Blue Perovskite Lasing Derived from Bound Excitons\nthrough Defect Engineering

All-inorganic\nperovskite films have emerged as promising candidates\nfor laser gain materials owing to their outstanding optoelectronic\nproperties and straightforward solution processing. However, the performance\nof blue perovskite lasing still lags far behind due to the inevitable\nhigh density of defects. Herein, we demonstrate that defects can be\nutilized instead of passivated/removed to form bound excitons to achieve\nexcellent blue stimulated emission in perovskite films. Such a strategy\nemphasizes defect engineering by introducing a deep-level defect in\nmixed-Rb/Cs perovskite films through octylammonium bromide (OABr)\nadditives. Consequently, the OA-Rb/Cs perovskite films exhibit blue\namplified spontaneous emission (ASE) from defect-related bound excitons\nwith a low threshold (13.5 μJ/cm<sup>2</sup>) and a high optical\ngain (744.7 cm<sup>–1</sup>), which contribute to a vertical-cavity\nsurface-emitting laser with single-mode blue emission at 482 nm. This\nwork not only presents a facile method for creating blue laser gain\nmaterials but also provides valuable insights for further exploration\nof high-performance blue lasing in perovskite films.