MAPbBr3 microcrystal synthesis. The synthesis is based on a ligand-assisted reprecipitation strategy (LARP). To 29.4 mg of PbBr2, 9.0 mg of methyl ammonium bromide (MABr) and 2 mL of dimethylformamide (DMF) were added to form a 40 µmol/mL solution (MA:Pb = 1:1). Malic acid or other acids were then added, and the mixture was stirred for 10 minutes at rt until a clear solution is obtained. 250 µL of the resulting clear solution were quickly added to 8 mL of toluene under vigorous stirring and a bright orange precipitate immediately formed. After a few seconds at rt under ambient conditions (20 °C / 30% humidity), 2µL of the solution were deposited on a thin semiconductive graphite sheet on duct-tape for scanning electron microscopy (SEM) observations. Synthesis of MLA•MA•QD4 (1). To 29.4 mg of PbBr2, 9.0 mg of methyl ammonium bromide (MABr) and 2 mL of dimethylformamide (DMF) were added to form a 40 µmol/mL solution (MA:Pb = 1:1). Malic acid (MLA, 43.0 mg, 4 equiv) was then added and the mixture stirred for 10 minutes at rt until a clear solution is obtained. Then, oleylamine (OAM, 39.6 µL, 1.5 equiv) was added to the clear solution and a white precipitate formed. Then, the solution was sonicated until it became a homogenously white suspension (~5 minutes). The resulting white precursor solution was slowly (one droplet every 6 seconds, 250 µL in total) added to 8 mL of toluene under vigorous stirring. The solution was then stirred for 3 h at rt under ambient conditions (20 °C / 30% humidity) and the solution gradually changed color, from clear to pale yellow. The resulting crude was centrifugated at 10,000 rpm for 10 minutes and the precipitate was discarded. Isolated QDs (solid) was obtained after precipitation by using 0.5 volume equivalents of dimethyl carbonate (DMC) as a washing solvent immediately followed by centrifugation at 12,000rpm for 12 minutes (Fig. in main text). These QDs were dispersed in toluene for further analysis, or in heptane (3.0 mg/mL) for device fabrication. Control experiments with distilled OAM were carried out with no differences noted when compared to as received OAM.