“In the field of micro-nano lasers, a new study introduces ethyl acetate as a green antisolvent to create high-quality quasi-2D perovskite films. This innovation enhances crystallinity, inhibits low n-phases, and extends gain lifetime, leading to a significant reduction in ASE threshold and high net modal gain. The optimized film enables a VCSEL with single-mode lasing and a high quality factor, advancing scalable photonic integration.”