A thermally controlled crystal-directed growth method for tin-based near-infrared II perovskite light-emitting diodes and its fabrication method

Abstract

This invention discloses a thermally regulated crystal-directed growth method for tin-based near-infrared II perovskite light-emitting diodes and its fabrication. The method includes dissolving a cesium source, a tin source, and antioxidant additives in an organic solvent, adding tin powder, stirring, and filtering to obtain a precursor solution; forming a hole transport layer on a conductive substrate; applying the precursor solution to the hole transport layer and annealing at 110°C to 150°C, causing the tin-based perovskite crystal to change from in-plane lateral growth to out-of-plane vertical growth, reducing the bottom area of ​​the grains and increasing their height, thus forming a light-emitting layer; and forming an electron transport layer and electrodes on the light-emitting layer. This method induces directional crystal growth through high-temperature annealing, and, combined with antioxidant additives, suppresses the oxidation of divalent tin at high temperatures, achieving a synergistic optimization of reducing grain boundary defects and balancing carrier injection. It eliminates the need for complex additives or interface modification layers, and the process is simple and reproducible, providing an effective solution for the fabrication of high-performance lead-free near-infrared II light-emitting devices.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a thermally controlled crystal-directed growth of 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 fields such as biomedical imaging, night vision, optical communication, drug monitoring, and iris recognition. Compared with traditional near-infrared I (700–900 nm) light sources, near-infrared II (900–1800 nm) light sources have shown great application potential in precision medicine, wearable devices, and other fields due to their advantages such as deeper tissue penetration, weaker autofluorescence, less tissue damage, and higher resolution.

[0003] Metal halide perovskites and their derivatives possess advantages such as narrow emission bandwidth, tunable optical bandgap, high photoluminescence quantum yield, and solution-processability, making them a research hotspot in the field of light-emitting diodes (LEDs) in recent years. Among them, tin-based halide perovskites are considered ideal materials to replace toxic lead-based perovskites due to their tunable bandgap and environmental friendliness. In particular, all-inorganic CsSnI3 perovskites, with emission wavelengths covering the near-infrared II region (e.g., 955 nm), have unique advantages in the field of biocompatible optoelectronic devices. However, currently, high-efficiency near-infrared perovskite LEDs are still mainly based on lead-based systems, with their emission wavelengths mostly limited to the near-infrared I region. Furthermore, the toxicity of lead severely restricts their application in biomedical and wearable devices.

[0004] Despite the immense potential of tin-based perovskites in near-infrared II emission, their device performance still faces significant challenges. First, the extremely rapid crystallization rate of tin-based perovskites makes nucleation and growth difficult to control, leading to numerous grain boundary defects and non-radiative recombination centers in the film, severely limiting luminescence efficiency. Second, the presence of divalent tin ions (Sn) in tin-based perovskites... 2+ It is easily oxidized to tetravalent tin ions (Sn). 4+ This oxidation process not only destroys the crystal structure of perovskite but also generates a large number of tin vacancy defects, triggering severe p-type self-doping and nonradiative recombination, leading to a serious imbalance in charge carrier transport. The combined effect of these problems makes the efficiency and stability of tin-based perovskite light-emitting diodes far lower than those of their lead-based counterparts.

[0005] To address the aforementioned issues, researchers have explored various strategies to regulate the crystallization process of tin-based perovskites and inhibit Sn²⁺ oxidation. For example, they have employed additive engineering to introduce organic or inorganic additives (such as naphthol sulfonates, biuret, and amino acid derivatives) to slow the crystallization rate and passivate defects; interface modification (such as potassium citrate modification of the hole transport layer) to induce directional interfacial crystallization; and component engineering (such as the introduction of GA) to... + Partially replaces Cs + To stabilize the crystal structure, some studies have employed low-temperature annealing (35–40°C) to induce preferential growth of perovskite crystals along specific crystal planes. However, most of these strategies rely on introducing additional chemical components (such as additives and interface modification layers), which not only increases process complexity but may also introduce insulating impurities, hindering charge transport. More importantly, while improving the quality of tin-based perovskite films, existing technologies have failed to effectively address the challenges of high-temperature annealing conditions for Sn... 2+ The fundamental contradiction between intensified oxidation and crystal orientation control: While high temperatures are beneficial for improving crystal quality, they also accelerate the oxidation of Sn. 2+ The oxidation and disproportionation decomposition of tin-based perovskites are also a concern. Furthermore, the carrier imbalance between over-injection of holes and under-injection of electrons caused by the inherent p-type self-doping characteristics in tin-based perovskites lacks effective physical control methods.

[0006] Therefore, there is an urgent need in the field for a preparation method that can simultaneously achieve optimized orientation, defect suppression, and balanced control of carrier injection in tin-based perovskite crystals without introducing additional chemical components. 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 thermally controlled crystal-directed growth tin-based near-infrared II perovskite light-emitting diode and its fabrication method, which aims to reduce grain boundary defects and optimize carrier injection balance.

[0008] To achieve the above objectives, the first aspect of this invention discloses a method for fabricating a thermally controlled crystal-directed growth method for tin-based near-infrared II perovskite light-emitting diodes, the method comprising: Step S1: Dissolve the cesium source, tin source, and antioxidant additive in an organic solvent, and add tin powder to maintain the stability of the valence state of tin in the solution. After stirring and mixing evenly, filter to obtain a tin-based perovskite precursor solution; wherein, the antioxidant additive is used to prevent tin ions from being oxidized by temperature. Step S2: Provide a conductive substrate and form a hole transport layer on the conductive substrate; Step S3: Apply the tin-based perovskite precursor solution to the hole transport layer, and anneal the tin-based perovskite precursor solution at a temperature range of 110℃-150℃ to form a tin-based perovskite luminescent layer; wherein, the annealing treatment at 110℃-150℃ causes the tin-based perovskite crystal to change from in-plane lateral growth to out-of-plane vertical growth, reducing the bottom area of ​​the grains and increasing their height, thereby reducing grain boundary defects and optimizing carrier injection balance; 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.

[0009] Optionally, step S3 specifically includes: The tin-based perovskite precursor solution is applied to the hole transport layer, and the tin-based perovskite precursor solution is annealed at 130°C to form a tin-based perovskite luminescent layer.

[0010] Optionally, the annealing process in step S3 is a stepped annealing process, specifically including: The tin-based perovskite precursor solution is annealed at a first temperature for a first time period, and then cooled to a second temperature for a second time period; wherein the first temperature is higher than the second temperature, the first temperature is 130°C to 150°C, and the second temperature is 110°C to 130°C.

[0011] Optionally, the antioxidant additive includes at least one of vitamin C, carbazole, formamidin thiocyanate, hesperidin, and cesium trifluoroacetate; the antioxidant additive inhibits Sn through coordination or thermal sacrifice mechanisms during the annealing process. 2+ Oxidized to Sn 4+ The tin powder undergoes a disproportionation reaction to dissolve the Sn already generated in the precursor solution. 4+ Restore to Sn 2+ .

[0012] Optionally, in step S3, after applying the tin-based perovskite precursor solution to the hole transport layer and before performing the annealing treatment, an antisolvent extraction step is further included: between 30 and 45 seconds after the start of spin coating, an antisolvent is dropped onto the tin-based perovskite precursor film; wherein the antisolvent is chlorobenzene.

[0013] Optionally, the application of the tin-based perovskite precursor solution to the hole transport layer in step S3 specifically involves: The tin-based perovskite precursor solution was applied to the hole transport layer by spin coating at a speed of 3000 rpm to 5000 rpm for a time of 30 to 90 seconds.

[0014] Optionally, the hole transport layer in step S2 is m-PEDOT:PSS, which is formed by spin-coating an aqueous solution of m-PEDOT:PSS onto the conductive substrate and annealing it at 130°C to 170°C for 10 to 20 minutes.

[0015] Optionally, the electron transport layer in step S4 is SPPO13, which is formed by spin-coating an SPPO13 solution onto the tin-based perovskite luminescent layer. The solvent of the SPPO13 solution is chlorobenzene, and the concentration is 1 mg / mL to 5 mg / mL.

[0016] Optionally, in step S4, the electrode is formed by sequentially depositing B3PYMPM, LiF, and Al through vacuum thermal evaporation. The deposition thickness of B3PYMPM is 30 nm to 70 nm, the deposition thickness of LiF is 1 nm to 3 nm, and the deposition thickness of Al is 60 nm to 100 nm.

[0017] The second aspect of this invention discloses a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode, which is prepared by any of the above-described methods.

[0018] The beneficial effects of this invention are as follows: 1. By controlling the annealing temperature to 110℃ to 150℃, this invention utilizes the vertical thermal gradient between the hot plate and the thin film to generate a strong vertical thermal driving force, causing tin-based perovskite crystals to change from in-plane lateral growth to out-of-plane vertical growth, resulting in a smaller grain bottom area and an increased height. This physical field intervention method is completely independent of additives, interface modification layers, and other additional chemical components, avoiding the obstruction of charge transport by insulating impurities, making the process simpler and lower in cost. In the prior art, achieving vertical orientation of perovskite crystals usually relies on additive assistance (such as amino-containing additives forming an intermediate structure with the precursor) or interface modification; this invention significantly simplifies the process flow. 2. This invention induces crystals to change from in-plane lateral growth to out-of-plane vertical growth through high-temperature annealing, resulting in a smaller grain bottom area and an increased height. The originally agglomerated and fused plate-like grains gradually decompose into discrete, independent microcrystals, reducing grain boundaries and interstitial voids, and significantly lowering the grain boundary defect density. 3. This invention physically controls the carrier injection ratio by changing the macroscopic geometry of the crystal: after the grains change from lateral growth to vertical growth, the bottom area shrinks, reducing the contact area with the hole transport layer and thus suppressing excessive hole injection; at the same time, the grain height increases, increasing the contact area with the electron transport layer and enhancing electron injection. This approach of using morphology to feed back into device physics spontaneously optimizes the electron and hole injection balance without changing the chemical composition of the material. In the prior art, improving the carrier imbalance in tin-based perovskites usually relies on complex doping or interface engineering; this invention provides a completely new physical control path. 4. This invention simultaneously introduces tin powder and antioxidant additives into the precursor solution to construct a double-layer antioxidant protection system: the tin powder neutralizes the Sn already generated in the precursor solution through a disproportionation reaction. 4+ Restore to Sn 2+ It continues to function during solution storage; antioxidant additives inhibit Sn through coordination or thermal sacrificial mechanisms during high-temperature annealing. 2+ Oxidized to Sn 4+ This provides active protection during the most vulnerable stage of annealing. Both mechanisms work synergistically at different stages to effectively address the protection of tin-based perovskites against Sn under high-temperature annealing conditions. 2+ The problem of easy oxidation.

[0019] In summary, this invention solves the long-standing problems of uncontrolled crystallization and Sn in the field of tin-based perovskite light-emitting diodes. 2+ The three core challenges of oxidation and carrier imbalance provide a simple, effective, and additive-free technical solution for the fabrication of high-performance lead-free near-infrared II light-emitting devices. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the process for the thermally controlled crystal directional growth of a tin-based near-infrared II perovskite light-emitting diode according to a specific embodiment of the present invention; Figure 2 This is a mechanism diagram of the thermally controlled directional growth strategy provided in a specific embodiment of the present invention, and SEM images of the surface and cross-section of the film at different annealing temperatures; Figure 3 This is an AFM image and grain height analysis diagram of CsSnI3 thin films prepared at different annealing temperatures according to a specific embodiment of the present invention; Figure 4 This is a specific embodiment of the present invention, showing the PL spectra of CsSnI3 films at different annealing temperatures, the curves of electronic devices annealed at different temperatures, and the PL spectra of CsSnI3 films treated at different annealing temperatures under 365nm LED continuous ultraviolet excitation. Figure 5 This is a photoelectric performance diagram of CsSnI3 perovskite light-emitting diodes annealed at different temperatures provided in a specific embodiment of the present invention; Figure 6 This is a transient electroluminescence measurement diagram of CsSnI3 perovskite light-emitting diodes annealed at different temperatures, provided in a specific embodiment of the present invention. Detailed Implementation

[0021] This invention discloses a thermally controlled crystal-directed growth method for tin-based near-infrared II perovskite light-emitting diodes and its fabrication. Those skilled in the art can refer to this document and appropriately modify the technical details to achieve the desired result. It is particularly important to note 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 clearly modify or appropriately change and combine 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.

[0022] This invention provides a method for fabricating tin-based near-infrared II perovskite light-emitting diodes through thermally controlled crystal directional growth, such as... Figure 1 As shown, the method includes: Step S1: Dissolve the cesium source, tin source, and antioxidant additive in an organic solvent, and add tin powder to maintain the stability of the valence state of tin in the solution. After stirring and mixing evenly, filter to obtain a tin-based perovskite precursor solution.

[0023] Among them, antioxidant additives are used to prevent tin ions from being oxidized by temperature.

[0024] It should be noted that in this step, the cesium source is cesium iodide (CsI), and the tin source is stannous iodide (SnI2) and stannous chloride (SnCl2), with a molar ratio of 1:1:0.05 to 0.2, preferably 1:1:0.1. The organic solvent is preferably dimethyl sulfoxide (DMSO), but is not limited thereto. The concentration of the precursor solution is preferably 0.2M to 0.3M, more preferably 0.25M. The role of the tin powder is to neutralize the Sn4+ generated from the oxidation of Sn²⁺ in the precursor solution through a disproportionation reaction. 4+ Restore Sn 2+ (Sn) 0 +Sn 4+ →2Sn 2+ This maintains the chemical stability of the precursor solution during preparation and storage. The amount of tin powder added is preferably 5 mg / mL to 20 mg / mL, more preferably 10 mg / mL. Antioxidant additives are used to inhibit Sn during subsequent high-temperature annealing. 2+ Oxidized to Sn 4+ The precursor solution contains, but is not limited to, at least one of vitamin C, carbazole, formamidin thiocyanate, hesperidin, and cesium trifluoroacetate. The stirring time is preferably 4 to 12 hours, more preferably 6 hours, to ensure that all components are fully dissolved at room temperature. Filtration is preferably performed using a 0.22 μm polytetrafluoroethylene (PTFE) syringe filter to remove insoluble particles and undissolved tin powder residue, obtaining a clear and transparent precursor solution.

[0025] In this specific embodiment, the antioxidant additive includes at least one of vitamin C, carbazole, formamidin thiocyanate, hesperidin, and cesium trifluoroacetate; the antioxidant additive inhibits Sn through coordination or thermal sacrifice mechanisms during the annealing process. 2+ Oxidized to Sn 4+ Tin powder reacts with the Sn already generated in the precursor solution via a disproportionation reaction. 4+ Restore to Sn 2+ .

[0026] It should be noted that the aforementioned antioxidant additives are uniformly dispersed in the solution during the precursor solution preparation stage and play a role in inhibiting Sn during the subsequent annealing process. 2+ The role of oxidation. The mechanisms of action vary slightly among different additives: Vitamin C (ascorbic acid) is a potent reducing agent that preferentially reacts with oxidizing agents at high temperatures, protecting Sn. 2+ Carbazole (CBZ) can anneal the generated Sn at approximately 150°C. 4 ⁺ Restored to Sn 2+Formamidinium thiocyanate (FASCN) decomposes at high temperatures to produce SCN⁻ ions, which have a strong coordination effect with Sn²⁺, thus alleviating heat-induced disproportionation decomposition; hesperidin is a natural polyphenol compound with both reducing and coordinating properties; cesium trifluoroacetate (CsTFA) can effectively inhibit Sn 2+ It oxidizes and passivates defects. The above additives can be used alone or in combination of two or more. When used in combination, they can exert a synergistic antioxidant effect through different mechanisms.

[0027] In conjunction with this antioxidant additive, the tin powder in the precursor solution undergoes a disproportionation reaction to remove the Sn already generated in the solution. 4+ Restore to Sn 2+ The two have a clear division of labor: tin powder mainly plays a role in the solution preparation and storage stages, continuously eliminating the generated Sn. 4 ⁺; Antioxidant additives are mainly activated during the high-temperature stage of annealing, actively inhibiting Sn. 2+ Oxidized to Sn 4+ The two work together at different stages and through different mechanisms to form a two-layer antioxidant protection system that addresses the symptoms in the solution stage and the root cause in the high-temperature stage.

[0028] Step S2: Provide a conductive substrate and form a hole transport layer on the conductive substrate.

[0029] It should be noted that in this step, the conductive substrate is preferably indium tin oxide (ITO) conductive glass, which is ultrasonically cleaned sequentially with detergent, deionized water, acetone, isopropanol, and ethanol before use, dried with nitrogen, and then subjected to plasma cleaning to remove surface organic matter and improve wettability. The hole transport layer is preferably m-PEDOT:PSS (modified poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid)), which is formed by spin-coating an aqueous solution of m-PEDOT:PSS onto the conductive substrate and then annealing. The m-PEDOT:PSS aqueous solution is obtained by mixing PEDOT:PSS and sodium poly(4-styrene sulfonate) (PSS:Na) aqueous solution in a certain proportion. The spin-coating speed is 3000 rpm to 5000 rpm, the annealing temperature is 130°C to 170°C, and the annealing time is 10 minutes to 20 minutes, preferably annealing at 150°C for 15 minutes. The m-PEDOT:PSS hole transport layer has suitable energy level matching and good film-forming properties, which is beneficial for efficient hole injection.

[0030] In this specific embodiment, the hole transport layer in step S2 is m-PEDOT:PSS, which is formed by spin-coating an aqueous solution of m-PEDOT:PSS onto a conductive substrate and annealing it at 130°C to 170°C for 10 to 20 minutes.

[0031] It should be noted that m-PEDOT:PSS (modified PEDOT:PSS) is modified by introducing sodium poly(4-styrene sulfonate) (PSS:Na) into conventional PEDOT:PSS to adjust its conductivity, work function, and hydrophilicity, thereby better matching its energy levels with the valence band top of tin-based perovskites and reducing the hole injection barrier. The m-PEDOT:PSS aqueous solution is prepared by mixing an aqueous PEDOT:PSS solution with an 80 mg / mL PSS:Na aqueous solution at a volume ratio of 1:0.7. After filtering the mixture through a 0.45 μm filter, it is spin-coated onto a conductive substrate at a speed of 3000 rpm to 5000 rpm, followed by annealing at 130°C to 170°C for 10 to 20 minutes, preferably at 150°C for 15 minutes. Annealing removes residual moisture from the m-PEDOT:PSS film and improves its crystallinity and conductivity. The thickness of the m-PEDOT:PSS hole transport layer is preferably 20 nm to 50 nm.

[0032] Step S3: Apply the tin-based perovskite precursor solution to the hole transport layer and anneal the tin-based perovskite precursor solution at a temperature range of 110℃-150℃ to form a tin-based perovskite luminescent layer.

[0033] Among them, the annealing treatment at 110℃-150℃ changes the tin-based perovskite crystal from in-plane lateral growth to out-of-plane vertical growth, reducing the bottom area of ​​the grain and increasing its height, thereby reducing grain boundary defects and optimizing the carrier injection balance.

[0034] It should be noted that, in this step, the precursor solution is preferably applied to the hole transport layer by spin coating, with a spin coating speed of 3000 rpm to 5000 rpm and a spin coating time of 30 to 90 seconds, preferably 4000 rpm for 60 seconds. During spin coating, preferably between the 30th and 45th seconds after the start of spin coating (more preferably the 38th second), an antisolvent (preferably chlorobenzene, in an amount of 400 μL to 600 μL, more preferably 500 μL) is added dropwise to the precursor film to extract excess solvent from the precursor film, promote rapid perovskite nucleation, and form a dense and uniform wet film. Subsequently, the wet film is transferred to a hot plate for annealing at a temperature of 110°C to 150°C for 5 to 20 minutes, preferably 10 minutes.

[0035] Within this temperature range, a significant vertical thermal gradient forms between the hot plate and the thin-film-substrate interface, with solvent evaporation predominantly vertically upward, generating a strong vertical thermal driving force. This driving force forces ions in the precursor to migrate and crystallize out-of-plane, transforming the tin-based perovskite crystal growth from in-plane lateral to out-of-plane vertical, resulting in a smaller grain base area and an increased grain height. Taking CsSnI3 as an example, as the annealing temperature increases from 90℃ to 150℃, the maximum grain height increases from approximately 83nm to approximately 150nm, while the grain base area decreases accordingly, leading to a reduction in substrate coverage. This shift in crystal growth mode brings two beneficial effects: First, the vertical growth mode effectively suppresses abnormal crystal aggregation and reduces grain boundary defects, significantly reducing the number of defect sites that were originally non-radiative recombination centers at the grain boundaries. Second, the reduction in the bottom area decreases the contact area between the perovskite emitting layer and the hole transport layer, thereby suppressing the injection of excessive holes. Meanwhile, the increase in grain height increases the contact area between the perovskite emitting layer and the subsequent electron transport layer, enhancing electron injection. The synergistic effect of these two factors optimizes the charge carrier injection balance in the device.

[0036] When the annealing temperature is below 110℃, the thermal driving force is insufficient to overcome the energy barrier for lateral growth. The crystal primarily grows in an in-plane lateral pattern, forming lamellar or dendritic grains. Grain boundary defects are dense, and hole injection is excessive, resulting in poor device performance. When the annealing temperature is above 150℃, although vertical crystal growth is more complete, excessively high temperatures severely exacerbate Sn growth. 2+ The disproportionation decomposition produces a large amount of Sn. 4+ Deep-level defects become strong nonradiative recombination centers in electroluminescent operation, which reduces device efficiency. Therefore, the annealing temperature range of 110°C to 150°C is the optimal range to balance the benefits of physical-directed growth and the suppression of chemical thermal decomposition, with 130°C being the preferred balance point between the two curves mentioned above.

[0037] In this specific embodiment, step S3 specifically includes: A tin-based perovskite precursor solution was applied to the hole transport layer, and the tin-based perovskite precursor solution was annealed at 130°C to form a tin-based perovskite luminescent layer.

[0038] It should be noted that within the temperature range of 110℃ to 150℃, 130℃ represents the optimal balance between the benefits of physically oriented growth and the suppression of chemical thermal decomposition. At an annealing temperature of 130℃, the vertical thermal driving force is sufficient to fully transform tin-based perovskite crystals from in-plane lateral growth to out-of-plane vertical growth, significantly reducing the grain bottom area, significantly increasing the grain height, and lowering the grain boundary defect density to a lower level. Simultaneously, at this temperature, Sn... 2+The disproportionation decomposition and oxidation were at a relatively mild level and did not have a serious negative impact on device performance. Transient electroluminescence measurements showed that the electron mobility of the device prepared by annealing at 130℃ reached 3.1 × 10⁻⁶. -5 cm 2 V -1 s -1 Significantly better than 90℃ (1.2×10⁻⁶) -5 cm 2 V -1 s -1 ), 110℃ (2.6×10 -5 cm 2 V - 1 s -1 ) and 150℃ (2.8×10¹⁰) -5 cm 2 V -1 s -1 The annealed devices demonstrated optimal electron injection and transport efficiency and the fastest carrier recombination rate (shortest delay time) at 130℃. The CsSnI3 perovskite LEDs fabricated based on 130℃ annealing achieved a maximum external quantum efficiency of 7.87%, a lifetime of 13.24 hours at a current density of 50 mA cm⁻², and 48.19 hours at a current density of 20 mA cm⁻².

[0039] In this specific embodiment, the annealing process in step S3 is a stepped annealing process, specifically including: The tin-based perovskite precursor solution is annealed at a first temperature for a first time period, and then cooled to a second temperature for a second time period; wherein the first temperature is higher than the second temperature, the first temperature is 130°C to 150°C, and the second temperature is 110°C to 130°C.

[0040] It should be noted that after the tin-based perovskite precursor solution is applied to the hole transport layer, it is first annealed at a first temperature for a first time period, and then annealed at a second temperature for a second time period. The first temperature is higher than the second temperature, with the first temperature being 130°C to 150°C and the second temperature being 110°C to 130°C. The advantage of this stepped annealing process is that the high temperature in the first stage (130°C to 150°C) provides a sufficiently strong vertical thermal driving force, inducing the tin-based perovskite crystal to transform from in-plane lateral growth to out-of-plane vertical growth, achieving a directional growth effect with a reduced bottom area and increased height of the grains; the low temperature in the second stage (110°C to 130°C) is used to reduce the annealing temperature after the crystal framework has been basically shaped, thereby reducing Sn. 2+ Exposure time at high temperatures, thereby inhibiting Sn 2+The disproportionation decomposition and oxidation processes minimize performance loss due to chemical decomposition while retaining the benefits of directional growth. The first and second time periods are each preferably 3 to 10 minutes independently, and the cooling method can be natural cooling or programmed temperature control cooling.

[0041] In this specific embodiment, step S3, after applying the tin-based perovskite precursor solution to the hole transport layer and before annealing, also includes an antisolvent extraction step: between 30 and 45 seconds after spin coating begins, an antisolvent is dropped onto the tin-based perovskite precursor film; wherein the antisolvent is chlorobenzene.

[0042] It should be noted that the specific operation of antisolvent extraction is as follows: Between 30 and 45 seconds (more preferably 38 seconds) after the start of spin coating, an antisolvent is dropped onto the precursor film. The preferred antisolvent is chlorobenzene, used in an amount of 400 μL to 600 μL, more preferably 500 μL. The working principle of antisolvent extraction is that antisolvents such as chlorobenzene have good miscibility with the main solvent (DMSO) of the perovskite precursor, but do not dissolve the perovskite component. When the antisolvent is dropped onto the surface of the rotating wet film, it rapidly extracts the DMSO solvent from the wet film, causing the perovskite component in the precursor solution to become instantaneously supersaturated and nucleate in large quantities, forming high-density crystal nuclei. This operation effectively avoids abnormal grain growth and agglomeration caused by slow solvent evaporation during subsequent annealing, providing a uniform nucleus basis for directional crystal growth during the high-temperature annealing stage. If the antisolvent is added before 30 seconds, the precursor film will not have spread sufficiently, resulting in uneven nucleation; if it is added after 45 seconds, the wet film will have partially dried, and the extraction effect of the antisolvent will decrease significantly. Therefore, the addition window from 30 seconds to 45 seconds is the key timing for achieving uniform nucleation.

[0043] In this specific embodiment, step S3 involves applying the tin-based perovskite precursor solution to the hole transport layer, specifically as follows: A tin-based perovskite precursor solution was applied to the hole transport layer using a spin coating method. The spin coating speed was 3000 rpm to 5000 rpm, and the spin coating time was 30 seconds to 90 seconds.

[0044] It should be noted that spin coating is suitable for the fabrication of small-area devices in the laboratory, as it is simple to operate and produces uniform and controllable film thickness. The spin coating speed is 3000 rpm to 5000 rpm, and the spin coating time is 30 to 90 seconds. Preferably, the spin coating speed is 4000 rpm, and the spin coating time is 60 seconds. Within this parameter range, a precursor wet film of moderate thickness (approximately 100 nm to 200 nm) and a smooth surface can be obtained. If the spin coating speed is too low (below 3000 rpm), the film thickness is too large, resulting in more solvent residue, which easily leads to pinholes and cracks after annealing. If the spin coating speed is too high (above 5000 rpm), the film is too thin, resulting in insufficient coverage and easily causing device leakage. The preferred environmental conditions during the spin coating process are: temperature 20°C to 30°C, and relative humidity below 20%.

[0045] 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.

[0046] It should be noted that, in this step, the preferred material for the electron transport layer is SPPO13 (2,7-bis(diphenylphosphino)-9,9'-spirodifluorene), which is prepared by dissolving SPPO13 in chlorobenzene to a concentration of 1 mg / mL to 5 mg / mL and spin-coating it onto the tin-based perovskite light-emitting layer at a rotation speed of 3000 rpm to 5000 rpm. The electrode is formed by sequentially depositing B3PYMPM (4,6-bis(3,5-di-3-pyridylphenyl)-2-methylpyrimidine), LiF (lithium fluoride), and Al (aluminum) through vacuum thermal evaporation. Specifically, the deposition thickness of B3PYMPM is 30 nm to 70 nm (preferably 50 nm), the deposition thickness of LiF is 1 nm to 3 nm (preferably 2 nm), and the deposition thickness of Al is 60 nm to 100 nm (preferably 80 nm). B3PYMPM serves as the electron transport / hole blocking layer, LiF as the electron injection layer, and Al as the cathode electrode; together, they constitute a highly efficient electron injection and transport system. The vacuum level during deposition is preferably below 5 × 10⁻⁶. -4 Pa, the deposition rate is optimized and controlled according to the material type. The effective light-emitting area of ​​the device is preferably 1 mm. 2 Up to 10mm 2 3mm is preferred 2 (e.g., 2mm × 1.5mm).

[0047] In this specific embodiment, the electron transport layer in step S4 is SPPO13, which is formed by spin-coating an SPPO13 solution onto a tin-based perovskite luminescent layer. The solvent of the SPPO13 solution is chlorobenzene, and the concentration is 1 mg / mL to 5 mg / mL.

[0048] It should be noted that SPPO13 (2,7-bis(diphenylphosphino)-9,9'-spirodifluorene) is an organic electron transport material with high electron mobility and a deep highest occupied molecular orbital (HOMO) level. It can effectively block hole leakage towards the cathode while promoting electron injection and transport. The SPPO13 solution is prepared by dissolving SPPO13 in chlorobenzene to a concentration of 1 mg / mL to 5 mg / mL. This solution is then spin-coated onto a tin-based perovskite luminescent layer at a speed of 3000 rpm to 5000 rpm. No annealing is required after spin-coating. The preferred thickness of the SPPO13 electron transport layer is 10 nm to 30 nm. Avoiding high-temperature annealing of this layer prevents secondary thermal damage to the tin-based perovskite luminescent layer.

[0049] In this specific embodiment, in step S4, the electrode is formed by sequentially depositing B3PYMPM, LiF and Al through vacuum thermal evaporation. The deposition thickness of B3PYMPM is 30nm to 70nm, the deposition thickness of LiF is 1nm to 3nm, and the deposition thickness of Al is 60nm to 100nm.

[0050] It should be noted that the electrode adopts a three-layer structure of "B3PYMPM / LiF / Al". B3PYMPM (4,6-bis(3,5-di-3-pyridylphenyl)-2-methylpyrimidine) serves as the electron transport / hole blocking layer, and its LUMO energy level matches that of SPPO13, further promoting electron injection and blocking holes. The deposition thickness of B3PYMPM is 30 nm to 70 nm, preferably 50 nm. LiF (lithium fluoride) serves as the electron injection layer, with a thickness of 1 nm to 3 nm, preferably 2 nm. Al serves as the cathode electrode, with a thickness of 60 nm to 100 nm, preferably 80 nm. The preferred conditions for vacuum thermal evaporation are: a vacuum level below 5 × 10⁻⁶. -4 The deposition rates of Pa, B3PYMPM, and LiF ranged from 0.1 nm / s to 0.5 nm / s, while the deposition rate of Al ranged from 0.5 nm / s to 2 nm / s. These three layers were deposited sequentially in a vacuum environment without vacuum breaking, ensuring clean interlayer interfaces and good contact.

[0051] To better illustrate the effect of annealing temperature on crystal orientation in this step, experimental examples of the relationship between annealing temperature and crystal orientation are provided below.

[0052] The embodiments propose a strategy of increasing the annealing temperature to control the directional growth of grains, shifting from in-plane lateral growth during low-temperature annealing to out-of-plane vertical growth during high-temperature annealing, while simultaneously reducing the bottom area and increasing the surface area and height. Figure 2As shown in the schematic diagram in Figure a, this improves the film quality. On the one hand, directional growth can suppress crystal aggregation, thereby reducing grain boundary defects. On the other hand, out-of-plane vertical growth can increase the contact area between the perovskite and the electron transport layer (ETL), while reducing the contact area between the perovskite and the hole transport layer (HTL), i.e., enhancing electron injection and reducing hole injection to achieve better charge carrier balance. Figure 2 a illustrates two different growth scenarios: low-temperature annealing and high-temperature annealing. Figure 2 a shows that high temperature causes grain growth to become vertical. Among these, Figure 2 In the figure, (a) is a mechanism diagram of the thermally controlled directional growth strategy. SEM images of the surface and cross-section of the film at different annealing temperatures: (b) 90℃, (c) 110℃, (d) 130℃, (e) 150℃.

[0053] To verify the thermally regulated directional growth of CsSnI3 thin films, the surface morphology and cross-section of the films at different temperatures were analyzed using scanning electron microscopy (SEM) in the examples. The results are as follows: Figure 2 As shown in Figure BE, under low annealing temperatures (90-110℃), the film exhibits a slow anisotropic growth trend, forming an inhomogeneous dendritic morphology with significant lateral fusion of grains. Therefore, agglomeration and incomplete crystallization between the original dendritic grains can be observed, leading to numerous grain boundary defects. These defects act as active sites for nonradiative recombination of charge carriers and ion migration, severely degrading the optoelectronic performance of the film and device. In contrast, under high annealing temperatures (130-150℃), the overall solvent evaporation rate accelerates. Driven by the inherent vertical thermal gradient at the film-substrate interface, the thermal driving force controlling solvent diffusion is significantly enhanced in the out-of-plane direction. Therefore, vertical solvent evaporation preferentially outpaces lateral evaporation, limiting the lateral diffusion of the precursor colloid and suppressing in-plane grain expansion. The initially agglomerated and fused lamellar grains gradually decompose into discrete, independent microcrystals. Simultaneously, grain boundaries and interstitial voids decrease, ultimately resulting in a more uniform film morphology. This evolution is consistent with… Figure 2 a and Figure 2 The grain height variation is consistent in the cross-sectional SEM images of the perovskite. It is worth noting that the reduced coverage indicates a smaller contact area between the perovskite and the hole transport layer, leading to less hole injection. This is beneficial for mitigating p-type doping characteristics and improving carrier balance.

[0054] Furthermore, the surface morphology was measured using atomic force microscopy (AFM) in the embodiments, and the evolution of grain height was confirmed, such as... Figure 3 , Figure 3 AFM images and grain height analysis of CsSnI3 films prepared at different annealing temperatures ((a) 90℃, (b) 110℃, (c) 130℃, (d) 150℃). Figure 3As shown in the diagram, with increasing annealing temperature, the grains gradually change from aggregated bulk grains to sparse small grains, with the maximum height increasing from 83 nm to 150 nm. This is consistent with the SEM results, jointly indicating that annealing conditions can effectively regulate the crystallization process of perovskite. This is mainly attributed to the enhanced thermal driving force, which promotes faster vertical grain growth and larger vertical dimensions. Conversely, in-plane lateral growth is suppressed, leading to grain bottom shrinkage. That is, the bottom area decreases while the surface area increases, resulting in reduced hole injection and increased electron injection, thereby improving device performance.

[0055] To assess the impact of thermally regulated directional growth on defects, the steady-state photoluminescence (PL) spectra of perovskite films were collected and analyzed in the examples. Figure 4 As shown, Figure 4 (a) shows the PL spectra of CsSnI3 films at different annealing temperatures, and (b) shows the curves of electronic devices annealed at different temperatures. PL spectra of CsSnI3 films treated at different annealing temperatures under 365nm LED continuous UV excitation: (c) 90℃, (d) 110℃, (e) 130℃, (f) 150℃.

[0056] from Figure 4 As can be seen, the PL intensity increases monotonically with annealing temperature, and the change in PLQY shows a similar trend, increasing from 6.95% (90℃) to 11.03% (150℃). Clearly, the radiative recombination of these films is significantly enhanced, which is attributed to the reduction of grain boundary defects by directional growth, thereby suppressing non-radiative recombination. Furthermore, the photostability of the CsSnI3 films was evaluated by continuously exciting them with a 365nm LED and monitoring the PL spectrum. Figure 4 As shown in Figure cf, the CsSnI3 film treated at a low annealing temperature (90℃) exhibits poor photostability, with the photoluminescence (PL) intensity rapidly quenching after 16 minutes of continuous UV excitation. With increasing annealing temperature, photostability gradually improves, and the decay of the PL intensity is delayed. Particularly for the film prepared at 150℃, the PL intensity remains almost unchanged after 240 minutes of continuous UV excitation. This is attributed to the reduction in grain boundary defects, which act as ion migration channels under continuous UV excitation.

[0057] Encouraged by the significant improvement in thin film quality, the examples further fabricated CsSnI3 perovskite light-emitting diodes with the structure ITO / m-PEDOT:PSS / CsSnI3 / SPPO13 / B3PYMPM / LiF / Al. Current density-voltage (JV) curves and radiance-voltage (RV) curves were recorded and are shown in... Figure 5 In ab, Figure 5Photoelectric properties of CsSnI3 perovskite light-emitting diodes annealed at different temperatures: (a) current density-voltage (JV) curves, (b) radiance-voltage (RV) curves, (c) external quantum efficiency-current density (EQE-J) curves, (d) electroluminescence spectra of perovskite light-emitting diodes annealed at 130℃ under different voltages, (e) EQEmax histogram statistics, and (f) normalized radiance decay curves. It can be seen that the current density and radiance of the corresponding devices based on films prepared at low annealing temperatures are lower than those prepared at high annealing temperatures. This is due to more grain boundary defects and charge carrier imbalance, leading to lower EQE (JV). Figure 5 c). Notably, the CsSnI3 perovskite light-emitting diode based on the thin film prepared at 130℃ exhibits excellent performance, with a maximum EQE of 7.87%, making it one of the most efficient all-inorganic near-infrared II perovskite light-emitting diodes reported to date. Furthermore, this device demonstrates excellent spectral stability, such as... Figure 5 As shown in Figure d, as the driving voltage increased from 1.6V to 6V, the emission peak remained almost constant at 955nm, which is attributed to the reduction of defects, which act as ion migration channels. Furthermore, the reproducibility and operational stability at different current densities were investigated in the examples. A total of 20 perovskite light-emitting diode devices were fabricated for statistical analysis. Figure 5 e). Furthermore, good operating lifetimes (T50) of 13.24 hours and 48.19 hours were achieved at current densities of 50 mA cm⁻² and 20 mA cm⁻², respectively, as shown in the figures. Figure 5 As shown in f. Furthermore, the examples summarize the performance comparison of this work with previously reported organic-inorganic hybrid tin-based perovskite light-emitting diodes. These results collectively highlight that thermally regulated crystal growth strategies can effectively reduce grain boundary defects, weaken p-type doping characteristics, and increase electron injection, thereby significantly improving device efficiency and stability. However, it should be noted that in previous characterizations, the film prepared at 150°C performed better than the film prepared at 130°C, but the corresponding device performance was the opposite. This difference can be reasonably explained by the spontaneous disproportionation of Sn²⁺ and the fundamental difference between the photoluminescence and electroluminescence working mechanisms. The thermal annealing process inevitably leads to Sn²⁺ disproportionation. 2+ Severe disproportionation and decomposition of components, this is Sn on the film surface and in the bulk phase. 4+ The primary intrinsic source of Sn formation. Therefore, in this study, in-situ surface oxidation and high-temperature annealing drive Sn formation. 2+ The synergistic effect of disproportionation increased Sn 4+Concentration reduces device performance. More importantly, the EQE of a perovskite light-emitting diode (LED) device can be quantitatively described by the formula EQE=PLQY•ηout•γ, where PLQY, ηout, and γ represent the photoluminescence quantum yield, light extraction efficiency, and the ratio of recombination charge carriers to total injected charge carriers in the emitting layer, respectively. Clearly, the overall performance of a perovskite LED depends not only on the photoelectric properties of the perovskite film but also strongly on several key device-level factors, including interfacial carrier injection balance, bulk charge transport kinetics and radiative recombination efficiency, as well as optical light extraction capability. CsSnI3 films prepared at 130℃ and 150℃ have different grain morphologies, which can modulate the interfacial contact conditions between the emitting layer and adjacent functional layers, leading to different carrier transport efficiencies and light extraction efficiencies.

[0058] To gain a deeper understanding of the radiative recombination behavior of charge carriers and to verify the above hypotheses, transient electroluminescence measurements were performed in this embodiment to explore carrier dynamics. By applying various pulse voltages to the CsSnI3 perovskite light-emitting diode, transient EL signals can be obtained, such as... Figure 6 As shown in ad. Figure 6 Transient electroluminescence (EL) measurements of CsSnI3 perovskite light-emitting diodes annealed at different temperatures: (ad) represents the transient EL signal at different pulse voltages, (e) represents the delay time extracted from the rising edge of the transient EL signal at different pulse voltages, and (f) represents the average electron mobility estimated from the delay time. EL intensity increases with increasing voltage. At the same voltage, the EL intensity of the device annealed at 130°C is higher than that of the device annealed at any other temperature, indicating stronger radiative recombination, which is consistent with steady-state EL measurements. Furthermore, the embodiments provide the evolution of the delay time (Δtd) extracted from the rising edge of the transient EL signal to compare charge carrier recombination rates, such as... Figure 6 As shown in e. Shorter times mean faster injection and transport, especially for minority carriers. The Δtd of the device annealed at 130°C is significantly lower than that of other devices, indicating faster electron injection and transport, resulting in higher luminous efficiency. Specific electron mobilities can also be calculated from these measurements, such as... Figure 6 As shown in f, the average values ​​of perovskite light-emitting diodes annealed at 90℃, 110℃, 130℃, and 150℃ are 1.2 × 10⁻⁶. -5 cm 2 V -1 s -1 2.6×10 -5 cm 2 V -1 s -1 3.1×10 -5 cm 2 V -1 s-1 and 2.8×10 -5 cm 2 V - 1 s -1 .

[0059] This invention, by controlling the annealing temperature between 110°C and 150°C, utilizes the vertical thermal gradient between the hot plate and the thin film to generate a strong vertical thermal driving force, transforming the in-plane lateral growth of tin-based perovskite crystals into out-of-plane vertical growth, resulting in a smaller grain base area and an increased grain height. This physical field intervention method is completely independent of additives, interface modification layers, or other additional chemical components, avoiding the obstruction of charge transport by insulating impurities, and making the process simpler and less costly. In the prior art, achieving vertical orientation of perovskite crystals usually relies on additive assistance (such as amino-containing additives forming an intermediate structure with the precursor) or interface modification; this invention significantly simplifies the process flow.

[0060] In this embodiment of the invention, high-temperature annealing induces crystals to change from in-plane lateral growth to out-of-plane vertical growth. The bottom area of ​​the grains is reduced and the height is increased. The originally agglomerated and fused plate-like grains are gradually decomposed into discrete independent microcrystals, reducing grain boundaries and interstitial voids, and significantly reducing the density of grain boundary defects.

[0061] This invention, through altering the macroscopic geometry of the crystal, physically modulates the carrier injection ratio: as the grains transition from lateral to vertical growth, the bottom area shrinks, reducing the contact area with the hole transport layer and thus suppressing excessive hole injection; simultaneously, the increased grain height expands the contact area with the electron transport layer, enhancing electron injection. This approach, utilizing morphology to influence device physics, spontaneously optimizes the electron-hole injection balance without altering the material's chemical composition. In existing technologies, improving carrier imbalance in tin-based perovskites typically relies on complex doping or interface engineering; this invention provides a novel physical control pathway.

[0062] In this embodiment of the invention, tin powder and antioxidant additives are simultaneously introduced into the precursor solution to construct a two-layer antioxidant protection system: the tin powder dissolves the Sn already generated in the precursor solution through a disproportionation reaction. 4+ Restore to Sn 2+ It continues to function during solution storage; antioxidant additives inhibit Sn through coordination or thermal sacrificial mechanisms during high-temperature annealing. 2+ Oxidized to Sn 4+ This provides active protection during the most vulnerable stage of annealing. Both mechanisms work synergistically at different stages to effectively address the protection of tin-based perovskites against Sn under high-temperature annealing conditions. 2+ The problem of easy oxidation.

[0063] In summary, the embodiments of the present invention solve the long-standing problems of uncontrolled crystallization and Sn in the field of tin-based perovskite light-emitting diodes. 2+ The three core challenges of oxidation and carrier imbalance provide a simple, effective, and additive-free technical solution for the fabrication of high-performance lead-free near-infrared II light-emitting devices.

[0064] This invention also provides a thermally controlled crystal-directed growth tin-based near-infrared II perovskite light-emitting diode, which is prepared by the preparation method provided in any of the above embodiments.

[0065] 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.

[0066] 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.

[0067] 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 thermally controlled crystal-directed growth method for tin-based near-infrared II perovskite light-emitting diode, characterized in that, The method includes: Step S1: Dissolve the cesium source, tin source, and antioxidant additive in an organic solvent, and add tin powder to maintain the stability of the valence state of tin in the solution. After stirring and mixing evenly, filter to obtain a tin-based perovskite precursor solution; wherein, the antioxidant additive is used to prevent tin ions from being oxidized by temperature. Step S2: Provide a conductive substrate and form a hole transport layer on the conductive substrate; Step S3: Apply the tin-based perovskite precursor solution to the hole transport layer, and anneal the tin-based perovskite precursor solution at a temperature range of 110℃-150℃ to form a tin-based perovskite luminescent layer; wherein, the annealing treatment at 110℃-150℃ causes the tin-based perovskite crystal to change from in-plane lateral growth to out-of-plane vertical growth, reducing the bottom area of ​​the grains and increasing their height, thereby reducing grain boundary defects and optimizing carrier injection balance; 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.

2. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, Step S3 specifically includes: The tin-based perovskite precursor solution is applied to the hole transport layer, and the tin-based perovskite precursor solution is annealed at 130°C to form a tin-based perovskite luminescent layer.

3. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The annealing process in step S3 is a stepped annealing process, specifically including: The tin-based perovskite precursor solution is annealed at a first temperature for a first time period, and then cooled to a second temperature for a second time period; wherein the first temperature is higher than the second temperature, the first temperature is 130°C to 150°C, and the second temperature is 110°C to 130°C.

4. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The antioxidant additive includes at least one of vitamin C, carbazole, formamidine thiocyanate, hesperetin, cesium trifluoroacetate; the antioxidant additive inhibits Sn 2+ from being oxidized to Sn 4+ by coordination or thermal sacrificial mechanism during the annealing process. The tin powder is produced by a centering reaction of Sn2+in the precursor solution 4+ reduction to Sn 2+ .

5. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, In step S3, after the tin-based perovskite precursor solution is applied to the hole transport layer and before the annealing treatment, an antisolvent extraction step is also included: between 30 seconds and 45 seconds after the spin coating begins, an antisolvent is dropped onto the tin-based perovskite precursor film; wherein the antisolvent is chlorobenzene.

6. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The step S3, which involves applying the tin-based perovskite precursor solution to the hole transport layer, specifically comprises: The tin-based perovskite precursor solution was applied to the hole transport layer by spin coating at a speed of 3000 rpm to 5000 rpm for a time of 30 to 90 seconds.

7. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The hole transport layer in step S2 is m-PEDOT:PSS, which is formed by spin-coating an aqueous solution of m-PEDOT:PSS onto the conductive substrate and annealing it at 130°C to 170°C for 10 to 20 minutes.

8. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, The electron transport layer in step S4 is SPPO13, which is formed by spin-coating an SPPO13 solution onto the tin-based perovskite luminescent layer. The solvent of the SPPO13 solution is chlorobenzene, and the concentration is 1 mg / mL to 5 mg / mL.

9. The method for fabricating a thermally controlled crystal-directedly grown tin-based near-infrared II perovskite light-emitting diode according to claim 1, characterized in that, In step S4, the electrode is formed by sequentially depositing B3PYMPM, LiF, and Al through vacuum thermal evaporation. The deposition thickness of B3PYMPM is 30 nm to 70 nm, the deposition thickness of LiF is 1 nm to 3 nm, and the deposition thickness of Al is 60 nm to 100 nm.

10. A thermally controlled crystal-directedly grown 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 9.

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