Organic element for low voltage electroluminescent devices
View Patent ↗An OLED device comprises a cathode, a light emitting layer and an anode, in that order, and, having located between the cathode and the light emitting layer, a further layer containing; (a) 10 vol % or more of a carbocyclic fused ring aromatic compound, and (b) a cyclometallated complex represented by Formula (4′) wherein: Z and the dashed arc represent two or three atoms and the bonds necessary to complete a 5- or 6-membered ring with M; each A represents H or a substituent and each B represents an independently selected substituent on the Z atoms, provided that two or more substituents may combine to form a fused ring or a fused ring system; j is 0-3 and k is 1 or 2; M represents a Group IA, IIA, IIIA and IIB element of the Periodic Table; and m and n are independently selected integers selected to provide a neutral charge on the complex; and provided that the complex does not contain the 8-hydroxyquinolate ligand. Such devices exhibit reduce drive voltage while maintaining good luminance.
1. An OLED device comprising a cathode, a light emitting layer and an anode, in that order, and, having located between the cathode and the light emitting layer, a non-light emitting further layer containing;
(a) a carbocyclic fused ring aromatic compound comprising greater than 10% of the layer by volume and represented by Formula (2):
wherein:
Ar 1 —Ar 4 represent independently selected aromatic groups;
R 1 -R 4 represent hydrogen or substituents independently selected from methyl, t-butyl, fluoro groups; and
(b) a cyclometallated complex comprising 20% or greater of the layer by volume and represented by Formula (4′)
wherein:
Z and the dashed arc represent three atoms and the bonds necessary to complete a 6-membered ring with M;
each A represents H or a substituent and each B represents an independently selected substituent on the Z atoms, provided that two or more substituents may combine to form a fused ring or a fused ring system;
j is 3 and k is 1;
M represents an alkali metal or alkaline earth metal; and
m and n are independently selected integers selected to provide a neutral charge on the complex.
2. The device of claim 1 wherein the light emitting layer emits blue light.
3. The device of claim 1 wherein the light emitting layer emits green light.
4. The device of claim 1 wherein the light emitting layer emits red light.
5. The device of claim 1 wherein the further layer is adjacent to the light-emitting layer.
6. The device of claim 1 wherein the carbocyclic fused ring aromatic compound in the further layer comprises 15% or greater of the layer by volume.
7. The device of claim 1 wherein the carbocyclic fused ring aromatic fused ring aromatic compound in the further layer comprises 25% or greater of the layer by volume.
8. The device of claim 1 wherein the carbocyclic fused ring aromatic compound in the further layer comprises 50-80% of the layer by volume.
9. The device of claim 1 wherein R 1 is the same as R 4 and neither are hydrogen, Ar 1 is the same as Ar 4 , and Ar 2 is the same as Ar 3 , in the compound of Formula (2).
10. The device of claim 1 wherein the carbocyclic fused ring aromatic compound is:
11. The device of claim 1 wherein the cyclometallated complex is selected from the group consisting of:
12. The device of claim 1 wherein the cyclometallated complex comprises 20-60% of the layer by volume.
13. The device of claim 1 wherein the layer containing (a) and (b) also includes (c) an elemental metal having a work function less than 4.2 eV.
14. The device of claim 13 wherein said elemental metal is present in the amount of from 0.1% to 15% by volume of the total material in the layer.
15. The device of claim 1 wherein M in the compound of Formula (4′) is lithium.