Pathways, Probes, and Puzzles of Broadband Luminescence in “Perovskite-Inspired” Materials

So-called “perovskite-inspired” materials share structural motifs with perovskites but often lack their defining crystallographic attributes. This leads to a variety of different properties, and classifying them under the same label creates possibilities for misinterpretation. A key example is broadband luminescence, which is frequently attributed to the recombination of self-trapped excitons (STEs). In addition to a crucial distinction between defect-mediated luminescence and STEs, which has long been neglected, there is a lack of attention to how exciton localization varies across these materials. Differentiation between Wannier–Mott and Frenkel excitons is often lacking. By refining the language used to describe these excitons in “perovskite-inspired” materials, we can better capture the fundamental differences governing light emission in these exciting compounds.