Patent Publication Number: US-2009236624-A1

Title: Organic light emitting device and organic light emitting display apparatus comprising the same

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for ORGANIC LIGHT EMITTING DEVICE AND ORGANIC LIGHT EMITTING DISPLAY APPARATUS COMPRISING THE SAME earlier filed in the Korean Intellectual Property Office on 18 Mar. 2008 and there duly assigned Serial No. 10-2008-0024904. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an organic light emitting device and an organic light emitting display apparatus including the same, and more particularly, to an organic light emitting device having an anode that has improved characteristics, and an organic light emitting display apparatus including the same. 
     2. Description of the Related Art 
     Recently, it is a trend that display apparatuses are replaced by portable and thin flat panel display apparatuses. Among the flat panel display apparatuses, field emission display apparatuses are emissive type display apparatuses that have received considerable attention as the next generation flat display apparatuses due to their large viewing angle, high contrast, and short response time. Organic light emitting devices, in which a light emitting layer is made from an organic material, have high brightness, low driving voltage, short response time, and can be polychrome. 
     An organic light emitting display apparatus is usually constructed with an organic light emitting device that includes an anode electrode, a cathode electrode, and an intermediate layer disposed between the anode electrode and the cathode electrode. The intermediate layer includes an organic light emitting layer and other organic materials. The organic light emitting device emits visible light by applying a voltage to the organic light emitting layer through electrodes. 
     In many cases, the anode electrode is made from indium tin oxide (ITO) having a high work function in order to smoothly inject holes into the organic light emitting layer. The anode electrode is formed with a certain pattern by using a wet etching method. The patterning of ITO, however, is not easy since ITO has a very low etching rate. After wet etching, incomplete-etch portions, that is, dim spots, remain in the anode electrode that is made from ITO, thereby, causing electrical failure. 
     Due to the above reasons, it is not easy to form an anode electrode that has a certain thickness due to the slow etching rate of ITO included in the anode electrode, and also results in many process limitations. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved organic light emitting device. 
     It is another object to provide an organic light emitting device having an anode electrode that can be easily patterned, and an organic light emitting display apparatus having the organic light emitting device. 
     According to an aspect of the present invention, an organic light emitting device is constructed with a first electrode including indium tungsten oxide (IWO), an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. 
     According to another aspect of the present invention, an organic light emitting device is constructed with a first electrode including a first layer and a second layer formed on the first layer, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The first layer is formed as a reflection layer to reflect the light generated from the organic light emitting layer. The second layer is interposed between the first layer and the organic light emitting layer, and includes IWO. 
     The first layer may be made from a material selected from a group consisting of Li, Ca, LiF/Al, Al, Mg, and Ag. 
     According to yet another aspect of the present invention, an organic light emitting device is constructed with a first electrode including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The first layer includes IWO. The second layer is formed as a reflection layer on a surface of the first layer that faces the organic light emitting layer to reflect the light generated from the organic light emitting layer. The third layer is interposed between the second layer and the organic light emitting layer, and includes IWO. 
     The second layer may be made from a material selected from a group consisting of Li, Ca, LiF/Al, Al, Mg, and Ag. 
     The first electrode may be an anode electrode and the second electrode may be a cathode electrode. 
     Light generated from the organic light emitting layer may be emitted in a direction towards the second electrode. 
     According to still an aspect of the present invention, an organic light emitting display apparatus is constructed with a substrate, a plurality of thin film transistors (TFTs) formed on the substrate, an insulating film covering the TFTs and having an opening, a first electrode formed on the insulating film and being electrically connected to the TFTs through the opening, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The first electrode includes IWO. 
     According to still yet another aspect of the present invention, an organic light emitting display apparatus is constructed with a substrate, a plurality of thin film transistors (TFTs) formed on the substrate, an insulating film covering the TFTs and having an opening, a first electrode formed on the insulating film and being electrically connected to the TFTs through the opening, and including a first layer and a second layer, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The first electrode includes IWO. The first layer is formed as a reflection layer on the insulating film so as to reflect the light generated from the organic light emitting layer. The second layer is interposed between the first layer and the organic light emitting layer, and includes IWO. 
     According to a further aspect of the present invention, an organic light emitting display apparatus is constructed with a substrate, a plurality of thin film transistors (TFTs) formed on the substrate, an insulating film covering the TFTs and having an opening, a first electrode which is formed on the insulating film, is electrically connected to the TFTs through the opening, and includes a first layer, a second layer, and a third layer, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The first electrode includes IWO. The second layer is formed as a reflection layer on a surface of the first layer that faces the organic light emitting layer to reflect the light generated from the organic light emitting layer. The third layer is interposed between the second layer and the organic light emitting layer, and includes IWO. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is a schematic cross-sectional view of an organic light emitting device constructed as an embodiment according to the principles of the present invention; 
         FIG. 2  is a schematic cross-sectional view of an organic light emitting device constructed as another embodiment according to the principles of the present invention; 
         FIG. 3  is a magnified cross-sectional view of portion A of  FIG. 2 ; 
         FIG. 4  is a schematic cross-sectional view of an organic light emitting device constructed as still another embodiment according to the principles of the present invention; 
         FIG. 5  is a magnified cross-sectional view of portion B of  FIG. 4 ; 
         FIG. 6  is a schematic cross-sectional view of an active type organic light emitting display apparatus constructed as an embodiment according to the principles of the present invention; 
         FIG. 7  is a schematic cross-sectional view of an active type organic light emitting display apparatus constructed as another embodiment according to the principles of the present invention; 
         FIG. 8  is a magnified cross-sectional view of portion C of  FIG. 7 ; 
         FIG. 9  is a schematic cross-sectional view of an active type organic light emitting display apparatus constructed as still another embodiment according to the principles of the present invention; and 
         FIG. 10  is a magnified cross-sectional view of portion D of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. 
       FIG. 1  is a schematic cross-sectional view of an organic light emitting device  100  constructed as an embodiment according to the principles of the present invention. Referring to  FIG. 1 , organic light emitting device  100  includes a substrate  101 , a first electrode  130 , an organic light emitting layer  140 , and a second electrode  150 . 
     Substrate  101  may be made from a transparent glass material that includes SiO 2  as a main component. Substrate  101 , however, is not limited thereto, and may be a plastic substrate made from a transparent plastic material. The plastic substrate maybe made from an insulating organic material selected from a group consisting of polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethyelenen napthalate (PEN), polyethyeleneterepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose tri-acetate (TAC), and cellulose acetate propionate (CAP). 
     If organic light emitting device  100  is a bottom emission type, in which a video image is displayed in a direction from organic light emitting layer  140  toward substrate  101 , substrate  101  must be made from a transparent material. If organic light emitting device  100  is a top emission type, in which a video image is displayed in a direction opposite to substrate  101 , that is, from organic light emitting layer  140  toward second electrode  150 , substrate  101 , however, may not necessarily be made from a transparent material, and may be made from a metal. If substrate  101  is made from a metal, the metal maybe at least one selected from a group consisting of carbon, iron, chrome, manganese, nickel, titanium, molybdenum, stainless steel (SUS), invar alloy, inconel alloy, and kovar alloy. Substrate  101 , however, is not limited thereto, and may be made from a metal foil. 
     First electrode  130  is formed on substrate  101 , and may be formed with a certain pattern using a photolithography method. First electrode  130  is made from indium tungsten oxide (IWO). IWO has a work function similar to that of ITO that is contemporarily used for forming first electrode  130 . IWO, however, has an etching rate greater than that of ITO. 
     More specifically, the characteristics of IWO and ITO are summarized in Tables 1 and 2. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Work function before 
                 Work function after 
               
               
                   
                 treating with UV O 3   
                 treating with UV O 3   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 ITO 
                 4.9 eV 
                 5.4 eV 
               
               
                   
                 IWO 
                 4.9 eV 
                 5.6 eV 
               
               
                   
                   
               
            
           
         
       
     
     Table 1 summarizes the work functions of IWO and ITO. From Table 1, it can be seen that IWO used for forming first electrode  130  according to the principles of the present embodiment has similar work functions before and after being treated with ozone (UV O 3 ) when compared to ITO, which is a material used for forming a contemporary first electrode. Thus, when first electrode  130  that includes IWO according to the present embodiment, is compared to the contemporary first electrode that includes ITO, the charge supply characteristic of first electrode  130  is not reduced. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Etching rate (nm/min) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 ITO 
                 58 
               
               
                   
                 IWO 
                 122 
               
               
                   
                   
               
            
           
         
       
     
     Table 2 summarizes the results of etching IWO and ITO in an acetic acid at a temperature of 40° C. IWO used for forming first electrode  130  according to the present embodiment has an etching rate twice faster or more than that of ITO. 
     Consequently, when first electrode  130  is patterned, first electrode  130  may be readily patterned since first electrode  130  includes IWO. That is, IWO has an etching rate twice faster or more than that of ITO used for forming the contemporary first electrode, and thus, first electrode  130  may be readily patterned without affecting other elements. 
     Organic light emitting layer  140  and second electrode  150  are formed on first electrode  130 . 
     Second electrode  150  may be formed as either a transparent electrode or a reflection electrode. If second electrode  150  is formed as a transparent electrode, second electrode  150  may be formed such that, after depositing Li, Ca, LiF/Ca, LiF/Al, Al, Mg, or a compound of these materials to face organic light emitting layer  140 , an auxiliary electrode or a bus electrode line is formed on the metal using a transparent conductive material such as ITO, IZO, ZnO or In 2 O 3 . second electrode  150  is formed as a reflection electrode, second electrode  150  may be formed by depositing Li, Ca, LiF/Ca, LiF/Al, Al, Mg, or a compound of these materials. 
     Organic light emitting layer  140  interposed between first electrode  130  and second electrode  150  emits light due to the driving of first electrode  130  and second electrode  150 . Organic light emitting layer  140  may be made from either a low molecular weight organic material or a polymer organic material. If organic light emitting layer  140  is made from a low molecular weight organic material, a hole transport layer (not shown) and a hole injection layer (not shown) are stacked in a direction towards first electrode  130 , from organic light emitting layer  140 , and an electron transport layer (not shown) and an electron injection layer (not shown) are stacked in a direction towards second electrode  150 , from organic light emitting layer  140 . 
     Besides the above layers, various layers may be stacked as necessary. Organic materials that may be used for forming organic light emitting layer  140  include copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), and tris-8-hydroxyquinoline aluminum (Alq3), and the present invention is not limited thereto. 
     If organic light emitting layer  140  is made from a polymer organic material, only a hole transport layer (HTL) (not shown) may be included in a direction towards first electrode  130 , from organic light emitting layer  140 . That is, the polymer hole transport layer is formed on first electrode  130  using poly-(2,4)-ethylene-dihydroxy thiophene (PEDOT) or polyaniline (PANI) by an inkjet printing method or a spin coating method. Organic light emitting layer  140  may be formed in a color pattern using a material such as poly-phenylenevinylene (PPV), soluble PPV&#39;s, cyano-PPV, or polyfluorene by using a contemporary inkjet printing method, a spin coating method, or a thermal transfer using a laser. 
     In organic light emitting device  100  according to the present embodiment, first electrode  130  includes IWO that has an etching rate twice faster or more than that of ITO. If the etching rate is high, the time required to form a pattern is reduced. If the etching time is long, elements that do not need to be etched are affected by an etching solution, and thus, it is difficult to obtain a desired pattern. 
     If a material has a low etching rate like ITO, incomplete-etch portions may occur after an etching process. Such etch-failure causes an undesired pattern, and thus, dim spots remain in an anode electrode that includes ITO, thereby, causing electrical failure. 
     First electrode  130  according to the present embodiment, however, includes IWO that has high etching rate, and thus, an etching time may be reduced and a desired pattern may be readily formed, thereby preventing an electrical failure. Also, IWO used to form first electrode  130  has a work function as high as ITO, and thus, IWO may act as an anode electrode that injects holes into organic light emitting layer  140 . 
       FIG. 2  is schematic a cross-sectional view of an organic light emitting device  200  constructed as another embodiment according to the principles of the present invention.  FIG. 3  is a magnified cross-sectional view of portion A of  FIG. 2 . 
     Organic light emitting device  200  includes a substrate  201 , a first electrode  230 , an organic light emitting layer  240 , and a second electrode  250 . Organic light emitting device  200  according to the current embodiment has a similar structure as organic light emitting device  100  of  FIG. 1 . 
     First electrode  230 , however, has a structure different from first electrode  130  of  FIG. 1 , and thus, for convenience of explanation, the difference will be mainly described. 
     First electrode  230  includes a first layer  231  and a second layer  232 . Referring to  FIG. 3 , first layer  231  of first electrode  230  is formed on substrate  201 , second layer  232  is formed on first layer  231 , and organic light emitting layer  240  is formed on second layer  232 . 
     First layer  231  is a reflection layer, and may be made from Li, Ca, LiF/Ca, LiF/Al, Al, or Mg. Second layer  232  is made from IWO. First layer  231  includes a metal having a high reflectance to function as a reflective layer. Light generated from organic light emitting layer  240  is reflected by first layer  231  and is emitted in a direction towards second electrode  250 . That is, organic light emitting device  200  according to the present embodiment has a top emissive type structure. 
     Since second layer  232  that contacts organic light emitting layer  240  includes IWO, second layer  232  has a work function similar to that of ITO, and thus, may function as an anode electrode. 
     IWO has an etching rate twice faster or more than that of the ITO. In the prior art, if second layer  232  is made from ITO, the patterning of first electrode  230  using a wet etching process is not easy due to the etching rate difference between first layer  231  and second layer  232 . 
     The ITO has a significantly low etching rate as compared to a metal such as Ag. Thus, in the prior art, in order to pattern first electrode  230 , the etching time is determined according to the etching time of ITO. Since the etching time is set according to the etching rate of ITO, first layer  231  of first electrode  230  is etched to a desired pattern earlier than the etching of second layer  232  is completed. As a result, when the etching of first electrode  230  is completed, first layer  231  is over-etched to result in an undesirable pattern or etching particles. 
     If the etching time is reduced to prevent first layer  231  from over-etching, second layer  232  that includes ITO may be incompletely etched, and thus, a desired pattern may not be obtained. Due to the above reason, the patterning of first electrode  230  is not easy in the prior art. 
     Second layer  232  of first electrode  230  according to present embodiment, however, includes IWO that does not affect the electrical characteristics of first electrode  230  since IWO has a work function similar to that of ITO. Also, patterning of first electrode  230  is easy since IWO has an etching rate twice faster or more than that of ITO. As a result, an organic light emitting device having significantly reduced electrical failures can be manufactured. 
       FIG. 4  is a schematic cross-sectional view of an organic light emitting device  300  constructed as another embodiment according to the principles of the present invention.  FIG. 5  is a magnified cross-sectional view of portion B of  FIG. 4 . 
     Organic light emitting device  300  is constructed with a substrate  301 , a first electrode  330 , an organic light emitting layer  340 , and a second electrode  350 . Organic light emitting device  300  according to the current embodiment has a similar structure as organic light emitting device  100  of  FIG. 1 . First electrode  330  of organic light emitting device  300 , however, has a structure different from first electrode  130  of  FIG. 1 , and thus, for convenience of explanation, the difference will be mainly described. 
     First electrode  330  is constructed with a first layer  331 , a second layer  332 , and a third layer  333 . Referring to  FIG. 5 , first layer  331  of first electrode  330  is formed on substrate  301 , second layer  332  is formed on first layer  331 , third layer  333  is formed on second layer  332 , and organic light emitting layer  340  is formed on third layer  333 . 
     First layer  331  is made from IWO. Since IWO has a high adhesion force with other elements, IWO may increase an adhesion force between first electrode  330  and substrate  301 . 
     Second layer  332  is formed as a reflection layer, and may be made from Li, Ca, LiF/Al, Al, Mg, or Ag. Second layer  332  is made from a metal having a high reflectance to function as a reflection layer. Light generated from organic light emitting layer  340  is reflected by second layer  332  and is emitted in a direction towards second electrode  350 . That is, organic light emitting device  300  according to present embodiment has a top emissive type structure. 
     Third layer  333  that contacts organic light emitting layer  340  includes IWO. Since IWO has a work function similar to that of ITO, first electrode  330  may function as an anode electrode. 
     IWO has an etching rate twice faster or more than that of ITO. Thus, first layer  331  and third layer  333  of first electrode  330  may be readily etched as compared to etching contemporary first and third layers  331  and  333  made from ITO. As a result, an organic light emitting device having significantly reduced electrical failures can be manufactured. 
     An organic light emitting display apparatus can be manufactured using the organic light emitting device according to the principles of the present invention. The organic light emitting display apparatus may be either passive matrix type (PM type) or active matrix type (AM type). In the present embodiments, for convenience of explanation, an AM type structure is described; however, the present invention can also be applied to the PM type structure. 
       FIG. 6  is a schematic cross-sectional view of an active type organic light emitting display apparatus  1000  constructed as an embodiment according to the principles of the present invention. Referring to  FIG. 6 , active type organic light emitting display apparatus  1000  is constructed with a substrate  1101 , a thin film transistor (TFT)  1120 , a passivation film  1117 , and an organic light emitting device  1170 . Organic light emitting device  1170  is constructed with a first electrode  1130 , an organic light emitting layer  1140 , and a second electrode  1150 . 
     Referring to  FIG. 6 , TFT  1120  is formed on a top surface of substrate  1101 . At least one  15  TFT is formed in each of pixels and is electrically connected to organic light emitting device  1170 . 
     Substrate  1101  may be made from a transparent material that includes SiO 2  as a main component. Substrate  1101 , however, is not limited thereto, and may be a plastic substrate made from a transparent plastic material. The plastic substrate may be made from an insulating organic material selected from a group consisting of polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethyelenen napthalate (PEN), polyethyeleneterepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose tri-acetate (TAC), and cellulose acetate propionate (CAP). 
     If organic light emitting device  1170  is a bottom emission type, in which a video image is displayed in a direction from light emitting device  1170  toward substrate  1101 , substrate  1101  must be made from a transparent material. If organic light emitting device  1170  is a top emission type, in which an image is displayed in a direction opposite to substrate  1101 , that is, in a direction from organic light emitting layer  1140  toward second electrode  1150 , substrate  1101  may not necessarily be made from a transparent material, and may be made from a metal. If substrate  1101  is made from a metal, the metal may be at least one selected from a group consisting of carbon, iron, chrome, manganese, nickel, titanium, molybdenum, stainless steel (SUS), invar alloy, inconel alloy, and kovar alloy. Substrate  1101 , however, is not limited thereto, and may be made from a metal foil. 
     A buffer layer  1102  may be formed on the top surface of substrate  1101  in order to provide the planarity of substrate  1101  and to block the penetration of impurity elements of SiO 2  or/and SiNx. 
     More specifically, a semiconductor layer  1110  having a certain pattern is formed on buffer layer  1102 . Semiconductor layer  1110  may be made from an inorganic semiconductor material such as amorphous silicon or poly silicon, and may be constructed with a source region, a drain region, and a channel region. 
     A gate insulating film  1111  is formed on semiconductor layer  1110  using SiO 2  or SiNx. Gate insulating film  1111  may be made from an inorganic material such as a metal oxide or a metal nitride, or may be made from an organic material such as an insulating polymer. 
     A gate electrode  1112  is formed on a certain region of gate insulating film  1111 . Gate electrode  1112  is connected to a gate line (not shown) that applies an ON/OFF signal for TFT  1120 . Gate electrode  1112  maybe made from a metal such as Au, Ag, Cu, Ni, Pt, Pd, Al, or Mo, or a metal alloy such as Al:Nd or Mo:W. Gate electrode  1112 , however, is not limited thereto. 
     An interlayer insulating layer  1114  is formed on gate electrode  1112 , and a source electrode  1115  and a drain electrode  1116  are formed to contact the source and drain regions, respectively, through contact holes. Source electrode  1115  and drain electrode  1116  may be made from a material such as Au, Pd, Pt, Ni, Rh, Ru, Ir, or Os, and also, may be made from Al or Mo, or an alloy made from at least two metals such as an Al:Nd alloy or a MoW alloy. Source electrode  1115  and drain electrode  1116 , however, are not limited thereto. 
     TFT  1120  formed in this way is covered by passivation film  1117  to protect TFT  1120 . Passivation film  1117  may be formed as either an inorganic insulating film or an organic insulating film. The inorganic insulating film may be made from SiO 2 , SiNx, SiON, Al 2 O 3 , TiO 2 , Ta 2 O 5 , HfO 2 , ZrO 2 , BST, or PZT, and the organic insulating film may be made from a general-use polymer such as PMMA or PS, a polymer derivative having a phenol group, an acryl group polymer, an imide group polymer, an ester group polymer, an amide group polymer, a fluorine group polymer, a p-xylene group polymer, a vinyl alcohol group polymer, or a blend of these polymers. Alternatively, passivation film  1117  maybe formed in a complex stack including layers of the inorganic insulating film and the organic insulating film. 
     First electrode  1130 , which will be an anode electrode, is formed on passivation film  1117 . A pixel defining layer  1118  is formed to cover first electrode  1130  and is made from an insulating material. After forming an opening  1119  in pixel defining layer  1118 , organic light emitting layer  1140  is formed in a region defined by opening  1119 . Afterwards, second electrode  1150 , which is a cathode electrode, is formed to cover the entire pixels. 
     First electrode  1130  may be patterned to a certain pattern using a photolithography method. Second electrode  1150  is disposed on first electrode  1130 , and can be used as a cathode electrode by being connected to an external terminal (not shown). In the case of the AM type organic light emitting display apparatus, first electrode  1130  may be formed on an entire active region on which an image is displayed. 
     First electrode  1130  is made from IWO that has a work function similar to that of ITO, which is mainly used for forming a contemporary first electrode. Thus, first electrode  1130  that is made from IWO according to the present embodiment, has a charge supply characteristic equivalent to that of a contemporary first electrode that is made from ITO. 
     Also, IWO has an etching rate twice faster or more than that of ITO. Thus, when first electrode  1130  is patterned, first electrode  1130  according to the present embodiment maybe readily patterned since first electrode  1130  includes IWO. That is, IWO has an etching rate twice faster or more than that of ITO, which is used for forming the contemporary first electrode, and thus, first electrode  1130  can be readily patterned without affecting other elements in active type organic light emitting display apparatus  1000 . 
     Second electrode  1150  may be formed as either a transparent electrode or a reflection electrode. If second electrode  1150  is formed as a transparent electrode, second electrode  1150  may be formed such that, after depositing a metal such as Li, Ca, LiF/Ca, LiF/Al, Al, Mg, or a compound of these materials to face organic light emitting layer  1140 , an auxiliary electrode or a bus electrode line is formed on the metal using a transparent conductive material such as ITO, IZO, ZnO or In 2 O 3 . If second electrode  150  is formed as a reflection electrode, second electrode  1150  may be formed by depositing Li, Ca, LiF/Ca, LiF/Al, Al, Mg, or a compound of these materials. 
     Organic light emitting layer  1140  interposed between first electrode  1130  and second electrode  1150  emits light due to the electrical driving of first electrode  1130  and second electrode  1150 . Organic light emitting layer  1140  may be made from either a low molecular weight organic material or a polymer organic material. If organic light emitting layer  1140  is made from a low molecular weight organic material, a hole transport layer (not shown) and a hole injection layer (not shown) are stacked in a direction towards first electrode  1130 , from organic light emitting layer  1140 , and an electron transport layer (not shown) and an electron injection layer (not shown) are stacked in a direction towards second electrode  1150 , from organic light emitting layer  1140 . 
     Besides the above layers, various layers may be stacked as necessary. Organic materials that may be used for forming organic light emitting layer  1140  includes copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), and tris-8-hydroxyquinoline aluminum (Alq3), and the present invention is not limited thereto. 
     In the case of a polymer organic layer made from a polymer organic material, only a hole transport layer (HTL) (not shown) may be included in a direction towards first electrode  1130 , from organic light emitting layer  1140 . That is, the polymer hole transport layer (HTL) is formed on first electrode  1130  using poly-(2,4)-ethylene-dihydroxy thiophene (PEDOT) or polyaniline (PANI) by an inkjet printing method or a spin coating method. Organic light emitting layer  1140  may be formed in a color pattern using a material such as poly-phenylenevinylene (PPV), soluble PPV&#39;s, cyano-PPV, or polyfluorene by using a contemporary inkjet printing method, a spin coating method, or a thermal transfer using a laser. 
     A sealing member (not shown) that seals organic light emitting device  1170  is formed on organic light emitting device  1170 . The sealing member is formed to protect organic light emitting device  1170  from external moisture or oxygen. In a top emissive type organic light emitting display apparatus, the sealing member is made from a transparent material. For this purpose, the sealing member may be a glass substrate, a plastic substrate, or a plurality of overlapped structures of an organic material and an inorganic material. 
     In active type organic light emitting display apparatus  1000  according to the present embodiment, first electrode  1130  is made from IWO that has an etching rate twice faster or more than that of ITO. If the etching rate is high, the time required to form a desired pattern is reduced. 
     First electrode  1130  may be readily etched since the etching rate of first electrode  1130  is high, and thus, a desired pattern may be readily formed. Accordingly, the formation of incomplete-etch portions maybe prevented, thereby preventing an electrical failure. Also, IWO used to form first electrode  1130  has a high work function similar to that of ITO, and thus, first electrode  1130  may act as an anode electrode that injects holes into organic light emitting layer  1140 . 
       FIG. 7  is a schematic cross-sectional view of an active type organic light emitting display apparatus  2000  constructed as another embodiment according to the principles of the present invention.  FIG. 8  is a magnified cross-sectional view of portion C of  FIG. 7 . 
     Active type organic light emitting display apparatus  2000  is constructed with a substrate  2101 , a TFT  2120 , a passivation film  2117 , and an organic light emitting device  2170 . Organic light emitting device  2170  is constructed with a first electrode  2130 , and organic light emitting layer  2140 , and a second electrode  2150 . 
     Active type organic light emitting display apparatus  2000  according to the present embodiment has a structure similar to active type organic light emitting display apparatus  1000  shown in  FIG. 6 ; however, first electrode  2130  of active type organic light emitting display apparatus  2000  has a structure different from first electrode  1130  of active type organic light emitting display apparatus  1000  shown in  FIG. 6 . Substrate  2101  and TFT  2120  under first electrode  2130  are similar to substrate  1101  and TFT  1120  of  FIG. 6 , and thus, the descriptions thereof will not be repeated, and, for convenience of explanation, the differences from the foregoing embodiment will be mainly described. 
     First electrode  2130  is constructed with a first layer  2131  and a second layer  2132 . Referring to  FIG. 8 , first layer  2131  of first electrode  2130  is formed on passivation film  2117 , second layer  2132  is formed on first layer  2131 , and organic light emitting layer  2140  is formed on second layer  2132 . 
     First layer  2131  is a reflection layer, and may be made from Li, Ca, LiF/Ca, LiF/Al, Al, or Mg. Second layer  2132  is made from IWO. First layer  2131  is made from a metal having a high reflectance so as to function as a reflective layer. Light generated from organic light emitting layer  2140  is reflected by first layer  2131  and is emitted in a direction towards second electrode  2150 . That is, active type organic light emitting device  2000  according to the present embodiment has a top emissive type structure. 
     Since second layer  2132  that contacts organic light emitting layer  2140  includes IWO, second layer  2132  has a work function similar to that of ITO, and thus, may function as an anode electrode. 
     IWO has an etching rate twice faster or more than that of ITO. In the prior art, if second layer  2132  is made from ITO, the patterning of first electrode  2130  using a wet etching process is not easy due to the etching rate difference between first layer  2131  and second layer  2132 . 
     ITO has a significantly slow etching rate as compared to a metal such as Ag. Thus, in the prior art, in order to pattern first electrode  2130 , the etching time is determined according to the etching time of ITO. Since the etching time is set according to the etching rate of ITO, first layer  2131  of first electrode  2130  is etched to a desired pattern earlier than the etching of second layer  232  is completed. As a result, when the etching of first electrode  2130  is completed, first layer  2131  is over-etched to result in an undesired pattern or etching particles. 
     If the etching time is reduced to prevent first layer  2131  from over-etching, second layer  2132  that includes ITO may be incompletely etched, and thus, a desired pattern may not be obtained. Due to the above reason, the patterning of first electrode  2130  is not easy in the prior art. 
     Second layer  2132  of first electrode  2130  according to the present embodiment, however, includes IWO that does not affect the electrical characteristics of first electrode  2130 , since IWO has a work function similar to that of ITO. Also, patterning of first electrode  2130  is easy since IWO has an etching rate twice faster or more than that of ITO. As a result, an organic light emitting device having significantly reduced electrical failures can be manufactured. 
       FIG. 9  is a schematic cross-sectional view of an active type organic light emitting display apparatus  3000  constructed as another embodiment according to the principles of the present invention.  FIG. 10  is a magnified cross-sectional view of portion D of  FIG. 9 . 
     Active type organic light emitting display apparatus  3000  is constructed with a substrate  3101 , a TFT  3120 , a passivation film  3117 , and an organic light emitting device  3170 . Organic light emitting device  3170  is constructed with a first electrode  3130 , and organic light emitting layer  3140 , and a second electrode  3150 . 
     Substrate  3101  under first electrode  3130  and TFT  3120  are similar to substrate  2101  and TFT  2120  of the previous embodiment, and thus, the descriptions thereof will not be repeated. For convenience of explanation, the differences from the foregoing embodiment will be mainly described. 
     First electrode  3130  is constructed with a first layer  3131 , a second layer  3132 , and a third layer  3133 . Referring to  FIG. 10 , first layer  3131  of first electrode  3130  is formed on passivation film  3117 , second layer  3132  is formed on first layer  3131 , third layer  3133  is formed on second layer  3132 , and organic light emitting layer  3140  is formed on third layer  3133 . 
     First layer  3131  is constructed with IWO. Since IWO has a high adhesion force with other elements, IWO may increase an adhesion force between first electrode  3130  and passivation film  3117 . As described above, passivation film  3117  protects and insulates TFT  3120  by covering TFT  3120 , and, in order to do so, passivation film  3117  may be either an organic insulating film or an inorganic insulating film. IWO has a high adhesion force as compared to a metal. An adhesion force between first electrode  3130  and passivation film  3117  maybe increased by forming first layer  3131  using IWO, which is a portion of first electrode  3130  that contacts passivation film  3117 . 
     Second layer  3132  is formed as a reflection layer, and may be made from Li, Ca, LiF/Al, Al, Mg, or Ag. Second layer  3132  is made from a metal having a high reflectance to function as a reflection layer. Light generated from organic light emitting layer  3140  is reflected by second layer  3132  and is emitted in a direction towards second electrode  3150 . That is, active type organic light emitting device  3000  according to the present embodiment has a top emissive type structure. 
     Third layer  3133  that contacts organic light emitting layer  3140  includes IWO. Since IWO has a work function similar to that of ITO, first electrode  3130  may function as an anode electrode. 
     IWO has an etching rate twice faster or more than that of ITO. Thus, first layer  3131  and third layer  3133  of first electrode  3130  may be readily etched as compared to the contemporary first and third layers made from ITO. As a result, an organic light emitting device having significantly reduced electrical failures can be manufactured. 
     An organic light emitting device and an organic light emitting display apparatus according to the principles of the present invention include an anode electrode having improved characteristics. Thus, the anode electrode can be readily patterned, and thus, electrical failure of the organic light emitting device can be reduced. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.