Synthesis of Hydride-Doped Perovskite Stannate with Visible Light Absorption Capability

Abstract

Narrow-gap semiconductors with visible light absorption capability have attracted attention as photofunctional materials. H–-doped BaSn0.7Y0.3O3−δ containing Sn­(II) species was recently reported to absorb visible light up to 600 nm, which represents the first demonstration of oxyhydride-based visible-light-absorbers. In the present study, a more detailed investigation was made to obtain information on the synthesis and properties of H–-doped perovskite-type stannate with respect to the A-site cation of the material and the preparation conditions. H–-doped ASn0.7Y0.3O3−δ (A = Ba, Ba0.5Sr0.5, and Sr) obtained by the reaction of ASn0.7Y0.3O3−δ precursors with CaH2 at 773 K under vacuum conditions was shown to have almost the same bandgap (ca. 2.1 eV), regardless of the A-site cation. Physicochemical measurements and theoretical calculations revealed that the identical bandgaps of H–-doped ASn0.7Y0.3O3−δ are due to the simultaneous shift of the midgap states composed of Sn2+ with the conduction band minimum. Experimental results also indicated that the appropriate preparation conditions with respect to Y3+-substitution and the temperature for the synthesis of the ASn0.7Y0.3O3−δ precursors were essential to obtain H–-doped products that have a low density of defects.

Influence of the Hydride Content on the Local Structure of a Perovskite Oxyhydride BaTiO3–xHx

“…With increasing the x value, the bond length of Ti–O–Ti becomes larger, causing a lattice expansion, as displayed in the XRD results (Figure ). Attenuation of the EXAFS oscillation with increasing the doped H – amount suggests the reduction of the long-range structural order due to random H – substitution, as reported previously. , …”

“…Attenuation of the EXAFS oscillation with increasing the doped H − amount suggests the reduction of the long-range structural order due to random H − substitution, as reported previously. 6,33 Considering the results of XANES and EXAFS, it can be concluded that increasing the H − concentration in Ba-TiO 3−x H x alters the local structure around the Ti center. The H − substitution relaxes the local distortion of the TiO 6 octahedron existing in the host BaTiO 3 , leading to the structural change from tetragonal to cubic.…”

Carrier Localization on the Nanometer‐Scale limits Transport in Metal Oxide Photoabsorbers

“…This high mobility is in line with one of the smallest effective masses reported for a metal oxide so far. [71] Therefore, this material seems to be promising despite the observed carrier localization. [72][73][74][75] On the other side, FeVO 4 exhibits especially poor transport since the TRMC amplitude is the lowest, and the OPTP signal was too small to be monitored and remained buried in the noise.…”

“…This high mobility is in line with one of the smallest effective masses reported for a metal oxide so far. [ 71 ] Therefore, this material seems to be promising despite the observed carrier localization. [ 72–75 ]…”