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 Cu2O 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 Cu2O 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. Copyright © 2016 John Wiley & Sons, Ltd. Cu2O was reactive sputtered as a new back contact material for CdTe solar cells. With an annealing of the finished solar cells and an improved front contact with CdS:O efficiencies of >15% could be achieved. The Cu2O acts as Cu source for the p‐doping of the CdTe and provides the p‐type contact material for the p‐i‐n structure of the solar cell. With a XPS interface experiment the band alignment between Cu2O and CdTe was investigated.