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

Abstract

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.