Synthesis and Irreversible Pressure-Induced Emission Enhancement of Ultrathin Lead-Free 2D Organic–Inorganic Hybrid Perovskite (i-OA)3BiBr6 Nanosheets at Room Temperature

2D bismuth-based perovskites have attention as a potentially transformative technology in optoelectronics due to their exceptional non-toxic and environmentally friendly properties. However, their practical applications are hindered by the low luminous efficiency caused by self-trapped excitons (STEs) under normal environmental conditions. Here, a new composition of lead-free ultrathin 2D perovskite nanosheet iso-octylamine bismuth bromide [(i-OA)₃BiBr₆] is synthesized, with thicknesses down to 1.1 nm, using a solution-based method and explored their stability. Notably, the behavior of STEs in these ultrathin nanosheets can be modulated through a pressure treatment strategy. After completely releasing the pressure, an optimal lattice distortion is stabilized, resulting in an 80-fold increase in irreversible pressure-induced emission. This finding highlights the critical roles of steric hindrance and hydrogen bonding cooperativity effects in the organic cationic layers, along with OA ligand passivation, in enhancing STE radiation recombination under ambient conditions. This advancement opens new possibilities for creating stable, bright STEs under ambient conditions, thus facilitating its potential applications in the fields of pressure sensing, display, and energy savings.