Vibrational and optoelectronic properties for intermediate band materials based on substituted chalcopyrites

Abstract

Novel materials for high efficiency photovoltaic solar cell have been study. Their vibrational and optical properties are the main objective of this work. The materials of interest are based on a chalcopyrite-type semiconductor (CuGaS2) with some Gallium atoms substituted by a transition metal atom. The insertion of the metal gives rise to the formation of an isolated band between the valence band and the conduction band of the host semiconductor. Here we present a frozen phonon ab-initio density functional theory calculations of the vibrational properties of the host chalcopyrite and the substituted alloys. This study can be used to calculate the phonon contribution to the free energy balance of formation and assess their thermodynamic viability. We have also carried out a study of the optoelectronic properties of these materials such as optical reflectivity and absorption coefficient. We demonstrate that the intermediate band increases the absorption of the material in the main region of the solar spectrum, as desired for photovoltaic applications.