Controlling electrons and excitons in the two dimensional limit

The growing family of monolayer materials such as graphene and transition metal dichalcogenides (TMDs) are a new class of two-dimensional nanomaterial with diverse electronic properties and strong quantum confinement of electrons and excitons. The versatility of these materials open up new fundamental scientific questions and enable applications as novel, highly-tunable optoelectronic and energy harvesting devices. In order to realize the full potential of these materials, we first need to understand the physics of in-plane defects and out-of-plane interfaces. We demonstrate that synthesis of high-quality and large-area monolayer materials such as graphene and molybdenum disulfide lead to one-dimensional grain boundaries that impact material properties. Next, we demonstrate that stacking monolayers of molybdenum disulfide leads to hybrid electronic states that we can tune through the introduction of interlayer twist. Finally, we utilize charge and energy transfer across van der Waals interfaces to build atomically thin photovoltaic systems.