Probing Charge Carrier Dynamics in 2D Perovskite-MoS₂ Heterostructure

The global rise in energy demand and frequent energy crises have underscored the need for efficient, sustainable energy solutions. These challenges have driven extensive research into advanced materials for energy conversion and optoelectronics. Heterostructure materials have shown promise due to their superior charge transfer and exciton dynamics. For instance, three-dimensional (3D) perovskite/transition metal dichalcogenide (TMD) heterostructures have been widely studied in solar cells and photodetectors due to their efficient charge transfer across interfaces. However, the nonlayered structure of 3D perovskites introduces dangling bonds at the interface, which hinder charge transfer and coupling efficiency.
In contrast, two-dimensional (2D) perovskite-monolayer or few-layer TMD heterostructures offer a more robust coupling mechanism, which can enhance charge transfer efficiency. Van der Waals interactions between these 2D materials can lead to type II band alignment, resulting in spatial separation of electrons and holes into distinct layers, which might favor the formation of interlayer excitons (IEs). Despite their potential in photovoltaics, fundamental studies on the charge carrier dynamics and IEs in 2D perovskite/monolayer TMD heterostructures remain unexplored.
These hybrid heterostructures are composed of two-dimensional (2D) transition metal dichalcogenides (TMDs) and perovskites hold immense potential for next-generation optoelectronic applications, such as photodetectors and solar cells. Among them, MoS₂, a TMD with high charge mobility and exceptional optoelectronic properties, coupled with halide perovskites, offers a promising platform for efficient charge transfer and exciton dissociation. This research investigates the ultrafast charge carrier dynamics at the heterointerface of 2D perovskite and MoS₂ heterostructures using femtosecond transient absorption spectroscopy (fs-TAS). Our study focuses on unraveling the underlying mechanisms that govern charge transfer and exciton dissociation within these heterostructures.
The heterostructures were prepared by stacking (PEA)₂PbI₄, a layered 2D perovskite, with few layer MoS₂. Upon photoexcitation at 475 nm, the system demonstrated efficient charge transfer. The kinetics of charge transfer were fitted using biexponential fits, which shows faster decay components in the heterostructure compared to pristine MoS₂, indicating charge transfer processes.
To further elucidate the dynamics, we employed a blocking layer, PMMA, to inhibit interfacial dynamics, observing a marked suppression of charge transfer. This confirmed the role of the heterojunction in facilitating efficient charge carrier dynamics. Our findings provide critical insights into the charge transfer mechanisms in 2D perovskite-TMD heterostructures and pave the way for optimizing these materials for high-performance optoelectronic devices. By tuning the material composition and band alignment, we aim to further enhance the charge separation efficiency and tailor the exciton dynamics for specific applications. Future work includes investigating the effects of halide alloying in the perovskite to fine-tune the valence band offset and modulate the rate of hole transfer, providing a pathway for designing heterostructures with improved optoelectronic performance.