Organic light emitting diode display

1. An organic light emitting diode display comprising:

a substrate;

a first electrode placed over the substrate, wherein the first electrode has a refractive index;

an organic emissive layer placed over the first electrode, wherein the organic emissive layer comprises a red light emitting layer, a green light emitting layer, and a blue light emitting layer, which are not overlapping with each other when viewing in a direction orthogonal to a display surface of the organic light emitting diode display;

a second electrode placed over the organic emissive layer; and

a refractive layer disposed between the substrate and the first electrode, wherein the refractive layer has a refractive index that is greater than the refractive index of the first electrode and is between about 2.2 to about 3.0 and wherein the refractive layer comprises a first refractive sub-layer disposed between the red light emitting layer and the substrate, a second refractive sub-layer disposed between the green light emitting layer and the substrate, and a third refractive sub-layer disposed between the blue light emitting layer and the substrate, wherein the first, second, and third refractive sub-layers substantially differ in thickness from each other and wherein the first refractive sub-layer is thicker than the second refractive sub-layer, and the third refractive sub-layer is thicker than the first refractive sub-layer and the second refractive sub-layer.

2. The organic light emitting diode display of claim 1 , wherein the refractive layer comprises at least one material selected from the group consisting of TiO 2 , ZnO 2 , and ZrO 2 .

3. The organic light emitting diode display of claim 1 , wherein the first electrode comprises a material substantially transparent for visible light, and the second electrode comprises a material substantially reflective for visible light.

4. An organic light emitting diode display comprising:

a substrate;

a first electrode substantially transparent with respect to visible light and having a refractive index, wherein the first electrode comprises:

a first sub-electrode;

a second sub-electrode; and

a third sub-electrode;

wherein the first, second and third sub-electrodes differ in thickness from each other;

a refractive layer disposed between the substrate and the first electrode, wherein the refractive layer has a refractive index that is greater than the refractive index of the first electrode and wherein the refractive layer comprises:

a first refractive sub-layer;

a second refractive sub-layer; and

and a third refractive sub-layer;

wherein the first, second, and third refractive sub-layers differ in thickness from each other, wherein the second sub-electrode is thicker than the first sub-electrode, which is thicker than the third sub-electrode;

a second electrode substantially reflective with respect to the visible light; and

an organic emissive layer placed between the first and second electrodes, wherein the organic emissive layer comprises a first main emitting layer configured to emit red light, a second main emitting layer configured to emit green light, and a third main emitting layer configured to emit blue light.

5. The organic light emitting diode display of claim 4 , wherein the first sub-electrode is interposed between the first refractive sub-layer and the first main emitting layer,

wherein the second sub-electrode is interposed between the second refractive sub-layer and the second main emitting layer,

wherein the third sub-electrode is interposed between the third refractive sub-layer and the third main emitting layer.

6. The organic light emitting diode display of claim 4 , wherein the refractive index of the refractive layer is between about 2.2 to about 3.0.

7. The organic light emitting diode display of claim 4 , wherein the insulating material comprises at least one of TiO2, ZnO2, and ZrO2.

8. The organic light emitting diode display of claim 4 , wherein the display is configured to permit a light beam emitted by the organic emissive layer to the first electrode to be transmitted through the first electrode and to the refractive layer.

9. The organic light emitting diode display of claim 4 , wherein the display is further configured to permit the light beam to be transmitted through the refractive layer and to the substrate.

10. The organic light emitting diode display of claim 1 , wherein the display is further configured to permit the light beam to be reflected at the refractive layer and back towards the first electrode.

11. The organic light emitting diode display of claim 4 , wherein the light beam is incident to the refractive layer through the first electrode at an incident angle greater than a critical angle of the refractive layer.

12. An organic light emitting diode display comprising:

a substrate;

a first electrode placed over the substrate, wherein the first electrode has a refractive index, wherein the first electrode comprises a first sub-electrode disposed between the red light emitting layer and the refractive layer, a second sub-electrode disposed between the green light emitting layer and the refractive layer, and a third sub-electrode disposed between the blue light emitting layer and the refractive layer, wherein the first, second and third sub-electrodes substantially differ in thickness from each other, wherein the first sub-electrode is thicker than the third sub-electrode, and the second sub-electrode is thicker than the first sub-electrode and the third sub-electrode;

an organic emissive layer placed over the first electrode, wherein the organic emissive layer comprises a red light emitting layer, a green light emitting layer, and a blue light emitting layer, which are not overlapping with each other when viewing in a direction orthogonal to a display surface of the organic light emitting diode display;

a second electrode placed over the organic emissive layer; and

a refractive layer disposed between the substrate and the first electrode, wherein the refractive layer has a refractive index that is greater than the refractive index of the first electrode and is between about 2.2 to about 3.0.

13. The organic light emitting diode display of claim 12 , wherein the red light emitting layer, the green light emitting layer and the blue light emitting layer have substantially the same thickness.