JP2021040029A - Microstructure, manufacturing method of microstructure, and photoelectric conversion element - Google Patents

Abstract

To provide a microstructure capable of suppressing carrier resistance loss in addition to an optical function that causes light scattering when applied to a light scattering layer of a photoelectric conversion element.SOLUTION: A microstructure (nanostructure 10) includes an insulating core portion 11, and a surface layer 12 that covers the core portion, and the surface layer is composed of a transition metal dichalcogenide. With such a configuration, when the microstructure is applied to a light scattering layer of a photoelectric conversion element, in addition to an optical function of causing light scattering, the resistance loss of the carrier can be suppressed.SELECTED DRAWING: Figure 1

Description

The present invention relates to microstructures, methods for manufacturing microstructures, and photoelectric conversion elements.

Conventionally, for example, in order to cause light scattering near the photoelectric conversion layer of a photoelectric conversion element and reduce optical loss, a light scattering layer in which nanometer-scale particles (nanoparticles) are dispersed is formed in the photoelectric conversion element. It is proposed to do.

As nanoparticles applicable to this type of light scattering layer, for example, nanoparticles whose surface is formed of an insulator having a refractive index smaller than that of the light absorption layer have been proposed (see Patent Document 1).
In addition, a light scattering film in which a light scattering body is formed of a nanostructured insulator such as titanium oxide, diamond, or silicon oxide and the light scattering body is embedded in a translucent and conductive medium has also been proposed ( See Patent Document 2).
Further, _{a dye-sensitized solar cell in which the surface of SiO 2} particles is coated with TiO ₂ nanoparticles is also known (see Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-055178 Japanese Unexamined Patent Publication No. 2006-171026

”Designed Synthesis of SiO2 / TiO2 Core / Shell Structure As Light Scattering Material for Highly Efficient Dye-Sensitized Solar Cells” ACS Appl. Mater. Interfaces 2013,5, 4815-4820

From the viewpoint of further improving the performance of the photoelectric conversion element, it is required to suppress the resistance loss of the carrier in the light scattering layer in addition to the optical function of causing light scattering in the light scattering layer.

The present invention has been made in view of the above circumstances, and when applied to a light scattering layer of a photoelectric conversion element, in addition to an optical function that causes light scattering, a minute amount capable of suppressing carrier resistance loss. The purpose is to provide a structure.

The microstructure according to one aspect of the present invention has an insulating core portion and a surface layer covering the core portion, and the surface layer is composed of a transition metal dichalcogenide.
Another aspect of the present invention is a method for producing a microstructure having an insulating core portion and a surface layer covering the core portion, wherein the surface layer is composed of a transition metal dichalcogenide. A step of preparing a first microstructure having an insulating surface, a step of forming a layer containing a transition metal element on the surface of the first microstructure to form a second microstructure, and a first step. 2. The step of carbonizing the layer containing the transition metal element of the microstructure to form a third microstructure having a surface layer of the transition metal dichalcogenide.

According to the present invention, it is possible to provide a microstructure capable of suppressing carrier resistance loss in addition to an optical function that causes light scattering when applied to a light scattering layer of a photoelectric conversion element.

It is a figure which shows typically the structural example of the nanostructure of this embodiment. It is a schematic diagram which shows the crystal structure example of a transition metal dichalcogenide. It is a flow chart which shows the example of the manufacturing method of the nanostructure of this embodiment. It is a schematic diagram which shows the structural example of the photoelectric conversion element of this embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
In the embodiment, in order to make the explanation easy to understand, structures or elements other than the main part of the present invention will be described in a simplified or omitted manner. Further, in the drawings, the same elements are designated by the same reference numerals. In the drawings, the shapes, dimensions, etc. of each element are schematically shown, and do not show the actual shapes, dimensions, etc.

<Structure of nanostructures>
FIG. 1A is a cross-sectional view schematically showing a configuration example of the nanostructure 10 of the present embodiment.
The nanostructure 10 is an example of a microstructure, and its overall shape is nanometer-scale particles. The nanostructure 10 is used, for example, as a material for a light scattering layer arranged between the photoelectric conversion layer and the electrode layer of the photoelectric conversion element.
The nanostructure 10 has an insulating core portion 11 and a surface layer 12 that covers the core portion 11.

(Core part 11)
The core portion 11 shown in FIG. 1 is a particle formed of an insulating material and having a spherical shape as a whole.
The core portion 11 includes, for example, silica (refractive index 1.47), alumina (refractive index 1.76), silicon nitride (refractive index 2.0), titania (refractive index 2.49), soda lime glass (refractive index). It is composed of a material selected from a material group such as a rate of 1.52), or a multilayer structure whose surface is coated with any material of the above material group.
Note that FIG. 1B shows an example in which the core portion 11 is a multilayer structure having an outer core portion 11a which is a coating layer on the surface side and an inner core portion 11b adjacent to the inside of the outer core portion 11a. It is a sectional view. In the present embodiment, an example in which the core portion 11 has a two-layer structure is shown, but the core portion 11 may be a multi-layer structure having three or more layers.

As shown in FIG. 1, when the core portion 11 is a spherical particle, the surface shape of the core portion 11 on which light is incident is spherical, so that the light reflection effect and the light scattering effect in the nanostructure 10 can be improved. it can. Further, it is considered that by forming the surface layer 12 along the spherical surface of the surface of the core portion 11, the effect of reducing the resistance loss of the carrier can be easily improved as described later.
However, the shape of the core portion 11 and the overall shape of the nanostructure 10 are not necessarily limited to a spherical shape. For example, the shape of the core portion 11 and the overall shape of the nanostructure 10 may be nanometer-scale wires, tubes, fibers, or the like.

The size of the core portion 11 is not particularly limited, but can be in the range of 100 nm to 1200 nm. For example, when the core portion 11 is spherical particles, the particle size of the core portion 11 can be in the range of 100 nm to 1200 nm.
Further, the size of the core portion 11 is set according to the wavelength of the light incident on the nanostructure 10, and the longer the wavelength of the incident light in the intended use, the larger the upper limit of the size of the core portion 11. Is preferable. For example, when the central wavelength of the incident light in the intended use is 1000 nm, the size of the core portion 11 is preferably 100 nm to 1000 nm. Further, in the above case, when the center wavelengths are 700 nm, 450 nm, and 300 nm, respectively, the size of the core portion 11 is preferably 100 nm to 700 nm, 100 nm to 450 nm, and 100 nm to 300 nm, respectively.

FIG. 1C is a cross-sectional view showing an example of a nanostructure 10 in which a surface layer 12 is formed on a core portion 11 of the multilayer structure shown in FIG. 1B.
As shown in FIGS. 1B and 1C, when the core portion 11 is a multi-layer structure, when light is incident on the nanostructure 10, light is reflected or scattered at the interface of each layer of the core portion 11. To do. At this time, if the refractive index of the outer core portion 11a located on the outermost side of the core portion 11 of the multilayer structure is made larger than the refractive index of the inner core portion 11b adjacent to the inside of the outer core portion 11a, a higher light reflection effect is obtained. Can be caused.

For example, in the core portion 11 of the multilayer structure, the material of the outer core portion 11a covering the surface of the core portion 11 is titania (refractive index 2.49), and the material of the inner core portion 11b is silica (refractive index 1.47). Is preferable. According to the above combination, the difference in refractive index between the outer core portion 11a and the inner core portion 11b can be increased in the core portion 11 of the multilayer structure, and the light reflection at the interface between the outer core portion 11a and the inner core portion 11b can be increased. The effect and light scattering effect can be increased. For example, when the nanostructure 10 is applied to the light scattering layer of the photoelectric conversion element, the surface on which the light scattering layer is arranged (for example, the back surface side of the light emitting surface of the light emitting element or the light receiving surface of the light receiving element) is provided with the above configuration. The light reflection effect on the back side) can be further improved.

(Surface layer 12)
The surface layer 12 shown in FIG. 1 is composed of a transition metal dichalcogenide (TMDC) and is a semiconductor or a conductor. Further, the surface layer 12 can transmit incident light inside the surface layer 12.

The transition metal dichalcogenide is a compound having a layered structure represented by the chemical composition of _{MX 2 in which} the transition metal element M and the chalcogen element X are bonded. In the transition metal dichalcogenide of the surface layer 12, the transition metal element M contains at least one of V, Ta, Mo, W, Ti, Nb, Hf, and Zr, and the chalcogen element X contains at least one of S, Se, and Te. Including one.

FIG. 2 is a schematic view of the crystal structure of a transition metal dichalcogenide having a laminated structure. FIG. 2 corresponds to a state in which the crystal structure is viewed from the direction in the ab plane that intersects the stacking direction (c-axis direction).
When the transition metal dichalcogenide has a laminated structure, a single layer is laminated in the c-axis direction, and each layer is bonded by a weak van der Waals force. Therefore, in the transition metal dichalcogenide, the resistivity in the ab plane in each layer has a characteristic lower than the resistivity in the c-axis direction, which is the direction of lamination.

In the present embodiment, it is preferable to form the surface layer 12 in an orientation in which the c-axis of the transition metal dichalcogenide is perpendicular to the surface of the core portion 11. As a result, in the surface layer 12 of the nanostructure 10, carriers can move in the ab plane of the transition metal dichalcogenide along the surface of the core portion 11. Since the resistivity in the ab plane is lower than that in the c-axis direction in the stacking direction, it is considered that the resistance loss of the carrier moving in the surface layer 12 of the nanostructure 10 can be reduced.
Although not particularly limited, for example, in a transition metal dichalcogenide in which the transition metal element M contains at least one of Mo, W, Hf, and Zr, the c-axis of the transition metal dichalcogenide is relative to the surface of the core portion 11. It is preferable to form the surface layer 12 in a vertical orientation.

Further, when the transition metal element M of the transition metal dichalcogenide contains at least one of Nb, V, Ta, and Ti, the resistivity is lower than that when these are not included, and the resistivity of the carrier on the surface layer 12 is reduced. The loss can be further reduced.

Therefore, when the transition metal element M of the transition metal dichalcogenide contains at least one of Nb, V, Ta, and Ti, the c-axis of the transition metal dichalcogenide is oriented so as to be perpendicular to the surface of the core portion 11. It is not necessary to form the surface layer 12. In other words, when the transition metal element M of the transition metal dichalcogenide contains at least one of Nb, V, Ta and Ti, the c-axis of the transition metal dichalcogenide is random or arbitrary with respect to the surface of the core portion 11. The surface layer 12 may be formed so as to be oriented in the direction of.

Here, as the transition metal dichalcogenide when the transition metal element M contains at least one of Nb, V, Ta, and Ti, (M, Mo) (Se, S) ₂ , M (Se, S) ₂ , It is preferable to use MSe ₂ or MS ₂ (where M is Nb, V, Ta, or Ti). The transition metal dichalcogenide described above is a material having a high work function and a low resistivity.

Generally, when the thickness of the surface layer 12 is reduced, the surface layer 12 is easily formed in an orientation in which the c-axis of the transition metal dichalcogenide is perpendicular to the surface of the core portion 11. Therefore, although not particularly limited, the thickness of the surface layer 12 of the nanostructure 10 is preferably 5 nm to 50 nm, and more preferably 30 nm or less.
When the c-axis of the transition metal dichalcogenide is oriented perpendicular to the surface of the core portion 11, the resistivity of the surface layer 12 is low. Therefore, the thickness of the surface layer 12 in this case may be a thickness corresponding to a few atomic layers.

For example, it is assumed that the nanostructure 10 is applied to a light scattering layer arranged between the photoelectric conversion layer and the electrode layer of the photoelectric conversion element, and the electrode layer facing the light scattering layer is on the hole transport side. .. In this case, the surface layer 12 of the transition metal dichalcogenide of the nanostructure 10 has a larger work function than the photoelectric conversion layer, and the surface layer 12 of the nanostructure 10 forms an ohmic contact with the photoelectric conversion layer.

For example, when the photoelectric conversion element is a light receiving element, the holes generated in the photoelectric conversion layer are transported to the electrode layer without causing a barrier. For example, when the photoelectric conversion element is a light emitting element, the holes injected from the electrodes are transported to the photoelectric conversion layer without causing a barrier.

Further, the refractive index of the surface layer 12 of the nanostructure 10 is preferably larger than the refractive index of the core portion 11. As a result, the light reflection effect at the interface between the surface layer 12 of the nanostructure 10 and the core portion 11 can be increased, and the light reflected from the nanostructure 10 can be increased.

For example, when the material of the surface layer 12 is MoSe ₂ , the refractive index is 3.25, and when _{the material of the surface layer 12 is MoS 2} , the refractive index is 4.0. On the other hand, when the material of the core portion 11 is any of silica, alumina, silicon nitride, titania, and soda lime glass, the refractive index of the core portion 11 is in the range of 1.47 to 2.49. Therefore, it can be seen that the refractive index of the surface layer 12 can be made larger than the refractive index of the core portion 11.

<Manufacturing method of nanostructures>
Hereinafter, the method for producing the nanostructure 10 of the present embodiment will be described with reference to the flow chart of FIG.

(Step S1)
As step S1, a first nanostructure with an insulating surface is prepared. The first nanostructure corresponds to the core portion 11, for example, a material such as silica, alumina, silicon nitride, titania, soda lime glass, or a multilayer whose surface side is covered with any of the above materials. Examples include nanoparticles such as structures. Commercially available nanoparticles can be used (see, for example, https://www.sigmaaldrich.com/japan/materialscience/nano-materials/nanopowders.html ).

(Step S2)
Next, as step S2, a layer containing a transition metal element M such as molybdenum is formed on the surface of the first nanostructure to form the second nanostructure. The transition metal element M contains at least one of V, Ta, Mo, W, Ti, Nb, Hf, and Zr.
Further, when the film thickness of the layer containing the transition metal on the surface of the first nanostructure is 30 nm or less, the transition metal dichalcogenide is oriented so that the c-axis is perpendicular to the surface of the core portion 11 of the nanostructure 10. The surface layer 12 of the above can be formed, which is preferable.

For example, when forming a layer containing a transition metal on the first nanostructure in step S2, a barrel-type sputtering film forming apparatus (barrel) that forms the film while rotating the barrel into which the first nanostructure is charged. Sputter) can be used. As a result, the first nanostructure can be uniformly and efficiently coated with a coating containing a transition metal.

When forming a layer containing a transition metal element on the surface of the first nanostructure by sputtering, a sputtering source containing Nb can be used. Alternatively, a sputtering source containing, for example, Mo as a transition metal element other than Nb may be used together with the sputtering source containing Nb. In this case, a layer containing Nb and Mo as transition metal elements can be formed on the surface of the first nanostructure.

Further, in step S2, the solution containing the first nanostructure and the transition metal element may be mixed and then dried. This also makes it possible to form a second nanostructure having a layer containing a transition metal element on the surface of the first nanostructure.

In this case, the solution containing the transition metal element preferably contains Mo or W. For example, ammonium thiomolybdate ((NH ₄ ) ₂ MoS ₄ ), ammonium thiotang state ((NH ₄ ) ₂ WS ₄ ) and those containing hydrates thereof can be mentioned. The solution containing the transition metal element may also contain sulfur, selenium or tellurium (Te).
When the solution contains sulfur, selenium or tellurium, even if the second nanostructure is heated in an atmosphere containing no chalcogen element in step S3 described later, it transitions to the surface of the first nanostructure. The nanostructure 10 (third nanostructure) having the surface layer 12 of the metal dichalcogenide can be formed.

(Step S3)
Next, as step S3, the layer containing the transition metal element in the second nanostructure is chalcogenized. As a result, the nanostructure 10 (third nanostructure) in which the surface layer 12 of the transition metal dichalcogenide is formed on the surface of the first nanostructure is formed.

In step S3, the second nanostructure is heat-treated in an atmosphere containing an element of chalcogen.
When selenium is formed as chalcogenide, a treatment of heating the second nanostructure in an atmosphere of a selenium source gas containing selenium (for example, hydrogen selenide or selenium vapor) is performed. When sulfurizing as chalcogenide, a treatment is performed in which the second nanostructure is heated in an atmosphere of a sulfur source gas containing sulfur (for example, hydrogen sulfide or sulfur vapor). The second nanostructure may be heat-treated in an atmosphere containing tellurium. In addition, the second nanostructure may be heated in an atmosphere containing a plurality of chalcogen elements. The heating temperature in these heat treatments is, for example, about 500 ° C.

For example, the transition metal element M contains at least one of Nb, V, Ta, and Ti, and by selecting selenium or sulfur as the atmosphere containing the chalcogen element, the transition metal dichalcogenide is (M, Mo) (Se, Se, S) ₂ , M (Se, S) ₂ , MSe ₂ or MS ₂ (where M is any of Nb, V, Ta, Ti) can form the surface layer 12.

When the layer containing the transition metal element M is formed by using the solution containing sulfur, selenium or tellurium in step S2, the second nanostructure is heated in the atmosphere containing no chalcogen element in step S3. You may. In this case, since the layer containing the transition metal element M contains the chalcogen element in advance, the nanostructure 10 having the surface layer 12 of the transition metal dichalcogenide can be formed on the surface of the first nanostructure.

Further, in the treatment of heating the second nanostructure in step S3, it is preferable to heat in an atmosphere containing hydrogen. In seleniumization and sulfurization, it is particularly preferable to use hydrogen selenide and hydrogen sulfide, and when these gases are not used, it is preferable to include hydrogen in the atmospheric gas. When heated in an atmosphere containing hydrogen, transition metal dichalcogenides can be formed at a lower temperature than in the case of chalcogenide in an atmosphere without hydrogen. The heating temperature when heating in an atmosphere containing hydrogen is, for example, 420 ° C to 500 ° C.
Through the above steps, the nanostructure 10 shown in FIG. 1 (A) or FIG. 1 (C) is completed.

<Structure of photoelectric conversion element>
Next, a configuration example of a photoelectric conversion element using the nanostructure 10 of the present embodiment will be described.
FIG. 4A is a cross-sectional view in the thickness direction showing a configuration example of the light receiving element 20A using the nanostructure 10.
The light receiving element 20A is an example of a photoelectric conversion element, and examples thereof include an optical sensor, a solar cell, and an image pickup element.

The light receiving element 20A shown in FIG. 4A has a substrate 21, a first electrode layer 22, a photoelectric conversion layer 23A, and a second electrode layer 24. The first electrode layer 22, the photoelectric conversion layer 23A, and the second electrode layer 24 are laminated on the substrate 21 in this order from the bottom in the drawing. The first electrode layer 22 is located on the back side of the light receiving surface, and the second electrode layer 24 is made of a transparent conductive film and faces the light receiving surface side on the upper side in the drawing. Although FIG. 4A shows an example in which the substrate 21 is arranged on the back surface side of the light receiving surface, instead of the substrate 21, a transparent substrate having translucency is used on the second electrode layer 24 side of the light receiving surface. It may be arranged.

The material of the photoelectric conversion layer 23A of the light receiving element 20A includes a VI group semiconductor, an I-III-VI _{group 2} compound semiconductor, an I- _2- II-IV-VI _{group 4} compound semiconductor, an II-VI group compound semiconductor, and III-V. Group compound semiconductors and organic semiconductors can be applied.

Further, a plurality of nanostructures 10 of the above embodiment are arranged at the interface of the photoelectric conversion layer 23A with the first electrode layer 22. Overlapping description of the structure of the nanostructure 10 will be omitted.
The surface layer 12 of the nanostructure 10 is in electrical contact with the first electrode layer 22. Further, the photoelectric conversion layer 23A and the surface layer 12 of the nanostructure 10 form a good ohmic contact.

The photoelectric conversion layer 23A has both a portion in contact with the nanostructure 10 and a portion in contact with the first electrode layer 22 on the surface facing the first electrode layer 22 (the back surface side of the light receiving surface). In other words, the first electrode layer 22 has both a portion in contact with the nanostructure 10 and a portion in contact with the photoelectric conversion layer 23A on the surface facing the photoelectric conversion layer 23A.

As a result, the surface layer 12 of the nanostructure 10 and the first electrode layer 22 form a fine uneven surface having conductivity at the interface portion between the photoelectric conversion layer 23A and the surface layer 12. In the light receiving element 20A of the present embodiment, both the surface layer 12 of the nanostructure 10 and the first electrode layer 22 serve as a conductive bonding interface and have a function of transporting carriers.
Therefore, the carriers generated in the photoelectric conversion layer 23A of the light receiving element 20A can reach the first electrode layer 22 through the transition metal dichalcogenide of the surface layer 12 without bypassing the nanostructure 10. Therefore, the resistance loss of the carrier from the photoelectric conversion layer 23A to the first electrode layer 22 can be reduced.

Here, when the insulating nanoparticles are arranged between the first electrode layer 22 and the photoelectric conversion layer 23A, the surface of the insulating nanoparticles does not have conductivity, so that the photoelectric conversion layer 23A and the first Only the portion where the electrode layer 22 comes into direct contact becomes the bonding interface. That is, when the insulating nanoparticles are arranged between the first electrode layer 22 and the photoelectric conversion layer 23A, the bonding interface with the photoelectric conversion layer 23A is compared with the light receiving element 20A shown in FIG. 4 (A). The area of the carrier becomes small, and the resistance loss of the carrier also becomes large.

Light is incident on the light receiving element 20A from the light receiving surface side. The light incident on the light receiving element 20A passes through the second electrode layer 24 and reaches the photoelectric conversion layer 23A, and a part of the light also reaches the nanostructure 10 and the first electrode layer 22.

A part of the light that has reached the surface layer 12 of the nanostructure 10 is reflected by the surface of the surface layer 12 and is incident on the photoelectric conversion layer 23A again. Further, the rest of the light that has reached the surface layer 12 of the nanostructure 10 is incident on the surface layer 12. Part of the light incident on the surface layer 12 of the nanostructure 10 is absorbed by the surface layer 12, but the other reaches the interface between the surface layer 12 and the core portion 11. Light is reflected or scattered on the surface of the core portion 11, the reflected light is incident on the surface layer 12 again, and light is scattered at the interface between the surface layer 12 and the photoelectric conversion layer 23A. The light incident on the core portion 11 also reaches the interface between the core portion 11 and the surface layer 12 again, excluding the light absorbed by the core portion 11, and causes reflection and scattering.

As described above, light is reflected or scattered at the interface between the surface layer 12 and the core portion 11 of the nanostructure 10, so that the reflected light from the back surface side of the light receiving surface in the light receiving element 20A increases. As a result, the light absorbed by the photoelectric conversion layer 23A increases, so that the optical loss of the light receiving element 20A can be reduced.

Further, FIG. 4B is a cross-sectional view in the thickness direction showing a configuration example of the light emitting element 20B using the nanostructure 10. The light emitting element 20B is an example of a photoelectric conversion element, and examples thereof include an LED (light emitting diode), an organic EL (electro-luminescence) element, and an inorganic EL element.

The light emitting element 20B shown in FIG. 4B has a substrate 21, a first electrode layer 22, a photoelectric conversion layer 23B, and a second electrode layer 24. The first electrode layer 22, the photoelectric conversion layer 23B, and the second electrode layer 24 are laminated on the substrate 21 in this order from the bottom in the drawing. The first electrode layer 22 is located on the back side of the light emitting surface, and the second electrode layer 24 is made of a transparent conductive film and faces the light emitting surface side on the upper side in the drawing. Although FIG. 4B shows an example in which the substrate 21 is arranged on the back surface side of the light emitting surface, instead of the substrate 21, a transparent substrate having translucency is used on the second electrode layer 24 side of the light emitting surface. It may be arranged.

Further, a plurality of nanostructures 10 of the above embodiment are arranged at the interface of the photoelectric conversion layer 23B with the first electrode layer 22. Since the configuration and arrangement of the nanostructure 10 are the same as those of the light receiving element 20A of FIG. 4A, duplicate description will be omitted.

In the light emitting element 20B, a voltage is applied between the first electrode layer 22 and the second electrode layer 24 to inject carriers into the photoelectric conversion layer 23B, and the carriers recombine in the photoelectric conversion layer 23B to emit light. .. At this time, in the first electrode layer 22 on which the nanostructure 10 is arranged, carriers are injected through the surface layer 12 of the nanostructure 10 in addition to the first electrode layer 22, so that resistance loss Is reduced.

Further, in the light emitting element 20B, a part of the light emitted from the photoelectric conversion layer 23B toward the first electrode layer 22 is incident on the nanostructure 10 and becomes the surface of the surface layer 12 or the surface layer 12. Reflection or scattering is generated at the interface of the core portion 11 toward the light emitting surface.
As a result, the amount of light emitted from the light emitting surface side is increased by the nanostructure 10, so that the optical loss in the light emitting element 20B can be reduced.

When the difference in refractive index between the first electrode layer 22 and the photoelectric conversion layer (23A, 23B) is small in the photoelectric conversion element, the reflectance at these interfaces becomes small. In particular, when the nanostructure 10 is used for the photoelectric conversion element having such specifications to increase the reflected light from the back surface side of the light receiving surface or the back surface side of the light emitting surface, the effect of reducing the optical loss becomes larger.
The light absorption coefficient of the core portion 11 of the nanostructure 10 is preferably smaller than that of the surface layer 12 and the photoelectric conversion layer (23A, 23B) of the nanostructure 10. As a result, the optical loss at the core portion 11 of the nanostructure 10 can be reduced.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the present invention. These embodiments can be implemented in various forms other than those described above, and various omissions, substitutions, changes, etc. can be made without departing from the gist of the present invention. These embodiments and variations thereof are included in the scope and gist of the present invention, and the inventions described in the claims and their equivalents are also included in the scope and gist of the present invention.

10 Nanostructure 11 Core part 11a Outer core part 11b Inner core part 12 Surface layer 20A Light receiving element 20B Light emitting element 21 Substrate 22 First electrode layer 23A, 23B Photoelectric conversion layer 24 Second electrode layer

Claims (15)

Insulating core and
It has a surface layer that covers the core portion, and has
The surface layer is a microstructure composed of a transition metal dichalcogenide. The microstructure according to claim 1, wherein the transition metal element of the transition metal dichalcogenide contains at least one of Mo, W, Hf, and Zr. The microstructure according to claim 2, wherein the surface layer is formed in an orientation in which the stacking direction of the transition metal dichalcogenide is perpendicular to the surface of the core portion. The microstructure according to claim 1, wherein the transition metal element of the transition metal dichalcogenide contains at least one of Nb, V, Ta, and Ti. The transition metal dichalcogenide is derived from (M, Mo) (Se, S) ₂ , M (Se, S) _{2 , MSe 2} or MS ₂ (where M is any of Nb, V, Ta and Ti). The microstructure of claim 4 to be selected. The microstructure according to any one of claims 1 to 5, wherein the interchalcogen element of the transition metal dichalcogenide contains at least one of S, Se, and Te. The microstructure according to any one of claims 1 to 6, wherein the refractive index of the core portion is smaller than the refractive index of the surface layer. The core portion is composed of a material selected from the material group of silica, alumina, silicon nitride, titania, and soda lime glass, or a multilayer structure whose surface side is coated with any material of the material group. The microstructure according to any one of claims 1 to 7. The core portion is a multi-layer structure having an outer core portion that covers the surface of the core portion and an inner core portion that is adjacent to the inside of the outer core portion.
The microstructure according to any one of claims 1 to 7, wherein the refractive index of the outer core portion of the multilayer structure is larger than the refractive index of the inner core portion. The microstructure according to claim 9, wherein the material of the outer core portion is silica and the material of the inner core portion is titania. The microstructure according to any one of claims 1 to 10, wherein the microstructure is a particle having a nanometer scale. A photoelectric conversion element comprising the microstructure according to any one of claims 1 to 11. A method for producing a microstructure having an insulating core portion and a surface layer covering the core portion, wherein the surface layer is composed of a transition metal dichalcogenide.
The process of preparing the first microstructure whose surface is insulating, and
A step of forming a layer containing a transition metal element on the surface of the first microstructure to form a second microstructure, and a step of forming the second microstructure.
A method for producing a microstructure, which comprises a step of chalcogenizing a layer containing a transition metal element of the second microstructure to form a third microstructure having a surface layer of a transition metal dichalcogenide. The method for producing a microstructure according to claim 13, wherein the transition metal element contains at least one of Mo, W, Hf, Zr, Nb, V, Ta, and Ti. The chalcogen element of the transition metal dichalcogenide contains at least one of S, Se and Te.
The method for producing a microstructure according to claim 13 or 14.

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