Layered structure, method for producing same, device, and particle dispersion liquid

Abstract

The present invention provides a structure that achieves durability, conductivity, and quantum efficiency at the same time at high levels. This layered structure is characterize by comprising a substrate and a high-density particle layer positioned on the substrate, and is also characterized in that: the high-density particle layer comprises nanoparticles in each of which an inorganic film is formed on the surface; the nanoparticles have a particle diameter of 1 nm to 50 nm inclusive; the high-density particle layer has a filling rate of the nanoparticles per unit volume of 30 vol% to 80 vol% inclusive; the inorganic film has a thickness of 0.1 nm to 5 nm inclusive; the energy level at the upper end of a valence band of the inorganic film is the same as or lower than the energy level at the upper end of a valence band of the nanoparticles; and the energy level at the lower end of a conduction band of the inorganic film is the same as or higher than the energy level at the lower end of a conduction band of the nanoparticles.

Description

Layered structure, method for manufacturing the same, device, and particle dispersion liquid 【0001】 The present invention relates to a layered structure, a method for manufacturing the same, a device, and a particle dispersion liquid. 【0002】 As one of the nano-semiconductor materials, quantum dots (QD) can be mentioned. This QD generally has photoluminescence characteristics (PL characteristics). Currently, there are technologies such as color conversion materials for displays, fluorescent labels for non-displays, and agricultural films that utilize the PL characteristics of such QD. 【0003】 In addition, QD generally also has electroluminescence characteristics (EL characteristics). Therefore, QD is widely used as a light-emitting material for displays by utilizing such EL characteristics. In addition, there are expectations for its use in various devices such as lasers and solar cells. 【0004】 As a prior art regarding QD that utilizes PL characteristics (sometimes referred to as "QD for PL applications"), encapsulation of QD using oxides by the sol-gel method and the like can be mentioned (for example, see Patent Document 1). Such technology is mainly aimed at improving durability and thinning the film. 【0005】 On the other hand, as a prior art regarding QD that utilizes EL characteristics (sometimes referred to as "QD for EL applications"), ligand exchange can be mentioned (for example, see Patent Document 2). Such technology is mainly aimed at improving conductivity. 【0006】 JP 2013-136498 A International Publication No. 2022 / 049715 A1 【0007】 Here, the present inventors are proceeding with studies on applying the above-described nano-semiconductors such as QD to devices that detect light (photodetectors, imagers, etc.). This study is based on focusing on the characteristics of the photoelectric effect (PE characteristics) of QD, leaving aside the above-described PL characteristics and EL characteristics. 【0008】For example, regarding devices that detect short-wavelength infrared (SWIR) light, indium gallium arsenide (InGaAs) is conventionally known as a compound semiconductor sensitive to the SWIR region. Accordingly, a device that performs SWIR region image sensing is known, obtained by flip-chip bonding such InGaAs to a CMOS (Complementary Metal-Oxide-Semiconductor) sensor that detects visible light. However, because InGaAs is very expensive, it hinders the market adoption of the above-mentioned device. 【0009】 Under these circumstances, a so-called QD-on-CMOS method, in which QDs with long-wavelength absorption characteristics are coated onto a CMOS sensor, can be considered as an inexpensive alternative technology for sensing the SWIR region. However, such alternative technologies, and by extension, technologies for coating nanoparticles such as QDs onto substrates such as CMOS, make it difficult to simultaneously achieve a high level of durability, conductivity, and quantum efficiency (i.e., the product of internal quantum efficiency and absorption rate) in the resulting structure. 【0010】 Furthermore, in the encapsulation technology described in Patent Document 1 mentioned above, heating exceeding the heat resistance temperature of the QD is often required to impart sufficient barrier properties with the oxide film, resulting in insufficient improvement in durability in many cases. In addition, the encapsulation technology described in Patent Document 1 is for PL applications that do not require conductivity, and therefore does not focus on conductivity at all. Moreover, there is room for improvement in terms of improving quantum efficiency. 【0011】 On the other hand, the ligand exchange technique described in Patent Document 2 mentioned above relates to EL applications, and conductivity can be increased by replacing a long-chain alkyl with a short-chain alkyl or inorganic ligand. However, with such a technique, it is difficult to protect the QD surface with high durability. Furthermore, there is room for improvement in terms of improving quantum efficiency. 【0012】Based on the above, focusing on PE properties, a structure is needed that achieves a balance of durability, conductivity, and quantum efficiency using nanosemiconductors such as QDs. Furthermore, if such a structure achieves a balance of durability, conductivity, and quantum efficiency, it may be possible to flexibly expand its applications to PL and EL. 【0013】 Therefore, the object of the present invention is to provide a structure and a method for manufacturing the same that exhibits a high degree of balance between durability, conductivity, and quantum efficiency. Furthermore, the object of the present invention is to provide a device comprising the layered structure described above. Furthermore, the object of the present invention is to provide a particle dispersion that can be equivalent to an intermediate product in the method for manufacturing the layered structure described above. 【0014】 The inventors of the present invention diligently investigated how to solve the above problems based on the technology for forming layers of nanoparticles such as QDs on substrates such as CMOS. As a result, they found that by optimizing the nanoparticles themselves and the packing density of the nanoparticle layers, a structure with multiple desired properties can be obtained. Furthermore, they also discovered a novel method for manufacturing such a structure. 【0015】 The means to solve the aforementioned problem are as follows: 【0016】 <1> A layered structure comprising a substrate and a high-density particle layer on the substrate, wherein the high-density particle layer contains nanoparticles on which an inorganic film is formed on its surface, the nanoparticles have a particle size of 1 nm or more and 50 nm or less, the high-density particle layer has a packing density of nanoparticles per unit volume of 30 vol% or more and 80 vol% or less, the inorganic film has a thickness of 0.1 nm or more and 5 nm or less, the energy level at the upper end of the valence band of the inorganic film is the same as or lower than the energy level at the upper end of the valence band of the nanoparticles, and the energy level at the lower end of the conduction band of the inorganic film is the same as or higher than the energy level at the lower end of the conduction band of the nanoparticles. 【0017】<2> A method for manufacturing a layered structure as described in <1>, comprising: a preparation step A of preparing a particle dispersion A1 in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound are dispersed in a solvent S1; a coating step A1 of applying the particle dispersion A1 to a substrate; a film-forming step A of applying at least one of light, heat, and moisture to the coated surface after the coating step A1 to form a coating film; a removal step A1 of removing the reacted ligands and the solvent S1 from the coating film after the film-forming step A1; and a coating step A2 of applying a dispersion A2 in which inorganic film-forming elements are dispersed in a solvent S2 to the coating film after the removal step A1. 【0018】 <3> A method for manufacturing a layered structure as described in <1>, comprising: a preparation step B, in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in a solvent S3; a coating step B, in which the particle dispersion B is applied to a substrate; and a film forming step B, in which, after the coating step B, light, heat, and moisture are applied to the coated surface to form a coating film. 【0019】 <4> The method for manufacturing a layered structure according to <3>, further comprising a sulfidation step of subjecting the inorganic film on the surface of the nanoparticles to a sulfidation treatment after the film formation step B. 【0020】 <5> A method for manufacturing a layered structure as described in <1>, comprising: a preparation step C of preparing a particle dispersion C1 in which nanoparticles to which a non-reactive ligand is bound are dispersed in a solvent S4; a coating step C1 of applying the particle dispersion C1 to a substrate; a removal step C1 of removing the solvent S4 from the particle dispersion C1 applied to the substrate after the coating step C1 to form a coating film; and a film forming step C of forming an inorganic element on the coating film. 【0021】 <6> A method for manufacturing a layered structure as described in <1>, comprising: a preparation step D of preparing a particle dispersion D in which nanoparticles to which a non-reactive ligand is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), are dispersed in a solvent S6; a coating step D of coating the particle dispersion D onto a substrate; and a removal step D of removing the solvent S6 from the particle dispersion D coated on the substrate after the coating step D. 【0022】 <7> A device characterized by comprising the layered structure described in <1>. 【0023】 <8> The device according to <7>, further comprising, in addition to the substrate and the high-density particle layer, at least one selected from an electrode layer, an electron transport layer and a hole transport layer. 【0024】 <9> A particle dispersion characterized by comprising nanoparticles or non-reactive ligands to which ligands that can react with at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), dispersed in a solvent. 【0025】 According to the present invention, it is possible to provide a structure and a method for manufacturing the same that exhibits a high degree of balance between durability, conductivity, and quantum efficiency. Furthermore, according to the present invention, it is possible to provide a device comprising the above-described layered structure. Furthermore, according to the present invention, it is possible to provide a particle dispersion that can correspond to an intermediate product in the method for manufacturing the above-described layered structure. 【0026】 This is a schematic cross-sectional view of a layered structure according to one embodiment of the present invention. This is a schematic flowchart illustrating the manufacturing method of a layered structure according to one embodiment of the present invention. This is a schematic flowchart illustrating the manufacturing method of a layered structure according to one embodiment of the present invention. 【0027】 The layered structure, its manufacturing method, device, and particle dispersion of the present invention will be described in detail below based on embodiments. 【0028】 <Layered Structure> A layered structure according to one embodiment of the present invention (hereinafter sometimes referred to as "the structure of this embodiment") comprises a substrate and a high-density particle layer on the substrate; the high-density particle layer contains nanoparticles on which an inorganic film is formed on its surface; the nanoparticles have a particle size of 1 nm or more and 50 nm or less; the high-density particle layer has a packing density of nanoparticles per unit volume of 30 vol% or more and 80 vol% or less; the inorganic film has a thickness of 0.1 nm or more and 5 nm or less; the energy level at the upper end of the valence band of the inorganic film is the same as or lower than the energy level at the upper end of the valence band of the nanoparticles, and the energy level at the lower end of the conduction band of the inorganic film is the same as or higher than the energy level at the lower end of the conduction band of the nanoparticles; each of these is a characteristic feature. 【0029】 The structure of this embodiment comprises a layer of nanoparticles on a substrate, and by forming an inorganic film of a predetermined thickness on the surface of the nanoparticles in the layer, surface defects of the nanoparticles are deactivated. Furthermore, inorganic materials (inorganic films) are more stable than organic materials and have a stronger bond with nanoparticles such as QDs. Moreover, inorganic materials are impermeable to oxygen and water. Therefore, by forming an inorganic film, the degradation of nanoparticles such as QDs can be suppressed without significantly worsening conductivity. In addition, the presence of defects on the surface of nanoparticles typically leads to poor quantum efficiency. For this reason, by forming a predetermined inorganic film on the surface of the nanoparticles in the nanoparticle layer and deactivating the surface defects of the nanoparticles, high quantum efficiency can be maintained. 【0030】Furthermore, it was found that by using predetermined nanoparticles with optimized particle size for the layer of nanoparticles (nanoparticles with an inorganic film formed on their surface), and by increasing the density of these nanoparticles, more specifically, by achieving a nanoparticle packing ratio of 30 vol% or more per unit volume, high conductivity and quantum efficiency can be maintained. Moreover, the combination of forming an inorganic film on the nanoparticles and increasing the density of the nanoparticles can be expected to produce a synergistic improvement in conductivity. Therefore, the structure of this embodiment exhibits a high degree of balance between durability, conductivity, and quantum efficiency. 【0031】 Furthermore, nanoparticles such as QDs can increase dark current due to crystal defects, leakage currents at the particle surface and interface, etc. In this regard, in the structure of this embodiment, an inorganic film is formed on the surface of the nanoparticles, so crystal defects are suppressed by passivation of the surface, and consequently, leakage currents caused by defects can be suppressed. Therefore, it can be said that the structure of this embodiment is designed to suppress dark current. 【0032】 The structure of this embodiment can be manufactured, for example, by a method for manufacturing layered structures, as described later. 【0033】 Figure 1 is a schematic cross-sectional view of the structure of this embodiment. The structure (layered structure) 1 shown in Figure 1 comprises at least a substrate 10 and a high-density particle layer 20 on the substrate 10. The structure 1 may have any one or more further layers between the substrate 10 and the high-density particle layer 20. Alternatively, the substrate 10 and the high-density particle layer 20 may be in direct contact with each other. Furthermore, the structure 1 may have any one or more further layers on top of the high-density particle layer 20. 【0034】 (Substrate) The substrate 10 is not particularly limited, and any substrate with desirable characteristics for the final product can be appropriately selected. Specifically, examples of substrates 10 include glass substrates, Si substrates, Si substrates on which a CMOS structure is formed, etc. Furthermore, the substrate 10 is preferably transparent. 【0035】 (High-density particle layer) The structure 1 of this embodiment includes a high-density particle layer 20 on the substrate 10. 【0036】 The thickness (layer thickness) of the high-density particle layer 20 is not particularly limited, but is preferably, for example, 10 nm or more and 500 μm or less. Furthermore, the thickness of the high-density particle layer is more preferably 10 nm or more and 10 μm or less. 【0037】 As shown in Figure 1, the high-density particle layer 20 is densely packed with nanoparticles 21. Furthermore, an inorganic film 22 is formed on the surface of these nanoparticles 21. 【0038】 In Figure 1, the inorganic film 22 is shown to be formed only on the outer surface of the aggregate of nanoparticles 21. However, in substance, the inorganic film 22 can be formed on the entire surface of each nanoparticle 21 (excluding the surface where the nanoparticles 21 are in direct contact with each other). 【0039】 In the structure 1 of this embodiment, the high-density particle layer 20 is required to have a packing rate of nanoparticles 21 per unit volume of 30 vol% or more. If the packing rate is less than 30 vol%, there is a risk that at least one of the conductivity and quantum efficiency will deteriorate. Furthermore, from the viewpoint of further improving at least one of the conductivity and quantum efficiency, the packing rate is preferably 50 vol% or more, preferably 60 vol% or more, and more preferably 65 vol% or more. On the other hand, from the viewpoint of theoretical limits, the packing rate is set to 80 vol% or less, and preferably 70 vol% or less. 【0040】The packing density of the nanoparticles 21 can be measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). In addition to TEM, the packing density of the nanoparticles 21 can also be evaluated by measuring the refractive index of the high-density particle film using a spectroscopic ellipsometer and comparing it with the refractive index of the bulk material. Furthermore, in measuring the packing density of the nanoparticles 21, the inorganic film 22 formed on the surface of the nanoparticles 21 is not considered (not counted as part of the packing density). The packing density of the nanoparticles 21 can be adjusted, for example, by changing the proportion of nanoparticles 21 in the particle dispersion in the manufacturing method of the layered structure described later (the higher the proportion, the higher the packing density). However, the method for adjusting the packing density of the nanoparticles 21 is not limited to this. 【0041】 The high-density particle layer 20 may be patterned (see Figures 2(C) and 3(B)). The pattern shape in this case is not particularly limited. If the pattern shape has a certain pitch, such pitch can be, for example, 1 μm or more. 【0042】 Furthermore, a layered structure comprising a patterned high-density particle layer can be manufactured, for example, by the manufacturing method of the layered structure described later. 【0043】 -Nanoparticles- In the structure 1 of this embodiment, nanoparticles 21 having a particle size of 1 nm or more and 50 nm or less are used. If the particle size of the nanoparticles 21 used exceeds 50 nm, there is a risk that the various properties such as PL properties, EL properties, and PE properties inherent to the nanoparticles 21, particularly QD, may not be fully exhibited. From a similar viewpoint, it is preferable that the particle size of the nanoparticles 21 used is 20 nm or less. The particle size of the above nanoparticles can be measured by observing the cross-section using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Furthermore, the interface of the nanoparticles observed by the above microscope can be identified, for example, by elemental analysis (mapping) such as energy-dispersive X-ray spectroscopy. In addition to TEM, the packing efficiency of the above nanoparticles can also be evaluated by measuring the refractive index of the high-density particle film using a spectroscopic ellipsometer and comparing it with the refractive index of the bulk. 【0044】 The nanoparticles 21 are not particularly limited and include, for example, quantum dots (QDs), nanowires, nanosheets, metal nanoparticles, oxide nanoparticles, ferroelectric nanoparticles, magnetic nanoparticles, polymer nanoparticles, carbon nanotubes, and nanoclusters. Furthermore, the quantum dots (QDs) are not particularly limited and can also be silicon quantum dots, graphene quantum dots, etc. The nanoparticles 21 may be a single type or a combination of two or more types. Preferably, the nanoparticles 21 are quantum dots (QDs). 【0045】 The shape of the nanoparticles 21 such as QDs is not particularly limited and may be, for example, a spherical three-dimensional shape (circular cross-sectional shape), a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branch-shaped three-dimensional shape, a three-dimensional shape with irregularities on the surface, or any combination thereof. 【0046】 The nanoparticles 21, such as QDs, may be of a core-shell type consisting of a core and a shell, or they may be of a shellless type. In the core-shell type, the shell may be formed on at least a part of the surface of the core, or it may cover the entire core. 【0047】 The shellless nanoparticles 21 may consist of a combination of elements selected from, for example, cadmium (Cd), zinc (Zn), and lead (Pb), and elements selected from sulfur (S), selenium (Se), and tellurium (Te). The quantum dots (QDs) may also consist of a combination of elements selected from, for example, indium (In), gallium (Ga), and aluminum (Al), and elements selected from phosphorus (P), nitrogen (N), and arsenic (As). Furthermore, the quantum dots (QDs) may also consist of a combination of elements selected from, for example, copper (Cu) and silver (Ag), elements selected from indium (In), gallium (Ga), and aluminum (Al), and elements selected from sulfur (S), selenium (Se), and tellurium (Te). Note that the material of the shellless nanoparticles 21 is typically different from the material of the inorganic film 22. 【0048】When the nanoparticles 21 are of the core-shell type, the core of the nanoparticles 21 is the same as that described above for the nanoparticles 21 of the shell-less type. Note that the material of the core of the nanoparticles 21 in the case of the core-shell type may be the same as or different from the material of the inorganic film 22. 【0049】 Note that the core of the shell-less type nanoparticles 21 and the core of the nanoparticles 21 in the case of the core-shell type are, particularly in the case of PL applications and EL applications, CdS, CdSe, CdTe, ZnTe, ZnSe, ZnS, ZnSeTe, InP, GaP, CuInSe ２ , CuInS ２ , CuGaSe ２ , CuGaS ２ , AgInSe ２ , AgGaSe ２ , or AgGaS ２ are preferably composed of. Further, the core of the shell-less type nanoparticles 21 and the core of the nanoparticles 21 in the case of the core-shell type are, particularly in the case of PE applications (when using PE characteristics), PbS, InAs, InSb, Ag ２ S, Ag ２ Se, HgTe, Ag ２ Te, or AgBiS ２ are preferably composed of. 【0050】 The shell of the nanoparticles 21 in the case of the core-shell type may be composed of a compound of, for example, one or more first elements selected from a metal element and silicon (Si), and one or more second elements selected from the elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb). 【0051】 Note that in this specification, the metal element refers to those excluding hydrogen (H) in Group 1, boron (B) in Group 13, carbon (C) and silicon (Si) in Group 14, nitrogen (N), phosphorus (P), and arsenic (As) in Group 15, and oxygen (O), sulfur (S), selenium (Se), and tellurium (Te) in Group 16 among the elements belonging to Groups 1 to 16 in the periodic table. 【0052】More specifically, the first element constituting the shell is preferably selected from Mn (manganese), Cu (copper), Ag (silver), zinc (Zn), cadmium (Cd), Hg (mercury), Ga (gallium), In (indium), Pb (lead), and Bi (bismuth). The first element may be a single element or a combination of two or more elements. 【0053】 More specifically, the second element constituting the shell is preferably selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), and antimony (Sb), and more preferably from sulfur (S), selenium (Se), tellurium (Te), and phosphorus (P). The second element may be a single element or a combination of two or more elements. 【0054】 Furthermore, in the case of a core-shell type, the material of the shell of the nanoparticle 21 may be the same as or different from the material of the inorganic film 22. 【0055】 At least a portion of the nanoparticles 21 in the high-density particle layer 20 may or may not have a ligand (described later) bound to them. However, from the viewpoint of achieving a desired packing density and from the viewpoint of employing the manufacturing method described later, it is preferable that the nanoparticles 21 in the high-density particle layer 20 do not have a ligand (particularly the organic portion of the ligand) bound to them. 【0056】- Inorganic Film - The inorganic film 22 formed on the surface of the nanoparticles 21 has a thickness of 0.1 nm or more and 5 nm or less. If the thickness of the inorganic film 22 is less than 0.1 nm, there is a risk that durability cannot be sufficiently improved. Also, if the thickness of the inorganic film 22 is greater than 5 nm, there is a risk that the desired nanoparticle packing density cannot be achieved, and consequently, that conductivity and quantum efficiency cannot be sufficiently improved. From a similar viewpoint, the thickness of the inorganic film 22 formed on the surface of the nanoparticles is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 2 nm or more, and preferably 4 nm or less. The thickness of the inorganic film 22 can be measured by observing the cross-section using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Furthermore, even if, for example, the nanoparticles 21 are of the core-shell type and the material of the shell and the material of the inorganic film 22 are the same, the interface between the shell and the inorganic film 22 can be identified, and the thickness of the inorganic film 22 can be measured. Such interfaces can be identified, for example, by elemental analysis (mapping) such as energy-dispersive X-ray spectroscopy. 【0057】 Preferably, the inorganic film 22 is composed of a compound of one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb). In this case, the quantum efficiency can be improved more significantly. 【0058】 More specifically, the first element is preferably selected from Mn (manganese), Cu (copper), Ag (silver), zinc (Zn), cadmium (Cd), Hg (mercury), Ga (gallium), In (indium), Pb (lead), and Bi (bismuth). The first element may be a single element or a combination of two or more elements. 【0059】More specifically, the second element is preferably selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), and antimony (Sb), and more preferably from sulfur (S), selenium (Se), tellurium (Te), and phosphorus (P). The second element may be a single element or a combination of two or more elements. 【0060】 Specific examples of compounds between the first and second elements include, for example, MnS and CuInSe. ２ CuInS ２ CuGaSe ２ CuGaS ２ Ag ２ S, Ag ２ Se, Ag ２ Te, AgBiS ２ AgInSe ２ AgGaSe ２ AgGaS ２ Examples include ZnS, ZnSe, ZnTe, ZnSeTe, CdS, CdSe, CdTe, HgTe, GaP, InP, InAs, InSb, PbS, etc. 【0061】 Furthermore, the inorganic film 22 may be CdS, CdSe, CdTe, ZnTe, ZnSe, ZnS, ZnSeTe, InP, GaP, or CuInSe, especially in the case of PL and EL applications. ２ CuInS ２ CuGaSe ２ CuGaS ２ AgInSe ２ AgGaSe ２ AgGaS ２ Preferably, the inorganic film 22 consists of PbS, InAs, InSb, or MnS. In particular, in the case of PE applications, the inorganic film 22 is preferably PbS, InAs, InSb, or Ag ２ S, Ag ２ Se, HgTe, Ag ２ Te, or AgBiS ２ It is preferable that it consists of PbS or MnS. 【0062】- Energy levels of nanoparticles and inorganic films - In the high-density particle layer 20, the nanoparticles 21 and inorganic films 22 must have the energy level at the upper end of the valence band of the inorganic film 22 being the same as or lower than the energy level at the upper end of the valence band of the nanoparticles 21, and the energy level at the lower end of the conduction band of the inorganic film 22 being the same as or higher than the energy level at the lower end of the conduction band of the nanoparticles 21. In other words, in the structure 1 of this embodiment, the band gap of the inorganic film 22 must completely cover the band gap of the nanoparticles 21. 【0063】 As can be seen from the description of the manufacturing method of the layered structure described later, the high-density particle layer 20 can be formed by using nanoparticles to which ligands that can react to at least one of light, heat, and moisture are bound. However, in this case, ligands may remain on the surface of the nanoparticles 21 before the inorganic film 22 is formed on the surface, and if such ligands (especially the organic portion of the ligands) remain exposed, durability and conductivity will be insufficient. Therefore, by replacing the ligands with an inorganic film 22 having a predetermined band gap on the surface of the nanoparticles 21, durability and conductivity can be highly balanced. 【0064】 Furthermore, if the nanoparticle 21 is of the core-shell type, the energy level at the upper end of the valence band of the inorganic film 22 must be the same as or lower than the energy level at the upper end of the valence band of the core of the nanoparticle 21, and the energy level at the lower end of the conduction band of the inorganic film 22 must be the same as or higher than the energy level at the lower end of the conduction band of the core of the nanoparticle 21, and the energy level at the lower end of the conduction band of the shell of the nanoparticle 21 must be the same as or higher than the energy level at the lower end of the conduction band of the shell of the nanoparticle 21. The energy levels at the upper end of the valence band and the energy levels at the lower end of the conduction band (i.e., band gap) of the shell of the nanoparticle 21 and the inorganic film 22 may be the same or different. On the other hand, it is preferable that the energy levels at the upper end of the valence band and the energy levels at the lower end of the conduction band of the core of the nanoparticle 21 and the inorganic film 22 are different from each other. 【0065】 The energy levels of the nanoparticles 21 can vary depending on their particle size (including the core particle size and shell thickness). Similarly, the energy levels of the inorganic film 22 can vary depending on its thickness. Therefore, it is crucial to select appropriate nanoparticles and inorganic films while taking these points into consideration. 【0066】 -Other- The high-density particle layer 20 may further contain halogen elements. More specifically, the inorganic film 22 of the high-density particle layer 20 may further contain halogen elements. 【0067】 Next, two embodiments will be described as methods for manufacturing the structure of the above-described embodiment. 【0068】 <Method for Manufacturing a Layered Structure (a)> The method for manufacturing a layered structure according to the first embodiment of the present invention (hereinafter sometimes referred to as "the manufacturing method of this embodiment (a)") is a method for manufacturing the structure of this embodiment described above, and is characterized by comprising: a preparation step A of preparing a particle dispersion A1 in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound are dispersed in a solvent S1; a coating step A1 of applying the particle dispersion A1 to a substrate; a film-forming step A of applying at least one of light, heat, and moisture to the coated surface after the coating step A1 to form a coating film; a removal step A1 of removing the reacted ligands and the solvent S1 from the coating film after the film-forming step A1; and a coating step A2 of applying a dispersion A2 in which inorganic film-forming elements are dispersed in a solvent S2 to the coating film after the removal step A1. 【0069】 According to the manufacturing method (a) of this embodiment, the structure of this embodiment described above, that is, a structure in which durability, conductivity, and quantum efficiency are highly correlated, can be manufactured. Furthermore, since the manufacturing method (a) of this embodiment does not require InGaAs, it has the advantage that the above-mentioned structure can be manufactured at low cost. 【0070】(Preparation Step A) In the manufacturing method (a) of this embodiment, as preparation step A, a particle dispersion A1 is prepared in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture (hereinafter sometimes referred to as "reactive ligands") are bound are dispersed in solvent S1. The reactive ligand is preferably a ligand that can react with light. Specific examples of ligands that can react with light will be described later. 【0071】 The above particle dispersion A1 is obtained, for example, by mixing nanoparticles and a reactive ligand in solvent S1 and stirring for a predetermined time. Binding of the reactive ligand to the nanoparticles is generally achieved at room temperature (25°C), but the mixing temperature can be appropriately selected as needed. The stirring time can also be appropriately selected to achieve the desired binding, but generally, about 2 minutes to about 24 hours is preferred. The stirring time can also be about 5 minutes to about 12 hours, or about 7 minutes to about 6 hours. 【0072】 Specific examples of solvent S1 include, for example, chloroform, chlorobenzene, cyclohexane, diethyl ether, hexane, heptane, methylene chloride, pentane, pyridine, tetrahydrofuran, toluene, and xylene. 【0073】 The proportion of nanoparticles (nanoparticles bound to reactive ligands) in particle dispersion A1 is not particularly limited, but can be, for example, 1% by mass or more and 90% by mass or less. By changing the proportion of nanoparticles in particle dispersion A1, the packing density of nanoparticles in the final high-density particle layer can be controlled. 【0074】 (Coating step A1) In the manufacturing method (a) of this embodiment, after the preparation step A, the particle dispersion A1 is coated onto the substrate as coating step A1. If the layered structure to be finally manufactured has a further layer between the substrate and the high-density particle layer, the particle dispersion A1 is coated onto the further layer. 【0075】The coating method is not particularly limited, but examples include spin coating, knife-edge coating, spray coating, gravure printing, and screen printing. 【0076】 The coating thickness is not particularly limited, but is preferably, for example, about 1 μm or more and about 1 mm or less. The coating thickness can also be about 1.5 μm or more and about 100 μm or less, or about 2 μm or more and about 50 μm or less. The coating thickness can be appropriately selected depending on the type of solvent S1, the proportion of nanoparticles in the particle dispersion A1, and the desired thickness of the final high-density particle layer. 【0077】 (Drying Process) In the manufacturing method (a) of this embodiment, a drying process may be performed after the coating process A1 (and before the film-forming process A). The temperature and time of the drying process can be appropriately selected depending on the type of solvent S1 and the coating thickness. The drying process can also be carried out using, for example, heated steam, an oven, infrared radiation, etc. 【0078】 (Film Forming Process A) In the manufacturing method (a) of this embodiment, after the coating process A1, a film is formed by applying at least one of light, heat, and moisture to the coated surface as a film forming process A. This application causes ligands (reactive ligands) bound to nanoparticles to react. More specifically, in film forming process A, at least one of light irradiation, heating, and humidification is applied to the coated surface. Preferably, only light is selected from light, heat, and moisture, or light and heat and / or moisture are selected. 【0079】 When applying light to the coated surface (light irradiation), the light used is not particularly limited as long as it reacts with the reactive ligand, but examples include ultraviolet light in the wavelength range of 230 to 365 nm. Other examples of light used include ArF laser light with a wavelength of 193 nm, mercury g-ray with a wavelength of 436 nm, etc. The irradiation time is not particularly limited, but can be, for example, 1 to 60 minutes. The illuminance when irradiating with light is not particularly limited, but can be, for example, 10 to 1000 mW / cm². ２ It can be done this way. 【0080】 When applying heat to the coated surface (heating), the heating temperature is not particularly limited as long as the reactive ligand reacts, but for example, it can be 50°C or higher, 80°C or higher, 90°C or higher, or 100°C or higher, and it can also be 300°C or lower, 120°C or lower, or 110°C or lower. The heating time is also not particularly limited, but for example, it can be 1 minute to 2 hours. 【0081】 When adding moisture to a coated surface (humidifying it), the humidification method is not particularly limited as long as the reactive ligand reacts with it, but examples include placing the substrate in a high-humidity environment, applying or spraying moisture onto the coated surface, or immersing the substrate in moisture. If the humidification method is placing the substrate in a high-humidity environment, the humidification method specifically involves leaving it at a humidity of 40-90% for several minutes to several hours. 【0082】 (Removal Step A1) In the manufacturing method (a) of this embodiment, after the film formation step A, the reacted ligand (particularly the organic portion of the ligand) and the solvent S1 are removed from the coating film as a removal step A1. This increases the density of nanoparticles in the coating film. It is believed that this increase in nanoparticle density is achieved by the reduction of the interparticle distance, van der Waals forces, etc., resulting from the removal of the ligand. The removal method is not particularly limited, but for example, a method is used in which a sufficient amount of solvent (solvent S1') is brought into contact with the coating film to dissolve the reacted ligand in the solvent (solvent S1'), and then the reacted ligand and solvent S1 are removed together with the solvent (solvent S1') by physical removal means (such as wiping), vacuum drying, and / or heating. 【0083】 Specific examples of solvent S1' are the same as those described above for solvent S1. Furthermore, solvent S1' may be the same as solvent S1, or it may be different. 【0084】(Coating step A2) In the manufacturing method (a) of this embodiment, as coating step A2, a dispersion A2 in which an inorganic film-forming element is dispersed in a solvent S2 is applied to the coating film after the removal step A1. By coating step A2, the inorganic film (containing the inorganic film-forming element and having a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles. In addition, even by coating step A2, the inorganic film formed on the surface of the nanoparticles may have a thickness exceeding 5 nm, but in that case, the inorganic film (containing the inorganic film-forming element and having a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles by performing the removal step A2 described later. Furthermore, by coating step A2, the high-density particle layer (with a nanoparticle packing rate of 30 vol% to 80 vol%) can be formed on the substrate. Even if the coating process A2 does not result in the formation of the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate, in that case, the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) can be formed on the substrate by performing the removal process A2 described later. The coating method is the same as that described above for coating process A1. 【0085】 Specific examples of solvent S2 are the same as those described above for solvent S1. Furthermore, solvent S2 may be the same as solvent S1, or it may be different. 【0086】 The dispersion A2 described above may further contain halogen elements. Examples of halogen elements include chlorine (Cl), bromine (Br), and iodine (I). When a halogen element is included, it is more preferably chlorine (Cl). 【0087】 The inorganic film-forming elements dispersed in the dispersion A2 are not particularly limited, but examples include one or more first elements selected from metallic elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb). Furthermore, it is preferable to use both the first and second elements as the inorganic film-forming elements. 【0088】 More specifically, the first element is preferably selected from Mn (manganese), Cu (copper), Ag (silver), zinc (Zn), cadmium (Cd), Hg (mercury), Ga (gallium), In (indium), Pb (lead), and Bi (bismuth). The first element may be a single element or a combination of two or more elements. 【0089】 More specifically, the second element is preferably selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), and antimony (Sb), and more preferably from sulfur (S), selenium (Se), tellurium (Te), and phosphorus (P). The second element may be a single element or a combination of two or more elements. 【0090】 When using both the first and second elements, the coating step A2 may involve coating a dispersion A2 in which both the first and second elements are dispersed in the solvent S2. In this case, the coating step A2 may be performed only once or repeatedly. 【0091】 Alternatively, when both the first and second elements are used, the coating step A2 may consist of a step of coating a dispersion A2' in which the first element is dispersed in solvent S2', and a step of coating a dispersion A2'' in which the second element is dispersed in solvent S2''. In this case, the coating step A2 may consist of a step of coating dispersion A2' and a step of coating dispersion A2'', each performed once or repeatedly. In this case, dispersion A2' may also further contain halogen elements. 【0092】(Removal Step A2) In the manufacturing method (a) of this embodiment, a removal step A2 may be provided after the coating step A2, in which the solvent S2 is removed from the coated dispersion A2. This ensures that an inorganic film (containing the above-mentioned inorganic film-forming elements and having a thickness of 0.1 nm to 5 nm) is formed on the surface of the nanoparticles, and that the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) is formed on the substrate. The removal method is not particularly limited, but examples include physical removal means (such as wiping), vacuum drying, and / or heating. Furthermore, even after the above-described removal step A1, some of the reacted ligand (especially the organic portion of the ligand) may remain in the coating film. In this case, this removal step A2 can more reliably remove the portion. 【0093】 <Manufacturing of a layered structure having a patterned high-density particle layer by manufacturing method (a)> The manufacturing method (a) of this embodiment described above can also be used to manufacture a layered structure having a patterned high-density particle layer. This will be explained below with reference to Figure 2. Note that, for convenience, the solvent is not shown in Figure 2. 【0094】 Specifically, in preparation step A of manufacturing method (a), a light-reactive ligand is used as the ligand. In film formation step A of manufacturing method (a), light is applied to the coated surface (light irradiation is performed), and at this time, the light irradiation of the coated surface is carried out with at least a part of the coated surface covered by a mask 30 (Figure 2(A)). At this time, the ligand 25 bound to the nanoparticles 21 reacts in the part that has been irradiated with light. The part covered by the mask 30 corresponds to the desired patterning. In this case, heat may be applied to the coated surface along with light in film formation step A. In this case, moisture may be applied to the coated surface along with light in film formation step A. 【0095】 Next, development is performed to remove the particle dispersion A1 (ligand 25, nanoparticles 21, solvent S1) from the parts that were not irradiated with light, thereby forming a coating film (patterned coating film). 【0096】Next, by performing the removal process A1 described above, the nanoparticles 21 become denser in the coating film (patterned coating film) (Figure 2(B)). 【0097】 Next, after the removal step A1, the coating step A2 described above is performed (if necessary, the removal step A2 described above is also performed after the coating step A2), thereby forming an inorganic film 22 (containing the inorganic film-forming elements described above and having a thickness of 0.1 nm to 5 nm) on the surface of the nanoparticles 21, and forming a patterned high-density particle layer 20 (with a nanoparticle packing rate of 30 vol% to 80 vol%) on the substrate 10 (Figure 2(C)). In this way, a layered structure 1 comprising the patterned high-density particle layer 20 can be manufactured. 【0098】 When forming a patterned high-density particle layer 20 according to the above, it is preferable that the light-reactive ligand 25 has the property of increasing its solubility in a solvent (e.g., solvent S1 and / or solvent S2) after reacting with light (e.g., photon energy). In this case, the patterned high-density particle layer 20 can be formed more easily. 【0099】 <Method for Manufacturing Layered Structures (b)> Furthermore, a method for manufacturing layered structures according to a second embodiment of the present invention (hereinafter sometimes referred to as "the manufacturing method of this embodiment (b)") is a method for manufacturing the structure of this embodiment described above, characterized by comprising: a preparation step B in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in a solvent S3; a coating step B in which the particle dispersion B is applied to a substrate; and a film forming step B in which, after the coating step B, light, heat, and moisture are applied to the coated surface to form a coating film. 【0100】According to the manufacturing method (b) of this embodiment, the structure of this embodiment described above, that is, a structure in which durability, conductivity, and quantum efficiency are highly correlated, can be manufactured. Furthermore, since the manufacturing method (b) of this embodiment does not require InGaAs, it has the advantage that the above-mentioned structure can be manufactured at low cost. Moreover, the manufacturing method (b) of this embodiment has further advantages in that the process is simplified compared to manufacturing method (a). 【0101】 (Preparation Step B) In the manufacturing method (b) of this embodiment, as preparation step B, a particle dispersion B is prepared, in which nanoparticles to which ligands that can react by at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in solvent S3. The first and second elements are elements for ultimately forming an inorganic film on the surface of the nanoparticles. The reactive ligand is preferably a ligand that can react by light. Specific examples of ligands that can react by light will be described later. 【0102】 The above particle dispersion B can be obtained, for example, by mixing nanoparticles, a reactive ligand, a first element, and a second element in solvent S3 and stirring for a predetermined time. Alternatively, the above particle dispersion B can also be obtained, for example, by mixing nanoparticles and a reactive ligand in solvent S3, stirring for a predetermined time, and then further mixing in the first element and the second element. The temperature and stirring time during mixing are the same as those described above for manufacturing process (a). 【0103】 Specific examples of solvent S3 are the same as those described above for solvent S1. 【0104】 More specifically, the first element is preferably selected from Mn (manganese), Cu (copper), Ag (silver), zinc (Zn), cadmium (Cd), Hg (mercury), Ga (gallium), In (indium), Pb (lead), and Bi (bismuth). The first element may be a single element or a combination of two or more elements. 【0105】 More specifically, the second element is preferably selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), and antimony (Sb), and more preferably from sulfur (S), selenium (Se), tellurium (Te), and phosphorus (P). The second element may be a single element or a combination of two or more elements. 【0106】 The proportion of nanoparticles (nanoparticles bound to reactive ligands) in particle dispersion B is not particularly limited, but can be, for example, 1% by mass or more and 90% by mass or less. By changing the proportion of nanoparticles in particle dispersion B, the packing density of nanoparticles in the final high-density particle layer can be adjusted. 【0107】 The particle dispersion B may further contain halogen elements. Examples of halogen elements include chlorine (Cl), bromine (Br), and iodine (I). When a halogen element is included, it is more preferably chlorine (Cl). 【0108】 (Coating Process B) In the manufacturing method (b) of this embodiment, after the preparation process B, the particle dispersion B is coated onto the substrate as a coating process B. If the layered structure to be finally manufactured has an additional layer between the substrate and the high-density particle layer, the particle dispersion B is coated onto the additional layer. The coating method is the same as that described above for manufacturing process (a). 【0109】 The coating thickness is not particularly limited. The coating thickness can be appropriately selected depending on the type of solvent S3, the proportion of nanoparticles in the particle dispersion B, and the desired thickness of the final high-density particle layer. 【0110】(Film Forming Process B) In the manufacturing method (b) of this embodiment, after the coating process B, a film forming process B is performed by applying at least one of light, heat, and moisture to the coated surface. This application causes the reactive ligands bound to the nanoparticles to react. More specifically, in the film forming process B, at least one of light irradiation, heating, and humidification is applied to the coated surface. Preferably, only light is selected from light, heat, and moisture, or light and heat and / or moisture are selected. By the film forming process B, an inorganic film (containing the first and second elements described above, with a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles. In addition, even with the film forming process B, the inorganic film formed on the surface of the nanoparticles may have a thickness exceeding 5 nm, but in that case, the inorganic film (containing the first and second elements described above, with a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles by performing the removal process B described later. Furthermore, the film-forming process B may form the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate. Note that the film-forming process B does not necessarily have to form the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate; however, in such cases, the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) can be formed on the substrate by performing the removal process B described later. 【0111】 The application of light, heat, and moisture is the same as described above for manufacturing method (a). 【0112】(Removal Step B) In the manufacturing method (b) of this embodiment, a removal step B may be included after the film formation step B, in which the reacted ligand (particularly the organic portion of the ligand) and the solvent S3 in the coating film are removed. Removal step B makes it possible to more reliably form an inorganic film (containing the first and second elements mentioned above, with a thickness of 0.1 nm to 5 nm) on the surface of the nanoparticles. Furthermore, removal step B makes it possible to more reliably form the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate. It is believed that the high density of the nanoparticles is more reliably achieved by the reduction of the interparticle distance, van der Waals forces, etc., resulting from the removal of the ligand. The removal method is not particularly limited, but examples include physical removal means (such as wiping), vacuum drying, and / or heating. 【0113】 (Sulfurization step) In the manufacturing method (b) of this embodiment, a sulfurization step may be performed after the film formation step B (or, if the removal step B is performed, typically after the removal step B) to apply a sulfurization treatment to the inorganic film on the surface of the nanoparticles. In particular, if an element other than sulfur (S) is selected as the second element to be dispersed in the particle dispersion B in the preparation step B (especially if oxygen (O) is selected), it is preferable to perform the above sulfurization step. By performing such a sulfurization step, the inorganic film on the surface of the nanoparticles can be made into a sulfide film. 【0114】 The method for sulfurizing inorganic films is not particularly limited, but for example, hydrogen sulfide (H) can be applied to the inorganic film. ２ One method is to bring S) into contact. 【0115】 <Manufacturing of a layered structure having a patterned high-density particle layer by manufacturing method (b)> The manufacturing method (b) of this embodiment described above can also be used to manufacture a layered structure having a patterned high-density particle layer. This will be explained below with reference to Figure 3. Note that, for convenience, the solvent is not shown in Figure 3. 【0116】Specifically, in the preparation step B of manufacturing method (b), a light-reactive ligand is used as the ligand. In the film-forming step B of manufacturing method (b), light is applied to the coated surface (light irradiation is performed), and at this time, the light irradiation of the coated surface is carried out with at least a part of the coated surface covered by a mask 30 (Figure 3(A)). At this time, the ligand 25 bound to the nanoparticles 21 reacts in the part that has been irradiated with light. The part covered by the mask 30 corresponds to the desired patterning. In this case, heat may be applied to the coated surface along with light in film-forming step B. In this case, moisture may be applied to the coated surface along with light in film-forming step B. 【0117】 Next, development is performed to remove the particle dispersion B (ligand 25, nanoparticles 21, solvent S3, first element / second element 26) from the parts that were not irradiated with light, and a coating film (patterned coating film) is formed. The coating film (patterned coating film) formed by development is typically a patterned high-density particle layer 20 on the substrate 10 (Figure 3(B)). In other words, by performing the above-described film-forming process B and development, an inorganic film 22 (containing the above-mentioned first and second elements, with a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles 21. Furthermore, by performing the above-described film-forming process B and development, a patterned high-density particle layer 20 (with a nanoparticle packing density of 30 vol% to 80 vol%) can be formed on the substrate 10. 【0118】 Furthermore, the removal step B described above may be performed after the development described above. Performing the removal step B described above more reliably forms an inorganic film 22 (containing the first and second elements described above, with a thickness of 0.1 nm to 5 nm) on the surface of the nanoparticles 21. Also, performing the removal step B described above more reliably forms a patterned high-density particle layer 20 (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate 10. 【0119】 In this way, a layered structure 1 comprising a patterned high-density particle layer 20 can be manufactured. 【0120】When forming a patterned high-density particle layer 20 according to the above, it is preferable that the light-reactive ligand 25 has the property of increasing its solubility in a solvent (e.g., solvent S3) after reacting with light (e.g., photon energy). In this case, the patterned high-density particle layer 20 can be formed more easily. 【0121】 <Method for Manufacturing a Layered Structure (c)> A method for manufacturing a layered structure according to a third embodiment of the present invention (hereinafter sometimes referred to as "the manufacturing method of this embodiment (c)") is a method for manufacturing the structure of this embodiment described above, characterized by comprising: a preparation step C of preparing a particle dispersion C1 in which nanoparticles to which non-reactive ligands are bound are dispersed in a solvent S4; a coating step C1 of applying the particle dispersion C1 to a substrate; a removal step C1 of removing the solvent S4 from the particle dispersion C1 applied to the substrate after the coating step C1 to form a coating film; and a film forming step C of forming an inorganic element on the coating film. 【0122】 According to the manufacturing method (c) of this embodiment, the structure of this embodiment described above, that is, a structure in which durability, conductivity, and quantum efficiency are highly correlated, can be manufactured. Furthermore, since the manufacturing method (c) of this embodiment does not require InGaAs, it has the advantage that the above-mentioned structure can be manufactured at low cost. 【0123】 (Preparation step C) In the manufacturing method (c) of this embodiment, as preparation step C, a particle dispersion C1 is prepared in which nanoparticles to which a non-reactive ligand is bound are dispersed in a solvent S4. 【0124】 In this specification, a non-reactive ligand refers to a ligand that does not react to light, heat, or moisture. Examples of non-reactive ligands include non-reactive organic ligands and non-reactive inorganic ligands. 【0125】Examples of non-reactive organic ligands include fatty acids such as oleic acid, octanoic acid, ethylhexanoic acid, myristic acid, and isostearic acid; amines such as butylamine, hexylamine, and octylamine; phosphines such as trioctylphosphine; and thiols such as hexanethiol and octanthiol. 【0126】 Examples of non-reactive inorganic ligands include Cl － , Br － , I － Halide ions such as S ２－ See ２－ Chalcogenide ions such as Zn ２＋ , Cd ２＋ In ３＋ Metal ions such as PO ４ ３－ Examples include phosphate ions such as phosphinate ions. 【0127】 When the ligand is a non-reactive organic ligand, the particle dispersion C1 can be obtained, for example, by mixing nanoparticles (without ligands) and a non-reactive organic ligand in solvent S4 and performing colloidal synthesis. The temperature and stirring time during mixing are the same as those described above in preparation step A. When the ligand is a non-reactive inorganic ligand, the particle dispersion C1 can be obtained by mixing nanoparticles to which a non-reactive organic ligand is bound and a salt corresponding to the non-reactive inorganic ligand in solvent S4, thereby substituting the non-reactive organic ligand with the non-reactive inorganic ligand. 【0128】 Specific examples of solvent S4 are the same as those described above for solvent S1. 【0129】 The proportion of nanoparticles (nanoparticles bound to non-reactive ligands) in the particle dispersion C1 is not particularly limited, but can be, for example, 0.1% to 90% by mass, 1% to 90% by mass, 0.1% to 40% by mass, or 1% to 40% by mass. By changing the proportion of nanoparticles in the particle dispersion C1, the packing density of nanoparticles in the final high-density particle layer can be controlled. 【0130】 (Coating step C1) In the manufacturing method (c) of this embodiment, after the preparation step C, the particle dispersion C1 is coated onto the substrate as a coating step C1. If the layered structure to be finally manufactured has a further layer between the substrate and the high-density particle layer, the particle dispersion C1 is coated onto the further layer. The coating method and coating thickness are the same as those described above for the preparation step A. 【0131】 (Removal Step C1) In the manufacturing method (c) of this embodiment, after the coating step C1, the solvent S4 in the particle dispersion C1 coated on the substrate is removed in a removal step C1 to form a coating film. Methods for removal include physical removal means (such as wiping), vacuum drying, and / or heating to remove the solvent S4. In addition, in the removal step C1, non-reactive ligands contained in the particle dispersion C1 coated on the substrate are also removed at the same time. As a result, the nanoparticle density in the coating film is increased. 【0132】 (Film Forming Process C) In the manufacturing method (c) of this embodiment, after the removal process C1, a film forming process C is performed to form an inorganic film-forming element on the coating film. The method for forming the inorganic film-forming element on the coating film is not particularly limited, but examples include "atomic layer deposition method" and "a method of applying a dispersion C2 in which the inorganic film-forming element is dispersed in a solvent S5 to the coating film." In other words, the film forming process C may be an atomic layer deposition process C in which the inorganic film-forming element is formed on the coating film by an atomic layer deposition method, or it may be a coating process C2 in which a dispersion C2 in which the inorganic film-forming element is dispersed in a solvent S5 is applied to the coating film. 【0133】If the film-forming process C is an atomic layer deposition process C, the film-forming process C (atomic layer deposition process C) forms an inorganic film (containing the above-mentioned inorganic film-forming elements and having a thickness of 0.1 nm to 5 nm) on the surface of the nanoparticles, and the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) is formed on the substrate. 【0134】 If the film-forming step C is a coating step C2, the inorganic film (containing the inorganic film-forming elements described above and having a thickness of 0.1 nm to 5 nm) may be formed on the surface of the nanoparticles by the film-forming step C (coating step C2). Even if the inorganic film formed on the surface of the nanoparticles by the film-forming step C (coating step C2) has a thickness exceeding 5 nm, in which case the inorganic film (containing the inorganic film-forming elements described above and having a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles by performing the removal step C2 described later. Furthermore, if the film-forming step C is a coating step C2, the inorganic film (containing the inorganic film-forming elements described above and having a thickness of 0.1 nm to 5 nm) may be formed on the surface of the nanoparticles by the film-forming step C (coating step C2). Even if the film-forming process C (coating process C2) does not result in the formation of the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) on the substrate, in that case, the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) can be formed on the substrate by performing the removal process C2 described later. 【0135】 The inorganic-forming elements formed in atomic layer deposition step C are the same as those described above in coating step A2. 【0136】 The method for forming the inorganic element in atomic layer deposition step C is not particularly limited and may be any known atomic layer deposition method. 【0137】The coating method in coating step C2 described above is the same as that described above for coating step A1. Furthermore, the specific example of solvent S5 is the same as that described above for solvent S1. Note that solvent S5 may be the same as or different from solvent S4. 【0138】 The dispersion C2 described above may further contain halogen elements. Examples of halogen elements include chlorine (Cl), bromine (Br), and iodine (I). When a halogen element is included, it is more specifically preferably chlorine (Cl). 【0139】 The inorganic film-forming elements dispersed in the dispersion C2 are not particularly limited, but examples include one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb). Furthermore, it is preferable to use both the first and second elements as the inorganic film-forming elements. 【0140】 More specifically, the first element is preferably selected from Mn (manganese), Cu (copper), Ag (silver), zinc (Zn), cadmium (Cd), Hg (mercury), Ga (gallium), In (indium), Pb (lead), and Bi (bismuth). The first element may be a single element or a combination of two or more elements. 【0141】 More specifically, the second element is preferably selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), phosphorus (P), arsenic (As), and antimony (Sb), and more preferably from sulfur (S), selenium (Se), tellurium (Te), and phosphorus (P). The second element may be a single element or a combination of two or more elements. 【0142】 When using both the first and second elements, the coating step C2 may involve coating a dispersion C2 in which both the first and second elements are dispersed in the solvent S5. In this case, the coating step C2 may be performed only once or repeatedly. 【0143】Alternatively, when both the first and second elements are used, the coating step C2 may consist of a step of coating a dispersion C2' in which the first element is dispersed in solvent S5', and a step of coating a dispersion C2'' in which the second element is dispersed in solvent S5''. In this case, the coating step C2 may consist of one step each of coating dispersion C2' and coating dispersion C2'', or it may consist of multiple steps. In this case, the dispersion C2' may also further contain halogen elements. 【0144】 (Removal step C2) If the film-forming step C is the coating step C2, a removal step C2 may be provided after the film-forming step C (coating step C2) to remove the solvent S5 from the coated dispersion C2. This ensures that an inorganic film (containing the inorganic film-forming elements mentioned above, with a thickness of 0.1 nm to 5 nm) is formed on the surface of the nanoparticles, and that the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) is formed on the substrate. Furthermore, even after the removal step C1 described above, some of the non-reactive ligand may remain in the coating film. In this case, this removal step C2 can more reliably remove that portion. The removal method is not particularly limited, but examples include physical removal means (such as wiping), vacuum drying, and / or heating. 【0145】 <Method for Manufacturing Layered Structures (d)> A method for manufacturing layered structures according to the fourth embodiment of the present invention (hereinafter sometimes referred to as "the manufacturing method of this embodiment (d)") is a method for manufacturing the structure of this embodiment described above, characterized by comprising: a preparation step D of preparing a particle dispersion D in which nanoparticles to which a non-reactive ligand is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), are dispersed in a solvent S6; a coating step D of coating the particle dispersion D onto a substrate; and a removal step D of removing the solvent S6 from the particle dispersion D coated on the substrate after the coating step D. 【0146】According to the manufacturing method (d) of this embodiment, the structure of this embodiment described above, that is, a structure in which durability, conductivity, and quantum efficiency are highly correlated, can be manufactured. Furthermore, since the manufacturing method (d) of this embodiment does not require InGaAs, it has the advantage that the above-mentioned structure can be manufactured at low cost. Moreover, the manufacturing method (d) of this embodiment has further advantages in that the process is simplified compared to manufacturing method (c). 【0147】 (Preparation Step D) In ​​the manufacturing method (d) of this embodiment, as preparation step D, a particle dispersion D is prepared in which nanoparticles to which a non-reactive ligand is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in solvent S6. The first and second elements are elements for ultimately forming an inorganic film on the surface of the nanoparticles. 【0148】 The above particle dispersion D can be obtained, for example, by mixing nanoparticles, a non-reactive ligand, a first element, and a second element in solvent S6 and stirring for a predetermined time. Alternatively, the above particle dispersion D can also be obtained, for example, by mixing nanoparticles and a ligand in solvent S6, stirring for a predetermined time, and then further mixing in the first and second elements. The temperature and stirring time during mixing are the same as those described above for preparation step A. 【0149】 The non-reactive ligand is the same as described above for preparation step C. The first and second elements are the same as described above for preparation step B. Furthermore, solvent S6 is the same as described above for solvent S1. 【0150】 The proportion of nanoparticles (nanoparticles bound to non-reactive ligands) in the particle dispersion D is not particularly limited, but can be, for example, 1% by mass or more and 90% by mass or less. By changing the proportion of nanoparticles in the particle dispersion D, the packing density of nanoparticles in the final high-density particle layer can be adjusted. 【0151】The particle dispersion D may further contain halogen elements. Examples of halogen elements include chlorine (Cl), bromine (Br), and iodine (I). If a halogen element is included, it is more preferably chlorine (Cl). 【0152】 (Coating Step D) In ​​the manufacturing method (d) of this embodiment, after the preparation step D, the particle dispersion D is coated onto the substrate as a coating step D. If the layered structure to be finally manufactured has a further layer between the substrate and the high-density particle layer, the particle dispersion D is coated onto the further layer. The coating method is the same as that described above for coating step A. The coating thickness is the same as that described above for coating step B. 【0153】 (Removal Step D) In ​​the manufacturing method (d) of this embodiment, after the coating step D, the solvent S6 in the particle dispersion D coated on the substrate is removed as a removal step D. In addition, in the removal step D, the non-reactive ligand contained in the particle dispersion D coated on the substrate is also removed at the same time. By the removal step D, an inorganic film (containing the first and second elements mentioned above, with a thickness of 0.1 nm to 5 nm) can be formed on the surface of the nanoparticles. Furthermore, by the removal step B, the high-density particle layer (with a nanoparticle packing density of 30 vol% to 80 vol%) can be formed on the substrate. The removal method is not particularly limited, but examples include physical removal means (such as wiping), vacuum drying, and / or heating. 【0154】 Alternatively, the sulfidation step described above may be performed after the removal step D. 【0155】 <Photoreactive Ligands> Photoreactive ligands can be used to bind to nanoparticles in the manufacturing methods of this embodiment described above ((a) and (b)). The photoreactive ligands are not particularly limited as long as they are photoreactive, and may be, for example, photoreactive organic ligands, photoreactive inorganic ligands, or photoreactive organic and inorganic hybrid ligands. 【0156】 Preferably, the light-reactive ligand has the property of increasing solubility in a solvent (e.g., solvent S1 and / or solvent S2, or solvent S3) after reacting with light (e.g., photon energy). In this case, the manufacturing method of this embodiment ((a) and (b)) can more reliably remove the ligand (particularly the organic portion of the ligand), and the quality of the resulting layered structure can be further improved. In addition, in this case, a patterned high-density particle layer can be formed more easily. 【0157】 The photoreactive organic ligand described above preferably contains a linking group, an activating group, and a photoreactive group in order to have the property of increasing solubility as described above. Such a photoreactive organic ligand is not particularly limited, but for example, the following formula (Ia): R-X-C(=W)-(CH ２ ) ｎ -T ... (Ia) [In the above formula (Ia), R is a group containing a monovalent or divalent or more aromatic group, and X is O, NH, N(R １ ) or S, R １ is an alkyl group or aryl group, W is O or S, n is an integer selected from 1 to 10, (CH ２ ) ｎ T may contain any branched group and / or any heteroatom, and T may contain a hydroxyl group (-OH), a thiol group (-SH), a disulfide group (-S-S-), or an amino group (-NHR ３ ), phosphine group (-PH ２ ), phosphine oxide group (-P(=O)R ４ R ５ ), trialkoxysilyl group (-Si(OR ６ ) ( OR ７ ) ( OR ８ )), carboxylic acids (-COOH), or their salts, cations, or anions, R ３ ~R ８ A compound represented by formula (Ib): R-X-C(=W)-Y-(CH ２ ) ｎ-T ... (Ib) [In the above formula (Ib), Y is O, NH or N(R ９ ) and R ９ Examples include compounds represented by [where is an alkyl group or an aryl group, and the other symbols are the same as in formula (Ia) above]. 【0158】 In the above formula (Ia), R- corresponds to the activating group; -X-C(=W)- corresponds to the photoreactive group; and -(CH ２ ) ｎ -T corresponds to a linking group. In the above formula (Ib), R- corresponds to an activating group; -X-C(=W)-Y- corresponds to a photoreactive group; -(CH ２ ) ｎ -T corresponds to a linking group. 【0159】 Examples of monovalent or divalent or more aromatic groups in R include phenyl, benzyl, biphenyl, naphthyl, andylacenyl, fluorenyl, phenantrenyl, azlenyl, phenalenyl, pyrene, perylene, and chrysene groups. In addition, the monovalent or divalent or more aromatic group in R may be a heterocyclic aromatic group containing oxygen, nitrogen, or sulfur. Examples of heterocyclic aromatic groups include furan, oxazole, isoxazole, isothiazole, indone, pyridine, pyridazine, pyrimidine, pyridone, pyrazine, pyrrole, pyrrolidinone, purine, quinoline, isoquinoline, imidazole, thiophene, or groups derived from thiazolium. 【0160】 A monovalent or divalent or more aromatic group in R is C １ -C ４ Alkyl; C １ -C ４ Alkoxy; C １ -C ４ Alkylthiol; F; Cl; Br; I; CN; NO ２ : COOH or its salt; C １ -C ４ Carboxyl; -CH ２ COOR １ (R １ (is an alkyl or aryl group); NH ２ NHR ２ Or NR２ R ３ (R ２ and R ３ are each independently an alkyl group or an aryl group); -CH ２ NHR ４ or -CH ２ NR ４ R ５ (R ４ and R ５ are each independently an alkyl group or an aryl group); sulfo; sulfonyl; etc. may be substituted. 【0161】 Specific examples of R include, for example, 4-tolyl, 4-tert-butylphenyl, 2-naphthyl, 2-anthracenyl, 2-fluorenyl, 4-(4-ethylphenyl)phenyl, 4-nitrophenyl, 4-nitrobenzyl, 2-nitro-5-methylbenzyl, 4,5-dimethoxy-2-nitrobenzyl, and 2,3-dimethoxy-2-nitrobenzyl. 【0162】 Specific examples of the organic ligand capable of reacting with the above light include compounds represented by the following formula; 【0163】 The organic ligand capable of reacting with the above light can be synthesized according to a conventional method. 【0164】 <Device> A device according to an embodiment of the present invention (hereinafter sometimes referred to as "the device of the present embodiment") includes the above-described layered structure, and is characterized by this. Such a device has high durability, conductivity, and quantum efficiency because it includes the above-described layered structure. Such a device is not limited to PE applications, but can also be applied to PL applications and EL applications. 【0165】 Specific examples of the above device include, for example, an imager, a solar cell, a display, a photodetector, a laser, a fluorescent label, an agricultural film, etc. 【0166】Furthermore, the above device can also be suitably used as a light-detecting sensor. Examples of light that such a sensor can detect include short-wavelength infrared (SWIR) light, near-infrared (also called NIR) light, visible light, medium-wavelength infrared (MWIR) light, long-wavelength infrared (LWIR) light, X-rays, and ultraviolet light. In order of increasing wavelength, these are X-rays (wavelength range of approximately 1 pm to 10 nm), ultraviolet light (wavelength range of approximately 10 to 380 nm), visible light (wavelength range of approximately 0.38 to 0.8 μm), NIR (wavelength range of approximately 0.75 to 1.4 μm), SWIR (wavelength range of approximately 1.4 to 3 μm), MWIR (wavelength range of approximately 3 to 8 μm), and LWIR (wavelength range of approximately 8 to 15 μm). 【0167】 The device of this embodiment may further include, in addition to the substrate 10 and the high-density particle layer 20, at least one of an electrode layer, an electron transport layer (ETL), and a hole transport layer (HTL). The electrode layer may be a single layer or two or more layers (for example, an anode layer and a cathode layer). Specifically, the device may have, for example, a structure consisting of, in order, a substrate (substrate 10); an electrode layer such as an anode layer (such as a metal layer); an electron transport layer (ETL) or a hole transport layer (HTL); a high-density particle layer (high-density particle layer 20); a hole transport layer (HTL) or an electron transport layer (ETL); and an electrode layer such as a cathode layer (such as a transparent conductive layer). Furthermore, the device of this embodiment may further include other layers other than those described above (for example, a microlens array layer, a metalens layer, etc.). 【0168】 <Particle Dispersion> A particle dispersion according to one embodiment of the present invention (hereinafter sometimes referred to as "the particle dispersion of this embodiment") is characterized in that nanoparticles to which a ligand that can react with at least one of light, heat, and water or an unreactive ligand is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in a solvent. 【0169】 The particle dispersion of this embodiment can be used, for example, in the manufacture of a layered structure obtained by coating nanoparticles such as QDs onto a substrate such as a CMOS. 【0170】 Furthermore, the particle dispersion of this embodiment corresponds to an intermediate product in the method for manufacturing the layered structure described above. More specifically, the particle dispersion of this embodiment corresponds to particle dispersion B in the manufacturing method (b) of this embodiment. Therefore, by using the particle dispersion of this embodiment, it is possible to manufacture the structure of this embodiment described above, that is, a structure in which durability, conductivity, and quantum efficiency are highly balanced. 【0171】 Specific examples and details of the particle dispersion in this embodiment are the same as those described above for particle dispersion B, and the above description can be incorporated therein. Furthermore, specific examples and details of the ligands, non-reactive ligands, nanoparticles, first element, second element, and solvent in the particle dispersion of this embodiment that are reactable by at least one of light, heat, and water are the same as those described above, and the above content can be incorporated therein. 【0172】 The particle dispersion of this embodiment is preferably a particle dispersion comprising nanoparticles to which ligands that can react by at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), dispersed in a solvent; more preferably a particle dispersion comprising nanoparticles to which ligands that can react by light are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), dispersed in a solvent. 【0173】 In addition, in the particle dispersion of this embodiment, the first element and the second element may combine to form a compound. 【0174】The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples. 【0175】 <Preparation of Nanoparticles (QDs)> Shellless nanoparticles, "InAs," were obtained by referring to the methods described in "Franke et al., Continuous injection synthesis of indium arsenide quantum dots emissive in the short-wavelength infrared, Nat Commun 7, 2016, 12749" and "Ginterseder et al., Scalable Synthesis of InAs Quantum Dots Mediated through Indium Redox Chemistry, Journal of the American Chemical Society, 2020, 142, 9, 4088-4092." Referring to the method described in "Tietze et al., Synthesis of NIR-Emitting InAs-Based Core / Shell Quantum Dots with the Use of Tripyrazolylarsane as Arsenic Precursor, Particle and Particle System Characterization, 2018, 35, 9, pp.1800175," we obtained core-shell type nanoparticles, "InAs / ZnS (core / shell)." Referring to the method described in International Publication No. 2015 / 075564, we obtained shell-less type nanoparticles, "PbS." 【0176】 <Preparation of salts corresponding to non-reactive organic ligands and non-reactive inorganic ligands> Commercially available salts corresponding to non-reactive organic ligands and non-reactive inorganic ligands were prepared. 【0177】 <Preparation of the circuit board> A comb-type electrode (GMT-ITO10 / 5, manufactured by Geomatec Co., Ltd.) was prepared as the circuit board. 【0178】<Preparation of Ligand-Bound Nanoparticles> Colloidal synthesis was performed on InAs, InAs / ZnS (core / shell), and PbS by reacting them with non-reactive organic ligands in organic solvents. This yielded nanoparticles to which non-reactive organic ligands were bound. Ligand exchange treatment was performed by mixing the InAs / ZnS (core / shell) to which non-reactive organic ligands were bound with salts corresponding to non-reactive inorganic ligands in organic solvents, thereby substituting the non-reactive organic ligands with non-reactive inorganic ligands. This produced InAs / ZnS (core / shell) to which non-reactive inorganic ligands were bound. The ligand-bound nanoparticles obtained here exist in an organic solvent state. In other words, a stock solution of ligand-bound nanoparticles was obtained here. 【0179】 <Fabrication of Layered Structure> (Example 1) The layered structure of Example 1 was fabricated according to the following procedure. 【0180】 -Preparation Process- The materials shown in Table 1 were used as the solvent for the ligand-bound nanoparticles and the nanoparticle dispersion. Under a nitrogen atmosphere at room temperature (20-30°C), the stock solution of ligand-bound nanoparticles was added dropwise to the solvent of the nanoparticle dispersion. After addition, stirring or sonication was performed to uniformly disperse the ligand-bound nanoparticles in the solvent of the nanoparticle dispersion. This yielded a particle dispersion (percentage of "ligand-bound nanoparticles" in the particle dispersion: 0.1-40% by mass). 【0181】 -Coating process 1- The obtained particle dispersion was dropped onto the substrate, and the substrate was rotated at a rotation speed of 500 to 3000 rpm for 10 to 60 seconds (spin coating method). This formed a coating film on the substrate. 【0182】 -Removal Step 1- After coating step 1, the substrate on which the coating film was formed was heated at 100°C for 20 minutes under reduced pressure nitrogen. This removed the ligand and octane (solvent of the nanoparticle dispersion) from the coating film. 【0183】- Atomic Layer Deposition Process - After the removal process 1, specifically, while maintaining the substrate temperature at 100 to 250°C and controlling the reaction chamber pressure to 10 to 500 Pa, trimethylaluminum (TMA) was supplied as a precursor to aluminum oxide, and water vapor or ozone was alternately introduced as an oxidizing agent. In each cycle, the supply time for the precursor was 0.1 to 1 second, and the supply time for the oxidizing agent was 0.1 to 1 second, with a nitrogen gas purge process (0.1 to 1 second) following each supply. By repeating this process 10 to 500 times, an aluminum oxide film (hereinafter sometimes referred to as "film A") was formed, and the layered structure of Example 1 was obtained. 【0184】 (Example 2) The preparation step to removal step 1 was performed in the same manner as in Example 1 described above. 【0185】 - Coating process 2 - Zinc chloride (ZnCl ２ ): 0.027 g was dissolved in approximately 25 g (approximately 25 mL) of dehydrated ethanol to obtain a dispersion in which zinc (Zn) is dispersed in ethanol (a dispersion in which the first element is dispersed in the solvent). Also, potassium sulfide (K ２ 0.018 g of sulfur (S) was dissolved in approximately 25 g (approximately 25 mL) of dehydrated ethanol to obtain a dispersion in which sulfur (S) was dispersed in ethanol (a dispersion in which the second element was dispersed in the solvent). In addition, 100 g of dehydrated ethanol was prepared as a rinse solution. Using the obtained dispersions and the prepared rinse solution, the following operations (1) to (4) (hereinafter sometimes referred to as "coating operations") were performed. The application of each dispersion and rinse solution was carried out by the same method as in coating step 1 (spin coating method). (1) A dispersion in which zinc (Zn) was dispersed in ethanol was applied to the coating film after removal step 1. (2) The rinse solution was applied twice to the coating film after (1). (3) A dispersion in which sulfur (S) was dispersed in ethanol was applied to the coating film after (2). (4) The rinse solution was applied twice to the coating film after (3). Subsequently, the above coating operation was repeated, with "on the coating film after removal step 1" in (1) being replaced with "on the coating film after (4)". This coating operation was performed a total of four times. As a result, a ZnS film (inorganic film, hereinafter sometimes referred to as "film B") was formed on the surface of the nanoparticles, and the layered structure of Example 2 was obtained. 【0186】 (Example 3) The layered structure of Example 3 was obtained by the same procedure as in Example 2, except that the above-described coating operation was performed a total of 12 times in coating step 2. The inorganic film formed by coating step 2 in the manufacture of the layered structure of Example 3 (i.e., the above-described coating operation was performed a total of 12 times) may hereafter be referred to as "C film". 【0187】 (Examples 4 and 7) Layered structures of Examples 4 and 7 were obtained by the same procedure as in Example 1, except that the ligand-bound nanoparticles and the solvent of the particle dispersion were as shown in Table 1. 【0188】 (Examples 5 and 8) Layered structures of Examples 5 and 8 were obtained by the same procedure as in Example 2, except that the ligand-bound nanoparticles and the solvent of the particle dispersion were as shown in Table 1. 【0189】 (Examples 6 and 9) The layered structures of Examples 6 and 9 were obtained by the same procedure as in Example 3, except that the ligand-bound nanoparticles and the solvent of the particle dispersion were as shown in Table 1. 【0190】 (Comparative Examples 1-4) The ligand-bound nanoparticles and the solvent for the particle dispersion were selected from those shown in Table 1, and the above-described preparation step to removal step 1 was performed to obtain the layered structures of Comparative Examples 1-4. 【0191】 In Table 1, the "Inorganic Film" column indicates the type of inorganic film in each layered structure, and "-" in Table 1 indicates that no inorganic film is formed on the surface of the nanoparticles. 【0192】 Apparatus: By observing the surface of the nanoparticles using a transmission electron microscope (TEM), it was confirmed that a predetermined inorganic film was formed on the surface of the nanoparticles in the layered structures of Examples 1 to 9. Furthermore, the composition of the high-density particle layer in the fabricated layered structures was confirmed by elemental analysis using energy-dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS). 【0193】Furthermore, in the layered structures of Examples 1 to 9, the energy level at the upper end of the valence band of the inorganic film is the same as or lower than the energy level at the upper end of the valence band of the nanoparticles, and the energy level at the lower end of the conduction band of the inorganic film is the same as or higher than the energy level at the lower end of the conduction band of the nanoparticles. In addition, for the layered structures of Examples 1 to 9, the particle size of the nanoparticles, the packing density of nanoparticles per unit volume in the high-density particle layer, and the thickness of the inorganic film were measured using the method described above. As a result, in the layered structures of Examples 1 to 9, the particle size of the nanoparticles was 1 nm or more and 50 nm or less, the packing density of the nanoparticles was 30 vol% or more and 80 vol% or less, and the thickness of the inorganic film was 0.1 nm or more and 5 nm or less. 【0194】 【0195】 *1 Film A: Aluminum oxide film *2 Film B: Inorganic film formed by performing the above-described coating operation a total of four times in coating step 2 *3 Film C: Inorganic film formed by performing the above-described coating operation a total of twelve times in coating step 2 【0196】 <Evaluation of Durability (PL Strength)> The PL peak strength (PL strength before heating) was measured for the layered structure of Example 1 that was fabricated. Next, the layered structure of Example 1 was placed on a hot plate heated to 70°C in the atmosphere and heated for 8 hours (heating conditions: in the atmosphere, 70°C, 8 hours). The PL peak strength (PL strength after heating) was measured for the layered structure of Example 1 after heating. Using the measured "PL strength before heating" and "PL strength after heating," the PL strength retention rate (%) was calculated using the following formula: PL strength retention rate (%) = (PL strength after heating × 100) / PL strength before heating The PL strength retention rate was also calculated for the layered structures of Examples 2 to 9 and Comparative Examples 1 to 4 that were fabricated using the method described above. The results are shown in Table 2. Here, a higher PL strength retention rate indicates higher durability. The PL peak intensity measurements described above were performed using photoluminescence spectroscopy with a spectrometer equipped with a near-infrared (NIR) compatible detector (e.g., an InGaAs photodiode). 【0197】Furthermore, the layered structures of Examples 1 to 9 and Comparative Examples 1 to 4 were each placed on a hot plate heated to 70°C inside a box humidified to 100% RH at room temperature under atmospheric conditions, and heated for 8 hours (heating conditions: atmospheric, 70°C, humidified, 8 hours). The PL peak intensity (PL intensity after heating) of each layered structure after heating was measured using the same method as described above. Next, the PL intensity retention rate (%) was calculated based on the formula described above. The results are shown in Table 2. Here, a higher PL intensity retention rate indicates higher durability. 【0198】 【0199】 <Evaluation of Conductivity 1> The photocurrent (nA) was measured for each of Examples 1 to 3 and Comparative Example 1. The measured value for Comparative Example 1 was set to 1.0, and the measured values ​​for Examples 1 to 3 were indexed. The results are shown in Table 3. 【0200】 Furthermore, the photocurrent (nA) was measured for Examples 4-6 and Comparative Example 2. The measured value for Comparative Example 2 was set to 1.0, and the measured values ​​for Examples 4-6 were indexed. The results are shown in Table 4. 【0201】 Furthermore, the photocurrent (nA) was measured for Examples 7-9 and Comparative Example 3. The measured value for Comparative Example 3 was set to 1.0, and the measured values ​​for Examples 7-9 were indexed. The results are shown in Table 5. 【0202】 Here, if the index is greater than 1.0, it indicates improved conductivity, that is, excellent conductivity. The photocurrent (nA) mentioned above was determined by I-V measurement. Specifically, electrodes were brought into contact with the fabricated layered structure using a probe station, and the layered structure was irradiated with a light source of 900 to 1200 nm. The current (nA) that flowed when the light source was irradiated was measured. The value obtained from this measurement was defined as the photocurrent (nA). The measuring device was a source meter (Keitley 2400 series), and the measurement conditions were an applied voltage of 0 to 10 V, a step size of 0.1 V, and a measurement time of 1 to 10 seconds per point. 【0203】 【0204】<Removal Process 2> Each of the prepared Examples 2, 3, 5, 6, 8, and 9 was heated at 100°C for 20 minutes under reduced pressure nitrogen. 【0205】 Furthermore, Examples 2, 5, 6, 8, and 9 used in "Evaluation of Conductivity 2" described later are layered structures after removal step 2. Also, Examples 2, 5, 8, and 9 used in "Evaluation of Durability (Changes in I-V Characteristics)" described later are layered structures after removal step 2. 【0206】 <Evaluation of Conductivity 2> The photocurrent (nA) was measured for both Example 2 and Comparative Example 1. The measured value for Comparative Example 1 was set to 1.0, and the measured value for Example 2 was indexed. The results are shown in Table 6. 【0207】 Furthermore, the photocurrent (nA) was measured for Example 5, Example 6, and Comparative Example 2. The measured value for Comparative Example 2 was set to 1.0, and the measured values ​​for Example 5 and Example 6 were indexed. The results are shown in Table 7. 【0208】 Furthermore, the photocurrent (nA) was measured for Example 8, Example 9, and Comparative Example 3. The measured value for Comparative Example 3 was set to 1.0, and the measured values ​​for Example 8 and Example 9 were indexed. The results are shown in Table 8. 【0209】 Here, if the index is greater than 1.0, it indicates improved conductivity, that is, excellent conductivity. The photocurrent (nA) measurement described above was performed using the same method as the photocurrent (nA) measurement in conductivity evaluation 1. 【0210】 【0211】<Evaluation of Durability (Changes in I-V Characteristics)> For each layered structure shown in Table 9, the photocurrent (nA) and dark current (nA) were measured. Using the measured photocurrent (nA) and dark current (nA), the separation factor (before heating) was calculated using the following formula: Separation factor = (Photocurrent (nA) - Dark current (nA)) / Dark current (nA) Next, each layered structure was placed on a hot plate heated to 70°C in the atmosphere and heated for 8 hours (heating conditions: atmosphere, 70°C, 8 hours). For each layered structure after heating, the photocurrent (nA) and dark current (nA) were measured. Using the photocurrent (nA) and dark current (nA) of the layered structure after heating, the separation factor (after heating) was calculated based on the above formula. The results are shown in Table 9. Here, if the separation factor after heating is greater than the separation factor before heating, or if the separation factor after heating and the separation factor before heating are the same, it indicates high durability, and also indicates that the increase in dark current is suppressed, and the signal separation in the weak light region is maintained or improved. Here, the photocurrent (nA) was determined by the same method as the photocurrent (nA) in conductivity evaluation 1. The dark current (nA) was determined by I-V measurement. Specifically, electrodes were brought into contact with the fabricated layered structure using a probe station, and the current (nA) flowing through the layered structure without irradiating it with a light source was measured. The value obtained by this measurement was defined as the dark current. 【0212】 【0213】Furthermore, for each of the layered structures shown in Table 10, the photocurrent (nA) and dark current (nA) were determined using the method described above. Using the measured photocurrent (nA) and dark current (nA), the separation factor (before heating) was calculated using the following formula: Separation factor = (Photocurrent (nA) - Dark current (nA)) / Dark current (nA) Next, each layered structure was placed on a hot plate heated to 70°C inside a box humidified to 100% RH at room temperature under atmospheric conditions, and heated for 8 hours (heating conditions: under atmospheric conditions, 70°C, humidified, 8 hours). For each layered structure after heating, the photocurrent (nA) and dark current (nA) were measured using the same method as described above. Using the photocurrent (nA) and dark current (nA) of the layered structure after heating, the separation factor (after heating) was calculated based on the above formula. The results are shown in Table 10. Here, if the separation factor after heating is greater than the separation factor before heating, or if the separation factor after heating and the separation factor before heating are the same, it indicates high durability, suppresses the increase in dark current, and maintains or improves signal separation in the low-light region. 【0214】 【0215】 Table 2 shows that Examples 1 to 3 according to the present invention had a higher PL strength retention rate compared to Comparative Example 1. Furthermore, Examples 4 to 6 according to the present invention had a higher PL strength retention rate compared to Comparative Example 2. Also, Examples 7 to 9 according to the present invention had a higher PL strength retention rate compared to Comparative Example 3. Therefore, it can be seen that the formation of a predetermined inorganic film on the surface of the nanoparticles improves durability. Furthermore, Examples 1 to 9 according to the present invention had a higher PL strength retention rate compared to Comparative Example 4. Therefore, it can be seen that the layered structure of this embodiment has high durability. 【0216】Tables 3 to 5 show that Examples 1 to 9 according to the present invention had a photocurrent (index) greater than 1.0. Furthermore, Tables 6 to 8 show that even after removal step 2, Examples 2, 5, 6, 8, and 9 according to the present invention had a photocurrent (index) greater than 1.0. Therefore, it can be seen that the conductivity of the layered structure of this embodiment is improved by the formation of a predetermined inorganic film on the surface of the nanoparticles. In Examples 1 to 9, the layered structure was fabricated using nanoparticles to which a non-reactive ligand was bound as the ligand. During the process of fabricating the layered structure (mainly removal step 1), at least a portion of the non-reactive ligand contained in the coating film is removed from the coating film, resulting in increased density of the high-density particle layer in the layered structure (the nanoparticle packing density becomes 30 vol% or more and 80 vol% or less). This is presumed to improve the conductivity of Examples 1 to 9. 【0217】 Tables 9 and 10 show that in the embodiment according to the present invention, the separation factor after heating was greater than the separation factor before heating, whereas in the comparative example, the separation factor after heating was smaller than the separation factor before heating. This indicates that the layered structure of this embodiment has high durability. Furthermore, it can be seen that the layered structure of this embodiment suppresses the increase in dark current and maintains or improves the signal separation degree in the low-light region. 【0218】 As described above, in the layered structure of the embodiment according to the present invention, a predetermined inorganic film is formed on the surface of the nanoparticles; in other words, the surface defects of the nanoparticles are inactivated in the layered structure of the embodiment according to the present invention. On the other hand, in the layered structure of the comparative example, the predetermined inorganic film is not formed on the surface of the nanoparticles, so the surface defects of the nanoparticles are not inactivated. Furthermore, it is thought that the inactivation of the surface defects of the nanoparticles reduces the number of traps at the interface, contributing to improved conductivity. And as a result of the inactivation of the surface defects of the nanoparticles, it is thought that the quantum efficiency is also improved at the same time. From the above, it is inferred that the layered structure of the embodiment has improved quantum efficiency compared to the layered structure of the comparative example. 【0219】From the above, it can be seen that the layered structure of this embodiment exhibits a high degree of balance between durability, conductivity, and quantum efficiency. 【0220】 According to the present invention, it is possible to provide a structure and a method for manufacturing the same that exhibits a high degree of balance between durability, conductivity, and quantum efficiency. Furthermore, according to the present invention, it is possible to provide a device comprising the above-described layered structure. Furthermore, according to the present invention, it is possible to provide a particle dispersion that can correspond to an intermediate product in the method for manufacturing the above-described layered structure. 【0221】 1. Layered structure 10. Substrate 20. High-density particle layer 21. Nanoparticles 22. Inorganic film 25. Ligand 26. First element / Second element 30. Mask

Claims

1. A layered structure comprising a substrate and a high-density particle layer on the substrate, wherein the high-density particle layer contains nanoparticles with an inorganic film formed on its surface, the nanoparticles have a particle size of 1 nm to 50 nm, the high-density particle layer has a packing density of nanoparticles per unit volume of 30 vol% to 80 vol%, the inorganic film has a thickness of 0.1 nm to 5 nm, the energy level at the upper end of the valence band of the inorganic film is the same as or lower than the energy level at the upper end of the valence band of the nanoparticles, and the energy level at the lower end of the conduction band of the inorganic film is the same as or higher than the energy level at the lower end of the conduction band of the nanoparticles.

2. A method for manufacturing a layered structure according to claim 1, comprising: a preparation step A of preparing a particle dispersion A1 in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound are dispersed in a solvent S1; a coating step A1 of applying the particle dispersion A1 to a substrate; a film-forming step A of applying at least one of light, heat, and moisture to the coated surface after the coating step A1 to form a coating film; a removal step A1 of removing the reacted ligands and the solvent S1 from the coating film after the film-forming step A1; and a coating step A2 of applying a dispersion A2 in which inorganic film-forming elements are dispersed in a solvent S2 to the coating film after the removal step A1.

3. A method for manufacturing a layered structure according to claim 1, comprising: a preparation step B of preparing a particle dispersion B in which nanoparticles to which ligands that can react with at least one of light, heat, and moisture are bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb) are dispersed in a solvent S3; a coating step B of applying the particle dispersion B to a substrate; and a film forming step B of applying at least one of light, heat, and moisture to the coated surface after the coating step B to form a coating film.

4. The method for manufacturing a layered structure according to claim 3, further comprising a sulfidation step of subjecting the inorganic film on the surface of the nanoparticles to a sulfidation treatment after the film formation step B.

5. A method for manufacturing a layered structure according to claim 1, comprising: a preparation step C of preparing a particle dispersion C1 in which nanoparticles to which non-reactive ligands are bound are dispersed in a solvent S4; a coating step C1 of coating the particle dispersion C1 onto a substrate; a removal step C1 of removing the solvent S4 from the particle dispersion C1 coated on the substrate after the coating step C1 to form a coating film; and a film forming step C of forming an inorganic element on the coating film.

6. A method for manufacturing a layered structure according to claim 1, comprising: a preparation step D of preparing a particle dispersion D in which nanoparticles to which a non-reactive ligand is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), are dispersed in a solvent S6; a coating step D of coating the particle dispersion D onto a substrate; and a removal step D of removing the solvent S6 from the particle dispersion D coated on the substrate after the coating step D.

7. A device characterized by comprising the layered structure described in claim 1.

8. The device according to claim 7, further comprising, in addition to the substrate and the high-density particle layer, at least one selected from an electrode layer, an electron transport layer, and a hole transport layer.

9. A particle dispersion characterized by comprising nanoparticles to which a ligand that is reactive or non-reactive in response to at least one of light, heat, and moisture is bound, one or more first elements selected from metal elements and silicon (Si), and one or more second elements selected from elements belonging to Group 16 of the periodic table, phosphorus (P), arsenic (As), and antimony (Sb), dispersed in a solvent.

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