OLED device with cyclobutene electron injection materials

1. An OLED device comprising a cathode, an anode, and having therebetween a light-emitting layer and further comprising a first layer between the light-emitting layer and the cathode containing a cyclobutene compound comprising a cyclobutene nucleus substituted in the 1-position with a five- or six-membered heteroaromatic ring group containing at least one trivalent nitrogen atom; substituted in the 2-position with an aromatic ring group; and substituted with a first methylene group in the 3-position and a second methylene group in the 4-position, provided said first and second methylene groups are further disubstituted in the 1′,1′-positions and the 1″,1″-positions with independently selected aromatic groups.

2. The OLED device of claim 1 wherein the heteroaromatic ring group is an azine group.

3. The OLED device of claim 2 wherein the azine group is selected from the group consisting of a pyridine group, a pyrazine group, a pyrimidine group, and a phenanthroline group.

4. The OLED device of claim 1 wherein the aromatic ring group in the 2-position is a five- or six-membered heteroaromatic ring group containing at least one trivalent nitrogen atom.

5. The OLED device of claim 1 wherein the cyclobutene compound is represented by Formula (I),

wherein:

Z represents the atoms necessary to complete a five- or six-membered aromatic ring containing at least one trivalent nitrogen; and

Ar 1 -Ar 5 each represents an independently chosen aryl group or heteroaryl group.

6. The OLED device of claim 5 wherein Z represents the atoms necessary to complete an azine ring group, Ar 1 represents a heteroaryl group, and each Ar 2 -Ar 5 represents an independently chosen aryl group having 6-24 carbon atoms.

7. The OLED device of claim 5 wherein Z represents the atoms necessary to complete a pyridine ring group and wherein the pyridine ring group contains no more than two fused rings.

8. The OLED device of claim 1 wherein the cyclobutene compound is represented by Formula (II),

wherein:

Az 1 and Az 2 each independently represent an azine group; and

Ar 2 —Ar 5 each represents an independently chosen aryl group having 6-24 carbon atoms.

9. The OLED device of claim 8 wherein Az 1 and Az 2 are the same and each Ar 2 -Ar 5 represents the same aryl groups having 6-24 carbon atoms.

10. The OLED device of claim 8 wherein Az 1 and Az 2 are selected from the group consisting of a pyridine group, a pyrazine ring group, a pyrimidine group, and a phenanthroline group.

11. The OLED device of claim 8 wherein Az 1 and Az 2 are the same and represent a pyridine ring group and wherein the pyridine ring group contains no more then two fused rings.

12. The OLED device of claim 8 wherein Az 1 and Az 2 are selected independently from the group consisting of:

13. The OLED device of claim 1 wherein:

(a) the first layer includes an alkali metal or alkali metal compound; or

(b) wherein a second layer, located between said first layer and the cathode and contiguous to the first layer, contains an alkali metal or alkali metal compound; and

(c) provided that both the first and second layers can contain an independently selected alkali metal or alkali metal compound.

14. The OLED device of claim 13 wherein the alkali metal compound comprises LiF or an organic lithium compound represented by Formula (III):

(Li + ) m (Q) n   Formula (III)

wherein:

Q is an anionic organic ligand; and

m and n are independently selected integers selected to provide a neutral charge on the complex.

15. The OLED device of claim 1 wherein:

(a) the first layer includes, in addition to the cyclobutene compound, a polycyclic aromatic hydrocarbon compound; or

(b) a third layer, located between said first layer and the light-emitting layer and contiguous to the first layer, includes the polycyclic aromatic hydrocarbon compound, provided that both the first and third layers can include an independently selected polycyclic aromatic hydrocarbon compound; and wherein,

(c) the polycyclic aromatic hydrocarbon compound comprises at least 3 fused aromatic rings and wherein the absolute difference in LUMO values between the polycyclic aromatic hydrocarbon compound and the cyclobutene compound is 0.3 eV or less.

16. The OLED device of claim 15 wherein the third layer includes an alkali metal or alkali metal compound.

17. The OLED device of claim 15 wherein the polycyclic aromatic hydrocarbon compound comprises an anthracene derivative of Formula (IV),

wherein:

R 1 and R 6 each independently represent an aryl group having 6-24 carbon atoms;

R 2 -R 5 and R 7 -R 10 are each independently chosen from hydrogen, alkyl groups having from 1-24 carbon atoms, and aryl groups having from 6-24 carbon atoms.

18. The OLED device of claim 15 wherein the polycyclic aromatic hydrocarbon compound comprises a fluoranthene derivative of Formula (V),

wherein:

R 11 -R 20 are independently chosen from hydrogen, alkyl groups having from 1-24 carbon atoms, and aromatic groups having from 6-24 carbon atoms, provided adjacent groups can combine to form fused aromatic rings.

19. The OLED device of claim 18 wherein R 11 and R 14 represent aryl groups having 6-24 carbon atoms, and R 12 , R 13 and R 15 -R 20 are independently chosen from hydrogen, alkyl groups having from 1-24 carbon atoms, and aryl groups having from 6-24 carbon atoms, provided adjacent groups cannot combine to form fused aromatic rings.

20. A cyclobutene compound represented by Formula (VI):

wherein:

Az 1 represents an azine group; and

Ar 2 represents an aryl group having 6-24 carbon atoms.