New materials for intermediate band photovoltaic cells. A theoretical and experimental approach

Abstract

Density functional theory calculations of certain transition-metal doped semiconductors show a partially occupied relatively narrow band located between valence band and conduction band. These novel systems, containing the metallic band, are called intermediate-band materials. They have enhanced optoelectronic properties which allow an increase in solar energy conversion efficiency of conventional solar cells. We previously proposed III-V, chalcopyrite and sulfide derived compounds showing desirable characteristics to produce the intermediate band of interest inside the band-gap. In order to obtain further intermediate-band material proposals, this work focuses on studing other compounds constituted mainly by tetravalent elements. The first proposal is vanadium substituting Sn atoms in SnS2 , the second one is composed by type II silicon clathrate with two possibilities: vanadium substituting Si and Ag occluded in the intra-crystalline cavities. UV-Vis-NIR spectra of some of these systems experimentally synthesized show an agreement with previous theoretical predictions