Pressure-Induced Structural Transition and Enhanced Photoelectric Properties of Tm₂S₃

Abstract Rare earth sesquisulfides have drawn growing attention in photoelectric applications because of their excellent electronic and photoelectric properties upon compression. We investigate the structural, electrical, and photoelectric properties of Tm 2 S 3 under high pressure through electrical impedance, UV-vis absorption, Raman spectroscopy, x-ray diffraction, and photoelectric measurements. It is found that δ -Tm 2 S 3 transforms into high-pressure α -phase around 5 GPa, accompanied by a substantial reduction in atomic distance, bandgap, and resistivity. Consequently, the photocurrent density and responsivity of Tm 2 S 3 exhibit dramatic increase behavior, achieving five orders of magnitude enhancement in α -phase compared with the initial δ -Tm 2 S 3 . Moreover, α -phase maintains a high photocurrent responsivity of three orders of magnitude after unloading. This work demonstrates significant enhancement of the photoelectric properties of Tm 2 S 3 by applying pressure, which paves the way for improving the performance of future photoelectric devices.