Novel pentagonal ternary monolayers: Design, stability, and high-efficiency solar energy conversion

In this work, first-principles calculations based on density functional theory (DFT) are employed to investigate the structural, mechanical, and optoelectronic properties of a series of penta-graphene-like monolayers. Structural, dynamical, and mechanical stability are confirmed by the absence of imaginary phonon modes and by compliance with the Born–Huang criteria for two-dimensional systems. The investigated monolayers exhibit indirect band gaps as calculated using the hybrid HSE06 functional, with values of 2.68, 1.91, 2.42, 1.79, 2.57, 1.91, 2.46, and 1.82 eV for AgAlS 4 , AgAlSe 4 , AgInS 4 , AgInSe 4 , CuAlS 4 , CuAlSe 4 , CuInS 4 , and CuInSe 4 , respectively. The optical absorption spectra indicate strong optical activity spanning the visible to ultraviolet regions. Excitonic effects are also significant, with binding energies ranging from 421 to 488 meV, indicating robust Coulomb interactions in these 2D materials. The theoretical Shockley–Queisser and maximum SLME limits predict upper-bound power conversion efficiencies up to 28.47%. In contrast, the directly computed SLME efficiencies are below 0.27% due to the ultrathin character and limited optical absorbance of the monolayers. Overall, the results demonstrate that penta-structured monolayers are promising candidates for next-generation optoelectronic and solar energy harvesting devices.