WO2014136898A1 - 有機薄膜、これを用いた有機半導体デバイスおよび有機トランジスタ - Google Patents
有機薄膜、これを用いた有機半導体デバイスおよび有機トランジスタ Download PDFInfo
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- WO2014136898A1 WO2014136898A1 PCT/JP2014/055824 JP2014055824W WO2014136898A1 WO 2014136898 A1 WO2014136898 A1 WO 2014136898A1 JP 2014055824 W JP2014055824 W JP 2014055824W WO 2014136898 A1 WO2014136898 A1 WO 2014136898A1
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- 0 *C1SC(c(cc2)cc3c2c([s]c2ccccc22)c2[s]3)=CC1 Chemical compound *C1SC(c(cc2)cc3c2c([s]c2ccccc22)c2[s]3)=CC1 0.000 description 3
- ZDZMEHGAIHUZOB-UHFFFAOYSA-N CC(CC1)SC1c1ccc2c([s]c3c4cccc3)c4[s]c2c1 Chemical compound CC(CC1)SC1c1ccc2c([s]c3c4cccc3)c4[s]c2c1 ZDZMEHGAIHUZOB-UHFFFAOYSA-N 0.000 description 1
- ANJXBRDJCRGQSY-UHFFFAOYSA-N CC1=CCC(c(cc2)cc3c2c([s]c2c4cccc2)c4[s]3)S1 Chemical compound CC1=CCC(c(cc2)cc3c2c([s]c2c4cccc2)c4[s]3)S1 ANJXBRDJCRGQSY-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having a potential-jump barrier or a surface barrier
- H10K10/40—Organic transistors
- H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
- H10K10/462—Insulated gate field-effect transistors [IGFETs]
- H10K10/484—Insulated gate field-effect transistors [IGFETs] characterised by the channel regions
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D495/00—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms
- C07D495/02—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms in which the condensed system contains two hetero rings
- C07D495/04—Ortho-condensed systems
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3491—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom
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- H—ELECTRICITY
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
- H10K85/6576—Polycyclic condensed heteroaromatic hydrocarbons comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene
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- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/731—Liquid crystalline materials
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- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/40—Thermal treatment, e.g. annealing in the presence of a solvent vapour
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/655—Aromatic compounds comprising a hetero atom comprising only sulfur as heteroatom
Definitions
- the present invention relates to an organic thin film having a highly ordered structure obtained from a liquid crystal substance, which can be suitably used for various devices, and further relates to an organic semiconductor device and an organic transistor using the thin film.
- Organic substances that can transport electronic charges by holes and electrons can be used as organic semiconductors, and can be used as photoconductors, photosensors, organic EL elements, organic transistors, organic solar cells, organic memory elements, etc. It can be used as a material for electronic devices.
- a thin film transistor using amorphous silicon or polycrystalline silicon is widely used as a switching element for a liquid crystal display device or an organic EL display device. It is used.
- these transistors using silicon are expensive to manufacture and are formed at high temperatures, so that they cannot be developed on plastic substrates with poor heat resistance.
- an organic transistor using an organic semiconductor as a channel semiconductor layer instead of a silicon semiconductor has been proposed.
- Patent Document 1 and Patent Document 2 include 2,7-substituted [1] benzothieno [3,2-b] [1] benzothiophene skeleton (hereinafter referred to as [1] benzothieno [3,2-b] [1 Benzothiophene is abbreviated as BTBT), and has been reported to exhibit a mobility equal to or higher than that of amorphous silicon.
- Liquid crystal materials are positioned as a new type of organic semiconductor that exhibits a high mobility ((10 ⁇ 4 cm 2 / Vs to 1 cm 2 / Vs)) that forms a self-organized molecular aggregate phase (liquid crystal phase).
- Liquid crystal substances are characterized by the fact that alignment defects peculiar to liquid crystals such as domain interfaces and disclinations are difficult to form electrically active levels.
- conventional amorphous organic semiconductor materials and crystalline organic semiconductor materials In fact, it has been clarified to have excellent characteristics that are not seen in the field of electronic devices such as photosensors, electrophotographic photoreceptors, organic EL devices, organic transistors, and organic solar cells. A prototype is being made.
- the liquid crystal material has a great feature that in the liquid crystal phase, it is possible to easily control the molecular orientation, which is generally difficult with non-liquid crystal materials.
- a liquid crystal material when a liquid crystal material is injected between two substrates, such as a liquid crystal cell, generally, at the liquid crystal phase temperature, the liquid crystal molecules generally lie on the surface of the substrate with respect to the molecular long axis.
- the molecular long axis tends to be easily aligned with the substrate surface.
- the thin film of liquid crystal aligned at the liquid crystal phase temperature is phase-changed to the crystal phase by lowering the temperature, thereby controlling the molecular orientation not only in the liquid crystal phase but also in the crystal phase (crystal thin film ) Can be easily produced. This is difficult to realize with a general non-liquid crystalline organic material.
- liquid crystal thin film liquid crystal phase thin film
- a liquid crystal substance can be said to be a material having a high degree of freedom as an organic semiconductor in that it can be applied to an electronic device as an organic semiconductor material not only as a liquid crystal thin film but also as a crystal thin film (for example, Non-Patent Document 1). ).
- the key is to form a thin film with a crystalline state.
- Patent Document 3 describes a design guideline for obtaining a liquid crystal material exhibiting high mobility.
- a liquid crystal material exhibiting high mobility.
- the organic thin film in any crystalline state is described. It is not known qualitatively or quantitatively whether organic transistors having high mobility and high performance stability can be obtained, and organic thin films and organic transistors having mobility and performance stability are not known. Development was an issue.
- An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide an organic thin film and an organic transistor having high performance stability as well as mobility.
- the organic thin film of the present invention is based on the above findings. More specifically, the organic thin film has a charge transporting molecular unit A having an aromatic condensed ring structure, a unit B as a side chain, and an N phase and an SmA phase. And an organic thin film having a bilayer structure obtained from a liquid crystal substance exhibiting a phase other than the SmC phase.
- liquid crystal substances include high-molecular liquid crystals and low-molecular liquid crystals.
- the liquid crystal phase generally has a high viscosity, so that ion conduction tends not to occur.
- a low molecular liquid crystal when ionized impurities are present, a low-order liquid crystal having a strong liquid property such as a nematic phase (N phase), a smectic A phase (SmA phase, hereinafter described in the same manner) or an SmC phase. In the phase, ionic conduction tends to be induced.
- ionized impurity refers to an electrically active impurity (that is, a HOMO level, a LUMO level, or both of them, which can become a trap of ions and charges generated by dissociation of ionic impurities.
- An impurity whose level is between the HOMO and LUMO levels of the liquid crystal substance is an ionized product generated by photoionization or charge trapping (for example, M. Funahashi and J. Hanna, Impurity effect). on charge carrier transport in Smetic liquid crystals, Chem.sPhys. Lett., 397,319-323 (2004), H. Ahn, A. Ohno, and Jo nt of Impurity in Smectic Liquid Crystals, Jpn. J. Appl. Phys., Vol. 44, referring to the No. 6A, 2005, pp. 3764-37687.).
- the above-described smectic liquid crystal material that forms a nematic phase or a molecular aggregate layer without molecular arrangement is included in the molecular layer. Since the SmA phase and the SmC phase that do not have order of molecular arrangement have high fluidity, ion conduction is easily induced, which is a big problem when used as an organic semiconductor.
- liquid crystal phase other than N phase, SmA phase and SmC phase having molecular order in the molecular layer, that is, higher-order smectic phase (SmB, SmB cryst , SmI, SmF, SmE, SmJ, SmG, SmK, SmH, and the like) have a characteristic that it is difficult to induce ionic conduction at this point (convenient when used as an organic semiconductor). Further, in general, since the alignment order is high as compared with a low-order liquid crystal phase, it exhibits high mobility. (Refer to H. Ahn, A. Ohno, and J. Hanna, “Impactity effects on charge carrier transport in various mesophases of Sequential liquid crystal”, J.p.
- the higher order liquid crystal phase with higher order of molecular arrangement in the smectic phase is higher It has been clarified to show mobility, and from the viewpoint of realizing high mobility as well as suppression of ion conduction, a liquid crystal substance exhibiting a high-order smectic phase is useful as an organic semiconductor.
- a liquid crystal material when used as an organic semiconductor in the form of a crystal thin film, a liquid crystal material in which a low-order liquid crystal phase (N phase, SmA phase, or SmC phase) having a strong liquid property appears in a temperature region immediately above the crystal phase. Then, when the element is heated above the temperature at which the liquid crystal phase appears, there is a big problem that the element is destroyed by heat due to fluidity.
- a liquid crystal substance that expresses a high-order smectic phase having molecular arrangement order in the molecular layer in the temperature region immediately above the crystal phase even when the element is heated to the liquid crystal temperature, the fluidity is high.
- the liquid crystal material Since the device is difficult to be destroyed because it is low, a liquid crystal material exhibiting a higher-order liquid crystal phase is required even when a crystal thin film of a liquid crystal material is applied to an electronic device as an organic semiconductor. Even if it is not a phase, it may be a substance exhibiting a metastable crystal phase). In other words, if the liquid crystal material is a liquid crystal material exhibiting a liquid crystal phase other than a strongly liquid low-order liquid crystal phase (N phase, SmA phase or SmC phase) or a material exhibiting a metastable phase, it is preferably used in the present invention. It can be used.
- the molecular orientation of the liquid crystal phase is ordered as the temperature decreases, so that in a high temperature region, the liquid crystal substance is a low-order liquid crystal phase with strong liquidity ( N phase, SmA phase, and SmC phase) appear, and it is well known that a higher-order liquid crystal phase or metastable crystal phase having the highest orientation order appears in a temperature region adjacent to the crystal phase temperature.
- a liquid crystal phase thin film is used as an organic semiconductor material, it can be used as an organic semiconductor in principle as long as it is a phase other than the above-mentioned strong liquid crystalline low-order liquid crystal phase.
- the aggregated phase appearing in is not a low-order liquid crystal phase (N phase, SmA phase or SmC phase) having a strong liquid property.
- the liquid crystal property in the low liquid crystal phase is strong, so the molecular orientation Is easier to control than the higher-order liquid crystal phase.
- an organic thin film showing not only high mobility but also high performance stability is provided.
- FIG. 2 is a drawing of XDR measurement in Example 1.
- FIG. 3 is a diagram for deriving mobility in the first embodiment. It is drawing which confirms the position of the sulfur atom after film forming (no post-processing). It is drawing which confirms the position of the sulfur atom after thermal annealing. 1 is a drawing of a single crystal of Compound 24. 1 is a drawing of a single crystal of Compound 24.
- this invention is comprised from the following items.
- (I) A film formed of a charge transporting molecular unit A having an aromatic condensed ring structure and a compound having unit B as a side chain, the compound having a bilayer structure An organic thin film characterized by that.
- (II) The compound according to (I), further comprising a hydrogen atom, a halogen, a lower alkyl group having 1 to 4 carbon atoms, or a cyclic structure unit C connected to the charge transporting molecular unit A by a single bond.
- Organic thin film is comprised from the following items.
- phase other than N phase, SmA phase, and SmC phase is a liquid crystal phase selected from the group consisting of SmB, SmBcrystal, SmI, SmF, SmG, SmE, SmJ, SmK, and SmH
- VI The organic thin film according to any one of (I) to (V), wherein the number of condensed rings (NA) of the charge transporting molecular unit A is 3 or more and 5 or less.
- the side chain unit B may have a substituent, an alkyl group having 2 to 20 carbon atoms, an optionally substituted alkenyl group having 2 to 20 carbon atoms, or a carbon group having 2 to 20 carbon atoms.
- X represents S, O, NH
- m is an integer of 0 to 17, and n is an integer of 2 or more.
- the cyclic structural unit C is unsubstituted or an aromatic hydrocarbon group having a halogen or a lower alkyl group having 1 to 4 carbon atoms as a substituent, or unsubstituted, or a halogen or carbon number 1 to 1 4 is a group represented by a heteroaromatic group having a lower alkyl group as a substituent, or any one of (II) to (X) below (3) or (4) Organic thin film as described in 2.
- Ar 1 is unsubstituted or an aromatic hydrocarbon group having a halogen or a lower alkyl group having 1 to 4 carbon atoms as a substituent, or an unsubstituted or halogen or lower alkyl group having 1 to 4 carbon atoms.
- Heteroaromatic group as a substituent Ar 2 is an aromatic hydrocarbon group which may have a substituent, R ′ is unsubstituted, or has a halogen or a lower alkyl group having 1 to 4 carbon atoms as a substituent
- (XII) In the method for producing an organic thin film according to any one of (I) to (XI), The manufacturing method of the organic thin film characterized by including the process of annealing this organic thin film.
- (XIII) An organic semiconductor device using the organic thin film according to any one of (I) to (XI).
- XIV An organic transistor using the organic thin film according to any one of (I) to (XI) as an organic semiconductor layer.
- XV An organic semiconductor device using an organic thin film obtained by the method for producing an organic thin film of (XII).
- (XVI) An organic transistor using an organic thin film obtained by the method for producing an organic thin film of (XII) as an organic semiconductor layer.
- the bilayer structure of the present invention refers to a bimolecular film structure in which two charge transporting molecular units A are paired face to face to form one layer.
- the ⁇ electron cloud is relatively expanded and the mobility is increased.
- the bilayer structure becomes a continuously grown crystal, whereby an organic thin film with few charge transfer defects, that is, high performance stability can be obtained.
- the bilayer structure of the present invention can be confirmed by synchrotron radiation X-ray scattering measurement.
- the synchrotron radiation X-ray scattering measurement includes small-angle X-ray scattering and wide-angle X-ray scattering.
- small angle X-ray scattering is a method of obtaining structural information of a substance by measuring X-rays scattered by irradiating the substance with X-rays and having a small scattering angle. Yes, the size, shape, regularity, and dispersibility of the internal structure are evaluated. The smaller the scattering angle, the larger the size of the corresponding structure.
- Wide-angle X-ray scattering is a technique for obtaining structural information of a substance by measuring X-rays scattered by irradiating the substance with X-rays and having a large scattering angle. Yes, structural information smaller than small-angle X-ray scattering can be obtained. In addition to being used for crystal structure analysis, information on the degree of orientation of the sample can also be obtained.
- Small-angle X-ray scattering measurement and wide-angle X-ray scattering measurement can be performed with a commercially available general-purpose X-ray apparatus, but large-sized radiation is used for measuring a small area of an organic thin film of 100 nm or less as used in an organic transistor. It is preferable to perform small-angle X-ray scattering measurement and wide-angle X-ray scattering measurement using synchrotron radiation X-rays with a large synchrotron radiation facility such as the optical facility SPring-8 (Spring Eight).
- SPring-8 is a large synchrotron radiation facility in the city of Harima Science Park in Hyogo Prefecture that can produce the world's highest performance synchrotron radiation. Synchrotron radiation accelerates electrons to almost the same speed as light. It is a thin and powerful electromagnetic wave that is generated when the traveling direction is bent by a magnet.
- the synchrotron X-rays available in SPring-8 are X-rays obtained by a commercially available general-purpose X-ray apparatus. Since it has a luminance of 100 million times that of a line, sufficient strength can be obtained even in the measurement of a very small area and a very thin film.
- An example of the measurement of synchrotron radiation X-ray scattering is shown below.
- the measurement mode is grazing incidence / small-angle X-ray scattering (Grazing Incident Small Angle Scattering / Wide Angle Scattering: GISAXS / WAXS), camera length 140mm, 2300mm, wavelength 0.1nm, X-ray incident angle 0.08 ° or 0.16 °, exposure time 1-5 seconds, measurement temperature 25 ° C, scattering angle range
- the structure of the thin film was obtained by analyzing the obtained two-dimensional X-ray scattering image by the following method.
- the position of the reflected X-ray beam center in the two-dimensional scattered image is determined from the X-ray incident angle at the time of measurement, and the scattering / diffraction intensity I on the straight line in the horizontal direction as viewed from the center of the reflected beam is taken.
- a one-dimensional scattering profile H was obtained as the scattering intensity I.
- the scattering / diffracting intensity I on a straight line in the vertical upward direction when viewed from the center of the reflected beam was taken, and a one-dimensional scattering profile V was obtained as the scattering intensity I with respect to the scattering angle 2 ⁇ from the center of the reflected beam.
- ⁇ [nm] is an X-ray wavelength of 0.1 nm.
- a periodic length of about 4 cm or the like derived from a periodic structure (plane spacing) having an orientation almost orthogonal to the molecular chain in the arrangement structure of the molecule is calculated.
- a period length of about 30 cm derived from the molecular length was calculated.
- this organic thin film has compound molecules standing perpendicular to the substrate, and is laminated every about 30 mm corresponding to the molecular length. It was confirmed that a bilayer structure was formed.
- liquid crystal substances when the compound having the charge transporting molecular unit A having an aromatic condensed ring structure and the unit B as a side chain is a liquid crystal compound, it can be more preferably used.
- liquid crystal substances particularly smectic liquid crystal substances, form a coherent phase (smectic liquid crystal phase) having a layered structure in a self-organized manner, so that it can be used as a precursor for forming a crystalline phase, thereby smoothing the surface. Excellent sex. This is because a uniform crystal film can be easily obtained over a large area.
- it since it has a liquid crystal phase, it is advantageous over non-liquid crystal materials in that heat treatment can be performed at the liquid crystal phase temperature.
- liquid crystal compounds exhibiting a liquid crystal phase described below are particularly preferable.
- the above “liquid crystal phase other than N phase, SmA phase, and SmC phase” is a liquid crystal phase selected from the group consisting of SmB, SmBcryst, SmI, SmF, SmE, SmJ, SmG, SmK, and SmH. It is preferable. This is because, when the liquid crystal material according to the present invention is used as an organic semiconductor in a liquid crystal phase, as described above, these liquid crystal phases have a low fluidity, so that it is difficult to induce ionic conduction, and the molecular alignment order is low. This is because high mobility can be expected in the liquid crystal phase.
- liquid crystal substance according to the present invention when used as an organic semiconductor in a crystal phase, these liquid crystal phases are less fluid than N phase, SmA phase, and SmC phase, so that the liquid crystal phase is increased by increasing the temperature. This is because the element is not easily destroyed even when it is transferred to.
- the liquid crystal phase appears only in the temperature lowering process, once crystallized, the crystal temperature region is widened, which is convenient for application in the crystal phase.
- the “phase other than the N phase, the SmA phase, and the SmC phase” is SmBcryst, SmE, SmF, SmI, SmJ, SmG, SmK, or SmH in the temperature lowering process.
- SmE and SmG which are higher-order Sm phases
- SmE and SmG are adjacent to the liquid crystal phase when the organic semiconductor material is heated from the crystal phase.
- a liquid crystal phase appearing in the temperature range Particularly preferred as a liquid crystal phase appearing in the temperature range.
- a liquid crystal substance in which a high-order liquid crystal phase appears in addition to a liquid-like low-order liquid crystal phase (N phase, SmA phase, or SmC phase) has high liquidity in the low-order liquid crystal phase. Since the molecular orientation is easier to control than the higher-order liquid crystal phase, the molecules are pre-aligned in the lower-order liquid crystal phase and then transferred to the higher-order liquid crystal phase. Since a liquid crystal thin film with few defects can be obtained, the quality of the liquid crystal thin film or the crystal thin film can be improved.
- the operating temperature required for a device using the liquid crystal material is usually ⁇ 20 ° C. to 80 ° C. Therefore, in the present invention, “phases other than N phase, SmA phase and SmC phase” appear. It is required that the temperature range to be ⁇ 20 ° C. or higher.
- the liquid crystal substance according to the present invention is used as an organic semiconductor in a crystal phase, it is effective to improve the quality by using a thin film in a liquid crystal state (liquid crystal thin film) as a precursor for producing a crystal thin film. For this reason, considering the simplicity of the process and the ease of selection of the substrate, the temperature at which the liquid crystal phase of the liquid crystal material appears is preferably 200 ° C. or lower.
- the organic semiconductor material that can be used in the present invention is an organic semiconductor material having a charge transporting molecular unit A having an aromatic condensed ring structure and a unit B as a side chain, and preferably further comprising a single bond with the unit A. It is an organic semiconductor material having a hydrogen atom, a halogen, a lower alkyl group having 1 to 4 carbon atoms, or a cyclic structural unit C connected thereto.
- Suitable charge transporting molecular unit A In organic semiconductors, the molecular site involved in charge transport is a conjugated ⁇ -electron unit consisting of an aromatic ring. Generally, the larger the size of the conjugated ⁇ -electron system, the more advantageous for charge transport, but the size of the ⁇ -electron system. However, the solubility in an organic solvent decreases and the melting point becomes high, so that there is a problem that a process at the time of synthesis or use as an organic semiconductor becomes difficult. For this reason, the number of condensed rings of the charge transporting molecular unit is preferably 3 or more and 5 or less.
- the charge transporting molecular unit A may include a heterocycle.
- the number of carbon atoms in each ring constituting the condensed ring is preferably 5 to 6 (that is, a 5 to 6 membered ring) for the convenience of synthesis.
- the heterocycle constituting the charge transporting molecular unit A is also preferably a 5-membered to 6-membered ring.
- the number of heterocycles is not particularly limited, but is preferably the following numbers.
- the melting point can be used as a guide. This is because the melting point gives a measure of the cohesive energy of the compound.
- a compound having a high melting point means a strong interaction between molecules at the time of agglomeration, which corresponds to easy crystallization and is convenient for inducing the expression of a higher-order liquid crystal phase. Therefore, the melting point of the compound constituting the unit A (the compound constituted when there is no bond with the unit B and the unit C) is preferably 120 ° C.
- a melting point of 120 ° C. or lower is not preferable because a low-order liquid crystal phase tends to develop.
- the compound constituting the unit A will be specifically described below with examples.
- the compound constituting the unit A in question here excludes the single bond with the unit C, and the position of the following unit A where the single bond is present It becomes a compound of the following formula (1) in which a hydrogen atom is substituted.
- the compound constituting the unit A is benzothieno [3,2-b] [1] benzothiophene, and the melting point of the benzothieno [3,2-b] [1] benzothiophene It is the melting point of the constituent compound.
- the unit C is the “another structure” part for giving the freedom of flip-flop motion.
- the unit C is preferably an aromatic condensed ring connected to the charge transporting unit A by a single bond or an alicyclic molecular structure.
- the number of rings is preferably 1 or more and 5 or less (more preferably 3 or less, particularly 1 to 2).
- the number of rings of the unit C is not particularly limited, but when the number of rings constituting the unit A is “NA” and the number of rings constituting the unit C is “NC”, NA ⁇ NC may be satisfied. preferable. More specifically, the following numbers are preferable.
- Unit C may contain a heterocycle.
- the heterocycle is preferably a 5-membered to 6-membered ring.
- the unit C is preferably an aromatic compound, an aromatic condensed ring compound, a cycloalkane, a cycloalkene, an alicyclic saturated compound containing a hetero atom, or the like, as exemplified below.
- cycloalkene cyclopentene, which is considered to have higher planarity than cyclohexene, is preferred.
- the unit A and the unit C need to be directly connected by a single bond.
- the unit B can be connected to the above unit A or unit C, for example. From the viewpoint of expanding the crystal temperature region when used as a crystal thin film, it is preferably connected to “one of” unit A or unit C described above.
- the unit B is preferably a hydrocarbon or a compound having a linear structure such as a saturated compound having a hetero atom, particularly preferably a hydrocarbon having 2 to 20 carbon atoms, or the general formula (2)
- the unit B existing as a side chain in at least one of the unit A and the unit C has a cyclic structure (A or C) to which the unit is bonded, and the cyclic structure is another cyclic structure (ie, C Or it is preferable that it exists in the position which is not adjacent with respect to the position connected or condensed with A).
- the example of the coupling position is as shown in the structure exemplified later.
- the bonding position of the unit B will be described using a specific compound used in the organic semiconductor material of the present invention.
- the unit A is benzothieno [3,2-b] [ 1] benzothiophene
- unit C is a phenyl group
- unit B is C 10 H 21
- unit A benzothieno [3,2-b] [1] benzothiophene
- unit B indicates that C 10 H 21 is bonded.
- the binding position can be similarly shown for the compounds of the present invention having other units.
- the number of repeating units A may be 1 or 2, but the entire structure of the compound as in compound 58 may be repeated. 1 may be 1 or 2.
- the transfer integral of a ⁇ -electron molecular unit that is related to charge transport, called a core, is large as a factor governing the charge transfer rate in a liquid crystal phase or a crystal phase that is molecularly oriented. Is important. In order to actually calculate this value by the quantum chemical method, it is necessary to determine the specific molecular arrangement between adjacent molecules in the target molecular aggregation state and perform the calculation. For example, a molecular structure having an extended ⁇ -electron system with redundancy is advantageous against fluctuations relative to each other's relative molecular positions.
- a rod-like and somewhat large size ⁇ -electron conjugated system is selected as the charge transporting molecular unit consisting of a ⁇ -electron conjugated system serving as a charge transport site.
- a condensed ring is used instead of using a small aromatic ring, which is often employed as the structure of liquid crystal molecules, for example, benzene, thiophene, etc., connected by a single bond to form a large ⁇ -electron conjugated system.
- a molecular unit having a large ⁇ -electron conjugated system depending on the structure is used.
- the number of condensed rings is preferably 3 or more, but if the number of rings is too large, the solubility in a solvent is lowered, so 5 or less is realistic.
- aromatic ring structures that is, in the present invention, benzene, pyridine, pyrimidine, thiophene, thiazole, imidazole, furan are used as aromatic ring structures, and these are condensed to form a rod-like three-ring structure, four-ring structure, and five-ring structure.
- the aromatic ⁇ -electron conjugated fused ring structure is preferable.
- a structure in which at least another rigid structure is connected to the above-mentioned aromatic ⁇ -electron conjugated condensed ring structure through a single bond is used as the main core structure constituting the liquid crystal molecule.
- a structure having the same or less number of rings as the aromatic ⁇ -electron conjugated condensed ring structure described above is selected, and may be 1 or 2.
- the structure is not necessarily an aromatic ring in a broad sense including a heterocycle, but an alicyclic ring structure such as cyclohexane or cyclopentane, or cyclohexene or cyclopentene containing a double bond. Also good.
- a flexible hydrocarbon for imparting rod-like molecular shape anisotropy and liquidity to a rigid molecular unit called a core portion.
- the basic design of the rod-like liquid crystal material is to connect the units and to have a structure in which they are basically arranged in a straight line.
- the core portion corresponds to a structure in which at least another rigid structure is connected to the above-mentioned aromatic ⁇ -electron conjugated condensed ring structure through a single bond. It is important for the connecting position of the unit B in the core part to give rod-like anisotropy as a whole molecule. In that case, the position of the unit B connected to the core part is either the unit A or the unit C as long as they are far from each other when viewed from the single bond connecting the unit A and the unit C. You may connect to both. Regarding the molecular shape when the units B are connected, it should be noted that, when the structure of the whole molecule has a large bend, it is generally difficult to induce a smectic phase.
- this molecular design can be given by the fluctuation width when the molecule of the core part is rotated about the single bond between the unit B and the core part. More specifically, the carbon atom to which the unit B is bonded and the carbon or hetero element located on the outermost side of the core part of the unit A or unit C not directly bonded to the unit B when the molecule is rotated are connected. If the angle between the straight line and the axis is ⁇ , and the blur width is described, this blur width ⁇ can increase the expression of the liquid crystal phase and the mobility, and is 90 ° or less, more preferably 60 °.
- the structure is preferably less than or equal to, more preferably less than or equal to 30 degrees.
- the angle formed by two single bonds is preferably 90 ° or more, more preferably 120 ° or more.
- a unit B structure containing a double bond or triple bond, or a hetero element such as oxygen, sulfur or nitrogen can also be used.
- a hetero element such as oxygen, sulfur or nitrogen
- a substance that exhibits a higher-order smectic liquid crystal phase and is useful as an organic semiconductor can be screened as necessary from among compounds satisfying the above-described molecular design.
- this screening basically, when used as an organic semiconductor in a liquid crystal phase, a higher order smectic phase is expressed, and when used as an organic semiconductor in a crystal phase, when cooled from a temperature higher than the crystal phase temperature, It is preferable to select one that does not develop a low-order liquid crystal phase adjacent to the crystal phase.
- This selection method can select a substance useful as an organic semiconductor material by making a determination according to a “screening method” described later.
- Scheme A shows the basic concept of the present invention.
- Unit A and unit C are called core parts in liquid crystal molecules, and unit B (preferably a unit having 3 or more carbon atoms) is arranged on one side or both sides of the core part in the molecular major axis direction of the core part.
- unit B preferably a unit having 3 or more carbon atoms
- the liquid crystal phase is stable in the substance in which the hydrocarbon chain is directly connected to the core part as in the examples of dialkylpentenecene and dialkylbenzothienobenzothiophene.
- the liquid crystal phase is not developed, or even if the liquid crystal phase is developed, only the low-order liquid crystal phase such as the SmA phase is developed (Non-Patent Document Liquid Crystal. Vol. 34. No. 9 (2007). ) 1001-1007. Liquid Crystal.Vol.30.No.5 (2003) 603-610).
- a hydrocarbon chain is connected to the structure (core part) in which another rigid structural unit is connected to such a charge transporting molecular unit, thereby giving the molecule anisotropy and liquidity of a rod-like molecular shape. Therefore, the liquid crystal phase can be induced with a high probability.
- a liquid crystal phase can often be developed.
- the appearance temperature region of the liquid crystal phase is often asymmetric between the temperature lowering process and the temperature increasing process. This generally helps to extend the liquid crystal phase temperature region to a low temperature during the temperature lowering process, and conversely to expand the crystal phase to a high temperature region during the temperature rising process.
- This characteristic means that when a polycrystalline thin film of a liquid crystal material is used as an organic semiconductor, the liquid crystal thin film can be produced at a lower temperature when the polycrystalline thin film is produced using the liquid crystal thin film (thin liquid crystal phase thin film) as a precursor.
- the process becomes easier.
- the fact that the crystal phase temperature in the temperature rising process spreads to a high region means that the thermal stability of the produced polycrystalline film is improved, which is convenient as a material.
- the developed liquid crystal phase is generally stabilized, which is convenient for application to a device using the liquid crystal phase.
- the usefulness of the substance according to the present invention basically exhibits a higher-order smectic phase when used as an organic semiconductor in a liquid crystal phase.
- the usefulness of the substance according to the present invention when used as an organic semiconductor in the crystalline phase, it is difficult to form cracks or voids in the crystalline thin film when cooled from a temperature higher than the crystalline phase temperature, and a low-order liquid crystal phase is expressed adjacent to the crystalline phase. It is made use of by choosing what does not.
- a liquid crystal phase other than a nematic phase, an SmA phase, or an SmC phase is expressed in a temperature region adjacent to the crystal phase, or when used as an organic semiconductor in a crystal phase.
- the criterion is that cracks and voids are less likely to form when the crystal phase is cooled and transitioned to a crystal phase from a temperature range higher than the crystal phase.
- test substance After the isolated test substance is purified by column chromatography and recrystallization, it is confirmed by thin layer chromatography on silica gel that the test substance shows a single spot (that is, not a mixture).
- the temperature at which this texture appears is defined as the crystallization temperature, and it is confirmed that the texture appearing in a temperature region higher than that temperature is not a nematic phase, SmA phase, or SmC phase.
- a characteristic schlieren texture expressed as a pincushion is observed, and when it shows an SmA phase or an SmC phase, it has a fan-like texture with a uniform structure in the region. Since the characteristic texture which has is observed, it can determine easily from the characteristic texture.
- the visual field changes instantaneously at the phase transition temperature, but the phase transition texture almost changes.
- the texture of the formed SmB phase, SmF phase, and SmI phase may be mistaken for the SmA phase and the SmC phase, so care should be taken.
- the energy levels of the HOMO and LUMO of the core part are also important.
- the HOMO level of an organic semiconductor is determined by dissolving a test substance in a dehydrated organic solvent such as dichloromethane to a concentration of, for example, 1 mmol / L to 10 mmol / L, and adding a supporting electrolyte such as a tetrabutylammonium salt.
- the HOMO level and LUMO level can be estimated from the difference between the peak potential and the reference potential, for example, a known substance such as ferrocene. If the HOMO level and LUMO level are outside the potential window of the organic solvent used, the HOMO-LUMO level is calculated from the absorption edge of the UV-visible absorption spectrum and subtracted from the measured level. Can be estimated. This method is referred to J. Pommerehne, H. Vestweber, W. Guss, sR. F. Mahrt, H. Bassler, aM. Porsch, and J. Daub, Adv. Mater., 1995, 551 (1995). be able to.
- the HOMO and LUMO levels of an organic semiconductor material provide a measure of electrical contact with the anode and cathode, respectively, and charge injection is limited by the size of the energy barrier determined by the difference from the work function of the electrode material. So be careful.
- the work function of a metal is often silver (Ag) 4.0 eV, aluminum (Al) 4.28 eV, gold (Au) 5.1 eV, calcium (Ca) 2.87 eV, as examples of materials used as electrodes.
- the work function difference between the organic semiconductor material and the electrode substance is preferably 1 eV or less, more preferably 0.8 eV or less. More preferably, it is 0.6 eV or less.
- the work function of the metal the following documents can be referred to as necessary. Reference D: Chemical Handbook Basic Edition Revised 5th Edition II-608-610 14.1 b Work Function (Maruzen Publishing Co., Ltd.) (2004)
- the size of the conjugated system can be used as a reference when selecting materials.
- Examples of “charge transporting molecular unit A” that can be suitably used in the present invention are as follows.
- X represents S, O, NH.
- annular structure unit C An example of the “annular structure unit C” that can be suitably used in the present invention is as follows. Unit C may be the same as unit A.
- Ar 1 of the substituent represented by the general formula (3) is not particularly limited as long as it is an aromatic hydrocarbon group that may have a substituent or a heteroaromatic group that may have a substituent.
- Ar 1 of the substituent represented by the general formula (3) is not particularly limited as long as it is an aromatic hydrocarbon group that may have a substituent or a heteroaromatic group that may have a substituent.
- the following can be mentioned.
- An unsubstituted monocyclic or polycyclic aromatic hydrocarbon group having 6 to 24 carbon atoms such as a p-terphenyl group or a quarterphenyl group,
- o-tolyl group m-tolyl group, p-tolyl group, 2,4-xylyl group, 2,6-xylyl group, mesityl group, duryl group, 4-ethylphenyl group, 4-n-propylphenyl group, 4
- An alkyl-substituted aromatic hydrocarbon group in which the aromatic hydrocarbon group is substituted with an alkyl group having 1 to 4 carbon atoms, such as isopropylphenyl group and 4-n-butylphenyl group;
- Ar 2 of the substituent represented by the general formula (3) is not particularly limited as long as it is an aromatic hydrocarbon group which may have a substituent, but examples thereof include the following. .
- 6 carbon atoms such as phenylene group, naphthylene group, azulylene group, acenaphthenylene group, anthrylene group, phenanthrylene group, naphthacenylene group, fluorenylene group, pyrenylene group, chrysenylene group, peryleneylene group, biphenylene group, p-terphenylene group, quarterphenylene group, etc.
- the aromatic hydrocarbon group is an alkyl group having 1 to 10 carbon atoms, such as a tolylene group, a xylylene group, an ethylphenylene group, a propylphenylene group, a butylphenylene group, a methylnaphthylene group, or a 9,9′-dihexylfluorenylene group.
- a substituted alkyl-substituted aromatic hydrocarbon group is an alkyl group having 1 to 10 carbon atoms, such as a tolylene group, a xylylene group, an ethylphenylene group, a propylphenylene group, a butylphenylene group, a methylnaphthylene group, or a 9,9′-dihexylfluorenylene group.
- Examples thereof include a halogenated aromatic hydrocarbon group in which the aromatic hydrocarbon group is substituted with a halogen such as a fluorine atom, a chlorine atom, or a bromine atom, such as a fluorophenylene group, a chlorophenylene group, or a bromophenylone group.
- a halogen such as a fluorine atom, a chlorine atom, or a bromine atom
- fluorophenylene group such as a fluorophenylene group, a chlorophenylene group, or a bromophenylone group.
- R ′ represented by the general formula (4) is a halogen atom such as a hydrogen atom, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, a chlorine atom, a bromine atom or an iodine atom. Is an atom.
- the “single bond” for linking the above units A and C which can be preferably used in the present invention, is a combination of carbons in the molecular major axis direction among the carbons constituting the cyclic structure of the units A and C. Choose so that the whole is a stick. That is, in the present invention, the carbon constituting the unit A and the carbon constituting the unit C are directly connected by a “single bond”.
- the unit B can be used in a linear form or a branched form, but a linear form is more preferred.
- the unit B preferably has 2 or more carbon atoms.
- the number of carbon atoms is further preferably 3-20.
- An increase in the number of carbons generally lowers the temperature of the liquid crystal phase, which is particularly convenient when used as an organic semiconductor in the liquid crystal phase.
- the solubility in an organic solvent is lowered, so that process suitability may be impaired.
- use of a structure containing oxygen, sulfur and nitrogen in unit B is effective in improving the solubility.
- a structure in which oxygen, sulfur and nitrogen atoms are not directly connected to the unit A or the unit C is preferable from the viewpoint of mobility, and from the viewpoint of chemical stability, the structure with the unit A or the unit B is preferable.
- the connection is preferably a structure in which oxygen, sulfur, and nitrogen are connected through two or more carbon atoms.
- the compound of unit A mentioned above may have a known and commonly used substituent capable of substituting for unit A.
- substituents are not limited as long as they do not hinder the problems of the present invention, but preferred substituents include the following. Aliphatic compounds having hetero atoms such as alkyl groups, halogen atoms, oxygen atoms, nitrogen atoms, sulfur atoms, alkenyl groups, alkynyl groups, thiophene, thienothiophene, benzothiophene, benzene, naphthalene, biphenyl, fluorene as substituents, Aromatic compounds such as pyridine, imidazole, benzothiazole, furan.
- substituents are not limited as long as they do not hinder the problem of the present invention, but preferred substituents include the following.
- Aliphatic compounds having hetero atoms such as alkyl groups, halogen atoms, oxygen atoms, nitrogen atoms, sulfur atoms, alkenyl groups, alkynyl groups, thiophene, thienothiophene, benzothiophene, benzene, naphthalene, biphenyl, fluorene as substituents, Aromatic compounds such as pyridine, imidazole, benzothiazole, furan.
- benzene, naphthalene, thiophene, thienothiophene, benzothiophene, and the like are particularly preferable because they can be expected to improve mobility by imparting planarity to the crystal structure of the compound.
- the annealing process may or may not be performed, but it is more preferable to perform the annealing process in order to improve mobility.
- the annealing process can be used to control the crystal phase used as a device material, such as improving the crystallinity of a film formed from a solution or the like, or transition from a metastable phase to a most stable phase due to a crystal polysystem.
- the annealing temperature is lower than the temperature at which the charge transporting molecular unit A having an aromatic condensed ring structure used in the present invention and the compound having the unit B as a side chain transition from a crystal to a liquid crystal.
- the temperature be as close as possible to the temperature at which the crystal transitions from the crystal.
- the close temperature varies depending on the target compound, but examples thereof include the transition temperature and a temperature within a range of about 10 to 20 ° C. lower than the transition temperature.
- There is no limitation on the annealing time but examples include a time of about 5 to 60 minutes.
- Transient photocurrent measurement by the Time-of-flight method means observation of photocharge generation and charge transport by light irradiation, and this measurement system realizes a photosensor using organic semiconductor materials. Corresponds to that. Therefore, it can be confirmed by this measurement that the organic semiconductor material of the present invention can be used for semiconductor device operation.
- the semiconductor device operation confirmation by such a method see, for example, Non-Patent Document Appl. Phys. Lett. , 74 No. 18 2584-2586 (1999).
- the organic semiconductor material of the present invention can be used as an organic transistor by producing an organic transistor and evaluating its characteristics.
- the semiconductor device operation confirmation by such a method, see, for example, Document S.A. F. Nelson, Y. -Y. Lin, D, J, Gundlach, and T. N. Jackson, Temperature-independent Transistors, Appl. Phys. Lett. 72No. 15 1854-1856 (1998) can be referred to.
- the liquid crystal material used in the present invention is basically composed of a condensed ring system in which three or more aromatic rings within 5 rings are connected in a rod shape (that is, generally linear) via a single bond.
- a structure in which a hydrocarbon chain unit having 3 or more carbon atoms is connected in the molecular long axis direction to any one of the structures in which the cyclic structure is connected in the molecular long axis direction of the condensed ring system is preferable.
- the liquid crystal material used in the present invention has at least one other cyclic structure of a condensed ring system via a single bond to a condensed ring system connected in the form of a rod of 3 or more aromatic rings within 5 rings.
- This is a structure in which a hydrocarbon chain unit having 3 or more carbon atoms is connected in the molecular long axis direction to any one of the structures connected in the molecular long axis direction. This is illustrated by taking the following substances (see figure) as examples.
- the compound group used in the present invention can be molecularly designed by appropriately combining the above-mentioned units A to C.
- Specific examples of the compound group include the following, but from the present invention, However, the compound group to be used is not limited to these.
- liquid crystal substances are also effective.
- Compound 24-1 (2-decylBTBT) is obtained from BTBT in two steps (Friedel-Crafts acylation) according to the literature (Liquid Crystals 2004, 31, 1367-1380 and Collect. Czech. Chem. Commun. 2002, 67, 645-664). (Wolff-Kishner reduction).
- H-nmr (270 MHz, CDCl 3 ): ⁇ 7.68 (d, 1H, J8.2 Hz, H-9), 7.67 (broadeneds, 1H, H-6), 7.62 (d, 1H, J8. 4 Hz, H-4), 7.23 (dd, 1H, J1.5, 8.2 Hz, H-8), 7.16 (d, 1H, J to 2 Hz, H-1), 6.81 (dd , 1H, J-2, 8.4 Hz, H-3), 3.84 (lightly broadcasteds, ⁇ 2H, NH 2 ), 2.73 (t, 2H, J-7.5 Hz, ArCH 2 ), 1.68 (Quant. 2H, J to 7.5 Hz, ArCH 2 CH 2 ), to 1.2 to 1.4 (m, 14 H, CH 2 x7), 0.87 (t, 3H, J to 7 Hz, CH 3 )
- a silicon wafer with a thermal oxide film (heavy doped p-type silicon (P + -Si), thermal oxide film (SiO 2 ) thickness: 300 nm) was cut into 20 ⁇ 25 mm, and this cut silicon wafer (hereinafter abbreviated as substrate) Ultrasonic cleaning was performed in the order of neutral detergent, ultrapure water, isopropyl alcohol (IPA), acetone, and IPA. Next, the compound of Synthesis Example 1 was dissolved in xylene to prepare a solution. The concentration of the solution was 1 wt% to 0.5 wt%.
- This solution and a glass pipette for applying the solution to the substrate are heated in advance on a hot stage to a predetermined temperature, and the substrate is placed on a spin coater placed in an oven. After raising the temperature to 100 ° C., the solution was applied onto the substrate, and the substrate was rotated (about 3000 rpm, 30 seconds). After stopping the rotation, the substrate was quickly taken out and cooled to room temperature. Further, the obtained organic thin film was thermally annealed at 120 ° C. for 5 minutes.
- the evaluation of the fabricated organic transistor was conducted by applying a sweep current to the gate electrode (P + -Si) using a source / measurement unit with two power supplies under normal atmospheric conditions. This was performed by measuring (transfer characteristics) while (Vsg: +10 to ⁇ 100 V) (voltage Vsd between source electrode and drain electrode: ⁇ 100 V). The mobility was calculated from the slope of ⁇ Id ⁇ Vg in the transfer characteristic by a well-known method using a saturation characteristic equation (FIG. 6).
- the sample as it was produced was “As coated”, the obtained organic thin film was thermally annealed at 120 ° C. for 5 minutes, “after annealing”, heated to a liquid crystal phase temperature of 160 ° C. and then rapidly cooled.
- the sample was named “160 ° C. fast cool”. In the sample that was rapidly cooled after heating to 160 ° C., a decrease in mobility was confirmed. In addition, the measurement of mobility was performed about five transistors, The average value and the standard deviation were described. The results are shown in Table 8.
- the above measurement sample was measured under the condition of 1 to 20 °.
- the structure of the thin film was calculated
- the position of the reflected X-ray beam center in the two-dimensional scattered image is determined from the X-ray incident angle at the time of measurement, and the scattering / diffraction intensity I on the straight line in the horizontal direction as viewed from the center of the reflected beam is taken.
- a one-dimensional scattering profile H was obtained as the scattering intensity I.
- the scattering / diffracting intensity I on a straight line in the vertical upward direction when viewed from the center of the reflected beam was taken, and a one-dimensional scattering profile V was obtained as the scattering intensity I with respect to the scattering angle 2 ⁇ from the center of the reflected beam.
- ⁇ [nm] is an X-ray wavelength of 0.1 nm.
- a periodic length of about 4 cm or the like derived from a periodic structure (plane spacing) in an orientation almost perpendicular to the molecular chain in the arrangement structure of the molecule is calculated.
- the molecular length of the compound is calculated.
- a period length of about 30 cm derived from the above was calculated. From the measurement principle of GISAXS / WAXS, information on the periodic structure in the plane of the thin film is obtained from the scattering profile H, and information on the periodic structure of the laminated state of the thin film is obtained from the scattering profile V.
- this organic thin film has compound molecules standing perpendicular to the substrate, and is laminated every about 30 mm corresponding to the molecular length. It was confirmed that a bilayer structure was formed. The results are shown in Table 8.
- the obtained two-dimensional X-ray scattering image is shown in FIG. From the scattered image, a peak derived from a constant stacking period is observed in the Y-axis direction from the beam center, whereas a bilayer structure can be confirmed from the fact that no peak is observed in the X-axis direction.
- Example 2 In Example 1, a liquid crystal substance of Compound 9 obtained according to WO2012 / 121393 was used in place of the compound of Synthesis Example 1, and the annealing conditions after the organic thin film formation was changed to one-minute annealing with toluene vapor. The results of evaluation in the same manner as in Example 1 are shown in Table 8.
- Example 3 evaluation was performed in the same manner as in Example 1 except that the liquid crystal substance of Compound 64 was used instead of the compound of Synthesis Example 1 and the annealing conditions after the organic thin film formation was changed to 130 ° C. for 30 minutes. did. The results are shown in Table 8.
- Example 4 In Example 1, except that the liquid crystal substance of Compound 23 was used instead of the compound of Synthesis Example 1, ethylbenzene was used instead of toluene, and the annealing conditions after the organic thin film formation were changed to 110 ° C. for 30 minutes. The results of evaluation in the same manner as in Example 1 are shown in Table 8.
- Example 1 In Example 1, the same evaluation as the method described in Example 1 was performed except that thermal annealing at 120 ° C. was not performed. The results are shown in Table 8. The obtained two-dimensional X-ray scattering image is shown in FIG. From the scattered image, concentric circles are observed from the center of the beam in the X-axis direction and the Y-axis direction, so that it can be confirmed that the liquid crystal substance is not aligned and exists separately.
- Example 2 (Comparative Example 2) In Example 2, the same evaluation as the method described in Example 2 was performed except that toluene vapor annealing for 1 minute was not performed. The results are shown in Table 8.
- Example 3 (Comparative Example 3) In Example 3, the same evaluation as the method described in Example 3 was performed except that thermal annealing at 130 ° C. was not performed. The results are shown in Table 8.
- Example 4 (Comparative Example 4) In Example 4, the same evaluation as the method described in Example 4 was performed, except that thermal annealing at 110 ° C. was not performed. The results are shown in Table 8.
- the core part of compound 24 (part composed of phenyl ring and benzothienobenzothiophene) has a Herringbone structure, and has a bilayer structure in which the core parts face each other. It was revealed.
- the profile by the TOF-SIMS in the thickness direction of sulfur atoms existing only in the core part (FIG. 7; approximately one molecule length).
- a peak of about 5 nm corresponding to the length of two molecules was observed in the distribution profile of sulfur atoms (FIG. 8).
- the polycrystalline thin film has a monolayer structure immediately after film formation, but with a bilayer with a core facing each other, similar to a single crystal obtained by recrystallization from a solution by thermal annealing at 120 ° C. It is thought that the structure changes.
- T1, T2, and T3 in the layer are 55, 17, and 43 meV, respectively (FIG. 9), and the layers between the cores facing each other It was also found that it has a significant value of about 8 meV (FIG. 10).
- the organic thin film having a bilayer structure of the present invention obtained from a specific liquid crystal substance can be expected to have high mobility because the aromatic ⁇ -conjugated system is continuously expanded, and is a high-quality organic material that is uniform and has few defects. It can be used as a semiconductor thin film. Specifically, it can be used for an optical sensor, an organic EL element, an organic transistor, an organic positive battery, an organic memory element, and the like.
Abstract
Description
一方、近年、従来はイオン伝導性と考えられてきた液晶物質の液晶相において、アモルファス有機半導体をはるかに上回る高い移動度を示す電子性伝導が見出され、液晶相を有機半導体として使用可能であることが明らかにされた。
(I)芳香族縮環系の構造を有する電荷輸送性分子ユニットAと、側鎖としてユニットBを有する化合物により形成される膜であって、該化合物がバイレイヤー構造を有して形成されることを特徴とする有機薄膜。
(II)前記化合物が更に、電荷輸送性分子ユニットAと単結合で連結された、水素原子、ハロゲン、炭素数1~4の低級アルキル基、又は環状構造ユニットCを有する(I)に記載の有機薄膜。
(III)芳香族縮環系の構造を有する電荷輸送性分子ユニットAと、側鎖としてユニットBを有する化合物が液晶化合物である請求項1又は2に記載の有機薄膜。
(IV)(I)~(III)のいずれかに記載の化合物が、N相、SmA相及びSmC相以外の相を示す(I)~(III)のいずれかに記載の有機薄膜。
(V)前記「N相、SmA相及びSmC相以外の相」が、SmB、SmBcrystal、SmI、SmF、SmG、SmE、SmJ、SmK、およびSmHからなる群から選ばれる液晶相である(I)~(IV)のいずれか一つに記載の有機薄膜。
(VI)前記電荷輸送性分子ユニットAの縮環の数(NA)が3以上5以下である(I)~(V)のいずれか一つに記載の有機薄膜。
(VII)前記電荷輸送性分子ユニットAのそれぞれの縮環を構成する個々の環が、炭素数5~6の環である(I)~(VI)のいずれか一つに記載の有機薄膜。
(VIII)前記環状構造ユニットCを構成する環の数(NC)と、電荷輸送性分子ユニットAの縮環数の数(NA)が下記の関係を満たす(II)~(VII)のいずれか一つに記載の有機薄膜。
NA≧NC
(IX)前記電荷輸送性分子ユニットAが一般式(1)で表される(I)~(VIII)のいずれか一つに記載の有機薄膜。
で表される基である(I)~(IX)のいずれか一つに記載の有機薄膜。
(XI)前記環状構造ユニットCが、無置換、或いは、ハロゲン又は炭素数1~4の低級アルキル基を置換基として持つ芳香族炭化水素基、又は、無置換、或いは、ハロゲン又は炭素数1~4の低級アルキル基を置換基として持つ複素芳香族基で表される基であるか、又は、下記(3)又は(4)の何れかである(II)~(X)のいずれか一つに記載の有機薄膜。
(XII)(I)~(XI)の何れかに記載の有機薄膜の製造方法において、
該有機薄膜をアニール化する工程を含むことを特徴とする有機薄膜の製造方法。
(XIII)(I)~(XI)のいずれか一つに記載の有機薄膜を用いてなる有機半導体デバイス。
(XIV)(I)~(XI)のいずれか一つに記載の有機薄膜を有機半導体層として用いる有機トランジスタ。
(XV)(XII)の有機薄膜の製造方法により得られる有機薄膜を用いてなる有機半導体デバイス。
(XVI)(XII)の有機薄膜の製造方法により得られる有機薄膜を有機半導体層として用いる有機トランジスタ。
本発明の有機薄膜がとるバイレイヤー構造について記載する。
本発明のバイレイヤー構造とは、2つの電荷輸送性分子ユニットAが向かい合わせに一対になって、一つの層を形成した2分子膜状の構造をいう。2つの電荷輸送性ユニットAが対になることで、相対的にπ電子雲が拡がり、移動度が高くなる。更に、液晶物質の自己組織化能により、このバイレイヤー構造が連続的に成長した結晶になることで、電荷移動の欠陥の少ない、即ち、高い性能安定性の有機薄膜を得ることができる。
放射光X線散乱の測定の一例を以下に示す。
本発明において、上記の「N相、SmA相およびSmC相以外の液晶相」は、SmB,SmBcryst、SmI、SmF、SmE、SmJ、SmG、SmK、およびSmHからなる群から選ばれる液晶相であることが好ましい。この理由は、本発明に関わる液晶物質を液晶相で有機半導体して用いる場合、既に述べたように、これらの液晶相は流動性が小さいためイオン伝導を誘起しにくく、また、分子配向秩序が高いため液晶相において高い移動度が期待できるからである。また、本発明に関わる液晶物物質を結晶相で有機半導体として用いる場合には、これらの液晶相は、N相、SmA相およびSmC相に比べて流動性が小さいため、温度の上昇により液晶相に転移した場合にも素子の破壊が起こりにくいためである。液晶相の発現が降温過程においてのみみられる場合は、一旦結晶化すると、結晶温度領域が広がるため、結晶相で応用する場合に好都合である。本発明では、降温過程において、「N相、SmA相及びSmC相以外の相」が、SmBcryst、SmE、SmF、SmI、SmJ、SmG、SmK、又はSmHであることを特徴とする。
本発明に使用できる有機半導体材料は、芳香族縮環系の構造を有する電荷輸送性分子ユニットAと、側鎖としてユニットBを有する有機半導体材料であり、好ましくは更に、ユニットAと単結合で連結された、水素原子、ハロゲン、炭素数1~4の低級アルキル基、又は環状構造ユニットCを有する有機半導体材料である。
有機半導体においては電荷輸送にあずかる分子部位は芳香環などからなる共役したπ電子系ユニットで、一般には共役したπ電子系のサイズが大きいほど電荷輸送には有利であるが、π電子系のサイズが大きくなると、有機溶媒に対する溶解度が低下し、また、高融点となるため、合成時、あるいは、有機半導体として利用する際のプロセスが難しくなるという問題がある。このため、電荷輸送性分子ユニットの縮環数は3以上5以下であることが好ましい。電荷輸送性分子ユニットAは、ヘテロ環を含んでもよい。該縮環を構成する個々の環の炭素数は、合成の利便性から5~6個(すなわち、5員環~6員環)であることが好ましい。
電荷輸送性分子ユニットAを構成するヘテロ環も、5員環~6員環であることが好ましい。ヘテロ環の数は、特に制限されないが、以下のような数であることが好ましい。
3個 1個
4個 1~2個
5個 1~3個(特に1~2個)
高次の液晶相の発現を目指す観点からユニットAを構成する化合物を選択する場合、その融点を目安とすることができる。融点はその化合物の凝集エネルギーの目安を与えるからである。融点が高い化合物は凝集時の分子間の相互作用が強いことを意味し、結晶化しやすいことにも対応し、高次の液晶相の発現を誘起するのに都合がよい。したがって、ユニットAを構成する化合物(ユニットB及びユニットCとの結合がないとした場合に構成される化合物)の融点は、120℃以上であることが好ましく、より好ましくは150℃以上であり、更に好ましくは180℃以上、特に、好ましくは200℃以上である。融点が、120℃以下であると、低次の液晶相の発現が起こりやすく、好ましくない。
対象とする化合物が下記式(5)である場合、ここで問題とするユニットAを構成する化合物は、ユニットCとの単結合を排除し、当該単結合していた、以下のユニットAの位置に水素原子が置換された、下記式(1)の化合物となる。
また、ユニットAの繰り返し数は1であっても良いし、2であってもよい。
本発明において、ユニットCは、フリップーフロップ運動の自由度を与えるための、「もう一つの構造」部である。ユニットCは、単結合で電荷輸送性ユニットAと連結された芳香族縮環、または、脂環式分子構造であることが好ましい。環数は1以上5以下(更には、3以下、特に1~2)であることが好ましい。
ユニットCの環数は、特に制限されないが、ユニットAを構成する環の数を「NA」とし、ユニットCを構成する環の数を「NC」とした場合に、NA≧NCであることが好ましい。より具体的には、以下のような数であることが好ましい。
3個 1~3個、更には1~2個(特に、1個)
4個 1~4個、更には1~3個(特に、1~2個)
5個 1~5個、更には1~4個(特に、1~3個)
ユニットBは、例えば、上記のユニットA又はユニットCに連結することができる。結晶薄膜として用いる場合の結晶温度領域を広げるという点からは、上記のユニットAまたはユニットCの「いずれか一方」に連結していることが好ましい。好ましいユニットBとしては、炭化水素、或いはヘテロ原子を有する飽和化合物等の直線状構造を有する化合物が好ましく、特に好ましくは、炭素数2~20の炭化水素、又は一般式(2)
で表される基を挙げることができる。
前記ユニットAと、ユニットCとの少なくとも一方に、側鎖として存在するユニットBは、該ユニットが結合している環状構造(AまたはC)において、該環状構造が他の環状構造(すなわち、CまたはA)と連結ないし縮合している位置に対して、隣接しない位置にあることが好ましい。その結合位置の例は、後述の例示する構造に示す通りである。
本発明においては、高い移動度を持つ液晶物質を実現するためには、次の点を考慮して分子設計を行うことが好ましい。
本発明において、上記の分子設計を満足する化合物中から、高次のスメクチック液晶相を発現し、有機半導体として有用な物質を、必要に応じてスクリーニングすることができる。このスクリーニングにおいて、基本的には、液晶相で有機半導体として用いる場合は高次のスメクチック相を発現すること、結晶相で有機半導体として用いる場合は、結晶相温度より高い温度から冷却したときに、結晶相に隣接して低次の液晶相を発現しないものを選ぶことが好ましい。この選択の方法は、後述する「スクリーニング法」にしたがって判定することにより、有機半導体材料として有用な物質を選択することができる。
液晶分子におけるコア部に対応する電荷輸送性分子ユニットとして、環数3以上の芳香族π-電子縮環系の分子ユニットを用いることにより、分子位置の揺らぎに対するtransfer積分の冗長性を確保でき、同様に、ベンゼンやチオフェンなどを複数、単結合で連結したπ-電子共役系の分子ユニットではなく、縮環構造を持つ分子ユニットを採用することにより、分子配座が固定されるため、transfer積分の増大が期待でき、移動度の向上に役立つ。
文献A:偏光顕微鏡の使い方:実験化学講第4版1巻、丸善、P429~435
文献B:液晶材料の評価:実験化学講座第5版27巻P295~300、丸善
:液晶科学実験入門日本液晶学会編、シグマ出版
文献D:化学便覧 基礎編 改訂第5版II-608-610 14.1 b仕事関数 (丸善出版株式会社)(2004)
本発明において好適に使用可能な「電荷輸送性分子ユニットA」を例示すれば、以下の通りである。Xは、S、O、NHを表す。
本発明において好適に使用可能な「環状構造ユニットC」を例示すれば、以下の通りである。ユニットCはユニットAと同一でも良い。
5-メチルチエニル基など、前記複素芳香族基が炭素数1~4のアルキル基で置換されたアルキル置換複素芳香族基、
トリレン基、キシリレン基、エチルフェニレン基、プロピルフェニレン基、ブチルフェニレン基、メチルナフチレン、9,9‘-ジヘキシルフルオレニレン基など、前記芳香族炭化水素基が炭素数1~10のアルキル基で置換されたアルキル置換芳香族炭化水素基、
本発明において好適に使用可能な、上記のユニットAおよびCを連結するための「単結合」は、ユニットAとユニットCの環状構造を構成する炭素のうち分子長軸方向にある炭素どうしを分子全体が棒状となる様に選ぶ。すなわち、本発明においては、ユニットAを構成する炭素と、ユニットCを構成する炭素とが、直接に「単結合」(single bond)で連結されている。
本発明において好適に使用可能な「ユニットAおよびユニットCの組合せ」(前記に従って連絡したもの)を例示すれば、以下の通りである。
ユニットBは、直鎖状でも、分枝状でも使用可能であるが、直鎖状である方が、より好ましい。該ユニットBの炭素数は、2個以上であることが好ましい。この炭素数は、更には3~20個であることが好ましい。炭素数の増加は一般に液晶相温度を低下させることになるため、特に、液晶相で有機半導体として用いる場合は都合が良い。しかし、一方で、炭素数が長すぎると有機溶媒に対する溶解度を低下させることになるため、プロセス適性を損なう場合がある。炭素数を用いる場合、ユニットB中に酸素、硫黄、窒素を含む構造の用いると、溶解度の改善には有効である。その際、直接、酸素、硫黄、窒素原子がユニットA、または、ユニットCを連結されない構造が移動度の点からは好ましく、化学的安定性の点からは、ユニットA,または、ユニットBとの連結は2以上の炭素を介した後、酸素、硫黄、窒素が連結する構造が好ましい。上記例示の中で、本発明の課題を解決するのに特に好適なユニットA、ユニットB、ユニットCの具体例として、以下を挙げることができる。
アルキル基、ハロゲン原子、酸素原子、窒素原子、硫黄原子等のヘテロ原子を有する脂肪族化合物、アルケニル基、アルキニル基、置換基としてのチオフェン、チエノチオフェン、ベンゾチオフェン、ベンゼン、ナフタレン、ビフェニル、フルオレン、ピリジン、イミダゾール、ベンゾチアゾール、フラン等の芳香族化合物。
チオフェン、チエノチオフェン、ベンゾチオフェン、ベンゼン、ナフタレン、ビフェニル、フルオレン、ピリジン、イミダゾール、ベンゾチアゾール、フラン、シクロペンテン、シクロヘキセン、テトラヒドロフラン、テトラヒドロピラン、テトラヒドロチオフェン、ピロリジン、ピペリジン
上記で挙げたユニットCの化合物には、公知慣用の置換基を有していてもよい。
炭素数2~20の直鎖アルキル基、
本発明の有機薄膜を作製する際には、アニール工程を行っても行わなくてもよいが、移動度の向上のためには、アニール工程を行った方がより好ましい。アニール工程は、溶液等から作製した膜の結晶性の向上や、結晶多系による準安定相から最安定相への転移など、デバイス材料として用いる結晶相の制御に活用することができる。
Time-of-flight法による過渡光電流の測定は、光照射による光電荷の発生と電荷輸送を観測することを意味しており、この測定系は、有機半導体材料を用いた光センサーを実現していることに対応する。したがって、この測定により、本発明の有機半導体材料が、半導体デバイス動作に使用可能なことが確認可能である。このような方法による半導体デバイス動作確認の詳細に関しては、例えば非特許文献Appl.Phys.Lett.,74 No.18 2584-2586(1999)を参照することができる。
本発明に使用する液晶物質は、基本的に、3環以上の5環以内の芳香環が棒状(すなわち、概ね直線状)に連結した縮環系に、単結合を介して、少なくとももう一つの環状構造を縮環系の分子長軸方向に連結させた構造のいずれか一方に、炭素数3以上の炭化水素鎖ユニットを分子長軸方向に連結させた構造であることが好ましい。
(b)相転移挙動(冷却過程)
*I:等方相、
N:ネマチック相、
SmA:スメクチックA相、
SmC:スメクチックC相、
SmE:スメクチックE相、
SmG:スメクチックG相、
SmX:高次のスメクチック相もしくは準安定な結晶、
K:結晶相
化合物24はWO2012/121393号公報に記載の方法によって、[1]benzothieno[3,2-b][1]benzothiophene(BTBTと略す)から、以下の(化32)示すスキームにより合成した。
化合物24-1(2.48g,6.52 mmol)のジクロロメタン(160mL)溶液を-50℃に冷却し(固体を析出する)、発煙硝酸の1.2Mジクロロメタン溶液(12mL)を30分で滴下した。-50℃で更に2時間撹拌した後、飽和炭酸水素ナトリウム水溶液(~13mL)を加え反応を停止した。分液して下層を取り、10%食塩水で洗浄、無水硫酸マグネシウムで乾燥し濃縮乾固して粗製固体(2.75g)を得た。この固体を2‐ブタノン(~40mL)から再結晶化し、化合物24-2の黄色結晶、1.86g (収率、67%)を得た。
化合物24-2(1.28g,30mmol),錫(0.92g)を酢酸(15mL)に懸濁し、約70℃で加熱、撹拌下、濃塩酸(2.7mL)をゆっくりと滴下した。さらに100℃で1時間反応後、10℃以下に冷却し固体を濾取した。この固体をクロロホルム(~100mL)に取り、濃アンモニア水、飽和食塩水で順次洗い、無水硫酸マグネシウムで乾燥後、濃縮乾固し粗製固体(1.1g)を得た。この固体をシリカゲルカラム(クロロホルム-シクロヘキサン1:1、1%トリエチルアミンを添加)で分離精製し、石油ベンジンから結晶化し、微灰色の化合物24-3の化合物0.86g(収率、72%)を得た。
化合物24-3(396mg,1mmol)のジクロロメタン(15mL)溶液に-15℃冷却下、BF3-Et2O(216mg),亜硝酸t‐ブチル(126mg)を滴下した。約1時間で反応温度を5℃まで上げた後、沃素(400mg),沃化カリウム(330mg)、沃化テトラブチルアンモニウム(25mg)のジクロロメタン-THF混液(1:2,3mL)の溶液を加えた。さらに加熱環流下、8時間反応した後、クロロホルムで希釈し、10%チオ硫酸ナトリウム、5M水酸化ナトリウム、10%食塩水で順次洗い、無水硫酸ナトリウムで乾燥し、濃縮乾固した。得られた濃褐色の粗製固体(500mg)をシリカゲルカラム(クロロホルム-シクロヘキサン、1:1)で精製し、クロロホルム-メタノールから結晶化した。さらに、リグロインから再結晶化し、化合物24-4の化合物228mg(収率、45%)を得た。
化合物24-4(228mg,0.45mmol)のジオキサン(8mL)溶液に、2Mリン酸三カリウム(0.45mL)、フェニルボロン酸(東京化成工業、110mg,0.9mmol)を加え、20分アルゴンガスをバブリングした後、テトラキス(トリフェニルホスフィン)パラジウム(東京化成工業、30mg,0.025mmol),トリシクロヘキシルホスフィン(和光純薬工業、13mg、0.045mmol)を加え、95℃で22時間加熱撹拌した。反応液をクロロホルムで希釈し、10%食塩水で洗い、下層を濃縮乾固して粗製固体(293mg)を得た。この固体をトルエンから再結晶化し、化合物24の化合物130mg(収率、63%)を得た。
合成例1において、C9H19COClの替わりに、C11H23COClを用いて化合物64(2-dodecyl-7-phenylBTBT)を合成した。
合成例1で得た化合物(化合物24)を用いて、以下の方法により、バイレイヤー構造およびトランジスタ特性を確認した。
熱酸化膜付シリコンウエハー(ヘビードープp型シリコン(P+-Si)、熱酸化膜(SiO2)厚さ:300nm)を20×25mmに切断後、この切断したシリコンウエハー(こののち基板と略す)を中性洗剤、超純水、イソプロピルアルコール(IPA)、アセトン、IPAの順に超音波洗浄を行った。
次に、合成例1の化合物をキシレンに溶解させ、溶液を調整した。溶液の濃度は1wt%から0.5wt%とした。この溶液、および、溶液を基板に塗布するガラス製のピペットを予め、ホットステージ上で所定の温度に加熱しておき、上記の基板をオーブン内に設置したスピンコータ上に設置し、オーブン内を約100℃に昇温した後、溶液を基板上に塗布し、基板を回転(約3000rpm、30秒)させた。回転停止後、基板を素早く取り出し室温まで冷却させた。更に、得られた有機薄膜を120℃、5分間の熱アニールを行った。
低角の面外XRD測定をRIGAKU RAD-2B(X線源 CuKα線 波長1.54Å、発散スリット1/6°、散乱スリット0.15mm、受光スリット1/6°)を用いてθ-2θスキャンで1°から5°まで測定した。
化合物24に関するデータを図5に示した。
更に、有機半導体層を塗布した基板に、真空蒸着法(2×10-6Torr)を用いて、金をメタルマスクを介してパターン蒸着することにより、ソース・ドレイン電極を形成した(チャネル長:チャネル幅=100μm:500μm)。
なお、移動度の測定は5つのトランジスタについて行い、その平均値と標準偏差を記載した。その結果を表8に示した。
抵抗率0.02Ω・cmのシリコン基板に、厚さ200nmの熱酸化膜(SiO2)を形成した。この上に、合成例1の化合物の0.5wt%キシレン溶液を直径1インチのシリコン基板上にバーコーター#26にて塗布、乾燥し、膜厚が約80nmの有機薄膜の測定試料を作製した。
実施例1において、合成例1の化合物の代わりにWO2012/121393号公報に従って得た化合物9の液晶物質を用い、有機薄膜成膜後のアニール条件をトルエン蒸気による1分間のアニールに変更した以外は、実施例1と同様の方法で評価した結果を表8に示した。
実施例1において、合成例1の化合物の代わりに化合物64の液晶物質を用い、有機薄膜成膜後のアニール条件を130℃、30分間に変更した以外は、実施例1と同様の方法で評価した。結果を表8に示した。
実施例1において、合成例1の化合物の代わりに化合物23の液晶物質を用い、トルエンの替わりにエチルベンゼンを用い、有機薄膜成膜後のアニール条件を110℃、30分間に変更した以外は、実施例1と同様の方法で評価した結果を表8に示した。
実施例1において、120℃の熱アニールを行わなかった以外、実施例1記載の方法と同様の評価を行った。結果を表8に示す。
また、得られた2次元エックス線散乱像を図2に示した。散乱像から、ビーム中心から同心円がX軸方向とY軸方向に観察されることからも、該液晶物質が配向せずバラバラに存在することが確認できる。
実施例2において、1分間のトルエン蒸気アニールを行わなかった以外、実施例2記載の方法と同様の評価を行った。結果を表8に示す。
実施例3において、130℃の熱アニールを行わなかった以外、実施例3記載の方法と同様の評価を行った。結果を表8に示した。
実施例4において、110℃の熱アニールを行わなかった以外、実施例4記載の方法と同様の評価を行った。結果を表8に示した。
化合物24の単結晶は、キシレン溶液から再結晶化により作製した。単結晶構造解析はRigaku社製のR-AXIS RAPID II/Rを用いて行った。多結晶薄膜における分子の配向の情報を得るためTOF-SIMSによる厚さ方向の組成分析を行なった。また、単結晶における分子配置よりTransferIntegralについても検討を加えた。
モノレイヤー構造をとる製膜直後の膜では、コア部にのみ存在する硫黄原子の厚さ方向のTOF-SIMSによるプロファイルには分布が見られないのに対し(図7;1分子長である約2.5nmごとに硫黄原子が存在)、120℃5分間の熱アニールを行った薄膜では、硫黄原子の分布プロファイルには2分子長に対応した約5nmごとのピークが観測され(図8)、バイレイヤー構造であることが判明した。
これらの結果を総合すると、多結晶薄膜は製膜直後ではモノレイヤー構造であるが、120℃の熱アニールにより、溶液から再結晶により得られた単結晶と同様に、コア部が向かい合ったバイレイヤー構造に変化するものと考えられる。
具体的には、光センサー、有機EL素子、有機トランジスタ、有機陽電池、有機メモリー素子などに用いることができる。
Claims (16)
- 芳香族縮環系の構造を有する電荷輸送性分子ユニットAと、側鎖としてユニットBを有する化合物により形成される膜であって、該化合物がバイレイヤー構造を有して形成されることを特徴とする有機薄膜。
- 前記化合物が更に、電荷輸送性分子ユニットAと単結合で連結された、水素原子、ハロゲン、炭素数1~4の低級アルキル基、又は環状構造ユニットCを有する請求項1に記載の有機薄膜。
- 芳香族縮環系の構造を有する電荷輸送性分子ユニットAと、側鎖としてユニットBを有する化合物が液晶化合物である請求項1又は2に記載の有機薄膜。
- 請求項1~3のいずれかに記載の化合物が、N相、SmA相及びSmC相以外の相を示す請求項1~3のいずれかに記載の有機薄膜。
- 前記「N相、SmA相及びSmC相以外の相」が、SmB、SmBcrystal、SmI、SmF、SmG、SmE、SmJ、SmK、およびSmHからなる群から選ばれる液晶相である請求項1~4のいずれか1項に記載の有機薄膜。
- 前記電荷輸送性分子ユニットAの縮環の数(NA)が3以上5以下である請求項1~5のいずれか1項に記載の有機薄膜。
- 前記電荷輸送性分子ユニットAのそれぞれの縮環を構成する個々の環が、炭素数5~6の環である請求項1~6のいずれか1項に記載の有機薄膜。
- 前記環状構造ユニットCを構成する環の数(NC)と、電荷輸送性分子ユニットAの縮環数の数(NA)が下記の関係を満たす請求項2~7のいずれか1項に記載の有機薄膜。
NA≧NC - 前記環状構造ユニットCが、無置換、或いは、ハロゲン又は炭素数1~4の低級アルキル基を置換基として持つ芳香族炭化水素基、又は、無置換、或いは、ハロゲン又は炭素数1~4の低級アルキル基を置換基として持つ複素芳香族基で表される基であるか、又は、下記(3)又は(4)の何れかである請求項2~10のいずれか1項に記載の有機薄膜。
- 請求項1~11のいずれかに記載の有機薄膜の製造方法において、
該有機薄膜をアニール化する工程を含むことを特徴とする有機薄膜の製造方法。 - 請求項1~11のいずれか1項に記載の有機薄膜を用いてなる有機半導体デバイス。
- 請求項1~11のいずれか1項に記載の有機薄膜を有機半導体層として用いる有機トランジスタ。
- 請求項12の有機薄膜の製造方法により得られる有機薄膜を用いてなる有機半導体デバイス。
- 請求項12の有機薄膜の製造方法により得られる有機薄膜を有機半導体層として用いる有機トランジスタ。
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