Exciton Diffusion in Two-dimentional Chiral Perovskites

Two-dimensional (2D) organic–inorganic hybrid perovskites emerged as a versatile platform for light-emitting and photovoltaic applications due to their unique structural design and chemical flexibility. Their properties depend heavily on the choice of the inorganic lead halide framework and the surrounding organic layers. Recently, the introduction of chiral cations into 2D perovskites has attracted major interest to induce chirality and tune the chiro-optical response. Importantly, their optical properties are dominated by tightly bound excitons that also serve as primary carriers for energy transport. The mobility of photo-injected excitons is thus important from the perspectives of fundamental material properties and optoelectronic applications, yet remains an open question. Here, exciton propagation in 2D chiral perovskites is demonstrated using transient photoluminescence microscopy and density-dependent transport over more than 100 nanometers at room temperature is revealed with diffusion coefficients as high as 2 cm² s⁻¹. Two distinct regimes of initially rapid propagation and subsequent localization are observed. Moreover, perovskites with enantiomer pure cations exhibit faster exciton diffusion than the racemic mixture, correlated with the impact of the material composition on the disorder. Altogether, the observations of efficient exciton diffusion highlight the potential of 2D chiral perovskites to merge chiro-optical properties with strong light-matter interaction and energy transport.