Abstract:
This document discloses an organic light emitting device comprising a first electrode and a wire comprising a contact part formed on a substrate, an insulating layer formed on the first electrode and a portion of the wire, the insulating layer comprising an opening which exposes a portion of the first electrode and a contact hole which exposes an entire upper surface of the contact part, an emission layer formed in the opening, a second electrode formed on the emission layer and the upper surface of the contact part though the contact hole.

Description:
CROSS-REFERENCE 
   This application claims priority to and the benefit of Korea Patent Application No. 10-2006-0032511, filed on Apr. 10, 2006, the entire content of which is incorporated herein by reference. 
   BACKGROUND 
   1. Field 
   The present invention relates to a light emitting device and a method for manufacturing the same. 
   2. Related Art 
   Among flat panel display devices, light emitting device has an advantage in that it has high response speed and low power consumption. The light emitting device can also be manufactured thin in size and light in weight because of not requiring backlight unit. 
   In particularly, organic light emitting device has an organic light emitting layer between an anode and a cathode. Holes from the anode and electrons from the cathode are combined within the organic light emitting layer to create hole-electron pairs, i.e., excitons. The organic light emitting device emits lights by energy generated while the excitons return to ground state. 
     FIG. 1A  is a plan view of a prior art light emitting device, and  FIG. 1B  is a cross sectional view taken along line A-A′ of  FIG. 1A . 
   Referring to  FIGS. 1A and 1B , the conventional light emitting device  100  comprises a substrate  110 , and anodes  120  and wires  125  formed on the substrate  110 , each wire  125  comprising a contact part  126  at an end of the wire  125 . Wires  125  may comprise a conductive layer  125 A and a metal layer  125 B disposed on the conductive layer  125 A. An insulating layer  130  is formed on the substrate  110  comprising the anodes  120  and wires  125  having contact parts  126 . The insulating layer  130  comprises openings  135 , each of which exposes a portion of each anode  120 , and contact holes  136 , each of which exposes a portion of each contact part  126 . 
   Emission layers  150  are disposed within the openings  135  of the insulating layer  130 , and barrier ribs  140  are formed on the insulating layer  130  in the shape of reverse taper. Cathodes  160  are disposed on the substrate  110  comprising the barrier ribs  140 . The cathodes  160  are patterned by the barrier ribs  140  and connected electrically to the contact parts  126  exposed by the contact holes  136  and the emission layers  150  formed within the openings  135 . 
   As can be seen from a contacting region indicated by alphabet ‘E’ of  FIG. 1B , the contact hole  136  is formed to expose a portion of an upper surface of the contact part  126 . Therefore, the contacting area of the contact part  126  and cathode  160  becomes narrow. 
   As a consequence, a peeling phenomenon of the insulating layer  130  can occur at the regions contact part  126  other than the regions exposed by the contact holes  136 . And interfacial resistance between the contact part  126  and cathode  160  can be increased because the contacting area between the contact part  126  and cathode  160  are very narrow. 
   SUMMARY 
   Accordingly, the present invention provides an organic light emitting device comprising a first electrode and a wire comprising a contact part formed on a substrate, an insulating layer formed on the first electrode and a portion of the wire, the insulating layer comprising an opening which exposes a portion of the first electrode and a contact hole which exposes an entire upper surface of the contact part, an emission layer formed in the opening, a second electrode formed on the emission layer and the upper surface of the contact part though the contact hole. 
   Also, the present invention provides a method of fabricating a light emitting device comprising, forming a first electrode and a wire comprising a contact part on a substrate, forming an insulating layer on the first electrode and a portion of the wire, the insulating layer comprising an opening which exposes a portion of the first electrode and a contact hole which exposes an entire upper surface of the contact part, forming an emission layer in the opening, forming a second electrode on the emission layer and the upper surface of the contact part though the contact hole. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a plan view of illustrating a prior art light emitting device. 
       FIG. 1B  is a cross sectional view taken along line A-A′ of  FIG. 1A . 
       FIG. 2A  is a plan view of a light emitting device according to an embodiment of the present invention. 
       FIG. 2B  is a cross sectional view taken along line B-B′ of  FIG. 2A . 
       FIGS. 3A to 3H  are plan views and cross sectional views for illustrating each process of a method for manufacturing a light emitting device according to an embodiment of the present invention. 
       FIGS. 4 to 6  are cross sectional views of a contact region according to other embodiments of the present invention. 
   

   DETAILED DESCRIPTION 
   An embodiment will be described with reference to the accompanying drawings. However, the present invention is not limited to one embodiment described below, but may be embodied in a variety of forms. In the drawings, if it is mentioned that a layer is positioned on a different layer or a substrate, the layer may be formed directly on the different layer or the substrate, or another layer may be interposed therebetween. Like reference numerals designate like elements. 
   An Embodiment 
     FIG. 2A  is a plan view of a light emitting device according to an embodiment of the present invention.  FIG. 2B  is across sectional view taken along line B-B′ of  FIG. 2A . 
   Referring to  FIGS. 2A and 2B , the light emitting device  200  according to an embodiment of the present invention comprises a substrate  210 , first electrodes  220  and wires  225  each having a contact part  226  at an end of the wire  225 , wherein the first electrodes  220  and the wires  225  are disposed on the substrate  210 . The first electrodes  220  may be anodes and comprise conductive films having high work functions. And, each wire  225  and contact part  226  comprise at least one conductive layer  225 A and can be formed as a multiple-structure which comprises multiple metal layers  225 B disposed on the conductive layer. 
   The conductive layer  225 A may comprise Indium Tin Oxide(ITO), Indium Zinc Oxide (IZO) or Indium Tin Zinc Oxide (ITZO), and the metal layer  225 B may comprise Molibden (Mo) or Aluminum(Al). Furthermore, the metal layer  225 B may be formed as a triple-layer structure which consists of a first Mo layer, an Al layer, and a second Molibden layer. 
   The wires  225  are connected to cathodes  260  to be subsequently formed to supply electrical signals. While the wires  225  are arranged alternately in the left and right directions to reduce dead spaces, the wiring patterns are not limited thereto. 
   An insulating layer  230  is disposed on the first electrodes  220  and a portion of wires  225 . The insulating layer  230  comprises openings  235  for exposing a portion of the first electrodes  220 , and emission layers  250  are disposed within the openings  235 . 
   The insulating layer  230  further comprises contact holes  236  for exposing entire upper surfaces of the contact parts  226 . Here, the contact holes  236  can also be formed to expose both upper surfaces and side surfaces of the contact parts  226 . 
   Barrier ribs  240  are formed on the insulating layer  230  in the shape of reverse taper, and second electrodes  260  are disposed on the substrate  220  comprising the barrier ribs  240 . The second electrodes  260  may be cathodes which have low work functions and can provide the emission layers  250  with electrons. And, the second electrodes  260  are patterned by the barrier ribs and formed on the emission layers  250  and contact holes  226  exposed by the contact holes  236 . 
   As can be seen through a contacting region marked by an alphabet ‘E’ of  FIG. 2B , the second electrode  260  can contact with upper and side surfaces of the contact part  226  through the contact hole  236 . Accordingly, as the contacting area between the second electrode  260  and contact part  226  increases, the interfacial resistance therebetween can be greatly lessened. Moreover, because the insulating layer  230  formed on the contact parts  226  are completely eliminated, the problem such as a peeling phenomenon of the insulating layer  230  which has occurred conventionally can be solved. 
   Hereinafter, a method for manufacturing a light emitting device according to an embodiment of the present invention will be described with reference to  FIGS. 3A to 3H . Here,  FIGS. 3B ,  3 D,  3 F, and  3 H each are cross sectional views taken along line C-C′ of each of  FIGS. 3A ,  3 C,  3 E, and  3 G. 
   Referring now to  FIGS. 3A and 3B , conductive layer is formed on a substrate  310  and then first electrodes  320  and wires  325  are formed by patterning the conductive layer. The first electrodes  320  are patterned in the shape of stripe and the wires  325  are spaced from the first electrodes  320  and each wire  325  has contact  326  at an end of the wire  325 . The conductive layer may comprise Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO) or Indium Tin Zinc Oxide (ITZO) . The wires  325  comprising the contact parts  326  can be formed as a multiple-layer by depositing a metal layer  325 B comprising Molibden or Al on the conductive layer  325 A and then patterning it in order to reduce their resistance. For example, the contact parts  326  and wires  325  can be formed as a quadruple-layer structure which consists of ITO/MO/Al/MO. 
   Referring to  FIGS. 3C and 3D , next, an insulating layer  330  is formed on the substrate comprising the first electrodes  320  and wires  325  having the contact parts  326 . The insulating layer  330  can be formed of silicon oxide (SiO2) or silicon nitride (SiNx). Subsequently, a portion of the insulating layer  330  is etched to form openings  335  for exposing a portion of the first electrodes  320  and contact holes  336  for exposing the contact parts  326 . Here, the contact holes  336  can also be formed to expose both upper surfaces and side surfaces of the contact parts  326 . 
   Referring to  FIGS. 3E and 3F , a negative photo-resist is coated on the insulating layer  330  and then exposed to light and developed thereby to form barrier ribs  340 . The barrier ribs  340  are crossing the first electrodes  320  and can be formed to be spaced from each other. And then, emission layers  350  are formed on the first electrodes  320  exposed by the openings  335 . Here, the emission layers  350  create excitons by recombining electrons and holes to emit lights. The emission layers  350  may comprise organic materials. 
   Returning now to  FIGS. 3G and 3H , the second electrodes  360  are formed on the emission layers  350 , upper and side surfaces of the contact parts  326  exposed by the contact holes  336 . The second electrodes  360  may be cathodes to supply electrons to the emission layers  350 , and may be patterned by the barrier ribs  340 . 
   Here, the contact part  326  has broader contacting area with the second electrode  360  than in the conventional light emitting device because its upper and side surfaces are both exposed by the contact hole  336 , and never leaves insulating layer on the contact part  326 . As a result, the light emitting device according to the present invention can reduce the contact resistance between the second electrodes and contact parts and thus reduce its driving voltage. Also, the light emitting device according to the present invention can prevent a peeling phenomenon which has occurred conventionally. 
   Other Embodiments 
     FIGS. 4 to 6  are cross sectional views of illustrating contact regions (E) of light emitting devices according to other embodiments of the present invention. 
   As shown in the contact region ‘E’ of  FIG. 4 , a contact part  426  formed as a multiple-layer structure of ITO/Mo/Al/Mo is disposed on a substrate  410 . On the contact part  426  there is disposed an insulating layer  430  comprising a contact hole  436  for exposing the entire upper surface of the contact part  426 . And, a second electrode  460  is disposed, which contacts with the entire upper surface of the contact part  426  through the contact hole  436 . In case of the light emitting device comprising the contacting region as shown in  FIG. 4 , the interfacial resistance between the second electrode  460  and contact part  426  is reduced because the contacting area therebetween is broad, and therefore the driving voltage of the light emitting device is lowered. 
   As shown in the contact region ‘E’ of  FIG. 5 , a contact part  526  formed as a multiple-layer structure of ITO/Mo/Al/Mo is disposed on a substrate  510 . On the contact part  526  there is disposed an insulating layer  530  comprising a contact hole  536  for exposing a portion of the upper and side surfaces of the contact part  526 . And, a second electrode  560  is disposed, which contacts with the entire upper surface and a portion of the side surfaces of the contact part  526  through the contact hole  536 . In case of the light emitting device comprising the contacting region as shown in  FIG. 5 , the interfacial resistance between the second electrode  560  and contact part  526  is reduced because the contacting area therebetween is broad, and therefore the driving voltage of a light emitting device is lowered. 
   The second electrode  560  is typically formed of Al. Therefore, in the case that the contact hole  536  is formed to expose the Al layer of the contact part  526  as shown in  FIG. 5 , the adherence strength between the second electrode  560  and contact part  526  can be enhanced and the interfacial resistance between the second electrode  560  and contact part  526  can be effectively reduced because the contact part  526  has the same material as the second electrode  560 . 
   As shown in the contact region ‘E’ of  FIG. 6 , a contact part  626  formed as a multiple-layer structure of ITO/Mo/Al/Mo is disposed on a substrate  610 . On the contact part  626  there is disposed an insulating layer  630  comprising a contact hole  636  for exposing a portion of the upper and side surfaces of the contact part  626 . And, a second electrode  660  is disposed, which contacts with a portion of the upper and side surfaces of the contact part  626  through the contact hole  636 . In case of the light emitting device comprising the contacting region as shown in  FIG. 6 , the interfacial resistance between the second electrode  460  and contact part  426  is reduced because the contacting area therebetween is broad, and therefore the driving voltage of the light emitting device can be lowered. 
   Although the present invention has been described with reference to certain exemplary embodiments, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims, and their equivalents.