Thickness-dependent exciton behavior in two-dimensional indium selenide

Abstract

A comprehensive investigation into the exciton behaviors in indium selenide (InSe) is yet to be conducted. Here, the power factor K, which can characterize the excitonic behaviors, was determined for InSe with varying thicknesses. The photoluminescence results suggest that defects play a dominant role in the recombination of excitons with varying thicknesses. Consequently, the free exciton peak at 931 nm, which is linked to the double exciton emission behavior, becomes obscured by the presence of a bound exciton peak at 980 nm resulting from defect-induced recombination. However, at specific thicknesses and power levels, the enhancement of quantum confinement effect coupled with a reduction in defect proportion enables the observation of the peak corresponding to free exciton. Furthermore, the extracted K values from the InSe photodetectors corroborated the aforementioned findings. The results presented here provide an in-depth understanding of exciton behavior in InSe and provide theoretical underpinning for the development of InSe-based optoelectronics.