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

Abstract

A thermoelectric element with improved output voltage, a power generating device, and a method for manufacturing a thermoelectric element are provided. [Solution] The thermoelectric element 1 does not require a temperature difference between the electrodes and comprises a first electrode 11, a second electrode 12 spaced apart from the first electrode 11, and an intermediate layer 20 provided between the first electrode 11 and the second electrode 12. The intermediate layer 20 is characterized by including a plurality of semiconductor units 21, 22 each consisting of a donor layer d and an acceptor layer a, and a recombination layer 23 which is conductive and is provided in contact between the plurality of semiconductor units 21, 22, and which combines electrons generated from one semiconductor unit 21 with holes generated from the other semiconductor unit 22.

Description

[Technical field]

[0001] The present invention relates to a thermoelectric element that does not require a temperature difference between electrodes, a power generating device, and a method for manufacturing a thermoelectric element. [Background technology]

[0002] In recent years, there has been active development of thermoelectric elements that generate electric energy by utilizing 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 variety of applications, compared to configurations that generate electric energy by utilizing a temperature difference applied to electrodes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6944168 Summary of the Invention [Problem to be solved by the invention]

[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 that exhibits orientation polarization, which makes it possible to stabilize the power generation efficiency of a thermoelectric element that does not require a temperature difference.

[0005] Here, in the thermoelectric element disclosed in Patent Document 1, the voltage of thermoelectric generation is estimated from the difference in work function between the positive and negative electrodes. However, during thermoelectric generation, the voltage may decrease due to the influence of the band gap of a CT (Charge Transfer) complex formed by the pn junction between the donor layer and the acceptor layer, the movement of carriers (electrons and holes), and the like. For this reason, the voltage actually obtained may be lower than the value estimated from the work function difference, and there is a concern that an output voltage suitable for the application may not be obtained. Therefore, there is a demand for an improvement in the output voltage.

[0006] The present invention has been devised in consideration of the above-mentioned problems, and its object is to provide a thermoelectric element, a power generation device, and a method for manufacturing a thermoelectric element that have improved output voltage. [Means for solving the problem]

[0007] A thermoelectric element in a first aspect of the present invention is a thermoelectric element that does not require a temperature difference between electrodes, and includes 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, the first electrode, the intermediate layer, and the second electrode are stacked in this order in a stacking direction; The intermediate layer is The layers are stacked in the stacking direction in contact with each other. A plurality of semiconductor units each having a donor layer and an acceptor layer as a pair; Among them, an acceptor layer of one of the semiconductor units and a donor layer of the other of the semiconductor units a recombination layer that is provided in contact with the semiconductor unit and combines electrons generated from one of the semiconductor units with holes generated from the other semiconductor unit. The semiconductor unit, the recombination layer, and the other semiconductor unit are stacked in this order in the stacking direction. It is characterized by:

[0008] The thermoelectric element according to a second aspect of the present invention is the thermoelectric element according to the first aspect of the present invention, characterized in that the semiconductor units have different temperature characteristics from each other.

[0009] A thermoelectric element according to a third aspect of the present invention is the thermoelectric element according to the first or second aspect of the present invention, characterized in that the recombination layer contains the same material as at least one of the first electrode and the second electrode.

[0010] A thermoelectric element according to a fourth aspect of the present invention is the thermoelectric element according to the first or second aspect of the present invention, characterized in that the recombination layer contains a material different from that of the first electrode and the second electrode.

[0011] A thermoelectric element according to a fifth aspect of the present invention is the thermoelectric element according to the fourth aspect of the present invention, characterized in that the recombination layer contains a material having a lower durability than the first electrode and the second electrode.

[0012] The power generation device in the sixth invention is characterized by comprising a thermoelectric element described in the first or second invention, a first wiring electrically connected to the first electrode, and a second wiring electrically connected to the second electrode.

[0013] A method for manufacturing a thermoelectric element according to a seventh aspect of the present invention is a method for manufacturing a thermoelectric element that does not require a temperature difference between electrodes, and includes a first electrode forming step of forming a first electrode, and forming a first electrode on a main surface of the first electrode. The plates are stacked in the stacking direction in contact with each other. The present invention has an intermediate layer forming step of forming an intermediate layer including a plurality of semiconductor units each having a donor layer and an acceptor layer as a pair, and a recombination layer having electrical conductivity and provided in contact with the plurality of semiconductor units, for combining electrons generated from one of the semiconductor units with holes generated from the other of the semiconductor units, and a second electrode forming step of forming a second electrode on a main surface of the intermediate layer opposite to a main surface facing the first electrode, the intermediate layer forming step being performed by forming one of the plurality of semiconductor units on the main surface of the first electrode. The donor layer and the acceptor layer are laminated in this order in the lamination direction. and forming the one of the semiconductor units. The acceptor layer The recombination layer is formed on a main surface opposite to a main surface facing the first electrode, and the other semiconductor unit is formed on a main surface opposite to a main surface facing the first electrode, of the main surfaces of the recombination layer. The donor layer and the acceptor layer are laminated in this order in the lamination direction. The present invention is characterized in that a Effect of the Invention

[0014] According to the first to sixth inventions, the thermoelectric element includes an intermediate layer including a plurality of semiconductor units, each of which has a donor layer and an acceptor layer as a pair, and a recombination layer provided between the plurality of semiconductor units. As a result, some of the carriers generated in each semiconductor unit can be recombined through the recombination layer, and a state in which the semiconductor units are connected in series can be realized. This can improve the output voltage of the thermoelectric element.

[0015] In particular, according to the second aspect of the present invention, the plurality of semiconductor units have different temperature characteristics. Therefore, for a semiconductor unit whose output voltage drops in a certain temperature range among the overlapping usable temperature ranges of the plurality of semiconductor units, the dropped output voltage can be complemented by combining the semiconductor unit whose output voltage is maintained in the corresponding temperature range. This makes it possible to suppress the drop in the output voltage of the thermoelectric element.

[0016] In particular, according to the third aspect of the present invention, the recombination layer contains the same material as at least one of the first electrode and the second electrode. Therefore, the electrode material can be used for the recombination layer, and the number of types of materials can be reduced. This simplifies the management of materials for the thermoelectric element.

[0017] In particular, according to the fourth aspect of the present invention, the recombination layer contains a material different from that of the first electrode and the second electrode. Therefore, a material with low durability can be applied to the intermediate layer, which has a smaller exposed area than the electrode material. This improves the selectivity of materials for the thermoelectric element.

[0018] In particular, according to the fifth aspect of the present invention, the recombination layer includes a material that is less durable than the first and second electrodes. Therefore, the recombination layer has a portion of its main surface protected by each electrode, and even if a material with low durability is used, the power generation output is less affected by deterioration of the main surface. This makes it possible to improve the material selectivity of the thermoelectric element and suppress a decrease in the power generation output.

[0019] According to the seventh aspect of the present invention, the method for manufacturing a thermoelectric element includes an intermediate layer forming step of forming a semiconductor unit, which is a set of a donor layer and an acceptor layer, on a main surface of a first electrode, forming a recombination layer on the main surface of the one semiconductor unit, and forming another semiconductor unit on the main surface of the recombination layer. As a result, some of the carriers generated in each semiconductor unit can be recombined through the recombination layer, and a state in which the semiconductor units are connected in series can be realized. This can improve the output voltage of the thermoelectric element. [Brief description of the drawings]

[0020] [Figure 1] 1(a) and 1(b) are schematic cross-sectional views showing an example of a thermoelectric element and a power generating device according to the present embodiment. [Diagram 2] 2(a) and 2(b) are schematic diagrams showing an example of the electronic state of an intermediate layer constituting the thermoelectric element of this embodiment. [Diagram 3] FIG. 3(a) is a schematic cross-sectional view showing an example of the electronic state of each component of a thermoelectric element, and FIG. 3(b) is a schematic cross-sectional view showing a comparative example of the electronic state of each component of a thermoelectric element. [Figure 4] FIG. 4 is a flowchart showing an example of a method for manufacturing a thermoelectric element in this embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a modified example of the thermoelectric element and the power generating device in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an example of a thermoelectric element 1, a power generating device 100, and a manufacturing method of a thermoelectric element 1 as an embodiment of the present invention will be described with reference to the drawings. In each figure, the height direction in which the electrodes are stacked is defined as a first direction Z, one planar direction that intersects with the first direction Z, for example, perpendicular to it, is defined as a second direction X, and another planar direction that intersects with each of the first direction Z and the second direction X, for example, perpendicular to it, is defined as a third direction Y. Also, the configurations in each figure are depicted diagrammatically for the purpose of explanation, and for example, the size of each configuration and the size comparison between the configurations may differ from those in the figures.

[0022] (Thermoelectric element 1, power generation device 100) FIG. 1 is a schematic cross-sectional view showing an example of a thermoelectric element 1 and a power generating device 100 according to the present embodiment.

[0023] As shown in FIG. 1(a), the power generating device 100 includes 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 generating device 100 including such a thermoelectric element 1 is mounted or installed on, for example, a heat source (not shown), and outputs electrical energy generated from the thermoelectric element 1 based on thermal energy of the heat source 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, by using the power generating device 100 as a main power source or an auxiliary power source.

[0024] Examples of heat sources for the thermoelectric element 1 include electronic devices or electronic components such as a CPU (Central Processing Unit), light-emitting elements such as LEDs (Light Emitting Diodes), engines of automobiles, production equipment in factories, the human body, sunlight, and environmental temperature. For example, electronic devices, electronic components, light-emitting elements, engines, and production equipment are artificial heat sources. The human body, sunlight, and environmental temperature are natural heat sources. A power generation device 100 including a thermoelectric element 1 can be installed inside, for example, an Internet of Things (IoT) device, a mobile device such as a wearable device, or an independent sensor terminal, and can be used as a replacement or supplement for a battery. 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, thermal energy generated by the artificial heat source or thermal energy possessed by the natural heat source into electrical energy to generate an electric current. The thermoelectric element 1 can be provided not only in the power generation device 100, but also in the mobile device, the independent sensor terminal, or the like. In this case, the thermoelectric element 1 itself can be an alternative or auxiliary part to a battery in the mobile device, the independent sensor terminal, or the like.

[0026] As shown in, for example, FIGS. 1(a) and 1(b), the thermoelectric element 1 includes a first electrode 11, a second electrode 12, and an intermediate layer 20. The first electrode 11 is provided apart from the second electrode 12. The intermediate layer 20 is provided between the first electrode 11 and the second electrode 12, and includes a plurality of semiconductor units (e.g., a first semiconductor unit 21 and a second semiconductor unit 22) each including a donor layer d and an acceptor layer a, and a recombination layer 23. The first semiconductor unit 21 includes a first donor layer 211 and a first acceptor layer 212 as a pair. The second semiconductor unit 22 includes a second donor layer 221 and a second acceptor layer 222 as a pair. Moreover, the recombination layer 23 has electrical conductivity and is provided between a plurality of semiconductor units (for example, between the first semiconductor unit 21 and the second semiconductor unit 22), and combines electrons generated from one semiconductor unit (for example, the first semiconductor unit 21 or the second semiconductor unit 22) with holes generated from another semiconductor unit (for example, the second semiconductor unit 22 or the first semiconductor unit 21). In this case, some of the carriers generated in each semiconductor unit can be recombined through the recombination layer 23, and a state in which the semiconductor units are connected in series can be realized. This makes it possible to improve the output voltage of the thermoelectric element 1. Similarly, the power generation device 100 including such a thermoelectric element 1, the first wiring 101, and the second wiring 102 can also improve the output voltage of the thermoelectric element 1.

[0027] Here, the first donor layer 211 and the second donor layer 221 indicate layers including an n-type semiconductor in which electrons act as majority carriers, and include at least one of an n-type impurity semiconductor including donor impurities and an intrinsic semiconductor. The first acceptor layer 212 and the second acceptor layer 222 indicate layers including a p-type semiconductor in which holes act as majority carriers, and include at least one of a p-type impurity semiconductor including acceptor impurities and an intrinsic semiconductor. In the following description, the donor layer d refers to the first donor layer 211 and the second donor layer 221, and the acceptor layer a refers to the first acceptor layer 212 and the second acceptor layer 222. The thermoelectric element 1 may also 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 described with reference to Figures 2(a)-2(b) and 3(a)-3(b). Figure 2(a) shows the energy levels of the first electrode 11, the second electrode 12, the donor layer d, and the acceptor layer a before lamination, and Figure 2(b) shows the energy levels after lamination. The value of each energy level increases toward the bottom in the figure.

[0029] The donor layer d has, for example, a HOMO (highest occupied molecular orbital) dH and a LUMO (lowest unoccupied molecular orbital) dL. The acceptor layer a has a HOMOaH and a LUMOaL different from those of the donor layer d. For example, the HOMOdH has a higher energy level than the HOMOaL. Note that, for example, when the donor layer d and the acceptor layer a include a plurality of layers, the adjacent layers have the above-mentioned HOMOdH, HOMOaH, and LUMOdL, LUMOaL. In addition, the first electrode 11 and the second electrode 12 have energy levels 11e and 12e corresponding to the work functions of the respective electrodes.

[0030] When thermal energy is applied to the thermoelectric element 1, for example, as shown in Fig. 2(b), an electron in the HOMOdH transitions to the LUMOaL of the adjacent acceptor layer a, generating a hole in the HOMOdH, which forms a CT complex at the interface between the donor layer d and the acceptor layer a.

[0031] Then, as shown in FIG. 3(a), for example, holes generated in the HOMOdH of the first donor layer 211 move to the first electrode 11 via the first donor layer 211 (action A in the figure). Also, electrons that have transitioned to the LUMOaL of the first acceptor layer 212 move to the recombination layer 23 via the first acceptor layer 212 (action A' in the figure). Similarly, holes generated in the HOMOdH of the second donor layer 221 move to the recombination layer 23 via the second donor layer 221 (action B in the figure). Also, electrons that have transitioned to the LUMOaL of the second acceptor layer 222 move to the second electrode 12 via the second acceptor layer 222 (action B' in the figure). At this time, the electrons that have moved by action A' and the holes that have moved by action B recombine in the recombination layer 23 (action C in the figure). This allows the thermoelectric element 1 to generate electricity.

[0032] For example, as shown in FIG. 3(b), when the recombination layer 23 is not provided between the first semiconductor unit 21 and the second semiconductor unit 22, that is, when the first acceptor layer 212 constituting the first semiconductor unit 21 and the second donor layer 221 constituting the second semiconductor unit 22 are provided adjacent to each other, electrons and holes are generated between the first acceptor layer 212 and the second donor layer 221. In this case, the electrons that have transitioned to the LUMOaL of the first acceptor layer 212 and the holes that have been generated in the HOMOdH of the second donor layer 221 cannot move toward the electrodes 11 and 12 (action D in the figure). As a result, this becomes a factor that inhibits the movement of other carriers (for example, electrons that have moved due to action A' and holes that have moved due to action B), and as a result, there is a concern that the power generation output cannot be improved. For this reason, the thermoelectric element 1 can improve the power generation output by providing the recombination layer 23 in contact between the multiple semiconductor units.

[0033] Each component will be described in detail below.

[0034] <First electrode 11, second electrode 12> The first electrode 11 and the second electrode 12 are provided, for example, spaced apart from each other along the first direction Z. The first electrode 11 is provided in contact with the substrate 51, for example.

[0035] The first electrode 11 and the second electrode 12 may be provided, for example, in contact with the same substrate 51. In this case, the first electrode 11 and the second electrode 12 are provided apart from each other along the second direction X or the third direction Y.

[0036] Each of the electrodes 11, 12 may be provided in a plurality of numbers, for example extending in the second direction X and the third direction Y. For example, one second electrode 12 may be provided facing the plurality of first electrodes 11 at different positions. Also, for example, one first electrode 11 may be provided facing the plurality of second electrodes 12 at different positions.

[0037] The thickness of the first electrode 11 and the second electrode 12 is, for example, not less than 1 nm and not more than 1 μm. The thickness of the first electrode 11 and the second electrode 12 may be, for example, not less than 1 nm and not more than 50 nm.

[0038] The first electrode 11 and the second electrode 12 may have different work functions, for example, the work function of the first electrode 11 being 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. This can further promote the movement of carriers between the electrodes. This can further stabilize the power generation efficiency.

[0039] The term "work function" refers to the minimum energy required to extract electrons from a solid into a vacuum, and indicates the difference between the vacuum level and the Fermi level. In this embodiment, the work function is described as being higher on the lower side than on the upper side of the electronic state shown in FIG. 2. For example, a material with a low work function tends to have electrons eject more easily than a material with a high work function. The work function can be measured using known measurement methods such as the Kelvin method, ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES).

[0040] Similarly to the work function, the "HOMO" and "LUMO" are described as HOMO and LUMO in which the lower side is higher than the upper side among the electronic states shown in FIG. 2. The HOMO and LUMO can be measured using a known measurement method. For example, the HOMO can be measured using the above-mentioned spectroscopy as well as a known measurement method such as photoemission yield spectroscopy (PYS). The LUMO can be calculated using measurement using inverse photoelectron spectroscopy (IPES) or an absorption spectrum.

[0041] In addition, for the "work function," "HOMO," and "LUMO" in this description, actual measured values ​​for each component of the thermoelectric element 1 are used, or known values ​​measured for the material, for example, may be used.

[0042] A conductive material is used as the material of the first electrode 11 and the second electrode 12. For example, the same material may be used as the material of the first electrode 11 and the second electrode 12. Furthermore, the first electrode 11 and the second electrode 12 may have different work functions.

[0043] The electrodes 11 and 12 may be made of a metal material consisting of a single element such as iron, aluminum, copper, gold, hafnium, or yttrium, or may be made of an alloy 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). The electrodes 11 and 12 may be made of a non-metallic conductive material such as silicon (Si: for example, p-type Si or n-type Si) and carbon-based materials such as graphene.

[0044] In particular, known conductive materials that do not have optical transparency can be used as the material of each of the electrodes 11 and 12. This makes it possible to prevent power generation caused by light transmitted through each of the electrodes 11 and 12. This makes it possible to suppress variations in power generation caused by factors other than heat. Note that the above-mentioned "light" refers to light in a wavelength range used in solar power generation, for example, light in a wavelength range of about 200 nm to 800 nm.

[0045] <Middle class 20> In the intermediate layer 20, as shown in, for example, FIGS. 1(a) to 1(b), the first semiconductor unit 21 is provided in contact with the first electrode 11, and the second semiconductor unit 22 is provided in contact with the second electrode 12. More specifically, the first donor layer 211 of the first semiconductor unit 21 is provided in contact with the first electrode 11, and the second acceptor layer 222 of the second semiconductor unit 22 is provided in contact with the second electrode 12. In addition, a recombination layer 23 is provided between the first semiconductor unit 21 and the second semiconductor unit 22. That is, the above-mentioned components are provided by stacking, for example, the first electrode 11, the first donor layer 211, the first acceptor layer 212, the recombination layer 23, the second donor layer 221, the second acceptor layer 222, and the second electrode 12 in this order.

[0046] The intermediate layer 20 may include at least one of an electron transport layer containing an electron transport material and a hole transport layer containing a hole transport material, for example, between the first semiconductor unit 21 and the first electrode 11 and between the second semiconductor unit 22 and the second electrode 12. The intermediate layer 20 may include at least one of an electron transport layer and a hole transport layer, for example, in at least one of the first semiconductor unit 21 and the second semiconductor unit 22. Note that, as the electron transport layer, a known electron transport material containing the same material as the acceptor layer a may be used, and as the hole transport layer, a known hole transport material containing the same material as the donor layer d may be used.

[0047] <Multiple semiconductor units> The multiple semiconductor units include, for example, a first semiconductor unit 21 and a second semiconductor unit 22. The multiple semiconductor units may include, for example, three or more semiconductor units each including a donor layer d and an acceptor layer a as a pair. Furthermore, the semiconductor unit may include at least one of the multiple donor layers d and the multiple acceptor layers a.

[0048] The multiple semiconductor units have, for example, different temperature characteristics. That is, the first semiconductor unit 21 and the second semiconductor unit 22 have, for example, different temperature characteristics. In this case, for a semiconductor unit whose output voltage drops in a certain temperature range among the overlapping usable temperature ranges of the multiple semiconductor units, the dropped output voltage can be complemented by combining it with a semiconductor unit whose output voltage is maintained in that temperature range. This makes it possible to suppress the drop in the output voltage of the thermoelectric element 1.

[0049] The donor layer d and the acceptor layer a are provided, for example, in contact with each other. The donor layer d and the acceptor layer a each include at least one layer. The donor layer d is in contact with, for example, the first electrode 11 and is separated from the second electrode 12. The acceptor layer a is in contact with, for example, the second electrode 12 and is separated from the first electrode 11.

[0050] The donor layer d and the acceptor layer a extend in the second direction X and the third direction Y, similarly to, for example, each of the electrodes 11, 12. The donor layer d and the acceptor layer a have the same shape as, for example, each of the electrodes 11, 12.

[0051] The donor layer d and the acceptor layer a may have a thickness of, for example, 1 nm or more and 1 μm or less. The donor layer d and the acceptor layer a may have a thickness of, for example, 1 nm or more and 50 nm or less.

[0052] The donor layer d, the acceptor layer a, and the recombination layer 23 are formed of solids. Therefore, there is no need to provide a support or the like for maintaining the distance (gap) between the electrodes 11 and 12. Here, when the electrodes 11 and 12 having different work functions are used, a columnar or frame-shaped support may be formed and the gap may be filled with a solvent or the like. In this case, due to the variation in the formation of the support, the gap between the opposing surfaces of the electrodes 11 and 12 may vary, which may result in a decrease in power generation efficiency. In response to this, the donor layer d and the acceptor layer a formed of solids are provided in the gap, which can suppress the variation in the gap between the opposing surfaces of the electrodes 11 and 12. This makes it possible to further stabilize the power generation efficiency.

[0053] The donor layer d is made of a material suitable for moving holes to the first electrode 11. The donor layer d may be, for example, an n-type semiconductor layer including an n-type semiconductor material. The donor layer d may also include, for example, a hole transport layer.

[0054] As the donor layer d, for example, organic materials such as 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''-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) are used. As the donor layer d, for example, n-type semiconductors such as ITO, ZnO, and Zn-Si-O are used, and for example, MoO x Materials containing doping materials such as V2O5, WO3, etc. may also be used.

[0055] The donor layer d may be made of a material containing an organic substance exhibiting orientation polarization, for example. In this case, it is particularly preferable to use α-NPD or mCP on the surface in contact with the acceptor layer a.

[0056] The acceptor layer a is made of a material suitable for transferring electrons to the second electrode 12. The acceptor layer a may be, for example, a p-type semiconductor layer including a p-type semiconductor material. The acceptor layer a may also include, for example, an electron transport layer.

[0057] As the acceptor layer a, for example, 3,4,9,10-perylenetetracarboxylic acid bisbenzimidazole (PTCBI), 60 , C 70Organic materials such as , 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) are used. As the acceptor layer a, a p-type semiconductor such as CuSnI may be used, or a material containing a doping material such as Cs2CO3, Li, Mg, or Ca may be used.

[0058] The acceptor layer a may be made of a material containing an organic substance exhibiting orientation polarization. In this case, it is particularly preferable to use TPBi, OXD-7, Alq3, Al(7-prq)3, Gaq3, BCP, Bpy-OXD, or B3PyMPM on the surface in contact with the donor layer d.

[0059] For example, the LUMOaL of the acceptor layer a is between the HOMOdH and LUMOdL of the donor layer d, and the HOMOaH of the acceptor layer a is higher than the HOMOdH of the donor layer d. In this case, the formation of a CT complex due to thermal excitation of electrons can be promoted at the interface between the donor layer d and the acceptor layer a.

[0060] For example, the work function of the first electrode 11 is between the HOMOdH and LUMOdL of the donor layer d, and the work function of the second electrode 12 is lower than the LUMOaL of the acceptor layer a. In this case, the energy barrier between the components that hinders the movement of carriers 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.

[0061] For example, the acceptor layer a may include a mixed layer. The mixed layer is a layer in contact with the donor layer d and formed by mixing two types of materials. In this case, for example, the acceptor layer a may include a transport layer provided between the mixed layer and the second electrode 12.

[0062] As the two kinds of materials used in the mixed layer, for example, the material used in the donor layer d and the material used in the transport layer are used. In this case, the parts corresponding to the above-mentioned HOMOdH, aH and each LUMOdL, aL can be formed in the mixed layer. Therefore, the range in which the CT complex is formed can be expanded, and the power generation efficiency can be improved.

[0063] In addition, a layer containing an organic material exhibiting orientation polarization exhibits orientation polarization (spontaneous polarization) spontaneously when the layer is formed, and has the property of maintaining a surface potential. Examples of organic materials exhibiting orientation polarization include copper phthalocyanine (CuPc), BCP (Bathocuproine), and copper phthalocyanine fluoride (F 16 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 (Alq3), tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-N3,N3,N6,N6-tetraphenyl-9H-carbazole-3,6,diamine (DACT-II), bis[2-(2-pyridinyl-N)phenyl-C](2,4-pentanedionato-O 2 ,O 4) Iridium(III) (Ir(ppy)2(acac)), (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN), 1,3-bis[2-(2,2'-bipyridin-6-yl)-1,3,4-oxadiazo-5-yl]benzene (Bpy-OXD), 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM), 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN), 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyl-2-pyridinyl)phenyl Examples of materials that can be used include tris(7-propyl-8-hydroxyquinolinato)aluminum (Al(7-prq)3), tris(5-chloro-8-hydroxyquinolinato)aluminum (Al(q-Cl)3), tris(8-hydroxyquinoline)-gallium (Gaq3), bis(8-quinolinolato)zinc (Znq2), and 3,4,5,6-tetra-9H-carbazol-9-yl-1,2-benzenedicarbonitrile (4CzPN). Any material can be used depending on the application.

[0064] The layer containing an organic material exhibiting orientation polarization may contain, for example, only one type of material. In this case, it is easier to maintain the surface potential specific to the material than when, for example, a material containing dispersed particles is used.

[0065] <Recombination layer 23> The recombination layer 23 combines electrons generated from one of the multiple semiconductor units with holes generated from the other semiconductor units. The recombination layer 23 is provided, for example, between the first semiconductor unit 21 and the second semiconductor unit 22 in contact therewith, and combines electrons generated from the first semiconductor unit 21 with holes generated from the second semiconductor unit 22.

[0066] The recombination layer 23 contains, for example, the same material as at least one of the first electrode 11 and the second electrode 12. In this case, the electrode material can be used for the recombination layer 23, and the number of types of materials can be reduced. This allows for simplification of material management for the thermoelectric element 1.

[0067] The recombination layer 23 may contain, for example, a material different from the first electrode 11 and the second electrode 12. In this case, a material with low durability can be applied to the intermediate layer 20, which has a smaller exposed area than the electrode material. This can improve the selectivity of the material for the thermoelectric element 1. The recombination layer 23 may also contain a material with lower durability than the first electrode 11 and the second electrode 12. In this case, the recombination layer 23 has a part of its main surface protected by the electrodes 11, 12, etc., and is less susceptible to the influence of deterioration of the main surface on the power generation output, even if a material with low durability is used. This can improve the selectivity of the material for the thermoelectric element 1 and suppress the decrease in the power generation output.

[0068] For example, metal materials such as Au, Mg, Ag, Al, Li, and alloys containing these are used as the recombination layer 23. For example, a material other than a metal may be used as the recombination layer 23, and more specifically, a material having a lower HOMO than the adjacent donor layer (including the second donor layer 221 of the second semiconductor unit 22) and a higher LUMO than the adjacent acceptor layer (including the first acceptor layer 212 of the first semiconductor unit 21) is used. By using an MgAg alloy, Al, AlLi alloy, or the like having low oxidation resistance as the recombination layer 23, the power generation output is less likely to be affected by deterioration of the main surface, even if a material having low oxidation resistance is used.

[0069] <Substrate 51> The substrate 51 is in contact with, for example, the first electrode 11, 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 FIG. 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.

[0070] The thickness of the substrate 51 is, for example, not less than 1 μm and not more than 10 mm, and can be any thickness as long as it is capable of fixing the first electrode 11 and the like.

[0071] For example, an insulating plate-like material can be used as the substrate 51, and known materials such as silicon, quartz, Pyrex (registered trademark) can be used. For example, a film-like material can be used as the substrate 51, and known film-like materials such as PET (polyethylene terephthalate), PC (polycarbonate), and polyimide can be used.

[0072] For example, a conductive material can be used for the substrate 51, and examples of such materials include iron, aluminum, copper, and alloys of aluminum and copper. Furthermore, materials such as conductive semiconductors, such as Si and GaN, as well as conductive polymers, may also be used for the substrate 51. When a conductive material is used for the substrate 51, wiring for connection to the first electrode 11 and the like is not required.

[0073] In particular, a known insulating material that does not have optical transparency or a known conductive material can be used as the material of the substrate 51. This makes it possible to prevent 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.

[0074] (Method of Manufacturing Thermoelectric Element 1) Next, an example of a method for manufacturing the thermoelectric element 1 in this embodiment will be described. Fig. 4 is a flow chart showing an example of a method for manufacturing the thermoelectric element 1 in this embodiment.

[0075] The method for manufacturing the thermoelectric element 1 includes a first electrode forming step S110, an intermediate layer forming step S120, and a second electrode forming step S130.

[0076] <First electrode formation step S110> In the first electrode formation step S110, the first electrode 11 is formed. In the first electrode formation step S110, the first electrode 11 is formed, for example, on the substrate 51 shown in FIG. 1(a). In this case, the first electrode 11 is formed, for example, after cleaning and baking the substrate 51. The first electrode 11 is formed, for example, by a sputtering method or a vacuum deposition method under a reduced pressure environment.

[0077] <Intermediate layer formation step S120> In the intermediate layer forming step S120, for example after the first electrode forming step S110, the intermediate layer 20 including a plurality of semiconductor units and a recombination layer 23 is formed on the main surface of the first electrode 11.

[0078] In the intermediate layer forming step S120, for example, a first semiconductor unit 21 is formed on the main surface of the first electrode 11. Then, a recombination layer 23 is formed on one of the main surfaces of the first semiconductor unit 21 opposite to the main surface facing the first electrode 11. Then, a second semiconductor unit 22 is formed on one of the main surfaces of the recombination layer 23 opposite to the main surface facing the first electrode 11. In this case, some of the carriers generated in each semiconductor unit can be recombined via the recombination layer 23, and a state in which the semiconductor units are connected in series can be realized. This allows the output voltage of the thermoelectric element 1 to be improved.

[0079] More specifically, in the intermediate layer formation step S120, for example, a first donor layer 211 constituting the first semiconductor unit 21 is formed on the main surface of the first electrode 11. Then, a first acceptor layer 212 constituting the first semiconductor unit 21 is formed on the main surface of the first donor layer 211 opposite to the main surface facing the first electrode 11. Then, a recombination layer 23 is formed on the main surface of the first acceptor layer 212 opposite to the main surface facing the first electrode 11.

[0080] Thereafter, a second donor layer 221 constituting the second semiconductor unit 22 is formed on one of the main surfaces of the recombination layer 23, the main surface opposite to the main surface facing the first electrode 11. Thereafter, a second acceptor layer 222 constituting the second semiconductor unit 22 is formed on one of the main surfaces of the second donor layer 221, the main surface opposite to the main surface facing the first electrode 11.

[0081] The donor layer d, the acceptor layer a, and the recombination layer 23 are formed by, for example, a vacuum deposition method, a spin coating method, an inkjet method, a slit coating method, a spray method, a gravure printing method, or a letterpress printing method.

[0082] <Second electrode formation step S130> In the second electrode forming step S130, for example, after the intermediate layer forming step S120, a second electrode 12 is formed on a main surface of the intermediate layer 20. In the second electrode forming step S130, for example, a second electrode 12 is formed on a main surface of the second acceptor layer 222 constituting the second semiconductor unit 22 included in the intermediate layer 20, the main surface opposite to the main surface facing the first electrode 11. The second electrode 12 is formed by, for example, a sputtering method or a vacuum deposition method under a reduced pressure environment.

[0083] By carrying out each of the above-mentioned steps, the thermoelectric element 1 of this embodiment is formed. Note that, for example, by forming each of the wirings 101, 102 and the like shown in Fig. 1(a), the power generating device 100 of this embodiment is formed.

[0084] In the above, in the intermediate layer forming step S120, an example has been shown in which the first semiconductor unit 21, the recombination layer 23, and the second semiconductor unit 22 are formed in this order on the main surface of the first electrode 11, but, for example, the second semiconductor unit 22, the recombination layer 23, and the first semiconductor unit 21 may be formed in this order on the main surface of the first electrode 11. In this case, in the second electrode forming step S130, the second electrode 12 may be formed on the main surface of the first semiconductor unit 21 opposite to the main surface facing the first electrode 11.

[0085] In addition, in the intermediate layer forming step S120, an example has been shown in which the first donor layer 211, the first acceptor layer 212, the recombination layer 23, the second donor layer 221, and the second acceptor layer 222 are formed in this order on the main surface of the first electrode 11, but for example, the first acceptor layer 212, the first donor layer 211, the recombination layer 23, the second acceptor layer 222, and the second donor layer 221 may be formed in this order on the main surface of the first electrode 11. In this case, in the second electrode forming step S130, the second electrode 12 may be formed on the main surface of the second donor layer 221 opposite to the main surface facing the first electrode 11.

[0086] (Modifications of Thermoelectric Element 1 and Manufacturing Method of Thermoelectric Element 1) Next, a modified example of the thermoelectric element 1 and the manufacturing method thereof will be described. The difference between the modified example and the above-described embodiment is that the recombination layer 23 constituting the intermediate layer 20 contains a plurality of conductive materials. Note that the description of the same configuration as the above-described configuration will be omitted.

[0087] <Recombination layer 23> 5, the recombination layer 23 includes a first conductive material 231 and a second conductive material 232. For the first conductive material 231 and the second conductive material 232, for example, a material similar to at least one of the first electrode 11 and the second electrode 12 is used.

[0088] The first electrode 11 and the first conductive material 231 may have different work functions, for example. The work function of the first electrode 11 is higher than the work function of the first conductive material 231, for example. In this case, an electric field can be formed between the first electrode 11 and the first conductive material 231 based on the difference in the amount of thermoelectrons generated from the first electrode 11 and the first conductive material 231. This can further promote carrier movement between the first electrode 11 and the first conductive material 231. This makes it possible to stabilize the power generation efficiency of the thermoelectric element 1.

[0089] The second conductive material 232 and the second electrode 12 may have different work functions, for example. The work function of the second conductive material 232 is higher than the work function of the second electrode 12, for example. In this case, an electric field can be formed between the second conductive material 232 and the second electrode 12 based on the difference in the amount of thermoelectrons generated from the second conductive material 232 and the second electrode 12. This can further promote carrier movement between the second conductive material 232 and the second electrode 12. This makes it possible to stabilize the power generation efficiency of the thermoelectric element 1.

[0090] As a first example of a combination of each component, ITO is used for the first electrode 11 and the second conductive material 232, and Al is used for the second electrode 12 and the first conductive material 231. In addition, for example, CuPc is used for the first donor layer 211 and the second donor layer 221, and F is used for the first acceptor layer 212 and the second acceptor layer 222. 16 CuPc, C 60 and BCP (electron transport layer). In this case, the recombination layer 23 is composed of the same material as the first electrode 11 and the same material as the second electrode 12, so that the number of types of materials can be reduced, and material management for the thermoelectric element 1 can be simplified. Even if Al, which has low oxidation resistance, is used for the first conductive material 231 of the recombination layer 23, part of the main surface is protected by the adjacent second conductive material 232 and first acceptor layer 212, so that the power generation output is less likely to be affected by deterioration of the main surface even without oxidation resistance treatment.

[0091] In a second example of a combination of each component, ITO is used for the first electrode 11, Al is used for the second electrode 12 and the first conductive material 231, and Au is used for the second conductive material 232. The first donor layer 211, the second donor layer 221, the first acceptor layer 212, and the second acceptor layer 222 are similar to the above first example. In this case, the recombination layer 23 can be made of Au, which has low abrasion resistance different from that of the first electrode 11 and the second electrode 12, and can be applied to the intermediate layer 20, which has a smaller exposed area than the electrode material, without performing abrasion resistance treatment, and the selectivity of materials for the thermoelectric element 1 can be improved.

[0092] <Intermediate layer formation step S120> In the intermediate layer formation step S120, a first conductive material 231 constituting the recombination layer 23 is formed, for example, on one of the main surfaces of the first semiconductor unit 21, opposite to the main surface facing the first electrode 11. In detail, for example, the first conductive material 231 is formed on one of the main surfaces of the first acceptor layer 212 constituting the first semiconductor unit 21, opposite to the main surface facing the first electrode 11. Thereafter, a second conductive material 232 constituting the recombination layer 23 is formed on one of the main surfaces of the first conductive material 231, opposite to the main surface facing the first electrode 11.

[0093] Thereafter, the second semiconductor unit 22 is formed on the principal surface of the second conductive material 232 constituting the recombination layer 23, which is opposite to the principal surface facing the first electrode 11. In detail, for example, the second donor layer 221 constituting the second semiconductor unit 22 is formed on the principal surface of the second conductive material 232, which is opposite to the principal surface facing the first electrode 11.

[0094] By carrying out each of the above-mentioned steps, the thermoelectric element 1 of this embodiment is formed. Note that, for example, by forming each of the wirings 101, 102 and the like shown in Fig. 1(a), the power generating device 100 of this embodiment is formed.

[0095] In the above, in the intermediate layer formation step S120, an example has been shown in which the first conductive material 231 and the second conductive material 232 are formed in this order on the main surface of the first acceptor layer 212, but, for example, the second conductive material 232 and the first conductive material 231 may be formed in this order on the main surface of the first acceptor layer 212. In this case, the second donor layer 221 may be formed on the main surface of the first conductive material 231 opposite to the main surface facing the first electrode 11.

[0096] According to this embodiment, the thermoelectric element 1 includes an intermediate layer 20 including a plurality of semiconductor units (first semiconductor unit 21, second semiconductor unit 22) each of which has a donor layer d and an acceptor layer a as a group, and a recombination layer 23 provided between the plurality of semiconductor units. As a result, some of the carriers generated in each semiconductor unit can be recombined via the recombination layer 23, and a state in which the semiconductor units are connected in series can be realized. This allows the output voltage of the thermoelectric element 1 to be improved.

[0097] According to this embodiment, the semiconductor units have different temperature characteristics. Therefore, when a semiconductor unit whose output voltage drops in a certain temperature range among the overlapping usable temperature ranges of the semiconductor units is combined with a semiconductor unit whose output voltage is maintained in the temperature range, the dropped output voltage can be compensated for. This makes it possible to suppress the drop in the output voltage of the thermoelectric element 1.

[0098] Moreover, according to this embodiment, the recombination layer 23 contains the same material as at least one of the first electrode 11 and the second electrode 12. Therefore, an electrode material can be used for the recombination layer 23, and the number of types of materials can be reduced. This allows for simplification of material management for the thermoelectric element 1.

[0099] Furthermore, according to this embodiment, the recombination layer 23 contains a material different from the first electrode 11 and the second electrode 12. Therefore, a material with low durability can be applied to the intermediate layer 20, which has a smaller exposed area compared to the electrode material. This allows for improved material selectivity for the thermoelectric element 1.

[0100] Furthermore, according to this embodiment, the recombination layer 23 contains a material that is less durable than the first electrode 11 and the second electrode 12. Therefore, the recombination layer 23 has a part of the main surface protected by the electrodes 11 and 12, and even if a material with low durability is used, the power generation output is less affected by deterioration of the main surface, etc. This allows the thermoelectric element 1 to have a high material selectivity and to suppress a decrease in the power generation output.

[0101] Moreover, according to this embodiment, the manufacturing method of the thermoelectric element 1 includes an intermediate layer forming step S120 of forming one semiconductor unit (the first semiconductor unit 21 or the second semiconductor unit 22) having a donor layer d and an acceptor layer a as a pair on the main surface of the first electrode 11, forming a recombination layer 23 on the main surface of the one semiconductor unit, and forming another semiconductor unit (the second semiconductor unit 22 or the first semiconductor unit 21) on the main surface of the recombination layer 23. Therefore, a part of the carriers generated in each semiconductor unit can be recombined via the recombination layer 23, and a state in which the semiconductor units are connected in series can be realized. This allows the output voltage of the thermoelectric element 1 to be improved.

[0102] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0103] 1: Thermoelectric element 11: 1st electrode 11e: (first electrode) energy level 12:Second electrode 12e: (second electrode) energy level 20: Middle class 21: First semiconductor unit 211: First donor tier 212: First acceptor layer 22: Second semiconductor unit 221: Second donor tier 222: Second acceptor layer 23: Recombination layer 231: First conductive material 232: Second conductive material 51: Substrate 51a: First substrate 51b: 2nd board 100: Power generation equipment 101: 1st wiring 102:Second wiring d: Donor layer a: acceptor layer S110: First electrode formation process S120: Intermediate layer formation process S130: Second electrode formation process X:Second direction Y: Third direction Z: 1st direction

Claims

1. A thermoelectric element that does not require a temperature difference between electrodes, A first electrode; a second electrode provided apart from the first electrode; an intermediate layer provided between the first electrode and the second electrode; Equipped with the first electrode, the intermediate layer, and the second electrode are stacked in this order in a stacking direction; The intermediate layer is a plurality of semiconductor units each including a pair of a donor layer and an acceptor layer that are stacked in the stacking direction and in contact with each other; a recombination layer that is conductive and is provided in contact with an acceptor layer of one of the semiconductor units and a donor layer of another of the semiconductor units among the plurality of semiconductor units, and that combines electrons generated from one of the semiconductor units and holes generated from the other of the semiconductor units; Including, One of the semiconductor units, the recombination layer, and the other semiconductor unit are stacked in this order in the stacking direction. A thermoelectric element characterized by:

2. The plurality of semiconductor units have different temperature characteristics. The thermoelectric element according to claim 1 .

3. The recombination layer contains the same material as at least one of the first electrode and the second electrode.

3. The thermoelectric element according to claim 1 or 2,

4. the recombination layer includes a material different from the first electrode and the second electrode; 3. The thermoelectric element according to claim 1 or 2,

5. The recombination layer includes a material that is less durable than the first electrode and the second electrode. The thermoelectric element according to claim 4 .

6. A thermoelectric element according to claim 1 or 2; A first wiring electrically connected to the first electrode; A second wiring electrically connected to the second electrode; To be prepared A power generating device characterized by:

7. A method for manufacturing a thermoelectric element that does not require a temperature difference between electrodes, comprising the steps of: a first electrode forming step of forming a first electrode; On a main surface of the first electrode, a plurality of semiconductor units each including a pair of a donor layer and an acceptor layer stacked in a stacking direction in contact with each other; a recombination layer that is conductive and is provided between the plurality of semiconductor units in contact therewith, and that combines electrons generated from one of the semiconductor units with holes generated from the other semiconductor units; An intermediate layer forming step of forming an intermediate layer comprising the steps of: a second electrode forming step of forming a second electrode on a main surface of the intermediate layer opposite to a main surface facing the first electrode; having The intermediate layer forming step includes: forming one of the plurality of semiconductor units on a major surface of the first electrode by stacking a donor layer and an acceptor layer in this order in the stacking direction; forming the recombination layer on a principal surface of the acceptor layer of the one of the semiconductor units opposite to a principal surface facing the first electrode; forming the other semiconductor unit by stacking a donor layer and an acceptor layer in this order in the stacking direction on a principal surface of the recombination layer opposite to a principal surface facing the first electrode; A method for manufacturing a thermoelectric element, comprising the steps of:

Images