Determination of the Electronic Structure and UV–Vis Absorption Properties of (Na_2–xCu_x)Ta₄O₁₁ from First-Principle Calculations

Abstract

Density functional theory (DFT) and density functional perturbation theory (DFPT) were applied to study the structural, electronic, and optical properties of a (Na2–x Cu x )Ta4O11 solid solution to accurately calculate the band gap and to predict the optical transitions in these materials using the screened coulomb hybrid (HSE06) exchange-correlation formalism. The calculated density of states showed excellent agreement with UV–vis diffuse reflectance spectra predicting a significant red-shift of the band gap from 4.58 eV (calculated 4.94 eV) to 2.76 eV (calculated 2.60 eV) as copper content increased from 0 to 83.3%. The band gap narrowing in these materials, compared to Na2Ta4O11, results from the incorporation of new occupied electronic states, which are strongly localized on the Cu 3d orbitals, and is located within 2.16–2.34 eV just above the valence band of Na2Ta4O11. These new occupied states, however, possess an electronic character localized on Cu, which makes hole mobility limited in the semiconductor.

Determination of the electronic, dielectric, and optical properties of sillenite Bi12TiO20 and perovskite-like Bi4Ti3O12 materials from hybrid first-principle calculations

“…For the calculation, the density functional theory (DFT) and density functional perturbation theory (DFPT) with both the standard Perdew-Burke-Ernzerhof (PBE) functional and the more accurate screened Coulomb hybrid Heyd-Scuseria-Ernzerhof (HSE06) functional were used. [7][8][9][10] Our choice of HSE06 was based on the previous reports of the widely used semiconductors in the fields of photocatalysis and photovoltaics, which showed high accuracy in predicting these photophysical properties compared with experimental data. [7][8][9][10][34][35][36] This result is distinctive from the small band gaps that were calculated using the standard PBE functional.…”

“…[7][8][9][10] Our choice of HSE06 was based on the previous reports of the widely used semiconductors in the fields of photocatalysis and photovoltaics, which showed high accuracy in predicting these photophysical properties compared with experimental data. [7][8][9][10][34][35][36] This result is distinctive from the small band gaps that were calculated using the standard PBE functional. 30,31,37 We emphasize here that our highly accurate characterization of these bismuth titanate compounds indicates that this material has remarkable photophysical properties, making it a promising material to be used in optoelectronic devices.…”

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

“…[ [50][51][52][74][75][76][77][78][79][80] However, our main focus on this study was to show the trend rather (relative difference) rather than giving absolute numbers. A systematic computational investigation of the impact of relevant self-intrinsic defects on the optoelectronic properties of BiVO4 at the HSE06 level of theory is indeed under progress and will be reported soon.…”

Polymorphism and Structural Distortions of Mixed-Metal Oxide Photocatalysts Constructed with α-U3O8 Types of Layers

“…Improved charge separation and photocatalytic/photoelectrochemical redox reactions have been proposed to be enhanced in these structures due to the preferential anisotropic diffusion of charge carriers along the BO 7 pentagonal bipyramid layers. The anisotropic charge diffusion is a result of the delocalization of the Nb 4d and the Ta 5d lowest-energy unoccupied crystal orbitals across the BO 7 pentagonal bipyramid layers, as confirmed by electronic structure calculations which show the largest band dispersion in these crystallographic directions [35,47,64,65,71,[122][123][124][125][126][127][128].…”