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

Narrow-gap semiconductors with visible light absorption capability have attracted attention as photofunctional materials. H--doped BaSn0.7Y0.3O3-delta containing Sn(II) species was recently reported to absorb visible light up to 600nm, which represents thefirst demonstration of oxyhydride-based visible-light-absorbers. In the present study, a more detailed investigation was made to obtaininformation on the synthesis and properties of H--doped perovskite-type stannatewith respect to the A-site cation of the material and the preparation conditions.H--doped ASn0.7Y0.3O3-delta(A = Ba, Ba0.5Sr0.5, and Sr) obtained by the reaction ofASn0.7Y0.3O3-delta precursors with CaH2at 773 K under vacuum conditions wasshown to have almost the same bandgap (ca. 2.1 eV), regardless of the A-sitecation. Physicochemical measurements and theoretical calculations revealed thatthe identical bandgaps of H--doped ASn0.7Y0.3O3-delta are due to the simultaneousshift of the midgap states composed of Sn2+with the conduction band minimum.Experimental results also indicated that the appropriate preparation conditionswith respect to Y3+-substitution and the temperature for the synthesis of the ASn0.7Y0.3O3-delta precursors were essential to obtain H--doped products that have a low density of defects