Physical properties of solvated charge carriers on one-dimensional semiconductors

When an excess charge carrier is added to a one-dimensional (1D) wide-band semiconductor nanostructure immersed in a polar solvent, the carrier can undergo self-localization into a large-radius adiabatic polaron. Using a simplified theoretical model for small-diameter structures, we study physical properties of the resulting 1D polarons: low-frequency dynamics, local optical absorption, and electron transfer to/from polarons. We show that the combined microscopic dynamics of the electronic charge density and the solvent leads to macroscopic Langevin dynamics of a polaron and to the appearance of local dielectric relaxation modes. Polaron mobility is evaluated as a function of system parameters. Numerical estimates indicate that the solvated carriers can have mobilities orders of magnitude lower than the intrinsic values. We find that about 90% of the local optical absorption strength is contained in the transition to the second lowest-energy localized electronic level formed in the polarization potential well, with the equilibrium transition energy larger than the binding energy of the polaron. Thermal fluctuations, however, can cause a very substantial---an order of magnitude larger than the thermal energy---broadening of the transition. The resulting broad absorption feature may serve as a signature for the optical detection of solvated charge carriers. To examine the activation energy of electron transfer from/to a 1D semiconductor, we generalize the Marcus theory description to the case of variable distributed charge densities. We specifically analyze thermally-activated electron transfer between a small species and a 1D semiconductor and between two parallel 1D structures. While quantitatively the activation energy would ordinarily be largely determined by small species, the qualitative difference for 1D polarons is clearly delineated. A useful observation is made that traditional Marcus expressions for transfer between two small species may be a good approximation for the discussed electron transfer process. For practical values of polaron binding energies, we find that thermal fluctuations can readily facilitate the electron transfer between neighboring 1D nanostructures.