Regulation of electronic and optical properties of monolayer black phosphorus by co-doping B and Si

The electronic and optical properties of B or Si single-doped phosphorene and ones of B and Si co-doped phosphorene are computed and compared by first-principles calculations. By B doping, the bandgap of phosphorene decreases from 0.92 to 0.65 eV, while Si doping directly changes the system from a direct bandgap semiconductor to metal. Compared with pristine phosphorene, the optical absorption of Si-doped phosphorene is red shifted. The optical absorption of black phosphorus can be regulated by changing the distance and position between B and Si. Therefore, bandgap engineering can be used to directly tune the optical absorption of the phosphorene system by the co-doping of B and Si.