Imaging Ultrafast\nCharge Transfer at Low-Dimensional\nLead Halide Perovskite Heterostructures

Addressing interface physics and related photoinduced\ndynamics\nis crucial to understand charge carrier paths and losses and ultimately\ndesign efficient optoelectronic devices. However, such dynamics are\noften masked when bulky systems are investigated. In this work, we\ncombine photoluminescence with ultrafast transient absorption microscopy\nto map charge transfer processes in few-layers-thick heterostructures\nmade of low-dimensional (C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>CH<sub>2</sub>NH<sub>3</sub>)<sub>2</sub>(CH<sub>3</sub>NH<sub>3</sub>)<sub>n‑1</sub>Pb<sub>n</sub>I<sub>3n+1</sub> perovskite flakes\nof different dimensionalities (<i>n</i> = 3) and (<i>n</i> = 1). We observe that the hole transfer process from the\n(<i>n</i> = 3) to the (<i>n</i> = 1) phase happens\nafter exciton diffusion on a time scale of tens of picoseconds, whereas\nelectron transfer is hindered by the high exciton binding energy and\nlow diffusion coefficient within the (<i>n</i> = 1) phase.\nThis study sets the stage for a deeper understanding needed for the\nsmart development of new heterostructure combinations with different\ndimensionalities and band alignments.