Active matrix organic electroluminescent display device including organic thin film transistor and method of manufacturing the display device

Provided is an active matrix organic electroluminescent (EL) display device including an organic thin film transistor (TFT), preferably n-type, having a higher aperture ratio and easily realized in an array structure. The display device includes a facing electrode; an intermediate layer including at least a light emitting layer on the facing electrode; a pixel electrode formed on the intermediate layer; a first electrode located on the pixel electrode and insulated from the pixel electrode; a second electrode located on the pixel electrode and coupled with the pixel electrode; an n-type organic semiconductor layer contacting the first electrode and the second electrode; and a first gate electrode located on the n-type organic semiconductor layer and insulated from the first electrode, the second electrode, and the n-type organic semiconductor layer.

BACKGROUND OF THE INVENTION

This application claims the priority of Korean Patent Application No. 10-2004-0046943, filed on Jun. 23, 2004, in the Korean Intellectual Property Office, which is hereby incorporated by reference for all purposes as if fully set forth herein.

1. Field of the Invention

The present invention relates to an active matrix organic electroluminescent (EL) display device using an organic thin film transistor (TFT), and more particularly, to an active matrix organic EL display device formed in an array structure, including an n-type organic TFT and having an aperture ratio of approximately 100%.

2. Description of the Related Art

FIG. 1is a plan view of a sub-pixel unit in a conventional active matrix electroluminescent (EL) display device, andFIG. 2is a cross-sectional view of the sub-pixel unit of the display device taken along line P1through P7ofFIG. 1.

Referring to the drawings, in conventional silicon thin film transistors (TFTs)110and150having a semiconductor layer180formed of silicon, the semiconductor layer180includes a source region and a drain region, both of which are doped by impurities of high concentration, and a channel region formed between these two regions. In addition, the silicon TFTs110and150include gate electrodes111and151insulated from the semiconductor layer180and positioned to correspond with the channel region, and source electrodes112and152and drain electrodes113and153contacting source regions and the drain regions, respectively.

However, the conventional silicon TFTs110and150are expensive, fragile, and cannot employ a plastic substrate since they are fabricated at a high temperature, for example, 300° C. or higher.

Flat panel display devices such as liquid crystal displays (LCD) or electroluminescent displays (ELD) use TFTs as switching devices and driving devices for controlling and operating pixels. In order to make flat panel display devices large, thin, and flexible, plastic materials are being considered for the substrate instead of glass. However, when plastic is used, manufacturing is difficult because the display device must be fabricated at a temperature below what is necessary for conventional silicon TFTs.

Since an organic TFT solves the above problems, much research is currently being performed into developing organic TFTs including the organic semiconductor layer.

FIG. 3is a schematic cross-sectional view of an organic EL display device including the conventional organic TFT. Referring toFIG. 3, an organic EL device210and an organic TFT220are formed on a substrate200. The organic EL device210includes a transparent electrode211, an organic light emitting layer212, and a metal electrode213, which are sequentially formed on the substrate200, and the organic TFT220includes a gate electrode221formed on the substrate200, a dielectric layer222formed on the gate electrode221, an organic semiconductor layer223formed on the dielectric layer222, and a source electrode224and a drain electrode225located on both sides of the organic semiconductor layer223on the dielectric layer222. The drain electrode225is connected to the transparent electrode211and the organic light emitting layer212of the organic EL device210.

However, since the organic EL device210is horizontal and parallel to the organic TFT220, the organic EL device210has a low apertureratio due to the size of the organic TFT220. When the aperture ratio is low, the light emitting intensity of the pixels of the display device needs to be increased, which reduces the lifespan of the display device.

To solve the above problem, Korean Patent Publication No. 2003-0017748 discloses an active matrix organic EL display device, in which an organic TFT and an organic EL device are stacked vertically.FIG. 4is a cross-sectional view of an organic EL display device including the organic TFT described above.

Referring toFIG. 4, an organic EL device310and an organic TFT330on a substrate300are divided vertically by a first insulating layer320. The organic EL device310includes a transparent electrode311, an organic light emitting layer312, and a metal electrode313, sequentially formed on the substrate300, and the organic TFT330includes a gate electrode331formed on the first insulating layer320, a second insulating layer332formed on the gate electrode331, a source electrode334and a drain electrode335formed on the second insulating layer332, and an organic semiconductor layer333connected to the source and drain electrodes334and335. In addition, the source electrode334is connected to the metal electrode313.

However, the above example is simply an organic EL device having one organic TFT, not an array of a plurality of organic EL devices having a plurality of organic TFTs. Thus it is difficult to use this single organic EL device to realize an actual useable active matrix organic EL display device including a plurality of organic EL devices.

In addition, in the structure disclosed in the Korean Patent Publication No. 2003-0017748, the organic TFT330has an inverted coplanar structure, but in order to realize the active matrix organic EL display device using the organic TFT330having such structure, complex processes are required, and the display device becomes more complex.

SUMMARY OF THE INVENTION

The present invention provides an active matrix organic electroluminescent (EL) display device having an organic thin film transistor (TFT), having an aperture ratio of approximately 100%, which is realized by an array.

According to an embodiment of the invention, there is provided an active matrix organic electroluminescent display device having an organic thin film transistor, the display device including a facing electrode, an intermediate layer comprising at least a light emitting layer on the facing electrode, a pixel electrode formed on the intermediate layer, a first electrode provided on the pixel electrode and insulated from the pixel electrode, a second electrode provided on the pixel electrode and connected with the pixel electrode, an n-type organic semiconductor layer contacting the first electrode and the second electrode, and a first gate electrode provided on the n-type organic semiconductor layer and insulated from the first electrode, the second electrode, and the n-type organic semiconductor layer.

According to another embodiment of the invention, there is provided a method of fabricating an active matrix organic electroluminescent display device including an organic thin film transistor, the method including forming a facing electrode on an entire surface of a substrate or in a predetermined pattern, forming an intermediate layer comprising at least a light emitting layer on the facing electrode, forming a pixel electrode of a predetermined pattern on the intermediate layer, forming a protective layer covering the pixel electrode on the entire surface of the substrate, forming a first contact hole in the protective layer to expose the pixel electrode, forming on the protective layer a second electrode connected with the pixel electrode through the first contact hole, a first electrode and a first capacitor electrode integral with each other, a fourth electrode, and a third electrode, forming an n-type organic semiconductor layer covering the electrodes on the entire surface of the substrate, forming a gate insulating layer on the n-type organic semiconductor layer or the entire surface of the substrate, forming a second contact hole in the n-type organic semiconductor layer and the gate insulating layer to expose the fourth electrode, and forming or the gate insulating layer a first gate electrode, a second capacitor electrode connected with the fourth electrode through the second contact hole, and a second gate electrode.

DETAILED DESCRIPTION OF THE INVENTION

Referring to a first embodiment of the present invention,FIG. 5is a schematic circuit diagram of the circuit of an active matrix electroluminescent (EL) display device including an n-type organic thin film transistor (TFT).FIG. 6is a circuit diagram of part “A” ofFIG. 5.FIG. 7is a schematic plan view of a sub-pixel unit of the active matrix organic EL display device including the n-type organic TFT.FIG. 8is a cross-sectional view of the sub-pixel unit of the active matrix organic EL display device including the n-type organic TFT taken along line Q5and Q6.FIG. 9is a schematic cross-sectional view of the sub-pixel unit of the active matrix organic EL display device including the n-type organic TFT taken along line Q1through Q3ofFIG. 7.FIG. 10is a schematic cross-sectional view of the sub-pixel unit of the active matrix organic EL display device including the n-type organic TFT taken along line Q1through Q5ofFIG. 7.

According to the first embodiment of the invention, but not limited thereto, an EL display device includes various pixel patterns according to the color of emitted light at a light emitting layer. For example, the pixels may each include red, green, and blue sub-pixels. The EL device is a current-driven light emitting device, and emits red, green, or blue light according to the current flowing between two electrodes to display an image.

The EL device includes a facing electrode, an intermediate layer including at least a light emitting layer formed on an upper portion of the facing electrode, and a pixel electrode on the intermediate layer. The present invention is not limited to the above described structure, and various structures of EL device may be applied.

A flat panel display device using the EL device has advantages over conventional display devices, e.g., cathode ray tube, such as superior brightness, higher contrast, wider viewing angle, etc.FIG. 5,FIG. 6,FIG. 7,FIG. 8,FIG. 9, andFIG. 10illustrate the active matrix EL display device in which a transistor is formed at every pixel to control the light emission of the pixel and/or a signal applied to that pixel. The present invention relates to an organic EL display device having the transistor, that is, for example, an n-type organic TFT.

Referring first toFIG. 5andFIG. 6, each sub-pixel unit includes a second organic TFT450that is driven by a driving circuit, a first organic TFT410driven by the second organic TFT450, and an organic EL device460driven by the first organic TFT410.

A third electrode452of the second organic TFT450is connected with the driving circuit through a first conducting line420, a second gate electrode451of the second organic TFT450is connected with the driving circuit through a second conducting line430, and a fourth electrode453of the second organic TFT450with connected to a second capacitor electrode (upper electrode,442) of a storage capacitor440and a first gate electrode411of the first organic TFT410.

In the above structure, the first conducting line420may be a data line transmitting data, and the second conducting line430may be a scan line. In the embodiment discussed withFIG. 6, the second organic TFT450operates as a switching transistor, and the first organic TFT410operates as a driving transistor. In the above described selection driving circuit, two or more transistors may be used. Hereinafter, the sub-pixels are described having two transistors, the switching transistor and the driving transistor.

Referring toFIG. 6andFIG. 7, a first capacitor electrode (lower electrode,441) of the storage capacitor440and a first electrode412of the first organic TFT410are connected with a third conducting line470, and a second electrode413of the first organic TFT410is connected with the pixel electrode462of the organic EL device460. As shown inFIG. 8,FIG. 9, andFIG. 10, the facing electrode461of the organic EL device460is separated from the pixel electrode462by a predetermined gap or distance, and an intermediate layer487including at least a light emitting layer is located between the facing and pixel electrodes461and462.

InFIG. 7, the organic TFTs410and450are provided on a right lower portion and a left upper portion of the sub-pixel unit, and the storage capacitor440is provided between the organic TFTs410and450. However, the organic TFTs410and450can be provided in parallel on the upper or lower portion of the sub-pixel unit, and more organic TFTs can be formed. Further, the organic TFTs410and450can be provided on a right upper portion and a left lower portion.

FIG. 7,FIG. 8, andFIG. 9show the physical structure of part “A” shown inFIG. 5andFIG. 6.FIG. 7shows the first conducting line420and the second conducting line430that are not shown inFIG. 8andFIG. 9. FurtherFIG. 8andFIG. 9show a substrate481, a gate insulating layer483, a protective layer485, and a pixel electrode462that are not shown inFIG. 7.

Referring to the drawings, when a scan signal is applied or transmitted to the second gate electrode451by the driving circuit, a conductive channel (not shown) is formed on the n-type organic semiconductor layer connecting the third electrode452with the fourth electrode453. For example, when the data signal is supplied to the third electrode452by the first conducting line420, the data signal is transmitted to the storage capacitor440and to the first TFT410. In addition, a conductive channel is formed on the n-type organic semiconductor layer connecting the first electrode412and the second electrode413and a signal from the third conducting line470is transmitted to the pixel electrode462.

InFIGS. 8,9, and10, a detailed structure of the sub-pixel unit is shown. Referring toFIG. 8, the facing electrode461is located on the entire upper surface of the substrate481, the intermediate layer487including at least the light emitting layer is formed on the facing electrode461, and the pixel electrode462is located on the intermediate layer487. The n-type first organic TFT410is connected with the organic EL device460, and the second electrode413of the n-type first organic TFT410is connected to the pixel electrode462of the organic EL device460. Thus, the pixel electrode462becomes a cathode electrode, and the facing electrode461corresponding to the pixel electrode462becomes an anode electrode. In the following descriptions, organic TFT refers to the n-type organic TFT.

When the organic EL device is a backlight emission type, the substrate481and the facing electrode461are made of a transparent material, and the pixel electrode462is made of a metal having a high light reflectivity.

When the organic EL device is a front emission type, the facing electrode461is made of a metal having a high light reflectivity, and the pixel electrode462, a protective layer485, an organic semiconductor layer480, and a gate insulating layer483that will be described later may be made of transparent materials. The EL device according to the present invention may be a backlight emission type, a front emission type, or a dual-emission type, that is, the light generated by the EL device may be emitted in at least one direction between the facing and pixel electrodes461and462.

When the facing electrode461is formed of the transparent material, the facing electrode461can be used as the cathode electrode. Therefore, an auxiliary electrode or a bus electrode line is made of a transparent electrode material, such as indium tin oxide (ITO), indium zinc oxide (IZO), ZnO, In2O3, or the like, and a metal having a small work function, such as Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or a compound thereof, is subsequently deposited to form a semi-permeable metal layer, thereby forming the facing electrode461having a dual structure. Further, when the facing electrode461is a reflective electrode, then Li, Ca, LiF/Ca, LiF/Al, Ag, Mg, or a compound thereof, is deposited on the substrate at a sufficient thickness to form the facing electrode461.

The facing electrode461may cover all the sub-pixels, or may be formed to correspond to each sub-pixel.

When the pixel electrode462, that is, the anode electrode, is formed of a transparent material, the pixel electrode462may be formed of ITO, IZO, ZnO, In2O3, or the like. When the pixel electrode462is a reflective electrode, the electrode is formed of ITO, IZO, ZnO, In2O3, or the like, and then one of the following: Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, or a compound thereof, is deposited thereon at a sufficient thickness to form a low resistance reflective layer. Further, when the pixel electrode462is a reflective layer, Au, Ni, Pt, or Pd may be used instead of the above structure. The pattern of the pixel electrode may be formed to correspond to each sub-pixel. However, the shape of the pattern is not limited thereto, and an organic material, such as a conductive polymer, may be used for the facing and pixel electrodes.

The organic EL device460includes the pixel electrode462which receives a signal from the second electrode413of the first organic TFT410, the facing electrode461, and the intermediate layer487including the light emitting layer, which is located between the pixel electrode462and the facing electrode461. The intermediate layer487is made of an organic material.

The organic EL device460may have a low-molecular weight organic layer or a polymer organic layer according to the type of organic material.

When the low-molecular weight organic layer is used to form the organic EL device460, the intermediate layer487may include a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) stacked in a single layer or multiple layer structure. The organic material such as copper phthalocyanine (CuPc), N,N-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) or tris-8-hydroxyquinoline aluminum (Alq3), may be used. When a charge is supplied to the facing and pixel electrodes, the holes and electrons are combined to generate exitons, and the exitons emit light by dropping from an excited state to a ground state.

As described above, when the pixel electrode462is the cathode electrode and the facing electrode461is the anode electrode, the intermediate layer487may include the HIL, HTL, EML, EIL, and ETL sequentially stacked or formed from the facing electrode461. It is well know that the intermediate layer487may include additional layers.

The low-molecular weight organic layer may be formed by heating and depositing/providing organic material under a vacuum. The structure of the intermediate layer487is not limited to the described above example, but may include various layers if necessary.

When the polymer organic layer is used as the intermediate layer487, the intermediate layer487may include the HTL and EML. As described above, when the pixel electrode462is the cathode electrode and the facing electrode461is the anode electrode, the intermediate layer487may include the HTL and EML sequentially stacked or formed from the facing electrode461.

The polymer HTL may be formed of poly-(2,4)-ehtylene-dihydroxy thiopene (PEDOT) or polyaniline (PANI) by inkjet printing, spin coating or the like. The polymer organic light emitting layer may be made of poly-phenylenevinylene (PPV), soluble PPV, Cyano-PPV, or polyfluorene, and a color pattern can be formed in a general way such as inkjet printing, spin coating, or thermal transfer using a laser. It is understood that the structure of the intermediate layer487is not limited to the above embodiment, and various layers may be included.

The protective layer485is formed on the organic EL device460having the above or substantially similar structure, a first contact hole485ais formed in the protective layer485to expose a portion of the pixel electrode462, and the second electrode413is formed on a predetermined region having the first contact hole485a. Consequently, the second electrode413is coupled with the pixel electrode462of the organic EL device460through the first contact hole485aformed in the protective layer485.

The first organic TFT410is formed on the protective layer485. According to a non-limiting embodiment of the invention, the first organic TFT410is an n-type organic TFT.

The structure of the first organic TFT410is described below with reference toFIG. 8. Referring toFIG. 8, the first electrode412and the second electrode413are formed on the protective layer485. The n-type organic semiconductor layer480is formed on the first electrode412and on the second electrode413. The n-type organic semiconductor layer480may be made of NTCDA, perylene tetracarboxylic dianhydride (PTCDA), copper hexadecarfluorophthalocyanine (F16CuPc), C60, pentacene, or PTCDI-C8, by a vacuum deposition technique, a thermal evaporation technique, or the like.

The first gate electrode411is formed on the gate insulating layer483. The first gate electrode411may be made of various conductive materials, such as a conductive metal, for example, MoW, Al, Cr, or Al/Cu, or a conductive polymer, by sputtering and photolithography, or by inkjet deposition. A portion of the first gate electrode411may overlap with the first electrode412and the second electrode413, as shown inFIG. 8, but is not limited thereto.

As described above, when the organic EL device460is formed on the substrate481and the first organic TFT410is formed on the organic EL device460, an aperture ratio of approximately 100% can be ensured in the backlight emission type, in which the light generated by the organic EL device460emits or travels through the substrate481. Therefore, since the charge mobility is low in the organic TFT, a large organic TFT may be used in order to increase the on-current. Thus, when the organic TFT is located on the same plane as the organic EL device, the aperture ratio may be reduced. However, when the organic TFT is located on or above the organic EL device, the aperture ratio is not reduced when the size of the organic TFT is increased.

In addition, the organic TFT410having a staggered type structure includes the first electrode412and the second electrode413, and the n-type organic semiconductor layer480, the gate insulating layer483, and the first gate electrode411formed on the gate insulating layer483. Such structure enables the second electrode413of the first organic TFT410to be coupled to the pixel electrode462of the organic EL device460. Therefore, since the contact hole485ais formed in the protective layer485located between the organic EL device460and the first organic TFT410, the second electrode413and the pixel electrode462of the organic EL device460can be connected with each other through the contact hole485a.

The structure of a second organic TFT450and a storage capacitor440that are connected to the first organic TFT410and the organic EL device460will be described with reference toFIG. 9.

The structure of the second organic TFT450is the same as the structure described above with respect to the first organic TFT410.

The storage capacitor440includes a first capacitor electrode441connected to the first electrode412of the first organic TFT410, and a second capacitor electrode442facing or parallel with the first capacitor electrode441and connected with the fourth electrode453of the second organic TFT450and the first gate electrode411of the first organic TFT410. The first capacitor electrode441may be integrally formed with the first electrode412, and the second capacitor electrode442may be integrally formed with the first gate electrode411.

The n-type organic semiconductor layer480and the gate insulating layer483are provided between the first capacitor electrode441and the second capacitor electrode442, and the n-type organic semiconductor layer480and the gate insulating layer483operate as dielectrics. In addition, the second capacitor electrode442is connected with the fourth electrode453of the second organic TFT450through a second contact hole483aformed in the n-type semiconductor layer480and the gate insulating layer483.

The storage capacitor440having the above structure operates to maintain the electric current flowing to the pixel electrode462, or increase the driving speed of the pixel electrode462.

FIG. 10is a schematic cross-sectional view of the first organic TFT410, the storage capacitor440, and the second organic TFT450, of the sub-pixel unit, which is taken along line Q1through Q5ofFIG. 7, in the active matrix organic EL display device including the organic TFT according to an embodiment of the invention.

Referring toFIG. 10, the first electrode412and the second electrode413of the first organic TFT410, the first capacitor electrode441of the storage capacitor440, and the third electrode452and the fourth electrode453of the second organic TFT450are each formed on the same plane. Also, the first gate electrode411of the first organic TFT410, the second capacitor electrode442of the storage capacitor440, and the second gate electrode451of the second organic TFT450are each formed on the same plane.

The above described structures of the first organic TFT410, the storage capacitor440, and the second organic TFT450simplifies the manufacturing of the active matrix organic EL display. In addition, referring toFIG. 10, since the organic EL device460is formed under or below the organic TFTs and the storage capacitor, an aperture ratio of approximately 100% can be provided in the backlight emission type, wherein the light generated by the organic EL device460emits or travels through the substrate481.

Since the organic TFT may be manufactured by a low-temperature process that does not affect the organic EL device460and the substrate481, the organic EL display device can be used. The facing electrode461of the organic EL device460is a transparent electrode, and the pixel electrode462is a reflective electrode.

FIG. 11is a cross-sectional view of a sub-pixel unit in an active matrix organic EL display device including an organic TFT according to a second embodiment of the invention.

Referring toFIG. 11, the organic EL device includes the facing electrode461provided on the substrate481, the intermediate layer487including the light emitting layer, and the pixel electrode462. In addition, two staggered structure n-type organic TFTs410and450and a storage capacitor440are formed on the organic EL device. The second electrode413of the first organic TFT between the two n-type organic TFTs410and450is coupled with the pixel electrode462of the organic EL device. The above described structure is the same as the structure of the first embodiment, except that a pixel definition layer486is formed on the facing electrode461. The pixel definition layer486divides or separates the sub-pixels formed of the organic EL devices.

The pixel definition layer486increases a gap located between an edge of the pixel electrode462and the facing electrode461in each sub-pixel and defines the light emitting region between the sub-pixels on the first electrode461. Thus, the pixel definition layer486prevents the electric field from being concentrated at the edge of the pixel electrode462, thereby preventing short circuits from occurring between the facing electrode461and the pixel electrodes462.

FIG. 12is a schematic plan view of portion of the sub-pixel units in the active matrix organic EL display device including the organic TFT according to a third embodiment of the invention.

As described above with respect to the first and second embodiments of the invention, the organic EL display device includes various pixel patterns according to the color of light emitted by the light emitting layer. For example, the pixels may each include red, green, and blue sub-pixels. Thus, the organic EL device is a current-driven light emitting device, and emits red, green, or blue light according to the current flowing between two electrodes to display a predetermined image. The colors may be generated by making the light emitting layer of the intermediate layer in the organic EL device emit red491, green492, or blue493light as shown inFIG. 12. The arrangement, order and position of the sub-pixels are not limited to the example shown inFIG. 12. For example, the sub-pixels may be arranged in stripes, mosaic, or delta arrangements. In addition, the structures of organic TFTs410and450and the storage capacitor440in the each sub-pixel unit are not limited to the examples shown inFIG. 12.

The sub-pixel492having the green light emitting layer may be made of 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizine (C545T), tri(8-hydroxyquinolato)aluminum (Alq3), or tris(2-(2-pyridylphenyl)-C,N))iridium(II) (Ir)ppy.

The sub-pixel493having the blue light emitting layer may be made of fluorene-based polymer, spirofluorene-based polymer, carbazole-based low molecular weight such as dicarbazole stilbene (DCS) (also referred to as bis[carbazole-(9)]-stilbene, or 4,4′-bis(2,2′-diphenylenethen-1-yl)-N,N′-bis (phenyl)benzidine (a-NPD).

FIG. 13is a schematic cross-sectional view of a sub-pixel unit of the active matrix organic EL display device including an organic TFT according to a fourth embodiment of the invention. Referring toFIG. 13, an organic EL device including the facing electrode461, the intermediate layer487including the light emitting layer, and the pixel electrode462is located on the substrate481, and two staggered type n-type organic TFTs410and450and the storage capacitor440are formed on the organic EL device. In addition, the second electrode413of the first organic TFT410is coupled with the pixel electrode462of the organic EL device. The above structure is the same as those of the above described embodiments of the invention, except that the structure is different from the third embodiment because the structure of the fourth embodiment includes a color filter495located between the substrate481and the facing electrode461.

That is, the organic EL display device of the third embodiment includes a light emitting layer that is made materials emitting red, green, and blue light to display a full-color image. However, in the organic EL display device according to the fourth embodiment, the light emitting layer emits white light, which passes through the color filter495, to produce red, green, or blue light. For example, the spectrum of the white light may include all visible wavelengths, or may have peaks corresponding to red, green, and blue light.

FIG. 14is a schematic cross-sectional view of a sub-pixel unit in the active matrix organic EL display device including an organic TFT according to a fifth embodiment of the invention. Referring toFIG. 14, an organic EL device including the facing electrode461, the intermediate layer487including the light emitting layer, and the pixel electrode462is located on the substrate481, and two staggered structure type n-type organic TFTs410and450and the storage capacitor440are formed on the organic EL device. In addition, the second electrode413of the first organic TFT410is connected with the pixel electrode462of the organic EL device. The above structure is the same as those of the above embodiments, except that the above structure includes a color conversion layer496located between the substrate481and the first electrode461.

The organic EL display device of the third embodiment includes a light emitting layer that is made of materials emitting red, green, and blue light. The organic EL display device of the fourth embodiment includes a layer emitting white light that passes through the color filter, which produces red, green, and blue light. However, in the organic EL display device according to the fifth embodiment, the light emitting layer emits blue light, which is converted into red, green, and blue light by the color conversion layer496, thereby displaying a predetermined full-color image.

FIG. 15,FIG. 16,FIG. 17, andFIG. 18are schematic cross-sectional views of stages in the process of fabricating the active matrix organic EL display device including the organic TFT according to the invention.

Referring toFIG. 15, the facing electrode461is formed on the entire surface of the substrate481or in each sub-pixel on the substrate481, and the intermediate layer487having the light emitting layer is formed on the facing electrode by one of several techniques, such as inkjet printing, spin coating, or thermal transfer. The pixel electrode462is then formed in each sub-pixel region on the intermediate layer487. In addition, after forming the protective layer485on the pixel electrode462, the first contact hole485aexposing part of the pixel electrode462is formed in the protective layer485of the each sub-pixel. The first contact hole485acan be formed by any of several techniques, such as a laser ablation technique (LAT), using a laser.

After performing the above process, the second electrode413coupled with the pixel electrode462through the first contact hole485a, the first electrode412and the first capacitor electrode441are integrally formed with each other, the fourth electrode453, and the third electrode452are formed as shown inFIG. 16. The second electrode413, the first electrode412, the first capacitor electrode441, the fourth electrode453, and the third electrode452can be formed by patterning in a deposition method using a shadow mask, or by inkjet printing.

After forming the second electrode413, the first electrode412, the first capacitor electrode441, the fourth electrode453, and the source electrode452, the n-type organic semiconductor layer480covering the above electrodes is formed on the entire surface of the substrate481by vacuum deposition or thermal evaporation as shown inFIG. 17. In addition, the gate insulating layer483is formed on the entire n-type organic semiconductor layer480by, for example, a spin coating technique, and the second contact hole483ais formed in the n-type organic semiconductor layer480and the gate insulating layer483to expose the fourth electrode453. The second contact hole483amay be formed by LAT, using a laser.

The first gate electrode411and second gate electrode451formed on the gate insulating layer483, and the second capacitor electrode442connected to the fourth electrode453through the second contact hole483aand formed on the first capacitor electrode441are fabricated by patterning in a deposition method using the shadow mask or by inkjet printing. Thus, the organic EL display device including the n-type organic TFT and the storage capacitor may be fabricated as shown inFIG. 18. Additionally, a sealing member and a front substrate may be formed on the organic EL devices and the organic TFTs fabricated according to the above described processes.

The organic EL display devices having the n-type organic TFT and the storage capacitor may be mass-produced through the above processes because all processes after forming the organic EL device460may be performed by evaporation or spin coating. In other words, to produce the organic TFT located on the organic EL device, the metal electrodes may be formed by a deposition patterning process using a shadow mask, the n-type organic semiconductor layer480can be formed by a spin coating technique or a deposition technique, and the gate insulating layer may be formed by the spin coating technique using the organic material. Therefore, the organic EL display device having the above described structure may be fabricated without damaging the organic EL device located under or below the display device.

Additionally, a process of forming the pixel definition layer may be performed added between the process of forming the facing electrode461and the process of forming of the intermediate layer487. In this case, after forming the facing electrode461, the material for the pixel definition layer is applied on the facing electrode461over the entire substrate481, and then the material is patterned by a patterning technique, such as photolithography, and baked or heat treated. Since the organic elements are not yet formed, high temperatures may be used to fabricate the pixel definition layer of the organic EL display device.

Additionally, the color filter that filters white light into red, green, and blue light may be formed on the substrate481before the processes of forming the light emitting layer included in the intermediate layer487and forming the facing electrode461. Alternatively, the color conversion layer that converts the blue light into red, green, and blue light may be formed on the substrate481before the processes of forming the light emitting layer and forming the facing electrode461.

The following are some of the benefits obtained from the organic EL display device including the organic TFTs and the method of fabricating the display device thereof.

An aperture ratio of 100% is obtainable since the n-type organic TFT is formed on the organic EL device.

The current applied to the organic EL device can be reduced while maintaining a given brightness, thereby reducing the power consumption and increasing the lifespan of the organic EL device, since the aperture ratio is approximately 100%.

Further, increasing the size of the organic TFT increases the on-current of the organic TFT. Since the organic TFT is located on an upper portion of the organic EL device, a sufficiently large organic TFT may be formed without reducing the aperture rate.

In addition, since the organic TFT is formed as a staggered structure type, the structure can be simplified.

Thus, since the active matrix organic EL device may be easily realized in an array structure, fabrication costs can be reduced by mass-producing the devices.