A type-II C2N/α-Te van der Waals heterojunction with improved optical properties by external perturbation

Abstract

C₂N with uniform honeycomb holes and a nitrogen lattice, whose vacant sites are partially filled by C₆ hexagons, has a great potential due to its editable properties. Here, by using first-principles calculations, a C₂N/α-Te van der Waals (vdW) heterojunction and its electronic properties modulated by a vertical strain and external electric field were systematically investigated. The results showed that the C₂N/α-Te vdW heterojunction had a unique type-II band alignment, whose indirect band gap value was 0.47/1.01 eV in DFT/HSE06. The band gap could be tuned by external perturbation from 0.49 eV to 1.16 eV in HSE06. A type-II to type-I transition occurred under an external electric field of 0.4 V Å⁻¹. Interestingly, the C₂N/α-Te vdW heterojunction possessed high optical absorption strength (∼10⁵) and broad spectrum width (ultraviolet to near-infrared region). These results indicate that the C₂N/α-Te heterojunction is promising for photovoltaic applications.