Tandem OLED device with intermediate connector

1. A tandem OLED device comprising:

(a) an anode;

(b) a cathode;

(c) at least two electroluminescent units disposed between the anode and the cathode, wherein each of the electroluminescent units includes at least one hole-transporting layer and one organic light-emitting layer; and

(d) an intermediate connector disposed between adjacent electroluminescent units,

wherein the intermediate connector includes an n-doped organic layer and an electron-accepting layer, the electron-accepting layer being disposed closer to the cathode than the n-doped organic layer,

wherein the n-doped organic layer includes an alkali metal and an organic alkali metal complex, and

wherein the intermediate connector further includes an undoped layer in contact with the n-doped layer on the side closer to the anode.

2. The tandem OLED device of claim 1 wherein the organic alkali metal complex includes a phenanthroline derivative.

3. The tandem OLED device of claim 2 wherein the alkali metal is lithium.

4. The tandem OLED device of claim 3 wherein the organic alkali metal complex includes lithium.

5. The tandem OLED device of claim 4 wherein the n-doped organic layer further includes an uncharged phenanthroline derivative.

6. The tandem OLED device of claim 1 wherein the organic alkali metal complex includes a chemical compound according to the following formula:

7. The tandem OLED device of claim 1 wherein the undoped layer includes an anthracene derivative.

8. The tandem OLED device of claim 7 wherein the undoped layer further includes an organic alkali metal complex.

9. The tandem OLED device of claim 8 wherein the organic alkali metal complex in the undoped layer is a salt of hydroxyquinoline.

10. The tandem OLED of claim 1 wherein the electron-accepting layer includes a hexaazatriphenylene derivative.