Studying the driving force of photoelectrochemical reactions on semiconductor electrodes under strong coupling conditions*

Strong exciton-polariton coupling hybridizes semiconductor and photon modes, splitting the energy levels of the system (Rabi splitting) and thus modifying the photonic, electronic, and chemical properties of the semiconductor. While there have been many demonstrations of using strong coupling to tune optical properties, there is very limited work showing tuning of chemical reactions in liquid electrolyte.

In this work we show progress towards moving strong coupling studies into an aqueous electrochemical environment. Our photoelectrode consists of a plasmonic thin film metal coated with a layer of semiconducting carbon nanotubes (CNTs). The plasmon is tuned to overlap with the ground state S11 exciton of the CNTs, leading to strong coupling. We measure charge transfer photocurrent as a function of potential for different redox species to test the hypothesis that the overpotential is reduced under strong coupling conditions.

As an open-polariton cavity system, our technique offers a way to study conventional photoelectrochemistry under strong coupling conditions, potentially opening the door to photonic control of chemical reactions.