Photothermal‐Mediated Carrier Dynamics in Ti ₃ C ₂ T <i> _x </i> MXene Revealed by Time‐Resolved Terahertz Spectroscopy

2D Ti₃C₂T_x MXene film exhibits exceptional electrical and thermal properties, yet the interplay between lattice thermal dissipation and carrier dynamics under photo-excitation remains unresolved. Using time-resolved terahertz spectroscopy, we systematically investigated photothermal-mediated carrier relaxation mechanisms in Ti₃C₂T_x MXene film by precisely varying layers. The slowest relaxation time exhibits a linear dependence on film thickness, mirroring lattice cooling dynamics governed by thermal boundary conductance (TBC). And by engineering interfacial TBC through substrate selection, effective modulation of transient carrier relaxation dynamics was furthermore demonstrated. These findings confirm the universal photothermal mediated carrier relaxation in Ti₃C₂T_x MXene film due to strong carrier-phonon coupling. Our insights establish interface engineering as a viable strategy to control the carrier relaxation process in Ti₃C₂T_x MXene, advancing their design for optoelectronic and energy conversion applications. This work bridges the critical gap between lattice thermal dissipation and carrier kinetics in MXene, offering new insights into heat-managed quantum material platforms.