2D XBiSe3(X = Ga, In, Tl) monolayers with high carrier mobility and enhanced visible-light absorption

Bi-based bracelet-like monolayer with negative in-plane Poisson's ratio and enhanced photocatalytic performance: a first-principles study

Auxetic materials are in high demand for advanced applications due to their relatively rare negative Poisson's ratio in two-dimensional materials. This study investigates the structural, mechanical, electronic, optical and photocatalytic properties of the AsBiTe3monolayer(ML) using first-principles calculations. Through analysis of phonon dispersion curves,ab-initiomolecular dynamics simulations, and Born conditions, we have confirmed the thermal, dynamic, and mechanical stability of the AsBiTe3monolayer. The study of the mechanical properties of this material revealed significant anisotropy and a bidirectional in-plane negative Poisson's ratio (NPR). In addition, electronic band structures calculated, with and without spin-orbit coupling (SOC) using the HSE functional, indicate that this monolayer exhibits the characteristics of an indirect-gap semiconductor around 1.17 and 1.32 eV, respectively. Notably, by assessing the optical properties of AsBiTe3monolayer, it has been found that this monolayer has a strong light-harvesting capability with an absorption coefficient higher than 105 cm-1in the visible region. Fascinatingly, under a biaxial 1%and 4%tensile and -2% compressive strain, the band edge of the AsBiTe3monolayer extends across the redox potential of water at pH = 0, 7 and 14, respectively. This suggests that this monolayer holds promise as a potential material for catalytic water splitting. These results should inspire further experimental and theoretical research, aimed at fully exploring the potential applications of this new class of 2D materials.

A semiconductor Sc2S3 monolayer with ultrahigh carrier mobility for UV blocking filter application

For humans, ultraviolet (UV) light from sun is harmful to our eyes and eye-related cells. This detrimental fact requires scientists to search for a material that can efficiently absorb UV light while allowing lossless transmission of visible light. Using an unbiased first-principles swarm intelligence structure search, we explored two-dimensional (2D) Sc-S crystals and identified a novel Sc₂S₃ monolayer with good thermal and dynamical stability. The optoelectronic property simulations revealed that the Sc₂S₃ monolayer has a wide indirect bandgap (3.05 eV) and possesses an ultrahigh carrier mobility (2.8 × 10³ cm² V^-1 s^-1). Remarkably, it has almost transparent visible light absorption, while it exhibits an ultrahigh absorption coefficient up to × 10⁵ cm^-1 in the ultraviolet region. Via the application of biaxial strain and thickness modulation, the UV light absorption coefficients of Sc₂S₃ can be further improved. These findings manifest an attractive UV blocking optoelectronic characteristic of the Sc₂S₃ configuration as a prototypical nanomaterial for the potential application in UV blocking filters.

Bandgap Shrinkage and Charge Transfer in 2D Layered SnS2 Doped with V for Photocatalytic Efficiency Improvement

Effects of electronic and atomic structures of V-doped 2D layered SnS₂ are studied using X-ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X-ray absorption fine structure measurements at V K-edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS₂ layers. X-ray absorption near-edge structure (XANES) reveals not only valence state of V dopant in SnS₂ is ≈4⁺ but also the charge transfer (CT) from V to ligands, supported by V L_α,β resonant inelastic X-ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo-excited electrons and effective carrier separation in layered SnS₂ . Additionally, valence-band photoemission spectra and S K-edge XANES indicate that the density of states near/at valence-band maximum is shifted to lower binding energy in V-doped SnS₂ compare to pristine SnS₂ and exhibits band gap shrinkage. These findings support first-principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V-doped SnS₂ .