Abstract:
An exemplary organic light emitting diode ( 20 ) includes a substrate ( 21 ), a first electrode ( 22 ) with a plurality of fluorinions therein, an organic emission stack ( 29 ), and a second electrode ( 28 ) sequentially stacked in that order. A related method for fabricating the organic emitting diode is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to, and claims the benefit of, a foreign priority application filed in China as Serial No. 200710074428.0 on May 11, 2007. The related application is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to organic light emitting diodes (OLEDs) and methods for fabricating OLEDs, and particularly to an OLED with a fluorine-ion-doped electrode and a method for fabricating the OLED. 
     BACKGROUND 
     OLED devices have begun to gradually replace cathode ray tube displays (CRTs) and liquid crystal displays (LCDs) in the marketplace. This is because OLED devices not only have a thinner profile, wider viewing angle, and less weight, but they also have faster response times and lower power consumption. Another advantage is the relatively simple structure of an OLED device, which typically includes an anode, a cathode, and an organic emission stack positioned therebetween. The simple structure permits the OLED device to be easily fabricated using relatively inexpensive manufacturing processes. 
     Referring to  FIG. 3 , a conventional OLED  10  includes a transparent substrate  11 , an anode  12 , an organic emission stack  19 , and a cathode  18  arranged in that order from bottom to top. The organic emission stack  19  includes several layers depending on its functions. The organic emission stack  19  usually includes a hole injection layer  13 , a hole transporting layer  14 , an emitting layer  15 , an electron transporting layer  16 , and an electron injection layer  17  arranged in that order from the anode  12  to the cathode  18 . 
     In operation, a positive electrical potential is applied between the anode  12  and the cathode  18 . Holes from the anode  12  are injected into the emitting layer  15  through the hole injection layer  13  and the hole transporting layer  14 . Electrons from the cathode are injected into the emitting layer  15  through the electron injection layer  17  and the electron transporting layer  16 . Accordingly, light beams are generated from the emitting layer  15  as a result of hole-electron recombination within the emitting layer  15 . 
     Generally, the anode  12  is made of a transparent conductive material with a high work function. For example, the anode  12  may be an indium tin oxide (ITO) layer. The hole injection layer  13  is made of organic material. However, a pure ITO layer has a hydrophilic property, and an organic layer has a lipophilic property. Because of these inconsistent properties, the anode  12  and the hole injection layer  13  cannot be combined together firmly. Furthermore, impurities, such as oxygen and water, are liable to be introduced between the anode  12  and hole injection layer  13 . These impurities can greatly impair the operability of the OLED  10  and reduce the working lifetime of the OLED  10 . 
     Accordingly, what is needed is an OLED and a method for fabricating the OLED which can overcome the above-described deficiencies. 
     SUMMARY 
     In one aspect, an organic light emitting diode includes a substrate, a first electrode with a plurality of fluorine ions therein, an organic emission stack, and a second electrode sequentially stacked in that order. 
     In another aspect, a method for fabricating an organic light emitting diode includes the steps of: providing a substrate, and forming a first electrode on the substrate; doping a plurality of fluorine ions into the first electrode; forming an organic emission stack on the first electrode; and forming a second electrode on the organic emission stack. 
     Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, isometric view of an OLED according to a preferred embodiment of the present invention. 
         FIG. 2  is a flowchart summarizing an exemplary method for fabricating the OLED of  FIG. 1 . 
         FIG. 3  is a schematic, side cross-sectional view of a conventional OLED. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic, isometric view of an OLED according to a preferred embodiment of the present invention. The OLED  20  includes a transparent substrate  21 , an anode  22 , an organic emission stack  29 , and a cathode  28  arranged in that order from bottom to top. 
     The transparent substrate  21  may for example be made of glass, quartz, sapphire or plastic. The anode  22  is made of transparent conductive material selected from indium tin oxide (ITO), indium zinc oxide (IZO), and indium cerium oxide (ICO). A plurality of fluorine ions (not shown) are doped in the anode  22 , so as to reduce a hydrophilic property and enhance a hydrophobic property of the anode  22 . 
     The organic emission stack  29  includes several layers depending on its functions. In the illustrated embodiment, the organic emission stack  29  includes a hole injection layer  23 , a hole transporting layer  24 , an emitting layer  25 , an electron transporting layer  26 , and an electron injection layer  27  arranged in that order from the anode  22  to the cathode  28 . 
     The cathode  27  is made of a metal or metal alloy. Illustrative metals and metal alloys include, but are not limited to, aluminum (Al), silver (Ag), yttrium (Yt), calcium (Ca), magnesium/silver (Mg/Ag), and the like. 
       FIG. 2  is a flowchart summarizing an exemplary method for fabricating the OLED  20 . The method includes: step S 1 , providing a substrate; step S 2 , forming an anode; step S 3 , doping fluorine ions; step S 4 , forming a hole injection layer and a hole transporting layer; step S 5 , forming an emitting layer; step S 6 , forming an electron transporting layer and an electron injection layer; and step S 7 , forming a cathode. 
     In step S 1 , the substrate  21  is provided. The substrate  21  is made of transparent material such as glass, quartz, sapphire or plastic. 
     In step S 2 , a transparent conductive film, such as an ITO film, an IZO film, or an ICO film, is formed on the substrate  21 , thereby obtaining the anode  22 . The anode  22  can be formed through any one of a deposition process, a sputtering process, a vacuum vapor deposition process, and the like. 
     In step S 3 , a plurality of fluorine ions (not shown) are doped into the anode  22 . The fluorine ions can be doped into the anode by an ion diffusion method or ion implantation method in a vacuum environment. Then a thermal activation process is performed on the anode  22 , in order to cure defects formed during the doping process. 
     After the fluorine ions are doped into the anode  22 , a solvent cleaning process is performed on the anode  22 . The cleaning process can be one or more of an ultrasonic cleaning process, a heat treatment process, a plasma treatment process using hydrogen, oxygen, ozone, etc., an ultraviolet-ozone (UV-ozone) treatment process, and/or a silane treatment process. Such cleaning processes clean impurities from the anode  22 , and lower an electronic energy level of the anode  22 . This facilitates electron injection into an ionization energy level of an upper organic layer formed in a subsequent step. Such cleaning processes also improve the interface properties between the anode  22  and an organic layer subsequently formed on the anode  22 . 
     In step S 4 , the hole injection layer  23  and the hole transporting layer  24  are sequentially formed on the anode  22 . The hole injection layer  23  is made of a material selected from copper phthalocyanine (CuPc) and 4,4′,4″-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine (MTDATA). The hole transporting layer  25  is made of N,N′-di(1-naphthyl)-N,N′-diphenyl-benzidine (NPD), or the like. The hole injection layer  23  and the hole transporting layer  24  helpful to provide the OLED  20  with a low starting voltage, and enhance a stability of the OLED  20 . 
     In step  5 , an organic layer (not labeled) is formed on the hole transporting layer  24 . The organic layer can for example be made of an organic polymer material, or a non-polymer material, or the like. The organic layer is formed by a method selected from a spin coating method, a vacuum vapor deposition method, a laser-induced thermal imaging method, and the like. The organic layer is then patterned, thereby forming the emitting layer  25 . 
     In step S 6 , the electron transporting layer  26  and the electron injection layer  27  are sequentially formed on the emitting layer  25 . The electron transporting layer  26  can for example be made of a material selected from a polycyclic hydrocarbon-based derivative, a heterocyclic compound, an aluminum complex, a gallium complex, any derivative of the foregoing, and the like. The electron injection layer  27  can for example be made of a material selected from alkali metals and alkali compounds with low work function, such as calcium, magnesium or lithium fluoride. 
     In step S 7 , a transparent conductive layer with low work function is formed on the electron injection layer  27 , thereby obtaining the cathode  28 . A thickness of the cathode  28  is in a range of 5 nm (nanometers) to 30 nm. The cathode  28  can for example be made of metals and metal alloys, such as Al, Ag, Yt, Ca, Mg/Ag, and the like. 
     In the above-described described OLED  20  and method for fabricating the OLED  20 , a plurality of fluorine ions are doped into the anode  22 . The fluorine ions enable the anode  22  to have a hydrophobic property. Accordingly, the anode  22  has an improved surface property. In particular, the anode  22  can be firmly combined with the organic emission stack  29 , and few or even no impurities are liable to be introduced between the anode  22  and the hole injection layer  23 . The fluorine-ion-doped anode  22  enhances the operability and prolongs a working lifetime of the OLED  20 . 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.