Thermoelectric element, power generation device, and method for manufacturing thermoelectric element
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-09
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026004595_13082026_PF_FP_ABST
Abstract
Description
Thermoelectric element, power generation device, and method for manufacturing a thermoelectric element
[0001] This invention relates to a thermoelectric element, a power generation device, and a method for manufacturing a thermoelectric element, which eliminate the need for a temperature difference between electrodes.
[0002] In recent years, there has been a great deal of activity in developing thermoelectric elements that generate electrical energy using thermal energy. In particular, thermoelectric elements that do not require a temperature difference have been proposed, such as the thermoelectric element disclosed in Patent Document 1. Such thermoelectric elements are expected to be used in a wider range of applications compared to configurations that generate electrical energy by utilizing the temperature difference applied to electrodes.
[0003] Patent No. 6944168
[0004] According to the thermoelectric element disclosed in Patent Document 1, at least one of the donor layer and the acceptor layer contains an organic material exhibiting oriented polarization. Therefore, it is possible to stabilize the power generation efficiency of a thermoelectric element that does not require a temperature difference.
[0005] In this case, the thermoelectric element disclosed in Patent Document 1 has a donor layer and an acceptor layer stacked in the stacking direction between the electrodes. In this case, holes generated by the separation of carriers at the interface between the donor layer and the acceptor layer may recombine with electrons in the acceptor layer. As a result, there is a concern that electrons and holes may not be able to reach each electrode, and that an output voltage suitable for the application cannot be obtained. Furthermore, because this thermoelectric element has a stacked structure, the interface area between the donor layer and the acceptor layer is limited, raising concerns that an output current suitable for the application cannot be obtained. Therefore, improvement of output voltage and output current is desired.
[0006] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a thermoelectric element, a power generation device, and a method for manufacturing a thermoelectric element, in which output voltage and output current are improved.
[0007] The thermoelectric element in the first invention is a thermoelectric element that eliminates the need for a temperature difference between electrodes, and is characterized by 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, which includes a bulk heterojunction structure layer.
[0008] The thermoelectric element in the second invention is characterized in that, in the first invention, the bulk heterojunction structure layer comprises a donor material containing planar molecules and an acceptor material containing spherical molecules.
[0009] The thermoelectric element in the third invention is characterized in that, in the first or second invention, the intermediate layer includes a donor layer provided in contact with the bulk heterojunction structure layer.
[0010] The thermoelectric element in the fourth invention is characterized in that, in the first or second invention, the intermediate layer contains an accelerator that promotes the formation of the bulk heterojunction structure layer.
[0011] The power generation device in the fifth invention is characterized by comprising a thermoelectric element described in the first or second invention, a first wiring connected electrically to the first electrode, and a second wiring connected electrically to the second electrode.
[0012] The method for manufacturing a thermoelectric element according to the sixth 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 including a bulk heterojunction structure layer after the first electrode formation step; and a second electrode formation step of forming a second electrode after the intermediate layer formation step.
[0013] The method for manufacturing a thermoelectric element in the seventh invention is characterized in that, in the sixth invention, the intermediate layer formation step is to form the bulk heterojunction structure layer by co-depositing a donor material and an acceptor material.
[0014] According to the first to fifth inventions, the intermediate layer includes a bulk heterojunction structure layer. Therefore, compared to conventional thermoelectric elements using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material when they move to the first electrode via the donor material can be reduced. This makes it possible to improve the output voltage of the thermoelectric element. In addition, compared to the laminated structure, the interface area between the donor material and the acceptor material can be expanded. This makes it possible to improve the output current of the thermoelectric element.
[0015] In particular, according to the second invention, the bulk heterojunction structure layer includes a donor material containing planar molecules and an acceptor material containing spherical molecules. That is, the donor materials and acceptor materials readily aggregate with each other, making it easier to form a bulk heterojunction structure layer. As a result, the bulk heterojunction structure layer can be formed more reliably, and the probability of recombination with electrons in the acceptor material can be more reliably reduced. This makes it possible to more reliably improve the output current of the thermoelectric element.
[0016] In particular, according to the third invention, the intermediate layer includes a donor layer provided in contact with the bulk heterojunction structure layer. That is, the bulk heterojunction structure layer is provided on the main surface of the donor layer. As a result, the bulk heterojunction structure layer can be formed more reliably, and the probability of recombination with electrons in the acceptor material can be more reliably reduced. This makes it possible to more reliably improve the output voltage of the thermoelectric element.
[0017] In particular, according to the fourth invention, the intermediate layer contains an accelerator that promotes the formation of the bulk heterojunction structure layer. Therefore, compared to the case where the accelerator is not included, a much larger interface area can be formed between the donor material and the acceptor material of the bulk heterojunction structure layer. As a result, the output current of the thermoelectric element can be improved more reliably.
[0018] According to the sixth and seventh inventions, the intermediate layer formation process involves forming an intermediate layer including a bulk heterojunction structure layer. Therefore, compared to conventional thermoelectric elements using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material as they move through the donor material can be reduced. This makes it possible to improve the output voltage of the thermoelectric element. Furthermore, compared to the laminated structure, the interface area between the donor material and the acceptor material can be expanded. This makes it possible to improve the output current of the thermoelectric element.
[0019] In particular, according to the seventh invention, in the intermediate layer formation process, a bulk heterojunction structure layer is formed by co-depositing a donor material and an acceptor material. This makes it possible to more reliably form the bulk heterojunction structure layer and more reliably reduce the probability that the generated holes recombine with electrons in the acceptor material. As a result, it is possible to more reliably improve the output voltage of the thermoelectric element.
[0020] Figures 1(a) and 1(b) are schematic cross-sectional views showing an example of a thermoelectric element and power generation device in this embodiment. Figures 2(a) and 2(b) are schematic diagrams showing an example of the electronic state of the intermediate layer constituting 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 is a graph showing the surface potential change according to the embodiment of the present invention. Figure 5 is a graph showing the result of taking the second derivative of the graph in Figure 4. Figure 6 is a graph showing the surface potential change according to the comparative example of the embodiment. Figure 7 is a graph showing the result of taking the second derivative of the graph in Figure 6.
[0021] 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.
[0022] (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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] The thermoelectric element 1 comprises 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 includes a bulk heterojunction structure layer. Here, the bulk heterojunction structure layer includes a donor material 21 and an acceptor material 22. In this case, compared to a conventional thermoelectric element using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material 22 when they move to the first electrode 11 via the donor material 21 can be reduced. This makes it possible to improve the output voltage of the thermoelectric element 1. Also, compared to the laminated structure, the interface area between the donor material 21 and the acceptor material 22 can be expanded, and the range in which a CT complex (charge transfer complex) is formed is expanded. This makes it possible to improve the output current of 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 output voltage and output current of the thermoelectric element 1 can also be improved.
[0027] Furthermore, the thermoelectric element 1 may include, for example, a substrate 51. The thermoelectric element 1 may also include, for example, a plurality of substrates 51a, 51b.
[0028] Next, the principle of thermoelectric power generation will be explained with reference to Figures 2(a) and 2(b). Figure 2(a) shows the energy levels of the donor material 21 and acceptor material 22 that constitute the first electrode 11, the second electrode 12, and the intermediate layer 20 before the pn junction, while Figure 2(b) shows the energy levels after the pn junction. The value of each energy level increases as you move downwards in the figures.
[0029] The donor material 21 has, for example, HOMO (Highest Occupied Molecular Orbital) 21H and LUMO (Lowest Unoccupied Molecular Orbital) 21L. The acceptor material 22 has HOMO 22H and LUMO 22L that are different from those of the donor material 21. HOMO 21H exhibits a higher energy level than LUMO 22L, for example. If the donor material 21 and acceptor material 22 include multiple materials, then adjacent materials have the aforementioned HOMO 21H, HOMO 22H, and LUMO 21L, LUMO 22L. Furthermore, the first electrode 11 and the second electrode 12 each have energy levels 11e and 12e corresponding to their respective work functions.
[0030] When thermal energy is applied to the thermoelectric element 1, for example, as shown in Figure 2(b), electrons from HOMO21H are transferred to LUMO22L of the adjacent acceptor material 22, generating holes in HOMO21H. As a result, a CT complex is formed at the interface between the donor material 21 and the acceptor material 22.
[0031] Then, for example, holes generated in the HOMO 21H of the donor material 21 move to the first electrode 11 via the donor material 21. Also, electrons that have transitioned to the LUMO 22L of the acceptor material 22 move to the second electrode 12 via the acceptor material 22. This enables power generation.
[0032] The details of each configuration are described below.
[0033] <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.
[0034] 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.
[0035] Each of the electrodes 11 and 12 extends, for example, in the second direction X and the third direction Y, and a plurality of them may be provided. For example, one second electrode 12 may be provided to face a plurality of first electrodes 11 at different positions. Also, for example, one first electrode 11 may be provided to face a plurality of second electrodes 12 at different positions.
[0036] The thicknesses of the first electrode 11 and the second electrode 12 are, for example, 1 nm or more and 1 μm or less. The thicknesses of the first electrode 11 and the second electrode 12 may be, for example, 1 nm or more and 50 nm or less.
[0037] The first electrode 11 and the second electrode 12 may, for example, have different work functions. The work function of the first electrode 11 is, for example, higher than the work function 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 thermoelectrons generated from each of the electrodes 11 and 12. Thereby, the movement of carriers between the electrodes can be further promoted. Thereby, further stabilization of the power generation efficiency can be achieved.
[0038] Note that the "work function" indicates the minimum energy required to extract an electron in a solid into a vacuum, and indicates the difference from the vacuum level to the Fermi level. In the present embodiment, among the electron states shown in FIG. 2, the lower side has a higher work function than the upper side. For example, a material with a low work function tends to have electrons jump out more easily than a material with a high work function. The work function can be measured using, for example, known measurement methods such as the Kelvin method, ultraviolet photoelectron spectroscopy (UPS: Ultraviolet Photoelectron Spectroscopy), X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy), and Auger electron spectroscopy (AES: Auger Electron Spectroscopy).
[0039] Furthermore, in the case of "HOMO" and "LUMO," similar to the work function, they are described as HOMO and LUMO, respectively, where the lower electronic state shown in Figure 2 is higher than the upper state. 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.
[0040] In addition, the "work function," "HOMO," and "LUMO" shown in this explanation can be measured values for each component of the thermoelectric element 1, or known values measured for materials may be used.
[0041] Conductive materials are used for the first electrode 11 and the second electrode 12. For example, the same material may be used for both the first electrode 11 and the second electrode 12. Furthermore, the first electrode 11 and the second electrode 12 may each have different work functions.
[0042] 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.
[0043] 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.
[0044] <Intermediate Layer 20> In the bulk heterojunction structure layer contained in the intermediate layer 20, materials including donor material 21 and acceptor material 22 are mixed three-dimensionally to form phases (regions) in which differences in material type and mixing ratio can be distinguished. Here, as examples of bulk heterojunction structure layers, in addition to structures in which the phase separation is completely separated into a pure donor material 21 phase and a pure acceptor material 22 phase, there are also structures in which the phase separation is not complete, and the degree of phase separation is small or large. Here, the greater the degree of phase separation, the more densely the phase separation is carried out throughout, and the larger the interface area of the pn junction between the donor material 21 and the acceptor material 22. Furthermore, as an example of bulk heterojunction structure layers, there are structures in which a phase with a higher mixing ratio of donor material 21 compared to the surroundings and a phase with a higher mixing ratio of acceptor material 22 compared to the surroundings can be distinguished.
[0045] The intermediate layer 20 is provided such that, for example, as shown in Figures 1(a) to 1(b), at least one of the donor material 21 and the acceptor material 22 is in contact with the first electrode 11, and at least one of the donor material 21 and the acceptor material 22 is in contact with the second electrode 12. The donor material 21 may, for example, be in contact with the first electrode 11 and separated from the second electrode 12. The acceptor material 22 may, for example, be in contact with the second electrode 12 and separated from the first electrode 11. The donor material 21 and the acceptor material 22 are provided, for example, in contact with each other. The donor material 21 and the acceptor material 22 each include at least one type.
[0046] The intermediate layer 20 may include, for example, a donor layer (not shown) provided in contact with the bulk heterojunction structure layer. That is, the bulk heterojunction structure layer is provided on the main surface of the donor layer. This donor layer serves as a base for co-depositing the donor material 21 and acceptor material 22 contained in the bulk heterojunction structure layer. In this case, the bulk heterojunction structure layer can be formed more reliably, and the probability of holes in the donor material 21 recombining with electrons in the acceptor material 22 can be reduced more reliably. As a result, the output voltage of the thermoelectric element 1 can be improved more reliably. The donor layer is used as a template for depositing the donor material 21 and acceptor material 22, for example, BP2T (5,5'-di(biphenyl-4-yl)-2,2'-bithiophene) or CuI (p-type inorganic semiconductor copper iodide), etc.
[0047] The intermediate layer 20 may include, for example, an electron transport layer containing an electron transport material and a hole transport layer containing a hole transport material, at least one of the above. In this case, the electron transport layer may be joined to the second electrode 12, or the hole transport layer may be joined to the first electrode 11.
[0048] The intermediate layer 20 extends in the second direction X and the third direction Y, similar to each electrode 11 and 12. The shape of the intermediate layer 20 is similar to that of each electrode 11 and 12.
[0049] The thickness of the intermediate layer 20 is, for example, 1 nm to 1 μm. The thickness of the intermediate layer 20 may also be, for example, 1 nm to 50 nm.
[0050] The intermediate layer 20 is made of 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 cause variations in the gap between the opposing surfaces of each electrode 11 and 12, potentially leading to a decrease in power generation efficiency. In contrast, by providing a solid intermediate layer 20 within the gap, variations in the gap between the opposing surfaces of each electrode 11 and 12 can be suppressed. This makes it possible to further stabilize power generation efficiency.
[0051] As the donor material 21, a material suitable for moving holes to the first electrode 11 is used. The donor material 21 may be, for example, a p-type semiconductor or a semiconductor containing a doping material. In addition, the donor material 21 may contain, for example, a hole transport material.
[0052] As donor material 21, materials such as copper phthalocyanine (CuPc), regioregular poly(3-hexylthiophene) (RR-P3HT), pentacene, and polythiophene (PT) can be used.
[0053] As the acceptor material 22, a material suitable for transferring electrons to the second electrode 12 is used. The acceptor material 22 may be, for example, an n-type semiconductor or a semiconductor containing a doping material. In addition, the acceptor material 22 may contain, for example, an electron transport material.
[0054] As the acceptor material 22, for example, C ６０ , copper phthalocyanine fluoride (F １６ CuPc), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), phenyl C ６１ Materials such as methyl butyrate (PCBM: [6,6]-Phenyl-C61-Butyric Acid Methyl Ester) and 3,4,9,10-perylenetetracarboxylate bizbenzimidazole (PTCBI) are used.
[0055] For example, the LUMO22L of the acceptor material 22 lies between the HOMO21H and LUMO21L of the donor material 21, and the HOMO22H of the acceptor material 22 is higher than the HOMO21H of the donor material 21. In this case, the formation of the CT complex by thermal excitation of electrons can be promoted at the interface between the donor material 21 and the acceptor material 22.
[0056] For example, the work function of the first electrode 11 is between the HOMO 21H and LUMO 21L of the donor material 21, and the work function of the second electrode 12 is lower than the LUMO 22L of the acceptor material 22. In this case, the energy barriers between each component that hinder carrier movement 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 power generation efficiency.
[0057] The donor material 21 is, for example, the CuPc, F mentioned above. １６ The acceptor material 22 may also contain planar molecules such as CuPc, RR-P3HT, pentacene, and polythiophene. ６０ It may also contain spherical molecules such as PCBM. That is, the donor materials 21 and acceptor materials 22 tend to aggregate easily, and a bulk heterojunction structure layer is easily formed. In this case, the bulk heterojunction structure layer can be formed more reliably, and the probability of holes in the donor material 21 recombining with electrons in the acceptor material 22 can be reduced more reliably. As a result, the output current of the thermoelectric element 1 can be improved more reliably.
[0058] <Substrate 51> The substrate 51 is in contact with the first electrode 11, for example, and is separated from the second electrode 12 and the intermediate layer 20. 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.
[0059] 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 second electrode 12, etc., can be fixed to it.
[0060] 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.
[0061] 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 the first electrode 11 and the second electrode 12 becomes unnecessary.
[0062] 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.
[0063] (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.
[0064] 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.
[0065] <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.
[0066] <Intermediate Layer Formation Process S120> In the intermediate layer formation process S120, for example, after the first electrode formation process S110, an intermediate layer 20 including a bulk heterojunction structure layer is formed. In this case, compared to a conventional thermoelectric element using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material 22 when moving through the donor material 21 can be reduced. This makes it possible to improve the output voltage of the thermoelectric element 1. Also, compared to the laminated structure, the interface area between the donor material 21 and the acceptor material 22 can be expanded. This makes it possible to improve the output current of the thermoelectric element 1.
[0067] In the intermediate layer formation step S120, for example, an intermediate layer 20 is formed on the main surface of the first electrode 11. The bulk heterojunction structure layer is formed, for example, under reduced pressure conditions by vacuum deposition, spin coating, inkjet, slit coating, spray, gravure printing, or letterpress printing.
[0068] In the intermediate layer formation step S120, for example, a bulk heterojunction structure layer may be formed by co-depositing a donor material 21 and an acceptor material 22. In this case, the bulk heterojunction structure layer can be formed more reliably, and the probability of the generated holes recombining with electrons in the acceptor material 22 can be reduced more reliably. This makes it possible to more reliably improve the output voltage of the thermoelectric element 1. In this case, in the intermediate layer formation step S120, for example, a bulk heterojunction structure layer may be formed by co-depositing a donor material 21 and an acceptor material 22 on the main surface of the donor layer described above.
[0069] <Second electrode formation step S130> In the second electrode formation step S130, for example, the second electrode 12 is formed after the intermediate layer formation step S120.
[0070] In the second electrode formation step S130, for example, the second electrode 12 is formed on the main surface of the intermediate layer 20 that is opposite to the main surface facing the first electrode 11. The second electrode 12 is formed, for example, by sputtering or vacuum deposition under reduced pressure.
[0071] 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), the power generation device 100 in this embodiment is formed.
[0072] (Modified Thermoelectric Element 1 and Method for Manufacturing Thermoelectric Element 1) Next, modified versions of the thermoelectric element 1 and the method for manufacturing the thermoelectric element 1 will be described. The difference between the above-described embodiment and the modified version is that the bulk heterojunction structure includes materials different from the donor material 21 and the acceptor material 22. Details similar to those described above will be omitted from the explanation.
[0073] The bulk heterojunction structure layer may contain, for example, an accelerator to promote phase separation between the donor material 21 and the acceptor material 22. In this case, compared to the case without the accelerator, the degree of phase separation can be improved by promoting phase separation between the donor material 21 and the acceptor material 22, and a very large interface area can be formed between the donor material 21 and the acceptor material 22 in the bulk heterojunction structure layer. This makes it possible to more reliably improve the output current of the thermoelectric element 1.
[0074] Furthermore, by including an accelerator having, for example, electron transport properties and / or hole transport properties in the bulk heterojunction structure layer, electron transport paths or hole transport paths can be formed more reliably. This makes it possible to further improve the output current of the thermoelectric element 1.
[0075] The bulk heterojunction structure layer may contain, for example, an electron-transporting material or a hole-transporting material other than the accelerator. In this case, electron or hole transport can be ensured, and if sufficient electrons and holes are generated, the output current of the thermoelectric element 1 can be further improved.
[0076] <Accelerators> Accelerators are additives that promote the formation of bulk heterojunction structural layers. Examples of accelerators include surfactants (e.g., nonionic surfactants), alkylsilanes, thiols, HMDS (hexamethyldisilazane), monolayers formed by self-assembly or self-assembly (SAM materials), saturated fatty acids, 1,8-octanedithiol (1,8-octanedithiol), 1,8-dibromooctane (1,8-dibromooctane), 1,8-diiodooctane (1,8-diiodooctane (DIO)), 1-chloronaphthalene (1-chloronaphthalene), N-methylpyrrolidone (NMP)), 1,8-octanedithiol (1,8-octanedithiol (OT)), etc.
[0077] According to this embodiment, the intermediate layer 20 includes a bulk heterojunction structure layer. Therefore, compared to conventional thermoelectric elements using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material 22 when they move to the first electrode 11 via the donor material 21 can be reduced. This makes it possible to improve the output voltage of the thermoelectric element 1. In addition, compared to the laminated structure, the interface area between the donor material 21 and the acceptor material 22 can be expanded. This makes it possible to improve the output current of the thermoelectric element 1.
[0078] Furthermore, according to this embodiment, the bulk heterojunction structure layer includes a donor material 21 containing planar molecules and an acceptor material 22 containing spherical molecules. That is, the donor materials 21 and the acceptor materials 22 readily aggregate with each other, making it easier to form a bulk heterojunction structure layer. As a result, the bulk heterojunction structure layer can be formed more reliably, and the probability of recombination with electrons in the acceptor material 22 can be more reliably reduced. This makes it possible to more reliably improve the output current of the thermoelectric element 1.
[0079] Furthermore, according to this embodiment, the intermediate layer 20 includes a donor layer provided in contact with the bulk heterojunction structure layer. That is, the bulk heterojunction structure layer is provided on the main surface of the donor layer. As a result, the bulk heterojunction structure layer can be formed more reliably, and the probability of recombination with electrons in the acceptor material 22 can be more reliably reduced. This makes it possible to more reliably improve the output voltage of the thermoelectric element 1.
[0080] Furthermore, according to this embodiment, the intermediate layer 20 contains an accelerator that promotes the formation of the bulk heterojunction structure layer. Therefore, compared to the case where the accelerator is not included, a much larger interface area can be formed between the donor material 21 and the acceptor material 22 of the bulk heterojunction structure layer. As a result, the output current of the thermoelectric element 1 can be improved more reliably.
[0081] Furthermore, according to this embodiment, in the intermediate layer formation step S120, an intermediate layer 20 including a bulk heterojunction structure layer is formed. Therefore, compared to a conventional thermoelectric element using a laminated structure of a donor layer and an acceptor layer, the probability of holes recombining with electrons in the acceptor material 22 when they move to the first electrode 11 via the donor material 21 can be reduced. As a result, the output voltage of the thermoelectric element 1 can be improved. In addition, compared to the laminated structure, the interface area between the donor material 21 and the acceptor material 22 can be expanded. As a result, the output current of the thermoelectric element 1 can be improved.
[0082] Furthermore, according to this embodiment, in the intermediate layer formation step S120, a bulk heterojunction structure layer is formed by co-depositing the donor material 21 and the acceptor material 22. Therefore, the bulk heterojunction structure layer can be formed more reliably, and the probability of the generated holes recombining with electrons in the acceptor material 22 can be more reliably reduced. As a result, the output voltage of the thermoelectric element 1 can be improved more reliably.
[0083] Next, an example related to the thermoelectric element 1 in the above-described embodiment will be explained. In this embodiment, the carrier generation status was confirmed based on the change in the surface potential Vsp by measuring the surface potential Vsp of the intermediate layer 20 during the intermediate layer formation process S120.
[0084] The surface potential Vsp changes in either a negative or positive direction depending on the difference between the work function of ITO of the first electrode 11 and the Fermi level of the object being measured. A negative change in the surface potential Vsp means that electrons are being injected and diffused from the first electrode 11 to the object being measured in order to match the Fermi level. A positive change in the surface potential Vsp means that holes are being injected and diffused from the first electrode 11 to the object being measured. In other words, in the region where the surface potential Vsp is changing, it can be interpreted that carriers (holes and electrons) are being injected and diffused. Furthermore, the second derivative of the surface potential Vsp (d) can be used as the amount of change in the surface potential Vsp. ２ V / dX ２ By calculating this, the regions where carriers are being injected and diffused can be further clarified, and the carrier generation status can be easily confirmed.
[0085] In this embodiment, the rotating Kelvin probe method was used to measure the surface potential Vsp in order to confirm the carrier generation mechanism at the interface between the donor material 21 and the acceptor material 22. The Kelvin method is a technique that precisely measures the surface potential Vsp by placing a probe close to a sample such as a metal or semiconductor with an insulator (vacuum in this embodiment) in between, and applying an appropriate vibration frequency to the probe, thereby measuring the displacement of the capacitor capacitance generated between the probe and the sample. However, this apparatus has a rotating mechanism that can replace the vibration of the probe with the displacement of the overlapping portion between the probe and the sample. When the potential across the capacitor formed by the overlapping portion between the sample with a surface potential Vsp and the probe differs from that formed by the vacuum, electron transfer occurs in the probe. Therefore, the rotating Kelvin probe method makes it possible to continuously measure the film thickness dependence of the surface potential Vsp while depositing a film.
[0086] In this embodiment, the measurement conditions involved using ITO as the first electrode 11 and forming an intermediate layer 20 on the surface of the ITO. The intermediate layer 20 consisted of a donor material 21, which is CuPc, and an acceptor material 22, which is F １６ CuPc was used. Furthermore, as an example of the present invention, a structure including a bulk heterojunction layer was formed, and as a comparative example, a structure without a bulk heterojunction layer was formed.
[0087] In the example of the present invention, CuPc as the donor material 21 and F as the acceptor material 22 １６ CuPc, and CuPc and F １６ A bulk heterojunction structure layer in which CuPc was co-evaporated was formed to form the intermediate layer 20. As a manufacturing method of the example of the present invention, a 100-nm-thick ITO substrate was set on the sample holder of a rotating Kelvin probe measurement device, and after starting the measurement of the surface potential Vsp, 50-nm-thick CuPc, 50-nm-thick bulk heterojunction structure layer, and 100-nm-thick F １６ CuPc were sequentially formed by vacuum evaporation. Regarding the bulk heterojunction structure layer, it was formed so that the molar ratio of CuPc and F １６ CuPc was 1:1.
[0088] In the comparative example, CuPc as the donor material 21 and F as the acceptor material 22 １６ Consisted of CuPc and did not include a bulk heterojunction structure layer in which CuPc and F １６ CuPc were co-evaporated. As a manufacturing method of the comparative example, a 100-nm-thick ITO substrate was set on a rotating Kelvin probe, and after starting the measurement of the surface potential Vsp, 100-nm-thick CuPc and 100-nm-thick F １６ CuPc were sequentially formed by vacuum evaporation.
[0089] Regarding the results of the example of the present invention, the measurement results of the surface potential Vsp are shown in FIG. 4, and the calculation results of the second derivative of the surface potential Vsp are shown in FIG. 5. Here, the horizontal axis "Thickness [nm]" indicates the thickness of the intermediate layer 20, and the vertical axis indicates the surface potential Vsp corresponding to the thickness of the intermediate layer 20. That is, it shows the increase and decrease of the surface potential Vsp when each material of the intermediate layer 20 is deposited on the first electrode 11 and the thickness continues to increase. Specifically, the position of 0 nm in thickness corresponds to the surface of the first electrode 11, and in the region of 50 nm or less in thickness indicated by the dotted line "CuPc Vsp", the increase and decrease of the surface potential Vsp of the donor material 21 are shown. Also, in the region of more than 50 nm and 100 nm or less in thickness indicated by the broken line "Co-deposition Vsp", the increase and decrease of the surface potential Vsp of the bulk heterojunction structure layer are shown. Also, the solid line "F １６In the region with a thickness exceeding 100 nm, indicated by "CuPc Vsp", the surface potential Vsp of the acceptor material 22 is shown to increase or decrease.
[0090] According to the results of the present invention example, as shown in Figure 4, for example, the F of the acceptor material 22 １６ In the CuPc layer, the surface potential Vsp is significantly shifted in the negative direction. This means that a CT (charge transfer) state is formed at the interface between the acceptor material 22 and the bulk heterojunction structure layer, and electrons generated at the CT interface are being injected and diffused into the acceptor material 22. Here, in the region with a thickness of more than 100 nm and less than or equal to 117 nm, i.e., within 17 nm from the interface of the acceptor material 22, the change in surface potential Vsp is clearly evident, and this is thought to be a region where electrons separated from the CT state are injected (injection region). On the other hand, in the region with a thickness of more than 117 nm, i.e., more than 17 nm from the interface of the acceptor material 22, the change in surface potential Vsp is linear, and this is thought to be a diffusion region where electron diffusion occurs. The injection region can be said to be between 100 nm and 117 nm in thickness, for example, as the second derivative of the surface potential Vsp shown in Figure 5 is zero at a thickness of more than 117 nm.
[0091] Next, regarding the results of the comparative example, the measurement results of the surface potential Vsp are shown in Figure 6, and the calculation results of the second derivative of the surface potential Vsp are shown in Figure 7. Note that the position with a thickness of 0 nm corresponds to the surface of the first electrode 11, and the region with a thickness of 100 nm or less, indicated by the dotted line "CuPc Vsp", shows the increase or decrease in the surface potential Vsp of the donor material 21. Also, the solid line "F １６ In the region with a thickness exceeding 100 nm, indicated by "CuPc Vsp", the surface potential Vsp of the acceptor material 22 is shown to increase or decrease.
[0092] According to the results of the comparative example, for example as shown in Figure 6, the F of the acceptor material 22 １６This is similar to the present invention example in that the surface potential Vsp in the CuPc layer is significantly shifted in the negative direction. Here, in the region with a thickness of more than 100 nm and less than or equal to 110 nm, i.e., within 10 nm from the interface of the acceptor material 22, the change in surface potential Vsp is clearly evident, and this is thought to be an injection region where electrons are injected. On the other hand, in the region with a thickness of more than 110 nm, i.e., more than 10 nm from the interface of the acceptor material 22, the change in surface potential Vsp is linear, and this is thought to be a diffusion region where electrons are diffused. The injection region can be said to be between 100 nm and 110 nm in thickness, for example, as the second derivative of the surface potential Vsp shown in Figure 7 is zero at a thickness of more than 110 nm.
[0093] From the above results, the carrier injection region of the present invention example is larger than that of the comparative example. Therefore, it is suggested that, according to the present invention example, the number of carriers generated at the CT interface of the thermoelectric element 1 having a bulk heterojunction structure layer can be improved, and the output current can be improved.
[0094] 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.
[0095] 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 21: Donor material 22: Acceptor material 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, including a bulk heterojunction structure layer.
2. The thermoelectric element according to claim 1, characterized in that the bulk heterojunction structure layer comprises a donor material containing planar molecules and an acceptor material containing spherical molecules.
3. The thermoelectric element according to claim 1 or 2, characterized in that the intermediate layer includes a donor layer provided in contact with the bulk heterojunction structure layer.
4. The thermoelectric element according to claim 1 or 2, characterized in that the intermediate layer contains an accelerator that promotes the formation of the bulk heterojunction structure layer.
5. 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.
6. 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 including a bulk heterojunction structure layer after the first electrode formation step; and a second electrode formation step of forming a second electrode after the intermediate layer formation step.
7. The method for manufacturing a thermoelectric element according to claim 6, characterized in that the intermediate layer formation step involves co-depositing a donor material and an acceptor material to form the bulk heterojunction structure layer.