Linear photogalvanic effects in Janus monolayer MoSSe with intrinsic defects

Linear photogalvanic effect (LPGE) in Janus monolayer MoSSe with six different central regions is investigated by using non-equilibrium Green's function technique combined with density functional theory. It is found that the photocurrent depends on the polarization angle theta of the incident light in the form of cos(2 theta). The maximum photocurrent appears at the polarization angle of 0 degrees and 90 degrees. The introduction of intrinsic defects increases the photocurrent at almost all photon energies. The maximum photocurrent in the cases of Se-Substituted S (SeS) and Se-Vacancy (VSe) are individually 35.7 and 30.2, which is more effective as compared to the cases in PGEs. The maximum extinction ratio of SSe-Transposed (TS-Se) and S-Vacancy (VS) defects are individually 74.7 and 62.1, which can effectively improve the polarization sensitivity of MoSSe photodetectors driven by PGE. These results are attributed to the reduction of the symmetry of the original monolayer MoSSe due to the intrinsic defects. The introduction of impurity energy band creates favorable conditions for electron transition. By contrast, TS-Se has the best performance because of its high photocurrent (16.8) and maximum photocurrent (74.4) at photon energy of 2.6 eV. These results provide an effective method to enhance the photocurrent of PGE by introducing intrinsic defects and are useful for the application of monolayer MoSSe in optoelectronic detection.