RU2730315C1 - Method of producing organic-inorganic complex halogenide monocrystals - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to production of monocrystals from solutions by chemical conversion of a solvent. Method of producing monocrystals of organo-inorganic complex halogenide (OICH) of composition ABX, where z = 1–2, k = 2–4, 0 < n ≤ 4, includes: A) preparation of a solution composition containing at least one polar solvent (S), solubility of OICH in which is equal to (C, T); reagent (M), taken in an amount providing a molar ratio M/S of 0.05 to 15, for chemical reaction with solvent S, product of which is at least one gaseous or liquid-phase compound, or mixture thereof (S), solubility of OICH in which is equal to (C, T), where C < C; components of organic glucose, which are represented by organic cation Aor an inorganic cation selected from cations of ammonium (NH), cesium (Cs) or rubidium (Rb) or a mixture thereof; polyvalent metal cation B; halogenide or pseudohalogen ion X, wherein in solution composition concentration [A] ranges from 0.1 M to 7M, concentration [B] ranges from 0.1M to 3.5M, concentration [X] ranges from 0.2 M to 10 M, and the solution composition has a concentration of OICH equal to or less than the solubility of OICH (C, T) in the solution with given ratio M/S; B) maintaining the resulting composition at a constant temperature T1 to achieve chemical conversion of at least 10 % S in S 1 ensures the formation of single crystals OICH.EFFECT: technical result is reduced solubility of components of OICH in solution by chemical conversion of solvent into product, which does not dissolve or poorly dissolve OICH in solution composition, from which crystallization is carried out, which facilitates production of monocrystals of specified chemical composition.12 cl, 1 tbl, 12 ex, 7 dwg

Description

Technology area

The invention relates to a technology for producing single crystals, in particular, to methods for producing single crystals of organic-inorganic complex halides from solutions due to the chemical conversion of the solvent.

Single crystals of organic-inorganic complex halides can be used as materials for photoelectric and optoelectronic devices, to create radiation detectors.

State of the art

Organo-inorganic complex halides (ONGC) are a relatively young, but extensive class of crystalline compounds, including compounds with a perovskite or perovskite-like structure, as well as other structural types. Many compounds of a number of organo-inorganic complex halides exhibit a complex of optical, electronic, and other functional properties, making them extremely promising materials for use in optoelectronic and photoelectric devices, the manufacture of detectors, sensors, lasers, and other areas of the semiconductor industry.

In particular, a number of works published in recent years indicate the successful use of single crystals of these compounds in the manufacture of solar cells with an efficiency higher than 17% [Chen Z. et al. Thin single crystal perovskite solar cells to harvest below-bandgap light absorption // Nature communications. - 2017. - T. 8. - No. 1. - C. 1890.], LEDs [Wang X. D. et al. Recent Advances in Halide Perovskite Single - Crystal Thin Films: Fabrication Methods and Optoelectronic Applications // Solar RRL. - 2019. - C. 1800294].

It is known from the prior art that ONCH single crystals are predominantly formed by crystallization from solutions, due to their high solubility in a number of polar solvents [So F. (ed.). World Scientific Handbook of Organic Optoelectronic Devices (Volumes 1 & 2): Volume 1: Perovskite Electronics Volume 2: Organic Photovoltaics (OPVs). - World Scientific]. Solution methods make it possible to obtain high quality ONKG monocrystals actually at moderate temperatures and without the use of sophisticated technical equipment. Hereinafter, the high quality of crystals is understood as a low concentration of structural defects, which is a necessary condition for the optoelectronic application of these materials.

Obtaining single crystals from solutions is possible due to the regulation of the solubility of these compounds through the action of physical or chemical factors. There are three main groups of methods for producing single crystals based on different approaches to regulating the solubility of a compound forming single crystals:

1.decreasing the temperature of the solution to achieve its saturation and crystallization

2. raising the temperature of the solution to achieve saturation and crystallization

3.introduction into the solution of the compound of a component that reduces solubility and causes crystallization

The first way [So F. (ed.). World Scientific Handbook of Organic Optoelectronic Devices (Volumes 1 & 2): Volume 1: Perovskite Electronics Volume 2: Organic Photovoltaics (OPVs). - World Scientific] provides for the use of liquid-phase systems, the solubility of ONCH in which increases with increasing temperature. To implement this method, use is made of solutions of the ONCH components in hydrohalic acids or solutions based on them.

The main disadvantage of this method is the need to use corrosive, hazardous to handle and unstable to oxidation of concentrated solutions of hydrohalic acids. In addition, the disadvantage is the need for careful control of the temperature (namely, its slow decrease) to ensure the level of supersaturation required for slow growth of a single crystal, but insufficient to initiate bulk nucleation.

The second way [Saidaminov M.I. et al. Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growth // Chem. Commun. Royal Society of Chemistry, 2015. Vol. 51, no. 100. P. 17658-17661] provides for the use of liquid-phase systems, the solubility of ONCH in which decreases with increasing temperature. To implement this method, solutions of the ONCH components in polar aprotic solvents such as gamma-butyrolactone (GBL), dimethylformamide (DMF), or dimethyl sulfoxide (DMSO) are used.

One of the disadvantages of the above method is the need for the crystallization process, as well as the removal of single crystals from the solution at an elevated temperature (120-150C). A decrease in the temperature of a solution in contact with a single crystal can lead to its partial dissolution, nonselective etching of the surface, or the formation of side phases of crystal solvates. Another disadvantage of this method is the possibility of unwanted chemical reactions in solutions at elevated temperatures. In particular, even upon contact with trace amounts of oxygen in iodide solutions at temperatures above 100 ° C, a rapid oxidation of iodide ions to iodine is observed. In addition, at elevated temperatures, the solvent can decompose or enter into chemical reactions with organic cations ONCH. In particular, several studies have shown the possibility of participation of the most popular solvents for obtaining single crystals of solvents DMF and DMSO in trans-amidation reactions with methylammonium cations with the formation of ammonium and dimethylammonium cations [Lee M. V et al. Transamidation of dimethylformamide during alkylammonium lead triiodide film formation for perovskite solar cells // J. Mater. Res. 2016. Vol. FirstView. P. 1-11], [So F. (ed.). World Scientific Handbook of Organic Optoelectronic Devices (Volumes 1 & 2): Volume 1: Perovskite Electronics Volume 2: Organic Photovoltaics (OPVs). - World Scientific]. In this case, the resulting ammonium and dimethylammonium cations are able to integrate into the structure of ONCH with a perovskite structure, replacing methylammonium cations. In this case, such a substitution occurs uncontrollably and can lead to a change in the optoelectronic properties of ONCH.

The third method [Zhou H. et al. Antisolvent diffusion-induced growth, equilibrium behaviors in aqueous solution and optical properties of CH ₃ MH ₃ PbI ₃ single crystals for photovoltaic applications // RSC Adv. Royal Society of Chemistry, 2015. Vol. 5, no. 104. P. 85344-85349], assumes the slow addition of a component that reduces the solubility of ONCH (antisolvent) to a concentrated solution of ONCH in a polar solvent. As the antisolvent, weakly polar low-boiling organic solvents such as chlorobenzene, dichloromethane, chloroform, diethyl ether are typically used. Dilution of the solution with a non-dissolving ONCH antisolvent leads to a salting-out effect. As a result, the solubility of ONCH in the resulting mixed solution (solvent-antisolvent-ONCH) decreases so much that its supersaturation in ONCH is achieved and crystallization begins. This method mainly uses solvents such as DMSO, DMF, GBL.

However, the implementation of the above method requires the implementation of a controlled slow supply of the antisolvent or controlled diffusion of its vapors to the ONCH solution, in order to smoothly achieve supersaturation in the latter with respect to the crystallizable component, which is necessary to obtain large single crystals. In practice, as a rule, controlled vapor diffusion is used, which is implemented in a closed sealed volume, which contributes to the complication of the technical process. Significant technical inconveniences can also represent a significant duration of the process of obtaining single crystals by this method, which is about 1 week [Shi D. et al. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals // Science. - 2015. - T. 347. - No. 6221. - C. 519-522.].

In addition, many of the antisolvents typically used in the implementation of the above method are highly volatile and toxic and / or carcinogenic substances, for example, chlorobenzene, toluene, dichloromethane, chloroform.

It should be noted that the above method is applicable only for a limited set of ONCH compositions, due to the possible predominant crystallization of solvates caused by the presence of a coordinating solvent in the mixture. In addition, there is still no information on the applicability of this method to the preparation of layered halide perovskite-like phases with more than 1 layers with a perovskite structure, as well as mixed cationic and mixed anionic organo-inorganic perovskites.

The above method is in technical essence the closest to the claimed invention and is selected as a prototype.

Terminology used

In the framework of this application, the term organic-inorganic complex halide (OCH) means crystalline compounds with the general formula A _n BX _{(nz + k)} containing a singly or doubly charged organic cation A ^{z +} (z = 1, 2), as well as a polyvalent metal cation B ^{k +} (k = 2, 3, 4) and a halide or pseudohalide ion X ^- , while the ratio A / B = n can take values in the range from 0 to 4 (including non-integer n values) depending on the coordination number and valence B ^{k +} and crystal structure motif. In most practically important options for the implementation of the proposed method, A ^{z +} - is selected from the number of singly charged (z = 1) substituted ammonium cations (primary, secondary, tertiary, quaternary), formamidinium, gaunidinium, acetamidinium cations, or inorganic ammonium cations (NH ₄ ⁺ ), cesium (Cs ⁺ ) or rubidium (Rb ⁺ ), or doubly charged (z = 2) alkyldiammonium cations, B ^{k +} is a polyvalent cation of Pb, Sn or Bi, X ^- - Cl ^- , Br ^- , I ^- .

In particular cases of the implementation of the invention, ONCH can have a perovskite-like structure. The term perovskite-like structure in the framework of the present application is understood to mean both the perovskite structure itself and those derived from the perovskite structure type. The term "perovskite-like compounds" or "perovskite-like phases" in the framework of this application refers to compounds and phases with a perovskite-like structure.

In particular, the term "halide perovskite" in the framework of this application denotes phases with the formula ABX ₃ having a cubic syngony or any other lower syngony (eg, tetragonal, rhombic), as well as mixtures of different phases of halide perovskites. The structure of halide perovskites consists of a three-dimensional network of vertex-articulated [BX6] octahedra or distorted octahedra, consisting of a central atom, component B (B ^{n +} cation) and six X atoms (X ^- anions).

In particular, phases with a perovskite-like structure are understood as phases of the so-called layered perovskites containing layers of vertex-articulated octahedra or distorted octahedra of composition [BX6] (perovskite layers) in at least one plane, alternating with some other layers.

Within the framework of the present application, the components of GOCH are understood to mean cation A ^{z +} , cation B ^{k +} , and anion X ^- contained in solution, in the composition of GOCH or in the composition of reagents, which are dissolved in a solution composition to obtain single crystals of GOCH from it.

The term "solution composition" in the context of the present technical solution is used to mean any solvent or mixture of solvents, or mixture of solvents containing any dissolved solid (eg, salts) or gaseous components (eg, hydrogen halides).

Under the dissolving ability [Rogovin, Zakhar Aleksandrovich, T. 1: "Fundamentals of chemistry and technology for the production of chemical fibers", Publisher: Chemistry, 1974, p. 55] solution composition in relation to the compound (for example, ONKG) at a given temperature is understood as the value, measured in concentration units (moles per liter - M or any other), numerically equal to the solubility of a given compound in a given solution composition at a given temperature. The solubility of a compound in a solvent or solution composition is a value measured in units of concentration and numerically equal to the concentration of a saturated solution of a given compound in a given solvent (solution composition) at a given temperature T.

In the framework of this application, the term neutral solvent in relation to GOCH refers to any solvent that does not dissolve GOCH, decompose it and does not form compounds with it.

The term chemical conversion of compound N to compound M in the framework of this application denotes any process of chemical conversion of compound N into compound M, the necessary condition of which is the occurrence of a chemical reaction, at least one of the reagents in which is N, and at least one of the products which is M. Numerically, the degree of chemical conversion denotes the proportion of reagent M converted to product N, indicated in%.

In the context of the present application, single crystals are understood to mean ONCH crystals with a linear size in any direction of 5 μm or more.

Disclosure of the essence of the invention

A technical problem is the need to overcome the disadvantages inherent in known analogs and the prototype by creating a technologically simple method for forming ONCG single crystals of a given chemical composition and structure from a solution at a constant temperature, without adding an antisolvent to the solution and with low time costs.

The technical result achieved with the use of the claimed invention is to provide the possibility of reducing the solubility of the components of the ONCH in solution by chemical conversion of the solvent into a product that does not dissolve or poorly dissolves ONCH directly in the solution composition from which crystallization is carried out, which contributes to the production of single crystals of a given chemical composition from solution at a constant temperature, without the use of special equipment, without adding an antisolvent to the solution and with low time costs.

The claimed technical result is achieved by the fact that the method for producing single crystals of an organo-inorganic complex halide (ONCH) of composition A _n BX _{(nz + k)} , where z = 1-2, k = 2-4, 0 <n≤4, includes:

A) preparation of a mortar composition containing

- at least one polar solvent (S), the solubility of the ONCH in which is equal to (C, T ₁ );

- reagent (M), taken in an amount providing a molar ratio M / S from 0.05 to 15, intended for a chemical reaction with a solvent S and providing its chemical conversion, the product of which is at least one gaseous or liquid-phase compound, or their a mixture (S ₁ ), the solubility of the ONCH in which is equal to (C ₁ , T ₁ ), where C ₁ <C;

- components of ONCG, which are used as

- an organic cation A ^{z +} or an inorganic cation selected from ammonium (NH ₄ ⁺ ), cesium (Cs ⁺ ) or rubidium (Rb ⁺ ) cations, or a mixture thereof;

- polyvalent metal cation B ^{k +} ;

- halide or pseudohalide ion X ^- , while in the solution composition the concentration [A ^{z +} ] is from 0.1 M to 7 M, the concentration [B ^{k +} ] is from 0.1 M to 3.5 M, the concentration [X ^- ] is from 0.2 M to 10 M ,

when this solution composition has a concentration of ONCH equal or less than the solubility of ONCH (C ₁ , T ₁ ) in solution with a given ratio M / S;

B) maintaining the obtained solution composition at a constant temperature T1 until a chemical conversion of at least 10% S to S ₁ is achieved, which ensures the formation of ONCH single crystals.

As a chemical reaction can be used

- solvolysis, while lactones or carbonic acid esters are used as the polar solvent S, and water or alcohol is used as the reagent M, or a non-oxidizing protic acid or a mixture thereof;

- esterification with the formation of an ester or a simple ether, while alcohols or ether alcohols or their mixture with a carboxylic acid are used as the polar solvent S, and a protic acid that does not oxidize the halide or pseudohalide ions X ^- or its solution is used as the reagent M.

As a solvolysis reaction can be used

- hydrolysis, in this case, as a reagent M, water is used in its pure form or water in the composition of an aqueous solution of protic acid, non-oxidizing halide or pseudohalide ions X ^- ;

- alcohol, while alcohol is used as a reagent M in pure form or as part of an alcoholic solution of protic acid, which non-oxidizes halide or pseudohalide ions X ^- .

Oxolan-2-one, δ-valerolactone, ε-caprolactone are used as lactone, dimethyl carbonate, propylene carbonate or ethylene carbonate is used as a carbonic ester, and as a protic acid that does not oxidize halide or pseudohalide ions X ^- , hydrochloric acid ^is used, acid, trichloroacetic acid, trifluoroacetic acid, phosphorous acid, hypophosphorous acid, methanol, ethanol, propanol, butanol are used as alcohol.

Methanol, ethanol, isopropanol, ethylene glycol are used as alcohol, acetic acid, propionic acid are used as carboxylic acid, methoxyethanol, ethoxyethanol, ethoxypropanol are used as etheroalcohol. Constant temperature T1 is understood to mean any temperature above the freezing point of the solution composition, and below the boiling point of the lowest-boiling component of the solution composition, taking into account an error of +/- 5 ° C. The composition is held in the range from 5 minutes to 30 days.

The A ^{z +} cation is selected from among singly charged (z = 1) substituted ammonium cations (primary, secondary, tertiary, quaternary), formamidinium, gaunidinium, acetamidinium cations, or inorganic ammonium (NH ₄ ⁺ ), cesium (Cs ⁺ ), or rubidium cations ( Rb ⁺ ), or double-charged (z = 2) alkyldiammonium cations, as B ^{k +} polyvalent cations Pb, Sn or Bi are used, as X ^- anions Cl ^- , Br ^- , I ^- or SCN ^{- are used} .

Reagent M can be used in the composition of the solution composition in a mixture with an additional reagent that is not consumed directly during the chemical conversion of the polar solvent S; in this case, hydrogen halides, organic acids, inorganic acids, non-oxidizing halide or pseudohalide ions X ^- are used as such an additional reagent. An organic polar solvent that does not react with component M can be added to the composition of the solution composition.

The claimed invention is illustrated by the following images:

FIG. 1 shows a diffraction pattern of a powder of MAPbI ₃ single crystals obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 2 of Table 1 in the section "Examples of implementation of the invention".

FIG. 2 shows a photograph of MAPbI ₃ perovskite monocrystals obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 2 of Table 1 in the section "Examples of implementation of the invention".

FIG. 3. shows the diffraction pattern of single crystals ground into powder FA _0.8 MA _0.2 PbI ₃ , obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 4 of Table 1

FIG. 4 shows a photograph of single crystals of FA _0.8 MA _0.2 PbI ₃ perovskite obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 4 of Table 1.

FIG. 5a. Shown is a photograph of a single crystal of the layered perovskite-like phase BA ₂ PbI ₄ , obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 5 of Table 1.

FIG. 5b shows a diffraction pattern of BA ₂ PbI ₄ single crystals ground into powder, obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 5 of Table 1.

FIG. 6 shows a photograph of a single crystal of the layered perovskite-like phase BA ₂ MAPb ₂ I ₇ , obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 7 of Table 1.

FIG. 7. shows the diffraction pattern of single crystals of BA ₂ MAPb ₂ I ₇ ground into powder, obtained by implementing a particular case of the proposed method, the conditions of which are indicated in line No. 7 of Table 1.

Implementation of the invention

The key difference of the proposed method for crystallization of organo-inorganic complex halides (ONCH) from solution is a new approach to the creation of supersaturation in solution, which promotes the onset of crystallization. Supersaturation (i.e., the achievement of a concentration of ONCH exceeding the concentration of its saturated solution in the solution composition) in the proposed method is achieved by a gradual decrease in the amount of polar organic solvent (S) in the solution composition occurs due to its consumption in the chemical reaction added initially to the composition of the solution composition with reagent M, which can be another ONKG solvent and / or a neutral component. In general, the reaction equation can be written as:

S + M = S ₁ .

The products of such a reaction can be gaseous and / or liquid compounds (S ₁ ), while the latter should exhibit a reduced dissolving ability to GOCH compared to S. The course of a chemical reaction in time with the participation of (S) as a reagent and the formation of (S ₁ ) as a product in the composition of the solution composition leads to a gradual chemical conversion of the polar solvent (S).

The decrease in the amount of solvent S in the solution composition in the proposed method occurs without evaporation, extraction or other physical removal in unchanged form, but exclusively due to consumption in a chemical reaction with component M, which is also consumable. It should be noted that in the proposed method, the solubility of ONCH in the solution composition decreases without additional addition to it after the preparation of any components, and as a result of the change in the composition of the solution composition itself over time, due to the chemical conversion of the "original" polar solvent S into products S ₁ .

A necessary condition for lowering the solubility of ONCH in the solution composition during chemical conversion is the lower solubility of ONCH in a mixture of the final composition containing a reduced amount of polar organic solvent S and an additional amount of conversion products S ₁ . This condition is achieved if the limiting concentration (or solubility) of GOCH in the solvent S exceeds its limiting concentration in S ₁ . Thus, as S and S _{1, in} principle, any pair of compounds can be taken, where S is able to dissolve ONCH in a relatively high concentration (preferably more than 0.5 M), and S _{1 is} not able to dissolve ONCH or dissolves it only in a lower less than 10%) than the solvent S. In addition, there must be a chemical reaction that converts the reagent S into the product S ₁ (S + M = S ₁ ). Examples of pairs S and S ₁ satisfying the stated conditions are: ethylene carbonate (ONCH solubility: 0.5-1.2 M) and ethylene glycol (ONCH solubility: 0.05-0.1 M), propylene carbonate (ONCH solubility: 0.4-1.1 M) and propylene glycol (ONCH solubility: 0.05 -0.1 M), ethanol (the solubility of ONCH in the presence of acetonitrile is up to 1.3 M) and diethyl ether (the solubility of ONCH in the presence of any solvents is less than 0.1 M).

Thus, if during a given time in a solution composition containing a solvent S and having a concentration of ONCH - C ₁ equal to the solubility of this ONCH in a solution composition of a given composition at a temperature T ₁ , a chemical conversion of a certain fraction (X) of solvent S into S ₁ was achieved, the solubility of a given ONCH in which is (C ₂ ), such that C ₂ <C ₁ , then in this solution composition supersaturation with respect to ONCH will inevitably be achieved and its crystallization will begin. It has been experimentally determined that the condition for the precipitation of single crystals from such a solution composition is to achieve a chemical conversion of at least 10% of the solvent S.

In the general case of the implementation of the proposed method to obtain single crystals, a solution composition is used with a concentration of ONCH O less than the solubility of this ONCH in a solution composition of this composition at a temperature T ₁ . In this case, the minimum fraction X of the solvent S that underwent chemical conversion S ₁ (or the minimum degree of chemical conversion) required for the initiation of crystallization can be determined as follows:

X≥ (C ₁ ) / (C ₂ ).

Among the chemical reactions used in the implementation of the claimed invention, two main groups can be distinguished, providing chemical conversion of the polar solvent and leading to a decrease in its concentration in the solution composition:

1) Solvolysis reactions involving at least one polar organic solvent S and a reagent M in the composition of a solution composition with the formation of liquid-phase or gaseous products, or their mixtures (S ₁ );

2) Esterification reactions involving at least one polar organic solvent (S) and reagent M in the composition of the solution composition with the formation of liquid-phase or gaseous products, or their mixture (S ₁ ).

In the first (1) case of the implementation of the proposed method, the hydrolysis reaction is used as a solvolysis reaction with the formation of liquid-phase components, the solubility of ONCH in which is lower than in the initial polar solvent. In this case, carbonic acid esters carbonates (propylene carbonate, ethylene carbonate and others), as well as lactones and other cyclic esters of carboxylic acids (3,6-dimethyl-1,4-dioxane-2,5-dione , 1,4-dioxane-2,5-dione, etc.), and water acts as a reagent M, in pure form or in a mixture with any other components (including hydrogen halides, organic acids and solvents). In particular, water can be added to the composition of the solution composition in the composition of concentrated acid solutions. However, regardless of the presence of additives, water remains the reagent involved and consumed in the hydrolysis reaction, so the molar ratio M / S is calculated precisely in relation to water as reagent M.

In particular, during the hydrolysis of ethylene carbonate and propylene carbonate, dibasic alcohols (S ₁ ) are formed - ethylene glycol and propylene glycol, respectively, in which the solubility of any GOCH is lower than the solubility of these GOCH in ethylene carbonate and propylene carbonate. Thus, as the hydrolysis proceeds, the amount of the polar solvent S in the reaction composition decreases, as a result of which the solubility of the ONCH decreases. Also, during the hydrolysis of carbonic acid esters, carbon dioxide (CO ₂ ) is formed, which escapes from the solution composition and does not affect the solubility.

In particular cases of the implementation of the proposed method, oxolan-2-one, δ-valerolactone, ε-caprolactone are used as a solvent S, subjected to chemical conversion due to hydrolysis, during the hydrolysis of which in an acidic medium, 4-hydroxybutanoic acid, 5-hydroxyvaleric acid are formed, respectively (S ₁ ), ε-hydroxycaproic acid, which are not able to dissolve ONCH at a concentration higher than 0.1 M. Since the solubility of various ONCH in these lactones is about 0.5-1.5 M, which makes it possible to obtain ONCH single crystals from solution compositions containing these solvents.

Acceleration of the chemical conversion of solvent S due to hydrolysis allows one to obtain crystals in high yield. A concentrated acid or acid solution can be added to the solution composition to accelerate the hydrolysis reaction. The most convenient is the addition of concentrated aqueous solutions of hydrohalic acids - HX (HCl _conc. , HBr _conc. , HI _conc. ) Since they contain the same anions as the crystallized substance (ONGA) and do not contaminate it. Also used are carboxylic acids and halogenated carboxylic acids, in particular trichloroacetic acid, as well as non-oxidizing inorganic acids, in particular phosphorous acid. The molar ratio of acid to solvent (HX / S) in the solution composition is selected in the range from 0.01 to 2.

In the second case of the implementation of the proposed method, the alcoholysis reaction is used as the solvolysis reaction. In this case, carbonic acid esters, carbonates (propylene carbonate, ethylene carbonate and others), as well as lactones, are used as the polar solvent (S), and alcohol or a mixture of alcohol with any other components (including hydrogen halides, acids and solvents). In this case, regardless of the composition of reagent M, the chemical component involved and consumed in the hydrolysis reaction is alcohol; therefore, the molar ratio M / S is calculated precisely in relation to the amount of alcohol in reagent M.

In the above case, the implementation of the proposed method as products of solvolysis (S ₁ ) can be glycols, ethers (diethyl glycol) or ether alcohols (monoethyl glycol), as well as dialkyl carbonates. The formation of solvolysis products was investigated and confirmed by Raman spectroscopy and NMR spectroscopy. In all of these liquid-phase alcoholysis products (S ₁ ), ONCH have a solubility of no higher than 0.1-0.2 M, which makes it possible to use alcoholysis reactions with the participation of monobasic alcohols for the chemical conversion of polar solvents and decrease the solubility of ONCH in the reaction mixture as the alcoholysis reaction proceeds ...

In a particular case of the implementation of the proposed method, single crystals of ONKG of the composition BA ₂ PbI ₄ and (NH ₄ ⁺ ) ₃ Bi ₂ I ₉ were obtained by keeping a mixture of ethylene carbonate (S), ethanol (M), and trichloroacetic or hydroiodic acid (HX / S <0.1) at 40 ° C for 3-6 hours.

In another case of the implementation of the proposed method, the polar solvent (S) enters into an esterification reaction with component (M) or one of the reagents in the composition of component M with the formation of an ester or simple ether that does not dissolve ONCH, which provides a decrease in solubility, achievement of supersaturation of the initial solution and crystallization ... In this case, alcohols and mixtures of alcohols and carboxylic acids are used as the polar solvent S.

In a particular case of the implementation of the proposed method, single crystals of ONCH of the composition MAPbBr ₃ were obtained by keeping a mixture of acetic acid (S), ethanol (M), and hydrobromic acid (HX / S <0.1) at 70 ° C for 3 hours.

It should be noted that it is known from the prior art that non-cyclic esters of carboxylic acids and ethers do not dissolve ONCH, therefore, in principle, crystallization of ONCH is possible from any solution composition containing a monobasic alcohol and carboxylic acid when creating conditions for esterification. In particular cases, to accelerate the esterification reaction, acids or aqueous solutions of acids, in particular, hydrohalic acids (HCl _conc. , HBr _conc. , HI _conc. ) Are added to the solution composition.

It should be noted that in all these implementations of the proposed method, the formation of single crystals is achieved by keeping the solution composition at a constant temperature with an accuracy of +/- 5 ° C. According to experimental data, deviations of the temperature from the initially specified by 5 ° C up or down leads to certain variations in the sizes of single crystals obtained over a given period of time. In this case, obtaining ONKG crystals of the same composition and structure from solutions of an identical composition using the proposed method is possible at different temperatures. It is preferable to implement the method at constant temperatures in the range from 25 ° C to 70 ° C, however, it has been experimentally established that its implementation is fundamentally possible at any temperature above the freezing point of the solution composition used and below the boiling point of the solution composition.

Carrying out the process at a lower temperature (T1 <25 ° C) leads to a slowdown in the chemical conversion of the solvent (S) and a slower achievement of supersaturation, which leads to a slowdown in the rate of formation of nuclei of ONCH crystals. As a result, the formation of larger single crystals (> 3 mm) is achieved. Carrying out the process at an elevated temperature (T1> 50 ° C) leads to a faster chemical conversion of the solvent (S) and to a rapid achievement of supersaturation of the solution composition in terms of ONCH (from tens of minutes to hours), which leads to the formation of a large number of small crystals (<1 mm). Thus, by setting the temperature T1, it is possible to control the size of the forming single crystals, which is demonstrated in the examples of the implementation of the method presented in Table 1.

Regardless of the specific composition of the solution composition, the implementation of the proposed method for producing ONKG crystals involves 2 main stages:

1) preparation of a solution composition containing ONCH components in a stoichiometric ratio, a polar solvent (S) entering into a chemical reaction and consumable, as well as a reagent (M) participating in the reaction with the solvent or providing its course.

2) maintaining the resulting mixture at a given temperature for a given time - either until the desired mass of crystals (yield) is obtained, or until monocrystals of the desired size are formed

The crystals are then taken out of the solution and, if necessary, washed with a neutral solvent (eg ethyl acetate).

Solvent S and reagent M in the initial solution composition are taken in a molar ratio M / S from 0.05 to 15, since this is the range that makes it possible to obtain single crystals. In this case, the reagent M can be added as in its pure form, in a mixture with any additional reagent other than the organic polar solvent S and not consumed directly during the chemical conversion of the polar solvent S. Thus, in particular cases of the invention, the reagent M is used directly water, as well as water in the composition of solutions of organic and inorganic acids (including concentrated) that do not oxidize halide or pseudohalide ions X ^- under the conditions of the conversion process (C ₁ , T ₁ ). In this case, the presence of additional components is not taken into account when calculating the molar ratio M / S, only the amount of substance of component M is taken into account.

The boundary values of the molar ratio M / S were determined empirically, for which:

1) Prepared a solution composition comprising

a) polar solvent S, which was taken as ethylene carbonate (EC) or propylene carbonate (PC)

b) reagent M, which was taken as an aqueous solution of concentrated hydroiodic acid (HI + H ₂ O) in the amount necessary to achieve this ratio H ₂ O / EC (H ₂ O / RS) in the solution composition

2) The solution composition (1) was added to the MAPbI ₃ (ONKG) powder, kept for 5 minutes with stirring, the saturated solution over the precipitate was taken and filtered

3) The filtered solution was saturated MAPbI solution composition ₃ (1) with the ratio H ₂ O / EC separated and kept separate portions at temperatures of 20 ° C and 80 ° C until the beginning of the formation of single crystals.

As a result, a solution composition with a ratio H ₂ O / EC = 0.05 fixed formation MAPbI ₃ single crystals after standing at 80 ° C for 12 hours, at a temperature of 20 ° C - for 36 hours, whereas the mortar compositions with a ratio H ₂ O / EC <0.05, no single crystal precipitation was observed even after holding for 7 days, regardless of temperature.

Similarly, when the solution composition prepared as described above was kept with a H ₂ O / EC = 15 ratio, the formation of single crystals was recorded at a temperature of 80 ° C for 8 hours, at a temperature of 20 ° C - within 24 hours, however, no single crystals were formed. even after standing for 7 days regardless of temperature.

For mortar compositions of a different composition, in particular, such as HI-H2O-propylene carbonate, CH ₃ COOH-H ₂ O-propylene carbonate, and for ONCG of various compositions (in particular, BA ₂ PbI ₄ , MAPbI ₃ , MA ₃ Bi ₂ I ₉ ) and any concentrations of ONCH, the experimentally determined lower limit of the M / S ratio, which allows crystallization, is greater than or equal to 0.05.

In particular cases of the implementation of the proposed method, in addition to the polar solvent undergoing a chemical reaction, the composition of the solution composition may include additional polar solvents that do not interact with the resulting OPKG, do not decompose or dissolve it in the presence of s ₁ , for example, acetonitrile (see examples in Table 1), nitromethane.

For the introduction of ONCH components into a solution at a given concentration, it is possible to use any soluble reagents (precursors) containing ONCH components (organic cation A ^{z +} (z = 1, 2) or an inorganic cation selected from NH ₄ ⁺ , Cs ⁺ , Rb ⁺ cations; polyvalent metal cation B ^{k +} (k = 2-4); halide or pseudohalide ion X ^- ). For convenience, in most of these examples of the synthesis of single crystals (Table 1), organic cation halides (MAI - methylammonium iodide, MABr - methylammonium bromide, FAI - formamidinium iodide, BAI - butylammonium iodide) and metal halides (PbI ₂ , PbBr ₂ , BiI ₃ ).

Examples of implementation of the invention

Table 1 shows the main significant parameters of the process of forming ONCG single crystals using the proposed method.

The amounts of reagents used to form ONCH single crystals of a given composition are indicated in the second column of the table; the third column indicates the initial composition of the solution composition (the amount of solvents immediately at the time of mixing); the fourth column indicates the temperature of the synthesis and the time during which it was carried out; the fifth column indicates the obtained crystalline phase according to X-ray phase analysis and the total mass of crystals obtained from the indicated amount of reagents; the sixth column shows the average crystal size.

The components of the GOCG in the presented table are:

in examples No. 1, 2, 3 methylammonium cation (MA ⁺ ) as the organic cation A ^{z +} , the Pb ²⁺ cation as the polyvalent metal cation B ^{k +} and iodide anion (I ^- ) as the anion X ^- ;

in example No. 4, methylammonium (MA ⁺ ) and formamidinium (FA ⁺ ) cations were taken as the organic cation A ^{z +} , the Pb ²⁺ cation was taken as the polyvalent metal cation B ^{k +,} and the iodide anion (I ^- ) was taken as the X ^- anion;

in examples No. 5, 6, butylammonium cation (BA ⁺ ) was taken as the organic cation A ^{z +, the} cation Pb ^{2+ was} taken as the polyvalent metal cation B ^{k +,} and the iodide anion (I ^- ) was taken as the anion X ^- ;

in example No. 7, methylammonium cation (MA ⁺ ) was taken as the organic cation A ^{z +, the} cation Pb ^{2+ was} taken as the polyvalent metal cation B ^{k +,} and the bromide anion (Br ^- ) was taken as the X ^- anion;

in example No. 8, methylammonium (MA ⁺ ) and butylammonium (BA ⁺ ) cations were taken as the organic cation A ^{z +} , the Pb ²⁺ cation was taken as the polyvalent metal cation B ^{k +,} and the iodide anion (I ^- ) was taken as the X ^- anion;

in example No. 9, the ammonium cation (NH ₄ ⁺ ) was taken as the A ^{z +} cation, the bismuth cation (Bi ³⁺ ) was taken as the polyvalent metal cation B ^{k +} , and the X ^- anion was the iodide anion (I ^- );

in example No. 10, methylammonium (MA ⁺ ) and formamidinium (FA ⁺ ) cations were taken as the organic cation A ^{z +} , the Pb ²⁺ cation was taken as the polyvalent metal cation B ^{k +} , and iodide (I ^- ) and bromide ^were taken as the X anion (Br ^- ) anions;

in example No. 11 the ethylenediammonium cation (EDA ²⁺ ) was taken as the organic cation A ^{z +, the} cation Pb ^{2+ was} taken as the polyvalent metal cation B ^{k +,} and the iodide anion (I ^- ) was taken as the X ^- anion.

For all examples in Table 1, for the composition of the solution composition, the organic solvent undergoing chemical conversion is indicated first. In particular, in examples No. 1, 2, 3, the solvent (S) to be converted is propylene carbonate, which undergoes hydrolysis under the action of water (reagent M) E added in the composition of a concentrated solution of hydroiodic acid HI _conc. (hydrogen iodide - an additional reagent), with the formation of carbon dioxide and propylene glycol (S ₁ ), which does not dissolve the crystallization product (MAPbI ₃ ). In examples # 4, solvent S is ethylene carbonate hydrolyzed to ethylene glycol (S ₁ ) under similar conditions; in example # 5, solvent S is a mixture of ethylene carbonate and diethyl carbonate hydrolyzed to ethylene glycol and ethanol (S ₁ ), respectively. In examples No. 6, 7 solvent S is ethanol, component M is acetic acid, which in the presence of a strong acid (HI _conc. / HBr _conc. ) Undergo esterification to form ethyl acetate (S ₁ ), which does not dissolve the crystalline product. Example No. 9 illustrates a particular case of the solvolysis reaction involving ethylene carbonate (S) and ethanol (M) in the presence of an additional reagent -HI _conc. acting as a catalyst.

Lines No. 1-3 in Table 1, using the example of organic-inorganic perovskite MAPbI _3, illustrate the possibility of controlling the growth rate of single crystals and their size in the proposed method. In all three experiments, the initial composition of the solution composition was taken the same, but then the solutions were kept at 3 different temperatures. At a maximum temperature of 60 ° C, the highest crystallization rate is observed; as a result, more than 70% of the solute (MAPbI ₃ ) precipitates as a crystalline precipitate in 2 hours. The size of the crystals in this case turns out to be minimal due to the rapid decomposition of the solvent at elevated temperatures and, accordingly, the rapid achievement of supersaturation of the solution. The maximum crystal size is observed at the minimum temperature (20 ° C), due to the slowest decrease in the solvent concentration and, accordingly, lower solution supersaturation, which promotes the slow growth of large crystals.

Claims (21)

1. A method of obtaining single crystals of an organic-inorganic complex halide (ONCH) of composition A _n BX _{(nz + k)} , where z = 1-2, k = 2-4, 0 <n≤4, including: A) preparation of a mortar composition containing - at least one polar solvent (S), the solubility of the ONCH in which is equal to (C, T ₁ ); - reagent (M) in an amount providing a molar ratio M / S from 0.05 to 15, intended for a chemical reaction with a solvent S and providing its chemical conversion, the product of which is at least one gaseous or liquid-phase compound, or a mixture thereof ( S ₁ ), the solubility of ONCH in which is equal to (C ₁ , T ₁ ), where C ₁ <C; - components of ONCG, which are used as - organic cation A ^{z +} or an inorganic cation selected from ammonium (NH4 ⁺ ), cesium (Cs ⁺ ) or rubidium (Rb ⁺ ) cations, or a mixture thereof; - polyvalent metal cation B _k ⁺ ; - halide or pseudohalide ion X ^- , while in the solution composition the concentration [A ^{z +} ] is from 0.1 M to 7 M, the concentration [B _k ⁺ ] is from 0.1 M to 3.5 M, the concentration [X ^- ] is from 0.2 M to 10 M, wherein the solution composition has a concentration of ONCH equal or less than the solubility of ONCH (C ₁ , T ₁ ) in solution with a given M / S ratio; B) maintaining the obtained solution composition at a constant temperature T1 until a chemical conversion of at least 10% S to S ₁ is achieved, which ensures the formation of ONCH single crystals. 2. The method according to claim 1, characterized in that solvolysis is used as a chemical reaction, while lactones or carbonic acid esters are used as polar solvent S, and water or alcohol or protic acid-non-oxidizing agent or their mixture is used as reagent M ... 3. A method according to claim 2, characterized in that hydrolysis is used as the chemical reaction of solvolysis, and as reagent M, water is used in its pure form or water in the composition of an aqueous solution of protic acid that does not oxidize halide or pseudohalide ions X ^- . 4. The method according to claim 3, characterized in that alcoholysis is used as the chemical reaction of solvolysis, and alcohol is used as the reagent M in pure form or as part of an alcoholic solution of protic acid that does not oxidize halide or pseudohalide ions X ^- . 5. The method according to claim 1, characterized in that esterification is used as a chemical reaction with the formation of an ester or a simple ether, while alcohols or ether alcohols or their mixture with a carboxylic acid are used as a polar solvent S, and a protic an acid that does not oxidize halide or pseudo-halide ions X ^- , or a solution thereof. 6. The method according to claim 3, characterized in that oxolan-2-one, δ-valerolactone, ε-caprolactone are used as the lactone, dimethyl carbonate, propylene carbonate or ethylene carbonate is used as the carbonic ester, and as the protic acid, which does not oxidize halide or pseudohalide ions X ^- , use hydrohalic acid, acetic acid, trichloroacetic acid, trifluoroacetic acid, phosphorous acid, hypophosphorous acid, as alcohol used methanol, ethanol, propanol, butanol. 7. The method according to claim 6, characterized in that methanol, ethanol, isopropanol, ethylene glycol are used as alcohol, acetic acid, propionic acid are used as carboxylic acid, methoxyethanol, ethoxyethanol, ethoxypropanol are used as etheroalcohol. 8. A method according to claim 1, characterized in that constant temperature T1 is understood as any temperature above the freezing point of the solution composition and below the boiling point of the lowest-boiling component of the solution composition. 9. The method according to claim 1, characterized in that the aging of the composition is carried out in the range from 5 minutes to 30 days. 10. The method according to claim 1, characterized in that the cation A ^{z + is} selected from among singly charged (z = 1) substituted ammonium cations (primary, secondary, tertiary, quaternary), formamidinium, gaunidinium, acetamidinium cations, or inorganic ammonium cations ( NH4 ⁺ ), cesium (Cs ⁺ ) or rubidium (Rb ⁺ ) or doubly charged (z = 2) alkyldiammonium cations, polyvalent Pb, Sn or Bi cations are used as B _k ⁺ , as X ^- anions Cl ^- , Br ^{- are used} , I ^- or SCN ^- . 11. The method according to claim 1, characterized in that the reagent M is added to the composition of the solution composition in a mixture with an additional reagent that is not consumed directly during the chemical conversion of the polar solvent S, while hydrogen halides, organic acids, inorganic acids are used as an additional reagent , non-oxidizing halide or pseudohalide ions X ^- . 12. The method according to claim 1, characterized in that an organic polar solvent not participating in the reaction with component M is added to the composition of the solution composition.

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