Solution-processable electron-transport materials and related organic optoelectronic devices

1. An optoelectronic device, comprising:

a first electrode;

a second electrode;

an active layer intermediate the first and second electrodes; and

a transport layer intermediate the second electrode and the active layer, wherein the transport layer comprises a compound of (1):

wherein R 1 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ;

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 3 , R 4 and R 5 are each independently selected from the group consisting of H and R 1 ; and

wherein all of R 1 -R 5 are not H.

2. The device of claim 1 , wherein the transport layer has solubility orthogonal to the solubility of the active layer.

3. The device of claim 1 , wherein the first electrode is an anode.

4. The device of claim 1 , wherein the first electrode comprises a material selected from the group consisting of indium-tin-oxide and fluorine-tin-oxide.

5. The device of claim 1 , wherein the second electrode is a cathode.

6. The device of claim 1 , wherein the second electrode comprises a material selected from the group consisting of aluminum, silver, and gold.

7. The device of claim 1 , further comprising a substrate adjacent the first or second electrode.

8. The device of claim 7 , wherein the substrate is glass or plastic.

9. The device of claim 7 , wherein the substrate is adjacent to the first electrode, wherein the substrate is glass, and wherein the first electrode is indium-tin-oxide.

10. The device of claim 1 , further comprising a hole-injection buffer layer intermediate the active layer and the first electrode.

11. The device of claim 10 , wherein the hole-injection buffer layer comprises poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) or polyaniline.

12. The device of claim 1 , wherein the active layer is a phosphorescent light-emitting material.

13. The device of claim 12 , wherein the active layer is a blue light-emitting material.

14. The device of claim 1 , wherein the active layer comprises a triplet emitter-doped poly(N-vinylcarbazole).

15. A method of fabricating a portion of an optoelectronic device comprising forming a transport layer on an active layer from a solution comprising a compound of (1) and a solvent, wherein the compound has a solubility in the solvent orthogonal to the solubility of the active layer in the solvent, and wherein the active layer is not solvated during forming of the transport layer

wherein the compound (1) is:

wherein R 1 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ;

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 3 , R 4 , and R 5 are each independently selected from the group consisting of H and R 1 ; and

wherein all of R 1 -R 5 are not H.

16. The method of claim 15 further comprising providing a first electrode abutting the active layer and a second electrode abutting the transport layer to provide an optoelectronic device.

17. The method of claim 16 , wherein the optoelectronic device is a blue, green, red and white phosphorescent light-emitting diode.

18. The method of claim 15 , wherein the solvent is a binary solvent.

19. The method of claim 18 , wherein the binary solvent comprises a mixture of water and formic acid.

20. The method of claim 19 , wherein the binary solvent is about one part water and from about 2 to about 10 parts formic acid.

21. The method of claim 19 , wherein the binary solvent is about one part water and about three parts formic acid.

22. The method of claim 18 , wherein the binary solvent comprises a mixture of water and one or more acids, each having a boiling point in the range of from about 70-160° C. and a pKa lower than 4.97.

23. The method of claim 22 , wherein the acid is a C 1 -C 4 carboxylic acid; wherein the carboxylic acid is selected from the group consisting of hydrogen-substituted, halogenated, fluorinated, and combinations thereof.

24. The method of claim 15 , wherein the solvent is a carboxylic acid selected from the group consisting of formic acid, acetic acid, 2-propenoic acid, 2-propynoic acid, lactic acid, maleic acid, trifluoroacetic acid, trifluorobutanoic acid, and trifluoropropionic acid, and combinations thereof.

25. The method of claim 24 , wherein the carboxylic acid has a boiling point in the range of from about 70-160° C. and a pKa lower than 4.97.

26. A method of fabricating a portion of an optoelectronic device, comprising forming a transport layer on an active layer from a solution comprising a charge-transport compound and a non-ionic solvent, wherein the charge-transport compound has a solubility in the solvent orthogonal to the solubility of the active layer in the solvent, wherein the charge-transport compound is a heterocyclic compound containing two or more imine nitrogens, and wherein the active layer is not solvated during forming of the transport layer.

27. The method of claim 26 , wherein the solvent is a binary solvent.

28. The method of claim 27 , wherein the binary solvent comprises a mixture of water and formic acid.

29. The method of claim 28 , wherein the binary solvent is about one part water and from about 2 to about 10 parts formic acid.

30. The method of claim 28 , wherein the binary solvent is about one part water and about three parts formic acid.

31. The method of claim 27 , wherein the binary solvent comprises a mixture of water and one or more acids, each having a boiling point in the range of from about 70-160° C. and a pKa lower than 4.97.

32. The method of claim 31 , wherein the acid is a C 1 -C 4 carboxylic acid; wherein the carboxylic acid is selected from the group consisting of hydrogen-substituted, halogenated, fluorinated, and combinations thereof.

33. The method of claim 26 , wherein the solvent is a carboxylic acid selected from the group consisting of formic acid, acetic acid, 2-propenoic acid, 2-propynoic acid, lactic acid, maleic acid, trifluoroacetic acid, trifluorobutanoic acid, and trifluoropropionic acid, and combinations thereof.

34. The method of claim 33 , wherein the carboxylic acid has a boiling point in the range of from about 70-160° C. and a pKa lower than 4.97.

35. The method of claim 26 , wherein the charge-transport compound is a heterocyclic compound containing three or more imine nitrogens.

36. The method of claim 26 , wherein the charge-transport compound is selected from the group consisting of:

(a) compound (1):

wherein R 1 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ;

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 3 , R 4 , and R 5 are each independently selected from the group consisting of H and R 1 ; and

wherein all of R 1 -R 5 are not H

(b) compound (2):

wherein R 1 is selected from the group consisting of alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ; and

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

(c) compound (3):

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

(d) compound (4):

wherein R 1 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ;

wherein R 2 is any of H, alkyl, aromatic, heteroaromatic,

and

wherein R 6 is independently selected from the group consisting of:

(e) 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),

(f) (2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI),

(g) 4,7-diphenyl-1,10-phenanthroline (BPhen),

(h) 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD),

(i) 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),

(j) 1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (OXD-7),

(k) tris(2,4,6-trimethyl-3-(pyridine-3-yl)phenyl)borane (3 TPYMB),

(l) 3,3′,5,5′-tetra[(m-pyridyl)-phen-3-yl]biphenyl (BP4mPy),

(m) 1,3,5-tri[(3-pyridyl)phen-3-yl]benzene (TmPyPB),

(n) 1,3-bis[3,5-di(pyridine-3-yl)phenyl]benzene (BmPyPhB), and

(o) combinations thereof.

37. The method of claim 26 , wherein the organic active layer comprises a mixture of one or more polymers and one or more phosphorescent triplet emitters.

38. The method of claim 37 , wherein the polymer is selected from the group consisting of poly(N-vinylcarbazole (PVK), poly(alkylfluorene) (PFO), and poly(p-phenylene) (PPP).

39. The method of claim 37 wherein the polymer has the band gap (E g ) greater than 2.5 eV.

40. The method of claim 37 , wherein the phosphorescent triplet emitter is selected from the group consisting of Iridium-, Ruthenium-, and Osmium-based metal-complexes.

41. The method of claim 37 , wherein the phosphorescent triplet emitter is selected from the group consisting of Tris(2-phenylpyridine)iridium(III) (Ir(ppy) 3 ), Bis(2-phenylpyridine)(acetylacetonate)iridium(III) (Ir(ppy) 2 (acac)), Tris[2-(p-tolyl)pyridine] iridium(III) (Ir(mppy) 3 ), Bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium III (FIrpic), Bis(2,4-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate iridium III (FIr6), Bis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate)iridium(III) (Ir(btp)2(acac)), Tris(1-phenylisoquinoline)iridium(III) (Ir(piq) 3 ) Bis(1-phenylisoquinoline)(acetylacetonate)iridium (III) (Ir(piq) 2 (acac)), Bis[1-(9,9-dimethyl-9H-fluoren-2-yl)-isoquinoline](acetylacetonate)iridium(III) (Ir(fliq) 2 (acac)), Bis[2-(9,9-dimethyl-9H-fluoren-2-yl)-quinoline](acetylacetonate)iridium(III) (Ir(flq) 2 (acac)), Bis(2-phenylbenzothiazolato)(acetylacetonate)iridium(III) (Bt 2 Ir(acac)), Osmium(II) bis(3-trifluoromethyl-5-(2-pyridyl)-pyrazolate)dimethylphenylphosphine (Os(fppz) 2 (PPhMe 2 ) 2 ) Osmium(II) bis(3-(trifluoromethyl)-5-(4-tert-butylpyridyl)-1,2,4-triazolate)diphenylmethylphosphine (Os(bpftz) 2 (PPh2Me) 2 ), and combinations thereof.

42. The method of claim 37 , wherein the organic active layer further comprises a charge transport compound.

43. The method of claim 42 , wherein the charge transport compound is selected from the group consisting of 1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl)benzene (OXD-7), 2-(4-Biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-Biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), and combinations thereof.

44. The method of claim 42 , wherein the charge transport compound is selected from the group consisting of N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), Di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC), 4,4′-Bis(carbazol-9-yl)biphenyl (CBP), N, N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB), and combinations thereof.

45. The method of claim 42 , wherein the charge transport compound has ionization potential value (IP) lower than 6.0 eV.

46. The method of claim 26 , wherein the organic active layer is selected from the group consisting of poly(N-vinylcarbazole) (PVK), N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), Di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC), 4,4′-Bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl)benzene (OXD-7), 2-(4-Biphenyl)-5-(4-tert-butylphenyl)1-3,4-oxadiazole (PBD), and combinations thereof.

47. The method of claim 15 , wherein the solvent has a neutral charge.

48. A compound (2):

wherein R 1 is selected from the group consisting of alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ; and

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

49. The compound of claim 48 , wherein the compound is:

50. The compound of claim 48 , wherein the compound is:

51. The compound of claim 48 , wherein the compound is:

52. The compound of claim 48 , wherein the compound is:

53. A compound (3):

wherein R 2 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

54. A compound (4):

wherein R 1 is independently selected from the group consisting of H, alkyl, aromatic, heteroaromatic,

wherein R 7 is any one of R 1 or R 2 ;

wherein R 2 is any of H, alkyl, aromatic, heteroaromatic,

and wherein R 6 is independently selected from the group consisting of