Photoluminescence Spectroelectrochemistry Study of CVD-2D MoS₂monolayers Transferred Onto a Conductive Transparent Electrode

Two-dimensional transition metal dichalcogenides (2D-TMDs) have been the focus of much research study in a variety of different fields such as sensing, supercapacitors, batteries, hydrogen evolution reactions, and catalysts. Monolayer 2D TMDs of MoS2have attracted particular attention in optoelectronics due to the transition of indirect to direct bandgaps with decreasing number of layers. Furthermore, the photoluminescence (PL) of monolayer MoS2can be tuned by increasing the ratio of excitons (electron and hole) to trions (two electrons and a hole) via chemical doping and localized surface plasmon resonance (LSPR). Electron withdrawing groups also have been used to produce p-type doping effects on the MoS2, which cause the ratio of trions to excitons to increase thereby increasing the PL. In this study, the effect of an electrochemical potential bias on PL from 2D MoS2synthesized by Chemical Vapor Deposition (CVD) and transferred onto a Indium-Tin-Oxide (ITO) electrode is examined. It was observed that a positive external bias caused an increase in the PL by three-fold at 0.8 V vs. Ag/AgCl in PBS buffer accompanied by a red shift in its peak position. The PL intensity and peak shift dependencies on scan rate, maximum oxidation potential, and spatial distribution of initial PL intensity and upon electrochemical potential bias and possible mechanism will be discussed in this presentation.