Electronic Properties of Monolayer and van der Waals Bilayer of Janus TiClI

In this work, the novel electronic properties of the Janus TiClI monolayer (ML) and van der Waals (vdW) bilayers (BLs) have been demonstrated. As a result of the strong spin–orbit coupling (SOC) together with the inversion symmetry breaking, the TiClI ML shows valley spin splitting of 62.67 meV at the K/K′ point. In magnetic V- and Cr-doped TiClI MLs, sizable valley polarization of 36.70 and 45.35 meV occurs, respectively. TiClI vdW BLs indicate typical type-II band alignment with a quite large band offset (>500 meV), and interestingly, the interlayer-polarization P_H is almost 100% for all considered stacking orders. In addition, the interlayer-polarization is insensitive to the interlayer distance. In this situation, the interlayer exciton and valley polarization lifetimes could be prolonged, and thus, TiClI vdW BLs provide new opportunities for light–energy conversion and valleytronics. As the interlayer distance decreases, the TiClI BLs of AB′ and AB stacking indicate a semiconductor-to-metal transition and are characterized by hole-doping, and the doping concentration can be further tuned by changing the interlayer distance.