The Auger process in multilayer WSe₂ crystals

Multilayer WSe₂ with a larger optical density of states and absorbance is regarded as a better candidate than its monolayer counterpart for next generation optoelectronic devices, however insight into carrier dynamics is still lacking. Herein, we experimentally observed an anomalous PL quenching with decreasing temperature for multilayer WSe₂. At a low temperature (77 K), the Auger processes govern carrier recombination in multilayer WSe₂, which are induced by a phonon bottleneck effect and strong photon absorption, and lead to PL quenching. From transient absorption spectroscopy, two distinct Auger processes are observed: a fast one (1-2 ps) and a slow one (>190 ps), which are caused by two different deep midgap defect-levels in WSe₂. Based on the Auger recombination model, these two Auger rates are quantitatively estimated at ∼6.69 (±0.05) × 10^-2 and 1.22 (±0.04) × 10^-3 cm² s^-1, respectively. Our current observations provide an important supplement for optimizing the optical and electric behaviors in multilayer WSe₂ based devices.