NOVELTY - The multilayer organic device (10) comprises a substrate bearing an anode (12) and a cathode, a first layer comprising a first organic semiconductor material, and a second layer comprising a doped second organic semiconductor material. The second layer is placed over the first layer, and the first and second layers are located between the anode and cathode. An average molecular weight of the first organic semiconductor material is higher than an average molecular weight of the second organic semiconductor material.    USE - Used as a multilayer organic device such as an organic electroluminescent device including a polymeric light emitting diode or a photoresponsive device including a solar cell forming a polymeric organic photovoltaic device.    ADVANTAGE - The multilayer organic device can be efficiently, economically and easily manufactured with excellent optoelectronic properties and improved lifespan.    DETAILED DESCRIPTION - The multilayer organic device (10) comprises a substrate bearing an anode (12) and a cathode, a first layer comprising a first organic semiconductor material, and a second layer comprising a doped second organic semiconductor material. The second layer is placed over the first layer, and the first and second layers are located between the anode and cathode. An average molecular weight of the first organic semiconductor material is higher than an average molecular weight of the second organic semiconductor material. The first and second organic semiconductor materials have the same highest occupied molecular orbital level. The first organic semiconductor material is provided in a layer on its own and made of a polymer, and acts as a host for a blue or blue-green light emissive material. The second organic semiconductor material is provided in an electroluminescent layer and in a blended layer with other polymers, dendrimers or small molecules and made of a polymer or an oligomer, and acts as a host for an emitting species, a host for phosphorescent moieties and a host for a blue or blue-green emissive material. An average length of the polymer of the first layer is higher than an average length of the polymer of the second layer. The first organic semiconductor polymer is provided in a charge transporting layer, which is a hole transport layer (16). The average molecular weights of the organic semiconductor materials are a high weight average molecular weight and a low weight average molecular weight. An INDEPENDENT CLAIM is included for a method of fabricating a multilayer organic device.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a multilayer organic device.    Multilayer organic device (10)    Anode (12)    Hole injection layer (14)    Hole transport layer (16)    Emissive layer. (18)