KR101986641B1 - Method of performing anion exchange for halide perovskite nanocrystal - Google Patents

Abstract

The present invention provides an anion exchange method of a halide perovskite nanocrystal capable of easily performing anion exchange and performing light emission in a visible light wavelength region. A method of anion exchange of halide perovskite nanocrystals according to an embodiment of the present invention includes the steps of: providing a first solution containing a first halide perovskite nanocrystal having a first halogen element; And adding an alkyl compound containing a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element To form a second solution including a second halide perovskite nanocrystal having the second halogen element by anion exchange with the second halide perovskite nanocrystal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an anion exchange method for halide perovskite nanocrystals,

The technical idea of the present invention relates to a method for post-treatment of halide perovskite nanocrystals, and more particularly to an anion exchange method of halide perovskite nanocrystals.

In order to realize high performance of photovoltaic cells and light emitting diodes, many hybrid organic-inorganic materials have been studied. Hybrid organic-inorganic materials have advantages of organic materials which are easy to control optical and electrical properties, high charge mobility, and mechanical and thermal stability They are all academically and industrially well-received. Among them, organometallic halide perovskite materials have a high color purity, are easy to control their color, and have a low synthesis cost, so that they are very likely to develop as luminous bodies. In addition, since the color purity is as high as about 20 nm, a light emitting device closer to natural color can be realized. In addition, photovoltaic devices using organic metal halide perovskites showed a power conversion efficiency of 22.1% and LEDs showed an external quantum efficiency of 11.7%.

Among the organometallic halide perovskite materials, CsPbX ₃ (where X is Cl, Br, and I) perovskite nanocrystals can be used to control the ratio of halogens in nanocrystals or to control the quantum confinement effect, And has a unique and attractive characteristic that can change the band energy of the antenna. The perovskite nanocrystals can be synthesized using a hot injection method. By controlling the ratio of halogen atoms, i.e. Cl, Br and I, in the halide perovskite nanocrystals, the energy bandgap of the halide perovskite nanocrystals can be adjusted, It is easy to adjust the emission spectrum with respect to the entire visible light range of 800 nm. The halide perovskite nanocrystals, when applied to light emitting diodes, can provide advantages such as a high photoluminescence quantum yield and a narrow emission peak.

Full-color spectral emission can be realized using halide perovskite nanocrystals synthesized through spontaneously induced halogen anion exchange, and various post-treatment studies have been conducted for this purpose. Generally, in this post-treatment, a polar solvent is used to dissolve the halide anion. However, such a polar solvent has a limitation in changing the halide perovskite nanocrystals, reducing the photoluminescence intensity, and changing the peak position. In addition, ion-binding materials have the potential as exchangeable cations. Recently, anion exchange methods have been developed by exposing CsPbBr ₃ and CsPbCl ₃ perovskite nanocrystals to ultraviolet rays together with dibromomethane and dichloromethane, respectively, by Parobek et al. Was reported. However, the above report merely shows the anion exchange phenomenon in a limited exchange area between Br and Cl only. Exposure to ultraviolet light has its limitations in the uniformity of the reaction control, which is due to the high absorption coefficient of perovskite materials in the ultraviolet region.

Korean Patent No. 10-1746337

The present invention also provides a method of anion exchange of a halide perovskite nanocrystal capable of easily performing anion exchange and performing light emission in a visible light wavelength region.

However, these problems are illustrative, and the technical idea of the present invention is not limited thereto.

According to an aspect of the present invention, there is provided an anion exchange method for halide perovskite nanocrystals, comprising: a first solution containing a first halide perovskite nanocrystal having a first halogen element; ; And adding an alkyl compound containing a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element To form a second solution including a second halide perovskite nanocrystal having the second halogen element by anion exchange with the second halide perovskite nanocrystal.

In some embodiments of the present invention, the first halide perovskite nanocrystal may be any of CsPbCl ₃ , CsPbBr ₃ , and CsPbI ₃ . In addition, the second halide perovskite nanocrystal may be any one of CsPbCl ₃ , CsPbBr ₃ , and CsPbI ₃ .

In some embodiments of the present invention, by the anion exchange, or changed in CsPbCl ₃ to CsPbBr _3, or changed in CsPbBr ₃ to CsPbCl _3, or changed in CsPbBr ₃ to CsPbI _3, or in CsPbI ₃ to CsPbBr ₃ Can be converted.

In some embodiments of the present invention, the first halogen element is bromine (Br), the second halogen element is chlorine (Cl), chloroform is added to the first solution containing bromine in a volume ratio of 0.1 By adding the trioctylphosphine in the range of not less than 5 times and not more than 5 times, the anion exchange can be performed.

In some embodiments of the present invention, the first halogen element is chlorine (Cl), the second halogen element is bromine (Br), bromoform is added to the first solution containing the chlorine in a volume ratio In the range of 0.1 to 2 times, and by adding the trioctylphosphine, the anion exchange can be performed from the chlorine to the bromine.

In some embodiments of the present invention, the first halogen element is iodine (I), the second halogen element is bromine (Br), bromoform is added to the first solution comprising iodine The anion exchange can be performed from the iodine to the bromine by adding the compound in a range of 0.1 to 2 times the volume ratio and adding the trioctylphosphine.

In some embodiments of the present invention, the first halogen element is bromine (Br), the second halogen element is iodine (I), the first solution comprising bromine is charged with iodoethane , The anion exchange may be performed from the bromine to the iodine by adding the trioctylphosphine in the range of 1% or more to 10% or less.

In some embodiments of the present invention, the concentration of the trioctylphosphine may range from greater than 0% to less than 30% by volume relative to the total solution.

In some embodiments of the present invention, the anion exchange may be performed at a temperature in the range of 20 < 0 > C to 70 < 0 > C.

In some embodiments of the present invention, the anion exchange can be terminated by diluting with acetonitrile in a volume ratio ranging from 5 to 7 times the total solution.

In some embodiments of the present invention, the anion exchange may be performed in the range of 1 minute to 60 minutes.

Halides according to the technical features of the present invention, the perovskite anion exchange method of the nanocrystals, through the organic halide solvent and a trioctyl phosphine a solution post-treatment controlled to a non-destructive using as a surfactant CsPbX ₃ Fe lobe The anion exchange of the skate nanocrystals can be successfully performed. To confirm the anion exchange mechanism of CsPbX ₃ perovskite nanocrystals, the decomposition energies of organic halide solutions were calculated using the DFT method. The anion exchange process can be completely reversible without losing the electronic and chemical properties of all kinds of CsPbX ₃ perovskite nanocrystals. The anion exchange method exhibits excellent reproducibility and can be easily controlled by the concentration of trioctylphosphine and the reaction time. The anion exchange process does not involve exchangeable cations, can prevent undesired lattice strain, and thus means the exchange of pure halides. With the protective properties of trioctylphosphine, the process can be broadly applied to various halide perovskite nanocrystals as a non-destructive halide exchange process.

The effects of the present invention described above are exemplarily described, and the scope of the present invention is not limited by these effects.

FIG. 1 is a flowchart showing an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.
2 is a schematic diagram illustrating nanocrystal synthesis and anion exchange in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.
FIGS. 3 to 5 are graphs showing ultraviolet-visible light absorption spectra and photoluminescence spectra of the halide perovskite nanocrystals before and after anion exchange according to an embodiment of the present invention. FIG.
FIG. 6 is a high-resolution transmission electron micrograph of a halide perovskite nanocrystal formed according to an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.
7 is a graph showing the size distribution of nanocrystals obtained from high-resolution transmission electron microscope photographs of halide perovskite nanocrystals formed according to an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Graph.
8 is a graph showing an X-ray diffraction pattern of a halide perovskite nanocrystal formed according to an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.
9 is a graph showing changes in Gibbs free energy of halogen atoms before and after application of trioctylphosphine in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.
10 is a schematic diagram showing a mechanism of interaction with a halogen atom by trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.
11 is a graph showing the mechanism of interaction with halogen atoms by trioctylphosphine in the case of Type I of FIG. 10 in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Fig.
12 is a graph showing the change in Gibbs free energy according to the position of a halogen atom in the alkyl molecule after application of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Graphs.
13 is a graph showing an FT-IR spectrum of a supernatant of a halide perovskite nanocrystal solution in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.
14 is a graph showing a ¹ H-NMR spectrum of a supernatant of a halide perovskite nanocrystal solution in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.
FIG. 15 is a graph showing changes in Gibbs free energy according to formation of by-products after application of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.
FIG. 16 is a graph showing a photoluminescence spectrum of a halide perovskite nanocrystal according to an embodiment of the present invention, in accordance with the concentration of trioctylphosphine. FIG.
17 is a graph showing an absorption spectrum according to a change in concentration of trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.
18 is a graph showing the X-ray photoelectron spectrum of the Br 3d peak region according to the concentration change of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention .
19 is a graph showing an X-ray photoelectron spectrum of a Cl 2p peak region according to a concentration change of trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention .
FIG. 20 is a graph showing a photoluminescence spectrum according to a reaction time in a halide perovskite nanocrystal anion exchange method according to an embodiment of the present invention. FIG.
FIG. 21 is a graph showing an absorption spectrum of a halide perovskite nanocrystal according to an embodiment of the present invention, with respect to the reaction time. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. The scope of technical thought is not limited to the following examples. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the present specification, the same reference numerals denote the same elements. Further, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing depicted in the accompanying drawings.

The present invention relates to a method for post-treatment of halide perovskite nanocrystals, and more particularly, to an anion exchange method for halide perovskite nanocrystals. Specifically, the post-treatment method uses an organic solvent to realize anion exchange of CsPbX ₃ (where X is Cl, Br, and I) perovskite nanocrystals, and this anion exchange is performed using CsPbCl ₃ <-> CsPbBr ₃ <-> In CsPbI ₃ , it is performed in a completely reversible manner and is performed in a simple manner in solution.

1 is a flowchart showing an anion exchange method (SlOO) of halide perovskite nanocrystals according to an embodiment of the present invention.

Referring to FIG. 1, an anion exchange method (S100) of halide perovskite nanocrystals includes the steps of: providing a first solution containing a first halide perovskite nanocrystal having a first halogen element S110); And adding an alkyl compound containing a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element And forming a second solution containing a second halide perovskite nanocrystal having the second halogen element by performing anion exchange with the first halide perovskite nanocrystal (S120).

The first halide perovskite nanocrystal may be any one of CsPbCl ₃ , CsPbBr ₃ , and CsPbI ₃ . In addition, the second halide perovskite nanocrystal may be any one of CsPbCl ₃ , CsPbBr ₃ , and CsPbI ₃ . Further, by the anion exchange, or changed from ₃ to CsPbCl CsPbBr _3, or changed from ₃ to CsPbBr CsPbCl _3, can be converted or changed in CsPbBr ₃ to CsPbI _3, or from ₃ to CsPbI CsPbBr _3.

Wherein the first halogen element is bromine (Br), the second halogen element is chlorine (Cl), and chloroform is added to the first solution containing bromine in a volume ratio of about 0.1 times to about 5 times And adding the trioctylphosphine, the anion exchange can be carried out.

Wherein the first halogen element is chlorine (Cl), the second halogen element is bromine (Br), and the bromoform is added to the first solution containing the chlorine in a volume ratio of 0.1 to 2 And adding the trioctylphosphine, the anion exchange can be performed from the chlorine to the bromine.

Wherein the first halogen element is iodine (I), the second halogen element is bromine (Br), the bromoform is added to the first solution containing iodine in a volume ratio of 0.1 to 2 times , And by adding the trioctylphosphine, the anion exchange can be performed from the iodine to the bromine.

Wherein the first halogen element is bromine (Br), the second halogen element is iodine (I), and the bromine-containing first solution is mixed with iodoethane in a volume ratio of 1% or more to 10% , And by adding the trioctylphosphine, the anion exchange can be performed from the bromine to the iodine.

The concentration of the trioctylphosphine may range from more than 0% to less than 30% by volume relative to the total solution. The anion exchange may be carried out at a temperature in the range of 20 [deg.] C to 70 [deg.] C. The anion exchange can be terminated by diluting with acetonitrile in a volume ratio ranging from 5 to 7 times the total solution. The anion exchange can be performed in a range of 1 minute to 60 minutes.

Example

Preparation of chemicals

The chemicals listed below were used. PbBr ₂ , PbCl ₂ , PbI ₂ , Octadecene, Oleic acid, Cs ₂ CO ₃ , Toluene, Chloroform, Trioctylphosphine (C ₂₄ H ₅₁ P) And Acetonitrile were purchased from Sigma-Aldrich. Oleylamine was purchased from Acros organics. Bromoform and PbBr ₂ were purchased from Alfa Aesar.

Halide Perovskite  Synthesis of nanocrystals

CsPbX ₃ perovskite nanocrystals in halide perovskite nanocrystals were synthesized according to the method of Protesescu et al., And the amount was increased by 5 times. Specifically, for the synthesis of CsPbBr ₃ , 0.94 mmol PbBr ₂ (ie, 345 mg) and 25 mL octadecyne were placed in a 100 mL three-necked flask and dried under vacuum at 120 ° C. for 1 hour. PbCl ₂ was used in the 264 mg For the synthesis of CsPbCl _3, a PbI ₂ was used in the 433 mg For the synthesis of ₃ CsPbI. 2.5 mL of oleic acid and 2.5 mL was added to oleyl amine Pb- halogen compound, and subsequently increasing the temperature to 150 ℃ and (However, the synthesis CsPbCl ₃ 180 ℃ Im) and maintained in an argon atmosphere. 2 mL of pre-synthesized Cs-oleate (Cs-oleate) was rapidly injected. The synthesis of the Cs oleic acid was carried out by introducing 0.163 g of Cs ₂ CO ₃ into 8 mL of octadecyne and 0.5 mL of oleic acid, degassing for 1 hour, converting to an argon atmosphere, and heating to 120 캜 before injection. Five seconds after injection, the nanocrystal solution was quickly cooled to room temperature using an ice bath. The synthesized nanocrystals were centrifuged at 4000 rpm for 10 minutes and re-dispersed in 3 ml toluene (concentration up to 70 mg / ml) to form a halide nanocrystal solution.

Anion exchange

The anion was exchanged with chlorine (Cl) in the following manner. The halide nanocrystal solution was diluted with chloroform in a volume ratio of 4 times (i.e., chloroform was added in a volume ratio of 3 times), and trioctylphosphine was added. Since the exchange rate of the halogen anion was slow, the solution was heated to 60 占 폚. The reaction was then terminated by adding acetonitrile in a volume ratio of 6 times the desired color. Precipitates were collected by centrifugation at 4000 rpm for 10 minutes.

The anion was exchanged with bromine (Br) in the following manner. The halide nanocrystal solution was diluted in two volume volumes with bromoform (i. E., The bromoform was added in a volume ratio of 1 fold) and trioctylphosphine was added. The termination of the reaction and the precipitation process are the same as the above-mentioned chlorine exchange.

The anion was exchanged with iodine (I) in the following manner. To the halide nanocrystal solution, 10 vol% iodoethane was added and trioctylphosphine was added. Since CsPbI ₃ nanocrystals have weak stability, trioctylphosphine should not exceed 10 vol% of the total solution for easy exchange and terminate the reaction before the nanocrystals change to the delta phase of CsPbI ₃ do. The precipitation step is the same as the chlorination described above.

Halide Perovskite  How to characterize nanocrystals

Ultraviolet-visible light absorption and photoluminescence analysis

Ultraviolet-visible light absorption spectra were measured using an Agilent Cary 5000. The photoluminescence (PL) spectrum was measured using an NF 900 from Edinburg Instrument and a xenon lamp was used as the excitation source. Samples for measurement were diluted with toluene and prepared using a 1 cm path length quartz cuvette.

X-ray diffraction pattern analysis

Samples for the X-ray diffraction pattern were prepared in powder form by precipitation through acetonitrile and centrifugation. The X-ray diffraction pattern was measured using a high power X-ray diffraction pattern instrument from Rigaku's D / MAX2500V / PC and using a graphite monochromator and a scintillation counter. The measurement conditions were 40 Kv, 200 mA, Cu-rotating anode, Cu Kα radiation, and λ was 0.1542 nm. The device operated at a Bragg angle ranging from 10 ° to 60 ° with a step size of 0.02 ° (2θ).

By-product detection (NMR, FT-IR)

Samples were prepared by obtaining supernatant from centrifuged PT-CsPbCl ₃ . To evaporate the acetonitrile used as the precipitation solvent, the supernatant was heated to 80 &lt; 0 &gt; C. ¹ H nuclear magnetic resonance (NMR) spectra were measured using Agilent VNMRS 600 at room temperature using deuterated chloroform (CDCl ₃ ) as the solvent. Fourier transform infrared spectra (FT-IR) were measured in an ATR mode using Agilent's Cary 620.

Transmission electron microscopy analysis

Transmission electron microscope (TEM) photographs were obtained using JEM02100 and JEM-2100F of Zeol (JEOL). Samples for TEM photographs were diluted 2-fold with toluene and prepared by dropping onto a Ted Pella carbon-coated copper grid.

X-ray photoelectron spectroscopy

Samples were prepared using spin coating on gold thin films of 80 nm thickness on silicon substrates with thin native oxides. X-ray photoelectron spectroscopy spectra were collected under a basic pressure of 1.0 x 10 &lt; ^-9 &gt; Torr using a monochromatic Al-K [alpha] X-ray source using Thermo Fisher Scientific's ESCALAB 250XI.

Halide Perovskite  Characteristic analysis of nanocrystals

The synthesized CsPbX ₃ perovskite nanocrystals were synthesized by varying the total amount according to the method described above. The synthesized CsPbX ₃ perovskite nanocrystals were surrounded by organic ligands oleic acid and oleylamine and dispersed in a nonpolar organic solvent such as chloroform, toluene, and octane.

For ion exchange in the solution state of CsPbX ₃ perovskite nanocrystals, the condition containing excess halogen anion is a prerequisite for the anion exchange process of perovskite nanocrystals. Since the perovskite nanocrystals have an unstable surface and strong ionic properties, the perovskite nanocrystals can easily collapse by the solvent. Thus, there have been many attempts to find a stable solvent that does not disrupt the perovskite nanocrystals.

Organic halide solvents are suitable solvent candidates that can disperse the perovskite nanocrystals without disintegrating, because organic halide solvents have non-polar properties and under normal conditions are poorly decomposed. The use of strong nucleophiles to generate halogen ions from the organic halide solvents is presented as a method for decomposing halogen-attached carbons in the reaction center using an organic S _N 2 reaction . After attacking the center of the alkyl halide by these strong nucleophiles, one halogen ion can be generated for one of the organic halides through the reaction.

The organic halide solvent has two functions: the first is a function to form a solution, and the second is a function to provide a halide ion to form a reactant. In addition, trioctylphosphine can also act as a strong nucleophile and an organic ligand in the S _N 2 chemical reaction to produce halogen ions.

The solution state ion exchange of CsPbX ₃ perovskite nanocrystals is as follows. To disperse the perovskite nanocrystals, an organic halide solvent is added to the synthesized CsPbX ₃ perovskite nanocrystals and then the CsPbX ₃ perovskite nanocrystals are mixed with the dissolved organic halides To the solution is added further trioctylphosphine. When the trioctylphosphine is added, the anion exchange of the CsPbX ₃ perovskite nanocrystals starts spontaneously, which can be visually confirmed by color change. In the anion exchange, the reaction rate and sensitivity can be easily controlled by controlling the concentration of the trioctylphosphine, the reaction time, and the temperature. In addition, the reaction can be easily terminated by using a precipitation method using an antisolvent. As previously reported, halide ions that are generated from organic halides and meet with trioctylphosphine reactants become spontaneously exchanged anions of perovskite nanocrystals.

2 is a schematic diagram illustrating nanocrystal synthesis and anion exchange in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.

Referring to FIG. 2, a CsPbX ₃ perovskite nanocrystal is shown as an example of a halide perovskite nanocrystal. As the synthesis method, Pb-oleic acid, halogen ion (X ^- ), and Cs oleic acid were mixed while heating, and CsPbCl ₃ perovskite nanocrystals (NC), CsPbBr ₃ perovskite nano Crystals or CsPbI ₃ perovskite nanocrystals were synthesized. It is also possible to add trioctylphosphine as a strong nucleophile in the post-treatment and also to exchange the halogen material in the halide perovskite nanocrystals using an alkyl halide (CHCl ₃ , CHBr ₃ , or CHI ₃ ) Respectively. For example, if CsPbCl ₃ perovskite nanocrystals are synthesized first and then replaced with Br instead of Cl, CsPbBr ₃ perovskite nanocrystals can be obtained by post treatment with CHBr ₃ solvent.

FIGS. 3 to 5 are graphs showing ultraviolet-visible light absorption spectra and photoluminescence spectra of the halide perovskite nanocrystals before and after anion exchange according to an embodiment of the present invention. FIG.

3 is a case where CsPbCl ₃ the anion exchange with CsPbBr _3, 4 when the CsPbBr ₃ are, and if an anion exchange with an anion exchange or CsPbI ₃ to CsPbCl _3, Figure 5 is CsPbI ₃ is an anion exchange with CsPbBr ₃ to be. 3 to 5, the ultraviolet-visible light absorption spectrum is indicated by a solid line and the light emission spectrum is indicated by a dotted line.

Referring to FIG. 3, it can be seen that the synthesized CsPbCl ₃ perovskite nanocrystal solution forms a CsPbBr ₃ perovskite nanocrystal by anion exchange by adding trioctylphosphine and bromoform together, It changed from transparent color to green.

4, the composite CsPbBr ₃ perovskite nanocrystals can be seen that the trioctyl phosphine and chloroform are added together by an anion exchange CsPbCl ₃ perovskite to form a nanocrystal, a clear from the green Color. In addition, CsPbBr ₃ perovskite nanocrystals were found to be added together with trioctylphosphine and iodoethene to form CsPbI ₃ perovskite nanocrystals, which changed from green to red.

5, the synthesized CsPbI ₃ perovskite nanocrystals can be seen that the trioctyl phosphine and bromoform are added it is by anionic exchange CsPbBr ₃ Fe lobe with Sky agent to form a nanocrystal, red To green

Referring to FIGS. 3 to 5, the anion exchange of the anion-exchanged perovskite nanocrystal solution was observed as a hue change, and it was confirmed by the change of the absorption peak and the photo-emission peak. The changed optical properties were completely consistent with the original CsPbCl ₃ , CsPbBr ₃ , and CsPbI ₃ . Through the post-solvent post-treatment (ie, anion exchange), CsPbCl ₃ <-> CsPbI ₃ <-> CsPbCl ₃ <-> CsPbCl ₃ is obtained through the optical properties changed in the visible light wavelength range of 400 nm to 800 nm ₃ can be reversibly and easily controlled. Further, the full width at half maximum (FWHM) of the halide perovskite nanocrystals after the anion exchange in the photoluminescence spectrum showed almost no enlargement after the anion exchange in all directions, It can be seen that the structure of the nanocrystals is not destroyed.

FIG. 6 is a high-resolution transmission electron micrograph of a halide perovskite nanocrystal formed according to an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.

In Figure 6, (a) it is a case where CsPbBr ₃ the anion exchange with CsPbCl _3, (b) is a case that did not perform the anion exchange as synthesized CsPbBr _3, (c) is CsPbBr ₃ is an anion exchange with CsPbI ₃ .

Referring to FIG. 6, it can be seen that the lattice spacing is changed by anion exchange. Specifically, the lattice spacing of the synthesized CsPbBr ₃ perovskite nanocrystals was 5.90 Å, and the lattice spacing of CsPbCl ₃ perovskite nanocrystals anion exchanged with Cl was decreased to 5.69 Å, and I The lattice spacing of the anion exchanged CsPbI ₃ perovskite nanocrystals increased to 6.14 Å.

7 is a graph showing the size distribution of nanocrystals obtained from high-resolution transmission electron microscope photographs of halide perovskite nanocrystals formed according to an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Graph.

Referring to FIG. 7, the synthesized CsPbBr ₃ perovskite nanocrystal (denoted by "Reference") has a size distribution of 10.37 ± 1.2 nm. Cl anion exchanged CsPbCl ₃ perovskite nanocrystals were changed to have a size distribution of 8.045 ± 0.79 nm and I anion exchanged CsPbI ₃ perovskite nanocrystals had a size distribution of 9.65 ± 1.3 nm Respectively. That is, the size of the nanocrystals was slightly reduced when the anions were exchanged with Cl and I. However, the nanocrystals retain the original cube shape and perovskite lattice structure even after anion exchange.

8 is a graph showing an X-ray diffraction pattern of a halide perovskite nanocrystal formed according to an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.

Referring to FIG. 8, the synthesized CsPbBr ₃ perovskite nanocrystal, Cl anion exchanged CsPbCl ₃ perovskite nanocrystal, and I anion exchanged CsPbI ₃ perovskite nanocrystal X-ray diffraction The pattern was shown and the content of trioctylphosphine (TOP) was varied. The content of trioctylphosphine means the volume ratio to the total solution. These X-ray diffraction pattern results show that the synthesized CsPbBr ₃ perovskite nanocrystals, Cl anion exchanged CsPbCl ₃ perovskite nanocrystals, I shows that the lattice intervals of the anion exchanged CsPbI ₃ perovskite nanocrystals are 5.952 Å, 5.876 Å, and 6.095 Å, respectively, which is consistent with the above-mentioned high resolution transmission electron microscopic results and previous reports

This X-ray diffraction pattern result clearly coincides with the above-mentioned high-resolution transmission electron microscopic result and the previous report.

In order to clarify the post-treatment chemistry, the post-solvent treatment (ie, anion exchange) of the halide perovskite nanocrystals was divided into three stages. This includes a common organic S _N 2 chemical reaction with strong nucleophiles, such as trioctylphosphine and trioctylphosphine oxide, and coordinating ligands such as tributylphosphine and alkyl halides. This reaction is similar to the phosphorousylide formation in the Wittig reaction. The mechanism of the proposed anion exchange reaction is as follows.

First step: SN + RC-X _n -> SN-CRX _{n -1} ⁺ + X ^-

Step 2: CsPbX ' ₃ + X ^- ->CsPbX' ₂ X + X ' ^-

Step ^{_{3: SN-CRX n -1 +}} + X '- -> SN + RCX n -1 X' or ^{_{SN-CRX n -1 + X '}} -

(Wherein SN is a strong nucleophile, R is an alkyl chain, X is a precursor halogen anion, and X 'is a target nanocrystal halogen anion)

In the first step, when the strong nucleophiles (SN) are contacted with the alkyl halide (RC-X _n ), the strong nucleophile-organic halide complex (SN-CRX _{n -1} ⁺ ) and the halogen ion X ^- ) is generated. In the second step, the perovskite nanocrystals (CsPbX ' ₃ ) are surrounded by the excess halogen ions (X ^- ) generated in the solution state and the anion-exchanged nanocrystals (CsPbX' ₂ X ) And a core halogen ion (X ' ^- ) extracted from the perovskite nanocrystal (CsPbX' ₃ ) are formed. According to a study by Koscher et al., When the CsPbX ₃ nanocrystals are surrounded by halide (X ' ^- ) ions in solution, excess halide (X ^- ) ions form the CsPbX ₃ nanocrystals And the CsPbX ' ₃ nanocrystals are spontaneously formed from the nanoparticles of the present invention. These results clearly show that the reaction of the second step is clearly supported. In the third step, the complexed strong nucleophiles (SN-CRX _n-1 ⁺ ) and the ionized organic halides are contacted with the halogen ion (X ' ^- ) generated in the nanocrystals to stabilize the solution state . Finally, as a result of the second step, RCX _{n -1} X 'substituted with CsPbX' ₂ X perovskite nanocrystals and halogen-substituted strong nucleophiles (SN) as a result of the third step are generated .

9 is a graph showing changes in Gibbs free energy of halogen atoms before and after application of trioctylphosphine in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.

In Fig. 9, (a), (c) and (e) show the case before the application of trioctylphosphine, and (b), (d) and (f) show cases after the application of trioctylphosphine. (A) and (b) are for CHBr ₃ , (c) and (d) are for CHCl ₃ , and (e) and (f) are for C ₂ H ₅ I.

9, in order to confirm the effect of strong nucleophiles, i.e., trioctylphosphine, in the decomposition of the organic halide in the reaction of the first step, separation of halogen atoms from organic halide molecules (i.e., alkyl molecules) The change in the Gibbs free energy (? G) was calculated with respect to the presence or absence of trioctylphosphine. For the calculation, DFT (Density functional theory) was used and the temperature was assumed to be 20 ° C. The DFT will be described in detail below.

Referring to Figures 9 (a), 9 (c) and 9 (e), before the application of trioctylphosphine, the decomposition of the halogen atoms obtained from the relative free energy according to the distance between the halogen atom and the carbon of the alkyl group The energy (ΔG _d ) was found to be -1.86 eV for Br, -2.19 eV for Cl, -2.04 eV for I, and the separation of halogen atoms was not energetically favored .

Referring to Figures 9 (b), 9 (d), and 9 (f), after the application of trioctylphosphine, the decomposition reaction of halogen atoms is changed to an exothermic reaction in all cases. The change in free energy is represented by the value of 0 eV when the halogen atoms are bonded, -1.29 eV for Br, -1.01 eV for Cl, and -1.41 for I. Thus, it can be seen that the trioctylphosphine molecule accelerates the decomposition of the halogen atom through the S _N 2 reaction from the organic halide.

The mechanism by which the halogen atom is decomposed from the halide by the trioctylphosphine will be described in detail with reference to FIGS. 10 to 12 below.

10 is a schematic diagram showing a mechanism of interaction with a halogen atom by trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.

10, (a), (b) and (c) are types showing the manner of interaction of trioctylphosphine with external halogen atoms, (d) in the case of CHBr ₃ , ₃ , and (f) is the case of C ₂ H ₅ I. The dashed arrows indicate the distance between the halogen atom after bonding with the trioctylphosphine and the carbon of the alkyl molecule.

Referring to FIG. 10, in consideration of the energy change (ΔE) due to decomposition of halogen atoms from the alkyl halide molecule, in all cases, "Type I" has a lower value than "Type II" and "Type III" Thus, it can be seen that the above-mentioned "Type I" is preferred in the combination of trioctylphosphine and halogen atoms.

11 is a graph showing the mechanism of interaction with halogen atoms by trioctylphosphine in the case of Type I of FIG. 10 in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Fig.

In Figure 11, (a) is illustrates a trioctyl phosphine corresponding to the Type I of Figure 10 (b) is a case of CHBr _3, (c) in the case of CHCl _3, (d) is a C ₂ H ₅ I is the case.

Referring to FIG. 11, both green and red indicate an isosurface. The red isotope represents lone pair electrons of the phosphorus atom of trioctylphosphine. The red arrows represent the interaction of the phosphorus atom with the carbon atom of the alkyl molecule. The blue arrows indicate the decomposition of halogen atoms from the alkyl molecule. The strain density analysis shows the electron charge density of the separated atoms, subtracted from the total charge density, so that chemical bonding can be examined. In the final state of the reaction of each alkyl halide and trioctylphosphine, the covalent bond is generated between the phosphorus atom of the trioctylphosphine and the carbon atom of the alkyl molecule by the non-covalent electron pair, The surface is indicated as 0.025 e / Å ³ .

In summary, the trioctylphosphine forms a chemical bond as electrons are shared by carbon atoms, and the halogen atom is separated from the alkyl group. This means that in the first step, it is SN-CRX _{n -1} ⁺ + X ^- . By this mechanism, it can be seen that, in the presence of trioctylphosphine, the decomposition free energy of the organic halide has a lower energy barrier, as compared with the case where trioctylphosphine is not present. In particular, in the case of C ₂ H ₅ I, it is expected that the reaction will be the most thermodynamically and dynamically as compared with other alkyl materials.

12 is a graph showing the change in Gibbs free energy according to the position of a halogen atom in the alkyl molecule after application of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention Graphs.

In FIG. 12, (a) shows the case of CHBr ₃ , and (b) and (d) show the case of CHCl ₃ . The red arrow indicates the distance between the phosphorus atom of the trioctylphosphine and the carbon atom of the alkyl molecule. And the blue arrow indicates the distance between the carbon atom of the alkyl molecule and the halogen atom. The temperature was assumed to be 20 ° C.

Referring to FIG. 12, it can be seen that the initial position of Br in CHBr ₃ for binding to the phosphorus atom of trioctylphosphine and the initial position of Cl in CHCl ₃ are different from those of FIG. 9, the energy barrier was changed from 0.83 eV to 1.17 eV in the case of CHBr ₃ , and the final energy was changed from -1.29 eV to -1.31 eV. In the case of CHCl ₃ , the energy barrier was changed from 0.92 eV to 1.35 eV, and the final energy was changed from -1.01 eV to -1.12 eV. Therefore, the change in the position of the halogen atoms increases the size of the energy barrier and can affect the path of the decomposition reaction.

13 is a graph showing an FT-IR spectrum of a supernatant of a halide perovskite nanocrystal solution in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.

13, the supernatant (supernatant) was evaporated in acetonitrile by heating the supernatant was obtained by centrifugation in the precipitation step of CsPbCl ₃ nanocrystals are replaced with a Br Cl CsPbBr from ₃ to obtain a high signal. Further, for comparison, FT-IR spectra of comparative substances such as trichloromethane (CHCl ₃ ), bromodichloromethane (CHBrCl ₂ ), dibromochloromethane (CHBr ₂ Cl), and tribromomethane (CHBr ₃ ) IR spectra were observed.

Referring to FIG. 13, it is possible to easily detect the difference in the bonding state of halogen atoms and carbon atoms in the range of 600 cm ^-1 to 800 cm ^-1 by FT-IR measurement. Compared to the methane (CHCl ₃₎ solvent trichloroethane, the supernatant was a new peak observed in a region of 650 cm ^-1 to 750 cm ^-1 range, specifically, a new peak at about 690 cm ^-1 and about 740 cm ^-1 Was observed. Since the peak was also found in the comparison of materials including, bromine, supernatant new carbon is not present in the methane (CHCl ₃₎ a solvent trichlorobenzene - it can be seen that the halogen bond is created.

14 is a graph showing a ¹ H-NMR spectrum of a supernatant of a halide perovskite nanocrystal solution in an anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.

In Fig. 14, the same supernatant as that of Fig. 13 was used as the supernatant. For comparison, a ¹ H-NMR spectrum of a comparative material such as bromochloromethane (CHBrCl ₂ ) was observed.

Referring to Figure 14, the presence of byproducts during the reaction can be clearly identified. The peak and the CHBrCl ₂ peaked at the same position of 7.43 ppm. This peak represents the undesired behavior of the third step, but the intensity of the expected by-product CHBrCl ₂ was relatively weak. This means that the production of by-products is not so much.

FIG. 15 is a graph showing changes in Gibbs free energy according to formation of by-products after application of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention.

In FIG. 15, (a) shows the case where CHClBr ₂ produced as a by-product bonds with trioctylphosphine, and (b) CHCl ₂ Br generated as a by-product binds with trioctylphosphine. The red arrow indicates the distance between the phosphorus atom of the trioctylphosphine and the carbon atom of the alkyl molecule. And the blue arrow indicates the distance between the carbon atom of the alkyl molecule and the halogen atom. The temperature was assumed to be 20 ° C.

Referring to FIG. 15, it can be seen that the production of by-products is not thermodynamically favorable by examining the free energy change by DFT calculation. Further, even in the presence of trioctylphosphine, the reaction for bonding with the trioctylphosphine appears to be an endothermic reaction. In addition, the energy barrier was about twice as large as that of FIG. 12. Therefore, it is analyzed that SN-CRX _n-1 ⁺ X 'will be generated better than byproducts (SN and RCX _{n -1} X).

The results of the anion exchange method of halide perovskite nanocrystals according to the technical idea of the present invention are similar to those reported in the past. However, conventional anion exchange methods controlled the amount of halide source to control the proportion of halides in the nanocrystals, because only nanocrystals and halide sources participated in the reaction. However, the anion exchange method of halide perovskite nanocrystals according to the technical idea of the present invention has a difference that can be controlled depending on the presence and content of trioctylphosphine.

Hereinafter, the change of the halide perovskite nanocrystal according to the concentration of trioctylphosphine will be examined. The rate of anion exchange is expected to be strongly influenced by the concentration of the nucleophile (i.e., trioctylphosphine) and can be predicted from the S _N 2 chemical kinetics as described in the first step above.

FIG. 16 is a graph showing a photoluminescence spectrum of a halide perovskite nanocrystal according to an embodiment of the present invention, in accordance with the concentration of trioctylphosphine. FIG.

17 is a graph showing an absorption spectrum according to a change in concentration of trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention.

Referring to FIG. 16 and FIG. 17, the synthesized CsPbBr ₃ nanocrystals (NC) are reacted for 10 minutes in a chloroform solution state, and then directly show changes in optical characteristics according to trioctylphosphine (TOP) concentration. The concentration of trioctylphosphine means the volume ratio to the total solution. By the reaction CsPbBr ₃ is gradually exchanged by CsPbCl _3. When the trioctylphosphine is at a high concentration (20%), the rate of anion exchange is faster, and after 10 minutes most of the Br atoms are exchanged for Cl halogen to form CsPbCl ₃ perovskite nanocrystals . Accordingly, as the concentration of trioctylphosphine increases as shown in FIG. 16, the peak of the photoluminescence spectrum shifts to a lower wavelength band, and the absorption spectrum shifts to a lower wavelength band as shown in FIG.

Table 1 is a table showing the photoluminescence peak value and the full width at half maximum (FWHM) according to the concentration of trioctylphosphine in the anion exchange method of the halide perovskite nanocrystal according to an embodiment of the present invention.

CsPBBr ₃ TOP 1% TOP 5% TOP 10% TOP 20% peak 505 484 459 450 439 FWHM (nm) 28 29 25 23 22

Referring to Table 1, as the concentration of trioctylphosphine increases, the wavelength and full width at half maximum (FWHM) corresponding to the position of the emission peak decrease.

As is known, hybrid compounds of Br and Cl in halide perovskite nanocrystals change optical properties in the intermediate wavelength region between 550 nm and 430 nm between CsPbBr ₃ and CsPbCl ₃ . With this simple manufacturing method, the perovskite nanocrystal characteristics can be easily controlled by simply changing the concentration of trioctylphosphine. That is, the emission of CsPbX ₃ perovskite nanocrystals can be achieved in the entire visible light wavelength range of 400 nm to 700 nm by controlling the concentration of trioctylphosphine.

X-ray photoelectron spectroscopy was performed to determine the atomic ratio of chemically reacted perovskite nanocrystals to the ratio of trioctylphosphine.

18 is a graph showing the X-ray photoelectron spectrum of the Br 3d peak region according to the concentration change of trioctylphosphine in the anion exchange method of halide perovskite nanocrystals according to an embodiment of the present invention .

19 is a graph showing an X-ray photoelectron spectrum of a Cl 2p peak region according to a concentration change of trioctylphosphine in an anion exchange method of a halide perovskite nanocrystal according to an embodiment of the present invention .

18 and 19, the synthesized CsPbBr ₃ nanocrystals (NC) were reacted in a chloroform solution for 10 minutes, and then the change in X-ray photoelectron spectrum according to the concentration of trioctylphosphine (TOP) . The concentration of trioctylphosphine means the volume ratio to the total solution. Referring to Fig. 18, the Br peak appears to be strongest in the region of 67 eV to 70 eV, and the intensity of the peak decreases as the concentration of trioctylphosphine increases. Further, referring to FIG. 19, the intensity of the peak in the range of 195 eV to 200 eV was increased as the concentration of trioctylphosphine was increased. These results show clearly the effect of the concentration of trioctyl phosphine in anion exchange with CsPbCl ₃ nanocrystals in CsPbBr ₃ nanocrystals. That is, increasing the concentration of trioctyl phosphine slows CsPbBr ₃ is increased the rate of anion exchange with CsPbCl ₃ nanocrystals in the nanocrystal.

Hereinafter, the change of the halide perovskite nanocrystal according to the reaction time will be examined.

FIG. 20 is a graph showing a photoluminescence spectrum according to a reaction time in a halide perovskite nanocrystal anion exchange method according to an embodiment of the present invention. FIG.

FIG. 21 is a graph showing an absorption spectrum of a halide perovskite nanocrystal according to an embodiment of the present invention, with respect to the reaction time. FIG.

In FIGS. 20 and 21, anion exchange with Cl or I with I based on CsPbBr ₃ perovskite nanocrystals. For example, "PT-CsPBCl ₃ 18m" in the drawings means that the anion-exchange was performed for 18 minutes to Cl. Tree concentration of octyl phosphine was 10% for the PT-CsPbCl ₃ in volume ratio was 5% for the PT-CsPbI ₃

Referring to FIGS. 20 and 21, the time of the anion exchange reaction can be controlled to achieve the emission of CsPbX ₃ nanocrystals in the entire visible light wavelength range of 400 nm to 700 nm.

Hereinafter, the DFT (Density functional theory) will be described in detail.

As described above, the density functional theory (DFT) was applied to investigate the function of trioctylphosphine for decomposing halogen atoms from alkyl halide molecules. All calculations for the DFT were performed using the DMol program 2017 R2 version of Material Studio. A generalized gradient approximation (GGA) including Perdew-Burke-Ernzerhof (PBE) was used for the exchange correlation energy. To illustrate the core electrons and the atomic orbital base set, we have applied a basic set of all the counterpart core processing and the 4.4 version of double numerical plus polarization (DNP), respectively. The spin polarization calculations were applied for all model systems and van der Waals interactions between molecules were considered by the Tkatchenko-Scheffler (TS) method. The collective criterion for geometric optimization was 1.0 × 10 ^-5 Ha for energy, 0.002 Ha / Å for force, and 0.005 Å for displacement. Note that optimization was performed under non-periodic boundary conditions. All calculations were performed under the implied environment using a conductor-like screening model (COSMO) with a 1: 1 mixture of CHBr ₃ and CHCl ₃ (or C ₂ H ₅ I) dielectric constants. Based on the dielectric constants of CHBr ₃ , CHCl ₃ , and C ₂ H ₅ I at 20 ° C, dielectric constants of a 1: 1 blend of CHBr ₃ and CHCl ₃ (or C ₂ H ₅ I) were calculated. That is, for CHBr ₃ and CHCl ₃ systems, the dielectric constant was 4.595 for CHBr ₃ : CHCl ₃ = 1: 1 and the CHBr ₃ : C ₂ H ₅ I = 1: 1 for CHBr ₃ and C ₂ H ₅ I systems , The dielectric constant was 5.941.

In order to calculate the transition state of the S _N 2 reaction between trioctylphosphine and alkyl halide molecules, the LST / QST method (complete single linear synchronous transit / quadratic synchronous transit) was performed at 0.002 Ha / Å root mean square , RMS) convergence. The method first LST searches the reaction path between adjacent positions, then performs conjugate slope minimization, and finally performs QST maximization. In order to calculate the correct energy barrier, the TS optimization process was repeated until only one imaginary frequency was detected in the TS.

The effect of trioctylphosphine on the decomposition of halogen atoms was studied by calculating the energy change (ΔE) and the Gibbs free energy change (ΔG) in each system. The energy change ([Delta] E) is calculated by the energy difference for the reference state for each system. The Gibbs free energy change (? G) is calculated by the following equation 1 at a temperature of 20 占 폚.

<Formula 1>

Here _, ΔH ^{20 ° C.} Is the enthalpy change from the reference state, and [Delta] S ^{20 [deg} .] ^C is the enthalpy change from the reference state.

DELTA G20 ^{DEG C} is expressed by the following equation (2).

<Formula 2>

Where U is the internal energy per mole, P is the pressure, V is the volume per mole and S is the entropy per mole. The subscript 'ref' represents the reference state in each system. (2) can be expressed by the following Equation (3) by applying the movement freedom and the energy change (? E) such as vibration, rotation and transfer.

<Formula 3>

Here, U '= E _vib + E _trans + E _rot , and U' _ref = E _{ref, v ib} + E _{ref, trans} + E _{ref, rot} . Note that these terms are calculated for cases where the system is optimally grounded.

As described above, three types of trioctylphosphine configurations depending on the direction of interaction with alkyl halide molecules have been considered to derive the optimal interaction configuration. Of these, "type I", ie phosphorus atoms arranged to perform interaction with alkyl halide molecules at the front line, was found to be the most stable configuration because the interaction energy is most appropriate.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. Will be apparent to those of ordinary skill in the art.

Claims (14)

Providing a first solution comprising a first halide perovskite nanocrystal having a first halogen element; And
Adding an alkyl material including a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element Anion exchanged to form a second solution comprising a second halide perovskite nanocrystal having the second halogen element,
The first halogen atom, is converted to bromine (Br), and the second halogen element is chlorine (Cl), and CsPbCl ₃ in the anion exchange by CsPbBr _3,
Chloroform is added to the first solution containing bromine in a volume ratio of 0.1 to 5 times and the trioctylphosphine is added to prepare the entire solution so that the anion exchange with the chlorine from the bromine Lt; / RTI &
And adjusting the concentration of the trioctylphosphine in the whole solution to adjust the reaction rate of the anion exchange. Providing a first solution comprising a first halide perovskite nanocrystal having a first halogen element; And
Adding an alkyl material including a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element Anion exchanged to form a second solution comprising a second halide perovskite nanocrystal having the second halogen element,
Wherein the first halogen element is chlorine (Cl), the second halogen element is bromine (Br), is converted from CsPbCl ₃ to CsPbBr ₃ by the anion exchange,
The bromoform is added to the first solution containing chlorine in a volume ratio of 0.1 to 2, and the trioctylphosphine is added to prepare the entire solution, whereby the anion Exchange is performed,
And adjusting the concentration of the trioctylphosphine in the whole solution to adjust the reaction rate of the anion exchange. Providing a first solution comprising a first halide perovskite nanocrystal having a first halogen element; And
Adding an alkyl material including a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element Anion exchanged to form a second solution comprising a second halide perovskite nanocrystal having the second halogen element,
Wherein the first halogen element is iodine (I), the second halogen element is bromine (Br), is converted from CsPbI ₃ to CsPbBr ₃ by the anion exchange,
Bromoform is added to the first solution containing iodine in a volume ratio of 0.1 to 2, and the trioctylphosphine is added to prepare the entire solution, whereby the bromine from the iodine to the bromine The anion exchange is performed,
And adjusting the concentration of the trioctylphosphine in the whole solution to adjust the reaction rate of the anion exchange. Providing a first solution comprising a first halide perovskite nanocrystal having a first halogen element; And
Adding an alkyl material including a trioctylphosphine and a second halogen element different from the first halogen element to the first solution to cause the first halogen element to react with the second halogen element Anion exchanged to form a second solution comprising a second halide perovskite nanocrystal having the second halogen element,
The first halogen atom, is converted to bromine (Br), and the second halogen element is CsPbI ₃ from iodine (I) and, CsPbBr ₃ by the anion exchange,
The bromine is added to the first solution containing bromine in the range of 1% to 10% by volume in terms of iodoethane and the trioctylphosphine is added to prepare the entire solution, The anion exchange is performed,
And adjusting the concentration of the trioctylphosphine in the whole solution to adjust the reaction rate of the anion exchange. delete delete delete delete delete delete The method according to any one of claims 1 to 4,
Wherein the concentration of the trioctylphosphine is in the range of more than 0% to 30% by volume with respect to the total solution. The method according to any one of claims 1 to 4,
Wherein the anion exchange is carried out at a temperature in the range of 20 &lt; 0 &gt; C to 70 &lt; 0 &gt; C. The method according to any one of claims 1 to 4,
Wherein the anion exchange is terminated by diluting with acetonitrile in a volume ratio ranging from 5 to 7 times with respect to the total solution. The method according to any one of claims 1 to 4,
Wherein the anion exchange is performed in a range of 1 minute to 60 minutes.

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