Mechanism of Charge Transport in Mixed-Valence 2D Layered Hybrid Bronze Materials

Abstract

Two-dimensional layered bronze (HB) materials are a new class of mixed-valence hybrid organic-inorganic metal oxides that demonstrate great potential as advanced functional materials for next-generation electronics. Recently, new hybrid vanadium bronze materials, (EV)V8O20 and (MV)V8O20, EV = ethyl viologen and MV = methyl viologen, have been introduced, with EV having ~3 orders of magnitude higher electrical conductivity than the MV system. Given their identical inorganic V-O layers and similar reduction potentials, the observed large difference in electrical conductivities is puzzling. Here, through accurate first-principles calculations coupled with MACE machine learning molecular dynamics (MD) simulations validated by accurate ab initio MD simulations, we provide mechanistic molecular-level insights into dominant charge transport and electrical conductivity pathways in these materials. Our detailed structural and electronic properties data identifies factors contributing to this significant difference in electrical conductivities of these materials. Our findings in this work offer clues and provide valuable insights into improving the electrical conductivity of hybrid bronze and similar materials in order to guide the design of next-generation materials with enhanced properties for future electronic and thermoelectric applications.