The line defects in two-dimensional Bi₂O₂S: enhanced photocurrents in the infrared region

Two-dimensional (2D) Bi2O2S is an ionic layered material that has been synthesized in recent experiments. In the present study, combining density functional theory and non-equilibrium Green's function method, we investigated the structures, and electronic and photoelectronic properties of the adsorption-, vacancy-, antisite- and exchange-type line defects in 2D Bi2O2S. The results show that the adsorption-type line defects can enhance the thermodynamic stability of 2D Bi2O2S and that the vacancy- and exchange-type line defects weaken the thermodynamic stability. However, the antisite-type line defects have complicated thermodynamic behaviors. The line defects usually give rise to great influences on the hole effective masses of 2D Bi2O2S and the line-defect-induced metallized phenomena or tunable band gaps were observed. Furthermore, the line defects have abundant photoelectronic properties in the visible region and suppress photocurrents in the ultraviolet region. Especially, we found the enhanced photocurrents in the infrared region.