Effects of Vacancy Defects on the Electronic and Optical Properties of Monolayer PbSe

Defect engineering is promising for tailoring the properties of atomically thin materials. By creating defects via Se vacancies, we study the optoelectronic properties of monolayer PbSe. We obtain the single-particle properties using the density functional theory plus a first-principles-based typical medium approximation. The absorption spectra are explored by solving the Bethe-Salpeter equation. Our results reveal that monolayer PbSe is defect-sensitive but defect-tolerant. The latter fingerprint is due to the absence of defect-induced in-gap, localized states. Our results predict that Se vacancies are the dominant defect type in disordered PbSe monolayer. We observe that increasing Se vacancy concentrations δ renormalize the energy bandgap E_g, which increased from 0.21 eV for the pristine to as high as 0.45 eV at high δ. The high tunability of the optoelectronic properties of monolayer PbSe using defect-engineering makes this material a candidate for exploring flexible electronic with potential technological applications in nanoelectronics.