Process for producing a perovskite active layer of metal halide

Abstract

The invention relates to a method for producing a perovskite active layer of metal halide, comprising a first fabrication step, in which a first wet film comprising perovskite material precursors is deposited in a solvent medium; then the first wet film is subjected to gas quenching, thus obtaining the first perovskite layer, the solvent medium having been removed and the perovskite material having crystallized. The method comprises at least a second fabrication step, during which the steps of the first step are repeated, to obtain the perovskite active layer. Figure for the abstract: Fig. 1D

Description

Title of the invention: Method for producing a perovskite active layer of metal halide technical field

[0001] The field of the invention is that of methods for producing a perovskite active layer of metal halide, for applications in the fields of, among others, photovoltaic devices, light-emitting diodes, and photodetectors. PREVIOUS STATE OF THE ART

[0002] Metal halide perovskites are among the promising semiconductor materials for the development of optoelectronic devices such as photovoltaic cells, light-emitting diodes, photodetectors, lasers, etc., due to their good optoelectronic properties.

[0003] Several processes for producing such a perovskite layer exist, such as spin coating of a wet film containing precursors of the perovskite material diluted in a solvent medium, followed by antisolvent quenching of the wet film.

[0004] Furthermore, document EP4265826A1 describes another embodiment method, which includes a step of depositing a wet film by blade coating followed by a gas quenching step.

[0005] However, there is a need to be able to produce a thick perovskite layer, for example, with a thickness of at least 0.8 pm, or even 1 pm or 1.2 pm. This is particularly relevant when the perovskite layer is required to completely cover pyramids on the deposition face of a textured underlying substrate. It is also relevant when a tandem photovoltaic device is to be produced.

[0006] It is then possible to increase the thickness of the wet film, or even to increase the molar concentration of the perovskite material precursors in this wet film. However, depositing a thicker wet film can lead to a non-homogeneous perovskite layer with insufficient crystalline quality. Furthermore, it can be difficult to further increase the molar concentration of the precursors in the wet film without rapidly exceeding the solubility limit. Description of the invention

[0007] The invention aims to remedy, at least in part, the drawbacks of the prior art, and more particularly to propose a method for producing a A perovskite active layer of metal halide, with a thickness of at least 0.8 pm, or even 1 pm or 1.2 pm, and whose perovskite material exhibits good crystalline quality. Another objective is to obtain such a perovskite active layer without having to deposit a thicker wet film or increase the molar concentration of precursors in the wet film.

[0008] To this end, the object of the invention is a method for producing a perovskite active layer of metal halide, comprising the following steps: • provide a substrate with a deposition face; • a first phase of production, to obtain a first perovskite layer, comprising the following steps: • deposit, on the deposition face, a first wet film containing precursors of the perovskite material in a solvent medium; • subject the first wet film to gas quenching, thus obtaining the first perovskite layer, the solvent medium having been removed and the perovskite material having crystallized.

[0009] According to the invention, the process comprises at least a second implementation phase, during which the steps of the first phase are repeated, to obtain the perovskite active layer: • deposit, on the first perovskite layer, a second wet film containing precursors of the perovskite material in a solvent medium, leading to a dissolution of the first underlying perovskite layer and thus to the obtaining of a new wet film; • subject the new wet film to gas quenching, thus obtaining the active perovskite layer, the solvent medium having been removed and the perovskite material having crystallized.

[0010] Some preferred but not limiting aspects of this implementation method are as follows.

[0011] The perovskite active layer may have a thickness of at least 0.8 pm.

[0012] The first embodiment may include a heat treatment step performed after gas quenching, which helps to remove the solvent medium from the first wet film. Furthermore, at least the second embodiment may also include a heat treatment step performed after gas quenching, which helps to remove the solvent medium from the new wet film.

[0013] The deposition steps can be carried out by coating, by sheet coating or by slotted die coating.

[0014] The first wet film and the second wet film may have identical thicknesses.

[0015] The first and second wet films may include the same precursors of the perovskite material.

[0016] The first wet film and the second wet film may have identical molar concentrations of precursors of the perovskite material.

[0017] The first wet film and the second wet film may have different molar concentrations of precursors of the perovskite material.

[0018] The gas quenching steps may have the same operating conditions, for example in terms of substrate temperature, position and orientation of a projection nozzle and speed of a gas flow projected onto the wet film.

[0019] A heat treatment step can be carried out following each gas quenching step in order to remove any residual solvent medium. The conditions can be identical during the heat treatment steps in terms of temperature and duration.

[0020] The perovskite material may have a molecular formula ABX3, where A corresponds to a cation or a combination of metallic or organic cations, B corresponds to one or more metallic elements, such as lead Pb, tin Sn, bismuth Bi, antimony Sb, and where X corresponds to one or more anions, in particular halides, selected from chloride, bromide, iodide and mixtures thereof.

[0021] Chemical element B can be lead in overstoichiometry.

[0022] The perovskite material may have a molecular formula CsxFA(i_x)Pb(IyBr(i_y))3, where FA is formamidinium.

[0023] The invention also relates to a method for manufacturing a photovoltaic device comprising the production of an n-type layer, a perovskite active layer produced by the method according to any one of the preceding characteristics, and a p-type layer.

[0024] The invention also relates to a perovskite-based stack comprising: a substrate having a deposition face; a perovskite active layer, covering the deposition face, formed of a perovskite material and crystalline Pbl2, having: a thickness of at least 0.8pm, and an ApK / Apbi2 ratio of at least 1.5, where APK is an area of ​​a peak associated with the perovskite material of an XRD spectrum of the perovskite active layer, and APbl2 is an area of ​​a peak associated with Pbl2. Brief description of the drawings

[0025] Other aspects, objects, advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0026] Fig.1A, Fig.1B, Fig.1C, Fig.1D, Fig.1E and Fig.1F illustrate different stages of a process for producing a perovskite active layer according to an embodiment;

[0027] [Fig.2A] illustrates cross-sectional views by scanning electron microscopy of a reference layer obtained by a process according to an example of the prior art (see [Fig.2A] left), and of a perovskite active layer obtained by a process according to a first embodiment (see [Fig.2A] right);

[0028] [Fig.2B] illustrates scanning electron microscopy top views of the same reference layer (see [Fig.2B] left), and of the same perovskite active layer (see [Fig.2B] right);

[0029] Fig. 2C illustrates XRD spectra of the same reference layer and the same active perovskite layer;

[0030] [Fig.3A] is a cross-sectional view of a perovskite active layer obtained by a process according to a second embodiment;

[0031] [Fig.3B] is a top view of the same perovskite active layer;

[0032] Figure [3C] illustrates the XRD spectra of Figure [2C] of the first embodiment, as well as the XRD spectrum of the perovskite active layer of the second embodiment;

[0033] [Fig.4A] illustrates top views by scanning electron microscopy of the same reference layer (see [Fig.4A] left), and of an active perovskite layer (see [Fig.4A] right) deposited on a textured substrate;

[0034] [Fig.4B] is an XRD spectrum of the perovskite active layer of [Fig.4A].

[0035] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0036] In the figures and throughout the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale in order to enhance the clarity of the figures. Moreover, the different embodiments and variants are not mutually exclusive and may be combined. Unless otherwise indicated, the terms "approximately," "about," and "in the order of" mean within 10%, and preferably within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are inclusive, unless otherwise stated.

[0037] The invention relates to a method for producing a perovskite active layer of metal halide, the thickness of which can be at least 0.8 pm, or even 1 pm or 1.2 pm, and of which the perovskite material has a high crystalline quality.

[0038] For this, the process of producing the perovskite active layer is based on a so-called "multi-deposition" approach, i.e. several successive depositions of a wet film, where each deposition step is followed by a gas quenching step of the deposited wet film.

[0039] Thus, the manufacturing process comprises a first phase for producing a first perovskite layer. This first phase includes, at a minimum, a step of deposition of a first wet film, followed by gas quenching of this first wet film. A heat treatment may also be performed. This yields a first perovskite layer.

[0040] According to the invention, the method of implementation comprises at least a second (or additional) phase in which the steps of the first phase are repeated, where the second wet film is deposited onto the first perovskite layer obtained previously, causing its dissolution. As detailed below, the active perovskite layer can have a thickness of at least 0.8 pm with a homogeneous and high crystalline quality.

[0041] In general, the process for producing the perovskite active layer comprises at least the following steps: • provide a substrate with a deposition face; • a first phase of production, to obtain a first perovskite layer, comprising the following steps: • deposit, on the deposition face, a first wet film containing precursors of the perovskite material in a solvent medium; • subject the first wet film to gas quenching, preferably followed by heat treatment, thus obtaining the first perovskite layer, the solvent medium having been removed and the perovskite material having crystallized; • at least one second implementation phase, carried out following the first phase and during which the steps of the first phase are repeated, to obtain the perovskite active layer: • deposit, on the first perovskite layer, a second wet film containing precursors of the perovskite material in a solvent medium, leading to a dissolution of the first underlying perovskite layer and thus to the obtaining of a new wet film; • subject the new wet film to gas quenching, followed if necessary by heat treatment, thus obtaining the active perovskite layer, the solvent medium of the new wet film having been removed and the perovskite material having crystallized;

[0042] By active perovskite layer, we mean an active layer, that is to say, absorbing in the desired spectral band, made of a perovskite crystalline material in the α phase (also called the dark phase). It is therefore not an amorphous layer or a photo-inactive layer where the material is in the γ phase (also called yellow phase). Some perovskite materials are known by an acronym, such as "MAPI" for CH3NH3PbI3, and "FAPI" for FAPbI3 where FA corresponds to formamidinium HC(NH2)2+.

[0043] The perovskite material of the active layer is a material with the empirical formula ABX3, where: • A corresponds to a cation or a combination of metallic or organic cations; • B corresponds to one or more metallic elements, such as lead Pb, tin Sn, bismuth Bi, antimony Sb; • X corresponds to one or more anions, in particular halides, chosen from chloride, bromide, iodide and their mixtures.

[0044] Furthermore, the material of the deposited perovskite layer may not be perfectly stoichiometric, but may exhibit a slight over-stoichiometry in element B, for example, lead. Thus, in the general formula ABX3, the quantity of B atoms is not exactly equal to 1, but may be slightly greater than 1, for example, between 1.01 and 1.10, for example, approximately 1.05. Moreover, the active perovskite layer may also contain BX2 crystals, for example, Pbl2. However, the manufacturing process according to the invention makes it possible to obtain a perovskite material of good crystalline quality, where the quantity of BX2 crystals is reduced.

[0045] Preferably, the perovskite material of the active layer has the empirical formula CsxFA (ix)Pb(IyBr(iy))3, where element A is CsFA, element B is lead, and element X is a halide selected from iodide, bromide and mixtures of these two elements.

[0046] The substrate, on which the deposition steps are performed, may be or may comprise a wafer-type plate with a thickness of several tens to several hundred microns, made of a semiconductor material, glass, sapphire, or other materials. It may comprise n-type or p-type layers, depending on the intended application. It rests on a substrate holder that can apply a desired temperature.

[0047] The substrate's deposition face may be flat, or it may exhibit structures such as pyramids, for example with dimensions (height and width at the base) on the order of a micron, for example, approximately 1 µm. These pyramids may be located, in particular, on the surface of mesas. The substrate may also exhibit roughness and / or undulations on scales of several tens or even hundreds of microns.

[0048] In the process of producing the perovskite active layer, each production phase includes a step of depositing a wet film comprising precursors of the perovskite material diluted in a solvent medium.

[0049] These deposition steps can be carried out on an industrial scale, for example on large surfaces (for example 5x5cm2 or even 15x15cm2), while allowing a thick (at least equal to 0.8 pm), homogeneous, active perovskite layer to be obtained, with good crystalline quality.

[0050] They can be carried out by blade coating, slot die coating, spin coating, among other methods. They are preferably carried out by blade coating or slot die coating, so as to obtain a wet film of constant thickness and homogeneous concentration (e.g. its molar concentration).

[0051] Preferably, the relative speed between the spreading blade (blade coating) or the deposition head (slot die coating) on ​​the one hand and the wet film on the other hand is between 1 and 100 mm / s, preferably between 15 and 45 mm / s, and preferably between 20 and 30 mm / s.

[0052] Each wet film is formed from a solution of perovskite material precursors diluted in a solvent medium. The solvent may be DMF and / or DMSO. The precursors may be selected, in particular, from CsX, FAY, PbZ2 and their combinations, with X, Y, and Z selected from I and Br. The additive FAQ may be present in the solution. Preferably, the solution is free of any other additives as well as MA+ (methylammonium) cations, the presence of which may alter the stability of the perovskite active layer. Preferably, the precursors are Pbl2, PbBr2, FAI, and Csl.

[0053] Preferably, the precursor solution has a lead molar concentration between 0.2 and 1.7 M, for example between 0.6 and 1.5 M, preferably between 1 and 1.3 M. It is also possible to use wet films having the same components and chemical elements but in different quantities, so that the molar concentration of element B, for example lead, is different from one wet film to another. For example, a first wet film (during the first phase) may be used with a lead molar concentration of cPb1, and a second wet film (during the second phase) with a lead molar concentration cPb2 higher or lower than cPb1. For example, cPb1 may be 0.2 M and cPb2 may be IM (as described later in the second embodiment).

[0054] The deposited wet film preferably has a constant thickness, for example between 2 and 16 µm, preferably between 2.5 and 8 µm, and preferably even more between 3 and 5 µm. Within this thickness range, and depending on Depending on the molar concentration of the first wet film, it is possible to obtain a first perovskite layer with a thickness of approximately 0.3 to 0.6 pm (with a lead molar concentration between 0.6 and µm). The fact that the manufacturing process according to the invention is of the "multi-deposition" type makes it possible to obtain a perovskite active layer of greater thickness, for example at least 0.8 pm, or even 1 pm, or even 1.2 pm.

[0055] Thus, the operating conditions during the deposition steps include, in particular, the technique used and the associated conditions, as well as the substrate temperature, among other things. Preferably, these operating conditions are identical during the different deposition steps of the manufacturing process.

[0056] During the gas quenching steps, the surface of the wet film is swept with a flow of gas, such as dry air, nitrogen, or argon (preferably an inert gas). Preferably, the entire surface of the wet film is swept.

[0057] This step can be performed while the wet film deposition step is still underway, or after it has been completed. A gas knife nozzle can be used. Its tip is positioned vertically relative to the free face of the wet film and can be inclined at a given angle to a plane passing through the wet film. This angle can be between 30° and 90°, for example, 50°. The length of the gas flow path can be between 3 and 6 mm, for example, between 3 and 4 mm.

[0058] The gas flow velocity can be measured at the nozzle outlet, i.e., at the tip of one of the nozzle's end lips. In [Fig. 1B] and 1E, the upper lip is shorter than the lower lip, but other configurations are possible. The gas flow velocity can be between 120 and 250 m / s. Furthermore, the nozzle's movement velocity relative to the wet film can be between 1 and 50 mm / s, for example, between 5 and 30 mm / s.

[0059] Thus, the operating conditions during the gas quenching steps include, among other things, the positioning and orientation of the spray nozzle relative to the free face of the wet film, the gas flow velocity and the nozzle travel speed, and the substrate temperature. Preferably, these operating conditions are identical during the different gas quenching steps of the manufacturing process.

[0060] Preferably, following each gas quenching step, a heat treatment can be carried out under an inert atmosphere. The temperature of the substrate, and preferably of the resulting stack (substrate and perovskite layer), is preferably between 70°C and 100°C, for a duration of, for example, between 5 and 60 minutes, or for example, between 5 and 30 minutes. This annealing step is advantageous for removing residual solvent following the gas quenching step.

[0061] Preferably, the operating conditions, in terms of temperature, duration and atmosphere, are identical during the different heat treatment stages of the manufacturing process.

[0062] Figures IA to 1F illustrate steps in a process for fabricating a perovskite active layer according to a first embodiment. Figures IA to IC relate to the first phase, and Figures 1D to 1F relate to the second phase. The process comprises two successive fabrication phases, where the operating conditions are identical. In this example, the perovskite active layer is fabricated to produce a tandem Si / PK photovoltaic cell, comprising a silicon heterojunction subcell in a PIN configuration and a perovskite-based subcell.

[0063] With reference to [Fig. 1 A], a substrate with a deposition face is first provided. This is achieved by depositing a thin passivation layer of intrinsic amorphous silicon (a-Si:H) onto the two opposite faces of a crystalline silicon (c-Si) wafer. Next, p-type and n-type doped silicon semiconductor layers are deposited onto the back and front faces of the crystalline silicon wafer, respectively. To establish electrical contact with the lower photovoltaic cell, an ITO / Ag multilayer is deposited on the back face, and an ITO layer, for example, 12 nm thick, is deposited on the front face. The deposition face is flat. During the deposition and gas quenching steps, the substrate is maintained at a constant temperature, in this case 40°C.

[0064] With further reference to [Fig. 1A], a first wet film Fl is deposited onto the dispensing face of the substrate S using a solution of perovskite material precursors diluted in a solvent medium. The precursor solution was prepared from Pbl2 (3.707 g), PbBr2 (1.453 g), FAI (1.631 g), and Csl (0.468 g) in 12 mL of solvent medium, in this case DMF (10.8 mL) and DMSO (1.2 mL). The molar concentration of lead is IM, and the Cs / Pb molar ratio is 15%. The precursor solution is stirred, for example, for 12 h at 40°C.

[0065] The deposition is carried out by blade coating. The distance between the end of the spreading blade and the deposition face is 70 pm. The relative speed of the spreading blade with respect to the substrate S is 20 mm / s, and the volume of ink used is 20 pL.

[0066] With reference to [Fig. IB], the first wet film FL is gas quenched. For this, a gas stream, here nitrogen, is applied to the free surface of the wet film Fl at a speed of 137 m / s. The gas stream projection nozzle is positioned so that the path length of the gas stream to the wet film Fl is 3.6 mm. Furthermore, the nozzle moves along the wet film Fl at a speed of, for example, 5 mm / s. It is oriented with respect to the free surface of the wet film. Fl so as to form an angle of 50°. This step causes a partial or total removal of the solvent medium, as well as the crystallization of the perovskite material.

[0067] With reference to [Fig. IC], the resulting perovskite Cl layer is then heat-treated. The substrate S is thus heated to 100°C for 5 min under an inert atmosphere. This optional but advantageous step essentially eliminates the residual solvent. A first perovskite Cl layer is thus obtained.

[0068] The second manufacturing phase is then carried out to obtain the active perovskite layer C2. The operating conditions of the deposition, gas quenching and heat treatment steps are identical to those of the first manufacturing phase.

[0069] With reference to [Fig. 1D], a second wet film F2 is deposited from the same precursor solution. The second wet film F2 is deposited directly onto the free face of the first perovskite layer Cl, again by blade coating. The operating conditions (temperature, relative speed, positioning of the spreading blade, etc.) are identical to those of the first deposition step.

[0070] It appears that this deposition step causes the total or partial dissolution of the underlying first perovskite layer Cl. A new wet film nF2 is then obtained, the quantity of solvent medium in which remains obviously equal to that of the second wet film F2, but with a molar concentration of precursors, and in particular a molar concentration of lead, higher than that of the second wet film F2. The thickness of the new wet film nF2 is greater than those of the first and second wet films Fl, F2.

[0071] With reference to [Fig. 1E], the new wet film nF2 is subjected to gas quenching. The operating conditions, in terms of the positioning and orientation of the spray nozzle, temperature, and travel speed, remain identical to those of the first gas quenching step. This step results in partial or total removal of the solvent medium, as well as crystallization of the perovskite material.

[0072] With reference to [Fig. 1F], the perovskite layer obtained is finally subjected to heat treatment. The substrate is thus heated to a temperature of 100°C for 5 min under an inert atmosphere.

[0073] The active perovskite layer C2, here with a thickness of approximately 1.2pm, is thus obtained after the removal of all the solvent medium from the new wet film nF2 and crystallization of the perovskite material.

[0074] We now seek to compare certain characteristics of the active perovskite layer obtained C2 according to the first embodiment with a reference layer. The reference layer here is identical to the first perovskite layer Cl, that is to say, the layer obtained at the end of the first phase of fabrication.

[0075] Figure 2A illustrates scanning electron microscope cross-sectional views of the reference layer (Fig. 2A, left) and the perovskite active layer obtained by the double-deposition process according to this embodiment of the invention (Fig. 2A, right). It appears that the perovskite active layer has a thickness (here of 1.2 pm) greater than that of the reference layer (here of approximately 0.6 to 0.7 pm). It is also noted that the perovskite active layer does not exhibit the holes that can be observed when attempting to quench a thick wet film with an antisolvent. Finally, a certain crystalline homogeneity is observed throughout the thickness of the perovskite active layer. It should be noted that crystalline domains of the perovskite material, composed of one or more crystalline grains, are visible here.

[0076] Figure 2B illustrates top views, again obtained with a scanning electron microscope, of the reference layer (Fig. 2B, left) and the perovskite active layer obtained by the double-deposition process according to this embodiment of the invention (Fig. 2B, right). It can be seen that the crystalline domains of the perovskite active layer are larger than those of the reference layer. Here too, an absence of holes, for example pinholes, is observed in the perovskite active layer.

[0077] Figure 2C illustrates XRD (X-ray diffraction) spectra of the Cl reference layer and the C2 perovskite active layer. It can be seen that the peak at 20° = 14° associated with the perovskite material (phase a, and crystallographic orientation (001)) has a greater intensity than that of the peak associated with the reference layer (20° = 12.5°). Furthermore, the peak associated with Pbl2 is less intense and narrower.

[0078] These perovskite layers can then be characterized using an ApK / Apbl2 ratio, where ApK is the area of ​​the peak associated with the perovskite material PK at 20°=14°, and APbl2 is the area of ​​the peak associated with Pbl2 at 20°=12.5°. In the case of the reference layer, the area APK is equal to 3499 and the area APbl2 is equal to 4590, leading to an APK / APbl2 ratio of 0.76. In contrast, in the case of the active perovskite layer, the area APK is equal to 6063 and the area APbl2 is equal to 1651, leading to an APK / APbl2 ratio of 3.67, which is almost 400% higher. The area is determined by calculating the integral under the considered curve using graphical analysis software.

[0079] The value of this APK / APbl2 ratio of the perovskite active layer is surprising, given that the second fabrication phase is carried out under the same conditions as the first fabrication phase. It reflects a better crystalline quality of the perovskite active layer compared to that of the reference layer, so that it should exhibit better long-term stability of its crystalline structure and therefore of its optoelectronic properties.

[0080] Note that the use of an initial precursor solution having a molar concentration of lead of 1.4M can lead to the formation, at the end of the two manufacturing phases, of a perovskite active layer of greater thickness, here of 1.5pm instead of 1.2pm.

[0081] In a second embodiment, the perovskite active layer is produced by a process identical to that of the first embodiment in terms of operating conditions, and which differs from it only in that the molar concentration of lead of the first wet film Fl is 0.2M while that of the second wet film F2 remains IM.

[0082] Figure 3A is a scanning electron microscope cross-sectional view of the perovskite active layer obtained by the double-deposition process according to this embodiment of the invention. It appears that the perovskite active layer has a thickness of approximately 0.9 to 1 pm, which is always greater than that of the reference layer (approximately 0.6 to 0.7 pm), but less than the 1.2 pm thickness of the perovskite active layer of the first embodiment. Furthermore, the perovskite active layer exhibits a certain crystalline homogeneity in thickness: there is no inhomogeneity in thickness that would result from the first wet film having a lower molar concentration of lead than the second wet film.

[0083] Fig. 3B is a top view of the perovskite active layer of Fig. 3A. As in the first embodiment, the crystal domains are larger than those of the reference layer. Here too, an absence of holes, for example pinholes, is noted in the perovskite active layer.

[0084] Figure 3C corresponds to Figure 2C above, to which the XRD spectrum of the C2' perovskite active layer of this second embodiment has been added. It can be seen that the peak of the PK perovskite material also exhibits a higher intensity than that of the reference layer. Furthermore, the peak associated with Pbl2 (20 = 12.5°) is similar to that of the C2 perovskite active layer of the first embodiment.

[0085] Furthermore, the ApK / Apbi2 ratio can also be calculated for this C2' perovskite active layer with a dilute first wet film: the APK area is equal to 4147 and the APbl2 area is equal to 2257, leading to an APK / APbl2 ratio of 1.84, representing a 140% improvement compared to the reference layer. The C2' perovskite active layer with a dilute first wet film therefore also exhibits better crystalline quality than the CL reference layer.

[0086] The invention also relates to a perovskite-based stack comprising a substrate having a deposition face, which is covered by a perovskite active layer formed of a perovskite material and crystalline Pbl2, the perovskite active layer having a thickness of at least 0.8 pm and a APK / Apbl2 ratio at least equal to 1.5, where APK is an area of ​​a peak associated with perovskite material from an XRD spectrum of the perovskite active layer, and APbi2 is an area of ​​a peak associated with Pbl2.

[0087] In a third embodiment, the perovskite active layer is not produced on a substrate with a flat deposition face, but on a textured (i.e., structured) substrate where the deposition face has pyramids of a characteristic size (base and height) on the order of Ipm. This configuration is encountered in particular during the fabrication of tandem photovoltaic devices, for example Si / PK or PK / PK. The objective here is to produce a perovskite active layer that continuously covers the pyramids.

[0088] Here, the first and second wet films are made from a precursor solution having a lead molar concentration of 1.4M. It was prepared by mixing 4.324g of Pbl2, 1.696g of PbBr2, 1.902g of FAI, and 0.546g of Csl in 10ml of a solvent medium consisting of 9ml of DMF and 1ml of DMSO.

[0089] The deposition, quenching and heat treatment steps are identical to those described in the first embodiment, except with regard to the distance between the end of the spreading blade and the deposition face, which is 90pm.

[0090] The reference layer is obtained at the end of the first manufacturing phase. In contrast, the active perovskite layer is obtained at the end of both manufacturing phases.

[0091] Figure 4A illustrates scanning electron microscope top views of the reference layer (Fig. 4A, left) and the perovskite active layer obtained by the double-deposition process according to this embodiment of the invention (Fig. 4B, right). It can be seen that, in the case of the reference layer, the apexes of some pyramids are visible (black areas), which shows that the reference layer does not continuously cover the pyramids. In contrast, in the case of the perovskite active layer, the pyramids are completely covered (no black areas). Furthermore, the perovskite active layer does not have any holes, as might be the case if a perovskite layer had been produced by a prior art "single-deposition" process.

[0092] Figure 4B is an XRD spectrum of the obtained perovskite active layer. It can be seen that the peak of the α phase of the perovskite material PK (20=14°) exhibits a consistently very high intensity, while the peak associated with Pbl2 (20=12.5°) is very weak and narrow. The APK / APbl2 ratio is therefore particularly high. The perovskite active layer thus also exhibits very good crystalline quality.

[0093] Specific embodiments have just been described. Various variants and modifications will be apparent to those skilled in the art.

Claims

Demands

1. A method for producing a perovskite active layer of metal halide, comprising the following steps: • providing a substrate having a deposition face; • a first production phase, to obtain a first perovskite layer, comprising the following steps: • depositing, on the deposition face, a first wet film comprising precursors of the perovskite material in a solvent medium; • subjecting the first wet film to gas quenching, thus obtaining the first perovskite layer, the solvent medium having been removed and the perovskite material having crystallized;• characterized in that it comprises at least a second manufacturing phase, during which the steps of the first phase are repeated, to obtain the perovskite active layer: • depositing, on the first perovskite layer, a second wet film comprising precursors of the perovskite material in a solvent medium, leading to a dissolution of the underlying first perovskite layer and thus to the obtaining of a new wet film; • subjecting the new wet film to gas quenching, thus obtaining the perovskite active layer, the solvent medium having been removed and the perovskite material having crystallized.

2. A method of embodiment according to claim 1, wherein the perovskite active layer has a thickness of at least 0.8 pm.

3. A method of embodiment according to claim 1 or 2, wherein the first embodiment stage comprises a heat treatment step carried out following gas quenching, contributing to the removal of the solvent medium from the first wet film, and at least the second embodiment stage also comprises a heat treatment step carried out following gas quenching, contributing to the removal of the solvent medium from the new wet film.

4. A method of implementation according to any one of claims 1 to 3, wherein the deposition steps are carried out by coating, by sheet coating or by slotted die coating.

5. A method of implementation according to any one of claims 1 to 4, wherein the first wet film and the second wet film have identical thicknesses.

6. A method of implementation according to any one of claims 1 to 5, wherein the first and second wet films comprise the same precursors of the perovskite material.

7. A method of implementation according to any one of claims 1 to 6, wherein the first wet film and the second wet film have identical molar concentrations of perovskite material precursors.

8. A method of implementation according to any one of claims 1 to 6, wherein the first wet film and the second wet film have different molar concentrations of perovskite material precursors.

9. A method of implementation according to any one of claims 1 to 8, wherein the gas quenching steps have the same operating conditions.

10. A method of implementation according to any one of claims 1 to 9, wherein a heat treatment step is carried out following each gas quenching step, so as to eliminate a residual solvent medium.

11. A method of implementation according to any one of claims 1 to 10, wherein the perovskite material has an empirical formula ABX3, where A corresponds to a cation or a combination of metallic or organic cations, B corresponds to one or more metallic elements, such as lead Pb, tin Sn, bismuth Bi, antimony Sb, and where X corresponds to one or more anions, in particular halides, selected from chloride, bromide, iodide and mixtures thereof.

12. A method of embodiment according to claim 11, wherein the chemical element B is lead in overstoichiometry.

13. A method of implementation according to any one of claims 1 to 12, wherein the perovskite material has a molecular formula Cs, FA(i_x)Pb(IyBr(i_y))3, where FA is formamidinium.

14. Method of manufacturing a photovoltaic device comprising the production of an n-type layer, a perovskite active layer produced by the method according to any one of the preceding claims, and a p-type layer.

15. Perovskite-based stack comprising: • a substrate having a deposition face; • a perovskite active layer, covering the deposition face, formed of a perovskite material and crystalline Pbl2, having: • a thickness of at least 0.8pm, and • an APK / APbl2 ratio of at least 1.5, where APK is an area of ​​a peak associated with the perovskite material of an XRD spectrum of the perovskite active layer, and APbl2 is an area of ​​a peak associated with Pbl2.

Images