WEB The limiting effect of interfacial band alignment on efficiency of earth-abundant chalcogenide photovoltaic materialsTuesday (02.06.2020) 14:31 - 14:31 Poster Room Part of:
Earth-abundant and environmentally-friendly Cu2-II-IV-VI4 (II = Sr, Ba; IV = Ge, Sn; VI = S,Se) are considered materials for the absorber layers in thin-film solar cells. Attempts to understand and improve optoelectronic properties of these newly emerged absorbers resulted in an efficiency of 5.2% in less than 2 years.
So far, however, the energy band alignment at the buffer/absorber interface received little attention; an information which is of crucial importance for designing high performance devices. Current contribution focuses on the band alignment between these materials and the CdS buffer. Using core level energies, band discontinuities are calculated at the buffer/absorber interface by first-principles calculations. The results yield a type-II band alignment between all Cu2-II-IV-VI4 absorbers and CdS, hence a negative ΔEc. Adoption of a negative ΔEc (cliff-like conduction band offset) at the buffer/absorber interface, however, gives rise to low open circuit voltage and high interface-related recombinations. Therefore, it is necessary to search for an alternative buffer material that forms a type-I band alignment with these absorbers, where the conduction band minimum and the valence band maximum are both localized on the absorber side.