JP5953864B2 - Organic thin film transistor - Google Patents

Description

  The present invention relates to an organic thin film transistor that can be used in devices such as organic electroluminescence elements, electronic tags, and liquid crystal display elements.

  As a semiconductor element provided with a semiconductor thin film, an organic thin film transistor provided with an organic semiconductor layer made of an organic semiconductor material as an organic thin film has attracted attention. The organic thin film transistor can be easily formed by a coating method using a solution containing an organic semiconductor material in its production, so that a large area device using the organic thin film transistor can be produced at low cost. There are advantages.

  In the organic thin film transistor, as the field effect mobility is higher, a larger amount of current can be flowed, and an excellent characteristic such as a wide range of adjustable current amount can be obtained. Therefore, studies for improving the field effect mobility of organic thin film transistors have been actively conducted.

JP 2008-235517 A JP 2008-18709 A

APPLIED PHYSICS LETTERS, 2007, 91, 243512 Journal of Applied Physics (JOURNAL OF APPLIED PHYSICS, 2009, 105, 024516)

  However, since the carrier mobility of the conventional organic semiconductor material is not always sufficient, the field effect mobility of the organic thin film transistor is not sufficient.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an organic thin film transistor having high field effect mobility.

  In order to achieve the above-mentioned object, the present inventors have studied paying attention to the charge trapped in the organic thin film transistor. As a result, it was found that the electric field effect mobility of the organic thin film transistor can be improved by capturing the charge different in polarity from the charge used for driving in the organic thin film transistor before driving the organic thin film transistor, and completed the present invention. It came to let you. That is, the present invention provides the following organic thin film transistor. In this specification, the charge used for driving is called “operation carrier”, and the trapped charge having a polarity different from that used for driving is called “captured counter electrode carrier”.

（式中、
Ａｒ^１およびＡｒ^２は、それぞれ独立に、３価の芳香族炭化水素基または３価の複素環基を表し、これらの基は置換基を有していてもよい。
Ｘ^１は、−Ｏ−、−Ｓ−、−Ｃ（＝Ｏ）−、−Ｓ（＝Ｏ）−、−ＳＯ_２−、−Ｃ（Ｒ^５０）（Ｒ^５１）−、−Ｓｉ（Ｒ^５２）（Ｒ^５３）−、−Ｎ（Ｒ^５４）−、−Ｂ（Ｒ^５５）−、−Ｐ（Ｒ^５６）−又は−Ｐ（＝Ｏ）（Ｒ^５７）−を表す。Ｒ^５０、Ｒ^５１、Ｒ^５２、Ｒ^５３、Ｒ^５４、Ｒ^５５、Ｒ^５６及びＲ^５７は、それぞれ独立に、水素原子、ハロゲン原子、アルキル基、アルキルオキシ基、アルキルチオ基、カルボキシル基又はシアノ基を表す。）
［１０］ 前記共役系高分子化合物が、式（２）で表される構造単位を有することを特徴とする、［８］または［９］に記載の有機薄膜トランジスタ。

（式中、
Ａｒ^３およびＡｒ^４は、それぞれ独立に、３価の芳香族炭化水素基または３価の複素環基を表し、これらの基は置換基を有していてもよい。
Ｘ^２及びＸ^３は、それぞれ独立に、−Ｏ−、−Ｓ−、−Ｃ（＝Ｏ）−、−Ｓ（＝Ｏ）−、−ＳＯ_２−、−Ｃ（Ｒ^５０）（Ｒ^５１）−、−Ｓｉ（Ｒ^５２）（Ｒ^５３）−、−Ｎ（Ｒ^５４）−、−Ｂ（Ｒ^５５）−、−Ｐ（Ｒ^５６）−又は−Ｐ（＝Ｏ）（Ｒ^５７）−を表す。Ｒ^５０、Ｒ^５１、Ｒ^５２、Ｒ^５３、Ｒ^５４、Ｒ^５５、Ｒ^５６及びＲ^５７は、前記と同じ意味を表す。） [1] An organic thin film transistor comprising a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer,
An organic thin film transistor having a counter electrode carrier trapped in the gate insulating layer and / or the organic semiconductor layer and driven by an operating carrier having a polarity different from that of the trapped counter electrode carrier.
[2] By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to [1], wherein the trapped counter electrode carriers are generated.
[3] By making the polarity of the potential of the source electrode and the potential of the drain electrode the same as the potential of the gate electrode,
The organic thin film transistor according to [1], wherein the trapped counter electrode carriers are generated.
[4] The organic thin film transistor according to [3], wherein the source electrode and the drain electrode have different potentials.
[5] A floating gate electrode is further provided in the gate insulating layer (provided that the floating gate electrode is provided in a region that does not overlap the source electrode in the thickness direction of the organic semiconductor layer).
By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to [1], wherein the trapped counter electrode carriers are generated in a floating gate electrode.
[6] The gate insulating film material constituting the gate insulating layer has a functional group having a function of capturing charges,
By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to [1], wherein the trapped counter electrode carrier is generated in the functional group.
[7] The trapped counter electrode carrier exists in a region that does not overlap the source electrode in the thickness direction of the organic semiconductor layer, according to any one of [1] to [6]. Organic thin film transistor.
[8] The organic thin film transistor according to any one of [1] to [7], wherein the organic semiconductor layer includes a conjugated polymer compound.
[9] The organic thin film transistor according to [8], wherein the conjugated polymer compound has a structural unit represented by the formula (1).

(Where
Ar ¹ and Ar ² each independently represent a trivalent aromatic hydrocarbon group or a trivalent heterocyclic group, and these groups optionally have a substituent.
X ¹ is —O—, —S—, —C (═O) —, —S (═O) —, —SO ₂ —, —C (R ⁵⁰ ) (R ⁵¹ ) —, —Si (R ^52). ) (R ⁵³ )-, -N (R ⁵⁴ )-, -B (R ⁵⁵ )-, -P (R ⁵⁶ )-or -P (= O) (R ⁵⁷ )-. R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ and R ⁵⁷ are each independently a hydrogen atom, halogen atom, alkyl group, alkyloxy group, alkylthio group, carboxyl group or cyano group. Represents. )
[10] The organic thin film transistor according to [8] or [9], wherein the conjugated polymer compound has a structural unit represented by the formula (2).

(Where
Ar ³ and Ar ⁴ each independently represent a trivalent aromatic hydrocarbon group or a trivalent heterocyclic group, and these groups optionally have a substituent.
X ² and X ³ are each independently —O—, —S—, —C (═O) —, —S (═O) —, —SO ₂ —, —C (R ⁵⁰ ) (R ⁵¹ ). -, -Si (R ⁵² ) (R ⁵³ )-, -N (R ⁵⁴ )-, -B (R ⁵⁵ )-, -P (R ⁵⁶ )-or -P (= O) (R ⁵⁷ )- Represent. R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ and R ⁵⁷ represent the same meaning as described above. )

  ADVANTAGE OF THE INVENTION According to this invention, an organic thin-film transistor with a high field effect mobility can be provided. The present invention can also provide an organic electroluminescence device, an electronic tag, and a liquid crystal display device including such an organic thin film transistor.

1 is a schematic cross-sectional view of a field effect organic thin film transistor according to a first embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 2nd Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 3rd Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 4th Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor which concerns on 5th Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 6th Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 7th Embodiment. It is a schematic cross section of the field effect type organic thin-film transistor concerning 8th Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as necessary. In the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted.

<Organic thin film transistor>
The organic thin film transistor of the present invention is an organic thin film transistor comprising a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer, and is captured by the gate insulating layer and / or the organic semiconductor layer. The counter carrier is configured to be driven by an operating carrier having a polarity different from that of the trapped counter electrode carrier.
The organic thin film transistor of the present invention is preferably a field effect organic thin film transistor. A field effect organic thin film transistor includes a source electrode and a drain electrode, an organic semiconductor layer serving as a current path between them, a gate electrode for controlling the amount of current passing through the current path, and an organic semiconductor layer disposed between the organic semiconductor layer and the gate electrode. An insulating layer. It is particularly preferable that the source electrode and the drain electrode are provided in contact with the organic semiconductor layer, and a gate electrode is provided with an insulating layer in contact with the organic semiconductor layer interposed therebetween.

  Hereinafter, a field effect organic thin film transistor, which is a representative example of the organic thin film transistor of the present invention, will be specifically described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a field effect organic thin film transistor according to the first embodiment. The field effect organic thin film transistor has a general structure among field effect organic thin film transistors.
The field effect organic thin film transistor of FIG. 1 includes a substrate 1, a gate electrode 4 formed on the substrate 1, an insulating layer 3 formed on the substrate 1 so as to cover the gate electrode 4, and an insulating layer 3 And the organic semiconductor layer 2 containing an organic semiconductor material formed so as to cover at least a part of the source electrode 5 and at least a part of the drain electrode 6.

  In the field effect organic thin film transistor, the organic semiconductor layer 2 serves as a current path (channel) between the source electrode 5 and the drain electrode 6. The gate electrode 4 controls the amount of current passing through the current path (channel) in the organic semiconductor layer 2 by applying a voltage. An undoped intrinsic semiconductor is used for the organic semiconductor layer 2 of the field effect organic thin film transistor. Therefore, when a negative voltage is applied to the gate electrode 4 depending on the combination of the organic semiconductor material used, the insulating layer, the electrode, etc., the device structure, or the like, the field effect organic thin film transistor is not connected to the insulating layer 3 of the organic semiconductor layer 2. When holes injected from the source electrode are accumulated near the interface and a positive voltage is applied to the gate electrode 4 and a p-type transistor through which a current flows, the source electrode near the interface between the insulating layer 3 of the organic semiconductor layer 2 There are n-type transistors in which injected electrons are accumulated and current flows. Holes in the p-type transistor correspond to operating carriers, and electrons in the n-type transistor correspond to operating carriers.

  When the organic semiconductor layer, electrode, and insulating layer used in the organic thin film transistor are selected appropriately, the structure of the organic thin film transistor is devised, or a large potential difference is provided between the electrodes provided in the organic thin film transistor, the operation is performed. Carriers having different polarities from the carriers can be injected. In this specification, a carrier having a polarity different from that of the operating carrier is defined as a counter electrode carrier.

  Organic thin film transistors capable of injecting counter electrode carriers include organic thin film transistors called bipolar transistors that operate as both p-type and n-type transistors. In the case of an ambipolar transistor, both holes and electrons can be operating carriers, but when driving as a p-type transistor, holes are defined as operating carriers, and when driving as an n-type transistor, electrons are operating carriers. It is defined as

  The counter electrode carrier injected into the organic thin film transistor may be trapped in the organic thin film transistor. In order to maintain an electrical neutral state while the counter electrode carrier is trapped, extra operating carriers are induced in the organic thin film transistor as compared with the case where the counter electrode carrier is not trapped. Therefore, the operating carrier density existing in the organic thin film transistor is larger than that in the case where there is no counter electrode carrier. As a result, the current density flowing between the source electrode and the drain electrode of the organic thin film transistor is improved, and the field effect mobility is increased. An effect is obtained.

  It is preferable that the density of the counter electrode carriers to be trapped is larger because the induced operating carrier density is increased and the field effect mobility is increased.

  From the viewpoint of sufficiently reducing the off-state current and obtaining stable characteristics even after repeated operations, in the voltage range in which the transistor is driven by operating carriers, counter-carriers are injected or trapped counter-carriers are outside the element. It is desirable that it is not released to any other position or moved to another position.

  The captured counter electrode carrier is released after a certain period of time. The time from the capture of the counter electrode carrier to the separation depends on the region to be captured and the energy level of the region to be captured. When the counter electrode carrier is detached, if the operation of injecting and capturing the counter electrode carrier again is performed, the characteristics before the separation can be obtained. Therefore, the longer the time from when the counter electrode carrier is captured to when it is separated, the more the characteristic does not change over a longer time, and therefore the number of times the counter electrode carrier is injected is reduced.

  The higher the temperature, the easier the trapped counter electrode carrier is detached. Therefore, it is preferable that the transistor of the present invention is provided with a radiator such as a heat sink or a cooling device because the effect of the present invention can be obtained for a long time.

  The counter electrode carrier is at least one selected from the group consisting of the gate electrode, the source electrode, and the drain electrode by setting at least one of the electrodes provided in the organic thin film transistor to a potential different from at least one of the other electrodes. It can be injected from one electrode. Furthermore, a new electrode different from the source electrode, the drain electrode, and the gate electrode can be provided, and counter electrode carriers can be injected from the new electrode.

  In the thickness direction of the organic semiconductor layer, when the counter electrode carrier is captured in a region overlapping with the source electrode, the threshold voltage may change. It is preferable to capture the counter electrode carrier in a region that does not overlap. Further, the region for capturing counter electrode carriers is preferably separated by 20% or more of the channel length from the region in contact with the source electrode in the thickness direction of the organic semiconductor layer, and is 50% or more of the channel length. It is more preferable that they are separated by.

  In order to capture counter electrode carriers in a region that does not overlap with the source electrode in the thickness direction of the organic semiconductor layer, it is preferable that the source electrode and the gate electrode have the same potential.

  In the thickness direction of the organic semiconductor layer, when a counter electrode carrier is captured in a region in contact with the drain electrode, since operating carriers are induced in the vicinity of the drain electrode, pinch-off in the vicinity of the drain electrode in the saturation region is less likely to occur. This is preferable because the density of current flowing between the source electrode and the drain electrode and field effect mobility can be further improved.

  When the counter electrode carrier is injected from the drain electrode, it is preferable because the counter electrode carrier is easily captured in the region near the drain electrode and is difficult to be captured in the region other than the vicinity of the drain electrode, compared with the case where the counter electrode carrier is injected from the gate electrode or the source electrode . In order to capture the counter-carrier in the vicinity of the drain electrode, the potential of the gate electrode and the potential of the source electrode are the same, and the potential of the drain electrode is different from the potential of the gate electrode and the source electrode, Counter electrode carriers can be injected from the drain electrode.

  When injecting the counter electrode carrier from the drain electrode, if the operating carrier is simultaneously injected into the organic thin film transistor from the source electrode, the counter electrode carrier disappears due to recombination, so that the counter electrode carrier cannot be efficiently captured. Sometimes. Depending on the material used for the organic thin film transistor, the structure, the surrounding environment, and the like, operating carriers may be injected from the source electrode even when the potential of the gate electrode and the potential of the source electrode are the same. In such a case, injection of operating carriers can be prevented by setting the potentials of the source electrode and the drain electrode to the same polarity as the potential of the gate electrode.

  In the case where the polarity of the potential of the source electrode and the potential of the drain electrode is the same as the potential of the gate electrode, and the potential difference between the potential of the gate electrode and the potential of the source electrode is large, And the counter electrode carriers are captured in a region overlapping with the source electrode in the thickness direction of the organic semiconductor layer, and the threshold voltage may change. Therefore, the potential difference between the gate electrode potential and the source electrode potential is preferably smaller than the potential difference between the gate electrode potential and the drain electrode potential.

The capture region of the counter electrode carrier is a gate insulating layer and / or an organic semiconductor layer (including an interface between the gate insulating layer and the organic semiconductor layer), but is an interface between the gate insulating layer and the organic semiconductor layer, Alternatively, a gate insulating layer is preferable because a trapping amount of a counter electrode carrier, a trapping region of the counter electrode carrier, and the like can be controlled by controlling a functional group present in the gate insulating layer.
For example, polar groups such as hydroxyl groups function as functional groups that capture charges, and alkyl groups and aryl groups function as functional groups that do not easily capture charges, so by selectively forming these functional groups, the counter electrode The trapping amount of the counter electrode carrier can be controlled by controlling the trapping region of the carrier or controlling the density of the functional group.

  In order to use the functional group that captures the charge, it is preferable to use a compound that forms a monomolecular film because it can be carried out by a simple process. For example, the gate insulating film material constituting the gate insulating layer is immersed in a solution obtained by dissolving a compound that forms the monomolecular film in an organic solvent to form a monomolecular film having a desired functional group on the surface of the gate insulating layer. A method of forming a monomolecular film having a desired functional group by applying a solution obtained by dissolving a compound that forms a monomolecular film in an organic solvent or the like by a printing method can be used. In addition, a monomolecular film having a desired functional group can be formed on the surface of the gate insulating layer by a gas phase reaction.

The monomolecular film can be formed, for example, by bonding a molecule having a group that binds to a hydroxyl group such as an organosilane compound or phosphonic acid on an insulating film having a hydroxyl group.
Examples of the organic silane compound include halogenated organic silane and alkoxy organic silane. When increasing the density of functional groups, trihalogenated organosilanes or trialkoxyorganosilanes that have three groups that bind to hydroxyl groups can be used to form organic silane monolayers that accumulate more densely. it can. As the insulating film having a hydroxyl group, silicon or various metal oxide films can be used. Further, an organic insulating film having a hydroxyl group such as polyvinylphenol, or an organic / inorganic composite material having a hydroxyl group such as silsesquioxane can be used.

  Examples of the functional group that easily traps charges include polar groups such as a hydroxyl group, a cyano group, a carbonyl group, a phenol group, an amino group (which may be substituted or unsubstituted), and a nitro group. Examples of the functional group that does not easily trap charges include nonpolar groups such as alkyl groups, aryl groups, monovalent heterocyclic groups, acetyl groups, vinyl groups, and pentafluorophenyl groups. Examples of the alkyl group include a methyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a tetradecyl group, a hexadecyl group, and an octadecyl group. Note that a monomolecular film having a high surface free energy having a short-chain alkyl group or the like as a surface functional group may have, for example, a crystal of an organic semiconductor layer formed in an upper layer, even if it has a nonpolar group that does not easily trap charges. In some cases, the charge is trapped by inhibiting the conversion.

  The functional group can be formed by selectively applying a solution containing a compound having a desired functional group by a printing method. Patterning is also possible by forming functional groups on the entire surface and then irradiating unnecessary portions with ultraviolet light or laser to remove the formed functional groups.

  When a solution containing a compound having a desired functional group is selectively applied by a printing method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, or a spray coating method. It is preferable to use a screen printing method, a flexographic printing method, an offset printing method, an ink jet printing method, a microcontact printing method, a gravure offset printing method, or the like.

  The density of the functional group can also be adjusted by changing the solution used for immersion treatment or printing, the concentration and amount of the gas phase used for the gas phase reaction, and the treatment time.

  In addition to the method of forming a monomolecular film, as a method of selectively providing a surface functional group on the gate insulating layer, for example, a photosensitive insulating material is used to form a gate insulating film material (reacting to specific light). The surface functional group can be selectively provided by irradiating the region that captures the counter electrode carrier with light that reacts with the gate insulating film material. is there.

  The coating liquid for forming the gate insulating layer may be selectively applied to control the region where the counter electrode carriers are captured. For example, by selectively coating a coating solution containing an insulating layer material that easily captures counter electrode carriers and a coating solution containing an insulating layer material that hardly captures counter electrode carriers, a region that selectively captures counter electrode carriers is formed. Can do. For gate insulation layer coating, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset printing method Ink jet printing method, micro contact printing method, gravure offset printing method and the like can be used. A gate insulating layer made of a different gate insulating film material may be provided by photolithography. In the case where a plurality of gate insulating layers are provided, it is preferable that the surfaces of these gate insulating layers be connected smoothly without impeding carrier transportability.

  Counter electrode carriers can also be captured by providing the second gate electrode in a region in the gate insulating layer where it is desired to capture the counter electrode carriers. The second gate electrode in the gate insulating layer is called a floating gate electrode, and the organic thin film transistor having the floating gate electrode is called a floating gate organic thin film transistor and is used for a nonvolatile memory or the like. Usually, the floating gate electrode is arranged in a region overlapping with the channel in the thickness direction of the organic semiconductor layer, and by injecting a counter electrode carrier into the floating gate electrode, an operating carrier is induced in the entire channel portion of the organic thin film transistor, and the transistor element To control the threshold voltage. By selectively forming the floating gate electrode, it can serve as a region for capturing the counter electrode carrier of the present invention.

  In the case where a floating gate electrode for capturing a counter electrode carrier is provided, it is preferable because a region for capturing the counter electrode carrier can be precisely controlled by the position of the gate electrode.

  The floating gate electrode for capturing the counter electrode carriers is preferably formed in a region that does not overlap with the source electrode in the thickness direction of the organic semiconductor layer, because the threshold voltage hardly changes. Further, the region where the floating gate electrode is formed is preferably separated from the region in contact with the source electrode by a length of 20% or more of the channel length in the thickness direction of the organic semiconductor layer, and the length of 50% or more of the channel length. It is particularly preferable that they are separated from each other.

  The floating gate electrode for capturing the counter-carrier is preferably formed in a region in contact with the drain electrode in the thickness direction of the organic semiconductor layer, because pinch-off hardly occurs and high current density and high field-effect mobility can be obtained. .

  When the floating gate electrode for capturing the counter electrode carrier is provided, the periphery is surrounded by the gate insulating film material constituting the gate insulating layer. Is preferred because it persists.

  In the case where a floating gate electrode for capturing the counter electrode carrier is provided, since the injection is performed through the gate insulating layer, it is preferable that the thinner the gate insulating layer is, the easier the injection is.

  The floating gate electrode includes the gate electrode, the source electrode, and the drain by setting the potential of at least one of the electrodes included in the organic thin film transistor to a potential different from the potential of at least one of the other electrodes. Counter electrode carriers can be injected from at least one electrode selected from the electrodes through the gate insulating layer. It is preferable to inject from an electrode installed at a position closest to the floating gate electrode.

  For the gate insulating layer provided with the floating gate electrode, for example, in the case of an organic thin film transistor having a bottom gate structure, if an oxide film formed on the surface of the gate electrode or the floating gate electrode is used, a thickness capable of easily injecting a counter electrode carrier And good insulation with respect to the operating carrier can be achieved. Furthermore, the insulation of the gate insulating layer using an oxide film is enhanced, the surface free energy of the gate insulating layer is controlled to facilitate the formation of an upper layer of the gate insulating layer, or the organic semiconductor formed on the gate insulating layer is formed. From the viewpoint of enhancing crystallinity, it is more preferable to form the above-described monomolecular film on the oxide film.

  In the case where the insulating layer is formed by oxidizing the gate electrode or the floating gate electrode, a method of forming highly doped silicon, aluminum, or the like as the electrode and oxidizing it by oxygen plasma treatment or heat treatment can be used. In particular, when aluminum is used as an electrode, a gate electrode or a floating gate electrode can be selectively formed by mask vapor deposition or the like, which is preferable.

  The electrode provided in the organic thin film transistor is preferably composed of a low resistance material, for example, gold, platinum, silver, copper, chromium, palladium, aluminum, indium, molybdenum, calcium, lithium fluoride, barium, titanium. It is particularly preferable to be composed of These materials may be used alone or in combination of two or more.

  In the case of injecting operating carriers from the source electrode and counter electrodes from the drain electrode, it is preferable to use the same material for the source electrode and the drain electrode because the process becomes simple.

  The electrode that easily injects holes into the organic semiconductor layer is particularly preferably composed of, for example, gold, platinum, silver, copper, chromium, palladium, aluminum, indium, and molybdenum.

  As an electrode material that easily injects electrons into the organic semiconductor layer, it is particularly preferable that the electrode material is made of, for example, gold, silver, copper, calcium, lithium fluoride, barium, titanium, or aluminum.

  As a method different from the method of injecting the counter electrode carrier from the above-mentioned electrode, for example, the counter electrode carrier is generated by the excitation of the organic semiconductor material constituting the organic semiconductor layer by light, and the counter electrode carrier is trapped in the organic thin film transistor. it can. By controlling the light intensity, the irradiation position, and the potential of the electrode at the time of irradiation, it is possible to capture the counter electrode carrier at an arbitrary position. The wavelength and intensity of the light used at this time are preferably those that do not deteriorate the components in the organic thin film transistor.

  In the case of capturing the counter electrode carrier by the above light, generation and capture of the counter electrode carrier is possible with sunlight, room light, or light generated in a device including the organic thin film transistor of the present invention. In the case where the organic thin film transistor is used under the condition of being irradiated with light, an operation for capturing the counter electrode carrier may be unnecessary, which is preferable.

  The organic semiconductor material used for the organic semiconductor layer will be described.

  The organic semiconductor material used for the organic semiconductor layer has carrier transport properties. Here, carrier transportability is a characteristic that allows carriers (meaning electrons and holes) to move within the structure when a structure such as a thin film is formed. The carrier transporting organic semiconductor compound which is one embodiment of the organic semiconductor material is an organic compound having a structure or an electronic state that can exhibit such carrier transporting property.

  Examples of the carrier transporting organic semiconductor compound include a carrier transporting polymer compound and a carrier transporting low molecular compound, and a carrier transporting polymer compound is preferable.

  Next, the carrier transporting low molecular weight compound used for the organic semiconductor layer will be described.

  Suitable carrier transporting low molecular weight compounds include low molecular weight compounds having a π-conjugated structure (for example, polycyclic aromatic compounds). Examples of the low molecular compound having a π-conjugated structure include a compound having a structure possessed by a carrier transporting polymer compound described later and having a polystyrene-equivalent number average molecular weight of less than 2,000.

  Examples of the polycyclic aromatic compound include naphthalene, anthracene, tetracene, rubrene, pentacene, benzopentacene, dibenzopentacene, tetrabenzopentacene, naphthopentacene, hexacene, heptacene, nanoacene, fluorene, fluoranthene, phenanthrene, chrysene, triphenylene, tetra Fen, picene, flumilen, tetraphen, pyrene, antanthrene, peropyrene, coronene, benzocoronene, dibenzocoronene, hexabenzocoronene, benzodicronene, perylene, terylene, diperylene, quaterylene, trinaphthylene, heptaphene, obalene, rubicene, violanthrone, isoviolanthrone , Circumanthracene, bisanthene, zestrene, heptazethrene, pyrans, keklen, tiger Sen, include derivatives of fullerene (C60, C70, C60-PCBM, C70-PCBM, etc.) and their compounds.

  The polycyclic aromatic compound may be a compound containing a hetero atom. Examples of the polycyclic aromatic compound containing a hetero atom include benzodithiophene, naphthodithiophene, anthradithiophene, tetradithiophene, pentadithiophene, hexadithiophene, dibenzothiophene, dibenzothienodibenzothiophene, thienothiophene, dithio Thienothiophene, tetrathienoacene, pentathienoacene, dibenzofuran, carbazole, dibenzosilole, benzodithiaazole, naphthodithiaazole, anthradithiazole, tetradithiaazole, pentadithiaazole, hexadithiaazole, thiazolo Thiazole, tetrathiafulvalene, dibenzothiafulvalene, dithiophenethiafulvalene, tetracyanoquinodimethane, tetracyanonaphthodimethane, naphthalenetetracarboxy Kkujiimido, include derivatives of perylenetetracarboxylic carboxylic diimide and these compounds. Further, compounds containing metals such as phthalocyanine, porphyrin, tetrabenzoporphyrin, triphenylamine, and derivatives of these compounds are also included in the polycyclic aromatic compound containing a hetero atom.

Examples of the derivative of the compound include a compound having a halogen atom or a monovalent group, and a quinone derivative of the compound. Specific examples of the halogen atom and monovalent group are the same as the specific examples of the halogen atom and monovalent group represented by R ¹ and R ² described later. For example, rubrene is mentioned as a derivative of tetracene. In addition, quinone derivatives of the compounds are also included in the compound derivatives. For example, pentacenedione is mentioned as a derivative of pentacene.

  The carrier transporting low molecular weight compound is preferably a polycyclic aromatic compound and more preferably a compound represented by the formula (3) because high field effect mobility can be expected.

In formula (3),
A, B and C each independently represent an aromatic ring or a heterocyclic ring.
n represents an integer of 2 to 8. When a plurality of A are present, they may be the same or different.
R ¹ and R ² each independently represents a halogen atom or a monovalent group.
s and t are each independently an integer of 0 to 4. When there are a plurality of R ^{1 s} , they may be the same or different. When there are a plurality of R ^{2 s} , they may be the same or different.

Examples of the halogen atom represented by R ¹ and R ² include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the monovalent group represented by R ¹ and R ² include an alkyl group, an aliphatic unsaturated hydrocarbon group, an aryl group, a heteroaryl group, an alkoxy group, an amino group, a carbonyl group, a nitro group, and a hydroxyl group. , A cyano group, an arylalkyl group, an aryloxy group, a heteroarylalkyl group, a heteroaryloxy group, and an alkylsilyl group.
These monovalent groups may be substituted with a substituent. Examples of the substituent include alkyl groups represented by R ¹ and R ² , aliphatic unsaturated hydrocarbon groups, aryl groups, heteroaryl groups, alkoxy groups, amino groups, carbonyl groups, nitro groups, hydroxyl groups, and cyano groups. , Arylalkyl group, heteroarylalkyl group, aryloxy group, heteroaryloxy group, and alkylsilyl group.

  The alkyl group may be linear or branched, and the carbon number thereof is preferably 1-20, and more preferably 1-16. Examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n -Heptyl group, n-octyl group, n-nonanyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n -Heptadecyl group, n-octadecyl group, n-nonadecyl group and n-eicosanyl group are mentioned.

  The aliphatic unsaturated hydrocarbon group may be linear or branched, and the carbon number thereof is preferably 1-20, and more preferably 1-16. Examples of the aliphatic unsaturated hydrocarbon group include a vinyl group, a 1-propenyl group, an allyl group, a propargyl group, an isopropenyl group, a 1-butenyl group, and a 2-butenyl group. From the viewpoint of chemical stability of the compound represented by the formula (3), a compound having one double bond or triple bond in the chain as the aliphatic unsaturated hydrocarbon group is preferable.

  The alkoxy group may be linear or branched, and the carbon number thereof is preferably 1-20, and more preferably 1-16. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

  The aryl group represents the remaining group obtained by removing one hydrogen atom directly bonded to the carbon atom constituting the ring from the aromatic hydrocarbon. 6-60 are preferable and, as for carbon number of an aryl group, 6-20 are more preferable. Examples of the aromatic hydrocarbon include benzene, fluorene, naphthalene and anthracene.

  The heteroaryl group represents a remaining group obtained by removing one hydrogen atom directly bonded to a carbon atom constituting a ring from a heterocyclic compound. 2-60 are preferable and, as for carbon number of a heteroaryl group, 3-20 are more preferable. Here, the heterocyclic compound means a compound in which at least one carbon atom of the ring is a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, a phosphorus atom, a boron atom, or a silicon atom, and an aromatic compound It is preferably a heterocyclic compound. Examples of the aromatic heterocyclic compound include a thiophene ring, a selenophene ring, and a furan ring.

The amino group may have a substituent. The number of carbon atoms of the amino group is usually 0 to 40 without including the number of carbon atoms of the substituent.
Examples of the substituent that the amino group may have include an alkyl group, an aryl group, and a heteroaryl group. Specific examples of the amino group having a substituent include a methylamino group, a dimethylamino group, a diethylamino group, a diisopropylamino group, a dicyclohexylamino group, a pyrrolidyl group, a piperidyl group, a phenylamino group, a diphenylamino group, and a 1-naphthylamino group. , 2-naphthylamino group, pyridylamino group and the like.

  In the arylalkyl group, the aryl moiety preferably has 6 to 60 carbon atoms, and more preferably 6 to 20 carbon atoms. Moreover, it is preferable that carbon number is 1-20, and, as for the alkyl part in an arylalkyl group, it is more preferable that it is 1-10.

  In the aryloxy group, the aryl moiety preferably has 6 to 60 carbon atoms, and more preferably 6 to 20 carbon atoms.

  The heteroarylalkyl group preferably has 4 to 60 carbon atoms and more preferably 4 to 20 carbon atoms in the heteroaryl moiety. The alkyl moiety in the heteroarylalkyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 10 carbon atoms.

  In the heteroaryloxy group, the heteroaryl moiety preferably has 4 to 60 carbon atoms, and more preferably 4 to 20 carbon atoms.

  Examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, a tert-butyldimethylsilyl group, a triisopropylsilyl group, and a tert-butyldiphenylsilyl group.

  In formula (3), A, B and C each independently represent an aromatic ring or a heterocyclic ring, and A and B, A and C are each condensed to each other. Here, “condensed with each other” means that a part of a bond forming one ring also forms a part of the other ring. Examples of A, B and C include a benzene ring, a hetero 6-membered ring, a hetero 5-membered ring, and a cyclopentadiene ring. These rings may have a substituent.

  Moreover, n which shows the repeating number of the ring represented by A is an integer of 2-8 from a viewpoint of carrier transportability, the integer of 2-6 is preferable, and the integer of 2-4 is more preferable.

As the aromatic ring or heterocyclic ring represented by A, a benzene ring which may have a substituent, a thiophene ring which may have a substituent, a selenophene ring which may have a substituent and a substituent A cyclopentadiene ring which may have a group is preferable, and a benzene ring which may have a substituent and a thiophene ring which may have a substituent are more preferable. When a plurality of A are present, they may be the same or different. A (when there are a plurality of A, at least one A) is preferably a heterocyclic 5-membered ring which may have a substituent, and a thiophene ring or a substituent which may have a substituent. A selenophene ring which may have is more preferable, and a thiophene ring which may have a substituent is more preferable. This is because the compound represented by the formula (3) can have higher carrier transportability by having at least one thiophene ring.
The aromatic ring or heterocyclic ring represented by B and C is preferably a benzene ring which may have a substituent.

Examples of the substituent that the aromatic ring or heterocyclic ring represented by A to C may have include a halogen atom and a monovalent group. Specific examples of the halogen atom and the monovalent group are the same as the specific examples of the halogen atom and the monovalent group represented by R ¹ and R ² described above.

  As a compound represented by the formula (3), a higher field effect mobility can be obtained, so that a compound represented by the formula (4), a compound represented by the formula (5), and a formula (6) are represented. The compound represented by formula (7), the compound represented by formula (8) and the compound represented by formula (9) are preferred.

In formula (4)-formula (9),
R ¹ , R ² , s and t have the same meaning as described above.
R ⁵ and R ⁶ each independently represents a hydrogen atom, a halogen atom or a monovalent group. When a plurality of R ⁵ are present, they may be the same or different. When a plurality of R ⁶ are present, they may be the same or different. Specific examples of the halogen atom and monovalent group represented by R ⁵ and R ⁶ are the same as the specific examples of the halogen atom and monovalent group represented by R ¹ and R ² described above.
X represents a sulfur atom, an oxygen atom or a selenium atom. A group represented by the formula (c) or a group represented by the formula (d) is represented. When two or more X exists, they may be the same or different. From the viewpoint of simplifying the production of the compounds represented by formulas (4) to (9), it is preferable that all Xs are the same.

In formula (c) and formula (d),
R ⁷ and R ⁸ each independently represents a hydrogen atom, a halogen atom or a monovalent group. R ⁷ and R ⁸ may be bonded to each other to form a ring together with the carbon atom or silicon atom to which each is bonded. Specific examples of the halogen atom and monovalent group represented by R ⁵ and R ⁶ are the same as the specific examples of the halogen atom and monovalent group represented by R ¹ and R ² described above.
The ring formed by R ⁷ and R ⁸ may be a monocyclic ring or a condensed ring, and may be a cyclic hydrocarbon or a heterocyclic ring, but a monocyclic hydrocarbon ring or a monocyclic ring containing an oxygen atom or a sulfur atom as a hetero atom Heterocycles are preferred. These rings may have a substituent. Examples of the substituent include a halogen atom and a monovalent group. Specific examples of the halogen atom and the monovalent group are the same as the specific examples of the halogen atom and the monovalent group represented by R ¹ and R ² described above.

  As a compound represented by Formula (4)-Formula (9), the compound represented by Formula (10a)-Formula (10i) is preferable.

In formula (10a)-formula (10i),
R ²⁰ and R ²¹ each independently represents a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a triisopropylsilylethynyl group, a phenyl group, or a phenyl group substituted with an alkyl group having 1 to 16 carbon atoms. An alkyl group and a triisopropylsilylethynyl group are preferable.

Among the compounds represented by formula (10a) to formula (10i), a compound represented by formula (10c) (hereinafter sometimes referred to as “BTBT”) is preferable because of higher carrier transportability. From the viewpoint of increasing the melting point of BTBT, R ²⁰ and / or R ²¹ is preferably a phenyl group or a phenyl group substituted with a C 1-16 alkyl group.

  Next, the carrier transporting polymer compound used for the organic semiconductor layer will be described.

  As the carrier transporting polymer compound, a polymer compound having a conjugated unsaturated structure (sometimes referred to as “conjugated polymer compound”) is preferable. The polymer compound having a conjugated unsaturated structure includes, for example, a structure selected from the group consisting of a structure containing a double bond, a structure containing a triple bond, a structure containing an aromatic ring, and an arylamine structure, alone or in combination. A homopolymer or copolymer having a conjugation extended as a whole of the polymer compound is preferable. When the carrier transporting polymer compound is a copolymer, it may be a random copolymer or a block copolymer.

  An ethylene structure is mentioned as a structure containing a double bond. The “ethylene structure” as used herein refers to a structure that becomes ethylene when two bonds for bonding with other structural units are replaced with hydrogen atoms. In addition, the same definition is applied in the following description of each “structure”. Moreover, an acetylene structure is mentioned as a structure containing a triple bond.

  Examples of the structure containing an aromatic ring include a monocyclic or polycyclic aromatic hydrocarbon structure and a monocyclic or polycyclic heterocyclic structure. Examples of monocyclic or polycyclic aromatic hydrocarbon structures include phenylene structure, naphthylene structure, fluorene structure, acenaphthene structure, phenanthrene structure, anthracene structure, fluoranthene structure, pyrene structure, perylene structure, rubrene structure, chrysene structure, and these Examples include a polynuclear condensed compound structure in which the rings constituting the structure are condensed.

  Specific examples of the monocyclic or polycyclic aromatic hydrocarbon structure include structures represented by formulas (11a) to (11f). Among these, a structure represented by the formula (11a) having a fluorene structure, a structure represented by the formula (11b), and a structure represented by the formula (11e) having a pyrene structure are particularly preferable. Note that in formulas (11a) to (11f), a bond to which a substituent is not attached means a bond that forms a bond with another structural unit.

In formulas (11a) to (11f),
R ¹¹ , R ¹² and R ¹⁴ each independently represents a hydrogen atom, a halogen atom or a monovalent group,
R ¹³ represents a halogen atom or a monovalent group.
u represents an integer of 0 or more. When there are a plurality of R ¹¹ , they may be the same or different. When there are a plurality of R ¹³ , they may be the same or different.
Specific examples of the halogen atom and monovalent group represented by R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are the same as the specific examples of the halogen atom and monovalent group represented by R ¹ and R ² described above. It is.
Two groups selected from R ¹¹ , R ¹² , R ¹³ and R ¹⁴ bonded to the same carbon atom or adjacent carbon atoms are bonded to each other to form a ring together with the carbon atoms to which they are bonded. It may be. The ring formed may be a monocyclic ring or a condensed ring, and may be a cyclic hydrocarbon or a heterocyclic ring, but a monocyclic cyclic hydrocarbon and a monocyclic heterocyclic ring containing an oxygen atom or a sulfur atom as a hetero atom preferable. These rings may have a substituent. Examples of the substituent include a halogen atom and a monovalent group. Specific examples of the halogen atom and the monovalent group are the same as the specific examples of the halogen atom and the monovalent group represented by R ¹ and R ² described above.

  Examples of the monocyclic heterocyclic structure include, for example, a furan structure, a thiophene structure, a pyrrole structure, a silole structure, an oxazole structure, an isoxazole structure, a thiazole structure, an isothiazole structure, an imidazole structure, and an oxadiazole, which are hetero five-membered ring structures. Examples thereof include a structure, a thiadiazole structure and a pyrazole structure, and a pyridine structure, a pyridazine structure, a pyrimidine structure, a pyrazine structure, a triazine structure and a tetrazene structure, which are hetero 6-membered ring structures.

  Examples of polycyclic heterocyclic structures include benzoxazole structures, benzothiazole structures, benzimidazole structures, quinoline structures, isoquinoline structures, cinnoline structures, quinazoline structures, phthalazine structures, benzothiadiazole structures, benzotriazine structures, And phenazine structure, phenanthridine structure, acridine structure, carbazole structure, dibenzofuran structure, dibenzothiophene structure, dibenzosilole structure, diphenylene oxide structure, thienothiophene structure, thiazolothiazole structure, dithienothiophene structure, benzobisthiophene structure And a polycyclic condensed ring structure such as a benzobisthiazole structure.

Examples of the monocyclic or polycyclic heterocyclic structure include, for example, a structure in which a structure represented by Formula (12a) to Formula (12q) and a structure represented by Formula (12a) to Formula (12q) are bonded together. Structure is mentioned.
Among the monocyclic or polycyclic heterocyclic structures, from the viewpoint of obtaining higher mobility, a structure represented by the formula (12a), a condensed structure in which a plurality of structures represented by the formula (12a) are bonded, Two or more of the structures represented by the formula (12a) have passed through, but the structure is preferable, the structure represented by the formula (12a) in which Z is a sulfur atom, and the formula (12a) in which Z is a sulfur atom. A structure in which two or more of a condensed structure in which a plurality of structures represented by the formula (1) are bonded and a structure represented by the formula (12a) in which Z is a sulfur atom is transferred is particularly preferable.
Examples of the condensed structure in which a plurality of structures represented by the formula (12a) are bonded include a structure represented by the formula (12f). Two or more of the structures represented by the formula (12a) have passed through, but examples of the structure include a structure represented by the formula (12c) and a structure represented by the formula (12n).
In the following formula, a bond to which no substituent is attached means a bond that forms a bond with another structural unit.

In formula (12a)-formula (12q),
R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and u represent the same meaning as described above. When there are a plurality of R ¹⁴ , they may be the same or different. In particular, R ¹³ and R ¹⁴ are preferably hydrogen atoms.
Z represents a hetero atom such as an oxygen atom, a sulfur atom, a nitrogen atom, a phosphorus atom, a boron atom, or a silicon atom, preferably an oxygen atom or a sulfur atom, and particularly preferably a sulfur atom.

  Examples of the arylamine structure include a triphenylamine structure, an N, N′-diphenylbenzidine structure, an N, N′-1,4-phenylenediamine structure, a diphenylnaphthylamine structure, and two phenyl moieties in these structures. Examples include a structure in which carbon atoms are bonded directly or through a hetero atom. Examples of the structure in which two carbon atoms of the phenyl moiety in these structures are bonded directly or via a hetero atom include an N-phenylphenoxazine structure and an N-phenylphenothiazine structure.

  The carrier transporting polymer compound is preferably a polymer having a single structural unit or a combination of a plurality of structural units including the structure described above.

The carrier transporting polymer compound has a structural unit represented by the above formula (1) and a structural unit represented by the formula (2), thereby realizing high mobility and high solubility in an organic solvent. Therefore, it is preferable because the counter carrier can be more easily injected. In the above structure, the formulas (11a) to (11d), the formula (12c), the formula (12f), the formula (12h), the formula (12i), the formula (12k), and the formulas (12m) to (12p) Since it corresponds to the structural unit represented by Formula (1) or the structural unit represented by Formula (2), it is preferable. The halogen atom, alkyl group, alkyloxy group, alkylthio group, carboxyl group and cyano group represented by R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ and R ⁵⁷ are as described above. Specific examples of the halogen atom and monovalent group represented by R ¹ and R ² are the same.

  In a preferred embodiment of the carrier transporting polymer compound, a carbon atom adjacent to a carbon atom in which a bond with an adjacent structural unit is formed is unsubstituted (that is, bonded to a hydrogen atom). ) Or a halogen atom (defined as condition 1). The structure represented by the above formula (11a), formula (11c), formula (11d), formula (11f), formula (12a) to (12k), formula (12m) to (12p) satisfies the condition 1. It is preferable to obtain.

In another preferred embodiment of the carrier transporting polymer compound, at least one end of a bond formed between the structural units is an atom on the 5-membered ring in the structural unit including the 5-membered ring. (It is defined as condition 2). In order to satisfy the condition 2 when the structural units represented by the formulas (12a) to (12g), the formula (12j), and the formulas (12n) to (12q) are at least one of two adjacent structural units preferable.
When the carrier transporting polymer compound satisfies at least one of the above conditions 1 and 2, the conjugated unsaturated structure in the polymer compound is well formed, and the carrier transporting property of the carrier transporting polymer compound is further increased. There is a tendency to be good.

  The structural unit represented by the formula (12c), the formula (12f), or the formula (12n) is preferable because it is represented by the formula (1) or the formula (2) and can satisfy the conditions 1 and 2 described above.

  As the carrier transporting polymer compound, those having a combination of structural units shown in Table 1 or Table 2 ((13a) to (13o)) are preferable. Furthermore, the combination (13e), the combination (13f), and the combination (13g) are more preferable because they include the structural unit represented by the formula (1) or the formula (2) and can satisfy the above-described conditions 1 and 2. is there. In addition, all the codes | symbols in the general formula in a table | surface represent the same meaning as the above.

  The carrier transporting polymer compounds having combinations (13a) to (13o) in Table 1 and Table 2 are represented by the weights represented by Formula (14a) to Formula (14s) described in Table 3 or Table 4. Coalescence is preferred. In particular, the polymer represented by the formula (14g), the formula (14h), or the formula (14i) includes the structural unit represented by the formula (1) or the formula (2) and satisfies the above-described conditions 1 and 2. Therefore, it is more preferable. M in Table 3 and Table 4 represents an integer of 1 or more. The range of m is preferably a range in which the number average molecular weight of the polymer in terms of polystyrene is 3,000 or more, more preferably 5,000 to 1,000,000, and 10,000 to 500,000. A range of

  The terminal structure of the carrier transporting polymer compound is preferably a stable structure from the viewpoint of the characteristics and durability of the organic thin film transistor when used in the organic semiconductor layer of the organic thin film transistor. When the above-mentioned polymer has an unstable end group, it is preferable to replace the unstable group with a stable end group or to protect the end.

Examples of the stable end group include the aryl group and heteroaryl group represented by R ¹ and R ² described above.

  From the viewpoint of increasing the solubility of the carrier transporting polymer compound in an organic solvent, etc., and further simplifying the application of the organic semiconductor material, the terminal group is an alkyl group which may be fluorine-substituted, fluorine-substituted. An aliphatic unsaturated hydrocarbon group which may be substituted, an aryl group which may be substituted with fluorine, or an alkoxy group which may be substituted with fluorine is preferred. The terminal group is also preferably a group having a conjugated structure continuous with the main chain forming the conjugated structure of the carrier transporting polymer compound, for example. Examples of such a terminal group include those containing an aryl group or heteroaryl group (monovalent aromatic heterocyclic group) bonded to the main chain via a carbon-carbon bond. In addition, when several polymeric terminal groups exist, they may be same or different, respectively.

As a method for forming the organic semiconductor layer included in the organic thin film transistor, in addition to the vacuum deposition method, for example, a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating Method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset printing method, ink jet printing method, dispenser printing method, nozzle coating method, capillary coating method, microcontact printing method, etc., and these The coating method which combined these methods is mentioned. Examples of the coating method combining these methods include a gravure offset printing method in which a gravure coating method and an offset printing method are combined. When these coating methods are used, not only a thin film having a high carrier transport property can be obtained, but also a device having a large area can be easily formed.
Among the coating methods, spin coating, ink jet printing, flexographic printing, screen printing, microcontact printing, gravure coating, offset printing, and gravure / offset printing are preferred.

  In preparing the solution used for the coating method, a method of dissolving or dispersing the compound forming the organic semiconductor layer in a solvent is used. The solvent is not particularly limited as long as it can dissolve or disperse the compound to be used satisfactorily. For example, unsaturated hydrocarbon solvents such as toluene, xylene, mesitylene, tetralin, decalin, bicyclohexyl, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, carbon tetrachloride, chloroform, dichloromethane, dichloroethane, chlorobutane, bromobutane Halogenated saturated hydrocarbon solvents such as chloropentane, bromopentane, chlorohexane, bromohexane, chlorocyclohexane and bromocyclohexane, halogenated unsaturated hydrocarbon solvents such as chlorobenzene, dichlorobenzene and trichlorobenzene, tetrahydrofuran, tetrahydropyran, etc. An ether solvent or the like can be appropriately selected and applied. From the viewpoint of satisfactorily forming a thin film, the content of components other than the solvent in the coating solution is preferably about 0.1 to 5% by mass. When the compound to be used is not sufficiently dissolved, heating as described later may be performed.

  In the formation of the organic semiconductor layer, a thin film is formed by applying such a coating solution onto a predetermined substrate. At this time, when the coating solution contains a solvent, it is preferable to remove the solvent simultaneously with the coating or after the coating.

  Such application may be performed in a heated state. This makes it possible to apply a high-concentration coating solution, to form a more uniform thin film, and to select and use materials that have been difficult to apply at room temperature. Application in a heated state can be performed, for example, by using a pre-heated application liquid or by applying the substrate while heating.

  In the organic thin film transistor, from the viewpoint of further improving the carrier transport property of the organic semiconductor layer, a step of imparting a predetermined orientation to the organic semiconductor layer thus formed may be further performed. In the oriented organic semiconductor layer, since the molecules constituting the organic semiconductor layer are aligned in one direction, the carrier transportability tends to be further improved.

  As the alignment method, for example, a method known as a liquid crystal alignment method can be used. Among them, a rubbing method, a photo-alignment method, a shearing method (shear stress application method), a coating method for controlling the drying direction such as a pulling coating method, and the like are easy to use because the alignment method is simple. A sharing method is preferred.

  The organic semiconductor layer may partially contain the solvent used at the time of manufacture and other inevitable components. From the viewpoint of having good carrier transportability and from the viewpoint of easily forming a sufficiently strong organic thin film, it is preferably 1 nm to 100 μm, more preferably 2 nm to 1000 nm, further preferably 5 nm to 500 nm, Especially preferably, it is 20 nm-200 nm.

  As the gate insulating layer, a gate insulating film made of an inorganic insulator or an organic insulator can be used. Examples of the inorganic insulator include silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, and titanium oxide. Examples of the organic insulator include polyethylene, polyester, polyimide, polyphenylene sulfide, organic glass, polyvinyl alcohol, polyvinyl phenol, polyparaxylene, and polyacrylonitrile. In addition, an inorganic insulator and an organic insulator may be used individually by 1 type, or may use 2 or more types together. The thickness of the gate insulating layer is preferably 50 to 1000 nm.

  For the gate electrode, metal such as gold, platinum, silver, copper, chromium, palladium, aluminum, indium, molybdenum, low resistance polysilicon, low resistance amorphous silicon, tin oxide, indium oxide, indium / tin oxide (ITO ) Or the like can be used. These materials may be used alone or in combination of two or more. Further, a highly doped silicon substrate may be used as the gate electrode. A highly doped silicon substrate has both a property as a gate electrode and a property as a substrate. Therefore, when a highly doped silicon substrate is used, in the organic thin film transistor in which the substrate and the gate electrode are in contact with each other, the description of the substrate in the following diagram may be omitted. The thickness of the gate electrode is preferably 0.02 to 100 μm.

  The source electrode and the drain electrode are preferably made of a low-resistance material, and the thickness of each of the source electrode and the drain electrode is preferably 0.02 to 1000 μm.

  Examples of the substrate include a glass substrate, a flexible film substrate, a plastic substrate, and the like. The thickness of the substrate is preferably 10 to 2000 μm.

  In the organic thin film transistor, a layer made of a compound different from the organic semiconductor material contained in the organic semiconductor layer may be interposed between the source and drain electrodes and the organic semiconductor layer. By interposing such a layer, the contact resistance between the source and drain electrodes and the organic semiconductor layer may be reduced, and the carrier mobility of the organic thin film transistor may be further increased.

  The layer made of a compound different from the organic semiconductor material contained in the organic semiconductor layer includes a low molecular compound having an electron or hole transport property, an alkali metal, an alkaline earth metal, a rare earth metal, and a complex of these metal and an organic compound. Halogens such as iodine, bromine, chlorine and iodine chloride; sulfur oxide compounds such as sulfuric acid, anhydrous sulfuric acid, sulfur dioxide, and sulfates; nitric oxide compounds such as nitric acid, nitrogen dioxide, and nitrates; perchloric acid, hypochlorous acid, etc. A layer composed of an aromatic thiol compound such as an alkyl thiol compound, an aromatic thiol, and a fluorinated alkyl aromatic thiol.

  Next, a representative example of a field effect organic thin film transistor other than the field effect organic thin film transistor according to the first embodiment will be described with reference to the drawings.

  FIG. 2 is a schematic cross-sectional view of a field effect organic thin film transistor according to the second embodiment. 2 includes a substrate 1, a gate electrode 4 formed on the substrate 1, a gate insulating layer 3 formed on the substrate 1 so as to cover the gate electrode 4, and a gate electrode. 4 is an organic semiconductor layer 2 formed on the gate insulating layer 3 formed below, and an organic semiconductor layer so as to partially cover the surface of the organic semiconductor layer 2 formed on the gate insulating layer 3 2 and a source electrode 5 and a drain electrode 6 formed on the substrate 2.

  FIG. 3 is a schematic cross-sectional view of a field effect organic thin film transistor according to the third embodiment. The field effect organic thin film transistor shown in FIG. 3 covers the substrate 1, the source electrode 5 and the drain electrode 6 formed on the substrate 1, and at least a part of the source electrode 5 and at least a part of the drain electrode 6. The organic semiconductor layer 2 formed in this way, the gate insulating layer 3 formed on the organic semiconductor layer 2, and the gate electrode 4 formed on the gate insulating layer 3.

  FIG. 4 is a schematic cross-sectional view of a field effect organic thin film transistor according to the fourth embodiment. The field effect organic thin film transistor shown in FIG. 4 is formed on the organic semiconductor layer 2 so as to partially cover the surface of the substrate 1, the organic semiconductor layer 2 formed on the substrate 1, and the organic semiconductor layer 2. A source electrode 5 and a drain electrode 6, a gate insulating layer 3 formed so as to cover at least a part of the source electrode 5 and at least a part of the drain electrode 6, and a gate electrode 4 formed on the insulating layer 3. Is provided.

  FIG. 5 is a schematic cross-sectional view of a field effect organic thin film transistor according to a fifth embodiment. 5 includes a substrate 1, a gate electrode 4 formed on the substrate 1, a gate insulating layer 3 formed on the substrate 1 so as to cover the gate electrode 4, and a gate insulating layer. 3 so as to cover the floating gate electrode 7 provided in the gate electrode 3, the source electrode 5 and the drain electrode 6 formed on the gate insulating layer 3, and at least a part of the source electrode 5 and at least a part of the drain electrode 6. And an organic semiconductor layer 2 formed.

  FIG. 6 is a schematic cross-sectional view of a field effect organic thin film transistor according to a sixth embodiment. The field effect organic thin film transistor shown in FIG. 6 includes a substrate 1, a gate electrode 4 formed on the substrate 1, a gate insulating layer 3 formed on the substrate 1 so as to cover the gate electrode 4, and gate insulation. The floating gate electrode 7 provided in the layer 3, the organic semiconductor layer 2 formed on the gate insulating layer 3 on which the gate electrode 4 is formed below, and the gate insulating layer 3 are formed on the bottom. A source electrode 5 and a drain electrode 6 formed on the organic semiconductor layer 2 so as to partially cover the surface of the organic semiconductor layer 2 are provided.

  FIG. 7 is a schematic cross-sectional view of a field effect organic thin film transistor according to a seventh embodiment. The field effect organic thin film transistor shown in FIG. 7 covers the substrate 1, the source electrode 5 and the drain electrode 6 formed on the substrate 1, and at least a part of the source electrode 5 and at least a part of the drain electrode 6. Formed on the organic semiconductor layer 2, the gate insulating layer 3 formed on the organic semiconductor layer 2, the floating gate electrode 7 provided in the gate insulating layer 3, and the gate insulating layer 3. And a gate electrode 4.

  FIG. 8 is a schematic cross-sectional view of a field effect organic thin film transistor according to an eighth embodiment. The field effect organic thin film transistor shown in FIG. 8 is formed on the organic semiconductor layer 2 so as to partially cover the surface of the substrate 1, the organic semiconductor layer 2 formed on the substrate 1, and the organic semiconductor layer 2. Source electrode 5 and drain electrode 6, gate insulating layer 3 formed to cover at least part of source electrode 5 and at least part of drain electrode 6, and floating gate electrode provided in gate insulating layer 3 7 and a gate electrode 4 formed on the gate insulating layer 3.

<Method for producing organic thin film transistor>
Hereinafter, a method for manufacturing an organic thin film transistor will be described using the organic thin film transistor of the first embodiment shown in FIG. 1 as an example.

  Although it will not restrict | limit especially if the board | substrate 1 does not inhibit the characteristic as an organic thin-film transistor, A glass substrate, a flexible film substrate, and a plastic substrate can also be used.

  First, the gate electrode 4 is formed on the substrate 1 by vapor deposition, sputtering, plating, CVD, or the like. Note that an n− type silicon substrate doped with a high concentration may be used as the gate electrode 4.

  Next, the insulating layer 3 is formed on the gate electrode 4 by CVD, plasma CVD, plasma polymerization, thermal evaporation, thermal oxidation, anodic oxidation, cluster ion beam evaporation, LB method, spin coating method, casting. , Micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset printing method, inkjet printing method, etc. To do. When a highly doped n-type silicon substrate is used as the gate electrode 4, a silicon oxide film can be formed by thermally oxidizing the surface, and the silicon oxide film is insulated. It may be used as the layer 3.

  Next, the source electrode 5 and the drain electrode 6 are formed on the insulating layer 3 by vapor deposition, sputtering, plating, CVD, or the like. Although not shown in FIG. 1, a layer for promoting charge injection may be provided between the source electrode 5 and the drain electrode 6 and the organic semiconductor layer 2 thereafter.

  And when forming the organic-semiconductor layer 2 on the insulating layer 3, it is preferable on manufacture to use a compound soluble in an organic solvent as an organic-semiconductor material. The organic thin film transistor of the present invention uses a solution obtained by dissolving an organic semiconductor material in an organic solvent, spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, It can be produced by a dip coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, an ink jet printing method, a microcontact printing method, a gravure offset printing method, or the like.

  After producing the organic thin film transistor, a protective film is preferably formed on the organic thin film transistor in order to protect the element. With this protective film, the organic thin film transistor is shielded from the atmosphere, and deterioration of the characteristics of the organic thin film transistor can be suppressed. Moreover, the influence at the time of forming the display device driven on an organic thin-film transistor with a protective film can be reduced.

  Examples of the method for forming the protective film include a method of covering with a UV curable resin, a thermosetting resin, an inorganic SiONx film, or the like. In order to effectively cut off from the atmosphere, it is preferable to carry out the steps from the preparation of the organic thin film transistor to the formation of the protective film without exposure to the atmosphere (for example, in a dry nitrogen atmosphere or in a vacuum).

  The organic thin-film transistor of this invention can be used suitably for an organic electroluminescent element, an electronic tag, and a liquid crystal display element.

  Examples will be shown below for illustrating the present invention in more detail, but the present invention is not limited to these examples.

<Example 1: Production and evaluation of organic thin film transistor 1>
The surface of the heavily doped n-type silicon substrate to be the gate electrode was thermally oxidized to form a silicon oxide film having a thickness of 50 nm as a gate insulating layer. Next, a source electrode and a drain electrode having a channel length of 100 μm and a channel width of 1 mm were formed on the silicon oxide film by a photolithography process. The source electrode and the drain electrode were formed by laminating chromium and gold in this order from the silicon oxide film side. The substrate on which the source and drain electrodes were formed was ultrasonically cleaned with acetone for 10 minutes, and then irradiated with ozone UV for 20 minutes to provide hydroxyl groups on the gate insulating film. Thereafter, the substrate was immersed in a toluene diluted solution of phenylethyltrichlorosilane for 2 minutes to silane-treat the surface of the substrate, and phenylethyl groups were provided on the gate insulating film.

  The compound represented by the formula (14i), which is an organic semiconductor material, is dissolved in o-dichlorobenzene, which is a solvent, to prepare a solution having a compound concentration of 0.5% by mass, and the solution is filtered through a membrane filter. Thus, a coating solution was prepared.

  Thereafter, the obtained coating solution is applied to the side of the substrate on which the source electrode and the drain electrode are formed by spin coating, whereby a thin film of the compound represented by formula (14i) having a thickness of about 27 nm is formed. Formed. Then, it baked for 30 minutes with the hotplate set to 170 degreeC in the glove box substituted with nitrogen. The thin film of the compound represented by the formula (14i) functions as an organic semiconductor layer.

  The organic thin film transistor 1 produced as described above was operated as a p-type transistor. The gate voltage Vg is set to 0 V, the source voltage Vs is set to 0 V, the drain voltage Vd is set to −40 V, electrons as counter electrode carriers are injected from the drain electrode over about 10 seconds, and then the source voltage Vs is set to 0 V and the drain voltage Vd is set. Was set to -10V, and the transistor characteristics were measured under the condition that the gate voltage Vg was changed to 0 to -10V. Table 5 shows the field-effect mobility (mobility) of the organic thin film transistor 2 calculated from the transfer characteristics obtained by such measurement.

<Comparative Example 1: Production and Evaluation of Organic Thin Film Transistor C1>
The surface of the heavily doped n-type silicon substrate to be the gate electrode was thermally oxidized to form a silicon oxide film having a thickness of 50 nm as a gate insulating layer. Next, a source electrode and a drain electrode having a channel length of 100 μm and a channel width of 1 mm were formed on the silicon oxide film by a photolithography process. The source electrode and the drain electrode were formed by laminating chromium and gold in this order from the silicon oxide film side. The substrate on which the source and drain electrodes were formed was ultrasonically cleaned with acetone for 10 minutes, and then irradiated with ozone UV for 20 minutes to provide hydroxyl groups on the gate insulating film. Thereafter, the substrate was immersed in a toluene diluted solution of phenylethyltrichlorosilane for 2 minutes to silane-treat the surface of the substrate, and phenylethyl groups were provided on the gate insulating film.

  The compound represented by the formula (14i), which is an organic semiconductor material, is dissolved in o-dichlorobenzene, which is a solvent, to prepare a solution having a compound concentration of 0.5% by mass, and the solution is filtered through a membrane filter. Thus, a coating solution was prepared.

  Thereafter, the obtained coating solution is applied to the side of the substrate on which the source electrode and the drain electrode are formed by spin coating, whereby a thin film of the compound represented by formula (14i) having a thickness of about 27 nm is formed. Formed. Then, it baked for 30 minutes with the hotplate set to 170 degreeC in the glove box substituted with nitrogen. The thin film of the compound represented by the formula (14i) functions as an organic semiconductor layer.

  The organic thin film transistor element C1 manufactured as described above was operated as a p-type transistor. The transistor characteristics were measured under the condition that the source voltage Vs was set to 0 V, the drain voltage Vd was set to −10 V, and the gate voltage Vg was changed to 0 to −10 V. Table 5 shows the field effect mobility (mobility) of the organic thin film transistor C1 calculated from the transfer characteristics obtained by the measurement.

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Organic semiconductor layer, 3 ... Gate insulating layer, 4 ... Gate electrode, 5 ... Source electrode, 6 ... Drain electrode, 7 ... Floating gate electrode

Claims (10)

An organic thin film transistor comprising a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and an organic semiconductor layer,
A counter electrode carrier trapped in an interface between the gate insulating layer and the organic semiconductor layer or the gate insulating layer , and an operating carrier having a polarity different from that of the trapped counter electrode carrier,
The counter electrode carrier induces the operating carrier in the vicinity of the interface with the gate insulating layer of the organic semiconductor layer ;
And driven by the induced motion carrier,
Organic thin film transistor. By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to claim 1, wherein the trapped counter electrode carriers are generated. By making the polarity of the potential of the source electrode and the potential of the drain electrode the same as the potential of the gate electrode,
The organic thin film transistor according to claim 1, wherein the trapped counter electrode carriers are generated.   The organic thin film transistor according to claim 3, wherein the potential of the source electrode and the potential of the drain electrode are different. A floating gate electrode is further provided in the gate insulating layer (however, the floating gate electrode is provided in a region not overlapping with the source electrode in the thickness direction of the organic semiconductor layer).
By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to claim 1, wherein the trapped counter electrode carriers are generated in a floating gate electrode. The gate insulating film material constituting the gate insulating layer has a functional group having a function of capturing charges,
By setting the potential of the gate electrode and the potential of the source electrode to the same potential, and setting the potential of the drain electrode to a potential different from the potential of the gate electrode and the potential of the source electrode,
The organic thin film transistor according to claim 1, wherein the trapped counter electrode carrier is generated in the functional group.   The organic thin film transistor according to any one of claims 1 to 6, wherein the trapped counter electrode carrier is present in a region that does not overlap the source electrode in a thickness direction of the organic semiconductor layer.   The organic thin film transistor according to any one of claims 1 to 7, wherein the organic semiconductor layer contains a conjugated polymer compound. 9. The organic thin film transistor according to claim 8, wherein the conjugated polymer compound has a structural unit represented by the formula (1).

(Where
Ar ¹ and Ar ² each independently represent a trivalent aromatic hydrocarbon group or a trivalent heterocyclic group, and these groups optionally have a substituent.
X ¹ is —O—, —S—, —C (═O) —, —S (═O) —, —SO ₂ —, —C (R ^5).
0 ) (R ⁵¹ )-, -Si (R ⁵² ) (R ⁵³ )-, -N (R ⁵⁴ )-, -B (R ⁵⁵ )
^{-, - P (R 56)} - or ^{-P (= O) (R 57} ) - represents a. R ⁵⁰ , R ⁵¹ , R ⁵² ,
R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ and R ⁵⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkyloxy group, an alkylthio group, a carboxyl group or a cyano group. ) The organic thin film transistor according to claim 8 or 9, wherein the conjugated polymer compound has a structural unit represented by the formula (2).

(Where
Ar ³ and Ar ⁴ each independently represent a trivalent aromatic hydrocarbon group or a trivalent heterocyclic group, and these groups optionally have a substituent.
X ² and X ³ are each independently —O—, —S—, —C (═O) —, —S (═O) —, —SO ₂ —, —C (R ⁵⁰ ) (R ⁵¹ ). -, -Si (R ⁵² ) (R ⁵³ )-, -N (R ⁵⁴ )-, -B (R ⁵⁵ )-, -P (R ⁵⁶ )-or -P (= O) (R ⁵⁷ )- Represent.
R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ and R ⁵⁷ are each independently a hydrogen atom, halogen atom, alkyl group, alkyloxy group, alkylthio group, carboxyl group or cyano group. Represents. )

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