Improved spin-photodetector performance in Janus WSSe nanoribbons by enhancing the spin photogalvanic effect

The spin photogalvanic effect (SPGE) in Janus monolayer WSSe is systematically studied using nonequilibrium Green's function (NEGF) combined with density functional theory (DFT). Intrinsic defects such as S vacancies, Se vacancies, and Se-S swap defects introduce localized mid-gap states that modulate light absorption and carrier transitions but only marginally affect spin splitting and spin-polarized photocurrents. To enhance SPGE, substitutional doping with transition metals including Fe, Co, and Ni is explored, with Ni doping showing the most significant enhancement of spin polarization and photocurrent amplitude, particularly at high photon energies. External bias further modulates the spin current, enabling polarization reversal. These findings highlight a synergistic modulation strategy-combining intrinsic defect engineering, targeted transition metal doping, and bias control-for optimizing spin-dependent optoelectronic performance in Janus WSSe nanodevices.