Highly luminescent and stable bright-blue CH3NH3Pb(Cl/Br)3 perovskite quantum dots with in-situ formed silica shell

• Mixed Cl/Br-PQDs with bright-blue emission were facilely synthesized from silane-capped Br-PQDs using anion-exchange method. • The interplay between surface-capped silane and OAm + ligands determined the morphology of Cl/Br-PQDs. • Cl/Br-PQDs exhibited high luminous efficiency and photostability due to in-situ grown silica which prevented the migration of halogen ions and detachment of OAm + . Current chloride-bromine mixed perovskite quantum dots (PQDs) suffered from low luminescence efficiency and instability due to migration-nature of ionic species and high defect density. To tackle these challenges, herein a novel type of CH 3 NH 3 Pb(Cl/Br) 3 PQDs (Cl/Br-PQDs) were synthesized via a two-step method. Briefly, pristine silane-capped Br-PQDs were prepared, followed by anion exchange using oleylammonium chloride (OAm-Cl) and in-situ formation of silica shell. The optimal feeding ratio of Cl/Br was determined to be 1:1, which yielded colloidal Cl/Br-PQDs possessing a strong 464-nm emission, a high photoluminescence quantum yield of 94.6% and ultrahigh stability. The high quantum yield was attributed to efficient defects passivation by doped Cl − ions and silica-shell-locked OAm + ligands, whilst the high stability was to silica-shell-restricted migration of halogen ions. Such a combinational strategy of anion exchange and in-situ growth of silica shell may provide an effective solution for synthesis of mixed PQDs with high quality. In-situ formed silica shell functionally protected the post-adhered OAm + and Cl − ions on the surface of PQDs, by which the prepared Cl/Br-PQDs showed high luminous efficiency and photostability.