Exciton and Hot Charge Carrier Dynamics in a MoS2/(PEA)2PbI4 2D Heterostructure

Understanding charge carrier dynamics in two-dimensional (2D) semiconductors and their heterostructures is crucial for advancing their application in optoelectronic devices. In this work, two different 2D semiconductors, MoS2 and phenethylammonium lead iodide, (PEA)2PbI4 (a 2D perovskite), are physically coupled, and the excited-state dynamics are probed using femtosecond transient absorption measurements. Electron transfer from (PEA)2PbI4 to MoS2 and hole transfer from MoS2 to (PEA)2PbI4 were established by performing experiments at different excitation wavelengths (475 and 675 nm). The electron transfer step involved ultrafast hot-electron transfer (<1 ps) from (PEA)2PbI4 to MoS2, followed by thermalization. The electron and hole transfer between the 2D layers of the heterostructure was suppressed when a layer of poly(methyl methacrylate) (PMMA) was inserted between the two layers, thus breaking their interactions. The wavelength-dependent exciton and hot carrier dynamics in 2D heterostructures presented in this study have broad applications in energy conversion and optoelectronic devices.