Unravelling the correlated electronic and optical properties of BaTaO₂N with perovskite-type structure as a potential candidate for solar energy conversion

Abstract

We report on the first principles calculation of the electronic, structural and optical properties of BaTaO2N, using density functional theory (DFT) and finite difference time domain (FDTD) methods. Band structure calculations were performed to calculate the direct and indirect bandgaps of the material. Density of states and Mulliken charge analysis as well as the electronic contour maps were established to determine the type of bonding and hybridization between the various electronic states. The dielectric constant, reflectivity, absorption, optical conductivity and energy-loss function were also calculated. Moreover, FDTD was used to investigate the optical properties of a larger and more reliable structure of BaTaO2N powder in good agreement with the reported experimental parameters. The calculated electronic, structural and optical properties showed the potential of BaTaO2N for solar energy conversion and optoelectronic applications.

Fabrication of BaTaO2N Thin Films by Interfacial Reactions of BaCO3/Ta3N5 Layers on a Ta Substrate and Resulting High Photoanode Efficiencies During Water Splitting

“…The anode photocurrents significantly increased with increasing film thickness to a maximum at 600 nm, after which these values decreased with further increases in thickness to 680 nm. Because the surface morphology of the BaTaO 2 N layer was unchanged with increasing thickness, and the conductivity of the BaTaO 2 N particles has been reported to be similar across grain boundaries and in the bulk, the effects of grain boundaries on the electron transfer properties of the film are believed to be negligible. Thus, the photocurrent enhancement observed in conjunction with increasing BaTaO 2 N layer thickness can simply be ascribed to an increase in light absorption by the BaTaO 2 N, which, in turn, promotes the excitation of electrons.…”

“…Unfortunately, this material absorbs light beginning only at a wavelength of approximately 520 nm, which is much shorter than the desired value for solar energy usage. The valence bands of oxynitrides comprise hybridized O2p–N2p atomic orbitals that enable the absorption of visible light . Among these materials, barium tantalum oxynitride (BaTaO 2 N) is one of the most important candidates because it has an absorption edge close to 670 nm and is stable under light irradiation in concentrated alkaline solutions as the anode in the electrolysis reaction.…”

“…The valence bands of oxynitrides comprise hybridized O2p-N2p atomic orbitals that enable the absorption of visible light. [6][7][8] Thin films of barium tantalum oxynitride (BaTaO 2 N) with thicknesses of 150-680 nm are grown on TaN/Ta substrates via the interfacial reaction of BaCO 3 /Ta 3 N 5 layers in a N 2 atmosphere. A TaN thin film is first deposited on a Ta substrate by the Ar/N 2 ion sputtering of a Ta target, and then covered with a TaO x layer by Ar/O 2 sputtering.…”

NH3-Assisted Flux Growth of Cube-like BaTaO2N Submicron Crystals in a Completely Ionized Nonaqueous High-Temperature Solution and Their Water Splitting Activity

“…9 Previously, X-ray absorption fine structure, 10 electron diffraction, 11 neutron diffraction, 12 and pair-distribution-function 13 analyses have shown that the real structure of BaTaO 2 N is based on irregularly deformed Ta(O,N) 6 …”

Unveiling the role of carbon defects in the exceptional narrowing of m-ZrO2 wide-bandgap for enhanced photoelectrochemical water splitting

“…The real 𝑅(𝜎) and imaginary 𝐼𝑚(𝜎) parts of the optical conductivity represent the inphase current and out-phase inductive currents, respectively. The in-phase current is usually accompanied by liberation of heat energy due to the resistance [81] . In Figure 1S (c) and 3S, the in-phase current dominates over the range 0-34.5 eV (resistance domain)…”