Figure 3.

Kinetic Monte Carlo simulation of light-induced halide phase segregation in FA_0.67MA_0.33Pb(I_0.67Br_0.33)_3(1–z) with a vacancy concentration (z) of 0.005. Snapshots show the iodide (red), bromide (blue), and vacancy (green) distributions in the three-dimensional lattice (a) at the beginning, (b) after 100 000 KMC steps, and (c) after 150 000 KMC steps. The iodide-rich domain is highlighted in the center of the simulation box. (d–f) Radial distribution functions of iodide, bromide, and vacancy that correspond to the selected snapshots. The dashed line indicates the boundary between the iodide-rich region and the mixed region. The gray region represents the highlighted domains in panels (a)–(c). Note that the radial distribution reflects the probability of finding a bromide or iodide ion at a distance of r from the center. For estimating the number of ions at a certain distance, one would need to multiply the radial distribution with 4πr².