A white light supercontinuum was employed as broadband probe (see Supporting Information for experimental details). DT was directly performed on the solutions, with the same concentration used for photocatalytic studies, i.e. 1g/L in the case of H2 production (Fig. ) and 0.5 g/L in the case of NH3 production (Fig. ). This suggests that g-C3N4 helps in keeping optical excitations in the perovskite and the HER happens at perovskite sites.