Polaron Dynamics Controlled by Tunable Surface Plasmons in MXenes

MXenes have garnered significant interest in energy conversion and catalysis due to their exceptional optical and electronic properties. The extended lifetime of photocarriers and high carrier mobility can be attributed to large polarons in MXenes. Therefore, it is crucial to comprehend the fundamental dynamics of polarons in MXenes. Here, we report a comprehensive analysis of the small polarons using ultrafast spectroscopy. Small polarons are found to form efficiently under transversal surface plasmon (SP) excitation. Under interband transition (IBT) and longitudinal SP excitation, small polaron formation is less efficient. In the thermal migration stage, multipolar surface plasmon excitation measurements reveal that heat flows both vertically and laterally across the flakes under transversal SP and IBT excitation and predominantly migrates laterally in plane under longitudinal SP excitation. Our findings offer critical insights into the polaron dynamics of MXenes and are valuable in the advancement of MXene-based devices.