A tin-based near-infrared two-region perovskite light-emitting diode and a preparation method thereof

Abstract

This invention discloses a tin-based near-infrared II perovskite light-emitting diode and its fabrication method, comprising: forming a hole transport layer on a conductive substrate; forming a buried interface modification layer containing 2-fluoro-5-(methylsulfonyl)aniline on the hole transport layer; applying a tin-based perovskite precursor solution onto the buried interface modification layer to form a tin-based perovskite light-emitting layer; and forming an electron transport layer and electrodes on the light-emitting layer. FMSA is formed via sulfonyl groups and Sn. 2+ Coordination to suppress Sn 2+ Oxidation and reduction of p-type self-doping, through amino groups and I groups ‑ Intermolecular interactions are formed to regulate the crystallization rate and improve the morphology of the luminescent layer. Fluorine atoms are used to modulate the interfacial energy level arrangement to suppress excessive hole injection and promote carrier injection balance. This method can simultaneously suppress Sn... 2+ Oxidation, regulation of crystallization rate, and optimization of interface energy level arrangement are used to obtain tin-based near-infrared II perovskite light-emitting diodes that combine high efficiency and long operating life.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a tin-based near-infrared II perovskite light-emitting diode and its fabrication method. Background Technology

[0002] Near-infrared light-emitting diodes (NIR LEDs) have broad application prospects in night vision, biomedical imaging, biometric recognition, and optical communication. Metal halide perovskite materials are considered ideal candidate materials for constructing high-performance NIR LEDs due to their advantages such as solution processability, tunable bandgap, narrow emission half-width, and high photoluminescence quantum yield. Currently, the emission of high-efficiency perovskite LEDs (PeLEDs) is mainly limited to the first near-infrared window (NIR-I, 700~900 nm). In contrast, the second near-infrared window (NIR-II, 900~1700 nm) has advantages such as invisible emission, deeper tissue penetration, and lower scattering, making it more valuable for applications in biomedicine and night vision.

[0003] While lead-based perovskites have achieved external quantum efficiencies exceeding 30%, their inherent biotoxicity and environmental risks severely limit their practical applications and commercialization. Tin-based perovskites, possessing similar optoelectronic properties to lead-based perovskites and being environmentally friendly, are considered ideal alternatives. Among them, the all-inorganic CsSnI3 perovskite emits in the NIR-II region (approximately 945 nm) and exhibits better thermal and environmental stability compared to organic-inorganic hybrid tin perovskites, making it an ideal light-emitting material for constructing high-performance NIR-II PeLEDs.

[0004] However, the performance of tin-based perovskite optoelectronic devices still lags far behind that of lead-based devices. Firstly, the outer 5s... 2 The weak orbital electron binding energy leads to Sn 2+ It is easily oxidized to Sn 4+ Sn 4+ The formation of tin vacancies and other deep-level defects leads to severe nonradiative recombination and introduces unfavorable p-type self-doping, degrading film quality and device performance. Secondly, SnI2 exhibits stronger Lewis acidity than PbI2, resulting in faster reaction kinetics with perovskite precursors. This leads to excessively rapid and uncontrollable crystallization rates, poor film morphology, low coverage, high pinhole density, and the generation of numerous defect states. Furthermore, the PEDOT:PSS hole transport layer, widely used in tin-based perovskite devices, suffers from energy level mismatch, hindering efficient carrier injection and balancing. This layer also easily induces degradation at the perovskite buried interface, exacerbating interfacial nonradiative recombination.

[0005] To address these issues, researchers have explored various strategies, such as using additive engineering to regulate crystallization and inhibit Sn.2+ Oxidation can improve film quality through interface modification or optimize crystal structure stability through composition engineering. However, these strategies usually only address single-level issues and cannot simultaneously address crystallization control, defect passivation, and energy level matching, resulting in difficulties in simultaneously improving device efficiency, brightness, and stability.

[0006] Therefore, it is necessary to develop a method that can simultaneously suppress Sn 2+ The preparation method of oxidation, regulating the crystallization rate and optimizing the interfacial energy level arrangement is of great significance for realizing efficient, high-brightness and stable tin-based near-infrared II perovskite light-emitting diodes. Summary of the Invention

[0007] In view of the aforementioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a tin-based near-infrared II perovskite light-emitting diode and its fabrication method, aiming to provide a method capable of simultaneously suppressing Sn 2+ Tin-based near-infrared II perovskite light-emitting diodes with oxidation, controlled crystallization rate, and optimized interfacial energy level arrangement.

[0008] To achieve the above objectives, the first aspect of this invention discloses a method for fabricating a tin-based near-infrared II perovskite light-emitting diode, the method comprising: Step S1: Provide a conductive substrate and form a hole transport layer on the conductive substrate; Step S2: A buried interface modification layer is formed on the hole transport layer; wherein the material of the buried interface modification layer comprises 2-fluoro-5-(methanesulfonyl)aniline (FMSA); Step S3: Apply the tin-based perovskite precursor solution to the buried interface modification layer so that the tin-based perovskite precursor solution forms a tin-based perovskite luminescent layer; Step S4: An electron transport layer is formed on the tin-based perovskite light-emitting layer, and an electrode is formed on the electron transport layer to obtain a perovskite light-emitting diode; The FMSA achieves synergistic regulation of the tin-based perovskite luminescent layer through the sulfonyl, amino, and fluorine atoms in its molecule. The sulfonyl group is used to react with Sn in the tin-based perovskite light-emitting layer. 2+ Coordination to suppress Sn 2+ Oxidizes and reduces p-type self-doping in the tin-based perovskite luminescent layer; The amino group is used to react with I in the tin-based perovskite light-emitting layer. - Intermolecular interactions are formed to regulate the perovskite crystallization rate and improve the morphology of the tin-based perovskite luminescent layer; The fluorine atoms are used to adjust the interfacial energy level arrangement of the tin-based perovskite luminescent layer to suppress excessive hole injection and promote carrier injection balance.

[0009] Optionally, step S2 includes: A first FMSA solution is spin-coated onto the hole transport layer to form a first modified sublayer; A second FMSA solution is spin-coated onto the first modified sublayer to form a second modified sublayer; wherein the concentration of the first FMSA solution is higher than the concentration of the second FMSA solution, such that: the first modified sublayer is used to adjust the energy level alignment on the surface of the hole transport layer to reduce the hole injection barrier and acts as a dense barrier layer to suppress interface leakage current; the second modified sublayer is used to interact with the Sn at the bottom of the tin-based perovskite luminescent layer through its sulfonyl groups. 2+ Coordination to passivate interface defects, and through its amino groups with I - Intermolecular interactions are formed to slow down the crystallization rate.

[0010] Optionally, step S3 includes: A first precursor solution is provided, and FMSA is added to the first precursor solution to perform a pre-coordination reaction to form a solution containing FMSA-Sn. 2+ The tin-based perovskite precursor solution of the complex; wherein the reaction temperature of the pre-coordination reaction is 25~60℃ and the reaction time is 0.5~24 hours; The tin-based perovskite precursor solution was spin-coated onto the buried interface modification layer and annealed to achieve Sn before perovskite crystallization. 2+ Pre-passivation is performed to form a tin-based perovskite luminescent layer.

[0011] Optionally, after step S3, the method further includes: FMSA is dissolved in an antisolvent to form a post-treatment solution; The post-treatment solution is applied to the surface of the tin-based perovskite luminescent layer and subjected to a second annealing treatment, so that FMSA molecules penetrate into the grain boundaries and top interface of the tin-based perovskite luminescent layer, and together with the FMSA of the buried interface modification layer, they form a three-in-one passivation structure of buried interface-bulk grain boundary-top interface.

[0012] Optionally, the embedded interface modification layer is self-assembled by dynamic spin coating or immersion; the concentration of the FMSA solution is 0.5~10 mg / mL, the spin coating speed is 2000~6000 rpm, the spin coating time is 20~60 seconds, the annealing temperature is 70~120℃, and the annealing time is 5~30 minutes.

[0013] Optionally, the hole transport layer is a PEDOT:PSS layer or a self-assembled monolayer based on FMSA; the conductive substrate is ITO conductive glass; the electron transport layer is made of SPPO13, B3PYMPM, or a combination of both; and the electrode is a LiF / Al composite electrode.

[0014] Optionally, after applying the tin-based perovskite precursor solution to the buried interface modification layer in step S3, the process further includes: annealing; the annealing temperature is 70~120℃, the annealing time is 5~30 minutes, and the annealing atmosphere is an inert gas protective atmosphere or a vacuum environment.

[0015] The second aspect of the present invention discloses a tin-based near-infrared II perovskite light-emitting diode, which is prepared by any of the above-described preparation methods.

[0016] The beneficial effects of this invention are as follows: 1. This invention introduces a buried interface modification layer containing 2-fluoro-5-(methylsulfonyl)aniline between the hole transport layer and the tin-based perovskite luminescent layer. By utilizing the synergistic effect of three functional groups in the same molecule, it simultaneously solves the three major technical problems that tin-based perovskites have long faced: the interaction between sulfonyl groups and Sn. 2+ Coordination inhibits Sn 2+ Oxidation and reduction of p-type self-doping, amino groups and I - Intermolecular interactions modulate the crystallization rate and improve film morphology, while fluorine atoms regulate the interfacial energy level arrangement and optimize carrier injection balance. These three functions are integrated into the same molecule and the same modification layer, resulting in a simple and convenient process that achieves simultaneous improvements in device efficiency, brightness, and stability without the need for multilayer structures or multiple additives. 2. This invention further employs a concentration-gradient bilayer FMSA modification structure. The first modification sublayer (high concentration) and the second modification sublayer (low concentration) achieve spatial partitioning of functions within the same molecular system: the bottom layer enhances the energy level regulation and interfacial blocking function of the hole transport layer surface through high-density sulfonyl groups, while the top layer concentrates on defect passivation and crystallization regulation of the perovskite bottom interface through low-density sulfonyl groups and amino groups. This gradient structure allows each layer to focus on its most effective function, avoiding the functional trade-offs that occur when a single concentration layer simultaneously addresses energy level regulation and defect passivation, thus further optimizing the overall regulation effect of the buried interface. 3. This invention further adds FMSA to the perovskite precursor solution for a pre-coordination reaction, making FMSA-Sn... 2+The complex is formed in solution. Compared to simply placing FMSA at the buried interface (acting only on the bottom interface) or directly forming a film after simple mixing, the pre-coordination treatment allows the passivation effect of FMSA to be pre-placed around the tin source before crystallization. This enables more uniform introduction into the perovskite bulk grain boundaries and, together with the FMSA in the buried interface modification layer, forms a dual passivation system of "interface + bulk," further reducing the bulk defect density and suppressing nonradiative recombination. 4. Furthermore, after the formation of the perovskite luminescent layer, this invention further uses an antisolvent to carry FMSA into the grain boundaries and top interface of the luminescent layer, performing secondary passivation on the dangling bonds at the top interface and the bulk grain boundary defects. This post-treatment step, in conjunction with the FMSA in the buried interface modification layer, acts on the bottom, bulk, and top of the perovskite luminescent layer, respectively, forming a full-area defect passivation structure of the buried interface-bulk grain boundary-top interface. This minimizes the defect density in each region, comprehensively suppresses nonradiative recombination, and further improves the stability and luminous efficiency of the device.

[0017] In summary, this invention, through an FMSA buried interface modification strategy, for the first time integrates three functions in a single molecule: sulfonyl coordination passivation, amino hydrogen bond crystallization regulation, and fluorine atom energy level optimization. This synergistically solves the long-standing Sn problem in tin-based perovskites. 2+ Overcoming three major technical challenges—oxidation, excessively rapid crystallization, and carrier imbalance—achieved simultaneous breakthroughs in efficiency, brightness, and stability, providing a novel technical path for the development of high-performance lead-free near-infrared optoelectronic devices. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the chemical interaction between CsSnI3 and FMSA provided in a specific embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the regulation of the crystallization and morphology of CsSnI3 perovskite thin films by FMSA buried interface modification according to a specific embodiment of the present invention. Figure 4 This is a comparative schematic diagram of the optical and photoelectric properties of CsSnI3 and CsSnI3-FMSA thin films provided in a specific embodiment of the present invention; Figure 5 This is a schematic diagram comparing the carrier transport and transient electroluminescence characteristics of CsSnI3 and CsSnI3-FMSA PeLEDs provided in a specific embodiment of the present invention; Figure 6 This is a schematic diagram comparing the performance of CsSnI3 and CsSnI3-FMSA PeLEDs devices according to a specific embodiment of the present invention. Detailed Implementation

[0019] This invention discloses a tin-based near-infrared II perovskite light-emitting diode and its fabrication method. Those skilled in the art can refer to the content of this document and appropriately modify the technical details to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0020] This invention provides a method for fabricating a tin-based near-infrared II perovskite light-emitting diode, such as... Figure 1 As shown, the method includes: Step S1: Provide a conductive substrate and form a hole transport layer on the conductive substrate.

[0021] It should be noted that a conductive substrate is provided, and a hole transport layer is formed on this conductive substrate. The conductive substrate is preferably ITO conductive glass, which is ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol before use, and then dried with nitrogen before undergoing ultraviolet-ozone treatment to improve surface hydrophilicity. The hole transport layer is formed on the conductive substrate by spin coating, and its material can be selected from PEDOT:PSS or a self-assembled monolayer based on FMSA. After spin coating, the substrate with the hole transport layer is placed on a heating platform for annealing to remove solvent and improve the conductivity and surface morphology of the film.

[0022] Step S2: A buried interface modification layer is formed on the hole transport layer; wherein the material of the buried interface modification layer includes 2-fluoro-5-(methanesulfonyl)aniline (FMSA).

[0023] It should be noted that a buried interface modification layer is formed on the hole transport layer, and the material of this modification layer contains 2-fluoro-5-(methylsulfonyl)aniline (FMSA). FMSA is a multifunctional small organic molecule containing three functional groups: sulfonyl (S=O), amino (-NH2), and fluorine (-F). The formation of this modification layer can be achieved through methods including, but not limited to, dynamic spin coating or immersion self-assembly. Specifically, FMSA is dissolved in an organic solvent to prepare a solution of a certain concentration, and this solution is applied to the surface of the hole transport layer by spin coating, followed by annealing to form a uniform and stable modification layer of FMSA molecules on the surface of the hole transport layer. This modification layer is located between the hole transport layer and the subsequently formed perovskite luminescent layer, i.e., at the "buried interface," and is therefore called the buried interface modification layer. The preferred concentration of the FMSA solution is 0.5~10 mg / mL, the preferred spin coating speed is 2000~6000 rpm, the preferred spin coating time is 20~60 seconds, the preferred annealing temperature is 70~120℃, and the preferred annealing time is 5~30 minutes.

[0024] In this specific embodiment, step S2 includes: A first FMSA solution is spin-coated onto the hole transport layer to form a first modified sublayer; A second FMSA solution is spin-coated onto the first modified sublayer to form a second modified sublayer. The concentration of the first FMSA solution is higher than that of the second FMSA solution, such that: the first modified sublayer is used to adjust the energy level alignment on the surface of the hole transport layer to reduce the hole injection barrier and acts as a dense barrier layer to suppress interfacial leakage current; the second modified sublayer is used to allow the Sn at the bottom of the tin-based perovskite luminescent layer to pass through its sulfonyl groups. 2+ Coordination to passivate interface defects, and through its amino groups with I - Intermolecular interactions are formed to slow down the crystallization rate.

[0025] The embedded interface modification layer includes a first modification sublayer and a second modification sublayer.

[0026] It should be noted that a concentration gradient bilayer structure can be used when forming the buried interface modification layer. Specifically, firstly, a first FMSA solution is spin-coated onto the hole transport layer to form a first modified sublayer; then, a second FMSA solution is spin-coated onto the first modified sublayer to form a second modified sublayer. The concentration of the first FMSA solution is higher than that of the second FMSA solution, and the areal density of sulfonyl groups in the first modified sublayer is greater than that in the second modified sublayer. The first and second modified sublayers together constitute the buried interface modification layer.

[0027] In this bilayer structure, the first modified sublayer (bottom layer), due to its high FMSA concentration and denser molecular packing, primarily functions to regulate the energy level arrangement on the surface of the hole transport layer to lower the hole injection barrier. Simultaneously, it acts as a dense organic barrier layer to suppress interfacial leakage current and the upward diffusion of acidic impurities from PEDOT:PSS. The second modified sublayer (top layer), due to its lower FMSA concentration and looser molecular packing, primarily functions to connect its sulfonyl groups with the Sn group at the bottom of the subsequently formed tin-based perovskite luminescent layer. 2+ Coordination to passivate interface defects, and through its amino groups with I - Intermolecular interactions are formed to slow down the crystallization rate. The two layers of FMSA achieve functional spatial partitioning through concentration differences—the bottom layer focuses on energy level regulation and interface protection, while the top layer focuses on defect passivation and crystallization control—thus achieving multiple optimizations of the buried interface within the same molecular system. The concentration of the first FMSA solution is preferably 2–10 mg / mL, and the concentration of the second FMSA solution is preferably 0.5–2 mg / mL; the thickness of the first modified sublayer is preferably 5–20 nm, and the thickness of the second modified sublayer is preferably 2–10 nm.

[0028] In this specific embodiment, the embedded interface modification layer is self-assembled by dynamic spin coating or immersion; the concentration of FMSA solution is 0.5~10 mg / mL, the spin coating speed is 2000~6000 rpm, the spin coating time is 20~60 seconds, the annealing temperature is 70~120℃, and the annealing time is 5~30 minutes.

[0029] It should be noted that the buried interface modification layer can be formed by dynamic spin coating or immersion self-assembly. Dynamic spin coating refers to adding FMSA solution dropwise onto the surface of a rotating substrate, using centrifugal force to spread the solution evenly and evaporate the solvent to form a thin film. Immersion self-assembly refers to immersing the substrate with a hole transport layer into an FMSA solution, allowing FMSA molecules to spontaneously form an ordered monolayer on the surface of the hole transport layer through chemical adsorption. Regardless of the method used, the concentration of the FMSA solution is preferably 0.5~10 mg / mL. When using spin coating, the preferred spin coating speed is 2000~6000 rpm, and the preferred spin coating time is 20~60 seconds; after spin coating, the preferred annealing temperature is 70~120℃, and the preferred annealing time is 5~30 minutes. The selection of the above parameter range is based on the following considerations: when the concentration is too low, FMSA molecules are difficult to form a complete coating layer, while when the concentration is too high, the film layer may be too thick and the molecules may be disordered; spin coating speed and time affect the uniformity and repeatability of film thickness; annealing temperature and time affect the complete removal of solvent and the anchoring strength of FMSA molecules on the substrate surface.

[0030] Step S3: Apply the tin-based perovskite precursor solution to the buried interface modification layer so that the tin-based perovskite precursor solution forms a tin-based perovskite luminescent layer.

[0031] It should be noted that a tin-based perovskite precursor solution is applied to the buried interface modification layer, followed by annealing to form a tin-based perovskite luminescent layer. The tin-based perovskite is preferably all-inorganic CsSnI3, and its precursor solution is prepared by dissolving CsI and SnI2 in an organic solvent at a 1:1 molar ratio. The precursor solution is applied to the substrate with the FMSA buried interface modification layer by spin coating, followed by annealing. The annealing temperature is preferably 70-120℃, the annealing time is preferably 5-30 minutes, and the annealing atmosphere is preferably an inert gas protective atmosphere or a vacuum environment. During the annealing process, the Cs in the precursor solution... + Sn 2+ and I - A chemical reaction occurs and crystallization occurs, forming a CsSnI3 perovskite luminescent layer.

[0032] In the above process, FMSA achieves synergistic regulation of the tin-based perovskite luminescent layer through three functional groups in its molecule. Specifically, the sulfonyl group (S=O) serves as a Lewis base site, and the lone pair electrons on its oxygen atom interact with the uncoordinated Sn atom in CsSnI3. 2+ Formation of coordinate bonds, which can inhibit Sn 2+ Oxidized to Sn 4+ This reduces the p-type self-doping concentration in the film caused by tin vacancies or Sn²⁺ oxidation. The amino group (-NH₂) reacts with I₂ in CsSnI₃. - Formation of intermolecular interactions (such as NH...I) - Hydrogen bonding reduces the nucleation rate of perovskite precursors, slows crystal growth, and thus improves the grain morphology and crystal orientation of the film. Fluorine atoms (-F), with their strong electronegativity, regulate the energy level arrangement between the CsSnI3 perovskite luminescent layer and hole transport layer through interfacial dipole effects, lowering the work function and shifting the Fermi level upwards on the perovskite surface, thereby suppressing excessive hole injection and promoting carrier injection balance.

[0033] In this specific embodiment, after applying the tin-based perovskite precursor solution to the buried interface modification layer in step S3, the process further includes: annealing; the annealing temperature is 70~120℃, the annealing time is 5~30 minutes, and the annealing atmosphere is an inert gas protective atmosphere or a vacuum environment.

[0034] It should be noted that in step S3, after applying the tin-based perovskite precursor solution to the buried interface modification layer, annealing is required to transform the precursor into perovskite crystals. The preferred annealing temperature is 70–120°C, and the preferred annealing time is 5–30 minutes. The selection of the annealing temperature needs to balance crystallization quality and film stability—too low a temperature results in insufficient crystallization, leaving a large amount of non-perovskite phase in the film; too high a temperature may accelerate the crystallization of Sn. 2+ Oxidation leads to film degradation. The annealing atmosphere is preferably an inert gas protective atmosphere (such as nitrogen or argon) or a vacuum environment to prevent oxygen and water vapor in the air from reacting with Sn during the annealing process. 2+ A reaction occurs.

[0035] In this specific embodiment, step S3 includes: A first precursor solution is provided, and FMSA is added to the first precursor solution to carry out a pre-coordination reaction to form a compound containing FMSA-Sn. 2+ A solution of tin-based perovskite precursor for the complex; wherein the reaction temperature of the pre-coordination reaction is 25~60℃ and the reaction time is 0.5~24 hours; A tin-based perovskite precursor solution was spin-coated onto a subsurface interface modification layer and then annealed to achieve Sn crystallization before perovskite crystallization. 2+ Pre-passivation is performed to form a tin-based perovskite luminescent layer.

[0036] It should be noted that FMSA pre-coordination treatment can be used when forming the tin-based perovskite luminescent layer. Specifically, a CsSnI3 precursor solution is first provided, and FMSA is added to this precursor solution to carry out a pre-coordination reaction, forming an FMSA-Sn layer. 2+ A tin-based perovskite precursor solution containing a complex. The pre-coordination reaction refers to the reaction whereby the sulfonyl group in the FMSA molecule reacts with the Sn group in the precursor solution before perovskite crystallization. 2+ Pre-coordination occurs to form a stable complex. The preferred reaction temperature for this pre-coordination reaction is 25–60 °C, and the preferred reaction time is 0.5–24 hours. The preferred molar ratio of FMSA to Sn²⁺ is 0.5:1–5:1.

[0037] After pre-coordination reaction, FMSA-Sn will be present. 2+ The tin-based perovskite precursor solution of the complex was spin-coated onto the buried interface modification layer and then annealed. During this process, FMSA-Sn... 2+ FMSA in the complex has already interacted with Sn 2+ Chemical bonds are formed, allowing Sn²⁺ to be protected and passivated by FMSA before crystallization, thus achieving Sn… 2+The "pre-passivation" process is more effective than simply mixing the additive into the precursor solution and then spin-coating it into a film. 2+ Oxidation during crystallization and more uniformly introducing the passivation effect of FMSA into the perovskite phase grain boundaries. Furthermore, reducing agents (such as SnF2, SnCl2, or a combination of both) can be added to the precursor solution to further enhance Sn... 2+ Its antioxidant effect.

[0038] In this specific embodiment, after step S3, the method further includes: FMSA is dissolved in an antisolvent to form a post-treatment solution; The post-treatment solution was applied to the surface of the tin-based perovskite luminescent layer and subjected to a second annealing treatment. This allowed FMSA molecules to penetrate into the grain boundaries and top interface of the tin-based perovskite luminescent layer, forming a three-in-one passivation structure of the buried interface, bulk grain boundary, and top interface together with the FMSA in the buried interface modification layer.

[0039] It should be noted that after forming the tin-based perovskite luminescent layer, FMSA post-treatment can be performed. Specifically, FMSA is dissolved in an antisolvent to form a post-treatment solution, which is then applied to the surface of the formed tin-based perovskite luminescent layer for a secondary annealing treatment. The antisolvent is an organic solvent that has a certain dissolving ability for perovskite materials but will not destroy their crystal structure; it can be selected from chlorobenzene, toluene, diethyl ether, ethyl acetate, or any combination thereof. The concentration of FMSA in the post-treatment solution is preferably 0.5~10 mg / mL. The preferred temperature for the secondary annealing treatment is 70~120℃, and the preferred time is 5~30 minutes.

[0040] During the post-processing, FMSA molecules, along with the antisolvent, penetrate into the grain boundaries and top interface of the tin-based perovskite luminescent layer, passivating defects at the bulk grain boundaries and dangling bonds at the top interface. This post-processing step works in conjunction with the FMSA in the buried interface modification layer—the FMSA in the buried interface modification layer passivates the bottom interface, while the FMSA introduced in the post-processing passivates the bulk grain boundaries and top interface—thus forming a full-area defect passivation structure of buried interface-bulk grain boundary-top interface. This three-dimensional passivation scheme of "bottom + bulk + top" can minimize the defect density in each region of the perovskite film and comprehensively suppress nonradiative recombination.

[0041] Step S4: An electron transport layer is formed on the tin-based perovskite light-emitting layer, and an electrode is formed on the electron transport layer to obtain a perovskite light-emitting diode.

[0042] FMSA achieves synergistic regulation of the tin-based perovskite luminescent layer through the sulfonyl, amino, and fluorine atoms in its molecule. Sulfonyl groups are used with Sn in tin-based perovskite luminescent layers. 2+ Coordination to suppress Sn 2+ Oxidizes and reduces p-type self-doping in tin-based perovskite luminescent layers; Amino groups are used in tin-based perovskite luminescent layers for I... - Intermolecular interactions are formed to regulate the crystallization rate of perovskite and improve the morphology of the luminescent layer of tin-based perovskite; Fluorine atoms are used to modulate the interfacial energy level arrangement of the tin-based perovskite luminescent layer to suppress excessive hole injection and promote carrier injection balance.

[0043] It should be noted that an electron transport layer is formed on the tin-based perovskite emitting layer, and an electrode is formed on the electron transport layer to obtain a perovskite light-emitting diode. The electron transport layer material can be selected from SPPO13, B3PYMPM, or a combination of both, and is deposited on the perovskite emitting layer by thermal evaporation. The electrode is preferably a LiF / Al composite electrode, which is also formed on the electron transport layer by thermal evaporation. Thus, the fabrication of a tin-based near-infrared II perovskite light-emitting diode is completed, with an emission wavelength in the range of 900–1100 nm.

[0044] In this specific embodiment, the hole transport layer is a PEDOT:PSS layer or a self-assembled monolayer based on FMSA; the conductive substrate is ITO conductive glass; the electron transport layer is made of SPPO13, B3PYMPM, or a combination of both; and the electrode is a LiF / Al composite electrode.

[0045] It should be noted that, regarding the material selection for each layer of the device, the hole transport layer can be a PEDOT:PSS layer or a self-assembled monolayer based on FMSA. PEDOT:PSS is short for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), a widely used hole transport material. A self-assembled monolayer based on FMSA refers to an ordered monolayer spontaneously formed on the surface of a conductive substrate through chemisorption of FMSA molecules. It can be used as both a hole transport layer and a buried interface modification layer. The conductive substrate is preferably ITO (indium tin oxide) conductive glass, which has high light transmittance and good conductivity. The electron transport layer material can be SPPO13 (a phosphine oxide electron transport material), B3PYMPM (a pyrimidine electron transport material), or a combination of both. The electrode is a LiF / Al composite electrode, where LiF serves as the electron injection layer and Al as the conductive electrode layer, and the two are deposited sequentially by thermal evaporation.

[0046] This invention, through the introduction of a buried interface modification layer containing 2-fluoro-5-(methylsulfonyl)aniline between the hole transport layer and the tin-based perovskite luminescent layer, utilizes the synergistic effect of three functional groups in the same molecule to simultaneously solve three major technical challenges long faced by tin-based perovskites: the interaction of sulfonyl groups and Sn. 2+ Coordination inhibits Sn 2+ Oxidation and reduction of p-type self-doping, amino groups and I - Intermolecular interactions modulate the crystallization rate and improve film morphology, while fluorine atoms regulate the interfacial energy level arrangement and optimize carrier injection balance. These three functions are integrated into the same molecule and the same modification layer, resulting in a simple and convenient process that simultaneously improves device efficiency, brightness, and stability without the need for multilayer structures or multiple additives.

[0047] This invention further employs a concentration-gradient bilayer FMSA modification structure. The first modified sublayer (high concentration) and the second modified sublayer (low concentration) achieve functional spatial partitioning within the same molecular system: the bottom layer enhances the energy level modulation and interface blocking functions of the hole transport layer surface through high-density sulfonyl groups, while the top layer concentrates on defect passivation and crystallization regulation at the perovskite bottom interface through low-density sulfonyl groups and amino groups. This gradient structure allows each layer to focus on its most effective function, avoiding the functional trade-offs that occur when a single concentration layer simultaneously addresses energy level modulation and defect passivation, thereby further optimizing the overall regulation effect of the buried interface.

[0048] In a further embodiment of the invention, FMSA is added to the perovskite precursor solution to perform a pre-coordination reaction, thereby enabling FMSA-Sn... 2+ The complex is formed in solution. Compared to simply placing FMSA at the buried interface (acting only on the bottom interface) or directly forming a film after simple mixing, the pre-coordination treatment allows the passivation effect of FMSA to be pre-placed around the tin source before crystallization. This enables it to be introduced more uniformly into the perovskite bulk phase grain boundaries and, together with the FMSA in the buried interface modification layer, form a dual passivation system of "interface + bulk phase". This further reduces the bulk defect density and suppresses non-radiative recombination.

[0049] In this embodiment of the invention, after the formation of the perovskite luminescent layer, FMSA is carried by an antisolvent and penetrated into the grain boundaries and top interface of the luminescent layer to perform secondary passivation on the dangling bonds at the top interface and the bulk grain boundary defects. This post-processing step works in conjunction with the FMSA in the buried interface modification layer. The three act on the bottom, bulk, and top of the perovskite luminescent layer, respectively, forming a full-area defect passivation structure of the buried interface-bulk grain boundary-top interface. This minimizes the defect density in each region, comprehensively suppresses nonradiative recombination, and further improves the stability and luminous efficiency of the device.

[0050] In summary, this invention, through an FMSA-based buried interface modification strategy, for the first time integrates three functions within the same molecule: sulfonyl coordination passivation, amino hydrogen bond crystallization regulation, and fluorine atom energy level optimization. This synergistically solves the long-standing Sn problem in tin-based perovskites. 2+ Overcoming three major technical challenges—oxidation, excessively rapid crystallization, and carrier imbalance—achieved simultaneous breakthroughs in efficiency, brightness, and stability, providing a novel technical path for the development of high-performance lead-free near-infrared optoelectronic devices.

[0051] To better illustrate the regulatory role of FMSA in the crystallization of tin-based perovskite luminescent layers, the embodiments of the present invention are illustrated with the following examples: The chemical interaction between CsSnI3 and FMSA can be as follows: Figure 2 As shown, Figure 2 In the figures, (a) electrostatic potential of FMSA molecules; (b) optimized multidentate co-adsorption configuration of FMSA on CsSnI3 surface; (c) formation energy of Cs, Sn and I vacancy defects; (d) ELF plots of CsSnI3 and (e) CsSnI3-FMSA; (f) FTIR spectra of FMSA and CsSnI3-FMSA films; (g) XPS Sn 3d spectra of CsSnI3 and CsSnI3-FMSA films; and (h) XPS O 1s spectra of FMSA and CsSnI3-FMSA films. Figure 2 In this context, Formation Energy (eV) — defect formation energy, Defect Types — defect type, Wavenumber (cm⁻¹) — wavenumber, Transmittance (au) — transmittance, Binding Energy (eV) — binding energy, and Intensity (au) — intensity.

[0052] We also calculated the formation energies of Cs, Sn, and I vacancy defects in CsSnI3 and CsSnI3-FMSA surfaces. Figure 1 c). After FMSA adsorption, the vacancy formation energies significantly increased, indicating that FMSA molecules can effectively suppress the nucleation and formation of lattice point defects, reducing the number of non-radiative recombination centers in perovskites from the source. Furthermore, we performed electronic localization function (ELF) and charge density difference (CDD) calculations to reveal the nature of interfacial interactions. (ELF distribution diagram) Figure 1 (d) and (e) clearly reveal the localized electron accumulation at the S=O-Sn²⁺ bond, intuitively demonstrating the chemical bonding properties between FMSA and CsSnI3.

[0053] To accurately study the interfacial interaction between FMSA and CsSnI3, we performed Fourier transform infrared (FTIR) measurements on FMSA and CsSnI3-FMSA films. Figure 2 The S=O stretching vibration peaks at 1140 cm⁻¹ and 1192 cm⁻¹ in FMSA show a significant redshift in CsSnI₃-FMSA, confirming the formation of the S=O-Sn²⁺ coordination bond. This is attributed to the lone pair electrons of the S=O functional group donating electrons to the empty 5s orbital of Sn²⁺. Simultaneously, the NH bending vibration peak (1631 cm⁻¹)... -1 ) and CF stretching vibration peak (1212 cm) -1 The redshift also occurred, further confirming the interaction between FMSA and CsSnI3. In addition, we performed X-ray photoelectron spectroscopy (XPS) measurements to investigate the interaction mechanism between FMSA and CsSnI3. The Sn 3dXPS spectrum of CsSnI3-FMSA (…) Figure 2 f) Compared to the original CsSnI3, it is significantly shifted towards the direction of lower binding energy, and Sn 4 The ⁺ ratio decreased. Simultaneously, the O 1s XPS energy spectrum of the CsSnI3-FMSA thin film ( Figure 2 g) relative to pure FMSA ( Figure 2 g) A significant shift occurred towards the direction of higher binding energy. These characteristic spectral changes confirm that the S=O group and Sn... 2+ Electron transfer and coordination bond formation between them effectively suppress Sn. 2+ Oxidation improves the quality of perovskite films.

[0054] The effect of FMSA-modified buried interface on the crystallization and morphology of CsSnI3 perovskite films, such as... Figure 3 As shown, (a) in-situ annealing PL spectra of CsSnI3 and (b) CsSnI3-FMSA films; (c) normalized PL intensity evolution curves extracted from in-situ PL results; (d) SEM images of CsSnI3 and (e) CsSnI3-FMSA films; and (f) XRD patterns of CsSnI3 and CsSnI3-FMSA films. Figure 3 In this context, Wavelength (nm) — wavelength, PL Intensity (au) — photoluminescence intensity, 2θ (degree) — twice the diffraction angle, and Intensity (au) — diffraction intensity.

[0055] The crystallization kinetics of CsSnI3 thin films were monitored using in-situ annealing photoluminescence (PL) spectroscopy. Figure 3(a–c) The CsSnI3 film exhibited a rapid increase in PL intensity within only 25 s of annealing and tended to saturate after 60 s, indicating a faster nucleation process. In contrast, no obvious PL signal was observed in the CsSnI3-FMSA film before 45 s of annealing, and its PL intensity showed a continuous upward trend, indicating improved crystallinity and reduced defect density. This can be attributed to the strong anchoring effect of FMSA on CsSnI3, which effectively reduced the nucleation rate of perovskite, slowed down the crystallization process, and passivated defects inside the film.

[0056] Meanwhile, the surface morphology of CsSnI3 and CsSnI3-FMSA films was analyzed using scanning electron microscopy (SEM). Figure 3 (d, e) The CsSnI3 film exhibits typical dendritic grain characteristics, which is due to the uneven film growth caused by the low nucleation barrier on the PEDOT:PSS surface and the subsequent rapid perovskite nucleation. After the introduction of FMSA molecules, dendritic grain growth is significantly suppressed, resulting in more dense square / circular grains. The GCR decreases slightly from 45.27% in the CsSnI3 film to 42.43% in the CsSnI3-FMSA film, indicating a reduction in the contact area between the perovskite layer and HTL, which helps suppress excessive hole injection.

[0057] In addition, the crystal structure and crystallization properties of the perovskite thin film were studied by X-ray diffraction (XRD). Figure 3 f). All diffraction peaks of both films were in good agreement with the standard card (PDF#43-1162) of CsSnI3, and the intensity of the (110) and (220) crystal plane diffraction peaks of the CsSnI3-FMSA film was significantly enhanced, indicating that the FMSA modification did not change the intrinsic crystal phase structure of CsSnI3, but promoted the preferred orientation growth of perovskite grains and significantly improved the crystallinity of the film.

[0058] Figure 4 Optical and photoelectric properties of CsSnI3 and CsSnI3-FMSA thin films are shown. Among them, (a) steady-state PL spectrum (excitation at the buried interface); (b, c) in-situ PL evolution spectrum under continuous ultraviolet excitation (detection at the buried interface); (d) TRPL spectrum of CsSnI3 and CsSnI3-FMSA thin films; (e) SCLC JV curve of single hole / single electron device; (f) IV curve of ITO / perovskite / Al device; (g, h) KPFM surface potential distribution map; (i) schematic diagram of Fermi level shift due to work function reduction. Figure 4 In this context, Current density (mA cm⁻²) — milliamperes per square centimeter (mA / cm²), Current — current (mA), and Voltage (V) — voltage. Figure 4 It can be seen that the embodiments of the present invention have made significant progress in optical and optoelectronic properties.

[0059] Figure 5 Carrier transport and transient electroluminescence characteristics of CsSnI3 and CsSnI3-FMSA PeLEDs. (a, b) TEL curves under different pulse voltages; (c) average carrier mobility; (d) Nyquist impedance spectra of the devices in the off state (before turning on) and (e) in the on state (after turning on); (f) CV curves. Figure 5 In this context, EL Intensity (au) — electroluminescence intensity, MeanMobility (cm² V⁻¹ s⁻¹) — average carrier mobility, Impedance Real (Ohm) — real part of impedance, Impedance Imag (Ohm) — imaginary part of impedance, Voltage (V) — voltage, and Capacitance (nF) — capacitance value.

[0060] Specifically, transient electroluminescence (TEL) measurements showed that the FMSA device exhibited a faster EL rise rate and higher saturation intensity, indicating enhanced radiative recombination and reduced trap density. EIS and CV measurements further confirmed that FMSA modification reduced interface charge accumulation, suppressed leakage current, effectively regulated hole injection, and improved electron injection efficiency. These improvements collectively stem from the optimization of energy level alignment and defect passivation achieved by FMSA, ultimately enabling the device to achieve more efficient radiative recombination at lower current densities, laying the foundation for improved EQE and stability.

[0061] Figure 6 Performance of PeLEDs devices based on CsSnI3 and CsSnI3-FMSA. (a) Schematic diagram of device structure; (b) Current density-voltage-radiance (JVR) curves; (c) External quantum efficiency versus current density (EQE-J) curves; (d) Statistical distribution of radiance and (e) EQE; (f) Operating lifetime at 20 mA cm⁻² (T 50 (g) Steady-state output radiance and EQE of CsSnI3-FMSA PeLEDs operating at a high current density of 300 mA cm⁻²; (h) EL spectra at different driving voltages; (i) Performance comparison with CsSnI3 PeLEDs.

[0062] Specifically, (a) the device structure is first shown; (b) and (c) the significant improvements in efficiency (EQE up to 7.1%) and brightness (213 W sr⁻¹ m⁻²) of the FMSA device are demonstrated through JVR and EQE-J curves; (d) and (e) the high reproducibility of the fabrication process is demonstrated through the statistical distribution of 48 devices; and (f) the T… 50 The lifetime curve (204.6 h) demonstrates a significant extension in operational stability (2.5 times that of the control group), (g) further verifying stable operation at high current densities (300 mA cm⁻²), (h) verifying no shift in the EL emission wavelength (945 nm) under different voltages, and (i) highlighting the advancement and breakthrough of this invention through a comprehensive performance comparison with previously reported CsSnI₃ PeLEDs. In summary, Figure 6 The comparison is based on five dimensions: efficiency, brightness, stability, repeatability, and overall performance.

[0063] This invention also provides a tin-based near-infrared II perovskite light-emitting diode, which is prepared by the tin-based near-infrared II perovskite light-emitting diode preparation method provided in any of the above embodiments.

[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0065] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for fabricating a tin-based near-infrared II perovskite light-emitting diode, characterized in that, The method includes: Step S1: Provide a conductive substrate and form a hole transport layer on the conductive substrate; Step S2: A buried interface modification layer is formed on the hole transport layer; wherein the material of the buried interface modification layer comprises 2-fluoro-5-(methanesulfonyl)aniline (FMSA); Step S3: Apply the tin-based perovskite precursor solution to the buried interface modification layer so that the tin-based perovskite precursor solution forms a tin-based perovskite luminescent layer; Step S4: An electron transport layer is formed on the tin-based perovskite light-emitting layer, and an electrode is formed on the electron transport layer to obtain a perovskite light-emitting diode; The FMSA achieves synergistic regulation of the tin-based perovskite luminescent layer through the sulfonyl, amino, and fluorine atoms in its molecule. The sulfonyl group is used to react with Sn in the tin-based perovskite light-emitting layer. 2+ Coordination to suppress Sn 2+ Oxidizes and reduces p-type self-doping in the tin-based perovskite luminescent layer; The amino group is used to react with I in the tin-based perovskite light-emitting layer. - Intermolecular interactions are formed to regulate the perovskite crystallization rate and improve the morphology of the tin-based perovskite luminescent layer; The fluorine atoms are used to adjust the interfacial energy level arrangement of the tin-based perovskite luminescent layer to suppress excessive hole injection and promote carrier injection balance.

2. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, Step S2 includes: A first FMSA solution is spin-coated onto the hole transport layer to form a first modified sublayer; A second FMSA solution is spin-coated onto the first modified sublayer to form a second modified sublayer; wherein the concentration of the first FMSA solution is higher than the concentration of the second FMSA solution, such that: the first modified sublayer is used to adjust the energy level alignment on the surface of the hole transport layer to reduce the hole injection barrier and acts as a dense barrier layer to suppress interface leakage current; the second modified sublayer is used to interact with the Sn at the bottom of the tin-based perovskite luminescent layer through its sulfonyl groups. 2+ Coordination to passivate interface defects, and through its amino groups with I - Intermolecular interactions are formed to slow down the crystallization rate.

3. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, Step S3 includes: A first precursor solution is provided, and FMSA is added to the first precursor solution to perform a pre-coordination reaction to form a solution containing FMSA-Sn. 2+ The tin-based perovskite precursor solution of the complex; wherein the reaction temperature of the pre-coordination reaction is 25~60℃ and the reaction time is 0.5~24 hours; The tin-based perovskite precursor solution was spin-coated onto the buried interface modification layer and annealed to achieve Sn before perovskite crystallization. 2+ Pre-passivation is performed to form a tin-based perovskite luminescent layer.

4. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, After step S3, the method further includes: FMSA is dissolved in an antisolvent to form a post-treatment solution; The post-treatment solution is applied to the surface of the tin-based perovskite luminescent layer and subjected to a secondary annealing treatment, which allows FMSA molecules to penetrate into the grain boundaries and top interface of the tin-based perovskite luminescent layer, forming a three-in-one passivation structure of the buried interface-bulk grain boundary-top interface together with the FMSA of the buried interface modification layer.

5. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The embedded interface modification layer is self-assembled by dynamic spin coating or immersion; the concentration of the FMSA solution is 0.5~10 mg / mL, the spin coating speed is 2000~6000 rpm, the spin coating time is 20~60 seconds, the annealing temperature is 70~120℃, and the annealing time is 5~30 minutes.

6. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The hole transport layer is a PEDOT:PSS layer or a self-assembled monolayer based on FMSA; the conductive substrate is ITO conductive glass; the electron transport layer is made of SPPO13, B3PYMPM, or a combination of both; and the electrode is a LiF / Al composite electrode.

7. The method for fabricating a tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, Step S3, after applying the tin-based perovskite precursor solution to the buried interface modification layer, further includes: annealing treatment; the annealing temperature is 70~120℃, the annealing time is 5~30 minutes, and the annealing atmosphere is an inert gas protective atmosphere or a vacuum environment.

8. A tin-based near-infrared II perovskite light-emitting diode, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

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