Abstract:
An organic light emitting display device, which may maximize aperture ratio of a pixel while also reducing the perception of a dark spot when a sub-pixel is partially short-circuited. The organic light emitting display device includes a plurality of pixels having sub-pixels. Some of the sub-pixels may have a thin organic emission layer which makes them likely to short-circuit across the thin organic emission layer. These sub-pixels are formed as divided sub-pixels including at least two drive transistors and operate such that even if one part of the divided sub-pixel has a short circuit, the other part will continue to emit light. Accordingly, while luminance is reduced as a result of short circuiting, a completely dark spot will not appear in the place of the pixel including the short circuit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0108795, filed on Nov. 14, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.  
       BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an organic light emitting display device, and more particularly to an organic light emitting display device decreasing the perception of a dark pixel occurring due to a short-circuit between a first electrode and a second electrode of an organic light emitting diode.  
         [0004]     2. Discussion of Related Art  
         [0005]     Organic light emitting display devices are spontaneous emission devices that emit light by re-combination of electrons supplied from a cathode and holes supplied from an anode. An electroluminescent (EL) display using the organic light emitting display device does not require additional back light, has a wider angle of visibility, higher response speed compared with a passive EL device, a lower direct current drive voltage, and can be formed in a ultra-thin pattern. Therefore, it may be implemented in a wall hanging type of display or a portable display.  
         [0006]     The organic light emitting display device is driven either by a passive matrix method or by an active matrix method using a thin film transistor. In a display driven according to the passive matrix method, an anode and a cathode are formed to intersect, and a line is selected to be driven. In a display driven according to the active matrix method, a thin film transistor is connected to each anode electrode (indium tin oxide (ITO)) and is driven by a voltage maintained by a capacitor, which is connected to a gate of the thin film transistor.  
         [0007]      FIG. 1  is a block diagram showing a conventional organic light emitting display device. The conventional organic light emitting display device includes a display region  10 , a data driver  20 , and a scan driver  30 .  
         [0008]     The display region  10  includes a plurality of data lines D 1 , D 2 , D 3  . . . Dm, and a plurality of scan lines S 1 , S 2 , S 3  . . . Sn, arranged to cross directions, and a plurality of pixels  11 . The data lines D 1 , D 2 , D 3  . . . Dm carry a data signal, and the scan lines S 1 , S 2 , S 3  . . . Sn carry a scan signal. The pixels  11  are formed at intersections of the data lines D 1 , D 2 , D 3  . . . Dm and the scan lines S 1 , S 2 , S 3  . . . Sn.  
         [0009]     The data driver  20  outputs a data signal indicating an image signal through the data lines D 1 , D 2 , D 3  . . . Dm. The scan driver  30  sequentially outputs a select signal through the scan lines S 1 , S 2 , S 3  . . . Sn to drive the pixel  11 . The pixel  11  may include sub-pixels.  
         [0010]      FIG. 2  is a circuit diagram showing one unit pixel of the conventional organic light emitting display device, and shows a representative pixel among n×m pixels of the display region in the organic light emitting display device shown in  FIG. 1 .  
         [0011]     As shown in  FIG. 2 , the circuit of pixel  11  includes an organic light emitting diode OLED, a switching transistor M 1 , a drive transistor M 2 , a capacitor Cst, a scan line Sn, and a data line Dm. When the pixel  11  includes sub-pixels, each sub-pixel would include a similar circuit.  
         [0012]     A gate of the switching transistor M 1  is connected to the scan line Sn, and a source thereof is connected to the data line Dm. The switching transistor M 1  transfers a data signal from the data line Dm to a gate of the drive transistor M 2  in response to a select signal from the scan line Sn. A source of the drive transistor M 2  is connected to a power source voltage ELVDD, and a capacitor Cst is connected between a gate and the source of the drive transistor M 2 . The capacitor Cst maintains the gate-source voltage V gs  of the drive transistor M 2  during a predetermined time period.  
         [0013]     A cathode b of the organic light emitting diode OLED is connected to a reference voltage ELVSS. The organic light emitting diode OLED emits light according to an electric current applied through the drive transistor M 2 . The reference voltage ELVSS connected to the cathode b of the organic light emitting diode OLED is less than the power source voltage ELVDD, and a ground voltage can be used as the reference voltage ELVSS.  
         [0014]     The electric current flowing through the organic light emitting diode OLED is expressed by a following equation 1:  
               I   OLED     =         β   2     ⁢       (       V   gs     -     V   th       )     2       =       β   2     ⁢       (       V   DD     -     V   data     -          V   th            )     2                 (   1   )             
 
 where, I OLED  is the electric current flowing through the organic light emitting diode OLED, V gs  is a voltage between a gate and a source of the drive transistor M 2 , V th  is a threshold voltage of the drive transistor M 2 , V data  is a data voltage, and β is a constant. 
 
         [0015]     As indicated in the equation 1, according to the pixel circuit shown in  FIG. 2 , an electric current corresponding to applied data voltage V data  is supplied to the organic light emitting diode OLED, so that the organic light emitting diode OLED emits light corresponding to the applied data voltage V data .  
         [0016]      FIG. 3  is a plan view showing one unit pixel of the conventional organic light emitting display device. This plan view may also correspond to a sub-pixel within a pixel.  
         [0017]     The conventional unit pixel includes a scan line  32  arranged along one direction, a data line  31  arranged along a direction intersecting the direction of the scan line  32 , and a power supply line  37  arranged parallel with the data line  31  to intersect the scan line  32 . Furthermore, the switching transistor  33  is connected to the scan line  32  and the data line  31 , respectively. A capacitor includes a lower electrode  35  and an upper electrode  36 . The lower electrode  35  is connected to one of source/drain electrodes  34  of the switching transistor  33  through a contact hole. The upper electrode  36  is connected to the power supply line  37  and is arranged at an upper side of the lower electrode  35  of the capacitor. A gate  38  of the drive transistor  39  is connected to the lower electrode  35  of the capacitor. The drive transistor  39  includes a source/drain electrode  40  that is connected to an anode electrode a through a via  41 .  
         [0018]     In the conventional unit pixel, the organic light emitting diode OLED includes the anode electrode a, an organic emission layer, and a cathode electrode b. The anode electrode a is formed on a substrate. The organic emission layer is formed over an upper surface of the anode electrode a. The cathode electrode b is formed over an upper surface of the organic emission layer. The cathode electrode b and the organic emission layer are not shown in  FIG. 3 .  
         [0019]     Furthermore, only the organic emission layer (shown in  FIG. 4 ) exists between the anode electrode a and the cathode electrode b. An insulation film exists around the anode electrode. This prevents the anode electrode a and the cathode electrode b from electrically conducting to each other without the current first passing through the organic emission layer.  
         [0020]     However, in the conventional organic light emitting diode OLED, one anode electrode and one cathode electrode are arranged in one unit pixel. During the manufacturing process, minute dust is interposed between the anode electrode and the cathode electrode. Due to patterning flaws and external pressure, the anode electrode and the cathode electrode that are to be insulated from each other, may contact and conduct, thereby causing a short. This is shown in  FIG. 4 .  
         [0021]      FIG. 4  is a cross-sectional view showing a short-circuit between an anode electrode and a cathode electrode of a conventional organic light emitting display device. Reference numeral a represents the anode electrode, reference numeral b represents the cathode electrode, and reference numeral c represents minute dust.  
         [0022]     As shown in  FIG. 4 , because the minute dust c penetrates the insulation film between the anode electrode a and the cathode electrode b, the anode electrode a and the cathode electrode b are short-circuited. Due to the short-circuit between the anode electrode a and the cathode electrode b, a cathode voltage ELVSS is applied to the anode electrode a. Accordingly, the drain current of the drive transistor, that corresponds to the data signal, flows into the shorted cathode electrode b instead of into the organic emission layer, thereby not emitting the intended color. This causes a dark pixel to be displayed and deteriorates the image.  
         [0023]     Typically, a unit pixel includes a plurality of sub-pixels. Each of the sub-pixels includes an organic film having a different material and thickness according to a color to be embodied. Many dark pixels due to a short-circuit between the anode electrode a and the cathode electrode b may occur at a sub-pixel formed by a thin organic emission layer. According to experimental results, the occurrence rate of a progressive dark pixel in a blue sub-pixel is more than 10 times other colors. An improved scheme is therefore desirable.  
       SUMMARY OF THE INVENTION  
       [0024]     Accordingly, embodiments of the present invention provide an organic light emitting display device which may maximize aperture ratio of a pixel while reducing the perception of the deterioration of a pixel when a sub-pixel of the pixel is short-circuited.  
         [0025]     Embodiments of the invention include an organic light emitting display device including a plurality of pixels, each pixel having at least two sub-pixel, wherein a sub-pixel having a thinner organic emission layer compared to other sub-pixels includes at least two drive transistors.  
         [0026]     One embodiment of the present invention provides an organic light emitting display device including a plurality of pixels formed where a plurality of scan lines and a plurality of data lines cross over one another or where the directions of the scan lines intersect the directions of the data lines. Each pixel includes at least one divided sub-pixel. The divided sub-pixel includes at least two drive transistors being electrically connected to each other to receive the same gate to source voltage. A data signal is transferred through the data lines to the drive transistors. The sub-pixel also includes an organic light emitting diode having first electrodes receiving an electric current corresponding to the drive transistors, organic emission layers being formed over the first electrodes, and second electrode being formed over the organic emission layers. When the pixel includes several sub-pixels, a sub-pixel having a thinner organic emission layer is formed as the divided sub-pixel.  
         [0027]     According to one aspect of the present invention, there is provided an organic light emitting display device including a plurality of pixel formed at intersections of directions of a plurality of scan lines and directions of a plurality of data lines, each unit pixel including at least one divided sub-pixel. A sub-pixel having an organic emission layer the thickness of which is thinner than any other sub-pixel includes is formed as a divided sub-pixel. The divided sub-pixel includes a switching transistor having a gate connected to the scan lines and a source connected to the data lines, a capacitor having a lower electrode connected to a drain of the switching transistor and an upper electrode connected to a power source, at least two drive transistors connected to each other to share the same gate to source voltage, a source of each drive transistor being connected to the power source and a drain of each being connected to the drain of the switching transistor, and an organic light emitting diode including first electrodes receiving an electric current corresponding to the drive transistors, organic emission layers being formed over the first electrodes, and second electrode being formed over the organic emission layers.  
         [0028]     According to one aspect of the present invention, there is provided an organic light emitting display device including a plurality of pixel formed at intersections of directions of a plurality of scan lines and directions of a plurality of data lines, each unit pixel including at least one divided sub-pixel. A sub-pixel having an organic emission layer the thickness of which is thinner than any other sub-pixel is formed as a divided sub-pixel and includes a switching transistor having a gate connected to the scan lines and a source connected to the data lines, a capacitor having a first electrode connected to a drain of the switching transistor and a second electrode connected to a power source, at least two drive transistors connected to each other to share the same gate to source voltage, sources of both of the drive transistors being commonly connected to the power source and a gate of each drive transistor being connected to the drain of the switching transistor, and an organic light emitting diode including first electrodes receiving an electric current corresponding to the drive transistors, organic emission layers being formed at the first electrodes, and a second electrode being formed on the organic emission layers.  
         [0029]     The organic light emitting display device according to the embodiments of the present invention includes a drive transistor and an organic light emitting diode having first electrodes and a second common electrode, which are formed at a sub-pixel of a pixel having an organic emission layer the thickness of which is thinner than any other sub-pixels. Accordingly, even when a short between one of the first electrodes and the second electrode occurs, organic light emitting diodes corresponding to the remaining first electrode emit light. As a result, it becomes difficult to visually recognize the deterioration of the unit pixel due to the occurrence of a dark pixel.  
         [0030]     In addition, the organic light emitting display device of the present invention can prevent a reduction in an aperture ratio in comparison with a case of having drive transistors, a first electrode, and an organic emission layer, which are formed at every one of the sub-pixels.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a block diagram showing a conventional organic light emitting display device.  
         [0032]      FIG. 2  is a circuit diagram showing a pixel of the conventional organic light emitting display device.  
         [0033]      FIG. 3  is a plan view showing a pixel of the conventional organic light emitting display device.  
         [0034]      FIG. 4  is a cross-sectional view showing a short-circuit between an anode electrode and a cathode electrode of an organic light emitting diode included in the conventional organic light emitting display device.  
         [0035]      FIG. 5A  is plan view of a pixel according to an embodiment of the present invention.  
         [0036]      FIG. 5B  is a circuit diagram of a divided sub-pixel having a thin organic emission layer according to an embodiment of the present invention.  
         [0037]      FIG. 6  is a circuit diagram of a divided sub-pixel including NMOS-type drive transistors according to an embodiment of the present invention.  
         [0038]      FIG. 7  is a plan view of a divided sub-pixel of an organic light emitting display device according to an embodiment of the present invention.  
         [0039]      FIG. 8  is a cross-sectional view of the divided sub-pixel of  FIG. 7  taken along a line I-I′ according to an embodiment of the present invention.  
         [0040]      FIG. 9  is a block diagram showing an organic light emitting display device according to the embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0041]      FIG. 5A  is a plan view of a unit pixel  500  according to an embodiment of the present invention. The unit pixel  500  is shown to include three sub-pixels  501 ,  502 ,  503 . A first sub-pixel  501  has an organic emission layer whose thickness is thinner than that of any other sub-pixel. The first sub-pixel  501  includes two drive transistors M 2 , M 3 , and two first electrodes a 1  and a 2 . The first sub-pixel  501  is, therefore, a divided sub-pixel. Each of other sub-pixels  502 ,  503  includes one drive transistor and a first electrode.  
         [0042]      FIG. 5B  is a circuit diagram showing a sub-pixel having a thin organic emission layer according to an embodiment of the present invention. The sub-pixel shown is a divided sub-pixel included in a representative pixel among n×m pixels, and is connected to a data line Dm and a scan line Sn.  
         [0043]     The circuit for the divided sub-pixel includes a switching transistor M 1 , a first drive transistor M 2 , a second drive transistor M 3 , a capacitor Cst, and an organic light emitting diode OLED having two anode electrodes a 1 , a 2 . The organic light emitting diode OLED also has a cathode electrode b corresponding to both anode electrodes a 1 , a 2 . In the exemplary embodiment shown, the first drive transistor M 2  and the second drive transistor M 3  are PMOS transistors.  
         [0044]     A gate of the switching transistor M 1  is connected to the scan line Sn. The switching transistor M 1  transfers a data voltage from the data line Dm connected to a source of the switching transistor M 1  to gates of the first and second drive transistors M 2 , M 3  in response to a select signal from the scan line Sn.  
         [0045]     A source of the first drive transistor M 2  is connected to a power source of voltage ELVDD, the gate thereof is connected to a drain of the switching transistor M 1 , and a drain of the first drive transistor is connected to the first anode electrode a 1  of the organic light emitting diode OLED.  
         [0046]     A source of the second drive transistor M 3  is connected to the power source of voltage ELVDD, the gate thereof is connected to the drain of the switching transistor M 1 , and a drain of the second drive transistor M 3  is connected to the second anode electrode a 2  of the organic light emitting diode OLED.  
         [0047]     That is, the sources of the first and second drive transistors M 2 , M 3  are connected in common and the gates of these two transistors are also connected together.  
         [0048]     The capacitor Cst is connected between the common node between the gates and the common node between the sources of the first and second drive transistors M 2 , M 3 . The capacitor Cst maintains a gate-source voltage Vgs during a predetermined time period.  
         [0049]     Cathode electrodes of the organic light emitting diode OLED are connected to a reference voltage ELVSS in common. The first and second anode electrodes a 1 , a 2  of the organic light emitting diode OLED are connected to the drains of the first and second drive transistors M 2 , M 3 , respectively. The organic light emitting diode OLED emits light corresponding to a current from the first and second drive transistors M 2 , M 3 .  
         [0050]     When a select signal is applied to the gate of the switching transistor M 1 , the switching transistor M 1  is turned on to transfer and store the data signal from the data line Dm to and in the capacitor Cst. Next, the data signal stored in the capacitor Cst is transferred to the first and second drive transistors M 2 , M 3 . Accordingly, the first drive transistor M 2  and the second drive transistor M 3  provide a drive current expressed by the equation 1 corresponding to the applied data signal to the organic light emitting diode OLED through the first and second anode electrodes a 1 , a 2 , respectively. The organic light emitting diode OLED emits light according to the drive currents received from the first and second drive transistors M 2 , M 3 .  
         [0051]     On the other hand, due to fabrication problems arising from external pressure or minute dust, one or both of the anode electrodes may be shorted to the cathode electrode b resulting in a defective pixel. If, for example, the second anode electrode a 2 , and the cathode electrode b are shorted, the drive current flowing through the second drive transistor M 3  connected to the second anode electrode a 2  shorts directly into the cathode electrode b, so the organic light emitting diode corresponding to the second anode electrode a 2  does not emit light.  
         [0052]     However, a normal current flows through the organic light emitting diode corresponding to the first anode electrode a 1 , causing this organic light emitting diode to emit light. In this case, the emission luminance is smaller because only one of the two diodes is emitting.  
         [0053]     However, since embodiments of the present invention do not result in a completely dark pixel, it becomes difficult to visually recognize the deterioration of the pixel.  
         [0054]     Although the first and second drive transistors M 2 , M 3  are shown as PMOS transistors in  FIGS. 5A and 5B , they can also be NMOS transistors.  
         [0055]      FIG. 6  is a circuit for a divided sub-pixel including NMOS-type drive transistors according to one embodiment of the present invention.  
         [0056]     The circuit of  FIG. 6  includes a switching transistor M 1 , a first drive transistor M 2 ′, a second drive transistor M 3 ′, a capacitor Cst, and an organic light emitting diode OLED having two cathode electrodes b 1 ′, b 2 ′ and a common anode electrode a′. The first drive transistor M 2 ′ and the second drive transistor M 3 ′ are NMOS transistors.  
         [0057]     A gate of the switching transistor M 1  is connected to a scan line Sn. The switching transistor M 1  transfers a data voltage from the data line Dm connected to a source of the switching transistor M 1  to gates of the first and second drive transistors M 2 ′ and M 3 ′ in response to a select signal from the scan line Sn.  
         [0058]     A source of the first drive transistor M 2 ′ is connected to a power source of voltage ELVSS, the gate of it is connected to a drain of the switching transistor M 1 , and a drain of the first drive transistor M 2 ′ is connected to the first cathode electrode b 1 ′ of the organic light emitting diode OLED.  
         [0059]     A source of the second drive transistor M 3 ′ is connected to a power source of voltage ELVSS, a gate thereof is connected to a drain of the switching transistor M 1 , and a drain of the second drive transistor M 3 ′ is connected to the second cathode electrode b 2 ′ of the organic light emitting diode OLED.  
         [0060]     That is, the sources of the first and second drive transistors M 2 ′ and M 3 ′ are connected together forming a common node and the gates of these two transistors are also connected together forming another common node.  
         [0061]     The capacitor Cst is connected between the common node connecting the gates of the first and second transistors M 2 ′ and M 3 ′ and the common node connecting the source of these two transistors. The capacitor Cst maintains a gate-source voltage Vgs for these two transistors during a predetermined time period.  
         [0062]     Anode electrodes of the organic light emitting diode OLED are both connected to a power source of voltage ELVDD. The commonly connected anode electrodes are shown as the common anode electrode a′. The first and second cathode electrodes b 1 ′ and b 2 ′ of the two organic light emitting diodes OLED are respectively connected to the drains of the first and second drive transistors M 2 ′ and M 3 ′.  
         [0063]     Since the driving operation of the sub-pixel circuit of  FIG. 6  can be understood by those skilled in the art based on the driving operation of the sub-pixel circuit of  FIGS. 5A and 5B , a detailed description of the operation of the circuit of  FIG. 6  is omitted. Further, a plan view and a cross-sectional view of a divided sub-pixel circuit will be explained based on a circuit using PMOS transistors.  
         [0064]      FIG. 7  is a plan view of a divided sub-pixel of an organic light emitting display device according to an embodiment of the present invention. This sub-pixel may be included in a pixel.  
         [0065]     The sub-pixel of  FIG. 7  includes a scan line  132  arranged in one direction, a data line  131  arranged along an intersecting direction of the scan line  132 , and a power supply line  137  arranged parallel with the data line  131  to intersect the scan line  132 .  
         [0066]     Furthermore, the switching transistor  133  is connected to the scan line  132  and the data line  131 . A capacitor includes a lower electrode  135  and an upper electrode  136 . The lower electrode  135  is connected to one of source/drain electrodes  134  of the switching transistor  133  through a contact hole. The upper electrode  136  is connected to the power supply line  137 . In the plan view shown, the upper electrode  136  is located over the lower electrode  135  of the capacitor.  
         [0067]     A gate  141  of the first drive transistor  140  is connected to the lower electrode  135  of the capacitor, and a source of this transistor is connected to the power supply line  137 . A gate  151  of the second drive transistor  150  is connected to the lower electrode  135  of the capacitor, and a source thereof is connected to the power supply line  137 .  
         [0068]     The organic light emitting diode OLED includes an anode electrode, which is divided into first and second anode electrodes a 1 , a 2 . An organic emission layer is formed over the first and second anode electrodes a 1 , a 2 , and a common cathode electrode is formed over the organic emission layer. The first anode electrode a 1  is connected to one of the source or drain electrodes of the first drive transistor  140  through a via. In the exemplary embodiment shown, the first anode electrode a 1  is connected to the drain  143  of the first drive transistor  140  through the via  144 . The second anode electrode a 2  is connected to one of the source or drain electrodes of the second drive transistor through a via. In the exemplary embodiment shown, the second anode electrode a 2  is connected to the drain electrode  153  of the second drive transistor  150  through the via  154 . The first and second anode electrodes a 1 , a 2  can be formed to have equal or different areas.  
         [0069]     Accordingly, for example, when the second anode electrode a 2  and the cathode electrode b short-circuit, a drive current from the second drive transistor  150  does not flow through the organic emission layer. Instead, the current flows directly to the cathode electrode b, with the result that light is not emitted from the portion of the organic emission layer corresponding to the short circuit. However, some light is still emitted because a drive current from the first drive transistor  140  still flows through another portion of the organic emission layer from the first anode electrode a 1 . In this example, an emission area of the unit pixel corresponding to the second anode electrode a 2  does not emit light, but an area corresponding to the first anode electrode a 1  continues to emit light. This results in emission of light at a reduced emission luminance. Yet, short circuiting in the unit pixel of the present invention does not result in a completely dark pixel. This causes a user to have difficulty in visually recognizing the deterioration of a pixel.  
         [0070]      FIG. 8  is a cross-sectional view of the sub-pixel of  FIG. 7  taken along a line I-I′.  
         [0071]     A buffer layer  205  may be formed on a substrate  200 , and first and second semiconductor layers  210 ,  220  are formed over the buffer layer  205 . The buffer layer  205  is not required. However, it can be formed to prevent introduction of impurities into the device from the substrate. The buffer layer  205  can be formed from silicon nitride (SiN x ) film, silicon oxide (SiO 2 ) film, or silicon nitrogen oxide (SiO x N y ) film. The first semiconductor layer  210  is formed from amorphous or crystalline silicon film. The first semiconductor layer  210  includes a source region  210   a , a drain region  210   b , and a channel region  210   c . The second semiconductor layer  220  is formed from amorphous or crystalline silicon film. The second semiconductor layer  220  includes a source contact region  220   a , a drain contact region  220   b , and a channel region  220   c . A gate insulation film  230  and gate electrodes  215 ,  225  are located over the substrate and above the first and second semiconductor layers  210 ,  220 . An interlay insulating film  240  is formed over the resulting object. Further, source/drain electrodes  217   a / 217   b ,  227   a / 227   b  are formed above the interlay insulation film but going through the layers of interlay insulation film and the gate insulation film to contact the source/drain regions  210   a / 210   b ,  220   a / 220   b  of the first and second semiconductor layers  210 ,  220 .  
         [0072]     A passivation layer  250  is formed over the source/drain electrodes  217   a / 217   b ,  227   a / 227   b  in order to protect the lower layers from external moisture or impurities during an etching step of the manufacturing process. The passivation layer  250  is formed from a laminate film of SiO 2 , SiN x , or SiO 2 /SiN x .  
         [0073]     A planarization layer  260  may be formed over the passivation layer  250 . First and second anode electrodes  270  and  280  are located over the planarization layer  260 . The first and second anode electrodes  270  and  280  can be formed from a transparent conductive material such as ITO or indium zinc oxide (IZO). However, the present invention is not limited to ITO and IZO anodes, and the anodes can be formed from a laminate film including a reflection film such as Al, Al alloy, Ag, or Ag alloy of high reflection rate, and a transparent conductive film such as ITO or IZO.  
         [0074]     The first anode electrode  270  contacts the source or drain electrodes  217   a ,  217   b , for example, the drain electrode  217   b , through a via  262  formed through the passivation layer  250  and the planarization layer  260 . The second anode electrode  280  contacts the source or drain electrodes  227   a ,  227   b , for example, the drain electrode  227   b , through a via  263  formed through the passivation layer  250  and the planarization layer  260 .  
         [0075]     A pixel defining layer (PDL)  285  is formed over the first and second anode electrodes  270  and  280 . As shown, the PDL  285  is etched to have two pixel opening regions so that the first and second anode electrodes  270  and  280  are exposed.  
         [0076]     An organic emission layer  290  is formed on the portions of the first and second anode electrodes  270  and  280  that are exposed in the two pixel opening regions. A common cathode electrode  295  is formed over the organic emission layer  290 , so that an organic light emitting display device can be achieved.  
         [0077]     In the organic light emitting display device of one embodiment of the present invention, if a short-circuit occurs between one of anode electrodes and a cathode electrode of a sub-pixel that is susceptible to short-circuiting, the sub-pixel does not emit light while another sub-pixel corresponding to another anode electrode may continue to emit light in a normal fashion. Accordingly, it becomes difficult to visually recognize and perceive the deterioration of the pixel due to the occurrence of the short-circuit in one of the pixel&#39;s sub-pixels.  
         [0078]     A circuit for a divided sub-pixel including an organic light emitting diode having two drive transistors, two anode electrodes, and a common cathode electrode, which are formed at a sub-pixel having a relatively thin organic emission layer, was described with reference to  FIG. 5  to  FIG. 8 . The relatively thin dimension of the organic emission layer in the sub-pixel may render the sub-pixel conducive to short circuiting due to fabrication flaws. Similarly, and according to the principles described above, a circuit including an organic light emitting diode having more than two drive transistors may be used for some of the sub-pixels of a pixel. This circuit that may include n drive transistors, n anode electrodes, and a common cathode electrode, falls within the system and methods described above.  
         [0079]     Further, although the two drive transistors are shown as PMOS transistors in  FIG. 7  and  FIG. 8 , they may be instead NMOS transistors as shown in  FIG. 6 . In this case, the organic light emitting diode OLED includes two cathode electrodes and a common anode electrode. The two cathode electrodes are connected to drains of the two NMOS transistors, and the anode electrode is connected to a power source of voltage ELVDD. Sources of the two NMOS transistors are connected to a reference voltage ELVSS in common.  
         [0080]      FIG. 9  is a block diagram showing an organic light emitting display device according to the embodiments of the present invention. The organic light emitting display device of the embodiments of the invention includes a display region  910 , a data driver  920 , and a scan driver  930 . The display region  910  includes a plurality of data lines D 1 , D 2 , D 3  . . . Dm, and a plurality of scan lines S 1 , S 2 , S 3  . . . Sn, arranged to cross directions, and a plurality of pixels  911 . The data lines D 1 , D 2 , D 3  . . . Dm carry a data signal, and the scan lines S 1 , S 2 , S 3  . . . Sn carry a scan signal. The pixels  911  are formed at intersections of the data lines D 1 , D 2 , D 3  . . . Dm and the scan lines S 1 , S 2 , S 3  . . . Sn. The data driver  920  outputs a data signal indicating an image signal through the data lines D 1 , D 2 , D 3  . . . Dm. The scan driver  930  sequentially outputs a select signal through the scan lines S 1 , S 2 , S 3  . . . Sn to drive the pixel  911 . The pixels  911  may each include sub-pixels as described above. Each pixel  911  includes at least one divided sub-pixel.  
         [0081]     Although certain exemplary embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes might be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.