Near-field thermal radiation power generation element

Abstract

A near-field thermal-radiation power generation element that improves power generation efficiency by near-field thermal radiation is obtained by reducing a distance between a heat source and a photoelectric conversion unit as compared with that in the prior art. A near-field thermal-radiation power generation element (1) comprises a heat source (10), a photoelectric conversion unit (20), and a stopper (30). The heat source (10) has a heat source surface (10a). The photoelectric conversion unit (20) has a photoelectric-conversion-unit surface (20s) opposed to the heat source surface (10a). The stopper (30) connects the heat source surface (10a) and the photoelectric-conversion-unit surface (20s). The stopper (30) is made of a two-dimensional material.

Description

[Technical Field]

[0001] The present disclosure relates to a near-field thermal radiation power generation element. [Background technology]

[0002] In recent years, power generation technology that utilizes near-field light present near the surface of a heat source has been attracting attention. Light The shorter the distance between the power conversion unit and the heat source, the greater the energy that can be obtained. radiator and an actuator that maintains a predetermined distance between the power generating unit and the power generating unit (see, for example, Japanese Patent Application Laid-Open No. 2008-300626). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-300626 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the near-field thermal radiation power generation element described above, the distance that the infrared radiator can be brought close to the power generation unit is limited to several hundred nanometers, making it difficult to bring the photoelectric conversion unit as close as possible to the surface of the heat source where near-field light is present, and further improvement of power generation efficiency has been difficult.

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a near-field thermal radiation power generation element in which the power generation efficiency by near-field thermal radiation is improved by reducing the distance between the heat source and the photoelectric conversion unit compared to conventional methods. [Means for solving the problem]

[0006] A near-field thermal radiation power generation element according to the present disclosure includes a heat source, a photoelectric conversion unit, and a stopper. The heat source has a heat source surface. The photoelectric conversion unit has a photoelectric conversion surface. The photoelectric conversion surface faces the heat source surface. The stopper connects the heat source surface and the photoelectric conversion surface. The material of the stopper is a two-dimensional material. [Effects of the Invention]

[0007] According to the above, by making the distance between the heat source and the photoelectric conversion unit shorter than in the past, it is possible to obtain a near-field thermal radiation power generation element with improved power generation efficiency due to near-field thermal radiation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a near-field thermal radiation power generation element according to a first embodiment. [Figure 2] FIG. 2 is a perspective view showing the components of the near-field thermal radiation power generation element according to the first embodiment separated from each other. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a modified example of the near-field thermal radiation power generation element according to the first embodiment. [Figure 5] FIG. 4 is a cross-sectional view showing a modified example of the near-field thermal radiation power generation element according to the first embodiment. [Figure 6] FIG. 4 is a cross-sectional view showing a modified example of the near-field thermal radiation power generation element according to the first embodiment. [Figure 7] FIG. 4 is a cross-sectional view showing a modified example of the near-field thermal radiation power generation element according to the first embodiment. [Figure 8] 4 is a flowchart of a method for manufacturing a near-field thermal radiation power generation element according to the first embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a near-field thermal radiation power generation element according to a second embodiment. [Figure 10] FIG. 10 is a cross-sectional view taken along line XX in FIG. 9. [Figure 11] 10 is a flowchart of a method for manufacturing a near-field thermal radiation power generation element according to the second embodiment. [Figure 12]FIG. 10 is a cross-sectional view of a near-field thermal radiation power generation element according to a third embodiment. [Figure 13] FIG. 10 is a cross-sectional view of a near-field thermal radiation power generation element according to a fourth embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a near-field thermal radiation power generation element according to a fifth embodiment. [Figure 15] FIG. 13 is a cross-sectional view of a near-field thermal radiation power generation element according to a sixth embodiment. [Figure 16] FIG. 13 is a cross-sectional view of a near-field thermal radiation power generation element according to a seventh embodiment. [Figure 17] FIG. 13 is a cross-sectional view of a near-field thermal radiation power generation element according to an eighth embodiment. [Figure 18] FIG. 13 is a plan view of a photoelectric conversion member of a near-field thermal radiation power generation element according to a ninth embodiment. [Figure 19] FIG. 13 is a plan view showing a modified example of the photoelectric conversion member of the near-field thermal radiation power generation element according to the ninth embodiment. [Figure 20] FIG. 13 is a plan view showing a modified example of the photoelectric conversion member of the near-field thermal radiation power generation element according to the ninth embodiment. [Figure 21] FIG. 13 is a plan view showing a modified example of the photoelectric conversion member of the near-field thermal radiation power generation element according to the ninth embodiment. [Figure 22] FIG. 23 is a cross-sectional view of a near-field thermal radiation power generation element according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. Unless otherwise specified, the same or corresponding parts in the following drawings will be denoted by the same reference numerals, and the description thereof will not be repeated.

[0010] Embodiment 1 <Configuration of near-field thermal radiation power generation element> Fig. 1 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 1. Fig. 2 is a perspective view in which each component of the near-field thermal radiation power generation element 1 according to embodiment 1 is separated. Fig. 3 is a plan view of the near-field thermal radiation power generation element 1 in a cross section taken along line III-III in Fig. 1, as seen from the Y direction.

[0011] The near-field thermal radiation power generation element 1 shown in FIGS. 1 to 3 is, for example, a near-field thermal radiation power generation element 1 for power generation, and mainly includes a heat source 10, a photoelectric conversion unit 20, and a stopper 30. FIG. 2 is a three-dimensional view of the near-field thermal radiation power generation element 1 according to the first embodiment, in which the heat source 10, the photoelectric conversion unit 20, and the stopper 30 are separated from one another. That is, FIG. 1 is a cross-sectional view of the near-field thermal radiation power generation element 1, in which the heat source 10, the photoelectric conversion unit 20, and the stopper 30 are connected in the stacking direction (the Y direction in FIG. 1), as viewed from the Z direction. The Z direction is perpendicular to both the stacking direction (the Y direction in FIG. 1) and the flat direction (the X direction in FIG. 1). FIG. 3 is a cross-sectional view of the near-field thermal radiation power generation element 1 as viewed from the stacking direction.

[0012] The heat source 10 has a heat source surface 10a. The photoelectric conversion unit 20 has a photoelectric conversion surface 20s. The photoelectric conversion surface 20s faces the heat source surface 10a. The stopper 30 connects the heat source surface 10a and the photoelectric conversion surface 20s. The stopper 30 functions as a spacer that determines the distance between the heat source surface 10a and the photoelectric conversion surface 20s. The thickness of the stopper 30 in the Y direction (stacking direction) corresponds to the distance between the heat source surface 10a and the photoelectric conversion surface 20s. As shown in FIG. 3, two stoppers 30 are disposed at the ends of the photoelectric conversion surface 20s. From a different perspective, the two stoppers 30 are disposed at a distance from each other, sandwiching the center of the photoelectric conversion surface 20s. The heat source 10 may be any object that generates heat. The heat source 10 may be, for example, a device with a heat-generating part, a pipe, or the human body.

[0013] Photoelectric conversion unit 20 may be an electromagnetic wave detector that converts energy obtained from electromagnetic waves radiated from heat source 10 into electricity. Photoelectric conversion unit 20 may be, for example, an electromagnetic wave detector including a silicon substrate with a PN junction, an electromagnetic wave detector made of a compound semiconductor, or an electromagnetic wave detector that uses a thermocouple called a thermopile.

[0014] Here, a feature of the near-field thermal radiation power generation element 1 according to the first embodiment is that the material of the stopper 30 is a two-dimensional material. A two-dimensional material is a material that has a thickness equivalent to the thickness of an atomic layer. Therefore, by using a two-dimensional material as the material of the stopper 30, the distance between the heat source 10 and the photoelectric conversion unit 20, that is, the distance between the heat source surface 10a and the photoelectric conversion unit surface 20s, becomes as small as possible.

[0015] The spectrum of electromagnetic waves radiated from heat source 10 is determined by Wien's radiation law. Furthermore, according to the Stefan-Boltzmann law, heat source 10 radiates electromagnetic waves with energy proportional to the fourth power of the surface temperature of heat source 10. When heat source 10 is a blackbody, the emissivity of heat source 10 is 100%, and the energy due to radiant heat at this point is the maximum radiant energy. The energy at which this radiant energy is maximum is generally called the blackbody limit.

[0016] With conventional technology, it has been difficult to extract energy exceeding the blackbody limit as radiant energy. However, in recent years, technology that can extract energy exceeding the blackbody limit by using near-field light has been attracting attention. When the distance between a heat source and an electromagnetic wave detector is equal to or less than the wavelength of the electromagnetic waves radiated from the heat source, the surface of the electromagnetic wave detector suppresses the reflection of the electromagnetic waves radiated from the heat source. Specifically, it is preferable that the distance between the heat source and the electromagnetic wave detector be 1 μm or less. When these conditions are met, energy exceeding the blackbody limit can be obtained from the electromagnetic waves radiated from the heat source. This phenomenon is generally called near-field thermal radiation.

[0017] Due to the effect of near-field thermal radiation, in the near-field thermal radiation power generation element 1 according to the first embodiment, the shorter the distance between the heat source 10 and the photoelectric conversion unit 20 (which serves as the electromagnetic wave detector), the greater the radiant energy generated by near-field light. As shown in FIG. 1 , the distance in the Y direction between the heat source surface 10a and the photoelectric conversion unit surface 20s is defined as a first distance t1. When the first distance t1 is equal to or less than one-half to one-third of the wavelength of infrared light, the first distance t1 is the distance at which the effect of near-field thermal radiation is obtained. In particular, the shorter the first distance t1, the greater the effect of near-field thermal radiation, and the energy obtained by the near-field thermal radiation power generation element 1 increases exponentially. If the material constituting the stopper 30 is a two-dimensional material, the first distance t1 will be the smallest conceivable dimension of a physical structure.

[0018] A two-dimensional material is a material having a thickness equivalent to the thickness of an atomic layer. Therefore, to emphasize the thickness of the atomic layer, the two-dimensional material is sometimes called an atomic layer material. As shown in FIG. 1 , an atomic layer space 40 is a space formed between the heat source 10 and the photoelectric conversion unit 20 by a stopper 30 having a thickness of an atomic layer in the Y direction. In this way, the near-field thermal radiation power generation element 1 having the atomic layer space 40 can obtain not only the blackbody limit but also greater energy from the heat source 10 than the energy obtained using conventional near-field thermal radiation. In other words, the near-field thermal radiation power generation element 1 having the atomic layer space 40 is, in principle, the most efficient power generation element.

[0019] The electromagnetic waves detected by the photoelectric conversion unit 20 according to the first embodiment are, for example, visible light or infrared light. Note that the electromagnetic waves are not limited to visible light and infrared light. The electromagnetic waves may be, for example, light and radio waves such as X-rays, ultraviolet light, near-infrared light, terahertz (THz) waves, and microwaves.

[0020] The two-dimensional material that is the material of the stopper 30 according to the first embodiment is preferably an insulating material. In particular, boron nitride, which is an atomic layer material and has good insulating properties, is suitable as the material of the stopper 30 according to the first embodiment. In particular, if boron nitride is a hexagonal crystal system (hexagonal boron nitride), it will lattice-match with graphene. Therefore, if the material of the stopper 30 is hexagonal boron nitride, and if the material of the photoelectric conversion member 21 (see FIG. 9 ), which will be described later in the second embodiment, is graphene, the characteristics of the graphene will not be deteriorated. For this reason, hexagonal boron nitride is suitable as the material of the stopper 30.

[0021] The shape of the stopper 30 may be changed as appropriate as long as the stopper 30 does not prevent the formation of the atomic layer space 40. For example, in a plan view of the stopper 30 seen from the Y direction, the shape of the stopper 30 may be any of a rectangle, a square, a circle, and an annular shape. The number of stoppers 30 may be changed as appropriate as long as the stopper 30 does not prevent the formation of the atomic layer space 40. For example, the number of stoppers 30 arranged on the photoelectric conversion surface 20s may be one. The number of stoppers 30 arranged on the photoelectric conversion surface 20s may be two. The number of stoppers 30 arranged on the photoelectric conversion surface 20s may be three. The number of stoppers 30 arranged on the photoelectric conversion surface 20s may be four.

[0022] 4 to 7 show modified examples of the stopper 30 of the near-field thermal radiation power generation element 1 shown in Fig. 1 to Fig. 3. Each of Fig. 4 to Fig. 7 is a plan view of the cross section of the near-field thermal radiation power generation element 1 taken along line III-III in Fig. 1, viewed from the Y direction.

[0023] As shown in FIG. 4, the stopper 30 may have a rectangular planar shape in a plan view of the stopper 30 seen from the Y direction. Two stoppers 30 each having a rectangular planar shape may be arranged on the photoelectric conversion surface 20s. The two stoppers 30 may be arranged at an interval. The stoppers 30 may be arranged at a position away from the outer peripheral edge of the photoelectric conversion surface 20s. As shown in FIG. 5, the stopper 30 may have a square planar shape in a plan view of the stopper 30 seen from the Y direction. Four stoppers 30 each having a square planar shape may be arranged on all four sides of the photoelectric conversion surface 20s. As shown in FIG. 5, the photoelectric conversion surface 20s has a rectangular planar shape. The four stoppers 30 may be arranged at positions facing the corners of the photoelectric conversion surface 20s. The four stoppers 30 may be arranged at an interval from one another. The four stoppers 30 may be arranged in a matrix. As shown in FIG. 6, the stoppers 30 may have a circular planar shape when viewed from the Y direction. As shown in FIG. 6, the four stoppers 30 may be arranged on all four sides of the photoelectric conversion surface 20s when viewed from the Y direction. As shown in FIG. 7, the stoppers 30 may have a ring-shaped planar shape when viewed from the Y direction. The outer shape of the planar shape of the stoppers 30 may be rectangular. However, it is preferable that the area of ​​the stoppers 30 in a plane perpendicular to the Y direction is smaller than that of the photoelectric conversion surface 20s. This is because the smaller the contact area between the stoppers 30 and the heat source 10, the greater the amount of electromagnetic radiation detected by the photoelectric conversion unit, improving the power generation efficiency of the photoelectric conversion unit 20.

[0024] <Method for manufacturing a near-field thermal radiation power generation element> 8 shows a flowchart of a manufacturing method for the near-field thermal radiation power generation element 1 according to embodiment 1. The manufacturing method for the near-field thermal radiation power generation element 1 will be described below. Note that the manufacturing method will be described using hexagonal boron nitride, which is an atomic layer material, as an example of the material for the stopper 30.

[0025] 8, a preparation step (S1) is performed. In this step (S1), a heat source 10, a photoelectric conversion unit 20, and a stopper 30 are prepared. Existing elements can be used for the heat source 10 and the photoelectric conversion unit 20.

[0026] Next, a step (S2) of synthesizing a two-dimensional material is carried out. In this step (S2), a two-dimensional material using hexagonal boron nitride is synthesized using a thermal CVD method. Several methods have been proposed for synthesizing hexagonal boron nitride using a thermal CVD method, and any method can be used. For example, hexagonal boron nitride is grown on a metal catalyst. Alternatively, hexagonal boron nitride synthesized using other methods such as high-pressure pressing may also be used.

[0027] Next, a transferring step (S3) is performed. In this step (S3), the synthesized hexagonal boron nitride is transferred to the photoelectric conversion section 20. The transferring method can be the same as the method for transferring an atomic layer material such as graphene. The synthesized hexagonal boron nitride may be transferred to the heat source 10 instead of the photoelectric conversion section 20.

[0028] Next, a patterning step (S4) is performed. In this step (S4), the transferred hexagonal boron nitride is patterned into the shape shown in FIG. 2 using photolithography or the like. However, as long as the transferred hexagonal boron nitride serves as the stopper 30 according to the first embodiment and forms the atomic layer space 40, the transferred hexagonal boron nitride (stopper 30) does not need to be processed. After this, as an assembly step, the photoelectric conversion unit 20 and the heat source 10 are connected via the stopper 30. As a method for connecting the stopper 30 and the heat source 10, any connection method that fixes the relative positions of the heat source 10, stopper 30, and photoelectric conversion unit 20 can be used. In this manner, a near-field thermal radiation power generation element 1 as shown in FIGS. 1 to 3 can be obtained.

[0029] <Action and effect> A near-field thermal radiation power generation element 1 according to the present disclosure includes a heat source 10, a photoelectric conversion unit 20, and a stopper 30. The heat source 10 has a heat source surface 10a. The photoelectric conversion unit 20 has a photoelectric conversion surface 20s. The photoelectric conversion surface 20s faces the heat source surface 10a. The stopper 30 connects the heat source surface 10a and the photoelectric conversion surface 20s. The material of the stopper 30 is a two-dimensional material.

[0030] In this way, the thickness of the two-dimensional material corresponds to the thickness of the atomic layer, so the distance between the heat source 10 and the photoelectric conversion unit 20 is minimized. As a result, the first distance t1 between the heat source 10 and the photoelectric conversion unit 20 becomes the distance that is subject to near-field thermal radiation. In particular, the shorter the first distance t1, the greater the effect of near-field thermal radiation, and the energy obtained by the near-field thermal radiation power generation element 1 increases exponentially. In other words, it is possible to obtain not only the blackbody limit but also greater energy from the heat source 10 than the energy obtained using conventional near-field thermal radiation, in which the distance between the heat source 10 and the photoelectric conversion unit 20 is greater than the thickness of the two-dimensional material.

[0031] In the near-field thermal radiation power generation element 1, the stopper 30 is made of an insulating material. In this way, the exchange of electrical signals between the photoelectric conversion unit 20 and the heat source 10 can be blocked.

[0032] Embodiment 2 <Configuration of near-field thermal radiation power generation element> FIG. 9 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 2. FIG. 9 corresponds to FIG. 1. FIG. 10 is a plan view of the near-field thermal radiation power generation element 1 at the cross section taken along line XX in FIG. 9, viewed from the Y direction. The near-field thermal radiation power generation element 1 shown in FIGS. 9 and 10 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in FIGS. 1 to 3, but differs in that the structure of the photoelectric conversion unit 20 is a transistor structure. Specifically, as shown in FIG. 9, the photoelectric conversion unit 20 is an electromagnetic wave detector including a photoelectric conversion member 21 that is a two-dimensional material.

[0033] photoelectric conversion Department 20The photoelectric conversion element 21 mainly includes a photoelectric conversion element 21, a pair of electrodes 22, a substrate 23, and an insulating layer 24. The photoelectric conversion element 21 has a photoelectric conversion surface 20s (front surface). The photoelectric conversion surface 20s is the surface facing the heat source surface 10a. As shown in Figures 9 and 10, the pair of electrodes 22 are connected to the side surfaces of the photoelectric conversion element 21 so as to sandwich the photoelectric conversion element 21. The side surfaces of the photoelectric conversion element 21 are surfaces that connect the photoelectric conversion surface 20s of the photoelectric conversion element 21 to the back surface of the photoelectric conversion element 21. Photoelectric conversion element Material 21 The back surface of the electrode 22 is the surface opposite to the photoelectric conversion surface 20s. Each of the pair of electrodes 22 has a first electrode surface 22a and a second electrode surface 22b. The first electrode surface 22a faces the heat source surface 10a. The second electrode surface 22b is the surface opposite to the first electrode surface 22a. In other words, the side surface of the electrode 22 connecting the first electrode surface 22a and the second electrode surface 22b is connected to the side surface of the photoelectric conversion member 21. As shown in FIG. 9, the first electrode surface 22a and the photoelectric conversion surface 20s are on the same plane.

[0034] The substrate 23 has a first substrate surface 23a and a second substrate surface 23b. The second substrate surface 23b is the surface opposite to the first substrate surface 23a. The first substrate surface 23a and the second substrate surface 23b are formed to extend in the same direction and are, for example, parallel to each other. The substrate 23 is connected to the rear surface of the photoelectric conversion member 21 and the second electrode surface 22b via an insulating layer 24 on the first substrate surface 23a. The insulating layer 24 is formed on the first substrate surface 23a. When the electrode 22 is made of a metal, the adhesion between the electrode 22 and the insulating layer 24 is weak. Therefore, for example, an adhesive film (not shown) may be formed between the electrode 22 and the insulating layer 24. In other words, the pair of electrodes 22 may be disposed on the adhesive film. In this case, the adhesion between the electrode 22 and the insulating layer 24 is improved. Furthermore, an adhesive film need not be formed between the photoelectric conversion member 21 and the insulating layer 24. In other words, an adhesive film may be formed only between the pair of electrodes 22 and the insulating layer 24. In this case as well, the pair of electrodes 22 are connected to the side surfaces of the photoelectric conversion member 21. Alternatively, a configuration in which no adhesive film is formed (a configuration in which the photoelectric conversion member 21 and the pair of electrodes 22 are formed directly on the insulating layer 24) may be used. The end portions of the photoelectric conversion member 21 may be formed so as to extend to the upper surfaces of the pair of electrodes 22. In other words, the end portions of the photoelectric conversion member 21 may be connected to the upper surfaces of the pair of electrodes 22. An adhesive film may also be formed between the photoelectric conversion member 21 and the insulating layer 24.

[0035] Furthermore, with regard to the arrangement of the photoelectric conversion member 21 and the electrodes 22, the photoelectric conversion member 21 may be formed on the insulating layer 24, and the pair of electrodes 22 may be formed spaced apart on the photoelectric conversion member 21. In this case, an adhesive film may be formed between the photoelectric conversion member 21 and the electrodes 22. Alternatively, the pair of electrodes 22 may be formed so as to be directly connected to the photoelectric conversion member 21 without forming the adhesive film.

[0036] The substrate 23 serves to support the entire photoelectric conversion unit 20, which is an electromagnetic wave detector. The material of the substrate 23 may be, for example, an elemental semiconductor such as silicon (Si) or germanium (Ge). The material of the substrate 23 may be, for example, a compound semiconductor such as a III-V group semiconductor or a II-V group semiconductor. Compound semiconductors include, for example, mercury cadmium telluride (HgCdTe) and indium antimonide. hmm Examples of suitable materials include lead (InSb), lead selenium (PbSe), lead sulfur (PbS), cadmium sulfur (CdS), gallium nitride (GaN), silicon carbide (SiC), gallium phosphide (GaP), indium gallium arsenide (InGaAs), indium arsenide (InAs), and gallium antimony (GaSb). The substrate 23 may include a quantum well structure in which the direction of electron movement is constrained. Alternatively, the substrate 23 may include quantum dots in which the direction of electron movement is constrained in all three dimensions. The substrate 23 may have a band structure known as a Type-II superlattice. The Type-II superlattice may have a film structure known as a barrier type. The material of the substrate 23 may be a combination of the above materials or an amorphous semiconductor.

[0037] When the substrate 23 is made of silicon, the substrate 23 may be a high-resistivity silicon substrate or a substrate on which a thermal oxide film is formed. The thermal oxide film can also serve as the insulating layer 24. A silicon substrate doped with impurities may be used to form an electrode on the second substrate surface 23b.

[0038] The material of the substrate 23 may be a flexible material. When the substrate 23 is made of an elastic material such as polydimethylsiloxane (PDMS), the photoelectric conversion body 20 can be bent. For example, when the heat source 10 is a cylindrical pipe, the photoelectric conversion body 20 can be wrapped around the pipe. As a result, an atomic layer space 40 can be formed that conforms to the shape of the pipe. In this way, when the material of the substrate 23 is a flexible material, the shape of the photoelectric conversion body 20 can be appropriately changed depending on the shape of the heat source 10, and therefore a good atomic layer space 40 can be formed.

[0039] It is desirable that the first substrate surface 23a be flattened by mirror finishing or the like, because unevenness on the first substrate surface 23a would prevent the formation of the atomic layer space 40. In order to form a good atomic layer space 40, the insulating layer 24 may be formed by stacking multiple layers of hexagonal boron nitride on the first substrate surface 23a.

[0040] The insulating layer 24 disposed on the first substrate surface 23a is made of, for example, silicon oxide (SiO2). The material of the insulating layer 24 is not limited to silicon oxide, but may be, for example, tetraethyl orthosilicate (Si(OC2H5)4), silicon nitride (SiN), silicon nitride (Si3N4), hafnium oxide (HfO2), aluminum oxide (Al2O3), nickel oxide (NiO), boron nitride (BN), or a siloxane-based polymer material. In particular, the atomic arrangement of boron nitride (BN) is similar to that of graphene. Therefore, when the photoelectric conversion member 21 is made of graphene, even if boron nitride (BN) comes into contact with the graphene, it does not interfere with the movement of charges in the photoelectric conversion member 21 made of graphene. In other words, boron nitride does not degrade the performance, such as the electron mobility, of the photoelectric conversion member 21 made of graphene, and therefore is suitable as an undercoat film disposed on the back surface of the photoelectric conversion member 21.

[0041] A pair of electrodes 22 is provided on the insulating layer 24 via an adhesive film. The material of the electrodes 22 may be a metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), or palladium (Pd). The material that can be used to form the adhesive film may be chromium (Cr) or titanium (Ti). As described above, the adhesive film is insulated from the electrodes 22. layer 24 In each embodiment described later, the adhesive film may or may not be formed between the insulating layer 24 and the electrode 22. The shape of the electrode 22 is not particularly limited as long as it has a size or thickness that allows it to output an electrical signal.

[0042] The material of the electrode 22 may be a two-dimensional material. When the two-dimensional material constituting the photoelectric conversion member 21 is molybdenum disulfide (MoS2), the two-dimensional material constituting the electrode 22 can be graphene. In this way, not only the photoelectric conversion member 21 but also the electrode 22 is made of a two-dimensional material, so the electrode 22 does not hinder the formation of the atomic layer space 40. This improves the power generation efficiency of the near-field thermal radiation power generation element 1.

[0043] The pair of electrodes 22 act as a drain electrode and a source electrode, respectively. A bias voltage is applied between the pair of electrodes 22. Alternatively, a back gate voltage is applied to the second substrate surface 23b. This configuration is a typical field effect transistor. Electromagnetic waves radiated from the heat source 10 are irradiated onto the photoelectric conversion member 21 disposed between the drain electrode and the source electrode. As a result, the energy of the radiated electromagnetic waves is photoelectrically converted in the photoelectric conversion member 21, causing a change in current, which is extracted as an electrical signal. In this way, the energy of the electromagnetic waves radiated from the heat source 10 is converted into electricity.

[0044] The photoelectric conversion member 21 is disposed on the insulating layer 24. The photoelectric conversion member 21 is connected to a pair of electrodes 22. The photoelectric conversion member 21 only needs to be electrically connected to the electrodes 22 well, and may be connected to the first electrode surface 22a or the second electrode surface 22b of the electrodes 22. As shown in FIG. 9 , the electrodes 22 may be connected only to the side surfaces of the photoelectric conversion member 21. This structure in which the electrodes 22 are connected only to the side surfaces of the photoelectric conversion member 21 is called edge contact. This reduces the contact resistance between the photoelectric conversion member 21 and the electrodes 22, thereby improving the power generation efficiency of the near-field thermal radiation power generation element 1.

[0045] The material of the photoelectric conversion member 21 may be, for example, a two-dimensional material. The two-dimensional material constituting the photoelectric conversion member 21 is, for example, single-layer graphene. Since graphene has a Dirac cone-type band gap, when the two-dimensional material constituting the photoelectric conversion member 21 is graphene, the photoelectric conversion unit 20 can receive light from ultraviolet to terahertz. waveIn other words, the photoelectric conversion unit 20 using a two-dimensional material has higher power generation efficiency than an electromagnetic wave detector using a semiconductor with a general PN junction.

[0046] Here, graphene is a monoatomic layer of two-dimensional carbon crystal. The thickness of monolayer graphene is 0.34 nm, which is equivalent to one carbon atom. In other words, monolayer graphene is very thin. Furthermore, the carbon atom arrangement structure of graphene is a hexagonal honeycomb structure formed by the bonding of carbon atoms.

[0047] The two-dimensional material does not have to be single-layer graphene. For example, the two-dimensional material may be multilayer graphene. When the two-dimensional material is multilayer graphene, the stacking pattern of the carbon atom layers may be AB stacking or turbostratic stacking. AB stacking is a stacking pattern in which the stacking orientation angle is found in graphite in its natural state. Turbostratic stacking is also called random stacking. When the stacking pattern of the two-dimensional material is turbostratic, the method for producing the two-dimensional material may be determined appropriately. For example, a turbostratic structure portion may be formed by transferring a single layer of graphene produced by a CVD method multiple times. Furthermore, a turbostratic stacking pattern may be formed by supplying ethanol, methane, or the like as a carbon source onto a graphene substrate and growing graphene on the graphene substrate by a CVD method.

[0048] When the photoelectric conversion member 21 has a stacked structure of multilayer graphene consisting of two or more layers, the directions of the hexagonal lattice vectors of any two layers of graphene included in the stacked structure do not have to be the same. That is, the directions of the hexagonal lattice vectors of any two layers of graphene may be misaligned. Furthermore, the directions of the hexagonal lattice vectors of any two layers of graphene may be the same. In particular, when the photoelectric conversion member 21 has a stacked structure of multilayer graphene consisting of two or more layers, a band gap is formed in the photoelectric conversion member 21, making it possible to select the wavelength that can be absorbed from the heat source 10. That is, increasing the number of graphene layers increases the light absorptance of the photoelectric conversion member 21. This improves the sensitivity of the photoelectric conversion unit 20 as an electromagnetic wave detector.

[0049] Graphene may be a graphene nanoribbon cut into a strip-like shape with a width on the order of nanometers. The graphene structure may be any of a structure of a single graphene nanoribbon, a structure in which multiple graphene nanoribbons are stacked, or a structure in which graphene nanoribbons are periodically arranged on a plane. A structure in which graphene nanoribbons are periodically arranged is called a graphene metamaterial. When the photoelectric conversion member 21 has a structure in which graphene nanoribbons are periodically arranged, plasmon resonance occurs in the photoelectric conversion member 21. As a result, the sensitivity of the photoelectric conversion member 21 as a photodetector is improved.

[0050] Here, the surface plasmon resonance phenomenon that occurs due to the interaction between a metal surface and light, the phenomenon called pseudo-surface plasmon resonance that occurs on metal surfaces outside the visible light or near-infrared light range, and the resonance phenomenon that occurs in metamaterials (plasmonic metamaterials) or metasurfaces that artificially manipulate wavelengths using structures smaller than the wavelength of electromagnetic waves are referred to as surface plasmon resonance, plasmon resonance, or simply resonance, without distinguishing between the names.

[0051] In addition to graphene, the two-dimensional material may be, for example, a transition metal dichalcogenide (TMD), black phosphorus, silicene (an atomic sheet having a two-dimensional honeycomb structure of silicon atoms), or germanene (an atomic sheet having a two-dimensional honeycomb structure of germanium atoms). Examples of transition metal dichalcogenides include molybdenum disulfide (MoS2), tungsten disulfide (WS2), and tungsten diselenide (WSe2). Thus, the two-dimensional material may be graphene, a transition metal dichalcogenide, black phosphorus, silicene (an atomic sheet having a two-dimensional honeycomb structure of germanium atoms), or germanene (an atomic sheet having a two-dimensional honeycomb structure of germanium atoms). Examples of transition metal dichalcogenides include molybdenum disulfide (MoS2), tungsten disulfide (WS2), and tungsten diselenide (WSe2). Do The material may include any one selected from the group consisting of black phosphorus, silicene, germanene, graphene nanoribbons, and borophene. Alternatively, the material may be a two-dimensional material in which these materials are stacked.

[0052] <Method for manufacturing a near-field thermal radiation power generation element> 11 shows a flowchart of a method for manufacturing the near-field thermal radiation power generation element 1 according to embodiment 2. The method for manufacturing the near-field thermal radiation power generation element 1 according to embodiment 2 will be described below.

[0053] As shown in FIG. 11, a preparing step (S1a) is performed. 1 In step a), a flat substrate 23 made of silicon or the like is prepared.

[0054] Next, the step (S2a) of forming an insulating layer is performed. In this step (S2a), an insulating layer 24 is formed on the first substrate surface 23a of the substrate 23. For example, if the substrate 23 is made of silicon, the insulating layer 24 may be silicon oxide (SiO2) formed by thermal oxidation. Alternatively, the insulating layer 24 may be formed by a CVD method or a sputtering method.

[0055] Next, the step (S3a) of forming an electrode is performed. In this step (S3a), electrode 22 made of a metal is formed. The metal is gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), palladium (Pd), or another metal. To improve adhesion between electrode 22 and insulating layer 24, an adhesive film may be formed between electrode 22 and insulating layer 24. The material of the adhesive film is, for example, chromium (Cr) or titanium (Ti). After forming a resist mask using photolithography or EB lithography, electrode 22 is formed by depositing a metal layer on the resist mask by vapor deposition, sputtering, or another method.

[0056] Next, a step (S4a) of forming a photoelectric conversion member 21 is performed. In this step (S4a), the photoelectric conversion member 21 made of a two-dimensional material is formed on the electrode 22 and the insulating layer 24. When the two-dimensional material is graphene, the graphene may be formed by epitaxial growth, or graphene formed in advance by a CVD method may be transferred and attached. Alternatively, graphene that has been mechanically peeled off may be transferred. Thereafter, the graphene coated with a resist mask is etched and patterned with oxygen plasma using photolithography or the like. This removes unnecessary graphene from areas other than the area where the graphene is in contact with the channel portion or the electrode 22. In this way, the photoelectric conversion member 21 that will become the channel portion is formed. The photoelectric conversion unit 20 according to the second embodiment is obtained by the above steps. Note that the electrode 22 may be formed on the photoelectric conversion member 21 after it is formed.

[0057] Next, a step (S5a) of forming the stopper 30 is performed. This step (S5a) includes the steps of synthesizing the two-dimensional material (S2) through patterning (S4) in the manufacturing method of the first embodiment. The material of the stopper 30 is preferably boron nitride, but hexagonal boron nitride may also be used. When the material of the photoelectric conversion member 21 is graphene, graphene and hexagonal boron nitride are lattice-matched, so the electronic performance of the graphene is not impaired. For example, when hexagonal boron nitride is used as an underlayer for graphene, the carrier mobility of graphene is improved by approximately three times compared to a normal oxide film. This is because the sensitivity of the photoelectric conversion unit 20 is approximately proportional to the carrier mobility of graphene. Therefore, when the material of the photoelectric conversion member 21 is graphene and the material of the stopper 30 is hexagonal boron nitride, the power generation efficiency of the photoelectric conversion unit 20 as an electron detector is highest. Thereafter, in the same manner as in the manufacturing method of the near-field thermal radiation power generation element according to embodiment 1, the photoelectric conversion unit 20 and the heat source 10 are connected via the stopper 30 in the assembly process. In this manner, the near-field thermal radiation power generation element 1 as shown in Fig. 9 or 10 can be obtained.

[0058] <Action and effect> In the near-field thermal radiation power generation element 1, the photoelectric conversion unit 20 includes a photoelectric conversion member 21. The photoelectric conversion member 21 has a photoelectric conversion surface 20s. The material of the photoelectric conversion member 21 is a two-dimensional material. In this way, by appropriately selecting the type and configuration of the two-dimensional material constituting the photoelectric conversion member 21, the power generation efficiency of the near-field thermal radiation power generation element can be improved. For example, when the two-dimensional material constituting the photoelectric conversion member 21 is graphene, the photoelectric conversion unit 20 can convert light from ultraviolet to terahertz. wave As a result, the power generation efficiency of the near-field thermal radiation power generation element 1 is improved.

[0059] In the near-field thermal radiation power generation element 1, the photoelectric conversion unit 20 includes a substrate 23, an insulating layer 24, and a pair of electrodes 22. The pair of electrodes 22 are connected to the photoelectric conversion member 21. The insulating layer 24 is formed between the substrate 23 and the electrodes 22. In this way, the structure of the photoelectric conversion unit 20 becomes a transistor structure using a two-dimensional material, and the transistor-type photoelectric conversion unit 20 becomes capable of energy conversion by near-field thermal radiation.

[0060] In the near-field thermal radiation power generation element 1, the material of the electrode 22 is a two-dimensional material. In this way, not only the photoelectric conversion member 21 but also the electrode 22 is a two-dimensional material, so the electrode 22 does not hinder the formation of the atomic layer space 40. This improves the power generation efficiency of the near-field thermal radiation power generation element 1. For example, when the two-dimensional material constituting the photoelectric conversion member 21 is molybdenum disulfide (MoS2), graphene can be used as the two-dimensional material constituting the electrode 22. With this configuration, the power generation efficiency of the near-field thermal radiation power generation element 1 can be improved.

[0061] In the near-field thermal radiation power generation element 1, the substrate 23 is flexible. This allows the shape of the photoelectric conversion section 20 to be changed appropriately depending on the shape of the heat source 10. As a result, even if the heat source surface 10a is not flat, a good atomic layer space 40 can be formed. This allows the power generation efficiency of the near-field thermal radiation power generation element 1 to be improved.

[0062] In the near-field thermal radiation power generation element 1, the material of the photoelectric conversion member 21 is any one selected from the group consisting of a single-layer two-dimensional material, a multilayer two-dimensional material, and a turbostratic two-dimensional material. In this way, for example, increasing the number of layers of the two-dimensional material increases the light absorption rate of the photoelectric conversion member 21. This improves the sensitivity of the photoelectric conversion unit 20 as an electromagnetic wave detector. Furthermore, when the material of the photoelectric conversion member 21 is a turbostratic two-dimensional material, the mobility in the photoelectric conversion member 21 increases, and the high independence of each layer stacked in the two-dimensional material further improves the sensitivity of the photoelectric conversion unit 20.

[0063] In the near-field thermal radiation power generation element 1, the material of the photoelectric conversion member 21 is graphene. The material of the stopper 30 is hexagonal boron nitride. In this way, the photoelectric conversion member 21 and the stopper 30 are lattice-matched. Hexagonal boron nitride not only has insulating properties, but also has an atomic arrangement similar to that of graphene. Therefore, when hexagonal boron nitride comes into contact with graphene, it suppresses a decrease in the electron mobility of graphene, thereby improving the power generation efficiency of the near-field thermal radiation power generation element 1.

[0064] Embodiment 3 <Configuration of near-field thermal radiation power generation element> Fig. 12 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 3. Fig. 12 corresponds to Fig. 9. The near-field thermal radiation power generation element 1 shown in Fig. 12 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in Figs. 9 and 10, but differs in that at the connection portion between the stopper 30 and the photoelectric conversion part 20, the stopper 30 is in contact only with the photoelectric conversion surface 20s of the photoelectric conversion member 21.

[0065] The stopper 30 in the near-field thermal radiation power generation element 1 according to the second embodiment is in contact not only with the photoelectric conversion surface 20s but also with the first electrode surfaces 22a of the pair of electrodes 22. On the other hand, the stopper 30 in the near-field thermal radiation power generation element 1 according to the third embodiment is not in contact with the first electrode surfaces 22a of the electrodes 22, but is in contact only with the photoelectric conversion surface 20s.

[0066] In this way, the influence of the electrode 22 or other wiring is eliminated in forming the atomic layer space 40. Therefore, it is desirable to dispose the stopper 30 on the photoelectric conversion surface 20s in order to form the atomic layer space 40. In this case, when the material of the stopper 30 is hexagonal boron nitride and the material of the photoelectric conversion member 21 is graphene, the power generation efficiency of the near-field thermal radiation power generation element 1 can be effectively improved.

[0067] <Action and effect> In the near-field thermal radiation power generation element 1, the stopper 30 is connected only to the photoelectric conversion surface 20s. This eliminates the influence of the electrode 22 or other wiring on the formation of the atomic layer space 40. As a result, a good atomic layer space 40 can be formed, and the power generation efficiency of the near-field thermal radiation power generation element 1 can be improved.

[0068] Embodiment 4 <Configuration of near-field thermal radiation power generation element> Fig. 13 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 4. Fig. 13 corresponds to Fig. 12. The near-field thermal radiation power generation element 1 shown in Fig. 13 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in Fig. 12, but differs in that the stopper 30 has a porous or striped shape in the cross-sectional view of the near-field thermal radiation power generation element 1 as viewed from directions perpendicular to both the X and Y directions. Specifically, as shown in Fig. 13, through holes are formed in the stopper 30 so as to extend from the surface connected to the heat source surface 10a to the surface connected to the photoelectric conversion surface 20s.

[0069] When the stopper 30 is configured as a single layer, the stopper 30 may have pores. In the near-field thermal radiation power generation element 1, the heat source 10 and the photoelectric conversion unit 20 are connected via the stopper 30. When the near-field thermal radiation power generation element 1 is in use, pressure is applied to the heat source 10 and the photoelectric conversion unit 20 in the Y direction, and if the stopper 30 has a porous or striped shape, the impact of this pressure is alleviated. As a result, the durability of the near-field thermal radiation power generation element 1 can be improved, and the product's lifespan can be extended.

[0070] <Action and effect> In the near-field thermal radiation power generation element 1, either a through-hole or a void is formed in the stopper 30. This improves the durability of the photoelectric conversion unit 20. That is, when the near-field thermal radiation power generation element 1 is used, pressure is applied to the heat source 10 and the photoelectric conversion unit 20 in the Y direction. Therefore, if the stopper 30 has a shape in which either a through-hole or a void is formed, the impact caused by the pressure is alleviated. As a result, the durability of the near-field thermal radiation power generation element 1 is improved, and the life of the near-field thermal radiation power generation element 1 can be extended.

[0071] Embodiment 5 <Configuration of near-field thermal radiation power generation element> Fig. 14 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 5. Fig. 14 corresponds to Fig. 9. The near-field thermal radiation power generation element 1 shown in Fig. 14 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in Figs. 9 and 10, but differs in that the photoelectric conversion member 21 has a PN junction. Specifically, as shown in Fig. 14, the photoelectric conversion member 21 made of a two-dimensional material includes an N-type region 21n and a P-type region 21p.

[0072] The N-type region 21n and the P-type region 21p are joined together as a PN junction. The surface where the N-type region 21n and the P-type region 21p are joined is formed to extend in the Y direction. The surface where the N-type region 21n and the P-type region 21p are joined is disposed so as to be sandwiched between a pair of electrodes 22. That is, one of the pair of electrodes 22 is connected to the N-type region 21n, and the other of the pair of electrodes 22 is connected to the P-type region 21p. In this way, when the photoelectric conversion member 21 made of a two-dimensional material is used as a channel, a bias voltage is applied to the photoelectric conversion member 21. That is, there is no need to apply a bias voltage from an external power source to the photoelectric conversion member 21. As a result, the power generation efficiency (energy conversion efficiency) of the near-field thermal radiation power generation element 1 is improved.

[0073] Various methods can be used to form a PN junction in the photoelectric conversion member 21. For example, an N-type region 21n and a P-type region 21p are formed by contacting a doping material that supplies carriers (holes or electrons) with the photoelectric conversion member 21 made of a two-dimensional material. Therefore, the photoelectric conversion member 21 is in a state where a pseudo-PN junction is formed. In this way, when the left region of the photoelectric conversion member 21 in FIG. 14 is the P-type region 21p and the right region is the N-type region 21n, the extraction efficiency of an electrical signal from the left electrode 22l connected to the P-type region 21p and the extraction efficiency of an electrical signal from the right electrode 22r connected to the N-type region 21n are both improved. This improves the sensitivity of the photoelectric conversion unit 20 as an electromagnetic wave detector.

[0074] The doping material may be any material that generates a charge imbalance and induces polarization, for example, the doping material may be an organic material, a metal, a semiconductor, an insulator, a two-dimensional material, or a mixture of any of these materials.

[0075] The doping material may be, for example, a positive photoresist. Do When the doping material is a positive photoresist, the region where the positive photoresist is formed becomes the P-type region 21p of the photoelectric conversion member 21.

[0076] The positive photoresist is formed on the photoelectric conversion member 21 by, for example, a photolithography process. This eliminates the need for a process of forming a mask that comes into contact with the photoelectric conversion member 21. In the process of forming the mask, there is a risk that the photoelectric conversion member 21 may be damaged. By eliminating the need for this process of forming the mask, it is possible to reduce the risk of damaging the photoelectric conversion member 21, and also to simplify the process of manufacturing the photoelectric conversion member 21.

[0077] The doping material may be, for example, a material having a polar group. The doping material may be, for example, a material having an electron-withdrawing group. If the doping material is a material having an electron-withdrawing group, the electron density of the photoelectric conversion member 21 decreases. The material having an electron-withdrawing group is, for example, a material having a halogen, a nitrile group, a carboxyl group, or a carbonyl group.

[0078] The doping material may also be, for example, a material having an electron-donating group. If the doping material is a material having an electron-donating group, the electron density of the photoelectric conversion member 21 increases. The material having an electron-donating group is, for example, a material having an alkyl group, a hydroxyl group, or an amino group.

[0079] The doping material may be, for example, a material that supplies molecules to the photoelectric conversion member 21. The doping material may be, for example, a liquid layer or a gas layer containing molecules. The photoelectric conversion member 21 may be immersed in the liquid layer or exposed to the gas layer. In this way, carriers are supplied from the liquid layer or gas layer to the photoelectric conversion member 21 at the molecular level.

[0080] When the photoelectric conversion member 21 made of a two-dimensional material and a metal come into contact with each other, due to the difference between the work function of the metal and the work function of the photoelectric conversion member 21 made of graphene or the like, carriers (holes or electrons) are doped from the metal to the photoelectric conversion member 21. As a result, the Fermi level of the photoelectric conversion member 21 or the contact resistance between the photoelectric conversion member 21 and the metal changes.

[0081] 14, if the right electrode 22r is formed of a metal material different from that of the left electrode 22l, the energy gap of the region of the photoelectric conversion member 21 that contacts the right electrode 22r will be different from the energy gap of the region that contacts the left electrode 22l. In other words, a pseudo-PN junction is formed within the photoelectric conversion member 21. Even in this case, the extraction efficiency of the electric signal (current) from the left electrode 22l and the extraction efficiency of the electric signal from the right electrode 22r are both improved. As a result, the sensitivity of the photoelectric conversion unit 20 as an electromagnetic wave detector is improved, and a bias voltage is no longer necessary, thereby improving the power generation efficiency of the near-field thermal radiation power generation element 1.

[0082] <Action and effect> In the near-field thermal radiation power generation element 1, the photoelectric conversion member 21 has a PN junction. In this way, the photoelectric conversion section 20 does not require a bias voltage, and the power generation efficiency of the near-field thermal radiation power generation element 1 is improved.

[0083] Embodiment 6 <Configuration of near-field thermal radiation power generation element> FIG. 15 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 6. FIG. 15 corresponds to FIG. 12. The near-field thermal radiation power generation element 1 shown in FIG. 15 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in FIG. 12, but differs in that the photoelectric conversion surface 20s is closer to the heat source surface 10a than the first electrode surface 22a of the electrode 22. Specifically, as shown in FIG. 15, the first distance t1 is smaller than the second distance t2. The second distance t2 is the distance in the Y direction from the heat source surface 10a to the first electrode surface 22a. In other words, the photoelectric conversion surface 20s is closer to the heat source surface 10a than the first electrode surface 22a. In this way, the thickness of the electrode 22 in the Y direction does not interfere with the formation of the atomic layer space 40.

[0084] <Action and effect> In the near-field thermal radiation power generation element 1, the electrode 22 has a first electrode surface 22a. The first electrode surface 22a is a surface facing the heat source surface 10a. The first distance t1 is smaller than the second distance t2. The first distance t1 is the distance from the heat source surface 10a to the photoelectric conversion surface 20s. The second distance t2 is the distance from the heat source surface 10a to the first electrode surface 22a. In this way, the photoelectric conversion surface 20s is closer to the heat source surface 10a than the first electrode surface 22a, so the thickness of the electrode 22 in the Y direction does not prevent the formation of the atomic layer space 40.

[0085] Embodiment 7 <Configuration of near-field thermal radiation power generation element> FIG. 16 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to the seventh embodiment. FIG. 16 corresponds to FIG. 9. The near-field thermal radiation power generation element 1 shown in FIG. 16 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in FIGS. 9 and 10, but differs in that the heat source 10 has a two-dimensional material layer 11 as a covering layer. Specifically, as shown in FIG. 16, the two-dimensional material layer 11 is formed on the surface (lower surface) of the heat source 10 facing the stopper 30. The surface of the two-dimensional material layer 11 (the surface facing the stopper 30) serves as the heat source surface 10a. The stopper 30 is connected to the heat source surface 10a. The heat source 10 may include a cover that covers the heat source 10. The two-dimensional material layer 11 may be formed on the surface of the cover facing the stopper 30.

[0086] Here, when graphene is stacked, the distance between graphenes is smallest if the stacking structure has a stacking pattern that results in an AB stack with a stable stacking orientation. On the other hand, when the stacking structure has a stacking pattern other than an AB stack, the distance between graphenes is larger than the distance between graphenes when the stacking pattern is an AB stack. This is because a repulsive force occurs between the stacked graphenes. By utilizing this characteristic, when the two-dimensional material layer 11 and the photoelectric conversion member 21 are made of graphene, the repulsive force acts between the two-dimensional material layer 11 and the photoelectric conversion member 21, forming a favorable atomic layer space 40. For example, when viewed at the atomic layer level, the lower surface of the heat source 10 (the surface on which the two-dimensional material layer 11 is formed) has irregularities. The heat source surface 10a, which is the surface of the two-dimensional material layer 11 formed on the lower surface, may also have irregularities due to the irregularities of the lower surface. However, when the two-dimensional material layer 11 is formed on the lower surface, a repulsive force acts between the photoelectric conversion member 21 and the two-dimensional material layer 11, forming an atomic layer space 40 microscopically. That is, even if the lower surface and the heat source surface 10a of the heat source 10 are uneven, a good atomic layer space 40 is formed. In this way, the power generation efficiency of the near-field thermal radiation power generation element 1 is improved. Furthermore, the space between the two-dimensional material layer 11 and the photoelectric conversion member 21 may be kept in vacuum.

[0087] <Action and effect> In the near-field thermal radiation power generation element 1, the heat source 10 includes a two-dimensional material layer 11. The two-dimensional material layer 11 has a heat source surface 10a. The two-dimensional material layer 11 is made of a two-dimensional material. In this way, when the material of the photoelectric conversion member 21 and the two-dimensional material layer 11 is graphene, a repulsive force acts between the photoelectric conversion member 21 and the two-dimensional material layer 11, and a good atomic layer space 40 is formed even if there are irregularities on the heat source surface 10a. As a result, the power generation efficiency of the near-field thermal radiation power generation element 1 is improved.

[0088] Embodiment 8 <Configuration of near-field thermal radiation power generation element> Fig. 17 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 8. Fig. 17 corresponds to Fig. 9. The near-field thermal radiation power generation element 1 shown in Fig. 17 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in Figs. 9 and 10, but differs in that the material of the substrate 33 is a photosensitizer. When the material of the substrate 33 is a photosensitizer, a photogating effect occurs in the photoelectric conversion unit 20.

[0089] The photogating effect will be explained below. Assume that the material of the photoelectric conversion member 21 is graphene. Compared to ordinary semiconductors, graphene has a high electron mobility, and a small change in voltage results in a large change in current. To utilize this property of graphene, the material of the substrate 33 is a photosensitizer. A photosensitizer is a material that generates a voltage change at a specific wavelength. The photosensitizer does not have to be the material of the substrate 33. The photosensitizer may be disposed, for example, near the photoelectric conversion member 21 made of graphene. For example, the photosensitizer may be formed on the photoelectric conversion member 21, and there are no restrictions on the location of the photosensitizer as long as it is adjacent to the photoelectric conversion member 21.

[0090] Of the electromagnetic waves radiated from the heat source 10, silicon or a compound semiconductor functions as a photosensitizer (also called a photosensitizing layer) for visible light. For infrared light, a ferroelectric or the like functions as a photosensitizing layer. When electromagnetic waves are incident on the photosensitizing layer, a voltage change occurs in the graphene due to photoelectric conversion or the pyroelectric effect. As a result, the change in current generated in the graphene becomes 10 to 10,000 times larger than when there is no photosensitizing layer. By using a photosensitizer, the photoelectric conversion unit 20 can extract such a large current. For this reason, the photoelectric conversion unit 20 can detect electromagnetic waves radiated from the heat source 10 with high sensitivity. R This effect is called the optical gate effect.

[0091] The use of such a material (photosensitizer) that generates the photogate effect can improve the power generation efficiency of the near-field thermal radiation power generation element 1. In particular, when the substrate 33 is a ferroelectric, a change in bias voltage can be applied to the graphene without applying a back gate voltage to the graphene, thereby improving the power generation efficiency of the near-field thermal radiation power generation element 1.

[0092] The ferroelectric may be a material that generates polarization when electromagnetic waves having a wavelength to be detected are incident on the ferroelectric. The ferroelectric may include, for example, any material selected from the group consisting of barium titanate (BaTiO), lithium niobate (LiNbO), lithium tantalate (LiTaO), strontium titanate (SrTiO), lead zirconate titanate (PZT), strontium tantalate bismuthate (SBT), bismuth ferrite (BFO), zinc oxide (ZnO), hafnium oxide (HfO), or organic polymer polyvinylidene fluoride ferroelectrics (PVDF, P(VDF-TrFE), P(VDF-TrFE-CTFE), etc.). The ferroelectric may also be a material in which multiple layers of the above different materials are stacked or mixed.

[0093] As the ferroelectric, a material other than the above-mentioned materials can be used as long as it is a pyroelectric that exhibits a pyroelectric effect. Specifically, the pyroelectric that constitutes the ferroelectric may be a material that generates a polarization change in response to a change in thermal energy inside the pyroelectric. With regard to the pyroelectric effect described above, electromagnetic waves simply act as a source of thermal energy. Therefore, the magnitude of the pyroelectric effect does not fundamentally depend on the wavelength components contained in the electromagnetic waves. In other words, when a pyroelectric is used as the ferroelectric that constitutes the photosensitizing layer, Pyroelectric materials It is sensitive to a wide range of wavelength components of the electromagnetic waves generated from the heat source 10. Therefore, it is possible to efficiently generate power using a wide range of electromagnetic waves.

[0094] <Action and effect> In the near-field thermal radiation power generation element 1, the photoelectric conversion section 20 contains a photosensitizer. This causes a photogating effect in the photoelectric conversion section 20, making it possible to extract a voltage change generated in the photoelectric conversion member 21 as a large differential current. As a result, the photoelectric conversion section 20 can detect electromagnetic waves radiated from the heat source 10 with high sensitivity. R This improves the power generation efficiency of the near-field thermal radiation power generation element 1.

[0095] Embodiment 9 <Configuration of near-field thermal radiation power generation element> Fig. 18 is a plan view showing the photoelectric conversion member 21 of the near-field thermal radiation power generation element 1 according to embodiment 9. Figs. 19 to 21 are plan views showing modified examples of the photoelectric conversion member 21 of the near-field thermal radiation power generation element 1 shown in Fig. 18. The near-field thermal radiation power generation element 1 shown in Figs. 18 to 21 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in Figs. 9 and 10, but differs in that the shape of the photoelectric conversion member 21 is a shape that generates plasmon resonance.

[0096] 18 to 21 are plan views of the photoelectric conversion member 21 as viewed from the Y direction. The photoelectric conversion member 21 may have any shape as long as plasmon resonance occurs. For example, as shown in FIG. 18, the photoelectric conversion member 21 may have a plurality of through holes 21h. The plurality of through holes 21h may be periodically arranged in each of the X direction and the Z direction. That is, the plurality of through holes 21h may be arranged in a matrix. The Z direction is a direction perpendicular to each of the X direction and the Y direction. The planar shape of the plurality of through holes 21h may be any shape, for example, a circular shape. The planar shape of the plurality of through holes 21h may be, for example, an elliptical shape. Note that the planar shape of the outer periphery of the photoelectric conversion member 21 is, for example, a rectangular shape, but may be any other shape.

[0097] 19, the planar shape of the plurality of through holes 21h may be quadrangular. The planar shape of the plurality of through holes 21h may be square or rectangular. The planar shape of the plurality of through holes 21h may be polygonal, such as triangular or pentagonal. The planar shapes of the plurality of through holes 21h may be different from each other.

[0098] The dimensions of the plurality of through holes 21h may be the same or different. The distance (interval) between two adjacent through holes 21h may be equal in either the X direction or the Z direction. of The spacing between the through holes 21h may vary in either the X direction or the Z direction. The variation in spacing in either the X direction or the Z direction may be periodic or non-periodic. The spacing between two adjacent through holes 21h in the X direction may be larger than the spacing between two adjacent through holes 21h in the Z direction. The spacing between two adjacent through holes 21h in the Z direction may be larger than the spacing between two adjacent through holes 21h in the X direction.

[0099] As shown in Fig. 20, the photoelectric conversion member 21 may be composed of a plurality of photoelectric conversion member portions 21a arranged side by side at intervals in the Z direction. Each of the plurality of photoelectric conversion member portions 21a has a linear shape extending along the X direction. As shown in Fig. 20, the widths of the plurality of photoelectric conversion member portions 21a in the Z direction may be the same or different. Furthermore, the distance in the Z direction between two adjacent photoelectric conversion member portions 21a may vary periodically or non-periodically depending on the position in the Z direction.

[0100] As shown in FIG. 21 , the photoelectric conversion member 21 may be composed of a plurality of photoelectric conversion member portions 21a spaced apart from one another in the Z direction and a plurality of photoelectric conversion member portions 21b arranged in a matrix in each of the X and Z directions. The photoelectric conversion member portions 21a are arranged so as to connect two adjacent photoelectric conversion member portions 21b. In FIG. 21 , the photoelectric conversion member portions 21a are arranged so as to connect two adjacent photoelectric conversion member portions 21b in the X direction. The plurality of photoelectric conversion member portions 21a, 21b may be formed in the same layer, or the photoelectric conversion member portion 21b may be stacked on a portion of the photoelectric conversion member portion 21a. Alternatively, the photoelectric conversion member portion 21a may be stacked on a portion of the photoelectric conversion member portion 21b.

[0101] In the photoelectric conversion member 21 shown in Fig. 21, plasmon resonance occurs due to a plurality of photoelectric conversion member portions 21b arranged in a matrix (two-dimensionally periodically). Electron-hole pairs generated by photoelectric conversion are excited by this resonance and reach the electrode 22 (see Fig. 10) through a plurality of photoelectric conversion member portions 21a arranged one-dimensionally periodically. In this way, photoelectric conversion occurs without polarization dependency, improving the sensitivity of the photoelectric conversion unit 20.

[0102] As described above, when the shape of the photoelectric conversion member 21 has a periodic or aperiodic pattern, plasmon resonance determined by the pattern occurs in the photoelectric conversion member 21. When the shape of the photoelectric conversion member 21 has a periodic pattern, the plasmon resonance wavelength is constant. On the other hand, when the shape of the photoelectric conversion member 21 has a non-periodic pattern, multiple resonances occur, resulting in a multi-wavelength plasmon resonance wavelength. If the interval between the plasmon resonance wavelengths is narrow, the wavelengths of electromagnetic waves that the photoelectric conversion member 21 can absorb become wider. In this way, when the shape of the photoelectric conversion member 21 has a periodic or aperiodic pattern, plasmon resonance occurs, improving the electromagnetic wave absorption rate in the photoelectric conversion member 21. For example, even when the material constituting the photoelectric conversion member 21 contains graphene, if the photoelectric conversion member 21 does not have a periodic or aperiodic pattern, the white light absorption rate is approximately 2%, but the white light absorption rate in the photoelectric conversion member 21 shown in Figures 18 to 21 improves to a maximum of 100%. As a result, the near-field thermal radiation power generation element 1 according to the ninth embodiment has high sensitivity because it includes the photoelectric conversion member 21 shown in FIGS.

[0103] The plasmon resonance wavelength is also affected by the refractive index of the substrate 23 and insulating layer 24. For example, if the substrate 23 is made of silicon, the photoelectric conversion unit 20 including the photoelectric conversion member 21 shown in FIG. 20 can detect mid-infrared wavelengths by simply setting the width of each photoelectric conversion member portion 21a in the Z direction to 200 nm and the spacing between two adjacent photoelectric conversion member portions 21a in the Z direction to 300 nm. The width and spacing in the Z direction of the multiple photoelectric conversion member portions 21a can be changed as appropriate depending on the wavelength to be detected.

[0104] <Action and effect> In the near-field thermal radiation power generation element 1, the photoelectric conversion member 21 has a shape that generates plasmon resonance. For example, when the shape of the photoelectric conversion member 21 has a periodic or aperiodic pattern, plasmon resonance occurs and the absorption rate of electromagnetic waves in the photoelectric conversion member 21 is improved.

[0105] Embodiment 10 <Configuration of near-field thermal radiation power generation element 1> FIG. 22 is a cross-sectional view of a near-field thermal radiation power generation element 1 according to embodiment 10, as seen from the Y direction. The near-field thermal radiation power generation element 1 shown in FIG. 22 basically has the same configuration as the near-field thermal radiation power generation element 1 shown in FIGS. 9 and 10, but differs in that it includes a plurality of photoelectric conversion sections 20 according to any one of embodiments 1 to 9. Like FIG. 3, FIG. 22 is a plan view showing the photoelectric conversion sections 20 and stoppers 30. Specifically, the photoelectric conversion section 20 is composed of a first photoelectric conversion section 20a, a second photoelectric conversion section 20b, a third photoelectric conversion section 20c, and a fourth photoelectric conversion section 20d. The stoppers 30 are composed of a first stopper 30a, a second stopper 30b, a third stopper 30c, and a fourth stopper 30d.

[0106] The first photoelectric conversion section 20a has a first photoelectric conversion surface 20sa facing the heat source surface 10a (see FIG. 9). The first stopper 30a connects the heat source surface 10a and the first photoelectric conversion surface 20sa. The second photoelectric conversion section 20b has a second photoelectric conversion surface 20sb facing the heat source surface 10a. The second stopper 30b connects the heat source surface 10a and the second photoelectric conversion surface 20sb. The third photoelectric conversion section 20c has a third photoelectric conversion surface 20sc facing the heat source surface 10a. The third stopper 30c connects the heat source surface 10a and the third photoelectric conversion surface 20sc. The fourth photoelectric conversion section 20d has a fourth photoelectric conversion surface 20sd facing the heat source surface 10a. The fourth stopper 30d connects the heat source surface 10a and the fourth photoelectric conversion surface 20sd. The number of photoelectric conversion units 20 constituting the photoelectric conversion unit 20 may be two or more, for example, may be four as shown in FIG. 22. The number of stoppers 30 can be changed appropriately depending on the number of photoelectric conversion units 20. For example, if the number of photoelectric conversion units 20 is four, the number of stoppers 30 may be four. At least one stopper 30 may be arranged for each photoelectric conversion unit 20.

[0107] As shown in FIG. 22 , the first to fourth photoelectric conversion units 20a, 20b, 20c, and 20d as the multiple photoelectric conversion units 20 are arranged in a matrix, i.e., periodically in the X and Z directions. The multiple photoelectric conversion units 20 are arranged in a 2×2 array. However, the number and arrangement of the multiple photoelectric conversion units 20 and stoppers 30 are not limited to this. For example, the multiple photoelectric conversion units 20 may be arranged in a 3×3 or larger array. The multiple photoelectric conversion units 20 may be arranged side by side at intervals along either the X or Z direction. Furthermore, the multiple photoelectric conversion units 20 may not be arranged periodically but may be arranged at different intervals. The wavelength ranges of electromagnetic waves detected by each of the multiple photoelectric conversion units 20 may be the same as each other. The wavelength ranges of electromagnetic waves detected by each of the multiple photoelectric conversion units 20 may be different from each other. In other words, the multiple photoelectric conversion units 20 may each have different detection wavelength selectivities. When the multiple photoelectric conversion units 20 can detect electromagnetic waves in different wavelength ranges, the near-field thermal radiation power generation element 1 can detect at least two or more different wavelength components of the electromagnetic waves radiated from the heat source 10. Furthermore, power generation from the multiple photoelectric conversion units 20 is possible, improving the power generation efficiency of the near-field thermal radiation power generation element 1. The multiple photoelectric conversion units 20 may be joined to each other with bumps, wires, or the like, which is called hybrid joining.

[0108] <Action and effect> In the near-field thermal radiation power generation element 1, the photoelectric conversion section 20 includes a first photoelectric conversion section 20a and a second photoelectric conversion section 20b. The stopper 30 includes a first stopper 30a and a second stopper 30b. The photoelectric conversion section surface 20s includes a first photoelectric conversion section surface 20sa and a second photoelectric conversion section surface 20sb. The first photoelectric conversion section 20a has a first photoelectric conversion section surface 20sa facing the heat source surface 10a. The second photoelectric conversion section 20b has a second photoelectric conversion section surface 20sb facing the heat source surface 10a. The first stopper 30a connects the heat source surface 10a and the first photoelectric conversion section surface 20sa. The second stopper 30b connects the heat source surface 10a and the second photoelectric conversion section surface 20sb. In this way, the near-field thermal radiation power generation element 1 can detect at least two or more different wavelength components of the electromagnetic waves radiated from the heat source 10. In other words, photoelectric conversion is possible in multiple photoelectric conversion units 20, which further improves power generation efficiency.

[0109] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0110] 1 Near-field thermal radiation power generation element, 10 heat source, 10a heat source surface, 11 two-dimensional material layer, 20 photoelectric conversion portion, 20a first photoelectric conversion portion, 20b second photoelectric conversion portion, 20s photoelectric conversion portion surface, 20sa first photoelectric conversion portion surface, 20sb second photoelectric conversion portion surface, 21 photoelectric conversion member, 21a photoelectric conversion member portion, 21h through hole, 21n N-type region, 21p P-type region, 22, 22l, 22r electrode, 22a first electrode surface, 22b second electrode surface, 23, 33 substrate, 23a first substrate surface, 23b second substrate surface, 24 insulating layer, 30 stopper, 30a first stopper, 30b second stopper, 40 atomic layer space, t1 first distance, t2 second distance.

Claims

1. a heat source having a heat source surface; a photoelectric conversion unit having a photoelectric conversion surface facing the heat source surface; a stopper that connects the heat source surface and the photoelectric conversion surface; The material of the stopper is a two-dimensional material.

2. the photoelectric conversion unit includes a photoelectric conversion member having the photoelectric conversion surface, The near-field thermal radiation power generation element according to claim 1 , wherein the material of the photoelectric conversion member is a two-dimensional material.

3. The photoelectric conversion unit is A substrate; a pair of electrodes connected to the photoelectric conversion member; The near-field thermal radiation power generation element according to claim 2 , further comprising an insulating layer formed between the substrate and the electrode.

4. The near-field thermal radiation power generation element according to claim 3 , wherein the material of the electrodes is a two-dimensional material.

5. the electrode has a first electrode surface facing the heat source surface, The near-field thermal radiation power generation element according to claim 3 , wherein a first distance from the heat source surface to the photoelectric conversion surface is shorter than a second distance from the heat source surface to the first electrode surface.

6. The near-field thermal radiation power generation element according to claim 3 , wherein the substrate is flexible.

7. The near-field thermal radiation power generation element according to claim 2 or 3, wherein the photoelectric conversion member has a shape that generates plasmon resonance.

8. 4. The near-field thermal radiation power generation element according to claim 2, wherein the material of the photoelectric conversion member is any one selected from the group consisting of a single-layer two-dimensional material, a multi-layer two-dimensional material, and a turbostratic two-dimensional material.

9. The near-field thermal radiation power generation element according to claim 2 or 3, wherein the stopper is connected only to the photoelectric conversion surface.

10. The near-field thermal radiation power generation element according to claim 2 or 3, wherein the photoelectric conversion member has a PN junction.

11. The near-field thermal radiation power generation element according to claim 1 , wherein the photoelectric conversion part contains a photosensitizer.

12. The near-field thermal radiation power generation element according to claim 1 , wherein the stopper is made of an insulating material.

13. the material of the photoelectric conversion member is graphene, The near-field thermal radiation power generation element according to claim 2 , wherein the stopper is made of boron nitride.

14. The near-field thermal radiation power generation element according to claim 1 , wherein the stopper has either a through-hole or a void formed therein.

15. the heat source includes a two-dimensional layer of material having the heat source surface; The near-field thermal radiation power generation element according to claim 1 , wherein the two-dimensional material layer is made of a two-dimensional material.

16. the photoelectric conversion unit includes a first photoelectric conversion unit and a second photoelectric conversion unit, The stopper includes a first stopper and a second stopper, the photoelectric conversion surface includes a first photoelectric conversion surface and a second photoelectric conversion surface, the first photoelectric conversion unit has a first photoelectric conversion unit surface facing the heat source surface, the second photoelectric conversion unit has a second photoelectric conversion unit surface facing the heat source surface, the first stopper connects the heat source surface and the first photoelectric conversion surface; The near-field thermal radiation power generation element according to claim 1 , wherein the second stopper connects the heat source surface and the second photoelectric conversion surface.

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