Seminar Abstract:

Two-dimensional transition metal dichalcogenide materials such as MoS2 can be synthesized as a monolayer with unique optoelectronic properties suitable for utilization in transistors, infotronics, solar energy conversion, and electrochemical catalysis. However, proliferation of point defects leads to reduced performance due to competing nonradiative recombination processes introduced by defect-driven midband trap states. Chemical vapor deposition (CVD) synthesis is a leading method for producing TMD materials with controllable morphology, composition, and layer thickness. In this seminar, rational synthetic design will be explored as a mechanism for passivating defects without the need for post-synthetic treatments. In particular, the synthesis of Moiré twisted-bilayer MoS2 is investigated, beginning with a recent theoretical study (J. Amer. Chem. Soc. 2026, 148 (33), 36230–36240) where simulated twisted-bilayer MoS2 formed a multi-domain Moiré superlattice with localized enhanced carrier lifetimes even when considering recombination at defect sites. Experimentally, CVD synthesis has been used to produce twisted-bilayer MoS2 with a wide range of twist angles with observable Moiré superlattice “patterns” in bilayer regions (Nat. Commun. 2024, 15, 562). Raman and Photoluminescence spectroscopy analysis showed that local structural environments and carrier behaviors changed as a function of twist angle. However, clear-cut trends could not be established, likely due to the impact of defects in the samples. The potential consequences of defect-carrier interactions will be considered in the context of the published Raman and PL data, and potential methods for future isolation and direct study of defect-carrier interactions in twisted-bilayer TMD materials will be discussed.