Two-dimensional monolayer BiSnO: a novel wide-band-gap semiconductor with high stability and strong ultraviolet absorption.

The exploration of two-dimensional (2D) wide-band-gap semiconductors (WBGSs) holds significant scientific and technological importance in the field of condensed matter physics and is actively being pursued in optoelectronic research. In this study, we present the discovery of a novel WBGS, namely monolayer BiSnO, using first-principles calculations in conjunction with the quasi-particle GWapproximation. Our calculations confirm that monolayer BiSnOexhibits moderate cleavage energy, positive phonon modes, mechanical resilience, and high temperature resistance (up to 1000 K), which demonstrate its structural stability, flexibility, and potential for experimental realization. Furthermore, band-structure calculations reveal that monolayer BiSnOis a typical WBGS material with a band-gap energy () of 3.61 eV and possesses a unique quasi-direct electronic feature due to its quasi-flat valence band. The highest occupied valence flat-band originates from the electronic hybridization between Bi-6and O-2states, which are in close proximity to the Fermi level. Remarkably, monolayer BiSnOexhibits a high absorption capacity for ultraviolet light spanning the UVA to UVC regions, displaying optical isotropy absorption and an unusual excitonic effect. These intriguing structural and electronic properties establish monolayer BiSnOas a promising candidate for the development of new multi-function-integrated electronic and optoelectronic devices in the emerging field of 2D WBGSs.