(Invited) Photophysics of Hybrid Semiconductor Nanostructure in Photocatalytic Hydrogen Generation Applications

Semiconductor nanostructures possess a number of applications in solar energy conversion.  This includes using colloidal quantum dots in solar cells and, more recently, using analogous nanostructures such as nanowires (NWs) in photocatalytic applications.  Here we describe recent work to understand the photocatalytic response of solution-synthesized CdSe NWs within the context of hydrogen generation.  Various CdSe NW-based systems such as core/shell structures and hybrid metal nanoparticle/semiconductor NW hybrid systems have been studied.  In all cases, femtosecond transient differential absorption spectroscopy has been used to reveal relevant carrier relaxation processes in these materials as well as the flow of charges across the different heterointerfaces that are present.  By correlating these transient absorption results to results from accompanying hydrogen generation efficiency measurements, we have, in turn, rationalized the response of these materials, clarifying the role that different heterojunctions play in establishing both charge separation and hydrogen generation efficiencies.