Design of Ferroelectric Double Perovskite Oxides as Photovoltaic Materials

Abstract

In ferroelectric-based photovoltaic materials, spontaneous polarization is expected to couple with the electronic and optical properties of the materials, and such materials have drawn attention as photovoltaic solar cells. Here, we utilize hybrid improper ferroelectricity to induce ferroelectric polarization in selected A-site layered and B-site rock-salt AA′BB′O 6 double perovskites and propose an alternate route to design ferroelectric photovoltaic semiconductors. First-principles density functional theory calculations and ab initio molecular dynamics simulations are performed to investigate the optical, electronic, and ferroelectric properties. We consider RbLaMnWO 6 and RbYMnWO 6 as model systems to pursue this study. We identify that these materials are semiconductors with a minimalist forbidden energy gap (E g ) of 2.31 and 2.14 eV, respectively. This facilitates their absorption within the visible light region, thus enabling them to be exploited for optical device applications. The optical transition occurring in RbLaMnWO 6 reveals the relationship between the absorption spectrum and its electronic structure. We notice a low ferroelectric switching barrier in the case of RbLaMnWO 6 , whereas a low band gap is espied in RbYMnWO 6 . To utilize the large visible spectra, we lower the band gap of RbYMnWO 6 from 2.14 to 1.67 eV by strain engineering. Similar structural, electronic, and optical properties are obtained for A-site substitution (A = K, Na). Further, molecular dynamics simulations show a polarization switching occurring at a temperature (T) of ∼400 K in RbLaMnWO 6 . This, in turn, enhances the dielectric response of RbLaMnWO 6 during switching and can be a potential candidate for designing optoelectronic materials where the structure− property relation can be controlled by electric field and/or temperature.

Electrically Detectable Photoinduced Polarization Switching in a Molecular Prussian Blue Analogue

“…To explore the polarization switching of the single crystals, the current during the phase transition before and after irradiation were evaluated with the pyroelectric measurement system. − A single-crystal sample was sandwiched between silver pastes on its (001) and (00–1) surfaces, which are perpendicular to the long axis of the single crystal (Figure S7a). During the thermodynamic phase transition, a negative peak for the pyroelectric current was observed at T (↓) = 145 K in the cooling process, and a peak in the opposite direction was detected in the heating process at T (↑) = 168 K, which is indicative of a polarization change.…”

MXene–MOF architectural hybrid-supported nickel single-atom catalysts for hydrogen evolution reactions

“…For these systems, using a 4 × 4 × 2 k-mesh, the geometry relaxations were carried out until changes in the total energy between relaxations, steps are within 1 × 10 −6 eV and atomic forces on each of the atoms were smaller than 0.01 eV Å −1 . 75 Based on the absorption energy, the free energy of the absorption state was computed following Wang's report. The hydrogen absorption site was validated by comparing the absorption energy of hydrogen at various sites on the catalyst surface.…”