Continuous deposition of perovskite films

Abstract

The present invention provides a method for producing a perovskite material, the method comprising the steps of: i. depositing a first metal halide precursor; and ii. depositing a second metal halide precursor, the halide component in the second metal halide precursor being different from the first metal halide precursor, and the first and second metal halide precursors being deposited separately; and iii. Deposition of an inorganic halide precursor; and / or iv. depositing a first organohalide precursor; and v. optional deposition of a second organohalide precursor different from the first organohalide precursor; vi. optional deposition of a third organohalide precursor different from the first and second organohalide precursors; whereby a mixed halide perovskite material is formed. Steps i, ii, and, if present, step iii, are carried out by physical vapor deposition.

Description

[Technical field]

[0001] The present invention relates to a continuous deposition process for producing perovskite thin films containing mixed halide components, where the final perovskite may have a typical ABX3 structure or a dual perovskite A2BB'X6 structure. The process has a layer-by-layer system that includes successive depositions of perovskite precursors. The process, or parts of the process, can be repeated multiple times to produce a perovskite film of the desired thickness and to mitigate impurities in the mixed halide perovskite structure. [Background technology]

[0002] Solar energy conversion is one of the most promising technologies to provide renewable energy. Currently, crystalline Si holds a share of more than 95% in the PV market, demonstrating high performance of more than 26% power conversion efficiency (PCE). However, Si is currently approaching a maximum performance of about 29% PCE. To further reduce the cost, the efficiency needs to be improved by more than 30%. For example, a promising way to improve Si photovoltaic devices is to use tandem solar cells, where Si often serves as the bottom cell with a band gap of 1.1 to 1.2 eV. However, to ensure that such tandem cells are efficient, a suitable top cell with an appropriate larger band gap eV needs to be found.

[0003] One class of photovoltaic materials that has attracted great interest in recent years are the organic-inorganic halide perovskites. This class of materials has a perovskite crystal structure with the general formula ABX3. Another class of perovskite crystal structure is the double perovskite formula A2BB'X6. These materials exhibit favorable tunable bandgaps of 1.1 to 2.5 eV, high absorption coefficients, and long diffusion lengths, and such compounds have been found to be ideal as absorbers in single-junction photovoltaic devices, and as absorbers for the top, middle, and bottom cells in multi-junction devices.

[0004] Thus, the described processes and their corresponding perovskites are suitable for use in semiconductor devices, such as single or multi-junction solar cells, including photovoltaic devices, perovskite-silicon tandem cells, all-perovskite tandem solar cells, perovskite-perovskite-silicon tandem cells, perovskite-CdTe tandem cells, perovskite-CuZnSnSSe tandem cells, perovskite-CuZnSnS tandem cells, and perovskite-CI GS tandem cells.

[0005] Such perovskites can be synthesized by a variety of techniques, ranging from solution processes such as spin-coating and blade-coating to dry processes such as thermal deposition processes, vapor deposition processes including chemical vapor deposition (CVD) and aerosol-assisted CVD. Often, wet process methods are used to produce complex multi-component perovskite compositions, as dry processes tend to become more complex when additional components are introduced into the perovskite structure. For example, in International Publication No. WO2018026326A1, complex 3D perovskites with improved crystallinity are synthesized by treating a halide perovskite solution with deuterium oxide.

[0006] However, dry processes offer an advantageous method for producing perovskites because they are generally more scalable and less damaging to pre-existing device layers than solution processes. For perovskites to be suitable for tandem applications, they need to be of high phase purity and produced by scalable deposition methods.

[0007] Co-evaporation has also been employed in the past to synthesize multi-component perovskites, i.e., perovskites containing multiple halides, metals, or organic ions in their structure. However, co-evaporation has proven to be a difficult and expensive technique to control. This is because more evaporation sources require monitoring of deposition rates and respective temperatures to ensure the desired final stoichiometric result. Deposition of the organic components is particularly difficult as it requires more care and control and therefore needs to be performed using different settings than the inorganic components. Furthermore, multi-deposition of inorganic layers often results in the generation of secondary phases and therefore degrades device performance. Conversely, when using continuous vapor deposition, precursors can be deposited in a step-by-step layer-by-layer fashion. Although this process may require more steps, it involves an economical and straightforward process that is often linear and useful for manufacturing perovskite solar cells in in-line production, leading to precisely defined layer thicknesses and reproducible layers of pure phases, resulting in higher quality and more uniform films. Summary of the Invention [Problem to be solved by the invention]

[0008] Thus far, sequential deposition has been used to synthesize ABX3 and A2BB'X6 type perovskites, thus achieving great success with the final materials. However, the ability to synthesize complex multicomponent perovskites via sequential deposition, particularly for mixed halide perovskites, has yet to be achieved.

[0009] Kam et al. ("Efficient mixed-cation mixed-halide perovskite solar cells by all-vacuum sequential deposition with metal oxide electron transport layers", Solar RRL, Vol. 3, 7, 1900050, 2019) combined sequential vapor deposition and co-evaporation to produce multicomponent perovskites, MA 0.56 FA 0.44 PbI 2.67 Br 0.33has been synthesized. The process involves premixing PbI2 and PbBr2 salts to form a single mixed lead halide precursor, which is then evaporated onto a substrate. This was followed by premixing MAI and FAI in a single evaporation source, subliming onto the existing mixed lead halide layer, and then annealing in situ to finally form a mixed cation mixed halide perovskite. Although this resulted in high quality, uniform single crystal thickness perovskite films, it is difficult to fully control the stoichiometry when premixing PbI2 and PbBr2.

[0010] Because the boiling point of PbI2 is higher than that of PbBr2, PbI2 tends to be the predominant precursor in the crucible, while the bromine compounds are preferentially evaporated, so it is difficult to fully manipulate the amount of I:Br and control the stoichiometry.

[0011] Additionally, US2020328077A1 discloses a vapor phase deposition method for forming perovskite precursors, including deposition of one or more organic precursors, inorganic precursors, metal halide precursors, and / or alkali halide precursors. The precursors can be evaporated together or individually, but are ultimately deposited as one "component vapor," meaning a mixture of all precursor vapors, forming the final perovskite film.

[0012] Thus, metal halide precursors are deposited together via one vapor mixture, offering similar challenges with respect to stoichiometric control and the formation of poorly mixed phases. In Guo et al. ("Sequential Deposition of High-Quality Photovoltaic Perovskite Layers via a Scalable Printing Method," Advanced Functional Materials, Vol. 29, 24, 2019), a scalable sequential two-step deposition "blade coating" approach was implemented to create MAPbI3 perovskite thin films, whereby PbI2 is deposited first and excess solvent is removed by vacuum extraction, followed by a second deposition step of MAI and a final thermal annealing step. This method produces films with complete surface coverage and optimal crystallinity, ultimately resulting in devices exhibiting a respectable PCE of up to 16.71%. However, this technique has not proven to be a practical solution for the synthesis of complex multicomponent perovskites, especially with respect to the mixed halide components, which often result in complex intrinsic impurity phases. This is usually due to the variety of complex precursor materials used in preparing mixed halides. In particular, when the two organic precursors contain A cations of very different sizes relative to each other, the possibility of phase separation is high because the tolerance factor of the perovskite is more likely to deviate from the ideal stabilized structure. For example, the smaller cations (e.g., Cs + ) in a lattice composed of larger cations (e.g., FA + The inclusion of cations such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 112, 123, 134, 140, 141, 152, 163, 170, 184, 196, 197, 198, 199, 200, 213, 220, 230, 240, 250, 265, 270, 280

[0013] The sequential evaporation method has also been implemented by Reinoso et al. ("Improved properties of hybrid halide perovskite thin films prepared by sequential evaporation for planar solar cells", Materials (Basel), 12(8), 1394, 2019) to synthesize FAPbI3 and MAPbI3 perovskite films. A high vacuum scheme with virtual instrumentation allowing electronic control of the temperature and deposition rate of the two evaporation sources was employed with the goal of making highly uniform, crystalline and reproducible films. A two-step process was implemented, where first a crucible of PbI2 precursor is evaporated and deposition is carried out until the desired thickness is achieved. Next, MAI or FAI precursor is evaporated onto the PbI2 layer, followed by annealing at 100 to 140 °C for 20 min under N2. Although this method demonstrates the formation of single-phase films with optimized morphology using sequential deposition, only two steps are implemented and the resulting perovskite is merely a simple single halide structure composed of few components. Thus, in view of Guo et al. and Reinoso et al., there remains a need to find scalable methods that can be used to fabricate complex perovskite and dual perovskite structures.

[0014] Quasi-2D-3D hybrid perovskite light-emitting layers for use in LED devices have been fabricated by Fu et al. ("Scalable all-vapor deposition fabrication of efficient light-emitting diodes using hybrid 2D-3D perovskite nanostructures", Advanced Functional Materials, Vol. 30, 39, 2020), where a three-step layer-by-layer sequential deposition method is employed. The first step is the vapor-phase deposition of PbBr2 on ITO, followed by sequential deposition of CsBr and butylammonium bromide (BABr), and finally the deposition of (BA)2CsBr of the desired thickness by thermal treatment. n-1 Pb n Br 3n+1Perovskite films were formed. Various ratios of BABr / (BABr+CsBr) were investigated to control the molecular structure of the material, whereby a ratio of 0 resulted in a 2D structure and a ratio of 1 resulted in a 3D structure. Thus, by manipulating this composition ratio along with the annealing temperature and film thickness, a quasi-2D-3D hybrid perovskite was synthesized, which is a mixture of 2D and 3D phases. Obviously, forming a single-phase perovskite remains a challenge.

[0015] Similarly, GB2577492A discloses a process for improving the crystallinity of 3D organic-inorganic metal halide perovskites by converting the 2D perovskite material into a desired 3D perovskite material. The process involves forming a layer of a 2D perovskite material, rather than a typical perovskite precursor, on a substrate, and subjecting the layer to a reaction step to convert the 2D perovskite material into a 3D perovskite analogue. Various deposition methods can be used, such as PVD, CVD, and solution deposition. For example, (PEA)2PbI4 can be deposited first, followed by FAI:FABr, to obtain the final 3D perovskite FAPbI2Br.

[0016] Fu et al. provide the first sequential method for depositing perovskites containing three or more components, i.e., mixed organic-inorganic perovskites. However, none of the above prior art techniques have achieved the gas-phase deposition synthesis of mixed halide perovskites, especially those containing triple or quadruple cations. It is well known that PbI2 and PbBr2 do not mix well due to their different crystal structures, often resulting in poorly mixed films that inhibit perovskite formation. Thus, most sequential deposition studies have focused on depositing layers that are structurally compatible, easily mix, and result in a simple final perovskite system. As seen in Kam et al., pre-treating PbI2 and PbBr2 at high temperatures before co-evaporation is one way to attempt a single mixed halide phase, but it has demonstrated the stoichiometric and process control difficulties inherent to the co-evaporation process. Thus, currently, most mixed halide perovskites are primarily produced using solution deposition methods, which are not necessarily scalable and are not ideal for producing highly uniform multi-component perovskites.

[0017] In addition, Ngqoloda et al. ("Mixed-halide perovskite solar cells via PbICl and PbCl precursor films by low-pressure sequential chemical vapor deposition," Solar Energy, Vol. 215, pp. 179-188, 2021) reported that the mixed-halide lead perovskite film MAPbI x Cl 1-To obtain MAPbI, a three-step sequential deposition is carried out. The steps consist of successive depositions of PbCl2 vapor, followed by PbI2 vapor (providing cumulatively a PbICl film thickness of 143 nm), and a final deposition of MAI vapor. Furthermore, during the successive depositions of the lead halide films, no Cl substitution by iodine was observed, but a reaction was demonstrated to occur leading to the formation of a pure single lead chloride iodide phase (PbICl). Instead, the substitution of Cl by iodine ions occurred only during the transformation to the perovskite phase. Nggoloda provides a chemical vapor deposition process (CVD), whereas the present invention discloses a physical (thermal) vapor deposition (PVD) process. However, it is well known that single A-cation perovskite materials are not complex structures. Thus, MAPbI x Cl 1-x Forming perovskites of this type, firstly, does not provide many impurities, if any, at all. As more complex structures and additional components are introduced into the perovskite, undesirable impurity phases become more prevalent. The present invention provides a means to synthesize structurally complex perovskites while simultaneously removing such impurities.

[0018] Moreover, it is well known in the art that CVD processes tend to require more complex and tightly coordinated setups, such as a chamber for the initial evaporation of the precursors and a separate gas supply chamber. Thermal PVD, on the other hand, is considered a more standardized industrial process, often requiring less temperature and conditions, allowing the precursors to be evaporated in solid form. Thin films made by PVD tend to exhibit superior resistance properties, such as with respect to ablation, which is key to improving the lifetime of perovskite-based devices.

[0019] However, a challenge with PVD is forming a complex, structurally stable, and phase pure final film, especially when multiple different structural materials are deposited. Thus, the method of the present invention provides a means to mitigate impurities in the final perovskite phase and deposit crystalline films by the preferred PVD method.

[0020] Double perovskites are also promising materials for use as photoactive materials and have attracted more attention in recent years as an alternative to solve some of the instability and lead-based toxicity issues of typical hybrid perovskites. Similar to standard perovskite structures, double perovskite films are mostly formed by solution processes. Recently, Wang et al. ("Vapor-phase deposited Cs2AgBiCl6 double perovskite films for highly selective and stable ultraviolet photodetectors", Advanced Science, Vol. 7, 11, 2020) used sequential vapor deposition to fabricate high-quality Cs2AgBiCl6 double perovskite films, which had balanced stoichiometry, enhanced morphology, and highly oriented crystallinity and exhibited an indirect band gap of 2.41 eV. The sequential vapor deposition method involves layer-by-layer vapor deposition of CsCl, BiCl3, and AgCl on a prepared substrate, followed by annealing in N2 ambient, which constitutes one complete cycle of deposition. Wang reported that thicker films of the desired thickness could be obtained simply by repeating the deposition cycle. Similarly, Luo et al. ("Efficient and stable warm-white light emission from lead-free halide double perovskites," Nature, 563, 541-545, 2018) reported the synthesis of Bi-doped and Na-alloyed Cs2Ag via hydrothermal synthesis and successive thermal evaporation of CsCl, InCl3, BiCl3, NaCl and AgCl, as well as a final annealing step. x Na 1-x InCl6 was synthesized. Although these methods have yielded controlled and ideal stoichiometries, the synthesis of complex dual perovskites containing a) mixed halide components and b) mixed organic-inorganic components has yet to be realized. As with standard perovskite structures, the compatibility of some precursors may pose a problem in developing uniform and structurally complex films containing many different ions.

[0021] Thus, currently, deposition of mixed halide double perovskites is only achieved by solution processing methods, as illustrated by Nath et al. ("Synthesis and study of different properties of single halide and mixed halide double perovskites", nanoGe Conference, April 23, 2020), where an anti-solvent precipitation process is reported. Chini et al. ("Lead-free stable mixed halide double perovskites Cs2AgBiBr6 and Cs2AgBiBr 6-x Cl x ("Mixed-halide double perovskites Cs2AgBiX6 (X=Br, I) with tunable optical properties via anion exchange", ChemSusChem, 20 Oct 2021;14(20):4507-4515) each provide a spin-coating method. Nath and Chini discuss the advantages of using mixed-halide perovskites, namely the tunability of the absorption spectrum, structural stability, and band gap malleability, especially with increasing Cl content. Meanwhile, Wu reports an anion exchange mechanism using volatile organic iodide salts. However, naturally, all these solution processes suffer from scalability issues and thus are of questionable industrial applicability.

[0022] Minimal research has been carried out on the synthesis of double perovskites by dry processing techniques, and even less on the formation of more complex multicomponent structures by successive depositions. Mixed halide or mixed organic-inorganic double perovskites have also not been fully explored in the art.

[0023] The present invention therefore aims to solve the problems of typical dry processes experienced in the field by developing a simplified, often linear, process for producing homogeneous complex multi-component perovskites and / or dual perovskite layers with desired thickness, excellent quality and uniformity. In the field, the large number of precursors required to synthesize complex multi-component mixed halide perovskites generally favors multi-source evaporation or solution-based techniques. However, the unique sequential process of the present invention performs high temperature deposition and / or optional intermittent annealing, which induces a high level of molecular reorganization, resulting in films with excellent crystallinity and high quality, naturally improving device properties. [Means for solving the problem]

[0024] In a first aspect of the present invention, a method as claimed in claim 1 is provided.

[0025] Increasing the number of components (A and / or B cations and / or number of X halides) in the ABX3 perovskite formula offers advantages in terms of material / device performance and environmental stability. However, the introduction of multiple components into perovskite films often requires very complex dry processes, and in either case the stability and quality of the film is often compromised. Although these can be carried out through solution processes, problems often arise in scaling up and maintaining the film quality and device efficiency established at the lab scale.

[0026] The present invention provides the synthesis of high performance multi-component perovskites through sequential deposition of each separate precursor. Complex films of controlled thickness are performed on a step-by-step basis, without the need for prior processing or simultaneous management of multiple precursor sources. Thus, a series of multiple halide precursor compounds can be deposited sequentially to obtain mixed halide perovskite films. As a result, the present invention employs simple deposition processes that are often linear and thus easily amenable to industrial scale-up (where the process or parts of the process can be repeated if necessary) to obtain specific final stoichiometries and thicknesses. Even more advantageously, the majority of precursors suitable for the present invention are halide compounds, which often exist naturally in solid form and can be directly utilized in the claimed thermal PVD process. Thus, the described processes and their corresponding perovskites are suitable for use in 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, perovskite-CdTe tandem cells, perovskite-CuZnSnSSe tandem cells, perovskite-CuZnSnS tandem cells, and perovskite-CIGS tandem cells.

[0027] In the literature, one can find solutions to synthesize multicomponent mixed halide perovskites through various complex techniques. However, in many cases, these solutions have more opportunities for error when trying to monitor several precursors, or they simply do not result in highly or homogeneous uniform films. In particular, it is well known that unfavorable mixed phases are formed when halide precursors such as PbI2 and PbBr2 are deposited together. These do not mix homogeneously, which creates a diffusion barrier for the organic cations and thus inhibits perovskite formation. These compounds do not mix very well due to their different thin film crystal structures or polycrystalline structures, which in turn prevents the formation of solid solutions and even pure and stable perovskites. Mixed halide perovskites are particularly important for photovoltaic applications, since by varying the ratio of halides, one can tune the band gap of the material and optimize the light harvesting properties of the perovskite photoactive region. Additionally, the tunability of these mixed halide compositions can make materials suitable for many different cell configurations, such as single-junction and multi-junction cells, and their bandgaps can be tailored to match various absorbing materials in adjacent cells.

[0028] The method of the present invention provides a clear solution to the problems experienced in the art of producing good quality mixed halide perovskite films using sequential deposition methods, especially when the metal halide deposition steps are kept separate. The method provides highly crystalline perovskite materials, which inevitably improves overall device performance. The method employs a simplified and versatile deposition process, allowing step-to-step adjustment of conditions and step order. The claimed sequential process also allows the synthesis of phase-pure perovskites with minimal precursor materials required at each stage, since fewer impurities are introduced by using the method of the present invention. Thus, waste and material costs are also reduced. Overall, less control is required, cost-effectiveness, and the adaptability of the process facilitates a much easier transition to large-scale in-line production. [Brief description of the drawings]

[0029] [Figure 1A] FIG. 1 shows the XRD pattern of the perovskite FA1-aCsaPb(I1-yBry) trilayer fabricated by multi-deposition method. [Figure 1B] FIG. 1 shows the XRD pattern of the perovskite FA1-aCsaPb(I1-yBry) trilayer fabricated by sequential deposition. [Diagram 2] Figure 1 shows an overlay of XRD patterns of the perovskite layer in Figure 1 fabricated by both methods. The continuous line is for the sequential method and the dashed line is for the multi-deposition method. The asterisks indicate the peaks formed by the impurity CsPb2X5 phase in the multi-deposition method. [Diagram 3] Figure 2 shows current density (IV) curves of tandem photovoltaic devices fabricated with perovskite layers according to Figure 1. The curves were formed by the multilayer method (circle coordinates) and the sequential deposition method (cross coordinates). [Figure 4A] FIG. 2 shows XRD patterns of perovskite films according to the formula in FIG. 1 formed by a fully sequential method (solid line) and a partially sequential method in which two precursors are co-deposited (dashed line). [Figure 4B] FIG. 2 shows IV curves of perovskite films according to the formula in FIG. 1 produced by a fully continuous method (solid line) and by a partially continuous method in which the two components are co-deposited (cross coordinates). [Diagram 5] FIG. 2 shows a schematic diagram of a multi-deposition process in which two metal halides are co-deposited with an inorganic halide to produce a perovskite film. Exemplary materials for each source are provided to produce a perovskite film of the formula in FIG. [Figure 6]1 shows a schematic diagram of a sequential deposition method according to the present invention. The metal halide is deposited separately, but the metal halide and inorganic halide are co-deposited to form a perovskite film. Exemplary materials for each source are provided to produce a perovskite film of the formula in FIG. [Figure 7] FIG. 1 shows a schematic diagram of a fully sequential deposition method. All precursors are deposited in separate steps to produce a perovskite film. Exemplary materials for each source are provided to produce a perovskite film of the formula in FIG. [Figure 8] FIG. 13 illustrates a linear sequential deposition setup showing source distance and evaporation plume overlap and direction for a set of different compound materials on a substrate. [Figure 9] FIG. 1 shows a linear sequential deposition setup with non-overlapping source plumes (A) and overlapping source plumes (B). [Figure 10A] Figure 13 shows the XRD pattern of the perovskite film according to the formula of Example 4, prepared by a partial sequential method: two precursors PbI2 / CsI are co-deposited, followed by sequential deposition of PbBr2, FAI and GAI. [Figure 10B] FIG. 13 shows the IV curves of a tandem solar cell having a perovskite film according to the formula of Example 4, fabricated by a fractional sequential method. [Figure 11A] Figure 13 shows the XRD pattern of the perovskite film according to the formula of Example 5 prepared by a partial sequential method: two precursors PbI2 / CsI are co-deposited, followed by sequential deposition of PbBr2, PbCl2 and FAI. [Figure 11B] FIG. 13 shows the IV curves of a tandem solar cell containing a perovskite film according to the formula of Example 5, fabricated by a fractional sequential method. [Figure 12A] FIG. 13 shows the XRD pattern of the perovskite film prepared by the partial sequential method according to the formula of Example 6. [Figure 12B]FIG. 13 shows the IV curves of a tandem solar cell with a perovskite film according to the formula of Example 6, fabricated by a partially sequential method in which the two components are co-deposited. [Figure 13] FIG. 13 shows the XRD pattern of a perovskite film according to the formula of Example 7 made by a fully sequential method including deposition of SnI2, PbCl2 and FAI. [Figure 14] FIG. 13 shows an XRD pattern of a perovskite film according to the formula of Example 8, made by a multi-film deposition method (not according to the invention). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention provides a method for producing a perovskite material, comprising the steps of: i. depositing a first metal halide precursor; ii. depositing a second metal halide precursor, wherein a halide component in the second metal halide precursor is different from a halide component of the first metal halide precursor, and the first and second metal halide precursors are deposited separately; iii. Deposition of an inorganic halide precursor; and / or iv. depositing a first organohalide precursor; v. optional deposition of a second organohalide precursor different from the first organohalide precursor; vi. optionally depositing a third organohalide precursor different from the first and second organohalide precursors; having A mixed halide perovskite material is formed, A method is provided, wherein steps i.ii. and iii. (if present) are performed by physical vapor deposition.

[0031] In the method of the present invention, at least one of steps iii. and iv. is essential, and steps v. and vi. are optional.

[0032] In a preferred embodiment of the present invention, all steps are performed by physical vapour deposition, i.e. the present invention provides a method for producing a perovskite material in which a precursor is deposited on a substrate by physical vapour deposition, the method comprising the steps of: i. depositing a first metal halide precursor; ii. depositing a second metal halide precursor, wherein a halide component in the second metal halide precursor is different from a halide component of the first metal halide precursor, and the first and second metal halide precursors are deposited separately; iii. Deposition of an inorganic halide precursor; and / or iv. depositing a first organohalide precursor; v. optional deposition of a second organohalide precursor different from the first organohalide precursor; vi. optionally depositing a third organohalide precursor different from the first and second organohalide precursors; having A perovskite material containing mixed halides is formed. The present invention provides a method for producing high purity and uniform films by a manageable stepwise process. There may be at least three or four (or more) steps. The term "precursor" refers to a material that is a precursor of the final perovskite material, i.e., the precursor is deposited and then reacted to form the final product. Physical vapor deposition processes generally involve thermal evaporation of the precursor into a gas phase, which generally then condenses on a substrate to form a thin film. This process generally does not involve a chemical reaction step with the substrate.

[0033] Any steps not performed by physical vapor deposition (e.g., deposition of any organohalide precursors) may be performed by any means that effectively deposits the material. The organohalide precursors may be deposited, for example, by solution deposition. However, in a preferred embodiment, all steps are performed by physical vapor deposition.

[0034] The steps may be performed in any order.

[0035] Mixed halide materials are perovskites that contain two or more different halide anions. Preferably, there are two different halide anions, but in different embodiments, there may be three different halide anions.

[0036] The method may further include (vii) a final annealing step, whereby the deposited material is heated to improve the morphology and crystallinity of the final film. The final annealing step may be performed under vacuum or in air at atmospheric pressure. The temperature is adjusted to the evaporation temperature of each precursor material and may range, for example, from 80 to 800° C., and may vary from about 10 to 200° C., depending on the configuration of the tool used. -6 From 10 -5 The deposition temperature for PbBr2 and PbI2, for example, is estimated to be >380° C. In some cases, the structural properties of the film can be further improved by additional intermittent annealing steps between depositions.

[0037] The method of the present invention may be carried out under vacuum, typically by vacuum vapor deposition onto a substrate. This may be done, for example, under a N2 atmosphere, for about 10 -7 From 10 -3 It may be carried out in a vacuum chamber with a base pressure of 1000 mbar. The chamber may have individual evaporation sources, each containing a precursor.

[0038] It is important that the first and second metal halide precursors are deposited separately, in separate and distinct steps.

[0039] The steps in the method may be performed consecutively, i.e., one after the other, with no or minimal overlap.

[0040] Each step may be performed sequentially such that the method is a fully sequential deposition process. Alternatively, the method may be a partial sequential deposition process, where at least steps (i) and (ii) are deposited sequentially. The term "sequential (sequential) deposition" refers to a stepwise continuous vapor deposition process of individual precursors from respective evaporation sources, when the steps are performed by physical vapor deposition, whereby there is a minimal degree of overlap of precursor deposition between each step. This minimal overlap means that a maximum of 10% (preferably a maximum of 5%) of the precursor plume from the previous step is allowed to mix with the precursor plume of the next deposition step (i.e., the adjacent source) as the precursor is evaporated. The amount of plume overlap can be measured by modeling the setup of a sequential deposition tool and inputting information on the relevant materials and conditions (e.g., source distance, temperature, evaporation rate, source angle, etc.). Alternatively, the thin film composition mixture produced by the overlapping plumes can be measured post-deposition using depth profiling scientific methods such as time-of-flight secondary ion mass spectrometry (ToF-SIMS).

[0041] Repeated deposition of each precursor can be performed to obtain a multilayer stack. The term multilayer stack refers to a stack of two or more different thin films. For example, a stack may be (AB) n where A and B are two separate membranes and n is the number of repeats of the AB bilayer. The same principle applies to multilayer stacks with two or more different membranes.

[0042] As noted above, there may be some overlap between the various steps in the process, and some of the steps may be performed simultaneously, i.e. at the same time, provided that steps (i) and (ii) are kept separate.

[0043] Annealing may be performed between steps if necessary. The precursors from each step are in solid form and may each be placed in a separate crucible, which are aligned to be deposited in sequence. The separation distance between the crucibles (sources) determines whether the precursors are deposited in a substantially sequential manner (as shown by FIG. 8) or simultaneously. For example, two crucibles may be close enough to be deposited substantially together, while a third crucible may be far enough away to be deposited sequentially.

[0044] Additionally, any of steps (i) through (vi) may be repeated one or more times to achieve a particular film thickness. In one embodiment, the sequence of steps may be pre-determined and upon completion represents a single cycle. This cycle may then be repeated one or more additional times to form a deposition cycle. The number of cycle repetitions may affect the thickness and final composition of the perovskite material.

[0045] The final perovskite material may be a typical ABX3 perovskite or a dual perovskite of the A2BX6 type. The final formed perovskite material is a thin film having a thickness in the range of 50 nm to 2000 nm, preferably 100 nm to 1500 nm, more preferably 300 to 1200 nm.

[0046] Figure 8 shows an example of a linear sequential deposition process setup. Each source contains a different material (A, B, C), and the distance between the sources can vary (d1). Thus, the distance between the sources affects the amount of plume overlap (d2).

[0047] The angles of adjacent source sources can also affect the amount of plume overlap. Figure 9 shows that when the source sources are not angled relative to one another and are not far enough apart, no plume overlap is expected, and therefore separate deposition occurs from each source (A). Figure 9 also shows that when two source sources are close enough and angled relative to one another (B), there is some plume overlap, resulting in substantially simultaneous deposition of material on the substrate (co-deposition).

[0048] Any order of deposition steps may be utilized, any step may be repeated, and the same material or step may be repeated sequentially.

[0049] Step (i) Step (i) of the method of the present invention comprises depositing a first metal halide precursor from an evaporation source onto a substrate. The metal halide is initially present in solid form and is sublimated at the required temperature for the respective precursor, allowing the precursor to travel through the gas phase and finally contact the substrate and be deposited as a solid film. Step (i) need not be performed first in the method and may be performed at any time.

[0050] In a preferred embodiment, the metal halide may be a salt of the general formula BX2, where B is preferably Pb 2+ or Sn 2+ and X is selected from the group consisting of Cl - , Br - , I - Preferably, X is a halide anion selected from B - or I -The BX2 metal halide salt may be in any solid form, such as powder, pellets, or granules, and may be evaporated at a temperature according to the same sublimation temperature of the salt. Preferably, the deposited film is selected from PbI2, PbBr2, PbCl2, SnF2, SnCl2, SnI2, and SnBr2. Preferably, the final perovskite film is of the usual perovskite general formula ABX3, where A, B, and X may have one or more different A, B, and X ions occupying the respective sites.

[0051] In another embodiment, the metal halide is a salt of the general formula BX, where B is preferably Ag. + , Au + , In + and more preferably B is selected from Ag + X is selected from Cl - , Br - , I - Preferably, X is a halide anion selected from B - or I - The BX metal halide salts may be in any solid form, such as powder, pellets, or granules, and may be evaporated at a temperature range selected according to the same sublimation temperature of the salt. Preferably, the deposited film is selected from AgI and AgBr.

[0052] Metal halides should not be confused with inorganic halides used in later steps of the process of the present invention. Thus, metal halides do not have the general formula AX defined for inorganic halides below. The cation in the metal halide is not derived from an alkali metal. For example, metal halides do not have the general formula AX, where A is, for example, Cs + , K + , Rb + and X is a halide anion.

[0053] In another embodiment, the metal halide is a salt of the general formula BX3, where B is preferably Bi 3+, Al 3+ , Sb 3+ , Ge 3+ and Ga 3+ More preferably, B is selected from the group consisting of Bi 3+ and Al 3+ X is selected from Cl - , Br - , I - Preferably, X is a halide anion selected from B - or I - The BX2 metal halide salt may be in any solid form, including powder, pellets, or granules, and may be evaporated at a temperature range depending on the sublimation temperature of the salt identity. Preferably, the deposited film is selected from BiI3, BiBr3, AlI3, and AlBr3.

[0054] In another embodiment, an additional metal halide precursor having a halide component different from the halide components of steps (i) and (ii) may be included in the process as an additive. This additional halide component is not present in the final perovskite formula. Preferably, the additional metal halide precursor acting as an additive is PbCl2. These additives may be suitably incorporated into any other embodiment described herein.

[0055] Step (ii) Step (ii) of the method of the present invention comprises depositing a precursor, which is a second metal halide, from an evaporation source onto a substrate. Step (ii) is separate from step (i), i.e. the plumes of the first and second metal halide precursors are not mixed by more than 10% (preferably 5% or less) and the two precursors are not deposited in a single step. In general, the precursor of step (ii) is provided to a source separate from the precursor of step (i). The metal halide is initially present in solid form and can be sublimated at the required temperature of the individual precursor. Step (ii) need not be performed in a particular order and can be performed at any time, provided that it is separate from step (i).

[0056] In a preferred embodiment, the metal halide in step (ii) may be a salt of the general formula BX2 as defined in step (i), except that the halide component is different from that in step (i). Preferably, the deposited precursor is selected from PbCl2, PbI2, PbBr2, SnCl2, SnF2, SnI2, and SnBr2.

[0057] In a preferred embodiment, the deposition in steps (i) and (ii) may include the following preferred precursors: PbI2 and PbBr2 PbI2 and SnBr2 SnI2 and SnBr2 PbBr2 and SnI2 SnI2 and PbCl2 Here, each precursor may be deposited in either step (i) or (ii).

[0058] In another embodiment, the metal halide in step (ii) may be a salt of the general formula BX as defined in step (i). However, if BX is a precursor in step (ii), then BX3 is preferably the precursor in step (i). Similarly, in an embodiment in which the metal halide in step (ii) is a salt of the general formula BX3 as defined in step (i), then BX is preferably the precursor in step (i). In steps (i) and (ii), the halide components are different.

[0059] In embodiments in which the metal halide in steps (i) and (ii) is selected from BX and BX3, the final perovskite film is a film of the dual perovskite general formula A2BX6, otherwise A2(B I B II )X6.

[0060] In another embodiment, the final triple mixed halide may be formed by repeating one of steps (i) or (ii) with a metal halide having a different halide component than that already deposited in steps (i) and (ii). For example, PbBr2 may be deposited in step (i) and PbI2 may be deposited in step (ii), and instead of depositing PbCl2, steps (i) or (ii) may be repeated. These steps may be performed in any order and repeated as many times as desired, as long as they do not include steps in which the metal halide precursors are co-evaporated with each other.

[0061] If the metal halide precursors have the same structure, they may be co-evaporated, for example PbCl2 and PbBr2, which have orthorhombic lattices, can be co-deposited to form a well-mixed crystalline film.

[0062] Step (iii) Step (iii) of the method of the present invention comprises depositing an inorganic halide from an evaporation source onto a substrate. The inorganic halide is usually initially present in solid form and is sublimed at the required temperature of the respective precursor. Step (iii) does not have to be performed in a particular order and can be performed at any time.

[0063] The inorganic halide may have the general formula AX, where A is a monovalent inorganic cation, typically comprising an alkali metal cation, preferably Cs. + , K + , Rb + More preferably, A is selected from Cs + and X is Cl - , Br - , I - Preferably, X is selected from the group consisting of Br - or I - In a preferred embodiment, AX is selected from CsI and CsBr.

[0064] As stated above, the inorganic halide is not the same as the metal halide used in step (i).

[0065] In one embodiment, the precursor from step (iii) may be co-evaporated with one of the precursors from either step (i) or (ii) and deposited on the substrate in essentially a single step, for example, PbI2 from step (i) or (ii) and CsI from step (iii) may be co-evaporated.

[0066] The term co-evaporation means that evaporation from each evaporation source occurs to some degree simultaneously, with the evaporation periods of each source overlapping with one another. As noted above, the overlap represents the percentage of mixing of the plumes of each precursor and is generally determined by the distance between the evaporation sources and / or their respective angles. Two sources that are sufficiently close together and angled relative to one another can be deposited with enough overlap for "co-evaporation" to occur and thus represent a single deposition step. Additionally, if desired, a co-evaporation step may be performed that involves depositing precursors from two closely spaced source sources substantially simultaneously.

[0067] So, the following: i. depositing a first metal halide; and ii. Co-evaporation of a second metal halide with an inorganic halide; and / or iii. depositing a first organic halide; and iv. Optionally, depositing a second organohalide different from the first organohalide; and v. optionally depositing a third organic halide different from the first and second organic halide; There is provided a method of manufacturing a perovskite material in which there are two or more successive deposition steps, comprising: forming a mixed halide-containing perovskite material, the steps may be performed in any order.

[0068] Step (iv) Step (iv) of the method of the present invention comprises depositing an organic halide on a substrate. Preferably, the organic halide is deposited from an evaporation source, but may be deposited by other means such as solution deposition. In one embodiment, the organic halide is initially present in solid form and is sublimed at the required temperature of the respective precursor. Step (iv) may be performed in any order.

[0069] The organic halide may have the general formula A'X, where A' is formamidinium (FA + ), methylammonium (MA + ) or ethylammonium (EA + ), preferably A is a monovalent organic cation such as MA + and F.A. + X is selected from Cl - , Br - , I - Preferably, X is selected from the group consisting of Br - or I - In a preferred embodiment, A'X is selected from MAI, MABr, FAI and FABr.

[0070] In a preferred embodiment, the precursors in each step are (i) BX2, (ii) BX2 different from (i), (iii) AX, and (iv) A'X, forming a typical ABX3 perovskite structure, where A, B and X may have one or more different A, B and X ions occupying their respective sites.

[0071] In another embodiment, the precursors in steps (i) and (ii) are selected from BX and BX3, (iii) is AX and (iv) is A'X, forming a double A2BX6 perovskite structure.

[0072] Steps (v) and (vi) Steps (v) and (vi) of the method of the present invention are both optional steps and comprise depositing a second and a third organohalide, respectively, on a substrate. Typically, the second and third organohalides, if present, are deposited on the substrate from separate evaporation sources. In one embodiment, the organohalides are initially present in solid form and are sublimated at the required temperature of the respective precursors. Steps (v) and (vi) can be performed in any order.

[0073] The organic halide of step (v) may be of the general formula A″X, where A″X is different from A′X from step (iv). Preferably, A″ is FA + , M.A. + , E.A. + , guanidinium (GA + ), benzyl ammonium (BzA + ), Dimethylammonium (DMA + ), imidazolium (Im + ), Acetamidinium (Ac + ), Phenylethylammonium (PEA + ) and butylammonium (BA + ), and more preferably A″ comprises a monovalent organic cation such as MA + , F.A. + , E.A. + and G.A. + X is selected from Cl - , Br - , I - and preferably, X is a halide anion selected from the group consisting of Br - or I - In a preferred embodiment, A"X is selected from MAI, MABr, FAI, FABr, GAI and GABr.

[0074] The organic halide of step (vi) may be of the general formula A'"X, where A'"X is different from A'X from step (iv) and A"X from step (V). Preferably, A'" is FA + , M.A. + , E.A. +, G.A. + , D.M.A. + ,Im + , Ac + , P.E.A. + , BzA + and B.A. + and more preferably A''' includes monovalent organic cations such as FA, MA and GA. + X is selected from Cl - , Br - , I - Preferably, X is a halide anion selected from B - or I - In a preferred embodiment, A'''X is selected from MAI, MABr, FAI, FABr, GAI, GABr.

[0075] In a preferred embodiment, only one of steps (v) or (vi) is present and the final perovskite has the general formula AA'A"BX3. In a further preferred embodiment, steps (v) and (vi) are both present and the final perovskite has the general formula AA'A"A"'BX3. The final perovskite general formula may further comprise multiple B and X ions.

[0076] In another embodiment, only one of steps (v) or (vi) is present and the final perovskite has the general formula (AA'A"2BX6). In yet another embodiment, both steps (v) and (vi) are present and the final perovskite has the general formula (AA'A"A"')2BX6. The final perovskite general formula may further have multiple B and X ions.

[0077] In one embodiment, any two of the organic precursors of steps (iv) through (vi) can be co-evaporated with one another and deposited on a substrate in essentially a single step. For example, FAI from step (iv) can be co-evaporated with the precursor MAI from step (v); or the precursor GAI from step (vi).

[0078] Accordingly, there is provided a method for producing a perovskite material, comprising: i. depositing a first metal halide; and ii. depositing a second metal halide; and iii. Deposition of inorganic halides; and / or iv. co-evaporation of the first organic halide with the second organic halide; and v. Optionally, depositing a third organic halide different from the first and second organic halide. wherein there are three or more successive deposition steps, including: forming a mixed halide-containing perovskite material; and wherein the steps may be performed in any order.

[0079] In another embodiment, there may be two or more steps in which simultaneous co-evaporation is performed. These two or more steps in which simultaneous co-evaporation occurs may be derived from one of the precursors of step (i) or (ii) and the precursor of step (iii), and / or any two of the precursors of steps (iv) to (vi).

[0080] Accordingly, there is provided a method for producing a perovskite material, comprising: i. depositing a first metal halide; and ii. co-evaporation of a second metal halide with an inorganic halide; and iii. co-evaporation of the first organic halide with the second organic halide; and v. Optionally, depositing a third organic halide different from the first and second organic halide. wherein there are three or more successive deposition steps, including: forming a mixed halide-containing perovskite material; and wherein the steps may be performed in any order.

[0081] In one embodiment, any precursors from steps (i) to (vi) may be co-evaporated with each other, except for the precursors from steps (i) and (ii), but the precursors from steps (i) and (ii) must always be deposited sequentially with respect to each other. During co-evaporation, the precursors in their separate sources are deposited on the substrate in a substantially single step. For example, PbI2 from step (i) or (ii) and CsI from step (iii) may be co-evaporated. The deposition may be performed in any order.

[0082] In another embodiment, there may be two or more steps in which co-deposition occurs. These two or more steps in which co-deposition occurs may be obtained from any combination of precursors from steps (i) to (vi), except for the precursors from steps (i) and (ii). The deposition may be performed in any order.

[0083] In some embodiments, organic halides may be included in the process as additives. These additives are not present in the final perovskite, but instead function as additives that passivate defects at grain boundaries and surfaces. Typically, these additives have a monovalent organic A cation with an ionic radius greater than 2.53 Å, referred to herein as a "large" A cation. Preferably, the monovalent organic cation is EA + , G.A. + , BzA + , D.M.A. + ,Im + , Ac + , P.E.A. + and B.A. + These additives may be suitably incorporated into any of the other embodiments described herein. The respective radii of such organic cations in the perovskite environment can be found, for example, in Cheetham et al., Chem. Sci., 2015, 6, 3430, and Travis et al., Chem. Sci., 2016, 7, 4548-4556.

[0084] Material Typically, the methods of the invention involve the formation of thin film mixed halide perovskite materials, the band gap of which is typically between 1.1 eV and 2.5 eV.

[0085] Perovskite materials are mixed halide materials, i.e., they contain two or more different halide anions. Typically, the halide anions are selected from I, Cl and Br.

[0086] In a preferred embodiment of the invention, the perovskite material comprises two or more monovalent cations.

[0087] In one embodiment of the invention, a perovskite of general formula ABX3 is produced, where the cations at the A-site do not comprise (or consist of) methylammonium (MA). In a preferred embodiment, the cations at the A-site comprise a monovalent organic cation and / or a monovalent inorganic cation. The monovalent inorganic cation is preferably Cs. The organic cation is preferably FA. The B-site preferably comprises Pb. Preferably, two or more different halide anions are present. In one embodiment, three different halide anions may be present.

[0088] Preferably the perovskite material formed by the method of the present invention has the general formula (I): A a A' b A''cA''' d B x B' 1-x (X y X' 1-y )3 Where: A is a monovalent inorganic cation; A' is a first monovalent organic cation; A″ is a second monovalent organic cation; A''' is a third monovalent organic cation; all A cations A, A', A", and A''' are different from one another; B is a divalent metal cation; B' is a divalent metal cation different from B; X is a halide anion; X' is a halide anion different from X; 0≦a<1, 0≦b<1, 0≦c<1, ≦d<1, a+b+c+d=1, 0≦x<1, and 0 <y<1、 B and B' are independently a divalent metal cation; X and X' are halide anions.

[0089] In the preferred embodiment, 0 <a<1および / または0<b<1である。

[0090] In one embodiment, the method may comprise steps (i) to (v), whereby each step is carried out sequentially to form the final triple cation mixed halide perovskite. Preferably, the material is a triple cation dual halide perovskite.

[0091] In another embodiment, the method may comprise steps (i) to (vi), whereby each step is carried out sequentially to form the final quaternary cation mixed halide perovskite. Preferably, the material is a quaternary cation dual halide perovskite.

[0092] One particularly preferred material is FA. 1-a Cs a Pb(I 1-y Br y )3, where x and y are independently in the range of 0.05 to 0.95. In a preferred embodiment, y is in the range of 0.1 to 0.4 and x is in the range of 0.1 to 0.5.

[0093] In another embodiment, the perovskite material formed by the method of the present invention is a double perovskite of general formula (II): (A a A' b )2(B x B' 1-x )(X y X' 1-y )6 Where: A is a monovalent inorganic cation; A' is a first monovalent organic cation; B is a trivalent metal cation; B' is a monovalent metal cation; X is a halide anion; X' is a halide anion different from X; 0≦a≦1, 0≦b<1, a+b=1, 0 <x<1、 0 <y<1であり、 The material is a double or 2D perovskite.

[0094] In another embodiment of the present invention, there is provided a semiconductor device having a photoactive layer comprising a mixed organic-inorganic halide perovskite material formed according to the first aspect of the present invention.

[0095] In another embodiment, the semiconductor device is a photovoltaic device having a photoactive region, the photoactive region comprising a thin film of perovskite material formed according to the first aspect of the present invention, the thin film of perovskite material having a thickness in the range from 50 nm to 2000 nm. Further, the photoactive region may comprise an n-type region comprising at least one n-type layer, and a layer of perovskite material in contact with the n-type region.

[0096] The photovoltaic device may have an n-type region including at least one n-type layer, a p-type region including at least one p-type layer, and a layer of perovskite material disposed between the n-type and p-type regions. Thus, the photovoltaic device configuration may have a regular nip structure or an inverted pin structure.

[0097] In another embodiment of the present invention, a multi-junction photovoltaic device is provided having two or more subcells, a first subcell having a photovoltaic device as described above and another subcell having a photoactive layer with a bandgap between 1.1 and 2.5 eV, each of the subcells having a bandgap that is tunable within this range.

[0098] 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, in which the top, middle or bottom subcell comprises a perovskite as described herein in an all-perovskite, perovskite-Si, perovskite-CIGS, perovskite-CdTe, perovskite-CuZnSnSSe, perovskite-CuZnSnS, heterojunction device.

[0099] In another embodiment of the present invention there is provided an optoelectronic device comprising a perovskite material formed according to the first aspect of the present invention.

[0100] In some embodiments, the substrate may be a flat, planar surface. Alternatively, the substrate may have a root mean square roughness (R rms The material of the substrate can be selected from glass, fluorine-doped tin oxide (FTO), indium tin oxide (ITO), or Si substrate.

[0101] definition The term "inorganic halide" refers to a compound that includes an inorganic metal cation bound to one or more halide anion moieties, subject to the balance of the respective valences of the cation and anion. Preferably, the inorganic metal cation is selected from an alkali metal or an alkaline earth metal.

[0102] The term "metal halide" refers to a compound that includes a metal cation bound to one or more halide anion moieties, subject to the balance of the respective valences of the cations and anions. Preferably, the metal cation is a monovalent, divalent or trivalent metal that does not belong to Groups 1 or 2 of the Periodic Table.

[0103] The term "organohalide" refers to a compound that includes an organic cation bound to one or more halide anion moieties, subject to the balance of the respective valences of the cation and anion. Preferably, the organic halide includes a monovalent ammonium cation that is singly bonded to a halide anion to form an ammonium halide.

[0104] The term "deposition cycle" refers to a particular ordered linear sequence that includes a discrete number of vapor phase depositions that, once completed, constitute a single "cycle." Once a "cycle" is completed, the process is repeated or "cycled" one or more times to obtain a perovskite having a desired thickness. The term "linear" sequence refers to a process in which a single deposition step is approximately processed at one point and, once completed, proceeds to the next deposition step.

[0105] The term "double perovskite" refers to a perovskite composition that can host two different transition metal ions at the B site, where one of the transition metal ions is a monocation and the other is a trication, and the overall general formula is A2(B I B II ) X6, where A is one or more organic and / or inorganic monocations, and B I consists of one or more metal monocations, BIII consists of one or more metal trications and X is a halide.

[0106] The term "photoactive" as used herein refers to a region, layer, or material that can respond photoelectrically to light. Thus, a photoactive region, layer, or material can absorb energy carried by photons of light, thereby generating electricity (e.g., by the generation of either electron-hole pairs or excitons).

[0107] The term "perovskite" as used herein refers to a material having a three-dimensional crystal structure related to that of CaTiO3 or a material containing a layer of a material having a structure related to that of CaTiO3. The structure of CaTiO3 is represented by the general formula ABX3, where A and B are cations of different sizes and X is an anion. In the unit cell, the A cations are (0,0,0), the B cations are (1 / 2,1 / 2,1 / 2), and the X anions are (1 / 2,1 / 2,0). The A cations are usually larger than the B cations. It is clear to those skilled in the art that when A, B, and X are varied, the different ion sizes can distort the structure of the perovskite material from that adopted by CaTiO3 to a distorted structure with lower symmetry. Also, when the material contains a layer with a structure related to that of CaTiO3, the symmetry is lower. Materials containing layers of perovskite materials are well known. For example, the structure of the material with K2NiF4 type structure includes layers of perovskite material. It is clear to those skilled in the art that perovskite materials are represented by the general formula [A][B][X]3, where [A] is at least one cation, [B] is at least one cation, and [X] is at least one anion. When the perovskite contains two or more A cations, the different A cations may be distributed on the A site in a regular or disordered manner. When the perovskite contains two or more B cations, the different B cations may be distributed on the B site in a regular or disordered manner. When the perovskite contains two or more X anions, the different X anions may be distributed on the X site in a regular or disordered manner. The symmetry of perovskites containing two or more A cations, two or more B cations, or two or more X cations is often lower than that of CaTiO3.

[0108] As mentioned in the previous paragraph, the term "perovskite" as used herein refers to (a) a material having a three-dimensional crystal structure related to that of CaTiO3, or (b) a material comprising layers of material having a structure related to that of CaTiO3. Although both of these categories of perovskites can be used in the device according to the invention, in some circumstances it is preferred to use perovskites of the first category (a), i.e. perovskites having a three-dimensional (3D) crystal structure. Such perovskites usually comprise a 3D network of perovskite unit cells with no separation between the layers. On the other hand, perovskites of the second category (b) include perovskites having a two-dimensional (2D) layered structure. Perovskites having a two-dimensional layered structure may have layers of perovskite unit cells separated by (intercalated) molecules. An example of such a two-dimensional layered perovskite is [2-(1-cyclohexenyl)ethylammonium]2PbBr4. 2D layered perovskites tend to have high exciton binding energy, which favors the generation of bound electron-hole pairs (excitons) under photoexcitation rather than free charge carriers. Bound electron-hole pairs may not be mobile enough to reach the p-type or n-type contacts where they can migrate (ionize) and generate free charge. As a result, to generate free charge, the exciton binding energy must be overcome, which represents an energy cost to the charge generation process, leading to lower voltages and lower efficiency in photovoltaic cells. On the other hand, perovskites with 3D crystal structures tend to have much lower exciton binding energies (on the order of thermal energy) and thus can generate free carriers directly following photoexcitation. Thus, the perovskite semiconductors used in the devices and processes of the present invention are preferably perovskites of the first category (a), i.e., perovskites with three-dimensional crystal structures. This is particularly preferred when the optoelectronic device is a photovoltaic device.

[0109] The perovskite material used in the present invention can absorb light, thereby generating free charge carriers. Thus, the perovskite used is a light-absorbing perovskite material. However, it will be apparent to those skilled in the art that the perovskite material may also be a perovskite material that can emit light by accepting both electron and hole charges, which then recombine to emit light. Thus, the perovskite used may also be a light-emitting perovskite.

[0110] As will be appreciated by those skilled in the art, the perovskite material used in the present invention may be a perovskite that functions as an n-type electron transporting semiconductor when photodoped. It may also be a perovskite that functions as a p-type hole transporting semiconductor when photodoped. Thus, the perovskite may be an n-type, a p-type, or an intrinsic semiconductor. In a preferred embodiment, the perovskite used functions as an n-type electron transporting semiconductor when photodoped. The perovskite material exhibits ambipolar charge transport and therefore may function as both n-type and p-type semiconductors. In particular, the perovskite may function as both n-type and p-type semiconductors depending on the type of junction formed between the perovskite and the adjacent material.

[0111] The perovskite semiconductors used in the present invention are typically photosensitized materials, i.e. materials that are capable of both photogeneration and charge transport.

[0112] The term "mixed halide" as used herein refers to a compound containing at least two different halides. The term "halide" refers to the anion of an element selected from group 17 of the periodic table of the elements, i.e., a halogen. Typically, the halide anion refers to a fluoride, chloride, bromide, iodide, or astatide anion.

[0113] As used herein, the term "metal halide perovskite" refers to a perovskite whose general formula includes at least one metal cation and at least one halide anion. As used herein, the term "organometal halide perovskite" refers to a metal halide perovskite whose general formula includes at least one organic cation.

[0114] The term "organic material" has its usual meaning in the art. Typically, organic material refers to a material that includes one or more compounds that include carbon atoms. As will be appreciated by those skilled in the art, an organic compound may include a carbon atom that is covalently bonded to another carbon atom, or a hydrogen atom, or a halogen atom, or a chalcogen atom (e.g., an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom). It will be appreciated by those skilled in the art that the term "organic compound" does not typically include compounds that are primarily ionic, such as carbides.

[0115] The term "organic cation" refers to a cation that contains carbon. The cation may contain other 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.

[0116] As used herein, the term "semiconductor" refers to a material that has an electrical conductivity intermediate 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.

[0117] The term "n-type" as used herein refers to a region, layer, or material that includes an extrinsic semiconductor that has a higher concentration of electrons than holes. Thus, in n-type semiconductors, electrons are the majority carriers and holes are the minority carriers, and these are therefore electron transporting materials. Thus, the term "n-type region" as used herein refers to a region of one or more electron transporting (i.e., n-type) materials. Similarly, the term "n-type layer" refers to a layer of an electron transporting (i.e., n-type) material. An electron transporting (i.e., n-type) material can be a single electron transporting compound or elemental material, or a mixture of two or more electron transporting compounds or elemental materials. An electron transporting compound or elemental material can be undoped or doped with one or more dopant elements.

[0118] The term "p-type" as used herein refers to a region, layer, or material that includes an extrinsic semiconductor that has a higher concentration of holes than electrons. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers, and therefore, they are hole transporting materials. Thus, the term "p-type region" as used herein refers to a region of one or more hole transporting (i.e., p-type) materials. Similarly, the term "p-type layer" refers to a layer of hole transporting (i.e., p-type) materials. A hole transporting (i.e., p-type) material may be a single hole transporting compound or elemental material, or a mixture of two or more hole transporting compounds or elemental materials. A hole transporting compound or elemental material may be undoped or doped with one or more dopant elements.

[0119] As used herein, the term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band in a material. One of ordinary skill in the art can readily determine the band gap of a material without undue experimentation.

[0120] The term "layer" as used herein refers to any structure that is substantially laminar in form (e.g., extends substantially in two perpendicular directions, but has limited extension in a third perpendicular direction). A layer may have a thickness that varies over the extent of the layer. Typically, a layer has a substantially constant thickness. As used herein, the "thickness" of a layer refers to the average thickness of the layer. The thickness of a layer can be readily measured, for example, by using a microscope, such as an electron microscope, of a cross-section of a film, or by surface profilometry, for example, using a stylus profilometer.

[0121] Also, polycrystalline materials are solids that are composed of many separate crystals or grains, with grain boundaries at the interface between any two crystals or grains in the material. Thus, polycrystalline materials can have both interparticle / interstitial porosity and intraparticle / internal porosity. The terms "interparticle porosity" and "interstitial porosity" as used herein refer to holes between the crystals or grains of a polycrystalline material (i.e., grain boundaries), while the terms "intraparticle porosity" and "internal porosity" as used herein refer to holes within individual crystals or grains of a polycrystalline material. In contrast, a single crystal or monocrystalline material is a solid in which the crystal lattice is continuous and unbroken throughout the volume of the material, and thus there are no grain boundaries and no interparticle / interstitial porosity.

[0122] The term "compact layer" as used herein refers to a layer that does not have meso- or macro-porosity. Compact layers can sometimes have micro- or nano-porosity.

[0123] Thus, the term "scaffolding material" as used herein refers to a material that can act as a support for another material. Thus, the term "porous scaffolding material" as used herein refers to a material that is itself porous and that can act as a support for another material.

[0124] The term "transparent" as used herein refers to a material or object through which visible light can pass largely unimpeded, resulting in a clear view of the object behind. Thus, the term "semi-transparent" as used herein refers to a material or object that has a transmission (or equivalently called transmittance) between a transparent material or object and an opaque material or object for visible light. Typically, a transparent material has an average transmittance of about 100%, or 90 to 100%, for visible light (generally light having a wavelength between 370 and 740 nm). Typically, an opaque material has an average transmittance of about 0%, or 0 to 5%, for visible light. A semi-transparent material or object typically has an average transmittance of 10 to 90%, typically 40 to 60%, for visible light. Unlike many translucent objects, semi-transparent objects do not typically distort or blur images. Light transmittance can be measured using conventional methods, for example, by comparing the intensity of the incident light to the intensity of the transmitted light.

[0125] The term "electrode" as used herein refers to a conductive material or object through which current flows into or out of an object, substance, or region. The term "negative electrode" as used herein refers to the electrode through which electrons leave a material or object (i.e., an electron collecting electrode). The negative electrode is commonly referred to as the "anode." The term "positive electrode" as used herein refers to the electrode through which holes leave a material or object (i.e., a hole collecting electrode). The positive electrode is commonly referred to as the "cathode." In a photovoltaic device, electrons flow from the positive electrode / cathode to the negative electrode / anode, and conversely, holes flow from the negative electrode / anode to the positive electrode / cathode.

[0126] The term "front electrode" as used herein refers to an electrode disposed on the side or surface of a photovoltaic device that is intended to be exposed to sunlight. Thus, the front electrode is typically required to be transparent or semi-transparent so that light can pass through the electrode to reach the photoactive layer disposed below the front electrode. Thus, the term "back electrode" as used herein refers to an electrode disposed on the side or surface of a photovoltaic device opposite the side or surface that is intended to be exposed to sunlight.

[0127] The term "charge transporter" refers to a region, layer, or material through which charge carriers (i.e., particles that carry an electric charge) can move freely. In semiconductors, electrons act as the mobile negative charge carriers and holes act as the mobile positive charges. Thus, the term "electron transporter" refers to a region, layer, or material that typically reflects holes and allows electrons to flow easily (holes are the absence of electrons that are considered mobile carriers of positive charge in semiconductors). Conversely, the term "hole transporter" refers to a region, layer, or material that typically reflects electrons and allows holes to flow easily through.

[0128] The term "volatile compound" as used herein refers to a compound that is easily removed by evaporation or decomposition. For example, a compound that is easily removed by evaporation or decomposition at a temperature of 150°C or less, or for example at a temperature of 100°C or less, is a volatile compound. "Volatile compound" also includes compounds that are easily removed by evaporation via decomposition products. Thus, a volatile compound X may be one that is easily evaporated by evaporation of X molecules, or a volatile compound X may be one that is easily evaporated by decomposition to form two compounds Y, Z that are easily evaporated. For example, an ammonium salt is a volatile compound and may be evaporated as a molecule of the ammonium salt or as a decomposition product, such as ammonium and a hydrogen compound (e.g., hydrogen halide). Thus, a volatile compound X may have a relatively high vapor pressure (e.g., 500 Pa or more) or a relatively high decomposition pressure (e.g., 500 Pa or more for one or more decomposition products), also referred to as dissociation pressure.

[0129] The term "conform" as used herein refers to an object that has substantially the same shape or form as another object. Thus, a "conformal layer" as used herein refers to a layer of material that conforms to the contours of the surface on which it is formed. In other words, the form of the layer is such that the thickness of the layer is approximately constant across the majority of the interface between the layer and the surface on which it is formed.

[0130] Photovoltaic Devices The perovskite material of the present invention may be used in semiconductor devices, preferably photovoltaic devices, where the perovskite material is advantageously configured to act as a light absorber / photosensitizer within the photoactive region of the photovoltaic device.

[0131] The photoactive region may comprise a thin film of perovskite material, preferably the thin film of perovskite material has a thickness of from 50 nm to 2000 nm, preferably from 100 nm to 1500 nm, more preferably from 300 to 1200 nm.

[0132] The photoactive region may comprise an n-type region comprising at least one n-type layer and a layer of perovskite material in contact with the n-type region.

[0133] The photoactive region may have an n-type region comprising at least one n-type layer, a p-type region comprising at least one p-type layer, and a layer of perovskite material disposed between the n-type and p-type regions.

[0134] The photoactive region may comprise a layer of perovskite material free of open porosity. The layer of perovskite material may form a planar heterojunction with one or both of the n-type and p-type regions.

[0135] Alternatively, but less preferably, the layer of perovskite material may be in contact with a porous scaffold material disposed between the n-type and p-type regions. The porous scaffold material may comprise or consist essentially of either a dielectric material and a semiconducting / charge transport material. The layer of perovskite material may then be disposed within / conformally to the pores of the surface of the porous scaffold material. Alternatively, the layer of perovskite material may fill the pores of the porous scaffold material and form a cap layer on the porous scaffold material, which may consist of a layer of photoactive material without open porosity.

[0136] The photovoltaic device further comprises a first electrode and a second electrode, the photoactive region being disposed between the first electrode and the second electrode, the first electrode contacting the n-type region of the photoactive region and the second electrode contacting the p-type region of the photoactive region. The first and second electrodes may comprise a transparent or light-transmitting conductive material, and the second electrode may comprise a metal or a second light-transmitting conductive material. The first electrode may be an electron collecting electrode and the second electrode may be a hole collecting electrode.

[0137] The photovoltaic device may further have a first electrode and a second electrode, the photoactive region being disposed between the first electrode and the second electrode, the first electrode contacting the p-type region of the photoactive region and the second electrode contacting the n-type region of the photoactive region. The first electrode may comprise a transparent or light-transmitting conductive material, and the second electrode may comprise a metal or a second light-transmitting conductive material. The first electrode may be a hole collecting electrode and the second electrode may be an electron collecting electrode.

[0138] The photovoltaic device may have a multi-junction structure including a first subcell disposed above a second subcell, the first subcell having a photoactive region including a perovskite material. The photovoltaic device may have a monolithically integrated structure. In a monolithically integrated multi-junction photovoltaic device, two or more photovoltaic subcells are deposited directly on each other and are therefore electrically connected in series. The photovoltaic device may further have an intermediate region connecting the first subcell to the second subcell, each intermediate region having one or more interconnect layers. In a four-terminal (4T) tandem photovoltaic device, the two subcells, each having two terminals, are deposited separately from each other and are connected via an external circuit. An electrical insulator is interposed between the two subcells.

[0139] The photovoltaic device having a multi-junction structure may further include a first electrode and a second electrode, and the first subcell and the second subcell may be disposed between the first electrode and the second electrode.

[0140] A first electrode may then contact the p-type region of the first subcell, the first electrode comprising a transparent or semi-transparent conductive material. The first electrode may be a hole collecting electrode and the second electrode may be an electron collecting electrode. In a tandem monolithic device, the second electrode contacts the second subcell, the first and second electrodes forming an outer member at either end of the device. An intermediate layer is disposed between the first and second subcells.

[0141] Alternatively, the first electrode may be in contact with the n-type region of the first subcell, the first electrode comprising a transparent or semi-transparent conductive material. The first electrode is an electron collecting electrode, while the second electrode is a hole collecting electrode. In a tandem monolithic device, the second electrode is in contact with the second subcell, and the first and second electrodes form an external member at either end of the device. An intermediate layer is disposed between the first and second subcells.

[0142] If the photovoltaic device has a multi-junction structure, the second sub-cell of the photovoltaic device may comprise any of a second perovskite material, crystalline silicon, amorphous silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS).

[0143] In another embodiment, the multi-junction solar cell can include three subcells. The present invention covers perovskite layers with band gaps in the range of 1.1 to 2.5 eV, which meet each of the subcell requirements in the multi-junction. For example, the upper cell has a perovskite layer according to the present invention with a band gap in the range of 2.0 to 2.5 eV, the middle subcell has a perovskite layer according to the present invention with a band gap in the range of 1.5 to 2.0 eV, and the lower subcell has a subcell with an energy band gap in the range of 1.1 to 1.4 eV, for example, crystalline silicon or a narrow band gap perovskite layer. The band gaps of each subcell can vary relative to each other and depending on the shape of the cell. In general, the upper cell has a wider band gap, the lower subcell has a lower band gap, and the band gap of the middle subcell fits partway between the values ​​of the upper and lower subcells. Either the upper, middle, or lower subcell can have a perovskite layer according to the present invention.

[0144] For any subcell in a perovskite-free multi-junction device according to the invention, the perovskite layer may be prepared as described in International Publication Nos. WO2013 / 171517, WO2014 / 045021, WO2016 / 198889, WO2016 / 005758, WO2017 / 089819 and the references "Photovoltaic Solar Energy: From Fundamentals to Applications", edited by Angele Reinders and Pierre Verlinden, Wiley-Blackwell (2017) ISBN-13: 978-1118927465 and "Organic-Inorganic Halide Perovskite Photovoltaics: From Fundamentals to Applications", Nam-Gyu Park et al., Springer (2016) ISBN-13: 978-3319351124.

[0145] In a preferred device of the invention, the photoactive layer is a compact layer without open porosity. Standard definitions of the terms "compact layer" and "without open porosity" are given in International Publication No. WO 2016 / 079477.

[0146] Working Example Example 1 Mixed halides, i.e., FA 1-a Cs a Pb(I 1-y Br y Experiments were conducted to compare the results of a multi-deposition method and a sequential deposition method to synthesize FAI, where y and x are independently in the range of 0.05 to 0.95. The non-inventive multi-deposition (co-evaporation) method involved the deposition of BX2 metal halides, which were deposited by co-evaporating the BX2 metal halides from a single chamber. The inorganic halide CsI was co-evaporated with the metal halides. Thus, PbI2, PbBr2, and CsI were all co-evaporated, followed by the deposition of FAI. This is shown in the schematic diagram of FIG. 5.

[0147] In contrast, in the sequential deposition method according to the present invention, the vapor deposition of metal halides is separated (i.e., the BX2 metal halide is not co-evaporated) as shown in FIG. 6. Instead, PbI2 and the inorganic halide CsI are co-evaporated, followed by the sequential deposition of PbBr2, which is then followed by the sequential deposition of FAI. This deposition process is referred to as a "partial" sequential deposition, since at least one step involves the co-evaporation of precursors. However, since the BX2 metal halide is not co-evaporated, this is still within the scope of the present invention. The deposition of each of these layers was followed by annealing in an oven at 80 to 200° C. for 20 minutes up to 5 hours to obtain the final perovskite layer.

[0148] Figures 1A and 1B show the FAs fabricated by the multi-film deposition method and the sequential film deposition method, respectively. 1-a Cs a Pb(I 1-y Br y)3 perovskite. Figure 2 shows a direct overlay of the XRDs of the perovskite layers formed by each method. Clearly, the multi-deposition method shows more additional impurity phases (represented by asterisks), namely, the peak at ~11° and the high intensity impurity peak at 12.5°, which represents PbI2. In contrast, the sequential method showed a pure perovskite structure with relatively minimal residual metal halides (PbI2). The large impurity phases in the multi-deposition pattern are expected to be due to the bonding of the metal halide layers. This is formed when they are deposited together and is extremely difficult to transform when the halide salt FAI is subsequently deposited. These phases are likely to be a mixture of inorganic components such as PbI2, PbBr2, and CsI. The XRD of the multi-deposition method shows three main phases; 1) a large amount of unreacted PbI2 remains in the XRD pattern (≈12.5°), 2) a small perovskite peak (≈14°), and 3) an additional phase at about 11°, which is the mixed metal halide phase CsPb2X5, where X consists of the mixed halides.

[0149] Thus, high quality perovskite films can be formed by the continuous deposition method as shown in Figure 2. The XRD pattern of the continuous deposition method shows two main phases; 1) a small amount of unreacted metal halide PbI2, and 2) a strong perovskite peak at about 14°. This has several advantages, such as improved processing efficiency and film quality. The resulting perovskite has fewer structural impurities, so stable and efficient devices are more easily achieved. Thin layers of halide salts can be used, which inevitably reduces production costs and minimizes waste.

[0150] Example 2 The photovoltaic device characteristics of the perovskite layers obtained by the multi-deposition method and the continuous deposition method were also evaluated. For each method, tandem photovoltaic devices were fabricated using the perovskite layer of Example 1 as the upper subcell and a Si lower subcell. Figure 3 shows the current density (IV) curves obtained by the two deposition methods. The device fabricated by the continuous method had a high V OCIt is clearly seen that the multi-layer device shows higher power conversion efficiency in terms of the IV curve and fill factor (FF). The performance degradation in the multi-layer device is shown by an S-shaped curve in the IV graph as an example. This indicates the formation of a barrier at one of the interfaces, which can be attributed to an impurity phase formed in the perovskite film via this method.

[0151] Example 3 Similar results occur for a fully continuous deposition system without co-evaporation of the precursors (i.e., each precursor is deposited separately). Therefore, a comparison of the fully continuous and partially continuous methods shown in Example 1 was also performed. In the fully continuous method, the perovskite film FA 1-a Cs a Pb(I 1-y Br y ) 3 was fabricated in the same sequential manner as in Example 1, except that all of the precursors were deposited separately, as illustrated by the (A+B+C+D) scheme in Figure 7. A fully sequential tandem perovskite device was also fabricated following the method of Example 2.

[0152] Clearly, the XRD patterns of both types of sequential perovskite films are nearly identical (FIG. 4A), suggesting that the fully sequential deposition method also removes impurities and results in crystalline perovskite. The I-V curves of the devices from each deposition method are also reasonably equivalent (FIG. 4B), again highlighting that comparable power efficiencies are obtained when perovskite films are deposited using the fully sequential method. These results indicate that the partially or fully sequential methods (both according to the present invention) provide desirable device characteristics compared to the multi-deposition method (not according to the present invention).

[0153] Example 4 Another experiment was carried out following the partially sequential deposition conditions and materials of Example 1, except that additional organic halides were sequentially deposited to form a more complex multicomponent triple-cation perovskite: FA 1-a-b Cs a GA b Pb(I1-y Br y A tandem perovskite device of this composition was also fabricated according to the method of Example 2.

[0154] In this example, a layer of guanidinium halide (GAI) was deposited after the deposition of FAI. Large cations such as guanidinium can efficiently enter the perovskite lattice and increase the overall stability of the perovskite film against thermal or moisture degradation.

[0155] The XRD pattern in Figure 10A shows that this partially continuous method produced crystalline and phase-pure FA. 1-a-b Cs a GA b Pb(I 1-y Br y 10B shows that three films were produced. Furthermore, the I-V curves in FIG. 10B show that devices with complex perovskite compositions containing large cations still exhibit higher power conversion efficiency when produced by the partially sequential method according to the present invention compared to the multi-deposition method described in Example 1.

[0156] Example 5 Another experiment was carried out following the partial sequential deposition conditions and materials of Example 1, except that additional metal halides were sequentially deposited to form more complex multicomponent triple-halide perovskites: FA 1-a-b Cs a GA b Pb(I 1-y-z Br y Cl z A tandem perovskite device of this composition was also fabricated according to the method of Example 2.

[0157] In this example, a layer of lead chloride (PbCl2) was deposited after the deposition of PbBr2 and before the deposition of the FAI layer.

[0158] The XRD pattern in Figure 11A shows that the partially continuous method produced crystalline and phase-pure FA. 1-a Cs a Pb(I 1-y-z Bry Cl z 11B shows that a 3-layer film was formed. Furthermore, the IV curves in FIG. 11B demonstrate that devices with complex perovskite compositions, when fabricated by the partially sequential method, still exhibit high power conversion efficiency compared to the multi-layer deposition method described in Example 1. This example further shows that the sequential deposition method of metal halides surprisingly maintains phase-pure crystalline perovskite despite the many halide components.

[0159] Example 6 Another experiment was carried out following the conditions and materials of the partially continuous deposition method of Example 1, but changing the deposition order. Thus, the same perovskite composition FA 1-a Cs a Pb(I 1-y Br y ) 3 was synthesized. A tandem perovskite device of this composition was also fabricated according to the method of Example 2.

[0160] In this example, PbI2 and CsI were co-evaporated first (instead of PbBr2 and CsI as in Example 1), followed by deposition of FAI and then PbBr2.

[0161] The XRD pattern in Fig. 12A shows that the partially deposited FA was crystalline and phase-pure. 1-a Cs a Pb(I 1-y Br y ) three films were produced. The IV curves in FIG. 12B also show that varying the deposition order and the identity of the metal halide co-evaporated with the inorganic halide does not affect the device characteristics. In fact, higher power conversion efficiencies are achieved compared to the multi-deposition method described in Example 1. Thus, this example shows the applicability of the sequential method to different orders and different combinations of precursors for co-evaporation (when no metal halide is co-evaporated).

[0162] Example 7 Another experiment was carried out in which tin halide was deposited instead of lead halide as one of the metal halides to form a complex multicomponent mixed-metal perovskite.

[0163] In this example, SnI2 was deposited first, followed by PbCl2 and FAI, respectively, in succession, thus using a fully sequential deposition method. Each of these layers was annealed in an oven at 80 to 200 °C for 20 minutes and up to 5 hours, as in Example 1, to obtain the final perovskite layer.

[0164] The XRD patterns in Fig. 13 show that crystalline and phase-pure FA was synthesized in a completely continuous manner. 1-a Cs a Sn 1-x Pb x (I 1-y Cl y )3 films were formed. Thus, this example demonstrates that a continuous process can be used to sequentially deposit films of two or more metal halides, differing in both metal and halide anions, while maintaining a substantially impurity-free crystalline composition.

[0165] Example 8 Another comparative (not according to the invention) multi-deposition experiment was carried out in which two metal halides were co-deposited and therefore co-deposited, in a similar manner to the multi-deposition method of Example 1, but without the CsI precursor.

[0166] In this example, PbI2 and PbBr2 were co-deposited, followed by deposition of FAI to form the perovskite film FAPb(I 1-y Br y )3 was formed.

[0167] The XRD in FIG. 14 clearly shows that the formation of perovskite is greatly hindered by the mixing of PbI2 and PbBr2 components, since the most intense peak is the impurity PbI2 (12°) peak. Furthermore, it can be seen that the characteristic perovskite peak (~14°) is greatly reduced. Clearly, the separation of the deposition of metal halides according to the present invention is favorable for the formation of perovskite with minimal impurities.

[0168] In conclusion, it has been confirmed that efficient photovoltaic devices can be produced by using a sequential deposition process (partially or completely) to synthesize crystalline perovskite films. The claimed method also offers many advantages in terms of process control of the individual layers / components and the ability to employ a completely in-line production process that is simple, efficient, and essential for the industrialization of the technology. As shown in the above examples, the sequential deposition method according to the invention can consistently produce high-quality crystalline films of complex perovskites spanning compositions including several organic and inorganic A cations, mixed metal B cations, and multiple halide anions. The process is extremely versatile and does not require any particular order as long as the deposition of the metal halides is separated.

Claims

1. 1. A method of producing a perovskite material, comprising: i. depositing a first metal halide precursor; ii. depositing a second metal halide precursor, wherein the halide component in the second metal halide precursor is different from the halide component of the first metal halide precursor, and the first and second metal halide precursors are deposited separately; below iii. deposition of an inorganic halide precursor, and / or iv. Deposition of the first organic halide precursor At least one step of and A mixed halide perovskite material is formed, Steps i. and ii. are carried out by physical vapor deposition; A method wherein step iii., if present, is performed by physical vapor deposition.

2. moreover, v. depositing a second organic halide precursor different from the first organic halide precursor.

2. The method of claim 1, comprising:

3. moreover, vi. depositing a third organohalide precursor different from the first and second organohalide precursors.

2. The method of claim 1, comprising:

4. moreover, vii. Final annealing step 2. The method of claim 1, comprising:

5. When present, steps i. through v. are performed by physical vapor deposition; 10. The method of claim 1, wherein all steps are preferably performed by physical vapor deposition.

6. 10. The method of claim 1 for producing a thin film of a perovskite material.

7. The method of claim 1 , wherein three or more precursors are vapor-deposited sequentially onto a substrate.

8. Step iii. is present, 10. The method of claim 1, wherein the deposition of the first metal halide precursor and the inorganic halide precursor is carried out together in a co-evaporation step.

9. The method of claim 1 , wherein the steps are performed in any order.

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

11. 2. The method of claim 1, wherein the first and second metal halide precursors in steps i. and ii. independently comprise a divalent cation.

12. The method of claim 11, wherein each divalent cation is independently selected from Pb 2+ and Sn 2+ .

13. The first metal halide precursor has the general formula BX 2 and The second metal halide precursor has the general formula BX' 2 and 2. The method of claim 1, wherein each B may be the same or different and is selected from a metal cation; and X and X' are different and each independently selected from a halide anion.

14. The first metal halide precursor has the general formula BX and the second metal halide precursor has the general formula BX' 3 or vice versa, 2. The method of claim 1, wherein each B, which may be the same or different, is a metal cation, and X and X' are different and independently selected from halide anions.

15. The inorganic halide precursor in step iii. has the general formula AX, 10. The method of claim 1, wherein A comprises a monovalent metal cation and X is a halide anion.

16. The method of claim 15, wherein A is selected from Cs, K, and Rb.

17. The inorganic halide precursor in step iii) is Cs ＋ 2. The method of claim 1, wherein the iodide is selected from the group consisting of bromides and iodides of

18. When present, the first, second, and third organohalide precursors have the general formula A'X, A"X, and A'"X, respectively; 10. The method of claim 1, wherein A', A" and A'" are independently selected from monovalent organic cations.

19. The first organic halide precursor has the general formula A'X:

19. The method of claim 18, wherein A' is selected from MA, FA, and EA.

20. The second organic halide precursor has the general formula A″X:

19. The method of claim 18, wherein A" is selected from MA, FA, GA, EA, BzA, BA, DMA, Im, PEA and Ac.

21. The third organic halide precursor has the general formula A'''X, 19. The method of claim 18, wherein A''' is selected from MA, FA, GA, EA, BzA, BA, DMA, Im, PEA and Ac.

22. 2. The method of claim 1, wherein the halide components of the first and second metal halide precursors in steps i. and ii. are independently selected from iodide, chloride, and bromide.

23. The method of claim 22, wherein the halide components of the first and second metal halide precursors in steps i. and ii. are independently selected from iodide and bromide.

24. 10. The method of claim 1, wherein the second metal halide precursor has a different metal component than the first metal halide precursor.

25. The perovskite material has the general formula (I): A a A' b A”cA’’’ d B x B' 1-x (X y X' 1-y ) 3 and where: A is a monovalent inorganic cation; A' is a first monovalent organic cation; A″ is a second monovalent organic cation; A''' is a third monovalent organic cation; where: all A cations A, A', A" and A''' are different from one another; B is a divalent metal cation; B' is a divalent metal cation different from B, X is a halide anion; X' is a halide anion different from X; 0≦a＜1、 0≦b＜1、 0≦c＜1、 0≦d＜1、 a + b + c + d = 1, 0≦x<1, and 0＜y＜1 The method of claim 1, wherein

26. 10. The method of claim 1, wherein the method is a layer-by-layer deposition performed one or more times in a linear sequence.

27. 10. The method of claim 1, wherein the method is carried out one or more times to obtain a desired thickness of perovskite in the range of 50 to 2000 nm.

28. 1. A method of fabricating a multi-junction photovoltaic device having two or more subcells, comprising: the first sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region comprising a perovskite material prepared by a method according to any one of claims 1 to 27; 28. A method according to claim 1, wherein another sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region, the photoactive region comprising a perovskite material prepared by a method according to any one of claims 1 to 27.

29. 2. A perovskite material obtained by the method of claim 1.

30. A semiconductor device having a photoactive region comprising the perovskite material of claim 29.

31. 31. The semiconductor device of claim 30, wherein the semiconductor device is a photovoltaic device having a photoactive region.

32. 32. The photovoltaic device of claim 31 , wherein the photoactive region comprises a thin film of perovskite material.

33. A photovoltaic device as described in claim 32, wherein the thickness of the thin film of the perovskite material is in the range of 50 nm to 2000 nm.

34. 1. A multi-junction photovoltaic device having two or more subcells, the first sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region comprising a perovskite material prepared by a method according to any one of claims 1 to 27; 28. A multi-junction photovoltaic device wherein another sub-cell comprises a photovoltaic device, the photovoltaic device having a photoactive region, the photoactive region may comprise a perovskite material prepared by the method of any one of claims 1 to 27.

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