Electroluminescent materials and devices
The present invention relates to heteroleptic electroluminescent metal complexes and to their preparation and use in electroluminescent devices, particularly to electroluminescent compounds having the general chemical formula:
1. An electroluminescent compound having the following general chemical formula:
wherein R 1 , R 2 , R 3 and R 4 can be the same or different and are independently selected from the group consisting of hydrogen; substituted and unsubstituted hydrocarbyl groups; substituted and unsubstituted aliphatic groups; substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures; aryloxy groups; fluorocarbon groups; halogens; and thiophenyl groups; further wherein R 1 , R 2 and R 3 can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer; M is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum; and the sum (n+1) is equal to the valency of M.
2. An electroluminescent compound as claimed in claim 1 wherein at least one of R 1 , R 2 , R 3 and R 4 includes a group selected from alkoxy groups, aryloxy groups, carboxy groups, substituted and unsubstituted phenyl groups, fluorophenyl groups, biphenyl groups, phenanthrene groups, anthracene groups, naphthyl groups, fluorene groups, and heterocyclic groups.
3. An electroluminescent compound as claimed in claim 1 , wherein M is iridium and n is 2.
4. An electroluminescent compound as claimed in claim 1 wherein at least one of R 1 , R 2 , R 3 and R 4 includes a group selected from aliphatic groups and aromatic groups.
5. An electroluminescent compound as claimed in claim 1 wherein R 2 is a phenyl group or a substituted phenyl group.
6. An electroluminescent device comprising: (i) a first electrode; (ii) a second electrode; and, (iii) a layer of an electroluminescent material according to claim 1 positioned between said first and second electrodes.
7. An electroluminescent device according to claim 6 further comprising a layer of a hole transmitting material positioned between the first electrode and the layer of electroluminescent material.
8. An electroluminescent device according to claim 7 wherein the hole transmitting material is a polyaromatic amine.
9. An electroluminescent device according to claim 7 wherein the hole transmitting material is a copolymer of aniline.
10. An electroluminescent device according to claim 7 wherein the hole transmitting material is a conjugated polymer.
11. An electroluminescent device according to claim 7 wherein the hole transmitting material is a conjugated polymer selected from the group consisting of poly (p-phenylenevinylene) (PPV) and copolymers of PPV.
12. An electroluminescent device according to claim 6 wherein the electroluminescent material is mixed with a hole transmitting material.
13. An electroluminescent device according to claim 6 wherein a layer of an electron transmitting material is positioned between an electrode that serves as a cathode element and the layer of electroluminescent material.
14. An electroluminescent device according to claim 13 wherein the electron transmitting material is a metal quinolate.
15. An electroluminescent device according to claim 13 wherein the electron transmitting material is a metal quinolate selected from the group consisting of aluminum quinolate, zirconium quinolate and lithium quinolate.
16. An electroluminescent device according to claim 13 wherein the electron transmitting material is selected from the group consisting of:
(a) a material having the general chemical formula Mx(DBM) n where Mx is a metal, DBM is dibenzoyl methane, and n is the valency of Mx;
(b) a cyano anthracene
(c) a polystyrene sulphonate; and,
(d) a compound having a general chemical formula selected from the group consisting of:
17. An electroluminescent device according to claim 6 wherein an electron transmitting material is mixed with the electroluminescent material.
18. An electroluminescent device according to claim 6 wherein the first electrode comprises a transparent, electricity-conducting glass electrode.
19. An electroluminescent device according to claim 6 wherein the second electrode comprises a material selected from the group consisting of aluminum, calcium, lithium, magnesium, alloys thereof, and silver/magnesium alloys.
20. A method of preparing an electroluminescent compound having the general chemical formula
wherein R 1 , R 2 , R 3 and R 4 can be the same or different and are independently selected from the group consisting of hydrogen; substituted and unsubstituted hydrocarbyl groups; substituted and unsubstituted aliphatic groups; substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures; aryloxy groups; fluorocarbon groups; halogens; and thiophenyl groups; further wherein R 1 , R 2 and R 3 can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer, said method comprising the step of reacting a compound having the general chemical formula
with a compound having the general chemical formula
where R 1 , R 2 , R 3 and R 4 are defined as above; X is an anion; M is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum; and the sum (n+1) is equal to the valency of M.