Role of Exciton Diffusion in the Efficiency of Mn\nDopant Emission in Two-Dimensional Perovskites

Two-dimensional (2D)\nmetal-halide perovskites have promising characteristics\nfor optoelectronic applications. By incorporating Mn<sup>2+</sup> ions\ninto the perovskite structure, improved photoluminescence quantum\nyield can be achieved. This has been attributed to the formation of\ndefect states that act as efficient recombination centers. Here, we\nmake use of transient photoluminescence microscopy to characterize\nimportant material parameters of Mn<sup>2+</sup>-doped 2D perovskites\nwith different doping levels. From these measurements, we visualize\nthe importance of exciton transport as an intermediate step in the\nexcitation of Mn<sup>2+</sup>. We model the spatiotemporal dynamics\nof the excited states to extract the diffusion constant and the transfer\nrate of the excitations to the Mn dopant sites. Interestingly, from\nthese models, we find that the average distance an exciton needs to\ntravel before transferring to a Mn site is significantly larger than\nexpected from the Mn concentration obtained from elemental analysis.\nThese insights are critical from a device design perspective.