Organic electroluminescent devices

1. An organic light emitting device comprising:

an anode;

a cathode;

an organic light emissive layer disposed between the anode and the cathode, wherein the organic emissive layer comprises one or more host material and an organic phosphorescent emissive dopant material; and

an electron blocking layer comprising a neat film of the organic phosphorescent emissive dopant material disposed between the organic emissive layer and the anode.

2. The device of claim 1 , wherein the electron blocking layer is a neat film of the organic phosphorescent emissive dopant material.

3. The device of claim 1 , wherein the organic phosphorescent emissive dopant material is a carbene based compound having a carbene ligand coordinated to a metal center.

4. The device of claim 3 , wherein the carbene based compound has the structure:

wherein M is a metal; ring D is an aromatic cyclic, heterocyclic, fused cyclic, or fused heterocyclic ring,

wherein ring D can be optionally substituted with one or more substitutents R 2 ;

R 1 and R 2 are independently selected from H, alkyl, alkenyl, alkynyl, aralkyl, CN, CF 3 , CO 2 R′, C(O)R′, C(O)NR′ 2 , NR′ 2 , NO 2 , OR′, SR′, SO 2 , SOR′, SO 3 R′, halo, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group; R 3 is H, alkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group; and additionally or alternatively, two R groups on the same or adjacent ring, together may form independently a 5 or 6-member cyclic group, which is a cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl; and wherein said cyclic group may be substituted by one or more substituents J;

each substituent J is independently selected from the group consisting of R′, CN, CF 3 , C(O)OR′, C(O)R′, C(O)NR′ 2 , NR′ 2 , NO 2 , OR′, SR′, SO 2 , SOR′, or SO 3 R′, and additionally, or alternatively, two J groups on adjacent ring atoms may form a fused 5- or 6-membered aromatic group;

each R′ is independently selected from halo, H, alkyl, alkenyl, alkynyl, heteroalkyl, aralkyl, aryl, and heteroaryl;

Z 1 and Z 2 are selected from a bond, O, S, or NR′;

A 1 , A 2 , A′, and A″ are independently selected from C, N, or P;

(X—Y) is selected from a photoactive ligand or an ancillary ligand;

a is 0, 1, 2, 3, or 4;b is 0, 1, or 2;

m is a value from 1 to the maximum number of ligands that may be attached to metal M;

m+n is the maximum number of ligands that may be attached to metal M.

5. The device of claim 4 , wherein the carbene based compound is selected from the group consisting of:

wherein c is 0, 1, or 2; and

wherein R 4 is selected from H, alkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group.

6. The device of claim 3 , wherein the carbene based compound is Ir(pmp) 3 .

7. The device of claim 4 , wherein M is selected from the group consisting of Ir, Pt, Pd, Rh, Re, Ru, Os, Ti, Pb, Bi, In, Sn, Sb, Te, Al, Ga, Au, and Ag.

8. The device of claim 7 , wherein M is Ir.

9. The device of claim 8 , wherein m is 3 and n is 0.

10. The device of claim 3 , wherein the carbene ligand has the structure;

wherein ring D is an aromatic cyclic, heterocyclic, fused cyclic, or fused heterocyclic ring, wherein ring D can be optionally substituted with one or more substituents R 2 ;

R 1 and R 2 are independently selected from H, alkyl, alkenyl, alkynyl, aralkyl, CN, CF 3 , CO 2 R′, C(O)R′, C(O)NR′ 2 , NR′ 2 , NO 2 , OR′, SR′, SO 2 , SOR′, SO 3 R′, halo, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group; R 3 is H, alkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group; and additionally or alternatively, two R groups on the same or adjacent ring, together may form independently a 5 or 6-member cyclic group, which is a cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl; and wherein said cyclic group may be substituted by one or more substituents J;

each substituent J is independently selected from the group consisting of R′, CN, CF 3 , C(O)OR′, C(O)R′, C(O)NR′ 2 , NR′ 2 , NO 2 , OR′, SR′, SO 2 , SOR′, or SO 3 R′, and additionally, or alternatively, two J groups on adjacent ring atoms may form a fused 5- or 6-membered aromatic group;

each R′ is independently selected from halo, H, alkyl, alkenyl, alkynyl, heteroalkyl, aralkyl, aryl, and heteroaryl;

Z 1 is selected from a bond, O, S, or NR′;

A 1 and A 2 are independently selected from C, N, or P; and

a is 0, 1, 2, 3, or 4;b is 0, 1, or 2.

11. The device of claim 10 , wherein the carbene ligand is selected from:

wherein c is 0, 1, or 2.

12. The device of claim 10 , wherein the carbene ligand is selected from the group consisting of:

wherein c is 0, 1, or 2; and

wherein R 4 is selected from hydrogen, alkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group.

13. The device of claim 4 , wherein each of R 1 is H or an alkyl having 1-15 carbons and each of R 2 is H or an alkyl having 1-15 carbons.

14. The device of claim 13 , wherein M is Ir or Pt.

15. The device of claim 4 , wherein D is a 5-membered aromatic heterocyclic ring.

16. The device of claim 15 , wherein D is selected from the group consisting of

wherein R4 is selected from hydrogen, alkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, substituted aryl, substituted heteroaryl, or a heterocyclic group.

17. The device of claim 4 , wherein D is a 6-membered aromatic heterocyclic ring.

18. The device of claim 17 , wherein D is

19. The device of claim 4 , wherein D-Z 1 is

20. The device of claim 1 , further comprising a hole blocking layer disposed between the organic emissive layer and the cathode;

wherein the organic emissive layer and the electron blocking layer forming an emissive layer/electron blocking layer interface and the organic emissive layer and the hole blocking layer forming an emissive layer/hole blocking layer interface; and

wherein the organic phosphorescent emissive dopant material is present in the organic emissive layer with a graded doping concentration wherein the doping concentration is linearly graded from highest concentration at the emissive layer/electron blocking layer interface, to lowest concentration at the emissive layer/hole blocking layer interface.

21. A device comprising one or more organic light emitting devices of claim 1 .