Copper (I) Oxide (Cu₂O) based back contact for p‐i‐n CdTe solar cells

In this paper a promising solution for the notorious problem of manufacturing a stable low ohmic back contact of a CdTe thin film superstrate solar cell is presented without using elemental copper. Instead we have used a Cu 2 O layer inserted between the CdTe absorber and metal contact (Au). In contrast to the barrier free band alignment gained by using the transitivity rules, XPS measurements show a barrier in the valence band of the Cu 2 O layers directly after deposition, which results in a low performing JV curve. The contact can be improved by a short thermal treatment resulting in efficiencies superior to copper based contacts for standard CdS/CdTe hetero junction solar cells prepared on commercial glass/FTO substrates. By replacing the CdS window layer with a CdS:O buffer layer efficiencies of >15% could be achieved.