A spray pyrolysis route to the undoped ZnO layer of Cu(In,Ga)(S,Se)2 solar cells

The undoped ZnO in the window layer of Cu(In,Ga)(S,Se)₂ solar cells is deposited here by a non-vacuum spray pyrolysis method yielding solar cells of similar efficiencies to cells prepared with the standard sputtered layer. The spray pyrolysis method allows the undoped ZnO to be deposited in sequence on the same apparatus or in-line directly after deposition of the spray-‘ILGAR’ (ion layer gas reaction) In₂S₃ buffer layer. Thus it is highly suitable for manufacturing, not only is spray pyrolysis economical, avoiding the need for two target sputtering systems, but for monolithic integrated modules the second ‘P2’ scribe, carried out to interconnect cells, can be undertaken before sputtering permitting the highly doped ZnO:Al front contact to directly connect to the rear Mo back contact.