US Patent 7329984 Organic EL devices

Organic EL devices having a light-emitting layer having a fluorescent dopant, a light-emitting layer having a phosphorescent dopant, and a non-light-emitting interface layer provided between an anode and a cathode wherein the light-emitting layer having a fluorescent dopant is provided nearer to the cathode than the light-emitting layer having a phosphorescent dopant and wherein the non-light-emitting interface layer is provided between the light-emitting layer having a fluorescent dopant and the light-emitting layer comprising a phosphorescent dopant.