JP2009302328A - Organic transistor and organic semiconductor element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic transistor which is remarkably excellent not only in transistor characteristics and endurance but also in reliability of the transistor characteristic. <P>SOLUTION: An organic transistor 10 includes: an organic semiconductor layer 1 comprising an organic semiconductor material; a metal oxide layer 2 which is formed to be in contact with the organic semiconductor layer 1 and comprises a metal oxide; and a source electrode 3 and a drain electrode 4 which are formed to be conductive to the metal oxide layer 2 and comprise a conductive material. The organic semiconductor material is a so-called wide gap material having a benzothiophene frame and a benzoselenophene frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic transistor using an organic semiconductor material and an organic semiconductor element using the same.

  In recent years, semiconductor transistors typified by TFTs tend to expand their applications with the development of display devices. Such a semiconductor transistor functions as a switching element when electrodes are connected via a semiconductor material.

Conventionally, as a semiconductor material used for the semiconductor transistor, an inorganic semiconductor material such as silicon (Si), gallium arsenide (GaAs), or indium gallium arsenide (InGaAs) has been used. A semiconductor transistor using such an inorganic semiconductor material is also used for a display TFT array substrate of a display element.
On the other hand, as the semiconductor material, an organic semiconductor material made of an organic compound is also known. Such an organic semiconductor material has an advantage that it can be enlarged at a lower cost than the inorganic semiconductor material, can be formed on a flexible plastic substrate, and is stable against mechanical impact. Researches assuming application to display devices such as flexible displays typified by electronic paper have been actively conducted.

  A transistor using such an organic semiconductor material (hereinafter referred to as an organic transistor) is required to have further improved performance as its application expands. In particular, in addition to further improving the transistor characteristics typified by the threshold voltage, mobility, subthreshold coefficient, and the like, improvement in durability against oxygen and light is a problem. In this respect, the organic transistor is often determined by the performance of the organic semiconductor material, so that the transistor characteristics and durability of the organic transistor are improved. There has been a need to develop materials.

  To date, typical examples of organic semiconductor materials used in organic transistors include pentacene or polythiophenes, and these organic semiconductor materials have been widely used practically because of their excellent transistor characteristics. However, as the application of organic transistors has been expanded in recent years, further improvement in performance has been demanded. However, elements manufactured using conventional organic semiconductor materials have not always been sufficient in terms of durability. Here, “durability” refers to the resistance of the element to oxygen and light.

Under such circumstances, in recent years, materials having a benzothiophene skeleton or a benzoselenophene skeleton are known as new organic semiconductor materials (for example, Non-Patent Document 1). Since the organic semiconductor material having these skeletons is a so-called wide gap material having a large HOMO-LUMO energy gap, it is stable against oxygen and light, and thus has been a weak point of the conventional organic semiconductor transistor. It has an advantageous aspect in that it can be improved, and has attracted attention as a novel organic semiconductor material. However, although such a wide gap material can surely exhibit superior characteristics in terms of durability, since it is a wide gap material, it has a large HOMO-LUMO energy gap. Compared with organic semiconductor materials, there is a problem that transistor characteristics are inferior, and it has been difficult to use practically.

  It is known that in an organic transistor, transistor characteristics can be improved by forming a layer made of a metal oxide between an organic semiconductor layer and a source electrode and a drain electrode (for example, Non-Patent Document 2, 3) Durability cannot be improved even by such a method.

  Further, in addition to the above-described transistor characteristics and durability, it is desired to improve the reliability of transistor characteristics in organic transistors. However, in the past, useful methods that can improve such reliability have been observed. It was not put out. Here, “reliability” refers to the resistance of an element when a certain voltage is continuously applied (bias stress).

Kazuo Takimiya etal, "2,7-Diphenyl [1] benzothieno [3,2-b] benzothiophen, A New Organic Semiconductor for Air-Stable Organic Field-Effect Tansistor with Mobilities up to 2.0cm2V-1s-1" J.AM. CHEM.SOC.2006,128,12604 Daisuke Kumaki “Reducing the contact resistance of bottom-contact pantacen thin-film transistors by using a MoOx carrier injection layer” Appl. Phys. Lett. 92,013301 (2008) Chih-Wei Chu et.al.``High-performance organic thin-film transistors with metal oxide / metal bilayer electrode '' Appl.Phys.Lett.87,193508 (2005)

  The present invention has been made in view of such problems, and it is a main object of the present invention to provide an organic transistor that not only has excellent transistor characteristics and durability, but also has excellent transistor characteristic reliability. It is what.

  As a result of diligent studies to solve the above problems, the inventors of the present invention have heretofore identified a specific structure from among wide gap materials that have been difficult to be practically used as organic semiconductor materials due to poor transistor characteristics. By selecting and using an organic semiconductor material having a layer made of a metal oxide having a specific work function in relation to the organic semiconductor material so as to be in contact with the organic semiconductor layer, transistor characteristics may be unexpected. In addition to finding a significant improvement, it has also been found that the reliability of transistor characteristics, which was not thought to be improved even when using a layer made of a metal oxide, is improved. Thus, the present invention has been completed.

  That is, in order to solve the above problems, the present invention provides an organic semiconductor layer made of an organic semiconductor material, a metal oxide layer made of a metal oxide and in contact with the organic semiconductor layer, and the metal oxide layer. An organic transistor having a source electrode and a drain electrode made of a conductive material, wherein the organic semiconductor material has a molecular structure represented by any of the following formulas (I) to (III): An organic transistor, wherein the work function of the metal oxide is smaller than the ionization potential of the organic semiconductor material and larger than the work function of the conductive material. provide.

  In the above formulas (I) to (III), X represents S or Se, and in the above formula (I), Y independently represents an alkyl group or a phenyl group.

According to the present invention, an organic semiconductor material having a structure represented by any one of the above formulas (I) to (III) is used for the organic semiconductor layer, and the work function of the organic oxide layer is the organic By using a metal oxide that is smaller than the ionization potential of the semiconductor material and larger than the work function of the conductive material used for the source electrode and the drain electrode, an organic transistor having significantly excellent transistor characteristics and durability is obtained. Can do. In addition, by using a combination of the organic semiconductor material and the metal oxide, an organic transistor having excellent transistor characteristic reliability can be obtained.
Thus, according to the present invention, it is possible to provide an organic transistor that not only has excellent transistor characteristics and durability, but also has excellent transistor characteristic reliability.

  In the present invention, the metal oxide is preferably molybdenum oxide. Since the work function of molybdenum oxide is relatively close to the work function of the organic semiconductor material having the structure represented by any of the above formulas (I) to (III), molybdenum oxide is used as the metal oxide. It is because the transistor characteristic and durability of the organic transistor of this invention can be improved more by being used. Further, when molybdenum oxide is used as the metal oxide, the reliability of transistor characteristics can be further improved.

  In the present invention, the organic semiconductor material has a structure represented by the formula (I), and Y in the formula (I) is an alkyl group having 1 to 18 carbon atoms. Is preferred. Thereby, in the organic semiconductor layer in the present invention, the arrangement regularity of the organic semiconductor material can be improved, and as a result, the transistor characteristics of the organic transistor of the present invention can be further improved. Further, by using the organic semiconductor material as described above, the organic semiconductor material can be used as a solvent, and the organic semiconductor layer can be easily formed. As a result, the organic transistor of the present invention is manufactured. It is because it can be made excellent in aptitude.

  The present invention also provides an organic semiconductor element having a substrate and a plurality of organic transistors formed on the substrate, wherein the organic transistor is the organic transistor according to the present invention. A semiconductor device is provided.

  According to the present invention, since the organic transistor according to the present invention is used, an organic semiconductor element having excellent transistor characteristics and durability and excellent transistor characteristic reliability can be obtained.

  The organic transistor of the present invention has an effect that not only transistor characteristics and durability are remarkably excellent, but also reliability of transistor characteristics is excellent.

The present invention relates to an organic transistor and an organic semiconductor element using the same.
Hereinafter, these inventions will be described in order.

A. Organic Transistor First, the organic transistor of the present invention will be described. As described above, the organic transistor of the present invention includes an organic semiconductor layer made of an organic semiconductor material, a metal oxide layer made of a metal oxide formed so as to be in contact with the organic semiconductor layer, and energizing the metal oxide layer. And having a source electrode and a drain electrode made of a conductive material, wherein the organic semiconductor material is represented by any of the following formulas (I) to (III) in the molecular structure: It has a structure, and the work function of the metal oxide is smaller than the ionization potential of the organic semiconductor material and larger than the work function of the conductive material.

Such an organic transistor of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the organic transistor of the present invention. As illustrated in FIG. 1, an organic transistor 10 of the present invention includes an organic semiconductor layer 1 made of an organic semiconductor material, and a metal oxide layer 2 made of a metal oxide so as to be in contact with the organic semiconductor layer 1. The metal oxide layer 2 is formed so as to be energized, and has a source electrode 3 and a drain electrode 4 made of a conductive material.
In such an example, in the organic transistor 10 of the present invention, a compound having a structure represented by any of the above formulas (I) to (III) is used as the organic semiconductor material used for the organic semiconductor layer 1. In addition, the work function of the metal oxide used for the metal oxide layer 2 is smaller than the ionization potential of the organic semiconductor material and larger than the work function of the conductive material.
As illustrated in FIG. 1, the organic transistor of the present invention normally functions as a transistor by using the gate electrode 5 and the gate insulating layer 6.

Here, in FIG. 1, as an example of the organic transistor of the present invention, the one having a so-called bottom gate / top contact type structure is illustrated, but the organic transistor of the present invention is limited to the one having such a structure. Is not to be done.
The structure of the organic transistor of the present invention will be described in detail below.

  According to the present invention, an organic semiconductor material having a structure represented by any one of the above formulas (I) to (III) is used for the organic semiconductor layer, and the work function of the organic oxide layer is the organic By using a metal oxide that is smaller than the ionization potential of the semiconductor material and larger than the work function of the conductive material used for the source electrode and the drain electrode, an organic transistor having significantly excellent transistor characteristics and durability can be obtained. it can. In addition, by using a combination of the organic semiconductor material and the metal oxide, an organic transistor having excellent transistor characteristic reliability can be obtained.

Since the organic semiconductor material used in the present invention has a large HOMO-LUMO energy gap, its semiconductor characteristics are inferior to those of typical organic semiconductor materials such as polythiophenes and pentacenes. Even if it is used for the above, it is said that it is difficult to obtain an organic transistor having desired characteristics. In the present invention, a material that is not necessarily preferable as a material used for an organic transistor in the past is used in combination with a metal oxide having a predetermined work function, thereby eliminating a drawback due to a large HOMO-LUMO energy gap. At the same time, the present inventors have succeeded in obtaining an organic transistor that is excellent in transistor characteristics and durability by maintaining the high durability against oxygen and light inherently provided in the wide gap material.
Here, although it has been conventionally known that a certain transistor characteristic can be improved to some extent by forming a layer made of a metal oxide in an organic transistor, an organic semiconductor material having a predetermined structure in the present invention, and a predetermined The transistor characteristic improvement effect obtained by combining metal oxides having a work function of 2 is significantly more than the degree of transistor characteristics that are conventionally expected to be improved by using a layer made of metal oxide for an organic transistor. It is a large one, and a remarkable effect peculiar to the present invention can be recognized here.
For example, as important transistor characteristics of an organic transistor, mobility, subthreshold coefficient, threshold voltage, and the like can be cited. When a conventional organic semiconductor material (for example, dioctylquarterthiophene) is used in combination with a metal oxide, Although the mobility can be improved by about 1.3 times, there is almost no change in the subthreshold coefficient and the threshold voltage. In the present invention, this is significantly surpassed, and by using a metal oxide, for example, the mobility is about twice, the subthreshold coefficient is about 1/4, and the threshold voltage is about 1/3. It is possible to obtain. As described above, the organic transistor of the present invention is formed by forming a layer made of a metal oxide having a specific work function, and using an organic semiconductor material that has conventionally been difficult to use practically. It is possible to obtain an organic transistor having characteristics superior to those of typical organic semiconductor materials. In addition, the organic transistor of the present invention has an advantage of not only excellent transistor characteristics but also excellent durability due to the use of a wide gap material.

Furthermore, the organic transistor of the present invention has an effect that the transistor characteristics are excellent in addition to the above-described effects.
As described above, it has been known that transistor characteristics are improved to some extent by forming a layer made of a metal oxide in an organic transistor, but it is not known at all that other effects can be obtained. It was. In this regard, the organic transistor of the present invention not only improves the transistor characteristics but also improves the reliability of the transistor characteristics by combining an organic semiconductor material having a specific structure and a metal oxide having a predetermined work function. It is possible to obtain an extraordinary effect that the effect of improvement can be obtained. As described above, the effect of improving the reliability of the transistor characteristics could not be predicted from the conventional technical level, and in this respect, the remarkable effect peculiar to the present invention is recognized. It is something that can be done.
Therefore, according to the present invention, it is possible to provide an organic transistor that not only has excellent transistor characteristics and durability, but also has excellent transistor characteristic reliability.

The organic transistor of the present invention has at least an organic semiconductor layer, a metal oxide layer, a source electrode, and a drain electrode. Usually, a gate electrode and a gate insulating layer, which are essential components as an organic transistor, are used. It is. Furthermore, the organic transistor of the present invention may have any configuration other than the above as necessary.
Hereafter, each structure used for this invention is demonstrated in order.

1. Organic Semiconductor Layer First, the organic semiconductor layer used in the present invention will be described. The organic semiconductor layer used in the present invention uses an organic semiconductor material having a structure represented by any one of the above formulas (I) to (III) in the molecule. The organic transistor of the present invention is excellent in the action with the metal oxide layer described later by using the organic semiconductor material having the structure represented by any of the above formulas (I) to (III). Transistor characteristics, durability, and reliability of transistor characteristics can be exhibited.

  The organic semiconductor material used in the present invention is not particularly limited as long as it has a structure represented by any of the above formulas (I) to (III), and is used for a metal oxide layer described later. Depending on the kind of the metal oxide to be produced, the method for producing the organic transistor of the present invention, the use of the organic transistor, etc., it can be appropriately selected and used. Further, the organic semiconductor material used in the present invention is not limited to one type, and two or more types may be used as necessary.

  Here, the organic transistor of the present invention can exhibit excellent transistor characteristics when the organic semiconductor material is regularly arranged in the organic semiconductor layer, so that the organic semiconductor material is represented by the above formula (I). When using what has the structure represented, it is preferable that Y in said Formula (I) is a thing which does not affect the arrangement | sequence of the organic-semiconductor material in the said organic-semiconductor layer, especially the arrangement | sequence of the said organic-semiconductor material It is preferable to promote the above. From this point of view, Y in the above formula (I) is preferably an alkyl group. Furthermore, when an alkyl group is used as Y in the above formula (I), if the number of carbon atoms constituting the alkyl group is too large, there is a possibility of hindering charge transfer in the organic semiconductor layer, and the number of carbon atoms is too small. In addition, the solubility of the organic semiconductor material in the solvent may be impaired, and the process of forming the organic semiconductor layer may be complicated. Therefore, when an alkyl group is used as Y in the above formula (I), the number of carbon atoms is preferably in the range of 1-18, more preferably in the range of 3-16. More preferably, it is in the range of 4-12.

  As a specific example of the organic semiconductor material used in the present invention, for example, a material represented by the following formula can be exemplified.

  The thickness of the organic semiconductor layer used in the present invention is not particularly limited as long as it is within a range in which desired transistor characteristics can be expressed in the organic semiconductor layer, depending on the type of the organic semiconductor material. Depending on the use of the organic transistor of the present invention, the structure of the organic transistor, and the like, it can be determined as appropriate. In particular, the thickness of the organic semiconductor layer used in the present invention is preferably 1000 nm or less, more preferably in the range of 5 nm to 300 nm, and particularly preferably in the range of 20 nm to 100 nm.

2. Next, the metal oxide layer used in the present invention will be described. The metal oxide layer used in the present invention is formed so as to be in contact with the above-described organic semiconductor layer and to be energized to a source electrode and a drain electrode described later. In addition, the metal oxide layer used in the present invention has a work function smaller than the ionization potential of the organic semiconductor material described above as a metal oxide constituting the metal oxide layer, and a conductive material used for a source electrode and a drain electrode described later. What is larger than the work function is used. The organic transistor of the present invention can achieve excellent transistor characteristics and durability in combination with the organic semiconductor material having a specific structure used for the organic semiconductor layer described above by using the metal oxide having such a work function. In addition, excellent reliability of transistor characteristics can be exhibited.

  As the metal oxide used for the metal oxide layer in the present invention, the work function is smaller than the ionization potential of the organic semiconductor material described above, and the work function of the conductive material used for the source electrode and the drain electrode described later is used. The material is not particularly limited as long as it is larger than the above, and can be appropriately selected according to the type of the organic semiconductor material and the conductive material. Among them, the metal oxide used in the present invention has a smaller work function difference from the ionization potential of the organic semiconductor material than the work function of the conductive material used for the source electrode and the drain electrode. It is preferable. It is because the transistor characteristics and reliability of the organic transistor of the present invention can be further improved by using a metal oxide having such a work function. In particular, the metal oxide used in the present invention preferably has a difference from the ionization potential of the organic semiconductor material in the range of 0 eV to 1 eV, more preferably in the range of 0 eV to 0.6 eV, What is in the range of 0 eV-0.2 eV is still more preferable. Because the difference between the work function of the metal oxide and the work function of the organic semiconductor material is within such a range, the transistor characteristics and reliability of the organic transistor of the present invention can be further improved. is there.

Here, the ionization potential of the organic semiconductor material indicates a value obtained as follows.
(1) Using molecular orbital calculation software (Gaussian 03), the molecular structure is optimized using B3LYP / 6-31G (d).
(2) The energy calculation is performed using B3LYP / 6-311 ++ G (d, p) using the optimized structure.
(3) The absolute value of the calculated highest occupied orbit (HOMO) energy is defined as the ionization potential.

  The work function of the metal oxide can be measured by using, for example, an atmospheric photoelectron spectrometer (AC-3 manufactured by Riken Keiki Co., Ltd.).

  The specific value of the work function of the metal oxide used in the present invention is relatively determined in relation to the work functions of the organic semiconductor material and the conductive material, and is particularly preferable. Is not specified.

  Specific examples of the metal oxide used in the present invention include molybdenum oxide, tungsten oxide, vanadium pentoxide, ruthenium oxide, nickel oxide and the like. In the present invention, any of these metal oxides can be preferably used, and among these, molybdenum oxide is preferably used. Since the work function of molybdenum oxide is close to the ionization potential of the organic semiconductor material having the structure represented by any of the above formulas (I) to (III), molybdenum oxide is used as the metal oxide. This is because the transistor characteristics and reliability of the organic transistor of the present invention can be most improved.

  In addition, the metal oxide used for this invention may be only one type, or may be two or more types.

  The aspect in which the metal oxide layer is formed in the present invention is particularly limited as long as it is an aspect in which the metal oxide layer is formed so as to be in contact with the organic semiconductor layer described above and to be energized with a source electrode or a drain electrode described later. It is not a thing. Therefore, the source and drain electrodes and the metal oxide layer may be formed so as to be in contact with each other, or another layer having a low resistance so as not to inhibit current may be formed therebetween. . In addition, the metal oxide layer in this invention is formed separately so that it may energize about each of the source electrode and drain electrode which are mentioned later.

  The thickness of the metal oxide layer used in the present invention can be appropriately determined according to the structure of the organic transistor of the present invention, and is not particularly limited. It is preferably within the range of 0.1 nm to 50 nm, more preferably within the range of 0.5 nm to 30 nm, and even more preferably within the range of 1 nm to 20 nm.

3. Next, the source electrode and drain electrode used in the present invention will be described. The source electrode and the drain electrode used in the present invention are each formed so as to energize the above-described metal oxide layer. In addition, the source electrode and the drain electrode used in the present invention are made of a conductive material having a work function smaller than that of the metal oxide constituting the metal oxide layer described above.

  The conductive material used for the source electrode and the drain electrode in the present invention is not particularly limited as long as it has a work function smaller than that of the metal oxide used for the metal oxide layer described above. . Among them, the conductive material used in the present invention preferably has a difference from the work function of the metal oxide used in the metal oxide layer in the range of 0 eV to 2.5 eV, and in the range of 0 eV to 2 eV. Some are more preferable, and those within the range of 0 eV to 1.5 eV are more preferable. Here, as described above, the metal oxide used for the metal oxide layer has a work function smaller than the ionization potential of the organic semiconductor material used for the organic semiconductor layer described above. The work function of the conductive material used for the electrode is naturally smaller than the ionization potential work function of the organic semiconductor material.

Specific examples of conductive materials used in the present invention include, for example, metal materials, conductive polymers such as PEDOT: PSS and polyaniline, charge transfer complexes such as TTF-TCNQ, etc. Among them, it is preferable to use a metal material in the present invention.
Specific examples of the metal material include Mn, In, Bi, Ta, Ag, Al, V, Nb, Ti, Zn, Cr, W, Mo, Cu, Fe, Co, Au, Pd, Ni, Ir, and A metal material such as Pt can be given. In the present invention, any of these metal materials can be suitably used, but Au is preferably used.

  Note that only one type of conductive material may be used in the present invention, or two or more types may be used. Further, the same conductive material may be used for the source electrode and the drain electrode, or different conductive materials may be used.

4). The gate electrode and the gate insulating layer The organic transistor of the present invention has at least the organic semiconductor layer, the metal oxide layer, the source electrode, and the drain electrode in the above-described manner. In the present invention, the organic transistor functions as an organic transistor. Usually, a gate electrode and a gate insulating layer are used for the expression. Since the gate electrode and the gate insulating layer used in the present invention are generally the same as the gate electrode and the gate insulating layer used in the organic transistor, detailed description thereof is omitted here.

6). Arbitrary Configuration The organic transistor of the present invention may have an arbitrary configuration other than the above. The arbitrary structure used for the organic transistor of the present invention is not particularly limited, and a structure having an arbitrary function can be appropriately selected and used according to the application and structure of the organic transistor of the present invention. As such an arbitrary configuration, a passivation layer formed on the outermost surface of the organic transistor of the present invention and having a function of preventing the organic semiconductor layer from deteriorating with time can be exemplified.

  Examples of the passivation layer used in the present invention include those made of fluororesins such as paraxylylene resins, fluoroethylene, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVD), and polymethyl methacrylate (PMMA). And those made of an acrylic resin such as an epoxy resin, a cardo resin, a silicone resin, or an organic-inorganic hybrid material.

7). Organic Transistor The organic transistor of the present invention has a configuration in which a metal oxide layer is in contact with the organic semiconductor layer and is energized with the source electrode and the drain electrode. Therefore, the structure of the organic transistor of the present invention is not particularly limited as long as it has such a structure, and an appropriate structure should be selected and used according to the use of the organic transistor of the present invention. Can do.

The structures that can be taken by the organic transistor of the present invention can be broadly classified into two types: a top gate structure and a bottom gate structure. Hereinafter, the structure of the organic transistor of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic view showing an example of the organic transistor of the present invention having a bottom gate type structure. As illustrated in FIG. 2A, the organic transistor 10 of the present invention includes a gate electrode 5, a gate insulating layer 6 formed on the gate electrode 5, and an organic formed on the gate insulating layer 6. A semiconductor layer 1, a source electrode 3 and a drain electrode 4 formed on the organic semiconductor layer 1, and a metal oxide formed between the source electrode 3 and the drain electrode 4 and the organic semiconductor layer 1. It may have a structure composed of the layer 2.
The embodiment in which the organic transistor of the present invention has a bottom-gate structure is a so-called bottom-gate structure in which a source electrode 3 and a drain electrode 4 are disposed on an organic semiconductor layer 1 as illustrated in FIG. A top contact structure may be used, or, as illustrated in FIG. 2B, the source electrode 3 and the drain electrode 4 are formed on the side of the gate insulating layer 6 of the organic semiconductor layer 1. It may have a bottom gate / bottom contact structure.
Furthermore, the aspect in which the organic transistor of the present invention has the bottom gate / bottom contact structure is such that the metal oxide layer 1, the source electrode 3 or the drain electrode is formed on the gate insulating layer 6 as illustrated in FIG. 4 may have a structure formed in this order, or the source electrode 3 or the drain electrode 4 and the metal oxide layer 2 may be formed on the gate insulating layer 6 as illustrated in FIG. May have a structure formed in this order.

FIG. 3 is a schematic view showing an example of the organic transistor of the present invention having a top gate type structure. As illustrated in FIG. 3A, the organic transistor 10 of the present invention is formed on the organic semiconductor layer 1, the gate insulating layer 6 formed on the organic semiconductor layer 1, and the gate insulating layer 6. A gate electrode 5, a metal oxide layer 2 formed so as to be in contact with the organic semiconductor layer 1, and a source electrode 3 and a drain electrode 4 formed so as to energize the metal oxide layer 2. You may have. The embodiment in which the organic transistor of the present invention has a top gate type structure is a so-called top gate structure in which a source electrode 3 and a drain electrode 4 are disposed on an organic semiconductor layer 1 as illustrated in FIG. It may be a top contact structure or may have a so-called top gate / bottom contact structure as illustrated in FIG.
Further, the organic transistor of the present invention has the top gate / bottom contact structure in which the source electrode 3 or the drain electrode 4 is formed on the metal oxide layer 2 as illustrated in FIG. It may have a structure, or may have a structure in which a source electrode 3 or a drain electrode 4 is formed on a metal oxide layer 2 as illustrated in FIG. .

8). Manufacturing method of organic transistor The organic transistor of the present invention uses a material having a structure represented by any one of the above formulas (I) to (III) as the organic semiconductor material, and has a specific work as the metal oxide. Except for using a material having a function, it can generally be produced by a known method as a method for producing an organic transistor.

B. Organic Semiconductor Element Next, the organic semiconductor element of the present invention will be described. As described above, the organic semiconductor element of the present invention includes a substrate and a plurality of organic transistors formed on the substrate, and the organic transistor is the organic transistor according to the present invention. It is a feature.

Such an organic semiconductor element of the present invention will be described with reference to the drawings. FIG. 4 is a schematic cross-sectional view illustrating an example of the organic semiconductor element of the present invention. As illustrated in FIG. 4, the organic semiconductor element 20 of the present invention includes a substrate 11 and a plurality of organic transistors 10 formed on the substrate 11.
In such an example, the organic semiconductor element 20 of the present invention is characterized in that the organic transistor 10 is the organic transistor according to the present invention.

  According to the present invention, since the organic transistor according to the present invention is used, an organic semiconductor element having excellent transistor characteristics and durability and excellent transistor characteristic reliability can be obtained.

The organic semiconductor element of the present invention has at least a substrate and an organic transistor, and may have any other configuration as necessary.
Hereafter, each structure used for this invention is demonstrated in order.

1. Organic Transistor First, the organic transistor used in the present invention will be described. The organic transistor used in the present invention is the organic transistor according to the present invention. The organic semiconductor element of the present invention has excellent performance in the use of the organic transistor according to the present invention excellent in transistor characteristics, durability and reliability.
Here, the organic transistor used in the present invention is the same as that described in the above section “A. Organic transistor”, and thus the description thereof is omitted here.

2. Substrate Next, the substrate used in the present invention will be described. The substrate used in the present invention supports the organic transistor.
The substrate used in the present invention can be appropriately determined according to the use of the organic semiconductor element of the present invention and is not particularly limited. Therefore, the substrate used in the present invention may be a flexible substrate having flexibility, or a rigid substrate having no flexibility.
Specific examples of the substrate used in the present invention include, for example, polyimide, polyethylene naphthalate, polyethylene terephthalate, polyethersulfone, polycarbonate, polyetherimide, polyetheretherketone, polyetherketone, polyphenylene sulfide, liquid crystal polymer, epoxy Examples thereof include a resin, a silicone resin, a finol resin and the like.

3. Organic Semiconductor Element The organic semiconductor element of the present invention can be used for any application where a switching function by an organic transistor is required, and is particularly preferably used for a display device. The display device using the organic semiconductor element of the present invention is not particularly limited as long as each pixel contributing to image display has a configuration switched by each organic transistor included in the organic semiconductor element. . Examples of the display device having such a configuration include a liquid crystal display device, an electrophoretic display device, and an organic EL display device.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be specifically described with reference to examples.

[Example]
On a silicon substrate having a thermal silicon oxide film of 100 nm, dioctylbenzothienobenzothiophene (C8BTBT) is vacuum-deposited by 25 nm to form an organic semiconductor layer, and then a molybdenum oxide 13 nm film is formed to form a metal oxide layer. Finally, Au was deposited by 50 nm to form a source electrode and a drain electrode. Thereby, a bottom gate top contact organic transistor element was produced.

[Comparative Example 1]
A dioctylbenzothienobenzothiophene was vacuum-deposited by 25 nm on a silicon substrate having a thermal silicon oxide film of 100 nm to form an organic semiconductor layer, and then Au was deposited by 50 nm to form a source electrode and a drain electrode. Thereby, a bottom gate top contact organic transistor element was produced.

[Comparative Example 2]
After forming an organic semiconductor layer by vacuum-depositing dioctyl quarterthiophene (8QT8) on a silicon substrate having a thermal silicon oxide film of 100 nm to a thickness of 25 nm, a metal oxide layer is formed by forming a molybdenum oxide film of 13 nm. A source electrode and a drain electrode were formed by evaporating 50 nm of Au. Thereby, a bottom gate top contact organic transistor element was produced.

[Reference example]
A dioctyl quarter thiophene (8QT8) was vacuum-deposited by 25 nm on a silicon substrate having a thermal silicon oxide film of 100 nm to form an organic semiconductor layer, and then Au was deposited by 50 nm to form a source electrode and a drain electrode. Thereby, a bottom gate top contact organic transistor element was produced.

[Evaluation]
In order to calculate the mobility, the subthreshold coefficient, and the threshold voltage for the organic transistor elements fabricated in the above Examples, Comparative Examples, and Reference Examples, gate voltage-drain current measurement was performed. In addition, in order to confirm the reliability of transistor characteristics, bias stress measurement was performed at a gate voltage of −20 V and a drain voltage of −3 V. Here, the subthreshold coefficient represents a gate voltage required for the drain current to increase by an order of magnitude. From the viewpoint that low voltage driving is possible, it can be said that the smaller the value, the better the transistor. The threshold voltage is an x-axis extrapolated value of a straight line of gate voltage-drain current characteristics, and it is known that a value closer to 0 V is a better transistor. By measuring the bias stress, the time constant τ of current decay can be obtained from the obtained plot. The larger this value, the higher the reliability of the transistor obtained. Here, in any measurement, a 237 type source measure unit manufactured by Keithley Instruments Inc. and a 6487 type picoammeter manufactured by Keithley Instruments Inc. were used. The measurement conditions were a gate voltage of −20V and a drain voltage of −3V.

As for the organic transistor element manufactured in the example, FIG. 5A shows the gate voltage-drain current, and FIG. 5B shows the bias stress characteristic.
For the organic transistor element fabricated in Comparative Example 1, FIG. 6A shows the gate voltage-drain current characteristics, and FIG. 6B shows the bias stress characteristics. In FIG. 6, the data of the examples are also plotted.
For the organic transistor element fabricated in Comparative Example 3, FIG. 7 shows the gate voltage-drain current characteristics.

  Tables 1 and 2 show the parameters calculated based on FIGS. As shown in Table 1, in the present invention, by using a combination of an organic semiconductor material having a specific structure and a metal oxide layer, any of mobility, subthreshold coefficient, threshold voltage, and time constant can be obtained. It can be seen that the characteristics are greatly improved. On the other hand, as shown in Table 2, when organic semiconductor materials other than those specified in the present application are used, even if a metal oxide layer made of molybdenum oxide is used, mobility, subthreshold coefficient, threshold value There is almost no change in voltage.

It is a schematic sectional drawing which shows an example of the organic transistor of this invention. It is a schematic sectional drawing which shows the other example of the organic transistor of this invention. It is a schematic sectional drawing which shows the other example of the organic transistor of this invention. It is a schematic sectional drawing which shows an example of the organic-semiconductor element of this invention. It is a graph which shows the characteristic of the organic-semiconductor element of this invention. It is a graph which shows the characteristic of an organic-semiconductor element. It is a graph which shows the characteristic of an organic-semiconductor element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Organic semiconductor layer 2 ... Metal oxide layer 3 ... Source electrode 4 ... Drain electrode 5 ... Gate electrode 6 ... Gate insulating layer 10 ... Organic transistor 11 ... Substrate 20 ... Organic semiconductor element

Claims (4)

An organic semiconductor layer made of an organic semiconductor material, a metal oxide layer made of a metal oxide, formed so as to be in contact with the organic semiconductor layer, and made of a conductive material, formed so as to energize the metal oxide layer An organic transistor having a source electrode and a drain electrode,
The organic semiconductor material has a molecular structure represented by any of the following formulas (I) to (III), and the work function of the metal oxide is an ionization potential of the organic semiconductor material. An organic transistor characterized by being smaller than and larger than the work function of the conductive material.

In the above formulas (I) to (III), X represents S or Se, and in the above formula (I), Y independently represents an alkyl group or a phenyl group.   The organic transistor according to claim 1, wherein the metal oxide is molybdenum oxide.   The organic semiconductor material has a structure represented by the above formula (I), and Y in the above formula (I) is an alkyl group having 1 to 18 carbon atoms, The organic transistor of Claim 1 or Claim 2. An organic semiconductor element having a substrate and a plurality of organic transistors formed on the substrate,
An organic semiconductor element, wherein the organic transistor is the organic transistor according to any one of claims 1 to 3.

Images