Preventing Anion Exchange between Perovskite Nanocrystals by Confinement in Porous SiO₂ Nanobeads

All-inorganic CsPbX₃ (X = Cl, Br, I) perovskite nanocrystals (NCs) are highly attractive due to their outstanding optical and electrical properties. However, poor stability and easy anion exchanges between CsPbX₃ nanocrystals with different halides limit their applications in light-emitting diodes (LEDs). To solve the problems, we developed an approach to in situ synthesize CsPbX₃ NCs into porous silica colloidal spheres, which can effectively prevent anion exchange and increase photo stability. Based on our results, we first proved that the anion exchange between CsPbX₃ nanocrystals is mainly driven by physical collision of the nanocrystals, not requiring a bridge such as a solvent. We subsequently used an optimized ratio of green, red, and blue SiO₂/CsPbX₃ composites as solid-state luminescent materials to fabricate single-layer white light-emitting diodes (WLEDs). No anion exchanges have been observed in the LED fabrication and lighting process.