The modulation of electronic properties and mechanism analysis of the surface functionalization of TH-BP

The novel two-dimensional material TH-BP possesses highly anisotropic carrier mobility and excellent visible light absorption range, showing potential applications in the fields of optoelectronics and photocatalysis. In this paper, the first-principles method was employed to theoretically predict the impact of hydrogenation and fluorination on the surface of TH-BP on its electronic structure, achieving the mutual transformation between the semiconductor band characteristics and metallic band characteristics of TH-BP. It was found that an increase in surface adsorption not only leads to an enhancement of the bandgap width of TH-BP but also enables the transition from indirect to direct bandgap at a H adsorption rate of 50 %. Concurrently, the effective mass of electrons was significantly reduced after functionalization, which is beneficial for improving mobility. Analysis has shown that the changes in electronic properties are caused by the transformation of originally sp² hybridized atoms to sp³ hybridized ones after the adsorption of H/F atoms, which results in the breaking of double bonds, the disappearance of π bonds, and the elimination of the energy bands contributed by π bonds, leading to changes in the band structure.