Patent Publication Number: US-2010109519-A1

Title: Organic electroluminescence device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of and claims priority benefit of U.S. application Ser. No. 11/554,604, filed on Oct. 31, 2006, now pending. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a light emitting device and a fabricating method thereof, and more particularly to an organic electroluminescence (OEL) device and a fabricating method thereof. 
     2. Description of Related Art 
     The OEL device has the features such as self luminescence, wide visual angle, high reply speed, low driving voltage and full color, and recently it may be utilized to be applied in the organic electroluminescence display. Generally speaking, the OEL device comprises an anode, a cathode and an organic light emitting layer located between the two electrodes. When the current passes between the anode and the cathode, and the electrons and the electron holes are combined in the organic light emitting layer to generate the excitons, the organic light emitting layer may generate the light emitting mechanism of different colors according to the material features. 
     In order to increase the ray utilization efficiency of the OEL device, usually another light enhanced layer is further disposed.  FIG. 1  is a schematic view of a conventional OEL device. Referring to  FIG. 1 , the OEL device  100  comprises a glass substrate  110 , an anode  120 , an organic light emitting layer  130 , a cathode  140 , a cover plate  150  and a light enhanced layer  160 . Particularly, the ray  132  emitted from the organic light emitting layer  130  may be enhanced through the light enhanced layer  160 , so as to increase the ray utilization efficiency. 
     However, in the process of fabricating the OEL device  100  as shown in  FIG. 1 , the light enhanced layer  160  is adhered to the cover plate  150 , thus an air gap  170  is generally generated between the cover plate  150  and the light enhanced layer  160 . Therefore, a part of the ray  132  may generate the unnecessary scattering because of the influence of the air gap  170 , thus reducing the light enhancing effect of the light enhanced layer  160 . In order to solve the problem, in the prior art, mostly a refraction index matching glue (not shown) is used to fill in the air gap  170 , or a microlens array is disposed to improve the ray utilization efficiency. 
       FIG. 2  is a schematic view of another conventional OEL device. Referring to  FIG. 2 , the OEL device  200  comprises a glass substrate  210 , an anode  220 , an organic light emitting layer  230 , a cathode  240  and a cover plate  250 . It should be noted that in the method of fabricating the OEL device  200 , firstly a microlens array  212  is fabricated on the glass substrate  210  by reactive ion etching (RIE). Next, the components such as the anode  220 , the organic light emitting layer  230 , the cathode  240  and the cover plate  250  are fabricated on the glass substrate  210 . 
     To sum up, because the microlens array  212  is disposed on the light exit path, the ray utilization efficiency of the OEL device  200  is increased. However, the process of fabricating the microlens array  212  on the glass substrate  210  by RIE is complicated, so it is not good for the mass production of the OEL device  200 , and it is not good for reducing the production cost either. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention is directed to provide an OEL device, so as to improve the light emitting effect, solve the problem of light scattering, and reduce the production cost. 
     The invention is further directed to provide a method of fabricating the OEL device, so as to solve the problem of generating the air gap between the film layers, and reduce the production cost. 
     The invention provides an OEL device, which comprises a polymeric substrate, a plurality of light enhanced structures, a barrier layer, a first electrode, an organic light emitting layer and a second electrode. The polymeric substrate has a first surface and a second surface. The light enhanced structures are disposed on the first substrate. The barrier layer is disposed on the second surface. The first electrode is disposed on the barrier layer. The organic light emitting layer is disposed on the first electrode. The second electrode is disposed on the organic light emitting layer. 
     In an embodiment of the invention, the light enhanced structures and the polymeric substrate are integrated as one piece. 
     In an embodiment of the invention, the material of the barrier layer is one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof. 
     In an embodiment of the invention, the material of the polymeric substrate is a moldable polymeric material. 
     In an embodiment of the invention, the material of the polymeric substrate is one selected from among polymethyl methacrylate (PMMA, acrylic), polydimethylsiloxane (PDMS), polyimide, poly carbonate (PC), polystyrene (PS), polyethylene terephthalate (PET) and the combination thereof. 
     In an embodiment of the invention, the OEL device further comprises a protective layer disposed on the second electrode, and the material of the protective layer is one selected from among glass, metal, polymer and the combination thereof. 
     In an embodiment of the invention, the OEL device further comprises a sealant wrapping the organic light emitting layer. 
     In an embodiment of the invention, the material of the first electrode comprises transparent conductive material, and the transparent conductive material is, for example, indium tin oxide (ITO), indium zinc oxide (IZO) or thin-metal with the thickness in nano-scale. 
     In an embodiment of the invention, the material of the second electrode comprises metal. 
     The invention further provides an OEL device, which comprises a substrate, a first electrode, an organic light emitting layer, a second electrode, a polymeric substrate, a plurality of light enhanced structures and a barrier layer. The first electrode is disposed on the substrate. The organic light emitting layer is disposed on the first electrode. The second electrode is disposed on the organic light emitting layer. The polymeric substrate is disposed above the second electrode, and the polymeric substrate has a first surface and a second surface, and the first surface is opposite to the second electrode. The light enhanced structures are disposed on the second surface. The barrier layer is disposed on the first surface or the second surface. 
     In an embodiment of the invention, the light enhanced structures and the polymeric substrate are integrated as one piece. 
     In an embodiment of the invention, when the barrier layer is disposed on the first surface, the OEL device further comprises a buffer layer disposed between the barrier layer and the second electrode. The material of the buffer layer is, for example, one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof. 
     In an embodiment of the invention, when the barrier layer is disposed on the second surface and covers the light enhanced structures, the polymeric substrate is located on the second electrode. 
     In an embodiment of the invention, when the barrier layer is disposed on the second surface and covers the light enhanced structures, the OEL device further comprises a buffer layer disposed between the polymeric substrate and the second electrode. The material of the buffer layer is for example one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof. 
     In an embodiment of the invention, the material of the barrier layer is one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof. 
     In an embodiment of the invention, the material of the polymeric substrate is a moldable polymeric material. 
     In an embodiment of the invention, the material of the polymeric substrate is one selected from among PMMA, PDMS, polyimide, poly carbonate (PC), polystyrene (PS), polyethylene terephthalate (PET) and the combination thereof. 
     In an embodiment of the invention, the OEL device further comprises a sealant wrapping the organic light emitting layer. 
     In an embodiment of the invention, the material of the first electrode comprises metal. 
     In an embodiment of the invention, the material of the second electrode comprises the transparent conductive material. The transparent conductive material comprises ITO, IZO or thin-metal with the thickness in nano-scale. 
     The invention further provides a method of fabricating the OEL device, which comprises providing a polymeric substrate having a first surface and a second surface, wherein a plurality of light enhanced structures is formed on the first surface; forming a barrier layer on the second surface; forming a first electrode on the barrier layer; forming an organic light emitting layer on the first electrode; and forming a second electrode on the organic light emitting layer. 
     In an embodiment of the invention, the method of forming the light enhanced structures on the first surface comprises molding method or injection molding method. 
     In an embodiment of the invention, the method of forming the barrier layer on the second surface comprises coating method or evaporation method. 
     In an embodiment of the invention, the method of fabricating the OEL device further comprises forming a protective layer on the second electrode. 
     In an embodiment of the invention, the method of fabricating the OEL device further comprises providing a sealant to wrap the organic light emitting layer. 
     The invention further provides a method of fabricating the OEL device, which comprises providing a substrate; forming a first electrode on the substrate; forming an organic light emitting layer on the first electrode; forming a second electrode on the organic light emitting layer; providing a polymeric substrate disposed above the second electrode, wherein the polymeric substrate has a first surface and a second surface, the first surface is opposite to the second electrode, and a plurality of light enhanced structures is formed on the second surface; and forming a barrier layer on the first surface or the second surface. 
     In an embodiment of the invention, the method of providing the polymeric substrate comprises forming a polymeric material layer on the substrate; and pressing the polymeric material layer with a mold to form the light enhanced structures on the second surface. 
     In an embodiment of the invention, when the barrier layer is formed on the first surface, the method of fabricating the OEL device further comprises forming a buffer layer between the barrier layer and the second electrode. 
     In an embodiment of the invention, when the barrier layer is formed on the second surface, the polymeric substrate is directly disposed on the second electrode. 
     In an embodiment of the invention, when the barrier layer is formed on the second surface, the method of fabricating the OEL device further comprises forming a buffer layer between the polymeric substrate and the second electrode. 
     In an embodiment of the invention, the method of fabricating the OEL device further comprises providing a sealant to wrap the organic light emitting layer. 
     The OEL device of the invention adopts the polymeric substrate with the light enhanced structures, so the ray utilization efficiency of the polymeric substrate may be increase. Further, the OEL device adopts the barrier layer, so as to increase the waterproof function of the polymeric substrate. Moreover, the method of fabricating the OEL device of the invention fabricates the polymeric substrate by molding method or injection molding method. Therefore, the OEL device can be in mass production so as to lower the production cost. Further, in the fabricating process, the method of fabricating the OEL device may prevent the generation of the air gap, thus avoiding the light scattering. 
     In order to the make aforementioned and other features and advantages of the invention comprehensible, embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic view of a conventional OEL device. 
         FIG. 2  is a schematic view of another conventional OEL device. 
         FIGS. 3A˜3F  are schematic sectional views of a flow of fabricating the OEL device of the first embodiment of the invention. 
         FIGS. 4A˜4F  are schematic sectional views of a flow of fabricating the OEL device of the second embodiment of the invention. 
         FIG. 5  is a schematic view of the OEL device of the third embodiment of the invention. 
         FIGS. 6A˜6B  are schematic views of the steps of providing the polymeric substrate of the fourth embodiment of the invention. 
         FIGS. 7A˜7B  are schematic sectional views of a part of the flow of fabricating the OEL device of the fifth embodiment of the invention. 
         FIGS. 8A˜8B  are schematic sectional views of a part of the flow of fabricating the OEL device of the sixth embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The First Embodiment 
       FIGS. 3A˜3F  are schematic sectional views of a flow of fabricating the OEL device of the first embodiment of the invention. The embodiment is about the fabricating of a bottom emission OEL device. 
     Referring to  FIG. 3A , firstly a polymeric substrate  310  having a first surface  312  and a second surface  314  is provided, wherein a plurality of light enhanced structures  320  is formed on the first surface  312 . In the present embodiment, the method of forming the light enhanced structures  320  on the first surface  312  may be molding method or injection molding method. Particularly, the light enhanced structures  320  and the polymeric substrate  310  may be the construction that is integrated as one piece. As compared with the method of fabricating the microlens array  212  by RIE as shown in  FIG. 2  in the conventional art, it is easier to fabricate the polymeric substrate  310  with the light enhances structures  320 , so it can be in mass production so as to lower the production cost. 
     Moreover, the material of the polymeric substrate  310  as shown in  FIG. 3A  may be moldable polymeric material, particularly, may be one selected from among PMMA, PDMS, polyimide, poly carbonate (PC), polystyrene (PS), polyethylene terephthalate (PET) and the combination thereof. Therefore, it is easy to make the shape of the light enhanced structures  320  on the polymeric substrate  310 , and the polymeric substrate  310  and the light enhanced structures  320  may be made to be light transmissive. 
     Next, referring to  FIG. 3B , a barrier layer  330  is formed on the second surface  314 . In an embodiment, the method of forming the barrier layer  330  on the second surface  314  is, for example, coating method, evaporation method or another suitable method, and the material of the barrier layer  330  is one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof. Generally speaking, the waterproof function of the polymeric substrate  310  is poor. Therefore, the waterproof function of the polymeric substrate  310  may be improved by disposing the barrier layer  330 . 
     Then, referring to  FIG. 3C , a first electrode  340  is formed on the barrier layer  330 . In an embodiment, the method of forming the first electrode  340  may be sputtering, evaporation method or another suitable method. The material of the first electrode  340  comprises transparent conductive material, and the transparent conductive material is, for example, ITO, IZO or another suitable material. 
     Then, referring to  FIG. 3D , an organic light emitting layer  350  is formed on the first electrode  340 . In an embodiment, the method of forming the organic light emitting layer  350  is, for example, coating method, evaporation method or another suitable method, and the type of the organic light emitting layer  350  is not limited in the invention. 
     Then, referring to  FIG. 3E , a second electrode  360  is formed on the organic light emitting layer  350 . The method of forming the second electrode  360  may be sputtering, evaporation method or another suitable method. The material of the second electrode  360  comprises metal, and the type of the metal is not limited in the invention. 
     After the fabricating steps as shown in  FIGS. 3A˜3E , the bottom emission OEL device  300  as shown in  FIG. 3E  is formed. The OEL device  300  comprises a polymeric substrate  310 , a plurality of light enhanced structures  320 , a barrier layer  330 , a first electrode  340 , an organic light emitting layer  350  and a second electrode  360 . The polymeric substrate  310  has a first surface  312  and a second surface  314 . The light enhanced structures  320  are disposed on the first surface  312 . The barrier layer  330  is disposed on the second surface  314 . The first electrode  340  is disposed on the barrier layer  330 . The organic light emitting layer  350  is disposed on the first electrode  340 . The second electrode  360  is disposed on the organic light emitting layer  350 . 
     Particularly, because the first electrode  340  is of the transparent conductive material, and the second electrode  360  is of the metal material, the ray emitted from the organic light emitting layer  350  may exit downwardly through the polymeric substrate  310 . Moreover, the materials and the advantages of all the components are described in the method of fabricating the OEL device  300 , which will not be described herein. 
     Moreover, the method of fabricating the OEL device  300  of the embodiment further comprises forming a protective layer  370  on the second electrode  360 , as shown in  FIG. 3F . The material of the protective layer  370  is, for example, one selected from among glass, metal, polymer and the combination thereof. 
     Further, referring to  FIG. 3F , the method of fabricating the OEL device  300  of the embodiment further comprises providing a sealant  380  to wrap the organic light emitting layer  350 . The material of the sealant  380  may be the UV cure adhesive, thermal cure adhesive or another similar material. Therefore, the OEL device  300  is packaged by using the protective layer  370  and the sealant  380 , so as to further avoid the external moisture from entering into the organic light emitting layer  350 . As such, the working life of the OEL device  300  is prolonged. 
     To sum up, in the method of fabricating the OEL device  300  in the first embodiment, the polymeric substrate  310  with the light enhanced structures  320  is fabricated by using molding method or injection molding method, therefore it may be in mass production to lower the production cost of the OEL device  300 . 
     Moreover, the OEL device  300  may improve the ray utilization efficiency by the light enhanced structures  320 . Further, by disposing the barrier layer  330 , the waterproof function of the OEL device  300  is effectively improved. 
     The Second Embodiment 
       FIGS. 4A˜4F  are schematic sectional views of a flow of fabricating the OEL device of the second embodiment of the invention. The embodiment is about the fabricating of a top emission OEL device. 
     Referring to  FIG. 4A , firstly a substrate  410  is provided. The substrate  410  may be a glass substrate, a plastic substrate or another kind of substrate. 
     Next, referring to  FIG. 4B , a first electrode  420  is formed on the substrate  410 . In an embodiment, the method of forming the first electrode  420  may be sputtering, evaporation method or another suitable method. The material of the first electrode  420  is, for example, metal, and the type of the metal is not limited in the invention. 
     Then, referring to  FIG. 4C , an organic light emitting layer  430  is formed on the first electrode  420 . In an embodiment, the method of forming the organic light emitting layer  430  is, for example, coating method, evaporation method or another suitable method, and the type of the organic light emitting layer  430  is not limited in the invention. 
     Then, referring to  FIG. 4D  a second electrode  440  is formed on the organic light emitting layer  430 . In an embodiment, the method of forming the second electrode  440  may be sputtering, evaporation method or another suitable method. The material of the second electrode  440  comprises transparent conductive material, and the transparent conductive material is, for example, ITO, IZO, thin-metal with the thickness in nano-scale (e.g. less than 20 nm) or another suitable material. 
     After that, referring to  FIG. 4E , a polymeric substrate  450  is provided, and the polymeric substrate  450  is made to be disposed above the second electrode  440 , wherein the polymeric substrate  450  has a first surface  452  and a second surface  454 . The first surface  452  is opposite to the second electrode  440 , and a plurality of light enhanced structures  460  is formed on the second surface  454 . In the present embodiment, the polymeric substrates  450  are components fabricated by molding method or injection molding method. The material of the polymeric substrate  450  has been described in the first embodiment, which will not be described herein. 
     Referring to  FIG. 4F , then, a barrier layer  470  is formed on the first surface  452 . The method of forming the barrier layer  470  is, for example, coating method or another suitable method, and the material of the barrier layer  470  is, for example, oxide, nitride, photo-resist, epoxy, parylene or the combination thereof. 
     In the embodiment, when the barrier layer  470  is formed on the first surface  452 , the method of fabricating the OEL device further comprises forming a buffer layer  480  between the barrier layer  470  and the second electrode  440 . The method of forming the buffer layer  480  is, for example, coating method or another suitable method, and the material of the buffer layer  480  is, for example, one selected from among oxide, nitride, photo-resist, epoxy, parylene and the combination thereof, or other suitable materials. More particularly, by coating the buffer layer  480  on the second electrode  440 , the barrier layer  470  may be prevented from directly contacting with the second electrode  440 , so as to avoid the barrier layer  470  from damaging the second electrode  440 . 
     After the steps of  FIGS. 4A˜4F , the top emission OEL device  400  as shown in  FIG. 4F  is formed. The OEL device  400  comprises a substrate  410 , a first electrode  420 , an organic light emitting layer  430 , a second electrode  440 , a polymeric substrate  450 , a plurality of light enhanced structures  460  and a barrier layer  470 . The first electrode  420  is disposed on the substrate  410 . The organic light emitting layer  430  is disposed on the first electrode  420 . The second electrode  440  is disposed on the organic light emitting layer  430 . The polymeric substrate  450  is disposed above the second electrode  440 , the polymeric substrate  450  has a first surface  452  and a second surface  454 , and the first surface  452  is opposite to the second electrode  440 . The light enhanced structures  460  are disposed on the second surface  454 . The barrier layer  470  is disposed on the first surface  452 . Particularly, in the present embodiment, when the barrier layer  470  is disposed on the first surface  452 , the OEL device  400  further comprises a buffer layer  480  disposed between the barrier layer  470  and the second electrode  440 . 
     The materials of the components are described in the method of fabricating the OEL device  400 , so it will not be described herein. Moreover, referring to  FIG. 4F , a sealant  490  may also be used to wrap the organic light emitting layer  430 , so as to improve the waterproof function of the OEL device  400 . 
     To sum up, in the method of fabricating the OEL device  400  in the second embodiment, the polymeric substrate  450  with the light enhanced structures  460  is fabricated by using molding method or injection molding method, thus the polymeric substrate  450  may be in mass production so as to lower the production cost of the OEL device  400 . Moreover, the light enhanced efficiency of the OEL device  400  is improved by the light enhanced structures  460 . By disposing the barrier layer  470 , the waterproof function of the OEL device  400  is effectively improved. Particularly, by disposing the buffer layer  480 , the barrier layer  470  may be avoided from damaging the second electrode  440 . 
     The Third Embodiment 
     The third embodiment is similar to the second embodiment. It is also about the fabricating method and the structure of a top mission OEL device.  FIG. 5  is a schematic view of the OEL device of the third embodiment of the invention. 
     Referring to  FIGS. 4A˜4E  and  FIG. 5 , firstly, in the third embodiment, the steps as shown in  FIGS. 4A˜4D  are used to fabricate an OEL device having the substrate  410 , the first electrode  420 , the organic light emitting layer  430  and the second electrode  440 . Then, as shown in  FIG. 4E , a polymeric substrate  450  is provided. 
     It should be noted that the difference between the present embodiment and the second embodiment is that in the third embodiment, the barrier layer  470  is not formed between the second electrode  440  and the polymeric substrate  450 . As shown in  FIG. 5 , when the barrier layer  470  is formed on the second surface  454 , the polymeric substrate  450  is directly disposed on the second electrode  440 . 
     After the above steps, the OEL device  401  as shown in  FIG. 5  is formed, which comprises a substrate  410 , a first electrode  420 , an organic light emitting layer  430 , a second electrode  440 , a polymeric substrate  450 , a plurality of light enhanced structures  460  and a barrier layer  470 . The first electrode  420  is disposed on the substrate  410 . The organic light emitting layer  430  is disposed on the first electrode  420 . The second electrode  440  is disposed on the organic light emitting layer  430 . The polymeric substrate  450  is disposed on the second electrode  440 , the polymeric substrate  450  has a first surface  452  and a second surface  454 , and the first surface  452  is opposite to the second electrode  440 . The light enhanced structures  460  are disposed on the second surface  454 . The barrier layer  470  is disposed on the second surface  452 . The materials of the components are described above, so it will not be described herein. 
     Particularly, in the present embodiment, when the barrier layer  470  is disposed on the second surface  454  and covers the light enhanced structures  460 , the polymeric substrate  450  is located on the second electrode  440 . In this manner, the fabricating of the buffer layer  480  may be omitted, so as to simplify the structure of the OEL device  401 . 
     Also, the polymeric substrate  450  may serve as the protective layer itself to protect the OEL device  401 . Further, the barrier layer  470  directly covering on the second surface  454  of the polymeric substrate  450  may improve the waterproof function of the polymeric substrate  450 , so as to prevent the moisture from damaging the organic light emitting layer  430 . 
     Moreover, referring to  FIG. 5 , the sealant  490  may also be used to wrap the organic light emitting layer  430  and package the OEL device  401 , so as to improve the waterproof function of the OEL device  401 . 
     The Fourth Embodiment 
     The fourth embodiment is similar to the third embodiment. The difference between the two is illustrated as follows. In the steps of the third embodiment, the polymeric substrate  450  with the light enhanced structures  460  is fabricated by molding method or injection molding method, as shown in  FIG. 4E . However, in the fourth embodiment, the step of providing the polymeric substrate  450  is directly performed on the OEL device. 
       FIGS. 6A˜6B  are schematic views of the steps of providing the polymeric substrate of the fourth embodiment of the invention. Referring to  FIGS. 4A˜4D ,  FIGS. 6A˜6D  and  FIG. 5 , firstly, in the present embodiment, the steps as shown in  FIGS. 4A˜4D  are used to fabricate the OEL device having the substrate  410 , the first electrode  420 , the organic light emitting layer  430  and the second electrode  440 . Then, the steps of  FIGS. 6A˜6D  are adopted to directly fabricate the polymeric substrate  450  with the light enhanced structures  460  on the OEL device. 
     Referring to  FIG. 6A , firstly, a polymeric material layer  450   a  is formed on the substrate  410 . The method of forming the polymeric material layer  450   a  may be coating method, evaporation method or another suitable method, and the material of the polymeric material layer  450   a  may be moldable polymeric material, more specifically, may be one selected from PMMA, PDMS, polyimide, poly carbonate (PC), polystyrene (PS), polyethylene terephthalate (PET) and the combination thereof, or other suitable materials. It should be noted that the polymeric material layer  450   a  is fabricated on the OEL device, and covers the second electrode  440 . 
     Then, as shown in  FIG. 6B , the polymeric material layer  450   a  is pressed by using a mold  500 , so as to form the light enhanced structures  460  on the second surface  454 . The pressing action of the mold  500  is performed along the pressing direction A. Therefore, in this step, the polymeric substrate  450  with the light enhanced structures  460  is directly formed on the OEL device, and during the process of the pressing action, the air gap (not shown) between each film layer is removed. Therefore, the ray emitted by the organic light emitting layer  430  may not be affected by the air gap, so as to improve the light enhanced efficiency of the OEL device. 
     Particularly, the barrier layer  470  is further formed on the polymeric substrate  450 , and a sealant  490  is formed to wrap the organic light emitting layer  430 , so as to form the OEL device  401  the same as that in  FIG. 5 . Moreover, the OEL device structure fabricated by the steps is the same as the OEL device of the third embodiment (as shown in  FIG. 5 ), so the components and the materials are not illustrated again here. 
     The Fifth Embodiment 
     The fifth embodiment is similar to the second embodiment. It is also about the fabricating of the top emission OEL device.  FIGS. 7A˜7B  are schematic sectional views of a part of the flow of fabricating the OEL device of the fifth embodiment of the invention. Referring to  FIGS. 4A˜4D ,  FIG. 4F  and  FIGS. 7A˜7B , firstly, in the fifth embodiment, the steps as shown in  FIGS. 4A˜4D  are used to fabricate the OEL device having the substrate  410 , the first electrode  420 , the organic light emitting layer  430  and the second electrode  440 . 
     After the steps of  FIGS. 4A˜4D , referring to  FIG. 7A , the buffer layer  480  and the barrier layer  470  are formed in sequence on the second electrode  440 , wherein the buffer layer  480  is located between the second electrode  440  and the barrier layer  470 . 
     The material of the buffer layer  480  is, for example, parylene. Because parylene is relatively rigid, it is difficult to be used to directly fabricate the light enhanced structures  460 . 
     Therefore, referring to  FIG. 7B , a polymeric material layer  450   a  is formed on the barrier layer  470 , and the polymeric material layer  450   a  is pressed by using a mold  500  along the pressing direction A, such that the polymeric material layer  450   a  forms the polymeric substrate  450  with the light enhanced structures  460 . Moreover, a sealant  490  is also fabricated, so as to form the OEL device  400  with the structure as shown in  FIG. 4F . 
     It should be noted that in the present embodiment, the polymeric material layer  450   a  is directly formed on the OEL device, and it is pressed to form the polymeric substrate  450  with the light enhanced structures  460 . Therefore, each film layer may be combined tightly to prevent the generating of the air gap, so as to improve the light exit efficiency of the OEL device  400 . Also, by disposing the barrier layer  470 , the waterproof function of the OEL device  400  is improved. 
     The Sixth Embodiment 
     The sixth embodiment is similar to the fifth embodiment. It is also about the fabricating of the top emission OEL device. The difference of the present embodiment and the fifth embodiment is that in the present embodiment, the barrier layer  470  is formed on the second surface  454  of the polymeric substrate  450 . 
       FIGS. 8A˜8B  are schematic cross-sectional views of a part of the flow of fabricating the OEL device of the sixth embodiment of the invention. Referring to  FIGS. 4A˜4D  and  FIGS. 8A˜8B , firstly, in the sixth embodiment, the steps as shown in  FIGS. 4A˜4D  are also used to fabricate the OEL device having the substrate  410 , the first electrode  420 , the organic light emitting layer  430  and the second electrode  440 . 
     Then, referring to  FIG. 8A , the buffer layer  482  and the polymeric material layer  450   a  are formed in sequence on the second electrode  440 . Then, the polymeric material layer  450   a  is pressed by using the mold  500  along the pressing direction A, so as to form the polymeric substrate  450  with the light enhanced structures  460  as shown in  FIG. 8B . 
     Next, referring to  FIG. 8B , the barrier layer  470  is formed on the polymeric substrate  450 . That is, when the barrier layer  470  is formed on the second surface  454 , the method of fabricating the OEL device further comprises forming a buffer layer  482  between the polymeric substrate  450  and the second electrode  440 . The method of forming the buffer layer  482  is, for example, coating method, and the material of the buffer layer  482  is, for example, one selected from oxide, nitride, photo-resist, epoxy, parylene and the combination thereof, or other suitable materials. 
     Referring to  FIG. 8B , the OEL device  402  fabricated by the above steps comprises a substrate  410 , a first electrode  420 , an organic light emitting layer  430 , a second electrode  440 , a polymeric substrate  450 , a plurality of light enhanced structures  460  and a barrier layer  470 . The first electrode  420  is disposed on the substrate  410 . The organic light emitting layer  430  is disposed on the first electrode  420 . The second electrode  440  is disposed on the organic light emitting layer  430 . The polymeric substrate  450  is disposed above the second electrode  440 , the polymeric substrate  450  has a first surface  452  and a second surface  454 , and the first surface  452  is opposite to the second electrode  440 . The light enhanced structures  460  are disposed on the second surface  454 . The barrier layer  470  is disposed on the second surface  454 . 
     Particularly, in the invention, when the barrier layer  470  is disposed on the second surface  454  and covers the light enhanced structures  460 , the OEL device  402  further comprises a buffer layer  482  disposed between the polymeric substrate  450  and the second electrode  440 . Likewise, as shown in  FIG. 8B , the sealant  490  may be used to wrap the organic light emitting layer  430 , so as to improve the waterproof function of the OEL device  402 . 
     In each embodiment, the method of providing the polymeric substrate  450  may be that the polymeric substrate  450  with the light enhanced structures  460  is fabricated separately, and then the polymeric substrate  450  is adhered to other film layers; or firstly, the OEL device is fabricated by the steps of  FIGS. 4A˜4D , then the polymeric material layer  450   a  is coated on the OEL device, and the polymeric material layer  450   a  is pressed by using the mold  500 , so as to form the polymeric substrate  450  with the light enhanced structures  460 . 
     Moreover, by disposing the barrier layer  470 , the buffer layer  480  and the buffer layer  482 , the fabricating of the OEL device may have superior waterproof function and better element capability. 
     To sum up, the OEL device and fabricating method thereof of the invention comprise the following advantages. 
     (1) The OEL device adopts the polymeric substrate with the light enhanced structures, thus improving the ray utilization efficiency. 
     (2) The OEL device has a barrier layer, thus improving the waterproof function of the OEL device. 
     (3) In the method of fabricating the OEL device, the polymeric substrate with the light enhanced structures is fabricated by molding method or injection molding method. Therefore, the OEL device may be in mass production so as to lower the production cost. 
     (4) In the process of the method of fabricating the OEL device, the air gap existing between the film layers may be eliminated, thus improving the light enhanced effect of the OEL device. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.