Thin film, control method, and improvement method

Abstract

This thin film includes a plurality of inorganic chains comprising a perovskite substance and constituting a chain-like structure, and a chiral molecule. At a boundary section between the inorganic chains that are adjacent, the chiral molecule is bonded to the inorganic chains via a functional group covalently bonded to one asymmetric carbon atom constituting the chiral molecule, thereby forming a helical structure formed as a result of the chiral molecule surrounding the periphery of the inorganic chain. Said asymmetric carbon atom covalently bonded to the functional group is an asymmetric carbon atom, from among a plurality of asymmetric carbon atoms of the chiral molecule, that is at a position where the helical angle of the helical structure is not at a minimum value.

Description

Thin films, control methods, and enhancement methods

[0001] This application claims priority to Japanese Patent Application No. 2024-73948, filed on April 30, 2024, the contents of which are incorporated herein by reference.

[0002] Polarization image sensors are known that utilize polarization phenomena to visualize information about the structure and properties of various objects. A polarization image sensor includes a polarizer array with multiple groups of four polarizers with different polarization directions, and a photodiode array with multiple photodiodes arranged facing each polarizer group. Linearly polarized light signals transmitted through the four polarizers in the same group are converted into electrical signals by the photodiodes and output as information for one pixel. From the linearly polarized light output signal, three Stokes parameters can be calculated by combining the sum and difference of the intensities of orthogonal polarization components, and these parameters can be used to quantify the state of the transmitted light.

[0003] However, it is difficult to visualize states such as birefringence and stress distribution observed when an object is bent using only the three Stokes parameters obtained from linearly polarized light. It is known that these states can be visualized using Stokes parameters calculated from the intensity of circularly polarized light, and a technology for detecting circularly polarized light is needed. Furthermore, detecting circularly polarized light using the polarization image sensor described above requires an additional wave plate, which significantly reduces sensitivity. Therefore, a technology for directly detecting circularly polarized light is needed.

[0004] Patent Document 1 discloses a thin film for detecting circularly polarized light, which is made of a perovskite-type material and includes a plurality of inorganic layers constituting a layered structure and / or a plurality of inorganic chains constituting a chain structure, and chiral molecules contained in at least a portion of the boundaries between adjacent inorganic layers and / or adjacent inorganic chains, wherein the chiral molecules are either S-type chiral molecules or R-type chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, and the crystal structure of the perovskite-type material is oriented in a predetermined direction.

[0005] International No. 2021-241554

[0006] Currently, there is a demand for a thin film having a higher circularly polarized light absorption intensity than the thin film of Patent Document 1. In addition, there is a demand for a technique for adjusting the circularly polarized light absorption intensity.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a thin film having excellent circularly polarized light absorption strength, and a method for controlling and improving circularly polarized light absorption strength using the thin film.

[0008] In order to solve the above problems, the present invention proposes the following means. <1> A thin film according to aspect 1 of the present invention is a thin film for detecting circularly polarized light, comprising: a plurality of inorganic chains made of a perovskite-type substance and constituting a chain structure; and chiral molecules, wherein the chiral molecules are chiral molecules having a plurality of asymmetric carbon atoms (excluding R-(+)-1-(1-naphthyl)ethylamine and S-(-)-1-(1-naphthyl)ethylamine), and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chain via a functional group covalently bonded to one of the asymmetric carbon atoms constituting the chiral molecule, thereby forming a helical structure formed by the chiral molecules surrounding the inorganic chain, and the chiral molecules are either S-chiral molecules or R-chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, and the crystal structure of the perovskite-type substance is oriented in a specific direction, and The asymmetric carbon atom covalently bonded to the functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule where the helical angle of the helical structure does not exhibit the smallest value. <2> Aspect 2 of the present invention relates to the thin film of Aspect 1, wherein the difference between the value of the helical angle when the functional group is covalently bonded to the asymmetric carbon atom at a position where the helical angle does not exhibit the smallest value and the value when the functional group is covalently bonded to the asymmetric carbon atom at a position where the helical angle exhibits the smallest value may be 1° or more. <3> Aspect 3 of the present invention relates to the thin film of Aspect 1 or 2, wherein the chiral molecule is a polycyclic aromatic compound, and the aromatic ring possessed by the polycyclic aromatic compound is an aromatic ring having a covalent structure sharing one side of a benzene ring, and the functional group is bonded to a carbon atom adjacent to the carbon atom constituting the covalent structure, and the perovskite-type material and the chiral molecule are a compound ABX composed of three types of ions A, B, and X. ３wherein the ion B and the ion X form a plurality of units having an octahedral structure, and the octahedral structures of adjacent units share one face; and wherein the ion A is the polycyclic aromatic compound containing an ethylammonium ion, the ion B is a lead ion or a tin ion, and the ion X may contain a bromine atom and / or a chlorine atom. <4> Aspect 4 of the present invention is the thin film of Aspect 3, wherein the number of benzene rings may be three or more. <5> Aspect 5 of the present invention is the thin film of Aspect 3, wherein the aromatic ring may be an anthracene ring. <6> Aspect 6 of the present invention is the thin film of Aspect 4, wherein the aromatic ring may have at least one of a halogen and a cyano group as a substituent other than at a terminal end. <7> Aspect 7 of the present invention is the use of the thin film of any one of Aspects 1 to 6 for circular polarization detection. <8> A control method of aspect 8 of the present invention is a method for controlling circularly polarized light absorption intensity detected by a circular polarization detection device, comprising: a plurality of inorganic chains made of a perovskite-type substance and constituting a chain structure; and chiral molecules, wherein the chiral molecules are chiral molecules having a plurality of asymmetric carbon atoms, and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chain via a functional group covalently bonded to one of the asymmetric carbon atoms constituting the chiral molecules, thereby forming a helical structure formed by the chiral molecules surrounding the inorganic chain, and the chiral molecules are either S-type chiral molecules or R-type chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, the crystal structure of the perovskite-type substance is oriented in a certain direction, and The method includes a step of disposing a thin film, in which the asymmetric carbon atom covalently bonded to the functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule that does not exhibit the smallest helical angle of the helical structure, as a light-receiving layer of a circular polarization detection device.<9> A method for improving a ninth aspect of the present invention is a method for improving the circularly polarized light absorption intensity of a thin film for detecting circularly polarized light, the method comprising: increasing the helical angle of the helical structure by substituting the chiral molecules with substituted chiral molecules having a higher packing effect in order to increase the space filling rate of the perovskite-type substance and the chiral molecules in a space formed by both substances within the helical structure of the inorganic chain; the thin film is made of the perovskite-type substance and comprises: a plurality of the inorganic chains constituting a chain structure; and the chiral molecules, each of the chiral molecules having a plurality of asymmetric carbon atoms; and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chain via a functional group covalently bonded to one asymmetric carbon atom constituting the chiral molecule, thereby forming the helical structure formed by the chiral molecules surrounding the inorganic chain; The chiral molecules are either S-chiral molecules or R-chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, the crystal structure of the perovskite-type substance is oriented in a certain direction, and the perovskite-type substance and the chiral molecules are a compound ABX composed of three types of ions A, B, and X. ３wherein the ion B and the ion X form a plurality of units having an octahedral structure, and the octahedral structures of adjacent units share one face. <10> Aspect 10 of the present invention is the method for improving aspect 9, wherein the asymmetric carbon atom covalently bonded to the functional group may be the asymmetric carbon atom at a position among the plurality of asymmetric carbon atoms possessed by the chiral molecule that does not exhibit the smallest helical angle of the helical structure. <11> Aspect 11 of the present invention is the method for improving aspect 9 or aspect 10, wherein the difference between the helical angle of the helical structure based on the chiral molecule before substitution and the helical angle of the helical structure based on the substituted chiral molecule after substitution may be 1° or more. <12> Aspect 12 of the present invention is the method for improving any one of aspects 9 to 11, wherein the difference between the helical pitch of the helical structure based on the chiral molecule before substitution and the helical pitch of the helical structure based on the substituted chiral molecule after substitution may be 0.2 Å or more. <13> A thirteenth aspect of the present invention is the method for improving any one of aspects 9 to 12, wherein the substituted chiral molecule may be a chiral molecule that increases the potential energy of intermolecular interaction between the perovskite-type substance and the chiral molecule within the helical structure of the inorganic chain.

[0009] According to the above-described aspects of the present invention, it is possible to provide a thin film having excellent circularly polarized light absorption strength, and a method for controlling and improving circularly polarized light absorption strength using the thin film.

[0010] 1 is a cross-sectional view of a thin film according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of a circular polarization detection element according to one embodiment of the present invention; FIG. 3 is a circular dichroism spectrum of Example 1; FIG. 4 is a circular dichroism spectrum of Reference Example 1; FIG. 5 is a cross-sectional view (a-face, 100 plane) of a thin film according to one embodiment of the present invention (aromatic rings of chiral molecules: naphthalene rings), in which a helical structure formed by chiral molecules surrounding an inorganic chain is viewed from the top side in the axial direction (vertical direction) of the inorganic chain; FIG. 6 is a cross-sectional view (b-face, 011 plane) of a thin film according to one embodiment of the present invention (aromatic rings of chiral molecules: naphthalene rings), in which a helical structure formed by chiral molecules surrounding an inorganic chain is viewed from the side in the direction perpendicular to the axial direction of the inorganic chain (horizontal direction). FIG. 1 shows the packing state of chiral molecules surrounding an inorganic chain in the helical structure of a thin film according to one embodiment of the present invention (aromatic ring of the chiral molecule: 9,10-disubstituted anthracene ring) (upper figure: a-face, 100 plane; lower figure: b-face, 011 plane).

[0011] Hereinafter, thin films, preparation methods, and improvement methods according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for ease of understanding, and the dimensional ratios of each component may not necessarily be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications can be made within the scope of the present invention.

[0012] FIG. 1 is a cross-sectional view schematically illustrating the configuration of a thin film 100 according to one embodiment of the present invention. The thin film 100 is a thin film for detecting circularly polarized light, and is a thin film made of a perovskite-type substance 101 to which chirality has been imparted. The thin film 100 is made of the perovskite-type substance 101, and includes a plurality of inorganic chains 102 constituting a chain structure, and chiral molecules 103. Note that while FIG. 1 illustrates an example in which an amino group (specifically, an ethylamino group) is used as the functional group of the chiral molecule 103, the functional group used in the present invention is not limited to an ethylamino group.

[0013] Each inorganic chain 102 is, for example, a chain structure with a diameter of about 1 nm, and is composed of a plurality of perovskite-type substances that constitute a part of a compound ABX3 composed of three types of ions A, B, and X, and form a polycrystalline structure. The crystal structure of the perovskite-type substance has a textured structure and is oriented in a certain direction. Here, "oriented in a certain direction" means, for example, that the ions exist in a substantially regular and substantially uniform state in a direction determined within a specific range. Specifically, the crystal structure of the perovskite-type substance is composed of a plurality of unitary elements (BX) each having an octahedral structure, in which ions B and X are arranged. ６ ) ４－ The octahedral structures of adjacent units share one face. Ion B is located at the center of the octahedron, and ion X is located at a vertex of the octahedron. Ion A is located at a position circumscribing the octahedral structure of each unit. Ion A is a chiral molecule 103. In other words, the perovskite-type material and the chiral molecule constitute a compound ABX3 composed of three types of ions A, B, and X.

[0014] The inorganic chains 102 are arranged by sharing faces between octahedral structures, and the inorganic chains 102 are surrounded by chiral molecules 103. This allows the inorganic chains 102 to form a helical structure, which can impart the ability to directly detect circularly polarized light. Furthermore, the octahedral structures sharing faces can increase the ability to absorb circularly polarized light.

[0015] Examples of ion A include aromatic compounds (polycyclic aromatic compounds) containing alkylammonium ions. Examples of ion B include lead ions and tin ions. Examples of ion X include halogen ions. Examples of halogen ions include F. － , Cl － ,Br － and I － The halogen ions include I － is preferred.

[0016] The chiral molecules 103 are chiral molecules having multiple asymmetric carbon atoms (excluding R-(+)-1-(1-naphthyl)ethylamine and S-(−)-1-(1-naphthyl)ethylamine). At the boundaries 104 between adjacent inorganic chains 102, the chiral molecules 103 are bonded to the inorganic chains 102 (the perovskite-type substance on the surface of the inorganic chains 102) via functional groups (an ethylamino group in FIG. 1 ) covalently bonded to one asymmetric carbon atom constituting the chiral molecules 103, thereby forming a helical structure in the thin film 100 in which the chiral molecules 103 surround the inorganic chains 102. More specifically, the chiral molecules 103 are bonded to the perovskite-type substance 101 via the functional groups covalently bonded to the asymmetric carbon atoms constituting the chiral molecules 103. This functional group is a substituent that can have an electric charge, and the substituent and the perovskite-type substance can form a bond via a halogen ion. The functional group is preferably an alkylamino group. ３ ＋ ) is, for example, (PbI ６ ) ４－ I － By bonding with (PbI ６ ) ４－ Chirality is generated in the inorganic chain 102 composed of the above, and a new circularly polarized light absorption ability is exhibited. The chiral molecule 103 preferably has one or more benzene rings, preferably two or more. The chiral molecule 103 more preferably has three or more benzene rings. Furthermore, if the chiral molecule 103 is a polycyclic aromatic compound and the aromatic ring contained in the chiral molecule 103 is an aromatic ring (fused aromatic ring) with a structure (covalent structure) in which one side of the benzene ring is shared, such as a naphthalene ring or an anthracene ring, this is preferable because the circularly polarized light absorption intensity is increased. The aromatic ring contained in the chiral molecule 103 is preferably an anthracene ring. The functional group of the chiral molecule 103 that binds to the perovskite-type material is preferably bound to a carbon atom adjacent to the carbon atom that constitutes the covalent structure (i.e., at the ortho position, not the meta or para position).

[0017] When the chiral molecule 103 is a pi-conjugated extended molecule based on a compound having three or more benzene rings, it is preferable to have at least one of a halogen and a cyano group as a substituent at a site other than the terminal of the aromatic ring, as a way to suppress the CH / π interaction (which is a relatively weak interaction mainly in the vertical direction) and improve the π / π interaction. Here, "having at least one of a halogen and a cyano group as a substituent at a site other than the terminal of the aromatic ring" refers to, for example, introducing a halogen atom (e.g., Cl, Br, I) or a cyano group into a non-condensing carbon atom (i.e., a carbon atom at a non-condensing position adjacent to a carbon atom at a condensing position) of a benzene ring located at the center of a compound having three or more benzene rings (e.g., anthracene). Introducing a halogen atom (e.g., Cl, Br, I) or a cyano group in this way can generate steric hindrance due to the halogen atom or cyano group. This suppresses the CH / π interaction, while at the same time suppressing the charge repulsion by causing a shift in the overlap state of the aromatic rings, and also improves the attractive π / π interaction by allowing the π electron sites of the aromatic rings to overlap mainly due to dispersion forces.

[0018] 7 is a diagram (upper diagram: a-face, 100 plane; lower diagram: b-face, 011 plane) showing the packing state of chiral molecules 103 when the chiral molecule is a pi-conjugated extended molecule based on 9,10-disubstituted anthracene (the substituent is indicated by X in FIG. 7 ), a compound having three benzene rings and in which a halogen atom (e.g., Cl, Br, I) or a cyano group is introduced to the non-condensing carbon atom of the benzene ring located at the center of the aromatic ring. It can be seen from FIG. 7 that introducing a halogen atom (e.g., Cl, Br, I) or a cyano group into the aromatic ring (e.g., Cl, Br, I) or a cyano group into the aromatic ring (e.g., Cl, Br, I) can (1) generate steric hindrance due to the halogen atom or cyano group, and (2) cause a shift in the overlap state of the aromatic ring, thereby improving the degree of overlap at the pi-electron site of the aromatic ring.

[0019] Chiral molecules 103 exist in the R-configuration and the S-configuration. Chiral molecules 103 in the R-configuration or the S-configuration strongly absorb either right-handed or left-handed circularly polarized light. Here, an R-configuration is one in which four different bonding groups are bonded to the asymmetric carbon, with the one with the smallest atomic number placed furthest away and the remaining three bonding groups arranged clockwise from largest to smallest atomic number, and an S-configuration is one in which they are arranged counterclockwise. Examples of R-configurations include R-(+)-1-(1-naphthyl)ethylamine shown in the following formula (1) and R-(+)-1-(2-naphthyl)ethylamine shown in the following formula (3). Examples of S-configurations include S-(-)-1-(1-naphthyl)ethylamine shown in the following formula (2) and S-(-)-1-(1-naphthyl)ethylamine shown in the following formula (4).

[0020]

[0021]

[0022]

[0023]

[0024] It is preferable to include only S-chiral molecules 103 or R-chiral molecules 103, or chiral molecules 103 in which the abundance ratio of one is higher than the abundance ratio of the other, so that the crystal structure of the perovskite material is oriented in a specific direction. In this way, a chiral structure in the R- or S-configuration can be induced in the perovskite material containing multiple inorganic chains 102 that form a chain structure, and circularly polarized light can be directly detected.

[0025] In the chiral molecule 103, the asymmetric carbon atom covalently bonded to the functional group (an amino group in FIG. 1 ; hereinafter, sometimes referred to as the linking functional group) is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule 103 where the helical angle of the helical structure does not exhibit the smallest value. Here, the helical angle Ψ is expressed by the following formula (A). In the following formula (A), r is the radius r of the helical structure and the pitch p of the helical structure (incidentally, since the pitch p corresponds to three units, one unit is expressed as p / 3). Whether the asymmetric carbon atom covalently bonded to the linking functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule 103 where the helical angle of the helical structure does not exhibit the smallest value can be confirmed, for example, by the following method.

[0026] A stable molecular structure is determined using structural optimization calculations (energy minimization calculations), and the helical structure of the inorganic chain 102 formed is determined for a model of a predetermined chiral molecule 103 using computer-based molecular simulations to display the structure three-dimensionally and X-ray structural analysis using single crystals. Whether the asymmetric carbon atom is located at a position where the helical angle of the helical structure does not exhibit the smallest value can be determined by changing the bonding position of the asymmetric carbon atom (the asymmetric carbon atom bonded to the binding functional group) relative to the aromatic ring in the model of the chiral molecule 103 and determining the helical structure at each position. For example, after estimating the helical structure of the inorganic chain 102 for a predetermined model, the bonding position of the asymmetric carbon atom to which the binding functional group is bonded is changed in the model, and the helical structure of the inorganic chain 102 formed is determined using the above-described method. Subsequently, the same estimation process is repeated until the helical angles are estimated for all possible bonding positions of the asymmetric carbon atoms to which the binding functional groups are bonded in the model. After the estimation is complete, the asymmetric carbon atom bonded to the bonding functional group of the model with the smallest helical angle is designated as the asymmetric carbon atom with the smallest helical angle of the helical structure. The asymmetric carbon atoms at positions where the helical angle of the helical structure is not the smallest are designated as asymmetric carbon atoms bonded to the bonding functional group of a model other than the model with the smallest helical angle. This allows for improved circularly polarized light absorption intensity.

[0027]

[0028] The model of the chiral molecule 103 used to estimate the helical structure of the inorganic chain 102 has, for example, an aromatic ring having a site capable of bonding to an asymmetric carbon atom, a binding functional group that bonds to the inorganic chain 102, and an asymmetric carbon atom that bonds to the aromatic ring and the binding functional group. The molecular weight of the chiral molecule model is, for example, 100 or more and 1000 or less. The aromatic ring of the model may have a substituent. The substituent is not particularly limited. The number of substituents on the aromatic ring of the model is, for example, 1 to 2. The functional group that bonds to the asymmetric carbon atom other than the aromatic ring and the functional group is not particularly limited, and may be, for example, a hydrogen atom or an alkyl group.

[0029] An example of the embodiment will be described in which the asymmetric carbon atom covalently bonded to the binding functional group in the chiral molecule 103 is an asymmetric carbon atom that is located at a position that does not exhibit the smallest helical angle of the helical structure among the multiple asymmetric carbon atoms possessed by the chiral molecule 103.

[0030] One embodiment of such a chiral molecule 103 includes an aromatic ring having a site capable of bonding to an asymmetric carbon atom, a binding functional group bonded to the inorganic chain 102, and an asymmetric carbon atom bonded to the aromatic ring and the binding functional group, and the asymmetric carbon atom is covalently bonded to one of the carbon atoms included in the combination of two carbon atoms among the plurality of carbon atoms included in the aromatic ring that does not result in the longest distance between the two carbon atoms. Here, the "distance between the two carbon atoms" may be determined by calculating the three-dimensional structure of the molecule using Molecular Orbital Program Package (MOPAC).

[0031] Another embodiment of the chiral molecule 103 includes an aromatic ring having a site capable of bonding to an asymmetric carbon atom, a binding functional group bonded to the inorganic chain 102, and an asymmetric carbon atom bonded to the aromatic ring and the binding functional group, and the asymmetric carbon atom is covalently bonded to a carbon atom at a position that is not the longest distance from the center of the aromatic ring among the carbon atoms of the aromatic ring, where none of the bonds form the ring skeleton of the aromatic ring. Here, the "center of the aromatic ring" is the center of a sphere surrounding the structure obtained by calculation using the above-mentioned MOPAC for only the aromatic ring (i.e., unsubstituted aromatic ring) that forms the skeleton of the chiral molecule 103. The "distance from the center" is the distance from the center calculated above to the target carbon.

[0032] In another embodiment of such chiral molecule 103, chiral molecule 103 has an aromatic ring having a site capable of bonding to an asymmetric carbon atom, a binding functional group that bonds to the inorganic chain, and an asymmetric carbon atom that bonds to the aromatic ring and the binding functional group, and the asymmetric carbon atom is covalently bonded to the carbon atom that is located at the shortest distance from the center of the aromatic ring among the multiple carbon atoms in the aromatic ring, among the carbon atoms whose bonds do not all form the ring skeleton of the aromatic ring.

[0033] When the helical radius r is substantially constant for a given value of the helical angle ψ, it is preferable that the difference (helical angle difference) between the value when the functional group is covalently bonded to an asymmetric carbon atom at a position that does not exhibit the smallest value and the value when the functional group is covalently bonded to an asymmetric carbon atom at a position that exhibits the smallest value is 1° or more. By doing so, the circularly polarized light absorption intensity can be improved. The helical angle difference is preferably 2° or more. More preferably, the helical angle difference is 3° or more. Incidentally, the helical radius r is basically a value determined depending on the ionic radius of the halogen ion molecule, and therefore can be considered to be substantially constant in the chain structure according to the present invention.

[0034] When the helical radius r is substantially constant for a helical pitch p, it is preferable that the difference (helical pitch difference) between the value when the functional group is covalently bonded to an asymmetric carbon atom at a position that does not exhibit the smallest value and the value when the functional group is covalently bonded to an asymmetric carbon atom at a position that exhibits the smallest value is 0.2 Å or more. This can further improve the circularly polarized light absorption intensity of the thin film 100. Incidentally, the helical radius r is basically a value determined depending on the ionic radius of the halogen ion molecule, and therefore can be considered to be substantially constant in the chain structure according to the present invention.

[0035] As a method other than the above molecular simulation, as described in the examples below, XRD analysis of the chain structure can be used to identify the helical structure of the formed inorganic chain 102, thereby calculating the helical angle and helical pitch of the helical structure, and considering and estimating a model that can improve the circularly polarized light absorption intensity.

[0036] Preferably, the chiral molecules 103 are chiral molecules that increase the potential energy of intermolecular interactions between the perovskite-type material 101 and the chiral molecules 103 within the helical structure of the inorganic chains 102. Examples of such molecules include molecules having functional groups or structures with self-organizing ability, such as alkyl groups or aromatic rings. In this specification, "self-organizing ability" refers to the ability to self-organize and form a specific structure under specific conditions. In the case of chiral molecules having alkyl groups, longer alkyl chains increase crystallinity, so it is preferable that the alkyl group has six or more carbon atoms. If the area of ​​the aromatic rings in the polycyclic aromatic compound, which is the chiral molecule 103, increases or the number of interacting benzene rings increases, the arrangement space becomes more restricted and the molecules tend to stack on a plane. Therefore, increasing the number of benzene rings in the chiral molecules is preferable because it facilitates enhancing the packing effect of the helical structure of the inorganic chains 102. It is preferable that the number of benzene rings in the chiral molecules 103 is three or more. The aromatic ring of the chiral molecule 103 is preferably a fused aromatic ring.

[0037] FIG. 1 illustrates an example in which the chiral molecules 103 form an organic layer 105 at the boundary 104, and the organic layer 105 covers the inorganic chains 102. The inorganic chains 102 may be connected to other inorganic chains 102 in the b-axis direction via the organic layer 105. Furthermore, aromatic rings of the chiral molecules 103 bonded to the inorganic chains may be stacked in the c-axis direction. The number of linked inorganic chains 102 is not limited. When the thin film 100 is used in a circular polarization detection element or the like, the thickness of the thin film 100 is preferably approximately 100 nm or more and 500 nm or less, from the viewpoint of facilitating the flow of current in the thickness direction D.

[0038] In order to allow the perovskite-type material to absorb the irradiated light and to transmit the irradiated light efficiently, the surface roughness Ra (arithmetic mean roughness) of each thin film 100 is preferably 1 nm or more and 30 nm or less. Furthermore, if the arithmetic mean roughness Ra of the thin film 100 is 30 nm or less, leakage from the circular polarization detection device 120 can be suppressed. The arithmetic mean roughness Ra can be measured using, for example, an atomic force microscope (AFM). When measuring using an atomic force microscope, for example, an atomic force microscope manufactured by Shimadzu Corporation can be used, and the arithmetic mean roughness Ra can be obtained from an observation image obtained by setting the scanning range and scanning mode to appropriate values ​​(specifically, for example, scanning mode: dynamic mode).

[0039] In addition, since the perovskite-type substance needs to efficiently absorb the irradiated light, the absorption intensity per unit thickness of the thin film 100 must be 50,000 cm －１ More than 500,000cm －１ It is desirable that the absorption intensity per unit thickness is the value of the peak wavelength of the peak with the highest absorption intensity. The absorption intensity of the thin film 100 is measured by a transmission method.

[0040] 2 is a cross-sectional view of a circular polarization detection device 120 including a thin film 100. The circular polarization detection device 120 is mainly formed by laminating an anode layer 106, a thin film 100, and a cathode layer 107 in this order. At least one of the anode layer 106 and the cathode layer 107 has optical transparency so that the perovskite-type material in the thin film 100 absorbs light (circularly polarized light). The anode layer 106 is formed on one side of the thin film 100 in the thickness direction, and is made of, for example, SnO ２ , TiO ２ The cathode layer 107 may be bonded to the other side of the thin film 100 in the thickness direction via a cathode-side adhesive layer 108 (electron transport layer) made of, for example, BCP (Bathocuproine (registered trademark)), spiro-MeOTAD, TPD, or the like. When the anode layer 106 is optically transparent, the anode-side adhesive layer 108 is also optically transparent. When the cathode layer 107 is optically transparent, the cathode-side adhesive layer 109 is also optically transparent.

[0041] In the circular polarization detection device 120, the inorganic chains 102 constituting the thin film 100 have a polycrystalline structure, and therefore the light absorption of the thin film 100 is large (for example, absorption intensity at a wavelength of 375 nm: approximately 50,000 cm －１ The thin film 100 has a high conductivity (carrier diffusion length of approximately 1 μm or more) and a high conductivity (carrier diffusion length of approximately 1 μm or more). Therefore, when the light irradiated onto the thin film 100 is circularly polarized or contains circularly polarized light, a current due to the absorbed circularly polarized light can be detected. Note that by using only R- or S-chiral molecules, a chiral structure with an R- or S-configuration can be induced in the perovskite structure, and right-handed circularly polarized light or left-handed circularly polarized light can be selectively absorbed, allowing the resulting current to be detected.

[0042] (Method for Producing Chain Structures) The shape of the perovskite-type material can be controlled by adjusting the ratio of the perovskite-type material precursor, chiral molecules, and organic halide. For example, the thin film 100 can be produced by the following procedure. First, 0.5 mol / L to 2 mol / L of the perovskite-type material precursor, which serves as the raw material for the thin film 100, 0.5 mol / L to 2 mol / L of the chiral molecules, and 1 mol / L or less (preferably 0.4 mol / L to 0.8 mol / L) of an organic halide that can be sublimated by heating and reacts with some of the constituent elements of the perovskite-type material are dissolved in a solvent (first step). Examples of solvents that can be used include dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone. In addition, when multiple inorganic chains substantially form a chain structure, it is preferable to calculate and mix the ratio so that the chiral molecules are 0.75 molecules or less per molecule of Pb ion in the inorganic chain 102.

[0043] Examples of precursors of perovskite-type materials include lead halides. Examples of organic halides include methylammonium halides and formamidinium halides. Preferred examples of the halogen atoms contained in the lead halides and organic halides include bromine, chlorine, and iodine atoms.

[0044] Next, the solution (mixture) obtained in the first step is dropped onto a separately prepared base substrate using a spin coating method, and the base substrate obtained after dropping the solution is rotated at 1000 rpm to 5000 rpm to form a pre-treatment coating film on the base substrate (second step). The material of the base substrate is not limited.

[0045] Next, the untreated coating film is heated using a heating device to sublimate the organic halide contained in the untreated coating film (third step), thereby obtaining a thin film composed of a polycrystalline inorganic layer and chiral molecules distributed therebetween. Here, it is preferable that the heating temperature is about 70°C or higher and 120°C or lower, and the heating time is about 15 minutes or higher and 60 minutes or lower.

[0046] By carrying out the second and third steps without crystallizing the solution obtained in the first step, the inorganic chains 102 of the thin film 100 obtained through the third step become polycrystalline, with a textured structure and preferentially oriented in a specific direction rather than randomly.

[0047] By forming a positive electrode layer 107 on one side in the thickness direction of the thin film 100 obtained through the third step and a negative electrode layer 106 on the other side using a known film formation method such as vacuum deposition or sputtering, it is possible to obtain a circular polarization detector 120 that can output information about circular polarization as an electrical signal. Note that a positive electrode-side adhesive layer 109 and a negative electrode-side adhesive layer 108 may be formed between the thin film 100 and the positive electrode layer 107 and between the thin film 100 and the negative electrode layer 106, respectively, using a known film formation method such as vacuum deposition, spin coating, or sputtering.

[0048] As described above, in the thin film 100 of this embodiment, the chiral molecules 103 induce chirality in the arrangement of the inorganic chains 102, thereby enabling the absorption wavelength range of circularly polarized light by the inorganic chains 102 to be expanded to a wide range of 350 nm to 800 nm.

[0049] Furthermore, because the inorganic chains 102 have a polycrystalline structure and are highly conductive, by connecting electrodes to both ends in the thickness direction, when the light irradiated onto the thin film 100 is circularly polarized or contains circularly polarized light, it is possible to detect a current caused by the circularly polarized light absorbed by the inorganic chains 102. That is, inorganic chains 102 formed using only R-configuration chiral molecules or S-configuration chiral molecules can selectively absorb right-handed circularly polarized light or left-handed circularly polarized light, and detect the resulting current. Furthermore, even when the abundance ratio of either the R- or S-configuration is higher than the abundance ratio of the other, it is possible to induce an R- or S-configuration chiral structure in the perovskite structure, selectively absorb right-handed circularly polarized light or left-handed circularly polarized light, and detect the resulting current.

[0050] Furthermore, the thin film 100 of this embodiment does not require a polarizer or a wave plate to detect circularly polarized light, resulting in a high extinction ratio, making it possible to directly detect circularly polarized light with high sensitivity and high resolution, which was impossible to directly detect with conventional photodetectors.

[0051] Therefore, the thin film 100 of this embodiment can be used as a circular polarization detection element, and various devices incorporating this element, such as a polarization camera, can be realized. By directly detecting circularly polarized light, information such as the intensity distribution of birefringence, which cannot be obtained with linearly polarized light, can be obtained.

[0052] (Method for controlling circularly polarized light absorption intensity) The method for controlling circularly polarized light absorption intensity of the present disclosure is a method for controlling circularly polarized light absorption intensity detected by a circular polarization detection device, and includes a perovskite-type substance 101, a plurality of inorganic chains 102 constituting a chain structure, and chiral molecules 103, wherein the chiral molecules 103 are chiral molecules having a plurality of asymmetric carbon atoms, and at boundaries 104 between adjacent inorganic chains 102, the chiral molecules 103 are bonded to the inorganic chains 102 via functional groups covalently bonded to one of the asymmetric carbon atoms constituting the chiral molecules 103, thereby forming a circle around the inorganic chains 102. The method includes a step of providing a thin film as a light-receiving layer of a circular polarization detection device, the thin film having a helical structure formed by chiral molecules 103 surrounding the chiral molecules 103, the chiral molecules 103 being either S-chiral molecules or R-chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, the crystal structure of the perovskite-type material 101 being oriented in a specific direction, and the asymmetric carbon atom covalently bonded to the functional group being at a position among the multiple asymmetric carbon atoms in the chiral molecules 103 that does not exhibit the smallest helical angle of the helical structure. The above-mentioned circular polarization detection device 120 has a thin film 100 provided as a light-receiving layer. The circular polarization detection device 120 can control the circularly polarized light absorption intensity by the circular polarization detection device 120 by changing the chiral molecules 103 in the thin film 100 so as to satisfy the above-mentioned conditions.

[0053] (Method for Improving Circularly Polarized Light Absorption Intensity) The method for improving circularly polarized light absorption intensity of the present disclosure is a method for improving the circularly polarized light absorption intensity of a thin film 100 for detecting circularly polarized light, and includes a step of increasing the helical angle of the helical structure by substituting the chiral molecules 103 with substituted chiral molecules having a higher packing effect in order to increase the space-filling rate of the perovskite-type material 101 and the chiral molecules 103 in the space formed by both materials within the helical structure of the inorganic chain. In this way, the circularly polarized light absorption intensity of the thin film 100 can be further improved.

[0054] Examples of substituted chiral molecules with a higher packing effect include molecules having functional groups or structures with self-organizing ability, such as alkyl groups or aromatic rings. For example, when the chiral molecule 103 before substitution is a chiral molecule having an alkyl group, the longer the alkyl chain, the higher the crystallinity of the self-organization, so the substituted chiral molecule is preferably a chiral molecule having an alkyl group longer than the chiral molecule 103 before substitution. When the chiral molecule 103 before substitution has an aromatic ring, the larger the aromatic ring or the greater the number of interacting benzene rings, which restricts the arrangement space and makes it easier for the molecules to stack on a plane, so the substituted chiral molecule is preferably a chiral molecule having a larger number of benzene rings (the number of benzene rings in the fused aromatic rings) than the chiral molecule before substitution.

[0055] The difference between the helical angle of the helical structure based on the chiral molecule 103 before substitution and the helical angle of the helical structure based on the substituted chiral molecule (substitution helical angle difference) is preferably 1° or more. When the substitution helical angle difference is 1° or more, the circularly polarized light absorption intensity of the thin film 100 can be further improved.

[0056] It is preferable that the difference between the helical pitch of the helical structure based on the chiral molecule 103 before substitution and the helical pitch of the helical structure based on the substituted chiral molecule (substitution helical pitch difference) is 0.2 Å or more. The helical pitch can be determined by estimating the helical structure using the method described above. A substitution helical pitch difference of 0.2 Å or more can further improve the circularly polarized light absorption intensity of the thin film 100.

[0057] The thin film, control method, and improvement method of the present disclosure have been described above. Note that the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, the components in the above-described embodiments can be appropriately replaced with well-known components without departing from the spirit of the present invention.

[0058] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0059] Example 1 A thin film was produced by carrying out the thin film manufacturing method according to the above embodiment in the following procedure. 1 g of R-(+)-1-(2-naphthyl)ethylamine (R-2-NEA) was mixed with 500 μL of hydrogen iodide (HI), and the resulting mixture was stirred at 0°C for 2 hours to obtain 2.8 g of R-(+)-1-(2-naphthyl)ethylamine hydroiodide ((R-2-NEA)I). Subsequently, 500 μL of dimethylformamide (DMF) was used as a solvent, and lead iodide (PbI) was added to the mixture. ２ 230 mg of ((R-2-NEA)I) and 112 mg of ((R-2-NEA)I) were mixed, and the resulting mixture was stirred at 70°C for 1 hour to prepare a solution containing the raw materials for the thin film. The prepared solution was applied to a separately prepared base substrate, and a pre-treatment coating film was formed by spin coating. The pre-treatment coating film thus formed was heated at 100°C for 30 minutes to obtain (R-2-NEA)PbI. ３ A thin film of 1000 nm was obtained.

[0060] The obtained thin film was subjected to XRD analysis etc., as described below, to calculate various physical properties related to the chain structure and the helical structure (see Figures 5(b) and 6(b)). 1) Physical properties related to the chain structure (unit cell parameters) (1) a = 8.1275 (2) (2) b = 8.5429 (2) (3) c = 24.9490 (7) (4) α = β = γ = 90° (5) P2 １ 2 １ 2 １(Chiral space group) 2) Physical properties of the helical structure (1) Helical angle ψ 32.7° (2) Helical radius r 2.5 Å (3) Helical pitch p 24.4 Å

[0061] 5(b) and 6(b), Figures 5(a) and 6(a) show that the chiral molecules are more densely packed in the helical structure formed by the inorganic chains surrounded by the chiral molecules, and the space filling ratio of the perovskite-type material constituting the inorganic chains and the chiral molecules in the space formed by both materials is higher. This state increases the helical angle of the helical structure and improves the circularly polarized light absorption intensity of the thin film.

[0062] (Reference Example 1) A thin film was prepared in the same manner as in Example 1, except that R-1-NEA was used instead of R-2-NEA. The obtained thin film was subjected to XRD analysis, etc., as described below, to calculate various physical properties related to the chain structure and helical structure (see Figures 5(a) and 6(a)). 1) Physical properties related to the chain structure (unit cell parameters) (1) a = 8.0573 (11) (2) b = 8.3568 (12) (3) c = 25.318 (4) (4) α = β = γ = 90° (5) P2 １ 2 １ 2 １ (Chiral space group) 2) Physical properties of the helical structure (1) Helical angle ψ 33.6° (2) Helical radius r 2.6 Å (3) Helical pitch p 24.2 Å

[0063] 5(a) and 6(a), Figures 5(b) and 6(b) show that the chiral molecules are more loosely packed in the helical structure formed by the inorganic chains surrounded by the chiral molecules, resulting in a lower space-filling ratio of the perovskite-type material constituting the inorganic chains and the chiral molecules in the space formed by both materials. This results in a smaller helical angle of the helical structure and a lower circularly polarized light absorption intensity of the thin film.

[0064] (XRD Measurement) For Example 1 and Reference Example 1, the X-ray diffraction pattern of each thin film was measured at room temperature by the X-ray diffraction (XRD) method using a RUGAKU SmartLab 9kW or MiniFlex X-ray diffraction measurement device. For this measurement, a CuKα radiation source was used. The tube voltage and tube current during measurement were 40 kV and 15 mA, respectively. The measurement conditions were an ω of 1.25° and an accumulation time of 10° / min. The physical properties of the chain structure and the helical structure described above were determined based on the results of the XRD measurement.

[0065] (Circular dichroism spectrum measurement) Measurement was carried out for Example 1 and Reference Example 1 using a circular dichroism spectrometer (JASCO J-1500) to obtain the circular dichroism spectrum of each thin film.

[0066] FIG. 3 shows the circular dichroism spectrum of Example 1. The vertical axis of FIG. 3 represents the CD signal intensity (mdeg), and the horizontal axis of FIG. 3 represents the wavelength. FIG. 4 shows the circular dichroism spectrum of Reference Example 1. The vertical axis of FIG. 4 represents the CD signal intensity (mdeg), and the horizontal axis of FIG. 4 represents the wavelength. As shown in FIGS. 3 and 4 , it was confirmed that the helical angle of the helical structure of the perovskite-type material can be adjusted by changing the position of the asymmetric carbon atom bonded to the binding functional group in the aromatic ring of the chiral molecule, and that the detection sensitivity of circularly polarized light can be adjusted by increasing the helical angle. That is, it was found that high circularly polarized light absorption intensity can be obtained by selecting the asymmetric carbon atom covalently bonded to the functional group at a position that does not exhibit the smallest helical angle of the helical structure among the multiple asymmetric carbon atoms possessed by the chiral molecule.

[0067] The thin film of the present disclosure has excellent circularly polarized light absorption strength and is therefore highly industrially applicable.

[0068] 100 Thin film, 101 Perovskite material, 102 Inorganic chain, 103 Chiral molecule, 104 Interface, 105 Organic layer

Claims

1. A thin film for detecting circularly polarized light, comprising: a plurality of inorganic chains made of a perovskite-type substance and constituting a chain structure; and chiral molecules, wherein the chiral molecules are chiral molecules having a plurality of asymmetric carbon atoms (excluding R-(+)-1-(1-naphthyl)ethylamine and S-(-)-1-(1-naphthyl)ethylamine), and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chain via a functional group covalently bonded to one of the asymmetric carbon atoms constituting the chiral molecule, thereby forming a helical structure formed by the chiral molecules surrounding the inorganic chain; and the chiral molecules are either S-chiral molecules or R-chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, and the crystal structure of the perovskite-type substance is oriented in a specific direction; and a thin film, wherein the asymmetric carbon atom covalently bonded to the functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule, where the helical angle of the helical structure does not exhibit the smallest value.

2. The thin film according to claim 1, wherein the difference between the value of the helical angle when the functional group is covalently bonded to the asymmetric carbon atom at a position that does not exhibit the smallest value and the value when the functional group is covalently bonded to the asymmetric carbon atom at a position that exhibits the smallest value is 1° or more.

3. The chiral molecule is a polycyclic aromatic compound, and the aromatic rings of the polycyclic aromatic compound have a covalent structure in which one side of a benzene ring is shared, and the functional group is bonded to a carbon atom adjacent to the carbon atom constituting the covalent structure, and the perovskite-type substance and the chiral molecule are a compound ABX composed of three types of ions A, B, and X. ３ the ion B and the ion X form a plurality of unit units each having an octahedral structure, and the octahedral structures of adjacent unit units share one face; the ion A is the polycyclic aromatic compound containing an ethylammonium ion, the ion B is a lead ion or a tin ion, and the ion X contains a bromine atom and / or a chlorine atom.

4. The thin film according to claim 3, wherein the number of benzene rings is 3 or more.

5. The thin film according to claim 3, wherein the aromatic ring is an anthracene ring.

6. The thin film according to claim 4, which has at least one substituent selected from the group consisting of a halogen and a cyano group at a position other than the terminal of the aromatic ring.

7. A method for controlling circularly polarized light absorption intensity detected by a circular polarization detection device, comprising: a plurality of inorganic chains made of a perovskite-type substance and constituting a chain structure; and chiral molecules, wherein the chiral molecules are chiral molecules having a plurality of asymmetric carbon atoms, and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chain via a functional group covalently bonded to one of the asymmetric carbon atoms constituting the chiral molecules, thereby forming a helical structure formed by the chiral molecules surrounding the inorganic chain; and the chiral molecules are either S-type chiral molecules or R-type chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, and the crystal structure of the perovskite-type substance is oriented in a certain direction; and a control method comprising a step of installing a thin film, as a light-receiving layer of a circular polarization detection device, in which the asymmetric carbon atom covalently bonded to the functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule that does not exhibit the smallest value of the helical angle of the helical structure.

8. A method for improving the circularly polarized light absorption intensity of a thin film for detecting circularly polarized light, comprising the step of increasing the helical angle of the helical structure by substituting the chiral molecules with substituted chiral molecules having a higher packing effect in order to increase the space filling rate of the perovskite-type substance and the chiral molecules in the space formed by both substances within the helical structure of the inorganic chain, wherein the thin film is made of the perovskite-type substance and comprises: a plurality of the inorganic chains constituting a chain structure; and the chiral molecules, wherein the chiral molecules are chiral molecules having a plurality of asymmetric carbon atoms, and at the boundary between adjacent inorganic chains, the chiral molecules are bonded to the inorganic chains via a functional group covalently bonded to one asymmetric carbon atom constituting the chiral molecules, thereby forming the helical structure formed by the chiral molecules surrounding the inorganic chains, The chiral molecules are either S-chiral molecules or R-chiral molecules, or the abundance ratio of either is higher than the abundance ratio of the other, the crystal structure of the perovskite-type substance is oriented in a certain direction, and the perovskite-type substance and the chiral molecules are a compound ABX composed of three types of ions A, B, and X. ３ wherein the ions B and X form a plurality of units each having an octahedral structure, and the octahedral structures of adjacent units share one face.

9. The method for improving the chiral structure according to claim 8, wherein the asymmetric carbon atom covalently bonded to the functional group is the asymmetric carbon atom at a position among the multiple asymmetric carbon atoms possessed by the chiral molecule that does not result in the smallest helical angle of the helical structure.

10. The method for improving a chiral molecule according to claim 8, wherein the difference between the helical angle of the helical structure based on the chiral molecule before substitution and the helical angle of the helical structure based on the substituted chiral molecule after substitution is 1° or more.

11. The method for improving a chiral molecule according to claim 8, wherein the difference between the helical pitch of the helical structure based on the chiral molecule before substitution and the helical pitch of the helical structure based on the substituted chiral molecule after substitution is 0.2 Å or more.

12. The method of claim 8, wherein the substituted chiral molecule is a chiral molecule that increases the intermolecular interaction potential energy between the perovskite material and the chiral molecule within the helical structure of the inorganic chain.

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