Heterojunctions Based on Amorphous Silicon: A Versatile Surface Engineering Strategy To Tune Peak Position of Redox Monolayers on Photoelectrodes

摘要

Heterojunctions are typically used to generate large photo-voltages and to influence the direction of flow of charge carriers on photovoltaic and photocatalytic devices. Herein, we propose how heterojunctions can be used as a pathway for tuning the peak position of redox active monolayers. This was possible by exploring the principle of contact between materials in heterojunctions leading to a common equilibrium Fermi level for both sides of the heterojunction. The phenomenon was demonstrated with thin layers of intrinsic amorphous silicon deposited on platinum, indium tin oxide, and either n-type or p-type crystalline silicon electrodes. At fixed light-intensity conditions, the potential required for electron transfer of a model redox probe was modulated according to the substrate on which the amorphous silicon was deposited. This allowed us to alter the peak position of a redox process occurring on the electrolyte side of the junction despite it being isolated from the underlying conducting material. We show how such an effect can be explored in a potential range that encompasses any of the redox monolayers electroactive in aqueous electrolytes.