Y. Noguchi, Y. Taniguchi, R. Inoue
Feb 19, 2020
Citations
0
Influential Citations
17
Citations
Journal
Nature Communications
Abstract
Titanium oxide materials have multiple functions such as photocatalytic and photovoltaic effects. Ferroelectrics provide access to light energy conversion that delivers above-bandgap voltages arising from spatial inversion symmetry breaking, whereas their wide bandgap leads to poor absorption of visible light. Bandgap narrowing offers a potential solution, but this material modification suppresses spontaneous polarization and, hence, sacrifices photovoltages. Here, we report successive-redox mediated ferrophotovoltaics that exhibit a robust visible-light response. Our single-crystal experiments and ab initio calculations, along with photo-luminescence analysis, demonstrate that divalent Fe 2+ and trivalent Fe 3+ coexisted in a prototypical ferroelectric barium titanate BaTiO 3 introduce donor and acceptor levels, respectively, and that two sequential Fe 3+ /Fe 2+ redox reactions enhance the photogenerated power not only under visible light but also at photon energies greater than the bandgap. Our approach opens a promising route to the visible-light activation of photovoltaics and, potentially, of photocatalysts. Photovoltaic response from normal ferroelectric materials generates large voltages but low current due to poor absorption of visible light. Noguchi et al. dope ferrous and ferric ion couple into barium titanate crystals to enhance the photogeneration at photon energies both below and above bandgap.