TWI450429B - Organic thin film transistor and method for preparing thereof - Google Patents

Description

Organic thin film transistor and method of manufacturing same Field of invention

The invention relates to an organic thin film transistor and a manufacturing method thereof, and more particularly to improving the interface property between an organic semiconductor layer and a source/drain electrode, and increasing the injection of the carrier from the source/drain electrode to the organic semiconductor layer. The ability to improve the electrical performance of an organic thin film transistor of a transistor, and its method of manufacture.

Background technique

Organic thin film transistors using organic materials as semiconductor layers have been studied since 1980, and many studies are being conducted worldwide.

Since the manufacturing process of the organic thin film transistor is simple and inexpensive, and can be performed at a low temperature compared to the existing germanium thin film transistor, it can satisfy the large and thin size and flexibility properties required in recent flat panel displays.

The performance of the organic thin film transistor is evaluated by field effect activity, Ion/Ioff ratio, low limit voltage and sub-low limit slope, etc., and it actually approaches the performance of the germanium thin film transistor.

Moreover, the effectiveness of the organic thin film transistor is based on the crystallinity of the organic semiconductor layer, the charge property of the interface between the gate insulating film and the organic semiconductor layer, and the carrier is injected into the interface between the source/drain electrode and the organic semiconductor layer. Ability depends on the ability.

However, the increase in contact resistance due to the energy barrier between the organic semiconductor layer of the organic thin film transistor and the source/drain electrode makes the carrier difficult to inject, which deteriorates the properties of the organic thin film transistor. Therefore, different attempts have been made to solve the above problems.

In order to solve the above problems of the prior art, an object of the present invention is to provide an organic thin film transistor including an organic buffer layer interposed between an organic semiconductor layer and a source/drain electrode. The interfacial properties between the organic semiconductor layer and the source/drain electrodes, and the energy barrier between the organic semiconductor and the metal electrode to reduce the contact resistance to enhance the ability of the carrier to be injected, thereby improving the performance of the transistor, and including Organic thin film transistor organic light emitting display.

Another object of the present invention is to provide a method for fabricating an organic thin film transistor comprising simultaneously coating an organic buffer layer on a source electrode and a drain electrode, or selectively coating it by electrochemical coating. On the source or drain electrode.

In order to achieve the above objectives, the present invention provides an organic thin film transistor comprising: a source electrode and a drain electrode; an organic semiconductor layer electrically connected to the source electrode and the drain electrode; and an organic buffer layer, It is interposed between the source electrode and the organic semiconductor layer and/or between the drain electrode and the organic semiconductor layer; a gate electrode is insulated from the source electrode, the drain electrode and the organic semiconductor layer; and a gate An insulating film for insulating the gate electrode from the source electrode, the drain electrode, and the organic semiconductor layer.

The present invention also provides a method for fabricating an organic thin film transistor comprising interposing an organic buffer layer between a source/drain electrode and an organic semiconductor layer, wherein the organic buffer layer is coated by electrochemical coating At least one of the source electrode and the drain electrode.

The present invention also provides an organic light emitting display comprising the organic thin film transistor of the present invention; and an organic light emitting device electrically connected to the organic thin film transistor.

According to the present invention, the interface properties between the organic semiconductor layer and the source/drain electrodes and the ability of the carrier to be injected can be improved to improve the transistor performance. Also, the organic buffer layer can be selectively applied to the source electrode, the drain electrode, or the source/drain electrode by electrochemical coating.

Simple illustration

1 is a cross-sectional view schematically showing an apparatus and method for forming an organic buffer layer by electrochemical coating according to a preferred embodiment of the present invention;

2 is a cross-sectional view schematically showing a cross section of an organic thin film transistor according to a preferred embodiment of the present invention;

Figure 3 is a cross-sectional view schematically showing a cross section of an organic thin film transistor according to another preferred embodiment of the present invention.

Invention mode

The invention will now be described in detail.

The organic thin film electro-crystal system of the present invention comprises a source electrode and a drain electrode; an organic semiconductor layer electrically connected to the source electrode and the drain electrode; and an organic buffer layer interposed between the source electrode and the organic Between the semiconductor layers and/or between the drain electrode and the organic semiconductor layer; a gate electrode insulated from the source electrode, the drain electrode and the organic semiconductor layer; and a gate insulating film for the gate The electrode is insulated from the source electrode, the drain electrode, and the organic semiconductor layer.

The organic buffer layer may be made of a thiophene-based compound or a quinone-thiophene-based compound.

Dithienothiophene, propenylthiophene, thienothiophene or a derivative thereof can be used as the thiophene-based compound. Specifically, the thiophene-based compound is represented by one of the following Chemical Formulas 1 to 5:

(wherein R ₂ and R ₃ are independently hydroxy, alkyl, cycloalkyl, alkoxy, cycloalkoxy or thioalkoxy groups, preferably hydroxy, C ₁ -C ₁₈ alkyl, alkane An oxy or thioalkoxy group; and m is an integer from 1 to 6)

(wherein Ar is a C ₄ -C ₁₈ thienyl group)

The acene-thiophene-based compound can be represented by one of the following Chemical Formulas 6 to 14:

[Chemical Formula 7]

(wherein R ₁ is independently a hydroxy, alkyl, cycloalkyl, alkoxy, cycloalkoxy or thioalkoxy group, preferably hydroxy, C ₁ -C ₁₈ alkyl, alkoxy or Thioalkoxy; and n is independently 1 or 2).

The organic buffer layer is not coated by spin coating, dipping or the like according to the prior art, but is coated by an electrochemical coating method, so that it can be selectively applied to the source electrode, the drain electrode or the source. On the pole/dip electrode. Electrochemical coating avoids the spin coating or dip-coating of the overall surface coating of the prior art, and it allows an organic buffer layer to be applied to only a desired portion to maintain superior properties.

The source/drain electrode may be formed as a single layer or a plurality of layers, and is composed of a group selected from the group consisting of Al, Ag, Mo, Au, Pt, Pd, Ni, Ir, Cr, Ti, MoW, or an alloy thereof. Made of at least one. Also, the source/drain electrodes may be made of a transparent material such as ITO, IZO, ZnO, and In ₂ O ₃ .

The organic semiconductor layer may be made of at least one selected from the group consisting of pentacene, tetracene, anthracene, naphthalene, α-6-thiophene, α-4-thiophene, anthracene, and fluorene.蔻, 苝tetracarboxy quinone imine, 苝 tetracarboxy dianhydride, polythiophene, poly-3-hexyl thiophene, polyparaphenylene vinyl, polyparaphenylene, polyfluorene, polythiophene ethylene, polythiophene Cycloaromatic copolymer, oligoacene of naphthalene, oligothiophene of α-5-thiophene, anthraquinone, pyromellitic dianhydride, dipyridinium pyromellitic acid, ruthenium tetracarboxylic dianhydride, hydrazine Dicarboxylic acid diamine imide and its derivatives.

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

1 is a cross-sectional view schematically showing a method of forming an organic buffer layer by electrochemical coating according to a preferred embodiment of the present invention.

Referring to Fig. 1, a substrate (2) on which a source/drain electrode (31, 33, 35, 37) is formed is immersed in a mixed solution of an electrolyte and a solvent, wherein a reference electrode is formed (1). ) and back plate electrodes (3). TBAB (ammonium tetrabutylammonium tetrafluoroborate) can be used as the electrolyte. MC (dichloromethane) can be used as a solvent.

Using Epsilon CV (Cycle Voltammetry), a voltage is applied to the source/drain electrodes of the sample substrate (2) by controlling its level while applying a constant voltage to the reference electrode (1) (31, 33, 35) , 37) and between the back plate electrodes (3). Then, an organic buffer layer (41, 43, 45, 47) is formed on the source/drain electrodes (31, 33, 35, 37) of the sample substrate (2). Specifically, if the source/drain electrodes (31, 33, 35, 37) of the sample substrate (2) are simultaneously connected and a voltage is applied to the back substrate (3) and the source/drain electrodes The organic buffer layer (41, 43, 45, 47) can be simultaneously formed on the source/drain electrodes. If only the source electrodes are connected and a voltage is applied, the organic buffer layer may be formed only on the source electrodes (31, 35). If only the drain electrodes are connected and a voltage is applied, the organic buffer layer may be formed only on the drain electrodes (33, 37).

As described above, the organic buffer layer (41, 43, 45, 47) may be formed on the source/drain electrodes (31, 33, 35, 37) excluding the gate insulating film.

Fig. 2 is a cross-sectional view schematically showing an organic thin film transistor according to a preferred embodiment of the present invention.

Referring to FIG. 2, a source electrode (31), a drain electrode (33), and an organic semiconductor layer electrically connected to the source electrode (31) and the drain electrode (33) (51) is disposed on the substrate (11).

The source electrode (31) and the drain electrode (33) may be made of a conductive material as described above, and deposited on the entire surface of the substrate by photolithography and patterned, or deposited only on the base by the mask. The material is then formed on the substrate (1) as soon as it is determined. The source electrode (31) and the drain electrode (33) are preferably formed by thermal deposition using a shadow mask.

The organic semiconductor layer (51) electrically connected to the source electrode (31) and the drain electrode (33) is not directly in contact with the source electrode (31) and the drain electrode (33), but is separately An organic buffer layer (41, 43) between the source electrode (31) and the organic semiconductor layer (51) and between the drain electrode (33) and the organic semiconductor layer (51) is systematically connected to the source electrode ( 31) and the drain electrode (33). Therefore, in the case of the interleaved organic thin film transistor as shown in Fig. 2, the source electrode (31) and the drain electrode (33) are formed on the substrate (11), and then the organic buffer layer (41, 43) The source electrode (31) and the drain electrode (33) were formed by the method shown in Fig. 1 and dried in an oven at 140 ° C for 2 hours, and then an organic semiconductor (51) was formed thereon.

The organic semiconductor layer (51) can be formed by thermal deposition using a shadow mask at a rate of 0.2 Å/sec, a substrate temperature of 80 ° C, and a vacuum of 1 x 10 ^-7 torr.

On the organic semiconductor layer (51), a gate insulating film (23) is disposed. The gate insulating film (23) is such that a gate electrode (21) formed thereon is insulated from the source electrode (31), the drain electrode (33), and the organic semiconductor layer (51). Also, it may be made of an inorganic substance such as a metal oxide, such as cerium oxide, cerium nitride, aluminum oxide, or the like, or it may be composed of, for example, polyvinyl phenol, polyvinyl alcohol, Made of organic materials such as polymethyl methacrylate, polystyrene, or the like.

On the gate insulating film (23), a gate electrode (21) made of a conductive material such as Al is disposed. The gate electrode (21) can be formed by thermal deposition using a shadow mask.

Although the organic thin film transistor according to the embodiment of Fig. 2 is of a staggered type, the present invention is not limited thereto.

Figure 3 is a cross-sectional view showing an organic thin film transistor according to another preferred embodiment of the present invention. As shown in FIG. 3, the present invention can also be applied to an inverted coplanar organic thin film transistor in which a source electrode (35) and a drain electrode (37) are disposed on a gate electrode (25), an organic semiconductor. The layer (53) is disposed on the source electrode (35) and the drain electrode (37), and a gate insulating film (37) is disposed on the source/drain electrodes (35, 37) and the gate electrode (25) between. In this example, the organic buffer layer (45, 47) is disposed between the source/drain electrodes (35, 37) and the organic semiconductor layer (53).

As described above, the organic thin film electro-crystal system of the present invention comprises an organic buffer layer interposed between the organic semiconductor layer and the source/drain electrodes, thereby improving the interfacial property therebetween and the ability of the carrier to be injected, thereby improving the device of the transistor. nature.

The present invention also provides an organic light emitting display comprising the organic thin film transistor of the present invention and an organic light emitting device electrically connected to the organic thin film transistor.

The organic light emitting display may belong to different types such as an active matrix (AM) type.

Because the organic light emitting display of the present invention comprises organic according to the present invention A thin film transistor that accurately images the input signal.

The invention will be described with reference to the following examples, however, these examples are only intended to illustrate the invention and the scope of the invention is not limited thereto.

Example 1

As shown in Fig. 2, the source/drain electrodes (31, 33) are formed on a substrate (11) by thermal deposition using a shadow mask. Au was used as the electrode material.

Then, the sample substrate (2) on which the source/drain electrodes (31, 33) are formed is immersed in a mixed solution of the electrolyte TBAB (ammonium tetrabutylammonium tetrafluoroborate) and the solvent MC (methylene chloride). Forming a reference electrode (1) and a backing plate electrode (3), and applying a voltage to the source/drain electrodes (31, 33) of the sample substrate (2) using Epsilon CV (cyclic voltammetry) and A constant voltage is simultaneously applied between the backing plate electrodes (3) to the reference electrode (1) to form an organic buffer layer (41, 43) on the source/drain electrodes (31, 33) of the sample substrate (2). The resulting organic buffer layer (41, 43) was dried in an oven at 140 ° C for 2 hours.

Then, on the organic buffer layer (41, 43), a shadow mask was used to form a pentacene by thermal deposition at a substrate temperature of 0.2 ° / sec under a vacuum of 1 x 10 ^-7 Torr. Organic semiconductor layer (51).

On the organic semiconductor layer (51), a gate insulating film (23) is formed using yttrium oxide, and a gate electrode (21) is formed on the gate insulating film (23) by thermal deposition using a shadow mask. Thus, a staggered organic thin film transistor was fabricated. Al is used as the gate electrode material.

Example 2

As shown in Fig. 3, a gate electrode (25) is formed on the substrate (13) by thermal deposition using a shadow mask. Al is used as the gate electrode material. Of course Thereafter, a gate insulating film (27) is formed on the gate electrode (25) by using yttrium oxide.

On the gate insulating film (27), source/drain electrodes (35, 37) are formed by thermal deposition using a shadow mask. Au was used as the electrode material.

As shown in Fig. 1, a sample substrate (2) including a gate electrode (25), a gate insulating film (27), and a source/drain electrode (35, 37) formed on a substrate (13) It is immersed in a mixed solution of TBAB (ammonium tetrabutylammonium tetrafluoroborate) and MC (dichloromethane), in which a reference electrode (1) and a back plate electrode (3) are formed. Then, using Epsilon CV (cyclic voltammetry), a voltage is applied between the source/drain electrodes (31, 33) of the sample substrate (2) and the back plate electrode (3) while applying a constant voltage to the reference electrode. (1) Thus, an organic buffer layer (45, 47) is formed on the source/drain electrodes (35, 37) excluding the gate insulating film (27). The resulting organic buffer layer (45, 47) was dried in an oven at 140 ° C for about 2 hours.

Then, on the organic buffer layer (45, 47), a pentacene system was formed by thermal deposition of a substrate temperature of 80 ° C and a rate of 0.2 Å / sec under a vacuum of 1 x 10 ^-7 Torr using a shadow mask. An organic semiconductor layer (53).

Industrial utilization

According to the present invention, the interface properties between the organic semiconductor layer and the source/drain electrodes and the ability of the carrier to be injected can be improved to improve the transistor performance. Also, the organic buffer layer can be selectively applied to the source electrode, the drain electrode or the source/drain electrode by an electrochemical coating method.

1‧‧‧ reference electrode

2‧‧‧Substrate (sample substrate) on which the source/drain electrodes are formed

3‧‧‧back plate electrode

11,13‧‧‧Substrate

21,25‧‧‧gate electrode

23,27‧‧‧Gate insulation film

31,35‧‧‧Source electrode

33,37‧‧‧汲electrode

41,43,45,47‧‧‧ organic buffer layer

51,53‧‧‧Organic semiconductor layer

1 is a cross-sectional view schematically showing an apparatus and method for forming an organic buffer layer by electrochemical coating according to a preferred embodiment of the present invention; 2 is a cross-sectional view schematically showing a cross section of an organic thin film transistor according to a preferred embodiment of the present invention; and FIG. 3 is a view schematically showing an organic thin film transistor according to another preferred embodiment of the present invention. A cross-sectional view of the cross section.

11. . . Substrate

twenty one. . . Gate electrode

twenty three. . . Gate insulating film

31. . . Source electrode

33. . . Bipolar electrode

41, 43. . . Organic buffer layer

51. . . Organic semiconductor layer

Claims (8)

An organic thin film transistor comprising: a source electrode and a drain electrode; an organic semiconductor layer electrically connected to the source electrode and the drain electrode; and an organic buffer layer disposed at the source electrode Between the organic semiconductor layer and/or the gate electrode and the organic semiconductor layer, and the organic buffer layer is made of a thiophene-based compound or an acene-thiophene-based compound; a pole electrode insulated from the source electrode, the drain electrode, and the organic semiconductor layer; and a gate insulating film for insulating the gate electrode from the source electrode, the drain electrode, and the organic semiconductor layer . The organic thin film transistor according to claim 1, wherein the thiophene-based compound is represented by one of the following chemical formulas 1 to 5: (wherein R ₂ and R ₃ are independently hydroxy, alkyl, cycloalkyl, alkoxy, cycloalkoxy or thioalkoxy groups, and m is an integer from 1 to 6) (wherein Ar is a C ₄ -C ₁₈ thienyl group). An organic thin film transistor according to claim 1, wherein the acene-thiophene-based compound is represented by one of the following Chemical Formulas 6 to 14: [Chemical Formula 6] [Chemical Formula 10] [Chemical Formula 13] (wherein R ₁ is independently a hydroxy, alkyl, cycloalkyl, alkoxy, cycloalkoxy or thioalkoxy group, and n is independently 1 or 2). The organic thin film transistor of claim 1, wherein the organic buffer layer is formed on at least one of the source electrode and the drain electrode by an electrochemical coating method. The organic thin film transistor according to claim 1, wherein the source/drain electrode is selected from the group consisting of Al, Ag, Mo, Au, Pt, Pd, Ni, Ir, Cr, Ti, MoW, ITO, IZO. At least one of a group consisting of ZnO and In ₂ O ₃ is made. The organic thin film transistor of claim 1, wherein the organic semiconductor layer is made of at least one selected from the group consisting of Form: pentacene, tetracene, anthracene, naphthalene, α-6-thiophene, α-4-thiophene, anthracene, erythrene, anthracene, anthracene tetracarboxydiimide, anthracene tetracarboxy dianhydride, polythiophene , poly-3-hexylthiophene, polyparaphenylene vinyl, polyparaphenylene, polyfluorene, polythiophene ethylene, polythiophene-heterocyclic aromatic copolymer, naphthalene oligoacene, α-5-thiophene Oligothiophene, anthraquinone, pyromellitic dianhydride, pyromellitic acid dinonimide, perylenetetracarboxylic dianhydride, perylenetetracarboxylic acid diimine and its derivatives. A method for fabricating an organic thin film transistor comprising placing an organic buffer layer between a source/drain electrode and an organic semiconductor layer, wherein the organic buffer layer is coated by an electrochemical coating method And at least one of the source electrode and the drain electrode, wherein the organic buffer layer is made of a thiophene-based compound or an acene-thiophene-based compound. An organic light-emitting display comprising the organic thin film transistor according to any one of claims 1 to 6; and an organic light-emitting device electrically connected to the organic thin film transistor.