High Efficiency Up‐Conversion Random Lasing from Formamidinium Lead Bromide/Amino‐Mediated Silica Spheres Composites

Abstract Formamidinium (HC(NH₂)⁺; FA) lead halide perovskites have emerged as potential candidates for solar cells, light‐emitting diodes, and lasing applications. However, the severely poor photostability of this material under UV irradiation seriously restricts the application on optoelectronic devices. In this paper, formamidinium lead halide (FAPbX₃) quantum dots (QDs) adhered uniformly on the surface of amino‐mediated silica (A‐SiO₂) spheres are successfully synthesized using a facile ligand‐assisted reprecipitation (LARP) method. Amazingly, the FAPbBr₃/A‐SiO₂ composites demonstrate excellent photostability after continuous illumination under UV lamps due to the effective suppression of the interactions and mutual contact between FAPbBr₃ particles. In addition, the up‐conversion random lasing with a high quality (Q) factor of 1307 and low threshold of 413.7 µJ cm^‐2 is successfully achieved from the FAPbBr₃/A‐SiO₂ composites at room‐temperature, which originates from the multiple random scattering of light and photon recycling provided by the silica spheres and the high gain characteristic of FAPbBr₃ QDs. Moreover, different from regular lasers, random lasing does not rely on a laser cavity, which is promising in angle‐unlimited optical performance and easy/low‐cost fabrication. This work will open the window of high‐performance random lasers for digital light projector, high speed imaging, and speckle‐free full‐field imaging application.