Irreversible pressure effect on phase transitions and bandgap narrowing of layered MoO3

Two-dimensional layered molybdenum trioxide (MoO3) holds significant importance in optoelectronics owing to its unique anisotropic structure and optical properties. Given that changes in structure can profoundly impact physical characteristics, it becomes imperative to explore new properties by means of acquiring different structures. Here, we report the irreversibility of structural evolution and optical properties of molybdenum trioxide under high pressure. The quenched MoO3 possesses a stable high-pressure phase MoO3-II, a narrowed bandgap (reduced by ∼25%) and a strong optical absorption at visible to infrared region compared to the initial low-pressure phase α-MoO3. These findings will facilitate the exploring of high-pressure phase materials under ambient conditions.