Extended photocarrier lifetime in graphene via 3R-stacked bilayer MoS2

Graphene exhibits exceptional carrier mobility but suffers from ultrafast photocarrier recombination, limiting its utility in optoelectronic applications. Here, we demonstrate prolonged photocarrier lifetimes in graphene through heterostructuring with monolayer as well as 2H- and 3R-stacked bilayer MoS 2 . Using ultrafast transient absorption spectroscopy with a probe photon energy below the MoS 2 bandgap, we selectively monitor carrier dynamics in graphene. While isolated graphene exhibits a photocarrier lifetime of only ∼ 1 ps, the slow decay component of the transient signal is progressively extended in heterostructures with monolayer, 2H-bilayer, and 3R-bilayer MoS 2 , reaching ∼ 100 ps in the 3R heterostructure. The substantially longer carrier lifetime associated with the slow decay component in the 3R heterostructure is attributed to the intrinsic out-of-plane electric field in 3R MoS 2 , which modifies interfacial hole transfer and suppresses carrier recombination. Analysis of the early-time dynamics further reveals moderately slower interlayer charge transfer with increasing MoS 2 thickness and with 3R stacking. These results demonstrate that stacking-order engineering in van der Waals heterostructures provides an effective route for controlling nonequilibrium carrier dynamics in graphene and related two-dimensional materials.