Pressure-induced Structural Transition and Enhanced Photoelectric Properties in Tm₂S₃

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.