Molecular junctions provide excellent testbeds for studying electronic structure at molecule-metal interfaces, representative of those found in solar light harvesting processes. Coupling of discrete molecular states to the continuous metallic states, together with the level alignment between frontier orbitals of molecules and Fermi level of the junction, determine the transport properties of molecular junctions. In addition, the phenomenological coupling parameters between the discrete molecular states and the continuum are necessary for constructing models to study charge dynamics at the interfaces, crucial for modeling and understanding solar light harvesting processes. First-principles calculation of the coupling parameters are then important for this purpose. In this work, we compute such coupling parameters in the context of molecular junction based on a non-equilibrium Green's function approach, and analyze the bias and energy dependence of such coupling parameters and their effect in transport properties. The coupling parameter is also the broadening of molecular resonance in the junction, which provides an unambiguous way to understand the transmission function in terms of molecular orbitals. Although developed in the context of molecular junction, the method is well applicable to more general molecule-metal interfaces that are related to dynamical processes in solar light harvesting.

Bias and energy dependent coupling between molecular states and metallic states in molecular junctions

251st National Meeting (2016)

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