Abstract:
An organic light emitting diode (OLED) display device and a method of fabricating the same are provided. An embodiment of the OLED display device comprises: a substrate; a secondary battery comprising a first electrode layer, a second electrode layer and an electrolyte layer interposed between the first and second electrode layers; a display panel comprising an array of organic light emitting diodes formed over the substrate, wherein the battery is interposed between the substrate and the display panel; and a power supply voltage line formed over the substrate and outside the display panel, wherein the power supply voltage line electrically interconnects the secondary battery and the display panel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 2006-0111180, filed on Nov. 10, 2006, the disclosure of which is hereby incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to an organic light emitting diode (OLED) display device and a method of fabricating the same, and more particularly, to an OLED display device having an integrated secondary battery capable of applying a voltage to a display panel, and a method of fabricating the same. 
         [0004]    2. Description of the Related Technology 
         [0005]    The cathode-ray tube (CRT) has been superseded by a flat panel display device (FPD) that can be fabricated to be lightweight and thin. Typical examples of the FPD include a liquid crystal display device (LCD) and an organic light emitting diode (OLED) display device. The OLED display device typically has a higher luminance and a wider viewing angle than the LCD, and may be made ultrathin since it typically does not need a backlight. 
         [0006]    In the OLED, electrons and holes may be injected through a cathode and an anode and recombine in an organic thin layer to form excitons. Thus, the OLED emits light in a specific range of wavelengths determined by the energy created by the excitons. 
         [0007]    The OLED display device may be classified into a passive matrix (PM) type and an active matrix (AM) type, depending on the driving method. The AM-type OLED display device may include a circuit that uses a thin film transistor (TFT). The PM-type OLED display device may be easily fabricated since the display region may include a simple matrix-type device with anodes and cathodes. However, the application range of the PM-type OLED display device is typically restricted to low-resolution, small-sized display devices because of the problems of resolution, the rise in driving voltage, and shortened life spans of materials. In the AM-type OLED display device, each pixel of a display device may include a TFT so that a constant amount of current can be supplied to each pixel to obtain stable luminescence. Also, since the AM-type OLED display device typically consumes low power, the AM-type OLED display device can realize high-resolution, large-sized display devices. 
         [0008]      FIG. 1  is a plan view of a display panel portion of an OLED display device. 
         [0009]    Referring to  FIG. 1 , a display panel portion  100  of the OLED display device can include a display panel  160  having a plurality of pixels, an upper power supply line  110 , which is disposed above the display panel  160  and applies a power supply voltage V DD , a lower power supply line  130 , which is disposed below the display panel  160  and applies the power supply voltage V DD , a reference voltage line  120 , which is disposed on one side of the display panel  160  and applies a reference voltage V SS , a scan driver  140 , which is disposed on the other side of the display panel  160  and outputs a scan signal, and a data driver  150 , which is disposed below the lower power supply line  130  and applies a data signal to the display panel  160 . 
         [0010]    The display panel  160  may include a plurality of pixels (not shown) formed in regions that may be defined by a plurality of scan lines (not shown) and a plurality of data lines (not shown). Each of the pixels may include a combination of red (R), green (G), and blue (B) sub-pixels and may receive the data signal and the scan signal from the data line and the scan line, respectively. 
         [0011]    The upper and lower power supply lines  110  and  130  may transmit a constant power supply voltage V DD  to the pixels of the display panel  160 . Thus, the upper and lower power supply lines  110  and  130  may be connected to the pixels of the display panel  160  and can apply the power supply voltage V DD  from an external power supply to the pixels. The upper and lower power supply lines  110  and  130  may be internally connected to each other. Although the upper and lower power supply lines  110  and  130  may receive separate voltages and apply the voltages to the pixels, the upper and lower power supply lines  110  and  130  generally receive the same voltage and apply the voltage to the pixels. 
         [0012]    The data driver  150  applies the data signal to the pixels through the data lines and the scan driver  140  applies the scan signal to the pixels through the scan lines, so that the pixels can be driven. 
         [0013]    The display panel portion  100  of the OLED display device can receive the power supply voltage V DD  from the external power supply and apply the power supply voltage V DD  to the pixels. In this case, since the voltage applied from the external power supply can differ from the voltage to be applied to the pixels, the OLED display device can require an additional voltage controller, such as a DC-DC converter. As a result, the circuit configuration of the OLED display device can become complicated. 
       SUMMARY 
       [0014]    According to one embodiment, an organic light emitting diode (OLED) display device comprises: a substrate; a secondary battery comprising a first electrode layer, a second electrode layer and an electrolyte layer interposed between the first and second electrode layers; a display panel comprising an array of organic light emitting diodes formed over the substrate, wherein the battery is interposed between the substrate and the display panel; and a power supply voltage line formed over the substrate and outside the display panel, wherein the power supply voltage line electrically interconnects the secondary battery and the display panel. 
         [0015]    According to another embodiment a method of fabricating an OLED display device comprises: providing a substrate; forming a secondary battery over the substrate comprising a first electrode layer, a second electrode layer and an electrolyte layer interposed between the first and second electrode layers; forming an array of transistor circuits over the secondary battery; and forming an array of organic light emitting diodes over the array of transistor circuits. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other features of the present disclosure will be described with respect to certain exemplary embodiments thereof with reference to the attached drawings in which: 
           [0017]      FIG. 1  is a plan view of a display panel portion of one example of an organic light emitting diode (OLED) display device; and 
           [0018]      FIGS. 2A through 2C  are cross-sectional views illustrating a method of fabricating an OLED display device according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The thicknesses of layers or regions shown in the drawings are exaggerated for clarity. The same reference numerals are used to denote the same elements throughout the specification. 
         [0020]      FIGS. 2A through 2C  are cross-sectional views illustrating a method of fabricating an organic light emitting diode (OLED) display device according to an exemplary embodiment. 
         [0021]    Referring to  FIG. 2A , the OLED display device according to an exemplary embodiment is formed by glass, synthetic resin, or stainless steel. A secondary battery including a first electrode layer  210 , an electrolyte layer  220 , and a second electrode layer  230  is formed on a substrate  200  having a pixel region A and a wiring region B. 
         [0022]    The first and second electrode layers  210  and  230  may have polarities opposite each other, and may be formed by coating an electrode active material layer (not shown) on the surface of an electrode collector (not shown). The electrode collector may be formed by a material selected from the group consisting of stainless steel, nickel, copper, aluminum, and an alloy thereof. Specifically, a positive electrode collector may be formed by aluminum or an aluminum alloy, and a negative electrode collector may be formed by copper or a copper alloy, so that the efficiency of the secondary battery can be maximized. 
         [0023]    A negative electrode active material layer, which is coated on a negative electrode collector, may be formed by a carbon material, such as crystalline carbon, amorphous carbon, a carbon composite, or a carbon fiber, a lithium metal, or a lithium alloy. Also, a positive electrode active material layer, which is coated on a positive electrode collector, may be formed by a lithium-containing transition metal oxide or lithium chalcogenide compound. For example, the positive electrode active material layer may be formed by LiCoO 2 , iNiO 2 , LiMnO 2 , LiMn 2 O 4 , or LiNi 1-x-y Co x M y O 2  (where 0≦x≦1, 0≦y≦1, 0≦(x+y)≦1, and M is a metal such as Al, Sr, Mg, and La). 
         [0024]    The electrolyte layer  220  may prevent a short circuit between the first electrode layer  210  and the second electrode layer  230  and provide a path through which lithium ions pass. According to an embodiment, the electrolyte layer  220  may be formed by a solid electrolyte, such as LiPON. Accordingly, the electrolyte layer  220  can be obtained by a deposition process typically used to fabricate an OLED display device such as, for example, a plasma-enhanced chemical vapor deposition (PECVD) or a sputtering process. 
         [0025]    Referring to  FIG. 2B , a first insulating layer  240  may be formed on the substrate  200  having the secondary battery so that the secondary battery is electrically insulated from an organic light emitting diode and a TFT to be formed in subsequent processes as described further below. The first insulating layer  240  may be of a material selected from the group consisting of a silicon oxide (SiO 2 ) layer, a silicon nitride (SiN X ) layer, and a stacked layer thereof. 
         [0026]    Thereafter, an amorphous silicon (a-Si) layer (not shown) may be deposited on the first insulating layer  240  in the pixel region A and then crystallized into a polycrystalline silicon (poly-Si) layer (not shown). The poly-Si layer may be patterned to form a semiconductor layer  245 , and a gate insulating layer  250  may be deposited on the substrate  200  over the semiconductor layer  245 . In the illustrated embodiment, the gate insulating layer  250  may be of a material selected from the group consisting of a silicon oxide (SiO 2 ) layer, a silicon nitride (SiN X ) layer, and a stacked layer thereof. 
         [0027]    A metal layer (not shown) for a gate electrode may be formed on the gate insulating layer  250 . The metal layer may be a single layer of aluminum (Al), or an aluminum alloy such as aluminum-neodymium (Al—Nd), or a double layer obtained by stacking an aluminum alloy on a molybdenum (Mo) alloy. The metal layer may then be etched using photolithography and etching processes to form a gate electrode  255  in a specific region corresponding with the semiconductor layer  245 . The specific region may be a region corresponding with a channel region  246  to be formed in a subsequent process as further described below. 
         [0028]    Subsequently, the semiconductor layer  245  may be doped with conductive impurity ions using the gate electrode  255  as a mask, thereby forming source and drain regions  244 . A region interposed between the source and drain regions  244  can function as the channel region  246 . In another case, the doping process may be performed using photoresist before the gate electrode  255  is formed. 
         [0029]    Referring to  FIG. 2C , an interlayer insulating layer  260  may be formed on the substrate  200  over the gate electrode  255 , and the gate insulating layer  250  and the interlayer insulating layer  260  in the pixel region A may be etched using photolithography and etching processes, thereby forming a first contact hole  262  partially exposing the source and drain regions  244  of the semiconductor layer  245 . Also, the gate insulating layer  250 , the interlayer insulating layer  260 , and the first insulating layer  240  in the wiring region B may be etched using photolithography and etching processes, thereby forming a second contact hole  266  partially exposing the second electrode layer  230  of the secondary battery. In the illustrated embodiment, before the gate insulating layer  250  is formed, the first insulating layer  240  in the wiring region B may be etched using photolithography and etching processes to form an opening partially exposing the second electrode layer  230 . Thereafter, portions of the gate insulating layer  250  and the interlayer insulating layer  260  corresponding with the opening may be etched using photolithography and etching processes during the formation of the first contact hole  262  in pixel region A, thereby forming the second contact hole  266  in wiring region B. 
         [0030]    Thereafter, source and drain electrodes  264  may be formed on the interlayer insulating layer  260  to be connected to the source and drain regions  244  through the first contact holes  262  in pixel region A. A power supply voltage line  268  may also be formed on the interlayer insulting layer  260  to be connected to the second electrode  230  of the secondary battery through the second contact hole  266  in wiring region B. The power supply voltage line  268  may be an upper power supply voltage line, a lower power supply voltage line, or a reference power supply voltage line. The source and drain electrodes  264  in pixel region A and the power supply voltage line  268  in pixel region B may be formed separately, but formed by the same material at the same time to facilitate the fabrication process. 
         [0031]    Although not shown in the figures, a protective layer may be formed on the TFT including the semiconductor layer  245 , the gate electrode  255 , the source and drain electrodes  264 , and the power supply voltage line  268 . Then, an organic light emitting diode (OLED) including a third electrode, one or more organic emission layers, and a fourth electrode may be formed on the protective layer in the pixel region A. According to one embodiment, a planarization layer may be formed on the protective layer, and the third electrode may include a reflective layer pattern. The planarization layer may be an organic insulating layer formed by acryl, an inorganic insulating layer formed by silicon oxide, or a stacked layer thereof. 
         [0032]    In the OLED display device according to an exemplary embodiment, a secondary battery may be formed in a lower portion and connected to a power supply voltage line, so that a power supply voltage can be transmitted to a plurality of pixels formed on the display panel. The voltage generated by the secondary battery typically ranges from 3V to 5V, while the voltage applied from the power supply voltage line to drive each of the pixels typically ranges from 4V to 5V. As a result, the OLED display device according to an exemplary embodiment can apply the voltage generated by the secondary battery located in the lower portion to each pixel without requiring an additional voltage controller, such as a DC-DC converter. 
         [0033]    Furthermore, in the OLED display device according to an exemplary embodiment, since an electrolyte layer of the secondary battery is formed by a solid electrolyte, the secondary battery may be obtained through a deposition process typically used to fabricate an OLED display device. Therefore, a semi-permanent power supply may be installed inside the OLED display device without the use of additional apparatus, so that even if an external power supply voltage is interrupted, the OLED display device can be driven for a predetermined amount of time. 
         [0034]    According to the embodiments described above, a secondary battery can be formed through a fabrication process typically used to form an OLED display device without the use of an additional apparatus. Also, the secondary battery may be connected to a power supply voltage line so that a power supply voltage generated by the secondary battery can be applied to each of the pixels without an additional voltage controller. As a consequence, circuit configuration for the OLED display device can be facilitated. 
         [0035]    Although embodiments of the present invention has been described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims, and their equivalents.