Quantifying Energy Level Alignment at Monolayer MoS₂/Electrolyte Interface

Transition metal dichalcogenides (TMDs) have unique optical and electronic properties for photo-electrocatalysis applications. The fundamental problem is that the interfacial energetics of TMD/electrolyte interfaces in photoelectrochemical cells are poorly understood. The weakly screened Coulomb potential leads to a large exciton energy and a strong renormalization of the bang gap energy as a function of carrier concentration. Hence, my talk will focus on quantifying how the conduction and valence band energies move as a function of applied potential in an electrochemical cell. To do so, we utilize potential-dependent spatially resolved absorption spectroscopy to quantify the energy levels of monolayer MoS2 in electrochemical cells. The spatially resolved measurements are necessary to distinguish monolayer from few layer-thick material on the sample and, therefore, simplifies data interpretation. I will discuss how we 1) use optical data to extract the carrier concentration of the semiconductor as a function of applied bias and 2) construct band energy diagrams as a function of applied potential.