Investigation of Many-Body Exciton Recombination and Optical Anisotropy in Two-Dimensional Perovskites Having Different Layers with Alternating Cations in the Interlayer Space

Two-dimensional (2D) perovskites with alternating cations in the interlayer space (ACI) represent a new type of structure with different physical properties compared to the more common Ruddlesden-Popper (RP) counterparts. Still, there is a lack of understanding of photophysical and optoelectronic properties. In our work, we have used transient absorption spectroscopy to get better insight into the nature of photoexcitations in ACI perovskites with varying layers. We observed that multiple exciton recombination predominates, compared to self-trapping of excitons, with increasing the number of layers (expressed by n). With decreasing n, the ACI perovskite shows less many-body exciton recombination due to a very fast self-trapping of the excitons. Furthermore, we observed that the optical anisotropy increases with increasing number of the inorganic layers as the polarization orientation increases. Comparing the photophysical properties of the three different systems, we suggest that ACI3 is most promising for photovoltaic and optical polarization devices.