Organic light emitting diode display

1. An organic light emitting diode display, including at least one organic light emitting diode (OLED) comprising:

a first electrode;

a hole injection layer on the first electrode;

an emission layer on the hole injection layer;

an electron injection layer on the emission layer; and

a second electrode on the electron injection layer,

wherein an absolute value of a difference between a work function of the first electrode and a work function of the second electrode is less than 0.5 eV, and the first electrode and the second electrode include materials different from each other;

wherein the hole injection layer is an at least three-layer multilayer that includes a first hole injection layer, a second hole injection layer, and a third hole injection layer, wherein:

an energy level of the second hole injection layer is less than an energy level of the third hole injection layer,

an energy level of the first hole injection layer is less than the energy level of the second hole injection layer,

the first hole injection layer is closest to the first electrode of the first, second, and third hole injection layers, and

the third hole injection layer is farthest from the first electrode of the first, second, and third hole injection layers; and

wherein the electron injection layer is an at least three-layer multilayer that includes a first electron injection layer, a second electron injection layer, and a third electron injection layer, wherein:

an energy level of the second electron injection layer is less than an energy level of the third electron injection layer,

an energy level of the first electron injection layer is less than the energy level of the second electron injection layer,

the first electron injection layer is farthest from the second electrode of the first, second, and third electron injection layers, and

the third electron injection layer is closest to the second electrode of the first, second, and third electron injection layers.

2. The organic light emitting diode display as claimed in claim 1 , wherein the hole injection layer has a HOMO (Highest Occupied Molecular Orbital) energy level between a HOMO energy level of the first electrode and a HOMO energy level of the emission layer.

3. The organic light emitting diode display as claimed in claim 1 , wherein the electron injection layer has an LUMO (Lowest Unoccupied Molecular Orbital) energy level between an LUMO energy level of the second electrode and an LUMO energy level of emission layer.

4. The organic light emitting diode display as claimed in claim 1 , wherein the hole injection layer has a HOMO energy level between a HOMO energy level of the first electrode and a HOMO energy level of the emission layer, and the electron injection layer has an LUMO energy level between an LUMO energy level of the second electrode and an LUMO energy level of the emission layer.

5. The organic light emitting diode display as claimed in claim 1 , further comprising a hole transport layer formed between the first electrode and the hole injection layer.

6. The organic light emitting diode display as claimed in claim 1 , further comprising an electron transport layer formed between the second electrode and the electron injection layer.

7. The organic light emitting diode display as claimed in claim 1 , wherein the work function of the first electrode is different from the work function of the second electrode.

8. An organic light emitting diode (OLED), comprising:

a first electrode;

a hole injection layer on the first electrode;

an emission layer on the hole injection layer;

an electron injection layer on the emission layer; and

a second electrode on the electron injection layer,

wherein an absolute value of a difference between a work function of the first electrode and a work function of the second electrode is less than 0.5 eV, and the first electrode and the second electrode include materials different from each other;

wherein the hole injection layer is an at least three-layer multilayer that includes a first hole injection layer, a second hole injection layer, and a third hole injection layer, wherein:

an energy level of the second hole injection layer is less than an energy level of the third hole injection layer,

an energy level of the first hole injection layer is less than the energy level of the second hole injection layer,

the first hole injection layer is closest to the first electrode of the first, second, and third hole injection layers, and

the third hole injection layer is farthest from the first electrode of the first, second, and third hole injection layers; and

wherein the electron injection layer is an at least three-layer multilayer that includes a first electron injection layer, a second electron injection layer, and a third electron injection layer, wherein:

an energy level of the second electron injection layer is less than an energy level of the third electron injection layer,

an energy level of the first electron injection layer is less than the energy level of the second electron injection layer,

the first electron injection layer is farthest from the second electrode of the first, second, and third electron injection layers, and

the third electron injection layer is closest to the second electrode of the first, second, and third electron injection layers.

9. The OLED as claimed in claim 8 , wherein:

the hole injection layer has a HOMO (Highest Occupied Molecular Orbital) energy level between a HOMO energy level of the first electrode and a HOMO energy level of the emission layer, and

the electron injection layer has an LUMO (Lowest Unoccupied Molecular Orbital) energy level between an LUMO energy level of the second electrode and an LUMO energy level of emission layer.

10. An organic light emitting diode (OLED), comprising:

a first electrode;

a hole injection layer on the first electrode;

an emission layer on the hole injection layer;

an electron injection layer on the emission layer;

a second electrode on the electron injection layer; and

a hole transport layer arranged between the first electrode and the hole injection layer and/or an electron transport layer arranged between the second electrode and the electron injection layer,

wherein: an absolute value of a difference between a work function of the first electrode and a work function of the second electrode is less than 0.5 eV, and the first electrode and the second electrode include materials different from each other;

wherein the hole injection layer is an at least three-layer multilayer that includes a first hole injection layer, a second hole injection layer, and a third hole injection layer, wherein:

an energy level of the second hole injection layer is less than an energy level of the third hole injection layer,

an energy level of the first hole injection layer is less than the energy level of the second hole injection layer,

the first hole injection layer is the closest hole injection layer to the first electrode of the first, second, and third hole injection layers, and

the third hole injection layer is the farthest hole injection layer from the first electrode of the first, second, and third hole injection layers; and

wherein the electron injection layer is an at least three-layer multilayer that includes a first electron injection layer, a second electron injection layer, and a third electron injection layer, wherein:

an energy level of the second electron injection layer is less than an energy level of the third electron injection layer,

an energy level of the first electron injection layer is less than the energy level of the second electron injection layer,

the first electron injection layer is farthest from the second electrode of the first, second, and third electron injection layers, and

the third electron injection layer is closest to the second electrode of the first, second, and third electron injection layers.