Thermoelectric element, power generation device, and method for manufacturing thermoelectric element

Abstract

[Problem] To provide: a thermoelectric element with improved material selectivity; a power generation device; and a method for manufacturing the thermoelectric element. [Solution] A thermoelectric element 1 is characterized by not requiring a temperature difference between electrodes and by comprising a first electrode 11, a second electrode 12 that is provided at a distance from the first electrode 11, and an intermediate layer 20 that is provided between the first electrode 11 and the second electrode 12 and contains an organic-inorganic perovskite compound. A power generation device 100 is characterized by comprising: first wiring 101 that is electrically connected to the first electrode 11; and second wiring 102 that is electrically connected to the second electrode 12. The organic-inorganic perovskite compound may be provided in contact with the first electrode 11 and / or the second electrode 12.

Description

Thermoelectric element, power generation device, and method for manufacturing a thermoelectric element

[0001] This invention relates to a thermoelectric element that does not require a temperature difference between electrodes, a power generation device, and a method for manufacturing a thermoelectric element.

[0002] In recent years, the development of thermoelectric elements that generate electrical energy using thermal energy has been actively carried out. In particular, regarding thermoelectric elements that do not require a temperature difference, for example, thermoelectric elements disclosed in Patent Document 1 have been proposed. Such thermoelectric elements are expected to be used in various applications compared to a configuration that generates electrical energy using the temperature difference applied to the electrodes.

[0003] Japanese Patent No. 6944168

[0004] According to the thermoelectric element disclosed in Patent Document 1, an organic substance that exhibits an orientation polarization is included in at least one of the donor layer and the acceptor layer. Therefore, it is possible to stabilize the power generation efficiency for a thermoelectric element that does not require a temperature difference. However, this thermoelectric element has a problem in material selectivity because the materials that can be used in at least one of the donor layer and the acceptor layer are limited to materials that exhibit an orientation polarization.

[0005] Therefore, the present invention has been devised in view of the above-described problems, and an object thereof is to provide a thermoelectric element, a power generation device, and a method for manufacturing a thermoelectric element in which material selectivity is improved.

[0006] The thermoelectric element in the first invention is a thermoelectric element that does not require a temperature difference between electrodes, and includes a first electrode, a second electrode provided separately from the first electrode, and an intermediate layer provided between the first electrode and the second electrode and containing an organic-inorganic perovskite compound.

[0007] The thermoelectric element in the second invention is characterized in that, in the first invention, the organic-inorganic perovskite compound is provided in contact with at least one of the first electrode and the second electrode.

[0008] The power generation device in the third invention is characterized by comprising a thermoelectric element according to the first or second invention, a first wiring connected electrically to the first electrode, and a second wiring connected electrically to the second electrode.

[0009] The method for manufacturing a thermoelectric element according to the fourth invention is a method for manufacturing a thermoelectric element that does not require a temperature difference between electrodes, and is characterized by comprising: a first electrode formation step of forming a first electrode; an intermediate layer formation step of forming an intermediate layer containing an organic-inorganic perovskite compound after the first electrode formation step; and a second electrode formation step of forming a second electrode after the intermediate layer formation step.

[0010] According to the first to third inventions, the thermoelectric element comprises an intermediate layer containing an organic-inorganic perovskite compound. That is, due to the electron transport and hole transport properties of the organic-inorganic perovskite compound, thermoelectric power generation is possible regardless of whether a donor layer or an acceptor layer is stacked and combined with the organic-inorganic perovskite compound. For this reason, a variety of semiconductor materials can be applied to the intermediate layer in combination with the organic-inorganic perovskite compound. This improves the material selectivity for the thermoelectric element.

[0011] In particular, according to the second invention, the organic-inorganic perovskite compound contained in the intermediate layer is provided in contact with at least one of the first electrode and the second electrode. Therefore, there is no need to provide a layer that does not contain the organic-inorganic perovskite compound between the organic-inorganic perovskite compound and the electrode, and the process of forming a layer between the organic-inorganic perovskite compound and the first and second electrodes can be omitted. This simplifies the manufacturing process for the thermoelectric element. Furthermore, the number of layers constituting the thermoelectric element can be reduced compared to the case where the organic-inorganic perovskite compound is not in contact with the first or second electrode. This makes it possible to miniaturize the thermoelectric element.

[0012] According to the fourth invention, the method for manufacturing a thermoelectric element includes an intermediate layer formation step of forming an intermediate layer containing an organic-inorganic perovskite compound. That is, due to the electron transport properties and hole transport properties of the organic-inorganic perovskite compound, thermoelectric power generation is possible regardless of whether a donor layer or an acceptor layer is laminated and combined with the organic-inorganic perovskite compound. For this reason, a variety of semiconductor materials can be applied to the intermediate layer in combination with the organic-inorganic perovskite compound. This improves the material selectivity for thermoelectric elements.

[0013] Figures 1(a) to 1(b) are schematic cross-sectional views showing an example of a thermoelectric element and power generation device in this embodiment. Figures 2(a) to 2(d) are schematic diagrams showing an example of the electronic state of each component of the thermoelectric element in this embodiment. Figure 3 is a flowchart showing an example of a method for manufacturing the thermoelectric element in this embodiment. Figure 4(a) is a schematic cross-sectional view showing a modified example of the thermoelectric element and power generation device in this embodiment, and Figure 4(b) is a schematic diagram showing a modified example of the electronic state of each component of the thermoelectric element. Figure 5 is a graph showing the power generation characteristics according to the embodiment of the present invention.

[0014] Hereinafter, an example of a thermoelectric element 1, a power generation device 100, and a method for manufacturing the thermoelectric element 1 as embodiments of the present invention will be described with reference to the drawings. In each figure, the height direction in which each electrode is stacked is defined as the first direction Z, one planar direction intersecting, for example, perpendicular to the first direction Z is defined as the second direction X, and another planar direction intersecting, for example, perpendicular to both the first direction Z and the second direction X is defined as the third direction Y. Furthermore, the configurations in each figure are schematically described for explanatory purposes, and the size of each component, the size comparison of each component, etc., may differ from those shown in the figures.

[0015] (Thermoelectric element 1, power generation device 100) Figure 1 is a schematic cross-sectional view showing an example of the thermoelectric element 1 and power generation device 100 in this embodiment.

[0016] As shown in Figure 1(a), the power generation device 100 comprises a thermoelectric element 1, a first wiring 101, and a second wiring 102. The thermoelectric element 1 converts thermal energy into electrical energy. The power generation device 100 equipped with such a thermoelectric element 1 is mounted or installed on, for example, a heat source (not shown), and uses the thermal energy of the heat source to output electrical energy generated from the thermoelectric element 1 to a load R via the first wiring 101 and the second wiring 102. One end of the load R is electrically connected to the first wiring 101, and the other end is electrically connected to the second wiring 102. The load R represents, for example, an electrical device. The load R is driven, for example, using the power generation device 100 as a main power source or auxiliary power source.

[0017] Examples of heat sources for the thermoelectric element 1 include electronic devices such as CPUs (Central Processing Units), electronic components, light-emitting elements such as LEDs (Light Emitting Diodes), engines in automobiles, factory production equipment, the human body, sunlight, and ambient temperature. For example, electronic devices, electronic components, light-emitting elements, engines, and production equipment are artificial heat sources. The human body, sunlight, and ambient temperature are natural heat sources. The power generation device 100 equipped with the thermoelectric element 1 can be installed inside, for example, IoT (Internet of Things) devices, mobile devices such as wearable devices, or autonomous sensor terminals, and can be used as a substitute or supplement for batteries. Furthermore, the power generation device 100 can also be applied to larger devices such as solar power generation.

[0018] The thermoelectric element 1 converts, for example, the thermal energy emitted by the artificial heat source or the thermal energy possessed by the natural heat source into electrical energy and generates an electric current. The thermoelectric element 1 can be installed not only within the power generation device 100, but the thermoelectric element 1 itself can also be installed inside the mobile device or the self-contained sensor terminal. In this case, the thermoelectric element 1 itself can serve as a substitute or auxiliary component for the battery in the mobile device or the self-contained sensor terminal.

[0019] The thermoelectric element 1 comprises, for example, a first electrode 11, a second electrode 12, and an intermediate layer 20, as shown in Figures 1(a) to 1(b). The first electrode 11 is provided at a distance from the second electrode 12. The intermediate layer 20 is provided between the first electrode 11 and the second electrode 12 and contains an organic-inorganic perovskite compound, which is a semiconductor material. That is, the intermediate layer 20, due to the electron transport and hole transport properties of the organic-inorganic perovskite compound, can sufficiently move electrons and holes generated inside by thermal excitation to the respective electrodes (first electrode 11, second electrode 12). Furthermore, thermoelectric power generation can be achieved by stacking and combining either a donor layer or an acceptor layer with the organic-inorganic perovskite compound. In this case, a variety of semiconductor materials can be applied to the intermediate layer 20 in combination with the organic-inorganic perovskite compound. This improves the material selectivity for the thermoelectric element 1. Similarly, in a power generation device 100 that includes such a thermoelectric element 1, a first wiring 101, and a second wiring 102, the material selectivity for the thermoelectric element 1 can also be improved. Here, an organic-inorganic perovskite compound refers to a perovskite compound in which organic ions and inorganic ions coexist.

[0020] The thermoelectric element 1 may, for example, have an intermediate layer 20 which includes a donor layer 21 and an acceptor layer 22. Here, the donor layer 21 is a layer containing donor impurities that donate electrons to the semiconductor. The acceptor layer 22 is a layer containing acceptor impurities that donate holes to the semiconductor. The thermoelectric element 1 may also include, for example, a substrate 51. The thermoelectric element 1 may include, for example, a plurality of substrates 51a, 51b.

[0021] Next, the principle of thermoelectric power generation will be explained with reference to Figures 2(a) to 2(d). Figure 2(a) shows the energy levels of the first electrode 11, second electrode 12, donor layer 21, and acceptor layer 22 before stacking, while Figures 2(b) to 2(d) show the energy levels after stacking. The value of each energy level increases as you move downwards in the figures.

[0022] The donor layer 21 has, for example, a HOMO (Highest Occupied Molecular Orbital) 21H and a LUMO (Lowest Unoccupied Molecular Orbital) 21L. The acceptor layer 22 has a different HOMO 22H and LUMO 22L than the donor layer 21. For example, HOMO 21H exhibits a higher energy level than LUMO 22L. If, for example, the donor layer 21 and acceptor layer 22 include multiple layers, then adjacent layers have the aforementioned HOMO 21H, 22H and LUMO 21L, 22L. Furthermore, the first electrode 11 and the second electrode 12 each have energy levels 11e and 12e corresponding to their respective work functions.

[0023] When thermal energy is applied to the thermoelectric element 1, for example, electrons in HOMO 21H transition to LUMO 22L in the adjacent acceptor layer 22, generating holes in HOMO 21H. This forms a CT complex. Then, the holes move to the first electrode 11 via the donor layer 21, and the electrons move to the second electrode 12 via the acceptor layer 22, enabling the thermoelectric element 1 to generate electricity.

[0024] Figures 2(a) and 2(b) show an example in which an acceptor layer 22 containing an organic-inorganic perovskite compound layer 22P is used. In this case, the combination of donor layer 21 and acceptor layer 22 is, for example, CuPc (copper phthalocyanine) and FAPbI ３ A combination of the above is used. Also, Figure 2(c) shows an example in which a donor layer 21 containing an organic-inorganic perovskite compound layer 21P is used. In this case, as a combination of the donor layer 21 and the acceptor layer 22, for example, FASnI ３ and F １６ A combination with CuPc (copper phthalocyanine fluoride) is used. Figure 2(d) also shows an example in which a donor layer 21 containing an organic-inorganic perovskite compound layer 21P and an acceptor layer 22 containing an organic-inorganic perovskite compound layer 22P are used. In this case, for example, FASnI is used as the combination of the donor layer 21 and the acceptor layer 22. ３ and FAPbi ３The combination of the above is used. Also, considering the energy levels of HOMO and LUMO, the above CuPc may be replaced with pentacene or P3HT (polyhexylthiophene), and the above F １６ CuPc may be replaced with PTCDA (perylenetetracarboxylic dianhydride). In this way, by using the organic-inorganic perovskite compound layer 21P (22P), a variety of donor and acceptor semiconductor materials can be applied to the thermoelectric element 1.

[0025] The details of each configuration are described below.

[0026] <First electrode 11, second electrode 12> The first electrode 11 and the second electrode 12 are provided spaced apart, for example, along the first direction Z. The first electrode 11 is provided in contact with the substrate 51, for example.

[0027] The first electrode 11 and the second electrode 12 may be provided in contact with the same substrate 51, for example. In this case, the first electrode 11 and the second electrode 12 are provided spaced apart along the second direction X or the third direction Y.

[0028] Each electrode 11, 12 may extend, for example, in a second direction X and a third direction Y, and multiple electrodes may be provided. For example, one second electrode 12 may be provided facing multiple first electrodes 11 at different positions. Also, for example, one first electrode 11 may be provided facing multiple second electrodes 12 at different positions.

[0029] The thickness of the first electrode 11 and the second electrode 12 is, for example, 1 nm or more and 1 μm or less. The thickness of the first electrode 11 and the second electrode 12 may also be, for example, 1 nm or more and 50 nm or less.

[0030] The first electrode 11 and the second electrode 12 may each have different work functions, for example, the work function of the first electrode 11 may be higher than that of the second electrode 12. In this case, an electric field can be formed between the electrodes based on the difference in the amount of thermionic electrons generated from each electrode 11 and 12. This can further promote the movement of carriers between the electrodes, thereby making it possible to further stabilize the power generation efficiency.

[0031] The "work function" refers to the minimum energy required to extract electrons from a solid into a vacuum, and represents the difference between the vacuum level and the Fermi level. In this embodiment, among the electronic states shown in Figures 2(a) to 2(d), the lower work function is described as being higher than the upper work function. For example, materials with a low work function tend to release electrons more easily than materials with a high work function. The work function can be measured using known measurement methods such as the Kelvin method, as well as ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES).

[0032] Furthermore, in the case of "HOMO" and "LUMO," similar to the work function, they will be described as HOMO and LUMO where the lower electronic state is higher than the upper state among the electronic states shown in Figures 2(a) to 2(d). In addition, HOMO and LUMO can be measured using known measurement methods. For example, HOMO can be measured using the spectroscopic methods described above, as well as known measurement methods such as photoemission yield spectroscopy (PYS). LUMO can be measured using, for example, inverse photoelectron spectroscopy (IPES) or calculated using absorption spectra.

[0033] In addition to using measured values ​​for each component of the thermoelectric element 1 as the "work function," "HOMO," and "LUMO" shown in this explanation, known values ​​measured for materials, for example, may also be used.

[0034] Conductive materials are used for the first electrode 11 and the second electrode 12. For example, the same material may be used for the first electrode 11 and the second electrode 12, in which case they may each have different work functions.

[0035] As the material for each electrode 11, 12, a single-element metallic material such as iron, aluminum, copper, gold, hafnium, or yttrium may be used, or an alloy material consisting of two or more elements such as MgAg (magnesium-silver alloy), MgAu (magnesium-gold alloy), APC (silver-palladium-copper alloy), ITO (indium tin oxide), IZO (indium zinc oxide), or AZO (Al-doped ZnO) may be used. As the material for each electrode 11, 12, a non-metallic conductor may be used, for example. Examples of non-metallic conductors include silicon (Si: for example, p-type Si or n-type Si) and carbon-based materials such as graphene.

[0036] In particular, known conductive materials that do not transmit light can be used as the material for each electrode 11 and 12. This prevents power generation caused by light transmitted through each electrode 11 and 12. This makes it possible to suppress variations in power generation caused by factors other than heat. The "light" mentioned above refers to light in the wavelength range used in solar power generation, for example, light in the wavelength range of approximately 200 nm to 800 nm.

[0037] <Intermediate layer 20> The intermediate layer 20 is provided between the first electrode 11 and the second electrode 12 and contains an organic-inorganic perovskite compound. The intermediate layer 20 includes a donor layer 21 and an acceptor layer 22, as shown in Figures 2(a) to 2(d), for example. The intermediate layer 20 includes at least one of the following: an organic-inorganic perovskite compound layer 21P that functions as a donor layer 21, and an organic-inorganic perovskite compound layer 22P that functions as an acceptor layer 22.

[0038] The organic-inorganic perovskite compound contained in the intermediate layer 20 may be provided in contact with at least one of the first electrode 11 and the second electrode 12. In this case, there is no need to provide a layer that does not contain the organic-inorganic perovskite compound between the organic-inorganic perovskite compound and each electrode 11, 12, and the process of forming a layer between the organic-inorganic perovskite compound and the first electrode 11 and the second electrode 12 can be omitted. This simplifies the manufacturing process for the thermoelectric element 1. Furthermore, the number of layers constituting the thermoelectric element 1 can be reduced compared to the case where the organic-inorganic perovskite compound is not in contact with the first electrode 11 or the second electrode 12. This makes it possible to miniaturize the thermoelectric element 1. In the examples of Figures 1(a) and 1(b), the donor layer 21 is provided in contact with the first electrode 11 and the acceptor layer 22 is provided in contact with the second electrode 12, without using an electron transport layer containing an electron transport material and a hole transport layer containing a hole transport material.

[0039] The intermediate layer 20 may include at least one of an electron transport layer and a hole transport layer, for example, between the donor layer 21 and the first electrode 11, and between the acceptor layer 22 and the second electrode 12.

[0040] <Donor layer 21, acceptor layer 22> The donor layer 21 and acceptor layer 22 are provided, for example, sandwiched between each electrode 11, 12 and in contact with each other. The donor layer 21 and acceptor layer 22 each consist of at least one layer. The donor layer 21 is, for example, in contact with the first electrode 11 and separated from the second electrode 12. The acceptor layer 22 is, for example, in contact with the second electrode 12 and separated from the first electrode 11. That is, the electrodes 11, 12, donor layer 21, and acceptor layer 22 described above are provided stacked in the order of, for example, the first electrode 11, donor layer 21, acceptor layer 22, and the second electrode 12.

[0041] The donor layer 21 and the acceptor layer 22 extend in the second direction X and the third direction Y, respectively, similar to the electrodes 11 and 12. The shapes of the donor layer 21 and the acceptor layer 22 are similar to those of the electrodes 11 and 12.

[0042] The thickness of the donor layer 21 and the acceptor layer 22 is, for example, 1 nm to 1 μm. The thickness of the donor layer 21 and the acceptor layer 22 may also be, for example, 1 nm to 50 nm.

[0043] The donor layer 21 and acceptor layer 22 are formed from solid material. Therefore, there is no need to provide support parts to maintain the distance (gap) between each electrode 11 and 12. However, when electrodes 11 and 12 with different work functions are used, columnar or frame-shaped support parts may be formed and the gap filled with a solvent or the like. In this case, variations in the formation of the support parts can lead to variations in the gap between the opposing surfaces of each electrode 11 and 12, potentially resulting in a decrease in power generation efficiency. In contrast, by providing the solid donor layer 21 and acceptor layer 22 within the gap, variations in the gap between the opposing surfaces of each electrode 11 and 12 can be eliminated. This makes it possible to further stabilize the power generation efficiency.

[0044] A material suitable for moving holes to the first electrode 11 is used as the donor layer 21. The donor layer 21 includes, for example, an organic-inorganic perovskite compound layer 21P. The donor layer 21 may also be an n-type semiconductor layer containing, for example, an n-type semiconductor material.

[0045] For example, the donor layer 21 may include N,N'-diphenyl-N,N'-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), 9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole (Tris-PCz), pentacene, 4,4',4' Organic materials such as '-tris[(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), phthalocyanine-based materials such as copper phthalocyanine (CuPc) and phthalocyanine (Pc), and polymer materials such as polyhexylthiophene (P3HT) are used. As the donor layer 21, n-type semiconductors such as ITO, ZnO, and Zn-Si-O are used, as well as MoOｘ 、 V ２ O ５ 、 WO ３ and other materials containing doping materials such as may be used.

[0046] As the donor layer 21, for example, a material containing an organic substance showing an orientation polarization may be used. At this time, particularly on the surface in contact with the acceptor layer 22, among examples of the organic material showing an orientation polarization described later, it is preferable to use α-NPD or mCP.

[0047] As the acceptor layer 22, a material suitable for moving electrons to the second electrode 12 is used. The acceptor layer 22 includes, for example, an organic-inorganic perovskite compound layer 22P. The acceptor layer 22 may be, for example, a p-type semiconductor layer containing a p-type semiconductor material.

[0048] As the acceptor layer 22, for example, 3,4,9,10-perylenetetracarboxylic acid bisbenzimidazole (PTCBi), C ６０ , C ７０ , bathophenanthroline (BPhen), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄TCNQ), 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), perylenetetracarboxylic acid dihydrate (PTCDA) and other organic materials are used. As the acceptor layer 22, in addition to using a p-type semiconductor such as CuSnI, for example, materials containing doping materials such as Cs ２ CO ３ , Li, Mg, Ca and other materials may be used.

[0049] As the acceptor layer 22, for example, a material containing an organic substance showing an orientation polarization may be used. At this time, particularly on the surface in contact with the donor layer 21, among examples of the organic material showing an orientation polarization described later, it is preferable to use TPB i, OXD-7, Alq₃, Al(7-prq)₃, Gaq₃, BCP, Bpy-OXD, or B3PyMPM.

[0050] Furthermore, the organic-inorganic perovskite compound layers 21P and 22P can be, for example, FASnCl ３ , MASnCl ３ MAPbCl ３ , FAPbCl ３ , CsPbCl ３ , CsSnCl ３ FASnBr ３ , CsPbBr ３ MAPbBr ３ FAPbBr ３ ,MASnBr ３ , CsSnBr ３ , CsPbI ３ MAPbI ３ , FAPbi ３ , CsSnI ３ , MASnI ３ FASnI ３ Organic-inorganic perovskite compounds such as these, or mixtures of two or more of these compounds, are used. MA (methylammonium) may be introduced as methylamine hydrobromide, and FA (formaminidium) may be introduced as formamine hydroiodide.

[0051] For example, the LUMO22L of the acceptor layer 22 is located between the HOMO21H and LUMO21L of the donor layer 21, and the HOMO22H of the acceptor layer 22 is higher than the HOMO21H of the donor layer 21. In this case, the formation of the CT complex by thermal excitation of electrons can be promoted at the interface between the donor layer 21 and the acceptor layer 22.

[0052] For example, the work function of the first electrode 11 is between the HOMO 21H and LUMO 21L of the donor layer 21, and the work function of the second electrode 12 is lower than the LUMO 22L of the acceptor layer 22. In this case, the energy barriers between each component that hinder the movement of electrons or holes can be reduced. That is, the movement of holes toward the first electrode 11 can be promoted, and the movement of electrons toward the second electrode 12 can be promoted. This makes it possible to improve the power generation efficiency.

[0053] For example, the acceptor layer 22 may include a mixed layer. The mixed layer is in contact with the donor layer 21 and is formed by mixing two types of materials. In this case, for example, the acceptor layer 22 may include a transport layer provided between the mixed layer and the second electrode 12.

[0054] Two types of materials can be used in the mixed layer, for example, the material used in the donor layer 21 and the material used in the transport layer. In this case, portions corresponding to each of the HOMO 21H, 22H and LUMO 21L, 22L described above can be formed within the mixed layer. This expands the range in which the CT complex is formed, making it possible to improve power generation efficiency.

[0055] Furthermore, layers containing organic materials that exhibit orientation polarization have the property of spontaneously exhibiting orientation polarization (spontaneous polarization) during layer formation, for example, and maintaining a surface potential. Examples of organic materials that exhibit orientation polarization include copper phthalocyanine (CuPc), BCP (Bathocuproine), and copper phthalocyanine fluoride (F). １６ CuPc) and others are used. In addition to the above, for example, 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD), 2,2',2''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), bis(2-methyl-8-quinolinolato)(p-phenylphenolato)aluminum (BAlq), 1,3-bis[(4-t-butylphenyl)-1,3,4-oxadiazole]phenylene (OXD-7), tris(8-quinolinolato)aluminum (Alq) ３ ), Tris(2-phenylpyridina)iridium(III)(Ir(ppy) ３ ), 9-[4-(4,6-diphenyl-1,3,5-triazine-2-yl)phenyl]-N3,N3,N6,N6-tetraphenyl-9H-carbazole-3,6,diamine(DACT-II),bis[2-(2-pyridinyl-N)phenyl-C](2,4-pentanediona-O ２ , O ４ Iridium (III) (Ir(ppy) ２(acac), (4s,6s)-2,4,5,6-tetra(9H-carbazole-9-yl)isophthalonitrile (4CzIPN), 1,3-bis[2-(2,2'-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene (Bpy-OXD), 4,6-bis(3,5-di(pyridine-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM), 4,5 -di(9H-carbazole-9-yl)phthalonitrile (2CzPN), 2-tert-butyl-4-(dicyanomethylene)-6-[2-(1,1,7,7-tetramethyljurolidine-9-yl)vinyl]-4H-pyran (DCJTB), 1,3-bis(N-carbazolyl)benzene (mCP), tris(7-propyl-8-hydroxyquinolinato)aluminum (Al(7-prq) ３ ), Tris(5-chloro-8-hydroxyquinolinato)aluminum (Al(q-Cl) ３ ), Tris(8-hydroxyquinoline)-gallium(Gaq ３ ), bis(8-quinolinolato)zinc (Znq ２ ), 3,4,5,6-tetra-9H-carbazole-9-yl-1,2-benzenedicarbonitric acid (4CzPN), etc., can be used, and any material can be used depending on the application.

[0056] The layer containing organic matter exhibiting oriented polarization may, for example, contain only one type of material. In this case, it is easier to maintain the material's characteristic surface potential compared to using a material in which particles or the like are dispersed.

[0057] <Substrate 51> The substrate 51 is in contact with the first electrode 11, for example, and is separated from the second electrode 12, the donor layer 21, and the acceptor layer 22. The substrate 51 fixes the first electrode 11. The substrate 51 may include, for example, a first substrate 51a and a second substrate 51b. In this case, for example as shown in Figure 1(b), the first substrate 51a is in contact with the first electrode 11, and the second substrate 51b is in contact with the second electrode 12.

[0058] The thickness of the substrate 51 is, for example, 1 μm or more and 10 mm or less, and can be any thickness as long as the first electrode 11 and the like can be fixed to it.

[0059] As the substrate 51, for example, an insulating plate-shaped material can be used, and known materials such as silicon, quartz, and Pyrex (registered trademark) can be used. The substrate 51 may also be a film-shaped material, and known film-shaped materials such as PET (polyethylene terephthalate), PC (polycarbonate), and polyimide may be used.

[0060] The substrate 51 can be made of a conductive material, such as iron, aluminum, copper, or an alloy of aluminum and copper. Alternatively, the substrate 51 may be made of conductive semiconductors such as Si or GaN, or conductive polymers. When a conductive material is used for the substrate 51, wiring for connecting to the first electrode 11 becomes unnecessary.

[0061] In particular, the substrate 51 can be made of a known insulating material that does not transmit light, or a known conductive material. This prevents power generation caused by light transmitted through the substrate 51. This makes it possible to suppress variations in power generation caused by factors other than heat.

[0062] (Method for manufacturing the thermoelectric element 1) Next, an example of a method for manufacturing the thermoelectric element 1 in this embodiment will be described. Figure 3 is a flowchart showing an example of a method for manufacturing the thermoelectric element 1 in this embodiment.

[0063] The method for manufacturing the thermoelectric element 1 comprises a first electrode formation step S110, an intermediate layer formation step S120, and a second electrode formation step S130.

[0064] <First Electrode Formation Step S110> The first electrode formation step S110 is for forming the first electrode 11. In the first electrode formation step S110, the first electrode 11 is formed on the substrate 51 shown in Figure 1(a), for example. At this time, the substrate 51 is cleaned and baked before the first electrode 11 is formed. The first electrode 11 is formed by sputtering or vacuum deposition under reduced pressure, for example.

[0065] <Intermediate Layer Formation Process S120> In the intermediate layer formation process S120, after the first electrode formation process S110, an intermediate layer 20 containing an organic-inorganic perovskite compound is formed. In this case, a variety of semiconductor materials can be applied to the intermediate layer 20 in combination with the organic-inorganic perovskite compound. This improves the material selectivity for the thermoelectric element 1.

[0066] In the intermediate layer formation step S120, for example, a donor layer 21 containing at least one layer is formed on the main surface of the first electrode 11. The donor layer 21 is formed, for example, by vacuum deposition or spin coating under reduced pressure. Subsequently, an acceptor layer 22 containing at least one layer is formed on the main surface of the donor layer 21. The acceptor layer 22 is formed, for example, by vacuum deposition, spin coating, inkjet, slit coating, spray, gravure printing, or letterpress printing.

[0067] As the donor layer 21, for example, an organic-inorganic perovskite compound layer 21P containing an organic-inorganic perovskite compound may be formed. As the acceptor layer 22, for example, an organic-inorganic perovskite compound layer 22P containing an organic-inorganic perovskite compound may be formed. The organic-inorganic perovskite compound layers 21P and 22P may be formed in the same manner as the donor layer 21 and the acceptor layer 22.

[0068] <Second electrode formation step S130> In the second electrode formation step S130, the second electrode 12 is formed after the intermediate layer formation step S120.

[0069] In the second electrode formation step S130, for example, the second electrode 12 is formed on the main surface of the intermediate layer 20. In the second electrode formation step S130, for example, the second electrode 12 is formed on the main surface of the acceptor layer 22 included in the intermediate layer 20. The second electrode 12 is formed, for example, by sputtering or vacuum deposition under a reduced pressure environment.

[0070] By carrying out the steps described above, the thermoelectric element 1 in this embodiment is formed. Furthermore, by forming the wiring 101, 102, etc., as shown in Figure 1(a), for example, the power generation device 100 in this embodiment is formed.

[0071] In the above example, a donor layer 21 is formed on the main surface of the first electrode 11 and an acceptor layer 22 is formed on the main surface of the donor layer 21 in the intermediate layer formation step S120. However, for example, an acceptor layer 22 may be formed on the main surface of the first electrode 11 and a donor layer 21 may be formed on the main surface of the acceptor layer 22. In this case, in the second electrode formation step S130, a second electrode 12 may be formed on the main surface of the donor layer 21.

[0072] (Modified Thermoelectric Element 1 and Method for Manufacturing the Thermoelectric Element 1) Next, modified versions of the thermoelectric element 1 and its manufacturing method will be described. The difference between the above-described embodiment and the modified version is that the combination of the donor layer 21 and the acceptor layer 22 in the intermediate layer 20 can be replaced with a single layer containing an organic-inorganic perovskite compound. Details similar to those described above will not be explained.

[0073] <Intermediate Layer 20> The intermediate layer 20 includes an organic-inorganic perovskite compound layer 20P containing an organic-inorganic perovskite compound, instead of the combination of a donor layer 21 and an acceptor layer 22, as shown in Figures 4(a) to 4(b), for example. The organic-inorganic perovskite compound layer 20P consists of a mixture of various materials. That is, the intermediate layer 20 does not include a donor layer 21 and an acceptor layer 22, and does not necessarily require a CT complex. Specifically, for example, when Spiro-OMeTAD is included in the organic-inorganic perovskite compound layer 20P, the Fermi level of the organic-inorganic perovskite compound is slightly higher than the LUMO of the organic-inorganic perovskite compound, so the energy level shifts to the higher side with respect to the LUMO in the region in contact with Spiro-OMeTAD. Through this mechanism, electrons and holes can be separated by thermal excitation without the need for a CT complex. In this case, the materials that can be used for the thermoelectric element 1 are not limited to materials that can form a CT complex, and a variety of organic-inorganic perovskite compounds can be applied. This improves the material selectivity for the thermoelectric element 1. Furthermore, compared to structures that require a CT complex, the number of layers can be reduced, and consequently the thickness of the thermoelectric element 1 can be reduced. This allows for miniaturization of the thermoelectric element 1. The intermediate layer 20 may include, for example, at least one of an electron transport layer and a hole transport layer between the organic-inorganic perovskite compound layer 20P and the first electrode 11, and between the organic-inorganic perovskite compound layer 20P and the second electrode 12.

[0074] Furthermore, the intermediate layer 20 may have a CT complex formed via the energy levels of impurities contained in the organic-inorganic perovskite compound. In this case, it is considered that there are many electron energy levels originating from the impurities within the range of energy levels that can be identified from the absorption edge of the compound. Specifically, for example, if the organic-inorganic perovskite compound layer 20P contains Spiro-OMeTAD, and there are many electron-filled impurity energy levels on the side with higher energy levels than the LUMO of the organic-inorganic perovskite compound (HOMO side), a CT complex will be formed between the energy levels of the impurities and the HOMO of Spiro-OMeTAD. Through this mechanism, electrons and holes can be separated by thermal excitation via the CT complex.

[0075] When thermal energy is applied to the thermoelectric element 1 of this modified example, for example, thermally excited electrons and holes are generated within the organic-inorganic perovskite compound layer 20P. Then, the holes in the organic-inorganic perovskite compound layer 20P move to the first electrode 11, and the electrons in the organic-inorganic perovskite compound layer 20P move to the second electrode 12 (action A shown by the arrow in Figure 4(b)), thereby enabling the thermoelectric element 1 to generate electricity.

[0076] <Intermediate layer formation step S120> In the intermediate layer formation step S120, for example, one layer of organic-inorganic perovskite compound layer 20P is formed on the main surface of the first electrode 11. The organic-inorganic perovskite compound layer 20P is formed, for example, by a spin coating method.

[0077] <Second electrode formation step S130> In the second electrode formation step S130, for example, the second electrode 12 is formed on the main surface of the organic inorganic perovskite compound layer 20P.

[0078] By carrying out the steps described above, the thermoelectric element 1 in this embodiment is formed. Furthermore, by forming the wiring 101, 102, etc., as shown in Figure 1(a), for example, the power generation device 100 in this embodiment is formed.

[0079] According to this embodiment, the thermoelectric element 1 and the power generation device 100 include an intermediate layer 20 containing an organic-inorganic perovskite compound. Therefore, a variety of semiconductor materials can be applied to the intermediate layer 20 in combination with the organic-inorganic perovskite compound. This improves the material selectivity for the thermoelectric element 1.

[0080] Furthermore, according to this embodiment, the organic-inorganic perovskite compound contained in the intermediate layer 20 is provided in contact with at least one of the first electrode 11 and the second electrode 12. Therefore, there is no need to provide a layer that does not contain the organic-inorganic perovskite compound between the organic-inorganic perovskite compound and the electrode (at least one of the first electrode 11 and the second electrode 12), and the process of forming a layer between the organic-inorganic perovskite compound and the first electrode 11 and the second electrode 12 can be omitted. This simplifies the manufacturing process for the thermoelectric element 1. In addition, the number of layers constituting the thermoelectric element 1 can be reduced compared to the case where the organic-inorganic perovskite compound is not in contact with the first electrode 11 or the second electrode 12. This makes it possible to miniaturize the thermoelectric element 1.

[0081] Furthermore, according to this embodiment, the method for manufacturing the thermoelectric element 1 includes an intermediate layer formation step S120 for forming an intermediate layer 20 containing an organic-inorganic perovskite compound. Therefore, a variety of semiconductor materials can be applied to the intermediate layer 20 in combination with the organic-inorganic perovskite compound. This improves the material selectivity for the thermoelectric element 1.

[0082] (Example 1: Voltage and Current) Next, an example related to the thermoelectric element 1 in the above-described embodiment will be explained. In this embodiment, the voltage and current were measured using a thermoelectric element 1 equipped with an intermediate layer 20 containing an organic-inorganic perovskite compound to confirm whether or not thermoelectric power generation was realized.

[0083] In this embodiment, a measuring element was formed by a method similar to the manufacturing method of the thermoelectric element 1 described above. ITO was used as the first electrode 11, and Au was used as the second electrode 12. SnO, with a thickness of approximately 30 nm, was placed between the electrodes. ２A layer containing an organic-inorganic perovskite compound with a thickness of approximately 650 nm, formed by heat-treating the organic-inorganic perovskite solution described later, and a Spiro-OMeTAD layer with a thickness of approximately 150 nm were stacked as an intermediate layer 20. The distance between electrodes is approximately 830 nm, which corresponds to the thickness of the intermediate layer 20.

[0084] The details of the manufacturing method for the thermoelectric element 1 used in this embodiment are as follows. First, a glass substrate is fixed to the sample stage of a spin coater, and SnO is poured onto the main surface of the substrate without using a filtration filter. ２ Add only four drops of the solution, rotate at 3000 rpm for 30 seconds to form a film, and then calcine at 150°C for 30 minutes to obtain SnO ２ A layer was formed. After that, SnO ２ 30 μL of a pre-prepared organic-inorganic perovskite solution was dropped onto the main surface of the layer using a filtration filter, and the solution was spread uniformly by rotating at 1000 rpm for 10 seconds. Then, the layer was spin-coated at 6000 rpm for 20 seconds until the solution reached an appropriate film thickness. Subsequently, while maintaining rotation at 6000 rpm for 10 seconds, 120 μL of chlorobenzene, a poor solvent for the constituent materials of the organic-inorganic perovskite compound, was dropped dropwise for a short time of about 0.5 seconds to remove excess organic-inorganic perovskite solution and poor solvent, thereby simultaneously promoting crystallization and thin-film formation. After that, the layer was annealed at 100°C for 45 minutes and then cooled for 10 minutes to form a layer containing the organic-inorganic perovskite compound. Subsequently, 40 μL of Spiro-OMeTAD solution was dropped onto the main surface of the layer containing the organic-inorganic perovskite compound using a filtration filter, and the film was deposited by rotating at 4000 rpm for 30 seconds to form a Spiro-OMeTAD layer. Finally, Au was deposited onto the main surface of the Spiro-OMeTAD layer.

[0085] As for organic-inorganic perovskite solutions, PbIBr ２ (0.2M):PbI ２ A solution was prepared by mixing a DMF (dimethylformamide) solution containing (1.15 M):MABr (0.2 M):FAI (1.1 M) with a DMSO (dimethyl sulfoxide) solution containing similar components in a 4:1 ratio, and then adding 26.3 μL of DMSO solution containing CsI (1.5 M) to this solution.

[0086] When the fabricated thermoelectric element 1 was connected to a voltmeter with an input impedance of 10 GΩ at room temperature of approximately 27°C, and the voltage across the thermoelectric element 1 was measured, it was able to maintain a voltage of approximately 380 mV for 1500 seconds from the start of measurement.

[0087] Furthermore, the temperature dependence of the current density of the fabricated thermoelectric element 1, with the second electrode 12 side as the source current side, was evaluated at ambient temperatures from 20°C to 80°C using J-V measurement. Specifically, after 7 minutes had elapsed since the substrate temperature of the thermoelectric element 1 stabilized at a predetermined temperature, the current density was obtained as the measurement result when the terminal voltage of the thermoelectric element 1 was 0V on the forward path (the direction in which the voltage increases) when the terminal voltage of the thermoelectric element 1 was oscillated back and forth in the order of -1V, 1V, and -1V. As a result, the current value of the thermoelectric element 1 was approximately 1.78 nA at 20°C, approximately 5.89 nA at 40°C, approximately 16.4 nA at 60°C, and approximately 18.7 nA at 80°C. The current density of the thermoelectric element 1 was approximately 44.6 nA / cm² at 20°C. ２ Approximately 147 nA / cm² at 40°C ２ Approximately 409 nA / cm² at 60°C ２ Approximately 466 nA / cm² at 80°C ２ Therefore, it was found that thermoelectric power generation was realized with thermoelectric element 1.

[0088] (Example 2: Power Generation Characteristics) In this example, a thermoelectric element 1 equipped with an intermediate layer 20 containing an organic-inorganic perovskite compound was used to evaluate the power generation characteristics under dark conditions.

[0089] As a method for evaluating the power generation characteristics, a measurement circuit consisting of a thermoelectric element 1, a changeover switch, a load resistor (500 kΩ), and a digital multimeter (DMM) was used. The specific evaluation procedure is as follows: First, as the first step, the changeover switch was set to a short circuit state (short), and the voltage difference between the electrodes was set to 0V, thereby discharging the charge accumulated inside the device. Next, as the second step, the changeover switch was set to an open circuit state (open), and the voltage change from the initial state where no charge existed between the electrodes was measured. This evaluation procedure allows for the direct evaluation of the electromotive force caused by the device itself, i.e., the open-circuit voltage (VOC), without the need for external voltage application as in conventional current-voltage (J-V) measurements.

[0090] In this example, an intermediate layer 20 was fabricated on the first electrode 11 under a nitrogen atmosphere using the same manufacturing method as in Example 1 described above, the second electrode 12 was fabricated under vacuum, and the assembly was sealed with sealing glass under a nitrogen environment. The first electrode 11 was made of ITO with a thickness of approximately 100 nm, and the second electrode 12 was made of Au with a thickness of approximately 70 nm. The intermediate layer 20 was made of SnO with a thickness of approximately 30 nm. ２ A layer containing an organic-inorganic perovskite compound with a thickness of approximately 650 nm, formed by heat-treating the organic-inorganic perovskite solution described later, and a Spiro-OMeTAD layer with a thickness of approximately 150 nm were laminated together.

[0091] The details of the manufacturing method for the thermoelectric element 1 used in this embodiment are as follows. First, a glass substrate coated with a 100 nm thick ITO transparent conductive film is used as the first electrode 11, and a commercially available SnO ２ A precursor solution, obtained by diluting a colloidal dispersion with ultrapure water, is added dropwise under a nitrogen flow, and a spin coat is performed at 3000 rpm for 30 seconds to obtain a uniform SnO. ２ A layer was formed. After that, SnO ２ The layer was heat-treated at 150°C for 30 minutes. Then, immediately before deposition of the organic-inorganic perovskite compound, an additional 15 minutes of UV-ozone treatment was applied to modify the surface condition and optimize the interfacial properties with the perovskite layer. Subsequently, ITO and SnO ２An organic-inorganic perovskite solution was dropped onto a substrate coated with [a specific coating], and spin-coated at 1000 rpm for 10 seconds as the first stage, and at 6000 rpm for 30 seconds as the second stage. Ten seconds before the spin-coating rotation stopped (20 seconds after the start of the second stage), 120 μL of chlorobenzene was rapidly dropped onto the center of the substrate as an antisolvent. After spin-coating was complete, the substrate was annealed at 100°C for 30 minutes.

[0092] For the formation of the hole transport layer (HTL) of thermoelectric element 1, a solution based on Spiro-OMeTAD was used. The HTL solution was prepared by adding 30 μL of 4-tert-butylpyridine (4-tBP), 18 μL of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 520 mg / mL in acetonitrile), and 29 μL of tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(III)tris(bis(trifluoromethane)sulfonimide) (FK-209, 300 mg / mL in acetonitrile) as dopants to improve performance. A uniform hole transport layer was formed on the perovskite layer by spin-coating this solution at 4000 rpm for 30 seconds. Subsequently, a gold thin film was deposited on the second electrode 12 by vacuum thermal deposition. ２ With the exception of the spin coating and annealing processes, all film formation processes were carried out under a nitrogen atmosphere. Finally, the film was sealed with sealing glass to prevent material degradation by oxygen and moisture from film formation to measurement.

[0093] In this embodiment, different types of organic-inorganic perovskite compounds with similar material systems were selected for measurement, and the power generation characteristics of the thermoelectric elements 1 manufactured for each were compared. For details, see FAPbI as Example 1 of the present invention. ３ As an example of the present invention, we have MAPbI ３ Using this method, we present FAPbI as Example 3 of the present invention. ３ and MAPbI ３ In addition, Cs containing Cs as a cation and Br as a halide ０．０５ (FA０．８５ MA ０．１５ ) ０．９５ Pb(I ０．８５ Br ０．１５ ) ３ We manufactured products using each of these materials.

[0094] The details of the organic-inorganic perovskite solution are as follows: For Example 1 of the present invention, 1.32 M FAI (formamidinium iodide) and PbI ２ A solution was prepared by mixing a DMF solution containing 1.32 M of lead iodide with a DMSO solution containing similar components in a volume ratio of 4:1. For Example 2 of the present invention, 1.32 M of methylamidinium iodide (MAI) and PbI were used. ２ A solution was prepared by mixing a DMF solution containing 1.32 M of the same component with a DMSO solution containing the same component in a volume ratio of 4:1. For Example 3 of the present invention, 1.10 M of FAI and PbI were used. ２ 1.12 M of methyl ammonium bromide, 0.20 M of MABr, PbBr ２ A DMF solution containing 0.20 M lead bromide and a DMSO solution containing similar components were prepared in a volume ratio of 4:1. A 1.5 M CsI (cesium iodide) stock solution was added to the DMSO to achieve a final CsI concentration of 0.08 M. For Invention Examples 1 and 3, the solutions were stirred at 70°C for 3 hours to ensure complete dissolution and uniform mixing. For Invention Example 2, the solutions were stirred at room temperature for 3 hours to ensure complete dissolution and uniform mixing. Immediately before use, the organic-inorganic perovskite solutions were filtered through a PTFE (polytetrafluoroethylene) membrane filter with a pore size of 0.2 μm to remove fine particles and undissolved substances.

[0095] The results of the present invention example are shown in Figure 5. The horizontal axis, Time[s], represents the elapsed time from the start of measurement, and the vertical axis represents the voltage V. Also, the dashed line "FAPbI" is shown. ３ The graph shown by " " represents the results of Example 1 of the present invention, with the dotted line "MAPbI ３ The graph shown by " shows the results of Example 2 of the present invention, with the solid line "Cs ０．０５ (FA ０．８５ MA ０．１５ ) ０．９５ Pb(I ０．８５Br ０．１５ ) ３ The graphs indicated by '' show the results for each of the three examples of the present invention.

[0096] According to the results of Example 1 of the present invention, the voltage as the saturation value of the open-circuit voltage VoC was approximately 130 [mV].

[0097] According to the results of Example 2 of the present invention, the voltage as the saturation value of the open-circuit voltage VoC was approximately 200 [mV].

[0098] According to the results of Example 3 of the present invention, the voltage as the saturation value of the open-circuit voltage VoC was approximately 300 [mV] or higher.

[0099] From the above results, it was observed that in all compositions of the present invention examples 1 to 3, after switching from a short-circuit state to an open-circuit state, the voltage between the electrodes increased over time and converged to a constant value. Furthermore, the saturation value of the open-circuit voltage VoC was highest in the order of present invention example 3, present invention example 2, and present invention example 1. Therefore, according to present invention examples 1 to 3, it was found that the thermoelectric element 1 having a layer containing an organic inorganic perovskite compound generated electromotive force under dark conditions, thus possessing power generation characteristics. Moreover, it was suggested that the inclusion of MA is particularly preferable because it improves the voltage, and that the inclusion of a mixture of MA and FA is even more preferable because it generates a higher electromotive force and further improves the power generation characteristics.

[0100] The reason why the open-circuit voltage VoC in Example 3 of the present invention is the highest is, for example, assumed to be the following:

[0101] Perovskite solar cells are devices that inherently exhibit power generation characteristics upon light irradiation. When light is irradiated onto a perovskite material, light absorption occurs in the perovskite layer. If the energy of the incident light is greater than or equal to the band gap energy of the perovskite material, electrons in the valence band are excited to the conduction band, and holes are generated in the valence band. At this time, electrons and holes form a bound state as excitons, but because perovskite materials have a relatively high dielectric constant, the exciton binding energy is small, around tens of meV, and they easily dissociate with thermal energy at room temperature, generating free carriers.

[0102] In the thermoelectric element 1 of the present invention, the generated free electrons and free holes are separated at the interface between the layer containing the organic-inorganic perovskite compound and the adjacent charge transport layer based on the difference in energy levels. In the thermoelectric element 1, the lower end of the conduction band of the electron transport layer (ETL) is located at a lower energy level than the lower end of the conduction band of the layer containing the organic-inorganic perovskite compound, so electrons move to the electron transport layer. Similarly, in the thermoelectric element 1, the upper end of the valence band of the hole transport layer (HTL) is located at a higher energy level than the upper end of the valence band of the layer containing the organic-inorganic perovskite compound, so holes move to the hole transport layer. Based on this transport process, the thermoelectric element 1 collects electrons that have reached the transparent electrode via the electron transport layer and holes that have reached the metal electrode via the hole transport layer at their respective electrodes. Then, by connecting an external circuit to the thermoelectric element 1, the collected charge flows through an external load and is extracted as electrical energy.

[0103] Under room temperature and dark conditions, there are no high-energy absorption sources, such as those required during light irradiation, necessary for carrier generation and transport processes. Therefore, the process of electrons in the valence band being directly excited to the conduction band is difficult to imagine from an energetic standpoint. Under these conditions, the only energy source that the device can absorb is the minute amount of thermal energy at room temperature. However, the thermal energy at room temperature is approximately 26 meV, which is significantly smaller than the band gap energy of perovskite materials (approximately 1.5–1.6 eV). For this reason, it is difficult for direct electron excitation from the valence band to the conduction band to occur solely by thermal energy.

[0104] In perovskite materials, it is widely known that defect levels and impurity levels are formed within the band gap due to point defects in the crystal lattice, interstitial atoms, and compositional heterogeneity. These levels are distributed discretely or continuously between the upper end of the valence band and the lower end of the conduction band and function as energetically intermediate states.

[0105] The inventors of the present invention considered that the power generation phenomenon of thermoelectric element 1 under dark conditions is due to a stepwise charge separation and transport mechanism mediated by these defect and impurity levels. Specifically, the process involves first, charge separation occurring at the interface between the defect and impurity levels in the layer containing the organic-inorganic perovskite compound and the hole transport layer, driven by a small amount of thermal energy at room temperature. Subsequently, the separated electrons sequentially transition between defect and impurity levels widely distributed within the layer containing the organic-inorganic perovskite compound via a hopping conduction mechanism utilizing thermal energy. Through this hopping conduction process, the electrons are finally transported to the lower end of the conduction band of the electron transport layer, achieving charge extraction to the external circuit.

[0106] The thermoelectric element 1 of Example 3 of the present invention consists of a multi-component system comprising a layer containing an organic-inorganic perovskite compound, with various constituent elements including cesium, formamidinium, methylammonium, iodine, and bromine. In such a multi-component system, the complexity of the composition increases the probability of formation of impurity levels and defect levels within the crystal lattice. As a result, it is presumed that a rich network of thermal energy-driven hopping conduction pathways is formed, contributing to the improvement of power generation characteristics in the dark.

[0107] On the other hand, FAPbI, an organic-inorganic perovskite compound included in the thermoelectric element 1 of the present invention example 1 ３ , and MAPbI, an organic inorganic perovskite compound contained in the thermoelectric element 1 of Example 2 of the present invention. ３ Compared to Example 3 of the present invention, it has a simpler composition and a limited range of constituent elements, which is why the formation density of defect and impurity levels is relatively low, and it is presumed that the dark-field power generation characteristics are lower than those of Example 3 of the present invention.

[0108] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0109] 1: Thermoelectric element 11: First electrode 11e: Energy level (of the first electrode) 12: Second electrode 12e: Energy level (of the second electrode) 20: Intermediate layer 20P: Organic-inorganic perovskite compound layer 21: Donor layer 21P: Organic-inorganic perovskite compound layer 22: Acceptor layer 22P: Organic-inorganic perovskite compound layer 51: Substrate 51a: First substrate 51b: Second substrate 100: Power generation device 101: First wiring 102: Second wiring S110: First electrode formation process S120: Intermediate layer formation process S130: Second electrode formation process X: Second direction Y: Third direction Z: First direction

Claims

1. A thermoelectric element that eliminates the need for a temperature difference between electrodes, comprising: a first electrode; a second electrode provided at a distance from the first electrode; and an intermediate layer provided between the first electrode and the second electrode, comprising an organic-inorganic perovskite compound.

2. The thermoelectric element according to claim 1, characterized in that the organic-inorganic perovskite compound is provided in contact with at least one of the first electrode and the second electrode.

3. A power generation device comprising: a thermoelectric element according to claim 1 or 2; a first wiring electrically connected to the first electrode; and a second wiring electrically connected to the second electrode.

4. A method for manufacturing a thermoelectric element that eliminates the need for a temperature difference between electrodes, comprising: a first electrode formation step of forming a first electrode; an intermediate layer formation step of forming an intermediate layer containing an organic-inorganic perovskite compound after the first electrode formation step; and a second electrode formation step of forming a second electrode after the intermediate layer formation step.

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