KR20070027939A - Pentacene precursors, pentacene, method for preparing them, organic thin film transistor using them - Google Patents

Abstract

Provided are pentacene precursors, which are synthesized by a Diels-Alder reaction, have high solubility in organic solvent, and produce pentacene via a retro Diels-Alder reaction by pyrolysis without using vacuum devices. The pentacene precursor is a Diels-Alder reaction product of an aromatic azine compound and a benzyne equivalent and comprises at least one -N=N- bridge on a 2 to 4-positioned benzene ring of the following formula(I). The aromatic azine compound is selected from phthalazine, pyridazine, or tetrazine. The benzyne equivalent is selected from tetrabromobenzene, 2,3-dibromonaphthalene, or phthalic anhydride.

Description

Pentacene Precursors, Pentacene, Methods of Making and Organic Thin Film Transistors Using the Same {Pentacene Precursors, Pentacene, Method for Preparing Them, Organic Thin Film Transistor Using Them}

1 is a scanning electron microscope (SEM) photograph of a pentacene thin film prepared by a method according to one embodiment of the present invention.

2 is a scanning electron microscope (SEM) photograph of a pentacene thin film prepared by a method according to another embodiment of the present invention.

3 is an X-ray diffraction (XRD) graph of a pentacene thin film prepared according to one embodiment of the present invention.

4 is a current-voltage curve of a pentacene thin film prepared according to one embodiment of the present invention.

The present invention relates to a pentacene precursor, a pentacene, a manufacturing method thereof, and an organic thin film transistor (OTFT) using the same. More specifically, the present invention relates to pentacene precursors synthesized using Diels-Alder reaction of aromatic azine compounds and benzine analogues, pentacene, methods for their preparation, and organic thin film transistors using the same.

In recent decades, development of organic materials having semiconductor properties and various application studies using them have been actively conducted. The field of application research using organic semiconductors such as electromagnetic shielding films, capacitors, organic electroluminescence (EL) displays, organic thin film transistors, solar cells, and memory devices using multiphoton absorption phenomena continues to expand. Particularly, the organic EL field is partly commercialized, and thus serves as a catalyst for activating applied research using organic materials in the electronic field. Organic thin film transistors using organic materials are expected to be used as active driving devices for organic EL. It is also expected for applications such as smart cards.

In addition, after the results of the research on the electrical oscillation characteristics using the organic semiconductor as an active layer, the interest as a laser diode has been attracting a lot of attention again. In addition, the solar cell fabricated with doped pentacene reaches a quantum leap of 2.4%, resulting in a significantly lower device manufacturing cost compared to inorganic materials, thus foreseeing a revolution in the solar cell market in the future.

In addition, since flexible electronic circuit boards are expected to be an important element technology for future industries, the development of organic thin film transistors capable of meeting these requirements is emerging as an important research field. Organic thin film transistors cannot be used in high-speed devices that use silicon (Si) or germanium (Ge) due to their low charge mobility due to the characteristics of organic semiconductors, but they are used when devices are fabricated over a large area, low temperature processes are required, or bending is required. Organic thin film transistors can be useful because they are possible, and particularly inexpensive.

The organic thin film transistors implemented on the plastic substrate may be applied to bendable liquid crystal display devices, or to drive electronic paper and organic light emitting devices, which have recently attracted great interest. In particular, recently developed electronic paper is a display device that does not require high charge mobility and fast switching speed by voltage driving, and is an advantageous technology to be applied to a large area that can be bent, and thus the application of the organic thin film transistor is very high.

Optimum organic thin film transistors exhibit excellent properties that outperform amorphous silicon (a-Si: H) devices. Pentacene has the largest charge-carrier mobility value (2.1 cm 2 / V · sec) among organic semiconductor materials, and has been reported to have an on / off current ratio of about 10 ⁸ . Flash rate is one of the most important characteristics in pixel-address devices in active matrix displays. Therefore, the application value of the organic thin film transistor using pentacene can be said to be very high.

However, pentacene itself is a low solubility organic material and is mainly used in organic thin film transistors through a dry process such as vacuum deposition. In addition to the dry process, there is a wet (solution) process as well as a method of depositing an organic material, and the wet process can reduce the unit cost by not using a vacuum equipment, and not only a large area process is possible, but also an inkjet printing method. The advantage of minimizing material waste is that if the pentacene can be applied to an organic thin film transistor through a wet process, its value can be very high.

Thus has been triggered active research on a method of forming a pentacene thin film through a wet process, a 1995 Philips Brown (Brown) and the like pentacene thin films through a wet process SiN _x Formed on top. They spin-coated a soluble precursor to form a thin film, and then heat-treated at a temperature of 140 ° C. in a vacuum to produce a pentacene thin film, which had a charge mobility of 9 × 10 ⁻³ cm 2 / V · sec and a flash rate of about The research results of 10 ⁵ were greatly influenced by the study of field-effect transistors using pentacene.

The soluble pentacene precursor recently announced by IBM was synthesized by Diels-Alder reaction using Lewis acid.The thin film was spin coated to form a thin film, followed by heat treatment at 130 ° C. under nitrogen atmosphere. Pentacene thin films were prepared and showed the best results in solution-based fabrication using soluble pentacene derivatives having a charge mobility of 0.13 cm 2 / Vsec and a blink rate of about 2 × 10 7.

However, very unstable to substituent N pentacene reaction during synthesis - the disadvantage that this has the disadvantage that sulfinyl amides (N -sulfinylamide) must be prepared separately of the compound, and because it uses an expensive starting material as pentacene economics have.

The known manufacturing method of pentacene is as follows.

As shown in Scheme 1, a known method for preparing pentacene is performed in two steps. That is, the first reaction forms pentacenequinone by combining o-phthalaldehyde with 1,4-cyclohexanedione and the second reaction is aluminum amalgam. Pentacene is synthesized via (Al (Hg)).

However, the above method has a disadvantage in that it is difficult to purify pentacene, which is a product after the second reduction reaction, and mercury, and thus has a health and environmental problem.

Lithium aluminum hydride (LiAlH4) is known to be used instead of mercury reduction. However, this method still has a problem of high temperature and difficulty in purification (Tetrahedron Lett. 2004, 45, 7287).

The present inventors, while studying the method for synthesizing pentacene, can synthesize a pentacene precursor having a novel structure by using a simple method using an aromatic azine compound and a benzine analogue. The present invention has been completed by discovering that pentacene can be synthesized with purity and further applicable to organic thin film transistors.

It is a first object of the present invention to provide a soluble pentacene precursor of a novel structure.

It is a second object of the present invention to provide a method for preparing a soluble pentacene precursor of a new structure.

It is a third object of the present invention to provide a method for preparing pentacene using a pentacene precursor having a novel structure.

It is a fourth object of the present invention to provide pentacene synthesized from a pentacene precursor of a novel structure.

A fifth object of the present invention is to provide an organic thin film transistor using pentacene precursor or pentacene.

In order to achieve the first object, the present invention is a Diels-Alder reaction product of an aromatic azine compound and a bezyne equivalent, and at least one of two or more benzene rings at positions 2 to 4 of the following formula (I): There is provided a pentacene precursor comprising a -N = N- bridge:

(Ⅰ)

(Ⅰ)

In order to achieve the second object, the present invention provides a method for preparing a pentacene precursor comprising the Diels-Alder reaction of an aromatic azine compound and a benzine analogue in an organic solvent.

In order to achieve the third object, the present invention comprises the steps of preparing a pentacene precursor by Diels-Alder reaction of an aromatic azine compound and benzine analog in an organic solvent; And a process for producing pentacene, which comprises pyrolyzing the pentacene precursor, or a method for preparing pentacene, comprising reacting an aromatic azine compound with a benzine analog in a organic solvent through microwave irradiation. .

In order to achieve the fourth object, the present invention provides a pentacene obtained through Diels-Alder reaction of an aromatic azine compound and a benzine analog.

In order to achieve the fifth object, the present invention provides an organic thin film transistor comprising an aromatic azine compound and a benzine analog containing a pentacene semiconductor layer formed of pentacene precursor or pentacene, which is a Diels-Alder reaction product.

Hereinafter, the present invention will be described in more detail.

The pentacene precursor according to the present invention is a Diels-Alder reaction product of an aromatic azine compound and a benzine analog, and includes at least one -N = N- bridge in the benzene ring at positions 2 to 4 of the following formula (I):

Formula 1

(Ⅰ)

(Ⅰ)

Preferred pentacene precursors according to the invention can be represented by the following structure (II) or (III):

(Ⅱ)

(Ⅱ)

(Ⅲ)

(Ⅲ)

The aromatic azine compound that is a starting material of the pentacene precursor according to the present invention may include, but is not limited to, phthalazine, pyridazine or tetrazine.

Another starting material, benzine analogue, may include tetrabromobenzene, 2,3-dibromonaphthalene or phthalic dianhydride. It is not limited.

A method for preparing a pentacene precursor according to the present invention includes a Diels-Alder reaction of an aromatic azine compound and a benzine analog in an organic solvent.

In this case, the aromatic azine compound and the benzine analog are preferably reacted in a molar ratio of 1: 1 to 4: 1.

The organic solvent may include an aromatic compound having 1 to 10 carbon atoms substituted or unsubstituted with a hydrogen atom, a halogen atom, an alkoxy group, an amino group, a hydroxy group, a thiol group, a nitro group, or a cyano group, preferably halogenbenzene, Toluene, xylene, ethylene chloride, chloroform, chloronaphthalene, carbon tetrachloride, ethyl acetate, hexane, ether, diethyl ether, tetrahydrofuran, N, N-dimethylformamide, 1,4-dioxane, N-methylpyrrolidone Or analogs thereof, but is not limited thereto.

In addition, a base is optionally required in the Diels-Alder reaction between the aromatic azine compound and the benzine analog, and in this case, n-butyl lithium, s-butyl lithium, t-butyl lithium, NaNH _2, and the like may be used.

The Diels-Alder reaction may occur within a range of -40 to the reflux temperature of the organic solvent, and the Diels-Alder reaction time may vary depending on the type of starting material, the type of the organic solvent, and the reaction temperature, but may be 1 to ~. It is preferable to wake up for 12 hours.

In the preparation of the pentacene precursor according to the present invention, the Diels-Alder reaction may proceed in one or two stages depending on the type of starting material, that is, the type of aromatic azine compound and benzine analog.

Specifically, when tetrabromobenzene is used as the phthalazine and benzine analog as the aromatic azine compound, pentacene precursor is synthesized in one step by reacting phthalazine and tetrabromobenzene in the presence of a base in an organic solvent in the presence of a base. do.

Also, when 2,3-dibromonaphthalene is used as tetrazine and benzine analog as an aromatic azine compound, the pentacene precursor is first reacted with tetrazine and 2,3-dibromonaphthalene in the presence of a base in an organic solvent, Subsequently, 2,3-dibromonaphthalene is added in the presence of a base to proceed to the second reaction and synthesized in two steps.

On the other hand, when phthalazine and phthalic anhydride are used as the phthalazine as the aromatic azine compound, when the phthalazine and the phthalic anhydride are subjected to microwave irradiation in a organic solvent to deal with Diels-Alder, a pentacene precursor is synthesized, and immediately Pentacene is synthesized.

The method for preparing pentacene precursor according to the present invention may optionally further include purifying a product obtained through the Diels-Alder reaction.

The method for preparing pentacene according to the present invention includes preparing a pentacene precursor by Diels-Alder reaction of an aromatic azine compound and a benzine analog, and pyrolyzing the pentacene precursor.

In the method for preparing pentacene according to the present invention, the step of preparing the pentacene precursor is as described above, and the step of pyrolyzing the pentacene precursor is performed without purification of the pentacene precursor prepared by the Diels-Alder reaction. Proceed to pyrolysis by heating. Nitrogen gas is released through such pyrolysis, and the pentacene precursor is converted into pentacene.

The heating temperature and the heating time may vary depending on the type of starting material and the heating means, but the heating temperature is preferably in the range of room temperature to 200 ° C, more preferably 60 to 120 ° C. Moreover, in the case of a heating time, the range of 30 second-30 minutes is preferable.

On the other hand, pentacene according to the present invention can be prepared directly without a separate heating process by reacting Diels-Alder through the microwave irradiation of the aromatic azine compound and the benzine analogue in an organic solvent. In this case, the microwave is preferably irradiated for a time of 1 to 30 minutes at a dose of 100 ~ 300W.

Pentacene obtained through the process for preparing pentacene according to the present invention has the following structural formula IV:

(Ⅳ)

(Ⅳ)

Pentacene precursor or pentacene prepared according to the present invention can be used in the semiconductor layer of the organic thin film transistor.

Since the pentacene precursor is soluble, when used as a semiconductor layer material of an organic thin film transistor, the semiconductor layer can be formed by a wet process such as spin coating, inkjet printing, or dipping as well as a dry process. In addition, when pentacene is used as the semiconductor layer material, the semiconductor layer can be formed by a dry process, for example, a vacuum deposition method or an organic vapor deposition method.

An organic thin film transistor including a semiconductor layer formed by a wet process using the pentacene precursor may include dissolving a pentacene precursor in an organic solvent; Applying a pentacene precursor onto the substrate; And heating the coated substrate to form the pentacene semiconductor layer.

In this case, chloroform, tetrahydrofuran, toluene, xylene may be used as the organic solvent for dissolving the pentacene precursor, and it is preferable that the pentacene precursor is dissolved in a concentration of 0.5 to 2% by weight in the organic solvent.

In addition, pentacene precursor solution may be applied to the substrate through any of the general methods in the art.

The heating step may be performed by heating for 30 seconds to 30 minutes in the temperature range of room temperature to 200 ℃.

In the wet process, the crystal shape and electrical properties of the pentacene semiconductor layer produced according to the process conditions, for example, the type of solvent for dissolving the pentacene precursor, the concentration of the solution, the heating temperature and time, the coating speed, the presence or absence of substrate treatment, and the like. Since changes in properties can occur, process conditions can be appropriately selected as required.

 Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to the following Example.

Synthesis Example  One

Availability Pentacene  Synthesis of Precursor 3

0.393 g (1.0 mmol) of tetrabromobenzene was added to the dried toluene solvent, the temperature was lowered to -78 ° C, and 1.37 mL (2.2. Mmol) of n-butyllithium was added thereto. The temperature was raised to -23 ° C, 0.39 g (3 mmol) of phthalazine was added, and the temperature was again raised to room temperature and maintained for 12 hours. Water was added, the organic layer was extracted, and the solvent was dried to obtain 0.30 g of the target compound pentacene precursor (3). (91% yield)

1 H-NMR (CDCl 3) ppm: 7.31-7.28 (m, 4H), 7.19-7.09 (m, 4H), 6.99 (s, 2H), 3.90 (s, 4H)

GCMS: 278

Pentacene  synthesis

0.30 g of the pentacene precursor obtained above was heated at a temperature of 150 ° C. for 1 hour to obtain 0.23 g of pentacene. (93% yield)

Synthesis Example  2

Availability Pentacene  Preparation of Precursor 7

0.286 g (1.0 mmol) of 2,3-dibromonaphthalene was added to the dried toluene solvent, the temperature was lowered to -78 ° C, and 0.69 mL (1.1. Mmol) of n-butyllithium was added thereto. The temperature was raised to −23 ° C., and 0.082 g (1 mmol) of tetrazine was added thereto, followed by raising to room temperature and maintaining for 1 hour. After the temperature was lowered to −78 ° C., 0.286 g (1.0 mmol) of 2,3-dibromonaphthalene and 0.69 mL (1.1. Mmol) of n-butyllithium were added thereto. The temperature was raised to room temperature and maintained for 12 hours. Water was added, the organic layer was extracted, and the solvent was dried to obtain 0.27 g of the target compound pentacene precursor (7). (89% yield)

1 H-NMR (CDCl 3) ppm: 7.65-7.55 (m, 4H), 7.54-7.44 (m, 4H), 7.40 (s, 4H), 3.90 (s, 4H)

GCMS: 278

Pentacene  synthesis

0.27 g of the pentacene precursor obtained above was heated at a temperature of 150 ° C. for 1 hour to obtain 0.22 g of pentacene. (90% yield)

Synthesis Example  3

Pentacene  Produce

0.218 g (1.0 mmol) of phthalic anhydride (8) and 0.26 g (2 mmol) of phthalazine (2) were dissolved in 10 mL of N-methylpyrrolidone solvent. The reaction was carried out for 1 to 30 minutes at room temperature using a microwave reactor to obtain 0.25 g of the target compound pentacene. (90% yield)

GCMS: 278

Example  One

The pentacene precursor (3) obtained in Synthesis Example 1 was dissolved in a toluene solvent at a concentration of 2% by weight. The low temperature silicon oxide (LTO) / Au S / Au D substrate was then surface treated with HMDS. To the surface treated substrate, pentacene precursor solution was spin coated at a speed of 1000 rpm. Subsequently, the pentacene semiconductor layer was manufactured by heating at 120 ° C. for 5 minutes under a nitrogen atmosphere. In order to confirm the surface crystal shape of the prepared pentacene semiconductor layer, a photograph was taken with a scanning electron microscope (SEM) and the photograph is shown in FIG. 1.

Example  2

The pentacene precursor (3) obtained in Synthesis Example 1 was dissolved in a chloroform solvent at a concentration of 2% by weight. The low temperature silicon oxide (LTO) / Au S / Au D substrate was then surface treated with HMDS. To the surface treated substrate, pentacene precursor solution was spin coated at a speed of 1000 rpm. Subsequently, the pentacene semiconductor layer was manufactured by heating at 90 ° C. for 30 minutes in a nitrogen atmosphere. In order to confirm the surface crystal shape of the prepared pentacene semiconductor layer, a photograph was taken with a scanning electron microscope (SEM) and the photograph is shown in FIG. 2.

1 and 2, even when the same concentration and heating conditions are the same, it can be seen that the crystal form of pentacene produced according to the solvent is different.

Example  3

The pentacene precursor (3) obtained in Synthesis Example 1 was dissolved in a chloroform solvent at a concentration of 2% by weight. The low temperature silicon oxide (LTO) / Au S / Au D substrate was then surface treated with HMDS. To the surface treated substrate, pentacene precursor solution was spin coated at a speed of 1000 rpm. Subsequently, the pentacene semiconductor layer was manufactured by heating at 120 ° C. for 5 minutes under a nitrogen atmosphere.

Test Example  One

The X-ray diffraction (XRD) graphs of the pentacene semiconductor layers obtained in Examples 2 and 3 and commercial pentacene were examined. The results are shown in FIG.

Specifically, FIG. 3 shows X-ray diffraction (XRD, X-raydiffraction) of a thin film (graph (b)) heated for 5 minutes at 120 ° C. for pentacene precursor and a thin film (graph (c)) heated at 90 ° C. for 30 minutes. Comparing the graph with the commercial XENT graph of pentacene (graph (a)) shows that the characteristic peak of pentacene appears stronger when heated at 120 ° C. It can be seen from FIG. 3 that pentacene is formed by pyrolysis from the pentacene precursor.

Test Example  2

The electrical properties of the organic thin film transistor in which the pentacene thin film layer was formed on the LTO substrate prepared in Example 1 were measured, and the results are shown graphically in FIG. 4. It was confirmed from the graph that the charge mobility had a value of 5.42 × 10 ⁻⁵ cm 2 / V · sec and the on / off ratio had a value of 8.18.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is possible.

As mentioned above, the present invention discloses a novel structure of soluble pentacene precursor, an organic semiconductor material that can be used in organic thin film transistor (OTFT) devices.

Pentacene precursor according to the present invention is prepared by the Diels-Alder reaction, solubility in organic solvents can be prepared through the Retro Diels-Alder reaction by pyrolysis without using a vacuum equipment.

In addition, by using the pentacene precursor according to the present invention as a starting material, it is possible to manufacture a pentacene thin film for organic semiconductor having high mobility and high blink rate.

In particular, since the soluble pentacene precursor can form a semiconductor layer through wet processes such as spin coating and inkjet printing, the production cost can be drastically lowered compared to the conventional vacuum deposition method, and the low temperature process allows the organic polymer. It can be easily used for a flexible substrate such as, and can be advantageously applied to fabricate an organic transistor element on a large-area plastic substrate.

In addition, by using a novel method of synthesizing pentacene using microwaves according to the present invention, a high yield of pentacene can be produced by a simple process.

Claims (20)

Penta is a Diels-Alder reaction product of an aromatic azine compound and a bezyne equivalent and includes at least one -N = N- bridge in the benzene ring at positions 2 to 4 of the following formula (I). Sen precursor: Formula 1

(Ⅰ) The method of claim 1, Pentacene precursors represented by the following formula (II): Formula 2

(Ⅱ) The method of claim 1, Pentacene precursors represented by the following formula (III): Formula 3

(Ⅲ) The method of claim 1, The aromatic azine compound is pentacene precursor, characterized in that selected from phthalazine (pyrazine), pyridazine (pyridazine) or tetrazine (tetrazine). The method of claim 1, The benzine analogue is selected from tetrabromobenzene, 2,3-dibromonaphthalene or phthalic anhydride pentacene precursor. A process for preparing a pentacene precursor, comprising the step of reacting an aromatic azine compound with a bezyne equivalent in Diels-Alder in an organic solvent. The method of claim 6, After the Diels-Alder reaction, further comprising purifying the Diels-Alder reaction product. The method of claim 6, The organic solvent may be a hydrogen atom, a halogen atom, an alkoxy group, an amino group, a hydroxy group, a thiol group, a nitro group or a cyano group substituted or unsubstituted aromatic compound having 1 to 10 carbon atoms, characterized in that the method for producing a pentacene precursor . The method of claim 6, The Diels-Alder reaction is a method for producing a pentacene precursor, characterized in that occurs within the range of -40 to the reflux temperature of the organic solvent. The method of claim 6, The Diels-Alder reaction is a process for producing a pentacene precursor, characterized in that the reaction of phthalazine as an aromatic azine compound and tetrabromobenzene as a benzine analog in the presence of a base in an organic solvent. The method of claim 6, The Diels-Alder reaction was first reacted with tetrazin as an aromatic azine compound and 2,3-dibromonaphthalene as a benzine analog in the presence of a base in an organic solvent, followed by addition of 2,3-dibromonaphthalene in the presence of a base. Method for producing a pentacene precursor, characterized in that the second reaction proceeds in two steps. The method of claim 6, The Diels-Alder reaction is a one-step process for producing a pentacene precursor, characterized in that the phthalazine as an aromatic azine compound and the phthalic anhydride as a benzine analog by microwave irradiation in an organic solvent. Preparing a pentacene precursor by reacting an aromatic azine compound with a benzine analog in Diels-Alder in an organic solvent; And pyrolysing the pentacene precursor. The method of claim 13, The pyrolysis step is a method for producing pentacene is heated at a temperature of room temperature to 200 ℃. A method for preparing pentacene, comprising the step of reacting an aromatic azine compound and a benzine analogue with Diels-Alder through microwave irradiation in an organic solvent. The method of claim 15, The microwave is a method for producing pentacene that will be irradiated for 1 to 30 minutes. An organic thin film transistor comprising a pentacene semiconductor layer formed by a wet process from a pentacene precursor which is a Diels-Alder reaction product of an aromatic azine compound and a benzine analog.   An organic thin film transistor comprising a pentacene semiconductor layer formed by a dry process from pentacene obtained by a Diels-Alder reaction of an aromatic azine compound and a benzine analog. The method of claim 17, The wet process is an organic thin film transistor, characterized in that selected from the group consisting of spin coating method, inkjet printing method, screen printing method, and dipping (dipping) method. The method of claim 18, The dry process is an organic thin film transistor, characterized in that selected from the vacuum deposition method or organic vapor deposition method.

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