Fig. 2: Mechanism of light-induced halide segregation.
From: Unified theory for light-induced halide segregation in mixed halide perovskites
a Nucleation of an I-rich phase from a mixed I/Br phase under illumination. The compositional free energy favours mixing, but this is dominated by a free energy decrease favouring demixing due to funneling of electrons and holes into low-band gap I-rich nuclei that grow by inward diffusion of I and outward diffusion of Br. b Band gap as a function of relative Br concentration x for the different compounds.
