Frenkel Exciton d Perovskite-inspired materials aim to replicate the exceptional optoelectronic performance of lead-halide perovskites (LHPs), while avoiding issues of toxicity and operational stability. For decades, the standard materials design approach for identifying novel inorganic semiconductors has been chemical substitution, where the undesirable elemental constituents (e.g. toxic Pb 2+ in LHPs) are replaced by more favorable counterparts, while retaining the same structural motifs. For example, in the diamond-cubic crystal family, research moved from Group IV elements Si and Ge to II-VI compounds like CdTe -to yield direct rather than indirect electronic band gaps -and then further splitting into the I-III-VI 2 (e.g. CuInSe 2 ) and I 2 -II-IV-VI 4 families (e.g. Cu 2 ZnSnS 4 ) -to give earth-abundant compositions. While strategies such as dimensional modification 2 and disorder engineering have recently risen in popularity, elemental substitution remains the prevailing design approach.