More Efficient Photovoltaic Materials by Metal Substitution in Sulphides Compounds: Theoretical Predictions and Experimental Results

Abstract

Trabajo presentado en EUROMAT: European Congress and Exhibition on advanced materials and processes, celebrado en Sevilla (España) del 8 al 13 de septiembre de 2013.The introduction of a properly chosen transition metal at high concentration into an octahedral semiconductor provides in-gap delocalized and partially occupied levels required by the Intermediate Band (IB) concept. We have verified with accurate DFT calculations including Van der Waals forces, that layered semiconductors as SnS2 or ZnIn2S4 can provide this situation when an octahedral cation in their structure is partially substituted by an element such as vanadium. The Van der Waals cleavage plane (0001) of these layered semiconductors is characterized by hexagonal arrays of close packed chalcogenide ions which are covalently bound within X-M-X sandwiches. This is an ideal substrate to study fundamental aspects of the metal/semiconductor interaction. Experimental work made via wet chemistry methods verifies that new absorption features appear in the optical absorption spectrum which matches the predicted DFT-based theoretical absorption results. Moreover, simple photocatalytic tests with these two materials, show spectral responses which evidence in both cases a very substantial ability to use sub-bandgap photons to drive electron and hole transfers at the material interface with scarce efficiency degradation by recombination effects. The results show that these materials have the appropriate characteristics for building photovoltaic devices of boosted efficiency using the whole range of the visible light spectrumPeer Reviewe