Isothermal pressure-derived metastable states in 2D hybrid perovskites showing enduring bandgap narrowing

Significance Metastable materials often exhibit unexpected striking properties that are not available in stable state. While metastable states are generally achieved by rapid cooling of materials from high temperature, it is imperative to explore other nonthermal routes to access metastable states, especially for heat-vulnerable materials. Here, we report that work by pressure, namely, a compression−decompression cycle under ambient temperature, can drive thermosusceptible organic−inorganic hybrid perovskites to their metastable state, in which the perovskites show enduring bandgap narrowing for significantly broadened solar absorption. This pressure-derived route provides a fundamental path to obtain metastable materials with unprecedented performance.