Intermediate band materials: a way to use a broader solar spectrum range in photocatalysis

Trabajo presentado en la International conference on new advances in materials research for solar fuels production, celebrada en Granada del 12 al 14 de junio de 2013.Capturing as much of the solar spectrum as possible is a must for any processes, as for example those using heterogeneous photocatalysis, which try to harvest and store solar energy in form of fuel. The prototypical photocatalysts TiO2 and ZnO are unable to fulfill this aim, therefore other materials are sought. Enough chemical redox potential must be built in the photocatalyst to drive the desired reaction; in the case of water splitting (the >Holy Grail> in this field) this implies, considering the unavoidable losses, having a bandgap of ca. 1.8 eV or higher, implying that IR light cannot be used. This restriction can be circumvented, however, if one can use in photocatalysis the intermediate band (IB) principle, recently proposed for photovoltaics. [1] In this scheme, insertion of a delocalized and partially occupied band inside the gap of a semiconductor allows exciting electrons across the full bandgap using two subbandgap energy photons, mimicking the photosynthesis Z scheme but allowing using as well higher energy photons for the direct bandgap excitation.Peer Reviewe