KR101572260B1 - Organic Semi-Conductor Low Molecular And Organic Thin Film Transistor Comprising The Same - Google Patents

Abstract

The present invention provides an organic semiconductor low molecular weight compound represented by the following formula (1).

Wherein R ₁ and R ₂ are each independently selected from the group consisting of a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, phenyl, naphthalene, and anthracene, R ₁ and R ₂ may be the same or different from each other, and each of R ₁ and R ₂ may be the same or different from each other.

Organic thin film transistor

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic semiconductor low molecular material and an organic thin film transistor including the organic semiconductor low molecular material.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film transistor, and more particularly, to an organic thin film transistor including an organic semiconductor low molecule.

BACKGROUND ART Organic thin film transistors (OTFTs) generally include a substrate, a gate electrode, a gate insulating layer, a source electrode and a drain electrode, and an organic active layer, and an organic active layer is formed on the source electrode and the drain electrode (TC) type in which a source electrode and a drain electrode are formed by mask evaporation or the like on an organic active layer and a Bottom Contact (BC) type.

Inorganic semiconductor materials such as silicon (Si) have been generally used as organic active layers of organic thin film transistors (OTFTs). However, due to the large size and low cost of displays, inorganic materials requiring high temperature vacuum processes have been replaced with organic semiconductor materials Research is underway.

Recently, a lot of organic semiconductor materials for an organic thin film transistor (OTFT) channel layer have been studied and their transistor characteristics have been reported. Many low-molecular-weight or high-molecular-weight organic semiconductor materials studied include melocyanine, phthalocyanine, pentacene, and thiophene polymer, and the thin film formation is mainly dependent on a vacuum process.

Although OTFTs using low-molecular-weight materials do not reach the characteristics of polymer-based OTFTs, a solution process such as a printing technique is used to fabricate a low-cost large-area It has the advantage of being able to process.

As mentioned above, although the characteristics of the TFT device such as the charge mobility of the organic semiconductor polymer material are lower than that of the pentacene, which is a low molecular material, there is an advantage that the TFT can be manufactured inexpensively through the solution process.

However, in order to commercialize an OTFT, it is necessary to satisfy important parameters of excellent electrical characteristics and fairness. To do so, it is necessary to have the advantages of low molecular weight and high molecular weight organic semiconductors together.

Therefore, it is required to develop a low-molecular organic semiconductor material having a new structure having advantages of a solution process of a polymer-based OTFT and excellent electrical characteristics of a low molecular weight OTFT.

Accordingly, the present invention provides an organic semiconductor low molecular material having excellent electrical characteristics and high solubility, and an organic thin film transistor including the same.

In order to achieve the above object, an organic semiconductor low molecular compound according to an embodiment of the present invention may be represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ and R ₂ are each independently selected from the group consisting of a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, phenyl, naphthalene, and anthracene, R ₁ and R ₂ may be the same or different from each other, and each of R ₁ and R ₂ may be the same or different from each other.

X may be a sulfur (S) atom.

X may be a nitrogen (N) atom.

X may be an oxygen (O) atom.

Wherein Y is a 5 or hexagonal ring compound containing a heteroatom and the 5 or hexagonal ring compound containing the heteroatom is selected from the group consisting of nitrogen (N), oxygen (O), sulfur (S) and selenium Or a five-membered or six-membered heteroaryl group substituted with one.

When X and Y are substituted with nitrogen (N), R ₃ and R ₄ are each independently selected from hydrogen, a linear or branched alkyl group having 1 to 6 carbon atoms, an aryl group including phenyl, naphthalene, anthracene, thiophene, Dibenzofurans, dibenzothiophenes, dibenzofurans, pyridines, and the like.

The heteroaryl group and the aryl group may be any one selected from compounds represented by the following general formula (2).

Where X is N-H, O, S or Se.

In addition, the organic thin film transistor according to an embodiment of the present invention includes a gate electrode, a gate insulating layer, an organic active layer, a source electrode, and a drain electrode, wherein the organic active layer includes the organic semiconductor molecule of claim 1 can do.

The organic active layer may be formed of any one selected from the group consisting of a screen printing method, a printing method, a spin coating method, and an ink jet method.

The gate electrode, the source electrode, and the drain electrode may be formed of at least one selected from the group consisting of Au, Ag, Al, Ni, and ITO. .

The present invention provides an organic semiconductor low molecular material having excellent electrical characteristics and high solubility and an organic thin film transistor including the same.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view illustrating an organic thin film transistor according to an embodiment of the present invention.

Referring to FIG. 1, an organic thin film transistor 100 according to an embodiment of the present invention includes a substrate 110, a gate electrode 120, a gate insulating layer 130, an organic active layer 140, a source electrode 150a And a drain electrode 150b.

The substrate 110 supports the structure of the organic thin film transistor. The substrate 110 may be made of glass, plastic, metal, or a composite or a laminate thereof, but is not limited thereto.

The gate electrode 120 may be formed of any one selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), nickel (Ni), and indium tin oxide (ITO) Cr, Ti, Cu, Mo, W, Pd, Pt, Sn, Mg, or alloys thereof. .

The gate electrode 120 may have a thickness of 30 to 500 nm and may be formed by chemical vapor deposition, sputtering, electroless plating, spin coating, or the like.

The gate insulating layer 130 may be made of silicon oxide (SiOx) or silicon nitride (SiNx), but not limited thereto. The gate insulating layer 130 may be formed of titanium oxide (TiOx), barium oxide (BaO), lead oxide (PbO), magnesium oxide ), And the like.

The gate insulating layer 130 may have a thickness of 10 to 150 nm and may be formed by vacuum deposition, sputtering, thermal CVD, thermal oxidation, or anodic oxidation.

The organic active layer 140 may have a thickness of several nanometers to several micrometers, and preferably a thickness of 10 nm to 250 nm. The organic active layer 140 may be formed by a screen printing method, a printing method, a spin coating method, an ink jet method, or the like, but is not limited thereto.

The organic active layer 140 may be made of an organic semiconductor low molecular weight compound represented by the following general formula (1).

[Chemical Formula 1]

Wherein R ₁ and R ₂ are each independently selected from the group consisting of a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, phenyl, naphthalene, and anthracene, R ₁ and R ₂ may be the same or different from each other, and each of R ₁ and R ₂ may be the same or different from each other.

In Formula 1, X may be a sulfur (S) atom, a nitrogen (N) atom, or an oxygen (O) atom.

In formula (1), Y is a 5 or hexagonal ring compound containing a hetero atom, and the 5 or hexagonal ring compound containing a hetero atom is selected from the group consisting of nitrogen (N), oxygen (O), sulfur (Se). ≪ / RTI >

When X and Y in the formula (1) are substituted with nitrogen (N), R ₃ and R ₄ may be hydrogen, a linear or branched alkyl group having 1 to 6 carbon atoms, an aryl group including phenyl, naphthalene, Thiophene, furan, dibenzothiophene, dibenzofuran, and pyridine.

Here, the heteroaryl group and the aryl group may be any one selected from compounds represented by the following general formula (2).

(2)

Where X is N-H, O, S or Se.

The source electrode 150a and the drain electrode 150b may be formed of one selected from the group consisting of Au, Ag, Al, Ni, and ITO. The present invention is not limited to this, and examples of the material include, but are not limited to, Cr, Ti, Cu, Mo, W, Pd, Pt, Sn, Based alloy.

The gate electrode 120 may have a thickness of 30 to 500 nm and may be formed by chemical vapor deposition, sputtering, electroless plating, spin coating, or the like.

Although the organic thin film transistor according to one embodiment of the present invention described above is of the top contact (TC) type in which the source electrode and the drain electrode are located on the organic active layer, the present invention is not limited thereto, and a source electrode and a drain electrode may be formed under the organic active layer (BC) type.

The organic active layer of the organic thin film transistor including the organic semiconductor molecule according to an embodiment of the present invention may be formed as follows.

The precursor solution containing the organic semiconductor low-molecular compound represented by Formula 1 and the organic solvent may be coated on the substrate to form a coating layer, and then the coating layer may be heat-treated to form an organic active layer.

The precursor solution may include the organic semiconductor low molecular weight compound represented by Formula 1, and the organic semiconductor low molecular weight compound may be 0.01 to 30 wt% of the precursor solution.

The organic solvent may be used for aliphatic hydrocarbons such as hexane and heptane, and may be used for aromatic hydrocarbons such as toluene, pyridine, quinoline, anisole, mesitylene and xylene. Further, it may be a ketone-based solvent such as methyl isobutyl ketone, 1-methyl-2-pyrrolidinone, cyclohexanone or acetone, or an ether-based solvent such as tetrahydrofuran or isopropyl ether. Alternatively, it may be an acetate-based solvent such as ethyl acetate, butyl acetate or propylene glycol methyl ether acetate. Alcohol solvents such as isopropyl alcohol and butyl alcohol or amide solvents such as dimethylacetamide and dimethylformamide may be used .

When the precursor solution containing the organic semiconductor low-molecular compound and the organic solvent is prepared, the precursor solution is coated on the substrate to form a coating film.

At this time, as a method of coating the precursor solution, a coating method such as spin coating, dip coating, roll coating, screen coating, spray coating, spin casting, screen printing or inkjet can be used. More preferably, a screen printing method, a printing method, a spin coating method, an ink jetting method, or the like can be used.

Next, the organic active layer can be formed by heat-treating the formed coating film. The heat treatment process may be performed at a temperature of 40 to 250 ° C in a vacuum or nitrogen atmosphere, an argon atmosphere or an air atmosphere, and may be heat-treated for 1 to 100 minutes.

Hereinafter, the organic semiconductor low molecular material and the organic thin film transistor including the organic semiconductor molecule of the present invention will be described in detail in the following Synthesis Examples and Examples. However, the following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Synthetic example

1) Preparation of dibromo-dibenzothiophene

After dissolving 10 g of dibenzothiophene in 100 mL of acetic acid, 6.4 mL of a 2, 3 equivalent of bromine was slowly dropped at 80 ° C. After the reaction was completed, the reaction mixture was immediately filtered, washed several times with distilled water, and reprecipitated in methanol to obtain dibromo-di Benzothiophene.

2) Preparation of 5-hexylthiophene boronic ester derivative

5 g of hexylthiophene was dissolved in 100 mL of THF, and then 19.2 mL of 1.7 M n-BuLi was slowly dropped at 0 ° C. After stirring for 30 minutes, 10.9 g of 2-isopropoxy-4,4'-5,5'-tetramethyl-1,3,2-dioxaborane was added. After stirring for 24 hours, the reaction mixture was extracted with distilled water and ether. Next, the filtrate was distilled under reduced pressure, and the residue was separated into a silica column treated with triethylamine to obtain a 5-hexylthiophene boronic ester derivative.

3) Preparation of dithiophenyl-dibenzothiophene derivative

Dibromo-dibenzothiophene, thiophene boronic ester and palladium catalyst were added and dissolved in toluene. Then, 2M sodium carbonate aqueous solution and Eli 큇 336 (phase transfer catalyst) were put in. The mixture was then stirred at 80 < 0 > C for 24 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, and methanol was dropped to obtain a precipitate. Then, the resulting precipitate was filtered and dissolved again in chlorobenzene at 100 DEG C, and the precipitate was recovered again. The resulting precipitate was filtered and vacuum dried to obtain a dithiophenyl-dibenzothiophene derivative.

Example

Hereinafter, an embodiment in which an organic thin film transistor is manufactured using the dithiophen yl-dibenzothiophene derivative obtained in the above-mentioned synthesis example is described.

≪ Example 1 >

Gold used as a gate electrode on the cleaned plastic substrate was deposited to a thickness of 1000 Å by a sputtering method and then patterned to form a gate electrode. Then, a silicon oxide film used as a gate insulating film was deposited to a thickness of 1000 Å by a CVD method. At this time, the substrate was washed with isopropyl alcohol for 10 minutes before the organic semiconductor material was evaporated, dried and used.

Thereafter, the dithiophenyl-dibenzothiophene derivative synthesized in the above Synthesis Example was subjected to OTS treatment for 30 seconds in an octadecyl trichlorosilane solution diluted in hexane to a concentration of 10 mM, washed with acetone, dried, Dissolved in toluene at a concentration of 2 wt%, spin-coated on the substrate to a thickness of 700 ANGSTROM at 1000 rpm, and annealed at 100 DEG C for 1 hour in an argon atmosphere to form an organic active layer.

Thereafter, gold used as a source electrode and a drain electrode was deposited on the organic active layer to a thickness of 1200 ANGSTROM by sputtering, thereby manufacturing a top-contact type organic thin film transistor.

≪ Example 2 >

An organic thin film transistor was fabricated under the same process conditions as in Example 1 except for the step of OTS treatment of the dithiophenyl-dibenzothiophene derivative.

≪ Example 3 >

An organic thin film transistor was fabricated under the same process conditions as in Example 1, except for the step of annealing the organic thin film transistor.

<Example 4>

An organic thin film transistor was fabricated under the same process conditions as in Example 1 except for the step of OTS treatment of the dithiophenyl-dibenzothiophene derivative and the annealing of the organic active layer.

In order to measure the electrical characteristics of the organic thin film transistor including the organic active layer prepared according to Examples 1 to 4, current transfer characteristics were measured using Semiconductor Characterization System (4200-SCS) manufactured by KEITHLEY. The calculated charge mobility and blocking leakage current are shown in Table 1 below.

The charge mobility was obtained from the current transfer equation of the saturation region using the current transfer curve of FIG. 2, and a graph was obtained from the slope of (I _SD ) ^1/2 and V _G as a variable.

Wherein I _SD is the source-and-drain current, μ or μ _FET is also the charge transfer, and C ₀ is oxide capacitance, W is the channel width, and L is channel length, V _G is the gate voltage, V _T Is the threshold voltage.

Further, the blocking leakage current (I _off ) was a current flowing when the off state was obtained, and a minimum current was obtained from the off state to the current ratio.

The crystallinity of the organic active layer prepared according to Examples 1 to 4 was measured using XRD (X-Ray Diffraction) diffraction peaks and is shown in FIG.

Charge mobility (㎠ / Vs) Breaking leakage current (A) Example 1 6.51 x 10 ^-4 10 ^-4 Example 2 2.27 x 10 ^-5 10 ^-2 Example 3 3.18 x 10 ^-4 10 ^-3 Example 4 1.23 × 10 ^-4 10 ^-3

Referring to Table 1, the organic thin film transistor using the organic semiconductor small molecule of the present invention as an organic active layer can form an organic active layer through a soluble process. In the case of Example 1, the organic thin film transistor exhibits a high charge mobility It can be seen that the blocking leakage current is also excellent.

Further, as shown in Fig. 3, it can be seen that the crystallinity of the organic active layers of Examples 1 and 3 is excellent.

Therefore, the organic thin film transistor according to an embodiment of the present invention can have excellent electrical characteristics, and the organic active layer can be formed by a solubilized process, thereby reducing the manufacturing cost.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

1 illustrates an organic thin film transistor according to an embodiment of the present invention.

2 is a graph showing a current transfer curve of an organic thin film transistor according to an embodiment of the present invention.

3 is a graph of XRD measurement of an organic active layer of an organic thin film transistor according to an embodiment of the present invention.

Claims (12)

1. An organic semiconductor low molecular weight compound represented by the following formula (1). [Chemical Formula 1]

Wherein R ₁ and R ₂ are each independently a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, an aryl group selected from phenyl, naphthalene or anthracene, , Dibenzothiophene, dibenzofuran or pyridine, wherein R ₁ and R ₂ are the same or different from each other. delete delete delete delete delete The method according to claim 1, Wherein the heteroaryl group and the aryl group are any one selected from the group consisting of compounds represented by the following general formula (2). (2)

Where X is N-H, O, S or Se. 1. An organic thin film transistor comprising a gate electrode, a gate insulating layer, an organic active layer, a source electrode and a drain electrode, Wherein the organic active layer comprises the organic semiconductor molecule of claim 1. 9. The method of claim 8, Wherein the organic active layer is formed of any one selected from the group consisting of a screen printing method, a printing method, a spin coating method, and an ink jet method. 9. The method of claim 8, Wherein the gate electrode, the source electrode, and the drain electrode are formed of at least one selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), nickel (Ni), and indium tin oxide transistor. The method according to claim 1, Wherein R ₁ and R ₂ are each independently a linear alkyl group having 1 to 12 carbon atoms. 12. The method of claim 11, (1) is a compound represented by the following general formula (3). (3)

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