Organic light emitting display device for enhancing efficiency

1. An organic light emitting display device comprising:

a first emission part between a first electrode and a second electrode, the first emission part including a first hole transport layer and a first emission layer; and

a second emission part on the first emission part, the second emission part including a second hole transport layer and a second emission layer,

wherein a thickness of the second hole transport layer is greater than a thickness of the first hole transport layer.

2. The organic light emitting display device of claim 1 , wherein the thickness of the first hole transport layer is 20 nm or less.

3. The organic light emitting display device of claim 1 , wherein the first emission part further comprises an electron blocking layer.

4. The organic light emitting display device of claim 3 , wherein a thickness of the electron blocking layer is greater than the thickness of the first hole transport layer, the thickness of the electron blocking layer being within a particular range that results in enhanced efficiency of the first emission layer in comparison with a conventional electron blocking layer having a thickness outside of the particular range.

5. The organic light emitting display device of claim 3 , wherein a sum of the thickness of the first hole transport layer and a thickness of the electron blocking layer is 40 nm or less.

6. The organic light emitting display device of claim 3 , wherein the first hole transport layer and the electron blocking layer are formed of a same material.

7. The organic light emitting display device of claim 3 , wherein a triplet energy level of the electron blocking layer is within a range of 2.7 eV to 2.9 eV.

8. The organic light emitting display device of claim 3 , wherein a triplet energy level of the electron blocking layer is greater than a triplet energy level of the first hole transport layer, and a thickness of the electron blocking layer is 30 nm or less.

9. The organic light emitting display device of claim 3 , further comprising: a third emission part on the second emission part, the third emission part including a third hole transport layer and a third emission layer.

10. The organic light emitting display device of claim 9 , wherein a thickness of the third hole transport layer is less than a thickness of the second hole transport layer.

11. The organic light emitting display device of claim 9 , wherein at least one among the first hole transport layer and the third hole transport layer comprises a material having a triplet energy level within a same range as a range of a triplet energy level of the electron blocking layer.

12. The organic light emitting display device of claim 9 , wherein when the third hole transport layer includes a material having a triplet energy level within a same range as a range of a triplet energy level of the electron blocking layer of the first emission part, a thickness of the electron blocking layer in the first emission part is less than the thickness of the first hole transport layer.

13. The organic light emitting display device of claim 9 , wherein at least one among the first emission layer and the third emission layer includes one among a blue emission layer, a deep blue emission layer, and a sky blue emission layer.

14. The organic light emitting display device of claim 1 , wherein at least one among the first electrode and the second electrode is a semitransmissive electrode.

15. An organic light emitting display device comprising:

a first emission part between a first electrode and a second electrode, the first emission part including a first hole transport layer, an electron blocking layer, and a first emission layer; and

a second emission part on the first emission part, the second emission part including a second hole transport layer and a second emission layer,

wherein a thickness of the first hole transport layer is less than a thickness of the electron blocking layer.

16. The organic light emitting display device of claim 15 , wherein a sum of the thickness of the first hole transport layer and the thickness of the electron blocking layer is 40 nm or less.

17. The organic light emitting display device of claim 15 , wherein a triplet energy level of the electron blocking layer is higher than a triplet energy level of the first hole transport layer.

18. The organic light emitting display device of claim 15 , wherein the first hole transport layer and the electron blocking layer are formed of a same material.

19. The organic light emitting display device of claim 15 , further comprising: a third emission part on the second emission part, the third emission part including a third hole transport layer and a third emission layer.

20. The organic light emitting display device of claim 19 , wherein at least one among the first hole transport layer and the third hole transport layer comprises a material having a triplet energy level within a same range as a range of a triplet energy level of the electron blocking layer.

21. The organic light emitting display device of claim 19 , wherein at least one among the first emission layer and the third emission layer inludes one among a blue emission layer a deep blue emission layer, and a sky blue emission layer.

22. The organic light emitting display device of claim 19 , wherein a thickness of the third hole transport layer is less than a thickness of the second hole transport layer.

23. The organic light emitting display device of claim 15 , wherein a thickness of the second hole transport layer is greater than the thickness of the first hole transport layer.

24. The organic light emitting display device of claim 15 , wherein at least one among the first electrode and the second is a semitransmissive electrode.