Method for preparing multi-component perovskite

Abstract

The present invention provides a method of forming a perovskite material from a plurality of evaporation sources comprising co-sublimating to form a perovskite material from (i) a first evaporation source comprising a mixture of co-sublimable organic halides wherein the organic halides comprise: a. A first organic halide comprising an organic cation A; b. A second organic halide comprising an organic cation A'different from A and having a greater ionic radius than the first organic cation A; and (ii) a second evaporation source comprising one or more metal halides of formula (I): B (XyX '1-y) 2 (I); wherein B is a divalent metal cation, X and X'are different halides, 0 < = y; 1; and (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 additional evaporation sources; wherein the perovskite material comprises three or more different cations at the A-position. Perovskite materials and semiconductor devices, generally photovoltaic devices, are also provided.

Description

Field of the Invention

[0001] The present invention relates to a co-sublimation deposition method for preparing a multi-component perovskite film, wherein the multi-component perovskite film comprises at least 3 or 4 cations at the A position, one or two cations at the B position, and one, two or more halide components, wherein fewer evaporation sources are required than the number of components. The present invention also includes the use of a large monovalent cation additive that can co-sublimate with another organic monovalent cation to improve the crystallinity and thermal stability of the final perovskite material. Background of the Invention

[0003] Solar energy conversion is one of the most promising technologies for providing renewable energy.

[0004] One class of photovoltaic materials that has recently attracted significant interest is the organic-inorganic halide perovskites. Materials of this type have a perovskite crystal structure with the general formula ABX3. It has been found that these materials exhibit favorable band gaps, high absorption coefficients, and long diffusion lengths, making such compounds ideal as absorbers in photovoltaic devices.

[0005] General techniques for synthesizing perovskite thin films can include wet solution methods such as spin coating, inkjet and doctor blade coating, or alternatively dry methods such as evaporation methods, which include thermal evaporation, chemical vapor deposition (CVD) and aerosol-assisted CVD. Dry methods such as vapor deposition are ideal solvent-free technologies to minimize damage to existing device layers and better control film thickness and uniformity. Wet methods are often used to prepare complex multi-component perovskite compositions because dry methods tend to become more complicated when additional components are introduced into the perovskite structure. In particular, for perovskites containing several different components (e.g., more than 4), co-evaporation vacuum deposition techniques can become a challenge to control. Such multi-component perovskites require multiple evaporation sources, each with their own settings that need to be monitored, and careful control of the various deposition rates of each corresponding precursor, making the entire process complex and expensive, especially when one or more precursors are sublimated in the same source.

[0006] An attempt to overcome this practical complexity is reported by Kam et al., “Efficient Mixed-CationMixed-Halide Perovskite Solar Cells by All-Vacuum Sequential Deposition UsingMetal Oxide Electron Transport Layer,” Solar RRL, Vol. 3, 7, 2019. The article discusses the preparation of mixed perovskites using a vapor deposition method that requires a single quartz crystal microbalance (QCM) to deposit the lead halide in the first step, followed by the deposition of the organic iodide, rather than multi-source co-evaporation. Initially, the PbI2 and PbBr2 salts are mixed in an optimized ratio and evaporated together by a heating current and subsequently deposited on the substrate. Second, methylammonium iodide (MAI) and formamidine iodide (FAI) are also mixed in an optimized ratio and co-sublimed due to their similar sublimation temperatures, allowing similar deposition rates on the corresponding mixed lead halide films. Despite the successful synthesis of multicomponent perovskites, the introduction of additional steps instead of a single simultaneous deposition did not solve the problem of implementing a simplified “all-in-one” co-evaporation method that advantageously speeds up processing time and helps maintain the homogeneity of the final perovskite material.

[0007] In addition, Ball et al., “Low-bandgap FA for photovoltaic materials 1–x Cs x Sn 1–y Pb y Dual-Source Coevaporation of Low-Bandgap FA I3 Perovskite 1–x Cs x Sn 1–y Pb y I3 Perovskites for Photovoltaics”, ACS Energy Lett. 2019, 4, 11, 2748-2756, 2019, provides a dual-source co-evaporation method to prepare multi-component perovskites, namely FA 1-x Cs x Sn 1-y Pb yI3. A mixture of metal iodides of Cs, Pb and Sn cations is prepared in a single crucible source, melted under an inert atmosphere, and then allowed to cool naturally to room temperature. SnF2 is also doped into this mixture to regulate crystallization and suppress the formation of impurity phases in the final film. Separately, FAI is provided by a second source. The two sources are then co-evaporated to produce a crystalline low bandgap perovskite film. Although it is possible to minimize the number of evaporation sources to only two to make five-component perovskites, in general, this type of perovskite suffers from poor stability, particularly since the Sn component is more susceptible to oxidation. SnF2 is a well-known passivating agent, providing excess Sn 2+ ions to compensate for the oxidized Sn 4+ However, the material does not necessarily have improved thermal stability—a key challenge for most complex perovskites. Therefore, optimized processing is still needed to obtain stable perovskites.

[0008] Previous research on wide-bandgap triple-cation perovskites vacuum deposited by 4-source co-sublimation has been conducted by Gil-Escrig et al. (Vacuum Deposited Triple-Cation Mixed-Halide Perovskite Solar Cells, Advanced Energy Materials, Vol. 8, No. 14, 2018). In particular, it was shown that 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, where CsBr is Cs + and Br - However, in order to increase the band gap (E g > 1.7eV), a large amount of Br must be doped -, resulting in equally large cesium concentrations, which leads to irregular morphology and ultimately poor device performance. Therefore, the selection of precursors for mixed halide components requires careful consideration. Therefore, mixing two different metal halides in a single source is preferred for better control of the stoichiometry. Therefore, Muñoz et al. ("Room temperature vacuum-deposition of CsPbI2Br perovskite films from multiple-sources and mixed halide precursors", Chem. Mater., 32, 8641, 2020) conducted further studies similar to Gil-Escrig et al., in which the precursors PbI2 and PbBr2 were instead pre-mixed, while CsI was used as a cesium source. This method produced uniform CsPbI2Br perovskite films, however, their thermal stability was found to be significantly insufficient. Therefore, despite the use of co-evaporation methods of mixed halides, it remains challenging to control all parameters of perovskite films. Often, another feature, such as additive engineering, is necessary to overcome the lack of stability.

[0009] Otalora et al., "Hybrid perovskite films deposited by thermal evaporation from a single source," J Mater Sci: Mater Electron, 2021, present a method for depositing MAPbI3 films by thermal evaporation from a single source. However, this method only supports the deposition of very simple perovskites with only one type of A, B, and X ions. Furthermore, very specific pressures, temperatures, and solvents must be investigated to ensure that morphologies that are more desirable than those from co-evaporation from two sources and electrical properties similar to those from co-evaporation from two sources are obtained.

[0010] Additive engineering to improve the stability characteristics of perovskites has been attempted in the art. Recent focus has turned to large cation additive engineering, such as partial substitution of A cation sites with guanidinium (GA) ions. For example, Jodlowski et al., “Largeguanidinium cation mixed with methylammonium in lead iodide perovskites for 19% efficient solar cells”, Nature Energy, 2, 927-9279, 2017, inserted GA into some A units of the MAPbI3 structure during spin coating, resulting in perovskites with enhanced thermal and environmental stability due to the availability of H bonds with favorable orientations within the inorganic framework. On this basis, Zhang et al., “Guanidinium induced phase separated perovskite layer for efficient and highly stable solar cells”, J. Mater. Chem. A, 2019, 7, 9486-9496, spin-coated 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, also showed enhanced stability characteristics. Modulating GA content induced 3DCs FAMA 1-x GA x and phase separation of hexagonal δ-FAPbI3. GA-based perovskites are reported to have minimal hysteresis and excellent optoelectronic properties.

[0011] Similarly, Yerramilli et al. (“Phenyl Ethylammonium Iodide introduction into inverted triple cation perovskite solar cells for VOC and stability”) OCand stability”, Organic Electronics, 93, 2021”). It was found that incorporation of phenylethylammonium (PEA) into FAMACs-based perovskite compositions improved the film morphology by providing uniform films with few pinholes. The perovskite films were synthesized using a one-step solution-based method.

[0012] Although additive engineering is a useful technique for solution-processed perovskites, 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, demonstrated the fabrication of perovskites by dual-source vacuum deposition, also employing large cation additive engineering with phenethylammonium. The method involves co-sublimation deposition of phenethyl ammonium lead iodide (PEAI) and PbI2 to form 2D layers on either side of a 3D MAPI layer of PEA2PbI4. As a result, the 2D iodide (PEA2PbI4) forms layers on either side of the 3D MAPbI3 film. However, the unfavorable orientation of the 2D perovskite with respect to MAPI may lead to hindered charge extraction and no signs of surface passivation compared to the corresponding solution-processed methods. SUMMARY OF THE INVENTION

[0014] According to a first aspect of the present invention, a method as claimed in claim 1 is provided.

[0015] Increasing the number of components in the ABX3 (B = Pb, Sn) perovskite formula (particularly the number of A cations and / or X halides) brings advantages in terms of material / device performance and environmental stability. However, vacuum co-evaporation requires a corresponding increase in the number of evaporation sources, which in turn increases the complexity of the deposition process.

[0016] The present invention provides a method for synthesizing high-performance multi-component perovskites by a streamlined co-evaporation method, which requires fewer sources than existing components, which further promotes partial substitution of the A position with a large cationic additive to impart enhanced thermal stability. Therefore, the method and its corresponding perovskite are suitable for semiconductor devices such as photovoltaic devices, single-junction solar cells 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.

[0017] Solutions suitable for the thermal instability of solvent-processed perovskites can be found in the literature. However, in many cases these solutions do not lead to the same effect in perovskites prepared by sublimation (see for example the effect of adding large cations, which form quasi-2D perovskites at the surface of solution-processed perovskites, but not when prepared by sublimation, ACS Energy Lett. 2019, 4, 12, 2893–2901).

[0018] The method of the present invention provides a clear solution to the problems encountered in the prior art; the ability to impart improved thermal stability through additive engineering while maintaining a crystalline single phase perovskite structure through an efficient and manageable simultaneously operated vacuum deposition method. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0021] FIG. 1 schematically illustrates the melting of mixed lead halide Pb(I 1-x Br x )3Elemental and stoichiometric analysis of materials and subsequent films deposited as a single precursor.

[0022] FIG. 2A illustrates the use of triple cation perovskite FAMACsPb(I 1-x Br x )3 Current density versus voltage (JV) curves of multiple perovskite solar cells under simulated solar illumination.

[0023] FIG. 2B illustrates the triple cation perovskite FAMACsPb(I) prepared after thermal stress at 85°C for 5 h in N2 atmosphere. 1-x Br x )3Solar cells.

[0024] FIG. 3A schematically illustrates the triple cation perovskite FAMACsPb(I 1-x Br x )3 Stacked XRD patterns obtained during continuous light soaking “as-prepared”, 2 days, 7 days and 9 days under constant illumination of 1 sun.

[0025] FIG. 3B schematically illustrates the triple cation perovskite FAMACsPb(I 1-x Br x )3 Stacked XRD patterns obtained during continuous heat treatment at 85 °C for “as prepared”, 2 days, 7 days and 9 days.

[0026] Figure 4Illustrated are the XRD patterns of three perovskite types with cations; FAMACs, FAGACs and FAMAGACs, “as prepared” (fresh) and after thermal stress at 85 °C in N2 atmosphere for one week (aged).

[0027] FIG. 5A schematically illustrates the quadruple cation perovskite FAGAMACsPb(I 1-x Br x )3 Stacked XRD patterns obtained during continuous light soaking “as prepared”, 2 days, 7 days, 28 days and 37 days under constant illumination of 1 sun.

[0028] FIG. 5B schematically illustrates the quadruple cation perovskite FAGAMACsPb(I 1-x Br x )3 Stacked XRD patterns obtained during continuous heat treatment at 85°C for “as prepared”, 2 days, 7 days, 28 days and 37 days.

[0029] FIG. 6 graphically illustrates the time-dependent variation in power conversion efficiency (PCE) of GA-based solar cells fabricated by vacuum deposition and stored in a N 2 atmosphere at 85° C. in the dark. DETAILED DESCRIPTION OF THE INVENTION

[0031] The method of the present invention may include 3 or 4 evaporation sources, wherein some of these sources contain a mixture of multiple precursors. In addition to the B cation (s), the resulting perovskite material ABMX3 contains three or more different cations (at the A position, i.e., present as A, A', A").

[0032] The present invention provides a method for reducing the number of available sources by co-sublimation of multiple organic halides, wherein preferably one of the organic halides comprises an organic monocation and the other comprises a larger organic cation (hereinafter alternatively referred to as a "cation additive"). In another aspect of the present invention, the number of sources can be reduced even further by preparing a mixed inorganic / metal halide precursor, such as CsI+CsBr or PbI2+PbBr2. As described below, the method of the present invention can be divided into multiple steps. Multiple steps involve co-sublimation from multiple sources. Co-sublimation refers to the sublimation of various components from each evaporation source together or simultaneously, so that there is at least some overlap between the sublimation from each source.

[0033] The method of the invention is generally carried out under vacuum, usually by vacuum deposition onto the substrate. This can be carried out in a vacuum chamber under a N2 atmosphere. The chamber can be equipped with individual evaporation sources, for example, which can have their own independent temperature controller and shutter. Each source can have its own dedicated QCM sensor above, and an additional sensor mounted close to the substrate to measure the total deposition rate. The temperature of the method is customized for each chamber, for example, it can range from 100°C to 500°C, with a constant pressure of about 10 -6 millibar.

[0034] Step (i)

[0035] Step (i) of the method of the present invention utilizes a first evaporation source comprising a mixture of co-sublimable organic halides that sublimate together (convert from solid to gas). Typically, the 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 can be placed in the same evaporation source to deposit the final single-phase material due to the proximity of their sublimation temperatures. Co-sublimation (or co-evaporation) is further explained in the textbook "OLED Fundamentals - Materials, Devices, and Processing of Organic Light-Emitting Diodes" (edited by Daniel J. Gaspar and Evgueni Polikarpov, 2015, page 195), where it is explained that co-evaporation depends on the evaporation temperature of two or more materials, and the proportion of each material is controlled by the respective evaporation rate.

[0036] Similar co-sublimation temperatures can refer to "coherent evaporation" and "non-coherent evaporation." "Coherent evaporation" refers to precursors that have been mixed together and have close sublimation temperatures within 20°C (and preferably within 15°C or within 10°C) of each other so that they evaporate efficiently as a single phase. Alternatively, the materials can be mixed together to form a new material or alloy that then evaporates coherently at a temperature different from that of the independent entities.

[0037] The Handbook of Thin Film Technology (edited by Leon I. Maissel and Reinhard Glang, 1970, Chapter 1, page 65, Section 6a) provides a general understanding of the term "coherent evaporation" in the art. That is, deposition of a compound film from a single vapor source requires that the material enter the gaseous state in the form of intact molecules. Alternatively, if the molecules dissociate, if the components have equal volatility, then coherent evaporation occurs. Thus, as discussed above, evaporation occurs through a single phase and depends on the characteristics and properties of each precursor.

[0038] "Non-coherent evaporation" refers to precursors that are present in the same crucible but not necessarily mixed to form a single entity, i.e., the precursors exist as two different phases such that they do not enter the gaseous state as intact molecules in a single gas phase, or are not equally volatile to dissociate in unison. The precursors can be heated separately, so the respective sublimation temperatures only need to be 50-150°C close. When they are heated, the vapor streams of the two phases mix to form the first evaporation source. For example, a crucible containing two precursors can be heated at a temperature range covering the evaporation temperatures of the respective precursors to ultimately allow them to co-evaporate, but as different gas phases.

[0039] Preferably, in step (i), one of the organic halides comprises a single A cation such as amidinium (i.e., A is FA), and the other comprises a cation A' having an ionic radius greater than the ionic radius of the first organic cation A, preferably amidinium (FA). In other words, the ionic radius of the organic cation A' is preferably greater than 2.53 Å (and hereinafter referred to as a large single cation 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. In addition, Shannon et al., Acta Cryst. (1969), B25, 925-945, outline methods for determining effective ionic radii, providing radii of various elements in different coordination environments, such as the radii of Pb and Cs. Therefore, these resources can be used to calculate the Goldschmidt tolerance factor to estimate the stability and distortion of the perovskite structure.

[0040] Preferably, the A cation is a monovalent organic cation that can co-sublime with A' when both organic cations A and A' are present as halides (generally, iodides). Preferably, when present as a halide, A has a sublimation temperature similar to that of A'. Further preferably, A is selected from FA and MA. Even more preferably, A is FA. The corresponding organic halide of the A cation generally comprises a halide anion, and is, for example, FAI.

[0041] Preferably, the A' cation is a monocation, typically a large monocation. A' may be an ammonium organic cation, typically selected from guanidinium (GA), dimethylammonium (DMA), ethylammonium (EA), imidazolium (Im), phenethylammonium (PEA), acetamidine (Ac) and benzyl ammonium (BzA). Most preferably, A' is GA. The corresponding organic halide typically contains an iodide anion, and is, for example, GAI.

[0042] It has been found that the large organic halide can be mixed with a first organic halide such as an organic ammonium salt (e.g., manually, by rapid mixing or ball milling), and the two component materials can be sublimated from the same evaporation source. In a preferred embodiment, the co-sublimation of the two precursors is simultaneous.

[0043] In an alternative embodiment, the co-sublimation is non-coincident. In this embodiment, the monovalent organic A cation may be methylammonium (MA).

[0044] Temperature-stable perovskites with a wide range of compositions can be prepared by co-subliming organic halides with large ammonium salts, such as guanidinium iodide (GAI). This is unexpected because such large cations usually do not fit into the reserved A cation sites in 3D perovskites but often lead to severe lattice distortion and aggravate halide segregation.

[0045] Large monovalent organic cations with ionic radius greater than 2.53 Å and smaller monovalent organic cations are generally provided as halides in the first evaporation source and co-evaporated. This is facilitated by the close sublimation temperatures and similar deposition rates of the two cation components, as shown in Table 1.

[0046] For example, a suitable combination of precursors in the first evaporation source may be FAI and GAI, or FABr and GABr.

[0047] All of these organohalides are commercially available in their solid powder form. These cationic salts are in solid form and can be mixed together before the evaporation step by any mechanical method including manual grinding such as ball milling or rapid mixing. During the evaporation stage, the two salts can be sublimated from the solid phase to the gas phase for deposition onto the substrate.

[0048] 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 the A site in perovskites with large cations such as GA affects the structural stability of the entire perovskite structure. For example, GA increases the number of hydrogen bonding (HX bonding) interactions compared to other cations such as MA or FA. The available HX bonds interact with the inorganic framework, which directly improves thermal stability. Hydrogen bonding can also enhance grain size, charge carrier transport, and passivate uncoordinated halide ions within grain boundaries, thereby improving the crystallinity and electronic properties of the perovskite. Although one would expect that the crystal distortion is caused by the large cations, the localized MA cations in the adjacent cavities maintain the 3D structure.

[0049] Perovskites can be generally represented by the formula AMX3 or ABX3. The use of large cations at the A site clearly demonstrates stabilization benefits to the perovskite structure. However, combined vacuum deposition of large monovalent cations coupled with smaller monovalent cations has not been demonstrated, perhaps because it was not expected that the larger cations would enter the A site of the perovskite lattice via sublimation methods. Vacuum deposition is a particularly attractive technique because not only can the quality of the perovskite film be better controlled, but the scalability of the technique facilitates the method for large-scale industrial manufacturing.

[0050] Thus, the present invention surprisingly demonstrates that large cations can actually co-sublimate with smaller monovalent organic cations such as FA, resulting in thermally stable and crystalline perovskite structures.

[0051] Table 1

[0052] Organic iodides Ionic radius of cation (Å) Sublimation temperature (℃) FAI 2.53 160-180 GAI 2.78 160-170 DMAI 2.72 160-170

[0053] Exemplary List of Organic Halides and Their Corresponding Vacuum Deposition Rates and Sublimation Temperatures

[0054] The sublimation temperatures provided in Table 1 are estimated ranges, but these temperatures vary with source, crucible type, temperature measurement type, chamber, pressure, and thermocouple position on the QCM observing evaporation.

[0055] Step (ii)

[0056] The second evaporation source may include a single metal halide BX2. Preferably, the second evaporation source includes two metal halides, i.e., BX2 and BX'2, which are generally mixed together in a crucible in a previous step and heated at a temperature exceeding the highest melting point of any selected precursor under an inert atmosphere such as N2 until they have formed a melt. The melt is then allowed to recrystallize at room temperature, wherein 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 BX2 and BX'2. When the stoichiometrically mixed precursors form a single mixture, consistent evaporation will then generally maintain the initial ratio. In an alternative embodiment, two different metal halides can be combined in the same evaporation source without the need for a previous step, whereby they are non-consistent co-evaporations. Table 2 provides a list of deposition rates and melting temperatures of the corresponding bromides and iodides of some preferred metal halides. The compounds listed in Table 2 can all be purchased from Sigma Aldrich in their desired solid form, and if necessary, they are ready for pretreatment heating together to form a single precursor phase.

[0057] Table 2

[0058] Metal Halide Melting temperature (℃) Sublimation temperature (℃) <![CDATA[PbI2]]> 402 ~400 <![CDATA[PbBr2]]> 373 ~300 <![CDATA[PbCl2]]> 501 ~450

[0059] List of lead halides and their corresponding vacuum deposition rates and melting temperatures

[0060] 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):

[0061] B(X y X' 1-y )2 (I)

[0062] wherein B is a divalent metal cation, X and X' are different halides, and 0≤y<1.

[0063] In the step prior to step (ii), we have discovered that two metal halide salts can react to form a new single mixed halide component which sublimes as a 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 forms PbI y Br 1-y , before this step PbBr2 and PbI2 are mixed and heated in an inert atmosphere.

[0064] Optionally, the B cation is different for each halide precursor, so that BX2 and B'X'2 or BX2 and B'X2 are mixed to give formula (IA) B x B' 1-x (Xy X’ 1-y )2, where B and B' are different and 0 < x < 1 and 0 ≤ y < 1.

[0065] B and B' are preferably selected from Sn and Pb.

[0066] In this case, in step (ii), the second evaporation source may comprise two mixed metal halides selected from:

[0067] a) PbI2 and SnI2 to obtain a single precursor phase Pb x Sn 1-x I2;

[0068] b) PbBr2 and SnBr2 to obtain a single precursor phase Pb x Sn 1-x Br2;

[0069] c) PbI2 and SnBr2 to obtain a single precursor phase Pb x Sn 1-x (I 1-y Br y )2; and

[0070] d) PbBr2 and SnI2 to obtain a single precursor phase Pb x Sn 1-x (I 1-y Br y )2

[0071] where 0 < x < 1 and 0 ≤ y < 1.

[0072] In embodiments where y > 0 in step (ii), two different metal halides are mixed (i.e., the halide components are different).

[0073] The metal halide salts can be lead halide salts, such as PbI2 and PbBr2 or PbBr2 and PbCl2. The metal halide salts can be mixed at high temperature under ambient pressure. This advantageously makes it possible to use a reduced number of evaporation sources.

[0074] The preparation may involve mixing two materials in a crucible and melting them at high temperature (>350 °C) in a nitrogen atmosphere under ambient pressure to avoid oxidation. The resulting compound mainly consists of a new mixed halide phase, which can sublime as a single component during the co-evaporation process.

[0075] In one embodiment, the final perovskite may comprise three different halide materials. The third halide may be introduced from another metal halide co-evaporation source. Alternatively, the third metal halide may also be premixed with the other two metal halides in a crucible and heated under an inert atmosphere to evaporate and deposit on the substrate in a consistent or non-consistent manner. Preferably, the third halide is selected from PbI2, PbBr2, PbCl2, SnI2, SnCl2, SnBr2 or SnF2.

[0076] In another embodiment, the compound having a different formula (I) B (X y X' 1-y )2 halide component / halide component of those halide components can be included in the method as an additive. The 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 can be appropriately incorporated into any other embodiment described herein.

[0077] Step (iii)

[0078] Optional step (iii) of the process of the present invention comprises providing a preferably monovalent organic halide (such as MAI) in a third evaporation source. This may be accompanied by an optional step (iv) of a fourth evaporation source, which 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 absent and step (iv) is present, and so an inorganic halide is provided in the third evaporation source to produce a triple cation perovskite.

[0079] Therefore, there may be 3 or 4 A-site cations in perovskite materials.

[0080] The organic part of the organic halide in step (iii) is preferably selected from MA and FA. The halide part is preferably selected from I, Br and Cl. The organic halide in step (iii) is generally different from the organic halide used in step (i).

[0081] Three or four evaporation sources can be co-evaporated simultaneously to produce the final single-phase perovskite film. The term simultaneous co-evaporation means that the evaporation from each source should occur substantially simultaneously. When evaporating, the plumes from each source can have at least 10% overlap with each other, preferably at least 20% overlap, more preferably at least 30%, 40%, 50%, 60%, 70%, 80%, 90% or substantially complete (100%) overlap. When the second evaporation source comprises BX2, this can be sublimated directly in the co-evaporation stage (ii) without any prior preparation steps with another precursor. In one embodiment, step (iv) may comprise CsI or CsBr to produce a single or mixed halide final material. When a final single halide material is desired, the halide composition of the Cs halide can be the same as the halide composition of the lead halide of step (ii). When a final dual mixed halide with a preferred stoichiometry is desired and step (ii) comprises only BX2, there are two ways to obtain a mixed dual halide composition. In one embodiment, the preferred stoichiometric ratio of BX2 and CsX' can be evaporated from different sources according to their steps, where X and X' are different halides. In another embodiment, the mixed halide composition originates from a previous preparation step (iii) or (iv), for example from a mixture of two inorganic halides, one of which has a different halide composition than the material (materials) of step (ii).

[0082] When it is desired to have a final triple mixed halide with a preferred stoichiometry, and step (ii) comprises only BX2 and BX'2, there are two ways to obtain the mixed triple halide composition. In one embodiment, the preferred stoichiometric ratios of BX2, BX'2 and CsX'' can be evaporated according to their steps and from different sources, where X, X' and X" are different halides. In another embodiment, the triple mixed halide composition is derived from a previous preparation step (iii) or (iv), for example from a mixture of two inorganic halides, both of which have a different halide composition than the material of step (ii).

[0083] 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 exceeding the highest melting point of any selected precursor until they have formed a melt. The melt is then allowed to recrystallize at room temperature, wherein 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 and CsI. Table 3 provides the melting temperatures and deposition rates of the CsI and CsBr compounds, highlighting the proximity of their sublimation temperatures and identical deposition rates. The Cs mixed halide precursor thus occupies a third evaporation source that co-sublimates with the first and second evaporation sources.

[0084] Optionally, a fourth evaporation source may also be introduced, wherein the fourth evaporation source may comprise an inorganic halide such as CsI or CsBr, and the third evaporation source may comprise an organic halide selected from organic monocations such as MA and FA cations, whereby no precursor organic cations are the same in the process.

[0085] In another embodiment of the invention, the second evaporation source in step (ii) may alternatively consist of the preparation of two mixed metal mixed halide reagents such as BX2 and B'X'2. For example, PbI2 and SnBr2, or equivalently 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 allowed to recrystallize at room temperature, wherein a solid mixed halide mixed metal single phase precursor is formed. The halide and metal stoichiometry of the final precursor phase can be determined by the initial ratio of BX2 to B'X'2.

[0086] For the foregoing embodiments, 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, whereby no one precursor organic cation is the same.

[0087] Cs salts are available directly from standard suppliers in their powder form, ready for pretreatment to form a single precursor phase.

[0088] Step (iv)

[0089] Step (iv) may include introducing an inorganic halide component. Step (iii) may or may not be present, so there may be three or four evaporation sources. Optionally, where four evaporation sources are used, an inorganic halide is provided in the fourth evaporation source and an organic halide is provided in the third evaporation source, wherein all A cations in the final composition are different from each other.

[0090] The inorganic portion of the inorganic halide component is preferably selected from Cs and Rb, and is preferably Cs.

[0091] Thus, the method may comprise four evaporation sources, wherein in step (ii), BX2 is provided in an evaporation source, in step (iv), a mixed Cs halide is provided in a fourth evaporation source, and an organic halide is provided in a third evaporation source.

[0092] In this embodiment, a fourth evaporation source may be used to deposit a quadruple cation perovskite comprising an organic halide selected from organic monocations such as MA, FA and EA cations, preferably MA, whereby none of the precursor organic cations are the same.

[0093] In yet another embodiment, the second evaporation source can consist of the preparation of BX2 and B'X2 to obtain a mixed metal homogenous halide precursor. For example, any two of PbCl2, PbBr2 and PbI2, or any two of SnCl2, SnF2, SnBr2 and SnI2 can be mixed in a crucible and can be 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 allowed to recrystallize at room temperature, wherein a solid mixed metal single phase precursor is formed. The metal stoichiometry of the final precursor phase can be determined by the initial ratio of BX2 to B'X2.

[0094] When the second evaporation source comprises only a single halide, as in step (iii), step (iv) may comprise CsI or CsBr to produce a single or mixed halide final material. When a final single halide material is desired, the halide composition of the Cs halide is the same as the halide composition of the lead halide of step (ii). When a final mixed halide with a preferred stoichiometry is desired, there are two ways to obtain a mixed halide composition. In one embodiment, BX2 and CsX' in a preferred stoichiometric ratio may be evaporated in their separate steps and chambers, where X and X' are different halides. In another embodiment, the mixed halide composition is derived from a prior preparation step (iv), for example from a mixture of inorganic halides.

[0095] The preferred inorganic halides CsI and CsBr can be mixed together in a crucible and heated under an inert atmosphere such as N2 at a temperature exceeding the highest melting point of any selected precursor until they have formed a melt. The melt is then allowed to recrystallize at room temperature, wherein 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 and CsI. Thus, the Cs mixed halide precursor occupies a third (or fourth) evaporation source, which co-sublimates with the first and second evaporation sources to deposit a triple or quadruple cation double halide perovskite film on a substrate.

[0096] Optionally, it is also possible to use a further evaporation source (in step (iii)) comprising an organic halide selected from MA cations, whereby no single precursor organic cation is identical.

[0097] Table 3

[0098] Metal Halide Melting temperature (℃) Sublimation temperature (℃) C 626 ~500 Cb 636 ~400

[0099] List of cesium halides and their corresponding melting and sublimation temperatures.

[0100] The temperatures listed in Tables 1-3 are provided as a guide only and will naturally change when the process is scaled up. Similarly, the deposition rate of each precursor will be greatly affected by the temperature and pressure employed and may therefore also change when scaled up (T. Neubert, M. Vergöhl, Optical Thin Films and Coatings, 2013).

[0101] For all embodiments, the preferred thickness of the multi-component perovskite is 50 to 2000 nm, preferably 100 nm to 1500 nm, determined by the deposition rate of each respective precursor under vacuum conditions below atmospheric pressure. Once the perovskite film has been deposited onto the substrate, the film can then be annealed at a temperature ranging from 50 to 300° C., for example, for 1 minute to 6 hours, to promote and ensure a crystalline film with a uniform morphology, whereby the large additive cations have successfully entered the perovskite lattice. Specific process conditions may affect the number of large cations that enter the lattice. However, within the recommended temperature range, the incorporation of at least some large cations can be expected. In some cases, large cations can also act as defect passivation additives on grain boundaries and surfaces and are therefore not incorporated into the final perovskite formula. These passivation additives can be appropriately incorporated into any other embodiment described herein.

[0102] Material

[0103] Generally, the methods of the present invention involve forming thin film perovskite materials, wherein the band gap is generally between 1.1 eV and 2.5 eV.

[0104] The perovskite material is preferably a mixed halide material, i.e. comprising two or more different halides. It may contain two different halides. Alternatively, three different halide anions may be present.

[0105] The perovskite material formed by the method of the present invention generally has formula (II):

[0106] A a A' b A'' c A''' d B x B' 1-x (X y X' 1-y )3,

[0107] in;

[0108] A is a first monovalent organic cation which can co-sublime with A' when both organic cations A and A' are present as halides (preferably iodides);

[0109] A' is a second monovalent organic cation;

[0110] A″ and A″ are independently a monovalent inorganic cation or another monovalent organic cation;

[0111] wherein all A cations are different from each other and there are at least three A cations;

[0112] 0 <a<1

[0113] 0 <b<1

[0114] 0 <c<1

[0115] 0≤d<1

[0116] a+b+c+d = 1

[0117] 0≤x<1; and 0≤y<1;

[0118] B and B' are independently divalent metal cations;

[0119] X and X' are halide anions.

[0120] In a preferred embodiment, the perovskite material formed by the method of the present invention has the following formula:

[0121] A a A' b A'' c A''' d B x B' 1-x (X y X' 1-y )3,,(III)

[0122] in:

[0123] A is a monovalent organic cation which, when present in a halide, can co-sublime with A';

[0124] A' is a monovalent organic cation with an ionic radius greater than 2.53 Å;

[0125] A" is a monovalent inorganic cation or a monovalent organic cation;

[0126] and A''' is a monovalent inorganic cation or a monovalent organic cation;

[0127] wherein all A cations are different from each other, and;

[0128] 0 <a<1

[0129] 0 <b<1

[0130] 0 <c<1

[0131] 0≤d<1

[0132] a + b + c + d = 1

[0133] 0 ≤ x < 1

[0134] and 0 ≤ y < 1.

[0135] In these two embodiments, 0 < y < 1 is preferred, i.e., the halide components are different.

[0136] A is a monovalent organic cation which has a sublimation temperature similar to A' when present as a halide, preferably iodide. As in the final product of formula (II), the halide part is selected from X or X'.

[0137] In a preferred embodiment, A is FA. In a further preferred embodiment, A' is selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidinium (Ac), and phenethylammonium (PEA), preferably, where A' is GA.

[0138] A'' and A''' are also different from each other and can be selected from any of the following:

[0139] (i) organic cations which generally include MA, FA, EA, preferably MA and / or;

[0140] (ii) Cs ions.

[0141] The X and X' anions are also different from each other and are selected from halides including Cl, Br, and I, preferably, where the halide is I and / or Br.

[0142] The B cation is selected from Pb 2+ and Sn 2+ , where B' is different from B and is also selected from Pb 2+ and Sn 2+ .

[0143] In one embodiment, the method can include 3 evaporation sources, where in step (ii) of the method, one or more metal halides are provided in a single source, and in step (iii) of the method, either an inorganic halide or an organic halide is provided in a third evaporation source, producing a triple-cation perovskite.

[0144] Such perovskite can be selected from the following formula:

[0145] FA a GA b MA c Pb(I y Br 1-y )3, FA a GAb 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、MA a BzA 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 )、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(Iy 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 PEA b Cs c Sn(I y Br 1-y )3、FA a Ac b Cs c Pb(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 Im b MA c Pb(I y Br 1-y )3, FA a Im b MA c Sn(I y Br 1-y )3, FA a PEA b MA c Pb(I y Br 1-y )3, FA a PEA b MA 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 MA 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 MA 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;

[0146] where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1 and 0 ≤ y < 1.

[0147] In another embodiment, the method may include 3 evaporation sources, wherein in step (ii) of the method, a mixture of metal halides, each metal halide having a different metal component, is provided in a single source, and in step (iii) or (iv) of the method, an inorganic halide or an organic halide is provided in a third evaporation source to produce a triple cation mixed metal perovskite.

[0148] The perovskite may be selected from the following formula:

[0149] 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 BZ b MA c Pb x Sn 1-x (I y Br 1-y 3. FA a BZ b Cs c Pb x Sn 1-x (I y Br 1-y 3. MA a BZ 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 Pbx 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 )、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、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;

[0150] where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1, 0 < x < 1 and 0 ≤ y < 1.

[0151] In another embodiment, the method can include 4 evaporation sources, wherein in step (ii) of the method, one or more metal halides are provided in a single source, and wherein in steps (iii) and (iv) of the method, an inorganic halide is provided in a fourth evaporation source and an organic halide is provided in a third evaporation source to produce a quadruple cation perovskite material.

[0152] Such perovskite can be selected from the following formula:

[0153] 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 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, FAa 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 Br 1-y )3;

[0154] Where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1 and 0 ≤ y < 1.

[0155] In another embodiment, the method can include 4 evaporation sources, wherein in step (ii) of the method, a mixture of metal halides is provided in a single source, each metal halide having a different metal component, and in step (iii) of the method, an inorganic halide is provided in a third evaporation source and an organic halide is provided in a fourth evaporation source to produce a quadruple-cation mixed-metal perovskite material.

[0156] The perovskite may be selected from the following formula:

[0157] FA a GA b MA c Cs d Pb x Sn 1-x (I y Br 1-y 3. FA a BZ 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 1x (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;

[0158] where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1, 0 < x < 1 and 0 ≤ y < 1.

[0159] In another aspect of the present invention, there is provided a new perovskite of the following formula:

[0160] 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 Br1-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、FA a PEA b MA c Pb(I y Br 1-y )3、FA a PEAb MA 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 MA 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 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 (Iy 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 )、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;

[0161] where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c = 1, 0 < x < 1 and 0 < y < 1; and

[0162] 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 MAc 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、FAa Ac b MA c Cs d Pb x Sn 1-x (I y Br 1-y )3;

[0163] Where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1, 0 < x < 1 and 0 < y < 1.

[0164] In another embodiment of the present invention, a semiconductor device is provided that has a photoactive layer comprising an organic-inorganic metal halide perovskite material formed according to the first aspect of the present invention.

[0165] In another embodiment, the semiconductor device is a photovoltaic device having a photoactive region, wherein the photoactive region comprises a thin film of a perovskite material formed according to the first aspect of the present invention, and the thickness of the thin film of the perovskite material is in the range of 50 to 2000 nm, preferably 100 nm to 1500 nm. Additionally, the photoactive region may include: an n-type region including at least one n-type layer; and a perovskite material layer in contact with the n-type region.

[0166] The photovoltaic device may include an n-type region comprising at least one n-type layer; a p-type region comprising at least one p-type layer; and a perovskite material layer disposed between the n-type region and the p-type region.

[0167] In another embodiment of the present invention, a multi-junction photovoltaic device is provided, wherein the device includes two or more sub-cells, the first sub-cell includes a photovoltaic device as defined above having a bandgap of 1.1 to 2.5 eV, and the additional sub-cells include a second photoactive material having a complementary bandgap.

[0168] 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, wherein, depending on the geometry of the device, in an all-perovskite, perovskite-Si, perovskite-CIGS, perovskite-CuZnSnSSe tandem cell, perovskite-CuZnSnS tandem cell, or perovskite-CdTe heterojunction device, one or more of the top, middle, or bottom sub-cells contain the perovskite described herein.

[0169] In another embodiment of the present invention, a photoelectric device comprising a perovskite material formed according to the first aspect of the present invention is provided.

[0170] In some embodiments, the optoelectronic device may include a substrate. The substrate may be a flat plane. Alternatively, the substrate may be a root mean square roughness (Rrms ) is greater than or equal to 50 nm. The material of the substrate can be selected from glass, such as fluorine-doped tin oxide (FTO), indium tin oxide (ITO) or silicon (Si).

[0171] Details

[0172] definition

[0173] As used herein, the term "photoactive" refers to a region, layer or material that is capable of photoelectrically responding to light. Thus, a photoactive region, layer or material is capable of absorbing energy carried by photons in light, which energy then results in the generation of electricity (e.g., by generating electron-hole pairs or excitons).

[0174] As used herein, the term "perovskite" refers to a material having a three-dimensional crystal structure related to the three-dimensional crystal structure of CaTiO3 or a material comprising a layer of a material having a structure related to the structure of CaTiO3. The structure of CaTiO3 can be represented by the formula ABX3, wherein A and B are cations of different sizes, and X is an anion. In the unit cell, the A cation is (0, 0, 0), the B cation is (1 / 2, 1 / 2, 1 / 2), and the X anion is (1 / 2, 1 / 2, 0). The A cation is generally larger than the B cation. The technician will understand that when A, B and X are changed, the different ion sizes can cause the structure of the perovskite material to be distorted from the structure adopted by CaTiO3 to a distorted structure of lower symmetry. If the material contains a layer having a structure related to the structure of CaTiO3, the symmetry will also be lower. Materials comprising a layer of perovskite material are well known. For example, the structure of a material adopting a K2NiF4-type structure includes a layer of perovskite material. The skilled person will appreciate that the perovskite material can be represented by the formula [A][B][X]3, wherein [A] is at least one cation, [B] is at least one cation, and [X] is at least one anion. When the perovskite contains more than one A cation, the different A cations can be distributed in an ordered or disordered manner on the A positions. When the perovskite contains more than one B cation, the different B cations can be distributed in an ordered or disordered manner on the B positions. When the perovskite contains more than one X anion, the different X anions can be distributed in an ordered or disordered manner on the X positions. The symmetry of a perovskite containing more than one A cation, more than one B cation, or more than one X cation will generally be lower than the symmetry of CaTiO3.

[0175] As mentioned in the preceding paragraph, as used herein, the term "perovskite" refers to (a) a material having a three-dimensional crystal structure related to that of CaTiO3, or (b) a material comprising a layer of material, wherein the layer has a structure related to that of CaTiO3. Although both classes of perovskites may be used in devices according to the present invention, in certain cases it is preferred to use the first class of perovskites, (a), i.e., perovskites having a three-dimensional (3D) crystal structure. Such perovskites generally comprise a 3D network of perovskite unit cells without any separation between the layers. On the other hand, the second class of perovskites (b) comprises perovskites having a two-dimensional (2D) layered structure. Perovskites having a 2D layered structure may comprise layers of perovskite unit cells separated by (embedded) molecules; an example of such a 2D layered perovskite is [2-(1-cyclohexenyl)ethylammonium]2PbBr4. 2D layered perovskites tend to have high exciton binding energies, which favor the generation of bound electron-hole pairs (excitons) rather than free charge carriers upon photoexcitation. Bound electron-hole pairs may not be able to move sufficiently to reach a p-type or n-type contact, where they can then transfer (ionize) and generate free charges. Therefore, in order to generate free charges, the exciton binding energy must be overcome, which represents the energy cost of the charge generation process and leads to lower voltage and lower efficiency in photovoltaic cells. In contrast, perovskites with a 3D crystal structure tend to have much lower exciton binding energies (on the order of thermal energy) and can therefore generate free carriers directly after photoexcitation. Therefore, the perovskite semiconductor employed in the devices and methods of the present invention is preferably a first type perovskite, (a), i.e. a perovskite with a three-dimensional crystal structure. This is particularly preferred when the optoelectronic device is a photovoltaic device.

[0176] The perovskite material employed in the present invention is a material that can absorb light and thereby generate free charge carriers. Thus, the perovskite employed is a perovskite material that absorbs light. However, the skilled person will appreciate that the perovskite material may also be a perovskite material that can emit light by receiving charges—both electrons and holes—that subsequently recombine and emit light. Thus, the perovskite employed may be a light-emitting perovskite.

[0177] As will be appreciated by the skilled person, the perovskite material used in the present invention can be a perovskite that acts as an n-type electron transport semiconductor when light doped. Alternatively, it can be a perovskite that acts as a p-type hole transport semiconductor when light doped. Therefore, the perovskite can be n-type or p-type, or it can be an intrinsic semiconductor. In a preferred embodiment, the perovskite used is a perovskite that acts as an n-type electron transport semiconductor when light doped. The perovskite material can exhibit bipolar charge transport, and therefore acts as both an n-type semiconductor and a p-type semiconductor. Specifically, depending on the type of junction formed between the perovskite and the adjacent material, the perovskite can act as both an n-type semiconductor and a p-type semiconductor.

[0178] Typically, the perovskite semiconductors used in the present invention are photoactive materials, ie, materials capable of performing both photogeneration and charge transport.

[0179] As used herein, the term "mixed halide" refers to a compound comprising at least two different halides. The term "halide" refers to an anion of an element selected from Group 17 of the periodic table, i.e., an anion of a halogen. Typically, the halide anion refers to a fluoride anion, a chloride anion, a bromide anion, an iodide anion, or an astatide anion.

[0180] As used herein, the term "metal halide perovskite" refers to a perovskite whose formula comprises at least one metal cation and at least one halide anion. As used herein, the term "organometallic halide perovskite" refers to a metal halide perovskite whose formula comprises at least one organic cation.

[0181] The term "organic material" is used in its ordinary sense in the art. Generally, an organic material refers to a material comprising one or more compounds containing carbon atoms. As will be understood by those skilled in the art, an organic compound may comprise a carbon atom covalently bonded to another carbon atom, or to a hydrogen atom, or to a halogen atom, or to a chalcogen atom (e.g., an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom). For example, those skilled in the art will understand that the term "organic compound" generally does not include compounds that are primarily ionic, such as carbides.

[0182] The term "organic cation" refers to a cation that contains carbon. The cation may contain additional elements, 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.

[0183] As used herein, the term "semiconductor" refers to a material having a conductivity value between that of a conductor and that of a dielectric. A semiconductor may be an n-type semiconductor, a p-type semiconductor, or an intrinsic semiconductor.

[0184] As used herein, the term "n-type" refers to a region, layer or material that includes an extrinsic semiconductor having an electron concentration greater than that of holes. Therefore, in an n-type semiconductor, electrons are majority carriers and holes are minority carriers, so they are electron transport materials. Therefore, as used herein, the term "n-type region" refers to a region of one or more electron transport (i.e., n-type) materials. Similarly, the term "n-type layer" refers to a layer of electron transport (i.e., n-type) materials. The electron transport (i.e., n-type) material can be a single electron transport compound or elemental material, or a mixture of two or more electron transport compounds or elemental materials. The electron transport compound or elemental material can be undoped or doped with one or more dopant elements.

[0185] As used herein, the term "p-type" refers to a region, layer or material that includes an extrinsic semiconductor having a hole concentration greater than the hole concentration of electrons. In a p-type semiconductor, holes are the majority carriers and electrons are the minority carriers, so they are hole transport materials. Therefore, as used herein, the term "p-type region" refers to a region of one or more hole transport (i.e., p-type) materials. Similarly, the term "p-type layer" refers to a layer of hole transport (i.e., p-type) materials. The hole transport (i.e., p-type) material can be a single hole transport compound or elemental material, or a mixture of two or more hole transport compounds or elemental materials. The hole transport compound or elemental material can be undoped or doped with one or more dopant elements.

[0186] 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. A skilled artisan can readily measure the band gap of a material without undue experimentation.

[0187] As used herein, the term "layer" refers to any structure that is substantially laminar in form (e.g., substantially extending in two perpendicular directions, but having limited extension in a third perpendicular direction). A layer may have a thickness that varies over the range of the layer. Typically, a layer has an approximately constant thickness. As used herein, the "thickness" of a layer refers to the average thickness of the layer. The thickness of a layer can be readily measured, for example, by using microscopic examination, such as electron microscopy of a cross section of a film, or by surface profilometry, for example, using a stylus profilometer.

[0188] As used herein, the term "porous" refers to a material in which pores are arranged. Thus, for example, in a porous material, a pore is a volume within the body of the material in which there is no material. Individual pores may be of the same size or of different sizes. The size of a pore is defined as the "pore size". For most phenomena involving porous solids, the limiting size of a pore is the limiting size of its smallest dimension, which, in the absence of any further precision, is referred to as the width of the pore (i.e., the width of a slit-shaped pore, the diameter of a cylindrical or spherical pore, etc.). When comparing cylindrical and slit-shaped pores, in order to avoid misleading variations in size, the diameter of the cylindrical pore (rather than its length) should be used as its "pore width" (Rouquerol, J. et al., (1994) Recommendations for the characterization of porous solids (Technical Report). Pure and Applied Chemistry, 66 (8)). In a previous IUPAC document (J. Haber. (1991) Manual on catalyst characterization (Recommendations 1991). Pure and Applied Chemistry.), the following distinctions and definitions were used: micropores have a width (i.e., pore diameter) less than 2 nm; mesopores have a width (i.e., pore diameter) of 2 nm to 50 nm; and macropores have a width (i.e., pore diameter) greater than 50 nm. In addition, nanopores can be considered to have a width (i.e., pore diameter) less than 1 nm.

[0189] The pores in a material may include "closed" pores as well as open pores. Closed pores are pores in a material that are non-connected cavities, i.e., pores that are isolated within the material and not connected to any other pores and therefore cannot enter the fluid to which the material is exposed. On the other hand, such fluids will have access to "open pores". J. Rouquerol et al. discuss the concepts of open porosity and closed porosity in detail.

[0190] Thus, open porosity refers to the fraction of the total volume in a porous material in which fluid flow can effectively occur. It therefore excludes closed pores. The term "open porosity" is interchangeable with the terms "connected porosity" and "effective porosity" and is often simply simplified to "porosity" in the art. Thus, as used herein, the term "no open porosity" refers to a material that has no effective porosity. Thus, a material that has no open porosity generally has no macropores and no mesopores. However, a material that has no open porosity may include micropores and nanopores. Such micropores and nanopores are generally too small to have a negative impact on a material that desires low porosity.

[0191] In addition, a polycrystalline material is a solid composed of many separated crystallites or grains, with grain boundaries at the interface between any two crystallites or grains in the material. Therefore, a polycrystalline material can have both intergranular / interstitial porosity and intragranular / internal porosity. As used herein, the terms "intergranular porosity" and "interstitial porosity" refer to the pores (i.e., grain boundaries) between the crystallites or grains of a polycrystalline material, while the terms "intragranular porosity" and "internal porosity" as used herein refer to the pores within a single crystallite or grain of a polycrystalline material. In contrast, a single crystal or single crystalline material is a solid in which the crystal lattice is continuous and uninterrupted throughout the volume of the material, so that there are no grain boundaries and intergranular / interstitial porosity.

[0192] As used herein, the term "dense layer" refers to a layer without mesopores or macropores. A dense layer may sometimes have micropores or nanopores.

[0193] Thus, as used herein, the term "scaffold material" refers to a material that is capable of acting as a support for another material. Thus, as used herein, the term "porous scaffold material" refers to a material that is itself porous and that is capable of acting as a support for another material.

[0194] As used herein, the term "transparent" refers to a material or object that allows visible light to pass through almost undisturbed so that the object behind can be clearly seen. Therefore, as used herein, the term "translucent" refers to a material or object whose transmittance (alternatively and equivalently referred to as transmittance) to visible light is between that of a transparent material or object and that of an opaque material or object. Generally, a transparent material will have an average visible light transmittance of about 100% or 90% to 100% (usually light with a wavelength of 370 to 740 nm). Generally, an opaque material will have an average visible light transmittance of about 0% or 0 to 5%. A translucent material or object will generally have an average visible light transmittance of 10 to 90%, generally 40 to 60%. Unlike many translucent objects, a semi-transparent object generally does not distort or blur an image. The transmittance of light can be measured using conventional methods, such as by comparing the intensity of the incident light with the intensity of the transmitted light.

[0195] As used herein, the term "electrode" refers to a conductive material or object through which electric current enters or leaves an object, substance, or region. As used herein, the term "negative electrode" refers to an electrode through which electrons leave a material or object (i.e., an electron collecting electrode). Negative electrodes are generally referred to as "anodes". As used herein, the term "positive electrode" refers to an electrode through which holes leave a material or object (i.e., a hole collecting electrode). Positive electrodes are generally referred to as "cathodes". In photovoltaic devices, 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.

[0196] As used herein, the term "front electrode" refers to an electrode disposed on the side or surface of a photovoltaic device intended to be exposed to sunlight. Therefore, the front electrode generally needs to be transparent or translucent to allow light to pass through the electrode to the photoactive layer disposed below the front electrode. Therefore, as used herein, the term "back electrode" refers to an electrode disposed on the side or surface of a photovoltaic device opposite to the side or surface intended to be exposed to sunlight.

[0197] The term "charge transporter" refers to an area, layer, or material through which charge carriers (i.e., particles that carry an electric charge) 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 an area, layer, or material through which electrons can flow easily and will generally reflect holes (holes are electrons that are not present as mobile carriers of positive charge in semiconductors). Conversely, the term "hole transporter" refers to an area, layer, or material through which holes can flow easily and will generally reflect electrons.

[0198] As used herein, the term "volatile compound" refers to a compound that is easily removed by evaporation or decomposition. For example, at a temperature of less than or equal to 150°C, or, for example, at a temperature of less than or equal to 100°C, a compound that is easily removed by evaporation or decomposition would be a volatile compound. "Volatile compounds" also include compounds that are easily removed by evaporation of decomposition products. Thus, a volatile compound X can be easily evaporated by evaporation of X molecules, or a volatile compound X can be easily evaporated by decomposing to form two easily evaporated compounds Y and Z. For example, an ammonium salt can be a volatile compound and can evaporate as an ammonium salt molecule or as a decomposition product, such as ammonium and a hydrogen compound (e.g., a hydrogen halide). Therefore, a volatile compound X can have a relatively high vapor pressure (e.g., greater than or equal to 500 Pa) or can have a relatively high decomposition pressure (e.g., greater than or equal to 500 Pa for one or more decomposition products), which can also be referred to as a dissociation pressure.

[0199] As used herein, the term "conformal" refers to an object that is substantially identical in form or shape to another object. Thus, as used herein, a "conformal layer" refers to a layer of material that conforms to the contours of the surface on which the layer is formed. In other words, the morphology of the layer is such that the thickness of the layer is approximately constant across most of the interface between the layer and the surface on which the layer is formed.

[0200] As used herein, the term "co-evaporation" refers to heating two or more materials or mixtures of materials in separate sources in a high vacuum chamber until they begin to evaporate and are subsequently deposited simultaneously on a substrate. The term is interchangeable with the term "co-sublimation".

[0201] As used herein, the term "large organic cation" refers to a monovalent organic cation having an ionic radius greater than 2.53 Å that is capable of occupying the A site of the perovskite structure. As used herein, the term "additive" refers to a component that can be added to the perovskite formula to improve the optoelectronic properties of the perovskite material and the performance characteristics of the corresponding perovskite solar cell device. Therefore, as used herein, the term "large organic cation additive" refers to an organic cation having an ionic radius greater than 2.53 Å that is capable of occupying the A site of the perovskite structure and thus improving the characteristics of the perovskite material and / or perovskite device.

[0202] The term "optoelectronic device" includes photovoltaic devices, photodiodes (including solar cells), phototransistors, photomultipliers, photoresistors, and light-emitting diodes, among others.

[0203] Photovoltaic equipment

[0204] The perovskite material of the present invention can be used in semiconductor devices, preferably photovoltaic devices. The perovskite material is advantageously configured to act as a light absorber / photosensitizer in the photoactive region of a photovoltaic device.

[0205] The photoactive region may include a thin film of a perovskite material, and preferably the thin film of the perovskite material has a thickness of 50 nm to 2000 nm, preferably 100 nm to 1500, and even more preferably 300 nm to 1200 nm.

[0206] The photoactive region may include an n-type region including at least one n-type layer and a perovskite material layer in contact with the n-type region.

[0207] The photoactive region may include an n-type region including at least one n-type layer, a p-type region including at least one p-type layer, and a perovskite material layer disposed between the n-type region and the p-type region.

[0208] The photoactive region may include a layer of perovskite material without open porosity. The layer of perovskite material may then form a planar heterojunction with one or both of the n-type region and the p-type region.

[0209] Alternatively, although less preferred, the layer of perovskite material may be in contact with a porous support material disposed between the n-type region and the p-type region. The porous support material may comprise or consist essentially of any of a dielectric material and a semiconductor / charge transport material. The layer of perovskite material may then be disposed within the pores of the porous support material / conform to the surface of the porous support material. Alternatively, the layer of perovskite material may fill the pores of the porous support material and form a capping layer on the porous support material, wherein the capping layer consists of a layer of photoactive material without open porosity.

[0210] The photovoltaic device may further include a first electrode and a second electrode, wherein the photoactive region is disposed between the first electrode and the second electrode, wherein the first electrode is in contact with the n-type region of the photoactive region, and the second electrode is in contact with the p-type region of the photoactive region. The first electrode and the second electrode may then 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 may then be an electron collecting electrode, and the second electrode is a hole collecting electrode.

[0211] The photovoltaic device may further include a first electrode and a second electrode, wherein the photoactive region is disposed between the first electrode and the second electrode, wherein the first electrode is in contact with the p-type region of the photoactive region, and the second electrode is in contact with the n-type region of the photoactive region. The first electrode may then comprise a transparent or light-transmitting conductive material, and the second electrode may comprise a metal or a second light-transmitting conductive material. The first electrode may then be a hole collecting electrode, and the second electrode is an electron collecting electrode.

[0212] The photovoltaic device may have a multi-junction structure comprising a first subcell disposed above a second subcell, the first subcell comprising a photoactive region comprising a perovskite material. The photovoltaic device may then have a monolithic 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 thus electrically connected in series. The photovoltaic device may then further include an intermediate region connecting the first subcell to the second subcell, wherein each intermediate region comprises one or more interconnect layers.

[0213] The photovoltaic device having the multi-junction structure may further include a first electrode, a second electrode, wherein the first sub-cell and the second sub-cell are disposed between the first electrode and the second electrode.

[0214] The first electrode may then be in contact with the p-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent conductive material. The first electrode may then be a hole collecting electrode, and the second electrode an electron collecting electrode. In a tandem monolithic device, the second electrode will be in contact with the second subcell, such that the first and second electrodes form an external component at either end of the device. The intermediate layer is located between the first and second subcells.

[0215] Alternatively, the first electrode may be in contact with the n-type region of the first subcell, and wherein the first electrode comprises a transparent or semi-transparent conductive material. The first electrode may then be an electron collecting electrode, and the second electrode a hole collecting electrode. In a tandem monolithic device, the second electrode will be in contact with the second subcell, such that the first and second electrodes form an external component at either end of the device. The intermediate layer is located between the first and second subcells.

[0216] When the photovoltaic device has a multi-junction structure, the second subcell of the photovoltaic device may include any one of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS).

[0217] As an alternative, a multi-junction solar cell may include three sub-cells. The present invention covers perovskite layers with band gaps in the range of 1.1-2.5 eV, meeting the requirements of each sub-cell in the multi-junction. For example, a top cell with a perovskite layer according to the present invention has a band gap in the range of 2.0-2.5 eV, a middle sub-cell with a perovskite layer according to the present invention has a band gap of 1.5 to 2.0 eV, and a bottom sub-cell includes a sub-cell with a band gap in the range of 1.1 to 1.4 eV, such as, for example, crystalline silicon or a narrow band gap perovskite layer. The band gap of each sub-cell may be different from each other and depends on the geometry of the cell. Typically, the top cell may have a wider band gap and the bottom sub-cell may have a lower band gap, with the middle sub-cell band gap being provided between these top and bottom sub-cell values. Any of the top, middle or bottom sub-cells may have a perovskite layer according to the present invention.

[0218] The perovskite layer can be prepared as described in WO2013 / 171517, WO2014 / 045021, WO2016 / 198889, WO2016 / 005758, WO2017 / 089819 and in the reference books Photovoltaic Solar Energy: From Fundamentals to Applications, edited by Angèle Reinders and Pierre Verlinden, Wiley-Blackwell (2017) ISBN-13: 978-1118927465 and Organic-Inorganic Halide Perovskite Photovoltaics: From Fundamentals to Device Architectures, edited by Nam-Gyu Park et al., Springer (2016) ISBN-13: 978-3319351124.

[0219] In a preferred device of the invention, the photoactive layer is a dense layer without open porosity.

[0220] The invention will now be illustrated by the following examples. Example

[0221] Example 1

[0222] Preparation and analysis of mixed halide precursors

[0223] Part of the method for reducing the number of evaporation sources required for co-evaporation of multiple precursors involves a combination of mixed metal halide precursors, such as a combination of PbI2 and PbBr2. The two materials are mixed in a single crucible and melted at high temperatures >350°C under ambient pressure and in a N2 atmosphere to avoid oxidation. The resulting compound provides a new mixed halide alloying phase, which can be further sublimated as a single precursor in one evaporation source as part of the co-evaporation process.

[0224] To confirm the sublimation of mixed metal halides as a single entity, X-ray photoelectron spectroscopy (XPS) was used to characterize a 200 nm mixed lead halide film Pb(I 1-x Br x )3 were subjected to compositional and stoichiometric analysis for consecutive deposition runs. These compounds were then compared to their powder precursor counterparts, as shown in Figure 1. The stoichiometry maintained for each component of the molten mixed lead halide in each run indicates that the material behaves as a single precursor upon evaporation.

[0225] Example 2

[0226] Performance analysis of standard triple-cation double halide perovskites

[0227] The performance characteristics of standard triple cation dihalide perovskites fabricated using the claimed co-evaporation method were also investigated. Planar pin-configuration solar cells were initially fabricated using ITO electrodes coated with a thin hole transport layer (HTL) of poly(triarylamine) (PTAA). -1 , 0.3 Å s -1 , 0.4 Å s -1 and 1.3 Å s -1 The deposition rate is 10 -6 The perovskite light absorber layer FAMACsPb(I) was prepared by vacuum co-deposition of the precursors FAI, MAI, CsI and the molten mixed halide phase from Example 1 at 100 mbar. 1-x Br x )3. The sublimation temperature of the precursor is about 155°C for FAI, about 125°C for MAI, and about 100°C for Pb(I 1-x Br x)3 is about 310°C for CsI and about 485°C for CsI. 60 and a silver top electrode covers the membrane.

[0228] Although respectable PCEs of >16% were obtained for these cells, the thermal stability after stressing on a hot plate at 85 °C in a N2 atmosphere was poor, showing significant degradation of the power characteristics, especially the V OC (Figures 2A and 2B).

[0229] Similarly, Figure 3B shows the results of X-ray diffraction (XRD) of the triple-cation perovskite measured ex situ periodically at different time intervals of continuous thermal stress, i.e., “as prepared”, 2 days, 7 days, and 9 days. By day 9, a significant increase in the PbI2 degradation peak at ~12.7° is observed, while the intensity of the main perovskite peak at ~14.3° decreases; clear signs of degradation.

[0230] In addition, the samples were subjected to light soaking experiments and periodically analyzed by XRD as described above. The films were kept under constant light at 35°C with an intensity of 1 sun equivalent. As shown in Figure 3A, a modest rise in the PbI2 signal was observed after only 2 days.

[0231] These results highlight the insufficient stability of triple-cation vacuum-deposited triple-cation CsMAFA perovskites under thermal stress, an important requirement to ensure the lifetime of PV devices.

[0232] Example 3

[0233] Performance analysis of multi-component perovskites with large cation additives

[0234] As described in Example 2, standard triple cation dihalide perovskites fail to exhibit acceptable thermal stability. According to the present invention, a large cation additive, GA, was inserted into the A position of the structure to determine the effect on stability.

[0235] In order to form the quadruple cationic FAGAMACsPb(I 1-x Br x )3, FAI and GAI were mixed in the same evaporation source at a ratio of 10:1 and mixed with CsI, MAI and Pb(I 1-x Br x )3 are co-evaporated together to form the perovskite film, using the same deposition rate and temperature for each chamber, as detailed in Example 2.

[0236] The triple cation FAGACsPb(I 1-x Br x )3, similarly by combining FAI and GAI as described above in one source, CsI in another source, the mixed halide composition in a third source, and co-evaporating all three sources.

[0237] Also according to Example 2, using FAI, MAI, CsI and Pb(I 1-x Br x )3, a reference triple cationic formula without any large cationic additives, namely FAMACsPb(I 1-x Br x )3.

[0238] Subsequently, all films were thermally stressed at 85 °C in N2 and monitored over a week. X-ray diffraction (XRD) was used to distinguish any structural evolution, such as the formation of degradation phases (PbI2 peaks), e.g. Figure 4 shown.

[0239] The presence of GA in both triple and quadruple cations significantly enhances thermal stability compared to the reference GA-free compounds, with no decay peaks in the "as-prepared" films and significantly smaller degradation peaks after 1 week of thermal treatment. Some minority delta phases are also present, but they are not necessarily detrimental to the material, as they are reported to maintain the stability of the perovskite, as demonstrated in Pavlovetc et al., "Suppressing Cation Migration in Triple-Cation Lead Halide Perovskites", ACSEnergy Lett. 2020, 5, 2802.

[0240] In addition, Figure 5B shows the ex situ obtained XRD patterns of the quadruple cation perovskite analyzed at different stages over a total time of 37 days. The crystallinity of the main peak is maintained at each stage, with no obvious growth of the degradation signal, while for the triple cation lacking the “bulky” additive, the degradation is even accelerated in less than a week, as shown in Figure 3B.

[0241] As shown in Figure 5A, in parallel with the XRD measurements, the quadruple cation was also photo-soaked, whereby the structural integrity was maintained without any significant degradation PbI2 products.

[0242] To further evaluate the combined power and stability device properties of GA-doped multicomponent perovskites, the quadruple cation FAGAMACsPb(I 1-x Br x ) 3. During the continuous thermal stress, the cells were found to maintain 80% of their initial efficiency (Figure 6), illustrating the excellent performance characteristics of the vacuum deposited GA-containing films.

[0243] The present invention includes the following aspects:

[0244] 1. A method of forming a perovskite material from multiple evaporation sources, comprising co-sublimating to form a perovskite material from:

[0245] (i) a first evaporation source comprising a mixture of co-sublimable organic halides, wherein the organic halides include:

[0246] a first organic halide comprising an organic cation A;

[0247] b. a second organic halide comprising an organic cation A 'different from A and having an ionic radius larger than that of the first organic cation A; and

[0248] (ii) a second evaporation source comprising one or more metal halides having formula (I):

[0249] B(X y X' 1-y )2 (I)

[0250] wherein B is a divalent metal cation, X and X' are different halides, and 0≤y<1; and

[0251] (iii) one or more additional organic halides from one or more additional evaporation sources; and / or

[0252] (iv) one or more inorganic halides from one or more additional evaporative sources;

[0253] The perovskite material comprises three or more different cations.

[0254] 2. A method according to aspect 1, wherein the perovskite material comprises a mixed halide, and thus wherein 0 <y<1。

[0255] 3. A method according to aspect 1 or 2, wherein the perovskite material comprises three or more different monovalent cations.

[0256] 4. A method according to any preceding aspect, comprising 3 or 4 evaporation sources.

[0257] 5. The method according to any preceding aspect, wherein the first and second organic halides comprise the same halide.

[0258] 6. The method according to any preceding aspect, wherein the second organic halide in step (i) comprises a monovalent cation A'.

[0259] 7. The method according to any preceding aspect, wherein the one or more organic halides in step (iii) and / or the one or more inorganic halides in step (iv) comprise monovalent cations.

[0260] 8. The method according to any preceding aspect, wherein the first organic halide comprises an organic cation A which is a monovalent organic cation, which is preferably FA.

[0261] 9. A method according to any preceding aspect, wherein the second organic halide comprises an organic monocation A' having an ionic radius greater than that of the first organic cation A and preferably selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidine (Ac) and phenethylammonium (PEA), preferably wherein A' is GA.

[0262] 10. The method according to any of the preceding aspects, which includes a prior step before the step (i) of preparing the first evaporation source, the prior step including mixing two cationic halide salts by a mechanical mixing method.

[0263] 11. The method according to any of the preceding aspects, wherein step (ii) includes a prior step of forming a compound of formula (I) B(X y X’ 1-y )2, the prior step including mixing one or more metal halides, BX2 and / or BX’2, and heating in an inert atmosphere.

[0264] 12. The method according to aspect 11, wherein B(X y X’ 1-y )2 is PbI y Br 1-y , and the step includes mixing PbBr2 and PbI2 and heating in an inert atmosphere.

[0265] 13. The method according to aspect 11, wherein the one or more metal halides BX2 and BX’2 contain two different B cations and two different halide anions, such that formula (I) is B x B’ 1-x (X y X’ 1-y )2, where 0 < x < 1 and 0 < y < 1, and B is a divalent metal cation different from B’, preferably, where B and B’ are selected from Pb and Sn.

[0266] 14. The method according to aspect 11, wherein in step (ii), the second evaporation source comprises two mixed metal halides selected from:

[0267] a) PbI2 and SnI2 to obtain a single precursor phase Pb x Sn 1-x I2;

[0268] b) PbBr2 and SnBr2 to obtain a single precursor phase Pb x Sn 1-x Br2;

[0269] c) PbI2 and SnBr2 to obtain a single precursor phase Pb x Sn 1-x (I 1-y Br y )2; and

[0270] d) PbBr2 and SnI2 to obtain a single precursor phase Pb x Sn 1-x (I 1-y Bry ) 2;

[0271] where 0 < x < 1 and 0 < y < 1.

[0272] 15. The method according to any one of the foregoing aspects, which includes step (iv), wherein an inorganic halide is provided, preferably, wherein the inorganic halide is CsI or CsBr.

[0273] 16. The method according to aspect 15, which includes 4 evaporation sources, and wherein in step (ii) y > 0, such that two different metal halides are mixed, and in step (iii) an organic halide is provided in a third evaporation source, and in step (iv) an inorganic halide is provided in a fourth evaporation source.

[0274] 17. The method according to aspect 16, wherein the two metal halides being mixed are PbI2 and PbBr2, to obtain a single precursor phase Pb(I y Br 1-y )2 in step (ii), where 0 < y < 1.

[0275] 18. The method according to aspects 1 and 3 to 11, when not dependent on aspect 2, which includes 4 evaporation sources, and wherein in step (ii), y = 0, such that only one halide component is provided in the perovskite material, and in step (iii), an organic halide is provided in a third evaporation source, and wherein an inorganic halide is provided in step (iv), preferably, wherein the inorganic halide is CsI or CsBr.

[0276] 19. The method according to aspects 1 and 3 to 11, when not dependent on aspect 2, which includes 4 evaporation sources, and wherein in step (ii), y = 0, such that only one halide component is provided in step (ii), and in step (iii), an organic halide is provided in a third evaporation source, and wherein the prior step of preparing (iv) includes heating two inorganic halides, preferably CsI and CsBr, together in a single evaporation source in an inert atmosphere to obtain a precursor of a mixed halide phase according to formula (II) Cs(I z Br 1-z ) where 0 < z < 1.

[0277] 20. The method according to any one of the foregoing aspects, wherein in step (iii), CsI is provided in a third evaporation source and MAI is provided in a fourth evaporation source.

[0278] 21. The method according to any one of the foregoing aspects, which is used to form a thin film of a perovskite material.

[0279] 22. A method according to any preceding aspect, wherein the perovskite material has a band gap of 1.1 to 2.5 eV.

[0280] 23. A method according to any preceding aspect, wherein the perovskite material has formula (II):

[0281] A a A' b A'' c A''' d B x B' 1-x (X y X' 1-y )3 (II),

[0282] in;

[0283] A is a first monovalent organic cation, which can co-sublime with A' when both A and A' are in the form of halides;

[0284] A' is a second monovalent organic cation having a larger ionic radius than A;

[0285] A'' and A''' are independently selected from a monovalent inorganic cation or another monovalent organic cation;

[0286] wherein all A cations are different from each other and there are at least three A cations;

[0287] 0 <a<1

[0288] 0 <b<1

[0289] 0 <c<1

[0290] 0≤d<1

[0291] a+b+c+d = 1

[0292] 0≤x<1; and 0≤y<1;

[0293] B and B' are independently selected from divalent metal cations;

[0294] And X and X' are independently selected from halide anions.

[0295] 24. The method according to aspect 23, wherein A'' and A''' are different from each other and are selected from any one of the following:

[0296] (iii) an organic cation comprising MA or FA, preferably MA and / or;

[0297] (iv) Cs or Rb cations, preferably Cs.

[0298] 25. The method according to aspect 23 or 24, wherein X and X' are different from each other and are selected from: Cl, Br and I, preferably, wherein the halides X and X' are I and Br.

[0299] 26. A method according to any one of aspects 23 to 25, wherein B is Pb 2+ or Sn 2+ , optionally, wherein B' is different from B and is also selected from Pb 2+ or Sn 2+ .

[0300] 27. A perovskite material obtainable by a method according to any preceding aspect.

[0301] 28. A perovskite material comprising a quaternary cationic dihalide and optionally a mixed metal selected from:

[0302] 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 BZ 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 BZ b MA c Cs d Sn(I y Br1-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 cCs 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;

[0303] Where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1, 0 < x < 1 and 0 < y < 1.

[0304] 29. A perovskite material comprising a triple cation double halide and optionally a mixed metal selected from:

[0305] 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 Br1-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 Acb 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、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 bCs 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 Pb 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 Pbx 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;

[0306] Where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, a + b + c + d = 1, 0 < x < 1 and 0 < y < 1.

[0307] 30. A semiconductor device having a photoactive region comprising a perovskite material as described in any one of aspects 27 to 29.

[0308] 31. The semiconductor device according to aspect 30, wherein the semiconductor device is an optoelectronic device, preferably a photovoltaic device having a photoactive region.

[0309] 32. A photovoltaic device comprising a photovoltaic material prepared by the method according to any one of aspects 1 to 26, wherein the photovoltaic device includes a photoactive region comprising a thin film of a perovskite material, and the thickness of the thin film of the perovskite material ranges from 50 nm to 2000 nm.

[0310] 33. The photovoltaic device according to aspect 32, wherein the photoactive region includes: an n-type region including at least one n-type layer; and a perovskite material layer in contact with the n-type region.

[0311] 34. The photovoltaic device according to aspect 32 or 33, wherein the photoactive region comprises: an n-type region comprising at least one n-type layer;

[0312] a p-type region including at least one p-type layer; and

[0313] A perovskite material layer is disposed between the n-type region and the p-type region.

[0314] 35. A multi-junction photovoltaic device comprising two or more sub-cells, the first sub-cell comprising a photovoltaic device as described in any of Aspects 32 to 34, and the other sub-cells comprising a photoactive layer, which may optionally include a perovskite layer prepared according to any of Aspects 1 to 26.

Claims

1. A method of forming a perovskite material from multiple evaporation sources, comprising co-sublimating to form a perovskite material from: (i) a first evaporation source comprising a mixture of co-sublimable organic halides, wherein the organic halides include: a first organic halide comprising an organic cation A; b. a second organic halide comprising an organic cation A 'different from A and having an ionic radius larger than that of the first organic cation A; and (ii) a second evaporation source comprising one or more metal halides having formula (I): B(X y X’ 1-y )2 (I) wherein B is a divalent metal cation, X and X' are different halides, 0≤y<1; and (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 additional evaporative sources; Wherein, in addition to the B cation(s), the perovskite material further comprises three or more different cations.

2. The method according to claim 1, wherein the precursors in the first and second evaporation sources can be sublimated either uniformly or non-uniformly, wherein the sublimation temperature difference of the precursors for uniform sublimation is up to 20°C and the sublimation temperature difference of the precursors for non-uniform sublimation is 50 to 150°C.

3. The method according to claim 1 or 2, wherein the halide in the organic and / or inorganic halide is selected from iodine and bromine.

4. A process according to any one of claims 1 to 3, wherein the one or more further organohalides in step (iii) are different from the first organohalide.

5. A method according to any preceding claim, wherein the perovskite material comprises a mixed halide (0 <y<1)。 6. A method according to any preceding claim, wherein the perovskite material comprises three or more different monovalent cations.

7. A method according to any preceding claim, comprising 3 or 4 evaporation sources.

8. The method according to any preceding claim, wherein the first organic halide comprises an organic cation A which is a monovalent organic cation, preferably which is MA or FA, even more preferably FA.

9. A method according to any preceding claim, wherein the second organic halide comprises an organic monocation A' having an ionic radius greater than that of the first organic cation A and preferably selected from guanidinium (GA), dimethylammonium (DMA), benzylammonium (BzA), ethylammonium (EA), imidazolium (Im), acetamidine (Ac) and phenethylammonium (PEA), preferably wherein A' is GA.

10. A process according to any preceding claim, wherein step (ii) comprises forming a y X' 1-y )2 compound, the previous step comprising mixing one or more metal halides, BX2 and / or BX'2 and heating in an inert atmosphere.

11. The method according to claim 10, wherein the one or more metal halides BX2 and BX'2 comprise two different B cations and two different halide anions such that 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.

12. A method according to any preceding claim, comprising step (iv) wherein an inorganic halide is provided, preferably wherein the inorganic halide is Cs based, even more preferably wherein the inorganic halide is CsI or CsBr.

13. The method according to claim 12, which includes 4 evaporation sources, and wherein in step (ii) y > 0, such that two different metal halides are mixed, and in step (iii) an organic halide is provided in the third evaporation source, and in step (iv) an inorganic halide is provided in the fourth evaporation source, preferably, wherein MAI is provided in the third evaporation source, and CsI is provided in the fourth evaporation source.

14. A method according to claim 13, wherein the two metal halides to be mixed are PbI2 and PbBr2 to obtain a single precursor phase Pb(I y Br 1-y )2, where 0 <y<1。 15. The method according to claim 1, which includes 4 evaporation sources, and wherein in step (ii), y = 0, such that only one halide component is provided in the perovskite material, and in step (iii), an organic halide is provided in the third evaporation source, and wherein an inorganic halide is provided in step (iv), preferably, wherein the inorganic halide is CsI or CsBr.

16. A method according to claim 1, comprising 4 evaporation sources, and wherein in step (ii), y=0, so that only one halide component is provided in step (ii), and in step (iii), the organic halide is provided in a third evaporation source, and wherein the preceding step of preparing (iv) comprises heating two inorganic halides, preferably CsI and CsBr together in a single evaporation source in an inert atmosphere to obtain Cs(I) according to formula (II) z Br 1-z ) of a mixed halide phase, wherein 0 <z<1。 17. The method according to any one of the preceding claims, which is used to form a thin film of a perovskite material, and the thin film of the perovskite material preferably has a band gap of 1.1 to 2.5 eV.

18. The method according to any one of the preceding claims, wherein the perovskite material has the formula (II): HAS a HAS' b HAS'' c HAS''' d B x B' 1-x (X y X' 1-y )3 (II), wherein; A is a first monovalent organic cation, which can co-sublime with A' when both A and A' are present in the form of halides; A' is a second monovalent organic cation having a larger ionic radius than A; A'' and A''' are independently selected from monovalent inorganic cations or additional monovalent organic cations; wherein all A cations are different from each other, and there are at least three A cations; 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; and X and X' are independently selected from halide anions; Preferably, wherein X and X' are different from each other, and are selected from: Cl, Br, and I, and even more preferably, wherein the halides X and X' are I and Br.

19. The method according to claim 18, wherein B is Pb 2+ or Sn 2+ , optionally, wherein B' is different from B and is also selected from Pb 2+ or Sn 2+ .

20. A method for manufacturing a multi-junction photovoltaic device including two or more sub-cells, the first sub-cell includes a photovoltaic device, wherein the photovoltaic device includes a photoactive region, and the photoactive region contains a perovskite material prepared by the method according to any one of claims 1 to 19; and the additional sub-cells include photovoltaic devices, wherein the photovoltaic devices include photoactive regions, and the photoactive regions optionally contain a perovskite material prepared by the method according to any one of claims 1 to 19.

21. A perovskite material, which can be obtained by the method according to any one of claims 1 to 19.

22. The perovskite material according to claim 21, wherein B is selected from Pb and Sn, wherein one or more additional organic halides in step (iii) are different from the first organic halide, and wherein the one or more inorganic halides, when present, contain Cs as the inorganic part.

23. A perovskite material, which contains a quadruple cation double halide and optionally a mixed metal, and is selected from: 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、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 and 0 < y < 1, or a perovskite material comprising a triple cation double halide and optionally a mixed metal selected from: 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、FA a PEA b MA c Pb(I y Br 1-y )3、FA a PEA b MA 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 MA 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 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 Pb 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 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 and 0 < y < 1.

24. A semiconductor device having a photoactive region comprising a perovskite material as claimed in any one of claims 22 to 23, preferably, wherein the semiconductor device is an optoelectronic device, more preferably a photovoltaic device having a photoactive region.

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