Abstract
While the functionalization of silicon electrode surfaces with molecularly dissolved chromophores paves the way to create diverse redox-responsive interfaces, leveraging nanoscale objects derived from π-conjugated organic building blocks to modulate the electronic structures of Si hybrids remains vastly elusive. This study uncovers a redox-controlled stabilization effect exclusive to silicon electrodes functionalized with monolayers that are derived from perylene bisimide (PBI) nanoaggregates. For this class of n-type hybrid nanomaterials, we highlight that the cathodic potential required to inject negative charge carriers into the conduction band of the PBI monolayer can be reversibly stabilized by more than 375 mV through modulation of the maximum anodic potential (MAP) employed during the anodic cycle (i.e., +0.5 or +1.5 V vs Ag/AgCl). The magnitude of this redox-controlled stabilization effect is shown to be dictated by the structure–function relationships of the PBI nanoaggregates exploited to construct the monolayers on Si electrodes. Using a set of control experiments, we demonstrate that such a redox-controlled stabilization effect is not observed for monolayers derived from molecularly dissolved PBI precursors and for Si electrode precursors that feature a low density of anchoring groups. Supported by density functional theory calculations that highlight a significant structural reorganization of a model, partially p-doped PBI nanoaggregates, the data presented herein indicate that a MAP of +1.5 V versus Ag/AgCl is accompanied by a structural reorganization of the monolayers built exclusively from PBI π-aggregates. We propose that conformational perturbations engendered at a high anodic potential (+1.5 V) lead to the emergence of electronic states that further facilitate electron injections. The results uncovered herein establish a proof of principle that transferring the structure–function relationships of π-aggregates on inorganic electrodes delivers a powerful method to construct nanoscale semiconducting interfaces whose conduction band energies are redox-controlled in a reversible manner. This effect may establish the foundation for a new class of memory effect as the anodic potentials (write) dictate the current density at a given cathodic potential (read).
