In situ silica coating-directed synthesis of orthorhombic methylammonium lead bromide perovskite quantum dots with high stability

Luminescent perovskite quantum dots (QDs) had attracted great attention by virtue of the merits of color-tunable and narrow-band emissions. However, sofar reported perovskite QDs suffered from instability more or less. In this work, a type of silica-coated orthorhombic CH 3 NH 3 PbBr 3 QDs (SiO 2 -QDs) with greatly improved stability was reported. The SiO 2 -QDs were one-pot synthesized using a reprecipitation-encapsulation method assisted with an amine functional silane, which not conly controlled the crystallization of QDs, but also encapsulated QDs with a silica layer simultaneously. More interestingly, the in situ encapsulation of silica shell induced the presence of orthorhombic perovskite that was thought to be unstable at room temperature. This is the first report of orthorhombic CH 3 NH 3 PbBr 3 QDs, as far as we are concerned. The orthorhombic SiO 2 -QDs exhibited narrow-band green luminescence with a quantum yield of 78%, and a high production yield of ∼70   wt%. Moreover, stability of SiO 2 -QDs was considerably improved due to silica-coating. White-LEDs were also successfully fabricated with the green SiO 2 -QDs and a red commercial phosphors using a noncontact configuration. These results demonstrated that the orthorhombic SiO 2 -QDs held great promise for high-performance display or lighting technology.