Method for Producing Multicomponent Perovskites

Abstract

The present invention provides a method for forming a perovskite material from multiple evaporation sources, comprising the steps of: (i) a first evaporation source comprising a mixture of co-sublimable organic halides, The organic halide is a. a first organic halide comprising an organic cation A; b. A second organic halide containing an organic cation A' different from A and having a larger ionic radius than the first organic cation A. A first evaporation source having (ii) a second evaporation source comprising one or more metal halides having formula (I): B(X y X' 1-y )2(I) a second evaporation source, where B is a divalent metal cation, X and X' are different halides, and 0≦y<1; (iii) one or more additional organic halides from one or more additional evaporation sources; and / or (iv) one or more inorganic halides from one or more separate evaporation sources; co-subliming from the solution to form a perovskite material; A method is provided wherein the perovskite material comprises three or more different cations in addition to the B cations.

Description

[Technical field]

[0001] The present invention relates to a co-sublimation deposition process for producing multicomponent perovskite thin films having at least three or four cations in the A-position, one or two cations in the B-position, and one, two or more halide components, requiring fewer evaporation sources than the number of components. The invention also includes the use of large monovalent cation additives, which can be co-sublimed with another organic monovalent cation to improve the crystallinity and thermal stability of the final perovskite material. [Background technology]

[0002] Solar energy conversion is one of the most promising technologies for providing renewable energy.

[0003] One class of photovoltaic materials that has attracted great interest in recent years is the organic-inorganic halide perovskites. This class of materials has a perovskite crystal structure, which has the general formula ABX3. These materials exhibit favorable bandgaps, high absorption coefficients and long diffusion lengths, and such compounds have been found to be ideal as absorbers in photovoltaic devices.

[0004] Typical techniques for synthesizing perovskite thin films can range from wet solution processes such as spin coating, inkjet, and blade coating, or alternatively dry processes such as deposition techniques including thermal evaporation, chemical vapor deposition (CVD), and aerosol-assisted CVD. Dry processes such as deposition are ideal solvent-free techniques, minimizing damage to pre-existing device layers and providing better control of film thickness and uniformity. When producing complex multi-component perovskite compositions, wet processing methods are often used because dry processes tend to become more complex as additional components are introduced into the perovskite structure. In particular, co-evaporation vacuum deposition techniques can be challenging to control perovskites that contain several different components (e.g., four or more components). Such multi-component perovskites require many evaporation sources, each with its own settings that are monitored, as well as close control of the various deposition rates of each corresponding precursor, resulting in an overall complex and expensive process, especially when more than one precursor is sublimed from the same source.

[0005] An attempt to overcome such implementation complexities is reported in "Efficient mixed-cation mixed-halide perovskite solar cells by all-vacuum sequential deposition with metal oxide electron transport layer" by Kam et al., Solar RRL, Vol. 3, 7, 2019. In this paper, the preparation of mixed perovskites using a gas-phase process with a first step in a single quartz crystal microbalance (QCM) is explored, where instead of co-volatilizing multiple sources, lead halides are deposited and then organic iodides are deposited. First, PbI2 and PbBr2 salts are mixed in an optimal ratio, co-evaporated by a heating current, and then deposited on a substrate. Next, methylammonium iodide (MAI) and formamidinium iodide (FAI) are mixed in an optimal ratio and co-sublimated due to their close sublimation temperatures, allowing similar deposition rates for the corresponding mixed lead halide films. Although multi-component perovskites are synthesized, the introduction of an extra step as opposed to a single co-deposition does not address the issue of implementing a simplified "all-in-one" co-evaporation process, which would significantly accelerate processing time and help maintain the uniformity of the final perovskite material.

[0006] In addition, Ball et al.'s "Low-bandgap FAs for photovoltaics" 1-x Cs x Sn 1-y Pb y In "Dual-source co-evaporation of I3 perovskites," ACS Energy Lett. 2019, 4, 11, pp. 2748-2756, 2019, we investigated the multicomponent perovskites, i.e., FA 1-x Cs x Sn 1-y Pb yA method of dual source co-evaporation to produce I3 is provided. In a single crucible source, a mixture of metal iodides of cations Cs, Pb and Sn is prepared, melted under inert atmosphere and then naturally cooled to room temperature. SnF2 is also added to this mixture to control the crystallization and inhibit the formation of impurity phases in the final film. Separately, FAI is provided in the second source source. The two source sources are then co-evaporated to produce crystalline low band gap perovskite thin films. Although the number of evaporation sources is minimized to two and five-component perovskites can be produced, generally this type of perovskite has low stability, especially due to the Sn component being easily oxidized. SnF2 is a well-known passivation agent and can be used to remove excess Sn. 2+ Sn ions are provided and oxidized 4+ However, this material does not necessarily improve the thermal stability, which is a key issue for most complex perovskites. Therefore, there is still a need to optimize the process to obtain stable perovskites.

[0007] Previous work on vacuum deposition of wide bandgap trivalent cation perovskites by four-source cosublimation has been done by Gil-Escrig et al. (Vacuum-deposited trivalent cation mixed halide perovskite solar cells), Advanced Energy Materials, Vol. 8, Issue 14, 2018). In particular, Cs 0.5 FA 0.4 MA 0.1 Pb(I 0.83 Br 0.17 )3 Perovskite films can be prepared from PbI2, CsBr, FAI, and MAI. CsBr is a + and Br - However, to increase the band gap (Eg>1.7 eV), a significant amount of Br is required. -must be incorporated, resulting in a similarly large cesium concentration, which leads to irregular morphology and poor properties of the resulting devices. Therefore, careful consideration is required to select the precursors for the mixed halide compounds. Therefore, it is preferable to mix two different metal halides in a single source source to better control the stoichiometry. Therefore, further studies similar to those of Gil-Escrig et al. have been carried out by Munoz et al. ("Room-temperature vacuum deposition of CsPbI2Br perovskite films from multiple source and mixed halide precursors", Chem. Mater., 32, 8641, 2020). Here, CsI was used as the cesium source, while the precursors PbI2 and PbBr2 were premixed instead. Although this process resulted in uniform CsPbI2Br perovskite films, their thermal stability was found to be significantly insufficient. Therefore, despite using a mixed halide co-evaporation process, it is difficult to control all parameters of the perovskite films. To overcome the lack of stability, additional features such as additional engineering are often required.

[0008] Otalora et al., "Hybrid perovskite films deposited by single-source thermal evaporation," J Mater Sci: Mater Electron, 2021, provides a method to deposit MAPbI3 films by single-source thermal evaporation. However, this method only supports the deposition of very simple perovskite films, using only one type of A, B, and X ions. Furthermore, very specific pressures, temperatures, and solvents need to be explored to obtain favorable morphology and electrical properties similar to those obtained by co-evaporation from two sources.

[0009] Addition engineering to improve the stability properties of perovskites has been attempted in the past. Recent interest has been directed to the addition engineering of large cations, such as partial replacement of A cation sites with guanidinium (GA) ions. For example, Jodlowski et al., "Large guanidinium cations mixed with methylammonium in lead iodide perovskites for 19% efficient solar cells," Nature Energy, 2, 927-9279, 2017, reported that the insertion of GA into some of the A units of the MAPbI3 structure during the spin-coating process leads to perovskites with improved thermal and environmental stability due to the availability of H-bonds with preferred orientation within the inorganic framework. Based on this, Zhang et al., "Guanidinium-induced phase-separated perovskite layers for efficient and highly stable solar cells," J. Mater. Chem. A, 2019, 7, 9486-9496, reported the development of a complex quadruple cation perovskite, Cs 0.05 (FA 0.83 (MA 1-x GA x ) 0.17 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 was spin-coated, which showed improved and stable properties. By adjusting the GA content, the 3D CsFAMA 1-x GA x Phase separation of hexagonal δ-FAPbI3 and δ-FAPbI3 was induced. GA-based perovskites have been reported to have minimal hysteresis and excellent optoelectronic properties.

[0010] Similarly, Yerramilli et al. ("Introduction of Phenylethylammonium Iodide into Inverted Triple Cation Perovskite Solar Cells for VOC and Stability", Organic Electronics, 93, 2021) found that the introduction of phenylethylammonium (PEA) into FAMACs-based perovskite compositions improved the film morphology, resulting in uniform films with very few pinholes. A one-step solution-based method is used to synthesize the perovskite films. Summary of the Invention [Problem to be solved by the invention]

[0011] Additive engineering is a useful technique for solution-processed perovskites, but this type of structural effect is often not reproducible by sublimation techniques. For example, La-Placa et al., "Vacuum-deposited 2D / 3D perovskite heterojunctions," ACS Energy Lett. 2019, 4, 12, 2893-2901, demonstrates the fabrication of perovskites by dual-source vacuum deposition, using additive engineering of large cations with phenethylammonium. The method involves co-sublimation deposition of phenethylammonium lead iodide (PEAI) and PbI2, resulting in the formation of 2D layers on either side of a 3D MAPI layer of PEA2PbI4. As a result, the 2D iodide (PEA2PbI4) formed layers on either side of the 3D MAPI film. However, the unfavorable orientation of the 2D perovskite relative to MAPI hinders charge extraction and tends to provide less evidence of surface passivation compared to the corresponding solution-processed method. [Means for solving the problem]

[0012] In a first aspect of the present invention, a method as claimed in claim 1 is provided.

[0013] Increasing the number of components (especially the number of A cations and / or X halides) in the ABX3 (B=Pb, Sn) perovskite formation offers advantages in terms of material / device properties and environmental stability. However, vacuum co-evaporation requires a corresponding increase in the number of evaporation sources, which increases the complexity of the deposition process.

[0014] The present invention provides the synthesis of high performance multi-component perovskites via an efficient co-evaporation process that requires fewer sources than the components present, which further facilitates partial substitution of the A-site with large cationic additives to enhance thermal stability. Thus, the described process and its corresponding perovskites are suitable for use in semiconductor devices and photovoltaic devices, single or multi-junction solar cells, including perovskite-silicon tandem cells, all-perovskite tandem solar cells, perovskite-perovskite-silicon cells, perovskite-CdTe tandem cells, perovskite-CuZnSnSSe tandem cells, perovskite-CuZnSnS tandem cells, and perovskite-CIGS tandem cells.

[0015] In the literature, solutions to thermal instability can be found that apply to solvent-processed perovskites. However, in many cases, these solutions do not produce the same effect in perovskites prepared by sublimation (see, for example, the effect of adding large cations to the surface of solution-processed perovskites to form quasi-2D perovskites, but not when prepared by sublimation. ACS Energy Lett. 2019, 4, 12, 2893-2901).

[0016] The method of the present invention provides a clear solution to previously experienced problems, an efficient and manageable co-operating vacuum deposition process that provides improved thermal stability through additive engineering while maintaining a crystalline single-phase perovskite structure.

[0017] The invention will now be described more particularly, by way of example, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows elemental and stoichiometric analysis of mixed lead halide Pb(I1-xBrx)3 material after melting and subsequent films deposited as single precursors. [Figure 2A] FIG. 1 shows current density vs. voltage (JV) curves under simulated solar illumination for several perovskite solar cells based on triple-cation perovskite FAMACsPb(I1-xBrx)3. [Figure 2B] Figure 2 shows the as-prepared triple-cation perovskite FAMACsPb(I1-xBrx)3 solar cell after thermal stress at 85 °C for 5 h in N2 atmosphere. [Figure 3A] FIG. 14 shows stack-up XRD patterns of the “as-prepared” triple-cation perovskite FAMACsPb(I1-xBrx)3 obtained under 1 sun constant illumination for 2, 7 and 9 days of continuous light exposure. [Figure 3B] FIG. 1 shows stacked XRD patterns of the “as-prepared” triple-cation perovskite FAMACsPb(I1-xBrx)3 acquired over periods of successive heat treatment at 85 °C for 2, 7 and 9 days. [Figure 4] FIG. 1 shows XRD patterns of three cation-containing perovskite formulations, namely FAMACs, FAGACs, and FAMAGACs, “as prepared” (fresh) and after thermal stress at 85° C. for 1 week under N2 atmosphere (aged). [Figure 5A] Figure 1 shows stacked XRD patterns of the quaternary cation perovskite FAGAMACsPb(I1-xBrx)3 obtained "as prepared" under constant irradiation of 1 sun and over periods of continuous photoirradiation of 2, 7, 28 and 37 days. [Figure 5B] FIG. 1 shows stack-up XRD patterns obtained for the quaternary cation perovskite FAGAMACsPb(I1-xBrx)3 "as prepared" at 85 °C and over periods of successive heat treatment of 2, 7, 28 and 37 days. [Figure 6] FIG. 1 shows the power conversion efficiency (PCE) over time of GA-based solar cells prepared by vacuum deposition kept in a N2 atmosphere at 85° C. in the dark. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The method of the invention may include three or four evaporation sources, some of which contain a mixture of precursors. The resulting perovskite material ABMX3 contains three or more different cations (present as A, A', A'' in the A site) and a B cation.

[0020] The present invention provides a method for reducing the number of source sources that can be used by co-sublimating organic halides. Preferably, one of the organic halides contains an organic monocation and the other contains a larger organic cation (hereinafter referred to as "cation additive"). In another aspect of the present invention, the number of source sources can be further reduced by preparing mixed inorganic / metal halide precursors, such as CsI+CsBr or PbI2+PbBr2. The method of the present invention can be divided into multiple steps, as shown below. The multiple steps include co-sublimation from multiple source sources. Co-sublimation means that various components from each evaporation source are sublimated together or simultaneously, so that there is at least some overlap between the sublimations from each source source.

[0021] The process of the invention is usually carried out under vacuum, typically by vacuum deposition onto a substrate. This may be carried out in a vacuum chamber under N2 atmosphere. The chamber may be equipped with individual evaporation sources, for example with their own independent temperature controllers and shutters. Each source may have a dedicated QCM sensor on it and may have an additional sensor placed close to the substrate to measure the overall deposition rate. The temperature of the process is tailored to each chamber, for example in the range of 100°C to 500°C, with a temperature of about 10 -6 It may be a constant pressure of mbar.

[0022] Step (i) Step (i) of the method of the present invention utilizes a first evaporation source containing a mixture of co-sublimable organic halides that are sublimed together (converted from solid to gas). In general, co-sublimable organic halides have similar co-sublimation temperatures. The term "similar co-sublimation temperatures" as used herein refers to two different precursors (e.g., organic halides) that are placed in the same evaporation source and can deposit a final single-phase material due to the degree of closeness of their sublimation temperatures. Co-sublimation (or co-evaporation) is further explained in the book "OLED Fundamentals - Materials, Devices, and Processing of Organic Light-Emitting Diodes" (Daniel J. Gaspar and Evgueni Polikarpov, eds., 2015, p. 195). It is described that co-evaporation depends on the evaporation temperatures of two or more materials, and the ratio of each material is controlled by the respective evaporation rates.

[0023] Similar co-sublimation temperatures can refer to both "compatible evaporation" and "non-compatible" evaporation. "Compatible evaporation" refers to precursors that are mixed together and have close sublimation temperatures within 20°C (and preferably 15°C or 10°C) of each other so that they effectively evaporate as a single phase. Alternatively, materials may be mixed to form a new material or alloy, and then compatible evaporated at a different temperature from the separate substances.

[0024] The Handbook of Thin Film Technology (Leon I. Maissel and Reinhard Glang, 1970, Chapter 1, page 65, chapter 6a) provides a general understanding of the term "compatible evaporation" in the art: deposition of a compound film from a single vapor source requires that the material enter the gaseous state in intact molecular form. Alternatively, if the molecules dissociate, compatible evaporation occurs if the components are equally volatile. Thus, as previously mentioned, evaporation occurs through a single phase and depends on the identity and properties of each precursor.

[0025] "Non-compatible evaporation" refers to precursors that are present in the same crucible but do not necessarily mix to form a single substance. That is, the precursors exist as two different phases that do not enter the gaseous state as complete molecules in a single vapor phase or have equal volatility to compatible dissociate. These precursors can be heated separately and therefore only require a proximity of 50 to 150 °C at their respective sublimation temperatures. While being heated, the vapor streams of the two phases mix to form the first evaporation source. For example, a crucible containing two precursors is heated over a temperature range that covers the evaporation temperature of each precursor, allowing for their eventual co-evaporation as separate gas phases.

[0026] Preferably, in step (i), one of the organic halides contains an A monocation, such as formamidinium (i.e., A is FA), and the other contains a cation A' having an ionic radius larger than the ionic radius of the first organic cation A (preferably formamidinium (FA)). In other words, the ionic radius of the organic cation A' is preferably larger than 2.53 Å (hereinafter referred to as large monocation or large cation additive). The respective radii of organic cations in perovskite environments can be found in Cheetham et al., Chem.Sci., 2015, 6, 3430 and Travis et al., Chem.Sci., 2016, 7, 4548-4556. Furthermore, Shannon et al., Acta Cryst. (1969), B25, 925-945, outlines a method for determining the effective ionic radius, providing radii for various elements in different coordination environments, such as Pb and Cs. Therefore, these resources are useful for the calculation of the Goldschmidt resistance factor to estimate the stability and distortion of the perovskite structure.

[0027] Preferably, the A cation is a monovalent organic cation that is co-sublimable with A' when both organic cations A and A' are present as halides (typically iodides). Preferably, A has a similar sublimation temperature as A' when present as a halide. More preferably, A is selected from FA and MA. Even more preferably, A is FA. Each organic halide of the A cation usually contains a halide anion, for example FAI.

[0028] Preferably, the A' cation is a monocation, typically a large monocation. A' is an organic cation of the ammonium system, typically selected from the group consisting of guanidinium (GA), dimethylammonium (DMA), ethylammonium (EA), imidazolium (Im), phenylethylammonium (PEA), acetamidinium (Ac), and benzylammonium (BzA). Most preferably, A' is GA. Each organic halide typically contains an iodide anion, such as GAI.

[0029] It is understood that this larger organohalide can be mixed (e.g., by hand, high speed mixing, or ball milling) with a first organohalide, such as an organoammonium salt, and the two-component material can be sublimed from the same evaporation source. In a preferred embodiment, co-sublimation of the two precursors is compatible.

[0030] In another embodiment, co-sublimation is incompatible. In this embodiment, the monovalent organic A cation may be methylammonium (MA).

[0031] Temperature-stable perovskites with multiple components can be prepared by co-subliming organic halides with large ammonium salts, such as guanidinium iodide (GAI). This is unexpected, since such large cations generally do not fit into the A cation sites retained in 3D perovskites. Typically, large lattice distortions are introduced, exacerbating halide segregation.

[0032] A large monovalent organic cation, with an ionic radius greater than 2.53 Å, and a smaller monovalent organic cation are typically provided as halides in a first evaporation source and coevaporated. This is facilitated by the close sublimation temperatures and similar deposition rates of the two cation components, as shown in Table 1.

[0033] For example, a suitable combination of precursors in the first evaporation source may be FAI and GAI, or FABr and GABr.

[0034] All of these organic halides are commercially available in the form of solid powders. These cationic salts are in solid form and can be mixed together by any mechanical means, including manual grinding such as ball milling or speed mixing, prior to the evaporation step. During the evaporation step, the two salts sublime from the solid into the gas phase and can be deposited on a substrate.

[0035] As reported by Unlu et al., "Understanding the Interplay of Stability and Efficiency in A-Site Engineered Lead Halide Perovskites," APL Materials 8, 070901, 2020, partial occupancy of A-sites in perovskites by large cations such as GA influences the structural stabilization of the overall perovskite structure. For example, GA increases the number of hydrogen bond (HX bond) interactions over other cations such as MA or FA. The available HX bonds interact with the inorganic framework and directly improve the thermal stability. Hydrogen bonds can also enhance grain size, charge carrier transport, and passivate uncoordinated halide ions in grain boundaries, thus improving the crystallinity and electronic properties of perovskites. Although crystal distortions are expected to occur due to large cations, MA cations localized in adjacent cavities maintain the 3D structure.

[0036] Perovskites can usually be represented by the general formula AMX3 or ABX3. The advantage of using large cations in the A-site for stabilization of the perovskite structure has been clearly shown. However, vacuum deposition combining large monovalent cations combined with smaller monovalent cations has not been demonstrated, as larger cations are not expected to enter the A-site of the perovskite lattice via sublimation methods. Vacuum deposition is a particularly attractive technique, as it allows better control over the quality of the perovskite film, as well as the scalability of the technique favors large-scale industrial manufacturing of this approach.

[0037] Thus, the present invention surprisingly demonstrates that large cations can indeed be co-sublimed with small monovalent organic cations such as FA to produce thermally stabilized crystalline perovskite structures.

[0038] [Table 1] The sublimation temperatures given in Table 1 are estimated ranges, but these will vary depending on the source, crucible type, type of temperature measurement, chamber, pressure and thermocouple position. Evaporation is monitored with a QCM.

[0039] Step (ii) The second evaporation source may include a single metal halide, BX2. Preferably, the second evaporation source includes two metal halides, namely BX2 and BX'2, which are usually mixed together in a crucible in a previous step and heated under an inert atmosphere such as N2. The temperature is above the highest melting point of any selected precursors and heated until they form a melt. The melt is then recrystallized at room temperature to form a solid mixed halide single phase precursor. The halide stoichiometry of the final mixed halide precursor phase can be determined by the initial ratio of BX2 and BX'2. If the stoichiometrically mixed precursors form a single mixture, the subsequent compatible evaporation will usually maintain the initial ratio. In another embodiment, two different metal halides may be combined in the same evaporation source without the need for a previous step, whereby they are non-compatible co-evaporated. Table 2 provides a list of deposition rates and melting points of the corresponding bromides and iodides of some suitable metal halides. All of the compounds listed in Table 2 can be purchased from Sigma Aldrich in the desired solid form and, if necessary, prepared for pre-heating together to form a single precursor phase.

[0040] [Table 2] In other words, in step (ii) of the method of the present invention, a second evaporation source is provided which comprises one or more halides having formula (I). B(X y X' 1-y )2(I) where B is a divalent metal cation, X and X' are different halides, and 0≦y<1.

[0041] It has been found that in a step prior to step (ii), two metal halide salts react to form a new single mixed halide component that can be sublimed as one new material. This step generally involves mixing one or more metal halides, such as BX2 and / or BX'2, and heating in an inert atmosphere. Preferably, this step involves the reaction of PbI y Br 1-y is formed, and prior to this step, PbBr2 and PbI2 are mixed and heated in an inert atmosphere.

[0042] If necessary, the B cations are different for each halide precursor, for example, BX2 and B'X'2 or BX2 and B'X2 are mixed, and the general formula (IA)B x B' 1-x (X y X' 1-y )2 is obtained, where B and B' are different and 0 <x<1および0≦y<1である。

[0043] Preferably, B and B' are selected from Sn and Pb.

[0044] In this case, in step (ii), the second evaporation source comprises two mixed metal halides selected from: a) A single precursor phase Pb from PbI2 and SnI2 x Sn 1-x I2 produces; b) PbBr2 and SnBr2 form a single precursor phase, Pb x Sn 1-x Br2 is produced; c) A single precursor phase, Pb, from PbI2 and SnBr2 x Sn 1-x (I 1-y Br y )2 is generated; d) A single precursor phase, Pb, from PbBr2 and SnI2 x Sn 1-x (I 1-y Br y )2 is generated.

[0045] where 0 <x<1かつ0≦y<1である。

[0046] In embodiments where y>0 in step (ii), two different metal halides are mixed (ie, the halide components are not the same).

[0047] The metal halide salt may be a lead halide salt, such as PbI2 and PbBr2, or PbBr2 and PbCl2. The metal halide salts may be mixed at elevated temperatures and atmospheric pressures. This is advantageous as it reduces the number of evaporation sources used.

[0048] The preparation involves mixing the two materials in a crucible and melting them at high temperature (>350 °C) under nitrogen atmosphere at ambient pressure to avoid oxidation. The resulting compound consists mainly of a new mixed halide phase, which can be sublimed as a single component in a co-evaporation process.

[0049] In one embodiment, the final perovskite may include three different halide materials. The third halide may be introduced from an additional metal halide co-evaporation source. Alternatively, the third metal halide may be premixed with two other metal halides in a crucible, heated under an inert atmosphere, and conformally or non-conformally evaporated and deposited on a substrate. Preferably, the third halide is selected from PbI2, PbBr2, PbCl2, SnI2, SnCl2, SnBr2, or SnF2.

[0050] In another embodiment, the compound of formula (I)B(X y X' 1-y An additional metal halide precursor having a halide component different from that of PbCl2 may be included in the process as an additive. This additional halide component is not present in the final perovskite formula. Preferably, the additional metal halide precursor acting as an additive is PbCl2. These additives may be suitably incorporated into any of the other embodiments described herein.

[0051] Step (iii) Optional step (iii) of the method of the invention preferably comprises providing a monovalent organic halide (such as MAI) to a third evaporation source. This may be supplemented by optional step (iv) of a fourth evaporation source. The fourth evaporation source may comprise an inorganic halide such as CsI or CsBr. At least one of steps (iii) or (iv) must be present, so there may be three or four evaporation sources, i.e. steps (i), (ii) and (iii), steps (i), (ii) and (iv), or steps (i), (ii), (iii) and (iv). In one embodiment, step (iii) is not present and step (iv) is present, so an inorganic halide is provided to the third evaporation source and a triple cation perovskite is produced.

[0052] Thus, there may be three or four A-site cations in a perovskite material.

[0053] The organic moiety of the organohalide in step (iii) is preferably selected from MA and FA. The halide moiety is preferably selected from I, Br and Cl. The organohalide in step (iii) is typically different from the organohalide used in step (i).

[0054] Three or four sources can be co-evaporated simultaneously to produce a final single-phase perovskite film. The term co-evaporation simultaneously means that the evaporation from each source occurs substantially simultaneously. During evaporation, the plumes from each source may include at least 10% overlap with each other, preferably at least 20% overlap, more preferably at least 30%, 40%, 50%, 60%, 70%, 80%, 90% overlap, or substantially complete (100%) overlap. If the second source includes BX2, it may be directly sublimated in the co-evaporation step (ii) without any prior preliminary step with another precursor. In an embodiment, step (iv) may have CsI or CsBr, producing a single or mixed halide final material. If a final single halide material is desired, the halide component of the Cs halide may be the same as the halide component of the lead halide of step (ii). When a final dual mixed halide with a preferred stoichiometry is desired and step (ii) includes only BX2, there are two routes by which a mixed dual halide composition can be obtained. In one embodiment, the preferred stoichiometric ratio of BX2 and CsX' may be evaporated according to their steps and separate sources, where X and X' are different halides. In another embodiment, the mixed halide components may be obtained from a previous preparation step of (iii) or (iv), e.g., derived from a mixture of two inorganic halides, where one has a different halide component than the material of step (ii).

[0055] If a final triple mixed halide with a suitable stoichiometry is desired and step (ii) involves only BX2 and BX', there are two routes by which the mixed triple halide composition can be formed. In one embodiment, the suitable stoichiometric ratio of BX2, BX'2 and CsX'' may be evaporated according to those steps and separate sources, where X, X' and X'' are different halides. In another embodiment, the triple mixed halide component is obtained from a previous preparation step of (iii) or (iv), e.g., derived from a mixture of two inorganic halides, both of which have different halide components relative to the materials of step (ii).

[0056] The preferred inorganic halides, CsI and CsBr, are mixed together in a crucible and heated under an inert atmosphere, such as N2, at a temperature above the highest melting point of any selected precursor to form a melt. The melt is then recrystallized at room temperature to form a solid mixed halide single phase precursor. The halide stoichiometry of the final mixed halide precursor phase can be determined by the initial ratio of CsBr to CsI. Table 3 provides the melting temperatures and deposition rates of the CsI and CsBr compounds, highlighting the closeness of their sublimation temperatures and equal deposition rates. Thus, the Cs mixed halide precursor occupies a third evaporation source, which is co-sublimated with the first and second evaporation sources.

[0057] If necessary, a fourth evaporation source may also be introduced. The fourth evaporation source may include an inorganic halide such as CsI or CsBr, and the third evaporation source may include an organic halide selected from organic monocations such as MA and FA cations, so that none of the precursor organic cations in the method are the same.

[0058] In another embodiment of the invention, the second evaporation source in step (ii) may instead consist of the preparation of two mixed metal mixed halide reagents such as BX2 and B'X'2. For example, PbI2 and SnBr2, or similarly PbBr2 and SnI2, may be mixed in a crucible and melted under an inert atmosphere such as N2 at a temperature according to the highest melting point of any precursor to form a melt. The melt is then recrystallized at room temperature to form a solid mixed halide mixed metal single phase precursor. The halide and metal stoichiometry of the final precursor phase can be determined by the initial ratio of BX2 to B'X'2.

[0059] For the above embodiment, the third or fourth evaporation source may comprise an inorganic halide such as CsI or CsBr, or an organic halide selected from MA and FA cations, such that none of the precursor organic cations are the same.

[0060] Cs salts can be procured directly from standard suppliers in powder form ready for pretreatment to form a single precursor phase.

[0061] Step (iv) Step (iv) may include the introduction of an inorganic halide component. Step (iii) may be present or absent, and thus there may be three or four evaporation sources. Optionally, when four evaporation sources are used, the fourth evaporation source is provided with an inorganic halide and the third evaporation source is provided with an organic halide. All A cations are different from each other in the final composition.

[0062] The inorganic portion of the inorganic halide component is preferably selected from Cs and Rb, and is preferably Cs.

[0063] Thus, the method may comprise four evaporation sources, where in step (ii) the evaporation sources are provided with BX2, and in step (iv) the fourth evaporation source is provided with mixed Cs halides and the third evaporation source is provided with an organic halide.

[0064] In this embodiment, a fourth evaporation source may be used to deposit a quadruple cation perovskite, which contains an organic halide selected from organic monocations such as MA, FA and EA cations, with MA being preferred, such that none of the precursor organic cations are the same.

[0065] In yet another embodiment, the second evaporation source may consist of the preparation of BX2 and B'X2 to obtain the same halide precursor of mixed metals. For example, any two of PbCl2, PbBr2, and PbI2, or any two of SnCl2, SnF2, SnBr2, and SnI2 may be mixed in a crucible and melted at a temperature according to the highest melting point of any precursor under an inert atmosphere such as N2 to form a melt. The melt is then recrystallized at room temperature to form a solid mixed metal single phase precursor. The metal stoichiometry of the final precursor phase may be determined by the initial ratio of BX2 to B'X2.

[0066] Similar to step (iii) where the second evaporation source contains just a single halide, step (iv) may contain CsI or CsBr to produce a final material of single or mixed halides. If a final single halide material is desired, the halide component of the Cs halide is the same as that of the lead halide of step (ii). If a final mixed halide with a suitable stoichiometry is desired, there are two routes by which the mixed halide composition can be obtained. In one embodiment, the suitable stoichiometric ratios of BX2 and CsX' may be evaporated in their separate steps and chambers. X and X' are different halides. In another embodiment, the mixed halide component is obtained from a previous preparation step of (iv), for example from a mixture of inorganic halides.

[0067] The preferred inorganic halides, CsI and CsBr, may be mixed in a crucible and heated under an inert atmosphere, such as N2, at a temperature above the highest melting point of any selected precursor until they form a melt. The melt is then recrystallized at room temperature, where a solid mixed halide single phase precursor is formed. The halide stoichiometry of the final mixed halide precursor phase can be determined by the initial ratio of CsBr to CsI. Thus, the Cs mixed halide precursor constitutes the third (or fourth) evaporation source, which is co-sublimated with the first and second ones to deposit triple or quadruple cation dual halide perovskite films on the substrate.

[0068] Also, if desired, a different evaporation source may be used (in step (iii)) that contains an organic halide selected from the MA cations, such that none of the precursor organic cations are the same.

[0069] [Table 3] The temperatures listed in Tables 1 to 3 are for reference purposes and may of course change when the process is scaled up. Similarly, the deposition rate of each precursor is greatly affected by the temperature and pressure used and may therefore change during scale up (T. Neubert, M. Vergohl, Optical Thin Films and Coatings, 2013).

[0070] In all embodiments, the multi-component perovskite has a preferred thickness of 50 to 2000 nm, preferably 100 nm to 1500 nm. This is governed by the deposition rate of each precursor under vacuum conditions below atmospheric pressure. Once the perovskite film is deposited on the substrate, the film is then annealed at a temperature in the range of 50 to 300° C., for example for 1 minute to 6 hours, to promote and ensure a uniform morphology of the crystalline film. This allows for good incorporation of the large additive cations into the perovskite lattice. The specific process conditions may affect the amount of large cations that enter the lattice. However, within the recommended temperature range, at least some incorporation of large cations is expected. Also, in some cases, the large cations act as additives that passivate defects at grain boundaries and surfaces, and therefore are not incorporated into the final perovskite formula. These passivating additives may be suitably incorporated into any of the other embodiments described herein.

[0071] material Typically, the method of the present invention involves the formation of a thin film perovskite material, the bandgap of which is typically in the range of 1.1 eV and 2.5 eV.

[0072] The perovskite material is preferably a mixed halide material, i.e. it contains two or more different halides. It may contain two types of halide. Alternatively, there may be three different halide anions.

[0073] Typically, the perovskite material formed by the method of the present invention has the general formula (II): A a A' b A'' c A''' d B x B' 1-x (X y X' 1-y )3 wherein A is a first monovalent organic cation capable of co-sublimation with A' when both organic cations A and A' are present as halides (preferably iodides); A' is a second monovalent organic cation; A'' and A''' are independently a monovalent inorganic cation or another monovalent organic cation. wherein all A cations are different from each other, and at least three of these are present; 0 <a<1、 0 <b<1、 0 <c<1、 0≦d<1, a+b+c+d=1, 0≦x<1 and 0≦y<1, B and B' are independently a divalent metal cation; X and X' are halide anions.

[0074] In a preferred embodiment, the perovskite material formed by the method of the present invention has the general formula: A a A' b A'' c A''' d B x B' 1-x (X y X' 1-y )3(III) where A is a monovalent organic cation capable of co-sublimation with A' when present in the halide; A' is a monovalent organic cation having an ionic radius greater than 2.53 Å; A'' is a monovalent inorganic cation or a monovalent organic cation; A''' is a monovalent inorganic cation or a monovalent organic cation; where all A cations are different from each other, 0 <a<1、 0 <b<1、 0 <c<1、 0≦d<1, a+b+c+d=1, 0 ≤ x < 1, 0 ≤ y < 1.

[0075] In both of these embodiments, preferably 0 < y < 1, i.e., the halide components are different.

[0076] When A is present as a halide, preferably an iodide, it is a monovalent organic cation having a sublimation temperature similar to that of A'. The halide moiety is selected from X or X' as in the final product of formula (II).

[0077] In a preferred embodiment, A is FA. In a more preferred embodiment, A' is selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidinium (Ac), and phenylethylammonium (PEA), and preferably, A' is GA.

[0078] Also, A' and A'' are different from each other and may be selected from any of the following: (i) A group of organic cations usually including MA, FA, EA, preferably MA, and / or (ii) Cesium ions.

[0079] Also, the X and X' anions are different from each other and are selected from the group of halides including Cl, Br, and I, and preferably, the halide is I and / or Br.

[0080] The B cation is selected from Pb 2+ and Sn 2+ and B' is different from B but is selected from Pb 2+ and Sn 2+ and.

[0081] In one embodiment, the method may have three evaporation sources, where in step (ii) of the method one or more metal halides are provided to a single source and in step (iii) of the method either an inorganic halide or an organic halide is provided to a third evaporation source to provide a triple cation perovskite.

[0082] Such perovskites may be selected from the following formulas: FA a GA b MA c Pb(I y Br 1-y ) 3, FA a GA b Cs c Pb(I y Br 1-y )3, MA a GA b Cs c Pb(I y Br 1-y ) 3, FA a BzA b MA c Pb(I y Br 1-y ) 3, FA a BzA b Cs c Pb(I y Br 1-y )3, MAaBzA b Cs c Pb(I y Br 1-y ) 3, FA a DMA b Cs c Pb(I y Br 1-y ) 3, FA a DMA b MA c Pb(I y Br 1-y )3, MA a DMA b Cs c Pb(I y Br 1-y ) 3, FA a GA b MA c Sn(Iy Br 1-y )3、FA a GA b Cs c Sn(I y Br 1-y )3、MA a GA b Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Sn(I y Br 1-y )3、FA a BzA b Cs c Sn(I y Br 1-y )3、MA a BzA b Cs c Sn(I y Br 1-y )3、FA a DMA b Cs c Sn(I y Br 1-y )3、FA a DMA b MA c Sn(I y Br 1-y )3、MA a DMA b Cs c Sn(I y Br 1-y )、FA a Im b Cs c Pb(I y Br 1-y )3、FA a Im b Cs c Sn(I y Br 1-y )3、FA a PEA b Cs c Pb(I y Br 1-y )3、FA a Ac b Cs c Pb(I y Br 1-y )3、FAa Ac b Cs c Sn(I) y Br 1-y )3、FA a BzA b AND c Pb(I) y Br 1-y )3、FA a BzA b AND c Sn(I) y Br 1-y )3、FA a I am b AND c Pb(I) y Br 1-y )3、FA a I am b AND c Sn(I) y Br 1-y )3、FA a TO BE b AND c Pb(I) y Br 1-y )3、FA a TO BE b AND c Sn(I) y Br 1-y )3、FA a EA b Cs c Pb(I) y Br 1-y )3、FA a EA b AND c Pb(I) y Br 1-y )3、FA a EA b Cs c Sn(I) y Br 1-y )3、FA a EA b AND c Sn(I) y Br 1-y )3、MA a EA b Cs c Pb(I) y Br 1-y )3、MA a EA b Csc Sn(I y Br 1-y )3. where 0 <a<1、0<b<1、0<c<1、a+b+c=1、0≦y<1である。

[0083] In another embodiment, the method may have three evaporation sources, where in step (ii) of the method a mixture of metal halides, each having a different metal component, is provided to a single evaporation source, and in steps (iii) or (iv) of the method either an inorganic halide or an organic halide is provided to a third evaporation source to provide the triple cation mixed metal perovskite.

[0084] Such perovskites may be selected from the following formulas: FA a GA b MA c Pb x Sn 1-x (I y Br 1-y ) 3, FA a GA b Cs c Pb x Sn 1-x (I y Br 1-y )3, MA a GA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3, FA a BzA b MA c Pb x Sn 1-x (I y Br 1-y ) 3, FA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y )3, MA a BzA b Cs c Pb x Sn1-x (I y Br 1-y )3、FA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b MA c Pb x Sn 1-x (I y Br 1-y )3、MA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a Im b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a Im b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a PEA b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a PEA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a Ac b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a Ac b Cs c Pb x Sn 1-x (I yBr 1-y ) 3, FA a EA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3, FA a EA b MA c Pb x Sn 1-x (I y Br 1-y )3, MA a EA b Cs c Pb x Sn 1-x (I y Br 1-y )3; where 0 <a<1、0<b<1、0<c<1、a+b+c=1、0<x<1、0≦y<1である。

[0085] In another embodiment, the method may have four evaporation sources, where in step (ii) of the method one or more metal halides are provided to a single evaporation source, and in steps (iii) and (iv) of the method an inorganic halide is provided to a fourth evaporation source and an organic halide is provided to a third evaporation source to produce a quaternary cation perovskite material.

[0086] Such perovskites may be selected from the following formulas: FA a GA b MA c Cs d Pb(I y Br 1-y ) 3, FA a EA b MA c Cs d Pb(I y Br 1-y ) 3, FA a BzA b MA c Cs d Pb(I y Br 1-y ) 3, FA a DMA b MAc Cs d Pb(I y Br 1-y )3、FA a GA b MA c Cs d Sn(I y Br 1-y )3、FA a EA b MA c Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Cs d Sn(I y Br 1-y )3、FA a DMA b MA c Cs d Sn(I y Br 1-y )3、FA a Im b MA c Cs d Pb(I y Br 1-y )3、FA a Im b MA c Cs d Sn(I y Br 1-y )3、FA a PEA b MA c Cs d Pb(I y Br 1-y )3、FA a PEA b MA c Cs d Sn(I y Br 1-y )3、FA a Ac b MA c Cs d Pb(I y Br 1-y )3、FA a Ac b MA c Cs d Sn(I y Br1-y )3; where 0 <a<1、0<b<1、0<c<1、0<d<1、a+b+c+d=1、0≦y<1である。

[0087] In another embodiment, the method may have four evaporation sources, where in step (ii) of the method a mixture of metal halides, each having a different metal component, is provided to a single evaporation source, and in step (iii) of the method an inorganic halide is provided to a third evaporation source and an organic halide is provided to a fourth evaporation source to obtain a quaternary cation mixed metal perovskite material.

[0088] Such perovskites may be selected from the following formulas: FA a GA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a BzA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a EA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a DMA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a Im b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a PEAb MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a Ac b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3; where 0 <a<1、0<b<1、0<c<1、0<d<1、a+b+c+d=1、0<x<1、0≦y<1である。

[0089] In yet another aspect of the present invention there are provided new perovskites of the general formula: MA a GA b Cs c Pb(I y Br 1-y ) 3, FA a BzA b MA c Pb(I y Br 1-y ) 3, FA a BzA b Cs c Pb(I y Br 1-y )3, MA a BzA b Cs c Pb(I y Br 1-y )3, MA a DMA b Cs c Pb(I y Br 1-y ), F.A. a GA b MA c Sn(I y Br 1-y ) 3, FA a GA b Cs c Sn(I y Br 1-y )3, MA a GA b Cs c Sn(Iy Br 1-y )3、FA a BzA b MA c Sn(I y Br 1-y )3、FA a BzA b Cs c Sn(I y Br 1-y )3、MA a BzA b Cs c Sn(I y Br 1-y )3、FA a DMA b Cs c Sn(I y Br 1-y )3、FA a DMA b MA c Sn(I y Br 1-y )3、MA a DMA b Cs c Sn(I y Br 1-y )、FA a Im b Cs c Sn(I y Br 1-y )3、FA a PEA b Cs c Pb(I y Br 1-y )3、FA a PEA b Cs c Sn(I y Br 1-y )3、FA a Ac b Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Pb(I y Br 1-y )3、FA a BzA b MA c Sn(I y Br 1-y )3、FAa I am b AND c Pb(I) y Br 1-y )3、FA a I am b AND c Sn(I) y Br 1-y )3、FA a TO BE b AND c Pb(I) y Br 1-y )3、FA a TO BE b AND c Sn(I) y Br 1-y )3、FA a EA b Cs c Sn(I) y Br 1-y )3、FA a EA b AND c Sn(I) y Br 1-y )3、MA a EA b Cs c Pb(I) y Br 1-y )3、MA a EA b Cs c Sn(I) y Br 1-y )3、FA a EN b AND c Pb x Sn 1-x (I y Br 1-y )3、FA a EN b Cs c Pb x Sn 1-x (I y Br 1-y )3、MA a EN b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b ANDc Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y )3、MA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b MA c Pb x Sn 1-x (I y Br 1-y )3、MA a DMA b CsPb x Sn 1-x (I y Br 1-y )、FA a Im b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a Im b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a PEA b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a PEA b Cs c Pb x Sn1-x (I y Br 1-y )3、FA a Ac b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a Ac b Cs c Pb x Sn 1-x (I y Br 1-y )3; ここで、0<a<1、0<b<1、0<c<1、0<d<1、a+b+c=1、0<x<1、0<y<1であり、 FA a EA b MA c Cs d Pb(I y Br 1-y )3、FA a BzA b MA c Cs d Pb(I y Br 1-y )3、FA a DMA b MA c Cs d Pb(I y Br 1-y )3、FA a GA b MA c Cs d Sn(I y Br 1-y )3、FA a EA b MA c Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Cs d Sn(I y Br 1-y )3、FA a DMA b MA c Cs d Sn(I y Br 1-y)3、FA a Im b MA c Cs d Pb(I y Br 1-y )3、FA a Im b MA c Cs d Sn(I y Br 1-y )3、FA a PEA b MA c Cs d Sn(I y Br 1-y )3、FA a Ac b MA c Cs d Pb(I y Br 1-y )3、FA a Ac b MA c Cs d Sn(I y Br 1-y )3、FA a GA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3、FA a EA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3、FA a Im bMA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a PEA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3, FA a Ac b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3; where 0 <a<1、0<b<1、0<c<1、0<d<1、a+b+c+d=1、0<x<1、0<y<1である。

[0090] In yet another embodiment of the present invention there is provided a semiconductor device having a photoactive layer comprising an organic-inorganic metal halide perovskite material formed according to the first aspect of the present invention.

[0091] In another embodiment, the semiconductor device is a photovoltaic device having a photoactive region, said photoactive region comprising a thin film of perovskite material formed according to the first aspect of the present invention, the thin film of perovskite material having a thickness in the range of 50 to 2000 nm, preferably in the range of 100 nm to 1500 nm. Further, 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.

[0092] The photovoltaic device may have 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 and p-type regions.

[0093] In another embodiment of the present invention, there is provided a multi-junction photovoltaic device having two or more subcells, a first subcell having a bandgap between 1.1 and 2.5 eV as described above, and a further subcell having a second photoactive layer having a complementary bandgap.

[0094] In one embodiment of the present invention, the photovoltaic device may be a single junction device. In another embodiment, the photovoltaic device may be a multi-junction device, where one or more of the top, middle or bottom subcells, depending on the device geometry, comprise a perovskite as described herein in an all-perovskite, perovskite-Si, perovskite-CIGS, perovskite-CuZnSnSSe tandem cell, perovskite-CuZnSnS tandem cell or perovskite-CdTe heterojunction device.

[0095] In another embodiment of the present invention there is provided an optoelectronic device comprising a perovskite material formed according to the first aspect of the present invention.

[0096] In some embodiments, the optoelectronic device may include a substrate. The substrate may have a flat surface. Alternatively, the substrate may have a root mean square roughness (R rms The substrate may have a textured surface having a fluorine-doped tin oxide (FTO) or a glass, such as indium tin oxide (ITO), or silicon (Si).

[0097] Detailed explanation definition The term "photoactive" as used herein refers to a region, layer, or material that can respond photoelectrically to light. Thus, a photoactive region, layer, or material can absorb energy carried by photons of light and thereby generate electricity (e.g., by generating either electron-hole pairs or excitons).

[0098] The term "perovskite" as used herein refers to a material having a three-dimensional crystal structure related to that of CaTiO3 or a material containing a layer of a material having a structure related to that of CaTiO3. The structure of CaTiO3 is represented by the formula ABX3, where A and B are cations of different sizes and X is an anion. In a single cell, the A cations are at (0,0,0), the B cations are at (1 / 2,1 / 2,1 / 2), and the X anions are at (1 / 2,1 / 2,0). The A cations are usually larger than the B cations. It will be apparent to those skilled in the art that as A, B, and X are varied, the different ion sizes will distort the structure of the perovskite material from that adopted by CaTiO3 to a distorted structure with low symmetry. Also, if the material has a layer containing a structure related to that of CaTiO3, the symmetry will be lower. Materials containing layers of perovskite materials are well known. For example, the structure of a material that adopts a K2NiF4 type structure includes a layer of perovskite material. It is clear to those skilled in the art that perovskite materials can be represented by the general formula [A][B][X]3. [A] is at least one cation, [B] is at least one cation, and [X] is at least one anion. When a perovskite contains two or more A cations, the different A cations may be distributed on the A site in an orderly or disordered manner. When a perovskite contains two or more B cations, the different B cations may be distributed on the B site in an orderly or disordered manner. When a perovskite contains two or more X anions, the different X anions may be distributed on the X site in an orderly or disordered manner. The symmetry of perovskites that contain two or more A cations, two or more B cations, or two or more X cations is often less than that of CaTiO3.

[0099] As mentioned before, the term "perovskite" as used herein refers to (a) a material having a three-dimensional crystal structure related to that of CaTiO3, or (b) a material comprising layers of material having a structure related to that of CaTiO3. Although both of these categories of perovskites may be used in the device according to the invention, in some circumstances it is preferred to use perovskites of the first category (a), i.e. perovskites having a three-dimensional (3D) crystal structure. Such perovskites usually comprise a 3D network of perovskite unit cells, with no separation between the layers. On the other hand, perovskites of the second category (b) include perovskites having a two-dimensional (2D) layered structure. Perovskites having a two-dimensional layered structure may have layers of perovskite unit cells separated by (intercalated) molecules. One example of such a two-dimensional layered perovskite is [2-(1-cyclohexenyl)ethylammonium]2PbBr4. 2D layered perovskites tend to have high exciton binding energy, which is more favorable for the formation of bound electron-hole pairs (excitons) under photoexcitation than free charge carriers. Bound electron-hole pairs cannot move sufficiently to reach the p-type or n-type contacts where they can then migrate (ionize) to generate free charge. As a result, to generate free charge, the exciton binding energy needs to be overcome, which represents an energy cost to the charge generation process, leading to lower voltages and lower efficiency in photovoltaic cells. On the other hand, perovskites with 3D crystal structures tend to have much lower exciton binding energies (on the order of thermal energy) and are therefore able to generate free carriers directly following photoexcitation. Thus, the perovskite semiconductors used in the devices and processes of the present invention are preferably perovskites of the first category (a), i.e., perovskites with a three-dimensional crystal structure. This is particularly preferred when the optoelectronic device is a photovoltaic device.

[0100] The perovskite material used in the present invention can absorb light and thereby generate free charge carriers. Therefore, the perovskite used is a light absorbing perovskite material. However, it will be understood by those skilled in the art that the perovskite material can also be a perovskite material that can emit light by accepting both electron and hole charges, which then recombine to emit light. Therefore, the perovskite used can be a light emitting perovskite.

[0101] As will be appreciated by those skilled in the art, the perovskite material used in the present invention may be a perovskite that functions as an n-type electron transporting semiconductor when photodoped. Alternatively, it may be a perovskite that functions as a p-type hole transporting semiconductor when photodoped. Thus, the perovskite may be an n-type, a p-type, or an intrinsic semiconductor. In a preferred embodiment, the perovskite used functions as an n-type electron transporting semiconductor when photodoped. The perovskite material exhibits ambipolar charge transport and therefore functions as both an n-type and a p-type semiconductor. In particular, the perovskite may function as both an n-type and a p-type semiconductor depending on the type of junction formed between the perovskite and the adjacent material.

[0102] Typically, the perovskite semiconductors used in the present invention are photosensitive materials, i.e. materials capable of both light generation and charge transport.

[0103] The term "mixed halide" as used herein refers to a compound containing at least two different halides. The term "halide" refers to an anion of an element selected from group 17 of the periodic table of the elements, i.e., a halogen. Typically, the halide anion refers to a fluoride, chloride, bromide, iodide, or astatide anion.

[0104] As used herein, the term "metal halide perovskite" refers to a perovskite whose general formula includes at least one metal cation and at least one halide anion. As used herein, the term "organometal halide perovskite" refers to a metal halide perovskite whose general formula includes at least one organic cation.

[0105] The term "organic material" is given its usual meaning in the art. Typically, organic materials refer to materials that include one or more compounds that include carbon atoms. As will be understood by those skilled in the art, organic compounds may include a carbon atom that is covalently bonded to another carbon atom, or a hydrogen atom, or a halogen atom, or a chalcogen atom (e.g., an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom). It will be understood by those skilled in the art that the term "organic compound" does not generally include compounds that are predominantly ionic, such as carbides.

[0106] The term "organic cation" refers to a cation that contains carbon. The cation may contain another element, for example, the cation may contain hydrogen, nitrogen, or oxygen. The term "inorganic cation" refers to a cation that is not an organic cation. By default, the term "inorganic cation" refers to a cation that does not contain carbon.

[0107] The term "semiconductor" as used herein refers to a material that has an electrical conductivity between that of a conductor and that of a dielectric. Semiconductors may be n-type, p-type, or intrinsic.

[0108] The term "n-type" as used herein refers to a region, layer, or material that includes an extrinsic semiconductor that has a higher concentration of electrons than holes. Thus, in n-type semiconductors, electrons are the majority carriers and holes are the minority carriers, and therefore they are electron transporting materials. Thus, the term "n-type region" as used herein 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 (i.e., n-type) material. An electron transporting (i.e., n-type) material can be a single electron transporting compound or elemental material, or a mixture of two or more electron transporting compounds or elemental materials. An electron transporting compound or elemental material can be undoped or doped with one or more dopant elements.

[0109] The term "p-type" as used herein refers to a region, layer, or material that includes an extrinsic semiconductor that has a higher concentration of holes than electrons. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers, so they are hole transporting materials. Thus, the term "p-type region" as used herein refers to a region of one or more hole transporting (i.e., p-type) materials. Similarly, the term "p-type layer" refers to a layer of a hole transporting (i.e., p-type) material. A hole transporting (i.e., p-type) material can be a single hole transporting compound or elemental material, or a mixture of two or more hole transporting compounds or elemental materials. A hole transporting compound or elemental material can be undoped or doped with one or more dopant elements.

[0110] As used herein, the term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band in a material. One of ordinary skill in the art can readily determine the band gap of a material without undue experimentation.

[0111] The term "layer" as used herein refers to any structure that is substantially laminar in form (e.g., extends substantially in two perpendicular directions, but has limited extension in a third perpendicular direction). A layer may have a thickness that varies over the extent of the layer. Typically, a layer has a substantially constant thickness. As used herein, the "thickness" of a layer refers to the average thickness of the layer. The thickness of a layer may be readily measured, for example, by using a microscope, such as an electron microscope, of a cross-section of the film, or by surface profilometry, for example, using a stylus profilometer.

[0112] The term "porous" as used herein refers to a material in which pores are located. Thus, for example, in a porous material, a pore is a volume in the body of a material that is free of material. The individual pores may be of the same size or of different sizes. The size of the pores is defined as the "pore size". In most phenomena involving porous solids, the limiting size of a pore is the size of its smallest dimension, which, without any further clarification, is referred to as the width of the pore (i.e., the width of a slit-like pore, the diameter of a cylindrical or spherical pore, etc.). To avoid misinterpretation of the change in scale when comparing cylindrical and slit-like pores, the diameter of a cylindrical pore (rather than its length) should be used as the "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 have been adopted in previous IUPAC documents (J. Haber. (1991)). Manual of Catalyst Characterization (Recommendations 1991). Pure and Applied Chemistry: Micropores have a width (i.e., pore size) of less than 2 nm, mesopores have a width (i.e., pore size) of 2 to 50 nm, and macropores have a width (i.e., pore size) of more than 50 nm. Nanopores may also be considered to have a width (i.e., pore size) of less than 1 nm.

[0113] Pores in a material can include "closed" pores and open pores. Closed pores are pores in a material that are unconnected cavities, i.e., pores that are isolated within the material and not connected to any other pores, and therefore cannot be accessed by fluids to which the material is exposed. On the other hand, "open pores" are accessible by such fluids. The concepts of open and closed porosity are discussed in detail in J. Rouquerol et al.

[0114] Thus, open porosity represents the percentage of the total volume of a porous material through which fluid flow can effectively occur. Thus, closed pores are excluded. The term "open porosity" is interchangeable with the terms "connected porosity" and "effective porosity" and is commonly abbreviated in the art as simply "porosity". Thus, the term "no open porosity" as used herein refers to a material that has no effective porosity. Thus, a material that has no open porosity typically has no macropores or mesopores. However, a material that has no open porosity may include micropores and nanopores. Such micropores and nanopores are very small and usually have no negative effect on materials where low porosity is desired.

[0115] Also, polycrystalline materials are solids composed of many separate crystals or particles, with grain boundaries present at the interface between any two crystals or particles in the material. Thus, polycrystalline materials can have both interparticle / interstitial porosity and intraparticle / internal porosity. The terms "interparticle porosity" and "interstitial porosity" as used herein refer to the pores between the crystals or particles of a polycrystalline material (i.e., grain boundaries), while the terms "intragranular porosity" and "internal porosity" as used herein refer to the pores inside the individual crystals or particles of a polycrystalline material. On the other hand, a single crystal or monocrystalline material is a solid in which the crystal lattice is continuous and undisintegrated throughout the volume of the material, there are no grain boundaries, and there is no interparticle / interstitial porosity.

[0116] The term "compact layer" as used herein refers to a layer that does not have meso- or macro-porosity. Compact layers may sometimes have micro- or nano-porosity.

[0117] Thus, the term "scaffolding material" as used herein refers to a material that can act as a support for another material. Thus, the term "porous scaffolding material" as used herein refers to a material that is itself porous and that can act as a support for another material.

[0118] The term "transparent" as used herein refers to a material or object that allows visible light to pass through it with little obstruction, allowing a clear view of the object behind it. Thus, the term "semi-transparent" as used herein refers to a material or object that has a transmission (or equivalently referred to as transmittance) between a transparent material or object and an opaque material or object for visible light. Typically, a transparent material has an average transmission of about 100%, or 90 to 100%, for visible light (generally light having a wavelength between 370 and 740 nm). Typically, an opaque material has an average transmission of about 0%, or 0 to 5%, for visible light. A semi-transparent material or object typically has an average transmission of 10 to 90%, typically 40 to 60%, for visible light. Unlike many translucent objects, a semi-transparent object does not typically distort or blur the image. The transmission of light can be measured in the usual manner, for example, by comparing the intensity of the incident light with the intensity of the transmitted light.

[0119] The term "electrode" as used herein refers to a conductive material or object through which current flows to or from an object, substance, or region. The term "negative electrode" as used herein refers to an electrode through which electrons are emitted from a material or object (i.e., an electron collecting electrode). A negative electrode is typically referred to as an "anode." The term "positive electrode" as used herein refers to an electrode through which holes are emitted from a material or object (i.e., a hole collecting electrode). A positive electrode is typically referred to as a "cathode." In a photovoltaic device, electrons flow from the positive electrode / cathode to the negative electrode / anode, and holes flow from the negative electrode / anode to the positive electrode / cathode.

[0120] The term "front electrode" as used herein refers to an electrode provided on the side or surface of a photovoltaic device that is intended to be exposed to sunlight. Thus, the front electrode is typically required to be transparent or semi-transparent so that light can pass through the electrode to reach the photoactive layer provided below the front electrode. Thus, the term "back electrode" as used herein refers to an electrode provided on the side or surface of a photovoltaic device opposite the side or surface that is intended to be exposed to sunlight.

[0121] The term "charge transporter" refers to a region, layer, or material through which charge carriers (i.e., particles that carry an electric charge) can move freely. In semiconductors, electrons act as mobile negative charge carriers and holes act as mobile positive charges. Thus, the term "electron transporter" refers to a region, layer, or material through which electrons can flow readily and which typically reflects holes (holes are the absence of electrons that are considered the mobile carriers of positive charge in semiconductors). Conversely, the term "hole transporter" refers to a region, layer, or material through which holes can flow readily and which typically reflects electrons.

[0122] 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 of 150°C or less, or for example at a temperature of 100°C or less, is a volatile compound. "Volatile compound" also includes compounds that are easily removed by evaporation via decomposition products. Thus, a volatile compound X may be easily evaporated by evaporation of X molecules, or a volatile compound X may be easily evaporated by decomposing to form two compounds Y, Z that are easily evaporated. For example, an ammonium salt is a volatile compound and may volatilize as a molecule of the ammonium salt or as a decomposition product, such as ammonium and a hydrogen compound (e.g., hydrogen halide). Thus, a volatile compound X may have a relatively high vapor pressure (e.g., 500 Pa or more) or a relatively high decomposition pressure (e.g., 500 Pa or more for one or more decomposition products), the latter also referred to as dissociation pressure.

[0123] The term "conform" as used herein refers to an object that is substantially the same in form or shape as another object. Thus, a "conformal layer" as used herein refers to a layer of material that conforms to the contours of the surface on which it is formed. In other words, the morphology of the layer is such that the thickness of the layer is approximately constant across the majority of the interface between the layer and the surface on which it is formed.

[0124] The term co-evaporation as used herein refers to two or more materials or mixtures of materials being heated at separate sources in a high vacuum chamber to initiate evaporation and then deposited simultaneously onto a substrate. This term is interchangeable with the term "co-sublimation."

[0125] The term "large organic cation" as used herein refers to a monovalent organic cation that can occupy the A-site of the perovskite structure and has an ionic radius of greater than 2.53 Å. The term "additive" as used herein refers to a component that can be added to a perovskite formulation to improve the optoelectronic properties of the perovskite material and the performance characteristics of the corresponding perovskite solar cell device. Thus, the term "large organic cation additive" as used herein refers to an organic cation with an ionic radius of greater than 2.53 Å that can occupy the A-site of the perovskite structure and thus improve the characteristics of the perovskite material and / or perovskite device.

[0126] The term "optoelectronic device" includes photovoltaic devices, photodiodes (including solar cells), phototransistors, photomultipliers, photoresistors, light emitting diodes, and the like.

[0127] Photovoltaic Devices The perovskite material of the present invention may be used in semiconductor devices, preferably photovoltaic devices, where the perovskite material is advantageously configured to act as a light absorber / photosensitizer within the photoactive region of the photovoltaic device.

[0128] The photoactive region may comprise a thin film of perovskite material, preferably the thin film of perovskite material has a thickness of from 50 nm to 2000 nm, preferably from 100 nm to 1500 nm, more preferably from 300 to 1200 nm.

[0129] The photoactive region may have an n-type region comprising at least one n-type layer and a layer of perovskite material in contact with the n-type region.

[0130] The photoactive region may have 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 and p-type regions.

[0131] The photoactive region may comprise a layer of perovskite material free of open porosity. The layer of perovskite material may form a planar heterojunction with one or both of the n-type and p-type regions.

[0132] Alternatively, but less preferably, the layer of perovskite material may be in contact with a porous scaffold material disposed between the n-type and p-type regions. The porous scaffold material may comprise or consist essentially of any dielectric and semiconducting / charge transport material. The layer of perovskite material may then be disposed within the pores of the porous scaffold material and conformal with the surface of the porous scaffold material. Alternatively, the layer of perovskite material may fill the pores of the porous scaffold material and form a cap layer on the porous scaffold material. The cap layer is comprised of a layer of photoactive material without open porosity.

[0133] The photovoltaic device further comprises a first electrode and a second electrode, the photoactive region being disposed between the first electrode and the second electrode, the first electrode contacting the n-type region of the photoactive region and the second electrode contacting the p-type region of the photoactive region. The first and second electrodes may comprise a transparent or light-transmitting conductive material, and the second electrode may comprise a metal or a second light-transmitting conductive material. The first electrode is an electron collecting electrode and the second electrode is a hole collecting electrode.

[0134] The photovoltaic device further comprises a first electrode and a second electrode, the photoactive region being disposed between the first electrode and the second electrode, the first electrode contacting the p-type region of the photoactive region and the second electrode contacting the n-type region of the photoactive region. The first electrode may comprise a transparent or light-transmitting conductive material, and the second electrode may comprise a metal or a second light-transmitting conductive material. The first electrode is a hole collecting electrode and the second electrode is an electron collecting electrode.

[0135] The photovoltaic device may have a multi-junction structure with a first subcell disposed above a second subcell, the first subcell including a photoactive region including a perovskite material. The photovoltaic device may have a monolithically integrated structure. In a monolithically integrated multi-junction photovoltaic device, two or more photovoltaic subcells are deposited directly on top of each other and are therefore electrically connected in series. The photovoltaic device may further include intermediate regions connecting the first subcell to the second subcell, each intermediate region having one or more interconnect layers.

[0136] The photovoltaic device having a multi-junction structure may further include a first electrode and a second electrode, and the first subcell and the second subcell may be disposed between the first electrode and the second electrode.

[0137] A first electrode may then be in contact with the p-type region of the first subcell, the first electrode comprising a transparent or semi-transparent conductive material. The first electrode is a hole collecting electrode and the second electrode is an electron collecting electrode. In a tandem monolithic device, the second electrode is in contact with the second subcell, the first and second electrodes forming external components at either end of the device. An intermediate layer is disposed between the first and second subcells.

[0138] Alternatively, the first electrode may be in contact with the n-type region of the first subcell, the first electrode comprising a transparent or semi-transparent conductive material. The first electrode is an electron collecting electrode and the second electrode is a hole collecting electrode. In a tandem monolithic device, the second electrode is in contact with the second subcell, the first and second electrodes forming external components at either end of the device. An intermediate layer is disposed between the first and second subcells.

[0139] If the photovoltaic device has a multi-junction structure, the second sub-cell of the photovoltaic device may comprise any of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS).

[0140] Alternatively, the multi-junction solar cell may include three subcells. The present invention covers perovskite layers with bandgaps ranging from 1.1 to 2.5 eV that meet each of the subcell requirements in the multi-junction. For example, the top cell has a perovskite layer according to the present invention with a bandgap ranging from 2.0 to 2.5 eV, the middle subcell has a perovskite layer according to the present invention with a bandgap ranging from 1.5 to 2.0 eV, and the bottom subcell includes a subcell with an energy bandgap ranging from 1.1 to 1.4 eV, e.g., crystalline silicon or a narrow bandgap perovskite layer. The bandgaps of each subcell may vary relative to each other and depending on the cell geometry. In general, the top cell has a wider bandgap, the bottom subcell has a lower bandgap, and the bandgap of the middle subcell fits somewhere between these top and bottom subcell values. Any of the top, middle, or bottom subcells may have a perovskite layer according to the present invention.

[0141] The perovskite layer may be prepared as described in International Publication Nos. WO2013 / 171517, WO2014 / 045021, WO2016 / 198889, WO2016 / 005758, WO2017 / 089819, and in the references "Photovoltaic Solar Energy: From Fundamentals to Applications", edited by Angele Reinders, Pierre Verlinden, Wiley-Blackwell (2017) ISBN-13: 978-1118927465, and "Organic-Inorganic Halide Perovskite Photovoltaics: From Fundamentals to Device Architectures", Nam-Gyu Park et al., Springer (2016) ISBN-13: 978-3319351124.

[0142] In preferred devices of the present invention, the photoactive layer is a compact layer without open porosity.

[0143] The following examples illustrate the invention.

[0144] Working Example Example 1 Preparation and analysis of mixed halide precursors Part of the approach to reduce the number of sources required for co-evaporation of multiple precursors involved the combination of mixed metal halide precursors, such as PbI2 and PbBr2. The two materials were mixed in a single crucible and melted at high temperatures above 350 °C, ambient pressure, and under N2 atmosphere to avoid oxidation. The resulting compound provided a new mixed halide alloy phase, which could be further sublimed as a single precursor in one source as part of the co-evaporation process.

[0145] To confirm the sublimation of the mixed metal halides as a single substance, X-ray photoelectron spectroscopy (XPS) was used to measure the sublimation of 200 nm mixed lead halide thin films, Pb(I 1- xBr x Compositional and stoichiometric analyses were performed on three successive deposition runs. These compounds were then compared to their powder precursor counterparts, as shown in Figure 1. The maintenance of the stoichiometry of each component of the molten mixed lead halide across runs indicates that the material behaves as a single precursor upon evaporation.

[0146] Example 2 Performance analysis of standard triple-cation dual-halide perovskites The performance characteristics of standard triple cation dual halide perovskites prepared using the claimed co-evaporation method were also investigated. Planar pin-configuration solar cells were first fabricated with ITO electrodes coated with a thin hole transport layer (HTL) of poly(triarylamine) (PTAA). Next, 10 μm films of the precursors FAI, MAI, CsI, and the melt mixed halide phase from Example 1 were deposited at deposition rates of 0.6 Å / s, 0.3 Å / s, 0.4 Å / s, and 1.3 Å / s, respectively. -6 The perovskite light absorbing layer FAMACsPb(I 1-x Br x The sublimation temperatures of the precursors were approximately 155°C for FAI, approximately 125°C for MAI, and approximately 100°C for Pb(I1-x Br x The temperatures were approximately 310°C for CsI and 485°C for CsI. 60 The film was capped with a silver top electrode. Although these cells achieved a respectable PCE of over 16%, their thermal stability after stress on a hotplate at 85 °C in a N2 atmosphere was poor and they showed significant degradation in power characteristics, especially VOCs after 5 h (Figures 2A and 2B).

[0147] Similarly, Figure 3B shows X-ray diffraction (XRD) results of periodic ex-situ measurements of triple-cation perovskite over continuous thermal stress at different time intervals over "as-prepared", 2 days, 7 days, and 9 days. By day 9, a large increase in the decomposition PbI2 peak at ~12.7° and a decrease in the intensity of the main perovskite peak at ~14.3° were observed, a clear indication of decomposition.

[0148] Light soaking experiments were also performed on the samples and periodically analyzed by XRD as previously described. The films were maintained under constant illumination of 1 sun equivalent intensity at 35 °C. As shown in Figure 3A, a moderate increase in the PbI2 signal is observed after only 2 days.

[0149] These results highlight the poor stability of triple-cation vacuum-deposited triple-cation CsMAFA perovskite under thermal stress, a key requirement to ensure the lifetime of PV devices.

[0150] Example 3 Performance analysis of large cation-additive multicomponent perovskites Standard triple cation double halide perovskites do not exhibit acceptable thermal stability, as described in Example 2. In the present invention, a large cation additive, namely GA, is introduced into the A-site of the structure and its effect on stability is determined.

[0151] Quadruple cation FAGAMACsPb(I 1-x Br xTo form CsI, MAI, and Pb(I), FAI and GAI were mixed in the same evaporation source in a ratio of 10:1, and the same deposition rate and temperature were used for each chamber as shown in Example 2. 1-x Br x ) were co-evaporated with three separate sources to form perovskite films.

[0152] Similarly, by combining FAI and GAI from one source, CsI from another, and a mixed halide composition from a third source as previously described, and coevaporating all three sources, the triple cation FAGACsPb(I 1-x Br x ) 3 was also synthesized.

[0153] In addition, FAI, MAI, CsI, and Pb(I 1-x Br x A reference triple cation formulation without a large cation additive, i.e., FAMACsPb(I) was prepared according to Example 2 using four separate sources of FAMACsPb(I). 1-x Br x ) 3 was synthesized.

[0154] All films were then thermally stressed at 85 °C in N2 and monitored for one week. X-ray diffraction (XRD) was used to identify the occurrence of any structure, such as the formation of decomposed phases (PbI2 peaks), as shown in Figure 4.

[0155] The presence of GA in both triple and quaternary cations significantly enhanced the thermal stability compared to the reference GA-free compound, with no decay peaks present in the "as-prepared" films and significantly smaller degradation peaks after 1 week of heat treatment. Some minor delta phases are also present, but these are not necessarily detrimental to the material. They are described as maintaining the stability of the perovskite, as shown in Pavlov et al., "Suppression of cation migration in triple cation lead halide perovskites," ACS Energy Lett. 2020, 5, 2802.

[0156] Furthermore, Figure 5B shows the ex-situ collected XRD patterns for the quadruple-cation perovskite analyzed at various stages over a full 37-day period. There is no discernible growth of the decomposition signal and the crystallinity of the main peak is maintained at each stage, whereas in the case of the triple-cation without the "big" additive, the decomposition is accelerated even within a week, as can be seen in Figure 3B.

[0157] A quaternary cation light soak was also performed in parallel with the XRD measurements, which maintained the structural integrity and did not reveal any significant decomposition products of PbI2, as shown in Figure 5A.

[0158] To further evaluate the combined power and stability device properties of the GA-incorporated multicomponent perovskites, the quaternary cation FAGAMACsPb(I 1-x Br x The PCE of 3 was evaluated over a one-month period of high temperature stress at 85 °C in a N2 atmosphere. Over the period of continuous thermal stress, the cells were observed to maintain 80% of their initial efficiency (Figure 6), demonstrating the superior performance characteristics of the vacuum-deposited GA-containing films.

[0159] The present invention includes the following aspects. 1. A method for forming a perovskite material from multiple evaporation sources, comprising: (i) a first evaporation source comprising a mixture of co-sublimable organic halides, The organic halide is a. a first organic halide comprising an organic cation A; b. A second organic halide containing an organic cation A' different from A and having a larger ionic radius than the first organic cation A. A first evaporation source having (ii) a second evaporation source comprising one or more metal halides having formula (I): B(X y X' 1-y )2(I) Here, B is a divalent metal cation, X and X' are different halides, and 0 ≦ y < 1. A second evaporation source, (iii) one or more other organic halides from one or more other evaporation sources, and / or (iv) one or more inorganic halides from one or more other evaporation sources, co-sublime to form a perovskite material, wherein the perovskite material contains three or more different cations in addition to the B cation. A method. 2. The method according to aspect 1, wherein the perovskite material contains a mixed halide, and thus 0 < y < 1. 3. The method according to aspect 1 or 2, wherein the perovskite material contains three or more different monovalent cations. 4. The method according to any one of aspects 1 to 3, including three or four evaporation sources. 5. The method according to any one of aspects 1 to 4, wherein the first and second organic halides contain the same halide. 6. The method according to any one of aspects 1 to 5, wherein the second organic halide in step (i) contains a monovalent cation A'. 7. The method according to any one of aspects 1 to 6, wherein the one or more organic halides in step (iii) and / or the one or more inorganic halides in step (iv) contain a monovalent cation. 8. The method according to any one of aspects 1 to 7, wherein the first organic halide contains an organic cation A that is a monovalent organic cation, preferably FA. 9. The method according to any one of aspects 1 to 8, wherein the second organic halide contains an organic monocation A' having an ionic radius larger than that of the first organic cation A, preferably selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidinium (Ac), and phenylethylammonium (PEA), and preferably A' is GA. 10. The method according to any one of aspects 1 to 9, including a step of mixing two cationic halide salts by a mechanical mixing method before the step (i) of preparing the first evaporation source. 11. Step (ii) has a preceding step of forming a compound of general formula (I) B(X y X’ 1-y )2, The method according to any one of aspects 1 to 10, the step having a step of mixing one or more metal halides, BX2 and / or BX’2, and a step of heating in an inert atmosphere. 12. B(X y X’ 1-y )2 is PbI y Br 1-y , and the method according to aspect 11, the step having a step of mixing PbBr2 and PbI2 and heating in an inert atmosphere. 13. The one or more metal halides BX2 and BX’2 include two different B cations and two different halide anions, The general formula (I) is B x B’ 1-x (X y X’ 1-y )2, where 0 < x < 1 and 0 < y < 1, B is a divalent metal cation different from B’, and preferably B and B’ are selected from Pb and Sn, the method according to aspect 10. 14. In step (ii), the second evaporation source is as follows: a) PbI2 and SnI2 from which a single precursor phase Pb x Sn 1-x I2 is obtained; b) PbBr2 and SnBr2 from which a single precursor phase Pb x Sn 1-x Br2 is obtained; c) PbI2 and SnBr2 from which a single precursor phase Pb x Sn 1-x (I 1-y Br y )2 is obtained; and d) Pb x Sn 1-x(I 1-y Br y )2 is obtained, PbBr2 and SnI2; The method according to embodiment 11, having two mixed metal halides selected from , where 0 < x < 1, 0 < y < 1. 15. Having step (iv) of providing an inorganic halide, Preferably, the inorganic halide is CsI or CsBr, the method according to any of embodiments 1 to 14. 16. Comprising four evaporation sources, In step (ii), y > 0, and two different metal halides are mixed, In step (iii), an organic halide is provided to a third evaporation source, In step (iv), an inorganic halide is provided to a fourth evaporation source, the method according to embodiment 15. 17. In step (ii), the two metal halides to be mixed are PbI2 and PbBr2, and a single precursor phase Pb(I y Br 1-y )2 is obtained, where 0 < y < 1, the method according to embodiment 16. 18. When not dependent on embodiment 2, comprising four evaporation sources, In step (ii), y = 0, and only one halide component is provided in the perovskite material, In step (iii), an organic halide is provided to a third evaporation source, In step (iv), an inorganic halide is provided, preferably, the inorganic halide is CsI or CsBr, the method according to embodiments 1, and 3 to 11. 19. When not dependent on embodiment 2, comprising four evaporation sources, In step (ii), y = 0, and in step (ii), only one halide component is provided, In step (iii), an organic halide is provided to a third evaporation source, (iv) The preparatory step for preparing involves, under an inert atmosphere, heating the two inorganic halides, preferably CsI and CsBr, together in a single evaporation source, and Cs(I z Br 1-z ), where 0 < z < 1, to obtain a precursor of a mixed halide phase, the method according to embodiment 1, and embodiments 3 to 11. 20. The method according to embodiments 1 to 19, wherein in step (iii), CsI is provided to a third evaporation source and MAI is provided to a fourth evaporation source. 21. The method according to embodiments 1 to 20 for forming a thin film of a perovskite material. 22. The method according to embodiments 1 to 21, wherein the perovskite material has a band gap of 1.1 to 2.5 eV. 23. The perovskite material has the general formula (II), A a A’ b A’’ c A’’’ d B x B’ 1-x (X y X’ 1-y )3(II) where, when both A and A’ are present as halides, A is a first monovalent organic cation capable of co-sublimation with A’, A’ is a second monovalent organic cation having an ionic radius larger than that of A, A’’ and A’’’ are independently selected from a monovalent inorganic cation or another monovalent organic cation, all A cations are different from each other and at least three kinds exist, 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 ≤ d < 1, a + b + c + d = 1, 0 ≤ x < 1 and 0 ≤ y < 1, B and B’ are independently selected from divalent metal cations, 23. The method of any one of the preceding embodiments, wherein X and X' are independently selected from halide anions. 24. A' and A''' are different from each other, (iii) the group of organic cations containing MA or FA, preferably MA; and / or (iv) Cs or Rb cations, preferably Cs 24. The method of embodiment 23, wherein the 25. The method according to embodiment 23 or 24, wherein X and X' are different from each other and are selected from Cl, Br and I, preferably the halides X and X' are I and Br. 26.B is Pb 2+ or Sn 2+ and B' is different from B as necessary, Pb 2+ or Sn 2+ 26. The method of any one of aspects 23 to 25, selected from the group consisting of 27. A perovskite material obtainable by the method according to any one of embodiments 1 to 26. 28. A perovskite material comprising a quaternary cation double halide and optionally mixed metals, FA a GA b MA c Cs d Pb(I y Br 1-y ) 3, FA a EA b MA c Cs c Pb(I y Br 1-y ) 3, FA a BzA b MA c Cs d Pb(I y Br 1-y ) 3, FA a DMA b MA c Cs d Pb(I y Br 1-y ) 3, FA a GA b MA c Csd Sn(I y Br 1-y )3、FA a EA b MA c Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Cs d Sn(I y Br 1-y )3、FA a DMA b MA c Cs d Sn(I y Br 1-y )3、FA a Im b MA c Cs d Pb(I y Br 1-y )3、FA a Im b MA c Cs d Sn(I y Br 1-y )3、FA a PEA b MA c Cs d Sn(I y Br 1-y )3、FA a Ac b MA c Cs d Pb(I y Br 1-y )3、FA a Ac b MA c Cs d Sn(I y Br 1-y )3、FA a GA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b MA c Cs d Pbx Sn 1-x (I y Br 1-y )3, FA a EA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3, FA a DMA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3, FA a Im b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3, FA a PEA b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3, FA a Ac b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3 selected from, where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1, 0 < x < 1, 0 < y < 1, perovskite material. 29. A perovskite material comprising a triple cation double halide and, optionally, a mixed metal, MA a GA b Cs c Pb(I y Br 1-y )3, FA a BzA b MA c Pb(I y Br 1-y )3, FA a BzAb Cs c Pb(I y Br 1-y )3、MA a BzA b Cs c Pb(I y Br 1-y )3、MA a DMA b Cs c Pb(I y Br 1-y )、FA a GA b MA c Sn(I y Br 1-y )3、FA a GA b Cs c Sn(I y Br 1-y )3、MA a GA b Cs c Sn(I y Br 1-y )3、FA a BzA b MA c Sn(I y Br 1-y )3、FA a BzA b Cs c Sn(I y Br 1-y )3、MA a BzA b Cs c Sn(I y Br 1-y )3、FA a DMA b Cs c Sn(I y Br 1-y )3、FA a DMA b MA c Sn(I y Br 1-y )3、MA a DMA b Cs c Sn(I y Br 1-y )、FA a Im b Cs c Sn(Iy Br 1-y )3、FA a TO BE b Cs c Pb(I) y Br 1-y )3、FA a TO BE b Cs c Sn(I) y Br 1-y )3、FA a Ac b Cs c Sn(I) y Br 1-y )3、FA a BzA b AND c Pb(I) y Br 1-y )3、FA a BzA b AND c Sn(I) y Br 1-y )3、FA a I am b AND c Pb(I) y Br 1-y )3、FA a I am b AND c Sn(I) y Br 1-y )3、FA a TO BE b AND c Pb(I) y Br 1-y )3、FA a TO BE b AND c Sn(I) y Br 1-y )3、FA a EA b Cs c Sn(I) y Br 1-y )3、FA a EA b AND c Sn(I) y Br 1-y )3、MA a EA b Cs c Pb(I) y Br 1-y )3、MAa EA b Cs c Sn(I y Br 1-y )3、FA a GA b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a GA b Cs c Pb x Sn 1-x (I y Br 1-y )3、MA a GA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b MA c Pb x Sn 1-x (I y Br 1-y )3、FA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y )3、MA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y )3、FA a DMA b MA c Pb x Sn 1-x (I y Br 1-y )3、MA a DMA b Cs c Pbx Sn 1-x (I y Br 1-y ) 3, FA a Im b MA c Pb x Sn 1-x (I y Br 1-y ) 3, FA a Im b Cs c Pb x Sn 1-x (I y Br 1-y ) 3, FA a PEA b MA c Pb x Sn 1-x (I y Br 1-y ) 3, FA a PEA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3, FA a Ac b MA c Pb x Sn 1-x (I y Br 1-y ) 3, FA a Ac b Cs c Pb x Sn 1-x (I y Br 1-y ) 3, where 0 <a<1、0<b<1、0<c<1、0<d<1、a+b+c+d=1、0<x<1、0<y<1である、ペロブスカイト材料。30. A semiconductor device having a photoactive region comprising the perovskite material of any of embodiments 27 to 29. 31. The semiconductor device of aspect 30, wherein the semiconductor device is an optoelectronic device, preferably a photovoltaic device having a photoactive region. 32. A photovoltaic device comprising a photovoltaic material prepared according to any one of the methods of embodiments 1 to 26, a photoactive region comprising a thin film of a perovskite material; A photovoltaic device, wherein the thickness of the thin film of the perovskite material is in the range of 50 nm to 2000 nm. 33. The photovoltaic device of embodiment 32, wherein the photoactive region comprises an n-type region comprising at least one n-type layer, and a layer of the perovskite material in contact with the n-type region. 34. The photoactive region comprises: an n-type region including at least one n-type layer; a p-type region including at least one p-type layer; a layer of perovskite material disposed between the n-type region and the p-type region; 34. The photovoltaic device of embodiment 32 or 33, having the following structure: 35. A multi-junction photovoltaic device having two or more subcells, The first subcell comprises a photovoltaic device according to any one of embodiments 32 to 34; A multi-junction photovoltaic device, wherein another subcell comprises a photoactive layer, the photoactive layer optionally comprising a perovskite layer prepared according to any one of the embodiments 1 to 26.

Claims

1. 1. A method of forming a perovskite material from multiple evaporation sources, comprising: (i) a first evaporation source comprising a mixture of co-sublimable organic halides, The organic halide is a. a first organic halide comprising an organic cation A; b. A second organic halide containing an organic cation A' different from A and having a larger ionic radius than the first organic cation A. A first evaporation source having (ii) a second evaporation source comprising one or more metal halides having the following formula (I): B(X y X’ 1-y ) 2 (I) a second evaporation source, where B is a divalent metal cation, X and X' are different halides, and 0≦y<1; (iii) one or more additional organic halides from one or more additional evaporation sources; and / or (iv) one or more inorganic halides from one or more separate evaporation sources; co-subliming from the solution to form a perovskite material; The perovskite material comprises three or more different cations in addition to the B cations.

2. the precursors in the first and second evaporation sources are sublimated or non-sublimated; 2. The method of claim 1, wherein the difference in sublimation temperatures of the precursors for conformal sublimation is at most 20° C. and the difference in sublimation temperatures of the precursors for non-conformal sublimation is between 50 and 150° C.

3. 2. The method of claim 1, wherein the halides in the organic and / or inorganic halides are selected from iodine and bromine.

4. 2. The method of claim 1, wherein the one or more additional organohalides in step (iii) are different from the first organohalide.

5. 2. The method of claim 1 , wherein the perovskite material comprises mixed halides (0<y<1).

6. 10. The method of claim 1, wherein the perovskite material comprises three or more different monovalent cations.

7. The method of claim 1 comprising three or four evaporation sources.

8. 2. The method of claim 1, wherein the first organic halide comprises an organic cation A that is a monovalent organic cation, preferably MA or FA, and more preferably FA.

9. 2. The method of claim 1, wherein the second organic halide comprises an organic monocation A' having a larger ionic radius than the first organic cation A and is preferably selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidinium (Ac) and phenylethylammonium (PEA), preferably A' is GA.

10. Step (ii) is the step of reacting B (X y X' 1-y ) 2 and forming a compound of formula (I) The step comprises the step of: 2 and / or BX' 2 and heating under an inert atmosphere.

11. The one or more metal halides BX 2 and BX' 2 contains two different B cations and two different halide anions, The general formula (I) is B x B' 1-x (X y X' 1-y ) 2 11. The method of claim 10, wherein 0<x<1 and 0<y<1, and B is a divalent metal cation different from B', preferably B and B' are selected from Pb and Sn.

12. (iv) providing an inorganic halide; 2. The method of claim 1, wherein the inorganic halide is preferably Cs-based, more preferably CsI or CsBr.

13. Contains four evaporation sources, In step (ii), y>0 and two different metal halides are mixed; In step (iii), an organic halide is provided in a third evaporation source; In step (iv), an inorganic halide is provided in a fourth evaporation source; The method of claim 12, wherein preferably MAI is provided in the third evaporation source and CsI is provided in the fourth evaporation source.

14. In step (ii), the two metal halides to be mixed are PbI 2 and PbBr 2 and a single precursor phase, Pb(I y Br 1-y ) 2 14. The method of claim 13, wherein y is obtained where 0<y<1.

15. Contains four evaporation sources, In step (ii), y=0 and only one halide component is provided in the perovskite material; In step (iii), an organic halide is provided in a third evaporation source; 2. The method of claim 1, wherein in step (iv) an inorganic halide is provided, preferably said inorganic halide being CsI or CsBr.

16. Contains four evaporation sources, In step (ii), y=0, and in step (ii), only one halide moiety is provided; In step (iii), an organic halide is provided in a third evaporation source; The preceding step of preparing (iv) comprises heating the two inorganic halides, preferably CsI and CsBr, together in a single evaporation source under an inert atmosphere to give Cs(I z Br 1-z 2. The method of claim 1, wherein z is a mixture of 0 and 1, and ...

17. 2. The method of claim 1, comprising forming a thin film of a perovskite material, preferably having a band gap of 1.1 to 2.5 eV.

18. The perovskite material has the general formula (II): HAS a HAS' b HAS'' c HAS''' d B x B' 1-x (X y X' 1-y ) 3 (II) Where: when A and A' are both present as halides, A is a first monovalent organic cation capable of co-subliming with A'; A' is a second monovalent organic cation having a larger ionic radius than A; A″ and A′″ are independently selected from a monovalent inorganic cation or another monovalent organic cation; All A cations are different and there are at least three of them; 0＜a＜1、 0＜b＜1、 0＜c＜1、 0≦d＜1、 a + b + c + d = 1, 0≦x<1 and 0≦y<1, B and B' are independently selected from divalent metal cations; X and X' are independently selected from halide anions; Preferably, X and X' are different from each other and are selected from Cl, Br and I; More preferably, the halides X and X' are I and Br.

19. B is Pb 2＋ or Sn 2＋ and if necessary, B' is different from B, Pb 2＋ or Sn 2＋ 20. The method of claim 18, wherein the compound is selected from the group consisting of

20. 1. A method for fabricating a multi-junction photovoltaic device comprising two or more subcells, comprising: the first sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region comprising a perovskite material prepared according to a method according to any one of claims 1 to 19; 20. A method according to claim 1, wherein the other sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region, optionally comprising a perovskite material prepared according to the method of any one of claims 1 to 19.

21. 20. A perovskite material obtainable by the method according to any one of claims 1 to 19.

22. B is selected from Pb and Sn; the one or more further organohalides in step (iii) are different from the first organohalide; 22. The perovskite material of claim 21 , wherein the one or more inorganic halides, when present, include Cs as an inorganic moiety.

23. A perovskite material comprising a quaternary cation double halide and optionally mixed metals, FA a EA b MA c Cs d Pb(I y Br 1-y ) 3 、FA a BzA b MA c Cs d Pb(I y Br 1-y ) 3 、FA a DMA b MA c Cs d Pb(I y Br 1-y ) 3 、FA a GA b MA c Cs d Sn(I y Br 1-y ) 3 、FA a EA b MA c Cs c Sn(I y Br 1-y ) 3 、FA a BzA b MA c Cs d Sn(I y Br 1-y ) 3 、FA a DMA b MA c Cs d Sn(I y Br 1-y ) 3 、FA a Im b MA c Cs d Pb(I y Br 1-y ) 3 、FA a Im b MA c Cs d Sn(I y Br 1-y ) 3 、FA a PEA b MA c Cs d Sn(I y Br 1-y ) 3 、FA a Ac b MA c Cs d Pb(I y Br 1-y ) 3 、FA a Ac b MA c Cs d Sn(I y Br 1-y ) 3 、FA a GA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 、FA a BzA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 、FA a EA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 、FA a DMA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 、FA a Im b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 、FA a PEA b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 , F.A. a Ac b MA c Cs d Pb x Sn 1-x (I y Br 1-y ) 3 where 0<a<1, 0<b<1, 0<c<1, 0<d<1, a+b+c+d=1, 0<x<1, 0<y<1; or A perovskite material comprising a triple cation double halide and optionally mixed metals, MA a GA b Cs c Pb(I y Br 1-y ) 3 、FA a BzA b MA c Pb(I y Br 1-y ) 3 、FA a BzA b Cs c Pb(I y Br 1-y ) 3 、MA a BzA b Cs c Pb(I y Br 1-y ) 3 、MA a DMA b Cs c Pb(I y Br 1-y )、FA a GA b MA c Sn(I y Br 1-y ) 3 、FA a GA b Cs c Sn(I y Br 1-y ) 3 、MA a GA b Cs c Sn(I y Br 1-y ) 3 、FA a BzA b MA c Sn(I y Br 1-y ) 3 、FA a BzA b Cs c Sn(I y Br 1-y ) 3 、MA a BzA b Cs c Sn(I y Br 1-y ) 3 、FA a DMA b Cs c Sn(I y Br 1-y ) 3 、FA a DMA b MA c Sn(I y Br 1-y ) 3 、MA a DMA b Cs c Sn(I y Br 1-y )、FA a Im b Cs c Sn(I y Br 1-y ) 3 、FA a PEA b Cs c Pb(I y Br 1-y ) 3 、FA a PEA b Cs c Sn(I y Br 1-y ) 3 、FA a Ac b Cs c Sn(I y Br 1-y ) 3 、FA a BzA b MA c Pb(I y Br 1-y ) 3 、FA a BzA b MA c Sn(I y Br 1-y ) 3 、FA a Im b MA c Pb(I y Br 1-y ) 3 、FA a Im b MA c Sn(I y Br 1-y ) 3 ,BYE a TO BE b AND c Pb(I) y Br 1-y ) 3 ,BYE a TO BE b AND c Sn(I) y Br 1-y ) 3 ,BYE a EA b Cs c Sn(I) y Br 1-y ) 3 ,BYE a EA b AND c Sn(I) y Br 1-y ) 3 、MA a EA b Cs c Pb(I) y Br 1-y ) 3 、MA a EA b Cs c Sn(I) y Br 1-y ) 3 ,BYE a EN b AND c Pb x Sn 1-x (I) y Br 1-y ) 3 ,BYE a EN b Cs c Pb x Sn 1-x (I) y Br 1-y ) 3 、MA a EN b Cs c Pb x Sn 1-x (I) y Br 1-y ) 3 ,BYE a BzA b AND c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a BzA b Cs c Pb x Sn 1-x x(I y Br 1-y ) 3 、MA a BzA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a DMA b MA c Pb x Sn 1-x (I y Br 1-y ) 3 、MA a DMA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a Im b MA c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a Im b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 、FA a PEA b MA c Pb x Sn 1-x (I y Br 1-y ) 3 , F.A. a PEA b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 , F.A. a Ac b MA c Pb x Sn 1-x (I y Br 1-y ) 3 , F.A. a Ac b Cs c Pb x Sn 1-x (I y Br 1-y ) 3 where 0<a<1, 0<b<1, 0<c<1, 0<d<1, a+b+c+d=1, 0<x<1, 0<y<1.

24. 24. A semiconductor device having a photoactive region comprising the perovskite material of claim 23, Preferably said semiconductor device is an optoelectronic device, more preferably a photovoltaic device having a photoactive region.

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