Stability OLED materials and devices
Organic light emitting materials and devices comprising phosphorescent metal complexes comprising ligands comprising aryl or heteroaryl groups substituted at both ortho positions are described. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.
1. A phosphorescent compound, wherein the phosphorescent compound is a neutral metal complex of a bidentate, tridentate, tetradentate, pentadentate, or hexadentate ligand;
wherein the ligand comprises:
a first ring directly bonded to the metal, the first ring being an imidazole;
a second ring as a substitution on the first ring and not directly bonded to the metal, the second ring being an aryl or heteroaryl ring substituted at both ortho positions by groups other than H or halide, wherein the ortho position substitutions do not form a fused ring with the second ring;
a third ring as a substitution on the first ring, the third ring being an aryl or heteroaryl ring directly bonded to the metal;
wherein the metal complex is an organometallic complex;
wherein the metal is selected from the group consisting of the non-radioactive metals with atomic numbers greater than 40; and
wherein the photoluminescent emission spectrum of the phosphorescent compound is blue-shifted compared to a comparative compound of identical structure except without the ortho position substitutions on the second ring.
2. The phosphorescent compound of claim 1 , wherein both the ortho position substitutions on the second ring are aryl or heteroaryl groups.
3. The compound according to claim 2 , wherein the metal is selected from the group consisting of Re, Ru, Os, Rh, Ir, Pd, Pt, and Au.
4. The compound according to claim 3 , wherein the metal is selected from the group consisting of Os, Ir, and Pt.
5. The compound according to claim 4 , wherein the metal is Ir.
6. The compound according to claim 2 , wherein the second ring is further substituted by one or more aryl, heteroaryl, or electron withdrawing groups.
7. The compound according to claim 6 , wherein the second ring is further substituted by a triphenylene group.
8. The compound according to claim 6 , wherein the second ring is further substituted by a group that comprises a carbazole.
9. The compound according to claim 2 , wherein the substituents at the ortho positions of the second ring are diarylaminoaryl groups.
10. The compound according to claim 2 , which has a highest energy peak in a phosphorescence emission spectrum at a wavelength less than about 480 nm.
11. The compound according to claim 2 , which is a homoleptic compound.
12. The compound according to claim 2 , which is a heteroleptic compound.
13. The compound according to claim 2 , which is a sublimable compound.
14. The compound according to claim 2 , wherein the second ring is attached to a nitrogen atom of the first ring.
15. The compound according to claim 2 , wherein the first and third rings collectively comprise a monoanionic bidentate ligand.
16. The compound according to claim 2 , wherein the third ring is selected from the group consisting of phenyl, pyridyl, thiophenyl, furanyl, pyrrolyl, triazolyl, and pyrimidyl.
17. The compound according to claim 2 , wherein the third ring is a phenyl ring substituted by one or two fluorine groups.
18. The compound according to claim 2 , wherein the first and third rings are comprised within a monoanionic tridentate ligand.
19. The compound according to claim 2 , wherein the first and third rings collectively comprise a neutral bidentate ligand.
20. The compound according to claim 2 , wherein the metal complex comprises a bidentate, monoanionic, N,N-donor ligand.
21. The compound according to claim 2 , wherein the metal complex comprises a carbene donor.
22. The compound according to claim 21 , wherein the carbene donor is part of a bidentate, monoanionic ligand.
23. The compound according to claim 2 , wherein the triplet energy of the arene or heteroarene corresponding to the second ring is greater than about 2.5 eV.
24. The compound according to claim 2 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 230 g/mol.
25. The compound according to claim 2 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 430 g/mol.
26. The compound according to claim 2 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 530 g/mol.
27. The compound according to claim 2 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 750 g/mol.
28. The compound according to claim 2 , wherein the calculated singlet-triplet gap of the compound is less than about 0.4 eV.
29. The compound according to claim 2 , wherein the calculated singlet-triplet gap of the compound is less than about 0.3 eV.
30. The compound according to claim 2 , wherein the calculated singlet-triplet gap of the compound is less than about 0.2 eV.
31. The compound according to claim 2 , wherein the calculated singlet-triplet gap of the compound is less than about 0.1 eV.
32. The compound according to claim 2 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.1 V.
33. The compound according to claim 2 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.2 V.
34. The compound according to claim 2 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.3 V.
35. The compound according to claim 2 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.4 V.
36. The compound according to claim 2 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.5 V.
37. The compound according to claim 2 , wherein delta E is less than about 0.6 eV;
wherein:
delta E =(triplet energy)−(modified electrochemical gap);
the triplet energy is the energy of the highest energy peak in the phosphorescence emission spectrum of said metal complex, in eV; and
the modified electrochemical gap is the difference between the oxidation potential of the metal complex and the reduction potential of the neutral compound corresponding to the ligand.
38. The compound according to claim 37 , wherein delta E is less than about 0.5 eV.
39. The compound according to claim 37 , wherein delta E is less than about 0.4 eV.
40. The compound according to claim 37 , wherein delta E is less than about 0.3 eV.
41. The compound according to claim 37 , wherein delta E is less than about 0.2 eV.
42. An organic light emitting device comprising an anode, a cathode, and an emissive layer, wherein the emissive layer is located between the anode and the cathode, and the emissive layer comprises a phosphorescent compound according to claim 2 , and optionally a host.
43. The compound according to claim 1 , wherein the first ring is coordinated via a first nitrogen to the metal.
44. The compound according to claim 43 , wherein the second ring is attached to a second nitrogen of the first ring.
45. The compound according to claim 1 , wherein the metal is selected from the group consisting of Re, Ru, Os, Rh, Ir, Pd, Pt, and Au.
46. The compound according to claim 45 , wherein the metal is selected from the group consisting of Os, Ir, and Pt.
47. The compound according to claim 46 , wherein the metal is Ir.
48. The compound according to claim 1 , wherein the second ring is further substituted by one or more aryl, heteroaryl, or electron withdrawing groups.
49. The compound according to claim 1 , wherein the second ring is further substituted by a triphenylene group.
50. The compound according to claim 1 , wherein the second ring is further substituted by a group that comprises a carbazole.
51. The compound according to claim 1 , wherein the groups other than H or halide are alkyl groups.
52. The compound according to claim 51 , wherein the groups other than H or halide are alkyl groups comprising two or more carbons.
53. The compound according to claim 1 , wherein the groups other than H or halide are aryl groups.
54. The compound according to claim 1 , wherein the groups other than H or halide are heteroaryl groups.
55. The compound according to claim 1 , which has a highest energy peak in a phosphorescence emission spectrum at a wavelength less than about 480 nm.
56. The compound according to claim 1 , which is a homoleptic compound.
57. The compound according to claim 1 , which is a heteroleptic compound.
58. The compound according to claim 1 , which is a sublimable compound.
59. The compound according to claim 1 , wherein the first and third rings collectively comprise a monoanionic bidentate ligand.
60. The compound according to claim 59 , wherein the third ring is a benzene, naphthalene, quinoline, isoquinoline, pyridine, pyrimidine, pyridazine, pyrrole, oxazole, thiazole, oxadiazole, thiadiazole, furan, or thiophene ring.
61. The compound according to claim 59 , wherein the third ring is selected from the group consisting of phenyl, pyridyl, thiophenyl, furanyl, pyrrolyl, triazolyl, and pyrimidyl.
62. The compound according to claim 1 , wherein the first and third rings collectively comprise a monoanionic tridentate ligand.
63. The compound according to claim 1 , wherein the first and third rings collectively comprise a neutral bidentate ligand.
64. The compound according to claim 1 , wherein the groups other than H or halide are selected from either (i) the group consisting of methyl, ethyl, n-propyl, isopropyl, and tert-butyl, or (ii) the following groups:
wherein:
R 1a-e are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F;
in addition, any two of R 1a-e may be linked to form a ring.
65. The compound according to claim 1 , wherein the second ring is selected from 2,6-dimethylphenyl; 2,4,6-trimethylphenyl; 2,3,4,5,6-pentamethylphenyl; 2,6-dimethyl-4-phenylphenyl; 2,6-dimethyl-4-(3,5-dimethylphenyl)phenyl; 2,6-dimethyl-4-(2,6-dimethylphenyl)phenyl; 2,6-dimethyl-4-(4-pyridyl)phenyl; 2,6-dimethyl-4-(2,6-dimethyl-4-pyridyl)phenyl; 2,4-dimethyl-3-naphthyl; 2,6-dimethyl-4-cyanophenyl; 2,6-dimethyl-4-(9-carbazolyl)phenyl; 2,6-dimethyl-4-(9-phenyl-3-carbazolyl)phenyl; 2,6-dimethyl-4-(2,6-dimethyl-4-cyanophenyl)phenyl; 2,6-di-isopropylphenyl; 2,4,6-tri-isopropylphenyl; 2,6-di-isopropyl-4-phenylphenyl; 2,6-di-isopropyl-4-(3,5-dimethylphenyl)phenyl; 2,6-di-isopropyl-4-(2,6-dimethylphenyl)phenyl; 2,6-di-isopropyl-4-(4-pyridyl)phenyl; 2,6-di-isopropyl-4-(2,6-dimethyl-4-pyridyl)phenyl; 2,4-di-isopropyl-3-naphthyl; 2,6-di-isopropyl-4-cyanophenyl; 2,6-di-isopropyl-4-(9-carbazolyl)phenyl; 2,6-di-isopropyl-4-(9-phenyl-3-carbazolyl)phenyl; 2,6-di-isopropyl-4-(2,6-dimethyl-4-cyanophenyl)phenyl; 2,6-di-tert-butylphenyl; 2,6-di-tert-butyl-4-(3,5-dimethylphenyl)phenyl; 2,6-bis(trimethylsilyl)phenyl; 2,6-bis(dimethylphenylsilyl)phenyl; and 2,6-bis(trimethylsilyl)-4-(3,5-dimethylphenyl)-phenyl; 2,6-di-phenylphenyl; 2,6-di(4-isopropylphenyl)-4-isopropylphenyl; 2,6-di(4-isopropylphenyl)-4-methylphenyl; 2,6-di(4-isopropylphenyl)-4-tert-butylphenyl; 2,4,6-triphenylphenyl; 2,6-di-(4-isopropylphenyl)phenyl; 2,6-di-(3,5-dimethylphenyl)phenyl; 2,4,6-tri(4-isopropylphenyl)phenyl; 2,6-di-(4-tert-butylphenyl)phenyl; 2;6-di-(4-fluorophenyl)phenyl; 2,6-di-(9-carbazolyl)-4-isopropylphenyl; 2,6-di-(9-phenyl-3-carbazolyl)-4-isopropylphenyl; 2,6-di-(4-methoxyphenyl)phenyl; 2,6-diphenyl-4-fluorophenyl; 2,6-di-(2-triphenylenyl)phenyl; 2,6-di-(2-triphenylenyl)-4-isopropylphenyl; 2,6-di-(2,6-dimethyl-4-pyridyl)phenyl; 2,6-di-(4-cyanophenyl)-4-isopropylphenyl; 2,6-di-2-naphthylphenyl; 2,6-di-(4-phenylphenyl)-4-isopropylphenyl; 2,6-di-(3-phenylphenyl)-4-isopropylphenyl; 2,6-di-(4-diphenylaminophenyl)phenyl; 2,6-di-(4-dimethylaminophenyl)phenyl; 2,6-di-(4-trimethylsilylphenyl)phenyl; 2,6-di-(4-triphenylsilylphenyl)phenyl; 2,6-di-(4-diphenylmethylsilylphenyl)phenyl; and c1-c7 and c9 as follows:
wherein:
R 1a-e are each independently selected from the group consisting of hydrocarbyl comprising two or more carbons, heteroatom substituted hydrocarbyl, aryl, and heteroaryl;
R b-d are each independently selected from the group consisting of H, F, cyano, alkoxy, aryloxy, hydrocarbyl, heteroatom substituted hydrocarbyl, aryl, and heteroaryl; in addition, any two of R 1b-d may be linked to form a ring; and
Ar 1,2,3 are each independently aryl or heteroaryl.
66. The compound according to claim 1 , wherein the first ring is selected from f1-f4 as follows:
wherein:
Ar sr is the second ring;
R 1a,b are each independently selected from the group consisting of hydrogen, hydrocarbyl, and heteroatom substituted hydrocarbyl, cyano, and F; in addition, R 1a,b may be linked to form a ring; and
for rings f2, f3, and f4: R 2a is the third ring;
for ring f1: R 2b is the third ring and R 2a is selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F.
67. The compound according to claim 1 , wherein the third ring is selected from t1-t10 as follows:
wherein:
Ar fr is the first ring;
Ar 1 is aryl or heteroaryl; and
R 1a-d are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; in addition, any two of R 1a-d may be linked to form a ring.
68. The compound according to claim 1 , wherein the ligand is selected from I1-I7, I20-I22, I41-I46 as follows:
wherein:
Ar 1 is aryl or heteroaryl;
wherein:
R 1a-i are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F;
R 2a,b are each independently selected from the group consisting of hydrocarbyl comprising two or more carbons, heteroatom substituted hydrocarbyl, aryl, and heteroaryl;
wherein:
R 1a-i are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F;
Ar 1 is aryl or heteroaryl;
Ar 3a is 4-isopropylphenyl; and
Ar 3b is 3,5-dimethylphenyl.
69. The compound according to claim 1 , wherein the metal complex is selected from the following:
wherein:
Ar 3 is aryl or heteroaryl;
m is 1, 2 or 3; and
n is an integer selected to satisfy the valency of the metal;
wherein:
Ar 3a is 4-isopropylphenyl; and
Ar 3b is 3,5-dimethylphenyl;
wherein:
R 2a-c , R 1a-d , R 1f-h , and R 1j-q are each independently selected from the group consisting of hydrogen, hydrocarbyl, heteroatom substituted hydrocarbyl, cyano, and F; and wherein R 1e and R 1i are each independently aryl, heteroaryl, or alkyl; with the proviso that, for any of the preceding variables that represent an ortho position substitution on the second ring, the variable represents a group that is not H or a halide;
Ar 1-3 are aryl or heteroaryl, with the proviso that for any Ar 1 that is a substitution on the first ring, Ar 1 is the second ring;
Ar sr is the second ring;
Ar c is 9-carbazolyl or substituted 9-carbazolyl;
L n are ancillary ligands, which may be the same or different;
m is 1, 2 or 3;
n is an integer selected to satisfy the valency of M; and
M is a metal selected from the group consisting of Re, Ru, Os, Rh, Ir, Pd, Pt, and Au; and compounds m1-m72 as follows:
Specific
General
Structure
Structure
R 1a
R 1b
R 1c
R 1d
R 1e
R 1f
m1
gs1
CH 3
H
CH 3
H
H
H
m2
gs1
CH 3
H
CH 3
H
H
F
m3
gs1
CH 3
H
CH 3
F
H
F
m4
gs1
CH 3
H
CH 3
F
Ph
F
m5
gs1
1 Pr
H
1 Pr
H
H
H
m6
gs1
1 Pr
H
1 Pr
H
H
F
m7
gs1
1 Pr
H
1 Pr
F
H
F
m8
gs1
1 Pr
H
1 Pr
F
Ph
F
m9
gs1
Ph
1 Pr
Ph
H
H
H
ml 0
gs1
Ph
1 Pr
Ph
H
H
F
ml 1
gs1
Ph
1 Pr
Ph
F
H
F
m12
gs1
Ph
1 Pr
Ph
F
Ph
F
m13
gs1
Ph
1 Pr
Ph
H
H
H
m14
gs1
Ph
1 Pr
Ph
H
H
F
m15
gs1
Ph
1 Pr
Ph
F
H
F
m16
gs1
Ph
1 Pr
Ph
F
Ph
F
m17
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m18
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m19
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m20
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
m21
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m22
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m23
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m24
gs1
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
m25
gs2
CH 3
H
CH 3
H
H
H
m26
gs2
CH 3
H
CH 3
H
H
F
m27
gs2
CH 3
H
CH 3
F
H
F
m28
gs2
CH 3
H
CH 3
F
Ph
F
m29
gs2
1 Pr
H
1 Pr
H
H
H
m30
gs2
1 Pr
H
1 Pr
H
H
F
m31
gs2
1 Pr
H
1 Pr
F
H
F
m32
gs2
1 Pr
H
1 Pr
F
Ph
F
m33
gs2
Ph
1 Pr
Ph
H
H
H
m34
gs2
Ph
1 Pr
Ph
H
H
F
m35
gs2
Ph
1 Pr
Ph
F
H
F
m36
gs2
Ph
1 Pr
Ph
F
Ph
F
m37
gs2
Ph
1 Pr
Ph
H
H
H
m38
gs2
Ph
1 Pr
Ph
H
H
F
m39
gs2
Ph
1 Pr
Ph
F
H
F
m40
gs2
Ph
1 Pr
Ph
F
Ph
F
m41
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m42
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m43
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m44
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
m45
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m46
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m47
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m48
gs2
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
m49
gs3
CH 3
H
CH 3
H
H
H
m50
gs3
CH 3
H
CH 3
H
H
F
m51
gs3
CH 3
H
CH 3
F
H
F
m52
gs3
CH 3
H
CH 3
F
Ph
F
m53
gs3
1 Pr
H
1 Pr
H
H
H
m54
gs3
1 Pr
H
1 Pr
H
H
F
m55
gs3
1 Pr
H
1 Pr
F
H
F
m56
gs3
1 Pr
H
1 Pr
F
Ph
F
m57
gs3
Ph
1 Pr
Ph
H
H
H
m58
gs3
Ph
1 Pr
Ph
H
H
F
m59
gs3
Ph
1 Pr
Ph
F
H
F
m60
gs3
Ph
1 Pr
Ph
F
Ph
F
m61
gs3
Ph
1 Pr
Ph
H
H
H
m62
gs3
Ph
1 Pr
Ph
H
H
F
m63
gs3
Ph
1 Pr
Ph
F
H
F
m64
gs3
Ph
1 Pr
Ph
F
Ph
F
m65
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m66
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m67
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m68
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
m69
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
H
m70
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
H
H
F
m71
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
H
F
m72
gs3
3,5-Me 2 Ph
H
3,5-Me 2 Ph
F
Ph
F
wherein gs1, gs2, and gs3 are:
70. The compound according to claim 1 , wherein the metal complex comprises a bidentate, monoanionic, N,N-donor ligand.
71. The compound according to claim 1 , wherein the metal complex comprises a carbene donor.
72. The compound according to claim 71 , wherein the carbene donor is part of a bidentate, monoanionic ligand.
73. The compound according to claim 1 , wherein the triplet energy of the arene or heteroarene corresponding to the second ring is greater than about 2.5 eV.
74. The compound according to claim 1 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 230 g/mol.
75. The compound according to claim 74 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 430 g/mol.
76. The compound according to claim 74 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 530 g/mol.
77. The compound according to claim 74 , wherein the molecular weight of the arene or heteroarene corresponding to the second ring is greater than about 750 g/mol.
78. The compound according to claim 1 , wherein the calculated singlet-triplet gap of the compound is less than about 0.4 eV.
79. The compound according to claim 78 , wherein the calculated singlet-triplet gap of the compound is less than about 0.3 eV.
80. The compound according to claim 78 , wherein the calculated singlet-triplet gap of the compound is less than about 0.2 eV.
81. The compound according to claim 78 , wherein the calculated singlet-triplet gap of the compound is less than about 0.1 eV.
82. The compound according to claim 1 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.1 V.
83. The compound according to claim 82 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.2 V.
84. The compound according to claim 82 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.3 V.
85. The compound according to claim 82 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.4 V.
86. The compound according to claim 82 , wherein the reduction potential of the ligand is less negative than that of the corresponding ligand with a methyl group in place of the second ring by at least about 0.5 V.
87. The compound according to claim 1 , wherein delta E is less than about 0.6 eV; wherein:
delta E =(triplet energy)−(modified electrochemical gap);
the triplet energy is the energy of the highest energy peak in the phosphorescence emission spectrum of said metal complex, in eV; and
the modified electrochemical gap is the difference between the oxidation potential of the metal complex and the reduction potential of the neutral compound corresponding to the ligand.
88. The compound according to claim 87 , wherein delta E is less than about 0.5 eV.
89. The compound according to claim 87 , wherein delta E is less than about 0.4 eV.
90. The compound according to claim 87 , wherein delta E is less than about 0.3 eV.
91. The compound according to claim 87 , wherein delta E is less than about 0.2 eV.
92. An organic light emitting device comprising an anode, a cathode, and an emissive layer, wherein the emissive layer is located between the anode and the cathode, and the emissive layer comprises a phosphorescent compound according to claim 1 , and optionally a host.
93. The compound of claim 1 , wherein the emission spectrum of the compound has a peak wavelength at less than 500 nm.