Dynamic Molecular Conformational Isomerization-Driven Halide Exchange of Perovskite Enabling Ultrastable and Low-Threshold Violet-Blue Lasing.

Halide perovskite is rising as a promising candidate for lasing applications owing to its excellent luminescence properties and the facile, economical construction of a microcavity. However, developing violet-blue perovskite lasers, which typically rely on bromide-chloride mixed halide systems, has long been hindered by uncontrollable crystallization and high defect density caused by poor crystal quality. Here, we develop an isomerization-driven halide exchange strategy for the growth of chloride mixed wide-band gap perovskite, which is fundamentally distinct from the violent, unregulated processes of traditional methods. This mild and kinetically controlled reaction enables the formation of uniform, highly crystallized violet-blue perovskite films with drastically reduced defect density and suppressed nonradiative recombination. As a result, an ultralow amplified spontaneous emission threshold of 1.4 μJ cm-2 is achieved at 423 nm, which is 5.1 times lower than the best previously reported value. More importantly, a random and single-mode laser threshold of 2.6 and 6.5 μJ cm-2 at 423 nm is achieved. The robust and homogeneous structure enables exceptional operational stability, with a T95 lifetime exceeding 7 × 107 pulses under intense excitation (25× threshold) in ambient conditions without encapsulation. This work establishes a generalizable, universal paradigm for synthesizing high-quality wide-band gap perovskites, which provides a versatile and robust method for the development of advanced violet-blue optoelectronic devices.