ZnO/Sn:ln_2O_3 and ZnO/CdTe band offsets for extremely thin absorber photovoltaics

摘要

Band alignments were measured by x-ray photoelectron spectroscopy for thin films of ZnO on polycrystalline Sn:In_2O_3 (ITO) and single crystal CdTe. Hybrid density functional theory calculations of epitaxial zinc blende ZnO(OOl) on CdTe(OOl) were performed to compare with experiment. A conduction band (CB) offset of -0.6 eV was measured for ZnO/ITO, which is larger than desired for efficient electron injection. For ZnO/CdTe, the experimental conduction band offset of 0.25 eV is smaller than the calculated value of 0.67 eV, possibly due to the TeO_x layer at the ZnO/CdTe interface. The measured conduction band offset for ZnO/CdTe is favorable for photovoltaic devices.