Effect of tensile strain on the electronic structure, optical absorptivity, and power conversion efficiency of the BC6N/ZnO van der Waals heterostructure

Abstract

van der Waals heterostructures (vdWHs) have attracted significant interest as unique structures for application in nanoelectronic devices. A novel BC6N/ZnO vdWH was prepared by superimposing BC6N semiconductor wafers onto a hexagonal ZnO monolayer. The electronic structure, optical absorptivity, and power conversion efficiency (PCE) of BC6N/ZnO vdWH under tensile strain were studied using first-principles calculations. The band structure of the BC6N/ZnO vdWH exhibited a type-I band alignment with a direct bandgap of 1.92 eV. The type-I direct bandgap transformed into a type-II indirect bandgap when the uniaxial and biaxial tensile strains were increased to 10 %. Although the bandgap of the BC6N/ZnO vdWH increased (from 1.92 to 2.20 eV) monotonically with uniaxial strain (0–10 %), it was nearly independent of biaxial strain. The BC6N/ZnO vdWH exhibited a wide range and strong optical absorption in the ultraviolet (UV)–visible range; the absorptivity curve was red-shifted, and the optical absorptivity significantly increased in the UV region with increasing tensile strain. The PCE of BC6N/ZnO vdWH reached 22.5 % and 15.3 % under 10 % biaxial and uniaxial strains, respectively. The tunable electronic structure, excellent optical absorptivity, and ultrahigh PCE of BC6N/ZnO vdWH can be used in designing two-dimensional high-efficiency photovoltaic devices.