Modulation of Exciton Transport in Few-Layer and Bulk Tungsten Disulfide under Hydrostatic Pressure

Transition-metal dichalcogenides (TMDs) are atomically thin semiconductors with outstanding optoelectronic properties, but their applications in high-performance optoelectronic devices are often limited by low intrinsic mobility. Using a diamond anvil cell (DAC) combined with transient absorption spectroscopy, pressure-dependent exciton transport and relaxation dynamics were systematically investigated in few-layer (5 layers) and bulk WS₂. Within the pressure range of 0 to 2 GPa, hydrostatic pressure induces a nonmonotonic evolution of exciton mobility, reaching maximum enhancements of approximately 3 times and 5 times in few-layer and bulk WS₂, respectively. Simultaneously, the exciton lifetimes are reduced by approximately 4 times and 7 times. Complementary photoluminescence (PL) and Raman measurements reveal that pressure-enhanced interlayer coupling and lattice compression jointly modulate the electronic structure and exciton relaxation pathways, leading to accelerated relaxation dynamics. The nonmonotonic variation in exciton mobility can be attributed to a competitive mechanism between pressure-regulated band broadening effects (reduced effective mass and enhanced dielectric shielding) and increased defect scattering and lattice scattering. It is worth noting that after pressure release, the mobility remains higher and the lifetime is slightly shorter than the initial values. These results reveal the correlated evolution of exciton mobility and lifetime in WS₂, identify an optimal pressure window for exciton transport, and elucidate the mechanism of pressure-regulated exciton dynamics, providing insights into the development of high-mobility, fast-response optoelectronic devices.