Tunable Broadband Molecular Emission in Mixed-Organic-Cation Two-Dimensional Hybrid Perovskites

The ability to controllably enhance or suppress the luminescence contributions from different species in layered two-dimensional (2D) hybrid perovskites is beneficial for developing color-tunable broadband emitters. In particular, for 2D perovskites exhibiting interlayer sensitized triplet emission from their organic cations, the final molecular emission profiles are often influenced by intermolecular interactions between neighboring chromophores. Embedding these chromophores within an inert host cation is an emerging strategy for controlling the degree of intermolecular coupling and thereby influencing the formation of isolated monomer versus multimolecular states. In this work, we demonstrate tunable broadband emission from 2D perovskites containing varying amounts of a naphthalene chromophore mixed with hexylammonium cations. Across the series of perovskites, emission from free or self-trapped excitons and naphthalene triplet monomers or excimers contributes to wide color tunability from green to yellow to orange. These results suggest that organic-cation mixing may be a generalizable approach for modifying photophysical outcomes in 2D hybrid perovskites.