Patent Publication Number: US-2005121600-A1

Title: [organic electroluminescent device and fabricating method therefor]

Description:
BACKGROUND OF INVENTION  
      1. Field of the Invention  
      The present invention relates to an organic electroluminescent device and a fabricating method therefor, and more particularly to an organic electroluminescent device having photo-detectors and a fabricating method for integrating the organic electroluminescent device and photo-detectors.  
      2. Description of the Related Art  
      Computer, communication and consumer products have become the main trend of high technology. Portable electronic devices are also the essential products of development. Of course, displays are also included. Today, the displays include Plasma Display Panel (PDP), Liquid Crystal Display (LCD), Electro-luminescent Display, Light Emitting Diode Display, Vacuum Fluorescent Display, Field Emission Display (FED) and Electro-chromic Display.  
      Compared with these displays, the organic electroluminescent display, however, has advantages of self-luminescence, wide viewing angle, high resolution, low power consumption, easy manufacturing process, low costs, low operational temperature, fast response speed, low driving voltage, etc. It has potential application and can become the main trend for the next generation displays.  
      An organic electroluminescent device uses an organic electroluminescent material serving for display, which is composed of a pair of electrodes and an organic electroluminescent layer. When a current is applied to the device, electrons and holes recombine within the organic electroluminescent layer and generate photons. Therefore, light having different colors accordingly is generated depending on the material property of the organic electroluminescent layer.  
      However, a full-color organic electroluminescent display has different brightness degradation for red, green and blue light pixels. If the brightness degradation of different colors is not consistent, it will affect the performance of the display. Therefore, how to maintain the brightness stability of different colors of the full-color organic electroluminescent display is an essential issue that should be resolved.  
     SUMMARY OF INVENTION  
      Therefore, the object of the present invention is to provide an organic electroluminescent device and a method therefore for resolving the issue of different degradations between red, green and blue pixels which create brightness unstability of the colors.  
      The present invention discloses an organic electroluminescent device, which comprises a transparent substrate, a plurality of pixels, a red-light detector, a green-light detector and a blue-light detector, wherein the pixels disposed on the transparent substrate comprise a plurality of red-light pixels, a plurality of green-light pixels and a plurality of blue-light pixels. Each of the pixels comprises, in sequence, a transparent anode, an organic electroluminescent layer and a metal cathode. The transparent anode is disposed on the transparent substrate. In addition, the red-light detector is disposed adjacent to the red-light pixels on the transparent substrate, the green-light detector is disposed adjacent to the green-light pixels on the transparent substrate and the blue-light detector is disposed adjacent to the blue-light pixels on the transparent substrate. Each of the red-light detector, the green-light detector and the blue-light detector comprises, in sequence, a metal anode, an electroluminescent layer and a metal cathode. The metal anode is disposed on the transparent substrate. The metal anode is a non-transparent metal layer and the electroluminescent layer is an organic material or an inorganic material. Moreover, the organic electroluminescent device of the present invention further comprises driving units coupled to each of the pixels, and each of the red-light detector, the green-light detector and the blue-light detector are coupled to transfer units. The driving units and the transfer units are coupled to a control unit. Therefore, when an organic electroluminescent layer of a pixel degrades, causing the reduction of brightness, the detector adjacent thereto detects the degradation.  
      Therefore, the transfer unit transmits the signal generated from the detector to the control unit. According to the degradation of the pixel, the control unit controls the driving unit increasing driving current to the pixel and maintaining the predetermined brightness of the pixel.  
      The present invention also discloses a method for fabricating an organic electroluminescent device. The method comprises: providing a transparent substrate; forming a plurality of pixels on the transparent substrate, wherein the pixels comprise a plurality of red-light pixels, a plurality of green-light pixels and a plurality of blue-light pixels; forming a red-light detector on the transparent substrate adjacent to the red-light pixels; forming a green-light detector on the transparent substrate adjacent to the green-light pixels; and forming a blue-light detector on the transparent substrate adjacent to the blue-light pixels. In the present invention, the step of forming the pixels, the red-light detector, the green-light detector and the blue-light detector comprises forming a patterned transparent anode and a patterned metal anode on the transparent substrate; forming an organic electroluminescent layer on the transparent anode and a electroluminescent layer on the metal anode; and forming a metal cathode on the organic electroluminescent layer and the electroluminescent layer for forming the pixels and the detectors. Moreover, the present invention further comprises coupling a driving unit to each of the pixels, and coupling each of the red-light detector, the green-light detector and the blue-light detector to transfer units.  
      Therefore, when an organic electroluminescent layer of a pixel degrades, causing the reduction of brightness, the detector adjacent thereto detects the degradation. In another word, the transfer unit transmits the signal generated from the detector to the control unit. According to the degradation of the pixel, the control unit controls the driving unit increasing driving current to the pixel and maintaining the predetermined brightness of the pixel.  
      The organic electroluminescent device and the method applied therefore can resolve the issues of different brightness degradation of pixels and brightness unstableness of colors by detecting the brightness of the pixels and controlling the current applied thereto.  
      In order to make the aforementioned and other objects, features and advantages of the present invention understandable, a preferred embodiment accompanied with figures is described in detail below. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a schematic structure showing a preferred embodiment of an organic electroluminescent device in accordance with the present invention.  
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is a schematic structure showing a preferred embodiment of an organic electroluminescent device in accordance with the present invention.  
      The pixels disposed on the transparent substrate comprise a red-light pixel, a green-light pixel and a blue-light pixel.Please referring to  FIG. 1 , the organic electroluminescent device of the present invention comprises a transparent substrate  100 , a plurality of pixels  110   a ,  110   b  and  110   c , a red-light detector  111   a , a green-light detector  111   b  and a blue-light detector  111   c.    
      The transparent substrate  100  has a red-light area  101   a , a green-light area  101   b  and a blue-light area  101   c . The pixels  110   a ,  110   b  and  110   c  disposed on the transparent substrate  100  comprise a red-light pixel  110   a  within the red-light area  101   a , a green-light pixel  110   b  within the green-light area  101   b  and a blue-light pixel  110   c  within the blue-light area  101   c . The pixels  110   a ,  110   b  and  110   c  comprise transparent anodes  102   a ,  102   b  and  102   c  disposed on the transparent substrate  100  respectively, organic electroluminescent layers  104   a ,  104   b  and  104   c  disposed on the transparent anodes  102   a ,  102   b  and  102   c  respectively and metal cathodes  106   a ,  106   b  and  106   c  disposed on the organic electroluminescent layers  104   a ,  104   b  and  104   c  respectively.  
      In addition, the red-light detector is disposed adjacent to the red-light pixels on the transparent substrate, the green-light detector is disposed adjacent to the green-light pixels on the transparent substrate and the blue-light detector is disposed adjacent to the blue-light pixels on the transparent substrate. The transparent anodes  102   a ,  102   b  and  102   c  comprise transparent material, such as indium-tin oxide or indium-zinc oxide. The metal cathodes  106   a ,  106   b  and  106   c  comprise, for example, aluminum, aluminum/lithium fluorine, calcium, magnesium/silver alloy or silver. The organic electroluminescent layer  104   a ,  104   b  and  104   c  comprise a hole injection layer (not shown), a hole transporting layer (not shown), a light-emitting layer (not shown), an electron transporting layer (not shown), and an electron injection layer (not shown). The organic electroluminescent layer  104   a  is, for example, a red-light small molecular organic electroluminescent material or a red-light polymer electroluminescent material. The organic electroluminescent  104   b  is, for example, a green-light small molecular organic electroluminescent material or a green-light polymer electroluminescent material. The organic electroluminescent  104   c  is, for example, a blue-light small molecular organic electroluminescent material or a blue-light polymer electroluminescent material.  
      The red-light detector  111   a  is adjacent to the red-light pixel  110   a  on the transparent substrate  100 , i.e., within red-light area  101   a . The green-light detector  111   b  is adjacent to the green-light pixel  110   b  on the transparent substrate  100 , i.e., within the green-light area  101   b . The blue-light detector  111   c  is adjacent to the blue-light pixel  110   c  on the transparent substrate  100 , i.e., within the blue-light area  101   c.    
      The red-light detector  111   a , the green-light detector  111   b  and the blue-light detector  111   c  comprise metal anodes  112   a ,  112   b  and  112   c  disposed on the transparent substrate  100 , electroluminescent layers  114   a ,  114   b  and  114   c  disposed on the metal anodes  112   a ,  112   b  and  112   c  respectively and metal cathodes  116   a ,  116   b  and  116   c  disposed on the organic electroluminescent layers  114   a ,  114   b  and  114   c  respectively. In the present invention, the metal anodes  112   a ,  112   b  and  112   c  are a non-transparent metal layer for preventing interference to the detectors  111   a ,  111   b  and  111   c  due to the light from the transparent substrate  100 . The metal anodes  112   a ,  112   b  and  112   c  have the same or different material of the metal cathodes  116   a ,  116   b  and  116   c . The electroluminescent layers  114   a ,  114   b  and  114   c  are an organic material or an inorganic material.  
      In the present invention, the method of forming the pixels  110   a ,  110   b  and  110   c , the red-light detector  111   a , the green-light detector  111   b  and the blue-light detector  111   c  comprises forming patterned transparent anodes  102   a ,  102   b  and  102   c  and patterned metal anodes  112   a ,  112   b  and  112   c  on the transparent substrate  100 ; forming organic electroluminescent layers  104   a ,  104   b  and  104   c  on the transparent anodes  102   a ,  102   b  and  102   c  respectively and electroluminescent layers  114   a ,  114   b  and  114   c  on the metal anodes  112   a ,  112   b  and  112   c  respectively; and forming metal cathodes  106   a ,  106   b  and  106   c  on the organic electroluminescent layers  104   a ,  104   b  and  104   c  respectively and metal cathodes  116   a ,  116   b  and  116   c  on the electroluminescent layer  114   a ,  114   b  and  114   c  respectively for forming the pixels  110   a ,  110   b  and  110   c  and the detectors  111   a ,  111   b  and  111   c.    
      Because a portion of light generated from the organic electroluminescent device goes out of the device, a portion of light generates a wave-guide phenomenon within the transparent substrate  100  and another portion of light generates a wave-guide phenomenon between the transparent anodes  102   a ,  102   b  and  102   c  and the organic electroluminescent layers  104   a ,  104   b  and  104   c . Therefore, a light guider (not shown) adjacent to the pixels  110   a ,  110   b  and  110   c  can induce the light within the device and transmits to the detectors  111   a ,  111   b  and  111   c . When the energy of the light entering the detectors  111   a ,  111   b  and  111   c  is less than the band gap, no electron-hole will be generated. When the energy of the light entering the detectors  111   a ,  111   b  and  111   c  is larger than the band gap, electrons will be activated from valance band to conduction band and electron-hole is therefore generated. By the currents generated from the detectors  111   a ,  111   b  and  111   c , the brightness of the pixels  110   a ,  110   b  and  110   c  can be detected.  
      Moreover, the pixels  110   a ,  110   b  and  110   c  of the organic electroluminescent device of the present invention further comprise driving units  108   a ,  108   b  and  108   c  coupled to the pixels  110   a ,  110   b  and  110   c , and the red-light detector  111   a , the green-light detector  111   b  and the blue-light detector  111   c  are coupled to transfer units  118   a ,  118   b  and  118   c . The driving units  108   a ,  108   b  and  108   c  and the transfer units  118   a ,  118   b  and  118   c  are coupled to a control unit  120 .  
      Therefore, when organic electroluminescent layers  104   a ,  104   b  and  104   c  of pixels  110   a ,  110   b  and  110   c  degrade, causing the reduction of brightness, the detectors  111   a ,  111   b  and  111   c  adjacent thereto detect the degradation. In another word, the transfer units  118   a ,  118   b  and  118   c  transmit the signals generated from the detector  111   a ,  111   b  and  111   c  to the control unit  120 . According to the degradation of the pixels  110   a ,  110   b  and  110   c , the control unit  120  controls the driving units  108   a ,  108   b  and  108   c  increasing driving current to the pixels  110   a ,  110   b  and  110   c  and maintaining the predetermined brightness of the pixels  110   a ,  110   b  and  110   c.    
      Therefore, the organic electroluminescent device and the method applied therefore can resolve the issues of different brightness degradation of pixels and brightness unstableness of colors by detecting the brightness of the pixels and controlling the current applied thereto.  
      Moreover, the pixels of the organic electroluminescent device have the process and material similar to those of the detectors. It can simplify the manufacturing process and reduce costs thereof.  
      Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be constructed broadly to include other variants and embodiments of the invention which may be made by those skilled in the field of this art without departing from the scope and range of equivalents of the invention.