Abstract
This study investigates the structural stability and electronic, mechanical, excitonic, and optical properties of 2D-XI2 (X = Si, Ge, Sn, Pb) monolayers using both first-principles and semiempirical calculations. Our findings reveal that this group has semiconductor characteristics with band gaps from 2.35 to 3.28 eV at the HSE06 level. The excitonic effects are significant with exciton binding energies between 372 and 422 meV. They present a maximum solar harvesting efficiency, at the Shockley-Queisser limit, considering an electron-hole coupling of 16.37%. These findings indicate that these structures are promising for future optoelectronic applications, showing excellent visible and ultraviolet response and enhancing the photovoltaic cell performance.