First-principles analysis of desired inherent photovoltaic functionalities of tetragonal CuAlX₂ (X=O, S, Se and Te)

Ternary A^ⅠB^ⅢC semiconductors are significant for today's electronic equipment and solar cell applications due to their intriguing properties. In this article, first-principles calculations are employed to comprehensively study the fundamental photovoltaic properties, such as the lattice thermodynamics and phonon stability, band gap, antibonding character of band-edge states, electron and hole effective masses, exciton binding energy and optical absorption coefficient of CuAlX₂ (X ​= ​S, Se and Te) materials. Outcomes demonstrate that CuAlS₂, CuAlSe₂ and CuAlTe₂ compounds have nice mechanical stability, thermodynamic and phonon stability. Compared with CuAlS₂ and CuAlSe₂ crystals, CuAlTe₂ possesses the more appropriate band gap value, smaller binding energy, higher light absorption and utilization efficiency. Due to their high exciton binding energy and Bohr radius, CuAlS₂ and CuAlSe₂ are limited to solar cell absorber applications. Certainly, other properties of CuAlS₂ do not meet conditions like wide band gap value, heavy carrier effective masses and low absorption coefficient. According to direct photovoltaic functionality screening, we find CuAlTe₂ crystal should be a good photovoltaic absorber.