Functionalization of Electrode Surfaces with Reactive Supramolecular Oligomers Enables the Control of Monolayer Properties to Restore Electrochemical Reversibility

Abstract

The functionalization of conducting silicon (Si) substrates with redox-active probes delivers hybrid semiconducting interfaces whose electronic functions are parameterized by the molecular conformations of monolayers. However, it remains challenging to build electronically homogeneous semiconducting interfaces using flat, π-conjugated derivatives that are prone to aggregation, as structural heterogeneity in the solid state unequivocally engenders ill-defined electronic domains. This limitation has notoriously hampered the development of n-type semiconducting Si interfaces derived from rylene dyes, which possess enticing applications in solar energy capture and conversion. Herein, this challenge is overcome by using supramolecular oligomers derived from reactive naphthalene diimide (NDI) units as structural templates to control the electrochemical response of semiconducting monolayers at Si interfaces. Specifically, conducting Si surfaces functionalized with NDI noncovalent assemblies exhibit reversible electrochemical signals and reduction potentials stabilized by more than 100 mV compared to semiconducting interfaces derived from molecularly derived precursors. Leveraging density functional theory and molecular dynamics simulations, the potentiometric properties recorded experimentally are assigned to discrete NDI conformations, which are parameterized by the aggregation state of the precursors in solution. These findings delineate a novel strategy to control the electronic structure homogeneity of semiconducting interfaces constructed from dyes infamously known to form ill-defined electronic domains.