Heterostructure multilayer thin films comprised of electroactive polymers such as poly(thiophene acetic acid), sulfonated polyaniline, poly(pyridinium acetylene) and a poly(p-phenylene vinylene) precursor have been successfully fabricated via a process based on the spontaneous self-assembly of conjugated polyions on to a substrate. The process involves the alternate dipping of a substrate into a dilute solution of a polycation followed by dipping into a dilute solution of a polyanion, with one or both of the polyions being a conjugated polymer. This process can be repeated as many times as desired to build multilayer thin films of conducting polymers in which each layer deposited is only 5-20 angstrom in thickness. Since it is a molecular level deposition process, it is possible to build heterostructure thin films with complex molecular architectures and thicknesses that are controllable at the molecular level.