A new class of superlattices consisting of alternate layers of quasi-one-dimensional (Q1D) conducting polymers is theoretically considered. Although both compositional and doping superlattices are possible, only the doping superlattices are considered in detail. In particular, expressions for the two-dimensional density of electrons and holes in a solitonic as well as a polaronic doping superlattice are obtained. Next, these quantities are used to discuss the optical absorption coefficient, a(w), and the photoconductive response of these Q1D superlattices. Due to the presence of nonlinear excitations such as solitons and polarons in doped conducting polymers, the optical absorption arises not only from the usual interband transition but also from the transitions involving localized levels in the Peierls energy gap. The absorption coefficient is a tunable quantity for the Q1D superlattices since the effective band gap can be tailored to suit the radiation wavelength of interest. In addition, for a certain range of doping levels these superlattices exhibit a new kind of solitonic and polaronic "semimetallic" behavior. Finally, certain means of experimentally measuring a(w) for photon energies smaller than the Peierls gap are described and novel features including the device applications of Q1D superlattices and related modulated structures are discussed.
J. D. Gunton,
"Quasi-One-Dimensional Doping Superlattices", Proc. SPIE 0792, Quantum Well and Superlattice Physics, (11 August 1987); doi: 10.1117/12.940821; https://doi.org/10.1117/12.940821