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, MoS 2 and phenethylammonium lead iodide, (PEA) 2 PbI 4 (a 2D perovskite), are physically coupled, and the excited-state dynamics are probed using femtosecond transient absorption measurements. Electron transfer from (PEA) 2 PbI 4 to MoS 2 and hole transfer from MoS 2 to (PEA) 2 PbI 4 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) 2 PbI 4 to MoS 2, 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.