Large birefringence in the quasi-one-dimensional material Sb2Se3: A DFT investigation of electronic and optical anisotropy

Abstract

Investigation of the optical and electronic properties of the quasi-one-dimensional semiconductor Sb2Se3 is performed with density functional theory, which takes into consideration the spin–orbit coupling and the on-site Coulomb self-interaction. Sb2Se3 has an orthorhombic crystal structure and belongs to the Pnma space group. The pronounced dispersion along the R−U, Z−Γ, Γ−Y, and S−X high-symmetry directions and low dispersion along the U−Z and Y−S directions confirm the layered structure, with strong bonding interactions along the [001] direction, as well as along the [010] direction, along which the SbSe6 and SbSe7 chains are aligned, and weak van der Waals interactions along the [100] direction. The material is a semiconductor with an indirect bandgap of 1.2 eV. Sb2Se3 exhibits appreciable carrier mobility and low carrier recombination rates in the plane of the layers, indicating its applicability in solar and photovoltaic devices. Simulated X-ray photoelectron spectra show that the photoelectron emission occurs from the Se p, Sb s, and Se s atomic orbitals, while for high-energy X-rays, photoelectron emission is mainly from Sb s orbital. Sb2Se3 possesses appreciable anisotropy in its refractive index, absorption coefficient, reflectivity, extinction coefficient, and optical conductivity. Sb2Se3 is a negative biaxial crystal, in which the principal optical axis X→a, Y→b, and Z→c. It possesses uniform birefringence in the IR region until the optical cutoff edge at 1030 nm. The material shows strong unidirectional linear dichroism in the wavelength range from 300 nm to 620 nm, with linear dichroism conversion at 275 nm. The energy loss is isotropic for slow electrons below 4.0 eV, but for highly energetic electrons it varies along different crystal directions. Sb2Se3 is a promising material for optoelectronic and polarimetric applications because of its desirable bandgap of 1.2 eV, linear dichroism conversion, and large optical anisotropy, refractive index, dielectric constant, and absorption coefficient.