Exciton and Hot Charge Carrier Dynamics in a MoS<sub>2</sub>/(PEA)<sub>2</sub>PbI<sub>4</sub> 2D Heterostructure.

Ghosh, Bikram; Kamat, Prashant V; Hartland, Gregory V · ACS Nano · 2025

basic_science · Level V

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Abstract

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