Organic light emitting diode having electron and hole mobility in light emitting layer and display using the same

1. An organic light emitting diode comprising a pair of electrodes and a stack including a hole transport layer, a light emitting layer, and an electron transport layer, the stack being intermediate between the electrodes, the light emitting layer being of a material having hole mobility and electron mobility equal to or lower than hole mobility of the hole transport layer and electron mobility of the electron transport layer, respectively,

wherein the organic light emitting diode satisfies the relationship: 0.1≦μ(e2)/μ(h2)≦10, wherein μ(e2) is electron mobility of the light emitting layer and μ(h2) is hole mobility of the light emitting layer.

2. The organic light emitting diode as claimed in claim 1 , wherein the light emitting layer is of a material having hole mobility and electron mobility in equilibrium.

3. The organic light emitting diode as claimed in claim 1 , wherein a balance of electron supply and hole supply to the light emitting layer is in equilibrium.

4. The organic light emitting diode as claimed in claim 1 , wherein the light emitting layer contains a hole transport material and an electron transport material.

5. The organic light emitting diode as claimed in claim 4 , wherein the electron transport material is an aromatic heterocyclic compound having at least one hetero atom in the molecule thereof.

6. The organic light emitting diode as claimed in claim 5 , wherein the light emitting layer contains at least one of the same electron transport material as the electron transport layer and the same hole transport material as the hole transport layer.

7. The organic light emitting diode as claimed in claim 1 , wherein the light emitting layer contains a phosphorescent material.

8. A display having a display area comprising the organic light emitting diode as claimed in claim 1 .