Significant Enhancement of Optoelectronic Properties in CuInP₂S₆ via Pressure-Induced Structural Phase Transition

Quaternary layered transition metal thiophosphate CuInP2S6 (CIPS) has attracted extensive research interest because of its outstanding optical and ferroelectric properties. Pressure tuned phase transition is an efficient method to regulate the properties of functional materials in situ, yet there is still much to explore. Herein, we studied the pressure-regulated optoelectronic properties of CIPS and found a four-stage evolution of photoresponsivity under compression. The photoresponse of CIPS barely changes with pressure initially but increases dramatically above 4.2 GPa. Under further compression, the photoresponse first shows a decrease above 7.5 GPa and then a significant increase up to 23.5 GPa. Remarkably, the photoresponse at the highest pressure enhances by two orders of magnitude compared with the starting value. To investigate the origin of these abnormal variations in CIPS, high-pressure UV-vis absorption, Raman, and XRD measurements were conducted and a phase transition from Cc to P3 symmetry was found at approximately 4.0 GPa. We suggest that the pressure-modulated optoelectronic properties in CIPS are closely related to the conductivity change of CIPS caused by its structural phase transition. Our study spotlights the outstanding pressure regulation of optoelectronic properties in CIPS, which paves the way for modifying the behavior of other optoelectronic materials.