ZnO–GaN heterostructured nanosheets for solar energy harvesting: computational studies based on hybrid density functional theory

Abstract

Through hybrid density functional theory, we computationally designed two-dimensional ZnO–GaN heterostructured nanosheets, and investigated their structural, electronic and optical properties. As a result of the type-II band alignment of ZnO and GaN, both bare (ZnO)_m(GaN)_n and hydrogenated H-(ZnO)_m(GaN)_n (m, n ≥ 3) nanosheets have band gaps below 3.0 eV with visible-light absorption accordingly, which is confirmed by computed optical properties. Also, photo-induced electrons and holes are directly separated and spatially confined in the ZnO and GaN regions, respectively, which is preferable for restraining ultrafast recombination of photo-excited e⁻–h⁺ pairs. Moreover, due to the perfect lattice matching of ZnO and GaN crystals, the heterostructured ZnO–GaN nanosheets have few crystal defects at the interfaces, which act as excitons' recombination centres. ZnO–GaN heterostructured nanosheets are promising high-performance materials for solar harvesting.