Organic light emitting device comprising polar matrix, metal dopant and silver cathode
The present invention relates to an electronic device comprising at least one light emitting layer between an anode and a substantially silver cathode, the device further comprising between the cathode and the anode at least one mixed layer comprising (i) at least one substantially covalent electron transport matrix compound comprising at least one polar group selected from phosphine oxide group or diazole group, and (ii) in substantially elemental form, an electropositive element selected from substantially non-radioactive alkali metals, alkaline earth metals, rare earth metals, and transition metals of the fourth period of the Periodic table having proton numbers 22, 23, 24, 25, 26, 27, 28, 29.
1. Electronic device comprising at least one light emitting layer between an anode and a substantially silver cathode, the device further comprising between the cathode and the anode at least one mixed layer comprising
(i) at least one substantially covalent electron transport matrix compound comprising at least one polar group selected from phosphine oxide group or diazole group, and
(ii) in substantially elemental form, an electropositive element selected from substantially non-radioactive alkali metals, alkaline earth metals, rare earth metals, or transition metals of the fourth period of the Periodic table having proton numbers 22, 23, 24, 25, 26, 27, 28, 29, wherein the mixed layer is an electron transporting layer, an electron injecting layer, or a charge generating layer, wherein the electron transporting layer or the electron injecting layer is adjacent to and in direct contact with the cathode.
2. Electronic device according to claim 1 , wherein the reduction potential of the electron transport matrix compound, if measured by cyclic voltammetry under the same conditions, has the value which is more negative than the value obtained for at least one of tris(2-benzo[d]thiazol-2-yl)phenoxyaluminum, 9,9′,10,10′-tetraphenyl-2,2′-bianthracene, 2,9-di([1,1′-biphenyl]-4-yl)-4,7-diphenyl-1,10-phenanthroline, 2,4,7,9-tetraphenyl-1,10-phenanthroline, 9, 10-di(naphthalen-2-yl)-2-phenylanthracene, 2,9-bis(2-methoxyphenyl)-4,7-diphenyl-1,10-phenanthroline, 9,9′-spirobi[fluorene]-2,7-diylbis(diphenylphosphine oxide), 4,7-diphenyl-1,10-phenanthroline, 1,3,5-tris(1-phenyl -1H-benzimidazol-2-yl)benzene, pyrene, and [1,1′-binaphthalen]-2,2′-diylbis(diphenylphosphine oxide).
3. Electronic device according to claim 1 , wherein the silver content in the cathode is at least 99.5 weight %.
4. Electronic device according to claim 1 , wherein the electropositive element is selected from Li, Na, K, Be, Mg, Ca, Sr, Ba, Sc, Y, La, Sm, Eu, Tb, Yb, Lu, Ti, V, or Mn.
5. Electronic device according to claim 1 , wherein the phosphine oxide group is part of a substantially covalent structure comprising at least three carbon atoms directly attached to the phosphorus atom of the phosphine oxide group and having overall count of covalently bound atoms in the range 16-250 atoms.
6. Electronic device according to claim 1 , wherein the phosphine oxide group is selected from phosphine oxide substituted with three monovalent hydrocarbyl groups or one divalent hydrocarbylene group forming with the phosphorus atom a ring and one monovalent hydrocarbyl group, and the overall count of carbon atoms in the hydrocarbyl groups and the hydrocarbylene group is 8-80 carbon atoms.
7. Electronic device according to claim 1 , wherein the diazole group is an imidazole group.
8. Electronic device according to claim 1 , wherein the electron transport matrix compound comprises a conjugated system of at least ten delocalized electrons.
9. Electronic device according to claim 1 , wherein the electron transport matrix compound comprises at least one aromatic or heteroaromatic ring.
10. Electronic device according to claim 9 , wherein the electron transport matrix compound comprises at least two aromatic or heteroaromatic rings which are either linked by a covalent bond or condensed.
11. Electronic device according to claim 1 , wherein the molar ratio of the electropositive element to the electron transport compound is lower than 0.5.
12. Electronic device according to claim 1 , wherein the molar ratio of the electropositive element to the electron transport compound is higher than 0.01.
13. Electronic device according to claim 1 , which is an inverted device.
14. Electronic device according to claim 1 , which is a top-emitting device with the cathode having thickness less than 30 nm.
15. Electronic device according to claim 1 , wherein the silver cathode is corrugated and/or combined with a light-scattering layer.
16. Electronic device according to claim 5 , wherein the covalently bound atoms are selected from C, H, B, Si, N, P, 0 , S, F, Cl, Br, or I.
17. Electronic device according to claim 5 , wherein the overall count of covalently bound atoms is in the range 64-160 atoms.
18. Electronic device according to claim 6 , wherein the overall count of carbon atoms in the hydrocarbyl groups and the hydrocarbylene group is 32-54 carbon atoms.
19. Electronic device according to claim 1 , wherein the molar ratio of the electropositive element to the electron transport compound is lower than 0.10.
20. Electronic device according to claim 1 , wherein the molar ratio of the electropositive element to the electron transport compound is higher than 0.08.
21. Electronic device according to claim 1 , wherein the substantially silver cathode is a single-layer cathode.