Advanced theoretically engineeing of novel photovoltaic intermediate band materials based on metal doped chalcogenides

Abstract

In the present work properties of derived chalcogenide compounds are obtained quantum mechanically using beyond Density Functional Theory (DFT) calculations and several candidates are proposed to be novel photovoltaic materials for the design of intermediate band solar cells with enhanced efficiencies. Substituting appropriately some Ga atoms with transition metals can give a compound with a narrow, partially-filled electronic band located inside the host semiconductor forbidden energy band-gap. Optical properties according to the experimental band-gap of the host semiconductor are obtained for both TiCu4Ga3S8 and CrCu4Ga3S8 The band . originated from the 3d states of the transition metal plays a determining role in the absorption of low energy photons. The effect of the strong correlation present in the 3d-Ti electrons of TiCu4Ga3S8 is also studied by first principles. As a result a value of 0.6 eV for U is found. This value turns out to be lower than that of other Ti based compounds. From a subsequent GGA+U calculation the effect of the correlation is reasoned to be not dangerous for the formation of an isolated intermediate band.