Ab initio prediction of semiconductivity in a novel two-dimensional Sb 2 X 3 (X= S, Se, Te) monolayers with orthorhombic structure

$$\hbox {Sb}_2\hbox {S}_3$$ and $$\hbox {Sb}_2\hbox {Se}_3$$ are well-known layered bulk structures with weak van der Waals interactions. In this work we explore the atomic lattice, dynamical stability, electronic and optical properties of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers using the density functional theory simulations. Molecular dynamics and phonon dispersion results show the desirable thermal and dynamical stability of studied nanosheets. On the basis of HSE06 and PBE/GGA functionals, we show that all the considered novel monolayers are semiconductors. Using the HSE06 functional the electronic bandgap of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers are predicted to be 2.15, 1.35 and 1.37 eV, respectively. Optical simulations show that the first absorption coefficient peak for $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers along in-plane polarization is suitable for the absorption of the visible and IR range of light. Interestingly, optically anisotropic character along planar directions can be desirable for polarization-sensitive photodetectors. Furthermore, we systematically investigate the electrical transport properties with combined first-principles and Boltzmann transport theory calculations. At optimal doping concentration, we found the considerable larger power factor values of 2.69, 4.91, and 5.45 for hole-doped $$\hbox {Sb}_{{2}}\hbox {S}_{{3}}$$ , $$\hbox {Sb}_{{2}}\hbox {Se}_{{3}}$$ , and $$\hbox {Sb}_{{2}}\hbox {Te}_{{3}}$$ , respectively. This study highlights the bright prospect for the application of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ nanosheets in novel electronic, optical and energy conversion systems.