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

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 CH3NH3Pb(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.