Theoretical Insights into a High-Performance Optical Absorption in GaSeS/InSeS 2D van der Waals Heterostructure for Photovoltaic Applications

Abstract

Advances in heterostructure design are transforming electronic and optoelectronic technologies, with particular focus on Janus monolayer-based heterojunctions. These heterojunctions, arising from the broken symmetry of 2D materials, offer new possibilities for ultra-thin, high-performance vertical p-n heterojunction solar cells. In this study, we examine the electronic structure and optical properties of a 2D GaSeS/InSeS heterostructure, formed through van der Waals interactions, based on first-principles calculations using density functional theory (DFT). The heterostructure consists of Janus group III chalcogenide GaSeS and InSeS monolayers (MLs). The electronic properties show that both the AA and AB stacking configurations exhibit indirect semiconductor band gaps, with values of 1.3207 eV and 1.3452 eV using the PBE (Perdew-Burke-Ernzerhof) functional, and 2.0997 eV and 2.1242 eV using the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional, respectively. Both configurations also display the characteristic features of type-II heterojunctions, which promote efficient separation of photogenerated electrons and holes. Charge density analysis reveals a transfer of charge from GaSeS to InSeS. Furthermore, optical analysis shows that both stacking configurations (AA and AB) exhibit similar absorbance spectra, primarily in the UV range, with peak absorption around 11.6 × 10⁵ cm⁻¹. Within the visible spectrum, the maximum absorption rate for both configurations is 2.8 × 10⁵ cm⁻¹. The 2D GaSeS/InSeS heterostructure holds great potential as a high-performance material for future photovoltaic devices, with promising applications in both photovoltaic cells and optoelectronic systems.