First-principles study: Effect of biaxial strain on the optoelectronic properties of O-doped monolayer GaSe

This paper focuses on the effect of biaxial tensile-compressive strain on the structural stability and photoelectric properties of O-doped monolayer GaSe based on the first calculations. This study demonstrates that the pure structure has good thermal stability at room temperature. The most stable doping is indicated by the O doped formation energy, which is the smallest (-2.57 eV) after doping with atoms B, C, N, O, and F. The O-doped system attains its most stable configuration after applying a strain of -4 %. The introduction of impurity energy levels following atomic doping leads to a considerable decline of the band gap. For the pure structure and O-doped system, the tensile strain leads to a steady decrease in the band gap; compressive strain first increases and then decreases the band gap. Contrasted with the pure structure, applying strains of -6 % and -8 % causes the O-doped system to switch from an indirect to a direct bandgap, increasing the material's photovoltaic conversion efficiency. The absorption peak of monolayer GaSe shifts to the blue with tensile strain. The O-doped system after applying a strain of -8 % performs optimally in terms of light absorption and reflection. The results provide a theoretical basis for applying monolayer GaSe in optoelectronics.