High‐Quality Speckle‐Free Imaging Enabled by Low‐Threshold Blue Random Lasers Based on Quasi‐2D Perovskites

ABSTRACT Blue semiconductor lasers are essential for advanced optoelectronic and imaging applications. Quasi‐2D metal halide perovskites have emerged as promising gain media owing to their excellent and tunable optical properties. However, the realization of efficient blue quasi‐2D perovskite lasers remains challenging due to phase inhomogeneity and defect‐induced nonradiative losses. Here, we develop a high‐performance blue perovskite random laser for speckle‐free imaging via additive engineering. By introducing 1‐aza‐18‐crown‐6 (A18C6), the quality of quasi‐2D perovskite films is significantly improved, exhibiting smoother and more continuous surfaces as well as a more uniform phase distribution. This improvement originates from the coordination interaction between A18C6 and undercoordinated Pb 2+ ions, which regulates crystallization behavior and optimizes film morphology. As a result, the suppression of low‐dimensional phases reduces nonradiative recombination and accelerates energy funneling, leading to efficient optical gain. Consequently, a low‐threshold blue quasi‐2D perovskite random laser with a threshold as low as 11.4 µJ/cm 2 is achieved. The resulting laser source further enables high‐quality speckle‐free imaging with significantly reduced speckle contrast. These findings provide an effective strategy for developing high‐performance micro‐ and nanoscale semiconductor lasers and highlight the potential of quasi‐2D perovskite lasers for advanced imaging applications.