Charge and Energy Transfer Across the Organic-Inorganic Interfaces of Two Dimensional Lead Halide Perovskites

Creating heterojunctions enables the amalgamation of optimal properties from diverse materials, effectively bypassing individual bottlenecks. The essential photophysical phenomena in these materials are propelled by charge and energy transfer across these heterojunctions, making a comprehensive understanding of these processes imperative for optimizing such systems for energy conversion and harvesting applications. In our work on pyrene-based quasi-2D lead iodide perovskites, we explore how band engineering can instigate the formation of distinctive excited states and diverse optical phenomena. We conduct an in-depth analysis of their underlying mechanisms, also examining their competition with other parasitic processes. For the <i>n</i> =1 perovskite, efficient triplet energy transfer (TET) occurs from the inorganic sublattice to the organic layer, within the Marcus inverted domain. This transfer is driven by quantum tunneling, resulting in rarely witnessed temperature-invariant TET rates. On the other hand, the<i> n</i> =2 perovskite exhibits no TET. Instead, we observe the emergence of long-lived and mobile ‘interlayer’ excitons, originating from ultrafast charge transfer across the organic-inorganic interface.