Electron Transport in Disordered Molecular Adlayers and Molecular Junctions

This thesis contains a number of computational studies with the overarching goal of understanding the effects of structural disorder on electron transport in nano-scale architectures. The simulations in this work model a range of time and length scales and explore electron transport across molecular adlayer films, molecular junctions, and molecularly linked nanoparticle arrays. In the first chapter, Monte Carlo simulations are used to study the structure and phase behavior of adlayer films composed of chains containing internal dipoles. Phase transitions in the films as well as chain dynamics are found to depend on the strength of the dipoles. In the next chapter, the effects of phase behavior on electronic diffusion within an adlayer film are explored using kinetic Monte Carlo simulations. Electrons hop between redox-active chains in a monolayer composed of redox-active and redox-passive moieties. The mechanism of charge transport depends on the mobility of the chains in the adlayer film, which in turn is sensitive to the packing structure of the chains.;Shifting the focus from supramolecular assemblies to single-molecule junctions, electron transport properties of metal-molecule-metal junctions are calculated using a combination of electronic structure calculations and a Green's function formalism. The effects of sigma-delocalization on the conductance in oligosilane-bridged molecular junctions are investigated, and results show that sigma-delocalization causes strong dependence of the junction conductance on molecular conformation. Next, molecular dynamics simulations are combined with quantum transport calculations to study how structural fluctuations affect junction conductance. A mechanically-activated molecular switch is proposed, and its mechanical and electron transport properties are characterized.;Finally, a multi-scale computational approach is used to study electron transport through a disordered, molecularly linked nanoparticle array. A combination of molecular dynamics simulations, quantum transport calculations, and kinetic Monte Carlo simulations is employed to study electronic motion on a range of time and length scales. Potential advantages and disadvantages of studying single-molecule junctions using nanoparticle-array architecture are discussed. This final project connects the studies of electronic motion in two-dimensional assemblies (adlayer films) with calculations of single-molecule conductance.