We observe a new electroluminescent(EL) peak from a two-layer polymer device, which does not appear in EL spectra of each layer. The polymers of both layers are poly(p-phenylenevinylene) derivative with monoalkoxy substituents, poly(2-methoxy-1,4-phenylene-vinylene, abbreviated as PMPV derivatives), but dialyzed for different periods respectively. A new peak is located at 590 nm and has comparable intensity. The origin of this peak is attributed to the emissive transition at the interface between two emitting layers, which is supported by the transient EL experiment. The multilayer device showed typical diode characteristics and large enhancement of quantum efficiency.