Organic electroluminescent device

1. Organic electroluminescent device comprising a first electrode, at least one second electrode, at least one emission layer and at least one electron transport region, wherein the emission layer and the electron transport region are arranged between the at least one second electrode and the first electrode and the electron transport region is arranged between the emission layer and the at least one second electrode, wherein the at least one electron transport region comprises

a) a first electron transport layer; and

b) a performance enhancement layer, the performance enhancement layer having a refractive index of ≤1.6 at a wavelength of 1,200 nm;

wherein

the first electron transport layer is arranged between the emission layer and the performance enhancement layer; and

the performance enhancement layer is arranged between the first electron transport layer and the at least one second electrode, and the performance enhancement layer further comprises an n-type dopant.

2. Organic electroluminescent device according to claim 1 , wherein the electron transport region further comprises an electron injection interlayer, wherein the electron injection interlayer is arranged between the first electron transport layer and the performance enhancement layer.

3. Organic electroluminescent device according to claim 1 , wherein the organic electroluminescent device is an organic light emitting diode or an organic electroluminescent transistor.

4. Organic electroluminescent device according to claim 1 , wherein the performance enhancement layer comprises a low refractive material selected from the group consisting of silsesquioxanes, alkanes, perfluoroalkanes, perfluoroalkyl phosphonic acids, perfluorophosphine oxides, and metal fluorides.

5. Organic electroluminescent device according to claim 4 , wherein the silsesquioxane is represented by the general formula Si x R x O 1.5x , wherein R is a hydrocarbyl group which may comprise at least one heteroatom selected from the group consisting of B, Si, N, P, O, and S, and/or which may comprise at least one substituent which is a halogen atom; and x is selected from 6, 8, 10, 12, 14, or 16.

6. Organic electroluminescent device according to claim 4 , wherein the alkane is selected from alkane having 18 to 60 carbon atoms.

7. Organic electroluminescent device according to claim 4 , wherein the metal fluoride is selected from LiF, NaF, KF, or mixtures thereof.

8. Organic electroluminescent device according to claim 4 , wherein the low refractive material is selected from

LiF, or mixtures thereof.

9. Organic electroluminescent device according to claim 1 , wherein the n-type dopant is selected from alkali metal, alkaline earth metal, rare earth metal, organic complexes thereof, or halides thereof, or is a compound represented by one of the following formulae

or mixtures thereof.

10. Organic electroluminescent device according to claim 1 , comprising, in this order, the first electrode, a p-type doped hole transport layer, optionally a first hole transport layer, optionally a second hole transport layer, the emission layer, the first electron transport layer, optionally the electron injection interlayer, the performance enhancement layer, and the at least one second electrode.

11. Organic electroluminescent device according to claim 1 , wherein the first electron transport layer does not comprise an n-type dopant.

12. Organic electroluminescent device according to claim 10 , wherein the electron injection interlayer is an n-type doped electron transport layer.