Core-Shell Perovskite Fibers Enabling Dual- Emission and Random Lasing in Various

2 ABSTRACT: Random lasing (RL) from perovskites is highly attractive for achieving specklefree imaging owing to its low spatial coherence. However, the intrinsic instability of perovskites limits their practical applications. Here, to overcome this, we encapsulate different metal-halide perovskites in a hydrophobic poly(methyl methacrylate) matrix and fabricate core-shell perovskite composite fibers via coaxial electrospinning. The composite exhibits a uniform distribution of perovskites, resulting in single- and dual-color emitting perovskite fibers. The dual-emissive fibers demonstrate remarkable water resistance, maintaining emission after 9 days. Their emission persists even under combined thermal stress (50 °C) and UV exposure in water for up to 40 min. Notably, the green-emitting core-shell fibers exhibit stable RL behavior in diverse environments, including air, water, and an acidic medium (pH=3), highlighting their robustness in extreme environments. Furthermore, RL from these fibers enables speckle-free imaging with an ultra-low speckle contrast (K = 0.008), compared to a conventional CW laser.