For the flow synthesis of perovskite quantum dots (PQDs), four computer-controlled syringe pumps (PHD ULTRA, Harvard Apparatus and Fusion 4000, Chemyx syringe pump) were loaded with 20 ml stainless steel syringes for each of the two precursors and two oleic acid (OA) concentrations. Shown in Fig. S2, the two OA concentrations of each precursor are combined and mixed in a braided micromixer before entering the primary T-junction referenced throughout the study. To ensure stable flow, the flow ratio at any tee-junction never exceeded 1:5. Sampling and waste lines used a 0.75 mm ID FEP tube.