Resonant Dipole–Dipole Interaction: A Protocol to Amplify Weaker PL Emission in 2D MoS2

Abstract

The decade old challenge of achieving excitons at room temperature in conventional bulk semiconductors, limiting their applications in photonic communication, has been overcome by the discovery of noncryogenic stable excitonic emission in 2D transition-metal dichalcogenides. The pioneering detection of stable excitonic emission under ambient conditions in the 2D family was achieved with MoS₂, featuring characteristic twin-peaked photoluminescence spectra characterized by a pronounced A exciton peak, alongside a weaker B exciton peak. The accessibility and applicability of weaker exciton emissions are very limited as compared to prominent exciton emissions, which restricts the vast possibility of usage of weaker excitonic emissions spread across a broad spectral range. In this article, we have demonstrated a simple approach to selectively enhance weaker exciton emission through resonant dipole–dipole interaction. Our approach involves the utilization of a hybrid heterojunction, where the spectral overlap of excitonic emission between two materials leads to the dipole–dipole resonance effect and subsequently increases emission intensity. We have targeted the inherently low-intensity B exciton emission feature of MoS₂ and coupled it with cuprous oxide (Cu₂O) thin films, leveraging the strong spectral overlap between the intrinsic excitonic emission bands of Cu₂O and the B exciton. Furthermore, we employed finite element analysis to investigate the impact of the extinction response on the B exciton enhancement. Our approach provides versatility in selectively augmenting weaker exciton emission by leveraging the exploitation of exciton resonance between two materials, thereby amplifying emission intensity at the targeted wavelength.