BR122023000590B1 - PEROVSKITE MATERIAL AND METHOD FOR PRODUCING A PEROVSKITE MATERIAL - Google Patents

Abstract

A perovskite material of general formula A1-xA?xBX3-yX?y is provided, where A is a formamidinium cation (HC(NH)2)2+), A? is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide, and X? is bromide, and x is greater than 0 and equal to or less than 0.4 and y is greater than 0 and less than or equal to 3. Also provided is a method of producing the perovskite material, and formulations for use in forming this material.

Description

The present patent application is a split application of the invention patent application BR112017026691-1, dated 06/10/2016.

FIELD OF INVENTION

[001] The present invention relates to a perovskite material that has a bandgap that makes it suitable for use in multijunction photovoltaic devices and improved stability, and methods and formulations for producing this material.

HISTORY OF THE INVENTION

[002] During the last forty years or so, there has been an increasing realization of the need to replace fossil fuels with suitably safer energy sources. The new energy source must also have a low environmental impact, be highly efficient, and be easy to use and cost-effective to produce. For this purpose, solar energy is seen as one of the most promising technologies, however, the high cost of manufacturing devices that capture solar energy, including high material costs, has historically prevented its widespread use.

[003] Every solid has its own characteristic energy band structure, which determines a wide range of electrical characteristics. Electrons are capable of transitioning from one energy band to another, but each transition requires a specific minimum energy and the amount of energy required will be different for different materials. Electrons obtain the energy needed for the transition by absorbing both a phonon (heat) and a photon (light). The term “bandgap” refers to the range of energetic difference in a solid where no electron states can exist, and generally means the energetic difference (in electron volts) between the top of the valence shell and the bottom of the band gap. driving. The efficiency of a material used in a photovoltaic device, such as a solar cell, under normal sunlight conditions is a function of the bandgap for that material. If the bandgap is too high, most daylight photons cannot be absorbed; If it is too low, then most of the photons have much more energy than needed to excite the electrons between the band gap, and the rest will be wasted. The Shockley-Queisser limit refers to the maximum theoretical amount of electrical energy that can be extracted per photon from incoming light and is approximately 1.34 eV. The focus of much of the recent work on photovoltaic devices has been to seek materials that have a bandgap as close to this maximum as possible.

[004] One class of photovoltaic materials that has attracted significant interest has been hybrid organic-inorganic halide perovskites. Materials of this type form an ABX3 crystal structure, which has been found to show a favorable band gap, a high absorption coefficient and long diffusion lengths, making these compounds ideal as an absorber in photovoltaic devices. Early examples of hybrid organic-inorganic metal halide perovskite material are reported by Kojima, A et al. (2009) Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc., 131(17), pp.6050-6051, in which these perovskites were used as the sensitizer in liquid electrolyte-based photoelectrochemical cells. Kojima et al. reported that the highest obtained solar energy conversion efficiency (or power energy conversion efficiency, PCE) was 3.8%, although in this system the perovskite absorbers deteriorate rapidly and the cells reduced in performance after just 10 minutes.

[005] Subsequently, Lee, M et al., (2012) Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites. Science, 338(6107), pp.643-647 reported a “meso-superstructured solar cell”, in which the liquid electrolyte was replaced by a solid-state hole conductor (or hole transport material, HTM), spiro- MeOTAD. Lee et al. reported a significant increase in the conversion efficiency obtained, also achieving greatly improved cell stability as a result of avoiding the use of a liquid solvent. In the examples described, CH3NH3PbI3 perovskite nanoparticles take on the role of the sensitizer within the photovoltaic cell, injecting electrons into a mesoscopic TiO2 frame and the holes into solid-state HTM. Both TiO2 and HTM act as selective contacts through which charge carriers produced by photoexcitation of perovskite nanoparticles are extracted.

[006] Additional work described in WO2013/171517 revealed how using mixed-anion perovskites as a sensitizer/absorber in photovoltaic devices, instead of single-anion perovskites, results in more stable and highly efficient photovoltaic devices. In particular, this paper reveals that the superior stability of mixed-anion perovskites is highlighted by the finding that the devices exhibit negligible color bleaching during the device fabrication process, while also exhibiting total solar energy conversion efficiencies of more than 10 %. In comparison, equivalent single-anion perovskites are relatively unstable, with bleaching occurring rapidly when fabricating films from single-halide perovskites at ambient conditions.

[007] More recently, WO2014/045021 described planar heterojunction (PHJ) photovoltaic devices comprising a thin film of a photoactive perovskite absorber disposed between n-type (electron transport) and p-type (hole transport) layers. Unexpectedly, it was discovered that good device efficiencies could be obtained using a compact (i.e., no effective/open porosity) thin film of photoactive perovskite, as opposed to the requirement for a mesoporous composite, demonstrating that perovskite absorbers can function in high efficiencies in simple device architectures.

[008] Recently, some research into the application of perovskites in photovoltaic devices has focused on the potential of these materials to increase the performance of conventional silicon-based solar cells by combining them with a perovskite-based cell in a parallel/multijunction arrangement. In this regard, a multijunction photovoltaic device comprises several separate subcells (i.e., each with its own photoactive region) that are “stacked” on top of each and that together convert more of the solar spectrum into electricity, thus increasing the overall efficiency of the device. To this end, each photoactive region of each subcell is selected so that the bandgap of the subcell guarantees that it will efficiently absorb photons from a specific segment of the solar spectrum. This has two important advantages over conventional single-junction photovoltaic devices. Firstly, the combination of several photoactive regions/subcells with different bandgaps ensures that a wider range of incidental photons can be absorbed by a multijunction device, and secondly, each photoactive region/subcell will be more effective at extracting energy from the photons within the relevant part of the spectrum. In particular, the lowest bandgap of a multijunction photovoltaic device will be smaller than that of a typical single-junction device, so that a multijunction device will be able to absorb photons that have less energy than those that can be absorbed by a single junction device. Furthermore, for those photons that would be absorbed by both a multijunction device and a single junction device, the multijunction device will absorb those photons more efficiently, as having bandgaps closer to the photon energy reduces thermalization losses.

[009] In a multijunction device, the upper photoactive region/subcell in the stack has the highest bandgap, with the bandgap of the lower photoactive regions/subcells reducing toward the bottom of the device. This arrangement maximizes photon energy extraction as the upper photoactive region/subcell absorbs higher energy photons while allowing transmission of lower energy photons. Each subsequent photoactive region/subcell then extracts energy from the photons closest to its bandgap, thus minimizing thermalization losses. The lower photoactive region/subcell then absorbs all remaining photons with energy above its bandgap. When designing multijunction cells it is therefore important to choose the photoactive regions/subcells with the right bandgaps in order to optimize solar spectrum collection. In this regard, for a parallel photovoltaic device comprising two photoactive regions/subcells, an upper photoactive region/subcell and a lower photoactive region/subcell, it has been shown that the lower photoactive region/subcell should have a bandgap of approximately 1.1 eV, while the photoactive region/upper subcell should have a bandgap of approximately 1.7 eV (Coutts, T et al. (2002). Modeled performance of polycrystalline thin-film tandem solar cells. Progress in Photovoltaics: Research and Applications, 10(3), pp.195-203).

[010] Consequently, there has been interest in developing hybrid organic-inorganic perovskite solar cells for use in parallel photovoltaic devices, given that the bandgap of these perovskite materials can be attenuated from approximately 1.5 eV to above 2 eV when varying the halide composition of organometal halide perovskites (Noh, J. et al. (2013). Chemical Management for Colorful, Efficient, and Stable Inorganic-Organic Hybrid Nanostructured Solar Cells. Nano Letters, p.130321112645008). However, to date the stability of hybrid organic-inorganic perovskites has proven to be an obstacle to their potential use in commercially viable photovoltaic devices. In particular, while introducing mixed halides into hybrid perovskite compositions allows attenuation of the bandgap, these mixed-halide hybrid perovskites are typically even less stable than comparable single-halide perovskites.

SUMMARY OF THE PRESENT INVENTION

[011] The inventors have developed a photoactive perovskite material that has a bandgap that makes it suitable for use in multijunction photovoltaic devices and improved stability. In particular, the inventors have developed a photoactive perovskite material having a bandgap in the region of 1.6 to 2.3 eV, for use in an upper subcell in a parallel photovoltaic device in combination with a lower subcell of the lower bandgap, and which has improved stability. The inventors have also developed methods and formulations for producing such a photovoltaic device.

[012] The present inventors have surprisingly found that the introduction of small amounts of cesium cations (Cs+) into a formamidinium metal halide perovskite helps in stabilizing the crystal structure to the desired phase without causing a reduction in the thermal stability of the perovskite. . This is particularly surprising since it is unexpected that a mixture of FA and Cs cations would result in a solid perovskite due to the difference in the relative sizes of the FA and Cs cations.

[013] According to a first aspect, a photovoltaic device is provided comprising a photoactive region, the photoactive region comprising a perovskite material of general formula (I):

[014] where A is a formamidinium (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide and X' is bromide; and where 0 < x < 0.4 and 0 < y < 3. The bandgap of the perovskite material can be from 1.60 eV to 2.30 eV, and is preferably from 1.65 eV to 1.75 eV .

[015] The divalent inorganic cation B can be any divalent metal cation and, optionally, is at least one cation selected from Pb2+ and Sn2+. Preferably, the divalent inorganic cation B is a lead (II) cation (Pb2+).

[016] Preferably, the perovskite material has the formula: where FA is a formamidinium cation ((HC(NH)2)2+)), Cs is a cesium cation (Cs+), Pb is a lead (II) cation (Pb2+), I is iodide (I- ) and Br is bromide (Br-). Optionally, x is then greater than or equal to 0.05 and less than or equal to 0.25, and is preferably equal to any of 0.05, 0.10, 0.15, 0.20 and 0.25. Optionally, y is greater than 0 and less than 1.5, is more preferably greater than 0 and equal to or less than 1.0, and is more preferably greater than 0 and equal to or less than 0.6. The perovskite material is preferably configured to function as a light absorber/photosensitizer within the photoactive region. The photoactive region may comprise a thin film of the perovskite material, and preferably the thickness of the thin film of the perovskite material is 100 nm to 1000 nm, and more preferably 200 nm to 700 nm, and even more preferably 300 nm. at 600 nm. The photoactive region may comprise an n-type region comprising at least one n-type layer, and a layer of perovskite material in contact with the n-type region. The photoactive region may comprise an n-type region comprising at least one n-type layer, a p-type region comprising at least one p-type layer; and a layer of the perovskite material disposed between the n-type region and the p-type region. The photoactive region may comprise a layer of perovskite material without open porosity. The layer of perovskite material can then form a planar heterojunction with one or both of the n-type regions and the p-type region. Alternatively, the layer of perovskite material may be in contact with a porous scaffold material that is disposed between the n-type region and the p-type region. The porous scaffold material may comprise or consist of essentially any dielectric material and a semiconductor/charge-carrying material. The layer of perovskite material can then be disposed within the pores of/be insulated with a surface of the porous scaffold material. Alternatively, the layer of perovskite material may fill the pores of the porous frame material and form a boundary layer over the porous frame material, which boundary layer consists of a layer of the photoactive material without open porosity. The photovoltaic device may further comprise a first electrode and a second electrode, with the photoactive region being disposed between the first and second electrodes, wherein the first electrode is in contact with the n-type region of the photoactive region and the second electrode is in contact with the p-type region of the photoactive region. The first electrode may then comprise a transparent or semi-transparent electrically conductive material and the second electrode may comprise a metal. The first electrode may then be an electron-collecting electrode, while the second electrode is a hole-collecting electrode. The photovoltaic device may further comprise a first electrode and a second electrode, with the photoactive region being disposed between the first and second electrodes, wherein the first electrode is in contact with the p-type region of the photoactive region and the second electrode is in contact with the n-type region of the photoactive region. The first electrode may then comprise a transparent or semi-transparent electrically conductive material, and the second electrode may comprise a metal. The first electrode may then be a hole-collecting electrode, while the second electrode is an electron-collecting electrode. The photovoltaic device may have a multijunction structure comprising a first subcell disposed over a second subcell, the first subcell comprising the photoactive region comprising the perovskite material. The photovoltaic device can then have a monolithically integrated structure. In a monolithically integrated multijunction photovoltaic device, the two or more photovoltaic subcells are deposited one on top of the other and are therefore electrically connected in series. The photovoltaic device may then further comprise an intermediate region that connects the first subcell to the second subcell, wherein each intermediate region comprises one or more interconnection layers. The photovoltaic device having a multijunction structure may further comprise a first electrode, a second electrode, with the first subcell and the second subcell disposed between the first and second electrodes. The first electrode may then be in contact with the p-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent electrically conductive material. The first electrode may then be a hole-collecting electrode, while the second electrode is an electron-collecting electrode. In a parallel device, the second will then be in contact with the second subcell. Alternatively, the first electrode may be in contact with the n-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent electrically conductive material. The first electrode may then be an electron-collecting electrode, while the second electrode is a hole-collecting electrode. In a parallel device, the second electrode will then be in contact with the second subcell. When the photovoltaic device has a multijunction structure, the second subcell of the photovoltaic device may comprise any of a second material of perovskite, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS or CuInGaSe (CIGS). According to a second aspect, there is provided a method of producing a photovoltaic device comprising a photoactive material, which photoactive material comprises a perovskite of general formula (I):

[017] where A is a formamidinium cation (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide and X' is bromide , and where 0 < x < 0.4 and 0 < y < 3. The method comprises a step (a) of arranging a second region over a first region, which second region comprises a layer of photoactive material. For example, the first region may be an n-type region comprising at least one n-type layer.

[018] The method may further comprise a step (b) of arranging a third region on the second region. The first region may then be an n-type region comprising at least one n-type layer and the Third region may then be a p-type region comprising at least one p-type layer. Alternatively, the first region may be a p-type region comprising at least one p-type layer and the third region may then be an n-type region comprising at least one n-type layer.

[019] Step (a) of arranging a second region over the first region may comprise producing a solid layer of perovskite material by depositing a chemical solution. The step of producing a solid layer of the perovskite material by chemical solution deposition may comprise (i) forming a precursor solution comprising precursors of the perovskite material dissolved in a solvent system, (ii) disposing/depositing a layer of the precursor solution, and (iii) removal from the solvent system to produce a solid layer of perovskite material.

[020] The precursors of the perovskite material may comprise a first precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) in a first halide anion, a second precursor compound comprising the cation of cesium (Cs+) (A') and both the first halide anion and a second halide anion, and a third precursor compound comprising the divalent inorganic cation (B) and the second halide anion, wherein the first halide anion is one of iodide (X) and bromide (X') and the Second halide is the other of iodide (X) and bromide (X'). The precursors of the perovskite material may further comprise a fourth precursor compound comprising the divalent inorganic cation (B) and the first halide anion.

[021] Alternatively, the precursors of the perovskite material may comprise a first precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and a first halide anion, a second precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and a sacrificial organic anion (Y), a third precursor compound comprising the cesium cation (Cs+) (A') and both the first halide anion as a second halide anion, and a fourth precursor compound comprising the divalent inorganic cation (B) and a second halide anion, wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and iodide (X)). The precursors of the perovskite material may further comprise a fifth precursor compound comprising the divalent inorganic cation (B) and the first halide anion.

[022] The method may then further comprise enabling the removal of a volatile compound comprising the sacrificial organic anion (Y) and the formamidinium cation (HC(NH)2)2+) (A) from the deposited layer of the precursor solution . Preferably, the step of enabling removal of a volatile compound comprises heating the deposited layer of the precursor solution or exposing the deposited layer of the precursor solution.

[023] The sacrificial organic anion (Y) can be an organic anion of the formula RCOO-, ROCOO-, RSO3-, ROP(O)(OH)O- or RO-, where R is H, substituted alkyl or not C1-10 substituted, C2-10 substituted or unsubstituted alkenyl, C2-10 substituted or unsubstituted alkylline, C3-10 substituted or unsubstituted cycloalkyl, C3-10 substituted or unsubstituted heterocyclyl or substituted or unsubstituted aryl. Preferably, the sacrificial organic anion (Y) is any of formate (HCOO-), acetate (CH3COO-), propanoate (C2H5COO-), butanoate (C3H7COO-), pentanoate (C4H10COO-) and benzoate (C6H5COO-). Preferably, the second precursor compound is any of Formamidinium acetate (HC(NH)2)2+), Formamidinium formate (HC(NH)2)2+) or Formamidinium propanoate (HC(NH)2)2+). .

[024] The solvent system may comprise one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP) and dimethylacetamide (DMAc), and preferably in which the system solvent comprises DMF.

[025] Alternatively, the step of producing a solid layer of perovskite material by depositing a chemical solution may comprise (i) forming a first precursor solution comprising one or more precursors of the perovskite material dissolved in a first solvent system, (ii) disposing/depositing a layer of the first precursor solution, (iii) removing the first solvent system to form a solid layer comprising the one or more precursors, (iii) forming a second precursor solution comprising one or more precursors additional perovskite material dissolved in a second solvent system and (iv) treating the solid layer comprising the one or more precursors with the second precursor solution and reacting therewith the one or more precursors and the one or more additional precursors to produce a solid layer of perovskite material.

[026] The one or more precursors of the perovskite material may then comprise a first precursor compound comprising the divalent inorganic cation (B) and a first halide anion. The one or more additional precursors of the perovskite material may then comprise a second precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and both the first halide anion and a second halide anion, and a third precursor compound comprising the cesium (Cs+) cation (A') and the second halide anion, wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and bromide (X').

[027] The first solvent system may comprise one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP) and dimethylacetamide (DMAc), and preferably in which the solvent system comprises DMAc. The second solvent system comprises one or more solvents that are capable of dissolving the one or more additional precursors and that are orthogonal to the one or more solvents of the first solvent system. Optionally, the second solvent system comprises 2-propanol (IPA).

[028] When the photovoltaic device has a multijunction structure comprising a first subcell and one or more additional subcells, wherein the first subcell comprises the layer of perovskite material, the method may further comprise providing an additional subcell, arranging an intermediate region in the additional subcell, and formation of the first subcell in the intermediate region.

BRIEF DESCRIPTION OF THE DRAWINGS

[029] The present invention will now be more particularly described by means of examples still with reference to the attached drawings, in which:

[030] Figure 1a schematically illustrates a single junction photovoltaic device;

[031] Figure 1b schematically illustrates a multijunction photovoltaic device;

[032] Figure 2a schematically illustrates a perovskite-based single-junction photovoltaic device that has a regular structure;

[033] Figure 2b schematically illustrates a perovskite-based single-junction photovoltaic device that has an inverted structure;

[034] Figure 3a schematically illustrates an exemplary perovskite-based single-junction photovoltaic device that has an extremely thin absorbent cellular architecture (ETA);

[035] Figure 3b schematically illustrates an exemplary perovskite-based single-junction photovoltaic device that has a meso-superstructured solar cell (MSSC) architecture;

[036] Figure 3c schematically illustrates a perovskite-based single-junction photovoltaic device that has a flat/planar junction architecture;

[037] Figure 4a schematically illustrates a perovskite-based single-junction photovoltaic device that has a regular structure;

[038] Figure 4b schematically illustrates a perovskite-based single-junction photovoltaic device that has an inverted structure;

[039] Figure 5a schematically illustrates an exemplary perovskite-based parallel photovoltaic device that has a crystalline silicon bottom subcell;

[040] Figure 5b schematically illustrates an exemplary perovskite-based parallel photovoltaic device that has a bottom subcell of CIGS, CIS or CZTSSe;

[041] Figure 5c schematically illustrates an exemplary perovskite-based parallel photovoltaic device that has a bottom subcell comprising a second photosensitive/light-absorbing perovskite material;

[042] Figure 6a shows the XRD pattern of four different perovskite materials;

[043] Figure 7a shows an SEM image of a perovskite material of general formula MA1-xCsxPbI3-yBry;

[044] Figure 7b shows an SEM image of a perovskite material with the general formula FA1-xCsxPbI3-yBry;

[045] Figure 8 shows UV-Vis absorption spectra of four different perovskite materials of general formula FA1-xCsxPbI3-yBry;

[046] Figures 9a and 9b show the UV-Vis absorption spectra of five different perovskite materials of general formula MA1-xCsxPbI3-yBry;

[047] Figure 10 shows photographs of four perovskite materials of different compositions (A to D) before, during and after the thermal stability test;

[048] Figure 11 shows the XRD pattern of five different perovskite materials;

[049] Figure 12 shows the XRD pattern of five additional different perovskite materials; It is

[050] Figure 13 shows the XRD pattern of four additional different perovskite materials.

DETAILED DESCRIPTION DEFINITIONS

[051] The term “photoactive”, as used herein, refers to a region, layer or material that is capable of responding to light photoelectrically. A photoactive region, layer or material is therefore capable of absorbing the energy carried by photons in light, which then results in the generation of electricity (e.g. by generating both electron-hole pairs and excitons).

[052] The term “perovskite”, as used herein, refers to a material with a three-dimensional crystal structure related to that of CaTiO3 or a material comprising a layer of material, which layer has a structure related to that of CaTiO3. The structure of CaTiO3 can be represented by the formula ABX3, where A and B are cations of different sizes and X is an anion. In the unit cell, A cations are at (0,0,0), B cations are at (1/2, 1/2, 1/2), and X anions are at (1/2, 1/2, 0). Cation A is generally larger than cation B. The skilled artisan will recognize that when A, B, and X are varied, the different ion sizes can cause the structure of the perovskite material to distort from the structure adopted by CaTiO3 to a distorted structure of lower symmetry. Symmetry will also be lower if the material comprises a layer that has a structure related to that of CaTiO3. Materials comprising a layer of perovskite material are well known. For example, the structure of materials adopting the K2NiF4 type structure comprises a layer of perovskite material. The skilled artisan will recognize that a perovskite material can be represented by the formula [A][B][X]3, where [A] is at least one cation, [B] is at least one cation, and [X] is at least an anion. When the perovskite comprises more than one A cation, the different A cations can be distributed over the A sites in an ordered or disordered fashion. When the perovskite comprises more than one B cation, the different B cations can be distributed over the B sites in an ordered or disordered fashion. When the perovskite comprises more than one X anion, the different X anions can be distributed over the X sites in an ordered or disordered fashion. The symmetry of a perovskite comprising more than one A cation, more than one B cation, or more than one X cation will generally be smaller than that of CaTiO3.

[053] As mentioned in the previous paragraph, the term “perovskite”, as used herein, refers to (a) a material with a three-dimensional crystal structure related to that of CaTiO3 or (b) a material comprising a layer of material, wherein the layer has a structure related to that of CaTiO3. Although both of these categories of perovskite can be used in the devices according to the invention, it is preferable in some circumstances to use a perovskite from the first category, (a), that is, a perovskite that has a three-dimensional (3D) crystal structure. These perovskites typically comprise a 3D network of perovskite unit cells without any separation between layers. Perovskites in the second category, (b), on the other hand, include perovskites that have a two-dimensional (2D) layer structure. Perovskites that have a 2D overlapping structure can comprise layers of perovskite unit cells that are separated by molecules (intercalated); an example of this 2D overlapping perovskite is [2-(1-cyclohexenyl)ethylammonium]2PbBr4. 2D overlapping perovskites tend to exhibit high exciton binding energies, which favors the generation of bonding electron-hole pairs (excitons), rather than uncharged carriers, upon photoexcitation. The electron-hole pair bond may not be mobile enough to reach the p-type or n-type contact, where it can then transfer (ionize) and generate free charge. Consequently, in order to generate free charge, the exciton binding energy must be overcome, which represents an energetic cost for the energy generation process and results in a lower voltage in a photovoltaic cell and a lower efficiency. In contrast, perovskites that have a 3D crystal structure tend to have much lower exciton binding energies (on the order of thermal energy) and can therefore generate free carriers directly after photoexcitation. Suitably, the perovskite semiconductor employed in the devices and processes of the invention is preferably a perovskite of the first category, (a), that is, a perovskite that has a three-dimensional crystal structure. This is particularly preferable when the device is a photovoltaic device.

[054] The perovskite material used in the present invention is capable of absorbing light and, therefore, generating chargeless carriers. Therefore, the perovskite employed is a light-absorbing perovskite material. However, the skilled artisan will recognize that the perovskite material could also be a perovskite material capable of emitting light, by accepting charge, both electrons and holes, which subsequently recombines and emits light. Thus, the perovskite used could be a light-emitting perovskite.

[055] As the skilled person will recognize, the perovskite material employed in the present invention may be a perovskite that acts as a semiconductor that transports n-type electrons when photodoped. Alternatively, it could be a perovskite that acts as a p-type hole-carrying semiconductor when photodoped. Therefore, the perovskite can be n-type or p-type, or it can be an intrinsic semiconductor. In preferred embodiments, the perovskite employed is one that acts as a semiconductor that transports n-type electrons when photodoped. Perovskite material can exhibit ambipolar charge transport and therefore acts as an n-type and p-type semiconductor. In particular, perovskite can act as an n-type and p-type semiconductor that depends on the type of junction formed between the perovskite and an adjacent material.

[056] Typically, the perovskite semiconductor used in the present invention is a photosensitizing material, that is, a material that is capable of performing both photogeneration and charge transport.

[057] The term “mixed anion”, as used herein, refers to a compound that comprises at least two different anions. The term “halide” refers to an anion of an element selected from Group 17 of the Periodic Table of the Elements, that is, of a halogen. Typically, halide anion refers to a fluoride anion, a chloride anion, a bromide anion, an iodide anion, or an astatide anion.

[058] The term “metal halide perovskite”, as used herein, refers to a perovskite, the formula of which contains at least one metal cation and at least one halide anion. The term “organometal halide perovskite”, as used herein, refers to a metal halide perovskite, the formula of which contains at least one organic cation.

[059] The term “organic material” takes its normal meaning in the art. Typically, an organic material refers to a material comprising one or more compounds comprising a carbon atom. As one skilled in the art would understand, an organic compound may comprise a carbon atom covalently bonded to another carbon atom, or to a hydrogen atom, or to a halogen atom, or to a chalcogen atom (for example, a hydrogen atom). oxygen, a sulfur atom, a selenium atom or a tellurium atom). The skilled artisan will understand that the term "organic compound" does not normally include compounds that are predominantly ionic, such as carbides, for example.

[060] The term “organic cation” refers to a cation that comprises carbon. The cation may comprise additional elements, for example, the cation may comprise hydrogen, nitrogen or oxygen.

[061] The term “semiconductor”, as used herein, refers to a material with electrical conductivity intermediate in magnitude between that of a conductor and a dielectric. The semiconductor can be an n-type semiconductor, p-type semiconductor, or an intrinsic semiconductor.

[062] The term “dielectric”, as used herein, refers to the material that is an electrical insulator or a very weak conductor of electrical current. The term dielectric therefore excludes semiconductor materials such as titanium. The term dielectric, as used herein, typically refers to materials that have a bandgap equal to or greater than 4.0 eV (Titanium's bandgap is approximately 3.2 eV).

[063] The term “n-type”, as used herein, refers to a region, layer or material comprising an extrinsic semiconductor with a higher concentration of electrons than holes. In n-type semiconductors, electrons are therefore majority carriers and holes are minority carriers and are therefore electron-transporting materials. The term “n-type region”, as used herein, therefore refers to a region of one or more electron-transporting (i.e., n-type) materials. Similarly, the term “n-type layer” refers to a layer of an electron-transporting material (i.e., an n-type). An electron-transporting material (i.e., an n-type) could be a single electron-transporting compound or elementary material, or a mixture of two or more electron-transporting compounds or elementary materials. An electron-transporting compound or elementary material may be undoped or doped with one or more doping elements.

[064] The term “p-type”, as used herein, refers to a region, layer or material that comprises an extrinsic semiconductor with a greater concentration of holes than electrons. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers, and are therefore the transport materials. The term “p-type region”, as used herein, therefore refers to a region of one or more orifice-bearing (i.e., p-type) materials. Similarly, the term “p-type layer” refers to a layer of an orifice-bearing material (i.e., a p-type). A hole-transporting material (i.e., a p-type) could be a single hole-transporting compound or elementary material, or a mixture of two or more hole-transporting compounds or elementary materials. A compound carrying hole or elemental material may be undoped or doped with one or more doping elements.

[065] The term “gap band”, as used herein, refers to the energetic difference between the upper part of the valence layer and the lower part of the conduction band in a material. The skilled artisan can easily measure the bandgap of a material without excessive experimentation.

[066] The term “layer”, as used herein, refers to any structure that is substantially laminar in shape (for example, extending substantially in two perpendicular directions, but limited in its extension in the third perpendicular direction). A layer may have a thickness that varies over the length of the layer. Typically, a layer has approximately constant thickness. The “thickness” of a layer, as used herein, refers to the average thickness of a layer. The thickness of the layers can be easily measured, for example, by using microscopy, such as electron microscopy of a cross-section of a film, or by surface profilometry, for example, using a tip profilometer.

[067] The term “porous”, as used herein, refers to a material in which pores are arranged. Thus, for example, in a porous material the pores are volumes within the body of the material where there is no material. Individual pores can be of the same or different sizes. Pore size is defined as “pore size”. The limiting size of a pore, for most phenomena in which porous solids are involved, is its smallest dimension which, in the absence of any further precision, is referred to as the pore width (i.e., the width of a pore slit-shaped, the diameter of a cylindrical or spherical pore, etc.). To avoid a misleading scale change when comparing cylindrical and slit-shaped pores, one should use the diameter of a cylindrical pore (rather than its length) as its “pore width” (Rouquerol, J. et al. (1994). Recommendations for the characterization of porous solids (Technical Report). Pure and Applied Chemistry, 66(8)). The following distinctions and definitions were adapted from previous IUPAC documents (J. Haber. (1991) Manual on catalyst characterization (Recommendations 1991). Pure and Applied Chemistry.): micropores have widths (i.e., pore sizes) less than 2 nm; Mesopores have widths (i.e., pore sizes) of 2 nm to 50 nm; and Macropores have widths (i.e., pore sizes) greater than 50 nm. Furthermore, nanopores can be considered to have widths (i.e., pore sizes) smaller than 1 nm.

[068] Pores in a material may include “closed” pores as well as open pores. A closed pore is a pore in a material that is an unconnected cavity, that is, a pore that is isolated within the material and not connected to any other pore and that cannot, therefore, be accessed by a fluid to which the material is exposed. As an “open pore”, on the other hand, it would be accessible by such a fluid. The concepts of open and closed porosity are revealed in detail in J. Rouquerol et al.

[069] Therefore, open porosity refers to the fraction of the total volume of the porous material in which fluid flow would effectively occur. Therefore, it excludes closed pores. The term “open porosity” is interchangeable with the terms “connected porosity” and “effective porosity”, and in the art is commonly reduced to simply “porosity”. The term “open porosity” as used herein therefore refers to a material without effective porosity. Thus, a material without open porosity normally does not have macropores or mesopores. A material without open porosity may comprise micropores and nanopores, however. These micropores and nanopores are typically too small to have a negative effect on a material for which low porosity is desired.

[070] Furthermore, polycrystalline materials are solids that are composed of several separate crystallites or grains, with grain boundaries at the interface between any two crystallites or grains in the material. A polycrystalline material can therefore have interparticle/interstitial porosity and intraparticle/internal porosity. The terms “interparticle porosity” and “interstitial porosity,” as used herein, refer to pores between the crystallites or grains of the polycrystalline material (i.e., the grain boundaries), while the terms “intraparticle porosity” and “internal porosity ”, as used herein, refers to pores within the crystalline or individual grains of the polycrystalline material. In contrast, a single crystal or monocrystalline material is a solid in which the crystal lattice is continuous and intact throughout the volume of the material, such that there are no grain boundaries and no interparticle/interstitial porosity.

[071] The term “compact layer”, as used here, refers to a layer without mesoporosity or macroporosity. A compact layer can sometimes have microporosity or nanoporosity.

[072] The term “frame material”, as used herein, therefore refers to a material that is capable of acting as a support for an additional material. The term "porous scaffold material", as used herein, therefore refers to a material that is itself porous, and which is capable of acting as a support for an additional material.

[073] The term “transparent”, as used herein, refers to the material or object allowing visible light to pass through almost untouched, so that the objects behind can be observed distinctly. The term “semi-transparent”, as used herein, therefore refers to a material or object that has a transmission (alternatively and equivalently referred to as a transmittance) to visible light intermediate between a transparent material or object and an opaque material or object. Typically, a transparent material will have an average transmission for visible light (generally light with a wavelength of 370 to 740 nm) of approximately 100%, or 90 to 100%. Typically, an opaque material will have an average transmittance for visible light of approximately 0%, or 0 to 5%. A semitransparent material or object will typically have an average transmittance for visible light of 10 to 90%, typically 40 to 60%. Unlike many translucent objects, semitransparent objects typically do not distort or blur images. Transmission for light can be measured using routine methods, for example, by comparing the intensity of incident light with the intensity of transmitted light.

[074] The term “electrode”, as used herein, refers to a conductive material or object through which electrical current enters or leaves an object, substance or region. The term “negative electrode,” as used herein, refers to an electrode through which electrons leave a material or object (i.e., an electron-collecting electrode). A negative electrode is usually referred to as an “anode”. The term “positive electrode,” as used herein, refers to an electrode through which holes leave a material or object (i.e., a hole-collecting electrode). A positive electrode is usually referred to as a “cathode”. Within a photovoltaic device, electrons flow from the positive electrode/cathode to the negative electrode/anode, while holes flow from the negative electrode/anode to the positive electrode/cathode.

[075] The term “front electrode”, as used herein, refers to the electrode provided on that side or surface of a photovoltaic device that is intended to be exposed to sunlight. The front electrode is therefore normally required to be transparent or semi-transparent, so as to allow light to pass through the electrode to the photoactive layers beneath the front electrode. The term "back electrode", as used herein, therefore refers to the electrode provided on that side or surface of a photovoltaic device that is opposite the side or surface that is intended to be exposed to sunlight.

[076] The term “charge carrier” refers to a region, layer or material through which a charge carrier (i.e., a particle carrying an electrical charge), is free to move. In semiconductors, electrons act as mobile negative charge carriers and holes act as mobile positive charges. The term “electron carrier” therefore refers to a region, layer or material through which electrons can flow easily and which will normally reflect holes (a hole being the absence of an electron which is considered to be a mobile carrier of positive charge in a semiconductor). On the other hand, the term “hole carrier” refers to a region, layer, or material through which holes can easily flow and which will normally reflect electrons.

[077] The term “consisting essentially of” refers to a composition that comprises the components of which it essentially consists, as well as other components, provided that the other components do not materially affect the essential characteristics of the composition. Typically, a composition consisting essentially of certain components will comprise greater than or equal to 95% by weight of these components or greater than or equal to 99% by weight of these components.

[078] The term “volatile compound”, as used herein, refers to a compound that is easily removed by evaporation or decomposition. For example, a compound that is easily removed by evaporation or decomposition at a temperature less than or equal to 150 °C or, for example, at a temperature less than or equal to 100 °C, would be a volatile compound. “Volatile compound” also includes compounds that are easily removed by evaporation through decomposition products. Therefore, a volatile compound X can easily evaporate through evaporation of molecules of X, or a volatile compound For example, ammonium salts can be volatile compounds, and can evaporate as ammonium salt molecules or as decomposition products, for example, ammonium and a hydrogen compound (for example, a hydrogen halide). Thus, a volatile compound decomposition), which can also be referred to as a dissociation pressure.

DEVICE STRUCTURE

[079] Figures 1a and 1b schematically illustrate the photovoltaic devices 100a, 100b according to the present invention. In Figures 1a and 1b, the photovoltaic devices 100a, 100b comprise each transparent or semi-transparent front electrode 101a, 101b and a rear electrode 102a, 102b, with a photoactive region 110a, 110b disposed between the front and rear electrodes, wherein the photoactive region comprising a perovskite material of general formula (I):

[080] where A is a formamidinium cation (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, and X is iodide and X' is bromide, with the value of x being greater than 0 and equal to or less than 0.4 and the value of y being greater than 0 and less than or equal to 3.

[081] The perovskite material is configured to function as a light absorber/photosensitizer within the photoactive region. Furthermore, the perovskite material in the photoactive region can also be configured to provide charge transport. In this regard, perovskite materials are capable of acting not only as a light absorber (i.e. photosensitizer) but also as an n-type, p-type or intrinsic (i-type) semiconductor (charge carrier) material. A perovskite material can therefore act as a photosensitizer and as the n-type semiconductor material. The perovskite material can therefore take on the roles of light absorption and long-range charge transport.

[082] In Figure 1a, the illustrated photovoltaic device 100a includes a single photoactive region 110a disposed on the front 101a and rear electrodes 102a, wherein the photoactive region 110a comprises a perovskite material of general formula (I). Therefore, Figure 1a illustrates a single-junction photovoltaic device.

[083] Figure 1b then illustrates a multijunction photovoltaic device 100b that includes a first subcell 110b in which the photoactive region comprises a perovskite material of general formula (I) and one or more additional subcells 120 disposed between the front 101b and rear electrodes 102b. In particular, Figure 1b illustrates a monolithically integrated multijunction photovoltaic device in which each subcell 110b, 120 is connected to an adjacent subcell by an intermediate region 130 comprising one or more interconnection layers (e.g., a recombination or junction layer). tunnel). In a monolithically integrated multijunction photovoltaic device, the individual subcells are electrically connected in series, which results in the need for a recombination layer or a tunnel junction and current matching. In contrast, in a mechanically stacked multijunction photovoltaic device, the individual subcells are provided with separate electrical contacts and therefore contact each other and do not require current matching. However, the additional size and cost of additional contacts and substrates, and the difficulties of heating dispersion make mechanically stacked structures less favorable than monolithically integrated structures.

[084] Figures 2a and 2b schematically illustrate separate embodiments of single junction photovoltaic devices 100a that have a photoactive region 110a comprising a perovskite material of general formula (I). In each of these embodiments, the photoactive region 110a comprises an n-type region 111a comprising at least one n-type layer, a p-type region 112a comprising at least one p-type layer, and a layer of perovskite material 113a disposed between the n-type region and the p-type region.

[085] The n-type region comprises one or more n-type layers. Generally the n-type region is an n-type layer, that is, a single n-type layer. In other embodiments, however, the n-type region may comprise an n-type layer and a separate n-type exciton blocking layer or hole blocking layer.

[086] An exciton blocking layer is a material that has a wider bandgap than the photoactive material, but has its conduction band or valence band closely matched with those of the photoactive material. If the conduction band (or lowest free molecular orbital energy levels) of the exciton blocking layer is closely aligned with the conduction band of the photoactive material, then electrons can pass from the photoactive material to and through the exciton blocking layer , or through the exciton layer and into the photoactive material, and we call this an n-type exciton blocking layer. An example of this is batocuproin (BCP), as described in P. Peumans, A. Yakimov, and S. R. Forrest, “Small molecular weight organic thin-film photodetectors and solar cells” J. Appl. Phys. 93, 3693 (2001) and Masaya Hirade, and Chihaya Adachi, “Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance” Appl. Phys. Lett. 99, 153302 (2011).

[087] An n-type layer is a layer of an electron transport material (i.e., an n-type). An n-type material may be a single n-type compound or elemental material, or a mixture of two or more n-type compounds or elemental materials, which may be undoped or doped with one or more doping elements. An n-type layer may comprise an organic or inorganic n-type material.

[088] A suitable inorganic n-type material can be selected from a metal oxide, a metal sulfide, a metal selenide, a metal telluride, a perovskite, amorphous Si, an n-type group IV semiconductor, a group III-V type n, a group II-VI type n semiconductor, a group I-VII type n semiconductor, a group IV-VI type n semiconductor, a group V-VI type n semiconductor, and a of group II-V type n, any of which may be doped or undoped. Typically, the n-type material is selected from a metal oxide, a metal sulfide, a metal selenide and a metal telluride. Therefore, the n-type material may comprise an inorganic material selected from oxide of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or an oxide of a mixture of two or more of said metals. ; a sulfide of cadmium, tin, copper, zinc or a sulfide of a mixture of two or more of said metals; a selenide of cadmium, zinc, indium, gallium or a selenide of a mixture of two or more of said metals; or telluride of cadmium, zinc, cadmium or tin, or a telluride of a mixture of two or more of said metals.

[089] Examples of other semiconductors that may be suitable n-type materials, for example, if they are n-doped, include elemental or compound semiconductors of group IV; Amorphous Si; group III-V semiconductors (e.g. gallium arsenide); group II-VI semiconductors (e.g. cadmium selenide); group I-VII semiconductors (e.g. cuprous chloride); group IV-VI semiconductors (e.g. lead selenide); group V-VI semiconductors (e.g. bismuth telluride); and group II-V semiconductors (e.g. cadmium arsenide).

[090] Other n-type materials can also be used, including organic and polymeric electron transport materials, and electrolytes. Suitable examples include, among others, a fullerene or a fullerene derivative, an organic electron transport material comprising a perylene or a derivative thereof, or poly{[N,N0-bis(2-octyldodecyl)-naphthalene-1 ,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,50-(2,20-bitiophene)} (P(NDI2OD-T2)).

[091] The p-type region comprises one or more p-type layers. Generally, the p-type region is a p-type layer, that is, a single p-type layer. In other embodiments, however, the p-type region may comprise a p-type layer and a p-type exciton blocking layer or electron blocking layer. If the valence shell (or highest occupied molecular orbital energy levels) of the exciton blocking layer is closely aligned to the valence shell of the photoactive material, then holes can pass from the photoactive material to and through the exciton blocking layer. , or through the exciton blocking layer and into the photoactive material, and we call this a p-type exciton blocking layer. an example of this is tris[4-(5-phenylthiophene-2-yl)phenyl]amino, as described in Masaya Hirade, and Chihaya Adachi, “Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance” Appl . Phys. Lett. 99, 153302 (2011).

[092] A p-type layer is a layer of a material that carries orifice (i.e., a p-type). The p-type material may be a single p-type compound or elemental material, or a mixture of two or more p-type compounds or elemental materials, which may be undoped or doped with one or more doping elements. A p-type layer may comprise an inorganic or organic p-type material.

[093] Suitable p-type materials can be selected from polymeric or molecular hole carriers. Suitable p-type materials include molecular hole carriers, polymeric hole carriers and copolymer hole carriers. A p-type material may, for example, be a molecular hole-bearing material, a polymer or copolymer comprising one or more of the following moieties: thiophenyl, phenelenyl, dithiazolyl, benzothiazolyl, diketopyrrolopyrrolyl, ethoxydithiophenyl, amino, triphenyl amino, carbozolyl, ethylene diozithiophenyl , dioxythiophenyl, or fluorenyl. Therefore, a p-type material employed in the photovoltaic device of the invention may, for example, comprise any of the above-mentioned molecular hole-carrying materials, polymers or copolymers. In one embodiment, the p-type regions comprise an orifice transport material.

[094] A p-type layer of the photovoltaic device may comprise spiro-OMeTAD (2,2',7,7'-tetracys-(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene)), P3HT (poly(3-hexylthiophene)), PCPDTBT (Poly[2,1,3-benzothiadiazol-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3 ,4-b']dithiophene-2,6-diyl]]), PVK (poly(N-vinylcarbazole)), poly(3-hexylthiophene), poly[N,N-diphenyl-4-methoxyphenylamino-4',4 ''-diyl], sexithiophene, 9,10-bis(phenylethynyl)anthracene, 5,12-bis(phenylethynyl)naphthacene, diindenoperylene, 9,10-diphenylanthracene, PEDOT-TMA, PEDOT:PSS, perfluoropentacene, perilene, poly( phenylene oxide), poly(phenylene p-sulfide), quinacridone, rubrene, 4-(dimethylamino)benzaldehyde diphenylhydrazone, 4-(dibenzylamino)benzaldehyde-N,Ndiphenylhydrazone or phthalocyanines.

[095] The device illustrated in Figure 2a has what is considered a regular structure for a perovskite-based single junction photovoltaic device, in which the front electrode 101a is in contact with the n-type region 111a of the photoactive region 110a and the rear electrode 102a is in contact with the p-type region 112a of the photoactive region 110a (Docampo, P. et al. (2013) Efficient organometal trihalide perovskite planar-heterojunction solar cells on flexible polymer substrates. Nat Comms, 4). The front electrode 101a therefore functions as a negative (electron-collecting) electrode, while the rear electrode 102a functions as a positive (hole-collecting) electrode.

[096] By way of example, in the exemplary device structure illustrated in Figure 2a, the front electrode may comprise a transparent conductive oxide (TCO), such as a tin-doped indium oxide (ITO), fluorine-doped tin oxide ( FTO), etc., the n-type region may comprise one or more layers of the n-type material (e.g., where each layer of the n-type material may comprise an n-type material selected from those detailed above), the p-type region may comprise one or more layers of p-type material (e.g., where each layer of p-type material may comprise a p-type material selected from those described above), and the back electrode may comprise a high work function metal, such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Au).

[097] In contrast, the device illustrated in Figure 2b has what is considered an inverted structure for a perovskite-based single-junction photovoltaic device in which the front electrode 101a is in contact with the p-type region 112a of the photoactive region 110a and the rear electrode 102a is in contact with the n-type region 111a of the photoactive region 110a. The front electrode 101a therefore functions as a positive electrode (hole collecting), while the rear electrode 102a functions as a negative electrode (electron collecting).

[098] By way of example, in the exemplary device structure illustrated in Figure 2b, the front electrode may comprise a transparent conductive oxide (TCO), such as a tin-doped indium oxide (ITO), fluorine-doped tin oxide ( FTO), etc., the p-type region may comprise one or more layers of the p-type material (e.g., where each layer of the p-type material may comprise a p-type material selected from those described above), the n-type region may comprise one or more layers of n-type material (e.g., where each layer of n-type material may comprise an n-type material selected from those detailed above), and the back electrode may comprise a high work function metal, such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Au).

[099] Both devices illustrated in Figures 2a and 2b include an n-type region and a p-type region, with the perovskite photoactive material arranged between the n-type region and the p-type region, so that the n-type region ( which transports electron) and the p-type region (which carries hole) act to change charge in the perovskite material towards the respective electrodes. However, it is also possible for these devices to include only a charge-carrying region. In particular, it has been demonstrated that functional photovoltaic devices comprising a photoactive perovskite can be formed without any hole-transporting materials, such that the photoactive perovskite is in direct contact with an electrode and/or metal layer (see, Etgar, L ., Gao, P. & Xue, Z., 2012. Mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells. J. Am. Chem. Soc., 2012, 134 (42), pp 17396-17399). In these devices, the photoactive perovskite takes on the roles of light harvester and hole carrier, so that an additional hole-transporting material is redundant.

[100] Figures 3a to 3c illustrate some exemplary embodiments of a perovskite-based single-junction photovoltaic device.

[101] In Figures 3a and 3b, the photoactive region 110a of the photovoltaic device 100a comprises a porous region 114a, wherein the porous region 114a comprises a layer of perovskite material 113a of formula (I) that is in contact with a material of porous frame 115a which is disposed between the n-type region 111a and the p-type region 112a. In this embodiment, the layer of perovskite material 113a is provided as a coating over the porous frame material 115a, thereby forming a substantially insulating layer on the surface of the porous frame, so that the perovskite material 113a is disposed within the porous frame. . The p-type region 112a comprises a charge-carrying material, then fills the pores of the porous region 114a (i.e., the pores of the perovskite-coated porous scaffold) and forms a boundary layer over the porous material. In this regard, the boundary layer of the load-carrying material consists of a layer of the load-carrying material without open porosity.

[102] In Figure 3a, the illustrated photovoltaic device 100a has what has been referred to as an extremely thin absorbing cellular architecture (ETA) in which an extremely thin layer of light-absorbing perovskite material is provided at the interface between n-type semiconductors ( e.g. TiO2) and p-type (e.g. HTM) nanostructured and interpenetrating. In this arrangement, the porous frame material 115a within the photoactive region 110a comprises a semiconductor/charge-carrying material.

[103] In Figure 3b, the illustrated photovoltaic device 100a has what has been referred to as a meso-superstructured solar cell (MSSC) architecture in which an extremely thin layer of light-absorbing perovskite material is provided on an insulating frame material. mesoporous. In this arrangement, the porous frame material 115a within the photoactive region 110a comprises a dielectric material (e.g., Al2O3).

[104] In Figure 3c, the photoactive region 110a comprises a layer of perovskite material 113a of formula (I) without open porosity. As described above, a material without open porosity typically has neither macropores nor mesopores, but may have micropores and nanopores (and therefore may have intercrystalline pores). The layer of perovskite material 113a therefore forms a planar heterojunction with one or both of the n-type region 111a and the p-type region 112a. Both the n-type region 111a and the p-type region 112a can be arranged on the perovskite material layer 113a without open porosity. In this regard, since the perovskite material layer 113a is without open porosity, no n-type or n-type material infiltrates the perovskite material to form a bulky heterojunction; instead of forming a planar heterojunction with perovskite material. Normally the layer of perovskite material 113a without open porosity is in contact with the n-type region and the p-type region, and then forms a planar heterojunction with the n-type region and the p-type region.

[105] In Figure 3c, the photovoltaic device 100a illustrated then has a thin-film planar heterojunction device architecture in which a thin solid layer of light-absorbing perovskite material is provided between the n-type planar layers (e.g. , TiO2) and p-type semiconductors (e.g. HTM). In this arrangement, the device does not include a porous frame material.

[106] In an alternative embodiment, the photoactive region may comprise a layer of the perovskite material of formula (I), wherein the perovskite material fills the pores of a porous frame material and forms a boundary layer of the perovskite material over the porous frame material, wherein the boundary layer of the perovskite material is not infiltrated by the porous frame material. The layer of perovskite material is then in contact with the porous scaffold material. Typically the boundary layer consists of a layer of open porosity-free perovskite material that then forms a planar heterojunction with one of the n-type region and the p-type region.

[107] In yet a further embodiment, the photoactive region may comprise a layer of the perovskite material of formula (I), wherein the perovskite material is itself porous. A charge transport material then fills the pores of the porous region of the perovskite material and forms a boundary layer over the porous perovskite material. In this regard, the boundary layer of the load-carrying material consists of a layer of the load-carrying material without open porosity.

[108] Depending on the specific arrangement of the device, the thickness of the photoactive region is typically 300 nm to 3000 nm. Generally the thickness of the photoactive region is 400 nm to 2000 nm. For example, the thickness can be from 500 nm to 1500 nm.

[109] In order to provide highly effective photovoltaic devices, the absorption of the absorber should ideally be maximized in order to generate an ideal amount of current. Consequently, when using a perovskite as the absorber in a photovoltaic device, the thickness of the perovskite layer should ideally be on the order of 300 to 600 nm in order to absorb most of the sunlight that crosses the visible spectrum. In particular, in a solar cell, the perovskite layer generally must be thicker than the absorption depth (which is defined as the film thickness required to absorb 90% of the incident light of a given wavelength, which, for the perovskite materials of interest, it is typically above 100 nm if significant light absorption is required across the entire visible spectrum (400 to 800 nm)), such as the use of a photoactive layer in photovoltaic devices with a thickness less than 100nm can be detrimental to device performance.

[110] Typically, therefore, the layer thickness of the perovskite material is greater than 100 nm. The layer thickness of the perovskite material in the photovoltaic device can, for example, be 100 nm to 1000 nm. The layer thickness of the perovskite material in the photovoltaic device may, for example, be 200 nm to 700 nm, and is preferably 300 nm to 600 nm.

[111] The front electrode may have a thickness of 100 nm to 700 nm, for example, 100 nm to 400 nm. For example, the thickness may be 400 nm. The rear electrode has a thickness of 10 nm to 500 nm, for example, from 50 nm to 200 nm. For example, the thickness of the back electrode may be 150 nm.

[112] The n-type region comprises one or more n-type layers. the n-type region can have a thickness of 50 nm to 1000 nm. For example, the n-type region may have a thickness of 50 nm to 500 nm, or 100 nm to 500 nm. Where the n-type region comprises a compact layer of an n-type semiconductor, the compact layer has a thickness of 50 nm to 200 nm, typically a thickness of approximately 100 nm.

[113] The p-type region comprises one or more p-type layers. the p-type region can have a thickness of 50 nm to 1000 nm. For example, the p-type region may have a thickness of 50 nm to 500 nm, or 100 nm to 500 nm.

[114] Where the photoactive region comprises a porous frame material, the layer thickness of the porous frame material may have a thickness of 5 nm to 500 nm, or 100 nm to 300 nm. For example, the layer thickness of the porous scaffold may be 10 nm to 50 nm.

[115] Where the photoactive region comprises a boundary layer of perovskite material over the porous region, the thickness of the boundary layer may be greater than, equal to, or less than the thickness of the porous region. The thickness of the boundary layer is typically 10 nm to 1000 nm or, for example, 100 nm to 700 nm. A boundary layer that has a thickness of at least 100 nm is generally preferred. The thickness of the porous region is generally 5 nm to 1000 nm. More typically, it is 5 nm to 500 nm or, for example, 30 nm to 200 nm.

[116] Figures 4a and 4b illustrate schematically separate embodiments of multijunction photovoltaic devices 100b that have a first subcell 110b comprising a perovskite material of general formula (I) and one or more additional subcells 120.

[117] In each of these embodiments, the multijunction photovoltaic device 100b has a monolithically integrated structure that therefore comprises only two electrodes, the front electrodes 101b and the rear electrodes 102b, with the first subcell 110b and the one or more additional subcells 120 arranged between the two electrodes. Furthermore, since the monolithically integrated structure comprises only two electrodes, each subcell is connected to an adjacent photoactive region by an intermediate region 130, wherein each intermediate region comprises one or more interconnection layers. For example, the interconnection layers may comprise any one of a recombination layer and a tunnel junction.

[118] In each of these embodiments, the first subcell 110b further comprises an n-type region 111b, which comprises at least one n-type layer, a p-type region 112b, which comprises at least one p-type layer, with a layer of perovskite material 113b disposed between the n-type region 111b and the p-type region 112b.

[119] By way of example, each of the one or more additional subcells 120 of the multijunction photovoltaic device 100b may comprise any one of a second photoactive material of perovskite, amorphous silicon, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS or CuInGaSe (CIGS) .

[120] The device illustrated in Figure 4a has what is considered a regular structure for the perovskite-based multijunction photovoltaic device 100b, wherein the front electrode 101b is in contact with the p-type region 112b of the first subcell 110b comprising the perovskite material 113b of general formula (I) and the rear electrode 102b is in contact with one of one or more additional subcells 120. The front electrode 101b therefore functions as a positive (hole collecting) electrode, while the rear electrode 101b 102b works as a negative electrode (which collects electrons).

[121] In Figure 4a, the illustrated multijunction photovoltaic device 100b is a parallel device comprising two photoactive subcells 110b, 120, wherein the top/top/first subcell 110b comprises a photosensitive/light-absorbing perovskite material 113b of formula (I) and bottom/bottom/second subcell 120 may, for example, comprise a subcell based on crystalline silicon.

[122] By way of example, in this exemplary structure, the front electrode 101b may comprise a transparent conductive oxide (TCO), such as a tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc. , the p-type region 112b may comprise one or more layers of p-type material (e.g., where each layer of p-type material may comprise a p-type material selected from those detailed above), the n-type region 111b may comprise a or more layers of n-type material (e.g., where each layer of n-type material may comprise an n-type material selected from those detailed above), and the back electrode 102b may comprise a high work function metal, such as gold (Au ), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Au). By way of example, the intermediate region 130 could comprise a recombination layer that comprises an ITO layer.

[123] In contrast, the device illustrated in Figure 4b has what is considered an inverted structure for a perovskite-based multijunction photovoltaic device 100b, in which the front electrode 101b is in contact with the n-type region 111b of the first subcell 110b and the rear electrode 102b is in contact with one of one or more additional subcells 120. The front electrode 101b therefore functions as a negative electrode (which collects electrons), while the rear electrode 102b functions as a positive electrode (which collects hole ).

[124] In Figure 4b, the illustrated multijunction photovoltaic device 100b is a parallel device comprising two photoactive subcells 110b, 120, wherein the top/top/first subcell 110b comprises a photosensitive/light-absorbing perovskite material 113b of formula (I) and the bottom/bottom/second subcell 120 may, for example, comprise a subcell based on crystalline silicon.

[125] By way of example, in this exemplary structure, the front electrode 101b may comprise a transparent conductive oxide (TCO), such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc., the n-type region 111b may comprise one or more layers of n-type material (e.g., where each layer of n-type material may comprise an n-type material selected from those detailed above, the p-type region 112b may comprise one or more layers of p-type material (e.g., wherein each layer of p-type material may comprise a p-type material selected from those detailed above), and the back electrode 102b may comprise a high work function metal such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Au).By way of example, the intermediate region 130 could comprise a recombination layer comprising an ITO layer.

[126] Figures 5a to 5c illustrate some additional exemplary embodiments of multijunction photovoltaic devices having a first subcell comprising a perovskite material of general formula (I) and one or more additional subcells.

[127] Figure 5a illustrates an example of a parallel photovoltaic device, wherein the top/top/first subcell comprises a photosensitive/light-absorbing perovskite material and the bottom/bottom/second subcell comprises a crystalline silicon subcell. . In this exemplary embodiment, the crystalline silicon subcell comprises an amorphous silicon/crystalline silicon (SHJ) heterojunction that makes use of a crystalline silicon wafer (c-Si) as a photoactive absorber and amorphous silicon (a-Si) thin films. for joint formation and surface passivation. The crystalline silicon subcell comprises a p-type a-Si emitter, an intrinsic a-Si passivation/buffer layer, an n-type c-Si photoactive absorber, another intrinsic a-Si passivation/buffer layer, and a back surface field (BSF) layer made of n-type a-Si.

[128] Figure 5b illustrates an example of a parallel photovoltaic device, wherein the top/top/first subcell comprises a photosensitive/light-absorbing perovskite material and the bottom/bottom/second subcell comprises a CIGS, CIS subcell. or CZTSSe. In this exemplary embodiment, the lower subcell comprises a photoactive absorber (p-type) of CIGS, CIS or CZTSSe and a buffer layer (n-type) of CdS.

[129] Figure 5c illustrates an example of a parallel photovoltaic device, wherein the top/top/first subcell comprises a photosensitive/light-absorbing perovskite material and the bottom/bottom/second subcell comprises a second perovskite material. photosensitive/light absorbing.

MULTIJUNCTION DEVICE

[130] Accordingly, there is provided the multijunction photovoltaic device comprising a first (upper) subcell and a second (lower) subcell, wherein the first subcell comprises a light-absorbing perovskite material having a general formula (I) of:

[131]

[132] where A is a formamidinium cation (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide, and X' is bromide , and where 0 < x < 0.4 and 0 < y < 3. Preferably, the multijunction photovoltaic device is a parallel photovoltaic device comprising two photoactive regions, wherein the first photoactive region is the upper part of the photoactive region and the The second photoactive region is the lower part of the photoactive region.

[133] The first subcell may comprise an n-type region comprising at least one n-type layer and a layer of perovskite material in contact with the n-type region. The first subcell may comprise an n-type region comprising at least one n-type layer, a p-type region comprising at least one p-type layer, and a layer of perovskite material disposed between the n-type region and the n-type region. P.

[134] The multijunction photovoltaic device may further comprise a first electrode, and a second electrode, wherein the first subcell and the second subcell are disposed between the first and second electrodes.

[135] The first electrode may then be in contact with the p-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent electrically conductive material. The first electrode may then be a hole-collecting electrode, while the second electrode is an electron-collecting electrode.

[136] Alternatively, the first electrode may be in contact with the n-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent electrically conductive material. The first electrode may then be an electron-collecting electrode, while the second electrode is a hole-collecting electrode.

[137] The second photoactive region may comprise any of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS or CuInGaSe (CIGS).

[138] Preferably, the second subcell comprises a crystalline silicon subcell, and more preferably the crystalline silicon subcell comprises a silicon heterojunction (SHJ), and even more preferably the crystalline silicon subcell comprises an amorphous silicon:crystalline silicon heterojunction .

[139] The perovskite material can then have formula (II):

[140] where FA is a formamidinium cation ((HC(NH)2)2+)), Cs is a cesium cation (Cs+), Pb is a lead (II) cation (Pb2+), I is iodide (I-) and Br is bromide (Br-). Preferably, x is then equal to or greater than 0.05 and less than or equal to 0.25, and is more preferably equal to any of 0.05, 0.10, 0.15, 0.20 and 0.25. Preferably, y is then greater than 0 and less than 1.5, is more preferably greater than 0 and less than or equal to 1.0, and is even more preferably 0.6.

[141] The multijunction photovoltaic device may have a monolithically integrated structure. The multijunction photovoltaic device may then further comprise an intermediate region that connects the first subcell to the second subcell, wherein the intermediate region comprises one or more interconnection layers.

PEROVSKITE MATERIAL

[142] As noted above, in the photovoltaic devices of the present invention, the photoactive region comprises a perovskite material of general formula (I):

[143] where A is a formamidinium cation (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide, and X' is bromide , with the value of x being greater than 0 and less than or equal to 0.4 and the value of y being greater than 0 and less than or equal to 3.

[144] The bandgap of the perovskite material of formula (I) is therefore tunable to between 1.60 eV to 2.30 eV, which makes it particularly suitable for use in the upper part of the subcell of a multijunction photovoltaic device when combined with one or more additional subcells. The one or more additional subcells may comprise any one of a second photoactive material of perovskite, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS or CuInGaSe (CIGS). Preferably, the bandgap of the perovskite material is 1.65 eV to 1.75 eV, since the perovskite material is then ideal for use in an upper subcell of a parallel photovoltaic device, wherein the lower subcell preferably has band gap of approximately 1.1 eV. In particular, when the bandgap of the perovskite material is between 1.65 eV and 1.75 eV, the perovskite material is then ideal for use in an upper subcell of a parallel photovoltaic device, wherein the lower subcell comprises silicon. crystalline.

[145] The at least one divalent inorganic cation (B) is then preferably any divalent metal cation. For example, the at least one divalent inorganic cation (B) can be selected from Pb2+ and Sn2+, and is preferably a lead (II) cation (Pb2+).

[146] As detailed above, in the perovskite material of formula (I), the value of x is greater than 0 and less than 1. The value of x is normally greater than 0 and less than or equal to 0.80, it is preferably greater than 0 and less than or equal to 0.55, and is more preferably greater than 0 and less than or equal to 0.40. For example, the value x may be approximately 0.25, 0.5, or 0.75, and is preferably equal to any one of 0.05, 0.10, 0.15, 0.20, and 0.25.

[147] As detailed above, in perovskite material of formula (I), the value of y is greater than 0 and less than or equal to 3. The value of y is normally greater than 0 and less than 1.5, it is preferably greater than 0 and less than or equal to 1.0, and is preferably greater than or equal to 0.25 and less than or equal to 1.0. For example, the value x may be approximately 0.3, 0.6, 1 or 1.5, and is preferably 0.6.

[148] In a preferred embodiment, the perovskite material has the formula:

[149] where FA is a formamidinium cation ((HC(NH)2)2+)), Cs is a cesium cation (Cs+), Pb is a lead cation (Pb2+), I is iodide (I- ) and Br is bromide (Br-). The value of x is greater than 0 and less than or equal to 0.40 and the value of y can be greater than 0 and less than or equal to 3. Preferably, y is greater than 0 and is less than 1.5, more preferably y is greater than 0 and is less than or equal to 1.0, and even more preferably is greater than 0 and less than or equal to 0.6.

METHOD OF PRODUCING A PHOTOVOLTAIC DEVICE

[150] Also provided is a method of producing a photovoltaic device comprising a photoactive material, which photoactive material comprises a perovskite of general formula (I). The method comprises a step (a) of arranging a second region over a first region, the second region of which comprises a layer of photoactive material. For example, the first region may then be an n-type region comprising at least one n-type layer.

[151] The method may further comprise a step (b) of arranging a third region on the second region. The first region may be an n-type region comprising at least one n-type layer and the third region may then be a p-type region comprising at least one p-type layer. Alternatively, the first region may be a p-type region comprising at least one p-type layer and the third region may then be an n-type region comprising at least one n-type layer.

[152] Step (a) of arranging a second region over the first region normally comprises producing a solid layer of perovskite material by depositing a chemical solution. Typically, the step of producing a solid layer of perovskite material by chemical solution deposition comprises both a one-step and a two-step deposition process.

[153] In the one-step process, the step of producing a solid layer of the perovskite material comprises: (i) forming a precursor solution comprising precursors of the perovskite material dissolved in a solvent system; (ii) arranging/depositing a layer of the precursor solution; and (iii) removing the solvent system to produce a solid layer of perovskite material.

[154] Optionally, step (a) of arranging a second region on the first region further comprises, subsequent to the step in which a solid layer of the perovskite material is produced, a step of curing the solid layer of the perovskite material. The step of curing the solid layer of the perovskite material would typically involve heating the solid layer of the perovskite material to an elevated temperature for a set period, where the temperature and period of time used for the curing step depend on the specific composition. of perovskite material. In this regard, the skilled artisan will easily be able to determine a suitable temperature and period for curing a solid layer of a perovskite material when using well-known procedures that do not require excessive experimentation. In particular, it is noted that the expert will be aware that the exact temperature and period used for the curing step will depend on variations in the equipment and apparatus used to carry out the curing step, so that the selection of values for these parameters It is a routine matter for the expert.

[155] In the step one process, the perovskite material precursors typically comprise:

[156] - a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+))(A) and a first halide anion;

[157] - a second precursor compound comprising the cesium cation (Cs+)(A') and both the first halide anion and a second halide anion; and a third precursor compound comprising the divalent inorganic cation (B) and the second halide anion;

[158] wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and iodide (X).

[159] Preferably, the precursors of the perovskite material further comprise a fourth precursor compound comprising the divalent inorganic cation (B) and the first halide anion. More preferably, the first precursor compound comprises the formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, the second precursor compound comprises the cesium cation (Cs+) (A') and the first halide anion, the third precursor compound comprises the inorganic divalent metal cation (B) and the second halide anion, and the fourth precursor compound comprises the inorganic divalent metal cation (B) and the first halide anion.

[160] By way of example, precursors of perovskite material may comprise a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and iodide (X), a second compound precursor comprising the cesium (Cs+) cation (A') and iodide (X), a third precursor compound comprising the divalent metal cation (B) and iodide (X), and a fourth precursor compound comprising the divalent metal cation (B) and bromide (X'). Expanding on this example, the first precursor compound may have the formula AX, the second precursor compound may have the formula A'X, the third precursor compound may have the formula BX2, and the fourth precursor compound may have the formula BX'2.

[161] By way of further example, the precursors of the perovskite material may comprise a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and bromide (X'), a second precursor compound comprising the cesium (Cs+) cation (A') and bromide (X'), a third precursor compound comprising the divalent inorganic cation (B) and bromide (X'), and a fourth precursor compound comprising the cation divalent inorganic (B) and iodide (X). Expanding on this example, the first precursor compound may have the formula AX', the second precursor compound may have the formula A'X', the third precursor compound may have the formula BX'2, and the fourth precursor compound may have the formula BX2.

[162] In this one-step process, the solvent system in which perovskite material precursors are dissolved typically comprises one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP) and dimethylacetamide (DMAc). Preferably, the solvent system comprises any one of DMF, DMSO, DMF, a mixture of DMF and CHP, and DMAc. Preferably, the solvent system consists of DMAc.

[163] In this one-step process, the proportion of the amount of each of the precursor compounds used in the precursor solution depends on the fraction/proportion of each of the ions (determined by the values of x and y) present in the specific composition of the perovskite material. Therefore, the skilled artisan would easily be able to determine the appropriate amounts of each of the precursor compounds for a perovskite material of a specific composition.

[164] In the one-step process, the perovskite material precursors may alternatively comprise:

[165] - a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion;

[166] - a second precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and a sacrificial organic anion (Y);

[167] - a third precursor compound comprising the cesium (Cs+) cation (A') and either the first halide anion or a second halide anion; It is

[168] - a fourth precursor compound comprising the divalent inorganic cation (B) and a second halide anion;

[169] wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and iodide (X).

[170] Preferably, the precursors of the perovskite material further comprise a fifth precursor compound comprising the divalent inorganic cation (B) and the first halide anion. More preferably, the first precursor compound comprises the Formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, the second precursor compound comprises the Formamidinium cation ((HC(NH)2 )2+)) (A) and a sacrificial organic anion (Y), the third precursor compound comprises the cesium cation (Cs+) (A') and the first halide anion, the fourth precursor compound comprises the divalent inorganic cation (B) and the second halide anion, and the fifth precursor compound comprises the divalent inorganic cation (B) and the first halide anion.

[171] In this process, the sacrificial organic anion (Y) forms a volatile compound (AY) with the formamidinium cation ((HC(NH)2)2+)) (A). As discussed herein, volatile compounds are those compounds that are easily removed by evaporation, either by evaporation of the compound itself or by evaporation of decomposition products of the compound. Without wishing to be bound by theory, it is believed that the presence of this volatile compound (AY) during the reaction decreases the crystallization of the perovskite material and thus improves the crystal structure of the resulting perovskite material.

[172] The process may further comprise making it possible to remove a volatile compound comprising the sacrificial organic anion (Y) and the formamidinium cation ((HC(NH)2)2+)) (A) from the deposited layer of the solution precursor. The step of enabling removal of the volatile compound (AY) may comprise allowing the volatile compound to evaporate, decompose, or evaporate and decompose. Thus, the step of enabling the volatile compound to be removed may comprise heating the deposited layer of the precursor solution or exposing the deposited layer of the precursor solution. Generally the substrate and/or solution is heated to remove the volatile compound.

[173] Typically, the volatile compound (AY) is more volatile than a compound consisting of the formamidinium cation ((HC(NH)2)2+)) (A) and the first halide anion and/or a compound that consists of the cesium (Cs+) cation (A') with the first halide anion and/or the second halide anion (i.e., the first precursor compound and the third precursor compound). Whether one compound is more volatile than another is easily measured. For example, thermogravimetric analysis can be performed and the compound that loses a certain mass (e.g., 5% mass) at the lowest temperature is the most volatile. Generally the temperature at which the volatile compound (comprising the sacrificial organic anion (Y) and the formamidinium cation ((HC(NH)2)2+)) (A)) loses 5% of mass (after heating to from room temperature, e.g., 20°C) is more than 25°C lower than the temperature at which a compound consisting of the formamidinium cation ((HC(NH)2)2+)) (A) and the first anion halide and/or compound consisting of the cesium cation (Cs+) (A') with the first halide anion and/or the second halide anion has a loss of 5% in mass (after heating from room temperature, e.g. example, 20°C). For example, if a compound consisting of the formamidinium cation ((HC(NH)2)2+)) (A) and the first halide anion has a 5% mass loss at a temperature of 200 °C, the compound Volatile normally has a loss of 5% mass at a temperature of 175 °C or lower.

[174] The sacrificial organic anion (Y) can be an organic anion of formula RCOO-, ROCOO-, RSO3-,ROP(O)(OH)O- or RO-, where R is H, substituted alkyl or not C1-10 substituted, C2-10 substituted or unsubstituted alkenyl, C2-10 substituted or unsubstituted alkynyl, C3-10 substituted or unsubstituted cycloalkyl, C3-10 substituted or unsubstituted heterocyclyl or substituted or unsubstituted aryl. In particular, the sacrificial anion can be formate (HCOO-), acetate (CH3COO-), propanoate (C2H5COO-), butanoate (C3H7COO-), pentanoate (C4H10COO-) or benzoate (C6H5COO-).

[175] The Second precursor compound may therefore comprise a compound of formula AY, where A is the formamidinium cation ((HC(NH)2)2+)) and Y is the sacrificial organic anion. Preferably, the second precursor compound is Formamidinium acetate (HC(NH)2)2+), Formamidinium formate (HC(NH)2)2+) or Formamidinium propanoate (HC(NH)2)2+).

[176] In this one-step process, the solvent system in which the perovskite material precursors are dissolved typically comprises one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2- pyrrolidone (CHP) and dimethylacetamide (DMAc). Preferably, the solvent system comprises any of DMF, DMSO, DMF, a mixture of DMF and CHP, and DMAc. Preferably, the solvent system consists of DMF.

[177] The precursor solution is normally eliminated by processing the solution. For example, a composition comprising the precursor compounds and a solvent system may be eliminated on the substrate, for example, by spin coating or, for example, by graveur coating, slot dye coating, screen printing, inkjet, scalpel coating or spray coating.

[178] In the two-step process, the step of producing a solid layer of perovskite material comprises: (i) forming a first precursor solution comprising precursors of the perovskite material dissolved in a first solvent system; (ii) arranging/depositing a layer of the first precursor solution; (iii) removing the first solvent system to form a solid layer of the one or more precursors; (iv)) formation of a second precursor solution comprising additional precursors of the perovskite material dissolved in a second solvent system; and (v)) treating the solid layer of the one or more precursors with the second precursor solution and thereby reacting with the one or more precursors and the one or more additional precursors to produce a solid layer of the perovskite material.

[179] Optionally, step (iv) of treating the solid layer of the one or more precursors with the second precursor solution comprises depositing the second precursor solution on the solid layer of the one or more precursors, and heating the second precursor solution over the solid layer of the one or more precursors to produce a solid layer of the perovskite material. The step of heating the second precursor solution onto the solid layer of the one or more precursors would normally involve heating to an elevated temperature for a set period, wherein the temperature and period used for the heating step depend on the specific composition of the starting material. perovskite. In this regard, the skilled artisan would easily be able to determine a suitable temperature and period for the heating step when using well-known procedures that do not require excessive experimentation. In particular, it is noted that the expert will be aware that the exact temperature and period used for the heating step will depend on variations in the equipment and apparatus used to carry out the heating step, so that the selection of values for these parameters is a routine matter for the expert.

[180] In the two-step process, the precursors of the perovskite material in the first precursor solution typically comprise:

[181] - a first precursor compound comprising the divalent inorganic cation (B) and a first halide anion.

[182] Additional precursors of the perovskite material in the second precursor solution then comprise:

[183] - a second precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and both the first halide anion and a second halide anion, and

[184] - a first precursor compound comprising the cesium (Cs+) cation (A') and both the first halide anion and the second halide anion;

[185] wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and bromide (X').

[186] By way of example, the precursors of the perovskite material in the first precursor solution may comprise a first precursor compound comprising the divalent inorganic cation (B) and iodide (X). Additional precursors of the perovskite material in the second precursor solution may then comprise a second precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and iodide (X) or bromide (X'), and a third precursor compound comprising the cesium cation (Cs+) (A') iodide (X) or bromide (X'). Expanding on this example, the first precursor compound may have the formula BX2, the second precursor compound may have the formula AX or AX', and the third precursor compound may have the formula A'X' or A'X'. Preferably, if the second precursor compound is of formula AX, then the third precursor compound is of formula A'X', and if the second precursor compound is of formula AX', then the third precursor compound is of formula A'X.

[187] By way of further example, the precursors of the perovskite material in the first precursor solution may comprise a first precursor compound comprising the divalent inorganic cation (B) and bromide (X'). Additional precursors of the perovskite material in the second precursor solution may then comprise a second precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and iodide (X) or bromide (X'), and a third precursor compound comprising cesium (Cs+) cation (A') and iodide (X) or bromide (X'). Expanding on this example, the first precursor compound may have the formula BX'2, the second precursor compound may have the formula AX or AX', and the third precursor compound may have the formula A'X or A'X'. Preferably, if the second precursor compound is of formula AX, then the third precursor compound is of formula A'X', and if the second precursor compound is of formula AX', then the third precursor compound is of formula A'X.

[188] In the two-step process, the first solvent system may comprise one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP), and dimethylacetamide (DMAc ). Preferably, the first solvent system comprises any one of DMF, DMSO, DMF, a mixture of DMF and CHP, and DMAc. The second solvent system then comprises one or more solvents that are capable of dissolving the one or more additional precursors and that are orthogonal to the one or more solvents of the first solvent system.

[189] Furthermore, when the photovoltaic device has a multijunction structure, such that the photovoltaic device comprises a first subcell and one or more additional subcells, the method then further comprises providing an additional subcell, arranging an intermediate region over the additional subcell and formation of the first subcell over the intermediate region. The step of forming the first subcell in the intermediate region then comprises step (a) or steps (a) and (b) highlighted above.

FORMULATION FOR USE IN THE FORMATION OF PEROVSKITE MATERIAL

[190] Furthermore, a formulation is provided for use in forming a photosensitive/light-absorbing perovskite material of general formula (I). The formulation comprises precursor compounds of the perovskite material.

[191] In one embodiment, the precursors of the perovskite material in the formulation comprise a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, a second compound precursor comprising the cesium (Cs+) cation (A') and both the first halide anion and a second halide anion, and a third precursor compound comprising the divalent inorganic cation (B) and the second halide anion, wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and iodide (X)).

[192] Preferably, the precursors of the perovskite material in the formulation further comprise a fourth precursor compound comprising the divalent inorganic cation (B) and the first halide anion. More preferably, the first precursor compound comprises the formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, the second precursor compound comprises the cesium cation (Cs+) (A') and the first halide anion, the third precursor compound comprises the inorganic divalent metal cation (B) and the second halide anion, and the fourth precursor compound comprises the inorganic divalent metal cation (B) and the first halide anion.

[193] The at least one divalent inorganic cation (B) can be any divalent metal cation. Preferably, the at least one divalent inorganic cation (B) is selected from Pb2+ and Sn2+, and is most preferably a lead (II) cation (Pb2+).

[194] In a preferred embodiment, the formulation comprises a first precursor compound comprising a formamidinium cation ((HC(NH)2)2+)) and a first halide anion, a second precursor compound comprising a cesium cation (Cs+ ) and the first halide anion, a third precursor compound comprising a lead(II) cation (Pb2+) and the first halide anion, and a fourth precursor compound comprising a lead(II) cation (Pb2+) and a second anion halide, wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and iodide (X)).

[195] In an alternative embodiment, the precursors of the perovskite material in the formulation comprise a first precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, a second precursor compound comprising the formamidinium cation ((HC(NH)2)2+)) (A) and a sacrificial organic anion (Y), a third precursor compound comprising the cesium cation (Cs+) (A') and both the first halide anion and a second halide anion, and a fourth precursor compound comprising the divalent inorganic cation (B) and a second halide anion, wherein the first halide anion is one of iodide (X) and bromide (X ') and the second halide is the other of iodide (X) and iodide (X)).

[196] Preferably, the precursors of the perovskite material in the formulation further comprise a fifth precursor compound comprising the divalent inorganic cation (B) and the first halide anion. More preferably, the first precursor compound comprises the Formamidinium cation ((HC(NH)2)2+)) (A) and a first halide anion, the second precursor compound comprises the Formamidinium cation ((HC(NH)2 )2+)) (A) and a sacrificial organic anion (Y), the third precursor compound comprises the cesium cation (Cs+) (A') and the first halide anion, the fourth precursor compound comprises the divalent inorganic cation (B) and the second halide anion, and the fifth precursor compound comprises the divalent inorganic cation (B) and the first halide anion.

[197] The sacrificial organic anion (Y) can be an organic anion of the formula RCOO-, ROCOO-, RSO3-, ROP(O)(OH)O- or RO-, where R is H, substituted alkyl or not C1-10 substituted, C2-10 substituted or unsubstituted alkenyl, C2-10 substituted or unsubstituted alkynyl, C3-10 substituted or unsubstituted cycloalkyl, C3-10 substituted or unsubstituted heterocyclyl or substituted or unsubstituted aryl. In particular, the sacrificial anion can be formate (HCOO-), acetate (CH3COO-), propanoate (C2H5COO-), butanoate (C3H7COO-), pentanoate (C4H10COO-) or benzoate (C6H5COO-).

[198] Preferably, the second precursor compound is Formamidinium acetate (HC(NH)2)2+), Formamidinium formate (HC(NH)2)2+) or Formamidinium propanoate (HC(NH)2)2+ ).

[199] Furthermore, a precursor solution for use in forming a photosensitive/light-absorbing perovskite material of general formula (I) can be provided by dissolving the precursor compounds of the formulations described above in a suitable solvent system. The precursor solution therefore comprises a solution of the cations and anions that comprise each of the precursor compounds.

[200] In one embodiment, the precursor solution therefore comprises a solution of a formamidinium cation ((HC(NH)2)2+)) A, a cesium cation (Cs+)A', at least one cation of divalent metal B, iodide X and bromide X'. Preferably, the ratio of ions A : A' : B : X : X' in the precursor solution is 1-x : x : 1 : 3-y : y, where 0 < x < 0.4 and 0 < y < 3 .

[201] In an alternative embodiment, therefore, it comprises a solution of a formamidinium cation ((HC(NH)2)2+))A, a cesium cation (Cs+)A', at least one divalent metal cation B , iodide X, bromide X', and a sacrificial organic anion (Y). Preferably, the ratio of ions A : A' : B : X : X' in the precursor solution is 1-x : x : 1 : 3-y : y, where 0 < x < 0.4 and 0 < y < 3 .

[202] Typically, the solvent system in which the perovskite material precursors are dissolved comprises one or more solvents selected from dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP) and dimethylacetamide (DMAc). Preferably, the solvent system comprises any one of DMF, DMSO, a mixture of DMF and CHP, and DMAc. When the precursors of the perovskite material do not include a sacrificial organic anion, the solvent system preferentially consists of DMAc. Alternatively, when the perovskite material precursors include a sacrificial organic anion, the solvent system preferably consists of DMF.

[203] The perovskite material of general formula (I) can therefore be obtained by dissolving the precursor compounds of the formulation described above in a suitable solvent system, and thus forming the precursor solution described above, depositing the precursor solution onto a suitable substrate, and subjecting the substrate to a temperature and pressure regime that facilitates the removal of the one or more solvents comprising the solvent system. Where the precursor compounds include a compound comprising a sacrificial organic anion (Y), the substrate must be subjected to a temperature and pressure regime that also facilitates the removal of a volatile compound comprising the sacrificial organic anion (Y) and the cation formamidinium ((HC(NH)2)2+)) (A).

EXAMPLES

[204] In the exemplary embodiments detailed below, perovskite materials were formed as films by spin-coating deposit of a solution. In these embodiments, the solid precursors for the perovskite materials were weighed and mixed together in a flask. This mixture was then loaded into a glove box where the solvent was added to a final solution having 38% by weight of the perovskite precursors.

[205] To dissolve the solids, the mixture was heated with continuous stirring to 100 °C, forming a solution that was yellow and transparent. Once all solids were in solution, the solution was removed from the hot plate and allowed to cool to room temperature. The final solution was then filtered before depositing.

[206] The solution was spin coated onto a substrate (i.e., glass, FTO or ITO) inside the glove box with spin speeds ranging between 3000 and 4000 rpm depending on the desired final film thickness for 60 seconds. In these exemplary embodiments, the resulting perovskite films were between 350 nm and 500 nm thick. Although lower speeds can be used, this would result in thicker films.

[207] Immediately after the film deposit is moved to a hot plate set at the desired temperature, where the curing temperature depends on the curing time required. For these particular embodiments, the temperature can be varied from 130 to 150 °C with curing times between 10 and 30 minutes. No obvious change in the final film was observed when varying the curing parameters in that range.

[208] The resulting perovskite thin films were then characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm the formation of the perovskite and the formation of a continuous film that is suitable for incorporation into photovoltaic devices. .

[209] Figure 6 shows the XRD pattern of four different perovskite materials. The left side (A) of Figure 6 shows the XRD diffraction pattern of the three different perovskite materials of general formula FA1-xCsxPbI3-yBry, with x = 0.25 and y = 0, 0.3 and 0.6, respectively , each produced using the method described above. The FA:Cs ratio was therefore constant between each of the materials, but from top to bottom there is a reduction in the I:Br ratio, with top perovskite material including no Br for the purpose of comparison with perovskite materials described herein. . The right side (A) of Figure 6 then shows the XRD diffraction pattern of a perovskite material of general formula MA1-xCsxPbI3-yBry, with x = 0.75 and y = 0.6, produced using the method described above. The peaks in each XRD diffraction pattern of Figures 6 illustrate that the resulting materials have the crystal structures expected of the intended perovskite materials.

[210] Figure 7a then shows an SEM image of a perovskite material of general formula MA1-xCsxPbI3-yBry with x = 0.75 and y = 0.6, while Figure 7b then shows an SEM image of a material of perovskite with general formula FA1-xCsxPbI3-yBry, with x = 0.25 and y = 0.6, both produced using the method described above. The images in Figures 7a and 7b show that the perovskite material films produced using the method described above are continuous and homogeneous.

[211] Figure 8 shows the UV-Vis absorption spectra of four different perovskite materials of general formula FA1-xCsxPbI3-yBry, with x = 0.25 and y = 0, 0.3, 0.6 and 1, 5, respectively, each produced using the method described above. The FA:Cs ratio was therefore constant between each of the materials, but there is a reduction in the I:Br ratio, with one of the perovskite materials including no Br for the purpose of comparison with the perovskite materials described here. On the graph wavelength in nm is plotted on the x-axis and absorption in arbitrary units is plotted on the y-axis. From the absorption spectra, the optical bandgap (Eg) of each of the perovskite materials was estimated to be approximately 1.55 eV for y = 0, approximately 1.60 eV for y = 0.3, approximately 1.66 eV for y = 0.6 and approximately 1.91 eV for y = 1.5.

[212] Figures 9a and 9b show the UV-Vis absorption spectra of five different perovskite materials of general formula MA1-xCsxPbI3-yBry, each produced using the method described above.

[213] Figures 9a show the UV-Vis absorption spectra of three different perovskite materials of general formula MA1-xCsxPbI3-yBry with x = 0.5 and y = 0.3, 0.6 and 1.5, respectively. Figures 9b then show the UV-Vis absorption spectra of two additional perovskite materials of general formula MA1-xCsxPbI3-yBry with x = 0.75 and y = 0.6 and 1.5, respectively. In graphs, wavelength in nm is plotted on the x-axis and absorption in arbitrary units is plotted on the y-axis. From the absorption spectra, the optical bandgap (Eg) of each of the perovskite materials was estimated to be approximately 1.68 eV for x = 0.5 and y = 0.3, approximately 1.80 eV for x = 0 .5 and y = 0.6, approximately 1.85 eV for x = 0.5 and y = 1.5, approximately 1.77 eV for x = 0.75 and y = 0.6, and approximately 1.96 eV for x = 0.75 and y = 1.5.

[214] To compare conventional perovskite materials with perovskite materials according to the invention, the following perovskite materials were manufactured on a glass substrate: perovskite material A having the formula MAPbI3, perovskite material B having the formula formula MA0.5FA0.5PbI3, perovskite material C having the formula MA0.25Cs0.75PbI2.4Br0.6, and perovskite material D having the formula FA0.75Cs0.25PbI2.4Br0.6. These devices were then placed on a hot plate for 540 minutes at 150 °C in an ambient atmosphere (with 40% relative humidity) to test the thermal stability of the perovskite materials. Figure 8 shows photographs of each of the various perovskite materials (A to D) before, during, and after thermal stability testing.

[215] As expected, the perovskite materials were all initially black in color. As can be seen in Figure 8, visually the films of perovskite material A and perovskite material B show some discoloration (yellowing in the upper right corner) after 280 minutes, while perovskite material C and perovskite material D do not show visible discoloration. Over a period of 540 minutes, perovskite material A and perovskite material B degraded significantly, with a substantial color change from black to yellow (where yellow indicates the formation of PbI2), whereas the film of perovskite material Perovskite C shows limited degradation, changing color from black to brown, while perovskite D material does not show any signs of degradation.

ADDITIONAL EXAMPLES

[216] In the exemplary embodiments detailed below, perovskite materials were formed as films by spin-coating deposit of a solution. In these embodiments, the solid precursors for the perovskite materials were weighed and mixed in a flask. This mixture was then loaded into a glove box, where solvent was added for a final solution that has 37 wt% perovskite precursors. Immediately after the film deposit has been moved to a hot plate set at the desired temperature, where the curing temperature depends on the curing time required. For these particular embodiments, the temperature was approximately 150 °C for a curing time of approximately 10 minutes.

[217] The resulting perovskite thin films were then characterized by X-ray diffraction (XRD) to confirm the formation of the perovskite.

[218] Figure 11 shows the XRD patterns of the five different perovskite materials of composition FA1-xCSxPbl3 (0.05 < x < 0.25). In the XRD diffraction patterns of Figure 11(A), all maxima correspond to the trigonal symmetry (space group: P3m1) of FAPbI3. Traces of PbI2 and FTO are observed as well, however, there is no signal that corresponds to the yellow polymorph. Figure 11(B) then shows the shift in the first perovskite peak, from which it can be seen that the maxima are exchanged for higher values 2θ indicating a reduction in cellular parameters that adjust to the partial replacement of FA with a smaller cation , like Cs. Therefore, a solid solution is formed in the range 0.05 < x < 0.25.

[219] Figure 12 shows the XRD patterns of five different perovskite materials of composition FA1-XCsxPbI3 (0.30 < x < 0.50). In the XRD diffraction patterns of Figure 12(A), additional maxima (marked with a filled circle) correspond to the CsPbI3 phase, and these peaks are more defined as the value of x increases (i.e., as the amount of Cs increases). Figure 8(B) then shows the shift in the first perovskite peak; however, there is no obvious shift in the peak, indicating that no more Cs can be introduced into the FAPbI3 perovskite. This experiment establishes the range in which Cs can partially replace FA in the FAPbI3 perovskite to form the black polymorph, avoiding the yellow phase and leaving the phases more thermostable.

[220] Figure 13 shows the XRD patterns of four different perovskite materials of the composition FA1-XCsxPbI3 with x = 0.25, and 1.5 < y < 3.

[221] It will be recognized that the individual items described above may be used by themselves or in combination with other items shown in the drawings or described in the description and those items mentioned in the same passage as a different or the same drawing, as they need not be used in combination with each other.

[222] Furthermore, although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated to be within the scope of the appended claims. For example, those skilled in the art will recognize that although the above described embodiments of the invention all relate to photovoltaic devices , aspects of the invention may be equally applicable to other optoelectronic devices. In this regard, the term “optoelectronic devices” includes photovoltaic devices, photodiodes (including solar cells), phototransistors, photomultipliers, photoresistors and light-emitting diodes, etc. in particular, although in the embodiments described above the perovskite photoactive material is used as a light absorber/photosensitizer, it can also function as a light-emitting material by accepting charge, both electrons and holes, which subsequently recombines and emits light.

Claims (12)

1. PEROVSKITE MATERIAL of general formula (I): wherein A is a formamidinium cation (HC(NH)2)2+), A' is a cesium cation (Cs+), B is at least one divalent inorganic cation, X is iodide and X' is bromide; and where 0 < x < 0.4 and 0 < y < 3. 2. PEROVSKITE MATERIAL, according to claim 1, characterized in that a bandgap of the perovskite material is from 1.60 eV to 2.30 eV, and is preferably from 1.65 eV to 1.75 eV. 3. PEROVSKITE MATERIAL according to any one of claims 1 or 2, characterized in that B is at least one inorganic cation selected from Pb2+ and Sn2+, and is preferably Pb2+. 4. PEROVSKITE MATERIAL, according to any one of claims 1 to 3, characterized in that the perovskite material has the formula: where FA is a formamidinium cation (HC(NH)2)2+), Cs is a cesium cation (Cs+), Pb is a lead (II) cation (Pb2+), I is iodide (I-) and Br is bromide (Br-). 5. PEROVSKITE MATERIAL, according to claim 4, characterized in that 0.05 < x < 0.25, and preferably x is equal to any of 0.05, 0.10, 0.15, 0.20 and 0 .25. 6. PEROVSKITE MATERIAL, according to one of claims 4 or 5, characterized by 0 < y < 1.5, 0 < y ^ 1.0, 0 < y < 0.6 and is preferably 0.6. 7. METHOD FOR PRODUCING A PEROVSKITE MATERIAL, as defined in any of claims 1 to 6, characterized in that the perovskite material is in the form of a solid layer; wherein the method comprises chemical solution deposition and: (i) forming a precursor solution comprising precursors of the perovskite material dissolved in a solvent system; (ii) arranging/depositing a layer of the precursor solution; and (iii) removing the solvent system to produce a solid layer of perovskite material. 8. METHOD, according to claim 7, characterized in that the precursors of the perovskite material comprise: a first precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and a first halide anion; a second precursor compound comprising the cesium (Cs+) cation (A') and the first halide anion or a second halide anion; and a third precursor compound comprising the divalent inorganic cation (B) and the second halide anion; wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and bromide (X'). 9. METHOD, according to claim 8, characterized in that the precursors of the perovskite material further comprise a fourth precursor compound comprising the divalent inorganic cation (B) and the first halide anion. 10. METHOD, according to claim 9, characterized in that the precursors of the perovskite material comprise: a first precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and a first halide anion; a second precursor compound comprising the formamidinium cation (HC(NH)2)2+) (A) and a sacrificial organic anion (Y); a third precursor compound comprising the cesium (Cs+) cation (A') and the first halide anion or a second halide anion; and a fourth precursor compound comprising the divalent inorganic cation (B) and a second halide anion; wherein the first halide anion is one of iodide (X) and bromide (X') and the second halide is the other of iodide (X) and bromide (X')). 11. METHOD, according to claim 10, characterized in that the sacrificial organic anion (Y) is an organic anion of formula RCOO-, ROCOO-, RSO3-, ROP(O)(OH)O- or RO-, wherein R is H, C1-10 substituted or unsubstituted alkyl, C2-10 substituted or unsubstituted alkenyl, C2-10 substituted or unsubstituted alkynyl, C3-10 substituted or unsubstituted cycloalkyl, C3-10 substituted or unsubstituted heterocyclyl, or aryl replaced or not replaced. 12. METHOD, according to claim 11, characterized by the step of producing a solid layer of the perovskite material by chemical solution deposition comprising: (i) forming a first precursor solution comprising one or more dissolved precursors of the perovskite material in a first solvent system; (ii) arranging/depositing a layer of the first precursor solution; (iii) removing the first solvent system to form a solid layer comprising the one or more precursors; (iv)) formation of a second precursor solution comprising one or more additional precursors of the perovskite material dissolved in a second solvent system; and (v)) treating the solid layer comprising the one or more precursors with the second precursor solution and thereby reacting the one or more precursors and the one or more additional precursors to produce a solid layer of the perovskite material.