Organic light emitting diode device including multiple hole injection layers

1. An organic light emitting diode device, comprising:

a first electrode;

a second electrode facing the first electrode; and

a light emitting member disposed between the first electrode and the second electrode, the light emitting member including at least two light emitting units including a first light emitting unit and a second light emitting unit stacked on the first light emitting unit, the first and second light emitting units each displaying a different color,

wherein the first light emitting unit includes a first hole injection layer, a second hole injection layer directly on the first hole injection layer, a first hole transport layer directly on the second hole injection layer, and a first emission layer, a difference between a HOMO energy level of the first hole injection layer and a LUMO energy level of the second hole injection layer being smaller than about 0.5 eV,

wherein the second light emitting unit includes a third hole injection layer, a second hole transport layer, and an second emission layer, and

the first hole injection layer includes a different material from the first hole transport layer.

2. The organic light emitting diode device as claimed in claim 1 , wherein an ionization energy of the first hole injection layer is higher than an electron affinity of the second hole injection layer.

3. The organic light emitting diode device as claimed in claim 1 , wherein an ionization energy of the first hole injection layer is about 4.5 to about 6.5 eV, and

an electron affinity of the second hole injection layer is about 4.3 to about 6.3 eV.

4. The organic light emitting diode device as claimed in claim 1 , wherein an ionization energy of the second hole injection layer is higher than an ionization energy of the first hole injection layer and an ionization energy of the first hole transport layer.

5. The organic light emitting diode device as claimed in claim 1 , wherein the first hole injection layer and the second hole injection layer have different compositions.

6. The organic light emitting diode device as claimed in claim 5 , wherein the HOMO energy level of the first hole injection layer is different from the LUMO energy level of the second hole injection layer.

7. The organic light emitting diode device as claimed in claim 6 , wherein:

the first hole injection layer includes a triphenylamine derivative, and

the second hole injection layer includes a hexaazatriphenylene derivative.

8. The organic light emitting diode device as claimed in claim 1 , wherein:

the first hole injection layer includes a triphenylamine derivative, and

the second hole injection layer includes a hexaazatriphenylene derivative.

9. The organic light emitting diode device as claimed in claim 1 , wherein:

the first hole injection layer includes N,N′-diphenyl-N,N-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, and

the second hole injection layer includes 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.

10. The organic light emitting diode device as claimed in claim 1 , wherein the second hole injection layer is thinner than the first hole injection layer.

11. The organic light emitting diode device as claimed in claim 10 , wherein the second hole injection layer has a thickness of about 10 to about 200 Å.

12. The organic light emitting diode device as claimed in claim 1 , wherein the first light emitting unit or the second light emitting unit includes a red light emitting unit, a green light emitting unit, a blue light emitting unit, an orange light emitting unit, a white light emitting unit, or a combination thereof.

13. The organic light emitting diode device as claimed in claim 1 , wherein white color light is displayed from a single organic light emitting diode by combining lights of at least two light emitting units each displaying a different color.

14. The organic light emitting diode device as claimed in claim 1 , wherein the first light emitting unit further comprises a first electron transport layer disposed on the first emission layer,

wherein the first electron transport layer is directly adjacent to the third hole injection layer of the second light emitting unit.

15. The organic light emitting diode device as claimed in claim 1 , wherein the third hole injection layer of the second light emitting unit is disposed directly on the first electron transport layer of the first light emitting unit.