Polymer and organic light emitting device

1. A polymer comprising a repeat unit of formula (Ia):

wherein:

M is a metal;

R is a backbone repeat group;

n is 1 or 2;

Sp is a spacer group;

w is 0 or 1;

L 1 is a mono- or bidentate coordinating group;

L 2 is a mono- or bidentate coordinating group and is the same or different in each occurrence;

---- represents a second metal to ligand bond in the case where L 1 or L 2 is a bidentate ligand; and

at least one of L 1 and L 2 is substituted with a group of formula (II):

wherein:

m is 0 or 1;

each Ar 1 , Ar 2 , and Ar 3 is independently in each occurrence, an aryl or heteroaryl that is unsubstituted or substituted with one or more substituents; and

any two of Ar 1 , Ar 2 , and Ar 3 linked to the same N atom are optionally linked by a direct bond or a divalent linking group.

2. The polymer according to claim 1 , wherein M is iridium.

3. The polymer according to claim 1 , wherein:

R is —(Ar 6 ) p —;

p is 1, 2, or 3; and

each Ar 6 is independently aryl or heteroaryl.

4. The polymer according to claim 3 , wherein Ar 6 is phenyl that is unsubstituted or substituted with one or more substituents.

5. The polymer according to claim 4 , wherein R is an unsubstituted or substituted repeat unit of formula:

6. The polymer according to claim 1 , wherein each L 1 and L 2 are independently ligands comprising a bidentate group of formula (III):

wherein Ar 4 and Ar 5 are the same or different; are optionally fused together; and are independently an aryl or heteroaryl that is unsubstituted or substituted with one or more sub stituents; and wherein X 1 and Y 1 are the same or different and are independently carbon or nitrogen.

7. The polymer according to claim 6 , wherein said bidentate group is a 2-phenylpyridine group.

8. The polymer according to claim 1 , wherein m is 1.

9. The polymer according to claim 1 , wherein one of Ar 1 , Ar 2 , and Ar 3 is bound directly to L 1 or L 2 .

10. The polymer according to claim 1 , wherein w is 0.

11. The polymer according to claim 1 , wherein Sp is selected from the group consisting of C 1-20 alkyl and phenyl-C 1-20 alkyl, and wherein one or more non adjacent C atoms of C 1-20 alkyl are optionally replaced with O, S, or COO.

12. The polymer according to claim 1 , comprising a repeat unit of formula (IV) or (V), which is unsubstituted or substituted with one or more substituents:

13. The polymer according to claim 1 , wherein the polymer contains 0.5-40 mol of the repeat units of formula (Ia), (IV), or (V):

14. The polymer according to claim 1 , wherein a photoluminescent spectrum of the polymer has a peak at a wavelength in the range 540-620 nm.

15. The polymer according to claim 1 , comprising one or more co-repeat units.

16. The polymer according to claim 15 , comprising an arylene co-repeat unit that is unsubstituted or substituted with one or more substituents.

17. A formulation comprising:

a polymer according to claim 1 ; and

at least one solvent.

18. An organic light-emitting device comprising an anode, a cathode, and a light-emitting layer between the anode and the cathode, wherein the light-emitting layer comprises a polymer according to claim 1 .

19. The organic light-emitting device according to claim 18 , wherein the device is a white light emitting device.

20. A method of forming an organic light-emitting device comprising an anode, a cathode, and a light-emitting layer between the anode and the cathode, the method comprising the step of forming the light-emitting layer over one of the anode or cathode, and forming the other of the anode or cathode over the light-emitting layer, wherein the light-emitting layer is formed by depositing the formulation according to claim 17 and evaporating the at least one solvent.

21. The polymer according to claim 1 , wherein M is iridium and the polymer comprises less than 7.8 mol % of the repeat unit of formula (Ia).