Organic light emitting diode using phase separation and method of fabricating the same

Abstract

Provided are an organic light emitting diode (OLED) using phase separation and a method of fabricating the same. The method includes preparing a transparent substrate. A first light path control layer is formed on the transparent substrate. The first light path control layer includes a mixture of a first medium and a second medium having a lower refractive index than the first medium using the phase separation. An anode, an organic emission layer, and a cathode are sequentially stacked on the first light path control layer. In this method, an OLED with improved light extraction efficiency can be fabricated using a simple and inexpensive process.

1 . An organic light emitting diode (OLED) using phase separation, comprising:
 a transparent substrate;   a first light path control layer disposed on the transparent substrate, and including a mixture of a first medium and a second medium having a lower refractive index than the first medium using phase separation; and   an anode, an organic emission layer (EML), and a cathode sequentially stacked on the first light path control layer.   
     
     
         2 . The OLED of  claim 1 , further comprising at least one of a first refraction layer interposed between the transparent substrate and the first light path control layer and a second refraction layer interposed between the first light path control layer and the anode. 
     
     
         3 . The OLED of  claim 1 , further comprising a second light path control layer disposed under the transparent substrate, and including a mixture of a third medium and a fourth medium having a lower refractive index than the third medium using the phase separation. 
     
     
         4 . The OLED of  claim 3 , further comprising a third refraction layer interposed between the transparent substrate and the second light path control layer. 
     
     
         5 . The OLED of  claim 1 , wherein the first medium has a refractive index of 2.0 or more and less than 3.0, and the second medium has a refractive index of 1.0 or more and less than 2.0. 
     
     
         6 . The OLED of  claim 1 , wherein the first medium is formed of at least one selected from the group consisting of tin oxide (SnO 2 ), titanium oxide (TiO 2 ), cadmium oxide (CdO), zirconium oxide (ZrO 2 ), tantalum oxide (Ta 2 O 3 ), and hafnium oxide (HfO 2 ). 
     
     
         7 . The OLED of  claim 1 , wherein the second medium is formed of at least one selected from the group consisting of silicon oxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), silicate glass, and silicon oxide-titanium oxide (SiO 2 —TiO 2 ) or a mixture of pores containing air or vacuum and the at least one material. 
     
     
         8 . The OLED of  claim 2 , wherein the first and second refraction layers are formed of at least one of tin oxide (SnO 2 ), titanium oxide (TiO 2 ), cadmium oxide (CdO), zirconium oxide (ZrO 2 ), tantalum oxide (Ta 2 O 3 ), hafnium oxide (HfO 2 ), silicon oxide-titanium oxide (SiO 2 —TiO 2 ), aluminum oxide-titanium oxide (Al 2 O 3 —TiO 2 ), silicate glass, and a silicon oxide-aluminum oxide (SiO 2 —Al 2 O 3 ) solid solution, and
 wherein the first refraction layer has a refractive index higher than that of the transparent substrate and lower than that of the first medium, and the second refraction layer has a refractive index higher than that of the anode and lower than that of the first medium. 
 
     
     
         9 . The OLED of  claim 4 , wherein the third refraction layer is formed of at least one of tin oxide (SnO 2 ), titanium oxide (TiO 2 ), cadmium oxide (CdO), zirconium oxide (ZrO 2 ), tantalum oxide (Ta 2 O 3 ), hafnium oxide (HfO 2 ), silicon oxide-titanium oxide (SiO 2 —TiO 2 ), aluminum oxide-titanium oxide (Al 2 O 3 —TiO 2 ), silicate glass, and a silicon oxide-aluminum oxide (SiO 2 —Al 2 O 3 ) solid solution, and
 wherein the third refraction layer has a refractive index higher than that of the transparent substrate and lower than that of the third medium. 
 
     
     
         10 . The OLED of  claim 1 , wherein the second medium has a pillar shape perpendicular to the transparent substrate. 
     
     
         11 . A method of fabricating an organic light emitting diode (OLED) using phase separation, comprising:
 preparing a transparent substrate;   forming a first light path control layer on the transparent substrate, the first light path control layer including a mixture of a first medium and a second medium having a lower refractive index than the first medium using phase separation; and   sequentially stacking an anode, an organic EML, and a cathode on the first light path control layer.   
     
     
         12 . The method of  claim 11 , wherein forming the first light path control layer comprises:
 preparing a mixture solution of a precursor of the first medium and a precursor of the second medium;   coating the mixture solution on the transparent substrate;   gelling the coated mixture solution by heating to form a coating layer phase-separated into the first and second media having different refractive indices; and   calcining the coating layer.   
     
     
         13 . The method of  claim 11 , further comprising, before forming the first light path control layer, forming a first refraction layer on the transparent substrate, the first refraction layer having a refractive index higher than that of the transparent substrate and lower than that of the first medium. 
     
     
         14 . The method of  claim 11 , further comprising, before stacking the anode, forming a second refraction layer on the first light path control layer, the second refraction layer having a refractive index higher than that of the anode and lower than that of the first medium. 
     
     
         15 . The method of  claim 12 , wherein the precursor of the first medium is any one of a titanium-alkoxide-based material such as titanium methoxide, titanium ethoxide, titanium propoxide, or titanium butoxide and a chloro-titanium-alkoxide-based material such as chloro titanium methoxide, chloro titanium ethoxide, chloro titanium propoxide, or chloro titanium butoxide; and the precursor of the second medium is one selected from the group consisting of a trialkyloxyvinylsilane-based material, a tetraalkyloxysilane-based material, an allyltrialkylsilane-based material, a tetraalkylsilane-based material, a diphenylsilane-based material, a tetraphenylsilane-based material, an aminoalkyloxysilane-based material, a silsesquioxane-based material, a silsesquioxane-siloxane-based material, and a silsesquioxane-silane-based material. 
     
     
         16 . The method of  claim 13 , wherein forming the first refraction layer comprises:
 coating, on the transparent substrate, a solution formed of a titanium-alkoxide-based material such as titanium methoxide, titanium ethoxide, titanium propoxide, or titanium butoxide; a solution formed of a chloro-titanium-alkoxide-based material such as chloro titanium methoxide, chloro titanium ethoxide, chloro titanium propoxide, chloro titanium butoxide, or chloro titanium triisopropoxide; or a mixture solution of one selected from the titanium-alkoxide-based material and the chloro-titanium-alkoxide-based material with one selected from the group consisting of a trialkyloxyvinylsilane-based material, a tetraalkyloxysilane-based material, an allyltrialkylsilane-based material, a tetraalkylsilane-based material, a diphenylsilane-based material, a tetraphenylsilane-based material, an aminoalkyloxysilane-based material, a silsesquioxane-based material, a silsesquioxane-siloxane-based material, and a silsesquioxane-silane-based material;   gelling the coated solution by leaving the coated solution at room temperature or heating the coated solution to form a coating layer; and   calcining the coating layer.   
     
     
         17 . The method of  claim 12 , further comprising adding distilled water and at least one selected from the group consisting of methanol, ethanol, isopropyl alcohol, and butanol to the mixture solution in order to control the concentration and gelation rate of the mixture solution. 
     
     
         18 . The method of  claim 12 , further comprising adding at least one selected from the group consisting of hydrochloric acid, acetic acid, nitric acid, sulfuric acid, and oxalic acid to the mixture solution in order to control the gelation rate and phase separation rate of the mixture solution and the shape and size of the second medium. 
     
     
         19 . The method of  claim 12 , further comprising adding at least one selected from the group consisting of acetyl acetone, ethylene glycol, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, and polyvinyl pyrrolidone to the mixture solution in order to control the viscosity, gelation rate, and phase separation rate of the mixture solution and the shape and size of the second medium. 
     
     
         20 . The method of  claim 11 , further comprising forming a second light path control layer under the transparent substrate, the second light path control layer including a mixture of a third medium and a fourth medium having a lower refractive index than the third medium using phase separation.