Optical Tuning of Exciton and Trion Emissions in Monolayer Phosphorene

TL;DR

This study uses optical interferometry to accurately identify monolayer phosphorene and investigates its exciton and trion dynamics, revealing high binding energies and carrier lifetimes, advancing understanding of its optoelectronic properties.

Contribution

We developed a rapid optical method for layer identification and characterized exciton and trion behaviors in monolayer phosphorene, revealing unprecedented binding energies and carrier dynamics.

Findings

Exciton binding energy ~0.3 eV in monolayer phosphorene.

First observation of large trion binding energy (~100 meV).

Carrier lifetime of ~220 ps comparable to other 2D materials.

Abstract

Monolayer phosphorene provides a unique two-dimensional (2D) platform to investigate the fundamental dynamics of excitons and trions (charged excitons) in reduced dimensions. However, owing to its high instability, unambiguous identification of monolayer phosphorene has been elusive. Consequently, many important fundamental properties, such as exciton dynamics, remain underexplored. We report a rapid, noninvasive, and highly accurate approach based on optical interferometry to determine the layer number of phosphorene, and confirm the results with reliable photoluminescence measurements. Furthermore, we successfully probed the dynamics of excitons and trions in monolayer phosphorene by controlling the photo-carrier injection in a relatively low excitation power range. Based on our measured optical gap and the previously measured electronic energy gap, we determined the exciton binding energy to be ~0.3 eV for the monolayer phosphorene on SiO2/Si substrate, which agrees well with theoretical predictions. A huge trion binding energy of ~100 meV was first observed in monolayer phosphorene, which is around five times higher than that in transition metal dichalcogenide (TMD) monolayer semiconductor, such as MoS2. The carrier lifetime of exciton emission in monolayer phosphorene was measured to be ~220 ps, which is comparable to those in other 2D TMD semiconductors. Our results open new avenues for exploring fundamental phenomena and novel optoelectronic applications using monolayer phosphorene.