Thermomechanical regulation of quasi-2D perovskite photonic structures via nanoimprint.

Nanoimprint lithography (NIL) offers a scalable route to high-resolution patterning of perovskite photonic devices; however, the performance potential of NIL-patterned perovskite photonic structures remains largely unrealized because of limited understanding of perovskite thermomechanical behavior during imprinting. Here, we provide a mechanistic framework elucidating the coupled thermomechanical processes governing NIL in quasi-two-dimensional Dion-Jacobson perovskites. We show that imprinting in the cubic phase uniquely enables the simultaneous enhancement of viscoelastic deformability and mechanical hardness, facilitating high-fidelity pattern transfer while preserving structural integrity. We further uncover a spacer-dependent mechanical-optical trade-off: Flexible spacers promote plastic flow and surface planarization, yielding higher-Q resonances, whereas rigid spacers enhance crystallinity during Ostwald ripening-driven recrystallization, reducing lasing thresholds. Leveraging these insights, we demonstrate bound-state-in-the-continuum perovskite lasers achieving a record-high Q factor (up to 36,000) and low lasing thresholds (down to 5 microjoules per square centimeter) in separately optimized devices, while sustaining stable single-mode emission for over 151 hours under ambient conditions.