Stacked organic electroluminescent devices

1. A light-emitting device comprises a plurality of stacks of organic EL elements, wherein one organic EL element of a stack overlaps at least a portion of another organic EL element of the same stack, the organic EL elements of the same stack are electrically separate, one organic EL element of one stack is electrically connected in series to another organic EL element in an adjacent stack, and each organic EL element comprises an organic EL material disposed between a pair of electrodes.

2. The light emitting device of claim 1 wherein each series of organic EL elements is activated with a different current level.

3. The light-emitting device of claim 1 , wherein one of the electrode comprises a material selected from the group consisting of indium tin oxide, tin oxide, indium oxide, zinc oxide, indium zinc oxide, zinc indium tin oxide, antimony oxide, carbon nanotubes, silver, gold, and mixtures thereof.

4. The light-emitting device of claim 1 , wherein one of the electrode is a cathode and comprises a material selected from the group consisting of K, Li, Na, Mg, Ca, Sr, Ba, Al, Ag, Au, In, Sn, Zn, Zr, Sc, Y, elements of the lanthanide series, alloys thereof, mixtures thereof, Ag—Mg alloy, Al—Li alloy, In—Mg alloy, Al—Ca alloy, LiF, KF, and NaF.

5. The light-emitting device of claim 1 , wherein one of the electrode is a cathode and comprises a material selected from the group consisting of indium tin oxide, tin oxide, indium oxide, zinc oxide, indium zinc oxide, zinc indium tin oxide, antimony oxide, carbon nanotubes, and mixtures thereof.

6. The light-emitting device of claim 5 , wherein the cathode is a layer having a thickness from about 1 nm to about 10 nm.

7. The light-emitting device of claim 1 , wherein the organic EL material comprises a material selected from the group consisting of poly(n-vinylcarbazole); polyfluorene; poly(alkylfluorene); poly(praraphenylene); poly(p-phenylene vinylene); polythiophene; poly(pyridine vinylene); polyquinoxaline; poly(quinoline); and derivatives thereof.

8. The light-emitting device of claim 1 , wherein the organic EL material comprises polysilane.

9. The light-emitting device of claim 8 , wherein the polysilane is selected from the group consisting of poly(di-n-butylsilane), poly(di-n-pentylsilane), poly(di-n-hexylsilane), poly(methylphenylsilane), and poly{bis(p-butylphenyl)silane}.

10. The light-emitting device of claim 1 , wherein the organic EL material comprises a material selected from the group consisting of organo-metallic complexes of 8-hydroxyquinoline, aluminum-acetylacetonate, gallium-acetylacetonate, and indium-acetylacetonate, aluminum-(picolymethylketone)-bis{2,6-di(t-butyl)phenoxide}, scandium-(4-methoxy-picolylmethlketone)-bis(acetylacetonate), and mixtures thereof.

11. The light-emitting device of claim 1 , wherein organic EL elements of the same stack emit different light colors.

12. The light-emitting device of claim 1 , wherein organic EL elements that are electrically connected in series comprise the same organic EL material.

13. The light-emitting device of claim 1 , wherein each series of organic EL elements is activated with a different voltage level.