Exciton diffusion in two-dimensional metal-halide perovskites

Abstract

Two-dimensional perovskites, in which inorganic layers are stabilized by organic spacer molecules, are attracting increasing attention as a more robust analogue to the conventional three-dimensional metal-halide perovskites. However, reducing the perovskite dimensionality alters their optoelectronic properties dramatically, yielding excited states that are dominated by bound electron-hole pairs known as excitons, rather than by free charge carriers common to their bulk counterparts. Despite the growing interest in two-dimensional perovskites for both light harvesting and light emitting applications, the full impact of the excitonic nature on their optoelectronic properties remains unclear, particularly regarding the spatial dynamics of the excitons within the two-dimensional (2D) plane. Here, we present direct measurements of in-plane exciton transport in single-crystalline layered perovskites. Using time-resolved fluorescence microscopy, we show that excitons undergo an initial fast, intrinsic normal diffusion through the crystalline plane, followed by a transition to a slower subdiffusive regime as excitons get trapped. Interestingly, the early intrinsic exciton diffusivity depends sensitively on the exact composition of the perovskite, such as the choice of organic spacer. We attribute these changes in exciton transport properties to strong exciton-phonon interactions and the formation of large exciton-polarons. Our findings provide a clear design strategy to optimize exciton transport in these systems.

arXiv comment22 pages, 4 figures, and supporting information

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• Negative diffusion of excitons in quasi-two-dimensional systems
• Exciton Delocalization Suppresses Polariton Scattering
• Photoluminescence decay of mobile carriers influenced by imperfect quenching at particle surfaces with subdiffusive spread
• Robust Surface-Induced Enhancement of Exciton Transport in Magic-Angle-Oriented Molecular Aggregates
• Chasing Charge Carriers: Diffusion Dynamics in Mixed-n Quasi-Two-Dimensional Colloidal MAPbBr3 Perovskites
• Unveiling Photoluminescence Signatures of Magneto-Optical Coupling in Layered Hybrid Manganese Chloride Perovskites