Formation of Near-IR Excitons in Low-Dimensional CuSbS₂

Abstract

The electronic and optical properties of low-dimensional semiconductors are typically quite different from those of their bulk counterparts. Yet, the optical gap of two-dimensional copper antimony disulfide (CuSbS2) does not dramatically change with decreasing thickness of the material. The absorption onset remains at about 1.5 eV in the monolayer, bilayer, and bulk materials. Using density functional theory and many-body perturbation theory, we rationalize this behavior through the interplay of quantum confinement, electron–hole interactions, and the formation of surface states. Specifically, the spatial confinement in thin layers induces strongly bound optical transitions in the near-infrared region. Our results explain the optical properties in copper antimony disulfide platelets of varying thickness and set these materials as potential candidates for novel photovoltaic devices and near-infrared sensors.

Electromagnetic Response and Optical Properties of Spherical CuSbS2 Nanoparticles

“…The real and imaginary components of the permittivity of CuSbS 2 used herein were obtained from a previous study using Density Functional Theory [16] and have been averaged over the three orthogonal axes in order to estimate optical properties. Their values are provided in Figure 1.…”

“…In this work, we focus on the fundamental size-dependent optical and NIR properties of CuSbS 2 nanoparticles as individual spheres and embedded in a layer at low volume fractions (0.01%). The material properties are described by the complex dielectric function previously calculated using Density Functional Theory (DFT) [16,17] and Many-Body Perturbation Theory [18].…”

Electromagnetic response and optical properties of anisotropic CuSbS2 nanoparticles

“…CuSbS 2 is an unconventional semiconductor material and is emerging as a promising photovoltaic material due to its optical band gap that falls within the optimum range for solar cells [149,150], varying between 1.3´1.5 eV p0.82´0.95 µm) [151,152,153,154]. The permittivity of CuSbS 2 was taken from a study using Density Functional Theory with the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional [155]. The microscopic dielectric tensor was obtained for bulk and a monolayer of CuSbS broaden and shift to longer wavelengths.…”