Intercalation, in which foreign molecules are inserted within the interlayer interfaces of the layered materials, has been spotlighted as an enticing strategy to elicit exotic properties in layered two-dimensional materials. Intercalation allows various host-guest combinations and modifications of chemical, electrical, optical, and magnetic properties. BiI₃, which has a layered lattice structure and bandgap of about 1.8eV, absorbs and emits a photon at visible wavelength under room temperature conditions. Despite BiI₃’s considerable potentials to be adopted in a broad spectrum of optoelectronics, the power conversion efficiency of BiI₃ based optical devices remains below 1%. Such characteristics are attributed to high anisotropy and indirect bandgap of BiI₃. Hence, further improving its...[ Read more ]

Intercalation, in which foreign molecules are inserted within the interlayer interfaces of the layered materials, has been spotlighted as an enticing strategy to elicit exotic properties in layered two-dimensional materials. Intercalation allows various host-guest combinations and modifications of chemical, electrical, optical, and magnetic properties. BiI₃, which has a layered lattice structure and bandgap of about 1.8eV, absorbs and emits a photon at visible wavelength under room temperature conditions. Despite BiI₃’s considerable potentials to be adopted in a broad spectrum of optoelectronics, the power conversion efficiency of BiI₃ based optical devices remains below 1%. Such characteristics are attributed to high anisotropy and indirect bandgap of BiI₃. Hence, further improving its optical performances requires a rational design of the crystal architecture through a comprehensive understanding of the luminescence mechanisms. Here, high-purity single crystal BiI₃ nanoplates are prepared via the thermal PVD method to provide a platform to probe the intrinsic properties of BiI₃. Then monovalent alkali metal cations K+ and Rb+ are intercalated within the interplanar van der Waals gap. Our results demonstrate that alkali metal cations can be successfully intercalated via vapor phase reaction and mediate the structure and bandgap properties of BiI₃, owing to the Moss-Burstein effect. This work provides insights into adopting intercalation strategies as a scalable method for bandgap engineering of layered halide materials.