Achieving Direct Bandgap and Optoelectronic Enhancement in Scalable Stacked MoS ₂ Monolayers

Abstract Near unity photoluminescence quantum yield in monolayer MoS 2 , makes it an excellent candidate for optoelectronic applications. In contrast, bulk MoS 2 experiences a transition from a direct to an indirect bandgap, which diminishes its potential for optoelectronic devices. In this work, the ability to preserve the direct bandgap of MoS 2 while simultaneously enhancing its absorption, mobility, and other optoelectronic properties via stacking monolayers is demonstrated. A scalable method for stacking large‐area monolayer MoS 2 films grown by chemical vapor deposition (CVD) is presented. The approach employs poly(methyl methacrylate) (PMMA) as a carrier polymer and an aluminum mesh to support the films during transfer from the donor to the receiver substrate, maintaining its geometry and preventing folding. The assembled monolayer stacks exhibit a monotonic increase in photoluminescence (PL), absorption, and mobility, while retaining monolayer‐like Raman signatures and a direct bandgap. Notably, a four‐layer stack demonstrates a remarkable increase of more than 225% in PL, 250% in absorption, and 94% in field‐effect mobility compared to single‐monolayer MoS 2 . The preservation of monolayer‐like Raman and direct bandgap behavior in the stacks is attributed to an increased interlayer spacing and twist angle observed between the layers.