In order to meet today’s growing global energy demands, Hybrid Molecular/Materials (HMM) devices represent one novel approach for high efficiency, low-cost semiconductor devices needed to couple solar cells with catalysts for renewable chemical fuels production (e.g. H2, CO). In our work, HMM devices are fabricated via two primary methods: molecular functionalization and metal oxide growth. Both of these strategies facilitate protection of the silicon surface, while providing reactive sites for catalysis or attachment of catalysts. In order to interlink the molecular and materials components, a modular dimethoxyphenyl-triflate building block (diOMePhOTf) has been synthesized for multiple purposes within the HMM architecture. Firstly, this building block will be utilized as a spacing unit derivatized with bulky siloxy groups to attain steric spacing as suitable for surface passivation by atomic layer deposition (ALD). Secondly, the para-triflate on the spacing linker offers a reactive site for the surface growth of a conducting molecular wire through iterative Negishi couplings of biphenyl linkers. Conveniently, these precursors are also synthesized from diOMePhOTf with 4-bromophenylboronic acid via Suzuki coupling. Surface attachment and wire growth are investigated by X-ray Photoelectron Spectroscopy (XPS). Lastly, the siloxy and dimethoxy groups on the molecular wire can be deprotected in situ to expose the free hydroxy groups to promote nucleation during ALD. The cooperativity between the molecular and materials components will be evaluated by quantifying electron transport through the HMM multi-layer at varying molecular wire lengths and ALD thicknesses (Al2O3, TiO2). Additionally, vinylferrocene redox markers can be coupled to the molecular wires (before and after ALD) for cyclic voltammetry measurements to derive apparent rate constants (kapp) and decay constants (β). These measurements will elucidate the electron transfer mechanism, and consequently aid in optimizing device performance.

Functionalization of Si(111) with sterically spaced molecular wires intercalated within ALD-deposited metal oxides for electron transfer applications

251st National Meeting (2016)

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