Quasi-two-dimensional perovskite energy funnel turn-off locking method and application

Abstract

This invention discloses a method and application for locking the energy funnel shut-off in a quasi-two-dimensional perovskite. The method includes preparing a quasi-two-dimensional perovskite film with a multi-n-phase distribution on a substrate, and introducing bifunctional molecules containing thiol groups and interfacial interaction groups during film formation. The bifunctional molecules regulate the local interphase organization and crystallization behavior between different n-phases in the quasi-two-dimensional perovskite, weakening the interphase energy transfer from the wide-bandgap small-n-phase to the narrow-bandgap large-n-phase, thus changing the quasi-two-dimensional perovskite energy funnel from an open state to a shut-off state. Subsequently, an alkenyl crosslinking agent and a photoinitiator are introduced, and selective illumination induces a thiol-alkene crosslinking reaction between the thiol groups of the bifunctional molecules and the alkenyl crosslinking agent, forming a crosslinking network in the light-receiving region and fixing the bifunctional molecules, thereby achieving spatially selective locking of the energy funnel shut-off state. This invention can be applied to fields such as multicolor displays, optical coding, anti-counterfeiting labels, information encryption, and flexible optoelectronic devices.

Description

Technical Field

[0001] This invention relates to a method and application for locking off a quasi-two-dimensional perovskite energy funnel, belonging to the fields of perovskite luminescent materials, quasi-two-dimensional perovskite phase engineering, and optical patterning technology. Background Technology

[0002] Perovskite halide materials have attracted widespread attention in recent years in fields such as light-emitting diodes, photodetectors, displays, and optical coding due to their excellent light absorption, high radiative recombination efficiency, and tunable luminescence properties. However, traditional three-dimensional perovskite materials still face problems in practical applications, including spectral instability, ion migration, phase separation, and time-varying luminescent regions, making it difficult to maintain stable emission color, intensity, and spatial uniformity over long periods. For applications requiring stable color output, spatial patterning, and multi-level information encoding, these problems severely limit the further application of perovskite luminescent materials.

[0003] Compared to three-dimensional perovskites, quasi-two-dimensional perovskites, due to their quantum confinement in the vertical direction, typically possess higher exciton binding energies, stronger structural stability, and greater freedom in interface modulation. Therefore, quasi-two-dimensional perovskites are considered more suitable for efficient, stable, and tunable luminescent systems. However, during the film formation process of quasi-two-dimensional perovskites, it is often difficult to achieve a completely uniform distribution of organic spacer cations, leading to the formation of multiple quantum wells of varying thicknesses within the film—a multiphase structure with different n-phases coexisting. These different n-phases have different band gaps, with the smaller n-phase having a wider band gap and the larger n-phase having a narrower band gap, thus creating a natural energy gradient from high-energy to low-energy phases within the film.

[0004] In the aforementioned multi-n-phase quasi-two-dimensional perovskite system, photoexcitation typically involves a rapid transfer of excitons from the wide-bandgap, small-n-phase to the narrow-bandgap, large-n-phase; this process is commonly referred to as the energy funnel effect. While the energy funnel effect contributes to improved long-wavelength luminescence efficiency to some extent, its unidirectional energy convergence also concentrates luminescence primarily in the low-bandgap phase. This results in quasi-two-dimensional perovskite films generally exhibiting only single long-wavelength luminescence, making it difficult to simultaneously achieve stable multi-color luminescence output within the same film. For applications such as multi-color displays, optical encoding, anti-counterfeiting identification, and information encryption, relying solely on a single luminescence channel is clearly insufficient to meet the demands for high capacity, multiple levels, and spatial addressability.

[0005] In existing technologies, to achieve patterned luminescence in perovskite materials, methods such as inkjet printing, quantum dot inks, composite microarrays, electrohydrodynamic printing, or traditional photolithography are commonly used to construct luminescent patterns. While these methods can achieve patterned or pixelated luminescence to some extent, most still rely on a single luminescent color or a single optical channel. The pattern information primarily originates from the intensity difference between luminescent and non-luminescent areas, rather than from the modulation of multi-color energy channels within the same material system. Therefore, existing patterned perovskite luminescence technologies still have shortcomings in terms of information capacity, color dimensionality, spatial programmability, and long-term stability.

[0006] Existing research on the modulation of the energy funnel effect in quasi-two-dimensional perovskites has largely focused on altering the phase distribution and emission wavelength through compositional adjustments, variations in halogen ratios, design of spacer cations, or optimization of crystallization conditions. However, these methods typically involve global control, making it difficult to achieve pixel-level, region-selective energy funnel switching control within the same thin film. Furthermore, if the emission color is adjusted solely by changing the solution composition, the resulting state is easily affected by subsequent solvent treatment, illumination, humidity, and ion migration, making stable spatial locking difficult to achieve. In other words, existing methods often only alter the "emission outcome," but struggle to achieve addressable shutdown and non-volatile locking of the energy flow path.

[0007] On the other hand, from a physical perspective, if the interphase coupling between the small n-phase and the large n-phase can be weakened, allowing the excited states that were originally rapidly pumped to the low-energy phase to be retained and radiatively recombine in the high-energy or intermediate-energy phase, it may be possible to obtain multicolor emission in a single quasi-two-dimensional perovskite thin film. However, simply suppressing energy transfer is insufficient to meet the requirements of device applications, because the suppressed energy funnel state also needs to be spatially fixed to form a stable and readable emission pattern. Especially in applications such as anti-counterfeiting labels, information encryption, optical coding, and display pixels, the material must not only have multicolor emission capabilities but also possess characteristics such as clear pattern boundaries, stable colors, controllable development, and a certain degree of tolerance to environmental disturbances.

[0008] Therefore, there is an urgent need to propose a novel method for regulating the energy flow of quasi-two-dimensional perovskites. This method should first weaken the energy transfer between different n-phases through molecular interface modulation, thereby putting the energy funnel into a shut-off state, without destroying the layered crystal structure of the quasi-two-dimensional perovskite. Then, through photoinduced crosslinking, this shut-off state should be locked within a selected region, achieving spatially addressable regulation and stable maintenance of the energy funnel state. This method should simultaneously consider multicolor emission, patterned processing, state stability, and process compatibility, thus meeting the application requirements in fields such as multicolor display, optical encoding, anti-counterfeiting identification, information encryption, and perovskite light-emitting devices. Summary of the Invention

[0009] The purpose of this invention is to provide a method and application for locking the energy funnel shut-off in quasi-two-dimensional perovskite films, addressing the problem that in existing quasi-two-dimensional perovskite films, energy typically transfers rapidly from a wide-bandgap, small-n phase to a narrow-bandgap, large-n phase, resulting in the films primarily exhibiting single-wavelength emission and difficulty in spatially selectively fixing and maintaining the long-term stability of multi-color emission states. This invention, while maintaining the layered crystal structure and good film quality of the quasi-two-dimensional perovskite, first modulates the energy funnel effect between different n phases through molecular interface control, and then spatially selectively locks the shut-off state through a photoinduced thiol-ene crosslinking reaction, thereby obtaining a stable, patternable, and programmable multi-color emitting quasi-two-dimensional perovskite film.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] On one hand, the present invention provides a quasi-two-dimensional perovskite energy funnel shut-off locking method, comprising the following steps:

[0012] S1. Provide a substrate and prepare a quasi-two-dimensional perovskite thin film containing a multi-n phase distribution on the substrate;

[0013] S2. In the process of film formation of the quasi-two-dimensional perovskite film, bifunctional molecules containing thiol groups and interfacial interaction groups are introduced to regulate the local interphase structure between different n-phase quasi-two-dimensional perovskites and weaken the interphase energy transfer from the wide bandgap small n-phase to the narrow bandgap large n-phase, thereby changing the energy funnel of the quasi-two-dimensional perovskite from the open state to the closed state.

[0014] S3. Introduce a photopatterning system containing an alkenyl crosslinking agent and a photoinitiator onto a quasi-two-dimensional perovskite film containing the bifunctional molecules;

[0015] S4. Selectively irradiate the quasi-two-dimensional perovskite film to cause the thiol-olefin crosslinking reaction between the thiol group of the bifunctional molecule and the alkenyl crosslinking agent, thereby forming a crosslinking network in the light-received area and fixing the bifunctional molecule.

[0016] S5. The unlit area is developed to obtain a quasi-two-dimensional perovskite film in which the energy funnel is spatially selectively locked in the off state.

[0017] Furthermore, the quasi-two-dimensional perovskite film is a layered lead halide perovskite film with multiple n-phase coexisting structures, wherein the small n-phase has a wider band gap and the large n-phase has a narrower band gap. When the energy funnel is not turned off, the photoexcitation energy is transferred from the small n-phase to the large n-phase and mainly produces long-wavelength emission.

[0018] Furthermore, the quasi-two-dimensional perovskite film is a Ruddlesden-Popper type quasi-two-dimensional perovskite film, with the general formula R2A. n-1 Pbn X 3n+1 , where R is an organic spacer cation, A is a monovalent cation, X is a halide ion, and n is the number of lead halide octahedral layers.

[0019] Furthermore, the organic spacer cation R includes the phenylethylamine cation PEA. + , Butylamine cationic BA + Benzylamine cationic BAz + At least one of the following; the monovalent cation A includes Cs + MA + FA + At least one of the following; the halide ion X includes I - ,Br - Cl - At least one of the following; preferably, the quasi-two-dimensional perovskite film is PEA2Cs. n-1 Pb n I 3n+1 Quasi-two-dimensional perovskite thin films.

[0020] Furthermore, the quasi-two-dimensional perovskite film exhibits long-wavelength emission when the bifunctional molecule is not introduced; after the bifunctional molecule is introduced, the long-wavelength emission is weakened, and short-wavelength and / or mid-wavelength emission occurs; wherein the long-wavelength emission peak is located in the range of 650-720 nm, the short-wavelength emission peak is located in the range of 540-590 nm, the mid-wavelength emission peak is located in the range of 590-640 nm, and the quasi-two-dimensional perovskite film still maintains the quasi-two-dimensional perovskite layered crystal structure after treatment with the bifunctional molecule.

[0021] Furthermore, the bifunctional molecule is an organic small molecule containing both a thiol group and an interfacial interaction group. The interfacial interaction group includes at least one of a carboxyl group, a hydroxyl group, an amino group, a phosphonic acid group, and a sulfonic acid group, which are used to form hydrogen bonds, electrostatic interactions, coordination interactions, or combinations thereof with organic spacer cations, halide ions, or lead halide octahedral frameworks in quasi-two-dimensional perovskites to regulate the local interphase structure between different n phases. The thiol group of the bifunctional molecule is used for subsequent thiol-ene crosslinking reactions.

[0022] Furthermore, the bifunctional molecule is an organic small molecule containing both thiol and carboxyl groups, preferably thioglycolic acid (TGA) with the structural formula HS-CH2-COOH. The carboxyl group of TGA interacts with the organic spacer cation or halide ion in the quasi-two-dimensional perovskite, and the thiol group of TGA is used for subsequent thiol-ene crosslinking reaction.

[0023] Furthermore, the bifunctional molecule induces the formation of local morphology reconstruction regions in the quasi-two-dimensional perovskite film. These local morphology reconstruction regions serve as separating structures between adjacent different n-phases, increasing the effective distance between phases and weakening interphase coupling, thereby reducing the energy transfer efficiency from the small n-phase to the large n-phase.

[0024] Furthermore, the alkenyl crosslinking agent includes at least one of polyfunctional acrylate compounds, vinyl compounds, and allyl compounds, preferably pentaerythritol triacrylate PETA.

[0025] Further, the photoinitiator includes at least one of 2,2-dimethoxy-2-phenylacetophenone (DMPA), hydroxy ketone photoinitiators, and acylphosphine oxide photoinitiators, preferably DMPA; under light irradiation, DMPA generates free radicals and induces the thiol groups of TGA to form sulfur free radicals, which undergo an addition reaction with the carbon-carbon double bonds in PETA to form a crosslinked network containing CS bonds.

[0026] Furthermore, the selective illumination is any one of mask ultraviolet exposure, laser direct writing, digital micromirror projection exposure, or photolithography exposure; the selective illumination uses ultraviolet light with a wavelength of 300-420nm, preferably 365nm ultraviolet light; the development treatment uses a non-polar or weakly polar organic solvent to remove uncrosslinked, weakly adsorbed, or unfixed organic components, preferably toluene as the developer.

[0027] Furthermore, in the light-receiving region, the bifunctional molecules are fixed by a cross-linking network, which suppresses the energy transfer from the wide-bandgap small n-phase to the narrow-bandgap large n-phase in this region, thereby enhancing the emission of short-wavelength or mid-wavelength molecules; in the unlight-receiving region, the bifunctional molecules are not cross-linked or are partially removed, thus forming different energy funnel states and different emission colors compared to the light-receiving region.

[0028] Furthermore, by adjusting the amount of the bifunctional molecule added, the concentration of the alkenyl crosslinking agent, the concentration of the photoinitiator, the exposure dose, the exposure time and / or the development time, the degree of energy funnel shut-off and the color contrast of the multicolor luminescent pattern are controlled; the multicolor luminescent pattern includes at least one of text, icons, grids, pixel arrays, QR codes, anti-counterfeiting patterns, and information encryption patterns.

[0029] On the other hand, the present invention also provides a quasi-two-dimensional perovskite multicolor luminescent film prepared by the above method, wherein the quasi-two-dimensional perovskite multicolor luminescent film includes at least one energy funnel turn-off locked region and at least one unlocked region, wherein the energy funnel turn-off locked region and the unlocked region have different interphase energy transfer efficiencies and different luminescent colors.

[0030] Furthermore, the energy funnel shut-off locking region contains a cross-linking network formed by bifunctional molecules and an alkenyl cross-linking agent, the cross-linking network including sulfide bonds formed by the reaction of TGA and PETA.

[0031] Furthermore, the quasi-two-dimensional perovskite multicolor luminescent film exhibits spatially resolvable multicolor luminescent patterns under ultraviolet light excitation.

[0032] Furthermore, the present invention also provides an application of the method in optical coding devices, anti-counterfeiting tags, or light-emitting devices. This includes the preparation of a quasi-two-dimensional perovskite multicolor light-emitting thin film by the method.

[0033] Furthermore, the anti-counterfeiting label is pre-set with a multi-color luminescent pattern that can be read under specific lighting conditions.

[0034] Furthermore, the light-emitting device includes the quasi-two-dimensional perovskite multicolor light-emitting thin film as a light-emitting layer, a color conversion layer, a patterned light-emitting layer, or a light field modulation layer.

[0035] Furthermore, the quasi-two-dimensional perovskite multicolor luminescent film can be used for multicolor display, optical coding, anti-counterfeiting identification, information encryption, flexible optoelectronic devices, perovskite light-emitting diodes, or patterned light-emitting devices.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) This invention breaks through the traditional mode in which energy in quasi-two-dimensional perovskites is usually unidirectionally converged from the wide-bandgap small n phase to the narrow-bandgap large n phase, thus mainly producing single long-wavelength light emission. By introducing bifunctional molecules to regulate the local interphase organization between different n phases, the interphase energy transfer from the small n phase to the large n phase is weakened, and the energy funnel of the quasi-two-dimensional perovskite is changed from the open state to the closed state, thereby releasing the short-wavelength and mid-wavelength light emission channels and realizing multicolor light emission in a single thin film.

[0038] (2) This invention proposes a "lock-on-off" LASO strategy, which divides the energy funnel control into two consecutive steps: "switch off" and "lock". First, the energy funnel is turned off by bifunctional molecules such as TGA, and then the off state is fixed in a selected region by a thiol-olefin photocrosslinking reaction. Compared with simple component control or overall doping methods, this invention can achieve spatially addressable control and non-volatile maintenance of the energy flow path.

[0039] (3) The present invention can achieve energy funnel modulation without significantly destroying the quasi-two-dimensional perovskite layered crystal structure. The bifunctional molecules mainly change the coupling relationship between different n phases through interfacial interactions and local morphology reconstruction, rather than simply destroying the perovskite framework or generating a completely new luminescent phase. Therefore, it is beneficial to maintain the continuity, crystal orientation and basic photoelectric properties of the film.

[0040] (4) The present invention has good optical patterning capability. By means of mask ultraviolet exposure, laser direct writing or projection exposure, bifunctional molecules such as TGA can be selectively fixed in different areas of the thin film to form spatially resolved multicolor light-emitting areas, so as to realize the construction of complex patterns such as text, icons, grids, pixel arrays, QR codes, anti-counterfeiting patterns and information encryption patterns.

[0041] (5) The cross-linking network formed by the present invention can improve the chemical stability and environmental tolerance of the patterned area. After the bifunctional molecules in the light-receiving area are fixed by the cross-linking network, the loss or rearrangement of molecules under the action of subsequent development, storage, light, oxygen and water vapor can be reduced, so that the multicolor luminescent pattern can maintain clearer boundaries and more stable color output.

[0042] (6) This invention has strong process compatibility and platform extensibility. The quasi-two-dimensional perovskite composition, bifunctional molecules, alkenyl crosslinking agents, photoinitiators, exposure methods and development methods used can all be replaced or optimized according to the actual material system. Therefore, it is not only suitable for the preparation of multicolor luminescent patterns on rigid substrates, but also for application scenarios such as flexible optoelectronic devices, perovskite light-emitting diodes, optical coding, anti-counterfeiting labels, information encryption and display devices. Attached Figure Description

[0043] Figure 1 This is a diagram illustrating the mechanism and morphological characterization of the energy funnel effect induced by TGA in quasi-two-dimensional perovskites. (a) Schematic diagram of interphase energy transfer from the small n-phase to the large n-phase in multi-n-phase quasi-two-dimensional perovskites; (b) Schematic diagram of the changes in energy transfer paths between different n-phases without and after the addition of TGA, where the localized separation structure induced by TGA weakens interphase coupling; (c) Femtosecond transient absorption spectra of quasi-two-dimensional perovskite films at different delay times; (d) Transient kinetic curves extracted at 566 nm, 608 nm, and 650 nm, respectively, used to characterize the energy funnel process from the high-energy phase to the low-energy phase; (e) Scanning electron microscope images of quasi-two-dimensional perovskite films with different TGA contents, used to show the TGA-induced localized striped morphology reconstruction.

[0044] Figure 2These are the spectral and structural characterization diagrams of TGA suppressing the energy funnel of quasi-two-dimensional perovskite and maintaining its layered crystal structure. (a) Photoluminescence spectra of quasi-two-dimensional perovskite films with different TGA contents, showing that the emission is mainly at a long wavelength of 680 nm without TGA, while the emission at 680 nm is suppressed after the addition of TGA, and emission channels at 570 nm and 617 nm appear; (b) Absorption spectra of quasi-two-dimensional perovskite films with different TGA contents, used to illustrate that TGA does not simply generate new small n phases, but weakens the interphase energy transfer between existing different n phases; (c) X-ray diffraction patterns of films without TGA and with TGA; (d) GIWAXS pattern of film without TGA; (e) GIWAXS pattern of film with TGA; (f) XPS patterns of Pb 4f in films without TGA and with TGA, used to characterize the changes in the local chemical environment of Pb after the introduction of TGA.

[0045] Figure 3 This is a photo-patterning method and mechanism characterization diagram based on the thiol-alkene reaction to achieve TGA spatial locking. (a) Schematic diagram of the photo-patterning reaction mechanism, in which the photoinitiator DMPA generates free radicals under ultraviolet light irradiation and induces the thiol-alkene reaction between the thiol group of TGA and the alkenyl group of PETA; (b) S 2p XPS pattern of quasi-two-dimensional perovskite film without the addition of PETA; (c) S 2p XPS pattern after the addition of PETA and photo-crosslinking; (d) Calculation results of adsorption energy or formation energy of TGA, sulfur free radicals, PETA and crosslinked sulfide structure on the quasi-two-dimensional perovskite surface; (e) Schematic diagram of the reaction of TGA and PETA to undergo thiol-alkene reaction and form RS-R1 crosslinked structure.

[0046] Figure 4These are the luminescence distribution, morphology, stability, and time-resolved spectral characterization of thiol-olefin crosslinked patterned quasi-two-dimensional perovskite films. (a) PL mapping of the “NJU” patterned region measured in the 570 nm emission channel; (b) PL mapping of the “NJU” patterned region measured in the 617 nm emission channel, where the 570 nm and 617 nm channels show opposite spatial intensity distributions, indicating that the spatially selective fixation of TGA alters the local energy funnel efficiency; (c) AFM height map of the patterned film, with the inset showing the corresponding “NJU” emission pattern; (d) Luminescence photographs of the patterned samples with positive and negative masks during storage from day 2 to day 5, used to compare the pattern stability of cross-linked and uncross-linked regions; (e) Three-dimensional AFM morphology of the patterned region; (f) TRPL decay curves of films without and with TGA in the 500-700 nm full-band spectrum; (g) TRPL decay curve of the 570 nm high-energy emission channel; (h) TRPL decay curve of the 617 nm low-energy emission channel, used to verify the inhibitory effect of TGA on the energy funnel process.

[0047] Figure 5 These are images showing the patterning and time-response imaging results of quasi-two-dimensional perovskite multicolor microstructures. (a) An optical microscopic image of a 423 ppi pixel array prepared using the method of this invention, showing a pixel pitch of approximately 60 μm and good array repeatability; (b) Optical microscopic images of various dual-color microstructure patterns, including micrometer grids, sun patterns, circular badge patterns, and QR code patterns, illustrating the applicability of this method to complex graphics and high-density information encoding; (c) High-fidelity reproduction results of complex logo patterns; (d) Continuous imaging results at different time points under continuous illumination excitation, showing that the preset pattern gradually appears over time, exhibiting time-response development characteristics.

[0048] Figure 6 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can make equivalent substitutions or conventional adjustments to the two-dimensional perovskite composition, substrate type, bifunctional molecule types, crosslinking agent, photoinitiator, exposure method, developer, and process parameters, all of which should fall within the scope of protection of the present invention.

[0050] This embodiment provides a quasi-two-dimensional perovskite energy funnel turn-off locking method based on a "lock-after-switch-off" (LASO) strategy. This method is implemented on a quasi-two-dimensional perovskite thin film platform, including a substrate, a multi-n-phase quasi-two-dimensional perovskite thin film formed on the substrate, a bifunctional molecule for turning off the energy funnel effect, an alkenyl crosslinking agent and a photoinitiator for locking the turn-off state, and a mask or photolithography system for spatially selective exposure. The quasi-two-dimensional perovskite thin film contains multiple quantum well structures with different n-phases. The smaller n-phase has a wider bandgap, while the larger n-phase has a narrower bandgap. In the untreated state, photoexcitation energy typically transfers from the smaller n-phase to the larger n-phase, primarily generating long-wavelength emission. This invention introduces a bifunctional molecule during film formation to first weaken the interphase energy transfer between different n-phases, causing the energy funnel to change from an open state to a turn-off state. Subsequently, a photoinduced thiol-alkene crosslinking reaction fixes this turn-off state in a selected region, thereby obtaining a spatially resolvable and stably maintained multicolor emission pattern.

[0051] Specifically, this embodiment uses a Ruddlesden-Popper type quasi-two-dimensional perovskite thin film, whose general formula can be expressed as R2A. n-1 Pb n X 3n+1 Where R is an organic spacer cation, A is a monovalent cation, X is a halide ion, and n represents the number of lead halide octahedral layers. Preferably, the quasi-two-dimensional perovskite film is PEA2Cs. n-1 Pb n I3 n+1 Quasi-two-dimensional perovskite thin films. PEA + As an organic spacer cation, Cs is beneficial for maintaining the layered perovskite structure; + Pb 2+ and I - The film forms a lead halide octahedral framework. Because the distribution of organic spacer cations during film formation is difficult to control precisely, multiple quantum wells of varying thicknesses, i.e., multiple coexisting n-phase structures, are formed within the film. The bandgap differences between the different n-phases create a natural energy gradient, causing excited states generated by the smaller n-phase to transfer to the larger n-phase, thus creating an energy funnel effect. The paper points out that the n-phase dispersion in quasi-two-dimensional perovskites produces energy transfer from a wide bandgap phase to a narrow bandgap phase, causing the film to typically exhibit energy funnel behavior.

[0052] In this embodiment, the bifunctional molecule is preferably thioglycolic acid (TGA), with the structural formula HS–CH2–COOH. TGA contains both carboxyl and thiol groups. The carboxyl group is used to form hydrogen bonds, electrostatic interactions, or interfacial interactions with organic spacer cations, halide ions, and lead halide skeletons in the quasi-two-dimensional perovskite, while the thiol group is used for subsequent thiol-ene crosslinking reactions. Specifically, the carboxyl group of TGA can react with PEA...+ The ammonium groups in the PEA form hydrogen bonds and interact with the perovskite interface to form OH···I, C=O···HN, etc., making TGA more likely to be distributed in the interface region between different n phases, rather than directly inserted into the inorganic octahedral framework. The paper clearly points out that PEA + Hydrogen bonds can form between the ammonium group and the carboxyl group of TGA, causing TGA to tend to be located in the interface region between different n phases.

[0053] In the preparation process, a quasi-two-dimensional perovskite precursor solution is first prepared, and then a certain amount of TGA is added to it. This allows TGA to participate in the phase structure regulation of the quasi-two-dimensional perovskite during subsequent film formation and annealing. The amount of TGA added can be adjusted according to the target energy funnel shut-off level, for example, it can be set to 0.28 mmol or 0.57 mmol, or it can be adjusted proportionally according to the total amount of precursor, film thickness, and target emission color. Subsequently, the TGA-containing precursor solution is coated onto a substrate. The coating method can be spin coating, blade coating, spray coating, slot coating, or inkjet printing; the substrate can be a rigid substrate such as glass, quartz, silicon wafer, or ITO glass. After coating, annealing is performed to form a TGA-containing quasi-two-dimensional perovskite film.

[0054] like Figure 1 As shown, in quasi-two-dimensional perovskite films without TGA, the different n-phases are relatively close together, and photoexcitation energy is transferred from the wide-bandgap small n-phase to the narrow-bandgap large n-phase, ultimately resulting in radiative recombination mainly occurring in the large n-phase. With the addition of TGA, TGA induces the formation of stripe-like or locally reconstructed morphology regions through interfacial interactions and local crystallization regulation. These regions can serve as separating structures between different n-phases, increasing the effective distance between adjacent n-phases, weakening near-field interphase coupling, and thus reducing the energy transfer efficiency from the small n-phase to the large n-phase. The paper points out that TGA-induced local morphology reconstruction can increase the effective separation distance between adjacent n-phases, thereby reducing near-field non-radiative energy transfer and suppressing the energy funnel from the small n-phase to the large n-phase.

[0055] The energy funnel process described above can be verified using femtosecond transient absorption tests. For example... Figure 1 As shown in (c) and (d), multiple bleaching signals at 566 nm, 608 nm, and 650 nm can be observed in the film under 400 nm excitation. Among them, the 566 nm and 608 nm signals decay rapidly over time, while the 650 nm signal is relatively enhanced in subsequent delay times and exhibits a behavior of first rising and then decaying. This indicates that the excited state in the high-energy phase gradually transfers and fills the low-energy phase, which is consistent with the interphase energy funnel mechanism in quasi-two-dimensional perovskites.

[0056] like Figure 2As shown, the addition of TGA significantly alters the luminescence behavior of quasi-two-dimensional perovskite films. Films without TGA primarily exhibit long-wavelength emission around 680 nm, indicating effective energy concentration in the low-bandgap, large-n phase. With TGA addition, the 680 nm emission is significantly weakened, while short-wavelength and mid-band emission peaks appear at approximately 570 nm and 617 nm, indicating the release of radiative recombination channels between the small-n and mid-n phases. With increasing TGA content, the 570 nm emission further strengthens, indicating a further improvement in the energy funnel shut-off. The paper explicitly states that the addition of TGA suppresses 680 nm emission and introduces 570 nm and 617 nm emission channels, suggesting a weakening of interphase energy transfer.

[0057] It's important to note that the role of TGA is not to cut the large n-phase into new small n-phases. Absorption spectroscopy shows that absorption shoulders exist around 2.03 eV, 2.19 eV, and 2.38 eV, regardless of the addition of TGA, corresponding to optical characteristics around n≈3, n≈2, and n≈1, respectively. Therefore, TGA primarily weakens the interphase energy transfer between existing different n-phases, allowing the existing small n-phase or intermediate n-phase to participate more directly in luminescence, rather than altering the spectrum by generating new small n-phases.

[0058] Meanwhile, the addition of TGA does not disrupt the basic layered crystal structure of the quasi-two-dimensional perovskite. XRD and GIWAXS tests show that the film retains the typical RP-type (001) orientation after the addition of TGA; the (002) peak position in GIWAXS remains basically unchanged, indicating that the average interlayer spacing and basic layered structure are maintained. The paper points out that both XRD and GIWAXS after TGA treatment show that the layered structure and orientation of the quasi-two-dimensional perovskite are not destroyed. In addition, a new C=O stretching vibration peak appears near approximately 1700 cm⁻¹ in FTIR, further indicating that the carboxyl groups of TGA are introduced into the film.

[0059] After the energy funnel is shut off, this embodiment further performs a "locking" step. Specifically, an alkenyl crosslinking agent and a photoinitiator are introduced onto the surface of the TGA-containing quasi-two-dimensional perovskite film. Preferably, the alkenyl crosslinking agent is pentaerythritol triacrylate (PETA), and the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone (DMPA). PETA and DMPA can be dissolved in a suitable organic solvent to form a photopatterning system and coated onto the surface of the TGA-containing quasi-two-dimensional perovskite film.

[0060] like Figure 3As shown, under ultraviolet light irradiation, DMPA generates free radicals, which induce the thiol groups in TGA to form sulfur free radicals. These sulfur free radicals further undergo an addition reaction with the carbon-carbon double bonds in PETA, forming a thioether crosslinked structure containing CS bonds, thereby constructing a crosslinked network. This crosslinked network can covalently anchor TGA in the light-receiving region, fixing the energy funnel-off state of that region. The paper points out that DMPA acts as a photoinitiator, PETA provides alkenyl groups, and TGA provides thiol groups. Under ultraviolet light, the sulfur free radicals of TGA react with the C=C bonds of PETA to form CS linkages and anchor TGA.

[0061] In this embodiment, selective illumination is preferably performed using 365 nm photomask UV exposure. A photomask with a preset pattern is placed over the film, followed by 365 nm UV irradiation, causing the TGA and PETA in the exposed area to undergo a thiol-olefin crosslinking reaction. The unexposed area does not undergo or experiences minimal crosslinking. After exposure, the film is treated with a developer to remove uncrosslinked, weakly adsorbed, or unfixed organic components. Preferably, the developer is toluene. After development, the TGA in the exposed area is fixed by the crosslinking network and remains in an energy funnel-off state; the TGA in the unexposed area can be partially removed or redistributed, thus forming different energy funnel states and different emission colors compared to the exposed area.

[0062] like Figure 3 As shown in (b) and (c), S 2p XPS can be used to characterize whether the thiol-ene reaction occurs. In the absence of PETA or without the formation of a crosslinked network, an S 2p signal associated with TGA thiol activation or coordination can be observed; after the addition of PETA and UV irradiation, the S 2p signal... 3 / 2 The peak shifts to approximately 163.46 eV, corresponding to the R–S–R1 structure of the thioether, indicating that the thiol group of the TGA is consumed and a new CSC link is formed. The paper points out that this change in S 2p binding energy provides direct evidence for the transformation of surface thiols into a cross-linked thioether network.

[0063] Furthermore, DFT calculations can be used to verify the stability of this crosslinked structure. The -SH group of TGA has weak surface interactions, while forming sulfur radicals that interact with Pb. 2+ The adsorption energy decreased significantly after coordination, indicating that the intermediate state has a strong surface binding ability; the R–S–R1 structure formed by the thiol-olefin addition of TGA and PETA has a negative formation energy, indicating that the obtained crosslinked network has thermodynamic stability and is not prone to reverse reaction or desorption.

[0064] like Figure 4As shown, after the above LASO treatment, spatially resolvable multicolor luminescent patterns can be formed on the same quasi-two-dimensional perovskite film. Under the 570 nm luminescence channel, the exposed pattern area exhibits strong luminescence; while under the 617 nm luminescence channel, the pattern area and the background area show opposite spatial intensity distributions. This indicates that the thiol-olefin crosslinking treatment can spatially selectively fix the TGA, change the local n-phase energy transfer efficiency, and thus control the local emission wavelength. The paper points out that the 570 nm and 617 nm PL mappings show opposite trends, indicating that the TGA, after spatially selectively fixed, forms different local n-phase ratios and different energy funnel efficiencies.

[0065] To verify pattern stability, this embodiment uses both positive and negative masks to prepare samples, which are then stored at room temperature and certain humidity for several days for comparison. Figure 4 As shown in (d), the cross-linked fixed regions maintained clearer pattern boundaries and more stable emission colors during storage; while the uncross-linked regions were more prone to TGA migration, removal, or phase composition changes, leading to reduced pattern contrast. The paper points out that after five days of storage at 25°C and 40% humidity, the cross-linked exposed regions maintained high stability, while the uncross-linked regions showed more obvious phase evolution and pattern contrast decay.

[0066] To further demonstrate the suppressive effect of TGA on the energy funnel, time-resolved photoluminescence (TRF) tests can be performed on the samples. For example... Figure 4 As shown in (f) to (h), during detection across the 500-700 nm wavelength range, the average lifetime increased from 0.445 ns to 5.072 ns after the addition of TGA, while the proportion of fast-decaying components decreased from 98.7% to 14.2%, indicating a significant weakening of the fast channels associated with energy transfer. In the 570 nm high-energy channel, the proportion of fast components decreased, indicating a weakening of donor-acceptor transfer; in the 617 nm low-energy channel, the average lifetime decreased from 7.80 ns to 6.58 ns, and the slow tail shortened, indicating that the low-energy acceptor channel lost continuous feeding from high-energy donors. These results collectively demonstrate that TGA reduces the effective D→A energy transfer rate and suppresses the energy funnel in quasi-two-dimensional perovskites.

[0067] like Figure 5As shown, the method in this embodiment is not only applicable to simple text patterns, but also to the construction of high-density pixel arrays, line grids, sun patterns, badge patterns, QR code patterns, and complex logo patterns. For example, it can prepare a light-emitting pixel array with a resolution of 423 ppi and a pixel pitch of approximately 60 μm, and it can also prepare a micron-sized line grid pattern with a linewidth of approximately 15 μm. The above results demonstrate that the present invention has good pattern transfer repeatability, boundary clarity, and compatibility with complex graphics, making it suitable for anti-counterfeiting, information encryption, and optical encoding. The paper points out that this method can prepare various complex patterns such as 423 ppi pixel arrays, line grids, badges, and QR codes, showing its potential for high-density information integration.

[0068] In another preferred embodiment, the present invention can also achieve time-responsive pattern development. For example... Figure 5 As shown in (d), under continuous 365 nm illumination, the preset pattern gradually emerges from an initial low-contrast state. The contrast between the pattern and the background increases with irradiation time, exhibiting a photoresponsive development process from "invisible" to "visible." The paper indicates that under continuous 365 nm illumination, the 70% development time is approximately 6.05 s, and the 90% development time is approximately 8.2 s, demonstrating that the system exhibits second-level time-response development characteristics.

[0069] The complete process flow of this embodiment can be summarized as follows: First, the quasi-two-dimensional perovskite composition and substrate are selected according to the target emission color and pattern application; then, a quasi-two-dimensional perovskite precursor solution is prepared and TGA is added to it; subsequently, a TGA-containing quasi-two-dimensional perovskite film is formed on the substrate by spin coating or other coating methods, so that TGA regulates the interphase structure between different n phases and shuts off the energy funnel during the film formation process; then, a photopatterning system composed of PETA and DMPA is introduced on the film surface; then, thiol-olefin crosslinking is induced in the exposed area by 365 nm mask exposure or laser direct writing; finally, toluene is used for development to remove unfixed components, resulting in a quasi-two-dimensional perovskite film with spatially resolvable multi-color emission patterns.

[0070] In this invention, TGA, PETA, DMPA, and toluene are only preferred embodiments. Those skilled in the art can, according to actual needs, replace TGA with other bifunctional molecules containing interfacial interaction groups such as thiol and carboxyl, hydroxyl, amino, phosphonic acid, or sulfonic acid groups; replace PETA with other multifunctional acrylate, vinyl, or allyl crosslinking agents; replace DMPA with other photoinitiators capable of generating free radicals under ultraviolet or visible light; replace 365 nm mask exposure with laser direct writing, digital micromirror projection exposure, or other photolithography methods; and replace toluene with a nonpolar or weakly polar developer that minimizes damage to the two-dimensional perovskite host structure and can remove unfixed organic components. All such substitutions, as long as they still achieve the LASO technology concept of "first turning off the energy funnel, then locking the off state," should be considered equivalent embodiments of this invention.

[0071] In summary, this embodiment achieves energy funnel shut-off by introducing TGA during the quasi-two-dimensional perovskite film formation process, and achieves spatially selective locking of the shut-off state through thiol-ene photocrosslinking induced by the PETA / DMPA system. This ultimately yields a quasi-two-dimensional perovskite thin film possessing multi-color emission, patterned processing, state stability, and process compatibility. Based on the design concept described in this embodiment, those skilled in the art can extend it to other quasi-two-dimensional perovskite components, different halogen systems, flexible substrates, multi-color display devices, perovskite light-emitting diodes, anti-counterfeiting labels, optical coding, and information encryption platforms. As long as the core remains the same—shutting off the energy funnel between different n-phases through molecular regulation and locking the shut-off state through crosslinking reactions—it should be considered an equivalent embodiment of the present invention.

Claims

1. A method for locking off a quasi-two-dimensional perovskite energy funnel, characterized in that, Includes the following steps: S1. Provide a substrate and prepare a quasi-two-dimensional perovskite thin film containing a multi-n phase distribution on the substrate; S2. In the process of film formation of the quasi-two-dimensional perovskite film, bifunctional molecules containing thiol groups and interfacial interaction groups are introduced to regulate the local interphase structure between different n-phase quasi-two-dimensional perovskites and weaken the interphase energy transfer from the wide bandgap small n-phase to the narrow bandgap large n-phase, thereby changing the energy funnel of the quasi-two-dimensional perovskite from the open state to the closed state. S3. Introduce a photopatterning system containing an alkenyl crosslinking agent and a photoinitiator onto a quasi-two-dimensional perovskite film containing the bifunctional molecules; S4. Selectively irradiate the quasi-two-dimensional perovskite film to cause the thiol-olefin crosslinking reaction between the thiol group of the bifunctional molecule and the alkenyl crosslinking agent, thereby forming a crosslinking network in the light-received area and fixing the bifunctional molecule. S5. The unlit area is developed to obtain a quasi-two-dimensional perovskite film in which the energy funnel is spatially selectively locked in the off state.

2. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, The quasi-two-dimensional perovskite film is a Ruddlesden-Popper type quasi-two-dimensional perovskite film with the general formula R2A. n-1 Pb n X 3n+1 Where R is an organic spacer cation, A is a monovalent cation, X is a halide ion, and n is the number of lead halide octahedral layers; the organic spacer cation R includes phenylethylamine cation PEA. + , Butylamine cationic BA + Benzylamine cationic BAz + At least one of the following; the monovalent cation A includes Cs + MA + FA + At least one of the following; the halide ion X includes I - ,Br - Cl - At least one of the following; preferably, the quasi-two-dimensional perovskite film is PEA2Cs. n-1 Pb n I 3n+1 Quasi-two-dimensional perovskite thin films.

3. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, The quasi-two-dimensional perovskite film exhibits long-wavelength emission when the bifunctional molecule is not introduced; after the bifunctional molecule is introduced, the long-wavelength emission is weakened, and short-wavelength and / or mid-wavelength emission occurs; wherein the long-wavelength emission peak is located in the range of 650-720 nm, the short-wavelength emission peak is located in the range of 540-590 nm, the mid-wavelength emission peak is located in the range of 590-640 nm, and the quasi-two-dimensional perovskite film still maintains the quasi-two-dimensional perovskite layered crystal structure after treatment with the bifunctional molecule.

4. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, The bifunctional molecule is an organic small molecule containing both a thiol group and an interfacial interaction group. The interfacial interaction group includes at least one of a carboxyl group, a hydroxyl group, an amino group, a phosphonic acid group, and a sulfonic acid group, which are used to form hydrogen bonds, electrostatic interactions, coordination interactions, or combinations thereof with organic spacer cations, halide ions, or lead halide octahedral frameworks in quasi-two-dimensional perovskites. Preferably, the bifunctional molecule is an organic small molecule containing both a thiol group and a carboxyl group, more preferably a mercaptoacetic acid (TGA) with the structural formula HS-CH2-COOH, wherein the carboxyl group of TGA interacts with the organic spacer cations or halide ions in quasi-two-dimensional perovskites, and the thiol group of TGA is used for subsequent thiol-ene crosslinking reactions.

5. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, The alkenyl crosslinking agent includes at least one of polyfunctional acrylate compounds, vinyl compounds, and allyl compounds, preferably pentaerythritol triacrylate PETA; the photoinitiator includes at least one of 2,2-dimethoxy-2-phenylacetophenone DMPA, hydroxy ketone photoinitiators, and acylphosphine oxide photoinitiators, preferably DMPA; under light irradiation, DMPA generates free radicals and induces the thiol groups of TGA to form sulfur free radicals, which undergo an addition reaction with the carbon-carbon double bonds in PETA to form a crosslinking network containing CS bonds.

6. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, The selective illumination is any one of mask ultraviolet exposure, laser direct writing, digital micromirror projection exposure, or photolithography exposure; the selective illumination uses ultraviolet light with a wavelength of 300-420nm, preferably 365nm ultraviolet light; the development treatment uses a non-polar or weakly polar organic solvent to remove uncrosslinked, weakly adsorbed, or unfixed organic components, preferably toluene as the developer.

7. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, In the light-receiving region, bifunctional molecules are fixed by a cross-linked network, which suppresses the energy transfer from the wide-bandgap small n-phase to the narrow-bandgap large n-phase in this region, thereby enhancing short-wavelength or mid-wavelength luminescence. In the unlit region, the bifunctional molecules are not cross-linked and fixed or are partially removed, thus forming a different energy funnel state and a different emission color compared to the lit region.

8. The method for shutting off and locking a quasi-two-dimensional perovskite energy funnel according to claim 1, characterized in that, By adjusting the amount of the bifunctional molecule added, the concentration of the alkenyl crosslinking agent, the concentration of the photoinitiator, the exposure dose, the exposure time and / or the development time, the degree of energy funnel shut-off and the color contrast of the multicolor luminescent pattern are controlled; the multicolor luminescent pattern includes at least one of text, icons, grids, pixel arrays, QR codes, anti-counterfeiting patterns, and information encryption patterns.

9. The quasi-two-dimensional perovskite multicolor luminescent thin film prepared by the method according to any one of claims 1 to 8, characterized in that, The quasi-two-dimensional perovskite multicolor luminescent film includes at least one energy funnel turn-off locked region and at least one unlocked region. The energy funnel turn-off locked region and the unlocked region have different interphase energy transfer efficiencies and different emission colors. The energy funnel turn-off locked region contains a crosslinking network formed by bifunctional molecules and an alkenyl crosslinking agent. The crosslinking network contains a thioether bond structure. The quasi-two-dimensional perovskite multicolor luminescent film exhibits a spatially resolvable multicolor emission pattern under ultraviolet light excitation.

10. The application of the method according to any one of claims 1 to 8 in an optical encoding device, anti-counterfeiting label, or light-emitting device, characterized in that, The invention includes a quasi-two-dimensional perovskite multicolor luminescent film prepared by a method; wherein the anti-counterfeiting label has a pre-set multicolor luminescent pattern that can be read under specific lighting conditions, and the luminescent device includes the quasi-two-dimensional perovskite multicolor luminescent film as a luminescent layer, a color conversion layer, a patterned luminescent layer, or a light field modulation layer; the quasi-two-dimensional perovskite multicolor luminescent film is used for multicolor display, optical encoding, anti-counterfeiting identification, information encryption, flexible optoelectronic devices, perovskite light-emitting diodes, or patterned light-emitting devices.

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