Method of forming a perovskite film for optoelectronic devices

Abstract

A method of forming a perovskite film for an optoelectronic device is provided, the method comprising: applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate, wherein the hydrophilic region is bounded by a hydrophobic boundary; spreading the perovskite precursor solution over the hydrophilic region, wherein the perovskite precursor solution is retained within the hydrophilic region by at least a portion of the hydrophobic boundary; and drying the perovskite precursor solution to form a perovskite film on the hydrophilic region.

Description

Technical Field

[0001] This invention relates to a method for forming a perovskite film for optoelectronic devices. The method includes: applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate, and drying the perovskite precursor solution to form a perovskite film on the hydrophilic region. When the perovskite solution is applied, in response to the adhesive force between the solution and the surface of the hydrophilic region, the perovskite solution can spread over the hydrophilic region and can be retained within the hydrophilic region by defining a hydrophobic boundary. The invention also relates to a system comprising a substrate containing a hydrophilic region and an applicator for applying the perovskite precursor solution to at least a portion of the hydrophilic region. Background of the Invention

[0003] Thin-film solar cells, including perovskite light-absorbing layers, are currently attracting significant interest in the field of renewable energy generation. Perovskite films also have potential applications in many other optoelectronic devices, including light-emitting diodes (LEDs), photodiodes, transistors, and memory.

[0004] Perovskite light-absorbing films used in optoelectronic devices are characterized by a hybrid organic-inorganic perovskite crystal structure. Typically, such perovskites include repeating crystal planes in three dimensions and contain organic cations (A), such as methylammonium (MA) or formamidinium (FA), and metal cations (M) (typically Pb). 2+ or Sn 2+ Organic cations and halide anions (X) (I, Br, Cl), according to the general formula AMX3. These 3D perovskite materials possess many attractive properties for photovoltaic applications, including high light absorption coefficients, high charge carrier mobility, and fabrication via low-cost solution processing techniques. Disadvantages of 3D perovskites include low environmental stability due to weak photoinduced interactions between organic cations and surrounding halide anions, and the susceptibility of organic cations to hydrolysis upon exposure to moisture.

[0005] Layered 2D perovskites, consisting of two-dimensional perovskite crystal "plates" composed of multiple AMX3 monolayers, are attracting increasing attention in optoelectronic applications, partly due to their significantly higher stability compared to 3D perovskites. The chemical formula for Ruddlesden-Popper type 2D perovskites is R2A. n-1 M n X 3n+1n = 1 → ∞, where R is a large organic cation, such as phenylethylammonium (PEA) or butylammonium (BA), n corresponds to the average number of monolayers in each crystalline perovskite lattice, and A, M, and X are as described with respect to 3D perovskites. The longer alkyl chains or aromatic moiety of these larger cations act as spacers between the lattices, thus stabilizing the perovskite crystal structure. Furthermore, the hydrophobic nature of the cationic spacers is thought to reduce the penetration of water molecules into the perovskite lattice, thereby contributing to extended device lifetime in high-humidity environments. However, the efficiency of solar cells incorporating 2D perovskites remains relatively low compared to their 3D perovskite counterparts.

[0006] Many reported studies rely on spin-coating techniques to produce high-quality perovskite films. While these methods are effective for laboratory experiments, they are not suitable for commercial-scale production and cannot produce films with specific target shapes on substrates. Therefore, a key requirement for the widespread adoption of perovskite optoelectronic devices (whether based on 2D or 3D structures) is the development of low-cost and scalable manufacturing technologies capable of producing high-quality perovskite films, and preferably also capable of producing perovskite films with a wide variety of shapes and configurations.

[0007] Techniques such as slot-die coating and printing have been proposed for producing 3D perovskite films, including roll-to-roll (R2R) processes on flexible substrates. However, slot-die coating is not suitable for producing many desired film shapes, and quality control of perovskite films remains a challenge. In principle, printing offers greater flexibility in terms of perovskite film shape, but controlling the thickness of the perovskite film is challenging due to the difficulty in accurately and consistently loading the precursor solution over the target area. Furthermore, the printed precursor solution tends to coalesce on the substrate before drying, complicating the generation of finely resolved and tightly positioned perovskite film features.

[0008] For 2D perovskite films, scaling up is considered particularly challenging because the orientation of the 2D crystalline layers in the film affects device performance. To date, no satisfactory scalable technology has been developed for preparing high-quality 2D perovskite films.

[0009] Therefore, there is still a need for new methods for forming perovskite films for optoelectronic devices that at least partially address one or more of the aforementioned drawbacks, or provide useful alternatives.

[0010] References to patent documents or other matters given in this document as prior art should not be construed as an admission that the priority date of any such document or matter was known or that the information contained therein is part of common general knowledge. Summary of the Invention

[0011] According to a first aspect, the present invention provides a method for forming a perovskite film for an optoelectronic device, the method comprising: applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate, wherein the hydrophilic region is defined by a hydrophobic boundary; spreading the perovskite precursor solution over the hydrophilic region, wherein the perovskite precursor solution is retained within the hydrophilic region by at least a portion of the hydrophobic boundary; and drying the perovskite precursor solution to form a perovskite film on the hydrophilic region.

[0012] In some implementations, the perovskite precursor solution spreads over the hydrophilic region in response to the adhesion between the perovskite precursor solution and the surface of the hydrophilic region.

[0013] In some implementations, a certain volume of perovskite precursor solution is applied, sufficient to cover the entire hydrophilic region. This volume can be selected to produce the target thickness of the perovskite film based on the known surface area of ​​the hydrophilic region and the known concentration of the perovskite precursor solution.

[0014] In some implementations, the perovskite precursor solution is completely retained in the hydrophilic region through a hydrophobic boundary.

[0015] In some embodiments, the substrate includes a surface layer comprising a hydrophilic composition, and the hydrophilic region is located on the surface layer. The surface layer may have a thickness between about 20 nm and about 2000 nm.

[0016] In some embodiments, the hydrophilic region comprises a hydrophilic composition selectively located on a hydrophobic surface of the substrate, and the hydrophobic surface adjacent to the hydrophilic region defines a hydrophobic boundary. The water contact angle of the hydrophobic surface can be greater than 50°, for example, greater than 60°, and can be determined, for example, by placing a 2 μL droplet on a dry surface and measuring the water contact angle using a water contact angle measurement system (e.g., Dataphysics OCA 15EC). The hydrophobic surface can be selected from polymer surfaces and metal surfaces.

[0017] The hydrophilic composition can be a hydrophilic semiconductor, such as a hole transport semiconductor, used to transfer charge to and / or from a perovskite film in an optoelectronic device, which can be selected from PEDOT:PSS and conjugated polymers having ionic or polar side chains.

[0018] In some embodiments, the hydrophilic region is a region of the hydrophilic surface of the substrate, and a hydrophobic composition selectively located on the hydrophilic surface and adjacent to the hydrophilic region defines the hydrophobic boundary. The water contact angle of the hydrophobic composition can be greater than 50°, for example greater than 60°, or greater than 90°, for example determined by placing a 2 μL droplet on a dry surface and measuring the water contact angle using a water contact angle measurement system (e.g., Dataphysics OCA 15EC). The hydrophobic composition may contain at least one selected from hydrophobic polymers, hydrophobic small organic molecules, metals, and metal oxides. The hydrophobic composition may be present at least partially on the hydrophilic surface in the form of a line. In some such embodiments, the line defines the hydrophobic boundary of adjacent hydrophilic regions of the substrate, and the method includes applying a perovskite precursor solution to portions of the adjacent hydrophilic regions respectively to form an unconnected perovskite film on the adjacent hydrophilic regions. The thickness of the line can be less than about 1 mm, preferably less than about 0.5 mm.

[0019] In some implementations, perovskite films are formed by hydrophobic boundaries in geometric shapes, patterns, or markings.

[0020] According to a second aspect, the present invention provides a method for forming a perovskite film for an optoelectronic device, the method comprising: applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate; spreading the perovskite precursor solution over the hydrophilic region in response to an adhesive force between the perovskite precursor solution and the surface of the hydrophilic region; and drying the perovskite precursor solution to form a perovskite film on the hydrophilic region.

[0021] In some embodiments of the second aspect, the hydrophilic region is defined by a hydrophobic boundary, wherein at least a portion of the perovskite precursor solution is retained within the hydrophilic region through the hydrophobic boundary.

[0022] In some embodiments of the second aspect, the substrate includes a surface layer containing a hydrophilic composition, and the hydrophilic region is located on the surface layer. The surface layer may have a thickness between about 20 nm and about 2000 nm. The hydrophilic composition may be a hydrophilic semiconductor, such as a hole-transfer semiconductor, for transferring charge to and / or from a perovskite film in an optoelectronic device, and may be selected from PEDOT:PSS and conjugated polymers having ionic or polar side chains.

[0023] In some embodiments of the first and second aspects, the water contact angle of the hydrophilic region is less than 45°, for example less than 30°, or less than 10°, for example determined by placing a 2 μL droplet on a dry surface and measuring the water contact angle using a water contact angle measurement system (e.g., Dataphysics OCA 15EC).

[0024] In some embodiments of the first and second aspects, the viscosity of the perovskite precursor solution is from 0.6 to 600 mPa·s.

[0025] In some embodiments of the first and second aspects, during drying, the temperature of the perovskite precursor solution on the hydrophilic region is at least 30°C, for example, in the range of 40°C to 80°C.

[0026] In some embodiments of the first and second aspects, the method further includes heating the substrate to a temperature of at least 30°C, for example, in the range of 40°C to 80°C, at least one of the following: before, during, and after application. In some such embodiments, the substrate is heated before application.

[0027] In some embodiments of the first and second aspects, the method includes applying a perovskite precursor solution to a plurality of hydrophilic regions of a substrate, respectively, to form a perovskite film on each hydrophilic region. The perovskite film can be patterned on the substrate.

[0028] In some embodiments of the first and second aspects, the perovskite precursor solution is a lead (Pb) perovskite precursor solution. The Pb concentration in the perovskite precursor solution may be less than 0.7 mol / L, for example less than 0.6 mol / L, or less than 0.5 mol / L, for example between about 0.2 and about 0.3 mol / L.

[0029] In some embodiments of the first and second aspects, the perovskite precursor solution is a 2D perovskite precursor solution. The 2D perovskite may be R2A. n-1 Pb n X 3n+1 The form of (BA)₂(MA)₃Pb₄I₃ is given, wherein each A is independently an organic cation selected from methylammonium (MA) and formamidinium (FA), each R is an organic cation larger than each A, such as selected from phenylacetium (PEA) and butylammonium (BA), and each X is independently a halide anion. 2D perovskites may have the form (BA)₂(MA)₃Pb₄I₃. 13 In the form of.

[0030] In some embodiments of the first and second aspects, applying the perovskite precursor solution includes drop-coating the perovskite precursor solution onto a hydrophilic region.

[0031] In some embodiments of the first and second aspects, applying the perovskite precursor solution includes applying a line of the perovskite precursor solution onto the hydrophilic region.

[0032] In some embodiments of the first and second aspects, the method further includes supplying a substrate in the form of a roll below the applicator, wherein the applicator applies a perovskite precursor solution to at least a portion of the hydrophilic region as the hydrophilic region is supplied through the applicator.

[0033] According to a third aspect, the present invention provides a system comprising: a substrate containing a hydrophilic region, wherein the hydrophilic region is defined by a hydrophobic boundary; and an applicator for applying a perovskite precursor solution to at least a portion of the hydrophilic region, wherein once applied, the perovskite precursor solution spreads over the hydrophilic region and remains within the hydrophilic region through at least a portion of the hydrophobic boundary.

[0034] In some embodiments of the third aspect, the system further includes a feeder configured to supply a substrate in the form of a roll below the applicator, wherein the applicator is configured to apply a perovskite precursor solution to at least a portion of the hydrophilic region as the hydrophilic region is supplied through the applicator.

[0035] In some embodiments of the third aspect, the system further includes a heater to heat the substrate to a temperature of at least 30°C, for example, a temperature in the range of 40°C to 80°C. The heater may include a heating surface configured to contact the substrate at least once before, during, and after application.

[0036] In some embodiments of the third aspect, the system further includes a reservoir containing a perovskite precursor solution for application by an applicator.

[0037] In some implementations of the third aspect, the applicator is configured to drop a perovskite precursor solution onto a hydrophilic region.

[0038] In some embodiments of the third aspect, the applicator is configured to apply lines of the perovskite precursor solution onto the hydrophilic region.

[0039] According to a fourth aspect, the present invention provides a perovskite film for optoelectronic devices, which is produced by a method according to any embodiment disclosed herein.

[0040] When the terms “comprise”, “comprises” and “comprising” are used in the specification (including the claims), they should be interpreted as specifying the said feature, integer, step or component, but do not exclude the presence of one or more other features, integers, steps or components or groups thereof.

[0041] Other aspects of the invention are set forth in the following detailed description of the invention. Brief description of the attached diagram

[0043] Embodiments of the present invention will be described herein by way of example only, with reference to the accompanying drawings, wherein:

[0044] Figure 1A typical thin-film solar cell structure is schematically depicted, including a perovskite film that can be produced by the method according to the invention.

[0045] Figure 2 A method for forming a perovskite film according to an embodiment of the present invention is illustrated schematically.

[0046] Figure 3 A method for forming a perovskite film according to another embodiment of the present invention is illustrated schematically.

[0047] Figure 4 A method for forming a perovskite film according to another embodiment of the present invention is illustrated schematically.

[0048] Figure 5 These are photographs of star-shaped, pentagonal, and heart-shaped perovskite films produced in Embodiment 2 of the present invention.

[0049] Figure 6 This is a photograph of a perovskite film in the form of adjacent rectangular parallel stripes or wavy stripes produced in Embodiment 2 of another embodiment of the present invention.

[0050] Figure 7 A method for forming a perovskite film according to the embodiment of the present invention used in Example 3 is illustrated schematically.

[0051] Figure 8 A photograph shows the sequence of spreading and drying of the perovskite precursor solution according to an embodiment of the present invention used in Example 3.

[0052] Figure 9 The ultraviolet-visible absorption spectrum and photoluminescence (PL) emission spectrum of the perovskite film produced according to the embodiment of the present invention used in Example 3 are shown.

[0053] Figure 10 The light absorption analysis across the diameter of the perovskite film is shown. The perovskite film was produced according to the embodiment of the invention used in Example 3.

[0054] Figure 11 The image is a cross-sectional image of the perovskite film produced according to the embodiment of the present invention used in Example 3, taken by scanning electron microscopy.

[0055] Figure 12 X-ray diffraction patterns of perovskite films produced by drying at room temperature and 50°C according to the embodiment of the present invention used in Example 4 are depicted.

[0056] Figure 13 It is a histogram of the power conversion efficiency of a solar cell containing a perovskite layer, which is produced in the same manner as evaluated in Example 5 according to an embodiment of the present invention.

[0057] Figure 14 This is a graph of current density-voltage (JV) curves obtained by forward and reverse scanning of a solar cell containing a perovskite layer produced according to an embodiment of the invention evaluated in Example 5.

[0058] Figure 15 The method of coating a perovskite precursor solution onto a substrate using a slot die, as described in Example 7, is illustrated schematically.

[0059] Figure 16 These are photographs of perovskite films of varying thicknesses produced in Example 8 according to an embodiment of the present invention by applying a perovskite precursor solution of varying volume to a hydrophilic region of similar square size.

[0060] Figure 17 It shows in Figure 16 Light absorption analysis across the entire width of the perovskite film is shown.

[0061] Figure 18 This is a photograph of a perovskite film in the shape of an elongated strip produced in Embodiment 9 of another embodiment of the present invention. Invention Details

[0063] This invention relates to a method for forming a perovskite film for optoelectronic devices. The method typically includes: applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate, and drying the perovskite precursor solution to form a perovskite film on the hydrophilic region.

[0064] Once applied, the perovskite precursor solution spreads over the hydrophilic regions, covering the initially uncovered portions. This spreading is driven by adhesive forces between the polar perovskite precursor solution and the hydrophilic surface, strong enough to overcome cohesive forces in the solution and minimize its surface area. Therefore, the hydrophilicity of the hydrophilic regions allows for the formation of a thin, uniform wet film before drying to produce perovskite crystals. This mode of perovskite film formation thus distinguishes it from spin coating, where the solution is non-selectively applied to the substrate, high centrifugal forces cause the solution to flow over and out of the edges of the rotating substrate and / or dewet from selected areas on the substrate, and the solution dries simultaneously and rapidly due to enhanced convection caused by rotation.

[0065] The inventors have discovered that spreading provides high-quality perovskite films with a satisfactory, consistent thickness. For example, such films offer superior solar cell performance compared to films with similar perovskite loadings and compositions but prepared using slit-die coating techniques. Furthermore, because the construction of the perovskite film is independent of the precision of applying the precursor solution to the substrate, this method is particularly suitable for scalability and process reproducibility.

[0066] In a preferred embodiment of the invention, the hydrophilic region of the substrate is defined by a hydrophobic boundary, and the perovskite precursor solution is retained within the hydrophilic region along at least a portion of the hydrophobic boundary. The perovskite precursor solution is applied only to a portion of the hydrophilic region and then spread over the substrate across the initially uncovered area until it reaches the hydrophobic boundary and is retained within the hydrophilic region through that boundary. It is not intended to be theoretically constrained, but it is believed that in at least some embodiments, solution retention is controlled by the repulsion of the polar precursor solution by the hydrophobic material of the boundary. The hydrophobic boundary advantageously allows the perovskite film to form on the substrate in various arbitrary shapes without requiring precise placement of the precursor solution. Furthermore, since the precursor solution will tend to fill the hydrophobically defined hydrophilic region without overflowing the boundary, the thickness of the resulting perovskite film can be varied and controlled solely based on the volumetric loading of the precursor solution.

[0067] In some preferred embodiments of the invention, the temperature of the precursor solution is increased during at least the drying step. This can be achieved by heating the substrate before, during, and / or after the application of the precursor solution. Heating the substrate is considered to facilitate the spread of the solution in the hydrophilic regions, so heating the substrate before the application of the precursor solution may be advantageous. Furthermore, in at least some embodiments, the increased temperature of the precursor solution during drying improves the crystal morphology of the resulting perovskite film. In particular, the inventors have found that forming a 2D perovskite film during a heated drying step produces a vertical, self-assembled orientation of 2D perovskite crystal sheets, i.e., perpendicular to the substrate surface, which improves performance in solar cell applications.

[0068] Optoelectronic devices

[0069] The disclosed method is considered particularly useful for forming perovskite films for solar cells, and it will be convenient to further discuss the invention in the context of such devices. However, the invention is considered applicable to a wide range of other optoelectronic devices, including but not limited to light-emitting diodes, photodiodes, transistors, and memories.

[0070] Perovskite solar cell structures typically include a perovskite light-harvesting film sandwiched between a hole-transporting (p-type) semiconductor layer and an electron-transporting (n-type) semiconductor layer. The perovskite has a band gap, which is typically tuned to absorb a broad range of the visible spectrum, and sufficient diffusion distance to allow charge separation to pass through the charge transport layer to the adjacent conductive electrode.

[0071] Figure 1 The image depicts a typical thin-film solar cell structure comprising a perovskite light-absorbing layer 11, a hole transport layer 12, an electron transport layer 13, a conductive bottom electrode 14, and a conductive back contact electrode 15. Optionally, the device is constructed by sequentially applying functional layers to a substrate 16. The substrate 16, the bottom electrode 14, and the hole transport layer 12 are transparent, such that in use, the solar cell is configured to be illuminated by light 17, which passes through the transparent substrate 16 and layers 14 and 12 and is absorbed by the perovskite film 11. Photoelectrons 18, generated by photoelectrolysis, are then extracted to the back contact electrode 15 via the electron transport layer 13, while holes 19 are extracted to the bottom electrode 14 via the hole transport layer 12. Electrons travel through an external circuit 20 and recombine with holes at the cathode, thus enabling electrical work to be performed in the electrical components 21 of the circuit.

[0072] Alternatively, a transparent electron transport layer 12 and a hole transport layer 13 can be used (according to...). Figure 1 The device is manufactured using the number (of the device). In this case, electrons 19 are extracted to the bottom electrode 14 via the electron transport layer 12, while holes 18 are extracted to the back contact electrode 15 via the hole transport layer 13.

[0073] Perovskite precursor solution

[0074] This invention includes the step of applying a perovskite precursor solution to a hydrophilic region of a substrate. As used herein, a perovskite precursor solution is a solution containing dissolved ionic components that, when concentrated (e.g., by drying), crystallize to form a perovskite structure. A wide variety of such perovskite precursor solutions have been previously reported, and this invention is considered broadly applicable to the formation of perovskite films using these materials. Typically, the precursor solution preferably contains each component in substantially the stoichiometric ratio of the target perovskite structure; however, it should be understood that solutions significantly deviating from this ideal state can be used to form perovskite structures.

[0075] The perovskite precursor solution contains dissolved divalent metal cations (M), which can be Pb. 2+ or Sn 2+ Pb is preferred 2+ The perovskite precursor solution contains an inorganic anion (X), which can be a halide ion, such as I... - ,Br - or Cl - It has been reported that the band gap of perovskites can be tuned by the relative proportion of halide ions, and correspondingly, the selection and proportion of halide ions in the solution can be chosen. In some embodiments, the halide ions are predominantly or solely I-. -The perovskite precursor solution contains a monovalent organic cation, at least a portion of which is a small organic cation (A) capable of incorporating into the AMX3 perovskite unit structure, such as methylammonium (MA) or formamidinium (FA). In some embodiments, a portion of the organic cation is a larger organic cation (R), such as phenylethylammonium (PEA), butylammonium (BA), isobutylammonium (iso-BA), pentylammonium (PentA), and propylammonium (PropA).

[0076] Precursor solutions can be prepared by dissolving the precursor salt in a solvent. Precursor salts typically consist of component cations and anions, and therefore have the forms MX2, AX, and RX. The solvent is usually a polar solvent because it must be able to dissolve the component ions. Furthermore, the solvent should have suitable volatility to allow it to dry on the substrate, thereby allowing the perovskite to crystallize. A suitable solvent is dimethylformamide (DMF). It will be appreciated that perovskite precursor solutions are inherently polar due to the polarity of the support solvent and the content of the dissolved salt.

[0077] Once the perovskite precursor solution is applied, it is required to spread over the surface of the hydrophilic region. Therefore, the solution should have a suitable viscosity to allow for this spreading. In some embodiments, a suitable viscosity is lower than that typically desired by coating or printing methods such as slot-mode coating or gravure printing. This viscosity can be in the range of 0.6 to 600 mPa·s. In the case of the lead perovskite precursor solution in DMF, the inventors have found that a suitable viscosity is less than 0.7 mol / L of Pb concentration, for example less than 0.6 mol / L, or less than 0.5 mol / L, or about 0.3 mol / L.

[0078] In some embodiments, the perovskite precursor solution is a 3D perovskite precursor solution. As used herein, a 3D perovskite precursor solution is a solution that produces a 3D perovskite crystal structure upon drying.

[0079] In some embodiments, the perovskite precursor solution is a 2D perovskite precursor solution. As used herein, a 2D perovskite precursor solution is a solution that produces a 2D perovskite crystal structure upon drying. The 2D perovskite precursor solution can produce a crystal with the formula R2A. n-1 M n X 3n+1 (where n = 1 → ∞) Ruddlesden-Popper type 2D perovskite. In some embodiments, n is less than or equal to about 5. In some embodiments, n is 4 or 5. In some embodiments, R is selected from one or more of BA, iso-BA, PEA, PentA, and PropA. In some embodiments, A is MA, and M is Pb. 2+ And X is I - In some embodiments, the 2D perovskite has the formula R2A3M4X13 Where R is BA, A is MA, and M is Pb, arbitrarily chosen. 2+ And X is I - This precursor solution can be prepared by dissolving PbI₂, MAI, and BAI in a solvent, such as dimethylformamide (DMF), at a molar ratio of 4:3:2, for example, for 1 hour at 70°C. In some embodiments, the 2D perovskite has the formula R₂A₄M₅X. 16 Optionally, R is selected from BA, iso-BA, PEA, PentA, and PropA, A is MA, and M is Pb. 2+ X is I - .

[0080] The inventors have found that the method of the present invention is particularly advantageous for preparing 2D perovskite films. The substantially continuous process of spreading the precursor solution under adhesive force control, followed by drying to crystallize the perovskite, produces well-controlled 2D perovskite film thickness. Furthermore, the opportunity to raise the temperature during application and drying allows for the acquisition of highly oriented, vertical 2D crystal morphologies. Another advantage is that the process can be carried out in air, i.e., without any humidity control.

[0081] The perovskite precursor solution may contain a variety of additives that have been reported to produce favorable perovskite properties in optoelectronic devices. For example, FA or cesium cations may be added. Additives such as NH4SCN and / or NH4Cl may also be included.

[0082] The base including the hydrophilic area

[0083] The substrate comprises at least one hydrophilic region to which a precursor solution is applied. As used herein, according to the principles disclosed herein, the hydrophilic region is a region of the substrate comprising a surface that is sufficiently hydrophilic to wet and spread the perovskite precursor solution. A simple way to quantify surface hydrophilicity is by the water contact angle, for example, by placing a 2 μL droplet on a dry surface using a laboratory contact angle system (e.g., Dataphysics OCA 15EC). In some embodiments, the water contact angle of the hydrophilic region is less than 45°, for example less than 30°, or less than 20°, or less than 10°.

[0084] The entire substrate can be composed of a hydrophilic material. However, in some embodiments, the substrate includes a surface layer formed of a hydrophilic composition, and then hydrophilic regions form at least a portion of this surface layer. In such... Figure 1 In the case of a solar cell or various other optoelectronic devices schematically shown, the hydrophilic surface layer may be a semiconductor layer 12, which may be a hole transport layer or an electron transport layer depending on the device construction.

[0085] In embodiments where the hydrophilic surface layer is a hole transport semiconductor layer, the hydrophilic composition of this layer can be poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS). The PEDOT:PSS film exhibits suitable hydrophilicity: the inventors have determined that the water contact angle, measured 1 second after drop-off, is 24-25°, decreasing to less than 5° after 10 seconds, and then stabilizing (this dynamic behavior is believed to be due to water absorption into the PEDOT:PSS layer). Furthermore, the transparency of the PEDOT:PSS layer is particularly advantageous for solar cell applications. Other suitable hole transport semiconductor layers may include other semiconductor conjugated polymers with ionic or polar side chains reported in the art, such as those disclosed in the Journal of Colloid and Interface Science 2018, 26, 21-26, or inorganic hole transport layers such as NiO. x .

[0086] The thickness of the hydrophilic surface layer can be between about 20 nm and about 2000 nm, typically less than 1000 nm. This layer can be deposited on the substrate using standard methods, including coating and printing methods. In some embodiments, as will be described in more detail below, the hydrophilic surface layer can be patterned onto the substrate to define the structure of the perovskite film subsequently produced by the method of the present invention. Therefore, printing techniques such as screen printing, inkjet printing, and gravure printing are particularly preferred.

[0087] In some implementations, the substrate containing the hydrophilic region is a flexible substrate that can be configured to be suitable for roll-to-roll (R2R) manufacturing technology. Optionally, the hydrophilic surface layer and the perovskite precursor solution are sequentially applied to the roll during the R2R production process.

[0088] hydrophobic boundary

[0089] In embodiments of the invention, the hydrophilic region is defined by a hydrophobic boundary. As used herein, a hydrophobic boundary is a region or line that borders the hydrophilic region and has a sufficiently hydrophobic (relative to) surface, such that the perovskite precursor solution adjacent to the boundary is selectively retained within the hydrophilic region according to the principles disclosed herein, for example as a result of spreading over the hydrophilic region and reaching the boundary.

[0090] In some embodiments, the substrate itself has a hydrophobic surface, and the hydrophilic region is formed by a hydrophilic composition selectively located on the hydrophobic surface. In such cases, the hydrophobic surface adjacent to the hydrophilic region can provide a hydrophobic boundary.

[0091] refer to Figure 2For example, the surface of substrate 31 is hydrophobic. A hydrophilic layer 32 (e.g., a PEDOT:PSS coating with a thickness of about 30 nm) is formed on substrate 31 in a rectangular form, thereby defining a rectangular hydrophilic region 33 on the substrate. Adjacent regions of substrate 31 define a rectangular hydrophobic boundary 35 around the hydrophilic region.

[0092] It should be understood that the hydrophilic layer can be provided in any desired shape, including geometry, markings, and patterns. Furthermore, it is not necessary for the hydrophobic boundary provided by the adjacent hydrophobic substrate surface to completely surround the hydrophilic region. For example, a narrow strip of hydrophilic layer can be created across the width or length of the substrate, such that the hydrophilic region is only hydrophobically defined on both sides.

[0093] A hydrophilic layer can be selectively formed on a substrate using known methods, such as coating or printing techniques like screen printing, inkjet printing, and gravure printing. It is also contemplated that the hydrophilic composition can be selectively positioned on a hydrophobic surface in ways other than applying discrete surface layers. For example, the hydrophilic composition can be selectively infiltrated into the porous surface of the hydrophobic substrate, or regions of the substrate can be selectively surface-modified to transform the hydrophobic surface into a hydrophilic composition. In another variation, regions or lines of a continuous hydrophilic surface layer can be selectively removed, for example by abrasion, dissolution, or etching, to expose the underlying hydrophobic substrate, thereby creating a hydrophobic boundary.

[0094] The hydrophobic surface of the substrate can have a water contact angle greater than 50°, for example, greater than 60°. The hydrophobic surface can be selected from polymer surfaces and metal surfaces. A suitable hydrophobic substrate is polyethylene terephthalate (PET), which can be used as a roll substrate in R2R manufacturing processes.

[0095] In some embodiments, the substrate has a hydrophilic surface, which may optionally be provided by a hydrophilic surface layer disclosed herein. A hydrophobic composition is then selectively positioned on the hydrophilic surface to provide a hydrophobic boundary for a specific hydrophilic region on a broader hydrophilic substrate surface.

[0096] Reference Figure 3 For example, the surface of substrate 61 is hydrophilic because a hydrophilic surface layer 62 is present. The hydrophilic layer 62 (e.g., a PEDOT:PSS coating with a thickness of about 30 nm) can be coated onto substrate 61 using known techniques. Then, a hydrophobic composition 64 is applied to the surface of the hydrophilic layer 62 in the form of rectangular lines. The rectangular hydrophobic boundary 65 formed by composition 64 thus defines a rectangular hydrophilic region 63 on the substrate.

[0097] The hydrophobic boundary can define any desired shape of the hydrophilic region, including geometry, markings, and patterns. The line width of the hydrophobic boundary is not considered particularly limited, provided that sufficient hydrophobic composition is provided to retain the perovskite precursor solution. In some embodiments, the line width is less than 5 mm, or less than 1 mm, or less than 0.5 mm. The hydrophobic boundary does not necessarily completely enclose the hydrophilic region. For example, an elongated hydrophilic region on a hydrophilic substrate surface may be defined only on both sides by lines of the hydrophobic composition. Furthermore, the hydrophobic boundary can be discontinuous, such as a dotted line of the hydrophobic composition along the edge of the target hydrophilic region. Therefore, it should be understood that the limitations on the construction of the hydrophobic boundary do not exceed the requirement that it can retain the perovskite precursor solution according to the principles disclosed herein.

[0098] Hydrophobic compositions that form boundaries can create surface layers or raised lines above hydrophilic surfaces, or they can penetrate into porous surfaces of hydrophilic substrates. It is also considered that selective surface modification to locally convert hydrophilic surfaces into hydrophobic compositions can create hydrophobic boundaries on hydrophilic substrates.

[0099] Hydrophobic compositions can be applied using known techniques, including coating, printing, and line application by nozzles or needles. The hydrophobic composition can also be applied as an ink formulation along with a volatile carrier fluid that evaporates upon application.

[0100] Hydrophobic compositions can typically contain any suitable hydrophobic material, including hydrophobic polymers, waxes, small organic molecules, metals, and metal oxides. Examples of suitable materials are hydrophobic poly(triarylamine) (PTAA) polymers, such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]. In some embodiments, the water contact angle of the hydrophobic composition is greater than 50°, for example greater than 60°, or greater than 90°. The hydrophobic composition can be chosen to exist as a substantially solidified and non-volatile composition within the hydrophobic boundary. However, it is not excluded that the hydrophobic composition can be a liquid, such as a viscous liquid. Furthermore, the hydrophobic composition can be volatile, provided that it remains on a hydrophilic substrate for a sufficient time to retain the perovskite precursor solution in the method of the present invention.

[0101] As disclosed herein, a hydrophobic boundary can include lines of a hydrophobic composition formed on the hydrophilic surface of a substrate. Therefore, these lines can define the hydrophobic boundaries of adjacent hydrophilic regions to which the perovskite precursor solution is also applied. In this way, close but unconnected perovskite films can be prepared on a hydrophilic substrate.

[0102] Applying, spreading and shaping perovskite precursor solutions

[0103] The method of the present invention includes the step of applying a perovskite precursor solution to at least a portion of a hydrophilic region of a substrate, such that the perovskite precursor solution is then spread over the hydrophilic region.

[0104] In some embodiments, at least the hydrophilic region of the substrate is heated before, during, and / or after the application of the precursor solution. Heating the substrate before or during application can advantageously help the solution spread over the hydrophilic region. Furthermore, this heating can advantageously increase the temperature of the precursor solution during the drying step, as will be described in more detail below. The substrate can be heated to a temperature of at least 30°C, for example, 40°C to 80°C.

[0105] Because this invention does not rely on the precise placement of the perovskite precursor solution on the hydrophilic region of the substrate, a variety of application methods can be employed. For example, the perovskite precursor solution can be appropriately drop-coated onto the hydrophilic region according to its structure, or applied as lines. Single-site drop-coating may be particularly suitable for small, enclosed hydrophilic regions, while lines may be more suitable for elongated hydrophilic regions. Coating or printing techniques can also be used.

[0106] The solution can be applied to one or more portions of any size in the hydrophilic region. The perovskite precursor solution can optionally be applied separately to more than one portion of the hydrophilic region, allowing coalescence during spreading; this may be preferred for regions with larger surface areas. When the perovskite precursor is applied, the substrate is typically substantially horizontal, allowing the solution to spread over the hydrophilic region and form a uniformly distributed wet film.

[0107] Given that some methods of the present invention form the resulting perovskite film by spreading the precursor solution until it is repelled by a hydrophobic boundary, it is preferable to selectively apply the precursor solution to hydrophilic regions (or regions) on the substrate. Therefore, in some embodiments, the precursor solution is not applied to or over the hydrophobic boundary or other hydrophilic regions on the substrate. However, it will be understood that, according to the principles disclosed herein, selectively applying the precursor solution to a portion of the hydrophilic region includes application not only away from but also adjacent to the hydrophobic boundary defining the hydrophilic region, provided that the solution can then spread over the hydrophilic region and be retained by the hydrophobic boundary.

[0108] Optionally, the perovskite precursor solution can be applied in an R2R process. The substrate can thus be supplied in roll form below an applicator, which applies the perovskite precursor solution to the hydrophilic region of the substrate as it is fed through the applicator. The roll can be heated in-line, for example, on a heated backing plate, before, during, and / or after application.

[0109] Once applied to one or more portions of the hydrophilic region, the perovskite precursor solution spreads onto the hydrophilic region of the substrate. The solution spreading responds to the adhesive forces between the polar perovskite precursor solution and the surface of the hydrophilic region; gravity may also play a role. However, spreading does not depend on centrifugal force. Therefore, in embodiments of the invention, the hydrophilic region does not rotate or turn at all during the coating or spreading of the precursor solution.

[0110] In embodiments of the invention, as previously disclosed herein, a hydrophilic region is defined by a hydrophobic boundary. Upon application, the perovskite precursor solution spreads over the hydrophilic region until it encounters the hydrophobic boundary. The solution is then retained within the hydrophilic region by at least a portion of the hydrophobic boundary.

[0111] The solution can be retained substantially along the entire hydrophobic boundary. This is preferably the case, for example, when the hydrophobic boundary completely surrounds the hydrophilic region. For this purpose, a certain volume of perovskite precursor solution should be applied to cover the entire hydrophilic region.

[0112] The advantage of this invention lies in its ability to control the thickness of the perovskite film solely based on the volumetric loading of the precursor solution. This is because different volumes of precursor solution can be selectively retained on hydrophilic regions of similar size and hydrophobically defined boundaries. Furthermore, the surface area of ​​the target hydrophilic region and the concentration of the perovskite composition are typically known. Therefore, the thickness of the perovskite film can be precisely controlled by selecting the applied volume of the precursor solution. Obviously, this control is only significant within the thickness range, as applying an excessive volume of precursor solution can lead to undesirable overflow across the hydrophobic boundary.

[0113] In some implementations, the solution is retained only along a portion of the hydrophobic boundaries. For example, when an elongated hydrophilic region is defined by two parallel hydrophobic boundaries, a perovskite precursor solution line applied along the middle of the region will spread outwards until it encounters and is retained by the two hydrophobic boundaries. Well-structured elongated strips of perovskite films with parallel edges can be produced without filling the entire hydrophilic region, for example... Figure 18 As shown in the image.

[0114] In some embodiments, adjacent hydrophilic regions of the substrate are separated by a common hydrophobic boundary. As disclosed herein, this common boundary can be a line of hydrophobic composition formed on the hydrophilic surface of the substrate. Alternatively, layers of hydrophilic composition can be selectively positioned adjacent to each other on the hydrophobic substrate, with the middle line of the underlying hydrophobic substrate serving as the common hydrophobic boundary. The advantage of this invention is that tightly positioned but unconnected perovskite films can be prepared in this manner because the common hydrophobic boundary prevents the precursor solution applied in each hydrophilic region from coalescing. In contrast, tightly positioned printed features without boundary separation are prone to coalescing, especially on hydrophilic substrates. The inventors believe that the method of this invention can be used to prepare discontinuous perovskite films with intervals of less than 1 mm or less than 0.5 mm.

[0115] The method of the present invention is therefore suitable for preparing multiple perovskite films with similar or different structures on a substrate surface, since the perovskite precursor solution can be applied separately to each hydrophilic region on the substrate. In this way, a variety of perovskite film patterns and shapes can be produced for functional and / or aesthetic reasons.

[0116] Drying the precursor solution

[0117] The method of the present invention includes the step of drying a perovskite precursor solution to form a perovskite film on a hydrophilic region of a substrate. Although drying typically begins immediately after the application of the precursor solution, the drying rate is usually controlled such that perovskite crystallization does not begin until the solution has spread to the required extent in the hydrophilic region.

[0118] In some embodiments, the temperature of the perovskite precursor solution is raised in the hydrophilic regions as the solution is dried to form a perovskite film. The solution can be heated indirectly, i.e., by heating the substrate. The temperature during drying provides primary control over the solvent evaporation rate, and it should be understood that the preferred temperature may depend on the properties of the perovskite precursor solution, particularly the solvent. In some embodiments, the temperature of the precursor solution during drying is at least 30°C, for example, in the range of 40°C to 80°C, or in the range of about 45°C to about 65°C.

[0119] In the case of 2D perovskite precursor solutions, the inventors discovered that the drying temperature range provides excellent vertical alignment of the 2D crystalline perovskite structure, thereby improving performance in solar cell applications. Furthermore, a suitable balance is provided between spreading rate and drying rate, for example, when using DMF as a solvent.

[0120] Once the perovskite film crystallizes, it can be subjected to further processing steps, including annealing at higher temperatures to remove residual solvents.

[0121] Implementation Plan

[0122] Now refer to Figure 2 Embodiments of the present invention are described herein. As described herein, a hydrophilic layer 32 (e.g., a printed PEDOT:PSS coating with a thickness of about 30 nm) is selectively located on a hydrophobic substrate 31 (e.g., a PET film). Thus, the surface of the hydrophilic layer 32 provides a rectangular hydrophilic region 33, which is defined by a hydrophobic boundary 35 formed by adjacent regions of the substrate 31.

[0123] For example, the substrate 31 is heated to a temperature of approximately 60°C to 70°C via a heated backplate (not shown). Figure 2 As shown in (a), the perovskite precursor solution 36 is then drop-applied from the applicator 37 (e.g., a needle) onto the central portion 38 of the hydrophilic region 33. The perovskite precursor solution 36 can be a 2D perovskite precursor solution, for example, a solution of PbI2, MAI, and BAI in DMF with a molar ratio of 4:3:2, and a Pb concentration of approximately 0.3 mol / L. Due to the hydrophilicity of the hydrophilic region 33, the precursor solution spreads isotropically in the outward direction according to Fick's first law, forming a thin wet film.

[0124] like Figure 2 As shown in (b), the perovskite precursor solution 36 spreads until it reaches the hydrophobic boundary 35, where it remains in the hydrophilic region 33 through the boundary portion 35a, while continuing to spread on the hydrophilic region 33. Figure 2 As shown in (c), the precursor solution 36 covers the entire hydrophilic region 33 and is retained along the entire hydrophobic boundary 35. Optionally, an additional volume of the precursor solution 36 may be added before or after complete coverage of the hydrophilic region 36 to ensure that sufficient total volume is added to cover the hydrophilic region and achieve the target perovskite film thickness.

[0125] Due to the heating of substrate 31, the wet film of perovskite precursor solution 36 is dried at an elevated temperature, for example, above 50°C but below 70°C. This elevated temperature promotes drying while still allowing the precursor solution 36 to fully spread before perovskite crystallization begins. Once the concentration of the perovskite solution reaches the crystallization point during drying, perovskite crystallization typically begins from the edges of the wet film until the entire wet film is crystallized. Figure 2 As shown in (d), the perovskite film 39 is thus selectively formed on a substrate 31 in a rectangular shape defined by a hydrophilic region 33 and a hydrophobic boundary 35. A favorable vertical (i.e., out-of-plane) orientation of the 2D perovskite crystals in the film 39 is also achieved due to the increased drying temperature. Once crystallized, the film can then be further dried and heated, including annealing at higher temperatures (e.g., at about 100°C) to produce the final perovskite film suitable for optoelectronic devices.

[0126] Now refer to Figure 3Another embodiment of the invention is described. As described herein, a hydrophilic surface layer 62 (e.g., a PEDOT:PSS coating with a thickness of about 30 nm) is provided over the surface of a substrate 61. A rectangular hydrophobic boundary 65, formed by lines of a hydrophobic composition 64 (e.g., PTAA) applied to the hydrophilic surface layer 62, defines a hydrophobic boundary around a rectangular hydrophilic region 63 of the surface layer.

[0127] For example, the substrate 61 is heated to a temperature of approximately 60°C to 70°C by means of a heated backplate (not shown). Figure 3 As shown in (a), the perovskite precursor solution 66 is then drop-applied from the applicator 67 (e.g., a needle) onto the central portion 68 of the hydrophilic region 63. The perovskite precursor solution 66 can be a 2D perovskite precursor solution similar to solution 36, or alternatively, another precursor solution, such as a 3D perovskite precursor solution. Due to the hydrophilicity of the hydrophilic region 63, the precursor solution 66 spreads isotropically in the outward direction according to Fick's first law, forming a thin wet film.

[0128] like Figure 3 As shown in (b), the perovskite precursor solution 66 spreads until it reaches the hydrophobic boundary 65, where it remains in the hydrophilic region 63 through the boundary portion 65a, while continuing to spread on the hydrophilic region 63. Figure 3 As shown in (c), the precursor solution 66 eventually covers the entire hydrophilic region 63 and remains along the entire hydrophobic boundary 65.

[0129] Due to the heating of substrate 61, the wet film of perovskite precursor solution 66 dries at an elevated temperature, which is suitable for promoting drying while still allowing the precursor solution 66 to fully spread before perovskite crystallization begins. The drying of the precursor solution then initiates perovskite crystallization, and the elevated temperature also gives the resulting perovskite crystals a favorable orientation. Figure 3 As shown in (d), the perovskite film 69 is thus selectively formed on a substrate 61 in a rectangular shape defined by a hydrophilic region 63 and a hydrophobic boundary 65.

[0130] Now refer to Figure 4 Another embodiment of the invention is described. A substrate 91 has a hydrophilic surface 92 (which may be, for example, a PEDOT:PSS surface coating with a thickness of about 30 nm). Parallel lines of a hydrophobic composition 94 with a width less than 1 mm are present on the hydrophilic surface 92. Thus, elongated hydrophobic regions 93a-93d are defined on the substrate surface 92, wherein lines forming hydrophobic boundaries 65 define the hydrophilic regions on both sides. Therefore, hydrophilic regions 93a and 93b are adjacent but separated by a common hydrophobic boundary 95, and the same applies to hydrophilic regions 93b and 93c, and hydrophilic regions 93c and 93d.

[0131] For example, the substrate 91 is heated to a temperature of approximately 60°C to 70°C using a heated backplate (not shown). Then, the perovskite precursor solution 96 is applied in a linear fashion along the center of the hydrophilic region 93 using an applicator 97 (moving in the direction indicated by the arrow). Figure 4 As shown, precursor solution 96 has been applied to hydrophilic regions 93a, 93b, and 93c, and is being applied to hydrophilic region 93d. The perovskite precursor solution 96 can be a 2D perovskite precursor solution similar to solution 36, or alternatively, another precursor solution, such as a 3D perovskite precursor solution.

[0132] As seen with respect to hydrophilic region 93d, the precursor solution 96 spreads outwards after application, forming a thin wet film until it reaches the hydrophobic line boundary 95, where it remains within the hydrophilic region. Finally, as seen with respect to hydrophilic regions 93a, 93b, and 93c, the precursor solution 96 covers the entire width of the hydrophilic region and is retained along the full length of the hydrophobic boundary 65, adjacent to which the precursor solution was applied. Although adjacent hydrophilic regions 93 are very close, the precursor solution 96 in adjacent regions does not coalesce due to the shared hydrophobic boundary 95. Furthermore, the thickness of the wet film covering the hydrophilic region can be controlled by the volume distribution rate and / or the drawing speed of the applicator 97.

[0133] Due to the heating of substrate 91, the wet film of perovskite precursor solution 96 in each hydrophilic region dries at the increased temperature. For example... Figure 4 As shown in the hydrophilic region 93c, after the solution has spread to the desired extent, drying causes crystallization from the solution 96, thereby forming a perovskite film 99. Thus, a tightly positioned but unconnected perovskite film 99 is selectively formed on the substrate 91.

[0134] system

[0135] The present invention also relates to a system for performing the method of the invention. The system generally includes: a substrate comprising a hydrophilic region as disclosed herein; and an applicator for applying a perovskite precursor solution to at least a portion of the hydrophilic region. According to the principles disclosed herein, once applied, the perovskite precursor solution will spread over the hydrophilic region. In embodiments of the invention, as disclosed herein, the hydrophilic region of the substrate is defined by a hydrophobic boundary. Therefore, once applied, the solution will be retained within the hydrophilic region along at least a portion of the hydrophobic boundary.

[0136] This system can be configured to form perovskite films using a roll-to-roll process. Therefore, the system may also include a feeder configured to supply a substrate in roll form below the applicator. The feeder can be configured to unwind the roll from a feed roller, feeding it horizontally a sufficient distance to allow application, spreading, and drying, for example, across a backing plate, and forward to a rewinding roller. The applicator can then be positioned above the horizontal portion of the roll and configured to apply a perovskite precursor solution to the hydrophilic region of the substrate as the roll is fed through the applicator. It should be understood that the roll can be stationary or moving during the application of the precursor solution, and the applicator itself can be stationary or moving during application, depending on the target size and geometry of the perovskite film to be formed.

[0137] The applicator can be configured to drop a perovskite precursor solution onto a hydrophilic region, or to apply lines of the perovskite precursor solution onto a hydrophilic region. The system may further include a reservoir containing the perovskite precursor solution for application via the applicator.

[0138] The system may include a heater configured to heat the substrate to a temperature of at least 30°C, for example, a temperature in the range of 40°C to 80°C. The heater may be a heated surface, such as a backing plate, configured to contact the substrate before, during, and / or after the application of the precursor solution.

[0139] Based on the principles disclosed herein, for example when configured for roll-to-roll manufacturing, the system can also be configured to generate hydrophilic regions and / or hydrophobic boundaries on the substrate prior to the application of the perovskite precursor solution. Furthermore, the system can be configured to apply an additional layer to the substrate after the formation of the perovskite film. Therefore, it is conceivable that solar cells, for example having… Figure 1 The solar cell shown has the following structure. Example

[0140] The present invention is described with reference to the following embodiments. It should be understood that these embodiments are illustrative and do not limit the invention described herein.

[0141] Material

[0142] PbI₂ was obtained from Alfa Aesar. Methylammonium iodide (MAI) and butylammonium iodide (BAI) were obtained from GreatcellSolar. Anhydrous solvents were obtained from commercial laboratory suppliers, including Sigma-Aldrich. Patterned indium tin oxide (ITO) glass was obtained from Shenzheng Display Photoelectric Materials Co., Ltd., China. PEDOT:PSS dispersion (Baytron P AI 4083) was obtained from HC Starck. [6,6]-Phenyl C 61 Methyl butyrate (PC) 61 BM) was obtained from Nano-C. Ethoxylated polyethyleneimine (PEIE) was obtained from Aldrich, 80% ethoxylation solution.

[0143] Material characterization

[0144] Light transmission mapping was performed using an Epson Perfection V700 photogrammetric scanner. UV-Vis absorption spectra were recorded using a Lambda35 Perkin-Elmer absorption spectrometer. Photoluminescence (PL) spectra were recorded using a fluorescence spectrophotometer (LS55, Perkin-Elmer). Cu K2 was used in Rigaku SmartLab. α XRD was performed using radiation. Atomic force microscopy (AFM) was performed using a Veeco Dimension 3100 microscope (tap mode). The cross-section of the film was measured using a dual-beam focused ion beam scanning electron microscope (FIB-SEM) system. The film thickness was measured using a Dektak profilometer. The water contact angle was measured using a contact angle system (Dataphysics OCA15EC) with a 2 μL droplet placed on a dry surface. Ten repeated measurements were performed for each surface.

[0145] Solar cell performance testing

[0146] Using a Keithley 2400 Source Meter under inert atmosphere with standard solar radiation (AM 1.5G, 100mW / cm²) -2 The J–V curve was measured. Light intensity was calibrated using a reference cell (Hamamatsu S1133 with a KG5 filter and a photosensitive area of ​​2.8 × 2.4 mm), certified by NREL (PV Measurements). The light intensity was measured at 1000 W from a 1000 W xenon lamp mounted on an Oriel AAA solar simulator. -2 Calibration under AM 1.5G illumination.

[0147] External quantum efficiency (EQE) spectra were collected in ambient atmosphere using custom equipment. The light source (Oriel 150W xenon lamp) was chopped to 27Hz, and electrical signals were collected under short-circuit conditions using a low-noise current preamplifier (SR570, Stanford Research Systems) and a lock-in amplifier (SR830 DSP, Stanford Research Systems). A standard filtered Si cell from Peccell Limited (cross-calibrated with a standard reference cell traceable to NREL) was used as a reference.

[0148] Example 1. Preparation of perovskite precursor solution

[0149] 2D perovskite (BA)2(MA)3Pb4I was prepared by the following method. 13 Precursor solution: PbI₂, MAI, and BAI in a molar ratio of 4:3:2 were stirred in dimethylformamide (DMF) at 70°C for 1 hour. Pb was prepared in this manner. 2+ The concentration is 0.9 mol L. -1 0.7 mol L -1 0.5 mol L -1 0.3 mol L -1 and 0.2 mol L -1 The solution.

[0150] 2D perovskite (iso-BA)2(MA)4Pb5I was prepared by the following method. 16 Precursor solution: PbI₂, MAI, and isobutylammonium iodide (iso-BAI) in a molar ratio of 5:4:2 were stirred in dimethylformamide (DMF) at 70 °C for 1 hour. Pb was prepared in this manner. 2+ The concentration is 0.3 mol L. -1 The solution.

[0151] 2D perovskite (BA)2(MA)4Pb5I was prepared by the following method. 16 Precursor solution: PbI₂, MAI, and BAI in a molar ratio of 5:4:2 were stirred in dimethylformamide (DMF) at 70°C for 1 hour. Pb was prepared in this manner. 2+ The concentration is 0.3 mol / L. -1 The solution.

[0152] 2D perovskite (PEA)2(MA)4Pb5I was prepared by the following method. 16 Precursor solution: PbI₂, MAI, and phenylethyl ammonium iodide (PEAI) in a molar ratio of 5:4:2 were stirred in dimethylformamide (DMF) at 70 °C for 1 hour. Pb was prepared in this manner.2+ The concentration is 0.3 mol L. -1 The solution.

[0153] 2D perovskite (pentylammonium)2(MA)4Pb5I was prepared by the following method. 16 Precursor solution: PbI₂, MAI, and pentylammonium iodide in a molar ratio of 5:4:2 were stirred in dimethylformamide (DMF) at 70°C for 1 hour. Pb was prepared in this manner. 2+ The concentration is 0.3 mol L. -1 The solution.

[0154] 2D perovskite (propylammonium)2(MA)4Pb5I was prepared by the following method. 16 Precursor solution: PbI₂, MAI, and propylammonium iodide in a molar ratio of 5:4:2 were stirred in dimethylformamide (DMF) at 70°C for 1 hour. Pb was prepared in this manner. 2+ The concentration is 0.3 mol L. -1 The solution.

[0155] Example 2. Preparation of a 2D perovskite film on a glass substrate

[0156] The size is 21G×1. 1 Using a 4 / 4 laboratory syringe needle and an automated pump to control the flow rate, lines of a fluid composition are drawn onto the surface of an ITO glass substrate. The needle thus deposits ink lines on the substrate comprising the hydrophobic poly(triarylamine) (PTAA) polymer poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]. The glass substrate has a hydrophilic surface characterized by a water contact angle of 36° ± 1.7°. The water contact angle of PTAA exceeds 90° (approximately 105° reported in Nat Commun. 2015, 6, 7747). By drawing boundary lines on the hydrophilic substrate surface with hydrophobic ink, the shaped area of ​​the surface can be selectively covered with a perovskite precursor solution using a method described above.

[0157] The substrate was placed on a hot plate in the air and heated to 50°C. Then Pb 2+ The concentration is 0.3 mol L. -1 (BA)2(MA)3Pb4I 13 The precursor solution is drop-applied (within less than 1 second) onto the hydrophilic substrate surface in the target area, flowing isotropically across the substrate surface. The polar precursor solution wets the hydrophilic ITO surface, thus spreading on the surface in the form of a thin film. However, once the liquid precursor solution reaches the boundary lines, it is repelled by the hydrophobic ink, thus remaining within the forming area of ​​the glass substrate. The volume of the precursor solution is sufficient to cause complete filling of the forming area, while retaining all the applied solution within the boundary lines.

[0158] Within less than one minute of drying on the hot plate, the transparent yellow wet film begins to turn into a brown solid, indicating the formation of perovskite crystals. After approximately 70 seconds, a uniform perovskite film forms over the entire formed area (for a 50mm × 50mm substrate; smaller areas require less time).

[0159] In this way, a uniform perovskite film can be used to selectively cover well-defined, closed shapes such as stars, pentagons, and hearts. Figure 5 As shown. Furthermore, it is generated in the following manner: Figure 6 The perovskite film shown features adjacent rectangular parallel stripes 201 or wavy stripes 202: a series of non-intersecting hydrophobic ink lines are drawn on the substrate, and the solution is gradually drop-coated along the length of the area between each pair of hydrophobic ink lines. The elongated substrate area is thus selectively covered by the perovskite film without completely surrounding the area with hydrophobic ink boundaries. Furthermore, the single lines of hydrophobic ink define the hydrophobic boundaries between adjacent areas of the substrate, thus allowing for the close-proximity generation of unconnected perovskite films, i.e., separated by narrow gaps 203.

[0160] Example 3. Preparation of 2D perovskite films on PEDOT:PSS coated substrates

[0161] Patterned indium tin oxide (ITO) glass was cleaned sequentially using a cleaning agent (Deconex 12PA cleaning solution), deionized water, acetone, and isopropanol via ultrasonic treatment, followed by UV-ozone treatment for 15 minutes. A PEDOT:PSS solution was prepared by mixing 1 mL of PEDOT:PSS dispersion, 1 mL of deionized water, and 1.6 mL of isopropanol, and then spin-coated onto the patterned ITO glass substrate at 5000 rpm for 30 seconds. The substrate was then heated in air on a hot plate at 150°C for 10 minutes and then cooled to room temperature. This PEDOT:PSS coating exhibits a hydrophilic surface, characterized by a water contact angle of 24-25° measured 1 second after drop, decreasing to less than 5° after 10 seconds, and then stabilizing.

[0162] like Figure 7 As illustrated in the diagram, the PEDOT:PSS coated substrate 301 was then placed on a hot plate 302 at 50°C and left in air for at least 2 minutes, followed by Pb... 2+ The concentration is 0.3 mol L. -1 (BA)2(MA)3Pb4I 13 Equal portions of the perovskite precursor solution 302 were drop-coated onto the center of the substrate. Figure 7 (a) The solution spreads isotropically on substrate 301. Figure 7(b) and dried within 2 minutes by thermally induced evaporation of DMF vapor 304. Figure 7 (b) thereby forming an approximately circular perovskite film 305 on the substrate surface. Figure 7 (d). The substrate 304 was then further heated at 100°C for 2 minutes.

[0163] Figure 8 Photographs (a)-(d) depict the spreading of 60 μL of the precursor solution onto a PEDOT:PSS coated surface over approximately 40 seconds to form a disk with a final diameter of approximately 50 mm (dashed lines representing the perimeter of the disk are superimposed for clarity). Figure 8 In (e)-(f), it can be seen that the initial drying of the wet film produces perovskite crystals at the edge of the disk. Then, drying and crystallization rapidly spread throughout the remaining part of the disk. Figure 8 (g)), and the process is completed within 70 seconds. Figure 8 (h). Therefore, the perovskite loading in the perovskite film on the substrate is approximately 0.0013 mol / m. 2 Based on Pb, the perovskite film is highly reflective, indicating a smooth surface.

[0164] Another 2D perovskite film was prepared in the same manner, except that 6 μL of the same precursor solution was drop-coated onto the surface and spread into a disk with a diameter of approximately 25 mm. The UV-Vis absorption spectrum and photoluminescence (PL) emission spectrum of this perovskite film are as follows: Figure 9 As shown in the image, the spectrum exhibits absorption peaks at 566 nm, 605 nm, and 643 nm, characteristic of 2D perovskites, with an absorption onset at 776 nm corresponding to a calculated absorption band gap of 1.6 eV. The maximum PL emission is at 781 nm.

[0165] The light absorption analysis results of the same perovskite film are shown in Figure 10 Except at the end of the disk, the absorbance varies very little across the entire film, indicating that the film has a very uniform thickness.

[0166] Atomic force microscopy analysis revealed that the self-assembled 2D perovskite film possessed a tightly packed and smooth surface with a root mean square (RMS) roughness of 6.43 nm, significantly lower than that of 3D perovskite films prepared using conventional solvent engineering methods. The grain size in the 2D perovskite film was approximately 1 μm.

[0167] like Figure 11 As shown, cross-sectional scanning electron microscopy reveals that a uniform 2D perovskite film 401 with a thickness of approximately 0.9 μm and very low surface roughness is formed on a thin PEDOT:PSS layer 402, which itself is uniformly formed on an ITO layer 403.

[0168] Example 4. Effect of Temperature

[0169] A 2D perovskite film was prepared again using the method described in Example 3, thereby transferring Pb 2+ The concentration is 0.3 mol L. -1 (BA)2(MA)3Pb4I 13 Six-μL aliquots of the precursor solution were drop-coated onto a PEDOT:PSS-coated substrate, allowing the film to spread on the PEDOT:PSS surface and dry to form a perovskite film disk. However, the effect of temperature was investigated by comparing results obtained from drop-coating and drying on substrates at room temperature and on substrates heated to 50°C. The resulting films were analyzed by X-ray diffraction (XRD), such as... Figure 12 As shown.

[0170] When prepared at room temperature, the perovskite film exhibited a diffraction pattern similar to the calculated powder diffraction pattern, indicating that the crystals in the film are randomly oriented. In contrast, for the film prepared at 50 °C, only two main peaks were observed at 14.04 °C and 28.28 °C. These two peaks are characteristic of the vertical orientation of the 2D perovskite crystals, i.e., the methylammonium lead iodide plates are aligned perpendicular to the substrate surface. This highly ordered vertical orientation is desirable in many optoelectronic devices because it provides an efficient charge transport path for photogenerated charge carriers to move from the bulk perovskite to adjacent charge transport layers.

[0171] Example 5. Manufacturing and Testing of Solar Cells

[0172] Solar cells were fabricated entirely in air using the method of Example 3 to produce a disk of perovskite film on a 25×25 mm substrate comprising ITO glass spin-coated with PEDOT:PSS. (BA)₂(MA)₃Pb₄I 13 Six-μL aliquots of the precursor solution were drop-coated onto the surface of PEDOT:PSS. The effects of drop-coating / drying temperature and precursor solution concentration on the performance of the solar cells were investigated, as shown in Tables 1 and 2 below.

[0173] PC in chloroform 61 BM (10mg mL) -1 Spin-coating was applied to the 2D perovskite layer at 1000 rpm for 30 seconds. Then, ethoxylated polyethyleneimine (PEIE) (0.05% w / w in isopropanol) was spin-coated onto the PC. 61 On the BM layer, the temperature was maintained at 4000 rpm for 30 seconds. Finally, 100 nm Ag was deposited by shadow evaporation to obtain a 0.1 cm layer. 2 The active area.

[0174] As shown in Table 1, optimal solar cell performance was obtained when the precursor solution was drop-coated and dried at 50–60 °C. This result is consistent with the observations in Example 4, because the increased temperature induces the vertical orientation of 2D perovskite crystals on the substrate, thereby improving the migration of photogenerated charge carriers from the bulk perovskite film to the adjacent charge-transport layers (i.e., PEDOT:PSS and PC). 61 The charge transport path in BM). Although good results were still obtained at 70°C, it is believed that at higher temperatures (i.e., 70°C and above), the drying rate may become too high to allow the solution to spread uniformly on the surface, which may result in uncontrolled disk size, varying film thickness, or poor crystal quality in the film.

[0175] Table 1

[0176]

[0177] a Open circuit voltage; b Short-circuit current density; c Fill factor; d Power conversion efficiency (the data in parentheses is the average of measurements from at least 8 cells, and the data outside the parentheses is the highest recorded value).

[0178] As shown in Table 2, with approximately 0.5 mol L... -1 Pb 2+ Or lower (BA)2(MA)3Pb4I 13 Optimized solar cell performance was achieved with a precursor solution concentration of 0.3 mol L⁻¹. -1 Pb 2+ The best results were obtained. At this concentration, a film thickness of approximately 400 nm can be achieved. The solution at this concentration has a suitable viscosity, allowing it to flow easily over the hydrophilic PEDOT:PSS surface to form a wet film, which is then dried to produce a uniform 2D perovskite layer.

[0179] Table 2

[0180]

[0181] a Open circuit voltage; b Short-circuit current density; c Fill factor; d Power conversion efficiency (the data in parentheses is the average of measurements from at least 8 batteries, and the data outside parentheses is the highest recorded value).

[0182] As can be seen from Tables 1 and 2, for 0.3 mol L⁻¹ drop-coating / drying at 50 °C... -1 Pb 2+The precursor solution yielded optimized results. A total of 80 cells were fabricated using optimized conditions to study performance reproducibility; these cells had a diameter of 0.1 cm⁻¹. 2 The active region. For example... Figure 13 As shown, most cells exhibited PCE in the range of 13% to 14%, demonstrating the robustness of the method, even when preparing perovskite films in air without any humidity control.

[0183] The optimal-performing battery delivers 1.14V V during forward scanning. oc 18.8 mA / cm 2 J sc 69.5% FF, 14.9% PCE. (For example...) Figure 14 As shown, the current density-voltage (JV) curves obtained by forward and reverse scans showed no significant hysteresis, with a PCE of 14.8% obtained in the reverse scan. The steady-state PCE of the cell, recorded using maximum power point (MPP) tracking, was 14.8%, consistent with the JV measurement. An external quantum efficiency (EQE) spectrum of 17.8 mA / cm² was obtained. 2 The integrated photocurrent showed satisfactory good agreement with the results measured by JV. The PCE was also found to be very stable, showing no signs of performance degradation after being stored in a nitrogen glove box for more than 5 months.

[0184] Example 6. Solar cells with different perovskites

[0185] Solar cells were fabricated using the method of Example 5, but using various perovskite precursor solutions (Pb concentration of 0.3 mol / L) prepared as in Example 1. -1 The results are shown in Table 3 below.

[0186] Table 3

[0187]

[0188] a Open circuit voltage; b Short-circuit current density; c Fill factor; d Power conversion efficiency (the data in parentheses is the average of measurements from at least 8 cells, and the data outside the parentheses is the highest recorded value).

[0189] These results demonstrate that this method is effective for a range of different R2A sequences. n-1 Pb n X 3n+1 The perovskite precursor solution exhibits versatility, including varying R and n values ​​for the organic cation. Using (iso-BA)₂(MA)₄Pb₅I₃... 16The best result can be obtained, which produces a PCE of 15.45.

[0190] Example 7. Fabrication and testing of solar cells by slit die coating (comparative)

[0191] An ITO glass substrate (5cm × 5cm) with a PEDOT:PSS coating was prepared as described in Example 3. Figure 15 As shown in the diagram, a slit-die coating device 502 is used to coat a sample containing 0.7 mol L... -1 Pb 2+ (BA)2(MA)3Pb4I 13 A 2D perovskite precursor solution was used to coat the PEDOT:PSS coating surface of a 501 substrate heated to 50°C. The coating speed was 9 mm / s. -1 The slit dimensions are 13 mm wide and 25 mm long. Under these conditions, the viscosity and loading rate of the precursor solution prevent the applied liquid layer 503 from flowing outwards across the substrate surface, instead remaining essentially within the rectangular strip defined by the slit width. Once applied, the precursor solution dries on the substrate to form a crystalline perovskite film 504. The substrate is then further heated at 100°C for 2 minutes on another hot plate. PC is then deposited as described in Example 5. 61 The BM, PEIE, and Ag layers are used to form a solar cell.

[0192] The thickness of the resulting perovskite film was similar to that of the optimal device produced in Example 5, approximately 400 nm. However, the perovskite film deposited by the slit die exhibited poor uniformity, and some pinholes were observed.

[0193] The solar cell performance of multiple identically manufactured cells was evaluated as described in Example 5. Table 4 below shows a comparison of the best-performing solar cells produced using the slit die coating method compared to those produced using the method of Example 5. From these results, it is clear that excellent performance was achieved by applying a low concentration of the precursor and allowing it to flow through the hydrophilic substrate before heat drying.

[0194] Table 4

[0195]

[0196] a Open circuit voltage; b Short-circuit current density; c Fill factor; d Power conversion efficiency

[0197] Example 8. Preparation of shaped 2D perovskite films with varying thicknesses on a PEDOT:PSS coated substrate.

[0198] An ITO glass substrate (5cm × 5cm) with a PEDOT:PSS coating was prepared as described in Example 3. Then, hydrophobic lines in the shape of squares (approximately 25mm × 25mm) were drawn on the surface of the PEDOT:PSS coating using a syringe needle, as described in Example 2.

[0199] The substrate was then placed on a hot plate in the air and heated to 50°C. Then Pb... 2+ The concentration is 0.3 mol L. -1 (BA)2(MA)3Pb4I 13 The precursor solution is drop-coated onto a hydrophilic PEDOT:PSS surface within a target square, allowing it to flow isotropically across the surface. A polar precursor solution wets the surface, spreading it as a thin film. Once the liquid precursor solution reaches the boundary line, it is repelled by the hydrophobic ink and thus retained within the square region. Within less than two minutes, the transparent, yellow wet film dries, forming a perovskite film.

[0200] Volumes of 4, 5, 6, 8, and 10 μL were dropped onto squares of similar size in this manner. The resulting perovskite square films were numbered 601, 602, 603, 604, and 605, respectively. Figure 16 As shown.

[0201] The light absorption analysis results of these perovskite films are shown in Figure 17 As can be seen, since the wet film is confined within a hydrophobic boundary, the film absorption is related to the volume of the added precursor solution. Therefore, the thickness of the perovskite film can be controlled based on the volumetric loading of the precursor solution.

[0202] Example 9. Preparation of shaped 2D perovskite films on PEDOT:PSS coated substrates

[0203] A thin rectangular strip (13 mm wide) of PEDOT:PSS is coated onto a polyethylene terephthalate (PET) film substrate using a slit-die coating apparatus. This PEDOT:PSS coating has a hydrophilic surface, characterized by a water contact angle of less than 5°. In contrast, the uncoated PET substrate has a water contact angle of 67-68°, and droplets are very stable and do not spread over the surface.

[0204] Place the substrate on a hot plate in air and heat to 50°C. Dispense Pb along the center of the PEDOT:PSS coated strip using a syringe. 2+ The concentration is 0.3 mol L. -1The perovskite precursor solution was applied in strips, with the substrate moving beneath the syringe at a speed of 0.2 m / s and the precursor solution being dispensed at a rate of 25 μL / min. Once applied, the precursor solution flowed outwards across the hydrophilic PEDOT:PSS surface, forming a thin film. However, once the liquid precursor solution reached the hydrophobic boundary defined by the PET film adjacent to the edge of the PEDOT:PSS coating, it was repelled by the hydrophobic PET and thus retained within the rectangular strips. Within less than two minutes of drying on a hot plate, the transparent yellow wet film transformed into crystalline perovskite. Therefore, as... Figure 18 As shown, a rectangular strip of crystalline perovskite film 701 with the same width as the underlying PEDOT:PSS layer 702 (shown as dashed lines for clarity) is formed on a PET substrate 703.

[0205] Example 10 (Comparative).

[0206] According to the method in Example 2, a PTAA (poly[bis(4-(phenyl)(2,4,6-trimethylphenyl)amine poly(triarylamine) solution (2 mg mL)) was used. -1 Draw two parallel hydrophobic lines about 1 cm apart on an ITO glass substrate (2.5 × 2.5 cm) in chlorobenzene and let it dry in the air for 5 minutes.

[0207] Then Pb 2+ The concentration is 0.3 mol L. -1 (BA)2(MA)3Pb4I 13 A perovskite precursor solution (approximately 200 μl) was dropped onto the substrate, ensuring complete coverage of the substrate with a thin layer of the solution. This was performed at room temperature or 60 °C. In both cases, the solution did not dewet, resulting in unconnected perovskite precursor films separated by hydrophobic lines. At 60 °C, the precursor solution dried over a period of approximately 6 minutes without dewetting, forming a non-uniform perovskite film extending above the hydrophobic lines. The results demonstrate that, without rotating the substrate to induce dewetting, perovskite films of arbitrary shapes cannot be formed on substrates containing both hydrophilic and hydrophobic regions by immersing the substrate in the precursor solution.

[0208] Those skilled in the art will understand that the invention described herein is readily adaptable and modifiable beyond the specific circumstances described. It should be understood that this invention includes all such variations and modifications falling within the spirit and scope of the invention.

Claims

1. A method for forming a 2D perovskite film for optoelectronic devices, the method comprising: A 2D perovskite precursor solution is applied to at least a portion of a hydrophilic region of a substrate, wherein the hydrophilic region is defined by a hydrophobic boundary and wherein the 2D perovskite precursor solution is selectively applied to the hydrophilic region. In response to the adhesion between the 2D perovskite precursor solution and the surface of the hydrophilic region, and without rotating the hydrophilic region, the 2D perovskite precursor solution is spread over the hydrophilic region, wherein the perovskite precursor solution spreads until it reaches at least a portion of the hydrophobic boundary and remains in the hydrophilic region through at least a portion of the hydrophobic boundary, thereby forming a wet film of the 2D perovskite precursor solution on the hydrophilic region. and A wet film of a 2D perovskite precursor solution is dried to allow the perovskite to crystallize and thus have a hybrid organic-inorganic perovskite crystal structure comprising metal cations, organic cations and halide ions, thereby forming a 2D perovskite film on the hydrophilic region. The 2D perovskite precursor solution is a Pb perovskite precursor solution, and the Pb concentration in the 2D perovskite precursor solution is less than 0.7 mol / L.

2. The method of claim 1, wherein the water contact angle of the hydrophilic region is less than 45°, determined by placing a 2 μL droplet on a dry surface and measuring the water contact angle using a Dataphysics OCA 15EC water contact angle measurement system.

3. The method according to claim 1, wherein the 2D perovskite precursor solution has a viscosity in the range of 0.6 to 600 mPa·s.

4. The method according to claim 1, wherein during drying, the temperature of the 2D perovskite precursor solution in the hydrophilic region is at least 30°C.

5. The method of claim 1, further comprising heating the substrate to a temperature in the range of 40°C to 80°C at least one of the following: before, during, and after application.

6. The method of claim 1, wherein a volume of 2D perovskite precursor solution sufficient to cover the entire hydrophilic region is applied, and wherein the volume is selected to produce a target thickness of the 2D perovskite film based on the known surface area of ​​the hydrophilic region and the known concentration of the 2D perovskite precursor solution.

7. The method of claim 1, wherein the substrate comprises a surface layer containing a hydrophilic composition, and the hydrophilic region is on the surface layer.

8. The method of claim 7, wherein the surface layer has a thickness between 20 nm and 2000 nm.

9. The method of claim 1, wherein the hydrophilic region comprises a hydrophilic composition selectively located on a hydrophobic surface of the substrate, and a hydrophobic surface adjacent to the hydrophilic region defines a hydrophobic boundary.

10. The method of claim 9, wherein the water contact angle of the hydrophobic surface is greater than 50°, determined by placing a 2 μL droplet on the dry surface and measuring the water contact angle using a Dataphysics OCA 15EC water contact angle measurement system.

11. The method of claim 9, wherein the hydrophobic surface is selected from hydrophobic polymer surfaces and hydrophobic metal surfaces.

12. The method according to any one of claims 7 to 11, wherein the hydrophilic composition is a hydrophilic semiconductor for transferring charge to and / or from a 2D perovskite film.

13. The method of claim 1, wherein the hydrophilic region is a region of the hydrophilic surface of the substrate, and the hydrophobic composition selectively located on the hydrophilic surface adjacent to the hydrophilic region defines the hydrophobic boundary.

14. The method of claim 13, wherein the water contact angle of the hydrophobic composition is greater than 50°, determined by placing a 2 μL droplet on a dry surface and measuring the water contact angle using a Dataphysics OCA 15EC water contact angle measurement system.

15. The method according to claim 13 or claim 14, wherein the hydrophobic composition comprises at least one selected from hydrophobic polymers, hydrophobic small organic molecules, hydrophobic metals, and hydrophobic metal oxides.

16. The method of claim 13 or claim 14, wherein the hydrophobic composition is present at least partially in the form of lines on the hydrophilic surface.

17. The method of claim 16, wherein the lines define hydrophobic boundaries between adjacent hydrophilic regions of the substrate, and the method includes applying the 2D perovskite precursor solution to portions of the adjacent hydrophilic regions to form unconnected 2D perovskite films on the adjacent hydrophilic regions.

18. The method according to claim 1, wherein the Pb concentration in the 2D perovskite precursor solution is less than 0.5 mol / L.

19. The method according to claim 1, wherein the 2D perovskite film is R2A. n-1 Pb n X 3n+1 In the form of , where each A is independently an organic cation selected from methylammonium and formamidinium, each R is an organic cation larger than each A, and each X is independently a halide anion.

20. The method of claim 1, wherein applying the 2D perovskite precursor solution comprises: The 2D perovskite precursor solution is drop-coated onto the hydrophilic region, or lines of the 2D perovskite precursor solution are applied to the hydrophilic region.

21. The method of claim 1, further comprising supplying a substrate in the form of a roll below the applicator, wherein the applicator applies a 2D perovskite precursor solution to at least a portion of the hydrophilic region as the hydrophilic region is supplied through the applicator.

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