Distinct Photoemission Behaviors in Monolayer WSe₂: Unidirectional Asymmetry From Edge Defects Versus Bidirectional...

2D transition metal dichalcogenides (TMDs) hold promise for next-generation flexible optoelectronic devices owing to their atomic thickness. The performance of such devices is fundamentally governed by the excitation, relaxation, and recombination of photogenerated carriers. Defect engineering based on point defects has been used to manipulate these carrier dynamics, yet the potential of alternative strategies such as 1D defects or external plasmonic fields remains unexplored. Here, by combining time-resolved photoemission electron microscopy (TR-PEEM) with first-principles calculations, we demonstrate that 1D edge-structural defects in monolayer WSe₂ induce an asymmetric broadening of the photoelectron energy distribution, preferentially extending to high-energy states, in stark contrast to the behavior of 0D point defects. By introducing a plasmonic synergistic effect, we further demonstrate that the near-field effect synergizes with the edge defects, boosting the photoelectron yield to approximately 369.8% (relative to the intrinsic region) while TR-PEEM reveals no significant lifetime penalty relative to the edge-rich region. This system induces a bidirectional extension of the photoelectron energy distribution, amplifying both low- and high-energy photoelectron signals. Our findings reveal that boundary-induced symmetry breaking and electronic reconstruction can relax the trade-off between carrier generation and recombination, offering a pathway toward high-efficiency, low-loss optoelectronic devices based on 2D materials.