(FA-acetate, 99%) were purchased from Sigma-Aldrich and used as received unless otherwise specified. CsPbI3 QD synthesis. The synthesis was performed following the method reported in our previous publications with slight modification. 1,2 First, 20 mL of ODE is mixed with 1.25 mL of OA containing 0.407 g of Cs2CO3. This was degassed at 120°C for 20 min under vacuum in a three-neck flask to form Cs-oleate. The Cs-oleate precursor was kept under N2 instead of vacuum after Cs2CO3 was completely dissolved in the solution. Then the PbI2 precursor was formed by mixing 0.5 g of PbI2 and 25 mL of ODE in a three-neck flask and heated at 120°C for 20 min under vacuum. A preheated mixture of OA and OAm (135°C, 2.5 mL each) was transferred into the PbI2 solution that was kept at 120°C under vacuum. After the PbI2 completely dissolved in the solution, the reaction flask was heated to the desired temperature (140, 160, or 180°C) under flowing N2. Then 2 mL of the Cs-oleate precursor was swiftly injected into the reaction flask. In general, smaller nanocrystals are obtained with lower growth and larger are obtained with higher temperature, but some sizes overlap this trend when using the size selective precipitation. Immediately after the reaction, the mixture was quenched by submerging the flask into an ice bath within 3 s after the injection. After cooling to room temperature, 70 mL of MeOAc was added into the colloidal solution and the mixed solution was centrifuged at 7500 rpm for 5 min.