The present invention relates to an electroluminescent device including an anode and a cathode capable of being electrically connected to a power supply and a voltage regulator, and a multi-layered polymer structure, between the anode and cathode, including a first polymer layer which includes a hole transfer polymer contacting the anode and a second polymer layer which includes an n-type conjugated polymer contacting the cathode, wherein changes in the voltage of current passing through the electroluminescent device change the color of electroluminescent emissions from the multi-layered polymer structure.