CN114315591A

CN114315591A - Preparation of MAPbX3Method of nanowires

Info

Publication number: CN114315591A
Application number: CN202111663383.7A
Authority: CN
Inventors: 王伟建
Original assignee: Individual
Current assignee: Zhongmao Green Energy Technology Xi'an Co ltd
Priority date: 2021-07-27
Filing date: 2021-12-31
Publication date: 2022-04-12
Anticipated expiration: 2041-12-31
Also published as: CN114315591B

Abstract

Preparation of MAPbX₃Method of nanowires, the method of the invention combines PbX with a metal oxide₂Dissolving in deionized water, stirring for several minutes, standing and aging for a period of time to obtain the one-dimensional Pb (OH) X nanowire. Then the Pb (OH) X nanowires were exposed to MAX vapors and converted to MAPbX₃A nanowire. MAPbX prepared without using any organic solvent, acid or alkali in the preparation process₃The nanowires have similar optical properties to nanowires prepared from organic solvents. The green manufacturing method can reduce the pollution to the environment in the industrial process and can obviously reduce the cost.

Description

Preparation of MAPbX3Method of nanowires

Technical Field

The invention belongs to the field of lead-halogen perovskite, and particularly relates to MAPbX₃A method for preparing nanowires.

Background

The perovskite material has a general structural formula of ABX₃A andb is two cations and x is an anion. Wherein MAPbBr₃The crystal is a typical perovskite structure material, and the A site is organic cation CH₃NH₃ ⁺Pb at the B site²⁺And x is halogen ion Br^-。MAPbBr₃The crystal belongs to the cubic system. The structure is characterized in that: (1) octahedrons composed of B-site ions and x-site ions are connected with each other through A-site ions at vertexes to form a stable three-dimensional network structure, and the structure is higher in stability than a common edge and coplanar connection structure: (2) the common vertex connection can make the gap of octahedron larger than that of common edge or common plane connection, so that when filling with larger size organic amine ion, the stable structure can be maintained, and the diffusion and migration of defect are facilitated. The peculiar crystal structure enables the crystal to have a plurality of unique physicochemical properties, and has a larger application prospect in the chemical and physical fields.

In addition, there are many methods for preparing pb (oh) X hydroxoplumbite in the prior art, such as the method introduced in the doctor's paper (the synthesis, characterization and analysis application of the ancient aromatic low-dimensional nano material [ D ]. Tianjin: southern development university, 2008) for rapidly synthesizing pb (oh) Br of one-dimensional dimension/nanowire by microwave-ultrasonic wave composite assistance, in the preparation process, the lead salt and the bromine-containing plasma liquid are heated at the traditional temperature of 70 ℃ or are heated by adopting microwave, ultrasonic or a combination mode of microwave, ultrasonic or the combination mode to obtain the one-dimensional Pb (OH) Br nanowire, the pb (oh) Br obtained when heating alone is used is 20-30 microns in diameter, pb (OH) Br with a diameter of 0.1-2 microns can be obtained when plasma bromide is used in combination with microwave or ultrasonic means, but the preparation process is complex, the preparation process of the plasma bromine salt is complex, and the energy consumption of the ultrasound or the microwave is high.

The prior art CN110387223A and CN110589877A both disclose a preparation method of one-dimensional micron Pb (OH) Br, which is characterized in that PbBr is adopted₂DMSO is used as a solvent of the precursor, and oleic acid and oleylamine are used as ligands, so that one-dimensional micron Pb (OH) Br can be prepared at normal temperature by stirring. The preparation method also needs a large amount of precursor solvent and ligand to prepare the one-dimensional micron Pb (OH) Br, has higher preparation cost and the same advantage as that of the preparation methodThe use of the solvent also brings certain negative effects to the separation of products in the later period and the environmental pollution.

In the prior art, CN108807986A discloses a preparation method of a basic lead chloride micro-nano structure crystal, which adopts deionized water as a solvent, but triethylamine must be added as a precipitating agent in the preparation process, and the obtained product is in a small rod shape, the length of the small rod is about 300-1600nm, the thickness is about 30-40nm, but a toxic triethylamine reagent needs to be added in the preparation process, so that the environment is easily polluted, and the cost is high.

And MAPbX₃The preparation principle of (2) is simple, and the general reaction equation can be briefly described as follows: CH (CH)₃NH₃X+PbX₂＝CH₃NH₃PbX₃Various techniques have been used to grow MAPbX from solution₃A perovskite single crystal. Including solution cooling, inverse temperature difference crystallization, top seed crystal solution growth, antisolvent steam assisted crystallization, etc. These methods involve changing the state parameters such as temperature and vapor pressure to supersaturate the solution and obtain the driving force for crystal growth, thereby precipitating crystals from the solvent. These current processes require different types of organic solvents which are environmentally hazardous and costly.

Disclosure of Invention

In order to overcome the disadvantages of the prior art mentioned above, the object of the present invention is to propose a process for preparing CH without using any organic solvent, acid and base₃NH₃PbX₃(i.e., MAPbX)₃) Green method of nanowires. According to the elemental distribution of Pb (OH) X, only the most desirable PbX is used₂And deionized water to obtain Pb (OH) X. Then the Pb (OH) X nanowires were exposed to MAX vapors and converted to MAPbX₃A nanowire. Prepared MAPbX₃The nanowires have similar optical properties to nanowires prepared in the prior art using organic solvents. The green manufacturing method can reduce the pollution to the environment in the industrial process and can obviously reduce the cost.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

firstly, PbX is firstly added₂Dissolving in deionized water, stirring for a period of time, standing and aging for a period of time to obtain one-dimensional nano linear precipitate. And centrifuging to take the precipitate, placing the precipitate in an oven, and drying to obtain the Pb (OH) X nanowire. The diameter of the nanowire can be controlled within 500nm, so that the one-dimensional nanowire structure is formed.

Preferably, the X is one or more of halogens F, Cl, Br or I.

Preferably, the stirring speed is controlled at 600-900 r/min.

Preferably, the stirring time is controlled within 2-5 min.

Preferably, the stirring temperature is controlled to be 30-80 ℃.

Preferably, the standing aging time is 4 to 12 hours.

Then spin-coating Pb (OH) X nanowires on the quartz stone plate, and then coating CH₃NH₃Placing X powder at the bottom of the beaker, and finally placing the quartz stone plate paved with Pb (OH) X nanowires in the middle of the beaker, wherein the Pb (OH) X nanowires face CH₃NH₃And (3) sealing the beaker for soaking the powder X in oil bath at a certain temperature for a certain time.

Taking Pb (OH) Br nanowires as an example, the principle that one-dimensional Pb (OH) Br nanowires can be obtained by controlling the temperature, stirring speed and stirring time of the manufacturing process is that reaction formulas (1), (2) and (3) can be utilized. As shown by the following analysis, water is a weak electrolyte and ionizes to form Pb (OH) Br precipitate^-1(ii) a The ionization of water can be improved by rapid stirring and temperature rise, and more OH is generated^-1Likewise, PbBr can be increased₂To generate more Pb²⁺And Br^-1(ii) a Also, Pb is accelerated²⁺、Br^-1And OH^-1The collision and reaction occur; this helps to produce more Pb (OH) Br precipitate more quickly. The structure of the Pb (OH) Br nanowire can be the self-assembly of Pb (OH) Br nanocrystals, and the Pb (OH) Br nanocrystals are directionally adsorbed along a certain crystal plane to generate a one-dimensional nanowire structure.

H₂O＝H⁺+OH^-1

PbBr₂＝Pb²⁺+2Br^-1

Pb²⁺+Br^-1+OH^-1＝Pb(OH)Br↓

When the stirring reaction temperature is higher than 80 ℃, one-dimensional pb (oh) Br nanowires with uniform size cannot be formed due to the excessively fast generation speed of pb (oh) Br.

2. The next time the invention prepares MAPbBr in wet chemistry₃In the process (2), due to the strong coordination bond of Pb-Br in the precursor solution, a Pb-Br co-angle octahedron is formed firstly, and the phenomenon is widely accepted. After MABr injection, MA⁺The ions are gradually filled into the octahedral gaps to neutralize the charges and support the Pb-Br three-dimensional skeleton to form stable MAPbBr₃And (4) crystals. Unlike Pb under wet-chemical preparation conditions²⁺The ions can diffuse freely in the system, and Pb in the system²⁺The ions are fixed in the lattice of Pb (OH) Br. This determined MAPbBr₃Must start on the pb (oh) Br surface. Since no additional chemicals were used during our synthesis, the surface of pb (oh) Br was not covered by any organic ligands. Thus, when MABr gas reaches the surface of Pb (OH) Br, a reaction occurs at the surface to form a first layer of [ PbBr₆]Octahedron. This layer is the nucleus for perovskite growth, further evaporation favors Br^-And MA⁺The ions diffuse into Pb (OH) Br and gradually react to form MAPbBr₃. The entire conversion process requires precise control of the reaction time. MAPbBr was synthesized by this simple transformation using Pb (OH) Br as template₃The nanowire approach is efficient, easy to operate, and ultimately green, with advantages for industrial applications.

Finally, we monitored the structural evolution as the evaporation time of the MABr powder increased in order to elucidate the transformation process of hydroxoplumbite to perovskite. According to the results of example 2, no MAPbBr was observed during the first 20min of the oil bath reaction₃Because pb (oh) Br dominates the product (fig. 3 k). After 60min of reaction, MAPbBr₃The (110) plane of (A) shows a characteristic diffraction peak (21.2 °), indicating MAPbBr₃Is performed. After 360min of reaction, MAPbBr₃All diffraction peaks of (1) and no diffraction peak of Pb (OH) Br. Indicating complete conversion of Pb (OH) Br to MAPbBr₃To elucidate the transformation process of hydrohalite to perovskite, we monitored the structural evolution as the evaporation time of MABr powder was increased. No MAPbBr was observed during the first 20min of the reaction₃Because pb (oh) Br dominates the product (fig. 3 k). After 60min of reaction, MAPbBr₃The (110) plane of (A) shows a characteristic diffraction peak (21.2 °), indicating MAPbBr₃Forming of (1). After 360min of reaction, MAPbBr₃All diffraction peaks of (1) and no diffraction peak of Pb (OH) Br. Indicating complete conversion of Pb (OH) Br to MAPbBr₃。

As shown in I of fig. 3, no significant absorption peak was detected in the initial stage. When more MABr gas is introduced into the reaction system, the absorption in the range of 530nm to 550nm is enhanced, indicating MAPbBr₃Is performed.

As the results of fig. 4 also show, elemental mapping of individual nanowires showed the coexistence of Pb, Br, C and N elements 360 minutes after Pb (oh) Br reaction with MABr gas (fig. 4 a). However, to confirm that the Pb (OH) Br nanowires had been fully converted to MAPbBr₃Nanowires, we have made confocal fluorescence measurements at different depths of a single nanowire by varying the depth of focus of the excitation laser (fig. 4b and c). The nanowires were cut into 16 layers (fig. 4 c). Fluorescence images of each slice layer were collected (fig. 4 d). Weak fluorescence was observed at the top and bottom of the nanowires, while strong fluorescence was observed in the middle of the nanowires (fig. 4 d). This phenomenon is associated with MAPbBr₃The morphology of the nanowires was completely identical, indicating that Pb (OH) Br was completely converted to MAPbBr₃。

Compared with the prior art, the invention has the following beneficial effects:

1. the method adopts deionized water as a solvent, and PbX is added at a certain temperature and stirring speed₂Dissolving in deionized water, and stirring for several minutes to obtain one-dimensional nano linear precipitate. The preparation process is simple, pollution-free and environment-friendly, and the diameter of the obtained product can be controlledAround a few hundred nanometers.

2. The invention further provides a method for preparing CH without using any organic solvent, acid and alkali₃NH₃PbX₃(MAPbX₃) Green method of nanowires, MAPbX prepared thereby₃The nanowires have similar optical properties to nanowires prepared from organic solvents. The green manufacturing method can reduce the pollution to the environment in the industrial process and can obviously reduce the cost.

Drawings

FIG. 1 shows MAPbBr according to the invention₃Preparation schematic diagram of the nanowire;

FIG. 2 is a representation of Pb (OH) Br nanowires prepared in example 1, wherein (a) the XRD pattern; (b) and (c) SEM images of nanowires with different magnifications; (d) AFM images; (e) the crystal structure of Pb (OH) Br; (f) and (g) TEM images of nanowires with different magnifications; (h) EDS face scan.

FIG. 3 shows the experimental results of Pb (OH) Br nanowires and MABr vapor at different reaction times, including SEM images (a, b) after reaction time of 0.5 min; (c, d)2 minutes; (e, f)30 minutes; (g, h)2 h; (i, j)6 h; (k) XRD spectrogram; (I) ultraviolet-visible absorption spectra of Pb (OH) Br nanowires after reaction with MABr vapor for different times; PL spectrum (m).

FIG. 4 shows MAPbBr prepared by reaction of Pb (OH) Br nanowires with MABr vapor for 6h₃A nanowire. Wherein, (a) MAPbBr₃A spectrum of the nanowires; (b) MAPbBr₃A fluorescence microscope image of the nanowires; (c) a schematic view of a slice taken in the thickness direction; (d) fluorescence microscopy images of different sections.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

The method adopts deionized water as a solvent, and PbBr is added at a certain stirring temperature and stirring speed₂Dissolving in deionized water, and stirring for several minutes to obtain one-dimensional nano linear precipitate. And centrifuging to take the precipitate, placing the precipitate in an oven, and drying to obtain the Pb (OH) Br nanowire. The diameter of the nanowire can be controlled within 500nm, so that the one-dimensional nanowire structure is formed, the stirring temperature is controlled to be 30-70 ℃, and the preferable temperature is 30-50 ℃. The stirring speed is controlled at 600-900r/min, and the stirring time is controlled at 2-5 min.

Then exposing Pb (OH) Br nanowires to MABr vapor to convert into MAPbBr₃A nanowire. The reaction temperature can be 50-200 ℃, preferably 100-160 ℃, and the reaction time is 0.5-400min, preferably 120-360 min.

The present invention is further illustrated by the following examples, but is not limited thereto.

Example 1

Adding 0.22g of lead bromide into 30ml of deionized water, stirring at the rotating speed of 700r/min for 5 minutes at 30 ℃, centrifuging at 3000r/min to obtain precipitates, placing the precipitates in an oven, and drying at 70 ℃ to obtain Pb (OH) Br nanowires, wherein the width of the nanowires is about 0.17 micrometer, and the average length of the nanowires is about 7 micrometers.

The pb (oh) Br nanowires obtained in example 1 were characterized as shown in fig. 2: (a) XRD pattern. (b) And (c) SEM images of nanowires with different magnifications. (d) AFM imaging. (e) Crystal structure of Pb (OH) Br. (f) And (g) TEM images of nanowires with different magnifications. (h) EDS face scan.

Example 2

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). Sealing the beaker, and gasifying in an oil bath at 130 deg.C for 0.5min, 2min,30min、120min、360min。

SEM images of the Pb (OH) Br nanowires obtained in example 2 after 0.5min gasification are shown in FIG. 2(a, b).

Example 3

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). The beaker was sealed and the gassing time was 2min in an oil bath at 130 ℃.

SEM images of the Pb (OH) Br nanowires obtained in example 2 after 2min gasification are shown in FIG. 3(c, d).

Example 4

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). The beaker was sealed and the gassing time was 20min in an oil bath at 130 ℃.

The Pb (OH) Br nanowires obtained in example 2 were gasified for 20min and the product was characterized as shown in FIG. 3(k, l, m). FIG. 3(k) is the XRD pattern of the product obtained by gasifying Pb (OH) Br nanowires for 20min, which can be obtained from the XRD pattern, and the product is mainly Pb (OH) Br. FIG. 3(l) is an absorption spectrum of a product obtained by gasifying Pb (OH) Br nanowires for 20min, which can be obtained from the absorption spectrum, and trace MAPbBr begins to appear in the product₃. FIG. 3(k) is an emission spectrum of a product obtained by gasifying a Pb (OH) Br nanowire for 20min, which can be obtained from the emission spectrum, and the product begins to appear a trace amount of MAPbBr₃。

Example 5

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). Sealing the beakerThe gasification time in an oil bath at 130 ℃ was 30 min.

SEM images of the Pb (OH) Br nanowires obtained in example 2 after 30min gasification are shown in FIG. 3(e, f).

Example 6

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). The beaker was sealed and the gassing time was 60min in an oil bath at 130 ℃.

The Pb (OH) Br nanowires obtained in example 2 were gasified for 60min, and the product was characterized as shown in FIG. 3(k, l, m). FIG. 3(k) is an XRD pattern of a product obtained by gasifying Pb (OH) Br nanowires for 60min, which can be obtained from the XRD pattern and shows a small amount of MAPbBr₃. FIG. 3(l) is an absorption spectrum of a product obtained by gasifying Pb (OH) Br nanowires for 60min, which can be obtained from the absorption spectrum, and a small amount of MAPbBr begins to appear in the product₃. FIG. 3(k) is an emission spectrum of a product obtained by gasifying Pb (OH) Br nanowires for 60min, which is obtained from the emission spectrum, and a small amount of MAPbBr begins to appear in the product₃。

Example 7

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). The beaker was sealed and the gassing time was 120min in an oil bath at 130 ℃.

SEM images of the Pb (OH) Br nanowires obtained in example 2 after being gasified for 120min are shown in FIG. 3(g, h).

Example 8

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powderAnd finally (process two, fig. 1). The beaker was sealed and the gassing time was 240min in an oil bath at 130 ℃.

The Pb (OH) Br nanowires obtained in example 2 were gasified for 240min, and the product was characterized as shown in FIG. 3(k, l, m). FIG. 3(k) is an XRD pattern of a product obtained by gasifying Pb (OH) Br nanowires for 240min, which can be obtained from the XRD pattern, and the product shows a large amount of MAPbBr₃. FIG. 3(l) is an absorption spectrum of a product obtained by gasifying Pb (OH) Br nanowires for 240min, which can be obtained from the absorption spectrum, and a large amount of MAPbBr begins to appear in the product₃. FIG. 3(k) is an emission spectrum of a product obtained by gasifying Pb (OH) Br nanowires for 240min, which is obtained from the emission spectrum, and a large amount of MAPbBr begins to appear in the product₃。

Example 9

The pb (oh) Br nanowires prepared in example 1 were spin coated on a quartz stone plate. Then 0.1gCH₃NH₃Br powder was placed in the bottom of a 100ml beaker. Placing a quartz glass material coated with Pb (OH) Br nanowires facing CH in the middle of a beaker₃NH₃Br powder (process two, fig. 1). The beaker was sealed and the gassing time was 360min in an oil bath at 130 ℃.

The Pb (OH) Br nanowires obtained in example 2 were gasified for 360min, and the product was characterized as shown in FIGS. 3(k, l, m) and 4. FIG. 3(k) is an XRD pattern of the product obtained by gasifying Pb (OH) Br nanowire for 360min, which can be obtained from the XRD pattern and is completely MAPbBr₃. FIG. 3(l) shows MAPbBr as a product obtained by gasifying Pb (OH) Br nanowires for 360min₃The absorption spectrum of (a). FIG. 3(k) shows MAPbBr as a product obtained by gasifying Pb (OH) Br nanowires for 360min₃The emission spectrum of (a). FIG. 4 shows MAPbBr as a product obtained by gasifying Pb (OH) Br nanowires for 360min₃The characterization of (1); wherein, (a) MAPbBr₃A spectrum of the nanowires; (b) MAPbBr₃A fluorescence microscope image of the nanowires; (c) a schematic view of a slice taken in the thickness direction; (d) fluorescence microscopy images of different sections.

Example 10

Adding 0.22g of lead chloride into 30ml of deionized water, stirring at the rotating speed of 700r/min for 5 minutes at 30 ℃, standing and aging for 12 hours, centrifuging at 3000r/min to obtain a precipitate, placing the precipitate in an oven, and drying at 70 ℃ to obtain Pb (OH) Cl nanowires, wherein the width of the nanowires is about 150 nanometers, and the average length of the nanowires is about 6 micrometers.

Example 11

Adding 0.22g of lead iodide into 30ml of deionized water, stirring at the rotating speed of 700r/min for 5 minutes at 30 ℃, standing and aging for 12 hours, centrifuging at 3000r/min to obtain a precipitate, placing the precipitate in an oven, and drying at 70 ℃ to obtain Pb (OH) I nanowires, wherein the width of the nanowires is about 150 nanometers, and the average length of the nanowires is about 5 micrometers.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. Preparation of MAPbX₃A method of nanowires, characterized by the steps of: firstly, water is adopted as a solvent, and PbX is stirred at a certain stirring temperature and stirring speed₂Dissolving in deionized water, stirring for a period of time, standing and aging for a period of time to obtain one-dimensional nanowire precipitate Pb (OH) X, and exposing the Pb (OH) X nanowire to CH₃NH₃In X steam, conversion to MAPbX₃A nanowire.

2. The method of claim 1, wherein X is one or more of the halogens F, Cl, Br, or I.

3. The method of claim 1, wherein the pb (oh) X nanowires have a diameter dimension of 0.17-1 micron.

4. The method of claim 1, wherein the stirring temperature is controlled to be 30-50 degrees celsius.

5. The method as claimed in claim 1, wherein the stirring speed is controlled at 600-900 r/min.

6. The method of claim 1, wherein the stirring time is controlled to be 2-5 min.

7. The method of claim 1, wherein the stirring temperature is controlled to be 30-80 degrees celsius.

8. The method of claim 1, wherein the Pb (OH) X nanowires are coupled with CH₃NH₃The specific process of the X steam is as follows: spin coating Pb (OH) X nanowires on quartz stone plate, and then coating CH₃NH₃Placing X powder at the bottom of the beaker, and finally placing the quartz stone plate paved with Pb (OH) X nanowires in the middle of the beaker, wherein the Pb (OH) X nanowires face CH₃NH₃And (3) sealing the beaker for soaking the powder X in oil bath at a certain temperature for a certain time.

9. The method according to claim 1, wherein the temperature of the steam reaction is 50 to 200 ℃ and the reaction time is 0.5 to 400 min.

10. One-dimensional MAPbX prepared by the preparation method according to any one of claims 1-9₃A nanowire.