Ab initio study of M2SnBr6 (M = K, Rb, Cs): Electronic and optical properties
University of New South Wales - Sydney, 2052, Australia
Received: 6 June 2016
Accepted: 12 September 2016
In this work, the ground-state properties of the solution processable semiconductor M2SnBr6 (M = K, Rb, Cs) have been computed using density functional theory. Similarities in the band structures are observed among these three materials and are shown to result from minimal contributions of the cation to electronic states near the Fermi level. A fundamental bandgap of 1.2 eV is predicted for the materials, which is close to the ideal bandgap for single-junction photovoltaic applications. However, in reality, a larger bandgap is expected because DFT calculations with the PBE functional underestimate the gap. Material optical properties including dielectric constants, reflective indices, reflectance and absorption coefficients are shown to be competitive for solar-energy harvesting. The ionization energies are 6 eV below the vacuum level, while effective masses are relatively small around 0.3, with light hole masses comparable to those of electrons.
PACS: 78.20.Ci – Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) / 71.15.Mb – Density functional theory, local density approximation, gradient and other corrections / 78.20.-e – Optical properties of bulk materials and thin films
© EPLA, 2016