title: Simulation Evidence of Hexagonal-to-Tetragonal ZnSe Structure Transition: A Monolayer Material with a Wide-Range Tunable Direct Bandgap.
abstract: 2D material with tunable direct bandgap in the intermediate region (i.e., ≈2-3 eV) is key to the achievement of high efficiency in visible-light optical devices. Herein, a simulation evidence of structure transition of monolayer ZnSe from the experimental pseudohexagonal structure to the tetragonal structure (t-ZnSe) under lateral pressure is shown, suggesting a possible fabrication route to achieve the t-ZnSe monolayer. The as-produced t-ZnSe monolayer exhibits highly tunable bandgap under the biaxial strains, allowing strain engineering of t-ZnSe's bandgap over a wide range of 2-3 eV. Importantly, even under the biaxial strain up to 7%, the t-ZnSe monolayer still keeps its direct-gap property in the desirable range of 2.40-3.17 eV (corresponding to wavelength of green light to ultraviolet). The wide-range tunability of direct bandgap appears to be a unique property of the t-ZnSe monolayer, suggesting its potential application as a light-emitting 2D material in red-green-blue light emission diodes or as complementary light-absorption material in the blue-yellow region for multijunction solar cells. The straddling of the band edge of the t-ZnSe monolayer over the redox potential of water splitting reaction also points to its plausible application for visible-light-driven water splitting.
authors: Department of Chemistry University of Nebraska-Lincoln Lincoln NE 68588 USA.
authors: Lei
authors: L
authors: Li
authors: Hefei National Laboratory for Physical Sciences at Microscale and Collaborative Innovation Center of Chemistry for Energy Materials University of Science and Technology of China Hefei Anhui 230026 P.R. China.
authors: Pengfei
authors: P
authors: Li
authors: Department of Chemistry University of Nebraska-Lincoln Lincoln NE 68588 USA.
authors: Ning
authors: N
authors: Lu
authors: Department of Chemistry University of Nebraska-Lincoln Lincoln NE 68588 USA.
authors: Jun
authors: J
authors: Dai
authors: Department of Chemistry University of Nebraska-Lincoln Lincoln NE 68588 USA; Hefei National Laboratory for Physical Sciences at Microscale and Collaborative Innovation Center of Chemistry for Energy Materials University of Science and Technology of China Hefei Anhui 230026 P.R. China.
authors: Xiao Cheng
authors: XC
authors: Zeng
keywords: light emitting and absorption; strain engineering; tetragonal ZnSe monolayer; wide‐range tunable direct bandgap