Ternary Cu3BiY3(Y= S, Se, and Te) for Thin-Film Solar Cells

Abstract

ABSTRACTVery recently, Cu3BiS3has been suggested as an alternative material for photovoltaic (PV) thin-film technologies. In this work, we analyze the electronic and optical properties of Cu3BiY3with the anion elementsY= S, Se, and Te, employing a first-principles approach within the density function theory. We find that the three Cu3BiY3compounds have indirect band gaps and the gap energies are in the region of 1.2–1.7 eV. The energy dispersions of the lowest conduction bands are small, and therefore the direct gap energies are only ∼0.1 eV larger than the fundamental gap energies. The flat conduction bands are explained by the presence of localized Bip-states in the band gap region. Flat energy dispersion implies a large optical absorption, and the calculations reveal that the absorption coefficient of Cu3BiY3is larger than 105cm−1for photon energies of ∼2.5 eV. The absorption is stronger than other Cu-S based materials like CuInS2and Cu2ZnSnS4. Thereby, Cu3BiY3has the potential to be a suitable material in thin-film PV technologies.