Tunable electronic structure and enhanced optical properties of blue phosphorene via adsorption of alkali metal atoms

We use first-principles method to investigate the electronic and optical properties of blue phosphorene (BP) adsorbed by alkali metal atoms. Alkali metal atoms form bonds with adjacent three phosphorus atoms at the hollow (H) and valley (V) sites, resulting in higher adsorption energies than that at the Top (T) site. Alkali metal atoms adsorbed on the H, V and T sits all transfer charges to BP, forcing the intrinsic BP energy band to shift towards negative energy, resulting in its transition from semiconductor to metal. The BP adsorbed by Li atoms at the H and V sits exhibit excellent optical properties. The light absorption coefficient spectrum shows a clear absorption peak in the infrared region, and the absorption width covers the entire near-infrared light. In addition, the coefficient and width of the absorption peak will further increase with the rise of the number of adsorbed Li atoms.