Radiation emitting device

1. A radiation-emitting device comprising:

a substrate;

a first electrode and a second electrode; and

at least one emitter layer arranged between the first and second electrodes, said emitter layer comprising a matrix material, 0.5-5% by weight of a radiation emitting emitter and 5-30% by weight of a phosphorescent exciton scavenger,

wherein the proportion by weight of said exciton scavenger is higher than that of said radiation emitting emitter,

wherein the current efficiency of said emitter layer is increased by at least 10% compared to an emitter layer without exciton scavenger, and

wherein the exciton scavenger has an emission maximum at a shorter wavelength than the radiation emitting emitter.

2. The radiation-emitting device according to claim 1 , wherein the radiation emitting emitter is a phosphorescent emitter.

3. The radiation-emitting device according to claim 1 , wherein an electron transport layer is arranged between electrode and emitter layer, and the LUMO of the exciton scavenger is lower than that of the electron transport layer.

4. The radiation-emitting device according to claim 3 , wherein the difference in the emission maxima is at least 15 nm.

5. The radiation-emitting device according to claim 1 , wherein the radiation emitted by the emitter layer is essentially generated by the radiation emitting emitter.

6. The radiation-emitting device according to claim 1 , wherein the intensity of the normalized emission of the emission maximum of the exciton scavenger in the emitter layer is not more than 10% of the intensity of the emission maximum of the radiation emitting emitter.

7. The radiation-emitting device according to claim 1 , wherein the intensity of the normalized emission of the emission maximum of the exciton scavenger in the emitter layer is not more than 10% of the normalized emission of the emission maximum of the exciton scavenger in a layer which consists of the matrix material and the exciton scavenger.

8. The radiation-emitting device according to claim 1 , wherein the exciton lifetime on the radiation emitting emitter in the emitter layer is longer than on the exciton scavenger.

9. The radiation-emitting device according to claim 1 , wherein the external quantum efficiency η ext of the emitter layer is increased by at least 20% compared to an emitter layer without exciton scavenger.

10. The radiation-emitting device according to claim 1 , wherein the photoluminescence quantum yield of the radiation emitting emitter is greater than that of the exciton scavenger.

11. The radiation-emitting device according to claim 1 , wherein the LUMO of the radiation emitting emitter is higher than that of the matrix and/or of the exciton scavenger.

12. The radiation-emitting device according to claim 1 , wherein the layer thickness of the emitter layer is 10 to 40 nm.

13. The radiation-emitting device according to claim 1 , having at least one further emitter layer.

14. The radiation-emitting device according to claim 13 , wherein the at least one further emitter layer comprises a radiation emitting emitter and an exciton scavenger.

15. The radiation-emitting device according to claim 1 , wherein an overlap of the radiation emitted by the first emitter layer and that emitted by the at least one further emitter layer results in emission of white light.