Type-II band alignment and high spectroscopic-limited efficiency in Ti2CO2/MoGe2N4 van der Waals heterostructure

This work presents a comprehensive investigation of the van der Waals heterostructure (vdW-HS) composed of monolayers Ti₂CO₂ and MoGe₂N₄, exploring its potential for sustainable energy applications. The heterostructure exhibits a minimal lattice mismatch of approximately 0.3% between the constituent monolayers, ensuring coherent interfacing and structural compatibility. Phonon dispersion calculations confirm dynamic stability with no imaginary frequencies throughout the entire Brillouin zone. The AIMD simulations and elastic stiffness constants confirms the thermodynamic and mechanical stability of the vdW-HS Ti₂CO₂/MoGe₂N₄. Electronic structure analyses reveal that all stacking configurations yield identical band structures, characterized by an indirect band gap of 0.37 eV, as calculated using the Heyd−Scuseria−Ernzerhof (HSE06) functional with spin-orbit coupling. Notably, the vdW-HS exhibits a favorable type-II band alignment, promising for advanced optoelectronic applications. Furthermore, the valence band edge is suitably positioned to drive photocatalytic oxygen evolution reaction (OER), but not favorable for hydrogen evolution reaction (HER). The material also demonstrates a substantial static dielectric constant of 5.9, along with pronounced optical absorption in the visible spectrum and intense absorption of 1.4 × 10⁶ cm^-1 in the ultraviolet region. Importantly, the spectroscopic limited maximum efficiency (SLME) approaches ∼28.5%, surpassing that of several benchmark thin-film photovoltaic materials. These results underscore the promise of vdW-HS Ti₂CO₂/MoGe₂N₄ as a high-performance candidate for next-generation optical absorber material for green energy technologies.