Strong Visible‐Light Absorption and Hot‐Carrier Injection in TiO2/SrRuO3 Heterostructures

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 (TiO2) 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.