JP5408474B2 - Method for controlling molecular orientation direction of charge transporting amorphous thin film and method for producing charge transporting amorphous thin film - Google Patents

Description

  The present invention relates to a highly charge transportable amorphous thin film whose molecular orientation direction is controlled, a method for producing the same, and a method for controlling the molecular orientation direction, and further relates to an organic semiconductor element using the same.

  In recent years, in the electronic device field, technological development relating to organic electronic devices using organic semiconductor materials has been actively promoted. This organic semiconductor material is used for a desired device as a thin film (Non-patent Document 1). For example, in the case of an organic EL element, a structure in which a thin film obtained from an organic semiconductor material is stacked and sandwiched between a pair of electrodes is generally used. In the case of an organic transistor, a method of forming an organic semiconductor thin film on a substrate on which a gate electrode, a source electrode, and a drain electrode are arranged is one of general methods.

  Important factors governing the characteristics of these organic electronic devices include charge transport characteristics and interfacial smoothness of organic thin films. Organic thin films can be broadly classified into two types: crystalline thin films and amorphous thin films. In the crystalline thin film, the charge transport property is enhanced because the higher-order structure of the organic semiconductor material molecules in the crystal is regularly arranged. However, since the smoothness of the surface of the thin film is reduced due to crystals and crystal agglomeration that occur during thin film formation, the in-plane uniformity is reduced, and leakage occurs in devices that flow current in the thickness direction formed by the laminated structure of thin films. Problems such as current, electrical shorts, and deterioration of durability occur. On the other hand, in an amorphous thin film, since there is no regularity of the higher order structure of the organic semiconductor material molecules in the thin film, the charge transport property is lowered. However, since no crystal formation occurs during the formation of the thin film, a smooth thin film surface can be obtained. For this reason, it can be said that an amorphous thin film is preferable to a crystalline thin film from the viewpoint of surface uniformity and stability of a device in which current flows in the thickness direction. That is, a thin film capable of achieving both charge transport characteristics and interfacial smoothness has been demanded, but it has been a difficult task.

  For example, in an organic EL element configured by laminating and sandwiching a thin film obtained from an organic semiconductor material between a pair of electrodes, the surface uniformity and stability of the device can be achieved by using an amorphous thin film as the organic semiconductor thin film. A smooth interface favorable for the property is obtained. In this case, if an organic thin film whose molecular orientation direction is controlled in the horizontal direction can be used as the organic thin film, it is expected that the charge transportability is improved and the light extraction efficiency is improved, but this is difficult with the conventional technology. It was. Further, in an organic transistor element obtained by forming an organic semiconductor thin film on a substrate on which a gate electrode, a source electrode, and a drain electrode are arranged, a crystalline material is used for the purpose of obtaining high charge transport characteristics between the source and drain electrodes. Although a thin film is used, there has been a problem of a decrease in charge transport characteristics and a decrease in interfacial smoothness due to crystal grain boundaries and crystal aggregation in the thin film.

  In order to solve such problems, it has been proposed to produce an organic amorphous thin film with controlled molecular orientation by spin coating a low molecular weight organic material under strong electric field conditions (Patent Document). 1). However, in this report, information on the molecular orientation state of the obtained organic thin film is not disclosed, and the second-order nonlinear optical effect is only clarified as the characteristics given by the obtained thin film. In addition, in an organic EL device, attempts have been made to use an alignment-controlled thin film by using a conductive liquid crystal compound for the carrier transport layer (Patent Documents 2 and 3), but a method for obtaining an amorphous thin film is disclosed. In addition, the characteristics as an organic EL element were not sufficient. Recently, some of the present inventors have reported that when a styryl compound is deposited as a π-conjugated material, the orientation in the horizontal direction has priority over the substrate. However, it has not been possible to show a specific organic semiconductor element utilizing a factor, a change in charge transport characteristics due to priority of horizontal alignment, or a priority of horizontal alignment (Non-Patent Documents 2 and 3).

JP-A-6-330018 Japanese Patent Laid-Open No. 2001-167887 JP 2001-167888 A

Evolving organic semiconductor, NTS Corporation 2006 Organic Electronics 10 (2009) 127-137 Applied Physics Letters 93 (2008) 173302

  An object of the present invention is to provide a charge transporting amorphous thin film having a controlled molecular orientation and a control method.

  As a result of intensive studies to solve such problems, the present inventors have a relatively elongated structure with a molecular weight range of 400 to 2500 having a glass transition point of 60 ° C. or higher without showing a clear melting point. It has been found that a charge transporting amorphous film in which the orientation direction of a π-conjugated compound is controlled can be obtained by controlling the substrate temperature when an amine-based π-conjugated compound is deposited on a substrate. Reached.

  The present invention does not show a clear melting point, has a glass transition point of 60 ° C. or higher, has a molecular weight in the range of 400 to 2500, and is a charge transporting amine-based π-conjugated compound, The substrate temperature is controlled when a π-conjugated compound having a ratio (L / D) of the length (L) to the diameter (D) of the inscribed minimum diameter cylinder of 2.5 or more is deposited on the substrate. Thus, the orientation direction control method of the charge transporting amorphous film is characterized in that the orientation direction of the π-conjugated compound is controlled.

（ここで、Ar₁〜Ar₃は独立に、２価の炭素数６〜３０の芳香族炭化水素基を表し、Ar₄〜Ar₇は、独立に、炭素数６〜３０の芳香族炭化水素基を表し、Ar₄とAr₅を構成する２つの芳香族炭化水素基が直接結合又は置換基を介して結合してAr₄とAr₅が置換するNとで縮合複素環を形成しても良く、Ar6とAr7を構成する２つの芳香族炭化水素基が直接結合又は置換基を介して結合してAr6とAr7が置換するNとで縮合複素環を形成しても良い。L₁〜L₂は独立に、エチレン基又はアセチレン基を表す。ｌ、ｍ、ｎ、ｏ及びｐは０〜６の整数を表すが、ｌ、ｎ又はｐの何れか１つは０ではない。） Examples of the π-conjugated compound include π-conjugated compounds represented by the following formula (1).

(Here, Ar _{1 to} Ar ₃ independently represent a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and Ar _{4 to} Ar ₇ independently represent an aromatic hydrocarbon having 6 to 30 carbon atoms. A group of two aromatic hydrocarbon groups constituting Ar ₄ and Ar ₅ may be bonded directly or through a substituent to form a condensed heterocyclic ring with N substituted by Ar ₄ and Ar ₅ well, Ar6 and two aromatic hydrocarbon group constituting the Ar7 is a direct bond or bonded to through a substituent Ar6 and Ar7 good also form a fused heterocycle with N replacing .L ₁ ~L ₂ independently represents an ethylene group or an acetylene group, and l, m, n, o, and p represent an integer of 0 to 6, but any one of l, n, and p is not 0.)

  Further, the present invention provides a charge transport characterized by controlling the orientation direction of a π-conjugated compound by controlling the substrate temperature when the π-conjugated compound represented by the above formula (1) is deposited on a substrate. Is a method for producing a conductive amorphous film.

（ここで、Ar₁〜Ar₃、L₁〜L₂及びl〜ｐは、式（１）と同じ意味である。） Examples of the π-conjugated compound represented by the formula (1) include a π-conjugated compound represented by the following formula (2) or (3) as a preferable compound.

(Here, Ar _{1 to} Ar ₃ , L _{1 to} L _2, and l to p have the same meaning as in formula (1).)

（ここで、Ar₂は、式（１）と同じ意味である。）

(Here, Ar ₂ has the same meaning as in formula (1).)

  Furthermore, in the present invention, the temperature of the substrate to be deposited is controlled in the range of 0 ° C. to the glass transition point of the π conjugated compound −30 ° C., and the molecular orientation of the π conjugated compound is controlled in the horizontal direction with respect to the substrate. The method for producing a charge transporting amorphous thin film as described above.

The charge-transporting amorphous thin film manufactured by the manufacturing method of the charge-transporting amorphous thin film, an organic semiconductor device had use the charge-transporting amorphous thin film.

  The charge transporting amorphous thin film with controlled molecular orientation according to the present invention has the characteristics of high charge transporting characteristics by controlling the molecular orientation direction in addition to the interface smoothness of the amorphous thin film. Have both. Therefore, by using this thin film for an organic semiconductor element, an organic semiconductor element having both amorphous characteristics and characteristics by molecular orientation direction control, which has been difficult in the past, can be obtained. For example, by laminating a thin film that prioritizes horizontal orientation with respect to the substrate, it is possible to improve characteristics in an element such as an organic EL element or an organic thin film solar cell. Further, according to the control method of the present invention, it is possible to obtain a charge transporting amorphous thin film whose molecular orientation direction is controlled by a simple operation of changing the substrate temperature to a temperature within a specific range.

This is an XRD measurement result of an out-of-plane method for a charge transporting amorphous thin film with controlled molecular orientation. It is a result of XRD measurement by In Plane method of charge transporting amorphous thin film with controlled molecular orientation.

  Hereinafter, the present invention will be described in detail.

  In the method for controlling the orientation direction of the charge transporting amorphous film of the present invention, the π-conjugated compound that becomes the charge transporting amorphous film does not exhibit a clear melting point, has a glass transition point of 60 ° C. or higher, and has a molecular weight. The charge transportable amine-based π-conjugated compound is in the range of 400 to 2500. The ratio (L / D) of the length (L) to the diameter (D) of the minimum diameter cylinder inscribed by this π-conjugated compound is 2.5 or more. Here, (L / D) is a numerical value that defines the length of the molecule of the π-conjugated compound. In the case of an elongated molecule, the effect of controlling the orientation is great. Therefore, (L / D) is preferably in the range of 3-10. The amine-based conjugated compound is preferably a compound having an amino group or an N-heterocyclic group at the end of the compound skeleton (aromatic ring-containing skeleton). Among the compounds represented by Formula (1), there are compounds represented by Formula (2) and Formula (3).

The amino group is preferably an aromatic amino group represented by —N (Ar) ₂ (wherein Ar is an aromatic group). The N-heterocyclic group is a cyclic amino group, and N-heterocyclic groups such as an N-carbazolyl group, an N-phenoxazinyl group, and an N-phenothiazinyl group bonded to the end of the compound skeleton with an N atom are preferable. A preferable π-conjugated compound is a compound represented by the formula (1).

In formula (1), Ar _{1 to} Ar ₃ independently represent a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and Ar _{4 to} Ar ₇ independently represent an aromatic group having 6 to 30 carbon atoms. It represents a hydrocarbon group, Ar ₄ and Ar ₅ or Ar ₆ and Ar ₇ is, Ar ₄ 2 one aromatic hydrocarbon group constituting to Ar ₇ is linked via a direct bond or a substituent Ar ₄ and Ar ₅ or Ar ₆ and N substituted by Ar ₇ may form a condensed heterocyclic ring. Further, —NAr ₆ Ar ₇ or —NAr ₆ and Ar ₇ may form a cyclic amino group. Here, the condensed heterocyclic ring is understood to be a structure in which there is a heterocyclic ring containing N at the center and an aromatic hydrocarbon group condensed on both sides thereof. Specific examples include an N-carbazolyl group, but are not limited to three rings, may be four or more rings, and may have a substituent. L < ₁ > -L < ₂ > represents an ethylene group or an acetylene group independently. l, m, n, o, and p represent an integer of 0 to 6, but any one of l, n, and p is not 0. The total of l, m, n, o and p is preferably in the range of 2 to 10, which is related to the above (L / D). Further, when l, m, n, o, or p is an integer greater than 6, the molecular weight of the π-conjugated compound becomes large, so that vapor deposition film formation becomes difficult. p is an integer of 0 to 3, and any one of l, n, and p may be an integer that is not 0.

  The π-conjugated compound preferably has a ratio (L / D) of 2.5 or more of the length (L) and the diameter (D) of the cylinder with the smallest diameter inscribed by the molecules of the π-conjugated compound. When L / D becomes large, the molecular weight of the π-conjugated compound becomes large, which makes it difficult to form a film by vapor deposition. Preferably they are 2.5 or more and 10.0 or less, Especially preferably, they are 2.5 or more and 5.0 or less.

  In the control method of the present invention, when the π-conjugated compound is vapor-deposited on the substrate, the orientation direction of the π-conjugated compound is controlled by controlling the substrate temperature, thereby aligning the resulting charge transporting amorphous film. Is to control. That is, it has been found that the arrangement in the horizontal direction (parallel to the substrate) is given priority by lowering the substrate temperature during vapor deposition. Therefore, the orientation or degree of orientation of the charge transporting amorphous film is controlled by changing the substrate temperature during vapor deposition. Therefore, in the present invention, the substrate temperature is controlled to achieve a desired orientation. The temperature range to be changed is in the range of 0 ° C. to less than the melting point, preferably 0 ° C. to Tg, more preferably 0 ° C. to (Tg-30 ° C.). In the range of 0 ° C. to (Tg-30 ° C.), the horizontal arrangement takes precedence, and the orientation of the charge transporting amorphous film is controlled in the horizontal direction. Here, Tg is the glass transition temperature (° C.) of the π-conjugated compound. Even in this range, the horizontal arrangement is prioritized as the temperature is lower. Therefore, by setting the substrate temperature low, the degree of horizontal alignment can be increased, and by setting it high, the degree of horizontal alignment can be reduced, so the charge mobility in the film thickness direction can be controlled. A possible charge transporting amorphous film can be formed.

  The method for producing a charge transporting amorphous film of the present invention is a charge transporting property in which the orientation direction of the π conjugated compound is controlled by changing the substrate temperature when the π conjugated compound is deposited on the substrate. This is a method for producing an amorphous film.

  By controlling the substrate temperature as described above, a charge transporting amorphous film in which the orientation direction of the π-conjugated compound is controlled can be obtained. Therefore, in the manufacturing method of the present invention, the charge transporting amorphous film is obtained by changing the substrate temperature to a desired orientation. The temperature range to be changed is the above range, but is preferably 0 ° C to (Tg-30 ° C). In this range, a charge transporting amorphous film in which the arrangement in the horizontal direction has priority and the orientation is controlled in the horizontal direction is obtained.

  As the π-conjugated compound used in the method for producing a charge transporting amorphous film of the present invention, the compounds described in the method for controlling the orientation direction of the charge transporting amorphous film of the present invention can be used. Preferably, it is a compound represented by Formula (1). Among the compounds represented by formula (1), preferred compounds include compounds represented by formulas (2) and (3).

In the formula (2), Ar _{1 to} Ar ₃ , L _{1 to} L ₂ and 1 to p have the same meaning as Ar _{1 to} Ar ₃ , L _{1 to} L ₂ and _{1 to} p in the formula (1). In the formula (3), Ar ₂ has the same meaning as Ar ₂ in the formula (1).

In the formula (1), Ar _{1 to} Ar ₃ are divalent hydrocarbon aromatic groups generated by taking two hydrogens from a hydrocarbon aromatic compound having 6 to 30 carbon atoms, and Ar _{4 to} Ar ₇ is a monovalent hydrocarbon-based aromatic group generated by removing one hydrogen from a hydrocarbon-based aromatic compound having 6 to 30 carbon atoms. Examples of the hydrocarbon-based aromatic compound include benzene and biphenyl. Terphenyl, naphthalene, anthracene, tetracene, phenanthrene, chrysene, coronene, fluorene, and the like. Although the example of the aromatic hydrocarbon compound which gives the said hydrocarbon-type aromatic group is shown below, it is not limited to these. Although the example shown below is an example which does not have a substituent, if a carbon number is the said range, it can have a substituent like an alkyl group.

  The π-conjugated compound used for vapor deposition in the control method or the production method of the present invention does not exhibit a clear melting point, and exhibits a glass transition point of 60 ° C. or higher. A preferable Tg is 60 to 300 ° C., and a Tg exceeding this temperature requires a large apparatus load to control the substrate temperature when performing vapor deposition and film formation on the substrate. Further, it is not preferable because sublimation of the π-conjugated compound occurs. The molecular weight of the π-conjugated compound is in the range of 400 to 2500, and preferably in the range of 400 to 1000. When this molecular weight is exceeded, vapor deposition film formation becomes difficult.

  The charge transporting amorphous thin film in which the molecular orientation of the π-conjugated compound is controlled to be horizontal with respect to the substrate has a substrate temperature in the range of 0 ° C. to less than the melting point, preferably 0 ° C. to Tg, more preferably It is obtained by adjusting to 0 ° C. to (Tg-30 ° C.). Within this temperature range, if the temperature is set low, the horizontal orientation becomes higher.

  As the substrate used in the present invention, either a crystalline or amorphous substrate can be used. For example, as a crystalline substrate, a single crystal substrate made of silicon, sapphire or the like, a substrate on which an organic single crystal or a polycrystalline thin film is formed in advance, and an amorphous inorganic conductive oxide such as ITO is formed on glass. The substrate etc. which were done can be illustrated. Examples of the amorphous substrate include a substrate obtained by forming an amorphous inorganic conductive oxide on glass, and a substrate obtained by previously forming an organic amorphous thin film.

  The substrate temperature is controlled by changing the ambient temperature of the system in which the substrate is present, passing a heating or cooling medium through a holding member that holds the substrate, or passing a current.

  The kind of substrate and the temperature of the substrate at the time of vapor deposition are selected depending on the target molecular orientation direction as described above. For example, in the case of aiming at molecular orientation in the horizontal direction with respect to the substrate, the substrate temperature is set in the above range, and the substrate can be either crystalline or non-crystalline.

  The charge transporting amorphous thin film with controlled molecular orientation according to the present invention can be rephrased as an amorphous thin film with charge transporting properties and controlled molecular orientation. Here, the film thickness of the thin film is 10 nm to 1000 nm. In general, amorphous means that the higher order structure of the molecule has no regularity and shows a random state. This state can be judged from the fact that a halo peak is observed by powder X-ray diffraction and a sharp diffraction peak is not observed. In contrast, an amorphous thin film with controlled molecular orientation can be judged to be amorphous because a halo peak is observed by powder X-ray diffraction, and it can be judged to be amorphous, as well as multi-incidence angle spectroscopic ellipsometry and ultraviolet / visible. The presence of molecular orientation is confirmed from the optical anisotropy observed in the analysis of the absorption spectrum.

In general, the following formula (a) is known for the relationship between the optical anisotropy and the molecular orientation direction (Non-patent Document 2).
^{S = 3 / 2cos 2 θ-} 1/2 = (k e -k o) / (k e + 2k o) formula (a)
(Here, S is orientation parameter, k _e is extinction coefficient in the direction perpendicular to the substrate, k _o denotes the extinction coefficient of the horizontal direction to the substrate.)

In formula (a), k _e and k _o is can be obtained by optical evaluation of the thin film on the substrate, for example, it can be determined by a multi-incident angle spectroscopic ellipsometry. By using this equation, the molecular orientation direction in the thin film can be quantified. For example, the S value is 0 when the thin film does not have optical anisotropy, and the S value is −0.5 when the molecular orientation direction in the thin film is completely horizontal to the substrate. In the charge transporting thin film in which the molecular orientation of the present invention is controlled, in the case of the charge transporting amorphous thin film in which the molecular orientation of the π-conjugated compound is controlled in the horizontal direction with respect to the substrate, the S value is −0.2 to A value in the range of -0.5 is shown.

  In the charge transporting amorphous thin film in which the molecular orientation direction of the present invention is controlled, anisotropy is confirmed in the charge transporting property. That is, since the charge transporting anisotropy is confirmed according to the above-described molecular orientation direction, for example, the charge mobility in the horizontal direction and the vertical direction of the thin film on the substrate is different. When the molecular orientation direction in the thin film is the horizontal direction, the charge mobility in the vertical direction increases when the charge mobility in the horizontal direction is compared with the charge mobility in the vertical direction.

  The charge mobility can be evaluated by various methods. For example, the TOF method or the FET method can be used.

  Various organic electronic devices can be obtained by using the charge transporting amorphous thin film with controlled molecular orientation obtained by the production method of the present invention. For example, elements such as organic EL elements and organic thin film solar cells can be obtained by laminating thin films that prioritize horizontal orientation with respect to the substrate. In the case of an organic EL device, for example, it can be obtained by forming a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode on an ITO glass substrate. In this case, the charge transporting amorphous thin film with controlled molecular orientation of the present invention can be used in one or more layers selected from a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer. In the case of an organic thin film solar cell, for example, it is obtained by forming a p-type semiconductor layer, an n-type semiconductor layer, and a cathode on an ITO glass substrate. At this time, the charge transporting amorphous thin film with controlled molecular orientation of the present invention can be used for either one or both of the p-type semiconductor layer and the n-type semiconductor layer.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
A charge transporting amorphous thin film is prepared using a π-conjugated compound represented by the following formula (4) (BSB-Cz, glass transition point; 116 ° C., L / D = 3.01).

A glass substrate with an ITO electrode controlled at 25 ° C. (hereinafter referred to as an ITO glass substrate) is coated with a BSB-Cz thin film at a vacuum degree of 3.0 × 10 ⁻³ Pa or less on a surface of the ITO electrode by a vacuum evaporation method. Vapor deposition was performed at a thickness of 100 nm in seconds. By optical evaluation of the ITO glass substrate having the obtained BSB-Cz thin film by multi-incidence angle spectroscopic ellipsometry, the extinction coefficient in the direction perpendicular to the substrate of the BSB-Cz thin film on the ITO glass substrate and the substrate On the other hand, the extinction coefficient in the horizontal direction was obtained. By using the obtained value and formula (a), it was found that the orientation parameter of the BSB-Cz thin film on the ITO glass substrate was -0.31. Since the molecular orientation parameter takes a value of -0.2 to -0.5, the BSB-Cz molecule in the BSB-Cz thin film on the ITO glass substrate is controlled in the horizontal direction with respect to the substrate. Was confirmed. As a result of AFM observation of the BSB-Cz film on the ITO glass substrate, it was confirmed that R _rms was 1.1 nm and high surface smoothness was obtained. From these results, it was found that the BSB-Cz thin film on the ITO glass substrate had a molecular orientation in the horizontal direction with respect to the substrate.

Example 2
A silicon (100) substrate having a BSB-Cz thin film was obtained in the same manner as in Example 1 except that a silicon (100) substrate was used instead of the glass substrate having an ITO electrode. For the silicon (100) substrate having the obtained BSB-Cz thin film, the vertical direction extinction coefficient and the horizontal direction extinction coefficient were calculated for the orientation parameters in the same manner as in Example 1. Since this orientation parameter was -0.33, it was confirmed that the BSB-Cz molecules in the BSB-Cz thin film were controlled in the horizontal direction with respect to the substrate. In addition, as a result of XRD evaluation of the BSB-Cz film on the silicon (100) substrate by the Out of Plane method, a sharp diffraction peak derived from silicon (002) and a halo peak indicating amorphous were confirmed. . The results are shown in FIG. In addition, as a result of the In Plane method, a halo peak indicating amorphous was confirmed. The results are shown in FIG.

Example 3
A BSB-Cz thin film was obtained in the same manner as in Example 2 except that the control temperature of the silicon (100) substrate was 90 ° C. The orientation parameters of the BSB-Cz thin film on the substrate were calculated by optical evaluation of silicon (100) having the obtained BSB-Cz thin film by multi-incidence angle spectroscopic ellipsometry. This orientation parameter was -0.10, and it was confirmed that the BSB-Cz molecules in the BSB-Cz thin film on the silicon (100) substrate were not controlled in the horizontal direction with respect to the substrate. Note that the thin film whose orientation is not controlled is useful for applications where such properties are desired.

Example 4
The charge mobility of the charge transporting amorphous thin film whose molecular orientation was controlled in the horizontal direction with respect to the substrate of the π-conjugated compound represented by the formula (4) was evaluated.
By depositing BSB-Cz on the ITO electrode surface of a glass substrate having an ITO electrode controlled at 25 ° C. under a vacuum degree of 3.0 × 10 ⁻³ Pa or less, the ITO glass A glass substrate with an ITO electrode is formed by forming a BSB-Cz thin film on the ITO electrode surface of the substrate at a thickness of about 1000 nm at a rate of 2.0 Å / sec, and further laminating a semitransparent aluminum thin film by 15 nm by the same vacuum deposition method. A device was formed by laminating a BSB-Cz thin film (deposited at 25 ° C.) and an aluminum thin film on top. As a result of evaluating the charge mobility of the obtained multilayer device by the TOF (time of flight) method, the electron mobility was 4 × 10 ⁻⁴ cm ² / Vs and the hole mobility was 0.58 MV / cm at the electric field strength. It was 7 × 10 ⁻⁴ cm ² / Vs.

Example 5
The charge mobility of the charge transporting amorphous thin film whose molecular orientation by the π-conjugated compound represented by the formula (4) is not controlled was evaluated.
In Example 2, the same operation was performed except that the glass substrate having the ITO electrode was controlled at 110 ° C., and the BSB-Cz thin film (deposited at 25 ° C.) and the translucent aluminum thin film were formed on the glass substrate having the ITO electrode. The element which laminated | stacked was produced. As a result of evaluating the charge mobility of the obtained device by the TOF (time of flight) method, the electron mobility was 8 × 10 ⁻⁵ cm ² / Vs and the hole mobility was 4 at an electric field strength of 0.58 MV / cm. × 10 ^-4 cm ² / Vs.

Examples 6-7
Using a π-conjugated compound represented by the following formula (5) (BSP-Cz, L / D = 2.63) and a π-conjugated compound represented by the following formula (6) (L / D = 2.89), A charge transporting amorphous thin film with molecular orientation controlled in the horizontal direction with respect to the substrate was prepared.

  In Example 1, the same operation was carried out except that the compound 5 represented by the formula (5) and the compound 6 represented by the formula (6) were used in place of BSB-Cz, and a thin film was obtained. Asked. The parameter S of compound 5 was -0.29, and the parameter S of compound 6 was -0.28.

Examples 8-10
In Example 1, instead of a glass substrate having an ITO electrode, a quartz substrate, a glass substrate having a silver thin film (100 nm), a π-conjugated compound represented by the following formula (7) (CBP, glass transition point: 62 ° C., L /D=1.85) was used except that a silicon substrate deposited by vapor deposition (50 nm) was used to form a BSB-Cz thin film, and the molecular orientation parameter S of the thin film was determined. The parameter S was -0.45 for the quartz substrate, -0.36 for the glass substrate having a silver thin film (100 nm), and -0.39 for the silicon substrate having a CBP thin film.

Comparative Examples 1 and 2
The same as Example 1 except that CBP (L / D = 1.85) and the π-conjugated compound (BCS, L / D = 2.06) represented by the following formula (8) were used instead of BSB-Cz. Then, the molecular orientation parameter S was obtained. The molecular orientation parameter S was -0.07 for CBP and -0.17 for BCS.

Claims (6)

  A clear melting point, a glass transition point of 60 ° C. or higher, a molecular weight in the range of 400 to 2500, and a charge transporting amine-based π-conjugated compound, the smallest diameter inscribed by the π-conjugated compound When the π-conjugated compound having a ratio (L / D) of the cylinder length (L) to the diameter (D) of 2.5 or more is deposited on the substrate by controlling the substrate temperature, π A method for controlling the orientation direction of a charge transporting amorphous film, comprising controlling the orientation direction of a conjugated compound. The method for controlling the orientation direction of a charge transporting amorphous film according to claim 1, wherein the π conjugated compound is a π conjugated compound represented by the following formula (1).

(Here, Ar _{1 to} Ar ₃ independently represent a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and Ar _{4 to} Ar ₇ independently represent an aromatic hydrocarbon group having 6 to 30 carbon atoms. And two aromatic hydrocarbon groups constituting Ar ₄ and Ar ₅ may be bonded directly or through a substituent to form a condensed heterocyclic ring with N substituted by Ar ₄ and Ar _5. Two aromatic hydrocarbon groups constituting Ar6 and Ar7 may be bonded directly or through a substituent to form a condensed heterocycle with N substituted by Ar6 and Ar7.L _{1 to} L ₂ Independently represents an ethylene group or an acetylene group, and l, m, n, o and p represent an integer of 0 to 6, but any one of l, n and p is not 0.) A π-conjugated compound represented by the following formula (1) that does not show a clear melting point, has a glass transition point of 60 ° C. or higher, and has a molecular weight of 400 to 2500, and is the minimum diameter inscribed by the π-conjugated compound When a π-conjugated compound having a ratio (L / D) of the cylinder length (L) to diameter (D) of 2.5 or more is deposited on the substrate by controlling the substrate temperature, A method for producing a charge transporting amorphous film, characterized by controlling an orientation direction of a compound.

(Here, Ar _{1 to} Ar ₃ independently represent a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and Ar _{4 to} Ar ₇ independently represent an aromatic hydrocarbon group having 6 to 30 carbon atoms. And two aromatic hydrocarbon groups constituting Ar ₄ and Ar ₅ may be bonded directly or through a substituent to form a condensed heterocyclic ring with N substituted by Ar ₄ and Ar _5. Two aromatic hydrocarbon groups constituting Ar6 and Ar7 may be bonded directly or through a substituent to form a condensed heterocycle with N substituted by Ar6 and Ar7.L _{1 to} L ₂ Independently represents an ethylene group or an acetylene group, and l, m, n, o and p represent an integer of 0 to 6, but any one of l, n and p is not 0.) The method for producing a charge transporting amorphous thin film according to claim 3, wherein the π-conjugated compound represented by the formula (1) is a π-conjugated compound represented by the following formula (2).

(Here, Ar _{1 to} Ar ₃ independently represent a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and L _{1 to} L ₂ independently represent an ethylene group or an acetylene group. L, m , N, o, and p represent an integer of 0 to 6, and any one of l, n, and p is not 0.) The method for producing a charge-transporting amorphous thin film according to claim 3, wherein the π-conjugated compound represented by the formula (1) is a π-conjugated compound represented by the following formula (3).

(Here, Ar ₂ represents a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms.)   The temperature of the substrate to be deposited is controlled in the range of 0 ° C. to the glass transition point of the π-conjugated compound −30 ° C., and the molecular orientation of the π-conjugated compound is controlled to be horizontal with respect to the substrate. The method for producing a charge transporting amorphous thin film according to claim 3.

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