solid solution where a mismatch in energy between s and p atomic orbitals of Sb and Bi is found. It is of relevance to report here this novel tuning strategy for defective perovskites which allows to achieve significant lower band gap values through metal alloying instead of the usual halide mixing which is known to be the main strategy to modulate the absorption edge in these systems. Cs3Sb2(Br1-xIx)9 System