Method for improving spectrum heat resistance of perovskite nanocrystal and photoelectric device thereof through anion post-treatment

Abstract

The invention provides a method for improving spectrum heat resistance of perovskite nanocrystals and photoelectric devices thereof through anion post-treatment, and belongs to the technical field of semiconductor nanomaterials and photoelectric devices. According to the method, an organic group-anion compound is used for carrying out solution post-treatment on the perovskite nanocrystal, and the thermal excitation formation energy of the defect is remarkably improved through the vacancy defect that anions occupy the surface of the nanocrystal, so that the thermally induced fluorescence quenching phenomenon is effectively inhibited. The processed perovskite nanocrystal can maintain excellent fluorescence intensity under a heating condition, and a photoelectric device assembled by using the perovskite nanocrystal as a luminescent layer also shows significantly improved electroluminescent spectrum stability in a high-temperature working environment. The method is simple in process and suitable for various perovskite material systems and device structures, and an effective scheme is provided for solving the thermal stability problem of the perovskite material.

Description

Technical Field

[0001] This invention relates to the field of semiconductor nanomaterials and optoelectronic devices, specifically to a method for anion post-treatment to improve the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices. Background Technology

[0002] Perovskite nanocrystals are considered a core material for next-generation lighting and display technologies due to their outstanding advantages such as pure and tunable luminescence color and simple fabrication. However, a major obstacle to their practical application lies in their poor thermal stability. When the ambient temperature rises, atoms (or ions) on the surface of the nanocrystals are easily dislodged due to thermal vibration, forming numerous surface defects. These defects become "traps" that capture photogenerated electrons and holes, causing them to recombine nonradiatively, consuming energy as heat instead of emitting light. This phenomenon, known as "thermoluminescence quenching," directly leads to a decrease in the fluorescence efficiency of the nanocrystals and causes problems such as reduced brightness, color shift, and rapid efficiency decay in optoelectronic devices (such as LEDs) based on them, severely hindering their commercialization. Currently, the industry lacks a universal method to effectively improve the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices.

[0003] To this end, an anion post-treatment method is proposed to improve the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices. Summary of the Invention

[0004] The present invention aims to solve the problems mentioned in the background art by providing a method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment.

[0005] The specific technical solution is as follows: A method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment includes the following steps: Step 1: Prepare solutions A and B with concentrations of 0.01 mmol / mL to 0.2 mmol / mL respectively. Mix solutions A and B at a volume ratio of 1:1, sonicate for 0.5 to 2 hours, centrifuge at high speed, and take the supernatant to obtain solution C with a concentration of 0.005 mmol / mL to 0.1 mmol / mL. Step 2: Take 10 μL to 100 μL of the C solution obtained in Step 1 and add it to a perovskite nanocrystal solution with a concentration of 10 mg / mL to 20 mg / mL. Stir for 0.5 hours to 2 hours in a temperature range of 25°C to 100°C. Step 3: Add antisolvent to the solution obtained in Step 2, and centrifuge at high speed to remove unreacted precursor solution to obtain anion-treated perovskite nanocrystals. Step four: Prepare an octane solution of the nanocrystals obtained in step three with a mass concentration of 1 mg / mL to 20 mg / mL for use in assembling perovskite nanocrystal optoelectronic devices.

[0006] This method employs anion post-treatment steps, including solution preparation, mixing, sonication, centrifugation, stirring, and anti-solvent treatment, to effectively modify the surface of perovskite nanocrystals. After anions occupy vacancy defects on the nanocrystal surface, they increase the thermal excitation formation energy of the defects, thereby reducing thermally induced nonradiative recombination and enhancing the fluorescence stability of the nanocrystals under heating conditions. Ultimately, this method endows the nanocrystals and their assembled optoelectronic devices with excellent spectral heat resistance, suppressing performance degradation under high-temperature environments.

[0007] The above-mentioned anion post-treatment method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices, wherein solution A is one of bis(dodecyl dimethyl ammonium bromide) toluene solution, bis(decyl dimethyl ammonium bromide) toluene solution, or bis(octyl dimethyl ammonium bromide) toluene solution.

[0008] By limiting solution A to a specific organic ammonium salt solution (such as a dodecyl dimethyl ammonium bromide toluene solution), it is ensured that the organic cations can form stable complexes with the anions, effectively adsorbing and covering the nanocrystal surface. This enhances the anion transport efficiency and surface defect repair capability, enabling the nanocrystals to form a uniform protective layer and further improving their thermal stability.

[0009] The above-mentioned anion post-treatment method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices, wherein the B solution is an aqueous solution of potassium salt, sodium salt or ammonium salt containing fluoride ions, chloride ions, bromide ions, iodide ions, sulfide ions, sulfate ions, phosphate ions, hydrogen phosphate ions, dihydrogen phosphate ions or nitrate ions.

[0010] By limiting the presence of multiple anion types (such as fluoride ions and sulfate ions) in solution B, selective occupation of defect sites with different properties on the surface of perovskite nanocrystals can be achieved. This diverse repair mechanism improves the comprehensiveness and adaptability of defect repair, enabling the nanocrystals to maintain stable optical properties even under complex thermal environments.

[0011] The above-mentioned anion post-treatment method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices, wherein the perovskite nanocrystals are lead-based perovskite nanocrystals, manganese-based perovskite nanocrystals, tin-based perovskite nanocrystals, or germanium-based perovskite nanocrystals.

[0012] By extending the types of perovskite nanocrystals to lead-based, manganese-based, tin-based, or germanium-based materials, this method demonstrates its applicability to various perovskite material systems. This versatility ensures that nanocrystals with different compositions can achieve surface defect repair through anionic post-treatment, thereby universally improving their spectral heat resistance and expanding the application range of the technology.

[0013] The above-mentioned anion post-treatment method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices, wherein the optoelectronic device is a light-emitting diode, the structure of which includes a transparent conductive electrode substrate, a hole injection layer or a hole transport layer, a light-emitting layer, an electron injection layer or an electron transport layer, and a metal electrode.

[0014] By defining the optoelectronic device as a light-emitting diode and describing its multilayer structure (such as transparent conductive electrodes, hole / electron transport layers, etc.), it is ensured that the processed nanocrystals, as the light-emitting layer, can work collaboratively with other parts of the device. This structural design allows the heat resistance advantage of the nanocrystals to be fully utilized at the device level, maintaining the device's luminous efficiency and stability at high temperatures.

[0015] The above-mentioned anion post-treatment method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices, wherein the transparent conductive electrode substrate is ITO conductive glass, FTO conductive glass, or a flexible conductive substrate; the hole injection layer or hole transport layer is selected from at least one of PEDOT:PSS, Spiro-OMeTAD, TFB, TPD, SOCP, CBP, F8, P3HT, PTAA, NiO, CuI, CuSCN, MoOx, Poly-TPD, PVK, TCTA, or PEDOT / PFI; the luminescent... The layer is anion-treated perovskite nanocrystals prepared by the method of any one of claims 1 to 4; the electron injection layer or electron transport layer is selected from at least one of TPBi, PBD, BCP, PCBM, magnesium-doped zinc oxide, polyethyleneimine-modified zinc oxide, TiO2, ZnO, Al2O3, Zn2SnO4, SnO2, WO3, B3PYMPM, BPhen, TmPyPB, calcium acetylacetonate, or PFN; the metal electrode is selected from at least one of cesium carbonate and aluminum, lithium fluoride and aluminum, calcium and aluminum, calcium, nickel, aluminum, silver, or gold.

[0016] By further specifying the specific materials for each layer of the device (such as PEDOT:PSS as the hole transport layer and TPBi as the electron transport layer), the energy level matching and interface characteristics within the device were optimized. This reduced nonradiative recombination losses of charge carriers, enhanced the overall thermal stability and luminescence performance of the device, and enabled the treated nanocrystals to operate reliably in the device for a long period of time.

[0017] The present invention also provides anion-treated perovskite nanocrystals, which are prepared by the above method and have improved spectral heat resistance by occupying vacancy defects on their surface with anions.

[0018] This solution directly protects the anion-treated perovskite nanocrystals prepared by the method. Surface defects are effectively occupied by anions, reducing the probability of thermally excited defects and giving the nanocrystals inherent high-spectral heat resistance. This product can be directly used in various optoelectronic applications, maintaining fluorescence performance in thermal environments without additional processing.

[0019] In the above-mentioned anion-treated perovskite nanocrystals, the anion is F. - Cl - ,Br - I - S 2- SO4 2- PO4 3- HPO4 2- H2PO4 - and NO3 - .

[0020] By further defining the types of anions adsorbed on the nanocrystal surface, targeted repair of surface vacancy defects by specific anions (such as fluoride or phosphate ions) is ensured. This selectivity enhances the efficiency and stability of defect repair, making the nanocrystals less prone to fluorescence quenching at high temperatures, thus improving product reliability and applicability.

[0021] The present invention also provides an optoelectronic device, wherein the light-emitting layer of the optoelectronic device comprises the above-mentioned anion-post-treated perovskite nanocrystals.

[0022] This solution protects optoelectronic devices containing the anion-treated nanocrystals. Because the light-emitting layer uses heat-resistant nanocrystals, the device can suppress the performance degradation of the light-emitting layer at high temperatures, maintain stable current density-voltage characteristics and external quantum efficiency, extend the device's lifespan, and improve display or lighting effects.

[0023] The present invention also provides an application for improving the spectral heat resistance of perovskite nanocrystals, wherein the perovskite nanocrystals are treated by the above method to suppress the decay of their fluorescence intensity under heating conditions.

[0024] This application scheme clarifies the value of the method in improving the spectral heat resistance of perovskite nanocrystals. By suppressing fluorescence intensity decay under heating conditions through anion post-treatment, the nanocrystals maintain their optical properties in thermal stress environments, providing a reliable foundation for the fabrication and operation of optoelectronic devices, especially suitable for high-temperature applications.

[0025] The present invention has the following beneficial effects: This invention successfully solves the above-mentioned problems through a simple anion post-processing technique, bringing significant overall performance improvements to perovskite nanocrystals and their optoelectronic devices: 1. Significantly enhanced spectral thermal stability: The treated perovskite nanocrystals maintain high fluorescence intensity across a wide temperature range from room temperature to higher temperatures, with significantly suppressed attenuation. This means that the nanocrystals themselves are greatly more resistant to high-temperature environments.

[0026] 2. Improved High-Temperature Performance of Optoelectronic Devices: LED devices assembled using treated nanocrystals as the light-emitting layer exhibit a significant leap in the stability of their electroluminescence performance under elevated temperatures. The degradation trend of brightness, current efficiency, and external quantum efficiency with increasing temperature is significantly mitigated, ensuring reliable operation of the devices in complex thermal environments.

[0027] 3. High versatility and good process compatibility: This method is applicable to various perovskite material systems such as lead-based and tin-based materials, and can be used in conjunction with various anions such as fluorine, sulfur, and phosphate, demonstrating good material versatility. Furthermore, the entire post-processing procedure is simple and can be seamlessly integrated with existing nanocrystal synthesis and device fabrication processes, making it easy to promote. Attached Figure Description

[0028] Figure 1 Fluorescence intensity-temperature decay curves for CsPbBr3 nanocrystals post-treated with fluoride ions. Figure 2 The fluorescence intensity-temperature decay curve of CsPbBr3 nanocrystals after sulfur ion post-treatment is shown. Figure 3 The fluorescence intensity-temperature decay curve of CsPbBr3 nanocrystals after bromide ion post-treatment is shown. Figure 4 The fluorescence intensity-temperature decay curve of CsPbBr3 nanocrystals after iodine ion post-treatment is shown. Figure 5 The fluorescence intensity-temperature decay curve of CsPbBr3 nanocrystals after phosphate ion post-treatment. Figure 6 Current density-voltage decay curves as a function of temperature for LED devices assembled from untreated CsPbBr3 nanocrystals. Figure 7 Brightness-voltage decay curves as a function of temperature for LED devices assembled from untreated CsPbBr3 nanocrystals. Figure 8 External quantum efficiency-current density decay curves as a function of temperature for LED devices assembled from untreated CsPbBr3 nanocrystals; Figure 9Current density-voltage decay curves as a function of temperature for LED devices assembled with bromide ion-treated CsPbBr3 nanocrystals. Figure 10 Brightness-voltage decay curves as a function of temperature for LED devices assembled with bromide-treated CsPbBr3 nanocrystals. Figure 11 External quantum efficiency-current density decay curves of LED devices assembled with bromide ion-treated CsPbBr3 nanocrystals as temperature. Figure 12 Current density-voltage decay curves as a function of temperature for LED devices assembled with CsPbBr3 nanocrystals treated with fluorine ions. Figure 13 Brightness-voltage decay curves as a function of temperature for LED devices assembled with CsPbBr3 nanocrystals treated with fluorine ions. Figure 14 External quantum efficiency-current density decay curves of LED devices assembled with fluorine ion-treated CsPbBr3 nanocrystals as a function of temperature. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0031] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] See attached document Figure 1-14 The following three embodiments are provided: Example 1: Fluorine ion post-treatment improves the thermal stability of CsPbBr3 nanocrystals and their LED devices Technical solution: 1. Preparation of treatment solutions: Weigh disodium dodecyl dimethyl ammonium bromide and dissolve it in toluene to prepare solution A with a concentration of 0.05 mmol / mL. Weigh sodium fluoride and dissolve it in deionized water to prepare solution B with a concentration of 0.05 mmol / mL. Mix solutions A and B at a volume ratio of 1:1, sonicate for 1 hour, then centrifuge at 10,000 rpm for 5 minutes. Collect the supernatant to obtain DDA with a concentration of 0.025 mmol / mL. + -F - Complex (solution C).

[0034] 2. Nanocrystal post-treatment: 1 mL of a 10 mg / mL CsPbBr3 nanocrystal toluene solution was taken. 30 μL of the above C solution was added, and the mixture was stirred continuously at 25 °C for 0.5 hours. Then, excess ethyl acetate was added as a countersolvent, and the mixture was centrifuged at 10,000 rpm for 2 minutes. The supernatant was removed to obtain fluoride-treated CsPbBr3 nanocrystal solids. Finally, the nanocrystals were redispersed in n-octane to form a 15 mg / mL dispersion for later use.

[0035] 3. Device Assembly: On a pre-patterned ITO glass substrate, a PEDOT:PSS hole injection layer (approximately 35 nm thick) and a Poly-TPD hole transport layer (approximately 30 nm thick) were sequentially spin-coated. Then, the fluorine ion post-treatment CsPbBr3 nanocrystal dispersion prepared above was spin-coated as a light-emitting layer (approximately 25 nm thick). Next, TPBi was sequentially deposited as an electron transport layer (approximately 40 nm thick), LiF as an electron injection layer (approximately 1 nm thick), and Al as a metal electrode (approximately 100 nm thick) via vacuum evaporation. Finally, the device was encapsulated using UV-curable adhesive.

[0036] Technical effects: 1. CsPbBr3 nanocrystals post-treated with fluoride ions exhibit excellent spectral thermal stability, as the fluorescence intensity decreases with increasing temperature when heated in solution.

[0037] 2. LED devices assembled with these nanocrystals exhibit effectively suppressed decay in electroluminescence spectrum, brightness, and external quantum efficiency as ambient temperature increases, resulting in a significant improvement in device efficiency and stability at high temperatures.

[0038] Working principle: Fluoride ions (F) - With its small ionic radius and high electronegativity, it can effectively diffuse and occupy bromine vacancy defects on the surface of CsPbBr3 nanocrystals. These bromine vacancies are the main nonradiative recombination centers leading to thermo-induced fluorescence quenching. (The text abruptly ends here, likely due to an incomplete translation or missing information.) - With the occupation of these defects, the surface defect state density decreases, and the defect formation energy increases. This means that under thermally excited conditions, the probability of electron-hole pairs undergoing nonradiative recombination through these defects is greatly reduced, and more charge carriers emit light through radiative recombination, thus macroscopically manifesting as enhanced fluorescence intensity and thermal stability of device efficiency.

[0039] Experimental data: 1. Temperature-dependent fluorescence spectroscopy (temperature range 25℃ to 110℃) was performed on nanocrystalline toluene solutions before and after treatment. The results showed that the fluorescence intensity of the untreated nanocrystalline solution decreased rapidly during the heating process, while the fluorescence intensity of the fluoride-treated nanocrystalline solution remained at a high level throughout the temperature range, and the decay curve was extremely flat.

[0040] 2. Temperature performance tests were conducted on the packaged LED devices (temperature range 25℃ to 70℃). Data showed that at the highest test temperature, the maximum brightness of the device based on fluorine ion-treated nanocrystals decreased only slightly compared to room temperature, and the external quantum efficiency curve remained largely unchanged without significant roll-off. In contrast, the brightness and efficiency of the control device (untreated nanocrystals) deteriorated sharply at high temperatures.

[0041] Example 2: Sulfur ion post-treatment enhances the thermal stability of CsPbBr3 nanocrystals Technical solution: 1. Preparation of the treatment solution: Solution A was prepared as in Example 1. Sodium sulfide was weighed and dissolved in deionized water to prepare solution B with a concentration of 0.05 mmol / mL. Subsequent mixing, sonication, and centrifugation were performed as in Example 1 to obtain DDA. + -S 2- Complex (solution C).

[0042] 2. Nanocrystal post-treatment: Measure 1 mL of a 10 mg / mL CsPbBr3 nanocrystal toluene solution. Add 30 μL of the above C solution to the solution and stir continuously at 50 °C for 1 hour. Subsequent antisolvent washing, centrifugation, and redispersion steps are the same as in Example 1 to obtain a sulfide-post-treated CsPbBr3 nanocrystal n-octane dispersion.

[0043] Technical effects: 1. Sulfide ion post-treatment also significantly improved the fluorescence thermal stability of CsPbBr3 nanocrystals. Under high temperature conditions, the treated nanocrystals can maintain strong fluorescence emission for a long time.

[0044] 2. This method provides another effective anion selection besides halide ions for improving the thermal stability of nanocrystals.

[0045] Working principle: Sulfide ions (S 2- The ionic radius of ) and the bromide ion (Br) - The differences are significant, but it can be compared with lead (Pb). 2+ This allows for stronger bonding, thereby stably passivating lead-related defects (such as insufficiently coordinated Pb) on the nanocrystal surface. 2+ This strong bonding is not easily broken under thermal disturbance, providing a robust surface protective layer for the nanocrystals, effectively suppressing the generation of thermally activated surface trap states, thereby reducing non-radiative recombination channels and enhancing the bulk thermal stability of the nanocrystals.

[0046] Experimental data: Temperature-dependent fluorescence spectroscopy showed that the fluorescence intensity-temperature curve of the sulfide-ion post-treated CsPbBr3 nanocrystals fell between that of the untreated sample and the fluoride-ion treated sample, but was significantly higher than that of the untreated sample. Throughout the entire test temperature range, the fluorescence intensity retention was significantly better than that of the untreated nanocrystals, demonstrating the effectiveness of sulfide-ion treatment.

[0047] Example 3: Phosphate ion post-treatment improves the thermal stability of perovskite nanocrystal LEDs. Technical solution: 1. Preparation of the treatment solution: Solution A was prepared as in Example 1. Disodium hydrogen phosphate was weighed and dissolved in deionized water to prepare solution B with a concentration of 0.05 mmol / mL. Subsequent mixing, sonication, and centrifugation were performed as in Example 1 to obtain DDA. + -HPO4 2- Complex (solution C).

[0048] 2. Nanocrystal post-treatment: The treatment target was changed to a CsPbI3 nanocrystal toluene solution (concentration 12 mg / mL). The treatment process was the same as in Example 2, resulting in a phosphate ion-treated CsPbI3 nanocrystal n-octane dispersion.

[0049] 3. Device assembly: The device structure and preparation process are similar to those in Example 1. The only difference is that the light-emitting layer material is replaced with the phosphate ion post-treatment CsPbI3 nanocrystals prepared in this example.

[0050] Technical effects: 1. This embodiment demonstrates that the method of the present invention is equally applicable to perovskite nanocrystals with different compositions (such as iodide bromide).

[0051] 2. Phosphate ion post-treatment significantly improves the spectral stability of CsPbI3 nanocrystalline LED devices under high-temperature operating conditions, effectively preventing color shift and efficiency drop caused by heat generation.

[0052] Working principle: hydrogen phosphate ions (HPO4) 2- As a polyatomic anion, it has a relatively large molecular structure and carries two negative charges. It can interact with the surface of nanocrystals through multiple sites, not only passivating ion vacancy defects but also potentially crosslinking adjacent nanocrystals to form a more stable surface structure. This "multi-point anchoring" effect makes the surface passivation layer more thermodynamically stable, allowing it to function effectively for a long time even under the continuous heat generated during device operation, thus ensuring the photoelectric performance of the light-emitting layer.

[0053] Experimental data: 1. The assembled LED devices were subjected to aging tests under constant current drive, and the junction temperature was monitored. The experiment showed that, under the same driving conditions and temperature rise conditions, the device based on phosphate ion-treated CsPbI3 nanocrystals exhibited significantly smaller changes in the peak position and full width at half maximum (FWHM) of the electroluminescence spectrum compared to the control device based on untreated nanocrystals.

[0054] 2. The current efficiency-voltage characteristic curves of the device at higher ambient temperatures show that the efficiency roll-off phenomenon of the treated device is significantly alleviated, indicating that the non-radiative recombination of the light-emitting layer inside the device is effectively suppressed at high temperatures.

[0055] The above three embodiments collectively demonstrate the universality and effectiveness of the anion post-processing method of this application, which can provide a simple and reliable way to improve the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices.

[0056] Working principle: The core working principle of this invention lies in "surface defect passivation and thermal activation energy enhancement".

[0057] The surface of perovskite nanocrystals contains numerous dangling bonds and ionic vacancies (such as halogen vacancies), which are the main nonradiative recombination centers leading to fluorescence quenching. These defects are more easily activated upon heating, trapping charge carriers.

[0058] This method utilizes organic group-anionic complexes (such as DDA) + -X - The nanocrystals undergo post-processing. The mechanism of action is as follows: 1. Targeted migration and adsorption: Organic cations (DDA) in the complex + Due to the affinity of its long alkyl chain for the nanocrystalline surface, it can effectively anchor the entire composite to the nanocrystalline surface.

[0059] 2. Anion occupies the vacancy: Subsequently, the anion (X) carried in the complex... - , such as F - ,S 2- ,PO4 3- (etc.) will diffuse and precisely occupy the anion vacancies on the surface of nanocrystals.

[0060] 3. Increasing the defect formation energy: When anion fills a vacancy, it is equivalent to repairing the "wound" on the crystal lattice surface. This transforms the defect site from an unstable, high-energy state that easily traps charge carriers to a stable, inert low-energy state. To form a defect at this location again, a higher energy barrier needs to be overcome; that is, the thermal excitation formation energy of the defect is increased.

[0061] 4. Suppression of nonradiative recombination: At high temperatures, the formation and activation of surface defects are strongly suppressed due to the increased defect formation energy. Therefore, the probability of electrons and holes being trapped by defects and undergoing nonradiative recombination is greatly reduced, and more charge carriers can emit fluorescence through radiative recombination, thus exhibiting excellent spectral heat resistance on a macroscopic scale.

[0062] How to use: The implementation process of this invention is clear and simple to operate, and mainly includes the following four core steps: 1. Preparation of the complex solution: First, prepare an oil phase A solution (e.g., dodecyl dimethyl ammonium bromide / toluene solution) containing a long-chain organic ammonium salt and an aqueous phase B solution (e.g., sodium fluoride / aqueous solution) containing the target anion. Mix the two solutions in a specific ratio and sonicate to allow the cations and anions to combine and form a complex soluble in the organic solvent. After centrifugation and purification, obtain a clear solution C.

[0063] 2. Post-treatment of nanocrystals: A certain amount of C solution was taken and directly added to the pre-synthesized perovskite nanocrystal solution, and stirred at a suitable temperature. During this period, the composite and nanocrystals were in full contact, completing the anionic surface modification process.

[0064] 3. Purification to obtain the final product: Add an antisolvent (such as ethyl acetate) to the reaction system to precipitate the treated nanocrystals. Then remove the mother liquor containing unreacted impurities by high-speed centrifugation to obtain high-purity, anion-treated perovskite nanocrystal solids.

[0065] 4. Assembling optoelectronic devices: The purified nanocrystals are redispersed in a suitable solvent (such as n-octane) to form a uniform ink. Subsequently, using standard solution processing techniques (such as spin coating), this ink is used as the light-emitting layer and integrated sequentially with other functional layers (hole / electron transport layer, electrodes, etc.) to finally assemble a structurally complete perovskite nanocrystal optoelectronic device (such as an LED).

[0066] Furthermore, in this invention, the increase in the thermal excitation formation energy of defects in perovskite nanocrystals after anion post-treatment satisfies the following equation: ; This equation is used to quantitatively calculate the thermal excitation formation energy of defects on the surface of nanocrystals after processing, providing a quantitative basis for improving the spectral heat resistance.

[0067] The derivation of the equation is as follows: 1. Physical model construction: The essence of thermo-induced fluorescence quenching in perovskite nanocrystals is a chain process of "defect thermal excitation - carrier trapping - non-radiative recombination". The defect thermal excitation formation energy (E...) defect The ion content is a key parameter that determines the process and needs to be improved through anion post-treatment.

[0068] Original nanocrystal defect formation energy (E defect,pristine It is determined by the intrinsic lattice energy of the material and is a fundamental constant.

[0069] The interaction energy between anions and defects on the nanocrystal surface is the key to improvement, and two major mechanisms need to be considered: electrostatic interaction and adsorption coverage effect.

[0070] 2. Step-by-step derivation: Step 1: Calculation of electrostatic interaction energy. The electrostatic interaction energy between anion (charge q) and defect sites (carrying opposite charges) is related to the ionic radius (r). anion It is inversely proportional to the dielectric constant of nanocrystals (ε). NC ), solvent dielectric constant (ε) solvent The interaction is inversely proportional to the actual interaction strength. By introducing the anion adsorption efficiency coefficient (α, 0 < α ≤ 1), we correct for the actual interaction strength and obtain the electrostatic interaction term: .

[0071] Step 2: Adsorption Coverage Effect Correction. The coverage of defects by anions is related to the anion concentration (C). anion ), initial defect concentration (C) vacancy,initialRelated to this, using a logarithmic function. To describe the coverage pattern of "rapid increase at low concentrations and tendency to saturate at high concentrations," a bonding strength factor (γ, which is related to the anion type, such as F) is introduced. - γ=1.8, S 2- (γ=2.3) Corrects for bonding differences among different anions.

[0072] Step 3: Integration of comprehensive constants. A proportionality constant k (unit: eV·nm·√(F / m)·mol / L) is introduced to unify the dimensions and fit the experimental data, ultimately obtaining the complete equation.

[0073] Parameter description table:

[0074] Example (based on Example 1): 1. Known parameters (fluoride ion treated CsPbBr3 nanocrystals): E defect,pristine =1.0eV, k=0.025eV·nm·√(F / m)·mol / L, q=1.6×10 -19 C; α = 0.92 (adsorption efficiency of fluoride ions in the toluene-water system), γ = 1.8 (F - With Pb 2+ Bond strength); r anion =0.095nm, ε NC =22F / m, ε solvent =2.4F / m; C anion =0.025mmol / mL; C vacancy,initial =3×10 16 cm -3 .

[0075] 2. Calculation process: Middle term 1 = ; ; .

[0076] Middle Item 2 ; ; .

[0077] 3. Result Verification: The actual measured thermal excitation formation energy of defects in the treated CsPbBr3 nanocrystals was 2.31 eV, calculated by DFT. The error between this value and the calculated value was only 1.5%, which verified the accuracy of the equation.

[0078] Technical effects: 1. Quantitative performance improvement: Achieves quantitative correlation between "anion post-treatment process - defect formation energy - spectral heat resistance", solving the problem that existing technologies cannot quantitatively evaluate the treatment effect.

[0079] 2. Guiding Process Optimization: Optimal parameters can be derived by back-engineering equations. For example, if the defect formation energy needs to be increased to 2.5 eV, the required C can be calculated. anion The concentration should be 0.032 mmol / mL to avoid blind experimentation.

[0080] 3. Expanded applicability: It can be adapted to different perovskite systems (lead-based, tin-based, etc.) and anion types. The calculation can be performed by adjusting the parameters, which reflects the universality of the method.

[0081] Working principle and process: 1. Input parameters: Determine the type of perovskite nanocrystals (obtain ε) NC C vacancy,initial ), anion type (obtain q, r) anion , γ), processing system (acquiring ε) solvent α) and the concentration of the treatment solution (C) anion ).

[0082] 2. Equation Calculation: Substituting into the equation, we obtain the thermally activated formation energy E of the treated defect. defect,treated .

[0083] 3. Effect determination: If E defect,treated ≥1.8eV indicates that the spectral heat resistance of the nanocrystals meets the requirements for high-temperature applications (e.g., fluorescence intensity retention rate ≥80% at 70℃).

[0084] 4. Process Adjustment: If the calculated value does not meet the standard, increase C. anion Parameters were optimized by methods such as selecting anions with larger γ values, and the calculations were repeated until the target was met.

[0085] 5. Device verification: The qualified nanocrystals were used for optoelectronic device assembly, and the consistency between the predicted results of the equation and the actual device performance was verified by variable temperature electroluminescence test.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment, characterized in that, Includes the following steps: Step 1: Prepare solutions A and B with concentrations of 0.01 mmol / mL to 0.2 mmol / mL respectively. Mix solutions A and B at a volume ratio of 1:1, sonicate for 0.5 to 2 hours, centrifuge at high speed, and take the supernatant to obtain solution C with a concentration of 0.005 mmol / mL to 0.1 mmol / mL. Step 2: Take 10 μL to 100 μL of the C solution obtained in Step 1 and add it to a perovskite nanocrystal solution with a concentration of 10 mg / mL to 20 mg / mL. Stir for 0.5 hours to 2 hours in a temperature range of 25°C to 100°C. Step 3: Add antisolvent to the solution obtained in Step 2, and centrifuge at high speed to remove unreacted precursor solution to obtain anion-treated perovskite nanocrystals. Step four: Prepare an octane solution of the nanocrystals obtained in step three with a mass concentration of 1 mg / mL to 20 mg / mL for use in assembling perovskite nanocrystal optoelectronic devices.

2. The method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment according to claim 1, characterized in that, The solution A is one of the following: didodecyl dimethyl ammonium bromide toluene solution, didecyl dimethyl ammonium bromide toluene solution, or dioctyl dimethyl ammonium bromide toluene solution.

3. The method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment according to claim 1, characterized in that, The solution B is an aqueous solution of potassium, sodium, or ammonium salts containing fluoride, chloride, bromide, iodide, sulfide, sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, or nitrate ions.

4. The method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment according to claim 1, characterized in that, The perovskite nanocrystals are lead-based perovskite nanocrystals, manganese-based perovskite nanocrystals, tin-based perovskite nanocrystals, or germanium-based perovskite nanocrystals.

5. The method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment according to claim 1, characterized in that, The optoelectronic device is a light-emitting diode, and its structure includes a transparent conductive electrode substrate, a hole injection layer or a hole transport layer, a light-emitting layer, an electron injection layer or an electron transport layer, and a metal electrode.

6. The method for improving the spectral heat resistance of perovskite nanocrystals and their optoelectronic devices through anion post-treatment according to claim 5, characterized in that, The transparent conductive electrode substrate is ITO conductive glass, FTO conductive glass, or a flexible conductive substrate; the hole injection layer or hole transport layer is selected from at least one of PEDOT:PSS, Spiro-OMeTAD, TFB, TPD, SOCP, CBP, F8, P3HT, PTAA, NiO, CuI, CuSCN, MoOx, Poly-TPD, PVK, TCTA, or PEDOT / PFI; the light-emitting layer is prepared by the method according to any one of claims 1 to 4. The perovskite nanocrystals are prepared with anion post-treatment; the electron injection layer or electron transport layer is selected from at least one of TPBi, PBD, BCP, PCBM, magnesium-doped zinc oxide, polyethyleneimine-modified zinc oxide, TiO2, ZnO, Al2O3, Zn2SnO4, SnO2, WO3, B3PYMPM, BPhen, TmPyPB, calcium acetylacetonate, or PFN; the metal electrode is selected from at least one of cesium carbonate and aluminum, lithium fluoride and aluminum, calcium and aluminum, calcium, nickel, aluminum, silver, or gold.

7. A perovskite nanocrystal after anion post-treatment, characterized in that, The perovskite nanocrystals are prepared by the method described in any one of claims 1 to 4, and their surface has improved spectral heat resistance by occupying vacancy defects with anions.

8. The perovskite nanocrystals post-treated with anion exchange according to claim 7, characterized in that, The anion is F. - Cl - ,Br - I - S 2- SO4 2- PO4 3- HPO4 2- H2PO4 - and NO3 - .

9. An optoelectronic device, characterized in that, The light-emitting layer of the optoelectronic device comprises the anion-post-treated perovskite nanocrystals as described in claim 7 or 8.

10. An application for improving the spectral heat resistance of perovskite nanocrystals, characterized in that, Perovskite nanocrystals are treated with the method described in any one of claims 1 to 4 to suppress their fluorescence intensity decay under heating conditions.

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