promising micro-nano structure preparation technology to replace photolithography. However, the nanoimprinting method suffers from template deformation during the imprinting process, which seriously affects the repeatability and fidelity of the imprinting.

[0004] Compared to the commonly used patterning methods mentioned above, the emerging femtosecond laser processing, through a non-mechanical contact process, provides high energy within a limited area. It has been proven to enable programmed ablation and flexible removal of various materials without damaging existing structures on the substrate, which is beneficial for the development of multi-component devices. Furthermore, due to the ultrashort pulses of femtosecond lasers, the induced material ionization, lattice melting, and Coulomb explosion-induced ablation or thermal vaporization phenomena occur within just a few picoseconds, far shorter than the material thermal diffusion time (nanosecond scale). This minimizes the impact on surrounding materials, resulting in ablation patterns with high precision and clear edges, and offering advantages such as high efficiency and good controllability.

[0005] To date, femtosecond laser direct writing has proven to be an effective technique for the precise fabrication and engineering of material microstructures in both time and space. Dong et al. reported a femtosecond laser-printed three-dimensional (3D) patterning technique for perovskite quantum dots, successfully achieving reversible in-situ formation and decomposition of perovskite within a glass matrix. By adjusting the laser power density or extending the exposure time, the patterned diameter of the laser-irradiated area could be increased from 30 μm to 65 μm. However, quantum dot patterning within glass requires high excitation power and additional heating, posing a challenge for industrial applications (see Nat. Photonics 14, 82-88 (2020)). Gan et al. utilized the nonlinear absorption and energy deposition induced by femtosecond lasers to form laser-processed nanocomposites of arbitrary shapes at the micrometer scale by controlling the focusing position of the laser in the precursor solution, achieving a minimum linewidth of 1.2 μm (see J. Mater. Chem. C 8, 3409-3417 (2020)). Although femtosecond laser direct writing has been proven to be a sub-diffraction imaging technique, the resolution of direct writing is still affected by the Airy disk diameter (1.22λ / NA, where λ and NA are the objective wavelength and numerical aperture, respectively). Clearly, shorter laser wavelengths or larger numerical apertures are beneficial for improving resolution, but fluorescent materials such as perovskites are more sensitive to short-wavelength light, and the numerical aperture of the objective cannot be increased indefinitely. Therefore, high-resolution patterning technology for femtosecond laser direct writing of fluorescent materials remains a significant challenge.

[0006] In conclusion, developing a new technology for efficient, stable, and high-precision patterned perovskite thin films is crucial. Summary of the Invention

[0007] To address the shortcomings and deficiencies of the existing technologies, this invention provides a high-precision patterning method suitable for perovskite thin films, thereby broadening the applications of perovskite in high-resolution displays, anti-counterfeiting, and encryption. This invention utilizes the ultra-high peak intensity of femtosecond lasers, combined with the digital processing characteristics of laser direct-write systems, to achieve high-precision laser ablation patterning in designated areas on perovskite thin films. It can achieve a minimum feature size of 80 nm, approximately λ / 10 of the exposure source, breaking the optical diffraction limit—something unattainable by other patterning techniques. Furthermore, the patterned perovskite thin films prepared by this invention exhibit excellent water and oxygen stability, maintaining over 90% of their original luminescence intensity after 120 days of storage under laboratory conditions. Even under harsh conditions, they can be used long-term in integrated devices.

[0008] The femtosecond laser direct-writing perovskite described in this invention has several significant characteristics: First, the femtosecond laser pulse width is extremely short, on the order of femtoseconds (10^6). -15While the energy density of a femtosecond laser after focusing can reach 10 s), 14 -10 15 W / cm 2 The magnitude is on the order of magnitude, and the resulting electric field strength can reach 10. 10 The perovskite film exhibits several advantages: firstly, the addition of high-concentration polymers, such as PMMA, to the perovskite film results in a lower thermal conductivity (0.14 ± 0.2 W / mK) compared to that of perovskite CsPbI3 (0.45 ± 0.05 W / mK). This allows for precise control of the laser ablation points to achieve higher resolution patterns. Secondly, the perovskite film does not absorb in the selected 700-1080 nm femtosecond laser band. The laser direct writing process involves nonlinear multiphoton absorption, meaning that the effective intensity curve of the laser spot becomes narrower and steeper as the laser intensity approaches the ablation threshold. By precisely controlling the laser intensity, only a small portion of the focused spot exceeds the perovskite ablation threshold, allowing the feature size to exceed the optical diffraction limit. Thirdly, the preparation method using a polymer matrix to encapsulate the perovskite film yields films with high flatness and uniformity, free from obvious pores or cracks on the film surface. This makes it suitable for high-precision laser direct writing. Furthermore, the polymer effectively isolates the perovskite from contact with water and oxygen, improving stability.

[0009] One object of the present invention is to provide a high-precision patterning method for perovskite thin films, the high-precision patterning method for perovskite thin films comprising the following steps:

[0010] S1. Add the polymer and perovskite precursor to the solvent, heat and stir to obtain a perovskite precursor solution.

[0011] S2. Coat the perovskite precursor solution onto the substrate to obtain a perovskite precursor film.

[0012] S3. Anneal the perovskite precursor film to obtain a perovskite film;

[0013] S4. The perovskite thin film is processed using femtosecond laser direct writing technology to obtain a high-precision patterned perovskite thin film.

[0014] in,

[0015] The perovskite is a nanocrystalline perovskite;

[0016] In the perovskite film, the polymer mass fraction is 70-90%;

[0017] The wavelength of the femtosecond laser is 700-1080nm;

[0018] In the spot formed by the femtosecond laser, the energy of the femtosecond laser follows a Gaussian distribution curve from the center to the periphery. The peak energy of the Gaussian distribution curve reaches 200mW, and the energy decreases from the middle of the Gaussian distribution curve to both sides.

[0019] Furthermore, the pulse width of the femtosecond laser is 50-200 fs.

[0020] Furthermore, the power of the femtosecond laser is 0.1-200mW.

[0021] Furthermore, the laser spot diameter is 0.5-50 μm.

[0022] Further, the polymer is selected from one or more of polyvinylidene fluoride, polymethyl methacrylate, polyvinyl acetate, cellulose acetate, polysulfone, polyamide, polyimide, polycarbonate, polystyrene, polyvinyl chloride, polyvinyl alcohol, ABS plastic, or polyacrylonitrile; the polymer is a transparent resin matrix, and the perovskite is distributed in the transparent resin matrix; specifically, the transparent resin matrix is ​​a transparent material dissolved in dimethylformamide, dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide polar solvents.

[0023] Furthermore, the perovskite precursor solution is a homogeneous, viscous, transparent solution. The polymer and the perovskite precursor are completely dissolved; the polymer has a mass fraction of 1-50%, and the perovskite precursor has a mass concentration of 5-10%.

[0024] Furthermore, in the perovskite thin film, the molecular formula of the perovskite is ABX3;

[0025] in,

[0026] A is selected from Cs + CH3NH 3+ Or CH5N 2+ One or more of the following;

[0027] B is selected from one or more of In, Ag, Al, Ti, Ge, Sn, Pb, Sb, Bi, Cu, or Mn;

[0028] X is selected from Cl - ,Br - or I - One or more of them.

[0029] Furthermore, the thermal conductivity of the perovskite is 0.4-10 W / mK; the thermal conductivity of the polymer is 0.1-0.5 W / mK.

[0030] Furthermore, the perovskite film is a smooth and uniform polymer-coated perovskite film with the molecular formula CsPbCl. m Br 3-m and CsPbBr m I 3-m , where the value of m ranges from 0 to m to 3.

[0031] Furthermore, in step S1, the heating temperature is 50-90℃; the stirring time is 1-5 hours.

[0032] Furthermore, in step S3, the annealing temperature is 60-90℃ and the time is 10-30 min.

[0033] Furthermore, the thickness of the perovskite film is 0.01-500 μm.

[0034] Furthermore, in step S4, the laser-irradiated area undergoes ablation or thermal vaporization phenomena caused by material ionization, lattice melting, and Coulomb explosion, thereby achieving the ablation and removal of the perovskite film and obtaining micropatterns. Femtosecond laser precision engineering has advantages such as large area, high throughput, and far-field nanofabrication, and focusing it on perovskite films can achieve simple and reliable pattern ablation.

[0035] Another object of the present invention is to provide the application of the above-mentioned high-precision patterning method for perovskite thin films in the fields of high-resolution display, anti-counterfeiting or encryption.

[0036] The present invention has the following beneficial effects:

[0037] (1) This invention proposes a simple femtosecond laser direct writing method to prepare high-precision patterned perovskite thin films. An iceberg effect exists during the interaction between the femtosecond laser and nanocrystalline perovskite: when the laser intensity approaches the ablation threshold, the iceberg effect is highly nonlinearly correlated with the femtosecond laser intensity; that is, the more photons absorbed simultaneously, the narrower and steeper the effective intensity curve of the spot. This invention precisely controls the laser intensity so that only a small portion of the focused spot exceeds the perovskite ablation threshold, thereby allowing the feature size to exceed the optical diffraction limit, reaching λ / 10 of the exposure source, with a minimum linewidth of 80 nm. Due to the ultrashort pulse of the femtosecond laser, the induced ablation phenomenon occurs only within a few picoseconds, far shorter than the material's thermal diffusion time (nanosecond scale). Furthermore, based on the difference in thermal conductivity between perovskite and polymers, the laser ablation range can be precisely controlled, minimizing the impact on surrounding materials, resulting in high-precision patterns with clear edges, and enabling the preparation of high-quality micro and nanoscale patterns.

[0038] (2) Compared with traditional patterning methods, the present invention can obtain high-precision fluorescent patterned films in a specified area with high precision and efficiency without the need for a vacuum environment, templates, or complex post-processing. Since nanoscale patterns can store more information at the same size, they can promote applications with higher integration. The patterning technology proposed in this invention provides a promising manufacturing candidate for data storage, anti-counterfeiting, and high-security information encryption.

[0039] (3) Sensitivity to environmental factors such as oxygen and humidity has always been one of the obstacles to the practical application of perovskite. The present invention utilizes a polymer matrix to encapsulate perovskite, which can effectively isolate it from contact with water and oxygen. The resulting patterned perovskite film has excellent water and oxygen stability and is expected to be used for a long time even under harsh conditions. Attached Figure Description

[0040] Figure 1 A flowchart of the preparation of a high-precision patterned perovskite thin film in Example 1 is shown.

[0041] Figure 2 A transmission electron microscope (TEM) image of the perovskite thin film prepared in Example 1 is shown.

[0042] Figure 3 The image shows the fluorescence emission and absorption spectrum of the perovskite thin film prepared in Example 1 under ultraviolet excitation.

[0043] Figure 4 SEM images of the patterned perovskite thin film prepared in Example 1 with sub-diffraction feature sizes and schematic diagrams of the iceberg effect of the nonlinear absorption process are shown.

[0044] in,

[0045] Figure 4 (a) shows a SEM image of the patterned perovskite film with sub-diffraction feature size prepared in Example 1;

[0046] Figure 4 (b) shows a schematic diagram of the iceberg effect in the nonlinear absorption process of the perovskite thin film prepared in Example 1.

[0047] Figure 5 The images show fluorescent and SEM images of the patterned QR code, South China Normal University logo, and Chinese element pattern of the perovskite thin film prepared in Example 1 under ultraviolet excitation.

[0048] in,

[0049] Figure 5 (a) shows a patterned QR code under ultraviolet excitation and its SEM image;

[0050] Figure 5(b) shows the logo of South China Normal University under ultraviolet excitation and its SEM image;

[0051] Figure 5 (c) shows the fluorescence image and SEM image of the Chinese element pattern under ultraviolet excitation.

[0052] Figure 6 The optical path diagram of the femtosecond laser patterning technique used in Example 2 is shown.

[0053] Figure 7 A planar SEM image of the perovskite thin film prepared in Example 2 is shown.

[0054] Figure 8 The fluorescence emission pattern of the perovskite thin film prepared in Example 2 under ultraviolet excitation is shown.

[0055] Figure 9 The color gamut range achieved by the perovskite thin film prepared in Example 2 in the International Committee on Color (CIE) 1931 color coordinates is shown, and compared with the NTSC standard color gamut.

[0056] Figure 10 The image shows a fluorescence image of the patterned "South China Normal University" lettering on a high-precision patterned perovskite thin film prepared in Example 2 under ultraviolet excitation.

[0057] Figure 11 The photoluminescence (PL) intensity variation of the perovskite thin film prepared in Example 2 is shown under laboratory conditions.

[0058] Figure 12 The photoluminescence (PL) intensity change of the perovskite thin film prepared in Example 2 in deionized water is shown.

[0059] Figure 13 Bright-field microscopy images of the perovskite thin films prepared in Comparative Example 2 are shown.

[0060] Figure 14 The fluorescence image of the patterned micro fast response code (QR code) of Application Example 1 under ultraviolet excitation is shown.

[0061] Figure 15 A schematic diagram is shown illustrating the acquisition of fluorescent micro-fast response codes and ACSII encryption information in Application Examples 1 and 2 of this invention using a smartphone, a portable ultraviolet lamp, and a microscope.

[0062] Figure 16 The fluorescence image of the patterned binary 7-bit ASCII code under ultraviolet excitation is shown in Application Example 2. Detailed Implementation

[0063] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0064] Unless otherwise stated, the raw materials, reactions, and post-processing methods mentioned in the examples are all commercially available raw materials and technical methods well known to those skilled in the art.

[0065] The average molecular weight of PMMA in the embodiments and comparative examples of this invention is 120,000, and it was purchased from Beijing Benoway Biotechnology.

[0066] The SEM tests in the embodiments and comparative examples of this invention were performed using a ZEISS Ultra 55 instrument / model.

[0067] The femtosecond laser used in this embodiment of the invention is a Coherent Chameleon instrument / model.

[0068] The fluorescence spectroscopy test in this embodiment of the invention was performed using a fluorescence spectrophotometer FL970.

[0069] The absorption spectroscopy test in this embodiment of the invention was performed using a Lambd 950 instrument / model.

[0070] Example 1

[0071] A high-precision patterning method for perovskite thin films, comprising the following steps:

[0072] S1. Add 0.5g PMMA, 0.1mmol PbI2, 0.1mmol CsI, and 0.05mmol OAI to 2.5ml DMF, heat and stir at 60℃ for 3h to obtain a perovskite precursor solution;

[0073] S2. The perovskite precursor solution is drop-coated onto a glass substrate, and then the glass substrate is placed on a spin coater. The vacuum pump is turned on, and the perovskite precursor film is obtained by spin coating at a speed of 2600 r / min for 30 s.

[0074] S3. Transfer the perovskite precursor film to a 90°C hot stage and heat anneal for 10 min to obtain a perovskite film.

[0075] S4. Import the pre-prepared pattern into the laser direct writing system, setting the laser wavelength to 800nm, pulse width to 200fs, laser power to 64mW, and spot diameter to 2μm. Then, place the perovskite film on a displacement platform and observe it using a CCD. Adjust the height of the displacement platform to focus the femtosecond laser onto the surface of the perovskite nanocrystalline film, and begin the patterning process. The femtosecond laser moves along a set path, resulting in a high-precision patterned perovskite film with a pattern size of 200×200μm. 2 .

[0076] In this embodiment, the perovskite film is a PMMA-coated CsPbI3 perovskite nanocrystalline film with both emission and absorption peaks located at 688 nm.

[0077] During the patterning process in this embodiment, the perovskite nanocrystals in the femtosecond laser irradiated area undergo ablation and thermal vaporization, exhibiting obvious red fluorescence in the dark field.

[0078] Figure 1 The flowchart of the preparation of high-precision patterned perovskite thin films in Example 1 is shown; from left to right, it shows the preparation of perovskite precursor films and the preparation of perovskite thin films.

[0079] Figure 2 Transmission electron microscopy (TEM) images of the perovskite thin films prepared in Example 1 are shown; Figure 2 As can be seen, the perovskite film prepared in Example 1 is a nanocrystalline film. The nanocrystals are coated with PMMA and uniformly dispersed in the polymer matrix, with an average size of 13.7 ± 1.4 nm.

[0080] Figure 3 The image shows the fluorescence emission and absorption spectrum of the perovskite thin film prepared in Example 1 under ultraviolet excitation.

[0081] Depend on Figure 3 It can be seen that the thin film has a PL peak with a full width at half maximum (FWHM) of 36 nm (94 meV) at 688 nm, which corresponds to the exciton absorption peak at 688 nm. Furthermore, the thin film shows no absorption in the 800 nm band; nonlinear multiphoton absorption occurs when information is written onto the thin film using an 800 nm femtosecond laser. The inset shows a physical image of the fluorescence emission of the thin film under ultraviolet excitation.

[0082] Figure 4 SEM images of the patterned perovskite thin film prepared in Example 1 with sub-diffraction feature sizes and schematic diagrams of the iceberg effect of the nonlinear absorption process are shown.

[0083] in,

[0084] Figure 4(a) shows a SEM image of the patterned perovskite film with sub-diffraction feature size prepared in Example 1;

[0085] Figure 4 (b) shows a schematic diagram of the iceberg effect in the nonlinear absorption process of the perovskite thin film prepared in Example 1.

[0086] Figure 5 The images show fluorescent and SEM images of the patterned QR code, South China Normal University logo, and Chinese element pattern of the perovskite thin film prepared in Example 1 under ultraviolet excitation.

[0087] in,

[0088] Figure 5 (a) shows a patterned QR code under ultraviolet excitation and its SEM image;

[0089] Figure 5 (b) shows the logo of South China Normal University under ultraviolet excitation and its SEM image;

[0090] Figure 5 (c) shows the fluorescence image and SEM image of the Chinese element pattern under ultraviolet excitation.

[0091] Example 2

[0092] A high-precision patterning method for perovskite thin films, comprising the following steps:

[0093] S1. Add 0.5g PMMA, PbX2, CsX, and AX to 2.5ml DMSO, heat and stir at 60℃ for 3h to obtain a perovskite precursor solution;

[0094] S2. The perovskite precursor solution is drop-coated onto a glass substrate, and then the glass substrate is placed on a spin coater. The vacuum pump is turned on, and the perovskite precursor film is obtained by spin coating at a speed of 2600 r / min for 30 s.

[0095] S3. Transfer the perovskite precursor film to a 90°C hot stage and heat anneal for 10 min to obtain a perovskite film.

[0096] S4. Import the pre-prepared pattern into the laser direct writing system, setting the laser wavelength to 800nm, pulse width to 200fs, laser power to 70mW, and spot diameter to 2μm. Then, place the perovskite film on a displacement platform and observe it using a CCD. Adjust the height of the displacement platform to focus the femtosecond laser onto the surface of the perovskite nanocrystalline film, and begin the patterning process. The femtosecond laser moves along a set path, resulting in a high-precision patterned perovskite film with a pattern size of 200×200μm.2 ;

[0097] In the perovskite precursor, X is selected from Cl, Cl m Br 3-m Br, Br m I 3-m One of I and II, where the value of m ranges from 0 to m to 3, as shown in Table 1.

[0098] Table 1. Selection, amount, and molecular formula of the perovskite precursor and the prepared perovskite

[0099]

[0100]

[0101] In this embodiment, the perovskite film is a PMMA-coated CsPbX3 nanocrystalline perovskite film. By adjusting the ratio of halides, the emission peak of the multicolor film is located at 422-688nm.

[0102] During the patterning process in this embodiment, the perovskite nanocrystals in the femtosecond laser irradiated area undergo ablation and thermal vaporization, exhibiting significant fluorescence in the dark field.

[0103] Figure 6 The optical path diagram of the femtosecond laser patterning technique used in Example 2 is shown.

[0104] Figure 7 A planar SEM image of the perovskite thin film prepared in Example 2 is shown; by Figure 7 It is known that the perovskite thin film has a smooth surface without obvious pores or cracks, making it suitable for high-precision femtosecond laser direct writing.

[0105] Figure 8 The fluorescence emission pattern of the perovskite thin film prepared in Example 2 under ultraviolet excitation is shown; Figure 8 It can be seen that the emission peak of CsPbCl3 is 422 nm; the emission peak of CsPbClBr2 is 485 nm; the emission peak of CsPbBr3 is 517 nm; and the emission peak of CsPbBr... 2.5 I 0.5 The emission peak of CsPbBr2I is 542 nm; the emission peak of CsPbBrI2 is 580 nm; the emission peak of CsPbBrI2 is 650 nm; and the emission peak of CsPbI3 is 688 nm.

[0106] Figure 9 The color gamut achieved by the perovskite thin film prepared in Example 2 in the CIE 1931 color coordinate system and its comparison with the NTSC standard color gamut are shown; Figure 9It is evident that the multicolor perovskite thin film prepared by this invention covers a wide color gamut and has broad application prospects in the display field.

[0107] Figure 10 The image shows a fluorescence image of the patterned "South China Normal University" lettering on a high-precision patterned perovskite thin film prepared in Example 2 under ultraviolet excitation.

[0108] Figure 11 The photoluminescence (PL) intensity change of the perovskite thin film prepared in Example 2 under laboratory conditions is shown; by Figure 11 It can be seen that after 120 days, the luminescence intensity of the blue, green and red perovskite films remained at 93.84%, 94.19% and 90.77% of the initial intensity, respectively.

[0109] Figure 12 The photoluminescence (PL) intensity change of the perovskite film prepared in Example 2 in deionized water is shown; by Figure 12 It can be seen that after soaking in deionized water for 31 days, these three films still exhibited significant luminescence properties, with their luminescence intensity remaining above 80% of the initial value.

[0110] Comparative Example 1

[0111] A high-precision patterning method for perovskite thin films is disclosed. The difference between this comparative example and Example 1 is that in step S3, a continuous-wave laser with a wavelength of 808 nm is used; the other components and preparation methods are the same as in Example 1. Because the energy of the continuous-wave laser is relatively low, it is insufficient to affect the perovskite thin film, and therefore cannot achieve an ablation effect.

[0112] Comparative Example 2

[0113] A high-precision patterning method for perovskite thin films is disclosed. The difference between this comparative example and Example 1 is that in step S3, the laser used is a femtosecond laser with a wavelength of 450 nm, while the other components and preparation methods are the same as in Example 1.

[0114] Figure 13 Bright-field microscopy images of the perovskite thin films prepared in Comparative Example 2 are shown.

[0115] Depend on Figure 13 It can be seen that a 450nm femtosecond laser cannot be used to pattern perovskite films because perovskite does not undergo nonlinear multiphoton absorption at this wavelength, thus making it impossible to ablate and remove the perovskite film to obtain micropatterns.

[0116] Comparative Example 3

[0117] A high-precision patterning method for perovskite thin films is disclosed. The difference between this comparative example and Example 1 is that no polymer is added in step S1, while the other components and preparation method are the same as in Example 1. Due to the lack of polymer encapsulation and the low concentration of precursor ions, the prepared perovskite thin film exhibits extremely weak fluorescence and quenches rapidly.

[0118] Comparative Example 4

[0119] A high-precision patterning method for perovskite thin films is disclosed. The difference between this comparative example and Example 1 is that in step S1, the amount of polymer added is 0.25g, while other components and preparation methods remain the same as in Example 1. Because the polymer mass is halved, the film thickness is reduced, and the encapsulation effect on the perovskite is weakened. Consequently, the prepared film exhibits poor fluorescence and stability, and the fluorescence disappears after 7 days.

[0120] Application Example 1

[0121] The high-precision patterning method for perovskite thin films proposed in this invention is applied to anti-counterfeiting.

[0122] The preparation method, raw materials, and amounts of the perovskite thin film in this application example are the same as in Example 1. Using the femtosecond laser direct-write patterning method of this invention, micro-fast response codes (QR codes) suitable for various information storage scenarios were designed and fabricated. Based on the simplicity of the fabrication and decoding process of this invention, coupled with its customizable patterning function, the application potential of this invention is demonstrated—users only need readily available ultraviolet light sources and portable microscopes to complete the decryption and identification of information, without the need for expensive equipment and professional training.

[0123] Figure 14 The fluorescence image of the patterned micro fast response code (QR code) of Application Example 1 under ultraviolet excitation is shown.

[0124] Application Example 2

[0125] The high-precision patterning method for perovskite thin films proposed in this invention is applied to optical encryption.

[0126] The preparation method, raw materials, and amount of raw materials used in this application example are the same as those in Example 1. The femtosecond laser direct writing patterning method of the present invention is used to encrypt the micro “SCNU” information on the perovskite film in combination with standard binary 7-bit ASCII code.

[0127] Specifically, the present invention patterns 20×20μm on a perovskite thin film. 2The solid and hollow fluorescent squares correspond to standard 7-bit ASCII codes "1" and "0", respectively. The uppercase letters "S", "C", "N", and "U" can be translated as "1010011", "1000011", "1001110", and "1010101", respectively. Using the patterning method of this invention, 28 fluorescent squares in 4 rows were written onto the perovskite film. In fluorescence and microscopy modes, these squares can be translated into the information "SCNU", demonstrating a simple new method for information storage and encryption. Based on its micro-size and high-precision characteristics, it significantly reduces the risk of counterfeiting while maintaining visual readability.

[0128] Figure 15 A schematic diagram is shown illustrating the acquisition of fluorescent micro-fast response codes and ACSII encryption information in Application Examples 1 and 2 of this invention using a smartphone, a portable ultraviolet lamp, and a microscope.

[0129] Figure 16 The fluorescence image of the patterned binary 7-bit ASCII code under ultraviolet excitation is shown in Application Example 2.

[0130] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0131] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-precision patterning method for perovskite thin films, characterized in that, The high-precision patterning method for the perovskite thin film includes the following steps: S1. Add the polymer and perovskite precursor to the solvent, heat and stir to obtain a perovskite precursor solution. S2. Coat the perovskite precursor solution onto the substrate to obtain a perovskite precursor film. S3. Anneal the perovskite precursor film to obtain a perovskite film; S4. The perovskite thin film is processed using femtosecond laser direct writing technology to obtain a high-precision patterned perovskite thin film. in, The perovskite is a nanocrystalline perovskite; In the perovskite film, the polymer has a mass fraction of 70-90%; The thermal conductivity of the perovskite is 0.4-10 W / mK; the thermal conductivity of the polymer is 0.1-0.5 W / mK. In step S1, the heating temperature is 50-90℃; the stirring time is 1-5 hours. In step S3, the annealing temperature is 60-90℃; the time is 10-30 minutes. In step S4, the wavelength of the femtosecond laser is 700-1080 nm; In the spot formed by the femtosecond laser, the energy of the femtosecond laser follows a Gaussian distribution curve from the center to the periphery. The peak energy of the Gaussian distribution curve reaches 200mW, and the energy decreases from the middle of the Gaussian distribution curve to both sides. The pulse width of the femtosecond laser is 50-200 fs; The power of the femtosecond laser is 0.1-200mW; The spot diameter of the femtosecond laser is 0.5-50 μm; The laser direct writing process involves nonlinear multiphoton absorption; By precisely controlling the laser intensity, a small portion of the focused spot exceeds the perovskite ablation threshold, thereby enabling the feature size to exceed the optical diffraction limit, reaching λ / 10 of the exposure source, with a minimum linewidth of 80nm.

2. The high-precision patterning method for perovskite thin films according to claim 1, characterized in that, The polymer is selected from one or more of polyvinylidene fluoride, polymethyl methacrylate, polyvinyl acetate, cellulose acetate, polysulfone, polyamide, polyimide, polycarbonate, polystyrene, polyvinyl chloride, polyvinyl alcohol, ABS plastic, or polyacrylonitrile.

3. The high-precision patterning method for perovskite thin films according to claim 1, characterized in that, In the perovskite thin film, the molecular formula of perovskite is ABX3; in, A is selected from Cs + CH3NH 3+ Or CH5N 2+ One or more of the following; B is selected from one or more of In, Ag, Al, Ti, Ge, Sn, Pb, Sb, Bi, Cu, or Mn; X is selected from Cl - ,Br - Or I - One or more of them.

4. The application of the high-precision patterning method for perovskite thin films according to any one of claims 1-3 in the fields of high-resolution display, anti-counterfeiting, or encryption.

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