Tuning the Electronic and Optical Properties of Monolayers As, Sb, and Bi via Surface Charge Transfer Doping

The novel stable two-dimensional (2D) monolayers As, Sb, and Bi have attracted much attention for their peculiar semiconducting electronic properties Tuning the electronic and optical properties of monolayers As, Sb, and Bi is essential to broaden their applications in electronic and optoelectronic devices. Herein, on the basis of the density functional theory (DFT) calculations, we proposed an effective surface charge transfer doping (SCTD) strategy to control the electronic and optical properties of monolayers As, Sb, and Bi. Two types of common p-/n-type surface dopants, that is, tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) and benzyl viologen (By), were chosen in this work. Our calculations revealed that F4-TCNQis capable of enhancing the p-type conductivity of the monolayers As, Sb, and Bi because of the charge transfer from the monolayers to F4-TCNQ while BV could transform the p-type monolayers As, Sb, and Bi into n-type semiconductors because of the injection of electrons from BV to the monolayers. Moreover, the optical property calculations demonstrated that the F4-TCNQ and BV modifications could significantly enhance the optical absorption of monolayers As, Sb, and Bi in the lower light energy regions, yielding potential applications of these semiconductor monolayers in high-efficiency optoelectronic devices as new light absorber materials. Our results unveil that SCTD is an effective way to tune the electronic and optical properties of monolayers As, Sb, and Bi, thus broadening their applications in electronic and optoelectronic devices.