Noguchi Yuji, Taniguchi Yuki, Inoue Ryotaro, Miyayama Masaru
Department of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-Ku, Tokyo, 113-8654, Japan.
Division of Physics, Institute of Liberal Education, School of Medicine, Nihon University, Tokyo, 173-8610, Japan.
Nat Commun. 2020 Feb 19;11(1):966. doi: 10.1038/s41467-020-14763-6.
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 and trivalent Fe coexisted in a prototypical ferroelectric barium titanate BaTiO introduce donor and acceptor levels, respectively, and that two sequential Fe/Fe 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.
氧化钛材料具有多种功能，如光催化和光伏效应。铁电体可实现光能转换，产生因空间反演对称性破缺而产生的带隙以上电压，但其宽带隙导致对可见光的吸收较差。带隙变窄提供了一种潜在的解决方案，但这种材料改性会抑制自发极化，从而牺牲光电压。在此，我们报道了具有强大可见光响应的连续氧化还原介导的铁光光伏效应。我们的单晶实验、从头算计算以及光致发光分析表明，二价铁和三价铁共存于典型铁电体钛酸钡（BaTiO₃）中，分别引入施主和受主能级，并且两个连续的Fe/Fe氧化还原反应不仅在可见光下，而且在光子能量大于带隙时都能增强光生功率。我们的方法为光伏以及潜在的光催化剂的可见光激活开辟了一条有前景的途径。
