They show well-defined absorption edges which red shift with the increase of iodide amount (x), as further confirmed by the trend of the band gap calculated from the Tauc plots (reported in the Supplementary Information, Figure ) and shown in Figure . By increasing the iodide content (x) from DA2GeBr4, the band gap significantly reduces from 2.74 eV (x=0) to about The photoluminescence (PL) response of the DA2Ge(Br1-xIx)4 system is reported in Figure . From x=0 to x= 0.25 the emission at RT is nearly absent, while from x = 0.50 it becomes detectable, and increases as function of the iodide content reaching its maximum for DA2GeI4. The emission is very broad and shapeless, it covers most of the visible spectrum (from about 500 to 800 nm), and its feature at RT seems not to be significantly affected by the halide alloying. This broadband emission may be a consequence of the presence of trapping