Strong visible-light absorption and hot-carrier injection in TiO 2/SrRuO3 heterostructures

Abstract

Correlated electron oxides prove a diverse landscape of exotic materials' phenomena and properties. One example of such a correlated oxide material is strontium ruthenate (SrRuO3) which is known to be a metallic itinerant ferromagnet and for its widespread utility as a conducting electrode in oxide heterostructures. We observe that the complex electronic structure of SrRuO3 is also responsible for unexpected optical properties including high absorption across the visible spectrum (commensurate with a low band gap semiconductor) and remarkably low reflection compared to traditional metals. By coupling this material to a wide band gap semiconductor (TiO 2) we demonstrate dramatically enhanced visible light absorption and large photocatalytic activities. The devices function by photo-excited hot-carrier injection from the SrRuO3 to the TiO2 and the effect is enhanced in thin films due to electronic structure changes. This observation provides an exciting new approach to the challenge of designing visible-light photosensitive materials. The correlated electron "metal" SrRuO3 exhibits strong visible light absorption. Overlaid on the AM1.5G solar spectrum, it can be seen that SrRuO3 absorbs more than 75 times more light than TiO2. The structural, chemical, and electronic compatibility of TiO2 and SrRuO3 further enables the fabrication of heterojunctions with exciting photovoltaic and photocatalytic response driven by hot-carrier injection. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.