Band Gap Reduction in ZnO and ZnS by Creating Layered ZnO/ZnS Heterostructures.
Wurtzite-type zinc oxide (ZnO) and zinc sulfide (ZnS) have electronic band gaps that are too large for light-harvesting applications. Using screened hybrid density-functional methods, we show that the band gaps of ZnO and ZnS can be dramatically reduced by creating layered ZnO/ZnS bulk heterostructures in which m contiguous monolayers of ZnO alternate with n contiguous monolayers of ZnS. In particular, the band gap decreases by roughly 40% upon substitution of every tenth monolayer of ZnS with a monolayer of ZnO (and vice versa) and becomes as low as 1.5 eV for heterostructures with m = 3 to m = 9 contiguous monolayers of ZnO alternating with n = 10 - m monolayers of ZnS. The predicted band gaps of layered ZnO/ZnS heterostructures span the entire visible spectrum, which makes these materials suitable for photovoltaic device engineering.
Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
Amin
A
Torabi
Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
Viktor N
VN
Staroverov
band gap engineering; bulk heterostructures; density-functional theory; light harvesting; quantum ESPRESSO; wurtzite