Ab initio prediction of semiconductivity in a novel two-dimensional Sb2X3 (X= S, Se, Te) monolayers with orthorhombic structure

Sb 2S 3 and Sb 2Se 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 Sb 2S 3, Sb 2Se 3 and Sb 2Te 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 Sb 2S 3, Sb 2Se 3 and Sb 2Te 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 Sb 2S 3, Sb 2Se 3 and Sb 2Te 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 Sb 2S 3, Sb 2Se 3, and Sb 2Te 3, respectively. This study highlights the bright prospect for the application of Sb 2S 3, Sb 2Se 3 and Sb 2Te 3 nanosheets in novel electronic, optical and energy conversion systems. © 2021, The Author(s)

Structural, electronic and optical properties of ABTe2 (A = Li, Na, K, Rb, Cs and B = Sc, Y, La): Insights from first-principles computations

International audienceIn this contribution, ternary telluride ABTe2 compounds are proposed as promising candidates for n-type semiconductor materials in photovoltaic and photochemical devices. We report the successful calculations of the most fundamental properties needed in the previous applications such as the effective mass, dielectric constant and the exciton binding energy. This latter one has been evaluated from the density functional theory (DFT) method in the first time for these materials. An easy dissociation for hole-electron pair is suggested due to the small value of exciton binding energy at room temperature (i.e., lower than the thermal energy, 25 meV) for most of the studied compounds. The band structure and density of states of ABTe2 are calculated using the hybridHSE06 functional, PBE0 and in addition the pure GGA-PBE functionals. Additionally, to elucidate the optical properties of these compounds, the complex dielectric function and optical reflectivity were computed for a wide range of photon radiation. Therefore, ABTe2 materials are expected to be promising candidates for visible light driven photovoltaic and photocatalytic devices

Semiconducting chalcogenide alloys based on the (Ge, Sn, Pb) (S, Se, Te) formula with outstanding properties: A first-principles calculation study

Very recently, a new class of the multicationic and -anionic entropy-stabilized chalcogenide alloys based on the (Ge, Sn, Pb) (S, Se, Te) formula has been successfully fabricated and characterized experimentally [Zihao Deng et al., Chem. Mater. 32, 6070 (2020)]. Motivated by the recent experiment, herein, we perform density functional theory-based first-principles calculations in order to investigate the structural, mechanical, electronic, optical, and thermoelectric properties. The calculations of the cohesive energy and elasticity parameters indicate that the alloy is stable. Also, the mechanical study shows that the alloy has a brittle nature. The GeSnPbSSeTe alloy is a semiconductor with a direct band gap of 0.4 eV (0.3 eV using spin–orbit coupling effect). The optical analysis illustrates that the first peak of Im(ε) for the GeSnPbSSeTe alloy along all polarization directions is located in the visible range of the spectrum which renders it a promising material for applications in optical and electronic devices. Interestingly, we find an optically anisotropic character of this system which is highly desirable for the design of polarization-sensitive photodetectors. We have accurately predicted the thermoelectric coefficients and have calculated a large power factor value of 3.7 × 1011 W m–1 K–2 s–1 for p-type. The high p-type power factor is originated from the multiple valleys near the valence band maxima. The anisotropic results of the optical and transport properties are related to the specific tetragonal alloy unit cell