Interlayer excitons have become hot candidates for solar cell applications due to their long lifetimes and high mobilities, that make them promising for efficient charge extraction. They have been widely investigated in transition metal dichalcogenides and their heterostructures, but observing them in 2D perovskites has eluded us so far. Theoretical works, however, predict that if the coupling between the organic and inorganic layers of the perovskite is strong enough, obtaining these charge separated excitonic states should be possible. In this study, we design 2D perovskites with energy landscapes suitable for forming such ‘interfacial’ excitons. Our results show that these species form by ultrafast charge transfer occurring over a few to tens of picoseconds, can live for a few µs, and can diffuse at rates comparable to those reported for intralayer Wannier excitons in 2D hybrid perovskites. Furthermore, their properties and dynamics can be tuned by varying the quantum well thickness of the perovskites. Thus, by establishing interfacial excitons in this material, this work makes a stride towards expanding the functionalities of potential perovskite solar cells.

Interfacial excitons in two-dimensional organic-inorganic perovskites

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