Top emission organic light emitting diode display using auxiliary electrode to prevent voltage drop of upper electrode
An organic light emitting diode (OLED) display. The OLED display includes: a lower electrode formed on a layer on an insulating substrate having a thin film transistor. The lower electrode is electrically connected to the thin film transistor. An auxiliary electrode is formed on the same layer as the lower electrode, and a pixel defining layer is formed on edges of the lower electrode, thereby defining an opening which exposes a portion of the lower electrode. An organic layer is formed on the portion of the lower electrode exposed by the opening, and an upper electrode is formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode. An edge of the auxiliary electrode may have a taper angle of at least 90°.
1. An organic light emitting diode display, comprising:
a lower electrode formed on a first layer on an insulating substrate having a thin film transistor, the lower electrode being electrically connected to the thin film transistor;
an auxiliary electrode formed on the first layer, the auxiliary electrode having a top side and at least one edge forming an angle with the top side;
a pixel defining layer formed on edges of the lower electrode, thereby defining an opening which exposes a portion of the lower electrode;
an organic layer formed on the top side of the auxiliary electrode and the portion of the lower electrode exposed by the opening; and
an upper electrode formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode through the at least one edge.
2. The organic light emitting diode display as claimed in claim 1 , wherein the auxiliary electrode includes an edge with a taper angle of greater than 90°, such that a portion of the auxiliary electrode away from the first layer is wider than a portion of the auxiliary electrode adjacent the first layer.
3. The organic light emitting diode display as claimed in claim 2 , wherein the edge of the auxiliary electrode has the taper angle between 90° and 135°.
4. The organic light emitting diode display as claimed in claim 1 , wherein the auxiliary electrode prevents or reduces a voltage drop of the upper electrode.
5. The organic light emitting diode display as claimed in claim 1 , wherein the lower electrode and the auxiliary electrode are made of a conductive material having a work function larger than that of a material of the upper electrode.
6. The organic light emitting diode display as claimed in claim 1 , wherein the lower electrode and the auxiliary electrode are made of a material having low specific resistance and high reflectivity.
7. The organic light emitting diode display as claimed in claim 1 , wherein the lower electrode and the auxiliary electrode are made of a single layer or a multilayer.
8. The organic light emitting diode display as claimed in claim 1 , wherein the lower electrode and the auxiliary electrode are made of one selected from a group consisting of Al, Mo, MoW, Ti, Ag/ITO, Ag/Mow, and MoW/Al(Nd)/ITO.
9. The organic light emitting diode display as claimed in claim 1 , wherein the lower electrode and the auxiliary electrode are thicker than the organic layer.
10. The organic light emitting diode display as claimed in claim 9 , wherein the lower electrode and the auxiliary electrode each have a thickness of at least 3,000Å.
11. The organic light emitting diode display as claimed in claim 1 , wherein the auxiliary electrode is arranged in a linear pattern.
12. The organic light emitting diode display as claimed in claim 1 , wherein the auxiliary electrode is arranged in a grid pattern.
13. The organic light emitting diode display as claimed in claim 1 , wherein the auxiliary electrode is connected to a cathode inlet terminal of a pad portion.
14. The organic light emitting diode display as claimed in claim 1 , wherein a top surface of the auxiliary electrode has a length which is greater than or equal to that of a bottom surface of the auxiliary electrode.
15. The organic light emitting diode display as claimed in claim 14 , wherein the auxiliary electrode prevents or reduces a voltage drop of the upper electrode.
16. The organic light emitting diode display as claimed in claim 14 , wherein the length of the top surface of the auxiliary electrode has a range from a value equal to the length of the bottom surface of the auxiliary electrode to a sum of twice a thickness of the auxiliary electrode and the length of the bottom surface of the auxiliary electrode.
17. The organic light emitting diode display as claimed in claim 14 , wherein the lower electrode and the auxiliary electrode are thicker than the organic layer.
18. The organic light emitting diode display as claimed in claim 17 , wherein the lower electrode and the auxiliary electrode each have a thickness of at least 3,000Å.
19. An organic light emitting diode display, comprising:
a lower electrode formed on an insulating substrate having a thin film transistor, the lower electrode being electrically connected to the thin film transistor;
an auxiliary electrode formed on the insulating substrate, the auxiliary electrode having an edge with a taper angle greater than 90°, such that a portion of the auxiliary electrode away from the insulating substrate is wider than a portion of the auxiliary electrode proximate to the insulating substrate;
a pixel defining layer formed on edges of the lower electrode, thereby defining an opening which exposes a portion of the lower electrode;
an organic layer formed on the auxiliary electrode and the portion of the lower electrode exposed by the opening; and
an upper electrode formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode through the edge.