Abstract:
An organic light emitting device includes a first pixel displaying a first color, a second pixel adjacent to the first pixel and displaying a second color, and a third pixel adjacent to the first pixel or the second pixel and displaying a third color, wherein the first pixel includes a first and second subpixel units that output respective lights having different color characteristics.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and benefit of Korean Patent Application No. 10-2008-0037339 filed in the Korean Intellectual Property Office on Apr. 22, 2008, the entire contents of which application are incorporated herein by reference. 
     BACKGROUND 
     (a) Field of Invention 
     The present disclosure of invention relates to an organic light emitting device (OLED). 
     (b) Description of Related Technology 
     An organic light emitting device (OLED) typically includes a plurality of pixel units, and each pixel unit includes an organic light emitting element and a plurality of thin film transistors (TFT&#39;s) for driving the same. 
     The typical organic light emitting element includes an anode, a cathode, and an organic light emitting member disposed therebetween. The composition of each organic light emitting member is such that when activated it emits light corresponding to one of three colors such as the three primary colors red, green, and blue, or it emits white light. The material used for each organic light emitting member depends on the color or white light that the given organic light emitting member is intended to emits. A white light can be generated for example by stacking side-by-side or otherwise light emitting materials that emit red, green, and blue so that the synthesized light appears white. Moreover, in the case where the organic light emitting member emits white light, a color filter may be added over it to obtain light of a desired color. 
     However, light emitted from the respective pixel units may not have desired optical characteristics such as desired wavelength(s) or bandwidth or color purity due to variations in the material characteristics of the organic light emitting element and/or due to light interference by a thin film through which the unit generated light passes. Moreover, the range that can be displayed by the light may be limited. 
     SUMMARY 
     The present disclosure of invention provides an organic light emitting device of improved characteristics. An exemplary organic light emitting device in accordance with the disclosure includes a first pixel displaying a first color, a second pixel adjacent to the first pixel and displaying a second color, and a third pixel adjacent to the first pixel or the second pixel and displaying a third color, wherein the first pixel includes a first subpixel unit and a second subpixel unit emitting lights having different color characteristics. 
     The different color characteristics define substantially spaced apart color coordinates on a gamut map associated with the organic light emitting device such that the human eye perceives an expanded range of colors. 
     The first and second subpixel units may each have a multi-layered thin film structure, but the number of thin films in the first subpixel unit may be greater than that of the second subpixel thus providing substantially different processing of pre-emission light in the first subpixel unit and resulting in a substantially different output spectrum. In one embodiment, the first subpixel unit has a transflective electrode whereas the second subpixel unit does not. In one embodiment, the independently controllable first and second subpixel units are provided in the green light emitting area of a repeated RGB light producing structure. 
     The second pixel (e.g., Red) may have a multi-layered thin film structure including a second transflective electrode, and the third pixel (e.g., Blue) may have a multi-layered thin film structure including a third transflective electrode. The number of thin films in of each of the second and third pixel s may be the same as that of the first subpixel unit in the first pixel area (e.g., Green). 
     In the same or an alternate embodiment, the second pixel area may include third and fourth subpixel units emitting lights having respectively different color characteristics defined as spaced apart color coordinates on a color gamut map. The third and fourth subpixel units may have multi-layered thin film structures, where the number of thin films in the third subpixel unit may be the same as that for the first subpixel unit, and where the number of thin films in the fourth subpixel unit may be the same as that for the second subpixel unit. In one embodiment, the third subpixel unit includes a second transflective electrode. 
     The third pixel may have a multi-layered thin film structure including the third transflective electrode, and the number of thin films of the third pixel may be the same as that of the thin films of the first and third subpixel units. The first color may be red, the second color may be blue, and the third color may be green. 
     In the same or an alternate embodiment, the third pixel may include fifth and sixth subpixel units respectively emitting light having different color characteristics defined as spaced apart color coordinates on the color gamut map. The fifth and sixth subpixel units may each have a multi-layered thin film structure, where the number of thin films in the fifth subpixel unit may be the same as that of the first and third subpixels units, and where the number of thin films in the sixth subpixel unit may be the same as that of the second and fourth subpixel units. The fifth subpixel unit may include a third transflective electrode 
     An organic light emitting device in accordance with the disclosure may include: a thin film structure (e.g., TFT&#39;s) formed on a transparent substrate; first, second, and third transflective electrodes formed on the thin film structure; a first transparent electrode formed on the first transflective electrode; a second transparent electrode formed directly on the thin film structure and having a same drive voltage as applied to the first transparent electrode; a third transparent electrode formed on the second transflective electrode; a fourth transparent electrode formed on the third transflective electrode; a first organic light emitting member formed on the first transparent electrode and displaying a first color; a second organic light emitting member formed on the second transparent electrode and displaying the first color; a third organic light emitting member formed on the third transparent electrode and displaying a second color; a fourth organic light emitting member formed on the fourth transparent electrode and displaying a third color; and a common electrode formed on the first to fourth organic light emitting members. 
     The first color may be green, the second color may be red, and the third color may be blue. 
     The organic light emitting device may further include a fifth transparent electrode formed directly on the thin film structure and having a same drive voltage the third transparent electrode, and a fifth organic light emitting member formed on the fifth transparent electrode and displaying the second color. The first color may be red, the second color may be blue, and the third color may be green. 
     The organic light emitting device may further include a sixth transparent electrode formed directly on the thin film structure and having a same drive voltage as the fourth transparent electrode, and a sixth organic light emitting member formed on the sixth transparent electrode and displaying the third color. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are drawings showing respective possible pixel area and subpixel arrangements for an organic light emitting device in accordance with an exemplary first embodiment; 
         FIG. 2  is an equivalent circuit diagram of the organic light emitting device of  FIGS. 1A and 1B ; 
         FIG. 3  is a cross-sectional view schematically showing the organic light emitting device of  FIGS. 1A and 1B  including the multilayer thin film structures; 
         FIG. 4  is a spectral graph showing light intensity of the two subpixel units of  FIG. 3 ; 
         FIG. 5  is a graph showing a range of colors (gamut map) that the organic light emitting device of  FIG. 3  can display; 
         FIG. 6  is a drawing showing a pixel arrangement of an organic light emitting device in accordance with another exemplary embodiment; 
         FIG. 7  is a cross-sectional view schematically showing the organic light emitting device of  FIG. 6 ; 
         FIG. 8  is a gamut map showing a range of colors that the organic light emitting device of  FIG. 7  can display; and 
         FIG. 9  is a drawing showing a pixel arrangement of an organic light emitting device in accordance with yet another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure of invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. 
     In the drawings, the thickness of layers, films, panels, regions, etc., may be exaggerated for clarity. Like reference numerals generally designate like elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     First, an organic light emitting device in accordance with an exemplary first embodiment will be described in detail with reference to  FIGS. 1 to 5  below. 
       FIGS. 1A and 1B  show possible pixel and subpixel arrangements of organic light emitting devices in accordance with exemplary embodiments.  FIG. 2  is an equivalent circuit diagram of the organic light emitting devices shown in  FIGS. 1A and 1B .  FIG. 3  is a schematic cross-sectional view of the organic light emitting device shown in  FIGS. 1A and 1B .  FIG. 4  is a graph showing light intensity of two subpixels shown in  FIG. 3 .  FIG. 5  is a graph showing a range (gamut) of colors that the organic light emitting device shown in  FIG. 3  can selectively emit. 
     As shown in  FIGS. 1A and 1B , an organic light emitting device in accordance with the first exemplary embodiment includes a red pixel RP, a green pixel GP, and a blue pixel BP. The green pixel GP includes two subpixels GP 1  and GP 2  having different color characteristics. (See briefly  FIG. 4 .) For example, color coordinates in a gamut map of the greens that the two subpixels GP 1  and GP 2  respectively produce may be different from each other. 
     In the pixel and subpixel arrangement shown in  FIG. 1A , the red pixel RP and the blue pixel BP, which have rectangular light emitting areas with a width to length ratio of about 4:3, are aligned one above the other (and this pattern continues up and down the display panel column) while the two subpixels GP 1  and GP 2  of the green pixel GP have rectangular light emitting areas each with a width (X) to height (Y) ratio of about 2:3, where the heights of the two subpixels GP 1  and GP 2  respectively match the heights on the right sides (or alternatively left sides) respectively of the green pixel RP and the blue pixel BP positioned next to them. The total light emitting area of the two subpixels GP 1  and GP 2  may be substantially the same as that of each of the red pixel RP and the blue pixel BP. 
     In the pixel arrangement shown in  FIG. 1B , the red pixel RP, the green pixel GP, and the blue pixel BP, which are rectangles each with a width to length ratio of about 1:3, are arranged horizontally in a row. The two equally-sized subpixels GP 1  and GP 2  of the green pixel GP subdivide the GP areas in half and are arranged one above the other as shown (or alternatively in a reversed up/down order). 
     There may be various arrangements other than those shown in  FIGS. 1A and 1B  that provide similar effects and these are to be deemed within the scope of the present disclosure. 
     Each of the red pixel RP, the blue pixel BP, and the subpixels GP 1  and GP 2  of the green pixel GP may be independently activated by a respective data capture and LD driving circuit such as the one shown in  FIG. 2 . 
     Referring to  FIG. 2 , each pixel unit PX (or subpixel unit) is respectively connected to respective signal lines such as the illustrated  121 ,  171 , and  172 . 
     The signal lines includes a plurality of horizontal gate lines  121  for transmitting gate signals (or data capture scanning signals), a plurality of vertical data lines  171  for transmitting analog data signals, and a plurality of vertical driving voltage lines  172  for supplying driving voltages. The gate lines  121  extend substantially in a row direction and are substantially parallel to each other, and the data lines  171  extend substantially in a column direction and are substantially parallel to each other. Although the driving voltage lines  172  are shown as extending substantially in a column direction, they may extend in a row direction or in a column direction, or may be formed in a matrix or as an underlying circuit plane. 
     Each pixel or subpixel unit PX includes a switching transistor Qs, a driving transistor Qd, a storage capacitor Cst, and an organic light emitting element represented schematically as diode LD. 
     The switching transistor Qs includes a control terminal, an input terminal, and an output terminal, in which the control terminal is connected to a gate line  121 , the input terminal is connected to a data line  171 , and the output terminal is connected to the driving transistor Qd. The switching transistor Qs transmits a data signal sampled off from the data line  171  to the driving transistor Qd in response to an active scanning signal (e.g., pulse) received from the gate line  121 . 
     The driving transistor Qd also includes a control terminal, an input terminal, and an output terminal, in which the control terminal is connected to the switching transistor Qs and to a charge storage capacitor Cst, the input terminal is connected to a driving voltage line  172  (and to an opposed terminal of the charge storage capacitor Cst), and the output terminal is connected to the organic light emitting element LD. The driving transistor Qd applies an output current I LD  having a magnitude that varies according to a voltage difference between the control terminal and the output terminal as stored on the storage capacitor Cst. The storage capacitor Cst which is connected between the control terminal and the input terminal of the driving transistor Qd stores the data signal applied to the control terminal of the driving transistor Qd and maintains the stored data signal even after the switching transistor Qs is turned off. 
     The organic light emitting element LD, which is an organic light emitting diode (OLED), for example, has an anode connected to the output terminal of the driving transistor Qd and a cathode connected to a common voltage Vss. The organic light emitting element LD emits light having an intensity that depends on an output current I LD  of the driving transistor Qd, to thereby display a corresponding pixel of an image. 
     In one embodiment, the switching transistor Qs and the driving transistor Qd are n-channel field effect transistors (FET); however, at least one of the switching transistor Qs and the driving transistor Qd may be a p-channel FET instead. Moreover, the connection relationship among the transistors Qs and Qd, the storage capacitor Cst, and the organic light emitting element LD may be changed to provide similar functions but with different circuit arrangements depending on the types of transistors used. 
     If necessary, additional transistors (not shown) for compensating for threshold voltages of the driving transistor Qd and the organic light emitting element LD may be further provided in each pixel unit PX in addition to the switching transistor Qs and the driving transistor Qd. 
     The respective switching transistors Qs of the two subpixels GP 1  and GP 2  of the green pixel GP may be connected to a same gate line  121  and to a same data line  171 , and/or the two subpixels GP 1  and GP 2  of the green pixel GP may share at least one of the switching transistor Q 2  and the driving transistor Qd. Otherwise, the switching transistors Qs of the two subpixels GP 1  and GP 2  of the green pixel GP may be connected to different data lines  171  to thereby receive independent data signals or to different gate lines  121  to thereby be activated to capture respective data signals at different times. In this case, the respective luminance output by each of the two subpixels GP 1  and GP 2  is independently determined and a synthesized joint luminance of the two subpixels GP 1  and GP 2  may be made substantially equal to a target luminance within a gamut (see briefly  FIG. 5 ) which includes the maximum outputs of subpixels GP 1  and GP 2  as corner points. 
     Moreover, when it comes to commonly used organic light emitting materials, the green pixel GP often has higher electric-to-apparent luminosity conversion efficiency than the red pixel RP and the blue pixel BP. Accordingly, when a greater number of the two subpixels GP 1  and GP 2  of the green pixel GP are used than that of the red pixel RP and the blue pixel BP, it is possible to more efficiently improve the apparent luminosity and/or chrominance perceived by a human eye for given image data for the respective pixels RP, GP, and BP. Thus there is an advantage to bifurcating the green pixel GP into independently controllable subpixels GP 1  and GP 2  having differing emission spectra (see briefly  FIG. 4 ). 
     Next, the cross-sectional structure of the organic light emitting element LD of each of the pixels RP, GP, and BP shown in  FIGS. 1A and 1B  will be described with reference to  FIG. 3 . 
     In  FIG. 3 , R and B are added as suffixes to the reference numerals related to the red pixel (RP) and to the reference numerals related to the blue pixel (BP), respectively. G 1  and G 2  are added as suffixes to the reference numerals related to the first subpixel G 1  and the second subpixel G 2  of the green pixel GP, respectively. 
     The organic light emitting device in accordance with the present exemplary embodiment is provided in the form of a thin film on an insulation substrate made of transparent glass or plastic. The signal lines  121 ,  171 , and  172  and the transistors Qs and Qd (not shown in  FIG. 3 ) are disposed below the organic light emitting element LD and may be covered by a passivation layer (not shown). In this way, the signal lines  121 ,  171  and  172 , the transistors Qs and Qd, and the passivation layer on the substrate will be referred to as a thin film structure  100  underlying the four OLED regions shown distinctly in  FIG. 3 . 
     A plurality of three transflective electrodes  192 R,  192 G, and  192 B are formed on the thin film structure  100 . The second subpixel GP 2  of the green pixel GP does not include such a transflective electrode or its optical equivalent (e.g., two thinner and spaced apart transflective electrical conductors). 
     The transflective electrodes  192 R,  192 G, and  192 B may be made of a metal having high reflectance such as silver (Ag) or aluminum (Al), and may have a thickness of about 150 Å to 200 Å. In this way, when the thickness is small even if it is metal, the metal has transflective characteristics in which some incident light may be reflected and some may be transmitted through. 
     A plurality of four pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B are respectively formed as shown over the areas of the three transflective electrodes  192 R,  192 G, and  192 B and over the GP 2  area of the thin film structure  100 . Since the second subpixel GP 2  of the green pixel GP does not include a transflective electrode, the pixel electrode  191 G 2  is positioned directly on the thin film structure  100  in the corresponding region to be in contact with the thin film structure  100 . 
     The pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B may be made of a transparent conductive material such as ITO or IZO, and may have a thickness of about 300 Å to 3000 Å. The pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B may be connected to the driving transistor through a contact hole (not shown) formed on the passivation layer of the thin film structure  100 . 
     Organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B are formed on the pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B. The organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B emit light of colors corresponding to the respective pixels RP, GP, and BP, in which the organic light emitting members  370 G 1  and  370 G 2  of the first subpixel GP 1  and the second subpixel GP 2  of the green pixel GP may be made in one embodiment, of the same material with the same thickness and thus originally emit green light having the same color characteristics. The thicknesses of the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B may vary according to the pixels RP, GP, and BP, and the thickness may be reduced in the order of the red pixel RP, the green pixel GP, and the blue pixel BP. Otherwise, the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B may have the same thickness. 
     Each of the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B may have a multi-layered structure including a light emission layer (not shown) for emitting light and an auxiliary layer (not shown) for improving the light emitting efficiency of the light emission layer. The auxiliary layer may include an electron transport layer (not shown) and a hole transport layer (not shown) that achieve a balance of electrons and holes, and an electron injecting layer (not shown) and a hole injecting layer (not shown) that improve the injection of electrons and holes. The thicknesses of the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B may be adjusted according to the thickness of the respective hole transport layer. 
     A common electrode  270  for applying the common voltage VSS is formed on the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B. Although  FIG. 3  shows that the common electrodes  270  are all separated from the pixels RP and BP and the subpixels GP 1 , they may be all connected thereto, which is to simplify the process. The common electrode  270  may be made of a reflective metal including calcium (Ca), barium (Ba), magnesium (Mg), aluminum (Al), silver (Ag), etc. 
     In the above-described organic light emitting device, the three transflective electrodes  192 R,  192 G, and  192 B, the four pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B, as well as the four organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B, and the common electrode  270  form a corresponding four organic light emitting elements LD, in which the pixel electrodes  191 R,  191 G 1 ,  191 G 2 , and  191 B define the anode and the common electrode  270  defines the cathode. 
     The organic light emitting device emits light toward the bottom of the substrate  100  to display an image. In the case of the red pixel RP, the first subpixel GP 1  of the green pixel GP, and the blue pixel BP, light emitted from the organic light emitting members  370 R,  370 G 1 , and  370 B to the thin film structure  100  passes through the pixel electrodes  191 R,  191 G 1 , and  191 B and then it reaches the transflective electrodes  192 R,  192 G, and  192 B. The transflective electrodes  192 R,  192 G, and  192 B partially reflect the incident light toward the common electrode  270 , and the common electrode  270  reflects the partially reflected light back towards the transflective electrodes  192 R,  192 G, and  192 B. In this way, light reciprocating between the transflective electrode  192  and the common electrode  270  is subjected to an optical process such as interference before it is output through the transflective electrodes  192 R,  192 G, and  192 B to the outside if appropriate conditions are imposed. 
     In this case, since the light path varies according to the thicknesses of thin films interposed between the transflective electrodes  192 R,  192 G, and  192 B and the common electrode  270 , it is possible to obtain different light emissions having desired optical characteristics such as broad or narrow ranges of wavelengths of desired bandwidths and spectral shapes and color purity or nonpurity, if the thicknesses of the thin films are appropriately selected. For example, as described above, it is possible to obtain light having a desired one or more wavelengths by varying the thicknesses of the organic light emitting members  370 R,  370 G 1 , and  370 B according to the pixels or subpixels in which they reside. 
     However, if the thickness of the transflective electrodes  192  is too large, the luminance of emitted light may be reduced, whereas if it is too small, it may difficult if not impossible to obtain the desired optical characteristics. Accordingly, in one embodiment, the thicknesses of the transflective electrodes  192  is in the range of about 150 Å to about 200 Å as described above. 
     Meanwhile, since the second subpixel GP 2  of the green pixel GP does not include a transflective electrode  192 , light emitted from its organic light emitting member  370 G 2  is directly emitted to the outside whereas light emitted from the organic light emitting members  370 R,  370 G 1 , and  370 B is both directly emitted to the outside and reflectively bounced back and forth between the transflective electrode  192  and the common electrode  270  and then emitted to the outside. Thus for the second subpixel GP 2  the latter particular optical interference does not occur whereas of the first subpixel GP 1  as well as for pixels RP and BP it does to one extent or another depending on specifics of the utilized layer thicknesses. 
     In this way, the color characteristics of light emitted from the first subpixel GP 1  and the second subpixel GP 2  of the green pixel GP may be caused to be different. 
       FIG. 4  shows for one embodiment, how the intensity and spectra of light emitted from the first subpixel GP 1  and the second subpixel GP 2  may be made to vary. Light C 1  emitted from the first subpixel GP 1  shows a sharp peak in the vicinity of green (around 525 nm), whereas light C 2  emitted from the second subpixel GP 2  may be made to show a relatively flat peak plateau around 550 nm for example and a sharp rise at the wavelength corresponding to the peak of the GP 1  light C 1 . 
       FIG. 5  is a graph (gamut map) showing a range of colors that the red pixel RP, the blue pixel BP, and the two subpixels GP 1  and GP 2  of the green pixel GP in the organic light emitting device can display, which shows color coordinates on the Commission Internationale de l&#39;Eclairage (CIE) 1931 chromaticity diagram. 
     In  FIG. 5 , R, B, G 1 , and G 2  are examples of corner color coordinates for the maximum luminosity outputs of light emitted respectively by the red pixel RP, the blue pixel BP, and the two subpixels GP 1  and GP 2  of the green pixel GP, respectively. In  FIG. 5 , G represents is an example of what the color corner coordinate would have been if the green pixel GP had not been divided into two independently driven and differently outputting subpixels. W is a color coordinate point of white. 
     If the green pixel GP had not been divided into two independent subpixels, then it would be possible to display only the various colors bounded within the triangle defined by the color corner coordinates of R, G, and B. However, when the green pixel GP is divided into two independently controllable subpixels GP 1  and GP 2  in accordance with the present exemplary embodiment, it is possible to display colors within a quadrilateral area defined by the color coordinates of R, G 1 , G 2 , and B, and thus the range of colors (the available gamut) that can be displayed is increased by about 40%. 
     Since the range of colors that can be displayed in the present exemplary embodiment is increased relative to the conventional tri-color RGB-only configuration, it is possible to obtain colors within a broader range (inside the R-G 1 -G 2 -B gamut) even if the organic light emitting members  370 R,  370 G 1 ,  370 G 2 , and  370 B are formed with a same thickness for process convenience and even though the organic light emitting materials of G 1  and G 2  are the same (again for process convenience). 
     Next, an organic light emitting device in accordance with another exemplary embodiment will be described in detail with reference to  FIGS. 6  to  FIG. 8 . 
       FIG. 6  is a drawing showing a five pixels/subpixels arrangement (R 1 /R 2 ,G,B 1 /B 2 ) of an organic light emitting device in accordance with the second exemplary embodiment.  FIG. 7  is a cross-sectional view schematically showing the organic light emitting device of  FIG. 6 , and  FIG. 8  is a graph showing a range of colors (gamut map) that the organic light emitting device of  FIG. 7  can display. 
     As shown in  FIG. 6 , the organic light emitting device in accordance with the R 1 /R 2 ,G,B 1 /B 2  embodiment includes a red pixel area RP, a green pixel area GP, and a blue pixel area BP. Each of the red pixel area RP and the blue pixel area BP includes two independently controllable subpixel units, RP 1  and RP 2 , and BP 1  and BP 2 , respectively, which have different color characteristics. For example, color coordinates in the gamut map ( FIG. 8 ) of red that the two red subpixel units RP 1  and RP 2  display may be different from each other, and color coordinates in the gamut map of blue that the two blue subpixels BP 1  and BP 2  display may be different from each other. 
     In the pixel arrangement shown in  FIG. 6 , the red pixel area RP, the green pixel area GP, and the blue pixel area BP, are each a rectangle with a width to length ratio of about 1:3, and they are arranged horizontally in a row as shown. (In an alternate embodiments, the pixel arrangement can be rotated as desired, including to a 90° rotation.) The subpixels RP 1 , RP 2 , BP 1 , and BP 2  of the respective red pixel area RP and the blue pixel area BP have the same size and are arranged up and down. 
     There may be various arrangements other than that shown in  FIG. 6 . 
     Next, the cross-sectional structure of the organic light emitting elements (LD&#39;s) of each of the pixels RP, GP, and BP as shown in  FIG. 6  will be described with reference to  FIG. 7 . 
     In  FIG. 7 , G is added as a suffix to the reference numerals related to the green pixel area GP. R 1  and R 2  are added to the reference numerals related to the first subpixel RP 1  and the second subpixel RP 2  of the red pixel area RP, respectively, and B 1  and B 2  are added to the reference numerals related to the first subpixel BP 1  and the second subpixel BP 2  of the blue pixel area BP, respectively. 
     The cross-sectional structure of the organic light emitting device in accordance with the present exemplary embodiment is generally similar to that of  FIG. 3 . That is, the red pixel area RP and the blue pixel area BP are each divided into two independently controllable subpixel units RP 1  and RP 2 , and BP 1  and BP 2 , respectively, and the green pixel unit GP is not divided into two subpixels. However, the basic structures and operations of the respective pixels RP, GP, and BP are substantially the same. 
     In more detail, a plurality of transflective electrode  192 R,  192 G, and  192 B are formed on a thin film structure  100  of  FIG. 7  in the areas shown. The second subpixel unit RP 2  of the red pixel area RP and the second subpixel unit BP 2  of the blue pixel area BP do not include a transflective electrode and thus their light emission spectra are different from those of corresponding units RP 1  and BP 1 . 
     A plurality of pixel electrodes  191 R 1 ,  191 R 2 ,  191 G,  191 B 1 , and  191 B 2  are formed on the transflective electrodes  192 R,  192 G, and  192 B and directly on the thin film structure  100  in the respective areas as shown. Since the second subpixel unit RP 2  of the red pixel area RP and the second subpixel unit BP 2  of the blue pixel area BP do not include a transflective electrode, the pixel electrodes  191 R 2  and  191 B 2  are positioned directly on the thin film structure  100  in the corresponding region to be in contact with the thin film structure  100 . 
     Organic light emitting members  370 R 1 ,  370 R 2 ,  370 G,  370 B 1 , and  370 B 2  are formed on the pixel electrodes  191 R 1 ,  191 R 2 ,  191 G,  191 B 1 , and  191 B 2 , and a common electrode  270  is formed thereon. 
     The organic light emitting device shown in  FIGS. 6 and 7  may display colors within a range (gamut map) shown in  FIG. 8 .  FIG. 8  is a graph showing a range of colors that the two subpixels RP 1  and RP 2  of the red pixel RP, the two subpixels BP 1  and BP 2  of the blue pixel BP, and the green pixel GP can display, which shows color coordinates on the CIE 1976 chromaticity diagram. 
     In  FIG. 8 , colors that the organic light emitting device in accordance with the present exemplary embodiment can display are within a pentagon defined by the color coordinates of R 1 , R 2 , G, B 1 , and B. The area of this pentagon may represent an increase of as much as about 70% over that of the conventional RGB triangle. Thus, by using the configuration of  FIG. 8  or similar pentagon configurations in accordance with its spirit, designers can display a wider gamut of colors. 
     Finally, an organic light emitting device in accordance with yet another exemplary embodiment will be described in detail with reference to  FIG. 9 . 
       FIG. 9  is a drawing showing a six subpixels arrangement (R 1 /R 2 , G 1 /G 2 , B 1 /B 2 ) of an organic light emitting device in accordance with this yet another exemplary embodiment. 
     As shown in  FIG. 9 , the organic light emitting device in accordance with the present exemplary embodiment includes a red pixel area RP, a green pixel area GP, and a blue pixel area BP, and each of the respective pixel areas RP, GP, and BP includes two independently controllable and differently emitting subpixel units: RP 1  and RP 2 , GP 1  and GP 2 , and BP 1  and BP 2  having respective different color characteristics. For example, color coordinates in the gamut map (not shown) of red that the two subpixels RP 1  and RP 2  display may be different from each other, color coordinates of green that the two subpixels GP 1  and GP 2  display may be different from each other, and color coordinates of blue that the two subpixels BP 1  and BP 2  display may be different from each other. 
     In the pixel arrangement shown in  FIG. 9 , the red pixel area RP, the green pixel area GP, and the blue pixel area BP, which are each a rectangle with a width to length ratio of about 1:3, are arranged horizontally in a row. The subpixel units RP 1 , RP 2 , GP 1 , GP 2 , BP 1 , and BP 2  of the respective pixel areas RP, GP, and BP have the same size and are arranged up and down as shown. 
     The cross-sectional structure of the organic light emitting device shown in  FIG. 9  may be generally the same as that of the green pixel area GP shown in  FIG. 3  combined with those of the red and blue pixel areas RP and BP shown in  FIG. 6 . 
     When each of the pixel areas RP, GP, and BP is respectively divided into two independently controllable subpixel units: RP 1  and RP 2 , GP 1  and GP 2 , and BP 1  and BP 2  having different color coordinates in accordance with the present exemplary embodiment, the range of colors that can be displayed is further increased. 
     In this way, it is possible to improve optical characteristics of the organic light emitting device and further increase the range of colors that can be displayed. 
     The concepts from present disclosure of invention may be applied to various types of organic light emitting devices. 
     While this disclosure describes what is presently considered to be practical exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the disclosure.