JP2003282884A - Side gate type organic FET and organic EL - Google Patents

Abstract

(57) [Problem] To provide an organic FET which can be practically used even if an organic semiconductor amorphous thin film having low mobility is used. Further, the present invention provides an organic EL element which does not require a peripheral transistor and can have a large aperture ratio. SOLUTION: A side gate type organic FET is used. That is, the gate electrode 12 is erected on the substrate 11, and the carrier transfer layer 14 made of an organic semiconductor is also laminated on the substrate. The carrier transfer layer 14 is in contact with the gate electrode 12 via the insulating film 13. Then, a source electrode layer 15 and a drain electrode layer 16 are stacked on and under the carrier transfer layer 14. In the organic EL, two control electrodes are erected on a substrate, and an organic semiconductor light-emitting layer is stacked on the substrate, and the two control electrodes are in contact with each other via an insulating layer. Injection electrode layers are stacked above and below the light emitting layer. By applying voltages of different polarities to both control electrodes, holes and carriers recombine in the light emitting layer, and light emission occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a FET (Field Effect Transistor) and an EL (Electrolumine) using an organic semiconductor.
scence, electroluminescent device).

[0002]

2. Description of the Related Art Application of organic materials to electronic devices is based on organic EL (ELectroluminesc).
ence) was put into full-scale practical use, and Bell Laboratories JH Sho
Organic transistor using organic single crystal such as pentacene or α-sexithiophene
With the announcement of (Effect Transistor: OFET), actively driven organic devices have attracted a great deal of attention.

First, a conventional technique relating to an organic FET will be described. As shown in FIG. 5, the organic FET has a channel 53 between a source 51 and a drain 52 made of an organic semiconductor, and is structurally no different from a commonly used inorganic FET. However, in an inorganic semiconductor such as silicon, only one of electrons and holes serves as a carrier, whereas in an organic semiconductor, both can serve as carriers. For this reason, it is difficult to clearly distinguish p-type / n-type in organic semiconductors, and it is considered that a considerable amount of electrons are operating as carriers even in p-type semiconductors that are common in organic semiconductors.

At present, a problem of organic semiconductors is carrier mobility. At present, carrier mobility of organic semiconductor amorphous thin film is very slow, about 10 ^-6 cm ² / Vs,
It is difficult to obtain sufficient characteristics in terms of operating speed and power even when used for such purposes. Therefore, an organic FET using an organic single crystal has been proposed, but time and cost are a major obstacle to producing an organic single crystal. It also impairs the great advantage of organic semiconductor devices, which is the possibility of flexible devices.

The first object of the present invention is to solve the above problems related to the organic FET and provide an organic FET that can be practically used even if an organic semiconductor amorphous thin film having a low mobility is used.

Next, a conventional technique relating to organic EL will be described. As shown in FIG. 6, an organic EL having a normal structure is one in which a hole transport layer 62 and an electron transport layer (light emitting layer) 63 are laminated on a transparent substrate 61, and both are sandwiched by a transparent anode 64 and a cathode 65. is there. An organic EL material is used for the hole transport layer 62 and the light emitting layer 63.

The organic EL is a current control element, and as shown in FIG. 7, its emission brightness is almost proportional to the current (current density). However, with respect to the voltage, as shown in FIG. 8, the luminance (and the current, FIG. 9) in units of digits even with a slight voltage change.
Changes. Therefore, when an EL element is used as a display device that requires delicate brightness control, a circuit for converting a signal voltage into a drive current is required.

As an example, when it is attempted to control the light emission intensity of the organic EL by the active matrix system, the drive circuit is as shown in FIG. First, a voltage is applied to the gate line of the line to which the pixel belongs to turn on the transistor Tr1. During this period, when a data signal (display signal) is supplied to the source side electrode, this display signal is stored in the capacitor C because the write transistor Tr1 is in the conductive state. The conduction amount of the drive transistor Tr2 is controlled by the charge amount of the display signal accumulated in the capacitance C, and the amount of current supplied to the organic EL element of the pixel is determined.

The display device using the organic EL of the active matrix type has an operation duty of the organic EL.
Since it is close to 100%, ignoring the life of the EL element, there is an advantage that high luminance display can be performed by flowing a large current. However, as described above, since at least two transistors are required to drive one EL element, the cost of manufacturing the transistor is high, and the aperture ratio (the area of the light emitting part is equal to the area of the pixel (Value divided by) is low.

The present invention solves the problem of such an organic EL device, and provides an organic EL device which does not require a peripheral transistor and can have a large aperture ratio.

[0011]

First, a side gate type organic FET according to the present invention is arranged so that a) a gate electrode standing on a substrate and b) an insulating film are in contact with the gate electrode. And a c) a source electrode layer and a drain electrode layer, which are arranged above and below the carrier movement layer.

The organic EL device according to the present invention is an organic semiconductor device comprising: a) two or more control electrodes erected on a substrate; and b) arranged in contact with each control electrode via an insulating film. A) a light emitting layer composed of c), a pair of injection electrode layers arranged above and below the light emitting layer, and d) a light emission control circuit for applying a control voltage of opposite polarity to at least two control electrodes. It is characterized by

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the current FET
In general, the gate electrode is generally arranged parallel to the surface of the substrate. However, as shown in FIG.
By vertically arranging 2 on the substrate 11 and arranging on the side (side) of the carrier moving layer 14 also mounted on the substrate 11 (via the insulating film 13), the carrier moving distance can be shortened. (Because the channel width is a film thickness, it is in the nano order), and the contact area between the carrier transfer layer 14 and the source / drain electrodes 15 and 16 can be made very large. Therefore, the carrier transfer layer 14
Even if an amorphous organic semiconductor having a low carrier mobility is used, a FET having a sufficiently high switching speed and a large allowable current can be obtained. Further, in the conventional FET, since the source electrode, the channel, and the drain electrode must be arranged on the substrate at the same level, a complicated lithography process must be performed to form them. In the gate FET structure, since the source electrode, the carrier transfer layer (organic semiconductor layer), and the drain electrode layer are sequentially stacked on the substrate, the stacked structure can be easily constructed using a simple vapor deposition method or the like. Therefore, the range of selection of the electrode material is widened. In addition, a flexible device can be obtained by selecting a material.

For the source electrode and the drain electrode, electrodes that are advantageous for injecting carriers to be controlled are used. For example, in the case of electrons, LUMO (Lowest Unocc
An electrode (for example, Mg) having a work function suitable for upied Molecular Orbit, lowest unoccupied molecular orbital is used, and HOMO (Highest Occupied Molecular Orbit, highest occupied molecular orbital) and work function are matched for hole injection. Electrodes (eg IT
O = Indium Tin Oxide) is used.

The FET according to the present invention is shown in FIGS.
As shown in FIG. 2, the principle operation is achieved even if the gate electrode 12 is either positive or negative, but as shown in FIGS. Alternatively, the carrier density can be increased by disposing the gate electrode 22 (on the periphery). In this case, voltages of the same polarity are applied to the gate electrodes 22 on both sides or the periphery.

The structure of the side gate type organic FET shown in FIG. 2 will be described. A gate electrode 22 is erected on a substrate 21 made of a transparent material such as glass or polymer. Gate electrode 2
An insulating film 23 is formed around 2 by a method such as oxidizing the surface of the gate electrode 22. Further, a carrier transfer layer 24 made of an organic semiconductor is laminated on the substrate 21 so as to be in contact with the insulating film 23. An upper electrode 25 and a lower electrode 26 are stacked above and below the carrier transfer layer 24. One of the upper electrode 25 and the lower electrode 26 serves as a source electrode and the other serves as a drain electrode. In the case of an organic semiconductor, both hole electrons can serve as carriers as described above, and thus these can also be called cathode / anode.

Examples of the organic semiconductor constituting the carrier transfer layer 24 include N, N'-dimethylperylene-3,4,9,10-bisdicarboximide in the n-type (electron transport type) and Copper (II).
1,2,3,4,8,9,11,15,16,17,18,22,23,24,25-hexadecaflu
oro-29H, 31H-phtalocyanine, etc., p-type (hole transport type) Copper (II) phtalocyanine, pentacene, anthracene, acene such as tetracene, α-sexthiophene,
A thiophene oligomer or the like can be used. For the gate electrode 22, for example, gold, aluminum, silicon, polysilicon or the like or a transparent electrode can be used. Also,
For the source electrode and the drain electrode, alkali metal or alkaline earth metal having a low work function in the case of n-type, or an alloy thereof with aluminum, silver, etc., ITO or gold having a high work function in the case of p-type , Platinum, lead, etc. can be used.

Next, the organic EL according to the present invention will be described. In the organic FET having the structure shown in FIG. 2, as shown in FIG. 3, by applying voltages having different polarities to the gate electrodes 32 on both sides and mixing the organic EL material into the organic semiconductor layer 34, both gate electrodes 32 (control Holes and electrons generated in the vicinity of (also referred to as an electrode) recombine in the organic EL material (light emitter layer) to emit light. That is, the completion of the organic EL. The source electrode and the drain electrode are the injection electrode 35,
36.

In the organic EL device according to the present invention, since the hole / electron concentration can be controlled by the voltage applied to the control electrode 32 and the light emission amount can be controlled, the voltage can be directly controlled.
Therefore, the transistor for voltage-current conversion as shown in FIG. 10 becomes unnecessary, and the aperture ratio can be increased.

Conventional materials can be used as they are for the substrate, the electrodes, and the organic EL material.

In the case of organic EL, as shown in FIG. 4, by introducing a pn junction into the organic semiconductor layer, a larger amount of recombination can be generated. In addition, the organic EL of the present invention
Then, it is advantageous to increase the thickness of the organic semiconductor layer as compared with the conventional one, and thereby, the emission intensity can be increased and the reliability of the device can be expected to be improved.

The structure of the organic EL shown in FIG. 4 will be described. Positive and negative control electrodes 42 are provided upright on a substrate 41 made of a transparent material such as glass or polymer. An insulating film 43 is formed on the surfaces of both control electrodes 42 by oxidation or the like. Board 41
First, the transparent anode 46 is laminated on the upper surface, and then the hole transport layer 4
4 and the electron transport layer (light emitting layer) 45 are sequentially stacked. A cathode 47 is laminated on the electron transport layer 45.

Of course, the hole transport layer 44 and the electron transport layer 4
5 (and the anode / cathode) may be laminated in reverse.

The hole transport layer 44 may be formed of, for example, triphenyldiamine, 4,4 ', 4''-tris [3-methylphenyl (phenyl)
amino] triphenylamine, 4,4 ', 4''-tris [1-naphthyl (phe
nyl) amino] triphenylamine, 4,4 ', 4''-tris [2-naphthyl
(phenyl) amino] triphenylamine, 4,4 ', 4''-tris [biphen
yl-4-yl- (3-methylphenyl) amino] triphenylamine, 4,
4 ', 4''-tris [9,9-dimethyl-2-fluorenyl (phenyl) amino]
triphenylamine, 4,4 ', 4''-tri (N-carbazolyl) tripheny
lamine, 1,3,5-tris [N- (4-diphenylaminophemyl) phenyl
amino] benzene, 1,3,5-tris {4- [methylphenyl (phenyl) a
mino] phenyl} benzene, N, N'-di (biphenyl-4-yl) -N, N'-d
iphenyl- [1,1'-biphenyl] -4,4'-diamine, N, N, N ', N'-te
trakis (9,9-dimethyl-2-fluorenyl)-[1,1'-biphenyl]-
4,4'-diamine and the like can be used. The electron transport layer 45 includes, for example, a quinolinol aluminum complex and oxadiazole.
Derivative, 1,3,5-tris [5- (4-tert-butylphenyl) 1,3,4-oxa
diazol-2-yl] benzene, 5,5'-bis (dimesitylboryl) -2,2 '
-bithiophene, 5,5``-bis (dimesitylboryl) 2,2 ': 5'2'-t
erthiophene or the like can be used.

For the control electrode 42, for example, gold,
Aluminum, silicon, polysilicon or the like or a transparent electrode can be used. For the anode 46, ITO, indium zinc oxide, conductive polyaniline, or the like can be used. For the cathode 47, a magnesium silver alloy, a magnesium indium alloy, a magnesium copper alloy, an aluminum lithium alloy, or the like can be used.

In the structure of the current organic EL shown in FIG. 6, since the recombination region and the metal electrode are very close to each other, absorption of light by the metal electrode poses a problem even if a laser is used.
On the other hand, in the organic EL according to the present invention, there is a possibility that an injection type organic laser can be realized by thickly stacking a material having high FET mobility (mobility of commonly known organic semiconductors (for example, TOF method). And the IV mobility) and the FET mobility may differ).

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of a side gate type organic FET according to the present invention.

FIG. 2 is a cross-sectional view showing another configuration example of the side gate type organic FET according to the present invention.

FIG. 3 is a cross-sectional view showing a configuration example of a side gate type organic EL according to the present invention.

FIG. 4 is a sectional view showing another configuration example of the side gate type organic EL according to the present invention.

FIG. 5 is a cross-sectional view showing the configuration of a conventional organic FET.

FIG. 6 is a cross-sectional view showing a configuration of a conventional organic EL.

FIG. 7 is a graph showing the relationship between the current density of organic EL and the emission luminance.

FIG. 8 is a graph showing the relationship between the organic EL voltage and the emission luminance.

FIG. 9 is a graph showing the relationship between voltage and current density of organic EL.

FIG. 10 is a circuit diagram of an active matrix organic EL drive circuit.

[Explanation of symbols]

11, 21 ... Substrate 12, 22 ... Gate electrode 13, 23 ... Insulating film 14, 24 ... Carrier transfer layer 15, 25 ... Upper electrode 16, 26 ... Lower electrode 31, 41 ... Substrate 32, 42 ... Control electrodes 33, 43 ... Insulating film 34 ... Organic EL light emitting layer 44 ... Hole transport layer 45 ... Electron transport layer (light emitting layer) 35, 36, 46, 47 ... Injection electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazumi Matsushige             Kyoto University Venture, Yoshidahonmachi, Sakyo-ku, Kyoto             ー In business laboratory F-term (reference) 3K007 AB02 AB03 AB11 AB18 DB03                 5F110 AA07 BB01 CC09 DD01 DD02                       EE02 EE08 EE09 EE27 EE30                       FF22 GG05 HK02 HK03 HK07

Claims (4)

[Claims] 1. A) a gate electrode erected on a substrate, b) a carrier transfer layer made of an organic semiconductor and being in contact with the gate electrode via an insulating film, and c) the carrier transfer. A side-gate organic FET comprising: a source electrode layer and a drain electrode layer, which are disposed above and below the layer. 2. The side gate type organic FET according to claim 1, wherein the gate electrode is composed of two or more gate electrodes to which voltages of the same polarity are applied. 3. A) two or more control electrodes erected on a substrate, b) a light-emitting layer made of an organic semiconductor, which is arranged so as to be in contact with each control electrode through an insulating film, and c ) An organic EL device comprising: a pair of injection electrode layers disposed above and below the light emitting layer; and d) a light emission control circuit for applying a control voltage of opposite polarity to at least two control electrodes. 4. The organic material according to claim 3, wherein the light emitting layer is a laminate of an n-type active layer and a p-type active layer.
EL.