Twisted Light-Driven Exciton Dissociation for Enhanced Photoresponse in Monolayer MoS₂ Transistors

Two-dimensional monolayer transition metal dichalcogenides (TMDs) exhibit strong exciton binding energy due to Coulomb interactions, making exciton dissociation challenging. However, the use of orbital angular momentum (OAM) light, or twisted light, enables momentum-conserving transitions, potentially enhancing exciton dissociation and improving optoelectronic performance. In this work, we simultaneously explore the optical and electrical characteristics of a field-effect transistor (FET) fabricated from molybdenum disulfide (MoS₂) when exposed to OAM-carrying illumination. A significant reduction in exciton luminescence rates is observed, whereas a substantial enhancement in the device's conductance is detected as the OAM order of light is increased. Light with OAM effectively slows exciton recombination, as confirmed by time-resolved photoluminescence, while concurrently strengthening the probability of exciton dissociation. This shift in the balance between exciton recombination and dissociation is inferred to as the driving force behind the improved free carriers in the device. In addition, light-carrying OAM slightly improves the material's light absorption by facilitating additional transitions that were normally inaccessible. The implications of our study extend to the potential improvement in the performance of phototransistors, showcasing the multifaceted benefits of harnessing OAM light for advanced applications in optoelectronics.