Cage Balancing Enhances Optoelectronic and Lasing Performance in Stable Quasi-2D Tin Iodide Perovskites

= 2 perovskites with minimal distortion and excellent optoelectronic performance. The structural insights and cage-balancing approach revealed herein motivate the deliberate design of quasi-2D perovskites through the synergy of the spacer and cage cations, further paving the way for high-performance optoelectronic applications of stable tin halide perovskites.