Large area organic light emitting diode display

1. An organic light emitting diode display, comprising:

a substrate including a display area defining a plurality of pixel areas in a matrix manner and a non-display area surrounding the display area;

a thin film transistor disposed in each pixel area;

an auxiliary cathode electrode disposed at the same layer with an element of the thin film transistor, and covering the display area and the non-display area;

a planar layer on the thin film transistor and the auxiliary cathode electrode;

an anode electrode connected to the thin film transistor and disposed in each pixel area on the planar layer;

an organic light emission layer disposed on the anode electrode;

a cathode electrode covering the whole surface of the display area on the organic light emission layer;

a protective electrode covering the auxiliary cathode electrode exposed through a cathode contact hole and contacting the cathode electrode,

wherein the cathode contact hole includes a first cathode contact hole exposing some portions of the auxiliary cathode electrode disposed in the non-display area, and a second cathode contact hole exposing some portions of the auxiliary cathode electrode disposed in the display area;

wherein the organic light emission layer and the cathode electrode are stacked on the protective electrode covering the auxiliary cathode electrode exposed by the second cathode contact hole; and

wherein the protective electrode covers an exposed surface of the auxiliary cathode electrode through the first and the second cathode contact holes; and

a welding point electrically connecting the protective electrode, the cathode electrode, and the auxiliary cathode electrode at the second cathode contact hole.

2. The device according to the claim 1 , wherein the protective electrode includes the same material with the anode electrode.

3. The device according to the claim 1 , further comprising a ground line disposed at the outer circumstance of the substrate at the non-display area,

wherein the cathode electrode expands to the non-display area and contacts the ground line.

4. The device according to the claim 1 , wherein the thin film transistor includes:

a gate element formed on the substrate;

a gate insulating layer covering the gate element; and

a source-drain element overlapping with some portions of the gate element on the gate insulating layer, and covered by the planar layer,

wherein the auxiliary cathode electrode is disposed at the same layer and includes the same material with any one of the gate element and the source-drain element.

5. The device according to the claim 1 , further comprising a welding point electrically connecting the cathode electrode to the protective electrode.

6. The device according to the claim 1 , wherein the auxiliary cathode electrode includes:

a metal layer having a copper material; and

a conductive layer stacked with the metal layer.

7. An organic light emitting diode display, comprising:

a substrate including a display area defining a plurality of pixel areas in a matrix manner and a non-display area surrounding the display area;

a thin film transistor disposed in each pixel area;

an auxiliary cathode electrode disposed at the same layer with an element of the thin film transistor;

a planar layer on the thin film transistor and the auxiliary cathode electrode;

an anode electrode connected to the thin film transistor and disposed in each pixel area on the planar layer;

an organic light emission layer disposed on the anode electrode;

a cathode electrode covering the whole surface of the display area on the organic light emission layer;

a protective electrode covering the auxiliary cathode electrode exposed through a cathode contact hole and contacting the cathode electrode; and

a ground line disposed at the outer circumstance of the substrate at the non-display area,

wherein the protective electrode disposed apart from the anode electrode with a predetermined distance expands to the non-display area and contacts the ground line.