Fig. 1. Spin polarization mechanism and spectrum of PbI₂/WS₂ heterostructures.

a Schematic of the type-I heterostructure for the study of the carrier interlayer transportation. Both electrons and holes transfer from PbI₂ to WS₂. The images on the right are optical and AFM micrographs of a PbI₂/WS₂ heterostructure with a thickness of 9.2 nm. b Band structure for the PbI₂ thin film with a thickness of 20 layers, which is spin degenerate. c Schematic illustration of the polarized optical transitions in PbI₂ thin films. d Circularly polarized PL spectra from pure PbI₂ at room temperature. e Corresponding degree of polarization ρ of pure PbI₂ PL calculated from the PL spectra shown in figure (d). f Circularly polarized PL spectra of a representative PbI₂/WS₂ heterostructure at room temperature. g Corresponding degree of polarization ρ calculated from the PL spectra shown in figure (f). All length of the scale bar is 10 µm.