Highly Conducting, <i>n</i>-Type Bi₁₂O₁₅Cl₆ Nanosheets with Superlattice-like Structure

Abstract

Modulating the type and magnitude of electrical conductivity remains a basic requirement for a semiconductor’s widespread acceptability and use. Here, we convert nanosheets of BiOCl, a V–VI–VII ternary semiconductor, to an oxygen-rich Bi12O15Cl6 phase. In the process, the intrinsic conductivity switches from p-type to n-type. The phase change is achieved using a vacuum annealing step at 500 °C for 1 h. BiOCl nanosheets convert to the Bi12O15Cl6 phase via volatilization of BiCl3 resulting in a unique superlattice like structure with a periodicity of 1.48 nm. Correspondingly, the band gap decreases from 3.41 to 2.48 eV from the raising of the valence band edge. Activation energy for electrical conductivity reduces from 862 meV for BiOCl to 778 meV for Bi12O15Cl6, and a corresponding photoconductivity increase of 80× is observed. Density functional theory calculations predict changes to the valence band and increase in the Fermi level toward the conduction band edge for the Bi12O15Cl6 nanosheets—in accordance with experimental data. The availability of both p- and n-type ternary semiconducting systems widen the application base for Bi–O–Cl based materials.