Thermally Evaporated Deep-Blue Random Lasing in a CsPbCl ₃ Perovskite Film for Speckle-Free Imaging

Lead halide perovskites have emerged as promising candidates in the laser field, owing to their superior gain properties. However, the wide bandgap and high defect density of chloride-based perovskites result in poor radiative efficiency and severe nonradiative losses, which impede the development of deep-blue perovskite lasers. In this work, we successfully developed a high-quality CsPbCl₃ perovskite film and achieved deep-blue random lasing with excellent gain properties using a dual-source coevaporation strategy. The amplified spontaneous emission threshold is as low as 5.33 μJ/cm², and the net modal gain reaches 964 cm^-1, facilitated by rapid carrier accumulation (0.24 ps), a long gain lifetime of 44.9 ps, and efficient radiative recombination. Consequently, we achieved CsPbCl₃ perovskite random lasing with a low threshold of 6.50 μJ/cm². Furthermore, clear speckle-free imaging illuminated by random lasing is demonstrated with an impressively low speckle contrast of 0.012 and a high contrast-to-noise ratio of up to 9.2. This work highlights the ability of thermal coevaporation to broaden the prospects of deep-blue laser sources, paving the way for high-performance random lasers and integrated speckle-free imaging systems.