Light-emitting element

• US 10,586,934 B2
• Filed: 01/30/2019
• Issued: 03/10/2020
• Est. Priority Date: 02/16/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Shitagaki, Satoko, Seo, Satoshi, Ohsawa, Nobuharu, Inoue, Hideko, Suzuki, Kunihiko
• Primary Examiner(s): Rahman, Moin M
• Application Number:
  US16/261,698
• Publication Number:
  US 20190157577A1
• Time in Patent Office: 405 Days
• Field of Search: 257 13, 257 79-103, 257918, 257 40, 257642-643, 257759, 438 22- 47, 438 69, 438493, 438503, 438507, 438956
• CPC Class Codes: C07D 209/86 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to carbon atoms of the ring system
• CPC Class Codes: C07D 239/26 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 241/12 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 333/76 Dibenzothiophenes
• CPC Class Codes: C07D 409/10 linked by a carbon chain containing aromatic rings
• CPC Class Codes: C07D 471/04 Ortho-condensed systems
• CPC Class Codes: C07F 15/0033 Iridium compounds
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1074 containing more than three nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/90 Multiple hosts in the emissive layer
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/624 containing six or more rings
• CPC Class Codes: H10K 85/626 : containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• CPC Class Codes: H10K 85/631 : Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/633 : comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/636 : comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/6572 : comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: H10K 85/6576 : comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene

Abstract

A light-emitting element having high external quantum efficiency is provided. A light-emitting element having a long lifetime is provided. A light-emitting element is provided which includes a light-emitting layer containing a phosphorescent compound, a first organic compound, and a second organic compound between a pair of electrodes, in which a combination of the first organic compound and the second organic compound forms an exciplex (excited complex). The light-emitting element transfers energy by utilizing an overlap between the emission spectrum of the exciplex and the absorption spectrum of the phosphorescent compound and thus has high energy transfer efficiency. Therefore, a light-emitting element having high external quantum efficiency can be obtained.

Claims

1. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,

wherein one of the first organic compound and the second organic compound is a carbazole compound,

wherein the carbazole compound comprises a carbazol-3-yl group, and

wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

2. The light-emitting element according to claim 1,

wherein the first organic compound is a heterocyclic compound.

3. The light-emitting element according to claim 1, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

4. The light-emitting element according to claim 1, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

5. The light-emitting element according to claim 1,

wherein one of the electrodes comprises ytterbium.

6. The light-emitting element according to claim 1,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

7. The light-emitting element according to claim 1,

wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

8. The light-emitting element according to claim 1,

wherein a level of a triplet excitation energy of each of the first organic compound and second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

9. The light-emitting element according to claim 1,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

10. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,

wherein one of the first organic compound and the second organic compound is a carbazole compound,

wherein the carbazole compound comprises a first carbazole ring and a second cabazole ring,

wherein the first carbazole ring at 3-position bonds to the second carbazole ring at 3-position, and

wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

11. The light-emitting element according to claim 10,

wherein the first organic compound is a heterocyclic compound.

12. The light-emitting element according to claim 10, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

13. The light-emitting element according to claim 10, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

14. The light-emitting element according to claim 10,

wherein one of the electrodes comprises ytterbium.

15. The light-emitting element according to claim 10,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

16. The light-emitting element according to claim 10,

wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

17. The light-emitting element according to claim 10,

wherein a level of a triplet excitation energy of each of the first organic compound and second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

18. The light-emitting element according to claim 10,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

19. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,

wherein one of the first organic compound and the second organic compound is a carbazole compound,

wherein the carbazole compound comprises two cabazole rings, and

wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of a peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

20. The light-emitting element according to claim 19,

wherein the two cabazole rings directly bond to each other.

21. The light-emitting element according to claim 19,

wherein the first organic compound is a heterocyclic compound.

22. The light-emitting element according to claim 19, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

23. The light-emitting element according to claim 19, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

24. The light-emitting element according to claim 19,

wherein one of the electrodes comprises ytterbium.

25. The light-emitting element according to claim 19,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

26. The light-emitting element according to claim 19,

wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

27. The light-emitting element according to claim 19,

wherein a level of a triplet excitation energy of each of the first organic compound and second organic compound is higher than a level of a triplet excitation energy of the phosphorescent compound.

28. The light-emitting element according to claim 19,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

29. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an emission spectrum of the exciplex overlaps with a longest wavelength side absorption band in an absorption spectrum of the phosphorescent compound,

wherein a peak wavelength of the longest wavelength side absorption band is in a range from 490 nm to 530 nm, and

wherein an absolute value of a difference between an energy value of a peak of the emission spectrum and an energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

30. The light-emitting element according to claim 29, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

31. The light-emitting element according to claim 29, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

32. The light-emitting element according to claim 29,

wherein one of the electrodes comprises ytterbium.

33. The light-emitting element according to claim 29,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

34. The light-emitting element according to claim 29,

wherein the longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

35. The light-emitting element according to claim 29,

wherein a level of a triplet excitation energy of the exciplex is higher than a level of a triplet excitation energy of the phosphorescent compound.

36. The light-emitting element according to claim 29,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with the longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

37. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an absorption spectrum of the phosphorescent compound comprises a first absorption peak and a second absorption peak,

wherein the first absorption peak is located on a longest wavelength side in the absorption spectrum of the phosphorescent compound,

wherein the second absorption peak is located on a shorter wavelength side than the first absorption peak in the absorption spectrum,

wherein the second absorption peak is located next to the first absorption peak, and

wherein a peak of an emission spectrum of the exciplex is located on a longer wavelength side than the second absorption peak, and

wherein an absolute value of a difference between an energy value of the peak of the emission spectrum and an energy value of a peak of a longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

38. The light-emitting element according to claim 37, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

39. The light-emitting element according to claim 37, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

40. The light-emitting element according to claim 37,

wherein one of the electrodes comprises ytterbium.

41. The light-emitting element according to claim 37,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

42. The light-emitting element according to claim 37,

wherein a longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

43. The light-emitting element according to claim 37,

wherein a level of a triplet excitation energy of the exciplex is higher than a level of a triplet excitation energy of the phosphorescent compound.

44. The light-emitting element according to claim 37,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with a longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.

45. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer comprising a phosphorescent compound, a first organic compound and a second organic compound between the pair of electrodes,

wherein the first organic compound and the second organic compound are selected so as to form an exciplex,

wherein an absorption spectrum of the phosphorescent compound comprises a first absorption peak and a second absorption peak,

wherein the first absorption peak is located on a longest wavelength side in the absorption spectrum of the phosphorescent compound,

wherein the second absorption peak is located on a shorter wavelength side than the first absorption peak in the absorption spectrum,

wherein the second absorption peak is located next to the first absorption peak,

wherein a peak of an emission spectrum of the exciplex is closer to the first absorption peak than the second absorption peak, and

wherein an absolute value of a difference between an energy value of the peak of the emission spectrum and an energy value of a peak of a longest wavelength side absorption band in the absorption spectrum is 0.2 eV or less.

46. The light-emitting element according to claim 45, further comprising:

a hole injection layer,

wherein the hole injection layer comprise an aromatic amine compound and an electron acceptor.

47. The light-emitting element according to claim 45, further comprising:

a hole transport layer,

wherein the hole transport layer comprises an aromatic amine compound, and

wherein the aromatic amine compound comprises a fluorenyl group.

48. The light-emitting element according to claim 45,

wherein one of the electrodes comprises ytterbium.

49. The light-emitting element according to claim 45,

wherein the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the longest wavelength side absorption band in the absorption spectrum is 0.1 eV or less.

50. The light-emitting element according to claim 45,

wherein a longest wavelength side absorption band is an absorption wavelength corresponding to direct transition from a singlet ground state to a triplet excitation state.

51. The light-emitting element according to claim 45,

wherein a level of a triplet excitation energy of the exciplex is higher than a level of a triplet excitation energy of the phosphorescent compound.

52. The light-emitting element according to claim 45,

wherein one of the first organic compound and the second organic compound has higher content than the other, and

wherein a phosphorescence spectrum of the one overlaps with a longest wavelength side absorption band in the absorption spectrum of the phosphorescent compound.