Preparation method of patterned perovskite single crystal thin film array for flexible photoelectric device

Abstract

The invention relates to a preparation method of a patterned perovskite single crystal thin film array for a flexible photoelectric device, and belongs to the field of preparation of perovskite optoelectronic materials, a silicon master mask with a microstructure pattern is prepared through a photoetching technology, and a flexible template with a microcavity and a flexible cover layer with a hole array are obtained through replication of polydimethylsiloxane (PDMS); after the template is attached to a target substrate, the micro-cavity is filled with a perovskite precursor solution; then a cover layer is precisely attached, space confinement crystallization is carried out under the heating condition, a solution is supplemented through holes of the cover layer, and high-quality single crystals are formed through induction; and finally, stripping the template and the cover layer to obtain the patterned film array. Through the physical confinement effect of the PDMS template, the perovskite single crystal film array with high crystal quality, low defect density and clear pattern boundary is directly prepared on the flexible substrate, the template can be repeatedly used, and the process is green and economical. The prepared thin film can be directly used for constructing devices such as high-performance flexible photoelectric detectors and miniature LEDs.

Description

Technical Field

[0001] This invention relates to the field of perovskite optoelectronic material preparation technology, specifically to a method for fabricating patterned perovskite single-crystal thin film arrays for flexible optoelectronic devices. Background Technology

[0002] Halide perovskite single-crystal thin films, with their excellent optoelectronic properties (such as high carrier mobility, low defect density, and excellent light absorption and emission performance), have shown great application potential in the optoelectronic field. In devices such as solar cells, light-emitting diodes, lasers, and photodetectors, they can significantly improve photoelectric conversion efficiency, luminous brightness, and detection sensitivity. However, traditional fabrication techniques face several bottlenecks: First, poor film quality. Spin-coating is easily affected by substrate wettability and solvent evaporation rate, leading to uneven film thickness, edge thickening, or pinhole defects, and often resulting in polycrystalline structures. While vapor deposition can improve crystallinity, it is difficult to control film morphology, and it also suffers from high defect density. Second, insufficient patterning capability. Traditional methods struggle to achieve high-precision micro / nanostructure fabrication, failing to meet the requirements of device functional integration. This is especially true on flexible substrates, where the patterning difficulty of vapor deposition further increases. Third, the flexibility is poor. The surface roughness and thermal expansion coefficient of the flexible substrate make it easy for traditional methods to cause the film to crack and fall off. Moreover, the grain boundaries of polycrystalline films are prone to become crack initiation points under bending stress, which seriously affects the reliability and service life of the device.

[0003] Spatial confinement is an effective way to solve the above problems, but traditional rigid templates (such as SiO2 microcavities and metal masks) have drawbacks such as difficult demolding, high cost, and inability to adapt to flexible substrates. Polydimethylsiloxane (PDMS), as a flexible polymer material, has significant advantages: its elastic modulus is only 0.5-2 MPa, which allows it to fit tightly to curved substrates without film damage during demolding; it has excellent chemical inertness, is stable to organic solvents such as DMF and DMSO, and does not undergo side reactions with perovskite precursors; its gas permeability is far superior to plastics such as PP and PC, which can promote uniform solvent evaporation and reduce crystallization stress; it can be reused after cleaning, which greatly reduces manufacturing costs.

[0004] Based on this, the present invention combines PDMS templates with photolithography technology, and regulates the nucleation and growth kinetics of perovskite through physical confinement effect, so as to realize the direct preparation of high-quality and high-precision patterned single crystal thin films on flexible substrates, providing key technical support for the industrialization of flexible optoelectronic devices. Summary of the Invention

[0005] To address the problems of the prior art, this invention provides a method for fabricating patterned perovskite single-crystal thin-film arrays for flexible optoelectronic devices.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: Firstly, a method for fabricating a patterned perovskite single-crystal thin-film array for flexible optoelectronic devices includes the following steps: S1. Photolithography master fabrication: A photolithography master with a target microstructure pattern is fabricated on a silicon wafer using photolithography technology; S2. Preparation of PDMS template and capping layer: After mixing and degassing PDMS prepolymer with curing agent, it is poured onto the photolithography master, heated and cured, and then peeled off to obtain a PDMS flexible template with a microcavity structure corresponding to the target microstructure pattern, and a PDMS flexible capping layer with a hole array corresponding to the microcavity position. S3. Preparation of perovskite precursor solution: Dissolve halide perovskite raw material in an organic solvent to prepare perovskite precursor solution; S4. Precursor solution filling: The PDMS flexible template is attached to the target substrate, and the perovskite precursor solution is filled into the microcavity of the PDMS flexible template; S5. Cover layer bonding: Align and bond the PDMS flexible cover layer with the PDMS flexible template; S6. Confined crystal growth: The bonded assembly is heated to allow the precursor solution in the microcavity to crystallize and grow, forming a perovskite single crystal film. The precursor solution is then replenished through the capping pores until the crystal fills the microcavity. S7. Template peeling: After cooling, the PDMS flexible template and PDMS flexible capping layer are peeled off to obtain a patterned perovskite single crystal thin film array on the target substrate.

[0007] In one specific embodiment of the first aspect, the target microstructure pattern includes at least one of a circle, a linear array, a grid, or a custom complex pattern; the depth of the microcavity is 50-150 μm.

[0008] In one specific embodiment of the first aspect, the PDMS flexible template and the PDMS flexible capping layer are respectively bonded to the target substrate and to each other by thermocompression bonding.

[0009] In one specific embodiment of the first aspect, the halide perovskite has the general formula ABX3, wherein A is one or more of MA⁺, FA⁺, or Cs⁺, and B is Pb. 2 ⁺ or Sn 2 ⁺, X is one or more of Cl⁻, Br⁻ or I⁻; the organic solvent is γ-butyrolactone, DMF or a DMF / DMSO mixed solvent; the concentration of the precursor solution is 0.8-1.5M.

[0010] In one specific embodiment of the first aspect, the heat treatment employs a gradient heating method, including a first stage of pre-crystallization at 60-80°C for 1-3 hours, and a second stage of primary crystallization at a rate of 1°C / 3 min, heating to 90-110°C.

[0011] In one specific embodiment of the first aspect, after step S7 stripping, the perovskite single crystal thin film array is further subjected to a post-processing step, the post-processing including toluene vapor annealing or ultraviolet ozone treatment.

[0012] In one specific embodiment of the first aspect, the target substrate is a rigid substrate or a flexible substrate; the rigid substrate is glass or silicon wafer; the flexible substrate is PET or PEN, and a film is stably formed on a flexible substrate with a curvature radius greater than 2 mm.

[0013] In one specific embodiment of the first aspect, the PDMS flexible template and PDMS flexible capping layer, after being peeled off, can be reused after being cleaned and dried.

[0014] Secondly, the patterned perovskite single-crystal thin film array is prepared according to the method for preparing a patterned perovskite single-crystal thin film array for flexible optoelectronic devices. The array is composed of multiple mutually isolated perovskite single-crystal pixels or continuous perovskite single-crystal channels with regular boundaries, and the patterning accuracy is at the micrometer level.

[0015] Thirdly, a flexible optoelectronic device includes a patterned perovskite single-crystal thin film array and electrodes disposed in specific regions of the thin film array.

[0016] The beneficial effects of this invention are as follows: 1. Excellent crystal quality: The spatial confinement effect of PDMS precisely controls the position and growth direction of the crystal nuclei, resulting in single-crystal thin films with large grain size, low defect density, and complete surface coverage, ensuring high device performance; 2. Green and economical process: PDMS templates have strong chemical stability and can be reused, which significantly reduces raw material consumption and manufacturing costs, meeting the needs of sustainable development; 3. Multi-material system compatibility: It is suitable for different halogen components (such as MAPbI3, CsPbBr3, FAPbI3) and two-dimensional / three-dimensional perovskite heterostructures, and can be adapted to various substrates such as flexible (PET, PEN) and rigid (glass, silicon wafer). It can stably form films on flexible substrates with a curvature radius greater than 2mm. 4. Strong functional scalability: It can be extended to the patterned integration of materials such as CsPbBr3 quantum dots and P3HT organic semiconductors to meet the functional requirements of different devices; 5. High patterning precision: Relying on photolithography technology to achieve micron-level structural precision, the microcavity pattern can be designed as a pixel array (for micro LEDs) or a channel array (for photodetectors), directly defining the functional area of ​​the device; 6. Simplified device manufacturing process: This invention integrates the forming and patterning of perovskite thin films with the definition of the photosensitive / light-emitting units of the device in one step, reducing the damage and contamination of perovskite materials caused by subsequent processes such as photolithography and etching in traditional micro-nano fabrication, simplifying the device process and improving the yield.

[0017] 7. Excellent performance of flexible devices: Single-crystal thin films combine excellent crystal quality with mechanical flexibility, resulting in flexible optoelectronic devices with high luminous efficiency, detectivity, and good bending stability, meeting the application requirements of next-generation flexible electronic devices. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a MAPbI3 single-crystal linear array for photodetectors fabricated on a flexible PEN substrate, according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a CsPbBr3 pixel array for micro LED display fabricated on a flexible PEN substrate, provided by an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1 to 2 The method shown is for fabricating a patterned perovskite single-crystal thin film array for flexible optoelectronic devices.

[0022] This invention combines photolithography with the physical properties of PDMS thin films, and achieves thickness uniformity control, patterned growth and flexible integration of perovskite single crystal thin films by designing tunable microstructure templates.

[0023] To precisely control thickness and morphology, the depth and shape (circular, linear, grid, etc.) of PDMS microcavities can be designed, directly determining the thickness uniformity and pattern resolution of the perovskite film. A silicon master template is prepared using ultraviolet lithography, and the PDMS film replicates the master template pattern, achieving micron-level structural precision. The precursor solution is confined and filled into the microcavities through rolling or injection, ensuring uniform solution distribution. The density of nucleation sites within the confined space is controllable, inducing preferential grain orientation growth. During annealing, the thermal expansion coefficient of PDMS (310 ppm / ℃) matches that of perovskite, reducing film cracking caused by thermal stress. Furthermore, by designing the microcavity pattern of the PDMS template, material growth and device structure fabrication can be integrated. When the microcavities are designed as isolated dot arrays, independent perovskite single-crystal pixels are obtained, which can be directly used as light-emitting units for micro-LEDs or photosensitive pixels for image sensors. When the microcavities are designed as continuous linear arrays or grids, high-quality perovskite channels with regular boundaries are obtained, which can be directly used to construct the effective functional areas of high-performance photodetectors. This method enables precise "bottom-up" fabrication from materials to device prototypes.

[0024] Specifically, a method for fabricating a patterned perovskite single-crystal thin-film array for flexible optoelectronic devices includes the following steps: Step 1, Photolithography Master Preparation: Using ultraviolet lithography, electron beam lithography, or laser direct writing technology, the target microstructure pattern (including circles, linear arrays, grids, or custom complex patterns) is prepared on the silicon wafer to form a master. Step 2, PDMS template and capping layer preparation: PDMS prepolymer and curing agent are mixed at a mass ratio of 10:1, stirred and then vacuum degassed, poured onto the master plate, heated and cured at 80℃ for 2 hours, cooled and peeled off to obtain PDMS flexible template (microcavity depth 50-150μm) with corresponding microcavity structure and PDMS flexible capping layer with pore array. Step 3, preparation of perovskite precursor solution: Select halide perovskite (general formula ABX3, where A is one or more of MA⁺, FA⁺ or Cs⁺, and B is Pb). 2 ⁺ or Sn 2 Using γ-butyrolactone, DMF, or a DMF / DMSO mixed solvent as raw materials (where X is one or more of Cl⁻, Br⁻, or I⁻), a precursor solution with a concentration of 0.8-1.5M is prepared and stirred at 60-80℃ until completely dissolved. Step 4, Precursor solution filling: The PDMS flexible template is tightly bonded to the target substrate (rigid substrate is glass or silicon wafer; flexible substrate is PET or PEN) by thermoforming. The precursor solution is filled into the microcavities of the PDMS template by drop casting, rolling or injection, ensuring that the solution is evenly distributed and free of air bubbles. Step 5, precise bonding of the capping layer: Under an optical microscope, the PDMS flexible capping layer is precisely bonded to the template (pattern array bonding error is less than 10μm). The bonding is slowly unfolded from the top corner of the template, and then hot-pressed again to ensure tight contact at the interface. Step 6, confined crystal growth: The assembly is placed on a hot stage for heating treatment using a gradient heating method: the first stage is pre-crystallization at 60-80℃ for 1-3 hours, and the second stage is main crystallization at 90-110℃ at a rate of 1℃ / 3min; every 1-3 hours, the solution is added to the microcavity through the capping pores using a needle syringe filled with preheated precursor solution until the perovskite crystals fill the entire microcavity; Step 7, Template peeling and post-processing: After cooling to room temperature, gently peel the PDMS template and capping layer from one corner. The peeled PDMS template can be reused after cleaning and drying. Toluene vapor annealing is used to fill the grain boundary voids, or ultraviolet ozone treatment is used to remove surface organic matter to optimize film performance. Step 8, Electrode fabrication: Deposit a 50-100 nm thick metal electrode in a specific area of ​​the thin film using mask thermal evaporation or sputtering technology to complete the fabrication of the functional layer of the flexible photodetector or micro LED device.

[0025] Example 1: According to Figure 1 As shown, a MAPbI3 single-crystal linear array for photodetectors is fabricated on a flexible PEN substrate.

[0026] 1. Master fabrication: A linear array master with a linewidth of 100 μm, a spacing of 100 μm, and a depth of 50 μm is fabricated on a silicon wafer using ultraviolet lithography; simultaneously, a hole array master with a diameter of 50 μm, a center-to-center spacing of 200 μm, and a depth of 50 μm is fabricated (for capping layer fabrication). 2. Preparation of PDMS template and capping layer: PDMS prepolymer and curing agent are mixed at a mass ratio of 10:1, stirred and then degassed under vacuum. The mixture is poured onto the above master template, heated to 80°C for 2 hours and then carefully peeled off after cooling to obtain linear array microcavity PDMS template and porous array PDMS capping layer. 3. Substrate bonding: The cleaned ITO conductive layer-modified flexible PEN substrate is tightly bonded to the linear microcavity PDMS template by thermo-press bonding to ensure that there are no air bubbles at the interface; 4. Preparation of precursor solution: PbI2 and MAI were dissolved in a DMF:DMSO (4:1, v / v) mixed solvent at a molar ratio of 1:1, and heated and stirred at 80°C until completely dissolved to prepare a MAPbI3 precursor solution with a concentration of 1.3M. 5. Solution filling: The precursor solution is dropped onto the surface of the PDMS template and injected through microneedles. The flexibility and wettability of PDMS are used to ensure that the solution is uniformly filled into all microcavities. 6. Capping: The porous array PDMS capping layer is precisely bonded to the template under an optical microscope, and thermoforming bonding ensures tight contact at the interface; 7. Confined growth: The assembly was placed on a hot stage and heated to 105°C at a rate of 0.3°C / min, and crystallized at this temperature. The preheated precursor solution was injected through the capping pores at 2-hour intervals until the crystals filled the microcavities. 8. Peeling and post-processing: After cooling to room temperature, the PDMS template and capping layer are gently peeled off from one corner to obtain a linear array patterned MAPbI3 single crystal film on the PEN substrate. After toluene vapor annealing, it is used as the photosensitive channel of the photodetector, exhibiting a uniform and sensitive photoelectric response.

[0027] Example 2: According to Figure 2 As shown, a CsPbBr3 pixel array for micro LED displays is fabricated on a flexible PEN substrate.

[0028] 1. Master fabrication: A square micro-pit array master with a side length of 100μm, a depth of 50μm, and a center-to-center spacing of 200μm is fabricated on a silicon wafer using ultraviolet lithography; at the same time, a hole array master with a diameter of 50μm, a center-to-center spacing of 200μm, and a depth of 50μm is fabricated (for capping layer fabrication). 2. Preparation of PDMS template and capping layer: PDMS prepolymer and curing agent are mixed at a mass ratio of 10:1, stirred and then degassed under vacuum. The mixture is then poured onto a square micro-cavity master plate, cured at 80°C for 2 hours, cooled and peeled off to obtain a square micro-cavity array PDMS template and a pore array PDMS capping layer. 3. Substrate bonding: The cleaned ITO-modified PEN flexible substrate is precisely aligned and covered with the PDMS template, and uniform light pressure is applied to ensure tight conformal contact at the interface without any air bubbles. 4. Preparation of precursor solution: CsBr and PbBr2 were dissolved in DMF at a stoichiometric ratio of 1:2 and stirred at 60°C for 12 hours until completely dissolved to prepare a 1M CsPbBr3 precursor solution. 5. Solution filling: Drop the precursor solution onto the template surface and use a PDMS scraper at a 45° angle and a speed of 0.5 m / min to scrape it evenly so that the solution accurately fills the microcavity. Remove the excess solution. 6. Capping: The PDMS capping layer with perforated array is precisely bonded to the template, and hot-press bonding ensures that there are no gaps at the interface; 7. Confined growth: The assembly is heated on an 80°C hot stage to promote solvent evaporation and crystal nucleation; the preheated precursor solution is replenished through the capping pores every 1 hour until the crystals fill the microcavities and form independent CsPbBr3 pixels. 8. Lifting and Device Fabrication: After cooling to room temperature, the PDMS template is slowly peeled off at 180° to obtain a neatly arranged CsPbBr3 pixel array; metal electrodes are deposited using thermal evaporation technology, which can then be used as light-emitting units of a micro LED display to achieve electroluminescence.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating patterned perovskite single-crystal thin-film arrays for flexible optoelectronic devices, characterized in that, Includes the following steps: S1. Photolithography master fabrication: A photolithography master with a target microstructure pattern is fabricated on a silicon wafer using photolithography technology; S2. Preparation of PDMS template and capping layer: After mixing and degassing PDMS prepolymer with curing agent, it is poured onto the photolithography master, heated and cured, and then peeled off to obtain a PDMS flexible template with a microcavity structure corresponding to the target microstructure pattern, and a PDMS flexible capping layer with a hole array corresponding to the microcavity position. S3. Preparation of perovskite precursor solution: Dissolve halide perovskite raw material in an organic solvent to prepare perovskite precursor solution; S4. Precursor solution filling: The PDMS flexible template is attached to the target substrate, and the perovskite precursor solution is filled into the microcavity of the PDMS flexible template; S5. Cover layer bonding: Align and bond the PDMS flexible cover layer with the PDMS flexible template; S6. Confined crystal growth: The bonded assembly is heated to allow the precursor solution in the microcavity to crystallize and grow, forming a perovskite single crystal film. The precursor solution is then replenished through the capping pores until the crystal fills the microcavity. S7. Template peeling: After cooling, the PDMS flexible template and PDMS flexible capping layer are peeled off to obtain a patterned perovskite single crystal thin film array on the target substrate.

2. The manufacturing method according to claim 1, characterized in that, The target microstructure pattern includes at least one of a circle, a linear array, a grid, or a custom complex pattern; the depth of the microcavity is 50-150 μm.

3. The manufacturing method according to claim 1, characterized in that, The PDMS flexible template and the PDMS flexible capping layer are bonded to the target substrate and to each other by thermocompression bonding.

4. The manufacturing method according to claim 1, characterized in that, The general formula of the halide perovskite is ABX3, where A is one or more of MA⁺, FA⁺ or Cs⁺, and B is Pb. 2 ⁺ or Sn 2 ⁺, X is one or more of Cl⁻, Br⁻ or I⁻; the organic solvent is γ-butyrolactone, DMF or a DMF / DMSO mixed solvent; the concentration of the precursor solution is 0.8-1.5M.

5. The manufacturing method according to claim 1, characterized in that, The heat treatment adopts a gradient heating method, including a first stage of pre-crystallization at 60-80℃ for 1-3 hours, and a second stage of main crystallization at 90-110℃ at a rate of 1℃ / 3min.

6. The manufacturing method according to claim 1, characterized in that, After step S7 stripping, the process further includes a post-processing step of the perovskite single crystal thin film array, which includes toluene vapor annealing or ultraviolet ozone treatment.

7. The manufacturing method according to claim 1, characterized in that, The target substrate is a rigid substrate or a flexible substrate; the rigid substrate is glass or silicon wafer; the flexible substrate is PET or PEN, and the film is stably formed on a flexible substrate with a curvature radius greater than 2 mm.

8. The manufacturing method according to claim 1, characterized in that, The PDMS flexible template and PDMS flexible capping layer, after being peeled off, can be reused after cleaning and drying.

9. The patterned perovskite single-crystal thin film array prepared by the method according to any one of claims 1-8, characterized in that, The array consists of multiple isolated perovskite single-crystal pixels or continuous perovskite single-crystal channels with regular boundaries, and the pattern precision is at the micrometer level.

10. A flexible optoelectronic device, characterized in that, It includes the patterned perovskite single-crystal thin film array as described in claim 9, and electrodes disposed in specific regions of the thin film array.

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