CdTe Photoluminescence: Comparison of Solar-Cell Material with Surface-Modified Single Crystals

Low-temperature photoluminescence (PL) is used to study defect evolution during Cu diffusion into single-crystal CdTe under various atmospheres. PL reveals a zero-order phonon peak at 1.456 eV when Cu-coated CdTe is annealed at 400°C in an oxidizing atmosphere, but not under other tested conditions. A similar peak is seen in polycrystalline thin-film CdTe samples, which are known to contain copper and oxygen impurities. First-principles band structure calculations determined the likely defect assignment as a transition between a Cui-OTe donor complex and the valence band.