Field of the invention

The claimed invention relates to the field of materials science, namely, to methods of manufacturing for films made of crystalline materials. The crystalline material film obtained by the claimed method can be used, for example, for production of semiconductor applications, in particular, solar cells.

Background

Organic-inorganic complex halides and, in particular, perovskite-like lead halides are advanced materials for use in semiconductor devices, for example, as a light-absorbing material in solar cells, photodetectors, LEDs, etc. Thin films of these compounds are used to create planar semiconductor devices, such as solar cells. At the moment, there is a wide range of methods for obtaining hybrid lead halide films with a perovskite-like structure to create solar cells based thereon - the so-called Perovskite solar cells. The review paper (Park, Nam-Gyu, and Kai Zhu. 'Scalable fabrication and coating methods for perovskite solar cells and solar modules.' Nature Reviews Materials (2020): 1-18.) discloses main scalable approaches for the synthesis of hybrid lead halide films for the moment. Most often, the production of such compounds can be regarded as a binary reaction between a lead salt and an organic halide, e.g., for so called 3D perovskitelike lead halides and the most common model compound MAPbk (MA = CfLNHL) Pbb + MAI — MAPbE. In the vast majority of cases, this synthesis scheme is implemented in one stage (crystallization from the precursor solution applied to the substrate, simultaneous gas-phase deposition of precursors) or two stages (two-stage methods, in which each of the precursors is applied to the substrate separately, for example, using the solution or gas-phase approaches and then conditions for a complete chemical reaction between the compounds are to be created).

Alternative precursors can be metallic lead films and reactive polyhalide melts (RPMs). Their application was first described in WO2018124938A1.

In this case, films of semiconductor materials are produced, for example, by depositing RPM of mixture AX-X2 onto a Pb (or its compounds) film, where AX is an organic or inorganic halide and B2 is a halogen. This method has a number of advantages over classical approaches because it does not require the use of lead salt solutions and allows using a metal as the initial precursor. Metallic films are potentially more technologically advanced precursors as there is a number of proven industrial approaches for their application, such as vacuum magnetron sputtering. A disadvantage of the known method is the technical complexity of homogeneous applying of stoichiometric amount of RPM onto the surface of the metal (metal-containing precursor) to provide the target functional properties of the final film.

The problem of difficulty in achieving homogeneous application of RPM over the surface of the precursor film is partially solved when using RPM solutions instead of pure reactive polyhalides (similar solutions are disclosed in the publications RU 2712151 and RU 2685296). This approach is also described in [Belich, N. A., Petrov, A. A., Rudnev, P. O., Stepanov, N. M., Turkevych, I., Goodilin, E. A., & Tarasov, A. B. (2020). From metallic lead films to perovskite solar cells through lead conversion with polyhalides solutions. ACS Applied Materials & Interfaces]. These publications disclose a method based on applying of the AX-X2 mixture with a solvent or inhibitor of their reaction with a metal-containing precursor onto a film of the metal-containing precursor.

A potential disadvantage of these methods is the fundamental necessity of dosing the liquid containing AX and X2 onto the metal or metal-containing precursor, which complicates the synthesis procedure.

The closest by the technical essence to the claimed invention is the method described in publications WO2017195191, CN104250723B, as well as in papers [Rakita, Yevgeny, et al. "Metal to halide perovskite (HaP): an alternative route to HaP coating, directly from Pb (0) or Sn (0) films." Chemistry of Materials 29.20 (17): 8620-8629] n [He, Yingying, et al. "Using elemental Pb surface as a precursor to fabricate large area CH3NH3PbI3 perovskite solar cells." Applied Surface Science 389 (2016): 540-546]. Within the framework of the approach described in these publications, the film of metallic lead or tin is immersed into a solution of organic halide (AX) and iodine (X2) in an alcohol, whereby the metal is oxidized to form a hybrid halide film with a perovskite-like structure. A disadvantage of these approaches is the choice of the solvent system based on isopropyl alcohol to implement this experimental scheme, which leads to the production of films with non-optimal morphology and non-optimal functional properties. As a result, the power conversion efficiency of perovskite solar cells produced by these methods does not exceed 5%.

The technical problem to be solved by means of the claimed invention is the necessity to overcome the disadvantages inherent in analogues and prototypes at the expense of creation of a more simple and economic method for producing films of crystalline materials and, in particular, films of organic-inorganic complex halides, characterized by improved functional characteristics of the materials produced, in particular, by increase in the efficiency of the solar cells produced using the claimed method up to 13% and more.

Disclosure of invention The technical result achieved by using this invention consists of increasing the homogeneity of the obtained films of organic-inorganic complex halides by reducing the number of pinholes and reducing the surface roughness of the film, which contributes to improving the efficiency of the films when they are used as a light-absorbing material in thin- film solar cells.

The advantages of the claimed method are also the simplicity of synthesis implementation: chemical reaction occurs when a film of the metal-containing precursor is immersed into the reaction solution without necessity of dosed solution applying onto the surface of the metalcontaining precursor film, which provides higher controllability and reproducibility of the synthesis procedure with increase in the size of the film produced (as compared to RU 2712151 and RU 2685296). The solar cell based on the film produced by the claimed method is characterized by an increased efficiency (13% and higher) as compared to the prototype.

The claimed technical result is achieved by the fact that the method of producing a film of organic-inorganic complex halide with perovskite-like structure includes the following stages:

I) forming a layer of reagent B or B' on the carrier substrate;

II) bringing the layer surface of reagent B or B' into interaction with reagents AX and X2;

III) providing the reactive conversion course of the applied reagents; therefore in order to implement stage II the film, obtained at stage I, is immersed into a solution of the mixture of reagents AX and X2 into an organic solvent, and is keeping until completion of the reactive conversion to ensure the correct course of reaction B7B + AX + X2 — ► A _n BX( _nz +k) + ¥', where B represents the metal, B' represents the oxide or salt of B, AX represents organic or inorganic halide, X2 represents molecular halogen, A _n BX( _nz +k) represents organic-inorganic complex halide (OICH), Y' is a reaction by-product, z = 1, 2; k = 2, 3, 4; n = 0 -4, including noninteger values of n. The layer of reagent B or B' is a film that is formed on the top layer of the carrier substrate made of a material that is inert with respect to reagents B or B', AX and X2. The substrate top layer material is selected from among transparent conductive oxide materials, namely ITO, FTO, IZO, IO:H, NiO, or other alloyed oxide materials based on oxides of nickel, tin, indium and zirconium or other conductive materials, Ceo, PCBM, PEIE, TaTm, NPD, Cui, CuO _x , CU2O, PTAA, Spiro-TTB, CuGaO2 or their mixtures. One of the following metals or their mixture is used as reagent B: Pb, Sn, Bi, Cu, Eu, Sb, Cd, Ge, Ni, Mn, Fe, Co, Yb, Pd. Reagent B' is a halide, chalcogenide, nitrate or carbonate of B. The thickness of layer B or B' is selected in the range from 10 to 1000 nm. Reagent B(B') is applied using the application methods relevant to the listed classes of compounds, namely, by vacuum, gas or solution methods. As a reagent X2, one of the halogens I2, Br2, Ch or their mixture is selected. Anions of halogens (T, Br , Cl"), SCN’ or their mixtures are used as component X in reagent AX. Inorganic and organic cations as well as their mixtures are used as component A in reagent AX. Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , NH ₄ ⁺ , CU ⁺ , Pd ⁺ , Pt ⁺ , Ag ⁺ , Au ⁺ , Rh ⁺ , Ru ⁺ or their mixtures are used as inorganic cation A. Single charge substituted ammonium cations (NR ¹ R ² R ³ R ⁴ ) ⁺ with various organic substituents (R) containing the following functional groups such as aromatic fragments, diene groups, functional groups containing oxygen (hydroxyl, carbonyl, carboxyl), nitrogen (amino group, cyano group, etc.), sulphur (thiols, sulphoxides, etc.) or H atom are used as an organic cation A. As an organic solvent for reagents AX and X2, the solvent belonging to the number of inert or weak ones with respect to the organic-inorganic complex halides, characterized by the following parameters: (DN (Donor number) < 20 kCal/mol, p (Dipole moment) < 2.5 D, 6HB (Hansen parameter) < 10 (MPa) ^1/2 ) is used. Chloroform, chlorobenzene, o- dichlorobenzene, m-dichlorobenzene, p-xylene, toluene, dichloromethane, benzene, diethyl ether, anisole, iodobenzene, phenethole, decane, hexane, m-xylene, dibenzyl ether, bromobenzene, mesitylene, styrene, ethylbenzene, heptane, diethylcarbonate, 1,2-dichloroethane, ethylbenzene, ethyl acetate, tetrahydro furan, dioxane, etc., as well as their mixtures are used as the organic solvent. The solvent further comprises the addition of a solvent that is not inert or weak with respect to the organic-inorganic complex halides, namely, isopropyl alcohol, ethyl alcohol or butyl alcohol in an amount not exceeding 10 vol.%. The concentration of AX in the solution is from 0.001 mg/ml to 500 mg/ml, the concentration of X2 in the solution is from 1 to 500 mg/ml. At stage II, the substrate and solution temperatures are maintained between -20 °C and 200 °C. At stage II, the substrate is treated with the solution for a time ranging from 1 second to 48 hours. The film after treating with the solution is additionally subjected to posttreatment, which consists of washing the substrate in organic solvents, heat treatment at a temperature from 30 to 400°C for 1 to 7200 seconds or treatment in vacuum, in an atmosphere of inert gas, dry air, humid air, methylamine dimethylformamide (DMF) vapours, dimethylsulphoxide (DMSO), halogen vapours, or irradiation with visible, UV or IR light, or treatment with a solution solvent or a combination of the above-listed post-treatment types.

The key feature of the claimed approach is that the organic solvent for the reagents AX and X2 is an organic solvent belonging to the number of inert or weak ones with respect to the organic-inorganic complex halides. Such solvents are characterized by the following parameters: DN (Donor Number) < 20 kCal/mol, p (Dipole moment) < 2.5 D, 6HB (Hansen Parameter) < 10 (MPa) ^1/2 ). In particular, this type of solvents include chloroform, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-xylene, toluene, dichloromethane, benzene, diethyl ether, anisole, iodobenzene, phenethole, decane, hexane, m-xylene, dibenzyl ether, bromobenzene, mesitylene, styrene, ethylbenzene, heptane, diethylcarbonate, 1,2-dichloroethane, ethylbenzene, ethyl acetate, tetrahydro furan, dioxane, etc., as well as their mixtures. A more detailed description of this classification type of organic solvents is given in the publication [Tutantsev, Andrei Sergeevich, Natalia N. Udalova, Sergey A. Fateev, Andrey A. Petrov, Wang Chengyuan, Eugene G. Maksimov, Eugene A. Goodilin, and Alexey B. Tarasov. 'New Pigeonholing Approach for Selection of Solvents Relevant to Lead Halide Perovskites Processing.' The Journal of Physical Chemistry C (2020)].

The use of this solvent type avoids deterioration of the target film morphology, which may occur, in particular, in alcohol solvents which were used in the solutions being the closest as to the technical essence (WO2017195191, CN104250723B). The classical alcohols do not fit the criteria for the selection of optimal solvents described within the scope of this invention, as, for example, isopropanol, ethanol, methanol and butanol have 6HB > 15.

The recrystallization processes of hybrid perovskite films in alcohol solvents and deterioration of their morphology caused thereby are described, for example, in publication [Hsieh, Tsung-Yu, et al. "Crystal growth and dissolution of methylammonium lead iodide perovskite in sequential deposition: correlation between morphology evolution and photovoltaic performance." ACS Applied Materials & Interfaces 9,10 (2017): 8623-8633.]. According to the authors of this paper, the partial dissolution of lead compounds with the formation of [PbE] ² ' ions occurs in alcohol solvents containing organic iodides, which leads to a change in the film morphology and formation of pinholes therein. In solvents, which are inert or weak with respect to organic-inorganic complex halides, such effects of dissolution-recrystallization of lead- containing compounds are less pronounced. As a result, when hybrid perovskites are incubated in solvents of this type, no film recrystallization with the formation of pinholes is observed.

The claimed invention is explained by the following illustrations:

Fig.l on the left shows a microphotograph of the film of hybrid halide with a perovskitelike structure CH3NH3PM3 (MAPbh) produced by the claimed method. The diffractogram of this film is shown on the right (reflections relating to MAPbh are denoted with '*'). An expert will evidently recognize a relatively large crystallite size in the film (which confirms the improvement of the functional properties of the film) and the absence of impurities of unreacted components of reaction, such as metallic Pb.

Fig.2 on the left shows the IV-curve of a perovskite solar cell with FTO / TiO2 / SnO2 / MAPbh / Spiro-OMeTAD / Au architecture, in which the MAPbh film has been produced by the claimed method. Time dependence of the power conversion efficiency of the given solar cell is shown on the right, which is obtained by tracing the maximum power point. The resulting power conversion efficiency is substantially higher than that achieved in the closest counterparts, WO2017195191, CN104250723B. Fig.3 on the left shows a microphotograph of the film of hybrid halide with a perovskitelike structure MA _x FAi- _x PbI _y Br3- _y (MA = CH3NH3 ⁺ , FA =(NH2)2CH ⁺ ) produced by the claimed method. The diffractogram of this film is shown on the right (reflexes relating to MA _x FAi- _x PbIyBr3-y are denoted by '*'). An expert will evidently recognize a relatively large crystallite size in the film (which confirms the improvement of the functional properties of the film) and the absence of impurities of unreacted components of reaction, such as metallic Pb.

Fig.4 shows a photograph of the film MA _x FAi- _x PbI _y Br3- _y with the area of about 30 cm ² produced by the claimed method. The visual homogeneity of the film indicates the potential for further scaling of this synthesis method.

Terminology used

The following are selected terms and definitions used within the description of the claimed invention for the best understanding of its essence.

Perovskite-like structure, both the perovskite structure itself and structures derived from the perovskite structural type. The term 'perovskite-like compounds' or 'perovskite-like phases' for the purposes of this application refers to compounds and phases with a perovskite-like structure.

Halide with a perovskite-like structure or halide perovskite compounds with the ABX3 formula having a cubic crystal system or any other lower crystal system (for example, tetragonal, rhombical) as well as mixtures of various phases of halide perovskites. The structure of halide perovskites consists of a three-dimensional framework of corner-connected octahedrons [BXe] or distorted octahedrons consisting of a central atom - component B (cation B ⁿ⁺ ) and six atoms X (anions X'). In particular, phases of the so-called layered perovskites, whose formula differs from ABX3 are implied. Such compounds contain layers of corner-connected octahedrons or distorted octahedrons of [BXe] composition (perovskite layers) in at least one plane alternating with some other layers (for example, Aurivillius phases, Ruddlesden-Popper phases, Dion- Jacobson phases).

Organic-inorganic complex halide (OICH) refers to compounds, whose composition can be described as A _n BX( _nz +k) containing a single charged or double 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', at that the ratio A/B = n can take values in the range from 0 to 4 (including non- integer values of n) depending on the coordination number and valence of B ^k+ and the crystal structure motif. In particular cases, OICH can have a perovskite-like structure.

Inert or weak solvent for organic-inorganic complex halides is an organic solvent with characteristics that satisfy the following parameters:

DN (Donor number) < 20 kCal/mol, p (Dipole moment) < 2.5 D

6HB (Hansen parameter) < 10 (MPa) ^1/2

A more detailed description of this classification type of organic solvents is given in the publication [Tutantsev, Andrei Sergeevich, Natalia N. Udalova, Sergey A. Fateev, Andrey A. Petrov, Wang Chengyuan, Eugene G. Maksimov, Eugene A. Goodilin, and Alexey B. Tarasov. 'New Pigeonholing Approach for Selection of Solvents Relevant to Lead Halide Perovskites Processing.' The Journal of Physical Chemistry C (2020)]

The term 'stabilized efficiency of a solar cell' in this application means the solar cell efficiency obtained by tracing the maximum power point with evaluating the power conversion efficiency value ~ 120 seconds later after the beginning of efficiency tracing. This efficiency measurement approach is disclosed, for example, in patent US8963368B2 and in the paper by Wenger, Bernard, et al. 'Towards unification of perovskite stability and photovoltaic performance assessment.' arXiv preprint arXiv:2004.11590 (2020).

The spin coating method to be used in certain variations of implementation of the claimed invention is disclosed, for example, in the thesis paper (http://konf.x-pdf.ru/18fizika/632895-l-fotovoltaicheskie-st rukturi- osnove-organicheskih-poluprovodnikov-kvantovih-tochek-cdse.p hp );

- GOST R ISO 27911-2015 'National Uniform Measurement Assurance System (NMS). Chemical analysis of the surface. Scanning probe microscopy. Determining and calibrating the lateral resolution of a near-field optical microscope' (http ://doc s . cntd .ru/document/ 1200119068); po luchen i ya-pero vs kitnykh- so I nec hn ykh- ach eek . ht ml .

Vacuum sputtering techniques to be used in certain variations of the claimed invention (e.g. resistive thermal sputtering, magnetron sputtering, electron beam ("e-beam") sputtering are disclosed, for example, in

- the lecture (https://mipt.ru/upload/medialibrary/17b/skol_partl_pvd_doro zhkin.pdf);

- the book (Mattox, Donald M. Handbook of physical vapor deposition (PVD) processing. William Andrew, 2010, Chapters 6, 7).

The solution application methods to be used in certain variations of the claimed invention (ink-jet printing, screen printing, substrate immersion in a precursor solution (dip-coating), blade-coating, slot-die coating, aerosol spraying, ultrasonic spraying) are disclosed, for example, in

- the paper (Park, Nam-Gyu, and Kai Zhu. 'c.' Nature Reviews Materials (2020): 1-18.) In particular, the slot-die coating method is a method of applying a solution onto a moving substrate by extruding the solution through a slit die in close proximity to the substrate.

The electro spraying method to be used in certain variations of the claimed invention is disclosed, for example, in

- the paper Han, Sunghoon, et al. 'Efficient Planar-Heterojunction Perovskite Solar Cells Fabricated by High-Throughput Sheath-Gas-Assisted Electrospray.' ACS Applied Materials & Interfaces 10, 8 (2018): 7281-7288.

The screen printing method to be used in certain variations of the claimed invention is disclosed, for example, in

- GOST 13.2.004-89. Reprography. Copywriting. Screen printing devices (stencil duplicators). General technical requirements, (http://docs.cntd.ru/document/gost-13-2-004-89)

The aerosol jet printing method to be used in certain variations of the claimed invention is disclosed, for example, in

- the paper Yang, Chunhe, et al. 'Preparation of active layers in polymer solar cells by aerosol jet printing.' ACS applied materials & interfaces 3, 10 (2011): 4053-4058.

- the paper Bag, Santanu, James R. Deneault, and Michael F. Durstock. 'Aerosol-Jet-Assisted Thin-Film Growth of CH3NH3PbI3 Perovskites — A Means to Achieve High Quality, Defect-Free Films for Efficient Solar Cells.' Advanced Energy Materials 7, 20 (2017): 1701151.

Implementation of invention

In the implementation of the claimed method the following main stages of the process for producing films of crystalline materials can be highlighted:

Stage I: forming a layer of reagent B (B') (hereinafter, the notation B (B') refers to reagent B or B', which is an oxide or salt of B) on the top layer of the carrier substrate;

Stage II: immersion of the film obtained at stage I into the solution of the mixture of reagents AX and X2;

Stage III: taking out the film from the solution and its post -treatment. The post-treatment stage is additional.

The claimed invention can be implemented using known means and methods, including those in the conditions of industrial production.

It has been experimentally shown that physical and chemical processes occurring at all basic stages of the proposed process do not depend on the nature of the substrate material or the upper layer of the substrate if this material is selected from among those being inert in relation to reagents B(B'), AX and X2, as well as to the solvents to be used in the synthesis process under the experimental conditions (pressure, temperature, irradiation, etc.). The term 'top layer' of the carrier substrate for the purposes of the present description refers to that part of the substrate, to which reagent B (B') is applied at stage I.

The carrier substrate may be glass, polymeric film (e.g., polyethylene terephthalate, polydimethylsiloxane, polymethyl methacrylate, polyimides, etc.) or any other optoelectronic device, such as a solar cell.

In the most significant practical applications the transparent conducting oxide materials (ITO, FTO, IZO, IO:H, including other alloyed oxide materials based on nickel, tin, indium and zirconium), other electron conducting materials (TiO2, SnO2, Ceo, PCBM), hole conducting oxide materials (Cui, CuO _x , CU2O, CuGaO2, NiO, etc.) and their combinations are used as a top layer of the substrate. Potentially, any materials with sufficient chemical inertness towards the reagents to be used in the synthesis (the most chemically active reagents in the claimed scheme are halogens and mixtures of halogens with organic halides and organic solvents) can be used as a top layer of the substrate.

Metals can be used as reagent B. The most preferred are: Pb, Sn, Bi, Cu or their mixtures. Also, reagent B may contain additives as which (<20 wt%) Eu, Sb, Cd, Ge, Ni, Mn, Fe, Co, Yb, Pd or other elements may be used. The wide range of metals that can be used as a reagent in the implementation of this invention is caused by the similar chemical nature of their interaction with a number of polyhalides (AX + X2): each of the indicated metals can be oxidized by polyhalide to form the corresponding metal halide or complex metal halide. The reactive capacity of polyhalides is described, in particular, in the paper [Petrov, Andrey A., and Alexey B. Tarasov. 'Methylammonium polyiodides in perovskite photovoltaics: from fundamentals to applications.' Frontiers in Chemistry 8 (2020): 418.].

As reagent B', which includes component B, halides, chalcogenides, nitrates, carbonates and other salts of the above metals and their mixtures can be used. The most preferred reagents B and B' are: Pb, Sn, Pbh, Sub, PbBr2, PbCh, PbCOa and their mixtures.

In most practical applications, reagent B films with a thickness of 10 to 1000 nm are used. In the best case, films of Pbh with a thickness of 100 to 500 nm or metallic Pb with a thickness of 10 to 200 nm are used as reagent B.

Reagent B (B') can be applied using methods relevant to the listed compound classes, e.g. vacuum (resistive thermal evaporation, magnetron sputtering, e-beam sputtering), gas (CVD and similar approaches) or solution methods (spin coating, ink jet printing, screen printing, air jet printing, dip coating, blade coating, slot die coating, aerosol spraying including electrostatic spraying and ultrasonic spraying).

As reagent X2, halogens h, Br2, Ch or their mixtures can be used. The most preferred is . Anions of halogens (F, Br , Cl"), SCN’ or their mixtures can be used as component X in reagent AX.

As reagent AX, compounds containing component X and cation A can be used, with inorganic and organic cations as well as their mixtures being used as cation A. For example, Cs ⁺ is the most preferred in the role of inorganic cation A. Also, Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ and their mixtures, including Cs ⁺ mixtures, can be used in the role of inorganic cation A. Single charged substituted ammonium cations (NR ¹ R ² R ³ R ⁴ ) ⁺ with different organic substituents (R) can be used as organic cation A in most practical variations of the proposed method; the above-mentioned organic substituents, in turn, can contain different functional groups, such as aromatic fragments, diene groups, functional groups containing oxygen (hydroxyl, carbonyl, carboxyl), nitrogen (amino group, cyano group, etc.), sulphur (thiol, sulphoxide, etc.) or represent H atom. Most often in practically significant implementations the following cations are used in the role of organic cation: Cs ⁺ , Rb ⁺ , K ⁺ , CH3NH3 ⁺ , (NH2)2CH ⁺ , C(NH2)3 ⁺ , CH ₃ (CH ₂ )nNH ₃ ⁺ (n=l-15 including their isomers), phenylethylammonium cations, substituted phenylethylammonium cations and their mixtures.

An organic solvent belonging to the number of inert or weak ones with respect to the organic-inorganic complex halides is used as a solvent for reagents A and X2. Such solvents are characterized by the following parameters: DN (Donor Number) < 20 kCal/mol, p (Dipole moment) < 2.5 D, 6HB (Hansen parameter) < 10 (MPa) ^1/2 ). In particular, this type of solvents include chloroform, chlorobenzene, o -dichlorobenzene, m-dichlorobenzene, p-xylene, toluene, dichloromethane, benzene, diethyl ether, anisole, iodobenzene, phenethole, decane, hexane, m- xylene, dibenzyl ether, bromobenzene, mesitylene, styrene, ethylbenzene, heptane, diethylcarbonate, 1,2-dichloroethane, ethylbenzene, ethyl acetate, tetrahydrofuran, dioxane, etc., as well as their mixtures. A more detailed description of this classification type of organic solvents is given in the publication [Tutantsev, Andrei Sergeevich, Natalia N. Udalova, Sergey A. Fateev, Andrey A. Petrov, Wang Chengyuan, Eugene G. Maksimov, Eugene A. Goodilin, and Alexey B. Tarasov. 'New Pigeonholing Approach for Selection of Solvents Relevant to Lead Halide Perovskites Processing.' The Journal of Physical Chemistry C (2020)]. In particular, this publication describes how solvents with different combinations of values of the listed parameters (DN, p, 6HB) interact with organic-inorganic lead halide complexes. It is experimentally shown that the so-called "inert or weak solvents with respect to organic- inorganic complex halides" are characterized by weak solubility to lead halide components with a perovskite-like structure. The use of this type of solvents is a prerequisite for the successful implementation of the claimed invention, as it provides a low rate of perovskite film recrystallization, for example, according to the mechanism described in the paper [Hsieh, Tsung- Yu, et al. "Crystal growth and dissolution of methylammonium lead iodide perovskite in sequential deposition: correlation between morphology evolution and photovoltaic performance." ACS Applied Materials & Interfaces 9, 10 (2017): 8623-8633.].

In some implementations of the method, the solvent may contain additives (<10 vol. %) of solvents that are neither inert nor weak in respect to the organic-inorganic complex halides, such as an additive of isopropyl alcohol, ethyl alcohol, butyl alcohol.

A solution of reagents AX and X2 can be prepared by adding the required amounts of powders AX and X2 to an appropriate solvent or mixture of solvents. The solvent/reagent mixture is then stored in a sealed vessel for as long as necessary to achieve the required concentration of the solution as to reagents AX and X2.

To implement the invention, the concentration of AX in the solution can be from 0.001 mg/ml to 500 mg/ml, the concentration of X2 in the solution can be from 0.1 to 500 mg/ml.

In the course of solution preparation, the temperature influence (temperature maintenance) within the range from -20°C to +200°C can additionally be used.

In the process of implementing the claimed invention, the following chemical reaction scheme is carried out:

B + AX + X2 * A _n BX(nz+k) or

B' + AX + X2 * A _n BX(nz+k)+ Y', where B7B is either B', a substance that contains component B, or directly a pure substance B, Y' is the by-product of the reaction, which is obtained when an oxide or salt (B') was used as the precursor of component B. z = 1, 2; k = 2, 3, 4; n = 0 -4, including non- integer values of n rather than a pure substance B.

At Stage II, film B (B') is treated with AX + X2 solution for a period from 1 s to 48 h, with the temperature of the substrate and solution being maintained between -20 °C and 200 °C; then the substrate is taken out from the solution.

After completing the above mentioned stage, the film can be further posttreated stage III), using a thermal treatment at a temperature from 30°C to 400°C for 1 to 7200 seconds or stored in an inert gas atmosphere, dry air, humid air, solvent vapour (e.g. DMF, DMSO, methylamine, etc.), halogen vapours, or exposure to visible, UV or IR light, or solvent treatment, or a combination of the above post-treatment types.

Particular implementation cases

Case 1

To form the substrate, a layer of fluorine-doped tin oxide (resistance ~7 Q/n) was applied onto cleaned glass substrates (substrate carrier), followed by successive layers of TiCh (~20 nm, spray pyrolysis) and SnO _x (~7 nm, chemical deposition from solution) (top substrate layer). To implement the stage II, a 62 nm thick layer of metallic lead (reagent B) was applied onto the top layer of the substrate using vacuum thermoresistive evaporation. The temperatures of the substrates and the quartz thickness gauge were maintained at ~10 °C during sputtering. After evaporation, the substrates were transferred to an argon-filled glove box.

10 mg of methylammonium iodide (MAI) and 200 mg of I2 (reagents AX and X2) was added to 10 ml of toluene, after which this mixture was stirred for 8 hours at room temperature in an enclosed container. Upon expiry of 8 hours, the closed container accommodated a solution containing MAI and h in toluene and polyhalide MAI _X distributed over the walls and bottom of the container. A dosed volume of MAI and I2 solution without MAI _X inclusions was taken to perform the synthesis.

Then (stage II) the substrate Pb / SnO _x / TiCh / FTO / glass was immersed in the solution of MAI + I2 in toluene in a sealed container and was stored during 20 minutes at room temperature. Then (stage III) the substrate was extracted from the solution and successively washed with toluene and anhydrous isopropyl alcohol. Thereafter, the substrate was moved to the glove box (rel. humidity <5%) and annealed at 100°C for 30 minutes.

Next, a layer of p-conducting Spiro-OMeTAD material was applied onto the substrates and an electrode (Au) was sputtered. The stabilized power conversion efficiency of the perovskite solar cell, which was obtained by tracking the maximum power point, was equal to 13%, which demonstrates the potential significance of the proposed solution for further practical applications.

The results of scanning electron microscopy and X-ray diffraction phase analysis for M APbh films obtained by the claimed method are shown in Fig. 1.

The IV-curve and the time behavior of the efficiency for solar cells assembled on the basis of these films are shown in Fig. 2.

Case 2

100 mg of formamidinium iodide (FAI), 17 mg of methylammonium bromide (MABr) and 2 g of I2 was added to 100 ml of toluene, after which this mixture was stirred for 12 hours at room temperature in a closed container. Next, 5 mL of the resulting solution was transferred to a separate container, in which the Pb@SnO2@TiO2@FTO substrate was then immersed. The container was heated to 50°C and stored for 35 minutes, after which the substrate was taken out from the container (stage III) and washed successively with toluene and anhydrous isopropanol.

The results of scanning electron microscopy and X-ray phase analysis for MA _x FAi- _x PbI _y Br3- _y films obtained by the claimed method are shown in Fig. 3. A film of the composition MA _x FAi- _x PbI _y Br3- _y of larger size (6 x 5 cm) was obtained by a similar method, a photograph of this film is shown in Fig. 4.

Case 3

Table 1 below shows the materials obtained using the claimed synthesis method. The tables provide, respectively, the selected reagents B(B'), AX and X2, their amounts, solvent, solution temperature at stage 2 and treatment time at stage 2. The final composition of the films was established by X-ray diffraction phase analysis (XRD). This list demonstrates a fundamental possibility to obtain films of different classes of crystalline materials using the claimed method, in particular, halides and hybrid halides of transition metals (e.g., Cui and MACU2I3), halide perovskites (so called 3D perovskites with the general formula of ABX3) and organic-inorganic complex halides (2D perovskites such as BA2MAPb2l?).

Table 1

Case 4 Table 2 provides the options for producing materials using the claimed approach on different substrates with different top layers.

Table 2

These results demonstrate that the claimed approach is potentially feasible to obtain organic-inorganic complex halide films on any flat substrates having sufficient chemical inertness with respect to the reagents to be used in the course of synthesis (in particular, many oxides and iodides possess such inertness).

Case 5

Table 3 below provides the options for obtaining materials based on the claimed method using different options for post-treatment (stage III) of the halide films with a perovskite-like structure produced. Halide films with perovskite-like structure MAPbk were obtained on the SnO _x / TiCh / FTO substrate as follows: by vacuum thermal evaporation of the metallic lead films of about 62 nm thick were applied onto the SnO _x / TiCh / FTO substrates, after which the substrates were immersed in the MAI (1 mg/ml) + h solution (20 mg/ml) in toluene and stored in the solution for 40 min at room temperature. Then the substrates obtained were subjected to one of the seven types of post-treatment shown in Table 3. For example, as part of post-treatment No.4, the substrate was successively washed in toluene, then in anhydrous isopropyl alcohol, after that dried in an argon stream and annealed at 100°C for 30 min.

The substrates obtained were then examined by X-ray diffraction phase analysis (XRD) and test solar cells with the FTO / TiO2 / SnO _x / MAPbI ₃ / Spiro-OMeTAD / Au architecture were assembled from the substrates. The values of typical power conversion efficienies for the solar cells produced are shown in Table 3.

Table 3