Organic semiconductor element, strain sensor, vibration sensor, and method for manufacturing organic semiconductor element

Abstract

The present invention provides an organic semiconductor element, a strain sensor, a vibration sensor, and a method for manufacturing an organic semiconductor element that can obtain a desired resistance with a simple structure. In the vibration sensor, an organic semiconductor element (14) is formed on the surface of a flexible substrate (12). The organic semiconductor element (14) includes an organic semiconductor film (24) formed by forming a single crystal of an organic semiconductor into a film shape and a dopant film (25) formed on the surface of the organic semiconductor film (24). The dopant film (25) forms a charge transfer complex between a dopant constituting the dopant film (25) and an organic semiconductor of the organic semiconductor film (24), forming a doping layer (26) in which carriers are injected into the surface of the organic semiconductor film (24).

Description

Technical Field

[0001] The present invention relates to an organic semiconductor element, a strain sensor, a vibration sensor and a method for manufacturing the organic semiconductor element. Background Art

[0002] A strain sensor using an organic semiconductor element is known (for example, see Patent Document 1). The strain sensor of Patent Document 1 has an organic semiconductor film and a pair of electrodes, the organic semiconductor film being composed of an organic semiconductor single crystal thin film formed on a substrate, and the pair of electrodes being connected to the organic semiconductor film. When compressive or tensile stress is applied to the organic semiconductor film itself, the distance between the molecules of the organic semiconductor changes, the vibration magnitude of the molecules changes, and the mobility of the carriers of the organic semiconductor film changes. Strain is detected by detecting the change in the mobility of the carriers as, for example, a change in the resistance of the organic semiconductor film.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent International Publication No. 2016 / 121791 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, although it is known that organic semiconductors can be used as strain sensors or the like by utilizing changes in carrier mobility as described above, in order to use them as sensors, it is necessary to be able to obtain a desired resistance with a simple structure.

[0008] An object of the present invention is to provide an organic semiconductor element, a strain sensor, a vibration sensor, and a method for manufacturing an organic semiconductor element, which can obtain a desired resistance with a simple structure.

[0009] Means for solving problems

[0010] The organic semiconductor element of the present invention comprises: an organic semiconductor film formed as a single crystal of an organic semiconductor; and a doping layer formed on the surface of the organic semiconductor film.

[0011] The strain sensor of the present invention includes: the organic semiconductor element; a pair of electrodes electrically connected via the doping layer; and a deformable substrate having the organic semiconductor element formed on one surface thereof.

[0012] The vibration sensor of the present invention comprises: the organic semiconductor element; a pair of electrodes electrically connected via the doping layer; and a flexible substrate having one or both ends fixed thereto and the organic semiconductor element disposed on the surface of the flexible portion.

[0013] The method for manufacturing an organic semiconductor element of the present invention comprises: an organic semiconductor film forming step of forming an organic semiconductor film composed of a single crystal of an organic semiconductor on a substrate; and a dopant film forming step of forming a dopant film for supplying carriers to the surface of the organic semiconductor film.

[0014] Effects of the Invention

[0015] According to the present invention, by forming a doping layer on the surface of an organic semiconductor film formed as a single crystal of an organic semiconductor, a desired resistance can be obtained with a simple structure without destroying the crystal structure of the organic semiconductor film.

[0016] Furthermore, according to the present invention, by forming a dopant film on the surface of an organic semiconductor film, good doping can be performed without destroying the crystal structure of the organic semiconductor film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a perspective view showing the appearance of the vibration sensor according to the embodiment.

[0018] Figure 2 is a cross-sectional view showing the structure of a vibration sensor.

[0019] Figure 3 This is an explanatory diagram showing the relationship between the HOMO of an organic semiconductor and the LUMO of a dopant.

[0020] Figure 4 It is an explanatory diagram showing the process of forming an organic semiconductor film.

[0021] Figure 5 It is an explanatory diagram showing the step of forming a dopant film.

[0022] Figure 6 It is an explanatory diagram showing the relationship between the strain of an organic semiconductor film and the mobility of carriers.

[0023] Figure 7 It is an explanatory diagram showing an example of a vibration sensor in which both ends of a substrate are fixed.

[0024] Figure 8 It is an explanatory diagram showing an example of a pressure sensor using an organic semiconductor element.

[0025] Fig. 9 This is an explanatory diagram showing an example in which electrodes of an organic semiconductor element are provided in a comb-teeth shape.

[0026] Fig.10 This is an explanatory diagram showing a state in which an organic semiconductor film is doped using ion exchange.

[0027] Fig.11 This is a graph showing the relationship between strain and resistance change rate of an organic semiconductor element.

[0028] Fig.12 This is a graph showing the relationship between micro-strain and resistance change rate of an organic semiconductor element.

[0029] Fig.13 This is a graph showing changes in output voltage when the vibration sensor is vibrated at high speed.

[0030] Fig.14 This is a graph showing the temporal change in the current flowing when a constant voltage is applied to an organic semiconductor element. DETAILED DESCRIPTION

[0031] Figure 1 In the embodiment, the vibration sensor 10 includes a substrate 12 and a sensor portion S, and the sensor portion S includes an organic semiconductor element 14 formed on the surface of the substrate 12. The vibration sensor 10 uses the organic semiconductor element 14 as a strain detection element to detect the vibration of the object to be detected. It should be noted that an acceleration sensor that detects acceleration with the same structure as the vibration sensor 10 or various sensors that detect the tilt or movement of the object to be detected may also be used.

[0032] The substrate 12 is a rectangular plate-like component that is flexible, that is, it can be elastically deformed freely. One end of the substrate 12 in the length direction (Y direction) is fixed on the foot 13, and the vibration sensor 10 is a cantilever beam structure. The foot 13 is formed of a hard material and fixed on the object to be detected. Therefore, when the object to be detected has an acceleration in the up and down directions due to vibration, the substrate 12 is elastically deformed so that the other end of the substrate 12 moves in the up and down directions corresponding to the magnitude and direction of the above-mentioned acceleration. It should be noted that in this example, the case of detecting vibrations in the up and down directions is described, but the detected vibration direction is not limited to this. For example, when it is necessary to detect vibrations (acceleration) in the left and right directions, it is sufficient to fix the vibration sensor 10 on the object to be detected in such a way that the surface of the substrate 12 on which the sensor part S is formed faces either the left or right direction.

[0033] A sensor unit S is provided on one surface (the top surface in this example) of the substrate 12. The sensor unit S includes an organic semiconductor element 14, a pair of electrodes 16, 17, and leads 18, 19. The organic semiconductor element 14 is formed in a rectangular shape that is long in the width direction (X direction orthogonal to the Y direction) of the substrate 12. The organic semiconductor element 14 is stretched or compressed in the longitudinal direction of the substrate 12 by the elastic deformation of the substrate 12. In addition, the organic semiconductor element 14 is preferably provided at a position where it is stretched or compressed greatly when the substrate 12 is elastically deformed.

[0034] A pair of electrodes 16 and 17 are arranged at both ends of the organic semiconductor element 14 in the length direction of the substrate 12, that is, the direction in which the organic semiconductor element 14 is stretched or compressed. One end of a lead 18 is connected to the electrode 16, and one end of a lead 19 is connected to the electrode 17. The leads 18 and 19 are formed in a pattern in which the other ends thereof extend to one end of the substrate 12, and the organic semiconductor element 14 is connected to an external device via the leads 18 and 19.

[0035] like Figure 2 As shown, the substrate 12 of this example is a two-layer structure consisting of a glass plate 21 and a resin layer 22 formed on the surface of the glass plate 21, and an organic semiconductor element 14 is formed on the surface of the resin layer 22. The resin layer 22 is formed of, for example, polyparaxylene (Pylaron (registered trademark)). The thickness of the glass plate 21 is, for example, 100 to 500 μm, and the thickness of the resin layer 22 is about 20 to 200 μm. It should be noted that there is no particular limitation on the material and structure constituting the substrate 12, and a material formed into a plate of, for example, polyethylene naphthalate (PEN) or a substrate 12 consisting only of polyethylene naphthalate may be used instead of the glass plate 21.

[0036] The organic semiconductor element 14 has an organic semiconductor film 24 formed on the surface of the resin layer 22 and a dopant film 25 formed on the upper surface of the organic semiconductor film 24. Electrodes 16 and 17 are formed of gold (Au) at both ends of the organic semiconductor film 24. The organic semiconductor film 24 is composed of a single crystal of an organic semiconductor (an organic compound showing semiconductor properties) and is formed into a film. The thickness of the organic semiconductor film 24 is, for example, less than 10 nm. As an organic semiconductor constituting the organic semiconductor film 24, for example, 3,11-dioctyl dinaphthyl [2,3-d:2',3'--d'] benzo [1,2-b:4,5-b'] dithiophene (C8-DNBDT), which is a P-type organic semiconductor, is used.

[0037] As the P-type organic semiconductor constituting the organic semiconductor film 24, in addition to the above-mentioned C8-DNBDT, 3,11-didecyl dinaphtho[2,3-d:2',3'--d']benzo[1,2-b:4,5-b']dithiophene (C8-DNBDT) can be used. 10 -DNBDT), 3,9-dihexyl dinaphtho[2,3-b; 2',3-d]thiophene (C6-DNT), 2,9-dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (C 10-DNTT), 2,7-dioctylbenzothiophene [3,2-b][1]benzothiophene (C8-BTBT), and 6,13-bis (triisopropylsilylethynyl) pentacene. In addition, the organic semiconductor constituting the organic semiconductor film 24 may also be N-type. As an N-type organic semiconductor, dicyanopyrene-3,4:9,10-bis (dicarboximide) and the like can be used.

[0038] The dopant film 25 in which the dopant is formed into a film is used to form a doped doping layer 26 on the surface (interface with the dopant film 25) of the organic semiconductor film 24. The dopant film 25 is formed in a thin film on the surface of the organic semiconductor film 24 between the electrodes 16 and 17. As a dopant material for forming the dopant film 25, for example, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ, CAS No. (29261-33-4)) is used.

[0039] By forming the above-mentioned dopant film 25, a charge transfer complex between the dopant and the organic semiconductor is generated at the interface between the organic semiconductor film 24 and the dopant film 25. Figure 3 As shown, charge transfer occurs between the HOMO (Highest Occupied Molecular Orbital) of the organic semiconductor of the organic semiconductor film 24 and the LUMO (Lowest Unoccupied Molecular Orbital) of the dopant constituting the dopant film 25, and carriers (holes in this case) move to the surface of the organic semiconductor film 24 to form a doping layer 26.

[0040] When a P-type organic semiconductor is used as the organic semiconductor film 24, the dopant constituting the dopant film 25 only needs to satisfy the LUMO energy level (E LUMO ) is greater than the HOMO energy level (E HOMO ) is about 1eV lower (E HOMO -1) (E LUMO >E HOMO -1). When an N-type organic semiconductor is used as the organic semiconductor film 24, the dopant constituting the dopant film 25 only needs to satisfy the HOMO energy level (E' HOMO ) is smaller than the LUMO energy level (E') of the organic semiconductor of the organic semiconductor film 24. LUMO ) is about 1eV higher (E' LUMO +1) (E' HOMO <E' LUMO +1).

[0041] As dopant materials for P-type organic semiconductors, in addition to F4TCNQ, trimolybdenum 1-trifluoroacetyl-2-trifluoromethylethane-1,2-disulfide (Mo(tfd-COCF3)3), nitrogen ammonium hexafluoroantimonate (NO + SbF6 － ) etc. In addition, as dopant materials for N-type organic semiconductors, cobalt cyclopentadienyl ferrocene, decamethyl cobalt cyclopentadienyl ferrocene, ferrocene, 1,3-dimethyl-2-phenyl-2,3-dihydrobenzimidazole etc. can be used. Some of them become anions or cations themselves and act as dopants, and some of them act as dopants as a part of their ionization. For example, as shown in the following formula (1) and formula (2), F4TCNQ and Mo(tfd-COCF3)3 are examples of the former, and as shown in formula (3), NO + SbF6 - It is an example of the latter. It should be noted that Formulas (1) to (3) show the case where C8-DNBDT acts as a dopant in the organic semiconductor film 24.

[0042] [Number 1]

[0043] C8DNBDT+F4TCNQ

[0044] →[C8DNBDT] + [F4TCNQ] - …(1)

[0045] C8DNBDT+Mo(tfd-COCF3)3

[0046] →[C8DNBDT] + [Mo(tfd-COCF3)3] - …(2)

[0047] C8DNBDT+NO + SbF6 -

[0048] →[C8DNBDT] + [SbF6] - +NO(gas)…(3)

[0049] Next, the steps for producing the organic semiconductor element 14 are described. The production steps described below are examples and are not limited thereto. When producing the organic semiconductor element 14, the steps for forming the organic semiconductor film 24, the steps for forming the electrodes 16 and 17, and the steps for forming the dopant film 25 are sequentially performed.

[0050] like Figure 4As shown in FIG. 1 , the organic semiconductor film 24 is formed by, for example, an edge casting method. In the edge casting method, a scraper 31 is disposed above the substrate 12 in a manner substantially perpendicular to the substrate 12. At this time, the position of the scraper 31 in the vertical direction is adjusted so that the gap between the substrate 12 and the lower end of the scraper 31 is larger than the thickness of the organic semiconductor film 24 to be formed. While the substrate 12 is oriented in one direction (in the Figure 4 The solution 33 is supplied between the substrate 12 and the lower end of the scraper 31 while the substrate 12 moves (in the right direction in the example). At this time, the solution 33 is supplied from the upstream side (in the right direction) of the scraper 31 in the moving direction of the substrate 12. Figure 4 The solution 33 is supplied via the supply pipe 32 (in the example, the left side of the scraper 31). The solution 33 is a solution in which an organic semiconductor to be the organic semiconductor film 24 is dissolved in a solvent. As the solvent, for example, an aromatic compound (o-dichlorobenzene, etc.) can be used.

[0051] By the movement of the substrate 12 and the supply of the solution 33, the solvent of the solution 33 in the portion away from the scraper 31 evaporates on the downstream side of the scraper 31 in the direction of movement of the substrate 12, and the organic semiconductor is precipitated. Thus, a single crystal thin film of the organic semiconductor is formed to become the organic semiconductor film 24. It should be noted that although the substrate 12 is moved in this example, since the substrate 12, the scraper 31 and the supply pipe 32 only need to move relative to each other, for example, the scraper 31 and the supply pipe 32 may be moved instead of the substrate 12.

[0052] As the solution 33, a solution in which a polymer material and an organic semiconductor to be the organic semiconductor film 24 are dissolved in a solvent may be used. When such a solution 33 is used, during the evaporation of the solvent, the solution is separated into a polymer layer composed of the polymer material and a layer composed of the organic semiconductor, that is, the organic semiconductor film 24. As a result, an organic semiconductor film 24 in which the organic semiconductor is better oriented and crystallized is formed on the polymer layer.

[0053] As the above-mentioned polymer material, polymethyl methacrylate resin, poly (4-methylstyrene), poly (triarylamine), polystyrene, polyacrylonitrile, polyethylene, polyvinyl acetate, etc. can be used. In addition, as the solvent, there is no particular limitation as long as it is a solvent that dissolves both the organic compound and the polymer. For example, halogenated aromatic solvents such as chlorobenzene, 3-chlorothiophene, 1-chloronaphthalene, hydrocarbon solvents such as n-hexane and heptane, or non-halogenated aromatic solvents such as toluene, xylene, and tetralin can be used.

[0054] After the organic semiconductor film 24 is formed, the electrodes 16 and 17 are formed. The electrodes 16 and 17 are formed together with the leads 18 and 19 by, for example, vapor deposition.

[0055] After forming the electrodes 16 and 17, the dopant film 25 is formed. For example, Figure 5 As shown, the organic semiconductor film 24 and the substrate 12 are immersed in a solution 38 in a container 37, and then the solvent is evaporated, thereby forming a dopant film 25 on the surface of the organic semiconductor film 24. The solution 38 is a solution in which a dopant material is dissolved in a solvent. As the solvent, acetonitrile, butyl acetate, etc. can be used. By forming the dopant film 25 in this way, a doping layer 26 is formed.

[0056] The method for forming the dopant film 25 is not limited to the above method. For example, the dopant film 25 may be formed on the organic semiconductor film 24 by dropping a solution in which a dopant is dissolved onto the surface of the organic semiconductor film 24, spreading the solution and evaporating the solvent. Alternatively, the dopant film 25 may be formed by vapor-depositing a dopant on the surface of the organic semiconductor film 24.

[0057] The organic semiconductor element 14, i.e., the organic semiconductor film 24 including the doping layer 26, is compressed or stretched by the elastic deformation of the substrate 12. In this example, since the organic semiconductor element 14 is formed on the upper surface of the substrate 12, when the substrate 12 is bent and the other end of the substrate 12 moves downward, the organic semiconductor film 24 is stretched, and when the substrate 12 is bent and the other end moves upward, the organic semiconductor film 24 is compressed. The carrier mobility of the organic semiconductor film 24 changes according to the compression or tension, i.e., the strain. By detecting this change as a change in the resistance of the organic semiconductor element 14 via the electrodes 16 and 17, the acceleration of the object to be detected can be detected.

[0058] The reason why the carrier mobility of the organic semiconductor film 24 changes according to the strain is as follows. Figure 6 As schematically shown in the state of the organic semiconductor molecules in the organic semiconductor film 24, when the organic semiconductor film 24 is compressed and the compressive stress acts on the organic semiconductor film 24, the crystallization produces strain, the molecules are close to each other, the carriers are easy to move in the organic semiconductor, and the mobility of the carriers increases. In addition, when the molecules are close to each other, the vibration of the molecules decreases, so the carriers are easy to move in the organic semiconductor film 24, and the mobility of the carriers increases. On the contrary, when the organic semiconductor film 24 is stretched and the tensile stress acts on the organic semiconductor film 24, the crystallization produces strain, the molecules are separated from each other, the carriers are difficult to move in the organic semiconductor, and the mobility of the carriers decreases. In addition, when the molecules are separated from each other, the vibration of the molecules increases, so the carriers are difficult to move in the organic semiconductor film 24, and the mobility of the carriers decreases. Since the larger the compressive stress or tensile stress, the larger the crystallization strain of the organic semiconductor film 24, the larger the change in the carrier mobility becomes. In this way, the single-crystal organic semiconductor film 24 has the characteristic that the larger the strain applied, the larger the change in the carrier mobility.

[0059] As described above, the organic semiconductor film 24 formed of a single crystal can largely detect the change in resistance of the organic semiconductor film 24 relative to strain, and has a high detection sensitivity. In addition, it has a high responsiveness, that is, the resistance changes with respect to the change in vibration acceleration only after a short delay. Therefore, since the resistance of the organic semiconductor film 24 changes with the high-speed change of acceleration, the vibration sensor 10 can detect vibrations with higher frequencies, and it has good practicality as a vibration sensor.

[0060] However, since the polycrystalline organic semiconductor has different crystal structures in each organic semiconductor film, even if the same stress is applied and the same strain is applied, the same carrier mobility cannot be obtained. In contrast, the organic semiconductor film 24 in this example is a single crystal, and the crystal structure depends on the molecules of the organic compound. In addition, as mentioned above, since doping is only performed on the surface of the organic semiconductor film 24, its crystal structure will not be disturbed. Therefore, each organic semiconductor film 24 has the same crystal structure, and when the same stress is applied and the same strain is applied, the same carrier mobility can be obtained. Therefore, each organic semiconductor film 24 has the same characteristics.

[0061] In addition, a doping layer 26 is formed on the surface of the organic semiconductor film 24 in this example, and the conductivity of the doping layer 26 is greater than that of other parts of the organic semiconductor film 24. Therefore, in the organic semiconductor element 14 in this example, the change in the resistance of the doping layer 26 is detected as the change in the resistance of the organic semiconductor film 24 between the electrodes 16 and 17. In the case where the doping layer 26 is not formed, that is, when doping is not performed, if the resistance of the organic semiconductor film 24 is high and a high voltage is not applied, sometimes sufficient current (nominal current) will not flow through it, but through doping, it will become a resistor that flows through a sufficient nominal current even if a lower voltage is applied. In addition, by forming the doping layer 26, it is not necessary to set a gate electrode on the surface of the organic semiconductor film 24 to form a three-terminal structure, that is, the organic semiconductor film 24 can be used as a resistor whose resistance value changes according to strain with a simple structure. Moreover, since the doping layer 26 formed does not disturb the single crystal structure of the organic semiconductor film 24, the characteristics of the organic semiconductor film 24 being a single crystal will not be damaged.

[0062] When the vibration sensor 10 having the above structure is used to detect the vibration of the object to be detected, the foot portion 13 is fixed to the object to be detected. In addition, a measuring instrument is connected to the lead wires 18 and 19.

[0063] When the detected object vibrates, the substrate 12 is elastically deformed so that the other end moves in the up-down direction by inertial force. Through the elastic deformation of the substrate 12, the organic semiconductor film 24 including the doping layer 26 is compressed or stretched. As a result, the strain of the organic semiconductor film 24 changes, the mobility of the carriers of the doping layer 26 changes, that is, the resistance of the organic semiconductor element 14 changes. When the substrate 12 is elastically deformed in the direction in which the other end of the substrate 12 moves upward relative to one end, the organic semiconductor film 24 is compressed, so the carrier mobility increases, and the resistance of the organic semiconductor element 14 decreases. In addition, when the substrate 12 is elastically deformed in the direction in which the other end of the substrate 12 moves downward relative to one end, the organic semiconductor film 24 is stretched, so the carrier mobility decreases, and the resistance of the organic semiconductor element 14 increases. Moreover, since the size of the compression and stretching of the organic semiconductor film 24 also changes with the size of the deformation of the substrate 12, the resistance of the organic semiconductor film 24 that increases or decreases accordingly can be obtained. In this way, vibration is detected by the vibration sensor 10.

[0064] The vibration sensor 10 in the above example is a cantilever beam structure, but Figure 7 As shown, a beam structure with both ends fixed may be adopted in which both ends of the substrate 12 provided with the sensor unit S are fixed by a pair of legs 41 .

[0065] The vibration sensor of the above example is an application example using an organic semiconductor element. Figure 8 An example of a diaphragm pressure sensor 43 using an organic semiconductor element 14 is shown. The pressure sensor 43 includes a substrate 12 on which a sensor portion S is formed and a container 44. The structure of the sensor portion S and the substrate 12 is the same as that of the above example. The container 44 is a hollow box having an opening on one surface, and the opening is hermetically sealed by the substrate 12. According to the pressure sensor 43, due to the difference between the pressure of the space 45 inside the container 44 and the pressure outside the container 44, the substrate 12 is elastically deformed, and the organic semiconductor element 14 is compressed or stretched accordingly. As a result, the external pressure can be detected as the resistance of the organic semiconductor film 24.

[0066] In addition, for example, the substrate 12 on which the sensor portion S is formed may be formed only of a resin layer such as polyparaxylene, and formed into a thin film that can be bent, deformed, or stretched freely, thereby forming a strain sensor. According to the strain sensor, the strain of the surface of the object to be detected can be detected by fixing the substrate 12 to the surface of the object to be detected.

[0067] In the above examples, an organic semiconductor element is provided between a pair of electrodes, but it is also possible to Fig. 9As shown, the electrodes 16 and 17 are arranged in a comb-teeth shape, and an organic semiconductor element 14 is provided between the electrode 16 and the electrode 17 as one sensor unit S. In such a structure, the resistance value of the element between the electrode 16 and the electrode 17 can be adjusted.

[0068] Next, an example of doping based on ion exchange is described. In doping based on ion exchange, the starting dopant is replaced with the final dopant (ion) by ion exchange via an intermediate between the organic semiconductor of the organic semiconductor film 24 and a substance different from the target dopant (hereinafter referred to as "starting dopant"), thereby forming a charge transfer complex between the organic semiconductor of the organic semiconductor film 24 and the final dopant. Doping by this method can increase the doping amount.

[0069] When the organic semiconductor of the organic semiconductor film 24 is set to A, the starting dopant is set to B, the ion that can form a salt with the final dopant (ion) (hereinafter referred to as "spectator ion") is set to C, and the final dopant (ion) (hereinafter referred to as "substitute ion" in the case of ion exchange) is set to D, when the organic semiconductor is P-type, the doping based on ion exchange is as shown in the following formula (4), and when the organic semiconductor is N-type, the doping based on ion exchange is as shown in the following formula (5).

[0070] [Number 2]

[0071] A+B+C+D→[A] + [B] - +[C] + +[D] -

[0072] →[A] + [D] - +[C] + +[B] - …(4)

[0073] A+B+C+D→[A] - [B] + +[C] - +[D] +

[0074] →[A] - [D] + +[C] - +[B] + …(5)

[0075] In the doping based on ion exchange, a treatment solution 50 (see Fig.10), the treatment liquid 50 is formed by dissolving a starting dopant having the same polarity (anion or cation) as the substitute ion in a liquid of a salt composed of spectator ions and substitute ions, i.e., an ionic liquid. In addition, the salt composed of the spectator ions and substitute ions does not need to be a liquid itself, and can also be dissolved in an organic solvent such as acetonitrile or butyl acetate. The substrate 12 on which the organic semiconductor film 24 is formed is immersed in the treatment liquid 50 for a predetermined period of time, and then the substrate 12 is taken out of the treatment liquid 50, and the surface is dried by blowing or the like. As a result, the substitute ions are adsorbed on the surface of the organic semiconductor film 24, and a doping layer 26 is formed on the surface (interface) of the organic semiconductor film 24. At this time, an extremely thin dopant film 25 composed of the adsorbed substitute ions is formed on the surface of the organic semiconductor film 24.

[0076] It should be noted that the replacement ion is the first ion that becomes the dopant, and the initial dopant (ion) is the second ion that oxidizes or reduces the organic semiconductor. In addition, when doping is performed by ion exchange, as long as the treatment liquid 50 can be brought into contact with the surface of the organic semiconductor film 24 and react as described above, for example, the treatment liquid 50 can be applied to the surface of the organic semiconductor film 24, or dripped or spread.

[0077] like Fig.10 As schematically showing the doping state of the organic semiconductor of the organic semiconductor film 24 when it is of P-type, when the organic semiconductor film 24 is immersed in the above-mentioned treatment solution 50, a redox reaction between the organic semiconductor and the starting dopant represented by the following formula (6) occurs on the surface of the organic semiconductor film 24: Fig.10 (A)). That is, the organic semiconductor (cation [A] + ) and the starting dopant (anion [B] - ) constitutes an intermediate ([A] + [B] - ), at which point charge transfer occurs between the organic semiconductor and the starting dopant, and carriers (holes in this case) are injected into the organic semiconductor film.

[0078] [Number 3]

[0079]

[0080] The redox reaction between the organic semiconductor and the starting dopant shown in formula (6) is reversible. When the equilibrium state is reached, the amount of the intermediate generated no longer increases. That is, the doping of the organic semiconductor film 24 based on the starting dopant no longer proceeds after the equilibrium state is reached. However, by the presence of a larger amount of the starting dopant (anion [B] - ) alternative ions (anions [D]) that are more easily chemically paired with organic semiconductors -), as shown in the following formula (7), the starting dopant (anion [B] - ) is replaced by anion (anion [D] - ) Replacement (ion exchange) ( Fig.10 (B)). If this substitution occurs, a redox reaction between the organic semiconductor and the starting dopant occurs in order to maintain a balanced state, and the starting dopant (anion, [B] - ) replaced ions (anions, [D] - ) replacement.

[0081] [Number 4]

[0082] [A] + [B] - +[D] - →[A] + [D] - +[B] - …(7)

[0083] It should be noted that when the organic semiconductor film 24 is a P-type organic semiconductor C8-DNBDT, the starting dopant is F4TCNQ, the replacement ion is TFSI-, and the bystander ion is EMMI + When , the above equations (6) and (7) become the following equations (8) and (9).

[0084] [Number 5]

[0085]

[0086] [C8DNBDT] + [F4TCNQ] - +TFSI -

[0087] →[C8DNBDT] + [TFSI] - +F4TCNQ - …(9)

[0088] As a result of the above reaction, the surface of the organic semiconductor film 24 is in a state of being doped with substitutional ions. The amount of doping in the organic semiconductor film 24 that has been doped is greater than that in the case where the doping is performed by immersing the organic semiconductor film 24 in a solution in which only the starting dopant is dissolved. In addition, since the above reaction occurs on the surface of the organic semiconductor film 24, doping can be performed well without disturbing the crystal structure of the organic semiconductor film 24. Furthermore, it has been confirmed that the doping state of the organic semiconductor film 24 is enhanced in terms of thermal stability and stability in the atmosphere. As data showing stability in the atmosphere, Fig.142 shows the change over time of the current flowing when a certain voltage is applied to the organic semiconductor element 14. It should be noted that this also applies when the organic semiconductor of the organic semiconductor film 24 is of N-type.

[0089] As a P-type organic semiconductor, a single crystal is used and the HOMO energy level satisfies the prescribed conditions with respect to the LUMO energy level of the starting dopant as described later. In addition, as an N-type organic semiconductor, a single crystal is used and the LUMO energy level satisfies the prescribed conditions with respect to the HOMO energy level of the starting dopant as described later. When the organic semiconductor film 24 is formed by the above-mentioned edge casting method, an organic semiconductor dissolved in an organic solvent is used.

[0090] When a P-type organic semiconductor is used, F4TCNQ is used as a starting dopant. As such a starting dopant, 7,7,8,8-tetracyanoquinodimethane, Mo(tfd-COCF3)3, etc. can also be used.

[0091] In the case of using a P-type organic semiconductor, when the HOMO energy level of the organic semiconductor is VH1 (eV) and the LUMO energy level of the starting dopant is VL1 (eV), the condition of "VH1 ≤ VL1 + 1.0 (eV)" should be satisfied.

[0092] In the case of using a P-type organic semiconductor, the replacement ion uses an anion with a closed shell structure that can form a salt with a spectator ion. For example, as such a replacement ion, tetrafluoroborate (BF4), hexafluorophosphate (PF6), hexafluoroantimonate (SbF6), carbonate ion, sulfonate ion, nitrate ion, phosphate ion, thiocyanate ion, cyanate ion, chloride ion, bromide ion, iodide ion, triiodide ion, fluoride ion, trifluoro[tris(pentafluoroethyl)phosphoric acid (FAP), bis(trifluoromethanesulfonyl)imide (TFSI), bis(pentafluoroethanesulfonyl)imide (TFESI), bis(oxalate)borate ion (BOB), bis(malonate)borate ion (MOB), tetrakis(pentafluorophenyl)borate ion (PFPB), tetrakis(35-trifluoromethyl)phenylboric acid (TFPB), ferric chloride ion (FeCl4), etc. can be used.

[0093] In the case of using a P-type organic semiconductor, the spectator ion is a cation having a closed shell structure and can form a salt with the substitute ion. As the spectator ion, metal ions modified with metal ions and cyclic ethers, organic molecular ions and their derivatives, Li, Na, Cs, Mg, Ca, Cu, Ag, imidazolium, morpholinium, piperidinium, pyrridinium, pyrrolidinium, ammonium, phosphonium, etc. can be used.

[0094] When an N-type organic semiconductor is used, cobalt ocene is used as the starting dopant. As such a starting dopant, decamethylcobalt ocene, ruthenium ocene, ferrocene, 1,3-dimethyl-2-phenyl-2,3-dihydrobenzimidazole, etc. can be used.

[0095] In the case of using an N-type organic semiconductor, when the LUMO energy level of the organic semiconductor is VL2 (eV) and the HOMO energy level of the starting dopant is VH2 (eV), the condition of “VL2 ≥ VH2 - 1.0 (eV)” should be satisfied.

[0096] In the case of using an N-type organic semiconductor, the substitute ion uses a cation having a closed shell structure that can form a salt with a spectator ion. For example, as such a substitute ion, metal ions modified with metal ions and cyclic ethers, organic molecular ions and their derivatives, Li, Na, Cs, Mg, Ca, Cu, Ag, imidazolium, morpholinium, piperidinium, pyrridinium, pyrrolidinium, ammonium, phosphonium, etc. can be used.

[0097] In the case of using an N-type organic semiconductor, the spectator ion is an anion having a closed shell structure and is capable of forming a salt with a substitute ion. As the spectator ion, tetrafluoroborate (BF4), hexafluorophosphate (PF6), hexafluoroantimonate (SbF6), carbonate ion, sulfonate ion, nitrate ion, phosphate ion, thiocyanate ion, cyanate ion, chloride ion, bromide ion, iodide ion, triiodide ion, fluoride ion, FAP, TFSI, TFESI, BOB, MOB, PFPB, TFPB, FeCl4, etc. can be used.

[0098] In order to achieve the reaction in which the substituent ion is replaced by the starting dopant that forms the intermediate, the Gibbs energy of the system should be stabilized by the pairing of the starting dopant with the spectator ion, or by the pairing of the organic semiconductor with the substituent ion.

[0099] Example

[0100] In the examples, the characteristics of the organic semiconductor element 14 were measured using a sample having a sensor portion S formed on a substrate 12. It should be noted that the sample had the organic semiconductor element 14 formed at the center in the longitudinal direction of the substrate 12, and the center of the substrate 12 was bent in each measurement. Fig. 9 As shown, the electrodes 16 and 17 are arranged in a comb-teeth shape, and the organic semiconductor element 14 is arranged between the electrode 16 and the electrode 17. It should be noted that the leg portion 13 is not provided in each sample.

[0101] Fig.11 The results of measuring the resistance change rate with respect to strain ε for samples 1 to 3 made using different dopant films 25 are shown. In the organic semiconductor films 24 of samples 1 to 3, C8- is a single crystal of DNBDT, and the dopant constituting the dopant film 25 in sample 1 is Mo(tfd-COCF3)3 ﹣ , in sample 2 it is SbF6 ﹣ , in sample 3 it is TFSI ﹣ In sample 1, Mo(tfd-COCF3)3 was used as the dopant material, and in sample 2, NO ﹢ SbF6 ﹣ As the dopant material, the dopant film 25 was formed by immersing the organic semiconductor film 24 in a solution in which the dopant material was dissolved in a solvent. In sample 3, doping was performed using the above-mentioned ion exchange method, in which F4TCNQ was the starting dopant and TFSI ﹣ is the replacement ion, EMMI ﹢ It is a bystander ion.

[0102] The strain ε is obtained by "ε=h / 2r" when the organic semiconductor element 14 is stretched as "positive" and compressed as "negative", the thickness of the substrate 12 is h, and the radius of curvature of the organic semiconductor element 14 is r. In addition, the resistance change rate is obtained by "ΔR / R×100(%)" when the resistance of the organic semiconductor element 14 when the substrate 12 is not deformed is R and the increase in the resistance of the organic semiconductor element 14 when the substrate 12 is deformed is ΔR. The amount of change in the resistance of the organic semiconductor element 14 is obtained by connecting the leads 18 and 19 to the bridge circuit and obtaining the output voltage of the bridge circuit.

[0103] from Fig.11 As can be seen from the curve, the resistance change rate with respect to strain ε is roughly the same regardless of the dopant and doping method. The strain coefficient k (=(ΔR / R) / ε) of samples 1 to 3 is about 20 in the compression direction, which is about 10 times the value when metal is used as a strain detection element. The strain coefficient k of the organic semiconductor element 14 in the expansion direction is greater than the strain coefficient in the compression direction.

[0104] in addition, Fig.12 The results of measuring the resistance change rate for a small strain ε for Sample 4 are shown. In Sample 4, the organic semiconductor film 24 is C 10 -DNBDT single crystals were produced by ion exchange with TFSI ﹣ The organic semiconductor element 14 is a dopant. Fig.12 As can be seen from the curve, the organic semiconductor element 14 can detect strain with high sensitivity even for a small strain ε of less than 0.01%. The strain coefficient k of the organic semiconductor element 14 in the measured small strain region is 14, which is still highly sensitive compared to when metal is used as the element (K=2).

[0105] Fig.13 The results of measuring the output voltage from the bridge circuit connected to the sensor unit S when the substrate 12 of sample 4 is fixed at both ends and the center of the substrate 12 is mechanically vibrated in the vertical direction are shown. In this measurement, the frequency of the vibration is 1300 Hz, the amplitude is 5 μm, and two input voltages of 3 V and 0 V are measured. When the input voltage is 0 V, it can be considered that the output voltage is generated by the influence of electromagnetic induction generated by the high-speed movement of the circuit of the sensor unit S in the environmental magnetic field.

[0106] Since the output voltage corresponding to the input voltage of 3 V and the output voltage corresponding to the input voltage of 0 V are significantly different in magnitude, the output voltage corresponding to the input voltage of 3 V shows that the organic semiconductor element 14 changes in response to the vibration of 1300 Hz. From this result, it can be seen that the response speed of the organic semiconductor element 14 is less than 1 ms. In addition, it can be seen that it has a high sensitivity that can detect a small amplitude of 5 μm.

[0107] From the above results, it is understood that the organic semiconductor film 24 in which the doping layer 26 is formed from the dopant film 25 can obtain a desired resistance without disturbing the single crystal structure.

[0108] Description of Reference Numerals

[0109] 10: Vibration sensor

[0110] 12: Substrate

[0111] 14: Organic semiconductor components

[0112] 16, 17: Electrode

[0113] 24: Organic semiconductor film

[0114] 25: Dopant film

[0115] 26: Doping layer

[0116] 50: Treatment fluid

Claims

1. An organic semiconductor device, characterized in that: include: an organic semiconductor film formed as a single crystal of an organic semiconductor; a doping layer formed on the surface of the organic semiconductor film; a dopant film disposed on the surface of the organic semiconductor film, supplying carriers to the surface of the organic semiconductor film and forming the doping layer, wherein the dopant film is composed of anions with a closed shell structure or cations with a closed shell structure adsorbed on the surface of the organic semiconductor film, The organic semiconductor element is a resistor through which a nominal current flows when a voltage is applied between a pair of electrodes electrically connected via the doping layer.

2. A strain sensor, characterized in that: include: The organic semiconductor element according to claim 1; The pair of electrodes are electrically connected through the doped layer; as well as A deformable substrate is provided, and the organic semiconductor element is formed on one surface of the deformable substrate.

3. A vibration sensor, characterized in that: include: The organic semiconductor element according to claim 1; The pair of electrodes are electrically connected through the doped layer; as well as The substrate has flexibility, one end or both ends of the substrate are fixed, and the organic semiconductor element is arranged on the surface of the flexible portion.

4. A method for manufacturing an organic semiconductor element, characterized in that: include: an organic semiconductor film forming step of forming an organic semiconductor film composed of a single crystal of an organic semiconductor on a substrate; as well as a dopant film forming step of forming a dopant film for supplying carriers to the surface of the organic semiconductor film, wherein the dopant film is composed of anions with a closed shell structure or cations with a closed shell structure adsorbed on the surface of the organic semiconductor film, In the dopant film formation process, a treatment liquid is brought into contact with the surface of the organic semiconductor film, an intermediate between a second ion and the organic semiconductor is formed through an oxidation-reduction reaction, and the second ion of the intermediate is replaced by a first ion, wherein the first ion becomes a dopant, the second ion has the same polarity as the first ion and oxidizes or reduces the organic semiconductor, and the treatment liquid is formed by dissolving the second ion in an ionic liquid composed of the first ion as a cation or anion or an organic solvent in which a salt thereof is dissolved.

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