Synthesis of Cs 2 Ti 1-x Sn x Br 6 NCs. For the synthesis of mixed titanium-tin bromide VODPs, 4 ml of cesium oleate and 60 mg of DMOP were loaded in a 50 ml three-neck flask together with Sn(IV) acetate and Ti(IV) isopropoxide in different ratio (while the total Cs:B ratio was kept 2:2.5), 2 ml of ODE and 2 ml of OA. The solution was degassed through 3 cycles of argon and vacuum and heated at 110 °C for 35 minutes under vacuum. At this point, 574 µL (4.218 mmol) of TMSBr was injected and after 20 seconds the reaction was quenched by diluting the solution in 10 ml of toluene.