13 research outputs found
Strong Bulk Photovoltaic Effect in Planar Barium Titanate Thin Films
The bulk photovoltaic effect (BPE) leads to the generation of a photocurrent
from an asymmetric material. Despite drawing much attention due to its ability
to generate photovoltages above the band gap (), it is considered a weak
effect due to the low generated photocurrents. Here, we show that a remarkably
high photoresponse can be achieved by exploiting the BPE in simple planar
BaTiO (BTO) films, solely by tuning their fundamental ferroelectric
properties via strain and growth orientation induced by epitaxial growth on
different substrates. We find a non-monotonic dependence of the responsivity
() on the ferroelectric polarization () and obtain a remarkably
high BPE coefficient () of 10 1/V, which to the best of
our knowledge is the highest reported to date for standard planar BTO thin
films. We show that the standard first-principles-based descriptions of BPE in
bulk materials cannot account for the photocurrent trends observed for our
films and therefore propose a novel mechanism that elucidates the fundamental
relationship between and responsivity in ferroelectric thin films. Our
results suggest that practical applications of ferroelectric photovoltaics in
standard planar film geometries can be achieved through careful joint
optimization of the bulk structure, light absorption, and electrode-absorber
interface properties.Comment: 12 pages, 8 figure
Making cheaper labor: Domestic outsourcing and development in the Galilee
Middle Eastern Studie
Ferroelectric barium titanate derivatives containing Mo and Mg for transparent photovoltaic applications
Visible-light-absorbing potassium Niobate-Titanate-Molybdate ferroelectrics
Abstract
The interactions of ferroelectric (FE) perovskite oxides (ABO₃) with light are increasingly being studied for different applications, such as photovoltaics and optoelectronics. The combination of different cations at the A and B sites to form solid solutions allows tuning of the material’s properties and, most importantly, the band gap (Eg), which sets the wavelength range of light absorption. Classic FE perovskite oxides, such as BaTiO₃, KNbO₃, and PbTiO₃, exhibit Eg > 3 eV, which limits their implementation in visible-light-absorbing devices. Furthermore, the tuning of their Eg via a solid solution strategy to a lower Eg range is limited by the requirement for the presence of a d⁰ metal at the B site, which is necessary for the FE distortion, but leads to a larger Eg. This gives rise to the challenge of decreasing Eg, while maintaining FE distortion. Here, we use first-principles calculations to explore the FE and optical properties of the (KNbO3)x(KTi1/2Mo1/2O3)1−x(KNTM) perovskite oxide solid solution. The introduction of Ti⁴⁺ and Mo⁶⁺ into the parent KNbO₃ decreases the Eg to about 2.2 eV for x = 0.9, while preserving or enhancing polarization. Experimental fabrication and characterization show that the obtained KNTM material at x = 0.9 has an orthorhombic structure at room temperature and a direct gap of <2.2 eV, confirming first-principles-based predictions. These properties make KNTM a promising candidate for further studies and applications as a visible-light-absorbing FE material