MoSe2/BP heterobilayers with vacancy defects enhancing photovoltaic properties: A first-principles study

The effects of vacancy defects on the photovoltaic properties of molybdenum diselenide/boron phosphide (MoSe2/BP) heterojunctions were investigated by the first-principles calculation. The most stable MoSe2/BP heterojunctions were designed by adjusting the layer interfacial distance (2-4 & Aring;) and six possible stacking configurations according to density functional theory (DFT) calculations, and four prevalent vacancy-defect heterojunctions (VSe, VDSe1, VDSe2, VMo) were established. The results show that the electrical properties of MoSe2/BP heterojunctions are greatly improved by the defects, as calculated by first-principles calculation with the on-site HSE06 hybrid functional. The VSe and VDSe1 have the indirect bandgap and type-II band alignment, establishing a robust built-in electric field of -3.01 V, thereby enhancing the effective separation of photogenerated carriers. The VDSe2 has significant potential in photocatalysis due to its type-Z band alignment and compliance with the requisite band edge position. The VMo demonstrates type-I band alignment and diminishes the band gap from 0.92 eV to 0.41 eV with indirect-to-direct band gap transitions, which is conducive to the recombination of photogenerated carriers. The visible and near-infrared regions from 1.0 to 2.3 eV are characterized by exceptional optical absorption in all of the defective heterostructures that have been designed. These results show an effective method to modulate and improve the properties of MoSe2/BP heterostructures and explore their applications in optoelectronic devices.