Patent ID: 8148891

Claim:
An organic light emitting device, comprising: a) an anode; b) a hole transport layer; c) an organic emissive layer comprising an emissive layer host and an emissive dopant, wherein the HOMO of the emissive layer host is at least about 0.5 eV lower than the HOMO of the emissive dopant; d) an electron impeding layer, wherein the electron impeding layer has a thickness of about 20 Å to about 75 Å; e) an electron transport layer; and f) a cathode disposed, in that order, over a substrate; wherein: (i) the electron impeding layer consists essentially of the same material as the emissive layer host, or (ii) the organic emissive layer emits light with CIE coordinates of (X≦0.2, Y≦0.3), or (iii) the emissive dopant is selected from the group consisting of compounds 1-5.