Application of organic strong acid ligand in regulation and control of perovskite nanocrystal halogen activity

Abstract

The invention relates to an application of an organic strong acid ligand in regulation and control of perovskite nanocrystal halogen activity, the perovskite nanocrystal has a blue luminous AB BryCl3-y structure, the organic strong acid ligand is used as a chloride ion scavenger in an organic solvent, hydrogen ions provided by the organic strong acid ligand are combined with halogen ions in the organic solvent, and the halogen activity of the perovskite nanocrystal is regulated and controlled. Reversing the ionization reaction of the halogen hydride to form HX molecules in a non-ionization state; halogen in the organic solvent is composed of a chlorine element and a bromine element, and the organic strong acid ligand has selectivity and is preferentially combined with the chlorine element to form a non-ionized HCl molecule; the chlorine-bromine ratio of the perovskite nanocrystal is regulated and controlled by reducing the activity of a chlorine element in a reactant, and the light-emitting wavelength of the perovskite nanocrystal is gradually subjected to red shift along with the increase of the addition amount of the organic strong acid ligand. According to the invention, the halogen activity is adjusted through the acidic ligand, so that the light-emitting wavelength and internal defects of the inorganic core (namely the perovskite nanocrystal) are controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of perovskite quantum dot preparation, and in particular relates to the use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals. Background Art

[0002] The interesting features caused by the surface and size effects of nanomaterials have promoted the unprecedented rapid development of colloidal nanocrystals in the field of new generation luminescence and photovoltaics. In this context, perovskite nanocrystals have become a hot topic in the field of electroluminescence due to their wide color gamut, narrow emission and easy spectral tunability. Efficient blue electroluminescence is the most challenging step for perovskite nanocrystals to achieve further development.

[0003] A convenient way to achieve blue emission is by halogen doping in CsPbBr 3 The introduction of chlorine into the system allows for continuous spectral tuning over the entire range from green to deep blue, and the spectral emission can be easily adjusted by composition, providing great synthetic flexibility for perovskite nanocrystals with various wavelengths. For example, our company's previously applied Chinese patent with announcement number CN116904184B discloses a method for precise control of the emission wavelength of hybrid halogen blue light quantum dots.

[0004] However, mixed-halide perovskite nanocrystals suffer from low photoluminescence quantum yield (PLQY) caused by chloride defects. Controlling the chloride content and reducing chloride defects are key to improving the luminescence efficiency, especially for soft lattice perovskites. On the other hand, during the synthesis process, two factors synergistically dominate the properties of colloidal nanocrystals, namely, perovskite precursors and organic ligands, which evolve into the inorganic core of the nanocrystal (i.e., perovskite nanocrystals) and the organic ligand shell, respectively. Specifically, the concentration and activity of the perovskite precursors affect the composition and intrinsic properties of the inorganic core, while the organic ligands manipulate the structure, morphology, dispersity, and surface properties of the nanocrystals. In this context, the effects of organic ligands on the inorganic core of nanocrystals are usually overlooked.

[0005] Therefore, studying the effects of organic ligands on the inorganic core of nanocrystals, and further studying the effects of organic ligands on the system composition and internal defects of the inorganic core (i.e., perovskite nanocrystals) is of great significance for the synthesis of nanocrystals, and therefore needs to be improved. Summary of the invention

[0006] The present invention proposes the use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals. The halogen activity is regulated by the acidic ligand, thereby controlling the luminescence wavelength and internal defects of the inorganic core (i.e., perovskite nanocrystal).

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] Use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals, wherein the perovskite nanocrystals are AB Br with blue luminescence y Cl 3-y Structure, wherein: 0<y<3; A position is at least one of Cs, Rb, FA, MA, GA; B position is at least one of Pb, Sn or Cu;

[0009] The organic strong acid ligand acts as a chloride ion scavenger in the organic solvent. The hydrogen ions provided by the organic strong acid ligand combine with the halogen ions in the organic solvent and reverse the ionization reaction of the hydrogen halide to form HX molecules in a non-ionized state.

[0010] The halogen in the organic solvent consists of chlorine and bromine, and the organic strong acid ligand is selective and preferentially combines with chlorine to form non-ionized HCl molecules; by reducing the activity of chlorine in the reactant, the chlorine-bromine ratio of the perovskite nanocrystals is regulated, and as the amount of the organic strong acid ligand added increases, the luminescent wavelength of the perovskite nanocrystals gradually increases (wavelength red shift).

[0011] Furthermore, the organic strong acid ligand is partially ionized in the organic solvent to form hydrogen ions (H+) and corresponding acid radical ions, and the hydrogen ions (H+) are used to combine with the halogen ions in the organic solvent.

[0012] Furthermore, the halogen in the organic solvent comes from a B-site metal precursor and a mixed halogen source; the B-site metal precursor and the mixed halogen source jointly provide chlorine and bromine elements.

[0013] Further, the B-site metal precursor includes at least one of lead halide, copper halide and tin halide;

[0014] The mixed halogen source includes one or more of tetra-n-octylammonium bromide (TOAB), tetra-octylammonium chloride (TOAC), dodecylammonium bromide (DDAB), and dodecylammonium chloride (DDAC);

[0015] The organic solvent includes one or more of toluene, xylene and mesitylene.

[0016] Furthermore, the organic strong acid ligand includes at least one of benzenesulfonic acid, 4-dodecylbenzenesulfonic acid (DBSA), and trifluoromethanesulfonic acid (TFMSA).

[0017] Furthermore, the method for preparing the perovskite nanocrystals comprises the following steps:

[0018] Adding the organic strong acid ligand to the mixed precursor and mixing them evenly, then adding the monovalent cation precursor mixture to react, nucleating and growing until the quantum dots are fully grown to obtain the mixed halogen perovskite blue light nanocrystal crude solution, and finally purifying the mixed halogen perovskite blue light nanocrystal crude solution to obtain mixed halogen perovskite nanocrystals;

[0019] The mixed precursor is a mixture of a B-site metal precursor, a mixed halogen source and an organic solvent;

[0020] The monovalent cation precursor mixture is a mixture of a monovalent cation precursor composed of one or more cations selected from cesium (Cs), rubidium (Rb), formamidine (FA), methylammonium (MA), and aminoformamidine (GA) and a weakly acidic ligand.

[0021] Furthermore, the B-site metal precursor is lead halide, and the lead halide is lead chloride and lead bromide.

[0022] Further, the purification process is:

[0023] The anti-solvent ethyl acetate is added to the crude solution of the mixed halogen perovskite blue light nanocrystals, and the precipitate is dispersed in n-octane after centrifugation. The purification process is repeated two to three times to obtain the mixed halogen perovskite nanocrystals.

[0024] Furthermore, the monovalent cation precursor includes cesium carbonate (Cs 2 CO 3 ), cesium formate (CsHCOO), cesium acetate (CsAc), cesium trifluoroacetate (CsTFA), formamidine formate (FAHCOO), formamidine acetate (FA-Ac), methylamine acetate (MAAc), rubidium carbonate (Rb 2 CO 3 ), rubidium formate (RbHCOO), rubidium acetate (RbAc);

[0025] The weakly acidic ligand is bis(2,4,4-trimethylpentyl)phosphoric acid (PA).

[0026] Furthermore, the organic strong acid ligand can realize the controllable adjustment of the luminescent wavelength of the perovskite nanocrystal in the range of 445-482 nm. The perovskite nanocrystal is used to prepare a perovskite light emitting diode or perovskite ink or a light conversion film / plate.

[0027] Beneficial effects of the present invention:

[0028] (1) The synthesis of perovskite nanocrystals is usually carried out in a weakly polar organic solvent, such as 1-octadecene, octane or toluene, to minimize damage to the perovskite nanocrystals (this is because the preparation under a higher polarity will damage the structure of the perovskite nanocrystals). In the present invention, the organic strong acid ligand (taking DBSA as an example) has strong acidity and will partially ionize into H in the solvent of the synthetic nanocrystals. + and DBS - , which can adjust the halogen activity.

[0029] After DBSA was added to the reactants, the pH of the solution dropped from 6.0 to 1.0, illustrating the ionization process of DBSA in toluene. The combination of hydrogen ions generated by DBSA and halogens can reverse the ionization reaction of hydrogen halides to form HX with lower reactivity. Since the electronegativity of chlorine (3.16) is greater than that of bromine (2.96), chloride ions tend to be depleted from organic solvents to form non-ionized HCl molecules. This will greatly reduce the activity of halogens in the reactants, especially chlorine, and the wavelength will be red-shifted, thereby achieving controllable regulation of the chlorine-bromine ratio in the nanocrystals. It should be emphasized that only halogens in ionic form can participate in the synthesis of perovskite nanocrystals.

[0030] (2) In the present invention, as the amount of organic strong acid ligand added changes, the luminescent wavelength of the corresponding perovskite nanocrystals can be controlled and adjusted in the range of 445 to 482 nm. At the same time, as the amount of organic strong acid ligand added increases, the PLQY of the perovskite nanocrystals shows an overall increasing trend.

[0031] (3) The present invention provides a method for controlling the halogen ratio and performance in nanocrystals by changing the content of acidic ligands, so as to achieve a wide range of adjustment of the emission wavelength of nanocrystals and reduce internal defects without changing the halogen ratio in the precursor raw materials. The effect of controllably adjusting the emission wavelength of nanocrystals using only acidic ligands and completely passivating the surface and internal defects of nanocrystals is achieved. The synthesized nanocrystals have more excellent optical properties, and the prepared perovskite light-emitting diodes have high external quantum efficiency, which expands the function of acidic ligands in the nanocrystal synthesis process and promotes the application of perovskite nanocrystals in the field of full-color display. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The reaction mechanism of the organic strong acid ligand (taking DBSA as an example) of the present invention for regulating the halogen activity;

[0033] Figure 2 The UV-visible spectra of the perovskite nanocrystals obtained in Examples 1-5 and Comparative Example 1 of the present invention;

[0034] Figure 3The fluorescence spectra of the perovskite nanocrystals obtained in Examples 1-5 of the present invention and Comparative Example 1;

[0035] Figure 4 is the photoluminescence quantum yield of the perovskite nanocrystals obtained in Examples 1-5 of the present invention and Comparative Example 1;

[0036] Figure 5 The comparison diagram of the ultraviolet-visible spectra and fluorescence spectra of the halogen activity regulated by using different organic strong acid ligands in Example 1 and Example 6;

[0037] Figure 6 A comparison diagram of the fluorescence lifetimes of the perovskite nanocrystals prepared in Example 1 and Example 6;

[0038] Figure 7 is the UV-visible spectra of the perovskite nanocrystals prepared in Examples 6-10;

[0039] Figure 8 The external quantum efficiency-current density curves of the perovskite light-emitting diodes prepared using the perovskite nanocrystals prepared in Example 1 and Example 6. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Embodiment 1:

[0042] Preparation of cesium carbonate (Cs 2 CO 3 , 0.085mol / L), formamidine acetate (FA-Ac, 0.015mol / L) rubidium carbonate (Rb 2 CO 3 , 0.0085mol / L) di(2,4,4-trimethylpentyl)phosphoric acid (PA) solution as a monovalent cation precursor. Weigh 0.4mmol lead bromide (PbBr 2 )、0.1mmol lead chloride (PbCl 2), 0.725mmol tetraoctylammonium bromide (TOAB) is added to a 20ml sample bottle, 5ml ultra-dry toluene is added to the sample bottle, and continuous stirring is carried out for 4-5h to fully dissolve the medicine as a mixed precursor of lead source and halogen. Prepare 100mg / ml ultra-dry toluene solution of dodecyl ammonium chloride (DDAC) for standby use. Take 0.6ml4-dodecylbenzenesulfonic acid (DBSA, 1g / ml dissolved in ultra-dry toluene) and add it to the mixed precursor and stir for 4min. Then quickly inject 0.5ml of monovalent cation precursor solution, react for 2.5min, supplement 1ml of ultra-dry toluene solution of DDAC, and continue stirring for 4min. After a series of subsequent purification treatments, blue light perovskite nanocrystals with a luminescent wavelength of 470nm treated with DBSA are obtained.

[0043] In some embodiments, the method for purifying nanocrystals may include the following steps, but is not limited to this purification method: transferring the stock solution to a centrifuge tube for low-speed centrifugation, taking the supernatant after centrifugation, adding a certain amount of anti-solvent to precipitate the perovskite nanocrystals and performing high-speed centrifugation; dispersing the precipitate in octane or toluene, and filtering and collecting with a 0.22 μm organic filter head to obtain a blue light-emitting perovskite nanocrystal solution. Under certain conditions, the above steps can be repeated two to three times.

[0044] Embodiment 2-5:

[0045] The difference from Example 1 is that different amounts of DBSA are used for treatment to obtain a series of nanocrystals with different wavelengths.

[0046] Preparation of cesium carbonate (Cs 2 CO 3 , 0.085mol / L), formamidine acetate (FA-Ac, 0.015mol / L) rubidium carbonate (Rb 2 CO 3 , 0.0085mol / L) di(2,4,4-trimethylpentyl)phosphoric acid (PA) solution as a monovalent cation precursor. Weigh 0.4mmol lead bromide (PbBr 2 )、0.1mmol lead chloride (PbCl 2), 0.725mmol tetraoctylammonium bromide (TOAB) is added to a 20ml sample bottle, 5ml ultra-dry toluene is added to the sample bottle, and continuous stirring is performed for 4-5h to fully dissolve the medicine as a mixed precursor of a lead source and a halogen. An ultra-dry toluene solution of 100mg / ml dodecyl ammonium chloride (DDAC) is prepared for standby use. 0.2ml, 0.4ml, 0.8ml, and 1.0ml 4-dodecylbenzenesulfonic acid (DBSA, 1g / ml is dissolved in ultra-dry toluene) are taken respectively and added to the mixed precursor and stirred for 4min. 0.5ml of monovalent cation precursor solution is then rapidly injected, and after the reaction is carried out for 2.5min, 1ml of ultra-dry toluene solution of DDAC is supplemented, and continuous stirring is performed for 4min. After a series of subsequent purification treatments, blue light perovskite nanocrystals with luminous wavelengths of 460nm, 465nm, 476nm, and 482nm treated with DBSA are obtained.

[0047] Figure 1 This is the reaction mechanism of the acidic ligand DBSA regulating the activity of halogen. The strong acidic ligand DBSA is ionized into DBS in a non-polar solvent. - and H + , respectively combined with quaternary ammonium and halogen, resulting in a decrease in the activity of halogen anions, especially chloride ions, thereby reducing defects on the surface and inside of the nanocrystals and improving the optical properties of the nanocrystals.

[0048] Figure 2 and Figure 3 The UV-visible spectra and fluorescence spectra of the perovskite nanocrystals obtained in Examples 1-5 of the present invention and Comparative Example 1 are shown respectively. As the amount of DBSA added increases, the wavelength of the nanocrystals gradually redshifts, which comes from the regulation of the halogen activity of the nanocrystals by DBSA. At the same time, the optical properties of the nanocrystals are gradually improved.

[0049] like Figure 4 The photoluminescence efficiency comparison shown is derived from the DBSA-mediated halogen activity regulation, which causes the chlorine content in the system to decrease, thereby reducing the internal defects of the nanocrystals.

[0050] Embodiment 6:

[0051] The difference from Example 1 is that DBSA is replaced by 0.04 ml of trifluoromethanesulfonic acid (TFMSA), and the other steps are the same, that is, blue light perovskite nanocrystals with a luminescent wavelength of 470 nm treated with 0.04 ml of TFMSA are obtained.

[0052] Figure 5 The figure is a comparison of the UV-visible spectra and fluorescence spectra of the nanocrystals in Example 1 and Example 6 using different organic strong acid ligands to regulate the halogen activity and internal defects.

[0053] Figure 6 3. A comparison chart of the fluorescence lifetimes of the perovskite nanocrystals prepared in Example 1 and Example 6.

[0054] Embodiment 7-10:

[0055] The difference from Example 6 is that different addition amounts (0 ml, 0.01 ml, 0.02 ml, 0.03 ml) of trifluoromethanesulfonic acid (TFMSA) are used, and the other steps are the same.

[0056] Figure 7 The UV-visible spectra of the perovskite nanocrystals prepared in Examples 6 to 10 show that the wavelength red shift of the perovskite nanocrystals can be regulated by adding trifluoromethanesulfonic acid (TFMSA).

[0057] Comparative Example 1:

[0058] The difference from Example 1 is that DBSA is not used for treatment, and the other steps are the same. The perovskite nanocrystals without DBSA treatment have a luminescent wavelength of 445 nm.

[0059] Application examples:

[0060] A perovskite light-emitting diode comprises an ITO conductive glass, a hole injection layer, a hole transport layer, a perovskite nanocrystal light-emitting layer, an electron transport layer, and an electrode layer which are arranged in sequence, wherein the perovskite nanocrystal light-emitting layer is a perovskite nanocrystal spin-coated film prepared by the above-mentioned embodiments 1 and 6, respectively.

[0061] The hole injection layer may include one or more of nickel oxide (NiOx) and poly(3,4-ethylenedioxythiophene):poly(4-benzenesulfonic acid) (PEDOT:PSS).

[0062] The hole transport layer may include one or more of poly(9-vinylcarbazole) (PVK), poly[(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (PolyTPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and poly(9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole) (pF8Cz).

[0063] The electron transport layer may include one or more of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 2,4,6-tris[3-(diphenylphosphinoyl)phenyl]-1,3,5-triazole (PO-T2T), and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1"-terphenyl]-3,3"-diyl]bipyridine (TmPyPB).

[0064] Figure 8 The external nanocrystal efficiency-current density curves of the perovskite light-emitting diodes prepared using the perovskite nanocrystals prepared in Example 1 and Example 6. It can be seen that the nanocrystals treated with DBSA achieved a PLQY of 89%, and the corresponding perovskite nanocrystal light-emitting diodes obtained an external quantum efficiency of 24.5%.

[0065] In summary, we have demonstrated the control of halogen activity and internal defects of nanocrystals mediated by organic strong acid ligands. Taking the organic strong acid ligand DBSA as an example, it ionizes into DBS in low polarity solvents. - and H + , and interact with quaternary ammonium and halogen, respectively, to regulate the activity of the halogen. This reveals a new function of organic strong acid ligands, which allows controllable regulation of the nanocrystal composition, thereby inhibiting the formation of halogen-related internal defects. Example 1 of the present invention, blue-emitting nanocrystals centered at 470nm achieved a PLQY of about 89% and produced a perovskite nanocrystal light-emitting diode with an EQE of up to 24.5%, which is the highest efficiency of pure blue perovskite nanocrystal light-emitting diodes at present. Further research on the role of surface ligands in controlling surface and internal defects of nanocrystals is of great significance for promoting the development and application of perovskite nanocrystals in the field of semiconductor devices such as light-emitting diodes and solar cells.

[0066] The present invention illustrates the detailed preparation method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed preparation method, that is, it does not mean that the present invention must rely on the above-mentioned products and detailed preparation methods to be implemented. It should be clear to those skilled in the art that any improvement of the present invention, the combination or equivalent replacement of the raw materials of the product of the present invention, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. Use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals, characterized in that: The perovskite nanocrystal is AB Br with blue luminescence y Cl 3-y Structure, wherein: 0<y<3; A position is at least one of Cs, Rb, FA, MA, GA; B position is at least one of Pb, Sn or Cu; The organic strong acid ligand acts as a chloride ion scavenger in the organic solvent. The hydrogen ions provided by the organic strong acid ligand combine with the halogen ions in the organic solvent and reverse the ionization reaction of the hydrogen halide to form HX molecules in a non-ionized state. The halogen in the organic solvent consists of chlorine and bromine, and the organic strong acid ligand is selective and preferentially combines with the chlorine to form non-ionized HCl molecules; the chlorine-bromine ratio of the perovskite nanocrystals is regulated by reducing the activity of the chlorine in the reactants, and as the amount of the organic strong acid ligand added increases, the luminescence wavelength of the perovskite nanocrystals red-shifts.

2. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 1, characterized in that: The organic strong acid ligand is partially ionized in the organic solvent to form hydrogen ions (H+) and corresponding acid radical ions, and the hydrogen ions (H+) are used to combine with the halogen ions in the organic solvent.

3. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 2, characterized in that: The halogen in the organic solvent comes from a B-site metal precursor and a mixed halogen source; the B-site metal precursor and the mixed halogen source jointly provide chlorine and bromine elements.

4. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 3, characterized in that: The B-site metal precursor includes at least one of lead halide, copper halide and tin halide; The mixed halogen source includes one or more of tetra-n-octylammonium bromide (TOAB), tetra-octylammonium chloride (TOAC), dodecylammonium bromide (DDAB), and dodecylammonium chloride (DDAC); The organic solvent includes one or more of toluene, xylene and mesitylene.

5. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 1, characterized in that: The organic strong acid ligand includes at least one of benzenesulfonic acid, 4-dodecylbenzenesulfonic acid (DBSA), and trifluoromethanesulfonic acid (TFMSA).

6. Use of an organic strong acid ligand according to any one of claims 1 to 5 in regulating the halogen activity of perovskite nanocrystals, characterized in that: The method for preparing the perovskite nanocrystal comprises the following steps: Adding the organic strong acid ligand to the mixed precursor and mixing them evenly, then adding the monovalent cation precursor mixture to react, nucleating and growing until the quantum dots are fully grown to obtain the mixed halogen perovskite blue light nanocrystal crude solution, and finally purifying the mixed halogen perovskite blue light nanocrystal crude solution to obtain mixed halogen perovskite nanocrystals; The mixed precursor is a mixture of a B-site metal precursor, a mixed halogen source and an organic solvent; The monovalent cation precursor mixture is a mixture of a monovalent cation precursor composed of one or more cations selected from cesium (Cs), rubidium (Rb), formamidine (FA), methylammonium (MA), and aminoformamidine (GA) and a weakly acidic ligand.

7. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 6, characterized in that: The B-site metal precursor is lead halide, and the lead halide is lead chloride and lead bromide.

8. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 6, characterized in that: The purification process is as follows: The anti-solvent ethyl acetate is added to the crude solution of the mixed halogen perovskite blue light nanocrystals, and the precipitate is dispersed in n-octane after centrifugation. The purification process is repeated two to three times to obtain the mixed halogen perovskite nanocrystals.

9. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 6, characterized in that: The monovalent cation precursor includes one or more of cesium carbonate (Cs2CO3), cesium formate (CsHCOO), cesium acetate (CsAc), cesium trifluoroacetate (CsTFA), formamidine formate (FAHCOO), formamidine acetate (FA-Ac), methylamine acetate (MAAc), rubidium carbonate (Rb2CO3), rubidium formate (RbHCOO), and rubidium acetate (RbAc); The weakly acidic ligand is bis(2,4,4-trimethylpentyl)phosphoric acid (PA).

10. The use of an organic strong acid ligand in regulating the halogen activity of perovskite nanocrystals according to claim 1, characterized in that: The organic strong acid ligand can realize the controllable adjustment of the emission wavelength of the perovskite nanocrystal within the range of 445-482nm; The perovskite nanocrystals are used to prepare perovskite light-emitting diodes or perovskite inks or light conversion films / plates.

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