Organic light emitting display device

1. An organic light emitting display device, comprising:

a substrate;

a plurality of pixels on the substrate, each pixel having a first region configured to emit light and a second region configured to transmit external light;

a plurality of pixel circuit units, each pixel circuit unit being in the first region of each of the plurality of pixels and including at least one thin film transistor;

a plurality of first electrodes, each first electrode being in the first region of each of the plurality of pixels and being electrically connected to a respective pixel circuit unit, the first electrode having an island shape corresponding to a respective pixel of the plurality of pixels;

a first organic layer covering the plurality of first electrodes;

a second organic layer on the first organic layer, the second organic layer including an emission layer;

a third organic layer on the second organic layer, the third organic layer being positioned in the first region and outside a central portion of the second region; and

a second electrode having a first portion only on the third organic layer.

2. The organic light emitting display device as claimed in claim 1 , wherein the first organic layer includes at least one of a hole transport layer and a hole injection layer, and the third organic layer includes at least one of an electron transport layer and an electron injection layer.

3. The organic light emitting display device as claimed in claim 1 , wherein the third organic layer is only in the first region, the second electrode being only and directly on the third organic layer.

4. The organic light emitting display device as claimed in claim 1 , wherein the first organic layer is only in the first region, the third organic layer completely overlapping the first organic layer.

5. The organic light emitting display device as claimed in claim 1 , wherein the first organic layer is in the first region and the second region, the first organic layer extending beyond the third organic layer.

6. The organic light emitting display device as claimed in claim 5 , wherein the second electrode further comprises a second portion on the first organic layer in the second region, the first and second portions of the second electrode being connected to each other.

7. The organic light emitting display device as claimed in claim 6 , wherein a thickness of the second portion is smaller than a thickness of the first portion.

8. The organic light emitting display device as claimed in claim 1 , wherein the plurality of pixel circuit units overlaps the plurality of first electrodes, respectively.

9. The organic light emitting display device as claimed in claim 1 , wherein the first region of each of the plurality of pixels includes a light emission region and a circuit region, each of the plurality of pixel circuit units being in the circuit region, and each of the plurality of first electrodes being in the light emission region.

10. The organic light emitting display device as claimed in claim 9 , wherein the light emission region and the circuit region of the each of the plurality of pixels are adjacent to each other.

11. The organic light emitting display device as claimed in claim 1 , further comprising an insulating layer covering ends of each of the plurality of first electrodes, the third organic layer separating the second electrode from the insulating layer.

12. The organic light emitting display device as claimed in claim 1 , wherein the second electrode includes magnesium (Mg).