Patent ID: 8310147

Claim:
An organic light emitting element comprising: an anode over a substrate; a first layer over the anode, the first layer comprising a hole injecting material and a hole transporting material; a second layer over the first layer, the second layer comprising a host material and the hole transporting material; a third layer over the second layer, the third layer comprising a hole blocking material and the host material; a fourth layer over the third layer, the fourth layer comprising an electron injecting material and the hole blocking material; and a cathode over the fourth layer, wherein a luminescent material is doped in a portion of the second layer and a portion of the third layer, and wherein an energy difference between a highest occupied molecular orbit and a lowest unoccupied molecular orbit of the hole blocking material is larger than an energy differences between a highest occupied molecular orbit and a lowest unoccupied molecular orbit of the hole transporting material and the host material.