Two Janus Ga₂STe monolayers and their electronic, optical, and photocatalytic properties

Recently, two-dimensional Janus materials have attracted increasing interest due to their unique structure and novel properties. Based on density-functional and many-body perturbation theories (i.e. DFT + G₀W₀ + BSE methods), the electronic, optical, and photocatalytic properties of Janus Ga₂STe monolayers with two configurations are explored systematically. It is found that the two Janus Ga₂STe monolayers exhibit high dynamical and thermal stabilities and have desirable direct gaps of about 2 eV at the G₀W₀ level. Their optical absorption spectra are dominated by the enhanced excitonic effects, in which bright bound excitons possess moderate binding energies of about 0.6 eV. Most interestingly, Janus Ga₂STe monolayers show high light absorption coefficients (larger than 10⁶ cm^-1) in the visible light region, effective spatial separation of photoexcited carriers, and suitable band edge positions, which make them potential candidates for photoelectronic and photocatalytic devices. These observed findings enrich the deep understanding of the properties of Janus Ga₂STe monolayers.