Organic light emitting device and manufacturing method thereof

The present invention relates to an organic light emitting device including a substrate, an insulating layer disposed on the substrate, a first electrode disposed on the insulating layer, an organic light emitting member disposed on the first electrode, and a second electrode disposed on the organic light emitting member. The insulating layer includes a furrow corresponding to at least one edge of the first electrode, and at least a portion of the second electrode is disposed in the furrow.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2008-0030614, filed on Apr. 2, 2008, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light emitting device and a manufacturing method thereof.

2. Discussion of the Background

In general, in an active type of flat panel display, a plurality of pixels are arranged in a matrix form, and images are displayed by controlling the luminance of each pixel according to given display information

One such active matrix flat panel display device is an organic light emitting display, which is a self-emissive display device having low power consumption, a wide viewing angle, and a high response speed. Therefore, the organic light emitting display is being spotlighted as a next-generation display device to surpass the liquid crystal display (LCD).

The organic light emitting device includes an organic light emitting element, that is, two electrodes with an emission layer disposed therebetween. Electrons injected from one of the electrodes and holes injected from the other electrode are combined in the light emitting layer to form excitons, and the excitons release energy and cause light to be emitted.

The organic light emitting device also includes a driving transistor to drive the organic light emitting element and a switching transistor to apply data voltages to the driving transistor, and the transistors are the thin film transistor (TFT) type.

Light emitted from the emission layer of the organic light emitting device passes through various layers having different refractive indexes. However, when the light is totally reflected or is dissipated to the side, the light is not used to display the images and thus light efficiency may be decreased. To increase the light efficiency of the organic light emitting device, loss of the light emitted from the emission layer should be prevented.

SUMMARY OF THE INVENTION

The present invention provides an organic light emitting device that may prevent loss of light emitted from an emission layer.

The present invention discloses an organic light emitting device including a substrate, an insulating layer disposed on the substrate, a first electrode disposed on the insulating layer, an organic light emitting member disposed on the first electrode, and a second electrode disposed on the organic light emitting member. The insulating layer includes a furrow corresponding to at least one edge of the first electrode, and at least a portion of the second electrode is disposed in the furrow.

The present invention also discloses a method of manufacturing an organic light emitting device including depositing an insulating layer on a substrate, forming a furrow in the insulating layer, forming a first electrode on an inner surface of the furrow and the insulating layer, forming an organic light emitting member on the first electrode, and forming a second electrode on the organic light emitting member, wherein at least portion of the second electrode is disposed in the furrow.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Now, an organic light emitting device according to an exemplary embodiment of the present invention will be described with reference toFIG. 1.

FIG. 1is an equivalent circuit diagram of an organic light emitting device according to an exemplary embodiment of the present invention.

Referring toFIG. 1, an organic light emitting device according to the present exemplary embodiment includes a plurality of signal lines121,171, and172, and a plurality of pixels PX connected thereto. The pixels PX are arranged substantially in a matrix.

The signal lines include a plurality of gate lines121to transmit gate signals (or scanning signals), a plurality of data lines171to transmit data signals, and a plurality of driving voltage lines172to transmit a driving voltage. The gate signal lines121extend substantially in a row direction and are substantially parallel to each other, and the data lines171and the driving voltage lines172extend substantially in a column direction and are substantially parallel to each other.

Each pixel PX includes a switching transistor Qs, a driving transistor Qd, a capacitor Cst, and an organic light emitting element. The organic light emitting element functions as an organic light emitting diode (OLED) LD.

The switching transistor Qs has a control terminal connected to one of the gate lines121, an input terminal connected to one of the data lines171, and an output terminal connected to the driving transistor Qd. The switching transistor Qs transmits data signals applied to the data line171to the driving transistor Qd in response to a gate signal applied to the gate line121.

The driving transistor Qd has a control terminal connected to the switching transistor Qs, an input terminal connected to the driving voltage line172, and an output terminal connected to the organic light emitting element. The driving transistor Qd drives an output current ILDhaving a magnitude depending on the voltage between the control terminal and the input terminal thereof.

The capacitor Cst is connected between the control terminal and the input terminal of the driving transistor Qd. The capacitor Cst stores a data signal applied to the control terminal of the driving transistor Qd and maintains the data signal after the switching transistor Qs turns off.

The organic light emitting element has an anode connected to the output terminal of the driving transistor Qd and a cathode connected to a common voltage Vss. The organic light emitting diode LD emits light having an intensity depending on an output current ILDof the driving transistor Qd, thereby displaying images.

The switching transistor Qs and the driving transistor Qd are n-channel field effect transistors (FETs). However, at least one of the switching transistor Qs and the driving transistor Qd may be a p-channel FET or a thin film transistor using amorphous silicon as the semiconductor. In addition, the connections among the transistors Qs and Qd, the capacitor Cst, and the organic light emitting diode LD may be modified.

FIG. 2is a schematic diagram showing an arrangement of the pixels in an organic light emitting device according to an exemplary embodiment of the present invention. Referring toFIG. 2, the organic light emitting device according to an exemplary embodiment of the present invention includes red pixels R to display a red color, green pixels G to display a green color, blue pixels B to display a blue color, and white pixels W to display a white color, which are sequentially and alternately disposed. Four pixels including a red pixel R, a green pixel G, a blue pixel B, and a white pixel W form one group, and may be repeatedly arranged according to rows and/or columns. However, the arrangement and the shape of the pixels may vary. The red pixels R, the green pixels G, and the blue pixels B are basic pixels to display full colors, and the white pixels W are included to improve the luminance. However, the white pixels W may be omitted.

Next, the detailed structure of the organic light emitting device shown inFIG. 1andFIG. 2will be described with reference toFIG. 3,FIG. 4, andFIG. 5.

FIG. 3is a layout view of an organic light emitting device according to an exemplary embodiment of the present invention,FIG. 4is a cross-sectional view of the organic light emitting device shown inFIG. 3taken along line IV-IV, andFIG. 5is an enlarged view of portion “A” shown inFIG. 4.

Referring toFIG. 3andFIG. 4, a plurality of gate lines121, data lines171, and driving voltage lines172and a plurality of thin film transistor arrays are arranged on an insulating substrate110. The thin film transistor arrays include switching thin film transistors Qs and driving thin film transistors Qd that are disposed in and electrically connected to each pixel.

A first insulating layer180is formed on the thin film transistor array. The first insulating layer180may be made of an inorganic insulator or an organic insulator, and may have a flat surface.

A furrow186corresponding to the circumference of each pixel is formed in the first insulating layer180. The furrow186may include a through portion187that passes through the first insulating layer180. The through portion187of the furrow186exposes a portion of the driving thin film transistor Qd, and may be deeper than other portions of the furrow186. Alternatively, the depth of the furrow186may be uniform. That is, the through portion187of the furrow186may have the same depth as that of the remaining portions of the furrow186. On the other hand, the furrow186of the present exemplary embodiment is continuous along four edges of a pixel electrode191, but the furrow186may correspond to only one, two, or three edges of the pixel electrode191.

The pixel electrode191is formed on the first insulating layer180. A pixel electrode191is disposed in each pixel, and portions of the pixel electrode191near the edges thereof are disposed in the furrow186. One portion of the pixel electrode191is connected to the driving thin film transistor Qd through the through portion187of the furrow186. The pixel electrode191may be made of a transparent conductive material such as ITO or IZO.

A second insulating layer361is formed on the first insulating layer180. The second insulating layer361defines an opening365enclosing the edge of the pixel electrode191, and may be made of an organic insulator or an inorganic insulator. The second insulating layer361may be made of a photosensitive material including black pigments, and in this case, the second insulating layer361may function as a light blocking member.

An organic light emitting member370is formed on the pixel electrode191exposed through the opening365. The organic light emitting member370may be a light emission layer and may have a multi-layered structure including an auxiliary layer (not shown) to improve light emitting efficiency of a light emission layer as well as the light emission layer to emit light. The emission layer may include an organic material to uniquely emit light of one color among primary colors, such as red, green, or blue light, or may be a mixture of the organic material and an inorganic material. The organic light emitting device spatially mixes the light having primary colors emitted from the emission layer so as to display desired images. The organic light emitting device may include an emission layer to emit a white color to improve the luminance.

An electron transport layer (not shown) and a hole transport layer (not shown) to balance electrons and holes may be included in the auxiliary layer. Furthermore, an electron injection layer (not shown) and a hole injection layer (not shown) to enhance the injection of electrons and holes, or the like, may also be included in the auxiliary layer.

A common electrode270is formed on the organic light emitting member370and the second insulating layer361. The common electrode270may be made of a reflective metal such as aluminum (Al), calcium (Ca), barium (Ba), magnesium (Mg), and silver (Ag). The common electrode270is positioned in the furrow186disposed in each pixel.

The pixel electrode191, the organic light emitting member370, and the common electrode270form the organic light emitting element having the pixel electrode191as an anode and the common electrode270as a cathode, or vice versa.

An encapsulation layer (not shown) may be formed on the common electrode270. The encapsulation layer encapsulates the organic light emitting member370and common electrode270to prevent moisture penetration and/or oxidization.

Referring toFIG. 5, the light generated from the organic light emitting member370travels toward the substrate110to display the images, and the light emitted to the side of the organic light emitting member370is reflected by the common electrode270disposed in the furrow186and guided toward the substrate110. That is, in the structure according to the present exemplary embodiment, most of the light generated in the organic light emitting member370is emitted toward the substrate110and used to display the images. Accordingly, the light efficiency of the organic light emitting device may be increased.

Next, an organic light emitting device and a manufacturing method thereof according to another exemplary embodiment of the present invention will be described with reference toFIG. 6andFIG. 7.

FIG. 6is a layout view of an organic light emitting device according to another exemplary embodiment of the present invention, andFIG. 7is a cross-sectional view of the organic light emitting device shown inFIG. 6taken along line VII-VII.

A gate conductor including a plurality of gate lines121including a plurality of first control electrodes124aand a plurality of second control electrodes124bis formed on an insulating substrate110.

The gate lines121transmit gate signals and extend substantially in the transverse direction. Each gate line121includes an end portion129having a large area to contact another layer or an external driving circuit, and the first control electrodes124aextend upward from the gate lines121. The second control electrodes124bare spaced apart from the gate lines121and include a plurality of storage electrodes127extending in one direction.

A gate insulating layer140, which may be made of silicon nitride (SiNx) or silicon oxide (SiO2), is formed on the gate conductors121,124a,124b, and127.

A plurality of first semiconductors154aand a plurality of second semiconductors154b, which may be made of hydrogenated amorphous silicon (a-Si) or polysilicon, are formed on the gate insulating layer140. The first semiconductors154aoverlap the first control electrodes124aand the second semiconductors154boverlap the second control electrodes124b.

A plurality of pairs of first ohmic contacts163aand165aand a plurality of pairs of second ohmic contacts163band165bare respectively formed on the first and second semiconductors154aand154b. The first ohmic contacts163aand165aare disposed in pairs on the first semiconductors154a, and the second ohmic contacts163band165bare disposed in pairs on the second semiconductors154b.

A data conductor including a plurality of data lines171, a plurality of driving voltage lines172, and a plurality of first and second output electrodes175aand175bis formed on the ohmic contacts163a,163b,165a, and165band the gate insulating layer140.

The data lines171transmit data signals and extend in a longitudinal direction while crossing the gate lines121. Each data line171includes a plurality of first input electrodes173aextending toward the first control electrodes124aand an end portion179having a large area to contact another layer or an external driving circuit.

The driving voltage lines172transmit driving voltages and extend in the longitudinal direction while crossing the gate lines121. Each driving voltage line172includes a plurality of second input electrodes173bextending toward the second control electrodes124b, and a portion overlapping the storage electrodes127.

The first and second output electrodes175aand175bare spaced apart from each other, and are spaced apart from the data lines171and the driving voltage lines172. The first input electrodes173aand the first output electrodes175aare opposite to each other with respect to the first control electrodes124a, and the second input electrodes173band the second output electrodes175bare opposite to each other with respect to the second control electrodes124b.

The data conductors171,172,175a, and175bmay be made of a refractory metal such as molybdenum, chromium, tantalum, titanium, or alloys thereof.

The ohmic contacts163a,163b,165a, and165bare disposed between the semiconductors154aand154bthereunder and the data conductors171,172,175a, and175b, which may reduce contact resistance therebetween. The semiconductors154aand154binclude a portion between the input electrodes173aand173band the output electrodes175aand175b, and the exposed portions by the data conductors171,172,175a, and175b.

The control electrodes124aand124bmay be disposed on the semiconductors154aand154b, and the gate insulating layer140is also disposed between the semiconductors154aand154b, and the control electrodes124aand124b, in this case. Here, the data conductors171,172,173b, and175bmay be disposed on the gate insulating layer140, and they may be electrically connected to the semiconductors154aand154bthrough contact holes (not shown) formed in the gate insulating layer140. Alternatively, the data conductors171,172,173b, and175bmay be disposed under the semiconductors154aand154bsuch that they electrically contact the overlaying semiconductors154aand154b.

A color filter230is formed on the data conductor171,172,175a, and175band the exposed semiconductors154aand154b. The color filter230may be made of a photosensitive organic material including pigments, and may display a primary color such as red, green, or blue.

The first insulating layer180is formed on the color filter230. The first insulating layer180prevents the color filter230from lifting and may be made of an inorganic insulator such as silicon nitride or silicon oxide.

The first insulating layer180and the color filter230have a plurality of contact holes185to expose the first output electrodes175a, and the first insulating layer180, the color filter230, and the gate insulating layer140have a plurality of contact holes184to expose the second control electrodes124b. The first insulating layer180has a plurality of contact holes182to expose the end portions179of the data lines171, and the first insulating layer180and the gate insulating layer140have a plurality of contact holes181to expose the end portions129of the gate lines121.

The first insulating layer180and the color filter230include a furrow186that is formed to correspond to the circumference of each pixel. The furrow186includes a through portion187passing through the first insulating layer180and the color filter230. The through portion187of the furrow186exposes the portion of the driving thin film transistor Qd and may be deeper than the remaining portion of the furrow186. Alternatively, the depth of the furrow186may be uniform. That is, the through portion187of the furrow186may have substantially the same depth as the remaining portion of the furrow186. The furrow186including the through portion187may be made through half-tone exposure, and the depth thereof may vary according to the design.

A plurality of pixel electrodes191, a plurality of connecting members85, and a plurality of contact assistants81and82are formed on the first insulating layer180. They may be made of a transparent conductive material such as ITO or IZO.

A pixel electrode191is disposed in each pixel, and a portion of the pixel electrode191near an edge thereof is disposed in the furrow186. Another portion of each pixel electrode191is connected to the second output electrode175bthrough the through portion187of the furrow186.

The connecting members85are connected to the second control electrodes124band the first output electrodes175athrough the contact holes184and185.

The contact assistants81and82are respectively connected to the end portions129and179of the gate lines121and the data lines171through the contact holes181and182. The contact assistants81and82enhance the adhesion between the end portions129and179of the gate lines121and data lines171, and external devices, and protect them.

The second insulating layer361is formed on the first insulating layer180. The second insulating layer361defines a plurality of openings365enclosing edges of the pixel electrodes191, and is made of an organic insulator or an inorganic insulator. The second insulating layer361may be made of a photosensitive material including black pigments.

A plurality of organic light emitting members370is formed on the second insulating layer361and the pixel electrodes191. The organic light emitting member370may be an emission layer, and may have a multi-layered structure including the emitting layer and an auxiliary layer to improve the efficiency of light emission of the emitting layer.

The emission layer may include a plurality of sequentially deposited sub-emission layers of materials emitting red, green, and blue light, and may emit white light by combining their light wavelengths. Herein, the present invention is not limited to vertically forming the sub-emission layers, as the sub-emission layers may be horizontally formed. Also, the combination of light to emit the white light is not limited to red, green, and blue light. The sub-emission layers may be formed with various color combinations that emit the white light. The emission layer may have a plurality of sub-emission layers that are repeatedly deposited. For example, a red sub-emission layer, a blue sub-emission layer, and a green sub-emission layer are sequentially deposited, and then the red sub-emission layer, the blue sub-emission layer, and the green sub-emission layer may be repeatedly deposited.

The auxiliary layer may include at least one selected from an electron transport layer (not shown) and a hole transport layer (not shown), and an electron injecting layer (not shown) and a hole injecting layer (not shown).

A common electrode270is formed on the organic light emitting member370. The common electrode270may be made of a reflective metal such as aluminum (Al), calcium (Ca), barium (Ba), silver (Ag), or magnesium (Mg). The common electrode270is disposed in the furrow186disposed in each pixel.

In the above-described organic light emitting device, the switching control electrode124aelectrically connected to the gate line121, the switching input electrode173aelectrically connected to the data line171, and the switching output electrode175aform the switching thin film transistor Qs along with the switching semiconductor154a, and the channel of the switching thin film transistor Qs is formed in the switching semiconductor154abetween the switching input electrode173aand the switching output electrode175a. The driving control electrode124belectrically connected to the switching output electrode175a, the driving input electrode173belectrically connected to the driving voltage line172, the driving output electrode175bconnected to the pixel electrode191, and the driving semiconductor154bform the driving thin film transistor Qd, and the channel of the driving thin film transistor Qd is formed in the driving semiconductor154bbetween the driving input electrode173band the driving output electrode175b.

The pixel electrode191, the organic light emitting member370, and the common electrode270form the organic light emitting element, and the storage electrode127and the driving voltage line172that overlap each other form the storage capacitor Cst.

According to this structure, the light emitted from the organic light emitting member370travels toward the substrate110to display the images, and the light emitted from the side of the organic light emitting member370is reflected by the common electrode270disposed in the furrow186and travels toward the substrate110. Accordingly, most of the light generated from the organic light emitting member370is emitted toward substrate110and is used to display the images.

Next, a manufacturing method of the organic light emitting device will be described in detail.

A gate conductor including a plurality of gate lines121, a plurality of first and second control electrodes124aand124b, and a plurality of storage electrodes127, a gate insulating layer140, a plurality of first and second semiconductors154aand154b, a plurality of first and second ohmic contacts163a,165a,163b, and165b, a data conductor including a plurality of data lines171, a plurality of driving voltage lines172, and a plurality of first and second output electrodes175aand175b, a color filter230, and the first insulating layer180are sequentially formed on the substrate110.

Next, the first insulating layer180and the color filter230are patterned by photolithography to form a furrow186including a through portion187and a plurality of contact holes184and185. Here, the furrow186may be formed along with the through portion187and the contact holes184and185using a halftone exposure using a mask having slits or a translucent layer. For example, when a positive photosensitive film is coated on the first insulating layer180, and the furrow186, the through portion187, and the contact holes184and185are formed through the halftone exposure, the region corresponding to the through portion187is disposed on the transparent portion of the mask, the region corresponding to the furrow186is disposed on the semi-transparent portion of the mask, and the region without the furrow186is disposed on the opaque portion of the mask under the halftone exposure.

Next, a pixel electrode191is formed on the inner surface of the furrow186and the first insulating layer180. When forming the pixel electrode191, a connecting member85and contact assistants81and82are also formed. Next, a second insulating layer361including an opening365to expose the pixel electrode191is formed on the first insulating layer. An organic light emitting member370and a common electrode270are the sequentially formed on the pixel electrode191and the second insulating layer361. Here, at least a portion of the organic light emitting member370and the common electrode270is positioned in the furrow186.